Subscriber RF telephone system for providing multiple speech and/or data signals simultaneously over either a single or a plurality of RF channels

Description: TECHNICAL FIELD [Detailed description of the invention]

Background of the invention The present invention generally relates to communication systems, particularly to subscriber station telephone systems for simultaneously providing multiplex information signals through one or more radio frequency (RF) channels. Outline of the invention The present invention provides a system for wirelessly transmitting a multiplex information signal using a digital time division circuit between a base station and a plurality of subscriber stations. These subscriber stations may be fixed or mobile. The number of time division circuits is determined by the transmission quality of the signal. The base station is interconnected with an external information network that can be analog and / or digital. Information signals are selected from groups consisting of voice, data, facsimile, video, computers, and measurement signals. Mobile subscriber stations can selectively move relatively quickly and relatively slowly. The modulation level and power of the signal applied to the system are adjusted based on signal error detection in the system. The system provides spatial diversity by using multiple antennas that are selectively spaced apart from each other to provide relatively strong signal reception regardless of signal fading. Base stations operate through multiple RF channel pairs. The operation of each channel pair is transmission to process multiple given information signals received simultaneously through the telephone company's trunk line for simultaneous transmission to different subscriber stations over a given radio frequency (RF) channel. It is realized by a combination of a channel circuit and a receive channel circuit for processing multiple signals simultaneously received by RF channels given by different subscriber stations to provide information signals for transmission through the trunk line. In order to convert the information signal received through the trunk line into a digital signal sample, a separate converter is connected to each of the trunk lines. The transmission channel circuit simultaneously compresses the digital signal samples derived from the individual devices of the converter and simultaneously compresses the given number of individual signal compressors to provide a given number of individual signal compressors, respectively. Each of the compressed signals sequentially converts the compressed signal into a single transmit channel bit stream that occupies a repeating sequence slot position in the transmit channel bit stream associated with the predetermined device of the individual compressor. It comprises a channel control device connected to a compressor for combination and a device for providing a transmit channel signal for transmission through a predetermined RF channel in response to a transmit channel bit stream. The switch combines each individual converter with the indicated one of the individual compressors. The remote-connected processor device is coupled to the trunk line and responds to an input call request signal received through one of the trunk lines, and the switch is an individual with any one of the individual compressors connected to one trunk line. A transmit channel associated with one of the individual compressors so connected by a switch, which provides a slot allocation signal indicating whether it is to be connected to one of the converters. Allocate slots in the bitstream to one trunk line. This remote-connected processor maintains memory, and this memory slot is checked by the remote-connected processor when receiving an input call request, for a compressor associated with one of the slots not assigned to the other trunk line. It is assigned to provide a slot allocation signal that creates a connection. The calling processor is connected to the remote processor and responds to the slot allocation signal, completing the connection indicated by the slot allocation signal to the switch. The receive channel circuit is a receiver device that receives the receive channel signal and processes the receive channel signal to provide a receive channel bit stream containing individual compressed signals at different repeating sequence slot positions, each receiving channel bit. A given plurality of given to reconstruct a digital signal sample from the individual compressed signals associated with different slot positions in the stream and contained in each of the associated slot positions of the receive channel bitstream. Control for separating the individual signal synthesizer and the individual compressed signal from the receive channel bitstream and distributing the separated signal to the individual synthesizer associated with each time slot from which the signal was derived. Equipped with a device. The individual reconversion device reconverts the digital signal sample into an information signal because it is connected to each of the trunk lines and transmitted through each trunk line. Each of these individual reconversion means is associated with one of the individual conversion means and is further connected to the common trunk line of the trunk lines together with the related individual conversion means. The exchanger combines each individual reconverter with the indicated one of the individual synthesizer. The remote-connected processor responds to an input call request signal received through one trunk line, and the switch connects any one of the individual synthesizers to one of the individual reconverters connected to one trunk line. It provides a slot allocation signal to indicate if it is, thereby locating the slots in the receive channel bitstream associated with one of the individual synthesizers so connected by switch means. Allocate to one trunk line. The remote-connected processor maintains memory, and the slot in the receive channel bit stream of this memory is one of the slots that this remote-connected processor examines this memory and is not assigned to other trunk lines when receiving an input call request. It is assigned to provide the calling processor with a slot allocation signal to create a connection to the synthesizer associated with. The system of the present invention makes full use of the latest digital and large-scale integrated electronic technology to bring low-priced, reliable, and high-quality communication facilities to various markets. In one preferred embodiment, one fixed base station is installed centrally to communicate with a large number of subscriber stations installed in geographically nearby areas. The central base station can be connected to the central station of the public telephone company (Telco) network through a private private branch exchange (PBX) connected to the input telephone trunk line. The subscriber stations in the system may practically be either portable or mobile based on fixed station standards, and can operate on relatively slow or relatively fast movements. The subscriber station communicates with the base station via the UHF radio channel and with the user via a standard 2-wire DTMF push-button telephone device or RS-232C or non-standard telephone office (eg, 4-line). The system replaces existing wired regional subscriber loops or provides good telephone service to areas where wiring connections are infeasible or uneconomical. One feature of the system of the present invention is the ability to use time division multiple access (TDMA) to allow simultaneous multiplex use of frequencies within a given network. All possible high quality audio circuits can operate simultaneously on a given frequency channel (25KHz channel spacing). Four such circuits are used for explanatory purposes. This provides both spectral and economic advantages over existing analog radiotelephone systems that can only provide one line of call at a time for a given frequency. A feature of achieving low-cost fixed, mobile, and portable services is the use of low-speed digital voice coding (16Kbps), which combines spectrally effective digital modulation technology. For example, using a combination of 14.6Kbps voice coding technology and 16-level DPSK modulation, four simultaneous full-duplex calls are placed in the entire spectrum, especially within the 400-500MHz and 800-950MHz segments, with a single frequency interval of 25MHz. 20KHz Bw (bandwidth) channel pair support is possible. This combination provides good quality calls over a distance of at least 20km. To compete with wired services, it must accommodate a much larger population of subscribers than can be supported simultaneously with a given number of 25KHz channel pairs. For example, if a 12-channel pair system supported 47 simultaneous calls, the total off-hook + on-hook subscriber population would be 500 (in the case of the maximum constraint with the desired peak hour blocking probability). Therefore, a subscriber call control configuration that provides a reasonable call connection delay is also an important advantage of the present invention. Other features of the invention are described in connection with the description of preferred examples. Acronyms used herein A / D analog digital converter ADPCM Adaptive Differential Pulse Code Modulation AGC automatic gain control AM amplitude modulation BCC baseband control channel BPSK binary phase shift keying modulation BW bandwidth CCU Channel controller CODEC codec decoder DEMOD demodulator (modem receiver) D / A Digital Analog Converter dB decibel DID direct internal dial DMA direct memory access DPSK differential phase shift keying modulation DTMF dual tone multi-frequency signal scheme ECL Emitter-coupled logic FCC Federal Communications Commission FIFO first-in first storage device FIR Finite Impulse Response Filter Hz Hertz (cycle / sec) I homeomorph IF intermediate frequency Kbps kilobits per second KHz kilohertz Km km LSB least significant bit MDPSK multi-phase differential phase shift keying modulation MHz MHz MODEM Modem (integrated modulation / demodulator) MPM message processing module ms millisecond OCXO Reactor Control Crystal Oscillator PBX private branch exchange facility PCM pulse code modulation PSN Public Exchange Network PSTN Public switched telephone network or other carriers (Telco, etc.) Q Quadrature phase QPSK Quadrature Phase Shift Keying Modulation RBTG ringing sound generator RAM direct access storage RCC wireless control channel RELP Residual Excitation Linear Prediction RF radio frequency RFU radio frequency device RPU remote connection processor device ROM fixed storage device RX reception SHF VHF frequency (3,000-30,000MHz) SIN subscriber identification number SLIC subscriber loop interface circuit STIMU system timing device STU subscriber station telephone interface device SUBTU subscriber timing device TDM time division multiplexing TDMA time division multiple access Telco Telephone Company TX transmission UHF ultra high frequency UTX-250 A PBX, a switch with processing and interface functions, is appropriate but does not necessarily have to be a PBX. UW Unique Word VCU voice code decoder VCXO voltage controlled crystal oscillator VHF VHF frequency (30 ~ 350MHz) Configuration of the invention In the present invention, when a special band (for example, 454 to 460 MHz) is used in the examples, the present invention is similarly applicable to at least all VHF, UHF, and SHF bands. According to FIG. 1, the system of the present invention provides a subscriber telephone service using UHF radio between a subscriber station (S) 10 and a base station 11. The base station 11 provides a direct call connection between the wireless-based subscriber stations 10 and is connected to the telephone company (Telco) central station 12 to support calls to points outside the system. that. For example, the system shown operates on a pair of common carrier frequency channels within the 454MHz to 460MHz band. This special frequency set contains 26 designated channels. These channels have a allowed bandwidth of 20 KHz and a frequency interval of 25 KHz. The frequency interval between the transmit channel and the receive channel is 5 MHz with the lower frequency of the two frequencies assigned to the base station transmission as the center frequency. As mentioned above, this system can also be operated with other UHF channel pairs. The mode of transmission (transmission channel) from the base station to the subscriber station is based on time division multiplexing (TDM). Transmission (reception channel) from the subscriber station to the base station is based on the time division multiple access (TDMA) method. All systems are 47 CFR Designed to comply with FCC Parts 21, 22, and 90, and other relevant rules. Communication between base station 11 and subscriber station 10 is filtered by a full-duplex channel with a frequency spacing of 25 KHz in the 454-460 MHz band. Multiphase differential phase shift keying (MDPSK) ) Achieved digitally by modulation, thereby meeting the requirements for 20 KHz bandwidth as specified in FCC Regulations 21, 22, and 90 (ie, 21.105, 22.105, and 90.209). The system can also be used with other bandwidths and frequency intervals within all possible parts of the VHF, UHF, and SHF spectra. 25KHz each The symbol rate for the FCC channel is 16 km symbol / sec in each direction. Voice transmission is achieved by 16-level PSK modulation and voice digitization at a coding rate of 14.6 Kbps, selectively 2-level (BSKP) or 4-level (QPSK) modulation can be applied. .. Mixing of different modulation levels is possible on the same channel at the same time. With time division multiplexing, the system provides one call for every two multiplier phases at 14.6Kbps (two calls for four phases, four calls for 16 phases, etc.) or more for purposes at low rates. Yes, this is of course just an example, and various combinations of modem bits / symbols or phase and code decoder rates can be used as shown in the table below.<img file="JP2816349B2_D0001.tif" /><img file="JP2816349B2_D0002.tif" /> The base station can transmit and receive by any or all of the FCC 25 KHz interval frequency channels within the frequency band 454 to 460 MHz in which the channels are freely selectable. The channel frequency selection for each audio channel is automatically done by the base station, one channel at a time, but can be overridden by the interface of the operator control console provided at the base station. A base station can typically have a transmit power output of 100 watts for each frequency channel. The base station performs modulation control and time slot and frequency channel allocation for the subscriber station. In addition, the base station implements adaptive power control for the subscriber station for the purpose of minimizing sequential time slot differences and adjacent channel interference. Switching between the Telco trunk line and the TDM slot for the selected channel is preferably done by the base station using a digital switch, except that the digital switch is replaced by an analog switch. It is possible. The base station imparts triple space diversity capability with respect to the receiving channel. Subscriber stations can operate at 3-branch diversity, transmit power is typically adjustable between 0.1 and 25 watts, but can be adjusted in other power ranges as well. As long as voice communication through the subscriber station can be perceived in real-time full-duplex, the RF system operates in half-duplex by utilizing the appropriate time-division multiplex timing method. The subscriber station is coupled with any telephone instrument for voice communication, i.e. the telephone can be incorporated into this system. In addition, data connections such as the RS-232C standard 25-pin connection are available for 9600 band rate data transmission between subscribers. Base stations and subscriber stations can obtain working power from any possible power source, whether internal or external. FIG. 2 is a block diagram of an embodiment of a base station that supports simultaneous operation of two pairs of transmission / reception frequency channels. Each channel can handle up to 4 phone connections at the same time. In the preferred embodiment, there are many transmit / receive channel pairs, and each channel has several time slots. One of several available time slots is required for the radio control channel (RCC). The connection between the PSTN and the subscriber station is established and maintained within the private private branch exchange (PBX) within the base station. The PBX15 is a UTX-250 type system, an off-the-shelf developed by the United Technologies Building Systems Group. Many of the existing features of a typical PBX system are available for the Telco interface required by the system of the present invention. The PBX15 also converts audio information from / to the PSTN into a 64Kbps μ-law compressed pulse code modulation (PCM) digital sample. From this point onward, audio information is processed in digital form through the base station and the subscriber station up to the interface circuit connected to the subscriber telephone, or as the conditions of the subscriber transmitter and receiver allow. The digital audio information from the PBX 15 is then processed by an audio compression system known as the Decoder 16 that reduces the audio information rate from 64 Kbps to about 14.6 Kbps or less. The code decoder 16 performs this audio rate compression using either a residual excitation linear prediction (RELP) algorithm or an SBC encoder / decoder. Typically, four note decoders 16 belong to a single note decoder (VCU) 17 to perform audio compression for four or more time slots on each frequency channel. The VCU17 of each base station can handle four or more full-duplex connections to both the transmit and receive channels of each channel pair. The connection state by the PBX 15 determines which voice call is processed by which VCU17 and which code decoder 16 of the selected VCU17. The circuit of each VCU 17 is detailed in hardware so that voice calls for specific frequencies and slot allocations within the base station are always handled by the same VCU code decoder 16. Each VCU 17 is connected to a channel controller (CCU) 18. This CCU18 controls the TDMA function and also functions as a link level protocol processor. Each CCU 18 takes the transmit channel output of the corresponding VCU 17 code decoder 16 and transmits the data to the modem device 19 in the correct time slot and format. Each CCU18 determines the modulation level (eg, 2, 4, or 16 level RSK modulation) for use in broadcast communication, as controlled by the remote control processor device RPU20. Each CCU18 also processes control information for communication to the subscriber station through the radio control channel (RCC) time slot and during the overhead control bits of the voice channel. Each channel pair has a combination of VCU17, CCU18 and modem 19 connected in series. Properly formalized transmission data from each CCU 18 is transmitted to the corresponding modem 19 at a rate of 16K symbols / second. Each modem 19 takes these synchronization symbols and converts them to Gray-coded multi-level phase keyed (PSK) format. The transmit channel output of modem 19 is a modulated IF signal. This signal is fed to an RF / IF processor (RFU) 21, which converts the IF signal into an RF UHF signal in the 450 MHz range. The control signals for modem 19 and RFU21 are supplied by the corresponding CCU18 operating under the full control of RPU20. The UHF signal is amplified by the power amplification of the RFU21 and sent to the transmitting antenna 23 via the antenna interface device 22 for outdoor broadcast communication. The receiving function of a base station is essentially the opposite of the transmitting function. Each RFU21, modem 19, CCU18, VCU17, and PBX15 are originally full duplex. The remote control processor device (RPU) 20 is a central control processing unit that transmits connection data and control messages to the CCU. The RPU20 includes a general purpose computer based on the 6800 microprocessor that performs complex system management and control functions for setting up, releasing, and maintaining calls. The RPU20 is further served by a switch matrix 25 on the PBX15 between the telco decoder 16 and the Telco trunk line. Communicates with the call processor 24 in the PBX 15 to control the interconnection. Each subscriber station is a relatively small device located on each user's premises in the system. The subscriber station connects the user's standard telephone set and / or data terminal or integrated audio transmitter / receiver to the base station through UHF radio channels. The function of the subscriber station is very similar to the function of the base station. However, while base stations operate simultaneously on one or more frequency channels, each channel providing the ability to support several audio circuits, subscriber stations usually have only one frequency at a time. Works with respect to. Figure 3 is a block diagram of the subscriber station. The functional division is very similar to that of the base station (Fig. 2). The user interface function is performed by the subscriber telephone interface device (STU) in the subscriber station. Related functions within the base station are performed by the PBX module. The subscriber station's STU performs all the control functions of the subscriber station, just like the base station's RPF function. In the overall system control system, the subscriber station acts as a slave to the master base station. The STU can interface with an external device, that is, it can transmit and receive acoustically. Looking at the flow of data through the subscriber station, the user's voice, or data information, is first processed by the subscriber terminal equipment (STU) 27. The audio signal input from the user's telephone is received and digitized within the VCU28. The type of digitized audio signal is the same as the type used in PBX15 in the base station. The subscriber station has a VCU28, a CCU29, a modem 30a, and an RFU31a that perform the same functions as the similar device described above in the description of the base station system with respect to FIG. One difference in the operation of the subscriber station is that its operation is usually limited to only one audio channel at a time. The subscriber station operates essentially in half-duplex mode, transmitting one part of the TDMA frame and receiving another part of the TDM frame. For a frame size of 45 msec, the subscriber station's half-duplex characteristic is transparent to the user, who can call the continuous voice input from the other party and hear it at the other end of the connection. The modem 30a, as well as the STU27 and VCU28, can be duplicated to enable subscriber calls on one or more lines. By half-duplex operation of the subscriber station, the available subscriber station hardware can be used more effectively. The subscriber station's VCC and CCU function in essentially the same way as the base station, at least as far as the handling of voice data is concerned. However, the modem 30a is set up to operate in half-duplex mode so that the receiving or transmitting parts of the modem can be used, but not simultaneously. The direct savings in this case is that the RFU31a simply needs to operate in half-duplex mode. This saves power in that the RF power amplifier only works half the time. In addition, the RF transmitting antenna 32a can be switched to act as a second receiving antenna during the receiving portion of the frame using the RF antenna switch function. Moreover, it does not require a transmit / receive switch at all. Each subscriber station also has a diversity network that includes three modems and a diversity combiner circuit 33. This diversity combiner circuit 33 collects demodulated received information from each of the demodulators of the three modems 30a, 30b, and 30c and combines the three streams into a single sent to CCU29 for processing. Form the "best-guess" symbol stream. The demodulators or demodulators of the three modems 30a, 30b, 30c are connected to the separate RX RFU31a, 31b, 31c, which in turn connects them to the separate antennas 32a, 32b, 32c. In the base station, three receiving antennas, namely 34a, 34b, and 34c, are arranged at appropriate intervals from each other to provide an uncorrelated spatial diversity signal to be processed by the diversity network. The operation of the diversity network is transparent to the CCU function, so if the diversity function is not needed, it can always be replaced by the single modem function. The base station also has a spatial diversity network for each transmit / receive channel pair. This diversity network is not shown, but the base station diagram in Figure 2 is as shown in the subscriber station diagram in Figure 3, which shows the connection of the diversity network to a single transmit / receive channel pair. It is the same. Therefore, each transmit / receive channel pair in the base station actually includes three demodulators and one modem connected to the diversity combiner circuit as shown in FIG. Accurate timing synchronization between the base station and the subscriber station is important for the entire system. The master timing base for the entire system is created by the base station. All subscriber devices in a particular system must be synchronized to this timebase with respect to frequency, symbol timing and frame timing. The base station includes a system timing device (STIMU) that produces an extremely accurate timing reference clock signal of 80.000 MHz. This 80 MHz reference clock signal is frequency-decreased to generate a 16 KHz clock signal and a 22.222 Hz (duration 45 msec) frame strobe marker signal. All base station transmission timings arise from these three synchronous master reference signals. The 80MHz clock signal is used by modems 19 and RFU21 as accurate IF and RF frequency references. The 16KHz clock signal provides symbol rate timing for transmission over all base station frequencies. The 45msec marker signal is used to add the first symbol in the new frame. This marker signal has 1 symbol time (62.5 μsec, 1/16000) Only active for a period of (equal to Hz). All frequency channels in the base station use the same time reference for transmission, three timing signals (80MHz, 16KHz, and frame start {SOF} markers) are fed to each modem 19 in the base station, modem 19 Distribute the appropriate clock signal to CCU18 and RFU21 in the same series connection transmit / receive channel pair. The CCU18 uses this 16KHz and SOF marker to time the audio transmission and control the symbols according to the current frame structure for that frequency. The reception timing in the base station is basically the same as the transmission timing of the base station, that is, the SOF marker and the symbol clock signal must be exactly aligned between the transmission signal and the reception signal. However, since perfect timing synchronization cannot be expected from the transmission of the subscriber station, the reception timing of the modem 19 of the base station must match the input symbol from the subscriber station. This is necessary for the sampling period of the receiving function of the base station modem 19 to provide the best prediction for the symbol being received from the subscriber station. The small elastic buffer in the CCU 18 interfaced with the receive function of the modem 19 compensates for this slight timing skew. Subscriber stations in the entire system synchronize their time reference to the base station's master timebase. This synchronization is achieved by a multi-step procedure in which the subscriber station first obtains the base station time reference by using RCC messages from the base station. This procedure is described below. Once the subscriber station first completes the acquisition of the time reference from the base station, the tracking algorithm in the demodulator of the subscriber station modems 30a, 30b, 30c keeps the subscriber station's reception timing accurate. The subscriber station advances its own transmission to the base station by a small amount of time to offset the transmission round-trip delay caused by the arrangement of the subscriber station. As a result of this method, the transmissions from all the subscriber stations that the base station is receiving are in the correct phase relationship with each other. System Timing Device (STIMU) 35 provides a time reference for all transmissions within the base station. STIMU35 is a high precision (3x10) operating at a fixed frequency of 80MHz^-9) Has an obenized crystal oscillator. This basic clock frequency is divided by 5000 in STIMU35 to form a symbol clock signal of 16 KHz, and further divided by 720 to form a frame start (SOF) marker signal. These three time references are buffered and supplied to each of the base station modems. The subscriber timing device (SUBTU) (not shown in FIG. 3) supplies the subscriber station with an 80 MHz clock signal, a 16 KHz symbol timing signal, and a frame marker signal with a duration of 45 msec. These signals are the same as those in the base station STIMU, except that the 16KHz clock signal is used as the receive symbol timing in the subscriber station. The 16KHz clock signal is used as the transmission timing in the base station. The transmission timing in the subscriber station is given in a form in which the reception timing of the subscriber station is delayed. The amount of delay of this delay is variable and is determined by the placement calculation performed between the base station and the subscriber station. The timing reference signal for the subscriber station is supplied by a voltage controlled oscillator (VCXO) operating at a nominal frequency of 80 MHz. The actual frequency is adjusted by the subscriber station modem so that it is frequency locked to the timing reference of the base station when received at the subscriber RF device input point. protocol The following protocol defines procedures for system control, collision avoidance, and call transmission within the system, as well as the transmission frame structure. For system configuration, see the base station configuration described above in connection with Figure 2, unless otherwise noted. The system is 20KHz in the 450MHz spectral region with 25KHz intervals and several simultaneous lines per channel. You are using a full-duplex BW (bandwidth) channel. Each full-duplex channel consists of receive and transmit frequencies isolated by 5 MHz. The lower frequency of each channel is assigned to the base station for transmission and is called the forward frequency. The higher frequency of each channel, called the reverse frequency, is assigned to the subscriber station for transmission. Therefore, the base station transmits at the forward frequency and receives at the reverse frequency. The opposite is true for subscriber stations. The ability of a system to provide a spectrally effective way of transmitting several channels at a single frequency depends primarily on the workings of the modem. Modem 19 must operate in such a way as to obtain an efficiency of 3.2 bits / Hz when operating in 16-phase DPSK mode at a rate of 16K symbols / second. Modem 19 is a mechanism that, strictly speaking, converts one, two, four or more bit symbols from CCU18 into a phase-modulated IF carrier for transmission and reverses this process on the receiving side. is there. CCU18 controls all frame timing and mode selection. The interface between the CCU 18 and the modem 19 can consist of two 4-bit unidirectional synchronous (16K symbols / second) data buses (Tx and Rx). In addition, the 8-bit status / control bus provides control information to the modem and reports the status from the modem to CCU18. Modem 19 also provides CCU 18 with a master 16KHz symbol clock signal. At the base station, this clock signal is received from the master oscillator in the system timing device 35, and all base stations (and thus all systems) are synchronized with this signal. At the subscriber station, this clock is derived from the input symbol received from the base station. Therefore, all transmissions are associated with the base station time standard. The main function of the subscriber station's modem operation is to synchronize the intra-area subscriber clock signal to the base station time reference by decoding the timing from the received symbols. The transmitter modulator of the modem uses an FIR digital filter to generate a digital signal that represents the waveform used to modulate the RF carrier. The resulting digital stream is converted to analog format and mixed with an IF transmission frequency of 20.2 MHz. This signal is sent to the RFU for pre-transmission over, reconversion to RF, and amplification. The receiver demodulator of the modem captures the IF receive signal from RFU21 at a receive IF frequency of 20 MHz. This signal is down-converted to the baseband and further digitized by the A / D converter function. The resulting digital sample is processed by a microprocessor-based signal processor. This function performs a wave equalization and synchronization algorithm on the input sample and further demodulates the PSK signal to provide a symbol stream of 16K symbols / second. The signal processor also works in self-training mode, which is used to inform the processor that the analog filter used in the receive stream is incomplete. Once the signal processor is tuned, the demodulator's digital equalization process compensates the input sample to correct the above imperfections in the analog filter components. This technology enables the use of low-cost, low-tolerance analog configurations and adds the ability to demodulate weak or noisy signals to all systems. Symbols demodulated by the modem are output to the CCU18 at symbol rate during the receive function. Modem 19 provides the timing associated with this symbol stream. Both the base station and the subscriber station draw the receiver timing from the input / receive signal. A more detailed description and specifications of the modem's features and performance characteristics are given below in connection with Figure 25. The basic TDM / TDMA channels per subscriber provide a total of 16Kbps in each direction dedicated to each call. For the capacity of this channel, 1.43 Kbps in each direction is required for control overhead and demodulation preample, so the VCU operates at a fixed data rate of 14.57 Kbps. This is equivalent to "328 bits per code decoder frame period," which is defined as half the modem frame period, or 22.5 msec. Each channel is divided into "slots" by time division multiplexing (TDM) technology to accommodate a large number of calls per channel. These slots specify the system frame format. The length of the system frame consists of a given number of symbols. The system frame duration is optimized taking into account the voice coding rate and the number of acquired symbols required by modem 19 at the beginning of each burst. The number of slots in the system frame depends on the modulation level of the channel. For example, if the modulation level of the channel is QPSK, the system frame consists of 2 slots per frame. Increasing the modulation level of a channel increases the number of bits of information encoded for each symbol, thus increasing the data rate of the channel. In 16-level DPSK, the system frame is divided into four slots, each of which handles the voice data rate for one call. It is important to note that the number of symbol times required for modem synchronization remains constant even at high modulation levels. The format of the system frame ensures that the subscriber station modem 19 does not work in full dual mode (ie, performing transmit and receive at the same time). Therefore, the slots related to the reverse and forward frequencies are offset in time by at least one slot time. The system frame of this system has a fixed duration of 45 msec. The symbol transmission rate is fixed at 16K symbols / sec. Each symbol is transmitted for an equal amount of time, ie 1/16000 seconds (62.5 μsec). The result is a fixed rate of 720 symbols per frame, and these symbols are numbered from 0 to 719 from the start of the system frame. These 720 symbols can consist of 1, 2, or 4 information bits, respectively, corresponding to modulation rates of 2, 4, or 16 phases. The system frame time (45 msec) is further divided into two or four time division slots, depending on the modulation format for the slots that make up the frame. Each slot can be one of three slot types: (1) Radio Control Channel (RCC), (2) 4-ary Audio Channel, and (3) 16-ary Audio Channel. .. RCC is always transmitted in binary (two phase) modulation mode. Each RCC and 16-ary audio channel slot requires 180 symbols or 1/4 of the system frame period for transmission. 16-ary audio channels have 4 information bits per symbol (ie 2)⁴= 16 phases), so the 16-ary audio channel transmits 720 information bits per frame. This equates to a bit rate of 16 Kbps. Some of these bits are used for modem overhead and control purposes, resulting in a voice bit of 14.57 Kbps, a rate. The 4-ary audio channel slot requires 360 symbols for transmission, which is equal to half the system frame period. Each symbol of this slot type consists of one of four differential phases, and two bits (2 = 4 phases) are transmitted for each symbol. The resulting bit rate will be 16 Kbps, as for 16-ary audio channels. The same number of bits (not symbols) are reserved for modem overhead and control purposes, and the audio information rate is 14.57 Kbps as for the 16-ary audio channel slot type. A system frame of any frequency channel can consist of any combination of these three slot types within the five constraints below. 1. The maximum number of symbols (720) is transmitted in each system frame. To achieve this, a combination of three slot types can be shared for a given frequency. If all channel capacities are not filled in the base station frame transmission (for example, 720 or less symbols are transmitted in one frame), insert a null symbol to fill the frame capacity of 720 symbols. .. A null symbol is a symbol that does not have transmitted energy. 2. Only one frequency of the multi-frequency base station has the RCC slot type. Only one RCC is always operational in all systems. The frequency at which the RCC should operate shall be set by the system initialization parameters and changed only if the frequency channel becomes unavailable for any reason. The RCC slot should always be assigned to the first 180 symbols of the system frame (referred to as slot 0). 3. The base station frequency must be able to operate in a certain transmission mode. The subscriber station should transmit in a time that does not exceed 1/2 of the total frame time. When making a call, the subscriber station shall transmit only 25% of the time of the frame when operating in RCC or 16-ary audio channel mode. The subscriber station shall transmit only 50% of the time of the frame when operating in 4-ary audio channel mode. When making one call, the subscriber station can only transmit in one slot between any frames. 4. All 4-ary audio channels must start transmission with symbol number 0 or 360. That is, the first half of the frame can include a 4-ary audio channel in the second half. Five. Transmissions between forward and reverse frequencies shall be assigned such that the reverse message in a given slot begins transmission 180 symbols after the transmission of the forward frequency message. This prevents the requirement that the subscriber station transmit at the reverse frequency during simultaneous reception at the forward frequency. The above constraints up to four voice calls can be processed at a single frequency if all four calls are configured in the 16-ary voice channel format at operation in the range of the 14.4 Kbps code decoder. Slots within the system frame are numbered by the position of the frame structure. The numbering method does not have to be a serial numbering method. If one or more slots in the frame consist of a 4-ary audio channel slot type, the numbering scheme skips the second slot period contained in the longer 4-ary slot. skip) . Slot numbering for reverse frequency (ie, subscriber) transmissions is staggered with numbering for base station (forward frequency) transmissions. Therefore, the subscriber who receives the information in the slot 2 of the forward frequency transmits in the slot 2 of the reverse frequency which is offset by 1/2 frame in time. Tables 1-5 illustrate possible frame formats and the numbering associated with each slot.<img file="JP2816349B2_D0003.tif" /><img file="JP2816349B2_D0004.tif" /><img file="JP2816349B2_D0005.tif" /><img file="JP2816349B2_D0006.tif" /> See Figures 2-1 to 6-3 for a description of each slot symbol.<img file="JP2816349B2_D0007.tif" /> Table 3 describes the slot types for 180-symbol 16-ary audio channels. The first eight symbols of this slot type are called the FILTER STARTUP bits. The filter strap period, which is included at the beginning of all slot types, is the time when no energy is transmitted and the time when the receiver of modem 19 purges the filter in preparation for a new slot. The period following the filter startup is the BIT SYNC period. During this time, a demodulated 16-ary pattern that simulates an AC BPSK signal is transmitted. The receiver of modem 19 uses this field to establish the phase reference of the transmitter of modem 19. It then uses 12-bit codewords to determine synchronization between the subscriber station and the base station and to exchange control and status information. Code words are used to exchange connections, link quality, and the current state of power and timing adjustments. Each control word is coded to 10 bits using a Hamming code that allows single error correction and double error detection. The CCU18 determines the gain and loss of synchronization by detecting the number of consecutive code words received appropriately or improperly. CCU18 also sends the synchronization change to RPU20 of the base station. At the subscriber station, CCU29 sends a synchronous change to STU27. The Hamming code generates a 10-bit code by adding 5 parity bits to the 5 bits of information. Each parity bit is modulo-two for every bit in the code word, including the bit represented by the parity bit. Calculated by executing addition). Accompanied by all parity bits by placing only one bit (the position represented by the bit above), placing the parity bit in a position within the word, and placing the data bit in another position. The code word is sent with all the data bits contiguous, and this code can be visualized as follows.<img file="JP2816349B2_D0008.tif" /> When a codeword is received, the parity bit is calculated from the received data bit and compared to the received parity bit. If all the calculated parity bits are different from all received bits, then the calculated parity bits are XOR gated with the received bits, indicating that the bit addresses are incorrect. Two errors have been detected if all the calculated and received bits are equal and the other four bits are not equal. If all the parity bits are the same, the data is being received correctly. The other slots each have two voice code decoding packets containing 328 information bits. Table 2 shows the symbolic structure for 4-ary audio channels. This structure is almost the same as that of a 16-ary audio channel. The difference is that some symbol allocations depend on the number of fixed symbols required for overhead purposes on a slot-by-slot basis, while other bit allocations are made to a fixed number of bits. The radio control channel (RCC) causes the subscriber station to first obtain the system timing from the base station and generate an out-of-band signaling between the base station and the subscriber station. It works for a dual purpose that provides a basis for doing so. The format of the radio control channel slot is the same for the forward and reverse channels, except for the fields shown below. The first eight symbols of the control slot transmitted by the base station (forward channel) have an amplitude modulation gap (AM hole), which is the period during which no energy is transmitted. This gap is used by subscriber stations to identify control channels in a unique way. There are some extra symbols at the beginning and end of the reverse channel control slot so that the subscriber station does not have to worry if it deviates slightly from that timing. All slots have eight symbols of "null" transmission that form a filter start-up field that allows the modem to purge its receive filter in preparation for reception of a new slot. The next field in this slot is the fixed bit synchronization pattern. The transmitted pattern is an alternating BPSK signal. The receiving modem uses this field to establish a phase reference and frequency lock for the transmitting modem. The CCU18 constantly searches for a unique word (UW), which is a sequence of eight symbols, to identify the input RCC message. The base station CCU18 must thoroughly check for valid RCC messages in all RCC slots. The CCU18 performs this task by scanning a unique word in the window with ± 3 symbols for the nominal UW storage location based on master system timing. The search algorithm starts at the nominal UW position and shifts one symbol left or right until (1) finds the UW pattern and (2) confirms the correct RCC checksum. This search ends immediately if (1) and (2) are met or all possibilities are eliminated. Shift information, RCC messages, and power information are sent to the RPU 20 following a successful search. The subscriber station CCU29 may take one of two modes when receiving RCC data: frame search and monitor mode. The frame search mode is used to get the received frame timing from the input RCC data and is called automatically when RCC synchronization is lost. The monitor mode is the mode that is entered when the received frame synchronization is acquired. When in frame search mode, the subscriber station CCU29 must check all valid RCC messages immediately after the subscriber station receives the RCC slot. Similar to base station CCU18, CCU29 performs this task by scanning a unique word in the window with ± 3 symbols for the nominal UW storage location based on the timing derived from modem AM hole detection. .. The search algorithm starts at the nominal UW position and shifts one symbol left or right until (1) finds the UW pattern and (2) confirms the correct RCC checksum. This search ends when (1) and (2) are met or all possibilities are eliminated. The shift information from the successful search results is used to adjust the received frame indicator of CCU generation. The acquisition operation ends when the UW is in its nominal position and the above (1) and (2) are satisfied for three consecutive frames. STU27 receives this acquisition report when the acquisition of the frame instruction occurs. RCC messages are not delivered to STU27 while in frame search mode. When the acquisition of the frame instruction is completed, the subscriber station CCU29 enters the monitor mode and checks only the nominal UW position to avoid the possibility of false UW acquisition. If no UW is detected for 5 consecutive frames, the channel is declared out of sync and enters frame search mode (this condition should rarely occur and this system performance is poor). STU27 signals this out-of-sync condition. During monitor mode, an RCC message containing the correct checksum and subscriber ID number (SID) is sent to STU27. The rest of the slots are used to exchange information between the base station and the subscriber station. The data part consists of 12 bytes. The first 8 bits of data contain link fields that transfer information about system status conflicts, detections and reservations. The purpose of the link level protocol is to detect false messages about radio control channels. The link protocol also eliminates line contention for RCC slots. The link field has "idle transmission", "system busy", "collision", "transmission detected", and "slot reservation" bits. doing. These bits are set by the base station CCU18 and read by the subscriber station CCU29. The play transmission bit is set by the base station to indicate that the play message has been transmitted. When the subscriber device receives the slot in which this bit is set, the subscriber device performs normal synchronization and error checking, but if the message is received without error, the message is delivered to the respective RPU20 or STU27. do not. The system busy bit indicates that all voice channels have been assigned and that a new call request is refrained (for a certain predetermined time). The collision bit resolves a line conflict involving two or more subscriber stations attempting to transmit within the same control slot. The transmission detection bit indicates that the base station has detected transmission by the reverse control channel. The slot reservation bit reserves the next slot for the reverse control channel. The rest of the data part is used for addressing and information exchange during call set-up and disassembly procedures. Following the data part, there is a unique word for the slot and a 16-bit cyclic redundancy check (CRC) bit for the data part. CRC is used to detect errors that occur when transmitting RCC messages. The CRC algorithm involves dividing a block of data by a defined bit sequence and transmitting the remainder of this division as part of the data block. The CRC generation polynomial is given in the following form. P (X) = 1 + X⁵+ X¹²+ X¹⁶ (Equation 1) When performing a confirmation check on a message for which a CRC has been received, this message is not delivered from CCU18 to RPU21 at the base station or to STU27 by CCU29 at the subscriber station. If the subscriber station is first powered on and put on-line, the subscriber station must obtain standardized system timing and synchronization from the base station. This acquisition is achieved through transmission conversion by radio control channel (RCC) and refinement by voice channel. The events leading up to system acquisition are as follows. 1. When power is first applied at the subscriber station, the system initializes and the subscriber station CCU29 sends a series of commands to the demodulator of the subscriber station modems 30a, 30b, 30c leading to RCC acquisition. give away. 2. The demodulator of each modem 30a, 30b, 30c is first set to its tuning mode, during which the modem adjusts its receiver digital filter to the characteristics of the receiving analog filter. Analog filters can change their characteristics over time and temperature fluctuations. Each modem automatically adjusts its digital filter coefficient during the adjustment mode to compensate for these characteristic changes. After the CCU29 receives the status from the demodulators of the modems 30a, 30b, 30c for which the tuning sequence has been completed, the CCU sets the reception frequency to the default RCC frequency. After that, the CCU issues a command to the modem to acquire the RCC frequency and search for the characteristic amplitude modulation "gap" of the RCC called the AM hole. An AM hall is a period of 16 symbols in duration where no energy is transmitted at the start of RCC transmission from a base station. All other transmitted slot types include the transmission of only an 8-symbol "null". The eight extra symbols of null information at the beginning of a slot burst identify the burst as an RCC in a special way. 3. The first function of the demodulators of modems 30a, 30b, 30c is to perform coarse frequency acquisition, the received signal is processed in a digital phase-lock loop, and the subscriber station VCXO It is adjusted to the transmission frequency of the base station. After acquiring the frequency, the modem begins searching for the AM hole. The modem searches for a string of symbols that has little or no amplitude. When this column is detected for some frames, the modem asserts the "AM strobe" and initializes the CCU frame timing circuit. If no AM hole row is detected, the modem returns a status to the CCU that the RCC acquisition was unsuccessful. As a result, the CCU searches for the RCC frequency in the same direction. Four. After detecting the AM hole, the demodulators of modems 30a, 30b, and 30c perform refined frequency acquisition and initial bit adjustment. The first 60 symbols of the RCC control slot are the fixed bit period patterns used by the modem to lock to the phase (bit timing) of the base station. In this respect, the RX clock in the subscriber station is useful as a symbol clock. 5. The subscriber station CCU29 has received the coarse symbol timing adjustment from the modem via the AM strobe. After frequency acquisition and bit synchronization, the CCU inspects the data received by the modem and searches for RCC unique words. This unique word gives an absolute symbol count criterion for the frame. This causes the CCU to adjust its symbol counters to align these counters to this reference. The subscriber station is at this point aligned and locked to the base station transmission system timing (both frequency and symbol timing). 6. The rest of the system timing acquisition determines the distance delay between the base station and the subscriber station. This delay can range from 0 to 1.2 symbol times (one way) in the system. When the call is set up, the subscriber station sends a message to the base station through the RCC. 7. The base station modem 19 is constantly searching for new subscriber station bursting in. These bursts can be delayed by 0 to 3 symbols from the start of the base station master reference frame. During each slot, the demodulators of the base station modems 30a, 30b, and 30c search for transmission through the reverse RCC slot. All timing and phase information must be retrieved during the first part of the slot (preamble), otherwise the slot and its information will be lost. When receiving an inbound control slot, this opportunity is only once. Inbound control slots are received by the RCC's Aloha queuing scheme described below, so please refer to this bulleted description of the events leading to system acquisition. 8. 8. During each slot period, the base station modem 19 performs high-speed AGC adjustment and bit timing estimation during the first 60 symbol periods of the slot. The receiver clock signal is adjusted to compensate for the subscriber station's distance delay. The received data is then passed to the base station CCU18. CCU18 detects the storage location of the unique word in the stream and determines the integer distance delay between the base station and the subscriber station. Modem 19 passes AGC information to CCU18 to determine the TX power adjustment of the subscriber station. Modem 19 also supplies link quality and decimal time information to CCU18. Link quality is used to determine the presence or absence of a collision. Poor link quality measurements indicate poor signal quality, probably due to simultaneous transmission by more than one subscriber for the RCC slot. The decimal time estimate is the value calculated by modem 19 for the decimal distance delay between the base station and the subscriber station. 9. This power and distance delay information is processed by CCU18 and sent to RPU20, which formats this information in RCC format and transmits this information to the subscriber station through the RCC control slot. The subscriber station CCU18 decodes this information and makes the necessary adjustments to the transmit power and distance delay counters of both modem 19 and CCU18. The CCU18 updates its integer TX symbol frame counter and the modem TX clock decimal delay counter. 10. At the time of call connection to the subscriber station, the base station RPU20 allocates the frequency and slot allocation for the voice call. This information is transmitted by the RCC, and the subscriber station CCU29 adjusts the RX frequency and issues a command to the modem to start detecting the voice slot. AGC, timing and frequency information progresses from RCC operation to audio channel operation. This is possible because all frequencies in the system are synchronized to the same frame timing reference in the base station. 11. 11. A precision procedure is performed at the beginning of each voice connection to accurately set the timing of the subscriber station. During the precision phase, the voice channel communication is similar to the control channel, the modulation level is BPSK and the message is in RCC format, but no "AM" holes are generated at the base station, ie these new RCC messages are with CCU18. Exchanged only between CCU29. Modem 19 is set to precision mode at the base station and outbound control mode at the subscriber station. The subscriber station CCU29 generates a message during this precision phase, but most of this message has a fixed bit pattern followed by a variable part that indicates acceptance or rejection of previous messages received from the base station. .. The base-time modem 19 transmits timing and power adjustments from each received slot to CC18. The power adjustment is continuously sent to the subscriber station. Timing adjustment and control information indicating the continuation or completion of the precision mode is sent after the calculation period. The base station CCU18 collects the timing adjustments from the modem 19 for 30 frames, calculates the average value, and sends this adjustment value to the subscriber station CCU29. An additional 30 frames of precision operation are performed by the base station CCU18, and the results are sent again to the subscriber station CCU29. If the adjustment change received from modem 19 falls within the acceptable range, for example 1%, or the precision period consumes its maximum time limit, the precision phase is terminated by the base station CCU18 and the voice connection. Starts. When setting up and canceling the call, the subscriber station communicates with the base station by sending a message through the reverse RCC slot. The communication attributes of subscriber stations attempting to access the RCC are actually characterized as probabilistic. If a subscriber station wants to send a message to a base station, many subscriber stations are likely to try to send in the same slot, so some form of control mechanism to allow which subscriber station to send. Must be arbitrated in. The slotted Aloha scheme is suitable for the context of a large subscriber population that requires relatively rare direct access to RCC channels. The slotted aloha scheme allows subscriber stations to send messages through the designated RCC slot, regardless of whether other subscriber stations are trying to send in the same control slot. is there. If the transmission action is left uncontrolled, messages from different subscriber stations will be transmitted at the same time, resulting in a collision. To deal with this collision phenomenon, this scheme allows the base station to correctly receive the message from the subscriber station. After that, the base station needs to deliver an acknowledgment (ACK). If the ACK is not received within the maximum allotted time required for transmission and delay processing in each direction (approximately 1-2 frame time), the subscriber station must resend the message. Retransmission is likely to be caused by an error when receiving an ACK at the subscriber station. In general, the subscriber station cannot know the cause of the failure. For this reason, the subscriber station chooses a random delay prior to performing the retransmission to avoid a re-collision with another sender involved in the previous collision. The trouble with the Aloha scheme is that the channel becomes unstable if the random retransmission delay is not long enough. If this happens accidentally, the channel will fail due to retransmission and the throughput will drop to zero. Backoff technology minimizes this problem by increasing the average randomized retransmission delay of each subscriber station for continuous retransmissions. The complexity of stabilization control for collision retransmissions and access delays is that the delays are geometrically dispersed. It is necessary to operate the channel at a utilization rate much lower than 36% in order to avoid large delay changes. In particular, if the utilization rate does not exceed 20%, the need for more than one retransmission due to a collision cannot occur. Using a random delay of, for example, 8 frames for 45 msec, the total average delay for one retransmission is 450 msec (ie, what this delay includes on average: 1 frame delay of the original transmission, plus an acknowledgment. 1 frame delay, plus 8 frames random delay). To guarantee that the utilization rate does not exceed 20%, let T be the average time between call requests for each subscriber, N be the total number of subscribers, and F be the frame time for a value that does not exceed 36%. It must be taken into account that the rate is given by NF / T. If F = 45msec, N = 1000 subscribers, and T = 30 minutes, the utilization rate will be 1.5%. Therefore, for a maximum utilization value of 20%, the 1000 subscriber population, each calling every 1/2 minute on average, has an access delay of about 45 ms and an average access time when one retransmission is required. Can be supported in 45ms frame time with about 70-80ms. The price for a much lower average delay is an increase in delay change that does not exceed two retransmission times or one second for utilization of 20% or less. The Aloha scheme processing method appears to be suitable for systems with large subscriber populations that require relatively rare random access to control channels and expects a design goal of setup delay not exceeding 1 second. Population parameters Is to be achieved. On the other hand, polling and fixed TDMA techniques (methods) do not provide a favorable delay. All stages of the call process, including call establishment, call release, and slot connection, require information exchange through the control channel and / or the control portion of the voice slot, at each stage of the call process, the subscriber station and the base. The processing performed at the station will be described below. The subscriber identification number (SIN) and dial number of the subscriber station are two call control items that must be used for a call request to the base station (CALL REQUEST) each time the subscriber station makes a call. In the case of a subscriber station-to-subscriber station call, the user dials the number into a register in the subscriber station's storage. The user starts communication with the base station by pressing the transmission key, that is, by giving a time-out. Only for the radio channel used, the number is fully assembled and stored within the subscriber station. Thus, the subscriber can dial at a slow rate without disrupting the valuable Radio Control Channel (RCC) bandwidth or time. The sequence of messages generated by a subscriber station and a base station to establish a connection between two subscriber stations is shown in Figure 4, the control channel link level protocol is a channel. Used to check for various error conditions caused by errors. Further, the message received by the base station by the reverse control frequency is automatically acknowledged in the next control slot by the forward control frequency. The following section outlines the message exchange for establishing a call between the two subscriber stations. When the base station receives a CALL REQUEST message from subscriber station A on the control channel, the base station checks the received SIN for errors. If there is an error in the SIN, the message is discarded. Without a valid SIN, the base station cannot know the originator of the message. If the dialed number is incorrect or incomplete, the base station attaches the status information pointing out the problem and sends a CLEAR INDICATION message to the requesting subscriber station A via the forward control channel. Is sent. If the outgoing attempt is correct and possible (ie, the destination device is not busy), the audio channel is assigned to the outgoing subscriber station A and the base station is assigned to the destination subscriber station B. Send a PAGE in the form of an incoming call message with the forward control frequency. If destination subscriber station B does not respond to the PAGE with a CALL ACCEPTED message after two attempts, or returns a busy status display with a CLEAR-REQUEST message, the base The station sends a clear indication message to the calling subscriber station A stating that the busy status information (ie, destination device off-hook) or the destination subscriber station has not responded to the page. When the destination subscriber station B receives the incoming call, the call acceptance message is returned to the base station and the voice channel is assigned. When the audio channel synchronization is established, the destination subscriber station B produces an audible ringing tone that can be heard on the destination subscriber station B and a ringback sound to the destination subscriber station A through the audio channel. .. When the destination subscriber station B goes off hook, the control part of the voice slot changes from the sync-ring display to the sync-off hook display and the two subscriber stations. During the call progress (CALL PROGRESS) message is given through the voice channel via the base station. At this point, the destination subscriber station B terminates the audible ringing sound and cuts off the ringback sound from the voice channel. Here the call circuit is completed and voice / data exchange can be started. Call settings for external telephones are made in the same way as calls for other subscriber stations. The subscriber station simply dials the desired number and presses the send button or waits for the time out. This causes a radio request message to be generated for the base station. The base station decides whether to call another subscriber station or capture an external trunk line. In this case, the external trunk line is captured and the dialed number is out-pulsed to the trunk line. While this number is pulsed, the voice frequency is assigned to the calling subscriber station. When the subscriber station receives a CALL-CONNECT message, the subscriber station changes frequency and synchronizes itself with the assigned voice channel. When the voice channel becomes available, the subscriber station handset is disconnected from the local silence and connected to the external trunk line. From this point on, the destination Telco central station emits all ringing progress sounds. The incoming external call captures the trunk line at the base station. The transmitting central station sends 2 to 5 numbers that identify the unique number of the destination subscriber station's SIN directly to the base station through the internal dial (DID) trunk line. If the dialed subscriber station is not busy, the base station sends a page message (PAGE MESSEGE) through the RCC to the appropriate subscriber station. There are three possible situations here. First, the subscriber station receives the incoming call and the process proceeds as follows. Second, no response is received. In this case, the base station retries the call process twice. If the base station ends the number of retries without a response from the subscriber device, a ringback sound is generated in the transmitter device. The third state is that the subscriber station is dialing (ie, off-hook) and is returning a CUEAR-REQUEST message to the control channel. In this case, the busy tone is returned to the calling subscriber station. If the PAGE request is successful, an audio channel is assigned and an external ringing tone is emitted from the handset at the destination subscriber station, while an audible RING BACK tone is emitted from the subscriber station to the caller. Will be done. When the destination subscriber station answers the call (ie, the base station detects a switch from on-hook to off-hook), the external ringing tone and channel ringback message are eliminated. At this point, the voice channel is ready for call. The end of a normal call begins when the subscriber goes on and hooks. The base station detects the switch from off-hook to on-hook through the control part of the audio channel. When this switching is detected, the base station cancels the allocation of the audio channel. This channel cannot be reused until the base station confirms that the subscriber station has lost synchronization with respect to the channel. If the call during the disconnect process is for another subscriber, an on-hook indication is sent to the first subscriber station by the control part of the voice channel. The subscriber stations resynchronize with the RCC transmission and send a CLEAR-REQUEST message to the base station. The end of the call occurs 5 seconds after the base station loses wireless contact with the subscriber station. Voice connections can "disappear" due to fading or channel interference at the destination receiver. To determine if the connection is experiencing a failure, check the following conditions at the subscriber and base stations: That is, it checks whether the link quality value returned from the subscriber or the base station receiver is below a predetermined threshold for continuous reception, and whether word synchronization is detected for some continuous transmissions. The message sent from the base station is broadcast to all active subscriber stations. These messages are transmitted by the base station through the radio control channel. The purpose of the broadcast message is to notify all active subscriber stations of system operational changes (ie, RCC frequency changes, or command changes to the modem to enter self-test mode, etc.). The subscriber station does not acknowledge these messages. Remote control processing (processor) device The RPU functions as a control computer in the base station system. That is, the RPU interfaces with the CCU18 and PBX15 that communicate with the wireless device as shown in Fig. 2. The RPU20 adjusts the required functions for wireless pager processing. The RPU20 exchanges messages with subscriber stations, PBX15, and CCU18 to connect and disconnect. The call processing function includes allocation and cancellation of wireless channels. RPU20 also maintains a database that represents the current state of the system. This database contains information on the status of devices, subscriber stations, connections, and radio channels in the system. Call establishment begins when the RPU receives a message from the PBX call processor 24 for a call received from an outside line or from a subscriber for a call made to an external telephone or other subscriber. Communication from the subscriber comes in through the radio control channel (RCC) via the base station CCU18. The RPU20 allocates voice channels and exchanges messages with subscriber stations, PBX15, and CCU18 to establish a connection. Detachment begins when a message indicating that the telephone has been disconnected is received from the PBX15 or subscriber, or when a message indicating that synchronization has been lost through a wireless channel is received from CCU18. The RPU notifies CCU18 and PBX15 of the disconnection, and the RCC is deassigned. The RPU software performs the following functions. 1. Process subscriber, CCU, and PBX messages that control call setup, call release, and channel allocation. 2. Initialize and maintain the read / write system database. 3. To support a system control console that enables system inquiry and manual system control. 4. Handle the BBC interface by supporting the Baseband Control Channel (BCC) communication protocol through the 9600 baud asynchronous series interface. 5. Handle the PBX interface by supporting the PBX message protocol. as well as 6. Save the transaction log that supplies diagnostic and primitive billing data. The RPU software supports one serial interface to the PBX call processor 24. The software also supports a serial interface to each of the CCUs 18 in the base station configuration. RPU hardware includes a general purpose computer based on the Motorola Model 68000. The machine consists of a 1 Mbyte direct access storage (ROM) and a 10 Mbyte non-volatile hard disk storage. I / O consists of a system control console and eight synchronous serial data interfaces. As shown in Fig. 5, the RPU software packages include scheduler module 40, BCC interface module 41a, 41b, ...... 41n, PBX interface module 42, control console module 43, and logger module 44. , Message Processing Module (MPM) 45, and Database Module 46 to simulate the system. All modules, except database module 46, are called from scheduler module 40 to operate. These modules communicate with each other through the mailbox system. Database module 46 is based on the collection of subroutines to access information in the database. The scheduler module 40 provides the mainline code for the RPU software, which has an important role in scheduling and invoking all other modules. This module 40 also plays an important role in maintaining event timers and mail boxes that enable in-process and inter-process communication. BCC interface modules 41a, ...... 41n support serial synchronization interfaces and link level protocols. These modules also monitor the status of communication with CCUs18. The PBX interface module 42 supports a serial synchronization interface to the PBX call processor 24. The control console module 43 provides a system operator interface that enables system status queries and updates and message exchanges between the RPU 20 and other devices in the system. Logger module 44 provides primitive transaction information for diagnostic and system analysis purposes. The message processing module 46 processes all received RCC, BCC, and PBX messages. This module 46 also performs all subscriber call setups and cancellations not performed by PBX15 and allocates radio channels. In addition to the above, this module includes a background task to monitor the status of CCUs18. Database module 46 provides a consistent interface for all of the data structures needed for call processing. This module 46 includes a frequency allocation task for allocating radio channels. The RPU database has a structure that describes the system configuration including the information of all subscriber stations and the status of all radio channels. These structures are as follows. The RPU database contains baseband control channel (BCC) data structures for each CCU 18 in the system. The subscriber identification table (SIN table) contains a classification list of all valid subscribers. This list is categorized to facilitate subscriber validation. The SIN table has one entry for each subscriber in the system. The RPU software performs part of the subscriber device call process. This processing is performed by the message processing module. Call processing is accomplished by exchanging messages with MPM45, PBX module 42, and all BCC modules 41. Invoking a phone call from a subscriber station This section outlines the normal call setup process for subscriber-initiated telephone calls. The subscriber (outgoing subscriber) goes off-hook, dials a valid phone number (destination phone number), and presses the send button or waits for time out. The calling subscriber station sends a CALL REQUEST message to the base station through the control channel. The RPU BCC module 41 receives a radio request (RADIO REQUEST) message and delivers it to the MPM45. The MPM45 performs some simple validation of the dialed number and sends a radio request message to the PBX module 42, which delivers this message to the PBX control processor 24. The PBX call processor 24 verifies the validity of the dialed number and returns a place call (PLACE CALL) message to the RPU 20. The MPM45 allocates audio slots to outgoing subscriber stations. The MPM45 issues a CHANGE CHANNEL command to the CCU18 that has an audio slot assigned by the outgoing subscriber station, and the MPM45 issues a CALL CONNECT command to the outgoing subscriber station. Then, this command assigns a voice frequency and a slot to the calling subscriber station. The MPM45 issues an ALLOCATE message to the PBX call processor 24, which notifies the PBX call processor 24 to allocate a message channel. At this point, the calling subscriber station is fully set up. That is, it is in a state of waiting for a connection to the "destination" through the PBX switch matrix 25. It does not matter whether the "destination" is another subscriber station or a telephone that must be accessed by the Telco trunk line 14. Call reception of subscriber station This section outlines the processing of incoming calls to subscriber stations. The PBX call processor 24 determines that the telephone call is destined for the subscriber station. The PBX call processor 24 raises an INCOMING CALL message. This message contains information about the type of incoming call (nature), in particular whether the call came from an external trunk line 14 or from another subscriber station. The RPU PBX module 42 receives the PBX message from the PBX call processing device 24 and delivers this message to the MPM45. If this call comes from another subscriber station, the MPM45 should set the subscriber-to-subscriber index for both "outgoing" and "destination" subscriber stations and enter internal mode for the associated CCUs18. To command. The MPM45 generates a nomination (PAGE) message for the subscriber station specified in the incoming call message. The designated subscriber station responds with a call acceptance message. The MPM45 responds to the call acceptance message by issuing a channel change message to the appropriate CCU18 and a call connection message to the appropriate subscriber station. The MPM45 subsequently generates an allocation message to the PBX call processor 24, which completes a deterministic connection to the PBX switch matrix 25 for incoming calls. Drop-out recovery This section outlines the response of the RPU20 to channel fades during communication. CCU18, which controls the decaying audio channel, finds that channel 3 is out of sync. CCU18 raises a non-synchronous (NO-SYNC) event message. BCC module 41 receives this event message and delivers this message to MPM45. The MPM45 sends an ONHOOK message to the PBX call processor 24 to set the subscriber to idle and the channel to on-hook. Processing of incoming BCC messages BCC messages are sent from CCU18 to RPU20 via the 9600 baud asynchronous interface. The BCC module 41, which controls a specific CCU interface, reads the message and checks the link level information bit to check the integrity of the incoming message. If the BCC module 41 determines that the message is acceptable, an appropriate acknowledgment is returned to the sending CCU18. If the message is unacceptable, a retry or negative response is returned. Here the BCC module 41 sends a message to the MPM45. This message is submitted to the message processing mail box 348, which utilizes the mail box provided by the scheduler module 40. {See Figure 6} When there is no input from CCU18 and the BCC mail box containing the output message to CCU is empty, BCC module 41 "blocks" and control is transferred to scheduler module 40. Scheduler module 40 launches the next module in a round-robin schedule, which runs until it blocks. The scheduler module then starts the modules one after another. After some time, the scheduler module will start MPM45. The MPM45 reads the BCC message along with all the other messages queued in its mailbox 48. This BCC message is identified and processed. Such processing can include making changes to the database and generating new messages. Figure 6 illustrates the data path of the incoming message. Generate output BCC message FIG. 6 further illustrates the data path of the output BCC message, which is generated by MPM45 in response to a particular event. This message is configured within MPM45 and is sent to the BCC module that controls the destination CCU18. If all other required messages are sent after this message and there are no other messages in the MPM's mailbox 48, the MPM "blocks" and control is returned to the scheduler module. The BCC module reads the message from its mail box 49 and appends the appropriate link level bit to the output message. The BCC module then sends this message to the serial data port to CCU18. Processing RCC messages Since RCC messages are a type of BCC message, incoming RCC messages are treated exactly like incoming BCC messages. Also, the output RCC message is generated and transmitted in the same way as the output BCC message. Processing of incoming PBX messages The PBX message is received from the PBX call processing device 24. This message is sent to the RPU20 through the 9600 baud asynchronous interface. According to Figure 7, the RPU PBX module 42 reads the PBX message and sends it to the MPM mail box 48. When the PBX mailbox 50 with no more incoming characters and holding the output PBX message is empty, the RPU PBX module 42 "blocks" and control is returned to the scheduler module 40. The MPM45 reads PBX messages along with all other messages queued in Mailbox 48 of the MPM45. PBX messages are processed based on the type of message and the current state of the subscriber specified in the message. This process can include changes to the database, changes in the state of the subscriber, and the generation of new messages. Figure 7 illustrates the data path of the incoming PBX message. Generate output PBX message Again, according to Figure 7, the output PBX message is generated by the MPM45 in response to an event. This message is configured within MPM45 and sent to PBX module 42. After this message, and when all other required messages have been sent and there are no more messages in MPM Mailbox 48, MPM45 "blocks" and control is returned to scheduler module 40. The scheduler module 40 continues to start other modules in the continuous schedule until the RPU PBX module 42 is started. The RPU PBX module 42 reads the PBX message from its mail box 50 and sends the message to the serial data port to the PBX call processor 24. Generate logger message At each relevant point of the module in the RPU software package, a message containing the relevant information is posted to the logger module 44. This information is time marked and output to a file. Figure 8 illustrates the logger data path. Control console input / output module The input section of the control console module 43 provides command stimulation and recognition as well as command validity confirmation. Enabled control console commands have the ability to query and update the RPU database and send messages to the RPU module. The output from the control console display commands is output directly to the control console port. Scheduler module The scheduler module 40 can be thought of as a special system module, which plays an important role in scheduling all other RPU modules. The main role of scheduler module 40 is to select the next module to be executed and to provide internal and intercommunication. All various RPU modules are actually considered to be separate modules, but all modules are an application process of the Regulus operating system. It is the scheduler module 40 that performs the continuous dispatch of the other RPU modules 3. The scheduler module 40 manages the stack for each of the pseudo RPU modules by allocating a fixed portion of the stack space to each of the pseudo modules at startup. Just before each module is scheduled to run, the stack pointer is changed by the scheduler module to point to the appropriate stack address to pick the correct module. The memory map of RPU20 is shown in Figure 9. Each RPU module runs until it blocks. When one module blocks, it returns control to the scheduler that schedules and runs the next module. Modules can be blocked in several ways: by calling GETEVENT (), which blocks the module until one event is put on hold, or by calling WAIT (), which blocks for a few seconds, or BLOCK, which blocks during a cycle of continuous scheduling loops. It can be blocked by calling (). Another major function performed by the scheduler module 40 is inter-module communication between modules. Mailboxes are used as a means of sending and receiving messages between modules. Each module can check the mail in its mailbox by using the MAILREAD () call. In addition, a module can send mail to other modules by using the MAILSEND () call. The scheduler module maintains a separate mail box for each module in the scheduling loop. When one module sends a message to another, this message is copied to the destination mailbox. Later, when the execution order becomes the destination, the scheduler module checks the mail box to determine if there is a message in the mail box. If there is a message, scheduler module 40 will generate an event type MAIL that unblocks the module if it is blocked by GETEVENT () and is scheduled to run there. The event list is also maintained by the scheduler module for each module in the scheduling loop. Events can consist of mail or timer events. A mail event is generated when the scheduler module determines that a message is pending for the currently running module. The module can put a timer event on the event list by calling PUTEVENT () after waiting for the event to be generated. The scheduler module 40 checks the module's event list on a cycle-by-round basis through a series of scheduling loops that search for timer expiration. When the timer expires, the appropriate module is scheduled to run and the event is returned to the module through a call to GETEVENT (). The scheduler module 40 has a routine used to initialize the RS-232 interface between CCU18 and RPU20 and between PBX15 and RPU20. These routines, which have exclusive software control over the RS-232 interface, terminate the normal processing of the control sequence by the Regulus operating system. Other routines are used to clear the I / O buffer and read and write terminal inputs and outputs. Scheduler module 40 keeps track of system time for all modules with RP. BCC interface module Each BCC module 41 provides an interface between the CCU 18 and other software modules of the RPU 20. The exchange message between CCU18 and RPU20 consists of variable-length binary data transmitted over an asynchronous communication link. BCC module 41 has an important role in providing message integrity through communication links, including error detection, message ordering, and message acknowledgment. The hardware interface between CCU18 and RPU20 consists of a 9600 baud RS-232 asynchronous interface. Inputs to this module 41 include messages received from the CCU or from other RPU software modules. Messages are output from this module to the CCU via the RS-232 interface or to other RPU software via the appropriate mailbox. The purpose of this module 41 is to handle the message traffic between RPU20 and CCU18. This module 41 continuously checks the messages received from CCU18 and routes these messages to the appropriate RPU software module. Similarly, this module continuously checks for messages from other RPU software modules addressed to CCU18. It uses the Alternate Bit Protocol to limit unique messages (ie, negative responses) to one in each direction. The sequence and acknowledgment bits serve as the flow controls needed to achieve this function. This protocol is described in detail in the following sections. In the following description, the component that can process the message is called "main side (we)" or "main side (us)", and the other components are "other side (they)" or "other side". I'll call it "them". This protocol can be explained by showing the actions to be taken when receiving a message. There are simply four actions, which depend on two conditions. These conditions are determined by comparing the sequence of received messages and the acknowledgment bits with the expected bits. For an arriving message, the ACK bit is as expected if it is the same as the SEQ bit of the last message sent by the main party. Similarly, the SEQ bit is as expected if it differs from the SEQ bit of the last received message. In other words, the expected condition is that the incoming message responds affirmatively to the last message of the main side, and the main side also expects the new arrival to be a new message. The actions taken when receiving a message are summarized in the four combinations provided by the above conditions. 1. ACK [expectation], SEQ [expectation]. Mark the last sent message on the main side as being acknowledged (allowing the new message sent on the main side). Process the newly arrived message (acknowledge it with the next message sent by the master). 2. ACK [expected], SEQ [non-expected]. Mark the last sent message on the main side as being acknowledged (allowing the new message sent on the main side). Discard newly arrived messages (no acknowledgment). 3. ACK [non-expected], SEQ [expected]. If the main side has sent a message that the acknowledgment has not been completed, the message is resent. If the main side does not have such a message, something is wrong with the destination and the main side resets it as follows. Process newly arrived messages. 4. ACK [non-expected], SEQ [non-expected]. The final message on the main side has not been received at the destination. Resend the message. Discard the newly arrived message. The Reset bit is used to reset the SEQ and ACK bits. When the main side receives a message with the Reset bit turned on, the message should be accepted as a new message regardless of its SEQ bit, and the message should be acknowledged. Further, the ACK bit of the received message reflects the SEQ bit of the final message received by the other party from the main side. The main side should toggle this bit before sending the next message. As an example, when the main side receives a message in which the ACK / SEQ number is 4 (Reset = 1, ACK = 1, SEQ = 0), the ACK / SEQ number in the response is 1 (Reset = 0, ACK = 0). , SEQ = 1). If the protocol appears to be out of step, either side can perform the reset. If the main side receives a message from the other side and there are no new pending messages or the standard response does not arrive immediately, the main side shall acknowledge the message by sending a special ACK message. The ACK bit acknowledges the received message, but the SEQ bit does not change from the final message sent by the master. This causes the other party to process the acknowledgment and discard the newly arrived message. The content of this message is a null message. However, this message is discarded, so the content of this message should be irrelevant. PBX interface module The PBX module 42 provides an interface between the UTX-250 PBX call processor 24 and other software modules of the RPU 20. Messages exchanged between these two machines constitute an ASCII character oriented message exchange. ASCII characters are defined here as 7 or 8-bit ASCII. Both the PBX call processor 24 and the RPU 20 must be capable of accepting characters with odd parity, even parity, or no parity. The body of the message consists of variable length strings or printable characters. The hardware interface between the PBX call processor 24 and the RPU 20 consists of a 9600 baud RS-232 asynchronous interface. The PBX module 42 contains a message received from the PBX call processor 24 or another RPU software module. The message is output from this module to either the PBX call processor 24 or any other RPU software module via the appropriate mail box. The purpose of the PBX module 42 is to handle the message traffic between the RPU 20 and the PBX call processor 24. This module continuously checks the messages received from the PBX call processor 24 and routes these messages to the appropriate RPU software module. Similarly, this module continuously checks for messages from other RPU software modules addressed to the PBX call processor 24. All characters received from the PBX call processor 24 are checked for greater than the inequality sign at the beginning of the message or equal to the return character at the end of the message. This module has the ability to handle full dual message traffic. Control console module The control console module is an operator's window for grasping the current state of the RPU20. The control console provides the ability to display information about the current status of subscribers and radio channels, updated connections and channel status, and outgoing messages for PBX15 and CCUs18. The control console processes the input stream from the terminal and executes the desired command. The control console module 43 provides an interface to the base station operator terminal. The control console module 43 processes the input from the terminal and executes the command. The data is retrieved from the database and written to the database, the displayed data is output to the terminal screen, and the message is sent to other modules. The interface to this module includes: (1) Characters are input from the operator keyboard. (2) Characters are output on the operator screen. (3) The data is searched from the database and written to the database. (4) The message is sent to the PBX, BCC, and message processing module. Parser routines enter characters from the operator keyboard. Data entry stimuli are displayed at the beginning of each command line, data is stored, edit characters are processed, inputs are echoed on the display, and data is delimited within tokens. By giving the parser a set of data structures that describe all possible commands and valid tokens within each command, the parser recognizes the input data, responds to question marks, and data. Display a guide word for input. Each token is checked for the expected type of data, the keywords are matched to the list of acceptable entires, and the numbers are converted to integers. Upon completion of command line input, further verification is performed to check if the number is within range and to check the status of the system with a few commands before executing the command. Commands fall into three categories. That is, 1) a command to display information from the database, 2) a command to update the database, and 3) a command to send a message. Information can be displayed for each state of subscribers, connections, CCUs, and channels. All display commands require retrieval of information from a database and output of formalized data to an operator display. The update command has the ability to force a subscriber to connect to a particular channel and to enable or disable the channel. The update command is used to test the frequency allocation algorithm. All update commands write to the database. PBX, BCC, and RCC messages can be delivered from the console module 43 to various other modules in the system. The SENDMSG command stimulates the operator to get all the information needed for a message, and the message is formed and sent to the specified module. The PBX message is sent to the RPU PBX module 42, which sends this message to the PBX call processor 42. BCC and RCC messages are sent from RPU20 to CCUs18 via BCC module 41, which adds a link level protocol bit to the outgoing message. Input from CCUs18 is simulated and the message including both BCC and RCC messages is sent to MPM46. Logger module Logger module 44 has an important role in logging RPU events or messages. Logger Modul 44 consists of three disk files: a transaction log containing information similar to billing information, an error log consisting of error messages, and a system warning message. Maintain the message log. The logger module 44 consists of a set of subroutines called from other RPU modules. Each subroutine is responsible for indicating the time for the message and writing the message to the appropriate disk file. Each subroutine has a global flag that determines whether a message should be logged. This flag is set and reset using control console commands. Message Processing Module (MPM) The MPM45 implements a high-level call processing function between the PBX15 and the subscriber station, that is, call processing such as page start, voice channel allocation, and control of call progress sound for both the subscriber telephone and the external telephone. It plays a role in function. The MPM45 also processes the status messages it receives from CCUs18. For example, channel status information consisting of link quality or subscriber hook status is processed by MPM45. The MPM45 is configured as a state machine in which PBX and BCC messages are used as tokens for message processing state machines. The MPM45 processes the token by updating the database, outputting the required response, and then transitioning to the next state. The MPM45 uses the system mail box maintained by scheduling module 40 to send and receive messages to and from other RPU modules. In addition, MPM45 uses subroutines in the database module to search or update status information in the database. As mentioned above, the MPM45 is configured as a state machine. A token that forces the execution of a certain process consists of a message or a timeout. The MPM45 determines the type of token (ie, timer, RCC message, PBX message, etc.) and the subscriber station or channel affected by the token. The MPM45 processes the token by generating an appropriate message response and transitioning to the next state. The MPM45 is actually composed of two state tables. The RCC state machine shown in FIG. 10 is used to process a message from the PBX call processor 24 or a message from a subscriber station. To do. The channel state machine shown in Figure 11 is used to process the message received from CCU18. Initially, all subscriber stations are in the RCC idle state and all channels are in the channel idle state, indicating that there are no setup or in-progress connections. The state changes for a typical external to subscriber call are as follows: The external call message is received from the PBX call processor 24, and this message contains the telephone number of the destination subscriber station of the call. A PAGE message is sent to the subscriber station and the state of this subscriber station is set to PAGE. A CALL ACCEPT message is received from the subscriber station and the state of this subscriber station is set to ACTIVE. At this point, the channel is assigned and the PBX call processor 24, CCU18, and subscriber station are notified of the channel allocation. The channel is set to the RING SYNC-WAIT state (Fig. 11). When CCU18 marks the acquisition of synchronization, the channel state is set to SYNC RING. Finally, when CCU18 marks the subscriber station's off-hook completion, the channel is set to the SYNC OFFHOOK state. The SYNC OFFHOOK state indicates the establishment of a voice connection. A call from a subscriber to a subscriber begins with a call request message received from the calling subscriber station. The receiving subscriber station is set to the DIAL state and a radio request message is sent to the PBX call processor 24. The PBX call processing device 24 returns a PUACE CALL message to the outgoing subscriber station and an incoming call message to the destination subscriber station. In response to this place call message, a channel is assigned and the PBX call processor 24, CCU18, and calling subscriber station are notified of this channel allocation. The calling subscriber station's channel state is set to off-hook SYNC WAIT until the channel is synchronized. When the base station CCU18 detects transmission from the outgoing subscriber station, this CCU18 generates a SYNC off hook channel event message. The RPU20 processes this channel event message by changing the state of the channel to the SYNC off hook state. The incoming call message to the destination subscriber station is also processed in the same manner as the external call message described above. In addition, all channels involved in the connection are set to internal mode when both subscriber stations are in sync. Disconnection begins when one of the connection-related parties goes on and hooks. When a telephone outside the system hangs up, the MPM45 receives an on-hook message from the PBX call processor 24. When the subscriber station is in the on-hook state, CCU18 sends a message indicating that the subscriber station is in the on-hook state. In either case, the other party is notified that it has been disconnected, the channel is set to the DISCONNECT state, and the subscriber station is set to the TEARDOWN state. When the CCU18 indicates that it is out of sync, the channel and subscriber stations are returned to the idle state. Background tasks Background tasks are performed by MPM45. Background tasks first communicate with CCUs18 after a cold or warm restart. Also, when the system is up and running, background tasks monitor CCU18 to keep the database up-to-date and ensure RCC allocation. BCC messages generated by both CCUs18 and BCC module 41 are received from BCC module 41, and these messages are sent to CCUs18 via BCC module 41. The data is written to the database and retrieved from the database. Initially, a BASEBAND QUERY message is sent to all CCUs18 so that the RPU20 can determine the current state of the system. All information received from the baseband event or response message is stored in the RPU database. When the RPU20 receives a baseband event message indicating that the CCU18 is ready and not reset (ie, the CCU18 is not properly powered up), the frequency assigned to the CCU20 is marked as assigned. To. CCU18 then receives a CHANNEL QUERY message to update the database to the current system state. CCU initialization is performed each time each CCU18 completes a response to all unique inquiry messages or it is determined that the CCU18 is down. At this point, each CCU 18 marked ready and reset (ie, the CCU is properly powered up) is assigned a frequency. If CCU18 has not yet been assigned a control channel, RPU20 will attempt to assign a control channel. The first attempt by the RPU20 is to assign a control channel to the CCU18 for the first frequency that the subscriber station is searching for in the RCC. The next attempt will target any CCU18 with unused slot 0, and the final attempt will target the CCU18 with a connection for slot 0. If all in-use CCUs18 already have connections for slot 0, one of the connections for slot 0 will be disconnected and a control channel will be assigned to that slot. Once the RPU 20 is in communication with all CCUs 18, the state of CCUs 18 is monitored by the status message received from CCUs 18 or BCC module 41. BCC module 41 constantly monitors the communication path for each CCU18. The CCU18 is considered to be inactive if it receives a baseband event message indicating that the CCU18 is not ready, in which case the CCU18 is marked as unready in the database. In addition, all connections will be disconnected, all channels will be returned to their default state, and the frequencies assigned to CCU18 will be deassigned. If the CCU 18 has a control channel, a new control channel is assigned. When a baseband event message is received indicating that the CCU18 is ready and has been reset, the CCU18 will be assigned a frequency. If the control channel is not currently assigned to CCU18, the control channel is assigned to slot 0 of the reset CCU. When a baseband event message is received indicating that the CCU18 has lost communication with the RPU20, a channel query message (ie, one message for every four channels) is sent to that CCU18 and the RPU database. Is updated in the current state of each channel in the CCU. The current channel state and connection information is updated in the database in response to receiving each channel query message. If the channel is in the SYNC WAIT state, the subscriber is no longer considered to be involved in the connection and is disconnected. First, CCUs18 is inquired by RPU20 about the initial state. CCUs18 sends an event message every time it is started up or every time it changes state. By exchanging messages, the RPU database can be kept in the current state of the system. Database module Database module 46 has database interface routines needed to access the database, these routines are a concise single to the database for all modules that need access to the information in the database. Give a thread interface. Most of this access routine involves SIN and BCC tables. Access to all fields in these tables is provided by this access routine. The database module also plays an important role in database initialization at startup. All valid fields are initialized to the appropriate values by the initialization part of this database module. The database module also provides: (1) Routines that support TTY initialization. (2) A binary search routine for subscribers to search the SIN table. (3) Routines and tables to support frequency-CCU mapping. (4) Control of diagnostic display information. as well as (5) Frequency allocation. Database module 46 is a set of routines that control access to a database by other modules. By channelizing all accesses with a database routine, the database is virtually invisible to external modules. This allows the database to be modified without requiring any other modules to be updated. If the database changes, only the interface routines for the changed parts of the database need to be changed. Frequency allocation task The frequency allocation task performed by the RPU20 selects the appropriate frequencies and slots for subscriber stations that require audio channels. The selection algorithm takes into account the type of call (ie, internal or external call) and modulation level (ie, 16-ary or 4-ary). The frequency allocation task is functionally unrelated to database 46, but closely related to the data structures in the database. For this reason, this feature is technically a routine within database module 46, but is described separately from database module. The frequency allocation task is used by the MPM when setting up the call. This task provides widespread use of data structures within database modules. All frequency allocation requests fall into one of two categories. The first category is the External-source category and the second category is the Internal-destination category. The internal destination category covers the foreign part of the internal call (ie, the destination). The external source category covers all other cases, including external calls, regardless of the origin of incoming or output calls or internal calls. The input to the frequency allocation task consists of an index to the subscriber station SIN table requesting the channel and an index to the outgoing subscriber station SIN table. The outgoing subscriber station index is only valid when the channel is being set up for an internal destination call. At all times other than this time, the calling subscriber station index is defined as DB NULL with a pre-defined illegal index. These indexes provide access to all the information needed to allocate the appropriate channels (ie, frequencies and slots). If the frequency / slot combination is successfully allocated, the frequency allocation routine returns TRUE. If this allocation is unsuccessful, FALSE is returned. When the allocation is completed, the selected frequency and slot are entered in the SIN table of the subscriber station requesting frequency allocation. Each frequency is divided into 4 TDM slots. The RPU database maintains a count of the number of available slots at each location. If the allocation request falls under the external source category, the slot is selected from the slot position with the highest free count. Once a slot position is selected, the first frequency available for that slot is selected, in fact any slot may be selected if the request falls into this category. However, the method of the present invention tends to distribute the system load equally to all slots, and more importantly, it increases the probability of optimal slot allocation for both parties involved in internal calls. It is also clear from the system timing calculations that the optimal slot allocation for subscriber-to-subscriber calls is obtained by providing base station transmit slots for each subscriber in the same slot for different frequencies. Greater probability when it comes time to assign the caller of a subscriber-to-subscriber call to the most likely slot location so that the destination subscriber station can be assigned to the same slot location for different frequencies. Become. For example, if position No. 2 is the most likely position, it will be assigned. When the destination subscriber station allocation request is processed, it is likely that another slot at position No. 2 will be selected, thus allowing optimal slot-to-slot allocation. If the allocation request falls under the internal destination category, the slot to be allocated is selected from the selection table. The selection table records slot location allocations for destination subscribers in order from the most probable to the least probable. This order is based on the slot allocation of outgoing subscribers. So far, no mention has been made of the form of modulation. The reason for this is that the basic allocation rules are the same for 4-ary and 16-ary slot selection, with one important exception. That is, only slot 0 or slot 2 can be assigned to a 4-ary type connection. With this exception and the ability of the two subscriber stations to be configured in different modulation formats, a total of four unique selection tables are needed to cover all possible call combinations. The four tables are:<img file="JP2816349B2_D0009.tif" /> Each column in each table lists the ratings associated with that column. This rating indicates a preferred value for a particular slot. The most preferred slot is rated 1, followed by ratings 2 and 3. If two or more columns in the selection table have the same preferred value, they have the same rated number, followed by letters. For example, if the three columns are rated 2a, 2b, 2c, respectively, then these columns have the same preferred values and the order (a, b, c) is arbitrary.<img file="JP2816349B2_D0010.tif" /><img file="JP2816349B2_D0011.tif" /><img file="JP2816349B2_D0012.tif" /> The frequency allocation task has two inputs, which provide access to the definitive information needed for proper frequency and slot selection. The first input is the input to the SIN table of the subscriber station requesting the channel. This index allows the frequency allocation task to determine the default modulation format of the requesting subscriber station. The index also tells the routine where to put the result of the selection algorithm (eg, frequency number and slot number). The second input to the frequency allocation task displays the frequency / slot request category. The value of this second input is either an index into the SIN table or the previously defined illegal value DB NULL. Upon receipt of a valid index, the frequency allocation request must be identified as the destination of the subscriber-to-subscriber call and the selection table must be used. When a DB NULL is received, the request is determined to fall into the external source category and will use the "maximum possible slot location" algorithm. If the frequency / slot combination is successfully allocated, the frequency allocation task returns TRUE, and if allocation is not possible, returns FALSE. This task also activates one desired side. If the allocation is successful, the baseband call slot field in the SIN table is written for the requesting subscriber station. The frequency allocation algorithm can be divided into two stages. The first stage, called the classification stage, determines the category of the allocation request. The second stage, called the selection stage, finds and allocates frequency / slot combinations using the appropriate algorithm determined by the allocation request category. The classification stage first determines whether automatic frequency selection should be performed. If the requesting subscriber station is set to manual mode, the specified manual modulation level value, manual frequency value, and manual slot value will be discounted. Specify the frequency, slot, and modulation to be added. If the specified frequency slots are available, these frequency slots will be assigned to the requesting subscriber station. If the specified frequency / slot is unavailable, the routine returns a FALSE value. If the requesting subscriber station is set to automatic mode, further classification is required. After deciding to make an automatic selection, the frequency allocation algorithm determines the required category. The request categories are as follows. That is, "External-In" is used when the destination subscriber station is called from an external telephone, and "External-Out" is used when the outgoing subscriber station is calling an external telephone. Use "-Out)", use "Internal-Out" if the outgoing subscriber station is calling another subscriber station, and the destination subscriber station is from another subscriber station Use Internal-In if called. If the request is external-in, external-out, or internal-out, the slot location is selected by searching for the most probable location. Once a position is selected, all frequencies are sequentially searched until an empty slot at the desired position (or a pair of adjacent slots in the case of a 4-ary request) is found. At this point, the routine populates the SIN table with the appropriate value, returns a TRUE value, and exits. If the request falls into the last category (internal / in), more information is needed. When an internal / in-format request occurs, two more information bits are needed. The slot allocation and modulation format (4-ary or 16-ary) of the calling subscriber station must be extracted. When this is completed, an appropriate selection table is determined based on the modulation format between the outgoing subscriber station and the destination subscriber station. Once the table selection is complete, the calling subscriber station slot allocation is used to determine the appropriate selection table column to use. Each sequential element of the selected column has the same degree of favorable slot allocation or slightly inferior slot allocation. Examine this list to find available slots, starting from the most preferred position and ending with all slot positions. Each slot position (4-ary to connect for the slot pairs), carrying out the sequential search of the frequency until the actual slot (or slot pair) is found. The derived frequency and slot values are not entered in the appropriate SIN table description and the routine exits and returns the value TRUE. The "slot count" array holds the number of available slots for each slot position. These counts are maintained by the database module and quoted by the frequency allocation task. The SIN table contains relevant information for each of the subscriber stations recognized by the system. The following access is made to the SIN table. Modulation Level (Read): The modulation level of the subscriber station requesting the frequency is extracted from this table along with the modulation level of the outgoing subscriber station during the internal call setup. Slot Number (Read): The slot allocation of the calling subscriber station during the internal read setup must be extracted. Slot number (write): The slot allocation of the subscriber station requesting the channel is populated here. Baseband Index: The frequency allocation of the subscriber station requesting the channel is populated here. The BCC table is used by the frequency allocation routine to search for available frequency / slot combinations. The following access is made to the BCC table. Channel State (Read): The state of a channel is checked to determine the availability of that channel. Channel Status (Read): The channel status is checked to confirm that the specified channel is an audio channel. Channel State (Write): The channel state changes when the specified channel is selected for allocation. Channel control (write): The modulation format of the requesting subscriber station is written to the channel control byte. SIN / Index: Establishes a link from the selected channel to the requesting subscriber station. Frequency allocation routines access the database directly. This is necessary when considering speed and efficiency. Wherever possible, database interface routines are used to access the database from frequency allocation routines. Subscriber Telephone Interface Device (STU) In its basic operating mode, the STU delivers 63 Kbps of 2-wire analog signals interfaced from a standard telephone set. Convert to PCM coded digital sample. According to FIG. 12, the STU includes a subscriber line interface circuit (SLIC) 53 that is directly connected to the 500 pushbutton telephone set through line 37. SLIC53 provides the correct voltage and impedance characteristics for phone operation. In addition, the SLIC53 applies a "ring" current to the phone set and also performs "on-hook / off-hook" detection. The signal output of SLIC53 on line 54 is an analog voice frequency (VF) transmit and receive signal. These signals are sequentially converted into PCM samples by the PCM code decoder 55. The PCM code decoder 55 uses a μ-255 compression algorithm to digitize the audio signal into 8-bit samples at an 8KHz rate. The PCM code decoder 55 is full-duplex in character. The digitized audio sample is then fed to line 56 to the "mode selection" multiplexer (MUX) 57. The operating mode of the MUX is determined by the subscriber controller SCU58, which interfaces with the MUX57 by the transmit and receive FIFO59. The SCU58 essentially includes a Model 803 microcontroller. This SCU is attached to CCU29. Further control the operation of SLIC53 through the RS-232 interface circuit. STU works essentially in one of three different modes. The first mode, the most basic mode, is the voice mode. In this mode, the audio sample from the PCM code decoder 55 is transferred to the VCU28 through the mode selection MUX57 and the VCU excitation / receiver circuit 61, which is further processed to a bit rate from 64Kbps to 14.6. It is reduced to Kbps and sent out for transmission to the base station. The second mode of operation is the data mode. In this mode, the 64Kbps stream from / to VCU28 is independent of audio information, and the information transmitted to the base station is reformatted from an external data source transmitted at a channel data transmission rate of up to 14.6Kbps. Data stream. This STU also includes an RS-232 data port 62 that allows the connection of data equipment (eg, terminal equipment) through line 63 using a standard asynchronous RS-232 interface operating at a maximum transmission rate of 9600 baud. There is. The STU includes a UART and timer circuit 64 for synchronizing data from RS-232 data port 62. The VCU28 packets the synchronized data so that it can pass the channel limit of 14.6 Kbps. Full-duplex data transmission is supported in this mode. The third STU mode is the call setup mode. In this mode, data is not transmitted from STU27 to VCU28 via mode selection MUX57. However, the ringback tone generator 65 is connected to the mode selection MUX57. This circuit digitally synthesizes the sounds used in the call setting procedure, such as busy sounds and error sounds. When setting the call, the DTMF number dialed by the user is detected by the DTMF detection circuit 60 and processed by the SCU 58 to set the call. The ringing sound generation circuit 65 returns an appropriate signal sound to the user's headset. Ring generator 67 is connected to SLIC53. The timing generator 68 supplies a timing signal to the PCM code decoder 55, the VCU excitation / reception circuit 61, and the ringing sound generation circuit 65. Once the call settings are complete, the STU switches to either voice mode or data mode to communicate with the base station. Another requirement for STUs is to prepare for the removal of unwanted echo signals from remote connections. The delay of the voice signal going back and forth between the base station and the subscriber station will easily exceed 100 msec. All reflected signals due to impedance mismatch at either end result in an unpleasant echo return. This issue is handled within the base station by the echo cancellation system within the PBX function. The STU must be prepared for echo cancellation at the subscriber station. It is expected that at least 40 dB of echo attenuation will be obtained from this echo cancellation. However, since the reflection of interest lies between STU's SLIC53 and the intra-area phone set itself, the echo delay removed is very small. This distance is typically only a few tenths of a foot and the delay is essentially zero. The 8031 microprocessor 58 in the SCU functions as the RPU 20 and the PBX call processing device 24 in the base station. The microcontroller 58 communicates with the base station RPU20 and controls all individual functions of the STU27 by means of messages sent to the radio control channel (RCC). The SCTU also communicates with the subscriber station CCU29 through the baseband control channel (BCC). The RS-232 interface of the CCU29 operates at 9600 baud, and is used to transmit control information between the CCU29 and STU27 in the subscriber station. Voice code decoder (VCU) The voice code decoder (VCU) acts as four full-duplex RELP voice compression systems. The design of the VCU is the same for both base stations and subscriber stations. At the subscriber station, only 1/4 of all functions (ie, only one of the four channels) is used. The interface to STU27 within the subscriber station is the same as the interface used by each of the four PBX channels of the interface of base station VCU17. VCUs 17 and 28 use an all-digital scheme to implement the RELP voice algorithm, which is [United States Patent Application No. 667,466, Invention Name RELP Vocoder Implemented in Digital Signal Processor, filing date 1984. Inventor Philip J. Wilson, November 2,], and the disclosures of the application specification are included herein as related documents. Alternatively, a subband code decoder can be used. The processed data is supplied to the CCUs 18 and 29 connected to the common parallel bus interface controlled by the CCU software, which controls the modes and configurations within the CCUs 18 and 29. Send signals to VCUs 17 and 28. The operation modes, function explanations, and realization concepts related to VCUs 17 and 28 are described below. The interface between PBX15 and VCU17 is shown in Fig. 13. The interface between STU27 and VCU28 is shown in Figure 14. The STU27 interface is a subset of the PBX15 interface in that the STU27 provides only one full dual audio channel operation. The timing relationship between the PBX interface and the STU interface is the same, and these are as shown in Fig. 15. Table 10 shows the characteristics represented by the symbols used in Fig. 15.<img file="JP2816349B2_D0013.tif" /> According to FIG. 13, lines 70, 71, 72, and 73 of PBX SDAT 0, 1, 2, and 3 carry data signals from PBX 15 in the base station to VCU 17, and data signals in the subscriber station. Is transported from STU27 to VCU28 by STU SDAT 0 line 74 (Fig. 14). 8-bit μ-255 compressed series data is sent to the voice code decoder during the active portion of PBX / STU GATE 0 or PBX GATE 1 ... 3 at a clock rate of 256 KHz. The data is clocked in to VCUs 17 and 28 at the rising edge of the 256KHz clock. Lines 75, 76, 77, and 78 of VCU SDAT 0, 1, 2, and 3 carry data signals from the VCU in the base station to PBX15. Line 29 of VCU SDAT 0 carries data from VCU 28 in the subscriber station to STU 27. 8-bit μ-255 compressed series data is PBX / STU GATE 0 or PBX GATE at a clock rate of 256 KHz. It is sent from the voice code decoder to PBX15 or STU27 during the active high part of 1 ... 3. The data is clocked out of VCUs 17 and 28 at the rising edge of the 256KHz clock. Lines 80, 81, 82, and 83 of PBX GATE 0, 1, 2, and 3 carry the gate signal from PBX15 in the base station to VCU17. Line 84 of STU GATE 0 carries the gate signal from STU27 in the subscriber station to VCU28. The gate signal is an active high signal used to enable transfer of PBX / STU SDAT 0, PBX SDAT 1 ... 3, and VCD SDAT 0 ... 3. This gate signal is active for eight consecutive clock periods every 125 microseconds. Lines 85, 86, 87, and 88 of PBX CLK 0, 1, 2, and 3 carry a 256 KHz clock signal from PBX 15 in the base station to VCU 17. Line 89 of STU CLK 0 carries a 256 KHz clock signal from STU 27 in the subscriber station to VCU 28. 256KHz clock signals are PBX / STU SDAT 0 and PBX SDAT Used to clock 1 ... 3 signals to VCUs 17 and 28 and SDAT 0 ... 3 signals to PBX15 or STU27. However, these clocks are not synchronized with any of the clocks generated in VCU17, VCU28, CCU18, CCU29, or modems 19 and 30. At the base station, the PBX-VCU interface converts four channels of synchronous 64Kbps serial data into 8-bit parallel data, which parallel data is for four transmit audio code decoders 16 at a sampling rate of 8KHz. Placed in a usable state. At the subscriber station, only one channel (channel 0) is converted by the STU-VCU interface. The required clocks and gates are supplied by PBX15 and STU27. The PBX-VCU interface and the STU-VCU interface also serve a complementary function to the received voice code decoder. At the base station, 8-bit parallel data received from the four code decoder channels is converted into four 64Kbps synchronous serial channels for reverse transmission to the PBX15. At the subscriber station, one audio channel is converted and sent back to STU27. The hardware interface between VCU17, 28 and CCU18, 29 is shown in Figure 16. The timing relationships of the transmission and reception channels between the VCU and CCU are shown in FIGS. 17 and 18, respectively. Tables 11 and 12 show the characteristics represented by the symbols used in Figures 17 and 18, respectively. Figures 17 and 18 detail the events that occur between the V-CBTPs shown in Figures 19A and 19B. Definitions of the individual interfaces are given in the following sections.<img file="JP2816349B2_D0014.tif" /><img file="JP2816349B2_D0015.tif" /> Figures 19A and 19B show the timing relationships between the various transmit and receive call blocks transferred between VCU17, 28 and CCU18, 29 due to 16-level phase shift keying (PSK) modulation. .. At the top of Figure 19A is the system frame timing that is the basis for all transfers. This frame timing also applies to Fig. 19B. One modem frame is 45 msec long and contains four audio slots (ie channels). Each voice slot consists of two system voice block periods (SVBP) of call data, each of which requires 82 symbols (requires 5.125 msec) and a frame time of 1.0 msec. It has 16 additional overhead data symbols. For the transmit channel, one block of 328 bits (41 bytes) of the processed call is transferred from VCU17, 28 to CCU18, 29 prior to the start of each SVBP during the voice code decoding block transfer period (VCBTP). The VCU's 64Kbps input data stream associated with the processed call block is shown divided into 22.5msec long voice note decoding block periods (VCBPs). Looking at transmission channel 0 in FIG. 19A, the raw VC input data of OA1 and OB1 of VCBPs is related to the processed data of OA1 and OB1 of VCBTPs. Also, the VCBPs of channel 0 and channel 2 are staggered by 1/2 of the VCBP (ie, 11.25 msec) from the VCBPs of channel 1 and channel 3. For the receive channel (Figure 19B), one block of 328 bits (41 bytes) of processed calls is transferred from CCU18, 29 to VCU17, 28 at the end of each SVBP during the VCBTP period. As with the transmit channel, VCBP's time skew to VCBTP (time) skew is implementationation dependent, and the (maximum) offset of one VCBP is shown in Figure 19B. The relationship between the input data and the output data of the voice code decoder can be understood by referring to FIGS. 19A and 19B. For receive channel 0, the compressed call data transferred during the VCBTP OA10 and OB10 periods is associated with the processed decompressed data stream within the VCBPS OA10 and OB10 periods. The TCADDR line 90 carries channel address signals from CCUs 18 and 29 to VCUs 17 and 28. These three address lines are used to select the current transmit channel address. The TCDATA bus 91 carries transmit channel data signals between VCUs 17 and 28 and CCUs 18 and 29. The TCDAV line 92 transmits channel data available from VCU17, 28 to CCU18, 29. signal) is carried. The TCDAV / signal indicates to CCU18, 29 that a data byte is available in the TCDATA register. The TCDAV signal remains low level until the TCDACK signal is activated. The TCDACK line 93 carries a transmit channel data acknowledge signal from CCUs 18 and 29 to VCUs 17 and 28. The TCDACK / signal gates the data to the TCDATA bus and resets TODAV /. The TCSCWR line 94 carries a transmit channel status / control write signal from CCUs 18 and 29 to VCUs 17 and 28. The TCSCWR signal writes the voice code decoder control word to the appropriate transmit channel control register determined by the TCADDR line. The data is latched in a register at the rising edge of the TCSCWR signal. The TCSCRD line 95 carries a transmit channel status / control read signal from CCUs 18 and 29 to VCUs 17 and 28. The TCSCRD signal gates a status byte from the voice code decoder status register specified by the TCADDR line to the TCDATA bus. The BLOCKRQ line 96 carries a block request signal from CCUs 18 and 29 to VCUs 17 and 28. The BLOCKRQ signal initiates a 41-byte block of data transfer from the voice code decoder (specified by the TCADDR line) to the CCUs 18 and 29 over the TCDATA bus. BLOCKRQ is used by the speech decoder to activate VCBP timing. TCVORST line 97 from CCU18, 29 to VCU17, 28 transmit channel vcice codecreset signal) is carried. The transmit voice code decoder specified by the TCADDR line is reset. The RCA DDR line 98 carries a receive channel address signal from CCUs 18 and 29 to VCUs 17 and 28. These address lines are used to select the current receive channel address as follows: RCDATA bus 98 carries receive channel data signals between CCUs 18 and 29 and VCUs 17 and 28. The RCDAV line 100 carries a receive channel data available signal from CCUs 18 and 29 to VCUs 17 and 28. The RCDAV signal indicates that data bytes are available in the RODATA register for the voice code decoder specified by the RCA DDR line. The RCDAV signal gates data to the RCDATA bus and RCDATA registers and further resets the RCDACK line. The RCDACK line 101 carries a receive channel data acknowledge signal from VCUs 17 and 28 to CCUs 18 and 29. The RCDACK signal indicates to CCU18, 29 that the reading of data from the RCDATA register is complete and that other bytes may be transferred from CCU18, 29. The RCSCWR line 102 carries a receive channel status / control write signal from CCUs 18 and 29 to VCUs 17 and 28. The RCSCW signal writes the control word to the appropriate voice code decoder control register determined by the RCA DDR line. The data is latched in a register at the rising edge of the RCSCWR signal. RCSCRD line 103 connects VCU17, 28 to CCU18, 29 with channel status / control read. signal) is carried. The RCSCRD signal gates the voice code decoder status word from the status register specified by the RCADDR line to the RCDATA bus. The BLOCKRDY line 104 carries a block ready signal from CCUs 18 and 29 to VCUs 17 and 28. The BLOCKRDY signal initiates a 41-byte block of data transfer from CCUs 18 and 29 to the voice code decoder specified by the RCA DDR line. The BLOCKRDY signal is used by the voice code decoder to trigger VCBP timing. CCUs 18 and 29 are required to have available data bytes in the RCDATA register prior to the rising edge of the BLOCKRDY signal. The RCVCRST line 105 carries a receive channel vcice codec reset signal from CCUs 18 and 29 to VCUs 17 and 28. The voice code decoder specified by the RCA DDR line is reset by the RCVCRST signal. The receive channel VCU hardware receives 41-byte blocks of input data from CCUs 18 and 29 during the VCBTP period, as shown in Figure 20A. After data processing based on the current operating mode, 8-bit μ-law compressed data is transferred to the PBX (STU) interface module at an 8KHz rate. Data buffering is performed within VCU17,28 to simplify input / output requests for CCU18,29. As shown in Fig. 18, the following operation modes in which control information is exchanged between VCU17, 28 and CCU18, 29 via a set of control and status ports for each receive channel at the beginning of VCBTP. Is supported by a receiver decoder. In external mode, call bandwidth expansion is done at an input data rate of 14.6 Kbps (328 bits every 22.5 msec) and an output data rate of 64 Kbps. Call data can also include DTMF sounds. In internal mode, previously compressed 14.6Kbps call data is sent from CCU18, 29 via VCU17, 28 to PBX15 or STU27. Since the PBX15 or STU27 expects 64Kbps data, a padding of the data stream must occur. The output (64Kbps) data consists of idle byte (FF, hexadecimal) patterns until call data is available from CCUs 18 and 29. Synchronous bytes (55, hexadecimal) are output, followed by 41 previously processed data bytes, followed by an idle byte pattern. FIG. 20A shows an example of the input and output data timing and contents of 16PSK modulation. In silence mode, call data input blocks from CCUs 18 and 29 are consumed but not used. The output idle byte pattern (FF, hexadecimal) to PBX15 or STU27 is maintained to ensure line silence. In standby mode, continuous hardware diagnostic routines are executed and the resulting status is stored in the status register. Block transfer to CCU18, 29 does not occur until the operation mode is switched by the block request corresponding to VCBTPA. A new control word (and mode of operation) is read by the voice code decoder and diagnostic status information is delivered to CCUs 18 and 29. The transmit channel VCU hardware receives 8-bit μ-law compressed PCM (8KHz sampling rate) from the PBX / STU interface. After data processing based on the current operating mode, the output data is transferred to the CCUs 18 and 29 in 41-byte blocks during the voice code decoder block transfer period (VCBTP) as shown in Figure 19A. Data buffering is performed within VCU17,28 to simplify input / output requests for CCU18,29. As shown in FIG. 17, at the beginning of VCBTP, control information is exchanged between VCU17, 28 and CCU18, 29 via a set of control and status ports for each transmission channel. The following modes of operation are supported by the transmitter decoder. In external mode, call bandwidth compression is performed at an output data rate of 14.6 Kbps (328 bits every 22.5 msec). The processed call data is transferred to CCUs 18 and 29 in 41-byte blocks. Call data can also include dual-tone multi-frequency (DTMA) sounds. In internal mode, previously processed call data is sent from PBX15 or STU27 through VCU17,28 and to CCU18,29. The 64Kbps input data stream contains an idle byte pattern (FF, hex), one sync byte (55, hex), and 41 previously processed compressed calls until the next sync byte occurs. It consists of data bytes and additional idle bytes. The voice code decoder monitors the input data for synchronous bytes generated at the byte boundary and buffers 41 bytes of call data. The call block is transferred to CCUs 18 and 29 during the next VCBTP period as described above. FIG. 20B shows an example of the input / output data timing and contents of 16-PSK modulation. Segment 1 of the output channel is the sync byte and segment 2 is the processed call byte. The shaded segments show the idle byte pattern. Note that synchronization and call data bytes do not occur across VCBP boundaries. In silence mode, input call data from PBX15 or STU27 is consumed but not used. The 41-byte output call data to the CCU contains a silent voice pattern. In standby mode, continuous hardware diagnostic routines are executed and the resulting status is stored in the status register. Block transfer to CCU18 and 29 does not occur until the operation mode is switched by the block request corresponding to VCBTPA. New control words (and modes of operation) are read by VCUs 17, 28 and diagnostic status information is delivered to CCUs 18, 29. The code decoder frame is defined based on the implementation requirements of the RELP algorithm, but this frame must be an integer divisor of the voice coding block period (VCBP), immediately 22.5 msec. Due to the fact that PBX15 and STU27 operate asynchronously with internal system timing, means to detect, report and compensate for data overruns and underruns must be built into VCU17, 28. This condition occurs about once every 50,000 VCBPs. Since the detection of overruns and underruns depends on the implementation, reports of such errors are given in the status word. Data underflow can be compensated by repeating the final call each time it is required, and overflow can be handled by ignoring the speech sample (s) each time it is required. After any one (or all) code decoders have been reset, VCBTPA becomes the first block transferred from CCUs 18 and 29, for example as shown in Figure 19A. Control channel unit (CCU) The channel controller (CCU) performs similar functions in both the subscriber station and the base station. The hardware used by both stations is actually the same because of the CCU function. The software of the subscriber station is slightly different from the software of the base station. The CCU performs many functions related to the format change and timing of information related to the operation of time division transmission channels. The basic input to the CCU comes from four sources. First, there is a real digitized sample to be transmitted. These samples are transmitted from VCUs 17 and 28 to CCUs 18 and 29 (Figs. 2 and 3). This data can be a coded voice sample or data sample from RS-232 data port 10 in the STU (Figure 12). In both cases, the digital channel operates at 16 Kbps. The four channels can be processed concurrently by the CCU 18 when all four 16-level PSK transmission channels are operating at a working base station. The subscriber station CCU29 operates on only one stream, which can be located at any of the four slot positions associated with the TDMA frame indication scheme. The second input to the CCU is supplied from STU27 (in the subscriber station) or RPU20 (in the base station) via the baseband control channel (BCC). This second input provides control messages related to operating mode, status, and control information. Most of the BCC messages from CCU18, 29 are radio control channel (RCC) messages received by CCU18, 29. .. The CCUs 18 and 29 deliver the control information from the RCC message to the STU27 or RPU20, and receive the control message from the RPU20 or STU27 accordingly. This determines what action CCU18, 29 should take on the data from VCU17, 28. The third input source is the timing and sequence from modems 19, 30a. Provide data information. Modem 19 supplies the master clock signal used in the VCU-CCU-modem chain, and modems 19 and 30a provide sufficient bit tracking synchronization accuracy, RF AGC level settings, and sufficient. Provides status regarding the "goodness" indicator used by CCUs 18 and 29 to determine if reliable communication is taking place through the channel. The CCUs 18 and 29 attempt to control the "fine-tuning" of the instantaneous modems 19 and 30a operation with commands that change the transmit power level, AGC level, and timing / range calculation. Quality level measurements for modem transmissions are reported to RPU20 or STU27. The fourth input source is the actual modem data received as symbols of up to 4 bits each (depending on the modulation level). These symbols are buffered, demultiplexed, and output to the VCU17, 28 receiver for decoding. It provides AGC level settings and status regarding the "goodness" indicator used by CCUs 18 and 29 to determine if sufficiently reliable communication is taking place through the channel. The CCUs 18 and 29 attempt to control the "fine-tuning" of the instantaneous modems 19 and 30a operation with commands that change the transmit power level, AGC level, and timing / range calculation. Quality level measurements for modem transmissions are reported to RPU20 or STU27. The fourth input source is the actual modem data received as symbols of up to 4 bits each (depending on the modulation level). These symbols are buffered, demultiplexed, and output to the VCU17, 28 receiver for decoding. It provides AGC level settings and status regarding the "goodness" indicator used by CCUs 18 and 29 to determine if sufficiently reliable communication is taking place through the channel. The CCUs 18 and 29 attempt to control the "fine-tuning" of the instantaneous modems 19 and 30a operation with commands that change the transmit power level, AGC level, and timing / range calculation. Quality level measurements for modem transmissions are reported to RPU20 or STU27. The fourth input source is the actual modem data received as symbols of up to 4 bits each (depending on the modulation level). These symbols are buffered, demultiplexed, and output to the VCU17, 28 receiver for decoding. FIG. 21 is a block diagram of the CCU. The CCU architecture is essentially two unidirectional direct memory access (DMA) data channels with an intelligent microprocessor controller. The function of the DMA channel is to transfer data from the VCU to the modem or from the modem to the VCU. The CCU interface to the VCU has two parallel DMA buses, namely the TX bus 107 for the transmit channel (VCU CCU modem) and the RX bus 108 for the receive channel (modem CCU VCU). The data processed by the VCU's transmit circuit is stored in the VCU memory until the CCU requests a DMA transfer. During each block transfer period, 41 bytes are transferred to the CCU. Two of these blocks are transmitted by active audio channels (up to 4 audio channels in the base station) for each TDMA frame. The CCU receives these transmit bytes through the transmit voice code decoder interface module (TVCIM) 109 and stores them in the transmit memory module (TMM) 110. Depending on the particular mode of operation of the channel, the CCU processor contained within the microcontroller module (MCM) adds a control / synchronization heading to the encoded voice bytes, thereby transmitting the modem. Formalize a complete voice packet for transmission to the modem via the interface module 112. The MCM111 maintains frame timing information and transfers data to the modem at the correct time. The transmitted data is from the 8-bit byte format used by the CCU by the MCM111 to the format containing 1, 2, or 4 bits per symbol, depending on the modulation level of the slot, before being transferred to the modem. Is converted to. The inversion process is performed on the data received from the modem. Data from the modem is received by the receiving modem interface module (RMIM) 114 and stored in the receiving memory module (RMM) 115. This data is then converted from the 1, 2, or 4-bit / symbol format used by the modem to the 8-bit byte format used internally by the CCU and all other baseband processing. The overhead and control bits are the result of the MCM111 itself identifying the MCM111's Knowledge of the frame timing given to the frame timing module (FTM) by the modem and the various code words in the symbol stream. Therefore, it is removed by MCM111 from the input data stream of RX bus 108. The converted data is fed to the VCU through the Received Speech Decoder Interface Module (RVCIM) 117. The CCU also provides link-level control over radio control channel (RCC) transmission at base and subscriber stations. In the base station, only one CCU is configured by the RPU as the processing of the RCC channel. This CCU controls the reception and formalization of messages from the base station's RPU to the subscriber's STU controller. This control function of the CCU includes RCC message detection and error control as well as formalization and packetization of RCC information in preparation for transmission across wireless links. The CCU also detects collisions with the input RCC at the base station. The CCU controls the power and range calculation for the subscriber station performing the initial acquisition effort. The protocol for acquisition and other RCC functions are as described above. Figure 22 shows the software-implemented functional system of the CCU. The CCU has three separate data paths: transmit bus TX107, receive bus BX108, and microphone controller local bus 119. The microcontroller 111 shares the memory access (DMA) controller 120 and the TX bus 107, and also shares the director DMA controller (director DMA controller) and the RX bus 108. The microcontroller 111 uses these remote buses to control the DMA controller peripherals, the control / status register 122, and to access the transmit buffer memory 110 and the receive buffer memory 115. The control and status register 122 on the branch line of the microcontroller local bus 119 provides an interface to the RFU, modem, and CCU hardware. The RS-232C link 123 between the RPU and CCU is supported by the UART of the microcontroller chip 111. At subscriber stations, the RPU is replaced by the STU, but the interface remains the same. Microcontroller 111 has access to three physically separated RAM storage areas: local RAM, transmit buffer, and receive buffer, which is further divided into on-chip RAM and off-chip RAM. be able to. The transmit buffer and receive buffer can only be accessed by the microprocessor when their respective DMA controllers are idle. The transmit buffer 110 is divided into many different segments. Each segment has a skeleton of voice or RCC packets that are ready to be transmitted by the channel. Preambles and unique words (RCC only) are constants initialized by microcontroller 111 after a CCU reset. Code word (voice only), voice data, and RCC data are written to transmit buffer 110 by the microcontroller just prior to DMA transmission to modems 19, 30a. Since the RCC "null ACK" is a fixed message sent at a high frequency, it is stored in the transmission buffer 110 as an individual component. The receive buffer 115 is divided into many different segments. One segment is for storing audio data, which is stored and transmitted on a VCU block basis. RCC data is stored separately from audio data so that it can be retained for a long time. If desired, the microcontroller 111 can maintain a two-frame RCC history in the receive buffer 115, reducing the temporal subtleties of the RCC copy task (buffer to local RAM). Local RAM contains working variables used by microcontroller 111. One important data structure stored here supports the baseband control channel (BCC) between the CCU and RPU. One register bank of local RAM is allocated to provide basic queue information to RS-232C interrupt handlers. The pointer and length fields in this bank define an active transmit data block (TXDB) from which data is read and transmitted. The TXDB contains length and pointer information for the next TXDB in the queue, thereby forming a linked list. On the receiving side, a circular buffer is used to store the input data bytes. When the complete message is received, the interrupt handling routine flags the serial code and interrupts the message. Microcontroller 111 uses its local bus 119 to access the modem, RFU, and CCU control / status register 122. This bus also provides access to TX bus 107 and RX bus 108 through isolation logic 124 and 125, respectively. To avoid line contention, the remote buses 107 and 108 are only accessed by the microcontroller 111 when their respective DMA controllers 120 or 121 are idle. The CCU and RPU communicate via link 123 through a full-duplex RS-232C interface called the baseband control channel (BCC). Asynchronous characters are 8-bit binary and are transmitted at 9600 baud. One start bit and one stop bit are used for data byte frame indication. The message is terminated by a unique byte with byte stuffing that is used to avoid in-message occurrence of unique bytes. Alternate bit protocols and 8-bit checksums are used to ensure link integrity. Two external interrupts are supported by the microcontroller. One is generated by the transmit DMA controller 120 and the other is generated by the receive DMA controller 121. These interrupts occur when the respective controllers 120, 121 complete their block transfers, thereby releasing control of their bus to microcontroller 111. The BCC interface is driven by internal interrupts. The software is interrupted when receiving or transmitting bytes. At the base station, the CCU microcontroller 111 is responsible for controlling and monitoring the entire four channel data path, including its assigned VCU17, 28, CCU18, 29, modems 19, 30a, and RFU20, 31a. Have. At the subscriber station, the microcontroller 111 controls and monitors the same hardware, but supports only one data path. The CCU is ultimately controlled by the RPU (for base stations) or STU (for subscriber stations). The CCU provides the VCU with operating mode information. Mode switching occurs only at system slot boundaries. During the call compression operation, the CCU also provides the VCU with information about the location of the VCU blocks (there are two VCU blocks per system slot) within the system slot. VCU addressing is established by the CCU prior to data transfer, thereby completing the MUX / DEMUX task. The VCU status is read by the CCU after each block transfer and the appropriate statistics are maintained by the CCU. The CCU can also activate the VCU hard reset and / or the VCU. The microcontroller 111 provides the current modulation level to the symbol byte converter 126 on the RX bus 108 and the byte symbol converter 127 on the TX bus 107. The modem is given information about the type of data being received, i.e., whether it is RCC or voice by a different acquisition procedure used to receive that data. The modem provides the CCU with a fractional clock offset, AGC level, and link quality value per slot. CCU frequency allocation is done by RPU or STU. The CCU controls modem hard reset, self-testing or activation of receiver training mode. The CCU processes the full-duplex data flow via the transmit bus 107 and the receive bus 108. During a given slot time, the outgoing transmitted voice data in the VCU is block-transferred to the transmit buffer 110 via the transmit DMA controller 121. Since each block is 1 VCU block in length, two such transfers are required for each audio channel. Prior to the transfer, the CCU assigns an appropriate channel address to the VCU, thereby achieving the multiplexing operation. The preambles and code words stored in the transmit buffer 110 are sent prior to the VCU data at the beginning of each slot. The transmit DMA transfers data from the transmit buffer to the reclocking FIFO stock 128, while the modem receives data from the FIFO stock 128 as needed. The byte-symbol conversion is accomplished by the byte-symbol converter 127 during this transfer. Control of the transmit DMA peripheral is handled by the microcontroller, along with the generation and insertion of voice packet code words. The received data flow is completely symmetrical with that of the transmitting side. Data is written to the relocking FIAO stack 129 each time it emerges from modems 19 and 30a. The receive DMA controller 121 moves data from the FIFO stack 129 to the receive buffer 115 each time it is needed. The symbol byte conversion is achieved by the symbol byte converter 126 and the frame timing is achieved by the clock circuit 130. Byte boundary alignment occurs automatically once the channels are in sync. Once a complete VCU block is received, this block is DMA blocked to the appropriate VCU. Control of the receiving DMA controller is processed by the microcontroller 111. Code word detection is performed for every slot. Microcontroller 111 performs this task by copying and registering the code word in local RAM or the like and comparing it with a list of valid code words. For each slot period, modems 19, 30a provide a decimal symbol offset and an AGC value. These are read by the microcontroller 111 and properly decoded. If there is a power failure or distance failure, the subscriber station will be notified by the transmit code word of this failure. The transmission RCC data is synthesized in the transmission buffer 110 by the CCU according to the contents of the RCC message queue. When the RPU completes the transmission of the RCC message to the CCU, the message is formalized in the send buffer 110. If the transmission is incomplete, the NULL KNOWLEGE message fixedly stored in the transmit buffer 110 is used. Once RCC packets are available, RCC preambles, unique words, and RCC data are transferred to modems 19, 30a each time they are needed. The CCU performs collision detection and sets the outbonud RCC collision detection bit according to this detection result. The receive RCC data handler has two modes: "frame search" mode and "monitor" mode. In frame search mode, the RCC channel is considered to be out of sync. All input RCC messages must be synchronized using a unique word detection algorithm. In monitor mode, the RCC channels are in sync and the unique word search algorithm is not called. The base station is always in frame search mode because it is expected that the subscriber station will jump in due to an unexpected abnormal timing. At a subscriber station, the RCC data handler is in monitor mode unless the station has RCC synchronization. In frame search mode, unique word (UW) detection is performed after each RCC slot period. Microcontroller 111 performs this task by scanning the unique word in the window for the "nominal" unique word storage location. If the unique word is successfully detected, the CCU is given symbol timing information. The received RCC data is DMa transferred from the modems 19 and 30a to the receive buffer 115. When this transfer is complete, the RCC data is copied to the local microcontroller RAM for processing. Received RCC packets are waved by the CCU. RCC packets are delivered to the RPU only if a unique word is detected and the CRC is correct. During the operation of the RCC, the corresponding VCU channel is placed in a standby state, and neither the transmit data path 107 nor the receive data path 108 transfers data between the VCU and the CCU during this channel period. The software runs on the Intel 8031 microprocessor 111. Program storage is provided by an external EPROM on the microcontroller local bus. Software must respond to DMA service requests in real time and maintain a data flow of up to 64 Kbps in both directions without data loss. FIFO buffering by stacks 128 and 129 of the modem interface provides the required slack time for the microcontroller 111 to perform DMA block transfer and system control functions. The software is divided into five separate modules: supervisor, data transfer, BCC transceiver, BMM control, and utility modules. Each module is designed to have only one inlet and exit point, except for interrupt and error conditions. There are exceptions to this external utility module, which is classified as a utility routine that is accessed directly by other modules. Communication between modules is generally done by using global variables defined within individual data segments. The supervisor module has an initialization function, maintains overall program control, and performs basic self-testing functions. The data transfer module supports data transfer control by TX bus 107 and RX bus 108 for both voice and RCC, performs synchronization word detection for all modulation levels for both voice data and RCC data, and also with the CCU. Supports (CCU-RPU) RS-232 communication link 123 to and from the RPU. The BCC transceiver module performs the BCC transceiver duty, processes the BCC queue, formats the outgoing BCC message, processes the received BCC data, and transfers RCC data to and from the CCU via the BCC. Do it. The BBM control module controls the RFU, modem, VCU, and CCU hardware via registers and reads and decodes status information (eg, modem AGC, link quality, and symbol ambiguity) from these devices. Decode embedded codewords in the incoming audio channel, formalize the codewords for the outgoing audio channel, maintain real-time software / hardware timers, and do online self-testing carry out. Utility modules execute various utility routines accessed by other modules. CCU software is divided into four separate processes that operate essentially in parallel. That is, it is classified into BCC data, TX DMA, and RX DMA processes, which are interrupt-driven and called only when a particular event requests attention. All three event-driven processes are in the data transfer module. The remaining processes distributed among all modules are background processes that initialize, control, and monitor the other three processes. Each time a BCC message arrives from the RPU (or subscriber station STU), it is received and stored by the BCC data process. Once the complete message is received, the BCC data process notifies the background process via the mail box. The background process is poled this mailbox during its main loop, so it is detecting all new messages. The message is decrypted by a background process and the appropriate action is taken. All responses are written to the BCC message queue by a background process, and the BCC data process is notified without delay. The BCC message can initiate the reconstruction of the CCU data channel. The required control information is written to modems 19, 30a and VCUs 17, 28 at the appropriate time, the modem operates with respect to the new control word at each slot boundary. The VCU expects mode switching to occur on the first VCU block transfer at the slot boundary. The background process has the role of ensuring that the correct control timing is maintained. Status collection is done by the background, TX DMA, and RX DMA processes. The latter two processes collect status words from the TX and RX sides of the VCU, respectively. This is necessary because these status registers are only accessible via TX bus 107 and RX bus 108, which are idle for a limited period of time. The background process collects status information directly from modems 19, 30a via station register 122 on local bus 119. Once the collection is complete, all status information is collated by background processes and stored in specific status variables. Status requests received from the RPU are processed by background processes based on this status history. Some status information, such as AGC values and factorial bit offsets, may require CCU operation. Apart from being stored as status history, these data are used for subscriber station output and correction of distance obstacles. For RCC messages, power and distance information is sent directly to the RPU as part of the RCC. Background processes perform this function by formalizing BCC messages that contain RCC, AGC, and distance data. When a packet becomes available, it is placed on the transmit BCC queue and the BCC data process is notified. For voice channels, this status information is used to formalize the code words embedded in the output voice packet. Background processes perform formalization functions and control the transmission of code words through voice channels. All code words must be transmitted in 5 frames per line. This gives 5: 1 redundant coding. The TX DMA process automatically sends the codeword selected by the background process. The background process also maintains the software / hardware real-time clock. This is achieved by poled one of the 8031 timers and counting overflows. The real-time clock feature provides a time reference for software timeouts and other time-dependent events. The background process maintains system timing by pole the CCU hardware error indicator and checking if the data transfer event is occurring where it should occur within the system frame. Check to confirm. System frame indication information is provided through the system frame start status line and timer connected to the 16KHz clock 130. Data synchronization is done by a background process. The BCC data process responds to RS-232 interrupts that can occur in both the transmit and receive directions of the port. This process simply outputs another byte to the sender or inputs another byte to the input side. BCC data routines notify background processes by end-of-message delimiters on the receiving side. The TX DMA process and the RX DMA process process transmit and receive DMA channels. The data transfer function controlled by the software will be described step by step below. Events in the data transfer process are marked by DMA controller interrupts. This interrupt occurs after the DMA controller completes the allocated block transfer. Each walk-through begins at the beginning of each slot data transfer. It will be helpful to refer to Figures 23 and 24 when reading the explanations in this section. FIG. 23 is a timing diagram for transferring RCC and 16PSK audio data to the transmission bus of the CCU. FIG. 24 is a timing diagram for transferring RCC and 16PSK data to the receiving bus of the CCU. Figures 13 and 14 describe the characteristics of the symbols shown in Figures 23 and 24, respectively.<img file="JP2816349B2_D0016.tif" /><img file="JP2816349B2_D0017.tif" />Send function-RCC 1. Complete the "end of TXDMA transfer" interrupt. This indicates that the processing of the previous slot has been completed and that the processing of the next slot can be started. The TX DMA process is called. Write out control channel and modulation switching information. This information is required by modems 19, 30a and byte symbol converter 127. b. Format all pending RPU RCC messages in send buffer 110. If there is no pending message, a null acknowledgment message is generated and sent. c. Indicates the RCC preamble unique word and RCC data block to enable initialization of DMA transfers from transmit buffer 110 to modems 19 and 30a. d. Return from the interrupt and proceed to the background processing operation. Send function-voice 1. Receive the "end of TXDMA transfer" interrupt. This indicates that the processing of the previous slot has been completed and that the processing of the next slot can be started. The TX DMA process is called. a. Write out the audio channel and modulation switching information for the next slot. This information is required by modems 19, 30a and byte symbol converter 127. b. Select the VCU port address and enable DMA transfer from the VCU to the transmit buffer 110. c. Write the VCU control word. d. Interrupt the VCU to start the transfer. e. Return from the interrupt and proceed to the background processing operation. 2. Receive the end of TX DMA transfer interrupt. This signals that the transfer from the VCU to the transmit buffer is complete. The TX DMA process is called. Read the VCU stator word. b. Write the code word to send buffer 110. c. Indicates a voice preample code word and voice data block to enable initialization of DMA transfers from transmit buffer 110 to modems 19 and 30a. d. Return from the interrupt and proceed to the background processing operation. 3. Receives the "end of TX DMA transfer" interrupt. This indicates that the first half slot transfer from the transmit buffer 110 to the modems 19 and 30a is complete. The TX DMA process is called. Select the VCU port address and enable DMA transfer from the VCU to the transmit buffer. b. Write the VCU control word. c. Interrupt the VCU and start the transfer. d. Return from the interrupt and proceed to the background processing operation. 4. Receive the end of TX DMA transfer interrupt. This signals that the VCU-send buffer transfer is complete. The TX DMA process is called. Read the VCU status word. b. Initialize and enable the DMA controller 120 for transfer from the transmit buffer to the modem. c. Return from the interrupt and proceed to the background processing operation. Receive function-RCC 1. Receives the "end of RX DMA transfer" interrupt. This indicates that the processing of the previous slot has been completed and that the processing of the next slot can be started. The RX DMA process is called. Set up for BPSK modulation. This information is needed by the symbol byte converter 126. Modems 19 and 30a should have already received this information at this point. b. Enables initialization of DMA transfers from modems 19, 30a to transmit buffer 155 for RCC messages. c. Return from the interrupt and proceed to the background processing operation. AGC calculations and bit synchronization ambiguity processing operations should be performed at this point. 2. Receive the "RX DMA transfer end" interrupt. This interrupt signals that the RCC transfer from the modems 19 and 30a to the receive buffer 115 is complete. The RX DMA process is called. Post the RCC to local RAM. b. Return from the interrupt and proceed to the background processing operation. If a unique word is detected and the checksum is correct, prepare to send the received RCC to the RPU. Receive function-voice 1. Receive the "RX DMA transfer end" interrupt. This indicates that the processing of the previous slot has been completed and that the processing of the next slot can be started. The RX DMA process is called. Set up for audio data with the correct modulation. This information is needed by the symbol byte converter 126. The modem should have already received this information at this point. b. Initialize and enable the start of DMA transfer from modems 19 and 30a to the receive buffer for the first half slot of audio data. c. AGC calculations, bit synchronization ambiguities and code word processing operations that return from the interrupt and proceed to background processing operations should be performed at this point. 2. Receives the "end of RX DMA transfer" interrupt. This signals that the first half slot transfer from modems 19 and 30a to receive buffer 115 is complete. The RX DMA process is called. Select the VCU port address to enable DMA transfer from receive buffer 115 to the VCU. Interrupt the VCU and start the transfer. b. Return from the interrupt and proceed to the background processing operation. 3. Receive the "RX DMA transfer end" interrupt. This indicates that the slot transfer of the first half from the receive buffer 115 to the VCU is completed. The RX DMA process is called. Initialize and enable DMA controller 121 for modem-receive buffer transfer for late slots. b. Return from the interrupt and proceed to the background processing operation. 4. Receive the "RX DMA transfer end" interrupt. This indicates that the second half slot transfer from modems 19 and 30a to receive buffer 115 is complete. The TX DMA process is called. a. Select the VCU port address to enable DMA transfer from receive buffer 115 to the VCU. Interrupt the VCU and start the transfer. b. Return from the interrupt and proceed to the background processing operation. Running CCU software Software program execution begins as a result of a hardware reset and the program flow begins in the supervisor module. The supervisor module performs all hardware and software initialization processing prior to entering the main service loop. The supervisor module performs some kind of basic self-test after a hardware reset and after each request from the RPU. The main service loop accesses other modules in turn. The supervisor module design is designed to subdivide tasks into manageable time slices, ensuring that the main service loop has reasonable worst-case synchrony. Tasks that request a real-time response are processed through an interrupt service routine. Each interrupt service routine performs the minimum processing that satisfies the service request. This is to maintain the serializability of program execution as much as possible and to keep the interrupt queue to a minimum. Typically, an interrupt service routine will set a boolean to indicate that data has been transferred in and out of the interface and that an action has been taken. The code accessed from the main service loop is sequentially executed, and the processing of the information proceeds as desired. The CCU microcontroller 111 is a data flow machine in that software events are driven by the ingress and egress of data. machine). Accurate system timing provides a framework for this data flow, but software events are derived directly from the data flow rather than from system frame markers. This method of processing causes the software to respond to "truth" events (such as data I / O requests) rather than "artificial" events (such as system timing markers). The software relies on the hardware to translate the former synchronization action into an event that is synchronized to system frame timing. To achieve this, it is necessary to ensure that the software has something that is initialized and available before the system frame event occurs. Therefore, it is easily permissible for the CCU software to respond to an called event and complete a task within a limited time before it is overloaded. Since this real-time processing is driven by interrupts, considerable consideration is required in its design. There are four inevitably conflicting real-time events required for a microcontroller: transmit DMA service processing, receive DMA service processing, transmit RS-232 service processing, and RS-232 service processing. RS-232 interrupts have the lowest priority because they occur at a maximum rate of once per millisecond. The software is designed so that the 1 millisecond time constraint is not broken. Response times for voice and RCC data processing are more subtle and will be described below. The relative timing of the transmitting bus and the receiving bus with respect to the data transfer is shown in FIGS. 23 and 24. This figure shows the approximate time and shows the timing course in the worst case. The time multiplexing state of the transmitting bus and the receiving bus is clearly shown in this figure. The dark crosshairs shown on the transmission and reception paths are the respective buses (t)._S, T_RCC) Corresponds to the activity of the microcontroller. During this period, the DMA controllers 120 and 121 are idle, respectively. DMA controller setup (t_VCBThe short time between) corresponds to VCU block transfer, during this period the DMA controller is dedicated to each VCU. Remaining time (t_M0, T_M1, T_M2, T_M3), The DMA controllers 120 and 121 are dedicated to services for the modem interface. Reclocking FIFO stacks 128, 129 in the modem interface generate the basic timing constraints inherent in the timing diagram. FIFO Stax holds 16 symbols and provides 1 millisecond buffer time for underflow (TX) or overflow (RX). During this 1 millisecond, the CCU can use the transmit bus 107 or receive bus 108 to complete a block transfer to or from the VCU or transfer RCC data to local RAM. Upon power-up, the CCU software will perform an initial self-test and set the VCU, modem, and RFU to its default state. The microcontroller 111 monitors the system frame timing and starts performing block transfers to get the VCU to get the synchronization. Once the data transfer is initiated, the microcontroller 111 uses a DMA block end interrupt to hold the system timing. This interrupt is directly tied to the CCU's data throughput, which in turn leads to the 16KHz symbol clock 130. The VCU holds the system timing implicitly through the DMA transfer request generated by the microcontroller 111 as a result of the end-of-block interrupt. Microcontroller 111 continues to monitor frame timing to ensure that correct system operation is maintained. At the subscriber station, system startup still requires wireless synchronization, which is done by locating the RCC and then eliciting system timing. Once the reception timing is established, the microcontroller 111 establishes the transmission timing with the base station. The data transfer module supports real-time and background data transfer events in the CCU, data transfer is serviced to the transmit data path, the receive data path, the transmit BCC, and the receive BCC. All of these tasks require a real-time response for interrupt-driven events. This module also performs synchronization acquisition and monitoring as a background task. The transmit data path handler is called when the transmit DMA controller 120 requires service. This typically occurs following a DMA block transfer, at which point the DMA peripherals end of block. transfer) You are calling an interrupt. This interrupt is received by one of the two external interrupt lines on Model 8031 Microcontroller 111. The service required by the interrupt depends on the type of data transfer, ie RCC or voice, and the time of occurrence in the slot. The transmit data path interrupt occurs at the predictable time of each slot period. The interrupt time and duration are shown in Figures 23 and 24. For each interrupt occurrence, the microcontroller 111 is required to initialize the DMA peripheral for the next block transfer. This operation should be performed within 150 μs from the interrupt request to the completion of the interrupt. For RCC data, the first service request requires microcontroller 111 to format the RCC message in transmit buffer 110 prior to DMA transfer. This operation must be completed within 900 μs. This interrupt is given the highest priority because operations related to the transmission path are usually short and require a fast response. The only output from the transmit data path interrupt handler is the VCU status word collected after the VCU block transfer. This status word is parsed by the software in the BBM control module. The receive data path handler is called when the receive DMA controller 121 requires service. This typically occurs following a DMA block transfer, at which point the DMA peripheral is calling the block transfer end interrupt. This interrupt is received by one of the two external interrupt lines on the 8031 microprocessor 111. The service required by this interrupt depends on the type of data transfer, ie RCC or voice, and the time of occurrence in the slot. Received data path interrupts occur at the predictable time of each slot period. The interrupt time and duration are shown in FIGS. 23 and 24. For each interrupt occurrence, the microcontroller 111 is required to initialize the DMA controller 121 for the next block transfer. This operation should be performed within 150 milliseconds from interrupt request to interrupt completion if DMA initialization is the only task to be performed. For RCC data, the final service request requires microcontroller 111 to post an RCC message from receive buffer 115 to local RAM after a DMA transfer. This operation must be completed within 900 microseconds. Since the service operation of the transmission path can occur at this time, the reception path interrupt has a lower priority than the transmission path interrupt. The received data path interrupt handler makes the VCU status word available after each VCU block transfer, which is parsed by the software in the BBM control module. This handler also reads a new RCC message from the channel, which is decrypted within the BCC transceiver module. The BCC receiver module is realized by an on-chip RS-232UART. The UART is capable of generating one internal interrupt that is triggered each time a byte is received or transmitted. The BCC handler poles the status bit to determine which of the two cases caused the interrupt, and begins servicing the port accordingly. The baud rate generator is programmed to a nominal rate of 9600 baud, resulting in up to 1920 interrupts per second. Each interrupt must be serviced within a 1ms period to avoid data loss. BCC data transfer interrupts have a low priority because typical interrupt frequencies are low and response times are relatively long. The BCC data transfer handler uses pointers to queue or unqueue the data each time it is received or transmitted. Only link-level processing occurs here, including byte stuffing and end-of-message insertion. These actions are described in the description section of the system interface. Data processing rarely occurs in BCC transceiver modules, the main task of which is to process transmit, receive and BCC data paths while queuing or unqueuing data. The acquisition and monitoring of data synchronization described below is a key processing function of the BCC transceiver module. Detection of synchronization words involves synchronization operations at the symbol level. The term "synchronous word" is generic and is used for both unique words in RCC and code words in audio channels. A unique word (UW) is a fixed 8-bit pattern placed at the beginning of an RCC message. A code word (CW) is one of eight possible 8-bit patterns at the beginning of an audio channel that corresponds to that point in time. In addition to the role of synchronizing these words, code words are used to indicate connection status, power adjustment, and distance adjustment. The base station CCU must thoroughly search for valid RCC messages in all slots. The CCU performs this task by scanning the unique word in the window with ± 3 symbols for the nominal UW storage location based on master system timing. The search algorithm starts at the nominal UW storage location and shifts one symbol left or right until (1) finds the UW pattern and (2) confirms the correct RCC checksum. This search ends immediately if (1) and (2) are met or all possibilities are eliminated. Shift information, RCC messages, and power information are sent to the RPU following a successful search. At every voice slot, the base station CCU checks the received voice data for valid code words. Since valid symbol synchronization is not performed during voice operation, only the nominal code / word storage position is checked. If no codeword is detected for 5 consecutive frames, the channel is declared out of sync and the RPU is notified of this condition. It is up to the RPU to decide which appropriate action to take at this point. Synchronization is defined as that three of the five consecutive frames should be restored after a successful code word detection. The subscriber station's CCU may be in one of two modes, namely "frame search" or "monitor" mode, when receiving RCC data. The frame search mode is used to get the received frame timing from the input RCC data and is automatically called when the received RCC synchronization is lost. The monitor mode is a mode that is entered when the acquisition of received frame synchronization is completed. In frame search mode, the subscriber CCU must thoroughly search for valid RCC messages after every RCC slot. Like the base station CCU, the subscriber station CCU scans the unique word in the window for ± 3 symbols for the nominal UW storage location based on the timing derived from the modem's AM hole detection for this task. To execute. The search algorithm starts at the nominal UW storage location and shifts one symbol left or right until (1) finds the UW pattern and (2) confirms the correct RCC checksum. This search ends immediately if (1) and (2) are satisfied or all possibilities are eliminated. The shift information from the successful search is used to adjust the CCU-generated receive frame indicator. The acquisition operation ends when the above (1) and (2) are satisfied for three consecutive frames with the UW in its nominal storage position. When the acquisition of a frame instruction occurs, the STU is notified of the acquisition of this frame instruction. RCC messages are not delivered to the STU while in frame search mode. When the acquisition of the frame instruction is completed, the subscriber station CCU enters the monitor mode. Only the nominal UW storage location is checked to avoid the possibility of false UW acquisition. If no UW is detected for 5 consecutive frames, the channel is declared out of sync and enters search mode. The STU will be notified of this out-of-sync condition. During monitor mode, RCC messages with the correct checksum and SIN number are delivered to the STU. During all voice slots, the subscriber CCU checks the received voice data for the correct code word. Since valid symbol synchronization is not performed during voice operation, only the nominal code / word storage position is checked. Search for all possible codewords in this direction for the channel. Codewords can cause incremental changes in power and distance values for subscriber stations. Incremental distance changes can actually cause changes in symbols as well as decimal distance values. If no codeword is detected for 5 consecutive frames, the channel is declared out of sync and the STU is notified of this condition. Synchronization is defined as that three of the five consecutive frames should be restored after a successful code word detection. Other CCU considerations The transmit DMA transfer request between the transmit buffer 110 and the modems 19, 30a must be retrieved from all bits of the FIFO stack 128. This means that the FIFO stack 128 is always full when the DMA block transfer is complete. Received DMA transfer requests between modems 19, 30a and receive buffer 115 must be pulled from stack 129 and empty bits. This means that the FIFO stack 129 is always empty when the DMA block transfer is complete. The CCU controller software provides a gate that enables DMA transfers, but external controls must provide handshaking to initiate and maintain block transfers. This is important for modem interfaces where frame timing is sensitive. Microcontroller 111 should have the ability to put DMA transfers on hold. The software will not attempt to use the DMA bus during block transfers unless this control is used or the DMA peripherals are idle. Reclocking FIFO stacks 128 and 129 should be periodically auto-cleared (reset). The frame timing information must be available to the microcontroller 111. This information can take the form of a symbol clock that is input to the microcontroller's internal timer. If the RCC or voice packet is received by the CCU in sync, there is no need to shift the symbol to bring the packet to the byte boundary. This is applicable regardless of the modulation level. modem The modem operates in one of three modes of operation. At base stations, modems continue to provide full-duplex transmission and reception capabilities. When operating at a subscriber station, the modem operates in half-duplex mode, transmitting between one part of the TDMA frame and receiving during the other part of the TDMA frame. The third mode is the self-adapting adjustment mode. One modem design includes all these features. The modem performs the appropriate function in response to the keying signal input from the control CCU. The subscriber station modem 30a and the base station modem 19 are the same. A block diagram of the modem is shown in Figure 25. The modem transmitter includes a TX symbol filter 132, a digital-to-analog (D / A) converter 133, a 200 KHz bandpass filter 134, a mixer 135, and a TX (transmitter) timing control circuit 136. Modem reception includes a mixer 138, an analog-to-digital (A / D) converter 139, a FIFO stack 140, and a model TMS320 microprocessor 141. The modem transmitter transmits the information supplied by the CCU in 16-level PSK modulation. It is the responsibility of the receiving CCU to decode the data as DPSK, QPSK, or 16PSK. The modem sends without knowing the modulation level. The transmitter of the modem is fully hardware-equipped and does not require any adjustment, the symbols received from the CCU are encoded and the corresponding waveforms exhibit good interference characteristics and amplitude or group delay distortion. The waveform is shaped so that it will not be affected. The premise of this concept is that there is no strong interference signal (power density exceeding 30 to 40 dB) within the frequency band (within 50 to 100 KHz) close to the frequency band used. The transmitter of the modem uses a relatively wide IF wave (100KHz) so that the transmitted signal is not subject to amplitude or group delay distortion, and all harmonics generated by the digital wave performed in the baseband. I'm removing it. The TX symbol filter 132 is a fixed coefficient digital FIR (Finite-duration lmpulse-response) filter. This filter 132 simulates a hexapole filter with a sampling rate of "50 samples / symbol" for 6 symbol stays in the FIR filter. The modem receives symbols from its respective CCU at a rate of 16K symbols / second. These symbols are then converted to DPSK code for input to line 143 to FIR filter 132. The FIR algorithm requires every other symbol to be inverted before input to the FIR filter. Use Gray code for DPSK coding. This ensures that in the event of a symbol reception error, it is likely that the two symbols to the receiver code decoder are incorrect by only one bit. The impulse response of the FIR filter 132 is truncated at 6T (T = 1 / 16KHz). The FIR filter oversamples the symbols at a rate of 800 KHz so that all symbols are sampled 50 times during the 5T stay period of the symbols in the filter. This is equivalent to the sampling rate of 3T / 25 when the sampling period is T / 25, and the sample is output every 3T / 25. The output is skewed so that only the first and fourth, second and fifth, or third and sixth pairs of samples overlap at a time. Each of these time-length T / 25 samples is actually divided into two parts. The I part of the output is calculated in the first half of the sample period, and the Q part of the output is calculated in the second half of the sample period. Therefore, the actual rate at which the FIR filter 132 outputs data is 50 × 16KHz = 800KHz. The I and Q samplings are staggered by half the sample period, which is corrected by the FIR filter 132. The signal representing the multiplication of the symbol and impulse response in the FIR filter 132 and the two additions of these multiplications are provided by the 8K × 8 ROM on line 144 in response to the symbol received on line 143. The FIR filter 132 outputs a 10-bit digital sample to line 144 at a rate of 800 KHz. These values are supplied to the D / A converter 133 to generate an analog waveform on line 145. This waveform is a time-division I and Q waveform of the symbol to be transmitted, this divided waveform on line 145 is waved by a 200 KHz band filter 134 and then fed to mixer 135 through line 146. The local oscillator input of the mixer is the 20 MHz IF frequency signal on line 147. The I and Q components are then upconverted to the 20.2MHz IF output signal on line 148. The output signal of line 148 is supplied to a 20.2 MHz band filter (not shown) and provided to RFU21, 31a. The desired signal from the D / A converter 134 is centered at 200 KHz with a bandwidth of about 32 KHz. By multiplying the 200KHz waveform by 20MHz, the output waveform mixes the I and Q samples with the SIN and COS components of the IF frequency. Therefore, the 20MHz signal can be directly multiplied by the output waveform, and accurate component multiplication is automatically processed. Therefore, it does not require a separate SIN (IF) / COS (IF) generation circuit for multiplying the I / Q sample from the D / A as in the case of the receiver. It also eliminates isolation feedthrough in the mixer from baseband to the output of the mixer. The output data stored in the transmitter FIR filter 132 is calculated to correct any errors that are likely to occur due to the difference between the I and Q time values of 1 / 50T. The IF filter in the RFU (Figs. 28 and 29) also adds two values to form the correct transmit waveform because its bandwidth is relatively narrow relative to the IF frequency. At the modem receiver, the mixer 138 mixes the analog waveform received from the RFU on line 150 via a 20MHz band filter (not shown) with the 20MHz IF signal on line 151 and mixes this analog signal with the 20MHz IF signal on line 152. Down convert to baseband. The analog signal is then converted by the A / D converter 139 to a digital signal on line 153, which is stored in the FIFO stack 140 for processing by the microprocessor 141, which in turn has the frequency of the received digital signal. And bit tracking, as well as FIR wave processing and signal demodulation to the binary symbol stream supplied to line 154 to the CCU. In addition to the analog and digital signals processed by the modem, many control and status signals are sent and received to the modem. These signals are usually sent from the CCU to the modem. The modem also sends control signals to the RFU to control features such as transmit power level, frequency, AGC, and antenna switching for diversity communication. The modem interface is shown in Figures 26 and 27. The modem receives most of its input from the CCU. Other inputs are received from the RFU and timing device. The modem input is as follows. The lines below carry the described signals from CCUs 18 and 29 to modems 19 and 30a. The TX DATA line 156 carries a 4-bit symbol (2 bits for QPSK, 1 bit for BPSK) to be transmitted by the modem. MOD BUS157 is a bidirectional microprocessor bus that sends and receives control / status information to and from the modem. The MOD WR line 158 carries the control signal for the latch MOD BUS to the modem. The MOD RD line 159 carries control signals that bring modem status and other information into the MOD BUS for transmission to the CCUs 18 and 29. The MOD RESET line 160 carries control signals to reset the modem. MOD ADD line 161 carries address signals for different storage locations for latching values into the modem. The TX SOS line 162 carries a signal that initiates TX slot transmission. The RX SOS line 163 carries a signal that initiates reception in the RX slot. The IF RECEIVE line 165 carries the IF reception frequency input signal from the RFUs 21 and 31a to the modems 19 and 30a. The line below carries the described signal from the STIMU 35 to the modem 19. The 80MHz line 167 carries the 80MHz ECL clock signal. A similar signal is supplied to the modem 30a by a timing device (not shown) within the subscriber station. The 16KHz line 168 carries the master TX CLK signal used in the base station. The SOMF line carries the base station master frame start signal from STIMU. This signal is not used in the modem, but is delivered to CCUs 18 and 29. The lines below carry the described signals from modems 19, 30a to CCUs 18, 29. The TX CLK line 171 carries a 16KHz clock signal that gives the CCU symbol transmission timing. The symbol is clocked to the modem at the rising edge of this clock. At the base station, all slots have the same master TX CLK, so all signals from the base station are sent out at the same time. At the subscriber station, the TX CLK is offset by the modem by a fractional distance delay based on the information provided by the CCU. The RX CLK line 172 carries the 16KHz clock signal extracted from the received signal. This signal is always produced at the subscriber station, but is only supplied during control slot acquisition at the base station. This clock signal clocks out the received symbol to the CCU and gives the CCU symbol timing. The RX DATA line 173 carries a 4-bit receive symbol clocked by the RX CLK signal. The MOD SOMF line 175 transmits the SOMF signal from STIMU to the CCU in the base station. The AM STROBE line 176 carries a high to low transition to give the CCU a coarse frame marker when the RCC is acquired at the subscriber station. This is a pulsed one-shot line when microprocessor 141 determines the approximate location of the AM hole. The lines below carry the described signals from modems 19 and 30a to the respective RFUs 21 and 31a. The RF RX BUS178 is an 8-bit bus between the modem and the RFU section. This bus transmits AGC and frequency selection information to the RF RX section. The modem controls the transmitted AGC value and transmits the frequency selection information to the CCU. This frequency selection information is supplied to the modem by the CCU through MOD BUS157. In tune mode, the modem controls the RF RX frequency selection. The RF TX BUS179 is an 8-bit bus between the modem and the RFU TX section. This bus transmits the TX power level and frequency selection information to the RFU TX section. Since the modem has nothing to do with this information, this information is simply delivered to the RFU TX section. The RX80MHz REF line 180 carries the ECL 80MHz reference clock signal to the RFU RX section. The TX EM line 182 to the RFU TX section carries the signals that enable RF transmission. The RX EN line 183 to the RFU RX section carries signals that enable RF reception. The AGC WR line 184 carries a write strobe for latching AGC data to the RFU RX section. The RX-FREQWR line 185 carries a write strobe for writing frequencies to the RFU TX section. The PWR WR line 186 carries a write strobe for latching power information to the RFU TX section. The PWR RD line 187 carries a read strobe for reading back power information from the RFU TX section. The TXFREQ RD line 188 carries a read strobe for reading back the transmission frequency from the RFU TX section, and the TXAREQ WR line 189 carries a write strobe frequency write to the RFU TX section. The IF TRANMIT line 190 carries the IF frequency transmit signal to the RFU. The line below carries the described signal from modem 19 to STIMU35. The VCXO BUS192 is a 20-bit bus to the VCXO in the STIMU35 that has control information for frequency tracking. The VCXO WR line carries write pulses to the VCXO circuit to latch the VCXO BUS192 to the VCXO. A similar signal is carried from the modem 30a to the subscriber station timing device (not shown). The operation of the modem of the base station is assigned to the fixed RF frequency. Since the communication in the base station is full-duplex, the receiver and the transmitter of the modem operate at the same time. The modem is further assigned to be a control frequency channel modem, in which case it simply sends and receives information in wireless control channel (RCC) format during the allocated control slot period. All transmissions from the base station modem are clocked to the master TX CLK signal at 16KHz on line 171. Unlike the subscriber station modem, the base station modem 19 outputs to the CCU 18 a fractional part of the symbol time between the master TX CLK signal on line 171 and the derived RX CLK signal on line 172 on modem 19. This information is then sent to the subscriber station in the RCC, which causes the subscriber station to delay its transmission so that the signal received at the base station is synchronized with all other slots. The base station modem 19 also transmits null energy into the control slot to provide an RCC AM hole (establishing a frame reference) when the RFU transmits a null energy signnal. This no-carrier portion of the RCC transmission is used for the initial RX acquisition at the subscriber station. Modem 19 is unaware of the fact that the base station has four voice code decoders multiplexed by CCU 18 for four 16PSK subscriber station slot allocations. Modem 19 accepts a bitstream from CCU18 and treats the transmission as if it were a single code decoder subscriber station. All operation within the subscriber station modem 30a is derived from the received RX CLK signal on line 172 recovered from the received transmission. It acts as the master clock for the subscriber station. The TX CLK signal on line 171 for CCU29 is not the master clock as in a base station. This signal is derived from the RX CLK signal on line 172 and is delayed by a fraction of the time depending on what is selected by CCU29. This delay is determined by the distance between the base station and the subscriber station. The subscriber station CCU29 supplies this fractional hour information to the modem 30a through MOD BUS 157. Modem 30a counts this decimal delay itself. CCU29 counts the integer symbol delay inserted into the TX SOS signal on line 162, which is delayed by the correct number of symbols. This process adjusts the delay of signals arriving at all subscriber stations or base stations that differ in distance. Communication is a half-duplex system at the subscriber station. Therefore, communication is prohibited when the transmitter is idle. Since the modem 30a is set to receive mode when not actively transmitting, it is possible to monitor the gain level of the received signal to prepare for the arrival of a burst from the base station. The subscriber station modem 30a does not transmit the AM guard band to the RCC slot. Nothing is needed as the base station defines the frame. Unlike the fixed frequency base station modem 19, the subscriber station modem 30a can transmit or receive data on any of the 26 frequencies selected within the RFU by the CCU 29. Modems have many sources of delay that affect system timing as described above. This delay source includes analog filter delay, propagation delay, FIR filtering delay, and the like. These delays skew the TX and RX frames to each other, so careful consideration must be given to this skew. The delay between the TX SOS signal on line 162 of the base station and the first analog symbol "peak" received at the base station is +7.4 symbols. Therefore, a skew occurs between the TX slot and the RX slot. To correctly decode the input phase, the modem must start sampling about 3.5 symbols before the arrival of the "peak". Therefore, the scoo between the TX SOS signal and the start of RX sampling is about 4 symbols in time length. In a base station, the start of the RX slot occurs about 4T after the start of the TX slot. The start of the RX slot is defined as the time when the first analog sample is captured to detect the first "peak" received. The subscriber station clocks are all derived from the master 80MHz VCXO of the subscriber station timing device (not shown). This VCXO is controlled by an analog line from modem 30a. With this as a reference, all receive and transmit clocks are calculated. Modem 30a provides CCU29 with a 16KHz RX CLK signal on line 172 derived from the input data stream. The CCU29 can detect the unique word in the control channel by itself and determine the frame and slot markers from the unique word and the RX CLK signal on line 172. The AM Hall signal from the signal decoded by the modem tells the CCU29 where to look for the unique word. During the reception period of all slots, modems 19 and 30a perform frequency synchronization acquisition and continue tracking. At the subscriber station, the VCXO is under direct control of microprocessor 141 via a D / A converter. The microprocessor frequency acquisition and tracking algorithm calculates the changes in the VCXO required to maintain synchronization. At the base station, the OCXO on the STIMU35 is fixed and acts as the master clock for the system. Therefore, no frequency shift occurs during reception. During the reception period of all slots, modems 19 and 30a perform bit synchronization on the bit sync scramble of the received data stream. The algorithm is running a bit tracking loop inside the receiver. Microprocessor 141 has control over the 80MHz VCXO or OCXO variable frequency divider (control slot demodulation period only). Within the bit tracking loop, microprocessor 141 changes frequency division to obtain bit synchronization. When receiving an audio channel, the frequency division value has a step size of 0.1% at 16KHz, but this value can change even more by ± 50% during the control slot period. Frame synchronization is processed in completely different ways at base stations and subscriber stations. At the base station, the master SOMF (start of modem frame) is transmitted from the timing device on line 169 to CCU18 on line 175 via modem 19. This is the master SOMF signal used for all transmissions from the base station. From this signal and the master system symbol clock signal (16KHz), the CCU 18 can derive all slot and frame timings. At the subscriber station, frame synchronization is achieved by the CCU29 detecting a unique word in the received RCC data stream. For initial acquisition, modem 30a supplies line 176 with a one-shot approximate frame marker (AM STROBE). During the acquisition period, modem 30A searches for AM HOLE in the RCC, AM HOLE is detected, modem 30a counts its holes for several frames, followed by line 176 to CCU29 at the frame position of AM HOLE. Supply AM STROBE. The CCU29 uses this strobe marker to set up (window processing) an initial frame marker counter that can be updated to accurate frame sync (frame synchronization) by CCU software. This also means that AM HOLE has been detected and RCC has been obtained. Slot synchronization is under the control of CCUs 18 and 29. The signal TX SOS on line 162 and the signal RX SOS on line 163 are commands that cause modems 19 and 30a to start transmitting or receiving slots. These signals are synchronized with the TX CLK signal and RX CLK signal of line 171 respectively. The self-adaptive mode is a loopback state in which the modem enters to adjust the receiver's digital FIR filter coefficient to correct the characteristic degradation of all received analog filters that may occur over time or temperature. .. This analysis is performed by looping back transmitter data through an RF device and receiving known patterns to the receiver. This coefficient is optimized by the 5 constraint La Grangian system. These constraints are (1) received data stream, (2) 0.05T delayed data stream, (3) 0.05T advanced data stream, and (4) data from adjacent superior channels. Streams and (5) data streams from adjacent subchannels. During the adjustment period, the microprocessor 141 supplies a series of 32 symbol length adjustment patterns to the TX FIR filter 131 on line 143. This is done via a FIFO stack (not shown) that is enabled during the tuning mode. Lead / lag is achieved by a receive bit track circuit that skews the two streams by 0.05T. The CCUs 18 and 29 set the modems 19 and 30a to the adjustment mode, and cause the transmitter of the modem to read the special adjustment data from the FIFO stack mounted on the modem. The receiver is advanced / delayed by some tests. When processing is complete, the modem sends a status message to CCUs 18 and 29 indicating that the coefficients have been calculated. At this point, CCU18,29 tests the modem by setting the modem to normal operation, writing out the setting pattern, and issuing commands to RFU21, 31a to perform loopback, return data reading, and effectiveness testing. To do. The modem will be described in more detail in the United States patent application filed on the same day as the United States patent application, the title of the invention "Modem for subscriber RF telephone system", inventor Eric Paneth, David N. Critchlow and Moshe Yehushua. Yes, the disclosure is included here as a related document in this case. RF / IF device and antenna interface The RFU subsystem provides a communication channel link between the modem and the antenna at both the base station and the subscriber station. The RFU function as a linear amplitude and frequency conversion mechanism is transparent to the channel data and modulation characteristics. The antenna interface circuit for the subscriber station is shown in Figure 28. The RFU control logic circuit 192 is coupled to the transmitter antenna 32 and the three receiver antennas 32a, 32b, and 32c by an antenna interface circuit. The RFU control logic circuit 192 further interfaces the transmitter of the modem 30a and the receiver of the modems 30a, 30b, and 30c. In fact, 32 and 32a are the same antenna. The transmitter of the antenna interface includes an upconverter and amplifier circuit 193, a TX synthesizer 194, a power amplifier 196, and a TX / RX mode switch 197. The first receiver RX1 of the antenna interface includes a down converter and amplifier 198, an RX synthesizer 199, and a preamplifier 200 connected to switch 197. Each additional diversity receiver TX_n(n = 2, 3) includes a down converter and amplifier 202, an RX synthesizer 203, and a preamplifier 204. The RFU control logic circuit 192 supplies the following signal to the transmitter of the antenna interface in response to the signal received from the transmitter of the modem 30a. That is, (1) the TX enable signal on line 206 for the TX / RX switch 197 to enable transmission through the transmitter antenna 32, (2) the IF input signal on line 207 to the upconverter and amplifier 193, (3). ) Line 208 power control signal to the upconverter and amplifier 193, (4) clock reference signal of line 209 to TX synthesizer 194, and (5) channel selection signal to line 210 and TX synthesizer 194. The TX synthesizer 194 responds to the channel selection signal of line 210 by feeding line 211 to the upconverter and amplifier 193 with a TX frequency selection signal equal to the difference between the desired transmit frequency and the modem IF frequency. The RFU control logic circuit 192 supplies the following signals to each of the receivers of the antenna interface circuit in response to the signals received from the respective receivers of the modems 30a, 30b, and 30c. That is, (1) the TX enable signal of the line 213 for operating the down converter and the amplifier circuits 198 and 202 in the receive mode, and (2) the automatic gain control of the line 214 to the down converter and the amplifier circuits 198 and 202 (2). AGC) signal, (3) clock reference signal of line 215 to RX synthesizers 199, 203, and (4) channel selection signal to line 216 and RX synthesizers 199, 203. The RX synthesizers 199, 203 become the channel selection signal of line 216 by supplying the RX frequency selection signal equal to the difference between the desired reception frequency and the modem IF frequency to line 217 to the down converter and amplifier circuits 198, 202. respond. The down converter and amplifier circuits 198 and 202 supply the IF output signal to line 218 to the RFU control logic circuit 192 in order to transmit the IF output signal to the receivers of the modems 30a, 30b and 30c, respectively. The transmitter up-converter and amplifier circuit 193 receives the modulated IF signal of line 207, amplifies this signal, and converts it to the selected RF channel frequency. A combination of filters (not shown), amplifiers 196, 197 and level control circuitry (not shown) is used to provide the correct output levels and suppress unwanted signals at imagery and harmonic frequencies. The transmitter output frequency is the sum of the modem IF frequency and the modulation frequency synthesized at the 25 KHz stop from the reference frequency supplied by the modem. The subscriber station's RFU acts as a half-duplex transceiver with the receiver inactive during the transmission period. The burst rate of the transmitter is high enough to simulate full-duplex operation for the user. The assigned frequency channel is the one selected by the base station RPU. The antenna interface circuit of the base station is shown in Fig. 29. The RFU control logic circuit 219 is coupled to the transmitter antenna 23 and the three receiving antennas 34a, 34b, and 34c by an antenna interface circuit. The RFU control logic circuit 219 further interfaces with the transmitter of modem 19 and the receiver of modems 19, 19b, and 19c. (Modems 19b and 19c are diversity modems, not shown in Figure 2) The transmitter of the antenna interface includes an upconverter and amplifier circuit 220, a TX synthesizer 221, a power amplifier 222, a high power amplifier 223, a power detector 224, and a band filter 225. The first receiver RX1 of the antenna interface includes a down converter and amplifier 230, an RX synthesizer 231, a preamplifier 232, and a band filter 233. Each additional diversity receiver RXn includes a down converter and amplifier 234, an RX synthesizer 235, a preamplifier 236, and a band filter 237. The RFU control logic circuit 219 supplies the following signal to the transmitter of the antenna interface circuit in response to the signal received from the transmitter of the modem 19. That is, (1) the TX ON signal of line 239 to the upconverter and amplifier 220 to operate the transmitter to enable transmission by the transmitting antenna 23, (2) to line 240 and further to the upconverter and amplifier 220. IF input signal, (3) reference signal of line 241 to TX synthesizer 221 and (4) channel selection signal to line 243 and TX synthesizer 221. The TX synthesizer 221 responds to the channel selection signal of line 242 by feeding line 243 to the upconverter and amplifier 220 with an RX frequency selection signal equal to the difference between the desired transmit frequency and the modem IF frequency. The level control signal is supplied from the power detector 224 to line 244 to the upconverter and amplifier 220. The RFU control logic circuit 219 supplies the following signals to each of the receiving units of the antenna interface circuit in response to the signals received from the receiving units of the modems 19, 19b, and 19c. That is, (1) automatic gain control (AGC) signal of line 245 to down converter and amplifier circuits 230 and 234, (2) clock reference signal of line 246 to RX synthesizer 231, 235, and line 247 and RX synthesizer. Channel selection signal to 231, 235. RX synthesizers 231, 235 provide the channel selection signal of line 247 by supplying the RX frequency selection signal equal to the difference between the desired reception frequency and the modem IF frequency to line 248 to the down converter and amplifier circuits 230, 234. respond. The down converter and amplifier circuits 230 and 234 supply the IF output signal to line 249 to the RFU control logic circuit 219 in order to transmit the IF output signal to the receivers of the modems 19, 19b and 19c, respectively. The base station and subscriber station RFUs are identical except that an additional high power amplifier 223 is used to increase the transmit power of the base station's RF output. The basic function of RFU in any station is to convert the modulated IF (20.2MHz) signal from the transmitter of the modem to the desired RF transmission frequency of the 450MHz UHF range. The receiving side of the RF device performs the opposite function of down-converting the received 450MHz UHF signal to the 20MHz IF signal. The transmission frequency and reception frequency are offset from each other by 5MHz. The RF device is programmed by the CCU control function to operate at the different frequencies used in the entire system. Generally, the RFU of each base station is based on the given frequency allocation during system initialization. It is set and does not change. The number of RFUs at the base station matches the number of transmit and receive frequency channel pairs supported at the base station. The subscriber station's RFU will generally change the operating frequency for each new telephone connection. The RFU includes a variable AGC and a transmit power level regulator. The AGC gain factor is given by the modem based on the calculation of the receiver processor 141 in the modem. The transmit power level of the subscriber station is calculated by the CCU based on the message received from the base station on the RCC channel and other control parameters. If all slots on one frequency channel are not used, the RFU will send the idle pattern set by the CCU. If a complete frequency channel is not used, transmitters for that frequency can be disabled by CCU software through a modem. The switching time for the diversity switch shall be 50 microseconds or less. It is equipped with 3 antennas and 3 individual RF / IF devices. (1 transmission, 3 reception) Many parts of the base station RFU and antenna interface are the same as described above for subscriber stations. This section focuses on the differences. Base station RFUs and antenna interface circuits operate on a full-duplex basis. All transmitters and receivers typically operate on a 100% duty cycle. In addition, it is economically attractive for the base station to use a low noise figure receiver that operates at the highest possible transmit power and utilizes diversity. The transmitter is designed to operate at the maximum allowed power level without dynamic control. Receiving diversity is embodied by multiple receiving antennas and multiple modems. Base stations normally do not change the operating frequency or transmission power level during normal operation. The transmitter and receiver are fully tuned to each of the 26 channels. The transmitter of the base station antenna interface receives the modulated IF INPUT signal of line 239 from the modem and processes this signal in the same manner as the transmitter of the subscriber station described above. This signal is further amplified to the required power level and waved by the cavity preselector band filter 225 to reduce noise and spurious emission levels at the operating frequency of the coexisting receiver. The base station receiver of the antenna interface is a subscriber, except that cavity preselector band filters 233 and 237 are installed in front of the front end to help eliminate sensitivity degradation caused by coexistence or adjacent transmitters. It is the same as the one described for the station. Low noise preamplifiers are used to further reduce the available threshold signal levels. All antennas 23, 34a, 34b, 34c have 30 dB isolation for any other antenna. Further isolation is provided between the transmitting unit and the receiving unit in order to guarantee an isolation of about 80 dB between the transmitted signal and the received signal. Band filters, preamplifiers, and amplifiers are located near suitable transmit or receive antennas. Diversity reception processing Diversity reception is a channel fade below the permissible threshold. It is used to reduce the probability of fade). The diversity system has the ability to add three branch diversities to the route from the subscriber station to the base station and the route from the base station to the subscriber station. The diversity hardware at both the base station and the subscriber station is a completely new combination of "modem-RFU-antenna", which includes a special diversity combination circuit, three modems and their related RF devices, and an antenna. Have the ability. The diversity combination circuit 33 is shown only in the subscriber station system diagram of FIG. 3, but this circuit also exists in the base station in the same way as the subscriber station and is connected to both modems and the CCU. When operating with diversity reception, the base station or subscriber station uses three receiving antennas that are far enough apart to ensure that the fading characteristics of the received signal are not interrelated. These three antennas supply signals through the three identical receivers of the antenna interface to the RFU control logic, whose IF output goes to different modems for demodulation. The TMS320 microprocessor (diversity processor) of the diversity combination circuit 33 takes the output from the modem and emulates a single modem to provide a more reliable data stream to the rest of the system. The two tasks of performing diversity combinations and making the CCU look like a single modem are the roles of the diversity processor hardware and software. The diversity processor reads the data symbols, AGC values, signal + noise, absolute values, and phase errors (deviation of the detected phase from the ideal 22.5 degree reference vector) of those modems from the three modems. The algorithm used to determine the demodulated symbols uses a majority calculation of the signal-to-noise ratio for each modem to identify the modems with the most appropriate and correct answer. The diversity processor CCU interface register only needs 3 address bits because it does not need the extra registers used in the diversity processing function to carry information. Except, it is almost the same as the register in the modem. Since the I / O capacity of the TMS320 microprocessor is low and most of the processing content can be done with one kind of I / O register at a time, a special register holding the register address required at that time is used. For example, you must read the AGC value from each modem, select the highest value, and write the result to the I / O register of the diversity processor where it can be read by the CCU. Addressing these registers is most effective if the address of the AGC register is first written to the port that is configured on the modem address line. After that, the processor only needs to address the correct modem or microprocessor register bank, which can speed up I / O operations. In a subscriber station diversity system, each modem has its own timing device, and the timing signals used by the three modems in the diversity system do not necessarily have to be in phase. Since the modem clock signals of these three modems are not synchronized with each other, a latch is needed to hold the data symbol output from each modem until the diversity processor reads it. An important function of the diversity processor is to maintain communication between the CCU and the three modems. This communication must be fast enough to meet all of the CCU's requirements without overloading the diversity processor.

[Simple explanation of drawings]

FIG. 1 is a block diagram showing the RF subscriber telephone system of the present invention in general. FIG. 2 is a block diagram showing a preferred embodiment of a base station in the system of FIG. FIG. 3 is a block diagram of a preferred embodiment of a subscriber station in the system of FIG. Figure 4 shows the order of the messages generated by both subscriber stations and the base station to establish a connection between the two subscriber stations. Fig. 5 shows various data processing modules used in the remote control processor device (RFU) in the base station of Fig. 2. Fig. 6 shows the processing of input and output BCC messages by the RPU in the base station of Fig. 2. Fig. 7 shows the processing of input and output PBX messages by the RPU in the base station of Fig. 2. Figure 8 shows the processing of logger messages by the RPU in the base station of Figure 2, Figure 9 shows the map memory of the RPU in the base station of Figure 2, Fig. 10 shows the processing of messages related to the RCC status by the message processing module (MPM) shown in Fig. 5. Fig. 11 shows the processing of messages related to the channel status by the message processing MPM shown in Fig. 5. Fig. 12 is a block diagram of the subscriber terminal interface device (STU) in the subscriber station of Fig. 3. Figure 13 shows the signal interface between the PBX and VCU in the base station of Figure 2, Figure 14 (Sheet 1) shows the signal interface between the STU and VCU in the subscriber station of Figure 2, FIG. 15 is a diagram showing the timing relationship between the PBX-VCU interface signal shown in FIG. 13 and the STU-VCU interface signal shown in FIG. FIG. 16 (Sheet 11) shows the signal interface between the VCU and the CCU in the base station in FIG. 2 and the subscriber station in FIG. FIG. 17 is a diagram showing the timing relationship of the VCU-CCU signal interface with respect to the transmission channel signal shown in FIG. FIG. 18 is a diagram showing the timing relationship of the VCU-CCU signal interface shown in FIG. 16 with respect to the reception channel signal. Figures 19A and 19B show the timing relationship for the transmission and reception voice blocks transmitted between the VCU and CCU in the case of 16-level PSK modulation, respectively. Figure 20A shows the timing and content of input and output data for the receive channel between the VCU and PBX (or STU) in the case of 16-level PSK modulation. Fig. 20B shows the timing and contents of input and output data for the transmission channel between the VCU and PBX (or STU) in the case of 16-level PSK modulation. Fig. 21 (Sheet 5) is a block diagram of the CCUs of both the base station in Fig. 2 and the subscriber station in Fig. 3. Fig. 22 shows the software arrangement function system of the CCU in Fig. 21. Fig. 23 shows the timing diagram for transmitting RCC and 16-level PSK audio data by the transmission bus of CCU in Fig. 22. Fig. 24 is a timing diagram for transmitting RCC and 16-level PSK audio data by the receiving bus of the CCU in Fig. 23. Fig. 25 (Sheet 3) is a block diagram of the modems of the base station in Fig. 2 and the subscriber station in Fig. 3. FIG. 26 shows the signal interface between the CCU, modem, and STU in the base station of FIG. FIG. 27 shows the signal interface between the modem of the base station of FIG. 2 and the subscriber station of FIG. 3 and the RFU. Fig. 28 is a block diagram of the antenna interface circuit for the subscriber station in Fig. 3. FIG. 29 is a block diagram of the antenna interface circuit for the base station of FIG. Description of the sign of the main part 10 ...... Subscriber station, 11 ...... Base station 12 ...... Central station 15 ...... Private station exchange equipment, 16 ...... Mark decoder 17 ...... Single voice code decoder 18 ...... Channel control device 19 ...... Modem 20 ...... Remote control processor device 21 ...... RF / IF processing equipment 22 ...... Antenna interface device 24 ...... PBX call processing device 27 ...... Subscriber station terminal device, 28 ...... Voice code decoding device 29 ...... Channel control device 30a, 30b, 30c ...... Modem 32a, 32b, 32c ...... RF transmitting antenna 33 ...... Diversity combiner circuit 34a, 34b, 34c ...... Receiving antenna 35 ...... System timing device 40 ...... Scheduler module 41 ...... Baseband control channel module 42 ...... PBX module 43 ...... Control console module 44 ...... Logger module 45 ...... Message processing module 46 ...... Database module 48 ...... Message 50 ...... PBX Mail Box 55 ...... PCM code decoder, 57 ...... multiplexer 58 ...... Subscriber control device 59 ...... Transmit and receive FIFO 61 ...... VCU excitation / reception circuit 65 ...... Ring sound generation circuit, 66 ...... DTMF detection circuit 67 ...... Ring generator 68 ...... Timing generator, 107 ...... TX bus 108 ...... RX bus 109 ...... Transmit voice code decoder interface module 110 ...... Send memory module 111 ...... Microcontroller module 112 ...... Outgoing modem interface module 114 ...... Received modem interface module 115 ...... Receive memory module 117 ...... Received voice code decoder interface module 119 ...... Microcontroller Local Bus 120 ...... Send DMA controller 121 ...... Received DMA controller 122 ...... Control / status register 123 ...... Link 126 ...... Symbol byte converter 127 ...... Byte symbol converter 128 ...... Reclocking FIFO stock 129 ...... FIFO stack, 130 ...... clock circuit 131 ...... TX / FIR filter, 132 ...... FIR filter 134 ...... Band filter, 135 ...... Mixer 139 ...... A / D converter 141 ...... Microprocessor 192 ...... RFU control logic circuit, 193 ...... amplifier 194 ...... Synthesizer, 196 ...... Amplifier 197 ...... TX / RX mode switch 198 ...... Amplifier, 199 ...... RX Synthesizer 200 ...... Preamplifier, 202 ...... Amplifier 203 ...... Synthesizer, 204 ...... Preamplifier 219 ...... RFU control logic circuit, 222 ...... power amplifier 223 ...... High power amplifier, 224 ...... Power detector 225 ...... Band filter, 230 ...... Amplifier 231 ...... Synthesizer, 232 ...... Preamplifier 233 ...... Band filter, 234 ...... Amplifier 235 ...... Synthesizer, 236 ...... Preamplifier 237 ...... Band filter