Radio telephone system for subscriber position measurement with diversity transmission

The present invention relates to a two-way wireless communication system. In particular, the present invention relates to a radiotelephone system with a space diversity antenna and time diversity signal transmission for fading reduction and subscriber position measurement.

Wireless communication is diverse, such as signal fading, that is, variable multipath reflection in which the signal level at the receiver causes signal loss, transmission loss that fluctuates over time due to atmospheric conditions, and movement of a mobile receiver that draws obstacles into the signal path. It is adversely affected by fading, which is temporarily reduced for some reason. Signal fading causes poor reception and inconvenience, and in extreme cases causes interruption of call connection.

It is well known that various forms of signal diversity are used to reduce fading. For example, as shown in US Pat. No. 5,280,472, signal diversity mitigates the adverse effects of fading. There are three types of diversity: time diversity, frequency diversity and space diversity.

Time diversity is obtained by utilizing error correction coding in the form of iterations, insets or iterations. Error detection techniques combined with automatic retransmission provide a form of time diversity.

Frequency diversity spreads signal energy over a wide bandwidth to deal with fading. Frequency modulation is a form of frequency diversity. Another form of frequency diversity is code division multiple access (CDMA), also known as spread spectrum. Since it is originally a wideband signal, the CDMA signal is less susceptible to fading than a narrowband modulated signal. In general, since fading occurs only in a part of the radio frequency spectrum at any time, the spread spectrum signal is inherently less susceptible to the adverse effects of fading.

Space diversity is achieved by transmitting or receiving the same signal through two or more antennas separated from each other. Space Diversity provides an alternative signal path for protection when one signal path undergoes fading at any given time. Since the receiver receives the same signals separated from each other with a slight transmission delay, space diversity also occurs for some time. Differences in transmission delay require the receiver to be able to distinguish between incoming signals. One solution is to use multiple receivers with one receiver assigned to each incoming signal. For example, U.S. Pat. No. 5,280,472 is known to introduce a smaller delay than an information symbol into a space-diversity multi-antenna CDMA system to produce an artificial multipath time diversity signal with a two-chip delay or a few-chip delay. .. The CDMA system can distinguish between multiple equal signals arriving at the receiver with different propagation delays of two chips or more. Such a receiver is known as a Rake receiver. However, prior art systems require multiple CDMA receivers, one for each received CDMA signal. It is desirable to create a time-diversity CDMA signal reception system that does not require such multiple CDMA receivers.

The measurement or calculation of the position of the mobile device is known. Depending on the system, the position of the mobile device is measured with a fixed antenna. In other systems, the mobile unit calculates the position of its own station from multiple received signals. For bidirectional systems, communication links allow location data to be exchanged between both mobile subscribers and fixed systems. A variety of known systems use satellites or multiple antennas to transmit the location information of mobile station subscribers. For example, a multidirectional receiving antenna can be used for triangulation of the position of a mobile transmitter. In such a system, the fixed receiver calculates the position of the mobile station subscriber, and in other systems, the mobile subscriber station calculates the position of its own station from the received signal. For example, the Global Positioning System (GPS) is a double-entry satellite system that supplies signals that allow mobile subscriber stations to calculate their position on latitude and longitude. However, both satellite systems and GPS receivers for receiving satellite signals are expensive.

The combination of a GPS receiver and a cellular phone is shown in US Pat. No. 5,223,844. Such a combination provides, for example, a security warning service for deterring passenger car theft, that is, a service useful as a warning service that also activates a security service at the position of the passenger car by transmitting an alarm.

<patcit num="1"><text>USP 5 260 943</text></patcit>

<p> In general, it is desirable to provide a system that combines telephone or data services and location measurement at a low cost.</p><p> Time division multiple access (TDMA) in various combinations with CDMA and space diversity antennas to provide a variety of systems that are resistant to fading, reduce receiver costs, and allow mobile station subscribers to make position measurements. It is desirable to provide a system of time diversity signals used.</p>

<p> The present invention is embodied as a wireless communication system using time diversity and space diversity to reduce fading and simplify receiver design. Further, in the present invention, in order to realize a wireless communication system having a function of specifying the position of a subscriber station by using the same signal as the original communication signal for wireless communication, the time division signal is code-division (spread spectrum). It is embodied as a wireless communication system that multiplexes and supplies to a space diversity antenna.</p><p> More specifically, for example, data packets capable of carrying telephone voice signal traffic are transmitted from three different antennas at three different time points. Therefore, the receiver receives the same data packet from three different antennas at three different time points. The receiver uses the best data packets or a combination of those data packets to reduce the effects of fading.</p><p> In addition, the receiver uses the absolute time of incoming arrival and the extrapolated relative time of the above three data packets in order to calculate the distance from the above three transmitting antennas. First, the absolute distance to one antenna is calculated by the time required for the round-trip message. Next, the incoming time of the data packet from the other two antennas based on the universal time is expressed as the relative distance compared with the distance to the first antenna. Since all three antennas are at known fixed points, the receiver should be the intersection of three constant distance curves (a circle in two dimensions, the intersection of three spheres in three dimensions) and its own position. calculate. Alternatively, the mobile subscriber station sends raw delay measurement data to a fixed station or location measurement service center where the location of the mobile subscriber station is calculated.</p><p> More specifically, the present invention is embodied in a system using CDMA for modulation of TDMA signals transmitted from three space diversity antennas. In the first embodiment, the TDMA signal is used for multiple repeated transmissions of the same data packet from a transfer station with three space diversity antennas. In the second embodiment, the TDMA signal is used for multiple repeated transmissions of the same data packet from three transfer stations, each equipped with one of three space diversity antennas. The data packets may be either identical to each other or carry substantially the same information, but are modulated by different spreading codes or different segments of the same spreading code.</p>

<p> It is possible to provide a system that combines telephone service and subscriber position measurement at low cost.</p>

[System Description-First Example (Figs. 1, 2, 3, 8, 9)]

In the first embodiment of the present invention shown in FIG. 1, a mobile station user equipped with an antenna 10 is coupled to a CDMA transfer station 14. The CDMA transfer station 14 includes an antenna T16, an antenna A11, an antenna B12, and an antenna C13. Antennas A, B and C are mounted on separate structures or on a single mast as shown. The only physical requirement is that the spacing between these antennas be sufficient to achieve uncorrelated space diversity. A quarter wavelength interval is sufficient, but a minimum of 10 wavelength intervals is preferred. At 1GHz, 10 wavelengths are about 30 feet, and at 5GHz, 10 wavelengths are about 6 feet.

A mobile subscriber station antenna 10 (also referred to herein as a user terminal antenna, a subscriber station antenna, or simply antenna U) is coupled to antennas A, B, and C with a bidirectional radio link. The CDMA transfer station 14 is appropriately switched and connected to the public switched telephone network by a bidirectional wireless link via the antenna T.

During operation, the forward channel telephone voice traffic received by antenna T in the form of a data packet is transmitted at antenna A during time slot 1 and is repeated at antenna B during time slot 2 and at time slot 3. It is further repeated at antenna C during the period. All three repetitive data packets are sequentially received by antenna 10. In the opposite direction, data packets representing telephone voice traffic transmitted from antenna 10 are received at antennas A, B and C at about the same time. The CDMA transfer station 14 retransmits this reverse received packet to the public switched telephone network via the antenna T.

Figure 2 shows the differences between the support networks, namely the public switched telephone network 20, the telephone exchange center and central processing system device 22, and the CDMA transfer stations 26, 28, 30, 32, 34, 36 and 38. It is a schematic diagram of the system of this invention including the interconnection.

The user of the CDMA subscriber station 42 is coupled from the antenna 10 to the CDMA transfer station 38 via antennas A, B and C. The antenna T39 of the CDMA transfer station 38 carries the wireless TDMA telephone voice traffic to the antenna 25 of the base station 24. Each of the other CDMA transfer stations is connected to the telephone exchange center 22 by various interconnection means. The connection means W between the TDMA base station 24 and the CDMA transfer station 36 is a radio means having a TDMA channel configuration having six TDMA slots. This wireless TDMA distribution interconnect WE can be configured with a commercially available wireless local loop system such as the "Ultraphone" digital radiotelephone system released by InterDigital Communications. The TDMA time slot configuration is carried via the transfer station and becomes the time slot configuration of the slotted CDMA signal on the output side. The connection means WE is the same as the connection means W except that it has four W modules operating in parallel to provide basic connectivity for 24 audio channels. The connection means F uses an optical fiber cable that connects the telephone exchange center 22 to the CDMA transfer station without going through the radio base station. Since the connection means F (optical fiber cable) includes a modem having a TDM / TDMA channel configuration similar to W and WE, an interface with the transfer station can be easily obtained. The connection means FT (optical fiber cable that carries standard T1 multiplexing) between the telephone exchange center 22 and the CDMA transfer station 30 is an optical fiber cable that uses a standard T1 multiplexer as a channel combination means. Therefore, the transfer station that handles the WE connection means can easily adapt to the operation with the FT connection means. Connection C (coaxial cable) to CDMA transfer station 26 and connection CT (coaxial cable carrying T1 standard multiplex) to CDMA transfer station 28 are cable means that function similarly to F and FT, respectively. The connection means L to the CDMA transfer station 36 is a conditional electric line that carries a data stream up to 100 kb / s having the same configuration as the wireless TDMA connection means W. Connection means LE (not shown) Uses four conditional power lines to function in the same way as the connecting means WE. The connection means PG to the CDMA transfer station 34 is a gain function that interfaces with the transfer station.

A flexible fast response and an economical solution are achieved by using a combination of wireless and fiber optic cable media for connection to the transfer station and a common output air interface between the transfer station and the CDMA user terminal. It is also possible to use a normal telephone line adapted to handle 64 kb / s to 100 kb / s instead of the TDMA radio input to the transfer station. Also, connecting the input side of the transfer station to the output of the gain module is very cost effective. Since the air interface is the same for all of these interconnects, this extended idea is a cost-effective solution and a transient transfer medium.

In the system diagram of FIG. 3, telephone voice traffic via the public switched telephone network 20 is connected to a TDMA base station 24 having a TDMA signal transmission / reception antenna 25. Multiple CDMA transfer stations 44, 46, 48, 50 and 52 provide radiotelephone services to multiple subscribers 45 and 47. Each CDMA transfer station includes an antenna T for receiving TDMA signals and separate antennas A, B and C for communication with mobile station subscribers 45 and 47. For example, TDMA base station 24 has a radius of 35 miles covering a large number of CDMA transfer stations. Each CDMA transfer station typically has a reach of 5 miles and is separated by 3 miles to form a cellular coverage throughout the region. The subscriber station 45 communicates with the CDMA transfer station 46, and the subscriber station 47 communicates with the CDMA transfer station 50. As a subscriber moves within the system, another CDMA transfer station sends and receives signals to and from that subscriber station.

The alternative embodiment utilizes the high degree of connectivity described above to further disperse the three antennas used to achieve transmit space diversity. Wider distribution allows for compensation for multipath fading as well as fading due to communication failures. For example, when a CDMA user (antenna 10 in FIG. 1) goes behind a building or hill, signals from all three space diversity antennas of one transfer station are faded.

However, if the energy in each time slot is transmitted from different transfer stations as shown in FIG. 4, there is a high probability that all three transfer stations will not block at the same time. Therefore, the effects of fading due to obstacles can be randomized and approximated by multipath fading. Randomization is achieved by having the central controller assign different time slots to each other during the call setup process. When put into production using W or WE connection means, the capacity between the base station and the transfer station is hardly affected, but the number of TDMA receivers increases. However, there is also a diversity improvement in the link from the base station to the transfer station. In general, the impact on other power line connecting means is even smaller. The main advantage of using multiple transfer stations as the transmit diversity source is the evaluation of the signal quality from each transfer station on the user CDMA receiver and the individual time slots when a better quality link is found. It is possible to request the channel switching of the above, and it is possible to make a highly reliable and smooth transition when the user passes through one area.

[System Description-Second Example (Figs. 4, 5, 6 and 12)]

Figure 4 illustrates a radiotelephone distribution system with advanced space diversity. Similar to the previous example, the mobile user antenna 10 is coupled to the antenna A during the time slot 1, the antenna B during the time slot 2, and the antenna C during the time slot 3. However, antennas A, B and C are mounted on separate CDMA transfer stations 54, 56 and 58, respectively. More specifically, the antenna A60 is provided at the CDMA transfer station 54, the antenna B68 is provided at the CDMA transfer station 56, and the antenna C64 is provided at the CDMA transfer station 58. These transfer stations 54, 56 and 58 are coupled to the TDMA wireless digital telephone system via antennas 62, 70 and 66, respectively. The signal received from the antennas A, B, and C by the subscriber station antenna 10 is the same as the received signal having the configuration shown in FIG. However, since the antennas A, B, and C are located at the individual transfer stations 54, 56, 58, respectively, and separated from each other, the signal diversity is greatly improved in both transmission and reception.

The system configuration of FIG. 6 is the same as that of FIG. 2 except that each CDMA transfer station has antenna B or antenna B or C. For example, the CDMA transfer station A108 includes another antenna A109. The CDMA transfer station 106 has an antenna B107. Similarly, the CDMA transfer station 104 has an antenna C105. Therefore, the antenna 10 of the CDMA subscriber station 112 receives signals from each of the CDMA transfer stations 108, 106 and 104. These received signals are time division multiplexed signals in the sense that only one of the antennas A, B or C is transmitting to the antenna 10 at any time. However, during the transmission period, antennas A, B, and C supply code division multiple access to other users.

In this embodiment, each transfer station has only one type of antenna, namely antenna A, antenna B or antenna C. The system layout covering the service area is shown in Figure 5. As in the previous example, the public switched telephone network 72 is coupled to a TDMA base station 74 with a transmitting antenna 75 that covers an area about a radius of about 35 miles. Throughout the service area, the CDMA transfer stations are spaced in one direction 84 from each other and in the other direction 86 are arranged to cover the service area. Regular placement is shown for illustration. In practice, the CDMA transfer station is arranged to provide a range of communication that keeps multiple subscribers 88, 90 within the reach of the A, B and C antennas. For example, the CDMA transfer stations 76 and 82 are antenna A type, the CDMA transfer station 80 is antenna C type, and the CDMA transfer device 78 is antenna B type. Thus, subscriber 88 receives signals from CDMA transfer stations 76, 78 and 80, and subscriber 90 receives signals from CDMA transfer stations 82, 78 and 80.

The time slot configuration for use in the present invention is shown in FIG. Use six time slots. Time slots 1 and 2 are for reception, followed by time slot 3 for subscriber station transmission, followed by time slot 4, which is also used for reception. During time slots 5 and 6, the CDMA receiver means scans transmissions from other transfer stations.

[Call settings]

If line setup or transfer is required, the base station assigns base station frequency and transfer station frequency pairs, slots, and PN sequences. It then sends to the forwarding station all the allocations and designations of which subscriber will use the line. During the call setup, the transfer station transfers the slot and PN sequence allocations to the desired subscriber station. See, for example, Figure 17, which associates TDMA time slots 1 through 8 with users A through F, respectively. In a given time slot, eg time slot 2, the message to user B contains synchronization information 1701, common control data 1702 for system-wide functionality, individual control data 1704, and dedicated user traffic 1705 for user B. .. Dedicated user traffic 1705 is used to send signaling information and initialization data during the call setup period.

[Forward route]

Signal compression, decompression, and forward error correction (FEC) are performed at the base station. In the forward direction (toward the subscriber station), the base station continuously transmits, but the information in each slot is directed to a specific subscriber station.

For example, a base station transmits information on frequency fa during slot 1. The transfer station receives the information by demodulating the signal of frequency fa and reproducing the information only at the symbol level or the bit level during the period of this slot 1. The transfer station does not perform any decryption (ie, error correction, compression or decompression). Therefore, the transfer station design is simplified by receiving a coded signal from the TDMA base station. After reproduction at the symbol level, the received TDMA signal is combined with the assigned PN sequence and retransmitted from the transfer station as a CDMA signal at frequency fp without intentional delay. The transfer station stores this information received from the base station in the buffer memory. At the end of antenna A transmission, the chain of PN signals is modulated by the above information accumulated in the buffer and transmitted to antenna B via an appropriate transmitter. Therefore, using the same PN sequence, an information signal that is the same but contains an increment of a predetermined number of chips is transmitted by the antenna B. The relative position or the phase of the PN sequence with respect to the transmission information is different. At the end of the first iteration, a third read in the time slot buffer is made to form a third iteration of the information, which modulates the PN sequence chain, also in different phases via the appropriate transmitter. Transmit to antenna C.

[Subscriber station processing]

A subscriber station using the correct CDMA code receives the same content three iterations of a data packet from three antennas located at different locations during each period of the three slots containing the information signal iteration. Receive with. The subscriber station then compares the three reception results and selects the one with the best quality based on error rate, phase distortion, signal-to-noise ratio, and so on. In this way, space diversity transmission can be achieved. Only one antenna is required at the subscriber station. The subscriber station demodulates and decodes the signal, corrects errors, decompresses, and so on. A maximum likelihood combiner can be used to combine signal powers from all three time slots. Ideally, the energy of the received data packet is combined by the maximum value method before the minimum judgment.

During the third time slot T3, the subscriber station returns to the transfer station using the same PN sequence as when it was received. This PN sequence may be extracted from the reception result (after reproduction) or may be locally generated based on the original code received during the call setup period. Since the subscriber station does not transmit during the reception period, neither a diplexer nor a notch filter is required. A simple T / R (transmission / reception) selector switch is used to switch the transmission / reception of the antenna. Only one receiver is required for the subscriber station to achieve tri-branch diversity. The three chains required by the rake receiver are not needed in this invention.

It also provides the benefits of triple time-space redundancy with frequency protection provided by the extended spectrum without compromising capacitance. A three-branch diversity usually achieves a reduction of at least 10 dB (10x ratio) per deep fading. The interference level is tripled by three repeated transmissions of the same information signal, but the transmitter power level is reduced by a factor of 10 (10 dB) as the fading is reduced by 10 dB. Therefore, the amount of interference as a whole is reduced by a rate of 10/3 or by 5 dB. Since the link from the transfer station to the subscriber station operates in the self-interference mode, it is possible to use the subscriber lines at the same time, which is about three times as much as when the diversity is not used.

[Return route]

In the opposite direction (direction from the subscriber station to the transfer station), the three receiving devices are connected to the three antennas of the transfer station, respectively, to form a conventional three-branch space diversity. The above analysis of interference and the number of available lines is suitable for reverse transmission as well as for forward transmission, except that the information is transmitted only once and received simultaneously by the three base station antennas.

The present invention can increase the number of subscribers per frequency wave and is cost efficient. First, the subscriber station requires only one receiver. Second, the subscriber station does not need a diplexer. Third, the transfer station does not require any decoding or recoding of the signal. On the other hand, since the space diversity in the opposite direction is used, the number of subscriber stations per transmitter is the same, and the number of subscribers per receiver increases. On the contrary, the noise of the subscriber stations can be increased even if it is not fully utilized by increasing the number of subscriber stations.

The signal received by the transfer station from the subscriber station is returned from the transfer station to the base station in the same time slot without intentional delay (symbol-level or bit-level playback, without decoding). There is no additional delay in the practice of the present invention as long as the slot is in the same TDMA frame, or at least one frame period of the slot is used from the base station to the transfer station.

[Transfer Station-First Example (Figs. 8, 9 and 15)]

The CDMA transfer station receives a TDMA input on antenna T. The output side of the transfer station antennas A, B and C uses a CDMA configuration to reach a large number of subscribers in a relatively densely populated area. CDMA has several attributes that are desirable for this application. Broadband signals are inherently strong in multipath environments and are resistant to intentional or natural interference. The likelihood that selective fading will suppress the entire spectrum decreases with increasing transmission spectrum. High chip speed, or increased TW product, reduces the amount of anti-fading margin required to achieve the desired performance level.

Spread spectrum signals are inherently equipped with anti-multipath protection for anti-fading protection. However, the statistical model does not take into account the frequency of fading or the connection time. The specific terrain at each point and the degree of change in that terrain with respect to the receiver determines the actual fading pattern. For small cells with low antennas, the difference in path length of strong signals is likely to be small. The result is flat fading. That is, a spectrum spanning 10 to 15 MHz causes fading at the same time. Therefore, unless a spectrum of at least 25 or 35 MHz is available, the original anti-multipath protection characteristics of spread spectrum signals cannot be utilized for anti-flat fading protection. Also, it often does not result in multipathing with sufficient delay to take advantage of the additional rake receiver. Even if it does occur, the use of natural or artificial multipath requires an additional receiver / correlator in the CDMA user terminal. Therefore, in order to maintain reliable operation using only CDMA, the required additional margin for link power allocation, especially when the mobile user stops at one of the null points or the fixed machine user makes a small amount of position terrain. It is necessary to set the margin to at least 15 dB in case of moving.

The present invention utilizes another important property of spread spectrum systems, namely interference resistance, as a countermeasure for difficult multipath environments. The capacity of the CDMA system is limited by the amount of interference received by the desired receiver. The actual value of the transmitted data rate does not matter if the TW product is large enough to extract the desired signal from the interference. Therefore, in the present invention, the transmission information speed is increased in order to realize a transmission triple diversity that allows the transmission signal to be repeated three times from three different antennas and allows a 10dB reduction in the transmission power margin per high performance link. .. Therefore, even if the interference to the link is further added, the adverse effect can be easily overcome by the CDMA processing gain. That is, in high quality systems, the advantages from triple diversity far outweigh the drawbacks associated with increased interference.

A block diagram of the transfer station according to the first embodiment of the present invention is shown in FIG. 8 for forward channels. Connect the TDMA antenna 916 to the TDMA receiver 800 via the transfer receive switch 918. The output of the TDMA receiver 800 is connected to the demultiplexer 802 and the output is stored in the time slot buffer 806. The time multiplexer 808 accesses the contents of the time slot buffer 806 and supplies data packet output to a plurality of CDMA encoders 810 for antenna A transmission. The time multiplexer 808 also supplies data packet outputs to multiple CDMA encoders 812 for antenna C transmission. Similarly, the time multiplexer 808 supplies data packet outputs to multiple CDMA encoders 814 for antenna B transmission. Each is equipped with a plurality of multiple CDMA encoders 810, 812 and 814 corresponding to CDMA transmitters 816, 818 and 820, respectively. These CDMA transmitters are connected via antennas 822, 824 and 826 for antenna A transmission, antenna B transmission, and antenna C transmission, respectively.

The coordination and coordination of the TDMA receiver 800, the time slot buffer 806, the time multiplexer and the CDMA encoder are controlled by the synchronization and control device 804. The synchronization and control device 804 causes the plurality of CDMA encoders 810, 812 and 814 to include a position display (ID) indicating a specific transfer station in the transmission signals from the transmission antennas A, B and C.

The transfer station of FIG. 8 also includes a CDMA receiver and TDMA transmitter 900 whose details are shown in the block diagram of FIG. The TDMA transmitter is connected to the antenna 916 via the transmit / receive selector switch 918, and the CDMA receiver is connected to the antenna A, antenna B and antenna C via their respective diplexers as shown in more detail in FIG.

FIG. 9 is a block diagram of a transfer station illustrating the configuration of the processing signal in the reverse channel. Antennas A, B and C, indicated by reference numbers 822, 824 and 826, respectively, connect to CDMA receiver A902, CDMA receiver B904 and CDMA receiver C906, respectively. The output of each CDMA receiver A, B, and C is supplied to the maximum likelihood combiner 908, and the output is supplied to the memory buffer and the time slot multiplexer 910. The TDMA reception and CDMA transmission device 828 corresponding to the block diagram of FIG. 8 is connected to the other terminal of the transmission / reception switch 918.

FIG. 15 illustrates the antenna configuration of a forwarding station that allows antenna A, antenna B, and antenna C to be shared between TDMA and CDMA transmit and receive signals. The modulator 1502 is connected to the diplexers 1510, 1514 and 1518, which are connected to the antenna A1512, the antenna B1516 and the antenna C1520, respectively, via the time multiplexer 1503. The other inputs of the diplexers 1510, 1514 and 1518 are connected to the outputs of the demodulators 1504, 1506 and 1508, respectively.

During the operation of FIG. 8, the TDMA signal received by the antenna 916 is demultiplexed and stored in the time slot buffer 806. A data packet for a given subscriber is selected by the time multiplexer 808 during time slot 1 and the CDMA signal is encoded by one of the plurality of encoders 810 and transmitted from antenna A. The same packet is reselected by the time multiplexer 808 and the CDMA signal is encoded by one of the plurality of encoders 812 and transmitted from antenna B during the time slot 2. Finally, the same data packet is then selected by the time multiplexer 808, encoded by one of the plurality of encoders 814, and transmitted from antenna C during time slot 4.

See FIG. 9 for the reverse direction, CDMA transmissions from the subscriber station are received on antennas 822, 824 and 826 at about the same time during time slot 3. Each of the CDMA receivers 902, 904 and 906 receives the same data packet. The maximum likelihood combiner 904 combines power from all three time slots before a difficult decision. Generally, the signal with the highest intensity and no error is selected. After selection, the data packet is held in the memory buffer and time slot multiplexer 910 and waits for transmission from the TDMA transmitter 914 via antenna 916 to the appropriate time slot.

[Transfer Station-Second Example (Fig. 12)]

The transfer station according to the second embodiment of the present invention is shown in FIG. This transfer station is the same as the transfer stations in FIGS. 8 and 9 except that it has only one CDMA antenna A, B or C. More specifically, in FIG. 12, the antenna 1200 is connected to the TDMA receiver 1204 via the transmission / reception selector switch 1202. The output of the TDMA receiver 1204 is demultiplexed by the demultiplexer 1206 and stored in the time slot buffer 1208. The data packets stored in the time slot buffer 1208 are time-multiplexed by the multiplexer 1210 and supplied to one of the plurality of CDMA encoders 1212. The encoded CDMA signal is amplified by the CDMA transmitter 1214 and guided to antenna A1228 via the diplexer 1218.

Antenna A1228 also receives CDMA signals. To do this, a CDMA receiver 1226 is connected to antenna A1228 via a diplexer 1218 to supply received data packets to the combiner and time slot buffer 1224. The time multiplexer 1222 extracts the data packet in the time slot buffer 1224 and forms a time multiplex signal to the TDMA transmitter 1220. The TDMA transmitter 1220 is connected to the antenna 1200 via the transmit / receive selector switch 1202. The operation of this transfer station is controlled by the synchronization and control device 1216, which includes its own station location display (ID) and call setup parameters.

During operation, the transfer station receives the TDMA signal on the antenna T1200, demodulates the signal on the TDMA receiver 1204, demultiplexes it on the demultiplexer 1206, and stores it in the time slot buffer 1208. This data packet in time slot buffer 1208 is transmitted from antenna A during time slot 1. To that end, the time multiplexer 1210, CDMA encoder 1212 and CDMA transmitter 1214 read their respective data packets from the time slot buffer 1208 and encode the CDMA encoded signal to antenna A with the appropriate data packets. In the opposite route, the CDMA receiver 1226 simultaneously receives signals to antennas A, B and C in the entire time slot. The received data packet is demodulated with each PN code and stored in the time slot combiner buffer 1224 to which a separate time slot is assigned to each user. Next, the data packet is time-multiplexed by the multiplexer 1222 and transmitted from the antenna 1200 by the TDMA transmitter 1220 via the transmission / reception selector switch 1202.

The transfer station is a conversion point that converts a TDM / TDMA signal into a CDMA signal. CDMA signals, when properly designed, perform well against multipath interference. The input side of the transfer station is part of the structural distribution network. It is basically a relay point in the network, that is, the address to the CDMA end user also includes the address of the intermediate point (transfer station). In the general case, the CDMA end user travels and accesses the network via other transfer points, so it is necessary to provide the ability to give a transfer station address independent of the CDMA user's address. For fixed subscriber stations such as TDMA subscriber station 40 in Figure 2, this is not a problem except for backup route provision or anti-fading protection.

A suitable input network includes a large number of base stations, transfer stations and TDMA user stations as shown in FIG. Any time slot of any frequency can be assigned to any TDMA user or transfer station. In order to reduce the cost of the transfer station, it is proposed that when a CDMA user is connected via a specific transfer station, any other CDMA user assigned to that transfer station will also be allocated to the time slot of the same frequency as the user. To do. By properly managing this allocation, the number of TDMA radio elements can be significantly reduced. The base station 24 or telephone exchange center and central processing unit 22 manages radio resources and allocates frequencies, time slots and PN codes to ensure efficient use of spectrum and radio equipment. All frequencies, time slots and PN codes are assigned during the initial call setup.

The local transmission on the output side of the transfer station is CDMA, but each subscriber station is assigned a specific time slot of the time division signal. Therefore, the individual information speed increases with the number of time slots. However, the overall data rate for all subscribers remains the same, the overall transmit power for all signals remains the same, and is only redistributed. Since the individual time slots are turned off when there is no activity, the transmit power is reduced by about 3 dB for voice traffic. Since the same information is transmitted three times, the average transmission power increases by 5 dB. Therefore, the total value of the transmission power from each transfer station increases by 5dB by three transmissions, but can be reduced by 10dB by improving the diversity, so that a total reduction of 5dB in average power can be obtained. Overall, interference over other cells is reduced by 5 dB.

The base station (24 in Fig. 2) or the telephone exchange center and the central processing unit (22 in Fig. 2) also perform channel switching processing. There must be at least four time slots to gain diversity on the CDMA side, and one time slot for the CDMA receiver for scanning other transfer stations. The four time slots can only provide double diversity. According to the five time slots, the desired level of triple diversity can be achieved. Of course, by adding an additional receiver to the CDMA user terminal, parallel synchronization is possible to obtain a better synchronization signal. However, adding another receiver to the CDMA user terminal is a costly solution. Therefore, in the three time slots, there is only double diversity and there is no channel switching. The four time slots allow triple diversity for fixed CDMA subscribers and dual diversity for mobile CDMA subscribers. With more than six time slots, you have the opportunity to add flexibility to your channel configuration. FIG. 7 shows a CDMA user terminal time slot configuration for six time slots.

A triple antenna configuration in a transfer station is triple because it is used for the return link by simultaneously receiving a single burst from each active subscriber station on all three antennas in the allocated time slot to that subscriber station. Achieve space diversity as well. The overall timing configuration for forward and reverse CDMA links in the transfer station is shown in Figure 10A. Six time slots are shown for illustration, but as mentioned above, any number of time slots of 3 or more can be put into production, and the reasonable upper limit is about 32.

The order of transmission of the three active time slots can be distributed over the total number of time slots, and three or more time slots are also available. Mie diversity can reduce transmission power from CDMA user terminals by at least 5dB, and perhaps even more, but 5dB is comparable to forward link performance. In any case, the transmit power is controlled and maintained at a minimum level to maintain a high quality link. At higher frequencies, some antenna uncorrelation can be achieved even with smaller radios or areas. Therefore, the same transmission space diversity time diversity method used for forward links can be applied to reverse links. Significant improvements can be achieved with double diversity in most operating environments.

Each transfer station continuously transmits spread spectrum channels for synchronization and control. The synchronization and control channels specify specific transfer stations and manage user terminals throughout the period they are assigned to those transfer stations. Its synchronization and control channels carry no user traffic most of the time. The synchronization and control channels can consist of narrowband channels that are easy to capture and track. The information holding portion of the control signal has a pre-allocated time slot and includes system messages and signaling messages to all users assigned to a specific area covered by the transfer station. The processing gain is sufficient to allow the transfer station to include several time slot-arranged CDMA signals transmitted in parallel, thereby allowing sharing of the antenna array. Only one synchronization and control channel is required for a multi-slot CDMA module that integrates in a single location.

[Subscriber Bureau (Fig. 13)]

A block diagram of the subscriber station according to the present invention is shown in FIG. Antenna 1300 is connected to CDMA receiver 1304 via transmit / receive selector switch 1302. The output of CDMA receiver 1304 feeds data packets to data buffers 1306, 1308 and 1310. The combiner 1314 selects and combines the data held in buffers 1306, 1308 and 1310, supplies the output to the DA converter 1316, decompresses the compressed signal with the decompressing means in the converter, and outputs the audible frequency. Produces. The analog audible frequency input is supplied to the AD converter 1322 with data compression means. The output of the AD converter 1322 is a digital audible frequency signal sample assembled into data packets in memory buffer 3120. The CDMA transmitter 1318 encodes with the contents of the memory buffer 1320, and supplies the CDMA encoded signal to the antenna 1300 via the transmission / reception selector switch 1302. The CDMA subscriber station is synchronized by the synchronization and timing controller 1312, that is, the controller that also measures the signal delay for position measurement as described below.

In the forward direction, the CDMA receiver 1304 receives three identical data packets of each other, the first of those data packets into memory buffer 1306 during time slot T1 and the second in time slot T2. The third one is stored in the memory buffer 1308 during the period and the third one is stored in the memory buffer 1310 during the time slot T4. The combiner 1314 selects one or more of the stored contents of these memory buffers to be combined or selected as the best received data and supplies them to the DA converter 1316. This system is less susceptible to fading by using three time and space diversity data packets, and requires complex signal strength averaging because it uses the same receiver to demodulate all three samples. do not do.

In the opposite direction, the analog audible frequency input to the AD converter 1322 with built-in digital compression algorithm is converted to a data packet into buffer 1320. During the period of time slot T3, the CDMA transmitter 1318 encodes according to the contents of the buffer 1320 and transmits it as a CDMA signal from the antenna 1300.

Simplification of CDMA user terminals is a major consideration in this system. The main simplification is the ability to share time divisions of receivers, especially correlators with different functions. The ability to send and receive at different times simplifies the production of small portable user terminals. A single receiver sequentially receives three space diversity signals in three different time slots, then moves to another code to search for improved signals from other transfer stations. The same receiver is also used for capture and tracking. Since the user terminal does not receive during the time slot period during transmission, a diplexer and a notch filter are unnecessary. Since only one PN code is required at each time point, the PN code generation process is greatly simplified. Baseband processing can be achieved with a relatively slow ordinary processor.

In the time slot when the user terminal is not transmitting or receiving, the receiver can freely search for synchronization and control channels from other transfer stations. When the user terminal identifies a better synchronization and control channel than the one assigned to its own station, the user terminal sends a message to the network control device to the effect that the channel switching destination candidate has been identified. The network controller uses this message together with other information to determine the channel switching execution. The network control device sends a channel switching message to the target communication destination. The specific symbols of the codes to be searched by the user terminal are supplied from the network central control device via the transfer station accommodating those codes in the control channel.

[Time slot configuration (Figs. 10A, 10B, 11A, 11B, 17)]

Figure 10A shows the time slot allocation that multiplexes six simultaneous calls. Time slot allocation 1002 for transmission and time slot allocation 1004 for reception are illustrated. The items to be filled in each box are activities during the response time slot period. During time slot 1, antenna A transmits T1 to user 1, antenna B transmits T6 to user 6, and antenna C transmits T4 to user 4. At the same time, antennas A, B and C receive R5 from user 5. During the next time slot 2, antenna A transmits T2 to user 2, antenna B transmits T1 to user 1, and antenna C transmits T5 to user 5. At the same time, antennas A, B and C receive R6 from user 6. Continuing with reference to the chart of FIG. 10A, antenna A transmits T3 to user 3, antenna B transmits T2 to user 2, and antenna C transmits T6 to user 6 during time slot 3. At the same time, antennas A, B and C receive R1 from user 1.

Note that none of antennas A, B or C is transmitting to user 1 during time slot 3. During that period, user 1 is transmitting and the transfer station is receiving the signal from user 1 through all three antennas. However, during the time slot 4, a third transmission is made to user 1. That is, during the time slot 4, antenna A transmits T4 to user 4, antenna B transmits T3 to user 3, and antenna C transmits T1 to user 1. Time slots 5 and 6 are not used directly for data transfer to and from user 1. The time slot allocations shown in FIGS. 10A, 10B, 11A and 11B are consistent with FIG. 7, ie User 1 receives during the time slots 1, 2 and 4 and sends during time slot 3. ing. The pattern can be seen from the time slot allocation in Figure 10A by looking for the time of transmission of T1. Transmission of T1 appears at antennas A, B and C in time slots 1, 2 and 4, respectively. There is no transmission to T1 during the period of T3, but reference to receive time slot allocation 1004 shows that R1 is received from user 1 during the period of time slot 3. Since three transmissions and one reception occur simultaneously in any time slot, at least four addressable CDMAPN code sequences are required.

In this way, time division multiplexing is used in the sense that successive time slots carry data destined for different users. Also, code division multiplexing is used in the sense that a large number of PN code sequences enable simultaneous communication with a large number of users during each period of time division multiplexing. The result is a time-division-multiplexed code-division-multiplexed signal.

Figure 10B shows the time slot allocation for multiplexing 12 simultaneous calls. Time slot allocation 1006 for transmission and time slot allocation 1008 for reception are illustrated. Antenna A transmits T1 and T7 to users 1 and 7, respectively, antenna B transmits T6 and T12 to users 6 and 12, respectively, and antenna C transmits T4 and T10 to users 4 and 10, respectively, during time slot 1. Send each. At the same time, antennas A, B and C receive R5 and R11 from users 5 and 11, respectively.

The time slot allocations that multiplex the 24 simultaneous calls are shown in Figures 11A and 11B. FIG. 11A shows transmission from the transfer station (forward direction), and FIG. 11B shows transmission to the transfer station (reverse direction). The transmission time slot allocations 1102, 1104, 1106 and the reception time slot allocation 1108 are illustrated. For example, during time slot 5, antenna A transmits T5, T11, T17 and T23 (ie T5 to user 5, T11 to user 11, etc.) and antenna B sends T4, T10, T16 and T22. Transmit, antenna C transmits T2, T8, T14 and T20. At the same time (during time slot 5), antennas A, B and C receive R3, R9, R15 and R21 (ie, R3 from user 3, R9 from user 9, R15 from user 15, R21. From user 21).

In the case of Figure 10A, one CDMA encoder is required for each antenna to handle six simultaneous calls. Figure 10B requires two CDMA encoders per antenna to handle 12 simultaneous calls. Similarly, Figure 11A requires four CDMA encoders per antenna. So, for example, if 180 PN code sequences are available, handling 180 simultaneous calls would require 180/6 or 30 CDMA encoders per antenna. As the number of time slots increases with respect to the increase in the number of required accesses, the number of encoders decreases proportionally.

[Alternative system configuration (Figs. 14 and 16)]

The distance between the transfer station and the diversity antenna is extended by performance enhancements using wideband cables of 1000 feet or more. The transfer station sends the final stage radio frequency spread spectrum signal to the antenna via the cable. The antenna at the end of the cable is equipped with a radio frequency amplifier, and the production distribution signal by the cable provides the same improvement in communication failure as described for the multiple transfer station transmission diversity reception method.

However, a preferred embodiment uses frequency division multiplexing in which a single cable is shared and each antenna is assigned a different cable carrier frequency, instead of using a separate cable for each antenna. In this way, the desired signal is transmitted only from the antenna closest to the user to reduce interference. In yet another improvement, the cable distribution system integrates different elements into a regional personal communication system network. The basic building blocks are six time slot allocation CDMA modules that sequentially drive three antennas to achieve triple transmission space and time diversity. For simplicity, the design of a transfer station that handles incoming TDMA signals also uses a basic 6-time slot configuration. This 6 time slot module configuration can be easily applied to accommodate multiples of 12, 18, 24 and 30 or 32 time slots. Figure 14 shows the production of several different combinations. A preferred embodiment uses a wireless input such as W or WE as the input to the transfer station, but the cable distribution system also works reasonably well with the signal via the wire as the input.

In a cable-based personal communication system, the transfer station is returned to the central controller, eliminating the need for harsh environmental measures and remote power supply to reduce costs. In addition, the number of spare machines required and equipment maintenance costs can be reduced by arranging them in the same location and facilitating access. It also dynamically allocates forwarding stations as the traffic load fluctuates over time or weekly, thereby significantly reducing the total number of forwarding stations required. Although the bandwidth of this distribution system is increasing, the cost associated with the bandwidth increase is decreasing due to the development of the cable and fiber optic cable distribution system so that the increase can be absorbed at a low cost. The advantage of being able to choose from several interconnects is that the interconnect selection is a cost-effective choice determined by each device installation-related cost. Each network is expected to include significant or full interconnect selectivity.

The lower part of Fig. 14 shows the system configuration in which the transfer station is returned to the same location as the central controller. A normal bidirectional cable or fiber optic broadband distribution system 1402 is used to link the transfer station located near the central system and the antenna located at a remote location. The link between the transfer station located near the central system and each transfer station antenna provides considerable flexibility in configuring the wideband spectrum into a signal format. However, for simplicity, it is desirable to keep the TDMA protocol with time slot allocation CDMA triple space / time diversity air interface and the frequency conversion signal as a common air interface to each antenna.

Assign a separate center frequency to each antenna with a wideband wiring cable. The TDMA and CDMA line separation functions allow many users to communicate with the same antenna using the same cable frequency. The transfer station antenna at position N includes a transceiver tuned to the assigned cable frequency. The central controller sends and receives data packets in the final TDMA / CDMA waveform that represents telephone traffic at each assigned frequency of the wideband distribution cable 1402. That is, as shown in FIG. 16, each remote point is equipped with a remote transceiver (transmitter, receiver, local oscillator, diplexer and antenna) at point 1602. The devices located at remote points are relatively simple receivers, frequency converters and low power transmitters in both forward and reverse directions. A low power transmit amplifier is suitable because it has a smaller cell and uses triple diversity (three antennas and three time slots) for the link between the subscriber station and the system. The sender of the station line controller supplies the individual flow of information and the relevant signaling and control information at interface A'in FIG. 14, that is, the information displayed in the time slots that can be allocated in the form of packets.

The signaling information includes a called subscriber number, a code, a service outline, an authenticity code, and the like. Control information includes routing information (ie, designation of which base station, transfer station, antenna), power level, in-call or no-call state, channel switching message, and the like. A large amount of this information is transmitted before the start of line transmission of user information (telephone voice traffic), and a considerable amount of information is also transmitted during the period when the telephone voice traffic is actually transmitted to the line. A separate control channel is required even after the connection to the user is complete. The base station function translates this information into a protocol that forms the TDMA radio frequency spectrum at interface W, which is necessary for boundary formation with the TDMA air interface. The transfer station converts this TDMA protocol into a CDMA triple space / time diversity air interface protocol that accommodates time slots and transmits this signal first on antenna A, then on antenna B, and finally on antenna C (Figure 14). ..

The combined base station / transfer station (BT) module located near the central controller combines the base station function and the transfer station function, and converts the signal appearing in A'to a CDMA triple diversity air interface that accommodates a time slot. Combination BT modules can be achieved by direct combination of individual devices, and modules developed for combination base stations and transfer stations can also be integrated. The CDMA signal is branched at the output of the transfer station or the output of the BT module as shown in FIGS. 15 and 16. For transfer stations connected to their respective antennas with three different cables, they only need to switch the output at the appropriate time. When only one cable is used to reach all the antennas, the output of the transfer station is frequency-shifted at an appropriate time by converting the synthesizer frequency to the antenna assigned frequency. The BT module is also frequency azil.

It is important that the user information is repeated in each of the three time slots, while the PN codes continue and differ from each other in each time slot. Therefore, this iteration is not the same as for pseudo-multipath or emulated multipath. The PN code generator continues to operate without accumulating or resetting the PN sequence. The continuous generation of the PN code is easier to put into practice than the new launch of the PN sequence.

In the above description, the time slots are assumed to be continuous with each other, but this is not necessary if the order of jumps is known to the receiver side. In a preferred embodiment, the BT module transmits in two consecutive time slots and then receives a response signal from the user terminal. During the user transmission time slot period, the user terminal instructs the BT module not to transmit in the third diversity time slot if the first two time slots are sufficiently operational and position measurement is not required. By using only dual diversity, interference with other users can be reduced and the user receiver can be freed up to accomplish other functions.

The alternative method uses a 1/3 forward error correction code spread across all three time slots. The use of such a code improves performance if the error probabilities during each time slot period are approximately the same. If one time slot deteriorates significantly and the time slot can be identified, the deteriorated time slot is ignored, and if the performance continues to deteriorate, the antenna channel switching is requested to replace the time slot. Since the time slot statistics are considered to vary depending on the actual diversity channel statistics, a preferred alternative method does not use a forward error correction code over the three time slots. Even if the error detection and correction code is contained only in each time slot, the forward error correction code can be used over a plurality of time slots.

Given that there is data to be transmitted, each antenna transmits during each period of the time slot. Since the data is transmitted three times, there are three transmit CDMA signals in each time slot for each module assigned to that antenna. If there are four assigned modules to that antenna, then at any given time the four modules will support 24 users and the antenna will emit 12 CDMA signals during each time slot (see Figures 11A and 11B). .. If the duty factor is about 50%, only 6 CDMA signals are actually transmitted, and if the third time slot is not needed, 20 to 25%, then 4 or more CDMA signals are transmitted at each point in time. There are only five. The same antenna is used for the receiving side or the opposite direction (direction from the user to the transfer station) link.

As described above, the user CDMA terminal transmits for only one time slot period, and the transfer station simultaneously receives the transmission with three antennas, forming a receiver triple space diversity. As shown in FIGS. 15 and 16, the three received signals are supplied to the transfer station, that is, the BT module, via separate power lines or different frequencies and processed separately. The processed signals are added together using the maximum likelihood combiner. The S / I from each antenna path is measured and held in memory for a period of at least 10 time slots. The accumulated value of the signal statistics is used for the maximum likelihood coupling process. The accumulated signal statistics are also useful in the determination process for executing channel switching to other antennas.

The channel switching process for the BT cable network is based on the signals from each of the above antennas. The central processing unit receives information about the quality of the links in both directions. A forward link receives information from a user CDMA receiver operating on a particular antenna during the allocated time slot period specified on that link. Reverse links receive information about individual paths via different antennas. Information about the quality of the path through a particular antenna can be evaluated and compared to current paths through other antennas, or to other new paths that are subject to continuous search by the user terminal. If the current path through a particular time slot continues to deteriorate and a better path is available, the central controller assigns a new path (antenna) to the user terminal and informs the user terminal to that effect. ..

The channel switching process for the transfer station is the same except that this switching is generally a switch between transfer stations rather than a switch between antennas. When switching between transfer stations is performed, all three antennas related to the transfer station are channel-switched from the transfer station. Some transfer stations can be put into production with wide-spaced antennas. If you have a widely separated transfer station with an antenna, you can also use the channel switching process described above for the BT module.

Description of operation: A new subscriber powers on a CDMA user terminal and scans the sync code until it captures the code. Next, the CDMA user terminal sends a registration message. The transfer station receives this message and transfers it to the central control unit, which returns the input confirmation message to the user terminal to confirm the input. The central control device refers to the registration register of the new subscriber terminal, obtains a user overview, and stores it in a file for the activated user. The new user is registered in this way and all calls are transferred to this new service area.

There are 28 different synchronization codes, and one synchronization code is assigned to each area. Twenty-eight areas form one area, and the same sign is repeated in the adjacent areas. Transfer stations in one area are given different shifts or starting points for their own code. Therefore, each transfer station, or each wide-range antenna, has a identifiable code. The antenna or transfer station registered by the new user is known to the central controller, and all information is routed to the user via the node. The central controller provides the new user with different starting points for a set of codes or the user's current code to prepare for a particular search for a diversity path or channel switching destination candidate. This new user will continue to monitor synchronization and control channels for the duration of one half of his time slot. The other half of the time slot is scanned for better sync channels.

The user receives the call on the control channel, receives CDMA and time slot allocation, and sets up for the start of the call. When a user makes a service request, it also receives a CDMA code and time slot allocation for the duration of the call. The user terminal remains in this state until the end of the call unless the signal in one or all diversity paths is weakened. Since the user receiver continuously evaluates the quality of the incoming signal and scans for a new route with better quality, it detects the deterioration of the quality of the route and switches the quality deterioration state to a better quality switching destination. Inform the central controller with a list of candidates. The central controller directs channel switching and the user terminal moves to a new CDMA code and time slot. None of this behavior can be detected by the end user.

At the beginning of each time slot is a short resynchronization and reach adjustment unmodulated portion that does not contain user information, followed immediately by a short control message portion. These short bursts are transmitted with or without user information to be transmitted. If there is no user information to send, the control message confirms it and reduces the transmit power by 10 dB for the user information portion of the time slot. Note that four time slots are available for the forward channel to convey user information, depending on the agreement obtained between the user and the central controller. These time slots can also be turned off as described above to allow other users to access and increase capacity. Multi-hour slots are available for improved diversity or simultaneous transmission of faster data, multiple data channels or graphic channels with audio channels.

[Position measurement processing (Figs. 20, 21, 22, 23)]

FIG. 20 represents a passenger car and its antenna with a user antenna U and shows the wireless link of FIG. 1 or FIG. These radio links are assigned time slots as shown in Figure 10A. The wireless link AU receives the time slot allocation and is formed during the period of time slot 1. The wireless link BU is also a time slot allocation type and is formed during the period of slot 2. The wireless link AU is also a time slot allocation type and is formed during the period of slot 4. The wireless link AU establishes the absolute distance from U to antenna A. The distance to antenna A forms the basis for measuring the path length difference between the radio links AU and BU. Similarly, the path length of the wireless link AU can be used as a reference for measuring the path length difference between the wireless link AU and the CU.

Since the generation of all 1 vectors (for synchronization) is simultaneous for all three antennas, the distance to all three antennas can be derived from the difference in each arrival time of all 1 vectors within each time slot. A positioning center with the physical and geographic coordinates of all three antennas calculates the position of the user antenna U.

The geometry of position measurement is shown in Figures 20, 21, 22 and 23. In the first distance AU measurement, the user is confirmed at a certain point on the circle A in FIG. The second distance measurement determines the user located at a point on circle B. This fixed position can only be authentic at the intersections X and Z of these circles. Therefore, the location of this user is narrowed down to two possible points. The third distance measurement confirms the user at a point on the circle C. Since the user is also located on the circle C, it must be located at point Z. Further gaining distance to other antennas confirms the first set of measurements and often improves accuracy. When the terrain fluctuates significantly in the height direction, the constant distance circle becomes a constant distance sphere, and additional measurements can eliminate the uncertainty caused by the addition of the third dimension. The position measurement processing center converts these coordinates into user-friendly instructions. Distance measurement by the CDMA system is achieved as follows.

1. The PN code propagated between A and U acts as a measure. The required propagation time between A and U is the length of the link expressed as the product of the propagation time in microseconds and the chip speed in the megachip, which is a multiple of the length of the link, or the length is signal propagation. Allows you to "accumulate" in a link during a period. See Figure 20.

2. There are two ways to increase the number of chips that accumulate in the propagation path. One is to increase the path length, and the other is to increase the clock frequency of the chip. Increasing the clock frequency of a chip is similar to finer grading the scale. Therefore, the increase in the clock frequency of the chips causes a larger number of chips to be accumulated in the path delay, enabling more accurate measurement.

3. For the path length from antenna A to user terminal U and vice versa, the PN code is transmitted from A, the same PN code is retransmitted from the user terminal in the arrival phase, and returned at antenna A. It can be measured by comparing the received signal with the signal transmitted from the antenna first. By delaying the original signal until it matches the reflected received signal at point A on a chip-by-chip basis, and counting the number of chips that have slipped, the total delay is the distance between antenna A and antenna U. It is proportional to twice.

4. The accuracy of distance measurement is about 1/4 of the number of feet represented by one chip. The 1/4 chip is a production constraint that depends on how accurately the maximum correlation is detected and tracked. This error can be reduced by the autocorrelation method, but the 1/4 chip has a realistic definition.

5. For the measurement of the path length between the antenna A and the user terminal U described in Section 3 above, FIG. 22 shows the transmit signal 2202 and the receive signal 2204 of the antenna A. At a chip clock frequency of 10 megachips / sec, each chip displays 100 feet. The delay of 51 chips between the transmit signal 2202 and the receive signal 2204 represents the time required for the radio frequency signal to propagate back and forth between the subscriber station and the transfer station. Half of the round-trip propagation delay, the 25.5 chip, represents the distance to the antenna. Therefore, the distance from the antenna A to the user terminal antenna U is (51 × 100) / 2 = 2550 feet, for example, in FIG. The accuracy of this distance measurement is 25 feet (100/4 feet).

6. In this way, the distance AU is measured very accurately. As mentioned above, the receiver uses a single receiver for all time slots. While receiving time slot 1, the subscriber receiver cooperates with the base station to repeat the received waveform in the same phase without any delay in the user terminal. As described above, the base station receiver compares this reception phase with the transmission phase to calculate the absolute value of the distance. The base station then sends the distance value thus measured to the user terminal, which stores it for future reading and use. As mentioned earlier, what is important is the phase of the waveform, and if the starting point of all 1 vectors is maintained through the user terminal, the reverse link may be replaced with a new PN code of the same content. Similar codes described above include the same code shifted by a predetermined offset value.

7. The above-mentioned round-trip measurement method can be used to calculate the other two distances (up to antennas B and C) and store the calculation results in the user station memory. However, direct measurement of the distance to all three antennas is not necessary. See Figure 23. Information about all three routes can be collected with the same receiver. At that time, the receiver adjusts the path length difference at the start point of each time slot. Once adjusted, the code is stored in memory at the first time the receiver uses the antenna as an information channel, held until the receiver returns to this time slot, and the code taken out of memory is used for the tracking loop. Used as a starting point. Therefore, the receiver emulates three separate receivers, three separate sets of receiver parameters, one set for time slot 1, another set for time slot 2, time. It effectively maintains yet another pair for slot 3. The distance to the antennas B and C can be calculated by adding or subtracting the offset measured by the number of chips to the absolute value of the distance measurement for the link AU. In practice, this offset can be determined before the time slot is first used as an information channel, and this determination is made in the process of searching for a new path for channel switching. Measure delay and signal quality indicators and save to a potential channel switching destination file. These delay offset measurements are also used in additional distance measurements during the position measurement process.

More specifically with reference to the above example, the transmitted signal 2302 from antenna A represents the distance of the 25.5 chip from antenna A to the user terminal. The signal 2304 from antenna A received by antenna U is used as a reference for measuring the relative time of the signals from antennas B and C, that is, adjusting for different time slots in which these signals are arranged.

Since the timings of time slots 1, 2 and 3 are sequential, the real-time chip patterns of slots 2 and 3 do not overlap. However, after adjusting the time slot delay, the timing relationship is as shown in FIG. Through the adjustment for the time slot difference in this way, the signal 2306 received from the antenna B by the user terminal antenna U is received eight chips ahead (that is, offset from the signal from the antenna A). .. Similarly, the signal 2308 received from the antenna C by the user terminal antenna U is also received 6 chips ahead (that is, offset from the signal from the antenna C). The received signal is behind or ahead of the reference signal 2304 (ie, has a positive or negative delay). Preceding reception indicates that the antenna (B or C) is farther away than antenna A.

In FIG. 23, the distance from antenna B to antenna U is 25.5-8 = 17.5 chips. In feet, the 17.5 chip is 17.5 x 100 = 1750 feet, or path length BU. The distance from antenna C to antenna U is 25.5-6 = 19.5 chips. In feet view, the 19.5 chip is 19.5 x 100 = 1950 feet = path length CU. The position of the user terminal can be identified at the intersection of Z, that is, the circle A 2250 feet from the antenna A, the circle B 1750 feet from the antenna B, and the circle C 1950 feet from the antenna C.

Alternatively, position measurement can be achieved by calculating the intersection of two hyperbolas. The first hyperbola is the locus of points that make the distance difference from the two focal points constant, that is, the distance difference proportional to the delay difference between antenna A and antenna B. The second hyperbola is the locus of points that make the distance difference from the two focal points constant, that is, the distance difference proportional to the delay difference between antenna B and antenna C (or between antenna A and antenna C). .. Antenna A and antenna B are the focal points of the first hyperbola, and antenna B and antenna C are the focal points of the second hyperbola. In this way, the subscriber position can be calculated without the need for bidirectional signal exchange between the user terminal and the transfer station to achieve the first distance measurement.

[Location service (Figs. 18 and 19)]

Since the subscriber station receiver receives information from a known point via three different routes, the position identification information can be calculated by measuring the time when the message arrives with respect to a fixed reference time. The measurement accuracy depends on the chip speed, but the chip speed of 10 megachips per second is sufficiently accurate. There are several methods for position measurement and display, depending on how much signal processing is possible at the user terminal. The choice depends on who actually uses the information. It can be quite passive as it uses only relative chip offset information and gets a reference from the cell at the current position. The user can also locally calculate the position of his / her own station and display it as in the case of using the GPS system.

The GPS receiver displays longitude and latitude values. The location information can also be returned to the service-providing processing center. The processing center converts the longitude / latitude value into location information with geographical meaning such as the block number of a specific street.

Local positioning is especially attractive to people with security and health concerns. The service center manager can report to the police and designated family members, or place an abnormal condition inspection staff at the service center as part of the special charge. Of course, the service center can notify each individual of their current location and direct the route to the desired destination for a nominal fee. These services can be provided to users who are pedestrians or vehicle users. The guidance to the destination may be provided at once with detailed guidance, or may be a specific continuous intersection prompt provided by the user in the process of moving according to the suggested route. This prompt may be in the form of a voice command, such as a right turn at the next intersection, or a text display. Delivery trucks, taxis, ambulances, fire trucks, etc. may also be equipped with a special display screen showing a map of the relevant area with guidance. Guidance can be changed according to changes in road congestion. The advantage of the present invention is that public safety, convenience and productivity are greatly enhanced.

In the above system configuration, the separation between the antennas is sufficiently large in order to exhibit accurate positioning performance. With sufficient antenna-to-antenna separation to reduce triangulation errors to very small values by arranging the antennas to ensure sufficient independent paths to avoid flat fading due to interfering obstacles. To do. The additional cost associated with optimizing position measurement performance is negligible.

Position measurement information processing is performed by a third-party provider who owns and manages the position measurement center. Positioning services can be achieved in several ways. A preferred method is to build and maintain a location measurement file to turn the user terminal into a repository of all location information. When the location measurement center needs information, it makes an inquiry to the user terminal via a normal public exchange network (preferably a data packet). For confidentiality, it is preferable to provide for confidentiality during transmission and access code. The user terminal sends the position measurement information to the position measurement center via the public exchange network in response to the operation by the user. For example, when the user presses the alarm button, the wireless transmitter sends an alarm message to the position measurement center along with the position measurement information. The location measurement center responds according to the pre-configured guidance and the level of contract service. Since the user terminal internally generates code offset information, the only additional information that this cellular system needs to provide to the user terminal is the distance from the user terminal to one of the base stations / antennas and the one-way round trip distinction. Is. The distance information provided as a service to the user must identify the base station / antenna. All measurements must be performed within a time window of 100 ms, which would result in excessive error due to vehicle movement between measurement points. For a stopped vehicle or pedestrian, the time window for performing the position measurement may be much longer as there is little or no movement between measurement time points. Therefore, the distance measurement value sent from this system to the user terminal is the distance in feet display, the time in milliseconds display, the name of the measurement subject, and the like. When the user receives the distance message, the user accumulates the message, performs code offset measurement to several different antennas, and stores the composite information in the position measurement file if the signal level is sufficient. The position measurement file is retained until the user terminal wireless receiver receives a new distance message, and at the time of receiving the message, the user terminal wireless receiver performs the code offset measurement again and performs the position information display.

When the position measurement center issues an inquiry about the position of the user terminal wireless device, the wireless device sends the contents of the position information file. The position measurement center processes the data and converts it into very accurate map data, that is, position data on a specific street (which can be displayed on a normal street map). This system normally measures the distance to the subscriber station once per minute when the subscriber is in active receive mode of call standby with the receiver turned on. The time interval of the distance measurement is variable and can be adjusted according to the user's needs. The system sends this new distance value to the subscriber station, which stores it in a file, thereby making a new sign offset measurement. While the subscriber is talking, the user terminal is transmitting, the base station makes measurements every 10 seconds, and the system sends a message to the subscriber station when the distance fluctuates by more than 100 feet. Each time the user terminal receives the distance measurement value, the user terminal adds the local code offset measurement value and updates the file.

It will be appreciated that the user terminal location file is updated every second or more frequently as needed. Therefore, the system can locate all active users within a distance of approximately 100 feet. Higher accuracy and more frequent data updates are of course possible, but the number of these high-performance subscriber stations should be an exception rather than a principle because of the load on the data link. When the user presses the alarm button on the portable terminal, it sends the contents of the terminal placement specific file three times, which is long enough for the system to calculate a new distance and send a message to the user terminal. The user terminal makes several offset measurements and sends a new distance file three times. The alert message repeats once every 30 seconds until the battery runs out. A module (with a built-in dedicated battery) that emits an audible sound each time a wireless alarm message is transmitted can be added to the user terminal wireless device.

This system generates raw position identification information to be converted into human-readable map data on the user terminal. In general, the basic longitude, latitude, angle and distance calculations are fine. However, there is a need for a third party to convert this data into a format that is readily available to the general public as a service business. Since the user terminal has basic position measurement information, the information can be provided to a legitimate right holder who makes a request to the user terminal. The location information processing center periodically makes inquiries to contracted user terminals and maintains a file about the current position of those terminals. One potential service for subscribers with health problems is a service that monitors during exercise. If the subscriber has been stopped for a long time in an abnormal place and does not press the alarm button, the operator of the position measurement center requests the stopped subscriber for a pulse, etc., or dispatches a medical technician. Can be done. In case of emergency, the position measurement center operator knows the current position of the subscriber for assistance dispatch. On the other hand, when the alarm button is pressed, the alarm message is addressed to the location measurement center prepared for emergency response. The ability to track user terminals and provide assistance as a result of some action is useful in a variety of applications. Searching for stolen vehicles, detecting traffic congestion, preventing route confusion and reporting mischief are some examples of applications of the present invention.

As mentioned above, this system requires a matched zero time reference that spans different base stations, especially in a distributed configuration. The availability of a zero time reference reduces the time required for resynchronization when signals jump between antennas and also aids in search channel switching. The position measurement application capabilities described above allow the system to periodically self-calibrate by placing some user terminals in fixed positions as described above and setting appropriate zero times to those positions. By storing the correct answer in the central processing unit while the system is scanning those checkpoints, it is possible to display an error if the system is out of calibration. The same checkpoint is used during the process of introducing a variable delay by increasing or decreasing the execution delay.

The calibration process can be easily automated. Automation can be put into production in two ways. The first method scans the checkpoints once every minute to determine if any error has occurred. When the error reaches a significant level, the communication system contacts the position measurement center and informs the center of the corrections to be incorporated for the position measurement calculation. The latter method requires cooperation between the communication system and the position measurement center. A more autonomous method would be desired. The communication system itself could maintain a proper "zero" state by scanning checkpoints and providing the ability to insert or remove delay 1806 in the path, as described above.

Figure 18 illustrates a system with self-calibration. Once every minute, the system queries each checkpoint. As a result, the distance measurement is sent to checkpoint 1802, where the checkpoint receiver adds the code offset measurement and sends the contents of the position file to processor 1804, where the file received is a file containing the correct measurement. Will be compared. If the difference exceeds the threshold, processor 1804 calculates the amount of delay change required to keep the measured value within the permissible range and sends the corrected value to the controller. The controller maintains a file containing the variable delay 1806 to be inserted for each antenna. The controller changes the delay value in the file and incorporates new measurements to enable calibration. Changes that require a significant change in the delay value are unlikely to occur, but in the unlikely event that such a change occurs, the control device will not start the measurement including the section to be recalibrated. In this way, the position measurement function provides the service to the communication system. Self-calibration significantly reduces installation costs and allows the use of cheaper system components.

Positioning-related communications between the antenna device and the subscriber terminal can be split into several different links. The functions of these different links are (1) distance measurement (requires a two-way link but no call traffic), and (2) transmission of measurement information to the subscriber terminal (one-way data link except for possible retransmission requests). , (3) Code offset measurement (only user terminal required for reception, no data transfer), (4) Transmission of position measurement file to position measurement center or communication processor 1804 (data link is bidirectional in one direction) May be). Distance measurement is only possible on the system and requires a bidirectional link so it can be performed when a normal call channel is established and the system forms a short round trip connection when the terminal is in receive mode. Must.

A bidirectional link is required because the base station measures the sign phase difference between the signal transmitted to the user terminal and the signal received from the user terminal. In Figure 18, this functionality is achieved with processor 1804. In that sense, the system behaves like a radar with PN chip width pulses. The one-way data link message that conveys the distance information to the user terminal is usually a single message including an error correction code, and requires a return of an input confirmation message from the user terminal to the base station. The input confirmation message may be sent independently, or may be sent in addition to a part of the distance measurement function.

The code offset information is also stored in a file that can be accessed from outside the system. As described above, the user terminal time-shares one receiver from three different antennas via three independent paths that occur at different times. Therefore, this receiver sequentially tracks three independent paths. The PN code of each path is the same, and as mentioned above, the code has the same starting point for each antenna, but due to the difference in distance from the user terminal to these three antennas, the codes arriving at the user terminal are mutually exclusive. It has different sign phases. However, since the system cycle fluctuates rapidly from antenna to antenna, the receiver circulates between the received signals from each of these antennas. Therefore, the receiver maintains three start states and tracking loops for different time slots. The exact time is known in advance at the end of each time slot, the previous state is stored in the computer and recovered at the start of the next time slot assigned to the same antenna. Therefore, this processor emulates three different receivers. The receiver rapidly adjusts for the slight drift that occurs while locked to other antennas. Note that the receiver has a specific start state. In this way, the PN sequence is shifted to compensate for the distance difference between the path between the user terminal and the first antenna and the path between the user terminal and the second antenna. This difference is the sign offset. That is, the sign offset measures the distance difference. Therefore, the distance to the second antenna is also known without the need for closed-loop (bidirectional) measurements. The same process is performed for the third antenna.

Additional input to the location information file, i.e., four or more inputs, is also available using the normal search mode used by the user terminal radio to identify channel switching destination candidates. The user terminal radio device searches for pilot codes from nearby antennas to determine if the signals from those antennas are better than those from the three antennas currently in use. If it is determined to be of good quality, the user terminal notifies the system that appropriate candidates are available. The search process begins with the incoming PN signal from time slot 1, and if nothing is found in that state, the radio will reconfigure by adding one chip to the path length. The radio device continues chip addition until it finds a signal or exceeds the distance threshold. When the distance threshold is exceeded, the PN generator is reset to a new pilot code and restarted from zero offset distance. Therefore, when the radio device finds a new pilot code, the number of chips added up to that point is known to the radio device. The number of chips added is also the sign offset. This code offset value is stored in the position information file together with the code and time data for identifying the antenna. The radio device stores these data inputs in a position measurement file even if the data is not of better quality than the current signal. When the radio scans and finds a new antenna, it stores the four best findings in a position measurement file. As the scan continues, the older input data is replaced with new, better quality input data.

Since the required information is thus available in the user terminal position measurement file, the information is made available to qualified requesters. Location measurement services may be provided by the carrier or an independent service provider that competes with it. Other than that, there may be a large private positioning center operated by a large number of vehicle owners. The position measurement center 1902 receives the position measurement file via the public communication exchange network. See Figure 19. The switching network may be a circuit switching network or a packet switching network. Packet-switched networks are sufficient for this type of application.

It can be applied to enhance the function of the third generation wideband mobile wireless communication system by CDMA.

<figref num="1">A system diagram of a radiotelephone distribution system including a first embodiment of a transfer station according to the present invention.</figref><figref num="2">The block diagram of the 1st Example of the radiotelephone distribution system by this invention.</figref><figref num="3">The system diagram of the 1st Example of the radiotelephone distribution system by this invention.</figref><figref num="4">A system diagram of a radiotelephone distributed system including a second embodiment of a transfer station according to the present invention.</figref><figref num="5">The system diagram of the 2nd Example of the radiotelephone distribution system by this invention.</figref><figref num="6">The block diagram of the second embodiment of the radiotelephone distribution system according to this invention.</figref><figref num="7">The timing diagram of the time division multiple access for code division multiple access modulation by this invention.</figref><figref num="8">The block diagram of the 1st Example of the transfer station by this invention.</figref><figref num="9">The block diagram of the 1st Example of the transfer station by this invention.</figref><figref num="10A">It is a time slot allocation diagram of the radiotelephone distribution system by this invention, and is the figure which shows the time division multiplexing and code division multiplexing for six simultaneous calls.</figref><figref num="10B">It is a time slot allocation diagram of the radiotelephone distribution system by this invention, and is the figure which shows the time division multiplexing and code division multiplexing for 12 simultaneous calls.</figref><figref num="11A">It is a time slot allocation diagram of the radiotelephone distribution system by this invention, and is the figure which shows the time division multiplexing and code division multiplexing for 24 simultaneous calls.</figref><figref num="11B">It is a time slot allocation diagram of the radiotelephone distribution system by this invention, and is the figure which shows the time division multiplexing and code division multiplexing for 24 simultaneous calls.</figref><figref num="12">Block diagram of a second embodiment of a transfer station according to the present invention</figref><figref num="13">Block diagram of subscriber stations according to the present invention</figref><figref num="14">Block diagram of centralized integrated transfer station according to the present invention</figref><figref num="15">Block diagram of transfer station antenna configuration</figref><figref num="16">Block diagram of a distributed antenna configuration according to the present invention using a coaxial cable or an optical fiber cable</figref><figref num="17">Timing diagram of time-division multiple access for code division multiple access modulation according to the present invention</figref><figref num="18">System diagram showing the distributed antenna configuration of the present invention</figref><figref num="19">Block diagram of the system according to the invention with the position measurement center located outside the communication system</figref><figref num="20">Explanatory drawing of mobile subscriber station position calculation system by this invention</figref><figref num="21">The system of the present invention illustrating a mobile subscriber station location calculation method</figref><figref num="22">Timing diagram that illustrates how to calculate the distance from the subscriber station to the transmission transfer station</figref><figref num="23">Timing diagram that illustrates how to calculate the relative distance from the subscriber station to the two transmission and transfer stations</figref>

Code description

1,2,4 Receive 3 Transmission 5 Scan 6 Spare 10 CDMA Transfer Station 11,12,13,16 Antenna 14 CDMA (Code Division Multiple Access) Transfer Station 20 Public Communication Telephone Exchange 22 Telephone Exchange Center and Central Processing Equipment 24 TDMA (Time Division Multiple Access) Base Station 26 CDMA Transfer Station 40 TDMA Subscriber Station 42 CDMA Subscriber Station 54,56,58 Transfer Station 60,64,68 Antenna 72 Public Communication Telephone Exchange 74 TDMA Base Station 92 Telephone Exchange Center and Central Processing Equipment 94 TDMA Base Station 96,98,100,102,104,106,108 CDMA Transfer Station 110 TDMA Subscriber Station 112 CDMA Subscriber Station 800 TDMA Receiver 802 Demultiplexer 804 Synchronization and Control Equipment 806 Time Slot Buffer 808 Time Multiplexer 810,812,814 Multiple CDMA Encoders 816,818,820 CDMA Transmitter 828 TDMA Receiver CDMA Transmitter 900 CDMA Receiver Figure 9 TDMA Transmitter 902,904,906 CDMA Receiver 908 Maximum likelihood combiner 910 Memory buffer and time slot Multiplexer 912 Synchronization and control Equipment 914 TDMA transmitter