Method and apparatus for providing high speed data communications in a cellular environment

The present invention relates to a communication system. In particular, the present invention relates to new and improved methods and devices for performing high speed data communication in a wireless cellular communication environment.

With the progress of wireless communication technology, the demand for high-speed data services has increased rapidly even in wireless environments. Code division multiple access (CDMA) modulation is one of the most suitable digital radio transmission technologies for digital data transmission. Other methods of digital radio transmission include time division multiple access (TDMA) and frequency division multiple access (FDMA).

However, the spread spectrum modulation technique of CDMA is very advantageous over other modulation techniques. The use of CDMA technology in multiple access communication systems is disclosed in US Patent No. 4,901,307, "Spectrum Spread Multiple Access Communication System Using Satellite or Terrestrial Repeater", which has been transferred to the transferor of the present invention. The use of CDMA technology in multiple access communication systems is further disclosed in US Patent No. 5,103,459, "Signal Waveform Supplier and Method for CDMA Cellular Telephone Systems." Digital radio communications using CDMA modulation are TIA / EIA / IS-95-A mobile and base station compatibility in dual-mode wideband spread spectrum mobile phone systems by the Telephone Communications Industry Association (TIA). It is standardized by the standard (hereinafter referred to as IS-95).

Current wireless communication systems only allow communication at relatively low communication rates. Moreover, most current wireless communication systems are not optimized for the transmission of digital data, but rather for the transmission of voice information. Therefore, a method of high-speed transmission of digital data in a wireless environment is desired.

The present invention is a novel and improved device and method for transmitting digital data in a cellular environment. In the present invention, a plurality of adjacent cells of the cellular system are prevented from transmitting data at the same time. That is, if the first base station on one side of the cell boundary is transmitting, the second base station on the other side of the cell boundary is dormant during the transmission period of the first base station. .. This is because the noise transmitted from the adjacent cells is a major cause of interference, and if the noise from the adjacent cells can be reduced, the transmission rate of the output-limited base station can be dramatically increased.

In the present invention, all transmissions from the base station are transmitted at a fixed output level, and transmissions to each subscriber station in the cell are performed in a non-overlapping burst. Thus, during base station transmission, this transmission is directed to one subscriber station in the cell, thereby transmitting data to that subscriber station that maximizes the data rate available to the subscriber station. Therefore, it is possible to use the total amount of output available.

To clarify this, two different but related rates are shown. One is an information rate indicating the rate of the user-generated information bit. The second is the transmission rate, which is the rate of bits transmitted over the air.

When transmission is performed at a fixed output level, the amount of information that can be transmitted between the base station and the subscriber station varies with the technically known budget factor of the link. The most important link budget factor in wireless systems is the path loss between the base station and the subscriber station. Pass loss is strongly related to the distance between the base station and the subscriber station.

In the present invention, transmission to each subscriber station is performed at a fixed transmission output level. However, the transmission signal information rate does not correspond to the distance between the subscriber station and the base station. In the first embodiment, the information rate of transmission to the subscriber station is determined by selecting the coding rate of the transmission signal while keeping the transmission rate constant. In the second embodiment, the data rate of transmission to the subscriber station is determined by selecting a modulation format of the transmission signal that directly changes the information rate of transmission to the subscriber station.

<figref num="1">FIG. 1 is a schematic diagram showing typical cells in a geographical area.</figref><figref num="2">FIG. 2 is a schematic diagram showing the mutual relationship between the base station controller, the base station, and the subscriber station.</figref><figref num="3">FIG. 3 is an exemplary timing diagram and a schematic diagram of the frame format of the present invention.</figref><figref num="4">FIG. 4 is a block diagram showing the cells of the present invention.</figref><figref num="5">FIG. 5 is a block diagram showing a base station of the present invention.</figref><figref num="6">FIG. 6 is a block diagram showing a subscriber station of the present invention.</figref><figref num="7">FIG. 7 is a schematic diagram showing an example in which a cell is divided into many narrow sectors.</figref>

Detailed explanation

The features, objects, and effects of the present invention will become apparent from the drawings associated with reference numerals and the detailed description given below. In the following description, the same reference code is used to describe the cell or region supplied by the base station and the base station itself. In the present invention, two adjacent cells are prohibited from transmitting at the same time. As described above, in FIG. 1, if the base station 1 is transmitting, the base station 2A-2F is prevented from transmitting. Noise experienced by a transmitting base station in a cellular environment (N)₀) Is expressed by the following equation (1).

N₀= N_{b b}+ N_m+ N_t+ N_r (1) Where N_{b b}Noise from the base station of an adjacent cell, N_mIs interference from multipath reflections, N_tIs the thermal noise in the system, N_rMeans all other noise sources respectively.

Noise value (N₀) Limits the amount of information that can be transmitted by the output-restricted wireless communication system. The present invention prevents noise N from adjacent cells by blocking the simultaneous transmission of two adjacent cells._{b b}Is to be removed. Further, since the base station transmits to only one subscriber station at a time, all available energy can be used for transmission to that one subscriber station. Overall noise (N₀) Can be attenuated and the output available for transmission to a given subscriber station increased, which can greatly increase the available information rate for transmission to the subscriber station.

Referring to FIG. 2, the base station controller (BSC) 4 controls the operation of many base stations in a geographical area. In the present invention, BSC4 regulates the transmission of base stations 1, 2A-2F, and 3A-3F so that two adjacent cells do not transmit at the same time. In the present invention, the BSC4 transmits a signal to a selected one of the selected base stations 1, 2A-2F, 3A-3L, and instructs the selected base station to transmit during a predetermined time interval. To do.

In a preferred embodiment, the cells are grouped as a set of non-adjacent cells, and any of the cells in this set can be transmitted at the same time. For example, the first set of non-adjacent cells consists of cells 2A, 2C, 2E, 3C, 3K, 3G. The second set of non-adjacent cells consists of cells 2B, 2D, 2F, 3A, 3E, 3I. In this embodiment, BSC4 selects a subset of non-adjacent cells that can be transmitted, and any or all cells in the set of non-adjacent cells can be transmitted during the frame cycle.

With respect to the timing chart of FIG. 3, BSC4 sends a transmit message to base station 1 at time 0. More preferably, BSC4 sends a message to all base stations in a set of non-adjacent base stations, including base station 1. In response to that message, base station 1 sends during the time interval from 0 to T. At time T, BSC4 sends a message to base station 2A instructing base station 2A to transmit during the time interval between time T and time 2T. This process is repeated for each base station of base stations 2B-2F shown in FIG. At time 7T, BSC4 sends a message to base station 1 to transmit during the time interval between times 7T and 8T.

When one of the base stations 2A-2F is transmitting, it is possible that a subset of the base station 2A-2F is transmitting, as long as the two base stations do not share a common cell boundary. For example, if base station 2A is transmitting, then cells 1, 2B, 3F, 3E, 3D and 2E cannot transmit because they are adjacent to cell 2A. However, since cell 2C-2F is not adjacent to cell 2A, transmission is possible during this period. More preferably, the transmission time intervals are the same to reduce the management complexity of coordinating the transmission of the base station of the system. It should be noted that the use of time interval changes is predicted as possible.

In the exemplary embodiment shown in FIG. 3, the cell transmission cycle follows a simple and deterministic pattern. In this simple and decisive transmission cycle, it is recognized that each base station can transmit at a predetermined time without control by BSC4, so that the base station does not need to operate under the control of BSC4. In a preferred embodiment, the transmission cycle does not have to be determined in a simple and definitive pattern as shown in FIG.

In this preferred embodiment, the BSC 4 should transmit according to the amount of information queqed for transmission at a set of non-adjacent base stations or one base station base station. Select a set of base stations or one of the base stations. In that preferred embodiment, the BSC4 monitors the amount of messages in a set of non-adjacent base stations or in a queue maintained by each base station and base stations to transmit based on the amount of data in the queue. Select.

Each cell contains multiple subscriber stations, each of which requires data to be transmitted to them by the base station supplying this cell. In an exemplary embodiment, the base station specifies the identity of the subscriber station it is transmitting in the header. Referring to FIG. 3, in the first time interval (time 0 to T), base station 1 transmits to the selected subscriber station. In an exemplary embodiment, each frame has a duration of 2 ms. The transmitted data is given a header confirming the selected subscriber station.

In another embodiment, each cell is divided into narrow sectors, where each sector can be transmitted independently of transmission to other sectors within the cell. This is possible with a highly directional antenna, the design of which is technically known. FIG. 7 shows cell 600 supplied by base station 510, which is divided into sectors 500A-500O. In this embodiment, each cell of a similarly sectorized communication system transmits to a random sector or a subset of sectors within it. The possibility of duplicate simultaneous transmissions from adjacent sectors is small as long as each cell is divided into a sufficiently large number of sectors.

For Figure 3, all forward link transmissions have the same energy E₀Given in, it is generally the maximum transmit energy allowed by the government. Equation (2) is the fixed output (E)₀) Shows the general link budget analysis showing the relationship of the parameters of the wireless communication system with: E₀= R (bits / s) (dB) + (Eb / No) req (dB) + L_s(dB) + L_{o o}(dB) (2) Where E₀Is the fixed transmission energy of the base station, R is the transmission rate, (Eb / No) req is the required signal-to-noise ratio of the given error rate, and L_sIs a pass loss in decibels, L_{o o}Is another loss in decibels. Path loss L_sIs highly dependent on the distance between the base station and the subscriber station. In the present invention, the transmission rate, R, or required signal-to-noise ratio, (Eb / No) req, varies based on the distance between the base station and the subscriber station.

With respect to FIG. 4, the three subscriber stations 6A, 6B, and 6C are provided in the cell boundary line 10 and are supplied by the base station 1. The distances to the subscriber stations 6A, 6B and 6C are r1, r2 and r3, respectively. In another embodiment, the effective distance is used, which is the metric selected according to the path loss between the base station and the subscriber station. Those skilled in the art will recognize that the effective distance is related to, but not the same as, the physical distance between the base station and the subscriber station. Effective distance is related to both the course of the propagation path and the physical distance.

Returning to equation (2), path loss (L)_sThe effect of the difference in) can be offset by changing the value of (Eb / No) req to keep everything else constant. The value of (Eb / No) req is based on the error detection and correction techniques used to protect the transmitted data. The coding rate is the ratio of the number of binary symbols output from the encoder to the number of bits input to the encoder. In general, the higher the code rate of the transmitting system, the greater the protection for the transmitted signal and the lower the required signal-to-noise ratio (Eb / No) req for that signal. Thus, in the first exemplary embodiment of the invention, the coding rate of transmission to the subscriber station is selected based on the distance between the subscriber station and the base station. Communication systems have limited bandwidth, so higher code rates used result in lower system throughput.

In equation (2), path loss (L)_sThe effect of the difference in) can be offset by changing the value of the transmission rate R. The transmission rate R is given by: R = R_s Log₂M (3) Where R_sIs the number of symbols transmitted and M is the number of symbols in the modulation arrangement. As described above, when the distance between the subscriber station and the base station is large, the transmission rate R decreases. In the present invention, the transmission rate can be changed by changing the modulation format to one with more or fewer symbols in the modulation constellation. However, when the distance between the base station and the subscriber station is small, the transmission rate R increases. In the second exemplary embodiment, the symbolic rate is set by the choice of modulation format. The information rate is the rate at which the actual bits of unencoded user information are transmitted.

Assuming that the physical distance and the effective distance are closely related, base station 1 will transmit to subscriber station 6A at a lower information rate than it would transmit to subscriber station 6B. This is because the effective distance to the subscriber station 6A is longer than the effective distance to the subscriber station 6B.

In an exemplary embodiment, each subscriber station sends a message indicating its location to a base station that supplies the cell. In another embodiment, a technically known location detection method by a communications station is used to estimate the location of the subscriber station. Yet another embodiment uses the effective distance determined by the base station according to the measurement of path loss between the base station and the subscriber station. The measurement of the path loss can be performed by transmitting a signal of a known output from the base station and measuring the received output at the subscriber station. Similarly, the path loss can be measured by transmitting a signal of a known output of the subscriber station and measuring a known received output of the base station. The distance relationship between the base station and the subscriber station corresponds equally to the physical distance and the effective distance, respectively, based on the measured path loss.

In the present invention, an initial coding rate or modulation format is selected and given during the setup procedure. Next, the distance is calculated. If there is a sufficient change in distance, a new coding rate or modulation format will be selected according to the new distance during service.

In the first embodiment, the base station selects the coding rate according to the distance between the base station and the subscriber station. The base station transmits the selection coding rate instruction to the subscriber station receiving the instruction. The receiving subscriber station selects a decoding format suitable for use at the selected coding rate according to the selected coding rate.

In the second embodiment, the base station selects a modulation format based on the distance between the base station and the subscriber station. The base station then sends instructions for the selected modulation format to the receiving subscriber station. The receiving subscriber station sets up a demodulator suitable for receiving a signal modulated according to the selected modulation format according to the selected modulation format.

A block diagram of an exemplary embodiment of base station 1 is shown in FIG. A block diagram of an exemplary embodiment of Subscriber Bureau 6A is shown in FIG.

In the first embodiment, the coding rate for transmission to the subscriber station is selected according to the distance between the base station and the subscriber station. In this way, the information rate is varied by the transmit rate R, which remains fixed by selecting one of the plurality of coding rates. First, subscriber station 6A registers with base station 1. In this registration process, mobile station 6A notifies base station 1 of its existence and executes a basic system setup task as technically known. Embodiments relating to device registration are described in detail in US Patent No. 5,289,527, which has been transferred to the assignor of this application, under the title "How to Register a Mobile Communication Device".

As an exemplary embodiment, the subscriber station 6A signal generator 218 generates a location message and supplies this message to the transmit subsystem 216. Transmission subsystem 216 encodes, modulates, upconverts, amplifies the message, and supplies the message via a duplexer for transmission through antenna 200. The location message is received by antenna 120 and fed to receiver subsystem 118. The receiver subsystem 118 amplifies the received position message, downconverts it, demodulates it, decodes it, and supplies it to the transmission controller 104.

In an exemplary embodiment of the invention, mobile station 6A sends a message indicating the location to base station 1 during the registration process. Further, in its exemplary embodiment, the subscriber station 6A tracks its own movement, and if the distance changes by at least a certain amount, the subscriber station 6A sends an indication of its new location. As already mentioned, an alternative method of determining the location of the subscriber station or a method based on the measurement of path loss can be used. In an exemplary embodiment, location information is given to the transmit controller 104 of base station 1, which calculates the distance between base station 1 and subscriber station 6A.

Transmission controller 104 selects the encoder rate according to the distance between base station 1 and subscriber station 6A. In a preferred embodiment, the distance between base station 1 and subscriber station 6A is quantized into discrete values, as shown in FIG. In FIG. 4, all subscriber stations located between base station 1 and circle 7A receive information at the first code rate. All subscriber stations located between circles 7A and 7B receive information at the second code rate. All subscriber stations located between circles 7B and 7C receive information at the third code rate. For example, in FIG. 4, when transmitting to the subscriber station 6B close to the base station 1, the base station 1 uses the rate 1/2 code. However, when transmitting to subscriber station 6A far from base station 1, base station 1 uses a rate 1/8 code.

If the distance between the subscriber station and the base station is very large, a code with a higher code rate will be chosen. However, if the distance between the base station and the subscriber station is short, a lower coding rate is selected. The error correction and detection method used for subscriber station 6A allows a lower required signal-to-noise ratio (EbN0) req for a given error rate. Lower coding rates increase the number of errors that can be corrected and decrease the required signal-to-noise ratio (Eb / N0) req.

In the first embodiment, the transmission controller 104 selects the coding rate as described above and sends an instruction of the selected rate to the subscriber station 6A. In an exemplary embodiment, a message indicating the coding rate is transmitted on the paging channel during the registration process. Paging channels are used in wireless communication systems for sending short messages from base stations to subscriber stations. In a preferred embodiment, the wireless communication system allows base station 1 to change the coding rate with the following message transmitted on the traffic channel. One reason to change the code rate is that it is possible to change the position of subscriber station 6A.

In an exemplary embodiment, a message indicating the selective coding rate is given by the transmission controller 104 to the encoder 106 that encodes the message. The encoded symbol from the encoder 106 is supplied to the interleaver 108, which reconstructs the symbol according to a predetermined reordering format. In an exemplary embodiment, an interleaved symbol is supplied to the scrambler 110, which scrambles the interleaved signal according to the CDMA spread format disclosed in US Patents No. 4,901,307 and No. 5,103,459.

The spscrambled read signal is fed to a modulator 112 that modulates according to a predetermined modulation format. In an exemplary embodiment, the modulation format for the paging channel is quadrature phase shift keyed (QPSK) modulation. The modulated signal is supplied to the transmitter 114 which up-converts and amplifies the signal and transmits it by the antenna 116.

The transmitted message indicating the coding rate is received by the antenna 200 and fed to the receiver (RCVR) 202. The receiver 202 down-converts and amplifies this received signal and supplies it to the demodulator 204. The demodulator 204 demodulates the received signal. In embodiments, the demodulation format for the paging channel is the QPSK demodulation format. In an exemplary embodiment, the demodulated signal is fed to the equalizer 205. The equalizer 205 is a channel equalizer that reduces the influence of the propagation environment, such as the influence of multipath. The channel equalizer is a conventionally known one. The design and implementation of the channel equalizer is disclosed in the "Despreader" of US Patent No. 08 / 509,722, which has been transferred to the assignee of the present invention.

The equalized signal goes to the descrambler 206, which descrambles the signal according to the CDMA despreading format detailed in US Patents Nos. 4,901,307 and Nos. 5,103,459 described above. Be supplied. The dediffusion symbol is supplied to the de-interleaver 208 and reconstructed according to a predetermined de-interleaving format. The reconstructed symbol is fed to the decoder 210, which decodes the message indicating the selected coding rate and feeds the decoded message to the control processor 212.

In response to the decoded message, the control processor 212 supplies the decoder 210 with a signal indicating the decoding format used for high-speed data transmission. In that exemplary embodiment, the decoder 210 is capable of decoding a received signal according to a plurality of trellis decoding formats, each of which has a corresponding different coding format.

Returning to FIG. 5, the data to be transmitted to the subscriber stations (subscriber stations 6A, 6B, 6C) in cell 1 is supplied to the queue 100. The data is stored in queue 100 according to the subscriber station to which it should be transmitted. The data of the subscriber station 6A is stored in the memory 102A, the data of the subscriber station 6B is stored in the memory 102B, the data of the subscriber station 6C is stored in the memory 102C, and so on. The different storage elements (102A-102N) are for explanatory purposes only, queues generally consist of one memory device, and the different memory devices that are merely an example are the memories in that one device. It can be about the location.

In FIG. 3, at the first time interval (t = 0), the BSC 4 sends a message instructing the base station to transmit to the transmission controller 104. In response, the transmit controller 104 selects the time period during which the data is in the queue and the receiving subscriber station within its coverage area. In a preferred embodiment, the selection of the receiving subscriber station is based on the amount of data queued for transmission to the subscriber station within the coverage area. The transmission controller 104 selectively supplies a signal to one of the storage elements 102A-102N based on its selection of the receiving subscriber station. Further, according to the selected receiving subscriber station, the transmission controller 104 supplies the encoder 106 with a signal indicating the coding rate used for transmission to the selected subscriber station.

The transmission controller 104 supplies the encoder 106 with a header message identifying the receiving subscriber station. In one exemplary embodiment, the encoder 106 encodes a header message using the encoding format used to encode the header for transmission to all subscriber stations. In one exemplary embodiment, the header information is encoded separately from the rest of the data and therefore the subscriber station is transmitted in large quantities during the transmission interval if it is not for that subscriber station. There is no need to decrypt the data.

The transmission controller 104 then supplies a signal to the storage element 102A, instructing it to supply data, and the maximum amount of data that can be transmitted to the receiving subscriber station 6A during a predetermined time interval. Specify the value. The predetermined maximum value is the coding rate (R) selected by the fixed transmission rate R as shown in the following equation (4)._enc) Means the maximum amount of information that can be transmitted to the subscriber station 6A within the time interval T. MaxData = (R T) / R_enc (Four) Depending on the signal from the transmit controller 104, the storage element 102A supplies MaxData to the encoder 106 with less or the same amount of data.

The encoder 106 encodes the data using the selected encoding format and combines the encoded symbols of the data with the encoded symbols of the header message. In an exemplary embodiment, the encoder 106 encodes data at a plurality of convolutional coding rates. For example, the encoder 106 can encode data using rate 1/2, 1/3, 1/4 and 1/5 convolutional coding formats. The coding rate can be changed to essentially any rate by the combination of data puncturing and typically used encoders. The encoder 106 supplies the encoded symbol to the interleaver 108.

The interleaver 108 reconstructs the symbol according to a predetermined reconstruction format and supplies the reconstructed symbol to the scrambler 110. The scrambler scrambles this symbol according to a predetermined CDMA spread format and supplies the spread symbol to the modulator 112. Since only one subscriber station 6A is transmitting the signal, the use of the scrambler 110 is for scrambling data for security purposes, not for multiple access communication purposes, and is immune to narrow band noise. Note that it enhances immunity.

The modulator 112 modulates the diffused symbol according to a predetermined modulation format. In an exemplary embodiment, the modulator 112 is 16 QAM modulators. The modulator 112 supplies the modulated symbol to the transmitter (TMTR) 114. Transmitter 114 upconverts and amplifies the signal and transmits it via antenna 116.

The transmitted signal is received by the antenna 200 at the subscriber station 6A. The received signal is supplied to the receiver (RCVR) 202. The receiver 202 down-converts and amplifies the received signal. The received signal is supplied to a demodulator 204 that demodulates the signal according to a predetermined demodulation format. The demodulated signal is supplied to the equalizer 205, which is the channel equalizer described above. The channel equalized signal is supplied to the descrambler 206, which descrambles the signal according to the predetermined CDMA despread format described above. The deinterleaver 208 reconstructs the despreaded symbol and supplies it to the decoder 210.

In an exemplary embodiment, the decoder 210 first decodes the header message contained within the reconstructed symbol. The header message is supplied to the header checking means 214 confirming that the information being transmitted is intended to the subscriber station 6A. If the data was intended for subscriber station 6A, the rest of the data will be decrypted. If the header indicates that the data is intended for the user of subscriber station 6A, header check 214 provides the decoder 210 with a signal indicating that the remaining information should be decoded. In another embodiment, all information is decoded and the header is checked after the decoding step.

The decoder 210 decodes the symbol according to the selected decoding format from the control processor 212. The decoder 210 decodes the reconstructed symbol according to one of a plurality of trellis decoding formats selected based on the selected coding rate. The decrypted symbol is then supplied to the user of subscriber station 6A.

In the second embodiment, the transmission controller 104 selects the modulation format according to the distance between the base station and the mobile station. Base station 1 transmits an instruction of the selected modulation format to the subscriber station. The modulation format directly affects the transmit rate R. In equation (2), the path loss L_sAnd all parameters except transmission rate R are fixed in this case. A higher transmission rate (R) is transmitted using a modulation format that contains a larger set of modulation symbols. For example, 28 quadrature amplitude modulation (QAM) can be used for transmission to a subscriber station close to the base station. However, 16 QAM modulations are used for transmission to subscriber stations farther from the base station.

In an exemplary embodiment, subscriber station 6A sends a message to base station 1 indicating its location. In response, base station 1 selects a modulation format. As described above for the previous embodiment, the distance calculated by the transmit controller 104 is quantized. The modulation format is selected according to the quantized distance. Referring to FIG. 4, all subscriber stations located between base station 1 and circle 7A receive information using the first modulation format. All subscriber stations located between circles 7A and 7B receive information using the second modulation format. All subscriber stations located between circles 7B and 7C receive information using the third modulation format. For example, in FIG. 4, base station 1 uses the QPSK modulation format when transmitting to subscriber station 6B close to base station 1. Conversely, base station 1 uses 64 quadrature amplitude modulation (QAM) when transmitting to subscriber station 6A, which is far from base station 1. In an exemplary embodiment, a message indicating the selected modulation format is transmitted on the paging channel during the registration process. Again, in a preferred embodiment, the communication system allows base station 1 to change the modulation format with the following message transmitted over the paging channel.

The transmitted signal indicating the modulation format is received by the subscriber station 6A described above and supplied to the control processor 212. The control processor 212 supplies the demodulator 204 with a signal indicating the demodulation format used. In the second embodiment, the demodulator 204 can demodulate the received signal according to a plurality of demodulation formats. An appropriate demodulation format is selected depending on the signal from the control processor 212.

Returning to FIG. 5, the signal transmitted to the subscriber stations (subscriber stations 6A, 6B, 6C) in cell 1 is supplied to the queue 100. In the first time interval (t = 0), the BSC 4 sends a message instructing the base station 1 to transmit to the transmission controller 104. Depending on the signal, the transmission controller 104 selects the above-mentioned receiving subscriber station. The transmission controller 104 selectively supplies one signal to one of the storage elements 102A-102N based on its selection by the subscriber station. Further, according to the subscriber station's choice, the transmit controller supplies a signal indicating the selected modulation format to the modulator 112.

The transmission controller 104 supplies a header message to the encoder 106 that identifies the subscriber station to which the data is being sent. The encoder 106 encodes the header message as described above. The transmission controller 104 then instructs the storage element 102A to supply data and signals to the receiving subscriber station 6A to specify the maximum amount of data that can be transmitted during a predetermined time interval. Supply. The predetermined maximum value means the maximum amount of information that can be transmitted to the subscriber station 6A within a predetermined time interval at the selected rate as shown in the equation (4). MaxData = M R_s T (5) Where M is the number of modulation symbols used in the selected modulation format, R_sIs the symbol rate. In response to the signal from the transmit controller 104, the storage element 102A supplies the encoder 106 with an amount of data equal to or less than MaxData.

In a second embodiment, the encoder 106 encodes the data at a fixed encoding rate and combines the encoded symbol of the header message with the encoded symbol of the data. The encoder 106 supplies the encoded symbol to the interleaver 108. The interleaver 108 reconstructs the symbol according to a predetermined reconstruction format and supplies the reconstruction symbol to the scrambler 110. The scrambler 110 scrambles the symbols according to a predetermined CDMA spread format and supplies the scrambled symbols to the modulator 112.

The modulator 112 modulates the scrambled symbol according to the selected modulation format. In an embodiment, the modulator 112 maps the scrambled symbol to a modulation symbol according to a plurality of modulation formats. The modulator 112 supplies the modulated symbol to the transmitter (TMTR) 114. The transmitter 114 upconverts and amplifies the signal and transmits it via the antenna 116.

The transmission signal is received by the subscriber station 6A at the antenna 200. The received signal is supplied to the receiver (RCVR) 202. The receiver 202 down-converts and amplifies the received signal. The received signal is fed to a demodulator 204 that demodulates the signal according to the selected demodulation format. The demodulated signal is supplied to the equalizer 205 that channel equalizes the received signal as described above. The equalized signal is fed to the descrambler 206, which descrambles the signal according to a predetermined CDMA despread format. The deinterleaver 208 reconstructs the descrambled signals and supplies them to the decoder 210.

In an exemplary embodiment, the decoder 210 first decodes the header message contained in the reconstructed symbol. The header message is supplied to the header checking means 214 for confirming whether the transmitted information is intended for the subscriber station 6A. If the data is intended for subscriber station 6A, the rest of the data will be decrypted. If the header indicates that the data is intended for the user of subscriber station 6A, header check 214 sends a signal to the decoder 210 indicating that the remaining information should be decoded. In another embodiment, all information is decoded and the header is checked after the decoding process is complete. The decoder 210 decodes the symbol. The decrypted symbol is then supplied to the user of subscriber station 6A.

It should be noted that there may be systems that simultaneously change the coding rate and use the technique of changing the modulation format.

The above-mentioned description of a good embodiment is given to those skilled in the art who intend to use the present invention. Various variations of these embodiments will be possible to those skilled in the art, and comprehensive principles will be possible without the need for special competence with respect to other embodiments. Therefore, the present invention is not limited to the above-described embodiment, but covers a wide range that does not contradict the above-mentioned principles and novel features.<u style="single"> The inventions described in the claims of the original application of the present application are described below.</u><u style="single">[C1]</u><u style="single"> It is a method of communicating digital data from the 1st communication station to the 2nd communication station.</u><u style="single"> Determine the distance between the first communication station and the second communication station,</u><u style="single"> Select the information rate for transmission according to the distance,</u><u style="single"> The digital data is transmitted at the transmission rate.</u><u style="single">A digital data communication method having a process.</u><u style="single">[C2]</u><u style="single"> The method described in C1, wherein the step of selecting the information rate comprises selecting the coding rate of the digital data.</u><u style="single">[C3]</u><u style="single"> The method described in C1, wherein the step of selecting the information rate comprises selecting a modulation format of the digital data.</u><u style="single">[C4]</u><u style="single"> The method described in C1, wherein the step of selecting the coding rate comprises selecting one of a predetermined set of predetermined convolutional coding rates.</u><u style="single">[C5]</u><u style="single"> The step of determining the distance is</u><u style="single"> Send a location message from the first communication station to the second communication station,</u><u style="single"> Determine the distance according to the communication message</u><u style="single">The method described in C1 having a step.</u><u style="single">[C6]</u><u style="single"> The step of determining the distance is</u><u style="single"> Send a reference signal with a known output,</u><u style="single"> Measuring the received output of the reference signal,</u><u style="single"> Calculate the value of the distance according to the known output and the received output</u><u style="single">The method described in C1 having a step.</u><u style="single">[C7]</u><u style="single"> The step of transmitting the digital data at the data rate is the method described in C1 performed at a fixed maximum transmission energy.</u><u style="single">[C8]</u><u style="single"> The method according to C1, further comprising a step of blocking transmission by at least one adjacent first communication station when the first communication station is transmitting.</u><u style="single">[C9]</u><u style="single"> In a communication system in which a first communication station transmits digital data to a second communication station, the information rate of the digital data is determined according to a path loss between the first communication station and the second communication station, and the digital is determined. How to receive data</u><u style="single"> The signal indicating the information rate is received in the second communication.</u><u style="single"> The second communication station selects the reception format according to the data rate.</u><u style="single"> Receive the digital data according to the selected reception format</u><u style="single">A method of receiving digital data having a process.</u><u style="single">[C10]</u><u style="single"> The method described in C9, wherein the step of selecting the receiving format comprises selecting a decoding format.</u><u style="single">[C11]</u><u style="single"> The method described in C10, wherein the step of selecting the reception format comprises selecting a trellis decoding format.</u><u style="single">[C12]</u><u style="single"> The method described in C9, wherein the step of selecting the reception format comprises selecting a demodulation format.</u><u style="single">[C13]</u><u style="single"> A device for transmitting digital data from the 1st communication station to the 2nd communication station.</u><u style="single"> A transmission controller that selects a transmission format according to the distance between the first communication station and the second communication station and supplies a transmission format signal indicating the selected transmission format.</u><u style="single"> A device having a transmission system that receives the digital data and the transmission format signal and transmits the digital data according to the selected transmission format.</u><u style="single">[C14]</u><u style="single"> The transmission controller is the device described in C13 that selects the coding rate of the digital data.</u><u style="single">[C15]</u><u style="single"> The transmission controller is the device described in C13 that selects the modulation format of the digital data.</u><u style="single">[C16]</u><u style="single"> The transmission controller is the device described in C14 that selects one of a predetermined set of convolutional coding rates.</u><u style="single">[C17]</u><u style="single"> It also has a receiver subsystem that receives location messages from the second communication station.</u><u style="single"> The apparatus according to C13, wherein the transmission controller receives the position message and calculates the distance between the first communication station and the second communication station according to the position message.</u><u style="single">[C18]</u><u style="single"> It also has a receiver subsystem that receives a signal from the second communication station that informs the transmission energy.</u><u style="single"> The apparatus according to C13, wherein the transmission controller measures the energy of the received signal and calculates the distance between the first communication station and the second communication station according to the measured energy of the received signal. ..</u><u style="single">[C19]</u><u style="single"> The transmission system is the device according to C13 that transmits the digital data with a fixed maximum transmission energy.</u><u style="single">[C20]</u><u style="single"> The first communication station is a cellular base station that supplies to the first cell, the transmission controller further receives a transmission signal indicating a time interval for transmission, and the transmission signal is further transmitted by the first communication station. The device according to C13, which is given to prevent other base stations that supply cells adjacent to the first cell from transmitting when transmitting.</u><u style="single">[C21]</u><u style="single"> In a communication system, where the first communication station transmits digital data to the second communication station, the information rate of the digital data is determined according to the distance between the first communication station and the second communication station. The device for receiving data is</u><u style="single"> A receiver subsystem that receives a signal indicating the information rate in the second communication, and</u><u style="single"> The second communication station has a control processor that selects a reception format according to the data rate.</u><u style="single"> The receiver subsystem further receives the digital data according to the selected reception format.</u><u style="single">[C22]</u><u style="single"> The control processor is the device described in C21 that selects the decoding format.</u><u style="single">[C23]</u><u style="single"> The control processor is the device described in C22 that selects the trellis decoding format.</u><u style="single">[C24]</u><u style="single"> The control processor is the device described in C21 for selecting a demodulation format.</u>