KR20000016230A - Member unit for code division multiple access wireless communication system - Google Patents

Abstract

PURPOSE: A member unit for code division multiple access(CDMA) wireless communication system is provided to raise a band width efficiency and a data transmitting speed by not limiting a repetition size. CONSTITUTION: In method of modulation data for transmitting from a first member unit to a base station communicating with the member unit set, the method is comprising the steps of modulating a first data into a first crossing code for formation of a first channel data, modulating a second data into a second modulation code for formation of a second channel data, adding the first channel data and the second channel data for formation of an added data, and modulating the added data into a long code for formation of the modulated data.

Description

Subscriber unit for CDMA wireless communication system

Wireless communication systems, including cellular, satellite, and point-to-point communication systems, use radio links consisting of modulated radio frequency (RF) signals to transfer data between two systems. The use of wireless links is desirable for a number of reasons, such as increased mobility and reduced need for basic facilities compared to wireless line communication systems. One disadvantage of using a wireless link is that the communication capacity is limited by the limited amount of available RF bandwidth. This limited communication capacity is compared to wired communication where additional capacity can be added by additional wire line connections.

Because of the limited nature of the RF bandwidth, various signal processing techniques have been developed to increase the efficiency with which wireless communication systems utilize available RF bandwidth. The most widely used examples of signal processing techniques that make efficient use of bandwidth are IS-95 and its derivatives in the aviation interface standard published by the Telecommunication Industry Association (TIA) and primarily used in cellular telecommunication systems. For example, something like IS-95-A (hereafter commonly referred to as the IS-95 standard). The IS-95 standard, in combination with code division multiple access (CDMA) signal modulation technology, enables multiple communications on the same RF bandwidth. Combined with comprehensive power control, performing multiple communications over the same bandwidth, among other things, increases the frequency reuse compared to other wireless communications technologies, thereby increasing the total number of calls or other communications that can be performed in a wireless communications system. . The use of CDMA technology in a multiple access communication system is described in US Pat. No. 4,901,307, "Spectrum Spread Communication System Using Satellite or Terrestrial Repeater," and US Pat. No. 5,103,459, "Apparatus and Method for Generating Signal Waveforms in CDMA Cellular Telephone Systems." "And are assigned to the assignee of the present invention, which is hereby incorporated by reference.

1 is a schematic diagram of a cellular telephone system constructed in accordance with the use of the IS-95 standard. In operation, subscriber units 10a-d perform wireless communication by forming one or more RF interfaces with one or more base stations 12a-d using CDMA modulated RF signals. Each RF interface between base station 12 and subscriber unit 10 consists of a forward link signal transmitted from base station 12 and a reverse link signal transmitted from subscriber unit. Using the RF interface, communication with other users is performed by a mobile switching center (MTSO) 14 and a public switched telephone network (PSTN) 16. Although the use of additional RF or microwave links is known, the link between base station 12, MTSO 14 and PSTN 16 is generally formed via a wired connection.

In accordance with the IS-95 standard, each subscriber unit 10 transmits user data at a maximum data rate of 9.6 or 14.4 kbit / sec depending on the selected rate set via a single channel incoherent reverse link signal. An incoherent link is a link in which no phase information is used by the receiving system. A coherent link is a link that uses carrier signal phase information during processing by the receiver. Phase information is generally obtained in the form of a pilot signal, but can also be predicted from the transmitted data. The IS-95 standard requires 64 Walsh codes, each of which consists of 64 chips and is used for the forward link.

The use of single-channel incoherent reverse link signals with a maximum data rate of 9.6 or 14.4 kbit / sec as specified by IS-95 allows for wireless cellular telephones where typical communications are associated with the transmission of low rate digital data, such as digital voice or facsimile. It is very suitable for the system. The reason that the non-coherent reverse link is selected is that in a system in which up to 80 subscriber units 10 communicate with the base station 12 each with a bandwidth of 1.2288 MHz, each subscriber unit 10 interferes with each other. This is because the pilot signal required for transmission from (10) increases. Further, at a data rate of 9.6 or 14.4 kbit / sec, the interference between subscriber units is thus increased because the ratio of the transmission power of the user data to the transmission power of the predetermined pilot signal is large. The reason why a single channel reverse link is used is that it involves only one type of communication at a time, consistent with the use of wireline telephones, which is the basis of current wireless cellular communication. Furthermore, the complexity in single channel processing is small compared to the complexity in multi channel processing.

As digital communications advance, the demand for wireless data transmission is increasing in applications such as interactive file browsing and video conferencing. This increase changes the way the wireless communication system is used and changes the situation in which the associated RF interface is performed. In particular, data is transmitted at higher maximum rates and at more variable rates. In addition, since errors in data transmission are tolerated less than errors in audio information transmission, more reliable transmission is required. In addition, the number of data types has increased, which necessitates the need to transmit several types of data simultaneously. For example, it may be necessary to exchange data files while maintaining the audio or video interface. In addition, as the transmission rate from the subscriber unit increases, the number of subscriber units 10 communicating with the base station 12 per size of the RF bandwidth is reduced, which means that a higher data transfer rate is a smaller number of data processing capacity of the base station. This is because it is limited to the subscriber unit 10. In some cases, current IS-95 reverse links may not be suitable for all such environments.

The present invention relates to a communication system. In particular, the present invention relates to novel and improved apparatus and methods for high data rate CDMA wireless communications.

1 is a block diagram of a cellular telephone system.

2 is a block diagram of a subscriber unit and a base station constructed in accordance with an embodiment of the present invention.

3 is a block diagram of a BPSK channel encoder and a QPSK channel encoder constructed in accordance with an embodiment of the present invention.

4 is a block diagram of a transmission signal processing system constructed in accordance with an embodiment of the present invention.

5 is a block diagram of a reception processing system constructed according to an embodiment of the present invention.

6 is a block diagram of a finger processing system constructed in accordance with an embodiment of the present invention.

7 is a block diagram of a BPSK channel decoder and a QPSK channel decoder constructed in accordance with an embodiment of the present invention.

Accordingly, an object of the present invention is to provide a CDMA interface having a high bandwidth efficiency and a high data rate at which various kinds of communication can be performed.

An improved and novel method and apparatus for high speed CDMA wireless communication in accordance with the present invention is described. According to one embodiment of the present invention, a set of individually gain adjusted subscriber channels is formed through the use of an orthogonal subchannel code set with a small number of PN spreading chips per orthogonal waveform period. The data to be transmitted over one of the transport channels is encoded with low code rate error correction and repeated in sequence before being modulated and gain adjusted by one of the subchannel codes and summed with the data modulated using the other subchannel code. . The use of short orthogonal codes suppresses interference while allowing for repeatability for wide error correcting coding and time diversity to overcome the lolly fading typically encountered in terrestrial wireless systems. In an embodiment of the invention, a subchannel code set consists of four Walsh codes, each Walsh code being orthogonal to the remaining set and four chips in the period. The use of four subchannels is desirable because it allows shorter orthogonal codes to be used. However, the use of a larger number of channels and hence of longer codes is also possible.

In a preferred embodiment of the present invention, pilot data is transmitted over a first transmission channel and power control data is transmitted over a second transmission channel. The other two transport channels are used to transmit user data or signaling data, or non-specific digital data containing both. In an embodiment, one of the two unspecified transport channels is for BPSK modulation and the other is for QPSK modulation. This is done to represent the diversity of the system. In alternative embodiments, both channels may be BPSK or QPSK modulated. Before being modulated, unspecified data is encoded, which includes cyclic redundancy check (CRC) generation, convolutional encoding, interleaving, optional sequence repetition, and BPSK or QPSK mapping. By varying the repetition size and not limiting the repetition size to an integer number of symbol sequences, a wide range of transmission rates can be achieved, including high data rates. In addition, high data rates can be achieved by transmitting data simultaneously over two unspecified transport channels. In addition, by frequently updating the gain adjustments performed in each transmission channel, the overall transmission power used in the transmission system is kept to a minimum, thereby minimizing interference occurring between multiple transmission channel systems, thus increasing the overall system capacity. have.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

New and improved methods and apparatus for high speed CDMA wireless communication are described with reference to the reverse link transmission portion of a cellular telecommunication system. While the present invention is suitable for use in multipoint-to-point reverse link transmission of cellular telephone systems, the present invention is also suitable for the forward link. In addition, many other wireless communication systems can be enhanced in conjunction with the present invention, including satellite wireless communication systems, point-to-point wireless communication systems, and systems for transmitting radio frequency signals using coaxial or other broadband cables.

2 is a block diagram of a receiving and transmitting system comprised of a subscriber unit 100 and a base station 120 in accordance with one embodiment of the present invention. A first set of data (BPSK data) is received by the BPSK channel encoder 103, which is received by the modulator 104 and also generates a code symbol stream configured to perform BPSK modulation. The second data set (QPSK data) is received by QPSK channel encoder 102, which is also received by modulator 104 and also generates a code symbol stream configured to perform QPSK modulation. Modulator 104 also receives power control data and pilot data, which are modulated with BPSK and QPSK encoded data in accordance with code division multiple access (CDMA) techniques to provide RF processing system 106. Generate a set of modulation symbols received by the. The RF processing system 106 filters the modulation symbol set and upconverts it to a carrier frequency for transmission to the base station 120 using the antenna 108. Although only one subscriber unit 100 is shown, in a preferred embodiment multiple subscriber units communicate with a base station 120.

Within base station 120, RF processing system 122 receives the RF signal transmitted through antenna 121, performs band filtering, downconverts to baseband, and digitizes. Demodulator 124 receives the digital signal and performs demodulation by CDMA technology to form power control, BPSK and QPSK soft decision data. The BPSK channel decoder 128 decodes the BPSK soft decision data received from the demodulator 124 to generate an optimal estimate for the BPSK data, and the QPSK channel decoder 126 receives the QPSK soft decision received from the demodulator 124. Decode the data to generate an optimal estimate for the QPSK data. Optimal estimates for the first and second data sets are used for subsequent processing or sent to the next stage, and the received power control data is used directly or after decoding to transfer data to subscriber unit 100. Adjust the transmit power of the forward link channel used.

3 is a block diagram of a BPSK channel encoder 103 and a QPSK channel encoder 102 constructed in accordance with an embodiment of the present invention. Within the BPSK channel encoder 103, BPSK data is received by the CRC checksum generator 130, which generates a checksum for each 20ms frame of the first data set. The data frame along with the CRC check sum is received by the tail bit generator 132, which adds a tail bit consisting of eight logic zeros at the end of each frame to indicate the state at the end of the decoding process. . The frame including the code tail bits and the CRC check sum is received by the convolutional encoder 134, which performs a constraint length (K) 9, a rate (R) 1/4 convolutional encoding to encode an encoder input rate (E). Generate code symbols at four times the speed of _R ). In alternative embodiments of the present invention, other encoding speeds, including speed 1/2, are performed, but the use of speed 1/4 is desirable because of the optimal complexity performance characteristics. The block interleaver 136 performs bit interleaving on code symbols to provide time diversity for more reliable transmission in a fast fading environment. The interleaved symbols are received by the variable start point repeater 138, which repeats the interleaved symbol sequences a sufficient number N _R to provide a constant rate symbol stream, which is characterized by an output frame having a constant number of symbols and a number of symbols. Corresponds. Relaying the symbol sequence increases the time diversity for the data to overcome fading. In an embodiment, the constant number of symbols is 6,144 symbols for each frame making a symbol rate of 307.2 kps. In addition, the repeater 138 uses a different starting point to start relaying for each symbol sequence. When the N _R value needed to generate 6,144 symbols per frame is not an integer, the final relay is performed only for a portion of the symbol sequence. Accordingly, the final relayed symbol set is received by the BPSK mapper 139, which generates a BPSK code symbol stream (BPSK) of +1 and -1 values to perform BPSK modulation. In an alternative embodiment of the invention, the repeater 138 is placed in front of the block interleaver 136 such that the block interleaver 136 receives the same number of symbols for each frame.

Within QPSK channel encoder 102, QPSK data is received by CRC checksum generator 140, which generates a checksum for each 20ms frame. The frame containing the CRC check sum is received by the codedale bit generator 142, which adds a set of eight logic zero tail bits at the end of the frame. The frame containing the code tail bits and the CRC check sum is received by a convolutional encoder 144 that performs K = 9, R = 1/4 convolutional encoding to generate a symbol at four times the encoder input rate E _R. . Block interleaver 146 performs bit interleaving on the symbols, and as a result the interleaved symbols are received by variable start point iterator 148. The variable start point iterator 148 is interleaved by a sufficient number N _R using different starting points in the symbol sequence for each iteration to generate 12,288 symbols for each frame having a code symbol rate (ksps) of 614.4 kilosymbols per second. Repeat the sequence. When N _R is not an integer, the final iteration is performed for only part of the symbol sequence. The resulting repeat symbol generates a QPSK code symbol stream configured to perform QPSK modulation consisting of an in-phase QPSK code symbol stream of +1 and -1 values and an orthogonal QPSK code symbol stream (QPSK _Q ) of +1 and -1 values. Is received by the QPSK mapper 149. In another embodiment of the invention, the iterator 148 is positioned in front of the block interleaver 146 such that the block interleaver 146 receives the same number of symbols for each frame.

4 is a block diagram of the modulator 104 of FIG. 2 constructed in accordance with an exemplary embodiment of the present invention. The BPSK symbols from BPSK channel encoder 103 are modulated to Walsh code W ₂ using multiplier 150b, respectively, and the QPSK _I and QPSK _Q symbols from QPSK channel encoder 102 are multipliers 150c and 154d. Are modulated with the Walsh code W ₃ using Power control data PC is modulated by Walsh code W ₁ using multiplier 150a. Gain adjuster 152 receives pilot data PILOT consisting of logic levels associated with positive voltages in a preferred embodiment of the present invention and controls the amplitude in accordance with gain adjustment factor A ₀ . The PILOT signal provides phase and amplitude information to the base station to coherently demodulate the data transmitted over the remaining subchannels without providing user data, and scales the soft decision output for combination. Gain controller 154 controls the amplitude of Walsh code W ₁ modulated power control data according to gain control factor A ₁ , and gain controller 156 adjusts the amplitude of Walsh code W ₂ modulated BPSK channel data according to amplification variable A ₂ . Adjust Gain controllers 158a and 158b control the amplitude of quadrature code W ₃ modulated QPSK symbols, respectively, in accordance with gain control factor A ₃ . The four Walsh codes used in the preferred embodiment of the present invention are shown in Table I.

Table I

Walsh Code Modulation symbol W ₀ + + + + W ₁ +-+- W ₂ + +-- W ₃ +--+

It will be apparent to those skilled in the art that the W ₀ code may not efficiently perform modulation consistent with the processing of the pilot data shown. Power control data is modulated by the W ₁ code, BPSK data is modulated by the W ₂ code, and QPSK data is modulated by the W ₃ code. Once modulated with the appropriate Walsh code, the pilot, power control data and BPSK data are transmitted according to the BPSK technique, and the QPSK data (QPSK _I , QPSK _Q ) are transmitted according to the QPSK technique as described below. Not all orthogonal channels need to be used, and using only three Walsh codes out of four Walsh codes provided that only one user channel is provided applies to another embodiment of the present invention.

Using short orthogonal codes results in fewer chips per symbol, allowing for wider coding and repeatability compared to systems with long Walsh codes. This wide coding and repeatability prevents Rayleigh fading, an important source of error in terrestrial communications systems. Using different numbers of codes and code lengths is a technique of the present invention, but using a large set of long Walsh codes can prevent fading more efficiently. It is considered optimal because it uses four chip codes and the four channels flexibly provide various types of data as described below while maintaining a short code length.

Summer 160 sums the resulting amplitude control modulation symbols from gain adjusters 152, 154, 156, 158a to generate summed modulation symbols 161. PN spreading codes PN _I and PN _Q are spread by long code 180 using multipliers 162a and 162b. The resulting pseudonoise code provided by multipliers 162a and 162b is summed through complex multiplication using multipliers 164a-d and summers 166a and 166b and the gain-adjusted quadrature phase. It is used to modulate the symbol QPSK _Q. The resulting in-phase term X _I and quadrature term X _Q are filtered (not shown) and the carrier frequency in RF processing system 106 shown in a very simple form using multiplier 168 and in-phase and quadrature sinusoids. Is converted to. Offset QPSK transform can also be used in other embodiments of the present invention. The resulting in-phase and quadrature-converted signals are summed using a summer 170 and amplified by the main amplifier 172 according to the main gain controller A _M to generate a signal transmitted to the base station 120. . In a preferred embodiment of the invention, the signal is spread and then filtered with a 1.2288 MHz bandwidth to maintain compatibility with the bandwidth of an existing CDMA channel.

By using a variable rate repeater that provides multiple orthogonal channels through which data is transmitted and reduces the amount of repetition N _{R that} is executed in response to high speed input data, the above described methods and systems for processing a transmission signal may comprise a single subscriber device or other transmission. Allows the system to transmit data at various data rates. In particular, execution also by variable starting point repeater (138 or 148) of FIG. 3 can be by reducing the rate of repetition N _R, maintain a high-speed encoder input E _R. In another preferred embodiment of the present invention, half speed convolutional encoding is performed at a rate of repetition N _R increased by two. A set of typical encoder speeds E _R supported by various repetition rates N _R and encoding rates R equal to 1/4 and 1/2 for BPSK channels and QPSK channels are shown in Tables II and III, respectively.

Table II. BPSK Channel

label E _{R, BPSK} (bps) Encoder output R = 1/4 (bits / frames) N _{R, R = 1/4} (Repeat rate, R = 1/4) Encoder output R = 1/2 (bits / frames) N _{R, R = 1/2} (Repeat rate, R = 1/2) High speed-72 76,800 6,144 One 3,072 2 High speed-64 70,400 5,632 1 1/11 2,816 2 2/11 51,200 4,096 1 1/2 2,048 3 High speed-32 38,400 3,072 2 1,536 4 25,600 2,048 3 1,024 6 RS2-Full Speed 14,400 1,152 5 1/3 576 10 2/3 RS1-Full Speed 9,600 768 8 384 16 Board 850 68 90 6/17 34 180 12/17

Table III. QPSK Channel

label E _{R, QPSK} (bps) Encoder output R = 1/4 (bits / frames) N _{R, R = 1/4} (Repeat rate, R = 1/4) Encoder output R = 1/2 (bits / frames) N _{R, R = 1/2} (Repeat rate, R = 1/2) 153,600 12,288 One 6,144 2 High speed-72 76,800 6,144 2 3,072 4 High speed-64 70,400 5,632 2 2/11 2,816 4 4/11 51,200 4,096 3 2,048 6 High speed-32 38,400 3,072 4 1,536 8 25,600 2,048 6 1,024 12 RS2-Full Speed 14,400 1,152 10 2/3 576 21 1/3 RS1-Full Speed 9,600 768 16 384 32 Board 850 68 180 12/17 34 361 7/17

Tables II and III show that by varying the number of sequence repetitions N _R , various data rates include faster data rates. This is because the encoder input rate E _R corresponds to the constant minus data rate required to transmit the CRC, code tail bits and any other overhead information. As shown in Tables II and III, QPSK modulation can be used to increase the data rate. Commonly used speeds are provided in labels such as "fast-72 and fast-32". The speeds labeled Fast-72, Fast-64 and Fast-32 have traffic speeds of 72, 64 and 32 kbps, respectively, and are multiplexed with signaling and other control data with speeds of 3.6, 5.2 and 5.2 kbps. RS1-full speed and RS2-full speed correspond to IS-95 compliance communication systems and will receive information for compatibility. The null rate is a single bit transmission and is used to indicate the frame erasure part of the IS-95 standard.

The data rate can be increased by simultaneously transmitting data over two or more orthogonal channels that are implemented in addition to or instead of increasing the rate through a reduction in the repetition rate N _R. For example, a multiplexer (not shown) may partition a single data source into multiple data sources to be transmitted over multiple data subchannels. Thus, the overall transmission rate is either high speed transmission on a specific channel or multiple transmissions running simultaneously on multiple channels or both until the signal processing capacity of the receiving system is exceeded and error rates are not allowed or the maximum transmission power of the transmission system power is reached. Can be increased through.

Providing multiple channels increases flexibility in the transmission of other forms of data. For example, a BPSK channel is designated for voice information, and a QPSK channel is designated for transmission of digital data. This embodiment may be more generalized by specifying data for transmitting time sensitive data such as voice at a slower data rate and specifying other channels for transmitting less sensitive data such as digital files. In this embodiment, interleaving can be performed in large blocks for less time-sensitive data to increase time diversity. In another embodiment of the present invention, the BPSK channel performs main transmission of data, and the QPSK channel performs overflow transmission. Using an orthogonal Walsh code removes or reduces any interference between the set of channels transmitted from the subscriber device and minimizes the transmission energy required for successful reception at the base station.

In order to increase the processing capacity in the receiving system and increase the range in which the high transmission capacity of the subscriber device is available, pilot data is transmitted on one of the orthogonal channels. Using pilot data, coherent processing can be performed at the receiving system by determining and removing the phase offset of the reverse link signal. In addition, the pilot data can be used to optimally determine multipath signals received with different time delays before being coupled to the rake receiver. Once the phase offset is removed and the multipath signal is properly determined, the multipath signal can be combined such that the power that the reverse link signal has to be received for proper processing is reduced. Reduction of the required received power allows the high data rate to be successfully processed or vice versa to reduce interference between a set of reverse link signals. While any additional transmit power is required to transmit the pilot signal, the ratio of pilot channel power to total reverse link signal power is substantially lower than that associated with slow data rate digital voice data transmission cellular systems at high transmission rates. Thus, within a fast data rate CDMA system, the E _b / N _b gain obtained by the use of a coherent reverse link is more important than the additional power required to transmit pilot data from each subscriber device.

Using gain regulators 152-158 and main amplifier 172 increases the likelihood that the high transmission capacity of the system described above can be utilized by adapting the transmission system to various radio channel conditions, transmission rates and data types. . In particular, the transmit power of the channel required for proper reception changes over time, and the change condition is independent of other orthogonal channels. For example, during initial reception of a reverse channel signal, the power of the pilot channel needs to be increased to facilitate detection and synchronization at the base station. Once the reverse link signal is received, the required transmit power of the pilot channel is substantially reduced and varies depending on various factors including the moving speed of the subscriber device. Thus, the value of gain adjuster A ₀ is increased during signal reception and then decreased during communication. In another embodiment, these adjustment factors A ₁ need to transmit power control data at a low error rate when the error-tolerant information is transmitted over the forward link or the environment in which the forward link transmission is performed does not cause fading. Can decrease as it decreases. In one embodiment of the invention, the gain control factor A ₁ is reduced to zero whenever power control adjustment is unnecessary.

In another embodiment of the present invention, the gain control capability for each orthogonal channel or full reverse signal is determined by the use of a power control command transmitted by the base station 120 or other receiving system via the forward link signal. It is further improved by allowing to change the gain control of the signal. In particular, the base station can transmit power control information that requires the transmit power of the particular channel or entire reverse link signal to be adjusted. This is advantageous for many environments, including when two types of error-sensitive data such as digitized voice and digital data are transmitted over the BPSK and QPSK channels. In this case, base station 120 sets several target error rates for the two associated channels. If the actual error rate of the channel exceeds the target error rate, the base station controls the subscriber device to reduce the gain control of the channel until the actual error rate reaches the target error rate. This in some cases allows the gain control of one channel to be increased compared to the other. That is, the gain adjuster associated with the high error sensitive data is increased compared to the gain adjuster associated with the low error sensitive data. In other cases, the transmit power of the reverse link previously needs to be adjusted because of the fading condition or movement of the subscriber device 100. In this case, the base station 120 may perform the above function by transmitting a decoy power control command.

Thus, by allowing the gains of the four orthogonal channels to be adjusted individually and in relation to each other, the overall transmit power of the reverse link signal depends on whether the signal is pilot data, power control data, signaling data or other forms of user data. Thus, each data type can be maintained at the power required to successfully transmit it. Moreover, successful transmission can be defined differently for each data type. When transmitting at the minimum amount of power required, the maximum amount of data can be transmitted to the base station depending on the limited transmit power capacity of the subscriber device and the interference between subscriber devices is reduced. This reduction in interference increases the overall communication capacity of the entire CDMA wireless cellular system.

The power control channel used for the reverse link signal allows the subscriber unit to transmit power control information to the base station at various rates, including the rate of 800 power control bits per second. In a preferred embodiment of the present invention, the power control bit commands the base station to increase or decrease the transmit power of the forward link traffic channel used to transmit information to the subscriber unit. This power control bit is generally useful for controlling power at high speeds within a CDMA system, but is particularly useful in the context of high data rate communications involving data transmission, because digital data is more sensitive to errors and due to high speed transmission. This is because large amounts of data are corrupted even during very simple fading conditions. Assuming that the high speed reverse link transmission will be accompanied by a high speed forward link transmission, providing high speed transmission of power control over the reverse link further facilitates high speed communication within a CDMA wireless telecommunication system.

In an alternative embodiment of the invention, a set of encoder input rates E _R defined by a particular N _R is used to transmit a particular type of data. That is, data can be transmitted at a correspondingly adjusted relative N _R , at a maximum encoder input rate E _R or at a set of low encoder input rates E _R. In a preferred embodiment of the present invention, the maximum speeds correspond to the maximum speeds used in the IS-95 compliant wireless communication system referred to for Tables II and III as RS1-speed and RS2-½ speed, each of the lower speeds being It is about half of the next higher speed, resulting in a set of speeds consisting of full speed, half speed, quarter speed, and ear speed. Low data rates are generated by increasing the symbol repetition rate N _R to the value of N _R for rate set 1 and rate set 2 in the BPSK channels provided in Table IV.

label E _R , BPSK (bps) Encoder output R = 1/4 (bit frame) N _R , R = ¼ (Repeat rate, R = ¼) Encoder output R = ½ (bits / frames) N _R , R = ½ (Repeat rate, R = ½) RS2-speed 14,400 1,152 5 ⅓ 576 10 ⅔ RS2-½ speed 7,200 576 10 ⅔ 288 21 ⅓ RS2-¼ speed 3,600 288 21 ⅓ 144 42 ⅔ RS2-ear 1,900 152 40 8/19 76 80 16/19 RS1-Full Speed 9,600 768 8 384 16 RS1-½ speed 4,800 384 16 192 32 RS1-¼ speed 2,800 224 27 3/7 112 54 6/7 RS1- ear 1,600 128 48 64 96 Null 850 68 90 6/17 34 180 12/17

Table IV. RS1 and RS2 speed set (on BPSK channel)

The repetition rate for the QPSK channel is twice the repetition rate for the BPSK channel.

According to an exemplary embodiment of the present invention, when the data rate of the frame changes with respect to the previous frame, the transmission power of the frame is adjusted according to the change of the transmission rate. That is, the low rate frame is transmitted after the high rate frame, and the transmission power of the transmission channel for that frame is reduced during the low rate frame in proportion to a decrease in speed or the like. For example, during full frame transmission the transmit power of the channel is transmit power T and during the next half rate frame transmission the transmit power is transmit power T / 2. The reduction is performed by reducing the transmit power for the entire duration of the frame, but may be performed by reducing the transmit duty cycle so that some redundant information is "blank out". In some cases, the transmit power adjustment is made in combination with the closed loop power control mechanism so that the transmit power is further adjusted in response to the power control data transmitted from the base station.

5 is a block diagram of the RF processing system 122 and demodulator 124 of FIG. 2 configured in accordance with an exemplary embodiment of the present invention. Multipliers 180a and 180b downconvert the signals received from antenna 9121 into in-phase sinusoids and quadrature sinusoids that produce in-phase receive samples R _I and quadrature receive samples R _Q , respectively. It will be appreciated that the RF processing system 122 is in a very simple form and the signals are matched filtered and digitized (not shown) according to well known techniques. Receive samples R _I and R _Q are applied to finger demodulator 9422 in demodulator 124. Each finger demodulator 182 processes an instance of the reverse link signal transmitted by subscriber unit 100, and if such an instance is available, each instance of the reverse link signal is generated via a multipath phenomenon. . Although three finger demodulators are shown, the use of alternative numbers of finger processors is consistent with the present invention, including the use of a single finger demodulator 182. Each finger demodulator 182 generates a set of soft decision data consisting of power control data, BPSK data, QPSK _I data, and QPSK _Q data. Each set of soft decision data is timed in the corresponding finger demodulator 182, although time adjustment may be performed in the combiner 184 of another embodiment of the present invention. The combiner 184 sums the soft decision data sets received from the finger demodulator 182 to produce a single instance of power control data, BPSK data, QPSK _I data and QPSK _Q soft decision data.

6 is a block diagram of the finger demodulator of FIG. 5 configured in accordance with an exemplary embodiment of the present invention. R _I and R _Q are time adjusted using time adjustment 190 in accordance with the amount of delay induced by the transmission path of the particular instance of the reverse link signal to be processed. The long code 200 is mixed with the pseudonoise spreading codes PN _I and PN _Q using the multiplier 201, and the conjugate complex numbers of the resulting long code modulated PN _I and PN _Q spreading codes are term X _I and A multiplier 202 and a summer 204 that yield X _{Q are} then complex multiplied with the timed R _I and R _Q received samples. Three separate instances of the X _I and X _{Q terms} are demodulated using Walsh codes W ₁ , W ₂ and W ₃ respectively, and the Walsh demodulated data is passed through four demodulation chips using a four-to-one summer 212. Are added together. The fourth instance of the X _I and X _Q data is summed through four demodulation chips using summer 208 and then filtered using pilot filter 214. In a preferred embodiment of the present invention, pilot filter 214 performs averaging through a series of summations performed by summer 208, although other filtering techniques will be apparent to those skilled in the art. The filtered in-phase and quadrature pilot signals are modulated by the W ₁ , W ₂ Walsh code according to the BPSK modulated data through conjugate complex multiplication using a multiplier 216 and an adder 217 that produce soft decision power control and BPSK data. Used to phase rotate and scale data. The W ₃ Walsh code modulated data is phase rotated using in-phase and quadrature filtered pilot signals in accordance with the QPSK modulated data using multiplier 218 and adder 219 to produce soft decision QPSK data. Soft decision power control data is summed via 384 modulation symbols by a 384 to 1 summer 222 that yields power control soft decision data. The phase rotated W ₂ Walsh code modulated data, W ₃ Walsh code modulated data, and power control soft decision data can then be used to combine. In another embodiment of the invention, encoding and decoding are likewise performed on power control data.

In addition to providing phase information, a pilot may be used in the receiving system to facilitate timing tracking. Timing tracking is performed by processing the received data at the previous (initial) one sample time, and at the subsequent (later) one sample time, and the current received sample is processed. To determine the closest match to the actual arrival time, the amplitude of the pilot channel at the initial and later sample times can be compared with the amplitude at the current sample time to determine the largest. If the signal at one of the adjacent sample times is larger than the signal at the current sample time, the timing can be adjusted to obtain the best demodulation result.

7 is a block diagram of a BPSK channel decoder 128 and a QPSK channel decoder 126 (FIG. 2) configured in accordance with an exemplary embodiment of the present invention. BPSK soft decision data from combiner 184 (FIG. 5) is received by accumulator 240, which stores a first sequence of 6,144 / N _R demodulation symbols in a received frame, where N _R is as described above. Depending on the transmission rate of the soft decision data, add each successive set of 6,144 / N _R demodulation symbols contained in the frame to the corresponding stored and accumulated symbols. The block interleaver 242 deinterleaves the accumulated soft decision data from the variable start point adder 240, and the Viterbi decoder 244 deinterleaves the soft decision data to generate hard decision data as well as the CRC check sum result. Decode In QPSK decoder 126, QPSK _I and QPSK _Q soft decision data from combiner 184 (FIG. 5) is demultiplexed by demultiplexer 246 into a single soft decision data stream, with a single soft decision data stream every 6,144. Received by accumulator 248, which accumulates the / N _R demodulation symbol, where N _R depends on the transmission rate of the QPSK data. The block deinterleaver 250 deinterleaves the soft decision data from the variable start point adder 248, and the Viterbi decoder 252 decodes the deinterleaved modulation symbol to generate hard decision data with the CRC check sum result. do. In another exemplary embodiment described above with respect to FIG. 3 where symbol repetition is performed before interleaving, accumulators 240 and 248 are placed after block deinterleavers 242 and 250. In certain embodiments of the present invention involving the use of an unknown rate set, each operates at a different rate, and the frames associated with the rate are selected based on the CRC checksum result for continued use. The use of other error checking methods is consistent with the practice of the present invention.

Therefore, a multi-channel, high speed, CDMA wireless communication system has been described. The detailed description is provided to enable any person skilled in the art to use the invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of inventive features. Therefore, the present invention is not limited to the embodiments shown herein, but a wide range of consistent with the principles and novel features described herein will be permitted.

Claims (11)

A method of generating modulated data for transmission from a first subscriber unit of a set of subscriber units to a base station in communication with the set of subscriber units, the method comprising: Modulating the first data with a first orthogonal code to produce first channel data; Modulating the second data with a second modulation code to produce second channel data; Summing the first channel data and the second channel data to produce summed data; And Modulating the summed data with a long code to produce the modulated data. The method of claim 1, Gain adjusting the first channel data; And And gain adjusting the second channel data. The method of claim 1, wherein the first data is pilot data and the second data is user data. The method of claim 1, Modulating the power control data with a third orthogonal code to produce third channel data; And Summing the third channel data to the summed data. 2. The method of claim 1, wherein the first channel data is pilot data and the second channel data is user data. The method of claim 4, wherein And gain adjusting the third channel data. The method of claim 1, Modulating in-phase third data with a third orthogonal code to generate in-phase third channel data; Modulating quadrature third data with the third orthogonal code to generate quadrature third channel data; Summing the in-phase third channel data to the summed data; And And complex multiplying the summed data and the quadrature third channel data by an in-phase spreading code and a quadrature spreading code. A first subscriber unit for transmitting a first reverse link signal comprising a first set of orthogonal subchannels; A second subscriber unit for transmitting a second reverse link signal comprising a second set of orthogonal subchannels; And And a base station for receiving the first reverse link signal and the second reverse link signal. 10. The method of claim 8, wherein each orthogonal channel is individually gain controlled in the first set of orthogonal subchannels, and each orthogonal channel is individually gain controlled in the second set of orthogonal subchannels. Communication system. In the method for transmitting a frame of data, Generating multiple symbols for each bit of data through convolutional coding to form a symbol sequence; Repeating the symbol sequence a number of times sufficient to generate a set of symbols comprising a predetermined number of symbols; Modulating each symbol from the symbol set into a first orthogonal code having less than 16 chips to produce a first orthogonal code modulated data; Combining the first orthogonal code modulated data and pilot data to produce combined data; And Transmitting the combined data. The method of claim 10, Gain adjusting the first orthogonally modulated data by a first amount; And And gain adjusting the pilot data by a second amount.