JP2006217243A - Radio communication system, radio communication terminal equipment, and handover control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reception quality in a radio communication terminal at the time of soft handover between the radio communication terminal and a plurality of base stations which perform communication by using a CDMA system, to improve utilization efficiency of radio resources, and to increase throughput. <P>SOLUTION: Each of the plurality of base stations generates punctured encoded data in which a bit determined by a puncture pattern is deleted from error correction encoded data by using the puncture pattern corresponding to each base station which determines the bit to be deleted from the error correction encoded data of transmission data to be transmitted to the radio communication terminal, and modulates, code-spreads, and transmits the punctured encoded data. When receiving respective signals transmitted from the plurality of base stations respectively, the radio communication terminal generates encoded data by using the remaining bit without being deleted in the respective base stations, which is present in at least one of two or more pieces of reception data obtained by inversely spreading and demodulating the respective received signals, and decodes the generated encoded data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless communication system using a code division multiple access (CDMA) system.

  When CDMA is used as a communication method, due to the characteristics of CDMA, multiple base stations transmit the same modulated signal in the same frequency band, and wireless communication terminals receive modulated signals transmitted from multiple base stations simultaneously. It is possible to perform a soft handover for combining processing. In this case, by increasing the signal power-to-interference and noise signal power ratio (SINR) by combining processing, the reception quality at the wireless communication terminal is improved as a result. The effect of increasing is obtained, and the effect of increasing the throughput can be obtained by controlling the modulation scheme and the coding rate at the same time.

  In addition, when a wireless communication terminal moves between base stations, the same modulated signal is transmitted from the plurality of base stations in the same frequency band. As a result, it is possible to move between base stations without interrupting communication. The effect becomes.

  In addition, when a soft handover can be performed in a wireless communication terminal, for example, depending on the characteristics of a communication service, a plurality of base stations select whether to transmit the same data or different data, and the same When transmitting data, the wireless communication terminal combines the same data transmitted from a plurality of base stations in the same way as soft handover, and when transmitting different data, a plurality of base stations differs from soft handover. There are some which selectively receive the effect of increasing the utilization efficiency of radio resources and the effect of increasing the throughput by individually receiving different data transmitted from a station (see, for example, Patent Document 1).

  As described above, conventionally, when a wireless communication terminal can communicate with a plurality of base stations, the wireless communication terminal combines and receives the same signal transmitted by the plurality of base stations. The utilization efficiency is increased or the throughput is increased.

  By the way, in wireless communication between a base station and a wireless communication terminal, for example, when the base station transmits data and the wireless communication terminal receives the data, the base station normally corrects transmission data for each predetermined block length. An environment in which the characteristics of the wireless communication channel fluctuate over time by performing coding and error detection coding, and the wireless communication terminal performs error correction decoding and error detection on the received data for each predetermined block length. In the lower case, the error rate of the transmission data is reduced.

  When the predetermined block length is sufficiently long with respect to the time variation period of the wireless channel characteristics, the wireless communication terminal combines the same signals transmitted by the plurality of base stations, thereby enabling wireless communication with sufficient diversity effect. The reception quality at the terminal is improved, and as a result, it is possible to obtain the effect of increasing the utilization efficiency of radio resources or increasing the throughput.

However, when the predetermined block length is short with respect to the time fluctuation period of the radio channel characteristics, that is, when the radio channel characteristics do not change so much within the predetermined block long term, in particular, a plurality of base stations in the radio communication terminal When there is a difference in the reception state represented by the signal power to interference and noise signal power ratio (SINR) of the transmitted data, it is difficult to obtain a sufficient diversity effect, so the reception quality at the wireless communication terminal is As a result, there is a problem that it is difficult to obtain the effect of increasing the utilization efficiency of radio resources or increasing the throughput. Note that since the predetermined block long-term tends to be shortened as further high-speed communication is required, it can be easily imagined that the above-mentioned problems become apparent as wireless communication develops.
JP 2003-111134 p. 5

  As described above, conventionally, when a wireless communication terminal performs soft handover with a plurality of base stations using the CDMA scheme, the error correction coding and error detection coding block lengths are particularly suitable for the wireless channel characteristics. When the reception state of data from a plurality of base stations received by the wireless communication terminal is short with respect to the time variation period, the reception quality at the wireless communication terminal is improved, and the use efficiency of the radio resource In addition, there is a problem that it is difficult to increase the throughput.

  Therefore, in view of the above problems, the present invention provides error correction coding and error detection coding block lengths when soft handover is performed between a radio communication terminal that performs communication using a CDMA system and a plurality of base stations. Handover control method capable of improving the reception quality in the radio communication terminal even when it is shorter than the time variation period of the radio channel characteristics, and as a result, increasing the utilization efficiency and throughput of radio resources, and An object of the present invention is to provide a radio communication system and a radio communication terminal apparatus using the same.

  (1) Each of a plurality of base stations in a radio communication system comprising a plurality of base stations and radio communication terminals is: (a) error correction of the same transmission data in the plurality of base stations to be transmitted to the radio communication terminals Encoding to generate error correction encoded data, and (b) error correction using a puncture pattern corresponding to the base station among a plurality of different puncture patterns in which bits to be erased are determined from the error correction encoded data Bits defined by the puncture pattern are erased from the encoded data, punctured encoded data is generated, (c) the punctured encoded data is modulated, and (d) the modulated punctured encoded data is spread. (E) A signal including punctured encoded data that has been code-spread is transmitted.

  The wireless communication terminal receives (f) each signal from a plurality of base stations, (g) despreads and demodulates each received signal, and (h) includes a plurality of received data obtained as a result of demodulation. Generate encoded data using bit data that remains without being deleted when generating punctured encoded data in each of a plurality of base stations that exist in at least one, (i) generated The encoded data is decoded.

  (2) Each puncture pattern corresponding to each of the plurality of base stations has at least one bit data of the error correction encoded data generated in each of the plurality of base stations. Bits to be erased are determined to exist, and the wireless communication terminal uses a plurality of base stations from each of a plurality of received data obtained as a result of demodulation based on each puncture pattern corresponding to each of the plurality of base stations. When the punctured encoded data is generated, the bit data remaining without being erased is recognized, and each bit data of the encoded data is determined based on each bit data remaining without being erased. Generate.

  According to the present invention, it is possible to improve reception quality at a radio communication terminal at the time of soft handover between a radio communication terminal that communicates using a CDMA system and a plurality of base stations, and to improve use efficiency and throughput of radio resources. Increase can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the soft handover state according to the present embodiment will be described with reference to FIG.

  In FIG. 1, a plurality of base stations (BS) 101-1 and 101-2 have 102-1 and 102-2 as communication areas, respectively. The base stations 101-1 and 101-2 are connected to the control station 104, and are connected to the communication network 105 via the control station 104. Since the wireless communication terminal 103a exists in the communication area 102-1 of the base station 101-1, it can communicate only with the base station 101-1. Since the wireless communication terminal 103b exists in the communication area 102-1 of the base station 101-1 and the communication area 102-2 of the base station 101-2, the wireless communication terminal 103b simultaneously with the plurality of base stations 101-1 and 101-2. Communication is possible. Furthermore, the wireless communication terminal 103c can communicate only with the base station 101-2 because it exists in the communication area 102-2 of the base station 101-2.

  In the present embodiment, a state in which communication can be performed simultaneously with a plurality of base stations, as in the case of the wireless communication terminal 103b, and a state in which communication is performed simultaneously is referred to as a soft handover state. In the soft handover state, the wireless communication terminal 103b observes the reception state of radio signals transmitted from a plurality of base stations, and notifies the control station 104 via any of the base stations, thereby enabling the control station It can be easily realized by the control of 104.

  Hereinafter, when it is not necessary to distinguish between the wireless communication terminals 103a to 103c, they are referred to as the wireless communication terminal 103, and when it is not necessary to distinguish between the base stations 101-1 to 101-2, they are referred to as the base station 101.

  In the soft handover state, in the downlink communication from the base station to the wireless communication terminal, the control station 104 sends the same data to the base stations 101-1 and 101-2 via the control network 104 from the communication network 105. Notice. The base stations 101-1 and 101-2 transmit the data as radio signals, and the radio communication terminal 103b receives each radio signal simultaneously. In uplink communication from the wireless communication terminal to the base station, the wireless communication terminal 103b transmits the transmission data as a wireless signal, and the base stations 101-1 and 101-2 receive the wireless signal. When the reception is successful, the transmission data is notified to the control station 104 and transmitted to the communication network 105 via the control station 104.

  A configuration example of the base station 101 to which the radio communication control method according to the present embodiment is applied will be described using FIG. In FIG. 2, the base station roughly includes a transmission unit 2, a control unit 3, and a reception unit 6. The transmitter 2 includes an antenna 201, a radio processing circuit 202, a first code multiplication circuit 203, a first data multiplexing circuit 204, a second data multiplexing circuit 205, a pilot generation circuit 206, a second code multiplication circuit 207, a modulation A circuit 208, a puncture processing circuit 209, an error correction coding circuit 210, and an error detection code addition circuit 211. The control unit 3 includes a higher-level I / F 301 and a control circuit 302. The reception unit 6 includes an antenna 601, a wireless A processing circuit 602, a demodulation circuit 603, and an error correction decoding circuit 604 are included.

  Next, the operation of each block of the transmission unit 2 of the base station in FIG. 2 will be described. N indicates the number of code division multiplexing.

  From the upper I / F 301, N-sequence transmission data is output and input to each of the N error detection code addition circuits 211. Each of the N error detection code addition circuits 211 generates and adds an error detection code to the corresponding transmission data input from the higher-level I / F 301 by a predetermined error detection method, and the corresponding error correction code To the circuit 210. Each of the N error correction coding circuits 210 performs error correction coding on the input transmission data to which the error detection code is added with a predetermined coding method and coding rate, and performs error correction coding. Data is generated and output to the corresponding puncture processing circuit 209. Each of the N puncture processing circuits 209 punctures the input error correction encoded data according to a predetermined puncture pattern, generates punctured encoded data, and outputs the punctured encoded data to the corresponding modulation circuit 208. . Each of the N modulation circuits 208 modulates the input punctured encoded data using a predetermined modulation method, and outputs the resulting modulation data to the corresponding second code multiplication circuit 207. . Each of the N second code multiplication circuits 207 has a code of a predetermined spreading factor that is predetermined in each second code multiplication circuit 207 and is orthogonal to the input modulation data. The code is multiplied and spread, and the resulting code spread signal is output to the second data multiplexing circuit 205.

  The second data multiplexing circuit 205 multiplexes the code spread signal output from each of the N second code multiplication circuits 205 and outputs the multiplexed signal to the first data multiplexing circuit 204. The pilot generation circuit 206 generates a pilot signal having a predetermined signal pattern and outputs the pilot signal to the first data multiplexing circuit 204. The first data multiplexing circuit 204 multiplexes the multiplexed signal output from the second data multiplexing circuit 205 and the pilot signal output from the pilot generation circuit 206 and outputs the multiplexed signal to the first code multiplication circuit 203. To do. Hereinafter, multiplexed signals and pilot signals are collectively referred to as signals.

  The first code multiplication circuit 203 has a scramble code typified by a pseudo-random sequence pre-assigned to the base station, multiplies the input signal by the scramble code, and sends it to the radio processing circuit 202. Output. The radio processing circuit 202 performs predetermined radio processing such as D / A conversion, quadrature modulation, up-conversion, band limitation, and power amplification on the input signal to generate a radio signal, and the radio signal is an antenna. 201. Note that the code division multiplexing number N, the encoding method and encoding rate, the puncture pattern, the modulation method, the spreading factor, and the like are notified from the control circuit 302, for example.

  The higher level I / F 301 operates as an I / F with the higher level protocol layer and the control station 104, and the control circuit 302 receives information notified from the control station 104 via the higher level I / F 301 or received by the receiving unit 6. The information notified from the wireless communication terminal 103 is used to control each circuit of the transmission unit 2 as described above and to control transmission data input to the transmission unit 2. For example, when the antenna 601 of the reception unit 6 receives a signal transmitted from the wireless communication terminal 103 b, the antenna 601 outputs the signal to the wireless processing circuit 602. The radio processing circuit 602 performs predetermined radio processing such as band limitation, down-conversion, orthogonal demodulation, A / D conversion, and the like on the input signal, and outputs a signal obtained as a result to the demodulation circuit 603.

  The demodulation circuit 603 demodulates the input signal and outputs it to the error correction decoding circuit 604. The error correction decoding circuit 604 decodes the input data based on a predetermined coding method and coding rate, and outputs data related to handover control to the control circuit 302, from the radio communication terminal 103, and the upper I / F 301. Information data to be transmitted to the communication network 105 via the I / F 301 is output to the I / F 301. When various information data related to handover control is transmitted from the wireless communication terminal 103 to the base station 101, if the data is transmitted without error correction coding in the wireless communication terminal 103, the data is demodulated. A configuration in which the circuit 603 outputs to the control circuit 302 may be employed.

  FIG. 3 shows a configuration example of the wireless communication terminal 103 to which the wireless communication control method according to the present embodiment is applied. In FIG. 3, the wireless communication terminal includes a reception unit 4, a control unit 5, and a transmission unit 7.

  The receiving unit 4 includes an antenna 401, a radio processing circuit 402, a synchronization circuit 403, a first code multiplication circuit 404, a second code multiplication circuit 405, a transmission path estimation circuit 406, a synthesis circuit 407, a demodulation circuit 408, and a data combination circuit. 409, an error correction decoding circuit 410, and an error detection circuit 411. The control unit 5 includes a high-order I / F 501 and a control circuit 502. The transmission unit 7 includes an error correction encoding circuit 704, a modulation circuit 703, and a wireless communication. A processing circuit 702 and an antenna 701 are provided. In order to realize soft handover, the first code multiplication circuit 404, the second code multiplication circuit 405, the transmission path estimation circuit 406, the synthesis circuit 407, and the demodulation circuit 408 must simultaneously receive in soft handover. As many as the number M of base stations that can be provided is provided.

  Next, the operation of each block of the wireless communication terminal 103 in FIG. 3 will be described. The antenna 401 outputs each received radio signal to the radio processing circuit 402. The radio processing circuit 402 performs predetermined radio processing such as band limitation, down-conversion, quadrature demodulation, A / D conversion, and the like on the input radio signal, and the synchronization signal 403 and M signals obtained as a result thereof. To the first sign multiplication circuit 404. The synchronization circuit 403 detects reception timing from each input signal, and notifies the M first code multiplication circuits 404 of the result. In wireless communication, since a multipath is usually generated due to arrival of a wireless signal via a plurality of wireless propagation paths, a plurality of reception timings are detected and each first code multiplication is performed. The circuit 404 is notified.

  The synchronization circuit 403 detects the reception timing, identifies the base station corresponding to each reception timing, and the reception status such as the reception timing, reception power, signal power versus interference, and noise signal power ratio (SINR) of each base station. Measure. Then, together with the detection result of the base station, the measured reception state of each base station is notified to the control circuit 502.

  Each of the M first code multiplication circuits 404 multiplies the input signal by the same code as the scramble code multiplied by the first code multiplication circuit 203 of the base station, and the resulting signal However, if the data includes a signal for the wireless communication terminal, it is output to the corresponding second code multiplication circuit 405, and if the signal is a pilot signal, it is output to the corresponding transmission path estimation circuit 406. .

  Each of the M second code multiplication circuits 405 corresponds to each base station and has the same code as the code multiplied by the second code multiplication circuit 207 of each base station. Each second code multiplication circuit 405 multiplies the input signal by the code possessed by the second code multiplication circuit 402 and despreads the resulting signal to the corresponding synthesis circuit 407. Output. Each of the M transmission path estimation circuits 406 performs transmission path estimation using the input pilot signal, and notifies the corresponding combining circuit 407 of the estimation result.

  Each of the M combining circuits 407 uses a transmission path estimation result notified from the corresponding transmission path estimation circuit 406 for the input signal to convert a plurality of received signals caused by multipaths, for example, to a maximum ratio. The signals are synthesized by a method such as synthesis and output to the corresponding demodulation circuit 408.

  Each of the M demodulation circuits 408 demodulates the input signal by a predetermined demodulation method, and outputs demodulated data (punctured encoded data) obtained as a result to the data combination circuit 409.

  The data combination circuit 409 generates encoded data (error correction encoded data) based on the input demodulated data and a puncture pattern corresponding to each base station, and outputs the encoded data to the error correction decoding circuit 410.

  In the data combining circuit 409, for example, instead of inserting dummy bits into the input demodulated data at the bit positions removed from the original error correction encoded data, each of the data combining circuits 409 is based on the puncture pattern corresponding to each base station. Bit data remaining without being erased at each base station is recognized from each demodulated data, and each bit data of encoded data is generated based on each bit data left without being erased. That is, the original error correction encoded data can be restored.

  The error correction decoding circuit 410 decodes the input encoded data based on a predetermined encoding method and encoding rate, and outputs the decoded data obtained as a result to the error detection circuit 411. The error detection circuit 411 detects an error in the input decoded data according to a predetermined error detection method, and outputs it to the upper I / F when there is no error. Also, the control circuit 502 is notified of the presence or absence of an error.

  As described above, when the radio communication terminal 103 performs soft handover, M first code multiplication circuits 404 provided for the maximum number of simultaneous reception base stations M and M second code multiplications are provided. Each of the circuit 405, the M transmission path estimation circuits 406, the M synthesis circuits 407, and the M demodulation circuits 408 is transmitted from a plurality of base stations identified by a scramble code corresponding to each base station. The above processing is performed on each data (the same data is transmitted from each base station).

  The upper I / F 501 operates as an interface with the upper protocol layer, and the control circuit 502 controls the receiving unit 4 based on the data received by the receiving unit 4 and the information notified from the receiving unit 4 and transmits the data. Controls output of transmission data to the unit 7.

  The control circuit 502 outputs data relating to handover control to be transmitted to the base station to the error correction coding circuit 704 of the transmission unit 7. The host I / F 501 outputs data to be transmitted to the communication network 105 via the base station to the error correction coding circuit 704 of the transmission unit 7.

  The error correction coding circuit 704 adds an error correction code to the input data, performs error correction coding at a predetermined coding method and coding rate, generates error correction coded data, and generates a modulation circuit. To 703.

  The modulation circuit 703 modulates the input error correction encoded data by a predetermined modulation method, and outputs a signal obtained as a result to the radio processing circuit 702.

  The radio processing circuit 702 performs predetermined radio processing such as D / A conversion, quadrature modulation, up-conversion, band limitation, and power amplification on the input signal to generate a radio signal, and the radio signal is an antenna. 701 is transmitted.

  When various information data related to handover control is transmitted from the wireless communication terminal 103 to the base station 101, if the data is transmitted without error correction coding in the wireless communication terminal 103, the data is controlled. A configuration in which the circuit 502 inputs to the modulation circuit 703 may be employed.

  FIG. 4 shows a sequence chart for explaining a radio communication control method related to soft handover according to the present embodiment, which corresponds to a plurality of base stations (in FIG. 1, corresponding to base stations 101-1 and 101-2, Here, a first base station and a second base station are shown), a control station (corresponding to the control station 104 in FIG. 1), and a wireless communication terminal (corresponding to the wireless communication terminal 103b in FIG. 1). 3 shows a control method at the start of soft handover in FIG. Note that FIG. 4 illustrates a case where the base station 2 is added to the communication target and the soft handover state is established when the wireless communication terminal is communicating with the base station 1.

  In FIG. 4, in a state where the wireless communication terminal is communicating with the first base station (step S1), an attempt is made to detect other base stations located in the vicinity, which is the above-described synchronization of the wireless communication terminal. Based on the information detected by the circuit 403, it can be realized by detecting whether or not there is a base station (a base station whose reception state is equal to or higher than a predetermined threshold) with which the control circuit 502 can communicate. When the wireless communication terminal detects the second base station as another communicable base station (step S2), the wireless communication terminal notifies the first base station that is already communicating (step S3). ). The notification includes the identifier, reception status, and the like as base station information.

  The first base station that has received the notification notifies the control station of this (step S4). The control station that has received the notification determines whether or not to perform soft handover for the wireless communication terminal. When it is determined that soft handover is to be performed (step S5), the control station notifies the second base station that soft handover is to be performed, that is, communication with the wireless communication terminal is to be performed (step S6). ). In addition, control parameters for soft handover (described later) are also notified (step S7). Further, the control station notifies the first base station that the soft handover is executed (step S8), and also controls the control parameters related to the existing communication and the second base station to be changed accordingly. The notified control parameter is also notified at the same time (step S9).

  The second base station that has received the notification starts transmission / reception of a radio signal with the radio communication terminal according to the notified control parameter (step S10), and thereby determines that the soft handover can be started. (Step S11). The control station that has received the notification notifies the first base station of this (step S12), and the first base station performs soft handover to the wireless communication terminal, that is, the existing communication (first communication). (The communication with one base station) is notified that the second base station is added (step S13), and the control parameters related to each base station notified from the control station are also notified (step S14). .

  The wireless communication terminal that has received the notification and the first base station that has performed the notification simultaneously change the control parameters that are changed due to the soft handover for the existing communication (steps S15 and S16).

  The wireless communication terminal starts reception of the wireless signal transmitted from the second base station according to the notified control parameter (step S17), thereby starting soft handover.

  FIG. 5 is a sequence chart for explaining another radio communication control method, and a plurality of base stations (first base station and second base station as in FIG. 4), control stations, and radio communication terminals. 3 shows a control method at the start of soft handover in FIG. Note that FIG. 5 illustrates a case where the second base station is added to the communication target and a soft handover state is established when the wireless communication terminal is communicating with the first base station. In FIG. 5, the same parts as those in FIG.

  In FIG. 5, in a state where the wireless communication terminal is communicating with the first base station (step S1), the wireless communication terminal attempts to detect other base stations located in the vicinity, which is the above-described synchronization of the wireless communication terminal. This can be realized by detecting whether there is a base station with which the control circuit 502 can communicate based on information detected by the circuit 403. When the wireless communication terminal detects the second base station as another communicable base station (step S2), the wireless communication terminal notifies the detection result to the first base station that is already communicating ( Step S3). The notification includes the identifier, reception status, and the like as base station information. The first base station that has received the notification notifies the control station of this (step S4). The control station that has received the notification determines whether or not to perform soft handover for the wireless communication terminal. When it is determined to implement soft handover (step S5), the control station performs soft handover for the second base station, that is, performs communication with the wireless communication terminal and is not related to soft handover. The control parameter is notified (step S21), and the first base station is notified that the soft handover is executed (step S22).

  The second base station that has received the notification starts transmission / reception of a radio signal with the radio communication terminal according to the notified control parameter (step S23), and thereby determines that the soft handover can be started. (Step S24). The control station that has received the notification notifies the first base station of this (step S25), and the first base station performs soft handover to the wireless communication terminal, that is, for the existing communication. To add the second base station (step S26).

  The wireless communication terminal that has received the notification starts reception of the wireless signal transmitted from the second base station (step S27), and is used in the first base station and the second base station, and is controlled by soft handover. The parameter is determined and notified to the first base station and the second base station (step S28). The first base station and the second base station that have received the notification simultaneously change the control parameters notified to the existing communication together with the wireless communication terminal (step S29 to step S31), so that the soft handover can be performed. Be started. Thereafter, the radio communication terminal may perform control so as to notify the first base station and the second base station of the control parameter changed due to the soft handover at a predetermined cycle. That is, step S28 to step S31 are repeated at a predetermined cycle.

  In the wireless communication control method shown in FIG. 4, the control station determines / changes the control parameters of each base station and notifies each base station. In the wireless communication control method shown in FIG. Shows a case where the control parameters of each base station are determined / changed and notified to each base station.

  Hereinafter, processing operations of the base station and the radio communication terminal for one unit of data to be subjected to error correction coding and error detection coding, that is, one data block (one block) will be described.

  (1) When the control parameter in the soft handover in FIGS. 4 and 5 is a puncture pattern, the processing operations of the main parts of the base station and the radio communication terminal will be described with reference to FIGS.

  FIG. 6 shows a control example of the error correction encoding circuit 210 and the puncture processing circuit 209 of a plurality of base stations. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, the error correction coding circuit 210 is output from the error detection code addition circuit 211 as shown in FIG. The transmission data is encoded at a coding rate R = 1/2. The puncture processing circuit 209 performs puncture pattern A “1110” (“1” represents a bit that is not erased and “0” represents a bit that is erased) for the error correction coded data output from the error correction coding circuit 210. Puncture using. The punctured encoded data obtained as a result is error correction encoded data with a coding rate R = 2/3.

  Under such control conditions, when the wireless communication terminal enters the soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. A puncture pattern A “1110” is assigned to a station, and a puncture pattern B “1101” that erases bits different from those erased by the puncture pattern A used in the first base station is assigned to a second base station. And puncture patterns are notified to the first and second base stations. In this case, the number of bits to be erased is the same between the punctured patterns A and B.

  Since it is in the soft handover state, the transmission data input to the error correction encoding circuit 210 of each base station is the same transmission data, and the error correction encoded data output from the error correction encoding circuit 210 is also Are the same.

  As a result, the coding rate after puncturing (after erasing the bit position designated by each puncture pattern) in the first and second base stations is R = 2/3, which is the software shown in FIG. Although it is the same as when not in the handover state, the error correction encoded data (punctured encoded data) after puncturing is transmitted with a partly different transmission at each base station because different bits are erased at each base station. It becomes data.

  FIG. 7 shows a control example of the data combining circuit 409 and the error correction decoding circuit 410 of the wireless communication terminal when the first and second base stations are controlled as shown in FIG. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, as shown in FIG. 7A, the data combining circuit 409 outputs the demodulated data ( A dummy bit is inserted into the punctured (erased) bit position according to the puncture pattern A “1110” with respect to the error correction encoded data that has been error correction encoded at the encoding rate R = 2/3. Further, the error correction decoding circuit 410 performs error correction decoding on the demodulated data with the dummy bits inserted. The error correction decoding in this case corresponds to the coding rate R = 1/2, but considering the fact that dummy bits are inserted, the substantial coding rate is R = 2/3.

  When the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. 7B, the data combining circuit 409 corresponds to each base station. The demodulated data with the coding rate R = 2/3 output from the demodulation circuit 408 is combined according to the puncture patterns A and B corresponding to each base station, and coded data (coding rate R = 1/2). Is generated.

  That is, in the data combining circuit 409, the bits (FIG. 7B) that remain without being removed from the demodulated data from the plurality of base stations are, for example, the first bit of the demodulated data from the first base station. And the first bit of the demodulated data from the second base station) are combined to generate bit data of the encoded data (first bit of the error correction encoded data in FIG. 7B), For bits left without being removed only in demodulated data from any one base station, the bit data is directly used as bit data of encoded data. For example, as shown in FIG. 7B, the third bit of the demodulated data from the first base station is removed from the demodulated data from the second base station and does not exist. The third bit of the demodulated data from the base station is used as it is as the third bit data of the encoded data. Further, as shown in FIG. 7B, the third bit of the demodulated data from the second base station is removed from the demodulated data from the first base station and is not present. The third bit of the demodulated data from the base station is used as it is as the fourth bit data of the encoded data.

  As described above, in the data combination circuit 409, based on the puncture pattern corresponding to each base station, from each demodulated data (corresponding to punctured encoded data generated by each base station), each base station The bit data remaining without being erased is recognized, and each bit data of the encoded data is generated based on each bit data remaining without being erased. That is, the original error correction encoded data can be restored.

  As shown in FIG. 7, in the case of soft handover, the wireless communication terminal does not insert dummy bits into the punctured encoded data. In the wireless communication terminal, the error correction decoding circuit 410 performs error correction decoding on the encoded data generated by the data combining circuit 409. In this case, the error correction decoding corresponds to the coding rate R = 1/2, and considering that no dummy bit is inserted as described above, the substantial coding rate is R = 1/2. .

  (2) When the control parameters in the soft handover in FIGS. 4 and 5 are the coding rate and the puncture pattern, the processing operations of the main parts of the base station and the radio communication terminal will be described with reference to FIGS. explain.

  FIG. 8 shows a control example of the error correction encoding circuit 210 and the puncture processing circuit 209 of a plurality of base stations. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, the error correction coding circuit 210 is output from the error detection code addition circuit 211 as shown in FIG. The transmission data is encoded at a coding rate R = 1/2. The puncture processing circuit 209 outputs the error correction encoded data output from the error correction encoding circuit 210 without performing puncturing using the puncture pattern A “1111” having no bits to be erased.

  Under such control conditions, when the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. The station is notified that the coding rate is to be changed from R = 1/2 to R = 1/3, and that the puncture pattern A having no bits to be deleted is changed to puncture pattern B “110”. . In addition, the encoding rate is set to R = 1/3 for the second base station, and a puncture pattern C “in which bits different from the puncture pattern B notified to the first base station are deleted. 101 "is notified. Since it is in the soft handover state, the transmission data input to the error correction encoding circuit 210 of each base station is the same transmission data, and the error correction encoded data output from the error correction encoding circuit 210 is also Are the same.

  As a result, the coding rate after puncturing in the first and second base stations is R = 1/2, which is the same as that in the soft handover state of FIG. 8A, but the error correction coded data after puncturing. (Punctured encoded data) is transmission data partially different in each base station because different bits are erased in each base station.

  FIG. 9 shows a control example of the data combining circuit 409 and the error correction decoding circuit 410 of the wireless communication terminal when the first and second base stations are controlled as shown in FIG. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, as shown in FIG. 9A, the data combining circuit 409 outputs the demodulated data output from the demodulation circuit 408, That is, error correction encoded data that has been subjected to error correction encoding at a coding rate R = 1/2 (here, not punctured as shown in FIG. 8) is output to error correction decoding circuit 410 as it is. . The error correction decoding circuit 410 performs error correction decoding on the input error correction encoded data. In this case, error correction decoding corresponds to a coding rate R = 1/2.

  When the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. 9B, the data combining circuit 409 corresponds to each base station. The demodulated data output from the demodulation circuit 408, that is, the punctured encoded data with the encoding rate R = 1/2, is encoded data (code) based on the puncture patterns B and C corresponding to each base station. Conversion rate R = 1/3).

  That is, in the data combining circuit 409, the bits remaining without being removed in the demodulated data (punctured encoded data) from the plurality of base stations (in FIG. 9B, for example, from the first base station) The first bit of the demodulated data and the first bit of the demodulated data from the second base station) are combined to generate bit data of the encoded data (the first bit of the encoded data in FIG. 9B). For the bits left without being removed only in the demodulated data from any one base station, the bit data is used as bit data of the encoded data as it is. For example, as shown in FIG. 9B, the second bit of the demodulated data from the first base station is removed from the demodulated data from the second base station and is not present. The bit of the second bit of the demodulated data from the base station is used as it is as the bit data of the second bit of the encoded data. Further, as shown in FIG. 9B, the second bit of the demodulated data from the second base station is removed from the demodulated data from the first base station and does not exist. The second bit of the demodulated data from the base station is used as it is as the third bit data of the encoded data.

  As described above, in the data combination circuit 409, based on the puncture pattern corresponding to each base station, from each demodulated data (corresponding to punctured encoded data generated by each base station), each base station The bit data remaining without being erased is recognized, and each bit data of the encoded data is generated based on each bit data remaining without being erased. That is, the original error correction encoded data can be restored.

  As shown in FIG. 9, in the case of soft handover, the wireless communication terminal does not insert dummy bits into the punctured encoded data. In the wireless communication terminal, the error correction decoding circuit 410 performs error correction decoding on the error correction encoded data generated by the data combining circuit 409. In this case, error correction decoding corresponds to a coding rate R = 1/3, and considering that no dummy bit is inserted as described above, the substantial coding rate is R = 1/3. .

  As described above, according to the above-described embodiment, when a radio communication terminal implements soft handover with a plurality of base stations using the CDMA scheme, the coding gain is improved and the use of radio resources is improved. There is an effect of increasing the efficiency or increasing the throughput.

  (3) Subsequently, radio signals received from a plurality of base stations in which the error correction coding and error detection coding block length is shorter than the time variation period of the radio channel characteristics and are in the soft handover state in the radio communication terminal A control parameter control method in soft handover, which is suitable when there is a difference in the reception state (for example, signal power, desired signal power versus interference and noise power ratio), will be described.

  (3-1) When the control parameters are a puncture pattern and a modulation scheme, processing operations of main parts of the base station and the radio communication terminal will be described using FIG. 10 and FIG. 10 and 11, in the wireless communication terminal, the reception state of the wireless signal transmitted from the second base station is inferior to the reception state of the wireless signal transmitted from the first base station. It explains about.

  FIG. 10 shows a control example of the error correction encoding circuit 210, the puncture processing circuit 209, and the modulation circuit 208 of a plurality of base stations. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, the error correction coding circuit 210 is output from the error detection code addition circuit 211 as shown in FIG. The transmitted data is encoded at a coding rate R = 1/3. The puncture processing circuit 209 punctures the error correction encoded data output from the error correction encoding circuit 210 with the puncture pattern A “110”, and the resulting punctured encoded data is sent to the modulation circuit 208. Output. The modulation circuit 208 modulates the input punctured encoded data using QPSK (Quadrature Phase Shift Keying) as a modulation method. As shown in FIG. 10 (a), in the first base station, after erasing 1 bit per 3 bits by the puncture pattern A, 2 bits of information are transmitted by 1 symbol by QPSK. The data is 2 symbols.

  Under such control conditions, when the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. The puncture pattern A “110” is notified to the station without changing the puncture pattern, and QPSK is notified without changing the modulation scheme.

  The reception state when the wireless signal from the second base station is received by the wireless communication terminal is inferior to the reception state when the wireless signal from the first base station is received by the wireless communication terminal. For the second base station, a puncture pattern B “001” in which more bits than the number of bits erased by the puncture pattern A notified to the first base station and bits different from the puncture pattern A are erased. Therefore, the modulation scheme is also different from the modulation scheme notified to the first base station (so that the number of symbols to be finally generated is the same) (in this case, the modulation multilevel is higher than QPSK). A small number of BPSK (Binary Phase Shift Keying) is notified.

  That is, in the first base station, 1 bit per 3 bits is erased by the puncture pattern A, and then 2 bits of information are transmitted in 1 symbol by QPSK, and in the 2nd base station, 3 bits per 3 bits by the puncture pattern B. Since 2 bits are erased and 1 bit of information is transmitted by 1 symbol by BPSK, the number of modulation symbols obtained after modulation by the modulation circuit 208 of the first and second base stations is 2 symbols per block. This is the same as that in the soft handover state in FIG.

  In addition, because of the soft handover state, the transmission data input to the error correction encoding circuit 210 of each base station is the same transmission data, and the error correction encoded data output from the error correction encoding circuit 210 is also Are the same. However, error correction encoded data (punctured encoded data) after puncturing is transmission data partially different at each base station because different bits are erased at each base station. Therefore, the modulation symbols obtained after modulation by the modulation circuit 208 of the first and second base stations are different from each other.

  FIG. 11 shows a control example of the demodulation circuit 408, the data combining circuit 409, and the error correction decoding circuit 410 of the wireless communication terminal when the first and second base stations are controlled as shown in FIG. . When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, as shown in FIG. 11A, the demodulation circuit 408 demodulates the modulation symbol by a demodulation method corresponding to QPSK. The data combining circuit 409 inserts dummy bits into the punctured bit positions in accordance with the puncture pattern A “110” for the modulated data output from the demodulation circuit 408. Further, the error correction decoding circuit 410 performs error correction decoding on the modulated data in which dummy bits are inserted. In this case, error correction decoding corresponds to a coding rate R = 1/3, but considering that dummy bits are inserted, a substantial coding rate is R = 1/2.

  When the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. 11B, the demodulation circuit 408 corresponding to each base station has a modulation scheme. A modulation symbol is demodulated by a demodulation method corresponding to each of QPSK and BPSK.

  Based on the modulation data output from each demodulation circuit 408 corresponding to each base station and the corresponding puncture patterns A and B, the data combining circuit 409 performs encoding as described in (1) and (2) above. Generate data. Further, the error correction decoding circuit 410 performs error correction decoding on the generated encoded data. In this case, error correction decoding corresponds to a coding rate R = 1/3.

  (3-2) When the control parameters are a puncture pattern and a spreading factor, processing operations of main parts of the base station and the radio communication terminal will be described with reference to FIGS. 12 and 13. 12 and 13, the reception state of the radio signal transmitted from the second base station is inferior to the reception state of the radio signal transmitted from the first base station in the wireless communication terminal. Describes.

  FIG. 12 shows an operation example of the error correction coding circuit 210, the puncture processing circuit 209, the modulation circuit 208, and the second code multiplication circuit 207 of a plurality of base stations. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, the error correction coding circuit 210 is output from the error detection code addition circuit 211 as shown in FIG. The transmitted data is encoded at a coding rate R = 1/3. The puncture processing circuit 209 punctures the error correction encoded data output from the error correction encoding circuit 210 with the puncture pattern A “110”, and the resulting punctured encoded data is sent to the modulation circuit 208. Output. The modulation circuit 208 modulates the input punctured encoded data using QPSK as the modulation method, and then the second code multiplier circuit 207 receives the modulation data input with the spreading code corresponding to the spreading factor SF = 4. Multiply As shown in FIG. 12 (a), the first base station erases 1 bit per 3 bits by the puncture pattern A, and then modulates with QPSK to make 2 bits of information become 1 symbol. By spreading using a spreading code corresponding to “4”, 8 blocks are transmitted per block.

  Under such control conditions, when the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. The station is notified of “110” without changing the puncture pattern and “4” without changing the spreading factor.

  The reception state when the wireless signal from the second base station is received by the wireless communication terminal is inferior to the reception state when the wireless signal from the first base station is received by the wireless communication terminal. For the second base station, a puncture pattern B “001” in which more bits than the number of bits erased by the puncture pattern A notified to the first base station and bits different from the puncture pattern A are erased. Therefore, “8” which is larger than the spreading factor notified to the first base station is also notified (so that the number of symbols finally generated is the same).

  That is, in the first base station, after deleting 1 bit per 3 bits by the puncture pattern A, 2 bits of information becomes 1 symbol by QPSK, and further, spreading is performed with a spreading code corresponding to the spreading factor “4”. As a result, 8 symbols per block are transmitted, and in the second base station, 2 bits per 3 bits are erased by the puncture pattern B, then 2 bits of information are converted to 1 symbol by QPSK, and the spreading factor is “8”. By performing spreading with a spreading code corresponding to, transmission is performed with 8 symbols per block as in the case of the first base station, which is the same as in the soft handover state of FIG. is there.

  In addition, because of the soft handover state, the transmission data input to the error correction encoding circuit 210 of each base station is the same transmission data, and the error correction encoded data output from the error correction encoding circuit 210 is also Are the same. However, error correction encoded data after puncturing (punctured encoded data) is partially different at each base station because different bits are erased at each base station. Accordingly, the spread symbols after the spread code multiplication output from the second code multiplication circuit 207 of the first and second base stations are different from each other.

  FIG. 13 shows a second code multiplication circuit 405, a demodulation circuit 408, a data combination circuit 409, and an error correction decoding circuit of the wireless communication terminal when the first and second base stations are controlled as shown in FIG. A control example 410 is shown. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, the second code multiplication circuit 405 supports the spreading factor “4” as shown in FIG. The demodulating circuit 408 demodulates the modulation symbol by a demodulation method corresponding to QPSK, and the data combining circuit 409 applies the demodulated data output from the demodulating circuit 408 to the demodulated data according to the puncture pattern A “110”. Insert a dummy bit at the punctured bit position. Further, the error correction decoding circuit 410 performs error correction decoding on the demodulated data with the dummy bits inserted. In this case, error correction decoding corresponds to a coding rate R = 1/3, but considering that dummy bits are inserted, a substantial coding rate is R = 1/2.

  When the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. 13B, the second code corresponding to the first base station The multiplication circuit 405 multiplies the spreading code corresponding to the spreading factor “4”, and the demodulation circuit 408 demodulates the modulation symbol by a demodulation method corresponding to QPSK. The second code multiplication circuit 405 corresponding to the second base station multiplies the spreading code corresponding to the spreading factor “8”, and the demodulation circuit 408 demodulates the modulation symbol by the demodulation method corresponding to QPSK.

  As described in (1) and (2) above, the data combining circuit 409 uses the demodulated data output from the demodulating circuit 408 corresponding to each base station and the corresponding puncture patterns A and B as described in (1) and (2) above. Is generated. Further, the error correction decoding circuit 110 performs error correction decoding on the generated encoded data. In this case, error correction decoding corresponds to a coding rate R = 1/3.

  (3-3) When the control parameters are a coding rate, a puncture pattern, and a modulation scheme, processing operations of main parts of the base station and the wireless communication terminal will be described with reference to FIGS. 14 and 15. 14 and 15, the reception state of the radio signal transmitted from the second base station in the wireless communication terminal is inferior to the reception state of the radio signal transmitted from the first base station. Describes.

  FIG. 14 illustrates operations of the error correction coding circuit 210, the puncture processing circuit 209, and the modulation circuit 208 of a plurality of base stations. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, the error correction coding circuit 210 outputs from the error detection code addition circuit 211 as shown in FIG. The transmitted data is encoded at an encoding rate R = 1/2. The puncture processing circuit 209 outputs the error correction encoded data output from the error correction encoding circuit 210 to the modulation circuit 208 without performing puncturing. The modulation circuit 208 modulates the input error correction encoded data using QPSK. As shown in FIG. 14 (a), in the first base station, 2 bits of information are transmitted in one symbol by performing modulation using QPSK as it is without puncturing the error correction coded data. Therefore, one block of transmission data is 2 symbols.

  Under such control conditions, when the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. The station is notified that the coding rate is to be changed from R = 1/2 to R = 1/3 and that the puncture pattern is to be changed to puncture pattern B “110”.

  The reception state when the wireless signal from the second base station is received by the wireless communication terminal is inferior to the reception state when the wireless signal from the first base station is received by the wireless communication terminal. For the second base station, a puncture pattern C “001” in which more bits than the number of bits erased by the puncture pattern B notified to the first base station and bits different from the puncture pattern B are erased. For this reason, the modulation scheme (so that the number of symbols to be finally generated is the same) is smaller than the modulation scheme notified to the first base station, and BPSK has a smaller amount of information transmission per symbol. Will be notified. Furthermore, the coding rate R = 1/3 is notified.

  That is, in the first base station, after performing error correction coding at a coding rate of “1/3”, 1 bit is erased per 3 bits by the puncture pattern B, and 2 bits of information is obtained by using QPSK. One symbol is transmitted at 2 symbols per block. The second base station performs error correction coding at a coding rate of “1/3”, erases 2 bits per 3 bits using the puncture pattern C, and uses BPSK to reduce 1 bit of information. Similarly to the case of the first base station, since it is transmitted with 2 symbols per block, it is the same as that in the soft handover state of FIG. 14A.

In addition, because of the soft handover state, the transmission data input to the error correction encoding circuit 210 of each base station is the same transmission data, and the error correction encoded data output from the error correction encoding circuit 210 is also Are the same. However, error correction encoded data (punctured encoded data) after puncturing is transmission data partially different at each base station because different bits are erased at each base station. Therefore, the modulation symbols obtained after modulation by the modulation circuit 208 of the first and second base stations are different from each other. In FIG. 15, the first and second base stations are controlled as shown in FIG. In this case, a control example of the demodulation circuit 408, the data combination circuit 409 and the error correction decoding circuit 410 of the wireless communication terminal is shown. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, as shown in FIG. 15A, the demodulation circuit 408 demodulates the modulation symbol by a demodulation method corresponding to QPSK. Then, the data combination circuit 409 outputs the demodulated data output from the demodulation circuit 408 to the error correction decoding circuit 410 as it is. The error correction decoding circuit 410 performs error correction decoding on the input demodulated data. In this case, error correction decoding corresponds to a coding rate R = 1/2.

  When the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. 15B, the demodulation circuit 408 corresponding to the first base station A modulation symbol is demodulated by a demodulation method corresponding to QPSK. Further, the demodulation circuit 408 corresponding to the second base station demodulates the modulation symbol by a demodulation method corresponding to BPSK.

  Based on the demodulated data output from the demodulation circuit 408 corresponding to each base station and the corresponding puncture patterns B and C, the data combining circuit 409 performs encoding as described in (1) and (2) above. Generate data. Further, the error correction decoding circuit 110 performs error correction decoding on the generated encoded data. In this case, error correction decoding corresponds to a coding rate R = 1/3.

  (3-4) When the control parameters are a coding rate, a puncture pattern, and a spreading factor, processing operations of main parts of the base station and the wireless communication terminal will be described with reference to FIGS. 16 and 17. 16 and 17, when the reception state of the radio signal transmitted from the second base station in the wireless communication terminal is inferior to the reception state of the radio signal transmitted from the first base station. Describes.

  FIG. 16 shows operations of the error correction coding circuit 210, the puncture processing circuit 209, the modulation circuit 208, and the second code multiplication circuit of a plurality of base stations. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, the error correction coding circuit 210 outputs from the error detection code addition circuit 211 as shown in FIG. The transmitted data is encoded at a predetermined encoding rate R = 1/2. The puncture processing circuit 209 outputs the error correction encoded data output from the error correction encoding circuit 210 to the modulation circuit 206 without performing puncturing. The modulation circuit 206 modulates the input error correction encoded data using QPSK, and outputs it to the second code multiplication circuit 207. The second code multiplication circuit 207 multiplies the input error correction coded data by the spreading code corresponding to the spreading factor “4”.

  As shown in FIG. 16 (a), in the first base station, the error correction encoded data is modulated by QPSK so that 2 bits of information become one symbol, and further, the spreading corresponding to the spreading factor “4” By spreading with a code, 8 blocks per block are transmitted.

  Under such control conditions, when the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. The station is notified that the error rate is to be changed from R = 1/2 to R = 1/3 and to be changed to puncture pattern B “110”. The diffusion rate is not changed.

  The reception state when the wireless signal from the second base station is received by the wireless communication terminal is inferior to the reception state when the wireless signal from the first base station is received by the wireless communication terminal. For the second base station, a puncture pattern C “001” in which more bits than the number of bits erased by the puncture pattern B notified to the first base station and bits different from the puncture pattern B are erased. Therefore, “8” which is larger than the spreading factor notified to the first base station is also notified (so that the number of symbols finally generated is the same). Also, the same modulation scheme QPSK as the modulation scheme in the first base station is notified to the second base station.

  That is, in the first base station, after erasing 1 bit per 3 bits by puncture pattern B, 2 bits of information becomes 1 symbol by QPSK, and further, spreading is performed with a spreading code corresponding to spreading factor “4” As a result, 8 symbols per block are transmitted, and in the second base station, 2 bits per 3 bits are erased by the puncture pattern B, then 2 bits of information are converted to 1 symbol by QPSK, and the spreading factor is “8”. By performing spreading with a spreading code corresponding to, transmission is performed with 8 symbols per block as in the case of the first base station, so that it is the same as in the soft handover state of FIG. is there.

  In addition, because of the soft handover state, the transmission data input to the error correction encoding circuit 210 of each base station is the same transmission data, and the error correction encoded data output from the error correction encoding circuit 210 is also Are the same. However, error correction encoded data (punctured encoded data) after puncturing is transmission data partially different at each base station because different bits are erased at each base station. Accordingly, the spread symbols after the spread code multiplication output from the second code multiplication circuit 207 of the first and second base stations are different from each other.

  FIG. 17 shows a second code multiplication circuit 405, a demodulation circuit 408, a data combination circuit 409, and an error correction decoding circuit of the wireless communication terminal when the first and second base stations are controlled as shown in FIG. A control example 410 is shown. When the wireless communication terminal does not perform soft handover and performs communication only with the first base station, as shown in FIG. 17A, the second code multiplication circuit 405 supports the spreading factor “4”. The demodulation circuit 408 demodulates the modulation symbol by a demodulation method corresponding to QPSK, and the data combining circuit 409 outputs the demodulated data output from the demodulation circuit 408 to the error correction decoding circuit 409 as it is. The error correction decoding circuit 409 performs error correction decoding on the input demodulated data. In this case, error correction decoding corresponds to a coding rate R = 1/2.

  When the wireless communication terminal enters a soft handover state and communicates with the second base station in addition to the first base station, as shown in FIG. 17B, the second code corresponding to the first base station The multiplication circuit 405 multiplies the spreading code corresponding to the spreading factor “4”, and the demodulation circuit 408 demodulates the modulation symbol by a demodulation method corresponding to QPSK. The second code multiplication circuit 405 corresponding to the second base station multiplies the spreading code corresponding to the spreading factor “8”, and the demodulation circuit 408 demodulates the modulation symbol by the demodulation method corresponding to QPSK.

  Based on the demodulated data output from the demodulation circuit 408 corresponding to each base station and the corresponding puncture patterns B and C, the data combining circuit 409 performs encoding as described in (1) and (2) above. Generate data. Further, the error correction decoding circuit 110 performs error correction decoding on the generated encoded data. In this case, error correction decoding corresponds to a coding rate R = 1/3.

  By applying the method described in the above (3-1) to (3-4) to a system in which a wireless communication terminal realizes soft handover with a plurality of base stations using the CDMA method, an error is particularly caused. When the correction coding and error detection coding block length is short with respect to the time variation period of the wireless channel characteristics, there is a difference in the reception state of the wireless signal transmitted by the plurality of base stations to be handed over in the wireless communication terminal Even at this time, it is possible to improve reception quality and coding gain in the radio communication terminal, and as a result, it is possible to increase the utilization efficiency and throughput of radio resources.

  (4) Next, the processing operation of the control circuit 502 of the wireless communication terminal that controls the control parameters as described in (1) to (3) will be described with reference to FIG. Here, as described with reference to FIG. 5, a case will be described in which a wireless communication terminal notifies a control parameter to a plurality of base stations. However, the control station as described with reference to FIG. The same applies to the case of notifying parameters to a plurality of base stations.

  In FIG. 18, when the control circuit 502 of the wireless communication terminal starts the soft handover in step S <b> 27 of FIG. 5, the handover is performed at a predetermined cycle (every predetermined time elapses) as shown in FIG. 5. The control regarding is started (step S101). That is, the reception statuses of a plurality of base stations to be handed over are acquired from the synchronization circuit 403 (step S102), these are compared, and if the difference in reception status is within a predetermined threshold (step S103), Proceeding to step S104, it is determined to apply the same control parameter in all base stations. Alternatively, only the puncture pattern is different (for example, the number of bits to be deleted is the same and the bits to be deleted are different at each base station), and all other control parameters (coding rate, modulation circuit modulation scheme, spreading factor) are all The control parameters of each base station are determined so as to be the same in each base station.

  On the other hand, when the difference in the reception state exceeds the threshold value (step S103), the process proceeds to step S107. For example, the base station with the worse reception state (at least for the base station with the lowest reception state) has the desired signal. Control parameters are determined so as to achieve a modulation scheme with high error tolerance (for example, BPSK has higher error tolerance than QPSK) and a large spreading factor to improve power-to-interference and noise signal power ratio (SINR) To do. In this case, for a base station with a poor reception state, the reception state is such that the number of symbols per block transmitted from each of a base station with a poor reception state and a good base station is the same. A puncture pattern having a larger number of bits to be erased than a puncture pattern to be assigned to a good base station is assigned. Then, a puncture pattern is assigned to each base station so that the bit position to be erased is different for each base station.

  For example, as described in (3-1) above, when QPSK and puncture pattern “110” are assigned as modulation schemes to a base station in a good reception state, the base station in a poor reception state For a base station (for example, a base station with the poorest reception state), it is determined that BPSK and puncture pattern “001” are assigned as modulation schemes.

  Further, as described in (3-2) above, when the spreading factor “4” and the puncture pattern “110” are assigned to the base station with good reception state, the base with the poor reception state is assigned. It is determined that a spreading factor “8” and a puncture pattern “001” are assigned to a station (for example, a base station having the poorest reception state).

  Further, as described in (3-3) above, the coding rate when the soft handover is performed in the error correction coding circuit 210 is lower than the coding rate when the soft handover is not performed. In addition, when assigning QPSK and puncture pattern “110” as a modulation scheme to a base station with a good reception state, a base station with a poor reception state (for example, a base station with the poorest reception state) ) For the modulation scheme BPSK and the puncture pattern “001”.

  Furthermore, as described in (3-4) above, the coding rate when the soft handover is performed in the error correction coding circuit 210 is lower than the coding rate when the soft handover is not performed. When a spreading factor “4” and a puncture pattern “110” are assigned to a base station with a good reception state, a base station with a poor reception state (for example, a base station with the poorest reception state). Station) is assigned a spreading factor “8” and a puncture pattern “001”.

  The control parameters of each base station determined in step S103 and step S107 are transmitted from the wireless communication terminal to each base station (step S105, step S28 in FIG. 5).

  The above steps S101 to S105 are continued as long as the handover is performed (step S106).

  As shown in FIG. 4, the control station determines the control parameter and determines the control parameter at the wireless communication terminal in FIG. A different part from the case where it notifies with respect to a some base station is demonstrated. That is, when the control station acquires from the wireless communication terminal (via a base station currently communicating with the wireless communication terminal) the reception state measured for each base station with which the wireless communication terminal can communicate (Step S4 in FIG. 4), similarly to Step S103, Step S104, and Step S107 in FIG. 18, the control station determines the control parameter of each base station (Step S5 in FIG. 4). The control station notifies each base station of the determined control parameters of each base station (steps S7 to S9 in FIG. 4).

  As described above, according to the above-described embodiment, when a wireless communication terminal performs soft handover with a plurality of base stations using the CDMA system, error correction coding and error detection coding block lengths are wireless. In the case where it is short with respect to the time variation period of the channel characteristics, there is a difference in the reception state of the radio signal transmitted from the plurality of base stations to be handed over in the wireless communication terminal, and even when the reception state changes with time, The reception quality and coding gain in the radio communication terminal can be improved, and as a result, the utilization efficiency and throughput of radio resources can be increased.

The figure for demonstrating a soft handover state. The figure which showed the structural example of the base station. The figure which showed the structural example of the radio | wireless communication terminal. The flowchart for demonstrating the radio | wireless communication control method regarding soft handover. The flowchart for demonstrating the other radio | wireless communication control method regarding soft handover. The figure for demonstrating the processing operation | movement of the principal part of a base station in case the control parameter of a soft handover is a puncture pattern. The figure for demonstrating the processing operation | movement of the principal part of a radio | wireless communication terminal when the control parameter of a soft handover is a puncture pattern. The figure for demonstrating the processing operation | movement of the principal part of a base station in case the control parameter of a soft handover is an encoding rate and a puncture pattern. The figure for demonstrating the processing operation | movement of the principal part of a radio | wireless communication terminal when the control parameter of a soft handover is an encoding rate and a puncture pattern. The figure for demonstrating the processing operation | movement of the principal part of a base station in case the control parameter of a soft handover is a puncture pattern and a modulation system. The figure for demonstrating the processing operation | movement of the principal part of a radio | wireless communication terminal when the control parameter of a soft handover is a puncture pattern and a modulation system. The figure for demonstrating the processing operation of the principal part of a base station in case the control parameter of a soft handover is a puncture pattern and a spreading factor. The figure for demonstrating the processing operation | movement of the principal part of a radio | wireless communication terminal when the control parameter of a soft handover is a puncture pattern and a spreading factor. The figure for demonstrating the processing operation | movement of the principal part of a base station in case the control parameter of a soft handover is a code rate, a puncture pattern, and a modulation system. The figure for demonstrating the processing operation | movement of the principal part of a radio | wireless communication terminal in case the control parameter of a soft handover is a code rate, a puncture pattern, and a modulation system. The figure for demonstrating the processing operation | movement of the principal part of a base station in case the control parameters of a soft handover are a coding rate, a puncture pattern, and a spreading | diffusion rate. The figure for demonstrating the processing operation | movement of the principal part of a radio | wireless communication terminal in case the control parameters of a soft handover are a coding rate, a puncture pattern, and a spreading | diffusion rate. The flowchart for demonstrating the processing operation of the control circuit of a radio | wireless communication terminal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2, 7 ... Transmission part, 3, 5 ... Control part, 4, 6 ... Reception part, 201 ... Antenna, 202 ... Wireless processing circuit, 203 ... 1st code multiplication circuit, 204 ... 1st data multiplexing circuit, 205 DESCRIPTION OF SYMBOLS 2nd data multiplexing circuit 206 ... Pilot generation circuit 207 ... 2nd code multiplication circuit 208 ... Modulation circuit 209 ... Puncture processing circuit 210 ... Error correction coding circuit 211 ... Error detection code addition circuit, 302 ... Control circuit 401 ... Antenna 402 ... Radio processing circuit 403 ... Synchronization circuit 404 ... First code multiplication circuit 405 ... Second code multiplication circuit 406 ... Transmission path estimation circuit 407 ... Synthesis circuit 408 ... demodulating circuit, 409 ... data combining circuit, 410 ... error correction decoding circuit, 411 ... error detection circuit, 502 ... control circuit.

Claims (11)

In a wireless communication system comprising a plurality of base stations and wireless communication terminals,
Each of the plurality of base stations is
Error correction encoding means for generating error correction encoded data by error correcting encoding transmission data to be transmitted to the wireless communication terminal;
Using the puncture pattern corresponding to the base station among a plurality of different puncture patterns defining bits to be erased from the error correction encoded data, the puncture is generated from the error correction encoded data generated by the error correction encoding means. Puncturing means for erasing bits defined by the pattern and generating punctured encoded data;
Modulation means for modulating the punctured encoded data;
Spreading means for code spreading the modulated punctured encoded data using a spreading code corresponding to the wireless communication terminal;
Transmitting means for transmitting a signal including code-spread punctured encoded data;
With
The wireless communication terminal is
Receiving means for receiving each signal from the plurality of base stations;
Despreading means for despreading each received signal;
Demodulation means for demodulating each despread signal;
Using bit data that remains in at least one of a plurality of received data obtained as a result of demodulation by the demodulating means and is not erased by the puncturing means of each of the plurality of base stations, Generating means for generating the digitized data;
Decoding means for decoding the encoded data generated by the generating means;
A wireless communication system comprising:   The error correction coding means of each of the plurality of base stations performs error correction coding at a lower coding rate than when the wireless communication terminal communicates with one base station. The wireless communication system described. Each puncture pattern used in the puncturing means of each of the plurality of base stations is the bit data of the error correction encoded data among the punctured encoded data generated by each of the plurality of base stations. The bits to be erased are defined such that they are present in at least one,
The generating means is not erased from each of the plurality of received data by the puncturing means of each of the plurality of base stations based on each puncture pattern used by the puncturing means of each of the plurality of base stations. 2. The wireless communication system according to claim 1, wherein the bit data of the encoded data is generated based on the bit data remaining without being erased by recognizing the bit data remaining in the data. .   In the plurality of puncture patterns, bits to be erased from the error correction encoded data are determined so that the bits to be erased from the error correction encoded data are different in each of the plurality of base stations. The wireless communication system according to claim 1. The puncturing means of a first base station of one of the plurality of base stations uses a puncture pattern in which bits having a number of bits different from the number of bits erased by the puncturing means of another base station are erased. To generate the punctured encoded data,
The wireless communication according to claim 1, wherein the modulation means of the first base station modulates punctured encoded data output from the puncture means with a modulation scheme different from that of other base stations. system. The puncturing means of a first base station of one of the plurality of base stations uses a puncture pattern in which bits having a number of bits different from the number of bits erased by the puncturing means of another base station are erased. To generate the punctured encoded data,
The wireless communication system according to claim 1, wherein the spreading means of the first base station code spreads the modulated punctured encoded data at a spreading factor different from that of other base stations.   At least one of a puncture pattern used by each of the puncture means of each of the plurality of base stations, a modulation scheme used by the modulation means, and a spreading factor of the spread means, each signal transmitted from each base station is 2. The wireless communication system according to claim 1, wherein the wireless communication system is determined based on a reception state when received by the wireless communication terminal. Using the puncture pattern corresponding to each base station that determines the bit to be erased from the error correction encoded data of the transmission data, the punctured encoded data in which the bit determined by the puncture pattern is deleted from the error correction encoded data Receiving means for receiving a plurality of signals transmitted from the transmitting means of a plurality of base stations each comprising a transmitting means for generating and modulating and code spreading the punctured encoded data; and
Demodulation means for despreading and demodulating each received signal to obtain a plurality of received data;
Generating means for generating encoded data using bits that remain in at least one of the plurality of received data and are not erased in each base station;
Decoding means for decoding the encoded data generated by the generating means;
A wireless communication terminal device comprising:   Based on the reception state when each signal transmitted from each base station is received by the receiving means, at least one of a puncture pattern, a modulation scheme and a spreading factor corresponding to each of the plurality of base stations is determined. The wireless communication terminal device according to claim 8, wherein:   Each base in which bits to be erased are determined so that each bit data of the error correction encoded data exists in at least one of the punctured encoded data generated in each of the plurality of base stations Based on each puncture pattern corresponding to a station, the bit data remaining without being erased is recognized by each of the plurality of base stations, and the code based on each bit data remaining without being erased is recognized. 9. The wireless communication terminal apparatus according to claim 8, wherein each bit data of the digitized data is generated. A handover control method between a plurality of base stations and radio communication terminals,
Each of the plurality of base stations uses a puncture pattern corresponding to each base station that defines a bit to be erased from error correction encoded data of transmission data to be transmitted to the wireless communication terminal. Generating punctured encoded data in which bits defined by the puncture pattern are erased, modulating and code spreading the punctured encoded data, and transmitting,
The wireless communication terminal receiving each signal transmitted from each of the plurality of base stations;
Despreading and demodulating each received signal to obtain a plurality of received data;
Generating encoded data using bits that remain in at least one of the plurality of received data and are not deleted at each base station; and
Decoding the generated encoded data;
A handover control method comprising:

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