JP2009290451A - Radio communication system, radio communication device, and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continue radio communication even when an error occurs. <P>SOLUTION: This radio communication device for transmitting user data to a communication destination device includes: a modulation class selecting part for selecting a modulation class for modulating user data on the basis of quality information acquired from data transmitted by the communication destination device; the number of repeating times determining part for determining the number of repeating times which is the number of times of repeatedly transmitting the same user data to the communication destination device on the basis of the quality information when the selected modulation class is the lowest modulation class among selectable modulation classes; and a data transmitting part for transmitting the user data to the communication destination device according to the selected modulation class data and the determined number of repeating times. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication system, a wireless communication apparatus, and a wireless communication method that can continue communication even when an error occurs.

  In wireless communication systems, the quality and characteristics of radio propagation paths (hereinafter referred to as “propagation path characteristics”) are likely to deteriorate, and transmission data and reception data do not match in radio communication between a radio base station and a radio communication terminal. (Hereinafter, “error”) occurs frequently.

  Therefore, in order to enable communication to continue even if an error occurs, error correction for correcting the error and automatic retransmission control for requesting the transmission side to retransmit received data in which an error has been detected on the receiving side Is widely used.

  In addition, an adaptive modulation scheme that selects a modulation scheme (modulation class) according to the quality of the radio propagation path is employed in order to allow radio communication to continue even if an error occurs. In this adaptive modulation scheme, when the quality of the radio channel is good, a modulation scheme (for example, 64 QAM (64 Quadrature Amplitude Modulation)) having a high bit rate but a low error tolerance and a high error rate is selected. On the other hand, when the quality of the radio channel is poor, a modulation scheme (for example, BPSK (Binary Phase Shift Keying)) having a low error rate but a low bit rate is selected.

In a wireless communication system adopting this adaptive modulation method, (A) selecting a modulation method for transmitting data by acquiring information indicating the quality of the wireless propagation path of the transmitted data from the data receiving side, (B) Since the data receiving side requests the modulation method for transmitting data to the data transmitting side and selects the modulation method on the transmitting side, the data is transmitted when the quality of the radio channel is poor. As the error rate increases, information indicating the quality of the radio channel and the error in the request signal that requires the modulation method also increase, and an appropriate modulation method can be selected according to the quality of the radio channel. In some cases, wireless communication cannot be continued. Therefore, in order to enable selection of an appropriate modulation scheme according to the quality of the radio propagation path, a technique has been proposed in which a request signal for requesting a modulation scheme is transmitted a plurality of times according to the quality of the radio propagation path. (For example, see Patent Document 1).
JP 2005-167389 A

  However, even if the quality of the radio channel is extremely poor and selectable, the highest error tolerance and the lowest error rate, but the radio communication with the modulation method having the lowest bit rate can be performed, the radio When the quality of the propagation path does not satisfy the required quality for the selected modulation method, the state where the data error rate is high continues, and wireless communication may not be continued.

  Therefore, the present invention has been made to solve the above-described problems, and among the selectable modulation classes (modulation methods), the modulation class (modulation method) having the lowest error rate but the lowest data rate. It is an object to provide a wireless communication system, a wireless communication apparatus, and a wireless communication method capable of continuing wireless communication even if it is difficult to continue wireless communication even if selected.

  A first feature of the present invention is a wireless communication system comprising a first wireless communication device and a second wireless communication device that transmits user data to the first wireless communication device, wherein the second wireless communication device Is selected by a modulation class selection unit that selects a modulation class for modulating the user data based on quality information acquired from data transmitted by the first wireless communication device, and the modulation class selection unit When the modulation class is the lowest modulation class among selectable modulation classes, the number of repetitions, which is the number of times the same user data is repeatedly transmitted to the first wireless communication device, is set to the lowest modulation class. The number of repetitions determining unit based on the quality information in the modulation class data regarding the modulation class selected in the modulation class selection unit, According to the repetition number determined by the serial number of repetitions determining unit, and summarized in that and a data transmission unit for transmitting said user data to said first wireless communication device.

  According to such a feature, the modulation class selected by the second wireless communication device based on the quality information acquired from the first wireless communication device has the lowest data rate among the selectable modulation classes, but the error rate. If the modulation class is the lowest and the lowest modulation class, the number of repetitions is determined. Thereby, even when the quality of the propagation path does not satisfy the required quality of the modulation scheme in the lowest modulation class and the data transmission error of the data received by the first wireless communication apparatus does not decrease, the propagation path quality is repeated according to the quality information. By determining the number of times, an appropriate number of repetitions can be used.

  Then, the second wireless communication device repeatedly transmits the same user data to the first wireless communication device according to the determined number of repetitions. Therefore, the first wireless communication apparatus only needs to be able to decode at least one of the received plurality of identical user data, and the quality of the propagation path is modulated in the lowest modulation class selected in the second wireless communication apparatus. A wireless communication system capable of continuing wireless communication even when the required quality of the system is not satisfied can be provided.

  A second feature of the present invention relates to the first feature of the present invention, wherein the iteration count determination unit increases the iteration count according to a decrease in a value indicating quality acquired as the quality information. The gist.

  A third feature of the present invention relates to the first feature or the second feature of the present invention, wherein the second wireless communication apparatus is a value indicating the quality acquired as the quality information and / or the number of repetitions. A control data generation unit that generates control data including any information on the number of repetitions determined by the determination unit, wherein the data transmission unit generates the control data in addition to the modulation class data and the user data The gist is to transmit the control data generated by the unit to the first wireless communication apparatus.

  A fourth feature of the present invention is related to the third feature of the present invention, wherein the second wireless communication apparatus includes the first wireless communication apparatus in addition to the modulation class data, the user data, and the control data. And transmitting the control data continuously with the transmission of the known data, wherein the known data that is a known data series is transmitted to the first wireless communication device. .

  A fifth feature of the present invention relates to the third feature of the present invention, wherein the control data generation unit generates a number of the control data corresponding to the number of repetitions determined by the repetition number determination unit, The gist of the data transmission unit is to transmit each of a plurality of the same user data together with the control data.

  A sixth feature of the present invention relates to the third feature of the present invention, wherein the first wireless communication apparatus receives the user data, the control data, and the modulation class data from the second wireless communication apparatus. A data receiving unit, a modulation class grasping unit for grasping the modulation class selected in the second wireless communication device according to the modulation class data received by the data receiving unit, and a modulation grasped by the modulation class grasping unit When the class is the lowest modulation class that can be selected in the second wireless communication apparatus, the number of repetitions determined in the second wireless communication apparatus is determined according to the control data received by the data reception unit. A repetition number specifying unit to be specified; and the user data received by the data receiving unit according to the repetition number specified by the repetition number specifying unit. A data decoding section for decoding the data, further comprising the the gist.

  A seventh feature of the present invention is a wireless communication device that transmits user data to a communication destination device, wherein the user data is modulated based on quality information acquired from data transmitted by the communication destination device. When the modulation class selected by the modulation class selection unit and the modulation class selected by the modulation class selection unit is the lowest modulation class among selectable modulation classes, the same user data is A repetition number determination unit that determines the number of repetitions that is the number of times of repeated transmission to a communication destination device based on quality information in the lowest modulation class, the modulation class data selected by the modulation class selection unit, and the number of repetitions Data for transmitting the user data to the communication destination device according to the number of repetitions determined by the determination unit. And summarized in that and a transmission unit.

  An eighth feature of the present invention is a wireless communication device that receives user data from a communication destination device, wherein the value indicating quality acquired as quality information in the communication destination device and / or the communication destination device are the same. A data receiving unit that receives from the communication destination device control data including information on the number of repetitions that is the number of times user data is repeatedly transmitted, and modulation class data related to a modulation class selected in the communication destination device; and the data reception The modulation class grasping unit for grasping the modulation class selected in the communication destination device and the modulation class grasped by the modulation class grasping unit can be selected in the communication destination device according to the modulation class data received by the communication unit. If the modulation class is the lowest modulation class, the number of repetitions is specified according to the control data received by the data receiver. A repeat count specification unit that, in accordance with the number of iterations specified by the repeat count specifying unit, and summarized in that and a data decoder which decodes the user data to which the data receiving unit receives.

  A ninth feature of the present invention is a wireless communication method used in a second wireless communication apparatus for transmitting user data to the first wireless communication apparatus, wherein quality information is obtained from the data transmitted by the first wireless communication apparatus. Obtaining a modulation class for modulating the user data based on the quality information obtained by the obtaining step, and the modulation class selected by the selecting step, Of the selectable modulation classes, the number of repetitions, which is the number of times the same user data is repeatedly transmitted to the first wireless communication device, is acquired by the reception quality acquisition unit when the modulation class is the lowest modulation class. Determining based on reception quality information; modulation class data selected in said selecting step; and said determination That according to the repetition number determined by step, and summarized in that and sending the user data to said first wireless communication device.

  According to the present invention, even when the modulation class (modulation method) having the lowest error rate and the lowest data rate that can be selected is selected, even when the quality of the wireless propagation path is difficult to continue, A wireless communication system, a wireless communication apparatus, and a wireless communication method capable of continuing wireless communication can be provided.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

  In the following, (1) schematic configuration of radio communication system, (2) detailed configuration of radio communication system, (3) repetitive transmission processing, (4) operation of radio communication system, (5) action and effect, (6) Other embodiments will be described.

(1) Schematic Configuration of Radio Communication System First, the overall schematic configuration of the radio communication system according to the present embodiment will be described using FIG. 1 and FIG.

(1.1) Overall Schematic Configuration FIG. 1 is an overall schematic configuration diagram of a wireless communication system 10 according to the present embodiment.

  As illustrated in FIG. 1, the wireless communication system 10 includes a wireless base station (second wireless communication device) 100 and a wireless communication terminal (first wireless communication device) 200.

  In this embodiment, the radio base station 100 and the radio communication terminal 200 select a modulation class corresponding to the time division multiple access-time division duplex (TDMA-TDD) scheme and the quality of the propagation path, and the modulation class Wireless communication (for example, wireless communication based on the iBurst (registered trademark) standard) using an adaptive modulation method that modulates data to be transmitted is performed.

  That is, communication in the direction from the radio communication terminal 200 to the radio base station 100 (hereinafter “uplink UL”) and communication in the direction from the radio base station 100 to the radio communication terminal 200 (hereinafter “downlink DL”) are performed. Are executed alternately.

  The radio communication terminal 200 has a function of acquiring a signal-to-interference noise power ratio (hereinafter referred to as “SINR (Signal to Interference and Noise Ratio)”) as information (quality information) regarding the quality of the propagation path in the downlink DL. . Then, the radio communication terminal 200 notifies the radio base station 100 of the acquired SINR. Also, the radio communication terminal 200 transmits the uplink user data UD in the uplink UL. The user data UD is data generated by an upper application (for example, VoIP or the like) executed in the wireless communication terminal 100.

  The radio base station 100 selects a modulation class for modulating data transmitted in the downlink DL based on the downlink DL SINR notified by the radio communication terminal 200. At this time, when the selected modulation class is the lowest modulation class among the selectable modulation classes, the radio base station 100 repeatedly transmits the same downlink user data UD in the downlink DL. Specifically, when the selected modulation class is the lowest modulation class, the radio base station 100 repeats the same downlink user data UD based on the SINR of the downlink DL notified by the radio communication terminal 200. The number of times of transmission (hereinafter referred to as “downlink repeat count DN”) is determined. Here, the lowest modulation class means a modulation method having the lowest data error rate and the lowest transmission rate among the modulation classes selectable in the radio base station 100.

  Then, the radio base station 100 notifies the radio communication terminal 200 of the selected modulation class and the acquired SINR or downlink repetition number DN.

(1.2) Frame Configuration Example FIG. 2 is a frame configuration diagram of a transmission frame used in the wireless communication system 10.

  As shown in FIG. 2, the transmission frame has a training symbol period T1 and an information symbol period T2. In the training symbol period T1, a known symbol sequence is transmitted in the radio base station 100 and the radio communication terminal 200. In the information symbol period T2, an unknown symbol sequence is transmitted in the radio base station 100 and the radio communication terminal 200.

  Further, the information symbol period T2 is transmitted in the control data period for transmitting the control data CD, the CRC code period for transmitting the CRC code CC, the user data period for transmitting the user data UD, and the uplink UL or the downlink DL. A section for transmitting modulation class data X indicating a modulation class when data to be modulated is modulated.

  The control data CD includes SINR, which is quality information, information indicating the number of downlink repetitions DN, a sequence number, and the like. The CRC code CC is an error detection code obtained by performing CRC calculation on the user data UD.

  Here, the control data CD is an important information element because it includes information on SINR and downlink repetition number DN that are quality information. Therefore, the control data CD is arranged immediately after the training symbol TS.

  In the wireless communication system 10, as shown in FIGS. 2A to 2C, transmission frames of different formats are used according to the number of downlink repetitions DN.

  FIG. 2A shows a format used when there is no repetition.

  FIG. 2B shows a format used when user data UD is repeatedly transmitted twice. In the format shown in FIG. 2B, two identical user data # 1 and # 2 are included in the user data section. In the format shown in FIG. 2B, the CRC code CC is generated from either one of the user data # 1 and # 2.

  FIG. 2C shows a format used when user data UD is transmitted three times repeatedly. In the format shown in FIG. 2C, three identical user data # 1 to # 3 are included in the user data section. In the format shown in FIG. 2C, the CRC code CC is generated from any one of the user data # 1 to # 3.

(2) Detailed Configuration of Radio Communication System Next, the configuration of the radio base station 100 and the configuration of the radio communication terminal 200 will be described using FIG. 3 and FIG. In the following, points related to the present invention will be mainly described.

(2.1) Configuration of Radio Base Station FIG. 3 is a functional block configuration diagram of the radio base station 100.

  As shown in FIG. 3, the radio base station 100 includes an antenna 101, an RF unit 102, a reception processing unit 103, an error correction decoding unit 104, a CRC code matching unit 105, an uplink quality information acquisition unit 106, a control unit 107, It includes a transmission / reception buffer unit 108, a communication I / F unit 109, a repetition count determination unit 110, a user data generation unit 111, a control data generation unit 112, a CRC code generation unit 113, an error correction encoding unit 114, and a transmission processing unit 115.

  The RF unit 102 transmits and receives wireless signals to the wireless communication terminal 100 via the antenna 111. The RF unit 110 includes an LNA, a power amplifier, an up converter, a down converter, and the like.

  The reception processing unit 103 demodulates user data UD, CRC code, modulation class data X, and control data CD from the received transmission frame.

  The error correction decoding unit 104 performs error correction decoding on the user data UD.

  The CRC code collation unit 105 collates the user data UD after error correction decoding and the CRC code CC.

  The uplink quality information acquisition unit 106 acquires SINR as the quality information of the propagation path in the uplink UL.

The control unit 107 selects a modulation class in the downlink DL from the SINR included in the control data CD of the transmission frame transmitted from the radio communication terminal 200 through the uplink UL. Then, it is determined whether or not the selected modulation class is the lowest modulation class among settable modulation classes. Then, when it is determined that the modulation class is the lowest modulation class, the control unit 107 outputs information on the value indicating the SINR in the downlink DL to the repetition determination unit 110. Also, the modulation class data X related to the selected modulation class is output to the error correction encoding unit 114.
Further, the control unit 107 controls the entire radio base station 100 and executes automatic reproduction control (ARQ).

  The communication I / F unit 109 functions as an interface with a communication network such as an IP network. The transmission / reception buffer unit 108 temporarily holds the user data UD from the communication I / F unit 109. The transmission / reception buffer unit 108 also temporarily stores user data UD to be passed to the communication I / F unit 109.

  The repetition count determining unit 110 has a table (see FIG. 5A) in which SINR indicating downlink DL quality information included in the control data CD received from the radio communication terminal 200 is associated with the downlink repetition count DN. Then, based on the table, the number of downlink repetitions DN is determined.

  The user data generation unit 111 reads out from the transmission / reception buffer unit 108 user data UD having a size suitable for the frame format corresponding to the downlink repeat count DN.

  The control data generation unit 112 generates control data CD including information indicating the SINR in the uplink UL, the modulation class in the downlink DL, and the number of downlink repetitions DN.

  The CRC code generation unit 113 performs a CRC calculation on the user data UD read by the user data generation unit 111, and generates a calculation result as a CRC code CC.

  The error correction encoding unit 114 encodes the user data UD, CRC code, modulation class data X, and control data CD. Here, the error correction encoding unit 114 may encode the user data UD, the CRC code, and the control data CD using an algorithm corresponding to the repetition code. Here, “algorithm corresponding to repetition code” means a simple repetition code (repetition code) and a decoding method (majority logic decoding) by majority logic (the same applies hereinafter).

  The transmission processing unit 115 modulates the encoded user data UD, CRC code, modulation class data X, and control data CD with a modulation scheme corresponding to the modulation class selected in the downlink DL. Also, the transmission processing unit 115 inserts the modulated user data UD, CRC code, modulation class data X, and control data CD into the transmission frame shown in FIG.

(2.2) Configuration of Radio Communication Terminal FIG. 4 is a functional block configuration diagram of the radio communication terminal 200.

  As shown in FIG. 4, the radio communication terminal 200 includes an upper layer processing unit 201, a transmission / reception buffer unit 202, a downlink quality information acquisition unit 203, a control data generation unit 204, a user data generation unit 205, a CRC code generation unit 206, An error correction coding unit 207, a transmission processing unit 208, an RF unit 209, an antenna 210, a reception processing unit 211, an error correction decoding unit 212, a CRC code collation unit 213, and a control unit 214 are included.

  The upper layer processing unit 201 has a function of processing an upper layer and executes an application. The transmission / reception buffer unit 202 temporarily holds the user data UD from the upper layer processing unit 201. The transmission / reception buffer unit 202 also temporarily stores user data UD to be passed to the upper layer processing unit 201.

  The downlink quality information acquisition unit 203 acquires SINR as propagation path quality information in the downlink DL that is wireless communication in the direction from the wireless base station 100 to the wireless communication terminal 200.

  The control data generation unit 204 generates control data CD including information on a value indicating SINR in the downlink DL.

  The user data generation unit 205 reads the user data UD from the transmission / reception buffer unit 202.

  The CRC code generation unit 206 performs CRC calculation on the user data UD read by the user data generation unit 205, and generates a calculation result as a CRC code CC.

  The error correction encoding unit 207 encodes the user data UD, the CRC code, the modulation class data X related to the modulation class in the uplink selected by the control unit 214, and the control data CD.

  The transmission processing unit 208 modulates the encoded user data UD, CRC code, modulation class data X, and control data CD with a modulation scheme corresponding to the modulation class set in the uplink UL. Also, the transmission processing unit 208 inserts the modulated user data UD, CRC code, modulation class data X, and control data CD into the transmission frame shown in FIG.

  The RF unit 209 transmits and receives radio signals to the radio base station 100 via the antenna 210. The RF unit 209 includes an LNA, a power amplifier, an up converter, a down converter, and the like.

  The reception processing unit 211 demodulates user data UD, CRC code, modulation class data X, and control data CD from the received transmission frame.

  The error correction decoding unit 212 performs error correction decoding on the user data UD. Here, the error correction decoding unit 213 may decode the user data UD using an algorithm corresponding to the repetition code.

  The CRC code collation unit 213 collates the user data UD after error correction decoding and the CRC code CC.

Whether the control unit 214 is the lowest modulation class among the modulation classes in which the modulation class in the downlink DL can be selected from the modulation class data included in the transmission frame transmitted from the radio base station 100 through the downlink DL. Know whether or not. Then, if it is determined that the modulation class is the lowest modulation class, the control unit 214 acquires the downlink repetition number DN included in the control data CD included in the transmission frame, and outputs it to the error correction decoding unit 212. In addition, an uplink modulation class is selected, and modulation class data X related to the uplink modulation class is output to error correction coding section 207.
Further, the control unit 214 controls the entire radio communication terminal 200 and executes automatic reproduction control (ARQ).

(3) Repetitive Transmission Processing Next, the repeated transmission processing executed by the radio base station 100 and the radio communication terminal 200 will be described using FIG. 5 and FIG.

  The radio base station 100 holds a table as shown in FIG. 5A in advance, and determines the downlink repeat count DN using the table. Specifically, the repetition count determining unit 110 of the radio base station 100 determines that the modulation class selected by the control unit 107 is the lowest modulation class (the modulation class in FIG. When the method is π / 2-BPSK and the modulation class is 0), each required SINR set in the lowest modulation class is set to a threshold (here, −3.5 dB, −2.5 dB, −1). .5 dB) and the number of downlink repetitions DN is determined according to the comparison result.

  As shown in FIG. 5 (b), the downlink repetition count DN is determined from the radio base station 100 when the modulation class selected according to SINR is the lowest modulation class 0 among the configurable modulation classes. As the SINR in the downlink DL in the direction of the wireless communication terminal 200 deteriorates, it increases stepwise. Further, when the modulation class selected by the radio base station 100 is 1 or more, it is set so that there is no repetition (the number of downlink repetitions DN is 1).

  FIG. 6 shows an example of user data generation when the number of repetitions is three. When the number of repetitions is 3, the divided data obtained by dividing the user data UD when there is no repetition is divided into three transmission frames.

  As a result, when the number of repetitions is 3, the effective transmission rate becomes 1/3 compared to the case without repetition, but the chance that the user data UD can be decoded can be tripled.

  Therefore, in the example of the table of FIG. 5A, when the downlink DL modulation class in the direction from the radio base station 100 to the radio communication terminal 200 is 0 (modulation scheme is π / 2-BPSK), the radio base station 100 determines whether the modulation class corresponds to any of 0a to 0c based on the SINR in the downlink DL. For example, when the modulation class corresponds to 0c, the user data UD is repeatedly transmitted three times. As a result, the radio communication terminal 200 can more reliably decode the user data UD.

(4) Operation of Radio Communication System Next, the operation of the radio communication system 10 will be described with reference to FIG.

  FIG. 7 is a flowchart showing an operation in the downlink DL.

  In step S101, the control unit 107 of the radio base station 100 acquires SINR, which is quality information in the downlink DL, included in the control data CD stored in the transmission frame received from the radio communication terminal 200.

  In step S102, the control unit 107 of the radio base station 100 selects a modulation class corresponding to the acquired SINR.

  In step S103, the control unit 107 of the radio base station 100 determines whether or not the selected modulation class is the lowest modulation class among settable modulation classes.

  In step S103, when the control unit 107 of the radio base station 100 determines that the modulation class is the lowest (corresponding to 0 in FIG. 5A) (corresponding to S103 Yes), in step S104, the repetition count determination unit 110 Determines whether the SINR in the downlink DL in the direction from the radio base station 100 to the radio communication terminal 200 satisfies the required SINR (the required SINR in the modulation class 0a) at which the downlink repetition number DN is one.

  In step S104, when the required number of downlink repetitions DN does not satisfy the required SINR (corresponding to S104 Yes), the repetition number determination unit 110 of the radio base station 100 responds to the SINR in the downlink DL in step S105. The downlink repeat count DN is determined.

  On the other hand, in step S104, when the required SINR that satisfies the downlink repetition count DN of 1 is satisfied (corresponding to S104 No), the repetition count determination unit 110 of the radio base station 100 repeats the downlink DL in step S106. It is determined that there is no number of times (the number of downlink repetitions is 1).

  After step S105 or step S106 is executed, in step S107, the user data generation unit 111 of the radio base station 100 reads the user data UD corresponding to the number of downlink repetitions DN from the transmission / reception buffer unit.

  In step S108, the control data generation unit 112 of the radio base station 100 generates the control data CD including the repetition number information indicating the downlink repetition number DN and the SINR in the uplink UL acquired by the uplink quality information acquisition unit 106. .

  After execution of step S108 or when the control unit 107 of the radio base station 100 does not select the lowest modulation class (corresponding to S103 No) in step S103, the CRC code of the radio base station 100 is obtained in step S109. The generation unit 113 generates a CRC code from the user data UD.

  In step S110, the error correction encoding unit 114 of the radio base station 100 encodes the user data UD, CRC code, modulation class data X, and control data CD.

  In step S111, the transmission processing unit 115 of the radio base station 100 modulates the encoded user data UD, CRC code, modulation class data X, and control data CD according to the modulation class selected by the control unit 107. Modulate by method.

  In step S112, the transmission processing unit 115 and the RF unit 102 of the radio base station 100 store the modulated user data UD, CRC code, modulation class data X, and control data CD in the transmission frame, and store the transmission frame. Transmit to the wireless communication terminal 200.

  In step S201, the RF unit 209 and the reception processing unit 211 of the radio communication terminal 200 demodulate the user data UD, CRC code, and control data CD stored in the transmission frame received from the radio base station 100.

  In step S202, the control unit 214 of the radio communication terminal 200 grasps the modulation class in the downlink DL included in the modulation class data X, and uses the lowest modulation class among the modulation classes that can be set by the radio base station 100. It is determined whether or not there is.

  When the control unit 214 of the wireless communication terminal 200 determines that the modulation class is the lowest modulation class (corresponding to 0 in FIG. 5A) in step S202 (corresponding to S202 Yes), the control unit 214 includes the control data CD in step S203. Based on the repeated number information, the downlink repeated number DN is specified. In addition, the control unit 214 stores the repetition count information.

  In step S204, the control unit 214 of the wireless communication terminal determines whether or not the user data UD stored in the transmission frame is user data UD that has been subjected to repeated transmission processing, from the identified number of downlink repetitions DN. To do.

  In step S205, the error correction decoding unit 212 of the wireless communication terminal 200 performs error correction decoding on the UN user data UD based on the downlink repetition count DN.

  On the other hand, when the control unit 214 of the wireless communication terminal 200 determines that the modulation class is not the lowest modulation class (corresponding to S202No), or when the control unit 214 determines that there is no repetition (corresponding to S204No), the wireless communication terminal Since there are no repetitions, the 200 error correction decoding unit 212 performs error correction decoding on the user data UD as usual.

  In step S207, the CRC code matching unit 213 of the wireless communication terminal 200 performs a CRC calculation on the decoded user data UD, and checks whether the calculation result matches the CRC code. If the calculation result and the CRC code do not match, the user data UD contains an error.

  In step S208, the control unit 214 of the wireless communication terminal 200 determines whether an error is detected in the user data UD.

  When an error is detected (corresponding to step S208 Yes), in step S209, the control unit 214 requests the radio base station 100 to retransmit the user data UD in which the error is detected. On the other hand, when no error is detected, the user data UD is stored in the transmission / reception buffer unit 202.

(5) Action / Effect According to the present embodiment, the downlink repeat count DN is determined based on quality information acquired from data transmitted by the wireless communication terminal 200. When the value indicating the quality information decreases, the error rate in the downlink DL also increases. Further, even if the modulation class for modulating data is selected and the lowest modulation class having a low data rate but a low error rate is selected, When the data transmission error is not reduced, an appropriate number of repetitions can be used by determining the number of downlink repetitions according to the quality information.

  Then, the radio base station 100 repeatedly transmits the same downlink user data UD to the radio communication terminal 200 according to the determined downlink repetition count DN. As a result, the radio communication terminal 200 only needs to be able to decode at least one of the received plurality of the same downlink user data UD, and even if the radio base station 100 changes to the lowest modulation class, the quality of the propagation path Communication can be continued even when the quality of the propagation path is such that the deterioration of the quality does not improve.

  In addition, according to the present embodiment, if a data transmission error is not reduced even if a modulation class with low data rate but low error rate is selected as a modulation class for modulating data, the value indicating quality information is lowered. Accordingly, the downlink repeat count DN is increased. Therefore, it is possible to reduce the data transmission error even when the quality of the propagation path is deteriorated while maintaining the effective transmission rate when the quality of the propagation path in the radio base station 100 and the radio communication terminal 200 is good. Wireless communication can be continued.

  According to the present embodiment, the radio base station 100 transmits to the radio communication terminal 200 the control data CD including the value indicating the quality information (SINR) and the information about the number of downlink repetitions DN. Thereby, the radio | wireless communication terminal 200 can determine whether transmission is performed repeatedly in downlink DL, or can determine the frequency | count DN of downlink repetition.

  According to the present embodiment, the radio base station 100 and the radio communication terminal 200 transmit the control data CD continuously with the transmission of the training symbol TS. Such a training symbol TS is mainly used for synchronization processing in the radio base station 100 and the radio communication terminal 200. For this reason, by transmitting the control data CD continuously with the transmission of the training symbol TS, the radio base station 100 and the radio communication terminal 200 can receive the control data CD with a small synchronization shift. CD can be transmitted stably.

  According to the present embodiment, the radio communication terminal 200 identifies the downlink repetition number DN determined in the radio base station 100 according to the control data CD, and decodes the downlink user data UD according to the identified downlink repetition number DN. To do. For this reason, it becomes possible to appropriately decode a plurality of the same downlink user data UD.

  According to the present embodiment, the radio base station 100 determines the downlink repetition count DN according to the control data CD, and transmits the downlink user data UD to the radio communication terminal 200 according to the determined downlink repetition count DN. The radio communication terminal 200 only needs to be able to decode at least one of the received plurality of the same downlink user data UD. Therefore, even if the radio base station 100 changes to the lowest modulation class, the quality of the propagation path deteriorates. Communication can be continued even in the case of propagation path quality that does not improve.

(6) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

(6.1) Modification Example of Control Data Arrangement In the above-described embodiment, one control data CD is included in the transmission frame. However, as shown in FIG. 8, a control data CD is provided for each user data UD. A frame configuration may be used. By making not only the user data UD but also the control data CD redundant, the control data CD can be stably transmitted.

(6.2) Modification Example of User Data Arrangement In the above-described embodiment, when the user data UD is repeatedly transmitted, the same user data UD is continuously transmitted. That is, the same user data UD is continuously arranged in the transmission frame. However, as shown in FIG. 9, the same user data UD may be transmitted separately. According to such a transmission method, an interleaving effect can be obtained and resistance to burst errors can be increased.

(6.3) Modification 1 of the wireless communication system
In the above-described embodiment, the repetition of the same user data in the downlink DL in the wireless communication system 10 in which the wireless base station 100 and the wireless communication terminal 200 perform wireless communication has been described. However, since the radio communication terminal 200 has the same configuration as the radio base station 100, the same user data is repeatedly transmitted not only in the downlink DL but also in the uplink UL. Is possible. In this case, the radio communication terminal 200 determines the number of uplink repetitions of user data to be transmitted based on the SINR and the modulation class in the uplink UL acquired from the radio base station 200.

(6.4) Modification 2 of the wireless communication system
In the above-described embodiment, the radio communication system 10 in which the radio base station 100 and the radio communication terminal 200 perform radio communication has been described. However, the present invention is not limited to wireless communication between a wireless base station and a wireless communication terminal, and can also be applied to a dynamic wireless communication system (for example, an ad hoc network) that performs wireless communication between a plurality of wireless communication terminals. In this case, one wireless communication terminal becomes the first wireless communication device, and another wireless communication terminal that communicates with the one wireless communication terminal becomes the second wireless communication device.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a frame block diagram of the transmission frame used in the radio | wireless communications system which concerns on embodiment of this invention. It is a functional block block diagram of the radio base station which concerns on embodiment of this invention. It is a functional block block diagram of the radio | wireless communication terminal which concerns on embodiment of this invention. It is explanatory drawing explaining the correspondence of quality information SINR and the number of times without repetition. It is a conceptual diagram which shows the example of user data generation | occurrence | production when the frequency | count of repetition is 3 times. It is a flowchart which shows the operation | movement in a downlink. It is a frame block diagram which shows the example of a change of control data arrangement | positioning. It is a conceptual diagram which shows the example of a change of user data arrangement | positioning.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Wireless communication system, 100 ... Wireless base station, 101 ... Antenna, 102 ... RF part, 103 ... Reception processing part, 104 ... Error correction decoding part, 105 ... CRC code collation part, 106 ... Uplink quality information acquisition part, DESCRIPTION OF SYMBOLS 107 ... Control part, 108 ... Transmission / reception buffer part, 109 ... Communication I / F part, 110 ... Repeat count determination part, 111 ... User data generation part, 112 ... Control data generation part, 113 ... CRC code generation part, 114 ... Error Correction encoding unit, 115 ... transmission processing unit, 200 ... wireless communication terminal, 201 ... upper layer processing unit, 202 ... transmission / reception buffer unit, 203 ... downlink quality information acquisition unit, 204 ... control data generation unit, 205 ... user data Generation unit, 206 ... CRC code generation unit, 207 ... Error correction coding unit, 208 ... Transmission processing unit, 209 ... RF unit, 210 ... Antenna 211 ... reception processing unit, 212 ... error correction decoding portion, 213 ... CRC code checking unit, 214 ... control unit

Claims (9)

A first wireless communication device;
A second wireless communication device for transmitting user data to the first wireless communication device;
A wireless communication system comprising:
The second wireless communication device is
A modulation class selection unit that selects a modulation class for modulating the user data based on quality information acquired from data transmitted by the first wireless communication device;
This is the number of times the same user data is repeatedly transmitted to the first wireless communication apparatus when the modulation class selected by the modulation class selection unit is the lowest modulation class among selectable modulation classes. A repetition number determination unit that determines the number of repetitions based on quality information in the lowest modulation class;
A data transmission unit that transmits the modulation class data related to the modulation class selected by the modulation class selection unit and the user data to the first wireless communication apparatus according to the repetition count determined by the repetition count determination unit;
A wireless communication system comprising:   The wireless communication system according to claim 1, wherein the number of repetitions determination unit increases the number of repetitions according to a decrease in a value indicating quality acquired as the quality information. The second wireless communication apparatus generates control data including information indicating either the value indicating the quality acquired as the quality information and / or the repetition count determined by the repetition count determination unit A data generation unit;
3. The wireless communication system according to claim 1, wherein the data transmission unit transmits the control data generated by the control data generation unit to the first wireless communication device in addition to the modulation class data and the user data. . The second wireless communication apparatus transmits known data that is a known data series in the first wireless communication apparatus to the first wireless communication apparatus in addition to the modulation class data, the user data, and the control data. And
The wireless communication system according to claim 3, wherein the first wireless communication device transmits the control data continuously with the transmission of the known data. The control data generation unit generates the number of the control data corresponding to the number of repetitions determined by the repetition number determination unit,
The wireless communication system according to claim 3, wherein the data transmission unit transmits each of a plurality of the same user data together with the control data. The first wireless communication device is:
A data receiving unit for receiving the user data, the control data, and the modulation class data from the second wireless communication device;
A modulation class grasping unit for grasping a modulation class selected in the second wireless communication device according to the modulation class data received by the data receiving unit;
When the modulation class grasped by the modulation class grasping unit is the lowest modulation class that can be selected by the second wireless communication device, the second wireless communication is performed according to the control data received by the data receiving unit. A repetition number specifying unit for specifying the number of repetitions determined in the apparatus;
A data decoding unit for decoding the user data received by the data receiving unit according to the number of repetitions specified by the repetition number specifying unit;
The wireless communication system according to claim 3. A wireless communication device that transmits user data to a communication destination device,
A modulation class selection unit that selects a modulation class for modulating the user data based on quality information acquired from data transmitted by the communication destination device;
When the modulation class selected by the modulation class selection unit is the lowest modulation class among selectable modulation classes, the number of repetitions is the number of times the same user data is repeatedly transmitted to the communication destination device. An iteration number determination unit that determines the quality based on the quality information in the lowest modulation class,
A data transmission unit for transmitting the user data to the communication destination device in accordance with the modulation class data selected by the modulation class selection unit and the number of repetitions determined by the repetition number determination unit;
A wireless communication device comprising: A wireless communication device that receives user data from a communication destination device,
Control data including a value indicating quality acquired as quality information in the communication destination device and / or information on the number of repetitions that is the number of times the communication destination device repeatedly transmits the same user data, and selection in the communication destination device A data receiving unit for receiving modulation class data related to the modulated modulation class from the communication destination device;
In accordance with the modulation class data received by the data receiving unit, a modulation class grasping unit for grasping the modulation class selected in the communication destination device;
Repetition for specifying the number of repetitions according to the control data received by the data receiving unit when the modulation class grasped by the modulation class grasping unit is the lowest modulation class selectable in the communication destination device The number identification part,
A data decoding unit for decoding the user data received by the data receiving unit according to the number of repetitions specified by the repetition number specifying unit;
A wireless communication device comprising: A wireless communication method used for a second wireless communication device for transmitting user data to a first wireless communication device,
Obtaining quality information from data transmitted by the first wireless communication device;
Selecting a modulation class for modulating the user data based on the quality information acquired by the acquiring step;
When the modulation class selected by the selecting step is the lowest modulation class among the selectable modulation classes, the repetition is the number of times the same user data is repeatedly transmitted to the first wireless communication device Determining the number of times based on the reception quality information acquired by the reception quality acquisition unit;
Transmitting the user data to the first wireless communication device according to the modulation class data selected in the selecting step and the number of repetitions determined in the determining step;
A wireless communication method comprising: