JP2008085939A - Communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve communication quality without deteriorating real-time properties in communication. <P>SOLUTION: There are provided: a transmission message data generation section 110 for generating transmission message data 110a; a transmission data generation section 120 for generating transmission data 120a by using a code that can be subjected to decoding processing repeatedly as an error correction code and performing encoding processing related to the error correction code to the transmission message data; a packet transmission section 160 for transmitting a transmission packet 100a based on the transmission data to the outside; a packet reception section 220 for generating a reception packet 220a based on the transmission packet transmitted by other devices; a reception data extraction section 250 for extracting transmission data 250a corresponding to the transmission data from the reception packet; and a reception message data generation section 280 for performing the decoding processing related to the error correction code to the reception data to generate reception message data 280a corresponding to the transmission message data. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication device that exchanges data with each other by performing wireless communication between a plurality of devices.

  Some of these main communication devices are used in inter-vehicle communication systems. Note that the “inter-vehicle communication system” refers to the position of the vehicle at a fixed update cycle by performing wireless communication between a plurality of vehicles. This is a system for exchanging vehicle data such as speed and speed, and content data such as moving images and voices at indefinite times (for example, Patent Document 1). The communication device is mounted on each vehicle and performs wireless communication with other communication devices at a constant operation cycle based on a predetermined program. Note that the operation cycle of the communication device in the inter-vehicle communication system is normally about 100 mS. The communication apparatus enters the transmission mode after about 100 mS, enters the reception mode, and then enters the transmission mode again. Hereinafter, the communication device may be referred to as a “vehicle”.

The inter-vehicle system, for example, exchanges vehicle data such as the vehicle's position and speed with each other, thereby causing traffic accidents such as encounter accidents at the intersection, right-straight accidents (accidents between right-turn vehicles and straight-ahead vehicles), rear-end collisions, etc. This system is used as a safety support system for preventing the above-mentioned problem, and as a comfort / entertainment system for improving amenity by exchanging content data such as moving images and sounds.
Japanese Patent Laid-Open No. 5-191331

  However, a communication device used in such an inter-vehicle communication system cannot realize high-quality communication without degrading the real-time property (rapid response) of communication, as will be described below. was there.

  That is, in the inter-vehicle communication system, the arrangement of communication devices and the arrangement of surrounding buildings change as each vehicle moves. As a result, the communication device is affected by multipath (radiation wave) or the like. Therefore, in the inter-vehicle communication system, the propagation characteristics of the carrier wave are poor. For this reason, the communication quality, that is, the characteristic in which the quality of received data in communication is a problem may be significantly deteriorated. In communication devices used in such inter-vehicle communication systems, it has been desired to improve communication quality. Therefore, in a conventional communication apparatus used in an inter-vehicle communication system, an error correction code such as a BCH (Baud Chaudhuri Hocquechem) code is used for communication in order to improve communication quality.

  The “BCH code” is a kind of block code and is a code having an arbitrary redundancy. The “block code” is a code that divides data into arbitrary bit blocks, encodes each block, and transmits the data. This BCH code is recommended by ARIB STD-T75 to be used as an error correction code for communication in road-to-vehicle communication systems. Note that “ARIB STD-T75” is a communication standard established by the Association of Radio Industries and Businesses that develops various standards for communication including road-to-vehicle communication systems. one of.

  In the road-to-vehicle communication system, one side machine called a roadside machine is fixed and does not move. On the other hand, in the inter-vehicle communication system, each vehicle moves. Therefore, the communication environment between vehicles is more severe than the road-vehicle communication system specialized in a specific environment around the roadside unit. In other words, the inter-vehicle communication system is more likely to cause communication failures than the road-to-vehicle communication system.

  In ARIB STD-T75, it is recommended to use a BCH code (in particular, a BCH (63, 51) code therein) as an error correction code. The “BCH (63, 51) code” is a BCH code in which (63-51) bits, that is, 12-bit redundancy is given to 51-bit data. However, block codes such as BCH codes generally have a low correction capability. Therefore, in a vehicle-to-vehicle communication system in which the communication environment is more severe than a road-vehicle communication system, a code having a low correction capability such as a BCH (63, 51) code adopted in “ARIB STD-T75” is used as an error correction code. As a result, error correction cannot be performed sufficiently, and communication failures frequently occur. That is, codes such as the BCH (63, 51) code have insufficient correction capability as error correction codes for the inter-vehicle communication system.

  A block code such as a BCH code needs to have high redundancy in order to perform high-quality communication. On the other hand, if the redundancy of a block code such as a BCH code is increased, the amount of calculation increases when performing decoding processing. A conventional communication device used in an inter-vehicle communication system uses a block code such as a BCH code as an error correction code. For this reason, the conventional communication apparatus requires a long time for the decoding process of the error correction code, and the real-time property (responsiveness) of communication is deteriorated. In other words, if the redundancy of a block code such as a BCH code is simply increased, processing takes time and realism is impaired.

  Therefore, the conventional communication device used in the inter-vehicle communication system has a problem that high-quality communication cannot be realized without degrading the real-time property of communication.

  In order to solve such a problem, an object of the present invention is to provide a communication device capable of realizing higher quality communication than a conventional communication device without degrading the real time property of communication. To do.

  In order to solve the above-described problem, a communication device according to the present invention includes a transmission message data generation unit, a transmission data generation unit, a packet generation unit, and a packet transmission unit as components on the transmission side. The receiving side includes a packet receiving unit, a received data extracting unit, and a received message data generating unit.

  The transmission message data generation unit is a functional unit that generates transmission message data.

  The transmission data generation unit may sometimes refer to a code that can be repeatedly decoded (hereinafter referred to as “iterable decoding code”) as an error correction code for message data (hereinafter simply referred to as “error correction code”). , And a function means for generating transmission data by performing an encoding process on the error correction code on the transmission message data. Here, “encoding process related to code” means that a code to be added is generated and a code is added to data to be encoded. In this “encoding process related to codes”, in addition to adding codes, predetermined processes such as bit rearrangement may be performed. The error correction code for the message data is preferably a turbo code or an LDPC (Low Density Parity Check) code.

The turbo code is a code having redundancy like a block code such as a BCH code. However, the turbo code is an iteratively decodable code, that is, a code that can be repeatedly decoded. In this turbo code, the time required for one decoding process is shorter than the time required for the decoding process of a block code such as a BCH code having the same degree of redundancy. Although the specific time varies depending on the calculation capability of the CPU, if the decoding process is performed by the CPU having the same calculation speed, the time required for the decoding process of the turbo code is the same as that of the BCH code having the same degree of redundancy. This is about a fraction of the time required for the decoding process. On the other hand, an LDPC code is a linear code defined by a very sparse check matrix, that is, a matrix with a very small number of non-zero elements in the matrix. The LDPC code includes a regular LDPC code and an irregular LDPC code. In the “regular LDPC code”, the Hamming weight (column weight) of any column of the check matrix H composed of m rows and n columns is $ w_c $, the Hamming weight (row weight) of any row is $ w_r $, When the value of $ w_c $ is sufficiently smaller than the size of m, it means the code C defined by the check matrix H. “_” Indicates that the subsequent character is a subscript. Thus, for example, “w_c” means “w _c ”. “Non-regular LDPC code” means a code C defined from a parity check matrix H in which the weight of each column or each row is not constant.

  The packet generation unit is a functional unit that generates a transmission packet based on transmission data.

  The packet transmission unit is a functional unit that generates a transmission packet by performing modulation processing on the transmission packet, and transmits the transmission packet to the outside.

  The packet receiving unit is a functional unit that receives a transmission packet transmitted by another device, performs demodulation processing, and generates a reception packet.

  The reception data extraction unit is a functional unit that extracts reception data corresponding to transmission data from the reception packet.

  The reception message data generation unit is a functional unit that generates reception message data corresponding to transmission message data by repeatedly performing decoding processing on the error correction code for message data on the reception data. Here, “decoding process related to code” means that the code is removed from the data to be subjected to the decoding process and data before the encoding process is generated. In this “decoding process related to codes”, in addition to removing codes, predetermined processes such as rearrangement of bits may be performed before or after code removal.

  This received message data generation unit can repeatedly perform the decoding process. The reception message data generation unit preferably repeats the decoding process until an error-free reception message data is generated with a predetermined maximum number of repetitions as an upper limit.

  This communication apparatus uses an iteratively decodable code as an error correction code for message data on the transmission side, performs an encoding process on the error correction code on the transmission message data, and performs error processing on the reception data on the reception side. The decoding process regarding the correction code is repeated. Thereby, this communication apparatus acquires the received message data corresponding to the transmission message data on the receiving side.

  In this communication apparatus, the reception side repeatedly performs the decoding process on the error correction code on the reception data, so that the reception data is gradually converted into an appropriate value, that is, before the encoding process on the error correction code is performed. Can be approximated to the transmitted data. Therefore, this communication device can realize higher quality communication than the conventional communication device.

  In addition, iteratively decodable codes such as turbo codes have higher redundancy than block codes such as BCH codes with the same coding rate, but the time required for one decoding process has the same degree of redundancy. This is about a fraction of the time required for decoding a block code such as a BCH code. Therefore, if this communication device repeats the decoding process about 1 to 3 times, it repeats the decoding process in a shorter time or more times than the conventional communication device. The received message can be acquired in the same time as the conventional communication device.

  In addition, this communication apparatus is good to perform an encoding process not only with respect to transmission message data but with respect to transmission message length data used as transmission header data.

  In this case, the communication device includes a transmission message length data generation unit, a transmission header in addition to the transmission message data generation unit, the transmission data generation unit, the packet generation unit, and the packet transmission unit described above as components on the transmission side. In addition to the above-described packet reception unit, reception data extraction unit, and reception message data generation unit, a reception header data extraction unit, a reception message length data generation unit, It becomes the composition which has.

  The transmission message data generation unit, the transmission data generation unit, the packet generation unit, and the packet transmission unit are as described above. The packet generator generates a transmission packet based on transmission header data and transmission data as well as transmission data.

  The transmission message length data generation unit is a functional unit that generates transmission message length data representing the size of transmission message data.

  The transmission header data generation unit is a functional unit that generates transmission header data by performing an encoding process on an error correction code for header data on transmission message length data. The error correction code for header data is preferably a turbo code or a general convolutional code.

  The packet receiving unit, the received data extracting unit, and the received message data generating unit are as described above.

  The reception header data extraction unit is a functional unit that extracts reception header data corresponding to transmission header data from a reception packet.

  The reception message length data generation unit is a functional unit that performs a decoding process on the header data error correction code on the reception header data and generates reception message length data corresponding to the transmission message length data.

  This communication apparatus performs a decoding process related to an error correction code not only on received message data but also on received header data. The received header data has a smaller number of bits than the received message data. Therefore, the communication device can easily determine whether or not the transmission packet transmitted from another device has been successfully received by performing the decoding process on the received header data. Therefore, the communication device prioritizes the decoding process for the received header data over the decoding process for the received message data, and when it is determined that the transmission packet has been successfully received, the received message data By performing the decryption process for, a useless decryption process in the case where reception of a transmission packet transmitted from another device has failed can be eliminated. As a result, the communication device can further suppress an increase in the amount of calculation and improve the real-time property.

  If reception of the transmission packet is successful, the communication apparatus may be able to generate received message data simply by performing a decoding process on the error detection code for message data with respect to the received message data. Therefore, the communication device can further improve the real-time property.

  The communication apparatus extracts the message part data and repeatedly performs the error detection process on the error detection code on the message partial data before repeatedly performing the decoding process on the error correction code on the received data. It is good to configure. According to this configuration, when it is determined that there is no error in the error detection process, it is possible to extract the received message data without error from the message partial data without repeatedly performing the decoding process on the received data. it can. Therefore, according to this configuration, it is possible to further suppress an increase in the amount of calculation, and communication with high real-time characteristics is possible.

  According to the communication device of the present invention, iteratively decodable codes such as turbo codes are used as error correction codes for message data. An iteratively decodable code such as a turbo code is obtained by repeatedly performing a decoding process, so that received message data is gradually transmitted to an appropriate value, that is, transmitted before performing an encoding process related to an iteratively decodable code such as a turbo code. It can be approximated to message data. Therefore, this communication device can realize higher quality communication than the conventional communication device.

  In addition, iteratively decodable codes such as turbo codes have higher redundancy than block codes such as BCH codes, but the decoding process can be performed once in a fraction of the time of block codes such as BCH codes. It can be carried out. Therefore, if this communication device repeats the decoding process about 1 to 3 times, the communication device repeats the decoding process in a shorter time or more than the conventional communication device. Even in such a case, the received message can be acquired in the same time as the conventional communication device.

  Therefore, according to the communication apparatus according to the present invention, the quality is higher than that of the conventional communication apparatus using the BCH (63, 51) code recommended by ARIB STD-T75 without degrading the real-time property of communication. Communication can be realized.

  Hereinafter, embodiments of the present invention will be described in the order of “configuration of communication device”, “turbo code”, “characteristic evaluation of turbo code”, and “operation of communication device” with reference to the drawings. In each drawing, common components and similar components are denoted by the same reference numerals, and redundant description thereof is omitted.

<Configuration of communication device>
The inter-vehicle communication system exchanges data between communication devices by performing wireless communication between the communication device mounted on each vehicle and the communication device. Note that a repeater (not shown) may be provided between the communication device and the communication device to relay radio waves. Since this repeater is not related to the gist of the present invention, detailed description thereof is omitted here.

  The configuration of the communication apparatus according to the present invention will be described below with reference to FIG. FIG. 1 is a functional block diagram of a communication apparatus according to the present invention.

  The communication device 100 includes a transmission-side device (hereinafter sometimes simply referred to as “transmission side”) 100A and a reception-side device (hereinafter also simply referred to as “reception side”) 100B.

  In the communication in the communication device 100, the data received by the receiving device 100B is temporarily stored in the main storage unit 290 and then read from the main storage unit 290 to perform a predetermined process. A series of these operations is defined by a program stored in the main storage unit 290 in a readable manner in advance. Hereinafter, description of this point is omitted.

  In the following description, “encoding process related to code” means that a code to be added is generated and a code is added to data to be encoded. In this “encoding process related to codes”, in addition to adding codes, predetermined processes such as bit rearrangement may be performed. Further, “decoding process related to code” means that the code is removed from the data to be decoded and data before the encoding process is generated. In this “decoding process related to codes”, in addition to removing codes, predetermined processes such as rearrangement of bits may be performed before or after code removal.

  The communication device 100 includes a main calculation unit 101 and a main storage unit 190 as components of the transmission side 100A. In addition, the communication device 100 includes a main calculation unit 201 and a main storage unit 290 as the receiving-side device 100B.

  The main calculation unit 101 of the transmission side 100A is a functional unit that performs various calculations. The main calculation unit 101 is constituted by a CPU. The main calculation unit 101 includes, for example, a timer 103, a transmission message data generation unit 110, a transmission data generation unit 120, a transmission message length data generation unit 130, a transmission header data generation unit 140, a packet generation unit 150, a packet transmission unit 160, and A transmission antenna 170 is provided.

  The timer 103 is a functional unit that measures elapsed time. Each component of the transmitting side 100A operates according to the elapsed time measured by the timer 103.

  The transmission message data generation unit 110 is a functional unit that generates transmission message data 110a.

  The transmission data generation unit 120 may call a code that can be repeatedly decoded (hereinafter referred to as “iterable decoding code”) as an error correction code for message data (hereinafter simply referred to as “error correction code”). And a function unit that generates transmission data 120a by performing an encoding process related to an error correction code on the transmission message data 110a.

  The transmission data generation unit 120 includes a message data error detection code encoding unit 122 and a message data error correction code encoding unit 124.

  In this embodiment, the message data error detection code encoding unit 122 uses a CRC (Cyclic Redundancy Checking) code as an error detection code for message data. The CRC code is a kind of Hamming code for error detection in data communication, and is used on a daily basis. Hereinafter, the error detection code encoder 122 for message data is referred to as a “first CRC code encoder 122”.

  In this embodiment, the error correction code encoding unit for message data 124 uses a turbo code as an error correction code for message data. The turbo code is an error correction code (hereinafter, referred to as “iteratively decodable code”) that can be repeatedly decoded, that is, repeatedly decoded. The turbo code is approximated to an appropriate value, that is, data before the encoding process every time the decoding process is repeated. Details of the turbo code will be described later. Hereinafter, the error correction code encoder 124 for message data is referred to as a “turbo code encoder 124”. In this embodiment, a turbo code, which is a kind of iteratively decodable code, is used as an error correction code for message data. This is because the turbo code is particularly preferable because it has characteristics as described later.

  The first CRC code encoding unit 122 generates the first transmission data 122a based on the transmission message data 110a and outputs the first transmission data 122a to the turbo code encoding unit 124. In this embodiment, the first transmission data 122a is data obtained by adding a CRC code to the transmission message data 110a. Further, the turbo code encoding unit 124 generates the second transmission data 124a based on the first transmission data 122a, and outputs the second transmission data 124a to the packet generation unit 150 as the transmission data 120a. In this embodiment, the second transmission data 124a is data obtained by adding a turbo code to the first transmission data 122a.

  The transmission message length data generation unit 130 is a functional unit that generates transmission message length data 130a representing the size of the transmission message data 110a.

  The transmission header data generation unit 140 is a functional unit that generates transmission header data 140a by performing an encoding process related to an error correction code for header data on the transmission message length data 130a. The error correction code for header data is preferably a turbo code, an LDPC (Low Density Parity Check) code, or a general convolutional code. In this embodiment, a turbo code is used as an error correction code for header data.

  The transmission header data generation unit 140 includes a header data error detection code encoding unit 142 and a header data error correction code encoding unit 144.

  In this embodiment, the header data error detection code encoding unit 142 uses a CRC code as an error detection code for header data. Hereinafter, the header data error detection code encoding unit 142 is referred to as a “second CRC code encoding unit 142”.

  In this embodiment, the header data error correction code encoder 144 uses a turbo code or a convolutional code as an error correction code for header data. Hereinafter, the header data error correction code encoding unit 144 may be simply referred to as an “error correction code encoding unit 144”.

  The second CRC code encoding unit 142 generates the first transmission header data 142a based on the transmission message length data 130a and outputs the first transmission header data 142a to the error correction code encoding unit 144. In this embodiment, the first transmission header data 142a is data obtained by adding a CRC code to the transmission message length data 130a. Further, the error correction code encoding unit 144 generates the second transmission header data 144a based on the first transmission header data 142a, and outputs the second transmission header data 144a to the packet generation unit 150 as the transmission header data 140a. To do. In this embodiment, the second transmission header data 144a is data obtained by adding a turbo code or a convolutional code to the first transmission header data 142a.

  The packet generation unit 150 is a functional unit that generates the transmission packet 150a based on the transmission header data 140a and the transmission data 120a.

  The packet transmission unit 160 generates a transmission packet 100a by performing processing such as modulation with a plurality of code sequences and conversion from a digital signal to an analog signal with respect to the transmission packet 150a, and generates a transmission packet 100a via the transmission antenna 170. Thus, it is a functional means for transmitting the transmission packet 100a to the outside.

  The main storage unit 190 of the transmission side 100A is a storage unit that stores various programs and data. The main storage unit 190 includes a RAM and a register.

  In FIG. 1, each component on the transmission side 100A is drawn so as to directly output various signals and data to the subsequent components. However, in practice, each component outputs various signals and data to the subsequent component via the main storage unit 190. That is, the former stage component stores various signals and data in the main storage unit 190, and the subsequent stage component reads the signal and data from the main storage unit 190. A series of these operations is defined by the program. Hereinafter, description of this point is omitted. Further, the transmitting side 100A operates according to the time measured by the timer 103. Hereinafter, description of this point is omitted.

  The main calculation unit 201 on the receiving side 100B is a functional unit that performs various calculations. The main arithmetic unit 201 is constituted by a CPU. The main calculation unit 201 includes, for example, a timer 203, a counter 205, a reception antenna 210, a packet reception unit 220, a reception header data extraction unit 230, a reception message length data generation unit 240, a reception data extraction unit 250, and a message partial data extraction unit 260. , A message data error detection code decoding unit 270 and a received message data generation unit 280 are provided.

  The timer 203 is a functional unit that measures elapsed time. Each component on the receiving side 100B operates according to the elapsed time measured by the timer 203.

  The counter 205 is a functional unit that counts the number n of times that a decoding process related to a turbo code for the first received data 250a described later is repeatedly performed.

  The packet receiving unit 220 receives a transmission packet (hereinafter also referred to as “other vehicle packet”) 100b transmitted by another device via the reception antenna 210, and converts the analog signal into a digital signal. Or functional means for generating a received packet 220a by performing processing such as demodulation by a plurality of code sequences and detection of a unique word.

  The reception header data extraction unit 230 is a functional unit that extracts reception header data (hereinafter also referred to as “first reception header data”) 230a corresponding to the transmission header data 140a from the reception packet 220a.

  The reception message length data generation unit 240 is a functional unit that performs a decoding process on the header data error correction code on the reception header data 230a to generate reception message length data 240a corresponding to the transmission message length data 130a. is there.

  The received message length data generation unit 240 includes a header data error correction code decoding unit 242 and a header data error detection code decoding unit 244.

  In this embodiment, the header data error correction code decoding unit 242 uses a turbo code or a convolutional code as an error correction code for header data. Hereinafter, the header data error correction code decoding unit 242 may be simply referred to as an “error correction code decoding unit 242”.

  In this embodiment, the header data error detection code decoding unit 244 uses a CRC code as the header data error detection code. Hereinafter, the header data error detection code decoding unit 244 is referred to as a “first CRC code decoding unit 244”.

  Note that the error correction code decoding unit 242 generates second reception header data 242a based on the reception header data 230a and outputs the second reception header data 242a to the first CRC code decoding unit 244. In this embodiment, the second reception header data 242a is data obtained by extracting a part other than the turbo code or the convolutional code from the reception header data 230a. Further, the first CRC code decoding unit 244 generates reception message length data 244a based on the second reception header data 242a, and outputs the reception message length data 244a as reception message length data 240a to the reception data extraction unit 250. To do. In this embodiment, the received message length data 244a is data obtained by extracting a part other than the CRC code from the second received header data 242a.

  Note that the first CRC code decoding unit 244 performs a detection process on an error detection code for header data (in this case, a CRC code) on the second received header data 242a. Here, the “detection process related to error detection code” means a decoding process on a data sequence that is a target of the detection process, that is, a process of removing the error detection code from the data series, and a result of the decoding process , And further, the presence or absence of an error as a result of the decoding processing is determined based on the error detection code. Here, the first CRC code decoding unit 244 performs a decoding process on the CRC code on the second received header data 242a, that is, a process of removing the CRC code from the second received header data 242a, thereby performing the decoding process. As a result, the second reception header data 242a from which the CRC code has been removed is generated, and the presence / absence of an error in the second reception header data 242a from which the CRC code, which is the result of the decoding process, has been removed based on the CRC code The process which determines is performed. Accordingly, the first CRC code decoding unit 244 determines whether there is an error in the second reception head data 242a. If it is determined that there is an error in this determination, it means that reception of the other vehicle packet 100b has failed. In this case, the communication device 100 cannot generate error-free received message data, so the operation of the receiving side 100B is stopped.

  In addition, the first CRC code decoding unit 244 outputs the received message length data 240a to the received data extracting unit 250. This is because the received data extracting unit 250 identifies the data format of the received packet 230a. This is because the extraction of the reception data 250a from the reception packet 220a is performed in a short time.

  The reception data extraction unit 250 is a functional unit that extracts reception data (hereinafter also referred to as “first reception data”) 250a corresponding to the transmission data 120a from the reception packet 220a.

  The message part data extraction unit 260 is a functional unit that extracts message part data 260a, which is data of a message part, from the received data 250a.

  The message data error detection code decoding unit 270 performs a decoding process on the message data error detection code on the message part data 260a, and receives message data corresponding to the transmission message data 110a (hereinafter referred to as "first message data"). It may be referred to as “received message data”) 270a. In this embodiment, the error detection code decoding unit 270 for message data uses a CRC code as an error detection code for message data. Hereinafter, the error detection code decoding unit 270 for message data is referred to as a “second CRC code decoding unit 270”.

  Second CRC code decoding section 270 generates first received message data 270a based on message partial data 260a and outputs the first received message data 270a to received message data storage section 292. In this embodiment, the first received message data 270a is data obtained by extracting a part other than the CRC code from the message part data 260a, that is, data of the message part.

  Note that the second CRC code decoding unit 270 performs detection processing related to an error detection code (in this case, a CRC code) for message data on the message part data 260a, that is, decoding related to a CRC code on the message part data 260a. Process, that is, a process of removing the CRC code from the message part data 260a to generate the message part data 260a from which the CRC code is removed as a result of the decoding process, and further, a decoding process based on the CRC code As a result, a process for determining whether or not there is an error in the message partial data 260a from which the CRC code has been removed is performed. Accordingly, the second CRC code decoding unit 270 determines whether there is an error in the message partial data 260a.

  If it is determined in this determination that there is an error, it means that the generation of the first received message data 270a without error has failed. In this case, second CRC code decoding section 270 generates first correct / incorrect determination data 270b indicating that there is an error in first received message data 270a, and outputs the first correct / incorrect data 270b to received message data generating section 280. Thus, the second CRC code decoding unit 270 causes the reception message data generation unit 280 to generate the second reception message data 284a.

  Further, if it is determined in this determination that there is no error, it means that the generation of the first received message data 270a without an error has succeeded. In this case, second CRC code decoding section 270 generates first correct / incorrect determination data 270b indicating that there is no error in first received message data 270a, and outputs the first correct / incorrect data 270b to received message data generating section 280. As a result, the second CRC code decoding unit 270 causes the reception message data generation unit 280 to wait without generating the second reception message data 284a.

  As described above, the second CRC code decoding unit 270 outputs the first correct / incorrect determination data 270b to the received message data generation unit 280. This is for instructing the reception message data generation unit 280 to generate the second reception message data 284a.

  Note that the communication apparatus 100 according to this embodiment is configured so that the first received message by the message partial data extracting unit 260 and the second CRC code decoding unit 270 is generated before the second received message data 284a is generated by the received message data generating unit 280. Data 270a is generated. This is because, when the other vehicle packet 100 is successfully received, a decoding process related to a simple error detection code (here, a CRC code) for message data is performed on the first received data 250a, This is because there is a high possibility that the received message data 270a without error can be generated. When the communication apparatus 100 can generate the first received message data 270a without error, the received message data generation unit 280 does not need to generate the second received message data 284a, and therefore the communication apparatus 100 can be performed in a short time (for example, about The received message data can be generated at 10 mS).

  The reception message data generation unit 280 is a functional unit that repeatedly performs a decoding process on an error correction code for message data on the reception data 250a to generate reception message data 280a corresponding to transmission message data. The received message data generation unit 280 can perform the decoding process repeatedly. The received message data generation unit 280 repeats the decoding process until an error-free received message data 280a is generated with a predetermined maximum number of repetitions as an upper limit.

  The received message data generation unit 280 includes a message data error correction code decoding unit 282 and a message data error detection code decoding unit 284.

  In this embodiment, the message data error correction code decoding unit 282 uses a turbo code as an error correction code for message data. Hereinafter, the error correction code decoding unit 282 for message data is referred to as a “turbo code decoding unit 282”.

  In this embodiment, the error detection code decoding unit 284 for message data uses a CRC code as an error detection code for message data. Hereinafter, the error detection code decoding unit 284 for message data is referred to as a “third CRC code decoding unit 284”.

  The turbo code decoding unit 282 generates second received data 282a based on the first received data 250a and outputs the second received data 282a to the third CRC code decoding unit 284. In this embodiment, the second received data 282a is data obtained by extracting a portion other than the turbo code from the first received data 250a. Further, the third CRC code decoding unit 284 generates reception message data 284a based on the second reception data 282a, and outputs the reception message data 284a as reception message data 280a to the reception message data storage unit 292. In this embodiment, the second received message data 284a is data obtained by extracting data other than the CRC code from the second received data 282a, that is, data of the message part.

  Note that the third CRC code decoding unit 284 performs detection processing on an error detection code for message data (here, a CRC code) on the second received data 282a. As a result, the third CRC code decoding unit 284 determines whether there is an error in the second received data 282a.

  If it is determined in this determination that there is an error, the generation of error-free second received data 282a has failed, that is, an error detection code for simple message data in the second received data 282a (here In this case, it means that error-free received message data cannot be generated only by performing a decoding process on the CRC code. In this case, the third CRC code decoding unit 284 generates second correct / incorrect determination data 284b indicating that there is an error in the second received data 282a, and outputs the second correct / incorrect determination data 284b to the turbo code decoding unit 282. As a result, the third CRC code decoding unit 284 causes the turbo code decoding unit 282 to generate new second received data 282a based on the previous second received data 282a.

  If it is determined that there is no error in this determination, the generation of error-free second received data 282a is successful, that is, an error detection code for simple message data in the second received data 282a. It means that error-free received message data can be generated simply by performing a decoding process on (here, CRC code). In this case, the third CRC code decoding unit 284 generates second correct / incorrect determination data 284b indicating that there is no error in the second received data 282a, and outputs the second correct / incorrect determination data 284b to the turbo code decoding unit 282. As a result, the third CRC code decoding unit 284 causes the turbo code decoding unit 282 to wait without generating the second received data 282a.

  In this way, the third CRC code decoding unit 284 outputs the second correct / incorrect determination data 284b to the turbo code decoding unit 282. This is to instruct the turbo code decoding unit 282 whether or not to generate new second received data 282a.

  The main storage unit 290 of the receiving side 100B is a storage unit that stores various programs and data. The main storage unit 290 includes a RAM and a register. The main storage unit 290 is provided with a storage area for storing various programs and data according to the operation. One of them is a received message data storage unit 292.

  The reception message data storage unit 292 is storage means for storing the reception message data 270a generated by the message data error detection code decoding unit 270 or the reception message data 280a generated by the reception message data generation unit 280.

  In FIG. 1, each component on the receiving side 100B is depicted so as to directly output various signals and data to the subsequent components. However, in practice, each component outputs various signals and data to the subsequent components via the main storage unit 290. That is, the former stage component stores various signals and data in the main storage unit 290, and the subsequent stage component reads the signal and data from the main storage unit 290. A series of these operations is defined by the program. Hereinafter, description of this point is omitted. The receiving side 100B operates according to the time measured by the timer 203. Hereinafter, description of this point is omitted.

<Turbo code>
Hereinafter, first, an outline of the turbo code will be described. The details of the “turbo code” are disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-31837 and others, and only the outline will be described here.

  The turbo code was proposed by Berrou et al. In 1993 as a kind of encoding / decoding system that realizes transmission characteristics close to the Shannon limit by realistic processing. “Shannon limit” refers to how low the CNR (Carrier vs. Noise Ratio) or Eb / No (where Eb is the power per bit and No is the noise power per 1 Hz) This represents a logical limit that allows error correction and that a data signal can be demodulated at a predetermined error rate, that is, a theoretical limit of a data transmission rate that can be transmitted without error.

  The turbo code is generated by an encoding unit having two or more parallel additional encoders and one or more interleavers. Each encoder is typically the same convolutional encoder, but may be different. The interleaver rearranges the data series in an arbitrary order.

  In the turbo code, a data sequence is input to a first encoder and input to a second encoder via an interleaver, and a first parity bit string is generated by the first encoder, and an interleaver is also generated. The second parity bit string is generated by the second encoder based on the data sequence, that is, the order is rearranged, and the first parity bit string and the second parity bit string are multiplexed or thinned out. Thus, a multiplexed parity bit string is generated, and further generated by multiplexing the multiplexed parity bit string and the data series.

  The turbo code is decoded into the original data sequence by the first decoder corresponding to the first encoder and the second decoder corresponding to the second encoder. At this time, the second decoder repeats the decoding process while feeding back the output generated by the one decoder. Each time the turbo code is repeatedly decoded, the turbo code approximates an appropriate value, that is, a data sequence before the encoding process. The turbo code “Turbo” is derived from a turbo engine that improves engine performance by feeding back exhaust.

  Hereinafter, specific configurations of the turbo code encoding unit and the decoding unit will be described with reference to FIGS. 4A and 4B are diagrams illustrating configurations of a turbo code encoding unit and a decoding unit. 4A shows the configuration of the turbo code encoder, and FIG. 4B shows the configuration of the turbo code decoder. In addition, the structure shown to FIG. 4 (A) and (B) is already a well-known thing.

  As shown in FIG. 4A, the turbo code encoder 124 includes an inter-leaver 310, a first encoder 320, a second encoder 330, a multiplexer 340, And a multiplexer 350. The configurations of the first and second encoders 320 and 330 may be the same or different. The first and second encoders 320 and 330 are also referred to as component encoders.

  In turbo code encoder 124, the transmission data sequence (first transmission data 122 a in the configuration shown in FIG. 1) is input to first encoder 320, interleaver 310, and multiplexer 350.

  When the data sequence is input, the first encoder 320 generates a first parity bit string in response to this and outputs the first parity bit string to the multiplexer 340.

  When the data series is input, the interleaver 310 rearranges the order of the data series in response to this and outputs the data series to the second encoder 330.

  When the rearranged data sequence is input, the second encoder 330 generates a second parity bit string in response to this and outputs it to the multiplexer 340.

  In response to the input of the first and second parity bit strings, the multiplexer 340 multiplexes or punctures the first parity bit string and the second parity bit string. The multiplexed parity bit string (hereinafter referred to as “multiplexed parity bit string”) is generated and output to the multiplexer 350.

  In response to the input of the multiplexed parity bit string, the multiplexer 350 multiplexes the previously input data series and the multiplexed parity bit string to output data (in the configuration shown in FIG. 2 transmission data 124a) is generated.

  On the other hand, as shown in FIG. 4B, the turbo code decoding unit 282 includes a first decoder 410, an interleaver 420, a second decoder 430, a deinterleaver 440, It has. The configurations of the first and second decoders 410 and 430 may be the same or different. These first and second decoders 410 and 430 are also referred to as component decoders.

  In turbo code decoding section 282, the received data sequence (first received data 250a in the configuration shown in FIG. 1) is input to first decoder 410 and interleaver 420. The first decoder 410 is a decoder corresponding to the first encoder 320.

  When the data sequence is input, the first decoder 410 performs a decoding process on the data sequence in response to the data sequence, and obtains a result of the decoding process of each data symbol and data representing the reliability (hereinafter referred to as a data sequence). (Referred to as “reliability data”) and output to the interleaver 420.

  When the interleaver 420 receives the decoding process result and reliability data from the first decoder 410, the interleaver 420 responds to this by receiving the decoding process result and the order of reliability data, and the previously input data. The sequence order is rearranged and output to the second decoder 430.

  When the rearranged decoding process result and the reliability data and the data series are input, the second decoder 430 performs the decoding process using the reliability data and the data series in response to the input. Thus, reliability data is generated and output to the deinterleaver 440.

  In response to the input of reliability data, the deinterleaver 440 rearranges the arrangement of the reliability data by the interleaver 420 and outputs it to the first decoder 410.

  The first decoder 410 again performs a decoding process on the data series. However, in the second and subsequent decoding processing repetitions, the first decoder 410 performs decoding based on the received data sequence and the reliability data output from the second decoder 430 via the deinterleaver 440. Process.

  The turbo code decoding unit 282 repeats such an operation several times to dozens of times. Thereafter, the turbo code decoding unit 282 makes a final determination on the reliability data in the second decoder 430, and outputs the determination result subsequently.

  Note that the rearrangement of the interleaver is the same in the turbo code encoding unit 124 and the turbo code decoding unit 282. The turbo code decoding unit 282 rearranges the reliability data in addition to the received data series. This is because the second decoder 430 arranges the reliability data and the received data series in the order of the parity bit string, and matches the data arrangement with the order of the second encoder 340.

  The turbo code is a code having redundancy like a block code such as a BCH code. However, the turbo code is an iteratively decodable code, that is, a code that can be repeatedly decoded. Each time the turbo code is repeatedly decoded, the turbo code approximates an appropriate value, that is, data before the encoding process. If an iteratively decodable code such as a turbo code has the same redundancy as that of a block code such as a BCH code, for example, the block is approximated to an appropriate value every time the decoding process is repeated. A correction capability superior to that of the code can be obtained.

  The communication apparatus 100 according to the present invention uses a turbo code, which is a kind of iteratively decodable code, as an error correction code for message data. Therefore, the communication device 100 can improve the correction capability over the conventional communication device.

  In addition, the iteratively decodable code such as a turbo code is shorter than the time required for the decoding process of a block code such as a BCH code having the same degree of redundancy, based on the demonstration data. It has been confirmed. Although the specific time varies depending on the calculation capability of the CPU, if the decoding process is performed by a CPU having the same calculation speed, for example, if the time required for the decoding process of the BCH code is about 50 mS, the same level. The time required for the decoding process of the turbo code having the redundancy of about 10 mS.

  However, since the turbo code is generated by multiplexing the above-described multiplexed parity bit string and the data sequence, the redundancy is higher than that of the BCH code if the coding rate is similar to that of the BCH code. However, even if the difference in redundancy is taken into account, the time required for the decoding process for each turbo code is ¼ to 1 times the time required for the decoding process for the BCH code having the same coding rate. / 3 or so. Therefore, the time required for the decoding process of the turbo code is shorter than the time required for the decoding process of the BCH code having the same coding rate.

  In this embodiment, the communication device 100 can generate the second received message data 284a by performing the decoding process 1 to 4 times in the received message data generating unit 280. Therefore, the communication device 100 can shorten the processing time compared to the conventional communication device.

  Moreover, the communication apparatus 100 generates the first received message data 270a by the message partial data extraction unit 260 and the second CRC code decoding unit 270 before the generation of the second received message data 284a by the received message data generation unit 280. Is going. Thereby, the communication apparatus 100 can omit the generation of the second received message data 284a by the received message data generation unit 280 when the first received message data 270a can be generated without error. Even with such a configuration, the communication device 100 has a shorter processing time than the conventional communication device.

<Characteristic evaluation of turbo code>
Hereinafter, characteristic evaluation when a turbo code is used as an error correction code will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of characteristic evaluation of an error correction code.

  FIG. 5 uses various codes as error correction codes for message data, and generates reception message data by performing decoding processing on error correction codes for message data on the reception data for each code. The characteristics of each received message data generated are shown.

  In FIG. 5, the horizontal axis is CNR (Signal to Noise Ratio: Carrier vs. Noise Ratio), and the vertical axis is BER (Bit Error Rate: Bit Error Ratio). Note that the example shown in FIG. 5 has been evaluated in a communication environment of a thermal noise environment.

  In FIG. 5, a curve C1 shows the characteristics of received message data when no error correction code is used, and a curve C2 shows the characteristics of received message data when a BCH (63, 51) code is used as an error correction code. The curve C3 shows the characteristics of the received message data when the BCH (63, 18) code is used as the error correction code, and the curve C4 shows the error correction of the turbo code whose coding rate is 1/3. The characteristics of received message data when used as a code are shown. The BCH (63, 51) code is a code that has been conventionally used as an error correction code recommended by ARIB STD-T75. The BCH (63, 18) code is a BCH code having a coding rate comparable to that of a turbo code with a coding rate of 1/3.

  The example shown in FIG. 5 indicates that the larger the slope of the curve, the lower the BER (bit error rate) at the same value of CNR (signal to noise ratio). Therefore, the example shown in FIG. 5 indicates that the larger the slope of the curve, the better the communication quality, that is, the characteristic that the quality of received data in communication is problematic. Therefore, as is apparent from FIG. 5, the communication apparatus can realize high-quality communication by using a turbo code as an error correction code.

<Operation of communication device>
In the inter-vehicle communication system, the communication device 100 measures the elapsed time using the timers 103 and 203, and repeats the transmission mode and the reception mode at a constant cycle. The “transmission mode” means an operation state in which each component on the transmission side 100A is operated and the transmission packet 100a is transmitted to another vehicle. In addition, the “reception mode” means an operation state in which each component on the receiving side 100B operates and receives the transmission packet 100b from another vehicle. Note that the operation cycle of the communication apparatus 100 is about 100 mS. That is, the time from the start time of the previous transmission mode to the start time of the next transmission mode is about 100 mS. Similarly, the time from the start time of the previous reception mode to the start time of the next reception mode is also about 100 mS. The communication device 100 enters the reception mode after entering the transmission mode for about 100 ms, and then enters the transmission mode again. The series of operations is performed by building various components (for example, each component for functioning as the communication device 100 in the main arithmetic units 101 and 201, which are stored in the main storage units 190 and 290 in a freely readable manner). Program), various data (for example, the operation cycle of the communication apparatus 100, the time in the transmission mode (hereinafter referred to as “transmission mode time”), the time in the reception mode (hereinafter referred to as “transmission mode time”). Etc.) (referred to as “reception mode time”). Hereinafter, description of this point is omitted.

  Hereinafter, with reference to FIG. 2, the operation of each component on the transmission side 100A of the communication apparatus 100 will be described. FIG. 2 is a flowchart showing the operation of each component on the transmission side of the communication apparatus.

  In the communication device 100, the main arithmetic unit 101 on the transmission side 100A previously stores various data from the main storage unit 190, for example, data such as the operation cycle of the communication device 100, the transmission mode time, and the start time of the previous transmission mode. And control its own operation based on the read data.

  Specifically, when the time measured from the start time of the previous transmission mode by the timer 103 reaches a time determined in advance as the operation period of the communication device 100, the main calculation unit 101 of the transmission side 100A transmits (However, when there is no start time of the previous transmission mode, that is, when the transmission mode is set for the first time, the transmission mode is set at an arbitrary predetermined time). At this time, the transmission message data generation unit 110 is activated.

  In response to this, the transmission message data generation unit 110 reads various vehicle data (for example, vehicle data indicating the position of the host vehicle) from the main storage unit 190 in response to this, and based on the read vehicle data, Transmission message data 110a to be transmitted to another vehicle is generated, and this transmission message data 110a is output to the first CRC code encoding unit 122 and the transmission message length data generation unit 130 (S105).

  When the transmission message data 110a is input from the transmission message data generation unit 110, the first CRC code encoding unit 122 responds to the encoding processing related to the CRC code for the transmission message data 110a, that is, the transmission message. A CRC code is generated based on the data 110a, and a process of adding the CRC code to the transmission message data 110a is performed to generate first transmission data 122a, which is output to the turbo code encoding unit 124 (S110).

  When the first transmission data 122a is input from the first CRC code encoding unit 122, the turbo code encoding unit 124 responds to this by performing an encoding process related to the turbo code on the first transmission data 122a, that is, A turbo code is generated based on the first transmission data 122a, a process of adding the turbo code to the first transmission data 122a is performed, and second transmission data 124a is generated and output to the packet generation unit 150 (S115).

  When the transmission message data 110a is input from the transmission message data generation unit 110 in S105, the transmission message length data generation unit 130 responds to this and indicates the size of the transmission message data 110a based on the transmission message data 110a. Transmission message length data 130a is generated and output to the second CRC code encoder 142 (S120).

  When the transmission message length data 130a is input from the transmission message length data generation unit 130, the second CRC code encoding unit 142 responds to this by performing an encoding process on the CRC code for the transmission message length data 130a, that is, Then, a CRC code is generated based on the transmission message length data 130a, a process of adding the CRC code to the transmission message length data 130a is performed, and the first transmission header data 142a is generated and output to the error correction code encoding unit 144 (S125).

  When the first transmission header data 142a is input from the second CRC code encoding unit 142, the error correction code encoding unit 144 responds to the error and corrects the head data for the first transmission header data 142a. Coding related to a code (for example, a turbo code or a convolutional code), that is, generating an error correction code based on the first transmission header data 142a, and adding an error correction code to the first transmission header data 142a; The second transmission header data 144a is generated and output to the packet generation unit 150 (S130). Here, it is assumed that a turbo code is used as an error correction code for head data.

  Note that the operations in S120 to S130 may be performed before or simultaneously with the operations in S110 to S115.

  The packet generator 150 receives the second transmission data 124a from the turbo code encoder 124 in S115, and further receives the second transmission header data 144a from the error correction code encoder 144 in S130. In response, the second transmission header data 144a and the second transmission data 124a are combined, and from the main storage unit 190, a preamble for notifying the transmission of data, a unique word indicating the configuration of the data to be transmitted, and the like. Read and add these to generate a transmission packet 150a and output it to the packet transmitter 160 (S135).

  When the transmission packet 150a is input from the packet generation unit 150, the packet transmission unit 160 responds to this by, for example, modulating the transmission packet 150a with a plurality of code sequences or converting a digital signal to an analog signal. A transmission packet 100a is generated by performing processing such as conversion to A, and is transmitted to another vehicle via the transmission antenna 170 (S140). Hereinafter, the transmission packet 100a transmitted by the host vehicle may be referred to as “own vehicle packet 100a”. Further, the transmission packet 100a transmitted by the other vehicle may be referred to as “another vehicle packet 100b”.

  Each component on the transmission side 100A of each communication device 100 repeats the above operations of S105 to S140 at regular intervals. However, the operation time (hereinafter referred to as “transmission mode time”) of each component on the transmission side 100A of the communication apparatus 100 is limited by the timer 103. The timer 103 measures an elapsed time after entering the transmission mode. When the measurement time reaches the transmission mode time, the operation of each component on the transmission side 100A is stopped and the next transmission mode is set. Each component of the transmitting side 100A is made to stand by.

  Hereinafter, with reference to FIGS. 3A and 3B, the operation of each component on the receiving side 100B of the communication apparatus 100 will be described. FIGS. 3A and 3B are flowcharts illustrating the operation of each component on the receiving side of the communication device.

  In the communication apparatus 100, the main calculation unit 201 on the receiving side 100B previously stores various data from the main storage unit 290, for example, data such as the operation cycle of the communication apparatus 100, the reception mode time, the start time of the previous reception mode, And control its own operation based on the read data.

  Specifically, when the measurement time from the start time of the previous reception mode by the timer 203 reaches a time predetermined as the operation period of the communication device 100, the main calculation unit 201 of the reception side 100B performs communication. The apparatus 100 enters the reception mode (however, when the start time of the previous reception mode does not exist, that is, when the reception mode is entered for the first time, the apparatus 100 enters the reception mode at a predetermined time point). At this time, the packet receiving unit 220 is activated.

  When activated, the packet receiving unit 220 senses a radio wave transmitted from a carrier, that is, another vehicle or other device, via the receiving antenna 210, and receives the other vehicle packet 100b in response to the activation. (S205).

  When receiving the other vehicle packet 100b, the packet receiving unit 220 responds to this by converting the other vehicle packet 100b from an analog signal to a digital signal, demodulating by a plurality of code sequences, detecting a unique word, etc. The received packet 220a is generated by performing the above process, and is output to the received header data extracting unit 230 and the received data extracting unit 250 (S210). The reception packet 220a corresponds to the transmission packet 150a generated by the packet generation unit 150 of the transmission side 100A.

  When the received packet 220a is input from the packet receiving unit 220, the received header data extracting unit 230 extracts the first received header data 230a that is header data from the received packet 220a in response to the received packet 220a, and corrects the error. It outputs to the encoding / decoding part 242 (S215). The first reception header data 230a corresponds to the second transmission header data 144a generated by the error correction code encoding unit 144 on the transmission side 100A.

  When the first reception header data 230a is input from the reception header data extraction unit 230, the error correction code decoding unit 242 responds to the error correction code for header data with respect to the first reception header data 230a. Decoding processing relating to (here, turbo code) is performed to generate second reception header data 242a, which is output to first CRC code decoding section 244 (S220). The second reception header data 242a corresponds to the first transmission header data 142a generated by the second CRC code encoding unit 142 on the transmission side 100A.

  When the second reception header data 242a is input from the error correction code decoding unit 242, the first CRC code decoding unit 244 performs detection processing on the second reception header data 242a in response to this (S225). In this detection process, the first CRC code decoding unit 244 performs a decoding process on the CRC code on the second received header data 242a, and the second received header data from which the CRC code has been removed as a result of the decoding process. 242a is generated, and further, based on the CRC code, it is determined whether or not there is an error in the result of the decoding process, that is, whether or not there is an error in the result of the decoding process (S230). The determination of whether there is an error in the result of the decoding process is performed by comparing the CRC code and the result of the decoding process to determine whether or not they match.

  In S230, when it is determined “Yes”, that is, when it is determined that there is an error in the result of the decoding process, the first CRC code decoding unit 244 determines that reception of the transmission packet 100b has failed. In this case, the first CRC code decoding unit 244 waits as it is without generating the received message length data 244a. Thereby, each component of the receiving side 100B enters a standby state. Therefore, in this case, each component on the receiving side 100B ends the current receiving operation and waits until it enters the next receiving mode.

  On the other hand, in S230, when it is determined “No”, that is, it is determined that there is no error in the result of the decoding process, the first CRC code decoding unit 244 determines that the transmission packet 100b has been successfully received. In this case, the operation of each component on the receiving side 100B proceeds to S235.

  In S230, when it is determined “No”, that is, when it is determined that there is no error in the result of the decoding process, the first CRC code decoding unit 244 responds to this by decoding the CRC code for the second received header data 242a. The received message length data 244a is generated as a result of the decoding process and output to the received data extraction unit 250 (S235).

  When the received message length data 244a is input from the first CRC code decoding unit 244, the received data extraction unit 250 responds to the data bit portion data from the received packet 220a input in S210, that is, The first received data 250a, which is data of the message part, is extracted and output to the message part data extracting unit 260 and the turbo code decoding unit 282 (S240).

  When the first received data 250a is input from the received data extracting unit 250, the message portion data extracting unit 260 responds to the data bit portion data from the first received data 250a, that is, the original message portion. The data is extracted, and this data is output as message partial data 260a to the second CRC code decoding unit 270 (S245).

  When the message part data 260a is input from the message part data extraction unit 260, the second CRC code decoding unit 270 performs a detection process on the message part data 260a in response to the message part data 260a (S250). In this detection process, the second CRC code decoding unit 270 performs a decoding process on the CRC code on the message part data 260a, and generates message part data 260a from which the CRC code is removed as a result of the decoding process. Further, based on the CRC code, it is determined whether or not there is an error in the result of the decoding process, that is, whether or not there is an error in the result of the decoding process (S255). The determination of whether there is an error in the result of the decoding process is performed by comparing the CRC code and the result of the decoding process to determine whether or not they match.

  In S255, if it is determined that there is an error in the result of the decoding process, the second CRC code decoding unit 270 determines that acquisition of received data corresponding to the first transmission data 122a has failed. To do. In this case, the operation of each component on the receiving side 100B proceeds to S270.

  On the other hand, in S255, when it is determined “No”, that is, when it is determined that there is no error in the result of the decoding process, the second CRC code decoding unit 270 has successfully acquired the received data corresponding to the first transmission data 122a. Is determined. In this case, the operation of each component on the receiving side 100B proceeds to S260.

  In S255, if it is determined that there is no error in the result of the decoding process, the second CRC code decoding unit 270 responds to this by decoding the CRC code for the message partial data 260a. The first received message data 270a is generated as a result of the decoding process, and is output to the received message data storage unit 292 (S260). Note that the first reception message data 270a corresponds to the transmission message data 110a generated by the transmission message data generation 110 of the transmission side 100A.

  When the first received message data 270a is input from the second CRC code decoding unit 270, the received message data storage unit 292 stores the first received message data 270a in a predetermined storage area in response to the input. (S265).

  If “Yes” in S255, that is, if it is determined that there is an error in the result of the decoding process, or if the received message data storage unit 292 stores the first received message data 270a in S265, the second CRC In response to this, the code decoding unit 270 indicates the result of the error detection process performed in S250, that is, the result of the determination as to whether or not there is an error in the result of the decoding process performed in S250. 1 correctness determination data 270b is generated and output to the turbo code decoding unit 282 (S270).

  When the first correct / incorrect determination data 270b is input from the second CRC code decoder 270, the turbo code decoder 282 responds to the first correct / incorrect determination data 270b, that is, the error detection performed in S250. It is determined whether or not the processing result means that there is an error (S275).

  In S275, when “Yes”, that is, when it is determined that the first correctness determination data 270b means that there is an error, the first reception message data 270a generated by the second CRC code decoding unit 270 is determined in advance. This means that the transmission message data 110a is different from the allowable range. In this case, the turbo code decoding unit 282 determines that acquisition of reception message data corresponding to the transmission message data 110a has failed. In this case, the operation of each component on the receiving side 100B proceeds to S280.

  On the other hand, if it is determined in S275 that “No”, that is, the first correct / incorrect determination data 270b means no error, the first received message data 270a generated by the second CRC code decoding unit 270 is This means that it matches the transmission message data 110a within a predetermined allowable range. In this case, the turbo code decoding unit 282 determines that the reception message data corresponding to the transmission message data 110a has been successfully acquired. In this case, the received message data storage unit 292 stores the first received message data 270a having no error. Therefore, the reception message data generation unit 280 does not need to generate the second reception message data 284a. Therefore, in this case, the turbo code decoding unit 282 waits as it is without generating the second received data 282a. Thereby, each component of the receiving side 100B enters a standby state. Therefore, in this case, each component on the receiving side 100B ends the current operation and waits until it enters the next reception mode.

  In S275, when “Yes”, that is, when it is determined that the first correctness determination data 270b means that there is an error, the turbo code decoding unit 282 is input in S240 in response to this. The first received data 250a is decoded with respect to the turbo code to generate first received data 250a from which the turbo code has been removed as a result of the decoding process with respect to the turbo code. From the result of the decoding process with respect to the turbo code, The data bit partial data is extracted to generate second received data 282a, which is output to the third CRC code decoding unit 284 (S280). The second reception data 282a corresponds to the first transmission data 122a generated by the first CRC code encoding unit 122 of the transmission side 100A. Note that the number of times (hereinafter referred to as “the number of iterations”) n that the decoding process related to the turbo code with respect to the first received data 250 a is repeatedly performed is counted by the counter 205. It is assumed that the number of iterations n is a value of 1 or more and is smaller than the maximum number of iterations set in the main storage unit 290 in advance. The number of iterations n is counted as the first time when the operation proceeds from S275 to S280, and is thereafter added once every time the operation returns from S315 to S280 described later.

  When the second reception data 282a is input from the turbo code decoding unit 282, the third CRC code decoding unit 284 performs a detection process on the second reception data 282a in response to this (S285). In this detection process, the third CRC code decoding unit 284 performs a decoding process on the CRC code on the second received data 282a, and the second reception from which the CRC code is removed as a result of the decoding process on the CRC code. Data 282a is generated, and based on the CRC code, it is determined whether or not there is an error in the result of the decoding process, that is, whether or not there is an error in the result of the decoding process (S290). The determination of whether there is an error in the result of the decoding process is performed by comparing the CRC code and the result of the decoding process to determine whether or not they match.

  In S290, when it is determined “Yes”, that is, when it is determined that there is an error in the result of the decoding process, the third CRC code decoding unit 284 determines that acquisition of the reception data corresponding to the first transmission data 122a has failed. To do. In this case, the operation of each component on the receiving side 100B proceeds to S305.

  On the other hand, in S290, when it is determined “No”, that is, when it is determined that there is no error in the result of the decoding process, the third CRC code decoding unit 284 has successfully acquired the received data corresponding to the first transmission data 122a. Is determined. In this case, the operation of each component on the receiving side 100B proceeds to S295.

  In S290, when it is determined “No”, that is, when it is determined that there is no error in the result of the decoding process, in response to this, the third CRC code decoding unit 284 decodes the CRC code for the second received data 282a. Processing is performed to generate second received message data 284a as a result of the decryption process, and output the received message data storage unit 292 (S295). Note that the second reception message data 284a corresponds to the transmission message data 110a generated by the transmission message data generation 110 of the transmission side 100A.

  When the second received message data 284a is input from the third CRC code decoding unit 284, the received message data storage unit 292 stores the second received message data 284a in a predetermined storage area in response to the input. (S300). The first received message data 270a and the second received message data 284a stored in the received message data storage unit 292 are transmitted to the outside as necessary.

  If “Yes” in S290, that is, if it is determined that there is an error in the result of the decoding process, or if the received message data storage unit 292 stores the second received message data 284a in S300, the third CRC In response to this, the code decoding unit 284 indicates the result of the error detection process performed in S285, that is, the result of the determination of whether or not there is an error in the result of the decoding process performed in S285. Two correctness determination data 284b is generated and output to the turbo code decoding unit 282 (S305).

  When the second correct / incorrect determination data 284b is input from the third CRC code decoder 284, the turbo code decoder 282 receives the second correct / incorrect determination data 284b, that is, the error detection performed in S285. It is determined whether or not the processing result means that there is an error (S310).

  In S310, when it is determined that “Yes”, that is, the second correctness determination data 284b means that there is an error, the second received message data 284a generated by the third CRC code decoding unit 284 is determined in advance. This means that the transmission message data 110a is different from the allowable range. In this case, the turbo code decoding unit 282 determines that acquisition of reception message data corresponding to the transmission message data 110a has failed. In this case, the operation of each component on the receiving side 100B proceeds to S315.

  On the other hand, in S310, when it is determined that “No”, that is, the second correctness determination data 284b means no error, the second received message data 284a generated by the third CRC code decoding unit 284 is determined. This means that it matches the transmission message data 110a within a predetermined allowable range. In this case, the turbo code decoding unit 282 determines that the reception message data corresponding to the transmission message data 110a has been successfully acquired. In this case, the received message data storage unit 292 stores the second received message data 284a having no error. Therefore, the received message data generation unit 280 does not need to generate new second received message data 284a. Therefore, in this case, the turbo code decoding unit 282 waits as it is without generating new second received data 282a. Thereby, each component of the receiving side 100B enters a standby state. Therefore, in this case, each component on the receiving side 100B ends the current operation and waits until it enters the next reception mode.

  The received message data storage unit 292 stores the first received message data 270a with no error if the number of repetitions n is the first. In addition, the received message data storage unit 292 stores the second received message data 284a having no error if the number of repetitions n is the second or later.

  In S310, when it is determined that “Yes”, that is, the second correctness determination data 284b means that there is an error, the turbo code decoding unit 282 responds to this from the counter 205 from the number of iterations n. Is read from the main storage unit 290, and it is determined whether or not the read iteration number n is less than the maximum iteration number (S315).

  In S315, if “Yes”, that is, if it is determined that the number of iterations n is less than the maximum number of iterations, the operation of each component on the receiving side 100B returns to S280. At this time, the counter 205 adds the number of iterations n once. Thereafter, each component on the receiving side 100B repeats the operations of S280 to S315. However, in this iterative operation, in S280, the turbo code decoding unit 282 assumes that the previous iteration count n is the i-th time, the result of the i-th turbo code decoding process for the first received data 250a is ( The decoding process regarding the i + 1) th turbo code is performed. That is, the turbo code decoding unit 282 extracts data of the data bit portion from the result of the i-th turbo code decoding process. Thereby, the turbo code decoding unit 282 generates new second received data 282a. Accordingly, each time the turbo code decoding unit 282 repeatedly performs the operation in S280, the second reception that gradually approximates the appropriate value, that is, the first transmission data 122a before performing the encoding process on the turbo code. Data 282a is newly generated. When the turbo code decoding unit 282 generates new second received data 282a, the turbo code decoding unit 282 outputs the second received data 282a to the third CRC code decoding unit 284. Based on the new second received data 282a, the third CRC code decoding unit 284 generates second received message data 284a or second correct / incorrect determination data 284b.

  In S315, if “No”, that is, if it is determined that the number of repetitions n is equal to or greater than the maximum number of repetitions, it is determined that acquisition of received message data corresponding to the transmission message data 110a has failed. In this case, the turbo code decoding unit 282 waits as it is without generating new second received data 282a. Thereby, each component of the receiving side 100B enters a standby state. Therefore, in this case, each component on the receiving side 100B ends the current operation and waits until it enters the next reception mode.

  Each component on the receiving side 100B of the communication apparatus 100 succeeds or fails to acquire the received message data corresponding to the transmitted message data 110a with the above-described operations of S205 to S315, with the maximum number of repetitions set as an upper limit. Until the measurement time by the timer 203 exceeds a preset reception mode time.

  According to the communication device 100 according to the present invention, the following effects can be obtained.

  That is, according to communication apparatus 100 according to the present invention, iteratively decodable codes such as turbo codes are used as error correction codes for message data. An iteratively decodable code such as a turbo code is obtained by repeatedly performing a decoding process, so that received data is gradually set to an appropriate value, that is, transmission data before performing an encoding process related to an iterable decodable code such as a turbo code. Can be approximated. Therefore, this communication device 100 can realize higher quality communication than the conventional communication device.

  In addition, iteratively decodable codes such as turbo codes have higher redundancy than block codes such as BCH codes, but the decoding process can be performed once in a fraction of the time of block codes such as BCH codes. It can be carried out. Therefore, if this communication device 100 repeats the decoding process about 1 to 3 times, the communication device 100 repeatedly performs the decoding process in a shorter time or more than the conventional communication device. Even in some cases, the received message can be acquired in the same time as the conventional communication device.

  Therefore, according to the communication device 100 according to the present invention, the communication device 100 is higher than the conventional communication device using the BCH (63, 51) code recommended by the ARIB STD-T75 without degrading the real-time property of communication. Quality communication can be realized.

  Such a communication device 100 is particularly effective in a vehicle-to-vehicle communication system having poor carrier wave propagation characteristics due to the influence of multipath or the like.

  In addition, the communication apparatus 100 extracts message part data and repeatedly performs error detection processing on the error detection code on the message partial data before repeatedly performing decoding processing on the error correction code on the received data. It is configured as follows. According to this configuration, when it is determined that there is no error in the error detection process, it is possible to extract the received message data without error from the message partial data without repeatedly performing the decoding process on the received data. it can. Therefore, according to this configuration, it is possible to further suppress an increase in the amount of calculation, and communication with high real-time characteristics is possible.

  The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the gist of the present invention.

  For example, the present invention can be applied not only to a vehicle-to-vehicle communication system but also to a communication device used in a communication system that mutually exchanges data by performing wireless communication between a plurality of devices.

  Further, for example, in the description of the above-described embodiment, a turbo code is used as an error correction code. However, decoding processing (hereinafter referred to as “iterative decoding processing”) may be performed repeatedly as in the case of a turbo code. Another error correction code may be used as long as it is a possible error correction code.

  Further, for example, in the above-described embodiment, the communication device 100 uses the transmission message data 110a to generate the first transmission data 122a. However, the communication device 100 may use control data such as a packet type, a transmission source vehicle ID, and a destination vehicle ID in addition to the transmission message data 110a. However, in this case, the communication device 100 generates the first transmission header data 142a using data representing the size of these control data instead of the transmission message length data 130a.

  For example, in the above-described embodiment, the communication device 100 uses the transmission message length data 130a for generating the first transmission header data 142a. However, the communication device 100 may use control data having a common size for all packets such as the packet type, the transmission source vehicle ID, and the destination vehicle ID in addition to the transmission message length data 130a.

  Further, for example, in the above-described embodiment, the communication apparatus 100 relates to a turbo code in which the number n of iterations becomes (i + 1) after the reception message data generation unit 280 determines correctness in the i-th error detection process ( i + 1) Decoding process is being performed. However, the communication apparatus 100 performs the i-th error detection process and the (i + 1) -th decoding process in parallel in the received message data generation unit 280, and determines that there is no error in the i-th error detection process. , (I + 1) th and subsequent decoding processes may be stopped. However, in this case, the communication apparatus 100 needs to use a plurality of turbo code decoding units 282 equal to the maximum number of iterations.

  Further, for example, in the above-described embodiment, an example is described in which a turbo code is used as an error correction code for message data. However, an LDPC (Low Density Parity Check) code may be used instead of a turbo code. Good.

  “LDPC code” was proposed by Gallager in the 1960s as a code that realizes transmission characteristics close to the Shannon limit. An LDPC code is a linear code defined by a very sparse check matrix, that is, a matrix with a very small number of non-zero elements in the matrix. The LDPC code includes a regular LDPC code and an irregular LDPC code. The LDPC code is described in various documents (for example, see “Low-density parity check code and its decoding method” (Masawa Wadayama, Trikeps)).

In the “regular LDPC code”, the Hamming weight (column weight) of any column of the check matrix H composed of m rows and n columns is $ w_c $, the Hamming weight (row weight) of any row is $ w_r $, When the value of $ w_c $ is sufficiently smaller than the size of m, it means the code C defined by the check matrix H. “_” Indicates that the subsequent character is a subscript. Thus, for example, “w_c” means “w _c ”.

  “Non-regular LDPC code” means a code C defined from a parity check matrix H in which the weight of each column or each row is not constant.

The parity check matrix of the LDPC code is as follows. That is, the transmission word $ m = (m_1, m_2,..., M_k) $ is assumed to be a length k-dimensional vector. The code word C is generated by calculating the product of k + 1 matrix G and m (C = mG). Note that the matrix G is referred to as a generator matrix. When a binary m * n matrix H has rank m and satisfies $ GH ^ T = 0 $ (where $ H ^ T $ is a transposed matrix of H), H is a parity check matrix of code C (parity check matrix). ). “^” Indicates that the subsequent character is a superscript. Therefore, for example, “H ^ T” means “H ^T ”.

  The decoding of the LDPC code is performed by the sum-product decoding method.

It is a figure which shows the structure of the communication apparatus which concerns on this invention. It is a figure which shows operation | movement of the transmission side of the communication apparatus which concerns on this invention. It is a figure (1) which shows operation | movement of the receiving side of the communication apparatus which concerns on this invention. It is FIG. (2) which shows the operation | movement of the receiving side of the communication apparatus which concerns on this invention. (A) And (B) is a figure which shows the structure of a turbo code encoding part and a decoding part. It is a figure which shows an example of the characteristic evaluation of an error correction code.

Explanation of symbols

100: Communication device (vehicle)
100A: Device on transmission side (transmission side)
100B: Device on the receiving side (receiving side)
101, 201 ... main arithmetic unit (CPU)
103, 203 ... timer 110 ... transmission message data generation unit 120 ... transmission data generation unit 122 ... message data error detection code encoding unit (first CRC code encoding unit)
124 ... Error correction code encoding unit for message data (turbo code encoding unit)
DESCRIPTION OF SYMBOLS 130 ... Transmission message length data generation part 140 ... Transmission header data generation part 142 ... Error detection code encoding part for header data (2nd CRC code encoding part)
144: header data error correction code encoding unit 150 ... packet generation unit 160 ... packet transmission unit 170 ... transmission antenna 190, 290 ... main storage unit (RAM, register)
205 ... counter 210 ... reception antenna 220 ... packet reception unit 230 ... reception header data extraction unit 240 ... reception message length data generation unit 242 ... header data error correction code decoding unit 244 ... header data error detection code decoding unit ( First CRC code decoding unit)
250 ... received data extraction unit 260 ... message partial data extraction unit 270 ... message data error detection code decoding unit (second CRC code decoding unit)
280 ... Received message data generation unit 282 ... Error correction code decoding unit for message data (turbo code decoding unit)
284 ... Error detection code decoding unit for message data (third CRC code decoding unit)
292 ... Received message data storage unit 100a ... Transmission packet 100b ... Transmission packet (other vehicle packet)
110a ... transmission message data 120a ... transmission data 122a ... first transmission data 124a ... second transmission data 130a ... transmission message length data 140a ... transmission header data 142a ... first transmission header data 144a ... second transmission header data 150a ... for transmission Packet 220a ... received packet 230a ... first received header data (received header data)
240a, 244a ... received message length data 242a ... second received header data 250a ... first received data (received data)
260a: Message partial data 270a: First received message data (received message data)
270b ... first correct / incorrect determination data 280a ... received message data 282a ... second received data 284a ... second received message data 284b ... second correct / incorrect determination data

Claims (13)

A transmission message data generation unit for generating transmission message data;
An iteratively decodable code that can be repeatedly decoded is used as an error correction code for message data, an encoding process related to the error correction code for the message data is performed on the transmission message data, and the transmission data is A transmission data generation unit to generate,
A packet generator for generating a packet for transmission based on the transmission data;
A packet transmission unit that modulates the transmission packet to generate a transmission packet, and transmits the transmission packet to the outside;
A packet receiving unit that receives a transmission packet transmitted by another device and performs a demodulation process to generate a reception packet;
A reception data extraction unit that extracts reception data corresponding to the transmission data from the reception packet;
A reception message data generation unit that repeatedly performs a decoding process on the error correction code for the message data on the reception data and generates reception message data corresponding to the transmission message data, Communication device. The communication device according to claim 1,
The transmission data generation unit
An error detection code encoding unit for message data for generating first transmission data by performing an encoding process on the error detection code for the message data on the transmission message data using an error detection code for message data; ,
An error correction code encoding unit for message data that performs encoding processing on the error correction code for the message data with respect to the first transmission data and generates second transmission data as the transmission data;
The received message data generation unit includes:
An error correction code decoding unit for message data that performs a decoding process on the error correction code for the message data on the received data and generates second received data corresponding to the first transmission data;
A message data error detection code decoding unit configured to perform a decoding process on the error detection code for the message data with respect to the second reception data and generate the reception message data. . The communication device according to claim 2,
A communication apparatus, wherein a CRC code is used as the error detection code for the message data, and a turbo code that is the iteratively decodable code is used as the error correction code for the message data. The communication device according to claim 2,
The error detection code decoding unit for message data of the received message data generation unit is
Performing error detection processing on the error detection code for the message data with respect to the second received data to determine whether there is an error with respect to the second received data;
When it is determined that there is an error in the second received data, an error is determined in the determination of whether there is an error in the second received data by setting a predetermined maximum number of repetitions as the upper limit number. Until the message data error correction code decoding unit generates new second received data until it is determined that there is no message data error correction code decoding unit; It is possible to repeatedly obtain an operation for determining whether there is an error with respect to the new second received data by acquiring new second received data, and determining whether there is an error with respect to the second received data. If it is determined that there is no message, the received message data is generated. A transmission message data generation unit for generating transmission message data;
An iteratively decodable code that can be repeatedly decoded is used as an error correction code for message data, an encoding process related to the error correction code for the message data is performed on the transmission message data, and the transmission data is A transmission data generation unit to generate,
A transmission message length data generation unit that generates transmission message length data representing the size of the transmission message data based on the transmission message data;
A transmission header data generation unit for generating transmission header data by performing an encoding process on the transmission message length data with respect to the error correction code for the header data using an error correction code for header data;
Based on the transmission header data and the transmission data, a packet generation unit that generates a transmission packet;
A packet transmission unit that modulates the transmission packet to generate a transmission packet, and transmits the transmission packet to the outside;
A packet receiving unit that receives a transmission packet transmitted by another device and performs a demodulation process to generate a reception packet;
A reception header data extraction unit that extracts reception header data corresponding to the transmission header data from the reception packet;
A reception message length data generation unit that performs a decoding process on the error correction code for the header data with respect to the reception header data, and generates reception message length data corresponding to the transmission message length data;
A reception data extraction unit that extracts reception data corresponding to the transmission data from the reception packet;
A reception message data generation unit that repeatedly performs a decoding process on the error correction code for the message data on the reception data and generates reception message data corresponding to the transmission message data, Communication device. The communication device according to claim 5, wherein
The transmission data generation unit
An error detection code encoding unit for message data for generating first transmission data by performing an encoding process on the error detection code for the message data on the transmission message data using an error detection code for message data; ,
An error correction code encoding unit for message data that performs encoding processing on the error correction code for the message data with respect to the first transmission data and generates second transmission data as the transmission data;
The transmission header data generation unit
Error detection code encoding for header data that generates first transmission header data by performing an encoding process on the error detection code for the header data on the transmission message length data using an error detection code for header data And
Header data for generating second transmission header data as the transmission header data by performing an encoding process on the error correction code for the header data on the first transmission header data using an error correction code for header data An error correction code encoding unit for
The received message length data generation unit includes:
An error correction code decoding unit for header data that performs a decoding process on the error correction code for the header data on the reception header data and generates second reception header data corresponding to the first transmission header data; ,
An error detection code decoding unit for header data that performs a decoding process on the error detection code for the header data with respect to the second reception header data and generates the reception message length data; and The data generator
An error correction code decoding unit for message data that performs a decoding process on the error correction code for the message data on the received data and generates second received data corresponding to the first transmission data;
A message data error detection code decoding unit configured to perform a decoding process on the error detection code for the message data with respect to the second reception data and generate the reception message data. . The communication device according to claim 6.
A CRC code is used as an error detection code for the message data,
As the error correction code for the message data, a turbo code that is the iteratively decodable code is used,
A communication apparatus using a CRC code as the error detection code for the header data and using a turbo code or a convolutional code as the error correction code for the header data. The communication device according to claim 6.
The header data error detection code decoding unit of the received message length data generation unit is:
Performing error detection processing on the error detection code for the header data with respect to the second received header data to determine whether there is an error with respect to the second received header data;
When it is determined that there is an error in determining whether there is an error in the second received header data, the received data extraction unit stops extracting the received data, and whether there is an error in the second received header data If it is determined that there is no error in the determination, the received data length data is generated and output to the received data extracting unit, thereby causing the received data extracting unit to extract the received data. A communication device. The communication device according to claim 6.
The error detection code decoding unit for message data of the received message data generation unit is
Performing error detection processing on the error detection code for the message data with respect to the second received data to determine whether there is an error with respect to the second received data;
When it is determined that there is an error in the second received data, an error is determined in the determination of whether there is an error in the second received data by setting a predetermined maximum number of repetitions as the upper limit number. Until the message data error correction code decoding unit generates new second received data until it is determined that there is no message data error correction code decoding unit; It is possible to repeatedly obtain an operation for determining whether there is an error with respect to the new second received data by acquiring new second received data, and determining whether there is an error with respect to the second received data. If it is determined that there is no message, the received message data is generated. The communication device according to claim 5, wherein
Furthermore, a message part data extraction unit that extracts message part data that is data of a message part from the received data;
A second message data error detection code decoding unit that performs a decoding process on the message data for the error detection code for the message data and generates the received message data corresponding to the transmission message data; A communication device comprising: The communication device according to claim 10.
The second message data error detection code decoding unit includes:
Performing error detection processing on the error detection code for the message data with respect to the message part data to determine whether there is an error in the message part data;
When it is determined that there is an error in the message part data, the reception message data generation unit generates the reception message data based on the reception data, and an error in the message part data. A communication apparatus comprising: generating the received message data based on the message partial data when it is determined that there is no error in the determination of the presence or absence of the message. The communication device according to claim 2,
A communication apparatus using a CRC code as the error detection code for the message data and using an LDPC code as the error correction code for the message data. The communication device according to claim 6.
A CRC code is used as an error detection code for the message data,
An LDPC code is used as an error correction code for the message data,
A communication apparatus using a CRC code as the error detection code for the header data and using a turbo code or a convolutional code as the error correction code for the header data.

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