JP2009017552A - Hybrid automatic retransmission request method, transmitter, receiver and communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method, system, and device that can improve reliability and availability of an HARQ and reduce a bandwidth necessary for feedback of information. <P>SOLUTION: The method includes a step where a reception side demodulates and decodes data transmitted from a transmission side, a step where when the occurrence of an error to the data from the transmission side is detected, the reception side feeds position information on a symbol including an unreliable information bit back to the transmission side as symbol position information based upon a distribution feature of symbols of information bits, and a step where the transmission side acquires a corresponding unreliable information bit in the data transmitted from the transmission side based upon the symbol position information fed back from the reception side and the distribution feature of symbols of the information bits, and then retransmits the unreliable information bit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication technical field, and more particularly, to a hybrid automatic repeat request method, a transmitter, a receiver, and a communication system.

  Currently, there are three basic error control methods, FEC, ARQ, and hybrid ARQ, which are combinations thereof, as methods for realizing highly reliable transmission of data communication. In these ways, hybrid ARQ has the best reliability and throughput performance. Hybrid ARQ is further classified into three types: HARQ-I, HARQ-II, and HARQ-III.

  Type I (chase combining) adds CRC (cyclic redundancy check) and encodes data using FEC. The receiver performs FEC decoding to check the packet, and if there is an error, resends the packet, discards the erroneous packet, and uses the same FEC code as in the first transmission at the time of retransmission. This is HARQ in the software layer and performs transmission control in RLC (Radio Link Control).

  Incremental redundancy techniques replace simple packet retransmissions. When the first decoding fails, the transmitter is requested to retransmit after adding redundant information, and the transmission packet is not discarded, and the combined packet is decoded at a low code rate. The retransmission packet is not exactly the same as the original transmission packet. The retransmission packet carries some additional redundant information and uses it for error correction, and combines the redundant information with the already received packet to obtain a stronger FEC. You can get the code. Usually, the IR proposal is divided into two types, partly IR and all IR. Partial IR is also referred to as HARQ-III, and every retransmission version includes all system information bits and some check information bits, each of which can be self-decoded, and a packet after combining multiple versions Can also self-decode.

  All IRs are also referred to as HARQ-II, and each retransmission version includes only check information bits and no system information bits. Each retransmission version cannot be self-decoded and can be decoded after being combined with other versions.

  Both HARQ-II and HARQ-III employ a synthesis technique to synthesize a duplicate transmitted multiple times at the receiving side, thereby obtaining a constant synthesis or coding gain. HARQ-II is a method based on adaptive error correction. The transmission of each frame is obtained by first adopting a high code rate, and the high code rate is obtained by periodically drilling a low code rate mother code. The CRC code is used for error detection of data on the receiving side. If the detection is not successful, the retransmission packet includes encoded information bits after punching, that is, incremental redundancy. This process continues until it is detected correctly or the number of retransmissions exceeds the maximum allowable number of retransmissions. The receiving side combines these drilling information bits with the initially transmitted data to improve the error correction probability. Such a method, unlike the HARQ-I and packet combining methods, can avoid retransmitting the entire frame, and can perform adaptive code rate adjustment based on the radio link.

  HARQ-II performs code rate adjustment that is adaptive to some extent, but such adjustment is not optimal for a specific channel environment. This is because the number and position of information bits to be retransmitted each time in HARQ-II is set in advance, but in the case of a specific channel environment, the number and position of retransmission information bits are adjusted adaptively, This is because optimal retransmission performance cannot be realized unless this is done.

  Furthermore, when unnecessary information is included in the retransmission data, the capacity and performance of the entire system are reduced. Therefore, in situations where the upstream bandwidth is very limited, it is necessary to improve HARQ reliability and effectiveness and reduce the bandwidth required for information feedback.

  An object of the present invention is to provide a method, a system, and an apparatus capable of improving the reliability and effectiveness of HARQ and reducing the bandwidth required for information feedback.

  The first feature of the present invention is a hybrid automatic retransmission request method, in which a receiving side detects a step of demodulating / decoding data transmitted from a transmitting side and that an error has occurred in data from the transmitting side In this case, the receiving side feeds back symbol position information including unreliable information bits to the transmitting side as symbol position information based on the distribution characteristics of the information bits in the symbol, and the transmitting side feeds back from the receiving side. Acquiring the corresponding unreliable information bits in the data transmitted from the transmission side based on the distribution characteristics of the symbol position information and the information bits in the symbols, and retransmitting the unreliable information bits; It is intended to include.

  A second feature of the present invention is a communication system that realizes a hybrid automatic retransmission request using a transmitter and a receiver, wherein the transmitter encodes and modulates transmission data. After receiving feedback regarding retransmission from the receiver, the reliability of the corresponding data in the data transmitted from the transmission side based on the symbol position information fed back from the reception side and the distribution characteristics in the symbols of the information bits. And a receiver that acquires unreliable information bits and retransmits unreliable information bits. The receiver demodulates and decodes transmission data from the transmitter and detects whether an error has occurred in the received transmission data. And a demodulating / decoding unit that detects that an error has occurred in the received transmission data, an unreliable information bit is generated based on a distribution feature in the symbol of the information bit. Get the Mareta symbol, it is an gist to include an acquisition unit for feeding back the symbol position information of the symbols in the transmitter.

  The third feature of the present invention is a receiver, which demodulates and decodes transmission data from the transmitter, detects whether an error has occurred in the received transmission data, and receives the received When it is detected that an error has occurred in the transmission data, a symbol including unreliable information bits is acquired based on the distribution characteristics of the information bits, and the acquired symbol position information is used as symbol position information. The gist is to include an acquisition unit that feeds back to the transmitter.

  A fourth feature of the present invention is a transmitter, which encodes and modulates transmission data, and a symbol fed back from the receiver after receiving feedback related to retransmission from the receiver. An acquisition unit configured to acquire corresponding unreliable information bits in data transmitted from the transmission side based on distribution characteristics in the position information and information bit symbols, and to retransmit the unreliable information bits. This is the gist.

  In the present invention, a hybrid automatic repeat request method based on reliability (that is, based on the value of the log likelihood ratio of information bits reflecting the reliability of information bits) is employed, and the position of information symbols on the transmission side that are not reliable Based on the information, the corresponding information bits that need to be retransmitted are retransmitted, so that the information bits that need to be retransmitted can be found more accurately and the reliability and effectiveness of HARQ can be improved, and the receiving side can improve the reliability to the transmitting side. Only symbol position information of information indicating no information bits is fed back, and a predetermined retransmission information bit threshold value can be appropriately set according to different communication environments, so that the amount of feedback information can be reduced.

  In order to improve the reliability and effectiveness of HARQ and reduce the amount of feedback information, the present invention provides a communication system capable of realizing a hybrid automatic repeat request method.

  FIG. 1 is a flowchart showing an overall flow of a hybrid automatic repeat request method according to an embodiment of the present invention.

  As shown in FIG. 1, the transmitter transmits data to the receiver (S101).

  When the receiver demodulates and decodes the received data and detects that an error has occurred in the data from the transmitter, the receiver requests the transmitter to retransmit (S102).

  The receiver feeds back symbol position information of symbols including unreliable information bits to the transmitter based on the distribution characteristics of information bits in symbols (that is, the correspondence between information bits and symbols) (S103). ).

  The transmitter finds the corresponding unreliable information bits based on the fed back symbol position information and the distribution characteristics of the information bits in the symbols, and retransmits the unreliable information bits (S104).

  After that, the receiver combines the data transmitted before by the transmitter using the retransmission data.

  Here, since the decoding method used in the receiver corresponds to the encoding method of the transmitter, both the transmitter and the receiver have distribution characteristics in the information bit symbol (that is, the correspondence between the information bit and the symbol). It should be understood that

  FIG. 2 is a block diagram illustrating an arrangement of a communication system according to an embodiment of the present invention.

  As shown in FIG. 2, the communication system of the present embodiment includes a transmitter 1 and a receiver 2. The transmitter 1 includes an encoding / modulation unit 11 and an acquisition unit 12, and the receiver 2 includes a demodulation / decoding unit 21 and an acquisition unit 22. The encoder / modulator 11 of the transmitter 1 and the demodulator / decoder 21 of the receiver 2 can be realized by a configuration for transmitting and receiving data in a conventional communication system, and a specific configuration and implementation process thereof are omitted here. To do.

  The encoding / modulation unit 11 of the transmitter 1 encodes and modulates the data to be transmitted using an encoding method (for example, Turbo, convolution integration, LDPC code, etc.) that can be decoded by the LLR value, and encodes the encoded data. The modulated data is transmitted to the receiver 2 as the first transmission data.

  The demodulator / decoder 21 of the receiver 2 receives the signal using a maximum posterior probability (MAP) decoding method (of course, a corresponding decoding method may be used for metrics other than the maximum likelihood value). The first transmission data is demodulated and decoded, and it is determined whether the first transmission data is correctly received. When it is determined that the first transmission data is correctly received, the ACK information is fed back to the transmitter 1; The log likelihood ratio value of each information bit in the received first transmission data is calculated, and the log likelihood ratio values of all information bits are transmitted to the acquisition unit 22.

  The acquisition unit 22 ranks the absolute values of the log likelihood ratio (LLR) values of all information bits from the demodulation / decoding unit 21 according to the values (the smaller the absolute value, the lower the reliability of the information bits). The least reliable information bits corresponding to the threshold value are acquired based on a predetermined retransmission information bit threshold value (if the threshold value is 60, the absolute value of LLR among the ranked absolute values is 60 Each information bit), and based on a pre-stored adaptive modulation / coding mapping table, each information symbol includes a total number of information bits equal to the retransmission information bit threshold value. Symbols including information bits having no information are selected, and symbol position information (unreliable symbol position information) is fed back to the transmitter 1. Here, as shown in FIG. 3, in the adaptive modulation / coding mapping table, the distribution feature of information bits in a symbol, that is, the relationship between the information bit position information and the symbol position information corresponding to the modulation / coding scheme. It is included. Of course, mapping tables corresponding to different encoding / modulation schemes may be stored in the transmitter and the receiver.

  When the transmitter 1 receives the information feedback, the acquisition unit 12 of the transmitter 1 uses the same pre-stored adaptive modulation / coding mapping table and the received symbol position information to determine the reliability detected by the receiver 2. No information bits are obtained, and only the unreliable information bits are retransmitted by the encoder / modulator 11.

  The above process is similarly applied to the second and third data transmissions, and in the retransmission process, only the retransmission data is detected to determine whether the data has been received correctly. When data is not correctly received, only symbol position information indicating information of unreliable information bits in retransmission data is fed back. As shown in FIG. 4, the present embodiment further provides three types of methods in which the receiver feeds back symbol position information.

  Scheme 1: Adding information bits representing symbol positions to the traditional ACK / NAK control channel.

  Method 2: Establishing an individual symbol position information control channel.

  Method 3: Establishing the symbol position information area in the data channel and distinguishing the position information from the true data.

  Hereinafter, a process in which the acquisition unit 22 according to the present exemplary embodiment acquires symbol position information will be described in detail.

  In this embodiment, there are multiple methods by which the acquisition unit 22 acquires symbol position information. For example, the first type of scheme is a scheme based on symbols and information bits, and the acquisition unit 22 acquires A information bits that are the least reliable as many as the number of retransmission information bit thresholds. Based on the distribution characteristics of the bits in the symbols, the symbol position information and the information bit position information in which the least reliable information bits satisfying a predetermined retransmission information bit threshold value are located are randomly acquired. In other words, the sum of the number of information bits included in the acquired symbol and the acquired information bit is equal to A corresponding to the acquired symbol position information and information bit position information.

  The second type is a method based on feedback of symbols that have not been ranked, and the acquisition unit 22 acquires A information bits having the least reliability corresponding to the retransmission information bit threshold, Based on the distribution characteristics in the symbols of non-information bits, the most reliable information bits are selected by prioritizing the symbols that contain the most unreliable information bits (the most reliable information bit number principle). A symbol containing a small amount is selected at random. That is, the sum of the number of information bits of a symbol including a plurality of least reliable information bits and the number of information bits of a symbol including a small amount of least reliable information bits is equal to A.

  The third type is a method based on feedback of ranked symbols, and the acquisition unit 22 has no reliability after acquiring retransmission information bit threshold value, that is, A least reliable information bits. Based on the distribution characteristics of the information bit symbols, a symbol including a plurality of least reliable information bits is preferentially selected, and among the A information bits, information bits with less reliability (A number) are selected. The information bits including the information bits corresponding to the relatively low LLR absolute value other than the least reliable information bits selected with priority are selected.

  Here, there is a possibility that one, two, or a plurality of information bits may be included in one symbol according to the encoding method and the code rate. Therefore, the fed symbol position information may indicate one, two, or a plurality of information bits. When selecting a symbol including a plurality of unreliable information bits according to the encoding method and code rate, for example, a symbol including n information bits having the least reliability is selected with priority. , N−1, n−2... Symbols included with the least reliable information bits may be selected in order.

  In the present invention, other methods may be used as a method for acquiring symbol position information. For example, a method of arbitrarily selecting a symbol satisfying a retransmission information bit threshold, or a symbol corresponding to a (a <A) least reliable information bits among A information bits is prioritized. In other words, a method based on the least reliable information bit principle or the like may be used.

  In other words, the principle of selecting the symbol that contains each (one or more) least reliable information bits is the principle of selecting the symbol that contains the most unreliable information bits (2), Alternatively, after selecting a symbol including the most unreliable information bits, a symbol including more unreliable information bits is selected from the remaining unreliable information bits (i.e., A symbol including a plurality of unreliable information bits is preferentially selected, the remaining information bits are ranked based on the LLR, and a symbol including an unreliable information bit is selected therefrom. ) In principle (2), select the symbols in order from the symbol containing the most unreliable information bits to the symbol containing only one unreliable information bit (reliable) (3) to select a symbol including n, n−1,..., 1 non-information bits, or a symbol including only the least reliable information bits ( 4), the principle (5) for selecting the least reliable information bit, the principle (6) for randomly selecting a symbol including an information bit having no reliability, or any two of these principles or Including multiple combination principles.

  Hereinafter, two specific examples for realizing acquisition of symbol position information will be described.

<Example 1>
Assuming that the transmitter 1 adopts a high-order modulation scheme 16QAM, the code rate is 1/2, and the frequency utilization efficiency is 2 bps / Hz, the receiver 2 decodes based on the MAP, and logs each information bit. The likelihood ratio value is calculated, and the absolute value of these values is ranked.

  The acquisition unit 22 determines the least reliable information bits for the threshold based on a predetermined retransmission information bit threshold A, and the A least reliable information based on the adaptive encoding / modulation mapping table. The symbol where the information bit is located and its position are found, and the position of the symbol containing two unreliable information bits is found first among these symbols. If the number of symbols meeting the above condition is B, the remaining AB * 2 symbols contain only one unreliable information bit. From the remaining A-B * 2 symbols, the least reliable (A-B * 2) / 2 symbols are selected. The (A−B * 2) / 2 symbols have the least reliable (A−B * 2) / 2 pieces of information among the remaining A−B * 2 unreliable information bits. Contains bits. Finally, the acquisition unit 22 feeds back the acquired B symbols and the position information (symbol position information) of the selected (AB * 2) / 2 symbols to the transmitter 1.

  The transmitter 1 finds corresponding information bits based on the fed back symbol position information and the corresponding adaptive modulation / coding mapping table, and retransmits these information bits.

<Example 2>
Assume that the transmitter 1 adopts a low-order modulation scheme QPSK, the code rate is 3/4, and the frequency utilization efficiency is 1.5 bps / Hz (based on the coding scheme, C symbols are two The receiver 2 decodes based on the MAP, calculates the log likelihood ratio value of each information bit, and includes these values. Rank the absolute value of.

  Based on a predetermined retransmission information bit threshold A, the acquisition unit 22 determines the most unreliable information bits for the threshold, and the unreliable information bits are located based on the adaptive encoding / modulation mapping table. And the position of the symbol containing two unreliable information bits is found first. Assuming that the number of symbols that meet the above condition is B, the remaining CB symbols contain two information bits, but there is only one unreliable information bit. From the remaining CB symbols, the symbols each including K least reliable information bits among the remaining (AB * 2) unreliable information bits are selected. From the remaining D symbols, A− (B + K) * 2 symbols including only one information bit are selected. Finally, the acquisition unit 22 feeds back the acquired position information (symbol position information) of B, K, A− (B + K) * 2 symbols to the transmitter 1.

  The transmitter 1 finds corresponding information bits based on the fed back symbol position information and the corresponding adaptive encoding / modulation mapping table, and retransmits these information bits.

  In the following, the change state of the feedback amount after adopting the hybrid automatic retransmission request method of the present embodiment will be exemplified.

  The communication system adopts the 16QAM, 1/2 code rate system, the length of information bits of the entire data is 1000 information bits, and the threshold of information bits that need to be retransmitted is 60 information bits Assume.

  The receiving side is required to feed back the position information of the 60 information bits to the transmitting side in order to notify the transmitting side of 60 information bits that need to be retransmitted. For the length of 1000 information bits, if the position information of one information bit is indicated by 10 information bits, 60 * 10 = 600 information bits are required to indicate the position information of 60 information bits. Is required. If the feedback method is based on symbol position feedback, in the case of 16QAM and 1/2 code rate, each symbol transmits two information bits, and transmission of 60 information bits requires 30 symbols. . Since there are 1000 * 2/4 = 500 symbols in the entire data, and the position information of each symbol is indicated by 9 information bits, the information bits necessary for indicating the position information of 30 symbols are as follows: 9 * 30 = 270. Therefore, according to the above example, the feedback information can be reduced from 600 information bits to 270 information bits by a method based on symbol feedback.

  Hereinafter, the performances of the hybrid automatic retransmission request method for feeding back symbol position information according to the present invention and the conventional fixed retransmission mode will be compared based on simulation results.

5, 6 and 7 show performance comparison diagrams between the hybrid automatic retransmission request method of the present invention and the conventional fixed retransmission mode. The parameters used for the simulation are as shown in Table 1. The modulation / coding methods employed are 16QAM and 64QAM. The encoding method is a Turbo code with a code rate of 1/2. The decoding method is iterative decoding, and the number of repetitions is 10. The maximum allowable number of retransmissions is 4, the information bit length is 900, the unreliable information bit threshold is 60, and the channel is a block fading channel. Here, FER is the frame error rate, Eb is the signal energy of each bit, and N0 is the noise power spectral density.

  Referring to FIG. 5, the HARQ based on feedback of ranked symbols, the HARQ based on feedback of unranked symbols, and the HARQ method based on symbols and information bits are hybrid automatic retransmissions in the conventional fixed retransmission mode. Compared to the request method, the system performance can be maintained and the amount of feedback information can be reduced. In the case of a method based on feedback of ranked symbols, the amount of information to be fed back is minimal.

  6 and 7, the hybrid automatic retransmission request method of the present invention can obtain a lower frame error rate and higher throughput than the conventional hybrid automatic retransmission request method in the fixed retransmission mode.

(Example of change)
The hybrid automatic retransmission request method of the present invention is further optimized to enable flexible and effective communication according to the channel environment. In the communication system according to the modification of the present invention, the transmitter 1 (base station side) may be configured to further include a switching unit (not shown). Depending on the feedback channel conditions, the switching unit may enable the transmitter 1 to operate in fixed retransmission mode (in this example, traditional incremental redundancy (IR) HARQ in the retransmission process in a low signal-to-interference noise ratio environment. In a high signal-to-interference / noise ratio environment, the transmitter 1 performs retransmission based on the operation method of the above-described embodiment, that is, the symbol position information fed back from the receiver 2. Switch to the method. This is because the HARQ method of the present invention can achieve the same performance as the traditional all-IR HARQ scheme in a low signal-to-interference noise ratio environment, where traditional incremental redundancy (IR) This is because the signaling overhead can be reduced by adopting the HARQ method. Of course, the transmitter 1 may adopt the HARQ scheme of the present invention in an environment with a low signal-to-interference noise ratio.

  Therefore, it is possible to improve HARQ reliability and effectiveness, reduce the bandwidth required for information feedback, and adopt a more appropriate communication method according to the channel environment, and provide a more flexible communication method. it can.

  As described above, in the present invention, the hybrid automatic repeat request method based on reliability (that is, based on the value of the log likelihood ratio of the information bits reflecting the reliability of the information bits) is adopted, and the transmission side has reliability. Since the corresponding information bits that need to be retransmitted are retransmitted based on the position information of no information symbols, the information bits that need to be retransmitted can be found more accurately, and the reliability and effectiveness of HARQ can be improved. Only the symbol position information of information indicating unreliable information bits is fed back to the transmitting side, and a predetermined retransmission information bit threshold can be appropriately set according to different communication environments, so that the amount of feedback information can be reduced. it can.

  Other advantages and modifications will be apparent to those skilled in the art from the above embodiments. Accordingly, the specific embodiments described above do not limit the present invention, and the above description is merely an example of a detailed and normative description of one type of the present invention. It is obvious to those skilled in the art that various improvements can be made on the premise that the principles of the present invention are not deviated, and these improvements also belong to the protection scope of the present invention.

5 is a flowchart illustrating an overall flow of a hybrid automatic retransmission request method according to an embodiment of the present invention. It is a flock figure which shows arrangement | positioning of the communication system by the Example of this invention. It is a figure which shows an example of the adaptive modulation and coding mapping table by the Example of this invention. FIG. 6 is a diagram illustrating a symbol position information feedback scheme of a receiver according to an embodiment of the present invention. It is a performance comparison diagram between the hybrid automatic retransmission request method of the present invention and the conventional fixed retransmission scheme. It is a performance comparison diagram between the hybrid automatic retransmission request method of the present invention and the conventional fixed retransmission scheme. It is a performance comparison diagram between the hybrid automatic retransmission request method of the present invention and the conventional fixed retransmission scheme.

Claims (18)

The receiving side demodulates and decodes the data transmitted from the transmitting side;
When it is detected that an error has occurred in data from the transmitting side, the receiving side transmits symbol position information including unreliable information bits as symbol position information based on the distribution characteristics of the information bit symbols. A step of feedback to the side,
Based on the symbol position information fed back from the receiving side and the distribution characteristics of the information bits in the symbol, the transmitting side acquires corresponding unreliable information bits in the data transmitted from the transmitting side, and there is no reliability. And a method of requesting retransmission of information bits.   When the receiving side demodulates and decodes the data from the transmitting side, calculates a metric value indicating the reliability of each information bit in the data, and matches the predetermined retransmission information bit threshold, the value of the metric The most reliable information bits in the data are acquired, and the total number of information bits included in each selected symbol is determined based on the modulation / coding mapping table stored in advance. 2. The hybrid automatic retransmission request method according to claim 1, further comprising: selecting a symbol including each least reliable information bit so that the position information of the selected symbol is fed back to a transmission side. .   The pre-stored modulation / coding mapping table includes a distribution feature of information bit symbols, and a principle of selecting a symbol including each least reliable information bit based on the modulation / coding mapping table The principle of selecting the symbol that contains the most unreliable information bits is the principle of selecting the symbol that contains the most unreliable information bits, and then selecting the symbol that contains the most unreliable information bits from the remaining unreliable information bits. The principle of selecting symbols that contain unreliable information bits, the principle of selecting symbols in the order of symbols that have the most unreliable information bits and symbols that have only one unreliable information bit, The principle of selecting symbols that contain only unreliable information bits, the principle of selecting the most unreliable information bits, unreliable Principles of selecting a symbol that contains multicast bits randomly, hybrid automatic repeat request method according to claim 2, characterized in that it comprises the principle of any two or more combination thereof principles.   3. The hybrid automatic retransmission request method according to claim 2, wherein the receiving side performs decoding based on the maximum posterior probability and calculates a log likelihood ratio value of each information bit of the received data.   The receiving side establishes a symbol position information area in a method of adding information bits representing symbol positions to a traditional ACK / NAK control channel, a method of establishing an individual symbol position information control channel, or a data channel, 5. The symbol position information is fed back to a transmitting side using any one of methods for distinguishing between the symbol position information and data to be actually transmitted. The hybrid automatic retransmission request method described in 1.   The transmitting side uses the fixed retransmission mode in an environment with a low signal-to-interference noise ratio according to the feedback channel state, and based on the symbol position information fed back from the receiving side in an environment with a high signal-to-interference noise ratio. 6. The hybrid automatic retransmission request method according to claim 5, wherein retransmission is performed. A communication system that implements a hybrid automatic repeat request using a transmitter and a receiver,
The transmitter is
An encoding / modulation unit for encoding / modulating transmission data;
After receiving feedback related to retransmission from the receiver, based on the symbol position information fed back from the receiving side and the distribution characteristics in the symbols of information bits, the corresponding unreliable information in the data sent from the sending side An acquisition unit for acquiring bits and retransmitting unreliable information bits,
The receiver
A demodulator / decoder that demodulates and decodes transmission data from the transmitter and detects whether an error has occurred in the received transmission data;
When it is detected that an error has occurred in the received transmission data, a symbol including unreliable information bits is acquired based on the distribution characteristics of the information bits, and symbol position information of the symbols is transmitted. A communication system comprising an acquisition unit that feeds back to the machine. In the receiver,
The demodulation / decoding unit demodulates and decodes the data from the transmission side, calculates a metric value indicating the reliability of each information bit of the data,
When the acquisition unit matches a predetermined retransmission information bit threshold value, the acquisition unit acquires the most unreliable information bit in the data based on the value of the metric, and stores it in the modulation / coding mapping table stored in advance. Based on this, the symbols including the least reliable information bits are selected so that the total number of information bits included in each selected symbol is equal to the retransmission information bit threshold, and the position information of the selected symbol is used as the symbol position. The communication system according to claim 7, wherein information is fed back to the transmitter as information.   The pre-stored modulation / coding mapping table includes a distribution feature of information bit symbols, and a principle of selecting a symbol including each least reliable information bit based on the modulation / coding mapping table The principle of selecting the symbol that contains the most unreliable information bits is the principle of selecting the symbol that contains the most unreliable information bits, and then selecting the symbol that contains the most unreliable information bits from the remaining unreliable information bits. The principle of selecting symbols that contain unreliable information bits, the principle of selecting symbols in the order of symbols that have the most unreliable information bits and symbols that have only one unreliable information bit, The principle of selecting symbols that contain only unreliable information bits, the principle of selecting the most unreliable information bits, unreliable Principles of selecting a symbol that contains multicast bit randomly communication system according to claim 8, characterized in that it comprises the principle of any two or more combination thereof principles.   The communication system according to claim 9, wherein the receiver calculates the value of the log likelihood ratio of each information bit of the received data by decoding based on the maximum posterior probability.   The receiver establishes a symbol position information area in a method of adding information bits representing symbol positions to a traditional ACK / NAK control channel, a method of establishing an individual symbol position information control channel, or a data channel, 11. The apparatus according to claim 7, further comprising a device that feeds back the symbol position information to the transmission side using any one of methods for dividing the symbol position information and the data to be actually transmitted. The communication system as described in any one.   The transmitter uses a fixed retransmission mode in a low signal-to-interference noise ratio environment, depending on the feedback channel condition, and the transmitter feeds back from the receiver in a high signal-to-interference noise ratio environment. The communication system according to claim 11, further comprising a switching unit configured to perform retransmission based on the symbol position information. A demodulator / decoder that demodulates and decodes transmission data from the transmitter and detects whether an error has occurred in the received transmission data;
When it is detected that an error has occurred in the received transmission data, a symbol including unreliable information bits is acquired based on the distribution feature of the information bit symbol, and the position information of the acquired symbol is represented as a symbol. And a receiver that feeds back position information to the transmitter. The demodulation / decoding unit demodulates and decodes data from the transmission side, calculates a metric value indicating the reliability of each information bit of the data,
When the acquisition unit matches a predetermined retransmission information bit threshold value, the acquisition unit acquires the most unreliable information bit in the data based on the value of the metric, and stores it in a modulation / coding mapping table stored in advance. Based on this, the symbols including the least reliable information bits are selected so that the total number of information bits included in each selected symbol is equal to the retransmission information bit threshold, and the position information of the symbols is transmitted to the transmitter. The receiver according to claim 13, wherein feedback is performed.   The pre-stored modulation / coding mapping table includes a distribution feature of information bit symbols, and a principle of selecting a symbol including each least reliable information bit based on the modulation / coding mapping table The principle of selecting the symbol that contains the most unreliable information bits is the principle of selecting the symbol that contains the most unreliable information bits, and then selecting the symbol that contains the most unreliable information bits from the remaining unreliable information bits. The principle of selecting symbols that contain unreliable information bits, the principle of selecting symbols in the order of symbols that have the most unreliable information bits and symbols that have only one unreliable information bit, The principle of selecting symbols that contain only unreliable information bits, the principle of selecting the most unreliable information bits, unreliable Principles of selecting a symbol that contains multicast bit randomly receiver according to claim 14, characterized in that it comprises the principle of any two or more combination thereof principles.   A method of adding information bits representing a symbol position to a traditional ACK / NAK control channel, a method of establishing an individual symbol position information control channel, or a symbol position information area in a data channel, and the symbol position information 16. The method according to claim 13, further comprising a device that further includes a device that feeds back symbol position information to the transmission side using any one of methods for distinguishing between data and data to be actually transmitted. The receiver as described in any one. An encoding / modulation unit for encoding / modulating transmission data;
After receiving feedback regarding retransmission from the receiver, based on the symbol position information fed back from the receiver and the distribution characteristics of the information bit symbols, corresponding unreliable information in the data transmitted from the transmission side A transmitter comprising: an acquisition unit that acquires bits and retransmits unreliable information bits.   Depending on the feedback channel conditions, in low signal-to-interference noise ratio environments, the transmitter uses the fixed retransmission mode, and in high signal-to-interference noise ratio environments, the symbol position at which the transmitter is fed back from the receiver. The transmitter according to claim 17, further comprising a switching unit configured to perform retransmission based on information.

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