JP2007036683A - Turbo decoder unit and decoding method, and radio communication terminal, radio base station and radio communication system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce wasteful use of decoding processing time and power consumption in turbo decoding, caused by repeated decoding processings, up to a preset maximum repetition count for a data unable to be decoded correctly. <P>SOLUTION: A turbo decoding processor 209 repeatedly performs decoding processings for the coding data included in a received radio signal, for the repetition count not exceeding the set maximum repetition count. When a reception quality deciding section 210 decides the reception quality does not satisfy a predetermined reception quality criterion, a maximum repetition count set 213 decreases the set value of the maximum repetition count. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a turbo decoder that performs error correction by repeatedly decoding received data encoded in wireless communication. Furthermore, the present invention relates to a decoding method using a turbo decoder, a radio communication terminal, a radio base station, and a radio communication system provided with the turbo decoder.

  In wireless communication, errors may occur in received data on the receiving side due to the influence of fading in the propagation path or noise caused by the amplifier of the receiving circuit. A decoding method using an error correction code is known as means for correcting such an error in received data. In the decoding method using an error correction code, an error correction code is added to an information bit on the transmission side and transmitted, and on the reception side, an error of the information bit is determined based on a certain relationship between the information bit and the error correction code. This is a correction method. Among decoding methods using an error correction code, a decoding method using a turbo code is known as a method having extremely high error correction capability even in a bad reception environment, and in 3GPP (3rd Generation Partnership Project), It is also adopted as a standard for error correction in WCDMA (Wideband Code Division Multiple Access) communication.

  In the decoding method using the turbo code, when receiving data is decoded on the receiving side, an operation of decoding again using the result of decoding once is repeatedly performed. The error correction capability can be remarkably improved by such feedback processing of decoded data. In general, the error correction capability improves as the number of repetitions increases.

  Usually, a preset value is used as the number of repetitions of the iterative decoding process. As this value, for example, a value estimated that a predetermined bit error rate can be secured under a predetermined condition by simulation or the like is used. However, if the decoding process is always performed with the set number of repetitions, the load on the decoding process time and power consumption increases. As a method for solving this problem, for example, in Patent Document 1, an error of an information bit is inspected for each decoding process, and even if it is less than the set number of repetitions (maximum number of repetitions), it can be correctly decoded. It is described that the iterative decoding process is terminated when it is determined. This method makes it possible to reduce the average number of iterations of the iterative decoding process without sacrificing the correction capability.

JP 2000-183758 A

  However, in the above method, the decoding process is repeated up to a preset maximum number of repetitions unless it is determined that decoding has been correctly performed in the iterative decoding process. Therefore, the decoding process is repeated up to the maximum number of repetitions until data that cannot be correctly decoded finally, and there is a problem that the processing time and power consumption associated therewith are wasted.

  The present invention has been made in order to solve the above-mentioned problem. For data that cannot be finally decoded correctly, the decoding processing time and power consumption associated with repeating the decoding processing up to a preset maximum number of repetitions is achieved. The purpose is to reduce waste.

In order to achieve the above object, a decoding method using a turbo decoder according to the present invention performs iterative decoding with the number of repetitions equal to or less than a set maximum number of repetitions for encoded data included in a received radio signal. A decoding method using a turbo decoder that performs processing, wherein a first step of determining whether or not a reception quality of the received radio signal satisfies a predetermined reception quality standard;
And a second step of reducing the set value of the maximum number of repetitions when it is determined in the first step that the reception quality does not satisfy the predetermined reception quality criterion.

  The decoding method using the turbo decoder further includes a third step of determining whether or not a decoding process state of the data subjected to the iterative decoding process satisfies a predetermined decoding process state criterion, In step 2, it is determined in the third step that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and in the first step, the reception quality does not satisfy the predetermined reception quality criterion. If it is determined, it may be a step of reducing the set value of the maximum number of repetitions.

  In the decoding method using the turbo decoder, when it is determined in the third step that the decoding processing state satisfies the predetermined decoding processing state criterion, information is obtained from the data subjected to the iterative decoding processing. Extracting a bit and performing the next iterative decoding process without changing the set value of the maximum number of repetitions, and determining in the third step that the decoding process state does not satisfy the predetermined decoding process state criterion And, when it is determined in the first step that the reception quality satisfies the predetermined reception quality criterion, a step of performing the next iterative decoding process without changing a set value of the maximum number of repetitions; In the step, it is determined that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and in the first step, the reception quality is the predetermined reception If it is determined not to satisfy the quality criteria may include the step of performing subsequent iterative decoding process by reducing the set value of the maximum number of repetitions.

  A turbo decoder, a radio base station, or a radio communication terminal according to the present invention performs a turbo decoding process of performing an iterative decoding process with a number of repetitions equal to or less than a set maximum number of repetitions on encoded data included in a received radio signal. A reception unit for determining whether or not a reception quality of the received radio signal satisfies a predetermined reception quality standard, and a reception quality determination unit And means for setting a maximum number of repetitions to reduce the set value of the maximum number of repetitions when it is determined that the reception quality does not satisfy the predetermined reception quality criterion.

  A wireless communication system according to the present invention includes a wireless communication terminal including a turbo decoding processing unit that performs iterative decoding processing at a number of repetitions equal to or less than a set maximum number of repetitions for encoded data included in a received wireless signal; A wireless communication system including a wireless base station, wherein the wireless communication terminal and the wireless base station receive quality determination means for determining whether reception quality of the received wireless signal satisfies a predetermined reception quality standard, When the reception quality determination unit determines that the reception quality does not satisfy the predetermined reception quality criterion, the reception quality determination unit includes a maximum repetition count setting unit that decreases a set value of the maximum repetition count.

  In the turbo decoder, the radio base station, the radio communication terminal, or the radio communication system, the maximum number of repetitions setting unit is configured so that the decoding process state determination unit determines that the decoding process state does not satisfy the predetermined decoding process state criterion. If it is determined and the reception quality determination means determines that the reception quality does not satisfy the predetermined reception quality criterion, the set value of the maximum number of repetitions may be decreased.

  In the turbo decoder, the radio base station, the radio communication terminal, or the radio communication system, when the decoding process state determining unit determines that the decoding process state satisfies the predetermined decoding process state criterion, the repetition is performed. The information processing apparatus further includes an information bit extracting unit that extracts information bits from the decoded data, and the maximum number of repetitions setting unit is configured to satisfy the predetermined decoding process state criterion in the decoding process state determining unit. Or when the decoding processing state determination unit determines that the decoding processing state does not satisfy the predetermined decoding processing state criterion and the reception quality determination unit determines that the reception quality satisfies the predetermined reception quality criterion. If it is determined that the condition is satisfied, the setting value of the maximum number of repetitions of the next iterative decoding process is not changed, and the decoding process state determination When the decoding processing state is determined not to satisfy the predetermined decoding processing state criterion and the reception quality determination unit determines that the reception quality does not satisfy the predetermined reception quality criterion, the next iterative decoding processing The set value of the maximum number of repetitions may be decreased.

  According to the present invention, wasteful decoding processing can be avoided by optimizing the set value of the maximum number of repetitions according to the reception quality of the received radio signal.

  Further, according to the present invention, when it is determined that the reception quality of the received radio signal does not satisfy the predetermined reception quality standard, the set value of the maximum number of repetitions is decreased. For this reason, it is possible to prevent the decoding process from being repeated up to a preset maximum number of repetitions for data that has a low reception quality and is highly likely not to be decoded correctly.

  Further, according to the present invention, the set value of the maximum number of repetitions can be decreased according to the determination results of both the reception quality and the decoding processing state of the received radio signal. For this reason, it is possible to prevent the decoding process from being repeated up to a preset maximum number of repetitions with respect to data that is highly likely not to be correctly decoded.

  As a result of the above, it is possible to reduce the waste of the decoding processing time and power consumption associated with repeating the decoding process up to a preset maximum number of repetitions for data that cannot be correctly decoded finally.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a wireless communication system according to an embodiment of the present invention. The wireless communication system includes at least a wireless communication terminal 101 and a wireless base station 111. The wireless communication terminal 101 includes a turbo encoder 103 for turbo-encoding transmission data and a turbo decoder 102 for decoding received turbo-encoded data. The radio base station 111 includes a turbo encoder 113 and a turbo decoder 112.

  In the radio base station 112, the transmission data is turbo-encoded in the turbo encoder 113. The turbo-encoded data is transmitted to the wireless communication terminal 101 as a wireless signal through the transmission unit 117 and the antenna 115 in the transmission / reception unit 114. In radio communication terminal 101, after receiving a radio signal by receiving unit 106 in transmitting / receiving unit 104 via antenna 105, turbo encoded data included in the radio signal is decoded by turbo decoder 102.

  Similarly, in the wireless communication terminal 101, transmission data is turbo encoded by the turbo encoder 103. The turbo-encoded data is transmitted to the radio base station 111 by a radio signal via the transmission unit 107 and the antenna 105 in the transmission / reception unit 104. In the radio base station 111, the radio signal is received by the reception unit 116 in the transmission / reception unit 114 via the antenna 115, and then turbo encoded data included in the radio signal is decoded by the turbo decoder 112.

  Next, the configuration of the turbo decoder and the receiving unit according to an embodiment of the present invention will be described. The turbo decoder shown below can be used as the turbo decoder 102 provided in the wireless communication terminal 101 or the turbo decoder 112 provided in the wireless base station 111 in the wireless communication system of FIG. Further, the following receiving unit can be used as the receiving unit 106 provided in the radio communication terminal 101 in the radio communication system of FIG. 1 or the receiving unit 116 provided in the radio base station 111.

  FIG. 2 is a block diagram illustrating a configuration of a turbo decoder and a receiving unit according to an embodiment of the present invention. The receiving unit 202 includes a receiver 203, a despreading processing unit 204, and a received power detection unit 205. The reception power detection unit 205 includes a signal wave power detection unit 206 and an interference wave power detection unit 207. The turbo decoder 208 includes a turbo decoding processing unit 209, a reception quality determination unit 210, a maximum repetition count setting unit 213, a hard decision processing unit 216, and an information bit extraction unit 217. The reception quality determination unit 210 includes a reception SIR calculation unit 211 and a reception SIR determination unit 212. SIR (Signal to Interference Ratio) is a signal wave interference wave power ratio of a received radio signal. The maximum repetition count setting unit 213 includes a maximum repetition count setting processing unit 214 and a memory 215.

  The operation of each block of the receiving unit 202 and the turbo decoder 208 is as follows.

  The receiving unit 202 performs reception processing such as despreading of a radio signal received via the antenna 201. The receiver 203 receives a radio signal via the antenna 201 and performs demodulation processing. The despreading processing unit 204 despreads the demodulated radio signal and outputs it to the turbo decoding processing unit 209 and the received power detection unit 205. The reception power detection unit 205 detects reception power of the received radio signal and notifies the reception quality determination unit 210 of information for calculating reception quality. Specifically, the signal wave reception power detection unit 206 detects the power of the signal wave necessary for information bit extraction from the received radio signal, and the interference wave power detection unit 207 detects the interference wave power and detects each of them. The result is notified to the reception SIR calculation unit 211.

  The turbo decoder 208 performs turbo decoding processing based on the data and information received from the receiving unit 202. The turbo decoding processing unit 209 performs iterative decoding processing on the encoded data notified from the despreading processing unit 204. Reception quality determination section 210 determines the reception quality of the received radio signal based on information for reception quality calculation notified from reception power detection section 205. Specifically, the reception SIR calculation unit 211 calculates the SIR of the received radio signal, and the reception SIR determination unit 212 determines whether or not the calculated SIR satisfies a predetermined reception quality standard. The determination result of the reception quality is notified to the maximum number of repetitions setting unit 213. The maximum iteration number setting unit 213 sets the maximum number of iterations of the iterative decoding process performed by the turbo decoding processing unit 209. The maximum number of iterations setting processing unit 214 calculates or determines the maximum number of iterations and notifies the turbo decoding processing unit 209. The memory 215 stores an initial value of the maximum number of repetitions, a current setting value, parameters used when determining the maximum number of repetitions, and the like. The hard decision processing unit 216 performs hard decision processing based on the output data from the turbo decoding processing unit 209. The information bit extraction unit 217 extracts information bits from the data string determined by the hard decision processing unit 216.

  Next, a specific configuration of the turbo decoding processing unit 209 will be described with reference to FIG. The turbo decoding processing unit 209 includes a processing unit 302 that executes iterative decoding processing and a control unit 303 that controls the operation of the processing unit 302. The processing unit 302 includes a first decoder 304, an interleaver 305, a second decoder 306, and a deinterleaver 308.

  Next, the operation of the turbo decoding processing unit 209 will be described with reference to FIG. The signal input from the despreading processing unit 204 to the turbo decoding processing unit 209 includes an information bit string and two types of parity bit strings (a first parity bit string and a second parity bit string). Both are bit strings transmitted from the transmission side. The information bits are bits that are finally extracted as received data, and the parity bits are bits used for a correction code.

  The first decoder 304 receives the first parity bit string generated and transmitted by the first encoder (not shown) on the transmission side together with the information bit string. The first decoder 304 decodes the information bits while performing error correction using the first parity bit, and the output is interleaved by the interleaver 305. On the other hand, the received information bit string is interleaved by the interleaver 305 and input to the second decoder 306. The second decoder 306 decodes information bits while performing error correction using the second parity bit string generated and transmitted by a second encoder (not shown) on the transmission side.

  Based on the decoded data obtained by interleaving the output data (decoded processing data) from the first decoder 304 and the decoded processing data from the second decoder 306, the hard decision processing unit 216 performs a hard decision. In the hard decision, for example, when both are matched, it is determined that they have been correctly decoded, and when they do not match, it is determined that they have not been correctly decoded.

  The determination result is notified to the control unit 303. If it is determined that decoding has been correctly performed, the hard decision processing unit 216 passes the decoding processing data from the second decoder 306 to the information bit extraction unit 217, and the control unit 303 ends the iterative decoding processing by the processing unit 302. To do. The information bit extraction unit 217 deinterleaves the decoded data and extracts information bits.

  If it is determined that the decoding has not been correctly performed, the decoded data from the second decoder 306 is deinterleaved by the deinterleaver 308, encoded by the encoder 308 with the same logic as the first encoder, 1 is input to the decoder 304, decoded, and interleaved by the interleaver 305. On the other hand, the first interleaved decoding process data from the first decoder 304 is encoded by the encoder 307 with the same logic as that of the second encoder, and is input to the second decoder 306 and decoded. Again, the hard decision processing unit 216 compares the decoded data with the second round and makes a hard decision. The above operation is repeated until it is determined that decoding has been correctly performed. In this way, the correction capability is improved by cyclically repeating the decoding process using two decoders.

  The control unit 303 is notified in advance of the maximum number of repetitions information, and when iterating up to the maximum number of repetitions, the iterative decoding process is terminated even if it is not determined that decoding has been correctly performed.

  Hereinafter, the iterative decoding process is used to mean a series of decoding processes that are cyclically repeated until a predetermined end condition is satisfied with the maximum number of repetitions as a limit as described above.

  The operation of the iterative decoding process described with reference to FIG. 3 is an example of a known turbo decoding technique, and the scope of the iterative decoding process in the present invention is not limited to this. For example, in FIG. 3, the decoding processing data is transmitted from the hard decision processing unit 216 to the information bit extraction unit 217. The decoding process data from the decoder 306 may be transmitted to the information bit extraction unit 217 via the deinterleaver 308. In this case, deinterleaving in the information bit extraction unit 217 is not necessary. Further, even when it is determined that the decoding can be correctly performed by the hard decision process, a method of always repeating the decoding process up to the maximum number of repetitions may be used.

  Next, the operation of the turbo decoder according to the embodiment of the present invention will be described. FIG. 4 is a flowchart illustrating an operation of a turbo decoder according to an embodiment of the present invention. First, it is determined whether the reception quality of the received radio signal satisfies a predetermined reception quality standard (S11). This determination is performed by the reception quality determination unit 210 based on information for reception quality calculation. The reception quality is determined by, for example, calculating the reception quality numerically and determining whether the calculated reception quality satisfies a predetermined reception quality standard. More specifically, the reception SIR calculation unit 211 calculates the SIR of the received radio signal, and the reception SIR determination unit 212 determines that the state where the calculated SIR is less than a predetermined reference value has continued for a predetermined time or more. In such a case, it is possible to use a method in which it is determined that the reception quality does not satisfy the standard, and in other cases, it is determined that the standard is satisfied.

  When it is determined in S11 that the reception quality does not satisfy the predetermined standard, the set value of the maximum number of repetitions is decreased (S12), and iterative decoding processing is performed (S13). The maximum repetition count setting unit 213 reduces the maximum repetition count setting value. On the other hand, if it is determined in S11 that the reception quality satisfies the predetermined standard, the iterative decoding process is performed without reducing the maximum number of repetitions (S13). At this time, a preset initial value is used as the maximum number of repetitions. The flow shown in FIG. 4 may be repeated at a predetermined cycle.

  According to this embodiment, when it is determined that the reception quality of the received radio signal does not satisfy the predetermined reception quality standard, the set value of the maximum number of repetitions is decreased. For this reason, it is possible to prevent the decoding process from being repeated up to a preset maximum number of repetitions for data that has a low reception quality and is highly likely not to be decoded correctly. As a result, it is possible to reduce the waste of the decoding processing time and power consumption associated with repeating the decoding process up to a preset maximum number of repetitions for data that cannot be correctly decoded finally.

  In addition, although the example which the reception quality determination part 210 determines SIR was shown above, it is not limited to this, What is necessary is just what can determine reception quality. For example, the reception quality may be determined based on the reception power and the signal noise power ratio (S / N).

  Next, the step (S11) of determining whether or not the reception quality of the received radio signal in FIG. 4 satisfies a predetermined reception quality standard will be described more specifically with reference to FIG. FIG. 5 is a graph plotting changes with time of SIR. In the same figure, the timing of data reception and the timing of iterative decoding processing are also shown.

  For data transmission, one frame is a radio frame of 10 ms. The iterative decoding process is performed at a cycle called a transmission time interval (TTI). TTI takes a value that is an integral multiple of the frame length (10 ms), which is the minimum unit of the radio interface. FIG. 5 illustrates a case where TTI is 20 ms which is twice the frame length. After receiving the data included in the first and second frames 511 and 512 from the left in the figure, these data are repeatedly decoded in the time zone 521. Similarly, the data included in the third and fourth frames 513 and 514 from the left are repeatedly decoded in the time zone 522. The same applies to the subsequent frames. In addition, the figure illustrates the case where TTI, that is, a period of 20 ms is used as the SIR measurement timing. However, SIR measurement is not limited to this period. In the figure, the first SIR plot 531 from the left shows the SIR value corresponding to the data repeatedly decoded in the time zone 521.

Regarding the determination of whether or not the reception quality of the received radio signal satisfies a predetermined reception quality criterion, when it is determined that the state where the SIR is less than the predetermined reference value has continued for a predetermined time or longer, the predetermined reception quality criterion is set. Judge that it does not meet. Specifically, the expression target SIR-SIR> SDiff (> 0)
When the state satisfying the condition continues for TSIR, it is determined that the reception quality standard is not satisfied. In other cases, it is determined that the reception quality standard is satisfied. Here, the target SIR is a target value used as a reference for reception quality determination. SDiff is a value that is assumed to be not correctly decoded when the SIR decreases by this value from the target SIR, and is set in advance. As TSIR, it is preferable to use TTI or more. If TSIR is equal to or greater than TTI, it is determined that the reception quality standard is not satisfied for a time equal to or longer than the time when data to be decoded is transmitted, and it is highly likely that such data includes bit errors. Because it is reasonable to think.

  In FIG. 5, as an example, determination regarding whether or not the reception quality standard when TSIR = TTI is satisfied will be described. The determination is made almost simultaneously with the SIR measurement timing. According to the figure, the timings of the third to fifth SIR plots 533, 534, and 535 from the left satisfy the above-described equation for more than TSIR. Therefore, it is determined that the reception quality standard is not satisfied at these timings. On the other hand, it is determined that the reception quality standard is satisfied at the timings of the first, second, and sixth SIR plots 531, 532, and 536 from the left.

  Next, the step (S12) of decreasing the set value of the maximum number of repetitions in FIG. 4 will be specifically described. In S12, when it is determined in S11 that the reception quality does not satisfy the predetermined standard, the set value of the maximum number of repetitions is decreased. Hereinafter, a preferred embodiment of S12 will be described.

  In the present embodiment, the step of S11 is performed at a predetermined cycle, and the set value of the maximum number of repetitions is decreased step by step whenever it is continuously determined that the reception quality does not satisfy the predetermined reception quality standard. It is characterized by that.

  Hereinafter, a specific example of a method of decreasing the set value of the maximum number of repetitions step by step will be described. In a normal state, an initial value Nmax0 is set as the maximum number of repetitions. The initial value of the maximum number of repetitions is stored in the memory 215 and used by the maximum number of repetitions setting processing unit 214 as necessary. Here, when it is determined in S11 that the reception quality does not satisfy the predetermined standard, a value obtained by multiplying Nmax0 by K is set as the next number of repetitions. Here, K represents a predetermined step size for reducing the number of repetitions, and takes a value in the range of 1> K> 0. The value of K is stored in the memory 215 and used by the maximum number of repetitions setting processing unit 214 as necessary. When the calculated maximum number of repetitions does not become an integer, processing such as carry-up may be performed. Further, also in the next step S11, when it is determined that the reception quality does not satisfy the predetermined standard, the value obtained by multiplying the above Nmax0 by K is further multiplied by K as the next number of repetitions. Is set. Hereinafter, the multiplication of the maximum number of repetitions of K is repeated every time it is continuously determined that the reception quality does not satisfy a predetermined criterion. However, when the set value of the maximum number of repetitions decreases to a predetermined value, a step of preventing further decrease may be included. In this way, every time it is continuously determined that the reception quality does not satisfy the predetermined reception quality standard, the set value of the maximum number of repetitions is decreased stepwise.

  The effect of reducing the set value of the maximum number of repetitions in steps will be described. For example, when the SIR gradually deteriorates, at the initial stage when the reception quality does not satisfy the predetermined reception quality standard, the SIR is close to the target SIR and is relatively good although it does not meet the standard. There is a high possibility that it is close to the state. Therefore, there is a possibility that the iterative decoding process may be performed satisfactorily as much as the set value of the maximum number of iterations is slightly reduced. However, if the set value of the maximum number of iterations is suddenly reduced, the possibility is lost. On the other hand, when the state where the SIR does not satisfy the predetermined reception quality standard continues for a long time, the SIR is likely to be in a relatively bad state. Therefore, the possibility that the iterative decoding process is performed satisfactorily is relatively low. As described above, the decoding process is not repeated up to the preset maximum number of repetitions by decreasing the set value of the maximum number of repetitions step by step in accordance with the time length when the reception quality does not satisfy the predetermined standard. While enjoying the effect, the probability that the iterative decoding process is satisfactorily performed is higher than when the set value of the maximum number of repetitions is rapidly decreased. For this purpose, K = 0.8 to 0.9 is particularly preferable.

  The preferred embodiment of S12 has been described above, but the technical scope of S12 is not limited to this, and the effect of the present invention can be obtained as long as the set value of the maximum number of repetitions is reduced. For example, in the above description, the example in which the set value of the maximum number of repetitions is decreased by multiplying the predetermined value (K) every time determination that the reception quality does not satisfy the predetermined reception quality standard is made continuously. Alternatively, it may be decreased by a predetermined value. Also included is a method in which the maximum number of iterations is set to 0, that is, the decoding process is not repeated. Furthermore, a method of preventing the decoding process itself from being performed once is also included.

  In the step (S13) of the iterative decoding process of FIG. 4, the maximum number of iterations decreased in S12 is applied. In FIG. 5, using the above example where TSIR = TTI is used, iterative decoding processing after the timing of SIR plots 533, 534, and 535, which is determined not to satisfy the reception quality criterion, that is, time zone 523 In the iterative decoding process of 524, 525, the reduced maximum number of repetitions set immediately before each is applied. On the other hand, in the iterative decoding process after the timings of the plots 531, 532, and 536 determined to satisfy the reception quality standard, that is, the iterative decoding process in the time zones 521, 522, and 526, the initial value is applied as the maximum number of repetitions. . Note that, when it is determined that the reception quality standard is satisfied from the state where it is determined that the reception quality standard is not satisfied, the maximum repetition count setting unit 213 sets the reduced maximum repetition count setting value to the initial value. Return to. The state in which it is determined that the reception quality standard is satisfied from the state in which it is determined that the reception quality standard is not satisfied specifically means the state of the timing in the SIR plot 536 in FIG.

  Next, the configuration of a turbo decoder according to another embodiment of the present invention will be described. FIG. 6 is a block diagram illustrating a configuration of a turbo decoder and a receiving unit according to another embodiment of the present invention. The turbo decoder 601 according to the present embodiment includes a decoding processing state determination unit 602 in addition to the embodiment shown in FIG. The decryption process state determination unit 602 determines the decryption process state of the hard-processed decryption process data. The determination result of the decoding process state is notified to the maximum number of repetitions setting unit 603.

  Next, the operation of the turbo decoder according to another embodiment of the present invention will be described. FIG. 7 is a flowchart illustrating an operation of a turbo decoder according to another embodiment of the present invention. First, iterative decoding processing is performed based on a predetermined maximum number of repetitions (S21). After the iterative decoding process is completed, the decoding process status of the hard-decisioned decoding process data is determined (S22). This determination is performed by the decoding processing state determination unit 602. Specifically, it is determined whether or not the decoding processing state of the decoding processing data satisfies a predetermined decoding processing state criterion. More specifically, when it is determined that the hard-decision decoded processing data includes a bit error, it is determined that the decoding processing state does not satisfy a predetermined decoding processing state criterion, and is determined not to include a bit error. If it is determined that the decoding processing state satisfies a predetermined decoding processing state criterion.

  When it is determined in S22 that the decoding processing state does not satisfy the predetermined decoding processing state criterion, the result of whether or not the reception quality of the received radio signal satisfies the predetermined reception quality criterion is referred to (S23). . The operation after S23 is the same as the operation described with reference to FIG. 4 and thus will not be described in detail. However, when the reception quality does not satisfy the predetermined reception quality standard, the set value of the maximum number of repetitions is decreased (S24). ) If the reception quality satisfies a predetermined reception quality criterion, the iterative decoding process is performed without reducing the maximum number of repetitions (S25). If it is determined in S22 that the decoding process state satisfies the predetermined decoding process state criterion, the iterative decoding process is performed without reducing the maximum number of repetitions (S25).

  According to the present embodiment, the set value of the maximum number of repetitions can be reduced according to the determination results of both the reception quality and the decoding processing state of the received radio signal. For this reason, it is possible to prevent the decoding process from being repeated up to a preset maximum number of repetitions with respect to data that is highly likely not to be correctly decoded. By reflecting the determination result of the decoding process state of the iterative decoding process performed immediately before, the credibility of the prediction that the next iterative decoding process cannot be correctly decoded is significantly increased. As a result, it is possible to reduce the waste of the decoding processing time and power consumption associated with repeating the decoding process up to a preset maximum number of repetitions for data that cannot be correctly decoded finally.

  Next, the method for determining the decryption processing state of the decryption processing data (S22) will be described more specifically. As the determination of the decoding processing state, when the output data from the turbo decoder that has been hard-determined is determined to contain a bit error by bit error inspection using a CRC (Cyclic Redundancy Check) code, the decoding processing state A method may be used in which it is determined that the state does not satisfy a predetermined decoding processing state criterion, and it is determined that the decoding processing state satisfies a predetermined decoding processing state criterion when it is determined that no bit error is included. it can. The CRC code is an error detection code attached separately from the turbo code. Separately, the error detection code is used because in the decoding by turbo code, a path is randomly selected when the path metrics are equal, and therefore a bit error may be included even if the hard decision is good. To supplement it. The CRC code may be transmitted by an upper layer. The method using the CRC code is an example, and other cyclic codes and linear codes may be used.

  Further, even when an error detection code such as a CRC code is not attached, the result of the hard decision may be used. For example, the bit error rate may be calculated by comparing the last decoded data of the iterative decoding process with the previous decoded data. The determination result in the hard decision processing unit 216 may be the result of the decoding process state determination. In this case, the hard decision processing unit 216 may be configured to also serve as the operation of the decoding process state determination unit 602. Further, instead of using the determination result of the hard decision processing unit 216 for the end point determination of the iterative decoding process in the turbo decoding processing unit 209, the determination result of the decoding process state determining unit 602 is used as the end point of the iterative decoding process iterative operation. It may be used for determination.

  Next, the operation of the turbo decoder according to still another embodiment of the present invention will be described. FIG. 8 is a flowchart illustrating an operation of a turbo decoder according to still another embodiment of the present invention. First, iterative decoding processing is performed based on a predetermined maximum number of repetitions (S31). After the iterative decoding process is completed, the decoding process status of the hard-decisioned decoding process data is determined (S32). This determination is performed by the decoding processing state determination unit 602. Specifically, it is determined whether or not the decoding processing state of the decoding processing data satisfies a predetermined decoding processing state criterion. More specifically, when it is determined that the hard-decision decoded processing data includes a bit error, it is determined that the decoding processing state does not satisfy a predetermined decoding processing state criterion, and is determined not to include a bit error. If it is determined that the decoding processing state satisfies a predetermined decoding processing state criterion.

  If it is determined in S32 that the decoding process state satisfies the predetermined decoding process state criterion, information bits are extracted (S33). If the next iterative decoding process is performed, the process returns to step S31, and the next iterative decoding is performed. If the next iterative decoding process is not performed, the process is terminated (S39). Information bit extraction is performed by the information bit extraction unit 317. Processing time and power consumption associated with information bit extraction processing for decoded processing data that is determined not to be decoded correctly by extracting information bits when it is determined that the decoding processing state satisfies a predetermined decoding processing state criterion Can be reduced.

  If it is determined in S32 that the decoding processing state does not satisfy the predetermined decoding processing state criterion, the result of whether or not the reception quality of the received radio signal satisfies the predetermined reception quality criterion is referred to (S34). . If the reception quality does not satisfy the predetermined reception quality standard, it is determined whether the set value of the maximum number of repetitions can be reduced (S37). This determination is performed by the maximum number of repetitions setting processing unit 604 with reference to the current setting value of the maximum number of repetitions stored in the memory 315. For example, when the set value of the maximum number of repetitions is a preset minimum value, it is determined that the set value of the maximum number of repetitions cannot be decreased, and in other cases, it is determined that the value can be decreased. If it is determined in S37 that the set value of the maximum number of iterations cannot be decreased, the process proceeds to a step (S39) for performing the next iterative decoding. If it is determined in S37 that the setting value for the maximum number of repetitions can be decreased, the setting value for the maximum number of repetitions is decreased (S38), and the process proceeds to S39.

  If the reception quality satisfies the predetermined reception quality standard in S34, it is referred to whether the previous reception quality satisfies the predetermined reception quality standard (S35). Information about the past reception quality (whether a predetermined reception quality standard has been satisfied, etc.) is stored in the memory 315 and is referred to by the maximum number of repetitions setting processing unit 604 as necessary. In S35, when the previous reception quality satisfies the predetermined reception quality standard, it means that the state in which the reception quality satisfies the predetermined reception quality standard continues, so the setting value of the maximum number of repetitions Without proceeding to S39. On the other hand, if the previous reception quality does not satisfy the predetermined reception quality standard in S35, it means that the reception quality has been satisfied from the state not satisfying the predetermined reception quality standard. In this case, The setting value of the maximum number of repetitions is returned to the initial value (S37), and the process proceeds to S39.

  Although the reception quality satisfies the predetermined reception quality standard by returning the set value of the maximum number of repetitions to the initial value at the timing when the reception quality is satisfied from the state not satisfying the predetermined reception quality standard, While preventing the problem of applying the set value of the maximum number of repetitions that has been reduced, the effect of reducing the set value of the maximum number of repetitions can be enjoyed the longest.

  This embodiment includes all the effects of the embodiment described in FIG. 4 or FIG. In addition, as a more specific method in each step, all the methods described so far can be applied.

It is a block diagram for demonstrating the radio | wireless communications system by one Embodiment of this invention. It is a block diagram for demonstrating the structure of the turbo decoder by one Embodiment of this invention. It is a block diagram for demonstrating the structure of a turbo decoding process part. 4 is a flowchart illustrating an operation of a turbo decoder according to an embodiment of the present invention. It is a graph for demonstrating the change with respect to the time of SIR and the timing of data reception and iterative decoding processing. It is a block diagram for demonstrating the structure of the turbo decoder by another embodiment of this invention. 6 is a flowchart illustrating an operation of a turbo decoder according to another embodiment of the present invention. 6 is a flowchart illustrating an operation of a turbo decoder according to still another embodiment of the present invention.

Explanation of symbols

102, 112, 208, 601 Turbo decoder 209 Turbo decoding processing unit 210 Reception quality determination unit 211 Reception SIR calculation unit 212 Reception SIR determination unit 213, 603 Maximum iteration count setting unit 216 Hard determination processing unit 217 Information bit extraction unit 602 Decoding Processing state determination unit

Claims (20)

A decoding method using a turbo decoder that performs iterative decoding processing with the number of repetitions equal to or less than a set maximum number of repetitions for encoded data included in a received radio signal,
A first step of determining whether reception quality of the received radio signal satisfies a predetermined reception quality standard;
A turbo decoder comprising: a second step of reducing a set value of the maximum number of repetitions when it is determined in the first step that the reception quality does not satisfy the predetermined reception quality criterion Decoding method using. A third step of determining whether or not a decoding process state of the data subjected to the repeated decoding process satisfies a predetermined decoding process state criterion;
In the second step, it is determined in the third step that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and in the first step, the reception quality satisfies the predetermined reception quality criterion. The decoding method using a turbo decoder according to claim 1, wherein if it is determined that the value is not satisfied, the setting value of the maximum number of repetitions is reduced. When it is determined in the third step that the decoding processing state satisfies the predetermined decoding processing state criterion, information bits are extracted from the data subjected to the iterative decoding processing, and the setting value of the maximum number of repetitions is changed. Without performing the next iterative decoding process,
When it is determined in the third step that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and in the first step, it is determined that the reception quality satisfies the predetermined reception quality criterion, Performing the next iterative decoding process without changing the set value of the maximum number of iterations;
When it is determined in the third step that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and in the first step, it is determined that the reception quality does not satisfy the predetermined reception quality criterion 3. A decoding method using a turbo decoder according to claim 2, further comprising a step of performing a next iterative decoding process by reducing a set value of the maximum number of repetitions. The first step is performed in a cycle in which the iterative decoding process is performed, and the reduced maximum repetition is applied to the iterative decoding process after it is determined in the first step that the reception quality does not satisfy the predetermined reception quality criterion. The decoding method using a turbo decoder according to claim 1, wherein the number of times is applied. The first step is performed in a predetermined period, and the set value of the maximum number of repetitions is decreased stepwise each time it is continuously determined that the reception quality does not satisfy the predetermined reception quality standard. The decoding method using the turbo decoder in any one of Claims 1-4 characterized by these. Performing the first step at a predetermined period, and returning the set value of the maximum number of repetitions to an initial value when the reception quality is satisfied from a state not satisfying the predetermined reception quality standard. A decoding method using the turbo decoder according to any one of claims 1 to 5. The first step calculates an SIR (Signal to Interference Ratio) of the received radio signal, and when it is determined that a state where the calculated SIR is less than a predetermined reference value has continued for a predetermined time or more, 7. The step of determining that reception quality does not satisfy the predetermined reception quality criterion, and determining that the reception quality satisfies the predetermined reception quality criterion otherwise. A decoding method using the turbo decoder as described above. In the third step, the decoding processing state is determined when the hard-determined output data from the turbo decoder is determined to contain a bit error by a bit error check using a CRC (Cyclic Redundancy Check) code. Is a step of determining that the decoding processing state satisfies a predetermined decoding processing state criterion when it is determined that the predetermined decoding processing state criterion is not satisfied and it is determined that no bit error is included. A decoding method using the turbo decoder according to claim 2. A turbo decoder including a turbo decoding processing unit that performs an iterative decoding process with a number of repetitions equal to or less than a set maximum number of repetitions for encoded data included in a received radio signal,
Reception quality determination means for determining whether or not the reception quality of the received radio signal satisfies a predetermined reception quality standard;
Turbo decoding, comprising: maximum repetition count setting means for reducing the set value of the maximum repetition count when the reception quality determination means determines that the reception quality does not satisfy the predetermined reception quality criterion vessel. A decoding process state determination unit for determining whether or not a decoding process state of the data subjected to the repeated decoding process satisfies a predetermined decoding process state criterion;
The maximum number of repetitions setting unit determines that the decoding process state determination unit does not satisfy the predetermined decoding process state criterion, and the reception quality determination unit determines that the reception quality is the predetermined reception quality. The turbo decoder according to claim 9, wherein when it is determined that the criterion is not satisfied, the set value of the maximum number of repetitions is decreased. When the decoding process state determination unit determines that the decoding process state satisfies the predetermined decoding process state criterion, the decoding process state determination unit further includes an information bit extraction unit that extracts information bits from the data that has been subjected to the iterative decoding process,
The maximum number of iterations setting unit is configured such that the decoding process state determining unit determines that the decoding process state satisfies the predetermined decoding process state criterion, or the decoding process state determining unit determines that the decoding process state is the predetermined process. When the reception quality determination means determines that the reception quality satisfies the predetermined reception quality criterion, the setting value of the maximum number of repetitions of the next iterative decoding process is determined. Without change, it is determined by the decoding processing state determination means that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and the reception quality determination unit determines that the reception quality does not satisfy the predetermined reception quality criterion 11. The turbo decoder according to claim 10, wherein if it is, the set value of the maximum number of iterations of the next iterative decoding process is decreased. A wireless communication terminal including a turbo decoding processing unit that performs iterative decoding processing with a number of repetitions equal to or less than a set maximum number of repetitions for encoded data included in a received wireless signal,
Reception quality determination means for determining whether or not the reception quality of the received radio signal satisfies a predetermined reception quality standard;
Radio communication, comprising: a maximum repetition count setting means for reducing a set value of the maximum repetition count when the reception quality determination means determines that the reception quality does not satisfy the predetermined reception quality criterion Terminal. A decoding process state determination unit for determining whether or not a decoding process state of the data subjected to the repeated decoding process satisfies a predetermined decoding process state criterion;
The maximum number of repetitions setting unit determines that the decoding process state determination unit does not satisfy the predetermined decoding process state criterion, and the reception quality determination unit determines that the reception quality is the predetermined reception quality. The wireless communication terminal according to claim 12, wherein when it is determined that the criterion is not satisfied, the set value of the maximum number of repetitions is decreased. When the decoding process state determination unit determines that the decoding process state satisfies the predetermined decoding process state criterion, the decoding process state determination unit further includes an information bit extraction unit that extracts information bits from the data that has been subjected to the iterative decoding process,
The maximum number of iterations setting unit is configured such that the decoding process state determining unit determines that the decoding process state satisfies the predetermined decoding process state criterion, or the decoding process state determining unit determines that the decoding process state is the predetermined process. When the reception quality determination means determines that the reception quality satisfies the predetermined reception quality criterion, the setting value of the maximum number of repetitions of the next iterative decoding process is determined. Without change, it is determined by the decoding processing state determination means that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and the reception quality determination unit determines that the reception quality does not satisfy the predetermined reception quality criterion 14. The wireless communication terminal according to claim 13, wherein if it is determined, the set value of the maximum number of repetitions of the next iterative decoding process is decreased. A radio base station including a turbo decoding processing unit that performs iterative decoding processing at a number of repetitions equal to or less than a set maximum number of repetitions for encoded data included in a received wireless signal,
Reception quality determination means for determining whether or not the reception quality of the received radio signal satisfies a predetermined reception quality standard;
A radio base comprising: a maximum repetition count setting means for reducing a set value of the maximum repetition count when the reception quality determination means determines that the reception quality does not satisfy the predetermined reception quality criterion; Bureau. A decoding process state determination unit for determining whether or not a decoding process state of the data subjected to the repeated decoding process satisfies a predetermined decoding process state criterion;
The maximum number of repetitions setting unit determines that the decoding process state determination unit does not satisfy the predetermined decoding process state criterion, and the reception quality determination unit determines that the reception quality is the predetermined reception quality. The radio base station according to claim 15, wherein when it is determined that the criterion is not satisfied, the set value of the maximum number of repetitions is decreased. When the decoding process state determination unit determines that the decoding process state satisfies the predetermined decoding process state criterion, the decoding process state determination unit further includes an information bit extraction unit that extracts information bits from the data that has been subjected to the iterative decoding process,
The maximum number of iterations setting unit is configured such that the decoding process state determining unit determines that the decoding process state satisfies the predetermined decoding process state criterion, or the decoding process state determining unit determines that the decoding process state is the predetermined process. When the reception quality determination means determines that the reception quality satisfies the predetermined reception quality criterion, the setting value for the maximum number of repetitions of the next iterative decoding process is determined. Without change, it is determined by the decoding processing state determination means that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and the reception quality determination unit determines that the reception quality does not satisfy the predetermined reception quality criterion The radio base station according to claim 16, wherein if it is, the set value of the maximum number of repetitions of the next iterative decoding process is decreased. A radio communication system including a radio communication terminal and a radio base station having a turbo decoding processing unit that performs iterative decoding processing with the number of repetitions equal to or less than a set maximum number of repetitions for encoded data included in a received wireless signal Because
The radio communication terminal and the radio base station, reception quality determination means for determining whether the reception quality of the received radio signal satisfies a predetermined reception quality standard,
Radio communication, comprising: a maximum repetition count setting means for reducing a set value of the maximum repetition count when the reception quality determination means determines that the reception quality does not satisfy the predetermined reception quality criterion system. The wireless communication terminal and the wireless base station further include a decoding processing state determination unit that determines whether or not a decoding processing state of the data subjected to the repeated decoding processing satisfies a predetermined decoding processing state criterion,
The maximum number of repetitions setting unit determines that the decoding process state determination unit does not satisfy the predetermined decoding process state criterion, and the reception quality determination unit determines that the reception quality is the predetermined reception quality. The wireless communication system according to claim 18, wherein when it is determined that the criterion is not satisfied, the set value of the maximum number of repetitions is decreased. The wireless communication terminal and the wireless base station extract information bits from the data that has been subjected to the iterative decoding process when the decoding process state determining unit determines that the decoding process state satisfies the predetermined decoding process state criterion An information bit extraction unit
The maximum number of iterations setting unit is configured such that the decoding process state determining unit determines that the decoding process state satisfies the predetermined decoding process state criterion, or the decoding process state determining unit determines that the decoding process state is the predetermined process. When the reception quality determination means determines that the reception quality satisfies the predetermined reception quality criterion, the setting value for the maximum number of repetitions of the next iterative decoding process is determined. Without change, it is determined by the decoding processing state determination means that the decoding processing state does not satisfy the predetermined decoding processing state criterion, and the reception quality determination unit determines that the reception quality does not satisfy the predetermined reception quality criterion 20. The radio communication system according to claim 19, wherein if it is determined, the set value of the maximum number of iterations of the next iterative decoding process is decreased.

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