JP5056247B2 - Decoder, receiving device, decoding method of encoded data, and communication system - Google Patents

Description

  The present invention relates to a decoder or the like that performs error correction decoding by an iterative decoding method.

As one of error correction techniques, attention is focused on a low density parity check (LDPC) code and a sum-product decoding method which is a decoding method thereof.
With this LDPC code, it is known that a decoding characteristic of 0.004 dB can be obtained up to the Shannon limit of the white Gaussian channel. In addition, since the sum-product decoding method performs decoding processing by parallel processing, the code length can be increased and the processing capability can be improved. As a decoding method, a min-sum decoding method is also known in which the sum-product decoding method is simplified.

In the above decoding method, error correction is performed by repeatedly performing decoding operations of row processing and column processing based on the log likelihood ratio calculated from the received signal. A decoding apparatus that performs error correction decoding of such an LDPC code is disclosed in Patent Document 1.
In the decoding device described in Patent Document 1, the row processing and the column processing are repeatedly performed repeatedly. Then, when the number of repetitions of row processing and column processing reaches a predetermined value, the repetition of row processing and column processing ends.

Japanese Patent Laid-Open No. 2005-269535

  In the case of the iterative decoding method performed in the conventional decoding device described in Patent Document 1, the decoding characteristics are improved if the number of repetitions is large. From this point of view, it is preferable that the number of decoding calculation iterations is set as large as possible. On the other hand, if the number of iterations is too large, useless iterative computation that does not affect error correction is performed, resulting in latency (delay) and unnecessary power consumption.

Thus, in the case of the iterative decoding method, the quality of the decoded data changes depending on how many times the decoding operation is repeated. Various adjustments should be made to do so.
However, in the decoding device described in Patent Document 1, since the number of iterations of the decoding operation is fixedly incorporated in the decoder, a situation occurs in which the number of iterations is too small or too large depending on the state of the communication path. As a result, decoding with a predetermined quality may not be performed, and latency (delay) and unnecessary power consumption may occur.

  In view of such a conventional problem, the present invention is a decoder capable of efficiently performing error correction decoding by an iterative decoding method so that the number of iterations of decoding operation can be adjusted according to the condition of a communication channel. The purpose is to provide.

Decoder of the present invention is a decoder for obtaining decoded data by performing error correction decoding on the transmitted coded data in the communication path, the coded data by repetition decoding method performed by iteratively decoding operation And a number of times determination unit for determining the number of iterations of the decoding operation based on the transmission characteristics of the communication path.

According to the above decoder, the number determining unit determines the number of decoding computation iterations by the decoding processing unit based on the transmission characteristics of the communication channel, and therefore adjusts the number of decoding computation iterations according to the channel conditions. Can do.
For this reason, it is possible to prevent the occurrence of decoding with a predetermined quality because the number of iterations is too small, or the occurrence of latency and unnecessary power consumption due to too many iterations. Can be performed efficiently.

In the decoder according to the present invention, the transmission characteristic of the communication path can be specified by, for example, the noise characteristic of the encoded data. In this case, the number determination unit uses a pilot signal included in the encoded data. based on the noise characteristics of the encoded data calculated not good if so to determine the number of iterations of the decoding operation Te.
The noise characteristics of the encoded data may be any index that can quantitatively evaluate noise mixed in the transmission path. For example, the signal noise ratio (SNR) is included in this, and noise power and noise are included. This includes the amount.
According to the above decoder, the noise characteristic of the encoded data, which is a parameter for determining the number of iterations of the decoding operation, is calculated using the pilot signal included in the encoded data. The noise characteristics can be obtained independently in the decoder, and the implementation is simple.

However, since the noise characteristics of the encoded data are obtained from the encoded data before decoding, the decoding result is fed back even if the number of iterations of the decoding operation is determined based solely on the noise characteristics. Can not do it.
Therefore, in the decoder of the present invention, an input port for inputting the error characteristic of the decoded data from the outside is further provided, and the transmission characteristic of the communication path is determined by the error characteristic of the decoded data input to the input port. It may be to identify, in this case, the number determination unit ing to determine the number of iterations of the decoding operation based on the error characteristics of the decoded data.
The error characteristics of the decoded data may be any index that can quantitatively evaluate errors included in the decoded data. For example, the error rate is included in this, and the error amount included in the decoded data is also included in this. included.

In the decoder of the present invention, when considering both the noise characteristics of the encoded data and the error characteristics of the decoded data input to the input port as the transmission characteristics of the communication path, the number of times In the determination unit, the larger number of iterations of the number of iterations of the decoding operation specified based on the noise characteristics of the encoded data and the number of iterations of the decoding operation specified based on the error characteristics of the decoded data is determined. It is preferable to select (Claim 1 ).
In this case, since the number determination unit selects the larger number of iterations, the number of iterations of the decoding operation is not reduced based on only the change of one parameter, and the decoding quality can be maintained.

A receiving device according to the present invention (Claim 2 ) is a receiving device that receives and decodes encoded data transmitted to a communication channel, and a demodulator that digitally demodulates the received encoded data and a demodulator And a decoder corresponding to claim 1 for decoding the digital signal of the encoded data.
The decoding method of the present invention (Claim 3 ) is a method for decoding encoded data to obtain decoded data by performing error correction decoding by iterative decoding on encoded data transmitted to a communication path, The number of iterations of the decoding operation specified based on the noise characteristics of the encoded data and the number of iterations of the decoding operation specified based on the error characteristics of the decoded data are selected and selected. Error correction decoding by the iterative decoding method is performed by the number of iterations .

Furthermore, a communication system according to the present invention (Claim 4 ) includes a transmitting device that transmits encoded data to a communication path, and a receiving device that receives and decodes the transmitted encoded data. A communication system having a decoder that repeatedly performs a decoding method on the received encoded data to obtain decoded data, wherein the receiving device specifies a decoding operation specified based on a noise characteristic of the encoded data And the larger number of iterations of the decoding operation specified based on the error characteristics of the decoded data, and error correction decoding by the iterative decoding method is performed at the selected number of iterations. Features.

According to the above receiving apparatus, decoding method, and communication system, the number of decoding calculation iterations is determined based on the transmission characteristics of the communication channel, and then error correction decoding is performed using the iterative decoding method. The number of arithmetic iterations can be adjusted.
For this reason, it is possible to prevent the occurrence of decoding with a predetermined quality because the number of iterations is too small, or the occurrence of latency and unnecessary power consumption due to too many iterations. Can be performed efficiently.
In addition, according to the reception apparatus, decoding method, and communication system, the number of iterations of the decoding operation specified based on the noise characteristics of the encoded data and the number of iterations of the decoding operation specified based on the error characteristics of the decoded data Of these, the larger number of iterations is selected, so that the number of iterations of the decoding operation is not reduced based on only the change of one parameter, and the decoding quality can be maintained.

As described above, according to the present invention, the number of decoding computation iterations can be adjusted according to the condition of the communication channel, so that error correction decoding by an iterative decoding method can be performed efficiently.
In addition, according to the present invention , the larger iteration of the number of iterations of the decoding operation specified based on the noise characteristic of the encoded data and the number of iterations of the decoding operation specified based on the error characteristic of the decoded data Since the number of times is selected, the number of iterations of the decoding operation is not reduced based on only the change of one parameter, and the decoding quality can be maintained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 is a diagram showing a configuration example of a communication system having a decoder according to the first embodiment of the present invention. As shown in FIG. 1, the communication system includes a transmission device (transmission-side communication device) S that transmits encoded data, and a reception device (reception-side communication device) R that receives and decodes the encoded data. ing.

The transmission device S adds a redundant bit for error correction to transmission information to generate a transmission code (encoded data), and a predetermined (K + M) bit code from the encoder 1 And a modulator 2 that modulates and outputs to the communication path 3 in accordance with the above method.
The encoder 1 adds M bits of redundant bits for parity calculation to the K bits of information to generate (K + M) bits of LDPC (low density parity check) encoded data. In the low density parity check matrix, rows correspond to redundant bits and columns correspond to code bits.

It should be noted that, in which bits of the (K + M) bits of LDPC encoded data, the K information bits and the M redundant bits are arranged as determined by the transmission side and the reception side. Also good.
The modulator 2 performs modulation such as amplitude modulation, phase modulation, code modulation, frequency modulation or orthogonal frequency division multiplexing modulation according to the configuration of the communication path 3.

  For example, when the communication path 3 is an optical fiber, the modulator 2 performs light intensity modulation (a kind of amplitude modulation) by changing the luminance of the laser diode according to the transmission information bit value. In other words, when the transmission data bit is “0”, it is converted to “+1”, and the light emission intensity of the laser diode is increased for transmission. When the transmission data bit is “1”, it is changed to “−1”. After conversion, the emission intensity of the laser diode is weakened and transmitted.

The receiving device R demodulates the modulated signal transmitted via the communication path 3 to demodulate the (K + M) bit digital code, and the (K + M) bit from the demodulator 4. And a decoder 5 that performs decoding processing on the code based on the parity check matrix to reproduce the original K-bit information.
The demodulator 4 performs demodulation processing according to the transmission form in the communication path 3. For example, in the case of amplitude modulation, phase modulation, code modulation, frequency modulation, orthogonal frequency division multiplexing modulation, etc., the demodulator 4 performs processing such as amplitude demodulation, phase demodulation, code demodulation, and frequency demodulation.

FIG. 2 is a diagram showing a list of correspondence relationships between output data of the modulator 2 and the demodulator 4 when the communication path 3 is an optical fiber.
In FIG. 2, as described above, when the communication path 3 is an optical fiber, the modulator 2 converts the transmission data to “1” when the transmission data is “0”, and the transmission laser diode (light emitting diode) When the emission intensity increases and the transmission data bit is “1”, it is converted to “−1”, and the emission intensity of the laser diode is reduced to transmit.

The light intensity transmitted to the demodulator 4 due to transmission loss in the communication path 3 has an analog intensity distribution from the strongest intensity to the weakest intensity. The demodulator 4 performs a quantization process (analog / digital conversion) on the input optical signal to detect the received light level.
FIG. 2 shows the received signal intensity when the light reception level is quantized in eight steps. That is, when the light reception level is data “7”, the light emission intensity is considerably high, and when the light reception level is “0”, the light intensity is considerably low.

Each received light level is associated with signed data and output from the demodulator 4. The output of the demodulator 4 is data “3” when the light reception level is “7”, and data “−4” when the light reception level is “0”. Therefore, the demodulator 4 outputs a multilevel quantized signal with respect to the 1-bit received signal.
The decoder 5 receives (K + M) bits of received encoded data (each bit includes multi-value information) input from the demodulator 4 and follows a sum-product decoding method or a min-sum decoding method. An original K-bit information is restored by applying an LDPC parity check matrix.

In FIG. 2, the demodulator 4 generates bits quantized to 8 levels. However, in general, the demodulator 4 can perform decoding using bits quantized to L values (L ≧ 2).
In FIG. 2, a binary signal may be generated by using a comparator to determine the level of the received signal using a certain threshold value.

FIG. 3 is a diagram schematically showing the configuration of the decoder 5.
In FIG. 3, the demodulator 4 and the communication path 3 are also shown.
The demodulator 4 includes a demodulation circuit 4a that demodulates a signal applied from the communication path 3, and an analog / digital conversion circuit 4b that converts an analog demodulated signal generated by the demodulation circuit 4a into a digital signal. Output data (encoded data) Xn from the digital conversion circuit 4 b is supplied to the decoder 5.

The decoder 5 includes a decoding circuit configured by a plurality of electronic circuits arranged on a semiconductor chip or a substrate. The decoder 5 has a data input port (data input terminal) 5a for encoded data Xn, and the data input port 5a is connected to the output of the analog / digital conversion circuit 4b.
The encoded data Xn given to the decoder 5 is L value (L ≧ 2) data. Since the encoded data Xn is multilevel quantized data, hereinafter, the data Xn may be referred to as a symbol.

The decoder 5 performs a decoding process on the input symbol Xn sequence according to a decoding method such as a so-called sum-product decoding method or a min-sum decoding method, and generates a code bit Cn as decoded data. The decoded data Cn is output from the data output port (data output terminal) 5b of the decoding circuit to the outside of the decoder 5.
The decoder 5 also includes a log likelihood ratio calculation unit 6 that generates the log likelihood ratio λn of the demodulated symbol Xn from the demodulator 4 and a decoding processing unit (also simply referred to as “processing unit”) that performs the decoding process. .) 7.

The log likelihood ratio calculation unit 6 generates a log likelihood ratio λn independently of the noise information of the received signal. Normally, when noise information is taken into consideration, this log likelihood ratio λn is given by Xn / (2 · σ · σ). Here, σ represents noise variance.
However, in this embodiment, the log likelihood ratio calculation unit 6 is formed of a buffer circuit or a constant multiplier circuit, and the log likelihood ratio λn is given by Xn · f. Here, f is a non-zero positive number.

  Further, in the min-sum decoding method, since the calculation is performed using the minimum value in the decoding process (row process) based on the parity check matrix, linearity is maintained in the signal processing. For this reason, processing such as normalization of output data according to noise information is unnecessary. In this case, by calculating the log-likelihood ratio without using noise information, the circuit configuration is simplified and the calculation process is also simplified.

  The decoding processing unit 7 includes a row processing unit 9 that performs row processing of the parity check matrix and a column processing unit 10 that performs column processing of the parity check matrix, and the operations of the row processing and the column processing are repeated. As is done, the output of the column processor 10 is provided to the row processor 9. That is, the row processing unit 9 and the column processing unit 10 are connected in a loop.

When the decoding method is the sum-product decoding method, the row processing unit 9 and the column processing unit 10 perform arithmetic processing according to the following equations (1) and (2), and perform processing on each element of the parity check matrix row. (Row processing) and processing (column processing) for each element for the column are repeatedly executed.
Specifically, the row processing unit 9 performs an operation for calculating the external value logarithmic ratio (first variable) αmn according to the equation (1), and the column processing unit 10 calculates the prior value logarithmic ratio βmn according to the equation (2). Perform the calculation.

In the above formulas (1) and (2), n′εA (m) \ n and m′εB (n) \ m mean elements other than themselves. For the external value log ratio αmn, n ′ ≠ n, and for the prior value log ratio βmn, m ′ ≠ m.
Further, the subscript “mn” indicating the position in the matrix of α and β is usually indicated by a subscript, but in this specification, it is indicated by “horizontal characters” for the sake of readability.
In the equation (1), f is a Gallager f function, and the function sign (x) is defined by the following equation (3).

In addition, the sets A (m) and B (n) have the set [1, N] = {1, 2, when the binary M · N matrix H = [Hmn] is the parity check matrix of the LDPC code to be decoded. .., N}.
A (m) = {n: Hmn = 1} (4)
B (n) = {m: Hmn = 1} (5)

That is, the subset A (m) means a set of column indexes where 1 (non-zero element) stands in the m-th row of the parity check matrix H, and the subset B (n) A set of row indexes where 1 (non-zero element) stands in the n-th column is shown.
In order to explain more specifically, for example, a check matrix H shown in FIG. 4 is considered.
In the parity check matrix H of FIG. 4, “1” is set in the first to third columns of the first row, “1” is set in the third and fourth columns of the second row, and the third “1” stands in the fourth column to the sixth column of the row. Therefore, in this case, the subset A (m) is as follows.

A (1) = {1, 2, 3}
A (2) = {3,4}
A (3) = {4, 5, 6}

Similarly, the subset B (n) is as follows.
B (1) = B (2) = {1}
B (3) = {1, 2}
B (4) = {2,3}
B (5) = B (6) = {3}

In the parity check matrix H, when a Tanner graph is used, the connection relationship between a variable node corresponding to a column and a check node corresponding to a row is indicated by “1”. This is referred to as “1” stands ”in this specification.
That is, as shown in FIG. 5, the variable nodes 1, 2, and 3 are connected to the check node X (first row), and the variable nodes 3 and 4 are connected to the check node Y (second row). The variable nodes 4, 5, and 6 are connected to the check node Z (third row).

This variable node corresponds to a column of the check matrix H, and check nodes X, Y, and Z correspond to each row of the check matrix H. Therefore, the parity check matrix shown in FIG. 4 is applied to a code having a code length of 6 bits in total including 3 information bits and 3 redundant bits.
In the LDPC parity check matrix H, the number of “1” s is small, and the parity check matrix is a low density, thereby reducing the amount of calculation. Each condition probability P (Xi | Yi) is propagated between the variable node and the check node, and a likely code is determined for each variable node according to the MAP algorithm. Here, the conditional probability P (Xi | Yi) indicates the probability of being Xi under the condition of Yi.

As shown in FIG. 3, the decoder 5 includes a determination unit 11 that determines the end of repetition of decoding operations including row processing and column processing.
The determination unit 11 determines whether or not the number of iterations of row processing and column processing has reached the number of end times. When the number of repetitions of row processing and column processing reaches the number of end times, the decoding processing unit 7 performs a decoding change. Terminate the calculation iteration.

Further, the determination unit 11 has a function of determining a code by using the external value log ratio αmn (or the prior value log ratio βmn) and the log likelihood ratio λn after the decoding operation is repeated.
Specifically, the determination unit 11 calculates Qn according to the following equation (6).

Furthermore, the determination unit 11 calculates an estimated code Cn that is decoded data according to the following equation (7).

In addition, the decoder 5 includes a number-of-times determination unit 12 that determines the number of iterations of decoding operation based on the signal-to-noise ratio (SNR) of the encoded data Xn, which is one of the parameters indicating the transmission characteristics of the communication path 3; A lookup table 13 referred to by the number determination unit 12 is provided. The determination unit 11 acquires the iteration number information In determined by the number determination unit 12.
The number-of-times determination unit 12 calculates the signal-to-noise ratio of the encoded data Xn by extracting the pilot signal included in the header portion of the encoded data Xn and the like and counting the correctness of the pilot signal extracted by the extraction circuit And an arithmetic circuit that can independently calculate the signal-to-noise ratio from the encoded data Xn input from the demodulator 4.

FIG. 6 shows an example of the lookup table 13.
In the example shown in FIG. 6, if the signal-to-noise ratio is 2 dB or less, the transmission characteristic of the communication path 3 is poor, so the number of repetitions is set to 20 which is relatively large. If the signal-to-noise ratio is in the range of 2 to 6 dB, the transmission characteristic of the communication path 3 is normal, and the number of repetitions is set to the normal 8 times. Further, if the signal-to-noise ratio is 6 dB or more, the transmission characteristic of the communication path 3 is good.

As described above, according to the decoder 4 of the present embodiment, the number determination unit 12 repeats the decoding operation by the decoding processing unit 7 based on the signal-to-noise ratio of the encoded data Xn indicating the transmission characteristics of the communication path. Therefore, the number of decoding calculation iterations can be adjusted according to the condition of the communication path.
For this reason, it is possible to prevent the occurrence of decoding with a predetermined quality because the number of iterations is too small, or the occurrence of latency and unnecessary power consumption due to too many iterations. Can be performed efficiently.

Further, according to the decoder 5 of the present embodiment, the parameter for determining the number of iterations of the decoding operation is the signal-to-noise ratio of the encoded data Xn, and the signal using the pilot signal included in the encoded data Xn Since the noise ratio is calculated, the signal-to-noise ratio for determining the number of iterations can be obtained autonomously in the decoder 5, and there is an advantage that the implementation is simple.
In the first embodiment, as the noise characteristics of the encoded data Xn, noise power or noise amount is calculated instead of the signal-to-noise ratio (SNR), and the number of iterations is determined based on this index. Good.

[Second Embodiment]
FIG.7 and FIG.8 is a figure which shows the structural example of the receiver R which has the decoder 5 which concerns on 2nd embodiment of this invention.
The decoder 5 of the second embodiment is different from that of the first embodiment in that it further includes an input port 5c for inputting the error rate of the decoded data Cn from the outside. The number of iterations of the decoding operation can be determined not only by the signal-to-noise ratio, which is the noise characteristic of the data Xn, but also by the error rate of the decoded data Cn input to the input port 5c.

In this embodiment, the communication control unit 30 is connected to the data output port 5b of the decoder 5, and a terminal device 40 such as a personal computer capable of calculating the error rate of the decoded data Cn is connected to the communication control unit 30. It is connected.
The terminal device 40 sends the error rate information Tx calculated from the decoded data Cn to the communication control unit 30, and this information Tx is input to the number determining unit 12 of the decoder 5 from the input port 5c. Yes.

FIG. 9 shows the lookup table 14 of the decoder 5 of the second embodiment, and FIG. 10 is a graph showing an example of the relationship between the signal-to-noise ratio (SNR) and the error rate.
For example, as shown in FIG. 10, the signal-to-noise ratio of the encoded data Xn and the error rate of the decoded data Cn generally have a one-to-one relationship in which the latter decreases as the former increases. Therefore, in the lookup table 14 shown in FIG. 9, the error rate range of the decoded data Cn corresponding to the range of the signal-to-noise ratio of the encoded data Xn, and the number of iterations of the decoding operation when those parameters are within the range. Are defined respectively.

The number-of-times determination unit 12 has a large number of repetitions of the decoding operation specified based on the signal-to-noise ratio of the encoded data Xn and the number of repetitions of the decoding operation specified based on the error rate of the decoded data Cn. The number of iterations is selected.
Thus, according to the decoder 5 of the present embodiment, the number of iterations of the decoding operation can be determined also from the error rate of the decoded data Cn, so that the decoding result of the decoding processing unit 7 is used as the iteration of the decoding operation. Feedback can be provided in determining the number of times.

In the present embodiment, the number determination unit 12 repeats the decoding operation specified based on the number of decoding operations specified based on the signal-to-noise ratio of the encoded data Xn and the error rate of the decoded data Cn. Of the number of times, the larger number of iterations is selected, so that the number of iterations of the decoding operation is not reduced depending on only the change of one parameter, and the decoding quality can be maintained appropriately.
In the second embodiment, the number of decoding calculation iterations may be determined based only on the error rate of the decoded data Cn.
In the second embodiment, as the error characteristic of the decoded data Cn, the error amount included in the decoded data Cn may be calculated instead of the error rate, and the number of iterations may be determined based on this index.

[Other Embodiments]
By the way, in the communication system of each of the above embodiments, the communication quality is improved by increasing the number of decoding iterations. However, the transmission rate may not be increased due to delay even if the number of iterations is excessively increased. And the number of iterations are in a trade-off relationship.

Trade-off mode Therefore, the transmission rate × (1−error rate) is used as an evaluation function, and control logic for determining the transmission rate and the number of iterations of the decoding operation is performed in the frequency determination unit 12 so that the evaluation function is maximized. You may make it let.
In this case, since the number of repetitions is determined so that the number of bits of data that normally arrives is maximized, the number of repetitions can be determined more appropriately in consideration of the relationship with the transmission rate.

  However, in this case, since not only the number of decoding computation iterations but also the transmission rate is autonomously changed on the reception device R side, information on the transmission rate determined on the reception device R side is transmitted to the transmission device S. It is necessary to add a function for notifying the receiving device R to the receiving device R.

○ Speed priority mode On the other hand, assuming a unidirectional communication environment such as broadcast communication, in this case, the transmission device S side may broadcast uniform data rather than considering the communication quality on the reception device R side. It is important.
Therefore, in such a case, it is recommended to use a communication system that gives priority to the transmission rate over the quality of each receiving device R and performs the following control.

That is, first, a predetermined transmission rate is determined in the transmission device S, and the number of iterations that can be performed at the transmission rate determined by the transmission device S is set as the upper limit value of the number of iterations of decoding operations performed in the reception device R. This upper limit value can be described in the header portion of the encoded data Xn and notified to the receiving device R side.
Then, the reception device R determines the number of iterations so that a desired communication quality is obtained within the range of the upper limit value determined by the transmission device S. If importance is placed on reducing power consumption, the number of iterations may be set to the minimum within the range of the upper limit value determined above.

○ Quality priority mode On the other hand, assuming the case of one-to-one bi-directional communication, in this case communication quality is regarded as important. First, after determining the number of iterations so that the desired communication quality can be obtained. The transmission rate may be determined based on the determined number of repetitions.

The present invention is not limited to the above embodiments.
For example, the decoder based on the iterative decoding method is not limited to the LDPC decoder, and may be a decoder based on another iterative decoding method such as a turbo decoder.

It is a schematic block diagram of the communication system of 1st embodiment. It is a figure which shows an example of a response | compatibility with transmission data and demodulation data. It is a block diagram of the decoder of 1st embodiment. It is a figure which shows an example of a check matrix. 5 is a Tanner graph of the parity check matrix shown in FIG. It is a figure which shows an example of a lookup table. It is a block diagram of the decoder of 2nd embodiment. It is a block diagram of the receiver of 2nd embodiment. It is a figure which shows an example of a lookup table. It is a graph which shows the relationship between a signal noise ratio and an error rate.

Explanation of symbols

1: Encoder 2: Modulator 3: Communication path 4: Demodulator 4a: Demodulator circuit 4b: Analog / digital conversion circuit 5: Decoder 5a: Encoded data input port 5b: Decoded data output port 5c: Error rate input Port 6: Log likelihood ratio calculation unit 7: Decoding processing unit 9: Row processing unit 10: Column processing unit 11: Determination unit 12: Number of times determination unit 13: Look-up table 14: Look-up table 30: Communication control unit 40: Terminal device S: Transmitting device R: Receiving device Xn: Encoded data Cn: Decoded data

Claims (4)

A decoder that obtains decoded data by performing error correction decoding on encoded data transmitted to a communication path,
A decoding processing unit that performs error correction decoding of the encoded data by an iterative decoding method that repeatedly performs a decoding operation;
A number-of-times determining unit that determines the number of iterations of the decoding operation based on the transmission characteristics of the communication path ;
An input port for inputting the error characteristics of the decrypted data from the outside, and
Transmission characteristics of the communication path are noise characteristics of the encoded data and error characteristics of the decoded data input to the input port,
The number-of-times determination unit is the larger number of iterations of the number of iterations of decoding specified based on the noise characteristics of the encoded data and the number of iterations of decoding specified based on error characteristics of the decoded data The decoder characterized by selecting . A receiving device that receives and decodes encoded data transmitted to a communication path,
A demodulator for digitally demodulating the received encoded data;
Receiving apparatus characterized by and a decoder according to claim 1 for decoding a digital signal of the coded data which are demodulated. There is a decoding method of encoded data to obtain decoded data by performing error correction decoding by an iterative decoding method on the encoded data transmitted to the communication path,
The number of iterations of the decoding operation specified based on the noise characteristics of the encoded data and the number of iterations of the decoding operation specified based on the error characteristics of the decoded data are selected and selected. A decoding method of encoded data, characterized in that error correction decoding by the iterative decoding method is performed by the number of iterations . A transmission device that transmits encoded data to a communication path; and a reception device that receives and decodes the transmitted encoded data. The reception device performs an iterative decoding method on the received encoded data. A communication system having a decoder that performs decoding to obtain decoded data,
The receiving apparatus determines the larger number of iterations of the number of iterations of the decoding operation specified based on the noise characteristics of the encoded data and the number of iterations of the decoding operation specified based on the error characteristics of the decoded data. A communication system comprising : selecting and performing error correction decoding by the iterative decoding method at a selected number of iterations .

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