CN115225202A - A concatenated encoding and decoding method - Google Patents

Abstract

The method for cascade coding and decoding adopts RS codes as external codes and adopts a multilayer coding idea as internal codes by utilizing the characteristic that low bits of each transmission symbol are easier to make mistakes than high bits after transmission data are modulated. The outer code of the cascade coding method adopts RS code, interweaves RS code word data, divides the interweaved data into bit data with preset quantity groups, codes each group of bit data by adopting code words with different code rates to obtain multi-layer sub-code word data with preset quantity groups, and modulates to obtain modulated data; wherein, the length of each group of multi-layer sub-code word data is consistent and respectively corresponds to different bits in the modulation data. The cascade coding method uses shorter code length to realize higher coding gain under the condition of certain code rate; the cascade decoding uses the low-order decoding result to assist in demodulating and decoding the high-order data in the channel receiving data, obtains higher decoding performance, and meets the decoding performance requirement of the Ethernet with the speed of over 400 Gb/s.

Description

A concatenated encoding and decoding method

technical field

The present application relates to the technical field of digital communication encoding and decoding, and in particular, to a concatenated encoding and decoding method.

Background technique

In a digital communication system, the source generates data and sends it out through the channel. However, the channel will cause interference to the transmitted data, so that the sink cannot correctly receive the transmitted data. Generally, the forward error correction (FEC) method is used to correct the errors generated in the transmission, that is, the data transmitting end encodes the data generated by the source, and the data receiving end uses the corresponding decoding algorithm to detect and correct the errors. The encoded data is transmitted to the sink.

According to the latest Ethernet standard, two RS codes (Reed-Solomon, Lisuo code) are applied to the Ethernet sublayer as FEC schemes, corresponding to the RS (528, 514) codes of the KR4 FEC scheme in the Ethernet standard and Corresponds to the RS(544,514) code of the KP4 FEC scheme in the Ethernet standard.

However, as the transmission rate of Ethernet is getting higher and higher, the Ethernet standard above 400Gb/s is being studied, and the decoding performance requirements of the FEC scheme are also getting higher and higher. Under the premise of a certain code rate, in order to increase the coding gain of the above-mentioned FEC scheme, the code length of the code word needs to be increased, but the increase of the code length will increase the complexity of the communication system and occupy too much hardware resources. Therefore, the above-mentioned FEC scheme of a single RS code word cannot meet the decoding performance requirements of Ethernet applications exceeding 400 Gb/s.

SUMMARY OF THE INVENTION

In order to solve the problem that the above single codeword FEC method cannot meet the decoding performance requirements of Ethernet applications exceeding 400Gb/s, the present application provides a concatenated encoding and decoding method through the following aspects.

A first aspect of the present application provides a concatenated encoding method, and the concatenated encoding method includes:

Receive the source data sent by the source;

RS encoding is performed on the source data to obtain RS codeword data;

Interleaving the RS codeword data according to a preset interleaving depth to obtain interleaved data;

The interleaved data are grouped to obtain a preset number of groups of bit data; wherein, the preset number is the number of bits corresponding to one symbol in the preset modulation mode, and each group of bit data corresponds to different preset modulation modes. bit;

Multi-layer coding is performed on the bit data of a preset number of groups to obtain multi-layer codeword data; wherein the multi-layer codeword data includes a preset number of groups of multi-layer sub-codeword data, and the lengths of each group of multi-layer sub-codeword data are consistent ; The check bit length in the multi-layer sub-code word data corresponding to the most significant bit in the preset modulation mode is less than the check bit length in the multi-layer sub-code word data corresponding to the least significant bit in the preset modulation mode;

The multi-layer codeword data is modulated according to a preset modulation mode to obtain modulated data for channel transmission.

Optionally, when the preset modulation mode is PAM4, the preset number of sets of bit data includes a set of high-order bit data and a set of low-order bit data;

The multi-layer encoding is performed on the bit data of the preset number of groups to obtain multi-layer codeword data, including:

Encoding the low-order bit data according to the first code rate to obtain low-order multi-layer sub-codeword data;

Encoding the high-order bit data according to the second code rate to obtain high-order multi-layer sub-codeword data;

The first code rate is less than the second code rate, the high-order multi-layer sub-codeword data corresponds to the most significant bit in the PAM4 modulation mode, and the low-order multi-layer sub-codeword data corresponds to the least significant bit in the PAM4 modulation mode.

Optionally, when the preset modulation mode is PAM4, the preset number of sets of bit data includes a set of high-order bit data and a set of low-order bit data;

The multi-layer encoding is performed on the bit data of the preset number of groups to obtain multi-layer codeword data, including:

Encoding the low-order bit data according to the third code rate to obtain low-order multi-layer sub-codeword data;

The high-order bit data is directly output without encoding, and the high-order multi-layer sub-codeword data is obtained;

The high-order multi-layer sub-codeword data corresponds to the most significant bit in the PAM4 modulation mode, and the low-order multi-layer sub-codeword data corresponds to the least significant bit in the PAM4 modulation mode.

A second aspect of the present application provides a concatenated decoding method for decoding modulated data obtained according to the concatenated encoding method described in the first aspect of the present application; the concatenated decoding method includes:

Perform a first demodulation process on the channel received data according to a preset modulation mode to obtain a first number of low-order demodulated data; decode the low-order demodulated data to obtain low-order data

Using the low-order bit data to assist in processing the channel received data to obtain a second quantity of high-order bit data; wherein, the first quantity plus the second quantity is equal to a preset quantity, and the preset quantity is a symbol corresponding to a preset modulation mode the number of bits;

Perform de-interleaving processing on high-order bit data and low-order bit data to obtain de-interleaving data;

RS decoding is performed on the deinterleaved data to obtain RS decoding data;

The RS decoded data is sent to the sink.

Optionally, when the preset modulation mode is PAM4, the first quantity and the second quantity are both equal to 1; the low-order bit data corresponds to the least significant bit in the modulation data, and the high-order bit data corresponds to the most significant bit in the modulation data;

The use of low-order bit data to assist in processing the channel received data to obtain high-order bit data, including:

When the most significant bit in the modulated data is not encoded in the multi-layer coding process, the second demodulation process is performed using a hard-decision method for the most significant bit of the channel received data using the auxiliary data of the low-order bits to obtain high-order bit data;

When the most significant bit in the modulated data is encoded in the multi-layer encoding process, the low-order bit data is used to assist in the third demodulation process using the hard decision method or the soft decision method for the most significant bit of the channel received data. The result is decoded to obtain high-order bit data; wherein, when the third demodulation process is performed by using a hard decision, the demodulation result is decoded by a hard decoding method; when the third demodulation process is performed by a soft decision method, The demodulation result is decoded by soft decoding.

Optionally, before sending the RS decoding data to the sink, the concatenated decoding method includes:

Perform iterative decoding on the RS decoded data to obtain RS iteratively decoded data;

Send the RS iteratively decoded data to the sink;

Wherein, performing iterative decoding on the RS decoding data to obtain RS iterative decoding data, including:

Interleaving the RS decoded data to obtain iterative input data; wherein the iterative input data includes low-order iterative input data and high-order iterative input data;

Decoding low-order iterative input data to obtain low-order iterative bit data;

When the most significant bit in the modulated data is not encoded in the multi-layer encoding process, the second demodulation process is performed by using the low-order iterative bit data to assist the high-order iterative input data in a hard-decision manner to obtain high-order iterative bit data;

When the most significant bit in the modulated data is encoded in the multi-layer encoding process, the low-order iterative bit data is used to assist the high-order iterative input data to perform the third demodulation process in a hard-decision mode or a soft-decision mode, and the demodulation result is decoded. code to obtain high-order iterative bit data; wherein, when the third demodulation process is performed in the hard decision mode, the demodulation result is decoded in the hard decoding mode; when the third demodulation process is performed in the soft decision mode, the The demodulation result is decoded by soft decoding;

Perform de-interleaving processing on the high-order iterative bit data and the low-order iterative bit data to obtain de-interleaving iterative data;

Perform RS decoding on the deinterleaved iterative data to obtain RS iteratively decoded data;

The RS iteratively decoded data is sent to the sink.

Optionally, when the low-order iterative input data is decoded in a hard decoding manner, the check bit in the low-order iterative input data is set as the check bit in the low-order bit data.

Optionally, when the low-order iterative input data is decoded by soft decoding, the maximum likelihood ratio of the information bits in the low-order iterative data is set to be the most reliable, and the maximum likelihood ratio of the check bits in the low-order iterative input data is set to be the most reliable. is the maximum likelihood ratio in the low-order demodulated data.

Optionally, when performing the first demodulation process on the channel received data according to the PAM4 modulation mode, a hard decision method is used to obtain low-order demodulation data;

When decoding the low-order demodulated data, a hard decoding method is adopted to obtain low-order bit data.

Optionally, when performing the first demodulation process on the channel received data according to the PAM4 modulation mode, a soft decision mode is used to obtain low-order demodulation data;

When decoding the low-order demodulated data, a soft decoding method is used to obtain low-order bit data.

The present application provides a concatenated encoding and decoding method. In this application, after the transmission data is modulated, the low-order bits of each transmission symbol are more prone to errors than the high-order bits, and proposes a concatenated coding method in which the outer code adopts the RS code, and the inner code adopts the multi-layer coding idea and the corresponding level Linked decoding method. The outer code of the cascading coding method adopts RS code, and the RS codeword data is interleaved, and then the interleaved data is divided into a preset number of groups of bit data, and each group of bit data is performed using codewords with different code rates. encoding to obtain a preset number of groups of multi-layer sub-codeword data, and then modulating to obtain modulated data; wherein, each group of multi-layer sub-codeword data has the same length and corresponds to different bits in the modulation data respectively. The concatenated coding method achieves higher coding gain by using a shorter code length under a certain code rate.

When decoding, first demodulate and decode the low-order bits in the channel received data to obtain low-order bit data; use the low-order bit data to assist in processing the high-order bits in the channel received data to obtain high-order bit data; The low-order bit data is deinterleaved and RS decoded, and the RS decoded data is obtained and sent to the sink. The FEC solution using the concatenated encoding and decoding method provided by the present application can meet the decoding performance requirements of Ethernet applications exceeding 400 Gb/s.

Description of drawings

1 is a schematic structural diagram of a communication system using two codes to form concatenated codes;

2 is a schematic flowchart of a concatenated encoding method provided by an embodiment of the present application;

3 is a schematic diagram of a division manner for grouping interleaved data in a concatenated coding method provided by an embodiment of the present application;

4 is a schematic diagram of an example of MLC coding in a concatenated coding method provided by an embodiment of the present application;

Fig. 5 is a kind of constellation diagram example of modulated data in 16QMA modulation mode;

6 is a schematic flowchart of a cascade decoding method provided by an embodiment of the present application;

7 is a schematic diagram of an MLC encoding and decoding process in a cascaded decoding method provided by an embodiment of the present application;

FIG. 8 is a schematic diagram of a process of performing hard-decision demodulation on channel received data using the assistance of low-order bit data in a cascade decoding method provided by an embodiment of the present application;

9 is a schematic diagram of a process in which low-order bit data assists in processing channel received data to obtain high-order bit data in a cascade decoding method provided by an embodiment of the present application;

10 is a schematic diagram showing the comparison of the decoding performance simulation results of experimental group 1, comparison group 1 and comparison group 2;

11 is a schematic diagram of the comparison of the decoding performance simulation results of experimental group 2 and experimental group 3;

12 is a schematic diagram showing the comparison of the decoding performance simulation results of the experimental group 1, the experimental group 4, the experimental group 5 and the comparison group 1.

Detailed ways

In order to facilitate the explanation of the technical solution of the application, the concept of concatenated coding involved in the application is briefly introduced first.

A concatenated code is composed of two or more simple codes, and FIG. 1 exemplarily shows a schematic structural diagram of a communication system in which two codes form a concatenated code. As shown in Figure 1, the concatenated code consists of an outer code (usually non-binary) and an inner code (usually binary), which are two independent codes transmitted serially on a channel. The data sent by the source is first encoded with the outer code, then interleaved and then encoded with the inner code, and then transmitted through the channel. The concatenated code adopts a two-level decoding method at the decoding end, and the inner code is first decoded and deinterleaved. Then perform outer code decoding.

Referring to FIG. 2 , it is a schematic flowchart of the concatenated encoding method provided by the first embodiment of the present application. The concatenated encoding method includes steps 11 to 16 .

Step 11: Receive the source data sent by the source. The information source is the data generating end and the transmitting end in the communication system, which converts various messages into original electrical signals, and is referred to as source data in this application.

Step 12: Perform RS encoding on the source data to obtain RS codeword data.

In this embodiment, the outer code adopts the RS codeword. In the latest Ethernet standard, two RS codewords are used to encode the source data. RS codes are transmitted in the form of symbols. One is RS (528, 514) code, which corresponds to the KR4 FEC scheme in the Ethernet standard; among them, an RS code word has a total of 528 symbols and 514 information symbols. . The other is RS (544, 514) code, in which one RS code word has 544 symbols in total and 514 information symbols; it corresponds to the KP4 FEC scheme in the Ethernet standard. 1 symbol is 1 symbol (number of symbols), and 1 symbol=10 bits.

Step 13: Interleave the RS codeword data according to a preset interleaving depth to obtain interleaved data.

The symbol-level row-column interleaving is performed on the RS codeword data, and the preset interleaving depth is I, where I can be any positive integer. However, the delay will increase with the increase of I. In practical applications, an appropriate I should be configured according to requirements such as delay and throughput.

Step 14: Group the interleaved data to obtain a preset number of groups of bit data. The preset number is the number of bits corresponding to one symbol in the preset modulation mode, and each group of the bit data corresponds to different bits in the preset modulation mode.

Step 15: Multi-layer coding is performed on the bit data of a preset number of groups to obtain multi-layer codeword data; wherein, the multi-layer codeword data includes a preset number of groups of multi-layer sub-codeword data, and each group of multi-layer sub-codewords. The length of the data is the same; the length of the parity bit in the multi-layer sub-codeword data corresponding to the most significant bit in the preset modulation mode is smaller than the check bit length in the multi-layer sub-codeword data corresponding to the least significant bit in the preset modulation mode bit length.

In this embodiment, the execution process of steps 14-15 is described by adopting the PAM4 (4 Pulse Amplitude Modulation, fourth generation pulse amplitude modulation) modulation mode and using the RS (544, 514) code as the outer code. In PAM4 modulation, two bits are modulated into one symbol, and the preset number is equal to 2. Divide the interleaved data into N parts first, each part contains 2k bits of data, and divide the 2k bits of data into high-order bit data (k ₁ in total) and low-order bit data (k ₂ in total); wherein, 2k= k ₁ +k ₂ , k ₁ >k ₂ ; that is, the interleaved data is divided into two groups, the first group contains N pieces of k ₁ bit data, corresponding to the most significant bit (Most Significant Bit, MSB) in PAM4 modulation The second group contains N pieces of k ₂ -bit data, corresponding to the data on the least significant bit (Least Significant Bit, LSB) in the PAM4 modulation.

In practical applications, there are various ways to divide the 2k bit data into high-order bit data (k ₁ in total) and low-order bit data (k ₂ in total). FIG. 3 shows an example of a division manner of dividing 2k bit data into high-order bit data (k ₁ in total) and low-order bit data (k ₂ in total) given in this embodiment. As shown in Figure 3, the first 2k ₁ bit data in the 2k bit data are divided according to the order of parity, the odd number is the high-order bit data, the even number is the low-order bit data; the following (k ₂ -k ₁ ) data are the high-order bits data. In other examples, the division may also be performed in other orders, as long as 2k=k ₁ +k ₂ and k ₁ >k ₂ are satisfied, and the present application does not specifically limit the division method.

Multi-level coding (MLC) is performed on the high-order bit data and the low-order bit data to obtain multi-layer codeword data (referred to as MLC codeword data in this application). In this embodiment, taking the preset modulation mode as PAM4 as an example, the multi-layer codeword data includes two groups of MLC sub-codeword data. The BCH code is selected as the component code of MLC encoding, that is, the high-order bit data and the low-order bit data are encoded with BCH codes of different code rates, and two sets of MLC sub-codeword data with the same length are obtained; The length is n, and the length of one MLC codeword data is 2n.

Referring to FIG. 4 , it is a schematic diagram of an example of MLC encoding in this embodiment. We know from the calculation formula of the code rate (code rate=information bit length/code length) that when the code rate and code length are constant, the bit data length of the information bit is also constant. In Fig. 4, _k is the average value of _k1 and k2. In practical applications, according to the design requirements of the actual communication system, combined with the code rate rate and code length 2n of the MLC codeword, the information bit length 2k of the MLC codeword is deduced, and the appropriate k ₁ and k ₂ are further deduced.

In an implementation manner, in MLC encoding, the BCH code of the first code rate is used to encode the low-order bit data, and the BCH code of the second code rate is used to encode the high-order bit data to obtain the low-order multi-layer sub-codeword data and In the high-order multi-layer sub-codeword data, the first code rate is smaller than the second code rate, that is, the error correction capability of the low-order multi-layer sub-codeword data is higher than that of the high-order multi-layer sub-codeword data. Exemplarily, the BCH(360,320) code is used to encode the low-order bit data, and the error correction capability is 4; the high-order bit data is encoded by the BCH(360,340) code, the error correction capability is 2. Correspondingly, n=360, k ₁ =320, k ₂ =340.

In another implementation manner, the BCH code of the third code rate is used in the MLC encoding to encode the low-order bit data to obtain the low-order multi-layer sub-codeword data; the high-order bit data is not encoded, and the high-order multi-layer sub-codeword data is directly output. The codeword data, that is, the high-order multi-layer sub-codeword data, has no error correction capability. Exemplarily, the BCH (360, 320) code is used to encode the low-order bit data, corresponding k ₁ =320, k ₂ =360, and n=360.

其中，预设的交织深度设为2，外码采用RS(544，514)码，内码MLC码字的数据长度等于360(对应于高位比特数据没有纠错能力)+320(对应于低位比特数据的纠错能力为4，采用BCH(360，320)码)。In this embodiment, since the code lengths of the outer code and the inner code are different, the interleaved data is divided into N parts first, and then each part is encoded. N is determined according to the data length of the RS codeword, the preset interleaving depth, and the length of the information bits of the encoded codeword selected in the multi-layer encoding in step 15 . Exemplary,

Among them, the preset interleaving depth is set to 2, the outer code adopts RS (544,514) code, and the data length of the inner code MLC code word is equal to 360 (corresponding to the high-order bit data without error correction capability) + 320 (corresponding to the low-order bit data) The error correction capability of the data is 4, and the BCH (360, 320) code is used).

It should be noted that, in the above example, the BCH code is used as the component code for MLC encoding, and other codewords may also be used as the component code, for example, LDPC code or Polar code is used as the component code for MLC encoding.

Step 16: Modulate the multi-layer codeword data according to a preset modulation mode to obtain modulated data for channel transmission. In this embodiment, taking the PAM4 modulation method as an example, the corresponding bits of the high-order multi-layer sub-code word data (corresponding to the MSB in the modulation data) and the low-order multi-layer sub-code word data (corresponding to the LSB in the modulation data) are passed through PAM4 The modulation becomes a sign bit in the modulated data. Table 1 shows the correspondence between the multi-layer codeword data and the modulated data under the PAM4 modulation mode.

Table 1: Modulate multi-layer codeword data according to PAM4

(MSB, LSB) (0,0) (0,1) (1,0) (1,1) After PAM4 modulation -3 -1 1 3

It can be seen from the data form of the PAM4 modulated data in Table 1 that when the modulated data is less than 0, the corresponding highest bits are all 0, and when the modulated data is greater than 0, the highest bits are all 1. It can be seen from this that the most significant bit has the greatest influence on the value of the modulated data. Therefore, in the encoding process, encoding modes with different code rates are used for the bit data corresponding to the least significant bit and the most significant bit. In the decoding process, even if the least significant bit is decoded incorrectly, the value corresponding to the most significant bit can be determined only according to whether the modulated data is greater than 0 or less than 0.

5 is a schematic diagram of an example of a constellation diagram of 16QAM modulated data. Taking the unbolded two bits decoded as 00 as an example, the low-order auxiliary high-order demodulation process is shown in Table 2.

Table 2: 16QAM low-order auxiliary high-order demodulation process (take the low-order as 00 as an example)

No bold two 00 Re<1,Im>-j Re<1,Im<-j Re>1,Im>-j Re>1,Im<-j Bold two demodulation results 10 00 01

It should be noted that when data is modulated, a Gray code is generally used to reduce the possibility of errors and improve the decoding performance. However, in the coding method provided by this application, if the modulation is performed using Gray code, when the low-order bit data is used to assist in the demodulation and decoding of the high-order bit data, even if the low-order bit data is decoded correctly, the high-order bit data There is also a high chance of error. Therefore, in order to make the decoding result of the high-order bit data as reliable as possible, when the concatenated coding method of the present application is used to design the communication system, the modulation process does not use the Gray code.

This embodiment provides a concatenated encoding method. The concatenated encoding method includes receiving source data sent by a source; performing RS encoding on the source data to obtain RS codeword data; The interleaving depth is interleaved to obtain the interleaved data; the interleaved data is grouped to obtain a preset number of groups of bit data; wherein, the preset number is the number of bits corresponding to one symbol in the preset modulation mode, and each The group bit data corresponds to different bits in the preset modulation mode; multi-layer coding is performed on the bit data of a preset number of groups to obtain multi-layer codeword data; wherein the multi-layer codeword data includes a preset number of groups of multi-layer sub-codewords Data, the length of each group of multi-layer sub-codeword data is the same; the length of the parity bit in the multi-layer sub-codeword data corresponding to the most significant bit in the preset modulation mode is less than the length corresponding to the least significant bit in the preset modulation mode. Check bit length in the layer sub-codeword data; modulate the multi-layer codeword data according to a preset modulation method to obtain modulated data for channel transmission.

The concatenated coding method utilizes the characteristic that the low-order bits of each transmission symbol are more error-prone than the high-order bits after the transmission data is modulated, and the low-order bits and high-order bits of the modulation symbols respectively use inner codes with different error correction capabilities, and the modulated symbols Different bits provide different error correction capabilities. In the case of a certain code rate, using a shorter code length achieves a higher coding gain.

It should be noted that, in the above-mentioned first embodiment, the preset modulation mode is PAM4 as an example for description. The preset modulation mode in the concatenated coding method provided by the foregoing embodiment may also be other modulation modes.

Exemplarily, when the preset modulation mode is 16QAM, one symbol in the 16QAM modulation data corresponds to four bits, and the interleaved data is grouped to obtain four groups of bit data, one group of bit data corresponds to one of the 16QAM modulation data. bit. Corresponding to the order of modulation data from high to low, BCH(360,350), BCH(360,350), BCH(360,330), BCH(360,330) or BCH(360,350) can be selected as the constituent codes in the MLC codeword, respectively. BCH(360,340), BCH(360,340), BCH(360,330). As long as the following two conditions are met: after MLC encoding, the length of the MLC sub-codeword data is consistent, and the error correction capability of the MLC sub-codeword data corresponding to the least significant bit is higher than that of the MLC sub-codeword data corresponding to the most significant bit. The error correction capability of the codeword data.

Corresponding to the foregoing embodiments of the concatenated encoding method, the present application further provides an embodiment of a concatenated decoding method. Referring to FIG. 6 , it is a schematic work flow diagram of a concatenated decoding method provided by the second embodiment of the present application. The concatenated decoding method includes steps 21-26.

Step 21: Perform a first demodulation process on the channel received data according to a preset modulation mode to obtain a first number of groups of low-order demodulation data. Wherein, the channel received data refers to the modulated data obtained by the concatenated coding method provided by the first embodiment of the present application, which is transmitted through the channel and added with the channel noise signal.

In this embodiment, the first demodulation process is performed using a preset modulation mode corresponding to the concatenated coding method. The first demodulation process refers to demodulating low-order data in the channel received data to obtain low-order modulated data. When the preset modulation method in the aforementioned cascade coding method uses PAM4 modulation, the corresponding first demodulation process should also be demodulated according to the PAM4 modulation method, the first number is equal to 1, and the low-order demodulation data corresponds to PAM4 modulation. The least significant bit in the data; when 16QAM modulation is used in the preset modulation method in the aforementioned concatenated encoding method, the corresponding first demodulation process should also be demodulated according to the 16QAM modulation method, the first number is equal to 2, the low bit The demodulated data corresponds to the least significant bit and the next least significant bit in the 16QAM modulated data.

In step 21, the low-order demodulated data corresponds to the multi-layer sub-codeword data of the low-order part in the multi-layer codeword data in the concatenated coding method. Exemplarily, when the preset modulation mode is 16QAM, the low-order demodulated data corresponds to two sets of low-order multi-layer sub-codeword data, and when the preset modulation mode is PAM4, the low-order demodulation data corresponds to a group of multi-layer sub-codeword data corresponding to the least significant bit. Subcode data.

Step 22: Decode the low-order demodulated data to obtain low-order bit data.

In an implementation manner, the first demodulation process may be performed on the PAM4 modulated data in a hard-decision manner to obtain low-order demodulated data. Correspondingly, the low-order demodulated data is decoded in a hard decoding manner to obtain low-order bit data.

In another implementation manner, the first demodulation process may be performed on the PAM4 modulated data according to a soft decision method to obtain low-order bit data; correspondingly, the low-order demodulated data is decoded according to a soft decoding method to obtain low-order bits. data.

The soft decision + soft decoding method has good decoding performance and low bit error rate, but the complexity is slightly higher, and the channel needs to provide soft messages. The hard decision + hard decoding method has low complexity and lower decoding performance than the soft decision + soft decoding method, but does not require the channel to provide soft messages, which greatly reduces the power consumption of the equalizer. In practical applications, different decision modes may be selected to execute the first demodulation process according to the requirements of specific application scenarios.

In this embodiment, when the BCH code is selected as the component code of the MLC encoding in the concatenated encoding method, correspondingly, when the concatenated decoding is performed, the BM (Berlekamp-Massey) algorithm can be used for the hard decoding of the BCH code, and the soft The Chase-II algorithm can be used when decoding.

Step 23: Use the low-order bit data to assist in processing the channel received data to obtain high-order bit data of a second quantity group; wherein the first quantity plus the second quantity is equal to a preset quantity, and the The preset number is the number of bits corresponding to one symbol in the preset modulation mode.

In this embodiment, the decoding result of the low-order bits of the channel received data is used to assist the high-order demodulation of the channel received data. Referring to FIG. 7, it is a schematic diagram of an MLC encoding and decoding process. As shown in Figure 7, taking the PAM4 modulation method as an example, first demodulate the low-order bits of the channel received data to obtain the low-order demodulated data, and then decode the low-order demodulated data to obtain the low-order bit data; The channel receives data for demodulation to obtain high-order demodulated data, and decodes the high-order demodulated data to obtain high-order bit data. Among them, the AWGN channel in Fig. 7 refers to the Gaussian additive white noise channel, which is used to simulate the real channel noise.

Referring to FIG. 8 , a schematic diagram of a process of demodulating the modulated data using low-order bit data is provided. The demodulation method given in FIG. 8 adopts a hard-decision method to demodulate, and obtains binary high-order demodulation data. ; Among them, noise_symbol in Figure 8 represents the modulated data received by the channel. When the low-order bit data is 0 and the channel received data is greater than -1, the corresponding high-order demodulated data is 1; when the low-order bit data is 0 and the channel received data is less than -1, the corresponding high-order demodulated data is 0; when When the low-order bit data is 1 and the channel received data is greater than 1, the corresponding high-order demodulated data is 1; when the low-order bit data is 1 and the channel received data is less than 1, the corresponding high-order demodulated data is 0.

When the low-order bit data is used to assist in demodulating the channel received data in a soft-decision manner, the obtained high-order demodulated data is soft information, and the specific assisting process is similar to that in FIG.

In practical applications, when the low-order bit data is used to assist in demodulating the channel received data by hard decision, binary high-order demodulated data is obtained. Correspondingly, the high-order demodulated data is decoded by hard decoding. When the low-order bit data is used to assist in demodulating the channel received data by soft decision, high-order demodulated data of soft information is obtained, and correspondingly, soft decoding is used when decoding the high-order demodulated data.

Referring to FIG. 9 , taking the PAM4 modulation mode as an example, according to whether the most significant bit in the modulated data is encoded in the multi-layer coding process, a schematic diagram of the workflow of the low-order bit data assisted by processing the channel received data to obtain the high-order bit data is provided. .

When the most significant bits in the modulated data are not encoded in the multi-layer encoding process, decoding is also not required in the concatenated decoding process, and the high-order demodulated data is directly output. The above-mentioned use of the low-order bit data to assist in demodulating the channel received data adopts a hard decision method, and the obtained binary high-order demodulated data is directly output as high-order bit data. In this embodiment, the above-mentioned demodulation process is referred to as the second demodulation process. At this time, as shown in FIG. 9 , step 23 further includes step 231 - 1 , step 232 - 1 and step 233 .

Step 231-1, using the low-order bit data to assist in demodulating the channel received data by adopting a hard-decision manner to obtain binary high-order demodulation data. The specific demodulation process is shown in Figure 8.

Step 232-1, directly outputting the binary high-order demodulated data.

Step 233, obtaining high-order bit data.

When the most significant bits in the modulated data are encoded in the multi-layer encoding process, the high-order demodulated data needs to be decoded in the concatenated decoding process. In this embodiment, the demodulation process of obtaining the high-order demodulated data to be decoded is called the third demodulation process.

When the third demodulation process is performed in a hard-decision manner, the obtained high-order demodulated data is decoded in a hard-decoding manner. At this time, as shown in FIG. 9 , step 23 further includes step 231 - 2 , step 232 - 2 and step 233 .

Step 231-2, using the low-order bit data to assist in demodulating the channel received data by adopting a hard-decision manner to obtain binary high-order demodulation data. The demodulation process is shown in Figure 8.

Step 232-2, decode the binary high-order demodulated data by hard decoding.

Step 233, obtaining high-order bit data.

When the third demodulation process is performed in a soft-decision manner, the obtained high-order demodulated data is decoded in a soft decoding manner. At this time, as shown in FIG. 9 , step 23 further includes step 231 - 3 , step 232 - 3 and step 233 .

Step 231-3, using the low-order bit data to assist the demodulation of the channel received data by adopting a soft decision method to obtain high-order demodulated data of the soft information.

Step 232-3, decoding the high-order demodulated data of the soft information by soft decoding.

Step 233, obtaining high-order bit data.

In this embodiment, the execution process of step 21 to step 23 is called an MLC decoding process. When the first demodulation process in step 21 adopts the soft decision method, it is called MLC soft decoding. Further, the MLC soft decoding includes two forms of hard decision and soft decision when demodulating the channel received data with the aid of low-order bit data. When the first demodulation process in step 22 adopts the hard decision method, it is called MLC hard decoding. Further, MLC hard decoding includes two forms of hard decision and soft decision when demodulating the channel received data with the aid of low-order bit data. That is to say, MCL soft decoding includes two forms of low-order soft decision demodulation + high-order soft decision demodulation and low-order soft decision demodulation + high-order hard decision demodulation; MLC hard decoding includes low-order hard decision demodulation + high-order hard decision There are two forms of demodulation and low-order hard-decision demodulation + high-order soft-decision demodulation.

Step 24: Perform de-interleaving processing on the high-order bit data and the low-order bit data to obtain de-interleaved data.

Step 25: Perform RS decoding on the deinterleaved data to obtain RS decoded data.

Step 26: Send the RS decoded data to the sink.

The MLC decoding result is deinterleaved, restored to the order of RS codewords, and RS decoding is performed to obtain RS decoded data and send it to the sink. In this embodiment, the RS decoding adopts a hard decoding manner.

In this embodiment, the performance of the cascaded decoding method can also be increased by means of iterative decoding, that is, after the RS hard decoding is completed, the RS decoding data is used as the iterative input data, and MLC decoding and RS decoding are performed again. The decoding process is performed, and the obtained iterative decoding result is sent to the sink. Specifically, steps 31-36 are included.

Step 31: Interleave the RS decoded data to obtain iterative input data. It should be noted that, after the RS decoding data is interleaved, no encoding is required, and the interleaved data is directly used as the input data of the iterative decoding, which is again used as the input of the MLC decoding process. The iterative input data includes low-order iterative input data and high-order iterative input data.

Step 32: Decode the low-order iterative input data to obtain low-order iterative bit data. Taking the PAM4 modulation mode as an example, the low-order iterative input data is directly decoded first to obtain the low-order iterative bit data. Because the RS decoded data has no information about the check digit, the discarded check digit needs to be processed in the iterative input data obtained after the RS decoded data is interleaved. In one implementation, the low-order iterative input data is decoded by hard decoding, and the check digit in the iterative input data is set as the check digit of the data after the first low-order decoding, that is, in the low-order bit data In another implementation, soft decoding is used to decode the low-order iterative input data, and the maximum likelihood ratio of the information bits in the low-order iterative data is set as the most reliable, and the low-order iterative input data is The maximum likelihood ratio of the parity bits is set to the maximum likelihood ratio in the demodulated data of the lower bits.

Step 33: Use the low-order iterative bit data to assist in processing the high-order iterative input data to obtain high-order iterative bit data. Step 33 further includes step 331 and step 332 according to whether the most significant bit in the modulated data is encoded in the multi-layer encoding process.

Step 331, when the most significant bit in the modulated data is not encoded in the multi-layer encoding process, use the low-order iterative bit data to assist the high-order iterative input data to perform the second demodulation process in a hard-decision manner to obtain high-order iterative bit data.

Step 332, when the most significant bit in the modulated data is encoded in the multi-layer encoding process, use the low-order iterative bit data to assist the high-order iterative input data to perform the third demodulation process in a hard-decision mode or a soft-decision mode to obtain a high-order solution. Demodulation iterative data, decoding the high-order demodulation iterative data to obtain high-order iterative bit data. Further, when the third demodulation process is performed in a hard-decision manner, the high-order demodulation iterative data is decoded in a hard decoding manner; when the third demodulation process is performed in a soft-decision manner, the high-order demodulation iterative data is decoded. Decoding is performed by hard decoding.

In this embodiment, steps 32-33 are called the MLC iterative decoding process, wherein when the low-order iterative input data is decoded in a hard decoding manner, it is called the MLC hard iterative decoding process; When the input data is decoded by soft decoding, it is called the MLC soft iterative decoding process. Further, the MLC hard iterative decoding process includes two forms of low-order iterative hard decoding + high-order iterative hard decoding and low-order iterative hard decoding + high-order iterative soft decoding. The MLC soft iterative decoding process includes low-order soft decoding + high-order soft decoding. There are two forms of iterative soft decoding and low-order soft decoding + high-order iterative hard decoding.

Step 34: Perform de-interleaving processing on the high-order iterative bit data and the low-order iterative bit data to obtain de-interleaving iterative data.

Step 35: Perform RS decoding on the deinterleaved iterative data to obtain RS iteratively decoded data. In this embodiment, a hard decoding manner is used when performing RS decoding on the deinterleaved iterative data.

Step 36: Send the RS iteratively decoded data to the sink.

It should be noted that when the first demodulation process is performed on the channel received data transmitted by the channel to obtain low-order demodulation data in the hard-decision mode, the iterative decoding method needs to be adopted, and the decoded data obtained can meet the requirements of more than 400Gb/s. Ethernet performance requirements. That is to say, when the first demodulation process is performed in a hard-decision manner, the flow of the concatenated decoding method includes MLC hard decoding+RS decoding+MLC hard iterative decoding+RS decoding.

When the first demodulation process is performed on the modulated data transmitted by the channel to obtain low-order demodulation data, the method flow of the cascaded decoding may include a non-iterative method, that is, MLC soft decoding + RS decoding; Iterative decoding can be used, including two forms, one is MLC soft decoding + RS decoding + MLC soft iterative decoding + RS decoding, the other is MLC soft decoding + RS decoding + MLC hard decoding Iterative decoding + RS decoding.

A concatenated decoding method provided by the second embodiment of the present application is used to decode modulated data obtained by using the concatenated encoding method provided by the first embodiment of the present application, and the concatenated decoding method includes receiving data on a channel. Perform the first demodulation process according to the preset modulation mode to obtain low-order demodulated data; decode the low-order demodulated data to obtain low-order bit data; use the low-order bit data to assist in processing the channel received data to obtain high-order bit data; The high-order bit data and the low-order bit data are de-interleaved to obtain de-interleaved data; RS-decoding is performed on the de-interleaved data to obtain RS-decoded data; and the RS-decoded data is sent to the sink. The cascade decoding method uses the low-order bit data to assist in processing the high-order bits in the modulated data to obtain the high-order bit data, which ensures the decoding performance, reduces the complexity of the system, and reduces the time delay.

In order to further reflect the performance advantages of the concatenated encoding method and the concatenated decoding method provided by the present application, the present application uses the PAM4 modulation mode as an example to conduct comparative experiments.

In Comparative Experiment 1, the experimental group 1 used the RS code+MLC code concatenated encoding method provided by the first embodiment of the present application. In the component code of the MLC code, the BCH (360,320) code is used to encode the low-order bit data, and the error correction capability is 4. The high-order bit data is not encoded and has no error correction capability. The preset interleaving depth I=2. Among them, the interleaving depth I=2 has great potential to be compatible with the PCS (Physical Coding Sublayer, physical coding sublayer) of the existing Ethernet. Decoding is performed using the concatenated decoding method of MLC soft decoding+RS decoding provided by the second embodiment of the present application. Specifically, in the MLC soft decoding process, the channel received data is demodulated by using a soft decision method, Obtain the low-order demodulated data, use the Chase-II algorithm to decode the low-order demodulated data, and obtain the low-order bit data; the number of flip bits in the Chase-II algorithm is set to 3; the low-order bit data is used to assist the channel reception data. Adopt hard decision The demodulation method is used for demodulation, and the demodulation result is directly output to obtain the high-order bit data; the high-order bit data and the low-order bit data are deinterleaved to obtain the deinterleaved data, and the RS hard decoding is performed to obtain the RS decoding result.

The comparison group 1 uses the RS code+BCH code concatenated coding method; specifically, the outer code adopts the RS (544,514, t=15) code, ie the KP4 FEC scheme, and the inner code adopts the BCH (360,340) code. The code rates of the concatenated codes in the experimental group and the comparison group 1 are the same, and the Gray code is used in the PAM4 modulation process in the comparison group 1. Control group 2 used the KP4 FEC protocol.

The decoding performance corresponding to the three sets of coding methods in Comparative Experiment 1 is shown in Figure 10. Among them, experimental group 1 corresponds to 2RS+MLC_flip3 in Figure 10, comparison group 1 corresponds to 2RS+BCH360 (t=2) Gray code_flip3 in Figure 10, and comparison group 2 corresponds to RS(544,514) in Figure 10 . As can be seen from Figure 10, when the output BER (Bit Error Ratio, bit error rate) index reaches 1E-15, the SNR (Signal-Noise Ratio, signal-to-noise ratio) of the experimental group and the comparison group 1 relative to the comparison group 2 Compared with the comparison group 1, the decoding performance of the experimental group is improved by about 0.05dB. The flip in Figure 10 refers to the number of least reliable bits (flips) during BCH soft decoding.

Comparative experiment 2 verifies whether iterative decoding is required when MLC adopts hard decoding. In the concatenated encoding method of the experimental group 2, the preset interleaving depth I=4, and other settings are the same as those of the concatenated encoding method of the experimental group 1 in the comparative experiment 1. Experimental group 2 used the cascaded decoding method of MLC hard decoding + RS decoding. The concatenated coding method of experimental group 3 is the same as that of experimental group 2, and the iterative decoding method of MLC hard decoding + RS decoding + MLC hard iterative decoding + RS decoding is used for decoding.

The decoding performance corresponding to the two experimental groups in Comparative Experiment 2 is shown in Figure 11, where the FER (frame error rate) of the experimental group 2 corresponds to the FER-sim 4kp4 iter1 in Figure 11, and the BER (error rate) of the experimental group 2 code rate) corresponds to BER-sim4kp4 iter1 in Figure 11, the FER (Frame Error Rate, frame error rate) index of experimental group 3 corresponds to FER-sim4kp4 iter2 in Figure 11, and the BER index of experimental group 3 corresponds to Figure 11 The BER-sim 4kp4 iter2. The performance requirement of Ethernet above 400Gb/s is that the output BER is E-15 when the raw-BER is 2E-3. As can be seen from Figure 11, the decoding scheme of experimental group 2 needs a channel condition of about 1.8E-3 to meet the output BER of E-15, which cannot meet the performance requirements of Ethernet; the decoding scheme of experimental group 3 is in The channel conditions of about 2.8E-3 can meet the requirements, far exceeding the performance requirements of Ethernet.

It can be seen from Comparative Experiment 2 that when the first demodulation process is performed on the modulated data transmitted by the channel to obtain the low-order demodulation data in the hard-decision mode, the iterative decoding method is required, and the decoded data obtained can meet the requirements of 400Gb Performance requirements for Ethernet above /s.

Comparative experiment 3 compares the decoding performance of experimental group 1, experimental group 4, experimental group 5, and comparison group 1. The concatenated encoding method of experimental group 4 is the same as that of experimental group 1. The concatenated decoding method adopts the iterative decoding method of MLC soft decoding + RS decoding + MLC soft decoding + RS decoding. Therefore, in the MLC soft decoding process, the low-order decoding result is used to assist in the hard-decision demodulation of the high-order bits, and the high-order bit data is directly output. The concatenated encoding method of experimental group 5 is the same as that of experimental group 1. The concatenated decoding method adopts the iterative decoding method of MLC soft decoding+RS decoding+MLC hard iterative decoding+RS decoding.

The decoding performance results of Comparative Experiment 3 are shown in Figure 12; among them, Comparative Group 1 corresponds to 2RS+BCH360 (t=2) Gray code_flip3 in Figure 12, and Experimental Group 1 corresponds to 2RS+MLC_flip3 in Figure 12 , the experimental group 4 corresponds to the 2RS+MLC soft and hard iteration_flip3 in FIG. 12 , and the experimental group 5 corresponds to the 2RS+MLC soft and hard iteration_flip3 in FIG. 12 . As can be seen from Figure 12, when the interleaving depth is 2, the decoding performance curve is fitted and extended. When the output BER is equal to 1E-15, the decoding performance of experimental group 4 is improved by 0.28dB compared with that of experimental group 1. Compared with the experimental group 1, the decoding performance of the experimental group 5 is improved by about 0.12dB. It can be seen from the above analysis that the decoding performance of the concatenated decoding method can be increased by means of iterative decoding.

The specific embodiments provided above are just a few examples under the general concept of the present application, and do not constitute a limitation of the protection scope of the present application. For those skilled in the art, any other implementations expanded according to the solution of the present application without creative work fall within the protection scope of the present application.

Claims (10)

1. A method of concatenated coding, comprising:

receiving information source data sent by an information source;

RS coding is carried out on the information source data to obtain RS code word data;

interweaving the RS code word data according to a preset interweaving depth to obtain interweaved data;

grouping the interleaved data to obtain bit data of a preset number of groups; the preset number is the number of bits corresponding to one symbol in the preset modulation mode, and each group of bit data corresponds to different bits in the preset modulation mode;

carrying out multilayer coding on the bit data of a preset number of groups to obtain multilayer code word data; the multi-layer code word data comprises a preset number of groups of multi-layer sub-code word data, and the length of each group of multi-layer sub-code word data is consistent; the length of check bits in the multi-layer sub-code word data corresponding to the most significant bit in the preset modulation mode is less than the length of check bits in the multi-layer sub-code word data corresponding to the least significant bit in the preset modulation mode;

and modulating the multilayer code word data according to the preset modulation mode to obtain modulation data for channel transmission.

2. The concatenated coding method of claim 1, wherein when the predetermined modulation scheme is PAM4, the predetermined number of sets of bit data includes a set of high-order bit data and a set of low-order bit data;

the multi-layer coding is performed on the bit data of a preset number of groups to obtain multi-layer codeword data, and the multi-layer codeword data includes:

coding the low-order bit data according to a first code rate to obtain low-order multilayer sub-code data;

coding the high-order bit data according to a second code rate to obtain high-order multilayer subcode word data;

wherein the first code rate is less than the second code rate, the high-order multi-layer sub-codeword data corresponds to the most significant bits in the PAM4 modulation scheme, and the low-order multi-layer sub-codeword data corresponds to the least significant bits in the PAM4 modulation scheme.

3. The concatenated coding method of claim 1, wherein when the predetermined modulation scheme is PAM4, the predetermined number of sets of bit data includes a set of high-order bit data and a set of low-order bit data;

the multi-layer coding is performed on the bit data of the preset number of groups to obtain multi-layer code word data, and the multi-layer code word data comprises

Coding the low-order bit data according to a third code rate to obtain low-order multilayer subcode word data;

directly outputting the high-order bit data without encoding to obtain high-order multilayer subcode word data;

the high-order multi-layer sub-code data corresponds to the most significant bit in the PAM4 modulation mode, and the low-order multi-layer sub-code data corresponds to the least significant bit in the PAM4 modulation mode.

4. A concatenated decoding method, wherein the concatenated decoding method is used for decoding the modulation data obtained by the concatenated coding method according to any one of claims 1-3; the cascade coding method comprises the following steps:

executing a first demodulation process on channel receiving data according to a preset modulation mode to obtain a first quantity of groups of low-order demodulation data;

decoding the low-order demodulation data to obtain low-order bit data;

using the low-order bit data to assist in processing the channel receiving data to obtain a second number of groups of high-order bit data; the first number plus the second number is equal to a preset number, and the preset number is the number of bits corresponding to one symbol in the preset modulation mode;

de-interleaving the high-order bit data and the low-order bit data to obtain de-interleaved data;

performing RS decoding on the deinterleaved data to obtain RS decoded data;

and sending the RS decoding data to a signal sink.

5. The concatenated decoding method of claim 4, wherein when the predetermined modulation scheme is PAM4, the first number and the second number are both equal to 1; the lower bit data corresponds to the least significant bit of the modulated data, and the upper bit data corresponds to the most significant bit of the modulated data;

the processing the channel received data with the assistance of the low-order bit data to obtain high-order bit data includes:

when the most significant bit in the modulation data is not coded in the multi-layer coding process, the low-order bit data is used for assisting to execute a second demodulation process on the most significant bit of the channel receiving data in a hard decision mode to obtain the high-order bit data;

when the most significant bit in the modulation data is coded in a multilayer coding process, the low-order bit data is used for assisting to execute a third demodulation process on the most significant bit of the channel receiving data in a hard decision mode or a soft decision mode to obtain high-order demodulation data, and the high-order demodulation data is decoded to obtain the high-order bit data; when a third demodulation process is executed by adopting hard decision, decoding the high-order demodulation data by adopting a hard decoding mode; and when the third demodulation process is executed in a soft decision mode, decoding the high-order demodulation data in a soft decoding mode.

6. The concatenated decoding method of claim 5, wherein before the RS-decoded data is transmitted to a sink, the concatenated decoding method comprises:

performing iterative decoding on the RS decoded data to obtain RS iterative decoded data;

the RS iterative decoding data is sent to an information sink;

the iterative decoding is performed on the RS decoding data to obtain RS iterative decoding data, and the iterative decoding method comprises the following steps:

interweaving the RS decoding data to obtain iterative input data; wherein the iterative input data comprises lower iterative input data and higher iterative input data;

decoding the low-order iteration input data to obtain low-order iteration bit data;

when the most significant bit in the modulation data is not coded in the multi-layer coding process, the low-order iteration bit data is used for assisting to execute a second demodulation process on the high-order iteration input data in a hard decision mode, and the high-order iteration bit data is obtained;

when the most significant bit in the modulation data is coded in a multilayer coding process, the low-order iteration bit data is used for assisting in executing a third demodulation process on the high-order iteration input data in a hard decision mode or a soft decision mode, and a demodulation result is decoded to obtain high-order iteration bit data; when the third demodulation process is executed in a hard decision mode, decoding the demodulation result in a hard decoding mode; when the third demodulation process is executed in a soft decision mode, decoding the demodulation result in a soft decoding mode;

performing de-interleaving processing on the high-order iteration bit data and the low-order iteration bit data to obtain de-interleaved iteration data;

performing RS decoding on the de-interleaved iterative data to obtain RS iterative decoding data;

and sending the RS iterative decoding data to a signal sink.

7. The concatenated decoding method of claim 6, wherein when the lower iterative input data is decoded by a hard decoding method, the check bits in the lower iterative input data are set as the check bits in the lower bit data.

8. The concatenated decoding method of claim 6, wherein when the low-order iterative input data is decoded by soft decoding, a maximum likelihood ratio of information bits in the low-order iterative data is set to be most reliable, and a maximum likelihood ratio of check bits in the low-order iterative input data is set to be a maximum likelihood ratio in the low-order demodulated data.

9. The concatenated decoding method of claim 7, wherein the low-order demodulated data is obtained by a hard decision method when the first demodulation process is performed on the channel received data according to a PAM4 modulation scheme;

and obtaining the low-order bit data by adopting a hard decoding mode when decoding the low-order demodulation data.

10. The concatenated decoding method of any one of claims 5, 7, and 8, wherein the low-order demodulated data is obtained by using a soft-decision method when performing a first demodulation process on the channel received data according to a PAM4 modulation method;

and when decoding the low-order demodulated data, a soft decoding mode is adopted to obtain the low-order bit data.

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