Digital coding, decoding and communication method and system based on multilevel coded modulation

Abstract

The present invention discloses a digital encoding, decoding and communication method and system based on multilevel coded modulation, which relates to the field of digital communication modulation technology. The encoding method includes: dividing the information sequence to be transmitted into a first-level bit sequence and a second-level bit sequence according to the channel capacity ratio of the 4-PAM modulation system and the code length of the information sequence to be transmitted; performing polar code encoding on the first-level bit sequence to obtain a first-level encoded bit sequence; sequentially performing CCDM distribution matching and BCH code encoding on the second-level bit sequence to obtain a second-level encoded bit sequence; processing the second-level encoded bit sequence based on the first-level encoded bit sequence to obtain a processed second-level encoded bit sequence; and performing 4-PAM modulation on the first-level encoded bit sequence and the processed second-level encoded bit sequence by using a set partitioning mapping rule to obtain a modulation symbol sequence. The present invention improves the ability to reduce the probability of high-energy constellation points and improves the data transmission quality.

Description

Technical Field

[0001] The present invention relates to the field of digital communication modulation technology, and particularly to a digital encoding, decoding, and communication method and system based on multilevel coding modulation. Background Art

[0002] With the continuous development and application of communication technologies, people's demand for spectral efficiency is getting higher and higher. An important means to improve spectral efficiency is to use high-order modulation technologies. Polar codes are a new type of channel coding scheme. Combining polar codes with high-order modulation can achieve more efficient data transmission. Multilevel Coding (MLC) modulation is a high-order modulation technology suitable for polar codes. Its principle is to divide the data stream into multiple parallel sub-streams according to the modulation order and encode each sub-stream using different coding schemes. This technology is widely used in digital communication systems and can improve system performance and data transmission quality.

[0003] In an MLC system, the set partitioning mapping rule is adopted to maximize the capacity difference between each bit level, and at the same time, the code rate of each level is reasonably allocated according to the channel capacity of each level. At this time, its performance can reach the capacity limit of coding modulation. However, there is still a gap of 1.53 dB between the capacity limit of multilevel coding modulation and the Shannon limit, which can be compensated by Probabilistic Shaping (PS) technology. The PS technology reduces the occurrence probability of high-amplitude signal points carrying more energy, making the Euclidean distance between signal points larger at the same power level, and finally obtaining shaping gain. Figure 2 and Figure 3 respectively show the constellation diagrams of 4-PAM (Pulse Amplitude Modulation) modulation using the Gray mapping rule and the set partitioning mapping rule. According to Figure 3 , it can be seen that when using the Gray mapping rule to label signal points, only by making the occurrence probability of "1" in the second bit level greater than that of "0", the occurrence probability of intermediate signal points can be increased, thereby reducing the occurrence probability of high-energy constellation points. However, the commonly used rule in the PC-MLC system is the set partitioning mapping rule. According to Figure 2 , it can be seen that at this time, it is more difficult to reduce the occurrence probability of high-energy constellation points, resulting in lower data transmission quality. Summary of the Invention

[0004] The object of the present invention is to provide a digital encoding, decoding, and communication method and system based on multilevel coding modulation, which improves the ability to reduce the occurrence probability of high-energy constellation points, thereby improving data transmission quality.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A digital coding method based on multilevel coded modulation, comprising:

[0007] Determine the capacity ratio of the channel of a 4-PAM modulation system; the capacity ratio is the ratio of the capacity of the low-bit-level sub-channel of the channel to the capacity of the high-bit-level sub-channel;

[0008] Divide the to-be-transmitted information sequence into a first-level bit sequence and a second-level bit sequence according to the capacity ratio and the code length of the to-be-transmitted information sequence;

[0009] Perform polar code encoding on the first-level bit sequence to obtain a first-level encoded bit sequence;

[0010] Perform CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain a second-level encoded bit sequence;

[0011] Determine the flipping operation of the second-level encoded bit sequence based on the first-level encoded bit sequence; the flipping operation is to flip or not to flip;

[0012] Process the second-level encoded bit sequence according to the flipping operation of the second-level encoded bit sequence to obtain a processed second-level encoded bit sequence;

[0013] Adopt a set partitioning mapping rule to perform 4-PAM modulation on the first-level encoded bit sequence and the processed second-level encoded bit sequence to obtain a modulation symbol sequence.

[0014] Optionally, performing CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain a second-level encoded bit sequence specifically includes:

[0015] Perform CCDM distribution matching on the second-level bit sequence to obtain a shaped bit sequence;

[0016] Perform BCH code encoding on the shaped bit sequence to obtain the second-level encoded bit sequence.

[0017] A digital coding system based on multilevel coded modulation, comprising:

[0018] A capacity ratio determination module for determining the capacity ratio of the channel of a 4-PAM modulation system; the capacity ratio is the ratio of the capacity of the low-bit-level sub-channel of the channel to the capacity of the high-bit-level sub-channel;

[0019] A sequence decomposition module for dividing the to-be-transmitted information sequence into a first-level bit sequence and a second-level bit sequence according to the capacity ratio and the code length of the to-be-transmitted information sequence;

[0020] The first encoding module is used to perform polar code encoding on the first-level bit sequence to obtain a first-level encoded bit sequence;

[0021] The second encoding module is used to sequentially perform CCDM distribution matching and BCH code encoding on the second-level bit sequence to obtain a second-level encoded bit sequence;

[0022] The first flipping determination module is used to determine the flipping operation of the second-level encoded bit sequence based on the first-level encoded bit sequence; the flipping operation is flipping or not flipping;

[0023] The first processing module is used to process the second-level encoded bit sequence according to the flipping operation of the second-level encoded bit sequence to obtain a processed second-level encoded bit sequence;

[0024] The modulation module is used to perform 4-PAM modulation on the first-level encoded bit sequence and the processed second-level encoded bit sequence by using a set partitioning mapping rule to obtain a modulation symbol sequence.

[0025] A digital decoding method based on multi-level coding modulation includes:

[0026] Demodulating the received first-level modulation symbol subsequence to obtain a first-level log-likelihood ratio information sequence; the first-level modulation symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits of the first-level bit sequence in the received modulation symbol sequence; the first-level bit sequence is determined by partitioning the to-be-transmitted information sequence according to the channel capacity ratio of the 4-PAM modulation system and the code length of the to-be-transmitted information sequence; the modulation symbol sequence is determined by encoding and modulating the to-be-transmitted information sequence;

[0027] Performing hard decision on the first-level log-likelihood ratio information sequence to obtain an estimated value of the first-level encoded bit sequence;

[0028] Performing polar code decoding on the first-level log-likelihood ratio information sequence to obtain a first-level decoded bit sequence;

[0029] Demodulating the received second-level modulation symbol subsequence to obtain a second-level log-likelihood ratio information sequence; the second-level modulation symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits of the second-level bit sequence in the received modulation symbol sequence; the second-level bit sequence is determined by partitioning the to-be-transmitted information sequence according to the channel capacity ratio of the 4-PAM modulation system and the code length of the to-be-transmitted information sequence;

[0030] Performing hard decision on the second-level log-likelihood ratio information sequence to obtain an estimated value of the second-level encoded bit sequence;

[0031] Determine the flipping operation of the second-level log-likelihood ratio information sequence based on the estimated value of the first-level coded bit sequence; the flipping operation is to flip or not to flip;

[0032] Process the second-level log-likelihood ratio information sequence according to the flipping operation of the second-level log-likelihood ratio information sequence to obtain a second-level bit sequence to be decoded;

[0033] Perform block code decoding and CCDM de-distribution matching on the second-level bit sequence to be decoded in sequence to obtain a second-level decoded bit sequence;

[0034] Merge the first-level decoded bit sequence and the second-level decoded bit sequence to obtain the information sequence to be transmitted.

[0035] Optionally, perform hard decision on the first-level log-likelihood ratio information sequence to obtain an estimated value of the first-level coded bit sequence, specifically including:

[0036] Determine the binary value of each bit in the first-level log-likelihood ratio information sequence;

[0037] Wherein, for any current bit in the first-level log-likelihood ratio information sequence:

[0038] Judge whether the value of the current bit is greater than 0;

[0039] If so, determine the binary value of the current bit as 1;

[0040] If not, determine the binary value of the current bit as 0;

[0041] Determine the sequence composed of the binary values of all bits in the first-level log-likelihood ratio information sequence as the estimated value of the first-level coded bit sequence.

[0042] Optionally, perform hard decision on the second-level log-likelihood ratio information sequence to obtain an estimated value of the second-level coded bit sequence, specifically including:

[0043] Determine the binary value of each bit in the second-level log-likelihood ratio information sequence;

[0044] For any current bit in the second-level log-likelihood ratio information sequence:

[0045] Judge whether the value of the current bit is greater than 0;

[0046] If so, determine the binary value of the current bit as 1;

[0047] If not, determine the binary value of the current bit as 0;

[0048] Determine the sequence formed by the binary values of all bits in the second-level log-likelihood ratio information sequence as the estimated value of the second-level coded bit sequence.

[0049] A digital decoding system based on multi-level coded modulation, comprising:

[0050] A first-level demodulation module, configured to demodulate the received first-level modulation symbol subsequence to obtain a first-level log-likelihood ratio information sequence; the first-level modulation symbol subsequence is a sequence composed of bits corresponding to the serial numbers of each bit in the first-level bit sequence in the received modulation symbol sequence; the first-level bit sequence is determined by dividing the to-be-transmitted information sequence according to the channel capacity ratio of the 4-PAM modulation system and the code length of the to-be-transmitted information sequence; the modulation symbol sequence is determined by encoding and modulating the to-be-transmitted information sequence;

[0051] A first hard decision module, configured to perform hard decision on the first-level log-likelihood ratio information sequence to obtain an estimated value of the first-level coded bit sequence;

[0052] A first-level decoding module, configured to perform polar code decoding on the first-level log-likelihood ratio information sequence to obtain a first-level decoded bit sequence;

[0053] A second-level demodulation module, configured to demodulate the received second-level modulation symbol subsequence to obtain a second-level log-likelihood ratio information sequence; the second-level modulation symbol subsequence is a sequence composed of bits corresponding to the serial numbers of each bit in the second-level bit sequence in the received modulation symbol sequence; the second-level bit sequence is determined by dividing the to-be-transmitted information sequence according to the channel capacity ratio of the 4-PAM modulation system and the code length of the to-be-transmitted information sequence;

[0054] A second hard decision module, configured to perform hard decision on the second-level log-likelihood ratio information sequence to obtain an estimated value of the second-level coded bit sequence;

[0055] A second flip determination module, configured to determine a flip operation of the second-level log-likelihood ratio information sequence based on the estimated value of the first-level coded bit sequence; the flip operation is to flip or not to flip;

[0056] A second processing module, configured to process the second-level log-likelihood ratio information sequence according to the flip operation of the second-level log-likelihood ratio information sequence to obtain a second-level bit sequence to be decoded;

[0057] A second-level decoding module, configured to perform block code decoding and CCDM de-distribution matching on the second-level bit sequence to be decoded in sequence to obtain a second-level decoded bit sequence;

[0058] A decoding completion module, configured to combine the first-stage decoded bit sequence and the second-stage decoded bit sequence to obtain the information sequence to be transmitted.

[0059] A digital communication method based on multilevel coded modulation, comprising:

[0060] Determining a capacity ratio of a channel of a 4-PAM modulation system; the capacity ratio being a ratio of a capacity of a low-bit-level sub-channel of the channel to a capacity of a high-bit-level sub-channel of the channel;

[0061] Dividing the information sequence to be transmitted into a first-stage bit sequence and a second-stage bit sequence according to the capacity ratio and a code length of the information sequence to be transmitted;

[0062] Performing polar code encoding on the first-stage bit sequence to obtain a first-stage encoded bit sequence;

[0063] Successively performing CCDM distribution matching and BCH code encoding on the second-stage bit sequence to obtain a second-stage encoded bit sequence;

[0064] Determining a flipping operation of the second-stage encoded bit sequence based on the first-stage encoded bit sequence; the flipping operation being flipping or not flipping;

[0065] Processing the second-stage encoded bit sequence according to the flipping operation of the second-stage encoded bit sequence to obtain a processed second-stage encoded bit sequence;

[0066] Performing 4-PAM modulation on the first-stage encoded bit sequence and the processed second-stage encoded bit sequence by using a set partitioning mapping rule to obtain a modulation symbol sequence;

[0067] Transmitting the modulation symbol sequence by using the channel;

[0068] Demodulating a received first-stage modulation symbol subsequence to obtain a first-stage log-likelihood ratio information sequence; the first-stage modulation symbol subsequence being a sequence composed of bits corresponding to the sequence numbers of the bits of the first-stage bit sequence in the modulation symbol sequence;

[0069] Performing hard decision on the first-stage log-likelihood ratio information sequence to obtain an estimated value of the first-stage encoded bit sequence;

[0070] Performing polar code decoding on the first-stage log-likelihood ratio information sequence to obtain a first-stage decoded bit sequence;

[0071] Demodulating a received second-stage modulation symbol subsequence to obtain a second-stage log-likelihood ratio information sequence; the second-stage modulation symbol subsequence being a sequence composed of bits corresponding to the sequence numbers of the bits of the second-stage bit sequence in the modulation symbol sequence;

[0072] Perform a hard decision on the second - level log - likelihood ratio information sequence to obtain an estimated value of the second - level coded bit sequence;

[0073] Based on the estimated value of the first - level coded bit sequence, determine the flipping operation of the second - level log - likelihood ratio information sequence; the flipping operation is to flip or not to flip;

[0074] Process the second - level log - likelihood ratio information sequence according to the flipping operation of the second - level log - likelihood ratio information sequence to obtain a second - level bit sequence to be decoded;

[0075] Perform block - code decoding and CCDM distribution matching on the second - level bit sequence to be decoded in sequence to obtain a second - level decoded bit sequence;

[0076] Merge the first - level decoded bit sequence and the second - level decoded bit sequence to obtain the information sequence to be transmitted.

[0077] A digital communication system based on multi - level coded modulation, comprising:

[0078] A capacity ratio determination module, configured to determine the capacity ratio of the channel of a 4 - PAM modulation system; the capacity ratio is the ratio of the capacity of the low - bit - level sub - channel to the capacity of the high - bit - level sub - channel of the channel;

[0079] A sequence decomposition module, configured to divide the information sequence to be transmitted into a first - level bit sequence and a second - level bit sequence according to the capacity ratio and the code length of the information sequence to be transmitted;

[0080] A first encoding module, configured to perform polar code encoding on the first - level bit sequence to obtain a first - level coded bit sequence;

[0081] A second encoding module, configured to perform CCDM distribution matching and BCH code encoding on the second - level bit sequence in sequence to obtain a second - level coded bit sequence;

[0082] A first flipping judgment module, configured to determine the flipping operation of the second - level coded bit sequence based on the first - level coded bit sequence; the flipping operation is to flip or not to flip;

[0083] A first processing module, configured to process the second - level coded bit sequence according to the flipping operation of the second - level coded bit sequence to obtain a processed second - level coded bit sequence;

[0084] A modulation module, configured to perform 4 - PAM modulation on the first - level coded bit sequence and the processed second - level coded bit sequence by using a set - partitioning mapping rule to obtain a modulation symbol sequence;

[0085] A transmission module, configured to transmit the modulated symbol sequence by using the channel;

[0086] A first-stage demodulation module, configured to demodulate the received first-stage modulated symbol subsequence to obtain a first-stage log-likelihood ratio information sequence; the first-stage modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits in the first-stage bit sequence in the modulated symbol sequence;

[0087] A first hard decision module, configured to perform hard decision on the first-stage log-likelihood ratio information sequence to obtain an estimated value of the first-stage coded bit sequence;

[0088] A first-stage decoding module, configured to perform polar code decoding on the first-stage log-likelihood ratio information sequence to obtain a first-stage decoded bit sequence;

[0089] A second-stage demodulation module, configured to demodulate the received second-stage modulated symbol subsequence to obtain a second-stage log-likelihood ratio information sequence; the second-stage modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits in the second-stage bit sequence in the modulated symbol sequence;

[0090] A second hard decision module, configured to perform hard decision on the second-stage log-likelihood ratio information sequence to obtain an estimated value of the second-stage coded bit sequence;

[0091] A second flip determination module, configured to determine a flip operation of the second-stage log-likelihood ratio information sequence based on the estimated value of the first-stage coded bit sequence; the flip operation is to flip or not to flip;

[0092] A second processing module, configured to process the second-stage log-likelihood ratio information sequence according to the flip operation of the second-stage log-likelihood ratio information sequence to obtain a second-stage bit sequence to be decoded;

[0093] A second-stage decoding module, configured to perform block code decoding and CCDM de-distribution matching on the second-stage bit sequence to be decoded in sequence to obtain a second-stage decoded bit sequence;

[0094] A decoding completion module, configured to combine the first-stage decoded bit sequence and the second-stage decoded bit sequence to obtain the information sequence to be transmitted.

[0095] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0096] The present invention discloses a digital encoding, decoding, and communication method and system based on multilevel coded modulation. By modifying the structure of the MLC system, using Constant Composition Distribution Matching (CCDM) and BCH coding, introducing bit flipping operations, and determining whether to flip the bits in the second level according to the coding result of the first level, the difficulty of obtaining the target distribution in modulation schemes using set partitioning mapping rules is solved, the ability to reduce the probability of high-energy constellation points appearing is improved, and thus the data transmission quality is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0098] Figure 1 Schematic flow chart of the digital encoding method based on multilevel coded modulation provided in Embodiment 1 of the present invention;

[0099] Figure 2 Constellation diagram using set partitioning mapping rules under 4-PAM modulation;

[0100] Figure 3 Constellation diagram using Gray mapping rules under 4-PAM modulation;

[0101] Figure 4 Schematic diagram of the polar code multilevel coded modulation probability shaping system model based on 4-PAM modulation for implementing the digital communication method based on multilevel coded modulation in Embodiment 5;

[0102] Figure 5 Schematic diagram of the two-bit level channel capacity using set partitioning mapping rules under 4-PAM modulation;

[0103] Figure 6 Schematic diagram of the implementation system structure of CCDM;

[0104] Figure 7 Schematic diagram of the implementation system structure of bit flipping;

[0105] Figure 8 Schematic diagram of the probability distribution of 4-PAM modulation symbols;

[0106] Figure 9 Comparison chart of the error performance between the uniform distribution scheme and the probability shaping scheme. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0107] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0108] The object of the present invention is to provide a digital encoding, decoding and communication method and system based on multilevel coded modulation, aiming to improve the ability to reduce the occurrence probability of high-energy constellation points, thereby improving the data transmission quality.

[0109] To make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0110] Embodiment 1

[0111] Figure 1 It is a schematic flowchart of a digital encoding method based on multilevel coded modulation provided in Embodiment 1 of the present invention. As Figure 1 shown, the digital encoding method based on multilevel coded modulation in this embodiment includes:

[0112] Step 101: Determine the capacity ratio of the channels in a 4-PAM modulation system; the capacity ratio is the ratio of the capacity of the low-bit-level sub-channel to the capacity of the high-bit-level sub-channel of the channel.

[0113] Step 102: Divide the information sequence to be transmitted into a first-level bit sequence and a second-level bit sequence according to the capacity ratio and the code length of the information sequence to be transmitted.

[0114] Step 103: Perform polar code encoding on the first-level bit sequence to obtain a first-level encoded bit sequence.

[0115] Step 104: Perform CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain a second-level encoded bit sequence.

[0116] As an optional implementation manner, step 104 specifically includes:

[0117] Perform CCDM distribution matching on the second-level bit sequence to obtain a shaped bit sequence.

[0118] Perform BCH code encoding on the shaped bit sequence to obtain a second-level encoded bit sequence.

[0119] Step 105: Determine the flipping operation of the second-level encoded bit sequence based on the first-level encoded bit sequence; the flipping operation is to flip or not to flip.

[0120] Step 106: Process the second-level coded bit sequence according to the flipping operation of the second-level coded bit sequence to obtain the processed second-level coded bit sequence.

[0121] Step 107: Use the set partitioning mapping rule to perform 4-PAM modulation on the first-level coded bit sequence and the processed second-level coded bit sequence to obtain a modulated symbol sequence.

[0122] Embodiment 2

[0123] To implement the digital coding method based on multilevel coding modulation in Embodiment 1, this embodiment also provides a digital coding system based on multilevel coding modulation, including:

[0124] A capacity ratio determination module, configured to determine the capacity ratio of the channels of a 4-PAM modulation system; the capacity ratio is the ratio of the capacity of the low-bit-level sub-channel and the high-bit-level sub-channel of the channel.

[0125] A sequence decomposition module, configured to divide the to-be-transmitted information sequence into a first-level bit sequence and a second-level bit sequence according to the capacity ratio and the code length of the to-be-transmitted information sequence.

[0126] A first coding module, configured to perform polar code coding on the first-level bit sequence to obtain a first-level coded bit sequence.

[0127] A second coding module, configured to sequentially perform CCDM distribution matching and BCH code coding on the second-level bit sequence to obtain a second-level coded bit sequence.

[0128] A first flipping judgment module, configured to determine the flipping operation of the second-level coded bit sequence based on the first-level coded bit sequence; the flipping operation is flipping or not flipping.

[0129] A first processing module, configured to process the second-level coded bit sequence according to the flipping operation of the second-level coded bit sequence to obtain the processed second-level coded bit sequence.

[0130] A modulation module, configured to perform 4-PAM modulation on the first-level coded bit sequence and the processed second-level coded bit sequence by using the set partitioning mapping rule to obtain a modulated symbol sequence.

[0131] Embodiment 3

[0132] A digital decoding method based on multilevel coding modulation, including:

[0133] Step 201: Demodulate the received first-level modulated symbol subsequence to obtain a first-level log-likelihood ratio information sequence; the first-level modulated symbol subsequence is a sequence composed of the bits corresponding to the sequence numbers of the bits of the first-level bit sequence in the received modulated symbol sequence; the first-level bit sequence is determined by dividing the to-be-transmitted information sequence according to the channel capacity ratio of the 4-PAM modulation system and the code length of the to-be-transmitted information sequence; the modulated symbol sequence is determined by encoding and modulating the to-be-transmitted information sequence.

[0134] Step 202: Perform a hard decision on the first-level log-likelihood ratio information sequence to obtain an estimated value of the first-level encoded bit sequence.

[0135] As an optional implementation manner, step 202 specifically includes:

[0136] Determine the binary value of each bit in the first-level log-likelihood ratio information sequence.

[0137] Wherein, for any current bit in the first-level log-likelihood ratio information sequence:

[0138] Judge whether the value of the current bit is greater than 0.

[0139] If so, determine the binary value of the current bit as 1.

[0140] If not, determine the binary value of the current bit as 0.

[0141] Determine the sequence composed of the binary values of all bits in the first-level log-likelihood ratio information sequence as the estimated value of the first-level encoded bit sequence.

[0142] Step 203: Perform polar code decoding on the first-level log-likelihood ratio information sequence to obtain a first-level decoded bit sequence.

[0143] Step 204: Demodulate the received second-level modulated symbol subsequence to obtain a second-level log-likelihood ratio information sequence; the second-level modulated symbol subsequence is a sequence composed of the bits corresponding to the sequence numbers of the bits of the second-level bit sequence in the received modulated symbol sequence; the second-level bit sequence is determined by dividing the to-be-transmitted information sequence according to the channel capacity ratio of the 4-PAM modulation system and the code length of the to-be-transmitted information sequence.

[0144] Step 205: Perform a hard decision on the second-level log-likelihood ratio information sequence to obtain an estimated value of the second-level encoded bit sequence.

[0145] As an optional implementation manner, step 205 specifically includes:

[0146] Determine the binary value of each bit in the second-level log-likelihood ratio information sequence.

[0147] For any current bit in the second-level log-likelihood ratio information sequence:

[0148] Determine whether the value of the current bit is greater than 0.

[0149] If so, determine the binary value of the current bit as 1.

[0150] If not, determine the binary value of the current bit as 0.

[0151] Determine the sequence composed of the binary values of all bits in the second-level log-likelihood ratio information sequence as the estimated value of the second-level coded bit sequence.

[0152] Step 206: Based on the estimated value of the first-level coded bit sequence, determine the flipping operation of the second-level log-likelihood ratio information sequence; the flipping operation is to flip or not to flip.

[0153] Step 207: Process the second-level log-likelihood ratio information sequence according to the flipping operation of the second-level log-likelihood ratio information sequence to obtain the second-level bit sequence to be decoded.

[0154] Step 208: Perform block code decoding and CCDM dematching on the second-level bit sequence to be decoded in sequence to obtain the second-level decoded bit sequence.

[0155] Step 209: Combine the first-level decoded bit sequence and the second-level decoded bit sequence to obtain the information sequence to be transmitted.

[0156] Embodiment 4

[0157] To implement the digital decoding method based on multi-level coded modulation in Embodiment 3, this embodiment further provides a digital decoding system based on multi-level coded modulation, including:

[0158] A first-level demodulation module, configured to demodulate the received first-level modulation symbol subsequence to obtain a first-level log-likelihood ratio information sequence; the first-level modulation symbol subsequence is a sequence composed of bits corresponding to the serial numbers of the bits in the first-level bit sequence in the received modulation symbol sequence; the first-level bit sequence is determined by dividing the information sequence to be transmitted according to the capacity ratio of the channel of the 4-PAM modulation system and the code length of the information sequence to be transmitted; the modulation symbol sequence is determined by encoding and modulating the information sequence to be transmitted.

[0159] A first hard decision module, configured to perform hard decision on the first-level log-likelihood ratio information sequence to obtain an estimated value of the first-level coded bit sequence.

[0160] A first-level decoding module, configured to perform polar code decoding on the first-level log-likelihood ratio information sequence to obtain a first-level decoded bit sequence.

[0161] The second - stage demodulation module is used to demodulate the received second - stage modulated symbol subsequence to obtain the second - stage log - likelihood ratio information sequence; the second - stage modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of each bit of the second - stage bit sequence in the received modulated symbol sequence; the second - stage bit sequence is determined by dividing the to - be - transmitted information sequence according to the capacity ratio of the channels of the 4 - PAM modulation system and the code length of the to - be - transmitted information sequence.

[0162] The second hard - decision module is used to perform hard - decision on the second - stage log - likelihood ratio information sequence to obtain an estimated value of the second - stage coded bit sequence.

[0163] The second flip - judgment module is used to determine the flip operation of the second - stage log - likelihood ratio information sequence based on the estimated value of the first - stage coded bit sequence; the flip operation is either flipping or not flipping.

[0164] The second processing module is used to process the second - stage log - likelihood ratio information sequence according to the flip operation of the second - stage log - likelihood ratio information sequence to obtain the second - stage bit sequence to be decoded.

[0165] The second - stage decoding module is used to perform block - code decoding and CCDM de - distribution matching on the second - stage bit sequence to be decoded in sequence to obtain the second - stage decoded bit sequence.

[0166] The decoding completion module is used to merge the first - stage decoded bit sequence and the second - stage decoded bit sequence to obtain the to - be - transmitted information sequence.

[0167] Embodiment 5

[0168] Embodiment 3 utilizes a polar - code multi - level coding modulation probability shaping system model as shown in Figure 4 to implement a digital communication method based on multi - level coding modulation. The digital communication method based on multi - level coding modulation includes:

[0169] Step 1: Determine the capacity ratio of the channels of the 4 - PAM modulation system; the capacity ratio is the ratio of the capacity of the low - bit - level sub - channel and the high - bit - level sub - channel of the channel.

[0170] Specifically, as shown in Figure 5 , first, it is necessary to calculate the capacity of each bit - level sub - channel (including 2 bit - level sub - channels, namely the low - bit - level sub - channel and the high - bit - level sub - channel) in the 4 - PAM modulation symbol (in Figure 5 , the capacity of the low - bit - level sub - channel is expressed as the capacity of the first - stage equivalent sub - channel, and the capacity of the high - bit - level sub - channel is expressed as the capacity of the second - stage equivalent sub - channel).

[0171] Step 1 specifically includes:

[0172] 1a) First, calculate the capacity limit of the 4-PAM modulation system according to formula (1).

[0173] Among them, A represents the set of signal constellation points, |A| = 2 m , |A| represents the number of constellation points, m represents the modulation order; E(·) represents the operation of taking the mean; X represents the channel input symbol, Y represents the channel output symbol, x′ represents a certain constellation point in the set of signal constellation points, and P Y|X (·) represents the operation of finding the channel transition probability.

[0174] 1b) According to Calculate the sub-channel capacity C of the i-th bit level i (i = 1, 2), and the calculation formula is as follows:

[0175]

[0176] Among them, A(x 0 x 1 ...x i ) represents the set of signal constellation points of the constellation diagram composed of a group of constellation points, (x 0 x 1 ...x i ) is a group of binary vectors, indicating that the dimension of this group of constellation diagrams, that is, the order is i. Through (x 0 x 1 ...x i ) a group of constellation points can be determined; represents the operation of taking the mean of the parameters of (x 0 x 1 ...x i ).

[0177] 1c) Based on the above formula, perform simulation. Through Monte Carlo simulation, the channel capacities of each bit level as shown in Figure 5 can be obtained. Figure 5 The horizontal axis E s / N0 in is the symbol signal-to-noise ratio, that is, the ratio of the energy of each symbol to the noise power spectral density, representing the degree of interference of the noise in the channel on the transmitted signal.

[0178] 1d) Determine the code rate allocation of each bit level according to the ratio of the channel capacities of each bit level and the total code rate (adjusted according to the actual situation. For example, if a communication system with a code rate of 0.5 is to be designed, the total code rate can be set to 0.5).

[0179] Step 2: Divide the information sequence to be transmitted into a first-level bit sequence and a second-level bit sequence according to the capacity ratio and the code length of the information sequence to be transmitted.

[0180] Specifically, the information sequence u to be transmitted in the equiprobable information source S is segmented according to the ratio of the two-bit sub-channel capacity to obtain the first-level bit sequence u 1 and the second-level bit sequence u 2 .

[0181] Step 3: Perform polar code encoding on the first-level bit sequence u 1 to obtain the first-level encoded bit sequence c 1 .

[0182] Step 4: Perform CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain the second-level encoded bit sequence.

[0183] As an alternative implementation, Step 4 specifically includes:[[]]

[0184] Perform CCDM distribution matching on the second-level bit sequence u 2 to obtain the shaping bit sequence b 2 . The shaping bit sequence b 2 is a sequence with unequal probabilities of "0" and "1". Among them, the implementation system structure of CCDM is as Figure 6 shown.

[0185] Perform BCH code encoding on the shaping bit sequence b 2 to obtain the second-level encoded bit sequence c 2 .

[0186] Step 5: Determine the flipping operation of the second-level encoded bit sequence c 1 based on the first-level encoded bit sequence c 2 ; The flipping operation is to flip or not flip.

[0187] Specifically, as Figure 7 shown, traverse each bit in c 1 . If the current bit in c 1 is "1", then flip the highest-level codeword c 2 (flipping means changing 0 to 1 and 1 to 0). If the current bit in c 1 is "0", then c 2 is not flipped.

[0188] Step 6: Process the second-level encoded bit sequence according to the flipping operation of the second-level encoded bit sequence to obtain the processed second-level encoded bit sequence x 2 . At this time, at the two-bit level, an equiprobable first-level encoded bit sequence c 1 can be obtained at the first bit level, and a second-level encoded ratio sequence x 2 with a higher probability of "1" than "0" at the second bit level.

[0189] Step 7: Using the set partitioning mapping rule, for the first-level coded bit sequence (at this time, in Figure 4 , the first-level coded bit sequence is represented by x 1 ) and the processed second-level coded bit sequence x 2 perform 4-PAM modulation to obtain a modulated symbol sequence X. The symbol probability distribution after 4-PAM modulation is as Figure 8 shown. Figure 8 In , the horizontal axis is the distribution of constellation signal points, that is, the energy magnitude carried by the signal points. The vertical axis is the value of the probability distribution.

[0190] Step 8: Use the channel to transmit the modulated symbol sequence X.

[0191] Specifically, transmit the modulated symbol through an additive white Gaussian noise (AWGN) channel with the channel model y = x + n. Where y is the channel output symbol, x is the channel input symbol, and n represents Gaussian noise with a mean of 0 and a variance of σ 2 .

[0192] Step 9: Demodulate the received first-level modulated symbol subsequence to obtain the first-level log-likelihood ratio information sequence L1; the first-level modulated symbol subsequence is a sequence composed of the bits corresponding to the sequence numbers of each bit of the first-level bit sequence in the received modulated symbol sequence Y.

[0193] Step 10: Perform a hard decision on the first-level log-likelihood ratio information sequence L1 to obtain an estimated value of the first-level coded bit sequence

[0194] As an optional implementation manner, step 10 specifically includes:

[0195] Determine the binary value of each bit in the first-level log-likelihood ratio information sequence .

[0196] Where, for any current bit in the first-level log-likelihood ratio information sequence :

[0197] Judge whether the value of the current bit is greater than 0.

[0198] If so, determine the binary value of the current bit as 1.

[0199] If not, determine the binary value of the current bit as 0.

[0200] Determine the sequence composed of the binary values of all bits in the first-level log-likelihood ratio information sequence as the estimated value of the first-level coded bit sequence

[0201] Step 11: Perform polar code decoding on the first-level log-likelihood ratio information sequence to obtain the first-level decoded bit sequence

[0202] Step 12: Demodulate the received second-level modulation symbol subsequence to obtain the second-level log-likelihood ratio information sequence L2; the second-level modulation symbol subsequence is a sequence composed of the bits in the received modulation symbol sequence Y corresponding to the sequence numbers of the bits in the second-level bit sequence.

[0203] Step 13: Perform hard decision on the second-level log-likelihood ratio information sequence L2 to obtain an estimated value of the second-level coded bit sequence.

[0204] As an optional implementation manner, Step 13 specifically includes:[[]]

[0205] Determine the binary value of each bit in the second-level log-likelihood ratio information sequence L2.

[0206] For any current bit in the second-level log-likelihood ratio information sequence L2:[[]]

[0207] Judge whether the value of the current bit is greater than 0.

[0208] If so, determine the binary value of the current bit as 1.

[0209] If not, determine the binary value of the current bit as 0.

[0210] Determine the sequence composed of the binary values of all bits in the second-level log-likelihood ratio information sequence L2 as the estimated value of the second-level coded bit sequence.

[0211] Step 14: Based on the estimated value of the first-level coded bit sequence, determine the flipping operation of the second-level log-likelihood ratio information sequence L2; the flipping operation is to flip or not to flip. The determination of the flipping operation is the same as in Step 5.

[0212] Step 15: Process the second-level log-likelihood ratio information sequence according to the flipping operation of the second-level log-likelihood ratio information sequence to obtain the second-level bit sequence to be decoded

[0213] Step 16: Perform block code decoding and CCDM demapping matching on the second-level bit sequence to be decoded in sequence to obtain the second-level decoded bit sequence

[0214] Step 17: Combine the first-level decoded bit sequence and the second-level decoded bit sequence to obtain the information sequence to be transmitted.

[0215] To verify the performance of each embodiment in the present invention, the embodiments of the present invention are compared with the traditional polar code multi-stage coding modulation system under 4-PAM modulation, and the simulation results are as Figure 9 shown Figure 9 wherein, Uniform represents the uniform scheme. PS represents the probability shaping scheme of the present invention. R is the system code rate. E b / N0 is the bit signal-to-noise ratio, that is, the ratio of the energy of each bit to the noise power spectral density, representing the degree of interference of the noise in the channel on the transmitted signal. From this Figure 9 it can be seen that when the code length of the information to be transmitted is 1024, in two working scenarios with code rates of 0.61 and 0.74, at the same bit error rate, the signal-to-noise ratio required by the PS scheme is lower, that is, the performance of the PS scheme is better, and the shaping gain can be effectively obtained. This simulation result proves the effectiveness of the present invention in designing the probability shaping scheme for the polar code multi-stage coding modulation system.

[0216] Embodiment 6

[0217] To implement the digital communication method based on multi-stage coding modulation in Embodiment 5, the present embodiment further provides a digital communication system based on multi-stage coding modulation, including:

[0218] A capacity ratio determination module, configured to determine the capacity ratio of the channel of the 4-PAM modulation system; the capacity ratio is the ratio of the capacity of the low-bit-level sub-channel of the channel to the capacity of the high-bit-level sub-channel.

[0219] A sequence decomposition module, configured to divide the information sequence to be transmitted into a first-level bit sequence and a second-level bit sequence according to the capacity ratio and the code length of the information sequence to be transmitted.

[0220] A first encoding module, configured to perform polar code encoding on the first-level bit sequence to obtain a first-level encoded bit sequence.

[0221] A second encoding module, configured to perform CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain a second-level encoded bit sequence.

[0222] A first flip judgment module, configured to determine the flip operation of the second-level encoded bit sequence based on the first-level encoded bit sequence; the flip operation is to flip or not to flip.

[0223] A first processing module, configured to process the second-level encoded bit sequence according to the flip operation of the second-level encoded bit sequence to obtain a processed second-level encoded bit sequence.

[0224] A modulation module, which is used to perform 4-PAM modulation on the first-level encoded bit sequence and the processed second-level encoded bit sequence according to the set partitioning mapping rule to obtain a modulated symbol sequence.

[0225] A transmission module, which is used to transmit the modulated symbol sequence through a channel.

[0226] A first-level demodulation module, which is used to demodulate the received first-level modulated symbol subsequence to obtain a first-level log-likelihood ratio information sequence; the first-level modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits in the first-level bit sequence in the received modulated symbol sequence.

[0227] A first hard decision module, which is used to perform hard decision on the first-level log-likelihood ratio information sequence to obtain an estimated value of the first-level encoded bit sequence.

[0228] A first-level decoding module, which is used to perform polar code decoding on the first-level log-likelihood ratio information sequence to obtain a first-level decoded bit sequence.

[0229] A second-level demodulation module, which is used to demodulate the received second-level modulated symbol subsequence to obtain a second-level log-likelihood ratio information sequence; the second-level modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits in the second-level bit sequence in the received modulated symbol sequence.

[0230] A second hard decision module, which is used to perform hard decision on the second-level log-likelihood ratio information sequence to obtain an estimated value of the second-level encoded bit sequence.

[0231] A second flip judgment module, which is used to determine the flip operation of the second-level log-likelihood ratio information sequence based on the estimated value of the first-level encoded bit sequence; the flip operation is either flipping or not flipping.

[0232] A second processing module, which is used to process the second-level log-likelihood ratio information sequence according to the flip operation of the second-level log-likelihood ratio information sequence to obtain a second-level bit sequence to be decoded.

[0233] A second-level decoding module, which is used to perform block code decoding and CCDM de-distribution matching on the second-level bit sequence to be decoded in sequence to obtain a second-level decoded bit sequence.

[0234] A decoding completion module, which is used to merge the first-level decoded bit sequence and the second-level decoded bit sequence to obtain an information sequence to be transmitted.

[0235] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section. Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A digital coding method based on multi-level coded modulation, characterized in that, The digital coding method based on multilevel coding modulation includes: Determine the capacity ratio of the channel of a 4-PAM modulation system; the capacity ratio is the ratio of the capacity of the low-bit-level sub-channel of the channel to the capacity of the high-bit-level sub-channel; According to the capacity ratio and the code length of the information sequence to be transmitted, divide the information sequence to be transmitted into a first-level bit sequence and a second-level bit sequence; Perform polar code encoding on the first-level bit sequence to obtain a first-level encoded bit sequence; Perform CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain a second-level encoded bit sequence; Determine the flipping operation of the second-level encoded bit sequence based on the first-level encoded bit sequence; the flipping operation is to flip or not to flip; Process the second-level encoded bit sequence according to the flipping operation of the second-level encoded bit sequence to obtain a processed second-level encoded bit sequence; Use the set partitioning mapping rule to perform 4-PAM modulation on the first-level encoded bit sequence and the processed second-level encoded bit sequence to obtain a modulation symbol sequence.

2. The digital coding method based on multilevel coded modulation according to claim 1, wherein Performing CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain a second-level encoded bit sequence specifically includes: Perform CCDM distribution matching on the second-level bit sequence to obtain a shaped bit sequence; Perform BCH code encoding on the shaped bit sequence to obtain the second-level encoded bit sequence.

3. A digital coding system based on multi-level coded modulation, characterized in that, The digital coding system based on multilevel coding modulation includes: A capacity ratio determination module for determining the capacity ratio of the channel of a 4-PAM modulation system; the capacity ratio is the ratio of the capacity of the low-bit-level sub-channel of the channel to the capacity of the high-bit-level sub-channel; A sequence decomposition module for dividing the information sequence to be transmitted into a first-level bit sequence and a second-level bit sequence according to the capacity ratio and the code length of the information sequence to be transmitted; A first encoding module for performing polar code encoding on the first-level bit sequence to obtain a first-level encoded bit sequence; A second encoding module for performing CCDM distribution matching and BCH code encoding on the second-level bit sequence in sequence to obtain a second-level encoded bit sequence; A first flipping judgment module for determining the flipping operation of the second-level encoded bit sequence based on the first-level encoded bit sequence; the flipping operation is to flip or not to flip; A first processing module for processing the second-level encoded bit sequence according to the flipping operation of the second-level encoded bit sequence to obtain a processed second-level encoded bit sequence; A modulation module for performing 4-PAM modulation on the first-level encoded bit sequence and the processed second-level encoded bit sequence using the set partitioning mapping rule to obtain a modulation symbol sequence.

4. A digital decoding method based on multi-level coded modulation, characterized in that, The digital decoding method based on multilevel coding modulation includes: Demodulate the received first - stage modulated symbol subsequence to obtain a first - stage log - likelihood ratio information sequence; the first - stage modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of each bit of the first - stage bit sequence in the received modulated symbol sequence; the first - stage bit sequence is determined by partitioning the to - be - transmitted information sequence according to the capacity ratio of the channel of the 4 - PAM modulation system and the code length of the to - be - transmitted information sequence; the modulated symbol sequence is determined by encoding and modulating the to - be - transmitted information sequence; Perform a hard decision on the first - stage log - likelihood ratio information sequence to obtain an estimated value of the first - stage encoded bit sequence; Perform polar code decoding on the first - stage log - likelihood ratio information sequence to obtain a first - stage decoded bit sequence; Demodulate the received second - stage modulated symbol subsequence to obtain a second - stage log - likelihood ratio information sequence; the second - stage modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of each bit of the second - stage bit sequence in the received modulated symbol sequence; the second - stage bit sequence is determined by partitioning the to - be - transmitted information sequence according to the capacity ratio of the channel of the 4 - PAM modulation system and the code length of the to - be - transmitted information sequence; Perform a hard decision on the second - stage log - likelihood ratio information sequence to obtain an estimated value of the second - stage encoded bit sequence; Based on the estimated value of the first - stage encoded bit sequence, determine the flipping operation of the second - stage log - likelihood ratio information sequence; the flipping operation is either flipping or not flipping; Process the second - stage log - likelihood ratio information sequence according to the flipping operation of the second - stage log - likelihood ratio information sequence to obtain a second - stage bit sequence to be decoded; Perform block code decoding and CCDM de - distribution matching on the second - stage bit sequence to be decoded in sequence to obtain a second - stage decoded bit sequence; Merge the first - stage decoded bit sequence and the second - stage decoded bit sequence to obtain the to - be - transmitted information sequence.

5. The digital decoding method based on multilevel coded modulation according to claim 4, wherein Performing a hard decision on the first - stage log - likelihood ratio information sequence to obtain an estimated value of the first - stage encoded bit sequence specifically includes: Determine the binary value of each bit in the first - stage log - likelihood ratio information sequence; Among them, for any current bit in the first - stage log - likelihood ratio information sequence: Judge whether the value of the current bit is greater than 0; If so, determine the binary value of the current bit as 1; If not, determine the binary value of the current bit as 0; Determine the sequence composed of the binary values of all bits in the first - stage log - likelihood ratio information sequence as the estimated value of the first - stage encoded bit sequence.

6. The digital decoding method based on multilevel coded modulation according to claim 4, wherein Performing a hard decision on the second - stage log - likelihood ratio information sequence to obtain an estimated value of the second - stage encoded bit sequence specifically includes: Determine the binary value of each bit in the second - stage log - likelihood ratio information sequence; For any current bit in the second - stage log - likelihood ratio information sequence: Judge whether the value of the current bit is greater than 0; If so, determine the binary value of the current bit as 1; If not, determine the binary value of the current bit as 0; Determine the sequence composed of the binary values of all bits in the second - stage log - likelihood ratio information sequence as the estimated value of the second - stage encoded bit sequence.

7. A digital decoding system based on multilevel coded modulation, characterized in that The digital decoding system based on multi - level coded modulation includes: A first - stage demodulation module, configured to demodulate the received first - stage modulation symbol subsequence to obtain a first - stage log - likelihood ratio information sequence; the first - stage modulation symbol subsequence is a sequence composed of bits corresponding to the serial numbers of each bit of the first - stage bit sequence in the received modulation symbol sequence; the first - stage bit sequence is determined by partitioning the to - be - transmitted information sequence according to the capacity ratio of the channels of the 4 - PAM modulation system and the code length of the to - be - transmitted information sequence; the modulation symbol sequence is determined by encoding and modulating the to - be - transmitted information sequence; A first hard - decision module, configured to perform hard - decision on the first - stage log - likelihood ratio information sequence to obtain an estimated value of the first - stage coded bit sequence; A first - stage decoding module, configured to perform polar - code decoding on the first - stage log - likelihood ratio information sequence to obtain a first - stage decoded bit sequence; A second - stage demodulation module, configured to demodulate the received second - stage modulation symbol subsequence to obtain a second - stage log - likelihood ratio information sequence; the second - stage modulation symbol subsequence is a sequence composed of bits corresponding to the serial numbers of each bit of the second - stage bit sequence in the received modulation symbol sequence; the second - stage bit sequence is determined by partitioning the to - be - transmitted information sequence according to the capacity ratio of the channels of the 4 - PAM modulation system and the code length of the to - be - transmitted information sequence; A second hard - decision module, configured to perform hard - decision on the second - stage log - likelihood ratio information sequence to obtain an estimated value of the second - stage coded bit sequence; A second flip - judgment module, configured to determine the flip operation of the second - stage log - likelihood ratio information sequence based on the estimated value of the first - stage coded bit sequence; the flip operation is either flipping or not flipping; A second processing module, configured to process the second - stage log - likelihood ratio information sequence according to the flip operation of the second - stage log - likelihood ratio information sequence to obtain a second - stage bit sequence to be decoded; A second - stage decoding module, configured to perform block - code decoding and CCDM de - distribution matching on the second - stage bit sequence to be decoded in sequence to obtain a second - stage decoded bit sequence; A decoding - completion module, configured to combine the first - stage decoded bit sequence and the second - stage decoded bit sequence to obtain the to - be - transmitted information sequence.

8. A digital communication method based on multilevel coded modulation, characterized in that, The digital communication method based on multi - level coded modulation includes: Determining the capacity ratio of the channels of the 4 - PAM modulation system; the capacity ratio is the ratio of the capacity of the low - bit - level sub - channels of the channel to the capacity of the high - bit - level sub - channels; Dividing the to - be - transmitted information sequence into a first - stage bit sequence and a second - stage bit sequence according to the capacity ratio and the code length of the to - be - transmitted information sequence; Performing polar - code encoding on the first - stage bit sequence to obtain a first - stage coded bit sequence; Performing CCDM distribution matching and BCH - code encoding on the second - stage bit sequence in sequence to obtain a second - stage coded bit sequence; Determining the flip operation of the second - stage coded bit sequence based on the first - stage coded bit sequence; the flip operation is either flipping or not flipping; Process the second - level encoded bit sequence according to the flipping operation of the second - level encoded bit sequence to obtain the processed second - level encoded bit sequence; Adopt the set - partitioning mapping rule to perform 4 - PAM modulation on the first - level encoded bit sequence and the processed second - level encoded bit sequence to obtain a modulation symbol sequence; Use the channel to transmit the modulation symbol sequence; Demodulate the received first - level modulation symbol subsequence to obtain a first - level log - likelihood ratio information sequence; the first - level modulation symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits of the first - level bit sequence in the modulation symbol sequence; Perform a hard decision on the first - level log - likelihood ratio information sequence to obtain an estimated value of the first - level encoded bit sequence; Perform polar code decoding on the first - level log - likelihood ratio information sequence to obtain a first - level decoded bit sequence; Demodulate the received second - level modulation symbol subsequence to obtain a second - level log - likelihood ratio information sequence; the second - level modulation symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits of the second - level bit sequence in the modulation symbol sequence; Perform a hard decision on the second - level log - likelihood ratio information sequence to obtain an estimated value of the second - level encoded bit sequence; Based on the estimated value of the first - level encoded bit sequence, determine the flipping operation of the second - level log - likelihood ratio information sequence; the flipping operation is to flip or not to flip; Process the second - level log - likelihood ratio information sequence according to the flipping operation of the second - level log - likelihood ratio information sequence to obtain a second - level bit sequence to be decoded; Perform block code decoding and CCDM dematching on the second - level bit sequence to be decoded in sequence to obtain a second - level decoded bit sequence; Merge the first - level decoded bit sequence and the second - level decoded bit sequence to obtain the information sequence to be transmitted.

9. A digital communication system based on multilevel coded modulation, characterized in that, The digital communication system based on multilevel coded modulation includes: A capacity ratio determination module for determining the capacity ratio of the channel of a 4 - PAM modulation system; the capacity ratio is the ratio of the capacity of the low - bit - level sub - channel and the high - bit - level sub - channel of the channel; A sequence decomposition module for dividing the information sequence to be transmitted into a first - level bit sequence and a second - level bit sequence according to the capacity ratio and the code length of the information sequence to be transmitted; A first encoding module for performing polar code encoding on the first - level bit sequence to obtain a first - level encoded bit sequence; A second encoding module for performing CCDM matching and BCH code encoding on the second - level bit sequence in sequence to obtain a second - level encoded bit sequence; A first flipping judgment module for determining the flipping operation of the second - level encoded bit sequence based on the first - level encoded bit sequence; the flipping operation is to flip or not to flip; A first processing module for processing the second - level encoded bit sequence according to the flipping operation of the second - level encoded bit sequence to obtain the processed second - level encoded bit sequence; A modulation module, configured to perform 4-PAM modulation on the first-level encoded bit sequence and the processed second-level encoded bit sequence according to the set partitioning mapping rule to obtain a modulated symbol sequence; A transmission module, configured to transmit the modulated symbol sequence through the channel; A first-level demodulation module, configured to demodulate the received first-level modulated symbol subsequence to obtain a first-level log-likelihood ratio information sequence; the first-level modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits in the first-level bit sequence in the modulated symbol sequence; A first hard decision module, configured to perform hard decision on the first-level log-likelihood ratio information sequence to obtain an estimated value of the first-level encoded bit sequence; A first-level decoding module, configured to perform polar code decoding on the first-level log-likelihood ratio information sequence to obtain a first-level decoded bit sequence; A second-level demodulation module, configured to demodulate the received second-level modulated symbol subsequence to obtain a second-level log-likelihood ratio information sequence; the second-level modulated symbol subsequence is a sequence composed of bits corresponding to the sequence numbers of the bits in the second-level bit sequence in the modulated symbol sequence; A second hard decision module, configured to perform hard decision on the second-level log-likelihood ratio information sequence to obtain an estimated value of the second-level encoded bit sequence; A second flip determination module, configured to determine a flip operation of the second-level log-likelihood ratio information sequence based on the estimated value of the first-level encoded bit sequence; the flip operation is to flip or not to flip; A second processing module, configured to process the second-level log-likelihood ratio information sequence according to the flip operation of the second-level log-likelihood ratio information sequence to obtain a second-level bit sequence to be decoded; A second-level decoding module, configured to perform block code decoding and CCDM demap matching on the second-level bit sequence to be decoded in sequence to obtain a second-level decoded bit sequence; A decoding completion module, configured to merge the first-level decoded bit sequence and the second-level decoded bit sequence to obtain the information sequence to be transmitted.

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