A reliability parameter aided low complexity polar code rate matching method

Abstract

The application claims a reliability parameter assisted low complexity polar code rate matching method, belonging to the technical field of wireless communication. In view of the problem that the recursive structure of polar code makes it difficult to select suitable puncturing bits during rate matching, a polar code puncturing bit selection algorithm based on reliability parameters is proposed. Based on the analysis of the decoding process of polar code and the influence of the box operation on the selected puncturing bits, a kind of information bit reliability parameter is defined to calculate the reliability of the candidate puncturing bits. The optimal puncturing bits are selected by solving the maximum reliability parameter minimum value through iteration. In view of the problem that the existing polar code rate matching method has high complexity, an interleaving algorithm based on rate matching parameter mapping and a pruning serial cancellation list decoding algorithm are proposed, which avoids the secondary sorting calculation of the interleaver and simplifies the updating strategy of the calculation unit of the decoder. The proposed polar code rate matching method can not only improve the rate matching coding gain, but also effectively reduce the calculation complexity.

Description

Technical Field

[0001] The present invention relates to a polar code rate matching method, and in particular to a reliability parameter-assisted low-complexity polar code rate matching method, belonging to the technical field of wireless communications. Background Art

[0002] In 2008, Arikan first proposed a new fundamental concept for channel coding, namely channel polarization, at the International Conference on Information Theory (ISIT). He further elaborated on this concept in a 2009 paper published in Transactions on Information Theory, proposing a new coding scheme called polar codes. The paper provided a precise construction method for polar codes and demonstrated for the first time that they achieve the Shannon limit channel capacity. Due to their excellent performance with medium to long block lengths and low decoding complexity, they have now been standardized for use in 5G eMBB data channels.

[0003] In ideal error-correcting coding theory, the channels of digital communication systems are often ideal channels free of noise and interference. Channel state information (CSI) can be accurately estimated at the transmitting end of these ideal channels. With this state information, coding parameters can be set according to current coding requirements. However, in real-world communications, channel conditions and system resources can fluctuate rapidly. For example, in locations far from a base station or when people are moving at high speeds, channel state information is often difficult to accurately estimate. To improve communication reliability and transmission efficiency, channel coding parameters (such as code length, code rate, and information bit length) must be able to be continuously adjusted according to actual conditions during information transmission. This technique for adjusting coding parameters is called rate matching.

[0004] However, rate matching technology for polar codes still faces challenges: polar codes are fixed-rate block codes, making it difficult to select an appropriate code rate for transmission when the CSI is unknown at the transmitter. Selecting a code rate that is too high can cause decoding failure when channel capacity is low; selecting a code rate that is too low can result in low transmission efficiency. Therefore, selecting the most appropriate rate matching bit is crucial. However, current rate matching schemes suffer from significant performance loss and lack metrics that qualitatively and quantitatively describe the rate matching process. To address this issue, the present invention proposes a polar code rate matching method based on reliability parameters to quantify these metrics. By analyzing the log-likelihood ratio information propagation from the channel output to the information bit, it is found that the LLR reliability of the information bit traversing the direct path is strongly affected by the channel output. By analyzing the information propagation paths during the decoding process, the direct path of the information bit is defined as the path from the information bit to the channel output with the fewest box-add operations (box-add operations reduce output reliability). Taking into account the gain of adjacent paths to the direct path in the summation operation, an information bit reliability metric is introduced. The drilling positions are found step by step through the basis while maximizing the minimum reliability score in the reliability parameters. Summary of the Invention

[0005] The present invention aims to solve the above problems in the prior art. It proposes a low-complexity polar code rate matching method assisted by reliability parameters. The technical solution of the present invention is as follows:

[0006] A reliability parameter-assisted low-complexity polar code rate matching method comprises the following steps:

[0007] 101. Initialize and obtain polar code rate matching parameters, including information sequence length K, encoding code length N, target code length M, and code rate defined as R = K / N.

[0008] 102. Construct an information sequence u and add CRC check bits before polarization coding.

[0009] 103. Polarization coding, outputting a coding sequence;

[0010] 104. Determine the puncturing position and puncturing parameters, calculate the code length according to the code rate required by the dynamic link, and thus determine the parameters of the puncturing method to be used. The number of punctures is recorded as P = MN.

[0011] 105. Puncture the coded sequence according to the puncturing parameters determined in 104. The process of determining the puncturing position is the design of the puncturing pattern. The puncturing pattern vector is defined as a vector p = (p1, p2, ..., p N ), where p i ∈{0,1},i=1,2,…,N,p in the vector i =0 means that the i-th bit corresponds to the perforated bit;

[0012] 106. Reliability sorting sequence obtained by the punching algorithm Interleave the punctured sequence to obtain an interleaved sequence

[0013] 107. The transmitting end modulates the bit-interleaved sequence and then transmits the modulated sequence.

[0014] 108. The receiving end receives the modulated signal transmitted through the wireless channel and performs rate dematching to obtain a coding sequence, denoted as y.

[0015] 109. Optimize the decoder structure according to the puncturing pattern determined in 104, optimize the update strategy of the check nodes and variable nodes in the polar code serial cancellation column (SCL) decoding structure using puncturing parameter mapping, set the log-likelihood ratio of the virtual channel caused by puncturing to 0 at the decoding end, and output the optimized SCL decoder;

[0016] 110. Use the SCL decoder optimized in 109 to perform polar code decoding. Pass the decoded candidate sequence through a CRC checker. If the check passes, output the candidate sequence. Otherwise, return to continue SCL decoding.

[0017] Furthermore, the step 103, polarization coding, outputting the coding sequence, is specifically as follows: first constructing a generator matrix Among them B N represents a bit-reversal permutation matrix; represents the kernel matrix; Indicates doing n times of Kronecker product; then polarization coding is performed according to the generator matrix, and the output coding sequence is The channel input sequence set (u1,u2,…,u N ).

[0018] Furthermore, the step 104 determines the puncturing position and puncturing parameters, calculates the code length according to the code rate required by the dynamic link, and thus determines the puncturing parameters of the adopted method, and denotes the number of punctures as P=MN. The specific steps include:

[0019] (1) Initialization

[0020] Input: Initial perforation pattern and the target drilling position number 0<P≤NK;

[0021] (2) Candidate set

[0022] Construct candidate punctured bit sets represents the frozen bit set, π i-1 represents the puncturing pattern traversal list, i∈(1,2,…,N), the set contains all the unpunctured bits;

[0023] (3) Update reliability parameters

[0024] For each candidate bit Do the following:

[0025] a. Introduce reliability parameter update calculation and store reliability parameter sequence s b :=s(Π i-1 ∪{b})

[0026]

[0027] s k Represents the reliability parameter; r j The gain that the adjacent path brings to the current direct path; represents the set of adjacent paths that have a gain on the direct path through the summation operation; represents the information bit set; w H is the channel transition probability at that location; represents the i-th bit of the k-th stage; a is a weighting factor obtained through simulation calculation;

[0028] b. Sort the reliability parameter sequence in ascending order to obtain s b Sorting sequence

[0029] (4) Find a new drilling location

[0030] a. Find new puncturing bits by maximizing the minimum value in the reliability parameter sequence in turn; for j from 1 to K, select The largest candidate bit is placed into the candidate set:

[0031]

[0032] b. If there is only one candidate bit in Σ, then the candidate bit becomes the new puncture bit and jumps out of the loop, otherwise update the candidate set

[0033] (5) Update the drilling mode

[0034] a. If there is only one candidate bit in ∑, update the puncturing pattern Π i :=Π i-1 ∪Σ;

[0035] b. If there are multiple candidate positions and all candidate positions have been traversed, the position with the smallest index π = minΣ and the puncturing pattern π is updated i :=Π i-1 ∪{π}.

[0036] Furthermore, the step 105 specifically includes the following steps: estimating and sorting the reliability of each polarized subchannel using a Gaussian approximation (GA) based on the puncturing positions determined in step 104, selecting K polarized subchannels with the highest reliability from the N polarized subchannels to place information bits, and placing frozen bits in the remaining NK subchannels, thereby constructing an information sequence u, specifically including:

[0037] For AWGN channels, set the channel input to x , the output is set to y, the system uses binary phase shift keying BPSK modulation, then there is

[0038] y=(-2x+1)+n (0.3)

[0039] Among them, the value range of information bit x is 0 or 1, n is the noise interference encountered during channel transmission, n~N(0,σ 2 ), then the log-likelihood ratios (LLRs) of the AWGN channel are expressed as,

[0040]

[0041] Output signal y~N(0,σ 2 ), then the log-likelihood ratio LLR(y) has a mean of 2 / σ 2 , with a variance of 4 / σ 2 Gaussian distribution of each polarization channel The probability density function of the LLR value is The distribution of To express it, then in the calculation process of the LLRs mean, there is the following recursive relationship,

[0042]

[0043]

[0044] in, and represent the mean and variance of the log-likelihood ratio in the AWGN channel;

[0045] The expression of the function is,

[0046]

[0047] Due to the analysis, When it is greater than 0, it is a monotonically decreasing function, and Will Simplified to,

[0048]

[0049] After recursive operation of equations (1.5) and (1.6), the mean of the target channel log-likelihood ratio is obtained Then, according to the integral operation of formula (1.8), each polarization channel can be obtained Reliability metric P e (A i ).

[0050] Furthermore, the step 106 is specifically as follows: the reliability parameter of the sequence is obtained by using the reliability parameter-assisted puncturing algorithm. The reliability of any bit channel s i Uniquely corresponds to the coded bit x at the corresponding position in the codeword i , i=1,2,…,N, right Sort by size from small to large, and the resulting sequence is the index number of the polar code bit channel reliability sorting, so that Introduce interleaving register to store reliability parameters; Arrange them in a staggered manner, that is, the one with the largest capacity value is placed in the first place, the smallest in the second place, the second largest in the third place, and so on, completing the position alternation of the bit channel reliability parameters to obtain the interleaved target sequence. For the first interleaved sequence, the correlation is determined based on the output of the minimum polarization operation unit in the polarization process, and the two symbols with the strongest correlation are placed at farther positions in the symbol sequence to obtain the second interleaved sequence.

[0051] Furthermore, the step 108 in which the receiving end receives the modulated signal transmitted through the wireless channel and performs rate dematching to obtain a coded sequence, denoted as y, specifically includes:

[0052] In the decoding structure of the two-bit polarization unit, when y1 is punctured, the log-likelihood ratios (LLRs) of u1 and u2 can be directly obtained by LLR(u1)=LLR(y1) and LLR(u2)=LLR(y2).

[0053] Furthermore, the step 109 specifically includes: generating a matrix According to the puncturing bit selection method, puncturing is performed at the coding bit end in the order of index from small to large, F j,k and G j,k Represent the kth box operator and sum operator of the jth layer decoding structure respectively, so that a group of F j,k and G j,k Computing modules form a computing unit.

[0054] Furthermore, the decoder optimization criterion is as follows: for the i-th puncturing position ui , i=1,2,…,M, let (b n ,b n-1 ,…,b1) represents the binary form of the position, then for any bit b k = 0, correspondingly, some calculation units of the jth layer in the decoding structure can be omitted, that is, these omitted calculation units can be directly replaced by registers. The decoding part first obtains the transition probability of each sub-channel by separating the composite channel. Since the SCL decoding algorithm retains multiple decoding paths, a parameter is needed to measure and evaluate the performance of each path when continuously updating the path storage and finally making a decision output on the decoding. Therefore, a parameter is defined Indicates the lth extended path when decoding to the i-th position The path metric is defined as

[0055]

[0056] in, is the polarization channel log-likelihood ratio at the current location, is the output sequence after encoding; analysis shows that the larger the transition probability, the smaller the metric value of the corresponding path, so L candidate paths with the smallest path metric values ​​are selected; the candidate sequence after decoding is subjected to CRC check, and if the check result passes, the sequence is retained and output, otherwise it is decoded again.

[0057] The advantages and beneficial effects of the present invention are as follows:

[0058] 1. The present invention adopts a low-complexity polar code rate matching method assisted by a reliability parameter. By analyzing the direct path and adjacent paths in the polar code decoding path, a reliability parameter is introduced, and the most suitable puncturing bits are found based on this parameter, effectively reducing the performance loss caused by the rate matching technology. 2. By using the Gaussian approximation algorithm to construct the information bits and sort the puncturing bits, the applicable scenarios are improved and the coding complexity is effectively reduced. 3. By introducing an interleaving register to store the reliability parameters, secondary calculations are avoided and the computational complexity is reduced. The addition of a secondary interleaving operation improves the error correction performance. 4. By mapping the rate matching parameters to the SCL decoder, some calculation units in the decoding structure are omitted. These omitted calculation units can be directly replaced by registers, thereby reducing space complexity and time complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The present invention provides a low-complexity polar code rate matching method assisted by reliability parameters in a preferred embodiment.

[0060] Figure 2 FIG. 4 is a block diagram of a rate matching system for polar codes in an embodiment.

[0061] Figure 3 Schematic diagram of the structure of a polar code decoding unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] The following will describe the technical solutions in the embodiments of the present invention in detail with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention.

[0063] The technical solution of the present invention to solve the above technical problems is:

[0064] Figure 2 This is a block diagram of the rate matching system of the polar code of the present invention, consisting of Figure 2 It can be seen that the polar code transmission model of the present invention includes a CRC encoder unit, a polar coding unit, a rate matching unit, a de-rate matching unit, an SCL decoding unit, and a CRC check unit. The rate matching unit determines the number of puncturing bits based on the estimated wireless channel state and selects the optimal puncturing bits using the rate matching method proposed in the present invention.

[0065] The present invention proposes a reliability parameter-assisted low-complexity polar code rate matching method based on the decoding path such as Figure 3 As shown in the figure, by analyzing the propagation of log-likelihood ratio (LLR) information from the channel output to the information bit, it is found that there are certain paths (called direct paths) along which the reliability of the LLR value of the information bit is strongly affected by the channel output. By analyzing the information propagation paths during the decoding process, the direct path of the information bit is defined as the path from the information bit to the channel output with the least number of box-add operations (box-add operations reduce output reliability). The gain of the adjacent path to the direct path in the summation operation is considered. Because the gain of the adjacent path with frozen bits is stronger than that of the path with information bits, a reliability parameter is introduced to evaluate the reliability of the information bit:

[0066]

[0067] Using this basis, the algorithm gradually finds punctured bits while maximizing the minimum reliability score in the reliability parameter sequence. The algorithm finds a new punctured bit among the unpunctured coded bits that maximizes the minimum reliability parameter in formula (1.17). The algorithm continues searching for new punctured bits until it reaches the target number of punctured bits.

[0068] A reliability parameter-assisted low-complexity polar code rate matching method is characterized in that: the method assumes that the information sequence length is K, the encoding code length is N, the code rate is defined as R=K / N, and the target code length is M, and includes the following steps:

[0069] 101. Initialize and obtain polar code rate matching parameters, including information sequence length K, encoding code length N, and target code length M.

[0070] 102. Construct an information sequence u and add CRC check bits before polarization coding.

[0071] 103. Polar coding, output coding sequence, specifically: first construct the generator matrix Among them B N represents the bit reversal permutation matrix; represents the kernel matrix; Indicates doing n times of Kronecker product. Then polarization coding is performed according to the generator matrix, and the output coding sequence is

[0072] 104. Determine puncturing locations and puncturing parameters. Specifically, calculate the code length based on the required code rate of the dynamic link, thereby determining the puncturing parameters of the adopted method. The number of punctures is denoted as P = MN. The puncturing locations are determined based on the reliability parameter and the puncturing algorithm proposed in the present invention.

[0073] 105. Puncture the coded sequence according to the puncturing parameters determined in 104. The process of determining the puncturing position is also called the design of the puncturing pattern. The puncturing pattern vector is defined as a vector p = (p1, p2, ..., p N ), where p i ∈{0,1},i=1,2,…,N,p in the vector i = 0 means that the i-th bit corresponds to the puncturing bit. For example, assuming the required code length M = 5 and the mother code length N = 8, the number of bits that need to be punctured is NM = 3. After reliability-selective puncturing, the puncturing pattern is p = (0, 1, 0, 1, 0, 1, 1, 1), that is, the 1st, 3rd, and 5th bits of the codeword after the encoder are punctured. Before being transmitted to the channel, the message carried by these three bits needs to be discarded. Output coded sequence after puncturing

[0074] 106. Reliability sorting sequence obtained by the punching algorithm Interleave the punctured sequence to obtain an interleaved sequence

[0075] 107. The transmitting end modulates the bit-interleaved sequence and then transmits the modulated sequence.

[0076] 108. The receiving end receives the modulated signal transmitted through the wireless channel and performs rate dematching to obtain a coding sequence, denoted as y.

[0077] 109. Optimize the decoder structure according to the puncturing pattern determined in 104, optimize the update strategy of the check nodes and variable nodes in the polar code SCL decoding structure using the mapping of puncturing parameters, set the log-likelihood ratio of the virtual channel caused by puncturing to 0 at the decoding end, and output the optimized SCL decoder.

[0078] 110. Use the SCL decoder optimized in 109 to perform polar code decoding. Pass the decoded candidate sequence through a CRC checker. If the check passes, output the candidate sequence. Otherwise, return to continue SCL decoding.

[0079] Furthermore, in step 101, the optimal puncturing bit selection is ensured by maximizing the minimum reliability parameter. This method can effectively reduce the error performance loss of the punctured polar code. The specific steps include:

[0080] (1) Initialization

[0081] Input: Initial perforation pattern and the target drilling position number 0<P≤NK

[0082] (2) Candidate Set

[0083] Construct candidate punctured bit sets This set contains all the unpunched bits.

[0084] (3) Update reliability parameters

[0085] For each candidate bit Do the following:

[0086] a. Introduce reliability parameter update calculation and store reliability parameter sequence s b :=s(Π i-1 ∪{b})

[0087]

[0088] s k Represents the reliability parameter; r j The gain (information bits or frozen bits) that the adjacent path brings to the current direct path; represents the set of adjacent paths that have a gain on the direct path through the summation operation; represents the information bit set; w H is the channel transition probability at that location; represents the i-th bit in the k-th stage; a is a weighting factor obtained through simulation calculation.

[0089] b. Sort the reliability parameter sequence in ascending order to obtain s b Sorting sequence

[0090] (4) Finding new puncturing positions

[0091] a. Find new puncturing positions by maximizing the minimum of the sequence of reliability parameters in turn. For j from 1 to K, select the candidate position that maximizes and put it into the candidate set:

[0092]

[0093] b. If there is only one candidate position in ∑, then the candidate position becomes the new puncturing position and jump out of the loop, otherwise update the candidate set

[0094] (5) Update the puncturing pattern

[0095] a. If there is only one candidate position in ∑, then update the puncturing pattern Π i : = Π i-1 ∪∑

[0096] b. If there are multiple candidate positions and all candidate positions have been traversed, then index the smallest position π = min∑ and update the puncturing pattern Π i : = Π i-1 ∪{π}.

[0097] Further, the step 105 is to estimate and sort the reliabilities of each polar subchannel by using Gaussian Approximation (GA) on the puncturing positions determined according to step one, select K subchannels with the highest reliabilities from N polar subchannels to place information bits, and place frozen bits in the remaining N-K subchannels, thereby constructing an information sequence u. Specifically, the step 105 includes the following steps:

[0098] For an AWGN channel, the input of the channel is set as x , the output is set as y, and the system is modulated by binary phase shift keying (BPSK), so

[0099] y = (-2x + 1) + n (0.13)

[0100] where the value range of the information bit x is 0 or 1, n is the noise interference encountered during channel transmission, and n ~ N (0, σ 2 ). Then the log-likelihood ratio (LLR) of the AWGN channel can be expressed as,

[0101]

[0102] where since the input is usually subject to independent Gaussian distribution, the output signal y ~ N (0, σ 2 ), and at this time the log-likelihood ratio (LLR) (y) is the mean value of 2 / σ2 , with a variance of 4 / σ 2 Since the Gaussian distribution can be completely determined by the mean and variance, the probability density function can be calculated by only obtaining the mean and variance. When using the Gaussian approximation, due to the mathematical relationship between the mean and variance, we only need to calculate the mean of the log-likelihood ratio. In the AWGN channel, each polarization channel The probability density function of the LLR value is The distribution can be used To express it, then in the calculation process of the LLRs mean, there is the following recursive relationship,

[0103]

[0104]

[0105] The expression of the function is,

[0106]

[0107] Due to the analysis, When it is greater than 0, it is a monotonically decreasing function, and In order to reduce the calculation and complexity, we can Simplified to,

[0108]

[0109] After recursive operation of equations (1.13) and (1.14), the mean of the target channel log-likelihood ratio can be obtained: Then, according to the integral operation of formula (1.16), the polarization channels can be obtained Reliability metric P e (A i ).

[0110] Furthermore, the reliability parameter-assisted low-complexity polar code rate matching method according to claim 1 is characterized in that: 106, specifically: the reliability parameter of the sequence obtained by the reliability parameter-assisted puncturing algorithm is The reliability of any bit channel s i = (i = 1, 2, ..., N) uniquely corresponds to the coded bit x at the corresponding position in the codeword i =(i=1,2,…,N), right Sort by size from small to large, and the resulting sequence is the index number of the polar code bit channel reliability sorting, so that Introduce interleaving register to store reliability parameters to avoid secondary calculation; Arrange them in a staggered manner, that is, the one with the largest capacity value is placed in the first place, the smallest in the second place, the second largest in the third place, and so on, completing the position alternation of the bit channel reliability parameters to obtain the interleaved target sequence. For the first interleaved sequence, the correlation is determined based on the output of the minimum polarization operation unit in the polarization process, and the two symbols with the strongest correlation are placed at farther positions in the symbol sequence to obtain the second interleaved sequence. The interleaving algorithm proposed in this invention first calculates the reliability of polarization channels based on the mapping relationship between coded bits and polarization channels. High-reliability bit channels are then interleaved with low-reliability bit channels. Using the high-reliability bit channels to assist in decoding the low-reliability bit channels, this improves the error correction performance of the polarization code while maintaining low complexity. Secondly, the resulting interleaved bit sequence is sorted from largest to smallest based on correlation, with the two most strongly correlated bits positioned as far apart as possible in the sequence (i.e., the sequence is interleaved based on correlation strength). This prevents two highly correlated bits from experiencing simultaneous errors due to the same channel fading.

[0111] Furthermore, the reliability parameter-assisted low-complexity polar code rate matching method according to claim 1 is characterized in that: 108 and 109 are specifically: in the decoding structure of the two-bit polar unit, when y1 is punctured, the log likelihood ratio (LLR) of u1 and u2 can be directly obtained by LLR(u1)=LLR(y1) and LLR(u2)=LLR(y2). For the generator matrix According to the puncturing bit selection method, puncturing is performed at the coding bit end in the order of index from small to large, F j,k and G j,k The kth box operator and sum operator represent the jth layer decoding structure respectively. The decoder optimization criterion is as follows: for the i-th (i=1,2,…,M) puncturing position u i , let (b n ,b n-1 ,…,b1) represents the binary form of the position, then for any bit b k= 0, some computational units in the jth layer of the decoding structure can be omitted. These omitted computational units can be directly replaced by registers, reducing both space and time complexity. The decoding part first separates the composite channel to obtain the transition probabilities of each subchannel. It then uses the corresponding decision formula to obtain the decoding result. When selecting branches at each layer, it retains a table of multiple candidate paths, using the breadth-first search principle, with each decoding path reserved for subsequent processing. The candidate sequence after decoding is subjected to a CRC check. If the check result passes, the sequence is retained and output; otherwise, decoding is performed again.

[0112] The systems, devices, modules or units described in the above embodiments may be implemented by computer chips or entities, or by products with certain functions.

[0113] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0114] The above embodiments should be understood as merely illustrating the present invention and not as limiting the scope of protection of the present invention. After reading the contents of the present invention, technicians may make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A reliability parameter-assisted low-complexity polar code rate matching method, characterized in that: The following steps are involved:

101. Initialize and obtain polar code rate matching parameters, including information sequence length K, encoding code length N, target code length M, and code rate defined as R = K / N.

102. Construct an information sequence u and add CRC check bits before polarization coding.

103. Polarization coding, outputting a coding sequence; 104. Determine the puncturing position and puncturing parameters, calculate the code length according to the code rate required by the dynamic link, and thus determine the parameters of the puncturing method to be used. The number of punctures is recorded as P = MN.

105. Puncture the coded sequence according to the puncturing parameters determined in 104. The process of determining the puncturing position is the design of the puncturing pattern. The puncturing pattern vector is defined as a vector p = (p1, p2, ..., p N ), where p i ∈{0,1},i=1,2,…,N,p in the vector i =0 means that the i-th bit corresponds to the perforated bit; 106. Reliability sorting sequence obtained by the punching algorithm Interleave the punctured sequence to obtain an interleaved sequence 107. The transmitting end modulates the bit-interleaved sequence and then transmits the modulated sequence.

108. The receiving end receives the modulated signal transmitted through the wireless channel and performs rate dematching to obtain a coded sequence, denoted as y.

109. Optimize the decoder structure according to the puncturing pattern determined in 104, optimize the update strategy of the check nodes and variable nodes in the polar code serial cancellation column (SCL) decoding structure using puncturing parameter mapping, set the log-likelihood ratio of the virtual channel caused by puncturing to 0 at the decoding end, and output the optimized SCL decoder; 110. Use the SCL decoder optimized in 109 to perform polar code decoding. Pass the decoded candidate sequence through the CRC checker. If the candidate sequence passes the check, the candidate sequence is output; otherwise, the process returns to continue SCL decoding. The step 104 determines the puncturing position and puncturing parameters, calculates the code length according to the code rate required by the dynamic link, and thus determines the puncturing parameters of the adopted method, and denotes the number of punctures as P=MN. The specific steps include: (1) Initialization Input: Initial perforation pattern and the target drilling position number 0<P≤NK; (2) Candidate Set Construct candidate punctured bit sets represents the frozen bit set, π i-1 represents the puncturing pattern traversal list, i∈(1,2,…,N), the set contains all the unpunctured bits; (3) Update reliability parameters For each candidate bit Do the following: a. Introduce reliability parameter update calculation and store reliability parameter sequence s b :=s(Π i-1 ∪{b}) s k Represents the reliability parameter; r j The gain that the adjacent path brings to the current direct path; represents the set of adjacent paths that have a gain on the direct path through the summation operation; represents the information bit set; w H is the channel transition probability at that location; represents the i-th bit of the k-th stage; a is a weighting factor obtained through simulation calculation; b. Sort the reliability parameter sequence in ascending order to obtain s b Sorting sequence (4) Find a new drilling location a. Find new puncturing bits by maximizing the minimum value in the reliability parameter sequence in turn; for j from 1 to K, select The largest candidate bit is placed into the candidate set: b. If there is only one candidate bit in ∑, then the candidate bit becomes the new puncturing bit and jumps out of the loop, otherwise update the candidate set (5) Update the drilling mode a. If there is only one candidate bit in ∑, update the puncturing pattern Π i :=Π i-1 ∪Σ; b. If there are multiple candidate positions and all candidate positions have been traversed, the position with the smallest index π = minΣ and the puncturing pattern π is updated i :=Π i-1 ∪{π}.

2. The reliability parameter-assisted low-complexity polar code rate matching method according to claim 1, wherein: The step 103, polar coding, outputting the coding sequence, is specifically as follows: first constructing a generator matrix Among them B N represents the bit reversal permutation matrix; represents the kernel matrix; Indicates doing n times of Kronecker product; then polarization coding is performed according to the generator matrix, and the output coding sequence is The channel input sequence set (u1,u2,…,u N ).

3. The reliability parameter-assisted low-complexity polar code rate matching method according to claim 1, wherein: The step 105 specifically includes the following steps: estimating and sorting the reliability of each polarized subchannel using a Gaussian approximation (GA) based on the puncturing positions determined in step 104, selecting K polarized subchannels with the highest reliability from N polarized subchannels to place information bits, and placing frozen bits in the remaining NK subchannels, thereby constructing an information sequence u. Specifically, the steps include: For the AWGN channel, let the channel input be x, the output be y, and the system uses binary phase shift keying BPSK modulation, then we have y=(-2x+1)+n (0.3) Among them, the value range of information bit x is 0 or 1, n is the noise interference encountered during channel transmission, n~N(0,σ 2 ), then the log-likelihood ratios (LLRs) of the AWGN channel are expressed as, Output signal y~N(0,σ 2 ), then the log-likelihood ratio LLR(y) has a mean of 2 / σ 2 , with a variance of 4 / σ 2 Gaussian distribution of each polarization channel The probability density function of the LLR value is The distribution of To express it, then in the calculation process of the LLRs mean, there is the following recursive relationship, in, and represent the mean and variance of the log-likelihood ratio in the AWGN channel; The expression of the function is, Due to the analysis, When it is greater than 0, it is a monotonically decreasing function, and Will Simplified to, After recursive operation of equations (0.5) and (0.6), the mean of the target channel log-likelihood ratio is obtained: Then, according to the integral operation of formula (0.8), each polarization channel can be obtained Reliability metric P e (A i ).

4. The reliability parameter-assisted low-complexity polar code rate matching method according to claim 1, wherein: The step 106 is specifically as follows: using the reliability parameter-assisted puncturing algorithm to obtain the reliability parameter of the sequence The reliability of any bit channel s i Uniquely corresponds to the coded bit x at the corresponding position in the codeword i , i=1,2,…,N, right Sort by size from small to large, and the resulting sequence is the index number of the polar code bit channel reliability sorting, so that Introduce interleaving register to store reliability parameters; Arrange them in a staggered manner, that is, the one with the largest capacity value is placed in the first place, the smallest in the second place, the second largest in the third place, and so on, completing the position alternation of the bit channel reliability parameters to obtain the interleaved target sequence. For the first interleaved sequence, the correlation is determined based on the output of the minimum polarization operation unit in the polarization process, and the two symbols with the strongest correlation are placed at farther positions in the symbol sequence to obtain the second interleaved sequence.

5. The reliability parameter-assisted low-complexity polar code rate matching method according to claim 1, wherein: The step 108 in which the receiving end receives the modulated signal transmitted via the wireless channel and performs rate matching to obtain a coded sequence, denoted as y, specifically includes: In the decoding structure of the two-bit polarization unit, when y1 is punctured, the log-likelihood ratios (LLRs) of u1 and u2 can be directly obtained by LLR(u1)=LLR(y1) and LLR(u2)=LLR(y2).

6. The reliability parameter-assisted low-complexity polar code rate matching method according to claim 5, characterized in that: The step 109 specifically includes: generating a matrix According to the puncturing bit selection method, puncturing is performed at the coding bit end in the order of index from small to large, F j,k and G j,k Represent the kth box operator and sum operator of the jth layer decoding structure respectively, so that a group of F j,k and G j,k Computing modules form a computing unit.

7. The reliability parameter-assisted low-complexity polar code rate matching method according to claim 5, wherein: The decoder optimization criterion is as follows: for the i-th puncture position u i ,i=1,2,…,M,let(b n ,b n-1 ,…,b1) represents the binary form of the position, then for any bit b k = 0, correspondingly, some calculation units of the jth layer in the decoding structure can be omitted, that is, these omitted calculation units can be directly replaced by registers. The decoding part first obtains the transition probability of each sub-channel by separating the composite channel. Since the SCL decoding algorithm retains multiple decoding paths, a parameter is needed to measure and evaluate the performance of each path when continuously updating the path storage and finally making a decision output on the decoding. Therefore, a parameter is defined Indicates the lth extended path when decoding to the i-th position The path metric is defined as in, is the polarization channel log-likelihood ratio at the current location, is the output sequence after encoding; analysis shows that the larger the transition probability, the smaller the metric value of the corresponding path, so L candidate paths with the smallest path metric values ​​are selected; the candidate sequence after decoding is subjected to CRC check, and if the check result passes, the sequence is retained and output, otherwise it is decoded again.

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