A low-complexity BPL decoder with adaptive code length

Abstract

The present invention discloses an adaptive code length low complexity BPL decoder, comprising the following steps: inputting a code length N, a list size L and a maximum number of iterations; selecting the number of permuted factor graphs according to the list size; performing decoding on each permuted factor graph and saving the decoding result; and determining the final decoding result by finding the minimum Euclidean distance. The present invention can select a suitable decoder structure according to the code length, thereby improving the BP decoding performance and greatly reducing the decoding complexity.

Description

Technical Field

[0001] The present invention relates to the technical field of decoding 5G polar codes, and in particular to a BPL decoder with adaptive code length and low complexity. Background Art

[0002] Internet technology has advanced significantly in recent years, generating massive amounts of data and information that are placing higher demands on existing communication systems. Fifth-generation mobile communication systems (5G), a current research hotspot, focus on addressing ultra-high-speed, ultra-reliable, and low-latency data transmission. These challenges place even greater demands on channel coding, a core module of the physical layer of wireless communications. Polar codes, recently proposed, originate from channel polarization and are currently the only channel coding method capable of achieving Shannon-limited transmission. Driven by the concerted efforts of academia and industry, research on Polar codes has yielded substantial results in recent years. In November 2016, 3GPP decided to standardize Polar codes as the short code for control channels in eMBB scenarios. However, existing decoders exhibit high decoding complexity and slow response times. Summary of the Invention

[0003] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0004] In view of the above existing problems, the present invention is proposed.

[0005] Therefore, the present invention provides an adaptive code length low-complexity BPL decoder, which reduces decoding complexity while ensuring decoder performance.

[0006] In order to solve the above technical problems, the present invention provides the following technical solution: comprising the following steps:

[0007] Input code length N, list size L and maximum number of iterations;

[0008] Select the number of permutation factor graphs based on the list size;

[0009] Decode on each permuted factor graph and save the decoding results;

[0010] The final decoding result is determined by finding the minimum Euclidean distance.

[0011] As a preferred solution of the adaptive code length low complexity BPL decoder of the present invention, when decoding each permuted factor graph, two matrices are opened for storage, L N×n+1 and RN×n+1 The initial values ​​of all elements in the matrix are 0.

[0012] As a preferred solution of the adaptive code length low complexity BPL decoder of the present invention, when decoding the factor graph, the following steps are also included:

[0013] The received log-likelihood ratio LLR is used as the rightmost input data in the factor graph and filled into the n+1th column of L. The prior LLR of the source bit is used as the leftmost input data in the factor graph and filled into the first column of R. Specifically,

[0014] L i,n+1 =LLR,1≤i≤N

[0015]

[0016] Among them, L i,n+1 is the n+1th column of matrix L, R i,1 is the first column of matrix R, A is the information bit index set, A c is the frozen bit index set.

[0017] As a preferred solution of the adaptive code length low complexity BPL decoder of the present invention, when decoding the factor graph, the following steps are also included: n The column consisting of the leftmost 2×2 modules of the polar code is denoted as the first column. Similarly, the column consisting of the rightmost 2×2 modules is denoted as the nth column. Each column has N / 2 2×2 modules, which are labeled as the 1st, 2nd, …, N / 2th modules from top to bottom. Then, (i, j), 1≤i≤N / 2, 1≤j≤n represents the i-th 2×2 module in the j-th column.

[0018] As a preferred solution of the adaptive code length low complexity BPL decoder described in the present invention, round-trip scheduling is used for decoding.

[0019] As a preferred solution of the adaptive code length low complexity BPL decoder described in the present invention, when performing decoding operation, the node information of the four code components is first removed, and then the R information from left to right and the L information from right to left are calculated as a whole. After completing one iteration, the next iteration is continued until the actual number of iterations reaches the set maximum number of iterations, and the decoding is completed.

[0020] As a preferred solution of the adaptive code length low complexity BPL decoder of the present invention, after decoding, hard decision is performed according to the following formula to obtain the source sequence (u1, u2, ..., u N ) and the codeword sequence (x1, x2, …, x N ), their decision formula is:

[0021]

[0022]

[0023] is the decoded information bit sequence, is the decoding codeword sequence, L i,1 and R i,1 The first column of matrices L and R, respectively. i,n+1 and R i,n+1 are the n+1th columns of matrices L and R respectively.

[0024] As a preferred solution of the adaptive code length low complexity BPL decoder of the present invention, when determining the decoding result, the best decoding result x is selected from L decoding results. s , where s is determined by the following formula:

[0025]

[0026] Where s is the position of the specific minimum codeword sequence of the received signal, y is the received signal, N is the code length, s l is the BPSK symbol of the lth codeword sequence, is the Euclidean distance.

[0027] As a preferred solution of the adaptive code length low complexity BPL decoder of the present invention, the four component codes are specifically as follows:

[0028] The code length is 8, the first 6 nodes are frozen bits, and the last 2 nodes are information bits. Remove After that, R 3,i The update formula is as follows:

[0029]

[0030] The code length is 8, the first two nodes are frozen bits, and the last six nodes are information bits. Remove After that, R 3,i The update formula is as follows:

[0031]

[0032] Where g(x,y)=sign(x)sign(y)min{|x|,|y|}, the functions sign(x) and sign(y) are used to take the signs of x and y, and the function min{|x|,|y|} is used to take the minimum value of x and y;

[0033] The code length is 8, the first 5 nodes are frozen bits, and the last 3 nodes are information bits. Remove After that, R 3,i The update formula is as follows:

[0034]

[0035] Among them, L i,k is the element in the i-th row and k-th column of matrix L, L i,k+4 is the element in the i-th row and k+4-th column of matrix L, i,k-4 is the element in the i-th row and k-4th column of matrix L, min|L i,k +L i,k+4 |To obtain L i,k ,L i,k+4 Minimum value, min|L i,k +L i,k-4 |To obtain L i,k ,L i,k-4 The minimum value.

[0036] The code length is 8, the first 3 nodes are frozen bits, and the last 5 nodes are information bits. Remove After that, R 3,i The update formula is as follows:

[0037]

[0038] Wherein, j1 is the initial position of the component code.

[0039] The beneficial effects of the present invention are as follows: the present invention ensures decoding performance while greatly reducing decoding complexity and improving decoding speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0041] Figure 1 Flowchart of the present invention.

[0042] Figure 2 is the factor graph of the polar code with N=8.

[0043] Figure 3 For the present invention Simplified diagram of the composition code.

[0044] Figure 4 For the present invention Simplified diagram of the composition code.

[0045] Figure 5 For the present invention Simplified diagram of the composition code.

[0046] Figure 6 For the present invention Simplified diagram of the composition code.

[0047] Figure 7 This is the simulation result of the present invention. DETAILED DESCRIPTION

[0048] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0049] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0050] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0051] The present invention is described in detail with reference to schematic diagrams. For ease of illustration, cross-sectional views of device structures may be partially enlarged and not to scale when describing embodiments of the present invention. Furthermore, the schematic diagrams are merely illustrative and should not limit the scope of the present invention. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0052] In the description of the present invention, it should be noted that the terms "upper, lower, inner, and outer" and other references to orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In this disclosure, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, removable, or integral connections. They may also refer to mechanical, electrical, or direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure.

[0054] Example 1

[0055] Reference Figures 1 to 6 , which is the first embodiment of the present invention, provides an adaptive code length low complexity BPL decoder, comprising the following steps:

[0056] S1: Input code length N, list size L and maximum number of iterations;

[0057] S2: Select the number of permutation factor graphs based on the list size;

[0058] S3: Decode on each permuted factor graph and save the decoding results. The decoding process is:

[0059] (S301) When decoding each permuted factor graph, two matrices are opened for storage, L N×n+1 and R N×n+1 The initial values ​​of all elements in the matrix are 0;

[0060] (S302) The received log-likelihood ratio LLR is used as the rightmost input data in the factor graph and is filled into the n+1th column of L. The prior LLR of the source bit is used as the leftmost input data in the factor graph and is filled into the first column of R. Specifically,

[0061] L i,n+1 =LLR,1≤i≤N

[0062]

[0063] Among them, L i,n+1 is the n+1th column of matrix L, R i,1 is the first column of matrix R, A is the information bit index set, Ac is the frozen bit index set;

[0064] (S303) The length is N=2 n The column consisting of the leftmost 2×2 modules of the polar code is denoted as the first column. Similarly, the column consisting of the rightmost 2×2 modules is denoted as the nth column. In each column, there are N / 2 2×2 modules, which are labeled as the 1st, 2nd, …, N / 2th modules from top to bottom. Then, (i, j), 1≤i≤N / 2, 1≤j≤n represents the i-th 2×2 module in the j-th column.

[0065] (S304) Decoding is performed using round-trip scheduling. First, the node information of the four code components is removed. Then, the R information from left to right and the L information from right to left are calculated as a whole. After completing one iteration, the iteration is continued until the actual number of iterations reaches the set maximum number of iterations. At this point, decoding is completed.

[0066] (S305) After decoding, hard decision is performed according to the following formula to obtain the source sequence (u1, u2, ..., u N ) and the codeword sequence (x1, x2, …, x N ), their decision formula is:

[0067]

[0068]

[0069] is the decoded information bit sequence, is the decoding codeword sequence, L i,1 and R i,1 The first column of matrices L and R, respectively. i,n+1 and R i,n+1 are the n+1th columns of matrices L and R respectively;

[0070] S4: Determine the final decoding result by finding the minimum Euclidean distance.

[0071] Furthermore, when determining the decoding result, the best decoding result x is selected from the L decoding results. s , where s is determined by the following formula:

[0072]

[0073] Where s is the position of the specific minimum codeword sequence of the received signal, y is the received signal, N is the code length, s l is the BPSK phase shift keying symbol of the lth codeword sequence, is the Euclidean distance.

[0074] Furthermore, the four component codes are as follows:

[0075] The code length is 8, the first 6 nodes are frozen bits, and the last 2 nodes are information bits. Remove After that, R 3,i The update formula is as follows:

[0076]

[0077] The code length is 8, the first two nodes are frozen bits, and the last six nodes are information bits. Remove After, R 3,i The update formula is as follows:

[0078]

[0079] Where g(x,y)=sign(x)sign(y)min{|x|,|y|}, the functions sign(x) and sign(y) are used to take the signs of x and y, and the function min{|x|,|y|} is used to take the minimum value of x and y;

[0080] The code length is 8, the first 5 nodes are frozen bits, and the last 3 nodes are information bits. Remove After that, R 3,i The update formula is as follows:

[0081]

[0082] Among them, L i,k is the element in the i-th row and k-th column of matrix L, L i,k+4 is the element in the i-th row and k+4-th column of matrix L, i,k-4 is the element in the i-th row and k-4th column of matrix L, min|L i,k +L i,k+4 |To obtain L i,k ,L i,k+4 Minimum value, min|L i,k +L i,k-4 |To obtain L i,k ,L i,k-4 The minimum value.

[0083] The code length is 8, the first 3 nodes are frozen bits, and the last 5 nodes are information bits. Remove After that, R 3,i The update formula is as follows:

[0084]

[0085] Wherein, j1 is the initial position of the component code.

[0086] Example 2

[0087] In order to verify the technical effect of this method, this embodiment simulates the code length N, K = 1024,512, which is currently widely used in 5G, and the code rate is 0.5. The transmission channel is BPSK-AWGN channel and the number of iterations is 60. The simulation results in this case are as follows: Figure 7 As shown in the figure, it can be seen that the method proposed in the present invention has similar performance to the existing BP decoder.

[0088] In terms of complexity, the complexity of the decoder proposed in the present invention is much lower than that of the traditional BP decoder. Table 1 shows the complexity comparison of the four component codes and the common BP decoding when the component code length is 8 in one iteration.

[0089] Table 1

[0090]

[0091] It is not difficult to see from Table 1 that and The complexity of the code is reduced by nearly 86% compared with the complexity of ordinary BP decoding. and The complexity of the composed code is reduced by nearly 40% compared with the complexity of the existing BP decoding.

[0092] It can be verified from the above that the present invention can greatly reduce the complexity of decoding and improve the decoding speed while ensuring the decoding performance.

[0093] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An adaptive code length low complexity BPL decoder, characterized by: include, Input code length N, list size L and maximum number of iterations; Select the number of permutation factor graphs based on the list size; Decode on each permuted factor graph and save the decoding results; The final decoding result is determined by finding the minimum Euclidean distance; When decoding the factor graph, The following steps are included: the received log-likelihood ratio LLR is used as the rightmost input data in the factor graph, and is filled into the n+1th column of L; the prior LLR of the source bit is used as the leftmost input data in the factor graph, and is filled into the first column of R. Specifically, in, is the n+1th column of matrix L, is the first column of matrix R, A is the information bit index set, A c is the frozen bit index set; When performing decoding operations, the four node information components of the code are first removed, and then the R information from left to right and the L information from right to left are calculated as a whole. After completing one iteration, the next iteration is continued until the actual number of iterations reaches the set maximum number of iterations, and the decoding is completed. The four component codes are as follows: The code length is 8, the first 6 nodes are frozen bits, and the last 2 nodes are information bits. , remove back, The update formula is as follows: The code length is 8, the first two nodes are frozen bits, and the last six nodes are information bits. , remove back, The update formula is as follows: in, ,function To take the sign of x,y, the function To get the minimum value of x, y; The code length is 8, the first 5 nodes are frozen bits, and the last 3 nodes are information bits. , remove back, The update formula is as follows: in, is the element in the i-th row and k-th column of matrix L, is the element in the i-th row and k+4-th column of matrix L, is the element in the i-th row and k-4th column of matrix L, To obtain The minimum value, To obtain The minimum value in the code is denoted as , remove back, The update formula is as follows: Wherein, j1 is the initial position of the component code.

2. The adaptive code length low complexity BPL decoder according to claim 1, wherein: When decoding each permuted factor graph, two matrices are stored. and The initial values ​​of all elements in the matrix are 0.

3. The adaptive code length low complexity BPL decoder according to claim 1 or 2, wherein: When decoding the factor graph, the following steps are also included: n The column consisting of the leftmost 2×2 modules of the polar code is recorded as the first column. Similarly, the column consisting of the rightmost 2×2 modules is recorded as the nth column. There are N / 2 2×2 modules in each column, which are marked as the 1st, 2nd, ..., N / 2 modules from top to bottom. Then, represents the i-th 2×2 module in the j-th one.

4. The adaptive code length low complexity BPL decoder according to claim 3, wherein: After decoding, hard decision is made according to the following formula to obtain the source sequence of L permutation factor graphs: and codeword sequence , their decision formula is: is the decoded information bit sequence, is the decoding codeword sequence, and are the first columns of matrices L and R respectively, and are the n+1th columns of matrices L and R respectively.

5. The adaptive code length low complexity BPL decoder according to claim 1, wherein: When determining the decoding result, select the best decoding result x from L decoding results s , where s is determined by the following formula: Among them, s is the position of the specific minimum codeword sequence of the received signal, y is the received signal, N is the code length, For the l BPSK symbols of a codeword sequence, is the Euclidean distance.

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