CN112104379A

CN112104379A - Polarization code confidence propagation dynamic flip decoding method based on key set

Info

Publication number: CN112104379A
Application number: CN202010864035.5A
Authority: CN
Inventors: 张小军; 韩晓文; 陈达; 曾庆田; 陈成官; 烟晓凤; 李恒忠; 郭华; 崔建明; 张德学; 王道岩
Original assignee: Shandong University of Science and Technology
Current assignee: Shandong University of Science and Technology
Priority date: 2020-08-25
Filing date: 2020-08-25
Publication date: 2020-12-18
Anticipated expiration: 2040-08-25
Also published as: CN112104379B

Abstract

The invention provides a polarization code confidence coefficient propagation dynamic reversal decoding method based on a key set, which comprises the steps of carrying out confidence coefficient propagation decoding on a polarization code, combining with a cyclic redundancy check auxiliary early stop standard, carrying out cutoff judgment on a decoding result of each iteration in advance, combining with a node log likelihood ratio absolute value to generate a dynamic reversal position when a preset maximum iteration frequency is reached and CRC check fails, further combining with a static key set to construct a reversal matrix, and improving decoding performance through bit reversal. Simulation results show that under the condition that the frame error rate is 0.001 and the number of time reversal digits omega is 2, compared with a CS-omega-based bit reversal confidence coefficient propagation decoder, the polar code confidence coefficient propagation dynamic reversal decoding method based on the key set improves the gain by about 0.17dB, and compared with an original BP decoding algorithm, improves the gain by about 0.77 dB.

Description

Polarization code confidence propagation dynamic flip decoding method based on key set

Technical Field

The invention relates to Polar Code (Polar Code) decoding, in particular to a Polar Code confidence Propagation (BP) dynamic flip-flop decoding method based on a Critical Set (CS).

Background

In the international information theory ISIT conference in 2008, Erdal Arikan professor Erdal Arikan first proposed a concept of Channel Polarization (Polar Polarization), and named a given Channel coding method as a Polar Code (Polar Code), which is a Channel coding method strictly proven to reach Channel capacity, and has low coding and decoding complexity and excellent performance. As the length of the polar code continues to increase, the channel capacity can be approximated by selecting a reliable channel with channel capacity close to 1 for transmitting information directly over it. In 2016, the 5G short code scheme discussion of 3GPP RAN 187 conference, it was determined that polarization code became the eMBB control channel coding standard.

The Arikan professor firstly proposes a Belief Propagation (BP) decoding algorithm, and although the BP algorithm adopts a parallel processing mode and has higher throughput, the existing BP decoding algorithm has defects, so that it is important to find a better decoding scheme to improve the decoding performance.

The bit flipping method is a decoding method capable of remarkably reducing the error rate, the flipping bit position is determined through the error rate of channel transmission and the statistics of the error-prone position in the decoding process, the initial information of the bit position which is most prone to error in the initial decoding process is replaced by infinite positive and negative, the bit flipping is realized, and then the decoding error probability is reduced in the decoding process.

A polarization code confidence propagation dynamic reversal decoding method based on a key set is adopted in a Successive Cancellation (SC) decoding algorithm at first, and after a bit reversal decoding program of the SC is carried out, the error rate is obviously reduced. However, in the continuous decoding process, the bit flipping algorithm of the SC has an obvious decoding delay condition, and is poor in performance under the conditions of computational complexity and decoding duration.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a polarization code confidence coefficient propagation dynamic reversal decoding method based on a key set.

The invention provides a polarization code Belief Propagation (BP) dynamic reversal decoding method based on a Critical Set (CS), which comprises the following steps:

step S1: carrying out belief propagation decoding on the polarization code to generate an original decoding result sequence;

step S2: performing CRC on the original decoding result sequence, outputting the original decoding result when the CRC passes, or generating an original dynamic overturn position after sequencing the absolute value of a node pair Likelihood Ratio (LLR) according to the original decoding result;

step S3: constructing a static overturn key set as a column of overturn matrixes according to the error rate of channel transmission, wherein the error rate of channel transmission is the channel transmission error rate obtained by calculating Bhattacharyya parameters, density evolution or Gaussian approximation and the like after channel polarization;

step S4: entering a one-bit flipping program, and flipping the polarization code according to the column of flipping matrices to generate a one-bit flipping result sequence;

step S5: and performing CRC (cyclic redundancy check) on the one-bit upset result sequence, and outputting an upset decoding result when the CRC passes the CRC.

Preferably, in step S5, when the CRC check is not passed, the method further includes the following steps:

step S6: according to the one-bit flipping decoding result, after ascending sorting of absolute values of the node LLRs, selecting the minimum position of the absolute values of the node LLRs to generate a second row of dynamic flipping positions, combining the original dynamic flipping positions and a static flipping key set to construct two groups of two rows of flipping matrices, and entering a two-bit flipping program;

step S7: turning the polarization code according to the two groups of two columns of turning matrixes to generate two groups of bit turning decoding result sequences;

step S8: and performing CRC (cyclic redundancy check) on the two groups of bit flip decoding result sequences, outputting an original decoding result when the two groups of bit flip decoding result sequences pass the CRC, otherwise, judging whether the number of rows of the flip key set is greater than the preset maximum number of rows, and executing next row flip according to a two-bit flip matrix when the number of rows of the flip key set is not greater than the preset maximum number of rows.

Preferably, in step S8, when the CRC check is not passed and the preset maximum number of rows is reached, the method further includes the following steps:

step S9: according to the two-bit flip decoding result, after ascending sorting of absolute values of the node LLRs, selecting the minimum position of the absolute values of the node LLRs to generate a third row of dynamic flip positions, combining the original dynamic flip positions, the second row of dynamic flip positions and a static flip key set to construct two groups of three rows of flip matrixes, and entering a three-bit flip program;

step S10: according to the two groups of three-column overturning matrixes, overturning the polarization code to generate a three-bit overturning decoding result sequence;

step S11: and performing CRC (cyclic redundancy check) on the three-bit flip decoding result sequence, outputting an original decoding result when the CRC passes, otherwise, judging whether the number of rows of the flip key set is greater than the preset maximum number of rows, executing next row flip according to the three-bit flip matrix when the number of rows of the flip key set is not greater than the preset maximum number of rows, otherwise, outputting decoding failure, and ending the decoding process.

Preferably, when constructing the flip matrix, specifically:

step M1: and constructing a first column of the turnover matrix, and sequencing the turnover matrix from large to small according to the error rate of channel transmission, wherein the error rate of channel transmission is obtained by calculating Bhattacharyya parameters, density evolution or Gaussian approximation and the like after channel polarization. Selecting Q bit positions with the maximum error rate, wherein Q is the maximum element number of a static overturn key set, and taking the static overturn key set as a first column of an overturn matrix;

step M2: constructing a second column of the flip matrix, sequencing the absolute values of the node LLRs of the original decoding result sequence and the one-bit flip decoding result sequence from small to large, and correspondingly obtaining the bit positions of Q +1 minimum node LLR absolute values as the second column of the flip matrix;

preferably, when performing one-bit flipping, that is, when the number of flipping bits ω is 1, specifically:

step N1: starting from the first row of the flip matrix, replacing the initial information of the ω positions of the first row by positive and negative infinity (+ ∞, - ∞), wherein + ∞and- ∞representpositive infinity and negative infinity, respectively;

step N2: calculating the turnover number k, k being 2^ω-1, when k is 0, performing step N3, when k is 1, performing step N4;

step N3: converting k into an omega-bit binary number b, wherein if omega is 1, b is 0, and replacing initial information of the position of the first row and the first column of the flip matrix with- ∞;

step N4: converting k into an omega-bit binary number b, wherein if omega is 1, b is 1, and replacing initial information of the position of the first row and the first column of the flip matrix with + ∞;

step N5: entering a second row of the flip matrix, and executing the step N2;

step N6: after the Q-th row of the flip matrix is executed, the process proceeds to step S5.

Preferably, when two-bit flipping is performed, that is, when the number of flipping times ω is 2, specifically:

step N2: calculating the turnover number k, k being 2^ω-1, when k is 0, performing step N3, when k is 1, performing step N4, when k is 2, performing step N5, when k is 3, performing step N6;

step N3: converting k into an omega-bit binary number b, wherein omega is 2, then b is 00, and replacing initial information of the positions of a first row, a first column and a first row, a second column of the flip matrix with infinity;

step N4: converting k into an omega-bit binary number b, wherein omega is 2, b is 01, and the initial information of the position of the first row and the first column of the turnover matrix is replaced by infinity and the position of the first row and the second column of the turnover matrix is replaced by + ∞;

step N5: converting k into an omega-bit binary number b, wherein omega is 2, then b is 10, and replacing the initial information of the position of the first row and the first column of the flip matrix with + ∞ and the position of the first row and the second column with infinity;

step N6: converting k into an omega-bit binary number b, wherein omega is 2, b is 11, and replacing initial information of the positions of a first row, a first column and a first row, a second column of the flip matrix by + ∞;

step N7: entering a second row of the flip matrix, and executing the step N2;

step N8: after the Q-th row of the flip matrix is executed, the process proceeds to step S8.

Preferably, when performing three-bit flipping, that is, when the number of flipping bits ω is 3, specifically:

step N2: calculating the turnover number k, k being 2^ω-1, k-0, then step N3 is performed, k-1, then step N4 is performed, k-2Step N5 is executed, when k is 3, step N6 is executed, when k is 4, step N7 is executed, when k is 5, step N8 is executed, when k is 6, step N9 is executed, when k is 7, step N10 is executed;

step N3: converting k into an omega-bit binary number b, wherein omega is 3, then b is 000, and replacing initial information of the positions of the first row, the first column, the first row, the second column and the first row, the third column of the flip matrix with- ∞;

step N4: converting k into an omega-bit binary number b, wherein b is 001 if omega is 3, replacing the initial information of the position of the first row and the first column of the flip matrix with- ∞, replacing the initial information of the position of the first row and the second column with- ∞, and replacing the initial information of the position of the first row and the second column with + ∞;

step N5: converting k into an omega-bit binary number b, wherein omega is 3, b is 010, replacing initial information of a position of a first row and a first column of the flip matrix with- ∞, replacing initial information of a position of a first row and a second column with + ∞, and replacing initial information of a position of a first row and a second column with- ∞;

step N6: converting k into an omega-bit binary number b, wherein if omega is 3, b is 011, replacing the initial information of the position of the first row and the first column of the flip matrix with- ∞, replacing the initial information of the position of the first row and the second column with + ∞, and replacing the initial information of the position of the first row and the second column with + ∞;

step N7: converting k into an ω -bit binary number b, wherein ω is 3, then b is 100, replacing the initial information of the position of the first column in the first row of the flip matrix with + ∞, replacing the initial information of the position of the second column in the first row with- ∞, and replacing the initial information of the position of the second column in the first row with- ∞;

step N8: converting k into an omega-bit binary number b, wherein b is 101 if omega is 3, replacing initial information of the position of the first row and the first column of the flip matrix with + ∞, replacing initial information of the position of the first row and the second column with- ∞, and replacing initial information of the position of the first row and the second column with + ∞;

step N9: converting k into an omega-bit binary number b, wherein omega is 3, b is 110, replacing initial information of the position of the first row and the first column of the flip matrix with + ∞, replacing initial information of the position of the first row and the second column with + ∞, and replacing initial information of the position of the first row and the second column with- ∞;

step N10: converting k into an omega-bit binary number b, wherein omega is 3, then b is 111, and replacing initial information of the positions of a first row, a first column, a first row, a second column and a first row, a third column of the flip matrix by + ∞;

step N11: entering a second row of the flip matrix and executing the step N2;

step N12: after the Q-th row of the flip matrix is executed, the process proceeds to step S11.

Preferably, in step S2, the sorting of the absolute values of the LLRs of the original decoding results is performed in an ascending order according to the absolute values of the LLRs of the nodes, and when the absolute values are equal, the sorting is performed in a descending order according to the error rate of the channel transmitted by the channel, so as to obtain a sorting sequence according to the position.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the key set CS is determined according to the error rate of channel transmission, the node LLR absolute value is combined to construct the turnover matrix, and under the condition that the turnover number can be flexibly adjusted, the number of multi-bit turnover attempts can be controlled and reduced, the polar code decoding performance is improved, and the decoding complexity is reduced. Simulation results show that under the condition that the frame error rate is 0.001 and the number of time reversal digits omega is 2, compared with a CS-omega-based bit reversal confidence coefficient propagation decoder, the polar code confidence coefficient propagation dynamic reversal decoding method based on the key set improves the gain by about 0.17dB, and compared with an original BP decoding algorithm, improves the gain by about 0.77 dB.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a flowchart illustrating steps of a polarization code confidence propagation dynamic flipping decoding method based on a key set according to an embodiment of the present invention;

FIG. 2 is a diagram of an example of (8,4) polar code encoding in an embodiment of the present invention;

FIG. 3 is a graph of frame error rate according to an embodiment of the present invention;

fig. 4 is a flowchart illustrating an embodiment of a polar code confidence propagation dynamic flipping decoding method based on a key set.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

In the embodiment of the present invention, a polar code encoding process is first performed, where the polar code encoding includes: after channel polarization, polarization channel is obtained by calculating Babbitt parameters and the like

Transmission error rate P (A)_i) Wherein A is_iThe polar channel with index i

The carried bit is received with errors after transmission, P (A)_i) The smaller the channel, the more stable, i.e. reliable, the channel. And selecting K most reliable channels from the N polarized channels according to the reliability to transmit information bit sequences, wherein the K most reliable channels are generally 1, and the rest N-K channels transmit fixed bits known by a receiving end and are generally 0. Vector obtained by mixing the bit sequences

And core generator matrix

Kronecker product of (n times)

Multiplying to obtain a code sequence

Wherein

As a generator matrix, the following is the expression:

wherein

n＝log₂N，

Representing n times the power of Kronecker.

Obtained by encoding through bit reverse sequence

Rearranging the sequence to obtain the coding sequence after reverse order

By pi (i) representing the function of inversion, then there is x_i＝v_π(i). The anti-order function pi (i) can be expressed as: the serial number i is represented by (b) in binary₁,b₂,...,b_n) I.e. by

Then at this time pi (i) can be represented as (b) in binary_n,b_n-1,...,b₁). Representing the reverse rearrangement as a one-dimensional matrix B, then

Thus, the coding sequence after reverse order can be expressed as

By constructing a generator matrix G of order N_NCoding is carried out, the expression is

After channel transmission, the received code word sequence is obtained at the receiving end as

Codeword estimation in a decoder

If u is_iIs a fixed bit, then

Otherwise, when i ∈ a, the log-likelihood ratio of each bit channel is as follows:

wherein the content of the first and second substances,

representing the log-likelihood ratio of the channel in row i,

and

probabilities of 0 and 1 being transmitted for the ith row channel.

Fig. 2 shows a schematic diagram of (8,4) polarization encoding, in which the left column of numbers corresponds to the babbitt parameter values of the polarization channels, and in order to construct the planned encoding, the lower bus parameter channel numbers 4, 6, 7, 8 are selected for transmitting information bits, and the other four channels transmit fixed bits. Mixing information bit and fixed bit sequence, multiplying with generated matrix (modulo two addition operation) to obtain coded sequence

Obtaining the final coding sequence after reverse order rearrangement

Then respectively pass through the channels W₁ ⁸And carrying out transmission.

In the embodiment of the present invention, the method for dynamically flipping and decoding polarization code confidence propagation based on a key set, as shown in fig. 1, includes the following steps:

step S2: checking the original decoding result sequence according to a cyclic redundancy check assisted (CRC aid, CA) early stop standard, outputting an original decoding result when the CRC passes the check, or selecting a node LLR (log likelihood ratio) minimum absolute value position as an original dynamic overturn position after the LLR absolute value sequence is carried out according to the original decoding result;

and sorting the absolute values of the LLRs of the nodes of the BP decoding result in an ascending sorting mode according to the absolute values of the LLRs of the nodes, and when the absolute values are equal, sorting in a descending sorting mode according to the error rate of the channel transmitted by the channel, and finally obtaining a sorting sequence according to the position.

step S5: and performing CRC (cyclic redundancy check) on the one-bit overturning result sequence, outputting an overturning decoding result when the CRC passes, otherwise, judging whether the number of rows of the overturning key set is greater than the preset maximum number of rows, and executing next row overturning according to the one-bit overturning matrix when the number of rows of the overturning key set is not greater than the preset maximum number of rows.

In step S5, when the CRC check is not passed and the preset maximum number of rows is reached, the method further includes the following steps:

In step S8, when the CRC check is not passed and the preset maximum number of rows is reached, the method further includes the following steps:

In the embodiment of the present invention, when constructing the flip matrix, specifically, the following steps are performed:

in the embodiment of the present invention, when performing one-bit flipping, that is, when the number of flipping bits ω is 1, specifically:

step N5: entering a second row of the flip matrix, and executing the step N2;

In the embodiment of the present invention, when two-bit flipping is performed, that is, when the number of flipping times ω is 2, specifically:

step N7: entering a second row of the flip matrix, and executing the step N2;

In the embodiment of the present invention, when performing three-bit flipping, that is, when the flipping bit number ω is 3, specifically:

step N2: calculating the turnover number k, k being 2^ω-1, k is 0, step N3 is performed,when k is 1, step N4 is executed, when k is 2, step N5 is executed, when k is 3, step N6 is executed, when k is 4, step N7 is executed, when k is 5, step N8 is executed, when k is 6, step N9 is executed, when k is 7, step N10 is executed;

step N11: entering a second row of the flip matrix and executing the step N2;

In a more specific embodiment, a polar code confidence propagation dynamic reversal decoding method based on a key set is as follows:

BP decoding iteration is carried out firstly, CRC check is carried out after each iteration, and before the preset maximum iteration times are reached, if the CRC check is passed, iteration is skipped, and a decoding result is output;

if the maximum iteration times are reached, the CRC still does not pass, generating an original dynamic turning position according to an original decoding result after ascending sequencing of absolute values of node LLRs (log likelihood ratio), constructing a column of turning matrixes according to a column of CS (circuit switched) sets, then entering a one-bit turning program with omega being 1, performing CRC check after each iteration, and jumping out of the iteration and outputting a decoding result if the CRC passes before the maximum iteration times are reached;

if the maximum iteration times are reached, the CRC still fails, ascending order sorting of absolute values of the node LLRs is carried out on the node information according to the last iteration result of each overturn, and the bit position with the minimum absolute value of the node LLR of the frame is screened out:

i_2_1{i＝min(|node_data[i]|)}

i_2_2{i＝min(|node_data[i]|)}

wherein, node _ data [ i ] represents the node LLR value of the ith row, judges whether the minimum bit position i _2_1 is equal to the minimum bit position i _2_2, if the two are equal, the minimum bit position i _2_1 is arranged at the second position of the flip matrix; if the two are not equal, combining a column of CS sets, respectively placing the minimum bit position i _2_1 and the minimum bit position i _2_2 at the second position of the turnover matrix, combining the original dynamic turnover position to generate two columns of bit turnover key sets with the length of Q, and entering a two-bit turnover program.

Performing CRC check in each iteration process of the two-bit overturning program, and jumping out of iteration and outputting a decoding result if the CRC check is passed before the preset maximum iteration times are reached;

if the maximum iteration times are preset, CRC check is still not passed, minimum node LLR sequence sequencing is carried out according to the decoding result after each bit overturning bit position is overturned, and the bit position with the minimum frame node LLR absolute value is screened out:

i_3_1{i＝min(|node_data[i]|)}

i_3_2{i＝min(|node_data[i]|)}

i_3_3{i＝min(|node_data[i]|)}

i_3_4{i＝min(|node_data[i]|)}

judging whether the minimum bit positions i _3_ i are equal to each other, selecting the i _3_ i positions which are not equal to each other, combining a column of CS sets, respectively placing the non-equal i _3_ i at the third position of the flip matrix, generating two groups of three columns of bit flip key sets with the length of Q, and entering a three-bit flip decoding program.

Performing CRC (cyclic redundancy check) in the iteration process of the three-bit overturning program, and jumping out of iteration and outputting a decoding result if the CRC passes before the preset maximum iteration times are reached, wherein the decoding is finished; if the CRC still fails after the preset maximum iteration times are reached, the reverse decoding fails, the decoding result of the original BP iteration is output, and the decoding is finished.

A specific example of ω ═ 2 is shown in fig. 4, and specifically includes:

step 1, firstly, 1024 position reliability propagation decoding is carried out, and left information node s [ i ] [10] inf _ L at the rightmost end of the decoder and right information node s [ i ] [0] inf _ R at the leftmost end are respectively updated to channel LLR absolute values and + ∞, wherein node s [ i ] [ j ] represents node LLR information of the jth column in the ith row, node s [ i ] [ j ] inf _ L represents left information of the jth column node in the ith row of the decoder, and node s [ i ] [ j ] inf _ R represents right information of the jth column in the ith row:

Nodes[i][10].inf_L＝LLR[i]

Nodes[i][0].inf_R＝+∞

then executing the step (2);

step 2: carrying out traditional BP decoding iteration to update the left information sequence L of i rows and j columns_i,jAnd a right information sequence R of i rows and j columns_i,jWhere i 1,2, 1024 denotes the code length, i.e., the number of decoding rows, j 1,2, …, 10, denotes the order of the decoding factor graph:

L_i,j＝g(L_i+1,2j-1,L_i+1,2j+R_i,j+N/2)

L_i,j+N/2＝g(R_i,j,L_i+1,2j-1)+L_i+1,2j

R_i+1,2j-1＝g(R_i,j,L_i+1,2j+R_i,j+N/2)

R_i+1,2j＝g(R_i,j,L_i+1,2j-1)+R_i,j+N/2

after reaching the preset maximum iteration times, the left information sequence of the leftmost column node reaching the maximum iteration times is processed

And the leftmost node right information sequence reaching the maximum iteration number

Judging sign bit and estimating value sequence of iteration result

And (3) carrying out hard decision:

sequencing the obtained decoding iteration result sequence node s _ data [1024] in an ascending manner according to the absolute value of the node LLR to obtain the minimum position mllr _ de of the absolute value of the node LLR of the current decoding, and executing the step (3);

and step 3: performing CRC on the decoding result sequence;

and 4, step 4: if the CRC passes, the decoding is successful, a decoding result is output, and if the CRC does not pass, the step 5 is carried out;

and 5: setting the turnover frequency t as 0, and constructing a column of turnover matrix M (Q, 1) according to a column of static turnover key set, namely a CS set:

carrying out step 6;

step 6: performing a one-bit flipping procedure of ω ═ 1 according to a column of flipping matrix M (Q, 1), and performing substitution of positive and negative infinity (+ ∞, - ∞) for initial information of a bit position in the t-th row in M (Q, 1), where + ∞and- ∞respectivelyrepresent positive infinity and negative infinity:

Nodes[CS_i][0].inf_R＝-∞

Nodes[CS_i][0].inf_R＝+∞

entering step 7;

and 7: step 3 is executed, if the CRC passes, decoding is successful, and a decoding result is output; if t < ═ Q and t +1 do not pass the CRC check, the process proceeds to step 6; if t is greater than Q, entering step 8;

and 8: the minimum node LLR absolute value position mllr _ de screened out from the decoding result of the iteration of the original decoding program, and the decoding result of the iteration of the one-bit flipping program is sequenced through the magnitude of the LLR absolute value of the channel node, and 2 groups of minimum node LLR absolute value positions mllr _ omega are screened out_1，1[Q]，mllr_ω_1，2[Q]Entering step 9;

and step 9: and (3) constructing two groups of two columns of bit flipping key sets M (Q, 2) according to the minimum node LLR absolute value position generated in the step (8) and a single column of static flipping positions constructed by combining the channel error rate:

step 10 is carried out;

step 10: setting the turnover frequency t as 0; according to M (Q, 2), a two-bit flip program of ω ═ 2 is performed, and initial information of the bit position of the t-th row in M (Q, 2) is replaced by positive and negative infinity (+ ∞, - ∞), where + ∞and- ∞respectivelyrepresent positive infinity and negative infinity:

Nodes[CS_j][0].inf_R＝-10000；Nodes[mllr_ω_1，i[t]][0].inf_R＝-∞

Nodes[CS_j][0].inf_R＝10000；Nodes[mllr_ω_1，i[t]][0].inf_R＝+∞

Nodes[CS_j][0].inf_R＝10000；Nodes[mllr_ω_1，i[t]][0].inf_R＝-∞

Nodes[CS_j][0].inf_R＝-10000；Nodes[mllr_ω_1，i[t]][0].inf_R＝+∞

and

Nodes[CS_j][0].inf_R＝10000；Nodes[mllr_de][0].inf_R＝+∞

Nodes[CS_j][0].inf_R＝10000；Nodes[mllr_de][0].inf_R＝-∞

Nodes[CS_j][0].inf_R＝-10000；Nodes[mllr_de][0].inf_R＝+∞

Nodes[CS_j][0].inf_R＝-10000；Nodes[mllr_de][0].inf_R＝-∞

wherein mllr _ ω_1，j[t]J in (1) is according to mllr _ ω_1，1[t]，mllr_ω_1，2[t]If mllr _ ω is determined as a result of the comparison of (c)_1，1[t]＝mllr_ω_1，2[t]J is 1, mllr _ ω_1，j[t]＝mllr_ω_1，1[t](ii) a If mllr _ ω_1，j[t]！＝mllr_ω_1，1[t]J is 1 and 2, mllr _ ω, respectively_1，j[t]＝mllr_ω_1，1[t]， mllr_ω_1，j[t]＝mllr_ω_1，2[t]；

Executing the step 11;

step 11: step 3 is executed, if the CRC passes, decoding is successful, and a decoding result is output; if t < ═ Q and t +1 do not pass the CRC check, then go to step 6 ═ 10; if t > Q, entering step 12;

step 12: if the decoding fails, the whole decoding process is ended.

The polarization code confidence coefficient propagation dynamic flip decoding method based on the key set is a bit decoding method for constructing absolute values of node LLRs (threshold value LLRs) generated in the iterative process of CS and BP decoding by combining the channel transmission error rate. By constructing a decoding turnover matrix, judging whether a bit turnover program is needed or not by using CRC check, and carrying out bit turnover on bit positions in the turnover matrix in the turnover program, the reliability of BP iterative decoding is improved.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims

1. A polarization code confidence propagation dynamic reversal decoding method based on a key set is characterized by comprising the following steps:

step S2: performing CRC on the original decoding result sequence, outputting the original decoding result when the CRC passes, or selecting the position with the minimum absolute value of the LLR of the node as the original dynamic overturn position after the absolute value of the node pair number likelihood ratio is sequenced according to the original decoding result;

step S3: constructing a static overturn key set as a column of overturn matrixes according to the error rate of channel transmission, wherein the error rate of channel transmission is the error rate of channel transmission obtained by calculating Babbitt parameters, density evolution or Gaussian approximation after channel polarization;

2. The method for polar code confidence propagation dynamic reversal decoding based on key set according to claim 1, wherein in step S5, when CRC check is not passed, it is determined whether the number of rows of the reversal key set is greater than the preset maximum number of rows, and when the number of rows is not greater than the preset maximum number of rows, the next row reversal is performed according to a one-bit reversal matrix, and the method further includes the following steps:

step S8: and performing CRC (cyclic redundancy check) on the two groups of bit-flipping decoding result sequences, and outputting a bit-flipping decoding result when the two groups of bit-flipping decoding result sequences pass the CRC.

3. The method for polar code confidence propagation dynamic reversal decoding based on key set according to claim 2, wherein in step S8, when CRC check is not passed, it is determined whether the number of rows of the reversal key set is greater than the preset maximum number of rows, and when the number of rows is not greater than the preset maximum number of rows, the next row reversal is performed according to the two-bit reversal matrix, and when the number of rows is greater than the preset maximum number of rows, the method further includes the following steps:

4. The polar code confidence propagation dynamic reversal decoding method based on the key set according to claim 3, wherein when constructing the reversal matrix, specifically:

step M1: constructing a first column of a turnover matrix, and sequencing the first column according to the error rate of channel transmission from large to small, wherein the error rate of channel transmission is obtained by calculating Babbitt parameters, density evolution or Gaussian approximation after channel polarization; selecting Q bit positions with the maximum error rate, wherein Q is the maximum element number of a static overturn key set, and taking the static overturn key set as a first column of an overturn matrix;

step M2: and constructing a second column of the flip matrix, sequencing the absolute values of the node LLRs of the original decoding result sequence and the one-bit flip decoding result sequence from small to large, and correspondingly obtaining the bit positions of Q +1 minimum node LLR absolute values as the second column of the flip matrix.

5. The method according to claim 1, wherein when performing one-bit flipping, that is, when the number of flipping bits ω is 1, the method specifically comprises:

step N5: entering a second row of the flip matrix, and executing the step N2;

6. The method of claim 2, wherein when two-bit flipping is performed, that is, when the number of flipping times ω is 2, the method specifically comprises:

step N7: entering a second row of the flip matrix, and executing the step N2;

step N8: after the Q-th row of the flip matrix is executed, the process proceeds to step S11.

7. The method according to claim 3, wherein when performing three-bit flipping, that is, when the flipping bit number ω is 3, specifically:

step N2: calculating the turnover number k, k being 2^ω-1, when k is 0, performing step N3, when k is 1, performing step N4, when k is 2, performing step N5, when k is 3, performing step N6, when k is 4, performing step N7, when k is 5, performing step N8, when k is 6, performing step N9, when k is 7, performing step N10;

step N11: entering a second row of the flip matrix and executing the step N2;

8. The method as claimed in claim 1, wherein the step S2 of sorting absolute values of LLRs of the original decoding results into ascending sorting according to absolute values of LLRs of the nodes, and when the absolute values are equal, sorting the absolute values into descending sorting according to error rates of channels transmitted through the channels, so as to obtain a sorting sequence according to positions.