SLM mechanism and system for reducing peak-to-average power ratio of OFDM system based on polarization code

Abstract

The invention discloses an SLM mechanism and system for reducing the peak-to-average power ratio of an OFDM system based on a polarization code, and belongs to the technical field of communication. By using the coset code characteristic of the polarization code and pre-calculating the modulation signal vector corresponding to the PAPR bit, a plurality of candidate OFDM signals can be generated only by a single polarization encoder and a modulator, and the hardware complexity of a transmitter is significantly reduced. A receiver adopts an improved belief propagation (BP) algorithm (BP-GF), and combined with a G matrix early termination criterion and frozen bit check, joint detection and decoding can be realized without side information transmission.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and more particularly to an SLM mechanism and system for reducing the peak-to-average power ratio of an OFDM system based on polar codes. Background Art

[0002] Orthogonal frequency-division multiplexing (OFDM) is a multi-carrier modulation scheme adopted in 5G. Due to its high peak-to-average power ratio (PAPR), it will cause nonlinear distortion when passing through a power amplifier. The selected mapping (SLM) scheme effectively reduces the PAPR by generating multiple OFDM signals and selecting the signal with the minimum PAPR for transmission.

[0003] Traditional SLM receivers do not know which OFDM signal is transmitted, so side information (SI) is required. Currently, SLM receiver schemes that do not require the transmission of SI have emerged using polar code structures and polar decoding. However, some of these schemes need to decode all bits of the extended information set, including the frozen bit indices for the SLM method, and as the coding rate increases, the error correction performance will decrease; some detect which candidate signal is transmitted according to the path metric calculated by successive cancellation list (SCL) decoding. However, due to the serial decoding nature of SCL, this method has the defects of high complexity and high latency.

[0004] Therefore, how to propose an SLM mechanism and system for reducing the peak-to-average power ratio of an OFDM system based on polar codes, which takes into account low complexity and high efficiency while ensuring the PAPR optimization effect, is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides an SLM mechanism and system for reducing the peak-to-average power ratio of an OFDM system based on polar codes, aiming to solve the problems existing in the prior art such as high hardware complexity, large decoding delay, and the change of error correction performance with the coding rate.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention proposes an SLM mechanism for reducing the peak-to-average power ratio of an OFDM system based on polar codes, including:

[0008] Construct a sub - matrix of the generating matrix based on the generating matrix corresponding to the extended information set and the Hamming weight, and combine the PAPR metric to obtain a PAPR set;

[0009] In the PAPR set, use the coset code property to obtain offline multiple modulation signal vectors corresponding to different PAPR bits;

[0010] The multiple modulation signal vectors generate multiple OFDM candidate signals through modulo - 2 multiplication and Fourier transform;

[0011] Calculate the PAPR values of the multiple OFDM candidate signals, and select the OFDM candidate signal with the minimum PAPR value as the transmission signal;

[0012] Detect and decode through an SLM receiver based on the BP - GF algorithm to identify the transmission signal.

[0013] Preferably, constructing a sub - matrix of the generating matrix based on the generating matrix corresponding to the extended information set and the Hamming weight, and combining the PAPR metric to obtain a PAPR set, includes:

[0014] Use the Bhattacharyya parameter method to construct an extended information set with cardinality k + l, and obtain the generating matrix corresponding to the extended information set

[0015] In the generating matrix corresponding to the extended information set Select the rows with Hamming weight within a preset range to obtain a sub - matrix of the generating matrix

[0016] Perform Monte Carlo simulation on the polar - coded OFDM system, and calculate the PAPR metric according to the original PAPR based on the sub - matrix of the generating matrix and the new PAPR after bit - by - bit flipping;

[0017] Arrange in descending order according to the PAPR metric, and select the first l indices from the sub - matrix of the generating matrix as the PAPR set.

[0018] Preferably, using the coset code property to obtain offline multiple modulation signal vectors corresponding to different PAPR bits, includes:

[0019] For each PAPR bit, generate a coset codeword according to the polar code coset code property;

[0020] Perform BPSK modulation on the coset codeword to obtain a modulation signal vector;

[0021] Offline pre - calculate the modulation signal vectors corresponding to all PAPR bits, and store them in a lookup table to form an offline modulation signal vector set.

[0022] Preferably, the multiple modulation signal vectors generate multiple OFDM candidate signals through modulo-2 multiplication and Fourier transform, including:

[0023] Modulating the codeword of the initial polar code into a reference BPSK signal;

[0024] Through element-wise modulo-2 multiplication, multiplying the reference BPSK signal with multiple modulation signal vectors in the offline modulation signal vector set symbol by symbol to obtain multiple modulated signals after phase rotation;

[0025] Performing inverse fast Fourier transform on each modulated signal after phase rotation to generate multiple OFDM candidate signals.

[0026] Preferably, the BP-GF algorithm includes:

[0027] Obtaining parameters and initializing them, where the parameters include the leftmost R message matrix and the rightmost L message matrix, the R message matrix contains information bits, frozen bits, and PAPR bits, and the L message matrix includes channel log-likelihood ratios;

[0028] Iteratively updating the parameters according to the rules of the flooding BP algorithm;

[0029] In each round of iteration, calculating the source data to be estimated and the codeword to be estimated according to the updated parameters, and checking whether both the early termination condition based on the G matrix and the parity check condition of the sum of frozen bits are satisfied; if satisfied, stop the iteration and output the decoding result; otherwise, continue the iteration until the maximum number of iterations is reached;

[0030] If the early termination condition based on the G matrix and the parity check condition of the sum of frozen bits are not both satisfied within the maximum number of iterations, calculate the Euclidean distance between all the codewords to be estimated and the received signal, and select the codeword to be estimated with the minimum Euclidean distance as the decoding result.

[0031] On the other hand, the present invention also discloses an SLM system for reducing the PAPR of an OFDM system based on polar codes to implement the above mechanism, including a transmitter and a receiver;

[0032] The transmitter includes a set determination module, a modulation signal vector acquisition module, a candidate signal calculation module, and a transmission signal selection module;

[0033] The set determination module constructs a submatrix of the generator matrix based on the generator matrix corresponding to the extended information set and the Hamming weight, and combines the PAPR metric to obtain a PAPR set;

[0034] The modulation signal vector acquisition module offline obtains multiple modulation signal vectors corresponding to different PAPR bits in the PAPR set by using the coset code characteristic;

[0035] In the candidate signal calculation module, the multiple modulation signal vectors generate multiple OFDM candidate signals through modulo-2 multiplication and Fourier transform;

[0036] The transmission signal selection module calculates the PAPR values of the multiple OFDM candidate signals and selects the OFDM candidate signal with the minimum PAPR value as the transmission signal;

[0037] The receiver includes an algorithm-optimized decoding module, which performs detection and decoding through an SLM receiver based on the BP-GF algorithm to identify the transmission signal.

[0038] Preferably, the modulation signal vector acquisition module includes:

[0039] A coset codeword generation unit, for each PAPR bit, generates a coset codeword according to the characteristics of the polar code coset code;

[0040] A coset codeword modulation unit, which performs BPSK modulation on the coset codeword to obtain a modulation signal vector;

[0041] An offline storage unit stores the modulation signal vectors corresponding to all PAPR bits in a lookup table to form an offline modulation signal vector set.

[0042] Through the above technical solutions, the present invention discloses an SLM mechanism and system for reducing the peak-to-average power ratio of an OFDM system based on polar codes. Compared with the prior art, it has the following beneficial effects:

[0043] 1. The PAPR bits of the present invention are a small part of the frozen bits, and the modulation signal vectors corresponding to the PAPR bits can be pre-calculated offline. Multiple phase-rotated modulation symbols can be obtained using only one polar encoder and one modulator, reducing Q - 1 polar code encoders and Q - 1 BPSK modulators, realizing a lower-complexity SLM transmitter without code rate loss.

[0044] 2. The receiver uses the BP-GF algorithm to enhance the detection ability to adapt to the SLM transmitter without the need to transmit side information SI. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0046] Figure 1Schematic diagram of the method provided by the present invention;

[0047] Figure 2 Schematic diagram of the working process of the transmitter provided by the present invention;

[0048] Figure 3 Comparison graph of PAPR reduction performance of the method of the present invention when the code length N = 1024;

[0049] Figure 4 Comparison graph of PAPR reduction performance of the method of the present invention when the code length N = 128;

[0050] Figure 5 Comparison graph of FER between the BP-GF-based receiver and the BP-G algorithm proposed by the present invention on the AWGN channel;

[0051] Figure 6 Comparison graph of FER performance between the BP-GF-based receiver and the BP-G algorithm proposed by the present invention on the ITU Pedestrian B channel;

[0052] Figure 7 Factor graph corresponding to the polarization code generation matrix. Detailed implementation manners

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0054] The polarization code is defined by three parameters where the code length is N = 2 n . According to the selected design criterion and code rate, the N synthetic channels are divided into information-bit channels and frozen-bit channels. The cardinality of the information-bit set is the code rate is R = K / N, the frozen-bit set is denoted as F, and all the frozen bits u F are set to zero. This design method is called set construction. Currently, there are many set construction methods, such as Bhattacharyya parameter, quantization density evolution, etc. The input u of the polarization encoder includes two parts: information bits and frozen bits, which are respectively placed at the indices corresponding to the information-bit set and the frozen-bit set .

[0055] The calculation formula for the codeword c of the polarization code is as follows:

[0056]

[0057] where is an N*N generation matrix and is a polarization matrix which is the n-th Kronecker power of or respectively represent the sub-matrices composed of the rows corresponding to the sets or indexed, and addition and multiplication are performed in the modulo 2 field. Polar code encoding can avoid this matrix multiplication with a complexity of O(NlogN). The basic decoding of polar codes includes the SC and BP algorithms. Compared with the SC algorithm, the BP algorithm is easy to parallelize and supports soft input / soft output. The flooding type BP iterative decoding is a message passing algorithm executed on the factor graph corresponding to the polar code generation matrix. As

[0058] shown, the factor graph consists of n = log2 N stages. The nodes of the factor graph are labeled with integer pairs (i, j), where 1 ≤ i ≤ n + 1 and 1 ≤ j ≤ N. The BP decoder performs update iterations, where messages are propagated through each node (i, j): in each iteration, Figure 7 the messages are updated from left to right, and the messages are updated from right to left, where t = 0, 1,... is the time index. In this embodiment, all messages are assumed to be in the form of log-likelihood ratio (LLR). Figure 7 In each decoding stage of

[0059]

[0060] there are 4 identical processing elements (PEs), and the node update rule of the basic processing element is as shown in Equation (2): Here,

[0061] is called the boxplus operator. max When the iteration process reaches the preset number of times Iter the source data to be estimated at the leftmost node and the codeword to be estimated at the rightmost node and are calculated respectively according to their respective

[0062]

[0063] The hard decision formula is as follows:

[0064]

[0065] An early termination criterion (ETC) based on the G matrix is introduced to reduce the decoding delay. If the condition is met The decoding process will be stopped according to this criterion.

[0066] On the one hand, referring to Figure 1-2 , an SLM mechanism for reducing the peak-to-average power ratio (PAPR) of an OFDM system based on polar codes is proposed in an embodiment of the present invention, including:

[0067] S1. Construct a sub-matrix of the generator matrix based on the generator matrix corresponding to the extended information set and the Hamming weight, and combine the PAPR metric to obtain a PAPR set, including:

[0068] Using the Bhattacharyya parameter method, construct an extended information set with a cardinality of k + l to obtain the generator matrix corresponding to the extended information set

[0069] Select rows with Hamming weights within a preset range in the generator matrix corresponding to the extended information set to obtain a sub-matrix of the generator matrix In this embodiment, the preset range of the Hamming weight is 2 N-3 to 2 N-1 .

[0070] Perform Monte Carlo simulation on the polar-coded OFDM system, and calculate the PAPR metric according to the original PAPR (PAPR0) based on the sub-matrix of the generator matrix and the new PAPR (PAPR1) after bit-by-bit flipping. The calculation formula is |log(PAPR1) - log(PAPR0)|;

[0071] Arrange in descending order according to the PAPR metric, and select the first l indices from the sub-matrix of the generator matrix as the PAPR set The remaining indices are used for information bit transmission.

[0072] Determine the information bit set the frozen bit set or and the PAPR set After that, the working process of the PC-SLM transmitter in the embodiment of the present invention is as Figure 2 shown.

[0073] S2. In the PAPR set, obtain multiple modulated signal vectors corresponding to different PAPR bits offline by using the coset code property, including:

[0074] S21. For each PAPR bit, generate a coset codeword according to the polar code coset code property;

[0075] Specifically, given a data block u of length N, the input u of the polar encoder is divided into three parts and which are used as information bits, frozen bits, and PAPR bits respectively. Based on Q = 2 l different PAPR bits multiple OFDM signal candidates carrying the same information are generated, where l is the number of PAPR bits, which is set to all zeros. All possible l-bit vectors are organized into a matrix called PAPRbits, where each row corresponds to an l-bit binary number from 0 to Q - 1.

[0076] Since the polar code is a coset code, for each candidate q (where q = 0, 1,..., Q - 1) in the PC-SLM scheme, different are used to generate coset codewords. The q-th codeword c is generated by the following formula (q) :

[0077] c (q) = c (0) + c q (5)

[0078] where is the codeword of the initial polar code, is the coset codeword, represents the submatrix G formed by the index rows in the PAPR set .

[0079] S22. The coset codeword is BPSK modulated to obtain a modulated signal vector, specifically a BPSK signal vector, which is a real-domain vector with elements from the set {+1, –1}.

[0080] S23. Offline pre-compute the modulated signal vectors corresponding to all PAPR bits and store them in a lookup table to form an offline modulated signal vector set. The transmitter can quickly retrieve the modulated signal vectors from the table, thus significantly simplifying real-time operations.

[0081] S3. Multiple modulated signal vectors generate multiple OFDM candidate signals through modulo-2 multiplication and Fourier transform, including:

[0082] S31. Modulate the codeword of the initial polar code to a reference BPSK signal;

[0083] S32. Through element-wise modulo-2 multiplication, multiply the reference BPSK signal with multiple modulated signal vectors in the offline modulated signal vector set symbol by symbol to obtain multiple phase-rotated modulated signals.

[0084] Modulate the codeword c (q) into a BPSK signal X (q) .

[0085] X (q) = BPSK(c (q) ) = BPSK(c (0) + c q )(6)

[0086] where BPSK modulation is defined as BPSK(a) = 1 - 2a. For two vectors a and b operating in the modulo-2 field, BPSK(a + b) = BPSK(a) * BPSK(b). This means that the operation of adding two vectors and then performing BPSK modulation is equivalent to performing BPSK modulation on each vector separately and then performing multiplication.

[0087] Different from the Q candidate signals in the traditional SLM transmitter that require Q BPSK modulations, in this embodiment, by multiplying a modulation signal X (0) corresponding to an initial polar codeword c (0) with multiple modulation signal vectors P q to generate multiple phase-rotated modulation signals X (q) , as follows:

[0088]

[0089] The multiplication here is element-wise multiplication. Figure 2 The dashed box in

[0090] indicates that after steps (1) and (2), Q - 1 polar code encoders and Q - 1 BPSK modulators will no longer be needed.

[0091]

[0092] where X k ∈{-1, +1} is a BPSK symbol and N is the number of subcarriers.

[0093] S4. Calculate the PAPR values of the multiple OFDM candidate signals and select the OFDM candidate signal with the minimum PAPR value as the transmission signal, with the formula as follows:

[0094]

[0095] q * = argmin q PAPR(x (q) )(10)

[0096] The proposed SLM transmitter of the present invention can utilize offline pre-computation, and by using only one polar code encoder and one modulator, multiple modulated signals can be generated through modulo-2 multiplication. The modulo-2 multiplication can be implemented using a simple bitwise AND operation, and the circuit complexity can be negligible. Compared with the existing PC-SLM transmitter, the proposed SLM transmitter of the present invention has lower complexity.

[0097] S5. Detect and decode through the SLM receiver based on the BP-GF algorithm to identify the transmitted signal.

[0098] The BP-GF algorithm includes:

[0099] Obtain parameters and initialize them. The parameters include the leftmost R message matrix and the rightmost L message matrix. The R message matrix contains information bits, frozen bits, and PAPR bits. The L message matrix includes channel log-likelihood ratios. The initialization formulas are as follows:

[0100]

[0101] For the information bit index j, set indicating that the prior probabilities of 0 and 1 are equal. For the frozen bit index j, set because the decoder knows that these indices are set to 0, where K is a large number (set K = 100 in the simulation). The R messages corresponding to the PAPR set are initialized to K or -K, depending on the PAPR preset bit. All other and are set to 0. The initialization sub-function will clear the messages in all stages and use the new PAPR bits as the input of the R messages in the next round of BP iteration. The number 100 indicates that the reliability in the LLR domain is very high.

[0102] Iteratively update the parameters according to the rules of the flood-type BP algorithm;

[0103] In each round of iteration, calculate the source data to be estimated and the codeword to be estimated according to the updated parameters, and check whether both the early termination condition based on the G matrix and the parity check condition of the sum of the frozen bits are satisfied; if satisfied, stop the iteration and output the decoding result; otherwise, continue the iteration until the maximum number of iterations is reached;

[0104] If both the early termination condition based on the G matrix and the parity check condition of the sum of the frozen bits are not satisfied within the maximum number of iterations, calculate the Euclidean distance between all the codewords to be estimated and the received signal y, and select the codeword to be estimated with the minimum Euclidean distance as the decoding result, as follows:

[0105]

[0106] The BP-GF algorithm refers to Tables 1 and 2:

[0107] Table 1 BP-GF algorithm flow

[0108]

[0109] The input of the algorithm is the LLR of the channel output: Lch, the set of information bits The set of frozen bits The set of PAPR PAPRbits (if l = 2, then PAPRbits includes 00, 01, 10, 11, which is a 4-row matrix).

[0110] Lines 1 to 17 are the working process of the proposed SLM receiver. Lines 1 and 17 are the corresponding start and end. The process of the SLM receiver can be regarded as executing the BP algorithm Q times (i.e., for q = 1:Q do).

[0111] Line 2 is the initialization of the algorithm, which assigns values to the (n + 1)-th row of the L matrix and the 1st row of the R matrix respectively, corresponding to formula (11).

[0112] Line 3 is the initialization of the iterative process iI = 1, and a flag bit Flag = 1 is set (after the subsequent GFcheck() is executed, Flag may become 0).

[0113] Lines 4 to 12 execute the BP iterative algorithm: Line 4 sets the condition for the end of the iteration: i.e., iI ≤ Itermax and Flag = 1; Line 5 updates L and R using formula 2 in the document (this is the log-likelihood ratio (LLR) for the BP algorithm to update the confidence simultaneously left and right); The meaning of Line 6: When the number of iterations is less than 2n, Line 7 is executed, and formula (3) is used to assign values to and respectively. When reaching Line 8, GFcheck() will be called. The meaning of Line 8 if GFcheck(L,R) is to judge according to the execution result of GFcheck(), that is, if GFcheck() meets the condition and returns true, then Line 9 is executed, Flag = 0. If GFcheck() does not meet the judgment condition and returns false, Line 9 is not executed, that is, the value of Flag remains unchanged, still Flag = 1. If Flag = 0, then at Line 13, the current (Corresponding to the "return" in line 14), and break out of the current loop process (lines 1 - 17) (corresponding to the "break" in line 15), which is used as the result output by the receiver. If the execution from line 1 to line 17 is completed (i.e., calling GFcheck(), and no condition is met, and the previously set flag Flag is still 1), then execute line 19, MinEuclideanDistance, to calculate the Euclidean distance between all the codewords to be estimated and the received signal y, and select the path with the smallest Euclidean distance as the decoding result, corresponding to formula (12).

[0114] Table 2 Execution code of GFcheck

[0115]

[0116]

[0117] In the execution code of GFcheck, line 1 indicates that according to the log - likelihood ratio (LLR) of the first row of the L matrix and the first row of the R matrix (i.e., the first one in formula (3)), perform a hard decision according to formula (4), and assign the obtained result to Line 2 indicates that according to the log - likelihood ratio (LLR) of the (n + 1)-th row of the L matrix and the (n + 1)-th row of the R matrix (i.e., the second one in formula (3)), perform a hard decision according to formula (4), and assign the obtained result to Line 3 indicates that if the conditions and are both satisfied, then return true (line 4), otherwise return false (line 6).

[0118] Embodiments of the present invention further verify the effectiveness of this method. Use MATLAB to evaluate the method proposed by the present invention, and the performance of BPSK modulation on an additive white Gaussian noise (AWGN) channel and an International Telecommunication Union (ITU) Pedestrian B channel. The code length is set to 1024 and 128, and the code rate is set to 0.5. Determine the information bit set PAPR set and P q are obtained offline.

[0119] (1) PAPR performance

[0120] The complementary cumulative distribution function (CCDF) is used to measure the performance of PAPR reduction. Figure 3 and Figure 4 respectively show the PAPR reduction performance of the method proposed in the present invention. The number of branches Q in the SLM belongs to {4, 16, 64} and is used for N = 1024 and N = 128 respectively. For different code lengths N, the proposed scheme in the present invention has achieved significant PAPR reduction, and with the increase of the number of PAPR bits Q, the gain of PAPR reduction performance also increases. Specifically, when N = 1024 and the CCDF is 10 -4 at this time, compared with the initial polar-coded OFDM (PC-OFDM), the proposed PAPR reduction method in the present invention provides significant gains of about 9.2, 14.3, and 15.2 dB respectively for Q ∈ {4, 16, 64}.

[0121] (2) Frame Error Rate (FER) performance

[0122] Figure 5 The FER of the proposed SLM receiver based on the BP-GF algorithm in the AWGN channel is evaluated, where the maximum number of iterations is set to 60. As a comparison benchmark, the performance of the BP (BP algorithm with G-matrix-based ETC, BP-G) algorithm of the ETC based on the G matrix in the PC-OFDM system is evaluated. The number of candidates in the simulation is set to Q ∈ {4, 8}. Compared with the BP-G algorithm in the AWGN channel, the BP-GF receiver achieves consistent FER performance when Q = 4, and when Q = 8, it provides a signal-to-noise ratio (SNR) gain of 0.3 dB at FER = 10 -3 at this time.

[0123] Figure 6 Illustrates the comparison of the FER performance between the proposed BP-GF-based receiver and the BP-G algorithm receiver in the ITU Pedestrian B channel. In each transmission block, a cyclic prefix (CP) with a length of 16 is used, and the channel impulse response (CIR) of the ITU Pedestrian B fading channel model is shown in Table 3. The simulation results show that for Q = 4 or 8, the performance of the proposed BP-GF algorithm is better than that of BP-G, and it provides an SNR gain of 0.5 dB at FER = 8·10 -2 at this time.

[0124] Table 3 Channel Impulse Response (CIR) of ITU PedestrianB Channel Model

[0125] Path (Sampling Point) 1 3 10 15 27 43 Power Level (dB) -3.92 -4.82 -8.82 -11.92 -11.72 -27.82

[0126] On the other hand, the present invention also discloses an SLM system for reducing the peak-to-average power ratio of an OFDM system based on polar codes, which is used to implement the above mechanism and includes a transmitter and a receiver;

[0127] The transmitter includes a set determination module, a modulation signal vector acquisition module, a candidate signal calculation module, and a transmission signal selection module;

[0128] The set determination module constructs a sub-matrix of the generating matrix based on the generating matrix corresponding to the extended information set and the Hamming weight, and combines the PAPR metric to obtain a PAPR set;

[0129] The modulation signal vector acquisition module obtains multiple modulation signal vectors corresponding to different PAPR bits offline by using the coset code property in the PAPR set;

[0130] In the candidate signal calculation module, multiple modulation signal vectors generate multiple OFDM candidate signals through modulo-2 multiplication and Fourier transform;

[0131] The transmission signal selection module calculates the PAPR values of multiple OFDM candidate signals and selects the OFDM candidate signal with the minimum PAPR value as the transmission signal;

[0132] The receiver includes an algorithm optimization decoding module, and the algorithm optimization decoding module performs detection and decoding through an SLM receiver based on the BP-GF algorithm to identify the transmission signal.

[0133] Preferably, the modulation signal vector acquisition module includes:

[0134] A coset codeword generation unit, for each PAPR bit, generates a coset codeword according to the polar code coset code property;

[0135] A coset codeword modulation unit, modulates the coset codeword by BPSK to obtain a modulation signal vector;

[0136] An offline storage unit stores the modulation signal vectors corresponding to all PAPR bits in a lookup table to form an offline modulation signal vector set.

[0137] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0138] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A SLM mechanism for reducing the peak-to-average power ratio of an OFDM system based on polar codes, characterized in that, Including: Construct a sub - matrix of the generating matrix based on the generating matrix corresponding to the extended information set and the Hamming weight, and combine with the PAPR metric to obtain the PAPR set; In the PAPR set, utilize the coset code property to offline obtain multiple modulation signal vectors corresponding to different PAPR bits; The multiple modulation signal vectors generate multiple OFDM candidate signals through modulo - 2 multiplication and Fourier transform; Calculate the PAPR values of the multiple OFDM candidate signals, and select the OFDM candidate signal with the minimum PAPR value as the transmission signal; Detect and decode through an SLM receiver based on the BP - GF algorithm to identify the transmission signal.

2. The SLM mechanism for reducing the peak-to-average power ratio of an OFDM system based on polar codes according to claim 1, wherein Construct a sub - matrix of the generating matrix based on the generating matrix corresponding to the extended information set and the Hamming weight, and combine with the PAPR metric to obtain the PAPR set, including: Using the Bhattacharyya parameter method, construct an extended information set with cardinality k + l to obtain the generator matrix corresponding to the extended information set Select rows with Hamming weights within a preset range from the generator matrix corresponding to the extended information set to obtain a sub-matrix of the generator matrix Perform Monte Carlo simulation on the polar-coded OFDM system, and calculate the PAPR metric according to the original PAPR and the new PAPR after bit flipping one by one based on the sub-matrix of the generating matrix ​ Select the first l indices from the sub-matrix of the generating matrix as the PAPR set in descending order of PAPR metric ​ 3. A SLM mechanism for reducing the peak-to-average power ratio of an OFDM system based on polar codes according to claim 1, characterized in that, Utilize the coset code property to offline obtain multiple modulation signal vectors corresponding to different PAPR bits, including: For each PAPR bit, generate a coset codeword according to the polarization code coset code property; Perform BPSK modulation on the coset codeword to obtain a modulation signal vector; Offline pre - calculate the modulation signal vectors corresponding to all PAPR bits, and store them in a lookup table to form an offline modulation signal vector set.

4. A SLM mechanism for reducing the PAPR of an OFDM system based on polar codes according to claim 3, characterized in that, The multiple modulation signal vectors generate multiple OFDM candidate signals through modulo - 2 multiplication and Fourier transform, including: Modulate the codeword of the initial polarization code into a reference BPSK signal; Through element - by - element modulo - 2 multiplication, multiply the reference BPSK signal with multiple modulation signal vectors in the offline modulation signal vector set symbol - by - symbol to obtain multiple phase - rotated modulation signals; Perform inverse fast Fourier transform on each phase - rotated modulation signal to generate multiple OFDM candidate signals.

5. A SLM mechanism for reducing the peak-to-average power ratio of an OFDM system based on polar codes according to claim 1, characterized in that The BP - GF algorithm includes: Obtain parameters and initialize them. The parameters include the left - most R message matrix and the right - most L message matrix. The R message matrix contains information bits, frozen bits, and PAPR bits, and the L message matrix includes channel log - likelihood ratios; Iteratively update the parameters according to the flood - type BP algorithm rules; In each round of iteration, calculate the source data to be estimated and the codeword to be estimated according to the updated parameters, and check whether both the early - termination condition based on the G matrix and the parity - check condition of the sum of frozen bits are satisfied; if satisfied, stop the iteration and output the decoding result; otherwise, continue the iteration until the maximum number of iterations is reached; If both the early - termination condition based on the G matrix and the parity - check condition of the sum of frozen bits are not satisfied within the maximum number of iterations, calculate the Euclidean distance between all the codewords to be estimated and the received signal, and select the codeword to be estimated with the minimum Euclidean distance as the decoding result.

6. An SLM system for reducing the peak-to-average power ratio (PAPR) of an OFDM system based on polar codes, characterized in that, Including a transmitter and a receiver; The transmitter includes a set determination module, a modulation signal vector acquisition module, a candidate signal calculation module, and a transmission signal selection module; The set determination module constructs a sub - matrix of the generating matrix based on the generating matrix corresponding to the extended information set and the Hamming weight, and combines with the PAPR metric to obtain the PAPR set; In the modulation signal vector acquisition module, in the PAPR set, multiple modulation signal vectors corresponding to different PAPR bits are obtained offline by using the coset code characteristics; In the candidate signal calculation module, the multiple modulation signal vectors generate multiple OFDM candidate signals through modulo-2 multiplication and Fourier transform; The transmission signal selection module calculates the PAPR values of the multiple OFDM candidate signals and selects the OFDM candidate signal with the minimum PAPR value as the transmission signal; The receiver includes an algorithm optimization decoding module, and the algorithm optimization decoding module performs detection and decoding through an SLM receiver based on the BP-GF algorithm to identify the transmission signal.

7. The SLM system for reducing the PAPR of an OFDM system based on polar codes according to claim 6, characterized in that, The modulation signal vector acquisition module includes: A coset codeword generation unit that generates coset codewords for each PAPR bit according to the polarization code coset code characteristics; A coset codeword modulation unit that performs BPSK modulation on the coset codewords to obtain modulation signal vectors; An offline storage unit that stores the modulation signal vectors corresponding to all PAPR bits in a lookup table to form an offline modulation signal vector set.

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