A communication method, device and system for blind frame synchronization

Abstract

The present invention discloses a communication method, device and system for blind frame synchronization, belonging to the technical field of error correction coding and decoding; it includes: S1. The receiving end receives the data sent by the sending end for demodulation to obtain multiple frames of data encoded by polar codes; a frame synchronization offset is added to each frame of data respectively to obtain multiple candidate sequences; S2. The obtained multiple candidate sequences are respectively decoded by polar codes, and during the decoding process, by comprehensively calculating the probability that each frozen bit in the candidate sequence is correctly decoded, the probability that each candidate sequence is in the correct synchronization position is obtained, and the candidate sequence corresponding to the maximum probability is selected, and the corresponding frame synchronization position and decoding result are returned; the present invention ingeniously designs the above method to realize blind frame synchronization communication, with lower calculation complexity, shorter synchronization delay and better synchronization performance. At the same time, it can also make full use of the advantages of polar codes themselves to improve the reliability of communication.

Description

Technical Field

[0001] The present invention belongs to the technical field of error correction coding and decoding, and more specifically, relates to a communication method, device and system for blind frame synchronization. Background Art

[0002] In a digital communication system, data is usually transmitted in the form of "frames". At the receiving end, in order for the decoder to work properly, it is necessary to accurately find the starting position of a frame of data from the received sequence, and this process is called frame synchronization. In the frame synchronization process of traditional communication methods, pilot or training sequences specified by both the transmitter and the receiver are inserted into the transmitted sequence, and the receiving end detects the pilot or training sequence through correlation operations to determine the starting position of the frame. However, the synchronization link relying on data assistance is easily interrupted by noise interference, and as the load information in the data frame increases, the required pilot sequence or frame synchronization codeword becomes longer, thus increasing the overhead of the communication system and reducing the spectral efficiency.

[0003] To solve the above problems, an encoding-assisted blind frame synchronization communication method has been proposed, which uses the redundant information in error correction coding to determine the frame synchronization position through decoding. For example, in the blind frame synchronization communication method based on the parity-check matrix of a Low-density Parity-check (LDPC) code, the decoded codeword is multiplied by the parity-check matrix, and the position of frame synchronization is judged according to the probability that the result is equal to 0. However, this method is limited by the decoding performance of LDPC, the communication reliability is poor, there are multiple iterations, the complexity is high, and the synchronization delay is long.

[0004] Considering that polar codes are currently the only coding method that has been theoretically proven to reach the Shannon limit, and have shown better error correction performance than LDPC codes in medium and short code lengths. And currently, various decoding algorithms with low decoding complexity and excellent performance have been proposed, such as the Serial Cancellation (SC) algorithm, the Fast Simplified SC (Fast-SSC) algorithm, and the Soft Cancellation (SCAN) algorithm. Therefore, designing a polar code-assisted blind frame synchronization communication is of great significance for reducing link overhead and improving transmission reliability. However, different from other linear block codes, when the parity-check matrix of a polar code is multiplied by the decoded codeword, a fixed frozen bit value is always obtained, and the position of frame synchronization cannot be judged according to the probability that the result is equal to 0, that is, the position of frame synchronization cannot be judged through the parity-check matrix or syndrome, so it is urgent to design a polar code-assisted blind frame synchronization communication method to solve the above problems. Summary of the Invention

[0005] In view of the above deficiencies or improvement requirements of the prior art, the present invention provides a communication method, device and system for blind frame synchronization, which is used to solve the technical problems of poor reliability and long synchronization delay in the existing blind frame synchronization communication method.

[0006] To achieve the above object, in a first aspect, the present invention provides a communication method for blind frame synchronization, including the following steps:

[0007] S1. The receiving end receives the data sent by the sending end for demodulation, and obtains multiple frames of data encoded by polar codes; frame synchronization offsets are respectively added to each frame of data to obtain multiple candidate sequences;

[0008] S2. The obtained multiple candidate sequences are respectively decoded by polar codes, and during the decoding process, by comprehensively considering the probability that each frozen bit in the candidate sequence is correctly decoded, the probability that each candidate sequence is in the correct synchronization position is obtained, and the candidate sequence corresponding to the maximum probability is selected, and its corresponding frame synchronization position and decoding result are returned;

[0009] Among them, the data sent by the sending end is the data obtained by the sending end after sequentially encoding and modulating the transmission information by polar codes.

[0010] Further preferably, every 2N-length demodulated data corresponds to one frame of N-length data encoded by polar codes; the first N positions of the 2N-length demodulated data are respectively intercepted as the frame start positions to obtain N data sequences with a length of N, which are used as candidate sequences for one frame of data.

[0011] Further preferably, a synchronization metric value is used to reflect the probability that a candidate sequence is correctly decoded; the smaller the synchronization metric value of the candidate sequence, the greater the probability that the candidate sequence is in the correct synchronization position; among them, for the candidate sequence ω t the synchronization metric value SM t The calculation formula is as follows:

[0012]

[0013] Among them, A C is the index set of polar code frozen bits; LLR t [i] represents the log-likelihood ratio (Log Likelihood Ratio, LLR) of the i-th bit in the candidate sequence ω t ; N is the number of candidate sequences.

[0014] Further preferably, the SC decoding algorithm, Fast-SSC decoding algorithm, SCAN decoding algorithm or its derivative decoding is used to decode the candidate sequence by polar codes.

[0015] Further preferably, when the SC decoding algorithm is used to perform polar code decoding on the candidate sequence, the above-mentioned candidate sequence ω t The synchronization metric value SM t is simplified to: the sum of the absolute values of the LLRs of all frozen bits where the decision value is not equal to the decoded value.

[0016] Further preferably, when the Fast-SSC decoding algorithm is used to perform polar code decoding on the candidate sequence, the candidate sequence ω t The synchronization metric value SM t is simplified to: the sum of the synchronization metric values of each special node.

[0017] Further preferably, the calculation method of the synchronization metric value SM t [k] of the k-th special node is as follows:

[0018] When the k-th special node is a Rate-0 node, SM t [k] is the sum of the absolute values of the LLRs of all bits where the decision value is not equal to the decoded value in the k-th special node;

[0019] When the k-th special node is a Rate-1 node, SM t [k] is 0;

[0020] When the k-th special node is a REP node, SM t [k] is the sum of the absolute values of the LLRs of all bits where the decision value is not equal to the decision value of the LLR rep in the k-th special node; LLR rep is the sum of the LLRs of all bits in the k-th special node;

[0021] When the k-th special node is an SPC node, if the modulo-2 addition value of the LLRs of all bits in the k-th special node is equal to 0, then SM t [k] is 0; otherwise, SM t [k] is the minimum value of the absolute values of the LLRs of all bits in the k-th special node.

[0022] Further preferably, when the SCAN decoding algorithm is used to perform polar code decoding on the candidate sequence, the candidate sequence ω t The synchronization metric value SM t is: the sum of the absolute values of the LLRs of all frozen bits where the left information decision value in the decision layer after completing the maximum number of SCAN decoding iterations is not equal to the decoded value.

[0023] In a second aspect, the present invention provides a receiving end for executing the blind frame synchronization communication method provided in the first aspect of the present invention.

[0024] In a third aspect, the present invention provides a communication system for blind frame synchronization, including: a transmitting end and the receiving end provided in the second aspect of the present invention;

[0025] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0026] 1. The present invention provides a blind frame synchronization communication method for a receiving end. The receiving end adds frame synchronization offsets to each demodulated polar code data frame respectively to obtain a plurality of candidate sequences; for the obtained plurality of candidate sequences, a blind frame synchronization method assisted by polar codes is used. During the decoding process, the probability that the frozen bits in the candidate sequences are correctly decoded is calculated simultaneously, and the frame synchronization position and the decoding result corresponding to the candidate sequence with the largest probability are selected as the final result. The present invention takes into account that the limitation of the code length will lead to insufficient polarization, so that there is still a small amount of information in the frozen bits, and it is more likely to be correctly estimated at the synchronization position than at the asynchronous position, and the conclusion that the probability of correct decoding of the frozen bits at the correct frame synchronization position is the largest is obtained; based on this, the present invention ingeniously designs the above method to realize communication based on blind frame synchronization, with lower computational complexity, shorter synchronization delay, better synchronization performance, and at the same time can make full use of the advantages of polar codes themselves, greatly improving the transmission reliability.

[0027] 2. The blind frame synchronization communication method provided by the present invention has lower complexity compared with traditional communication methods; specifically, frame synchronization in traditional communication must receive the synchronization data auxiliary sequence completely and accurately to complete synchronization, while the communication method based on blind frame synchronization provided by the present invention does not require additional data assistance, and its link stability is better; frame synchronization assisted by polar codes reduces the channel resource overhead and improves the information transmission efficiency on the premise of ensuring the information bit error rate.

[0028] 3. Further, in the blind frame synchronization communication method provided by the present invention, the probability that the frozen bits in the candidate sequences are correctly decoded is represented in the form of LLR and converted into the logarithmic domain, so as to obtain a synchronization metric value to reflect the probability that the candidate sequences are correctly decoded, further reducing the computational complexity and improving the computational efficiency.

[0029] 4. Further, in the blind frame synchronization communication method provided by the present invention, when different decoding algorithms are adopted, the synchronization metric value formula of the candidate sequences is further simplified in combination with the characteristics of the decoding algorithms, thereby further reducing the computational complexity and improving the computational efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flowchart of a blind frame synchronization communication method based on polar codes provided in Embodiment 1 of the present invention;

[0031] Figure 2Flowchart of the blind frame synchronization communication method based on polar codes provided by the specific embodiment of the present invention;

[0032] Figure 3 Flowchart of SC decoding and synchronization metric value calculation provided by Embodiment 1 of the present invention;

[0033] Figure 4 Performance diagram of the blind frame synchronization communication method based on polar codes provided by Embodiment 1 of the present invention. Specific embodiments

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] Embodiment 1

[0036] A blind frame synchronization communication method, in which no frame synchronization pilot or training sequence is added to the data frame, and the starting position of the frame is found through blind frame synchronization based on polar codes.

[0037] Specifically, the blind frame synchronization based on polar codes is as Figure 1 shown, and includes the following steps:

[0038] S1. The receiving end receives the data sent by the sending end for demodulation to obtain multiple frames of data encoded by polar codes; a frame synchronization offset is added to each frame of data respectively to obtain a plurality of candidate sequences; wherein, the data sent by the sending end is the data obtained by the sending end after sequentially performing polar code encoding and modulation on the transmission information; specifically, after the sending end performs polar code encoding and modulation, it sends data without adding a frame synchronization pilot or training sequence.

[0039] Specifically, the number of candidate sequences is related to the frame length. For a polar code with a frame length of N, in order to ensure that the correct position of its frame synchronization must be in the candidate set, the receiving end needs at least 2N lengths of demodulated data. The first N positions of the demodulated data are respectively taken as the frame starting positions to obtain a set of demodulated candidate sequences Ω = {ω1, ω2, …, ω N}, where each candidate sequence ω t ,t = {1, 2, …, N}, and the length of each is N; the modulation and demodulation methods can be BPSK, QPSK, 16QAM, etc.

[0040] S2. Perform polar code decoding on each candidate sequence of each frame of data, and during the decoding process, obtain the probability that each candidate sequence is in the correct synchronization position by comprehensively considering the probability that each frozen bit in the candidate sequence is correctly decoded. Select the candidate sequence corresponding to the maximum probability, and return its corresponding frame synchronization position and decoding result;

[0041] Specifically, due to the limited code length resulting in insufficient polarization, there is still a small amount of information in the frozen bits. Therefore, the frozen bits are more likely to be correctly estimated at the synchronization position than at the asynchronous position, that is, the probability that the frozen bits at the correct frame synchronization position are correctly decoded is the largest. At the same time, the probability that the frozen bits are correctly estimated is characterized in the form of LLR and transformed into the logarithmic domain to simplify the calculation. Specifically, the calculation formula for the synchronization metric value is as follows:

[0042]

[0043] where A C is the index set of the polar code frozen bits; LLR t [i] represents the LLR of the i-th bit in the candidate sequence ω t ; N is the number of candidate sequences.

[0044] In an alternative embodiment, the synchronization metric value is used to reflect the probability that the frozen bits of the candidate sequence are correctly decoded; the smaller the synchronization metric value of the candidate sequence, the greater the probability that the frozen bits of the candidate sequence are correctly decoded. At this time, step S2 is: perform polar code decoding on each candidate sequence of each frame of polar code data, and during the decoding process, obtain the synchronization metric value of each candidate sequence by calculating the probability that the frozen bits in the candidate sequence are correctly decoded. Select the candidate sequence corresponding to the minimum synchronization metric value, and return its corresponding frame synchronization position and decoding result.

[0045] Furthermore, the polar code decoding algorithm can be selected from the SC decoding algorithm, Fast-SSC decoding algorithm, SCAN decoding algorithm, derivative decoding algorithms of the SC decoding algorithm, derivative decoding algorithms of the Fast-SSC decoding algorithm, derivative decoding algorithms of the SCAN decoding algorithm, etc. During the decoding process, calculate the synchronization metric value simultaneously, and simplify the calculation formula of the synchronization metric value according to different decoding methods to further improve the calculation efficiency.

[0046] In an alternative embodiment, the SC decoding algorithm is used to perform polar code decoding on the candidate sequence. At this time, based on the formula the above synchronization metric value formula can be simplified, so that the synchronization metric value SM t of the above candidate sequence ω t is further simplified to: the sum of the absolute values of the LLRs of all frozen bits where the decision value and the decoding value are not equal, that is:

[0047] If

[0048] wherein is the decoding value of the i-th bit in the candidate sequence ω t ; δ(LLR t [i]) is the decision value of the i-th bit in the candidate sequence ω t , which is the result of hard decision based on the current LLR, that is:

[0049]

[0050] Specifically, when decoding the bits in the candidate sequence ω t bit by bit, the synchronization metric value SM t is updated during this process: when decoding a frozen bit, if the decision value of the frozen bit is the same as the decoding value, then SM t remains unchanged; otherwise, a penalty is imposed, and the magnitude of the penalty value is the absolute value of the LLR of the current frozen bit.

[0051] The calculation method of the synchronization metric value of the derivative decoding algorithm of the SC decoding algorithm is the same as that of the SC decoding algorithm, which will not be elaborated here.

[0052] In an alternative embodiment, the Fast-SSC decoding algorithm is used to perform polar code decoding on the candidate sequence. At this time, the synchronization metric value SM t of the candidate sequence ω t can be further simplified to the sum of the synchronization metric values of all special nodes, that is:

[0053]

[0054] wherein, K1 is the number of nodes in the candidate sequence ω t ; SM t [k] is the synchronization metric value of the k-th special node of the candidate sequence ω t ; it should be noted that the calculation formula of the synchronization metric value here is equivalent to the calculation formula of the synchronization metric value in SC decoding, but it is applied in Fast-SSC and the form has changed.

[0055] Specifically, when the k-th special node is a Rate-0 node, the k-th special node only contains frozen bits, and the synchronization metric value SM t [k] of the k-th special node is jointly determined by the LLRs of all the bits included in the k-th special node, specifically, it is the sum of the absolute values of the LLRs of all the bits in the k-th special node where the decision value and the decoding value are not equal.

[0056] When the k-th special node is a Rate-1 node, the k-th special node only contains information bits, and SM t [k] is 0.

[0057] When the k-th special node is a REP node K, the k-th special node contains both frozen bits and information bits, specifically including (N K -1) frozen bits and 1 information bit, where N K is the number of bits in the REP node K. Specifically, the synchronization metric value SM t [k] is the sum of the absolute values of all the LLRs of the bits in the k-th special node whose decision values are not equal to the decision value of the LLR rep ; among them, LLR rep is the sum of the LLRs of all the bits in the k-th special node.

[0058] When the k-th special node is an SPC node K, the k-th special node contains both frozen bits and information bits, specifically including 1 frozen bit and (N K -1) information bits, where N K is the number of bits in the SPC node K. Specifically, if the modulo-2 addition value of all the LLRs of the bits in the k-th special node is equal to 0, then SM t [k] is equal to 0; otherwise, SM t [k] is equal to the minimum value of the absolute values of all the LLRs of the bits in the k-th special node.

[0059] It should be noted that the Fast-SSC decoding algorithm divides the bits in the candidate sequence into different special nodes for decoding, and the above special nodes are all bit sets.

[0060] Furthermore, the calculation method of the synchronization metric value of the derivative decoding algorithm of the Fast-SSC decoding algorithm is the same as that of the Fast-SSC decoding algorithm, which will not be elaborated here.

[0061] In an alternative implementation, the SCAN decoding algorithm is used to perform polar code decoding on the candidate sequence, and the synchronization metric value SM t of the candidate sequence ω t is the sum of the absolute values of all the LLRs of the frozen bits whose left information decision values and decoding values are not equal at the decision layer after completing the maximum number of iterations of the SCAN decoding, that is:

[0062] If

[0063] where t = {1, 2,..., N}; N is the number of candidate sequences; A C is the index set of the frozen bits; Lt [i] is the candidate sequence ω t After completing the maximum number of iterations of SCAN decoding, the left information of the i-th bit at the decision layer; is the candidate sequence ω t The decoding value of the i-th bit; δ(L t [i]) is L t [i]'s decision value;

[0064]

[0065] It should be noted that the calculation formula of the synchronization metric value here is equivalent to the calculation formula of the synchronization metric value in SC decoding, but it is only applied in SCAN and the form has changed.

[0066] The calculation method of the synchronization metric value of the derivative decoding algorithm of the SCAN decoding algorithm is the same as that of the SCAN decoding algorithm, which will not be elaborated here.

[0067] In order to further illustrate the blind frame synchronization communication method provided by the present invention, the following takes the SC decoding algorithm as an example and elaborates it in combination with a specific embodiment:

[0068] Figure 2 is the flowchart of the blind frame synchronization communication method provided by the present invention from the sending end to the receiving end. The blind frame synchronization communication method based on polar codes in this example is described in detail, and the method includes operations A1 - A4.

[0069] Operation A1, the sending end encodes the information bits with polar codes and sends them after modulation.

[0070] According to the embodiment of the present invention, the polar code length N = 512 is set, where the information bit length K = 256, and the frozen bit length is N - K = 256. The information bit index set is represented as A, and the frozen bit index set is represented as A C , and in this example, it is assumed that all frozen bits are 0.

[0071] The following describes the specific operations of the sending end, including A001 - A003.

[0072] In operation A001, the reliability sorting of all sub-channels is statistically calculated. Specifically, for example, using the Gaussian approximation method (E b / N0 = 2dB) to obtain K sub-channel indices with higher reliability, which form the information bit index set A. The remaining N - K sub-channels constitute the frozen bit index set A C .

[0073] In operation A002, information bits are placed on the information bit index set A, and frozen bits are placed on the frozen bit index set A C to obtain the pre-encoding sequence

[0074] In operation A003, the pre-encoded sequence is multiplied by the polar code encoding matrix G to obtain the polar code encoded codeword

[0075] In operation A004, the encoded codeword is modulated using Binary Phase Shift Keying (BPSK) modulation, and after obtaining the modulated symbol sequence, it is transmitted.

[0076] It should be understood that, according to actual needs, polar codes with other code lengths and code rates and other modulation methods can also be selected. Moreover, how to perform polar code encoding and how to modulate belong to the prior art in this field and are not the core content discussed in the present invention. Therefore, no further elaboration will be made.

[0077] Operation A2: The receiving end receives data, adds a synchronization offset after demodulation, and obtains candidate sequences.

[0078] The number of candidate sequences is determined by the encoding length of the polar code. After determining the number of candidates, a frame synchronization offset is added to obtain the candidate sequences. Specifically, since the encoded code length N = 512 in this embodiment and the BPSK modulation method is adopted, the total number of candidates is set to 512, and the receiving end needs to continuously receive data with a length of 1024 symbols. Taking the i-th bit after demodulation as the starting point, the received sequence with a length of 512 bits is used as the i-th candidate sequence ω i , and the candidate sequence set Ω = {ω1, ω2, …, ω 512} is obtained in sequence.

[0079] Operation A3: Successively perform SC decoding on each candidate sequence, and calculate the synchronization metric value corresponding to each candidate sequence, that is, the SM value, during the decoding process.

[0080] The flow of SC decoding and SM value calculation is as Figure 3 shown. According to the embodiment of the present invention, in operation A3, the t-th candidate sequence is selected for SC decoding, which specifically includes sub-operations A31 - A34.

[0081] In sub-operation A31, since SC decoding is serial decoding, if the i-th bit to be decoded is an information bit, then it enters sub-operation A32; if the i-th bit is a frozen bit, then it enters sub-operation A33.

[0082] In sub-operation A32, the information bit is determined according to the current LLR, and the SM value remains unchanged when encountering an information bit:

[0083] SM t [i] = SM t[i - 1], i ∈ A

[0084] wherein, SM t [i] represents the SM value when decoding the i-th bit in the t-th candidate sequence.

[0085] In sub-operation A33, since all frozen bits are 0, the decoded value of the frozen bits is 0. However, at this time, the SM value of the current sequence needs to be updated according to the decision value of the current LLR, that is:

[0086]

[0087] wherein, LLR t [i] represents the LLR of the i-th bit in the t-th candidate sequence, and SM t [i] represents the SM value when decoding the i-th bit in the t-th candidate sequence.

[0088] In sub-operation A34, it is judged whether the current bit is the last bit of decoding. If so, the decoding ends and the decoding result of the current candidate sequence is returned and the synchronization metric value SM t , and then go to operation A4; otherwise, let i = i + 1 and go to sub-operation A31.

[0089] In operation A4, it is judged whether the current candidate sequence is the last candidate sequence. If so, the decoding and blind frame synchronization end, and the sequence with the smallest SM is selected from {SM1, SM2,..., SM 512} as the final frame synchronization result, and the decoding result of this candidate sequence is returned; otherwise, the next candidate sequence is selected and operation A3 continues.

[0090] As Figure 4 shown is the performance graph of the blind frame synchronization communication method provided by the embodiment of the present invention; it can be seen from the figure that the frame error rate of the blind frame synchronization is almost the same as that of the SC decoding, indicating that the blind frame synchronization algorithm assisted by the polar code does not affect the decoding performance. At the same time, the synchronization error probability of the blind frame synchronization is better than the frame error rate of the blind frame synchronization, indicating that this method still maintains excellent synchronization performance in the case of decoding errors.

[0091] Embodiment 2,

[0092] A receiving end for performing the blind frame synchronization communication method provided in Embodiment 1 of the present invention.

[0093] The related technical solutions are the same as those in Embodiment 1 and will not be elaborated here.

[0094] Embodiment 3,

[0095] A communication system for blind frame synchronization, comprising: a sending end and a receiving end provided in Embodiment 2 of the present invention;

[0096] Among them, the sending end is used to sequentially perform polar code encoding and modulation on information bits and then send them to the receiving end.

[0097] The related technical solutions are the same as those in Embodiment 2 and will not be elaborated here.

[0098] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A communication method for blind frame synchronization, characterized in that, The method includes the following steps: S1. The receiving end receives the data sent by the sending end for demodulation to obtain multiple frames of data encoded by polar codes; Frame synchronization offsets are respectively added to each frame of data to obtain multiple candidate sequences; S2. The multiple obtained candidate sequences are respectively subjected to polar code decoding, and during the decoding process, by comprehensively considering the probabilities that each frozen bit in the candidate sequence is correctly decoded, the probabilities that each candidate sequence is in the correct synchronization position are obtained, and the candidate sequence corresponding to the maximum probability is selected, and its corresponding frame synchronization position and decoding result are returned; Among them, the data sent by the sending end is the data obtained by the sending end after sequentially performing polar code encoding and modulation on the transmission information; A synchronization metric value is used to reflect the probability that a candidate sequence is correctly decoded; the smaller the synchronization metric value of the candidate sequence, the greater the probability that the candidate sequence is in the correct synchronization position; Candidate sequence ω t has a synchronization metric value SM t The calculation formula is as follows: Among them, A C is the index set of the frozen bits of the polar code; LLR t [i] represents the log-likelihood ratio of the i-th bit in the candidate sequence ω t ; N is the number of candidate sequences.

2. The communication method for blind frame synchronization according to claim 1, wherein, The SC decoding algorithm, the Fast-SSC decoding algorithm, the SCAN decoding algorithm or their derivative decodings are used to perform polar code decoding on the candidate sequences.

3. The communication method for blind frame synchronization according to claim 2, characterized in that, When the SC decoding algorithm is used to perform polar code decoding on the candidate sequence, the candidate sequence ω t has a synchronization metric value SM t which is simplified to: the sum of the absolute values of the log-likelihood ratios of all frozen bits for which the decision value is not equal to the decoded value.

4. The communication method for blind frame synchronization according to claim 2, wherein When the Fast-SSC decoding algorithm is used to decode the polar code for the candidate sequence, the candidate sequence ω t has a synchronization metric value SM t which is simplified to: the sum of the synchronization metric values of each special node.

5. The communication method for blind frame synchronization according to claim 4, wherein Synchronization metric value SM of the k-th special node t [k] is calculated as follows: When the k-th special node is a Rate-0 node, SM t [k] is the sum of the absolute values of the log-likelihood ratios of all bit pairs where the decision value and the decoding value are not equal in the k-th special node; When the k-th special node is a Rate-1 node, SM t [k] is 0; When the k-th special node is a REP node, SM t [k] is the sum of the absolute values of the log-likelihood ratios of all bit pairs for which the decision value in the k-th special node is not equal to the decision value of LLR rep ; LLR rep is the sum of the log-likelihood ratios of all bits in the k-th special node; When the k-th special node is an SPC node, if the modulo-2 addition value of the magnitudes of the log-likelihood ratios of all bits in the k-th special node is equal to 0, then SM t [k] is 0; otherwise, SM t [k] is the minimum value of the absolute values of the log-likelihood ratios of all bits in the k-th special node.

6. The communication method for blind frame synchronization according to claim 2, wherein, When using the SCAN decoding algorithm to decode the polar code for the candidate sequence, the candidate sequence ω t has a synchronization metric value SM t which is: the sum of the absolute values of the log-likelihood ratios of all frozen bit pairs where the left information decision value at the decision layer after completing the maximum number of SCAN decoding iterations is not equal to the decoding value.

7. The communication method for blind frame synchronization according to any one of claims 1-6, characterized in that, Every 2N-length demodulated data corresponds to one frame of N-length data encoded by polar codes; the first N positions of the 2N-length demodulated data are respectively intercepted as the frame start positions to obtain N data sequences of length N as the candidate sequences of one frame of data.

8. A receiving end, characterized in that, A communication method for performing the blind frame synchronization according to any one of claims 1-7.

9. A communication system for blind frame synchronization, comprising: A sending end and the receiving end according to claim 8.

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