Research On LDPC Code-Aided Synchronization Technique

With the gradual formulation of 5G standards,the research on its key technologies is also in full swing on a global scale.LDPC code as a data channel coding scheme of 5G enhanced mobile broadband scenario is also one of the hot research directions at present.LDPC code has better decoding performance under the condition of low signal-to-noise ratio,which puts forward more strict requirements for receiver synchronization,that is,the system requires to successfully obtain synchronization information under the condition of low signal-to-noise ratio,so it is of great significance and value to study LDPC code-aided synchronization technology.The research contents of this paper are mainly divided into three aspects.In the aspect of LDPC code-aided carrier synchronization: firstly,the LDPC code-aided carrier coarse synchronization algorithm is studied,and the factors affecting the complexity of the algorithm are analyzed and discussed in detail.According to the column weight characteristics of parity check matrix of 5G LDPC code,the MSSO function expression in the algorithm is modified to reduce its complexity.Then based on 5G LDPC coding system,LDPC code-aided carrier phase synchronization algorithm is studied and optimized,For the problem that the phase estimation of the algorithm is not accurate when the LDPC code length is short,a method of joint multi-frame LDPC code-aided carrier phase estimation is proposed to improve the phase estimation accuracy.For the problem that the algorithm complexity is high when the LDPC code length is long,the phase estimation expression is simplified to reduce the complexity of the original algorithm.Finally,in view of the existing LDPC codes-aided carrier synchronization algorithm based on Costas loop in the problem of poor estimation performance when there is residual frequency deviation,this paper proposes a LDPC code-aided carrier frequency synchronization algorithm based on Costas loop,and compared with the existing mainstream of LDPC code-aided carrier frequency synchronization algorithm under different conditions of auxiliary simulation,the simulation results show that the proposed algorithm has a wider scope of synchronization and lower bit error rate.In the aspect of LDPC code-aided frame synchronization: Three LDPC code-aided frame synchronization algorithms are studied.Aiming at the high complexity of the LDPC codeaided frame synchronization algorithm based on the parity check soft information,the line weight feature of parity check matrix of the 5G LDPC code is utilized,and the check node with higher row weight is not iterated during the decoding iteration.The complexity of the existing LDPC code-aided frame synchronization algorithm based on M-value requires multiple decoding iterations and high complexity.The strong autocorrelation of PN sequences is used to optimize it,which makes the algorithm have better synchronization performance under lower decoding iterations.In the aspect of LDPC encoder of 5G standard: In this paper,a 5G LDPC encoder is designed,which uses real dual-port RAM instead of the traditional barrel shift register to realize cyclic shift,and a scheme of four parallel computational check vectors is adopted according to the structural characteristics of parity check matrix of the 5G LDPC code,and the encoder has lower delay,lower complexity and higher throughput.