Study On LDPC Decoding Algorithms For 5G Communications

As the demand for communication in human society increasing,the current communication system can no longer satisfy the requirements,and thus the fifth generation communication system(5G)is being developed.In the different future application scenarios,the 5G system will adopt the different coded modulation schemes to meet the technical requirements under various scenarios.Based on the above research background,this dissertation research decoding algorithms for low-density parity-check(LDPC)codes with short decoding delay and excellent decoding performance under the ultra reliable and low latency communications(u RLLC)scenario.The main contents and contributions of the dissertation are summarized as follows:For 5G u RLLC scenario,this dissertation first introduces the two-stage Decoding algorithm that is the belief propagation(BP)algorithm cascading list erasure decoding(LED)algorithm,namely BP-LED algorithm.Based on the BP-LED algorithm,this thesis propose an improved BP-LED algorithm to overcome the performance loss problem caused by the LLR oscillation phenomenon during iterative decoding,by considering the accumulated value of log-likelihood ratio(LLR)as reliable measures of the received bits of LED algorithm.The algorithm for short LDPC codes has better decoding performance and approximate maximum likelihood(ML)decoding performance,and is suitable for 5G uRLLC scenario.For the burst short packet services of 5G uRLLC scenario,we extend the binary BP-LED algorithm to short non-binary LDPC(NB-LDPC)codes and propose a decoding algorithm for NB-LDPC codes with near-ML performance,called non-binary BP-LED algorithm.Compared with binary LDPC codes,NB-LDPC codes have better burst-error-correcting capability.And the burst-error-correcting capability of NB-LDPC codes is better exhibited when we combine the binary LED algorithm with the non-binary BP algorithm.Moreover,the decoding complexity of this algorithm is almost the same as that of the first stage algorithm,and the decoding complexity caused by the second stage algorithm is negligible in hign SNRs.Similar to the binary BP-LED algorithm,the non-binary BP-LED algorithm is also suitable for 5G u RLLC scenario.For the continuous large packet services of 5G u RLLC scenario,we apply the non-binary BP-LED algorithm to non-binary Spatial Coupling LDPC(SC-LDPC)codes and propose a windowed decoding(WD)algorithm for non-binary SC-LDPC codes.Compared with the flooding schedule decoding(FSD)algorithm,the WD algorithm has low decoding complexity and short decoding time,but its decoding performance is not as good.In this dissertation,we apply the non-binary BP-LED algorithm to windowed decoding strategy of non-binary SC-LDPC codes and take advantage of the excellent decoding performance of the non-binary BP-LED algorithm to make up for the performance loss of the windowed decoding strategy.We also propose a WD algorithm with short decoding time and good decoding performance.The algorithm can achieve short decoding time,low decoding complexity and good decoding performance by selecting the appropriate window size,which is suitable for the continuous large data transmission of 5G u RLLC scenario.