Research On Improved SCANL Decoding Algorithm Of Polar Code And Its Application

In the face of the demand for massive connection scenarios for 5G communication,how to improve the reliability and spectrum utilization rate of communication is very important.On the one hand,channel coding technology is an important means to improve communication reliability.The performance of the polar code is related to the compilation code algorithm,and the excellent decoding algorithm can significantly improve the performance of the polar code.On the other hand,the SCMA system can enable multiple users to share the same spectrum resources,thereby increasing the spectrum utilization rate,but its communication reliability is not enough to meet scene needs.On the other hand,applying the polar code to the SCMA system can effectively meet the requirements of communication reliability and spectrum utilization rate,and the high efficiency receiver design in the polar code SCMA system is particularly important.This thesis mainly conducts in depth research on traditional SCANL decoding algorithm,and is committed to improving the computational complexity of the SCANL algorithm.Then apply the improved algorithm to the polar code SCMA system,and design the corresponding receiver model.The contributions of this thesis are summarized as follows:1.In order to improve the computational complexity of the SCANL decoding algorithm,this thesis first proposes a SSCANL decoding algorithm based on the approximate node deletion technique.By simplifying the calculation process related to the soft information returned by the frozen bit nodes,the algorithm approximately deletes the frozen bit nodes in the factor graph,thereby reducing the computational complexity of the decoding algorithm.Secondly,in order to further improve the computational complexity of the proposed algorithm,this thesis extends the proposed SSCANL decoding algorithm to SC-Fast-SSCANL decoding algorithm.The extended algorithm identifies various special nodes in the process of traversing the SCAN decoding factor graph each time,and designs corresponding low-complexity decoding methods,combined with syndrome check to decode ordinary nodes,the traversal depth of the factor graph is reduced and the computational complexity is reduced.Finally,according to the simulation results,the proposed SSCANL and SC-Fast-SSCANL decoding algorithms can both obtain decoding performance similar to the SCANL algorithm,but the two proposed algorithms have lower computational complexity,SC-Fast-SSCANL algorithm has the best effect of reducing computational complexity.Compared with the SCANL algorithm,the SC-Fast-SSCANL algorithm can reduce the number of addition operations by at least 83.1%and the number of multiplication operations by 86.5%.2.In order to improve the decoding performance of traditional joint iterative detection and decoding receivers,a C-JIDD-SSCANL receiver is proposed in this thesis.The receiver uses the superior performance of the SSCANL decoding algorithm to improve its own decoding performance.Secondly,in order to further improve the computational complexity of the proposed receiver,this thesis applies the SC-Fast-SSCANL decoding algorithm with lower computational complexity to the polar code decoder of the receiver,the C-JIDD receiver based on SC-Fast-SSCANL decoder is proposed.Finally,according to the simulation results,Under the condition of BER=10^-4,C-JIDD-SSCANL receiver can obtain performance gains of 0.65d B and 0.59d B compared with traditional JIDD-SCAN and C-JIDD-SCAN receivers.The decoding performance of the C-JIDD receiver based on the SC-Fast-SSCANL decoder is similar to that of the C-JIDD-SSCANL receiver,but it has lower computational complexity.