Research On Improvement Of Polar Code Encoding And Decoding Scheme In SCAM Scene

With the continuous development of various technologies of wireless communication and mobile communication,the application scenarios of mobile communication are becoming more and more abundant,and more and more application scenarios have in turn spawned more and better wireless communication technologies.The enhanced mobile broadband communication(eMBB)scenario is the core application scenario for improving the user experience.It requires lower bit error rate performance,higher throughput,and higher high-speed mobile communication capabilities.Channel coding originated from Shannon channel capacity theory and Hamming coding,followed by BCH code,RS code,LDPC code,Turbo code and other excellent coding methods.The polarization code is based on E.Arikan's research on channel polarization.An encoding method that is currently the only encoding method that has been shown to achieve channel capacity when transmitted over a binary discrete memoryless channel.The SCMA divides the frequency domain resources into multiple subcarriers and assigns them to each user according to the mapping relationship of the codebook.The user detector performs belief propagation in the factor graph through the channel estimation value,the noise estimation value,and the codebook information,thereby detecting each user's Code word information.This thesis first introduces the basic theory of polarization code and SCMA,studies the coding principle of polarization code,the decoding structure of various decoding methods,and compares the performance,output mode and complexity characteristics of various decoding methods.The principle of SCMA codebook mapping is introduced.The detection principle and message passing algorithm of SCMA user detector are studied.In the decoding mode,the SCAN decoding algorithm with soft information output mode and small decoding delay is studied,and a simplified SCAN(SSCAN)decoding algorithm is proposed.Two ways to reduce the decoding complexity are respectively It is a simplified left information update method and a pruning decoding algorithm,which reduces the calculation amount when a part of nodes are updated,and reduces the computational complexity and storage complexity of the SCAN algorithm.In this thesis,a new joint detection and decoding algorithm is proposed.The receiver adopts the loop iterative structure.The polarization code decoder uses the soft information output SSCAN decoding algorithm,and the user detects the MPA factor graph in the joint receiver.The SSCAN factor graph is combined,so that the internal information transmitted in the MPA factor graph and the factor graph information of the SSCAN algorithm are directly converted and iterated in the joint factor graph after being converted.Then the detection characteristics of the MPA receiver are studied,and the damping coefficient is proposed.The effects of different damping modes and different damping coefficient settings on the system performance are simulated and the optimal damping mode and optimal damping value are selected.Finally,the BER performance of the joint detection and decoding algorithm proposed in this paper and the original joint detection and decoding algorithm are analyzed.The proposed joint detection and decoding and the existing joint detection and decoding method based on feedback hard decision are compared.Performance differences.