General Decoder Architecture Design For Multimode Terminals

5G mobile communication system adopts LDPC codes and polar codes as the error correction coding schemes for data channels and control chan-nels in enhanced mobile broadband scenario,while 3G and 4G adopt turbo codes as the main channel coding schemes.For multimode mobile terminal baseband processing Devices,it is necessary to support the above three code patterns at the same time.The mainstream decoding algorithms of these three types of codes are different,and the use of independent hard cores will greatly increases the chip cost and power consumption.Therefore,this pa-per studies the general decoder architecture from the perspective of top-level algorithms for turbo codes,LDPC codes,and polar codes in 4G and 5G.In this paper,Turbo codes and polar codes are firstly represented by sparse bipartite graphs,which are regarded as LDPC-like codes,and both are decoded by using the LDPC BP algorithm.Aiming at the problem of the performance degradation of polar codes when decoding by LDPC-like BP algorithms,an LDPC-like BPL algorithm is proposed.Compared with traditional BP and SC decoding algorithms,it has better error performance,lower decoding latency and computational complexity.Based on the above research,a general decoder architecture based on sparse bipartite graphs is given.LDPC codes use layered BP decoding,Turbo codes use BP decod-ing,and polar codes use LDPC-like BPL decoding.The proposed decoder achieves a trade-off between error performance,decoding latency and com-putational complexity.Due to the differences in the structure of the three types of codes,the aforementioned general decoder architecture does not consider the impact of short cycles on the BP decoding performance of the turbo code and polar code.This paper further studies the general decoder architecture based on cyclic graphs.Based on the statistics and analysis of the numbers of 4 cylces,6 cylces,and 8 cylces in the polar code and Turbo code bipartite graphs,it is found that the bipartite graphs of the polar codes do not contain 4 cylces,and there are a large number of 4 cylces in the turbo bipartite graphs.Therefore,the performance of the turbo code deteriorates severely under the aforemen-tioned general decoder architecture.By analyzing the distribution of the 4cylces in the bipartite graphs of the LTE turbo code,a method based on the extended check matrix to eliminate the 4 cylces is given without destroying the original architecture.Based on the proposed architecture,compared with the BP algorithm,it gains 0.3d B at a block error rate of 10^-3,and has lower delay and computational complexity for LTE turbo codes.