Research On Turbo Codec Used In Mobile Communication

With the rapid development of mobile communication technology,people have higher and higher requirements for the reliability of information transmission.As an effective means to reduce information transmission errors,channel coding is a very important part of the mobile communication system.Turbo codec is one of the channel codes.Because of its excellent performance,it has been widely used in the communications industry since its introduction.This article mainly studies the Turbo codes used in the current mainstream mobile communication technologies,starting from the aspects of encoding and decoding,and improving the performance of Turbo codes.The coding mode determines the performance limit of the codec,and the performance limit of the Turbo code depends on the component code and the interleaver.The consensus bounds and weight spectrum analysis show that the main parameters affecting the performance of Turbo codes by component codes and interleavers provide a theoretical basis for the selection of component codes and the design of interleaver,a nd derive the optimal component codes.At the same time,this paper is inspired by common interleaver design methods to simplify S-pseudo-random interleaving.Turbo decoder directly determines the final output of the codec,and the decoding module directly affects the result.Therefore,the decoding module is the main research content of this article.The decoding algorithms of Turbo codes are mainly divided into MAP algorithm and SOVA algorithm.The MAP algorithm is a suboptimal algorithm based on the maximum posterior probability.The simplified log-MAP obtained by it and the main simplified algorithms have very good decoding results.it is good.However,the SOVA algorithm is simpler to calculate and saves computations in the same situation,but it is less effective than the MAP algorithm.The biggest feature of Turbo code decoding is that it performs multiple iterations on the decoding result.In the iterative process,the iterative information distribution is closely related to the decoding result,and it can be judged that the iteration stops.This paper simulates different scenarios and analyzes the simulation results,and proposes some feasible decoding schemes:(1)To solve the problem of too many iterations of the Linear-log-MAP algorithm,use a new quadratic linear fitting to improve its performance;(2)For SOVA external information distribution problems,perform optimization operations such as amplitude limiting,formula mapping,and adaptive amplitude change;(3)According to the channel estimation results,the concepts discussed for different SNR classifications apply to the design of iterative stopping criterion,adding CRC check and convergence judgment at the same time;(4)simplify the LLR with reference to the simplified scheme of log-MAP,which can reduce the errors introduced by the LLR;Among them,several improvements have been made to the SOVA algorithm and iterative stopping criterion,and simulations have been performed for all feasible solutions.Through the simulation and analysis of these solutions,this paper has designed a codec system suitable for mobile communication systems.