Simulation And Optimization Of Channel Coding Based On DMR System

With the further promotion of information construction, digital trunking communication system as a new generation of mobile communication system is developing rapidly in the world. Because digital trunking communication system has higher bandwidth efficiency, better command and scheduling functions, more diverse types of business and higher reliability, it will gradually replace analog trunking communication system on the market.This paper summarizes the characteristics and development status of digital trunking communication system, and communication protocol of DMR in physical layer, data link layer and call control layer are described and introduced. This paper mainly introduces forward error correction code, cyclic redundancy check code and interleaving technology. The key point of this paper is focusing on BPTC code and variable length BPTC code in DMR communication protocol.This paper proposes the soft-decision iterative decoding scheme based on the graph model, and Sum-product algorithm as the component decoder is applied to BPTC code. Belief propagation of Sum-product algorithm makes the received codes iterate until convergence in two components, so that it improves the performance of the decoder greatly. This paper also analyzes the syndrome decoding and soft-input hard-output decoding, and it compares three different decoding schemes. The soft-decision iterative decoding scheme has better coding gain in comparison of the conventional BPTC decoding. In addition, BER graphs of three decoding schemes based on Matlab are given. Compared with the syndrome decoding, simulation results show that SISO iterative decoding scheme using the sum-product algorithm decoding scheme has significant coding gain, but the process of computing is complicated. Soft-input hard-output decoding scheme takes both coding gain and computational complexity into account, and it is a better choice in the practical application. In this paper, the influence of the number of iterations on the iterative decoding schemes is researched, and the results provide a theoretical basis for practical application.