The Research On The Improved LDPC Decoding Algorithm And Its Combination With OFDM System

The development of the mobile Internet brings a lot of convenience to us. The number of the mobile data network user is growing rapidly, and the wireless communication business is also becoming diverse and develops toward big date direction. In order to meet the growing demand of the wireless data communication for the users in various regions, the research on the channel coding and decoding is becoming more and more significant.With the growing maturity of the iterative decoding technology, the Low-Density-Parity-Check Code becomes a research hotspot in the channel code field despite the high computational complexity and difficulty in realizing. This paper mainly studies the equalization of the complexity and decoding performance in the LDPC decoding process, and finally proposes the improved algorithm and strategy aiming at reducing computational complexity based on the supplementary verification of the system, which effectively combines the LDPC and OFDM technology.This paper firstly introduces the research background and present situation of the LDPC, and then proposes the improved algorithm based on the research of several conventional decoding algorithms. The LDPC decoding algorithm is featured as high computational complexity. In order to reduce the computational complexity, this paper firstly studies the Normalized and Offset algorithm, then estimates the parameters including α、β、λ existed in the iterative calculation, finally proposes Hybrid algorithm which is verified as low complexity of implementation and good decoding performance.This paper then proposes improved scheme through the analysis of the LDPC random decoding principle, and converts probability information into the randomly and uniformly distributed bit stream, sets maximum number of iterations (DC), and calculates iteratively. It finally comes to conclusion that the check bit presents a reduction trend and obtains the stability after a certain cycle at a certain time, at which the decoding result will not change again, and the rest will be meaningless. Therefore, in order to reduce the unnecessary operation, this paper proposes the adaptive stopping criterion which can effectively reduces the computational complexity. The simulation results reveal that the advance stopping criterion can drastically reduces decoding computation in the case of tiny decoding performance loss compared with the traditional method.In the end, this paper analyzes the principle and key technology on the OFDM, and compares the improved LDPC decoding algorithm and OFDM technology in different channel environments, which reveals the feasibility of the combination of the LDPC and OFDM, and also in Rayleigh channel, the communication system applied both LDPC and OFDM can obtain good performance.