The Research Of Log-BP Simplified Iterative Decoding Algorithm

Compared to Turbo codes, Low-density parity check codes has its own unique advantages. It has been got a lot of attention and research, and will apply to more and more communication systems.Among all decoding algorithms for LDPC codes, the performance of Log-BP algorithm is the best. But in the process of check node update, Log-BP algorithm needs to calculate the hyperbolic tangent function and inverse hyperbolic tangent function. Calculating these two functions greatly increases the complexity of the algorithm. The SSP(Simplified Sum-Product algorithm) algorithm is used to reduce the complexity of the hyperbolic tangent function and inverse hyperbolic tangent function by the method of piecewise functions. In this paper, the SSP algorithm is simulated.Due to the high complexity of the hyperbolic functions, this paper proposes the equal chord length simplified Log-BP algorithm. Since the linear approximation error affect the number of lines. This paper chooses the approximation error which is 0.02 and 0.095, and in order to compare the performance of our method with SSP algorithm, we select the minimum number of line is nine, the corresponding error is 0.095.In addition, this paper also proposes the equal distance simplified Log-BP algorithm. Since the linear approximation error affect the number of lines. This paper choices the approximation error which is 0.022 and 0.195, and in order to compare the performance of our method with SSP algorithm, therefore we select the minimum number of line is nine, the corresponding error is 0.195. In addition, in order to compare the performance of the equal chord length simplified algorithm, therefore select the same number of line, the corresponding error is 0.022.In this paper, the Log-BP algorithm, SSP algorithm, the equal chord length simplified algorithm, and the equal distance simplified algorithm are simulated. As can be seen from the results of the simulation, the performance of SSP algorithm, the equal chord length simplified algorithm and the equal distance simplified algorithm is worse than the Log-BP algorithm. Overall the performance of the equal chord length simplified algorithm and the equal distance simplified algorithm is better than SSP algorithm whenthe number of lines is the same. Overall the equal distance simplified algorithm is better than the equal chord length simplified algorithm. Although the performance of simplified algorithms are worse than Log-BP algorithm, but the computational complexity of the two simplified algorithms is greatly reduced.