Abstract:

he rateless codes designed by the methods which aim to maximize the coding rate can usually approach capacity. However a large number of iterations (theoretically infinite) are needed in the process of iterative decoding to achieve the desired bit error rate performance. Based on the asymptotic convergence analysis of extrinsic information transfer charts, an optimization design method for the degree distributions of nonsystematic accumulate rateless codes with a fixed number of decoding iterations is proposed and the mathematical model for optimization is formulated. The degree distributions satisfying the requirements can be obtained by solving the mathematical problem. Simulations show that, compared with the codes designed by the traditional maximizing coding rate method, for a given number of decoding iterations, the proposed design scheme can achieve better error correcting performance. What’s more, the less the number of iterations, the more obvious the advantage is.