Turbo codes with channel estimation and dynamic power allocation for anti-jam FH/SSMA

In this paper we study the performance of turbo codes in frequency-hopped spread spectrum multiple access networks (FH/SSMA). An iterative scheme for estimating the log likelihood ratio of the channel output is proposed. This scheme is compared with other techniques that provide tradeoffs between simplicity of implementation, BER performance, and robustness to channel variations. Based on the estimates of the jamming powers in the frequency dwells, a scheme for dynamically allocating the available power among the different dwells is developed. It is shown that the proposed dynamic power allocation technique improves the ability of FH/SSMA to combat slowly varying partial band jamming.