Diversity-Combining and Error-Correction Coding for FFH/MFSK Systems over Rayleigh Fading Channels under Multitone Jamming

The combined application of diversity and error-correction coding for combating multitone jamming (MTJ) in fast frequency-hopping/M-ary frequency-shift-keying (FFH/MFSK) systems over Rayleigh fading channels is investigated. A log-likelihood-combining metric which requires only easy-to-obtain system parameters for its computation is proposed. In addition, four soft-decision coding schemes which employ the proposed diversity-combining metric as decoding metric are considered. An upper bound on the bit error rate of the proposed metric is derived. Simulation results show that the proposed metric outperforms robust metrics. Moreover, the improvement is most substantial for low signal-to-jamming ratio (SJR). Performances of convolutional codes and turbo codes together with either bit-interleaving or symbol-interleaving are examined. Upper bounds are derived for the bit error rates of the convolutional coding schemes, and simulations are performed for all coding schemes. The results show that significant performance improvement can be achieved in difficult transmission conditions by changing the interleaving method from bit-interleaving to symbol-interleaving, but without changing the code. In particular, the symbol-interleaved turbo coding scheme is the best among the four for maintaining system performance at an acceptable level for most situations.