Diversity combining techniques for LDPC coded FFH/BFSK system over Rayleigh fading channel

Diversity combining is the pivotal technique in fast frequency hopping spread spectrum systems for combating partial-band interference and channel fading. A new suboptimal diversity combining technique, called Rayleigh Generalized Maximum-Likelihood Ratio Test (R_GMLRT), is proposed to mitigate the effect of jamming and fading. Based on the characteristic of signal distributing probability for the flat Rayleigh fading channel, the combining is carried out after obtaining the statistic maximum values of signal, interference and noise power. In this combining technique, the interference duty factor is needed, whereas a prior information of signal, interference or noise power is not required, and no channel or power resource is occupied, neither. The computer simulation results show, the anti-interference performance of R_GMLRT outperforms the traditional suboptimal combining techniques in existence. Especially, about 1dB gain is achieved when the interference exists on the whole spectrum band, which means it is quite fit for the flat Rayleigh fading channel with only background warm-noise.