A unified approach to time diversity combining for fast frequency hopped NCMFSK-anti-jam processing

Abstract

Frequency hopping (FH) spread spectrum is used in communications systems to provide protection against jamming. With fast FH, there are L/spl ges/1 hops per data symbol transmitted. In the presence of severe interference, additional protection can be obtained by processing the LM values obtained from the demodulator. This processing is termed diversity combining. Many powerful and robust types of diversity combining have been developed to reduce the effects of a large jamming signal on some of the L hops. In this paper, a survey of combining methods is presented. Simulation performance results are given for severe noise and multitone jamming (SJR=0.0 dB). It is found that bit error rates as high as 0.4 can be reduced to <0.1 for L<10 using any of several diversity combining methods.<>