Performance comparison of MFSK frequency-hopped multiple access systems with RTT decision over a Rayleigh fading channel

The effectiveness of erasure side information generated by Viterbi's ratio threshold test (RTT) decision for frequency-hopped multiple access (FHMA) systems with M-ary frequency shift keying (MFSK) is studied. The performances for M up to 16 are presented. The signaling for M=4 is revealed to be the best choice under any circumstances over the Rayleigh fading channel. Compared with binary frequency shift keying (BFSK), the signaling for M=4 can offer 30% and 45% performance gains in achievable maximum capacity for the synchronous and asynchronous hopping systems with hard decision in the receiver, respectively. With RTT decision, the performance of BFSK systems is improved significantly and the performance gap between the signaling for M=4 and M=2 can be reduced to 25% in asynchronous hopping systems. The effect of modulation bandwidth expansion, the variation of signal-to-noise ratio in modulation symbol, and different nature in hit period for both hopping types are discussed.