Performance analysis of a ratio-threshold diversity combining scheme in FFH/FSK spread spectrum systems under multitone jamming

A nonlinear diversity combining scheme using the Viterbi radio-threshold technique is discussed. The performances of the radio-threshold diversity combiner in fast frequency-hop spread-spectrum systems with M-ary frequency shift keying modulation (FFH/MFSK) under band multitone jamming without and with additive white Gaussian noise are analyzed. The exact bit error probabilities are computed by using an average computation model. The performances under band multitone jamming and under partial-band noise jamming are compared. For binary FSK modulation, the performances under the two types of jamming are almost the same, but for 8-ary FSK modulation, tone jamming is more effective against communications. The structure of the combiner is very simple. Another merit of this combiner is that its output can be directly fed to a soft-decision FEC decoder