Performance of a ratio-threshold diversity combining scheme in FFH/FSK spread spectrum systems in partial band noise interference

A diversity combining scheme using the Viterbi ratio-threshold technique is discussed. The performance of the ratio-threshold diversity combiner in fast frequency hop spread spectrum systems with M-ary frequency shift keying modulation (FFH/MFSK) in partial band noise interference and background thermal noise is analyzed. Exact bit error probabilities are computed by using an average computation model. The relationship between the system performance and the system parameters, such as the ratio-threshold, the diversity order, and the thermal noise level, is illustrated. The performance of the combining scheme under worst case interference is compared with that of soft linear combining with perfect side information. One merit of this combiner is that its output can be directly fed to a soft-decision forward error correction decoder