Multiple tone interference of frequency-hopped noncoherent MFSK signals transmitted over Ricean fading channels

Abstract

This paper investigates the performance degradation resulting from multitone interference of orthogonal, noncoherent frequency-hopped M-ary frequency-shift keyed receivers (FH/MFSK) where the effect of thermal and other wideband noise is not neglected. The multiple, equal power jamming tones are assumed to correspond to some or all of the possible FH M-ary orthogonal signaling tones. Furthermore, the channel is modeled as a Ricean fading channel, a possibility precluded when thermal noise is neglected; and both the signaling tones and the multiple interference tones are assumed to be affected by channel fading. Only band multitone interference is considered, and it is assumed that jammed hop bands contain a single interfering tone at one of the M possible signaling frequencies. When the information signal is not affected by fading but the multiple interference tones are, the effect on the overall performance of the FH/MFSK system is very small when the power of the individual interference tones is greater than or equal to the information signal power. When the information signal power exceeds the power of the individual interference tones, the counterintuitive result of poorer overall system performance when the multiple interfering tones experience fading as compared with when they do not, is obtained. This trend is accentuated as M increases. When the information signal experiences fading, the effect of fading multiple interference tones on overall system performance lessens, and for a Rayleigh faded information signal, fading of the multiple interference tones has no effect on overall system performance regardless of M.