The effect of Rician fading and partial-band interference on noise-normalized, fast frequency-hopped MFSK receivers

The performance of an M-ary orthogonal frequency-shift keying (MFSK) communication system using fast frequency-hopped spread spectrum waveforms transmitted over a frequency-nonselective, slowly fading channel with partial-band interference is analyzed. A procedure referred to as noise-normalization combining is used by the system receiver to minimize partial-band interference effects. Each hop is assumed to fade independently. The partial-band interference is modeled as a Gaussian process. Both the signal and the partial-band interference are assumed to be affected by the fading channel which is modeled as Rician. The effect of fading of the partial-band interference on worst-case receiver performance is relatively minor. When there is no signal fading or when the signal facing is Rician, the counter-intuitive result of poorer receiver performance when the partial-band interference experiences fading is obtained. This effect is most pronounced when the signal does not fade and the partial-band interference experiences Rayleigh fading