Noncoherent Hybrid DS-SFH Spread-Spectrum Multiple-Access Communications

The performance of noncoherent reception in synchronous and asynchronous hybrid direct-sequence/slow-frequency-hopped spread-spectrum multiple-access communication systems operating through additive white Gaussian noise channels is investigated. Systems with binary and -ary frequency-shift-keying modulation and noncoherent demodulation, as well as systems with differential-phase-shift keying modulation and differentially coherent demodulation, are examined and their probability of error is evaluated for random frequencyhopping patterns and signature sequences. The multiple-access capability of noncoherent hybrid spread spectrum is shown to be superior to that of noncoherent purely frequency-hopped spread spectrum and inferior to that of noncoherent purely directsequence spread spectrum for systems with the same bandwidth expansion. Comparison of hybrid systems with coherent and noncoherent demodulation shows a considerable loss in the performance of the noncoherent systems.