On the detection of a class of fast frequency-hopped multipleaccess signals

摘要

The capacity of a fast frequency-hopped multiple access (FHMA)nsystem is dictated by two major related design concerns: the hoppingnpattern and the receiver structure. This paper studies the impact ofnthese two factors. We present a maximum likelihood (ML) diversityncombiner for detecting asynchronous FHMA multilevel PSK (MPSK) signalsnin Rician fading channels and analyze the performance of a closenapproximation of the ML receiver. We compare systems using randomnhopping patterns and those using optimal hopping patterns of Einarssonn(1980). Performance comparisons between chip-synchronous andnchip-asynchronous systems are made as well. We propose and examine theneffectiveness of a two-stage multiuser detector, in which the firstnstage makes an initial decision while the second stage tries to reducenmultiple access interference (MAI) and resolve the ambiguity left by thenfirst stage detector. The MAI caused by undesired users is constitutednby a cochannel interference (CCI) contribution and an interchannelninterference (ICI) contribution. This detector is of modest complexitynand is capable of removing most of the CCI and part of the ICI. Twonmethods for mitigating MAI are also examined