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The capacity of a multilevel FSh' (MFSK), frequency-hopped multiple access (FHMA) system is dictated b y two major design concerns: the hopping pattern and the receiver structure. This paper studies the i:mpacts of both factors. W e present a maximum likelihood (ML) diversity combiner for asynchronous FHMA systems in Rayleigh fading and compare systems using random hopping patterns and those that use a set of optimal hopping patterns. On the other hand, a multiuser detector for an FHMA/MFSK system usually consists of two stages. The first stage makes an initial decision while the second stage tries to resolve the ambiguity and reduce the cochannel interference (CCI) left b y the first stage detector. After analyze the performance of the first stage detector thlat uses appropriate diversity combining, we then examine the effectiveness of a second stage detector which is a modification of an earlier structure developed b y Timor. This receiver is of modest complexity and is capable of removing most of the CCI. Moreover, we also find that it is insensitive t o power variations of the system users.

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