This paper addresses the problem of adjacent channel interference between minimum-shift keying (MSK)-type signals transmitted through Rayleigh fading channels. A receiver, based on the multiple-input, multiple-output antenna diversity concept and the maximum-likelihood criterion, allows the transmission of MSK-type signals with very small channel spacings, greatly improving the bandwidth efficiency of these signals. The concept of antenna diversity is used to greatly reduce the effects of adjacent channel interference for channels with Rayleigh fading. The results show that it is possible to transmit bit-synchronized MSK-type signals with a very small normalized channel spacing (e.g., /spl Delta/fT/sub b/=/spl plusmn/0.4) between channels, under almost any power imbalance between signals, with very small degradation in performance.

This paper addresses the problem of adjacent channel interference between constant-envelope signals, e.g., MSK-type signals. A technique, based on the BLAST concept, is used to greatly reduce the effects of adjacent channel interference (ACI) and co-channel interference (CCI), for channels with Rayleigh fading. The results show that it is possible to transmit these signals with a very small spacing between channels, under almost any power imbalance between signals, with very small degradation in performance! For example, it is shown that for MSK-type signals it is possible to operate at a channel spacing of 0.4/T/sub b/ with very little degradation in detectability performance, due to ACI. All the benefits of antenna diversity are achieved with very little loss due to ACI.