IMPACT OF DIVERSITY RECEPTION ON FADING CHANNELS WITH CODED MODULATION .3. COCHANNNEL INTERFERENCE

In previous work, we have studied the impact of diversity on coded dig ital communication systems operating over fading channels, In particul ar, we have shown that diversity may be thought of as a way of making the channel more similar to a Gaussian one, The present paper extends this analysis to fading channels affected by co-channel interference ( CCI), Three receiver models are examined, namely, with coherent detect ion and perfect channel-state information (CSI), with differential, an d with pilot-tone detection, We study the effect of diversity on the i rreducible error floor caused by CCI and fading, and the asymptotic be havior of the channel as the diversity order increases. Our results sh ow that, when perfect CSI is available, diversity is able to turn asym ptotically the channel into a CCI-free additive white Gaussian noise ( AWGN) channel with the same signal-to-noise ratio (SNR), On the other hand, differential and pilot-tone detection do not remove interference in the limit, Nevertheless, also with these detection schemes, divers ity achieves significant gains when the SNR is large enough, Calculati on of the channel cutoff rate provides guidelines for the design of co ded systems with CCI in fading environments, A wide range of examples, validated by computer simulation, illustrates our conclusions.