Co-channel and adjacent-channel interferences are major capacity-limiting impairments in cellular mobile and portable radio systems. For TDMA and FDMA systems interference considerations influence spectral efficiency by limiting frequency reuse; for spread spectrum (CDMA) systems, interference determines the code rate and bandwdith spreading factor that must be used. Thus receiver techniques which reduce the effect of interference are of great value in increasing the capacity or spectral efficiency of a cellular system as well as improving its bit error rate performance.
In this talk we give an overview of interference mitigation techniques which are relevant to digital mobile and portable radio systems. These techniques include optimum space diversity combining, adaptive equalization, and decision techniques exploiting knowledge the receiver may have on the interfers' signature waveforms in the case of CDMA. In many situations of interest, interference exhibits properties such as cyclostationarity, which strongly distinguish it from normal background noise, and which can be exploited to yield substantial gains in performance and/or capacity. We present recent results from our research on equalizers' effectiveness in suppressing cyclostationary co-channel and adjacent-channel interference in narrowband digital radio systems.