Co-channel interference suppression for TDMA mobile radio systems

A technique is described that enables a signal to be detected in the presence of high levels of like-modulated co-channel interference. In land mobile radio systems the extent to which a receiver can tolerate co-channel interference is one factor limiting the traffic carrying capacity of a network. Consequently any technique that enables the receiver to operate at lower signal to interference ratios can potentially provide a capacity improvement by allowing a greater re-use of the available frequencies. The technique described is particularly applicable to systems employing burst mode transmission and coherent detection. Examples of such systems include the European standard GSM and the North-American standard IS-54. Little attention has been given to the problem of detecting a signal in the presence of like-modulated interference, considering that in mobile radio systems co-channel interference is often the limiting factor rather than thermal or other noise sources. Receivers in mobile radio systems are often optimal or near optimal for the detection of a signal in the presence of Gaussian noise. In the paper a receiver structure is described that is optimal for the joint detection of both wanted and interfering signals in the presence of Gaussian noise. The performance of the technique has been demonstrated by Monte Carlo simulation when both wanted and interfering signals are subject to Rayleigh fading, and a selection of these results are presented