Signal design for co-channel interference suppression with applications to wireless communications
Co-channel interference is a major impairment in wireless systems with channel (frequency and/or time) re-use. In practice the performance of Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) systems is limited by a few dominant co-channel interferers. These can be removed by means of multiple antennas but it is difficult to demand this at the mobile because of technology limitations. The standard solution is to treat co-channel interference as Gaussian noise and to employ powerful channel codes. However, this solution is far from optimal since the decoder is using an inappropriate metric for decoding. In this paper it is shown that a more effective use of system redundancy is to design channel codes that are matched to an adaptive linear receiver, so that the combination provides interference suppression. It is shown that a simple one symbol parity check code is capable of suppressing one interferer, a repetition code of length N is capable of suppressing N - 1 interferers, and a code of K information symbols and N channel symbols is capable of suppressing N/K interferers.