An adaptive combiner for co-channel interference reduction in multi-user indoor radio systems

An efficient technique for co-channel interference suppression in multi-user indoor radio communication systems is presented. The proposed approach makes use of an antenna array in conjunction with an adaptive combiner that employs a training sequence to adjust the receiver to the desired co-user. A different training sequence known to the receiver is transmitted periodically with the information sequence of each co-user. Signals received at the diversity antennas are weighted and summed to produce a combined signal. The weight coefficients are adjusted such that the reception of the desired signal is enhanced and all interfering signals are attenuated. A complex least-mean-square algorithm based on the method of steepest descent is used for weight adjustment. Computer simulations are presented for a two-antenna system with coherent QPSK (quadrature phase-shift keying) signaling over frequency-nonselective Rayleigh fading channels, and in the presence of a single interferer