Joint frequency offset and delay profile estimation technique for nonlinear co-channel interference canceller

Co-channel interference is a major factor limiting spectral efficiency of cellular radio systems. A nonlinear co-channel interference canceller leading to a significant increase of traffic capacity of cellular systems has been investigated. In this scheme, a maximum-likelihood sequence estimation extended to cancel co-channel interference is combined with trellis-coded modulation to enhance the co-channel interference cancelling capability. However, the bit-error rate performance of this canceller is degraded if there exists a frequency offset between the desired signal and the interference signal. In this paper, a joint frequency offset and delay profile estimation technique for a nonlinear co-channel interference canceller is proposed. In this algorithm, frequency offset is simultaneously estimated during delay profile estimation using the residual error of delay profile estimation. Computer simulations have been performed to demonstrate the performance of the proposed algorithm. It is shown that the allowable frequency offset range of the proposed canceller is over 10 times as large as that of the conventional canceller without frequency offset compensator