Cochannel interference suppression for constant modulus signals

In this paper we investigate the single antenna interference cancellation (SAIC) for the GSM/EDGE system with the GMSK modulation. If the received signal is a superposition of the desired signal and constant modulus (CM) interference, the semi-blind method proposed by Berangi and Leung in 2001 can be used to suppress interference and thereby improve the receiver performance. However, they assume an ideal channel state information which is not available in practical cellular systems. Furthermore, the CM-SAIC algorithm is rather sensitive for channel estimation error and the suppression gain can be lost due to inaccurate estimation. For instance, the CM-SAIC with least squares (LS) channel estimation provides hardly any gain. Therefore we introduce a novel iterative channel estimation method based on the CM criterion. When combined with the CM-SAIC detector significant performance improvement can be achieved. In the presence of single dominant interfering signal we obtain up to 5 dB gain in TU3 channel.