Single Antenna Cochannel Interference Cancellation in Single Carrier Transmission Systems by Improved Prefiltering and Turbo Equalization

In this paper, a joint (multiuser) turbo equalizer performing single antenna interference cancellation (SAIC) for complex-valued modulation schemes is proposed. In order to improve the performance of a reduced-complexity equalizer for intersymbol interference (ISI) channels in different interference situations (overloaded system), an appropriate prefiltering approach is considered first. Oversampling is utilized for prefiltering in order to exploit excess bandwidth of the transmit signals. Additionally, the (inner) equalizer performance is optimized at low complexity by using an M-algorithm for generation of a survivor map on which a reduced-complexity BCJR algorithm for soft output detection is based. Performance is shown for different receiver variants, where the GSM/ EDGE system serves as an application example. It turns out that the proposed algorithm outperforms previously proposed SAIC algorithms for 8PSK, while being fully compatible to the packet data radio transmission schemes of the GSM/ EDGE standard for synchronous networks.