Turbo Equalization for Single Antenna Cochannel Interference Cancellation in Single Carrier Transmission Systems

In recent years, single antenna interference cancellation (SAIC) has evolved as an attractive method to increase the capacity of single carrier mobile radio networks like GSM/EDGE (enhanced data rates for GSM evolution). Different algorithms have been developed to improve the performance of the GSM system in severely interference limited scenarios exploiting the structure of the real-valued signal constellation adopted in GSM. For general complex-valued modulation, most known procedures are not applicable, as for a single antenna receiver the system gets overloaded and signals are not separable by e.g. linear operations. In this paper, cochannel interference mitigation with a reduced-complexity equalizer for intersymbol interference (ISI) channels in combination with an appropriate prefilter is considered. In order to enable SAIC for complex-valued modulation schemes, joint (multi-user) turbo equalization is applied. Performance is shown for different variants of the proposed basic scheme, where the GSM/EDGE system serves as an application example. One of the proposed variants is fully compatible to the packet radio transmission schemes of the GSM/EDGE standard and outperforms previously proposed SAIC algorithms for 8PSK.