Cochannel Interference Cancellation using Optimized Joint Equalization

Abstract — In this paper, single–carrier transmission impaired by cochannel interference is considered, which generally arises in a GSM / EDGE mobile radio network. Here, cochannel interference is created due to the reuse of the frequencies in nearby cells. In the case, that only a single antenna is available at the mobile receiver, the (multiple–input single–output) system is overloaded and equalization with low complexity is difficult. The optimum joint maximum–likelihood sequence estimation (JMLSE) algorithm would require a huge number of channel states to be considered in a corresponding Viterbi algorithm. The usage of a channel shortening filter in combination with a joint M–algorithm for detection was proposed in [1] in order to obtain good performance results at low complexity for single– antenna interference cancellation (SAIC) in the low–to–moderate carrier–to–interference power ratio (CIR) range, but unfortunately the M–algorithm has shown worse performance than joint delayed–decision feedback sequence estimation (JDDFSE) or joint reduced–state sequence estimation (JRSSE) for high CIRs. To solve this problem, we consider a combined scheme of JRSSE and the M–algorithm for joint detection of the desired user signal and one or more interferers, which corresponds to a special application of breadth–first sequence detection [2]. For the considered algorithm, each trellis state ν is equipped with a list of M (best) paths to be stored and processed forward. I