Improved signal detection for two-way wireless relaying networks under imperfect time synchronisation

Abstract

Most research on two-way wireless relaying networks (TWRNs) assumes perfect time synchronisation between the terminals and among the relays. This is, however, difficult to accomplish as the terminals and relays are randomly located. The lack of synchronisation causes inter-symbol interference which introduces a serious impairment and negatively impacts the network's performance. In this article, an enhanced interference cancellation (EIC)-based detector is proposed to mitigate the experienced performance degradation while maintaining low complexity. It uses an innovative iterative approach and also benefits of interference components of currently detected symbols using a modified maximum likelihood (ML) scheme. As a result, it shows significant performance improvement compared to the conventional detector under different conditions of imperfect synchronisation. In addition, two existing interference cancellation detectors that are originally proposed for one-way WRNs are extended to TWRNs, even though the timing error among the terminals is a unique issue for TWRNs and never occurs in one-way networks. Unlike the existing literature, the proposed detectors apply to networks with an arbitrary number of multiple-antenna relays. Numerical simulation is provided in terms of bit error rate, to show the improvement in performance when compared to the conventional detector. Moreover, it is shown that the EIC detector outperforms the extended detectors and provides 3 to 4 dB gain under moderate condition of imperfect synchronisation.