Low-complexity and full-diversity parallel interference cancellation for multiuser wireless relaying networks

In this paper, the multiuser interference of wireless relaying networks (WRNs) is considered. Two transmission protocols with an interference cancellation scheme are proposed, namely, the concurrentS − R−D-PICR,D protocol for decode-and-forward WRNs and the concurrentS − R − D-PICD protocol for amplify-and-forward WRNs. Unlike the existing protocols, these protocols allow the concurrent transmission in both phases of the transmission, and hence, higher spectral efficiency is offered while maintaining low decoding complexity. The concurrentS − R − D-PICR,D protocol achieves interference-free diversity without imposing any condition on the node's antenna number. However and similar to most existing protocols, this protocol requires the channel state information (CSI) of the users-relay links at the relay. In contrast, the concurrentS − R − D-PICD protocol achieves a better diversity order, given that the relay's antenna >8, whereas CSI is required only at the destination. Although the diversity's upper bound is not achieved, this protocol uses a simple relay as no CSI or encoding is required at the relay. In addition and unlike the existing protocols, the achievable diversity is determined by both the user's and the destination's antennas, and it is not sacrificed while the number of users is increased. This paper also establishes sufficient conditions for a space-time block code to achieve the mentioned diversity gain of the proposed protocols.