Power-Efficient Opportunistic Amplify-and-Forward Single-Relay Aided Multi-User SC-FDMA Uplink

In this contribution we exploit the benefits of combining the diversity gains arising from cooperation, multiple propagation paths and from the opportunistic scheduling of multiple users, for the sake of supporting a power-efficient single-relay assisted single-carrier frequency-division multiple-access uplink, where each relay supports a single user communicating over dispersive channels subject to large-scale fading. Based on the proposed joint frequency-domain equalisation and diversity combining aided receiver relying on the minimum mean-square error criterion, two different relay selection schemes designed for single-user and multi-user scenarios are investigated, which employ imperfect power control. Our results show that at a bit error ratio of 10^-4, the proposed receiver is capable of saving 2 dB power by achieving a higher cooperative diversity gain than the conventional receiver. Moreover, an approximately 6.8 dB and 8 dB transmit power reduction are attainable by invoking the proposed selective diversity oriented single-user and multi-user relay selection schemes, respectively. Most importantly, a power-efficiency improvement is gleaned from our multi-user relay selection scheme, which avoids the effects of deep shadowing and provides 9.7dB power reduction compared to the non-cooperation scenario.