A Cooperative Relaying Scheme without the Need for Modulation with Increased Spectral Efficiency

Future infrastructure based wireless systems are likely to use relaying due to energy savings, simpler roll-out of cellular networks, simpler increase of coverage and so forth. To increase the performance of relaying based systems cooperative relaying has emerged as an additional option to exploit spatial diversity. In order to allow for a fair comparison between single- hop and multi-hop schemes, an N-fold more spectrally efficient use of each link needs to be assumed for the multi-hop case. We propose a novel protocol relying on two relaying nodes which does not require the need for an increase in spectral efficiency in comparison to direct transmission. However, we achieve a better performance in the low SNR/high rate regime at the expense of a worse performance in the high SNR/low rate regime. The proposal is compared to direct transmission, conventional relaying, transmit diversity and a distinct cooperative relaying scheme considering their outage probability.