High Spectral Efficiency of Multiple-Relays Assisted Amplify-And-Forward Cooperative Transmissions Under Spatial Reuse

This work explores ways to boost the spectral efficiency of transmission schemes based on amplify-and-forward (AF) cooperation. While AF has usually been considered to suffer from bandwidth expansion due to the increased use of transmission resources, in a multiuser environment it is possible to overcome this limitation by either spatially reusing the transmissions from different relay terminals, or by using multiple relays. These two possibilities are not mutually exclusive and are studied below in the context of TDMA transmissions for the downlink. It is shown that under mild assumptions the interference generated during the relay transmission phases can be statistically modeled. The outage events generated by this interference are mitigated by an adaptive transmission rate scheme that maximizes the system throughput. This low complex implementation of multiuser AF provides significant throughput gains over a conventional TDMA non-cooperative scenario.