Optimal resource allocation for orthogonal frequency division multiplexing-based multi-destination relay systems

The authors propose an optimal resource allocation (RA) scheme for wireless multi-destination relay systems with orthogonal frequency division multiplexing (OFDM) modulation. The authors work is different in that they consider a practical downlink OFDM-based relay network, where a relay is used to help the source (base station) communicate with multiple out-of-range destinations (users), rather than a single destination (user) as assumed in most previous work. The proposed optimal RA scheme consists of subchannel allocation (SA), subchannel pairing and joint source-relay power allocation (PA). In particular, it is shown that both SA and joint source-relay PA play a dominant role in the three steps of RA. It is also demonstrated that the shorter the distance between the source and the relay, the more impact of multiuser diversity on the system capacity. By employing SA and joint source-relay PA only, a near-optimal performance can be achieved. This work can be extended to the multi-hop, multi-relay and multi-destination uplink/downlink OFDM system.