An Adaptive Transmission Scheme for AF-OFDM Relaying Systems with Sub-Carrier Mapping

Relay transmission is an efficient solution to combat wireless channel fading and to increase system throughput in future board communication. In amplify-and-forward(AF) OFDM relay system, since the channel between the first hop (source-relay) and the second hop (relay-destination) varies independently, proper sub-carrier mapping (SCM) at the relay has been shown to improve the average end-to-end capacity evidently. However SCM has a poor performance at low SNR. In this paper, assuming that perfect channel knowledge is available at the destination, an adaptive transmission scheme is proposed. The transmission scheme, which is based on instantaneous channel quality, is selected to offer maximum the end-to-end system capacity. The efficiency of the proposed solution is demonstrated by both analytical performance and simulations.