In this paper, we propose a location-aware relay selection (LARS) scheme based on geographical information in the distributed opportunistic relay (OR) communication system. The scheme aims to limit the contention among potential relays through dividing the whole relay selection region into some small nonoverlapping contending torus zones. If a relay lies in the specified contending zone and its local channels are better than the source-destination channel, it becomes a contending relay and will transmit a FLAG packet to signal the presence when its own timer expires. If no relay is selected in the previous contending zone, the current contending torus zone will be extended. The contention is an iterative course until the relay selection process completes. Performance analysis and simulation results show that the LARS scheme leads to a remarkable improvement in collision probability. Meanwhile the outage performance and consuming time of LARS scheme are closed to those of original OR scheme.
