Enhanced Collision Resolution via Cooperative Retransmissions

Traditional medium access control protocols are designed to avoid collisions. However, due to the random arrival nature of the network traffic, collisions cannot be completely avoided in a decentralized fashion. Recently a random access protocol for wireless networks was proposed that via cooperation of network nodes can resolve collisions and thus achieve high throughput. In this paper, we provide analytical expressions for the bit-error-rate (BER) performance of that scheme in a Rayleigh flat fading scenario. Our analysis indicates that the spatial diversity introduced by user cooperation enables lower BER than non-cooperative protocols that avoid collisions, such as ALOHA or TDMA. The BER performance shows that the cooperative random access protocol is best suited for variable rate traffic. The analytical results are validated via simulations. We propose a new relay selection scheme and a control scheme on transmission probability, that further enhance performance in terms of BER and throughput.