Performance analysis of cooperative diversity systems with multihop relays

Cooperative diversity has been proposed as an approach to improve the reliability of multihop networks in challenging environments where radio nodes may be disadvantaged due to shadowing. Nodes cooperate by relaying messages, which provides spatial and temporal diversity and may improve network performance in terms of latency and throughput rate. However, additional resources are required to achieve this benefit, in particular spectrum occupancy. In this report, an analytical cross-layer framework is developed to facilitate the investigation of reliable relaying schemes. It is shown that cooperative diversity can indeed improve the network performance; however, the throughput rate gains are limited to single relay nodes and a large number of multihop relays can degrade the spectral efficiency. Different network scenarios require different relaying schemes to achieve the best trade-off of performance and cost, indicating the need for coordinated cross-layer adaptivity.