Measurement-Based Analysis of Two-Hop Cooperative Relaying

For tactical military communications, ad hoc networks are an attractive choice because they can provide good area coverage without the vulnerabilities of any central node or base station. Their performance is, however, strongly dependent on the ability to maintain link quality information, and to distribute the changing routing tables, in a timely and efficient manner in highly mobile scenarios. A relatively new concept of cooperative relaying, in which several relay nodes simultaneously retransmits identical copies of the message on the same channel, is promising as it eliminates the need of routing. In this paper, we analyze the performance of an OFDM based cooperative simultaneous relaying scheme for two-hop networks. The networks are simulated based on measured channels for the individual links. The results are compared with the performance for the traditional single relay technique with optimal and suboptimal route information. The results show that the performance of the cooperative relaying scheme in the investigated scenario is equal to, or better than, the performance for the best route for the single relay scheme in a large majority of the simulated networks. However, some fraction of the networks shows a worse result for the cooperative scheme. This fraction decreases as the bandwidth increases. Furthermore, the performance for the cooperative relay scheme show significant increase in performance when compared to the single relay scheme for the next-best route. Moreover, we observe that the performance of the cooperative relay scheme, in general, is non-reciprocal with respect to the direction of transmission for a given pair of terminal nodes.