On the Effectiveness of Cooperation in Carrier Sense-Based Ad Hoc Networks

In this paper, we investigate the effectiveness of cooperative techniques in non-infrastructured ad hoc networks based on carrier sense access control. We point out, via analysis and detailed network simulations, that CSMA biases some fundamental statistics of geographical positioning of terminals available for cooperation. Not only may relay nodes refrain from cooperating due to the carrier sense mechanism, but also the spatial correlation of interference in the network is likely to compress potential cooperators within an area in the proximity of the source. Furthermore, our discussion highlights how issues that affect carrier sense based medium access strategies, such as hidden terminals, reduce the effectiveness of relaying strategies when implemented in large non-centralized networks. The combination of the aforementioned factors is shown to significantly diminish the performance gain granted by cooperative schemes widely studied in the literature from a theoretical perspective.