Cooperation in Carrier Sense Based Wireless Ad Hoc Networks - Part II: Proactive Schemes

TL;DR

This paper investigates proactive cooperation in carrier sense-based wireless ad hoc networks, revealing limitations due to medium access bias and interference dynamics, and concludes CSMA layers are unsuitable for effective cooperation in large networks.

Contribution

It provides a detailed analysis and simulation showing the inefficacy of proactive cooperation under CSMA, highlighting the impact of relay positioning and interference variability.

Findings

Reactive cooperation performance is limited by relay distribution bias.

Interference dynamics hinder the reliability of proactive cooperative links.

CSMA-based link layers are unsuitable for large-scale cooperative ad hoc networks.

Abstract

This work is the second of a two-part series of papers on the effectiveness of cooperative techniques in non-centralized carrier sense-based ad hoc wireless networks. While Part I extensively discussed reactive cooperation, characterized by relayed transmissions triggered by failure events at the intended receiver, Part II investigates in depth proactive solutions, in which the source of a packet exploits channel state information to preemptively coordinate with relays in order to achieve the optimal overall rate to the destination. In particular, this work shows by means of both analysis and simulation that the performance of reactive cooperation is reduced by the intrinsic nature of the considered medium access policy, which biases the distribution of the available relays, locating them in unfavorable positions for rate optimization. Moreover, the highly dynamic nature of interference that characterizes non-infrastructured ad hoc networks is proved to hamper the efficacy and the reliability of preemptively allocated cooperative links, as unpredicted births and deaths of surrounding transmissions may force relays to abort their support and/or change the maximum achievable rate at the intended receiver. As a general conclusion, our work extensively suggests that CSMA-based link layers are not apt to effectively support cooperative strategies in large-scale non-centralized ad hoc networks.