On Performance Improvement for 802.11-based Multi-hop Ad Hoc Wireless Networks

Abstract

Collision due to the hidden terminals in contention-based medium access control protocols is one of the main reasons of the poor end-to-end performance of wireless networks. In this paper, we present a novel approach for MAC protocol improvements for 802.11-based multi-hop ad-hoc wireless networks to reduce unnecessary collisions, resulting in performance enhancement. Our main idea is to reduce unnecessary collisions by introducing a new time interval, named CAI (Collision Avoidance Interval) for the node in the carrier sensing zone[6]. Specifically, in the context of 802.11, the four-way handshake is specified as a collision avoidance medium access protocol and the protocol behavior for the node in the carrier sensing zone is required to be modified when it senses a signal for CTS, such that the node defers transmitting a frame during CAI, unlike during EIFS in the 802.11 specification. We carry in-depth analysis of the protocol behavior and have conducted a comprehensive simulation to study the performance improvements. The simulation results show that the end-to-end performance is greatly increased and the number of dropped frames due to collision is significantly reduced as much as one half, and so is the throughput cost.

This work was supported by grant No. R01-2002-000-10934-0 (2005) from the Basic Research Program of the Korea Science & Engineering Foundation and by the Research Grant of KwangWoon University in 2003