A Reservation-Based Enhancement of IEEE 802.11 DCF Protocol

Oyunchimeg SHAGDAR
Suhua TANG
Masanori NOZAKI
Youiti KADO

IEICE TRANSACTIONS on Communications   Vol.E90-B    No.3    pp.538-548
Publication Date: 2007/03/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.3.538
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Network
802.11 WLAN,  reservation-based MAC,  DCF,  fairness,  

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IEEE 802.11 DCF is an asynchronous and distributed MAC protocol which does not require the existence of a central controller for medium access coordination. This flexibility, which is due to DCF's contention-based nature, comes at the expense of the overhead associated with contention resolution. The overhead consists of frame collision time and channel idle time, which is particularly severe when channel is saturated. In this paper, we present an enhancement of DCF which aims at reducing its contention resolution overhead by equipping it with a distributed reservation mechanism. The proposed reservation mechanism enhances collision avoidance mechanism of DCF by enforcing a partially ordered medium access through an implicit agreement between neighboring nodes. Simulation results, using ns-2 network simulator, show that the added reservation scheme 1) effectively reduces DCF's overhead and improves channel utilization particularly when node density and traffic load is high, 2) significantly enhance DCF's fairness.