A Priority Scheme for IEEE 802. 11 DCF Access Method

Dr-Jiunn DENG  Ruay-Shiung CHANG  

IEICE TRANSACTIONS on Communications   Vol.E82-B   No.1   pp.96-102
Publication Date: 1999/01/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Signaling System and Communication Protocol
wireless LAN,  CSMA/CA,  multimedia application,  priority,  

Full Text: PDF(665.4KB)>>
Buy this Article

IEEE 802. 11 is a standard for wireless LANs. The basic access method in its MAC layer protocol is the distributed coordination function (DCF) for the ad hoc networks. It is based on the mechanism of carrier sense multiple access with collision avoidance (CSMA/CA). DCF is used to support asynchronous data transmission. However, frames in DCF do not have priorities, making it unsuitable for real-time applications. With a little bad luck, a station might have to wait arbitrarily long to send a frame. In this paper, we propose a method to modify the CSMA/CA protocol such that station priorities can be supported. The method is simple, efficient and easy to implement in comparison to point coordination function (PCF), another access method in IEEE 802. 11 based on access points (base stations). Simulations are conducted to analyze the proposed scheme. The results show that DCF is able to carry the prioritized traffic with the proposed scheme.