The Distributed Contention in the Medium Access Control of IEEE 802.11 Wireless LANs: a Space and Time Perspective

This chapter will illustrate the new space and time perspective of the contention problem for the class of distributed random-access MAC protocols. This class of MAC protocol is fundamental because it is the basic access scheme in today’s Standard IEEE 802.11 MAC, the most widely deployed WLAN technology, and also the basis for new protocol enhancements aimed at obtaining higher performance (such as IEEE 802.11b and IEEE 802.11a) and QoS support (such as IEEE 802.11e). Many solutions and guidelines that have been inherited from the wired scenarios, and the preliminary wireless solutions proposed to overcome the distributed contention problem in both the time and space domains of wireless channels, will be illustrated in this chapter. Additionally, the resource-oriented design of the distributed contention-based MAC protocols will be emphasized. This is required, given the resource bottlenecks of wireless systems (as an example, limited channel bandwidth and battery energy), and given the challenging resource requirements of user applications that would make no concessions to the wireless Internet.