Improvements and performance analysis of IEEE 802.11 medium access protocols

In IEEE 802.11 standard development process, new physical and medium access layer techniques for higher throughput (IEEE 802.11n) and quality of service (IEEE 802.11e) enhancements are being designed on solid foundation of the distributed coordination function. None of these recently developed enhancements are immune to hidden node and hot-spot (congestion) problems. On the contrary, the increased operational bandwith of the higher throughput implementation makes them more prone to interference in limited number of IEEE 802.11 channels.;In this thesis, we extend the performance analysis of the distributed coordination function to enterprise networks configurations where networks are typically comprised of multiple access points. We propose an intelligent association algorithm that provides consistent higher throughput and better network-wide fairness independent of user load distribution within the network in comparison to the standard association algorithm.;Distributed coordination function is and will be the primary contention resolution algorithm of IEEE 802.11 systems. Identification and formulation of the common problems this channel access technique is facing in practical networks would give us a better understanding in terms of its limitations. In this work, we introduce a methodology to estimate the throughput performance of distributed coordination in unsaturated and hidden communication environments. Then by applying this methodology, we analytically estimate the abnormality in its fairness performance. The secondary channel access scheme of IEEE 802.11 is point coordination function, which does not suffer from hidden node and collision problems. We show that point coordination function in its current form has a poor throughput performance due to ignoring of the multi-rate transmission capability of users. We propose a new indexing algorithm for polling that increases the performance of point coordination function significantly.