Simulation Study of IEEE 802.11e Wireless LAN - Enhancements for Real Time Applications

The new IEEE 802.11 standard version, denoted by 802.11e, was developed in order to introduce mechanisms enabling handling of real time applications. In order to achieve the goal, the transmission channel access control procedure was modified. The new approach consists in distinguishing the time after which packet transmission of a certain class may begin. The developed mechanism is not yet deterministic, but based on the principle of increasing the probability of success. In consequence, quality of service levels (QoS) guaranteed by the network to different applications may be strongly dependent not only on the type and intensity of input traffic, but also on up-to-date results of random processes realised in different stations. The first part of this paper contains short descriptions of the original and modified method of controlling access to the transmission channel. Using the further presented results of simulation tests it is possible to determine system operation intervals in which the network guarantees the required quality of service to traffic streams of a given class. The summary contains most important conclusions from the comparison of working principles of both mechanisms as well as the executed experiments