Abstract
ABSTRACT Wireless local area networks (WLANs) are increasingly popular because they provide great flexibility to the users compared with wired networks. The first standard WLAN protocol was introduced in 1997 and called IEEE 802.11. It was followed in the next few years by a series of modifications to increase the bandwidth and to achieve higher transmission speeds. However, the modified standards were not designed to handle continuous data that is typical for real-time services and multimedia applications. Such applications require a network having special performance measures such as high bandwidth, low delay, and low jitter, which are collectively called quality-of-service (QoS). Considerable research efforts have been carried out to enhance QoS support for 802.11. Among them, 802.11e is the new standard which manages to enhance QoS by applying priority mechanisms on the WLAN traffic. This thesis presents a simulation study of the enhanced distributed channel access method (EDCA) in the new IEEE 802.11e standard protocol. This protocol is evaluated to verify that it achieves superior QoS performance for real-time applications compared with the earlier legacy protocol IEEE 802.11 DCF access method. The present work is carried out by conducting simulation experiments to compare the performance of both protocols. In particular, the QoS performance is evaluated using the most relevant QoS parameters that affect the performance of real-time applications, namely throughput, delay and jitter. This study aims at using quantitative methods to investigate the suitability of the enhanced IEEE 802.11e standard to handle continuous data. All simulation experiments are done using the popular network simulator NS2. This study confirmed that the enhanced IEEE 802.11e protocol is capable to allow real-time applications to efficiently use the wirelessii network with a higher priority compared to non-real-time applications. The study showed that the enhanced protocol guarantees superior QoS performance to voice and video traffic that is manifested in high throughput, low delay, and low jitter. This superior performance is maintained in all situations regardless of the network load and/or the ratio of real-time traffic to non-real-time traffic. The study has confirmed also that the enhanced protocol is fair with respect to non-real-time traffic, and will not force it to starve in the presence of an excessive realtime traffic.
