Qos Based Performance Analysis of Ieee 802.11 in Mac and Phy Layer Using Oar Algorithm

Abstract

An ad-hoc network is a collection of mobile hosts forming a temporary network on the fly, without using any fixed infrastructure. Quality of Service (QoS) is currently an active research in ad-hoc networks. QoS is the performance level of a service offered by the network to the user. The goal of QoS provisioning is to achieve a more deterministic network behavior, so that information carried by the network can be better delivered and network resources can be better utilized. A wireless Ad-hoc network consists of wireless nodes communicating without the need for a centralized administration, in which all nodes potentially contribute to the routing process. The fluctuations in channel quality affect the QoS metrics on each link and the whole end-to-end route. The interference from non-neighboring nodes affects the link quality. The idea of such networking is to support robust and efficient operation ad-hoc wireless networks in which all nodes potentially contribute to the routing process. Wireless channel fluctuates rapidly and the fluctuations severely affect multi-hop flows. As opposed to the wired network, the capacity of the wireless channel fluctuates rapidly due to various physical layer phenomena including fading and multi-path interference. In addition, background noise and interference from nearby nodes further affect the channel quality. In ad-hoc networks, the end-to-end quality of a connection may vary rapidly as change in channel quality on any link may affect the end-to-end QoS metrics of multi-hop paths. The commonly used QoS metrics are delay, bandwidth, jitter and throughput. The challenge faced by wireless networks is the constantly varying physical layer properties of the channel. For the efficient use of a multi-rate physical layer, an Opportunistic Auto Rate algorithm can be used which is very close to the MAC layer. It improves the throughput of the channel in the presence of multi-rate links in ad-hoc networks. An absolute QoS guarantees is difficult to provide, the relative QoS guarantees can be provided by service differentiation. However, to provide differentiated services, the 802.11 protocol needs to be modified and it proposes three ways to modify the DCF functionality of 802.11 to support service differentiation. It reduces packet delay to improve the system performance.