Research And Simulation Of Quality Of Service Scheme In IEEE 802.11e Networks

Recently, there has been a growing interest in the use of WLAN technology. WLAN attracts more and more customer because of its easy deployment, flexibility and so on. Examples of application range from standard Internet services, such as Web access, to real-time services with strict latency/throughput requirements, such as multimedia video and voice over IP. So the QoS became one of the most popular research topics.In order to support diverse application requirements, a new standard called IEEE 802.11e is proposed to improve QoS in WLAN networks. This standard provided differentiation mechanisms at the medium access control (MAC) layer, focusing on the QoS requirement of multimedia communication of family and office environment, such as voice, video and data services. In this article, 802.11e standard is described, and its differentiation mechanism, QoS parameters are analyzed and evaluated through OPNET simulation.However, although 802.11e provided WLAN QoS differentiation and endurance, gave high priority to voice and video services, there are a few remaining challenges that need to be addressed in order to enable comprehensive QoS support using 802.11e. Only MAC scheme design is not enough.In this article we provide an overview of a few of these challenges, describe their possible impact on QoS, and provide a survey of techniques that potentially could be used to address the identified challenges. There are three mains aspect: handling time-varying network conditions, adapting to varying application profiles, and managing link layer resources. In the third aspect, solutions mainly focus on MAC resource management, admission control and wireless access point selection. The purpose of wireless access point (AP) selection is to maximize the link resource using efficiency through load balancing. When there are several BSSs in WLAN network, this scheme is particularly important, for there are several access points available for one node. Till now, 802.11e do not define such scheme, what we use in research or industry is the scheme based on signal to noise ratio (SNR). The scheme do not consider load balancing of the network, so can not guarantee QoS. This article focused on AP selection scheme, did a survey of current research and proposed a new AP selection algorithm. This algorithm uses active scan pattern and use the network delay as main parameter of load measurement and AP selection.At last, this article implemented the proposed algorithm and original SNR based algorithm using the simulation tool OPNET. With the same load, the proposed algorithm can achieve larger throughput and lower network delay. The results show that the new algorithm can achieve larger throughput while ensuring the QoS requirement of voice and video services.