Investigation Of WLAN Based MAC Protocol Of AP For Mesh Networks

Wireless Mesh Network (WMN) is a new type of broadband wireless access network that combines the advantages of WLAN and the Ad hoc Networks.It has high reliability and flexibility. In recent years, multimedia applications are more and more popular, and wireless mesh networks are widely used in commercial environments. Therefore, it is crucial for wireless mesh networks to support Quality-of-Service(QoS). However, some distinct characteristics of wireless mesh networks, such as the multi-hop, distribution, self-organization and mobility, significantly impact the performance of the MAC protocol is the main factor to determine the efficiency of the shared wireless channel. An enhanced mechanism EDCA(Enhanced Distributed Channel Access) had been put forward in the IEEE 802.11e, which is an improved algorithm to support QoS.This thesis mainly focuses on how to provide the QoS in wireless mesh networks, where the topology is dynamic and the bandwidth is constrained. Towards to providing multimedia traffic as well as differentiating local and forward traffic, the work investigates the multi-channel MAC for wireless mesh networks based on IEEE 802.11e, and some original schemes are proposed. Firstly, the architecture, the differences between WMN and other networks, applications as well as some advantages of wireless mesh networks are introduced. The MAC protocol in WMN and investigates the multi-channel MAC mechanisms are analyzed and summarized.Secondly, this paper briefly introduces how 802.11e works and proposes an improved algorithm named D-EDCA.D-EDCA is a modified schemes based on EDCA.D-EDCA provides a new definition in which user level traffic map to the new priority, meanwhile it has a "differentiating local and forward traffic" function.Thirdly, we simulated the throughput of D-EDCA by changing the impact factors such as AIFS,CW PF and the number of stations. The parameters of D-EDCA need to be modified to achieve best performance. Increasing the AIFS, CWmin and PF of low priority traffic can improve the throughput of high priority traffic.Finally, the performance of D-EDCA in wireless mesh networks is investigated. Through a number of network simulations, we find that D-EDCA has better performance that EDCA. The revised D-EDCA is proposed by restricting the retransmitted times of the real-time traffics. Furthermore the performance of the revised D-EDCA schemes is analyzed briefly.