A Distributed Load-Balancing Algorithm for 802.11 Wireless Networks
Date Issued
2008
Date
2008
Author(s)
Hsu, Chiu-Chan
Abstract
In the past decade, IEEE 802.11 wireless local network has been more and more popular in most campus, home, and enterprise. Many people can access wireless network because its popularization and convenience. However, some disadvantages of association criterion in IEEE 802.11 are revealed when there are more and more users join in the wireless network. In other words, user load is often unevenly distributed among Access Points (APs) when the maximum signal strength criterion is widely used for selecting an AP. In original design of IEEE 802.11, every station (STA) must contend for the channel usage if it has data to transmit. And the contention window would be increased by an exponential law if collisions continue to occur. Therefore, how to alleviate the congestion situation and distribute load among all APs is critical for those IEEE 802.11 wireless network designed and deployed for large number of users.n recent years, many studies focus on the number of STAs associated with an AP as the load index of the AP. Some research works also take the total throughput of an AP as the load index. However, the load indexes can not reflect the accurate load of an AP because of the fluctuating characteristic in the physical layer of the wireless network. In the thesis, we propose a new load index which takes into account of the defer time during the contention and the average transmission overhead evaluated via a probabilistic model. Based on the load index definition, we then propose heuristic distributed load-balancing algorithm. In the proposal, STAs are allowed to associate with an AP dynamically and the distributed load-balancing algorithm can be executed by all APs to reach better load balancing in a large and congested WLAN environment.n order to verify the performance of the proposed load index and load-balancing algorithm, we execute the simulation program written in C language, and employ VoIP and Web traffic as the analyzing network applications. The simulation results show that the proposed load index and load-balancing algorithm can improve the VoIP quality, and the total web access throughput is improved overall.
Subjects
load balance algorithm
wireless
Type
thesis
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