1. For IEEE 802.11 Wireless LAN

2. Outline  Problem Description  AP-station association  Dynamic Load Balancing Channel Auto-selection Association Migration  Practical Concern

3. Problem Description  Given a set of access points and some mobile stations. How to distribute these stations to get maximal bandwidth utilization.  It is just a matching problem if the topology is fixed and bandwidth usage is predictable.

4. AP-station association  Stations always select the AP with highest received signal strength indicator (RSSI).  This make many stations associate with a few APs which implies poor bandwidth utilization.

5. Dynamic Load Balancing  Balanced load can be archived through three levels.  Channel auto-selection Let AP choose a channel with smallest interference automatically when it is booting up.  Association  Migration The AP may force some stations to move to other APs when necessary.

6. Association  First a station sends out probe request.  Then APs send back probe response with addition information such as the number of stations associated with the AP or channel utilization estimate (CUE).  The station choose the AP based on received information in hopes of getting a well balanced network.

7. Practical Concern  It is hard to change standards.  Load balanced among APs does not imply that all stations get the best quality. But one only care how to get as much resource as possible.  So it is reasonable to implement the whole algorithm in APs only.

8. References  S. Sheu and C. Wu, “Dynamic Load Balance Algorithm (DLBA) for IEEE 802.11 Wireless LAN”, Tamkang Journal of Science and Engineering, vol. 2, No 1, pp.45-52 (1999).  I. Papanikos and M. Logothetis, A Study on Dynamic Load Balance for IEEE 802.11b Wireless LAN, COMCON, 2001.  G. Sawma, I. Aib, K. Barbar, and G. Pujolle, A Recursive Load Balancing Technique for VoIP-dedicated WLANs, AICCSA 2008: 830-833