Effective Access Point Selection Algorithms for Handoffs in IEEE 802.11 Wireless LANs

Jyh-Cheng Chen

Associate Professor
Department of Computer Science and the Institute of Communications Engineering

NationalTsingHuaUniversity (NTHU), Hsinchu, Taiwan.

Abstract

IEEE 802.11 wireless LANs have been widely deployed. How toefficiently balance the traffic loads among Access Points (APs), whichwill lead to improved network utilization and higher quality of userexperience, has become an important issue. A key challenge is how toselect an AP to use during the handoff process in a way that willachieve overall load balance in the network. The conventionalapproaches typically use Signal-to-Noise Ratio (SNR) as the criterionwithout considering the load of each AP. In this talk, I will present the design and analysis of two effective new AP selection algorithms, which measure the IEEE 802.11 frame delays to assess the load of an AP, and use the results to determine which AP to use. The

design goal is to minimize the modifications to existing WLANs and makeselection decision simple but effective. The algorithms can beimplemented in software on mobile stations alone. There is no need to exchange information among APs. The proposed algorithms are fully compatible with the existing standards. They are also easy toimplement. Both mathematical analysis and simulation are developed to show that the proposed algorithms can significantly increase overall system throughput and reduce average frame delay.

Bio

Jyh-Cheng Chen is an Associate Professor with the Department of Computer Science and the Institute of Communications Engineering, National Tsing Hua University (NTHU), Hsinchu, Taiwan. Prior to joining NTHU as an Assistant Professor, he was a Research Scientist at Bellcore/Telcordia Technologies, Morristown, NJ, from August 1998 to August 2001. He haspublished over 70 papers. He is the holder of 15 U.S. patents, 3 P.R.C. patents, and 2 R.O.C. patents. He is a coauthor of the book "IP-Based Next-Generation Wireless Networks" published by John Wiley & Sons Inc. in January 2004. Dr. Chen received the 2000 Telcordia CEO Award, the 2001 SAIC ESTC (Executive Science and Technology Council) Publication Award, the 2004 NTHU Junior Faculty Research Award, and the 2006 NTHU Outstanding Teaching Award. Dr. Chen is a Technical Editor of the IEEE Wireless Communications. He was a guest editor of the IEEE Journal on Selected Areas in Communications, special issue on "All-IP Wireless Networks" in May 2004. He is the Technical Program Chair of the Ninth IFIP/IEEE International Conference on Mobile and Wireless Communications Networks (MWCN '07), which will be held in Ireland, September 2007. He was the Technical Program Chair of the 3rd IEEE International Conference on Information Technology: Research and Education (ITRE '05). He has been on the technical program committee of numerous international conferences, including the IEEE INFOCOM 2005-2006, IEEE GLOBECOM 2005-2007, IEEE ICC 2007-2008, and IEEE WCNC 2005-2006. He was a tutorial speaker of IEEE GLOBECOM 2002, 2003 and 2006 in the subject of next-generation wireless networks. He leads the development of WIRE1x, which is one of the most important implementations of IEEE 802.1x supplicant. He is a Senior Member of the IEEE, and a Senior Member of the ACM. He received his Ph.D. degree from the State University of New York (SUNY) at Buffalo in 1998.