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
National Tsing Hua University (NTHU), Hsinchu, Taiwan.
Abstract
IEEE 802.11 wireless LANs have been widely deployed. How to efficiently
balance the traffic loads among Access Points (APs), which will lead to improved
network utilization and higher quality of user experience, has become an important
issue. A key challenge is how to select an AP to use during the handoff process in a
way that will achieve overall load balance in the network. The conventional
approaches typically use Signal-to-Noise Ratio (SNR) as the criterion without
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 make selection
decision simple but effective. The algorithms can be implemented 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 to implement. 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 has published 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 NextGeneration 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.