A Study of WLAN-to-Cellular Handover Using Measured Building-Exit Data

• Published in: IEEE transactions on vehicular technology Vol. 58; no. 4; pp. 2044 - 2054
• Main Authors: Smadi, M., Azhari, V.S., Todd, T.D., Kezys, V.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-05-2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Access protocols; Algorithm design and analysis; Algorithms; Analytical models; Applied sciences; Area measurement; Business and industry local networks; Cellular networks; Computer networks; Construction; Electrical engineering. Electrical power engineering; Electrical power engineering; Exact sciences and technology; Information theory; Information, signal and communications theory; Joints; Land mobile radio cellular systems; Leg; Local area networks; Mathematical analysis; Mobile communication; Networks and services in france and abroad; Optimization; Outdoor; Power networks and lines; Telecommunications; Telecommunications and information theory; Telephone sets; Teleprocessing networks. Isdn; Users connections and in door installation; Valuation and optimization of characteristics. Simulation; Wireless communication; Wireless LAN; Wireless networks; Performance evaluation; Mobile radiocommunication; Multiple access; Wireless LAN; Wireless telecommunication; Outdoor installation; Information rate; Connection; Mobile communication; Data processing; Coverage; Algorithm; Information transmission; Indoor installation; Computer network; Call blocking; Analytical method; Handover; System simulation; Computer networks
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2008.2005104

Seamless wireless local area network (WLAN)-to-cellular handover can often be very difficult to achieve. A particularly bad scenario may occur when mobile users exit from indoor WLAN coverage to outdoors during active voice connections. In this paper, we report on a measurement-based study of this type of vertical handover (VHO) situation. The presented results come from measurements taken by traversing many indoor-to-outdoor paths for a large number of building exits while measuring multi-access-point (AP) WLAN coverage. The collected data was then processed to determine handover characteristics when optimal threshold-based handover triggering is used. Our results show that it is very difficult to successfully complete the handover unless the WLAN deployment has carefully been engineered. For WLAN deployments which restrict the use of lower data rates, we propose a limited data rate usage (LDU) algorithm that improves VHO performance without adversely affecting the WLAN capacity. Analytic models and simulations using the experimental data are presented, which show the improvements in call blocking when the LDU algorithm is used.