Chinese Journal of Computers   Full Text
Title	A Movement Trend Based Self-Adaptive Vertical Handoff Algorithm and Its Performance Evaluation
Authors	LIU Min1),3) LI Zhong-Cheng1) GUO Xiao-Bing2) ZHENG Kun1),3)
Address	1)(Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100080) 2)(Lenovo Corporate Research, Beijing 100085) 3)(Graduate University of the Chinese Academy of Sciences, Beijing 100049)
Year	2008
Issue	No.1(112—119)
Abstract &   Background	Abstract A combination of diverse but complementary wireless access technologies will improve wireless transmission performance and provide mobile users with ubiquitous connectivity. Vertical handoff is the basic requirement for the integration of heterogeneous wireless networks. During the vertical handoff procedure, handoff decision is a crucial issue for an efficient mobility. In this paper, we obtain the mathematical expressions of handoff conditions in traditional hysteresis based and dwelling-timer based handoff algorithms, and analyze their performance. Based on this, we propose a novel vertical handoff decision algorithm, which adaptively adjusts the handoff condition by analyzing the movement trend of mobile hosts and efficiently improves handoff performance. What′s more, the related computing requirement is very simple to be suitable for mobile devices with limited computing capacity. Simulations show that it can achieve a better integrative handoff performance compared with conventional hysteresis based and dwelling-timer based handoff algorithms. keywords heterogeneous wireless networks; vertical handoff; horizontal handoff; wireless local area networks; wireless wide area networks background A combination of diverse but complementary wireless access technologies will improve wireless transmission performance and provide mobile users with ubiquitous connectivity. In heterogeneous wireless networks, handoff can be separated into horizontal handoff and vertical handoff. A horizontal handoff is made between different access points using the same network interface. A vertical handoff is a handoff between access networks with different wireless technologies. Vertical handoff is the basic requirement for the integration of heterogeneous wireless networks. Compared with horizontal handoff, vertical handoff involves different wireless network technologies varying widely in terms of bandwidth, delay, coverage area, power consumption, etc. While significant work has been done on horizontal handoff mechanisms in homogeneous networks, there is not much literature available on vertical handoff in heterogeneous wireless networks. During the vertical handoff procedure, handoff decision is the most important step that affects the normal working of communication. An incorrect handoff decision may degrade the QoS of traffic and even break off current communication. With the support of the National Basic Research Program of China(973 Program) under grant No.2007CB310702 and the National Natural Science Foundation of China under grant No.90604016, the authors have done research on performance analysis and optimization of handoff algorithms in heterogeneous wireless networks. In this paper, the authors obtain the mathematical expressions of handoff conditions in the traditional handoff algorithms, and analyze their performance. Based on this, a novel vertical handoff decision algorithm has been proposed, which adaptively adjusts the handoff condition by analyzing the movement trend of mobile hosts and efficiently improves handoff performance. Simulations show that it can achieve a better integrative handoff performance compared with the conventional handoff algorithms. At present, with the support of the China Next Generation Internet (CNGI) project from the National Development and Reform Commission of China, the authors are developing the handoff management system based on the proposed algorithm and mobile IPv6 in heterogeneous wireless networks formed by wireless local area networks and wireless wide area networks.