Policy-Enabled Handoffs Across Heterogeneous Wireless Networks

1 Abstract \Access is the killer app" 3] is the vision of the Daedalus project at U.C. Berkeley. Being able to be connected seamlessly anytime anywhere to the best network still remains an unfulllled goal. Often, even determining the \best" network is a challenging task because of the widespread deployment of overlapping wireless networks. In this report, we describe a policy-enabled handoo system that allows users to express policies on what is the \best" wireless system at any moment, and make tradeoos among network characteristics and dynamics such as cost, performance and power consumption. We designed a performance reporting scheme estimating current network conditions, which serves as input to the policy speciication. A primary goal of this work is to make it possible to balance the bandwidth load across networks with comparable performance. We identiied the problem of handoo instability that may be caused by handoo synchronization, i.e., the scenario of many mobile hosts making the same handoo decision at essentially the same time. We use ran-domization to break such synchronizations. Given the current \best" network, our system also determines whether the handoo is worthwhile based on the handoo overhead and potential network usage duration. 2 Introduction Katz, et al. 8], has viewed today's collection of infrared, radio wireless LAN, cellular and satellite networks as an overlaid structure of room-size, building