A method for minimizing unnecessary handovers in heterogeneous wireless networks

In near future, various wireless access technologies will be used together to provide seamless and cost effective connectivity to mobile users. Multiple wireless access systems with overlapping coverage fields will be accessible to a mobile terminal with multiple interfaces. One problem arising from the availability of alternatives is the unnecessary occurrences of handovers (especially vertical ones) that lead to excessive resource consumption. To avoid this, a suite of algorithms need to be deployed to limit the number of handovers. In this paper, we present an algorithm which is run in the mobile terminal and minimizes the number of handovers when the device detects the presence of wireless local area network (WLAN) signals. Conventionally, a mobile terminal should switch from cellular to WLAN whenever WLAN connectivity is available, to make use of the WLAN's high speed and low cost as much as possible. However, a considerable proportion of these handovers will be detrimental to the call quality due to potential failures. Our algorithm reduces the number of handovers whenever the predicted traveling distance inside the WLAN cell is smaller than a threshold value. Through performance analysis we show that our algorithm successfully minimizes the probability of unnecessary handovers, and through simulation we discuss about the accuracy of the distance prediction based on the received signal strength measurements.