A Study Of Vertical Handover In Heterogeneous Networks

With the development of wireless network, today the wireless network environment is booming, the existing networks includes WLAN、WiMAX、2G、2.5G、3G、4G、 Bluetooth and so on, excluding the new coming network protocols which may be mem-bers of wireless network protocol family in the future. While different network proto-cols are suited to specified application scenarios, the user should switch to the appropri-ate network according to current network demand. How to handover and access among different networks, not only should the user identify different network protocols and network conditions, but also it needs an effective vertical handover algorithm. In this way, the networks condition and the communication performance of the mobile users can be optimized.This thesis introduces different vertical handover algorithms and analyses the advan-tages and disadvantages of different algorithms. This thesis proposes a vertical handov-er method applied to the real network environment, whose principle of switching to another network based on the relative position, signal strength, signal rate and so other factors. First, this thesis analyses and models two existing network protocols, and in-troduces the method of getting network signals which will do a help to sense and assess the network conditions now and to manage the network information periodically. Second, this algorithm takes the signal strength and signal rate as the switch principle as well as a signal power threshold which user gets the weighted signal power sum which is recorded by user among moving through the network. This method can avoid the frequent switch among different networks, reducing ping-pong effect. Last, simulation study of the handover algorithm is made to the scheme with OPNET software platform, while the performance of the method is analyzed and verified.