Abstract
The next-generation communication system will combine several different wireless access technologies with different coverage, bandwidth, cost and power consumption, such as IEEE802.11, GPRS/EDGA and WCDMA. Vertical handoff is the switching process between base stations with different wireless technologies. Discovering the reachable wireless networks is the first step for vertical handoff. The mobile terminal must discover the reachable wireless networks before performing vertical handoff. After discovering the reachable wireless networks, the mobile terminal decides whether to perform handoff or not relying on the demands of the running application, the resources of the reachable wireless networks and the moving speed. In this thesis, we proposed an ideal coverage concept and the adaptive interface activating method for the mobile terminal to discovery the reachable wireless network effectively. Moreover, we present two adaptive handoff decision methods for the mobile terminal to determine the handoff timing. The simulation results show that the proposed system discovery method can balance the power consumption and the system discovery time. Furthermore, the proposed adaptive handoff decision methods help the mobile terminal to decide the appropriate handoff timing.