A Vertical Handoff Decision Algorithm Based on Fuzzy Control in WiMAX and TD-SCDMA Heterogeneous Wireless Networks

Next generation wireless communication systems are expected to relay on integrated networks consisting of multiple wireless technologies. Heterogeneous wireless networks based, for instance, on systems such as WiMAX and TD-SCDMA can combine their respective advantages, offering a high Quality of Service (QoS) to mobile users. The vertical handoff decision is crucial to the integration of heterogeneous networks. In this paper, we propose a vertical handoff decision algorithm based on fuzzy control in WiMAX and TD-SCDMA heterogeneous wireless networks. The algorithm takes into consideration the factors of Received Signal Strength (RSS), Bandwidth, Network Delay, Service Cost and User Preference, uses the fuzzy control method to evaluate the performance of the available networks and makes a final handoff decision according to the service type of an ongoing session. We introduce a vertical handoff decision value for the real-time services (i.e., RVHD) to distinguish the importance of the five factors and find out the most appropriate network. A pre-decision method is employed in the proposed algorithm to make an early decision for a user with high mobility or very low RSS from the candidate network. Simulation results show that the algorithm can make accurate handoff decisions, reduce unnecessary handoffs and eliminate the ping-pong effect. The pre-decision method can save the system overhead and raise the efficiency of handoff decisions.