In the next generation of heterogeneous wireless network environment, to meet the network requirements of diverse services ,we propose a vertical handoff decision algorithm based on QoS evaluation that refine the handover unit to services. The proposed algorithm consider the needs of the services、 network conditions、 user preferences and other factors, and makes Analytic Hierarchy Process (AHP) and cost function combine to choose the target network that is best meet the requirements of services . Comparing with the vertical handoff decision based on RSS, simulation results show that the proposed method can take full account of the different QoS requirements of various services types to choose the appropriate network, and would not cause performance degradation.
