Abstract: Along with each kind of heterogeneous wireless network appearance one after another, many kinds of wireless network convergence foundation's vertical handoff technology has received widespread attention of the academic and the industrial world. Therefore, the next generation wireless network (NGWN) must support the vertical handoff technology to ensure that users can switch from a network to another or from one kind of transmission medium to another when maintained the continuity of the exist correspondence. This paper carries on the summary analysis of the present vertical handoff technology basic philosophy and the existence difficulty, simultaneously introduces a vertical handoff decision strategy using many kinds of decision factors, and elaborates its core thought and the handoff process.

Key words: network convergence, vertical handoff, heterogeneous network, decision strategy