| With the development of wireless network technology and the transformation of market demand and competition,the next generation of wireless communication networks will become the integrated heterogeneous IP networks in which all kinds of wireless access technologies are coexistence and they can cooperate with each other. The integration of different wireless networks will lead to many technical compatible problems. As a result, it is a great challenge for us to realize that some measures should be taken to satisfy anyone at anytime and anywhere in heterogeneous wireless networks. Therefore, vertical handoff, which is regarded as one of the core technology to integrate heterogeneous wireless networks has been not only a study hotspot but also the core technology and key feature of the next generation of wireless communication networks. This paper studies the handoff opportunity of vertical handoff in heterogeneous wireless networks and proposes the optimization of handoff opportunity algorithm based on dynamic threshold. The main characteristic of this paper can be described as follows:Firstly, we design an overlap area which is covered by WLAN and UMTS as the scenario for selecting optimal handoff opportunity. Following that, we divide typical wireless applications into two categories: one has strict requirements for QoS, i.e. QG application, and the other has flexible requirements for QoS, i.e. QF application.Secondly, this paper synthetically considers the information of networks, mobile stations as well as users requests and preference. Based on that, this paper proposes a threshold function in which the theory of chance constrained programming is applied to implement the optimization of handoff opportunity.Thirdly, this paper utilizes opportunity cost to select optimal handoff opportunity and we have further improved the model of handoff opportunity. Experimental results prove that our proposed algorithm based on dynamic threshold can select optimal handoff opportunity. As a result, it ensures the users to obtain better QoS and decreases cost to some extent... |
