The Investigation On Vertical Handoffs Strategies In Wireless Heterogeneous Networks

In the rapid development of wireless communication technology, people is ful y enjoying the great convenience it brings. In a manner of speaking, wireless communication technology is greatly changing people’s way of life. Simultaneously, as the rapid development of wireless technology, it becomes an inevitable trend that “5w”(Whoever, Whenever, Wherever, Whomever, Whatever) will turn into reality. In this context, In order to meet the different needs of different users, a variety of wireless access technology emerges in endlessly, but they inevitably have their limitations. Different wireless network access technology such as cel ular network(2G, 3G, LTE), WiMax, Wlan and wireless sensor networks can not simultaneously satisfy all the needs of users. The feasible solution is to achieve full coverage and service through the deployment of different wireless networks. Therefore, the integration of heterogeneous networks has become an important aspect of the wireless network research, and the switching problem is a top priority. Relative to relatively mature of the horizontal switch study, the research of vertical handover is currently less.The vertical handover of heterogeneous networks can general y be divided into three stages, network discovery, handover decision and switching execution. This paper mainly talks about the research on some related problems and the improvement on the existing strategy.In the network discovery and selection stage, compared to the traditional way of interval scan network and updating network candidate set at fixed time, this paper considers the moving speed of the mobile network node and the strength of the network received signal so that the mobile nodes can activate the interface according to the dynamic interval in the stage of network discovery and network selection.It can achieve a better balance between efficiency and final energy.In the handover decision stage, this paper presents a handover decision algorithm that considering switching cost and based on multi-objective decision. Compared to the traditional ways, this algorithm considers the inherent properties of the candidate networks, such as transmission speed, cost and delay, and the cost of network switching execution. Therefore, it is more realistic.In the handover execution stage, the existing SCTP-based vertical handoff scheme always results in the dips of network throughput.Because it adopts the Smaller and fixed congestion window when you switch to the new network.This paper makes improvements in this regard. We can set a reasonable congestion window size according to the network status of the new path to improve the throughput effectively. In addition, in the slow growth phase, we can monitor the network status to reduce the packet loss rate effectively.This paper also includes simulation aiming at the vertical handover strategy.The simulation performance shows that the strategy in this paper is better than the performance of the original program.