Research And Application Of Vertical Handoff Technology In Wireless Networks

A variety of wireless communication network systems are developing currently. They provide session and data services for users with their own advantages. In order to take advantage of these wireless resources, the next generation network will trend to be a integration of these kinds of diffident wireless networks. The vertical handoff technology is the basis of operator for heterogeneous wireless networks. It is to ensure the continuity of business and the quality of communication that is its final goal. WCDMA covers large but its transmission bandwidth is small, while WLAN has large bandwidth but covers small. So, the integration of WCDMA and WLAN can complement each other very well.In this paper, we mainly focus on the vertical handoff technique of a dual-mode intelligent mobile terminal in WCDMA-WLAN heterogeneous networks. We choose real-time voice session for its high QoS requirement to research vertical handoff algorithm and design vertical handoff strategy. Our target is to reduce the switch frequency, switch delay and improve the utilization of wireless resources. The main context as follows:1) Use Matlab to simulate the handoff algorithm based on RSS. During the vertical handoff,we find ping-pong effect and optimize it through adding hysteresis level and dwell time2) Analyze different business’requirements to QoS and calculate the bandwidth requirements of video streaming and voice conversation service. Aiming at voice service, a network selection algorithm based on QoS is proposed by using analytic hierarchy process. We use eigenvalue method to get the attribute weights.3) Relying on WCDMA-WLAN loosely coupled heterogeneous networks, we design a VoIP System as switching system. A handoff strategy including low power switch trigger, handoff decision based on QoS and handoff management by SIP is proposed. It is controlled by the terminal and can ensure the quality and continuity of the session effectively.4) Recently there is less vertical handoff technique used in specific applications. In this paper, we choose TI’s Da Vinci technology to design and develop a dual-mode voice mobile terminal. The functions of heterogeneous wireless network access, voice conversations and vertical handoff functions can be used to evaluate the performance of vertical handoff algorithm and strategy.After practical testing, the vertical handoff algorithm and strategy proposed in this paper is feasible. It can effectively ensure business continuity and quality of communication, maximize network utilization, and can also be directly applied to VoIP communications.