Research On Seamless Handoff Algorithm For Dedicated Wireless Mesh Network

As accessing the public information network's demand of the railway and highway's mobile users during their tours increases, the existing information network can not meet the accessing requirement of mobile users any more.Until recently, the standards established by IEEE for the WLAN based WMN (Wireless Mesh Network) is called the IEEE 802.11s standard. The IEEE 802.11s draft is a very good solution to the WMN. However, it is not made dedicatedly for the Vehicle to Land Communication Wireless Access System. So, when we put it in this application, it has some defects. Firsly, using the mesh topology of the WMN to solve the zonal topology of the Vehicle to Land Communication Wireless Access System has got very low efficiency. Secondly, IEEE 802.11s draft does not define seamless handoff. As a result, the vehicle has to break down the link first and then access the new MAP. In fact, it will take a relatively long time to accomplish this process and the network connection is broken down for some time. This is actually unacceptable for our continuous broadband access demand.After demonstraton and investigation, we have found that there isn't any complete technical method for the access of the railway or highway vehicles. So, we propose a CSHA (Cross-layer Seamless Handoff Algorithm) for the dedicated WMN. Our CSHA takes into account the signal strength, transmission hops and link state. This algorithm provides a solution to the Vehicle to Land Communication Wireless Access System which is now under- exploitation.In chapter one, the research background, contribution of this thesis and some related references and patents are outlined. Then the architechture, advantages and basic application of the WMN are analysed in chapter two. In chapter three, related handoff mechanisms in the IEEE 802.11 standard are analysed. In chapter four pre-scanning and dynamic caching layer-2 seamless handoff and the fast layer-3 handoffs in AODV-based IEEE 802.11 WMN schemes are presented. In chapter five, propoed CSHA is simulated and analysed.Finally, the thesis is concluded and the future work is prospected.