Research On Multi-hop Access Technology Supporting IP Roaming

The traditional LAN technology is widely used in the campuses, enterprises andorganizations, and is still one of the most widespread access manner. Besides, ADSLalso makes it convenient for family users to access internet. With the developmentof wireless technology, people expect more convenient access to the internet. WLANis adopted by more and more people, because it allows users to move in a smallrange. Network providers and users are bullish for the rising WiMAX technologywhich allows users to move in a larger metropolitan-area. Whether the technologyof LAN, ADSL, WLAN or WiMAX, they are all based on a fixed infrastructure.The problem is, the mobile users cannot process global IP roaming, in addition, itwill lose all connections if the fixed infrastructures are broken down. Therefore, theresearchers must face the following challenges before the wireless access technology iswidely used:The ability of network to provide global IP roaming for users. Mobile user isallowed to move in a global range while keeping connected with the internet, andanyone can contact the user through a permanent IP address.The ability of network to deal with emergency. In some urgent situation, con-nections with the nearby persons can still survive after the fixed infrastructuresare broken down.The ability of network to route packets in changeful topology. The networktopology changes frequently because of the ?oating users. Once a broken linkoccurs, the mobile user can process a fast recovery with low signaling cost toreduce packet drop ratio.The ability of fast handover and QoS assurance. Under frequent movements,the mobile user can handle fast handovers while keeping broadband internetconnections all the time, and guarantee QoS in a way.To solve the above problems, this thesis addresses on the scheme of global IProaming multi-hop access manner, including its implementing framework and proto-col extension, routing, fast handover and QoS assurance. The content of this the-sis includes issues about: (1) multi-hop access framework and protocol extension; (2) route reconstruction for the edge multi-hop access networks; (3) fast seamlesshandover of backbone resource reservation. The works in this thesis have been sup-ported by the National Science Foundation of China "Investigation of Wireless Mul-timedia Techniques based on Multimedia Transmission Property"(No.60202005) and"Internet-based interactive streaming delivery technique"(No.60302004) respectively.The contributions of this thesis include:1. Proposing a global IP roaming multi-hop access framework and its protocol ex-tension. The new framework merges multi-hop Ad hoc into its edge part andHMIPv6 into its backbone part. The multi-hop networks improve toughness,expand coverage, thus reduces disposal cost, and broadband access is also sup-ported; while HMIPv6 reduces signaling cost and handover delay in the intra-domain handovers. The existed HMIPv6 protocol is extended to support theregistrations with the internet gateways. This makes it possible for the MNsin the same edge MANET to communicate with each other directly. Thus, ithelps to reduce the backbone transmission burden, and is also helpful for theMN to establish internet connections quickly and handover seamlessly betweengateways.2. Proposing a cache bypass and local recovery based route reconstruction scheme.In the edge part of the global IP roaming multi-hop access manner, a routereconstruction scheme is proposed to reduce the rerouting signaling cost, increasethe amount and timeliness of backup routes, and further reduce packet dropratio and latency. The MN listens in all frames including data packets androuting control signaling in its free time, and maintains a neighbor list and localroute cache, thus well reduces signaling cost brought by the periodical HELLOmessages, and gains more usable route information. Once the intermediate nodedetects a broken link, fast route discovery and local recovery will be achievedaccording to local route cache and neighbors'route caches, thus routing controlsignaling and packet drop ratio are well reduced.3. Proposing a fast seamless handover scheme for resource reservation in the ping-pong type of movement. In the backbone part of the global IP roaming multi-hop access manner, in order to reduce signaling cost and handover delay ofresource reservation, the typical ping-pong type of movement is studied, and afast seamless handover scheme is proposed under a hierarchical architecture. TheMN is allowed to keep the old reservation for some time and to retrieve it quicklywhen the MN returns soon. Based on the simulation results, it can be observedthat, by setting the Reservation Active Flag (RAF) and the o?ine Count DownTimer (CDT), the scheme significantly reduces QoS signaling cost and handoverdelay. This helps to reduce network transmission burden and service interruptionfor ping-pong mobile user.4. Proposing an optimizing policy for the o?ine count down timer in the fast seam-less handover scheme. The fast seamless handover scheme well reduces QoShandover signaling and delay in case of a ping-pong type of movement by keep-ing the old reservation before the CDT expires. Whereas, in order to improvenetwork utilization, and to reduce the waste of resources and the e?ect on the cellcapacity due to withholding resources, the CDT cannot be increased infinitelyand need to be optimized. A simple expression for CDT optimization is derivedbased on a poisson mobility model. According to the previous mobility charac-teristic, the MN can easily set the optimal CDT for the best cost performanceof resource reservation.