Study Of Handoff And Mobility Management In Mobile IP

With the rapid development of Internet and wireless communication, Internet and wireless networks will integrate into a all IP mobile Internet architecture. Mobile Internet can support mobile node, meet the requirements of the people on the move to access information, and have broad prospects for development. Therefore, the research of the network-layer mobility support has attracted wide attention.The Mobile IP proposed by the IETF can support mobility on the Internet. It allows mobile nodes to connect to any links with a fixed IP address and maintain all on-going communications while changing links.To support mobility on the Internet, researchers have done a lot of fruitful work, and mobile IP protocol has become the most promising protocol with mobility support. However, Mobile IP is still in the research stage, there are many aspects have yet to be improved. The handoff and mobility management in mobile IP is a key problem that need to be resolved in the next generation of mobile Internet, and is an urgent need to achieve IP-based mobile computing. This paper analyzed the basic principle of Mobile IP, summarized research status and development trends of the network layer mobility management, and focused on the issue of mobile IP handoff and mobility management. The paper primarily include the following aspects:1. A dynamic threshold-based call admission control(DT-CAC) policy was proposed, which performs call admission control in mobile IP while mobile node switching subnet.New call blocking probability(CBP) and handoff call dropping probability(HDP) are two important connection level QoS parameters in wireless/mobile networks. CAC optimization goal is to maximize resource utilization while reduce HDP and CBP. Because mobile users are more sensitive to ongoing call dropping than new call blocking, the traditional CAC policies, in order to reduce HDP, usually results in obvious decrease of resource utilization and may lead to a high CBP. Through establishing a Markov model of wireless call admission, restricting the ratio of HDP to CBP, the proposed scheme can dynamically adjusts the call admission thresholds of handoff call and new call according to various network load conditions, reduce the handoff call dropping probability, and restrict the increase of new call blocking probability. Consequently, the scheme achieves a good trade-off between HDP and CBP. Simulation results show that DT-CAC outperforms existing protocols in terms of HDP, CBP, and resource utilization.2. To address the issue of resource scarcity in wireless mobile IP environment, a reward mechanism based dynamic optimization on call admission control(RBDO-CAC) was present.RBDO-CAC established a reward computing model of call admission of wireless cell based on Markov decision process, dynamically optimized call admission process according to the principle of maximizing the average system rewards. Simulation results show that RBDO-CAC scheme has the following advantages:1) Realization of maximizing system rewards enables system to accept calls request as many as possible, effectively improves system resources utilization; 2) The scheme dynamically calculates call admission threshold according to network load conditions, and can adapt to the dynamic changes of call traffic; 3) it effectively reduces system handoff call dropping probability and new call blocking probability, prevents unrestricted increase of new call blocking probability caused by the priority of handoff call.Under high call traffic load, resource utilization rate can be improved by 6%, and handoff call dropping probability and new call blocking probability can be reduced by about 8%.3. A new link layer assisted end-to-end mobile QoS(L2AMQ) guarantee scheme was proposed for the mobility management problem in mobile IP QoS guarantee.When a mobile node(MN) moves from one cell to another with an active flow, the data flow path changes and the flow ID and session ID that include care of address will change simultaneously. MN's prior reserved resources are no longer available and the service quality of the MN may degrade significantly due to the lack of resources reserved for the MN in the new region. L2AMQ combines hierarchical mobility management with link layer assisted handoff mechanism, establishes resource reservation in advance in the subnet which the MN will visit next by detecting link layer signal strength, to speed up the handoff process. When MN moves among subnets, L2AMQ reduces the QoS path handoff delay by minimizing the path variation and establishing resource reservation in advance. By introducing a new QoS object, L2AMQ can avoid using RSVP tunnel in hierarchical mobility management. Consequently, it reduces system overheads and saves system resources. Simulations and analyses show that L2AMQ outperforms existing protocols in terms of reservation blocking rates and session loss rates.4. A new mobile multicast scheme called mobility prediction based mobile multicast (MPBMM) was proposed for the mobility management problem in mobile IP multicast.Because multicast is efficient for one-to-many communication over the Internet, which effectively conserves the network bandwidth and processing capability of mobile node, it is significant to provide multicast mechanism in wireless mobile IP environment. However, the mobile multicast protocol must deal not only with dynamic group membership but also with dynamic member location. Obviously, mobile multicast protocol is more complicated than the multicast protocol in wired network. MPBMM combines the ideas of mobility prediction and hierarchical mobility management in mobile multicast. When a mobile node roams among subnets during a multicast session, it intends to reduce the delay of subnet handoff and minimize the loss of multicast packets by dynamic mobility prediction. Furthermore, MPBMM manages to optimize the delivery path of multicast packets,and avoid the problems of triangle routing and tunnel convergence by hierarchical mobility management. Simulation results show that the proposed scheme can minimize the loss of multicast packets, reduce the delay of subnet handoff, decrease the frequency of multicast tree reconfig-uration. When MN moves among subnets at different speeds (from 5to 25 m/s), the maximum loss ratio of multicast packets is less than 0.2%,the maximum inter-arrival time of multicast packets is 117ms, it can meet the QoS requirements of real-time services in wireless environment.