Research On The Key Technologies Of MANET Accessing Internet With Gateways

The flexibility, self-configurability and easy deployment of mobile ad hoc networks (MANET) are making these networks indispensable component in future mobile and wireless network architectures. However, most of the information people needed is still stored on Internet nowadays. The people expect naturally to own effective wireless mobile equipment to obtain the continuous, stable and quality guaranteed Internet information anytime and anywhere without actual physical location restriction. And additionally, with the advent of future wireless systems consisting of an integration of different heterogeneous wireless technologies, the interconnection of MANET to Internet is one of the areas which are becoming of paramount importance. This hybrid MANET will form easy deployable, economical effective supplement and expansion to existing infrastructure network.How to realize MANET accessing Internet has become a hot topic of the industry, and the study on relative question is still at the start stage at home. Because there are essential differences between MANET and Internet, it is not the easy matter to interconnect these two heterogeneous networks. Many key technology challenges, such as address autoconfiguration, gateway discovery, load balance, mobility management, QoS, gateway forwarding strategy and overhead control and so on, need to be solved. Taking these points as a warning, this paper studys and sums up pivotal questions and technologys in current MANET accessing Internet, including interconnection based on multi-path, load balance strategy, gateway deployment and selection, adaptive gateway discovery method, overhead control during accessing process, and gives corresponding solutions. The theoretical analysis and NS2 simulation have confirmed the validity of these methods. These researches have important meaning to further discuss and develop the application of MANET.This dissertation makes the following innovative work:(1) Design a MANET accessing Internet routing algorithm based on load balance. This algorithm avoids overload nodes and gateways according to node usability degree. It uses asymmetrical multipath transmission technology to disperse network load and improve accessing network performance. After validating on NS2 network simulation platform, it proves that the algorithm can balance network load and node energy consumption preferably, protect low energy nodes in network and prolong network lifetime effectively.(2) In view of research blank in gateway placement of accessing network, we studied the problem of gateway placement and selection in MANET accessing Internet. With a view to the crucial function of dynamic gateway in network accessing process, a new three-layer programming model for placement and selection dynamic gateway has been proposed. A decision node, which has coordination control function, was introduced into the model, and was used to harmonize the Utilization of gateways and routes. The three layers make decisions interactively to mediate the relationship between the network overall benefit and the node local interests. The model, as the basis of the gateway configuration, optimized the placement of the gateway. The simulation results indicate that the performance of delay, overhead and throughput has promoted after the model was introduced, and the validity of the model has been validated.(3) Design of an adaptive gateway discovery method. It adjusts gateway advertisement sending scope and interval to reduce network control overhead according to network real time status. In order to avoiding repeating transmit same message in network, which introduced massive unnecessary overhead, it controls the transmit authority to reduce the number of control messagees as more as possible. The simulation results show that this method owns large scale reduction in control overhead with a little average transmission delay as a price.(4) Design of a MANET accessing Internet routing algorithm based on mobile agent. The algorithm does not pre-set gateways. It provides accessing service by adding gateway function to ordinary MANET nodes using code migration function of mobile agent and achieves the aim of controlling gateway neatly. At the same time, the algorithm can recuce the number of control packets effectively by using mobile agents to collect and disseminate information. The simulation results show that, this algorithm can reduce network overhead obviously on the premise of guaranteeing intrinsic accessing performance, which validates the effectiveness of the algorithm.(5) According to the similar between ant searching path and mobile node searching gateway, and using pheromone's update process in ant colony algorithm for reference, an accessing network overhead control algorithm, which based on gateway pheromone, is proposed. This algorithm uses information carried in RREP (Route Reply) packet to update gateway pheromone. When the node searches available route, it computes transmission probability according to the pheromone density on the link, link bandwidth and delay. Then the node transmits the RREQ (Route Request) packet. Furthermore, it simulates pheromone's volatilization process in ant colony algorithm and adjusts gateway pheromone locally, which is more congruous to the network characteristics. The algorithm uses the method of keeping and updating gateway pheromone instead of conventional broadcasting gateway advertisement method, which avoids flooding overhead introduced from the process of broadcasting gateway advertisement. The analysis and simulation results indicate that this algorithm can reduce normalized routing overhead and improve packet delivery ratio at the condition of guaranteeing certain average end-to-end packet delivery latency. At the same time, it can work independently with bottom protocols, so it has reference value to specific application of MANET accessing Internet, which has limitation in hardware and link function.