Modeling And Analysis Of Several Problems In Mobile Ad Hoc Network

A mobile ad hoc network (MANET) is an important project in the 4th generation mobile communication network and has become one of the hottest issues in wireless cmmunication technology fields. In this dissertation, we mainly study several problems in the fields of routing protocol performance parameters and quality of service (QoS) routing algorithm for a MANET. On one hand, we quantificationally analyze several key performance parameters of the MANET by establish the corresponding models. On the other hand, we solve the shortcut collision problem successfully. The dissertation includes the work as follows:Firstly, we present a random graph model with spatial reuse for a dense MANET which using directional antennas. The analytic formula of several important performance parameters for the MANET are obtained under the DSR routing protocol, such as the average flooding distance, the probability generating function of the flooding distance, the probability of a flooding route to be symmetrically valid, the average time to find a symmetrically valid route and the cost to successfully route a data packet to its destination. We compare the two models with spatial reuse and without spatial reuse by evaluating these parameters. It is shown that the spatial reuse model is much more effcctive in terms of the performance of the dense network with directional antenna, because the bigger is the degree of spatial reuse, the smaller is the average flooding distance. the more little are the delay of routing discovery and the cost of success routing.Secondly, by establishing a discrete time Markov model with spatial reuse for a MANET, we analyze the performance of the network under the AODV routing protocol. The average route length and the probability to communicate within a limited hop distance are obtained. Several performance parameters of the route discovery and route maintain process are analytically studied, such as the probability generating function and the expectation of the flooding distabce. the probability that a route is discovered by a query packet with a "hop limit", the probability that a request packet finds a valid route, the average time needed to discover a valid route and the cost to successfully route a data packet to its destination. Furthermore, we present a concrete example based on the transmitter characteristic of directional antennas and obtain the corresponding results.Thirdly, we mainly discuss the shortcut collision which is a special phenomenon in tie QoS routing for a MANET. We present a more precise definition based on the original definition. We further obtain a distributed bandwidth reservation algorithm for QoS routing protocol to solve the shortcut collision problem. The numerical analysis shows that the largest reservation bandwidth of our algorithm is very close to the largest bandwidth available in the MANET.The results studied in this dissertation are forward to be a frame of reference to design or to optimize a MANET.