Modeling And Analysis Of Network QoS And Performance Evaluation

The dissertation studies two kinds of problems in the fields of the QoS and performance evaluation in the communication networks. On one hand, by establishing the Markovian model, we analyze several performance parameters under difference network environments which using reactive protocol in the Ad Hoc networks. On the other hand, we study the delay control problem for the high rate real-time traffic flows and propose a novel and efficient traffic flow control method.About the Ad Hoc networks, the dissertation mainly covers the works as follows: By establishing a discrete time Markovian model for the Ad Hoc networks, we analyze several important network performance parameters including the probability that a particular node is in the vicinity of another node, the average neighbor number of the node and the probability of a group of nodes which can construct a flooding path. In the dissertation, we also put forward a concrete construction method for the transition probability matrix and give the analytic formula for the parameter computation.We study the characteristic of the Route Discovery in the small-area Ad Hoc networks and construct the Sm-AHF model for the Route Discovery. Average flooding distance is the basic networks parameter used to evaluate the performance of the Route Discovery, so in this dissertation, we study it not only from theory but also from simulation. We give the theoretical formula for the conditional average flooding distance when the flooding distance is bounded. The simulator for the Sm-AHF model is also designed and implemented and the simulation results conform to the theoretical computation.By breaking the constraint of lack of spatial reuse in the small-area Ad hoc networks, a Ad hoc network is modelled so that the length of each link in the network is considered as a birth-death process, called n-SRBDM model, which allows spatial reuse n tunes in the floodings. We analyze the performance of the network based on the DSR(Dynamic Source Routing protocol), a famous reactive routing protocol. The performance parameters or characteristics of Route Discovery are studied such as the probability distribution or the expectation of the flooding distance, the probability that a route is discovered by a RREQ(route reqest) packet with a "hop limit", the probability that a RREQ packet finds a r-time-valid route or a symmetrical-valid route, and the average time needed to discover a valid route. For Route Maintenance, some route parameters are introduced and studied such as the average frequency of route recovery and the average time for a route to be valid. Giving the evaluation of these parameters, we have the performance comparison between the models allowing spatial reuse and no spatial reuse, which proves that the former is much more effective then the latter in route routing.About the delay control of the communication, the dissertation mainly includes the following works:In order to adjust and shape the real-time traffic flows for the purpose of reducing the network delay, we propose a simply and effective self-adaptive traffic flow control algorithm and design a (a, p, A)-regulator. We study the regulating characteristic of the (a, p, A)-regulator and give a group of analytical formulas used to optimize the regulating parameter, especially the critical rate p* is obtained in this dissertation, and by using it, we can make the regulator to work in the most reasonable state. We also analyze theoretically the upper bound of the delay for the data bit in the single (, , )-regulator and single regulated Multiplexer(including the general Multiplexer and LFCFS Multiplexer), and compare the delay bound with using the traditional (, )-regulator's.We further study the delay problem for the real-time traffic flows in the circle networks and multistage networks. When the (, , )-regulator is used in the general Multiplexer and LFCFS Multiplexer, the unique existing of the critical rate p* of the circle networks and multistage networks, the upper bound of the delay and the comparison resul...