| It is a stirring time for Internet and wireless communication technologies' rapid development during the past ten years. In order to carry out the ideals of communication "whenever, wherever, whoever, whomever and whatever to communicate", Internet technology and wireless communication technology are destined to be combined together to make Wireless Internet. One can enjoy all kinds of network services no matter where he is and when it is. There will be not only traditional voice and data applications but also many attractive new applications running in Wireless Internet, such as mobile video, mobile e-business, mobile e-learning etc. To support these new applications, how to guarantee quality of service (QoS) is one of the key technologies of Wireless Internet.Wireless Local Area Networks (WLAN) and mobile cellular network are two main wireless transmission network technologies for Wireless Internet. The progress of mobile cellular network's evolving to 3G systems is much slower than people's expectation because of high cost, limited bandwidth and limited services. WLAN gains more and more market because it is cheap and easy to install at the same time. Nowadays WLAN has become a strong competitor against mobile cellular network. In the predicable future, mobile cellular network will still be the most popular technology for Wireless Internet. WLAN will serve as the complenment. Since the QoS mechanisms of mobile cellular network are better developed than that of WLAN, the thesis pays more attention on the QoS issues in WLAN.Firstly, the performance of legacy DCF (Distributed Coordination Function) is analyzed. An analytical model is created based on Markov Chain analysis. Then the new DCF protocol supporting service differentiation is investigated. The most important mechanism to support service differentiation is to make the MAC parameters configurable. There are two kinds of configurable parameters: random backoff process parameters and inter frame space (IFS) parameters.Configurable random backoff process parameters consist of initial contention window, maximum backoff stage number, etc. An analytical model is created for configurable random backoff process. Derived from the analytical model, relative differentiation can be easily achieved by varying the initial contention window size in random backoff process. In this case, the saturation throughput of a station can be shown to be approximately inversely proportional to the initial contention window size being used by that station. This conclusion is very important for designing an admission control method.Distributed Inter-frame Space (DIFS) is used to make service differentiation based on the analysis. It is much complicated to create the analytical model for this case. We propose a general method to get the analytical model and test it for the case of two service classes.The numerical results show that proposed analytical models for IEEE802.11 WLAN are correct. The analytical models provide quantitative relationships between MAC parameters and the QoS obtained by each station, which are used to design admission control method.At the end of the thesis, a QoS provisioning framework is proposed. Connection admission control algorithm, resource reservation method and bandwidth borrowing algorithm are combined to make a distributed QoS control framework. The framework provides two granularities for QoS guarantee, one to guarantee QoS of the whole cell statistically, and the other to guarantee QoS of individual connection.In short, the research on Wireless Internet is a hot area now. The network must provide good QoS before it gains commercial success. The research of the thesis is supported by National Natural Science Foundation (Investigation of Wireless Multimedia Techniques based on Multimedia Transmission Property, No. 60202005). The QoS technology of IEEE802.11 WLAN is deeply investigated. And the resource management in mobile cellular network is also covered. The analytical models and admission control method proposed in the thesis...
|
PDF Full Text Request