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UBC Theses and Dissertations

Performance evaluation of the movable-slot TDM protocol and its application in metropolitan area networks Hon, Lenny Kwok-Ming


Movable-slot time-division multiplexing (MSTDM) is a medium access control protocol for the integration of voice and data in local area networks. In this thesis, the performance of this protocol is evaluated through mathematical analysis and simulation. Its application in metropolitan area networks is also studied. For the performance evaluation, a non-pre-emptive priority queuing model is first proposed for analysing the mean data delay characteristic of the slotted non-persistent carrier-sense multiple access with collision detection (CSMA/CD) protocol. Then this analytical approach is extended to the slotted MSTDM protocol with non-persistent data packet transmission, and its mean data delay performance is obtained. Numerical results from the analysis are shown and discussed. Moreover, simulation study of the MSTDM protocol is performed. Through the simulation results, the effects of this protocol on the general delay performances of voice and data are discussed. It is found that if first voice packets, which are generated at the beginning of talkspurts, are given a shorter retransmission delay than data packets, the channel-acquisition delay for voice sources can be reduced without sacrificing the data delay performance significantly. The simulation results are also used to verify the analytical results. As the comparisons show, the accuracy of the analysis is high although it is based on a simple approximate model. For the application of MSTDM in metropolitan area networks, a scheme which alleviates the distance and transmission rate constraints associated with this protocol is described. The approach is to divide the stations in a large area into regional groups, each operating in a different frequency band. Each group forms a sub-network which is part of the metropolitan area network. An access protocol is proposed for interconnecting these sub-networks. Also an analysis which finds the optimum number of sub-networks for interconnection is presented. The criterion is to minimize the mean data delay for communications in a sub-network.

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