|Asynchronous transfer mode over satellite
|Asynchronous transfer mode
Hong Kong Polytechnic University -- Dissertations
|vi, 89,  leaves : ill. ; 30 cm
|This dissertation reviews the major issues affecting the use of geostationary satellite systems to provide ATM (Asynchronous Transfer Mode) services. They include transmission link quality, error characteristics, propagation delay and bandwidth sharing. Among these, bandwidth sharing is studied in details. A dynamic bandwidth allocation scheme is proposed and analyzed in this dissertation, supported with simulations under various traffic environments. This scheme is designed using Agnelli (1990a) and Delli Priscoli (1989b) as the basic framework with a modification made to the bandwidth allocation algorithm. Agnelli (1990a) and Delli Priscoli (1989b) propose to allocate bandwidth dynamically, in a distributed processing manner, according to the demand of each terminal. This dissertation improves their algorithm by sharing the unclaimed bandwidth among all the terminals. This scheme is known as DR-TDMA (Distributed Reservation TDMA) which significantly improves the performance of the system under light loading. A further enhancement is proposed in this dissertation which gives priority to the terminal with the greatest reservation request. It further reduces the average access delay of highly bursty traffic considerably. This is known as DR-Q TDMA (Distributed Reservation/Long-queue favoured TDMA). A third scheme, which assigns fixed bandwidth to each terminal and ignores changes in traffic, is also simulated, as a comparison to the above newly designed schemes. By sharing unclaimed bandwidth among terminals, DR significantly reduces the latency of cell transmission during light load and at the same time provides dynamic responsiveness, flexibility and efficiency of dynamic access at moderate to high load. DR-Q is designed to improve the performance of bursty traffic. It maintains the advantages of DR and lowers the latency of a bursty source significantly by taking advantage of other less bursty sources in the system. The behaviours of the schemes under a wide range of traffic environments are analyzed in details. The discussions provide the groundwork to further refine the algorithm and adapt the schemes to produce a practical ATM satellite system.
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