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This thesis has to do with certain fundamental queues that are well established as models for delay in simple packet-switching concentrators and networks. We first revisit the single server queue with Poisson arrivals and general independent service times. We then work out a complete delay analysis for a traffic concentrating tandem network of queues with deterministic service and batch Poisson sources connected to every node; this is the most comprehensive analysis available for a network which is not of Jackson type. We also show how to (partially) extend the analysis to a concentrating tree network, and to an arrival process somewhat more general that batch Poisson. / The two parts of the thesis have a close methodological relationship. Our contribution in both cases is to rederive certain known results, and to produce a variety of new ones, using techniques that are essentially qualitative. Our particular view of the stochastic processes in question is guided by a very special queue discipline, namely Last Come First Served preemptive resume; by identifying certain structural features of the sample paths, one can read, almost without calculation, a host of statistics of common interest. The LCFS preemptive resume discipline also enables us: (i) to strengthen the connection between the single server queue with general independent service times and interarrival times, and the fluctuation theory of random walks; (ii) to strengthen the connection between the queue with Poisson arrivals and branching processes.

Schedulers in optical switches are still electronic, the performance of these units has a significant impact on the performance of the network and could form a bottleneck in high speed networks, such as AAPN. Four time-slotted scheduling algorithms are investigated in this study, PIM, iSlip, PHM and Adapted-SRA. The study addresses the performance of AAPN for each of the algorithms, and evaluates the hardware complexity, estimating the running time of the algorithms. Performance measures were collected from an OPNET model, designed to emulate AAPN. Furthermore, hardware complexity and timing constraints were evaluated through hardware simulations, for iSlip, and through analysis for the rest of the algorithms. iSlip confirmed its feasibility by meeting the 10us timing constraint set by AAPN. The study revealed the superiority of iSlip and PHM over PIM and Adapted-SRA.

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The advance of multi-media applications has prompted researchers to undertake the task of finding suitable methods to carry multi-media data through ad-hoc wireless networks. The task of finding suitable methods for this particular application is rather difficult to achieve since ad-hoc networks exhibit highly dynamic link connectivity and are prone to error from radio transmission through the physical environment. In addition to all of the above, the sole concern of the current protocols is the connectivity of wireless nodes. The connectivity is maintained by a set of network messages. Communicating nodes in an ad hoc network select only the shortest available path. In the event of traffic congestion, packets are simply dropped from the queue. The notion of multi-path scheme has been investigated by other researchers, and DSR is still the most popular choice to implement network adaptation for multi-media traffic. Most of the existing network adaptation methods however lack the fairness in multi-path selection. A new network adaptation module with the aid of fuzzy logic and depth first search can provide a better guarantee in packet delivery and better use of network resources. In addition to the new module, a comparative study has been done in this project for suitable update methods for the unused multi-paths. This is a weakness in the use of DSR multi-path scheme because DSR only updates active traffic paths. The simulation results in this thesis show that the new network adaptation module is capable of improving the performance of the network communications. / Thesis ([MEng(ElectricalEngineering)])--University of South Australia, 2004.

Thesis (PhD)--University of South Australia, 1994