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No description available.

Opportunistic Beamforming is a promising scheme with potential usage in a variety of applications ranging from cellular audio/video communications to wireless mesh-networks. However, some aspects in this scheme are open to further improvements, such as effective quality of service (QoS) provisioning, and efficient handling of sparse/realistic networks. We focus on the downlink channel of a multi-rate time-division multiplexing MISO (multiple input single output) point-to-multi-point wireless communication system, and design a cross-layer scheme. We employ a two-stage opportunistic scheduler. The scheduler receives channel state information in the form of SNR (signal to noise ratio) measurements from each terminal, and schedules one terminal in each time-slot. At the first stage in a time-slot a terminal is chosen, and our gradient descent channel estimator finds an estimation of its channel vector. Then the beamformer produces a beamforming vector in an adjacent pilot channel, or in the first part of the time-slot in the data channel. Our beamforming is based on the estimation of the channel, as opposed to the random beamformer used in the opportunistic beamforming. Each terminal measures its perceived SNR even when the channel is assigned to another terminal, and sends this information back to the basestation subject to a feedback-reduction policy. The scheduler uses the new channel state information for its second stage and assigns a terminal for the succeeding time-slot. The channel estimation procedure uses the reported SNRs for each terminal, which is a significantly lower feedback rate than the amount required for coherent beamforming. Our approach efficiently handles sparse/realistic networks, and also provides a better QoS than the opportunistic beamforming scheme. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2007-06-30 07:00:20.468

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A study of the minimum tooling requirements and strategies for efficient operation of Flexible Manufacturing Systems, FMS's, in Assembly set Production, ASP, i.e production in sets of parts to completely assemble one or more product units, is presented in this research work. The main investigating tool is a simulation model. With this model the tool groups to be loaded into machines and fixtured pallet requirements were studied in conjunction with two scheduling rules. One is a FCFS rule and the other is a new rule, called MRPAS, which schedules work on the basis of the number of parts still unfinished belonging to an Assembly Set. The results of the research work show that ASP can be efficiently carried out in FMS's. However this requires that a good system set-up and adequate operating strategies are used. In particular appropriate tooling levels and good tooling configurations,TC's, i.e. combinations of tools in groups to be loaded into the machines, must be established to achieve high FMS performance. Tooling combination and duplication heuristic rules and the simulation model can be used for achieving this aim. The heuristic approach is shown to be necessary due to the impossibility, in a reasonable time, of evaluating the performance of FMS's under the large number of alternative tooling configurations which are possible. The level of fixtured pallets used can also have a great influence on system performance. Appropriate levels of these resources to operate FMS's for given TC's can be established using the methodology developed in this work. It is also important that good scheduling rules are used. In the cases studied, the MRPAS rule produces the best performance expressed as the combination of FMS utilization and production of complete assembly sets. Moreover a very small assembly set batch size, ASBS, i.e. number of AS released together into the FMS, is likely to be preferable. In the cases studied an ASBS of one performed best overall.

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iv, 115 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1972) from the Dept. of Mathematics, University of Adelaide

Typescript (photocopy) / vii, 165 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Applied Mathematics, University of Adelaide, 1980