Optical buffers are essential components of future optical switches for resolving contentions among arriving packets. Currently, optical buffers are composed of Fiber Delay Lines (FDL). Unlike the conventional electronic buffer, optical buffer only has finite time resolution, which introduces a void period between two successive buffered packets. The void period leads to service interruptions and deteriorates the buffer performance. We develop a queueing system with exceptional service for the first packet in each busy period to model the buffer behavior. For the first time, the closed-form expressions of packet blocking probability and mean delay of optical buffer are derived. We show that the packet blocking probability can be minimized by finding the optimal FDL time granularity. This optimal granularity is neither sensitive to packet length distribution, nor sensitive to the buffer length, it is mainly determined by the traffic load. / Service interruption is a special case of varying service rate. A current trend in wireless communication is to enable devices to operate using many different transmission rates. This motivates us to develop the queueing models with varying service rate. We apply the continuous time Markov chain to characterize the service rate varying process, and develop a queueing system with Markov-modulated service rate. In this kind of problem, due to the complex interaction between the rate varying process and packet arrival process, it is hard to characterize the server state evolvement; this makes it difficult to get an analytical solution, even the server only has two service rates. To escape the trap, first, we develop a discrete time Markov chain to model the server state transition process, which makes our problem to be easily manipulated. Second, apart from the previous methods, we concentrate on the moments of the packet number in system. We find the recursive relationship between the moments of packet number, this fundamental relationship widely exists in the birth-death queue systems. Our results provide a new methodology to the design of communication systems with varying service rate. / This thesis is aimed to study the interaction between service interruption and the operation of communication systems, and develop analytical methods to help the design and optimization of communication systems with interrupted services. Our work are focused on two systems: optical buffer and wireless sensor network. The common ground of these two problems is they both present the features of service interruption. / Wireless sensor network is an ad hoc network consisting of hundreds of sensor nodes equipped with limited power sources, transmission range and functionality. A simple and effective way to save energy and prolong the network lifetime is to let the nodes interrupt their sensing and data transmission process, enter sleep mode randomly. However, sleep mode corresponds to low power consumption as well as to reduced network capacity, increased latency and slowed system response. We develop a queueing model with server shutting down in a varying neighborhood to model the behavior of sensor nodes, Combining the node queueing model and the network flow balance model, we construct an analytical framework to model the network performance, derive the network capacity, packet delivery delay and node responsive property. We also develop a node power consumption model, which takes the node sleep to active transition frequency into consideration. Our results demonstrate that the sleep/active dynamics produces the predominant impact on the average power consumption and packet delay, and properly choosing the time scale of sleep/active cycle is vital to design a power-efficient sensor network. / Liu Jianming. / "Apr. 2006." / Adviser: Tony Tong Lee. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6623. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 109-117). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_343791 |
| Date | January 2006 |
| Contributors | Liu, Jianming, Chinese University of Hong Kong Graduate School. Division of Information Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xiii, 117 p. : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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