4 research outputs found

    On timeslots scheduling algorithms of wireless ad hoc network.

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    Chau, Wai Shing.Thesis submitted in: October 2007.Thesis (M.Phil.)--Chinese University of Hong Kong, 2008.Includes bibliographical references (leaves 64-66).Abstracts in English and Chinese.Abstract --- p.iAcknowledgement --- p.iiChapter 1 --- Introduction --- p.1Chapter 1.1 --- Ad hoc network --- p.1Chapter 1.2 --- Outline of the thesis --- p.3Chapter 2 --- Background Study --- p.4Chapter 2.1 --- Multiple Access Control (MAC) --- p.4Chapter 2.1.1 --- Time Division Multiple Access (TDMA) --- p.5Chapter 2.1.2 --- Spatial TDMA (STDMA) --- p.5Chapter 2.2 --- Interference Models --- p.6Chapter 2.2.1 --- Primary and Secondary Interferences --- p.6Chapter 2.2.2 --- Interference-based Model --- p.7Chapter 2.2.3 --- Graph-based Model --- p.7Chapter 2.3 --- Scheduling in Graph-based Model --- p.8Chapter 2.3.1 --- Conflict Graph --- p.9Chapter 3 --- Scheduling Algorithms in Ring Networks --- p.11Chapter 3.1 --- Problem Formulation --- p.12Chapter 3.2 --- Regular Sequences --- p.14Chapter 3.3 --- Scheduling in Ring Networks with Even-number of Edges --- p.22Chapter 3.4 --- Scheduling in Ring Networks with an Odd-number of Edges --- p.26Chapter 3.4.1 --- Scheduling by Reducing a Ring Network with an Odd-number of Edges into a Ring- Network with an Even-number of Edges --- p.28Chapter 3.4.2 --- Scheduling by Shifting the Regular Sequences --- p.32Chapter 3.5 --- Discussion --- p.42Chapter 3.6 --- Conclusion --- p.42Chapter 4 --- Distributed Scheduling Algorithm for Ad Hoc Network --- p.43Chapter 4.1 --- Problem Formulation --- p.44Chapter 4.2 --- Distributed Scheduling Heuristic Algorithm --- p.44Chapter 4.2.1 --- Weight functions --- p.44Chapter 4.2.2 --- Main Algorithm --- p.46Chapter 4.3 --- Centralized algorithm on a chain network --- p.49Chapter 4.4 --- Performance of the Algorithm on Chain Network --- p.50Chapter 4.4.1 --- Comparison 1 --- p.51Chapter 4.4.2 --- Comparsion 2 --- p.52Chapter 4.4.3 --- Comparsion 3 --- p.53Chapter 4.5 --- Performance of the Algorithm on Random Conflict graph --- p.55Chapter 4.6 --- Discussion --- p.57Chapter 4.7 --- Special Graphs --- p.58Chapter 4.8 --- Conclusion --- p.61Chapter 5 --- Conclusion --- p.62Bibliography --- p.6

    CROSS-LAYER SCHEDULING PROTOCOLS FOR MOBILE AD HOC NETWORKS USING ADAPTIVE DIRECT-SEQUENCE SPREAD-SPECTRUM MODULATION

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    We investigate strategies to improve the performance of transmission schedules for mobile ad hoc networks (MANETs) employing adaptive direct-sequence spread-spectrum (DSSS) modulation. Previously, scheduling protocols for MANETs have been designed under the assumption of an idealized, narrowband wireless channel. These protocols perform poorly when the channel model incorporates distance-based path loss and co-channel interference. Wideband communication systems, such as DSSS systems, are more robust in the presence of co-channel interference; however, DSSS also provides multiple-access capability that cannot be properly leveraged with a protocol designed for narrowband systems. We present a new transmission scheduling protocol that incorporates link characteristics, spreading factor adaptation, and packet capture capability into scheduling and routing decisions. This provides greater spatial reuse of the channel and better adaptability in mobile environments. Simulation results demonstrate the merits of this approach in terms of end-to-end packet throughput, delay, and completion rate for unicast traffic. We also discuss two variations of the protocol: one provides a method for enhancing the network topology through exchange of local information, and the other leverages multi-packet reception (MPR) capability to enhance the network topology. We show that each approach is useful in networks with sparse connectivity. We conclude by studying the capacity of the networks used in previous sections, providing insight on methods for realizing further performance gains

    Application of genetic algorithm to wireless communications

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    Wireless communication is one of the most active areas of technology development of our time. Like all engineering endeavours, the subject of the wireless communication also brings with it a whole host of complex design issues, concerning network design, signal detection, interference cancellation, and resource allocation, to name a few. Many of these problems have little knowledge of the solution space or have very large search space, which are known as non-deterministic polynomial (NP) -hard or - complete and therefore intractable to solution using analytical approaches. Consequently, varied heuristic methods attempts have been made to solve them ranging from simple deterministic algorithms to complicated random-search methods. Genetic alcyorithm (GA) is an adaptive heuristic search algorithm premised on the evolutionary ideas of evolution and natural selection, which has been successfully applied to a variety of complicated problems arising from physics, engineering, biology, economy or sociology. Due to its outstanding search strength and high designable components, GA has attracted great interests even in the wireless domain. This dissertation is devoted to the application of GA to solve various difficult problems spotlighted from the wireless systems. These problems have been mathematically formulated in the constrained optimisation context, and the main work has been focused on developing the problem-specific GA approaches, which incorporate many modifications to the traditional GA in order to obtain enhanced performance. Comparative results lead to the conclusion that the proposed GA approaches are generally able to obtain the optimal or near-optimal solutions to the considered optimisation problems provided that the appropriate representation, suitable fitness function, and problem-specific operators are utilised. As a whole, the present work is largely original and should be of great interest to the design of practical GA approaches to solve realistic problems in the wireless communications systems.EThOS - Electronic Theses Online ServiceBritish Council (ORS) : Newcastle UniversityGBUnited Kingdo

    Multiscale Modeling of Inter-Vehicle Communication

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    Within this thesis, different modeling approaches at different scales in the domains of urban radio propagation, decentralized channel coordination, and information dissemination in inter-vehicle communication networks are investigated. The contributions reveal the suitability of existing models for network-oriented research, propose a novel information-centric modeling approach, and identify characteristics of inter-vehicle communication systems which determine key dependability aspects
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