The performance of space-time block codes in providing transmit diversity is severely degraded when strong localized interference is present. This problem is addressed by investigating a recently proposed coherent space-time block code decoding algorithm for unknown interference suppression. The algorithm assumes a Gaussian noise and interference approximation and is based on a cyclic-based maximum-likelihood estimation technique (CML). In this thesis, simulations are done applying CML in a coherent system with unstructured interference to validate previous work. An extension of these results is obtained by examining factors that affect CML performance and modifying CML for use in a noncoherent system. To improve bit error rate performance, a turbo code for channel coding was added to both systems. This addition required the development of reliability metrics for soft-information transfer between the space-time block code detector and the turbo code decoder. Significant coding gains exceeding 8dB at a bit error rate of are achieved for the turbo-coded system when compared to that of an uncoded system.

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A mobile ad hoc network (MANET) is a collection of mobile nodes that form a wireless network without the use of a fixed infrastructure or centralized administration, and every node acts as a host as well as a router. The topology of an ad hoc network changes frequently and unpredictably. The mobile nature and dynamic topology of MANETs make it very difficult to provide Quality-of-Service (QoS) assurance in such networks. Considering the limited bandwidth and battery power, finding routes that satisfy the bandwidth constraint of applications is a significant challenge. Ad hoc on-demand distance vector routing (AODV) is an on-demand routing protocol that only provides best-effort routes. QS-AODV is proposed in this thesis. It is based on AODV and creates routes according to the QoS requirements of the applications. It is shown that QS-AODV provides performance comparable to AODV under light traffic. In heavy traffic, QS-AODV provides higher packet delivery ratios and lower routing overheads, at a cost of slightly longer end-to-end delays as the routes in QS-AODV are not always the shortest. The effects of network size and mobility on the performance of QSAODV are shown.

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Approved for public release; distribution is unlimited / Orthogonal frequency division multiplexing (OFDM) is being used by wireless local area network (WLAN) standards, such as IEEE 802.11a, and wireless metropolitan area network (MAN) standards, such as IEEE 802.16a. OFDM is a very efficient communications scheme for wireless ADHOC networks. However, the wireless environment causes inter-symbol interference (ISI) and inter-carrier interference (ICI). Estimating the starting point of an OFDM symbol must be handled efficiently and effectively to reduce the errors. OFDM must be time synchronized to prevent inter-symbol interference (ISI) and inter-carrier interference (ICI). Many techniques exist to realize timing synchronization in OFDM systems. In this thesis, the need for timing synchronization, the timing errors, and the performance of different techniques under a variety of mobile channel models (indoor and outdoor) are investigated, and simulation performance results for each technique under different channel models are presented. / First Lieutenant, Turkish Army

Zhang Jun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 82-92). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Multipath Fading Channels --- p.1 / Chapter 1.2 --- Diversity --- p.3 / Chapter 1.3 --- Outline of the Thesis --- p.6 / Chapter 2 --- Background and Related Work --- p.8 / Chapter 2.1 --- Cooperative Diversity --- p.8 / Chapter 2.1.1 --- User Cooperation --- p.9 / Chapter 2.1.2 --- Cooperative Diversity --- p.10 / Chapter 2.1.3 --- Coded Cooperation --- p.12 / Chapter 2.2 --- Information-Theoretic Studies --- p.13 / Chapter 2.3 --- Multihop Cellular Networks --- p.15 / Chapter 2.3.1 --- MCN: Multihop Cellular Network --- p.15 / Chapter 2.3.2 --- iCAR: Integrated Cellular and Ad Hoc Relaying Systems --- p.17 / Chapter 2.3.3 --- UCAN: Unified Cellular and Ad Hoc Network Architecture --- p.17 / Chapter 2.4 --- Wireless Ad Hoc Networks --- p.18 / Chapter 2.5 --- Space-Time Processing --- p.20 / Chapter 3 --- Single-Source Multiple-Relay Cooperation System --- p.23 / Chapter 3.1 --- System Model --- p.23 / Chapter 3.2 --- Fixed Decode-and-Forward Cooperation System --- p.26 / Chapter 3.2.1 --- BER for system with errors at the relay --- p.28 / Chapter 3.2.2 --- General BER formula for single-source nr-relay cooperation system --- p.30 / Chapter 3.2.3 --- Discussion of Interuser Channels --- p.31 / Chapter 3.3 --- Relay Selection Protocol --- p.33 / Chapter 3.3.1 --- Transmission Protocol --- p.34 / Chapter 3.3.2 --- BER Analysis for Relay Selection Protocol --- p.34 / Chapter 4 --- Multiple-Source Multiple-Relay Cooperation System --- p.40 / Chapter 4.1 --- Transmission Protocol --- p.41 / Chapter 4.2 --- Fixed Cooperative Coding System --- p.43 / Chapter 4.2.1 --- Performance Analysis --- p.43 / Chapter 4.2.2 --- Numerical Results and Discussion --- p.48 / Chapter 4.3 --- Adaptive Cooperative Coding --- p.49 / Chapter 4.3.1 --- Performance Analysis of Adaptive Cooperative Coding System --- p.50 / Chapter 4.3.2 --- Analysis of p2(2) --- p.52 / Chapter 4.3.3 --- Numerical Results and Discussion --- p.53 / Chapter 5 --- Cooperative Multihop Transmission --- p.56 / Chapter 5.1 --- System Model --- p.57 / Chapter 5.1.1 --- Conventional Multihop Transmission --- p.58 / Chapter 5.1.2 --- Cooperative Multihop Transmission --- p.59 / Chapter 5.2 --- Performance Evaluation --- p.59 / Chapter 5.2.1 --- Conventional Multihop Transmission --- p.60 / Chapter 5.2.2 --- Cooperative Multihop Transmission --- p.60 / Chapter 5.2.3 --- Numerical Results --- p.64 / Chapter 5.3 --- Discussion --- p.64 / Chapter 5.3.1 --- Cooperative Range --- p.64 / Chapter 5.3.2 --- Relay Node Distribution --- p.67 / Chapter 5.3.3 --- Power Allocation and Distance Distribution (2-hop Case) --- p.68 / Chapter 5.4 --- Cooperation in General Wireless Ad Hoc Networks --- p.70 / Chapter 5.4.1 --- Cooperation Using Linear Network Codes --- p.71 / Chapter 5.4.2 --- Single-Source Single-Destination Systems --- p.74 / Chapter 5.4.3 --- Multiple-Source Single-Destination Systems --- p.75 / Chapter 6 --- Conclusion --- p.80 / Bibliography --- p.82 / Chapter A --- Proof of Proposition 1-4 --- p.93 / Chapter A.1 --- Proof of Proposition 1 --- p.93 / Chapter A.2 --- Proof of Proposition 2 --- p.95 / Chapter A.3 --- Proof of Proposition 3 --- p.95 / Chapter A.4 --- Proof of Proposition 4 --- p.96

In the first part of this thesis, we focus on Drive-thru Internet systems where access points (AP) are placed on roadsides and vehicles passing through the coverage range of the APs can download data from them. The amount of data downloaded by an individual user is affected not only by the scheduling algorithms, but also by the user dynamics, i.e. the movement of the vehicles which impacts the amount of time the vehicle spends in the AP's coverage range, as well as the number of contending vehicles for the AP's resources. We have developed practical analytical models with tractable solutions to characterize the data communication performance of a vehicle in a Drive-thru Internet system. A distinctive aspect of our models is that they combined both vehicular traffic theory and wireless network/protocol properties to investigate the effects of various system parameters on a drive-thru vehicle's data communication performance. / In the second part of this thesis, we examine resource sharing in wireless sensor networks in terms of the node access to the wireless medium. We propose an energy-efficient TDMA-based MAC protocol that significantly reduces energy consumption in the network, while efficiently handling network traffic load variations and optimizing channel utilization through a timeslots stealing mechanism and timeslots reassignment procedure. We have analytically derived the average delay performance of our MAC protocol, with and without the timeslots stealing feature. Our delay model, validated via simulations, shows that the timeslots stealing feature can substantially improve the protocol throughput in situations with varying and asymmetric traffic patterns. Simulation results show that the timeslots reassignment procedure is efficient in handling the longer timescale changes in the traffic load, while the timeslots stealing mechanism is better in handling the shorter timescale changes in the traffic patterns. / In wireless networks, the efficient sharing of scarce wireless spectral resources is important in order to provide guaranteed Quality-of-Service (QoS) to the wireless users. The effectiveness of resource sharing schemes in wireless networks are often heavily influenced by different aspects of the system behavior, such as user mobility, traffic dynamics and practical realization constraints. In this thesis, using analytical modeling and empirical measurement techniques, we investigate the impact of these system behaviors on the performance of resource sharing in wireless networks. In particular, we investigate the dynamic sharing of an access point's bandwidth resources among moving vehicles in a vehicular network, the adaptive sharing of the medium access resources among nodes with different and varying traffic loads in a wireless sensor network, and the practical implementation of network resources sharing among users and applications with different QoS requirements in 3G wireless networks. / The third part of this thesis focuses on our empirical investigations into the performance of practical implementation of resource sharing schemes in 3G wireless networks. We have investigated the performance of multiple commercial 3G networks in Hong Kong, in terms of their ability to provide service guarantees to different traffic classes as well as the fairness of the radio-link scheduler in allocating the bandwidth resources to multiple data calls in a saturated network. We have also investigated the data throughput, latency, video and voice calls handling capacities of the 3G networks under saturated network conditions. Our findings point to the diverse nature of the network resources allocation mechanisms and the call admission control policies adopted by different operators. Our results also show that the 3G network operators seem to have extensively customized their network configurations in a cell-by-cell manner according to the individual site's local demographics, projected traffic demand and the target coverage area of the cell. As such, the cell capacity varies widely not only across different operators but also across different measurement sites of the same operator. / by Tan, Wee Lum. / Adviser: Wing Cheong Lau. / Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 129-138). / 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.