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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

A comparison of timing methods in orthogonal frequency division multiplexing (OFDM) systems

Oz, Ersoy 09 1900 (has links)
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
12

Cooperative communications in wireless networks.

January 2006 (has links)
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
13

Performance analysis of resource sharing in wireless networks: analytical and empirical perspectives. / CUHK electronic theses & dissertations collection

January 2009 (has links)
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.
14

Characterizing the next generation wireless networks: capacity gain, backlog and delay. / 刻畫下一代無線網絡: 容量增益, 隊列長度和延遲 / CUHK electronic theses & dissertations collection / Ke hua xia yi dai wu xian wang luo: rong liang zeng yi, dui lie chang du he yan chi

January 2009 (has links)
First, we give the first formal study on stream control scheduling in wireless mesh networks with Multi-Input-Multi-Output (MIMO) antennas and study how much it can improve network capacity. We derive the upper bound of the optimal network capacity gain of stream control. We also propose an efficient stream control scheduling algorithm, GreedySC. Simulations show the network capacity of GreedySC is much larger than that of a previously proposed stream control scheduling algorithm, SCMA. / Second, we consider leveraging transmission power to improve the network capacity of wireless mesh networks. It is well-known that power control can improve network capacity significantly. However, recent works show conflicting results: network capacity may increase or decrease with higher transmission power under different scenarios. In this work, we give the first systematic study on this paradox. We prove that the the optimal network capacity is a non-decreasing function of higher transmission power. We also derive the upper bound of the optimal network capacity gain of power control. Finally, we give the reasons why network capacity may increase or decrease with higher transmission power in practice. Simulations verify our arguments. / The next generation wireless networks target at providing better quality of service for ubiquitous network access than nowaday wireless networks. Various technologies from the physical layer to the transport layer are proposed to realize this goal. A fundamental question is how to characterize the impact of a new technology on the performance of wireless networks, e.g., network capacity, backlog and delay. We propose to apply optimization theory for the network capacity characterization and apply stochastic network calculus for the backlog and delay characterization. However, the detailed characterization procedure depends on different problems. In this thesis, we first formally define network capacity, the (optimal) network capacity gain of a new technology, backlog and delay. Then we carry out systematic characterizations on the following three important issues in designing the next generation wireless networks. / Third, we take the first step to apply stochastic network calculus for the backlog and delay analysis of 802.11 wireless local networks. We prove the general stability condition of deriving stable backlog and delay for a wireless node. From this, we derive the specific stability condition of an 802.11 wireless node. Then we derive the stochastic service curve of an 802.11 node. Based on the service curve, we derive the backlog and delay bounds of the node. Simulations verify our analysis. / Wang, Yue. / Adviser: John C. S. Lui. / Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 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.
15

Characterizing interference in wireless mesh networks.

January 2007 (has links)
Hui, Ka Hung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 123-126). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction / Motivation --- p.1 / Chapter 2 --- Literature Review --- p.6 / Chapter 2.1 --- Introduction --- p.6 / Chapter 2.2 --- The Capacity-Finding Problem --- p.6 / Chapter 2.3 --- Interference Models --- p.8 / Chapter 2.4 --- Considering Interference in the Capacity-Finding Problem with Perfect Scheduling --- p.9 / Chapter 2.4.1 --- Conflict Graph --- p.10 / Chapter 2.4.2 --- Independent Set Constraints --- p.11 / Chapter 2.4.3 --- Row Constraints --- p.11 / Chapter 2.4.4 --- Clique Constraints --- p.12 / Chapter 2.4.5 --- Using the physical model --- p.13 / Chapter 2.5 --- Considering Interference in the Capacity-Finding Problem with Random Access --- p.15 / Chapter 2.6 --- Chapter Summary --- p.17 / Chapter 3 --- Partial Interference - Basic Idea --- p.18 / Chapter 3.1 --- Introduction --- p.18 / Chapter 3.2 --- Deficiencies in Previous Models --- p.18 / Chapter 3.2.1 --- Multiple Interferers --- p.19 / Chapter 3.2.2 --- Non-binary Behavior of Interference --- p.19 / Chapter 3.2.3 --- Impractical Perfect Scheduling --- p.21 / Chapter 3.3 --- Refining the Relationship between Interference and Throughput Degradation --- p.21 / Chapter 3.4 --- Capacity Gain by Exploiting Partial Interference . --- p.23 / Chapter 3.5 --- Chapter Summary --- p.28 / Chapter 4 --- Partial Interference in 802.11 --- p.29 / Chapter 4.1 --- Introduction --- p.29 / Chapter 4.2 --- The 802.11 Model --- p.29 / Chapter 4.2.1 --- Assumptions --- p.30 / Chapter 4.2.2 --- Transmission Probability Calculation --- p.31 / Chapter 4.2.3 --- Packet Corruption Probability Calculation --- p.34 / Chapter 4.2.4 --- Loading Calculation --- p.35 / Chapter 4.2.5 --- Summary --- p.36 / Chapter 4.3 --- Some Analytical Results --- p.37 / Chapter 4.4 --- A TDM A/CDMA Analogy --- p.40 / Chapter 4.5 --- Admissible (Stability) Region --- p.42 / Chapter 4.6 --- Chapter Summary --- p.44 / Chapter 5 --- Partial Interference in Slotted ALOHA --- p.45 / Chapter 5.1 --- Introduction --- p.45 / Chapter 5.2 --- The Finite-Link Slotted ALOHA Model --- p.46 / Chapter 5.2.1 --- Assumptions --- p.46 / Chapter 5.2.2 --- Stability of Slotted ALOHA --- p.46 / Chapter 5.3 --- Stability Region of 2-Link Slotted ALOHA under Partial Interference --- p.47 / Chapter 5.4 --- Some Illustrations --- p.50 / Chapter 5.5 --- Generalization to the M-Link Case --- p.53 / Chapter 5.6 --- Chapter Summary --- p.58 / Chapter 6 --- FRASA --- p.59 / Chapter 6.1 --- Introduction --- p.59 / Chapter 6.2 --- The FRASA Model --- p.60 / Chapter 6.3 --- Validation of the FRASA Model --- p.66 / Chapter 6.3.1 --- Simulation Results --- p.66 / Chapter 6.3.2 --- Comparison to Previous Bounds --- p.72 / Chapter 6.4 --- Convex Hull Bound --- p.75 / Chapter 6.5 --- p-Convexity --- p.80 / Chapter 6.6 --- Supporting Hyperplane Bound --- p.86 / Chapter 6.7 --- Extension to Partial Interference --- p.89 / Chapter 6.7.1 --- FRASA under Partial Interference --- p.90 / Chapter 6.7.2 --- Convex Hull Bound --- p.93 / Chapter 6.7.3 --- p-Convexity --- p.97 / Chapter 6.7.4 --- Supporting Hyperplane Bound --- p.101 / Chapter 6.8 --- Chapter Summary --- p.102 / Chapter 7 --- Conclusion and Future Works --- p.110 / Chapter 7.1 --- Conclusion --- p.110 / Chapter 7.2 --- Future Works --- p.111 / Chapter A --- Proof of (4.13) in Chapter 4 --- p.113 / Bibliography --- p.123
16

A wireless token ring approach for contention resolution in a wimax environment

Washington, Kyle. January 2006 (has links)
Thesis (M.S.)--State University of New York at Binghamton, Electrical Engineering Dept., 2006. / Includes bibliographical references.
17

Stretchable architectures for 3rd generation wireless networks

Lakkavalli, Shashidhar V. 02 May 2002 (has links)
Power is a valuable resource. It is invaluable when for mobile devices. Mobile devices, due to their mobility cannot get a continuous source of power and derive their power from a battery contained in them. The main consumer of power in the mobile is its transmitter. With a limited power capacity of the batteries, it is always desirable that the transmit power of the mobile be minimized. The aim of this thesis is to introduce a new architecture to minimize this problem. It is called as "Stretchable Architectures". The stretched architecture involves an intermediary between the Mobile Station and the Base Station to carry the call between them. This type of connection is called a Stretched connection. We explain the energy efficiency of a Stretched Connection when compared to a Direct connection between the Mobile Station and Base Station. We investigate the factors affecting a Stretched connection and propose different Stretchable Architectures, suitable for different applications. The "Stretched Architecture" is analyzed for the three 3G standards: Multi-carrier Direct Spread CDMA (CDMA2000), Wideband CDMA (WCDMA) and Time Division-CDMA (TD-CDMA). / Graduation date: 2002
18

A 2.4GHZ direct conversion mixer with offset cancellation

Schmidbauer, Hardy 27 February 2001 (has links)
Dynamic DC offset is one of the biggest problems preventing the implementation of single chip receivers. This thesis presents a 2.4GHz downconversion mixer designed to work with adaptive DC offset cancellation for a fully integrated direct conversion receiver. Offset can be removed by dynamically changing the PFET load bias in a Gilbert Cell type mixer. A dual-loop algorithm, which was developed in separate work, controls a current-steering DAC that dynamically changes the PFET load bias of the mixer. The mixer has a gain of 8dB, an IIP3 of l7dBm, and a noise figure of 15dB. In addition a CMOS RF Front-End incorporating the offset cancellation mixer is presented that meets the specifications for Bluetooth. / Graduation date: 2001
19

Wireless/mobile video delivery architecture

Sampath, Latha, January 2000 (has links) (PDF)
Thesis (M.S.)--University of Florida, 2000. / Title from first page of PDF file. Document formatted into pages; contains x, 78 p.; also contains graphics. Vita. Includes bibliographical references (p. 76-77).
20

Simulating and analyzing wireless railway control networks using NS-2 /

Craven, Paul Vincent. January 1900 (has links)
Thesis (Ph. D., Computer Science)--University of Idaho, March 11, 2009. / Major professor: Paul Oman. Includes bibliographical references (leaves 158-169). Also available online (PDF file) by subscription or by purchasing the individual file.

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