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Dissertations / Theses on the topic 'Wireless communication systems. Radio relay systems'

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Published: 4 June 2021
Last updated: 1 February 2022

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1

Dai, Gao Yang. "A novel soft forwarding technique for cooperative communication /." View abstract or full-text, 2010. http://library.ust.hk/cgi/db/thesis.pl?ECED%202010%20DAI.

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2

Xing, Chengwen, and 邢成文. "Linear minimum mean-square-error transceiver design for amplify-and-forward multiple antenna relaying systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44769738.

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3

Alotaibi, Faisal T. "Distributed space-time block coding in cooperative relay networks with application in cognitive radio." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10965.

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Spatial diversity is an effective technique to combat the effects of severe fading in wireless environments. Recently, cooperative communications has emerged as an attractive communications paradigm that can introduce a new form of spatial diversity which is known as cooperative diversity, that can enhance system reliability without sacrificing the scarce bandwidth resource or consuming more transmit power. It enables single-antenna terminals in a wireless relay network to share their antennas to form a virtual antenna array on the basis of their distributed locations. As such, the same diversity gains as in multi-input multi-output systems can be achieved without requiring multiple-antenna terminals. In this thesis, a new approach to cooperative communications via distributed extended orthogonal space-time block coding (D-EO-STBC) based on limited partial feedback is proposed for cooperative relay networks with three and four relay nodes and then generalized for an arbitrary number of relay nodes. This scheme can achieve full cooperative diversity and full transmission rate in addition to array gain, and it has certain properties that make it alluring for practical systems such as orthogonality, flexibility, low computational complexity and decoding delay, and high robustness to node failure. Versions of the closed-loop D-EO-STBC scheme based on cooperative orthogonal frequency division multiplexing type transmission are also proposed for both flat and frequency-selective fading channels which can overcome imperfect synchronization in the network. As such, this proposed technique can effectively cope with the effects of fading and timing errors. Moreover, to increase the end-to-end data rate, this scheme is extended for two-way relay networks through a three-time slot framework. On the other hand, to substantially reduce the feedback channel overhead, limited feedback approaches based on parameter quantization are proposed. In particular, an optimal one-bit partial feedback approach is proposed for the generalized D-O-STBC scheme to maximize the array gain. To further enhance the end-to-end bit error rate performance of the cooperative relay system, a relay selection scheme based on D-EO-STBC is then proposed. Finally, to highlight the utility of the proposed D-EO-STBC scheme, an application to cognitive radio is studied.
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4

Bui, Tuyen Thi Bich Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Superposition coding and modulation technique for wireless relay systems." Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/36827.

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Cooperative communication has been considered a promising technique used in wireless network to introduce diversity. Based on distributed architecture, cooperative network enables single-antenna users to share their information as a virtual multiple antenna array, which makes it possible to enhance the user data rates and obtain the diversity gain. Depending on the ways users share and process the information, practical user cooperation is mainly grouped in three modes: Amplify and Forward (AF), Decode and Forward (DF) and Compress and Forward (CF). Generally, DF outperforms AF in most practical implementation and is alternately the best by theoretical analysis. In particular, it is shown in theory that DF outperforms CF when the inter-user link is in good condition and vice versa. Considered as a capacity achieving approach, superposition encoding technique produces approximate Gaussian output signals. It is the power and spectral efficiency of the encoding scheme that make it useful for several wireless communication systems such as MIMO system, relay channels, and so on. The main goal of the thesis is to study how much superposition coding can help when applied to DF user cooperation. In particular, a new DF scheme with soft information relaying technique is proposed to overcome the performance degradation happening when the quality of the inter-user channel is bad. Based on the scheme, soft log-likelihood ratio (LLR) of the relay decoder is quantized, encoded, modulated by superimposition and then forwarded to the destination. The destination receiver employs an iterative superposition decoder and modified maximum a posteriori probability (MAP) decoder to recover the transmitted signal from the source. The performance of the scheme is evaluated by simulation. We show that the new scheme can significantly outperform the conventional DF scheme even in a poor inter-user channel. Furthermore, a new cooperative transmission strategy based on superposition and multiuser detection techniques is also investigated in the thesis. The new scheme is an improved DF scheme in which the two users take turns in being the relay for each other and the signal forwarded by each user is the superimposed data of both users. Here, interleavers are introduced in the superposition process as an efficient user separation tool, providing a large improvement in error performance and also facilitating the decoding process at the destination. Different types of iterative receivers are examined. The performance of the scheme is evaluated by simulation. It is shown that the new transmission scheme outperforms the conventional one in terms of both spectral and power efficiency.
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5

Negi, Ansuya. "Analysis of Relay-based Cellular Systems." PDXScholar, 2006. https://pdxscholar.library.pdx.edu/open_access_etds/2668.

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Relays can be used in cellular systems to increase coverage as well as reduce the total power consumed by mobiles in a cell. This latter benefit is particularly useful for mobiles operating on a depleted battery. The relay can be a mobile, a car or any other device with the appropriate communication capabilities. In thesis we analyze the impact of using relays under different situations. We first consider the problem of reducing total power consumed in the system by employing relays intelligently. We find that in a simulated, fully random, mobile cellular network for CDMA (Code Division Multiple Access), significant energy savings are possible ranging from 1.76 dB to 8.45 dB. In addition to reducing power needs, relays can increase the coverage area of a cell by enabling mobiles located in dead spots to place relayed calls. We note that use of relays can increase the useful service area by about 10% with real life scenarios. We observe that in heavy building density areas there is more need of relays as compared to low building density areas. However, the chance of finding relays is greater in low building density areas. Indeed, having more available idle nodes helps in choosing relays, so we conclude that unlike present day implementations of cellular networks, the base station should admit more mobiles (beyond the capacity of the cell) even if they are not placing calls since they can be used as relays. One constraint of using relays is the potential to add interference in the same cell and in neighboring cells. This is particularly true if the relays are not under power control. Based on our analysis, we conclude that in interference limited systems like CDMA the relays have to be under power control otherwise we will reduce the total capacity by creating more dead spots. Thus, we believe that either the base station should be responsible to allocate relays or relays should be provided with enough intelligence to do power control of the downlink. Finally, we show how utility of data services can be increased by use of relays.
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6

Zhang, Jin. "Relay and routing selection in relay-based wireless networks /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CSED%202009%20ZHANG.

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7

Caffery, James Joseph Jr. "Wireless location in CDMA cellular radio systems." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/15504.

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8

Alves, Hirley. "On the performance analysis of full-duplex networks." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1253.

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Nesta tese estudamos redes cooperativas em modo de operação Full-Duplex (FD). Para tanto, usamos conceitos de teoria da informação e da comunicação, além de estatística aplicada. Assim, fornecemos uma extensa análise de desempenho de sistemas cooperativos em modo FD. Além disso, demonstramos que a operação de relays em modo FD é possível, mesmo sofrendo intensos níveis de auto-interferência. Mostramos também sua aplicação em diversos cenários. Ademais, os resultados obtidos através deste trabalho servem como referência para o design e desenvolvimento de futuras tecnologias de comunicação sem-fio. Primeiramente, contribuímos com uma extensa revisão do estado da arte em comunicações em modo FD, especificamente relays FD, e além disto revisitamos as principais propriedades de esquemas de comunicação cooperativa. Analisamos de maneira extensiva o desempenho de esquemas com relays FD em ambientes com desvanecimento do tipo Rayleigh em termos probabilidade de falha de comunicação, vazão e eficiência energética. Além de todo arcabouço matemático introduzido nesta tese, também identificamos os casos em que sistemas cooperativos em mode Half-Duplex (HD) podem ser vantajosos comparados aos esquemas FD com auto-interferência. Assim, discutimos as relações de custo-benefício entre esquemas HD e FD e entre vazão e eficiência energética. A seguir, elaboramos o modelo estudado e estendemos os resultados iniciais para incorporar os casos com modelos mais gerais de desvanecimento, conhecidos como Nakagami-m. Estes resultados auxiliam na compreensão dos efeitos da auto-interferência residual e linha de visada em sistemas com relays FD. Por fim, contribuímos também com uma análise de desempenho de sistemas cooperativos seguros. Para tanto, usamos ferramentas da teoria da informação para aumentar a privacidade e confidencialidade da comunicação em canais sem-fio. Sendo assim, fornecemos um extenso arcabouço matemático para canais com desvanecimento composto. Além disto, demonstramos que, mesmo sofrendo forte auto-interferência, comunicação segura com relays FD pode também ser obtida, uma vez que segurança perfeita pode ser obtida.
In this thesis we study Full-Duplex (FD) cooperative networks from different perspectives, using concepts of information theory, communication theory and applied statistics. We provide a comprehensive performance analysis of cooperative communications systems operating with FD relays. We demonstrate that FD relaying is feasible even when experiencing strong self-interference, and we show its application under different scenarios. More importantly, the results attained through this work serve as a benchmark for design as well as deployment of current and future wireless communications technologies. Our first contribution is a comprehensive overview of the state-of-the-art on FD communications, more specifically on FD relaying, and we revisit some of the main properties of cooperative schemes. Another contribution comes from an extensive analysis of outage probability, throughput and energy efficiency of FD relaying over Rayleigh fading channels. Besides the mathematical framework introduced herein, we also show that in some cases cooperative Half-Duplex (HD) schemes achieve better performance than FD relaying with self-interference. Therefore, we draw a discussion on the trade-offs between HD and FD schemes as well as between throughput and energy efficiency. Then, we investigate the performance of FD relaying protocols under general fading settings, namely Nakagami-m fading. Our findings allow a better understanding of effects of the residual self-interference and line-of-sight on a FD relaying setup. Our final contribution lies on the performance analysis of secure cooperative networks relying on information theoretical metrics to provide enhanced privacy and confidentiality to wireless networks. Thus, we provide a comprehensive mathematical framework for composite fading channels. Even though experiencing strong self-interference, we demonstrate that FD relaying is feasible also under secrecy constraints, thus perfect secrecy can be achieved.
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9

Zhang, Shunqing. "Cooperative relay in the next generation wireless networks /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20ZHANGS.

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10

Liu, Yi. "The performance of future wireless communication systems." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:a2f0b75e-3b0d-406e-af1b-6c5038c18fae.

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Multimedia services provided through wireless networks, such as mobile television and video calls, have recently attracted great attention. These systems require higher data rates, better communication quality, and wider channel bandwidth compared with traditional wireless network services, such as voice calling and text messaging. In response to these demands, multiple-input multiple-output (MIMO) employing multiple antennas at both transmitter and receiver, has been investigated in recent years. Nevertheless, the major impediment in MIMO based wireless systems is the cost of the hardware due to the requirement of the complete radio frequency (RF) chain for each transmit and receive path. One technique named antenna subset selection has been proposed which can reduce the hardware complexity, for example, provide and smaller number of RF chains which are reconfigurable to serve multiple antennas, but retain good communication performance, such as increasing data rates and improving communication quality. On the other hand, network service providers have in recent years established wideband communication systems in order to provide more services and higher bandwidth to customers. However, this development lowers the communication link quality, since signals transmitted in wideband communication systems suffer frequency-selective fading. In order to reduce the fading, orthogonal frequency division multiplexing (OFDM) as a potential infrastructure in the fourth generation mobile communication networks is developed. Referring to the cost-performance ratio, an attractive future wireless system named antenna selection based MIMO-OFDM is considered to be widely utilized in civil wireless communications in near future. The working theory of antenna selection based MIMO-OFDM systems can be simply represented as that a data stream at each selected transmit/receiver antenna is sent/receive over a number of narrow band orthogonal subcarriers. This thesis addresses analysis of wireless channel and performance investigation of future wireless communication systems, such as MIMO and OFDM structures. Moreover, a novel significantly low computational complexity algorithm is introduced in this thesis, which is proposed for antenna selection MIMO-OFDM systems on the basis of multiple selection criteria. It is shown that the proposed selection algorithm clearly reduces the computational complexity load of the selection process and efficiently selects the optimum antenna subset of antenna selection MIMO-OFDM systems. The thesis concludes by outlining the advantage of the proposed antenna selection technique and points out its potential role in future wireless communications.
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11

Pratt, Jason Michael. "A software defined radio for research into cognitive radio." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Pratt2_09007dcc8049b35e.pdf.

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Thesis (M.S.)--University of Missouri--Rolla, 2007.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 7, 2007) Includes bibliographical references (p. 171-173).
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12

Thavarajah, Arunasala Iyer. "A study of fixed channel assignment algorithms for cellular mobile radio systems." Thesis, Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21241144.

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13

Kwon, Bongkyoung Kwon. "Adaptive frame structure and OFDMA resource allocation in mobile multi-hop relay networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31818.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Dr. John A. Copeland; Committee Member: Dr. George F. Riley; Committee Member: Dr. Henry L. Owen; Committee Member: Dr. Mary Ann Ingram; Committee Member: Dr. Patrick Traynor. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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14

Haines, D. M. "A study of novel receiver architectures for future communication systems." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282902.

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15

Xing, Zitong. "A dynamic radio channel allocation scheme for WLANs." Diss., Online access via UMI:, 2005.

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16

Lim, Christopher. "Optimizing access radio in multi-radio mesh network /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CSED%202009%20LIM.

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17

Wang, Xufang. "Multiresolution joint source and channel coding for wireless communications /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23340113.

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18

Erkal, Hakan. "Optimization Of Energy Harvesting Wireless Communication Systems." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613937/index.pdf.

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In an energy harvesting communication system, energy is derived from outside sources and becomes partially available at different points in time. The constraints induced by this property on energy consumption plays an active role in the design of efficient communication systems. This thesis focuses on the optimal design of transmission and networking schemes for energy harvesting wireless communication systems. In particular, an energy harvesting transmitter broadcasting data to two receivers in an AWGN broadcast channel assuming that energy harvests and data arrivals occur at known instants is considered. In this system, optimal packet scheduling that achieves minimum delay is analyzed. An iterative algorithm, DuOpt, that achieves the same structural properties as the optimal schedule is proposed. DuOpt is proved to obtain the optimal solution when weaker user data is ready at the beginning. A dual problem is defined and shown to be strictly convex. Taking advantage of the dual problem, uniqueness of the solution of the main problem is proved. Finally, it is observed that DuOpt is almost two orders of magnitude faster than the SUMT (sequential unconstrained minimization technique) algorithm that solves the same problem.
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19

Kim, Hyung Joon. "Multi-standard radio transceiver architectures and radio frequency front-end design." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1110399471.

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Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xv, 128 p.; also includes graphics (some col.). Includes bibliographical references (p. 125-128). Available online via OhioLINK's ETD Center
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20

Karlsson, Magnus. "Ultra-wideband Antenna and Radio Front-end Systems." Doctoral thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10338.

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The number of wireless communication applications increase steadily, leading to the competition for currently allocated frequency bands. Pressure on authorities around the world to permit communications in higher and wider frequency ranges to achieve higher wireless capacity than those existed in the past has resulted in several new specifications. The federal communication commission (FCC) in USA has unleashed the band 3.1-10.6 GHz for ultra-wideband radio (UWB) communications. The release has triggered a worldwide interest for UWB. Other regulatory instances throughout the world have issued use of UWB techniques as well. Capacity issues in form of data rate and latency have always been a bottleneck for broadened wireless-communication usages. New communication systems like UWB require larger bandwidth than what is normally utilized with traditional antenna techniques. The interest for compact consumer electronics is growing in the meantime, creating a demand on efficient and low profile antennas which can be integrated on a printed circuit board. In this thesis, some methods to extend the bandwidth and other antenna parameters associated with wideband usages are studied. Furthermore, methods on how to enhance the performance when one antenna-element is not enough are studied as well. The principle of antenna parallelism is demonstrated using both microstrip patch antennas and inverted-F antennas. Several techniques to combine the antennas in parallel have been evaluated. Firstly, a solution using power-splitters to form sub-arrays that covers one 500-MHz multi-band orthogonal frequency division multiplexing (OFDM) UWB is shown in Paper I. It is then proposed that the sub-bands are selected with a switching network. A more convenient method is to use the later developed frequency multiplexing technique as described in Paper V and VIII. Using the frequency multiplexing technique, selective connection of any number of antennas to a common junction is possible. The characteristic impedance is chosen freely, typically using a 50-Ω feed-line. Secondly, in Paper VIII a frequency-triplexed inverted-F antenna system is investigated to cover the Mode 1 multi-band UWB bandwidth 3.1-4.8 GHz. The antenna system is composed of three inverted-F antennas and a frequency triplexer including three 5th order bandpass filters. In Paper VI a printed circuit board integrated-triplexer for multi-band UWB radio is presented. The triplexer utilizes a microstrip network and three combined broadside- and edge-coupled filters. The triplexer is fully integrated in a four metal-layer printed circuit board with the minimum requirement on process tolerances. Furthermore, the system is built completely with distributed microstrips, i.e., no discrete components. Using the proposed solution an equal performance between the sub-bands is obtained. Finally suitable monopoles and dipoles are discussed and evaluated for UWB. In Paper X circular monopole and dipole antennas for UWB utilizing the flex-rigid concept are proposed. The flex-rigid concept combines flexible polyimide materials with the regular printed circuit board material. The antennas are placed entirely on the flexible part while the antenna ground plane and the dipole antenna balun are placed in the rigid part.
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21

Chek, Cho-hoi Michael, and 戚祖凱. "Coexistence techniques for heterogeneous mobile devices operating in uncoordinated radio spectrum." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29330725.

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22

Zhu, Ming. "High-capacity communication systems using advanced optical and wireless technologies." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53525.

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The increasing traffic demand from the use of 3G/4G, streaming, and other broadband wireless services exposes existing bottlenecks in the communications infrastructure and the coordination between the wireless network and its wired counterpart. While wireless systems are constantly evolving to newer generations and higher capacities, their supporting wired networks urgently require advancements in both architecture design and enabling technologies. New optical access systems specifically tailored for the unique natures of various wireless standards are investigated. This dissertation presents the design and experimental verification of high-capacity optical-wireless communication systems using advanced electrical and optical technologies. Technologies such as high level modulation and multiple-input and multiple-output (MIMO) to increase the spectral efficiency is approaching the Shannon limit. New frequency bands with larger bandwidth are to be explored; for example, millimetre wave (mm-wave) spectrum range (30-300 GHz), especially the license-free spectrum located in 60 GHz. Although fiber-optic systems excel in the high-bandwidth core network, as bandwidth demand increases, more and more progress has been made towards the usage of fiber in the last mile. Radio-over-Fiber (RoF) technology has been proposed as a cost-effective optical access solution to support high-speed wireless communications, especially at the mm-wave band. Signal processing and coordination are centralized at the central office (CO), making the system economical and simple to build, operate, and maintain. Moreover, RoF systems are capable of delivering radio signals with different frequencies and protocols simultaneously. Therefore, the advantage of integrated fiber wireless systems leads to the first research topic of this dissertation: multi-band multi-service RoF systems. With an emphasis on the uniformity of the RoF platform that accommodates both legacy wireless services and advanced mm-wave services, the first part of the dissertation presents two schemes - analog all-band RoF and band-mapped 60-GHz RoF - to cover distinct application scenarios. In the all-band RoF access architecture, lower RF signals, such as Wi-Fi and cellular signals, and 60-GHz signal are transmitted at their original carrier frequencies for both indoor and outdoor coverages. On the other hand, the band-mapped mm-wave RoF scheme, fully utilizing the wide 7-GHz bandwidth at 60 GHz, delivers multiple converged high-speed services only through 60-GHz wireless link, which is especially suited for in-building broadband wireless access. The experimental verification of an all-band RoF system featuring relaxed component requirement is introduced, followed by a real-time multi-service demonstration in the proposed band-mapped 60-GHz RoF system. This dissertation also presents the design, analysis, and experimental demonstration of next-generation high-capacity cellular networks to keep up with the ever-growing bandwidth demand and performance requirements. New mobile backhaul (MBH) architectures based on orthogonal frequency division multiple access (OFDMA) are proposed along with a simple and low-latency clock distribution and recovery scheme. The transmission of OFDMA signals in the dense wavelength division multiplexing (DWDM) network with flexible clock rates and DSP-free clock recovery is implemented. Also, a spectrally-efficient, low-complexity clock distribution and recovery scheme for OFDMA-based MBH in coherent ultra-dense WDM (UDWDM) system is demonstrated. Finally, mobile fronthaul (MFH) architectures based on subcarrier multiplexing (SCM) technology, which significantly reduces the requirements on both the number of wavelengths per cell site and the optical bandwidth of the optical transceivers, are systematically investigated. Additionally, two upstream schemes, tailored for the uplink (UL), are introduced to maintain low complexity, and more importantly, to achieve high spectral efficiency by wavelength sharing. Therefore, Internet-access-oriented optical-wireless systems using Wi-Fi and other emerging mm-wave technologies are developed along with the optical fronthaul and backhaul for cellular networks in this dissertation. Moreover, with the proposed techniques, heterogeneous networks can be seamlessly provided even with different services, radio nodes, and performance requirements.
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Chowdhury, Kaushik Roy. "Communication protocols for wireless cognitive radio ad-hoc networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29757.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Akyildiz, Ian; Committee Member: Ingram, Mary Ann; Committee Member: Blough, Douglas; Committee Member: Dovrolis, Konstantinos; Committee Member: Li, Ye. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Zhang, Yonghong. "Resource allocation for OFDM-based cognitive radio systems." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2828.

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Cognitive radio (CR) is a novel wireless communication approach that may alleviate the looming spectrum-shortage crisis. Orthogonal frequency division multiplexing (OFDM) is an attractive modulation candidate for CR systems. In this thesis, we study resource allocation (RA) for OFDM-based CR systems using both aggressive and protective sharing. In aggressive sharing, cognitive radio users (CRUs) can share both non-active and active primary user (PU) bands. We develop a model that describes aggressive sharing, and formulate a corresponding multidimensional knapsack problem (MDKP). Low-complexity suboptimal RA algorithms are proposed for both single and multiple CRU systems. A simplified model is proposed which provides a faster suboptimal solution. Simulation results show that the proposed suboptimal solutions are close to optimal, and that aggressive sharing of the whole band can provide a substantial performance improvement over protective sharing, which makes use of only the non-active PU bands. Although aggressive sharing generally yields a higher spectrum-utilization efficiency than protective sharing, aggressive sharing may not be feasible in some situations. In such cases, sharing only non-active PU bands is more appropriate. When there are no fairness or quality of service (QoS) considerations among CRUs, both theoretical analysis and simulation results show that plain equal power allocation (PEPA) yields similar performance as optimal power allocation in a multiuser OFDM-based CR system. We propose a low-complexity discrete bit PEPA algorithm. To improve spectrum-utilization efficiency, while considering the time-varying nature of the available spectrum as well as the fading characteristics of wireless communication channels and providing QoS provisioning and fairness among users, this thesis introduces the following novel algorithms: (1) a distributed RA algorithm that provides both fairness and efficient spectrum usage for ad hoc systems; (2) a RA algorithm for non-real-time (NRT) services that maintains average user rates proportionally on the downlink of multiuser OFDM-based CR systems; and (3) cross-layer RA algorithms for the downlink of multiuser OFDM-based CR systems for both real-time (RT) services and mixed (RT and NRT) services. Simulation results show that the proposed algorithms provide satisfactory QoS to all supported services and perform better than existing algorithms designed for multiuser OFDM systems.
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25

Pettersson, Stefan. "Radio resource management for wireless indoor communication systems : performance and implementation aspects." Doctoral thesis, KTH, Signals, Sensors and Systems, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3743.

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In this thesis, we investigate several radio resourcemanagement (RRM) techniques and concepts in an indoorenvironment with a dense infrastructure. Future wireless indoorcommunication networks will very likely be implemented atplaces where the user concentration is very high. At these hotspots, the radio resources must be used efficiently. The goalis to identify efficient RRM techniques and concepts that aresuitable for implementation in an indoor environment.

Handling the high level of co-channel interference is shownto be of paramount importance. Several investigations in thethesis point this out to be the key problem in an indoorenvironment with a dense infrastructure. We show that a locallycentralized radio resource management concept, the bunchconcept, can give a very high performance compared to othercommonly used RRM concepts. Comparisons are made withdistributed systems and systems using channel selection schemeslike CSMA/CA. The comparisons are primarily made by capacityand throughput analysis which are made by system levelsimulations. Results show that the centralized concept can give85 percent higher capacity and 70 percent higher throughputthan any of the compared systems.

We investigate several RRM techniques to deal with thechannel interference problem and show that beamforming cangreatly reduce the interference and improve the systemperformance. Beamforming, especially sector antennas, alsoreduce the transmitter powers and the necessary dynamic range.A comparison is made between the use of TD/CDMA and pure TDMAwhich clearly shows the performance benefits of usingorthogonal channels that separates the users and reduces theco-channel interference. Different channel selection strategiesare studied and evaluated along with various methods to improvethe capability of system co-existence.

We also investigate several practical measures to facilitatesystem implementation. Centralized RRM is suitable forguaranteeing QoS but is often considered too complex. With thestudied centralized concept the computational complexity can bereduced by splitting the coverage area into smaller pieces andcover them with one centralized system each. This reduces thecomplexity at the prize of lost capacity due to theuncontrolled interference that the different systems produce.Our investigations show that sector antennas can be used toregain this capacity loss while maintaining high reduction incomplexity. Without capacity loss, the computational complexitycan be reduced by a factor of 40 with sectoring. Theimplementation aspects also include installation sensitivity ofthe indoor architecture and the effect of measurement errors inthe link gains. The robustness against installation errors ishigh but the bunch concept is quite sensitive to largemeasurement errors in the studied indoor environment. Thiseffect can be reduced by additional SIR-margins of the radiolinks.

The studied bunch concept is shown to be promising for usein future wireless indoor communication systems. It provideshigh performance and is feasible to implement.

Keywords:Radio resource management, indoorcommunication, the bunch concept, centralized RRM, dynamicchannel allocation, channel selection, co-channel interference,power control, feasibility check, capacity, throughput, qualityof service, beamforming, downtilting, sector antennas,co-existence, computational complexity, sensitivity analysis,measurement errors, infrastructure, system implementation,WLAN, HiperLAN/2, IEEE 802.11.

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Baghersalimi, Gholamreza. "Multiple-access methods for broadband wireless communication on radio-over-fibre systems." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435901.

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Weng, Lingfan. "Analysis and allocation of radio resources in cooperative wireless networks /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20WENG.

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28

Wu, Victor Kai Yuen. "OFDM-based cooperative communications in a single path relay network and a multiple path relay network." Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-11092006-152421/.

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29

Hunter, Brandon Rosel. "Channel probing for an indoor wireless communications channel /." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd196.pdf.

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30

Lei, Sai-weng. "Adaptive interleaving for orthogonal frequency division multiplexing systems /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23295065.

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31

Zhou, Lin. "Energy efficient transmitter design with compact antenna for future wireless communication systems." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33104.

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This thesis explores a novel technique for transceiver design in future wireless systems, which is cloud radio access networks (CRANs) with single radio frequency (RF) chain antennas at each remote radio head (RRH). This thesis seeks to make three contributions. Firstly, it proposes a novel algorithm to solve the oscillatory/unstable behaviour of electronically steerable parasitic array radiators (ESPAR) when it provides multi-antenna functionality with a single RF chain. This thesis formulates an optimization problem and derives closed-form expressions when calculating the configuration of an ESPAR antenna (EA) for arbitrary signals transmission. This results in simplified processing at the transmitter. The results illustrate that the EA transmitter, when utilizing novel closed-form expressions, shows significant improvement over the performance of the EA transmitter without any pre-processing. It performs at nearly the same symbol error rate (SER) as standard multiple antenna systems. Secondly, this thesis illustrates how a practical peak power constraint can be put into an EA transceiver design. In an EA, all the antenna elements are fed centrally by a single power amplifier. This makes it more probable that during use, the power amplifier reaches maximum power during transmission. Considering limited power availability, this thesis proposes a new algorithm to achieve stable signal transmission. Thirdly, this thesis shows that an energy efficiency (EE) optimization problem can be formulated and solved in CRANs that deploy single RF chain antennas at RRHs. The closed-form expressions of the precoder and power allocation schemes to transmit desired signals are obtained to maximise EE for both single-user and multi-user systems. The results show that the CRANs with single RF chain antennas provide superior EE performance compared to the standard multiple antenna based systems.
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32

Jayasinghe, L. K. (Laddu Keeth Saliya). "Analysis on MIMO relaying scenarios in wireless communication systems." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526207391.

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Abstract The thesis concentrates on evaluating and improving performances of various multiple-input multiple-output (MIMO) relaying scenarios that are particularly relevant to future wireless systems. A greater emphasis is placed on important practical situations, considering relay deployments, availability of channel state information (CSI), limitations of spectrum, and information secrecy. Initially, the performance of a non-coherent amplify-and-forward (AF) MIMO relaying is analyzed when the relay is deployed with the relay-to-destination channel having a line-of-sight (LoS) path. The main attention is given to analyzing the performance of orthogonal space-time block coded based non-coherent AF MIMO system. Exact expressions of statistical parameters and performance metrics are derived considering the instantaneous signal-to-noise ratio (SNR) received at the destination. These performance metrics reveal that a strong LoS component in relay-destination channel always limits the performance promised by MIMO scattering environment when both nodes have multiple antennas. The thesis also considers scenarios in MIMO two-way relaying (TWR) with physical layer network coding (PNC) mapping at the relay. PNC mapping becomes complex with multiple streams being combined at the relay node. Joint precoder-decoder schemes are considered to ease this, and various studies are carried out depending on the CSI. The zero-forcing criterion is used at the nodes when perfect CSI is available. For the imperfect CSI scenario, a robust joint precoder-decoder design is considered. The precoder and decoder matrices are obtained by solving optimization problems, which are formulated to maximize sum-rate and minimize weighted mean square error (WMSE) under transmit power constraints on the nodes. Next, a precoder-decoder scheme for MIMO underlay device-to-device (D2D) communication system is investigated by considering two D2D modes; PNC based D2D and direct D2D. The joint design is based on minimizing mean square error (MSE) which is useful to mitigate interference, and to improve the performance of both D2D and cellular communications. Distributed and centralized algorithms are proposed considering bi-directional communication in both D2D and cellular communications. System performance is discussed with two transmit mode selection schemes as dynamic and static selection schemes. The results show that the PNC based D2D mode extends the coverage area of D2D communication. Finally, secure beamforming schemes for the PNC based MIMO TWR systems are investigated when multiple eavesdroppers are attempting to intercept the user information. The CSI of the user-to-eavesdropper channels is imperfect at the users. The channel estimation errors are assumed with both ellipsoidal bound and Gaussian Markov uncertainty models. Robust optimization problems are formulated considering both scenarios to design beamforming vectors at the users and relay. Numerical results suggest that the proposed algorithms converge fast and provide higher security
Tiivistelmä Tässä väitöskirjassa keskitytään arvioimaan ja parantamaan suorituskykyä useissa moniantennitoistinjärjestelmissä, jotka ovat ajankohtaisia tulevaisuuden langattomissa verkoissa. Erityisesti työssä analysoidaan tärkeitä käytännön tilanteita, sisältäen toistimien sijoittamisen, kanavatiedon saatavuuden, rajoitetun taajuuskaistan ja tiedon salauksen. Aluksi epäkoherentin, vahvistavan ja jatkolähettävän moniantennitoistimen suorituskykyä analysoidaan tilanteessa, jossa toistin on sijoitettu siten, että kohteeseen on suora yhteys. Suorituskyvyn arvioinnin pääkohteena on ortogonaalinen tila-aika-tason lohkokoodattu epäkoherentti vahvistava ja jatkolähettävä moniantennitoistin. Työssä johdetaan tarkat lausekkeet tilastollisille parametreille ja suorituskykymittareille ottaen huomioon hetkellinen signaalikohinasuhde vastaanottimessa. Nämä suorituskykymittarit ilmaisevat, että toistimen ja kohteen välillä oleva vahva suoran yhteyden komponentti rajoittaa sitä suorituskykyä, jota moniantennijärjestelmän hajontaympäristö ennustaa. Työssä tutkitaan myös kahdensuuntaisia moniantennitoistimia, jotka käyttävät fyysisen kerroksen verkkokoodausta. Koodauksesta tulee monimutkaista, kun monia datavirtoja yhdistetään toistimessa. Tämän helpottamiseksi käytetään yhdistettyä esikoodaus-dekoodausmenetelmää, jota tutkitaan erilaisten kanavatietojen tapauksissa. Täydellisen kanavatiedon tapauksessa käytetään nollaanpakotuskriteeriä. Epätäydellisen kanavatiedon tapauksessa käytetään robustia yhdistettyä esikoodaus-dekoodausmenetelmää. Esikoodaus- ja dekoodausmatriisit saadaan ratkaisemalla optimointiongelmat. Nämä ongelmat on muodostettu maksimoimaan summadatanopeus, ja minimoimaan painotettu keskineliövirhe, kun optimointirajoitteina ovat solmujen lähetystehot. Seuraavaksi esikoodaus-dekoodausmenetelmää tutkitaan moniantennijärjestelmässä, jossa käytetään kahdentyyppistä laitteesta-laitteeseen (D2D) kommunikaatiomenetelmää: fyysisen kerroksen verkkokoodaukseen pohjautuvaa D2D- ja suoraa D2D-kommunikaatiota. Yhteissuunnittelu perustuu keskineliövirheen minimointiin, joka on hyödyllistä, kun halutaan vähentää häiriötä ja parantaa molempien verkkojen suorituskykyä. Työssä ehdotetaan hajautettuja ja keskitettyjä algoritmeja tilanteessa, jossa käytetään kaksisuuntaista kommunikaatiota molemmissa verkoissa. Järjestelmän suorituskykyä arvioidaan, kun käytetään kahta eri lähetystilan valintaa, dynaamista ja staattista. Tulokset osoittavat, että fyysisen kerroksen verkkokoodaukseen pohjautuva D2D kasvattaa D2D-kommunikaatiojärjestelmän kantamaa. Lopuksi, turvallisia keilanmuodostustekniikoita arvioidaan fyysisen kerroksen verkkokoodaukseen pohjautuvassa kahdensuuntaisessa moniantennitoistinjärjestelmässä, kun useat salakuuntelijat yritävät siepata käyttäjätiedon. Käyttäjillä on epäideaalinen kanavatieto heidän ja salakuuntelijoiden välisten linkkien kanavista. Kanavatiedon estimointivirheitä arvioidaan ellipsoidisella ja Gauss-Markov-epävarmuusmallilla. Robustit optimointiongelmat, joissa suunnitellaan keilanmuodostusvektorit käyttäjän ja toistimen välille, muodostetaan molemmille malleille. Numeeriset tulokset osoittavat, että ehdotetut algoritmit konvergoituvat nopeasti ja tarjoavat korkeamman turvallisuuden
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33

He, Shuangchi. "Doubly-selective channel estimation and equalization using superimposed training and expansion models." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Dissertations/HE_SHUANGCHI_5.pdf.

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34

王徐芳 and Xufang Wang. "Multiresolution joint source and channel coding for wireless communications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225299.

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35

Xu, Ning. "Physical-Layer Network Coding for MIMO Systems." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc68065/.

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The future wireless communication systems are required to meet the growing demands of reliability, bandwidth capacity, and mobility. However, as corruptions such as fading effects, thermal noise, are present in the channel, the occurrence of errors is unavoidable. Motivated by this, the work in this dissertation attempts to improve the system performance by way of exploiting schemes which statistically reduce the error rate, and in turn boost the system throughput. The network can be studied using a simplified model, the two-way relay channel, where two parties exchange messages via the assistance of a relay in between. In such scenarios, this dissertation performs theoretical analysis of the system, and derives closed-form and upper bound expressions of the error probability. These theoretical measurements are potentially helpful references for the practical system design. Additionally, several novel transmission methods including block relaying, permutation modulations for the physical-layer network coding, are proposed and discussed. Numerical simulation results are presented to support the validity of the conclusions.
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36

鄭价昌 and Kai-cheong Chang. "Adaptive channel equalisation technique for wideband time-division multiple access digital mobile radio communications systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31212888.

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37

Chang, Kai-cheong. "Adaptive channel equalisation technique for wideband time-division multiple access digital mobile radio communications systems /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17590371.

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38

Chu, Xiaoli. "Ultra-wideband direct-sequence impulse radio wireless communications /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20CHU.

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39

Liu, Xiaoshan. "Mobility and radio resource management in heterogeneous wireless networks." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38233873.

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40

Olutade, Bolaji OmoLaja. "Thin film ZnO-based resonators for integrated wireless applications." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13547.

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41

Patel, Chirag S. "Wireless channel modeling, simulation, and estimation." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-03282006-200818/.

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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.
Andrew, Alfred, Committee Member ; Durgin, Gregory, Committee Member ; Li, Geoffrey, Committee Member ; Ingram, Mary Ann, Committee Member ; Stuber, Gordon, Committee Chair.
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42

Lo, Chi-ming. "Analytical evaluation of wireless digital communication performance over fading channels." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23295211.

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43

Todd, Stephen Ross Carleton University Dissertation Engineering Electrical. "Empirical evaluation of diversity techniques for indoor digital radio at 1.75 GHz." Ottawa, 1992.

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44

Raghavan, Anand. "Interference cancellation for collocated wireless radios." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-06272007-234911/.

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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.
Laskar, Joy, Committee Chair ; Cressler, John, Committee Member ; Kornegay, Kevin, Committee Member ; Tentzeris, Emmanouil, Committee Member ; Lee, Chang-Ho, Committee Member.
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45

Sng, Sin Hie. "Radio channel modeling for mobile ad hoc wireless networks." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSng.pdf.

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Thesis (M.S. in Engineering Science (Electrical Engineering))--Naval Postgraduate School, June 2004.
Thesis advisor(s): Murali Tummala, Roberto Cristi. Includes bibliographical references (p. 71). Also available online.
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46

Liu, Xiaoshan, and 劉曉杉. "Mobility and radio resource management in heterogeneous wireless networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38233873.

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47

Kelly, Ivy Yvonne. "The multipath fingerprint method for wireless E-911 location finding /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.

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48

Li, Kuo-Hui. "RF beamformers for high-speed wireless communications." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14768.

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Senguttuvan, Rajarajan. "Low-cost test, diagnosis, and tuning for adaptive radio frequency systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22575.

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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Chatterjee, Abhijit; Committee Member: Anderson, David; Committee Member: Durgin, Gregory; Committee Member: Swaminathan, Madhavan; Committee Member: Zhou, Hao-Min.
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50

Choi, Gi Wan. "Low-complexity and power-efficient wireless cooperative relay networks with enhanced reliability." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47721.

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In recent years, global mobile data traffic has been increasing exponentially as mobile devices pervade our daily lives. To cope with the ever growing demands for higher data rates and seamless connectivity, one solution is to drastically increase the number of macro base stations in the conventional cellular architecture. However, this results in high deployment costs. Deploying low-power nodes such as relays that do not require a wired backhaul connection within a macrocell is one of cost-effective ways to extend high data rate coverage range. Relays are typically deployed to increase signal strength in poor coverage areas or to eliminate dead spots. But more importantly, relays provide a natural diversity, called cooperative diversity. In addition to a direct signal from a base station, extra copies of the same signal are forwarded from relays. Utilizing this diversity at the destination can yield significant performance enhancements. Thus, cooperative relay strategies need to be considered to enable high data rate coverage in a cost-effective manner. In this dissertation, we consider a simple single-relay network and present low-complexity and power-efficient cooperative relay designs that can achieve low error rate. We first study decode-and-forward (DF) relay networks with a single antenna at each node, where the relay decodes the received signal and forwards the re-encoded information to the destination. In DF relay scheme, decoding at the relay is not perfect and the error-propagation phenomenon is a detrimental problem, preventing the destination from collecting the cooperative diversity. To enable cooperative diversity in DF relay networks, we adopt link-adaptive power-scaling relay strategies where the relay scales the transmission power of the re-encoded signal based on the reliability of the source-relay link. We generalize power-profile designs and analyze the diversity order enabled by the general power-profile designs. We provide necessary and sufficient conditions for the designs to enable full cooperative diversity at the destination. In the second part of this dissertation, we extend the power-scaling relay strategy to DF multi-input multi-output (MIMO) relay networks, where multiple antennas are adopted at each node, and show that full cooperative diversity can also be achieved here. To collect spatial diversity provided by multiple antennas without using maximum-likelihood equalizers (MLEs) or near-ML detectors which exhibit high complexity, channel-controlled automatic repeat request (CC-ARQ) scheme is developed for DF MIMO relay networks to enable spatial diversity with linear equalizers (LEs) maintaining low-complexity. We also show that joint cooperative and spatial diversity can be achieved at the destination when the power-scaling strategy and the CC-ARQ with LEs are combined. Finally, amplify-and-forward (AF) MIMO relay designs, where the relay simply amplifies the received signal and forwards it to the destination, are studied with consideration of peak-power constraints at the relay. One practical concern for AF relaying is that the output signal at the relay may suffer from large peak-to-average power ratio (PAR), which may cause nonlinear distortion and/or saturation in the transmitted signal due to the limited linear range of power amplifiers. Thus, we first investigate peak-power constrained power-scaling strategies and find a sufficient condition to enable joint cooperative and spatial diversity at the destination. Based on this study, we propose simple and practical AF MIMO relay designs with peak-power constraint at the relay. CC-ARQ is also applied to AF MIMO relay networks to reduce the decoding complexity.
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