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1
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.
Testo completo
2
Valenta, Václav. "Frequency synthesis for cognitive multi-radio". Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00597461.
Testo completoAbstract (sommario):
This doctoral thesis deals with design aspects of a reconfigurable frequency synthesizer for flexible radio transceivers in future cognitive multi-radios. The frequency bandwidth to be covered by this multi-radio synthesizer corresponds to the frequency bands of the most diffused wireless communication standards in the frequency band 800 MHz to 6 GHz. Since multi-standard operation is required, the synthesizer must fulfil the most stringent and sometimes conflicting requirements. Given these requirements, a novel approach for multi-mode frequency synthesis has been conceived. A hybrid phase locked loop based frequency synthesizer has been proposed and a novel switching protocol has been presented and validated on an experimental evaluation board. This approach combines fractional-N and integer-N modes of operation with switched loop filter topology. Compared to standard PLL techniques, the hybrid configuration provides a great flexibility in terms of reconfiguration and moreover, it offers relatively low circuit complexity and low power consumption. This architecture provides reconfiguration of the loop bandwidth, frequency resolution, phase noise and settling time performance and hence, it can adapt itself to diverse requirements given by the concerned wireless communication standards. Corresponding analyses, simulations and measurements have been carried out in order to verify the performance and functionality of the proposed solution. A part from the design of the multiband frequency synthesizer, a set of regional measurements of the radio spectrum utilization has been carried out in the framework of this dissertation research. These measurements are based on the energy detection principle and provide a close look at the degree of radio spectrum utilization in different regions, namely in the city of Brno in the Czech Republic and in the city of Paris and one of its suburbs in France. The goal of the experimental measurement campaign has been to estimate the degree of radio spectrum usage in a particular environment and to point out the fact that a new approach for radio spectrum management is inevitable
3
Panahandeh, Ali. "Multi-polarized sensing for cognitive radio". Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209586.
Testo completoAbstract (sommario):
In this thesis the multi-polarized Cognitive Radios are studied. Cognitive Radios are proposed as an interesting way to more efficiently use the frequency resources. A Cognitive Radio secondary user finds the frequency bands which are not utilized by primary users and communicates on them without interfering with the primary users. In order to achieve this goal the secondary user must be able to detect reliably and quickly the presence of a primary user in a frequency band. In this thesis, the impact of polarization on the spectrum sensing performances of cognitive radio systems is studied.First the depolarization occurring in the wireless channel is studied for two cognitive radio scenarios. This is done through an extensive measurement campaign in two outdoor-to-indoor and indoor-to-indoor scenarios where the parameters characterizing the radiowaves polarization are characterized at three different spatial scales: small-scale variation, large-scale variation and distance variation.
Second, a new approach is proposed in modeling of multi-polarized channels. The polarization of received fields is characterized from an electromagnetic point of view by modeling the polarization ellipse. Theoretical formulations are proposed in order to obtain the parameters characterizing the polarization ellipse based on the signals received on three cross-polarized antennas. A system-based statistical model of the time-dynamics of polarization is proposed based on an indoor-to-indoor measurement campaign. The analytical formulations needed in order to project the polarization ellipse onto a polarized multi-antenna system are given and it is shown how the model can be generated.
Third, the impact of polarization on the spectrum sensing performances of energy detection method is presented and its importance is highlighted. The performance of spectrum sensing with multi-polarized antennas is compared with unipolar single and multi-antenna systems. This analysis is based on an analytical formulation applied to the results obtained from the multi-polarized measurement campaign. The detection probability as a function of distance between the primary transmitter and the secondary terminal and the inter-antenna correlation effect on the spectrum sensing performance are studied.
An important limitation of energy detector is its dependence on the knowledge of the noise variance. An uncertainty on the estimation of the noise variance considerably affects the performance of energy detector. This limitation is resolved by proposing new multi-polarized spectrum sensing methods which do not require any knowledge neither on the primary signal nor on the noise variance. These methods, referred to as “Blind spectrum sensing methods”, are based on the use of three cross-polarized antennas at the secondary terminal. Based on an analytical formulation and the results obtained from the measurement campaign, the performances of the proposed methods are compared with each-other and with the energy detection method. The effect of antenna orientation on the spectrum sensing performance of the proposed methods and the energy detection method is studied using the proposed elliptical polarization model.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
4
Piao, Guihua. "Radio resource management for integrated services in multi-radio access networks". Kassel Kassel Univ. Press, 2006. http://www.uni-kassel.de/hrz/db4/extern/dbupress/publik/abstract.php?978-3-89958-269-7.
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5
Piao, Guihua. "Radio resource management for integrated services in multi-radio access networks". Kassel Kassel Univ. Press, 2007. http://d-nb.info/986595012/34.
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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.
Testo completoAbstract (sommario):
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
7
Naveed, Anjum Computer Science & Engineering Faculty of Engineering UNSW. "Channel assignment in multi-radio multi-channel wireless mesh networks". Awarded by:University of New South Wales. Computer Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41500.
Testo completoAbstract (sommario):
Channel assignment in wireless mesh network (WMN) aims at improving the network throughput by utilizing multiple orthogonal frequency channels to minimize the interference. Interference can be categorized as coordinated and non-coordinated, depending upon the relative location of the interfering links. Compared to coordinated interference, non-coordinated interference has a severe adverse impact on throughput. This thesis is based on the hypothesis that the network throughput can be improved significantly, if channel assignment minimizes non-coordinated interference with priority. We propose a static and centralized channel assignment scheme CCAS to show the effectiveness of the hypothesis. The cluster-based approach of CCAS minimizes non-coordinated interference with reduced complexity. CCAS improves the network throughput by upto 80%, compared to the existing schemes. We propose topology control scheme MATS that constructs low interference multipath network topology using a subset of links from physical topology. We report an additional improvement of upto 10% in the network throughput, when CCAS assigns channels to the links selected by MATS. In the final part of the thesis, we formulate generalized channel assignment as an optimization problem, accounting for real network traffic. The objective of the problem is to select the channels for links such that maximum incident traffic can be transmitted over the links, while ensuring a fair distribution of throughput amongst links and elimination of non-coordinated interference. For a given network and incident traffic, the solution to this problem generates the channel assignment resulting in optimal network throughput. We propose dynamic and distributed scheme LYCAS as an approximate solution to the problem. LYCAS employs MATS to construct network topology and cluster-based approach of CCAS to minimize non-coordinated interference. In addition, it periodically updates the assignment of channels to adapt to the changing traffic load. LYCAS achieves upto 68% of the optimal network throughput and upto 72% of optimal aggregate end-to-end throughput of multi-hop flows. It outperforms the existing schemes by a factor of 2.
8
Valois, Fabrice. "Auto-organisation de réseaux radio multi-saut". Habilitation à diriger des recherches, Université Claude Bernard - Lyon I, 2007. http://tel.archives-ouvertes.fr/tel-00272361.
Testo completoAbstract (sommario):
L'auto-organisation de réseaux radio multi-sauts a pour objectif de structurer/organiser un réseau à l'aide d'une structure logique. Pourquoi le structurer ? Pour introduire de la stabilité en ne tenant pas compte de voisins instables ou fortement mobiles, pour fédérer l'ensemble des noeuds, pour introduire une hiérarchie dans le réseau afin de faciliter le passage à l'échelle, pour introduire plus de capacité dans le réseau, etc. L'auto-organisation telle que nous la considérons vise à construire une topologie logique basée sur la topologie physique de telle sorte que les protocoles réseaux (routage, inondation, etc.) et applicatifs (agrégation et dissémination de données) soient plus efficace et plus robuste. La littérature propose essentiellement 4 façons de structurer un réseau en ayant recours aux tables de hachage distribuées (DHT), aux stratégies de clustering, à la construction d'overlays ou en construisant un réseau maillé logique. Bien entendu, il s'agit ici de proposer des protocoles localisés, voire distribuées. Dans nos travaux, nous avons proposé plusieurs algorithmes localisés de construction et de maintenance de backbone virtuel construit sous forme d'arbre ou de treillis. Après avoir étudié les propriétés intrinsèques de ces protocoles en termes de cardinalité, de convergence (auto-stabilisation), de complexité, etc. nous nous sommes intéressé à l'apport de ces structures logiques dans les problématiques réseaux. Ainsi, et que ce soit dans le domaine des réseaux ad hoc, des réseaux hybrides et des réseaux de capteurs, nous avons re-visité les principaux défis posés en développant des protocoles basés sur les auto-organisations proposées plutôt que de considérer le réseau à plat comme c'est souvent le cas. Des protocoles de routage unicast, de localisation, d'auto-configuration mais également de diffusion de données ont été proposés. L'ensemble des publications obtenues mettent en évidence la pertinence de cette démarche. A côté de ces travaux orientés réseaux nous avons montré, dans des travaux plus théoriques, l'apport en terme de stabilité que permettait l'auto-organisation notamment dans le cas de topologies fortement dynamique. Ce résultat est basé sur l'application de l'entropie statistique utilisée classiquement en thermodynamique. Ces travaux ont été menés depuis le point de vue théorique jusqu'à l'expérimentation.
9
Lee, Chungki. "Communication protocols in multi-hop radio networks". Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/8199.
Testo completo
10
Alexander, Paul. "Multi-frequency studies of powerful radio sources". Thesis, University of Cambridge, 1986. https://www.repository.cam.ac.uk/handle/1810/265339.
Testo completoAbstract (sommario):
This thesis is concerned with the physics of extragalactic radio - sources. Radio observations of a given source provide a powerful method with which to make direct measurements of the physical processes occuring within the la~ge-scale radio lobes and hotspots . Multi-frequency observations with up to five frequencies have been made for a number of ~ources using the Cambridge 5-km telescope and the Very Large Array. These data have been used to determine the change in radio spectra across the source . to obtain information about the way in which the electron population has evolved. Combining this with inferred magnetic field directions, the dynamics of seven sources have been examined. Additionally the hotspot advance speeds for a statistically representative sample of sources have -been derived. For 3C234 it was possible to test the assumptions used throughout the analysis. They were found to h6ld good to within the limits of error. The results are best interpreted within the framework of a fluid-dynamical model lobes as have recently been examined in numerical experiments. The general distibution of radiating plasma can be understood in terms of the flow of material out of the main accelerating regions (the hotspots - a basic beam model � is assumed thr6ughout) and its subsequent interaction with the surrounding medium, coupled with some precession of the radio jet. As well as looking at source dynamics , the detailed spectra have been used to search for areas of particle acceleration not associated with hotspots. Three sources have been found to have such regions, but large scale acceleration within the radio-lobes is not required . The derivation of ho tspot advance speed for a statistically representative sample has enabled statistical correlations to be investigated . Advance speed is found to be strongly correlated with power and this is discussed in the wider context of overall source models.
11
Amiri, Nehzad Maryam. "Channel assignment protocols for multi-radio multi-channel wireless mesh netwworks". Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/104156.
Testo completoAbstract (sommario):
The increasing demand for large and low cost wireless coverage, ranging from campus to city wide areas, has motivated a high interest in multi-hop communications with Wireless Mesh Networks (WMN) based on IEEE 802.11s as the
most recent and significant standard.
Channel Assignment (CA) is mechanism which selects the best channels for an individual wireless node or the entire network aiming to increase the capacity of the network. Channel assignment has been extensively researched for
multi-radio WMNs, but it is still very challenging when it comes to its implementation. Although IEEE 802.11s introduces new inter-working, routing and wireless frame forwarding at the link layer, the multi channel architecture receives less attention due to many unsolved challenges that arises while mesh service set works over multiple frequencies.
This research work tries to give a solution to the needs of designing an efficient channel assignment mechanism.
As a result we have proposed a new static channel assignment based on the fact that not all wireless links are practically useful. Our mechanism prunes the network topology by removing weak wireless links and improves the network
performance by reaching a more diverse channel-radio assignation solution.
Toward designing a distributed channel assignment we propose a new game theory based formulation of channel assignment which is applicable to a realistic scenario with imperfect information at each router. We have proposed a distributed and hybrid channel assignment protocol based on the game formulation. The proposed channel assignment makes wireless router to
be able to follow the unpredictable changes in the wireless environment.
We also investigated the types of channel assignment protocols which can be adapted to the IEEE 802.11s based mesh network and improve the network good-put in terms of data delivery ratio and end-to-end delay.
12
Thomas, Willie L. II, Samuel Berhanu e Nathan Richardson. "System Framework for a Multi-Band, Multi-Mode Software Defined Radio". International Foundation for Telemetering, 2014. http://hdl.handle.net/10150/577442.
Testo completoAbstract (sommario):
ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CAThis paper describes a system framework for a multi-band, multi-mode software defined radio (MBMM SDR) being developed for next-generation telemetry applications. The system framework consists of the multi-band front-end (MBFE), the multi-mode digital radio (MMDR), and the configuration and control (C2) sub-systems. The MBFE consists of an L/S/C-band transceiver architecture that provides wideband operation, band selection, and channel tuning. The MMDR consists of the software and firmware components for high-speed digital signal processing for the telemetry waveforms. Finally, the C2 consists of the software and hardware components for system configuration, control and status. The MBFE is implemented as a standalone hardware sub-system, while the MMDR and C2 are integrated into a single hardware subsystem that utilizes state-of-the-art system-on-chip (SoC) technology. Design methodologies, hardware architectures, and system tradeoffs are highlighted to meet next-generation telemetry requirements for improved spectrum efficiency and utilizations. Approved for public release; distribution is unlimited (412TW-PA-14281).
13
Habib, Usman. "Millimetre-wave radio-over-fibre supported multi-antenna and multi-user transmission". Thesis, University of Kent, 2018. https://kar.kent.ac.uk/71556/.
Testo completoAbstract (sommario):
In this thesis, various features of the RoF supported mmW communication for future wireless systems have been analysed including photonic generation of mmW for MIMO operation, performance analysis of mmW MIMO to achieve spatial diversity and spatial multiplexing with analog RoF fronthaul, and multi-user transmission in the 60 GHz-band using multiplexing-over-fibre transport and frequency-selective antenna. A low cost mmW generation system for two independent MIMO signals has been presented, consisting of a single optical Phase Modulator (PM). The different aspects of experimental analysis on RoF-supported mmW MIMO in this thesis, which were not considered before, include use of specific MIMO algorithm to understand the amount of improvement in coverage and data rate for a particular MIMO technique, performance comparison with SISO at several user locations, and verification of optimum RAU physical spacing for a particular transmission distance with the theoretical results. The results show that flexible and wider RAU spacings, required to obtain optimum performance in a mmW MIMO system, can be achieved using the proposed analog RoF fronthaul. The investigation was extended to verification of a method to individual measurement of mmW channel coefficients and performing MIMO processing, which shows that mmW channels are relatively static and analysis can be extended to much longer distances and making projections for N×N MIMO. For mmW multi-user transmission, a novel low cost, low complexity system using single RoF link and single RF chain with single transmitting antenna has been presented and characterized, which was based on large number of RF chains and multiple antenna units previously. The setup involves generation and RoF transport of a composite SCM signal, upconversion at the RAU and transmission of different frequency channels towards spatially distributed users using a frequency-selective Leaky-Wave-Antenna (LWA), to convert Frequency Division Multiplexing (FDM) in to Spatial Division Multiple Access (SDMA). Analysis on low user-signal spacing for the SCM shows the feasibility to serve a large number of users within a specific transmission bandwidth and experimental demonstration to achieve sum rate of 10Gb/s is shown by serving 20 users simultaneously. Furthermore, investigation on SNR degradation of high bandwidth signals due to beamsteering effect of the LWA and theoretical calculations of the sum data rate for different number of users is performed, which shows that the proposed system can provide much higher sum rates with high available SNR. It was also experimentally demonstrated that improvement in coverage and spectral efficiency is obtained by operating multiple LWAs using single RF chain. Finally, an experimental demonstration of a DWDM-RoF based 60 GHz multi-user transmission using single LWA is presented to show the feasibility to extend the setup for a multiple RAU based system, serving each at distinct optical wavelength and performing direct photonic upconversion at the RAU for low cost mmW generation.
14
Girnyk, Maksym. "Cooperative communication for multi-user cognitive radio networks". Licentiate thesis, KTH, Kommunikationsteori, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96794.
Testo completoAbstract (sommario):
In recent years, the main trend in wireless communications has been shifted from voice transmission to data-centric communication. This shift has caused an increase in the data rate requirements for future wireless communication systems. These requirements result in need for large bandwidth. Being a limited and thus expensive resource, wireless spectrum needs to be used efficiently. For higher spectral efficiency, new transmission techniques as well as new dynamic spectrum-allocationpolicies are needed. Cognitive radio is a promising approach for increasing spectral efficiency of wireless systems. By exploiting advanced signal processing techniques and sophisticated transmission schemes, cognitive radio devices allow to serve new wireless users within the existing crowded spectrum. Typically, a cognitive radio network is installed in parallel to an existing primary network, a legacy owner of the spectrum. The cognitive radio network adapts to its electro-magnetic environment in order to limit or even avoid the disturbance to the primary network. This thesis focuses on the underlay cognitive radio paradigm, which assumes that both the primary network and the ad hoc cognitive radio network operate within the same time and frequency band, as well as at the same geographic location. The cognitive network is able to estimate the interference caused to the primary network by means of channel training and possible feedback. This knowledge is then used to adjust the cognitive network’s transmissions in such a way that the disturbance to the primary network is below some acceptable threshold. In the first part of the thesis, we discuss the multi-hop line cognitive networks, in which the information content before reaching its destination passes through several hops from node to node within the cognitive network. In this way, transmission power at the source terminal may be decreased, thus producing less interference to the primary network. Moreover, the powers at each terminal within the cognitive network may be optimally allocated so that the interference constraint at the primary network is satisfied. This power allocation can be realized in both centralized and decentralized ways, depending on the available information about the channel state. We discuss both of these allocations subject to different interference constraints employed at the primary network. In the second part of the thesis, we discuss the reliability of transmission within the line cognitive ad hoc networks in terms of outage probability and diversity. We also illustrate the benefit of network coding for such networks and provide a heuristic algorithm for optimal scheduling. In the final part of the thesis, we study the uplink relay-assisted cellular cognitive radio scenario. Both, the cognitive network and the primary network, contain a set of multi-antenna users that communicate with a corresponding base station. The users create mutual interference and hence limit each other’s performance. Using certain mathematical tools originally developed within the field of statistical physics, we are able derive a closed-form expression for the ergodic mutual information for arbitrary channels inputs, which enables characterization of the achievable rate region of such scenario.QC 20120612
15
Luo, Jijun. "Joint radio resource management for multi-link terminals /". Aachen : Mainz, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016146959&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Xin, Qin. "Time efficient communication in multi-hop radio networks". Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408569.
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Keskin, Faruk. "Precoding for MIMO multi-user mobile radio downlinks". [Kaiserslautern] : [Universitätsbibliothek], 2007. http://d-nb.info/989961354/34.
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Batista, Rodrigo Lopes. "Radio resource allocation for coordinated multi-point systems". reponame:Repositório Institucional da UFC, 2011. http://www.repositorio.ufc.br/handle/riufc/10836.
Testo completoAbstract (sommario):
BATISTA. R. L. Radio resource allocation for coordinated multi-point systems. 2011 74 f. Dissertação (Mestrado em Engenharia de Teleinformática) - Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2011.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2015-02-27T19:26:14Z No. of bitstreams: 1 2011_dis_rlbatista.pdf: 1984568 bytes, checksum: fb73d12e218f0bf5048212826227d5bc (MD5)
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The International Telecommunications Union (ITU) established through the International Mobile Telecommunications (IMT)-Advanced a set of requirements for high performance of 4th Generation (4G) communication systems and, with the aim of meeting such requirements, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is considering a set of enhancements, referred to as LTE-Advanced. In the LTE-Advanced context, Coordinated Multi-Point (CoMP) communication appears as a promising technology to boost system throughput and to allow for an efficient Radio Resource Allocation (RRA). CoMP systems promise very high performance in terms of spectral efficiency and coverage benefits when perfect Channel State Information (CSI) is available at the transmitter. However, perfect CSI is difficult to obtain in CoMP systems due to an increased number of channel parameters to be estimated at the receiver and to be fed back to the transmitter. So, the performance of such systems is compromised when the CSI is not perfectly known during CoMP processing, which is an important problem to be addressed. Space Division Multiple Access (SDMA) grouping algorithms are usually employed in order to find a suitable set of users for spatial multiplexing. The largest SDMA group is not always the best group in a given data transmission such that higher gains might be achieved by dynamically adjusting the SDMA group size. Besides, algorithms that balance the Signal to Interference-plus-Noise Ratio (SINR) among different links might ensure a certain level of link quality and so provide a more reliable communication for the scheduled users. This master thesis provides system-level analyses for RRA algorithms that exploit coordination in the downlink of CoMP systems to implement adaptive resource reuse and so improve system throughput. Herein, RRA strategies which consider dynamic SDMA grouping, joint precoding and power allocation for SINR balancing are studied in CoMP systems assuming imperfect CSI in order to obtain a better approximation with regard to the real-world implementations. It is shown through system-level analyses that quite high throughput gains are achieved through intelligent RRA. In conclusion, the results show that Sequential Removal Algorithms (SRAs) and SINR balancing provide system spectral efficiency gains. However, a critical degradation on the performance of these RRA strategies due to imperfect CSI is also shown.
A União Internacional para Telecomunicações (ITU) estabeleceu através da iniciativa para o Sistema Avançado Internacional de Telecomunicações Móveis (IMT-Advanced), um conjunto de requisitos de alto desempenho para os sistemas de comunicação de quarta geração (4G) e, com o objetivo de atender tais requisitos, a Evolução de Longo Prazo (LTE) do Projeto de Parceria para a Terceira Geração (3GPP) está considerando um conjunto de melhorias, referidas como LTE-Avançado. No contexto do LTE-Avançado, a comunicação multi-ponto coordenada (CoMP) aparece como uma tecnologia promissora para aumentar a vazão do sistema e permitir uma Alocação de Recursos de Rádio (RRA) eficiente. Os sistemas CoMP prometem alto desempenho em termos de eficiência espectral e benefícios de cobertura quando a Informação do Estado do Canal (CSI) perfeita está disponível no transmissor. No entanto, CSI perfeita é difícil de se obter em sistemas CoMP devido a um alto número de parâmetros de canal a serem estimados no receptor e enviados para o transmissor. Assim, o desempenho de tais sistemas é comprometido quando a CSI não é perfeitamente conhecida durante o processamento CoMP tal que esse é um problema importante a ser abordado. Algoritmos de agrupamento para Múltiplo Acesso por Divisão no Espaço (SDMA) geralmente são utilizados a fim de encontrar um conjunto adequado de usuários para multiplexação espacial. O maior grupo SDMA nem sempre é o melhor grupo em uma transmissão de dados tal que maiores ganhos podem ser obtidos ajustando dinamicamente o tamanho do grupo SDMA. Além disso, os algoritmos que balanceiam a Razão Sinal-Interferência mais Ruído (SINR) entre diferentes canais podem garantir um certo nível de qualidade de canal e assim proporcionar uma comunicação mais confiável para os usuários agrupados. Esta dissertação de mestrado fornece análises em nível sistêmico para algoritmos de RRA que exploram a coordenação no enlace direto de sistemas CoMP para implementar reuso adaptativo de recursos e assim melhorar o desempenho do sistema. São estudadas aqui estratégias de RRA em sistemas CoMP que consideram agrupamento SDMA dinâmico, precodificação e alocação de potência conjuntas para balanceamento de SINR, sendo assumida CSI imperfeita a fim de conseguir maior aproximação com relação às implementaçõs em cenários reais. É mostrado através de análises em nível sistêmico que ganhos de vazão bastante altos são alcançados através de RRA inteligente. Em conclusão, os resultados mostram que Algoritmos de Remoção Sequencial (SRAs) e de balanceamento de SINR proporcionam ganhos de eficiência espectral do sistema. No entanto, é também mostrada uma degradação crítica no desempenho dessas estratégias de RRA devido à CSI imperfeita.
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Zandegran, Antony Jeyasehar Ansel. "Multi-operator, Multi-Radio Performance Monitoring and Context-Aware access Provision Test-bed". Thesis, KTH, Kommunikationssystem, CoS, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141707.
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Piao, Guihua [Verfasser]. "Radio resource management for integrated services in multi-radio access networks / Universität Kassel. Guihua Piao". Kassel : Kassel Univ. Press, 2007. http://d-nb.info/986595012/34.
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Papadopoulos, Dimitrios Filippos. "A power efficient linear multi-mode CMOS radio transmitter /". Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18122.
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Wu, Di. "Scalable multi-standard radio baseband for modern wireless communications /". Linköping : Department of of Electrical Engineering, Linköping University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-18208.
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Teeraparpwong, Pongsakorn. "Operator and radio resource sharing in multi-carrier environments". Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p1469262.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed October 20, 2009). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 54-56).
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Fortune, P. M. "Multi-level modulation schemes for digital cellular mobile radio". Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/421471/.
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Kumar, Sumit. "Architecture for simultaneous multi-standard software defined radio receiver". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS160.
Testo completoAbstract (sommario):
Motivés par les capacités du SDR, nous théorisons dans ce travail un récepteur de définition radio multi-standard simultané (SMS-SDR). Un récepteur SMS-SDR sera capable de décoder "simultanément" les informations de plusieurs standards sans fil hétérogènes utilisant le même frontal RF. Nos réseaux cibles sont des réseaux à accès aléatoire fonctionnant dans des bandes sans licence. Ces normes fonctionnent sans coordination centralisée et sont soumises à de graves brouillage entre canaux du même type de technologie (CT-CCI) car leurs bandes de fréquences de fonctionnement se chevauchent. Nous développons plusieurs nouveaux algorithmes de traitement du signal en bande de base afin d'éliminer l'ICC des récepteurs à une et plusieurs antennes. Nous avons choisi le cas de l'utilisation de signaux à bande étroite et à large bande, en accordant une attention particulière aux systèmes basés sur OFDM, l'OFDM étant une technique de couche physique essentielle des normes sans fil modernes telles que les familles IEEE 802.11 et 4G. Au cours du développement, nous nous concentrons sur les méthodes pouvant fonctionner de manière autonome dans le récepteur, c'est-à-dire sans aucune coopération de la part de l'émetteur ou de la station de base. De cette manière, ce sont des réseaux à accès aléatoire appropriés fonctionnant dans des bandes sans licence. De plus, les algorithmes peuvent être intégrés à l'infrastructure existante sans aucun effort significatif. Enfin, nos méthodes d'atténuation des interférences sont utilisées pour développer des arbres de décision qui recommandent la séquence d'étapes permettant d'atténuer les interférences entre deux signaux hétérogènes. Enfin, nous avons validé nos algorithmes en les implémentant à l'aide de SDRMotivated by the capabilities of the SDR, we theorize in this work a simultaneous multi-standard radio definition receiver (SMS-SDR). An SMS-SDR receiver will be able to "simultaneously" decode the information of several heterogeneous wireless standards using the same RF front end. Our target networks are random access networks operating in unlicensed bands. These standards operate without centralized coordination and are subject to serious interference between channels of the same type of technology (CT-CCI) because their operating frequency bands overlap. We are developing several new baseband signal processing algorithms to eliminate ICC from single and multi-antenna receivers. We chose the case of the use of narrow-band and broadband signals, paying particular attention to OFDM-based systems, OFDM being an essential physical layer technique of modern wireless standards such as IEEE families 802.11 and 4G. During development, we focus on methods that can operate autonomously in the receiver, that is, without any cooperation from the transmitter or base station. In this way, they are appropriate random access networks operating in unlicensed bands. In addition, the algorithms can be integrated into the existing infrastructure without any significant effort. Finally, our interference mitigation methods are used to develop decision trees that recommend the sequence of steps to mitigate interference between two heterogeneous signals. Finally, we validated our algorithms by implementing them using SDR
26
Sakki, Kranthi Kumar. "A Radio Frequency Identification Multi-Sensor Health Monitoring System". Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10262351.
Testo completoAbstract (sommario):
Health Monitoring Systems (HMS) are used to monitor physiological signals such as the blood pressure, heart rate, and temperature of patients. The use of a HMS for continuous monitoring of the Vital Signs of patients requiring constant medical supervision, is particularly important. The current project presents the development and implementation of a multi-sensor HMS to track and record multiple parameters of a patient (Electrocardiogram, pulse, temperature, and body position). The project development uses biomedical sensor technology for monitoring the physiological signals, Radio Frequency Identification (RFID) technology for patient identification, and the Internet of Things (IoT) for information transmission. Sensors attached to a patient’s body collect data that alert users to abnormal values via smart devices, such as mobile phones or laptops. Experimental testing of the multi-sensor HMS developed and implemented for this project, demonstrates the system’s effectiveness in sensing, collecting, and transmitting accurate patient information for remote monitoring.
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Suárez, Peñaloza Martha. "Architectures d'émetteurs pour des systèmes de communication multi-radio". Thesis, Paris Est, 2009. http://www.theses.fr/2009PEST1050.
Testo completoAbstract (sommario):
Cette thèse porte sur les architectures d’émission pour des terminaux mobiles multi-radio fonctionnant dans la bande de fréquences, 800 MHz - 6 GHz. Avec l’évolution constante des systèmes de communication, les terminaux doivent fonctionner dans plusieurs bandes de fréquences et modes, correspondant à une grande diversité de normes. Le concept d’une architecture multi-radio unique est une évolution de celui de l’émetteur-récepteur multistandard, caractérisé par une mise en parallèle des circuits pour chaque standard. Il permet alors d’optimiser coût et consommation. L’objet de l’étude est de concevoir des architectures d’émission flexibles, à la fois en fréquence et en format de modulation, capables de générer les formes d’ondes de tous les standards en respectant pour chacun le niveau de puissance en sortie et assurant un bon rendement. Ce type d’architectures pourrait, dans l’avenir, être utilisé pour des applications de radio cognitive. L’amplificateur de puissance est l’élément critique dans les émetteurs. Le principe de fonctionnement des amplificateurs impose un compromis entre la linéarité et le rendement en puissance. L’utilisation des amplificateurs en classes commutées permet d’améliorer les performances en rendement mais nécessite de revoir complètement les architectures classiques d’émission. Dans ce contexte, plusieurs architectures qui transforment les signaux avant l’amplificateur et qui peuvent être utilisées pour la multi-radio ont été considérées. Trois, en particulier, ont été analysées et comparées ; à savoir : l’architecture polaire avec codeur d’enveloppe sigma-delta, l’architecture polaire avec codeur d’enveloppe par largeur d’impulsion et l’architecture cartésienne sigma-delta. La validation a été faite sur les signaux les plus critiques en matière de dynamique de puissance et de bande passante, que sont les signaux LTE et WiMAX mobile. En sortie de l’amplificateur, le filtrage d’émission joue un rôle décisif et plusieurs technologies de filtrage sont envisageables. Dans ce cadre, on s’est plus particulièrement intéressé à la technologie BAW (Bulk Acoustic Wave) et un banc de filtres multi-radio a été synthétisé. Cette thèse a donc permis de chiffrer les performances clés d’un émetteur multi-radio à haut rendement en analysant du traitement en bande de base jusqu’au filtrage d’antenneThis research deals with wireless multi-radio transmitter architectures operating in the frequency band of 800 MHz – 6GHz. As a consequence of the constant evolution in the communication systems, the mobile transmitters must be able to operate at different frequency bands and modes according to existing standards specifications. The concept of a unique multi-radio architecture is an evolution of the multi-standard transceiver characterized by a parallelization of circuits for each standard. Multi-radio concept optimizes surface and power consumption. This study concentrates on flexible multi-radio architectures. This kind of architectures could be used in the future for cognitive radio applications. The power amplifier (PA) is the key element in transmitter architectures. Its operating principle establishes a trade-off between power efficiency and linearity. The utilization of a switched mode amplifier allows improving efficiency performances but implies a review of the classical transmitter architectures. Within this context, some architectures transforming the input signal of the PA and that are candidates for multi-radio applications are considered. In particular, three architectures have been analyzed and compared: the polar architecture with sigma-delta envelope modulator, the polar architecture with pulse width modulator and the cartesian sigma delta architecture. Validation is accomplished with the most critical signals in terms of power dynamics and frequency bandwidth; these are the LTE and mobile WiMAX. At the amplifier output, the band-pass filter plays a key role and many filtering technologies could be envisaged. In particular, we are interested in the BAW technology (Bulk Acoustic Wave) and a filter bank has been synthesized. This research has quantified the key performances of a high efficiency multi-radio transmitter by analyzing the system from baseband signal treatment to RF filtering before the antenna
28
Abaii, Mohammad. "Multi-cell radio resource management for future cellular systems". Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/843425/.
Testo completoAbstract (sommario):
Future mobile communications systems will be designed to support a wide range of data rates with complex and conflicting quality of service requirements. It is becoming more challenging to optimize radio resource management and maximise the system capacity whilst meeting the required quality of service from users' point of view. Traditional techniques have approached this problem by mainly focusing on resources within a cell and to large extent ignoring effects of multi-cell architecture leading to non uniform and unstable capacity across the network. This thesis first investigates the potential performance improvements obtained by developing novel distributed scheduling algorithms thereby highlighting the shortcomings of conventional single-cell scheduling techniques in a multi-cell system. It was found that distributed scheduling can achieve superior performance (up to 30% increased cell throughput) compared to conventional one in low/medium system loading. However, there is little advantage in case of heavily loaded system. The main achievement in this thesis is addressing this problem by proposal of a novel technique called Load Matrix, setting a new direction for future research on resource scheduling strategies in a multi-cell system. LM facilitates joint management of interference within and between cells for efficient allocation of radio resources. Simulation results provided show significant improvement in the resource utilization and overall network performance. Using LM technique, the average cell throughput can be increased between 30% to 50%. Results also show that maintaining cell interference within a margin as opposed to a hard target, can significantly improve resource utilization over time (longevity) and over the cells (uniformity). The thesis also compares the effect of ideal LM with practical and implementable versions with channel gain errors, information delay, and reducing LM database to adjacent cells. The conclusion was interesting as the performance degradation in practical LM compared to ideal LM was found to be negligible.
29
Shen, Tianning. "EXPERIMENTAL STUDY OF MULTIRATE MARGIN IN SOFTWARE DEFINED MULTIRATE RADIO". Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1263695252.
Testo completo
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Variano, Fabrizio. "Progettazione e valutazione di un protocollo MAC multi-radio multi-canale per reti wireless". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2726/.
Testo completo
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Choi, Sangil. "Minimum interference channel assignment for multicast in multi-channel multi-radio wireless mesh networks". [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1468073.
Testo completo
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Bales, Jason M. "Multi-channel hardware/software codesign on a software radio platform". Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3400.
Testo completoAbstract (sommario):
Thesis (M.S.)--George Mason University, 2008.Vita: p. 89. Thesis director: David D. Hwang. Submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering. Title from PDF t.p. (viewed Mar. 9, 2009). Includes bibliographical references (p. 85-88). Also issued in print.
33
Lau, Chiew Tong. "Multi-antenna and receiver slotted ALOHA packet radio systems with capture". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30727.
Testo completoAbstract (sommario):
The problem of data transmission in a packet radio system with one central base station and a number of mobile/stationary terminals is addressed. More specifically, the effects of possible collisions between packets on the inbound channel are investigated. Schemes which can be used to improve the performance are studied.
The use of capture to improve the performance of slotted ALOHA systems is discussed.
For a power group division scheme proposed by Metzner in which a capture effect is artificially induced, it is shown that in the two power group case, the higher power packet needs only be able to tolerate interference from up to three lower power packets in order to realize most of the achievable improvement of the infinite capture model. The evaluation of the performance for more than two power groups is also considered. A packet radio system in which a capture effect exists due to the fact that mobiles will generally be at different distances from the base station is also investigated. A number of different capture and spatial distribution models are discussed. Methods for evaluating the probability [formula omitted] of successful reception when there are [formula omitted] contending transmitters are examined. It is shown that a generalized capture model can be used to estimate [formula omitted] for an example system which uses non-coherent frequency shift keying modulation. This model can be applied to other systems as well. In most practical systems, the mobiles cannot get arbitrarily close to the base station. The effects of this constraint on [formula omitted] is examined. The dependence of the capture probability for a test mobile on its distance from the base station is also analyzed.
The use of multiple directional antennas and receivers in a slotted ALOHA system in
which the signals from the different transmitters are received with more or less the same powers is analyzed. It is shown that the performance of the system can be substantially improved by using directional antennas and multiple receivers. Results indicate that fewer than five antennas per receiver are required in order to achieve most of the achievable performance.
A finite population Markov model is used to evaluate the performance of a multi-antenna and receiver slotted ALOHA system in a mobile radio environment in which the signal power levels from different mobiles are no longer equal. The effects of three different antenna patterns, background noise and Rayleigh fading are studied. Here again, numerical results indicate that substantial gains are possible with the use of several antennas and receivers. It is also found that the dynamic behaviour of the system is improved.
The selection of the antennas to be connected to the receivers becomes an issue if the number of receivers at the base station is less than the number of antennas . Four antenna selection schemes are compared for three different channel models, assuming an ideal antenna pattern. It is found that the scheme which selects the antennas with the largest received signal powers is nearly optimum. The effects of using a more practical non-ideal antenna pattern are also discussed.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
34
Furuskär, Anders. "Radio resource sharing and bearer service allocation for multi-bearer service, multi-access wireless networks". Doctoral thesis, KTH, Signals, Sensors and Systems, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3502.
Testo completoAbstract (sommario):
Two expected characteristics of future wireless networks aresupport for multiple bearer services, which in turn enablemultiple end-user services, and the parallel use of multipleradio access technologies. This dissertation discusses radioresource management principles to improve capacity for suchmulti-bearer service, multi-access networks.
More specifically, it is first focused on how to mostefficiently share the radio resource between bearer servicegroups within one access technology. A general principle forsharing resources in interference limited systems is proposed,and its expected performance estimated. The proposedinterference balancing principle maximizes capacity byadjusting the power budgets per bearer service group so thatthe maximum tolerable interference levels are equal for allbearer services. To verify its validity, the interferencebalancing principle is applied to the 3rd generation cellularsystems GSM/EDGE and WCDMA in a set of multi-bearer servicecase studies. It is seen that interference balancing maystraightforwardly be introduced in these systems, and thatsignificant capacity gains over non-balanced scenarios can beachieved.
Secondly, how to best share traffic load between thedifferent sub-systems in a multi-access scenario isinvestigated. The capability to handle bearer services, andthereby also end-user services, typically differs betweensub-systems. The overall multi-access system capacity istherefore affected by the allocation of bearer services on tosub-systems. Based on this, a simple principle for findingfavorable, under certain constraints near-optimum, sub-systembearer service allocations is derived. It is seen that for agiven service mix combined capacities beyond the sum of thesub-system capacities may be achieved by using the favorablebearer service allocations. Significant capacity gains are alsoseen in a case study in which the bearer service allocationprinciple is applied to a combined GSM/EDGE and WCDMAmulti-access system. The bearer service type may be said toreflect an expected radio resource cost for supporting a userin each sub-system. By taking into account the actual radioresource cost, which may differ from the expected cost, whenassigning users to subsystems, further capacity gains areachievable.
35
Vollenbruch, Ulrich. "Design of reconfigurable digital phase locked loops for multi-standard, multi-band mobile radio terminals". München Verl. Dr. Hut, 2008. http://d-nb.info/992163412/04.
Testo completo
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Kim, Hyungwook. "CMOS radio-frequency power amplifiers for multi-standard wireless communications". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44786.
Testo completoAbstract (sommario):
The development of multi-standard wireless communication systems with low cost and high integration is continuously requested and accompanied by the explosive growth of the wireless communication market. Although CMOS technology can provide most building blocks in RF transceivers, the implementation of CMOS RF power amplifiers is still a challenging task. The objective of this research is to develop design techniques to implement fully-integrated multi-mode power amplifiers using CMOS technology.
In this dissertation, a load modulation technique with tunable matching networks and a pre-distortion technique in a multi-stage PA are proposed to support multi-communication standards with a single PA. A fully-integrated dual-mode GSM/EDGE PA was designed and implemented in a 0.18 um CMOS technology to achieve high output power for the GSM application and high linearity for the EDGE application. With the suggested power amplifier design techniques, fully-integrated PAs have been successfully demonstrated in GSM and EDGE applications.
In Addition to the proposed techniques, a body-switched cascode PA core is also proposed to utilize a single PA in multi-mode applications without hurting the performance. With the proposed techniques, a fully-integrated multi-mode PA has been implemented in a 0.18 um CMOS technology, and the power amplifier has been demonstrated successfully for GSM/EDGE/WCDMA applications.
In conclusion, the research in this dissertation provides CMOS RF power amplifier solutions for multiple standards in mobile wireless communications with low cost and high integration.
37
Koudouridis, Georgios. "Study of Multi-Radio Transmission Diversity in Heterogeneous Access Networks". Licentiate thesis, KTH, Kommunikationsnät, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122723.
Testo completoAbstract (sommario):
With the advent of multi-radio access (MRA), an integration of differentradio access technologies (RATs) into a heterogeneous radio access network(RAN) becomes feasible. Such integration allows a user to be at any instantof time served by one or multiple radio accesses (RAs) concurrently, where anRA constitutes an independent radio resource, such as a carrier or a channel,implemented by a single RAT. It also allows a user´s service demands to bemapped onto the aggregated network resources in a transparent and efficientway. An approach for the realization of such multi-radio integrated environmentsis through a unifying generic link layer (GLL) that provides joint radiolink processing and enables communication between nodes and devices acrossdifferent radio accesses.Based on the requirements on multi-access, an architecture that supportsMRA is suggested and the functions of GLL that aims at integrating andutilising multiple RATs are defined. We explore the potential for performanceimprovements through novel extensions of the transmission diversityparadigm which builds on GLL functions that enable multi-radio access selection.Multi-radio transmission diversity (MRTD) is defined as the dynamicselection of radio access for the transmission of a user´s data and it can bethought of as consisting of a packet scheduler operating across multiple radiointerfaces. Different MRTD schemes may be envisaged through combinationsof access re-selection rate, transmission parallelism and transmission redundancy.The re-selection rate refers to the rate at which radio access selectionis performed. It may range from multiple IP packets to one single MACframe. Switched MRTD corresponds to an access selection scheme where auser transmits via one RA at a time, while parallel MRTD corresponds to ascheme where simultaneous transmissions over multiple RAs are scheduled.Finally, redundancy refers to the transmission of copies of the same data overmultiple RAs to increase the possibility of correct reception.The benefits of MRTD are investigated by simulation studies on two multiradiocase scenarios, based on generic RATs and on specific RATs respectively.In the RAT generic scenario, switched MRTD has been evaluated for networktopologies of collocated and non-collocated RAs consisting of macroand pico-cells. In the case of collocated RAs, spectral efficiency is increasedby exploiting diversity in multi-path fading while in non-collocated RAs, thespectral efficiency increase is due to diversity exploitation in both shadowingand multi-path fading. Simulation results show that switched MRTD is mostadvantageous when the RAs provide comparable throughputs. Furthermore,when combined with multi-radio ARQ, MRTD significantly reduces packetloss and packet transmission delays. This is also shown in the specific radioaccesssimulation scenario where a delay sensitive voice service is studied. Inaddition, switched MRTD provides comparable gains to parallel MRTD interms of average packet transmission delay and packet loss, while using lessradio resources. In all cases, it is concluded that maximum performance isconditioned on the reporting delays of the channel quality indicator (CQI).Reporting delays of CQI that are half the channel coherence time render sucha complex MRTD mechanism less effective.QC 20130531
38
Keskin, Faruk [Verfasser]. "Precoding for MIMO multi-user mobile radio downlinks / Faruk Keskin". [Kaiserslautern] : [Universitätsbibliothek], 2007. http://d-nb.info/989961354/34.
Testo completo
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Kondareddy, Yogesh Reddy Agrawal Prathima. "MAC and routing protocols for multi-hop cognitive radio networks". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Electrical_and_Computer_Engineering/Thesis/Kondareddy_Yogesh_18.pdf.
Testo completo
40
Mannering, Elizabeth J. A. "A multi-wavelength study of radio-loud active galactic nuclei". Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619451.
Testo completoAbstract (sommario):
In part I. I construct a sample of radio-loud active galactic nuclei (AGN) host galaxies from the optical Sloan Digital Sky Survey (SDSS) and Faint Images of the Radio Sky at Twenty cm (FIRST). These have 1.4GHz luminosities in the range 1023 - 1025 WHZ-l, span redshifts 0.02 < z < 0.18, are brighter than rpetro < 17.77 mag and are constrained to 'early-type' morphology in colour space (u• - r• > 2.22 mag). Optical emission-line ratios (at > 311) are used to remove type 1 AGN and star-forming galaxies from the radio sample using BPT diagnostics. For comparison, a sample of radio-quiet galaxies with the same r• -band magnitude-redshift distribution as the radio sample is selected. I also create comparison radio and control samples derived by adding the NRAO VLA Sky Survey (NVSS), to quantify the effect of completeness on the results. I investigate the effective radii of the surface brightness profiles in the SDSS r and u bands in order to quantify any excess of blue colour in the inner region of radio galaxies. A ratio is defined, R = r e( r) Ir e( u), and maximum likelihood analysis is used to compare the average value of R and its intrinsic dispersion between samples. R is larger for the radio-loud AGN sample as compared to its control counterpart, and I conclude that the two samples are not drawn from the same population at > 99% significance. I discuss host galaxy features that cause the presence of a radio-loud AGN to increase the scale size of a galaxy in red relative to blue light, including excess central blue emission driven by star formation, point-like blue emission from the AGN itself, and/or diffuse red emission. I favour an explanation that arises from the stellar rather than the AGN light. Given that iii star formation proceeds over a longer time than radio activity, the difference suggests that a subset of galaxies has a structured predisposition to become radio loud. In Part 2, I report results from Chandra and XMM-Newton observations of seven nearby (z < 0.07) radio galaxies. Each source shows evidence of an X-ray emitting gas belt, 011hogonal to and lying between the radio lobes, coincident with a deficit in radio emission. Detection of weak emission from a second, more ex tended group-type environment is also reported, as well as inverse-Compton X-ray emissions from the radio lobes in six of the sources. The X-ray emission from the nuclei correlates well with the core 5 GHz flux densities, supporting an emission origin at the base of the jet. Three high-ionization narrow-line radio galaxies in the sample show evidence for an additional absorbed component, consistent with the model in which they are fuelled by a standard thin accretion disk, heavily absorbed in X-rays when edge-on to the observer. The work extends previous detection of lobe inverse-Compton X-ray emission into the FRI regime, and the magnetic-field estimates shows that these systems are close to equipartition, or slightly electron dominated, as is found for FR II sources in other studies. The origin of the gas belts is diverse. The work concludes that two of the belts (those of NGC 7385 and NGC 6109) are galactic coronae, flattened by the expanding radio lobes. The belts of3C 192 and 4C73.08 are attributed to accumulated gas from merging groups of galaxies residing within the gas belt. For 3C 386, the belt is consistent with a hot gas halo surrounding an isolated field elliptical In the case of 3C 35 and 3C 98, the gas belt is interpreted as fossil -group gas driven outwards by the expanding radio lobes. The morphological structure of the radio lobes and gas belt point to co-evolution. Furthermore, the radio sources are powerful enough to eject galaxy-scale gas out to the edges of the gas belts, and the ages of the belts and radio structures are comparable in both sources. The destruction of 3C 35 and 3C 98's atmospheres may offer clues as to how fossil systems are regulated: radio galaxies may need to be within a particular range of intermediate powers to displace and regulate fossil-group gas. I discuss the implications of the gas belts in 3C 35 and 3C 98 in terms of AGN fuelling and feedback.
41
Abdelnasser, Amr Adel Nasr. "Radio resource management techniques for multi-tier cellular wireless networks". IEEE Transactions on Mobile Computing, 2013. http://hdl.handle.net/1993/30993.
Testo completoAbstract (sommario):
There is a prolific increase in the penetration of user devices such as smartphones and tablets. In addition, user expectations for higher Quality of Service (QoS), enhanced data rates and lower latencies are relentless. In this context, network densification through the dense deployment of small cell networks, underlaying the currently existing macrocell networks, is the most appealing approach to handle the aforementioned requirements. Small cell networks are capable of reusing the spectrum locally and providing most of the capacity while macrocell networks provide a blanket coverage for mobile user equipment (UEs). However, such setup imposes a lot of issues, among which, co-tier and cross-tier interference are the most challenging.
To handle co-tier interference, I have proposed a semi-distributed (hierarchical) interference management scheme based on joint clustering and resource allocation (RA) for small cells. I have formulated the problem as a Mixed Integer Non-Linear Program (MINLP), whose solution was obtained by dividing the problem into two sub-problems, where the related tasks were shared between the Femto Gateway (FGW) and small cells. As for cross-tier interference, I have formulated RA problems for both the macrocell and small cells as optimization problems. In particular, I have introduced the idea of ``Tier-Awareness'' and studied the impact of the different RA policies in the macrocell tier on the small cells performance. I have shown that the RA policy in one tier should be carefully selected. In addition, I have formulated the RA problem for small cells as an optimization problem with an objective function that accounts for both RA and admission control (AC). Finally, I have studied cloud radio access network (C-RAN) of small cells which has been considered as a typical realization of a mobile network which is capable of supporting soft and green technologies in Fifth Generation (5G) networks, as well as a platform for the practical implementation of network multiple-input multiple-output (MIMO) and coordinated multi-point (CoMP) transmission concepts.February 2016
42
Roman, Mircea Cristian. "Heterogeneous parallel multi-radio transmission system in wireless vehicular communication". Thesis, Oxford Brookes University, 2016. https://radar.brookes.ac.uk/radar/items/cd528ff7-5eea-4b5c-992a-ef5c923c155b/1/.
Testo completoAbstract (sommario):
In the context of growing demand for mobile data and the emergence of ve hicular applications, heterogeneous networks will become a necessity to meet the various requirements of future Intelligent Transport Systems. The aim of this research work is to investigate the use of heterogeneous vehicular wireless net works with multiple independent Radio Access Technologies (RATs). A Multiple Interface Scheduling System (MISS) is proposed, based on a user perspective, where the vehicle has visibility of all the available RATs, with no modification to the fixed infrastructure, operator independent, to improve the performance of vehicular networks. Multi RAT solutions have been reported previously where the packets are scheduled at different layers of the OSI seven-layered architecture but they require modifying the routing protocols, have one IP address per RAT or involve designing specific solution for each RAT. To overcome these limita tions, the proposed approach is to schedule the packets at an intermediate layer located between the network layer and the MAC layer. This solution avoids any changes to the RAT standards, and maintains a single IP address. An adaptive scheduling algorithm has been devised which is comprised of automatic wireless access interface selection, intelligent bandwidth aggregation and allocation, seamless Quality of Service (QoS) support, and context-aware packet scheduling. The system dynamically selects the most suitable wireless technology in a given space and time, or it may use the technologies j ointly to maximise the throughput, or improve the reliability that can be achieved with a single radio technology. This work focusses on the uplink, and it addresses the scenario where the vehicle is treated as a data source. The evaluated wireless technologies include cellular (4G) and Wi-Fi (802.llp and 802.lln). The proposed scheme has been simulated and implemented in hardware to validate the performance of the proposed packet scheduler. The results and hardware implementation demonstrate that the scheduling algorithm is able to transfer packets transparently over multiple RATs to provide higher availabil ity and/or throughput together with prioritization of selected services, without requiring any change to existing wireless standards. In terms of scalability, the intermediate layer approach is shown to be suitable for supporting connectivity by increasing the availability of uplink connection with the current infrastruc ture. Such an approach is not only valid for heterogeneous vehicular networks but can be used by mobile devices and the future internet of things where the goal is to upload information from different devices anywhere and at any time.
43
Kozal, Ahmed Sultan Bilal. "Multi user cooperation spectrum sensing in wireless cognitive radio networks". Thesis, Liverpool John Moores University, 2015. http://researchonline.ljmu.ac.uk/4474/.
Testo completoAbstract (sommario):
With the rapid proliferation of new wireless communication devices and services, the demand for the radio spectrum is increasing at a rapid rate, which leads to making the spectrum more and more crowded. The limited available spectrum and the inefficiency in the spectrum usage have led to the emergence of cognitive radio (CR) and dynamic spectrum access (DSA) technologies, which enable future wireless communication systems to exploit the empty spectrum in an opportunistic manner. To do so, future wireless devices should be aware of their surrounding radio environment in order to adapt their operating parameters according to the real-time conditions of the radio environment. From this viewpoint, spectrum sensing is becoming increasingly important to new and future wireless communication systems, which is designed to monitor the usage of the radio spectrum and reliably identify the unused bands to enable wireless devices to switch from one vacant band to another, thereby achieving flexible, reliable, and efficient spectrum utilisation. This thesis focuses on issues related to local and cooperative spectrum sensing for CR networks, which need to be resolved. These include the problems of noise uncertainty and detection in low signal to noise ratio (SNR) environments in individual spectrum sensing. In addition to issues of energy consumption, sensing delay and reporting error in cooperative spectrum sensing. In this thesis, we investigate how to improve spectrum sensing algorithms to increase their detection performance and achieving energy efficiency. To this end, first, we propose a new spectrum sensing algorithm based on energy detection that increases the reliability of individual spectrum sensing. In spite of the fact that the energy detection is still the most common detection mechanism for spectrum sensing due to its simplicity. Energy detection does not require any prior knowledge of primary signals, but has the drawbacks of threshold selection, and poor performance due to noise uncertainty especially at low SNR. Therefore, a new adaptive optimal energy detection algorithm (AOED) is presented in this thesis. In comparison with the existing energy detection schemes the detection performance achieved through AOED algorithm is higher. Secondly, as cooperative spectrum sensing (CSS) can give further improvement in the detection reliability, the AOED algorithm is extended to cooperative sensing; in which multiple cognitive users collaborate to detect the primary transmission. The new combined approach (AOED and CSS) is shown to be more reliable detection than the individual detection scheme, where the hidden terminal problem can be mitigated. Furthermore, an optimal fusion strategy for hard-fusion based cognitive radio networks is presented, which optimises sensing performance. Thirdly, the need for denser deployment of base stations to satisfy the estimated high traffic demand in future wireless networks leads to a significant increase in energy consumption. Moreover, in large-scale cognitive radio networks some of cooperative devices may be located far away from the fusion centre, which causes an increase in the error rate of reporting channel, and thus deteriorating the performance of cooperative spectrum sensing. To overcome these problems, a new multi-hop cluster based cooperative spectrum sensing (MHCCSS) scheme is proposed, where only cluster heads are allowed to send their cluster results to the fusion centre via successive cluster heads, based on higher SNR of communication channel between cluster heads. Furthermore, in decentralised CSS as in cognitive radio Ad Hoc networks (CRAHNs), where there is no fusion centre, each cognitive user performs the local spectrum sensing and shares the sensing information with its neighbours and then makes its decision on the spectrum availability based on its own sensing information and the neighbours’ information. However, cooperation between cognitive users consumes significant energy due to heavy communications. In addition to this, each CR user has asynchronous sensing and transmission schedules which add new challenges in implementing CSS in CRAHNs. In this thesis, a new multi-hop cluster based CSS scheme has been proposed for CRAHNs, which can enhance the cooperative sensing performance and reduce the energy consumption compared with other conventional decentralised cooperative spectrum sensing modes.
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Maheshwarappa, Mamatha R. "Software defined radio (SDR) architecture for concurrent multi-satellite communications". Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/813388/.
Testo completoAbstract (sommario):
SDRs have emerged as a viable approach for space communications over the last decade by delivering low-cost hardware and flexible software solutions. The flexibility introduced by the SDR concept not only allows the realisation of concurrent multiple standards on one platform, but also promises to ease the implementation of one communication standard on differing SDR platforms by signal porting. This technology would facilitate implementing reconfigurable nodes for parallel satellite reception in Mobile/Deployable Ground Segments and Distributed Satellite Systems (DSS) for amateur radio/university satellite operations. This work outlines the recent advances in embedded technologies that can enable new communication architectures for concurrent multi-satellite or satellite-to-ground missions where multi-link challenges are associated. This research proposes a novel concept to run advanced parallelised SDR back-end technologies in a Commercial-Off-The-Shelf (COTS) embedded system that can support multi-signal processing for multi-satellite scenarios simultaneously. The initial SDR implementation could support only one receiver chain due to system saturation. However, the design was optimised to facilitate multiple signals within the limited resources available on an embedded system at any given time. This was achieved by providing a VHDL solution to the existing Python and C/C++ programming languages along with parallelisation so as to accelerate performance whilst maintaining the flexibility. The improvement in the performance was validated at every stage through profiling. Various cases of concurrent multiple signals with different standards such as frequency (with Doppler effect) and symbol rates were simulated in order to validate the novel architecture proposed in this research. Also, the architecture allows the system to be reconfigurable by providing the opportunity to change the communication standards in soft real-time. The chosen COTS solution provides a generic software methodology for both ground and space applications that will remain unaltered despite new evolutions in hardware, and supports concurrent multi-standard, multi-channel and multi-rate telemetry signals.
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Toomey, James IV. "The galactic center radio arc : a multi-frequency polarimetric study". Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4774.
Testo completoAbstract (sommario):
Despite the Radio Arc non-thermal filaments (NTFs) being discovered 30 years ago, their origin remain poorly understood. The Radio Arc NTFs have an unusually flat spectrum in the centimeter to millimeter spectrum with a predicted, though poorly constrained, turn-over between 30-200 GHz. With the recently upgraded wide-band capabilities of the VLA, we conducted a multi-frequency polarimetric study of the Radio Arc region. With observations at a set of low radio frequencies (continuous coverage over 2-6 GHz & 10-12 GHz), we imaged both the total and polarized intensity distributions at high angular resolution (<1"). Presented here are the preliminary results from four observations spanning May 2013 to February 2014 using the DnC, CnB, B & BnA array configurations. This study has produced the deepest continuum intensity images of the Radio Arc region to date, with a sensitivity an order of magnitude greater than previous surveys, and resulted in the detection of new structure and compact emission sources. These observations will serve as a pilot polarization study for larger, more complete polarimetric surveys of the Galactic center region.
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Wing, Joshua David. "A multi-wavelength study of galaxy clusters hosting radio sources". Thesis, Boston University, 2013. https://hdl.handle.net/2144/12891.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Galaxy clusters play an important role in understanding the formation of structure in the Universe and can be used to constrain cosmological parameters. Thousands of clusters are known in the nearby Universe, but few are confirmed at large distances. Remote clusters provide a view of the early Universe, and are important for studying galaxy evolution. Here, I describe a technique for finding distant clusters using bent, double-lobed radio galaxies. These radio sources are active galactic nuclei (AGN) that result from outflows of material surrounding supermassive black holes in the centers of massive galaxies. These outflows are typically bent as a result of the relative motion between the host galaxy and the surrounding hot gas that fills clusters. Using the Sloan Digital Sky Survey (SDSS) and the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey, I determine the frequency with which bent radio sources are associated with rich galaxy clusters in the nearby Universe (z < 0.5), as compared to non-bent radio sources. I find that > 60% of bent radio sources are located in rich cluster environments, compared to 10 - 20% of non-bent radio sources. Therefore, bent radio sources are efficient tracers for clusters and are useful as beacons of clusters at large distances. Bent radio sources may achieve their morphologies through large-scale cluster mergers that set the intracluster medium (ICM) in motion. Using a suite of substructure tests, I determine the significance of optical substructure in clusters containing radio sources. I find no preference for substructure in clusters with bent double-lobed sources compared to other types of radio sources, indicating that bent sources will not necessarily preferentially select clusters undergoing recent largescale mergers. Having established that bent radio sources efficiently locate clusters, I have obtained deep, follow-up observations at optical and near-infrared wavelengths to uncover associated distant cluster candidates. In addition, a large Spitzer Space Telescope survey is underway to observe all bent sources not detected in the SDSS. Follow-up observations reveal a large number of high-redshift candidates. Further study of these objects will lend insight into galaxy formation and evolution and feedback between an AGN and its environment at high-redshift for clusters with a range of masses.
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Yang, Xi. "Filter-less Architecture for Multi-Carrier Software Defined Radio Transmitters". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1321403816.
Testo completo
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Ertas, Tuncay. "Trellis coded multi-h CPM for digital mobile radio systems". Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358879.
Testo completo
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Ibar, Eduardo. "Deep multi-frequency radio observations of the SHADES fields and the nature of the faint radio populaton". Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3845.
Testo completoAbstract (sommario):
The two SCUBA HAlf-Degree Extragalactic Survey (SHADES) fields are amongst the richest places in the sky in terms of multi-wavelength coverage. They comprise an eastern section of the Lockman Hole (LH) and the central portion of the Subaru- XMM/Newton Deep Field (SXDF). In this thesis, I have obtained extremely deep, multi-frequency radio imaging of the SHADES fields using the GiantMetre-wave Radio Telescope (GMRT) and the Very Large Array (VLA), at 610MHz and 1.4GHz, respectively. These data are used to analyse the nature of the sub-milliJansky (sub-mJy) radio population, which has been hotly debated in the last few years: are they powered by star-forming or nuclear activity? To tackle the problem, I employ different approaches making use of the large variety of multi-wavelength data in the SHADES fields. I begin by analysing the spectral index, α610MHz 1.4GHz , of radio sources detected in the LH, to explore the dominant emission mechanism. Based on a robust 10 σ detection criterion, I find a constantmedian spectral index of α610MHz 1.4GHz ≈ −0.6 to −0.7 for sources between S1.4GHz ≈ 200 μJy and 10mJy. This result suggests that the galaxy population in the sub-mJy regime is powered by optically-thin synchrotron emission – starforming galaxies or lobe-dominated active galactic nuclei (AGN). Making use of X-ray observations in the LH, I show that the fraction of radio sources detected in the hard X-ray band (between 2 and 10 keV) decreases from 50 to 15 per cent between S1.4GHz ≈ 1mJy and . 100 μJy, which strongly suggests a transition from AGN to star-forming galaxies. Based on the deep, multi-wavelength coverage of the SXDF, I explore the behaviour of the far-infrared (FIR)/radio correlation as a function of redshift. I combine the q24 factor – the logarithmic flux density ratio between Spitzer 24-μm and VLA 1.4- GHz flux densities – with available photometric redshifts and find strong evidence that the correlation holds out to z ≈ 3.5. Based on M82-like k-corrections and using a high-significance (S1.4GHz > 300 μJy) radio sub-sample, I find a mean and scatter of q24 = 0.71 ± 0.47. Monte-Carlo simulations based on these findings show that fewer sources deviate from the correlation at fainter flux densities (i.e. fewer radioloud AGN). I predict that the radio-loud fraction drops from 50 per cent at ∼ 1mJy to zero at . 100 μJy. The validity of the FIR/radio correlation out to very high redshifts adds credibility to identifications of sub-millimetre (submm) galaxies (SMGs) made at radio wavelengths. Based on a sample of 45 radio-identified SMGs in the LH, I find a median radio spectral index of α610MHz 1.4GHz = −0.72 ± 0.07, which suggests that optically-thin synchrotron is the dominant radio emission mechanism. Finally, as anAppendix I include a theoretical treatment that constrains the average geometry of the dusty, torus-like structures believed to obscure a large fraction of the AGN population. I use the distribution of column densities (NH) obtained from deep ∼ 1Msec X-ray observations in the Chandra Deep Field South. I find that to reproduce the wide observed range of NH, the best torus model is given by a classical “donut”- shaped distribution with an exponential angular dependency of the density profile.
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Teixeira, de oliveira Carina. "Conception et optimisation de performance inter-couches dans les réseaux maillés radio multi-canal multi-interface". Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00771426.
Testo completoAbstract (sommario):
Dans cette thèse, nous nous concentrons sur la conception et l'optimisation de performances inter-couches dans les réseaux maillés radio multi-canal multi-interface. Afin de profiter de l'augmentation de la capacité de ces réseaux, un certain nombre de problèmes doit être résolu. La première contribution de cette thèse est une nouvelle classification et une évaluation formelle des différentes stratégies d'assignation de canaux et d'interfaces. Nous adressons en particulier la connectivité en termes de formation de topologie, densité de connexions et découverte de voisinage. La deuxième contribution présente des algorithmes de broadcast fonctionnant pour n'importe quelle stratégie d'assignation multi-canal multi-interface. Ces algorithmes garantissent qu'un paquet de broadcast est délivré avec une probabilité minimale à tous les voisins. La troisième contribution de cette thèse propose d'évaluer la capacité (débit) obtenue à travers les différentes solutions d'assignation de canaux et d'interfaces. Plus précisément, nous proposons trois formulations de programmation linéaire mixte pour modéliser le routage et les contraintes de partage de bande passante en présence d'interférences. Nous dérivons ensuite des bornes supérieures et inférieures pour deux stratégies MAC différentes. Notre dernière contribution propose de développer une solution de routage inter-couches pour les réseaux maillés multi-canal multi-interface. En particulier, nous proposons une métrique de qualité de lien estimant la bande passante résiduelle d'un lien. Un protocole de routage adapté permet ensuite de trouver les routes offrant le meilleur débit. Toutes nos contributions sont validées par des nombreuses simulations qui démontrent l'efficacité de nos solutions. En résumé, cette thèse fournit une analyse en profondeur des réseaux maillés radio multi-canal multi-interface, ainsi que des lignes directrices pour les concepteurs de réseaux afin de déployer des réseaux performants.