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1
Bannister, Keith. "Radio transients: Surveys and Techniques." Thesis, The University of Sydney, 2011. http://hdl.handle.net/2123/13293.
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I present two pilot surveys and a range of new algorithms to aid in planning and implementing wide-field radio surveys for transient and variable sources. The first pilot survey is a blind survey for transient and variable radio sources with the Molonglo Observatory Synthesis Telescope at 843~MHz. This survey discovered 53 highly variable sources and 15 transient sources and determined surface densities of $0.268 \unit{deg^{-2}}$ for variable sources and $1.3 \times 10^{-2} \unit{deg^{-2}}$ for transient sources, with associated timescales of between one day and three years. I also propose two new techniques which were developed for this survey. The first technique provides a post-imaging calibration for image gain. The second technique is a statistical method for verifying whether flux error measurements agree with the scatter in light curves over a population of sources. I also describe a follow-up survey for prompt radio emission from gamma ray bursts (GRBs) at 1.4~GHz. This survey used a single-dish telescope to automatically slew to a GRB position within 2~min of the gamma ray trigger and performed single-pulse, repeating and low-time resolution searches for variability. This survey discovered single, dispersed pulses following two long GRBs, which are possibly related to the delayed formation of a black hole at the centre of the GRBs. The high-time resolution measurements from this survey are some of the most constraining limits on prompt radio emission from GRBs to date. I also present two efficient new algorithms for detecting dispersed radio emission in interferometric data: the Chirpolator and the Chimageator. These two techniques excel in the regime of sparse arrays, where they both require substantially lower data rates, and the Chirpolator requires a much lower post-integrator operation rate than the existing algorithms. These techniques are well matched to future supercomputing architectures, where the arithmetic capability is outstripping the bandwidth capa! bility, and are therefore suitable for use by interferometer-based fast transient surveys. The surveys and techniques described in this thesis will have immediate application to upcoming surveys with the next generation of wide-field radio telescopes, such as the two transients surveys proposed for the Australian Square Kilometre Array Pathfinder.
2
Videv, Stefan. "Techniques for green radio cellular communications." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7988.
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This thesis proposes four novel techniques to solve the problem of growing energy consumption requirements in cellular communication networks. The first and second part of this work propose a novel energy efficient scheduling mechanism and two new bandwidth management techniques, while the third part provides an algorithm to actively manage the power state of base stations (BSs) so that energy consumption is minimized throughout the day while users suffer a minimal loss in achieved data rate performance within the system. The proposed energy efficient score based scheduler (EESBS) is based on the already existing principle of score based resource allocation. Resource blocks (RBs) are given scores based on their energy efficiency for every user and then their allocation is decided based on a comparison between the scores of the different users on each RB. Two additional techniques are introduced that allow the scheduler to manage the user’s bandwidth footprint or in other words the number of RBs allocated. The first one, bandwidth expansion mode (BEM), allows users to expand their bandwidth footprint while retaining their overall transmission data rate. This allows the system to save energy due to the fact that data rate scales linearly with bandwidth and only logarithmically with transmission power. The second technique, time compression mode (TCoM), is targeted at users whose energy consumption is dominated by signalling overhead transmissions. If the assumption is made that the overhead is proportional to the number of RBs allocated, then users who find themselves having low data rate demands can release some of their allocated RBs by using a higher order modulation on the remaining ones and thus reduce their overall energy expenditure. Moreover, a system that combines all of the aforementioned scheduling techniques is also discussed. Both theoretical and simulation results on the performance of the described systems are provided. The energy efficient hardware state control (EESC) algorithm works by first collecting statistical information about the loading of each BS during the day that is due to the particular mobility patterns of users. It then uses that information to allow the BSs to turn off for parts of the day when the expected load is low and they can offload their current users to nearby cell sites. Simplified theoretical, along with complete system computer simulation, results are included. All the algorithms presented are very straightforward to implement and are not computationally intensive. They provide significant energy consumption reductions at none to minimal cost in terms of experienced user data rate.
3
Li, Haibin. "Multiple access techniques for cognitive radio." Thesis, University of York, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546818.
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Webb, William. "QAM techniques for digital mobile radio." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385448.
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Shen, Juei-Chin. "Detection and estimation techniques in cognitive radio." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/detection-and-estimation-techniques-in-cognitive-radio(8d246e71-4484-4843-a1f4-4cce4504dd1c).html.
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Faced with imminent spectrum scarcity largely due to inflexible licensed band arrangements, cognitive radio (CR) has been proposed to facilitate higher spectrum utilization by allowing cognitive users (CUs) to access the licensed bands without causing harmful interference to primary users (PUs). To achieve this without the aid of PUs, the CUs have to perform spectrum sensing reliably detecting the presence or absence of PU signals. Without reliable spectrum sensing, the discovery of spectrum opportunities will be inefficient, resulting in limited utilization enhancement. This dissertation examines three major techniques for spectrum sensing, which are matched filter, energy detection, and cyclostationary feature detection. After evaluating the advantages and disadvantages of these techniques, we narrow down our research to a focus on cyclostationary feature detection (CFD). Our first contribution is to boost performance of an existing and prevailing CFD method. This boost is achieved by our proposed optimal and sub-optimal schemes for identifying best hypothesis test points. The optimal scheme incorporates prior knowledge of the PU signals into test point selection, while the sub-optimal scheme circumvents the need for this knowledge. The results show that our proposed can significantly outperform other existing schemes. Secondly, in view of multi-antenna deployment in CR networks, we generalize the CFD method to include the multi-antenna case. This requires effort to justify the joint asymptotic normality of vector-valued statistics and show the consistency of covariance estimates. Meanwhile, to effectively integrate the received multi-antenna signals, a novel cyclostationary feature based channel estimation is devised to obtain channel side information. The simulation results demonstrate that the errors of channel estimates can diminish sharply by increasing the sample size or the average signal-to-noise ratio. In addition, no research has been found that analytically assessed CFD performance over fading channels. We make a contribution to such analysis by providing tight bounds on the average detection probability over Nakagami fading channels and tight approximations of diversity reception performance subject to independent and identically distributed Rayleigh fading. For successful coexistence with the primary system, interference management in cognitive radio networks plays a prominent part. Normally certain average or peak transmission power constraints have to be placed on the CR system. Depending on available channel side information and fading types (fast or slow fading) experienced by the PU receiver, we derive the corresponding constraints that should be imposed. These constraints indicate that the second moment of interference channel gain is an important parameter for CUs allocating transmission power. Hence, we develop a cooperative estimation procedure which provides robust estimate of this parameter based on geolocation information. With less aid from the primary system, the success of this procedure relies on statistically correlated channel measurements from cooperative CUs. The robustness of our proposed procedure to the uncertainty of geolocation information is analytically presented. Simulation results show that this procedure can lead to better mean-square error performance than other existing estimates, and the effects of using inaccurate geolocation information diminish steadily with the increasing number of cooperative cognitive users.
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Koutitas, G. C. "Advanced physical techniques for radio channel modeling." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843649/.
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Wireless technology constitutes the basis of the majority of modem communication systems. The deployment of wireless systems mainly concerns data services such as mobile and broadcasting applications, or target identification and military services. The key element for the successful planning of any kind of wireless network is the detailed and in depth knowledge of the propagation channel. The mobility of the user and the physical obstructions that may intervene in the propagation path between the communication points cause distortion to the transmitted information. The understanding of the propagation conditions and the channel characterisation is achieved either by extensive measurement campaigns or by employing sophisticated propagation algorithms. Since the measurement campaign is an expensive and time consuming task, contemporary research is focused on the development of deterministic models that can accurately predict the channel behaviour in real environments. The demand for high data delivery services in modem communication systems requires the utilisation of large bandwidth at high frequency regions of the available spectrum. Therefore, asymptotic high frequency modelling techniques and relevant algorithms have emerged as the major propagation modelling tools for modern radio systems analysis and design. In this thesis, we address the problem of high frequency diffraction over complex structures and scenarios that incorporate a cascade of physical canonical obstructions in the propagation path between the two ends. New formulations are derived for field predictions over rounded surfaces and a cascade of multi-shape structures. The Uniform Theory of Diffraction (UTD) is applied in all the work and it is further extended to account for transition zone diffraction over scenarios that incorporate arbitrary multiple canonical objects being multi-shaped in nature. The concept of continuity equations and slope diffraction are also emphasized. The simulation results show uniform and accurate field predictions and extensive comparison tests are performed with other diffraction theories and measurements. The developed formulations are incorporated in a propagation tool for irregular terrain channel modelling. An unambiguous terrain modelling algorithm is synthesized and used to assign optimum fitted canonical shapes to the terrain irregularities. The results of the simulations are compared with real measurements over irregular scenarios and a very good fit is observed. The importance of the choice of the used canonical shape to the terrain modelling is also highlighted.
7
Rockliff, Simon C. "Frequency hopping techniques for digital mobile radio /." Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phr683.pdf.
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Jurkov, Alexander S. "Techniques for efficient radio frequency power conversion." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122558.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 293-304).
A diverse range of radio-frequency (RF) power applications demand RF power generation systems that allow for dynamic output power control while having the capability to efficiently deliver power into a varying load. While some of these existing and emerging applications are characterized with narrowband or single-frequency operation, others require operation over a range of frequencies. In such applications, the system architecture typically comprises an RF power amplifier (PA) or inverter along with a tunable impedance matching network (TMN). Electronically-controlled TMNs offer substantial benefits when it comes to the implementability of such highly reconfigurable and adaptive RF systems as they allow for proper impedance termination of the PA or inverter over the operating load and frequency range. This work explores the design of TMNs based on a solid-state technique that allows for faster and more accurate impedance matching compared to traditional approaches. The performance and design of such TMNs is demonstrated for plasma driving applications at 13.56 MHz. In addition, this work proposes techniques for designing switched-mode RF inverters that can operate efficiently over a wide load impedance range. These techniques are applied to the design of class E and class [Phi]2 inverter prototypes at 27.12 MHz, and their ability to handle large load modulation while maintaining high operating efficiency is demonstrated. The techniques presented in this work can be further applied to the integration of an RF power amplifier/inverter and a TMN into a single multi-transistor architecture capable of efficiently operating across frequency and load variation while providing dynamic output power control.
by Alexander Jurkov.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
9
Jayasinghe, Sankissa G. "Techniques of detection, estimation and coding for fading channels." Thesis, Loughborough University, 1989. https://dspace.lboro.ac.uk/2134/7282.
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The thesis describes techniques of detection, coding and estimation, for use in high speed serial modems operating over fading channels such as HF radio and land mobile radio links. The performance of the various systems that employ the above techniques are obtained via computer simulation tests. A review of the characteristics of HF radio channels is first presented, leading to the development of an appropriate channel model which imposes Rayleigh fading on the transmitted signal. Detection processes for a 4.8 kbit/s HF radio modem are then discussed, the emphasis, here, being on variants of the maximum likelihood detector that is implemented by the Viterbi algorithm. The performance of these detectors are compared with that of a nonlinear equalizer operating under the same conditions, and the detector which offers the best compromise between performance and complexity is chosen for further tests. Forward error correction, in the form of trellis coded modulation, is next introduced. An appropriate 8-PSK coded modulation scheme is discussed, and its operation over the above mentioned HF radio modem is evaluated. Performance comparisons are made of the coded and uncoded systems. Channel estimation techniques for fast fading channels akin to cellular land mobile radio links, are next discussed. A suitable model for a fast fading channel is developed, and some novel estimators are tested over this channel. Computer simulation tests are also used to study the feasibility of the simultaneous transmission of two 4-level QAM signals occupying the same frequency band, when each of these signals are transmitted at 24 kbit/s over two independently fading channels, to a single receiver. A novel combined detector/estimator is developed for this purpose. Finally, the performance of the complete 4.8 kbit/s HF radio modem is obtained, when all the functions of detection, estimation and prefiltering are present, where the prefilter and associated processor use a recently developed technique for the adjustment of its tap gains and for the estimation of the minimum phase sampled impulse response.
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Warner, Edward Steven. "Novel bandwidth utilization techniques for radio-determination systems." Thesis, Bangor University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316345.
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Fox, Richard N. "Effect of economic techniques on radio frequency utilization." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28139.
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Kotsopoulos, S. A. "Frequency planning techniques for cellular mobile radio systems." Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332176.
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VINHOZA, TIAGO TRAVASSOS VIEIRA. "RADIO RESEARCH MANAGEMENT TECHNIQUES FOR HIERARCHICAL CELL SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4460@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORSistemas de celulares de múltiplas camadas (hierarquizados) são úteis para acomodar densidade alta de tráfego mantendo a qualidade de serviço. Estes sistemas procuram agregar as vantagens dos sistemas micro e macrocelulares que são respectivamente: o aumento da capacidade do sistema e a carga de sinalização da rede. Neste trabalho são analisados aspectos de projeto e desempenho de estruturas hierarquizadas como: compartilhamento do espectro entre as camadas de micro- células e macro-células bem como o desempenho de diferentes estratégias de handoff entre essas camadas. Um outro objetivo do trabalho foi o desenvolvimento de uma ferramenta simples de simulação capaz de testar as diversas estratégias de handoff e o desempenho do sistema para diferentes soluções para a distribuição dos recursos de rádio entre camadas.
Multilayer cell systems are useful to accommodate high traffic densities while still satisfying the QoS requirements. These systems combine the advantages of microcellular and macrocellular systems which are: the increase of system capacity and the reduction of the number of handoffs, hence decreasing the signaling load. This work address design aspects such as spectrum sharing between the macrocell and microcell layers and the performance of different handoff strategies considering both layers. Another goal of this work was the development of a simple, but realistic, simulation tool which will allow obtaining the radio resources management results here presented.
14
Sellars, Malcolm Paul. "Low complexity equalization techniques for broadband indoor radio." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621727.
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Makhathini, Sphesihle. "Advanced radio interferometric simulation and data reduction techniques." Thesis, Rhodes University, 2018. http://hdl.handle.net/10962/57348.
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This work shows how legacy and novel radio Interferometry software packages and algorithms can be combined to produce high-quality reductions from modern telescopes, as well as end-to-end simulations for upcoming instruments such as the Square Kilometre Array (SKA) and its pathfinders. We first use a MeqTrees based simulations framework to quantify how artefacts due to direction-dependent effects accumulate with time, and the consequences of this accumulation when observing the same field multiple times in order to reach the survey depth. Our simulations suggest that a survey like LADUMA (Looking at the Distant Universe with MeerKAT Array), which aims to achieve its survey depth of 16 µJy/beam in a 72 kHz at 1.42 GHz by observing the same field for 1000 hours, will be able to reach its target depth in the presence of these artefacts. We also present stimela, a system agnostic scripting framework for simulating, processing and imaging radio interferometric data. This framework is then used to write an end-to-end simulation pipeline in order to quantify the resolution and sensitivity of the SKA1-MID telescope (the first phase of the SKA mid-frequency telescope) as a function of frequency, as well as the scale-dependent sensitivity of the telescope. Finally, a stimela-based reduction pipeline is used to process data of the field around the source 3C147, taken by the Karl G. Jansky Very Large Array (VLA). The reconstructed image from this reduction has a typical 1a noise level of 2.87 µJy/beam, and consequently a dynamic range of 8x106:1, given the 22.58 Jy/beam flux Density of the source 3C147.
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Thomas, Robin Rajan. "Optimisation of adaptive localisation techniques for cognitive radio." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/27076.
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Spectrum, environment and location awareness are key characteristics of cognitive radio (CR). Knowledge of a user’s location as well as the surrounding environment type may enhance various CR tasks, such as spectrum sensing, dynamic channel allocation and interference management. This dissertation deals with the optimisation of adaptive localisation techniques for CR. The first part entails the development and evaluation of an efficient bandwidth determination (BD) model, which is a key component of the cognitive positioning system. This bandwidth efficiency is achieved using the Cramer-Rao lower bound derivations for a single-input-multiple-output (SIMO) antenna scheme. The performances of the single-input-single-output (SISO) and SIMO BD models are compared using three different generalised environmental models, viz. rural, urban and suburban areas. In the case of all three scenarios, the results reveal a marked improvement in the bandwidth efficiency for a SIMO antenna positioning scheme, especially for the 1×3 urban case, where a 62% root mean square error (RMSE) improvement over the SISO system is observed. The second part of the dissertation involves the presentation of a multiband time-of arrival (TOA) positioning technique for CR. The RMSE positional accuracy is evaluated using a fixed and dynamic bandwidth availability model. In the case of the fixed bandwidth availability model, the multiband TOA positioning model is initially evaluated using the two-step maximum-likelihood (TSML) location estimation algorithm for a scenario where line-of-sight represents the dominant signal path. Thereafter, a more realistic dynamic bandwidth availability model has been proposed, which is based on data obtained from an ultra-high frequency spectrum occupancy measurement campaign. The RMSE performance is then verified using the non-linear least squares, linear least squares and TSML location estimation techniques, using five different bandwidths. The proposed multiband positioning model performs well in poor signal-to-noise ratio conditions (-10 dB to 0 dB) when compared to a single band TOA system. These results indicate the advantage of opportunistic TOA location estimation in a CR environment.Dissertation (MEng)--University of Pretoria, 2012.
Electrical, Electronic and Computer Engineering
unrestricted
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Huang, Qi. "Robust spectrum sensing techniques for cognitive radio networks." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/22012.
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Cognitive radio is a promising technology that improves the spectral utilisation by allowing unlicensed secondary users to access underutilised frequency bands in an opportunistic manner. This task can be carried out through spectrum sensing: the secondary user monitors the presence of primary users over the radio spectrum periodically to avoid harmful interference to the licensed service. Traditional energy based sensing methods assume the value of noise power as prior knowledge. They suffer from the noise uncertainty problem as even a mild noise level mismatch will lead to significant performance loss. Hence, developing an efficient robust detection method is important. In this thesis, a novel sensing technique using the F-test is proposed. By assuming a multiple antenna assisted receiver, this detector uses the F-statistic as the test statistic which offers absolute robustness against the noise variance uncertainty. In addition, since the channel state information (CSI) is required to be known, the impact of CSI uncertainty is also discussed. Results show the F-test based sensing method performs better than the energy detector and has a constant false alarm probability, independent of the accuracy of the CSI estimate. Another main topic of this thesis is to address the sensing problem for non-Gaussian noise. Most of the current sensing techniques consider Gaussian noise as implied by the central limit theorem (CLT) and it offers mathematical tractability. However, it sometimes fails to model the noise in practical wireless communication systems, which often shows a non-Gaussian heavy-tailed behaviour. In this thesis, several sensing algorithms are proposed for non-Gaussian noise. Firstly, a non-parametric eigenvalue based detector is developed by exploiting the eigenstructure of the sample covariance matrix. This detector is blind as no information about the noise, signal and channel is required. In addition, the conventional energy detector and the aforementioned F-test based detector are generalised to non-Gaussian noise, which require the noise power and CSI to be known, respectively. A major concern of these detection methods is to control the false alarm probability. Although the test statistics are easy to evaluate, the corresponding null distributions are difficult to obtain as they depend on the noise type which may be unknown and non-Gaussian. In this thesis, we apply the powerful bootstrap technique to overcome this difficulty. The key idea is to reuse the data through resampling instead of repeating the experiment a large number of times. By using the nonparametric bootstrap approach to estimate the null distribution of the test statistic, the assumptions on the data model are minimised and no large sample assumption is invoked. In addition, for the F-statistic based method, we also propose a degrees-of-freedom modification approach for null distribution approximation. This method assumes a known noise kurtosis and yields closed form solutions. Simulation results show that in non-Gaussian noise, all the three detectors maintain the desired false alarm probability by using the proposed algorithms. The F-statistic based detector performs the best, e.g., to obtain a 90% detection probability in Laplacian noise, it provides a 2.5 dB and 4 dB signal-to-noise ratio (SNR) gain compared with the eigenvalue based detector and the energy based detector, respectively.
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Almalfouh, Sami M. "Interference-aware resource management techniques for cognitive radio networks." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43736.
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The objective of the proposed research is to develop interference-aware resource
management techniques for CR networks that opportunistically operate within
the licensed primary networks spectrum and to investigate the application of such CR
techniques to emerging wireless networks.
In this thesis, we report on a set of laboratory experiments that we undertook
to analyze the interference between the CR-based wireless regional-area network
(WRAN) standard and the digital television (DTV) broadcasting system. We determined
the tolerable levels of WRAN interference into DTV receivers and studied
the effect of these interference levels on WRAN deployment.
Based on the need for efficient utilization of the primary network spectrum, we
propose efficient interference-aware radio resource allocation (RRA) techniques for
orthogonal frequency-division multiple access (OFDMA) CR networks. These RRA
techniques aim to maximize the CR network throughput and to keep the CR interference
to the primary network at or below a predefined threshold, known as the
"interference temperature" limit. Moreover, we propose a joint spectrum-sensing design
and power control algorithm that lead to increased CR network throughput and
efficient protection of the PUs from undue interference.
Interference coordination (IC) is considered a key technique for capacity maximization
in emerging heterogeneous wireless networks. We propose a CR-based IC
and RRA algorithm for OFDMA femtocell deployments to achieve efficient spectrum
utilization and maximum network throughput. CR is envisioned as a key enabling
technology for future wireless networks; our novel CR techniques will provide other
researchers useful tools to design such networks.
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Kumar, Bhupendra. "Performance of an underlay cooperative cognitive networks with a buffer-aided-relay." Thesis, IIT, Delhi, 2019. http://eprint.iitd.ac.in:80//handle/2074/8070.
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Park, Jongmin. "CMOS analog spectrum processing techniques for cognitive radio applications." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37230.
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The objective of the research is to develop analog spectrum processing techniques for cognitive radio (CR) applications in CMOS technology. CR systems aim to use the unoccupied spectrum allocations without any license when the primary users are not present. Therefore, the successful deployment of CR systems relies on their ability to accurately sense the spectrum usage status over a wide frequency range serving various wireless communication standards. Meanwhile, to maximize the utilization of the available spectrum segments, the bandwidth of the signal has to be highly flexible, so that even a small fraction of spectrum resources can be fully utilized by CR users. One of the key enabling technologies of variable bandwidth communication is a tunable baseband filter.
In this research, a reconfigurable CR testbed system is presented as groundwork for the researches related with CR systems. With the feasibility study on the multi-resolution spectrum sensing (MRSS) functionality, a method for determining sensing threshold for MRSS functionality is presented, and a fully integrated MRSS receiver in CMOS technology is demonstrated. On the other hand, a reconfigurable CMOS analog baseband filter which can change its bandwidth, type and order with high resolution for CR applications is presented. In sum, an analog spectrum sensing method as well as a highly flexible analog baseband filter architecture is established and implemented in CMOS technology. Both designs are targeting the utilization of the analog signal processing capability with the aid of the digital circuits.
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Joshi, S. K. (Satya Krishna). "Radio resource allocation techniques for MISO downlink cellular networks." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526217437.
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Abstract This thesis examines radio resource management techniques for multicell multi-input single-output (MISO) downlink networks. Specifically, the thesis focuses on developing linear transmit beamforming techniques by optimizing certain quality-of-service (QoS) features, including, spectral efficiency, fairness, and throughput. The problem of weighted sum-rate-maximization (WSRMax) has been identified as a central problem to many network optimization methods, and it is known to be NP-hard. An algorithm based on a branch and bound (BB) technique which globally solves the WSRMax problem with an optimality certificate is proposed. Novel bounding techniques via conic optimization are introduced and their efficiency is illustrated by numerical simulations. The proposed BB based algorithm is not limited to WSRMax only; it can be easily extended to maximize any system performance metric that can be expressed as a Lipschitz continuous and increasing function of the signal-to-interference-plus-noise (SINR) ratio. Beamforming techniques can provide higher spectral efficiency, only when the channel state information (CSI) of users is accurately known. However, in practice the CSI is not perfect. By using an ellipsoidal uncertainty model for CSI errors, both optimal and suboptimal robust beamforming techniques for the worst-case WSRMax problem are proposed. The optimal method is based on a BB technique. The suboptimal algorithm is derived using alternating optimization and sequential convex programming. Through a numerical example it is also shown how the proposed algorithms can be applied to a scenario with statistical channel errors. Next two decentralized algorithms for multicell MISO networks are proposed. The optimization problems considered are: P1) minimization of the total transmission power subject to minimum SINR constraints of each user, and P2) SINR balancing subject to the total transmit power constraint of the base stations. Problem P1 is of great interest for obtaining a transmission strategy with minimal transmission power that can guarantee QoS for users. In a system where the power constraint is a strict system restriction, problem P2 is useful in providing fairness among the users. Decentralized algorithms for both problems are derived by using a consensus based alternating direction method of multipliers. Finally, the problem of spectrum sharing between two wireless operators in a dynamic MISO network environment is investigated. The notion of a two-person bargaining problem is used to model the spectrum sharing problem, and it is cast as a stochastic optimization. For this problem, both centralized and distributed dynamic resource allocation algorithms are proposed. The proposed distributed algorithm is more suitable for sharing the spectrum between the operators, as it requires a lower signaling overhead, compared with centralized one. Numerical results show that the proposed distributed algorithm achieves almost the same performance as the centralized oneTiivistelmä Tässä väitöskirjassa tarkastellaan monisoluisten laskevan siirtotien moniantennilähetystä käyttävien verkkojen radioresurssien hallintatekniikoita. Väitöskirjassa keskitytään erityisesti kehittämään lineaarisia siirron keilanmuodostustekniikoita optimoimalla tiettyjä palvelun laadun ominaisuuksia, kuten spektritehokkuutta, tasapuolisuutta ja välityskykyä. Painotetun summadatanopeuden maksimoinnin (WSRMax) ongelma on tunnistettu keskeiseksi monissa verkon optimointitavoissa ja sen tiedetään olevan NP-kova. Tässä työssä esitetään yleinen branch and bound (BB) -tekniikkaan perustuva algoritmi, joka ratkaisee WSRMax-ongelman globaalisti ja tuottaa todistuksen ratkaisun optimaalisuudesta. Samalla esitellään uusia conic-optimointia hyödyntäviä suorituskykyrajojen laskentatekniikoita, joiden tehokkuutta havainnollistetaan numeerisilla simuloinneilla. Ehdotettu BB-perusteinen algoritmi ei rajoitu pelkästään WSRMax-ongelmaan, vaan se voidaan helposti laajentaa maksimoimaan mikä tahansa järjestelmän suorituskykyarvo, joka voidaan ilmaista Lipschitz-jatkuvana ja signaali-(häiriö+kohina) -suhteen (SINR) kasvavana funktiona. Keilanmuodostustekniikat voivat tuottaa suuremman spektritehokkuuden vain, jos käyttäjien kanavien tilatiedot tiedetään tarkasti. Käytännössä kanavan tilatieto ei kuitenkaan ole täydellinen. Tässä väitöskirjassa ehdotetaan WSRMax-ongelman ääritapauksiin sekä optimaalinen että alioptimaalinen keilanmuodostustekniikka soveltaen tilatietovirheisiin ellipsoidista epävarmuusmallia. Optimaalinen tapa perustuu BB-tekniikkaan. Alioptimaalinen algoritmi johdetaan peräkkäistä konveksiohjelmointia käyttäen. Numeerisen esimerkin avulla näytetään, miten ehdotettuja algoritmeja voidaan soveltaa skenaarioon, jossa on tilastollisia kanavavirheitä. Seuraavaksi ehdotetaan kahta hajautettua algoritmia monisoluisiin moniantennilähetyksellä toimiviin verkkoihin. Tarkastelun kohteena olevat optimointiongelmat ovat: P1) lähetyksen kokonaistehon minimointi käyttäjäkohtaisten minimi-SINR-rajoitteiden mukaan ja P2) SINR:n tasapainottaminen tukiasemien kokonaislähetystehorajoitusten mukaisesti. Ongelma P1 on erittäin kiinnostava, kun pyritään kehittämään mahdollisimman pienen lähetystehon vaativa lähetysstrategia, joka pystyy takaamaan käyttäjien palvelun laadun. Ongelma P2 on hyödyllinen tiukasti tehorajoitetussa järjestelmässä, koska se tarjoaa tasapuolisuutta käyttäjien välillä. Molempien ongelmien hajautetut algoritmit johdetaan konsensusperusteisen vuorottelevan kertoimien suuntaustavan avulla. Lopuksi tarkastellaan kahden langattoman operaattorin välisen spektrinjaon ongelmaa dynaamisessa moniantennilähetystä käyttävässä verkkoympäristössä. Spektrinjako-ongelmaa mallinnetaan käyttämällä kahden osapuolen välistä neuvottelua stokastisen optimoinnin näkökulmasta. Tähän ongelmaan ehdotetaan ratkaisuksi sekä keskitettyä että hajautettua resurssien allokoinnin algoritmia. Hajautettu algoritmi sopii paremmin spektrin jakamiseen operaattorien välillä, koska se vaatii vähemmän kontrollisignalointia. Numeeriset tulokset osoittavat, että ehdotetulla hajautetulla algoritmilla saavutetaan lähes sama suorituskyky kuin keskitetyllä algoritmillakin
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Ho, Ming-Ju. "System deployment and capacity enhancing techniques for mobile radio." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/14816.
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Radhi, Nazar Mortada. "Implementation of spectrum sensing techniques for cognitive radio systems." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/7381.
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This work presents a method for real-time detection of secondary users at the cognitive wireless technologies base stations. Cognitive radios may hide themselves in between the primary users to avoid being charged for spectrum usage. To deal with such scenarios, a cyclostationary Fast Fourier Transform accumulation method (FAM) has been used to develop a new strategy for recognising channel users under perfect and different noise environment conditions. Channel users are tracked according to the changes in their signal parameters, such as modulation techniques. MATLAB® Simulation tool was used to run various modulation signals on channels, and the obtained spectral correlation density function shows successful recognition between secondary and primary signals. We are unaware of previous efforts to use the FAM characteristics or other detection methods to make a distinction between channel users as presented in this thesis. A novel combination of both cognitive radio technology and ultra wideband technology is interdicted in this thesis, looking for an efficient and reliable spectrum sensing method to detect the presence of primary transmitters, and a number of spectrum-sensing techniques implemented in ultra wideband and cognitive radio component (UWB-CR) under different AWGN and fading settings environments. The sensing performance of different detectors is compared in conditions of probability of detection and miss detection curves. Simulation results show that the selection of detectors rely on the different fading scenarios, detector requirements and on a priori knowledge. Furthermore, result showed that the matched filter detection method is suitable for detecting signals through UWB-CR system under various fading channels. A general observation is that the matched filter detector outperforms the other detectors in all scenarios by an average of SNR=-20 dB in the level of probability of detection (Pd) , and the energy detector slightly outperforms the cyclostationary detector, in the level Pd at SNR=-20 dB. Furthermore, the thesis adapts novel detection models of cooperative and cluster cooperative wideband spectrum sensing in cognitive radio networks. In the proposed schemes, wavelet-based multi-resolution spectrum sensing and a proposed approach scheme are utilized for improving sensing performance of both models. On the other hand, cluster based cooperative spectrum sensing with soft combination Equal Gain Combination (EGC) scheme is proposed. The proposed detection models could achieve improvement of transmitter signal detection in terms of higher probability of detection and lower probability of false alarm. In the cooperative wideband spectrum sensing model, using traditional fusion rule, existing worst performance of false alarms by measurement is 78% of the sensing bands at an average SNR=5 dB; this compares with the proposed model, which is by measurement 19% false alarms of scanning spectrum at the same SNR for cluster cooperative wideband spectrum sensing. The proposed combining methods shows improvements of results with a high probability of detection (Pd) and low probability of false alarm (Pf) at an average SNR=-16 dB compared with other traditional fusion methods; this is illustrated through numerical results.
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Laurensen, David Irvine. "Indoor radio channel propagation modelling by ray tracing techniques." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/12397.
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In response to the requirement for a more detailed channel model based on the physical characteristics of the environment within which indoor radio communications operate, this thesis presents a channel model based on ray tracing techniques. The mathematical basis for the model is presented in terms of the electromagnetic properties of simple objects. The resulting model is coded into a simulation system which takes a description of a building in terms of the structure of internal walls, floors and ceilings. Through repeated application of the reflection process, a description of the channel impulse response is created for a given transmitter and receiver position from the multipath components generated. This model is applied, in progressing degrees of complexity, to two buildings for which narrowband physical measurements are available. Comparison is made between the measured results and the narrowband simulation results which leads to an analysis of the various propagation mechanisms involved in in-building communications. It is found that the model, while not accurately predicting the measured results, does produce a model that, considering the unknown parameters of the environment and experimental procedure, relates well to the channel experienced by a communication system. Wideband channel characteristics are determined from the simulation model, and found to give access to more detailed information on the channel than is obtainable through physical measurement. The results of the wideband simulations are compared with published material containing measurement results, and the relationship to the narrowband results already presented is shown.
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Sheethalnath, Praveen T. "Novel Site-Specific Techniques for Predicting Radio Wave Propagation." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33016.
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This thesis addresses various aspects related to site-specific propagation prediction using ray tracing techniques. Propagation prediction based on ray tracing techniques requires that all the different physical objects, which affect the propagation of radio waves, be modeled. The first part of the thesis concentrates on modeling the buildings and the terrain for the above-mentioned application. A survey of the various geographic products that are available to model the environment is presented. The different methods used to model the terrain are analyzed and the most suitable method for a ray based application is suggested. A method to model the buildings in an environment from commercially available data is described. A novel method to combine the building information with the terrain information is presented.
An in depth discussion of deterministic propagation prediction using ray tracing is presented in the latter half of the thesis. An overview of the various ray based algorithms that exists in the literature are presented and the limitations and the computational complexity of ray based methods are discussed. All ray based algorithms model the receivers as point objects and predict the propagation characteristics at a particular point in space. However, to optimize the design of a wireless broadcast or a point to multi point system such as a Wireless LAN (WLAN) or a cellular system, propagation characteristics at multiple points in space need to be known. The standard ray tracing algorithms can be notoriously time consuming when used to predict the characteristics of multiple receivers. A new, computationally less intensive algorithm to predict the propagation characteristics of multiple receivers is described. This algorithm significantly reduces the computation time by using â grid modeâ predictions for broadcast channels.Master of Science
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Brown, Ryan Jeffrey. "Radio frequency coil techniques and cardiovascular magnetic resonance imaging /." Access full-text from WCMC, 2009. http://proquest.umi.com/pqdweb?did=1708741461&sid=3&Fmt=2&clientId=8424&RQT=309&VName=PQD.
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Li, Xiaoyong. "Low noise design techniques for radio frequency integrated circuits /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/6013.
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Cumanan, Kanapathippillai. "Spatial diversity and optimization techniques for cognitive radio networks." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/10698.
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The explosive growth of wireless applications and high demand for wireless resources have created spectruIIl crisis. Many spectrnm occupancy measurements have shown that most of the allocated spectrum experiences inefficient utilization. Hence radically new approaches arc required for better utilization of spectrum. This has motivated the concept of opportunistic spectrum access in the licensed bands namely cogni ti ve radio technology. This intelligent wireless system has the potential to improve the spectrum utilization by enabling unlicensed users to access the licensed bands without disturbing the licensed users. In this thesis, spatial multiplexing techniques are studied for underlay cognitive radio networks where transmit beamformers arc designed to satisfy quality of service and interference constraints using convex optimization techniques. Robust schemes arc also proposed in the presence of imperfect channel state information at the basestation. To overcome the infeasibility issues encountered in the beamformer design, a joint resource allocation and admission control technique is proposed using the branch and bound optimi7, ation method. Finally, signal-to-interference and noise ratio (SINR) balancing techniques are developed for different types of interference constraints on the primary users using a max-min fairness approach. These SINR balancing techniques also solve the problem of infeasibility. The performance of all these new schemes has been verified using MATLAB simulation results.
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Al-Mathehaji, Yasir Ahmed Adbullah. "Intelligent spectrum management techniques for wireless cognitive radio networks." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3852.
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This thesis addresses many of the unique spectrum management chal- lenges in CR networks for the rst time. These challenges have a vital e ect on the network performance and are particularly di cult to solve due to the unique characteristics of CR networks. Speci cally, this thesis proposes and investigates three intelligent spectrum management tech- niques for CR networks. The issues investigated in this thesis have a fundamental impact on the establishment, functionality and security of CR networks. First, an intelligent primary receiver-aware message exchange protocol for CR ad hoc networks is proposed. It considers the problem of alleviat- ing the interference collision risk to primary user communication, explic- itly to protect primary receivers that are not detected during spectrum sensing. The proposed protocol achieves a higher measure of safeguard- ing. A practical scenario is considered where no global network topology is known and no common control channel is assumed to exist. Second, a novel CR broadcast protocol (CRBP) to reliably disseminate the broadcast messages to all or most of the possible CR nodes in the network is proposed. The CRBP formulates the broadcast problem as a bipartite-graph problem. Thus, CRBP achieves a signi cant successful delivery ratio by connecting di erent local topologies, which is a unique feature in CR ad hoc networks. Finally, a new defence strategy to defend against spectrum sensing data falsi cation attacks in CR networks is proposed. In order to identify malicious users, the proposed scheme performs multiple veri cations of sensory data with the assistance of trusted nodes.
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Jain, Ankit. "Detection on HF radio transmitters using passive geolocation techniques." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2019. http://www.theses.fr/2019IMTA0128/document.
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La transmission radioélectrique à longue distance dans la bande HF permet de couvrir de vastes zones géographiques à l’aide d’infrastructures légères et mobiles. Elle est donc bien adaptée pour établir des communications lors d’opérations militaires ou pour le déploiement rapide d'un réseau de communication agile lors d'opérations humanitaires. Dans ce contexte, il est important de pouvoir localiser les émetteurs inconnus par l’analyse des signaux électromagnétiques de communication. L’objectif de la thèse est de développer une technique de géolocalisation alternative et complémentaire, intitulée Time Difference of Arrival (TDoA), qui a rarement été étudiée dans le cas de la propagation ionosphérique. Dans un premier temps, l'algorithme de géolocalisation HF basé sur la technique TDoA est adapté et optimisé par des simulations paramétriques. Les résultats de simulation montrent que l'augmentation du nombre de récepteurs entraîne une amélioration significative de la précision de géolocalisation. Afin d'étudier la faisabilité de mise en oeuvre d'un système de géolocalisation HF basé sur la technique TDoA, plusieurs récepteurs HF pilotable à distance ont été développés à partir de modules de radio logicielle, et un réseau national de récepteurs a été déployé en France. Un concept original de sondage de canal croisé est proposé et décrit mathématiquement. Il permet d’évaluer les différences de durée de propagation entre les signaux reçus sur deux récepteurs synchronisés distincts. Les résultats expérimentaux collectés montrent qu'il est possible de localiser les émetteurs HF dans des conditions favorables avec une erreur de géolocalisation relative comprise entre 0,1 et 10% de la distance réelle au sol. Les données collectées lors de la campagne de mesure sont analysées de manière statistique afin d’évaluer la performance de l'algorithme de géolocalisation et de définir les paramètres les plus pertinents à prendre en compte pour déployer cette technique dans une approche opérationnelleLong-range radio transmission in the HF band can cover large geographical areas using light and mobile equipment. It is therefore well suited for communications during military operations orfor the rapid deployment of an agile communication network during humanitarian operations. In this context, it is important to determine the geographic location of the transmitters by analyzing the electromagnetic communication signals. The aim of the thesis is to develop an alternative, complementary geolocation technique, entitled Time Difference of Arrival (TDoA) that has rarely been studied in the case of ionospheric propagation. As a first step, HF geolocation algorithm based on TDoA is setup and analyzed by parametric software simulations. Simulation results demonstrate that increasing the number of receivers leads to a significant improvement in the geolocation accuracy. In order to study the feasibility of a practical HF geolocation system based on TDoA, multiple remotely controllable HF receivers are designed using software defined radio (SDR) modules and a country wide operational receiver network is deployed in France. A concept of cross-channel sounding along with its mathematical description is proposed to evaluate the propagation duration differences between the signals captured by two distinct receivers. Preliminary experimental results show that it is possible to locate the HF transmitters under favorable conditions with a relative geolocation error ranging from about 0.1 to 10% of the actual ground distance. Data captured during the large scale measurement campaign are analyzed statistically to evaluate the performance of the geolocation algorithm and define parameters that could be considered in an operational approach
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Ballicchia, Mauro. "Modeling and design techniques for radio frequency integrated circuits." Doctoral thesis, Università Politecnica delle Marche, 2008. http://hdl.handle.net/11566/242355.
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Dillon, Nicholas. "High brightness-sensitivity interferometry : techniques and applications." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330165.
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Nasif, Ahmed O. "Opportunistic spectrum access using localization techniques." Fairfax, VA : George Mason University, 2009. http://hdl.handle.net/1920/4572.
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Thesis (Ph.D.)--George Mason University, 2009.Vita: p. 146. Thesis director: Brian L. Mark. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical and Computer Engineering. Title from PDF t.p. (viewed Oct. 11, 2009). Includes bibliographical references (p. 138-145). Also issued in print.
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Morris, Kevin Andrew. "RF power amplifier linearisation using predistortion techniques." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/02819fd3-4c63-41b7-b7b3-df70c1e4ba85.
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Ng, Man-hung. "Bandwidth-efficient pilot-symbol-aided techniques for fading estimation in multipath fading channels." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22582174.
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Datsika, Eftychia. "Radio resource management techniques for QoS provision in 5G networks." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/664084.
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As numerous mobile applications and over-the-top (OTT) services emerge and mobile Internet connectivity becomes ubiquitous, the provision of high quality of service (QoS) is more challenging for mobile network operators (MNOs). Research efforts focus on the development of innovative resource management techniques and have introduced the long term evolution advanced (LTE-A) communication standard. Novel business models make the growth of network capacity sustainable by enabling MNOs to combine their resources. The fifth generation (5G) mobile networks will involve technologies and business stakeholders with different capabilities and demands that may affect the QoS provision, requiring efficient radio resource sharing.
The need for higher network capacity has introduced novel technologies that improve resource allocation efficiency. Direct connectivity among user equipment terminals (UEs) circumventing the LTE-A infrastructure alleviates the network overload. Part of mobile traffic is offloaded to outband device-to-device (D2D) connections (in unlicensed spectrum) enabling data exchange between UEs directly or via UEs-relays. Still, MNOs need additional spectrum resources and infrastructure. The inter-operator network sharing concept has emerged motivating the adoption of virtualization that enables network slicing, i.e., dynamic separation of resources in virtual slices (VSs). VSs are managed in isolation by different tenants using software defined networking and encompass core and radio access network resources allocated periodically to UEs. When UEs access OTT applications, flows with different QoS demands and priorities determined by OTT service providers (OSPs) are generated. OSPs’ policies should be considered in VS allocation. The coexisting technologies, business models and stakeholders require sophisticated radio resource management (RRM) techniques.
To that end, RRM is performed in a complex ecosystem. When D2D communication involves data concurrently downloaded by the mobile network, QoS may be affected by LTE-A network parameters (resource scheduling policy, downlink channel conditions). It is also affected by the relay selection, as UEs may not be willing to help unknown UE pairs and UEs’ social ties in mobile applications may influence willingness for D2D cooperation. Thus, effective medium access control (MAC) mechanisms should coordinate D2D transmissions employing advanced techniques, e.g., network coding (NC). When UEs access OTT applications, OSPs’ policies are not considered by MNOs in RRM and OSPs cannot apply flow prioritization. Network neutrality issues also arise when OSPs claim resources from MNOs aiming to minimize grade of service (GoS). OSPs’ intervention may delay flows’ accommodation due to the time required for OSP-MNO interaction and the time the flows spent waiting for resources.
This thesis proposes novel solutions to the RRM issues of outband D2D communication and VS allocation for OSPs in 5G networks. We present a cooperative D2D MAC protocol that leverages the opportunities for NC in D2D communication under the influence of LTE-A network parameters and its throughput performance analysis. The protocol improves D2D throughput and energy efficiency, especially for UEs with better downlink channel conditions. We next introduce social awareness in D2D MAC design and present a social-aware cooperative D2D MAC protocol that employs UEs’ social ties to promote the use of friendly relays reducing the total energy consumption. Motivated by the lack of approaches for OSP-oriented RRM, we present a novel flow prioritization algorithm based on matching theory that applies OSPs’ policies respecting the network neutrality and the analysis of its GoS and delay performance. The algorithm maintains low overhead and delay without affecting fairness among OSPs. Our techniques highlight the QoS improvement induced by the joint consideration of different technologies and business stakeholders in RRM design.A medida que varias aplicaciones móviles y servicios over-the-top (OTT) surgen y el Internet móvil se vuelve ubicua, la prestación de alta calidad de servicio (QoS) es desafiante para los operadores de red móvil (MNOs). Los estudios de investigación se enfocan en técnicas innovadoras para la gestión de recursos de red y han resultado en la especificación del estándar de comunicación long term evolution advanced (LTE-A). Modelos comerciales nuevos hacen que el crecimiento de la capacidad de red sea sostenible al permitir que MNOs combinen sus recursos. La quinta generación (5G) de redes móviles implicará tecnologías y partes comerciales interesadas con varias habilidades y demandas que pueden afectar la provisión de QoS y demandan la gestión eficaz de recursos de radio. La necesidad de capacidad de red más alta ha introducido tecnologías que hacen más eficiente la asignación de recursos. La conectividad directa entre terminales de equipos de usuarios (UEs) eludiendo la infraestructura LTE-A alivia la sobrecarga de red. Parte del tráfico es dirigido a conexiones de dispositivo a dispositivo (D2D) outband permitiendo la comunicación de UEs directamente o con relés. Los MNOs necesitan nuevos recursos de espectro e infraestructura. El intercambio de recursos entre MNOs ha surgido motivando la adopción de virtualización que realiza la segmentación de red i.e., la separación dinámica de recursos en trozos virtuales (VSs). Los VSs son administrados de forma aislada por inquilinos diferentes con software defined networking y abarcan recursos de red core y radio access asignadas periódicamente a UEs. Cuando UEs usan aplicaciones OTT, flujos de aplicación con demandas y prioridades definidas por proveedores de servicios OTT (OSPs) se generan. Las políticas de OSPs deben ser integradas en la asignación de VSs. La coexistencia de varias tecnologías y partes comerciales demanda técnicas sofisticadas de gestión de recursos radio (RRM). Con ese fin, la RRM se realiza en un ecosistema complejo. Si la comunicación D2D involucra datos descargados simultáneamente por la red móvil, los parámetros de red LTE-A (política de scheduling de recursos, condiciones de canal downlink) afectan el QoS. La selección de relés afecta el rendimiento porque los UEs no desean siempre ayudar a UEs desconocidos. Las relaciones sociales de los UEs en aplicaciones móviles pueden determinar la voluntad para la comunicación cooperativa D2D. Por lo tanto, mecanismos de control de acceso al medio (MAC) deben coordinar las transmisiones D2D con técnicas avanzadas ej., codificación de red. Si los UEs usan servicios OTT, las políticas de OSPs no son consideradas en RRM y los OSPs no emplean flujos prioritarios. Problemas de neutralidad de red surgen cuando los OSPs reclaman recursos de MNOs para minimizar el grado de servicio (GoS). La intervención de OSPs puede causar retraso en el servicio de flujos debido a la interacción OSP-MNO y el tiempo requerido para que los flujos reciban recursos. Esta tesis presenta soluciones nuevas para los problemas RRM de comunicación D2D outband y asignación de VSs a OSPs en redes 5G. Proponemos un protocolo D2D MAC cooperativo que explota las oportunidades de NC bajo la influencia de parámetros de red LTE-A y su análisis de rendimiento. El protocolo mejora el rendimiento y la eficiencia energética especialmente para UEs con mejores condiciones de canal downlink. Introducimos la conciencia social en el D2D MAC y proponemos un protocolo que utiliza relaciones sociales de UEs para elegir relés-amigos y reduce el consumo de energía. Dada la falta de técnicas que aborden el problema RRM de OSPs presentamos un algoritmo que aplique políticas de OSPs y respete la neutralidad usando la teoría de matching, y su análisis de GoS y retraso. El algoritmo induce bajo coste y retraso sin afectar la imparcialidad entre OSPs. Estas técnicas demuestran la mejora de QoS gracias a la consideración de tecnologas y partes comerciales diferentes en RRM.
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Ahriz, Roula Iness. "Application des techniques d'apprentissage à la géolocalisation par radio fingerprint." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://pastel.archives-ouvertes.fr/pastel-00546952.
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L'objectif de la thèse est d'améliorer la précision de localisation des personnes (ou objets) dans les environnements où le signal GPS est faible, voire inexistant, par exemple à l'intérieur de bâtiments. L'originalité de ce travail est d'utiliser des signaux radio reçus de sources extérieures pour effectuer la localisation à l'intérieur des bâtiments. Durant ce travail, des mesures des puissances reçues ont été effectuées dans diverses conditions. Étant données les difficultés liées aux processus expérimentaux (incertitude et bruit liés aux mesures), ce dernier point a constitué une première partie de ce travail de thèse. Le traitement et l'interprétation des mesures des puissances de signaux radio dans un environnement de propagation instable ont été un véritable défi durant cette étude. En effet, toutes les porteuses du réseau GSM ont été considérées et aucune hypothèse n'a été posée, à priori, sur leurs pertinences. Une seconde partie de la thèse a été justement consacrée à l'estimation de ces pertinences. Le problème de la détermination de la pièce dans laquelle se trouve le mobile a été considéré comme un problème de classification automatique : des méthodes d'apprentissage statistique (supervisé et semi‐supervisé) ont donc été mises en oeuvre. Le choix des méthodes utilisées a été fait sur la base des études menées sur les mesures des puissances. Des performances très satisfaisantes ont été obtenues, dans les pièces de deux bâtiments différents. Ces résultats ont ainsi confirmé l'apport des méthodes d'apprentissage statistique au problème de localisation par fingerprints.
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Weeraddana, P. C. (Pradeep Chathuranga). "Optimization techniques for radio resource management in wireless communication networks." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514296550.
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Abstract The application of optimization techniques for resource management in wireless communication networks is considered in this thesis. It is understood that a wide variety of resource management problems of recent interest, including power/rate control, link scheduling, cross-layer control, network utility maximization, beamformer design of multiple-input multiple-output networks, and many others are directly or indirectly reliant on the general weighted sum-rate maximization (WSRMax) problem. Thus, in this dissertation a greater emphasis is placed on the WSRMax problem, which is known to be NP-hard. A general method, based on the branch and bound technique, is developed, which solves globally the nonconvex WSRMax problem with an optimality certificate. Efficient analytic bounding techniques are derived as well. More broadly, the proposed method is not restricted to WSRMax. It can also be used to maximize any system performance metric, which is Lipschitz continuous and increasing on signal-to-interference-plus-noise ratio. The method can be used to find the optimum performance of any network design method, which relies on WSRMax, and therefore it is also useful for evaluating the performance loss encountered by any heuristic algorithm. The considered link-interference model is general enough to accommodate a wide range of network topologies with various node capabilities, such as singlepacket transmission, multipacket transmission, simultaneous transmission and reception, and many others. Since global methods become slow in large-scale problems, fast local optimization methods for the WSRMax problem are also developed. First, a general multicommodity, multichannel wireless multihop network where all receivers perform singleuser detection is considered. Algorithms based on homotopy methods and complementary geometric programming are developed for WSRMax. They are able to exploit efficiently the available multichannel diversity. The proposed algorithm, based on homotopy methods, handles efficiently the self interference problem that arises when a node transmits and receives simultaneously in the same frequency band. This is very important, since the use of supplementary combinatorial constraints to prevent simultaneous transmissions and receptions of any node is circumvented. In addition, the algorithm together with the considered interference model, provide a mechanism for evaluating the gains when the network nodes employ self interference cancelation techniques with different degrees of accuracy. Next, a similar multicommodity wireless multihop network is considered, but all receivers perform multiuser detection. Solutions for the WSRMax problem are obtained by imposing additional constraints, such as that only one node can transmit to others at a time or that only one node can receive from others at a time. The WSRMax problem of downlink OFDMA systems is also considered. A fast algorithm based on primal decomposition techniques is developed to jointly optimize the multiuser subcarrier assignment and power allocation to maximize the weighted sum-rate (WSR). Numerical results show that the proposed algorithm converges faster than Lagrange relaxation based methods. Finally, a distributed algorithm for WSRMax is derived in multiple-input single-output multicell downlink systems. The proposed method is based on classical primal decomposition methods and subgradient methods. It does not rely on zero forcing beamforming or high signal-to-interference-plus-noise ratio approximation like many other distributed variants. The algorithm essentially involves coordinating many local subproblems (one for each base station) to resolve the inter-cell interference such that the WSR is maximized. The numerical results show that significant gains can be achieved by only a small amount of message passing between the coordinating base stations, though the global optimality of the solution cannot be guaranteedTiivistelmä Tässä työssä tutkitaan optimointimenetelmien käyttöä resurssienhallintaan langattomissa tiedonsiirtoverkoissa. Monet ajankohtaiset resurssienhallintaongelmat, kuten esimerkiksi tehonsäätö, datanopeuden säätö, radiolinkkien ajastus, protokollakerrosten välinen optimointi, verkon hyötyfunktion maksimointi ja keilanmuodostus moniantenniverkoissa, liittyvät joko suoraan tai epäsuorasti painotetun summadatanopeuden maksimointiongelmaan (weighted sum-rate maximization, WSRMax). Tästä syystä tämä työ keskittyy erityisesti WSRMax-ongelmaan, joka on tunnetusti NP-kova. Työssä kehitetään yleinen branch and bound -tekniikkaan perustuva menetelmä, joka ratkaisee epäkonveksin WSRMax-ongelman globaalisti ja tuottaa todistuksen ratkaisun optimaalisuudesta. Työssä johdetaan myös tehokkaita analyyttisiä suorituskykyrajojen laskentatekniikoita. Ehdotetun menetelmän käyttö ei rajoitu vain WSRMax-ongelmaan, vaan sitä voidaan soveltaa minkä tahansa suorituskykymetriikan maksimointiin, kunhan se on Lipschitz-jatkuva ja kasvava signaali-häiriö-plus-kohinasuhteen funktiona. Menetelmää voidaan käyttää minkä tahansa WSRMax-ongelmaan perustuvan verkkosuunnittelumenetelmän optimaalisen suorituskyvyn määrittämiseen, ja siksi sitä voidaan hyödyntää myös minkä tahansa heuristisen algoritmin aiheuttaman suorituskykytappion arvioimiseen. Tutkittava linkki-häiriömalli on riittävän yleinen monien erilaisten verkkotopologioiden ja verkkosolmujen kyvykkyyksien mallintamiseen, kuten esimerkiksi yhden tai useamman datapaketin siirtoon sekä yhtäaikaiseen lähetykseen ja vastaanottoon. Koska globaalit menetelmät ovat hitaita suurien ongelmien ratkaisussa, työssä kehitetään WSRMax-ongelmalle myös nopeita paikallisia optimointimenetelmiä. Ensiksi käsitellään yleistä useaa eri yhteyspalvelua tukevaa monikanavaista langatonta monihyppyverkkoa, jossa kaikki vastaanottimet suorittavat yhden käyttäjän ilmaisun, ja kehitetään algoritmeja, joiden perustana ovat homotopiamenetelmät ja komplementaarinen geometrinen optimointi. Ne hyödyntävät tehokkaasti saatavilla olevan monikanavadiversiteetin. Esitetty homotopiamenetelmiin perustuva algoritmi käsittelee tehokkaasti itsehäiriöongelman, joka syntyy, kun laite lähettää ja vastaanottaa samanaikaisesti samalla taajuuskaistalla. Tämä on tärkeää, koska näin voidaan välttää lisäehtojen käyttö yhtäaikaisen lähetyksen ja vastaanoton estämiseksi. Lisäksi algoritmi yhdessä tutkittavan häiriömallin kanssa auttaa arvioimaan, paljonko etua saadaan, kun laitteet käyttävät itsehäiriön poistomenetelmiä erilaisilla tarkkuuksilla. Seuraavaksi tutkitaan vastaavaa langatonta monihyppyverkkoa, jossa kaikki vastaanottimet suorittavat monen käyttäjän ilmaisun. Ratkaisuja WSRMax-ongelmalle saadaan asettamalla lisäehtoja, kuten että vain yksi lähetin kerrallaan voi lähettää tai että vain yksi vastaanotin kerrallaan voi vastaanottaa. Edelleen tutkitaan WSRMax-ongelmaa laskevalla siirtotiellä OFDMA-järjestelmässä, ja johdetaan primaalihajotelmaan perustuva nopea algoritmi, joka yhteisoptimoi monen käyttäjän alikantoaalto- ja tehoallokaation maksimoiden painotetun summadatanopeuden. Numeeriset tulokset osoittavat, että esitetty algoritmi suppenee nopeammin kuin Lagrangen relaksaatioon perustuvat menetelmät. Lopuksi johdetaan hajautettu algoritmi WSRMax-ongelmalle monisoluisissa moniantennilähetystä käyttävissä järjestelmissä laskevaa siirtotietä varten. Esitetty menetelmä perustuu klassisiin primaalihajotelma- ja aligradienttimenetelmiin. Se ei turvaudu nollaanpakotus-keilanmuodostukseen tai korkean signaali-häiriö-plus-kohinasuhteen approksimaatioon, kuten monet muut hajautetut muunnelmat. Algoritmi koordinoi monta paikallista aliongelmaa (yhden kutakin tukiasemaa kohti) ratkaistakseen solujen välisen häiriön siten, että WSR maksimoituu. Numeeriset tulokset osoittavat, että merkittävää etua saadaan jo vähäisellä yhdessä toimivien tukiasemien välisellä viestinvaihdolla, vaikka globaalisti optimaalista ratkaisua ei voidakaan taata
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Wilson, James Edward. "Design techniques for first pass silicon in SOC radio transceivers." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180555088.
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Rahulamathavan, Yogachandran. "Mathematical optimization techniques for resource allocation in cognitive radio networks." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8982.
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Introduction of data intensive multimedia and interactive services together with exponential growth of wireless applications have created a spectrum crisis. Many spectrum occupancy measurements, however, have shown that most of the allocated spectrum are used inefficiently indicating that radically new approaches are required for better utilization of spectrum. This motivates the concept of opportunistic spectrum sharing or the so-called cognitive radio technology that has great potential to improve spectrum utilization. This technology allows the secondary users to access the spectrum which is allocated to the licensed users in order to transmit their own signal without harmfully affecting the licensed users' communications. In this thesis, an optimal radio resource allocation algorithm is proposed for an OFDM based underlay cognitive radio networks. The proposed algorithm optimally allocates transmission power and OFDM subchannels to the users at the basestation in order to satisfy the quality of services and interference leakage constraints based on integer linear programming. To reduce the computational complexity, a novel recursive suboptimal algorithm is proposed based on a linear optimization framework. To exploit the spatial diversity, the proposed algorithms are extended to a MIMO-OFDM based cognitive radio network. Finally, a novel spatial multiplexing technique is developed to allocate resources in a cognitive radio network which consists of both the real time and the non-real users. Conditions required for convergence of the proposed algorithm are analytically derived. The performance of all these new algorithms are verified using MATLAB simulation results.
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Al-Khaled, Fahad Sulaiman. "Efficient radio channel assignment techniques for mobile satellite communication networks." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391293.
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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.
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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
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Platts, Emma. "Computational analysis techniques using fast radio bursts to probe astrophysics." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33921.
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This thesis focuses on Fast Radio Bursts (FRBs) and presents computational techniques that can be used to understand these enigmatic events and the Universe around them. Chapter 1 provides a theoretical overview of FRBs; providing a foundation for the chapters that follow. Chapter 2 details current understandings by providing a review of FRB properties and progenitor theories. In Chapter 3, we implement non-parametric techniques to measure the elusive baryonic halo of the Milky Way. We show that even with a limited data set, FRBs and an appropriate set of statistical tools can provide reasonable constraints on the dispersion measure of the Milky Way halo. Further, we expect that a modest increase in data (from fewer than 100 FRB detections to over 1000) will significantly tighten constraints, demonstrating that the technique we present may offer a valuable complement to other analyses in the near future. In Chapter 4, we study the fine time-frequency structure of the most famous FRB: FRB 121102. Here, we use autocorrelation functions to maximise the structure of 11 pulses detected with the MeerKAT radio telescope. The study is motivated by the low time-resolution of MeerKAT data, which presents a challenge to more traditional techniques. The burst profiles that are unveiled offer unique insight into the local environment of the FRB, including a possible deviation from the expected cold plasma dispersion relationship. The pulse features and their possible physical mechanisms are critically discussed in a bid to uncover the nature and origin of these transients.
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Gismalla, Yousif Ebtihal. "Performance analysis of spectrum sensing techniques for cognitive radio systems." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/performance-analysis-of-spectrum-sensing-techniques-for-cognitive-radio-systems(157fe1af-717c-4705-a649-d809766cf5cb).html.
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Cognitive radio is a technology that aims to maximize the current usage of the licensed frequency spectrum. Cognitive radio aims to provide services for license-exempt users by making use of dynamic spectrum access (DSA) and opportunistic spectrum sharing strategies (OSS). Cognitive radios are defined as intelligent wireless devices capable of adapting their communication parameters in order to operate within underutilized bands while avoiding causing interference to licensed users. An underused band of frequencies in a specific location or time is known as a spectrum hole. Therefore, in order to locate spectrum holes, reliable spectrum sensing algorithms are crucial to facilitate the evolution of cognitive radio networks. Since a large and growing body of literature has mainly focused into the conventional time domain (TD) energy detector, throughout this thesis the problem of spectrum sensing is investigated within the context of a frequency domain (FD) approach. The purpose of this study is to investigate detection based on methods of nonparametric power spectrum estimation. The considered methods are the periodogram, Bartlett's method, Welch overlapped segments averaging (WOSA) and the Multitaper estimator (MTE). Another major motivation is that the MTE is strongly recommended for the application of cognitive radios. This study aims to derive the detector performance measures for each case. Another aim is to investigate and highlight the main differences between the TD and the FD approaches. The performance is addressed for independent and identically distributed (i.i.d.) Rayleigh channels and the general Rician and Nakagami fading channels. For each of the investigated detectors, the analytical models are obtained by studying the characteristics of the Hermitian quadratic form representation of the decision statistic and the matrix of the Hermitian form is identified. The results of the study have revealed the high accuracy of the derived mathematical models. Moreover, it is found that the TD detector differs from the FD detector in a number of aspects. One principal and generalized conclusion is that all the investigated FD methods provide a reduced probability of false alarm when compared with the TD detector. Also, for the case of periodogram, the probability of sensing errors is independent of the length of observations, whereas in time domain the probability of false alarm is increased when the sample size increases. The probability of false alarm is further reduced when diversity reception is employed. Furthermore, compared to the periodogram, both Bartlett method and Welch method provide better performance in terms of lower probability of false alarm but an increased probability of detection for a given probability of false alarm. Also, the performance of both Bartlett's method and WOSA is sensitive to the number of segments, whereas WOSA is also sensitive to the overlapping factor. Finally, the performance of the MTE is dependent on the number of employed discrete prolate spheroidal (Slepian) sequences, and the MTE outperforms the periodogram, Bartlett's method and WOSA, as it provides the minimal probability of false alarm.
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NOMBLOT, CHRISTOPHE. "Radio-anatomie du pelvis feminin : impact des nouvelles techniques d'imagerie." Toulouse 3, 1989. http://www.theses.fr/1989TOU31532.
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Hicheri, Nizar. "Approche unifiée des techniques de transmission radio sur voie descendante." Paris, CNAM, 2004. http://www.theses.fr/2004CNAM0473.
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Cette thèse présente tout d'abord un formalisme matriciel qui permet de représenter les approches DS-CDMA, MC-CDMA et OFDM de manière unifiée. On montre ainsi dans un premier temps que si l'on cherche des séquences d'étalement DS-CDMA qui sont orthogonales et dont l'orthogonalité résiste à une imprécision temporelle d'un élément de la séquence alors, obligatoirement, ces séquences sont les exponentielles complexes de Fourier. Une fois les formes d'ondes exprimées et les récepteurs développés, on s'intéresse aux performances comparées de ces différentes approches sur plusieurs canaux de propagation. Les trois formes d'onde donnent pour un contexte de voie descendante d'un système de radiocommunications des performances très similaires. On a ensuite introduit une nouvelle stratégie DS-CDMA appelée « Waterfilling CDMA ». Nous construisons ainsi une famille de séquences qui prennent en compte les caractéristiques du canalThis thesis presents first of all a matrix formalism that allows representing the DS-CDMA, MC-CDMA and OFDM approaches in a unified way. The formalism allows putting in light several basic results in very quick manner. We show thus if one looks for spreading orthogonal DS-CDMA sequences which stays orthogonal even with a temporal imprecision of one sequence element then, necessarily, these sequences are the complexes exponential of Fourier. Once waves form expressed and the receivers developed. We interested in compared performances of these different approaches on several channels propagation. In final, it appears that, outside material simplifications of a receiver in comparison with the other, the three wave forms give, for a downlink system radio-communications context, very similar performances. The formalism introduced in this thesis allows developing a new strategy of CDMA called in these works "Waterfilling CDMA". It is showed that in the same manner that the cyclic prefix can be used with profit in DS-CDMA, the waterfilling also can be used in this context. Thus we construct a spreading sequences family that take into account the channel characteristics
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Ryland, Kevin Sherwood. "Software-Defined Radio Implementation of Two Physical Layer Security Techniques." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/82055.
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This thesis discusses the design of two Physical Layer Security (PLS) techniques on Software Defined Radios (SDRs). PLS is a classification of security methods that take advantage of physical properties in the waveform or channel to secure communication. These schemes can be used to directly obfuscate the signal from eavesdroppers, or even generate secret keys for traditional encryption methods. Over the past decade, advancements in Multiple-Input Multiple-Output systems have expanded the potential capabilities of PLS while the development of technologies such as the Internet of Things has provided new applications. As a result, this field has become heavily researched, but is still lacking implementations. The design work in this thesis attempts to alleviate this problem by establishing SDR designs geared towards Over-the-Air experimentation.
The first design involves a 2x1 Multiple-Input Single-Output system where the transmitter uses Channel State Information from the intended receiver to inject Artificial Noise (AN) into the receiver's nullspace. The AN is consequently not seen by the intended receiver, however, it will interfere with eavesdroppers experiencing independent channel fading. The second design involves a single-carrier Alamouti coding system with pseudo-random phase shifts applied to each transmit antenna, referred to as Phase-Enciphered Alamouti Coding (PEAC). The intended receiver has knowledge of the pseudo-random sequence and can undo these phase shifts when performing the Alamouti equalization, while an eavesdropper without knowledge of the sequence will be unable to decode the signal.Master of Science
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Ellouz, Sofiane. "Techniques innovantes pour la testabilité des circuits intégrés radio-fréquence." Lyon, INSA, 2006. http://www.theses.fr/2006ISAL0068.
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Les circuits intégrés radio-fréquence subissent différents tests industriels pour vérifier leur conformité aux spécifications du client. Pour réduire l’impact économique du test, il est nécessaire de développer de nouvelles méthodes de tests. La notion de signature a été utilisée pour estimer des performances RF d’un CI à partir de la mesure de courants et tensions continus et en basse fréquence. Le manuscrit détaille tout d’abord une méthode de quantification de la pertinence d’un test. Il décrit ensuite la méthode innovante proposée, qui fait appel à la mise en œuvre des réseaux de neurones. Le manuscrit décrit des blocs de stabilité qui ont pour but d’augmenter la pertinence des mesures et leurs corrélations avec les grandeurs RF. Enfin le manuscrit décrit un flot de conception intégrant la stabilité. Des vérifications expérimentales ont été menées sur des CI industriels et sur un grand nombre de piècesRadio frequency integration-circuit suffers various industrial tests to verify the agreement to customer specifications. These RF specifications can hardly be assessed at wafer level. In order to reduce the economic impact of RF tests and to over cover the limitation in test performances, it is necessary to propose new test methods. Signatures are reasonable candidates for the estimation of RF performances based on DC low-frequency measurement. The manuscript first details the tests performances assessment. Then the test method is described and particularly neural networks are used and learning issues are addressed along with the pertinence of input data. Design for test blocs one also introduced to enhance the pertinence of neural network input data with respect to RF quantities. Finally, a design flow for testability is attempted. Commercial transceivers are used for experimental validation of the proposed methods
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Saideh, Michel. "Contributions on radio access techniques for future railway communications system." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I092.
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Avec l’automatisation croissante des fonctions de contrôle commande dans le domaine ferroviaire, on assiste aujourd’hui à une augmentation drastique des échanges d’information. Ces échanges sont cruciaux pour le déploiement du train autonome, la réduction des coûts d'exploitation et de maintenance, l’amélioration de la sécurité. En même temps, de nombreux nouveaux services d’information et de divertissement s’appuyant sur des systèmes de communication sont proposés aux passagers. Pourtant, il n’y a pas aujourd’hui de technologie unique qui puisse satisfaire tous les besoins exigeants en termes de performances. En conséquence, différents projets de recherche industrielle et académique sont en cours aux niveaux européen et international pour développer le système de communication mobile ferroviaire de demain (ou Future Railway Mobile Communication Système – FRMCS). Ce système s’appuiera sur la technologie IP et sera adaptatif, agnostique à la technologie radio et résilient aux évolutions technologiques. En outre, il devra offrir des débits de données élevés, une faible latence, une large bande passante et une utilisation efficace du spectre. Le FRMCS devra être en mesure de choisir en temps réel entre différentes technologies d’accès radio disponibles en fonction des besoins des applications et de l’environnement ferroviaire. Parmi les technologies d’accès disponibles, on peut citer le Wi-Fi, le LTE, les satellites et le standard 5G NR en cours de développement. Ainsi, les contributions de cette thèse de doctorat s’inscrivent dans le cadre du développement d’un système de communication adaptatif (ACS- Adaptable Communication System) pour le ferroviaire en considérant des technologies de pointe du futur standard 5G NR et au-delà. Différentes technologies clef ont récemment été proposées dans le cadre de la standardisation 5G et au-delà. Parmi celles-ci, les techniques d'accès radio jouent un rôle majeur sur les métriques clés, telles que l'utilisation efficace du spectre disponible, les débits de données élevés et la complexité du système émetteur-récepteur. Une des évolutions technologiques majeure dans ce domaine consiste en l’introduction de différentes techniques de modulation multi-porteuses (MCM- Multi-Carrier Modulation) et des techniques d’accès multiple non orthogonales (NOMA- Non-Orthogonal Multiple Access).Dans ce mémoire de thèse de doctorat, nous commençons par étudier les techniques MCM dans le contexte des défis posés par la grande vitesse ferroviaire. Une évaluation des performances est réalisée en considérant différents systèmes multi porteuses dans différents scénarios. La forme d'ondes FBMC (Filtered Bank Multi-Carrier) offre une grande robustesse dans des scénarios de forte mobilité tout en exploitant efficacement le spectre disponible. Cependant, les avantages de la modulation FBMC s'accompagnent d'interférences intrinsèques supplémentaires qui remettent en question les techniques de conception des émetteurs-récepteurs traditionnels. Ainsi, nous proposons différentes contributions qui concernent les techniques d’estimation et d’égalisation du canal pour la forme d’onde FBMC. Les contributions visent à augmenter les performances finales au prix d’une complexité supplémentaire négligeable si on compare à la littérature existanteNowadays, a huge amount of data exchanges is needed in the railway system. This is particularly to support autonomous train, reduce operation and maintenance costs, increase safety and security. In the same time, many new services are offered to passengers. There is no unique technology that can satisfy all these needs. Consequently, different industrial and academical research projects are on-going at European and International levels to develop the Future Railway Mobile Communications System (FRMCS). FRMCS will be IP-based, adaptable, agnostic to radio technology and resilient to technological evolutions. In addition, it should support high data rate, low latency, large bandwidth, and efficient spectrum utilization. The FRMCS is expected to be able to choose in real time between different available radio access technologies in function of applications needs and the surrounding railway environment. Among these technologies, we can mention the Wi-Fi, LTE, satellites and the 5G NR standard in development. Thus, the contributions of this PhD thesis are part of the development of an Adaptable Communication System (ACS) for the railway by considering cutting-edge technologies of the future 5G NR system and beyond. Different key enabling technologies have been proposed recently under the umbrella of 5G and Beyond communication systems. Among which, radio access techniques play major role over key metrics, such as the efficient utilization of the available spectrum, the high data rates, and the computational complexity of the transceiver system. One of the major technological evolution in that domain concerns the introduction of different Multi-Carrier Modulation (MCM) and Non-Orthogonal Multiple Access (NOMA) techniques. In this Ph.D thesis, we start by considering the MCM technology in the context of high speed railway. A performance evaluation study is conducted where different MCM schemes are highlighted in different scenarios. The Filtered Bank Multi-Carrier (FBMC) waveform presents high robustness to high mobility scenarios while exploiting the available spectrum efficiently. However, FBMC advantages come with additional built-in interference that challenges traditional transceiver design techniques. Thereby, we propose different contributions that handle the channel estimation and equalization aspects of the FBMC waveform. The contributions aims to assure better performance at the cost of negligible additional complexity compared with the literature
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Ahriz, Iness. "Application des techniques d'apprentissage à la géolocalisation par radio fingerprint." Paris 6, 2010. http://www.theses.fr/2010PA066355.
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L’objectif de la thèse est d’améliorer la précision de localisation des personnes (ou objets) dans les environnements où le signal GPS est faible, voire inexistant, par exemple à l’intérieur de bâtiments. L’originalité de ce travail est d’utiliser des signaux radio reçus de sources extérieures pour effectuer la localisation à l’intérieur des bâtiments. Durant ce travail, des mesures des puissances reçues ont été effectuées dans diverses conditions. Étant données les difficultés liées aux processus expérimentaux (incertitude et bruit liés aux mesures), ce dernier point a constitué une première partie de ce travail de thèse. Le traitement et l’interprétation des mesures des puissances de signaux radio dans un environnement de propagation instable ont été un véritable défi durant cette étude. En effet, toutes les porteuses du réseau GSM ont été considérées et aucune hypothèse n’a été posée, à priori, sur leurs pertinences. Une seconde partie de la thèse a été justement consacrée à l’estimation de ces pertinences. Le problème de la détermination de la pièce dans laquelle se trouve le mobile a été considéré comme un problème de classification automatique : des méthodes d’apprentissage statistique (supervisé et semi-supervisé) ont donc été mises en œuvre. Le choix des méthodes utilisées a été fait sur la base des études menées sur les mesures des puissances. Des performances très satisfaisantes ont été obtenues, dans les pièces de deux bâtiments différents. Ces résultats ont ainsi confirmé l’apport des méthodes d’apprentissage statistique au problème de localisation par fingerprints