Dissertations / Theses on the topic 'Wireless communication systems – Mathematical models'
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Lee, Wingyee Emily Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Scheduling real-time traffic in wireless networks." Awarded by:University of New South Wales. Electrical Engineering & Telecommunications, 2007. http://handle.unsw.edu.au/1959.4/40737.
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This dissertation concerns the problem of scheduling real-time traffic in wireless TDMA channels. The most important characteristic of real-time traffic is that it has straight end-to-end delay constraint. We begin the investigation by studying a scheduling principle which naturally achieves the best delay performance in stationary channel conditions. Since the resulting scheduling algorithm maintains equal flow delays across the whole system, it is termed the equal-delay policy. There are a number of advantages associated with this scheduling method. First, it is very simple and practical to implement in real system. Secondly, it can be easily modelled mathematically and admits an analytical solution, which is very important for the construction of an admission control algorithm, we present a mathematical model describing the dynamics of the scheduling system, as well as devising a tractable analytical solution to the problem. A third advantage of the equal-delay policy is that it can be easily extended to support flows with multiple delay constraints. We propose a multiple-class scheduling scheme based on similar allocation concepts as the equal-delay technique. The extended scheme can similarly be mathematically modelled and analytically characterized. A natural objection to the above proposed techniques is that wireless transmission resources can be under-utilized, since the scheduling algorithm pays no attention to the changing individual channel conditions. The reduction in channel utilization can also adversely affect the delay performance, We explain this phenomenon and study the impacts for a variety of different channel characteristics, Specifically, we propose an alternative channel-aware scheduling policy, which aims to maximize channel utilization while keeping a minimum probability of delay violation, The proposed channel-aware policy achieves near-optimal delay performance. However, unlike in the equal-delay case, the channel-aware policy is not practical to implement in a real system. The complicated system dynamics associated with the channel-aware scheme also hamper the development of a mathematical model and analytical solution for admission control. On the other hand, we observe from simulation results that under most circumstances, the equal-delay scheme achieves close to the pertonnance obtained by the channel-aware technique, With the additional benefits of simplicity and admitting analytical analysis. the equal-delay policy appears to be a more practical and suitable choice for scheduling real-time traffic in wireless networks.
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Li, Xiao, and 李驍. "Channel estimation and timing synchronization in cooperative communication systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841835.
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Sadeghi, Parastoo School of Electrical Engineering And Telecommunications UNSW. "Modelling, information capacity, and estimation of time-varying channels in mobile communication systems." Awarded by:University of New South Wales. School of Electrical Engineering And Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/32310.
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In the first part of this thesis, the information capacity of time-varying fading channels is analysed using finite-state Markov channel (FSMC) models. Both fading channel amplitude and fading channel phase are modelled as finite-state Markov processes. The effect of the number of fading channel gain partitions on the capacity is studied (from 2 to 128 partitions). It is observed that the FSMC capacity is saturated when the number of fading channel gain partitions is larger than 4 to 8 times the number of channel input levels. The rapid FSMC capacity saturation with a small number of fading channel gain partitions can be used for the design of computationally simple receivers, with a negligible loss in the capacity. Furthermore, the effect of fading channel memory order on the capacity is studied (from first- to fourth-order). It is observed that low-order FSMC models can provide higher capacity estimates for fading channels than high-order FSMC models, especially when channel states are poorly observable in the presence of channel noise. To explain the effect of memory order on the FSMC capacity, the capacities of high-order and low-order FSMC models are analytically compared. It is shown that the capacity difference is caused by two factors: 1) the channel entropy difference, and 2) the channel observability difference between the high-order and low-order FSMC models. Due to the existence of the second factor, the capacity of high-order FSMC models can be lower than the capacity of low-order FSMC models. Two sufficient conditions are proven to predict when the low-order FSMC capacity is higher or lower than the high-order FSMC capacity. In the second part of this thesis, a new implicit (blind) channel estimation method in time- varying fading channels is proposed. The information source emits bits ???0??? and ???1??? with unequal probabilities. The unbalanced source distribution is used as a priori known signal structure at the receiver for channel estimation. Compared to pilot-symbol-assisted channel estimation, the proposed channel estimation technique can achieve a superior receiver bit error rate performance, especially at low signal to noise ratio conditions.
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Min, Rui, and 闵瑞. "Channel estimation and data detection of OFDM systems under unknown channel order doppler frequency: from point-to-point to relaying systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47323930.
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Recently, there has been an increasing demand for OFDM system operating in
high mobility environment. In such situation, wireless channel is both
frequency-selective and time-varying, a.k.a. doubly-selective, making it hard for the
receiver to keep track of the channel state information (CSI). Moreover, the statistical
information of channel, e.g., tap positions, channel length, Doppler shifts and noise
power, is generally unknown to the receiver. In this thesis, two kinds of mobile
OFDM systems are investigated for data detection and channel estimation. Different
from previous works, which highly depend on the statistical information of the doubly
selective channel to deliver accurate channel estimation and data detection results, we
focus on more practical scenarios with unknown channel orders and Doppler
frequencies.
Firstly, point-to-point OFDM system with high mobility is considered. Due to
the unknown channel characteristics, we formulate the channel using GCE-BEM with
a large oversampling factor. The resulted GCE-BEM coefficients are sparse on
delay-Doppler domain and contain only a few nonzero elements. To enable the
identification of nonzero entries, sparsity enhancing Gaussian priors with Gamma
hyperpriors are adopted. An iterative algorithm is developed under variational
inference (VI) framework. The proposed algorithm iteratively estimate the channel,
recover the unknown data using Viterbi algorithm and learn the channel and noise
statistical information, using only limited number of pilot subcarrier in one OFDM
symbol.
Secondly, we investigate multihop amplify-and-forward (AF) OFDM system,
where system structure is generally unknown to the receiver due to the variable
number of hops and relaying paths in high mobility environment. We notice that in AF
relaying systems, the composite source-relay-destination channel is sufficient for data
detection. Then we integrate the multilink, multihop channel matrices into one
composite channel matrix, which turns out to have the same structure as the
point-to-point OFDM channel. The reformulated system model is more concise and a
similar iterative algorithm to that of the point-to-point case can be derived to estimate
the composite channel and detect data. This means that the proposed framework
applies to OFDM system under high mobility regardless of the system structure.
Simulation results show that the performance of the proposed algorithm is very
close to that of the optimal channel estimation and data detection algorithm, which
requires specific information of system structure, channel tap positions, channel
lengths, Doppler shifts as well as noise powers. It is worth noting that, the
close-to-ideal performance of the proposed algorithms is achieved with none of the
above information.published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
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Patel, Chirag S. "Wireless channel modeling, simulation, and estimation." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-03282006-200818/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.Andrew, Alfred, Committee Member ; Durgin, Gregory, Committee Member ; Li, Geoffrey, Committee Member ; Ingram, Mary Ann, Committee Member ; Stuber, Gordon, Committee Chair.
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Heo, Deukhyoun. "Silicon MOS field effect transistor RF/Microwave nonlinear model study and power amplifier development for wireless communications." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15618.
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Pirkl, Ryan J. "Measurement-based investigations of radio wave propagation: an exposé on building corner diffraction." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33961.
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Predicting performance metrics for the next-generation of multi-mode and multi-antenna wireless communication systems demands site-specific knowledge of the wireless channel's underlying radio wave propagation mechanisms. This thesis describes the first measurement system capable of characterizing individual propagation mechanisms in situ. The measurement system merges a high-resolution spatio-temporal wireless channel sounder with a new field reconstruction technique to provide complete knowledge of the wireless channel's impulse response throughout a 2-dimensional region. This wealth of data may be combined with space-time filtering techniques to isolate and characterize individual propagation mechanisms. The utility of the spatio-temporal measurement system is demonstrated through a measurement-based investigation of diffraction around building corners. These measurements are combined with space-time filtering techniques and a new linear wedge diffraction model to extract the first semi-mpirical diffraction coefficient. Specific contributions of this thesis are:
* The first ultra-wideband single-input multiple-output (SIMO) channel sounder based upon the sliding correlator architecture.
* A quasi 2-dimensional field reconstruction technique based upon a conjoint cylindrical wave expansion of coherent perimeter measurements.
* A wireless channel ``filming' technique that records the time-domain evolution of the wireless channel throughout a 2-dimensional region.
* High-resolution measurements of the space-time wireless channel near a right-angled brick building corner.
* The application of space-time filtering techniques to isolate the edge diffraction problem from the overall wireless channel.
* An approximate uniform geometrical theory of diffraction (UTD)-style linear model describing diffraction by an impedance wedge.
* The first-ever semi-empirical diffraction coefficient extracted from in situ measurement data.
This thesis paves the way for several new avenues of research. The comprehensive measurement data provided by channel "filming" will enable researchers to develop and implement powerful space-time filtering techniques that facilitate measurement-based investigations of radio wave propagation. The measurement procedure described in this thesis may be adapted to extract realistic reflection and rough-surface scattering coefficients. Finally, exhaustive measurements of individual propagation mechanisms will enable the first semi-empirical propagation model that integrates empirical descriptions of propagation mechanisms into a UTD-style mechanistic framework.
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McGarvey, Brian Scott. "Coupling of Solid-State and Electromagnetic Equations for the Computationally Efficient Time-Domain Modeling and Design of Wireless Packaged Geometries with NonlinearActive Devices." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14551.
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This document contains a proposal for the creation of a simulator that can accurately model the interaction of electromagnetic (EM) and semiconductor effects for modern wireless devices including nonlinear and/or active devices.
The proposed simulator couples the balanced semiconductor equations (charge, momentum, kinetic energy) with a FDTD full-wave Yee-based electromagnetic (EM) simulator. The resultant CAD tool is able to model the response of one semiconductor device to both small signal and DC bias based on the process parameters (material, charge distribution and doping) without any a-priori knowledge of the device performance characteristics, thus making it extremely useful in modeling and integrating novel devices in RF and Wireless topologies. As a proof of concept an n+--i--n+ diode will be simulated. In the future, more complicated structures, such as MODFETs, will be modeled as well.
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Nsoh, Stephen Atambire. "Resource allocation in WiMAX mesh networks." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Mathematics and Computer Science, c2012, 2012. http://hdl.handle.net/10133/3371.
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The IEEE 802.16 standard popularly known as WiMAX is at the forefront of the technological
drive. Achieving high system throughput in these networks is challenging due to
interference which limits concurrent transmissions. In this thesis, we study routing and link
scheduling inWiMAX mesh networks. We present simple joint routing and link scheduling
algorithms that have outperformed most of the existing proposals in our experiments. Our
session based routing and links scheduling produced results approximately 90% of a trivial
lower bound.
We also study the problem of quality of service (QoS) provisioning in WiMAX mesh
networks. QoS has become an attractive area of study driven by the increasing demand
for multimedia content delivered wirelessly. To accommodate the different applications,
the IEEE 802.16 standard defines four classes of service. In this dissertation, we propose a
comprehensive scheme consisting of routing, link scheduling, call admission control (CAC)
and channel assignment that considers all classes of service. Much of the work in the
literature considers each of these problems in isolation. Our routing schemes use a metric
that combines interference and traffic load to compute routes for requests while our link
scheduling ensures that the QoS requirements of admitted requests are strictly met. Results
from our simulation indicate that our routing and link scheduling schemes significantly
improve network performance when the network is congested.ix, 77 leaves : ill. ; 29 cm
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Jabbour, Imad W. "Simulation of models and algorithms for wireless communication systems." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38950.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.Includes bibliographical references (leaf 61).
The thesis presents a set of simulations of models and algorithms for wireless communication systems. The simulations are developed using graphical MATLAB interfaces, and cover the fundamentals of wireless channel modeling, the advantages and limitations of antenna beamforming in multiuser systems, and the underlying principles of OFDM. The thesis targets two types of audiences in particular: students and wireless industry professionals. For the former, it constitutes an excellent complement to lecture notes, and for the latter, it is an efficient way to review the key principles and technologies. In either case, the simulations provide an intuitive view of the addressed topics, thus allowing users to comprehend the basics of wireless channels and phenomena without delving into mathematical complexities.
by Imad W. Jabbour.
S.M.
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Moritz, Guilherme Luiz. "Comunicação cooperativa com codificação de rede e transferência sem fio de energia." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1369.
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Neste trabalho, considera-se uma rede sem fio cooperativa em que múltiplas fontes com restrições energéticas cooperam para transmitir informações independentes a um destino comum. Assume-se também que toda a energia disponível nas fontes é captada a partir de transmissões de radiofrequência realizadas pelo destino (o qual é considerado não possuir restrições de energia), sendo dependente das condições instantâneas do canal. Dessa forma, estabelece-se um protocolo de comutação temporal em que em parte do tempo as fontes são carregadas pelo destino, e no restante do tempo transmitem as suas informações. Utilizando-se a probabilidade de outage comométrica de desempenho, analisa-se o desempenho de alguns protocolos cooperativos com transferência sem fio de energia, a saber: decodifica-e-encaminha(EDF), cooperação por codificação de rede (ENC) e cooperação por codificação de rede generalizada (EGNC). Expressões fechadas são desenvolvidas para calcular a probabilidade de outage dos protocolos cooperativos descritos acima, assim como o tempo de carregamento ótimo para minimizar a referida probabilidade e a máxima taxa alcançável para uma probabilidade de outage alvo, mostrando que o protocolo EGNC apresenta o melhor desempenho dentre os protocolos cooperativos considerados e que a transmissão direta (sem cooperação). Simulações numéricas são realizadas para se comprovar a precisão das expressões desenvolvidas e finalmente se enumeram sugestões para a continuação do trabalho.In this work, we consider a multiuser cooperative wireless network where multiple energy-constrained sources have independent information to transmit to a common destination. The destination, which is assumed to be externally powered, is responsible for transferring energy wirelessly to the sources. The total amount of harvested energy is a function of instantaneous channel conditions. In this scenario, a time-switching protocol is developed where in a fraction of time the sources harvest energy and then use this energy to transmit information. Using the outage probability as a metric, we evaluate the performance of some energy transfer cooperative protocols, namely: energy transfer decode-and-forward (EDF), energy transfer network coding cooperation (ENC) and energy transfer generalized network coding cooperation (EGNC). We obtain a closed-form approximation for the system outage probability, as well as an approximation for the optimal energy transfer period that minimizes such outage probability showing that EGNC protocol presents the best performance among the considered protocols and when compared with the direct transmission. Numerical results are also presented to validate the theoretical results. Finally, suggestions about future works are presented.
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Rouf, Ishtiaq. "Statistical Analysis of Wireless Communication Systems Using Hidden Markov Models." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/43718.
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This thesis analyzes the use of hidden Markov models (HMM) in wireless communication systems. HMMs are a probabilistic method which is useful for discrete channel modeling. The simulations done in the thesis verified a previously formulated methodology. Power delay profiles (PDP) of twelve wireless receivers were used for the experiment. To reduce the computational burden, binary HMMs were used. The PDP measurements were sampled to identify static receivers and grid-based analysis. This work is significant as it has been performed in a new environment.
Stochastic game theory is analyzed to gain insight into the decision-making process of HMMs. Study of game theory is significant because it analyzes rational decisions in detail by attaching risk and reward to every possibility.
Network security situation awareness has emerged as a novel application of HMMs in wireless networking. The dually stochastic nature of HMMs is applied in this process for behavioral analysis of network intrusion. The similarity of HMMs to artificial neural networks makes it useful for such applications. This application was performed using simulations similar to the original works.
Master of Science
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Zhang, Guchun. "Models and performances of wireless MIMO and cooperative communication systems." Thesis, Aston University, 2009. http://publications.aston.ac.uk/15411/.
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Multiple-antenna systems offer significant performance enhancement and will be applied to the next generation broadband wireless communications. This thesis presents the investigations of multiple-antenna systems – multiple-input multiple-output (MIMO) and cooperative communication (CC) – and their performances in more realistic propagation environments than those reported previously. For MIMO systems, the investigations are conducted via theoretical modelling and simulations in a double-scattering environment. The results show that the variations of system performances depend on how scatterer density varies in flat fading channels, and that in frequency-selective fading channels system performances are affected by the length of the coding block as well as scatterer density. In realistic propagation environments, the fading correlation also has an impact on CC systems where the antennas can be further apart than those in MIMO systems. A general stochastic model is applied to studying the effects of fading correlation on the performances of CC systems. This model reflects the asymmetry fact of the wireless channels in a CC system. The results demonstrate the varied effects of fading correlation under different protocols and channel conditions. Performances of CC systems are further studied at the packet level, using both simulations and an experimental testbed. The results obtained have verified various performance trade-offs of the cooperative relaying network (CRN) investigated in different propagation environments. The results suggest that a proper selection of the relaying algorithms and other techniques can meet the requirements of quality of service for different applications.
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Wu, Bo. "On optimum system design for wireless communications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21955.pdf.
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Li, Yang. "Models and applications of wireless networks in rural environments." Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
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With the unprecedented growth of the communication industry that the world is experiencing, the demand from rural inhabitants for high quality communications at an economically affordable cost is growing. However, rural areas are rather restricted from deploying communication services due to the rough natural environment, and the shortage of rudimentary communication facilities and technical personnel. Appropriate models for building rural wireless networks and a concomitant simulation environment are, therefore, expected to enable the construction of technologically-optimal and economically-efficient networks in specified rural areas.The research has set up two independent models, one for the economic need and the other for the technical need of building networks in rural areas. One model was the Impact of Telecommunications Model, which disclosed the importance of building a wireless network in specified rural areas by choosing an economic parameter to forecast the profitability of the network. The other was the Service Model, which collected primitive data from given rural areas and abstracted these data by flowing them through four technical layers to form the predicted technical wireless network. Both of the models had been applied to real-world cases to demonstrate how to use them.
A simulation environment was finally designed and implemented to realize the above two models for the sake of instantiation. This environment could simulate the specified rural network by constructing a wireless network on the invented areas and evaluating its quality and economic efficiency. It was written in Scilab simulation language, which was an open source.
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Greyling, Neville. "An investigation into PCF-DCF behaviour of 802.11b networks." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4118.
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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: In recent years the demand for bandwidth has dramatically increased because of new applications for data and multimedia, and wireless technology has prevailed as a prominent technology for data connectivity, especially for home, office and last mile services. As wireless communications are dependant upon spectrum availability, which is communal, this scarce commodity in communication has to be used as efficiently as possible. Some aspects of this requirement are addressed in this project. We chose the IEEE 802.11b standard for this particular investigation because of its widespread use, the vast amount of applicable literature, the variety of software simulation tools and the ease with which equipment can be obtained. The IEEE 802.11 standard specified the Point Coordination Function as the de- terministic protocol. Recently research into this aspect has stagnated, and it was the purpose of this project to investigate how existing infrastructure networks could be improved by optimising some modes of the 802.11 protocol. The investigation also hoped to determine when to change between Distributed Coordination Function (DCF) and Point Coordination Function (PCF), and to provide an adaptive protocol to do so. This thesis presents mathematical models for the operation of DCF and PCF modes, which is compared with results from a network simulator (ns2), for theoretical veri- fication. A protocol is also proposed to dynamically switch between DCF and PCF, to harness the advantages they present.
AFRIKAANSE OPSOMMING: Die afgelope paar jaar het die aanvraag na bandwydte dramaties verhoog as gevolg van nuwe toepassings vir data en multimedia, en draadlose tegnologie het voorgekom as ’n dominante tegnologie vir data konnektiwiteit, veral vir die huis, kantoor en laaste myl dienste. Omdat draadlose kommunikasie afhanklik is van spektrum beskikbaarheid, wat gemeenskaplik is, moet hierdie skaars kommoditeit in kommunikasie so effektief moontlik gebruik word. Sekere aspekte van die vereiste sal in die tesis ondersoek word. Dit is besluit om die IEEE 802.11b standard vir die spesifieke ondersoek te gebruik as gevolg van die wye toepassing, die groot hoeveelheid beskikbare literatuur, die verskeidenheid simulasie sagteware en die gemak waarmee die toerusting bekom kan word. Die IEEE 802.11 standaard spesifiseer the Punt Koordinasie Funksie (PCF) as die deterministiese protokol vir die betrokke standaard. Onlangs het navorsing oor hierdie aspek gestagneer, en dit is die doel van die projek om te ondersoek hoe bestaande infrastruktuur netwerke moontlik verbeter kan word deur optimering van sekere modusse van die 802.11 protokol. Die ondersoek hoop ook om te bepaal wanneer die oorgang van die Distrubusie Koordinasie Funksie (DCF) en Punt Ko- ordinasie Funksie sal plaasvind, en om ’n dienooreenstemmende protokol te on- twikkel. Die tesis verskaf wiskundige modelle vir die werking van die DCF en PCF modusse, wat vergelyk word met resultate uit ’n netwerk simulator (ns2), vir teoretiese ver- ifikasie. ’n Protokol word ook voorgestel om dinamies te wissel tussen DCF and PCF, om die voordele wat die protokolle verskaf te gebruik.
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Salih, Omar S. "Error models for digital channels and applications to wireless communication systems." Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2686.
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Digital wireless channels are extremely prone to errors that appear in bursts or clusters. Error models characterise the statistical behaviour of bursty profiles derived from digital wireless channels. Generative error models also utilise those bursty profiles in order to create alternatives, which are more efficient for experimental purposes. Error models have a tremendous value for wireless systems. They are useful for the design and performance evaluation of error control schemes, in addition to higher layer protocols in which the statistical properties of the bursty profiles are greatly functional. Furthermore, underlying wireless digital channels can be substituted by generated error profiles. Consequently, computational load and simulation time can be significantly reduced when executing experiments and performing evaluation simulations for higher layer communications protocols and error control strategies. The burst error statistics are the characterisation metrics of error models. These statistics include: error-free run distribution; error-free burst distribution; error burst distribution; error cluster distribution; gap distribution; block error probability distribution; block burst probability distribution; bit error correlation function; normalised covariance function; gap correlation function; and multigap distribution. These burst error statistics scrutinise the error models and differentiate between them, with regards to accuracy. Moreover, some of them are advantageous for the design of digital components in wireless communication systems. This PhD thesis aims to develop accurate and efficient error models and to find applications for them. A thorough investigation has been conducted on the burst error statistics. A breakdown of this thesis is presented as follows. Firstly, an understanding of the different types of generative error models, namely, Markovian based generative models, context-free grammars based generative models, chaotic models, and deterministic process based generative models, has been presented. The most widely used models amongst the generative models have been compared with each other consulting the majority of burst error statistics. In order to study generative error models, error burst profiles were obtained mainly from the Enhanced General Packet Radio Service (EGPRS) system and also the Long Term Evolution (LTE) system. Secondly, more accurate and efficient generative error models have been proposed. Double embedded processes based hidden Markov model and three-layered processes based hidden Markov model have been developed. The two types of error profiles, particularly the bit-level and packet-level error profiles were considered. Thirdly, the deterministic process based generative models’ parameters have been tuned or modified in order to generate packet error sequences rather than only bit error sequences. Moreover, a modification procedure has been introduced to the same models to enhance their generation process and to make them more desirable. Fourthly, adaptive generative error models have been built in order to accommodate widely used generative error models to different digital wireless channels with different channel conditions. Only a few reference error profiles have been required in order to produce additional error profiles in various conditions that are beneficial for the design and performance evaluation of error control schemes and higher layer protocols. Finally, the impact of the Hybrid Automatic Repeat reQuest (HARQ) on the burst error statistics of physical layer error profiles has been studied. Moreover, a model that can generate predicted error sequences with burst error statistics similar to those of error profiles when HARQ is included has been proposed. This model is constructive in predicting the behaviour of the HARQ in terms of a set of higher order statistics rather than only predicting a first order statistic. Moreover, the whole physical layer is replaced by adaptively generated error profiles in order to check the performance of the HARQ protocol. The developed generative error models as well as the developed adaptive generative error models are expected to benefit future research towards the testing of many digital components in the physical layer as well as the wireless protocols of the link and transport layers for many existing and emerging systems in the field of wireless communications.
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Alparslan, Denizhan N. Sohraby Khosrow. "Modeling and analysis of generalized random mobility models for wireless ad hoc networks." Diss., UMK access, 2005.
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Thesis (Ph. D.)--School of Computing and Engineering. University of Missouri--Kansas City, 2005."A dissertation in telecommunication networking and computer networking." Advisor: Khosrow Sohraby. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed May 30, 2006. Includes bibliographical references (leaves 119-123). Online version of the print edition.
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Sridhara, Vinay. "Models and methodologies for realistic propagation simulation for urban mesh networks." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 182 p, 2007. http://proquest.umi.com/pqdweb?did=1362532761&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Liu, Lingjia. "On delay-sensitive communication over wireless systems." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2725.
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Kim, Seong-Pyo Mitchell Kenneth H. "Analytical models of throughput performance over multi-hop wireless and sensor networks." Diss., UMK access, 2004.
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Thesis (Ph. D.)--School of Computing and Engineering. University of Missouri--Kansas City, 2004."A dissertation in telecommunications networking and computer networking." Advisor: Ken Mitchell. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Feb. 24, 2006. Includes bibliographical references (leaves 141-146). Online version of the print edition.
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Muhi-Eldeen, Zaid M. H. "Stochastic propagation and planning models for broadband fixed wireless access links." Thesis, University of South Wales, 2008. https://pure.southwales.ac.uk/en/studentthesis/stochastic-propagation-and-planning-models-for-broadband-fixed-wireless-access-links(4ceba5cf-ef72-44a9-95d4-35bdb4e8dd30).html.
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Hydrogen technology has widely been acknowledged as a route to reduced carbon emissions and energy security. However, it is also recognised that technology development alone is not enough to cause a shift change in uptake and that public perception also needs to be considered. This paper identifies the public perception of hydrogen technology (with specific interest in biologically produced hydrogen) and determines whether it meets the public expectation in terms of its potential energetic output. The energetic viability of hydrogen (defined for this purpose as a net positive energy balance) is derived by determining the potential for agriculturally produced hydrogen using dark fermentative production techniques. A suitable range of energy crops have been identified using selection criteria including yield, harvest window and composition of the crops. Public perception of hydrogen energy was investigated through the use of two focus groups. This identified Welsh public opinions on the production and end use of hydrogen energy. Due to the rapid progress in wireless communication technologies and the increasing demands for new services; cutting edge techniques and research have developed wireless access delivery of broadband data. Such systems referred to as Broadband Fixed Wireless Access Systems (BFWA) or alternatively, Local Multipoint Distribution Systems (LMDS), are increasingly being regarded as a legitimate challenger to cable and digital subscriber lines (DSL), particularly in markets with poor cable or copper infrastructure. These systems have capabilities that go beyond the current WiFi and WiMAX technologies by providing users with higher bandwidths and faster data rates. The frequency of operation for such networks lies between 28 and 42 GHz according to the spectrum bands allocated for future LMDS networks. The presented work aims at proposing a generalized stochastic model for the LMDS urban/suburban propagation channel. The model is based on a physical electromagnetic representation of the millimetre wavelength channel, with particular emphasis on fading margins in line-of-sight (LOS) links. The study focuses on the analysis, modelling and measurements of the fading effects of signal scattering caused by building surfaces and the ground on the direct field in an LMDS link at millimetre waves. Outcomes have been validated against experimental results obtained in realistic propagation scenarios. More than 180 field measurement sets were taken at 40 GHz for model testing and validation purposes. The main innovation of this work is the solution proposed to address the problem of signal scatter at millimetre-wave lengths. The approach uses high-frequency approximations to the analytical solution given by Kirchhoff s tangent-plane representation of rough surfaces. The electromagnetic field and signal power at the receiver are considered random and are evaluated using the Physical Optics method over different possible realizations of the surface geometry and building architectural features. This has resulted in novel derivations of the mean field, mean power density and scatter distribution of the scattered field. In comparison to deterministic models, such as ray-tracing that require intensive computations and detailed (millimetric resolution) knowledge of topographical data that are almost impossible to obtain, the proposed model is rather efficient and yields accurate results. The model has also been employed in analysing the effects of building scatter on the variance of the main desired link and the adjacent- or co-channel interfering link arising from neighbouring cells in cellular LMDS networks. This has enabled predictions of signal-to-interference ratio statistics and distributions for a particular underlying propagation environment. Overall, compansons yielded very good agreements between measurements and predictions of the main statistical parameters, thus verifying the main assumptions relating to the received signal strength, as well as the validity of a Rician distribution in describing the signal envelope variability for both the main and interference links in complex millimetre-wave propagation environments.
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Hou, Yuen Tan. "Resource management in multimedia communication systems." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/478.
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Dankers, Wouter. "Learning wireless channel models to design real-time communications from vehicles." Thesis, Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-37475.
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The aim of this project is to analyze a data log of wireless packet traffic, and to produce: (1) models for dynamic fluctuations in wireless channel and link quality, and, (2) a design for real-time communications over the given wireless channel. The models and designs are useful in setting up real-time communications in a vehicular test track (www.astazero.com). The data log came from experimental measurements at the test track. From this data, we fitted simple models for packet losses and retransmissions in the wireless communication system. These models took the form of a combination of a statistical model for the packet losses, with a deterministic model for retransmissions of lost packets. Such fitted models can be used to predict the average quality of vehicle position monitoring based on periodically transmitted position information. Such predictions help us decide the feasibility of safe and reliable conduct of testing with two or more moving test objects.
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He, Shuangchi. "Doubly-selective channel estimation and equalization using superimposed training and expansion models." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Dissertations/HE_SHUANGCHI_5.pdf.
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Thiagarajan, Maheswaran. "Communication models for monitoring and mobility verification in mission critical wireless networks." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Thiagarajan_09007dcc80648bab.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 21, 2009) Includes bibliographical references (p. 74-77).
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Shekhar, Hemabh. "Multi-antenna physical layer models for wireless network design." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22681.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Ingram, Mary Ann; Committee Member: Andrew, Alfred; Committee Member: Copeland, John; Committee Member: Owen, Henry; Committee Member: Sivakumar, Raghupathy.
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Delangre, Olivier. "Caractérisation et modélisation du canal radio en chambre réverbérante." Thesis, Universite Libre de Bruxelles, 2008. http://www.theses.fr/2008LIL10144/document.
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L'utilisation d'une chambre réverbérante pour modéliser un canal de communication sans fil a récemment été proposée. La chambre réverbérante est une cavité métallique fermée dans laquelle se trouve une pale mécanique en mouvement permettant de modifier les conditions aux limites et d'ainsi obtenir en moyenne une répartition uniforme des champs. Cette cavité métallique fermée présente de nombreux avantages pour modéliser un canal de communication. Citons principalement le fait que l'environnement est reproductible grâce au mouvement de la pale. L'étude détaillée du canal de communication sans fil à l'intérieur de cet environnement est le sujet de cette thèse. Nous développons à la fois une approche théorique et expérimentale (dans 3 chambres réverbérantes différentes). En particulier, on caractérise ce canal dans les dimensions temporelles, fréquentielles et spatiales afin de dériver ensuite un modèle de canal. Nous nous intéressons en particulier aux systèmes sans fil multi-antennes car ceux-ci exploitent les trois dimensions (temps, fréquence, position). Ensuite, nous comparons l'environnement en chambre réverbérante au cas d'un environnement confiné, à savoir une voiture. Nous testons également une chaîne complète de transmission OFDM et SC-FDE sur base du modèle de canal en chambre développé dans cette thèse. Enfin, nous présentons un nouveau système de test composé de deux chambres réverbérantes couplées à l'aide d'un guide d'ondes dont les dimensions transverses peuvent être changées. Grâce à ce guide d'ondes, le degré de liberté du canal multi-antennes peut être contrôléThe subject of this thesis is the evaluation of the wireless channel model inside a reverberation chamber. A reverberation chamber is a metallic cavity with a mechanical stirrer whose aim is to stir the electric and magnetic fields inside the chamber. The main advantage of a reverberation chamber for channel modelling purpose is its ability to create an unlimited number of channel realizations. A complete characterization of the channel model is investigated in the three main dimensions (time, frequency and position). A theoretical and experimental approach (in 3 different reverberation chambers) is provided. Then a channel model is proposed. The focus is on multiple antennas systems. Their main characteristic is to take advantage of the three dimensions (including space). A full MIMO channel model is thus proposed and validated. Then, a measurement campaign in a car is compared with the measurements and the theory of the reverberation chamber. An OFDM and SC-FDE transmission scheme are applied on the previously developed channel model inside a reverberation chamber. The results are compared with a classical channel model. Finally, a new testbed is discussed. It is made of two reverberation chambers coupled through a waveguide whose transverse dimensions can be changed. The main advantage of this testbed is its ability to control the degree of freedom of the channel
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Börjesson, Maria. "Communication technology and travel demand models." Licentiate thesis, KTH, Infrastructure, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1640.
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Transportation planners have traditionally focused onphysical travel only, and disregarded the fact that other modesof communication may influence travel demand. However, moderntelecommunications are rapidly increasing the accessibility toactivities that previously only could be reached by physicaltransportation. This development calls for methods to analyseinteractions between telecommunications and transport systems.The objective of this thesis is to accomplish a betterunderstanding of if and how impacts of information technologycould be implemented in travel demand models. An important partof this issue is to investigate what kind of data that isneeded.
This thesis also aims at investigating whether theCommunication Survey, KOM, collected by Swedish Institute forTransport and Communications, SIKA, can be used to improvetransport modelling with respect to how moderntelecommunications influence travel demand. KOM is a one-daytravel and communication diary survey, including information onthe respondents telecommuting habits as well as socio-economicstatus. One problem was the small sample size in KOM, whichmade the analyses uncertain. Since KOM is collected on a yearlybasis, it is still possible to apply similar analysis methodswithin a few years, using a larger data set, which might enableextended analyses. The small sample in KOM available to date isbest suited for general descriptive analyses of communicationpatterns in Sweden. The main conclusions of the paper aretherefore connected to the methods and future datacollection.
The thesis includes three papers. The first paper tested amodel approach that assumes substitution between travel andnon-travel based communication, using the KOM database. Traveldemand models are in general constructed as nested logit modelswith frequency, mode and destination choice levels. In thepaper, non-travel based modes of communication were included inthe choice set of such a model. The non-travel based modes ofcommunication considered were Internet (and e-mail), ordinarymail and telephone contacts. The model was developed for postand bank activities only, since that was the only activity forwhich the numbers of contacts and trips were large enough toallow model estimation. Several conclusions could be drawn.Describing the utility of the non-travel based alternatives isdifficult and needs more research. The analysisis also verysensitive to how activities are defined. It is furtheressential that the data collection is more process orientedthan traditional cross-sectional data is when analysing traveland telecommunications interactions. That is, habits ofperforming particular activities, including both trips anddifferent types of contacts, must be studied. The second andthird papers investigate telecommuting. As a first step toreach the goal of forecasting telecommuting, the second paperexamined the characteristics of current telecommuters by use ofKOM. This was mainly accomplished by estimating a telecommutingadoption model of logit type. However, only 122 employees outof 7578 actually telecommutes full days at home. Thesetelecommuters work primarily in information- and service-basedindustrial sectors concerned with computers, finance orcommunication. The difficulties in describing the utility ofthe telecommunications based alternatives (representingno travel) concerned also the telecommutingadoption model. Also impacts on travel from telecommuting wereinvestigated. Comparing the average commuting distance showedthat employees who exclusively telecommute full days havelonger commuting distances than others, but that othertelecommuters do not have longer average commuting distances.Telecommuting in general does not seem to be influenced by lowaccessibility to the labour market.
The third paper used data collected from a working sitewithin the company Ericsson, located in the office district ofNacka Strand in Stockholm during the autumn 2002. Thetelecommuting frequency was substantially higher at Ericssonthan in the workforce as a whole. The propensity to adopttelecommuting was modelled as a function of socio-economicvariables and access to technical equipment, work tasksuitability and management attitudes, as perceived by theemployees. The focuswas to identify tools that the company canuse to promote telecommuting, and to find incentives for thecompany to promote telecommuting. Technical equipment, suitablework tasks and managers attitude were identified as constraintsfor telecommuting. The employees also perceived that theybecame more efficient and saved time when telecommuting.
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Sail, Siddharth Subhash. "On the applicability of random mobility models for swarm robot movements /." Online version of thesis, 2007. http://hdl.handle.net/1850/3939.
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Bose, Biswojit. "Bit error rate estimation in WiMAX communications at vehicular speeds using Nakagami-m fading model." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/530.
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The wireless communication industry has experienced a rapid technological evolution from its basic first generation (1G) wireless systems to the latest fourth generation (4G) wireless broadband systems. Wireless broadband systems are becoming increasingly popular with consumers and the technological strength of 4G has played a major role behind the success of wireless broadband systems. The IEEE 802.16m standard of the Worldwide Interoperability for Microwave Access (WiMAX) has been accepted as a 4G standard by the Institute of Electrical and Electronics Engineers in 2011. The IEEE 802.16m is fully optimised for wireless communications in fixed environments and can deliver very high throughput and excellent quality of service. In mobile communication environments however, WiMAX consumers experience a graceful degradation of service as a direct function of vehicular speeds. At high vehicular speeds, the throughput drops in WiMAX systems and unless proactive measures such as forward error control and packet size optimisation are adopted and properly adjusted, many applications cannot be facilitated at high vehicular speeds in WiMAX communications. For any proactive measure, bit error rate estimation as a function of vehicular speed, serves as a useful tool. In this thesis, we present an analytical model for bit error rate estimation in WiMAX communications using the Nakagami-m fading model. We also show, through an analysis of the data collected from a practical WiMAX system, that the Nakagami-m model can be made adaptive as a function of speed, to represent fading in fixed environments as well as mobile environments.
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Yang, Zhe. "Coexistence, Deployment and Business Models of Heterogeneous Wireless Systems Incorporating High Altitude Platforms." Doctoral thesis, Blekinge Tekniska Högskola, Avdelningen för elektroteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00551.
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The increased demand for broadband communications has led to the rapid development of the conventional terrestrial and satellite wireless communications systems. One of the main challenges to next generation wireless systems is to deliver high-capacity and cost-efficient solutions to cope with an increasing usage of broadband services and applications. In the recent years, an emerging competitive system has attracted the attention for providing wireless broadband communications and other services based on quasi-stationary aerial platforms operating in the stratosphere known by high altitude platforms (HAPs), and located 17-22 km above the earth surface. This solution has been described by the International Telecommunication Union (ITU) as "a new and long anticipated technology that can revolutionize the telecommunication industry''. The HAP systems provide important advantages such as low cost, high elevation angles, low propagation delay, easy and incremental deployment, flexibility in operation, broad coverage, broadcast and broadband capability, ability to move around in emergency situations, etc. Therefore, they have been proposed by ITU for the provision of fixed, mobile services and applications, e.g. the third generation (3G) services licensed by ITU and backbone link for terrestrial networks in remote areas. This thesis explores and investigates the wireless communication and techno-economic performance of terrestrial systems and HAPs. An overview of research and development on aerial platforms worldwide is given. Coexistence performance and techniques of heterogeneous systems to provide broadband wireless communications based on Worldwide Interoperability Microwave Access (WiMAX) are investigated. A heterogeneous scenario is developed to examine the coexistence performance of heterogeneous systems. The capacity and deployment aspects of HAPs are analyzed, and further compared with terrestrial Universal Mobile Telecommunications Systems (UMTS) through techno-economic studies including a proposed partnership based business model for HAPs. Performance of wireless sensor network applications via HAPs is also investigated, and shows the high potential of HAPs for large-area and long-endurance surveillance and emergency applications. The thesis shows that communications from the aerial platforms provide the best features of both terrestrial and satellite systems. HAPs can effectively coexist in a heterogeneous radio environment, and are competitive solutions in urban and suburban scenarios in terms of capacity, coverage and business perspective. This makes HAP a viable competitor and complement to conventional terrestrial infrastructures and satellite systems.
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Chen, Mo. "Data compression for inference tasks in wireless sensor networks." Diss., Online access via UMI:, 2006.
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Thesis (Ph. D.)--State University of New York at Binghamton, Department of Electrical Engineering, Thomas J. Watson School of Engineering and Applied Science, 2006.Includes bibliographical references.
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Yankopolus, Andreas George. "Adaptive Error Control for Wireless Multimedia." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5237.
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Future wireless networks will be required to support multimedia traffic in addition to traditional best-effort network services. Supporting multimedia traffic on wired networks presents a large number of design problems, particularly for networks that run connectionless data transport protocols such as the TCP/IP protocol suite. These problems are magnified for wireless links, as the quality of such links varies widely and uncontrollably.
This dissertation presents new tools developed for the design and realization of wireless networks including, for the first time, analytical channel models for predicting the efficacy of error control codes, interleaving schemes, and signalling protocols, and several novel algorithms for matching and adapting system parameters (such as error control and frame length) to time-varying channels and Quality of Service (QoS) requirements.
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Csinger, Andrew. "Implementing a normative theory of communication in a framework for default reasoning." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28954.
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This thesis presents a framework for inter-agent communication, represented
and partially implemented with default reasoning. I focus on the limited goal of determining the meaning for a Hearer-agent of an utterance ω by a Speaker-agent, in terms of the beliefs of the interlocutors.
This meaning is generally more than just the explicit propositional contents of ω, and more than just the Speaker's goal to convey her belief that ω.
One way of determining this meaning is to let the Hearer take stock of the implicit components of the Speaker's utterances. Among the implicit components of the meaning of ω, I show in particular how to derive certain of its presuppositions with a set of default schemata using a framework for default reasoning.
More information can be extracted from the communications channel
between interlocutors by adopting a normative model of inter-agent communication, and using this model to explain or 'make sense' of the Speaker's utterances. I construct such a model expressed in terms of a set of default principles of communication using the same framework for default reasoning.
The task of deriving the meaning of an utterance is similar to the job required of a user-interface, where the user is the Speaker-agent, and the interface itself is the Hearer-agent. The goal of a user-interface as Hearer is to make maximal use of the data moving along the communications channel between user and application.
The result is an integrated theory of normative, inter-agent communications
expressed within an ontologically and logically minimal framework.
This work demonstrates the development and application of a methodology for the use of default reasoning. The implementation of the theory is also presented, along with a discussion of its applicability
to practical user-interfacing. A view emerges of user-modelling as a component of a user-interface.Science, Faculty of
Computer Science, Department of
Graduate
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Song, Liying Tugnait Jitendra K. "Channel estimation and equalization for doubly-selective channels using basis expansion models." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Electrical_and_Computer_Engineering/Dissertation/Song_Liying_29.pdf.
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Pimpalkhare, Mangesh S. "Linearly repeatered communication systems using optical amplifiers." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-05042010-020243/.
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Yulei, W. U. "Performance modelling and evaluation of heterogeneous wired / wireless networks under Bursty Traffic. Analytical models for performance analysis of communication networks in multi-computer systems, multi-cluster systems, and integrated wireless systems." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4423.
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Computer networks can be classified into two broad categories: wired networks and wireless networks, according to the hardware and software technologies used to interconnect the individual devices. Wired interconnection networks are hardware fabrics supporting communications between individual processors in highperformance computing systems (e.g., multi-computer systems and cluster systems). On the other hand, due to the rapid development of wireless technologies, wireless networks have emerged and become an indispensable part for people's lives. The integration of different wireless technologies is an effective approach to accommodate the increasing demand of the users to communicate with each other and access the Internet. This thesis aims to investigate the performance of wired interconnection networks and integrated wireless networks under the realistic working conditions. Traffic patterns have a significant impact on network performance. A number of recent measurement studies have convincingly demonstrated that the traffic generated by many real-world applications in communication networks exhibits bursty arrival nature and the message destinations are non-uniformly distributed. Analytical models for the performance evaluation of wired interconnection networks and integrated wireless networks have been widely reported. However, most of these models are developed under the simplified assumption of non-bursty Poisson process with uniformly distributed message destinations. To fill this gap, this thesis first presents an analytical model to investigate the performance of wired interconnection networks in multi-computer systems. Secondly, the analytical models for wired interconnection networks in multi-cluster systems are developed. Finally, this thesis proposes analytical models to evaluate the end-to-end delay and throughput of integrated wireless local area networks and wireless mesh networks. These models are derived when the networks are subject to bursty traffic with non-uniformly distributed message destinations which can capture the burstiness of real-world network traffic in the both temporal domain and spatial domain. Extensive simulation experiments are conducted to validate the accuracy of the analytical models. The models are then used as practical and cost-effective tools to investigate the performance of heterogeneous wired or wireless networks under the traffic patterns exhibited by real-world applications.
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Rohani, Mehdiabadi Behrooz. "Power control for mobile radio systems using perceptual speech quality metrics." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0174.
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As the characteristics of mobile radio channels vary over time, transmit power must be controlled accordingly to ensure that the received signal level is within the receiver's sensitivity. As a consequence, modern mobile radio systems employ power control to regulate the received signal level such that it is neither less nor excessively larger than receiver sensitivity in order to maintain adequate service quality. In this context, speech quality measurement is an important aspect in the delivery of speech services as it will impact satisfaction of customers as well as the usage of precious system resources. A variety of techniques for speech quality measurement has been produced over the last few years as result of tireless research in the area of perceptual speech quality estimation. These are mainly based on psychoacoustic models of the human auditory systems. However, these techniques cannot be directly applied for real-time communication purposes as they typically require a copy of the transmitted and received speech signals for their operation. This thesis presents a novel technique of incorporating perceptual speech quality metrics with power control for mobile radio systems. The technique allows for standardized perceptual speech quality measurement algorithms to be used for in-service measurement of speech quality. The accuracy of the proposed Real-Time Perceptual Speech Quality Measurement (RTPSQM) technique with respect to measuring speech quality is first validated by extensive simulations. On this basis, RTPSQM is applied to power control in the Global System for Mobile (GSM) communication and the Universal Mobile Telecommunication System (UMTS). It is shown by simulations that the use of perceptual-based power control in GSM and UMTS outperforms conventional power control in terms of reducing the transmitter signal power required for providing adequate speech quality. This in turn facilitates the observed increase in system capacity and thus offers better utilization of available system resources. To enable an analytical performance assessment of perceptual speech quality metrics in power control, the mathematical frameworks for conventional and perceptual-based power control are derived. The derivations are performed for Code Division Multiple Access (CDMA) systems and kept as generic as possible. Numerical results are presented which could be used in a system design to readily find the Erlang capacity per cell for either of the considered power control algorithms.
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Liu, Qijia. "Power efficiency and diversity issues for peak power constrained wireless communications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34829.
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Along with the rapidly increasing demand for high data rate communications, orthogonal frequency division multiplexing (OFDM) has become a popular modulation in current and future communication standards. By distributing a high-speed data stream to many parallel low-rate data streams, OFDM is able to mitigate the detrimental effects of multipath fading using simple one-tap equalizers and achieve high spectral efficiency. However, the OFDM signal waveform suffers from large envelop variations, which are usually measured by the peak-to-average power ratio (PAR). In wireless transmitters, many RF components, especially the power amplifiers, are inherently nonlinear and peak power constrained. Therefore, low power efficiency and/or severe nonlinear distortions are the main shortcomings of OFDM systems.
In this dissertation, we develop algorithms and analyze performance bounds for peak power constrained wireless communications. To address the balance between power efficiency and nonlinear distortions, we model the peak power constrained OFDM systems in both statistical and deterministic manners. We first propose an error vector magnitude (EVM) optimization algorithm to strictly satisfy the distortion requirements in accordance with communication standards and provide the maximum power efficiency for OFDM transmitters without receiver-side cooperations. Moreover, we develop a multi-channel partial transmit sequence (MCPTS) PAR reduction method for OFDM-based frequency-division multiple access (OFDM-FDMA) multiuser systems, which can achieve significant power efficiency improvement without
using side information. Joint MCPTS and power allocation schemes are also proposed to improve the error performance of OFDM-FDMA systems.
Furthermore, diversity-enabled communication systems have practical merits in combating channel fadings. Therefore, in the second part of this dissertation, peak power constrained diversity techniques are proposed. The error performance of peak power constrained single-input multiple-output (SIMO) OFDM is studied. Several low-complexity SIMO-OFDM transceiver designs are presented to collect full antenna diversity with respective performance and complexity tradeoffs.
The next major piece of work in this dissertation addresses the design of peak power constrained amplify-and-forward (AF) cooperative networks, which enable the cooperative diversity with single-antenna terminals. The effects of the availability of channel state information and the peak power constraint on the diversity performance are theoretically studied. Design criteria for general diversity-enabled AF relaying strategies are established and further applied to the designs in peak power constrained networks. In the end, a general theorem that relates the diversity gain function with the probability density function of instantaneous signal-to-noise ratio is derived and used to analyze the diversity performance of relay selection schemes.
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Tummala, Dinesh. "Indoor Propagation Modeling at 2.4 GHz for IEEE 802.11 Networks." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4924/.
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Indoor use of wireless systems poses one of the biggest design challenges. It is difficult to predict the propagation of a radio frequency wave in an indoor environment. To assist in deploying the above systems, characterization of the indoor radio propagation channel is essential. The contributions of this work are two-folds. First, in order to build a model, extensive field strength measurements are carried out inside two different buildings. Then, path loss exponents from log-distance path loss model and standard deviations from log-normal shadowing, which statistically describe the path loss models for a different transmitter receiver separations and scenarios, are determined. The purpose of this study is to characterize the indoor channel for 802.11 wireless local area networks at 2.4 GHz frequency. This thesis presents a channel model based on measurements conducted in commonly found scenarios in buildings. These scenarios include closed corridor, open corridor, classroom, and computer lab. Path loss equations are determined using log-distance path loss model and log-normal shadowing. The chi-square test statistic values for each access point are calculated to prove that the observed fading is a normal distribution at 5% significance level. Finally, the propagation models from the two buildings are compared to validate the generated equations.
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Hassan, Syed Ali. "Stochastic modeling of cooperative wireless multi-hop networks." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42799.
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Multi-hop wireless transmission, where radios forward the message of other radios, is becoming popular both in cellular as well as sensor networks.
This research is concerned with the statistical modeling of multi-hop wireless networks that do cooperative transmission (CT). CT is a physical layer wireless
communication scheme in which spatially separated wireless nodes collaborate to form a virtual array antenna for the
purpose of increased reliability. The dissertation has two major parts. The first part addresses a special form of CT known as the Opportunistic Large Array (OLA). The second part addresses the signal-to-noise ratio (SNR) estimation for the purpose of recruiting nodes for CT.
In an OLA transmission, the nodes from one level transmit the message signal concurrently without any coordination with each other, thereby producing transmit diversity. The receiving layer of nodes receives the message signal and repeats the process using the decode-and-forward cooperative protocol. The key contribution of this research is to model the transmissions that hop from one layer of nodes to another under the effects of channel variations, carrier frequency offsets, and path loss. It has been shown for a one-dimensional network that the successive transmission process can be modeled as a quasi-stationary Markov chain in discrete time. By studying various properties of the Markov chain, the system parameters, for instance, the transmit power of relays and distance between them can be optimized. This optimization is used to improve the performance of the system in terms of maximum throughput, range extensions, and minimum delays while delivering the data to the destination node using the multi-hop wireless communication system.
A major problem for network sustainability, especially in battery-assisted networks, is that the batteries are drained pretty quickly during the operation of the network. However, in dense sensor networks, this problem can be alleviated by using a subset of nodes which take part in CT, thereby saving the network energy. SNR is an important parameter in determining which nodes to participate in CT. The more distant nodes from the source having least SNR are most suitable to transmit the message to next level. However, practical real-time SNR estimators are required to do this job. Therefore, another key contribution of this research is the design of optimal SNR estimators for synchronized as well as non-synchronized receivers, which can work with both the symbol-by-symbol Rayleigh fading channels as well as slow flat fading channels in a wireless medium.
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Visser, Schalk W. J. (Schalk Willem Jacobus). "Data capturing system using cellular phone, verified against propagation models." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16462.
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Thesis (MScIng)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: Data capturing equipment are an expensive part of testing the coverage of a deployed or planned wireless service. This thesis presents the development of such a data capturing system that make use of 1800MHz GSM base stations as transmitters and a mobile phone connected to a laptop as receiver. The measurements taken, are then verified against know propagation models. Datavaslegging toerusting wat gebruik word om die dekking van draadlose stelsels te toets is baie duur en moeilik bekombaar. Hierdie tesis beskryf die ontwikkeling van so ’n datavaslegger wat baie goedkoper is en maklik gebruik kan word. Dit maak gebruik van ’n sellulêr foon en GPS gekoppel aan ’n skootrekenaar, wat die ontvanger is. Cell C basis staties word gebruik as die senders. Die data wat gemeet is word dan geverifieer deur gebruik te maak van bestaande radio frekwensie voortplanting modelle.
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Alla, Sindhu. "A Study of Mobility Models based on Spatial Node Distribution and Area Coverage." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984231/.
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Mobile wireless sensor networks are not widely implemented in the real world, even after years of research carried out in this field. One reason is the lack of understanding of the impact that mobility has on network performance. The simulation and emulation of mobile wireless sensor networks is necessary before they are deployed for the real-world applications. This thesis presents a simulation-based study of different mobility models. The total area coverage that depends on the pattern of node movements is observed through simulations. The spatial distribution of node locations is also studied. Various synthetic mobility models available are explored based on their theoretical descriptions. ‘BonnMotion' is used as the network simulator for investigating different mobility scenarios. The results obtained after simulations are imported to MATLAB and the analysis of node movements is done through various plots and inferences from the data. The comparison of mobility models is also discussed based on their spatial node distribution in the simulated scenarios.
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Souza, Fabio Alexandre de. "Otimização dos parâmetros de um sistema de comunicação acústica subaquática para minimizar o consumo energético." Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/2746.
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CAPESNesta Tese de Doutorado propõe-se um modelo de consumo de energia para redes acústicas subaquáticas que leva em consideração as especificidades do ambiente subaquático, como a comunicação utilizando ondas acústicas, a dependência da largura de banda do canal com a perda de percurso, que varia tanto com a distância quanto com a frequência, e o ruído. O desvanecimento, resultado do multipercurso, normalmente modelado pelas distribuições Rayleigh e Rice nas transmissões terrestres, é modelado pela distribuição K, que melhor representa a severidade do ambiente subaquático. O modelo considera uma rede subaquática linear de múltiplos saltos e a possibilidade de retransmissões para calcular a energia total consumida para cada bit de informação transmitido com sucesso entre a fonte e o destino. A fim de obter o menor consumo de energia, a SNR e a frequência de operação também são otimizadas, sendo considerado o uso de códigos convolucionais, cuja taxa ótima que leva ao menor consumo é determinada. Uma análise teórica é desenvolvida para cenários com e sem limitação de atraso. No primeiro caso avalia-se o consumo de energia quando retransmissões não são permitidas ou devem ser limitadas e, portanto, uma FER residual deve ser tolerada. No segundo caso infinitas retransmissões são permitidas até que um pacote seja recebido sem erros. Para ambos cenários o número ótimo de saltos que minimiza o consumo de energia é determinado, e na sequência o impacto do número de tentativas de transmissão é considerado. Resultados numéricos são apresentados, mostrando que o esquema de múltiplos saltos é mais eficiente em termos de consumo de energia que a transmissão direta. Além disso, os resultados mostram que um número pequeno de tentativas de transmissão é suficiente para alcançar uma redução considerável no consumo de energia em redes de múltiplos saltos, limitando o atraso médio por pacote transmitido, o que é muito interessante em aplicações reais.
In this Thesis, an energy consumption model for underwater acoustic networks is proposed. The model takes into account the specificities of the underwater environment, such as the use of acoustic waves for communication, dependence of the underwater acoustic channel bandwidth with the path loss, which varies with both the distance and frequency, and noise. The fading, usually modeled by Rayleigh and Rice distributions on terrestrial communications, in this work, is modeled by the K distribution, which best represents the severity of the underwater environment. The model considers a linear multi-hop underwater network and the possibility of retransmissions to calculate the total energy consumed for each bit of information successfully transmitted between the source and the destination. In order to obtain the minimum energy, the SNR and the operating frequency are also optimized. The use of convolutional codes is considered and the optimal code rate, which leads to the minimum energy consumption, is determined. A theoretical analysis was developed for two scenarios: delay constrained and delay unconstrained networks, indicating the optimal number of hops which minimizes energy consumption. Next, the impact of the number of transmission trials was considered. A numerical analysis was also performed for both the scenarios. The numerical results validate the theoretical analysis, showing that the multi-hop scheme is more efficient in terms of energy consumption when compared to direct transmission. Furthermore, the results show that a small number of transmission trials is sufficient to achieve a considerable reduction in energy consumption in multi-hop networks, limiting the average delay per packet transmitted, which is very interesting in real applications.
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Mazandu, Gaston Kuzamunu. "Traffic Engineering using Multipath Routing Approaches." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/679.
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Fulton, Neale Leslie Aerospace & Mechanical Engineering Australian Defence Force Academy UNSW. "Regional airspace design: a structured systems engineering approach." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Aerospace and Mechanical Engineering, 2002. http://handle.unsw.edu.au/1959.4/38722.
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There has been almost fifteen years of political controversy surrounding changes to the rules and procedures by which aircraft conduct their flight within regional Australia. Decisions based on a predominately heuristic (rule of thumb) approach to design have had many adverse consequences for the integrity of the proximity warning function. A sound mathematical model is required to establish this function on a mature engineering foundation. To achieve this, the proximity warning function has been investigated as a hybrid-system. This approach recognises the dual nature of the design: that aircraft dynamics give rise to continuous mathematical models while the communication protocols controlling proximity require discrete mathematical approaches. The blending of each aspect has yielded a deeper insight into the operational limitations and failure modes of this function. The presentation of the thesis follows a design thread through the function. It begins with a description of existing standards and implementations. Risk models are then developed. The pilot interface is recognised as a primary design constraint. Mathematical models are then developed to describe the topology of flow, proximity dynamics, and the scheduling constraints associated with visual, voice, and data-link communications required by the proximity warning function. These analyses show that many aspects of design can be bounded by analytical formulae that bring new robustness to the design and resolve some of the misconceptions arising from the often inaccurate perceptions of present airspace operations. Failure modes, unaccounted for in existing designs are found to actually aggravate failure in the very situations in which the airspace design should be robust and should act to prevent collisions. In particular, there are divergences of performance between the demands required by the system design and the ability of the pilot to deliver such performances. In some cases, these failures may be traced to policy decisions such as service between Instrument Flight Rule and Visual Flight Rule category aircraft. On the basis of the conclusions of this research, a formal engineering review of the proximity warning function is required to assure the containment of the likelihood of mid-air collision for all future operations.
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Pendyala, Chandra Mohan. "On the optimal location of transmitters for micro-cellular radio communication system design." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07112009-040406/.
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Bradley, W. Scott. "Propagation modeling for land mobile satellite communications." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/74511.
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Satellite systems are being planned for two-way communication with mobile vehicles using UHF and L-band frequencies. Of special concern in the system design are the characteristics of propagation in suburban and rural areas where fading occurs due to multipath effects and vegetative shadowing. A review of the literature was performed to study these propagation impairments. Available experimental data are examined, compared, and summarized. Propagation through vegetation is studied in order to compare reported modeling efforts and to determine the parameter dependences of path loss. A simple deterministic path model is then presented to estimate vegetative path loss. An overall statistical model is also proposed to describe the signal level fading statistics. The statistical model is compared to data, and the deterministic path model is used to determine the mean of signal level distribution functions in the presence of shadowing.Master of Science
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Jan, Naeem A. "Anomalous Nature Of Metamaterial Inclusion and Compact Metamaterial-Inspired Antennas Model For Wireless Communication Systems. A Study of Anomalous Comportment of Small Metamaterial Inclusions and their Effects when Placed in the Vicinity of Antennas, and Investigation of Different Aspects of Metamaterial-Inspired Small Antenna Models." Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/16003.
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Metamaterials are humanly engineered artificial electromagnetic materials which produce electromagnetic properties that are unusual, yet can be observed readily in nature. These unconventional properties are not a result of the material composition but rather of the structure formed. The objective of this thesis is to investigate and design smaller and wideband metamaterial-inspired antennas for personal communication applications, especially for WiMAX, lower band and higher band WLAN applications. These antennas have been simulated using HFSS Structure Simulator and CST Microwave Studio software. The first design to be analysed is a low-profile metamaterial-inspired CPW-Fed monopole antenna for WLAN applications. The antenna is based on a simple strip loaded with a rectangular patch incorporating a zigzag E-shape metamaterial-inspired unit cell to enable miniaturization effect. Secondly, a physically compact, CSRR loaded monopole antenna with DGS has been proposed for WiMAX/WLAN operations. The introduction of CSRR induces frequency at lower WLAN 2.45 GHz band while the DGS has provided bandwidth enhancement in WiMAX and upper WLAN frequency bands, keeping the radiation pattern stable. The next class of antenna is a compact cloud-shaped monopole antenna consisting of a staircase-shaped DGS has been proposed for UWB operation ranges from 3.1 GHz to 10.6 GHz. The novel shaped antenna along with carefully designed DGS has resulted in a positive gain throughout the operational bandwidth. Finally, a quad-band, CPW-Fed metamaterial-inspired antenna with CRLH-TL and EBG is designed for multi-band: Satellite, LTE, WiMAX and WLAN.