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1
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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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.
3
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.<br>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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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.<br>Master of Science
5
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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Tufekcioglu, Refik. "Communication models in mobile computing systems and mobile agents." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA378775.
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Thesis (M.S. in Computer Science) Naval Postgraduate School, March 2000.<br>Thesis advisor(s): Michael, James B. "March 2000." Includes bibliographical references (p. 131-137). Also available in print.
7
Kwok, Wing Pong William. "A variety of queueing models for mobile communication systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/MQ46077.pdf.
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Xu, Benshuai. "Time varying channel models for 5G mobile communication systems." Thesis, University of Greenwich, 2014. http://gala.gre.ac.uk/13270/.
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Researchers all over the world are looking for ways of continuing the evolution of mobile communication technology to its fifth generation (5G). Providing high data rate information transfer to highly mobile users over time varying communication channels remains a shared obstacle. In this thesis, we contribute to these global efforts by providing further fundamental understanding of time varying channels in 5G mobile communication systems and overcome the obstacle. First, we reopen the door of research in the field of time varying communication channels. The door has almost been closed before by a well-accepted conclusion related to the types of channels. It was ‘proven’ that mutual information rate of the uniformly symmetric variable noise finite state Markov channel (USVNFSMC) was maximized by input signals of maximum information entropy. The result means time varying channels and time invariable channels are identical, regarding information rate maximization over input signal probability distribution. We provide evidence that assumptions for the results are not valid for time varying channels and replace them with more practical ones. We confirm, via input signals of non-uniform independent distribution and first order Markov chain, that the mutual information rate of the USVN-FSMC is maximized by input signals with information redundancy. Second, we provide a solution which dramatically reduces the waste of communication resources in estimating channel state information of time varying mobile communication channels. The orthodox method in dealing with time varying channels is that, the channel is “cut” to pieces in time domain to look like a sequence of time invariable channels for the purpose of state estimation. By doing this the capacity loss is staggering for n-times higher carrier frequency channels and n-dimensional multiple input and multiple output channels, eliminating almost entirely the capacity gain of these two most promising capacity-increasing techniques for 5G. We define the simplest finite state Markov model for time varying channels to explain the essential difference between information processing of time varying channels and time invariable channels. We prove that the full information capacity of the model can be achieved by the differential type encoding/decoding scheme without employing any conventional channel state estimator.
9
Ali, Syed Zahid. "A mathematical programming approach to cellular mobile radio network design." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269005.
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Ma, Chunyan. "Mathematical security models for multi-agent distributed systems." CSUSB ScholarWorks, 2004. https://scholarworks.lib.csusb.edu/etd-project/2568.
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This thesis presents the developed taxonomy of the security threats in agent-based distributed systems. Based on this taxonomy, a set of theories is developed to facilitate analyzng the security threats of the mobile-agent systems. We propose the idea of using the developed security risk graph to model the system's vulnerabilties.
11
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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Butgereit, Laura Lee. "A model for automated topic spotting in a mobile chat based mathematics tutoring environment." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1013741.
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Systems of writing have existed for thousands of years. The history of civilisation and the history of writing are so intertwined that it is hard to separate the one from the other. These systems of writing, however, are not static. They change. One of the latest developments in systems of writing is short electronic messages such as seen on Twitter and in MXit. One novel application which uses these short electronic messages is the Dr Math® project. Dr Math is a mobile online tutoring system where pupils can use MXit on their cell phones and receive help with their mathematics homework from volunteer tutors around the world. These conversations between pupils and tutors are held in MXit lingo or MXit language – this cryptic, abbreviated system 0f ryting w1ch l0ks lyk dis. Project μ (pronounced mu and indicating MXit Understander) investigated how topics could be determined in MXit lingo and Project μ's research outputs spot mathematics topics in conversations between Dr Math tutors and pupils. Once the topics are determined, supporting documentation can be presented to the tutors to assist them in helping pupils with their mathematics homework. Project μ made the following contributions to new knowledge: a statistical and linguistic analysis of MXit lingo provides letter frequencies, word frequencies, message length statistics as well as linguistic bases for new spelling conventions seen in MXit based conversations; a post-stemmer for use with MXit lingo removes suffixes from the ends of words taking into account MXit spelling conventions allowing words such as equashun and equation to be reduced to the same root stem; a list of over ten thousand stop words for MXit lingo appropriate for the domain of mathematics; a misspelling corrector for MXit lingo which corrects words such as acount and equates it to account; and a model for spotting mathematical topics in MXit lingo. The model was instantiated and integrated into the Dr Math tutoring platform. Empirical evidence as to the effectiveness of the μ Topic Spotter and the other contributions is also presented. The empirical evidence includes specific statistical tests with MXit lingo, specific tests of the misspelling corrector, stemmer, and feedback mechanism, and an extensive exercise of content analysis with respect to mathematics topics.
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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.<br>"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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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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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.<br>published_or_final_version<br>Electrical and Electronic Engineering<br>Master<br>Master of Philosophy
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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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Lazaro, de Barrio Oscar. "Dynamic radio resource management algorithms and traffic models for emerging mobile communication systems." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248855.
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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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<p>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.</p><p>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.</p><p>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.</p><p>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.</p>
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Goetz, Marieta. "Mobile business models in African rural communities." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2581.
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Thesis (MPhil (Information Science))--University of Stellenbosch, 2009.<br>Mobile telephone subscription in developing countries has increased by more than 500
percent since 2005, with Africa experiencing the highest growth rate globally. Amongst
Africa’s 306.5 million subscribers, recorded in 2008, an unexpectedly high adoption rate of
the technology by poor, often illiterate rural communities is observed. Mobile telephony
generally provides African rural users access to electronic communication for the first time.
Providing access to communication, information and knowledge, mobile phones present a
platform for economic and social interaction in rural Africa. The extent of the resulting
positive socio-economic impact on the developing world has lead to mobile telephony
increasingly being viewed as a potential development tool for the socio-economic upliftment
of the rural poor.
This thesis is inspired by the potential for value creation to end users of mobile telephony,
leading to the proposition that the rapid expansion of mobile telephony in rural Africa can
contribute significantly to the sustainability of these communities’ rural livelihoods. For this
proposition to be valid, mobile telephony has to provide value beyond being communication
tool. It has to provide value in income generating activities by increasing opportunities for
access to financial and social capital with mobile business models appropriate to the rural
African context.
To assess the appropriateness of mobile value offerings, the rural African context was
analyzed using the Sustainable Livelihoods Framework. Through multi-level analysis, the
challenges and issues that influence the lives of the rural poor were explored and the
dominant livelihood strategies in terms of income generating activities were identified. Apart
from agricultural income streams, waged labor, migration and micro-entrepreneurial
activities provide non-agricultural income streams.
Creating an appropriate mobile business ecosystem for rural Africa requires the collaboration
of a complex network of actors within a value constellation to co-produce value for the end
users. Three conditional factors were identified for mobile telephony and emerging mobile
business models to contribute successfully to sustainable livelihoods: adaptation of the
technology by providers, user appropriation to make the technology their own and the
assimilation of it into their livelihood strategies. These factors were researched for validation through the study of existing literature and reported case studies. It was found that these three
conditional factors were unequivocally met.
Firstly, the mobile telecommunication industry active in Africa is seen to successfully adapt
and innovate solutions that are relevant to African rural communities’ vulnerabilities and
livelihood strategies. Secondly, African mobile phone users have successfully adopted and
appropriated mobile telephony to create value for themselves in their livelihood strategies,
often independent of external interventions. They are claiming ownership of the technology
and not merely using it as a communication tool. Thirdly, by assimilating mobile telephony
into their livelihood strategies, value-creation within their income generating activities have
been made possible. This value creation is impacting users’ social and financial capital
positively.
This thesis concludes that mobile telephony and emerging mobile business models are
contributing to increasing African rural dwellers’ income generating potential, reducing their
vulnerability to shocks, and providing them with a voice; thereby contributing to sustainable
rural livelihoods.
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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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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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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.<br>Science, Faculty of<br>Computer Science, Department of<br>Graduate
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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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Zhou, Junyang. "Enhanced signal propagation models and algorithm selector for providing location estimation services within cellular radio networks." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/776.
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Wong, Ka Wai. "A comparative study and novel heuristic approach for the IEEE 802.16e mobile WiMAX power saving mechanism /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20WONG.
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Fung, Victor. "Bit error simulation of FSK, BPSK, and pi/4 DQPSK in flat and frequency-selective fading mobile radio channels using two-ray and measurement- based impulse response models." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08142009-040410/.
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Mateyisi, Mohau Jacob. "Polymer networks with mobile force-applying crosslinks." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6759.
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Thesis (MSc)--University of Stellenbosch, 2011.<br>ENGLISH ABSTRACT: We construct and study a simple model for an active gel of
exible polymer filaments
crosslinked by a molecular motor cluster that perform reversible work while translating
along the filaments. The filament end points are crosslinked to an elastic background.
In this sense we employ a simplified model for motor clusters that act as slipping links
that exert force while moving along the strands. Using the framework of replica theory,
quenched averages are taken over the disorder which originates from permanent random
crosslinking of network end points to the background. We investigate how a small motor
force contributes to the elastic properties of the network. We learn that in addition to
the normal elastic response for the network there is an extra contribution to the network
elasticity from the motor activity. This depends on the ratio of the entropic spring constant
for the linked bio-polymerchain to the spring constant of the tether of the motor.<br>AFRIKAANSE OPSOMMING: Ons konstrueer en bestudeer 'n eenvoudige model vir 'n aktiewe netwerk van
eksieble
polimeerfilamente wat deur grosse van molekulere motors aan mekaar verbind word wat
omkeerbare werk doen terwyl dit langs die filamente transleer. Die eindpunte van die filamente
is aan 'n elastiese agtergrond verbind. In hierdie sin benut ons 'n eenvoudige model
vir motorclusters wat as verskuifbare verbindings krag op die filamente tydens beweging
kan uitoefen. Nie-termiese wanorde gemiddeldes word geneem oor die wanorde wat deur
die lukrake permanente verbindings van netwerk eindpunte aan die agtergrond veroorsaak
word. Ons ondersoek hoe 'n klein motorkrag tot die elastiese eienskappe van die netwerk
bydra. Ons leer dat daar bo en behalwe die gewone elastiese respons vir die netwerk 'n
elastiese bydrae as gevolg van die motors se aktiwiteit voorkom. Dit hang af van die verhouding
van die entropiese veerkonstante van die biopolimerketting tot die veerkonstante
van die anker van die motor.
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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/.
Full textAbstract:
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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Cuvelliez, Charles. "Etudes des modèles d'implémentation des opérateurs de réseaux mobiles virtuels." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210895.
Full textAbstract:
This thesis addresses the phenomena of Mobile Virtual Network Operators (MVNO): often MVNO do not come from the telecom sector but they rent the network to mobile operators to become fully mobile operators on their own. So they compete directly not only with the other mobile operators but also with their hosting mobile operator.<p><p>Hosting MVNOs, supporting them from both operational and commercial perspectives are new challenges for the mobile operators: they have to set up a specific internal organization because they used to be a vertically integrated industrial structure. All of this represents tremendous changes for them.<p><p>This thesis describes first the strategic models for hosting MVNOs. The regulatory aspects, that are an essential driver for the liberalization of network economies, are then analyzed. The key point is: are the MVNO able to increase the efficiency and competitiveness of mobile markets.<p><p>Another important aspect is the modelling of a mobile network: the MVNOs will use some components while other components are unuseful for them. Without such model, it is impossible to derive the right costs and price to be charged to the MVNO in order to have a win win industrial model for both the MVNO and its hosting operator.<p><p>A case study of a corporate MVNO focusing on needs of multinationals is analyzed. Such case study describes all the steps for an economic actor to become MVNO from scratch. Such MVNO are not yet present although there is a market demand.<p>The last chapter makes a comparative study of the MVNO markets in the European Union.<p><p>Cette étude aborde le phénomène des opérateurs de réseaux mobiles virtuels ;il s’agit d’acteurs économiques - parfois sans lien aucun avec les télécommunications - qui louent le réseau d’opérateurs mobiles ;ils deviennent à leur tour opérateurs à part entière au point de devenir concurrent non seulement des autres opérateurs mobiles mais aussi de l’opérateur mobile qui leur a loué une partie de son réseau.<p><p>L’hébergement technique de l’opérateur virtuel, son support opérationnel et commercial, l’organisation que doit mettre en place l’opérateur mobile pour héberger son opérateur virtuel afin de partager avec lui son réseau sont des nouveaux défis auxquels les opérateurs mobiles, habitués à être des structures industrielles totalement intégrées verticalement, font face pour la première fois.<p><p>Cette étude traite des modèles d’implémentation des opérateurs de réseaux mobiles virtuels :elle aborde d’abord les aspects stratégiques qui fixent le cadre pour les opérateurs mobiles qui veulent ou sont forcés à héberger des opérateurs virtuels. Les aspects réglementaires, une composante essentielle des économies de réseaux en voie de libéralisation, sont ensuite étudiés, en particulier, comment les opérateurs virtuels peuvent contribuer à améliorer la compétitivité et la libéralisation de ces marchés.<p><p>L’étude modélise ensuite le réseau d’un opérateur mobile de façon à mettre en évidence les éléments à partager qui seront utilisés par l’opérateur virtuel. Cette modélisation est essentielle pour déterminer le coût de l’hébergement et du partage du réseau de façon à créer les conditions de rentabilité de ce modèle d’opérateur virtuel.<p><p>On aborde enfin un cas d’étude d’un candidat à devenir opérateur de réseau mobile virtuel qui souhaite répondre à la demande transnationale des grandes entreprises. Ce type d’opérateur virtuel est encore inexistant de nos jours.<p>Enfin, nous terminons par une étude comparée de la situation des opérateurs mobiles virtuels à travers l’Union Européenne.<p><p><br>Doctorat en sciences appliquées<br>info:eu-repo/semantics/nonPublished
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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.
Full textAbstract:
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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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.
Full textAbstract:
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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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.
Full textAbstract:
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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Ntinda, Maria Ndapewa. "Web-based M-learning system for ad-hoc learning of mathematical concepts amongst first year students at the University of Namibia." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1013174.
Full textAbstract:
In the last decade, there has been an increase in the number of web-enabled mobile devices, offering a new platform that can be targeted for the development of learning applications. Worldwide, developers have taken initiatives in developing mobile learning (M-learning) systems to provide students with access to learning materials regardless of time and location. The purpose of this study was to investigate whether it is viable for first year students enrolled at the University of Namibia (UNAM) to use mobile phones for ad-hoc learning of mathematical concepts. A system, EnjoyMath, aiming to assist students in preparing for tests, examinations, review contents and reinforce knowledge acquired during traditional classroom interactions was designed and implemented. The EnjoyMath system was designed and implemented through the use of the Human Centred Design (HCD) methodology. Two revolutions of the four-step process of the HCD cycle were completed in this study. Due to the distance between UNAM and Rhodes University (where the researcher was based), the researcher could not always work in close relation with the UNAM students. Students from the Extended Study Unit (ESU) at Rhodes University were therefore selected in the first iteration of the project due to their proximity to the researcher and their similar demographics to the first year UNAM students, while the UNAM students were targeted in the second iteration of the study. This thesis presents the outcome of the two pre-intervention studies of the first-year students' perceptions about M-learning conducted at Rhodes University and UNAM. The results of the pre-intervention studies showed that the students are enthusiastic about using an M-learning system, because it would allow them to put in more time to practice their skills whenever and wherever they are. Moreover, the thesis presents the different stages undertaken to develop the EnjoyMath system using Open Source Software (PHP and MySQL). The results of a user study (post-intervention) conducted with participants at UNAM, ascertained the participants' perception of the usability of the EnjoyMath system and are also presented in this thesis. The EnjoyMath system was perceived by the participants to be "passable"; hence an M-learning system could be used to compliment an E-learning system at UNAM.
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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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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.
Full textAbstract:
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.<br>ix, 77 leaves : ill. ; 29 cm
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Yan, Zhaohui. "Performance Analysis of A Banyan Based ATM Switching Fabric with Packet Priority." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/5199.
Full textAbstract:
Since the emergence of the Asynchronous Transfer Mode ( A TM ) concept, various switching architectures have been proposed. The multistage interconnection networks have been proposed for the switching architecture under the A TM environment. In this thesis, we propose a new model for the performance analysis of an A TM switching fabric based on single-buffered Banyan network. In this model, we use a three-state, i.e., "empty", "new" and "blocked" Markov chain model to describe the behavior of the buffer within a switching element. In addition to traditional statistical analysis including throughput and delay, we also examine the delay variation. Performance results show that the proposed model is more accurate in describing the switch behavior under uniform traffic environment in comparison with the "two-state" Markov chain model developed by Jenq, et. al.[4] [6] . Based on the "three-state" model, we study a packet priority scheme which gives the blocked packet higher priority to be routed forward during contention. It is found that the standard deviation of the network delay is reduced by about 30%.
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Niezen, Gerrit. "The optimization of gesture recognition techniques for resource-constrained devices." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01262009-125121/.
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Srirattana, Nuttapong. "High-Efficiency Linear RF Power Amplifiers Development." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6899.
Full textAbstract:
Next generation mobile communication systems require the use of linear RF power amplifier for higher data transmission rates. However, linear RF power amplifiers are inherently inefficient and usually require additional circuits or further system adjustments for better efficiency. This dissertation focuses on the development of new efficiency enhancement schemes for linear RF power amplifiers.
The multistage Doherty amplifier technique is proposed to improve the performance of linear RF power amplifiers operated in a low power level. This technique advances the original Doherty amplifier scheme by improving the efficiency at much lower power level. The proposed technique is supported by a new approach in device periphery calculation to reduce AM/AM distortion and a further improvement of linearity by the bias adaptation concept.
The device periphery adjustment technique for efficiency enhancement of power amplifier integrated circuits is also proposed in this work. The concept is clearly explained together with its implementation on CMOS and SiGe RF power amplifier designs. Furthermore, linearity improvement technique using the cancellation of nonlinear terms is proposed for the CMOS power amplifier in combination with the efficiency enhancement technique.
In addition to the efficiency enhancement of power amplifiers, a scalable large-signal MOSFET model using the modified BSIM3v3 approach is proposed. A new scalable substrate network model is developed to enhance the accuracy of the BSIM3v3 model in RF and microwave applications. The proposed model simplifies the modeling of substrate coupling effects in MOS transistor and provides great accuracy in both small-signal and large-signal performances.
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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.
Full textAbstract:
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.<br>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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Delangre, Olivier. "Caractérisation et modélisation du canal radio en chambre réverbérante." Thesis, Universite Libre de Bruxelles, 2008. http://www.theses.fr/2008LIL10144/document.
Full textAbstract:
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 contrôlé<br>The 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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De, Vega Rodrigo Miguel. "Modeling future all-optical networks without buffering capabilities." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210455.
Full textAbstract:
In this thesis we provide a model for a bufferless optical burst switching (OBS) and an optical packet switching (OPS) network. The thesis is divided in three parts. <p><p>In the first part we introduce the basic functionality and structure of OBS and OPS networks. We identify the blocking probability as the main performance parameter of interest. <p><p>In the second part we study the statistical properties of the traffic that will likely run through these networks. We use for this purpose a set of traffic traces obtained from the Universidad Politécnica de Catalunya. Our conclusion is that traffic entering the optical domain in future OBS/OPS networks will be long-range dependent (LRD). <p><p>In the third part we present the model for bufferless OBS/OPS networks. This model takes into account the results from the second part of the thesis concerning the LRD nature of traffic. It also takes into account specific issues concerning the functionality of a typical bufferless packet-switching network. The resulting model presents scalability problems, so we propose an approximative method to compute the blocking probability from it. We empirically evaluate the accuracy of this method, as well as its scalability.<br>Doctorat en Sciences de l'ingénieur<br>info:eu-repo/semantics/nonPublished
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"Improving mobile localization in wireless networks." Thesis, 2010. http://library.cuhk.edu.hk/record=b6075247.
Full textAbstract:
Because of its potential applications, mobile localization in wireless networks has attracted much attention recently. It is essential that a mobile user should be able to know its location anytime and anywhere. In practice, however, it is not always possible to obtain an accurate location of the mobile user; the presence of non-line-of-sight (NLOS) radio signal propagation and malicious beacons could cause considerable errors in localization. Therefore, NLOS identification and the detection of malicious beacons are important issues in localization. Existing NLOS identification methods usually assume that localization involving the use of NLOS radio signals cannot be performed in a consistent manner. However, the validity of the foregoing assumption has not been properly investigated. As a result, it is questionable whether these methods can be used to identify NLOS effectively. Existing malicious beacon identification methods require the cooperation of several detecting nodes for the verification of a location claim from a target node. They all suffer from one or both of the drawbacks: (i) not able to cope with a sparse network situation, and (ii) their design being based on a particular distance measurement technique. Moreover, even if NLOS propagation and malicious beacons can be identified, the following problem could arise: if the localization systems do not use the beacons involving NLOS propagation and the malicious beacons, they may not be able to locate a mobile user because of not having enough beacons.<br>In the first part of this thesis, we present a theoretical analysis of localization using NLOS radio signals, and show that the above-mentioned assumption would no longer be valid when the mobile user is located outside the convex hull of the underlying beacons. As a result, existing NLOS identification methods, as well as many localization approaches, could perform poorly. Extensive experiments on different wireless networks demonstrate that NLOS in localization and the localization error caused by NLOS have been greatly underestimated in previous studies. In the second part, we propose a general location verification scheme to identify malicious beacons. It employs a node-to-node approach for location estimation, and could use different measurement techniques; moreover, it supports secure location verification in sparse networks. The proposed verification scheme has been shown able to achieve satisfactory performance via extensive real world GPS-based wireless sensor network experiments. In the third part, we present a mobility enhanced localization (MEL) scheme. By introducing the user's mobility information into the localization process, the proposed MEL can work in the area where current mobile localization systems cannot locate a mobile user for not having enough beacons. Extensive real world GPS experimental results demonstrate the superiority of the proposed MEL scheme. With the proposed solutions to the above problems, we could obtain improved mobile localization.<br>Liu, Dawei.<br>Adviser: Moon-Chuen Lee.<br>Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: .<br>Thesis (Ph.D.)--Chinese University of Hong Kong, 2010.<br>Includes bibliographical references (leaves 90-97).<br>Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Abstract also in Chinese.
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Samarasinghe, Prasad Talpawila Kankanamge Don Aruna. "Mobile to mobile channel modelling for wireless communications." Phd thesis, 2014. http://hdl.handle.net/1885/156305.
Full textAbstract:
Wireless communication has been experiencing many recent advances in mobile to mobile (M2M) applications. M2M communication systems differ from conventional fixed to mobile systems by having both transmitter and receiver in low elevation and in motion. This raises the need to come up with new channel models and perform statistical analysis on M2M communication channels looking from a different perspective. This need motivated us to perform the research outlined in this thesis. In reviewing the literature we found that though in general the M2M channel models are sparse, a major gap exists in the non geometrical stochastic based mathematical channel models. In filling this gap, we develop a novel mathematical non geometrical stochastic multiple input multiple output (MIMO) M2M channel model for two dimensional (2D) and three dimensional (3D) scattering environments. This model is based on the underlying physics of free space wave propagation and can be used as a framework for any environment by selecting suitable complex scattering gain functions. In addition, we extend this novel model to multicarrier M2M which is the first multicarrier channel model in the non geometrical stochastic M2M category. Based on our novel M2M channel model, we carry out an extensive analysis in space-time correlation, space-frequency correlation and second order channel statistics. With the choice of suitable parameters, this analysis and channel model can be used for any wireless environment. Thus, we claim that our novel channel model together with the analysis performed in this thesis can be taken as a generalized framework. A significant contribution of our analysis is the consideration of the impact of transmitter and receiver speed to space-time and space-frequency correlation, which is not available in the literature. Using a von Mises-Fisher distribution as the angular power distribution, the usefulness of the derived temporal correlation function is discussed. The simulation results corroborate the fact that both space-time and space-frequency correlations are reduced when transmitter or receiver speed increases. The rate of reduction of space-time correlation in von Mises-Fisher distribution scattering environment is more than in the isotropic environment. Under second order channel statistics, we consider Rice, Rayleigh and Nakagami fading channels in four different non-isotropic scattering environments with angle of departure (AoD) and angle of arrival (AoA) distributions given by (i) separable Truncated Gaussian, (ii) separable von-Mises, (iii) truncated Gaussian bivariate and (iv) truncated Laplacian bivariate distributions. We show that the major second order statistics, namely, the level crossing rate (LCR) and the average fade duration (AFD), in different fading channels can be expressed in terms of known scattering coefficients of the AoD and AoA distributions. As the channel models and their respective measurements provide reliable knowledge of the channel for the design and analysis of M2M systems, the proposed channel model and the corresponding analysis will be useful for the design, testing and performance evaluation of future M2M communication systems.
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"On optimization of the resource allocation in multi-cell networks." 2009. http://library.cuhk.edu.hk/record=b5894075.
Full textAbstract:
Chen, Jieying.<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.<br>Includes bibliographical references (p. 58-62).<br>Abstract in English only.<br>Abstract --- p.i<br>Acknowledgement --- p.iii<br>Chapter 1 --- Introduction --- p.1<br>Chapter 1.1 --- Motivation --- p.1<br>Chapter 1.2 --- Literature Review --- p.5<br>Chapter 1.3 --- Contributions Of This Thesis --- p.7<br>Chapter 1.4 --- Structure Of This Thesis --- p.8<br>Chapter 2 --- Problem Formulation --- p.9<br>Chapter 2.1 --- The JBAPC Problem --- p.9<br>Chapter 2.2 --- The Single-Stage Reformulation --- p.12<br>Chapter 3 --- The BARN Algorithm --- p.15<br>Chapter 3.1 --- Preliminary Mathematics --- p.15<br>Chapter 3.1.1 --- Duality Of The Linear Optimization Problem --- p.15<br>Chapter 3.1.2 --- Benders Decomposition --- p.18<br>Chapter 3.2 --- Solving The JBAPC Problem Using BARN Algorithm --- p.21<br>Chapter 3.3 --- Performance And Convergence --- p.24<br>Chapter 3.3.1 --- Global Convergence --- p.26<br>Chapter 3.3.2 --- BARN With Error Tolerance --- p.26<br>Chapter 3.3.3 --- Trade-off Between Performance And Convergence Time --- p.26<br>Chapter 4 --- Accelerating BARN --- p.30<br>Chapter 4.1 --- The Relaxed Master Problem --- p.30<br>Chapter 4.2 --- The Feasibility Pump Method --- p.32<br>Chapter 4.3 --- A-BARN Algorithm For Solving The JBAPC Problem --- p.34<br>Chapter 5 --- Computational Results --- p.36<br>Chapter 5.1 --- Global Optimality And Convergence --- p.36<br>Chapter 5.2 --- Average Convergence Time --- p.37<br>Chapter 5.3 --- Trade-off Between Performance And Convergence Time --- p.38<br>Chapter 5.4 --- Average Algorithm Performance Of BARN and A-BARN --- p.39<br>Chapter 6 --- Discussions --- p.47<br>Chapter 6.1 --- Resource Allocation In The Uplink Multi-cell Networks --- p.47<br>Chapter 6.2 --- JBAPC Problem In The Uplink Multi-cell Networks --- p.48<br>Chapter 7 --- Conclusion --- p.50<br>Chapter 7.1 --- Conclusion Of This Thesis --- p.50<br>Chapter 7.2 --- Future Work --- p.51<br>Chapter A --- The Proof --- p.52<br>Chapter A.l --- Proof of Lemma 1 --- p.52<br>Chapter A.2 --- Proof of Lemma 3 --- p.55<br>Bibliography --- p.58
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Rockliff, Simon C. (Simon Charles). "Frequency hopping techniques for digital mobile radio / Simon C. Rockliff." 1990. http://hdl.handle.net/2440/19327.
Full textAbstract:
Bibliography: leaves [205]-213<br>viii, 214 leaves : ill ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>Thesis (Ph.D.)--University of Adelaide, 1991
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Rockliff, Simon C. (Simon Charles). "Frequency hopping techniques for digital mobile radio / Simon C. Rockliff." Thesis, 1990. http://hdl.handle.net/2440/19327.
Full text
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"Wireless access pricing." 2011. http://library.cuhk.edu.hk/record=b5894826.
Full textAbstract:
Leung, Kwan Fong.<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.<br>Includes bibliographical references (leaves 63-66).<br>Abstracts in English and Chinese.<br>Chapter 1 --- Introduction --- p.10<br>Chapter 1.1 --- Motivation and Overview --- p.10<br>Chapter 1.2 --- Thesis Outline --- p.13<br>Chapter 2 --- Problem Formulation --- p.15<br>Chapter 2.1 --- Basic Wireless Market Model --- p.15<br>Chapter 2.2 --- "User's Utility, Payment, Payoff, and Demand" --- p.17<br>Chapter 2.3 --- Network Costs --- p.18<br>Chapter 2.4 --- Access Price --- p.20<br>Chapter 3 --- Fixed Coverage Two Base Stations Model --- p.21<br>Chapter 3.1 --- Social Optimal User Pricing --- p.21<br>Chapter 3.2 --- Social Optimal Access Pricing --- p.24<br>Chapter 3.2.1 --- "Networks' Profit-Maximizing User Pricing Given Fixed Access Prices:TT1* (α1 α2) and TT2* (α1, α2)" --- p.24<br>Chapter 3.2.2 --- Social Optimal Access Pricing: αS1 and αS2 --- p.27<br>Chapter 3.3 --- Deregulated User Pricing and Access Pricing --- p.30<br>Chapter 3.3.1 --- User's Optimal Data Rate Demand in Stage III --- p.30<br>Chapter 3.3.2 --- Operators' User Pricing in Stage II --- p.30<br>Chapter 3.3.3 --- Operators' Access Pricing in Stage I --- p.31<br>Chapter 4 --- Full Coverage Two Base Stations Model --- p.34<br>Chapter 4.1 --- Full Coverage Wireless Market Model --- p.34<br>Chapter 4.2 --- Users' choice of service providers --- p.35<br>Chapter 4.3 --- Social Optimal User Pricing --- p.36<br>Chapter 4.3.1 --- Numerical study --- p.38<br>Chapter 4.4 --- Deregulated case - Profit-maximizing access price and user price --- p.41<br>Chapter 4.4.1 --- Numerical Study --- p.45<br>Chapter 5 --- Full Coverage Three Base Stations Model --- p.46<br>Chapter 5.1 --- Three base-stations Full Coverage Market Model --- p.46<br>Chapter 5.2 --- Social Optimal User Prices --- p.48<br>Chapter 5.2.1 --- Numerical Study --- p.50<br>Chapter 5.3 --- Deregulated scenario --- p.53<br>Chapter 5.3.1 --- Numerical Study --- p.57<br>Chapter 6 --- Conclusions and Future Work --- p.60<br>Bibliography --- p.63
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"Transport layer optimization for mobile data networks." 2010. http://library.cuhk.edu.hk/record=b5894706.
Full textAbstract:
Wan, Wing San.<br>"September 2010."<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2010.<br>Includes bibliographical references (p. 53-55).<br>Abstracts in English and Chinese.<br>Acknowledgements --- p.ii<br>Abstract --- p.iii<br>摘要 --- p.iv<br>Contents --- p.v<br>Chapter Chapter 1 --- INTRODUCTION --- p.1<br>Chapter Chapter 2 --- BACKGROUND AND RELATED WORK --- p.4<br>Chapter 2.1 --- Sender-receiver-based approaches --- p.4<br>Chapter 2.2 --- Sender-based approaches --- p.5<br>Chapter 2.3 --- Receiver-based approaches --- p.6<br>Chapter Chapter 3 --- TCP FLOW CONTROL REVISITED --- p.8<br>Chapter Chapter 4 --- OPPORTUNISTIC TRANSMISSION --- p.12<br>Chapter 4.1 --- Link bandwidth estimation --- p.16<br>Chapter 4.2 --- Reception rate estimation --- p.18<br>Chapter 4.3 --- Transmission scheduling --- p.19<br>Chapter 4.4 --- Performance --- p.21<br>Chapter Chapter 5 --- Local Retransmission --- p.23<br>Chapter 5.1 --- The blackout period --- p.24<br>Chapter 5.2 --- Proactive retransmission --- p.28<br>Chapter 5.3 --- Performance --- p.30<br>Chapter Chapter 6 --- Loss Event Suppression --- p.31<br>Chapter 6.1 --- RTT modulation --- p.32<br>Chapter 6.2 --- Performance --- p.35<br>Chapter Chapter 7 --- Fairness --- p.37<br>Chapter 7.1 --- Packet forwarding --- p.37<br>Chapter 7.2 --- Non-uniform bandwidth allocation --- p.41<br>Chapter Chapter 8 --- EXPERIMENTS --- p.43<br>Chapter 8.1 --- Experiment setup --- p.43<br>Chapter 8.2 --- Packet loss --- p.44<br>Chapter 8.3 --- Unaccelerated TCP throughput --- p.45<br>Chapter 8.4 --- Accelerated TCP throughput --- p.46<br>Chapter 8.5 --- Fairness --- p.47<br>Chapter 8.6 --- Mobile handset performance --- p.47<br>Chapter Chapter 9 --- FUTURE WORK --- p.49<br>Chapter 9.1 --- Dynamic AWnd control --- p.49<br>Chapter 9.2 --- Split-TCP --- p.50<br>Chapter 9.3 --- Dynamic resource allocation --- p.50<br>Chapter 9.4 --- Sender-based acceleration --- p.51<br>Chapter Chapter 10 --- CONCLUSION --- p.52<br>BIBLIOGRAPHY --- p.53
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"Sensor network deployment as least squares problems." 2011. http://library.cuhk.edu.hk/record=b5894525.
Full textAbstract:
Xu, Yang.<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.<br>Includes bibliographical references (leaves 99-104).<br>Abstracts in English and Chinese.<br>Chapter 1 --- Introduction --- p.1<br>Chapter 1.1 --- Background of Sensors and Sensor Networks --- p.2<br>Chapter 1.2 --- Introduction to Coverage Problems --- p.6<br>Chapter 1.3 --- Literature Review --- p.8<br>Chapter 1.3.1 --- Deterministic Deployment Methods --- p.9<br>Chapter 1.3.2 --- Dynamic Deployment Methods --- p.10<br>Chapter 1.4 --- A Brief Introduction to Least Squares Analysis --- p.13<br>Chapter 1.5 --- Thesis Outline --- p.15<br>Chapter 2 --- Mobile Sensor Network Deployment Problem --- p.18<br>Chapter 2.1 --- Sensor Coverage Models --- p.18<br>Chapter 2.1.1 --- Binary Sensor Models --- p.19<br>Chapter 2.1.2 --- Attenuated and Truncated Attenuated Disk Models --- p.20<br>Chapter 2.2 --- Problem Statement --- p.23<br>Chapter 3 --- Coverage Optimization as Nonlinear Least Squares Problems --- p.26<br>Chapter 3.1 --- Introduction --- p.26<br>Chapter 3.2 --- Network Deployment as Least Squares Problems --- p.28<br>Chapter 3.2.1 --- Assignment of Sample Points --- p.28<br>Chapter 3.2.2 --- Least Squares Function --- p.30<br>Chapter 3.2.3 --- Gauss-Newton Method --- p.33<br>Chapter 3.2.4 --- Solutions --- p.36<br>Chapter 3.3 --- Extension to Binary Sensor Models --- p.39<br>Chapter 3.3.1 --- Restrictions of Subgradient Methods --- p.40<br>Chapter 3.3.2 --- Sigmoid Functions --- p.42<br>Chapter 3.4 --- Convergence and Multiple Minima Issues --- p.44<br>Chapter 3.4.1 --- Convergence --- p.44<br>Chapter 3.4.2 --- Multiple Minima --- p.48<br>Chapter 3.5 --- Stopping Criteria --- p.52<br>Chapter 3.6 --- Summary --- p.53<br>Chapter 4 --- Experimental Results --- p.55<br>Chapter 4.1 --- Introduction --- p.55<br>Chapter 4.2 --- Numerical Examples --- p.56<br>Chapter 4.2.1 --- Examples of Attenuated Disk Models --- p.57<br>Chapter 4.2.2 --- Examples of Binary Sensor Models --- p.63<br>Chapter 4.3 --- Performance Metrics of Mobile Sensor Deployment Schemes --- p.68<br>Chapter 4.4 --- Comparison to Existing Methods --- p.74<br>Chapter 4.5 --- Summary --- p.81<br>Chapter 5 --- Conclusions --- p.83<br>Chapter 5.1 --- Conclusions --- p.83<br>Chapter 5.2 --- Future Research Directions --- p.85<br>Appendices --- p.87<br>Chapter A --- An Overview of Existing Deployment Methods --- p.88<br>Chapter A.1 --- Potential Fields and Virtual Forces --- p.88<br>Chapter A.2 --- Distributed Self-Spreading Algorithm --- p.92<br>Chapter A.3 --- VD-Based Deployment Algorithm --- p.96<br>Bibliography --- p.99
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Juma, Raymond Wekesa. "An optimisation approach for capacity enhancement in third generation (3G) mobile networks." Thesis, 2012. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000570.
Full textAbstract:
M. Tech. Electrical Engineering.<br>This study proposes a mathematical optimisation approach which invokes Genetic Algorithm (GA) for initialisation and application of Tabu Search (TS) algorithm in finding the sites of node Bs in the network to enable it have the potential to support an increased number of users requiring the increased number of services. The global optimisation can be obtained in terms of great probability as GA is applied to global search and TS is applied to the local search. The particular memory ability of TS can be integrated to GA and the prematurity of GA can be avoided by virtue of the hill-climbing ability of TS. The problem to be addressed is the determination of optimal locations of node Bs in the network based on the user distribution, while improving the QoS. The proposed approach considers the site selection as an integer problem and the site placement as a continuous problem. The two problems are focused on concurrently - finding the optimal number of node Bs that satisfies the capacity requirements in the network and hence QoS improvement. The proposed algorithm combines the strength of Genetic and Tabu Search algorithms in successive elimination of node Bs after their random distribution in the area of study. The results showed that the proposed approach produced fewer number of node Bs sites in the network that provided the required QoS. In addition, it exhibited high fitness function in the simulations meaning that it has the higher ability of achieving the objective function when it was compared to TS and GA.