Dissertations / Theses on the topic 'WIRELES COMMUNICATION'
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Kodikara, Patabandi C. K. "Multimedia communications over 3G wireless communication systems." Thesis, University of Surrey, 2004. http://epubs.surrey.ac.uk/844270/.
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This thesis addresses the transmission of video over third generation radio access networks. The first part of the thesis investigates the capabilities of Universal Terrestrial Radio Access Networks (UTRAN) in terms of the provision of multimedia communications. The error performance and traffic requirements of real-time video transmission over circuit switched and packet switched connections are examined. The effect of network parameter settings upon video performances is evaluated, and optimum radio bearer configurations for the transmission of video are derived. A method of estimating received video quality after transmission over error prone environments is developed. The quality estimation is based on a distortion model, which accurately models the overall distortion seen in decoder frame reconstruction. This includes quantisation distortion, concealment distortion, and error propagation. Based on the developed performance model, optimum MTU (Maximum Transfer Unit) size for efficient wireless video communications over a packet switched access network is derived. The second part of the thesis investigates quality enhancement techniques for multimedia traffic transmitted over wireless channels. Quality enhancement is achieved at three levels of the transmission process: link level, application level and system level. Link level quality enhancement techniques are designed to optimise the allocation of link level parameter values according to the media characteristics. A novel Unequal Error Protection scheme and a novel Unequal Power Allocation scheme are designed to exploit the inherent diversity in the subjective importance of different sections of compressed media. The algorithms are developed and analysed for transmission of video over 3G wireless systems. The effectiveness of these algorithms is demonstrated through the results of simulated transmission over a UMTS channel. Application level quality enhancement techniques are designed to explore the time-varying nature of the wireless channel. A number of link adaptation schemes are proposed for real time video communication and real-time video streaming over 3G wireless systems. These algorithms are designed to enhance the perceptual video quality, and the system utilisation. This is achieved by adapting the allocated radio network parameters and the source parameters, according to a feedback channel condition. Simulation results show a significant performance improvement compared to non-adaptive schemes. Finally, system level adaptation techniques are designed for efficient radio resource allocation in multi-user scenarios. Two adaptive resource allocation schemes are proposed and analysed for real-time video communications in a UMTS system. The proposed algorithms are shown to provide improved performances in terms of average received video quality and user satisfaction. Key words: Wireless Communication, Multimedia communication. Video Transmission.
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Wang, Shendi. "Efficient transmission design for machine type communications in future wireless communication systems." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23647.
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With a wide range of potential applications, the machine type communication (MTC) is gaining a tremendous interest among mobile network operators, system designers, MTC specialist companies, and research institutes. The idea of having electronic devices and systems automatically connected to each other without human intervention is one of the most significant objectives for future wireless communications. Low data rate transmission and the requirement for low energy consumption are two typical characteristics for MTC applications. In terms of supporting low cots MTC devices, industrial standards will be more efficient if designers can re-use many features of existing radio access technologies. This will yield a cost effective solution to support MTC in future communication systems. This thesis investigates efficient MTC waveform and receiver designs for superior signal transmission quality with low operational costs. In terms of the downlink receiver design, this thesis proposes a novel virtual carrier (VC) receiver system for MTC receivers, which aims to reduce the maximum bandwidth to improve the data processing efficiency and cost-efficiency by using analogue filters to extract only sub-carriers of interest. For the VC receiver systems, we thus reduce the sampling rate in order to reduce the number of subsequent processing operations, which significantly reduces the analogue-to-digital converter (ADC) cost and power consumption while providing high signal to interference noise ratio (SINR) and low bit to error rate (BER) to support low data rate MTC devices. Our theoretical equations account for the interference effect of aliasing on the sub-carrier location, and this helps the system designer to evaluate what kind of filters and receiver sampling rate can be used to balance the energy cost and detection performance. In terms of the uplink waveform design, considering the enhanced number of MTC devices in the future communication systems, i.e. the fifth generation (5G) communications, the same tight synchronisation as used in today appears not to be cost-effective or even possible. Synchronisation signals, which aim to provide a perfect time or frequency synchronisation in the current fourth generation (4G) communication systems (known as the long-term evolution, LTE), is much more costly for low data rate MTC transmissions. The system bandwidth will be significantly reduced if a base station tries to synchronise all received signals among hundreds or thousands MTC devices in one transmission time period. In terms of relaxing the synchronisation requirements, this thesis compares and analyses the side-lobe reduction performance for several candidate multi-carrier waveforms to avoid these problems. We also propose the infinite impulse response universal filtered multi-carrier (UFMC) system and the overlap and add UFMC system, which significantly reduce the processing complexity compared with the state of the art UFMC techniques. This thesis derives closed-form expressions for the interference caused by time offsets between adjacent unsynchronised MTC users. Our analytical equations can be used in both simple and complex time-offset transmission scenarios, and enable the system designer to evaluate the SINR, the theoretical Shannon capacity and the BER performance.
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Bezuidenhout, Quintus. "Satellite communications strategy selection for optimal LEO satellite communication." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71930.
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Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: A low earth orbit satellite system can be useful in numerous communication applications where physical connections are not possible. Communication time available from any point on earth to the satellite is less than one hour per day. This one hour is fragmented into smaller time slots due to the satellite orbiting. This is not much time to transfer data and there is even less time available to transfer data when there are other external factors affecting the system. It is thus crucial to optimise the satellite communications link so that more data can be transferred per orbit. The goal of this thesis is to improve the performance of a low earth orbit satellite communication channel by varying certain parameters of the system, such as the protocol used, modulation scheme, packet size, transmission power etc. and then to observe how these parameters influence the system. The protocols that were chosen to be implemented are CSMA-CA, CSMA-CA with DSSS technology and Round-Robin Polling. A simulator for each protocol was designed with the Opnet platform, so that specific parameters could be changed and the results observed, in order to optimise the communications link between the satellite and ground stations. The results showed that there is no particular configuration of modulation scheme, packet size, transmission power etc. presenting the best overall solution for LEO satellite communications. It must be considered what the specific LEO satellite application would be used for and the characteristics required by that specific application. A suitable configuration must subsequently be chosen from the set of configurations available to satisfy most of the application requirements.
AFRIKAANSE OPSOMMING: ’n Satelliet met ’n lae wentelbaan kan gebruik word in verskeie kommunikasie toepassings waar fisiese verbindinge nie noodwendig moontlik is nie. Die kommunikasietyd van enige punt van aarde af na die satelliet, is minder as een uur per dag. Hierdie tyd word nog verder verklein omdat die satelliet besig is om, om die aarde te wentel. ’n Uur is glad nie baie tyd om data oor te dra nie en in realiteit is daar nog minder tyd beskikbaar as daar eksterne faktore op die sisteem inwerk. Dus is dit baie belangrik om die satelliet kommunikasiekanaal te optimiseer sodat soveel moontlik data as moontlik oorgedra kan word per omwenteling. Die doel van hierdie tesis is om die deurset van die kommunikasiekanaal van n lae wentelbaan satelliet te optimiseer, deur verskeie parameters te verander soos, protokol wat gebruik word, modulasie skema, pakkie grootte, transmissiekrag ens. en dan waar te neem hoe dit die sisteem beïnvloed. Die protokolle wat geïmplementeer is, is CSMA-CA, CSMA-CA met DSSS tegnologie en Round-Robin Polling. ’n Simulator vir elke protokol was ontwerp in die Opnet simulasie platform, sodat die spesifieke parameters verander kon word om die resultate te bestudeer met die doel om die kommunikasiekanaal tussen die satelliet en grond stasies optimaal te benut. Die resultate het bewys dat daar geen spesifieke konfigurasie van modulasie skema, pakkie grootte, transmissiekrag ens. is wat die algehele beste oplossing is nie. Die spesifieke applikasie waarvoor die lae wentelbaan satelliet gaan gebruik word moet geanaliseer word sowel as die spesifieke karakteristieke van daai applikasie. Daarvolgens moet n unieke konfigurasie opgestel word wat meeste van die applikasie se behoeftes bevredig.
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Muhovic, Admir. "Secure Wireless Communication." Thesis, KTH, Kommunikationssystem, CoS, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92023.
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The need for and requests for utilization of wireless equipment are growing rapidly. Advantages of using wireless communication are easy to realize. Having access to electronically stored information no matter where you are is a big advantage. Furthermore, wireless communication is increasingly utilized in everyday work and there is a constant development of new wireless equipment. Today, utilization of wireless communication is very practical as well as effective. On the other hand, using wireless equipment and communication entails risk unless efforts are made to secure this communication. Some wireless protocols exist and are used, despite their being vulnerable to attacks. Additionally, the traffic can easily be eavesdropped. Incorrect installation of wireless equipment contributes to the vulnerabilities of wireless communication. Some of the IT-equipment available on the market today offers wireless communication. This equipment is increasingly used within FMV. Such equipment includes: laptops, PDAs, cellular phones, etc. This wireless equipment, according to FMV’s information security policy, must be approved from a security viewpoint before it can be used at FMV. Thus an analysis of risks associated with usage of wireless equipment must take place and the mechanisms necessary to ensure adequate security must be identified. The document “Requirements on Security Functions (Kraven på SäkerhetsFunktioner, KSF)” identifies the technical and/or administrative requirements for such equipment.</p> The aim of this thesis was to analyze if it is possible to utilize wireless equipment at FMV, specifically, if it can be connected to the internal LAN at FMV. In other words, the wireless equipment must be able to offer security protection corresponding to the information security class: HEMLIG/RESTRICTED. The thesis contains an analysis of which security functions are available on the market today and evaluates whether these security functions meet the requirements given in KSF. The result is a proposal for the best security mechanism(s) within the constraints of KSF and the available equipment. The thesis proposes a technical solution along with suitable security mechanisms. The advantages and drawbacks of each has been analyzed. Additionally, the thesis presents a number of (administrative) security policies in order to be able to handle security aspects which are not covered by the KSF.Behoven och efterfrågan av mobil och trådlös utrustning är i dagsläget allt större. Fördelarna med att använda sig av trådlös kommunikation är enkla att inse. Att kunna ha tillgång till elektroniskt lagrad information oavsett var man än befinner sig är en stor fördel. Vidare implementeras trådlös kommunikation allt mer i det vardagliga arbetet samtidigt som utrustning för denna sorts kommunikation är i ständig utveckling. I slutändan är användandet av trådlös kommunikation väldigt praktiskt samtidigt som det är effektivt. Användandet av trådlös utrustning och kommunikation medför ett risktagande då denna typ av kommunikation allmänt är osäker. Detta eftersom teknologin fortfarande är i utvecklingsfasen. De i dagsläget aktuella trådlösa protokollen är sårbara för attacker och det är dessutom enkelt att avlyssna trafiken. Felaktig installation av utrustning bidrar dessutom också till att den trådlösa kommunikationen blir sårbar. En del av den IT-utrustning som idag finns tillgänglig ute på marknaden och som alltmer används inom FMV har möjlighet att kommunicera trådlöst med omgivningen. Exempel på sådan utrustning är bärbara datorer, PDA:er, mobiltelefoner mm. Denna typ av utrustning, dvs. trådlös utrustning, skall enligt FMVs informationssäkerhetspolicy godkännas från säkerhetssynpunkt innan den får tas i bruk på FMV. Det innebär att man utför en analys av vilka risker som är förknippade med användandet av trådlös utrustning samt att man identifierar adekvata skyddsåtgärder. Till sin hjälp använder man sig av Kraven på SäkerhetsFunktioner (KSF) som består av tekniska och/eller administrativa krav. Syftet med detta examensarbete var att undersöka om det finns möjlighet att använda trådlös utrustning på FMV, dvs. att denna används på interna LAN på FMV. Med andra ord skall den trådlösa utrustningen kunna erbjuda ett skydd motsvarande högst informationssäkerhetsklassen HEMLIG/RESTRICTED (H/R). Examensarbetet innefattar en analys av vilka säkerhetsfunktioner idag finns tillgängliga ute på marknaden och utvärderar huruvida dessa säkerhetsfunktioner uppfyller kraven givna i Kraven på SäkerhetsFunktioner (KSF). Resultatet är ett förslag på de bästa säkerhetsmekanismerna inom restriktionerna av KSF och den tillgängliga utrustningen. Examensarbetet föreslår en teknisk lösning med lämpliga säkerhetsmekanismer. Dess för- och nackdelar har analyserats. Examensarbetet presenterar dessutom ett antal (administrativa) säkerhets policies som hanterar säkerhetsaspekter som inte omhändertas av KSF.
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Cottingham, David Naveen. "Vehicular wireless communication." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611258.
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Yin, Hujun. "Cross layer design and optimization of wireless networks /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5904.
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Dong, Lu. "MIMO Selection and Modeling Evaluations for Indoor Wireless Environments." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19767.
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Array-to-array, or multiple-input multiple-output (MIMO), links are known to provide extremely high spectral efficiencies in rich multipath environments, such as indoor wireless environments. The selection of a subset of receiver array antennas for a MIMO wireless link has been studied by many as a way to reduce cost and complexity in a MIMO system while providing diversity gain. Combined with a switched multi-beam beamformer, it becomes the beam selection system that can gain high signal-to-interference
ratio (SIR) improvement in an interference-imited environment.
The objective of this research is to evaluate the performance of low-complexity antenna or beam subset selection methods for small MIMO networks. The types of networks include (1) point-to-point MIMO links with out-of-system interference, (2)multi-user networks with a single, but possibly spatially distributed access point. We evaluate various selection techniques on measured indoor channels, which has not been done before. We propose a new practical selection metric, the peak-to-trough ratio of orthogonal frequency division multiplexing (OFDM) training symbols. We also compare antenna and beam selection on measured indoor channels under more general conditions than has previously been done. Finally, we consider some channel modeling issues associated with beamformers. We investigate the validity of three types of statistical MIMO channel models. A new beamformer is designed based on the ideal of the ``Weichselberger model.'
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Dagne, Carl, Johan Bengtsson, and Ingemar Lindgren. "Microwave Wireless Communication System." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-232.
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The purpose of the project was to develop the hardware to a microwave wireless system working
at the frequency 2.45 GHz. The functionality of the system should also be easy to understand
since the system is to be used in an educational purpose. Much time has been spent impedance
matching components, a task that proved to be harder than we expected. Other work that has been
is layout of all parts, filter construction and the writing of an easy to understand thesis. After the
parts had been completed, they were tested in a network analyzer and/or spectrum analyzer.
Successful full system test has been done up to 400 meters, the length the system is to be used
for.
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Herbert, Steven John. "Wireless communication in vehicles." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/280675.
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There is an increasing interest in the deployment of wireless communication systems in vehicles. The motivation for this work is to provide a fundamental characterisation of the in-vehicle Electromagnetic (EM) wave propagation environment, and to demonstrate how this can be used to aid the deployment of wireless communication systems in vehicles. The fundamental characterisation of the in-vehicle EM wave propagation environment presented in this dissertation yields a number of useful outcomes. The instantaneous impulse response of the in-vehicle channel is characterised, which is presented in the form of a statistical model for arriving rays. Noticing that it is impractical to undertake a full statistical characterisation of the time-varying impulse response, the time variation of the in-vehicle channel is instead characterised as a Doppler spread. This approach provides parameters which are sufficient to perform an information theoretic analysis to lower bound the capacity of the in-vehicle channel. For typical operating conditions, it is found that the channel capacity is approximately equal to that of the same channel with perfect channel state information available at the receiver. Having established the fundamental EM wave propagation characteristics for a single in-vehicle wireless channel, the EM properties of the cavity itself are characterised. This is achieved through a thorough investigation into the analogy between vehicle cavities and reverberation chambers, specifically considering the quality factor (and hence time constant), EM isolation, and electric field uniformity of typical vehicle cavities. This approach yields the important insight that the root mean square delay spread is approximately the same for all wireless links in a typical vehicle cavity. Also, that the angular spread of energy received at any given location (away from the cavity boundaries) is approximately uniform, and that over short distances the coherence distance is well defined, and hence Multiple Input Multiple Output antenna arrays should work well in vehicles. To what extent a typical wireless system can exploit this characterisation depends on how well the parameters can be estimated by a typical wireless communication system. This is also addressed, specifically investigating the estimation of the cavity time constant, and channel time variation. It is found that both of these can be estimated well using a typical wireless sensor network system.
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Jiang, Junyi. "Optical wireless communication systems." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/387239/.
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In recent years, Optical Wireless (OW) communication techniques have attracted substantial attention as a benefit of their abundant spectral resources in the optical domain, which is a potential solution for satisfying the ever-increasing demand for increased wireless capacity in the conventional Radio Frequency (RF) band. Motivated by the emerging techniques and applications of OW communication, the Institute of Electrical and Electronics Engineers (IEEE) had released the IEEE standard 802.15.7 for short-range optical wireless communications, which categorised the Physical layer (PHY) of the OW communication into three candidate-solutions according to their advantages in different applications and environments: 1) Physical-layer I (PHY I): Free Space Optical (FSO)communication employs high-intensity Light Emitting Diodes (LEDs) or Laser Diodes (LDs) as its transmitter. 2) Physical-layer II (PHY II) uses cost-effective, low-power directional white LEDs for the dual function of illumination and communication. 3) Physical III (PHY-III) relies on the so-called Colour-Shift Keying (CSK) modulation scheme for supporting high-rate communication. Our investigations can be classified into three major categories, namely Optical Orthogonal Frequency Division Multiplexing (OFDM) based Multiple-Input Multiple-Output (MIMO) techniques for FSO communications in the context of PHY I, video streaming in PHY-II and the analysis and design of CSK for PHY-III. To be more explicit, in Chapter 2 we first construct a novel ACO-OFDM based MIMO system and investigate its performance under various FSO turbulence channel conditions. However, MIMO systems require multiple optical chains, hence their power consumption and hardware costs become substantial. Hence, we introduced the concept of Aperture Selection (ApS) to mitigate these problems with the aid of a simple yet efficient ApS algorithm for assisting our ACO-OFDM based MIMO system. Since the channel conditions of indoor Visible Light Communication (VLC) environments are more benign than the FSO-channels of Chapter 2, directional white LEDs are used to create an “attocell” in Chapter 3. More specifically, we investigate video streaming in a multi-Mobile Terminals (MTs) indoor VLC system relying on Unity Frequency Reuse (UFR) as well as on Higher Frequency Reuse Factor based Transmission (HFRFT) and on Vectored Transmission (VT) schemes. We minimise the distortion of video streaming, while satisfying the rate constraints as well as optical constraints of all the MTs. In Chapter 4 we analyse the performance of CSK relying both on joint Maximum Likelihood (ML) Hard-Detection (HD), as well as on the the Maximum A posteriori (MAP) criterion-based Soft-Detection (SD) of CSK. Finally, we conceive both two- stage and three-stage concatenated iterative receivers capable of achieving a substantial iteration gain, leading to a vanishingly low BER.
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Du, Hao. "Optical wireless MIMO communication." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/70945/.
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This thesis provides an in-depth investigation and evaluation of infrared optical wireless MIMO communication systems to be applied in both indoor and outdoor environment. The principle objective of the research is to demonstrate both the advantages and disadvantages of the optical wireless MIMO systems using different modulation types. The first part provided analyses of important OW configurations using APD receivers using WMC model and SISO, MISO, SIMO and MIMO configuration. Thus, an analytical expression for 2-1 MISO, 1-2 SIMO and MIMO was successfully developed. This part also illustrates the coding gains possible using diversity schemes for APD OW systems. In the presence of strong fading, the SISO approach is rendered virtually useless, whereas diversity offers acceptable BER values. The results underpin the approach of this thesis, where indoor PIN diode based experimental measurements confirm the gains offered by diversity. In the second part of the work, several optical wireless MIMO systems applicable for the indoor environment are developed for three different modulation types, OOK modulation, PPM modulation and SIR-RZI modulation. These modulations are used in optical MIMO systems are studied for which, mathematical models that evaluate the BER performance of the MIMO system for different axis displacement and for different distances between transmitters and receivers. Based on the results, the PPM system has been shown to present the best BER performance, including high interference-resistance capability. A group of new mathematical models have been evaluated, which demonstrates a high level of correlation with the results derived from empirical models at 93%. Thus, the mathematical models developed and used for the specified evaluation appear to correspond reasonably well, and can be applied in future research on these aspects.
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Кovalenko, Viktoriya, and Oksana Tykhenko. "Wireless communication safety analysis." Thesis, Proceedings the Seventh World Congress «Aviation in the XXI-st Century», September 19 – 21, 2016. – P. 5.4.46 – 5.4.48, 2016. http://er.nau.edu.ua/handle/NAU/29355.
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Gao, Zihao. "Wireless Powered Communication Networks." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17169.
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The limited life time of batteries is a crucial issue in energy-constrained wireless communications. Recently, the radio frequency (RF) wireless energy transfer (WET) technique has been developed as a new practical method to extend the life time of wireless communication networks. Inspired by this, wireless-powered communication network (WPCN) has attracted much attention. Therefore, in this thesis, we consider practical WET and wireless-powered information transmission in WPCNs. First we investigate a WPCN with two nodes, in which an access point (AP) exchanges information with a wireless-powered user. The user is assumed to have no embedded energy supply and needs to harvest energy from RF signals broadcast by the AP. Differing from existing work that focuses on the design of wireless-powered communication with one-way information flow, we deal with a more general scenario where both the AP and the user have information to transmit. Considering that the AP and user can work in either half-duplex or full-duplex mode as well as having two practical receiver architectures at the user side, we propose five elementary communication protocols for the considered system. Moreover, we define the concept of a throughput region to characterize the tradeoff between the uplink and downlink throughput in all proposed protocols. Numerical simulations are finally performed to compare the throughput regions of the proposed five elementary protocols. To further the study on WPCN, we investigate a wireless-powered two-way relay system, in which two wireless-powered sources exchange information through a multi-antenna relay. Both sources are assumed to have no embedded energy supply and thus first need to harvest energy from the radio frequency signals broadcast by the relay before exchanging their information via the relay. We aim to maximize the sum throughput of both sources by jointly optimizing the time switching duration, the energy beamforming vector and the precoding matrix at the relay. The formulated problem is non-convex and hard to solve in its original form. Motivated by this, we simplify the problem by reducing the number of variables and by decomposing the precoding matrix into a transmit vector and a receive vector. We then propose a bisection search, a 1-D search and an iterative algorithm to optimize each variable. Numerical results show that our proposed scheme can achieve higher throughput than the conventional scheme without optimization on the beamforming vector and precoding matrix at the relay. Due to the high attenuation of RF energy over a long distance, RF based wireless-powered communication is usually designed for low-power scenarios, e.g., wireless-powered sensor networks. Recently, magnetic induction (MI) based WET has been proposed to wirelessly transfer a large amount of energy. Inspired by this, we investigate MI based WET in WPCN. Specifically, we study a MI based wireless-powered relaying network, in which a MI source transmits information to a MI destination, with the help of a MI based wireless powered relay. We propose four active relaying schemes, which consider different relaying modes and different energy harvesting receiver architectures at the relay. We then aim to maximize the end-to-end throughput of each scheme by using a bisection search, a water-filling algorithm, a Lagrange multiplier, quasi-convex programming and an iterative algorithm. We compare the proposed active relaying schemes with passive relaying. Numerical results show that the proposed relaying schemes with a decode-and-forward relaying mode significantly improve the throughput over passive relaying.
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Liu, Cheng. "Advanced system design and signal processing techniques for converged high-speed optical and wireless applications." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49058.
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The ever-increasing data traffic demand drives the evolution of telecommunication networks, including the last-mile access networks as well as the long-haul backbone networks. This Ph.D. dissertation focuses on system design and signal processing techniques for next-generation converged optical-wireless access systems and the high-speed long-haul coherent optical communication systems. The convergence of high-speed millimeter-wave wireless communications and high-capacity fiber-optic backhaul networks provides tremendous potential to meet the capacity requirements of future access networks. In this work, a cloud-radio-over-fiber access architecture is proposed. The proposed architecture enables a large-scale small-cell system to be deployed in a cost-effective, power-efficient, and flexible way. Based on the proposed architecture, a multi-service reconfigurable small-cell backhaul network is developed and demonstrated experimentally. Additionally, the combination of high-speed millimeter-wave radio and fiber-optic backhaul is investigated. Several novel methods that enable high-spectral-efficient vector signal transmission in millimeter-wave radio-over-fiber systems are proposed and demonstrated through both theoretical analysis and experimental verification. For long-haul core networks, ultra-high-speed optical communication systems which can support 1Terabit/s per channel transmission will soon be required to meet the increasing capacity demand in the core networks. Grouping a number of tightly spaced optical subcarriers to form a terabit superchannel has been considered as a promising solution to increases channel capacity while minimizing the need for high-level modulation formats and high baud rate. Conventionally, precise spectral control at transmitter side is required to avoid strong inter-channel interference (ICI) at tight channel spacing. In this work, a novel receiver-side approach based on “super receiver” architecture is proposed and demonstrated. By jointly detecting and demodulating multiple channels simultaneously, the penalties associated with the limitations of generating ideal spectra can be mitigated. Several joint DSP algorithms are developed for linear ICI cancellation and joint carrier-phase recovery. Performance analysis under different system configurations is conducted to demonstrate the feasibility and robustness of the proposed joint DSP algorithms, and improved system performance is observed with both experimental and simulation data.
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Guice, Robert J. Munoz Ramon J. "IEEE 802.16 Commercial Off The Shelf (COTS) technologies as a compliment to Ship To Objective Maneuver (STOM) communications." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FGuice.pdf.
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Thesis (M.S. in Information Technology Management)--Naval Postgraduate School, Sept. 2004.Thesis advisor(s): Rex Buddenberg. Includes bibliographical references (p. 103-105). Also available online.
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Athukorala, Lakshman. "Miniaturised bandpass filters for wireless communications." Thesis, University of Westminster, 2012. https://westminsterresearch.westminster.ac.uk/item/8z606/miniaturised-bandpass-filters-for-wireless-communications.
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The wireless industry has seen exceptional development over the past few decades due to years of sustained military and commercial enterprise. While the electromagnetic spectrum is becoming increasingly congested, there is a growing tendency to strive for higher bandwidths, faster throughputs, greater versatility, compatibility and interoperability in current and emerging wireless technologies. Consequently, an increasingly stringent specification is imposed upon the frequency utilization of wireless devices. New challenges are constantly being discovered in the development and realization of RF and microwave filters, which have not only sustained but fuelled microwave filter research over the many years. These developments have encouraged new solutions and techniques for the realization of compact, low loss, highly selective RF and microwave bandpass filters. The theme of this dissertation is the realization of planar compact performance microwave and RF bandpass filters for wireless communication systems. The work may be broadly categorised into three sections as follows. The first section presents a novel compact planar dual-mode resonator with several interesting and attractive features. Generally, planar microwave dual-mode resonators are known to half the filter footprint. However, it is found that the proposed resonator is capable of achieving further size reductions. In addition the resonator inherently possesses a relatively wide stopband as the lowest spurious harmonic resonance is observed at thrice the fundamental frequency. Properties of this resonator, such as these and more are explored in depth to arrive at an accurate electrical equivalent circuit, which is used as the basis for high order filter design. The application of these resonators in the design of bandpass filters is the subject of the second section. A general filter design procedure based on the equivalent circuit is presented to assist the design of all-pole filters. Alternatively, it is shown that generalised Chebyshev filters with enhanced selectivity may be developed with cross coupled resonator topologies. The discussions are supplemented with detailed design examples which are accompanied by theoretical, simulated and experimental results in order to illustrate the filter development process and showcase practical filter performance. The third section explores the possibility of employing these resonators in the development of frequency tunable bandpass filters. Preference is given to varactor diodes as the tuning element due to the numerous qualities of this device in contrast to other schemes. In particular, interest is paid to center frequency tuned filters with constant bandwidth. Tunable filters constructed with the dual-mode resonator are shown to have a relatively wide tuning range as well as significantly higher linearity in comparison to similar published works. In line with the previous section, experimental verification is presented to support and supplement the discussions.
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Yamashita, Shota. "Coexistence of Wireless Communication and Non-communication Systems." Kyoto University, 2018. http://hdl.handle.net/2433/232420.
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鄭价昌 and Kai-cheong Chang. "Adaptive channel equalisation technique for wideband time-division multiple access digital mobile radio communications systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31212888.
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Manescu, Corneliu. "Video and voice coding for mobile ad-hoc collaboration." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000740.
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Chang, Kai-cheong. "Adaptive channel equalisation technique for wideband time-division multiple access digital mobile radio communications systems /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17590371.
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Lo, Chi-ming. "Analytical evaluation of wireless digital communication performance over fading channels." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23295211.
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Neo, Soo Sim Daniel. "Free space optics communication for mobile military platforms." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FNeo.pdf.
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Benn, Leon Jacobus. "A Strategic business model for the introduction of mobile data services in an emerging economy the case of the South African market /." Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-06102005-093913.
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Krause, Wolfram O. "Wireless communication networks : structure and dynamics of wireless multi-hop ad hoc communication networks /." Lichtenberg (Odenw.) : Harland media, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015507583&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Schuster, Ulrich G. "Wireless communication over wideband channels /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17565.
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Lee, Kah Ping. "Turbo equalization in wireless communication." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/5844.
Full textAbstract:
Thesis (M.S.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 11, 2006) Includes bibliographical references.
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Pakravan, Mohammad Reza. "Indoor infrared wireless communication channels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0016/NQ57061.pdf.
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Ray, Adam A. Roppel Thaddeus A. "Cooperative robotics using wireless communication." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Thesis/RAY_ADAM_44.pdf.
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Lu, Yang. "UWB antennas for wireless communication." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569654.
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Ultra-wideband (UWB) technology is a promising solution to provide high data-rate transmission of the future wireless communication systems. The rapid development of UWB wireless communication systems has brought both challenges and: opportunities to novel UWB antenna designs. This thesis is concentrated on the analysis, design and measurement of compact antennas for UWB devices, which can be divided into three areas. / The first area investigated is small planar broadband antennas for wearable and positioning applications where the antennas with unidirectional radiation patterns may be preferred, since the energy will be focused on the desired direction. Furthermore, the interference from the environment behind the antenna can also be greatly minimised. Two low-profile broad band antennas with unidirectional radiation patterns are presented in this work. Their performance in terms of impedance bandwidth and radiation patterns is studied. Results show that they have a very broadband (>50% fractal bandwidth) and constant broadside unidirectional radiation patterns. Hence, they are good candidates and suitable for the in-body and radar applications The second research area is about the planar UWB monopole antennas. The radiation behaviour of the planar UWB monopole antenna is first investigated. It is found that an ultra-wide bandwidth of this type of antenna is achieved by both well-matched travelling wave modes and smooth transients between different higher order modes. However, there exists a common problem for the current planar UWB monopole antennas that their performance is heavily affected by the size of the ground plane. It is found that dimensional changes will influence the characteristic modes excited on the ground plane which directly affects the impedance and radiation of the antenna. A technique of cutting slots on the ground plane is then proposed to resolve the ground plane effect problem. The presence of the slots will introduce slot modes. Optimal slots can produce a strong coupling between the slot mode and the ground plane modes. This coupling makes the characteristic modes of planar UWB monopole insensitive to the size change of the ground plane, hence it effectively minimises the ground plane dependence of the antenna. Two different UWB monopole antennas are investigated using this technique. Both the simulated and measured results demonstrate that this method can indeed minimise the ground plane effects on the impedance matching and have very little effect on the other antenna parameters, such as radiation pattern, gain and I time domain performance. Additionally, a parametric study on the major geometric parameters related to the slots is performed to achieve an optimised design. The third area of my study is the measurement of UWB antenna radiation efficiency. Antenna radiation efficiency is one of the most important parameters when evaluating its performance. In the past, many different antenna efficiency measurement methods were proposed. However, how to measure the UWB antenna efficiency effectively is still a challenging issue. A novel source-stirred chamber/cap (SSC) method is proposed and developed to overcome the limitations of the existing methods. Different types of UWB antennas are employed as examples to demonstrate the usefulness of this new method. Promising results are obtained which prove the SSC method is very effective in measuring the UWB antenna efficiency. It is evident that this method has the potential to become a general antenna efficiency measurement approach.
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Liu, Luyan. "Wireless Communication in Smart Housing." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-37631.
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With the development of computer and information technology, information and network will be the inevitable trend of smart home which aims to offer a comfortable, efficient, and convenient home. In this thesis, the background, developments and limitations of smart home systems will be described. Wired and wireless technologies applied on the smart home network will be analyzed and a comparison of them will be made. Finally, the ZigBee technology is selected to design the wireless communication network. For the system design, the thesis describes an idea where cluster topology is chosen to design the smart home system and demonstrates the process of networking as well. Based on the Labview platform, a smart home system will be simulated to achieve the functions included in data acquisition, analysis, display and storage. More specially, I will focus on temperature monitoring and control of heating and cooling systems. Finally, an analysis of the advantages and disadvantages of the smart home system is given.
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Bourget, Marc A. (Marc Anthony) 1979. "Expanding the wireless communication paradigm." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87185.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002."June 2002."
Includes bibliographical references (leaves 44-45).
by Marc A. Bourget.
M.Eng.
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Music, Craig 1978. "Expanding the wireless communication paradigm." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8077.
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Ding, Yuan. "Directional modulation secured wireless communication." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676283.
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The main objective of this work was the development of the directional modulation (DM) technique, which is a promising keyless physical layer security means for securing wireless communication in free space. It is realized, from a summary of the state-of-the-art OM systems, that although the OM concept appears to be a competitive candidate to enhance the secrecy performance of the next generation of wireless communication, it suffers various fundamental problems, which makes the OM research carried out in an unsystematic and inefficient manner. In order to integrate the previous scattered OM efforts and further pave the path for its applications, in this thesis a theoretical OM framework has been established and some key concepts and OM architectures have been validated via well designed experiments.
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Schuster, Ulrich G. "Wireless communication over wideband channels." Konstanz Hartung-Gorre, 2008. http://d-nb.info/993286984/04.
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Alhartomi, Mohammed. "Collaborative optical wireless communication systems." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/13153/.
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ZHANG, LINCHAO. "Reliable Communication in Wireless Networks." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2537290.
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Wireless communication systems are increasingly being used in industries and infrastructures since they offer significant advantages such as cost effectiveness and scalability with respect to wired communication system. However, the broadcast feature and the unreliable links in the wireless communication system may cause more communication collisions and redundant transmissions. Consequently, guaranteeing reliable and efficient transmission in wireless communication systems has become a big challenging issue. In particular, analysis and evaluation of reliable transmission protocols in wireless sensor networks (WSNs) and radio frequency identification system (RFID) are strongly required.
This thesis proposes to model, analyze and evaluate self-configuration algorithms in wireless communication systems. The objective is to propose innovative solutions for communication protocols in WSNs and RFID systems, aiming at optimizing the performance of the algorithms in terms of throughput, reliability and power consumption. The first activity focuses on communication protocols in WSNs, which have been investigated, evaluated and optimized, in order to ensure fast and reliable data transmission between sensor nodes. The second research topic addresses the interference problem in RFID systems. The target is to evaluate and develop precise models for accurately describing the interference among readers. Based on these models, new solutions for reducing collision in RFID systems have been investigated.
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Toni, Laura <1982>. "Adaptive wireless multimedia communication systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2117/1/Laura_Toni_tesi.pdf.
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In recent years, due to the rapid convergence of multimedia services, Internet and wireless communications, there has been a growing trend of heterogeneity (in terms of channel bandwidths, mobility levels of terminals, end-user quality-of-service (QoS) requirements) for emerging integrated wired/wireless networks. Moreover, in nowadays systems, a multitude of users coexists within the same network, each of them with his own QoS requirement and bandwidth availability. In this framework, embedded source coding allowing partial decoding at various resolution is an appealing technique for multimedia transmissions. This dissertation includes my PhD research, mainly devoted to the study of embedded multimedia bitstreams in heterogenous networks, developed at the University of Bologna, advised by Prof. O. Andrisano and Prof. A. Conti, and at the University of California, San Diego (UCSD), where I spent
eighteen months as a visiting scholar, advised by Prof. L. B. Milstein and Prof. P. C. Cosman. In order to improve the multimedia transmission quality over wireless channels, joint source and channel coding optimization is investigated in a 2D time-frequency resource block for an
OFDM system. We show that knowing the order of diversity in time and/or frequency domain can assist image (video) coding in selecting optimal channel code rates (source and channel code rates). Then, adaptive modulation techniques, aimed at maximizing the spectral efficiency, are investigated as another possible solution for improving multimedia transmissions. For both slow and fast adaptive modulations, the effects of imperfect channel estimation errors are evaluated, showing that the fast technique, optimal in ideal systems, might be outperformed by the slow adaptive modulation, when a real test case is considered. Finally, the effects of co-channel interference and approximated bit error probability (BEP) are evaluated in adaptive modulation techniques, providing new decision regions concepts, and showing how the widely used BEP
approximations lead to a substantial loss in the overall performance.
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Toni, Laura <1982>. "Adaptive wireless multimedia communication systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2117/.
Full textAbstract:
In recent years, due to the rapid convergence of multimedia services, Internet and wireless communications, there has been a growing trend of heterogeneity (in terms of channel bandwidths, mobility levels of terminals, end-user quality-of-service (QoS) requirements) for emerging integrated wired/wireless networks. Moreover, in nowadays systems, a multitude of users coexists within the same network, each of them with his own QoS requirement and bandwidth availability. In this framework, embedded source coding allowing partial decoding at various resolution is an appealing technique for multimedia transmissions. This dissertation includes my PhD research, mainly devoted to the study of embedded multimedia bitstreams in heterogenous networks, developed at the University of Bologna, advised by Prof. O. Andrisano and Prof. A. Conti, and at the University of California, San Diego (UCSD), where I spent
eighteen months as a visiting scholar, advised by Prof. L. B. Milstein and Prof. P. C. Cosman. In order to improve the multimedia transmission quality over wireless channels, joint source and channel coding optimization is investigated in a 2D time-frequency resource block for an
OFDM system. We show that knowing the order of diversity in time and/or frequency domain can assist image (video) coding in selecting optimal channel code rates (source and channel code rates). Then, adaptive modulation techniques, aimed at maximizing the spectral efficiency, are investigated as another possible solution for improving multimedia transmissions. For both slow and fast adaptive modulations, the effects of imperfect channel estimation errors are evaluated, showing that the fast technique, optimal in ideal systems, might be outperformed by the slow adaptive modulation, when a real test case is considered. Finally, the effects of co-channel interference and approximated bit error probability (BEP) are evaluated in adaptive modulation techniques, providing new decision regions concepts, and showing how the widely used BEP
approximations lead to a substantial loss in the overall performance.
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Cavallari, Riccardo <1986>. "Human-Centric Wireless Communication Networks." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7444/1/tesi.pdf.
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This thesis covers two main topics: the design and performance
evaluation of Wireless Body Area Networks (WBANs), and the simulation
and mathematical modeling of Delay Tolerant Networks (DTNs).
Different Medium Access Control (MAC) protocols for WBANs are
implemented on dedicated hardware in order to evaluate, through
extensive measurement campaigns, the performance of the network in
terms of packet loss rate, delay and energy consumption. Novel
solutions to cope with body shadowing and to improve the coexistence
with other wireless technologies, are presented and evaluated. An
analytic model for the CSMA/CA protocol defined in the IEEE 802.15.6
standard is also presented.
The benefits of offloading part of the traffic carried by a wireless
backbone to a DTN composed of mobile nodes in a urban environment, is
also investigated. A more analytic approach, mainly using tools from
stochastic geometry and Markov chains theory, is used to develop a
mathematical framework for the evaluation of the performance of
routing rules for DTNs.
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Cavallari, Riccardo <1986>. "Human-Centric Wireless Communication Networks." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7444/.
Full textAbstract:
This thesis covers two main topics: the design and performance
evaluation of Wireless Body Area Networks (WBANs), and the simulation
and mathematical modeling of Delay Tolerant Networks (DTNs).
Different Medium Access Control (MAC) protocols for WBANs are
implemented on dedicated hardware in order to evaluate, through
extensive measurement campaigns, the performance of the network in
terms of packet loss rate, delay and energy consumption. Novel
solutions to cope with body shadowing and to improve the coexistence
with other wireless technologies, are presented and evaluated. An
analytic model for the CSMA/CA protocol defined in the IEEE 802.15.6
standard is also presented.
The benefits of offloading part of the traffic carried by a wireless
backbone to a DTN composed of mobile nodes in a urban environment, is
also investigated. A more analytic approach, mainly using tools from
stochastic geometry and Markov chains theory, is used to develop a
mathematical framework for the evaluation of the performance of
routing rules for DTNs.
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Sun, Zhi. "Reliable and efficient communication in wireless underground sensor networks." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41150.
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Wireless Underground Sensor Networks (WUSNs) are the networks of wireless sensors that operate below the ground surface. These sensors are either buried completely in soil medium, or placed within a bounded open underground space, such as underground mines and tunnels. WUSNs enable a wide variety of novel applications, including intelligent irrigation, underground structure monitoring, and border patrol and intruder detection.
This thesis is concerned with establishing reliable and efficient communications in the network of wireless sensor nodes that are deployed in either soil medium or underground mines and tunnels. In particular, to realize WUSNs in soil medium, two types of signal propagation techniques including Electromagnetic (EM) waves and Magnetic Induction (MI) are explored. For EM wave-based WUSNs, the heterogeneous network architecture and dynamic connectivity are investigated based on a comprehensive channel model in soil medium. Then a spatio-temporal correlation-based data collection schemes is developed to reduce the sensor density while keeping high monitoring accuracy. For MI-based WUSNs, the MI channel is first analytically characterized. Then based on the MI channel model, the MI waveguide technique is developed in order to enlarge the underground transmission range. Finally, the optimal deployment algorithms for MI waveguides in WUSNs are analyzed to construct the WUSNs with high reliability and low costs. To realize WUSNs in underground mines and tunnels, a mode-based analytical channel model is first proposed to accurately characterize the signal propagation in both empty and obstructed mines and tunnels. Then the Multiple-Input and Multiple-Output (MIMO) system and cooperative communication system are optimized to establish reliable and efficient communications in underground mines and tunnels.
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Boubaker, Nejib. "Ultra wide bandwidth spread spectrum impulse radio for wireless multi-access communications /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20BOUBAK.
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Skidmore, Roger Ray. "A Comprehensive Method and System for the Design and Deployment of Wireless Data Networks." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27611.
Full textAbstract:
Increasingly, wireless subscribers are demanding reliable data capabilities from wireless networks. The ability of wireless network engineers and Information Technology (IT) professionals to rapidly design, deploy, and maintain wireless communication systems that can provide strong, reliable data service is severely hampered by a lack of adequate systems and methods for simulating the performance of such networks a priori. Unlike older generation wireless systems that could be readily deployed on the basis of strong received signal strength and simple circuit-switched channel allocation protocols, modern and emerging wireless data networks are more noise and interference limited and rely on packet-based protocols. A heavier emphasis is needed on predicting and simulating throughput, bit error rate, frame error rate, user priority classes, and overall network capacity. This research provides wireless network engineers and IT professionals with a comprehensive system and method for the simulation and design of wireless communication systems that combines site-specific databases, equipment-specific distribution system modeling, and advanced ray tracing propagation analysis to directly predict throughput, frame error rate (FER), and other critical performance parameters for emerging wireless data networks.Ph. D.
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Stanković, Veljko. "Multi-user MIMO wireless communications." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985258039.
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Schmitt, Michael Philipp. "ARQ systems for wireless communications." Phd thesis, [S.l. : s.n.], 2002. http://elib.tu-darmstadt.de/diss/000269.
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Kim, Kihong. "Interference Mitigation in Wireless Communications." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7647.
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The primary objective of this thesis is to design advanced interference resilient schemes for asynchronous slow frequency hopping wireless personal area networks (FH-WPAN) and time division multiple access (TDMA) cellular systems in interference dominant environments. We also propose an interference-resilient power allocation method for multiple-input-multiple-output (MIMO) systems.
For asynchronous FH-WPANs in the presence of frequent packet collisions, we propose a single antenna interference canceling dual decision feedback (IC-DDF) receiver based on joint maximum likelihood (ML) detection and recursive least squares (RLS) channel estimation. For the system level performance evaluation, we propose a novel geometric method that combines bit error rate (BER) and the spatial distribution of the traffic load of CCI for the computation of packet error rate (PER). We also derived the probabilities of packet collision in multiple asynchronous FH-WPANs with uniform and nonuniform traffic patterns.
For the design of TDMA receivers resilient to CCI in frequency selective channels, we propose a soft output joint detection interference rejection combining delayed decision feedback sequence estimation (JD IRC-DDFSE) scheme. In the proposed scheme, IRC suppresses the CCI, while DDFSE equalizes ISI with reduced complexity. Also, the soft outputs are generated from IRC-DDFSE decision metric to improve the performance of iterative or non-iterative type soft-input outer code decoders.
For the design of interference resilient power allocation scheme in MIMO systems, we investigate an adaptive power allocation method using subset antenna transmission (SAT) techniques. Motivated by the observation of capacity imbalance among the multiple parallel sub-channels, the SAT method achieves high spectral efficiency by allocating power on a selected transmit antenna subset. For 4 x 4 V-BLAST MIMO systems, the proposed scheme with SAT showed analogous results. Adaptive modulation schemes combined with the proposed method increase the capacity gains. From a feasibility viewpoint, the proposed method is a practical solution to CCI-limited MIMO systems since it does not require the channel state information (CSI) of CCI.
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Anderson, Alan John. "Channel prediction in wireless communications." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/16188.
Full textAbstract:
Knowledge of the channel over which signals are sent is of prime importance in modern wireless communications. Inaccurate or incomplete channel information leads to high error rates and wasted bandwidth and energy. Although active channel measurement is commonly used to gain channel knowledge, it can only accurately represent the channel at the time the measurement was taken, makes energy and bandwidth demands, and adds significant complexity to the radio system. Due to the highly time variant nature of wireless channels, active measurements become invalid almost as soon as they are taken, making alternative approaches to predicting future behaviour highly attractive. Such systems would allow maximum advantage to be taken of the limited bandwidth available and make significant power savings. This thesis investigates a number of complementary technologies, leading towards a channel prediction scheme suitable for mobile devices. As a first step towards channel prediction, anomaly detection is investigated within periodic wireless signals to establish when radical changes in the channel occur. In pre- vious experiments, long monotonic sequences had been observed to coincide with certain anomalies but not others when using Kullback-Leibler Divergence (KLD) analysis, possibly allowing the characterisation of anomaly types. An investigation is described to explain the origin of these features in a rigorous mathematical sense. A proof is given for the causes of the monotonic sequences, followed by a discussion of the types of signal anomaly which would underly such a feature and the value of this information. The second part describes a novel channel characterisation method which uses a class of Recurrent Neural Network (RNN) called an Echo State Network (ESN). Using this tool, a channel characterisation system can be constructed without an explicit statistical or mathematical model of the wireless environment, relying instead on observed data. This approach is much more convenient than existing models which require detailed information about the wireless system's parameters and also allows for new channel classifications to be added easily. It is able to achieve double the correct classification rate of a conventional statistical classifier, and is computationally simple to implement, making it ideal for inclusion on low-power mobile devices. Following their successful use in characterisation, ESNs are used in the final part in an investigation into channel prediction in a number of different scenarios. They were however found to be unable to produce useful predictions for all but the most trivial channel models. An alternative method is described for indoor environments using an approach inspired by ray tracing. It is simple and computationally lightweight to implement, again making it suitable for mobile devices. Simulation results show that it can outperform pilot-assisted methods by a significant margin, while not wasting bandwidth on channel measurement.
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Shaheem, Asri. "Iterative detection for wireless communications." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0223.
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[Truncated abstract] The transmission of digital information over a wireless communication channel gives rise to a number of issues which can detract from the system performance. Propagation effects such as multipath fading and intersymbol interference (ISI) can result in significant performance degradation. Recent developments in the field of iterative detection have led to a number of powerful strategies that can be effective in mitigating the detrimental effects of wireless channels. In this thesis, iterative detection is considered for use in two distinct areas of wireless communications. The first considers the iterative decoding of concatenated block codes over slow flat fading wireless channels, while the second considers the problem of detection for a coded communications system transmitting over highly-dispersive frequency-selective wireless channels. The iterative decoding of concatenated codes over slow flat fading channels with coherent signalling requires knowledge of the fading amplitudes, known as the channel state information (CSI). The CSI is combined with statistical knowledge of the channel to form channel reliability metrics for use in the iterative decoding algorithm. When the CSI is unknown to the receiver, the existing literature suggests the use of simple approximations to the channel reliability metric. However, these works generally consider low rate concatenated codes with strong error correcting capabilities. In some situations, the error correcting capability of the channel code must be traded for other requirements, such as higher spectral efficiency, lower end-to-end latency and lower hardware cost. ... In particular, when the error correcting capabilities of the concatenated code is weak, the conventional metrics are observed to fail, whereas the proposed metrics are shown to perform well regardless of the error correcting capabilities of the code. The effects of ISI caused by a frequency-selective wireless channel environment can also be mitigated using iterative detection. When the channel can be viewed as a finite impulse response (FIR) filter, the state-of-the-art iterative receiver is the maximum a posteriori probability (MAP) based turbo equaliser. However, the complexity of this receiver's MAP equaliser increases exponentially with the length of the FIR channel. Consequently, this scheme is restricted for use in systems where the channel length is relatively short. In this thesis, the use of a channel shortening prefilter in conjunction with the MAP-based turbo equaliser is considered in order to allow its use with arbitrarily long channels. The prefilter shortens the effective channel, thereby reducing the number of equaliser states. A consequence of channel shortening is that residual ISI appears at the input to the turbo equaliser and the noise becomes coloured. In order to account for the ensuing performance loss, two simple enhancements to the scheme are proposed. The first is a feedback path which is used to cancel residual ISI, based on decisions from past iterations. The second is the use of a carefully selected value for the variance of the noise assumed by the MAP-based turbo equaliser. Simulations are performed over a number of highly dispersive channels and it is shown that the proposed enhancements result in considerable performance improvements. Moreover, these performance benefits are achieved with very little additional complexity with respect to the unmodified channel shortened turbo equaliser.
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Zyambo, Emmanuel Baleke. "High-speed wireless infrared communications." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275377.
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Parand, Farivar. "Cellular optical wireless communications systems." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270654.
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