To see the other types of publications on this topic, follow the link: Input/Output and Data Communications.
Dissertations / Theses on the topic 'Input/Output and Data Communications'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Input/Output and Data Communications.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Au, Kwok Shum. "Multiple-input multiple-output detection in wireless communications and data storage systems : performance and implementation issues /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20AU.
Full text
2
Chibesakunda, Mwelwa K. "A Methodology for Analyzing Power Consumption in Wireless Communication Systems." Thesis, University of Cape Town, 2004. http://pubs.cs.uct.ac.za/archive/00000102/.
Full textAbstract:
Energy usage has become an important issue in wireless communication systems. The energy-intensive nature of wireless communication has spurred concern over how best systems can make the most use of this non-renewable resource. Research in energy-efficient design of wireless communication systems show that one of its challenges is that the overall performance of the system depends, in a coupled way, on the different submodules of the system i.e. antenna, power amplifier, modulation, error control coding, and network architecture. Network architecture implementation strategies offer protocol software implementors an opportunity of incorporating low-power strategies into the design of the network protocols used for data communication.
This dissertation proposes a methodology that would allow a software protocol implementor to analyze the power consumption of a wireless communication system. The foundation of this methodology lies in the understanding of the formal specification of the wireless interface network architecture which can be used to predict the performance of the system. By extending this hypothesis, a protocol implementor can use the formal specification to derive the power consumption behaviour of the wireless system during a normal operation (transmission or reception of data). A high-level formalism like state-transition graphs, can be used to track the protocol processing behaviour and to derive the associated continuous-time Markov chains.
Because of their diversity, Markov reward models(MRM) are used to model the power consumption associated with the different states of a specified protocol layer. The models are solved analytically using the Mobius performance and dependability tool. Using the MRM accumulation and utilization measures, a profile of the power consumption is generated. Results from the experiments on the protocol layers show the individual power consumption and utilization of the different states as well as the accumulated power consumption of different protocol layers when compared. Ultimately, the results from the reward model solution can be used in the energy-efficient design of wireless communication systems.
Lastly, in order to get an idea of how wireless communication device companies handle issues of power consumption, we consulted with the wireless module engineers at Siemens Communication South Africa and present our findings on current practices in energy efficient protocol implementation.
3
Romeike, Ralf. "Output statt Input." Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2013/6431/.
Full textAbstract:
Die in der Fachdidaktik Informatik im Zusammenhang mit den Bildungsstandards seit Jahren diskutierte Outputorientierung wird mittelfristig auch für die Hochschullehre verbindlich. Diese Änderung kann als Chance aufgefasst werden, aktuellen Problemen der Informatiklehre gezielt entgegenzuwirken. Basierend auf der Theorie des Constructive Alignment wird vorgeschlagen, im Zusammenhang mit der Outputorientierung eine Abstimmung von intendierter Kompetenz, Lernaktivität und Prüfung vorzunehmen. Zusätzlich profitieren Lehramtsstudenten von den im eigenen Lernprozess erworbenen Erfahrungen im Umgang mit Kompetenzen: wie diese formuliert, erarbeitet und geprüft werden. Anforderungen an die Formulierung von Kompetenzen werden untersucht, mit Beispielen belegt und Möglichkeiten zur Klassifizierung angeregt. Ein Austausch in den Fachbereichen und Fachdidaktiken über die individuell festgelegten Kompetenzen wird vorgeschlagen, um die hochschuldidaktische Diskussion zu bereichern.
4
Tran, Tuan-Anh. "Multiple-input multiple-output optical wireless communications." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:094fbe23-88c3-49c4-b64b-a1de40674123.
Full textAbstract:
Visible-light optical wireless communications (OWC) is a potential technology that can help resolve the crowdedness of the radio-frequency bands, whilst conveniently exploiting energy-saving light-emitting diodes (LEDs) as transmitters for both illumination and communications. Since there usually are many LEDs in a lighting unit, OWC has a multi- input multi-output (MIMO) geometry which, thanks to its channel diversity, can offer wireless local networks at data-rates many times higher than possible with single-channel systems. In such systems, MIMO-detection methods to separate the different optical channels play an important role in improving the system performance by helping reduce cross-talk between channels. To measure the performance of a particular geometry for MIMO communications, a simulation study, reported in this thesis, found that, amongst the signal- independent metrics, the condition number may be used as a rough predictor of the performance, whilst the channel Signal-to-Interference-and-Noise Ratio (SINR) is the most appropriate for geometry assessment. Combined with the fact that the overall performance of a MIMO system is mostly dominated by its worst channel, this indicates that the most effective way to improve the system performance is to maximise the worst channel’s SINR. One of the possible solutions to improving the SINRs is to use holograms to steer the transmitter images such that their distributions over the photo-detectors reduce overlaps. As LEDs emit partially-coherent light, the beam steering has to be carried out with partially- coherent illumination. By using two lenses to parallelise and collect partially-coherent light before and after the hologram, respectively, the source and image intensity distributions, and the autocorrelation of the hologram can be related in a succinct mathematical relationship. This leads to the development of three computational algorithms based on the autocorrelation function to obtain a quantised hologram with the desired beam-steering capability. These algorithms have their cost functions and performance comparison done at the hologram plane instead of the image plane, which therefore takes less time than traditional image-based methods. Specifically, one of these algorithms is able to save significant time over both the other autocorrelation-based algorithms and the direct binary-search, by 33% and by 50% respectively. A simulation-based study and a corresponding experiment, both reported in this thesis, found that the one of the proposed algorithms had poor power efficiency, whilst the other two were both highly effective in generating digital holograms with precise and power-efficient beam-steering performance. Of these two algorithms, one had superior time performance and was likely the best of the three proposed autocorrelation-based algorithms for generating beam-steering holograms. MIMO-OWC simulation also demonstrated the capability of using beam-steering holograms to design the channel and improve the system performance. Combining reported findings, a strategy can be devised to optimise the throughput of an imaging MIMO-OWC system for a given transmitted power.
5
Liu, Shuiyin. "Lattice decoding for multi-input multi-output communications." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9248.
Full textAbstract:
This thesis is concerned with decoding for wireless communications. In particular, computationally efficient lattice decoding algorithms are exploited to further improve the system performance. Based on this idea, five technical chapters are presented in this thesis. In Chapter 2, we propose novel lattice decoding based on segment Lenstra-Lenstra-Lovász (LLL) algorithm to further reduce the decoding complexity of coded Multiple-Input Multiple-Output (MIMO) cooperative channel. In particular, we extend the original segment LLL algorithm to the complex version, and prove that it can achieve the optimal diversity-multiplexing tradeoff (DMT). In Chapter 3, we present randomized lattice decoding based on Klein's sampling technique, which is a randomized version of Babai's nearest plane algorithm (i.e., successive interference cancellation). We analyze and optimize the performance of randomized lattice decoding resulting in reduced decoding complexity, and propose a very efficient implementation of random rounding. Chapter 4 is concerned with bounded distance decoding (BDD) based embedding technique. The embedding technique is used to reduce the γ-BDD problem to 1/(2γ)-unique shortest vector problem 1/(2γ)-uSVP). WE prove that the Lenstra, Lenstra and Lovász (LLL) algorithm can achieve 1/(2γ)-BDD for γ ≈ O(2n) for embedding decoding. We also prove that BDD of the regularized lattice is optimal in terms of the DMT. In Chapter 5, we present a detailed study of the soft output MIMO decoding. We show that the randomized decoding algorithm is an efficient way to compute soft output. In order to improve soft output quality, we propose variants of soft output decoding based on the sampling technique and embedding technique. Moreover, we derive a lower bound on the search radius for which list-based decoding can provide a near optimal solution to soft output. In Chapter 6, the performance limits of lattice reduction-aided precoding are investigated. The proximity factor is defined to measure the worst-case transmission power gap to sphere precoding. The second moment over precoding region is defined to measure the average-case transmission power loss. Afterward, low dimension lattice precoding is proposed to further reduce the transmission power.
6
Dambul, Katrina D. "Multiple-input multiple-output (MIMO) in optical wireless communications." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558676.
Full textAbstract:
There is growing demand for indoor wireless communication systems with higher bandwidth and higher data rates. However, the crowded radio frequency (RF) spectrum has caused researchers to consider optical wireless systems. In this thesis, optical signals in the visible region of the spectrum are used. White LEDs are used as transmitters as they provide higher signal-to-noise (SNR) levels and a better link budget than the infrared alternative. Typical modulation bandwidths for white LEDs are limited to tens of MHz. Thus, multiple-input multiple-output (MIMO) transmission is considered as a means to increase data rate. The development of the indoor optical wireless MIMO system begins with the geometrical and mathematical analysis of a single-input single-output (SISO) system and a single-input multiple- output (SIMO) system. The same analysis is then performed for a MIMO system. For the MIMO system, an experimental demonstration using white LEDs and non-imaging receivers are reported. Results include coverage measurements and an SNR analysis. There are limitations using non- imaging receivers, such as coverage limitations and symmetry problems, which cause problem with signal recovery. To improve these limitations, imaging receivers are considered. The design and development of an experimental demonstration of an indoor optical wireless MIMO system with an imaging receiver is presented. The experimental setup consists of a transmitter with a 2 x 2 array of white LEDs and a receiver with a 3 x 3 photo detector array. The system transmits data at a bit rate of 2Mbit/s/channel. Detailed design specifications and optical design are presented. Results show that certain positions within the system coverage area have error-free operation. The BER and SNR analysis shows that the overall BER improves with the overall SNR. In order to exploit the full potential of the system, future work should focus on improving the SNR and BER of the system.
7
Najam, Ali Imran. "Multiple-input multiple-output antennas for ultra wideband communications." Grenoble INPG, 2010. http://www.theses.fr/2010INPG0043.
Full textAbstract:
La radio Ultra Large Bande (ULB) promet de nouveaux marchés dans les domaines des réseaux personnels hauts débits et de capteurs. De sorte à améliorer la robustesse du lien radio et le débit, l’association des techniques MIMO à l’ULB a été envisagée. En vue d’une réalisation pratique, un challenge fondamental reste la conception des antennes qui doivent répondre aux contraintes de l’ULB et des systèmes multi-antennaires, et aux contraintes physiques et économiques. Dans ce contexte, plusieurs nouveaux designs d’antennes MIMO ULB sont proposés. Leur caractérisation s’appuie sur les paramètres conventionnels utilisés en conception d’antennes ainsi que des paramètres spécifiques à l’ULB et au MIMO. En particulier, un nouveau design compact présentant une forte isolation grâce à l’insertion d’un stub sur le plan de masse est proposé. Une nouvelle méthode de modélisation du couplage mutuel, qui présente l’avantage d’offrir de nouvelles approches pour le compenser, est également introduiteUWB technology has rapidly emerged in the areas of WPAN and sensors networks featuring high data rate communications. The applications of UWB are limited to very short-range communications due to the extremely low transmitted power. The combination of MIMO techniques with UWB has been considered as a solution to improve the range. However, a fundamental challenge arises for the design of antennas that faces the constraints offered by UWB systems and multi-antennas systems, and the constraints of size and cost. In this context, several new UWB-MIMO antennas are proposed. Their characterization is based on the parameters relevant to conventional antenna design and the specific parameters relevant to the UWB-MIMO antenna design. In particular, a new compact design with high isolation by inserting the inverted-Y shaped stub on the ground plane is proposed. A new method for modelling the mutual coupling, is also introduced which has the advantage of offering new approach to compensate it
8
Löfving, Erik. "Organizing physical flow data : from input-output tables to data warehouses /." Linköping : Dept. of Mathematics, Univ, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/stat5s.pdf.
Full text
9
Coskun, Adem. "Downlink Transmission Techniques For Multi User Multi Input Multi Output Wireless Communications." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608750/index.pdf.
Full textAbstract:
Multi-user MIMO (MIMO-MU) communication techniques make use of available channel state information at the transmitter to mitigate the inter-user interference. The goal of these techniques is to provide the least interference at the mobile stations by applying a precoding operation. In this thesis a comparison of available techniques in the literature such as Channel Decomposition, SINR Balancing, Joint-MMSE optimization is presented. Novel techniques for the MIMO multi-user downlink communication systems, where a single stream is transmitted to each user are proposed. The proposed methods, different from the other methods in the literature, use a simple receiver to combat the interference. It has been shown that MRC based receivers are as good as more complicated joint MMSE receivers.
10
Khalid, Farhan [Verfasser]. "Hybrid Precoding for Multiuser Multiple-Input Multiple-Output Mobile Communications / Farhan Khalid." Aachen : Shaker, 2013. http://d-nb.info/1051575907/34.
Full text
11
Schneider, Daniel [Verfasser]. "Inhome Power Line Communications using Multiple Input Multiple Output Principles / Daniel Schneider." München : Verlag Dr. Hut, 2012. http://d-nb.info/1022535307/34.
Full text
12
Yu, Kai. "Modeling of Multiple-Input Multiple-Output Radio Propagation Channels." Licentiate thesis, KTH, Signals, Sensors and Systems, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1478.
Full textAbstract:
In recent years, multiple-input multiple-output (MIMO)systems appear to be very promising since they can provide highdata rates in environments with sucient scattering byexploiting the spatial domain. To design a real MIMO wirelesssystem and predict its performance under certain circumstances,it is necessary to have accurate MIMO wireless channel modelsfor dierent scenarios. This thesis presents dierent models forindoor MIMO radio propagation channels based on 5.2 GHz indoorMIMO channel measurements.The recent research on MIMO radio channel modeling isbriey reviewed in this thesis. The models are categorized intonon-physical and physical models. The non-physical modelsprimarily rely on the statistical characteristics of MIMOchannels obtained from the measured data while the physicalmodels describe the MIMO channel (or its distribution) via somephysical parameters. The relationships between dierent modelsare also discussed.For the narrowband case, a non line-of-sight (NLOS)indoor MIMO channel model is presented. The model is based on aKronecker structure of the channel covariance matrix and thefact that the channel is complex Gaussian. It is extended tothe line-of-sight (LOS) scenario by estimating and modeling thedominant component separately.As for the wideband case, two NLOS MIMO channel modelsare proposed. The rst model uses the power delay prole and theKronecker structure of the second order moments of each channeltap to model the wideband MIMO channel while the second modelcombines a simple single-input single-output (SISO) model withthe same Kronecker structure of the second order moments.Monte-Carlo simulations are used to generate indoor MIMOchannel realizations according to the above models. The resultsare compared with the measured data and good agreement has beenobserved.
13
Hernańdez, Correa Evelio. "Control of nonlinear systems using input-output information." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/11176.
Full text
14
Li, Ran. "Optical multiple input and multiple output (MIMO) in multimode fibre." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:1770da43-e93b-462b-866f-beb5f972ce06.
Full textAbstract:
Recently, there has been a dramatic increase in the amount of data transmission within short range local area networks (LAN). Multimode fibre (MMF) is widely used in local area networks because of its coupling and alignment along with the low cost of related components. Graded index MMF has become common due to the reduction in pulse spreading; however, as demands for high bandwidth increase towards a future gigabit rate network, the typical MMF using conventional transmission methods will not be suitable. Meanwhile, this increasing demand for high speed data transmission will soon reach the Shannon capacity limit of single mode fibres. After multiple input and multiple output (MIMO) technology was successfully used in wireless communication, the researcher realised that the same idea could also be applied to an optical fibre network. Optical MIMO techniques are gaining interest in order to create parallel channels over orthogonal modes in a MMF or a few mode fibre (FMF). This approach could lead to a significant increase in the bandwidth distance product and be employed in the next 40Gb/s or even 100Gb/s optical fibre transmission systems. Generally speaking, optical MIMO appears to be the best solution to the bandwidth limitation problem in either short distance MMF or long distance FMF systems. This thesis focuses on designing a simple, cost-effective, and energy efficient optical MIMO system based on MMFs. This proposed system can be realised by combining radial offset launching and annular multi-segment detectors. First, in the initial work, we performed a theoretical and numerical study of the key impairments of MMFs, and the mode propagation in an MMF was analysed mathematically. The variation in electrical field intensity for linearly polarised (LP) modes in the core region of an MMF and the analytical solutions for power coupling coefficients in either radial offset launching or centre launching were presented. In addition, the modal time delays, impulse response, and transfer function were all introduced. Subsequently, the near field intensity pattern (NFP) was simulated at the output facet of the MMF, which indicated that the overall NFP suffered from blurring when it contained mode mixing, and that the intensity pattern was particularly sensitive to the random phase. According to the spatial distribution of the NFP, the annular detector can be exploited more efficiently. All of the results were calculated and plotted using the MATLAB program. Secondly, the optical MIMO model in the multimode fibre was briefly summarised, including the MIMO channel matrix H expression, a mathematical expression of optical MIMO capacity, MIMO channel estimation and an equalization method. Two metrics can be used to characterise the MIMO channel performance: condition number and crosstalk at each receiver. The numerical results demonstrated that the new type of annular multi-segment detector exhibits superior performance compared to the conventional multiple single mode fibre (SMF) detectors, making them attractive for future optical MIMO systems. Finally, the core work of this thesis can be divided into two parts: the modelling of a 10Gb/s intensity modulation direct detection (IM-DD) optical MIMO MMF system; and the modelling of an advanced 10Gb/s coherent differential phase shift keying (DPSK) MIMO FMF system. In both simulation systems, the important transmission parameters of intra-group mode mixing, modal dispersion, chromatic dispersion, and mode attenuation were considered and discussed in detail. In the IM-DD optical MIMO system, the optimization of the transceiver can be based upon the laser spot size and the power flux distribution emitted by the transmitter. Results from the simulation showed that the intra-group mode mixing had a limited impact on system performance, and due to its inability to compensate for linear impairments, the IM-DD optical MIMO was not favourable for long distance transmission systems. Nevertheless, the new type of optical fibre FMF seems to be the most promising candidate for use in long haul transmission systems. Therefore, the well-known DPSK modulation format in conjugation with the coherent detection deployed in FMF was studied. Both heterodyne and intradyne detection schemes were analysed followed by mathematical derivation and numerical simulation; the results illustrated that similar system performances can be achieved in both schemes. Meanwhile, the coherent DPSK simulation results also demonstrated that the linear impairments were almost compensated by the frequency domain MIMO equalization process, which resulted in system performance being independent to transmission distance for up to 10km. This advantage proved that the coherent optical DPSK MIMO system can be employed in long haul networks. As with an IM-DD optical MIMO system, optimization of a coherent MIMO system was also possible. However, in contrast to the optimization of an IM-DD MIMO system, a trade-off had to be made between sufficient spatial diversity at the transceiver and differential modal delay caused by modal dispersion; consequently, the numerical results showed that the proposed coherent optical DPSK MIMO gained reasonable good results without using any active device, such as a spatial light modulator and a mode converter. In conclusion, this proposed optical MIMO system provided easy implementation and integration and is feasible for use in future optical communication systems.
15
Martin, Tracy A. "Analysis and simulation of disadvantaged receivers for multiple-input multiple-output communications systems." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5188.
Full textAbstract:
Approved for public release; distribution is unlimitedThis thesis investigates the simulation performance of Multiple-Input Multiple-Output (MIMO) communication systems. Uncoded narrowband and wideband MIMO systems are presented and simulated. The system is further refined with the addition of Space-Time Codes (STC) and Channel State Information at the Transmitter (CSIT). A disadvantaged receiver is subsequently introduced to the system lacking the optimization enjoyed by the native receiver. Simulation and analysis was conducted with multiple modulation schemes and antenna configurations. Rayleigh and Rician fading models are developed and simulated as the wireless channel. Receiver performance results based on MATLAB simulation are compared and presented.
16
Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
Full textAbstract:
The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated.
17
Emami, Forooshani Arghavan. "Configuration of multiple input multiple output antenna arrays for wireless communications in underground mines." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44951.
Full textAbstract:
In recent years, the underground mining community has begun to embrace standards-based short-range wireless communications technology as a key part of their strategy for enhancing the safety and productivity of their operations. Here, we show how the significant differences between wireless propagation in conventional surface environments and underground mines affect the design of modern wireless communications systems based upon multiple-input multiple-output (MIMO) antenna array technology. In order to achieve this goal, we have employed a variety of approaches to characterize wireless propagation (and MIMO-based wireless system performance) in underground environments representative of those found in modern hard rock mines, including: 1) field measurements collected using a custom-designed channel sounder in both a building service tunnel at the University of British Columbia and an underground lead-zinc mine at Myra Falls, BC, 2) simulations based upon ray-tracing in representative environments and 3) theoretical models based upon waveguide mode expansion in representative environments. We have used the results obtained: 1) to determine the reduction in the angular spread of multipath signals that arrive at the receiver in an underground mine compared to that observed in conventional surface environments and the manner in which it decreases with increasing transmitter-receiver separation and 2) to show that the antenna elements in MIMO antenna arrays used in underground environments must therefore be separated by several wavelengths (rather than the customary half-wavelength used in surface environments) in order to achieve acceptable performance. Further, the separation between the antennas must increase as the transmitter-receiver separation increases, higher order modes attenuate and, as a consequence, angular spread decreases. Other outcomes of this work include: 1) demonstration that the power azimuth spectrum (PAS) in underground mine environments can be modeled by a Gaussian distribution and 2) development of a novel technique based upon particle swarm optimization (PSO) for assessing and optimizing the performance of distributed-MIMO antenna systems in underground mine environments.
18
Sarris, Ioannis. "Multiple-input multiple-output communications at 5.2 and 60 GHz in line-of-sight conditions." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440008.
Full text
19
Garriga, Berga Carles. "A New Approach to the Synthesis of Fuzzy Systems from Input-Output Data." Doctoral thesis, Universitat Ramon Llull, 2005. http://hdl.handle.net/10803/9147.
Full textAbstract:
Fuzzy logic has been applied successfully to systems modeling for ages. One of its main advantages is that it provides an understandable knowledge representation. Nevertheless, most investigations have focused their efforts on achieving accurate models and by doing so, they have omitted the linguistic capabilities of fuzzy logic.This thesis researches into the issues related to intelligible fuzzy models, because since science demonstrated the use of fuzzy logic when searching optimal models in terms of error (in fact a fuzzy model is a universal approximator), some but few investigators have focused their efforts in order to achieve really intelligible models in spite of losing some accuracy.
In this work we propose a whole methodology able to find an intelligible fuzzy model in a local manner (rule by rule) from input-output data. In this sense we find the number and position of the necessary fuzzy sets and also the linguistic rules related to them. For this purpose we have developed a hierarchical process which takes into account several steps and techniques, some of which are original contributions.
The resulting method is very simple and also intelligible. Therefore, this solution performs the final models with a low computational cost, but furthermore, allows the tuning of its different options depending on the nature of the problem and the characteristics of the users.
In this thesis we explain the whole methodology and illustrate its advantages (but also its problems) with several examples which are benchmarks in most cases.
20
Bailey, Alastair S. "The estimation of input-output coefficients for agriculture from whole farm accounting data." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320135.
Full text
21
Wang, Jingming. "A recursive least-squares ASIC for broadband 8 x 8 multiple-input multiple-output wireless communications." Diss., Restricted to subscribing institutions, 2005. http://uclibs.org/PID/11984.
Full text
22
Welmers, Laura Hazel. "The implementation of an input/output consistency checker for a requirements specification document." Thesis, Kansas State University, 1985. http://hdl.handle.net/2097/9889.
Full text
23
YAMAMOTO, Shuichiro. "Reconstructing Data Flow Diagrams from Structure Charts Based on the Input and Output Relationship." Institute of Electronics, Information and Communication Engineers, 1995. http://hdl.handle.net/2237/15017.
Full text
24
Yang, Shaoshi. "Detection for multiple-input multiple-output systems : probabilistic data association and semidefinite programming relaxation." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/360710/.
Full textAbstract:
As a highly effective physical-layer interference management technique, the joint detection of a vector of non-orthogonal information-bearing symbols simultaneously transmitted over multiple-input multiple-output (MIMO) channels is of fundamental importance for high throughput digital communications. This is because the generic mathematical model of MIMO detection underpins a wide range of relevant applications including (but not limited to) the equalization of dispersive band-limited channels imposing intersymbol interference (ISI), the multiuser detection (MUD) in code-division multiple-access (CDMA) systems and the multi-stream detection for multiple-antenna based spatial-division multiplexing (SDM) systems. With the evolution of wireless networks, the “virtual MIMO” concept was conceived,which is also described by the generic mathematical MIMO model. MIMO detection becomes even more important, because the achievable performance of spectrum-efficient wireless networks is typically interference-limited, rather than noise-limited. In this thesis, a pair of detection methods that are well-suited for large-scale MIMO systems are investigated. The first one is the probabilistic data association (PDA) algorithm, which is essentially an interference-modelling approach based on iterative Gaussian approximation. The second one is the semidefinite programming (SDP) relaxation based approach, which approximates the optimal maximum likelihood (ML) detection problem to a convex optimization problem. The main advantage of both methods is that they impose a moderate computational complexity that increases as a polynomial function of the problem size, while providing competitive performance. The contributions of this thesis can be broadly categorized into two groups. The first group is related to the design of virtually antipodal (VA) detection of rectangular M-ary quadrature amplitude modulation (M-QAM) symbols transmitted in SDM-MIMO systems. As a foundation, in the first parts of Chapter 2 and Chapter 3 the rigorous mathematical relationship between the vector space of transmitted bits and that of transmitted rectangular M-QAM symbols is investigated. Both linear and nonlinear bit-to-symbol mappings are considered. It is revealed that the two vector spaces are linked by linear/quasi-linear transformations, which are explicitly characterized by certain transformation matrices. This formulation may potentially be applicable to many signal processing problems of wireless communications. For example, when used for detection of rectangular M-QAM symbol vector, it enables us to transform the conventional three-step “signal-to-symbol-to-bits” decision process to a direct “signal-to-bits” decision process. More specifically, based on the linear VA transformation, in Chapter 2 we propose a unified bit-based PDA (B-PDA) detection method for linear natural mapping aided rectangular M-QAM symbols transmitted in SDM-MIMO systems. We show that the proposed linear natural mapping based B-PDA approach attains an improved detection performance, despite dramatically reducing the omputational complexity in contrast to the conventional symbol-based PDA detector. Furthermore, in Chapter 3 a quasi-linear VA transformation based generalized low-complexity semidefinite programming relaxation (SDPR) detection approach is proposed for Gray-coded rectangular M-QAM signalling over MIMO channels. Compared to the linear natural mapping based B-PDA of Chapter 2, the quasi-linear VA transformation based SDPR method is capable of directly deciding on the information bits of the ubiquitous Gray-mapping aided rectangular M-QAM by decoupling the M-QAM constellation into several 4-QAM constellations. Moreover, it may be readily combined with the low-complexity bit-flipping based “hill climbing” technique for exploiting the unequal error protection (UEP) property of rectangular M-QAM, and the resultant VA-SDPR detector achieves the best bit-error rate (BER) performance among the known SDPR-based MIMO detectors conceived for high-order QAM constellations, while still maintaining the same order of polynomial-time worst-case computational complexity. Additionally, we reveal that the linear natural mapping based VA detectors attain the same performance provided by the binary reflected Gray mapping based VA detectors, but the former are simpler for implementation. Therefore, only if there are other constraints requiring using the nonlinear Gray mapping, it is preferable to use the linear natural mapping rather than the Gray mapping, when the VA detectors are used in uncoded MIMO systems. The second group explores the application of the PDA-aided detectors in some more sophisticated systems that are of great interest to the wireless research community. In particular, the design of iterative detection and decoding (IDD) schemes relying on the proposed low complexity PDA methods is investigated for the turbo-coded MIMO systems in Chapter 4 and 5. It has conventionally been regarded that the existing PDA algorithms output the estimated symbol-wise a posteriori probabilities (APPs) as soft information. In Chapter 4 and 5, however, we demonstrate that these probabilities are not the true APPs in the rigorous mathematical sense, but a type of nominal APPs, which are unsuitable for the classic architecture of IDD receivers. Moreover, our study shows that the known methods of calculating the bit-wise extrinsic logarithmic likelihood ratios (LLRs) are no longer applicable to the conventional PDA based methods when detecting M-ary modulation symbols. Additionally, the existing PDA based MIMO detectors typically operate purely in the probabilistic domain. Therefore, the existing PDA methods are not readily applicable to IDD receivers. To overcome this predicament, in Chapter 4 and Chapter 5 we propose the approximate Bayes’ theorem based logarithmic domain PDA (AB-Log-PDA) and the exact Bayes’ theorem based logarithmic domain PDA (EB-Log-PDA) detectors, respectively. We present the approaches of calculating the bit-wise extrinsic LLRs for both the AB-Log-PDA and the EB-Log-PDA, which makes them well-suited for IDD receivers. Furthermore, we demonstrate that invoking inner iterations within the PDA algorithms – which is common practice in PDA-aided uncoded MIMO systems – would actually degrade the IDD receiver’s performance, despite significantly increasing its overall computational complexity. Additionally, we investigate the relationship between the extrinsic LLRs of the proposed EB-Log-PDA and of the AB-Log-PDA. It is also shown that both the proposed AB-Log-PDA- and the EB-Log-PDA-based IDD schemes dispensing with any inner PDA iterations are capable of achieving a performance comparable to that of the optimal maximum a posteriori (MAP) detector based IDD receiver in the scenarios considered, despite their significantly lower computational complexity. Finally, in Chapter 6, a base station (BS) cooperation aided distributed soft reception scheme using the symbol-based PDA algorithm and soft combining (SC) is proposed for the uplink of multiuser multicell MIMO systems. The realistic 19-cell hexagonal cellular model relying on radical unity frequency reuse (FR) is considered, and local cooperation based message passing is used instead of a global message passing chain for the sake of reducing the backhaul traffic. We show that despite its moderate complexity and backhaul traffic, the proposed distributed PDA (DPDA) aided SC (DPDA-SC) reception scheme significantly outperforms the conventional non-cooperative benchmarkers. Furthermore, since only the index of the quantized converged soft information has to be exchanged between collaborative BSs for SC, the proposed DPDA-SC scheme is relatively robust to the quantization errors of the soft information exchanged. As an appealling benefit, the backhaul traffic is dramatically reduced at a negligible performance degradation.
25
Codreanu, M. (Marian). "Multidimensional adaptive radio links for broadband communications." Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514286223.
Full textAbstract:
Abstract
Advanced multiple-input multiple-output (MIMO) transceiver structures which utilize the knowledge of channel state information (CSI) at the transmitter side to optimize certain link parameters (e.g., throughput, fairness, spectral efficiency, etc.) under different constraints (e.g., maximum transmitted power, minimum quality of services (QoS), etc.) are considered in this thesis.
Adaptive transmission schemes for point-to-point MIMO systems are considered first. A robust link adaptation method for time-division duplex systems employing MIMO-OFDM channel eigenmode based transmission is developed. A low complexity bit and power loading algorithm which requires low signaling overhead is proposed.
Two algorithms for computing the sum-capacity of MIMO downlink channels with full CSI knowledge are derived. The first one is based on the iterative waterfilling method. The convergence of the algorithm is proved analytically and the computer simulations show that the algorithm converges faster than the earlier variants of sum power constrained iterative waterfilling algorithms. The second algorithm is based on the dual decomposition method. By tracking the instantaneous error in the inner loop, a faster version is developed.
The problem of linear transceiver design in MIMO downlink channels is considered for a case when the full CSI of scheduled users only is available at the transmitter. General methods for joint power control and linear transmit and receive beamformers design are provided. The proposed algorithms can handle multiple antennas at the base station and at the mobile terminals with an arbitrary number of data streams per scheduled user. The optimization criteria are fairly general and include sum power minimization under the minimum signal-to-interference-plus-noise ratio (SINR) constraint per data stream, the balancing of SINR values among data streams, minimum SINR maximization, weighted sum-rate maximization, and weighted sum mean square error minimization. Besides the traditional sum power constraint on the transmit beamformers, multiple sum power constraints can be imposed on arbitrary subsets of the transmit antennas.This extends the applicability of the results to novel system architectures, such as cooperative base station transmission using distributed MIMO antennas. By imposing per antenna power constraints, issues related to the linearity of the power amplifiers can be handled as well.
The original linear transceiver design problems are decomposed as a series of remarkably simpler optimization problems which can be efficiently solved by using standard convex optimization techniques. The advantage of this approach is that it can be easily extended to accommodate various supplementary constraints such as upper and/or lower bounds for the SINR values and guaranteed QoS for different subsets of users. The ability to handle transceiver optimization problems where a network-centric objective (e.g., aggregate throughput or transmitted power) is optimized subject to user-centric constraints (e.g., minimum QoS requirements) is an important feature which must be supported by future broadband communication systems.
26
Lamprecht, Erwin Cornelius. "Multiple-Input Single-Output system identification techniques using the pebble bed modular reactor data / E.C. Lamprecht." Thesis, North-West University, 2004. http://hdl.handle.net/10394/639.
Full textAbstract:
Models are used to describe the dynamic behaviour of a system, to predict
future outputs of the system and are useful when designing certain control
schemes.
An effective control scheme could be used to influence the dynamic behaviour
of a system in such a way that it exhibits more desirable dynamic behaviour.
A control system could be designed to increase the efficiency of a system.
This makes it obvious that accurate models are very useful.
The focus of this study is to use Multiple-Input Single-Output (MISO) system
identification techniques on data obtained from the Flownex simulation
package. These techniques are used to obtain a (MISO) mathematical model
for the Pebble Bed Modular Reactor (PBMR).
MISO system identification techniques are used in this project to study the
effect that the inputs have on each other. This information helps in the
understanding of processes within the system. The reason for studying the
MIS0 systems and not the Single-Input Single-Output (SISO) systems is
because the field of interest focuses on the effects the inputs have on each
other.Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2005.
27
Meterelliyoz, Kuyzu Melike. "Variance parameter estimation methods with re-use of data." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26490.
Full textAbstract:
Thesis (Ph.D)--Industrial and Systems Engineering, Georgia Institute of Technology, 2009.Committee Co-Chair: Alexopoulos, Christos; Committee Co-Chair: Goldsman, David; Committee Member: Kim, Seong-Hee; Committee Member: Shapiro, Alexander; Committee Member: Spruill, Carl. Part of the SMARTech Electronic Thesis and Dissertation Collection.
28
Schweizer, Andreas. "Analysis and optimisation of stable matching in combined input and output queued switches." Western Australian Telecommunications Research Institute, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0078.
Full textAbstract:
Output queues in network switches are known to provide a suitable architecture for scheduling disciplines that need to provide quality of service (QoS) guarantees. However, todays memory technology is incapable of meeting the speed requirements. Combined input and output queued (CIOQ) switches have emerged as one alternative to address the problem of memory speed. When a switch of this architecture uses a stable matching algorithm to transfer packets across the switch fabric, an output queued (OQ) switch can be mimicked exactly with a speedup of only two. The use of a stable matching algorithm typically requires complex and time-consuming calculations to ensure the behaviour of an OQ switch is maintained. Stable matching algorithms are well studied in the area in which they originally appeared. However, little is presently known on how the stable matching algorithm performs in CIOQ switches and how key parameters are affected by switch size, traffic type and traffic load. Knowledge of how these conditions affect performance is essential to judge the practicability of an architecture and to provide useful information on how to design such switches. Until now, CIOQ switches were likely to be dismissed due to the high complexity of the stable matching algorithm when applied to other applications. However, the characteristics of a stable matching algorithm in a CIOQ switch have not been thoroughly analysed. The principal goal of this thesis is to identify the conditions the stable matching algorithm encounters in a CIOQ switch under realistic operational scenarios. This thesis provides accurate mathematical models based on Markov chains to predict the value of key parameters that affect the complexity and runtime of a stable matching algorithm in CIOQ switches. The applicability of the models is then backed up by simulations. The results of the analysis quantify critical operational parameters, such as the size and number of preference lists and runtime complexity. These provide detailed insights into switch behaviour and useful information for switch designs. Major conclusions to be drawn from this analysis include that the average values of the key parameters of the stable matching algorithm are feasibly small and do not strongly correlate with switch size, which is contrary to the behaviour of the stable matching ii algorithm in its original application. Furthermore, although these parameters have wide theoretical ranges, the mean values and standard deviations are found to be small under operational conditions. The results also suggest that the implementation becomes very versatile as the completion time of the stable matching algorithm is not strongly correlated to the network traffic type; that is, the runtime is minimally affected by the nature of the traffic.
29
Labrador, Yuri. "Orthogonal Frequency Division Multiplexing Based Air Interfaces and Multiple Input Multiple Output Techniques in Cooperative Satellite Communications for 4th Generation Mobile Systems." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/107.
Full textAbstract:
Recently, wireless network technology has grown at such a pace that scientific research has become a practical reality in a very short time span. One mobile system that features high data rates and open network architecture is 4G. Currently, the research community and industry, in the field of wireless networks, are working on possible choices for solutions in the 4G system. The researcher considers one of the most important characteristics of future 4G mobile systems the ability to guarantee reliable communications at high data rates, in addition to high efficiency in the spectrum usage. On mobile wireless communication networks, one important factor is the coverage of large geographical areas. In 4G systems, a hybrid satellite/terrestrial network is crucial to providing users with coverage wherever needed. Subscribers thus require a reliable satellite link to access their services when they are in remote locations where a terrestrial infrastructure is unavailable. The results show that good modulation and access technique are also required in order to transmit high data rates over satellite links to mobile users. The dissertation proposes the use of OFDM (Orthogonal Frequency Multiple Access) for the satellite link by increasing the time diversity. This technique will allow for an increase of the data rate, as primarily required by multimedia applications, and will also optimally use the available bandwidth. In addition, this dissertation approaches the use of Cooperative Satellite Communications for hybrid satellite/terrestrial networks. By using this technique, the satellite coverage can be extended to areas where there is no direct link to the satellite. The issue of Cooperative Satellite Communications is solved through a new algorithm that forwards the received data from the fixed node to the mobile node. This algorithm is very efficient because it does not allow unnecessary transmissions and is based on signal to noise ratio (SNR) measures.
30
Heasman, Ray Edward. "The implementation of a core architecture for geophysical data acquisition." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1005256.
Full textAbstract:
This thesis describes the design, development and implementation of the core hardware and software of a modular data acquisition system for geophysical data collection. The primary application for this system is the acquisition and realtime processing of seismic data captured in mines. This system will be used by a commercial supplier of seismic instrumentation, ISS International, as a base architecture for the development of future products. The hardware and software has been designed to be extendable and support distributed processing. The IEEE-1394 High Performance Serial Bus is used to communicate with other CPU modules or peripherals. The software includes a pre-emptive multitasking microkernel, an asynchronous mailbox-based message passing communications system, and a functional IEEE-1394 protocol stack. The reasons for the end design and implementation decisions are given, and the problems encountered in the development of this system are described. A critical assessment of the match between the requirements for the project and the functionality of the implementation is made.
31
Tai, Yiyang. "Machine Learning Uplink Power Control in Single Input Multiple Output Cell-free Networks." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279462.
Full textAbstract:
This thesis considers the uplink of cell-free single input multiple output systems, in which the access points employ matched-filter reception. In this setting, our objectiveis to develop a scalable uplink power control scheme that relies only on large-scale channel gain estimates and is robust to changes in the environment. Specifically, we formulate the problem as max-min and max-product signal-to-interference ratio optimization tasks, which can be solved by geometric programming. Next, we study the performance of supervised and unsupervised learning approaches employing a feed-forward neural network. We find that both approaches perform close to the optimum achieved by geometric programming, while the unsupervised scheme avoids the pre-computation of training data that supervised learning would necessitate for every system or environment modification.Den här avhandlingen tar hänsyn till upplänken till cellfria multipla utgångssystem med en enda ingång, där åtkomstpunkterna använder matchad filtermottagning. I den här inställningen är vårt mål att utveckla ett skalbart styrsystem för upplänkskraft som endast förlitar sig på storskaliga uppskattningar av kanalökningar och är robusta för förändringar i miljön. Specifikt formulerar vi problemet som maxmin och max-produkt signal-till-störningsförhållande optimeringsuppgifter, som kan lösas genom geometrisk programmering. Därefter studerar vi resultatet av övervakade och okontrollerade inlärningsmetoder som använder ett framåtriktat neuralt nätverk. Vi finner att båda metoderna fungerar nära det optimala som uppnås genom geometrisk programmering, medan det övervakade schemat undviker förberäkningen av träningsdata som övervakat inlärning skulle kräva för varje system- eller miljöändring.
32
Shtarkalev, Bogomil Iliev. "Single data set detection for multistatic Doppler radar." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10556.
Full textAbstract:
The aim of this thesis is to develop and analyse single data set (SDS) detection algorithms that can utilise the advantages of widely-spaced (statistical) multiple-input multiple-output (MIMO) radar to increase their accuracy and performance. The algorithms make use of the observations obtained from multiple space-time adaptive processing (STAP) receivers and focus on covariance estimation and inversion to perform target detection. One of the main interferers for a Doppler radar has always been the radar’s own signal being reflected off the surroundings. The reflections of the transmitted waveforms from the ground and other stationary or slowly-moving objects in the background generate observations that can potentially raise false alarms. This creates the problem of searching for a target in both additive white Gaussian noise (AWGN) and highly-correlated (coloured) interference. Traditional STAP deals with the problem by using target-free training data to study this environment and build its characteristic covariance matrix. The data usually comes from range gates neighbouring the cell under test (CUT). In non-homogeneous or non-stationary environments, however, this training data may not reflect the statistics of the CUT accurately, which justifies the need to develop SDS methods for radar detection. The maximum likelihood estimation detector (MLED) and the generalised maximum likelihood estimation detector (GMLED) are two reduced-rank STAP algorithms that eliminate the need for training data when mapping the statistics of the background interference. The work in this thesis is largely based on these two algorithms. The first work derives the optimal maximum likelihood (ML) solution to the target detection problem when the MLED and GMLED are used in a multistatic radar scenario. This application assumes that the spatio-temporal Doppler frequencies produces in the individual bistatic STAP pairs of the MIMO system are ideally synchronised. Therefore the focus is on providing the multistatic outcome to the target detection problem. It is shown that the derived MIMO detectors possess the desirable constant false alarm rate (CFAR) property. Gaussian approximations to the statistics of the multistatic MLED and GMLED are derived in order to provide a more in-depth analysis of the algorithms. The viability of the theoretical models and their approximations are tested against a numerical simulation of the systems. The second work focuses on the synchronisation of the spatio-temporal Doppler frequency data from the individual bistatic STAP pairs in the multistatic MLED scenario. It expands the idea to a form that could be implemented in a practical radar scenario. To reduce the information shared between the bistatic STAP channels, a data compression method is proposed that extracts the significant contributions of the MLED likelihood function before transmission. To perform the inter-channel synchronisation, the Doppler frequency data is projected into the space of potential target velocities where the multistatic likelihood is formed. Based on the expected structure of the velocity likelihood in the presence of a target, a modification to the multistatic MLED is proposed. It is demonstrated through numerical simulations that the proposed modified algorithm performs better than the basic multistatic MLED while having the benefit of reducing the data exchange in the MIMO radar system.
33
Choi, Seung-Ho. "Severely Fading MIMO Channels." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1190.
Full textAbstract:
In most wireless communications research, the channel models considered experience less severe fading than the classic Rayleigh fading case. In this thesis, however, we investigate MIMO channels where the fading is more severe. In these environments, we show that the coefficient of variation of the channel amplitudes is a good predictor of the link mutual information, for a variety of models. We propose a novel channel model for severely fading channels based on the complex multivariate t distribution. For this model, we are able to compute exact results for the ergodic mutual information and approximations to the outage probabilities for the mutual information. Applications of this work include wireless sensors, RF tagging, land-mobile, indoor-mobile, ground-penetrating radar, and ionospheric radio links. Finally, we point out that the methodology can also be extended to evaluate the mutual information of a cellular MIMO link and the performance of various MIMO receivers in a cellular scenario. In these cellular applications, the channel itself is not severely fading but the multivariate t distribution can be applied to model the effects of intercellular interference.
34
Bhogi, Keerthana. "Two New Applications of Tensors to Machine Learning for Wireless Communications." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104970.
Full textAbstract:
With the increasing number of wireless devices and the phenomenal amount of data that is being generated by them, there is a growing interest in the wireless communications community to complement the traditional model-driven design approaches with data-driven machine learning (ML)-based solutions. However, managing the large-scale multi-dimensional data to maintain the efficiency and scalability of the ML algorithms has obviously been a challenge. Tensors provide a useful framework to represent multi-dimensional data in an integrated manner by preserving relationships in data across different dimensions. This thesis studies two new applications of tensors to ML for wireless communications where the tensor structure of the concerned data is exploited in novel ways.
The first contribution of this thesis is a tensor learning-based low-complexity precoder codebook design technique for a full-dimension multiple-input multiple-output (FD-MIMO) system with a uniform planar antenna (UPA) array at the transmitter (Tx) whose channel distribution is available through a dataset. Represented as a tensor, the FD-MIMO channel is further decomposed using a tensor decomposition technique to obtain an optimal precoder which is a function of Kronecker-Product (KP) of two low-dimensional precoders, each corresponding to the horizontal and vertical dimensions of the FD-MIMO channel. From the design perspective, we have made contributions in deriving a criterion for optimal product precoder codebooks using the obtained low-dimensional precoders. We show that this product codebook design problem is an unsupervised clustering problem on a Cartesian Product Grassmann Manifold (CPM), where the optimal cluster centroids form the desired codebook. We further simplify this clustering problem to a $K$-means algorithm on the low-dimensional factor Grassmann manifolds (GMs) of the CPM which correspond to the horizontal and vertical dimensions of the UPA, thus significantly reducing the complexity of precoder codebook construction when compared to the existing codebook learning techniques.
The second contribution of this thesis is a tensor-based bandwidth-efficient gradient communication technique for federated learning (FL) with convolutional neural networks (CNNs). Concisely, FL is a decentralized ML approach that allows to jointly train an ML model at the server using the data generated by the distributed users coordinated by a server, by sharing only the local gradients with the server and not the raw data. Here, we focus on efficient compression and reconstruction of convolutional gradients at the users and the server, respectively. To reduce the gradient communication overhead, we compress the sparse gradients at the users to obtain their low-dimensional estimates using compressive sensing (CS)-based technique and transmit to the server for joint training of the CNN. We exploit a natural tensor structure offered by the convolutional gradients to demonstrate the correlation of a gradient element with its neighbors. We propose a novel prior for the convolutional gradients that captures the described spatial consistency along with its sparse nature in an appropriate way. We further propose a novel Bayesian reconstruction algorithm based on the Generalized Approximate Message Passing (GAMP) framework that exploits this prior information about the gradients. Through the numerical simulations, we demonstrate that the developed gradient reconstruction method improves the convergence of the CNN model.Master of Science
The increase in the number of wireless and mobile devices have led to the generation of massive amounts of multi-modal data at the users in various real-world applications including wireless communications. This has led to an increasing interest in machine learning (ML)-based data-driven techniques for communication system design. The native setting of ML is {em centralized} where all the data is available on a single device. However, the distributed nature of the users and their data has also motivated the development of distributed ML techniques. Since the success of ML techniques is grounded in their data-based nature, there is a need to maintain the efficiency and scalability of the algorithms to manage the large-scale data. Tensors are multi-dimensional arrays that provide an integrated way of representing multi-modal data. Tensor algebra and tensor decompositions have enabled the extension of several classical ML techniques to tensors-based ML techniques in various application domains such as computer vision, data-mining, image processing, and wireless communications. Tensors-based ML techniques have shown to improve the performance of the ML models because of their ability to leverage the underlying structural information in the data. In this thesis, we present two new applications of tensors to ML for wireless applications and show how the tensor structure of the concerned data can be exploited and incorporated in different ways. The first contribution is a tensor learning-based precoder codebook design technique for full-dimension multiple-input multiple-output (FD-MIMO) systems where we develop a scheme for designing low-complexity product precoder codebooks by identifying and leveraging a tensor representation of the FD-MIMO channel. The second contribution is a tensor-based gradient communication scheme for a decentralized ML technique known as federated learning (FL) with convolutional neural networks (CNNs), where we design a novel bandwidth-efficient gradient compression-reconstruction algorithm that leverages a tensor structure of the convolutional gradients. The numerical simulations in both applications demonstrate that exploiting the underlying tensor structure in the data provides significant gains in their respective performance criteria.
35
Gopala, Kalyana. "Multiple Antenna Communications for 5G." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS352.
Full textAbstract:
Duplexage par division dans le temps (TDD) Massive Multiple Input Multiple Output (MaMIMO) dépend de la réciprocité de canal pour obtenir des informations d'état de canal au niveau de l'émetteur (CSIT). Toutefois, le canal numérique global de bout en bout n’est pas réciproque en raison de la présence de chaînes de transmission (Tx) et de réception (Rx), qui doivent être corrigées à l’aide de facteurs de calibration. Nous fournissons une expression simple et élégante du Cramér-Rao Bound (CRB) pour l’estimation des paramètres de calibration. Nous analysons des approches des moindres carrés existants et proposons des algorithmes optimaux. Nous considérons également la beamforming pour une liaison MIMO point à point variant rapidement dans le temps. Dans un système Orthogonal Frequency Division Multiplexing (OFDM), il en résulte une interférence entre porteuses (ICI). Avec une hypothèse de variation linéaire de canal à travers le symbole OFDM, il a été observé que le problème est similaire à celui d'une conception de beamformer MIMO par canal de diffusion à interférence (IBC). Le design du beamformer prend en compte le fenêtrage de réception en utilisant le préfixe cyclique en excès. En plus de la CSIT complète, nous étudions également des approches qui maximisent le Expected Weighted Sum Rate (EWSR) lorsque la Tx n’a qu’une connaissance partielle du canal. Premièrement, nous utilisons une approximation de système large qui fonctionne également bien pour un petit nombre d’antennes Tx et Rx. Nous analysons également la possibilité d’utiliser la métrique Expected-signal-expected-interference-WSR de signal EWSR. Enfin, les résultats expérimentaux sont présentésTime Division Duplexing (TDD) Massive Multiple Input Multiple Output (MaMIMO) with a massive number of base station (BS) antennas relies on channel reciprocity to obtain Channel State Information at Transmitter (CSIT). However the overall end to end digital channel is not reciprocal due to the presence of Transmit (Tx) and Receive (Rx) chains which need to be corrected using calibration factors. Our work provides a simple and elegant expression of the Cramer Rao Bound (CRB) for calibration parameter estimation. We provide analysis for the existing least squares approaches and propose optimal algorithms to estimate the calibration parameters. We also consider beamforming for a rapidly time-varying point to point MIMO link. In an Orthogonal Frequency Division Multiplexing (OFDM) sytem, this results in inter-carrier interference (ICI). With an assumption of linear channel variation across the OFDM symbol, it is observed that the beamformer design problem is similar to that of a MIMO Interfering Broadcast Channel (IBC) beamforming design. The beamformer design takes into account receive windowing using the excess cyclic prefix and the window is jointly designed with the Tx beamformer. In addition to full CSIT, we also investigate partial CSIT approaches that maximize Expected Weighted Sum Rate (EWSR) where the Tx has only partial knowledge of the channel. First, we use a large system approximation that also works well for a small number of Tx and Rx antennas to derive the beamformers. In our work, we also analyze the possibility of using the Expected-signal- expected-interference-WSR metric instead of the EWSR. Finally, experimental results on the Eurecom MaMIMO testbed are presented
36
Cheng, Kin On. "A multi-stage optical switch with output buffer using WDM for delay lines sharing /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20CHENG.
Full textAbstract:
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 77-79). Also available in electronic version. Access restricted to campus users.
37
Fischer, Elisabeth [Verfasser]. "Teaching Quality in Higher Education : A Field Study Investigating Effects between Input, Process, and Output Variables Using Multiple Data Sources / Elisabeth Fischer." Kassel : Universitätsbibliothek Kassel, 2019. http://d-nb.info/1201508843/34.
Full text
38
Abouzeid, Shadi. "A visual interactive grouping analysis tool (VIGAT) that takes mixed data types as input and provides visually interactive overlapping groups as output." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401309.
Full text
39
Atapattu, Lakmali Nadisha Kumari. "Channel tracking in SDMA-based multi-user MIMO-OFDM communications systems." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/65272/1/Lakmali_Atapattu_Thesis.pdf.
Full textAbstract:
Capacity of current and future high data rate wireless communications depend significantly on how well changes in the wireless channel are predicted and tracked. Generally, this can be estimated by transmitting known symbols. However, this increases overheads if the channel varies over time. Given today’s bandwidth demand and the increased necessity for mobile wireless devices, the contributions of this research are very significant. This study has developed a novel and efficient channel tracking algorithm that can recursively update the channel estimation for wireless broadband communications reducing overheads, therefore increasing the speed of wireless communication systems.
40
Dia'meh, Yousef Ali. "The optimization of multiple antenna broadband wireless communications : a study of propagation, space-time coding and spatial envelope correlation in Multiple Input, Multiple Output radio systems." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6361.
Full textAbstract:
This work concentrates on the application of diversity techniques and space time block coding for future mobile wireless communications. The initial system analysis employs a space-time coded OFDM transmitter over a multipath Rayleigh channel, and a receiver which uses a selection combining diversity technique. The performance of this combined scenario is characterised in terms of the bit error rate and throughput. A novel four element QOSTBC scheme is introduced, it is created by reforming the detection matrix of the original QOSTBC scheme, for which an orthogonal channel matrix is derived. This results in a computationally less complex linear decoding scheme as compared with the original QOSTBC. Space time coding schemes for three, four and eight transmitters were also derived using a Hadamard matrix. The practical optimization of multi-antenna networks is studied for realistic indoor and mixed propagation scenarios. The starting point is a detailed analysis of the throughput and field strength distributions for a commercial dual band 802.11n MIMO radio operating indoors in a variety of line of sight and non-line of sight scenarios. The physical model of the space is based on architectural schematics, and realistic propagation data for the construction materials. The modelling is then extended and generalized to a multi-storey indoor environment, and a large mixed site for indoor and outdoor channels based on the Bradford University campus. The implications for the physical layer are also explored through the specification of antenna envelope correlation coefficients. Initially this is for an antenna module configuration with two independent antennas in close proximity. An operational method is proposed using the scattering parameters of the system and which incorporates the intrinsic power losses of the radiating elements. The method is extended to estimate the envelope correlation coefficient for any two elements in a general (N,N) MIMO antenna array. Three examples are presented to validate this technique, and very close agreement is shown to exist between this method and the full electromagnetic analysis using the far field antenna radiation patterns.
41
Diameh, Yousef A. "The optimization of multiple antenna broadband wireless communications. A study of propagation, space-time coding and spatial envelope correlation in Multiple Input, Multiple Output radio systems." Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6361.
Full textAbstract:
This work concentrates on the application of diversity techniques and space time block coding for future mobile wireless communications.
The initial system analysis employs a space-time coded OFDM transmitter over a multipath Rayleigh channel, and a receiver which uses a selection combining diversity technique. The performance of this combined scenario is characterised in terms of the bit error rate and throughput. A novel four element QOSTBC scheme is introduced, it is created by reforming the detection matrix of the original QOSTBC scheme, for which an orthogonal channel matrix is derived. This results in a computationally less complex linear decoding scheme as compared with the original QOSTBC. Space time coding schemes for three, four and eight transmitters were also derived using a Hadamard matrix.
The practical optimization of multi-antenna networks is studied for realistic indoor and mixed propagation scenarios. The starting point is a detailed analysis of the throughput and field strength distributions for a commercial dual band 802.11n MIMO radio operating indoors in a variety of line of sight and non-line of sight scenarios. The physical model of the space is based on architectural schematics, and realistic propagation data for the construction materials. The modelling is then extended and generalized to a multi-storey indoor environment, and a large mixed site for indoor and outdoor channels based on the Bradford University campus.
The implications for the physical layer are also explored through the specification of antenna envelope correlation coefficients. Initially this is for an antenna module configuration with two independent antennas in close proximity. An operational method is proposed using the scattering parameters of the system and which incorporates the intrinsic power losses of the radiating elements. The method is extended to estimate the envelope correlation coefficient for any two elements in a general (N,N) MIMO antenna array. Three examples are presented to validate this technique, and very close agreement is shown to exist between this method and the full electromagnetic analysis using the far field antenna radiation patterns.
42
Islam, Md Faqhrul. "Impact of ubiquitous real-time information on bus passenger route choice." Thesis, Edinburgh Napier University, 2018. http://researchrepository.napier.ac.uk/Output/1508471.
Full textAbstract:
Over the last decade, Ubiquitous Real-time Passenger Information (URTPI) has become popular among public transport passengers. The effectiveness of URTPI and hence the value of the investments into the necessary systems can be increased with a clear understanding of how URTPI influences passenger behaviour. However, such an understanding is still limited and fragmented. In particular, very little is known about the impact of URTPI on route choice. This study fills this gap evaluating the impact of URTPI on bus passengers' route choice. A revealed preference survey methodology was adopted for data collection and two questionnaire surveys targeting bus users were carried out. Categorical Regression and discrete choice models, such as Binary Logit Model and Multinomial Logit Model, have been applied to analyse the survey data. The study reveals that trip length, passenger age and profession are the main factors influencing the use of URTPI.Having access toURTPI, the frequency of its use is strongly influenced by the attributes of information and social norms. Bus arrival time and bus stop location are the two most important contents of information. Changing time ofdeparture from the start and the boarding time are the two most popular actions taken by bus passengers after consulting URTPI. Passengers' decisions are influenced by information on bus arrival time, bus route, and walking distance. As a result of the impact of URTPI on passengers' choices, the demand distribution for bus runs could potentially be changed by 33% and for bus lines by 22%. The overall network demand distribution could be affected in 42% of cases as a result of consulting URTPI.This study implicates that while investing in tailoring the sources of URTPI, passengers' preferred attributes and contents of information should be considered. Transport planners and operators should take the potential impact of URTPI into account to make better predictions of the PT demand distribution.
43
Li, Linyu. "Economic growth in Sweden, 2000-2010 : The dot-com bubble and the financial crisis." Thesis, Högskolan Dalarna, Nationalekonomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:du-14883.
Full textAbstract:
Economic growth is the increase in the inflation-adjusted market value of the goods and services produced by an economy over time. The total output is the quantity of goods or servicesproduced in a given time period within a country. Sweden was affected by two crises during the period 2000-2010: a dot-com bubble and a financial crisis. How did these two crises affect the economic growth? The changes of domestic output can be separated into four parts: changes in intermediate demand, final domestic demand, export demand and import substitution. The main purpose of this article is to analyze the economic growth during the period 2000-2010, with focus on the dot-com bubble in the beginning of the period 2000-2005, and the financial crisis at the end of the period 2005-2010. The methodology to be used is the structural decomposition method. This investigation shows that the main contributions to the Swedish total domestic output increase in both the period 2000-2005 and the period 2005-2010 were the effect of domestic demand. In the period 2005-2010, financial crisis weakened the effect of export. The output of the primary sector went from a negative change into a positive, explained mainly by strong export expansion. In the secondary sector, export had most effect in the period 2000-2005. Nevertheless, domestic demand and import ratio had more effect during the financial crisis period. Lastly, in the tertiary sector, domestic demand can mainly explain the output growth in the whole period 2000-2010.
44
Nguyen, Nam Tran Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Training signal and precoder dsigns for channel estimation and symbol detection in MIMO and OFDM systems." Awarded by:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/43243.
Full textAbstract:
Research in wireless communications has been actively carried out in recent years. In order to enable a high data transmission rate, multiple-input multiple-output (MIMO) communications has been proposed and commonly adopted. Accurate channel identification and reliable data detection are major challenges in the implementation of a communications system operating over a wireless fading channel. These issues become even more challenging in MIMO systems since there are many more parameters involved in the estimation processes. This thesis, consisting of four major parts, focuses on applying convex optimization to solve design problems in both MIMO channel estimation and data detection. The first part proposes a novel orthogonal affine precoding technique for jointly optimal channel estimation and symbol detection in a general MIMO frequency-selective fading channel. Additionally, the optimal power allocation between the data and training signals is also analytically derived. The proposed technique is shown to perform much better than other affine precoding techniques in terms of detection error probability and computational complexity. The second part is concerned with the MIMO orthogonal frequency-division multiplexing (OFDM) systems. The superimposed training technique developed in the first part is applied and extended for MIMO-OFDM systems where all the involved transmitters and receivers are assumed to be uncorrelated. Analytical and numerical results confirm that the proposed design can efficiently identify the unknown wireless channel as well as effectively recover the data symbols, while conserving the transmission bandwidth. The third part considers training and precoding designs for OFDM under colored noise environment. The superiority of the proposed design over the previously-known design under colored noise is thoroughly demonstrated. The last part of the thesis develops the orthogonal affine precoder for spatially correlated MIMO-OFDM systems. The optimal superimposed training sequences are solved by tractable semi-definite programming. To have a better computational efficiency, two approximate design techniques are also presented. Furthermore, the non-redundancy precoder proposed in the third part is employed to combat channel correlation. As a result, the proposed designs are demonstrated to outperform other known designs in terms of channel estimation and data detection.
45
Öman, Andreas. "CO2-utsläpp och konsumtion : Förutsättningar för att påvisa och minska indirekta CO2-utsläpp i den enskilde individens konsumtion av varor." Thesis, Linköping University, Department of Water and Environmental Studies, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11308.
Full textAbstract:
IVL Svenska Miljöinstitutet utvecklade år 2001 – 2002 i projektet “Klimat.nu – Den stora miljöutmaningen”, ett webbaserat verktyg för att upplysa och vägleda individen i klimatfrågan. Verktygets syfte är att kvantifiera fossila koldioxidutsläpp som en konsekvens av individens energikonsumtion; hushållsel, drivmedel m.m. Syftet är även att individen ges råd om hur man minskar CO2-utsläpp genom att förändra sitt leverne. IVL Svenska Miljöinstitutet vill utöka beräkningsverktygets innehåll till att även omfatta konsumentvaror. Studien har sökt svar hur enskilda individers olika typer av varukonsumtion sättas i samband med CO2-utsläpp och vilka konsumentråd är rimliga att ge för att uppnå utsläppsminskningar, samt hur dessa minskningar kan kvantifieras.
I studien har ett systemanalytiskt tillvägagångssätt tillämpats och empirin har bestått av miljöexpanderad input-output-data (MIOA). Data har samlats in från Statistiska Centralbyrån (SCB) på miljöräkenskapernas data- och analyssidor. Insamlad data beskriver utsläpp som sker i varors livscykel till och med distribution till affär (indirekta utsläpp). Det är dock viktigt att ha varuklassers hela livscykel i åtanke så att försök till att minska konsumentens indirekta CO2-utsläpp inte leder till ökade totala utsläpp. Dataosäkerheter har identifierats, vilka visar att insamlad data underskattar varors indirekta CO2-utsläpp. Data grundar sig på antagandet att Sverige skulle ha producerat alla varor som importeras. I genomsnitt är ca 69 % av varors indirekta CO2-utsläpp av utländsk härkomst, dessa länder har vanligtvis högre utsläppsintensitet än Sverige i sina produktionsstrukturer. I Sverige finns data endast tillgänglig med ca tre års fördröjning. I sin nuvarande form representerar data trots osäkerheter en lägsta nivå på olika varuklassers indirekta CO2-utsläpp.
För att göra insamlad data funktionell i beräkningsverktyget prövades en metodik där utsläppsintensiteter beräknades. Utsläppsintensiteter tillgodoser kravet för att enskilda individers olika typer av varukonsumtion ska kunna kopplas till dess CO2-utsläpp. I beräkningsverktyget innebär det att utsläppsintensiteter integreras, som tillsammans med en viss summa pengar, utgör underlaget för att beräkna individens indirekta CO2-utsläpp. Ur ett individperspektiv är metodiken särskilt tilltalande eftersom pengar används som beräkningsenhet, enheten är något som individen oftast har lätt att relatera till. Användningen av utsläppsintensiteter möjliggör kvantifiering av en utsläppsminskning om individen spenderar en summa pengar på en varuklass med lägre utsläppsintensitet i stället en med högre. Med pengar som enhet kan även ”rebound-effekten” undvikas.
På grund av osäkerheter i dataunderlaget kan studien inte påvisa att förändrad konsumtion av varor leder till en faktisk utsläppsminskning. Störst sannolikhet att uppnå en faktisk minskning är dock om individen råds att fördela en summa pengar från en varuklass till en annan, i vilka det finns stora kvantitativa skillnader mellan utsläppsintensiteterna.
46
Öman, Andreas. "CO2-utsläpp och konsumtion : Förutsättningar för att påvisa och minska indirekta CO2-utsläpp i den enskilde individens konsumtion av varor." Thesis, Linköpings universitet, Tema vatten i natur och samhälle, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11308.
Full textAbstract:
IVL Svenska Miljöinstitutet utvecklade år 2001 – 2002 i projektet “Klimat.nu – Den stora miljöutmaningen”, ett webbaserat verktyg för att upplysa och vägleda individen i klimatfrågan. Verktygets syfte är att kvantifiera fossila koldioxidutsläpp som en konsekvens av individens energikonsumtion; hushållsel, drivmedel m.m. Syftet är även att individen ges råd om hur man minskar CO2-utsläpp genom att förändra sitt leverne. IVL Svenska Miljöinstitutet vill utöka beräkningsverktygets innehåll till att även omfatta konsumentvaror. Studien har sökt svar hur enskilda individers olika typer av varukonsumtion sättas i samband med CO2-utsläpp och vilka konsumentråd är rimliga att ge för att uppnå utsläppsminskningar, samt hur dessa minskningar kan kvantifieras. I studien har ett systemanalytiskt tillvägagångssätt tillämpats och empirin har bestått av miljöexpanderad input-output-data (MIOA). Data har samlats in från Statistiska Centralbyrån (SCB) på miljöräkenskapernas data- och analyssidor. Insamlad data beskriver utsläpp som sker i varors livscykel till och med distribution till affär (indirekta utsläpp). Det är dock viktigt att ha varuklassers hela livscykel i åtanke så att försök till att minska konsumentens indirekta CO2-utsläpp inte leder till ökade totala utsläpp. Dataosäkerheter har identifierats, vilka visar att insamlad data underskattar varors indirekta CO2-utsläpp. Data grundar sig på antagandet att Sverige skulle ha producerat alla varor som importeras. I genomsnitt är ca 69 % av varors indirekta CO2-utsläpp av utländsk härkomst, dessa länder har vanligtvis högre utsläppsintensitet än Sverige i sina produktionsstrukturer. I Sverige finns data endast tillgänglig med ca tre års fördröjning. I sin nuvarande form representerar data trots osäkerheter en lägsta nivå på olika varuklassers indirekta CO2-utsläpp. För att göra insamlad data funktionell i beräkningsverktyget prövades en metodik där utsläppsintensiteter beräknades. Utsläppsintensiteter tillgodoser kravet för att enskilda individers olika typer av varukonsumtion ska kunna kopplas till dess CO2-utsläpp. I beräkningsverktyget innebär det att utsläppsintensiteter integreras, som tillsammans med en viss summa pengar, utgör underlaget för att beräkna individens indirekta CO2-utsläpp. Ur ett individperspektiv är metodiken särskilt tilltalande eftersom pengar används som beräkningsenhet, enheten är något som individen oftast har lätt att relatera till. Användningen av utsläppsintensiteter möjliggör kvantifiering av en utsläppsminskning om individen spenderar en summa pengar på en varuklass med lägre utsläppsintensitet i stället en med högre. Med pengar som enhet kan även ”rebound-effekten” undvikas. På grund av osäkerheter i dataunderlaget kan studien inte påvisa att förändrad konsumtion av varor leder till en faktisk utsläppsminskning. Störst sannolikhet att uppnå en faktisk minskning är dock om individen råds att fördela en summa pengar från en varuklass till en annan, i vilka det finns stora kvantitativa skillnader mellan utsläppsintensiteterna.
47
Olwert, Craig Thomas. "A Computable General Equilibrium Model of the City with Optimization of its Transportation Network: Impacts of Changes in Technology, Preferences, and Policy." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1269369926.
Full text
48
Cho, Hyunkyoo. "Efficient variable screening method and confidence-based method for reliability-based design optimization." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/4594.
Full textAbstract:
The objectives of this study are (1) to develop an efficient variable screening method for reliability-based design optimization (RBDO) and (2) to develop a new RBDO method incorporated with the confidence level for limited input data problems. The current research effort involves: (1) development of a partial output variance concept for variable screening; (2) development of an effective variable screening sequence; (3) development of estimation method for a confidence level of a reliability output; and (4) development of a design sensitivity method for the confidence level.
In the RBDO process, surrogate models are frequently used to reduce the number of simulations because analysis of a simulation model takes a great deal of computational time. On the other hand, to obtain accurate surrogate models, we have to limit the dimension of the RBDO problem and thus mitigate the curse of dimensionality. Therefore, it is desirable to develop an efficient and effective variable screening method for reduction of the dimension of the RBDO problem. In this study, it is found that output variance is critical for identifying important variables in the RBDO process. A partial output variance, which is an efficient approximation method based on the univariate dimension reduction method (DRM), is proposed to calculate output variance efficiently. For variable screening, the variables that has larger partial output variances are selected as important variables. To determine important variables, hypothesis testing is used so that possible errors are contained at a user-specified error level. Also, an appropriate number of samples is proposed for calculating the partial output variance. Moreover, a quadratic interpolation method is studied in detail to calculate output variance efficiently. Using numerical examples, performance of the proposed variable screening method is verified. It is shown that the proposed method finds important variables efficiently and effectively.
The reliability analysis and the RBDO require an exact input probabilistic model to obtain accurate reliability output and RBDO optimum design. However, often only limited input data are available to generate the input probabilistic model in practical engineering problems. The insufficient input data induces uncertainty in the input probabilistic model, and this uncertainty forces the RBDO optimum to lose its confidence level. Therefore, it is necessary to consider the reliability output, which is defined as the probability of failure, to follow a probability distribution. The probability of the reliability output is obtained with consecutive conditional probabilities of input distribution type and parameters using the Bayesian approach. The approximate conditional probabilities are obtained under reasonable assumptions, and Monte Carlo simulation is applied to practically calculate the probability of the reliability output. A confidence-based RBDO (C-RBDO) problem is formulated using the derived probability of the reliability output. In the C-RBDO formulation, the probabilistic constraint is modified to include both the target reliability output and the target confidence level. Finally, the design sensitivity of the confidence level, which is the new probabilistic constraint, is derived to support an efficient optimization process. Using numerical examples, the accuracy of the developed design sensitivity is verified and it is confirmed that C-RBDO optimum designs incorporate appropriate conservativeness according to the given input data.
49
Anoh, Kelvin Ogbonnaya Okorie. "Advanced MIMO-OFDM technique for future high speed braodband wireless communications : a study of OFDM design, using wavelet transform, fractional fourier transform, fast fourier transform, doppler effect, space-time coding for multiple input, multiple output wireless communications systems." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14400.
Full textAbstract:
This work concentrates on the application of diversity techniques and space time block coding for future high speed mobile wireless communications on multicarrier systems. At first, alternative multicarrier kernels robust for high speed doubly-selective fading channel are sought. They include the comparisons of discrete Fourier transform (DFT), fractional Fourier transform (FrFT) and wavelet transform (WT) multicarrier kernels. Different wavelet types, including the raised-cosine spectrum wavelets are implemented, evaluated and compared. From different wavelet families, orthogonal wavelets are isolated from detailed evaluations and comparisons as suitable for multicarrier applications. The three transforms are compared over a doubly-selective channel with the WT significantly outperforming all for high speed conditions up to 300 km/hr. Then, a new wavelet is constructed from an ideal filter approximation using established wavelet design algorithms to match any signal of interest; in this case under bandlimited criteria. The new wavelet showed better performance than other traditional orthogonal wavelets. To achieve MIMO communication, orthogonal space-time block coding, OSTBC, is evaluated next. First, the OSTBC is extended to assess the performance of the scheme over extended receiver diversity order. Again, with the extended diversity conditions, the OSTBC is implemented for a multicarrier system over a doubly-selective fading channel. The MIMO-OFDM systems (implemented using DFT and WT kernels) are evaluated for different operating frequencies, typical of LTE standard, with Doppler effects. It was found that, during high mobile speed, it is better to transmit OFDM signals using lower operating frequencies. The information theory for the 2-transmit antenna OSTBC does not support higher order implementation of multi-antenna systems, which is required for the future generation wireless communications systems. Instead of the OSTBC, the QO-STBC is usually deployed to support the design of higher order multi-antenna systems other than the 2-transmit antenna scheme. The performances of traditional QO-STBC methods are diminished by some off-diagonal (interference) terms such that the resulting system does not attain full diversity. Some methods for eliminating the interference terms have earlier been discussed. This work follows the construction of cyclic matrices with Hadamard matrix to derive QO-STBC codes construction which are N-times better than interference free QO-STBC, where N is the number of transmit antenna branches.
50
Anoh, Kelvin O. O. "Advanced MIMO-OFDM technique for future high speed braodband wireless communications. A study of OFDM design, using wavelet transform, fractional fourier transform, fast fourier transform, doppler effect, space-time coding for multiple input, multiple output wireless communications systems." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14400.
Full textAbstract:
This work concentrates on the application of diversity techniques and space time block coding
for future high speed mobile wireless communications on multicarrier systems.
At first, alternative multicarrier kernels robust for high speed doubly-selective fading channel are
sought. They include the comparisons of discrete Fourier transform (DFT), fractional Fourier
transform (FrFT) and wavelet transform (WT) multicarrier kernels. Different wavelet types,
including the raised-cosine spectrum wavelets are implemented, evaluated and compared.
From different wavelet families, orthogonal wavelets are isolated from detailed evaluations and
comparisons as suitable for multicarrier applications. The three transforms are compared over a
doubly-selective channel with the WT significantly outperforming all for high speed conditions up
to 300 km/hr.
Then, a new wavelet is constructed from an ideal filter approximation using established wavelet
design algorithms to match any signal of interest; in this case under bandlimited criteria. The
new wavelet showed better performance than other traditional orthogonal wavelets.
To achieve MIMO communication, orthogonal space-time block coding, OSTBC, is evaluated
next. First, the OSTBC is extended to assess the performance of the scheme over extended
receiver diversity order. Again, with the extended diversity conditions, the OSTBC is
implemented for a multicarrier system over a doubly-selective fading channel. The MIMO-OFDM
systems (implemented using DFT and WT kernels) are evaluated for different operating
frequencies, typical of LTE standard, with Doppler effects. It was found that, during high mobile
speed, it is better to transmit OFDM signals using lower operating frequencies.
The information theory for the 2-transmit antenna OSTBC does not support higher order
implementation of multi-antenna systems, which is required for the future generation wireless
communications systems. Instead of the OSTBC, the QO-STBC is usually deployed to support
the design of higher order multi-antenna systems other than the 2-transmit antenna scheme.
The performances of traditional QO-STBC methods are diminished by some off-diagonal
(interference) terms such that the resulting system does not attain full diversity. Some methods
for eliminating the interference terms have earlier been discussed. This work follows the
construction of cyclic matrices with Hadamard matrix to derive QO-STBC codes construction
which are N-times better than interference free QO-STBC, where N is the number of transmit
antenna branches.