Thèses : « Antenna arrays. MIMO systems. Eigenfunctions »

1

Quist, Britton T. « Synthesis of optimal arrays for MIMO and diversity systems / ». Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd2160.pdf.

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Quist, Britton T. « Synthesis of Optimal Arrays For MIMO and Diversity Systems ». BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1244.

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This thesis proposes a method for determining the optimal antenna element radiation characteristics which maximize diversity gain given a specific power angular spectrum of the propagation environment. The method numerically constructs the eigenfunctions of the covariance operator for the scenario subject to constraints on the power radiated by each antenna as well as the level of supergain allowed in the solution. The optimal antenna characteristics are produced in terms of radiating current distributions along with their resulting radiation patterns. The results reveal that the optimal antennas can provide significantly more diversity gain than that provided by a simple practical design. Computational examples illustrate the effectiveness of adding additional elements to the optimal array and the relationship between aperture size or the description of the impinging field and the array performance. A synthesis procedure is proposed which uses genetic algorithm optimization to optimally place a reduced number of dipoles. The results from this procedure demonstrate that using the framework in conjunction with optimization strategies can lead to practical designs which perform well relative to the upper performance bound. Finally a novel array architecture is proposed where subsets of antennas are combined together into super-elements which are then combined in the same manner as the optimal array. The simplifications that result from the genetically optimized small array or the super-element array provide a design options which are feasible in many communication applications.

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Biswas, Sudip. « Future cellular systems : fundamentals and the role of large antenna arrays ». Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23470.

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In this thesis, we analyze the performance of three promising technologies being considered for future fifth generation (5G) and beyond wireless communication systems, with primary goals to: i) render 10-100 times higher user data rate, ii) serve 10-100 times more users simultaneously, iii) 1000 times more data volume per unit area, iv) improve energy efficiency on the order of 100 times, and iv) provide higher bandwidths. Accordingly, we focus on massive multiple-input multiple-output (MIMO) systems and other future wireless technologies, namely millimeter wave (mmWave) and full-duplex (FD) systems that are being considered to fulfill the above requirements. We begin by focusing on fundamental performance limits of massive MIMO systems under practical constraints such as low complexity processing, array size and limited physical space. First, we analyze the performance of a massive MIMO base station (BS) serving spatially distributed multi-antenna users within a fixed coverage area. Stochastic geometry is used to characterize the spatially distributed users while large dimensional random matrix theory is used to achieve deterministic approximations of the sum rate of the system. We then examine the deployment of a massive MIMO BS and the resulting energy efficiency (EE) by considering a more realistic set-up of a rectangular array with increasing antenna elements within a fixed physical space. The effects of mutual coupling and correlation among the BS antennas are incorporated by deriving a practical mutual coupling matrix which considers coupling among all antenna elements within the BS. Accordingly, the optimum number of antennas that can be deployed for a particular antenna spacing when EE is considered as a design criteria is derived. Also, it is found that mutual coupling effect reduces the EE of the massive system by around 40-45% depending on the precoder/receiver used and the physical space available for antenna deployment. After establishing the constraints of antenna spacing on massive MIMO systems for the current microwave spectrum, we shift our focus to mmWave frequencies (more than 100GHz available bandwidth), where the wavelength is very small and as a result more antennas can be rigged within a constrained space. Accordingly, we integrate the massive MIMO technology with mmWave networks. In particular, we analyze the performance of a mmWave network consisting of spatially distributed BS equipped with very large uniform circular arrays (UCA) serving spatially distributed users within a fixed coverage area. The use of UCA is due to its capability of scanning through both the azimuth as well as elevation dimensions. We show that using such 3D massive MIMO techniques in mmWave systems yield significant performance gains. Further, we show the effect of blockages and path loss on mmWave networks. Since blockages are found to be quite detrimental to mmWave networks, we create alternative propagation paths with the aid of relays. In particular, we consider the deployment of relays in outdoor mmWave networks and then derive expressions for the coverage probability and transmission capacity from sources to a destination for such relay aided mmWave networks using stochastic geometric tools. Overall, relay aided mmWave transmission is seen to improve the signal to noise ratio at the destination by around 5-10dB with respect to specific coverage probabilities. Finally, due to the fact that the current half duplex (HD) mode transmission only utilizes half the spectrum at the same time in the same frequency, we consider a multiuser MIMO cellular system, where a FD BS serves multiple HD users simultaneously. However, since FD systems are plagued by severe self-interference (SI), we focus on the design of robust transceivers, which can cancel the residual SI left after antenna and analog cancellations. In particular, we address the sum mean-squared-errors (MSE) minimization problem by transforming it into an equivalent semidefinite programming (SDP) problem. We propose iterative alternating algorithms to design the transceiver matrices jointly and accordingly show the gains of FD over HD systems. We show that with proper SI cancellation, it is possible to achieve gains on sum rate of up to 70-80% over HD systems.

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Anreddy, Vikram R. « Indoor MIMO Channels with Polarization Diversity : Measurements and Performance Analysis ». Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04112006-093641/.

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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.
Ingram Mary Ann, Committee Chair ; Durgin, Gregory David, Committee Member ; Williams, Douglas B, Committee Member.

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Chu, Min. « Phase-shifting techniques for wireless multiple-antenna transmitter applications / ». Thesis, Connect to this title online ; UW restricted, 2006. http://hdl.handle.net/1773/6002.

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Wennström, Mattias. « On MIMO Systems and Adaptive Arrays for Wireless Communication : Analysis and Practical Aspects ». Doctoral thesis, Uppsala University, Signals and Systems Group, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2604.

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This thesis is concerned with the use of multiple antenna elements in wireless communication over frequency non-selective radio channels. Both measurement results and theoretical analysis are presented. New transmit strategies are derived and compared to existing transmit strategies, such as beamforming and space-time block coding (STBC). It is found that the best transmission algorithm is largely dependent on the channel characteristics, such as the number of transmit and receive antennas and the existence of a line of sight component. Rayleigh fading multiple input multiple output (MIMO) channels are studied using an eigenvalue analysis and exact expressions for the bit error rates and outage capacities for beamforming and STBC is found. In general are MIMO fading channels correlated and there exists a mutual coupling between antenna elements. These findings are supported by indoor MIMO measurements. It is found that the mutual coupling can, in some scenarios, increase the outage capacity. An adaptive antenna testbed is used to obtain measurement results for the single input multiple output (SIMO) channel. The results are analyzed and design guidelines are obtained for how a beamformer implemented in hardware shall be constructed. The effects of nonlinear transmit amplifiers in array antennas are also analyzed, and it is shown that an array reduces the effective intermodulation distortion (IMD) transmitted by the array antenna by a spatial filtering of the IMD. A novel frequency allocation algorithm is proposed that reduces IMD even further. The use of a low cost antenna with switchable directional properties, the switched parasitic antenna, is studied in a MIMO context and compared to array techniques. It is found that it has comparable performance, at a fraction of the cost for an array antenna.

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Wennström, Mattias. « On MIMO systems and adaptive arrays for wireless communications : analysis and practical aspects / ». Uppsala : Signals and systems [Signaler och system], Univ. [distributör], 2002. http://publications.uu.se/theses/fulltext/91-506-1619-6.pdf.

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Gelal, Ece. « Cross-layer design for wireless networks using antenna arrays ». Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1899476681&SrchMode=2&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268335334&clientId=48051.

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Thesis (Ph. D.)--University of California, Riverside, 2009.
Includes abstract. Title from first page of PDF file (viewed March 11, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 149-156). Also issued in print.

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Kwun, Byong-Ok. « Robust beamforming for collaborative MIMO-OFDM wireless systems ». Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100228.

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Collaborative beamforming is a powerful technique to increase communication energy efficiency and range in an energy-constrained network. To achieve high performance, collaborative beamforming requires accurate knowledge of channel state information (CSI) at the transmitters (collaborative nodes). In practice, however, such exact knowledge of CSI is not available. A robust transmitter design based on partial CSI is required to mitigate the effects of CSI mismatches.
This thesis focuses on the design and evaluation of a beamforming scheme that is robust to CSI mismatches for collaborative multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) wireless systems. Using a max-min robust design approach, the robust beamformer is designed to maximize the minimum (worst-case) received signal-to-noise ratio (SNR) within a predefined uncertainty region at each OFDM subcarrier. In addition, several subcarrier power allocation strategies are investigated to further improve the robustness of collaborative systems. Numerical simulation results show that the robust beamformer offers improved performance over the nonrobust beamformers and the use of power allocation strategies among subcarriers further improves the system performance.

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Sfar, Sana. « Multiple array schemes for achieving high capacity and high diversity gains in wireless MIMO systems / ». View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20SFAR.

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Tsai, Jiann-An. « Combined Space-Time Diversity and Interference Cancellation for MIMO Wireless Systems ». Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27509.

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There is increasing interest in the exploitation of multiple-input and multiple-output (MIMO) channels to enhance the capacity of wireless systems. In this study, we develop and evaluate a channel model, evaluate the corresponding channel capacity, and design and analyze a simple orthogonal transmit waveform for MIMO channels in mobile radio environments. We also evaluate the system performance of various interference cancellation techniques when employing multiple-receive antenna in interference-limited systems. The first part of this dissertation presents two major contributions to MIMO systems. The analytical expression for space-time MIMO channel correlation is derived for a Rayleigh fading channel. The information-theoretic channel capacity based on this correlation is also evaluated for a wide variety of mobile radio channels. The second part of this dissertation presents two major contributions to the area of orthogonal waveform design. We analyze the bit-error-rate (BER) performance of a proposed space-time orthogonal waveform for MIMO mobile radio communications. The application of the proposed space-time orthogonal waveform to a conventional cellular system is also evaluated and briefly discussed. Finally, this dissertation investigates a number of interference cancellation techniques for multiple-receive antenna systems. Both adaptive beamforming and multiuser detection are evaluated for various signal waveforms over a variety of mobile radio channels.
Ph. D.

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Walkenhorst, Brett T. « Achieving near-optimal MIMO capacity in a rank-deficient LOS environment ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29672.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Ingram, Mary Ann; Committee Member: Durgin, Greg; Committee Member: Kenney, Steve; Committee Member: Landgren, Jack; Committee Member: Li, Ye. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Sobhanmanesh, Fariborz School of Electrical Engineering And Telecommunications UNSW. « Hardware implementation of V-BLAST MIMO ». Awarded by:University of New South Wales. School of Electrical Engineering And Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/24198.

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The exploitation of the theoretically enormous capacity achieved by the multiple transmit and receive antennas systems (MIMO) in a rich scattering communication channel has been the subject of vast body of research on the field of MIMO. In particular, the Vertically-layered Bell Laboratories Layered Space-Time (V-BLAST) is a well known MIMO architecture which has demonstrated the enormous capacity of 20-40 bit/s/Hz in an indoor propagation environment with realistic SNR and error rates. However, due to the intensive computation involved, it would be difficult to implement this architecture for high data rate communication systems. Some works have been done to improve the receiver complexity and performance by coding techniques, by different detection architectures. In this thesis, we have focused on QR-based decoders for V-BLAST MIMO. For a suitable V-BLAST detection implementation, we need to carefully consider the problem from algorithmic, arithmetic and architectural aspects. At the algorithmic level, the numerical stability and robustness should be considered. At the arithmetic level, signal quantization is important, and, at the architectural level, parallelism and pipelining require attention. We have performed the above mentioned optimization on the 1-pass QR factorization with back substitution SIC (Symbol Interference Cancellation) decoder in chapter 3. At first optimizations are made on the proposed algorithm and architecture using MATLAB simulations. Then a new architecture for the QR-factorizer as the core processor of the V-BLAST decoder is developed in chapter 4. This architecture uses only two low complexity CORDIC (Coordinate rotation digital computer) processors. The parameterized feature of the controller and address generator blocks of this architecture has provided a scalable architecture for the implementation of QR factorization for square matrix of any dimension. The reduced hardware complexity of the processors and its simple parameterized controller are two outstanding features of the architecture, resulting in a more suitable alternative architecture for QR factorization than traditional triangular systolic arrays. In the next phase of the research, new hardware architectures of the back substitution SIC decoder was developed for a 4 X 4 MIMO system with 16-QAM constellation scheme in chapter 5. The division operation for back substitution needs a complex hardware, and results in the numerical instability. In the proposed hardware the elimination of division and modification of multiplier has reduced the hardware complexity and led to numerical stability. In addition the pre decoding block was designed and optimized in terms of number of the pipeline registers and CORDIC rotator processors. The developed hardware is capable of processing 20 vectors data burst and results in a throughput of 149 Mb/s. The FPGA (Field Programmable Gate Array) and ASIC (Application specific Integrated Circuit) implementations of the proposed optimized architecture are presented in Chapter 5. We found that the equivalent gates and the core area in our design is less than 30% of other designs and the maximum clock frequency and the throughput is higher (175 %) than other works. Finally the improvements of the BER performance using the branching method and parallel architectures are presented in chapter 6. In this supplementary part to back substitution OSIC decoder, the final symbol vector is selected from 2 or 8 potential candidates based on the minimum Euclidean norm, which improves the BER between 3 to 7 db and gives a very close match to the original V-BLAST performance.

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Zhang, Shuai. « Investigating and Enhancing Performance of Multiple Antenna Systems in Compact MIMO/Diversity Terminals ». Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116402.

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Today, owners of small communicating device are interested in transmitting or receiving various multimedia data. By increasing the number of antennas at the transmitter and/or the receiver side of the wireless link, the diversity/Multiple-Input Multiple-Output (MIMO) techniques can increase wireless channel capacity without the need for additional power or spectrum in rich scattering environments. However, due to the limited space of small mobile devices, the correlation coefficients between MIMO antenna elements are very high and the total efficiencies of MIMO elements degrade severely. Furthermore, the human body causes high losses on electromagnetic wave. During the applications, the presence of users may result in the significant reduction of the antenna total efficiencies and highly affects the correlations of MIMO antenna systems. The aims of this thesis are to investigate and enhance the MIMO/diversity performance of multiple antenna systems in the free space and the presence of users. The background and theory of multiple antenna systems are introduced briefly first. Several figures of merits are provided and discussed to evaluate the multiple antenna systems. The decoupling techniques are investigated in the multiple antenna systems operating at the higher frequencies (above 1.7 GHz) and with high radiation efficiency. The single, dual and wide band isolation enhancements are realized through the half-wavelength decoupling slot, quarter-wavelength decoupling slot with T-shaped impedance transformer, tree-like parasitic element with multiple resonances, as well as the different polarizations and radiation patterns of multiple antennas. In the lower bands (lower than 960 MHz), due to the low radiation efficiency and strong chassis mode, the work mainly focused on how to directly reduce the correlations and enlarge the total efficiency. A new mode of mutual scattering mode is introduced. By increasing the Q factors, the radiation patterns of multiple antennas are separated automatically to reduce the correlations. With the inter-element distance larger than a certain distance, a higher Q factor also improved the total efficiency apart from the low correlation. A wideband LTE MIMO antenna with multiple resonances is proposed in mobile terminals. The high Q factors required for the low correlation and high efficiencies in mutual scattering mode is reduced with another mode of diagonal antenna-chassis mode. Hence, the bandwidth of wideband LTE MIMO antenna with multiple resonances mentioned above can be further enlarged while maintaining the good MIMO/diversity performance. The user effects are studied in different MIMO antenna types, chassis lengths, frequencies, port phases and operating modes. Utilizing these usefully information, an adaptive quad-element MAS has been proposed to reduce the user effects and the some geranial rules not limited to the designed MAS have also been given.

QC 20130121

EU Erasmus Mundus External Cooperation Window TANDEM

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Morris, Matthew Leon. « The Impact of Antenna and RF System Characteristics on MIMO System Capacity ». Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd978.pdf.

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Anderson, Adam L. « Unitary space-time transmit diversity for multiple antenna self-interference suppression / ». Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd500.pdf.

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Chang, Yong Jun. « Design of concurrent cooperative transmission systems on software-defined radios ». Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50360.

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Concurrent cooperative transmission (CCT) occurs when a collection of power-constrained single-antenna radios transmit simultaneously to form a distributed multi-input and multi-output (DMIMO) link. DMIMO can be a means for highly reliable and low-latency cooperative routing, when the MIMO channel is exploited for transmit and receive diversity; in this context, the range extension benefit is emphasized. Alternatively, DMIMO can be a means for high-throughput ad hoc networking, when the MIMO channel is used with spatial multiplexing. In both cases, concatenated DMIMO links are treated. The key contribution of this dissertation is a method of pre-synchronization of distributed single-antenna transmitters to form a virtual antenna array, in the absence of a global clock, such as a global positioning system (GPS) receiver or a network time protocol (NTP) to provide reference signals for the synchronization. Instead, the reference for synchronization comes from a packet, transmitted by the previous virtual array and simultaneously received by all the cooperative transmitters for the next hop. The method is realized for two types of modulation: narrowband non-coherent binary frequency-shift keying (NCBFSK) and wideband orthogonal frequency division multiplexing (OFDM). The pre-synchronization algorithms for transmission are designed to minimize the root-mean-square (RMS) transmit time, sampling and carrier frequency error between cooperative transmitters, with low implementation complexity. Since CCT is not supported by any existing standard or off-the-shelf radios, CT must be demonstrated by using software-defined radios (SDRs). Therefore, another contribution is a fully self-contained and real-time SDR testbed for CCT-based networking. The NCBFSK and OFDM systems have been designed and implemented in C++ and Python programming languages in the SDR testbed, providing practical performance of the CCT-based systems.

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Zajic, Alenka. « Space-time channel modeling, simulation, and coding ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26569.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Stuber,Gordon L.; Committee Member: Durgin, Gregory D.; Committee Member: Kim, Hyesoon; Committee Member: Li, Ye (Geoffrey); Committee Member: McLaughlin, Steven W.; Committee Member: Riley, George F.. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Milliner, David Louis. « Low-complexity list detection algorithms for the multiple-input multiple-output channel ». Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37248.

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Modern communication systems demand ever-increasing data rates. Meeting this increased demand is not easy due to regulation and fundamental physical constraints. The utilization of more than one antenna at both the transmitter and receiver produces a multiple-input multiple-output (MIMO) channel, thereby enabling (under certain channel conditions) increased data rates without the need for increased bandwidth or transmission power. Concurrent with this increase in bandwidth is an increase in the receiver's computational complexity which, for a brute-force detector, increases exponentially. For receivers that possess error correcting capabilities, the problem of constructing a detector with low computational complexity that allows for near-exact a posteriori detection is challenging for transmission schemes employing even a modest number of transmit antennas and modulation alphabet sizes. The focus of this dissertation is on the construction of MIMO detection algorithms with low and fixed computational complexity. Specifically, the detection algorithms in this dissertation generate a list of potential transmission vectors resulting in realizable communication receivers with low and fixed computational complexity combined with low error rate performance in both coded and uncoded systems. A key contribution in this dissertation is a breadth-first fixed-complexity algorithm known as the smart-ordered and candidate-adding algorithm that achieves a desirable performance-complexity tradeoff. This algorithm requires only a single pass of a search tree to find its list of transmission vectors. We then construct a framework within which we classify a large class of breadth-first detection algorithms. The design of receiver algorithms for MIMO systems employing space-time codes and error correction is an important area of study. In this dissertation we propose a low and fixed computational complexity algorithm for an increasingly significant algebraic space-time code known as the golden code. The notion of computational complexity is critical in the design of practical MIMO receivers. We provide an analysis of computational complexity in relation to list-based soft-output detection where, in some instances, bounds are placed on the computational complexity of MIMO detection. For this analysis we utilize a metric known as the number of branch metric computations. The value at which the log-likelihood ratio (LLR) of conditional probabilities for a transmitted bit being either a 1 or a 0 is 'clipped' has an impact on a system's error rate performance. We propose a new approach for determining LLR clipping levels that, in contrast to prior approaches which clip to a predetermined fixed LLR clipping level, exploits channel state information to improve the error rate performance of suboptimal detection algorithms. Orthogonal frequency-division (OFDM) multiplexing is an effective technique for combating frequency-selective wideband communication channels. It is common practice for MIMO-OFDM detectors to implement the same detector at each subcarrier, in which case the overall performance is dominated by the weakest subcarrier. We propose a hard-output list detection receiver strategy for MIMO-OFDM channels called nonuniform computational complexity allocation, whereby the receiver adapts the computational resources of the MIMO detector at each subcarrier to match a metric of the corresponding channel quality. The proposed nonuniform algorithm improves performance over uniform allocation.

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Chan, Francis Chun Ngai Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. « Statistical methods on detecting superpositional signals in a wireless channel ». Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/30596.

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The objective of the thesis is concerned on the problem of detecting superpositional signals in a wireless channel. In many wireless systems, an observed signal is commonly represented as a linear combination of the transmitted signal with the interfering signals dispersed in space and time. These systems are generally known as the interference-limited systems. The mathematical model of these systems is generally referred as a superpositional model. A distinguished characteristic of signal transmission in a time-varying wireless channel is that the channel process is not known a priori. Reliable signal reception inherently requires exploiting the structure of the interfering signals under channel uncertainty. Our goal is to design computational efficient receivers for various interference-limited systems by using advanced statistical signal processing techniques. The thesis consists of four main parts. Firstly, we have proposed a novel Multi-Input Multi-Output (MIMO) signal detector, known as the neighbourhood exploring detector (NED). According to the maximum likelihood principle, the space time MIMO detection problem is equivalent to a NP-hard combinatorial optimization problem. The proposed detector is a sub-optimal maximum likelihood detector which eliminates exhaustive multidimensional searches. Secondly, we address the problem of signal synchronization for Global Positioning System (GPS) in a multipath environment. The problem of multipath mitigation constitutes a joint estimation of the unknown amplitudes, phases and time delays of the linearly combined signals. The complexity of the nonlinear joint estimation problem increases exponentially with the number of signals. We have proposed two robust GPS code acquisition systems with low complexities. Thirdly, we deal with the problem of multipath mitigation in the spatial domain. A GPS receiver integrated with the Inertial Navigation System (INS) and a multiple antenna array is considered. We have designed a software based GPS receiver which effectively estimates the directions of arrival and the time of arrival of the linearly combined signals. Finally, the problem of communications with unknown channel state information is investigated. Conventionally, the information theoretical communication problem and the channel estimation problem are decoupled. However the training sequence, which facilitates the estimation of the channel, reduces the throughput of the channel. We have analytically derived the optimal length of the training sequence which maximizes the mutual information in a block fading channel.

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Spencer, Quentin H. « Transmission Strategies for Wireless Multi-user, Multiple-Input, Multiple-Output Communication Channels ». Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd378.pdf.

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Bouça, Patrícia Alexandra Pereira. « Antenna arrays for massive MIMO 5G and satellite systems ». Master's thesis, 2018. http://hdl.handle.net/10773/25601.

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Wireless telecommunications systems are growing and improving at a breakneck pace, and its demands must be ful lled with hardware modi cations. The fth-generation will demand a revolution since antennas are going to be designed for high frequency, millimeter wave bands, where there is a lot of unexploited spectrum worldwide. However, these frequencies get absorbed quite easily, for example, they su er high attenuation due to rain. This implies a decrease of radiated power. To solve some of the issues, antenna arrays have been studied due to their high versatility. This dissertation has the goal of designing and testing several solutions based on microstrip patch antennas. Initially, an analysis of the coupling between elements is performed as well as some proposed techniques to reduce it, through more compact spaces, without any gain decreasing. Finally, considering the space limitations, series antenna arrays are developed for satellite communications and presented an indepth study of antennas effciently employed for both transmission and reception simultaneously.
Os sistemas de telecomunicações sem fios continuam a crescer e a melhorar a um ritmo frenetico, por isso, novos requisitos tem de ser cumpridos com modificações ao nível do hardware. A quinta geração exigirá uma revolução, uma vez que as antenas serão projetadas para alta frequência, banda de ondas milimétricas, onde o espetro ainda não foi muito explorado. No entanto, estas frequências são absorvidas com facilidade como, por exemplo, na atmosfera devido á atenuação originada pela chuva. Para resolver estas limitações, os agregados de antenas têm sido estudados devido á sua versatilidade. Esta dissertação tem o objetivo de desenhar e testar várias soluções baseadas em antenas microstrip (patch). Inicialmente, é realizada uma avaliação do acoplamento entre elementos e propostas algumas técnicas de redução do mesmo, utilizando espaços mais compactos que o usual, mas prevenindo quaisquer diminuições de ganho. Por fim, tendo em vista a mesma limitação espacial, são desenvolvidos agregados de antenas em série direcionados para comunicações via satélite e apresentado um estudo detalhado de antenas para transmissão e recepção em simultâneo.
Mestrado em Engenharia Eletrónica e Telecomunicações

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Lu, Peng. « Performance evaluation and enhancement of MIMO broadcast channels ». Thesis, 2010. http://hdl.handle.net/1828/3299.

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In Multiple-Input Multiple-Output (MIMO) broadcast channels, the multi-antenna basestation transmits information to multiple non-cooperative mobile users simultaneously. Among various transmission schemes, zero-forcing beamforming (ZFBF) and random unitary beamforming (RUB) are of particular interest due to their low implementation complexity and ability to explore the multiplexing gain provided by multiple transmit antennas. To investigate the effects of multiuser diversity on sum-rate performance, previous studies of beamforming schemes in multiuser MIMO systems usually employ asymptotical analysis. In this work, while assuming channel gain follows Rayleigh flat fading, we study the sum-rate performance of ZFBF and RUB through exact mathematic analysis. For this purpose, we derive the statistics of selected users's effective channel gain, which enable us to calculate the sum rate accurately and efficiently. With derived sum-rate expressions, we evaluate and compare the sum-rate performance of MIMO broadcast channels with RUB and dual-transmit-antenna ZFBF. In addition, we apply this analytical method to study strategies that mitigate multiuser interference for RUB-based multiuser MIMO systems. The strategies we consider in the thesis include • Reducing the number of served users at a time. We present a new user scheduling scheme, which imposes a threshold On user's SINR for feedback load reduction and only activates those beams that are requested by feedback users. • Exploiting receive diversity. When receivers use more than one antennas, we evaluate the sum-rate performance gain offered by selection combining (SC) and optimum combining (OC) schemes, respectively. In addition to beamforming techniques, we study the symbol error rate (SER) performance of MIMO broadcast channels with vector perturbation (VP) precoding and quantized channel feedback. Based. on the established equivalent relations in terms of minimum mean square error (MMSE) and SER between quantized and perfect channel feedback cases, we investigate the tradeoff between feedback load and achievable diversity gain.
Graduate

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Yang, Yaoqing. « An experimental investigation of wideband MIMO channels for wireless communications ». Thesis, 2006. http://hdl.handle.net/2152/2673.

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Lee, Jia-Han, et 李佳翰. « Optimization of antenna arrays for the channel capacity of MIMO wireless communication systems ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/96734812139721863096.

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碩士
國立臺灣大學
電信工程學研究所
101
Along with the development of mobile communications, necessity and exchangeability of multimedia information of personal communication rapidly increase. Study to improve to achieve a better spectral efficiency and transmission quality within the limited bandwidth has become an important issue. In MIMO wireless communication systems, the techniques of spatial diversity and spatial multiplexing make both quality and rate ameliorate in transmission. However , the spatial correlation between the elements of antenna array significantly affects spectral efficiency and transmission quality. Miniaturization trend of mobile devices makes antenna spacing become even smaller than before, leading out the mutual coupling effect which increase channel capacity. Therefore, research of the spatial correlation, mutual coupling , and channel capacity functions under surrounding of 2-D signal arrival and 3-D signal arrival will be described first, as a valuation of efficiency. Then introduce chaotic particle swarm optimization and optimization of antenna arrays for the channel capacity. Compare the difference of using uniform antenna array and non-uniform antenna array. Present the optimal array geometry. Final,we will discuss the effect of spatial correlation and mutual coupling for channel capacity.

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Alibakhshikenari, M., B. S. Virdee, C. H. See, Raed A. Abd-Alhameed, F. Falcone et E. Limiti. « Surface wave reduction in antenna arrays using metasurface inclusion for MIMO and SAR systems ». 2019. http://hdl.handle.net/10454/18126.

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Yes
An effective method is presented for suppressing mutual coupling between adjacent radiating elements which is based on metasurface isolation for MIMO and synthetic aperture radar (SAR) systems. This is achieved by choking surface current waves induced over the patch antenna by inserting a cross-shaped metasurface structure between the radiating elements. Each arm of the cross-shaped structure constituting the metasurface is etched with meander-line slot (MLS). Effectiveness of the metasurface is demonstrated for a2×2antenna array that operates over six frequency sub-bands in X, Ku and K-bands. With the proposed technique, the maximum improvement achieved in attenuating mutual coupling between neighbouring antennas is: 8.5 dB (8-8.4 GHz), 28 dB (9.6-10.8 GHz), 27 dB (11.7-12.6 GHz), 7.5 dB (13.4-14.2 GHz), 13 dB (16.5-16.8 GHz) and 22.5 dB (18.5-20.3 GHz). Furthermore, with the proposed technique (i) minimum center-to-center separation between the radiating elements can be reduced to 0.26λ0, where λ0 is 8.0 GHz; (ii) use of ground-plane or defected ground structures are unnecessary; (iii) use of short-circuited via-holes are avoided; (iv) it eliminates the issue with poor front-to-back ratio; and (v) it can be applied to existing arrays retrospectively.
H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E0/22936/1

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Baraani, Dastjerdi Mahmood. « High-Performance Multi-Antenna Wireless for 5G and Beyond ». Thesis, 2020. https://doi.org/10.7916/d8-4q2c-1y14.

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Over the next decade, multi-antenna radios, including phased array and multiple-input-multiple-output (MIMO) radios, are expected to play an essential role in the next-generation of wireless networks. Phased arrays can reject spatial interferences and provide coherent beamforming gain, and MIMO technology promises to significantly enhance the system performance in the coverage, capacity, and user data rate through the beamforming or diversity/capacity gain which can substantially increase the range in wireless links, that are challenged from the transmitter (TX) power handling, receiver (RX) noise perspectives and a multi-path environment. Furthermore, the multi-user MIMO (MU-MIMO) can simultaneously serve multiple users which is vital for femtocell base stations and access points (AP). Full-duplex (FD) wireless, namely simultaneous transmission and reception at the same frequency, is an emerging technology that has gained attention due to its potential to double the data throughput, as well as provide other benefits in the higher layers such as better spectral efficiency, reducing network and feedback signaling delays, and resolving hidden-node problems to avoid collisions. However, several challenges remain in the quest for the high-performance integrated FD radios. Transmitter power handling remains an open problem, particularly in FD radios that integrate a shared antenna interface. Secondly, FD operation must be achieved across antenna VSWR variations and a changing EM environment. Finally, FD must be extended to multi-antenna radios, including phased array and multi-input multi-output (MIMO) radios, as over the next decade, they are expected to play an essential role in the next generation of wireless networks. Multi-antenna FD operation, however, is challenged not only by the self-interference (SI) from each TX to its own RX but also cross-talk SI (CT-SI) between antennas. In this dissertation, first, a full-duplex phased array circulator-RX (circ.-RX) is proposed that achieves self-interference cancellation (SIC) through repurposing beamforming degrees of freedom (DoF) on TX and RX. Then, an FD MIMO circ.-RX is proposed that achieves SI and CT-SI cancellation (CT-SIC) through passive RF and shared-delay baseband (BB) canceller that addresses challenges associated with FD MIMO operation. Wireless radios at millimeter-wave (mm-wave) frequencies enable the high-speed link for portable devices due to the wide-band spectrum available. Large-scale arrays are required to compensate for high path loss to form an mm-wave link. Mm-wave MIMO systems with digitization enable virtual arrays for radar, digital beamforming (DBF) for high mobility scenarios and spatial multiplexing. To preserve MIMO information, the received signal from each element in MIMO RX should be transported to ADC/DSP IC for DBF, and vice versa on the TX side. A large-scale array can be formed by tiling multiple mm-wave IC front-ends, and thus, a single-wire interface is desired between DSP IC and mm-wave ICs to reduce board routing complexity. Per-element digitization poses the challenge of handling high data-rate I/O in large-scale tiled MIMO mm-wave arrays. SERializer – DESerializer (SERDES) is traditionally being used as a high-speed link in computing systems and networks. However, SERDES results in a large area and power consumption. In this dissertation, a 60~GHz 4-element MIMO TX with a single-wire interface is presented that de-multiplexes the baseband signal of all elements and LO reference that are frequency-domain multiplexed on a single-wire coax cable.

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Forenza, Antonio. « Antenna and algorithm design in MIMO communication systems : exploiting the spatial selectivity of wireless channels ». Thesis, 2006. http://hdl.handle.net/2152/2457.

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Churms, Duane. « Comparison of code rate and transmit diversity in MIMO systems ». Thesis, 2016. http://hdl.handle.net/10539/21155.

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A thesis submitted in ful lment of the requirements for the degree of Master of Science in the Centre of Excellence in Telecommunications and Software School of Electrical and Information Engineering, March 2016
In order to compare low rate error correcting codes to MIMO schemes with transmit diversity, two systems with the same throughput are compared. A VBLAST MIMO system with (15; 5) Reed-Solomon coding is compared to an Alamouti MIMO system with (15; 10) Reed-Solomon coding. The latter is found to perform signi cantly better, indicating that transmit diversity is a more e ective technique for minimising errors than reducing the code rate. The Guruswami-Sudan/Koetter-Vardy soft decision decoding algorithm was implemented to allow decoding beyond the conventional error correcting bound of RS codes and VBLAST was adapted to provide reliability information. Analysis is also performed to nd the optimal code rate when using various MIMO systems.
MT2016

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Alibakhshikenari, M., B. S. Virdee, P. Shukla, C. H. See, Raed A. Abd-Alhameed, M. Khalily, F. Falcone et E. Limiti. « Interaction between closely packed array antenna elements using metasurface for applications such as MIMO systems and synthetic aperture radars ». 2018. http://hdl.handle.net/10454/16635.

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Yes
The paper presents a technique to enhance the isolation between adjacent radiating elements which is common in densely packed antenna arrays. Such antennas provide frequency beam-scanning capability needed in Multiple-Input Multiple-Output (MIMO) systems and Synthetic Aperture Radars (SARs). The method proposed here uses a metamaterial decoupling slab (MTMDS), which is located between radiating elements, to suppress mutual-coupling between the elements that would otherwise degrade the antenna efficiency and performance in both the transmit and receive mode. The proposed MTM-DS consists of mirror imaged Eshaped slits engraved on a microstrip patch with inductive stub. Measured results confirm over 9–11 GHz with no MTM-DS the average isolation (S12) is -27 dB; however, with MTM-DS the average isolation improves to -38 dB. With this technique the separation between the radiating element can be reduced to 0.66λo, where λ0 is free space wavelength at 10 GHz. In addition, with this technique there is 15% improvement in operating bandwidth. At frequencies of high impedance match of 9.95 GHz and 10.63 GHz the gain is 4.52 dBi and 5.40 dBi, respectively. Furthermore, the technique eliminates poor front-to-back ratio encountered in other decoupling methods. MTM-DS is also relatively simple to implement. Assuming adequate space is available between adjacent radiators the MTM-DS can be fixed retrospectively on existing antenna arrays, which makes the proposed method versatile.
Partially supported by innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET- 722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

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Thèses sur le sujet « Antenna arrays. MIMO systems. Eigenfunctions »

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