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Grabner, Mitchell John James. "Practical Robust MIMO OFDM Communication System for High-Speed Mobile Communication." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc799501/.
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This thesis presents the design of a communication system (PRCS) which improves on all aspects of the current state of the art 4G communication system Long Term Evolution (LTE) including peak to average power ratio (PAPR), data reliability, spectral efficiency and complexity using the most recent state of the art research in the field combined with novel implementations. This research is relevant and important to the field of electrical and communication engineering because it provides benefits to consumers in the form of more reliable data with higher speeds as well as a reduced burden on hardware original equipment manufacturers (OEMs). The results presented herein show up to a 3 dB reduction in PAPR, less than 10-5 bit errors at 7.5 dB signal to noise ratio (SNR) using 4QAM, up to 3 times increased throughput in the uplink mode and 10 times reduced channel coding complexity.
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SAXENA, GAURAV. "DESIGN AND ANALYSIS OF MICROWAVE COMPONENTS FOR MIMO COMMUNICATION SYSTEM." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18776.
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Wireless communication demands better channel capacity with a high data rate in the modern era. To fulfill these demands, the MIMO-communication systems are developed that use manifold antennas for transmitter and receiver end. MIMO is a state-of-art technology that improves the reliability of the communication systems by utilizing the diversity technique to mitigate the multi-path fading issues, where signals may come together belligerently at the receiver. Improve spectral efficiency is achieved by the total transmitted power spreading over the antennas. Thus, MIMO can increase channel capacities as well as the reliability of the communication system without sacrificing extra transmitted power or power spectrum. Several MIMO antennas have been designed in the literature to improve their characteristics in terms of impedance bandwidth; miniaturization & isolation improvement. The MIMO-communication systems with THz range are required for high data speed in Terabit/sec (Tbps). Also, it is providing very high throughput per device (from multiple Gbps to several Tera-bps) including per area efficiency (bps/km2). It is also predicted that the world monthly traffic in smartphones will be about 40 Peta-bytes in 2021, so the demand for MIMO antennas will be increased in the future. In this thesis, various microwave components for the MIMO wireless communication system has been analyzed and designed. Three major components designed and analyzed in this thesis are 1. MIMO Antennas 2. Metamaterial Absorber 3. UWB Microwave Filter MIMO Antennas: In this thesis, various MIMO antennas for UWB, SWB, and Multiband applications have been designed. Various decoupling techniques to avoid the
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interference between antenna elements are designed which enhancing the diversity
parameters with improved channel capacity for modern wireless applications. To mitigate
the interference between bands and to improve the reliability of the signals, a notch
characteristic has been introduced. SAR analysis also discusses in this thesis with the
human head and confirms that proposed MIMO antennas are in the acceptable range with
1g and 10g of bio tissues given by FCC and EU for mobile and other near field
applications. All the MIMO antennas with different frequency characteristics are discussed
in Chapter-2 to Chapter-6.
Metamaterial Absorber: To improve the isolation level in MIMO antennas as well
as to minimize the Radar Cross Section (RCS) and Electromagnetic Interference (EMI), a
design of multiband metamaterial absorber (MMA) for X-band applications has been
suggested. This MMA provides three high absorbance bands at 8.2GHz, 9.45GHz, and
12.45GHz with 99.4%, 96.4%, and 91.25% absorbance respectively. Proposed MMA is
polarization insensitive in all three bands with minimum RCS -33.2dBm2. This absorber
structure has designed on FR-4 (4.4) substrate having tanδ = 0.02 with unit cell
dimension 20×20×1mm3. So the proposed absorber is found appropriate for stealth
aircraft, RCS and EMC reduction, isolation in MIMO antenna, imaging, and sensing in the
X-band applications, discussed in Chapter-7.
UWB Microwave Filter: In this research work, the design of the UWB filter with
extended stopband characteristics by using a parallel-coupled line, open-ended line, multimode
resonator (MMR), and defected ground structure (DGS) has been presented. This
filter provides good return and insertion loss in the passband (3.1-10.6GHz) as well as
stopband (10.8-18GHz). The group delay of the filter is almost constant throughout the
passband. Detailed analysis of supportive coupled, feeding, and the open-ended line is
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verified with equivalent circuits. The prototype of the filter is compact as 22×20mm2 with
a 109% fractional bandwidth. The proposed filter is suited for recent weather reporting
Radar, Imaging, and Satellite receiver systems because simulated results have good
agreement with measured results as discussed in the Chapter-8.
RESEARCH OBJECTIVES:
The major objectives of the research work are listed below:
1. To enhance the impedance bandwidth of the MIMO antenna and microstrip filter for
various wireless applications.
2. To design and analyze the circularly polarized MIMO antenna for GPS, vehicular and
5G applications.
3. To enhance the isolation between the various elements of the MIMO antenna, to
improve the various diversity parameters.
4. To enhance the specific absorption ratio (SAR) performance of the MIMO antenna for
a handhold and mobile applications.
5. To design a Metasurface for stealth and isolation improvement in MIMO antenna
applications.
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Turpin, Michael J. "An investigation of a multiple-input-multiple-output communication system with the Alamouti Space-time code." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FTurpin.pdf.
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Liu, Ran, and Hao Liu. "Maximum Capacity Antenna Design for an Indoor MIMO UWB Communication System." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4476.
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Ultra-wideband (UWB) offers a high data rate transmission, however it only can be used in short distance communication due to its low power restricted by regulations, therefore it is applicable for an indoor scenario. Within an enclosed (indoor) scenario, there exist many possible multipaths of electromagnetic waves which lead to an effect known as fading [Big07]. Since SISO systems suffer severely from it, in contrast, multiple-output-multiple-input (MIMO) systems take advantage of this multipath/diversity effect. Typical MIMO system utilizes antenna arrays to generate subchannels, but it has no guarantee of orthogonal channels or maximum capacity. Using a new antenna synthesis algorithm, optimal subchannels can be computed by decomposing the MIMO channel into parallel SISO subchannels through the employment of sampling antennas. Thereafter optimal real word antennas can be designed according to the synthesized antenna radiation pattern which result in the reduced hardware. The goal of this thesis will be expressed as follows: Firstly, a good strategy planning to reduce computing effort should be realized since all the design parameters to be analyzed are frequency dependent. Furthermore, a systematic framework of the synthesis must be designed for the UWB band. Lastly, the corresponding real world antenna should be designed and verified. In this thesis, a systematic synthesis framework has be developed and analyzed for the UWB spectrum. The channel matrix acquisition, the design of the ‘sampling antennas’ along with the algorithm to decompose the MIMO channel into parallel independent SISO subchannels are discussed in detail. Two realizations of the real world antennas as well as all the challenges in the design process are also presented. As consequences, an antenna system with optimal radiation pattern has been synthesized. This antenna system radiates orthogonal channels with sufficient power and has fixed beamforming (direction optimized according to the scenario and with averaging over various positions along with rotations) at the transmitter and receiver. The maximum capacity takes into account the scenario, frequency band, physical available space for the antenna array and polarization (added degree of freedom). This work also organizes the antenna synthesis algorithm for UWB in a systematic framework, meeting the objectives of the project.In this thesis, a UWB antenna synthesis based on the averaging strategies for the predefined indoor communication scenarios has been proposed, which contains both the indoor communication theoretical analysis and real world realization. The algorithm can be applied in an arbitrary indoor scenario over ultra wideband frequency. All synthesized results demonstrated that the designed sampling antenna configuration is able to provide optimized solutions. The synthesis method is based on computing optimal antenna configurations for a MIMO ultrawideband system. In order to maximize the throughput, there exists a sampling volume for both transmit and receive antennas. As such, the face-centered and body-centered cubic antenna arrays are utilized. Given that the system operates in the UWB band with a cognitive feature, the type of antenna, orientation, placement and MIMO diversity scheme have been well investigated. The radiation patterns of the antenna array cover the sampling volume and the bandwidth cover the UWB band. The goal of this thesis work concentrates on the analysis of an indoor communication to find an optimum solution on the antenna configuration and placement. The final objective was to design and realize an optimal MIMO-UWB antenna system.
Add: Waldhornstrasse 19, Karlsruhe, 76131, Germany Tel: +49 176 34467663
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Yu, Yiwei. "MIMO block spread OFDMA system for next generation mobile communications." Access electronically, 2008. http://ro.uow.edu.au/theses/109.
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Huang, Wei. "Linear transceiver design in MIMO system with imperfect channel state information /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECE%202007%20HUANG.
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Yang, Yumeng. "MIMO radio-over-fibre distributed antenna system for next generation wireless communication." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270865.
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This thesis introduces low-cost implementations for the next generation distributed antenna system (DAS) using analogue radio over fibre. A multiple-input-multiple-output (MIMO) enabled radio over fibre (RoF) system using double sideband (DSB) frequency translation system is proposed. In such a system, the 2x2 MIMO signals can be transmitted to the remote antenna units (RAUs) from the base station via a single optical link. By using the DSB frequency translation, the original single-input-single-output (SISO) DAS can be upgraded into the MIMO DAS without implementing parallel optical links. Experimentally, the DSB frequency translation 2x2 MIMO RoF system transmits 2x2 LTE MIMO signals with 20MHz bandwidth in each channel via a 300m MMF link. The condition number of the system is < 10dB within the power equaliser bandwidth which means the MIMO system is well-conditioned and the crosstalk between the channels can be compensated by the MIMO signal processing. To install the DSB frequency translation system in a wideband service-agnostic DAS, the original MIMO signals need to be translated into unoccupied frequency bands over the DAS, which are usually occupied by specific applications that are not to be transmitted over the DAS. The frequency spectrum allocation of the wireless services is analysed showing that by choosing a particular LO frequency (2.2GHz in the UK), in the DSB frequency translation system, the original MIMO signals can always be translated into unoccupied frequency bands so that the same infrastructure can support multiple services. The idea of DSB frequency translation system can not only support MIMO radio over fibre but can also improve the SFDR of a general radio over fibre system. Because when the upper sideband and the lower sideband of the signal after translation are converted back to the original frequency band, the noise adds incoherently but the signals add-up coherently, this gives the system theoretically 2dB 3rd order SFDR improvement. If the idea of the DSB frequency translation is extended into a higher number of sidebands, the system SFDR can be further improved. Experimentally, the system 3rd order SFDR can be improved beyond the intrinsic optical link by 2.7dB by using quadruple sideband (QSB) frequency translation. It means the optical bandwidth in a general RoF system can be traded for the electrical SFDR. By integrating the analogue and the digital RoF systems, a hybrid DAS has been demonstrated, showing that the EVM dynamic range for the 4G LTE service (using digital RoF link) can be improved to be similar to the 3G UMTS service (using analogue RoF link), so that fewer number of RAUs for the LTE services are needed.
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Takele, Berta. "Performance Evaluation of Simple Space-Time Block Coding on MIMO Communication System." Thesis, Växjö University, Växjö University, School of Mathematics and Systems Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-6988.
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This thesis discuss on new technique called space time block coding (especially Alamouti's code) which is used to increase capacity and reliability of data transmission over time varying multi-path fading channel. The over all work of the thesis included in the following four chapters.
In chapter-1 we are going to cover some theoretical part which is useful to understand thesis work and in chapter-2 we will discuss the comparison between simple space time block code (Alamouti's code) and MRRC (Maximum Ratio Receiver Combining) which is receiver diversity and then in chapter-3 we will see the channel capacity & probability error performance for 2x2 Alamouti code over Rayleigh and Rice fading channel .Finally the conclusion and further work included in chapter-4.
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Sit, Yoke Leen [Verfasser]. "MIMO OFDM Radar-Communication System with Mutual Interference Cancellation / Yoke Leen Sit." Karlsruhe : KIT Scientific Publishing, 2018. http://d-nb.info/1185986332/34.
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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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Potter, Chris, Kurt Kosbar, and Adam Panagos. "Hardware Discussion of a MIMO Wireless Communication System Using Orthogonal Space Time Block Codes." International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606194.
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ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, CaliforniaAlthough multiple-input multiple-output (MIMO) systems have become increasingly popular, the existence of real time results to compare with those predicted by theory is still surprisingly limited. In this work the hardware description of a MIMO wireless communication system using orthogonal space time block codes (OSTBC) is discussed for two antennas at both the transmitter and receiver. A numerical example for a frequency flat time correlated channel is given to show the impact of channel estimation.
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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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Schulze, Shaun. "Accurate modelling and realisation of a 4th generation wireless communication system." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1194.
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Koch, Tobias. "On heating up and fading in communication channels." Konstanz Hartung-Gorre, 2009. http://d-nb.info/995318603/04.
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Girnyk, Maksym. "A Statistical-Physics Approach to the Analysisof Wireless Communication Systems." Doctoral thesis, KTH, Kommunikationsteori, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149868.
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Multiple antennas at each side of the communication channel seem to be vital for future wireless communication systems. Multi-antenna communication provides throughput gains roughly proportional to the smallest number of antennas at the communicating terminals. On the other hand, multiple antennas at a terminal inevitably increase the hardware complexity of the latter. For efficient design of such systems relevant mathematical tools, capable of capturing the most significant features of the wireless multi-antenna channel - such as fading, spatial correlation, interference - are essential. This thesis, based on the asymptotic methods from statistical physics and random matrix theory, develops a series of asymptotic approximations for various metrics characterizing the performance of multi-antenna systems in different settings. The approximations become increasingly precise as the number of antennas at each terminal grows large and are shown to significantly simplify the performance analysis. This, in turn, enables efficient performance optimization, which would otherwise be intractable. After a general introduction, provided in Chapter 2, this thesis provides four different applications of large-system analysis. Thus, Chapter 3 analyzes multi-antenna multiple-access channel in the presence of non-Gaussian interference. The obtained large-system approximation of the sum rate is further used to carry out the precoder optimization routine for both Gaussian and finite-alphabet types of inputs. Meanwhile, Chapter 4 carries out the large-system analysis for a multi-hop relay channel with an arbitrary number of hops. Suboptimality of some conventional detectors has been captured through the concept of generalized posterior mean estimate. The obtained decoupling principle allows performance evaluation for a number of conventional detection schemes in terms of achievable rates and bit error rate. Chapter 5, in turn, studies achievable secrecy rates of multi-antenna wiretap channels in three different scenarios. In the quasi-static scenario, an alternating-optimization algorithm for the non-convex precoder optimization problem is proposed. The algorithm is shown to outperform the existing solutions, and it is conjectured to provide a secrecy capacity-achieving precoder. In the uncorrelated ergodic scenario, a large-system analysis is carried out for the ergodic secrecy capacity yielding a closed-form expression. In the correlated ergodic scenario, the obtained large-system approximation is used to address the corresponding problem of precoder optimization. Finally, Chapter6 addresses a practical case of random network topology for two scenarios: i) cellular mobile networks with randomly placed mobile users and ii) wiretap channel with randomly located eavesdroppers. Large-system approximations for the achievable sum rates are derived for each scenario, yielding simplified precoder optimization procedures for various system parameters.QC 20140901
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Ng, Ka Wai. "Generalized bit and power allocation for single and multi-user OFDM MIMO system in frequency selective fading channel /." View abstract or full-text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20NG.
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ALONZO, Mario. "Distributed MIMO Systems for 5G and Beyond-5G Wireless Networks." Doctoral thesis, Università degli studi di Cassino, 2021. http://hdl.handle.net/11580/83801.
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Massive Multiple-Input-Multiple-Output (MIMO) is a recent technlogy that will be exploited for 5G and beyond-5G wireless network due to the constraints given by the future wireless networks, such as low latency and high spectral efficiency. In this thesis, MIMO systems have been taken into account in order to study two different network architectures. The former is called Cell-Free (CF), and it has been studied at millimeter Wave (mmWave) and microwave frequencies, and the latter is called Distributed Multiple Input Multiple Output (D-MIMO) for factory automation. The first chapter of this thesis gives an overview of massive MIMO, so why there is the need to exploit this technology and gives some mathematical concept. In the second chapter the CF at mmwave frequencies has been studied. The CF is a recent network architecture, in order to alleviate the cell-edge problem and thus increase the system performance of unlucky users that happen to be located very far from their serving Access Point (AP). In this architecture a large number of distributed APs, connected to a central processing unit (CPU), simultaneously and jointly serve a much smaller number of mobile Station (MS) or users. Both APs and users are equipped with multiple antennas. Then, it has been analyzed an architecture that generalizes the CF, the so called User-centric (UC), where each AP has to serve only a limited number of users. A power control algorithm has been introduced by resorting a method called successive lower bound maximization, aimed at maximizing the sum-rate and the energy efficiency. At mmwave, a lot of antennas can be employed, this means that there is the need of using hybrid architecture at each AP in order to reduce complexity and cost by using a small number of radio frequency (RF) chains. With CF or UC, channel estimation and beamforming are locally evaluated, reducing the traffic load on the backhaul network. So, a comparison between a fully digital (FD) and hybrid (HY) architecture will be shown. What it is possible to anticipate is that the FD architecture provides better performances than the hybrid one. In the numerical results, the performances in term of energy efficiency and sum-rate on Downlink and Uplink, with uniform and optimal power allocation and with a fully digital and hybrid architectures will be addressed. Then, this thesis also focuses on the comparison between D-MIMO and CF architectures for factory automation, at microwave frequencies. In this case, communications between actuators (ACs) and APs inside an industrial scenario is considered by adopting those different communication systems. Then, different transmission modes are taken into account, Joint transmission joint transmission (JT), Cell-Free transmission (CFT), single AP transmission (SAT), and User-centric transmission (UCT). In SAT mode each AC is served by only one AP. Even for this scenario a power control rule has been taken into account. In the end, in numerical section, it has been shown the performances in terms of SINR and achievable rate, evaluated with the finite block length capacity (FBLC) formula, when different transmission modes and beamformers are employed, and moreover the improvement given by the use of a power control.
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Wolf, Anne. "Robust Optimization of Private Communication in Multi-Antenna Systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-203827.
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The thesis focuses on the privacy of communication that can be ensured by means of the physical layer, i.e., by appropriately chosen coding and resource allocation schemes. The fundamentals of physical-layer security have been already formulated in the 1970s by Wyner (1975), Csiszár and Körner (1978). But only nowadays we have the technical progress such that these ideas can find their way in current and future communication systems, which has driven the growing interest in this area of research in the last years. We analyze two physical-layer approaches that can ensure the secret transmission of private information in wireless systems in presence of an eavesdropper. One is the direct transmission of the information to the intended receiver, where the transmitter has to simultaneously ensure the reliability and the secrecy of the information. The other is a two-phase approach, where two legitimated users first agree on a common and secret key, which they use afterwards to encrypt the information before it is transmitted. In this case, the secrecy and the reliability of the transmission are managed separately in the two phases. The secrecy of the transmitted messages mainly depends on reliable information or reasonable and justifiable assumptions about the channel to the potential eavesdropper. Perfect state information about the channel to a passive eavesdropper is not a rational assumption. Thus, we introduce a deterministic model for the uncertainty about this channel, which yields a set of possible eavesdropper channels. We consider the optimization of worst-case rates in systems with multi-antenna Gaussian channels for both approaches. We study which transmit strategy can yield a maximum rate if we assume that the eavesdropper can always observe the corresponding worst-case channel that reduces the achievable rate for the secret transmission to a minimum. For both approaches, we show that the resulting max-min problem over the matrices that describe the multi-antenna system can be reduced to an equivalent problem over the eigenvalues of these matrices. We characterize the optimal resource allocation under a sum power constraint over all antennas and derive waterfilling solutions for the corresponding worst-case channel to the eavesdropper for a constraint on the sum of all channel gains. We show that all rates converge to finite limits for high signal-to-noise ratios (SNR), if we do not restrict the number of antennas for the eavesdropper. These limits are characterized by the quotients of the eigenvalues resulting from the Gramian matrices of both channels. For the low-SNR regime, we observe a rate increase that depends only on the differences of these eigenvalues for the direct-transmission approach. For the key generation approach, there exists no dependence from the eavesdropper channel in this regime. The comparison of both approaches shows that the superiority of an approach over the other mainly depends on the SNR and the quality of the eavesdropper channel. The direct-transmission approach is advantageous for low SNR and comparably bad eavesdropper channels, whereas the key generation approach benefits more from high SNR and comparably good eavesdropper channels. All results are discussed in combination with numerous illustrationsDer Fokus dieser Arbeit liegt auf der Abhörsicherheit der Datenübertragung, die auf der Übertragungsschicht, also durch geeignete Codierung und Ressourcenverteilung, erreicht werden kann. Die Grundlagen der Sicherheit auf der Übertragungsschicht wurden bereits in den 1970er Jahren von Wyner (1975), Csiszár und Körner (1978) formuliert. Jedoch ermöglicht erst der heutige technische Fortschritt, dass diese Ideen in zukünftigen Kommunikationssystemen Einzug finden können. Dies hat in den letzten Jahren zu einem gestiegenen Interesse an diesem Forschungsgebiet geführt. In der Arbeit werden zwei Ansätze zur abhörsicheren Datenübertragung in Funksystemen analysiert. Dies ist zum einen die direkte Übertragung der Information zum gewünschten Empfänger, wobei der Sender gleichzeitig die Zuverlässigkeit und die Abhörsicherheit der Übertragung sicherstellen muss. Zum anderen wird ein zweistufiger Ansatz betrachtet: Die beiden Kommunikationspartner handeln zunächst einen gemeinsamen sicheren Schlüssel aus, der anschließend zur Verschlüsselung der Datenübertragung verwendet wird. Bei diesem Ansatz werden die Abhörsicherheit und die Zuverlässigkeit der Information getrennt voneinander realisiert. Die Sicherheit der Nachrichten hängt maßgeblich davon ab, inwieweit zuverlässige Informationen oder verlässliche Annahmen über den Funkkanal zum Abhörer verfügbar sind. Die Annahme perfekter Kanalkenntnis ist für einen passiven Abhörer jedoch kaum zu rechtfertigen. Daher wird hier ein deterministisches Modell für die Unsicherheit über den Kanal zum Abhörer eingeführt, was zu einer Menge möglicher Abhörkanäle führt. Die Optimierung der sogenannten Worst-Case-Rate in einem Mehrantennensystem mit Gaußschem Rauschen wird für beide Ansätze betrachtet. Es wird analysiert, mit welcher Sendestrategie die maximale Rate erreicht werden kann, wenn gleichzeitig angenommen wird, dass der Abhörer den zugehörigen Worst-Case-Kanal besitzt, welcher die Rate der abhörsicheren Kommunikation jeweils auf ein Minimum reduziert. Für beide Ansätze wird gezeigt, dass aus dem resultierenden Max-Min-Problem über die Matrizen des Mehrantennensystems ein äquivalentes Problem über die Eigenwerte der Matrizen abgeleitet werden kann. Die optimale Ressourcenverteilung für eine Summenleistungsbeschränkung über alle Sendeantennen wird charakterisiert. Für den jeweiligen Worst-Case-Kanal zum Abhörer, dessen Kanalgewinne einer Summenbeschränkung unterliegen, werden Waterfilling-Lösungen hergeleitet. Es wird gezeigt, dass für hohen Signal-Rausch-Abstand (engl. signal-to-noise ratio, SNR) alle Raten gegen endliche Grenzwerte konvergieren, wenn die Antennenzahl des Abhörers nicht beschränkt ist. Die Grenzwerte werden durch die Quotienten der Eigenwerte der Gram-Matrizen beider Kanäle bestimmt. Für den Ratenanstieg der direkten Übertragung ist bei niedrigem SNR nur die Differenz dieser Eigenwerte maßgeblich, wohingegen für den Verschlüsselungsansatz in dem Fall keine Abhängigkeit vom Kanal des Abhörers besteht. Ein Vergleich zeigt, dass das aktuelle SNR und die Qualität des Abhörkanals den einen oder anderen Ansatz begünstigen. Die direkte Übertragung ist bei niedrigem SNR und verhältnismäßig schlechten Abhörkanälen überlegen, wohingegen der Verschlüsselungsansatz von hohem SNR und vergleichsweise guten Abhörkanälen profitiert. Die Ergebnisse der Arbeit werden umfassend diskutiert und illustriert
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Osterno, Igor Sousa. "EstimaÃÃo de canal no enlace reverso de sistemas VL-MIMO multi-celulares." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14843.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorEste trabalho se propÃe a investigar e propor diferentes tÃcnicas de estimaÃÃo de canal de mÃltiplas entradas e mÃltiplas saÃdas (MIMO) para sistemas de comunicaÃÃo multiusuÃrio operando em regime de interferÃncia em cenÃrio de mÃltiplas cÃlulas. AtenÃÃo particular à dada ao caso onde as estaÃÃes rÃdio-base sÃo equipadas com arranjos de antenas apresentando grande quantidade de antenas, configurando o que se tem referido na literatura como sistemas de comunicaÃÃo MIMO de grande dimensÃo (VL-MIMO, do inglÃs: very large MIMO). Algumas destas tÃcnicas exploram as propriedades das grandes matrizes aleatÃrias e sÃo menos afetadas pela contaminaÃÃo de pilotos. Nesta dissertaÃÃo, os parÃmetros do canal VL-MIMO sÃo estimados a partir de uma decomposiÃÃo em autovalores (EVD, do inglÃs: eigenvalue-decomposition) da matriz de covariÃncia na saÃda do arranjo de antenas receptoras. Esta tÃcnica se mostra menos sensÃvel à presenÃa de interferÃncia do que outras que nÃo exploram propriedades especÃficas da matriz de canal VL-MIMO, como à o caso da soluÃÃo clÃssica dos mÃnimos quadrados (LS, do inglÃs: least-squares). Nesse contexto, propÃe-se ainda uma soluÃÃo para o fator de ambiguidade multiplicativa do mÃtodo baseado em EVD, utilizando um simples produto de Khatri-Rao. Na segunda parte desta dissertaÃÃo, as propriedades dos sistemas VL-MIMO sÃo empregadas num problema de localizaÃÃo de fontes, a fim de determinar a direÃÃo de chegada (DOA) dos sinais incidentes sobre o arranjo, provenientes da cÃlula em questÃo. Explorando o subespaÃo de representaÃÃo dos sinais interferentes, propÃe-se o uso de um algoritmo de classificaÃÃo de tipo MUSIC para estimar a matriz de canal de forma cega. O mÃtodo proposto converte os altos ganhos de resoluÃÃo dos arranjos VL-MIMO em capacidade de reduÃÃo de interferÃncia, podendo fornecer estimativas do canal adequadas, mesmo sob nÃveis fortes de interferÃncia e tambÃm em casos onde os sinais do usuÃrio desejado e dos interferentes sÃo altamente correlacionados espacialmente. Extensas campanhas de simulaÃÃo computacional foram realizadas, dandoum carÃter exploratÃrio a esta dissertaÃÃo no sentido de abranger diferentes cenÃrios e avaliar as tÃcnicas investigadas em comparaÃÃo com soluÃÃes jà consolidadas, permitindo assim a elaboraÃÃo de um panorama mais completo de caracterizaÃÃo dos problemas de estimaÃÃo de parÃmetros no caso VL-MIMO.
The aim of this dissertation is mainly to investigate and propose different channel estimation techniques for a multicell multiuser multiple-input multiple-output (MIMO) communication system. Particular attention is payed to the case that is referred to as very large (VL) MIMO (VL-MIMO) arrays, where the base stations are equipped with a great (or even huge) number of antenna sensors. Some of these techniques exploit properties issued from the (large) Random Matrices Theory and are therefore less affected by the so-called pilot contamination effect. In this work, the parameters of the VL-MIMO channel are estimated from the eigenvalue decomposition (EVD) of the output covariance matrix of the receive antenna array. This technique is more robust to the interference of signals from other cells compared with methods that do not exploit the specific properties of the VL-MIMO channel matrix, which is the case of the classical least squares (LS) solution. In this context, this work also proposes a simpler way to resolve the scaling ambiguity remaining from the EVD-based method using the Khatri-Rao product. The second part of this dissertation exploits the VL-MIMO properties on a source localization problem, aiming to determine the direction of arrival (DoA) of the signals impinging on the antenna array from a given desired cell. Based on the subspace representation of the outer cell interference signals, we propose a new blind MUSIC-like classification algorithm to estimate the channel matrix. The proposed technique convert the high resolution gains of the VL-MIMO arrays into ability to reduce power of undesired signals, yielding good channel estimates even under high interference power levels, and including cases where desired and undesired signals are strongly correlated. Computer simulations have been done in order to cope with different situations and propagation scenarios, thus yielding an exploratory character to our research and allowing us to evaluate and assess the investigated algorithms, comparing them to consolidated solutions in order to establish a complete overview of the parameter estimation problem in the VL-MIMO case.
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Chan, Francis Chun Ngai Electrical Engineering & 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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Choi, Lai U. "Multi-user MISO and MIMO transmit signal processing for wireless communication /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20CHOI.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 167-170). Also available in electronic version. Access restricted to campus users.
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Dong, Lu. "MIMO Selection and Modeling Evaluations for Indoor Wireless Environments." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19767.
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Array-to-array, or multiple-input multiple-output (MIMO), links are known to provide extremely high spectral efficiencies in rich multipath environments, such as indoor wireless environments. The selection of a subset of receiver array antennas for a MIMO wireless link has been studied by many as a way to reduce cost and complexity in a MIMO system while providing diversity gain. Combined with a switched multi-beam beamformer, it becomes the beam selection system that can gain high signal-to-interference
ratio (SIR) improvement in an interference-imited environment.
The objective of this research is to evaluate the performance of low-complexity antenna or beam subset selection methods for small MIMO networks. The types of networks include (1) point-to-point MIMO links with out-of-system interference, (2)multi-user networks with a single, but possibly spatially distributed access point. We evaluate various selection techniques on measured indoor channels, which has not been done before. We propose a new practical selection metric, the peak-to-trough ratio of orthogonal frequency division multiplexing (OFDM) training symbols. We also compare antenna and beam selection on measured indoor channels under more general conditions than has previously been done. Finally, we consider some channel modeling issues associated with beamformers. We investigate the validity of three types of statistical MIMO channel models. A new beamformer is designed based on the ideal of the ``Weichselberger model.'
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Ding, Zhihong. "ARQ Techniques for MIMO Communication Systems." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1385.pdf.
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Rico, Ulises Pineda. "Link Optimisation for MIMO Communication Systems." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503000.
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Zhang, Fan. "Diversity strategies for MIMO communication systems." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:530327bb-e4d9-4ce2-8140-312e7d175c05.
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This thesis proposes a joint spatial diversity scheme in MIMO systems in order to improve the transmission reliability of the wireless links, thereby to extend the transmission range and increase the information throughput. Cyclic delay diversity (CDD) and antenna selection are employed here for their low complexity, high flexibility, no spectrum efficiency reduction and high compatibility with many existing standards. A bit error performance bound for CDD system with orthogonal frequency division multiplexing and convolutional coding in multipath Rayleigh fading channel is generated, which renders a fundamental understanding of the mechanism of CDD and can be used instructively for CDD system design. A transmit cyclic delay diversity and receive antenna selection (TCDD/RAS) system is proposed here to achieve a performance gain with lower additional complexity and no data rate reduction compared with a transmit orthogonal space-time block coding (OSTBC) system, which is combined with the optimum receive antenna selection scheme. A hybrid system with both OSTBC and CDD in the transmitter and antenna selection in the receiver is also derived to avoid the high complexity requirement and data rate degradation of the OSTBC system as well as the performance loss of the CDD system. A receive antenna selection criterion for the TCDD/RAS system based on the previous performance analysis results is defined, however it demands high computational complexity. Therefore a much simpler and faster selection rule, named maximum minimum post-processing SNR criterion, is generated for the TCDD/RAS system in flat fading channels and another maximum group minimum post-processing SNR selection principle is developed in frequency selective channels. Both of these two selection rules achieve higher diversity gains with lower additional complexity compared with the traditional norm and capacity selection rules. Two relay systems embedded with the TCDD/RAS scheme are also constructed: the MIMO relay system and the cooperative relay system. The joint diversity scheme in the MIMO relay system obtains a higher diversity gain than in the cooperative relay system. Moreover, these two relay systems could be combined to a system with multiple cooperative relay nodes on which multiple antennas are deployed depending on the practical requirement in the future wireless communication systems.
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Ximenes, Leandro Ronchini. "Tensor-based MIMO relaying communication systems." reponame:Repositório Institucional da UFC, 2015. http://www.repositorio.ufc.br/handle/riufc/12931.
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XIMENES, L. R. Tensor-based MIMO relaying communication systems. 2015. 134 f. Tese (Doutorado em Engenharia de Teleinformática) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2015.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2015-06-24T12:23:49Z No. of bitstreams: 1 2015_tese_lrximenes.pdf: 22186309 bytes, checksum: b90a5d56afa23e69c67413686ac097d4 (MD5)
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In cooperative communication systems, two or more transmitting terminals are combined to increase the diversity and/or the power of the signals arriving at a particular receiver. Therefore, even if the devices do not have more than one antenna, or if a significant propaga- tion loss is present between the two communicating nodes, the various transmitting elements can act as a virtual antenna array, thus obtaining the benefits of the multiple antenna (MIMO) systems, especially the increase in the capacity. Recently, tensor decompositions have been introduced as an efficient approach for channel estimation in cooperative com- munication systems. However, among the few works devoted to this task, the utilization of the PARAFAC tensor decomposition for modeling the received signals did not allow the development of techniques for joint symbol and channel estimation. Aiming to avoid the use of pilot sequences, which limits the overall spectral efficiency by dedicating a portion of the bandwidth only for the channel estimation task, the objective of this thesis is to provide new tensor-based strategies, including transmission systems and semi-blind receivers, for one-way two-hop MIMO relaying systems. Based on a Khatri-Rao space-time coding at the source and two different Amplify-and-Forward (AF) relaying strategies, two transmission schemes are proposed. For these systems, named PT2-AF and NP-AF, the received signals at the destination node follow respectively a PARATUCK2 and a nested PARAFAC tensor model. Exploiting uniqueness properties of these tensor models which are established in the thesis, several semi-blind receivers are derived. Some of these receivers are of iterative form us- ing an ALS algorithm, whereas some other ones have closed-form solutions associated with Khatri-Rao factorizations. Some simulation results are finally presented to illustrate the per- formance of the proposed receivers which are compared to some state-of-the-art supervised techniques
Em comunicações cooperativas, dois ou mais terminais de transmissão são combinados para aumentar a diversidade e/ou a potencia dos sinais que chegam a um determinado receptor. Portanto, mesmo que os dispositivos não disponham de mais de uma antena, ou que então haja uma grande perda por propagação entre dois pontos comunicantes, os diversos elementos transmissores podem atuar como um arranjo virtual de antenas, obtendo-se assim vantagens dos sistemas de múltiplas antenas (MIMO), sobretudo o aumento da capacidade de transmissão. Recentemente, a chamada analise tensorial tem se mostrado uma abordagem eficiente então para a estimação de canais em sistemas com diversidade cooperativa. Contudo, nos poucos trabalhos dedicados a essa tarefa, a utilização da decomposição tensorial PARAFAC para a modelagem dos sinais recebidos não possibilitou o desenvolvimento de técnicas de estimação conjunta de canais e símbolos. Com a idéia de se evitar o uso de sequencias de treinamento, que limita a eficiência espectral da transmissão por dedicar uma parte da largura de banda apenas para a tarefa de estimação dos canais, o objetivo desta tese é prover novas estratégias de comunicação, em termos de sistemas de transmissão e receptores semi-cegos, baseados em tensores adaptados a sistemas cooperativos MIMO unidirecionais de dois saltos. Dois sistemas de transmissão são propostos utilizando uma codificação espaço-temporal do tipo Khatri-Rao na fonte e duas estrategias de processamento Amplify-and-Forward (AF) no relay. Para estes sistemas, nomeados PT2-AF e NP-AF, os sinais recebidos no chamado nó de destino satisfazem os modelos tensoriais do tipo PARATUCK2 e Nested PARAFAC. Explorando as propriedades de unicidade destes modelos tensoriais estabelecidas nesta tese, vários receptores semi-cegos são derivados. Alguns destes receptores são do tipo ALS, enquanto outros são de soluções baseadas na factorização de produtos de Khatri-Rao. Resultados de simulação são apresentados para ilustrar os desempenhos dos receptores propostos em comparação a alguns estimadores supervisionados
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Negrão, João Lucas. "Efficient detection : from conventional Mimo to massive Mimo communication systems." Universidade Estadual de Londrina. Centro de Tecnologia e Urbanismo. Programa de Pós-Graduação em Engenharia Elétrica, 2018. http://www.bibliotecadigital.uel.br/document/?code=vtls000218370.
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Ao longo deste trabalho, problemas relacionados aos sistemas de comunicação equipados com múltiplas antenas no transmissor e receptor (MIMO - Multiple- Input Multiple-Output) são analisados sob o ponto de vista de detecção clássica, da otimização não-linear, bem como da pré-codificação linear, desde MIMO convencional (algumas antenas no Tx e Rx) até sistemas MIMO de larga-escala (massivo). Inicialmente, a eficiência de detecção de vários detectores MIMO foi analisada sob a prerrogativa de canais altamente correlacionados, situação em que sistemas MIMO apresentam elevada perda de desempenho, além de, em alguns casos, uma crescente complexidade. Diante deste cenário, foi estudado especificamente o comportamento em termos do compromisso complexidade x taxa de erro de bits (BER - Bit Error Rate), para diferentes técnicas de detecção, como o cancelamento de interferências sucessivo (SIC), redução treliça (LR), bem como a combinação de cada uma destas às técnicas lineares de detecção. Nessa análise, também foram considerados diferentes estruturas de antenas uniformes com arranjos geométricos lineares (ULA - uniform linear array) e de arranjo planar (UPA - uniform planar array) em ambos transmissor e receptor. Além disso, também foram considerados diferentes número de antenas e ordem de modulação. Em seguida, o problema de detecção MIMO foi estudado sob uma perspectiva de otimização não-linear, visando especificamente alcançar o desempenho ótimo. Foi analisada a solução de detecção com relaxação semi-definida (SDR - semi- definite relaxation). O detector SDR-MIMO é uma abordagem eficiente capaz de atingir o desempenho muito próximo ao ótimo, especialmente para baixas e médias ordens de modulação. Concentramos nossos esforços no desenvolvimento de uma aproximação computacionalmente eficiente para o algoritmo de detecção de máxima verossimilhança (ML - Maximum Likelihood) MIMO baseado na programação semi-definida (SDP - Semidefinite Programming) para as constelações M-QAM. Finalmente, estuda-se um problema de alocação de potência com o objetivo de maximizar a capacidade de um canal de broadcasting MIMO massivo em uma única célula equipada com pré-codificação forçagem à zero (ZFBF - zero-forcing beamforming) e inversão de canal regularizado (RCI - regularized channel inversion) na estação rádio base (BS). Nosso objetivo é investigar esse problema considerando um sistema massivo no limite, ou seja, quando o número de usuários, K, e antenas na BS, M, tendem ao infinito porém com uma razão constante, β = K M . Primeiramente deriva-se a relação sinal-interferência mais ruído (SINR) para ambos os pré-codificadores escolhidos. Em seguida, investiga-se um esquemas de alocação de potência ótimo que maximiza a soma das capacidades por antena sob uma restrição de potência máxima disponível, conclui-se que o problema é convexo e que a alocação de potência ótima segue a estratégia de watter-filling (WF). Também estudou-se o problema relacionado à alocação de potência em um grupo finito de usuários separados em grupos e determinou-se o impacto desse esquema na capacidade total do sistema.Throughout this work, problems related to communication systems equipped with multiple antennas in the transmitter and receiver (MIMO - Multiple-Input Multiple-Output) are analyzed from the point of view of classical detection, nonlinear optimization, as well as linear pre-coding, from conventional MIMO (some Tx and Rx antennas) to large-scale (massive) MIMO systems. Initially, the detection efficiency of several MIMO detectors were analyzed under the prerogative of highly correlated channels, in which situation, MIMO systems present a high loss of performance, and, in some cases, an increasing complexity. Considering this scenario, we have specifically studied the behavior in terms of compromise complexity x bit error rate (BER), for different detection techniques, such as the successive interference cancellation (SIC), lattice reduction (LR), as well as the combination of each of these with linear detection techniques. In this analysis, different uniform antenna structures with uniform linear array (ULA) and planar array array (UPA) were also considered in both transmitter and receiver side. In addition, different number of antennas and order of modulation were also considered. Next, the MIMO detection problem was studied from a nonlinear optimization perspective, specifically aiming to achieve optimum performance. The detection solution with semi-defined relaxation (SDR - it semidefinite relaxation) were analyzed. The SDR-MIMO detector is an efficient approach capable of achieving near-optimal performance, especially for low and medium modulation orders. We focused our efforts on developing a computationally efficient approach for the maximum likelihood (ML) MIMO detection algorithm based on semi-definite programming (SDP) for M-QAM constellations. Finally, we study an optimal power allocation problem aiming to maximizes the sum-rate capacity of a single cell massive MIMO broadcast channel equipped with zero-forcing beamforming (ZFBF) and regularized channel inversion (RCI) precoding at the base station (BS). Our purpose is to investigate this problem in the large-scale system limit, i.e, when the number of users, K, and antennas at the BS, M, tend to infinity with a ratio β = K/M being held constant. We first derive the signal to interference plus noise (SINR) ratio for both chosen precoders. Then we investigate optimal power allocation schemes that maximize the sum-rate per antenna under an average power constraint and we show that the problem is convex and the power allocation follows the well-known Water-Filling strategy. We also studied a problem related to an optimal power allocation at a finite group of clustered users and determine the impact of this scheme in the ergodic sum-rate capacity.
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Piazza, Daniele Dandekar Kapil. "Reconfigurable antennas for adaptive MIMO communication systems /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3037.
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Fan, Ho Yin. "MIMO detection schemes for wireless communication /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202002%20FAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 64-66). Also available in electronic version. Access restricted to campus users.
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Chan, Wing Chau. "Performance limits of MIMO wireless communications /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?ECED%202006%20CHANW.
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Parashar, Karthick Nagarat. "System-level approaches for fixed-point refinement of signal processing algorithms." Rennes 1, 2012. http://www.theses.fr/2012REN1E015.
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Le problème de l'optimisation des systèmes utilisant l'arithmétique virgule fixe est un problème d'optimisation combinatoire de complexité NP-difficile. Savoir analyser et optimiser des applications complexes et de taille réelle est le thème central de cette thèse. Une technique de type diviser-pour-régner, où un système donné est décomposé en plusieurs petits sous-systèmes organisés selon une hiérarchie est au cœur de cette approche. Cette décomposition ouvre la voie à l'évaluation rapide de la précision et au problème d'optimisation hiérarchique de la largeur des données et des opérations du système. En raison de la réduction du nombre de variables, la convergence du problème d'optimisation hiérarchique vers une solution est beaucoup plus rapide que dans le cas classique. Le modèle "Single Noise Source" (SNS) est proposé pour étudier les statistiques des erreurs de quantification. Au lieu de simplement se concentrer sur la moyenne et la variance du bruit des erreurs dues à la quantification, il fournit également des formules analytiques pour dériver les paramètres statistiques des processus aléatoires produisant les erreurs de quantification équivalentes à une simulation en virgule fixe. En présence des opérations " non-lisses " (un- smooth) telles que la décision dans les modulations QAM, les fonctions Min() ou Max(), etc. , il est pour l'instant inévitable d'utiliser la simulation en virgule fixe. Une technique pour l'évaluation analytique des statistiques des erreurs de quantification en présence d'opérateurs non-lisses dans les graphes ne contenant pas de rebouclage est également proposée. Afin de tenir compte également des systèmes ayant des rebouclages, une technique hybride qui utilise le modèle SNS pour accélérer les simulations en virgule fixe est de plus proposée. Un cadre d'utilisation de l'optimisation convexe est proposé comme heuristique pour résoudre le problème d'optimisation des largeurs. Cette nouvelle technique améliore non seulement la qualité de la solution, mais permet de résoudre le problème plus rapidement que les approches itératives classiques. L'application des techniques proposées permet non seulement de réduire les coûts du système mais aussi une réduction de plusieurs ordres de grandeur dans le temps nécessaire pour optimiser les systèmes utilisant l'arithmétique virgule fixeThe fixed-point refinement problem is a combinatorial optimization problem whose search space grows exponentially. It is known to be NP-hard in complexity. Scalability issues involved in performing fixed-point refinement are the central theme of this thesis. A divide-and-conquer technique, where a given system is decimated to smaller sub-systems organized in a hierarchy is at the heart of this approach. This paves way for fast accuracy evaluation and the proposed hierarchical word-length optimization problem. Due to the reduction in number of variables, the convergence of hierarchical optimization problem to a solution is much faster than in the classical case. The single noise source (SNS) model has been proposed to study the quantization error statistics. Instead of just focusing on the average noise-power and mean of the errors due to quantization, it also provides analytical formulae for deriving statistical parameters of the random process generating quantization errors due to fixed-point simulation. In the presence of un-smooth operations such as QAM-slicing, Min() or Max() etc. , it is inevitable to use fixed-point simulation. A technique for analytical evaluation of quantization error statistics in the presence of un-smooth quantizers applicable for feed-forward networks is also proposed. In order to address systems with feedback involving un-smooth operations, a hybrid technique that makes use of the SNS model to accelerate fixed-point simulation is proposed. A convex-optimization framework is proposed as an improved heuristic to solve the word-length optimization problem. This not only improves the quality of the solution but also solves the problem much faster than classical iterative approaches. Application of the proposed techniques has resulted in improved reduction in system costs even and a reduction of several orders of magnitude in the over all time required for fixed-point refinement
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Luo, Tuo. "Performance enhancements in practical MIMO communications systems /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20LUO.
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Radji, Djelili. "Asymptotic optimal detection for MIMO communication systems." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121110.
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The high complexity of optimal detection for spatial multiplexing MIMO systems motivates the need for more practical alternatives. Among many suboptimal schemes reported in the literature, very few can be proven to provide close to optimal performance with low fixed complexity. In this thesis, we consider a class of list-based detectors that first generate a list of candidate decision vectors, and then the best candidate in the list is chosen as the final decision. First, we perform a diversity analysis of such schemes and derive sufficient conditions for achieving optimal performance asymptotically. We then introduce the Sel-MMSE-OSIC algorithm that employs list-based detection and a diversity maximizing channel partition procedure that yields asymptotic optimality. Then we propose the MMSE-ISTP scheme which is an improved asymptotically optimal fixed complexity algorithm that provides substantial complexity reductions over Sel-MMSE-OSIC. This scheme is based on simplified channel partition and efficient tree based list detection. Simulations results show that Sel-MMSE-OSIC and MMSE-ISTP yield performances that are nearly indistinguishable from optimal at almost all SNR levels for space uncorrelated systems. To achieve further reductions in complexity for large constellation sizes, a variable complexity version of the MMSE-ISTP scheme is proposed. The resulting algorithm is a variable complexity scheme that operates on a very small subset of candidates, and employs an improved channel partition preprocessing that not only reduces complexity but also guarantees high SNR optimality over space uncorrelated channels. Simulations results confirm that the proposed scheme provides significant complexity reductions over conventional variable complexity detection schemes.La haute complexité associée à la méthode optimale de détection pour les systèmes MIMO utilisant le multiplexage spatial motive la recherche d'alternatives plus pratiques. Parmi les nombreuses méthodes non optimales proposées dans la littérature, très peu peuvent théoriquement guarantir une performance quasi-optimale avec une complexité fixe et relativement basse. Dans cette thèse, nous considérons une classe de détecteurs utilisant une liste, qui premièrement génèrent une liste de vecteurs candidats et ensuite choisissent le meilleur candidat dans cette liste comme décision finale. Dans un premier temps nous faisons une analyse de diversité pour ces méthodes et dérivons des conditions suffisantes pour atteindre asymptotiquement une performance optimale. Nous introduisons ensuite l'algorithme Sel-MMSE-OSIC qui emploie une méthode de détection utilisant une liste et une méthode de partition du canal à diversité maximale permettant l'optimalité asymptotique. Après, nous proposons l'algorithme MMSE-ISTP qui apporte des réductions substantielles de complexité comparé à l'algorithme Sel-MMSE-OSIC tout en ayant une complexité fixe et étant asymptotiquement optimal. Cette méthode est basée sur une simplification de la partition du canal et une méthode de détection efficace utilisant une liste générée à partir d'un arbre de détection. Les résultats des simulations par ordinateur démontrent que Sel-MMSE-OSIC et MMSE-ISTP délivrent des performances pratiquement indissociables de la performance optimale pour tous les rapports signal-sur-bruit pour des canaux non corrélés dans l'espace. Pour atteindre des reductions additionnelles de complexité pour les grandes constellations, une version de MMSE-ISTP à complexité variable est ensuite proposée. L'algorithme qui en résulte est un algorithme à complexité variable qui opère sur un nombre réduit de candidats et emploie une méthode de partition du canal améliorée qui non seulement réduit la complexité mais aussi guarantit l'optimalité pour des rapports signal-sur-bruit élevés pour des canaux non corrélés dans l'espace. Les résultats des simulations par ordinateur confirment que l'algorithme proposé permet des réductions significatives de la complexité comparé aux techniques à complexité variable conventionnelles.
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Guo, Yongfang. "Precoding and equalization for MIMO communication systems /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Lee, Justine Bing. "Transceiver Designs for MIMO Relay Communication Systems." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/83305.
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Recently, the application of SWIPT in the energy-limited wireless system has attracted much attention from researchers due to the SWIPT technology provide the capability to prolong the limited lifetime of the wireless system. For a wireless communication system, a relay node helps to extend the network coverage, while the MIMO relay technique helps in enhancing the system performance. In this thesis, the investigation concerning the application of SWIPT in the MIMO relay system is investigated.
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Maharaj, Bodhaswar Tikanath Jugpershad. "MIMO channel modelling for indoor wireless communications /." Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-07292008-130655/.
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Li, Yabo. "Space-time encoding and decoding for MIMO systems and cooperative communication systems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.82 Mb., 155 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3205421.
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Wang, Dong. "Space-time trellis code design with simple decoding for MIMO communication systems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.87 Mb., 156 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3200526.
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Hoydis, Jakob. "Random matrix theory for advanced communication systems." Phd thesis, Supélec, 2012. http://tel.archives-ouvertes.fr/tel-00765458.
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Advanced mobile communication systems are characterized by a dense deployment of different types of wireless access points. Since these systems are primarily limited by interference, multiple-input multiple-output (MIMO) techniques as well as coordinated transmission and detection schemes are necessary to mitigate this limitation. Thus, mobile communication systems become more complex which requires that also the mathematical tools for their theoretical analysis must evolve. These must be able to take the most important system characteristics into account, such as fading, path loss, and interference. The aim of this thesis is to develop such tools based on large random matrix theory and to demonstrate their usefulness with the help of several practical applications, such as the performance analysis of network MIMO and large-scale MIMO systems, the design of low-complexity polynomial expansion detectors, and the study of random beamforming techniques as well as multi-hop relay and double-scattering channels. The methods developed in this work provide deterministic approximations of the system performance which become arbitrarily tight in the large system regime with an unlimited number of transmitting and receiving devices. This leads in many cases to simple and close approximations of the finite-size system performance and allows one to draw relevant conclusions about the most significant parameters. One can think of these methods as a way to provide a deterministic abstraction of the physical layer which substantially reduces the system complexity. Due to this complexity reduction, it is possible to carry out a system optimization which would be otherwise intractable.
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Sansrimahachai, Puttachad. "Blind source separation algorithms for MIMO communication systems." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419916.
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Berenguer, Ignacio. "Advanced signal processing techniques for MIMO communication systems." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614924.
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Shahriar, Chowdhury M. R. "Resilient Waveform Design for OFDM-MIMO Communication Systems." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56973.
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This dissertation addresses physical layer security concerns, resiliency of the Orthogonal Frequency Division Multiplexing (OFDM) and the Multiple Input Multiple Output (MIMO) systems; the `de-facto' air-interface of most wireless broadband standards including LTE and WiMAX. The major contributions of this dissertation are: 1) developing jamming taxonomy, 2) proposing OFDM and MIMO equalization jamming attacks and countermeasures, 3) developing antijam (AJ) MIMO systems, and 4) designing null space projected overlapped-MIMO radar waveform for spectrum sharing between radar and communications system.
First, we consider OFDM systems under various jamming attacks. Previous research is focused on jamming OFDM data transmissions. We focus on energy efficient attacks that can disrupt communication severely by exploiting the knowledge of target waveform. Specifically, these attacks seek to manipulate information used by the equalization algorithm to cause errors to a significant number of symbols, i.e., pilot tones jamming and nulling. Potential countermeasures are presented in an attempt to make OFDM waveform robust and resilient. The threats were mitigated by randomizing the location and value of pilot tones, causing the optimal attack to devolve into barrage jamming.
We also address the security aspects of MIMO systems in this dissertation. All MIMO systems need a method to estimate and equalize channel, whether through channel reciprocity or sounding. Most OFDM-based MIMO systems use sounding via pilot tones. Like OFDM attacks, this research introduces MIMO channel sounding attack, which attempts to manipulate pilot tones to skew the channel state information (CSI) at the receiver.
We describe methods of designing AJ MIMO system. The key insight is that many of the theoretical concepts learned from transmit beamforming and interference alignment (IA) in MIMO systems can be applied to the field of AJ and robust communications in the presence of jammers. We consider a realistic jamming scenario and provide a `receiver-only' and a transmitter `precoding' technique that allow a pair of two-antenna transceivers to communicate while being jammed by a malicious non-cooperative single-antenna adversary.
Finally, we consider designing a collocated MIMO radar waveform, which employs a new MIMO architecture where antenna arrays are allowed to overlap. This overlapped-MIMO radar poses many advantages including superior beampattern and improvement in SNR gain. We combine this radar architecture with a projection-based algorithm that allows the radar waveform to project onto the null space of the interference channel of MIMO communications system, thus enabling the coexistence of radar and communications system.Ph. D.
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Wu, Xiping. "Wireless communication systems based on spatial modulation MIMO." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10505.
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Spatial modulation (SM) is a unique single-stream, multiple-input multiple-output (MIMO) transmission technique. Unlike traditional MIMO schemes, SM sends out signals through a single active antenna, and achieves multiplexing gains by encoding information bits into the index of the currently active antenna. In contrast to multi-stream MIMO systems, this particular characteristic offers great superiority in two main aspects. Firstly, SM completely avoids inter-channel interference. Secondly, SM requires a single radio-frequency chain, regardless of the number of antennas used, and therefore exhibits a significant energy saving. However, the property of a single active antenna challenges the channel estimation process for SM: the transmit antennas have to be activated sequentially for sending pilot signals. As a result, the time consumed in pilot transmission is proportional to the number of transmit antennas. However, this fact has so far been neglected in related research. Also, published research on SM has focused on point-to-point communications, and few have covered a network perspective. In this thesis, a comprehensive study is undertaken on SM systems in single-user, multi-user and multi-cell scenarios. As a unique three-dimensional modulation scheme, SM enables a trade-off between the size of the signal constellation diagram and the size of the spatial constellation diagram. In this thesis, an optimum transmit structure is proposed for SM to employ an adaptive scale of antennas against channel correlations. Unlike traditional antenna selection methods, this new approach is not sensitive to fast fading, due to the exploitation of statistical channel state information (CSI) instead of instant CSI. The proposed transmit structure is demonstrated to have a near-optimal performance against exhaustive search, while achieving very low computational complexity. In addition, three novel methods are developed to improve the channel estimation process for SM. A first method estimates the entire MIMO channel by sending pilot signals through only one of the transmit antennas, among which the channel correlation is exploited. In a similar way but focusing on the receiver, a second method can improve the estimation accuracy without increasing the pilot sequence length. A third method balances the transmission power between pilot and data to minimise the bit error rate. A framework of combined channel estimation is also proposed, in which the three methods are jointly applied. Furthermore, the antenna allocation in multi-user SM is studied, in order to explore multi-user diversity gains. A method that jointly manages transmit antennas and receive antennas for all co-channel users is proposed. The aim of this new method is to maximise the channel capacity for each user, and the fairness among users is taken into account. It is demonstrated that the proposed method significantly improves the performance of multi-user SM, especially when serving a large number of users. Finally, a novel cooperative scheme is proposed for SM in a multi-cell scenario. Based on the concept of coordinated multi-point transmission (CoMP), this scheme enables the coordinated users to swap the base station antennas pertaining to them. A three-tier cellular architecture is further developed to switch between CoMP and the cooperative scheme.
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Bergman, Svante. "Bit loading and precoding for MIMO communication systems." Doctoral thesis, Stockholm : Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10622.
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Gopal, Lenin. "Robust transceiver designs for MIMO relay communication systems." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/643.
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The thesis investigates robust linear and non-linear transceiver design problems for wireless MIMO relay communication systems with the assumption that the partial information of the channel is available at the relay node. The joint source and relay optimization problems for MIMO relay systems are highly nonconvex, in general. We transform the problems into suitable forms which can be efficiently solved using standard convex optimization techniques. The proposed design schemes outperform the existing techniques.
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Nguyen, Khoa Xuan. "Transceiver Optimization for Interference MIMO Relay Communication Systems." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/48822.
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This thesis focuses on transceivers design for interference MIMO relay systems. Based on the MMSE criterion, several iterative algorithms are proposed to jointly optimize the source, relay, and receiver matrices subjecting to the individual power constraints at the source and the relay nodes. These algorithms have better performance than some existing algorithms and provide a better performance-complexity trade-off which is interesting in practical interference MIMO relay communication systems.
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Conder, Phillip. "Using multipath fading to increase performance of wireless communication systems." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061005.155049/index.html.
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Sharma, Maneesha. "Effective channel state information (CSI) feedback for MIMO systems in wireless broadband communications." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/71549/2/Maneesha_Sharma_Thesis.pdf.
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This research has analysed both reciprocity and feedback mechanisms in multi-antenna wireless systems. It has presented the basis of an effective CSI feedback mechanism that efficiently provides the transmitter with the minimum information to allow the accurate knowledge of a rapidly changing channel. The simulations have been conducted using MATLAB to measure the improvement when the channel is estimated at the receiver in a 2 X 2 multi-antenna system and compared to the case of perfect channel knowledge at the receiver.
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Chen, Runhua. "Multiuser MIMO systems in single-cell and multi-cell wireless communication." Thesis, 2007. http://hdl.handle.net/2152/3017.
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Chen, Chien-Chang, and 陳建昌. "Joint MIMO Precoder Design with Semidefinite Relaxation Detection in MIMO Communication System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/68672717676160212843.
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