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1
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.'
2
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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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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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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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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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.
7
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.
8
Zheng, Gan. "Optimization in linear multiuser MIMO systems." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557923.
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Zheng, Gan, and 鄭淦. "Optimization in linear multiuser MIMO systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557923.
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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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Kang, Deokwon. "MIMO beamforming in multiuser wireless environments." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 81 p, 2009. http://proquest.umi.com/pqdweb?did=1885755741&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Yan, Jie Bang. "On-chip and MIMO antennas for furture wireless communications /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20YAN.
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Zhang, Li. "Signal processing for future MIMO-OFDM wireless communication systems." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54757/.
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The combination of multiple-input multiple-output (MIMO) technology and orthogonal frequency division multiplexing (OFDM) is likely to provide the air-interface solution for future broadband wireless systems. A major challenge for MIMO-OFDM systems is the problem of multi-access interference (MAI) induced by the presence of multiple users transmitting over the same bandwidth. Novel signal processing techniques are therefore required to mitigate MAI and thereby increase link performance. A background review of space-time block codes (STBCs) to lever age diversity gain in MIMO systems is provided together with an introduction to OFDM. The link performance of an OFDM system is also shown to be sensitive to time-variation of the channel. Iterative minimum mean square error (MMSE) receivers are therefore proposed to overcome such time-variation. In the context of synchronous uplink transmission, a new two-step hard-decision interference cancellation receiver for STBC MIMO-OFDM is shown to have robust performance and relatively low complexity. Further improvement is obtained through employing error control coding methods and iterative algorithms. A soft output multiuser detector based on MMSE interference suppression and error correction coding at the first stage is shown by frame error rate simulations to provide significant performance improvement over the classical linear scheme. Finally, building on the "turbo principle", a low-complexity iterative interference cancellation and detection scheme is designed to provide a good compromise between the exponential computational complexity of the soft interference cancellation linear MMSE algorithm and the near-capacity performance of a scheme which uses iterative turbo processing for soft interference suppression in combination with multiuser detection.
14
Abaza, Mohamed. "Cooperative MIMO techniques for outdoor optical wireless communication systems." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0073/document.
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Au cours de la dernière décennie, les communications optiques en espace libre (FSO) ont pris de l’ampleur dans les deux domaines académiques et industriels. L’importance de FSO s’appuie sur la possibilité de faire un système de transmission économique et écologique avec un débit élevé et sans licence à l’opposition des systèmes de transmission radiofréquences (RF). Dans la plupart des travaux antécédents sur les systèmes multi-émetteurs, seulement les canaux décorrélés ont été considérés. Un canal décorrélé nécessite un espace suffisant entre les émetteurs. Cette condition devient difficile et non-réalisable dans certaines applications. Pour cette raison, nos études se focalisent sur les performances des codes à répétition RC (Repitition Codes) et les codes OSTBC (Orthogonal Space-Time Block Codes) dans des canaux log-normaux corrélés en utilisant une modulation d’intensité et une détection directe (IM/DD). En addition, les effets des différentes conditions météorologiques sur le taux d’erreur moyen (ABER) sont étudiés. Les systèmes FSO à multi-entrées/ multi-sorties MIMO (Multiple-Input Multiple-Output) avec une modulation SSK (Space Shift Keying) ont été abordés. Les résultats obtenus montrent que la SSK est supérieure aux RC avec une modulation d’impulsion (Multiple Pulse Amplitude Modulation) pour toute efficacité spectrale égale ou supérieure à 4 bit/s/Hz. Nous avons aussi analysé les performances d’un système à sauts multiples (Multi-Hop) et des relais à transmission directe (forward relays). Nos simulations montrent que le système ainsi considéré est efficace pour atténuer les effets météorologiques et les pertes géométriques dans les systèmes de communication FSO. Nous avons montré qu’un tel système avec plusieurs entrées et une sortie (MISO, i.e. multiple-input single-output) à sauts multiples est supérieur à un système MISO avec un lien direct (direct link) avec une forte atténuation. Pour satisfaire la demande croissante des réseaux de communication à débits élevés, la communauté scientifique s'intéresse de plus en plus aux systèmes FSO avec des relais full-duplex (FD). Pour ces derniers systèmes, nous avons étudié la probabilité d'erreur moyenne (ABER) et nous avons analysé leurs performances. En considérant des différentes conditions de transmission, les performances de relais FD ont été comparées à celles d'un système avec un lien direct ou des relais half-duplex. Les résultats obtenus montrent que les relais FD ont le minimum ABER. En conséquence, les résultats obtenus dans cette thèse sont très prometteurs pour la prochaine génération de FSOFree-space optical (FSO) communication has been the subject of ongoing research activities and commercial attention in the past few years. Such attention is driven by the promise of high data rate, license-free operation, and cheap and ecological friendly means of communications alternative to congested radio frequency communications. In most previous work considering multiple transmitters, uncorrelated channel conditions have been considered. An uncorrelated channel requires sufficient spacing between transmitters. However, this can be difficult and may not be always feasible in some applications. Thereby, this thesis studies repetition codes (RCs) and orthogonal space-time block codes performance in correlated log-normal FSO channels using intensity modulation and direct detection (IM/DD). Furthermore, the effect of different weather conditions on the average bit error rate (ABER) performance of the FSO links is studied. Multiple-input multiple-output (MIMO) FSO communication systems using space shift keying (SSK) modulation have been also analyzed. Obtained results show that SSK is a potential technique for spectral efficiencies equal or greater than 4 bits/s/Hz as compared to RCs with multiple pulse amplitude modulations. The performance analysis of a multi-hop decode and forward relays for FSO communication system using IM/DD is also considered in this thesis. It is shown that multi-hop is an efficient technique to mitigate atmospheric turbulence and different weather attenuation effects and geometric losses in FSO communication systems. Our simulation results show that multiple-input single-output (MISO) multi-hop FSO systems are superior to direct link and MISO systems over links exhibiting high attenuation. Meeting the growing demand for higher data rates communication networks, a system with full-duplex (FD) relays is considered. For such a system, the outage probability and the ABER performance are analyzed under different turbulence conditions, misalignment error and path loss effects. FD relays are compared with the direct link and half-duplex relays. Obtained results show that FD relays have the lowest ABER and the outage probability as compared to the two other systems. Finally, the obtained results in this thesis are very promising towards the next generation of FSO systems
15
Wu, Shangbin. "Massive MIMO channel modelling for 5G wireless communication systems." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/2889.
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Massive Multiple-Input Multiple-Output (MIMO) wireless communication systems, equipped with tens or even hundreds of antennas, emerge as a promising technology for the Fifth Generation (5G) wireless communication networks. To design and evaluate the performance of massive MIMO wireless communication systems, it is essential to develop accurate, flexible, and efficient channel models which fully reflect the characteristics of massive MIMO channels. In this thesis, four massive MIMO channel models have been proposed. First, a novel non-stationary wideband multi-confocal ellipse Two-Dimensional (2-D) Geometry Based Stochastic Model (GBSM) for massive MIMO channels is proposed. Spherical wavefront is assumed in the proposed channel model, instead of the plane wavefront assumption used in conventional MIMO channel models. In addition, the Birth-Death (BD) process is incorporated into the proposed model to capture the dynamic properties of clusters on both the array and time axes. Second, we propose a novel theoretical non-stationary Three-Dimensional (3-D) wideband twin-cluster channel model for massive MIMO communication systems with carrier frequencies in the order of gigahertz (GHz). As the dimension of antenna arrays cannot be ignored for massive MIMO, nearfield effects instead of farfield effects are considered in the proposed model. These include the spherical wavefront assumption and a BD process to model non-stationary properties of clusters such as cluster appearance and disappearance on both the array and time axes. Third, a novel Kronecker Based Stochastic Model (KBSM) for massive MIMO channels is proposed. The proposed KBSM can not only capture antenna correlations but also the evolution of scatterer sets on the array axis. In addition, upper and lower bounds of KBSM channel capacities in both the high and low Signal-to-Noise Ratio (SNR) regimes are derived when the numbers of transmit and receive antennas are increasing unboundedly with a constant ratio. Finally, a novel unified framework of GBSMs for 5G wireless channels is proposed. The proposed 5G channel model framework aims at capturing key channel characteristics of certain 5G communication scenarios, such as massive MIMO systems, High Speed Train (HST) communications, Machine-to-Machine (M2M) communications, and Milli-meter Wave (mmWave) communications.
16
Jayasinghe, L. K. (Laddu Keeth Saliya). "Analysis on MIMO relaying scenarios in wireless communication systems." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526207391.
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Abstract The thesis concentrates on evaluating and improving performances of various multiple-input multiple-output (MIMO) relaying scenarios that are particularly relevant to future wireless systems. A greater emphasis is placed on important practical situations, considering relay deployments, availability of channel state information (CSI), limitations of spectrum, and information secrecy. Initially, the performance of a non-coherent amplify-and-forward (AF) MIMO relaying is analyzed when the relay is deployed with the relay-to-destination channel having a line-of-sight (LoS) path. The main attention is given to analyzing the performance of orthogonal space-time block coded based non-coherent AF MIMO system. Exact expressions of statistical parameters and performance metrics are derived considering the instantaneous signal-to-noise ratio (SNR) received at the destination. These performance metrics reveal that a strong LoS component in relay-destination channel always limits the performance promised by MIMO scattering environment when both nodes have multiple antennas. The thesis also considers scenarios in MIMO two-way relaying (TWR) with physical layer network coding (PNC) mapping at the relay. PNC mapping becomes complex with multiple streams being combined at the relay node. Joint precoder-decoder schemes are considered to ease this, and various studies are carried out depending on the CSI. The zero-forcing criterion is used at the nodes when perfect CSI is available. For the imperfect CSI scenario, a robust joint precoder-decoder design is considered. The precoder and decoder matrices are obtained by solving optimization problems, which are formulated to maximize sum-rate and minimize weighted mean square error (WMSE) under transmit power constraints on the nodes. Next, a precoder-decoder scheme for MIMO underlay device-to-device (D2D) communication system is investigated by considering two D2D modes; PNC based D2D and direct D2D. The joint design is based on minimizing mean square error (MSE) which is useful to mitigate interference, and to improve the performance of both D2D and cellular communications. Distributed and centralized algorithms are proposed considering bi-directional communication in both D2D and cellular communications. System performance is discussed with two transmit mode selection schemes as dynamic and static selection schemes. The results show that the PNC based D2D mode extends the coverage area of D2D communication. Finally, secure beamforming schemes for the PNC based MIMO TWR systems are investigated when multiple eavesdroppers are attempting to intercept the user information. The CSI of the user-to-eavesdropper channels is imperfect at the users. The channel estimation errors are assumed with both ellipsoidal bound and Gaussian Markov uncertainty models. Robust optimization problems are formulated considering both scenarios to design beamforming vectors at the users and relay. Numerical results suggest that the proposed algorithms converge fast and provide higher securityTiivistelmä Tässä väitöskirjassa keskitytään arvioimaan ja parantamaan suorituskykyä useissa moniantennitoistinjärjestelmissä, jotka ovat ajankohtaisia tulevaisuuden langattomissa verkoissa. Erityisesti työssä analysoidaan tärkeitä käytännön tilanteita, sisältäen toistimien sijoittamisen, kanavatiedon saatavuuden, rajoitetun taajuuskaistan ja tiedon salauksen. Aluksi epäkoherentin, vahvistavan ja jatkolähettävän moniantennitoistimen suorituskykyä analysoidaan tilanteessa, jossa toistin on sijoitettu siten, että kohteeseen on suora yhteys. Suorituskyvyn arvioinnin pääkohteena on ortogonaalinen tila-aika-tason lohkokoodattu epäkoherentti vahvistava ja jatkolähettävä moniantennitoistin. Työssä johdetaan tarkat lausekkeet tilastollisille parametreille ja suorituskykymittareille ottaen huomioon hetkellinen signaalikohinasuhde vastaanottimessa. Nämä suorituskykymittarit ilmaisevat, että toistimen ja kohteen välillä oleva vahva suoran yhteyden komponentti rajoittaa sitä suorituskykyä, jota moniantennijärjestelmän hajontaympäristö ennustaa. Työssä tutkitaan myös kahdensuuntaisia moniantennitoistimia, jotka käyttävät fyysisen kerroksen verkkokoodausta. Koodauksesta tulee monimutkaista, kun monia datavirtoja yhdistetään toistimessa. Tämän helpottamiseksi käytetään yhdistettyä esikoodaus-dekoodausmenetelmää, jota tutkitaan erilaisten kanavatietojen tapauksissa. Täydellisen kanavatiedon tapauksessa käytetään nollaanpakotuskriteeriä. Epätäydellisen kanavatiedon tapauksessa käytetään robustia yhdistettyä esikoodaus-dekoodausmenetelmää. Esikoodaus- ja dekoodausmatriisit saadaan ratkaisemalla optimointiongelmat. Nämä ongelmat on muodostettu maksimoimaan summadatanopeus, ja minimoimaan painotettu keskineliövirhe, kun optimointirajoitteina ovat solmujen lähetystehot. Seuraavaksi esikoodaus-dekoodausmenetelmää tutkitaan moniantennijärjestelmässä, jossa käytetään kahdentyyppistä laitteesta-laitteeseen (D2D) kommunikaatiomenetelmää: fyysisen kerroksen verkkokoodaukseen pohjautuvaa D2D- ja suoraa D2D-kommunikaatiota. Yhteissuunnittelu perustuu keskineliövirheen minimointiin, joka on hyödyllistä, kun halutaan vähentää häiriötä ja parantaa molempien verkkojen suorituskykyä. Työssä ehdotetaan hajautettuja ja keskitettyjä algoritmeja tilanteessa, jossa käytetään kaksisuuntaista kommunikaatiota molemmissa verkoissa. Järjestelmän suorituskykyä arvioidaan, kun käytetään kahta eri lähetystilan valintaa, dynaamista ja staattista. Tulokset osoittavat, että fyysisen kerroksen verkkokoodaukseen pohjautuva D2D kasvattaa D2D-kommunikaatiojärjestelmän kantamaa. Lopuksi, turvallisia keilanmuodostustekniikoita arvioidaan fyysisen kerroksen verkkokoodaukseen pohjautuvassa kahdensuuntaisessa moniantennitoistinjärjestelmässä, kun useat salakuuntelijat yritävät siepata käyttäjätiedon. Käyttäjillä on epäideaalinen kanavatieto heidän ja salakuuntelijoiden välisten linkkien kanavista. Kanavatiedon estimointivirheitä arvioidaan ellipsoidisella ja Gauss-Markov-epävarmuusmallilla. Robustit optimointiongelmat, joissa suunnitellaan keilanmuodostusvektorit käyttäjän ja toistimen välille, muodostetaan molemmille malleille. Numeeriset tulokset osoittavat, että ehdotetut algoritmit konvergoituvat nopeasti ja tarjoavat korkeamman turvallisuuden
17
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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Bala, Erdem. "Multichannel, multiuser and multiple antenna wireless communication systems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 184 p, 2007. http://proquest.umi.com/pqdlink?did=1251904851&Fmt=7&clientId=79356&RQT=309&VName=PQD.
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Wu, Tianyu. "Design and analysis of wireless communication systems with limited CSIT feedback /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20WUT.
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Wu, Xiaoting. "Array signal processing for MIMO radar /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20WU.
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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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Shao, Ziyun, and 邵子韵. "Design and analysis of detection algorithms for MIMO wireless communication systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47752804.
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The increasing demand for high-mobility and high data rate in wireless
communications results in constraints and problems in the limited radio spectrum,
multipath fading, and delay spread.
The multiple-input multiple-output (MIMO) system has been generally
considered as one of the key technologies for the next generation wireless
communication systems. MIMO systems which utilize multiple antennas in both
the transmit side and the receive side can overcome the abovementioned
challenges since they are able to increase the channel capacity and the spectrum
usage efficiency without the need for additional channel bandwidth.
The detection algorithm is a big bottleneck in MIMO systems. Generally, it is
expected to fulfill two main goals simultaneously: low computational complexity
and good error rate performance. However, the existing detection algorithms are
either too complicated or suffering from very bad error-rate performance.
The purpose of this thesis is to comprehensively investigate the detection
algorithms of MIMO systems, and based on that, to develop new methods which
can reduce the computational complexity while retain good system performance.
Firstly, the background and the principle of MIMO systems and the previous work
on the MIMO decoding algorithms conducted by other researchers are thoroughly
reviewed. Secondly, the geometrical analysis of the signal detection is
investigated, and a geometric decoding algorithm which can offer the optimum
BLER performance is proposed. Thirdly, the semidefinite relaxation (SDR)
detection algorithms are extended to high-order modulation MIMO systems, and a
novel SDR detector for 256-QAM constellations is proposed. The theoretical
analysis on the tightness and the complexity are conducted. It demonstrates that
the proposed SDR detector can offer better BLER performance, while its
complexity is in between those of its two counterparts. Fourthly, we combine the
SDR detection algorithms with the sphere decoding. This is helpful for reducing
the computational complexity of the traditional sphere decoding since shorter
initial radius of the hyper sphere can be obtained. Finally, the novel
lattice-reduction-aided SDR detectors are proposed. They can provide
near-optimum error rate performance and achieve the full diversity gain with very
little computational complexity added compared with the stand-alone SDR
detectors.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
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Shao, Lei. "Code design for MIMO-OFDM(A) systems /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5859.
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Liu, Yi. "The performance of future wireless communication systems." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:a2f0b75e-3b0d-406e-af1b-6c5038c18fae.
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Multimedia services provided through wireless networks, such as mobile television and video calls, have recently attracted great attention. These systems require higher data rates, better communication quality, and wider channel bandwidth compared with traditional wireless network services, such as voice calling and text messaging. In response to these demands, multiple-input multiple-output (MIMO) employing multiple antennas at both transmitter and receiver, has been investigated in recent years. Nevertheless, the major impediment in MIMO based wireless systems is the cost of the hardware due to the requirement of the complete radio frequency (RF) chain for each transmit and receive path. One technique named antenna subset selection has been proposed which can reduce the hardware complexity, for example, provide and smaller number of RF chains which are reconfigurable to serve multiple antennas, but retain good communication performance, such as increasing data rates and improving communication quality. On the other hand, network service providers have in recent years established wideband communication systems in order to provide more services and higher bandwidth to customers. However, this development lowers the communication link quality, since signals transmitted in wideband communication systems suffer frequency-selective fading. In order to reduce the fading, orthogonal frequency division multiplexing (OFDM) as a potential infrastructure in the fourth generation mobile communication networks is developed. Referring to the cost-performance ratio, an attractive future wireless system named antenna selection based MIMO-OFDM is considered to be widely utilized in civil wireless communications in near future. The working theory of antenna selection based MIMO-OFDM systems can be simply represented as that a data stream at each selected transmit/receiver antenna is sent/receive over a number of narrow band orthogonal subcarriers. This thesis addresses analysis of wireless channel and performance investigation of future wireless communication systems, such as MIMO and OFDM structures. Moreover, a novel significantly low computational complexity algorithm is introduced in this thesis, which is proposed for antenna selection MIMO-OFDM systems on the basis of multiple selection criteria. It is shown that the proposed selection algorithm clearly reduces the computational complexity load of the selection process and efficiently selects the optimum antenna subset of antenna selection MIMO-OFDM systems. The thesis concludes by outlining the advantage of the proposed antenna selection technique and points out its potential role in future wireless communications.
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Zhu, Xu. "Wireless MIMO antenna systems for frequency selective fading channels /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20ZHU.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 116-118). Also available in electronic version. Access restricted to campus users.
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Fu, Shengli. "Space-time coding and decoding for MIMO wireless communication systems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.57Mb, 156 p, 2005. http://wwwlib.umi.com/dissertations/fullcit?3182631.
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Kurpjuhn, Tobias P. [Verfasser]. "Transmission Strategies in Wireless MIMO Communication Systems / Tobias P Kurpjuhn." Aachen : Shaker, 2004. http://d-nb.info/1170537502/34.
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Kuo, Ping-Heng. "Channel Variations in MIMO Wireless Communication Systems: Eigen-Structure Perspectives." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1212.
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Many recent research results have concluded that the multiple-input multiple-output (MIMO) wireless communication architecture is a promising approach to achieve high bandwidth efficiencies. MIMO wireless channels can be simply defined as a link for which both the transmitting and receiving ends are equipped with multiple antenna elements. This advanced communication technology has the potential to resolve the bottleneck in traffic capacity for future wireless networks. Applying MIMO techniques to mobile communication systems, the problem of channel fading between the transmitters and receivers, which results in received signal strength fluctuations, is inevitable. The time-varying nature of the mobile channel affects various aspects of receiver design. This thesis provides some analytical methodologies to investigate the variation of MIMO eigenmodes. Although the scope is largely focussed on the temporal variation in this thesis, our results are also extended to frequency variation. Accurate analytical approximations for the level crossing rate (LCR) and average fade duration (AFD) of the MIMO eigenmodes in an independent, identically distributed (i.i.d.) flat-fading channel are derived. Furthermore, since several channel metrics (such as the total power gain, eigenvalue spread, capacity and Demmel condition number) are all related to the eigenmodes, we also derive their LCRs and AFDs using a similar approach. The effectiveness of our method lies in the fact that the eigenvalues and corresponding channel metrics can be well approximated by gamma or Gaussian variables. Our results provide a comprehensive, closed-form analysis for the temporal behavior of MIMO channel metrics that is simple, robust and rapid to compute. An alternative simplified formula for the LCR for MIMO eigenmodes is also presented with applications to different types of autocorrelation functions (ACF). Our analysis has been verified via Monte Carlo computer simulations. The joint probability density function (PDF) for the eigenvalues of a complex Wishart matrix and a perturbed version of it are also derived in this thesis. The latter version can be used to model channel estimation errors and variations over time or frequency. Using this PDF, the probabilities of adaptation error (PAE) due to feedback delay in some adaptive MIMO schemes are evaluated. In particular, finite state Markov chains (FSMC) have been used to model rate-feedback system and dual-mode antenna selection schemes. The PDF is also applied to investigate MIMO systems that merge singular value decomposition (SVD)-based transceiver structure and adaptive modulation. A FSMC is constructed to investigate the modulation state entering rates (MSER), the average stay duration (ASD), and the effects of feedback delay on the accuracy of modulation state selection in mobile radio systems. The system performance of SVD-based transceivers is closely related to the quality of the channel information at both ends of the link. Hence, we examine the effect of feedback time delay, which causes the transmitter to use outdated channel information in time-varying fading channels. In this thesis, we derive an analytical expression for the instantaneous signal to interference plus noise ratio (SINR) of eigenmode transmission with a feedback time delay. Moreover, this expression implies some novel metrics that gauge the system performance sensitivity to time-variations of the steering vectors (eigenvectors of the channel correlation matrix) at the transmitter. Finally, the fluctuation of the channel in the frequency domain is of interest. This is motivated by adaptive orthogonal frequency division multiplexing (OFDM) systems where the signalling parameters per subcarriers are assigned in accordance with some channel quality metrics. A Gaussian distribution has been suggested to approximate the number of subcarriers using certain signalling modes (such as outage/transmission and diversity/multiplexing), as well as the total data rates, per OFDM realization. Additionally, closed-form LCRs for the channel gains (including the individual eigenmode gains) over frequency are also derived for both single-input single-output (SISO) and MIMO-OFDM systems. The corresponding results for the average fade bandwidth (AFB) follow trivially, These results may be useful for system design, for example by calculating the feedback overheads based on subcarrier aggregation.
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Al-Askery, Ali Jaber Abdulwahab. "Reduced complexity detection for massive MIMO-OFDM wireless communication systems." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3880.
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The aim of this thesis is to analyze the uplink massive multiple-input multipleoutput with orthogonal frequency-division multiplexing (MIMO-OFDM) communication systems and to design a receiver that has improved performance with reduced complexity. First, a novel receiver is proposed for coded massive MIMO-OFDM systems utilizing log-likelihood ratios (LLRs) derived from complex ratio distributions to model the approximate effective noise (AEN) probability density function (PDF) at the output of a zero-forcing equalizer (ZFE). These LLRs are subsequently used to improve the performance of the decoding of low-density parity-check (LDPC) codes and turbo codes. The Neumann large matrix approximation is employed to simplify the matrix inversion in deriving the PDF. To verify the PDF of the AEN, Monte-Carlo simulations are used to demonstrate the close-match fitting between the derived PDF and the experimentally obtained histogram of the noise in addition to the statistical tests and the independence verification. In addition, complexity analysis of the LLR obtained using the newly derived noise PDF is considered. The derived LLR can be time consuming when the number of receive antennas is very large in massive MIMO-OFDM systems. Thus, a reduced complexity approximation is introduced to this LLR using Newton’s interpolation with different orders and the results are compared to exact simulations. Further simulation results over time-flat frequency selective multipath fading channels demonstrated improved performance over equivalent systems using the Gaussian approximation for the PDF of the noise. By utilizing the PDF of the AEN, the PDF of the signal-to-noise ratio (SNR) is obtained. Then, the outage probability, the closed-form capacity and three approximate expressions for the channel capacity are derived based on that PDF. The system performance is further investigated by exploiting the PDF of the AEN to derive the bit error rate (BER) for the massive MIMO-OFDM system with different M-ary modulations. Then, the pairwise error probability (PEP) is derived to obtain the upper-bounds for the convolutionally coded and turbo coded massive MIMO-OFDM systems for different code generators and receive antennas. Furthermore, the effect of the fixed point data representation on the performance of the massive MIMO-OFDM systems is investigated using reduced detection implementations for MIMO detectors. The motivation for the fixed point analysis is the need for a reduced complexity detector to be implemented as an optimum massive MIMO detector with low precision. Different decomposition schemes are used to build the linear detector based on the IEEE 754 standard in addition to a user-defined precision for selected detectors. Simulations are used to demonstrate the behaviour of several matrix inversion schemes under reduced bit resolution. The numerical results demonstrate improved performance when using QR-factorization and pivoted LDLT decomposition schemes at reduced precision.
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Zhang, Guchun. "Models and performances of wireless MIMO and cooperative communication systems." Thesis, Aston University, 2009. http://publications.aston.ac.uk/15411/.
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Multiple-antenna systems offer significant performance enhancement and will be applied to the next generation broadband wireless communications. This thesis presents the investigations of multiple-antenna systems – multiple-input multiple-output (MIMO) and cooperative communication (CC) – and their performances in more realistic propagation environments than those reported previously. For MIMO systems, the investigations are conducted via theoretical modelling and simulations in a double-scattering environment. The results show that the variations of system performances depend on how scatterer density varies in flat fading channels, and that in frequency-selective fading channels system performances are affected by the length of the coding block as well as scatterer density. In realistic propagation environments, the fading correlation also has an impact on CC systems where the antennas can be further apart than those in MIMO systems. A general stochastic model is applied to studying the effects of fading correlation on the performances of CC systems. This model reflects the asymmetry fact of the wireless channels in a CC system. The results demonstrate the varied effects of fading correlation under different protocols and channel conditions. Performances of CC systems are further studied at the packet level, using both simulations and an experimental testbed. The results obtained have verified various performance trade-offs of the cooperative relaying network (CRN) investigated in different propagation environments. The results suggest that a proper selection of the relaying algorithms and other techniques can meet the requirements of quality of service for different applications.
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Alsaadi, Fuad Eid S. "MIMO MC-CDMA systems over indoor optical wireless communication channels." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/1902/.
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Optical wireless communication systems offer a number of advantages over their radio frequency counterparts. The advantages include freedom from fading, freedom from spectrum regulations and abundant bandwidth. The main limitations of optical wireless systems include background noise attributed to natural and artificial light sources and multipath propagation. The former degrades the signal to noise ratio while the latter limits the maximum achievable data rate. This thesis investigates the use of transmit power adaptation in the design of optical wireless spot-diffusing systems to increase the power associated with the main impulse response components, resulting in a compact impulse response and a system that is able to achieve higher data rates. The work also investigates the use of imaging diversity receivers that can reject the background noise components received in directions not associated with the signal. The two techniques help improve the optical wireless system performance. The multibeam transmitter and the multi-detector angle diversity receiver or imaging receiver form a multiple input multiple output (MIMO) system. The work also investigates additional methods that can improve the performance such as transmitter beam angle adaptation, and improved modulation and coding in the form of multi-carrier code division multiple access (MC-CDMA). Furthermore, the work investigates the robustness of a link design that adopts the combination of these methods in a realistic environment with full mobility.
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Eneh, Titus Ikechukwu. "Adaptive MMSE multiuser receivers in MIMO OFDM wireless communication systems." Thesis, University of Greenwich, 2011. http://gala.gre.ac.uk/8041/.
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In a bid to cope with challenges of increasing demand for higher data rate, better quality of service, and higher network capacity, there is a migration from Single Input Single Output (SISO) antenna technology to a more promising Multiple Input Multiple Output (MIMO) antenna technology. On the other hand, Orthogonal Frequency Division Multiplexing (OFDM) technique has emerged as a very popular multi-carrier modulation technique, thus it is considered as a promising solution to enhance the data rate of future broadband wireless communication systems. The first contribution of this thesis is the development of a low complexity adaptive algorithm that is robust against slow and fast fading channel scenarios, in comparison to the conventional individual parameter estimation by E. Teletar in his famous paper of 1999. Implementing the Adaptive MMSE Receivers in MIMO OFDM systems which I refer to (AMUD MIMO OFDM), combines the adaptive minimum mean square error multiuser receiver's scheme with prior information of the channel and interference cancelation in the spatial domain, achieves enhanced joint channel estimation and signal detection which makes the new technique effectively mobile. A mathematical analysis and simulation results to estimate the Information Capacity of Mobile Communication system with MMSE DFE and OFDM receivers were investigated. The capacity of a stationary channel with ISI is achievable by both the single carrier MMSE DFE and multicarrier modulation over narrow sub channels with OFDM receivers. The achieved capacity result shows that in both techniques single carrier and multicarrier, apart from different implementations are essentially identical when it comes to achievable criteria for information channel capacity. Lastly, AMUD MIMO OFDM were compared with both adaptive vector pre-coding and iterative system and their performance were fantastic, results shows that it will assure transmission over a high channel capacity.
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Yao, Yao, and 姚瑤. "Carrier synchronization techniques in MIMO systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31246230.
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Pan, Zhengang, and 潘振崗. "Generalized beamforming for downlink of multi-user MIMO systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29636139.
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Yu, Yuanning Petropulu Athina P. "Blind identification of possibly under-determined convolutive MIMO systems /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1863.
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Peng, Wei. "Non-linear detection algorithms for MIMO multiplexing systems." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558563.
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Peng, Wei, and 彭薇. "Non-linear detection algorithms for MIMO multiplexing systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558563.
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Dai, Xiaoguang, and 戴晓光. "Receiver complexity reduction of multiple-input multiple-output wireless communication systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46589508.
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Guo, Xiaoyong. "Space-time code design for wireless communication systems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 168 p, 2010. http://proquest.umi.com/pqdweb?did=1992441381&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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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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Roger, Varea Sandra. "Design and Implementation of Efficient Algorithms for Wireless MIMO Communication Systems." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/16562.
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En la última década, uno de los avances tecnológicos más importantes que han hecho culminar la nueva generación de banda ancha inalámbrica es la comunicación mediante sistemas de múltiples entradas y múltiples salidas (MIMO). Las tecnologías MIMO han sido adoptadas por muchos estándares inalámbricos tales como LTE, WiMAS y WLAN. Esto se debe principalmente a su capacidad de aumentar la máxima velocidad de transmisión , junto con la fiabilidad alcanzada y la cobertura de las comunicaciones inalámbricas actuales sin la necesidad de ancho de banda extra ni de potencia de transmisión adicional. Sin embargo, las ventajas proporcionadas por los sistemas MIMO se producen a expensas de un aumento sustancial del coste de implementación de múltiples antenas y de la complejidad del receptor, la cual tiene un gran impacto sobre el consumo de energía. Por esta razón, el diseño de receptores de baja complejidad es un tema importante que se abordará a lo largo de esta tesis.
En primer lugar, se investiga el uso de técnicas de preprocesado de la matriz de canal MIMO bien para disminuir el coste computacional de decodificadores óptimos o bien para mejorar las prestaciones de detectores subóptimos lineales, SIC o de búsqueda en árbol. Se presenta una descripción detallada de dos técnicas de preprocesado ampliamente utilizadas: el método de Lenstra, Lenstra, Lovasz (LLL) para lattice reduction (LR) y el algorimo VBLAST ZF-DFE. Tanto la complejidad como las prestaciones de ambos métodos se han evaluado y comparado entre sí. Además, se propone una implementación de bajo coste del algoritmo VBLAST ZF-DFE, la cual se incluye en la evaluación.
En segundo lugar, se ha desarrollado un detector MIMO basado en búsqueda en árbol de baja complejidad, denominado detector K-Best de amplitud variable (VB K-Best). La idea principal de este método es aprovechar el impacto del número de condición de la matriz de canal sobre la detección de datos con el fin de disminuir la complejidad de los sistemasRoger Varea, S. (2012). Design and Implementation of Efficient Algorithms for Wireless MIMO Communication Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16562
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Habib, Bachir. "MIMO Channel Hardware Simulator for LTE and 802.11ac Wireless Communication Systems." Thesis, Rennes, INSA, 2013. http://www.theses.fr/2013ISAR0023.
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Pour évaluer les performances des systèmes de communications sans fil, un simulateur matériel de canal MIMO (Multiple-Input Multiple-Output) est réalisé pour les nouveaux systèmes de communication. Il fournit la vitesse de traitement nécessaire et permet d’évaluer les performances en temps réel. Il permet de comparer les différents systèmes dans les mêmes conditions souhaitées. Les objectifs de ce travail concernent principalement les modèles de canal MIMO et l'architecture de bloc numérique du simulateur matériel.Le simulateur matériel conçu peut être configuré avec les nouveaux réseaux radio-mobiles (LTE) et les réseaux locaux sans fil (WLAN 802.11ac). Il utilise des modèles de canaux standardisés, comme le TGn IEEE 802.11n et le 3GPP-LTE, ou des résultats de mesures effectuées avec un sondeur de canalMIMO conçu et réalisé dans notre laboratoire. Récemment, le sondeur de canal a été utilisé au cours de campagnes de mesure pour des environnements à bord d’un navire et de l’extérieur-vers-l’intérieur (outdoor-to-indoor). Un algorithme est proposé pour que les réponses impulsionnelles mesurées soient compatibles avec la bande des signaux LTE. En outre, le modèle de Kronecker avec des évanouissements de Rayleigh est utilisé pour obtenir un canal variant dans le temps.Le simulateur doit être capable de reproduire différents types d'environnement. Dans ce contexte, de nombreux scénarios ont été proposés. Ils considèrent le mouvement à l'intérieur et à l'extérieur pour des environnements et des réseaux hétérogènes. Un algorithme est proposé et analysé pour basculer entre les environnements d’une manière continue. Ces réseaux offrent des services à travers un réseau cellulaire à l'aide du LTE et sont capables de maintenir le service lors du passage à un réseau local sans fil WLAN 802.11ac.Deux architectures pour le bloc numérique du simulateur matériel sont proposées. La première opère dans le domaine fréquentiel en utilisant des modules de transformée de Fourier rapide (FFT/IFFT). Dans ce contexte, une nouvelle architecture fréquentielle améliorée qui fonctionne avec des signaux d'entrée de longue durée est proposée. La seconde opère dans le domaine temporel en utilisant des filtres à Réponse Impulsionnelle Finie (FIR).Les architectures ont été implémentées sur des circuits programmables (FPGA : Field Programmable Gate Array) Virtex-IV de Xilinx. Leurs occupations sur FPGA, la précision des signaux de sortie et leur latence sont analysées et comparées. De plus, une solution basée sur un facteur d’échelle automatique (ASF: Auto-Scale Factor) est introduite pour augmenter la précision des signaux de sortieTo evaluate the performance of the emerging mobile and wireless communication systems, a Multiple-Input Multiple-Output (MIMO) channel hardware simulator is designed and implemented using the recent communication standards. It provides the processing speed required to the real-time performance evaluation and allows comparing various systems in the same test conditions. The objectives of this work mainly concern the MIMO channel models and the digital block architecture of the hardware simulator. The hardware simulator can be configured with Long Term Evolution (LTE) and Wireless Local Area Network (WLAN) 802.11ac signals. It uses standard channel models, as 3GPP LTE and TGn IEEE 802.11n. It also allows replaying measurement results obtained with the MIMO channel sounder designed and realized at our laboratory. In fact, data obtained during measurement campaigns onboard a ship and for outdoor-to-indoor environments were used. The measured impulse responses are pre-processed in order to make them compatible with LTE or 802.11ac signals. Moreover, timevarying channel models are obtained using Kronecker model with Rayleigh fading.The simulator must be able to reproduce different types of environment. In this context, many scenarios considering realistic people movements have been proposed. They involve movements in outdoor, indoor, outdoor-to-indoor or heterogeneous environments. An algorithm is proposed and described to switch between the environments in a continuous manner. Heterogeneous wireless communication systems are also considered. These systems provide service through a cellular network using LTE standard and are able to maintain the service when switching to a WLAN 802.11ac, for example.Two architectures for the digital block of the hardware simulator are proposed. The first operates in the frequency domain using Fast Fourier Transform (FFT/IFFT) modules. A new improved frequency architecture that works for streaming mode input signals is proposed. The second operates in time domain using Finite Impulse Response (FIR) filters.The architectures of the digital block of the hardware simulator are implemented on a Field Programmable Gate Array (FPGA) Virtex-IV from Xilinx. Their occupation on the FPGA, the accuracy of the output signals and their latency are analyzed and compared. Moreover, a new algorithm, based on an Auto-Scale Factor (ASF), is added for the time domain architecture. This algorithm improves the precision of the output signals
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Zhou, Quan. "Wireless Communications with MIMO Systems: Analysis and Practice." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-06122006-113941/.
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Multiple input multiple output (MIMO) systems using multiple transmit and receive antennas are widely considered as the vital breakthrough that will allow future wireless systems to achieve higher date rates and link reliability with limited bandwidth and power resources. In this dissertation, we address four interesting topics in the wireless MIMO systems, in both point-to-point and multiuser environments. First, in a point-to-point MIMO spatial diversity system, usually the probability distribution function (PDF) of the received SNR is rather involved, which leads to the difficulty in analyzing the average symbol error rate (SER). We provide a succinct result at the high SNR region. Second, in point-to-point wireless MIMO communications, in order to protect the transmitted data against random channel impairment, we consider the problem of link adaptation, including rate adaptation and power control to improve the system performance and guarantee certain quality of service. Third, in a multiuser MIMO wireless network, there is another form of diversity called multiuser diversity which can be exploited to increase the system throughput. By analyzing the scheduling gain (defined as the rate difference between the opportunistic scheduling and round-robin scheduling scheme), we provide a complete analysis on the interaction between the spatial diversity and multiuser diversity. Fourth, in a multiuser MIMO wireless network, we propose a crosslayer-based scheduling scheme that exploits Tomlinson-Harashima Precoding (THP) at the physical (PHY) layer to reduce the multiuser scheduling burden at the medium access control (MAC) layer. Compared with some existing scheduling schemes, the proposed scheme greatly reduces the scheduling complexity while simultaneously improves overall system performance.
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Michailidis, Evangelos. "MIMO antenna systems for next generation wireless communications." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1234.
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Multiple Input Multiple Output wireless communications systems require as the name implies multiple antennas at the transmit and receive side of a link, as all multiple elements operationally occupy the same spectrum, the capacity of carrying information is increased with no increase in the transmission bandwidth or power. Antennas destined for MIMO systems need to address the issue of adequate isolation between elements and the issue of the diversity performance of the array, these issues become challenging for mobile terminals. In this thesis dual band arrays for the mobile and the access point are proposed along with dual band mutual coupling reduction and radiation pattern improvement methods. First a dual band two element printed inverted F stacked monopole array is proposed for the mobile terminal. The single elements in the array are easily tuneable and achieve impedance matching from an open stub. The configuration is compact, with radiators distanced at 0.13λ0. By use of a grid of parasitically coupled printed lines mutual coupling is reduced by 9dB, where at the lower band at 2.4GHz, S12 = −18dB. Then a dual band two element printed dipole array is proposed for a pico–micro cell access point. The dipoles are fed by a printed balun which provides wide impedance bandwidth at two bands. To improve the radiation pattern at both frequencies the array is positioned above a dual band frequency selective surface, acting as an artificial magnetic conductor, thus allowing the screen to be placed 0.03λ0 from the array while maintaining good radiation efficiency. Finally a brief discussion of dual band surface wave suppression for printed antennas is presented. Here it is suggested that the surface waves can be eliminated by a superstrate at one band and by an EBG lattice at the second band. Initial experiments with different size superstrates and three periods of mushroom type EBG, show that mutual coupling can be reduced and the radiation pattern can be modified.
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Chan, Tsz Ho. "Link adaptation algorithms for MIMO-based WiMAX systems /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CSED%202007%20CHANT.
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Xu, Ning. "Physical-Layer Network Coding for MIMO Systems." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc68065/.
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The future wireless communication systems are required to meet the growing demands of reliability, bandwidth capacity, and mobility. However, as corruptions such as fading effects, thermal noise, are present in the channel, the occurrence of errors is unavoidable. Motivated by this, the work in this dissertation attempts to improve the system performance by way of exploiting schemes which statistically reduce the error rate, and in turn boost the system throughput. The network can be studied using a simplified model, the two-way relay channel, where two parties exchange messages via the assistance of a relay in between. In such scenarios, this dissertation performs theoretical analysis of the system, and derives closed-form and upper bound expressions of the error probability. These theoretical measurements are potentially helpful references for the practical system design. Additionally, several novel transmission methods including block relaying, permutation modulations for the physical-layer network coding, are proposed and discussed. Numerical simulation results are presented to support the validity of the conclusions.
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So, Daniel Ka Chun. "MIMO wireless communications in frequency selective fading channels /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20SO.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 136-144). Also available in electronic version. Access restricted to campus users.
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Lamahewa, Tharaka Anuradha. "Space-time coding and space-time channel modelling for wireless communications /." View thesis entry in Australian Digital Theses Program, 2006. http://thesis.anu.edu.au/public/adt-ANU20070816.152647/index.html.
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Kirsch, Nicholas J. Dandekar Kapil. "Experimental analysis of power control and element spacing for unobtrusive MIMO antenna systems /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3072.
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Lim, Chan-Ping Edwin. "Computational electromagnetic modeling for wireless channel characterization." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1158607443.
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