Дисертації з теми "Wireless MIMO Communications"
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1
Stanković, Veljko. "Multi-user MIMO wireless communications." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985258039.
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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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3
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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4
Sohaib, Sarmad. "Energy efficient cooperative wireless communications." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/energy-efficient-cooperative-wireless-communications(a852e1e2-04ad-4311-8004-53babe529e1b).html.
Повний текст джерелаАнотація:
Cooperative diversity exploits the broadcast nature of wireless channels and uses relays to improve link reliability. Most cooperative communication protocols are assumed to be synchronous in nature, which is not always possible in wireless communication. Also the relay nodes are assumed to be half duplex which in turn reduces the spectral efficiency. In this thesis, we first present a novel asynchronous cooperative communication protocol exploiting polarization diversity, which does not require synchronization at the relay node. Dual polarized antennas are employed at the relay node to achieve full duplex amplify-and-forward (ANF) communication. Hence the transmission duration is reduced which results into an increased throughput rate. Capacity analysis of the proposed scheme ascertains the high data rate as compared to conventional ANF. Bit error rate (BER) simulation also shows that the proposed scheme significantly outperforms both the non-cooperative single-input single-output and the conventional ANF schemes. Considering channel path loss, the proposed scheme consume less total transmission energy as compared to ANF and non-cooperative scheme in more practical distance range. Thus the proposed scheme is suitable for high rate and energy efficient relay-enabled communication. In addition to that, we also present a novel power allocation scheme for multiple relay nodes that results in efficient cooperative multiple-input multiple-output (MIMO) communication. Considering channel path loss, the total transmission energy is distributed between the source and the relay nodes. The energy distribution ratio between the relay and direct link is optimized such that the quality of received signal is maintained with minimum total transmission energy consumption. We calculate the energy distribution ratio analytically and verified it through computer simulation. With the new power allocation scheme, the system also obtains an increased channel capacity as compared to cooperative scheme with conventional equal power allocation and non-cooperative scheme. Optimal relay positioning with proposed energy allocation scheme is also explored to maximize the capacity.
5
Kim, Kihong. "Interference Mitigation in Wireless Communications." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7647.
Повний текст джерелаАнотація:
The primary objective of this thesis is to design advanced interference resilient schemes for asynchronous slow frequency hopping wireless personal area networks (FH-WPAN) and time division multiple access (TDMA) cellular systems in interference dominant environments. We also propose an interference-resilient power allocation method for multiple-input-multiple-output (MIMO) systems.
For asynchronous FH-WPANs in the presence of frequent packet collisions, we propose a single antenna interference canceling dual decision feedback (IC-DDF) receiver based on joint maximum likelihood (ML) detection and recursive least squares (RLS) channel estimation. For the system level performance evaluation, we propose a novel geometric method that combines bit error rate (BER) and the spatial distribution of the traffic load of CCI for the computation of packet error rate (PER). We also derived the probabilities of packet collision in multiple asynchronous FH-WPANs with uniform and nonuniform traffic patterns.
For the design of TDMA receivers resilient to CCI in frequency selective channels, we propose a soft output joint detection interference rejection combining delayed decision feedback sequence estimation (JD IRC-DDFSE) scheme. In the proposed scheme, IRC suppresses the CCI, while DDFSE equalizes ISI with reduced complexity. Also, the soft outputs are generated from IRC-DDFSE decision metric to improve the performance of iterative or non-iterative type soft-input outer code decoders.
For the design of interference resilient power allocation scheme in MIMO systems, we investigate an adaptive power allocation method using subset antenna transmission (SAT) techniques. Motivated by the observation of capacity imbalance among the multiple parallel sub-channels, the SAT method achieves high spectral efficiency by allocating power on a selected transmit antenna subset. For 4 x 4 V-BLAST MIMO systems, the proposed scheme with SAT showed analogous results. Adaptive modulation schemes combined with the proposed method increase the capacity gains. From a feasibility viewpoint, the proposed method is a practical solution to CCI-limited MIMO systems since it does not require the channel state information (CSI) of CCI.
6
Dong, Lu. "MIMO Selection and Modeling Evaluations for Indoor Wireless Environments." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19767.
Повний текст джерелаАнотація:
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.'
7
Zhou, Quan. "Wireless Communications with MIMO Systems: Analysis and Practice." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-06122006-113941/.
Повний текст джерелаАнотація:
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.
8
Michailidis, Evangelos. "MIMO antenna systems for next generation wireless communications." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1234.
Повний текст джерелаАнотація:
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.
9
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.
10
Jensen, Michael A., and Michael D. Rice. "SPACE-TIME CODING FOR WIRELESS COMMUNICATIONS." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/605605.
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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, CaliforniaSignal fading and intersymbol interference created by multipath propagation have traditionally limited the throughput on wireless communications systems. However, recent research has demonstrated that by using multiple antennas on both transmit and receive ends of the link, the multipath channel can actually be exploited to achieve increased communication throughput over single-antenna systems. This paper provides an introductory description of such multi-antenna communications systems, focusing on basic explanations of how they achieve capacity gains. Computed and measured capacity results are used to demonstrate the potential of these systems.
11
Dambul, Katrina D. "Multiple-input multiple-output (MIMO) in optical wireless communications." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558676.
Повний текст джерелаАнотація:
There is growing demand for indoor wireless communication systems with higher bandwidth and higher data rates. However, the crowded radio frequency (RF) spectrum has caused researchers to consider optical wireless systems. In this thesis, optical signals in the visible region of the spectrum are used. White LEDs are used as transmitters as they provide higher signal-to-noise (SNR) levels and a better link budget than the infrared alternative. Typical modulation bandwidths for white LEDs are limited to tens of MHz. Thus, multiple-input multiple-output (MIMO) transmission is considered as a means to increase data rate. The development of the indoor optical wireless MIMO system begins with the geometrical and mathematical analysis of a single-input single-output (SISO) system and a single-input multiple- output (SIMO) system. The same analysis is then performed for a MIMO system. For the MIMO system, an experimental demonstration using white LEDs and non-imaging receivers are reported. Results include coverage measurements and an SNR analysis. There are limitations using non- imaging receivers, such as coverage limitations and symmetry problems, which cause problem with signal recovery. To improve these limitations, imaging receivers are considered. The design and development of an experimental demonstration of an indoor optical wireless MIMO system with an imaging receiver is presented. The experimental setup consists of a transmitter with a 2 x 2 array of white LEDs and a receiver with a 3 x 3 photo detector array. The system transmits data at a bit rate of 2Mbit/s/channel. Detailed design specifications and optical design are presented. Results show that certain positions within the system coverage area have error-free operation. The BER and SNR analysis shows that the overall BER improves with the overall SNR. In order to exploit the full potential of the system, future work should focus on improving the SNR and BER of the system.
12
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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13
Mohammed, Karim Ossama. "A MIMO decoder accelerator for next generation wireless communications." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1875366181&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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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.
Повний текст джерелаАнотація:
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.
15
Burge, Joseph. "Polarisation MIMO indoor wireless communications using highly compact antennas and platforms." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/polarisation-mimo-indoor-wireless-communications-using-highly-compact-antennas-and-platforms(e23fb834-e17e-4434-88c9-90c57d99e055).html.
Повний текст джерелаАнотація:
In the indoor environment, multipath fading causes the received signal amplitude to fluctuate rapidly over space and frequency. Multiple-in multiple-out (MIMO) systems overcome this phenomenon through the use of multiple antennas on transmitters and receivers. This establishes multiple independent MIMO sub-channels between antenna pairs, which allows a theoretical increase in capacity which is linear with the number of antennas, while requiring no additional power or bandwidth expenditure. The capacity increase is reliant upon MIMO sub-channels being well decorrelated. Decorrelation may be achieved by separating antennas in space. On devices where space is limited, an alternative approach is to use antennas with orthogonal polarisations, which may be positioned closer together. Existing literature states that the performance of polarisation MIMO systems is typically inferior to that of spatial MIMO systems under diversity applications, but can be superior in multiplexing applications. These statements are based on the analysis of a statistical channel model, using channel conditions assumed to be typical of an ideal polarisation MIMO system. There is little existing literature which examines how close these assumptions are to a practical polarisation MIMO channel, or whether the above statements remain true of practical systems. This thesis presents a novel end-to-end, predominantly deterministic approach to the modelling of polarisation MIMO systems. A bespoke MIMO channel model is used to estimate capacity and error rate under diversity and spatial multiplexing applications in the indoor environment. The parameters of the channel model are obtained deterministically from a ray launching propagation model, using antenna patterns of orthogonally polarised small antenna systems positioned in the indoor environment. The individual differences in the channel gains and K-factors of each sub-channel are accounted for. Correlation is accounted for using a full correlation matrix, rather than the Kronecker model. Particular attention is paid to mutual coupling of closely spaced antennas. Using this analysis, it is shown that for practical antennas and systems conditions of the polarisation MIMO channel may differ from those assumed in literature. The effect of this in terms of channel capacity and system bit error rate is directly determined and presented. Performance of polarisation MIMO systems, using co-located and spatially separate orthogonally polarised antennas, is compared to that of spatial MIMO systems, which use co-polar antennas with limited spatial separation. Additionally, comparison is made between compact polarisation MIMO systems which use orthogonal linear polarised antennas and those using orthogonal circular polarised antennas. Further analysis examines the significant effect of objects in the antenna near-field regions. The effects of the presence of a metal case on antenna performance are presented, before its impact on the channel conditions and ultimately the resultant MIMO performance is shown.
16
Chung, Wei-Ho. "Fading modeling, MIMO channel generation, and spectrum detection for wireless communications." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1872903921&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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17
Hwang, Taewon. "Iterative Techniques Based on Energy Spreading Transform for Wireless Communications." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7509.
Повний текст джерелаАнотація:
The objective of the proposed research is to devise high-performance and low-complexity signal-detection algorithms for communication systems over fading channels. They include channel equalization to combat intersymbol interference
(ISI) and multiple input multiple output (MIMO) signal detection to deal with multiple access interference (MAI) from other transmit antennas. As the demand for higher data-rate and more efficiency wireless communications increases, signal detection becomes more challenging.
We propose novel transmission and iterative signal-detection techniques based on energy spreading transform (EST). Different from the existing iterative methods based on the turbo
principle, the proposed schemes are independent of channel coding. EST is an orthonormal that spreads a symbol energy over the symbol
block in time and frequency for channel equalization; space and time for MIMO signal detection with flat fading channels; and
space, time, and frequency for MIMO signal detection with frequency-selective fading channels. Due to the spreading, EST obtains diversity in the available domains for the specific application and increases the reliability of the feedback signal. Moreover, it enables iterative signal detection that has near
interference-free performance only at the complexity of linear detectors.
Either a hard or soft decision can be fed back to the interference-cancellation stage at the subsequent iteration. The soft-decision scheme prevents error propagation of the hard-decision scheme for a low SNR and improves the performance.
We analyze the performance of the proposed techniques. Analytical and simulation results show that these schemes perform very close
to the interference-free systems.
18
Veselinovic, N. (Nenad). "Iterative receivers for interference cancellation and suppression in wireless communications." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514275977.
Повний текст джерелаАнотація:
Abstract
The performance of conventional receivers for wireless communications may severely deteriorate in the presence of unaccounted interference. The effectiveness of methods for mitigating these effects greatly depends on the knowledge that is available about the interference and signal-of-interest (SOI), therefore making the design of robust receivers a great challenge. This thesis focuses on receiver structures for channel coded systems that exploit different levels of knowledge about the SOI and interference in an iterative fashion. This achieves both robustness and overall performance improvement compared to non-iterative receivers. Code division multiple access (CDMA) and spatial division multiple access (SDMA) systems are considered.
The overlay of a turbo coded direct-sequence spread-spectrum (DS-SS) system and strong digitally modulated tone interference is studied. An iterative receiver, which is capable of blind cancellation of both wideband and narrowband interference is proposed based on the adaptive self-reconfigurable -filter scheme. Asymptotic performance analysis of the iterative receiver shows that significant iteration gains are possible if the signal-to-interference-plus-noise-ratio (SINR) is relatively large and the processing gain (PG) of the SOI is relatively small.
Robust diversity detection in turbo-coded DS-SS system with statistically modeled interference is studied. A non-parametric type-based iterative receiver that estimates the probability density function (PDF) of interference-plus-noise is proposed. Its performance is shown to be rather robust to the number of interferers and their distances from the victim receiver and very similar to the performance of a clairvoyant receiver. Amazingly, this is achievable with no prior knowledge about the interference parameters. Furthermore, iteration gain is shown to significantly reduce the length of the pilot sequence needed for the PDF estimation.
A family of iterative minimum-mean-squared-error (MMSE) and maximum-likelihood (ML) receivers for convolutionally and space-time coded SDMA systems is proposed. Joint iterative multiuser-detection (MUD), equalization and interference suppression are proposed to jointly combat co-channel interference (CCI), inter-symbol-interference (ISI) and unknown CCI (UCCI) in broadband single-carrier systems. It is shown that both in convolutional and space-time coded systems the ISI and CCI interference can be completely eliminated if UCCI is absent. This is achievable with a number of receive antennas equal to the number of users of interest and not to the total number of transmit antennas. In case UCCI is present, the effectiveness of CCI and ISI cancellation and UCCI suppression depends on the effective degrees of freedom of the receiver. Receiver robustness can be significantly preserved by using hybrid MMSE/ML detection for the signals of interest, or by using estimation of the PDF of the UCCI-plus-noise.
A low complexity hybrid MMSE/ML iterative receiver for SDMA is proposed. It is shown that its performance is not significantly degraded compared to the optimal ML receiver. Its sensitivity to spatial correlation and a timing offset is assessed by using field measurement data. It was shown that the hybrid MMSE/ML receiver is robust against spatial correlation. The sensitivity to the timing offset is significantly reduced if the receiver performs UCCI suppression.
19
Hayes, Robert Lee Jr. "Precoded Linear Dispersion Codes for Wireless MIMO Channels." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131246446.
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Das, Gupta Jishu. "Effect of pedestrian movement on MIMO-OFDM channel capacity in an indoor environment." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/38632/1/Jishu_Das_Gupta_Thesis.pdf.
Повний текст джерелаАнотація:
The rapid growth of mobile telephone use, satellite services, and now the wireless Internet and WLANs are generating tremendous changes in telecommunication and networking. As indoor wireless communications become more prevalent, modeling indoor radio wave propagation in populated environments is a topic of significant interest. Wireless MIMO communication exploits phenomena such as multipath propagation to increase data throughput and range, or reduce bit error rates, rather than attempting to eliminate effects of multipath propagation as traditional SISO communication systems seek to do. The MIMO approach can yield significant gains for both link and network capacities, with no additional transmitting power or bandwidth consumption when compared to conventional single-array diversity methods. When MIMO and OFDM systems are combined and deployed in a suitable rich scattering environment such as indoors, a significant capacity gain can be observed due to the assurance of multipath propagation. Channel variations can occur as a result of movement of personnel, industrial machinery, vehicles and other equipment moving within the indoor environment. The time-varying effects on the propagation channel in populated indoor environments depend on the different pedestrian traffic conditions and the particular type of environment considered. A systematic measurement campaign to study pedestrian movement effects in indoor MIMO-OFDM channels has not yet been fully undertaken. Measuring channel variations caused by the relative positioning of pedestrians is essential in the study of indoor MIMO-OFDM broadband wireless networks. Theoretically, due to high multipath scattering, an increase in MIMO-OFDM channel capacity is expected when pedestrians are present. However, measurements indicate that some reductions in channel capacity could be observed as the number of pedestrians approaches 10 due to a reduction in multipath conditions as more human bodies absorb the wireless signals. This dissertation presents a systematic characterization of the effects of pedestrians in indoor MIMO-OFDM channels. Measurement results, using the MIMO-OFDM channel sounder developed at the CSIRO ICT Centre, have been validated by a customized Geometric Optics-based ray tracing simulation. Based on measured and simulated MIMO-OFDM channel capacity and MIMO-OFDM capacity dynamic range, an improved deterministic model for MIMO-OFDM channels in indoor populated environments is presented. The model can be used for the design and analysis of future WLAN to be deployed in indoor environments. The results obtained show that, in both Fixed SNR and Fixed Tx for deterministic condition, the channel capacity dynamic range rose with the number of pedestrians as well as with the number of antenna combinations. In random scenarios with 10 pedestrians, an increment in channel capacity of up to 0.89 bits/sec/Hz in Fixed SNR and up to 1.52 bits/sec/Hz in Fixed Tx has been recorded compared to the one pedestrian scenario. In addition, from the results a maximum increase in average channel capacity of 49% has been measured while 4 antenna elements are used, compared with 2 antenna elements. The highest measured average capacity, 11.75 bits/sec/Hz, corresponds to the 4x4 array with 10 pedestrians moving randomly. Moreover, Additionally, the spread between the highest and lowest value of the the dynamic range is larger for Fixed Tx, predicted 5.5 bits/sec/Hz and measured 1.5 bits/sec/Hz, in comparison with Fixed SNR criteria, predicted 1.5 bits/sec/Hz and measured 0.7 bits/sec/Hz. This has been confirmed by both measurements and simulations ranging from 1 to 5, 7 and 10 pedestrians.
21
Aljohani, Abdullah. "Advanced signal processing techniques for single-carrier Multi-user MIMO Wireless communications." Thesis, Loughborough University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510321.
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22
Jia, Yugang. "Stochastic approximations for reduced complexity signal processing algorithms in MIMO wireless communications." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435729.
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Abaza, Mohamed. "Cooperative MIMO techniques for outdoor optical wireless communication systems." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0073/document.
Повний текст джерелаАнотація:
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
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Tran, Le Chung. "Complex orthogonal space-time processing in wireless communications." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060726.133841/index.html.
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Gozali, Ran. "Space-Time Codes for High Data Rate Wireless Communications." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27193.
Повний текст джерелаАнотація:
Space-time codes (STC) are a class of signaling techniques, offering coding and diversity gains along with improved spectral efficiency. These codes exploit both the spatial and the temporal diversity of the wireless link by combining the design of the error correction code, modulation scheme and array processing. STC are well suited for improving the downlink performance, which is the bottleneck in asymmetric applications such as downstream Internet.
Three original contributions to the area of STC are presented in this dissertation. First, the development of analytic tools that determine the fundamental limits on the performance of STC in a variety of channel conditions. For trellis-type STC, transfer function based techniques are applied to derive performance bounds over Rayleigh, Rician and correlated fading environments. For block-type STC, an analytic framework that supports various complex orthogonal designs with arbitrary signal cardinalities and array configurations is developed. In the second part of the dissertation, the Virginia Tech Space-Time Advanced Radio (VT-STAR) is designed, introducing a multi-antenna hardware laboratory test bed, which facilitates characterization of the multiple-input multiple-output (MIMO) channel and validation of various space-time approaches. In the third part of the dissertation, two novel space-time architectures paired with iterative processing principles are proposed. The first extends the suitability of STC to outdoor wireless communications by employing iterative equalization/decoding for time dispersive channels and the second employs iterative interference cancellation/decoding to solve the error propagation problem of Bell-Labs Layered Space-Time Architecture (BLAST). Results show that remarkable energy and spectral efficiencies are achievable by combining concepts drawn from space-time coding, multiuser detection, array processing and iterative decoding.Ph. D.
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Wennström, Mattias. "On MIMO systems and adaptive arrays for wireless communications : analysis and practical aspects /." Uppsala : Signals and systems [Signaler och system], Univ. [distributör], 2002. http://publications.uu.se/theses/fulltext/91-506-1619-6.pdf.
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Chen, Runhua. "A layered space-time coded MIMO architecture for high-data-rate wireless communications /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202002%20CHEN.
Повний текст джерелаАнотація:
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 84-88). Also available in electronic version. Access restricted to campus users.
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Liu, Kejing. "Architectures for Symbol Timing Synchronization in MIMO Communications." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd484.pdf.
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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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Choi, Seung-Ho. "Severely Fading MIMO Channels." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1190.
Повний текст джерелаАнотація:
In most wireless communications research, the channel models considered experience less severe fading than the classic Rayleigh fading case. In this thesis, however, we investigate MIMO channels where the fading is more severe. In these environments, we show that the coefficient of variation of the channel amplitudes is a good predictor of the link mutual information, for a variety of models. We propose a novel channel model for severely fading channels based on the complex multivariate t distribution. For this model, we are able to compute exact results for the ergodic mutual information and approximations to the outage probabilities for the mutual information. Applications of this work include wireless sensors, RF tagging, land-mobile, indoor-mobile, ground-penetrating radar, and ionospheric radio links. Finally, we point out that the methodology can also be extended to evaluate the mutual information of a cellular MIMO link and the performance of various MIMO receivers in a cellular scenario. In these cellular applications, the channel itself is not severely fading but the multivariate t distribution can be applied to model the effects of intercellular interference.
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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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Sankar, Hari. "LDPC code-based bandwidth efficient coding schemes for wireless communications." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1780.
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Alizadeh, Ardalan. "Cognitive Communications for Emerging Wireless Systems." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1470226402.
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Pollock, Tony Steven, and tony pollock@nicta com au. "On Limits of Multi-Antenna Wireless Communications in Spatially Selective Channels." The Australian National University. Research School of Information Sciences and Engineering, 2003. http://thesis.anu.edu.au./public/adt-ANU20050418.143712.
Повний текст джерелаАнотація:
Multiple-Input Multiple-Output (MIMO) communications systems using multiantenna arrays simultaneously during transmission and reception have generated significant interest in recent years. Theoretical work in the mid 1990?s showed the potential for significant capacity increases in wireless channels via spatial multiplexing with sparse antenna arrays and rich scattering environments. However, in reality the capacity is significantly reduced when the antennas are placed close together, or the scattering environment is sparse, causing the signals received by different antennas to become correlated, corresponding to a reduction of the effective number of sub-channels between transmit and receive antennas. By introducing the previously ignored spatial aspects, namely the antenna array geometry and the scattering environment, into a novel channel model new bounds and fundamental limitations to MIMO capacity are derived for spatially constrained, or spatially selective, channels. A theoretically derived capacity saturation point is shown to exist for spatially selective MIMO channels, at which there is no capacity growth with increasing numbers of antennas. Furthermore, it is shown that this saturation point is dependent on the shape, size and orientation of the spatial volumes containing the antenna arrays along with the properties of the scattering environment. This result leads to the definition of an intrinsic capacity between separate spatial volumes in a continuous scattering environment, which is an upper limit to communication between the volumes that can not be increased with increasing numbers of antennas within. It is shown that there exists a fundamental limit to the information theoretic capacity between two continuous volumes in space, where using antenna arrays is simply one choice of implementation of a more general spatial signal processing underlying all wireless communication systems.
35
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.
Повний текст джерелаАнотація:
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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Hussain, Nasir. "Cooperative communication in relay assisted wireless access networks." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/103528/1/Nasir_Hussain_Thesis.pdf.
Повний текст джерелаАнотація:
This research investigates the benefits of user cooperation in wireless communications systems. The dynamics of wireless cooperative communication systems are studied by a comprehensive study of two essential characteristics of cooperation, optimal relay selection criteria and practical channel estimation. A novel relay selection model based on realistic channel estimation is proposed and analysed. Furthermore, the gains are experimentally evaluated using a wireless communication testbed. The outcomes of this research reveal that incorporating cooperative techniques with an adaptive relay selection strategy into existing wireless communication can significantly reduce the required power and the impact of wireless channel impairments.
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Tsai, Jiann-An. "Combined Space-Time Diversity and Interference Cancellation for MIMO Wireless Systems." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27509.
Повний текст джерелаАнотація:
There is increasing interest in the exploitation of multiple-input and multiple-output (MIMO) channels to enhance the capacity of wireless systems.
In this study, we develop and evaluate a channel model, evaluate the corresponding channel capacity, and design and analyze a simple orthogonal transmit waveform for MIMO channels in mobile radio environments.
We also evaluate the system performance of various interference cancellation techniques when employing multiple-receive antenna in interference-limited systems.
The first part of this dissertation presents two major contributions to MIMO systems.
The analytical expression for space-time MIMO channel correlation is derived for a Rayleigh fading channel. The information-theoretic channel capacity based on this correlation is also evaluated for a wide variety of mobile radio channels.
The second part of this dissertation presents two major contributions to the area of orthogonal waveform design. We analyze the bit-error-rate (BER) performance of a proposed space-time orthogonal waveform for MIMO mobile radio communications.
The application of the proposed space-time orthogonal waveform to a conventional cellular system is also evaluated and briefly discussed.
Finally, this dissertation investigates a number of interference cancellation techniques for multiple-receive antenna systems. Both adaptive beamforming and multiuser detection are evaluated for various signal waveforms over a variety of mobile radio channels.Ph. D.
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Lamahewa, Tharaka Anuradha, and tharaka lamahewa@anu edu au. "Space-Time Coding and Space-Time Channel Modelling for Wireless Communications." The Australian National University. Research School of Information Sciences and Engineering, 2007. http://thesis.anu.edu.au./public/adt-ANU20070816.152647.
Повний текст джерелаАнотація:
In this thesis we investigate the effects of the physical
constraints such as antenna aperture size, antenna geometry and
non-isotropic scattering distribution parameters (angle of
arrival/departure and angular spread) on the performance of coherent
and non-coherent space-time coded wireless communication systems.
First, we derive analytical expressions for the exact pairwise error
probability (PEP) and PEP upper-bound of coherent and non-coherent
space-time coded systems operating over spatially correlated fading
channels using a moment-generating function-based approach. These
analytical expressions account for antenna spacing, antenna
geometries and scattering distribution models. Using these new PEP
expressions, the degree of the effect of antenna spacing, antenna
geometry and angular spread is quantified on the diversity advantage
(robustness) given by a space-time code. It is shown that the number
of antennas that can be employed in a fixed antenna aperture without
diminishing the diversity advantage of a space-time code is
determined by the size of the antenna aperture, antenna geometry and
the richness of the scattering environment.
¶
In realistic channel environments the performance of space-time
coded multiple-input multiple output (MIMO) systems is significantly
reduced due to non-ideal antenna placement and non-isotropic
scattering. In this thesis, by exploiting the spatial dimension of a
MIMO channel we introduce the novel use of linear spatial precoding
(or power-loading) based on fixed and known parameters of MIMO
channels to ameliorate the effects of non-ideal antenna placement on
the performance of coherent and non-coherent space-time codes. The
spatial precoder virtually arranges the antennas into an optimal
configuration so that the spatial correlation between all antenna
elements is minimum. With this design, the precoder is fixed for
fixed antenna placement and the transmitter does not require any
feedback of channel state information (partial or full) from the
receiver. We also derive precoding schemes to exploit non-isotropic
scattering distribution parameters of the scattering channel to
improve the performance of space-time codes applied on MIMO systems
in non-isotropic scattering environments. However, these schemes
require the receiver to estimate the non-isotropic parameters and
feed them back to the transmitter.
¶
The idea of precoding based on fixed parameters of MIMO channels is
extended to maximize the capacity of spatially constrained dense
antenna arrays. It is shown that the theoretical maximum capacity
available from a fixed region of space can be achieved by power
loading based on previously unutilized channel state information
contained in the antenna locations. We analyzed the correlation
between different modal orders generated at the transmitter region
due to spatially constrained antenna arrays in non-isotropic
scattering environments, and showed that adjacent modes contribute
to higher correlation at the transmitter region. Based on this
result, a power loading scheme is proposed which reduces the effects
of correlation between adjacent modes at the transmitter region by
nulling power onto adjacent transmit modes.
¶
Furthermore, in this thesis a general space-time channel model for
down-link transmission in a mobile multiple antenna communication
system is developed. The model incorporates deterministic
quantities such as physical antenna positions and the motion of the
mobile unit (velocity and the direction), and random quantities to
capture random scattering environment modeled using a bi-angular
power distribution and, in the simplest case, the covariance between
transmit and receive angles which captures statistical
interdependency. The Kronecker model is shown to be a special case
when the power distribution is separable and is shown to
overestimate MIMO system performance whenever there is more than one
scattering cluster. Expressions for space-time cross correlations
and space-frequency cross spectra are given for a number of
scattering distributions using Gaussian and Morgenstern's family of
multivariate distributions. These new expressions extend the
classical Jake's and Clarke's correlation models to general
non-isotropic scattering environments.
39
Zhang, Wei Ma Xiaoli. "Lattice-reduction aided linear equalization for wireless communications over fading channels." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/master's/ZHANG_WEI_44.pdf.
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Li, Li. "Source and Channel Coding Strategies for Wireless Sensor Networks." Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc177226/.
Повний текст джерелаАнотація:
In this dissertation, I focus on source coding techniques as well as channel coding techniques. I addressed the challenges in WSN by developing (1) a new source coding strategy for erasure channels that has better distortion performance compared to MDC; (2) a new cooperative channel coding strategy for multiple access channels that has better channel outage performances compared to MIMO; (3) a new source-channel cooperation strategy to accomplish source-to-fusion center communication that reduces system distortion and improves outage performance. First, I draw a parallel between the 2x2 MDC scheme and the Alamouti's space time block coding (STBC) scheme and observe the commonality in their mathematical models. This commonality allows us to observe the duality between the two diversity techniques. Making use of this duality, I develop an MDC scheme with pairwise complex correlating transform. Theoretically, I show that MDC scheme results in: 1) complete elimination of the estimation error when only one descriptor is received; 2) greater efficiency in recovering the stronger descriptor (with larger variance) from the weaker descriptor; and 3) improved performance in terms of minimized distortion as the quantization error gets reduced. Experiments are also performed on real images to demonstrate these benefits. Second, I present a two-phase cooperative communication strategy and an optimal power allocation strategy to transmit sensor observations to a fusion center in a large-scale sensor network. Outage probability is used to evaluate the performance of the proposed system. Simulation results demonstrate that: 1) when signal-to-noise ratio is low, the performance of the proposed system is better than that of the MIMO system over uncorrelated slow fading Rayleigh channels; 2) given the transmission rate and the total transmission SNR, there exists an optimal power allocation that minimizes the outage probability; 3) on correlated slow fading Rayleigh channels, channel correlation will degrade the system performance in linear proportion to the correlation level. Third, I combine the statistical ranking of sensor observations with cooperative communication strategy in a cluster-based wireless sensor network. This strategy involves two steps: 1) ranking the sensor observations based on their test statistics; 2) building a two-phase cooperative communication model with an optimal power allocation strategy. The result is an optimal system performance that considers both sources and channels. I optimize the proposed model through analyses of the system distortion, and show that the cooperating nodes achieve maximum channel capacity. I also simulate the system distortion and outage to show the benefits of the proposed strategies.
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Zenteno, Efrain. "Digital Compensation Techniques for Transmitters inWireless Communications Networks." Doctoral thesis, KTH, Signalbehandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-167971.
Повний текст джерелаАнотація:
Since they appeared, wireless technologies have deeply transformed our society. Today, wireless internet access and other wireless applications demandincreasingly more traffic. However, the continuous traffic increase can be unbearableand requires rethinking and redesigning the wireless technologies inmany different aspects. Aiming to respond to the increasing needs of wirelesstraffic, we are witnessing a rapidly evolving wireless technology scenario.This thesis addresses various aspects of the transmitters used in wireless communications.Transmitters present several hardware (HW) impairments thatcreate distortions, polluting the radio spectrum and decreasing the achievabletraffic in the network. Digital platforms are now flexible, robust and cheapenough to enable compensation of HW impairments at the digital base-bandsignal. This has been coined as ’dirty radio’. Dirty radio is expected in future transmitters where HW impairments may arise to reduce transmitter cost or to enhance power efficiency. This thesis covers the software (SW) compensation schemes of dirty radio developed for wireless transmitters. As describedin the thesis, these schemes can be further enhanced with knowledge of thespecific signal transmission or scenarios, e.g., developing cognitive digital compensationschemes. This can be valuable in today’s rapidly evolving scenarioswhere multiple signals may co-exist, sharing the resources at the same radiofrequency (RF) front-end. In the first part, this thesis focuses on the instrumentation challenges andHWimpairments encountered at the transmitter. A synthetic instrument (SI)that performs network analysis is designed to suit the instrumentation needs.Furthermore, how to perform nonlinear network analysis using the developedinstrument is discussed. Two transmitter HW impairments are studied: themeasurement noise and the load impedance mismatch at the transmitter, asis their coupling with the state-of-the-art digital compensation techniques.These two studied impairments are inherent to measurement systems and areexpected in future wireless transmitters. In the second part, the thesis surveys the area of behavioral modeling and digital compensation techniques for wireless transmitters. Emphasis is placed on low computational complexity techniques. The low complexity is motivated by a predicted increase in the number of transmitters deployed in the network, from base stations (BS), access points and hand-held devices. A modeling methodology is developed that allows modeling transmitters to achieve both reduced computational complexity and low modeling error. Finally, the thesis discusses the emerging architectures of multi-channel transmittersand describes their digital compensation techniques. It revises the MIMOVolterra series formulation to address the general modeling problem anddrafts possible solutions to tackle its dimensionality. In the framework of multi-channel transmitters, a technique to compensate nonlinear multi-carrier satellite transponders is presented. This technique is cognitive because it uses the frequency link planning and the pulse-shaping filters of the individual carriers. This technique shows enhanced compensation ability at reduced computational complexity compared to the state-of-the-art techniques and enables the efficient operation of satellite transponders.QC 20150526
42
Zhang, Hua. "Orthogonal Frequency Division Multiplexing for Wireless Communications." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4960.
Повний текст джерелаАнотація:
OFDM is a promising technique for high-data-rate wireless communications because it can combat inter-symbol interference (ISI) caused by the dispersive fading of wireless channels. The proposed research focuses on techniques that improve the performance of OFDM-based wireless communications and its commercial and military applications. In particular, we address the following aspects of OFDM: inter-channel interference (ICI) suppression, interference suppression for clustered OFDM, clustered OFDM based anti-jamming modulation, channel estimation for MIMO-OFDM, MIMO transmission with limited feedback.
For inter-channel interference suppression, a frequency domain partial response coding (PRC) scheme is proposed to mitigate ICI. We derive the near-optimal weights for PRC that is independent on the channel power spectrum. The error floor resulting from ICI can be reduced significantly using a two-tap or a three-tap PRC. Clustered OFDM is a new technique that has many advantages over traditional OFDM. In clustered OFDM systems, adaptive antenna arrays are used for interference suppression. To calculate weights for interference suppression, we propose a polynomial-based parameter estimator to combat the severe leakage of the DFT based estimator due to the small size of the cluster. An adaptive algorithm is developed to obtain optimal performance. For high data rate military communications, we propose a clustered OFDM base spread spectrum modulation to provide both anti-jamming and fading suppression capability. We analyze the performance of uncoded and coded system. Employing multiple transmit and receive antennas in OFDM systems (MIMO-OFDM) can increase the spectral efficiency and link reliability. We develop a minimum mean-square-error (MMSE) channel estimator that takes advantage of the spatial-frequency correlations in MIMO-OFDM systems to minimize the estimation error. We investigate the training sequence design and two optimal training sequence designs are given for arbitrary spatial correlations. For a MIMO system, the diversity and array gains can be obtained by exploiting channel information at the transmitter. For MIMO-OFDM systems, we propose a subspace tracking based approach that can exploit the frequency correlations of the OFDM system to reduce the feedback rate. The proposed approach does not need recalculate the precoding matrix and is robust to multiple data stream transmission.
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Stanković, Veljko Haardt Martin. "Multi-user MIMO wireless communications /." 2007. http://www.gbv.de/dms/ilmenau/toc/528883909.PDF.
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Wu, Zhiyuan. "Design of turbo MIMO wireless communications." Thesis, 2006. http://spectrum.library.concordia.ca/9266/1/zhiyuan_wu_2006.pdf.
Повний текст джерелаАнотація:
Since the discovery of the significant gain in capacity provided by multiple antennas over fading channels, tremendous research and development efforts in academia and industry have been invested to multiple-input-multiple-output (MIMO) technology. However, difficulties still exist in the design of flexible MIMO transmission schemes. The overall goal of our study is to develop efficient turbo MIMO transceivers that are capacity-achieving and yet with reasonable complexity. First, we study the design of serially concatenated MIMO transmitters. For simpler design and flexible rate-versus-performance tradeoff, conventional encoders are used before a linear space-time modulator. A joint iterative receiver based on the turbo principle is assumed that precludes the use of Tarokh's design criteria for such a concatenated system. Extending the extrinsic information transfer (EXIT) charts to MIMO systems, design criteria that concern both the data rate and error performance are developed for the inner space-time (ST) modulator. Based on the new design criteria, an optimal space-time linear dispersion modulation scheme is presented. In addition, the tradeoff between constellation size and symbol rate for a given data rate is discussed. Simulation results are provided to verify the new design criteria and to demonstrate the merits of the proposed coded space-time modulation. For such a turbo MIMO transmitter, the abundance of highly developed outer decoders allows us to focus on the study on the inner multi-user detection (MUD). To start, a new parallel interference cancellation (PIC) MUD scheme is proposed. This detector can be used as a stand-alone multi-user detector in a non-iterative MIMO receiver. The new scheme employs a novel nonlinear minimum mean square error (MMSE) estimator as the soft decision device. The nonlinear estimator exploits the knowledge of symbol alphabet for refined estimates with smaller mean square error (MSE). Simulation results demonstrate that the proposed detector significantly outperforms the conventional detectors with comparable complexity. The nonlinear MMSE estimator is further extended to develop the soft-output MUD for iterative turbo MIMO receivers. The nonlinear estimation makes use of a priori information from the outer decoder and preliminary estimates gleaned from channel observation as well. With the new nonlinear MMSE estimator, a generalized SIC-MMSE scheme is proposed. Depending on the methods for generating preliminary estimates, two generalized SIC-MMSE detectors are proposed: a 2-staged SIC-MMSE and a recursive SIC-MMSE detectors. Analytical study and simulations are carried out to demonstrate the merits of the two proposed detectors. Last, tradeoffs among the components of the transmitter that affect error performance at the receiver are discussed to provide design guidelines for practice
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Marques, Pedro Manuel Martins. "MIMO transmission for 4G wireless communications." Doctoral thesis, 2009. http://hdl.handle.net/10216/58202.
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Marques, Pedro Manuel Martins. "MIMO transmission for 4G wireless communications." Tese, 2009. http://hdl.handle.net/10216/58202.
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Pan, Chien-Hung, and 潘建宏. "QRD-based MIMO Detection in Wireless Communications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/67742041084298699975.
Повний текст джерелаАнотація:
博士國立交通大學
電信工程研究所
100
Multiple input multiple output (MIMO) technology is a promising solution to provide higher spectral efficiency. However, the impairment of MIMO detection (MD) is caused by inter-antenna interference (IAI) and ill-conditioned problem. To better mitigate IAI, effective GA-MD associated with QR-based techniques exploit good initial setting, triangular form and diversity-based mutation (DM) are proposed. To prevent the ill-conditioned problem, we study conventional SV-based section criterion to find the precoder to optimize the performance of MD in the limited feedback systems. To optimize the section criterion, the QR-based selection criteria depending on effective decomposition and a larger bound among diagonal entries are proposed to resist the problem developed in switching and multi-mode precoding systems. The new criteria exploiting SVD and GMD perform a predetermined mode to find the precoder. The main benefits of the proposed criteria are their lower computational complexity and better detection performance. The proposed criteria are suitable not only for single user MIMO (SU-MIMO) system, but also for multi-user MIMO (MU-MIMO) system with the cooperative precoding. Performance analysis and computer simulations confirm that the proposed QR-based schemes attain the performance of existing schemes with a significantly lower complexity level.
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Maharaj, Bodhaswar Tikanath Jugpershad. "MIMO channel modelling for indoor wireless communications." Thesis, 2008. http://hdl.handle.net/2263/26801.
Повний текст джерелаАнотація:
This thesis investigates multiple-input-multiple-output (MIMO) channel modelling for a wideband indoor environment. Initially the theoretical basis of geometric modelling for a typical indoor environment is looked at, and a space-time model is formulated. The transmit and receive antenna correlation is then separated and is expressed in terms of antenna element spacing, the scattering parameter, mean angle of arrival and number of antenna elements employed. These parameters are used to analyze their effect on the capacity for this environment. Then the wideband indoor channel operating at center frequencies of 2.4 GHz and 5.2 GHz is investigated. The concept of MIMO frequency scaling is introduced and applied to the data obtained in the measurement campaign undertaken at the University of Pretoria. Issues of frequency scaling of capacity, spatial correlation and the joint RX/TX double direction channel response for this indoor environment are investigated. The maximum entropy (ME) approach to MIMO channel modelling is investigated and a new basis is developed for the determination of the covariance matrix when only the RX/TX covariance is known. Finally, results comparing this model with the established Kronecker model and its application for the joint RX/TX spatial power spectra, using a beamformer, are evaluated. Conclusions are then drawn and future research opportunities are highlighted.Thesis (PhD)--University of Pretoria, 2008.
Electrical, Electronic and Computer Engineering
unrestricted
49
Bhattacharjee, Birupaksha, and Sunil Gautam Panda. "Capacity analysis of underwater acoustic MIMO communications." Thesis, 2012. http://ethesis.nitrkl.ac.in/3642/1/capacity_analysis_of_mimo_acoustic_channel_for_underwater_communication-108EC003%2C108EC031.pdf.
Повний текст джерелаАнотація:
Multi-Input Multi-Output (MIMO) principle is based on transmitting digital data from Nt transmitters to Nr receivers within a frequency band. In the last decade, theoretical works and practical experiments in wireless and cellular networks have convincingly proved that MIMO
has been a real find in digital communications.
Nowadays, MIMO principle is being applied to underwater acoustic communications (UAC) and it is showing encouraging results. But very few research has been done on the relation
between different parameters of MIMO and its gain. Our primary purpose in this project is to analyse the MIMO gain theoretically using Shannon capacity analysis and suggest ways to maximize capacity with limited bandwidth by varying other parameters . As we will show in the later pages of this project that underwater acoustic channel (UAC) is
highly selective in frequency, data transmission cannot be increased by simply increasing the transmission bandwidth. This difficult situation can be found in wireless communication where there is an increasingly large requirement in high speed data transfer but available bandwidth is constrained by the frequency allocation law. In those communication fields where radio frequency is used , this bandwidth limitation problem has been overcome by introducing MIMO techniques, which provide significant gain in data transmission rate while keeping the transmission Bandwidth constant.In the previous years, the contribution of MIMO to UAC systems has mostly been
thoroughly analyzed via spatial modulation or multi-carrier modulation. Initial simulation and experimental results have showcased a larger gain over conventional single input single output (SISO) but the results strongly vary depending on the modulation scheme chosen by us and the
receiver algorithm as well as the underwater channel environment.
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Rath, Ranjan Kumar. "Adaptive MIMO technology for 4G." Thesis, 2012. http://ethesis.nitrkl.ac.in/3617/1/Adaptive_MIMO_technology_for_4G.pdf.
Повний текст джерелаАнотація:
The communication industry is one of the fastest growing industries. The cellular systems started in the 80’s with 1G have now reached to 4G. The growing demand of high data rates are increasing exponentially with time. The typical goals of a communication engineer are high speed communication for which the data rate should be high, better quality of signal for which we have to minimize the bit error rate as low as possible, less power consumption and VLSI implement ability. The 4G system ensures us data rate of 1Gbps which cannot be achieved by SISO systems and hence we go for MIMO system. The various benefits of MIMO are discussed in this report. The implementation of Alamouti scheme is also discussed and then the various methods of channel estimation are discussed and simulated.
The proposed MIMO system has distinguished advantages over the conventional SISO systems and this is being implemented in 4G cellular, MIMO radar and in various other emerging communication technologies.