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Keď som neni / When I am notRovenská, Ivana Unknown Date (has links)
Diploma work reflects the issue of psychospiritutarian transformation. In this way, a local specific video installation was created aimed at the sensual experience of the viewer. The Film has approximately thirteen minutes and contains four parts, which arose from the archive of the recorded audiovisual material spinning on the camera with a fixed 50mm lens from May 2018. A special role plays a visual relationship that is traditionally linked to this phenomenon.
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Partial channel knowledge based precoding for MIMO and cooperative communicationsBahrami, Hamid Reza. January 2007 (has links)
No description available.
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A Blind Space-Time Decorrelating RAKE Receiver in a DS-CDMA System in Multipath ChannelsXU, BIN 31 March 2004 (has links)
No description available.
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Gender and individual space-time accessibility: a gis-based geocomputational approachKim, Hyun-Mi 13 July 2005 (has links)
No description available.
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Space-Time Coding and Space-Time Channel Modelling for Wireless CommunicationsLamahewa, Tharaka Anuradha, tharaka.lamahewa@anu.edu.au January 2007 (has links)
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.
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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.
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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.
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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.
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On the performance gain of STFC-LDPC concatenated coding scheme for MIMO-WiMAXMare, Karel Petrus 29 November 2009 (has links)
In mobile communications, using multiple transmit and receive antennas has shown considerable improvement over single antenna systems. The performance increase can be characterized by more reliable throughput obtained through diversity and the higher achievable data rate through spatial multiplexing. The combination of multiple-input multiple-output (MIMO) wireless technology with the IEEE 802.16e-2005 (WiMAX) standard has been recognized as one of the most promising technologies with the advent of next generation broadband wireless communications. The dissertation introduces a performance evaluation of modern multi-antenna coding techniques on a MIMO-WiMAX platform developed to be capable of simulating space-selective, time-selective and frequency-selective fading conditions, which are known as triply-selective fading conditions. A new concatenated space-time-frequency low-density parity check (LDPC) code is proposed for high performance MIMO systems, where it is shown that the newly defined coding technique outperforms a more conventional approach by concatenating space-time blocks with LDPC codes. The analysis of the coding techniques in realistic mobile environments, as well as the proposed STFC-LDPC code, can form a set of newly defined codes, complementing the current coding schemes defined in the WiMAX standard. / Dissertation (MEng)--University of Pretoria, 2009. / Electrical, Electronic and Computer Engineering / unrestricted
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Framework and Analysis of Rate one and Turbo Coded MIMO-CDMA Communication SystemsKuguoglu, Akin Fahrettin 05 October 2006 (has links)
No description available.
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Performance Evaluation of Spatial Modulation and QOSTBC for MIMO SystemsAnoh, Kelvin O.O., Abd-Alhameed, Raed, Okorafor, G.N., Noras, James M., Rodriguez, Jonathan, Jones, Steven M.R. 21 July 2015 (has links)
Yes / Multiple-input multiple-output (MIMO) systems require simplified architectures that can maximize design parameters without sacrificing system performance. Such architectures may be used in a transmitter or a receiver. The most recent example with possible low cost architecture in the transmitter is spatial modulation (SM). In this study, we evaluate the SM and quasi-orthogonal space time block codes (QOSTBC) schemes for MIMO systems over a Rayleigh fading channel. QOSTBC enables STBC to be used in a four antenna design, for example. Standard QO-STBC techniques are limited in performance due to self-interference terms; here a QOSTBC scheme that eliminates these terms in its decoding matrix is explored. In addition, while most QOSTBC studies mainly explore performance improvements with different code structures, here we have implemented receiver diversity using maximal ratio combining (MRC). Results show that QOSTBC delivers better performance, at spectral efficiency comparable with SM.
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Performance Analysis of Space-Time Coded Modulation Techniques using GBSB-MIMO Channel ModelsNory, Ravikiran 06 June 2002 (has links)
Wireless systems are rapidly developing to provide high speed voice, text and multimedia messaging services which were traditionally offered by wire line networks. To support these services, channels with large capacities are required. Information theoretic investigations have shown that Multiple Input Multiple Output (MIMO) channels can achieve very high capacities. Space-Time Block Coding (STBC) and Bell Labs Layered Space-Time Architecture (BLAST) are two potential schemes which utilize the diversity offered by MIMO channels to provide reliable high date rate wireless communication. This work studies the sensitivity of these two schemes to spatial correlation in MIMO channels.
The first part of the thesis studies the effect of spatial correlation on the performance of STBC by using Geometrically Based Single Bounce MIMO (GBSB-MIMO) channel models. Performance is analyzed for two scenarios: one without scatterers in the vicinity of the transmitter and other with scatterers. In the second part of the thesis, the sensitivity of BLAST to spatial correlation is analyzed. Later, schemes which use the principles of Multilayered Space-Time Coded Modulation to combine the benefits of BLAST and STBC are introduced and their performance is investigated in correlated and uncorrelated Rayleigh fading. Results indicate that schemes using orthogonal design space-time block codes are reasonably robust to spatial correlation while schemes like BLAST are very sensitive as they depend on array processing to separate signals from various transmit antennas. / Master of Science
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Optimising cooperative spectrum sensing in cognitive radio networks using interference alignment and space-time codingYusuf, Idris A. January 2018 (has links)
In this thesis, the process of optimizing Cooperative Spectrum Sensing in Cognitive Radio has been investigated in fast-fading environments where simulation results have shown that its performance is limited by the Probability of Reporting Errors. By proposing a transmit diversity scheme using Differential space-time block codes (D-STBC) where channel state information (CSI) is not required and regarding multiple pairs of Cognitive Radios (CR's) with single antennas as a virtual MIMO antenna arrays in multiple clusters, Differential space-time coding is applied for the purpose of decision reporting over Rayleigh channels. Both Hard and Soft combination schemes were investigated at the fusion center to reveal performance advantages for Hard combination schemes due to their minimal bandwidth requirements and simplistic implementation. The simulations results show that this optimization process achieves full transmit diversity, albeit with slight performance degradation in terms of power with improvements in performance when compared to conventional Cooperative Spectrum Sensing over non-ideal reporting channels. Further research carried out in this thesis shows performance deficits of Cooperative Spectrum Sensing due to interference on sensing channels of Cognitive Radio. Interference Alignment (IA) being a revolutionary wireless transmission strategy that reduces the impact of interference seems well suited as a strategy that can be used to optimize the performance of Cooperative Spectrum Sensing. The idea of IA is to coordinate multiple transmitters so that their mutual interference aligns at their receivers, facilitating simple interference cancellation techniques. Since its inception, research efforts have primarily been focused on verifying IA's ability to achieve the maximum degrees of freedom (an approximation of sum capacity), developing algorithms for determining alignment solutions and designing transmission strategies that relax the need for perfect alignment but yield better performance. With the increased deployment of wireless services, CR's ability to opportunistically sense and access the unused licensed frequency spectrum, without causing harmful interference to the licensed users becomes increasingly diminished, making the concept of introducing IA in CR a very attractive proposition. For a multiuser multiple-input-multiple-output (MIMO) overlay CR network, a space-time opportunistic IA (ST-OIA) technique has been proposed that allows spectrum sharing between a single primary user (PU) and multiple secondary users (SU) while ensuring zero interference to the PUs. With local CSI available at both the transmitters and receivers of SUs, the PU employs a space-time WF (STWF) algorithm to optimize its transmission and in the process, frees up unused eigenmodes that can be exploited by the SU. STWF achieves higher performance than other WF algorithms at low to moderate signal-to-noise ratio (SNR) regimes, which makes it ideal for implementation in CR networks. The SUs align their transmitted signals in such a way their interference impairs only the PU's unused eigenmodes. For the multiple SUs to further exploit the benefits of Cooperative Spectrum Sensing, it was shown in this thesis that IA would only work when a set of conditions were met. The first condition ensures that the SUs satisfy a zero interference constraint at the PU's receiver by designing their post-processing matrices such that they are orthogonal to the received signal from the PU link. The second condition ensures a zero interference constraint at both the PU and SUs receivers i.e. the constraint ensures that no interference from the SU transmitters is present at the output of the post-processing matrices of its unintended receivers. The third condition caters for the multiple SUs scenario to ensure interference from multiple SUs are aligned along unused eigenmodes. The SU system is assumed to employ a time division multiple access (TDMA) system such that the Principle of Reciprocity is employed towards optimizing the SUs transmission rates. Since aligning multiple SU transmissions at the PU is always limited by availability of spatial dimensions as well as typical user loads, the third condition proposes a user selection algorithm by the fusion centre (FC), where the SUs are grouped into clusters based on their numbers (i.e. two SUs per cluster) and their proximity to the FC, so that they can be aligned at each PU-Rx. This converts the cognitive IA problem into an unconstrained standard IA problem for a general cognitive system. Given the fact that the optimal power allocation algorithms used to optimize the SUs transmission rates turns out to be an optimal beamformer with multiple eigenbeams, this work initially proposes combining the diversity gain property of STBC, the zero-forcing function of IA and beamforming to optimize the SUs transmission rates. However, this solution requires availability of CSI, and to eliminate the need for this, this work then combines the D-STBC scheme with optimal IA precoders (consisting of beamforming and zero-forcing) to maximize the SUs data rates.
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