Results 1  10
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16
On dimensionality for sparse multipath
 Proceedings. 7th Australian Communications Theory Workshop, 2006
, 2006
"... Abstract — We give a 2W T style result for the degrees of freedom of multipath signals that pass through spatially limited (sparse) scattering environments. The dimensionality scales with the circumference of the scattering region, and the total communications path length. We provide a direct compar ..."
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Abstract — We give a 2W T style result for the degrees of freedom of multipath signals that pass through spatially limited (sparse) scattering environments. The dimensionality scales with the circumference of the scattering region, and the total communications path length. We provide a direct comparison to the timefrequency case, where space replaces time. This is a rigorous wavefield examination of previous heuristic geometric arguments. I.
Maximal Ratio Combining Performance Analysis in Spatially Correlated Rayleigh Fading Channels with Imperfect Channel Knowledge
"... Abstract — New Results for the performance analysis of maximal ratio combining (MRC) using BPSK modulation in spatially correlated Rayleigh fading channels with imperfect channel knowledge are presented in terms of antenna array configuration and parameters of scatterer distributions. The utility of ..."
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Abstract — New Results for the performance analysis of maximal ratio combining (MRC) using BPSK modulation in spatially correlated Rayleigh fading channels with imperfect channel knowledge are presented in terms of antenna array configuration and parameters of scatterer distributions. The utility of recently developed expressions for bit error probability is enhanced by application of a spatial correlation formulation for arbitrarily spaced antennas and general scatterer distributions. The results of performance analysis give valuable insight into the performance of MRC in realistic Rayleigh fading scenarios with imperfect channel state information for both isotropic and nonisotropic fading scenarios. I.
Fading resistance of orthogonal spacetime block codes under spatial correlation
 in IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC
, 2004
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1 Fast Directional Spatially Localized Spherical Harmonic Transform
"... Abstract—We propose a transform for signals defined on the sphere that reveals their localized directional content in the spatiospectral domain when used in conjunction with an asymmetric window function. We call this transform the directional spatially localized spherical harmonic transform (direc ..."
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Abstract—We propose a transform for signals defined on the sphere that reveals their localized directional content in the spatiospectral domain when used in conjunction with an asymmetric window function. We call this transform the directional spatially localized spherical harmonic transform (directional SLSHT) which extends the SLSHT from the literature whose usefulness is limited to symmetric windows. We present an inversion relation to synthesize the original signal from its directionalSLSHT distribution for an arbitrary window function. As an example of an asymmetric window, the most concentrated bandlimited eigenfunction in an elliptical region on the sphere is proposed for directional spatiospectral analysis and its effectiveness is illustrated on the Mars topographic dataset. Finally, since such typical datasets on the sphere are of considerable size and the directional SLSHT is intrinsically computationally demanding depending on the bandlimits of the signal and window, a fast algorithm for the efficient computation of the transform is developed. The floating point precision numerical accuracy of the fast algorithm is demonstrated and a full numerical complexity analysis is presented. Index Terms—Signal analysis, spherical harmonics, 2sphere.
Spatial Precoder Design for SpaceTime Coded MIMO Systems: Based on Fixed Parameters of MIMO Channels
, 2005
"... Abstract — In this paper, we introduce the novel use of linear spatial precoding based on fixed and known parameters of multipleinput multipleoutput (MIMO) channels to improve the performance of spacetime coded MIMO systems. We derive linear spatial precoding schemes for both coherent (channel is ..."
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Abstract — In this paper, we introduce the novel use of linear spatial precoding based on fixed and known parameters of multipleinput multipleoutput (MIMO) channels to improve the performance of spacetime coded MIMO systems. We derive linear spatial precoding schemes for both coherent (channel is known at the receiver) and noncoherent (channel is unknown at the receiver) spacetime coded MIMO systems. Antenna spacing and antenna placement (geometry) are considered as fixed parameters of MIMO channels, which are readily known at the transmitter. These precoding schemes exploit the antenna placement information at both ends of the MIMO channel to ameliorate the effect of nonideal antenna placement on the performance of spacetime coded systems. In these schemes, the precoder is fixed for given transmit and receive antenna configurations and transmitter does not require any feedback of channel state information (partial or full) from the receiver. Closed form solutions for both precoding schemes are presented for systems with up to three receiver antennas. A generalized method is proposed for more than three receiver antennas. We use the coherent spacetime block codes (STBC) and differential spacetime block codes to analyze the performance of proposed precoding schemes. Simulation results show that at low SNRs, both precoders give significant performance improvement over a nonprecoded system for small antenna aperture sizes. Index Terms — Spacetime coding, channel modelling, linear precoder design, MIMO systems, nonisotropic scattering, spatial correlation. I.
Chapter 12 SPATIAL CHARACTERIZATION OF MULTIPLE ANTENNA CHANNELS
"... In this chapter we present a realistic new model for wireless multipleinput multipleoutput (MIMO) channels which is more general than previous models. A novel spatial decomposition of the channel is developed to provide insights into the spatial aspects of multiple antenna communication systems. By ..."
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In this chapter we present a realistic new model for wireless multipleinput multipleoutput (MIMO) channels which is more general than previous models. A novel spatial decomposition of the channel is developed to provide insights into the spatial aspects of multiple antenna communication systems. By exploiting the underlying physics of freespace wave propagation we characterize the fundamental communication modes of a physical aperture and develop an intrinsic capacity which is independent of antenna array geometries and array signal processing. We show there exists a maximum achievable capacity for communication between spatial regions of space, which depends on the size of the regions and the statistics of the scattering environment.
1 Impact of Mobile Acceleration on the Statistics of Rayleigh Fading Channel
"... Abstract — Clarke’s model of the received signal statistics in a mobile isotropic scattering environment assumes a constant mobile velocity, a consequence of which is that the autocorrelation function of the received signal and the Power Spectral Density (PSD) are independent of the absolute time. I ..."
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Abstract — Clarke’s model of the received signal statistics in a mobile isotropic scattering environment assumes a constant mobile velocity, a consequence of which is that the autocorrelation function of the received signal and the Power Spectral Density (PSD) are independent of the absolute time. In this contribution we relax the assumption of constant mobile velocity and analyze the statistics of the channel when the mobile receiver has a constant acceleration. First, we derive expressions for a general scattering environment and, then, specialize them to the case of isotropic scattering environment. The autocorrelation and PSD of the channel are not only a function of the lag, τ, but the absolute time index, n as well. There are now two kinds of PSDs: The conventional PSD, based on the wellknown WienerKhintchine theorem, gives the spectrum in the τ domain. The second PSD is concerned with the variation of the channel with time and gives the spectrum in the n domain. The simulation results suggest that the two PSDs show a pattern of periodicity which can be explained by considering asymptotic approximation of the Bessel function. Moreover, the magnitudes of the PSDs diminish with increasing τ or n such that the conventional PSD approaches uniform distribution over 0 to 2π when time n is large whereas the PSD of channel variation with time approaches zero for large τ. We give results on the basis of simulations and justify analytically, or heuristically. We also discuss different implications of these results. I.
Directional Random Scattering MIMO Channels: Entropy Analysis and Capacity Optimization
"... AbstractIn this paper, we study the effect of directional random scattering on the capacity of multipleinput multipleoutput (MIMO) systems. First, we use the spatial decomposition of the MIMO channel matrix to analyze the randomness (entropy) of directional scattering. The analysis shows that di ..."
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AbstractIn this paper, we study the effect of directional random scattering on the capacity of multipleinput multipleoutput (MIMO) systems. First, we use the spatial decomposition of the MIMO channel matrix to analyze the randomness (entropy) of directional scattering. The analysis shows that directional scatterers (with at least a null in the angular power spectrum) will no longer be random when the receiver observation radius is sufficiently large. Therefore, directional scattering limits the expected linear increase of MIMO capacity with increasing the number of antennas. Second, we consider the effect of receiver antenna arrangement (positions) on the capacity of MIMO systems. For any random scatterer with a given angular power spectrum, we show that it is possible to choose the receiver antenna arrangement with the optimum whitening of the MIMO channel matrix that, in turn, maximizes MIMO channel capacity.
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"... Exact pairwise error probability analysis of spacetime codes in spatially correlated fading channels Paper ..."
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Exact pairwise error probability analysis of spacetime codes in spatially correlated fading channels Paper
Electronics and Communication
"... The error probability floor evolves due to performance loss, thus there is a requirement of high energy and high bandwidth to get a desired link. The branches are assumed to be Rayleigh fading. With the increase number of receiver the signal to noise ratio to be improved and bit error rate of all br ..."
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The error probability floor evolves due to performance loss, thus there is a requirement of high energy and high bandwidth to get a desired link. The branches are assumed to be Rayleigh fading. With the increase number of receiver the signal to noise ratio to be improved and bit error rate of all branches are compared. This work confirms the benefit of choosing 2x2MIMO system instead of 1 transmits 2 receive MRC case.