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Interference alignment (IA) is a promising transmission technology enabling, essentially, the maximum achievable degrees of freedom (DOF) in $K$-user multiple-input–multiple-output (MIMO) interference channels. The ideal DOF of IA systems have been obtained using independent MIMO channels, which is, usually rarely observed in reality, particularly in indoor environments. Therefore, the data sum rate...
The reliability of spectrum sensing is a challenging issue in cognitive radio (CR) systems. In this paper, we validate the reliability of two spectrum sensing algorithms for pilot-added OFDM signals: time-domain symbol cross-correlation (TDSC) and periodical peaks of autocorrelation (PPA) with a real system in real environments. To validate, these two algorithms carry out detection function for real...
In cognitive radio networks, the task of spectrum sensing is required to be reliable at low signal-to-noise ratios (SNRs). Spectral correlation is an effective approach to satisfy the requirement. The algorithms based on statistic spectral correlation profiles are a good method as shown in some previous works. In this paper, we propose an algorithm with maximum ratio combination for the profiles to...
Cognitive radio constitutes a very promising solution to improve spectrum usage of communication systems. However, being equipped with MIMO antennas, the design of CR devices poses tremendous challenges. In this paper, antennas requirements as well as the limitations imposed on the system performance are reviewed. Well decoupled and reconfigurable antennas guarantee the flexibility needed during spectrum...
We consider an angular distribution for modeling the local scattering in the vicinity of the receiver or the transmitter. The Gaussian spatial distribution is extended to capture the correlation between the x-coordinate and the y-coordinate, which gives rise to a generalization to the uncorrelated Gaussian spatial distribution. The probability density function of the correlated Gaussian spatial distribution...
In this paper, we investigate the impact of the spatial correlation on the performance of the spatial multiplexing (SM) Multiple-Input Multiple-Output (MIMO) Ultra-WideBand (UWB) system in which both the pre-equalizer and pre-Rake-filter are deployed at the transmitter. The combination of the pre-equalizer and the pre-filter is to mitigate the Multiple-Stream Interference caused by transmitting several...
Spatial frequency approximation (SFA) of spatial fading correlation (SFC) is addressed for the case that the exact infinite summation of Bessel functions is inconvenient or infeasible. The angular spread is derived for semicircular scattering, especially characterized by uniform, Gaussian, Laplacian, and von Mises distributions. The semicircular scattering on the range (-1over2π, 1over2π] happens,...
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