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Wireless applications require the use of Power Amplifiers for signal transmission. Those are generally nonlinear devices, and there is a trade-off between efficiency and the signal distortion level, which degrades performance. Besides that, transmission waveforms suffer from spectral regrowth when non-linearities are present. Moreover, some power amplifiers also carry memory effects, which further...
This article describes image transmission in Through-The-Earth Communications (TTE), which are characterized by non-Gaussian impulsive atmospheric noise. We analyze the transmission of compressed and uncompressed image files. We verify the possibility of transmitting uncompressed analog images, which can be restored even with signal noise ratio (SNR) equal to −10 dB, and, based on the Structural Similarity...
This article describes image transmission in Through-The-Earth Communications (TTE), which are characterized by non-Gaussian impulsive atmospheric noise. We analyze the transmission of compressed and uncompressed image files. We verify the possibility of transmitting uncompressed analog images, which can be restored even with signal noise ratio (SNR) equal to −10 dB, and, based on the Structural Similarity...
The rapidly increasing penetration of smart phones and the associated exponential growth in the wireless data traffic result in an increasing energy consumption and, consequently, greater carbon dioxide (CO2) emissions. However, on account of operational costs and environmental worries, this increase should be taken into consideration for future cellular networks evolution. In this paper, we study...
Proper spectrum sensing is fundamental for the operation of cognitive radio networks, and must be performed not only reliably, i.e., with low false alarm and missed detection rates, but also as quickly as possible, which are usually conflicting requirements. In this contribution we propose the use of change detection techniques using adaptive RLS filters to detect spectrum occupancy, and show that...
Iterative correction can be employed to mitigate the distortion caused by nonlinear power amplifiers in OFDM systems. However, proposals found in the literature suppose that the receiver has perfect knowledge of the nonlinear conditions encountered in transmission. In this paper, we propose the use of the Extendend Kalman Filter and the Unscented Kalman Filter to estimate the nonlinear characteristics...
In a cognitive radio system where the primary user is a TDMA based system, spectrum sensing must be able to identify the occupation of both a frequency band and a time slot. Whereas this can be done by scanning each narrowband frequency channel in turns, we can also perform a wideband sampling of the transmitted signal, and identify simultaneously the occupied frequency bands and time slots by means...
This article addresses energy detection for spectrum sensing of M-ary quadrature amplitude modulation (QAM) systems. Analytical expressions are developed for the average probability of detection in these systems. The analytical results are validated by numerical simulations and comparisons with different approximated approaches found in the literature are made. We see that the approximations usually...
The widespread deployment of optical interconnects in data centers has renewed the interest in multimode fiber communications. Due to the complexity of modern transmission techniques, performance analysis relies on numerical simulations that require an accurate channel model to reflect reality with the needed precision. As there is no standard model for channel simulation, we investigate a deterministic,...
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