Capacity Limits of Spectrum-Sharing in Hoyt (Nakagami-q) Fading Channels

A channel capacity analysis is presented in this work for a spectrum-sharing cognitive radio link in which the fading experienced by the signal is modeled with the Hoyt (Nakagami-q) distribution. Based on a novel formulation of the squared Hoyt distribution derived by the authors, simple expressions for the capacity of the secondary link in a number of scenarios of interest are derived, which are given in terms of easy-to-compute finite-range integrals of elementary functions. The effect of fading severity in the secondary transmitter-primary receiver (ST-PR) and secondary transmitter-secondary receiver (ST-SR) links, and the impact of different antenna gains on the system performance are analyzed. We show that in the presence of severe fading for the ST-PR link, the capacity of the ST-SR link is increased.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO. Fondos FEDER. European Union Marie-Curie COFUND U-mobility program

Understanding the impact of line-of-sight in the ergodic spectral efficiency of cellular networks

In this paper we investigate the impact of lineof-sight (LoS) condition in the ergodic spectral efficiency of cellular networks. To achieve this goal, we have considered the kappa-mu shadowed model, which is a general model that provides an excellent fit to a wide set of propagation conditions. To overcome the mathematical complexity of the analysis, we have split the analysis between large and small-scale effects. Building on the proposed framework, we study a number of scenarios that range from heavily-fluctuating LoS to deterministic-LoS. Finally, we shed light on the interplay between fading severity and spectral efficiency by means of the amount of fading.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

An educational tool for understanding MPEG‐2 video compression and coding techniques

The understanding of the video encoding/decoding processes is a key skill for students of computer science, engineering, or telecommunications, especially those specialized in multimedia. The special characteristics of the video signals, and how such features are leveraged to compress the video frames using coding theory, are hard to understand for engineering students. In this paper, we describe MPEG-2 analyzer, an educational tool designed to provide a comprehensive and interactive way to understand MPEG-2 video compression and encoding techniques. We have used our tool to evaluate its usefulness in reinforcing the knowledge about the MPEG-2 video (de)coding process to Telecommunication Engineering students. Results show that the evaluation of the tool is very positive, and it has helped them to understand many of the complex concepts covered in the course.Funding for open access charge: Universidad de Málaga / CBUA

Analytical Characterization of Coverage Regions for STAR-RIS-aided NOMA/OMA Communication Systems

We provide an analytical characterization of the coverage region of simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-aided two-user downlink communication systems. The cases of orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) are considered, under the energy-splitting (ES) protocol. Results confirm that the use of STAR-RISs is beneficial to extend the coverage region, and that the use of NOMA provides a better performance compared to the OMA counterpart. However, the effect of imperfect successive interference cancellation degrades the performance of NOMA and needs to be considered for a realistic analysis

Hydrolysis study of bis-1,2-(triethoxysilyl)ethane silane by NMR

The hydrolysis process of bis-1,2-(triethoxysilyl)ethane (BTSE) was studied in aqueous and methanol solutions at pH 4. Nuclear magnetic resonance (NMR) evaluation of different solutions was carried out for 7 days. Unlike other researches, methanol-rich solutions are proven inadequate to reach a complete hydrolysis process. In water-rich solutions, hydrolysis takes place for 3 days, 85% of the silane molecules being transformed into silanols; this amount continues increasing up to the seventh day of hydrolysis.Authors wish to acknowledge the Ministry of the Environment (through project 136/PC08/3-11.2) for their financial support in this research