Rafael Asorey-Cacheda

Bio: Rafael Asorey-Cacheda is an academic researcher from Universidad Politécnica de Cartagena. The author has contributed to research in topics: Error detection and correction & Redundancy (engineering). The author has an hindex of 9, co-authored 56 publications receiving 378 citations. Previous affiliations of Rafael Asorey-Cacheda include University of Vigo & New Mexico State University.

A Survey on Cooperative Diversity for Wireless Networks

Abstract: Diversity, i.e. transmitting multiple replicas of a signal, may mitigate fading in wireless networks. Among other diversity techniques, the space diversity of multi-antenna systems is particularly interesting since it can complement other forms of diversity. The recent cooperative diversity paradigm brings the advantages of multi-antenna space diversity to single antenna networked devices, which, through cooperation and antenna sharing, form virtual antenna arrays. However, cooperative diversity is a complex technique and research on this topic is still in its early stages. This paper aims at providing a general survey on the theoretical framework; and the physical and medium access control proposals in the literature.

On Maximizing the Lifetime of Wireless Sensor Networks by Optimally Assigning Energy Supplies

Abstract: The extension of the network lifetime of Wireless Sensor Networks (WSN) is an important issue that has not been appropriately solved yet. This paper addresses this concern and proposes some techniques to plan an arbitrary WSN. To this end, we suggest a hierarchical network architecture, similar to realistic scenarios, where nodes with renewable energy sources (denoted as primary nodes) carry out most message delivery tasks, and nodes equipped with conventional chemical batteries (denoted as secondary nodes) are those with less communication demands. The key design issue of this network architecture is the development of a new optimization framework to calculate the optimal assignment of renewable energy supplies (primary node assignment) to maximize network lifetime, obtaining the minimum number of energy supplies and their node assignment. We also conduct a second optimization step to additionally minimize the number of packet hops between the source and the sink. In this work, we present an algorithm that approaches the results of the optimization framework, but with much faster execution speed, which is a good alternative for large-scale WSN networks. Finally, the network model, the optimization process and the designed algorithm are further evaluated and validated by means of computer simulation under realistic conditions. The results obtained are discussed comparatively.

Evaluation of historical bridges through recreation of GPR models with the FDTD algorithm

Abstract: This work presents the evaluation of a medieval masonry bridge that has suffered different restorations throughout history. Ground penetrating radar was used to define the internal state of the structure. Given that the heterogeneity in masonry complicates the interpretation of field data, numerical modelling was employed to improve such interpretation. The combination of photogrammetric and thermographic data, jointly with the development of custom algorithms, was used to create the synthetic model; while real GPR data supported the media characterization. The resulting data allowed for the interpretation of both composition and distribution of different materials in the interior of the bridge.

A Review of Aeronautical Electronics and Its Parallelism With Automotive Electronics

Abstract: Aeronautical electronics and communication technologies have evolved from the analog domain to the digital domain, and nowadays, planes are complex structures serviced by many standalone systems that communicate through data buses. Many of these systems have found applicability in other sectors. This paper reviews the most recent technologies in modern aircraft and identifies their application in the automotive sector. It also identifies automotive electronics as applied in planes.

FPGAs in Industrial Control Applications

Abstract: The aim of this paper is to review the state-of-the-art of Field Programmable Gate Array (FPGA) technologies and their contribution to industrial control applications. Authors start by addressing various research fields which can exploit the advantages of FPGAs. The features of these devices are then presented, followed by their corresponding design tools. To illustrate the benefits of using FPGAs in the case of complex control applications, a sensorless motor controller has been treated. This controller is based on the Extended Kalman Filter. Its development has been made according to a dedicated design methodology, which is also discussed. The use of FPGAs to implement artificial intelligence-based industrial controllers is then briefly reviewed. The final section presents two short case studies of Neural Network control systems designs targeting FPGAs.

A review of Ground Penetrating Radar application in civil engineering: A 30-year journey from Locating and Testing to Imaging and Diagnosis

Abstract: The GPR (Ground Penetrating Radar) conference in Hong Kong year 2016 marked the 30th anniversary of the initial meeting in Tifton, Georgia, USA on 1986. The conference has been being a bi-annual event and has been hosted by sixteen cities from four continents. Throughout these 30 years, researchers and practitioners witnessed the analog paper printout to digital era that enables very efficient collection, processing and 3D imaging of large amount of data required in GPR imaging in infrastructure. GPR has systematically progressed forward from “Locating and Testing” to “Imaging and Diagnosis” with the Holy Grail of ’Seeing the unseen’ becoming a reality. This paper reviews the latest development of the GPR’s primary infrastructure applications, namely buildings, pavements, bridges, tunnel liners, geotechnical and buried utilities. We review both the ability to assess structure as built character and the ability to indicate the state of deterioration. Finally, we outline the path to a more rigorous development in terms of standardization, accreditation, and procurement policy.

Enhancing Physical-Layer Secrecy in Multiantenna Wireless Systems: An Overview of Signal Processing Approaches

Abstract: This article provides an overview of the signal processing techniques used to enhance secrecy in the physical layer of multiantenna wireless communication systems. Motivated by results in information theory, signal processing techniques in both the data transmission and the channel estimation phases have been explored in the literature to enlarge the signal quality difference at the destination and the eavesdropper. In the data transmission phase, secrecy beamforming and precoding schemes are used to enhance signal quality at the destination while limiting the signal strength at the eavesdropper. Artificial noise (AN) is also used on top of beamformed or precoded signals to further reduce the reception quality at the eavesdropper. In the channel estimation phase, training procedures are developed to enable better channel estimation performance at the destination than at the eavesdropper. As a result, the effective signal-to-noise ratios (SNRs) at the two terminals will be different and a more favorable secrecy channel will be made available for use in the data transmission phase. Finally, future research directions are discussed.

LoRaWAN — A low power WAN protocol for Internet of Things: A review and opportunities

Abstract: The Internet of Things (IoT) vision requires increasingly more sensor nodes interconnected and a network solution that may accommodate these requirements accordingly. In wireless sensor networks, there are energy-limited devices; therefore techniques to save energy have become a significant research trend. Other issues such as latency, range coverage, and bandwidth are important aspects in IoT. It is considering the massive number of expected nodes connected to the Internet. The LoRaWAN (Low Power WAN Protocol for Internet of Things), a data-link layer with long range, low power, and low bit rate, appeared as a promising solution for IoT in which, end-devices use LoRa to communicate with gateways through a single hop. While proprietary LPWAN (Low Power Wide Area Network) technologies are already hitting a large market, this paper addresses the LoRa architecture and the LoRaWAN protocol that is expected to solve the connectivity problem of tens of billions of devices in the next decade. Use cases are considered to illustrate its application alongside with a discussion about open issues and research opportunities.