Search

This article belongs to the Special Issue Innovative Antenna Systems: Challenges, Developments, and Applications. In this article, we investigated the secrecy performance of a three-hop relay network system with Power Splitting (PS) and Energy Harvesting (EH). In the presence of one eavesdropper, a signal is transferred from source to destination with the help of a relay. The source signal transmits in full-duplex (FD) mood, jamming the relay transfer signals to the destination. The relay and source employ Time Switching (TS) and Energy Harvesting (EH) techniques to obtain the power from the power beacon. In this study, we compared the Secrecy Rate of two Cooperative Schemes, Amplify and Forward (AF) and Decode and Forward (DF), for both designed systems with the established EH and PS system. The Secrecy Rate was improved by 50.5% in the AF scheme and by 44.2% in the DF scheme between the relay and eavesdropper at 40 m apart for the proposed system in EH and PS. This simulation was performed using the Monto Carlo method in MATLAB. The authors appreciate the financial support from the Science and Technology Innovation Project of Zhengzhou 2019CXZX0037, the Special Project for Inter-Government Collaboration of State Key Research and Development Program 2016YFE0118400, and NSFC U1604159. Furthermore, the funding from the Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant 801538 is appreciated. Additionally, the partially supported from the Researchers Supporting Project number (RSP-2021/58), King Saud University, Riyadh, Saudi Arabia, is acknowledged.

Digital precoding techniques have been widely applied in multiple-input multiple-output (MIMO) systems to enhance spectral efficiency (SE) which is crucial in 5G New Radio (NR). Therefore, the 3rd Generation Partnership Project (3GPP) has developed codebook-based MIMO precoding strategies to achieve a good trade-off between performance, complexity, and signal overhead. This paper aims to evaluate the performance bounds in SE achieved by the 5G-NR precoding matrices in single-user (SU) and multi-user (MU) MIMO systems, namely Type I and Type II, respectively. The implementation of these codebooks is covered providing a comprehensive guide with a detailed analysis. The performance of the 5G-NR precoder is compared with theoretical precoding techniques such as singular value decomposition (SVD) and block-diagonalization to quantify the margin of improvement of the standardized methods. Several configurations of antenna arrays, number of antenna ports, and parallel data streams are considered for simulations. Moreover, the effect of channel estimation errors on the system performance is analyzed in both SU and MU-MIMO cases. For a realistic framework, the SE values are obtained for a practical deployment based on a clustered delay line (CDL) channel model. These results provide valuable insights for system designers about the implementation and performance of the 5G-NR precoding matrices. This work has received funding from the European Union (EU) Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie ETN TeamUp5G, grant agreement No. 813391. Also, this work has been partially funded by the Spanish National project IRENE-EARTH (PID2020-115323RB-C33/AEI/10.13039/501100011033).

This article belongs to the Special Issue Prospective Multiple Antenna Technologies for 5G and Beyond. In this paper, an umbrella-shaped patch antenna for future millimeter-wave applications for the 5G frequency band is presented. The proposed antenna resonates at multiple frequency bands, i.e., 28 GHz, 38 GHz, and 55 GHz (V-band) that have been globally allocated for 5G communications systems. The proposed antenna is designed using Rogers RT/duroid 5870, with a relative permittivity, loss tangent and thickness of 2.33 mm, 0.0012 mm and 0.79 mm, respectively. The antenna has an overall size of 8 mm × 8 mm which correspond to 0.7 λ × 0.7 λ, where λ is free space wavelength at the lowest resonance. Moreover, the wide bandwidth, high gain and tri band operational mode is achieved by introducing two stubs to the initial design. The antenna prototype was fabricated and validated experimentally. The comparison of the simulated and measured results demonstrates a good correlation. Additionally, the comparative analysis with state of the art work demonstrates that the proposed antenna offers compact size, simple geometrical configuration, wide bandwidth, high gain, and radiation efficiency which makes the proposed antenna a potential candidate for compact smart 5G devices. The authors appreciate financial support from Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant 801538. Moreover, this work was partially supported by the Antenna and Wireless Propagation Group (https://sites.google.com/view/awpgrp/home, assessed on 15 August 2021) and from the Researchers Supporting Project number (RSP-2021/58), King Saud University, Riyadh, Saudi Arabia.

This article belongs to the Special Issue Broadband Antennas and Antenna Arrays. Computation of the broadband antenna impedance behavior requires the wideband lumped equivalent circuit. This work aims to provide a comprehensive study of broadband antenna equivalent circuit models over broad frequency ranges for Internet of Things (IoT) applications using multiple approaches. The first approach is a Foster approximation, which is based on the antenna-simulated scattering parameters and impedance data. The second concerns a vector-fitting fitting approximation, which is based on the antenna-simulated impedance/admittance data. The studied antenna is modeled based on the radiating element"s geometry and the multifractal slots, in addition to the DGS (Defected Ground Plane) effects. Applying these techniques, wideband lumped equivalent circuits of the antenna have been computed which are in good agreement with measurement data. These models could be useful for the enhancement of the performance of a broadband antenna and its systematic design as well as offering the advantage of saving computation time for full-wave simulations and facilitating the solution of problems that have both an electromagnetic part as well as a circuit part. For further analysis, the Gaussian pulse has been generated to drive a time-domain analysis of the current and power response waveforms antenna behavior under load.

This article belongs to the Special Issue Innovative Antenna Systems: Challenges, Developments, and Applications. This article presents compact and novel shape ring-slotted antenna array operating at mmWave band on central frequency of 28 GHz. The proposed structure designed at 0.256 mm thin Roggers 5880 is composed of a ring shape patch with a square slot etched at the top mid-section of partial ground plane. Through optimizing the ring and square slot parameters, a high bandwidth of 8 GHz is achieved, ranging from 26 to 32 GHz, with a simulated gain of 3.95 dBi and total efficiency of 96% for a single element. The proposed structure is further transformed in a 4-element linear array manner. With compact dimensions of 20 mm × 22 mm for array, the proposed antenna delivers a high simulated gain of 10.7 dBi and is designed in such a way that it exhibits dual beam response over the entire band of interest and simulated results agree with fabricated prototype measurements.

This article belongs to the Special Issue Advances in System-on-Chip Design This paper presents the design of a high-performance 0.45-0.50 THz antenna on chip (AoC) for fabrication on a 100-micron GaAs substrate. The antenna is based on metasurface and substrate-integrated waveguide (SIW) technologies. It is constituted from seven stacked layers consisting of copper patch-silicon oxide-feedline-silicon oxide-aluminium-GaAs-copper ground. The top layer consists of a 2 × 4 array of rectangular metallic patches with a row of subwavelength circular slots to transform the array into a metasurface. This essentially enlarges the effective aperture area of the antenna. The antenna is excited using a coplanar waveguide feedline that is sandwiched between the two silicon oxide layers below the patch layer. The proposed antenna structure reduces substrate loss and surface waves. The AoC has dimensions of 0.8 × 0.8 × 0.13 mm3. The results show that the proposed structure greatly enhances the antenna¿s gain and radiation efficiency, and this is achieved without compromising its physical size. The antenna exhibits an average gain and efficiency of 6.5 dBi and 65%, respectively, which makes it a promising candidate for emerging terahertz applications. This work is partially supported by RTI2018-095499-B-C31, Funded by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER, UE).

This paper aims to compare different design alternatives of hardware-in-the-loop (HIL) for emulating power converters in Field Programmable Gate Arrays (FPGAs). It proposes various numerical formats (fixed and floating-point) and different approaches (pure VHSIC Hardware Description Language (VHDL), Intellectual Properties (IPs), automated MATLAB HDL code, and High-Level Synthesis (HLS)) to design power converters. Although the proposed models are simple power electronics HIL systems, the idea can be extended to any HIL system. This study compares the design effort of different coding methods and numerical formats considering possible synthesis tools (Precision and Vivado), and it comprises an analytical discussion in terms of area and speed. The different models are synthesized as ad-hoc modules in general-purpose FPGAs, but also using the NI myRIO device as an example of a commercial tool capable of implementing HIL models. The comparison confirms that the optimum design alternative must be chosen based on the application (complexity, frequency, etc.) and designers’ constraints, such as available area, coding expertise, and design effort.

This research article proposes a compact frequency and pattern reconfigurable flexible antenna for heterogeneous applications. A triangular monopole antenna with a semicircular stub is made frequency and pattern tunable by connecting and disconnecting two inverted L-shaped stubs utilizing diodes. When either of the stubs is connected to the radiator, a relative phase difference happens at both ends of the radiator that changes the direction of the electromagnetic radiations, consequently pattern reconfigurability can be obtain. Besides that, because of the reactive load introduced by the stubs, the antenna’s effective length has changed and, as a result, the frequency reconfigurability can be attained. The antenna features a compact size of 40 × 50 × 0.254 mm3 corresponding to 0.22λo × 0.27λo × 0.001λo, where λo is free-space wavelength at 1.65 GHz, while its operational bandwidth is from 1.65 GHz to 2.51 GHz, with an average gain and radiation efficiency of better than 2.2 dBi and 80%, exhibiting a pattern reconfigurability of 180° in the E-plane. The frequency of the proposed antenna can be switched from 2.1 GHz to 1.8 GHz by switching the state of both diodes in OFF and ON-state, respectively. The fabricated prototype of the antenna is tested to verify its performance parameters. In addition, to validate the proposed design, it has been compared with prior arts in terms of the overall size, reconfigurability type, flexibility, radio frequency (RF) switch type used for reconfigurability, and frequency bandwidth. The proposed antenna provides smaller size with a large bandwidth coverage alongside with discrete RF switch type with the advantages of flexibility and both frequency and pattern reconfigurability. As a result, the proposed compact flexible and pattern reconfigurable antenna is a promising candidate for heterogeneous applications, including the global system for mobile (GSM) band (1800 and 1900 MHz) and industrial, scientific and medical (ISM) band (2.4 GHz) along with well-known cellular communication bands of 3G, 4G, and long term evolution (LTE) bands ranging from 1700–2300 MHz around the globe.

In this paper, a compact rectifier, capable of harvesting ambient radio frequency (RF) power is proposed. The total size of the rectifier is 45.4 mm &times, 7.8 mm &times, 1.6 mm, designed on FR-4 substrate using a single-stage voltage multiplier at 900 MHz. GSM/900 is among the favorable RF Energy Harvesting (RFEH) energy sources that span over a wide range with minimal path loss and high input power. The proposed RFEH rectifier achieves measured and simulated RF-to-dc (RF to direct current) power conversion efficiency (PCE) of 43.6% and 44.3% for 0 dBm input power, respectively. Additionally, the rectifier attained 3.1 V DC output voltage across 2 k&Omega, load terminal for 14 dBm and is capable of sensing low input power at &minus, 20 dBm. The work presents a compact rectifier to harvest RF energy at 900 MHz, making it a good candidate for low powered wireless communication systems as compares to the other state of the art rectifier.

Currently, the use of machine learning models for developing intrusion detection systems is a technology trend which improvement has been proven. These intelligent systems are trained with labeled datasets, including different types of attacks and the normal behavior of the network. Most of the studies use a unique machine learning model, identifying anomalies related to possible attacks. In other cases, machine learning algorithms are used to identify certain type of attacks. However, recent studies show that certain models are more accurate identifying certain classes of attacks than others. Thus, this study tries to identify which model fits better with each kind of attack in order to define a set of reasoner modules. In addition, this research work proposes to organize these modules to feed a selection system, that is, a dynamic classifier. Finally, the study shows that when using the proposed dynamic classifier model, the detection range increases, improving the detection by each individual model in terms of accuracy.

This article belongs to the Special Issue Cloud Computing and Applications Multi-access Edge Computing (MEC) is proposed as a standard framework for the provision and consumption of applications and services in proximity to the end-users of network operators. Proximity has been identified as one of the enablers of the forthcoming 5G, where extreme low latency and large bandwidth will be necessary for some services. However, the need of proximity imposes to network operators the necessity of huge investments in order to distribute computing capabilities towards the access. A less investment intensive approach would consist on sharing infrastructures by integrating MEC environments from different operators or providers. This could open the door to new business models on the one hand, as well as to avoid restrictions in terms of space, energy of regulation, on the other. This paper overviews different integration options by analyzing the MEC framework defined by the European Telecommunications Standards Institute (ETSI) and identifying different architectural alternatives as well as the business and technical aspects that need to be taken into consideration for realizing such integration. This work has been partly funded by the European Commission through the projects EU-TW 5GDIVE (Grant Agreement no. 859881) and H2020 5GROWTH (Grant Agreement no. 856709). This information reflects the consortia views, but neither the consortia nor the European Commission are liable for any use that may be done of the information contained therein.

Selenium is often considered the de-facto standard framework for end-to-end web testing nowadays. It allows practitioners to drive web browsers (such as Chrome, Firefox, Edge, or Opera) in an automated fashion using different language bindings (such as Java, Python, or JavaScript, among others). The term ecosystem, referring to the open-source software domain, includes various components, tools, and other interrelated elements sharing the same technological background. This article presents a descriptive survey aimed to understand how the community uses Selenium and its ecosystem. This survey is structured in seven categories: Selenium foundations, test development, system under test, test infrastructure, other frameworks, community, and personal experience. In light of the current state of Selenium, we analyze future challenges and opportunities around it. This work has been supported by the European Commission under the H2020 project "MICADO" (GA-822717), by the Government of Spain through the project "BugBirth" (RTI2018-101963-B-100), by the Regional Government of Madrid (CM) through the project "EDGEDATA-CM" (P2018/TCS-4499) cofunded by FSE & FEDER, and by the project "Analytics using sensor data for FlatCity" (MINECO/ERDF, EU) funded in part by the Spanish Agencia Estatal de Investigación (AEI) under Grant TIN2016-77158-C4-1-R and in part by the European Regional Development Fund (ERDF).

This article belongs to the Section Computer Science & Engineering Online advertising is a wealthy industry that generated more than $100B in 2018 only in the US and delivers billions of ads to Internet users every day with. These impressive numbers have also attracted the attention of malicious players that try to exploit the online advertising ecosystem for their own benefit. In particular, one of the most harmful practices refers to malicious users that act as advertisers to deliver unsafe ads. The goal of these ads is to compromise the security of the users that receive those ads. This practice is referred to as Malvertising. Some reports have estimated the economic loss caused by malvertising to the online advertising sector to $1.1B in 2017. This paper is the first work that analyses and quantifies the impact of malvertising in Facebook. To accomplish this study, we rely on a dataset that includes more than 5 M ads delivered to 3 K Facebook users from 126 K advertisers between October 2016 and May 2018. Our results reveal that although the portion of advertisers (0.68%) and ads (0.17%) associated to malvertising is very low, 1/3 of the users in our study were exposed to malvertising. Finally, we also propose a novel solution to block malvertising ads in real-time in Facebook. The research leading to these results has received funding from: the European Union’s Horizon 2020 innovation action programme under grant agreement No 786741 (SMOOTH project) and the gran agreement No 871370 (PIMCITY project); the Ministerio de Economía, Industria y Competitividad, Spain, and the European Social Fund(EU), under the Ramón y Cajal programme (grant RyC-2015-17732); the Ministerio de Educación, Cultura y Deporte, Spain, through the FPU programme( Grant FPU16/05852); the Ministerio de Ciencia e Innovación under the project ACHILLES (Grant PID2019-104207RB-I00); the Community of Madrid synergic project EMPATIA-CM (Grant Y2018/TCS-5046); and the Fundación BBVA under the project AERIS.

Nowadays, the Hardware-In-the-Loop (HIL) technique is widely used to test different power electronic converters. These real-time simulations require processing large data at high speed, which makes this application very suitable for FPGAs (Field Programmable Gate Array) as they are capable of parallel processing. This paper provides an analytical discussion on three HIL models for a full-bridge converter. The three models use different possible numerical formats, namely float and fixed-point, the latter with and without optimizing the width of signals to the embedded DSP (Digital Signal Processors) blocks of the FPGA. The optimized fixed-point model (OFPM) uses three and two times fewer DSP blocks or LUTs (Look Up Tables), and the maximum achievable clock frequency is also up to 35 % and 25 % higher than the float model and non-optimized fixed-point model (nOFPM), respectively. Furthermore, the models’ accuracy is proportional to the clock frequency, thus the OFPM is also the most accurate model. Finally, the paper shows the differences in the simulation when the models include or not losses, proving that not including losses leads to high errors, especially during transients, This research was funded by Spanish Ministerio de Economía y Competitividad grant number TEC2013-43017-R

Image perception can vary considerably between subjects, yet some sights are regarded as aesthetically pleasant more often than others due to their specific visual content, this being particularly true in tourism-related applications. We introduce the ESITUR project, oriented towards the development of &rsquo, smart tourism&rsquo, solutions aimed at improving the touristic experience. The idea is to convert conventional tourist showcases into fully interactive information points accessible from any smartphone, enriched with automatically-extracted contents from the analysis of public photos uploaded to social networks by other visitors. Our baseline, knowledge-driven system reaches a classification accuracy of 64.84 &plusmn, 4.22% telling suitable images from unsuitable ones for a tourism guide application. As an alternative we adopt a data-driven Mixture of Experts (MEX) approach, in which multiple learners specialize in partitions of the problem space. In our case, a location tag is attached to every picture providing a criterion to segment the data by, and the MEX model accordingly defined achieves an accuracy of 85.08 &plusmn, 2.23%. We conclude ours is a successful approach in environments in which some kind of data segmentation can be applied, such as touristic photographs.

Network Functions Virtualization (NFV) is a key technology for network automation and has been instrumental to materialize the disruptive view of 5G and beyond mobile networks. In particular, 5G embraces NFV to support the automated and agile provision of telecommunication and vertical services as a composition of versatile virtualized components, referred to as Virtual Network Functions (VNFs). It provides a high degree of flexibility in placing these components on distributed NFV infrastructures (e.g., at the network edge, close to end users). Still, this flexibility creates new challenges in terms of VNF connectivity. To address these challenges, we introduce a novel secure link-layer connectivity platform, L2S. Our solution can automatically be deployed and configured as a regular multi-site NFV service, providing the abstraction of a layer-2 switch that offers link-layer connectivity to VNFs deployed on remote NFV sites. Inter-site communications are effectively protected using existing security solutions and protocols, such as IP security (IPsec). We have developed a functional prototype of L2S using open-source software technologies. Our evaluation results indicate that this prototype can perform IP tunneling and cryptographic operations at Gb/s data rates. Finally, we have validated L2S using a multi-site NFV ecosystem at the Telefonica Open Network Innovation Centre (5TONIC), using our solution to support a multicast-based IP television service. This article has partially been supported by the European H2020 FISHY Project (grant agreement 952644), and the TRUE5G project funded by the Spanish National Research Agency (PID2019-108713RB-C52/AEI/10.13039/501100011033).

The currently deployed contact-tracing mobile apps have failed as an efficient solution in the context of the COVID-19 pandemic. None of them has managed to attract the number of active users required to achieve an efficient operation. This urges the research community to re-open the debate and explore new avenues that lead to efficient contact-tracing solutions. This paper contributes to this debate with an alternative contact-tracing solution that leverages already available geolocation information owned by BigTech companies with very large penetration rates in most countries adopting contact-tracing mobile apps. Moreover, our solution provides sufficient privacy guarantees to protect the identity of infected users as well as precluding Health Authorities from obtaining the contact graph from individuals., 7 pages, 1 figure, 1 table; added acknowledgments

To address atmospheric attenuation and path loss issues in the mmwave portion of the spectrum, high gain and narrow beam antenna systems are essential for the next generation communication networks. This paper presents a novel hook-shaped antenna array for 28 GHz 5G mmwave applications. The proposed antenna was fabricated on commercially available Rogers 5880 substrate with thickness of 0.508 mm and dimensions of 10 × 8 mm2. The proposed shape consists of a circle with an arc-shaped slot on top of it and T-shaped resonating lengths are introduced in order to attain broad band characteristics having gain of 3.59 dBi with radiation and total efficiency of 92% and 86% for single element. The proposed structure is transformed into a four-element array with total size of 26.9 × 18.5 mm2 in order to increase the gain up to 10.3 dBi at desired frequency of interest. The four-element array is designed such that it exhibits dual-beam response over the entire band of interest and the simulated results agree with fabricated prototype measurements. The proposed antenna array, because of its robustness, high gain, and dual-beam characteristics can be considered as a potential candidate for the next generation 5G communication systems.

This article belongs to the Special Issue Millimeter and Terahertz Wireless Communications A new cost-efficient, low-loss Ka-band diplexer designed in inverted microstrip gap waveguide technology is presented in this paper. Gap waveguide allows to propagate quasi-TEM modes in the air between two metal plates without the need for contact between them by using periodic metasurfaces. The diplexer is realized by using a bed of nails as AMC (Artificial Magnetic Conductor), first modeled with a PMC (Perfect Magnetic Conductor) surface for design simplification, and two fifth order end-coupled passband filters (BPFs) along with a power divider. The experimental verification confirms that the two channels centered at 24 GHz and 28 GHz with 1 GHz of bandwidth show measured insertion losses of 1.5 dB and 2 dB and 60 dB of isolation between them. A slight shift in frequency is observed in the measurements that can be easily explained by the variation in the permittivity of the substrate. This research was funded by the Spanish Ministerio de Ciencia, Innovación y Universidades grant numbers [PID2019-107688RB-C21, TEC2016-79700-C2-R and TEC2017-86619-R].

This article belongs to the Special Issue Advanced Cybersecurity Services Design With the transformation in smart grids, power grid companies are becoming increasingly dependent on data networks. Data networks are used to transport information and commands for optimizing power grid operations: Planning, generation, transportation, and distribution. Performing periodic security audits is one of the required tasks for securing networks, and we proposed in a previous work autoauditor, a system to achieve automatic auditing. It was designed according to the specific requirements of power grid companies, such as scaling with the huge number of heterogeneous equipment in power grid companies. Though pentesting and security audits are required for continuous monitoring, collaboration is of utmost importance to fight cyber threats. In this paper we work on the accountability of audit results and explore how the list of audit result records can be included in a blockchain, since blockchains are by design resistant to data modification. Moreover, blockchains endowed with smart contracts functionality boost the automation of both digital evidence gathering, audit, and controlled information exchange. To our knowledge, no such system exists. We perform throughput evaluation to assess the feasibility of the system and show that the system is viable for adaptation to the inventory systems of electrical companies. This work has been supported by National R&D Projects TEC2017-84197-C4-1-R, TIN2017-84844-C2-1-R, by the Comunidad de Madrid project CYNAMON P2018/TCS-4566 and co-financed by European Structural Funds (ESF and FEDER), and by the Consejo Superior de Investigaciones Científicas (CSIC) under the project LINKA20216 ("Advancing in cybersecurity technologies", i-LINK+ program).

WebRTC is the umbrella term for several emergent technologies aimed to exchange real-time media in the Web. Like other media-related services, the perceived quality of WebRTC communication can be measured using Quality of Experience (QoE) indicators. QoE assessment methods can be classified as subjective (users&rsquo, evaluation scores) or objective (models computed as a function of different parameters). In this paper, we focus on VMAF (Video Multi-method Assessment Fusion), which is an emergent full-reference objective video quality assessment model developed by Netflix. VMAF is typically used to assess video streaming services. This paper evaluates the use of VMAF in a different type of application: WebRTC. To that aim, we present a practical use case built on the top of well-known open source technologies, such as JUnit, Selenium, Docker, and FFmpeg. In addition to VMAF, we also calculate other objective QoE video metrics such as Visual Information Fidelity in the pixel domain (VIFp), Structural Similarity (SSIM), or Peak Signal-to-Noise Ratio (PSNR) applied to a WebRTC communication in different network conditions in terms of packet loss. Finally, we compare these objective results with a subjective evaluation using a Mean Opinion Score (MOS) scale to the same WebRTC streams. As a result, we found a strong correlation of the subjective video quality perceived in WebRTC video calls with the objective results computed with VMAF and VIFp in comparison with SSIM and PSNR and their variants.

This article belongs to the Special Issue Innovative Technologies and Services for Smart Cities. Evidence of something unusual happening in urban areas can be collected from different data sources, such as police officers, cameras, or specialized physical infrastructures. In this paper, we propose using geotagged posts on location-based social networks (LBSNs) to detect crowd dynamics anomalies automatically as evidence of a potential unusual event. To this end, we use the Instagram API media/search endpoint to collect the location of the pictures posted by Instagram users in a given area periodically. The collected locations are summarized by their centroid. The novelty of our work relies on using the entropy of the sequence of centroid locations in order to detect abnormal patterns in the city. The proposal is tested on a data set collected from Instagram during seven months in New York City and validated with another data set from Manchester. The results have also been compared with an alternative approach, a training phase plus a ranking of outliers. The main conclusion is that the entropy algorithm succeeds inn finding abnormal events without the need for a training phase, being able to dynamically adapt to changes in crowd behavior. This research was partially funded by the Ministry of Economy and Competitiveness through TEC2017-84197-C4-1-R, TEC2017-84197-C4-2-R, TEC2014-54335-C4-2-R, and TEC2014-54335-C4-3-R, and the European Regional Development Fund (ERDF) and the Galician Regional Government under agreement for funding the Atlantic Research Center for Information and Communication Technologies (AtlantTIC).

In this work a heuristic optimization algorithm known as the Fruit fly Optimization Algorithm is applied to antenna design problems. The original formulation of the algorithm is presented and it is adapted to array factor and horn antenna optimization problems. Specifically, it is applied to the array factor synthesis of uniformly-fed, non-equispaced arrays and to the profile optimization of multimode horn antennas. Several numerical examples are presented and the obtained results are compared with those provided by a deterministic optimization based on a simplex method and another well-known heuristic approach, the Genetic Algorithm, This work was supported by contracts TEC2016-76070-C3-1-R (AEI/FEDER, UE) and S2013/ICE-3000 (Comunidad de Madrid).

Current trends towards on-edge computing on smart portable devices requires ultra-low power circuits to be able to make feature extraction and classification tasks of patterns. This manuscript proposes a novel approach for feature extraction operations in speech recognition/voice activity detection tasks suitable for portable devices. Whereas conventional approaches are based on either completely analog or digital structures, we propose a &ldquo, hybrid&rdquo, approach by means of voltage-controlled-oscillators. Our proposal makes use of a bank a band-pass filters implemented with ring-oscillators to extract the features (energy within different frequency bands) of input audio signals and digitize them. Afterwards, these data will input a digital classification stage such as a neural network. Ring-oscillators are structures with a digital nature, which makes them highly scalable with the possibility of designing them with minimum length devices. Additionally, due to their inherent phase integration, low-frequency band-pass filters can be implemented without large capacitors. Consequently, we strongly benefit from power consumption and area savings. Finally, our proposal may incorporate the analog-to-digital converter into the structure of the own features extractor circuit to make the full conversion of the raw data when triggered. This supposes a unique advantage with respect to other approaches. The architecture is described and proposed at system-level, along with behavioral simulations made to check whether the performance is the expected one or not. Then the structure is designed with a 65-nm CMOS process to estimate the power consumption and area on a silicon implementation. The results show that our solution is very promising in terms of occupied area with a competitive power consumption in comparison to other state-of-the-art solutions.

This paper presents a baseline roadmap for the evolution of 5G new radio over the next decade. Three timescales are considered, namely short-term (2022-ish), medium-term (2025-ish), and long-term (2030-ish). The evolution of the target key performance indicators (KPIs) is first analyzed by accounting for forecasts on the emerging use cases and their requirements, together with assumptions on the pace of technology advancements. The baseline roadmap is derived next by capturing the top-10 and next the top-5 technology trends envisioned to bring significant added value at each timescale. Being intrinsically predictive, our proposed baseline roadmap cannot assert with certainty the values of the target KPIs and the shortlisting of the technology trends. It is, however, aimed at driving discussions and collecting feedback from the wireless research community for future tuning and refinement as the 5G evolution journey progresses. This research was funded by the European Union's Horizon 2020 research and innovation programme under grant number No 824994.

This paper presents a new approach to suppress interference between neighbouring radiating elements resulting from surface wave currents. The proposed technique will enable the realization of low-profile implementation of highly dense antenna configuration necessary in SAR and MIMO communication systems. Unlike other conventional techniques of mutual coupling suppression where a decoupling slab is located between the radiating antennas the proposed technique is simpler and only requires embedding linear slots near the periphery of the patch. Attributes of this technique are (i) significant improvement in the maximum isolation between the adjacent antennas by 26.7 dB in X-band and &gt, 15 dB in Ku and K-bands, (ii) reduction in edge-to-edge gap between antennas to 10 mm (0.37 &lambda, ), and (iii) improvement in gain by &gt, 40% over certain angular directions, which varies between 4.5 dBi and 8.2 dBi. The proposed technique is simple to implement at low cost.