Cesar A. Azurdia-Meza

• Doctor of Philosophy in Electronics and Radio Engineering
• Professor (Associate) at University of Chile

This study introduces an event camera‐based optical camera communication system utilising pulse‐shaped waveform modulation leveraging the camera's high temporal resolution and sensitivity. The proposed scheme demonstrates reliable performance under controlled indoor conditions with a fixed transmitter–receiver distance, achieving bit error rate val...

This study investigates the impact of wall roughness on the performance of the Non-Line-of-Sight (NLOS) component in Visible Light Communication (VLC) systems designed for underground mining environments, adhering to safety and communication standards such as IEC 60079-28(intrinsic safety in explosive atmospheres) and IEEE 802.15.7 (VLC parameters)...

This paper presents an innovative approach to improving visible light communication (VLC) systems in total shadowing conditions by integrating intelligent reflecting surfaces (IRSs), angle diversity receivers (ADRs), and recurrent neural networks (RNNs). Two ADR configurations (pyramidal and hemispherical) are evaluated, along with signal combinati...

This paper proposes an experimental design and evaluation of visible light communication (VLC) based connectivity for smart and sustainable farming (SSF) by considering a controlled greenhouse environment. SSF integrates complete data-driven farming, allowing for precise control over humidity and temperature to produce high-quality yields. The regu...

On the one hand, visible light communication (VLC) based on light-emitting diode (LED) technology offers not only lighting but also communication for various applications such as short-range wireless access, the Industrial Internet of Things (IIoT), vehicular networks (VN)s, among others. On the other hand, experimentation is the final and determin...

Research on wireless communication in water environments is gaining attention due to its relevance in enabling and supporting new applications under the Underwater Internet of Things (UIoT) umbrella. Visible Light Communication (VLC) is one of the emerging communication technologies with the potential to contribute to this domain, especially concer...

The Internet of Things (IoT) has revolutionized the way we interact with our surroundings, offering many applications across various domains. This paper presents a novel IoT development kit that uses Narrowband technology to establish reliable and efficient connec-tivity to the Internet. The kit addresses key challenges in the current IoT implement...

This paper studies the performance of an automatic head-on vehicle collision warning system based on a decentralized sensing approach using radio frequency (RF) signals. To identify a vehicle moving toward another, a communication system is used in reception mode, and a continuous wave (CW) RF signal transmitted by a third vehicle driving behind as...

Cooperative vehicular systems require that vehicles fuse sensor data and broadcast one-hop safety messages containing their kinematic information to enable vehicular applications based on incident detection. Several congestion control mechanisms have been proposed to mitigate channel congestion resulting from the continuous transmission of safety m...

Over the past few years, there has been a growing interest in indoor positioning systems that use Visible Light Communication (VLC) technology in conjunction with light-emitting diodes (LEDs). These systems have become popular because of their ability to provide high bandwidth, and it is anticipated that wireless communication may expand into the v...

This article investigate the deployment of effective communication networks for smart IoT-based smart patient monitoring in medical facilities, advocating for the adoption of Visible Light Communication (VLC) technology. Initially, the physical scenario is analyzed, taking into account factors such as line-of-sight (LOS) and nonline-of-sight (NLOS)...

This paper presents a performance analysis of the Narrowband Internet of Things (NB-IoT) network coverage in urban outdoor environments, focusing on experimental measurements toward path loss modeling. Conducted in a major Latin American city, the study explores the deployment of NB-IoT in LTE guardband 28 (700 MHz), offering valuable information o...

This study aims to enhance the efficiency of Visible Light Communication (VLC) channels and contribute to the reduction of carbon emissions in underground communications by leveraging Polar Codes and Multiresolution Analysis (MRA). It uses a specific configuration of frozen bits for the implementation of Polar codes. Additionally, it integrates the...

Epilepsy affects millions worldwide, making timely seizure detection crucial for effective treatment and enhanced well-being. Electroencephalogram (EEG) analysis offers a non-intrusive solution, but its visual interpretation is prone to errors and requires a lot of time. Many existing works focus solely on achieving competitive levels of accuracy w...

This paper presents the idea of an automatic head-on-collision warning system based on a decentralized radio sensing (RS) approach. In this framework, a vehicle in receiving mode employs a continuous waveform (CW) transmitted by a second vehicle as a probe signal to detect oncoming vehicles and warn the driver of a potential head-on collision. Such...

This research delves into the application of Digital Twins (DTs) in the realm of smart agriculture, with a particular focus on greenhouse and underground environments. By integrating computer simulations with empirical testing, we validate our hypotheses. A novel approach has been introduced that uses Visible Light Communication (VLC) for data exch...

New communication systems require high spectral and energy efficiencies to meet the growing demand for services in future networks. In this paper, an efficient multiple parallel reconfigurable intelligent surfaces (RIS)-assisted multiuser (MU) multiple input-multiple output (MIMO) double quadrature spatial modulation (DQSM) downlink transmission sy...

Localization in hospitals can be valuable in improving different services in medical environments. In this sense, an accurate location system in this environment requires adequately enabling communication technology. However, widely adopted technologies such as Wireless Fidelity (WiFi), Bluetooth, and Radio Frequency Identification (RFID) are consi...

In recent years, some novel methods have been developed for the detection of diseases based on biomedical signals. In this article, a method for the automated detection of epilepsy seizures is presented by analyzing electroencephalogram (EEG) signals based on the wavelet transform. In the first step, the EEG signals are pre-processed with the Savit...

In this paper, a smart subband system for speaker counting is proposed by scattered microphone array (SMA) and using direction of arrival (DOA) estimation with adaptive eigenvalue decomposition (AED). Firstly, the recorded signals by central array are divided into subbands by using gammatone filter bank. Then, the adaptive generalized cross-correla...

This paper presents the coverage measurements and path loss results of a 5G indoor and outdoor signal within the 5G Laboratory located in the Department of Electrical Engineering of the University of Chile. An Ericsson AIR 5121 antenna and commercial base station that is in a fixed position inside the laboratory and a 5G router equipment (5G NR mmW...

The Riemann sum method (RSM) was introduced almost two decades ago as an efficient parameter computation method for the design of narrowband multiple-input multiple-output (MIMO) mobile fading channel simulators based on the sum-of-cisoids (SOC) principle. This method has been shown to be more accurate and less computationally expensive than other...

This paper presents an in-depth study into the necessity of efficient communication systems in underwater environments, with a primary focus on Underwater Visible Light Communication (UVLC). A novel path loss model that adapts to different water types is proposed to improve existing UVLC channel models. Validation against various scenarios, includi...

The importance of studying visible light communications (VLC) systems is present today and growing each day due to the possibilities of higher data rates, security, and various applications. In this manuscript, we study the behavior of the channel frequency response (CFR) considering different configurations of parameters and distances in an experi...

Chilean wine is one of the most consumed in the global market due to its excellent quality and wide variety of grape crops throughout the country, with Chile being the largest exporter of wine in the southern hemisphere. The characterization of wine quality is of vital importance for this industry, as the valuation of this product in the market dep...

Underground mining visible light communication (UM-VLC) is a promising solution to ensure the well-being of workers and facilitate their work. However, underground conditions present a significant divergence from widely studied indoor environments due to irregular walls, light scattering, and user mobility. The rough environmental conditions of und...

Indoor visible light communication (VLC) systems have been extensively studied; however, they present some problems when the main propagation channel component, called Line-of-Sight (LoS), is partially or totally blocked. The effect of this blockage can cause degradation of the received optical signal and decrease the performance of the VLC system....

This paper presents two precoding techniques for a reconfigurable intelligent surface (RIS)-assisted multi-user (MU) multiple-input multiple-output (MIMO) double quadrature spatial modulation (DQSM) downlink transmission system. Instead of being applied at the remote RIS, the phase shift vector is applied at the base station (BS) by using a double...

The expectation for communication systems beyond 5G/6G is to provide high reliability, high throughput, low latency, and high energy efficiency services. The integration between systems based on radio frequency (RF) and visible light communication (VLC) promises the design of hybrid systems capable of addressing and largely satisfying these require...

Memory analysis is critical to detecting malicious processes, as it can capture various characteristics and behaviors. However, although it is a field in full research, there are still some major obstacles in malware detection, such as optimizing the detection rate and countering advanced malware obfuscation. Since advanced malware uses obfuscation...

Optical Fiber Radio (RoF) systems based on OFDM meet the needs of high transmission and reception speeds, as well as offering greater reliability in the system. These systems are exposed to various disturbances, such as the thermal and shot noise of the photodetector, the amplified emission of optical links, and the relative phase intensity in the...

This paper presents a systematic approach for solving complex prediction problems with a focus on energy efficiency. The approach involves using neural networks, specifically recurrent and sequential networks, as the main tool for prediction. In order to test the methodology, a case study was conducted in the telecommunications industry to address...

Speech processing algorithms, especially sound source localization (SSL), speech enhancement, and speaker tracking are considered to be the main fields in this application. Most speech processing algorithms require knowing the number of speakers for real implementation. In this article, a novel method for estimating the number of speakers is propos...

The fingerprint is one of the most popular and used biometric traits for the identification of people, due to its bio-invariant characteristic, precision, and easy acquisition. One of the stages in the identification of fingerprints is classification, this has the objective of reducing the search times and the computational cost in the databases. C...

This paper presents the coverage measurements and path loss results of a 5G indoor signal within the 5G Experimental Center for New Generation Services (5G Laboratory) located in the Department of Electrical Engineering of the University of Chile. An Ericsson AIR 5121 antenna and commercial base station that is in a fixed position inside the labora...

This article proposes a novel method for detecting coronavirus disease 2019 (COVID-19) in an underground channel using visible light communication (VLC) and machine learning (ML). We present mathematical models of COVID-19 Deoxyribose Nucleic Acid (DNA) gene transfer in regular square constellations using a CSK/QAM-based VLC system. ML algorithms a...

This article proposes a novel method for detecting coronavirus disease 2019 (COVID-19) in an underground channel using visible light communication (VLC) and machine learning (ML). We present mathematical models of COVID-19 Deoxyribose Nucleic Acid (DNA) gene transfer in regular square constellations using a CSK/QAM-based VLC system. ML algorithms a...

Reliable wireless communications are crucial for ensuring workers' safety in underground tunnels and mines. Visible light communications (VLC) have been proposed as auxiliary systems for short-range wireless communications in underground environments due to their seamless availability, immunity to electromagnetic interference, and illumination capa...

In the context of underground mining, visible light communication systems have been proposed as auxiliary systems to traditional wireless communications, as they have the potential to provide greater reliability and flexibility to the latter. The visible light communication channel in an underground mine is much more complex than that of common in-...

Visible light communication (VLC) is considered an enabling technology for future 6G 1 wireless systems. Among the many applications in which VLC systems are used, one of them are harsh environments such as Underground Mining (UM) tunnels. However, these environments are subject to degrading environmental and intrinsic challenges for optical links....

Underground Mining (UM) is a harsh environment that involves multiple threats to worker safety and needs adequate wireless communications to ensure worker well-being and optimize miner efficiency. While radio frequency signals can be used to manage such tasks, several limitations exist to its potential, as multiple phenomena affect their quality. T...

Visible Light Communication (VLC) based systems are proving to be a promising candidate for the development of 6G communication networks. However, new developments in devices and materials need to be done to deal with the limitations and drawbacks of VLC. In the meantime, the work and the experiments done in this paper show that it's possible to im...

The IEEE 802.22 is a standard for wireless regional area networks to opportunistically operate in TV bands; however, sharing TV White Space (TVWS) spectrum creates a problem of coexistence because no mechanism is defined for coordinating channel usage among secondary networks. We propose a White Space Resource Sharing mechanism (WSRS) for fixed sec...

Visible Light Communications (VLC) have generated great interest in the scientific community in the last five years due to their great adaptation to harsh environments. Among the scenarios that can benefit from the advantages ofvVLC systems are Underground Mining (UM) tunnels. However,vthe physical phenomena and the irregularity of this environment...

In the past decade, visible light communication (VLC) technology has received increasing attention for numerous applications, including for indoor visible light positioning (VLP). The transmission medium for indoor VLP systems in industrial environments could include smoke particles, oil vapors, water mist, and industrial fumes. This work investiga...

The purpose of this paper is to present a multisensor system with quantum key exchange at the source level and non-binary data transmission at the channel level using the quantum AES algorithm. We differentiate between the classical paradigm based on numerical complexity and the quantum paradigm based on the uncertainty principle. Studies of Bit Er...

Wireless communication systems working in millimeter-wave (mmWave) frequency bandsoffer higher bandwidths than traditional radio frequency schemes. This technology allows multibeamsteering and data multiplexing with the help of massive multiple-input multiple-output (MIMO) systems.However, supporting large bandwidths at mmWave frequencies is challe...

This paper presents a reconfigurable intelligent surface (RIS) assisted multi-user (MU) multiple-input multiple-output (MIMO) system. Instead of being applied at the remote RIS, the phase shift vector is applied at the base station (BS) by using an additional precoding stage. The overall system performance is improved by incorporating a double quad...

This paper presents a reconfigurable intelligent surface (RIS) assisted multi-user (MU) multiple-input multiple-output (MIMO) system. Instead of being applied at the remote RIS, the phase shift vector is applied at the base station (BS) by using an additional precoding stage. The overall system performance is improved by incorporating a double quad...

This paper presents a reconfigurable intelligent surface (RIS) assisted multiuser (MU) multiple-input multiple-output (MIMO) system. Instead of being applied at the remote RIS, the phase shift vector is applied at the base station (BS) by using an additional precoding stage. The overall system performance is improved by incorporating a double quadr...

Underground Mining (UM) is a hostile industry that generally requires a wireless communication system as a cross-cutting axis for its optimal operation. Therefore, in the last five years, it has been shown that, in addition to radio-frequency-based communication links, wireless optical communications, such as Visible Light Communication (VLC), can...

Underground mining (UM) is an industry worldwide known for its hostile work environment; therefore, a proper communication system is essential to preserve the miners’ safety. However, the irregular features of UM tunnels as well as their environment prone to electromagnetic interference make it difficult to implement traditional wireless communicat...

In this paper, we analyze and compare the use and benefits of several combining schemes to create diversity at the optical receiver in a multi-cell indoor Visible Light Communication (VLC) system. Furthermore, its implementation in a pyramidal Angle Diversity Receiver (ADR) to mitigate Inter-Cell Interference (ICI) in the system is analyzed. Thus,...

Orthogonal frequency-division multiplexing (OFDM) is widely being used in different wide band technologies. Due to the nature of OFDM, the transmitted OFDM symbol is the superposition of several orthogonal subcarriers. This generates a high peak-to-average power ratio (PAPR), which degrades the overall system performance. In this manuscript, a new...

Multiple simultaneous sound source localization (SSL) is one of the most important applications in the speech signal processing. The one-step algorithms with the advantage of low computational complexity (and low accuracy), and the two-step methods with high accuracy (and high computational complexity) are proposed for multiple SSL. In this article...

Analytical expressions of the statistical distribution of the underground mining visible light communication (UM-VLC) square-channel gain are derived considering scattering, shadowing, and a random position and orientation of the receiver. These expressions are employed to compute the system’s bit error probability (BEP) considering shot and therma...

Visible light communication (VLC) systems have numerous applications in harsh environments, such as underground mining. However, the irregular tunnel features, the random orientation of the optical components, physical phenomena such as shadowing and scattering, as well as the inherent generation of non-linearities of the optical signal greatly aff...

Radio-over-fiber orthogonal frequency division multiplexing (RoF-OFDM) technology is negatively affected by laser phase noise and chromatic dispersion optical fiber. These impairments normally generate inter-carrier interference (ICI). An extreme learning machine (ELM)-based receiver for RoF-OFDM schemes is proposed to diminish the ICI effect. The...

For years, it has been a great challenge for Internet Service Providers (ISP) to predict traffic load or future demand, since each bit of traffic is an economic cost to operators. Additionally, more and more users are adopting the different telecommunication services as well as the ISP must provide more bandwidth and reliability. In this sense, the...

El Departamento de Ingeniería Eléctrica de la Universidad de Chile presentó en noviembre de 2021 un estudio que valida que el uso de las tecnologías TV White Spaces no genera interferencias con la recepción de señales de la televisión digital. Este informe permite promover de forma responsable el uso de espectro UHF para transmitir Internet en el...

In this paper, three orthogonal frequency division multiplexing (OFDM) schemes are simulated and applied in the underground mining visible light communication (UM-VLC) system. The schemes are asymmetrically clipped optical OFDM (ACO-OFDM), direct current (DC) biased optical OFDM (DCO-OFDM), and asymmetrically clipped DC biased optical OFDM (ADO-OFD...

Mobile/wireless networks aim to support diverse services with numerous and sophisticated requirements, such as energy efficiency, spectral efficiency, negligible latency, robustness against time and frequency selective channels, low hardware complexity, among others. From the central station to the base stations, radio-over-fiber orthogonal frequen...

The dynamism envisioned in future high-capacity gridless optical networks requires facing several challenges in distortion mitigation, such as the mitigation of interchannel interference (ICI) effects in any optical channel without information of their adjacent channels. Machine learning (ML)-based techniques have been proposed in recent works to e...

There has been increasing interest in the Internet of Space Things (IoST) paradigm, an extension of the traditional Internet of Things (IoT) system based on using satellites to serve terrestrial devices. In particular, the use of nanosatellites to establish direct-to-satellite links provides an attractive, low-cost architecture to achieve actual gl...

Underground mining is expected to lead the mining industry in the near future. Due to the advance of electronic devices and communications technologies, new safety regulations must be accomplished in order to operate underground mines safely and optimally. In 2006, the US government updated safety policies and introduced the PUBLIC LAW109-236. As a...

In this paper, a novel method is presented for estimating the number of speakers based on the microphone arrays. Firstly, a 3D snowflake nested microphone array (SNMA) is proposed for recording the speech signals. In the following, the steered response power (SRP) algorithm is implemented on subbands in limited spaces conditions for all microphone...

Multiple sound source localization (SSL) is one of the applicable and important areas in the speech signal processing. In this paper, a two-step method is proposed for multiple 3D SSL based on the time delay estimation (TDE) in combination with distributed microphone arrays (DMA). In the first step, the direction of speakers are estimated by the us...

In this paper, we present an extreme learning machine (ELM) neural network designed to perform multiple-input multiple-output (MIMO) detection for millimeter-wave (mm-wave) communications operating in the 28 GHz frequency band. The ELM strategy can perform online MIMO combining processing. This method does not require offline training like with dee...

Jamming attacks in wireless sensor networks (WSNs) scenarios are detrimental to the performance of these networks and affect the security and stability of the service perceived by users. Therefore, the evaluation of the effectiveness of smart environment platforms based on WSNs has to consider the system performance when data collection is executed...

In this work, the performance of four Machine Learning Algorithms (MLAs) applied to Cognitive Mobile Radio Networks (CMRNs) are analyzed. These algorithms are Coalition Game Theory (CGT), Naive Bayesian Classifier (NBC), Support Vector Machine (SVM), and Decision Trees (DT). The numerical results of the performance analysis of these algorithms are...

The opportunistic exchange of information between vehicles can significantly contribute to reducing the occurrence of accidents and mitigating their damages. However, in urban environments, especially at intersection scenarios, obstacles such as buildings and walls block the line of sight between the transmitter and receiver, reducing the vehicular...

Wireless vehicular communications are a promising technology. Most applications related to vehicular communications aim to improve road safety and have special requirements concerning latency and reliability. The traditional channel estimation techniques used in the IEEE 802.11 standard do not properly perform over vehicular channels. This is becau...

In autonomous driving, IEEE 802.11p-based vehicle-to-vehicle (V2V) communication is considered for overcoming the intrinsic limitations of sensors and supporting safety applications. In this letter, we evaluate the effectiveness of relevant awareness control approaches, such as ETSI DMG, IVTRC, and POSACC, to support the V2V-based overtaking applic...

An extreme learning machine (ELM)-based receiver for multi-user massive MIMO systems is introduced. The proposed ELM combining method, defined in the complex plane, is designed to directly perform MIMO combining processing to the received uplink signals, based on the adoption of the pilot symbols as training data. Numerical results show that by app...