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Alexandros-Apostolos A. Boulogeorgos

Alexandros-Apostolos A. Boulogeorgos

Dipl-Eng (MEng), PhD, Electrical & Computer Engineering, SMIEEE

About

126
Publications
41,832
Reads
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1,602
Citations
Additional affiliations
September 2017 - present
University of Piraeus
Position
  • Research Associate
February 2017 - present
University of Western Macedonia
Position
  • Lecturer
Description
  • Course: Cloud Computing, Microwave Communications, Mobile and Satelite Communications.
October 2016 - present
Aristotle University of Thessaloniki
Position
  • PostDoc Position
Education
October 2012 - October 2016
September 2006 - July 2012
Aristotle University of Thessaloniki
Field of study
  • Electrical and Computer Engineering

Publications

Publications (126)
Article
Full-text available
This paper is focused on providing the analytical framework for the quantification and evaluation of the joint effect of misalignment fading and hardware imperfections in the presence of multipath fading at terahertz (THz) wireless fiber extenders. In this context, we present the appropriate system model that incorporates the different operation, d...
Article
Full-text available
In this paper, we provide the theoretical framework for the performance comparison of reconfigurable intelligent surfaces (RISs) and amplify-and-forward (AF) relaying wireless systems. In particular, after statistically characterizing the end-to-end (e2e) wireless channel coefficient of the RIS- assisted wireless system, in terms of probability den...
Article
Full-text available
This article discusses the fundamental architectures for optical-wireless-systems for biomedical-applications. After summarizing the main applications and reporting their requirements, we describe the characteristics of the transdermal and in-body optical-channels (OCs) as well as the challenges that they impose in the design of communication syste...
Article
Full-text available
Machine learning (ML) empowers biomedical systems with the capability to optimize their performance through modeling of the available data extremely well, without using strong assumptions about the modeled system. Especially in nano-scale biosystems, where the generated data sets are too vast and complex to mentally parse without computational assi...
Preprint
Full-text available
Reconfigurable intelligent surfaces (RISs) empowered high-frequency (HF) wireless systems are expected to become the supporting pillar for several reliability and data rate hungry applications. Such systems are, however, sensitive to misalignment and atmospheric phenomena including turbulence. Most of the existing studies on the performance assessm...
Preprint
Full-text available
Terahertz (THz) band offers a vast amount of bandwidth and is envisioned to become a key enabler for a number of nextgeneration wireless applications. In this direction, appropriate channel models, encapsulating the large and small-scale fadingphenomena, need to be developed for both indoor and outdoor communications environments. The THz large-sca...
Article
Full-text available
The Internet of Vehicles (IoV) is an emerging paradigm, which is expected to be an integral component of beyond-fifth-generation and sixth-generation mobile networks. However, the processing requirements and strict delay constraints of IoV applications pose a challenge to vehicle processing units. To this end, multi-access edge computing (MEC) can...
Conference Paper
Full-text available
In this paper, we examine the potential for a reconfigurable intelligent surface (RIS) to be powered by energy harvested from information signals. This feature might be key to reap the benefits of RIS technology's lower power consumption compared to active relays. We first identify the main RIS power-consuming components and then propose an energy...
Article
Full-text available
In this paper, we analyze the performance of a reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicle (UAV) wireless system that is affected by mixture-gamma small-scale fading, stochastic disorientation and misalignment, as well as transceivers hardware imperfections. First, we statistically characterize the end-to-end channel f...
Article
Full-text available
This contribution focuses on extracting the theoretical framework for the assessment and evaluation of the joint effect of rain, beam misalignment and hardware imperfections at long-range outdoor terahertz (THz) wireless systems. In this direction, we first report an appropriate system model for outdoor THz wireless systems that take into account t...
Article
Long range wide area networks (LoRaWANs) have recently received intense scientific, research, and industrial interest. LoRaWANs play a pivotal role in Internet of Things (IoT) applications due to their capability to offer large coverage without sacrificing the energy efficiency and, thus the battery life, of end-devices. Most published contribution...
Chapter
Full-text available
In this chapter, we present two novel optical wireless-based cochlear implant architectures: (i) optical wireless cochlear implant (OWCI) and (ii) all-optical cochlear implant (AOCI). Both the architectures aim to decisively improve the reliability and energy efficiency of hearing restoration devices. To provide design and development guidelines, w...
Preprint
Full-text available
In this paper, we introduce a theoretical framework for analyzing the performance of multi-reconfigurable intelligence surface (RIS) empowered terahertz (THz) wireless systems subject to turbulence and stochastic beam misalignment. In more detail, we extract a closed-form expression for the outage probability that quantifies the joint impact of tur...
Article
Full-text available
Next generation in-to-out-of body biomedical applications have adopted optical wireless communications (OWCs). However, by delving into the published literature, a gap is recognised in modeling the in-to-out-of channel, since most published contributions neglect the particularities of different type of tissues. Towards this direction, in this paper...
Preprint
Full-text available
In this paper, we analyze the performance of a reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicle (UAV) wireless system that is affected by mixture-gamma small-scale fading, stochastic disorientation, and misalignment, as well as transceivers hardware imperfections. First, we statistically characterize the end-to-end channel...
Conference Paper
Full-text available
In this paper, we introduce a theoretical framework for analyzing the performance of multi-reconfigurable intelligence surface (RIS) empowered terahertz (THz) wireless systems subject to turbulence and stochastic beam misalignment. In more detail, we extract a closed-form expression for the outage probability that quantifies the joint impact of tur...
Article
Full-text available
Reconfigurable intelligent surfaces (RISs) empowered high-frequency (HF) wireless systems are expected to become the supporting pillar for several reliability and data-rate hungry applications. Such systems are, however, sensitive to misalignment and atmospheric phenomena including turbulence. Most of the existing studies on the performance assessm...
Article
Full-text available
The emergence of next-generation internet-of-things (NG-IoT) applications introduces several challenges for the sixth-generation (6G) mobile networks, such as massive connectivity, increased network capacity, and extremely low-latency. To countermeasure the aforementioned challenges, ultra-dense networking has been widely identified as a possible s...
Article
The sixth-generation era comes with the challenge of offering high-energy-efficiency and autonomy communications securely. In this direction, we report energy efficiency (EE), energy harvesting (EH), and secure performance employing power-collecting metasurface-coated devices capable of supporting ultra-low-power (ULP) transmissions. Contrary to re...
Preprint
Full-text available
Next generation in-to-out-of body biomedical applications have adopted optical wireless communications (OWCs). However, by delving into the published literature, a gap is recognised in modeling the in-to-out-of channel, since most published contributions neglect the particularities of different type of tissues. Towards this direction, in this paper...
Chapter
As the wireless world moves towards the beyond fifth-generation (B5G) era, innovative applications require higher reliability, data rates, and traffic demands. Technological advances, such as massive multiple-input multiple-output, full-duplexing, and high-frequency communications, have been advocated, due to their unfordable cost, power consumptio...
Article
Full-text available
As the wireless world moves towards the sixth generation (6G) era, the demand for supporting bandwidth-hungry applications in ultra-dense deployments becomes more and more imperative. Driven by this requirement, both the research and development communities have turned their attention to the terahertz (THz) band, where more than 20 GHz of contiguou...
Article
Full-text available
Sustaining a flexible and ubiquitously available high-data-rate network, capable of supporting a massive number of end-users, demands the exploitation of higher frequency bands, such as the terahertz (THz) band (0.1-10~THz). However, the utilization of THz wireless systems comes with a number of challenges, many of them associated with the very hig...
Conference Paper
Full-text available
In this work, the performance of a reconfigurable intelligent surface (RIS) assisted terahertz (THz) (0.1 − 10 THz) wireless system is evaluated in terms of average signal-to-noise ratio (SNR), ergodic capacity, and outage probability. It is assumed that the line-of-sight (LoS) link between the transmitter (TX) and the receiver (RX) is blocked by o...
Conference Paper
Full-text available
This contribution aims at experimentally validating the suitability of well known fading distributions in modeling the channel of indoor THz wireless systems. In particular the suitability of α-µ, Rice and Nakagami-m distributions is evaluated by fitting them to empirical channel measurements. The fitting performance is expressed in terms of the Ko...
Preprint
Full-text available
In this work, we examine the potential of autonomous operation of a reconfigurable intelligent surface (RIS) using wireless energy harvesting from information signals. To this end, we first identify the main RIS power-consuming components and introduce a suitable power-consumption model. Subsequently, we introduce a novel RIS power-splitting archit...
Article
Full-text available
With the vision to transform the current wireless network into a cyber-physical intelligent platform capable of supporting bandwidth-hungry and latency-constrained applications, both academia and industry turned their attention to the development of artificial intelligence (AI) enabled terahertz (THz) wireless networks. In this article, we list the...
Conference Paper
Full-text available
This work investigates the suitability of α-µ distribution to model line-of-sight (LoS) and non-line-of-sight (NLoS) multi-path fading in terahertz (THz) wireless systems. The goodness of fit of α-µ to the small-scale fading of the measured channels is evaluated in terms of the Kolmogorov-Smirnov (KS) test. The KS test revealed the capability of α-...
Conference Paper
Full-text available
Ultra-low latency connections for a massive number of devices are one of the main requirements of the next-generation tactile Internet-of-Things (TIoT). Grant-free non-orthogonal multiple access (GF-NOMA) is a novel paradigm that leverages the advantages of grant-free access and non-orthogonal transmissions, to deliver ultra-low latency connectivit...
Chapter
This chapter presents medium access control (MAC) approaches that are tailored to the terahertz (THz) communications systems. In more detail, after presenting the THz wireless communication systems particularities that are expected to influence the MAC, initial access (IA) scheme is presented that can be used to guarantee alignment between the base...
Technical Report
Full-text available
This white paper on AI and ML as enablers of beyond 5G (B5G) networks is based on contributions from 5G PPP projects that research, implement and validate 5G and B5G network systems. The white paper introduces the main relevant mechanisms in Artificial Intelligence (AI) and Machine Learning (ML), currently investigated and exploited for 5G and B5G...
Conference Paper
Dynamic dual-hop relaying network topologies that enable access to end-users through intermediate individual and commercial, static as well as moving, infrastructures are expected to become fundamental pillars of the sixth-generation wireless systems. Their main requirement is to ensure end-users information privacy. Motivated by this, the current...
Preprint
Full-text available
Optical wireless communications (OWCs) have been recognized as a candidate enabler of next generation in-body nano-scale networks and implants. The development of an accurate channel model capable of accommodating the particularities of different type of tissues is expected to boost the design of optimized communication protocols for such applicati...
Preprint
Full-text available
In this paper, we examine the potential for a reconfigurable intelligent surface (RIS) to be powered by energy harvested from information signals. This feature might be key to reap the benefits of RIS technology's lower power consumption compared to active relays. We first identify the main RIS power-consuming components and then propose an energy...
Article
Full-text available
The continuous positioning of a mobile user equipment (MU) in a prompt way is a fundamental requirement in several indoor applications related to ubiquitous computation, assisted living environments, and security/surveillance systems. Motivated by this fact, the current contribution reports a low-complexity visible light positioning (VLP) method su...
Article
Full-text available
This work discusses the optimal reconfigurable intelligent surface placement in highly-directional millimeter-wave links. In particular, we present a novel system model that takes into account the relationship between the transmission beam footprint at the RIS plane and the RIS size. Subsequently, based on the model we derive the end-to-end express...
Preprint
This paper presents an analytical pathloss model for reconfigurable intelligent surface (RIS) assisted terahertz (THz) wireless systems. Specifically, the model accommodates both the THz link and the RIS particularities. Finally, we derive a closed-form expression that returns the optimal phase shifting of each RIS reflection unit. The derived path...
Conference Paper
This paper presents an analytical pathloss model for reconfigurable intelligent surface (RIS) assisted terahertz (THz) wireless systems. Specifically, the model accommodates both the THz link and the RIS particularities. Finally, we derive a closed-form expression that returns the optimal phase shifting of each RIS reflection unit. The derived path...
Article
Full-text available
This paper presents a connectivity analysis of reconfigurable intelligent surface (RIS) assisted terahertz (THz) wireless systems. Specifically, a system model that accommodates the particularities of THz band links as well as the characteristics of the RIS is reported, accompanied by a novel general end-to-end (e2e) channel attenuation formula. Ba...
Book
Full-text available
This book includes high-quality papers presented at the International Conference on Communication, Computing and Electronics Systems 2020, held at the PPG Institute of Technology, Coimbatore, India, on 21–22 October 2020. The book covers topics such as automation, VLSI, embedded systems, integrated device technology, satellite communication, optica...
Conference Paper
Full-text available
In this work, we examine the use of reconfigurable intelligent surfaces (RISs) to create alternative paths from a transmitter to a receiver in millimeter-wave (mmWave) networks, when the direct link is blocked. In this direction, we evaluate the end-to-end signal-to-noise ratio (SNR) expression of the transmitter-RIS-receiver links that take into a...
Preprint
Full-text available
This work discusses the optimal placement of a reconfigurable intelligent surface (RIS) in a millimeter wave (mmWave) point-to-point link. In particular, we present a novel system model that takes into account the relationship between the transmission beam footprint size at the RIS plane and the RIS size. Moreover, we present the theoretical framew...
Article
Full-text available
Over the recent years, an increasing amount of research effort has been directed toward the development and optimization of optical cell stimulation (OCS) techniques, while electrical cell stimulation (ECS) has been perfected. This paper investigates the existing ECS and OCS methods from a communication perspective and, after summarizing the main b...
Preprint
In the recent years, the proliferation of wireless data traffic has led the scientific community to explore the use of higher unallocated frequency bands, such as the millimeter wave and terahertz (0.1-10 THz) bands. However, they are prone to blockages from obstacles laid in the transceiver path. To address this, in this work, the use of a reconfi...
Preprint
Full-text available
Machine learning (ML) empowers biomedical systems with the capability to optimize their performance through modeling of the available data extremely well, without using strong assumptions about the modeled system. Especially in nano-scale biosystems, where the generated data sets are too vast and complex to mentally parse without computational assi...
Preprint
This paper presents the analytic framework for evaluating the ergodic capacity (EC) of the reconfigurable intelligent surface (RIS) assisted systems. Moreover, high-signal-to-noise-ratio and high-number of reflection units (RUs) approximations for the EC are provided. Finally, the special case in which the RIS is equipped with a single RU is invest...
Article
Full-text available
In the present work, we investigate the impact of transceiver hardware imperfection on reconfigurable intelligent surface (RIS)-assisted wireless systems. In this direction, first, we present a general model that accommodates the impact of the transmitter (TX) and receiver (RX) radio frequency impairments. Next, we derive novel closed-form expressi...
Conference Paper
This paper presents the analytic framework for evaluating the ergodic capacity (EC) of the reconfigurable intelligent surface (RIS) assisted systems. Moreover, high-signal-to-noise-ratio and high-number of reflection units (RUs) approximations for the EC are provided. Finally, the special case in which the RIS is equipped with a single RU is invest...
Conference Paper
In the recent years, the proliferation of wireless data traffic has led the scientific community to explore the use of higher unallocated frequency bands, such as the millimeter-wave (mmWave) and terahertz (0.1 - 10) (THz) bands. However, they are prone to blockages from obstacles laid in the transceiver path. To address this, in this work the use...
Preprint
This paper focuses on quantifying the outage performance of terahertz (THz) relaying systems. In this direction, novel closed-form expressions for the outage probability of a dual-hop relaying system, in which both the source-relay and relay-destination links suffer from fading and stochastic beam misalignment, are extracted. Our results reveal the...
Conference Paper
This paper focuses on quantifying the outage performance of terahertz (THz) relaying systems. In this direction, novel closed-form expressions for the outage probability of a dual-hop relaying systems, in which both the source-relay and relay-destination links suffer from fading and stochastic beam misalignment, are extracted. Our results reveal th...
Preprint
Full-text available
In the present work, we introduce a novel cochlear implant (CI) architecture, namely all-optical CI (AOCI), which directly converts acoustic to optical signals capable of stimulating the cochlear neurons. First, we describe the building-blocks (BBs) of the AOCI, and explain their functionalities as well as their interconnections. Next, we present a...
Conference Paper
Full-text available
The paper studies the joint impact of phase noise (PN) and co-channel interference (CCI) in indoor terahertz (THz) uplink. We formulate the theoretical framework that quantifies the impact of PN on the transceiver antenna directivity by extracting exact closed-form and low-complexity tight approximations for the expected gains. Additionally, by emp...
Article
Full-text available
In the present work, we introduce a novel cochlear implant (CI) architecture, namely all-optical CI (AOCI), which directly converts acoustic to optical signals capable of stimulating the cochlear neurons. First, we describe the building-blocks (BBs) of the AOCI, and explain their functionalities as well as their interconnections. Next, we present a...
Preprint
In this paper, a novel hierarchical beamtracking approach, which is suitable for terahertz (THz) wireless systems, is presented. The main idea is to employ a prediction based algorithm with a multi-resolution codebook, in order to decrease the required overhead of tracking and increase its robustness. The efficiency of the algorithm is evaluated in...
Preprint
Full-text available
This article discusses the fundamental architectures for optical wireless systems for biomedical applications. After summarizing the main applications and reporting their requirements, {we describe the characteristics of the transdermal and in-body optical channels as well as the challenges that they impose in the design of communication systems.}...
Conference Paper
In this paper, a novel hierarchical beam-tracking approach, which is suitable for terahertz (THz) wireless systems, is presented. The main idea is to employ a prediction based algorithm with a multi-resolution codebook, in order to decrease the required overhead of tracking and increase its robustness. The efficiency of the algorithm is evaluated i...
Chapter
In order to countermeasure the high channel attenuation of the terahertz (THz) band, wireless systems operating in these frequencies employ high-gain antennas in both the transmitter (TX) and receiver (RX). The use of such antennas requires perfect antenna alignment, which, in practical implementations, is not possible. Moreover, due to the high pe...
Article
Full-text available
The development of time-lapse videos for the investigation of growing microbial colonies 1 has gained increasing interest, due to its low cost and complexity implementation. In the present 2 study, a simple experimental setup is proposed for periodic snapshot acquisition of a petri dish 3 cultivating a fungus of the genus Candida SPP; thus, creatin...
Article
Full-text available
This paper focuses on deriving expected values for the transmit (TX) and receive (RX) antenna gains in terahertz (THz) wireless fronthaul and backhaul links under stochastic beam misalignment, which is created by antenna movement coming from the building or antenna mast swaying. In particular, four different antenna movement models are considered:...
Article
Full-text available
This work aims to present the theoretical framework for the outage performance assessment of the joint impact of antenna misalignment and local oscillator (LO) phase noise (PHN) on terahertz (THz) wireless systems. In more detail, a closed form expression for the outage probability and a tight high signal to noise ratio (SNR) approximation were ext...
Preprint
The proliferation of wireless devices in recent years has caused a spectrum shortage, which led the scientific community to explore the potential of using terahertz (THz) communications. However, THz systems suffer from severe path attenuation, blockage, and antenna misalignment. In this paper, we present a relay-based blockage and antenna misalign...
Article
Full-text available
In the present paper, we investigate the impact of phase noise on multi-carrier wireless systems that employ non-orthogonal multiple access (NOMA). Specifically, we extract novel closed-form expressions for the outage probability. These expressions can quantify and evaluate the system performance for the general case in which different levels of in...