Search Results for author: George C. Alexandropoulos

Found 54 papers, 3 papers with code

Single- and Multi-Agent Private Active Sensing: A Deep Neuroevolution Approach

no code implementations15 Mar 2024 George Stamatelis, Angelos-Nikolaos Kanatas, Ioannis Asprogerakas, George C. Alexandropoulos

In this paper, we focus on one centralized and one decentralized problem of active hypothesis testing in the presence of an eavesdropper.

Anomaly Detection

Near-Field Channel Modeling for Holographic MIMO Communications

no code implementations14 Mar 2024 Tierui Gong, Li Wei, Chongwen Huang, George C. Alexandropoulos, Mérouane Debbah, Chau Yuen

Empowered by the latest progress on innovative metamaterials/metasurfaces and advanced antenna technologies, holographic multiple-input multiple-output (H-MIMO) emerges as a promising technology to fulfill the extreme goals of the sixth-generation (6G) wireless networks.

Towards Distributed and Intelligent Integrated Sensing and Communications for 6G Networks

no code implementations18 Feb 2024 Emilio Calvanese Strinati, George C. Alexandropoulos, Navid Amani, Maurizio Crozzoli, Giyyarpuram Madhusudan, Sami Mekki, Francois Rivet, Vincenzo Sciancalepore, Philippe Sehier, Maximilian Stark, Henk Wymeersch

This paper introduces the distributed and intelligent integrated sensing and communications (DISAC) concept, a transformative approach for 6G wireless networks that extends the emerging concept of integrated sensing and communications (ISAC).

DRL-Based Orchestration of Multi-User MISO Systems with Stacked Intelligent Metasurfaces

no code implementations14 Feb 2024 Hao liu, Jiancheng An, Derrick Wing Kwan Ng, George C. Alexandropoulos, Lu Gan

Stacked intelligent metasurfaces (SIM) represents an advanced signal processing paradigm that enables over-the-air processing of electromagnetic waves at the speed of light.

$1$-Bit SubTHz RIS with Planar Tightly Coupled Dipoles: Beam Shaping and Prototypes

no code implementations13 Feb 2024 Xianjun Ma, Yonggang Zhou, Qi Luo, Yihan Ma, Kyriakos Stylianopoulos, George C. Alexandropoulos

In this paper, a proof-of-concept study of a $1$-bit wideband reconfigurable intelligent surface (RIS) comprising planar tightly coupled dipoles (PTCD) is presented.

RIS-Augmented Millimeter-Wave MIMO Systems for Passive Drone Detection

no code implementations11 Feb 2024 Jiguang He, Aymen Fakhreddine, George C. Alexandropoulos

In the past decade, the number of amateur drones is increasing, and this trend is expected to continue in the future.

Multi-Agent Reinforcement Learning for Offloading Cellular Communications with Cooperating UAVs

no code implementations5 Feb 2024 Abhishek Mondal, Deepak Mishra, Ganesh Prasad, George C. Alexandropoulos, Azzam Alnahari, Riku Jantti

Effective solutions for intelligent data collection in terrestrial cellular networks are crucial, especially in the context of Internet of Things applications.

Decision Making Multi-agent Reinforcement Learning +2

Far- versus Near-Field RIS Modeling and Beam Design

no code implementations16 Jan 2024 Mohamadreza Delbari, George C. Alexandropoulos, Robert Schober, Vahid Jamali

In this chapter, we investigate the mathematical foundation of the modeling and design of reconfigurable intelligent surfaces (RIS) in both the far- and near-field regimes.

Metasurface-Based Receivers with $1$-bit ADCs for Multi-User Uplink Communications

no code implementations15 Jan 2024 Panagiotis Gavriilidis, Italo Atzeni, George C. Alexandropoulos

The massive Multiple-Input Multiple-Output (mMIMO) concept has been recently moving forward to extreme scales to address the envisioned requirements of next generation networks.

Jointly Optimal RIS Placement and Power Allocation for Underlay D2D Communications: An Outage Probability Minimization Approach

no code implementations21 Dec 2023 Sarbani Ghose, Deepak Mishra, Santi P. Maity, George C. Alexandropoulos

In the transformed problem, an expression for the average value of the signal-to-interference-noise ratio (SINR) at the D2D receiver is derived in closed-form.

Multi-Target Two-way Integrated Sensing and Communications with Full Duplex MIMO Radios

no code implementations16 Dec 2023 Muhammad Talha, Besma Smida, Md Atiqul Islam, George C. Alexandropoulos

In this paper, we propose a multiple input multiple output (MIMO) Full-Duplex Integrated Sensing and Communication System consisting of multiple targets, a single downlink, and a single uplink user.

RIS Position and Orientation Estimation via Multi-Carrier Transmissions and Multiple Receivers

no code implementations15 Nov 2023 Reza Ghazalian, Hui Chen, George C. Alexandropoulos, Gonzalo Seco-Granados, Henk Wymeersch, Riku Jäntti

In this paper, we consider a static user equipped with an RIS and study the RIS localization problem (i. e., joint three-dimensional position and orientation estimation), when operating in a system comprising a single-antenna transmitter and multiple synchronized single-antenna receivers with known locations.

Position

Autoregressive Attention Neural Networks for Non-Line-of-Sight User Tracking with Dynamic Metasurface Antennas

no code implementations30 Oct 2023 Kyriakos Stylianopoulos, Murat Bayraktar, Nuria González Prelcic, George C. Alexandropoulos

User localization and tracking in the upcoming generation of wireless networks have the potential to be revolutionized by technologies such as the Dynamic Metasurface Antennas (DMAs).

Position

Lyapunov-Driven Deep Reinforcement Learning for Edge Inference Empowered by Reconfigurable Intelligent Surfaces

no code implementations18 May 2023 Kyriakos Stylianopoulos, Mattia Merluzzi, Paolo Di Lorenzo, George C. Alexandropoulos

In this paper, we propose a novel algorithm for energy-efficient, low-latency, accurate inference at the wireless edge, in the context of 6G networks endowed with reconfigurable intelligent surfaces (RISs).

Data Compression Edge Classification +1

Performance of RIS-Aided Nearfield Localization under Beams Approximation from Real Hardware Characterization

no code implementations27 Mar 2023 Moustafa Rahal, Benoit Denis, Kamran Keykhosravi, Musa Furkan Keskin, Bernard Uguen, George C. Alexandropoulos, Henk Wymeersch

The technology of reconfigurable intelligent surfaces (RIS) has been showing promising potential in a variety of applications relying on Beyond-5G networks.

Specificity

Robust mmWave Beamforming by Self-Supervised Hybrid Deep Learning

no code implementations9 Mar 2023 Fenghao Zhu, Bohao Wang, Zhaohui Yang, Chongwen Huang, Zhaoyang Zhang, George C. Alexandropoulos, Chau Yuen, Merouane Debbah

Beamforming with large-scale antenna arrays has been widely used in recent years, which is acknowledged as an important part in 5G and incoming 6G.

STAR-RIS-Enabled Simultaneous Indoor and Outdoor 3D Localization: Theoretical Analysis and Algorithmic Design

no code implementations7 Feb 2023 Jiguang He, Aymen Fakhreddine, George C. Alexandropoulos

Recent research and development interests deal with metasurfaces for wireless systems beyond their consideration as intelligent tunable reflectors.

Compressive Sensing

RISs and Sidelink Communications in Smart Cities: The Key to Seamless Localization and Sensing

no code implementations9 Jan 2023 Hui Chen, Hyowon Kim, Mustafa Ammous, Gonzalo Seco-Granados, George C. Alexandropoulos, Shahrokh Valaee, Henk Wymeersch

A smart city involves, among other elements, intelligent transportation, crowd monitoring, and digital twins, each of which requires information exchange via wireless communication links and localization of connected devices and passive objects (including people).

RIS-Aided Monostatic Sensing and Object Detection with Single and Double Bounce Multipath

no code implementations14 Dec 2022 Hyowon Kim, Alessio Fascista, Hui Chen, Yu Ge, George C. Alexandropoulos, Gonzalo Seco-Granados, Henk Wymeersch

We propose a framework for monostatic sensing by a user equipment (UE), aided by a reconfigurable intelligent surface (RIS) in environments with single- and double-bounce signal propagation.

object-detection Object Detection

RIS-Enabled and Access-Point-Free Simultaneous Radio Localization and Mapping

no code implementations14 Dec 2022 Hyowon Kim, Hui Chen, Musa Furkan Keskin, Yu Ge, Kamran Keykhosravi, George C. Alexandropoulos, Sunwoo Kim, Henk Wymeersch

In the upcoming sixth generation (6G) of wireless communication systems, reconfigurable intelligent surfaces~(RISs) are regarded as one of the promising technological enablers, which can provide programmable signal propagation.

3D Localization with a Single Partially-Connected Receiving RIS: Positioning Error Analysis and Algorithmic Design

no code implementations5 Dec 2022 Jiguang He, Aymen Fakhreddine, Charles Vanwynsberghe, Henk Wymeersch, George C. Alexandropoulos

We particularly focus on the scenarios where the user is located in the far-field of all the R-RIS subarrays, and present a three-Dimensional (3D) localization method which is based on narrowband signaling and Angle of Arrival (AoA) estimates of the impinging signals at each single-receive-RF R-RIS subarray.

Holographic MIMO Communications: Theoretical Foundations, Enabling Technologies, and Future Directions

no code implementations2 Dec 2022 Tierui Gong, Panagiotis Gavriilidis, Ran Ji, Chongwen Huang, George C. Alexandropoulos, Li Wei, Zhaoyang Zhang, Mérouane Debbah, H. Vincent Poor, Chau Yuen

In this survey, we present a comprehensive overview of the latest advances in the HMIMO communications paradigm, with a special focus on their physical aspects, their theoretical foundations, as well as the enabling technologies for HMIMO systems.

Integrated Sensing and Communications with Reconfigurable Intelligent Surfaces

no code implementations2 Nov 2022 Sundeep Prabhakar Chepuri, Nir Shlezinger, Fan Liu, George C. Alexandropoulos, Stefano Buzzi, Yonina C. Eldar

Integrated sensing and communications (ISAC) are envisioned to be an integral part of future wireless networks, especially when operating at the millimeter-wave (mmWave) and terahertz (THz) frequency bands.

Compressed-Sensing-Based 3D Localization with Distributed Passive Reconfigurable Intelligent Surfaces

no code implementations27 Oct 2022 Jiguang He, Aymen Fakhreddine, Henk Wymeersch, George C. Alexandropoulos

In this paper, the programmable signal propagation paradigm, enabled by Reconfigurable Intelligent Surfaces (RISs), is exploited for high accuracy $3$-Dimensional (3D) user localization with a single multi-antenna base station.

Compressive Sensing

Joint Channel and Direction Estimation for Ground-to-UAV Communications Enabled by A Simultaneous Reflecting and Sensing RIS

no code implementations27 Oct 2022 Jiguang He, Aymen Fakhreddine, George C. Alexandropoulos

Hybrid Reconfigurable Intelligent Surfaces (HRISs), which are capable of simultaneous programmable reflections and sensing, are expected to play a significant role in future wireless networks, enabling various Integrated Sensing and Communication (ISAC) applications.

Joint User Localization and Location Calibration of A Hybrid Reconfigurable Intelligent Surface

no code implementations18 Oct 2022 Reza Ghazalian, Hui Chen, George C. Alexandropoulos, Gonzalo Seco-Granados, Henk Wymeersch, Riku Jäntti

The recent research in the emerging technology of reconfigurable intelligent surfaces (RISs) has identified its high potential for localization and sensing.

Position

Reconfigurable Intelligent Computational Surfaces: When Wave Propagation Control Meets Computing

no code implementations9 Aug 2022 Bo Yang, Xuelin Cao, Jindan Xu, Chongwen Huang, George C. Alexandropoulos, Linglong Dai, M'erouane Debbah, H. Vincent Poor, Chau Yuen

The envisioned sixth-generation (6G) of wireless networks will involve an intelligent integration of communications and computing, thereby meeting the urgent demands of diverse applications.

Simultaneous Indoor and Outdoor 3D Localization with STAR-RIS-Assisted Millimeter Wave Systems

no code implementations12 Jul 2022 Jiguang He, Aymen Fakhreddine, George C. Alexandropoulos

Simultaneously transmitting (refracting) and reflecting reconfigurable intelligent surfaces (STAR-RISs) have been recently identified to improve the spectrum/energy efficiency and extend the communication range.

Outdoor Localization

Pervasive Machine Learning for Smart Radio Environments Enabled by Reconfigurable Intelligent Surfaces

1 code implementation8 May 2022 George C. Alexandropoulos, Kyriakos Stylianopoulos, Chongwen Huang, Chau Yuen, Mehdi Bennis, Mérouane Debbah

The emerging technology of Reconfigurable Intelligent Surfaces (RISs) is provisioned as an enabler of smart wireless environments, offering a highly scalable, low-cost, hardware-efficient, and almost energy-neutral solution for dynamic control of the propagation of electromagnetic signals over the wireless medium, ultimately providing increased environmental intelligence for diverse operation objectives.

BIG-bench Machine Learning Multi-Armed Bandits

Differential Data-Aided Beam Training for RIS-Empowered Multi-Antenna Communications

no code implementations27 Apr 2022 Kun Chen-Hu, George C. Alexandropoulos, Ana García Armada

In this paper, a zero overhead beam training for RIS is proposed, relying on data transmission and reception based on non-CDS (NCDS).

Arbitrary Beam Pattern Approximation via RISs with Measured Element Responses

no code implementations14 Mar 2022 Moustafa Rahal, Benoît Denis, Kamran Keykhosravi, Furkan Keskin, Bernard Uguen, George C. Alexandropoulos, Henk Wymeersch

Smart radio environments (SREs) are seen as a key rising concept of next generation wireless networks, where propagation channels between transmitters and receivers are purposely controlled.

RIS-Enabled Self-Localization: Leveraging Controllable Reflections With Zero Access Points

no code implementations22 Feb 2022 Kamran Keykhosravi, Gonzalo Seco-Granados, George C. Alexandropoulos, Henk Wymeersch

In this paper, we introduce a novel use-case of the RIS technology in radio localization, which is enabling the user to estimate its own position via transmitting orthogonal frequency-division multiplexing (OFDM) pilots and processing the signal reflected from the RIS.

Position

Jointly Learned Symbol Detection and Signal Reflection in RIS-Aided Multi-user MIMO Systems

no code implementations14 Feb 2022 Liuhang Wang, Nir Shlezinger, George C. Alexandropoulos, Haiyang Zhang, Baoyun Wang, Yonina C. Elda

Reconfigurable Intelligent Surfaces (RISs) are regarded as a key technology for future wireless communications, enabling programmable radio propagation environments.

Channel Estimation with Simultaneous Reflecting and Sensing Reconfigurable Intelligent Metasurfaces

no code implementations11 Feb 2022 Haiyang Zhang, Nir Shlezinger, Idban Alamzadeh, George C. Alexandropoulos, Mohammadreza F. Imani, Yonina C. Eldar

As an indicative application of HRISs, we formulate and solve the individual channels identification problem for the uplink of multi-user HRIS-empowered systems.

Non-Coherent MIMO-OFDM Uplink empowered by the Spatial Diversity in Reflecting Surfaces

no code implementations4 Feb 2022 Kun Chen-Hu, George C. Alexandropoulos, Ana García Armada

As a benchmark, analytical expressions for the Signal-to-Interference and Noise Ratio (SINR) of the proposed system are presented.

DDU-Net: Dual-Decoder-U-Net for Road Extraction Using High-Resolution Remote Sensing Images

no code implementations18 Jan 2022 Ying Wang, Yuexing Peng, Xinran Liu, Wei Li, George C. Alexandropoulos, Junchuan Yu, Daqing Ge, Wei Xiang

Extracting roads from high-resolution remote sensing images (HRSIs) is vital in a wide variety of applications, such as autonomous driving, path planning, and road navigation.

Autonomous Driving

A New RIS Architecture with a Single Power Amplifier: Energy Efficiency and Error Performance Analysis

no code implementations18 Nov 2021 Recep A. Tasci, Fatih Kilinc, Ertugrul Basar, George C. Alexandropoulos

Reconfigurable intelligent surface (RIS)-assisted communication have recently attracted the attention of the wireless communication community as a potential candidate for the next $6$-th generation (6G) of wireless networks.

ADMM-DAD net: a deep unfolding network for analysis compressed sensing

1 code implementation13 Oct 2021 Vasiliki Kouni, Georgios Paraskevopoulos, Holger Rauhut, George C. Alexandropoulos

In this paper, we propose a new deep unfolding neural network based on the ADMM algorithm for analysis Compressed Sensing.

Non-Coherent Modulation for RIS-Empowered Multi-Antenna OFDM Communications

no code implementations9 Mar 2021 Kun Chen-Hu, George C. Alexandropoulos, Ana García Armada

The Reconfigurable Intelligent Surface (RIS) constitutes one of the prominent technologies for the next 6-th Generation (6G) of wireless communications.

Information Theory Information Theory

Self-Calibrating Indoor Localization with Crowdsourcing Fingerprints and Transfer Learning

no code implementations26 Jan 2021 Chenlu Xiang, Shunqing Zhang, Shugong Xu, George C. Alexandropoulos

Precise indoor localization is one of the key requirements for fifth Generation (5G) and beyond, concerning various wireless communication systems, whose applications span different vertical sectors.

Indoor Localization Transfer Learning

Multi-hop RIS-Empowered Terahertz Communications: A DRL-based Hybrid Beamforming Design

no code implementations22 Jan 2021 Chongwen Huang, Zhaohui Yang, George C. Alexandropoulos, Kai Xiong, Li Wei, Chau Yuen, Zhaoyang Zhang, Merouane Debbah

We investigate the joint design of digital beamforming matrix at the BS and analog beamforming matrices at the RISs, by leveraging the recent advances in deep reinforcement learning (DRL) to combat the propagation loss.

Uplink Beam Management for Millimeter Wave Cellular MIMO Systems with Hybrid Beamforming

no code implementations18 Jan 2021 George C. Alexandropoulos, Ioanna Vinieratou, Mattia Rebato, Luca Rose, Michele Zorzi

Hybrid analog and digital BeamForming (HBF) is one of the enabling transceiver technologies for millimeter Wave (mmWave) Multiple Input Multiple Output (MIMO) systems.

Information Theory Information Theory

Near-field Localization with a Reconfigurable Intelligent Surface Acting as Lens

1 code implementation12 Oct 2020 Zohair Abu-Shaban, Kamran Keykhosravi, Musa Furkan Keskin, George C. Alexandropoulos, Gonzalo Seco-Granados, Henk Wymeersch

Exploiting wavefront curvature enables localization with limited infrastructure and hardware complexity.

Signal Processing Information Theory Information Theory

Phase Configuration Learning in Wireless Networks with Multiple Reconfigurable Intelligent Surfaces

no code implementations9 Oct 2020 George C. Alexandropoulos, Sumudu Samarakoon, Mehdi Bennis, Merouane Debbah

Reconfigurable Intelligent Surfaces (RISs) are recently gaining remarkable attention as a low-cost, hardware-efficient, and highly scalable technology capable of offering dynamic control of electro-magnetic wave propagation.

Hybrid Beamforming for RIS-Empowered Multi-hop Terahertz Communications: A DRL-based Method

no code implementations20 Sep 2020 Chongwen Huang, Zhaohui Yang, George C. Alexandropoulos, Kai Xiong, Li Wei, Chau Yuen, Zhaoyang Zhang

Wireless communication in the TeraHertz band (0. 1--10 THz) is envisioned as one of the key enabling technologies for the future six generation (6G) wireless communication systems.

Channel Estimation for RIS-Empowered Multi-User MISO Wireless Communications

no code implementations4 Aug 2020 Li Wei, Chongwen Huang, George C. Alexandropoulos, Chau Yuen, Zhaoyang Zhang, Mérouane Debbah

We also discuss the downlink achievable sum rate computation with estimated channels and different precoding schemes for the base station.

Reconfigurable Intelligent Surfaces and Metamaterials: The Potential of Wave Propagation Control for 6G Wireless Communications

no code implementations19 Jun 2020 George C. Alexandropoulos, Geoffroy Lerosey, Merouane Debbah, Mathias Fink

Motivated by the late research excitement on the RIS potential for intelligent EM wave propagation modulation, we describe the status on RIS hardware architectures and present key open challenges and future research directions for RIS design and RIS-empowered 6G wireless communications.

Dynamic Metasurface Antennas for 6G Extreme Massive MIMO Communications

no code implementations14 Jun 2020 Nir Shlezinger, George C. Alexandropoulos, Mohammadreza F. Imani, Yonina C. Eldar, David R. Smith

Next generation wireless base stations and access points will transmit and receive using extremely massive numbers of antennas.

Holographic MIMO Surfaces for 6G Wireless Networks: Opportunities, Challenges, and Trends

no code implementations27 Nov 2019 Chongwen Huang, Sha Hu, George C. Alexandropoulos, Alessio Zappone, Chau Yuen, Rui Zhang, Marco Di Renzo, Mérouane Debbah

Future wireless networks are expected to evolve towards an intelligent and software reconfigurable paradigm enabling ubiquitous communications between humans and mobile devices.

Indoor Signal Focusing with Deep Learning Designed Reconfigurable Intelligent Surfaces

no code implementations19 May 2019 Chongwen Huang, George C. Alexandropoulos, Chau Yuen, Mérouane Debbah

Reconfigurable Intelligent Surfaces (RISs) comprised of tunable unit elements have been recently considered in indoor communication environments for focusing signal reflections to intended user locations.

Deep Learning for UL/DL Channel Calibration in Generic Massive MIMO Systems

no code implementations7 Mar 2019 Chongwen Huang, George C. Alexandropoulos, Alessio Zappone, Chau Yuen, Mérouane Debbah

We then leverage the trained deep neural network with the instantaneously estimated UL channel to calibrate the DL one, which is not observable during the UL transmission phase.

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