Search Results for author: Symeon Chatzinotas

Found 101 papers, 2 papers with code

Emerging NGSO Constellations: Spectral Coexistence with GSO Satellite Communication Systems

no code implementations19 Apr 2024 Flor Ortiz, Eva Lagunas, Almoatssimbillah Saifaldawla, Mahdis Jalali, Luis Emiliani, Symeon Chatzinotas

Moving onto operational aspects related to the sharing of spectrum, we introduce recent work on interference detection, identification, and mitigation and provide our vision of the emerging role of artificial intelligence (AI) in the aforementioned tasks.

Enhancing Indoor and Outdoor THz Communications with Beyond Diagonal-IRS: Optimization and Performance Analysis

no code implementations26 Mar 2024 Asad Mahmood, Thang X. Vu, Symeon Chatzinotas, Björn Ottersten

This work investigates the application of Beyond Diagonal Intelligent Reflective Surface (BD-IRS) to enhance THz downlink communication systems, operating in a hybrid: reflective and transmissive mode, to simultaneously provide services to indoor and outdoor users.

User-Centric Beam Selection and Precoding Design for Coordinated Multiple-Satellite Systems

no code implementations13 Mar 2024 Vu Nguyen Ha, Duy H. N. Nguyen, Juan C. -M. Duncan, Jorge L. Gonzalez-Rios, Juan A. Vasquez, Geoffrey Eappen, Luis M. Garces-Socarras, Rakesh Palisetty, Symeon Chatzinotas, Bjorn Ottersten

This paper introduces a joint optimization framework for user-centric beam selection and linear precoding (LP) design in a coordinated multiple-satellite (CoMSat) system, employing a Digital-Fourier-Transform-based (DFT) beamforming (BF) technique.

Interference analysis of Positioning Reference Signals in 5G NTN

no code implementations17 Jan 2024 Alejandro Gonzalez-Garrido, Jorge Querol, Henk Wymeersch, Symeon Chatzinotas

Accurate asset localization holds paramount importance across various industries, ranging from transportation management to search and rescue operations.


Performance Evaluation of Neuromorphic Hardware for Onboard Satellite Communication Applications

no code implementations12 Jan 2024 Eva Lagunas, Flor Ortiz, Geoffrey Eappen, Saed Daoud, Wallace Alves Martins, Jorge Querol, Symeon Chatzinotas, Nicolas Skatchkovsky, Bipin Rajendran, Osvaldo Simeone

Spiking neural networks (SNNs) implemented on neuromorphic processors (NPs) can enhance the energy efficiency of deployments of artificial intelligence (AI) for specific workloads.

Satellite Swarms for Narrow Beamwidth Applications

no code implementations21 Nov 2023 Juan A. Vásquez-Peralvo, Juan Carlos Merlano Duncan, Geoffrey Eappen, Symeon Chatzinotas

Satellite swarms have recently gained attention in the space industry due to their ability to provide extremely narrow beamwidths at a lower cost than single satellite systems.

Joint Computation and Communication Resource Optimization for Beyond Diagonal UAV-IRS Empowered MEC Networks

no code implementations13 Nov 2023 Asad Mahmood, Thang X. Vu, Wali Ullah Khan, Symeon Chatzinotas, Björn Ottersten

We propose a joint optimization strategy to reduce system's worst-case latency and UAV hovering time by optimizing BD-IRS-UAV deployment and resource allocation.


Supervised Learning Based Real-Time Adaptive Beamforming On-board Multibeam Satellites

no code implementations2 Nov 2023 Flor Ortiz, Juan A. Vasquez-Peralvo, Jorge Querol, Eva Lagunas, Jorge L. Gonzalez Rios, Marcele O. K. Mendonca, Luis Garces, Victor Monzon Baeza, Symeon Chatzinotas

Satellite communications (SatCom) are crucial for global connectivity, especially in the era of emerging technologies like 6G and narrowing the digital divide.


Genetic Algorithm-based Beamforming in Subarray Architectures for GEO Satellites

no code implementations2 Nov 2023 Juan Andrés Vásquez-Peralvo, Jorge Querol, Eva Lagunas, Flor Ortiz, Luis Manuel Garcés-Socarrás, Jorge Luis González-Rios, Victor Monzon Baeza, Symeon Chatzinotas

The incorporation of subarrays in Direct Radiating Arrays for satellite missions is fundamental in reducing the number of Radio Frequency chains, which correspondingly diminishes cost, power consumption, space, and mass.

Flexible Payload Configuration for Satellites using Machine Learning

no code implementations18 Oct 2023 Marcele O. K. Mendonca, Flor G. Ortiz-Gomez, Jorge Querol, Eva Lagunas, Juan A. Vásquez Peralvo, Victor Monzon Baeza, Symeon Chatzinotas, Bjorn Ottersten

Satellite communications, essential for modern connectivity, extend access to maritime, aeronautical, and remote areas where terrestrial networks are unfeasible.


Connecting Space Missions Through NGSO Constellations: Feasibility Study

no code implementations28 Sep 2023 Houcine Chougrani, Oltjon Kodheli, Ali Georganaki, Jan Thoemel, Chiara Vittoria Turtoro, Frank Zeppenfeldt, Petros Pissias, Mahulena Hofmann, Symeon Chatzinotas

This paper performs a feasibility study on the concept of connecting space missions to the network through commercial mega-constellations.

ML-based PBCH symbol detection and equalization for 5G Non-Terrestrial Networks

no code implementations26 Sep 2023 Inés Larráyoz-Arrigote, Marcele O. K. Mendonca, Alejandro Gonzalez-Garrido, Jevgenij Krivochiza, Sumit Kumar, Jorge Querol, Joel Grotz, Stefano Andrenacci, Symeon Chatzinotas

This paper delves into the application of Machine Learning (ML) techniques in the realm of 5G Non-Terrestrial Networks (5G-NTN), particularly focusing on symbol detection and equalization for the Physical Broadcast Channel (PBCH).

Harnessing Supervised Learning for Adaptive Beamforming in Multibeam Satellite Systems

no code implementations25 Sep 2023 Flor Ortiz, Juan A. Vasquez-Peralvo, Jorge Querol, Eva Lagunas, Jorge L. Gonzalez Rios, Luis Garces, Victor Monzon-Baeza, Symeon Chatzinotas

In today's ever-connected world, the demand for fast and widespread connectivity is insatiable, making multibeam satellite systems an indispensable pillar of modern telecommunications infrastructure.

Deep Reinforcement Learning for Backscatter Communications: Augmenting Intelligence in Future Internet of Things

no code implementations21 Sep 2023 Wali Ullah Khan, Eva Lagunas, Zain Ali, Asad Mahmood, Chandan Kumar Sheemar, Manzoor Ahmed, Symeon Chatzinotas, Björn Ottersten

Backscatter communication (BC) technology offers sustainable solutions for next-generation Internet-of-Things (IoT) networks, where devices can transmit data by reflecting and adjusting incident radio frequency signals.

Gateway Station Geographical Planning for Emerging Non-Geostationary Satellites Constellations

no code implementations19 Sep 2023 Victor Monzon Baeza, Flor Ortiz, Eva Lagunas, Tedros Salih Abdu, Symeon Chatzinotas

Among the recent advances and innovations in satellite communications, Non-Geostationary Orbit (NGSO) satellite constellations are gaining popularity as a viable option for providing widespread broadband internet access and backhauling services.

Terahertz-Band Direction Finding With Beam-Split and Mutual Coupling Calibration

no code implementations6 Sep 2023 Ahmet M. Elbir, Kumar Vijay Mishra, Symeon Chatzinotas

Terahertz (THz) band is currently envisioned as the key building block to achieving the future sixth generation (6G) wireless systems.

Energy-Efficient On-Board Radio Resource Management for Satellite Communications via Neuromorphic Computing

no code implementations22 Aug 2023 Flor Ortiz, Nicolas Skatchkovsky, Eva Lagunas, Wallace A. Martins, Geoffrey Eappen, Saed Daoud, Osvaldo Simeone, Bipin Rajendran, Symeon Chatzinotas

The latest satellite communication (SatCom) missions are characterized by a fully reconfigurable on-board software-defined payload, capable of adapting radio resources to the temporal and spatial variations of the system traffic.


Signal Processing Based Antenna Pattern Characterization for MIMO Systems

no code implementations18 Aug 2023 Chandan Kumar Sheemar, Jorge Querol, Symeon Chatzinotas

Furthermore, it grants a much wider research community the ability to independently perform APC for emerging complex 6G antenna systems, without relying on anechoic chambers.

IRS Assisted MIMO Full Duplex: Rate Analysis and Beamforming Under Imperfect CSI

no code implementations16 Aug 2023 Chandan Kumar Sheemar, Sourabh Solanki, Jorge Querol, Sumit Kumar, Symeon Chatzinotas

In this manuscript, we present a novel approach to jointly optimize active and passive beamforming in a multiple-input-multiple-output (MIMO) FD system assisted by an IRS for weighted sum rate (WSR) maximization.

Robust Beamforming for IRS Aided MIMO Full Duplex Systems

no code implementations15 Aug 2023 Chandan Kumar Sheemar, Jorge Querol, Sourabh Solanki, Sumit Kumar, Symeon Chatzinotas

We also analyze the achievable WSR of an IRS-assisted FD with imperfect CSI, for which the lower and the upper bounds are derived.

Robust Design

Reconfigurable Intelligent Surfaces Enhanced NOMA D2D Communications Underlaying UAV Networks

no code implementations29 Jul 2023 Wali Ullah Khan, Eva Lagunas, Asad Mahmood, Zain Ali, Symeon Chatzinotas, Björn Ottersten

The objective is to maximize the sum rate of NOMA D2D communications by simultaneously optimizing the power budget of D2D transmitter, NOMA power allocation coefficients of D2D receivers and passive beamforming of RIS while guaranteeing the quality of services of UAV user.

A Hybrid Optimization and Deep RL Approach for Resource Allocation in Semi-GF NOMA Networks

no code implementations18 Jul 2023 Duc-Dung Tran, Vu Nguyen Ha, Symeon Chatzinotas, Ti Ti Nguyen

In this design, a multi-agent deep Q network (MADQN) approach is employed to conduct the subchannel assignment (SA) among users.


Harnessing the Power of Swarm Satellite Networks with Wideband Distributed Beamforming

no code implementations10 Jul 2023 Juan Carlos Merlano Duncan, Vu Nguyen Ha, Jevgenij Krivochiza, Rakesh Palisetty, Geoffrey Eappen, Juan Andres Vasquez, Wallace Alves Martins, Symeon Chatzinotas, Björn Ottersten

The space communications industry is challenged to develop a technology that can deliver broadband services to user terminals equipped with miniature antennas, such as handheld devices.

RIS-Assisted Energy-Efficient LEO Satellite Communications with NOMA

no code implementations17 Jun 2023 Wali Ullah Khan, Eva Lagunas, Asad Mahmood, Symeon Chatzinotas, Björn Ottersten

Then, in step 2, given the transmit power, we design passive beamforming for RIS by solving the semi-definite programming.

Task-Oriented Communication Design at Scale

no code implementations15 May 2023 Arsham Mostaani, Thang X. Vu, Hamed Habibi, Symeon Chatzinotas, Bjorn Ottersten

Numerical results show striking improvements in reducing the computational complexity of obtaining VoI needed for the TOCD in a MAS problem without compromising the average return performance of the MAS.

Quantization Reinforcement Learning (RL)

Joint Optimization of 3D Placement and Radio Resource Allocation for per-UAV Sum Rate Maximization

no code implementations8 May 2023 Asad Mahmood, Thang X. Vu, Symeon Chatzinotas, Björn Ottersten

The main aim of this work is to derive an efficient technique for the allocation of radio resources, $3$D placement of UAVs, and user association matrices.

Energy-Efficient Precoding and Feeder-Link-Beam Matching Design for Bent-Pipe SATCOM Systems

no code implementations26 Apr 2023 Vu Nguyen Ha, Juan Carlos Merlano Duncan, Eva Lagunas, Jorge Querol, Symeon Chatzinotas

This paper proposes a joint optimization framework for energy-efficient linear precoding and feeder-link-beam matching design in a multi-gateway multi-beam bent-pipe satellite communication system.

Multi-Objective Optimization for 3D Placement and Resource Allocation in OFDMA-based Multi-UAV Networks

no code implementations25 Apr 2023 Asad Mahmood, Thang X. Vu, Shree Krishna Sharma, Symeon Chatzinotas, Björn Ottersten

The main aim of this work is to derive the optimal allocation of radio resources, 3D placement of UAVs, and user association matrices.

Two-tier User Association and Resource Allocation Design for Integrated Satellite-Terrestrial Networks

no code implementations19 Mar 2023 Hung Nguyen-Kha, Vu Nguyen Ha, Eva Lagunas, Symeon Chatzinotas, Joel Grotz

This paper presents a study of an integrated satellite-terrestrial network, where Low-Earth-Orbit (LEO) satellites are used to provide the backhaul link between base stations (BSs) and the core network.

Large-Scale Beam Placement and Resource Allocation Design for MEO-Constellation SATCOM

no code implementations11 Mar 2023 Vu Nguyen Ha, Eva Lagunas, Tedros Salih Abdu, Haythem Chaker, Symeon Chatzinotas, Joel Grotz

This paper presents a centralized framework for optimizing the joint design of beam placement, power, and bandwidth allocation in an MEO satellite constellation to fulfill the heterogeneous traffic demands of a large number of global users.


Energy-Efficient RIS-Enabled NOMA Communication for 6G LEO Satellite Networks

no code implementations9 Mar 2023 Wali Ullah Khan, Eva Lagunas, Asad Mahmood, Symeon Chatzinotas, Björn Ottersten

The proposed framework simultaneously optimizes the transmit power of ground terminals at LEO satellite and passive beamforming at RIS while ensuring the quality of services.

Near-Field Terahertz Communications: Model-Based and Model-Free Channel Estimation

no code implementations9 Feb 2023 Ahmet M. Elbir, Wei Shi, Anastasios K. Papazafeiropoulos, Pandelis Kourtessis, Symeon Chatzinotas

Unlike prior works which mostly ignore the impact of near-field beam-split (NB) and consider either narrowband scenario or far-field models, this paper introduces both a model-based and a model-free techniques for wideband THz channel estimation in the presence of NB.

Federated Learning

Network-Aided Intelligent Traffic Steering in 6G O-RAN: A Multi-Layer Optimization Framework

no code implementations6 Feb 2023 Van-Dinh Nguyen, Thang X. Vu, Nhan Thanh Nguyen, Dinh C. Nguyen, Markku Juntti, Nguyen Cong Luong, Dinh Thai Hoang, Diep N. Nguyen, Symeon Chatzinotas

To enable an intelligent, programmable and multi-vendor radio access network (RAN) for 6G networks, considerable efforts have been made in standardization and development of open RAN (O-RAN).

Scheduling Stochastic Optimization

BSA-OMP: Beam-Split-Aware Orthogonal Matching Pursuit for THz Channel Estimation

no code implementations5 Feb 2023 Ahmet M. Elbir, Symeon Chatzinotas

Terahertz (THz)-band has been envisioned for the sixth generation wireless networks thanks to its ultra-wide bandwidth and very narrow beamwidth.

Localization as a key enabler of 6G wireless systems: A comprehensive survey and an outlook

no code implementations4 Feb 2023 Stylianos E. Trevlakis, Alexandros-Apostolos A. Boulogeorgos, Dimitrios Pliatsios, Konstantinos Ntontin, Panagiotis Sarigiannidis, Symeon Chatzinotas, Marco Di Renzo

Finally, insights that arise from the presented analysis are summarized and used to highlight the most important future directions for localization in 6G wireless systems.

NBA-OMP: Near-field Beam-Split-Aware Orthogonal Matching Pursuit for Wideband THz Channel Estimation

no code implementations3 Feb 2023 Ahmet M. Elbir, Kumar Vijay Mishra, Symeon Chatzinotas

The sixth-generation networks envision the terahertz (THz) band as one of the key enabling technologies because of its ultrawide bandwidth.

LEO-to-User Assignment and Resource Allocation for Uplink Transmit Power Minimization

no code implementations2 Feb 2023 Hung Nguyen-Kha, Vu Nguyen Ha, Eva Lagunas, Symeon Chatzinotas, Joel Grotz

This paper aims to develop satellite-user association and resource allocation mechanisms to minimize the total transmit power for integrated terrestrial and non-terrestrial networks wherein a constellation of LEO satellites provides the radio access services to both terrestrial base stations (BSs) and the satellite-enabled users (SUEs).

Characterizing and Utilizing the Interplay between Quantum Technologies and Non-Terrestrial Networks

no code implementations15 Nov 2022 Hayder Al-Hraishawi, Junaid ur Rehman, Mohsen Razavi, Symeon Chatzinotas

Quantum technologies are increasingly recognized as groundbreaking advancements set to redefine the landscape of computing, communications, and sensing by leveraging quantum phenomena, like entanglement and teleportation.

Intelligent Traffic Steering in Beyond 5G Open RAN based on LSTM Traffic Prediction

no code implementations17 Oct 2022 Fatemeh Kavehmadavani, Van-Dinh Nguyen, Thang X. Vu, Symeon Chatzinotas

For this purpose, we propose a joint intelligent traffic prediction, flow-split distribution, dynamic user association and radio resource management (JIFDR) framework in the presence of unknown dynamic traffic demands.

Management Traffic Prediction

Grant-Free NOMA-OTFS Paradigm: Enabling Efficient Ubiquitous Access for LEO Satellite Internet-of-Things

no code implementations25 Sep 2022 Zhen Gao, Xingyu Zhou, Jingjing Zhao, Juan Li, Chunli Zhu, Chun Hu, Pei Xiao, Symeon Chatzinotas, Derrick Wing Kwan Ng, Bjorn Ottersten

With the blooming of Internet-of-Things (IoT), we are witnessing an explosion in the number of IoT terminals, triggering an unprecedented demand for ubiquitous wireless access globally.

An Overview of Channel Models for NGSO Satellites

no code implementations21 Sep 2022 Victor Monzon Baeza, Eva Lagunas, Hayder Al-Hraishawi, Symeon Chatzinotas

Satellite communications industry is currently going through a rapid and profound transformation to adapt to the recent innovations and developments in the realm of non-geostationary orbit (NGSO) satellites.

GEO Payload Power Minimization: Joint Precoding and Beam Hopping Design

no code implementations22 Aug 2022 Vu Nguyen Ha, Ti Ti Nguyen, Eva Lagunas, Juan Carlos Merlano Duncan, Symeon Chatzinotas

Regarding constraint on the maximum number of illuminated beams per time slot, the technical requirement is formulated as a sparse optimization problem in which the hardware-related beam illumination energy is modeled in a sparsity form of the LP vectors.

Terahertz-Band Channel and Beam Split Estimation via Array Perturbation Model

no code implementations7 Aug 2022 Ahmet M. Elbir, Wei Shi, Anastasios K. Papazafeiropoulos, Pandelis Kourtessis, Symeon Chatzinotas

For the demonstration of ultra-wideband bandwidth and pencil-beamforming, the terahertz (THz)-band has been envisioned as one of the key enabling technologies for the sixth generation networks.

Federated Learning

Rate Splitting Multiple Access for Cognitive Radio GEO-LEO Co-Existing Satellite Networks

no code implementations4 Aug 2022 Wali Ullah Khan, Zain Ali, Eva Lagunas, Symeon Chatzinotas, Björn Ottersten

We also propose two suboptimal schemes with fixed power allocation and random subcarrier beam assignment as the benchmark.

Terahertz-Band Integrated Sensing and Communications: Challenges and Opportunities

no code implementations2 Aug 2022 Ahmet M. Elbir, Kumar Vijay Mishra, Symeon Chatzinotas, Mehdi Bennis

The sixth generation (6G) wireless networks aim to achieve ultra-high data transmission rates, very low latency and enhanced energy-efficiency.

Federated Multi-Task Learning for THz Wideband Channel and DoA Estimation

no code implementations13 Jul 2022 Ahmet M. Elbir, Wei Shi, Kumar Vijay Mishra, Symeon Chatzinotas

This paper addresses two major challenges in terahertz (THz) channel estimation: the beam-split phenomenon, i. e., beam misalignment because of frequency-independent analog beamformers, and computational complexity because of the usage of ultra-massive number of antennas to compensate propagation losses.

Federated Learning Multi-Task Learning

Implicit Channel Learning for Machine Learning Applications in 6G Wireless Networks

no code implementations24 Jun 2022 Ahmet M. Elbir, Wei Shi, Kumar Vijay Mishra, Anastasios K. Papazafeiropoulos, Symeon Chatzinotas

Without channel estimation, the proposed approach exhibits approximately 60% improvement in image and speech classification tasks for diverse scenarios such as millimeter wave and IEEE 802. 11p vehicular channels.

BIG-bench Machine Learning

Joint Beam Hopping and Carrier Aggregation in High Throughput Multi-Beam Satellite Systems

no code implementations24 Jun 2022 Mirza Golam Kibria, Hayder Al-Hraishawi, Eva Lagunas, Symeon Chatzinotas, Björn Ottersten

Beam hopping (BH) and carrier aggregation (CA) are two promising technologies for the next generation satellite communication systems to achieve several orders of magnitude increase in system capacity and to significantly improve the spectral efficiency.

Deep Learning-Based Device-Free Localization in Wireless Sensor Networks

no code implementations16 Jun 2022 Osamah A. Abdullah, Hayder Al-Hraishawi, Symeon Chatzinotas

Location-based services (LBS) are witnessing a rise in popularity owing to their key features of delivering powerful and personalized digital experiences.

The Rise of Intelligent Reflecting Surfaces in Integrated Sensing and Communications Paradigms

no code implementations14 Apr 2022 Ahmet M. Elbir, Kumar Vijay Mishra, M. R. Bhavani Shankar, Symeon Chatzinotas

The intelligent reflecting surface (IRS) alters the behavior of wireless media and, consequently, has potential to improve the performance and reliability of wireless systems such as communications and radar remote sensing.

Opportunities for Physical Layer Security in UAV Communication Enhanced with Intelligent Reflective Surfaces

no code implementations31 Mar 2022 Wali Ullah Khan, Eva Lagunas, Zain Ali, Muhammad Awais Javed, Manzoor Ahmed, Symeon Chatzinotas, Björn Ottersten, Petar Popovski

Unmanned Aerial Vehicles (UAVs) are an important component of next-generation wireless networks that can assist in high data rate communications and provide enhanced coverage. Their high mobility and aerial nature offer deployment flexibility and low-cost infrastructure support to existing cellular networks and provide many applications that rely on mobile wireless communications.

Architectures and Synchronization Techniques for Distributed Satellite Systems: A Survey

no code implementations16 Mar 2022 Liz Martinez Marrero, Juan C. Merlano Duncan, Jorge Querol, Sumit Kumar, Jevgenij Krivochiza, Shree Krishna Sharma, Symeon Chatzinotas, Adriano Camps, Bjorn Otterstern

This article also provides an extensive list of applications and examples of synchronization techniques for DSS in addition to the most significant advances in other operations closely related to synchronization, such as inter-satellite ranging and relative position.

Energy Efficiency Optimization for Backscatter Enhanced NOMA Cooperative V2X Communications under Imperfect CSI

no code implementations3 Feb 2022 Wali Ullah Khan, Muhammad Ali Jamshed, Eva Lagunas, Symeon Chatzinotas, Xingwang Li, Bjorn Ottersten

Automotive-Industry 5. 0 will use beyond fifth-generation (B5G) technologies to provide robust, computationally intelligent, and energy-efficient data sharing among various onboard sensors, vehicles, and other devices.

Backscatter-Aided NOMA V2X Communication under Channel Estimation Errors

no code implementations3 Feb 2022 Wali Ullah Khan, Muhammad Ali Jamshed, Asad Mahmood, Eva Lagunas, Symeon Chatzinotas, Bjorn Ottersten

Then the RSUs transmit the superimposed signal to their serving vehicles in the second time slot exploiting decode and forward protocol.

When RIS Meets GEO Satellite Communications: A New Sustainable Optimization Framework in 6G

no code implementations1 Feb 2022 Wali Ullah Khan, Eva Lagunas, Asad Mahmood, Symeon Chatzinotas, Bjorn Ottersten

To enhance the effective gain, the signal delivery from satellite to the ground mobile terminal is also assisted by RIS which smartly shift the phase of the signal towards ground terminal.

THz-Empowered UAVs in 6G: Opportunities, Challenges, and Trade-Offs

no code implementations13 Jan 2022 M. Mahdi Azari, Sourabh Solanki, Symeon Chatzinotas, Mehdi Bennis

Envisioned use cases of unmanned aerial vehicles (UAVs) impose new service requirements in terms of data rate, latency, and sensing accuracy, to name a few.

Multi-layer Space Information Networks: Access Design and Softwarization

no code implementations15 Oct 2021 Hayder Al-Hraishawi, Mario Minardi, Houcine Chougrani, Oltjon Kodheli, Jesus Fabian Mendoza Montoya, Symeon Chatzinotas

Specifically, space-based Internet providers, such as Starlink, OneWeb, and SES O3b, can be utilized for broadband connectivity directly to/from the nanosatellites, which allows a larger degree of connectivity in space network topologies.

Earth Observation

Adapting to Dynamic LEO-B5G Systems: Meta-Critic Learning Based Efficient Resource Scheduling

no code implementations13 Oct 2021 Yaxiong Yuan, Lei Lei, Thang X. Vu, Zheng Chang, Symeon Chatzinotas, Sumei Sun

Low earth orbit (LEO) satellite-assisted communications have been considered as one of key elements in beyond 5G systems to provide wide coverage and cost-efficient data services.

Management Meta-Learning +1

Integration of Backscatter Communication with Multi-cell NOMA: A Spectral Efficiency Optimization under Imperfect SIC

no code implementations23 Sep 2021 Wali Ullah Khan, Eva Lagunas, Asad Mahmood, Zain Ali, Symeon Chatzinotas, Björn Ottersten, Octavia A. Dobre

This paper proposes a new optimization approach to enhance the spectral efficiency of nonorthogonal multiple access (NOMA)-BC network.

Frequency-packed Faster-than-Nyquist Signaling via Symbol-level Precoding for Multi-user MISO Redundant Transmissions

no code implementations14 Jul 2021 Wallace A. Martins, Symeon Chatzinotas, Björn Ottersten

This work addresses the issue of interference generated by co-channel users in downlink multi-antenna multicarrier systems with frequency-packed faster-than-Nyquist (FTN) signaling.

A Survey on Non-Geostationary Satellite Systems: The Communication Perspective

no code implementations12 Jul 2021 Hayder Al-Hraishawi, Houcine Chougrani, Steven Kisseleff, Eva Lagunas, Symeon Chatzinotas

The next phase of satellite technology is being characterized by a new evolution in non-geostationary orbit (NGSO) satellites, which conveys exciting new communication capabilities to provide non-terrestrial connectivity solutions and to support a wide range of digital technologies from various industries.


FedFog: Network-Aware Optimization of Federated Learning over Wireless Fog-Cloud Systems

no code implementations4 Jul 2021 Van-Dinh Nguyen, Symeon Chatzinotas, Bjorn Ottersten, Trung Q. Duong

data, users' heterogeneity), we first propose an efficient FL algorithm based on Federated Averaging (called FedFog) to perform the local aggregation of gradient parameters at fog servers and global training update at the cloud.

Federated Learning

LEO Satellite Constellations for 5G and Beyond: How Will They Reshape Vertical Domains?

no code implementations18 Jun 2021 Shicong Liu, Zhen Gao, Yongpeng Wu, Derrick Wing Kwan Ng, Xiqi Gao, Kai-Kit Wong, Symeon Chatzinotas, Bjorn Ottersten

The rapid development of communication technologies in the past decades has provided immense vertical opportunities for individuals and enterprises.

A Hybrid Architecture for Federated and Centralized Learning

no code implementations7 May 2021 Ahmet M. Elbir, Sinem Coleri, Anastasios K. Papazafeiropoulos, Pandelis Kourtessis, Symeon Chatzinotas

To address this common scenario, we propose a more efficient approach called hybrid federated and centralized learning (HFCL), wherein only the clients with sufficient resources employ FL, while the remaining ones send their datasets to the PS, which computes the model on behalf of them.

BIG-bench Machine Learning Federated Learning

Hybrid Relay-Reflecting Intelligent Surface-Aided Wireless Communications: Opportunities, Challenges, and Future Perspectives

no code implementations5 Apr 2021 Nhan Thanh Nguyen, Jiguang He, Van-Dinh Nguyen, Henk Wymeersch, Derrick Wing Kwan Ng, Robert Schober, Symeon Chatzinotas, Markku Juntti

In this paper, we provide an overview of a hybrid relay-reflecting intelligent surface (HR-RIS) architecture, in which only a few elements are active and connected to power amplifiers and radio frequency chains.

Terahertz-Band Joint Ultra-Massive MIMO Radar-Communications: Model-Based and Model-Free Hybrid Beamforming

no code implementations27 Feb 2021 Ahmet M. Elbir, Kumar Vijay Mishra, Symeon Chatzinotas

Wireless communications and sensing at terahertz (THz) band are increasingly investigated as promising short-range technologies because of the availability of high operational bandwidth at THz.

Federated Learning for Physical Layer Design

no code implementations23 Feb 2021 Ahmet M. Elbir, Anastasios K. Papazafeiropoulos, Symeon Chatzinotas

Model-free techniques, such as machine learning (ML), have recently attracted much interest towards the physical layer design, e. g., symbol detection, channel estimation, and beamforming.

Federated Learning Privacy Preserving

Coverage Probability of Distributed IRS Systems Under Spatially Correlated Channels

no code implementations18 Feb 2021 Anastasios Papazafeiropoulos, Cunhua Pan, Ahmet Elbir, Pandelis Kourtessis, Symeon Chatzinotas, John M. Senior

This paper suggests the use of multiple distributed intelligent reflecting surfaces (IRSs) towards a smarter control of the propagation environment.

Information Theory Information Theory

NB-IoT Random Access for Non-Terrestrial Networks

no code implementations20 Jan 2021 Houcine Chougrani, Steven Kisseleff, Wallace A. Martins, Symeon Chatzinotas

The satellite component is recognized as a promising solution to complement and extend the coverage of future Internet of things (IoT) terrestrial networks (TNs).


Broadband Non-Geostationary Satellite Communication Systems: Research Challenges and Key Opportunities

no code implementations20 Jan 2021 Hayder Al-Hraishawi, Symeon Chatzinotas, Björn Ottersten

Besides conventional geostationary (GSO) satellite broadband communication services, non-geostationary (NGSO) satellites are envisioned to support various new communication use cases from countless industries.


Machine Learning-Enabled Joint Antenna Selection and Precoding Design: From Offline Complexity to Online Performance

no code implementations18 Jan 2021 Thang X. Vu, Symeon Chatzinotas, Van-Dinh Nguyen, Dinh Thai Hoang, Diep N. Nguyen, Marco Di Renzo, Bjorn Ottersten

We investigate the performance of multi-user multiple-antenna downlink systems in which a BS serves multiple users via a shared wireless medium.

Information Theory Information Theory

Secure Vehicular Communications through Reconfigurable Intelligent Surfaces

no code implementations30 Nov 2020 Yun Ai, Felipe A. P. de Figueiredo, Long Kong, Michael Cheffena, Symeon Chatzinotas, Björn Ottersten

Reconfigurable intelligent surfaces (RIS) is considered as a revolutionary technique to improve the wireless system performance by reconfiguring the radio wave propagation environment artificially.

A Remote Carrier Synchronization Technique for Coherent Distributed Remote Sensing Systems

no code implementations20 Nov 2020 Juan Merlano Duncan, Liz Martinez-Marrero, Jorge Querol, Sumit Kumar, Adriano Camps, Symeon Chatzinotas, Bjorn Ottersten

Phase, frequency, and time synchronization are crucial requirements for many applications, such as multi-static remote sensing and communication systems.

Reconfigurable Intelligent Surface Optimal Placement in Millimeter-Wave Networks

no code implementations19 Nov 2020 Konstantinos Ntontin, Alexandros A. Boulogeorgos, Dimitrios Selimis, Fotis Lazarakis, Angeliki Alexiou, Symeon Chatzinotas

Subsequently, based on the model we derive the end-to-end expression of the received signal power and, furthermore, provide approximate closed-form expressions in the case that the RIS size is either much smaller or at least equal to the transmission beam footprint.

Information Theory Signal Processing Information Theory

Learning-Assisted User Clustering in Cell-Free Massive MIMO-NOMA Networks

no code implementations15 Nov 2020 Quang Nhat Le, Van-Dinh Nguyen, Nam-Phong Nguyen, Symeon Chatzinotas, Octavia A. Dobre, Ruiqin Zhao

To address this problem, we develop two efficient unsupervised machine learning (ML) based UC algorithms, namely k-means++ and improved k-means++, to effectively cluster users into disjoint clusters in cell-free massive multiple-input multiple-output (CFmMIMO) system.

Clustering Fairness

Reconfigurable Intelligent Surfaces in Challenging Environments: Underwater, Underground, Industrial and Disaster

no code implementations10 Nov 2020 Steven Kisseleff, Symeon Chatzinotas, Björn Ottersten

Challenging environments comprise a range of scenarios, which share the fact that it is extremely difficult to establish a communication link using conventional technology due to many impairments typically associated with the propagation medium and increased signal scattering.

Multi-Antenna Data-Driven Eavesdropping Attacks and Symbol-Level Precoding Countermeasures

no code implementations7 Nov 2020 Abderrahmane Mayouche, Wallace A. Martins, Christos G. Tsinos, Symeon Chatzinotas, Björn Ottersten

In this work, we consider secure communications in wireless multi-user (MU) multiple-input single-output (MISO) systems with channel coding in the presence of a multi-antenna eavesdropper (Eve).

Precoding for Satellite Communications: Why, How and What next?

no code implementations2 Nov 2020 Bhavani Shankar Mysore, Eva Lagunas, Symeon Chatzinotas, Bjorn Ottersten

Precoding has stood out as a promising multi-user transmission technique to meet the emerging throughput demand of satellite communication systems while awaiting the technological maturity for exploiting higher bands.

System Modelling and Design Aspects of Next Generation High Throughput Satellites

no code implementations6 Sep 2020 Shree Krishna Sharma, Jorge Querol, Nicola Maturo, Symeon Chatzinotas, Bjorn Ottersten

Future generation wireless networks are targeting the convergence of fixed, mobile and broadcasting systems with the integration of satellite and terrestrial systems towards utilizing their mutual benefits.

Vocal Bursts Intensity Prediction

Reconfigurable Intelligent Surfaces for Smart Cities: Research Challenges and Opportunities

no code implementations2 Sep 2020 Steven Kisseleff, Wallace A. Martins, Hayder Al-Hraishawi, Symeon Chatzinotas, Björn Ottersten

The concept of Smart Cities has been introduced as a way to benefit from the digitization of various ecosystems at a city level.

Short-Packet Communications for MIMO NOMA Systems over Nakagami-m Fading: BLER and Minimum Blocklength Analysis

no code implementations24 Aug 2020 Duc-Dung Tran, Shree Krishna Sharma, Symeon Chatzinotas, Isaac Woungang, Björn Ottersten

The achieved results show that MIMO NOMA can serve multiple users simultaneously using a smaller blocklength compared with MIMO OMA, thus demonstrating the benefits of MIMO NOMA for SPC in minimizing the transmission latency.

Downlink Transmit Design for Massive MIMO LEO Satellite Communications

no code implementations12 Aug 2020 Ke-Xin Li, Li You, Jiaheng Wang, Xiqi Gao, Christos G. Tsinos, Symeon Chatzinotas, Björn Ottersten

We show that, in this case, the design of precoding vectors can be simplified into that of scalar variables, for which an effective algorithm is developed.

UAV Relay-Assisted Emergency Communications in IoT Networks: Resource Allocation and Trajectory Optimization

no code implementations1 Aug 2020 Dinh-Hieu Tran, Van-Dinh Nguyen, Sumit Gautam, Symeon Chatzinotas, Thang X. Vu, Bjorn Ottersten

In this context, we aim to maximize the number of served IoT devices by jointly optimizing bandwidth, power allocation, and the UAV trajectory while satisfying each device's requirement and the UAV's limited storage capacity.

Traffic Simulator for Multibeam Satellite Communication Systems

1 code implementation14 Jul 2020 Hayder Al-Hraishawi, Eva Lagunas, Symeon Chatzinotas

This paper aims at developing a tool, multibeam satellite traffic simulator, that helps addressing these fundamental challenges, and more importantly, provides an understanding to the spatial-temporal traffic pattern of satellite networks in large-scale environments.


A Novel Heap-based Pilot Assignment for Full Duplex Cell-Free Massive MIMO with Zero-Forcing

no code implementations8 Jul 2020 Hieu V. Nguyen, Van-Dinh Nguyen, Octavia A. Dobre, Shree Krishna Sharma, Symeon Chatzinotas, Björn Ottersten, Oh-Soon Shin

This paper investigates the combined benefits of full-duplex (FD) and cell-free massive multiple-input multipleoutput (CF-mMIMO), where a large number of distributed access points (APs) having FD capability simultaneously serve numerous uplink and downlink user equipments (UEs) on the same time-frequency resources.

Robust Design

Energy Minimization in UAV-Aided Networks: Actor-Critic Learning for Constrained Scheduling Optimization

no code implementations24 Jun 2020 Yaxiong Yuan, Lei Lei, Thang Xuan Vu, Symeon Chatzinotas, Sumei Sun, Bjorn Ottersten

The conventional RL/DRL, e. g., deep Q-learning, however, is limited in dealing with two main issues in constrained combinatorial optimization, i. e., exponentially increasing action space and infeasible actions.

Combinatorial Optimization Q-Learning +1

Joint Forecasting and Interpolation of Graph Signals Using Deep Learning

no code implementations2 Jun 2020 Gabriela Lewenfus, Wallace Alves Martins, Symeon Chatzinotas, Björn Ottersten

We tackle the problem of forecasting network-signal snapshots using past signal measurements acquired by a subset of network nodes.

Time Series Time Series Prediction

Task-Oriented Data Compression for Multi-Agent Communications Over Bit-Budgeted Channels

no code implementations28 May 2020 Arsham Mostaani, Thang X. Vu, Symeon Chatzinotas, Björn Ottersten

Motivated by these recent developments, in this paper, we perform an indirect design of the communications in a multi-agent system (MAS) in which agents cooperate to maximize the averaged sum of discounted one-stage rewards of a collaborative task.

Autonomous Driving Data Compression +1

Joint User Grouping, Scheduling, and Precoding for Multicast Energy Efficiency in Multigroup Multicast Systems

no code implementations14 May 2020 Ashok Bandi, Bhavani Shankar Mysore R, Symeon Chatzinotas, Björn Ottersten

This paper studies the joint design of user grouping, scheduling (or admission control) and precoding to optimize energy efficiency (EE) for multigroup multicast scenarios in single-cell multiuser MISO downlink channels.


Federated Learning Meets Contract Theory: Energy-Efficient Framework for Electric Vehicle Networks

no code implementations4 Apr 2020 Yuris Mulya Saputra, Diep N. Nguyen, Dinh Thai Hoang, Thang Xuan Vu, Eryk Dutkiewicz, Symeon Chatzinotas

In this paper, we propose a novel energy-efficient framework for an electric vehicle (EV) network using a contract theoretic-based economic model to maximize the profits of charging stations (CSs) and improve the social welfare of the network.

Networking and Internet Architecture Signal Processing

Learning-Based Physical Layer Communications for Multi-agent Collaboration

no code implementations2 Oct 2018 Arsham Mostaani, Osvaldo Simeone, Symeon Chatzinotas, Bjorn Ottersten

In this work, it is demonstrated that the performance of the collaborative task can be improved if the agents learn jointly how to communicate and to act, even in the presence of a delay in the communication channel.

Information Theory Multiagent Systems Information Theory

Successive Convex Approximation Algorithms for Sparse Signal Estimation with Nonconvex Regularizations

no code implementations28 Jun 2018 Yang Yang, Marius Pesavento, Symeon Chatzinotas, Björn Ottersten

The proposed framework has several attractive features, namely, i) flexibility, as different choices of the approximate function lead to different type of algorithms; ii) fast convergence, as the problem structure can be better exploited by a proper choice of the approximate function and the stepsize is calculated by the line search; iii) low complexity, as the approximate function is convex and the line search scheme is carried out over a differentiable function; iv) guaranteed convergence to a stationary point.

Anomaly Detection Clustering

Constrained Bayesian Active Learning of Interference Channels in Cognitive Radio Networks

no code implementations23 Oct 2017 Anestis Tsakmalis, Symeon Chatzinotas, Björn Ottersten

The cognitive part of this sequential probing process is the selection of the power levels of the Secondary Users (SUs) which aims to learn the PU interference constraint with a minimum number of probing attempts while setting a limit on the number of harmful probing-induced interference events or equivalently of NACK packet observations over a time window.

Active Learning

Cannot find the paper you are looking for? You can Submit a new open access paper.