Search Results for author: Symeon Chatzinotas

Found 61 papers, 2 papers with code

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 have been widely recognized as one of the milestones towards the ongoing digital transformation, which will also trigger new disruptive innovations.

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.

Association Management +1

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

no code implementations25 Sep 2022 Xingyu Zhou, Zhen Gao, Jingjing Zhao, Juan Li, 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

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.

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

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.

Integration of NOMA with Reflecting Intelligent Surfaces: A Multi-cell Optimization with SIC Decoding Errors

no code implementations6 May 2022 Wali Ullah Khan, Eva Lagunas, Asad Mahmood, Zain Ali, Symeon Chatzinotas, Björn Ottersten

Reflecting intelligent surfaces (RIS) has gained significant attention due to its high energy and spectral efficiency in next-generation wireless networks.

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.

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

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

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.


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).

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.


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.

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.

Association 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

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 Prediction

Task-Based Information Compression for Multi-Agent Communication Problems with Channel Rate Constraints

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

We first show that this problem is equivalent to a form of rate-distortion problem which we call task-based information compression (TBIC).

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

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

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