Search Results for author: Björn Ottersten

Found 48 papers, 4 papers with code

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.

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.


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.

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.

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.

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.

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.

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.

Hybrid Beamforming in mmWave Dual-Function Radar-Communication Systems: Models, Technologies, and Challenges

no code implementations10 Sep 2022 Ziyang Cheng, Linlong Wu, Bowen Wang, Bhavani Shankar, Bin Liao, Björn Ottersten

As a promising technology in beyond-5G (B5G) and 6G, dual-function radar-communication (DFRC) aims to ensure both radar sensing and communication on a single integrated platform with unified signaling schemes.

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.

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.

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, Muhammad Asif 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.

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.

Double-Phase-Shifter based Hybrid Beamforming for mmWave DFRC in the Presence of Extended Target and Clutters

no code implementations5 Dec 2021 Ziyang Cheng, Linlong Wu, Bowen Wang, Bhavani Shankar M. R., Björn Ottersten

In millimeter-wave (mmWave) dual-function radar-communication (DFRC) systems, hybrid beamforming (HBF) is recognized as a promising technique utilizing a limited number of radio frequency chains.

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.

Optimal Sensor Placement for Source Localization: A Unified ADMM Approach

no code implementations8 Sep 2021 Nitesh Sahu, Linlong Wu, Prabhu Babu, Bhavani Shankar M. R., Björn Ottersten

Source localization plays a key role in many applications including radar, wireless and underwater communications.

Resource Allocation in Heterogeneously-Distributed Joint Radar-Communications under Asynchronous Bayesian Tracking Framework

no code implementations23 Aug 2021 Linlong Wu, Kumar Vijay Mishra, Bhavani Shankar M. R., Björn Ottersten

Optimal allocation of shared resources is key to deliver the promise of jointly operating radar and communications systems.

Heterogeneously-Distributed Joint Radar Communications: Bayesian Resource Allocation

no code implementations29 Jul 2021 Linlong Wu, Kumar Vijay Mishra, Bhavani Shankar M. R., Björn Ottersten

In this paper, we focus on a heterogeneous radar and communication network (HRCN), which consists of various generic radars for multiple target tracking (MTT) and wireless communications for multiple users.

Joint Radar-Communication

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.

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.


On the Performance of One-Bit DoA Estimation via Sparse Linear Arrays

no code implementations28 Dec 2020 Saeid Sedighi, M. R. Bhavani Shankar, Mojtaba Soltanalian, Björn Ottersten

Specifically, we first investigate the identifiability conditions for the DoA estimation problem from one-bit SLA data and establish an equivalency with the case when DoAs are estimated from infinite-bit unquantized measurements.

On the Secrecy Capacity of MIMO Wiretap Channels: Convex Reformulation and Efficient Numerical Methods

no code implementations10 Dec 2020 Anshu Mukherjee, Björn Ottersten, Le-Nam Tran

In the first method we capitalize on the accelerated DC algorithm which requires solving a sequence of convex subproblems, for which we propose an efficient iterative algorithm where each iteration admits a closed-form solution.

Information Theory Signal Processing 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.

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.

Joint Constellation Rotation and Symbol-level Precoding Optimization in the Downlink of Multiuser MISO Channels

no code implementations8 Nov 2020 Maha Alodeh, Björn Ottersten

This paper tackles the problem of the simultaneous interference among the multiple users in the downlink of a wireless multiantenna system.

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).

Widely-distributed Radar Imaging Based on Consensus ADMM

no code implementations4 Nov 2020 Ruizhi Hu, Bhavani Shankar Mysore Rama Rao, Ahmed Murtada, Mohammad Alaee-Kerahroodi, Björn Ottersten

In this paper, a novel $l_1$-regularized, consensus alternating direction method of multipliers (CADMM) based algorithm is proposed to mitigate artifacts by exploiting a widely-distributed radar system's spatial diversity.

Distributed Optimization

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.

Localization with One-Bit Passive Radars in Narrowband Internet-of-Things using Multivariate Polynomial Optimization

no code implementations29 Jul 2020 Saeid Sedighi, Kumar Vijay Mishra, M. R. Bhavani Shankar, Björn Ottersten

To support the low-capacity links to the fusion center (FC), the range estimates obtained at individual sensors are then converted to one-bit data.


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

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.


Vertex Feature Encoding and Hierarchical Temporal Modeling in a Spatial-Temporal Graph Convolutional Network for Action Recognition

no code implementations20 Dec 2019 Konstantinos Papadopoulos, Enjie Ghorbel, Djamila Aouada, Björn Ottersten

This paper extends the Spatial-Temporal Graph Convolutional Network (ST-GCN) for skeleton-based action recognition by introducing two novel modules, namely, the Graph Vertex Feature Encoder (GVFE) and the Dilated Hierarchical Temporal Convolutional Network (DH-TCN).

Action Recognition Skeleton Based Action Recognition

A Family of Deep Learning Architectures for Channel Estimation and Hybrid Beamforming in Multi-Carrier mm-Wave Massive MIMO

no code implementations20 Dec 2019 Ahmet M. Elbir, Kumar Vijay Mishra, M. R. Bhavani Shankar, Björn Ottersten

Hybrid analog and digital beamforming transceivers are instrumental in addressing the challenge of expensive hardware and high training overheads in the next generation millimeter-wave (mm-Wave) massive MIMO (multiple-input multiple-output) systems.

Bi-objective Framework for Sensor Fusion in RGB-D Multi-View Systems: Applications in Calibration

no code implementations23 May 2019 Hassan Afzal, Djamila Aouada, Michel Antunes, David Fofi, Bruno Mirbach, Björn Ottersten

In this work, we propose a sensor fusion framework based on a weighted bi-objective optimization for refinement of extrinsic calibration tailored for RGB-D multi-view systems.

3D Reconstruction Sensor Fusion

Inexact Block Coordinate Descent Algorithms for Nonsmooth Nonconvex Optimization

1 code implementation10 May 2019 Yang Yang, Marius Pesavento, Zhi-Quan Luo, Björn Ottersten

Interestingly, when the approximation subproblem is solved by a descent algorithm, convergence of a subsequence to a stationary point is still guaranteed even if the approximation subproblem is solved inexactly by terminating the descent algorithm after a finite number of iterations.

Anomaly Detection Retrieval

Localized Trajectories for 2D and 3D Action Recognition

no code implementations10 Apr 2019 Konstantinos Papadopoulos, Girum Demisse, Enjie Ghorbel, Michel Antunes, Djamila Aouada, Björn Ottersten

The Dense Trajectories concept is one of the most successful approaches in action recognition, suitable for scenarios involving a significant amount of motion.

3D Action Recognition

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

Optimal Multiuser Transmit Beamforming: A Difficult Problem with a Simple Solution Structure

2 code implementations1 Apr 2014 Emil Björnson, Mats Bengtsson, Björn Ottersten

A high signal power is achieved by transmitting the same data signal from all antennas, but with different amplitudes and phases, such that the signal components add coherently at the user.

Information Theory Information Theory

Capacity Limits and Multiplexing Gains of MIMO Channels with Transceiver Impairments

1 code implementation18 Sep 2012 Emil Björnson, Per Zetterberg, Mats Bengtsson, Björn Ottersten

The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas.

Information Theory Information Theory

Receive Combining vs. Multi-Stream Multiplexing in Downlink Systems with Multi-Antenna Users

1 code implementation11 Jul 2012 Emil Björnson, Marios Kountouris, Mats Bengtsson, Björn Ottersten

Analytic results are derived to show how user selection, spatial correlation, heterogeneous user conditions, and imperfect channel acquisition (quantization or estimation errors) affect the performance when sending the maximal number of streams or one stream per scheduled user---the two extremes in data stream allocation.

Information Theory Information Theory

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