Papers | Dr. Evangelos Vlachos

Paper Accepted at ICUAS 2026

Tue, 21 Apr 2026 00:00:00 +0000

We are pleased to announce that our paper has been accepted at the 2026 International Conference on Unmanned Aircraft Systems (ICUAS):

Hardware-Aware SE(3) Control Barrier Functions for Counter-UAS Interceptors with Directed Energy Payloads

Evangelos Vlachos, Panayiotis Kolios, and Christos Skliros

This paper addresses the safety-critical control problem of keeping a directed-energy phased-array payload’s boresight aimed at a target UAS during high-speed interception. We develop SE(3) Control Barrier Functions that enforce a field-of-view constraint on the interceptor’s attitude while respecting the physical limits of the onboard hardware, solved efficiently via ADMM at high update rates.

This work is supported by the EU Horizon Europe project EUSOME (Grant Agreement No. 101187121).

Paper Submitted to IEEE Wireless Communications Letters

Thu, 02 Apr 2026 00:00:00 +0000

We submitted a new paper to IEEE Wireless Communications Letters:

Geometry-Aware Regularization for Deep-Unfolded MIMO-OTFS Detection

Nikolaos Ntavanelos and Evangelos Vlachos

MIMO-OTFS systems suffer from non-uniform scaling across symbol components due to spatial and fractional Doppler–Delay coupling. This work introduces a geometry-aware coordinate-wise regularizer within a deep-unfolded Conjugate Gradient detector to exploit this structure.

Key contributions:

Gram matrix analysis: We prove that all diagonal variation in the MIMO-OTFS Gram matrix arises exclusively from inter-path coupling, analytically characterizing its non-uniform structure.
Deep-unfolded CG detector: A geometry-aware regularizer is embedded directly into the CG linear system, with per-component weights learned in a data-driven manner.
Robust performance: The proposed detector outperforms low-complexity baselines and approaches heavier neural architectures at medium-to-high SNR under both low- and high-mobility scenarios.

Paper Submitted to IEEE Transactions on Wireless Communications

Thu, 05 Mar 2026 00:00:00 +0000

We submitted a new paper to IEEE Transactions on Wireless Communications:

Multi-Functional Diversity via Flexible Spatial Partitioning for Massive MIMO ISAC

Evangelos Vlachos and Aryan Kaushik

In massive MIMO ISAC systems, conventional contiguous sub-array partitioning limits spatial degrees of freedom. This work introduces multi-functional selection diversity — a new gain mechanism that arises from assigning spatial beams to communication and radar based on their long-term channel statistics.

Key contributions:

Scaling laws: We prove that the dominant diversity component — spatial decoupling (leakage avoidance) — scales as log(N) with the array size, while signal alignment saturates.
DASP algorithm: A covariance-only framework that solves the combinatorial beam assignment with O(N log N) complexity, eliminating the need for instantaneous CSI.
Regime analysis: An analytical SNR threshold demarcating when spatial partitioning outperforms orthogonal resource slicing (e.g., TDM). Standard mmWave link budgets fall firmly in the partitioning-favorable regime.

Numerical results with up to 256 antennas confirm that flexible interleaved partitioning nearly doubles the spectral efficiency of resource slicing and strictly dominates contiguous sub-array approaches.

New Paper: Time series framework for modelling optical LEO satellite links

Mon, 01 Dec 2025 00:00:00 +0000

A novel time series approach is developed to accurately model and predict optical links between Low Earth Orbit (LEO) satellites.

New Paper: Design and Evaluation of a Simulation Framework for FMCW Radar Sensors Deployed on UAV Platforms

Mon, 06 Oct 2025 00:00:00 +0000

A novel simulation framework is developed to model and evaluate Frequency Modulated Continuous Wave (FMCW) radar sensors integrated with Unmanned Aerial Vehicle (UAV) platforms.

New Paper: ISAC for AAM: Integrated Sensing and Communication Technology for Advanced Air Mobility

Mon, 06 Oct 2025 00:00:00 +0000

Researchers develop an integrated sensing and communication technology to enhance safety and efficiency in advanced air mobility vehicles.

New Paper: Improving wideband massive mimo channel estimation with uav state-space information

Wed, 01 Oct 2025 00:00:00 +0000

The paper improves massive MIMO channel estimation by leveraging UAV state-space information to mitigate the effects of beam squint and enhance wideband channel accuracy.

New Paper: Biconvex Optimization for Time-Domain Channel Estimation Under Dual-Wideband Fading Conditions

Mon, 08 Sep 2025 00:00:00 +0000

This research develops a biconvex optimization approach to estimate time-domain MIMO channel matrices under dual-wideband fading conditions, addressing beam squint and ISI effects in single-carrier point-to-point systems.

New Paper: Time-domain channel estimation for extremely large MIMO THz communication systems under dual-wideband fading conditions

Mon, 08 Sep 2025 00:00:00 +0000

The paper presents a unified time-domain framework for estimating MIMO channel matrices in extremely large THz systems under dual-wideband fading conditions, mitigating beam squint and inter-symbol interference.

New Paper: Flexible hybrid precoding for integrated sensing and communications

Tue, 01 Jul 2025 00:00:00 +0000

Researchers propose flexible hybrid precoding schemes to optimize joint sensing and communication performance in resource-constrained wireless systems.

New Paper: Receiving RISs: Enabling channel estimation and autonomous configuration

Tue, 01 Jul 2025 00:00:00 +0000

A novel channel estimation protocol enables autonomous configuration of semi-passive Reconfigurable Intelligent Surfaces for receiving pilot signals in multi-antenna systems, leveraging beamspace sparsity and low-rank properties.

New Paper: Enabling Extended Reality Applications over 5G Mobile Networks

Thu, 01 Aug 2024 00:00:00 +0000

The study optimizes 5G network performance to support seamless and immersive extended reality experiences on-the-go.

New Paper: Velocity-aided channel estimation for spatially selective mmWave massive MIMO communications

Mon, 04 Sep 2023 00:00:00 +0000

This study introduces velocity-aided channel estimation for spatially selective mmWave massive MIMO communications, significantly improving channel estimation accuracy by incorporating vehicle velocity information.

New Paper: Covariance-based hybrid beamforming for spectrally efficient joint radar-communications

Sun, 28 May 2023 00:00:00 +0000

This paper develops a covariance-based hybrid beamformer for spectrally efficient joint radar-communications systems, enhancing interference mitigation and spectral efficiency by leveraging fewer RF chains than transmit antennas.

New Paper: Flexible hybrid beamforming for spectrally efficient 6g joint radar-communications

Sun, 28 May 2023 00:00:00 +0000

This research proposes a novel flexible hybrid beamforming scheme for spectrally efficient 6G joint radar-communications, enabling interference mitigation and improved system performance through reduced RF chain usage.

New Paper: Millimeter wave channel estimation for lens based hybrid MIMO with low resolution ADCs

Sun, 28 May 2023 00:00:00 +0000

This paper develops a novel channel estimation method for lens-based hybrid MIMO systems using low-resolution ADCs, significantly improving performance and enabling practical mmWave applications.

New Paper: Subset selection based RIS-aided beamforming for joint radar-communications

Wed, 01 Mar 2023 00:00:00 +0000

This research introduces a novel subset selection-based RIS-aided beamforming approach that maximizes spectral efficiency in joint radar-communications systems, enabling more efficient use of RF resources.

New Paper: Quantum computing-assisted channel estimation for massive MIMO mmWave systems

Mon, 03 Oct 2022 00:00:00 +0000

This research develops quantum computing-assisted channel estimation techniques to significantly improve computational efficiency in massive MIMO mmWave systems.

New Paper: Channel estimation for UAV-based mmwave massive MIMO communications with beam squint

Mon, 29 Aug 2022 00:00:00 +0000

The paper develops a novel channel estimation method for UAV-based mmWave massive MIMO systems with beam squint, improving accuracy by accounting for spatial selectivity in time-varying channels.

New Paper: Regularized Distributed MPC for UAV Networks: Stabilizing Coupled Motion and Hybrid Beam Alignment

Fri, 01 Jul 2022 00:00:00 +0000

Researchers develop a distributed model predictive control approach to stabilize coupled motion and hybrid beam alignment in UAV networks.

New Paper: Optimal mmwave sensor selection for bearing-only localization in smart environments

Tue, 28 Jun 2022 00:00:00 +0000

This research presents a novel optimal sensor selection technique for mmwave-based bearing-only localization in smart environments, improving accuracy and reducing computational complexity.

New Paper: Game-Theoretic Power and Rate Control in IEEE 802.11p Wireless Networks

Thu, 19 May 2022 00:00:00 +0000

Researchers develop game-theoretic algorithms to optimize power and rate control in vehicular networks, improving reliability and efficiency of IEEE 802.11p communication.

New Paper: Admm-based cooperative control for platooning of connected and autonomous vehicles

Mon, 16 May 2022 00:00:00 +0000

This research develops a novel ADMM-based cooperative control framework for platooning of connected autonomous vehicles, enabling efficient and collision-free acceleration adjustments.

New Paper: Green joint radar-communications: RF selection with low resolution DACs and hybrid precoding

Mon, 16 May 2022 00:00:00 +0000

This paper introduces a novel RF chain and DAC bit selection approach for sub-arrayed hybrid MIMO joint radar-communications systems, optimizing energy efficiency while preserving information rate.

New Paper: Towards 6G: Spectrally efficient joint radar and communication with radio frequency selection, interference and hardware impairments

Mon, 25 Apr 2022 00:00:00 +0000

This research contributes to 6G by developing a spectrally efficient joint radar-communication system that selects optimal radio frequencies, mitigates interference and hardware impairments, and achieves higher degrees of freedom.

New Paper: Joint bit allocation and hybrid beamforming optimization for energy efficient millimeter wave MIMO systems

Mon, 01 Mar 2021 00:00:00 +0000

The paper jointly optimizes digital-to-analog converter bit resolutions and hybrid beamforming matrices to achieve energy-efficient millimeter wave MIMO systems, introducing a novel decomposition of the hybrid precoder and combiner.

New Paper: Energy-efficiency maximization of hybrid massive MIMO precoding with random-resolution DACs via RF selection

Mon, 01 Feb 2021 00:00:00 +0000

This research introduces a novel hybrid massive MIMO precoding architecture using random-resolution DACs and RF selection to maximize energy-efficiency while preserving spectral-efficiency.

New Paper: Privacy preservation in industrial IoT via fast adaptive correlation matrix completion

Tue, 01 Dec 2020 00:00:00 +0000

This study develops a fast adaptive method for completing correlation matrices in industrial IoT networks, preserving privacy by adding noise that maximizes uncertainty while maintaining structural information.

New Paper: Radio-frequency chain selection for energy and spectral efficiency maximization in hybrid beamforming under hardware imperfections

Tue, 01 Dec 2020 00:00:00 +0000

Researchers develop an algorithm to optimize radio-frequency chain selection for efficient wireless transmission while minimizing hardware imperfections.

New Paper: Joint localization and channel estimation for UAV-assisted millimeter wave communications

Sun, 01 Nov 2020 00:00:00 +0000

This research develops a novel joint localization and channel estimation framework for UAV-assisted mmWave communications, enabling accurate positioning and MIMO channel coefficient estimation through beam-space representation and matrix completion.

New Paper: Energy efficiency maximization in millimeter wave hybrid MIMO systems for 5G and beyond

Tue, 27 Oct 2020 00:00:00 +0000

A novel energy-efficient beamformer maximizes millimeter wave hybrid MIMO system performance by optimizing DAC resolution and RF chain selection using Dinkelbach method and subset selection optimization.

New Paper: A hardware architecture for reconfigurable intelligent surfaces with minimal active elements for explicit channel estimation

Fri, 01 May 2020 00:00:00 +0000

A novel hardware architecture for reconfigurable intelligent surfaces minimizes active elements while enabling explicit channel estimation, a crucial step towards programmable wireless environments.

New Paper: Wideband channel tracking for millimeter wave massive MIMO systems with hybrid beamforming reception

Fri, 01 May 2020 00:00:00 +0000

A novel matrix-completion-based approach enables efficient wideband channel tracking in millimeter wave massive MIMO systems with hybrid beamforming reception, reducing training periods while maintaining accurate estimation.

New Paper: Dynamic RF chain selection for energy efficient and low complexity hybrid beamforming in millimeter wave MIMO systems

Sun, 01 Dec 2019 00:00:00 +0000

This paper introduces a novel dynamic RF chain selection framework that maximizes energy efficiency and minimizes complexity in millimeter wave MIMO systems through fractional programming and Dinkelbach method-based optimization.

New Paper: Energy efficient ADC bit allocation and hybrid combining for millimeter wave MIMO systems

Sun, 01 Dec 2019 00:00:00 +0000

This research optimizes ADC bit allocation and hybrid combining in millimeter wave MIMO systems, achieving highly energy-efficient solutions through a novel decomposition approach.

New Paper: Wideband MIMO channel estimation for hybrid beamforming millimeter wave systems via random spatial sampling

Sun, 01 Sep 2019 00:00:00 +0000

A novel random spatial sampling approach enables reliable wideband MIMO channel estimation in hybrid beamforming millimeter wave systems, overcoming hardware limitations and short coherence times.

New Paper: Energy efficient transmission of 3D meshes over mmwave-based massive mimo systems