1.
Vallejo, Luis; Mora, Jose; Ortega, Beatriz; Jin, Wei; Romero, Jaime; Tang, Jianming
Full-Duplex Transmissions in Heterogeneous Fiber-FSO-Wireless Converged Access Networks at Ka-Band Proceedings Article
In: 2025 Joint European Conference on Networks and Communications & 6G Summit (EuCNC/6G Summit), pp. 840–845, 2025, ISSN: 2575-4912, (ISSN: 2575-4912).
Abstract | Links | BibTeX | Tags: 5G mobile communication, B5G, bidirectional heterogeneous networks, converged networks, free-running lasers, Full-duplex system, fullduplex, Heterogeneous networks, Millimeter wave communication, mmWave, Phase shift keying, Radio links, Resource management, RF envelope detection, Throughput, Uplink, Wireless communication
@inproceedings{vallejo_full-duplex_2025,
title = {Full-Duplex Transmissions in Heterogeneous Fiber-FSO-Wireless Converged Access Networks at Ka-Band},
author = {Luis Vallejo and Jose Mora and Beatriz Ortega and Wei Jin and Jaime Romero and Jianming Tang},
url = {https://ieeexplore.ieee.org/document/11037218},
doi = {10.1109/EuCNC/6GSummit63408.2025.11037218},
issn = {2575-4912},
year = {2025},
date = {2025-06-01},
urldate = {2025-10-08},
booktitle = {2025 Joint European Conference on Networks and Communications & 6G Summit (EuCNC/6G Summit)},
pages = {840–845},
abstract = {To overcome the challenges associated with increased demands for mobile capacity and network densification in the 5 G and beyond era, this paper experimentally demonstrates full-duplex heterogeneous fiber-FSO-wireless converged links between the central office-baseband unit (CO-BBU) and the remote radio head (RRH). The centralization of active optical sources for the downlink (DL) and uplink (UL) enables dynamic resource sharing and allocation, optimizing wavelength utilization and improving overall network efficiency. The DL uses a directly modulated laser (DML) with free-running laser-assisted mmWave signal generation and envelope detection for the downstream, transmitting a 100 textbackslashtextMHz 16-textbackslashtextQAM signal at 39 GHz. The UL reuses the DL wavelength for upstream transmission, employing intensity modulation and direct detection (IM-DD) of a 100 MHz QPSK signal at 36.5 GHz. The bidirectional heterogeneous network comprises a 10 km SSMF, a 1.8 m FSO link, and a 3 m wireless radio link, providing flexibility for future networks. The results show successful transmissions of 16-QAM and QPSK signals up to 200 textbackslashtextMbit / textbackslashmathrms and 400 textbackslashtextMbit / textbackslashmathrms for DL and UL, respectively, under the full-duplex transmissions. Additionally, using 5G NR OFDM signals, a maximum bit rate of 2.15 textbackslashtextGbit / textbackslashmathrms and 1.07 Gbit/s is achieved for the DL and UL, respectively, demonstrating the cost-effectiveness of the proposed solution.},
note = {ISSN: 2575-4912},
keywords = {5G mobile communication, B5G, bidirectional heterogeneous networks, converged networks, free-running lasers, Full-duplex system, fullduplex, Heterogeneous networks, Millimeter wave communication, mmWave, Phase shift keying, Radio links, Resource management, RF envelope detection, Throughput, Uplink, Wireless communication},
pubstate = {published},
tppubtype = {inproceedings}
}
To overcome the challenges associated with increased demands for mobile capacity and network densification in the 5 G and beyond era, this paper experimentally demonstrates full-duplex heterogeneous fiber-FSO-wireless converged links between the central office-baseband unit (CO-BBU) and the remote radio head (RRH). The centralization of active optical sources for the downlink (DL) and uplink (UL) enables dynamic resource sharing and allocation, optimizing wavelength utilization and improving overall network efficiency. The DL uses a directly modulated laser (DML) with free-running laser-assisted mmWave signal generation and envelope detection for the downstream, transmitting a 100 textbackslashtextMHz 16-textbackslashtextQAM signal at 39 GHz. The UL reuses the DL wavelength for upstream transmission, employing intensity modulation and direct detection (IM-DD) of a 100 MHz QPSK signal at 36.5 GHz. The bidirectional heterogeneous network comprises a 10 km SSMF, a 1.8 m FSO link, and a 3 m wireless radio link, providing flexibility for future networks. The results show successful transmissions of 16-QAM and QPSK signals up to 200 textbackslashtextMbit / textbackslashmathrms and 400 textbackslashtextMbit / textbackslashmathrms for DL and UL, respectively, under the full-duplex transmissions. Additionally, using 5G NR OFDM signals, a maximum bit rate of 2.15 textbackslashtextGbit / textbackslashmathrms and 1.07 Gbit/s is achieved for the DL and UL, respectively, demonstrating the cost-effectiveness of the proposed solution.
2.
Nafees, Muhammad; Baniasadi, Mohammadamin; Hopgood, James R.; Safari, Majid; Thompson, John S.
Integrated Sensing and Communication for UAV Trajectory Optimization in Mixed FSO-RF Networks in Dynamic Weather Conditions Proceedings Article
In: 2025 IEEE Wireless Communications and Networking Conference (WCNC), pp. 1–6, 2025, ISSN: 1558-2612, (ISSN: 1558-2612).
Abstract | Links | BibTeX | Tags: 6G mobile communication, Autonomous aerial vehicles, Backhaul networks, free-space optical (FSO), Integrated sensing and communication, Meteorology, millimeter wave (mmWave), Millimeter wave communication, Optical attenuators, Optical feedback, Optical integrated sensing and communication (O-ISAC), Optical sensors, Sixth-generation (6G), Throughput, unmanned aerial vehicles (UAVs)
@inproceedings{nafees_integrated_2025,
title = {Integrated Sensing and Communication for UAV Trajectory Optimization in Mixed FSO-RF Networks in Dynamic Weather Conditions},
author = {Muhammad Nafees and Mohammadamin Baniasadi and James R. Hopgood and Majid Safari and John S. Thompson},
url = {https://ieeexplore.ieee.org/document/10978163},
doi = {10.1109/WCNC61545.2025.10978163},
issn = {1558-2612},
year = {2025},
date = {2025-03-01},
urldate = {2025-10-08},
booktitle = {2025 IEEE Wireless Communications and Networking Conference (WCNC)},
pages = {1–6},
abstract = {Integrated sensing and communication (ISAC) is expected to transform data transmission and real-time sensing, enhancing sixth-generation (6G) networks. Free-space optical (FSO) communication is a key 6G backhaul solution, complementing radio frequency (RF) technologies like millimeter wave (mmWave) for improved network reliability. However, adverse weather can significantly reduce FSO link reliability due to atmospheric attenuation. Such adverse weather conditions also increase the level of back-scattered light, potentially enabling the real-time sensing of the atmospheric channel gain at the transmitter side. Therefore, this paper proposes a novel optical ISAC (O-ISAC) framework, where the back-scattered light from the FSO communication signal is used as the sensing feedback signal. This O-ISAC framework is analyzed considering a single-cell network aided by an unmanned aerial vehicle (UAV) to support edge users. The UAV is connected to the gateway via a FSO backhaul link while estimating the FSO channel gain based on the back-scattered light and dynamically optimizing its trajectory. The aim of this adaptive O-ISAC system is to maximize the end-to-end network throughput of the edge users while considering FSO backhaul capacity and the UAV's directional antenna beamwidth and bandwidth allocation. Numerical results demonstrate that UAV can effectively optimize its trajectory by adjusting the antenna beamwidth and downlink bandwidth allocation at different weather conditions. The proposed framework is tested using hourly visibility data from Edinburgh, demonstrating that optical channel sensing is crucial for the system's overall performance.},
note = {ISSN: 1558-2612},
keywords = {6G mobile communication, Autonomous aerial vehicles, Backhaul networks, free-space optical (FSO), Integrated sensing and communication, Meteorology, millimeter wave (mmWave), Millimeter wave communication, Optical attenuators, Optical feedback, Optical integrated sensing and communication (O-ISAC), Optical sensors, Sixth-generation (6G), Throughput, unmanned aerial vehicles (UAVs)},
pubstate = {published},
tppubtype = {inproceedings}
}
Integrated sensing and communication (ISAC) is expected to transform data transmission and real-time sensing, enhancing sixth-generation (6G) networks. Free-space optical (FSO) communication is a key 6G backhaul solution, complementing radio frequency (RF) technologies like millimeter wave (mmWave) for improved network reliability. However, adverse weather can significantly reduce FSO link reliability due to atmospheric attenuation. Such adverse weather conditions also increase the level of back-scattered light, potentially enabling the real-time sensing of the atmospheric channel gain at the transmitter side. Therefore, this paper proposes a novel optical ISAC (O-ISAC) framework, where the back-scattered light from the FSO communication signal is used as the sensing feedback signal. This O-ISAC framework is analyzed considering a single-cell network aided by an unmanned aerial vehicle (UAV) to support edge users. The UAV is connected to the gateway via a FSO backhaul link while estimating the FSO channel gain based on the back-scattered light and dynamically optimizing its trajectory. The aim of this adaptive O-ISAC system is to maximize the end-to-end network throughput of the edge users while considering FSO backhaul capacity and the UAV's directional antenna beamwidth and bandwidth allocation. Numerical results demonstrate that UAV can effectively optimize its trajectory by adjusting the antenna beamwidth and downlink bandwidth allocation at different weather conditions. The proposed framework is tested using hourly visibility data from Edinburgh, demonstrating that optical channel sensing is crucial for the system's overall performance.
3.
Nguyen, Doan Hieu; Nguyen, Xuan Tung; Jeong, Seon-Geun; Chien, Trinh Van; Hanzo, Lajos; Hwang, Won-Joo
Hybrid Quantum Convolutional Neural Network-Aided Pilot Assignment in Cell-Free Massive MIMO Systems Journal Article
In: IEEE Transactions on Vehicular Technology, pp. 1–6, 2025, ISSN: 1939-9359.
Abstract | Links | BibTeX | Tags: Cell-free massive MIMO, Convergence, Convolutional neural networks, Integrated circuit modeling, Massive MIMO, Pilot Allocation, Quantum circuit, Quantum Machine Learning, Quantum state, Qubit, Throughput, Training, Vectors
@article{nguyen_hybrid_2025,
title = {Hybrid Quantum Convolutional Neural Network-Aided Pilot Assignment in Cell-Free Massive MIMO Systems},
author = {Doan Hieu Nguyen and Xuan Tung Nguyen and Seon-Geun Jeong and Trinh Van Chien and Lajos Hanzo and Won-Joo Hwang},
url = {https://ieeexplore.ieee.org/document/11091511},
doi = {10.1109/TVT.2025.3588212},
issn = {1939-9359},
year = {2025},
date = {2025-01-01},
urldate = {2025-10-08},
journal = {IEEE Transactions on Vehicular Technology},
pages = {1–6},
abstract = {A sophisticated hybrid quantum convolutional neural network (HQCNN) is conceived for handling the pilot assignment task in cell-free massive MIMO systems, while maximizing the total ergodic sum throughput. The existing model-based solutions found in the literature are inefficient and/or computationally demanding. Similarly, conventional deep neural networks may struggle in the face of high-dimensional inputs, require complex architectures, and their convergence is slow due to training numerous hyperparameters. The proposed HQCNN leverages parameterized quantum circuits (PQCs) relying on superposition for enhanced feature extraction. Specifically, we exploit the same PQC across all the convolutional layers for customizing the neural network and for accelerating the convergence. Our numerical results demonstrate that the proposed HQCNN offers a total network throughput close to that of the excessive-complexity exhaustive search and outperforms the state-of-the-art benchmarks.},
keywords = {Cell-free massive MIMO, Convergence, Convolutional neural networks, Integrated circuit modeling, Massive MIMO, Pilot Allocation, Quantum circuit, Quantum Machine Learning, Quantum state, Qubit, Throughput, Training, Vectors},
pubstate = {published},
tppubtype = {article}
}
A sophisticated hybrid quantum convolutional neural network (HQCNN) is conceived for handling the pilot assignment task in cell-free massive MIMO systems, while maximizing the total ergodic sum throughput. The existing model-based solutions found in the literature are inefficient and/or computationally demanding. Similarly, conventional deep neural networks may struggle in the face of high-dimensional inputs, require complex architectures, and their convergence is slow due to training numerous hyperparameters. The proposed HQCNN leverages parameterized quantum circuits (PQCs) relying on superposition for enhanced feature extraction. Specifically, we exploit the same PQC across all the convolutional layers for customizing the neural network and for accelerating the convergence. Our numerical results demonstrate that the proposed HQCNN offers a total network throughput close to that of the excessive-complexity exhaustive search and outperforms the state-of-the-art benchmarks.
4.
Goay, Amus Chee Yuen; Mishra, Deepak; Matthaiou, Michail; Seneviratne, Aruna
Range Maximization by Optimizing Tag-to-Tag Cooperative Backscatter Communication Journal Article
In: IEEE Transactions on Green Communications and Networking, pp. 1–1, 2025, ISSN: 2473-2400.
Abstract | Links | BibTeX | Tags: Backscatter, Backscatter communication, cooperation, green communication, Internet of Things, Protocols, Quality of service, range maximization, Reflection coefficient, Relays, Resource management, tag-to-tag network, Throughput, time allocation, Wireless communication, Wireless sensor networks
@article{goay_range_2025,
title = {Range Maximization by Optimizing Tag-to-Tag Cooperative Backscatter Communication},
author = {Amus Chee Yuen Goay and Deepak Mishra and Michail Matthaiou and Aruna Seneviratne},
url = {https://ieeexplore.ieee.org/document/11008574},
doi = {10.1109/TGCN.2025.3570568},
issn = {2473-2400},
year = {2025},
date = {2025-01-01},
urldate = {2025-10-08},
journal = {IEEE Transactions on Green Communications and Networking},
pages = {1–1},
abstract = {Backscatter communication (BackCom) is a wireless technology that transmits information wirelessly by modulating the reflection of an incident signal, offering the advantages of low power consumption and low cost. This paper introduces a novel cooperative timing protocol in a two-tag BackCom network, where a single reader communicates with two passive backscatter tags using a cooperative scheme. These tags encode their information by modulating the backscattered signal and then transmitting it back to the reader. In the considered tag-to-tag cooperative scheme, the tag closer to the reader assists the farther tag in relaying its information, effectively mitigating the doubly near-far problem commonly experienced in BackCom systems. The primary objective is to maximize the transmission range of the farther tag by jointly optimizing the proposed time allocation scheme and reflection coefficients while meeting the spectral efficiency and energy threshold constraints for the quality of service and sustainability requirements. This article formulates a non-convex optimization problem and proposes a solution methodology that efficiently approximates the optimized solution with low complexity. Numerical simulations are presented to analyze the effects of varying energy and spectral efficiency requirements on the maximized transmission range. The results demonstrate that the proposed tag-to-tag cooperative BackCom framework provides a significant performance improvement, with an average range gain of over 30% compared to the non-cooperative scheme.},
keywords = {Backscatter, Backscatter communication, cooperation, green communication, Internet of Things, Protocols, Quality of service, range maximization, Reflection coefficient, Relays, Resource management, tag-to-tag network, Throughput, time allocation, Wireless communication, Wireless sensor networks},
pubstate = {published},
tppubtype = {article}
}
Backscatter communication (BackCom) is a wireless technology that transmits information wirelessly by modulating the reflection of an incident signal, offering the advantages of low power consumption and low cost. This paper introduces a novel cooperative timing protocol in a two-tag BackCom network, where a single reader communicates with two passive backscatter tags using a cooperative scheme. These tags encode their information by modulating the backscattered signal and then transmitting it back to the reader. In the considered tag-to-tag cooperative scheme, the tag closer to the reader assists the farther tag in relaying its information, effectively mitigating the doubly near-far problem commonly experienced in BackCom systems. The primary objective is to maximize the transmission range of the farther tag by jointly optimizing the proposed time allocation scheme and reflection coefficients while meeting the spectral efficiency and energy threshold constraints for the quality of service and sustainability requirements. This article formulates a non-convex optimization problem and proposes a solution methodology that efficiently approximates the optimized solution with low complexity. Numerical simulations are presented to analyze the effects of varying energy and spectral efficiency requirements on the maximized transmission range. The results demonstrate that the proposed tag-to-tag cooperative BackCom framework provides a significant performance improvement, with an average range gain of over 30% compared to the non-cooperative scheme.
5.
Li, Qingchao; El-Hajjar, Mohammed; Cao, Kaijun; Xu, Chao; Haas, Harald; Hanzo, Lajos
Holographic Metasurface-Based Beamforming for Multi-Altitude LEO Satellite Networks Journal Article
In: IEEE Transactions on Wireless Communications, pp. 1–1, 2025, ISSN: 1558-2248, (arXiv:2501.04164 [cs]).
Abstract | Links | BibTeX | Tags: Array signal processing, Computer architecture, Downlink, holographic metasurface, hybrid beamforming, inter-satellite interference, Low Earth Orbit (LEO) satellite communication, Low earth orbit satellites, Metasurfaces, Precoding, Satellite broadcasting, Satellite communications, Satellites, stochastic geometry, Throughput
@article{li_holographic_2025,
title = {Holographic Metasurface-Based Beamforming for Multi-Altitude LEO Satellite Networks},
author = {Qingchao Li and Mohammed El-Hajjar and Kaijun Cao and Chao Xu and Harald Haas and Lajos Hanzo},
url = {https://ieeexplore.ieee.org/abstract/document/10844052/?casa_token=5kb4rgy_qqAAAAAA:Qy4zV9IQ3FSfC6Cy7it5EvcxjQM2a675RSsbRiRKNPsADHjWFXZ0VHem5zJ_dVf5IBDhE6R2sg},
doi = {10.1109/TWC.2025.3527962},
issn = {1558-2248},
year = {2025},
date = {2025-01-01},
urldate = {2025-02-24},
journal = {IEEE Transactions on Wireless Communications},
pages = {1–1},
publisher = {arXiv},
abstract = {Low Earth Orbit (LEO) satellite networks are capable of improving the global Internet service coverage. In this context, we propose a hybrid beamforming design for holographic metasurface based terrestrial users in multi-altitude LEO satellite networks. Firstly, the holographic beamformer is optimized by maximizing the downlink channel gain from the serving satellite to the terrestrial user. Then, the digital beamformer is designed by conceiving a minimum mean square error (MMSE) based detection algorithm for mitigating the interference arriving from other satellites. To dispense with excessive overhead of full channel state information (CSI) acquisition of all satellites, we propose a low-complexity MMSE beamforming algorithm that only relies on the distribution of the LEO satellite constellation harnessing stochastic geometry, which can achieve comparable throughput to that of the algorithm based on the full CSI in the case of a dense LEO satellite deployment. Furthermore, it outperforms the maximum ratio combining (MRC) algorithm, thanks to its inter-satellite interference mitigation capacity. The simulation results show that our proposed holographic metasurface based hybrid beamforming architecture is capable of outperforming the state-of-the-art antenna array architecture in terms of its throughput, given the same physical size of the transceivers. Moreover, we demonstrate that the beamforming performance attained can be substantially improved by taking into account the mutual coupling effect, imposed by the dense placement of the holographic metasurface elements.},
note = {arXiv:2501.04164 [cs]},
keywords = {Array signal processing, Computer architecture, Downlink, holographic metasurface, hybrid beamforming, inter-satellite interference, Low Earth Orbit (LEO) satellite communication, Low earth orbit satellites, Metasurfaces, Precoding, Satellite broadcasting, Satellite communications, Satellites, stochastic geometry, Throughput},
pubstate = {published},
tppubtype = {article}
}
Low Earth Orbit (LEO) satellite networks are capable of improving the global Internet service coverage. In this context, we propose a hybrid beamforming design for holographic metasurface based terrestrial users in multi-altitude LEO satellite networks. Firstly, the holographic beamformer is optimized by maximizing the downlink channel gain from the serving satellite to the terrestrial user. Then, the digital beamformer is designed by conceiving a minimum mean square error (MMSE) based detection algorithm for mitigating the interference arriving from other satellites. To dispense with excessive overhead of full channel state information (CSI) acquisition of all satellites, we propose a low-complexity MMSE beamforming algorithm that only relies on the distribution of the LEO satellite constellation harnessing stochastic geometry, which can achieve comparable throughput to that of the algorithm based on the full CSI in the case of a dense LEO satellite deployment. Furthermore, it outperforms the maximum ratio combining (MRC) algorithm, thanks to its inter-satellite interference mitigation capacity. The simulation results show that our proposed holographic metasurface based hybrid beamforming architecture is capable of outperforming the state-of-the-art antenna array architecture in terms of its throughput, given the same physical size of the transceivers. Moreover, we demonstrate that the beamforming performance attained can be substantially improved by taking into account the mutual coupling effect, imposed by the dense placement of the holographic metasurface elements.