1.
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.
2.
Zhang, Chao; Li, Qingchao; Xu, Chao; Yang, Lie-Liang; Hanzo, Lajos
Space-Air-Ground Integrated Networks: Their Channel Model and Performance Analysis Journal Article
In: IEEE Open Journal of Vehicular Technology, vol. 6, pp. 1501–1523, 2025, ISSN: 2644-1330.
Abstract | Links | BibTeX | Tags: Absorption, Atmospheric modeling, Attenuation, Bending, Channel model, Channel models, Doppler effect, Earth, Fading channels, goodput, Meteorology, Performance analysis, Rician channels, Space-air-ground integrated networks
@article{zhang_space-air-ground_2025,
title = {Space-Air-Ground Integrated Networks: Their Channel Model and Performance Analysis},
author = {Chao Zhang and Qingchao Li and Chao Xu and Lie-Liang Yang and Lajos Hanzo},
url = {https://ieeexplore.ieee.org/document/11018358},
doi = {10.1109/OJVT.2025.3575360},
issn = {2644-1330},
year = {2025},
date = {2025-01-01},
urldate = {2025-10-08},
journal = {IEEE Open Journal of Vehicular Technology},
volume = {6},
pages = {1501–1523},
abstract = {Given their extensive geographic coverage, low Earth orbit (LEO) satellites are envisioned to find their way into next-generation (6G) wireless communications. This paper explores space-air-ground integrated networks (SAGINs) leveraging LEOs to support terrestrial and non-terrestrial users. We first propose a practical satellite-ground channel model that incorporates five key aspects: 1) the small-scale fading characterized by the Shadowed-Rician distribution in terms of the Rician factor K, 2) the path loss effect of bending rays due to atmospheric refraction, 3) the molecular absorption modelled by the Beer-Lambert law, 4) the Doppler effects including the Earth's rotation, and 5) the impact of weather conditions according to the International Telecommunication Union Recommendations (ITU-R). Harnessing the proposed model, we analyze the long-term performance of the SAGIN considered. Explicitly, the closed-form expressions of both the outage probability and of the ergodic rates are derived. Additionally, the upper bounds of bit-error rates and of the Goodput are investigated. The numerical results yield the following insights: 1) The shadowing effect and the ratio between the line-of-sight and scattering components can be conveniently modelled by the factors of K and m in the proposed Shadowed-Rician small-scale fading model. 2) The atmospheric refraction has a modest effect on the path loss. 3) When calculating the transmission distance of waves, Earth's curvature and its geometric relationship with the satellites must be considered, particularly at small elevation angles. 3) High-frequency carriers suffer from substantial path loss, and 4) the Goodput metric is eminently suitable for characterizing the performance of different coding as well as modulation methods and of the estimation error of the Doppler effects.},
keywords = {Absorption, Atmospheric modeling, Attenuation, Bending, Channel model, Channel models, Doppler effect, Earth, Fading channels, goodput, Meteorology, Performance analysis, Rician channels, Space-air-ground integrated networks},
pubstate = {published},
tppubtype = {article}
}
Given their extensive geographic coverage, low Earth orbit (LEO) satellites are envisioned to find their way into next-generation (6G) wireless communications. This paper explores space-air-ground integrated networks (SAGINs) leveraging LEOs to support terrestrial and non-terrestrial users. We first propose a practical satellite-ground channel model that incorporates five key aspects: 1) the small-scale fading characterized by the Shadowed-Rician distribution in terms of the Rician factor K, 2) the path loss effect of bending rays due to atmospheric refraction, 3) the molecular absorption modelled by the Beer-Lambert law, 4) the Doppler effects including the Earth's rotation, and 5) the impact of weather conditions according to the International Telecommunication Union Recommendations (ITU-R). Harnessing the proposed model, we analyze the long-term performance of the SAGIN considered. Explicitly, the closed-form expressions of both the outage probability and of the ergodic rates are derived. Additionally, the upper bounds of bit-error rates and of the Goodput are investigated. The numerical results yield the following insights: 1) The shadowing effect and the ratio between the line-of-sight and scattering components can be conveniently modelled by the factors of K and m in the proposed Shadowed-Rician small-scale fading model. 2) The atmospheric refraction has a modest effect on the path loss. 3) When calculating the transmission distance of waves, Earth's curvature and its geometric relationship with the satellites must be considered, particularly at small elevation angles. 3) High-frequency carriers suffer from substantial path loss, and 4) the Goodput metric is eminently suitable for characterizing the performance of different coding as well as modulation methods and of the estimation error of the Doppler effects.