@misc{kazemi_real-time_2025,

title = {Real-Time Transmission of Uncompressed High-Definition Video Via A VCSEL-Based Optical Wireless Link With Ultra-Low Latency},

author = {Hossein Kazemi and Isaac N. O. Osahon and Tiankuo Jiao and David Butler and Nikolay Ledentsov and Ilya Titkov and Harald Haas},

url = {https://arxiv.org/abs/2507.23746},

doi = {10.48550/ARXIV.2507.23746},

year  = {2025},

date = {2025-01-01},

urldate = {2026-02-03},

publisher = {arXiv},

abstract = {Real-time transmission of high-resolution video signals in an uncompressed and unencrypted format requires an ultra-reliable and low-latency communications (URLLC) medium with high bandwidth to maintain the quality of experience (QoE) for users. We put forward the design and experimental demonstration of a high-performance laser-based optical wireless communication (OWC) system that enables high-definition (HD) video transmission with submillisecond latencies. The serial digital interface (SDI) output of a camera is used to transmit the live video stream over an optical wireless link by directly modulating the SDI signal on the intensity of a 940 nm vertical cavity surface emitting laser (VCSEL). The proposed SDI over light fidelity (LiFi) system corroborates error-free transmission of full HD (FHD) and 4K ultra-high-definition (UHD) resolutions at data rates of 2.97 Gb/s and 5.94 Gb/s, respectively, with a measured end-to-end latency of under 35 ns. Since SDI standards support various video formats and VCSELs are high-bandwidth and low-power devices, this presents a scalable and inexpensive solution for wireless connectivity between professional broadcast equipment using off-the-shelf SDI components.},

keywords = {electronic engineering, FOS: Electrical engineering, information engineering, LRDC, Signal Processing (eess.SP)},

pubstate = {published},

tppubtype = {misc}

}

@misc{safi_energy-efficient_2025,

title = {Energy-Efficient Precoding for Dense VCSEL-Based OWC Systems Under a Cooperative Broadcast Model},

author = {Hossein Safi and Asim Ihsan and Hossien B. Eldeeb and Bastien Bechadergue and Iman Tavakkolnia and Harald Haas},

url = {https://arxiv.org/abs/2508.18871},

doi = {10.48550/ARXIV.2508.18871},

year  = {2025},

date = {2025-01-01},

urldate = {2026-02-03},

publisher = {arXiv},

abstract = {As 6G and beyond aim for sustainable, high-capacity wireless connectivity, optical wireless communication (OWC) has emerged as a compelling solution.Recent advances in vertical-cavity surface-emitting laser (VCSEL) arrays have significantly enhanced OWC performance, enabling high-speed, low-power data transmission. However, dense VCSEL deployments introduce challenges related to interference and energy efficiency (EE). This paper proposes a scalable precoding framework for EE maximization in fully cooperative VCSEL-based OWC broadcast systems. We formulate a non-convex optimization problem to design the precoding matrix under practical optical constraints while guaranteeing minimum user rates. To solve this, we apply Dinkelbach's method to handle the fractional objective and the inner approximation technique to iteratively convexify and solve the problem. Simulation results show that our approach consistently outperforms regularized zero-forcing in terms of EE, particularly in large-scale deployments, demonstrating its potential for next-generation sustainable dense OWC networks.},

keywords = {FOS: Physical sciences, LRDC, Optics (physics.optics)},

pubstate = {published},

tppubtype = {misc}

}

@misc{younus_multi-segment_2025,

title = {Multi-Segment Photonic Power Converters for Energy Harvesting and High-Speed Optical Wireless Communication},

author = {Othman Younus and Behnaz Majlesein and Richard Nacke and Isaac N. O. Osahon and Carmine Pellegrino and Sina Babadi and Iman Tavakkolnia and Henning Helmers and Harald Haas},

url = {https://arxiv.org/abs/2510.06205},

doi = {10.48550/ARXIV.2510.06205},

year  = {2025},

date = {2025-01-01},

urldate = {2026-02-03},

publisher = {arXiv},

abstract = {The demand for energy-efficient high-speed wireless communication, coupled with the rapid rise of IoT devices, requires systems that integrate power harvesting with optical data reception to eliminate the need for charging or battery replacements. Recent advances have explored the use of solar cells as optical receivers for high-speed data detection alongside power harvesting. textbackslashacsGaAs-based textbackslashacpPPC provide six times greater electron mobility than silicon- or cadmium telluride-based cells, enabling faster data detection and improved power efficiency. However, their bandwidth is constrained by junction capacitance, which increases with active area, creating a trade-off between power output and data rate. To address this, we propose and test multi-segment textbackslashacsGaAs-based textbackslashAcpPPC that serve as both energy harvesters and data detectors. By segmenting the active area into 2, 4, or 6 subcells, forming circular areas with diameters of 1, 1.5, or 2.08textasciitildemm, we reduce capacitance and boost bandwidth while preserving light collection. Fabricated on a semi-insulating textbackslashacGaAs substrate with etched trenches for electrical isolation, the series-connected subcells optimize absorption and minimize parasitic effects. The textbackslashAcpPPC were used for an eye-safe 1.5textasciitildem optical wireless link, employing textbackslashacOFDM with adaptive bit and power loading. The system achieved a world record data rate of 3.8textasciitildeGbps, which is four times higher than prior works. The system converts 39.7textbackslash% of optical power from a beam of 2.3textasciitildemW, although the segmentation increases the sensitivity of the alignment. These findings provide new solutions for off-grid backhaul for future communication networks, such as 6th generation (6G) cellular.},

keywords = {electronic engineering, FOS: Electrical engineering, information engineering, LRDC, Signal Processing (eess.SP), Systems and Control (eess.SY)},

pubstate = {published},

tppubtype = {misc}

}

@misc{liu_comprehensive_2025,

title = {A Comprehensive Comparison between Terahertz and Optical Wireless Communications},

author = {Mingqing Liu and Hossein Kazemi and Majid Safari and Iman Tavakkolnia and Harald Haas},

url = {https://arxiv.org/abs/2503.23010},

doi = {10.48550/ARXIV.2503.23010},

year  = {2025},

date = {2025-01-01},

urldate = {2026-02-03},

publisher = {arXiv},

abstract = {This paper presents a comprehensive quantitative comparison between Terahertz (THz) communication (TeraCom) and optical wireless communication (OWC) technologies, focusing on both indoor and outdoor environments. We propose a comparison method for TeraCom and vertical-cavity surface-emitting laser (VCSEL)-based OWC in indoor scenarios, incorporating misalignment effects by modeling the THz antenna radiation pattern within a multi-ray THz channel model and using a Gaussian beam model for VCSEL-based OWC. Unified beamwidth parameters allow for a detailed analysis of misalignment impact on both systems. Furthermore, we develop power consumption models for each technology, integrating key parameters such as THz phase noise, VCSEL non-linearities, and photodetector bandwidth-area tradeoffs. These models enable an in-depth analysis of energy efficiency in indoor environments, including multi-transmitter coverage scenarios. For outdoor scenarios, we summarize existing stochastic channel models addressing path loss, pointing errors, and small-scale fading for free space optics (FSO) and THz links. We then apply these models to unmanned aerial vehicle (UAV) applications to assess performance in dynamic conditions. Our results provide critical insights into the suitability of each technology for various deployment scenarios.},

keywords = {electronic engineering, FOS: Electrical engineering, information engineering, LRDC, Signal Processing (eess.SP)},

pubstate = {published},

tppubtype = {misc}

}

@misc{dabiri_mrr-based_2025,

title = {MRR-Based Line-Laser Scanning for Reliable Vehicular Positioning and Optical Communication},

author = {Mohammad Taghi Dabiri and Hossein Safi and Rula Ammuri and Mazen Hasna and Khalid Qaraqe and Harald Haas and Iman Tavakkolnia},

url = {https://arxiv.org/abs/2512.12186},

doi = {10.48550/ARXIV.2512.12186},

year  = {2025},

date = {2025-01-01},

urldate = {2026-06-03},

publisher = {arXiv},

abstract = {High-speed vehicular environments require optical systems capable of joint sensing, positioning, and communication (JSPC) without mechanical tracking. Existing optical and integrated sensing-communication approaches often rely on point-source emitters or camera-based receivers, limiting spatial coverage and update rate under highway dynamics. This work introduces a new class of tracking-free optical JSPC systems that combine structured line-laser illumination with modulating retroreflector (MRR) arrays on vehicles. Two orthogonal line lasers perform synchronized longitudinal and transverse scanning to provide continuous, wide-area coverage across the roadway. A coverage-driven analytical framework models the coupling between beam divergence, scan geometry, and dwell-time allocation, enabling joint evaluation of sensing reliability and communication quality. An optimization scheme is developed to adapt scanning and divergence parameters for uniform coverage and power efficiency. Simulation results demonstrate significant improvements in spatial coverage uniformity, link stability, and reliability within a fixed scan period. These results establish a practical pathway toward scalable, turbulence-resilient optical architectures for next-generation vehicular JSPC networks.},

keywords = {electronic engineering, FOS: Electrical engineering, information engineering, LRDC, Signal Processing (eess.SP)},

pubstate = {published},

tppubtype = {misc}

}

@misc{safi_optimizing_2024,

title = {Optimizing Spatial Acquisition in Inter-Satellite FSO Links Under Beam jitter},

author = {Hossein Safi and Asim Ihsan and Iman Tavakkolnia and Harald Haas},

url = {https://www.repository.cam.ac.uk/handle/1810/374012},

doi = {10.17863/CAM.112232},

year  = {2024},

date = {2024-12-01},

urldate = {2024-10-30},

publisher = {Apollo - University of Cambridge Repository},

abstract = {The acquisition system is a key element in intersatellite free-space optics (FSO) links. Because satellite vibrations cause the scanning beam to jitter, making the acquisition process both challenging and time-consuming, minimizing acquisition time is crucial for the rapid establishment of an FSO link. In this paper, we present an optimization framework aimed at minimizing acquisition time while maintaining a predefined failure probability threshold. The optimization problem considers the total available power, the amount of overlap between the scanning beams (overlapping factor), and the beamwidth of the scanning beam. Additionally, we incorporate a weighting parameter to account for the varying power costs associated with adjusting the beamwidth and the overlapping factor. To solve this non-convex and NP-hard problem, we utilize an iterative successive convex approximation-based algorithm. When the cost of increasing laser power is high, the results show that as jitter variance increases, the optimal overlapping factor must also increase to maintain the acquisition success probability. Simultaneously, the beamwidth slightly decreases to adhere to power constraints. On the other hand, when the cost for increasing laser power is low, the optimal strategy involves maximizing the beamwidth and increasing the overlapping factor to mitigate jitter effects.},

keywords = {Free-space optics (FSO), LRDC},

pubstate = {published},

tppubtype = {misc}

}

@misc{liu_energy_2024,

title = {Energy Efficiency Comparison of THz and VCSEL-Based OWC for 6G},

author = {Mingqing Liu and Hossein Kazemi and Majid Safari and Iman Tavakkolnia and Harald Haas},

url = {https://www.repository.cam.ac.uk/handle/1810/375123},

doi = {10.17863/CAM.112916},

year  = {2024},

date = {2024-10-01},

urldate = {2024-10-30},

publisher = {Apollo - University of Cambridge Repository},

abstract = {Both optical wireless communications (OWC) and Terahertz (THz) communication systems are regarded as enablers for the 6th-generation (6G) networks. Facing the 6G requirements of ultra-dense and high-rate networks, vertical-cavity surface-emitting laser (VCSEL)-based OWC is considered as a strong contender for providing high data rates with ultra-small cells. Hence, this work quantitatively compares VCSEL-based OWC and THz communication in terms of energy efficiency. We derive the energy efficiency model for realistic systems by including non-linearity power conversion of VCSEL and area-bandwidth tradeoff of the photodiode (PD) for OWC, and gain and power loss in cascaded THz systems, respectively. Then, we formulate the similarity of embedding optical lenses into VCSEL-based system and high-directivity antenna into THz system to achieve high channel gain, i.e., leading to a gain-coverage tradeoff for both systems. Taking account of this performance tradeoff in analyzing two systems' energy efficiency, we show numerically the superiority of the VCSEL-based system, while the THz system is more robust in long-range scenarios due to a more relaxed relationship between pointing error and transmission distances. This study provides design guidelines for selecting appropriate technologies tailored to various 6G application scenarios from an energy efficiency perspective.},

keywords = {6G, Energy Efficiency, LRDC, Optical wireless communication, Vertical cavity surface emitting lasers},

pubstate = {published},

tppubtype = {misc}

}

@misc{yuri_leveraging_2024,

title = {Leveraging Time-domain Fingerprinting for Joint LiFi Position and Orientation Estimation},

author = {Jeon Yuri and Basu Amlan and Iman Tavakkolnia and Harald Haas},

url = {https://www.repository.cam.ac.uk/handle/1810/375328},

doi = {10.17863/CAM.113042},

year  = {2024},

date = {2024-10-01},

urldate = {2024-10-30},

publisher = {Apollo - University of Cambridge Repository},

abstract = {To support performance requirements for smart services in 6G, user positioning is a crucial component. Indoor user position and orientation estimation based on Light Fidelity (LiFi) system is considered as a promising technology, due to its high precision, along with its ease of installation. The main bottleneck of user position and orientation estimation in LiFi is a non-linearity between the metrics, such as the received signal strength (RSS), position and orientation. A deep learning-based estimation methodology holds promise for addressing this issue, because it can learn complex propagation features dependent on user position and orientation. To fully capitalize on this advantage in the time-domain, we propose utilizing both time-series RSS and its received time, i.e. time-of-arrival (ToA) fingerprints, along with a novel neural network architecture named Deep RSS-ToA Fusion Network (DRTFNet). Simulation results demonstrate that the proposed DRTFNet achieves positioning accuracy of less than 3 cm and orientation accuracy of less than 3 degrees, outperforming both the basic Convolutional Neural Network (CNN) architecture using only RSS data and other baseline systems with more light sources.},

keywords = {6G, LiFi, LRDC},

pubstate = {published},

tppubtype = {misc}

}