In this paper, we experimentally compare orthogonal frequency-division multiplexing (OFDM) and on-off keying (OOK) modulation in the context of the IEEE 802.15.13-2023 standard at bandwidths up to 50 MHz across a Li-Fi link with distances up to 5 m and a lateral offset up to 51°. Error vector magnitude (EVM) and bit error rate (BER) evaluations confirm that the high peak-to-average power ratio (PAPR) of OFDM limits the achievable transmission distance, but it offers higher data rates due to its higher spectral efficiency. Due to the lower PAPR, OOK-based Pulsed Modulation PHY (PM-PHY) shows a significantly higher link range. As the structure of the PM-PHY is based on OFDM symbols, the two solutions may also be combined to open a wider range of use cases for optical wireless communications.
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The performance of a visible light communication (VLC) system based on power domain non-orthogonal multiple access (PD-NOMA) is experimentally evaluated in this paper. The simplicity of the adopted non-orthogonal scheme is provided by the fixed power allocation method at the transmitter and the single one-tap equalization executed before the successive interference cancellation at the receiver. The experimental results proved the successful transmission of the PD-NOMA scheme with three users in VLC links of up to 2.5 m, after a proper choice of the optical modulation index. All users achieved error-vector magnitude (EVM) performances below FEC limits in all evaluated transmission distances. At 2.5 m, the user with the best performance reaches an EVM = 2.3 %.
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This paper describes the concept of a new algorithm to control an Unmanned Aerial System (UAS) for accurate autonomous indoor flight. Inside a greenhouse, Global Positioning System (GPS) signals are not reliable and not accurate enough. As an alternative, Ultra Wide Band (UWB) is used for localization. The noise is compensated by combining the UWB with the delta position signal from a novel optical flow algorithm through a Kalman Filter (KF). The end result is an accurate and stable position signal with low noise and low drift.
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In this project, Photons in Focus, researchers from The Hague University of Applied Sciences will work together with the company Photosynthetic to fabricate high-quality microlenses that will optimally focus light onto microscopic light detectors. Specifically, the microlenses will be designed to focus light onto superconducting nanowire single-photon detectors (SNSPDs) from the company Single Quantum. SNSPDs are cryogenic single-photon detectors with photon detection efficiencies up to 99% and timing resolutions down to 15 picosecond. Recently, Single Quantum has been developing arrays of SNSPDs for free-space biomedical imaging and deep space communications. The photon detection efficiency of these arrays is suboptimal, because 15-20% of the light falls onto nonsensitive areas. In Photons in Focus, fabrication of two types of microstructures will be explored for optimally focusing light onto these SNSPDs and improving the photon detection efficiency. First, 3-dimensional microlenses will be created at Photosynthetic using their method of dual-wavelength volumetric microlithography. Second, phase-reversal Fresnel zone plates will be fabricated using standard 2-dimensional photolithography at The Hague University of Applied Sciences. Both types of microstructures will be tested for their focusing properties and potential optical losses, and their ability to enhance to photon detection efficiency of SNSPDs in cryogenic conditions.
The increasing complexity of digital networks on which society depends on renders these networks increasingly vulnerable to attacks. Focusing on physical layer security, we propose to develop single-spatial-mode optical Physical Unclonable Functions (PUFs) as an authentication solution for quantum and classical communication links. These novel PUFs are read out through standard optical fibers or free-space links. Several implementations of single-mode PUFs are proposed exploiting the time / frequency domain for the encoding challenge / response space. Together with the PUFs, we will develop tools to generate challenge-forming few-photon light pulses and to validate PUF responses at the few-photon level and take specific steps toward wide implementation.
The demand for mobile agents in industrial environments to perform various tasks is growing tremendously in recent years. However, changing environments, security considerations and robustness against failure are major persistent challenges autonomous agents have to face when operating alongside other mobile agents. Currently, such problems remain largely unsolved. Collaborative multi-platform Cyber- Physical-Systems (CPSs) in which different agents flexibly contribute with their relative equipment and capabilities forming a symbiotic network solving multiple objectives simultaneously are highly desirable. Our proposed SMART-AGENTS platform will enable flexibility and modularity providing multi-objective solutions, demonstrated in two industrial domains: logistics (cycle-counting in warehouses) and agriculture (pest and disease identification in greenhouses). Aerial vehicles are limited in their computational power due to weight limitations but offer large mobility to provide access to otherwise unreachable places and an “eagle eye” to inform about terrain, obstacles by taking pictures and videos. Specialized autonomous agents carrying optical sensors will enable disease classification and product recognition improving green- and warehouse productivity. Newly developed micro-electromechanical systems (MEMS) sensor arrays will create 3D flow-based images of surroundings even in dark and hazy conditions contributing to the multi-sensor system, including cameras, wireless signatures and magnetic field information shared among the symbiotic fleet. Integration of mobile systems, such as smart phones, which are not explicitly controlled, will provide valuable information about human as well as equipment movement in the environment by generating data from relative positioning sensors, such as wireless and magnetic signatures. Newly developed algorithms will enable robust autonomous navigation and control of the fleet in dynamic environments incorporating the multi-sensor data generated by the variety of mobile actors. The proposed SMART-AGENTS platform will use real-time 5G communication and edge computing providing new organizational structures to cope with scalability and integration of multiple devices/agents. It will enable a symbiosis of the complementary CPSs using a combination of equipment yielding efficiency and versatility of operation.
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