ABSTRACT
This work reports the development of an efficient and precise indoor positioning system utilizing two-dimensional (2D) light detection and ranging (LiDAR) technology, aiming to address the challenging sensing and positioning requirements of the beyond fifth-generation (B5G) mobile networks. The core of this work is the implementation of a 2D-LiDAR system enhanced by an artificial neural network (ANN), chosen due to its robustness against electromagnetic interference and higher accuracy over traditional radiofrequency signal-based methods. The proposed system uses 2D-LiDAR sensors for data acquisition and digital filters for signal improvement. Moreover, a camera and an image-processing algorithm are used to automate the labeling of samples that will be used to train the ANN by means of indicating the regions where the pedestrians are positioned. This accurate positioning information is essential for the optimization of B5G network operation, including the control of antenna arrays and reconfigurable intelligent surfaces (RIS). The experimental validation demonstrates the efficiency of mapping pedestrian locations with a precision of up to 98.787%, accuracy of 95.25%, recall of 98.537%, and an F1 score of 98.571%. These results show that the proposed system has the potential to solve the problem of sensing and positioning in indoor environments with high reliability and accuracy.
ABSTRACT
This work reports the implementation of a fiber-optics and visible light communication (VLC)-based flexible optical distribution network for beyond the fifth generation of mobile networks (B5G) applications. The proposed hybrid architecture is composed of a 12.5-km single-mode fiber fronthaul based on the analog radio-over-fiber (A-RoF) technology, followed by a red, green, and blue (RGB)-based VLC link of 1.2 m. As a proof of concept, we experimentally demonstrate a successful deployment of a 5G hybrid A-RoF/VLC system without using pre-/post-equalization, digital pre-distortion, or individual filters for each color, by means of using a dichroic cube filter at the receiver side. The system performance is evaluated in terms of the root mean square error vector magnitude (E V M R M S ), in accordance with the 3rd Generation Partnership Project requirements, and as a function of the light-emitting diodes' injected electrical power and signal bandwidth.
ABSTRACT
Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole-dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole-dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie-Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.
