A New Vehicle Localization Scheme Based on Combined Optical Camera Communication and Photogrammetry

The demand for autonomous vehicles is increasing gradually owing to their enormous potential benefits. However, several challenges, such as vehicle localization, are involved in the development of autonomous vehicles. A simple and secure algorithm for vehicle positioning is proposed herein without massively modifying the existing transportation infrastructure. For vehicle localization, vehicles on the road are classified into two categories: host vehicles (HVs) are the ones used to estimate other vehicles' positions and forwarding vehicles (FVs) are the ones that move in front of the HVs. The FV transmits modulated data from the tail (or back) light, and the camera of the HV receives that signal using optical camera communication (OCC). In addition, the streetlight (SL) data are considered to ensure the position accuracy of the HV. Determining the HV position minimizes the relative position variation between the HV and FV. Using photogrammetry, the distance between FV or SL and the camera of the HV is calculated by measuring the occupied image area on the image sensor. Comparing the change in distance between HV and SLs with the change in distance between HV and FV, the positions of FVs are determined. The performance of the proposed technique is analyzed, and the results indicate a significant improvement in performance. The experimental distance measurement validated the feasibility of the proposed scheme

Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications

Orbital angular momentum (OAM) has aroused a widespread interest in many fields, especially in telecommunications due to its potential for unleashing new capacity in the severely congested spectrum of commercial communication systems. Beams carrying OAM have a helical phase front and a field strength with a singularity along the axial center, which can be used for information transmission, imaging and particle manipulation. The number of orthogonal OAM modes in a single beam is theoretically infinite and each mode is an element of a complete orthogonal basis that can be employed for multiplexing different signals, thus greatly improving the spectrum efficiency. In this paper, we comprehensively summarize and compare the methods for generation and detection of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications and technical challenges of OAM in communications, including free-space optical communications, optical fiber communications, radio communications and acoustic communications. To complete our survey, we also discuss the state of art of particle manipulation and target imaging with OAM beams

A Study on the Dynamic Manipulation of Structured Light Using Orbital Angular Momentum for Wireless Underwater Links

In this work, the dynamic generation of structured light modes was demonstrated using coherent, co-aligned beams carrying orbital angular momentum (CCOAM). These modes are created using sources with blue/green wavelengths to study the effects of propagation and applications underwater maritime environments. Three techniques are discussed and are compared to simulation using a Rayleigh-Sommerfeld propagation kernel: concentric phase plates, Mach-Zehnder Interferometry, and the HOBBIT (Higher Order Bessel Beams Integrated in Time). These three systems are used to examine the modal integrity, controllability, and unique applications. Structured CCOAM modes were first demonstrated using a 450 nm source and concentric phase plates and were propagated through 3 meters of turbid underwater environments. Beam coherence was measured using image registration, and the wavefronts were found to maintain their structure despite propagation through extreme turbidity. In addition, the source was amplitude modulated to verify that the mode structure can carry an amplitude modulation signal. Next, an interferometry approach is used so that the two interfering modes can be controlled separately. The relative phase is controlled between the two interfering modes by manipulating the optical path length that each mode travels using an electro-optic phase modulator. Phase modulation allows for precise yet limited control of the wavefront and structure. Two setups were examined, a fiber-to-free-space Mach-Zehnder interferometer, and a HOBBIT system with two inputs. Phase only control was demonstrated using sinusoidal modulation and an orthogonal frequency division multiplexing (OFDM) signal applied to the phase modulator. The modulated signals were successfully transmitted 3 and 6 meters through turbid water. Phase only modulation allowed for the transmission of a constant-amplitude signal, which provides nonlinear manipulation of the signal, such as amplification and harmonic generation, which are both crucial in creating high-power signals in the visible regime. The interferometry setups are very sensitive and a phase drift was found to occur due to temperature fluctuations and small movements of optical fiber in the setup, so a preliminary phase-lock loop was designed and tested to eliminate the phase drift. Without applied modulation, a RMS phase error of less than λ/30 was measured. Lastly an acousto-optic deflector (AOD) was added to the HOBBIT setup, which adds mode tunability in addition to amplitude and phase control. The traveling acoustic wave also induces a frequency shift in the optical signal producing a continuous modulation of the output CCOAM mode. This is demonstrated by using a pulsed 450 nm diode to strobe the signal. Operation in pulsed mode enables the system to perform a self-referencing wavefront recovery from which the total OAM was extracted

A Survey of Positioning Systems Using Visible LED Lights

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe