Visible Light Positioning and Communication Using Liquid Crystal Display Aided Receivers
To complement Wi-Fi and 5G, LED-based visible light communication (VLC) is required to support multiuser multiple-input multiple-output (MU-MIMO) communication scenarios, where multiple receivers are simultaneously provided with individual high-rate data links. However, these scenarios are among the main challenges of VLC, because neighboring light sources (LSs) cause modulated interference. As a solution approach, an innovative optical receiver has been developed at the Chair of Information and Coding Theory, Kiel University, which employs a liquid crystal display (LCD) as dynamic optical filter. This enables adaptive interference suppression. This cumulative dissertation continues investigations with the LCD-based receiver. In particular, a novel technique for angle-of-arrival (AoA) estimation of LSs is invented, which is based on the beamforming principle known from radar. Initially, a single LS is considered and properties influencing the AoA estimation are investigated. Then, the AoA estimation signal is modeled, the bar algorithm is developed to improve localization runtime, and compressive sensing algorithms are investigated. Further investigations reveal that successful AoA estimation of multiple LSs depends on their angular distance. For closely spaced LSs, a novel non-negative least squares (NNLS) algorithm is developed. Two experimental setups are built. The first confirms simulation results on LCD diffraction effects. The second confirms simulations on LS separation and includes the novel NNLS algorithm. To enable LS identification, the efficient joint light source identification and localization (JLIL) principle is developed. Simulations show that information on localization as well as on identification can be obtained jointly from the received signal. Furthermore, the JLIL principle resolves detection ambiguities.
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