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Christina

Publications and source records attributed to Christina.

4 recordsLinked to original sources

Ultra-Fast Device-Free Visible Light Sensing and Localization via Reflection-Based {\Delta}RSS and Deep Learning

We propose an Ultra-Fast, Device-Free Visible Light Sensing and Positioning system that captures spatiotemporal variations in single-LED VLC channel responses, using ceiling-mounted photodetectors, to accurately and non-intrusively infer human presence and position through optical signal reflection modeling. The system is highly adaptive and ready to serve different real-world sensing and positioning scenarios using one or more ML based models from the library of multi-architecture deep neural network ensembles we have developed.

eess.SP

Machine Learning based Radio Environment Map Estimation for Indoor Visible Light Communication

Novel radio map estimation in optical wireless communications is proposed based on ML prediction rather than simulation techniques. ML training is performed on simulation and experimentally generated synthetic data and in both cases, prediction is fast and of high accuracy. Among various models, Multi-Layer Perceptron (MLP) representation of indoor Visible Light Communication (VLC) systems outperforms the others with respect to RSS that is estimated for various indoor systems. The predicted RSS is very accurate and fast and requires a reduced set of training sample size with respect to other counterparts, making this solution very suitable for real time estimation of an indoor VLC system. It is shown that by tweaking MLP parameters, such as sample size, number of epochs and batch size, one can balance the desired level of inference accuracy with training time and optimize the model's performance to meet real-time requirements. Furthermore, experimental data from a PureLiFi system has been used in a proof-of-concept production of synthetic data radio map prediction based on MLP. Using SMOGN-generated synthetic data derived from fewer than 100 experimental measurements, our MLP model achieves strong regression performance on the experimental measurements, demonstrating successful synthetic-to-real generalization without direct training on the full experimental dataset.

eess.SP

Polarization Modulation in Quantum-Dot Spin-VCSELs for Ultrafast Data Transmission

Spin-Vertical Cavity Surface Emitting Lasers (spin-VCSELs) are undergoing increasing research effort for new paradigms in high-speed optical communications and photon-enabled computing. To date research in spin-VCSELs has mostly focused on Quantum-Well (QW) devices. However, novel Quantum-Dot (QD) spin-VCSELs, offer enhanced parameter controls permitting the effective, dynamical and ultrafast manipulation of their light emissions polarization. In the present contribution we investigate in detail the operation of QD spin-VCSELs subject to polarization modulation for their use as ultrafast light sources in optical communication systems. We reveal that QD spin-VCSELs outperform their QW counterparts in terms of modulation efficiency, yielding a nearly two-fold improvement. We also analyse the impact of key device parameters in QD spin-VCSELs (e.g. photon decay rate and intra-dot relaxation rate) on the large signal modulation performance with regard to optical modulation amplitude and eye-diagram opening penalty. We show that in addition to exhibiting enhanced polarization modulation performance for data rates up to 250Gbps, QD spin-VCSELs enable operation in dual (ground and excited state) emission thus allowing future exciting routes for multiplexing of information in optical communication links.

physics.optics

Triangle Decompositions of Planar Graphs

A multigraph G is triangle decomposable if its edge set can be partitioned into subsets, each of which induces a triangle of G, and rationally triangle decomposable if its triangles can be assigned rational weights such that for each edge e of G, the sum of the weights of the triangles that contain e equals 1. We present a necessary and sufficient condition for a planar multigraph to be triangle decomposable. We also show that if a simple planar graph is rationally triangle decomposable, then it has such a decomposition using only weights 0,1 and 1/2. This result provides a characterization of rationally triangle decomposable simple planar graphs. Finally, if G is a multigraph with the complete graph of order 4 as underlying graph, we give necessary and sufficient conditions on the multiplicities of its edges for G to be triangle and rationally triangle decomposable.

math.CO