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Chaos Synchronization in Visible Light Communications with Variable Delays Induced by Multipath Fading
摘要： Visible Light Communication (VLC) uses light-emitting diodes to provide wireless connectivity in public environments. Transmission security in this emerging channel is not trivial. Chaotic modulation techniques can provide encryption directly in the physical layer based on the random-alike evolution and strong synchronization prospect given by deterministic chaos. In secure chaotic inclusion or embedding methods, continuous-time chaos oscillator models need to be synchronized via a coupling carrier. Here we present a ?rst numerical simulation study for the impact of the variable delays induced by line-of-sight and non-line-of-sight multipath fading in complete chaotic synchronization. More precisely, we analyze a chaotic Colpitts oscillator that is simultaneously transmitting the carrier to several mobile receivers via nine spotlights. Such induced delays depend on both the receiver position and the carrier frequency, in?uencing the complete synchronization required in modulation via chaotic inclusion. Correlation values for several receiver positions and carrier frequencies are presented, examining the progressive emergence of the multipath effect and its impact on chaotic synchronization. We show that, for the chaotic oscillator and coupling applied in the de?ned room settings, complete chaotic synchronization can be achieved and that it is robust up to the tens of MHz region.
关键词： multipath channels,network security,chaotic communication,visible light communication,nonlinear systems,chaos synchronization
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC) - Kota Kinabalu, Malaysia (2018.10.7-2018.10.10)] 2018 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC) - Transformer-less Single Phase H2D4 Inverter with Voltage Controller for Grid-tied PV System
摘要： Nowadays the transformer-less photovoltaic (PV) grid connected inverter is more popular because of its higher efficiency, compact size and lower cost. The issue of leakage current is a technical challenge, which needs to be controlled carefully. Moreover, many inverter topologies have been proposed to proficient the inverter to control the reactive power to a certain point in order to maintain the power factor (PF) close to one. In case of solar PV system, voltage fluctuation and synchronization with the utility grid is the challenging issue. Therefore, in this paper a new transformer-less inverter is proposed consisting of four diodes and two IGBT switches called H2D4 topology. The proposed topology can overcome the issue of leakage current by maintaining the common mode (CM) voltage constant while maintain low total harmonic distortion (THD) and higher PF. Because of the minimum number of IGBT switches, the leakage current and the conduction loss decrease. Besides, the size of the system is also decreased. Additionally, voltage fluctuation and synchronization are controlled by a newly proposed voltage controlled closed loop system where duty ratio is controlled. The proposed topology and the existing neutral point clamped (NPC) and H6 topologies are simulated in MATLAB/Simulink software, to clarify the theoretical analysis. It is found that the voltage controller closed loop control system of H2D4 inverter topology more efficiently control the voltage fluctuation problems while maintaining a low current THD with higher efficiency and high PF as compared with the system without control topology.
关键词： Grid connection,voltage synchronization,utility grid,total harmonic distortion,transformer-less inverter,power factor,leakage current,reactive power
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Nara, Japan (2018.10.9-2018.10.12)] 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Exact Bit Error Rate Analysis for Optical-Wireless Framed-DOOK System
摘要： In this paper, the differential on-off keying (DOOK), which has the resistance of background noise and high transmission efficiency characteristic, is focused. Especially, framed-DOOK system with 2-bit synchronization signal, which proposed by authors for solving synchronization slip problem on DOOK system, is considered. In this paper, bit error probability theoretically in consideration of synchronization performance of the proposed system is derived and evaluated on optical-wireless channel. As the result, it is shown that the proposed system is effective on the optical-wireless OOK.
关键词： optical-wireless,DOOK,synchronization,framed-DOOK,bit error rate
更新于2025-09-04 15:30:14
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Deep motion tracking from multiview angiographic image sequences for synchronization of cardiac phases
摘要： In the diagnosis and interventional treatment of coronary artery disease, the 3D+time reconstruction of the coronary artery on the basis of X-ray angiographic image sequences can provide dynamic structural information. The synchronization of cardiac phases in the sequences is essential for minimizing the influence of cardiorespiratory motion and realizing precise 3D+time reconstruction. Key points are initially extracted from the first image of a sequence. Matching grid points between consecutive images in the sequence are extracted by a multi-layer matching strategy. Then deep motion tracking of key points is achieved by local deformation based on the neighboring grid points of key points. The local deformation is optimized by the Random Sample Consensus algorithm. Then, a simple harmonic motion model is utilized to distinguish cardiac motion from other motion sources (e.g. respiratory, patient movement, etc.). Next, the signal which is composed of cardiac motions is filtered by a band-pass filter to reconstruct the cardiac phases. Finally, the synchronization of cardiac phases from different imaging angles is realized by piece-wise linear transformation. The proposed method was evaluated using clinical X-ray angiographic image sequences from 13 patients. 85% matching points can be accurately computed by the deep motion tracking method. The mean peak temporal distance between the reconstructed cardiac phases and the electrocardiograph signal is 0.027s. The correlation between the cardiac phases of the same patient is over 89%. Compared with three other state-of-the-art methods, the proposed method accurately reconstructs and synchronizes the cardiac phases from different sequences of the same patient. The proposed deep motion tracking method is robust and highly effective in synchronizing cardiac phases of angiographic image sequences captured from different imaging angles.
关键词： coronary arteries,deep motion tracking,synchronization,X-ray angiographic image sequence,cardiac phase
更新于2025-09-04 15:30:14