研究目的
To develop a spatial carrierless amplitude and phase modulation (S-CAP) technique as a physical layer solution to improve the spectral efficiency of conventional CAP while maintaining low-complexity transceiver design for visible light communication systems.
研究成果
The S-CAP technique significantly improves spectral efficiency over conventional CAP by a factor of logM(MNt), with validated analytical models showing good agreement with simulations. Performance is influenced by channel gains, constellation points, and delay spread, mitigated by PFI and multiple PDs, achieving up to 43 dB SNR gain. It is a promising low-complexity solution for VLC systems, though multipath effects pose challenges.
研究不足
The study relies on simulations and analytical models, which may not fully capture real-world complexities. Multipath propagation effects are considered only up to second-order reflections, and user mobility is simulated by varying PD positions, which might not represent all practical scenarios. The effectiveness of PFI is limited in multipath-dominated regions.
1：Experimental Design and Method Selection:
The study employs simulation-based analysis using ray-tracing algorithms for channel modeling, derived analytical expressions for BER performance, and validation through Monte Carlo simulations. Theoretical models include CAP modulation, spatial modulation, and MIMO techniques.
2：Sample Selection and Data Sources:
Simulations are conducted in a virtual indoor environment with room dimensions of 5m x 5m x 3m, using specified LED and PD positions from tables in the paper. Channel impulse responses are generated using ray-tracing with up to second-order reflections.
3：List of Experimental Equipment and Materials:
LEDs and photodetectors (PDs) are used as transmitters and receivers, with parameters such as responsivity R, optical modulation index β, and electrical-to-optical conversion coefficient η. Noise is modeled as additive white Gaussian noise (AWGN).
4：Experimental Procedures and Operational Workflow:
Information bits are grouped, mapped to LED indices and CAP symbols, modulated, transmitted through optical channels, received, demodulated, and decoded using maximum likelihood detection. BER is calculated and compared under LOS and multipath conditions, with variations in PD positions to simulate user mobility.
5：Data Analysis Methods:
BER performance is analyzed using derived analytical expressions and union bound techniques. Results are plotted against signal-to-noise ratio per bit (γb), and factors like hmin, Δ|h|, and τrms are investigated.
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