研究目的
To characterize and compare the performance of IM/DD and coherent detection modulation techniques in FSO systems under weak turbulence, specifically by deriving BER expressions for M-PPM in terms of signal intensity to enable fair comparison with M-PSK and M-QAM.
研究成果
BPPM is more energy-efficient under adverse channel conditions (e.g., high scintillation index or low Eb/N0), while M-PSK performs better for high data transmission in weak turbulence. The derived BER expressions enable fair comparison, showing that turbulence significantly impacts system performance, requiring higher signal intensities to maintain BER.
研究不足
The study is confined to weak turbulence regimes (scintillation index <0.75) and log-normal channel models, which may not apply to moderate or strong turbulence. The analysis assumes specific conditions (e.g., frozen atmosphere, negligible dark current) and does not account for practical implementation challenges or real-world environmental variations.
1：Experimental Design and Method Selection:
The study uses analytical derivations and numerical simulations to model FSO systems under weak turbulence (log-normal channel with scintillation index <0.75). Theoretical models include log-normal distribution for irradiance fluctuations and Gauss-Hermite quadrature for numerical integration.
2：75). Theoretical models include log-normal distribution for irradiance fluctuations and Gauss-Hermite quadrature for numerical integration.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: No specific samples or datasets; the analysis is based on theoretical parameters and simulations with defined values (e.g., thermal noise levels, bit rates).
3：List of Experimental Equipment and Materials:
Not applicable as the paper is theoretical; however, it references components like Avalanche Photodetector (APD), PIN photodetector, and lasers for coherent detection in the context of FSO systems.
4：Experimental Procedures and Operational Workflow:
The methodology involves deriving BER expressions for different modulation techniques (M-PPM, M-PSK, M-QAM) using probability density functions of signal intensity and log-normal channel statistics. Numerical analysis is performed with parameters such as average irradiance, scintillation index, thermal noise, and Eb/N
5：Data Analysis Methods:
Data analysis includes numerical integration (e.g., using Gauss-Hermite approximation), plotting BER vs. various parameters (e.g., average irradiance, SNR), and comparing performance metrics across modulation techniques.
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