Performance analysis of FSO OFDM for 256-QAM scheme under optical diverse channel

This study presents a detailed performance evaluation of the proposed free space optical-orthogonal frequency division multiplexing (FSO-OFDM) system compared with conventional schemes such as orthogonal frequency division multiplexing (OFDM), filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and universal filtered multi-carrier (UFMC) under diverse optical channel conditions. Bit error rate (BER) results in Rayleigh fading channels indicate that the proposed method attains a BER of 10 −3 at only 6.2 dB Signal-to-Noise Ratio (SNR), yielding gains of 7.6 dB, 6.2 dB, 5.3 dB, and 3.4 dB over OFDM, FBMC, NOMA, and UFMC, respectively. In Rician fading channels, the same BER is achieved at just 5.4 dB SNR, with improvements of 7.2 dB, 5.8 dB, 4.8 dB, and 3.0 dB compared to the respective schemes. Peak-to-average power ratio (PAPR) analysis at a complementary cumulative distribution function (CCDF) of 10 −3 shows a value of 10.8 dB for the proposed system, reducing nonlinear distortions and improving amplifier efficiency. Capacity analysis confirms a peak of 300 units at 50 dB SNR, surpassing all competitors. Power spectral density (PSD) results reveal sidelobe suppression beyond −200 dBW/MHz, with significant out-of-band emission reductions. Overall, FSO-OFDM offers superior robustness, spectral efficiency, and throughput for high-capacity optical communication systems.