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    Efficient DC biased-PAM based OFDM for visible light communication system
    (Springer, 2022) Zaidan, Zahraa Mustafa; Bayat, Oğuz; Abdulkafi, Ayad Atiyah
    The need of high spectral efficiency to increase bandwidth utilization have been the main drivers for next generation optical wireless communication including visible light communication (VLC) systems. However, conventional optical techniques adopted Hermitian symmetry to satisfy the real and positive constraints of intensity modulation with direct detection based VLC systems on the cost of spectral efficiency loss. In this paper, a new direct current biased- pulse amplitude modulated based orthogonal frequency division multiplexing (DC-PAM-OFDM) is proposed to utilize all subcarriers without using Hermitian symmetry and hence provide more spectral efficiency for VLC systems. The proposed scheme ensures the real-valued optical signals by inserting PAM signal in frequency domain side of OFDM system, clipping, splitting, and rearranging the time domain signal instead of using Hermitian symmetry. This results in improving spectral efficiency by 100% compared to PAM based discrete multitoned modulation (DMT). In addition, theoretical analyses show that the proposed DC-PAM based OFDM scheme is more energy efficient than the PAM-DMT. Furthermore, simulation results show that the proposed scheme has better bit error rate performance and reduces the Peak-to-Average Power Ratio when compared with the existing methods under same spectral efficiency conditions.