Hybrid PAPR reduction schemes for different OFDM-based VLC systems

Abstract

Orthogonal frequency division multiplexing has been widely used in many radio frequency wireless communication standards as a preferable multicarrier modulation scheme. The modulated signals of a conventional orthogonal frequency division multiplexing system are complex and bipolar. In intensity-modulated direct detection optical wireless communications, transmitted signals should be real and unipolar due to non-coherent emissions of an optical light emitting diode. In this paper, different hybrid optical systems have been proposed to satisfy real and unipolar signals. Peak-to-average power ratio is one of the biggest challenges for orthogonal frequency division multiplexing-based visible light communications. They are based on a combination of non-linear companding techniques with spreading or precoding techniques. Simulation evaluation is performed under direct current-biased optical orthogonal frequency division multiplexing, asymmetrically clipped optical orthogonal frequency division multiplexing, and Flip-orthogonal frequency division multiplexing systems in terms of peakto-average power ratio, bit error rate, and spectral efficiency. The proposed schemes are investigated to determine a scheme with a low peak-to-average power ratio and an acceptable bit error rate. MATLAB TM software has been successfully used to show the validity of the proposed schemes.

A Hybrid NOMA/OFDM Model for Next Generation Communication Systems

“…In order to compare the performance of the three users, the BER of the three users is plotted as shown in Figs. 15,17,19 for NOMA/DCO-OFDM and Figs. 16, 18, 20 for NOMA/ACO-OFDM.…”

“…Hermitian symmetry can be utilized before the inverse fast Fourier transform (IFFT) to obtain real-valued set of data symbols [18]. and the middle subcarriers are set to be zero [19]. 9 10 Then, the output of the IFFT is the time-domain real-valued signal [20]:…”