On PAPR Reduction in Pilot-Assisted Optical OFDM Communication Systems

This paper presents a novel theoretical characterization of the pilot-assisted (PA) technique proposed for peak-to-average-power-ratio (PAPR) reduction in optical orthogonal frequency division multiplexing (O-OFDM). The two systems considered are direct-current biased O-OFDM (DCO-OFDM) and asymmetrically clipped O-OFDM (ACO-OFDM) in optical wireless communications. The DCO-OFDM and ACO-OFDM time-domain signals approach Gaussian and half-Gaussian distributions, respectively. The PA technique uses <inline-formula> <tex-math notation="LaTeX">$P$ </tex-math></inline-formula> iterations of a pilot sequence to rotate the phase of <inline-formula> <tex-math notation="LaTeX">$U$ </tex-math></inline-formula> data symbols within a PA O-OFDM frame and select the frame with the least PAPR. Thus, we utilize order statistics to characterize the PAPR distributions of the PA DCO-OFDM and ACO-OFDM system. The PA technique results in higher reduction in PAPR for high <inline-formula> <tex-math notation="LaTeX">$P$ </tex-math></inline-formula> but at the expense of increased complexity. In the theoretical framework developed, we are able to determine <inline-formula> <tex-math notation="LaTeX">$P$ </tex-math></inline-formula> that gives reasonable PAPR reduction gain. The theoretical analysis of PAPR reduction effects on the average optical and electrical signal power is studied. Results show that the PA technique is capable of reducing the optical energy per bit to noise power spectral density <inline-formula> <tex-math notation="LaTeX">$E_{\mathrm {b({opt})}}/N_{0}$ </tex-math></inline-formula> ratio required to meet target bit-error-rate in an additive white Gaussian noise channel. Comparisons of the analytical results of PA O-OFDM signal with that of computer simulations show very good agreement.