Abstract
In this paper, dual-branch pre-distorted enhanced asymmetrically clipped direct current (DC) biased optical orthogonal frequency division multiplexing (PEADO-OFDM) for underwater optical wireless communication (UOWC) is firstly proposed and simulated. The performances of PEADO-OFDM on the underwater optical channel model (UOCM) are analyzed and further compared with the typical ADO-OFDM. Using the Monte Carlo method for the modeling of UOCM, we adopt a double-gamma function to represent three different water qualities including clear, coastal and harbor waters. The full-duplex architecture enables the removal of Hermitian symmetry (HS) from conventional optical OFDM and can increase the spectral efficiency at the cost of hardware complexity. A new PEADO-OFDM transmitter is also proposed to reduce the complexity of the transmitter. The simulation results exhibit that our proposed dual-branch PEADO-OFDM scheme outperforms the typical ADO-OFDM scheme in spectral efficiency, bit error rate (BER) and stability over the underwater channels of three different water qualities.
Highlights
High-speed underwater communication plays an increasingly important role in oceanographic research, information transfer and marine development [1]
After performing the fast Fourier transform (FFT) operation to the clipped ACO-orthogonal frequency division multiplexing (OFDM) signals, the clipping noise can be obtained by extracting the data of the even subcarrier, which will be used as the pre-distorted signals
The obtained time-domain clipping noise can be used as pre-distortion signals, which will be subtracted by the DCOOFDM branch after the inverse fast Fourier transform (IFFT) operation
Summary
High-speed underwater communication plays an increasingly important role in oceanographic research, information transfer and marine development [1]. The impulse response calculated from the double-gamma function and Monte Carlo simulation has been shown to have a better fitting effect on real underwater models. PEADO-OFDM eliminates the inter-carrier interference (ICI) between the ACO-OFDM and the DCO-OFDM branches at the transmitter and is applied as the modulation scheme for downlink in a visible light communication (VLC). [15], we proposed a modified scheme in a practical full-duplex UOWC architecture and a low-complexity scheme of a transmitter, apart from transferring the compensation scheme in the ACO branch from a typical indoor model to various underwater channels. We apply PEADO-OFDM in the UOCM by further comparing it with a traditional ADO-OFDM scheme in the aspects of bit error rate (BER), stability and spectral efficiency
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