A novel PAPR reduction algorithm for DCO-OFDM/OQAM system in underwater VLC

Abstract

In the underwater visible light communication (VLC), the photon propagation scattering effect is obvious and the multipath effect is enhanced as the link distance increases. This paper uses orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) of filter bank multicarrier technology (FBMC), which is based on time frequency localization (TFL) filter, to overcome inter symbol interference (ISI) and inter carrier interference (ICI). Since light-emitting diode (LED) modulation needs positive modulation signal, we use the direct current (DC) bias to add on OFDM/OQAM signal so that the signal is positive. But, as the OFDM/OQAM is also multicarrier modulation system, the instantaneous fluctuation of OFDM/OQAM signal is bigger than single carrier modulation system and the nonlinear distortion is very serious. Therefore, this paper puts forward the modified overlapped selective mapping (M-OSLM) suppression algorithm to restrain the peak to average power ratio (PAPR), and optimizes the range of data symbol which affects on current data symbol by taking the characteristic of filter bank into consideration so that decrease PAPR. Thus, the instantaneous volatility of OFDM/OQAM signals is reduced in order to select the appropriate DC bias and reduce the clipping distortion. The simulation results show that compared with DC-biased cyclic prefix optical OFDM (DCO-CP-OFDM), DC-biased optical OFDM/OQAM (DCO-OFDM/OQAM) has a better overcoming ability on ISI of underwater wireless optical scattered channel. Meanwhile, the performance of PAPR reduction is greatly improved by M-OSLM algorithm. The signal-to-noise ratio (SNR) is improved by 3 dB averagely compared to DCO-CP-OFDM at the same bit error rate (BER).