Clipping noise mitigation using partial transmit sequence for optical OFDM systems

Orthogonal frequency division multiplexing (OFDM) is a promising technology to achieve higher data rates in optical wireless communication (OWC) systems. Unlike single carrier techniques, OFDM can easily handle inter-symbol interference (ISI) by adding a small redundancy, i.e., cyclic prefix (CP). However, due to the imperfections of optical transmitters, i.e., light-emitting-diodes (LEDs), and insufficient direct current (DC) biasing, OFDM signal with a large peak-to-average power ratio (PAPR) can be typically clipped double sidedly. Clipping results in a noise effect in frequency domain and degrades the performance. In this paper, we propose to mitigate clipping noise effect in waveform domain using a partial transmit sequence (PTS) based approach. In this approach, at the transmitter, the input data is multiplied by a sequence of phase factors that are properly selected to reduce the PAPR of the signals and thus minimize the clipping noise. Our results show that, at the expense of a reasonable bandwidth penalty due to the transmission of the phase factors to the receiver and extra complexity exponentially proportional to the number of the phase factors, clipping noise is decreased and a considerable improvement is obtained in the BER performance.