Performance of two dimensional asymmetrically and symmetrically clipping optical OFDM in AWGN

In this paper, we apply the modulation scheme of asymmetrically and symmetrically clipping optical (ASCO)-OFDM into two dimensional (2D) intensity modulation direct detection (IM/DD) optical wireless communications (OWC). The asymmetrically clipping optical (ACO)-OFDM symbols and the symmetrically clipping optical (SCO)-OFDM symbols are mapped into odd columns and even columns of transmitted matrices respectively. Due to an ASCO-OFDM signal consists of an ACO-OFDM signal and a SCO-OFDM signal, the average data rate of ASCO-OFDM is higher than that of ACO-OFDM. We show that the spectral efficiency of 2D ASCO-OFDM is twice as much as that of 2D ACO-OFDM. Moreover, compared with 2D ACO-OFDM with different constellation cases, 2D ASCO-OFDM reduces the Peak-to-Average power ratio (PAPR) by 2dB. The symbol error rate (SER) performance of 2D ASCO-OFDM is simulated under the environment of additive white Gaussian noise (AWGN) and it exhibits better SER performance than 2D ACO-OFDM in the same bit rate case.