An improved performance receiving technique for asymmetrically and symmetrically clipping optical (ASCO)-OFDM

In this paper, we propose an improved receiving technique for the asymmetrically and symmetrically clipping optical (ASCO)-OFDM intensity modulation direct detection (IM/DD) wireless communication system. In the ASCO-OFDM modulation scheme, the asymmetrically clipping optical (ACO)-OFDM symbols are modulated onto the odd subcarriers, and the symmetrically clipping optical (SCO)-OFDM symbols are modulated onto the even subcarriers. We found that the interference caused by clipping only affects the symbols on the even subcarriers. At the receiver, the ACO-OFDM symbols can be easily obtained by detecting the data on the odd subcarri-ers; the SCO-OFDM symbols can be successfully recovered by subtracting the estimated ACO-OFDM clipping noise and the SCO-OFDM clipping noise from the even subcarriers. The ACO-OFDM clipping noise is estimated from the received ACO-OFDM signals, and it can be reused to decrease the symbol error rate (SER) of ACO-OFDM signals. The SER of SCO-OFDM signals depend on the precision of ACO-OFDM signals. Thus, we apply an improved ACO-OFDM receiving technique in our current receiver to further improve the SER performance of SCO-OFDM signals as well as that of the whole system.