Various Indoor OFDM Optical Wireless Communication Systems and Performance Characteristics

In this paper, the performance of indoor OFDM(Orthogonal Frequency Division Multiplexing) optical wireless communication systems in the presence of LED clipping distortions is analysed. The Orthogonal frequency division multiplexing (OFDM) is used in many wired and wireless broadband communication systems because of its resilience in the presence of signal dispersion or multipath distortion. OFDM has not been used in practical optical communication systems because the bipolar wave form cannot be used in intensity-modulated systems. A novel unipolar form of OFDM, asymmetrically clipped optical OFDM (ACO-OFDM), has recently been developed. In the case of an AWGN channel, we compare ACO-OFDM and other modulation schemes. An ACO-OFDM (asymmetrically clipped optical OFDM) system produces half-wave symmetry time signal at the output section of the OFDM modulator by special assignment of subcarriers. Therefore, bipolar-unipolar conversion is obtained by clipping the signal at the zero level. The other technique, called DCO-OFDM (DC-biased optical OFDM), assigns data to all possible subcarriers to increase the data rate. The performance can be analysed by considering average electrical OFDM signal versus BER, DC power consumption versus transmitted optical power characteristics