Performance analysis of digitized multicarrier system for optical wireless communication

摘要

Optical wireless communication (OWC) in the infrared and visible range is an appealing technology, principally in environment arenas where radio communication encounters difficulties. One o f the most important subdivisions of OWC technology is the visible light communication (VLC) that uses visible light (VL) between the range 400 and 800 THz. VLC uses intensity modulation/direct detection (IM/DD). Hence the signals ought to be strictly real valued positive sequence. The fundamental modulation techniques such as on-off keying (OOK) and Pulse Position Modulation (PPM) are in accordance with existing constant current light emitting diode (LED) drivers, however it comes with one drawback of having low spectral efficiency and restricted feasible data rates of VLC. Orthogonal frequency-division multiplexing (OFDM) is one of the superior techniques that encode digital data on to multiple carrier frequencies and is widely known for providing high spectral efficiency. Despite of these advantages it comes with the disadvantage of high peak to average power ratio (PAPR) besides complicated Digital-to-Analog converter (DAC) and modification of LED drivers of VLC system being pre-requisite. Ln this paper, we present Delta-Sigma modulation (DSM) based OFDM which offers excellent robustness against noises and nonlinear distortions in VLC systems. The digital OFDM has been analyzed in terms of complementary cumulative distribution function (CCDF), error vector magnitude (EVM), bit error rate (BER) and received constellation diagram by means of MATLAB simulation to characterize the waveforms. Simulation results show that the DSM considerably enhances the system performance of digitized OFDM.