Asymmetrically Clipped-FSK Modulation for Energy Efficient Visible Light Communications

Abstract : In this article, we present proof-of-concept of Mary asymmetrically clipped (AC)-frequency-shift keying (FSK) for energy-efficient/low data rate visible light communications (VLC). M-ary AC-FSK uses the odd frequency waveforms from 2M-ary FSK; which exhibit half-wave symmetry. Owing to this half-wave symmetry, the negative amplitude excursions are clipped without loss of information. Hereby, we investigate the performance of three different receivers for M-ary AC-FSK exhibiting different complexities. These receivers are: (i) an optimal time-domain maximum likelihood (ML) receiver; (ii) 1tap discrete cosine transform (DCT) receiver; and (iii) a 2-tap harmonic receiver which exploits the spectral properties of AC-FSK waveforms. We shall exemplify that the 2-tap harmonic receiver overcomes the energy efficiency versus complexity trade-off that exists for optimal ML and 1-tap DCT receivers. Simulation results shall confirm that the performance of 2-tap harmonic receiver reaches the performance of the previously proposed unipolar (U)-FSK with the optimal receiver, but with a drastically reduced receiver complexity.