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Information rate of OFDM-based Optical Wireless Communication Systems with Non-linear Distortion

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Original languageEnglish
Pages (from-to)918 - 929
JournalJournal of Lightwave Technology
Issue number6
Publication statusPublished - Mar 2013


In this paper, a piecewise polynomial function is proposed as a generalized model for the non-linear transfer characteristic of the transmitter for optical wireless communications (OWC). The two general multi-carrier modulation formats for OWC based on orthogonal frequency division multiplexing (OFDM), direct-current-biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM), are studied. The non-linear distortion of the electrical signal-tonoise ratio (SNR) at the receiver is derived in closed form, and it is verified by means of a Monte Carlo simulation. This flexible and accurate model allows for the application of pre-distortion and linearization of the dynamic range of the transmitter between points of minimum and maximum radiated optical power. Through scaling and DC-biasing the transmitted signal is optimally conditioned in accord with the optical power constraints of the transmitter front-end, i.e. minimum, average and maximum radiated optical power. The mutual information of the optimized optical OFDM (O-OFDM) schemes is presented as
a measure of the capacity of these OWC systems under an average electrical power constraint. When the additional DC bias power is neglected, DCO-OFDM is shown to achieve the Shannon capacity when the optimization is employed, while ACO-OFDM exhibits a 3-dB gap which grows with higher information rate targets. When the DC bias power is counted towards the signal power, DCOOFDM
outperforms ACO-OFDM for the majority of average optical power levels with the increase of the information rate target or the dynamic range. The results can be considered as a lower bound on the O-OFDM system capacity.

    Research areas

  • Mutual information, non-linear distortion, OFDM, optical devices, wireless communication

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