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Principles of LED Light Communications by Harald Haas, Svilen Dimitrov

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3

Front-end non-linearity

3.1Introduction

Because of the p-n junction barrier and the saturation effect of the light emitting diode (LED), the transmitter front-end has a limited linear dynamic range. Single-carrier pulse modulated signals such as multi-level pulse position modulation (M-PPM) and multi-level pulse amplitude modulation (M-PAM) have a probability density function (PDF) of their intensity levels with finite support of values. As a result, these signals can be conditioned within the limited linear dynamic range and transmitted with negligible non-linear distortion. Multi-carrier signals based on optical orthogonal frequency division multiplexing (O-OFDM), such as direct-current-biased O-OFDM (DCO-OFDM) and asymmetrically clipped ...

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