Title: Non-linearity effects and predistortion in optical OFDM wireless transmission using LEDs

Authors: H. Elgala, R. Mesleh, H. Haas

Addresses: Department of Electrical Engineering and Computer Science, Jacobs University Bremen, Campus Ring 12, 28759-Bremen, Germany. ' Department of Electrical Engineering and Computer Science, Jacobs University Bremen, Campus Ring 12, 28759-Bremen, Germany. ' Institute for Digital Communications, Joint Research Institute for Signal and Image Processing, The University of Edinburgh, Edinburgh EH9 3JL, UK

Abstract: Orthogonal frequency division multiplexing (OFDM) is a promising technique to realise high-speed indoor optical wireless (OW) links through the exploitation of the high peak-to-average power ratio (PAPR) for intensity modulation (IM). However, the non-linear characteristic of a light emitting diode (LED) imposes limitations on the performance. In this paper, the impact of the non-linear characteristic on bit-error performance is analysed using a commercially available LED (OSRAM, SFH 4230). Also, the paper proposes a predistorter to overcome the non-linearities. The performance without compensation and after compensation is analysed via simulations in an additive white Gaussian noise (AWGN) environment. In this context, the bit-error performance is determined for different bias points and power back-off values applied to the OFDM signal modulating the LED intensity. It is shown that LED non-linearity can significantly degrade the performance. It is also demonstrated that this degradation can greatly be mitigated by using the proposed predistortion technique.

Keywords: orthogonal frequency division multiplexing; optical OFDM; optical wireless communication; light emitting diodes; LED nonlinearity; predistortion; free space optics; LEDs.

DOI: 10.1504/IJUWBCS.2009.029003

International Journal of Ultra Wideband Communications and Systems, 2009 Vol.1 No.2, pp.143 - 150

Available online: 20 Oct 2009 *

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