Sunday, November 28, 2010

Indoor Broadcasting via White Light LEDs and OFDM



Recently, visible light communication (VLC) technology has been gaining attention in both academia and industry. This is driven by the progress of white light emitting diode (LED) technology for solid-state lighting (SSL) and the potential of simultaneously using such LEDs for illumination and indoor wireless data transmission. This paper provides an overview about the technology and describes the physical layer implementation of a VLC system based on a modified version of the classical orthogonal frequency division multiplexing (OFDM) modulation technique. Besides, the paper presents a hardware prototype for short-range broadcasting using a white LED lamp. The OFDM system runs on DSP development boards. Off-the-shelf 9 LEDs and a single photo diode (PD) are utilized to build the analog front ends. The prototype allows investigating the influence of the electrical signal-to-noise ratio (SNR), constellation order, and channel coding on the bit-error performance. Theoretical and experimental results on optical path loss show close match. In this context, the influence of the LED beam angle on the horizontal coverage is highlighted.

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