PROJECT TITLE :
Visible Light Communications Using OFDM and Multiple LEDs
Visible-light communication (VLC) systems leverage solid-state illumination devices to make high-speed communication links. Orthogonal frequency-division multiplexing (OFDM) has been thought-about for these intensity-modulated/direct-detection (IM/DD) optical channels, but, it suffers from high peak-to-average power ratio (PAPR). Moreover, the implementation of linear, power-economical, high-current, wideband drivers is difficult. During this paper, the concept of spatial summing is developed where wideband, high PAPR OFDM signals are partitioned into many low-PAPR narrowband signals that are transmitted from multiple LEDs. The signals from different LEDs are allowed to add in space before being detected by a conventional OFDM receiver. Spatial optical-OFDM (THUS-OFDM) is proposed in which filtered subsets of carriers are emitted by each LED. Additionally, low-PAPR optical single-carrier FDMA (OSC-FDMA) is developed where different collections of LEDs act as virtual users in a very multiple-access scheme. The various variations of THEREFORE-OFDM and OSC-FDMA are compared to standard DC-biased optical (DCO) OFDM and are shown to realize lower PAPR and additional robustness to LED nonlinearities leading to error rate performance gains at high signal-to-noise ratios.
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