Implementation of a VLC HDTV Distribution System for Consumer Premises

A unidirectional, visible light communication (VLC) system intended for the distribution of Digital Video Broadcasting (DVB), high-definition television (HDTV) content to DVB compatible TVs within consumer premises is presented.

The system receives off-air HDTV content through a consumer grade DVB-T/T2 terrestrial set-top-box (STB) and re-encodes its Moving Picture Experts Group (MPEG) transport stream (TS) using a pulse position modulation (PPM) scheme called inversion offset PPM (IOPPM). The re-encoded TS is used to intensity modulate (IM) a blue light-emitting diode (LED) operating at a wavelength of 470 nm. Directed line-of-sight (DLOS) transmission is used over a free-space optical (FSO) channel exhibiting a Gaussian impulse response. A direct-detection (DD) receiver is used to detect the transmitted IOPPM stream, which is then decoded to recover the original MPEG TS. A STB supporting a high-definition multimedia interface (HDMI) is used to decode the MPEG TS and enable connectivity to an HD monitor.

The system is presented as a complementary or an alternative distribution system to existing Wi-Fi and power-line technologies. VLC connectivity is promoted as a safer, securer, unlicensed and unregulated approach. The system is intended to enable TV manufacturers to reduce costs by, firstly, relocating the TV’s region specific radio frequency (RF) tuner and demodulator blocks to an external STB capable of supporting DVB reception standards, and, secondly, by eliminating all input and output connectors interfaces from the TV. Given the current trend for consumers to wall-mount TVs, the elimination of all connector interfaces, except the power cable, makes mounting simpler and easier.

The operation of the final system was verified using real-world, off-air broadcast DVB-T/T2 channels supporting HDTV content. A serial optical transmission at a frequency of 66 MHz was achieved. The system also achieved 60 Mbit/s, error free transmission over a distance of 1.2 m without using error correction techniques.

The methodology used to realise the system was a top-down, modular approach. Results were obtained from electrical modelling, simulation and experimental techniques, and using time-domain and FFT based measurements and analysis. The modular approach was adopted to enable design, development and testing of the subsystems independently of the overall system.