Indoor optical wireless communication systems for broadband access

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Canada is among the leading nations in terms of access to broadband services. However, a 2008 OECD study indicated that many international competitors were eroding this initial lead in broadband penetration. An important factor in broadband penetration is the availability of suitable access methods. This research program develops new communications theory, algorithms and prototypes to improve the rates and reliability of indoor broadband optical wireless links. These links transmit data by modulating and detecting an optical intensity and provide high-rate, cost effective, interference-free indoor communications. In particular, this research considers indoor optical channels at both visible and infrared wavelengths. Visible light communication (VLC) channels employ white illumination LEDs whose energy efficiency is at least ten times greater than incandescent bulbs. An often overlooked feature of white LEDs is there significant modulation bandwidth. Inexpensive phosphor-based white LEDs have bandwidths in excess of 20MHz while RGB LEDs can have bandwidths in excess of 100MHz. While others have considered using white LEDs for illumination and communications, there has been little development of rigorous communication theory, algorithms and modulation for these links. This work will develop spectrally efficient signalling for indoor VLC channels to improve the available data rates focusing on three main approaches (i) optical MIMO techniques, (ii) bandwidth efficient modulation and (iii) equalization methods. A unique feature is the integration of dimming and colour selection into the modem design problem. In addition, VLC links must be integrated with power-line modems that will deliver data to allow wireless access in a room. At infrared wavelengths, high-speed dynamic spot diffusing (DSD) infrared communication systems will be investigated. Estimates indicate that data rates in excess of 1Gbps are possible in such links when imaging receivers are employed. Capacity maximizing path adaptation and short-length rateless code design will be developed. This research program will leverage existing hardware in our lab to develop prototypes to validate the developed algorithms.