I have often been asked; what is the motivation for VLC and Optical Wireless Communications? So, I wish to address the main motivation in this post.
The compound annual growth rate (CAGR) of mobile data usage per month for the next four years is estimated to be around 80% as can be determined from Figure 1. Assuming no extra additional radio frequency spectrum, this would mean that gains on spectrum efficiency have to be increased in the same manner through new technology, but it has been reported that the spectrum efficiency gains of cellular systems are slowing. In fact they are saturating, as can be seen from Figure 2. One solution to the emerging problem is the release of additional radio frequency spectrum for mobile communications, but unfortunately most of spectrum of interest (in the 1 GHz – 10 GHz region) is already in use, and identifying new radio frequency spectrum to keep up with exploding wireless data demand is impossible.
As a result of the problem I have highlighted, the Federal Communications Commission (FCC) has issued warning and has been speaking about a “looming spectrum crises”. This warning is underpinned by the recent report of GBI research in which they have shown a significant gap between required network capacity and the predicted available capacity. This gap is shown in Figure 3 where the forecast traffic per device is shown as well as the forecast available network traffic per device. If the expected trends prove to be true, we will see a shortfall of network capacity of about 97% in the year 2014. A spectrum crisis would be unavoidable.
I believe that it is the right time now to develop radically new solutions for future, post-LTE wireless networks. The approach taken is to consider an entirely different part of the electromagnetic spectrum – the infrared and visible light spectrum – that is largely unused for communication and more than 10,000 larger than the entire microwave spectrum.