How Much White-Space Capacity Is There?

The November 2008 FCC ruling allowing access to the television white-spaces prompts a natural question. What is the magnitude and geographic distribution of the opportunity that has been opened up? This paper takes a semi-empirical perspective and uses the FCC's database of television transmitters, USA census data from 2000, and standard wireless propagation and information-theoretic capacity models to see the distribution of data-rates available on a per-person basis for wireless Internet access across the continental USA. To get a realistic evaluation of the potential public benefit, we need to examine more than just how many white-space channels have been made available. It is also important to consider the impact of wireless "pollution" from existing television stations, the self-interference among white-space devices themselves, the population distribution, and the expected transmission range of the white-space devices. The clear advantage of the white-space approach is revealed through a direct comparison of the Pareto frontier of the new white-space approach and that corresponding to the traditional approach of refarming bands between television and wireless data service. Finally, the critical importance of economic investment considerations is shown by considering the status of rural versus urban areas. Based on technical considerations alone, whether we consider long- or short-range white-space systems, people in rural areas would seem to be the main beneficiaries of white-space systems. A power-law distribution even appears that suggests that many rural customers could enjoy tremendous data-rates. However, the fundamental need to recover investments by wireless ISPs couples the range inversely to the population density. This clips the tail of the power-law and shows that urban and suburban areas can actually get significant benefit from the TV white-spaces. Overall, the opportunity provided by TV white-spaces is shown to be potentially of the same order as the recent release of "beachfront" 700MHz spectrum for wireless data service.