Can Cognitive Radio Support Broadband Wireless Access?

One application of cognitive radios is to provide broadband wireless access (BWA) in the licensed TV bands on a secondary access basis. This concept is examined to see under what conditions BWA could be viable. Rural areas require long range communication which cognitive radios may not be able to support with enough secondary spectrum. Urban areas have less available spectrum and the BWA must use shorter ranges with greater spatial reuse. Furthermore, it is not clear what regulatory model would best support BWA. This paper considers demographic (urban, rural) and licensing (unlicensed, nonexclusive licensed, exclusive licensed) dimensions. A general BWA efficiency and economic analysis tool is developed and then example parameters corresponding to each of these regimes are derived. The results indicate that in rural areas an unlicensed model is viable and the additional spectrum would be useful despite existing unlicensed spectrum. In the densest urban areas the licensed models are not viable. This is not simply because there is less unused spectrum in urban areas. Urban area cognitive radios are constrained to short ranges and many broadband alternatives already exist. As a result the cost per subscriber is high. An unlicensed model is viable in urban areas, however the spectrum needs can be met with existing unlicensed spectrum. These results provide useful input for a variety of spectrum policy issues.