Spectrum Sharing-Carnegie Mellon University in Rwanda - Carnegie Mellon University


Policy-Based Radios for Spectrum Sharing

Broadband access is key to economic growth in the modern interconnected economy. Ironically, recent decisions by the U.S. Federal Communications Commission (FCC) will soon yield a new commercial wireless technology that may be even more useful for the expansion of broadband access in developing countries than in the U.S.  The FCC opened the door for “TV white space” devices that operate in spectrum allocated to television. These devices use geo-location technology and a database of TV transmitter locations to avoid harmful interference to TV. Led by the U.K. several other nations are also in the process of making it legal to use this technology.

TV white space devices are a special case of so-called policy-based radios, governed by policies that are machine-readable and easily modified. The ability to customize policies and even change them over time brings a flexibility that can greatly enhance effective use of spectrum, especially in developing nations, which have spectrum needs and resources that are somewhat different from the economies that tend to drive demand for wireless devices. 

Timothy X Brown, Visiting Professor of Electrical and Computer Engineering at Carnegie Mellon University in Rwanda and Jon M. Peha of Carnegie Mellon University suggest that policy based radios will have a role to play in broadband access. They presented a paper that argues that these radios can play a significant role for spectrum regulators to manage many aspects of the radio spectrum. Though there remain challenges to the widespread use of policy-base radios, the technology has developed to the point where its use should be considered.

Nevertheless, there are challenges to applying policy-based radio technology in order to meet the broadband needs of developing countries. There are significant differences in regulation, how the network will be used, and the underlying infrastructure that need to be addressed. Many countries have high-capacity transmission networks, but are severely limited in last-mile connections. Rwanda for instance has 2,300 kilometres of fibre optic cables connecting distant parts of this small country but limited distribution and access to the end users. Policy-based radio devices could provide this last-mile connectivity. 

TV white space frequencies are better suited to provide coverage in hilly or densely foliated terrain than higher frequencies. Moreover, if there were regulatory reform, the amount of spectrum that could be available to policy-based radio devices is likely to be much greater in places in developing countries than in major U.S. and U.K. markets, because there is spectrum that remains fallow in developing countries in part because this spectrum is unavailable in the largest markets; this prevents manufacturers, standards bodies, and regulators from unleashing wireless devices in these bands that would only be useful in smaller markets.

Policy-based radios are a flexible technology that supports different spectrum sharing models to enable access to more spectrum. Fallow and underutilized spectrum can be used through time-limited policies so that a spectrum manager can manage when, where and how spectrum can be accessed. By resolving the static allocation issues spectrum holders would be more willing to offer up spectrum thus making more spectrum available and less spectrum left fallow. This technology is especially important in developing countries that have underutilized spectrum that can be employed for economic growth while not precluding the use of future radio advances. This paper describes the key issues for regulators to consider in the use of policy-based radios in an effort to promote how they would be used in practice.