Allowing sensing as a supplement: An approach to the weakly-localized whitespace device problem

In this paper, we consider the problem of granting whitespace access to devices which have neither certified sensing capabilities nor a means of direct geolocation. These devices, called “slaves,” use a nearby “master” device to assist in determining which channels are available for secondary use. Such devices must be supported since even a “master” device which uses GPS for geolocation will need to become a “slave” when operating indoors where GPS operation is notoriously poor. The two regulatory bodies that are most active in this space, the Federal Communications Commission (FCC) in the United States and Ofcom in the United Kingdom, have similar yet slightly different approaches to the problem. While in the US the slave is directed to use the channels which are available at the master´s location, slaves in the UK are given operating parameters which should be reasonably safe anywhere within the master´s coverage area. We demonstrate in this paper that the first approach is too permissive while the latter is too conservative. Ultimately, we believe that the problems with these approaches are due to the misconception that whitespace devices need to determine their locations. In truth, the actual goal is to determine a set of channels on which it is safe for the device to transmit. For example, it is clear how a whitespace database (WSDB) should respond to a weakly-localized device which can reliably say “I am located either in New York City or San Francisco, but I don´t know which.” In this case, the WSDB should compute the set of channels which are simultaneously available for use in both NYC and SF, then direct the device to choose from that set. To demonstrate the power of this shift in perspective, we propose an enhancement to Ofcom´s necessarily-conservative approach which safely increases the number of whitespace channels available to slave devices via simply sensing for stro- g signals. However, our actual goal is much larger than a particular method. We believe that regulators should certify “localization” in a broader sense of the term, and this work simply serves as a proof-of-concept/need for that argument.