Whitespaces after the USA's TV incentive auction: A spectrum reallocation case study

Spectrum has traditionally been allocated for single uses and by now most of the “prime” spectrum has well-entrenched incumbent users. When a new service needs spectrum, there are two qualitatively distinct ways of making bandwidth available for it. A swath of incumbent users can be removed from a band, with the cleared band being reallocated for the new service. Alternatively, the new users can be allowed to utilize the interstitial spectrum holes (i.e. whitespaces) between incumbent users, with the requirement to protect the incumbents' QoS. But these can also be used in combination by partially clearing a band and opening up the rest for whitespace-style sharing. In this case, the ability of regulators to “repack” incumbents, e.g. alter their operating channels, can reduce the need to evict them. An open question has been how whitespaces and partial spectrum clearing interact with each other and the ability to repack incumbents. Do efficient repacks completely eliminate whitespaces? The USA FCC's upcoming incentive auction in the TV bands is the first large-scale attempt to repack a major band of spectrum in order to clear spectrum for LTE. This auction is meant to navigate the tradeoff between incumbent TV services and LTE networks. In preparation, the FCC has made a large and complex data set of repacking constraints available for the first time. We have repurposed this data and built our own repacking engine in order to study a more general version of the tradeoff between whitespaces and cleared spectrum. We conclude that (1) repacking enables clearing of significantly more spectrum than just removing incumbents; (2) the total amount of spectrum available for new uses is relatively insensitive to how incumbents are removed; (3) efficient repackings basically trade whitespace spectrum for cleared spectrum; (4) even the most efficient repackings leave plenty of whitespace - an amount that can be comparable with the amount of cleared spectrum.