  Traditional regulatory methods for spectrum licensing have been recently
identified as one of the causes for the under-utilization of the valuable radio
spectrum. Governmental agencies such as the Federal Communications Commission
(FCC) are seeking ways to remove stringent regulatory barriers and facilitate
broader access to the spectrum resources. The goal is to allow for an improved
and ubiquitous sharing of the precious radio spectrum between commercial
service providers.
  In this paper, we propose a novel noncooperative game theoretic approach, to
show how to foster more sharing of the radio spectrum via the use of regulatory
power. We define a two stage game in which the government regulators move
first, followed by the providers. The providers are incentivized by lower
spectrum allocation fees from the regulators in return for proof-of-sharing.
The providers are offered discounted spectrum bands, potentially at different
locations, but will be asked to provide coverage to users that are not
subscribed to them so as to maintain their subsidy incentives from the
government. In a simplification of the model, analytical expressions for the
providers' perfect equilibrium strategies are derived, and we argue for the
existence of the government's part of a perfect equilibrium. Our analysis shows
that through subsidization, the government can provide small service providers
a fair chance to compete with the large providers, thereby avoiding
monopolization in the market.
