Page 1 of 34 Enforcement in Dynamic Spectrum Access Systems Martin BH Weiss William H. Lehr Liu Cui Mohammed Altamimi Abstract The spectrum access rights granted by the Federal government to spectrum users come with the expectation of protection from harmful interference. As a consequence of the growth of wireless demand and services of all types, technical progress enabling smart agile radio networks, and on-going spectrum management reform, there is both a need and opportunity to use and share spectrum more intensively and dynamically. A key element of any framework for managing harmful interference is the mechanism for enforcement of those rights. Since the rights to use spectrum and to protection from harmful interference vary by band (licensed/unlicensed, legacy/newly reformed) and type of use/users (primary/secondary, overlay/underlay), it is reasonable to expect that the enforcement mechanisms may need to vary as well. In this paper, we present a taxonomy for evaluating alternative mechanisms for enforcing interference protection for spectrum usage rights, with special attention to the potential changes that may be expected from wider deployment of Dynamic Spectrum Access (DSA) systems. Our exploration of how the design of the enforcement regime interacts with and influences the incentives of radio operators under different rights regimes and market scenarios is intended to assist in refining thinking about appropriate access rights regimes and how best to incentivize investment and growth in more efficient and valuable uses of the radio frequency spectrum. 1 INTRODUCTION The future of wireless necessitates that we use our Radio Frequency (RF) resources more efficiently, which in turn, requires us to transition to a future in which spectrum is shared more intensively. The growing demand pressure for expanded access for legacy and new uses and the need for significant spectrum reform to enable such sharing was noted by the FCC's Spectrum Policy Task Force, was reaffirmed by the National Broadband Plan and the