The amount of wireless and mobile applications and devices is rapidly growing. This exponential growth might be hindered by a scarcity of suitable radio spectrum, a necessary but limited natural resource required for all wireless communications. Spectrum scarcity does not only slow down data growth, but may also disrupt existing communications. Cognitive radio may provide a solution to these issues, but although the concept seems promising, few products making use of CR have been brought to the market. This is due to significant uncertainties surrounding the appropriate economic scenario for CR, the regulatory framework and the technology enablers needed for such CR scenario. As business, regulatory and technical constraints are largely co-determined by each other, this paper proposes to align them, paving the road for the implementation of specific economic scenarios with appropriate regulation. First, from the business perspective, a taxonomy of possible economic scenarios for CR is proposed. Second, for each scenario a number of regulatory requirements – based on a European context – and characteristics are given. In doing so, it is argued that the economic scenarios are inherently distinct so that CR regulation should be customized for the type of scenario envisaged. Third, from the technology perspective, this article reviews the possible CR enablers, showing that spectrum sensing, CPC and geolocation database all have their strengths and weaknesses, and receive varying support from business and regulators. Based on the analysis it can be concluded that, although the introduction of CR does not seem problematic for the unlicensed scenario and the flexible operator scenario, more complex measures are required to enable CR to contribute to the implementation of spectrum pool—and spectrum market scenarios. It can also be concluded that, out of the three proposed alternatives, the geolocation database is the most likely candidate to be used for CR purposes. However, although this database is a clear favorite for applications within the TV White Spaces, spectrum sensing should not be discarded as a potential CR enabler for highly sensitive applications in high-density radio environments.
