A number of CR testbeds have been devised to enable the design, implementation, testing and performance
evaluation of CR engines. One of the most important testbed developed is the XG programme funded by DARPA. The XG programme aimed to provide dramatic improvements in assured military communications in support of a full range of worldwide deployments. This has been achieved with the development of enabling technology and system concepts to dynamically redistribute allocated spectrum. Through this programme, CORAL Cognitive (Policy) Radio Language (CORAL) has evolved [1, 2]. This language expresses various policy engines as well as reasoning techniques developed for the XG programme.

[1] Grit Denker, Daniel Elenius, RukmanSenanayake, Mark-Oliver Stehr, Carolyn Talcott and David Wilkins, Cognitive Policy Radio Language(CoRaL)A Language for Spectrum PoliciesXG Policy LanguageVersion 0.1, ICS-16763-TR-07-00, April 2007, Prepared forDefense Advanced Research Projects Agency

[2] DARPA XG Program (http://xg.csl.sri.com/)