ABSTRACTIt is well-known that cognitive radio (CR) is a fundamental solution to mitigate the spectrum scarcity of today's wireless communication systems. For the realization of CR, there are many obstacles to resolve, including technical and policy perspectives. Since CR is a very sensitive technology, it is particularly important to test the scheme with appropriate operation in a real environment. In this regard, we have developed a testbed of a regional spectrum sensing based CR system for digital TV (DTV) white space. The developed system has a centralized spectrum sensor, and according to the sensing results, mobile WiMAX system provides high quality multimedia service through the spectrum hole in DTV band. There is also a fast frequency hopping capability depending on the sensing results to minimize interference to the actual licensee, the primary DTV system. The performance analysis shows that the developed CR system has excellent performance satisfying the IEEE 802.22 requirements, and is suitable for use in the real environment.