Cognitive radios for dynamic spectrum access: from concept to reality

This article provides a comprehensive survey of cognitive radio technology, focusing on its application to dynamic spectrum access, especially from the perspective of realizing consumer- oriented CR networks. We first overview the state of the art in CR technology and identify its key functions across the protocol stack, such as spectrum sensing, resource allocation, CR MAC protocol, spectrum-aware opportunistic routing, CR transport protocol, QoS awareness, spectrum trading, and security. We also review the various schemes proposed for each of these functions and discuss the suitability, advantages, and limitations of their usage in the future CR market. Finally, we introduce the activities in CR research communities and industry in terms of development of real-life applications, such as IEEE 802.22, Ecma 392, and IEEE 802.11af (also known as Wi-Fi 2.0 or White-Fi), and then identify necessary steps for future CR applications.