As an effective technique to fully utilize the allocated spectrum resource and improve network capacity, cognitive radio (CR) [1, 2] has drawn a lot of attention in cellular networks. For example, CR is employed in IEEE 802.22 cellular systems to
provide broadband wireless access using television white space (TVWS) [3]. Another application of CR is for dynamic spectrum access (DSA) in multiple-radio-access-technology (multi-RAT) heterogeneous cellular networks, which has been
standardized in IEEE 1900.4 [4] and included in the end-to-end efficiency (E3) project of the European Telecommunications Standards Institute (ETSI) [5].