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Spectrum frequency is a valuable resource for wireless communication but very limited in its availability. Due to the extensive use and ever increasing demand of spectrum bands by wireless devices and newer applications, unlicensed band is becoming congested, while licensed bands are found mostly underutilized. To solve this problem of spectrum scarcity, cognitive radio (CR) devices can share licensed bands opportunistically in several ways. We analyze the three main dynamic sharing models (commons, shared-use, and exclusive-use) proposed in literature with extensive analysis of the exclusive-use model, which is the most promising as it provides benefits to both licensed and unlicensed users. In this model, CR-enabled service providers, also known as secondary service providers, can buy or lease spectrum from licensed, known as primary service providers, for both short and long duration and gain exclusive rights to access the spectrum. In this survey paper, exclusive-use trading approaches, namely, game theory, market equilibrium, and classical, hybrid and other models are reviewed extensively and their characteristics and differences are highlighted and compared. We also propose possible future research directions on exclusive-use CR model.
Hassan et al. (Sun,) studied this question.