Facilitating Current Terminals Accessing to Cognitive Radio Networks

More users are overcrowding into the partial band, which leads to relative scarcity of the spectrum. In the last decade, cognitive radio is widely regarded as promising technology, which promotes secondary users dynamically accessing to network in the spectrum overlay or underlay way. In the previous blueprint, individual terminals must first cognize spectrum holes, and then utilize the available band. However, there are many challenges for personal terminals with limited software and hardware to achieve the sensing task. We propose the strategy transferring spectrum sensing role of cognitive user to the centralized entity, minimizing terminal cost. We introduce spectrum-cognizing server (SCS) to determine the vacant spectrum. The server can further allocate unutilized spectrum to secondary users in the overlay way and control their transmission power in underlay mode. We argue that network with central SCS provides transparent spectrum service to end-users who can focus on data transmission. Consequently, subscribers who satisfy the wide band operation can seamlessly work in cognitive radio networks. We compare SCS, cooperative sensing and other database-enabled schemes in terms of terminal cost, sensing interference, solution to the hidden node problem and so on, thereby find that SCS has more advantages.