Privacy Preservation In Database-driven Cognitive Radio Networks

The concept of Cognitive Radio Networks(CRNs) was first proposed in 1999. It is considered to solve the problem of wireless spectrum wastage under the paradigm of fixed spectrum allocation. In CRNs, unregistered users(secondary users) can search and access the unoccupied spectrum(spectrum hole) temporarily to enhance the spectrum utilization of wireless spectrum. In traditional CRNs, secondary users should have to implement spectrum sensing to determine the available spectrum. Federal Communication Committee(FCC) proposed database-driven CRNs, in which secondary users could obtain available spectrum via querying the database instead of spectrum sensing based on the pre-established channel. Database-driven CRNs shifts the function of available spectrum retrieval from terminal devices to the central database and enable secondary users to obtain more accuracy available spectrum information and in the meaning time, simplify the deployment of the networks. In database-driven CRNs, secondary users get the available spectrum information via the process of spectrum query. In the process spectrum query, since the communication contents between secondary users and the database are correlated with the locations of primary users and secondary users, there are threats of privacy leaking. In this article, we identify that the database is able to infer the locations of secondary users based on the utilized channels of secondary users. On the other hand, secondary users could also infer the locations of primary users based on the spectrum availability information. For fixed users, we proposed a general location inference attack scheme, based on which the primary users and secondary users could be localized in a relative small area. For mobile secondary users, the database could also launch probabilistic tracking attack based on the collected information of channel utilization. To thwart the location and trajectory privacy leaking in spectrum query, we proposed an improved privacy preserving spectrum query scheme, in which secondary users obfuscate the submitted location, which could also be utilized to help determine the best channel. Then the database perturbs the locations of primary users before calculating the available spectrum information. Finally,secondary users estimate the location privacy level to determine the selected channel.We conduct experiments to verify the proposed location inference attacks and location protection schemes. The results of the experiments show that the privacy preserving schemes significantly improve the users’ location privacy and trajectory privacy in database-driven CRNs.