Abstract:
In this thesis study, we propose a security structure for spectrum sensing and decision scheme for a satellite assisted Cognitive Radio Network (CRN). The main goal of Cognitive Radio (CR) is to provide agility in the spectrum access and operations parameters. Hence, performance of wireless transmission can be optimized. Additionally, CR facilitates more efficient spectrum utilization which is a fundamental issue in the emerging communications paradigm of anytime-anywhere access. In order to provide spectrum agility, CRs have some additional functionalities (eg. remote configurability, spectrum analysis, primary user detection) different from the ones in wireless networks. These functionalities come at the expense of various challenges such as spectrum management and reliable primary user detection. In an infrastructure-based CRN where the network is divided into cells, spectrum management and resource allocation in each cell is managed by the base station (BS) of each cell. However, these may require extensive message exchanges among the BSs. Instead, a satellite with its wide coverage can assist the BSs to provide a more reliable spectrum environment map. Additionally, it can provide the management functionalities and regular policy updates by message broadcasts. Different from the conventional wireless networks, this structure–referred to as satellite assisted CRN, may be exposed to new security attacks. We investigate these security threats, evaluate their risk levels and provide cryptographic and noncryptographic counter-measures. This investigation points out which security services need to be employed in order to design a robust security scheme for this structure. Considering the properties and the restrictions of the CRN segment and the satellite segment, we design a two-tiered security structure. We apply confidentiality, entity and data origin authentication, cryptographic nonce and integrity security services to our security structure. Since these security services can be provided by using different security solutions, we present a detailed security and performance evaluation of the proposed security solution. The performance of proposed structure is analyzed under varying number of CRs in the network and varying CR handover frequency. The performance results show that the proposed approach is secure and efficient in terms of bandwidth usage and processing cost.
