The Research Of Security Issues In Cognitive Radio Networks

With the rapid development of the wireless communication technology, people have more and more demand on wireless communication services. As the number of wireless devices continues to increase, the requirements for the spectrum resources become more and more urgent. How to satisfy the spectrum demand is considered as an important issue in wireless communications. However, according to the report on actual spectrum usage measurement given by researchers, most of the allocated bands are largely under-utilized. Cognitive radio (CR) has been proposed to solve the problem of the inefficient spectrum usage. In cognitive radio networks (CRN), secondary users (SUs) are allowed to communicate in certain licensed spectrum band without causing harmful interference to primary users (PUs). As a promising technique to mitigate the spectrum scarcity problem, CR can significantly improve the spectrum efficiency for wireless communications.The network security is a key point to carry out wireless communication. Due to the characters of CRN, especially the cognitive functions and reconstruction features, there are new classes of security threats and challenges in CRN, compared with traditional wireless networks. Providing complete security schemes may prove to be the most important aspect to make cognitive radio a long-term commercially-viable concept. This paper concentrates on the security issues of CRN from two aspects: physical layer (PHY-layer) and MAC-layer.Firstly, security threats against PHY-layer are analysed. For the realization of the cognitive radio paradigm, several spectrum sensing schemes have been proposed, such as centralized and distributed schemes, and cooperative or non-cooperative spectrum sensing mechanisms. Unfortunately, the existing proposals for spectrum sensing introduce significant security leakages. Several classes of attacks are described in this part, such as Primary User Emulation attacks. To improve the accuracy of spectrum sensing, collaborative spectrum sensing is proposed. Based on collaborative spectrum sensing, we proposed a location-aware scheme to defend against PUE attacks and ensure the performance of spectrum sensing.Secondly, the security issues on the MAC-layer are discussed. Two types of MAC protocols are introduced: centralized MAC protocol and Ad-hoc MAC protocol. First, how Denial of Service (DoS) attack is launched in multi-hop cognitive radio network is studied.Then, greedy behaviours in MAC-layer in CRN are explored. Analysis and simulations indicate that such attacks can greatly affect the performance of CRN. For a centralized MAC protocol such as IEEE 802.22, the security sub-layer can be implemented to ensure the security of CRN. But the malicious secondary users in collaborative spectrum sensing can degrade the performance of spectrum sensing significantly. In this paper we propose a reputation-based collaborative spectrum sensing scheme to improve the security of cooperative sensing by mitigating the impacts of misbehaviours. Simulation results show that the proposed scheme can minimize the harmful influence from malicious SUs.