This article investigates the physical-layer security of CR networks, which are vulnerable to various newly arising attacks targeting the weaknesses of CR communications and networking. We first review a range of physical-layer attacks in CR networks, including primary user emulation, sensing falsification, intelligence compromise, jamming, and eavesdropping attacks. Then we focus on the physical-layer security of CR networks against eavesdropping and examine the secrecy performance of cognitive communications in terms of secrecy outage probability. We further consider the use of relays for improving CR security against eavesdropping and propose an opportunistic relaying scheme, where a relay node that makes CR communications most resistant to eavesdropping is chosen to participate in assisting the transmission from a cognitive source to its destination. It is illustrated that the physical- layer secrecy of CR communications relying on opportunistic relaying can be significantly improved by increasing the number of relays, showing the security benefit of exploiting relay nodes. Finally, we present some open challenges in the field of relay-assisted physical-layer security for CR networks.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China (Grant Nos. 61401223 and 61522109), the Natural Science Foundation of Jiangsu Province (Grant No. BK20140887), and the Key Project of Natural Science Research of Higher Education Institutions of Jiangsu Province (No. 15KJA510003).
- Physical layer
- Signal to noise ratio
- Wireless communication