Abstract
This paper studies the secure transmission in the dual-hop cognitive wiretap networks, where the secondary transmitter (Alice) aims to transmit confidential information to the secondary receiver (Bob) in the face of a multi-antenna relay (Relay), while the malicious eavesdropper (Eve) is used to eavesdrop the confidential information from Alice and Relay. To improve security, we design two transmission schemes, namely maximal-ratio combining/maximal-ratio transmission-selection combining (MRC/MRT-SC) with half-duplex (HD) receiver and maximal-ratio combining-zero forcing beamforming/maximal-ratio transmission-selection combining-zero forcing beamforming (MRC-ZFB/MRT-SC-ZFB) with full-duplex (FD) receiver. To evaluate the secrecy performance obtained from the proposed schemes comprehensively, the new closed-form and simple asymptotic expressions for the secrecy outage probability (SOP) and secrecy throughput (ST) of our considered networks with MRC-ZFB/MRT-SC-ZFB and MRC/MRT-SC schemes are derived, respectively. Thus, we explore the effect of various schemes on system secrecy performance in terms of SOP and ST. Analytical results and numerical simulations demonstrate that MRC-ZFB/MRT-SC-ZFB achieves better performance in the two proposed schemes. In particular, we show that the FD receiver plays a crucial role in designing the cognitive wiretap networks for protecting the legitimate link against attack from the malicious eavesdropping.
Highlights
The dramatic needs in wireless communications service have resulted in higher requirements for more spectrums
While for the FD operation, maximal-ratio combining (MRC)-zero forcing beamforming (ZFB)/maximal-ratio transmit (MRT)-selection combining (SC)-ZFB secure transmission schemes are proposed, Relay first adopts MRC scheme to receive the data forwarded from Alice and at the same time Bob uses the ZFB scheme to transmit artificial noise (AN) signals to reduce the illegal wiretapping of users at the first phase
The Monte Carlo simulations in all figures thoroughly coincide with the theoretical simulation curves, which verifies that the closed-form expression is derived correctly in this paper
Summary
The dramatic needs in wireless communications service have resulted in higher requirements for more spectrums. Cognitive radio networks (CRNs) aim to effectively address spectrum scarcity and have attracted much attention from the research communities [1,2,3,4]. CRNs, the unlicensed secondary users (SUs) can have access to the licensed primary users’ (PUs) spectrum in the condition that the interference power at the PU does not surpass a certain value [5]. Are CRNs expected to increase spectrum reuse, but they are taken the low complexity of implementation into consideration. The underlay scheme has attracted growing attention, where the interference of SUs to the PUs should be guaranteed not to exceed a given threshold
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