In this paper, we consider a multi-input-multi-output cognitive radio (MIMO-CR) system which consists of one secondary user (SU) and one secondary destination (SD), in which one eavesdropper (E) attempts to tap the information from SU to SD. All of the aforementioned nodes are equipped with multiple antennas. For enhancing physical layer security, we propose so-called optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes, which assume that the instantaneous wiretap channel information is known and unknown, respectively. We carry out the secrecy outage probability analysis for the proposed OAS and SAS schemes. In order to make a performance comparison, we also discuss the secrecy outage probability of single-input-single-output cognitive radio (SISO-CR) system. The secrecy outage performance of SAS is better than SISO but worse than OAS. Furthermore, as the numbers of antennas of SU and SD increase, the secrecy outage probability of OAS and SAS both have significant improvements.
In this paper, we consider a multi-input-multi-output cognitive radio (MIMO-CR) system which consists of one secondary user (SU) and one secondary destination (SD), in which one eavesdropper (E) attempts to tap the information from SU to SD. All of the aforementioned nodes are equipped with multiple antennas. For enhancing physical layer security, we propose so-called optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes, which assume that the instantaneous wiretap channel information is known and unknown, respectively. We carry out the secrecy outage probability analysis for the proposed OAS and SAS schemes. In order to make a performance comparison, we also discuss the secrecy outage probability of single-input-single-output cognitive radio (SISO-CR) system. The secrecy outage performance of SAS is better than SISO but worse than OAS. Furthermore, as the numbers of antennas of SU and SD increase, the secrecy outage probability of OAS and SAS both have significant improvements.
In this paper, we consider a multiple-input-multiple-output (MIMO) system consisting of one source, one destination, and one eavesdropper, where each node is equipped with an arbitrary number of antennas. To improve the security of source-destination transmissions, we investigate the antenna selection at the source and propose the optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes, depending on whether the source node has the global channel state information (CSI) of both the main link (from source to destination) and the wiretap link (from source to eavesdropper). Moreover, the traditional space-time transmission (STT) is studied as a benchmark. We evaluate the secrecy performance of STT, SAS, and OAS schemes in terms of the probability of zero secrecy capacity. Furthermore, we examine the generalized secrecy diversity of the STT, SAS, and OAS schemes through an asymptotic analysis of the probability of zero secrecy capacity as the ratio between the average gains of the main and wiretap channels tends to infinity. This is different from the conventional secrecy diversity that assumes an infinite signal-to-noise ratio (SNR) received at the destination under the condition that the eavesdropper has a finite received SNR. It is shown that the generalized secrecy diversity orders of the STT, SAS, and OAS schemes are the product of the number of antennas at source and destination. Additionally, numerical results show that the proposed OAS scheme strictly outperforms both the STT and the SAS schemes in terms of the probability of zero secrecy capacity.
We have examined the physical layer security of an underlay cognitive radio network (CRN) consisting of L legitimate receivers ( STX), a secondary transmitter ( STX), an eavesdropper (Eve), and a primary user (PU). All SRX and the PU are equipped with a single antenna while the STX and Eve are implemented with multiple antennas. The optimal antenna selection scheme (OAS) is adopted at the STX, which maximizes the secrecy capacity while a generalized receiver selection scheme is adopted at the SRX. The STX sends information to the SRX with the lthbest signal to noise ratio (SNR). The concise expressions for exact and asymptotic secrecy outage probability (SOP) for an arbitrary number of SRX, number of transmit antenna NA, and number of eavesdropper antenna NE have derived.
Abstract—In this paper, we consider a multiple-input multiple-output (MIMO) system consisting of one source, one destination and one eavesdropper, where each node is equipped with an arbitrary number of antennas. To improve the security of source-destination transmissions, we investigate the antenna selection at the source and propose the optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes, depending on whether the source node has the global channel state information (CSI) of both the main link (from source to destination) and wiretap link (from source to eavesdropper). Also, the traditional space-time transmission (STT) is studied as a benchmark. We evaluate the secrecy performance of STT, SAS, and OAS schemes in terms of the probability of zero secrecy capacity. Furthermore, we examine the generalized secrecy diversity of STT, SAS, and OAS schemes through an asymptotic analysis of the probability of zero secrecy capacity, as the ratio between the average gains of the main and wiretap channels tends to infinity. This is different from the conventional secrecy diversity which assumes an infinite signal-to-noise ratio (SNR) received at the destination under the condition that the eavesdropper has a finite received SNR. It is shown that the generalized secrecy diversity orders of STT, SAS, and OAS schemes are the product of the number of antennas at source and destination. Additionally, numerical results show that the proposed OAS scheme strictly outperforms both the STT and SAS schemes in terms of the probability of zero secrecy capacity. Index Terms—MIMO, antenna selection, space-time code, eavesdropping attack, secrecy diversity.
In this paper, we address the physical-layer security issue of a secondary user (SU) in a spectrum-sharing cognitive radio network (CRN) from an information-theoretic perspective. Specially, we consider a secure multiple-input single-output (MISO) cognitive radio channel, where a multi-antenna SU transmitter (SU-Tx) sends confidential information to a legitimate SU receiver (SU-Rx) in the presence of an eavesdropper and on the licensed band of a primary user (PU). The secrecy capacity of the channel is characterized, which is a quasiconvex optimization problem of finding the capacity-achieving transmit covariance matrix under the joint transmit power and interference power constraints. Two numerical approaches are proposed to derive the optimal transmit covariance matrix. The first approach recasts the original quasiconvex problem into a single convex semidefinite program (SDP) by exploring its inherent convexity; while the second one explores the relationship between the secure CRN and the conventional CRN and transforms the original problem into a sequence of optimization problems associated with the conventional CRN, which helps to prove that beamforming is the optimal strategy for the secure MISO CR channel. In addition, to reduce the computational complexity, three suboptimal schemes are presented, namely, scaled secret beamforming (SSB), projected secret beamforming (PSB) and projected cognitive beamforming (PCB). Lastly, computer simulation results show that the three suboptimal schemes can approach the secrecy capacity well under certain conditions.
This paper considers a multiple-input-multiple-output (MIMO) energy-harvesting (EH) system, which is made up of a source (S) and a destination (D) as well as an eavesdropper (E). In this system, S, D and E are equipped with multiple antennas and S can be charged by a power beacon (PB) in the EH phase of the total communication process. To enhance the physical-layer security, we propose optimal antenna selection (OAS) scheme and suboptimal antenna selection (SAS) scheme, relying on whether the global channel state information (CSI) is available or unavailable to S. Moreover, the analysis of the conventional space-time transmission (STT) is carried out as a baseline. In order to intuitively show the effect of the number of antennas on secrecy outage performance, the secrecy diversity analysis for STT, SAS and OAS schemes is carried out through the asymptotic secrecy outage probability as the MER (the average gains between main channel from S to D and wiretap channel from S to E) tends to infinity. Additionally, the results show that the secrecy diversities of STT, SAS and OAS are the product of the number of antennas at S and D, which has no relation to E. Furthermore, the research findings indicate that our proposed OAS scheme performs the best in terms of secrecy outage probability and STT scheme achieves the worst secrecy performance.
Secure data transmission in future high-capacity high-coverage multi-tier hierarchical networks, for which cognitive radio(CR) has emerged as an essential recipe, is of utmost importance. This paper investigates the secrecy outage performance of selection combining(SC) in CR networks(CRNs) over Rayleigh fading channels. In a single-input multiple-output(SIMO) wiretap channel, a secondary user transmits confidential messages to another secondary user, which is equipped with( 1)B Bn n ≥ antennas. Meanwhile, a passive eavesdropper, which is equipped with( 1)E En n ≥ antennas, intends to overhear the messages. Both the legal receiver and the eavesdropper adopt SC scheme to process the received multiple signals. The secondary transmitter uses the underlay strategy to guarantee the quality of service of the primary user without spectrum sensing. Compared to the work proposed by Maged Elkashlan et al. in Ref. [1], we present an alternative method to derive the closed-form expression for the secrecy outage probability(SOP) and develop a simplified SOP when the maximal transmit power at the secondary user is sufficiently high. Our results reveal the impact of the primary network on the secondary network with a multi-antenna wiretap channel and simulations are conducted to validate the accuracy of our proposed analytical models.