In this letter, we design a novel secure transmission scheme for dual-hop multiantenna spectrum sharing relaying systems over Rayleigh fading channels. To exploit the benefit of available multiple antennas, maximum ratio combining/zeroforcing beamforming (MRC/ZFB) scheme at the relay is proposed to enhance the secrecy performance. In doing so, we derive a novel exact closed-form expression of the secrecy outage probability, which enables us to evaluate the impact of system parameters on the secrecy performance. Moreover, we look into the high signal-to-noise ratio (SNR) regime, and present simple secrecy outage approximation for the proposed scheme, which reveals that the secrecy diversity order is NR- NP- NE, where NR, NP, and NE are the number of antennas at relay, primary receiver, and eavesdropper, respectively.
In this letter, we design a novel secure transmission scheme for dual-hop multiantenna spectrum sharing relaying systems over Rayleigh fading channels. To exploit the benefit of available multiple antennas, maximum ratio combining/zeroforcing beamforming (MRC/ZFB) scheme at the relay is proposed to enhance the secrecy performance. In doing so, we derive a novel exact closed-form expression of the secrecy outage probability, which enables us to evaluate the impact of system parameters on the secrecy performance. Moreover, we look into the high signal-to-noise ratio (SNR) regime, and present simple secrecy outage approximation for the proposed scheme, which reveals that the secrecy diversity order is NR- NP- NE, where NR, NP, and NE are the number of antennas at relay, primary receiver, and eavesdropper, respectively.
We investigate the secrecy performance of dual-hop amplify-and-forward multi-antenna relaying systems over Rayleigh fading channels, considering the direct link between the source and the destination. In order to exploit the available direct link and the multiple antennas for secrecy improvement, different linear processing schemes at the relay and different diversity combining techniques at the destination are proposed, namely: 1) zero-forcing/maximal ratio combining (ZF/MRC); 2) ZF/selection combining (ZF/SC); 3) maximal ratio transmission/MRC (MRT/MRC); and 4) MRT/SC. For all these schemes, we present new closed-form approximations for the secrecy outage probability. Moreover, we investigate a benchmark scheme, i.e., cooperative jamming/ZF (CJ/ZF), where the secrecy outage probability is obtained in exact closed-form. In addition, we present asymptotic secrecy outage expressions for all the proposed schemes in the high signal-to-noise ratio (SNR) regime, in order to characterize key design parameters, such as secrecy diversity order and secrecy array gain. The outcomes of this paper can be summarized as follows: 1) MRT/MRC and MRT/SC achieve a full diversity order of M + 1, ZF/MRC and ZF/SC achieve a diversity order of M, while CJ/ZF only achieves unit diversity order, where M is the number of antennas at the relay; 2) ZF/MRC (ZF/SC) outperforms the corresponding MRT/MRC(MRT/SC) in the low SNR regime, while becomes inferior to the corresponding MRT/MRC (MRT/SC) in the high SNR; and 3) all the proposed schemes tend to outperform the CJ/ZF with moderate number of antennas, and linear processing schemes with MRC attain better performance than those with SC.
This paper studies the secure transmission in cognitive wiretap relaying networks with full-duplex technique over Rayleigh channels, where a secondary user (SU) transmitter (Alice) aims to transmit confidential information to a multi-antenna legitimate SU receiver (Bob) in the presence of a multi-antenna relay (Relay), a primary user (PU) and a passive eavesdropper (Eve). For secrecy performance enhancement, we propose maximal-ratio combining-zero forcing beamforming/maximal-ratio transmission-selection combining-zero forcing beamforming (MRC-ZFB/MRT-SC-ZFB) scheme. The closed-form expression for the secrecy outage probability (SOP) of the CRNs with MRC-ZFB/MRT-SC-ZFB scheme is derived. From the analysis, we look into the high signal-to-noise ratio (SNR) regime, and present simple secrecy outage approximation for the proposed scheme, which reveals that the secrecy diversity order is min (NR, NRNB), where NRand NBare the number of antennas at Relay and Bob, respectively.
In this paper, we investigate the secrecy performance of dual-hop randomize-and-forward (RaF) cognitive wiretap networks over Rayleigh fading channels, in which the RaF relay is considered both as half-duplex (HD) and full-duplex (FD) operations. Specifically, for the HD, maximal-ratio combining/maximal-ratio transmission (MRC/MRT) is adopted at the RaF relay. For the FD, the RaF relay can simultaneously receive the signal from the source and transmit jamming signals to eavesdropper, and the selection combining-zero forcing beamforming/maximal-ratio transmit (SC-ZFB/MRT) and SC-ZFB/ZFB schemes are respectively adopted at the FD relay. To thoroughly assess the secrecy performance achieved from the proposed schemes, the closed-form expressions for the secrecy outage probability (SOP) of the dual-hop RaF cognitive wiretap channels with MRC/MRT, SC-ZFB/MRT and SC-ZFB/ZFB schemes are derived, respectively. In addition, we also provide simple asymptotic approximations for the SOP under two distinct scenarios, depending on the quality of the main and wiretap channels. Additionally, our analytical results and numerical simulations show the efficiency of our proposed solutions for both SC-ZFB/MRT and SC-ZFB/ZFB with FD cases and show considerable performance gains over MRC/MRT with HD scheme. Finally, for the proposed schemes, the SC-ZFB/ZFB scheme is beneficial to improve secrecy performance when the eavesdropper's channel is better than the main channel and the RaF relaying strategy achieves better secrecy performance than that of the decode-and-forward (DF) relaying strategy for dual-hop cognitive wiretap networks.
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.
In this paper, we investigate the secrecy performance of full-duplex multi-antenna spectrum-sharing wiretap networks in which a jamming signal is simultaneously transmitted by the full-duplex secondary receiver (Bob) based on the zero forcing beamforming (ZFB) algorithm. For the security enhancement, we propose the two antenna reception schemes: 1) random selection combining (RSC) where Bob selects LB antennas at random to combine the received signals and 2) generalized selection combining (GSC) where Bob selects LB strongest antennas to combine the received signals. We derive the exact closed-form expressions for the secrecy outage probability of full-duplex multi-antenna spectrum-sharing wiretap networks with ZFB algorithm. In order to explore a new design of the proposed schemes, we provide tractable asymptotic approximations for the secrecy outage probability in high signal-to-noise ratio regime under two distinct scenarios. From the analysis, we demonstrate that: 1) when the main channel is much better than the eavesdropper's channel, GSC/ZFB scheme achieves full diversity NB, while RSC/ZFB scheme only achieves partial diversity LB and 2) GSC/ZFB scheme achieves better secrecy performance than RSC/ZFB with different antenna numbers at Bob.
In this paper, we investigate the secrecy performance of the multi-antenna relaying networks over Rayleigh fading channels, by taking the reliability of the first link spanning the transmitter to the relays into consideration. To improve the secrecy performance, two secure transmission strategies are designed at relays, namely, 1) Maximal ratio combining/Transmitter antenna selection (MRC/TAS) and 2) MRC/Maximal ratio transmission (MRC/MRT), assisted by a friendly jammer. Specifically, in order to present the advantages of the two proposed schemes, we derive the exact closed-form expressions of the outage probability (OP) and intercept probability (IP) to evaluate the security-reliability tradeoff (SRT) of the considered system, respectively. From our theoretical analysis as well as simulation results, we find that a) our proposed schemes outperform the conventional scheme with no cooperative jammer (CJ), and b) the MRT scheme is superior to the TAS one conditioned on the same set of system parameters.