In this paper, we investigate the secrecy performance of an underlay spectrum sharing cognitive MIMO networks with the help of a cooperative jammer (Charlie), in which the secondary transmitter (Alice) aims to communicate with secondary receiver (Bob) in the presence of an eavesdropper (Eve). In order to analyze the impact of the imperfect channel state information (CSI), the CSI of the links between secondary network and primary network, Alice and Bob, Charlie and Eve are considered to be outdated, respectively. We propose the transmit antenna selection-maximal-ratio combining/zero forcing beamforming scheme (TAS-MRC/ZFB) to improve the secrecy performance of the considered networks. Furthermore, the exact and the asymptotic closed-form expressions of secrecy outage probability are provided to analyze the impacts of the outdated CSI and the proposed TAS-MRC/ZFB on the considered networks. The results reveal that the outdated CSI between secondary network and primary network has a significant impact on secrecy performance of the considered networks in the low signal-to-noise ratio (SNR) region, the outdated CSI between Charlie and Eve will significantly deteriorate the secrecy performance of the considered networks in high SNR region. Finally, Monte Carlo simulations are carried out to verify our analysis.
In this paper, we investigate the secrecy performance of an underlay spectrum sharing cognitive MIMO networks with the help of a cooperative jammer (Charlie), in which the secondary transmitter (Alice) aims to communicate with secondary receiver (Bob) in the presence of an eavesdropper (Eve). In order to analyze the impact of the imperfect channel state information (CSI), the CSI of the links between secondary network and primary network, Alice and Bob, Charlie and Eve are considered to be outdated, respectively. We propose the transmit antenna selection-maximal-ratio combining/zero forcing beamforming scheme (TAS-MRC/ZFB) to improve the secrecy performance of the considered networks. Furthermore, the exact and the asymptotic closed-form expressions of secrecy outage probability are provided to analyze the impacts of the outdated CSI and the proposed TAS-MRC/ZFB on the considered networks. The results reveal that the outdated CSI between secondary network and primary network has a significant impact on secrecy performance of the considered networks in the low signal-to-noise ratio (SNR) region, the outdated CSI between Charlie and Eve will significantly deteriorate the secrecy performance of the considered networks in high SNR region. Finally, Monte Carlo simulations are carried out to verify our analysis.
In this paper, we introduce transmit antenna selection/maximal-ratio combining (TAS/MRC) scheme in dual-hop randomize-and-forward (RaF) cognitive multiple-input multiple-output (MIMO) wiretap networks with outdated channel state information (CSI). In this network, the secondary transmitter adopts the TAS scheme to choose the antenna with the maximal received signal-to-noise ratio (SNR), while the secondary receiver and the eavesdropper adopt the MRC scheme to combine the received signals. To thoroughly assess the secrecy performance achieved by the TAS/MRC scheme and the impact of outdated CSI on the secrecy performance, we derive a new closed-form expression for the secrecy outage probability of dual-hop RaF cognitive MIMO wiretap networks. In order to achieve more insights on the application of TAS/MRC scheme, we further present tractable asymptotic secrecy outage probability at high SNR regimes under two distinct scenarios. From our analysis, several important concluding remarks are obtained as follows: 1) the RaF relaying strategy achieves better secrecy performance than that of the decode-and-forward relaying strategy for dual-hop cognitive MIMO wiretap networks; 2) outdated CSI decreases the secrecy diversity gain of the TAS/MRC scheme from NRmin (NA, NB) to (NR, NB) ; and 3) although TAS/MRC scheme cannot attain full secrecy diversity gain for the considered system with outdated CSI, it still can achieve an extra secrecy coding gain compared with the random antenna selection/MRC scheme.
This paper investigates a secure transmission in the multiple-input multiple-output (MIMO) cognitive wiretap networks, where a secondary transmitter (Alice) sends data to a secondary receiver (Bob) in the presence of an eavesdropper (Eve). In order to solve the problems of inter channel interference and inter antenna synchronization encountered by traditional MIMO technologies, the antenna transmission scheme is adopted at the transmitter. As a comparison, we design two different antenna transmission schemes, namely transmit antenna selection maximal-ratio combining (TAS-MRC) scheme and differential spatial modulation maximal-ratio combining (DSM-MRC) scheme, respectively. Moreover, due to outdated channel state information (CSI) of the interference link from Alice to the primary user (PU), we propose power control mechanism to protect the quality of service (QoS) of PU. Furthermore, the closed-form for the secrecy outage probability and the secrecy throughput with TAS-MRC and DSM-MRC schemes are derived to evaluate the secrecy performance, respectively. What's more, we explore the security diversity gain and coding gain based on the asymptotic secrecy outage probability. As the results, it demonstrates that DSM-MRC requires less CSI and is convenient for modulation and demodulation, but sacrifices some secrecy performance gains between two proposed schemes.
This paper investigates secure cooperative transmissions in a dual-hop MIMO relay system using a combined transmit antenna selection (TAS) and maximal-ratio combining (MRC) scheme over the Nakagami-m fading channels, where an adaptive decode-and-forward relaying protocol and an multi-antenna eavesdropper are considered. Due to the feedback delay, channel state information (CSI) for TAS might be outdated at both the source and the relay. To evaluate the secrecy performance of the TAS/MRC scheme and the impacts of outdated CSI, the closed-form expressions for the metrics of exact ergodic secrecy rate and exact secrecy outage probability are derived under both perfect and outdated CSI conditions in a channel feedback error model. In order to explicitly reveal the behaviors of the secrecy performance in high signal-to-noise ratio regime, asymptotic expressions for both the metrics are further derived. As validated by simulation results, analytically numerical results demonstrate that outdated the CSI always results in a loss in the secrecy performance, but the loss can be recovered by increasing the number of antennas at legitimate receivers. Furthermore, the outdated CSI yields a reduced secrecy diversity order, whereas only the perfect CSI leads to the full secrecy diversity order.
In this paper, we investigate the secrecy performance of a multiantenna cognitive wiretap network, where the secondary transmitter (Alice) communicates with the secondary receiver (Bob) in the presence of an eavesdropper (Eve). Specifically, we consider both half-duplex (HD) and full-duplex (FD) operations. For the HD, maximal-ratio combining (MRC) is adopted at Bob, while for the FD, we propose two jamming schemes to deteriorate the quality of the eavesdropper's channel, i.e., selection combining/selection jammer (SC/SJ) and SC/zero forcing beamforming (SC/ZFB). Assuming Rayleigh fading, exact closed-form expressions for the secrecy outage probability of the cognitive wiretap network are derived. In addition, we also provide simple asymptotic approximations for the secrecy outage probability under two distinct scenarios, depending on the quality of the main and wiretap channels. From the analytical results and numerical simulations, it is concluded that all the proposed schemes outperform the SC scheme; all the proposed schemes achieve full diversity when the main channel is much better than the eavesdropper's channel; MRC outperforms SC/SJ and SC/ZBF in the low interference threshold regime, while the opposite holds in the high interference one; and SC/ZFB always achieves better performance than SC/SJ, albeit with higher complexity.
In this paper, we analyze the secrecy performance of multi-antenna cognitive wiretap network, where the secondary transmitter (Alice) communicates with the secondary receiver (Bob) in the presence of an eavesdropper (Eve). Specifically, we investigate the cases of maximal-ratio combining (MRC) with half-duplex (HD) and selection combining/Zero forcing beamforming (SC/ZFB) scheme with full-duplex (FD) operation, respectively. Assuming the Rayleigh fading, closed-form expressions for the secrecy outage probability of cognitive wiretap channels with MRC and SC/ZFB are derived. Furthermore, we provide simple asymptotic approximations for the secrecy outage probability and find that both schemes achieve full diversity. In addition, simulation results reveal that MRC outperforms SC/ZBF in the low interference threshold regime, while the opposite holds in the high interference threshold regime.
This study investigates the secrecy outage performance of a single‐input multiple‐output underlay cognitive radio network (CRN) with outdated channel state information (CSI). The confidential messages are transmitted from transmitter to the destination, while a multi‐antenna eavesdropper exists. The maximal ratio combining and selection combining schemes are utilised at the receivers to improve the quality of the received signal‐to‐noise ratio. The exact and asymptotic closed‐form expressions of secrecy outage probability are derived, and simulation results are provided to verify the authors' proposed analytical results. The results reveal that imperfect CSI of main channels deteriorates the secrecy outage performance while that of eavesdropping and interfering channels has contrary effect, and only a unity diversity order can be obtained in underlay CRNs with imperfect CSI.