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.
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.
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.
In this paper, we analyze the security-reliability tradeoff (SRT) performance of the multi-relay cooperative networks over Nakagami-m fading channels. By considering the reliability of the first phase from the source to relay, a cooperative jamming (CJ) assisted secure transmission scheme is investigated to improve the security performance of the considered system. Specifically, we derive the approximate closed-form expression of the outage probability (OP) and exact closed-form expression of the intercepted probability (IP) for the CJ scheme to evaluate the SRT performance of the system. Finally, the simulation results verify the validity of our theoretical derivations and the advantage of the CJ scheme compared to the traditional scheme with no cooperative jammer.
Transmit beamforming is a diversity technique in multiple-input multiple-output (MIMO) systems. It improves the diversity order and enhances the information security of the MIMO systems. In this paper, we mathematically analyze the secure performance of a MIMO decode-and-forward (DF) relay system under the presence of an eavesdropper and with the imperfect channel state information (CSI) of the eavesdropping channel. To enhance the secrecy performance, we employ multiple antennas at all legitimate nodes and utilize two linear beamforming schemes, i.e., maximal ratio transmission (MRT) and transmission zero-forcing (TZF), at the transmitter and maximal ratio combining (MRC) scheme at the receiver. The probability density function (PDF) of the output SNR for different numbers of antennas at the transmitter and receiver is plotted and discussed. After that, we apply this PDF to derive the closed-form expressions of the secrecy outage probability (SOP) and ergodic secrecy capacity (ESC) of the considered MIMO-DF relay system over Rayleigh fading channels for MRT/MRC and TZF/MRC schemes. In addition, based on the obtained analysis results, we provide the location of the relay that minimizes the system SOPs. All the analysis results are validated by Monte-Carlo simulations. The results show that the TZF/MRC scheme provides better SOP and ESC than the MRT/MRC scheme. Moreover, the number of antennas at the legitimate nodes and the location of the eavesdropper significantly impact the secrecy performance.
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.
This paper investigates secure communications of energy harvesting untrusted relay networks, where the destination assists jamming signal to prevent the untrusted relay from eavesdropping and to improve the forwarding ability of the energy constrained relay. Firstly, the source and the destination transmit the signals to the relay with maximal ratio transmission (MRT) technique or transmit antenna selection (TAS) technique. Then, the destination utilizes maximal ratio combining (MRC) technique or receive antenna selection (RAS) technique to receive the forwarded information. Therefore, four transmission and reception schemes are considered. For each scheme, the closed-form expressions of the secrecy outage probability (SOP) and the connection outage probability (COP) are derived. Besides, the effective secrecy throughput (EST) metric is analyzed to achieve a good tradeoff between security and reliability. In addition, the asymptotic performance of EST is also considered at the high signal-to-noise ratio (SNR). Finally, simulation results illustrate that: (1) the EST of the system with MRT and MRC scheme are superior to other schemes, however, in the high SNR regime, the EST of the system with MRT scheme is inferior to TAS; and (2) for the source node, there exists an optimal number of antennas to maximize the EST of the proposed schemes.
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.