This paper investigates the security performance of maximal ratio combining (MRC) and optimum combining (OC) in single-input multi-output (SIMO) wiretap channels in an interference-limited environment. We assume that the legitimate receiver (Bob) and eavesdropper (Eve) are equipped with M and N antennas, respectively, and the received signals at Bob and Eve are corrupted by L interferences with equal transmission power. We consider a worst-case scenario where the channel state information (CSI) of the interference channels is available at Eve, so OC is applied at Eve for eavesdropping. Two different scenarios for Bob are considered: if the CSI of the interference channels is available, OC is applied for secure reception, otherwise, MRC is used instead. Exact and asymptotic expressions for the secrecy outage probability are derived in these two scenarios. Our results show that MRC and OC can achieve the same secrecy diversity order that depends on M only; however, OC can achieve higher array gain over MRC and the performance gap between them increases with M while decreases with L.
This paper investigates the security performance of maximal ratio combining (MRC) and optimum combining (OC) in single-input multi-output (SIMO) wiretap channels in an interference-limited environment. We assume that the legitimate receiver (Bob) and eavesdropper (Eve) are equipped with M and N antennas, respectively, and the received signals at Bob and Eve are corrupted by L interferences with equal transmission power. We consider a worst-case scenario where the channel state information (CSI) of the interference channels is available at Eve, so OC is applied at Eve for eavesdropping. Two different scenarios for Bob are considered: if the CSI of the interference channels is available, OC is applied for secure reception, otherwise, MRC is used instead. Exact and asymptotic expressions for the secrecy outage probability are derived in these two scenarios. Our results show that MRC and OC can achieve the same secrecy diversity order that depends on M only; however, OC can achieve higher array gain over MRC and the performance gap between them increases with M while decreases with L.
This paper advocates physical layer security of maximal ratio combining (MRC) in wiretap two-wave with diffuse power fading channels. In such a wiretap channel, we consider that confidential messages transmitted from a single antenna transmitter to an M-antenna receiver are overheard by an N-antenna eavesdropper. The receiver adopts MRC to maximize the probability of secure transmission, whereas the eavesdropper adopts MRC to maximize the probability of successful eavesdropping. We derive the secrecy performance for two practical scenarios: 1) the eavesdropper's channel state information (CSI) is available at the transmitter and 2) the eavesdropper's CSI is not available at the transmitter. For the first scenario, we develop a new analytical framework to characterize the average secrecy capacity as the principal security performance metric. Specifically, we derive new closed-form expressions for the exact and asymptotic average secrecy capacity. Based on these, we determine the high signal-to-noise ratio power offset to explicitly quantify the impacts of the main channel and the eavesdropper's channel on the average secrecy capacity. For the second scenario, the secrecy outage probability is the primary security performance metric. Here, we derive new closed-form expressions for the exact and asymptotic secrecy outage probability. We also derive the probability of nonzero secrecy capacity. The asymptotic secrecy outage probability explicitly indicates that the positive impact of M is reflected in the secrecy diversity order and the negative impact of N is reflected in the secrecy array gain. Motivated by this, we examine the performance gap between N and N+1 antennas based on their respective secrecy array gains.
This paper investigates the secrecy performance of maximal ratio combining (MRC) and selection combining (SC) with imperfect channel state information (CSI) in the physical layer. In a single-input multipleoutput (SIMO) wiretap channel, a source transmits confidential messages to the destination equipped with M antennas using the MRC/SC scheme to process the received multiple signals. An eavesdropper equipped with N antennas also adopts the MRC/SC scheme to promote successful eavesdropping. We derive the exact and asymptotic closed-form expressions for the ergodic secrecy capacity (ESC) in two cases: (1) MRC with weighting errors, and (2) SC with outdated CSI. Moreover, two important indicators, namely high signal-to-noise ratio (SNR) slope and high SNR power offset, which govern ESC at the high SNR region, are derived. Finally, simulations are conducted to validate the accuracy of our proposed analytical models. Results indicate that ESC rises with the increase of the number of antennas and the received SNR at the destination, and fades with the increase of those at the eavesdropper. Another finding is that the high SNR slope is constant, while the high SNR power offset is correlated with the number of antennas at both the destination and the eavesdropper.
In this paper, assuming an interference-limited eavesdropper scenario, the secrecy outage performance ofmultiple-input multiple-output wiretap channels with transmit antenna selection is investigated. Considering that the transmitter (Tx) and the receiver (Rx) are equipped with NA and NB antennas, respectively, while the passive eavesdropper is set with NE antennas, closed-form expressions for the secrecy outage probability and non-zerosecrecy rate are derived. In our analysis, both maximal-ratio combining (MRC) and selection combining (SC) are employed at the Rx, while the eavesdropper uses a MRC scheme. The derived outage expressions hold for arbitrary power distributed jamming signals and some of their special cases (i.e., distinct power distributed and equal power distributed jamming signals) are presented. An asymptotic analysis is carried out to show the impact of the number of jamming signals and number of antennas on the secrecy outage performance. Interestingly, our results show thatthe diversity order equals to min(M,NANB), with M denoting the number of jamming signals. This allows us to conclude that the number of jamming signals at the eavesdropper limits the secrecy performance via diversity such that a high number of antennas does not imply necessarily in a performance improvement, unless for a large number of jamming signals.
In this paper, assuming an interference-limited eavesdropper scenario, the secrecy outage performance of multiple-input multiple-output wiretap channels with transmit antenna selection is investigated.Considering that the transmitter (Tx) and the receiver (Rx) are equipped with NA and NB antennas, respectively, while the passive eavesdropper is set with NE antennas, closed-form expressions for the secrecy outage probability and non-zero secrecy rate are derived.In our analysis, a selection combining (SC) scheme is employed at the Rx, while the eavesdropper uses a maximal-ratio combining (MRC) one.The derived outage expressions hold for arbitrary power distributed jamming signals.An asymptotic analysis is carried out to show the impact of the number of jamming signals and number of antennas on the secrecy outage performance.Interestingly, our results show that the diversity order equals to min(M, NANB), with M denoting the number of jamming signals.
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 paper presents a detailed secrecy outage performance analysis of correlated multi-antenna wiretap channels with three popular diversity combining schemes, namely maximal ratio combining, selection combining, and equal gain combining at the legitimate receiver. For single input multiple output wiretap channels, both exact and asymptotic expressions are derived for the secrecy outage probability (SOP) of these systems. The findings suggest that, compared with the scenario where all the channels are independent, correlation of the main channels alone increases the SOP by a factor of 1/ det(U), where det(U) is the determinant of correlation matrix U. In contrast, in the high signal-to-noise ratio regime at the legitimate receiver, correlation between the main channels and the eavesdropper channels has a positive effect on SOP. Moreover, for multiple input and multiple output wiretap channels, the SOP of two transmit antenna selection (TAS) schemes are analyzed for the considered correlated channel model. The SOP relationship of the both TAS schemes is quantified by the secrecy array gain. Finally, numerical simulations are conducted to corroborate the analytical results.