To address secrecy performance in a multi-relay underlay wiretap spectrum sharing network, we present a secrecy rate-optimal relay and antenna selection scheme, which serves as a fundamental benchmark. It jointly selects a transmit antenna at a secondary source, a receive antenna at its destination, and a relay between them to maximize the secrecy rate at the destination under the malicious attempt of an eavesdropper. We derive exact and asymptotic expressions for the secrecy outage probability, which accurately reveal the secrecy diversity order and the coding gain. Under a proportional interference constraint, full secrecy diversity order is achieved only when the main link is stronger than the wiretap link, otherwise the diversity gain is lost. We then consider a practical scenario where the secondary users have only the mean channel power gains of the wiretap links. Under such channel state information (CSI), we propose a statistical CSI-based relay and antenna selection scheme and numerically show that this can be used as a better performance/complexity tradeoff. Both the schemes substantially outperform the conventional relay and antenna selection scheme, which requires no CSI about the wiretap links.
To address secrecy performance in a multi-relay underlay wiretap spectrum sharing network, we present a secrecy rate-optimal relay and antenna selection scheme, which serves as a fundamental benchmark. It jointly selects a transmit antenna at a secondary source, a receive antenna at its destination, and a relay between them to maximize the secrecy rate at the destination under the malicious attempt of an eavesdropper. We derive exact and asymptotic expressions for the secrecy outage probability, which accurately reveal the secrecy diversity order and the coding gain. Under a proportional interference constraint, full secrecy diversity order is achieved only when the main link is stronger than the wiretap link, otherwise the diversity gain is lost. We then consider a practical scenario where the secondary users have only the mean channel power gains of the wiretap links. Under such channel state information (CSI), we propose a statistical CSI-based relay and antenna selection scheme and numerically show that this can be used as a better performance/complexity tradeoff. Both the schemes substantially outperform the conventional relay and antenna selection scheme, which requires no CSI about the wiretap links.
This paper investigates the physical layer secrecy performance for an underlay wiretap spectrum sharing network with optimal relay and antenna selection (ORAS). It jointly selects a transmit antenna at a secondary source, a receive antenna at its destination, and a relay between them to maximize the secrecy rate at the destination under a passive eavesdropping scenario. We derive novel, exact expressions for secrecy outage probability (SOP) and secrecy throughput (ST) in a single integral-form. We also provide their accurate approximations in closed-form. Considering three distinct scenarios depending on whether the main link is stronger than the wiretap link and the nature of the primary interference constraint, we obtain different useful system design insights. Under a proportional interference constraint, secrecy diversity gain is achieved only when the main link is stronger than the wiretap link, otherwise the diversity gain is lost and leads to an SOP floor. Under a fixed interference constraint, the SOP floor is further increased. Through numerical results, we show the impact of different signal combining strategies by the eavesdropper on the SOP and ST. We also illustrate the efficacy of the ORAS scheme as compared to other relay and antenna selection schemes.
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.
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 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 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.
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.