This letter focuses on the self-interference cancellation problem for a secure two-way amplify-and-forward (AF) satellite communication system with eavesdropper at both the transmitter and the receiver. Several multi-antenna earth stations (ESs) aim to exchange messages through a multi-antenna satellite in two hops. We apply the frequency hopping multiple-term weighted fractional Fourier transform (FH-MWFRFT) with different transform orders at the earth stations in the first hop to eliminate the self-interference existing in the two-way communication and enhance the security. The second hop of the communication is secured by null space beamforming, which steer the signal to the null space of the eavesdroppers' channel. We demonstrate the improvement in secrecy capacity brought by the self-interference cancellation scheme via various simulation results and discussions. The simulations are carried out under the conditions of perfect channel state information (CSI) and imperfect CSI to verify the robustness of the proposed scheme.
This letter focuses on the self-interference cancellation problem for a secure two-way amplify-and-forward (AF) satellite communication system with eavesdropper at both the transmitter and the receiver. Several multi-antenna earth stations (ESs) aim to exchange messages through a multi-antenna satellite in two hops. We apply the frequency hopping multiple-term weighted fractional Fourier transform (FH-MWFRFT) with different transform orders at the earth stations in the first hop to eliminate the self-interference existing in the two-way communication and enhance the security. The second hop of the communication is secured by null space beamforming, which steer the signal to the null space of the eavesdroppers' channel. We demonstrate the improvement in secrecy capacity brought by the self-interference cancellation scheme via various simulation results and discussions. The simulations are carried out under the conditions of perfect channel state information (CSI) and imperfect CSI to verify the robustness of the proposed scheme.
This study investigates the information security problem in amplify‐and‐forward (AF) satellite transmission with eavesdroppers at both the transmitter and the receiver. Two multi‐antenna earth stations aim to exchange messages through a multi‐antenna satellite in two hops. The satellite channels (both uplink and downlink) are assumed to be shadowed‐Rician fading. In the first hop, the multiple term weighted fractional Fourier transform (MWFRFT) is adopted to secure the messages from the eavesdropper at the transmitter. To overcome the simplicity of parameters in MWFRFT, the authors enhance the MWFRFT with frequency hopping and propose the frequency hopping multiple term weighted fractional Fourier transform (FH‐MWFRFT) to improve the secrecy. In the second hop, the satellite broadcasts the signal to the receiver after null space beamforming (NSBF). Since the energy at the satellite is confined, the NSBF is simplified by applying the singular value decompose to avoid the complicate optimisation calculations at the satellite. The one‐way and two‐way transmission scenarios with full channel state information (CSI) and statistic CSI are both considered in this study. Simulation results demonstrate the proposed method could achieve a better security at the transmitter while maintain a similar secrecy performance to the optimisation method at the legitimate receiver.
This paper investigates the secure transmission in satellite communication systems, where a geostationary orbit (GEO) satellite serves an earth station while multiple eavesdroppers attempt to intercept the confidential message. Assuming that only the imperfect channel state information (CSI) of the wiretap channels are available, we propose a secure beamforming scheme to maximize the secrecy energy efficiency (SEE) of the earth station while satisfying the signal-noise-ratio (SNR) requirement at earth station, the secrecy constraints at eavesdroppers, and per-antenna power constraints at satellite antenna feeds. Since the formulated optimization problem is mathematically intractable, we propose a two-stage beamforming scheme to convert the original nonconvex problem into a solvable one and obtain the beamforming weight vectors. Numerical results are finally provided to verify the effectiveness of our proposed scheme.
In this paper, we study satellite secure communications with physical layer security techniques in the presence of multiple eavesdroppers. In order to increase the secrecy rate to the legitimate user, a terrestrial base station operates as a two-stage amplify-and-forward (AF) relay to assist the secure transmission. In the first stage, the legitimate user sends artificially generated noise to the satellite using paired carrier multiple access (PCMA) such that the artificial noise only degrades the eavesdroppers' channels. In the second stage, the base station forwards its received satellite signal to the legitimate user via beamforming. In this two-stage transmission, we consider two scenarios with non- colluding eavesdroppers and colluding eavesdroppers. We design beamforming schemes for both the two scenarios and compare the proposed beamforming schemes with the null-space beamforming scheme, which nulls out the signal leakages at all eavesdroppers. Simulation results demonstrate the proposed beamforming scheme performs better than the null-space beamforming scheme. It is also shown that the proposed terrestrial network aided satellite communication has a significant performance improvement of secure performance as compared to direct transmissions.
A weighted fractional Fourier transform (WFRFT) based on channel state information (CSI), aiming to safeguard the physical (PHY) layer security of wireless communication system, is proposed. With the proposed scheme, WFRFT is first applied to satellite communications such that the transmitted signal is distorted and can only be neutralized by inverse‐WFRFT with the same parameter. Moreover, by exploiting the physical properties of wireless channels, the CSI matrix is transformed as a secret key. In addition, by adding phase rotation (PR) factors to each branch of the WFRFT system, a new unitary matrix with the encryption properties is constructed, and hence, the satellite communications secrecy is reliably guaranteed due to the variation in signal characteristics. Finally, the efficacy of the security enhancement is evaluated in terms of the average bit error rate (BER) and the secrecy capacity. Simulation results show that the proposed encryption method can make the detection and demodulation more difficult for the eavesdropper.
This paper investigates the physical layer security of a satellite network, whose downlink spectral resource is shared with a terrestrial cellular network. We propose to employ a multi-antenna base station (BS) as a source of green interference to enhance secure transmission in the satellite network. By taking the mutual interference between these two networks into account, we first formulate a constrained optimization problem to maximize the instantaneous rate of the terrestrial user while satisfying the interference probability constraint of the satellite user. Then, with the assumption that imperfect channel state information (CSI) and statistical CSI of the link between the BS and satellite user are available at the BS, we present two beamforming (BF) schemes, namely, hybrid zero-forcing and partial zero-forcing to solve the optimization problem and obtain the BF weight vectors in a closed form. Moreover, we analyze the secrecy performance of primary satellite network by considering two practical scenarios, namely: Scenario I, the eavesdroppers CSI is unknown at the satellite and Scenario II, the eavesdroppers CSI is known at the satellite. Specifically, we derive the analytical expressions for the secrecy outage probability for Scenario I and the average secrecy rate for Scenario II. Finally, numerical results are provided to confirm the superiority of the proposed BF schemes and the validity of the performance analysis, as well as demonstrate the impacts of various parameters on the secrecy performance of the satellite network.
Full-duplex (FD) technique is very promising to support enormous data for 5G networks since it can greatly improve the spectrum efficiency. However, the secrecy performance of FD communication systems still remains largely unknown. As an initial step towards this end, this paper studies the physical layer security-based beamforming design in a FD two-way amplify-and-forward relay system, where two source nodes exchange messages with the assistance of an untrusted relay. The untrusted relay is willing to forward the messages and may also work as an eavesdropper to intercept the confidential messages. Our objective is to optimize the source and relay beamformers for maximizing the secrecy sum rate of the two-way communications with imperfect self-interference cancellation. For a specific system configuration, we first derive the expression of secrecy sum rate. By utilizing signal alignment technique and gradient method, we then propose two iterative algorithms to find the optimal source and relay beamforming matrices, respectively. Simulation results demonstrate that when the number of antennas at the relay is appropriate and the interference-to-noise ratio is in a low region the proposed FD scheme significantly improves the secrecy sum rate over conventional schemes.