In the multi-antenna satellite communication system, beamforming and artificial noise are usually adopted to enhance physical layer security. However, due to the long distance between the satellite and the terrestrial terminal, the coverage of the main lobe in the satellite downlink is so large that the eavesdropper can get into the coverage easily despite of using spot beams. When the eavesdropper is close to the legitimate user, the difference between the main channel and the wiretap channel is small, which makes the secrecy capacity decrease rapidly. This paper proposes a novel scheme to solve this problem by using two different beams which work on different frequencies to transmit the same signal to the legitimate user. This dual-beam dual- frequency scheme can enlarge the difference between the desired channel and the wiretap channel. Then, if we add some artificial noise set the proper beamforming vectors, the secrecy capacity will remain high when the eavesdropper is in the small zone near the legitimate user. In order to derive the artificial noise and the beamforming vectors, we transform the problem into a semidefinite problem and use CVX tools to solve the problem. Simulation results prove that this scheme can achieve high secrecy capacity even when the eavesdropper is very close to the legitimate user.
In the multi-antenna satellite communication system, beamforming and artificial noise are usually adopted to enhance physical layer security. However, due to the long distance between the satellite and the terrestrial terminal, the coverage of the main lobe in the satellite downlink is so large that the eavesdropper can get into the coverage easily despite of using spot beams. When the eavesdropper is close to the legitimate user, the difference between the main channel and the wiretap channel is small, which makes the secrecy capacity decrease rapidly. This paper proposes a novel scheme to solve this problem by using two different beams which work on different frequencies to transmit the same signal to the legitimate user. This dual-beam dual- frequency scheme can enlarge the difference between the desired channel and the wiretap channel. Then, if we add some artificial noise set the proper beamforming vectors, the secrecy capacity will remain high when the eavesdropper is in the small zone near the legitimate user. In order to derive the artificial noise and the beamforming vectors, we transform the problem into a semidefinite problem and use CVX tools to solve the problem. Simulation results prove that this scheme can achieve high secrecy capacity even when the eavesdropper is very close to the legitimate user.
Compared with terrestrial communication, satellite communication has played a crucial role in 6G communication as a result of wide-area coverage characteristics. Among them, beamforming scheduling and information security are critical research issues to improve system transmission performance. However, in geostationary earth orbit (GEO)-based satellite communication systems, owing to the wide-area coverage, ground users are susceptible to inter-beam interference caused by multibeam antennas at the satellite, and the information received by terrestrial users may be eavesdropped by air or terrestrial eavesdroppers. To this end, in this article, we propose a new robust security transmission strategy by combining beamforming and artificial noise (AN) techniques. Specifically, based on the actual satellite communication network scenario, the uncertain channel models are formulated as bounded uncertainty sets by considering the impact of imperfect channel state information of both legitimate and wiretap channels. Then, we build a bounded-constrained beamforming optimization to maximize the sum rate of legitimate users, while guaranteeing the constraints of total transmit power on the satellite and the minimum security rate of each legitimate user. Since the original problem is non-convex and mathematically intractable, we jointly exploit the successive convex approximation, Taylor series expansion, S-Procedure, and the semi-definite relaxation approach, with which the original problem can be transformed into a tractable one with a series of linear matrix inequality constraints. Furthermore, we propose an iterative algorithm to obtain the optimal beamforming and AN vectors. Finally, simulation results show that, compared with the existing algorithms, the proposed algorithm has better security and robustness.
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.
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.
This paper investigates the physical layer security (PLS) of a multibeam satellite communication system where the satellite transmits the private signal to a legitimate user (LU) which is intercepted by multiple eavesdroppers (Eves). By considering the imperfect channel state information (CSI) of Eve channels, we formulate the constrained problem to maximize the LU achievable secrecy rate (ASR) subject to secrecy rate outage probability constraint, the total satellite transmit power constraint and the LU rate constraint. Firstly, we adopt golden section method to transform the difficult original problem into a series easier sub-problem. Then, considering the nonconvex of sub-problem, we employ Bernstein inequality and semidefinite programming (SDP) to transform the sub-problem into solvable one. Then, we use standard software package to get the optimal beamforming (BF) weight vector through an iterative penalty-based algorithm. Finally, simulation results confirm the superiority and robustness of the designed BF scheme.
In this paper, we consider a low earth orbit satellite communication system with a legitimate user and an eavesdropper and investigate its secrecy performance. Considering the beam coverage of the satellites, we propose a system where a friendly jammer satellite transmits artificial noise signals only to eavesdroppers. We obtain the cumulative distribution functions (CDFs) of the signal-to-interference-plus-noise ratios taking into account the Nakagami-𝑚 fading and the positions of ground users and satellites. The CDFs are used to derive the analytical forms of the probability of non-zero secrecy capacity, secrecy capacity outage probability, and average secrecy capacity. In addition, for tractability and insight, asymptotic forms are also investigated at a high-power regime. Finally, we present the numerical results to validate the obtained expressions and show the diversity order of the secrecy capacity.
In satellite communication downlinks, physical layer security is challenging to achieve due to their broadcasting nature and Line-of-Sight channel characteristics. This paper provides a precoding algorithm to secure the downlinks of multiple users against multiple eavesdroppers with optimization of the minimum secrecy capacity. By the use of artificial noise, a positive secrecy capacity is achievable even if the number of eavesdroppers is higher than the number of beams. We demonstrate that a multiple-reflector antenna design provides a significantly higher secrecy and throughput performance when compared to a single-reflector design due to additional degrees of freedom, exhibited by the signal phases. The total vulnerability region is introduced as a new figure of merit with respect to unidentified eavesdroppers.