This paper investigates the physical layer security for a cognitive satellite-terrestrial Internet-of-Things (IoT) network where a secondary base station (BS) communicates with multiple secondary users (Us) in the presence of an adaptive eavesdropper, which performs eavesdropping when the channel quality of the eavesdropping link is good and performs jamming otherwise. We consider a real situation where mutual interference exists between primary and secondary networks. Considering multiple secondary users available, we propose suboptimal user scheduling and optimal scheduling schemes to improve the secure transmission of BS-Us. Specifically, a user that maximizes the secrecy capacity of the system will be selected in the optimal scheduling scheme, which assumes that the channel state information (CSI) of all links is available. By contrast, the suboptimal scheduling scheme only knows the main links’ CSI, so the user maximizing the CSI of the main links is chosen. We derive the exact and asymptotic closed-form secrecy outage probability expressions for suboptimal and optimal scheduling schemes. For comparison, we also obtain the exact and asymptotic closed-form secrecy outage probability expressions for round-robin scheme. Numerical results show that the suboptimal and optimal user scheduling schemes perform better than round-robin user scheduling scheme in terms of secrecy outage probability. In addition, the secrecy performance of proposed suboptimal and optimal schemes can be improved by increasing the number of secondary users.
This paper investigates the physical layer security for a cognitive satellite-terrestrial Internet-of-Things (IoT) network where a secondary base station (BS) communicates with multiple secondary users (Us) in the presence of an adaptive eavesdropper, which performs eavesdropping when the channel quality of the eavesdropping link is good and performs jamming otherwise. We consider a real situation where mutual interference exists between primary and secondary networks. Considering multiple secondary users available, we propose suboptimal user scheduling and optimal scheduling schemes to improve the secure transmission of BS-Us. Specifically, a user that maximizes the secrecy capacity of the system will be selected in the optimal scheduling scheme, which assumes that the channel state information (CSI) of all links is available. By contrast, the suboptimal scheduling scheme only knows the main links’ CSI, so the user maximizing the CSI of the main links is chosen. We derive the exact and asymptotic closed-form secrecy outage probability expressions for suboptimal and optimal scheduling schemes. For comparison, we also obtain the exact and asymptotic closed-form secrecy outage probability expressions for round-robin scheme. Numerical results show that the suboptimal and optimal user scheduling schemes perform better than round-robin user scheduling scheme in terms of secrecy outage probability. In addition, the secrecy performance of proposed suboptimal and optimal schemes can be improved by increasing the number of secondary users.
In this paper, we investigate the physical-layer security of a multi-user multi-eavesdropper cognitive radio system, which is composed of multiple cognitive users (CUs) transmitting to a common cognitive base station (CBS), {while multiple eavesdroppers may collaborate with each other or perform independently in intercepting the CUs-CBS transmissions, which are called the coordinated and uncoordinated eavesdroppers, respectively}. Considering multiple CUs available, we propose the round-robin scheduling as well as the optimal and suboptimal user scheduling schemes for improving the security of CUs-CBS transmissions against eavesdropping attacks. Specifically, the optimal user scheduling is designed by assuming that the channel state information (CSI) of all links from CUs to CBS, to primary user (PU) and to eavesdroppers are available. By contrast, the suboptimal user scheduling only requires the CSI of CUs-CBS links without the PU's and eavesdroppers' CSI. We derive closed-form expressions of the secrecy outage probability of these three scheduling schemes in the presence of {the coordinated and uncoordinated eavesdroppers}. We also carry out the secrecy diversity analysis and show that the round-robin scheduling achieves the diversity order of only one, whereas the optimal and suboptimal scheduling schemes obtain the full secrecy diversity, {no matter whether the eavesdroppers collaborate or not. In addition, numerical secrecy outage results demonstrate that for both the coordinated and uncoordinated eavesdroppers, the optimal user scheduling achieves the best security performance and the round-robin scheduling performs the worst.} Finally, upon increasing the number of CUs, the secrecy outage probabilities of the optimal and suboptimal user scheduling schemes both improve significantly.
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.
Satellite communication (SatCom) has attracted much attention due to its inherent characteristics. Security issues have gained severe concerns in SatCom since it is susceptible to be illegally eavesdropped by malicious ground stations within large-scale wireless coverage. In this paper, we investigate the physical layer security of a multiuser SatCom system in the presence of multiple eavesdroppers. Particularly, we propose a threshold-based scheduling scheme, where the geographically clustered eavesdroppers with both the colluded and collaborated eavesdropping scenarios are assumed. Specifically, closed-form expression for the secrecy outage probability (SOP) is derived for the passive eavesdropping scenario when the channel state information (CSI) of the eavesdroppers is unavailable. Moreover, we obtain a closed-form expression for the average secrecy capacity (ASC) of the considered system under the proposed user scheduling scheme. In order to get further insights of the proposed scheduling scheme at high signal-to-noise ratios (SNRs), the asymptotic analysis for the SOP and ASC is also demonstrated. Moreover, the reduced percentage with respect to number of user examination is also given, which validates the simplicity and efficiency of our proposed scheme compared to the traditional approaches. Numerical results deduce that with the proposed scheme, a comparable system performance with regard to the maximal selection (MS) scheme can be achieved.
This paper studies the physical-layer security of a multi-user multi-eavesdropper cellular network , which is composed of multiple users communicating with a base station while the eavesdroppers may intercept the communications from users to the base station (BS). The cellular network is a time-slotted system with simultaneously transmission, in each time slot, a single user is scheduled to transmit messages to BS while the remaining users opportunistically receive information. Considering multiple users available in the cellular network, we present three multi-user scheduling schemes, namely the round-robin scheduling scheme as well as the suboptimal and optimal user scheduling schemes to improve the security of communication (from users to BS) against eavesdropping attacks. We only need to assume that the channel state information (CSI) of the main link spanning from users to BS is known in the suboptimal scheduling. On the contrary, the optimal scheduling is designed by assuming that the CSI of the main link and wiretap link (spanning from users to the eavesdropper) are available. We further carry out secrecy diversity analysis and show that the round-robin always achieves only one diversity order, whereas the suboptimal and optimal user scheduling schemes achieve the full diversity. In addition, numerical results illustrate that the optimal scheduling performs the best and the round-robin has the worst performance in terms of the secrecy outage probability . Last, as the number of users increases, the secrecy outage probabilities of the suboptimal and optimal scheduling schemes decrease significantly.
In this paper, we explore the physical-layer security of a multi-user cellular network in the presence of an eavesdropper, which is made up of multiple users communicating with a base station while the eavesdropper may intercept the communications from users to the base station (BS). Considering that multiple users are available in cellular network, we present three multi-user scheduling schemes, namely the round-robin scheduling scheme, the suboptimal and optimal user scheduling schemes to improve the security of communication (from users to BS) against the eavesdropping attack. In the suboptimal scheduling, we only need to assume that the channel state information (CSI) of the main link spanning from users to BS are known. In contrast to the suboptimal scheduling, the optimal scheduling is designed by assuming the CSI of the main link and wiretap link (spanning from users to the eavesdropper) that are available. We obtain the calculus form of the secrecy outage probability to analyze the secrecy diversity performance. Secrecy diversity analysis is carried out, which shows that the round-robin always achieves only one diversity order, whereas the suboptimal and optimal user scheduling schemes achieve the full diversity order. In addition, the results of the secrecy outage show that the optimal scheduling has the best performance and the round-robin performs the worst in terms of defending against the eavesdropping attack. Lastly, as the number of users increases, both the secrecy outage probabilities of the suboptimal and optimal scheduling schemes have a significant secrecy performance improvement.
In this paper, we consider a cognitive radio (CR) network which is made up of multiple secondary users (SUs), a secondary destination (SD) and an eavesdropper (E) which may overhear the legitimate communication between SUs and SD. In order to ensure the secure communication from SUs to SD, we investigate round-robin scheduling and optimal user scheduling to prohibit eavesdropper attacking. In optimal user scheduling, the channel state information (CSI) of all links including SUs-D, SUs-E, primary user (PU)-D and PU-E are available. Because of intercept probability is an important metric of security for wireless communications, we discuss the intercept probability of both scheduling. To further present the impact of number of users on secrecy performance, we also analyze the secrecy diversity of round robin scheduling and optimal user scheduling. Final results indicate that round robin scheduling obtains only one diversity order, however optimal user scheduling achieves full diversity order. Additionally, optimal user scheduling performs better than round robin scheduling in terms of intercept probability and the secrecy performance will significantly improve as the number of users increases.