Consider secure transmissions over the downlink of a multiuser MISO system with independent confidential messages, each of which is intended for one of the users and should keep secret from others. We are interested in a scenario where users have individual secrecy rate requirements. This scenario is practical but has drawn little attention in the literature so far. In this paper, we propose a secrecy rate balancing algorithm which tries to fulfill the secrecy rate requirements of users, and maximizes the minimum margin which is defined as the difference between the available secrecy rate and the required rate for each user. This algorithm balances out all the secrecy rate margins until an equilibrium is reached. We derive a necessary condition for the optimal solution. Finally, theoretical results are illustrated by numerical simulations.
Consider secure transmissions over the downlink of a multiuser MISO system with independent confidential messages, each of which is intended for one of the users and should keep secret from others. We are interested in a scenario where users have individual secrecy rate requirements. This scenario is practical but has drawn little attention in the literature so far. In this paper, we propose a secrecy rate balancing algorithm which tries to fulfill the secrecy rate requirements of users, and maximizes the minimum margin which is defined as the difference between the available secrecy rate and the required rate for each user. This algorithm balances out all the secrecy rate margins until an equilibrium is reached. We derive a necessary condition for the optimal solution. Finally, theoretical results are illustrated by numerical simulations.
This paper investigates the ergodic secrecy sum-rate for the downlink multiuser MIMO system with independent confidential messages, each of which is intended for one of the users and should keep secret from others. We adopt zero-forcing beamforming with limited channel state information (CSI) feedback at the transmitter, and derive the closed-form expression for the ergodic secrecy sum-rate. Moreover, we analyze some of its asymptotic characteristics, which provide guidance on secure transmission design. Finally, all theoretical results are validated by numerical simulations.
A secure communication game is considered for the two-user MISO Gaussian interference channel with confidential messages, where each transmitter aims to maximize the difference between its secrecy rate and the secrecy rate of the other transmitter. In this novel problem, the weaker link tries to minimize the extra secret information obtained by its adversary, while the stronger link attempts to maximize it. We provide an information theoretic formulation for this non-cooperative zero-sum game scenario and determine that, under the assumption of Gaussian signaling at the transmitters, there exists a unique Nash equilibrium solution for the proposed problem. Moreover, we obtain in closed-form the optimal strategies (beamformers) at the transmitters that result in the Nash equilibrium. While the NE strategies are achievable in one shot when full channel state information is available at the transmitters (CSIT), we also propose an iterative step-by-step algorithm that converges to the NE point, but only requires limited CSIT. Numerical results are presented to illustrate the analytical findings and to study the role of different channel parameters on the NE strategies.
In this paper, we consider max-min fairness for a downlink two-user multi-input single-output (MISO) system with imperfect channel state information available at transmitter (CSIT) taking into account the total power constraint and the physical layer security. To handle the worst-case channel uncertainty of a potential eavesdropper (PE), we study the robust secure resource allocation algorithm which maximizes the minimum achieved worst-case secrecy rate among single-antenna legitimate users. In contrast to existing schemes adopted in the literature, we propose a rate-splitting (RS)-based secure transmission scheme, which advocates the dual use of a common message serving both as a desired message and artificial noise (AN) for legitimate users and the PE, respectively. Considering the non-convex resource allocation algorithm design problem, we apply the majorization maximization (MM) method to obtain a suboptimal iterative algorithm. In each iteration, a rank-constrained semi-definite program (SDP) is solved optimally by SDP relaxation (SDR). Simulation results demonstrate that our proposed robust secure beamforming scheme in the MISO-RS secure transmission system outperforms that of several baselines.
For multiuser Multiple-Input-Multiple-Output (MIMO) downlink systems where some receivers exist, several user selection schemes have been recently proposed. However, these user selection schemes do not take security into consideration. One possible scenario of wireless communication systems is that a transmitter sends confidential messages to multiple receivers in the presence of eavesdroppers. In this paper, we propose a user selection scheme with secrecy capacity for multiuser MIMO downlink system. We assume a system with a transmitter, some legitimate users and eavesdroppers where the transmitter wants to send data securely against eavesdroppers. In the proposed scheme, the transmitter selects a user set so that their secrecy capacities among legitimate users and eavesdroppers are larger than zero. Thus, the transmitter can send confidential messages to users securely. The proposed scheme can be applied to conventional scheduling schemes, such as maximum capacity (MAX) scheduling and proportional fairness (PF) scheduling. Simulation results show that the proposed scheme provides secure transmissions and has little degradation of performance of system capacity and fairness when applied to the conventional scheduling schemes. Hence, we show that the proposed scheme is an effective user selection scheme to guarantee secrecy of communication.
This work develops a beamforming framework for energy efficiency optimization in MIMO multi-user systems with confidentiality constraints. Two channel models are considered, namely, a broadcast channel with confidential messages (corresponding to single-cell downlink) and an interference channel with confidential messages (corresponding to multi-cell downlink), in which multiple messages are transmitted, and it must be ensured that only the intended receiver is able to perform data decoding, thus treating non-intended receivers as potential eavesdroppers. In this multi-user scenario, the new metric global secrecy energy efficiency is introduced and optimized. Moreover, the coupling among the secrecy energy efficiencies of different users is analyzed by providing an efficient way of computing the system secrecy energy efficiency Pareto boundary. Both contributions are achieved by developing an optimization framework which suitably combines fractional programming theory and sequential optimization theory. The proposed framework is provably convergent, enjoys affordable complexity, and fulfills first-order optimality properties. Finally, the closed form conditions are provided to support smart user selection algorithms for downlink transmission.
This paper proposes a secure users-oriented multiple-input and single-output non-orthogonal multiple access downlink transmission scheme, where multiple legitimate users are categorized as quality of service (QoS)-required users (QU) and the security-required users (SU) overheard by a passive eavesdropper. The basic idea is to exploit zero-forcing beamforming to cancel interference among SUs, and then several QUs are efficiently scheduled based on the obtained beamforming vectors to divide the legitimate users into several user clusters, in such a way that the QUs could share the concurrent transmissions and help to interfere with the eavesdropper to enhance SU secrecy. The goal is to maximize the achievable minimum secrecy rate and sum secrecy rate of all SUs, respectively, subject to the secrecy outage probability constraint of each SU and the QoS constraint of each QU. To provide a comprehensive investigation, we consider two extreme cases that the eavesdropper has perfect multiuser detection ability (lower bound of secrecy) or does not have multiuser detection ability (upper bound of secrecy). In the lower bound case, the Dinkelbach algorithm and the monotonic optimization-based outer polyblock approximation algorithm are proposed to solve the max-min secrecy rate and max-sum secrecy rate problems, respectively. As for the upper bound case, an alternative optimization-based algorithm is proposed to solve the two non-convex problems. Finally, the superiority of the proposed cases to the conventional orthogonal multiple access one is verified by numerical results.