Using the Alamouti space-time block code in conjunction with artificial noise (AN) is an effective approach to secure multiple access (MAC) transmission in the presence of eavesdroppers. Existing studies on this technique focus on the two-user transmission systems and single-antenna eavesdroppers. This letter proposes a novel approach that generalizes this technique to multiuser transmission schemes and multi-antenna eavesdroppers. Security gains are analyzed, and the minimum number of MAC users that should participate in generating the AN in order to secure their transmissions is characterized analytically.
Using the Alamouti space-time block code in conjunction with artificial noise (AN) is an effective approach to secure multiple access (MAC) transmission in the presence of eavesdroppers. Existing studies on this technique focus on the two-user transmission systems and single-antenna eavesdroppers. This letter proposes a novel approach that generalizes this technique to multiuser transmission schemes and multi-antenna eavesdroppers. Security gains are analyzed, and the minimum number of MAC users that should participate in generating the AN in order to secure their transmissions is characterized analytically.
We investigate the physical layer security of synchronous multiple access transmissions using the Alamouti space-time block code in fading channels where multiple users communicate with a single intended receiver in the presence of an eavesdropper. We propose an artificial-noise-aided technique to secure the transmissions by having the Alamouti users collaborate with each other, without exchanging information, to degrade the eavesdropper's channel. Unlike previous work, which assumes that the transmitters have complete knowledge of the legitimate as well as the eavesdropper's channels, our proposed technique requires no communications between the users, minimal knowledge of the legitimate channel, and no channel knowledge regarding the eavesdropper.
We investigate the physical layer security of synchronous multiple access transmissions using the Alamouti space-time block code in fading channels where multiple users communicate with a single intended receiver in the presence of an eavesdropper. We propose an artificial-noise-aided technique to secure the transmissions by having the Alamouti users collaborate with each other, without exchanging information, to degrade the eavesdropper's channel. Unlike previous work, which assumes that the transmitters have complete knowledge of the legitimate as well as the eavesdropper's channels, our proposed technique requires no communications between the users, minimal knowledge of the legitimate channel, and no channel knowledge regarding the eavesdropper.
We consider secure downlink multiple-input–multiple-output (MIMO) communications between a transmitter and multiple users when there exists a passive eavesdropper. A downlink main channel between the transmitter and a user is estimated through uplink pilot symbols in a time-division duplex mode. On the other hand, to hinder an eavesdropper from estimating the eavesdropper channel between the transmitter and the eavesdropper, the transmitter does not send any pilot symbols. The main channel is hence available at the transmitter only, while the eavesdropper channel is unavailable at any node. Assuming these channel state information (CSI) conditions, we propose a MIMO transmission method using space–time line code (STLC) with artificial noise (AN) for enhancing the physical layer security. The STLC enables noncoherent detection at the receiver, i.e., a user, without CSI and achieves full spatial diversity. We derive the lower bound of the secrecy sum rate for the proposed STLC transmission method without AN, with AN, and with AN and imperfect CSI. Moreover, numerical results verify that the proposed STLC scheme outperforms the conventional eigen-beamforming and the precoding space-time block code in terms of secrecy sum rate regardless of the signal-to-noise ratio, the number of transmit antennas, and the CSI uncertainty.
This paper analyze the problem of secret communication between two nodes over a wireless channel, in the presence of a passive eavesdropper. The effect of fading is also considered. It is assumed that the transmitter and receiver both have 2 antennas each while the eavesdropper consists of a single antenna. The article investigates this scenario using Alamouti Space Time Block Coding (STBC) and artificial noise. This approach significantly improves the physical layer security of the system. Moreover, the secrecy capacity of this system is also computed.
In this paper, we investigate secure and reliable transmission strategies for multi-cell multi-user massive multiple-input multiple-output systems with a multi-antenna active eavesdropper. We consider a time-division duplex system where uplink training is required and an active eavesdropper can attack the training phase to cause pilot contamination at the transmitter. This forces the precoder used in the subsequent downlink transmission phase to implicitly beamform toward the eavesdropper, thus increasing its received signal power. Assuming matched filter precoding and artificial noise (AN) generation at the transmitter, we derive an asymptotic achievable secrecy rate when the number of transmit antennas approaches infinity. For the case of a single-antenna active eavesdropper, we obtain a closed-form expression for the optimal power allocation policy for the transmit signal and the AN, and find the minimum transmit power required to ensure reliable secure communication. Furthermore, we show that the transmit antenna correlation diversity of the intended users and the eavesdropper can be exploited in order to improve the secrecy rate. In fact, under certain orthogonality conditions of the channel covariance matrices, the secrecy rate loss introduced by the eavesdropper can be completely mitigated.
In this paper, we investigate secure communications uplink transmissions, where there are a base station (BS) with M receive antennas, K mobile users each with a single antenna, and an eavesdropper with N receive antennas. The closed-form expressions of the achievable ergodic secrecy sum rates (ESSRs) for a random k users selection scheme in the high and low signal-to-noise ratio regimes are presented. It is shown that the scaling behavior of ESSR with respect to the number served users k can be quite different under different system configurations, determined by the numbers of the BS antennas and that of the eavesdropper antennas. In order to achieve multiuser gain, two low-complexity user selection schemes are proposed under different assumptions on the eavesdropper's channel state information. The closed-form expressions of the achievable ESSRs and the multiuser secrecy gains of the two schemes are also presented in both low and high SNR regimes. observe that, as k increases, the multiuser secrecy gain increases, while the ESSR may decrease. Therefore, when N much larger than M, serving one user with the strongest channel (Time Division Multiple Address-like) is a favorable secrecy scheme, where the ESSR scales with √2 log K.