In this paper, we present our study of an Eigenvector-based artificial noise-based jamming technique developed to provide increased wireless physical layer security in transmit-receive diversity systems and analyze the impact of channel estimation errors on system performance. Our simulation results showed that with knowledge of perfect channel state information, the technique provided secrecy capacity of approximately 7 bits/s/Hz for a normalized transmit power of 25 dB for a variety of transmit, receive, and eavesdropper configurations. We also describe a novel method to simulate generalized channel state information estimation errors. While other publications neglect the impact of these estimation errors, our simulations show that the secrecy capacity decreased rapidly as the channel estimation errors increased. For instance, at 25% error the secrecy capacity of the jamming technique was only slightly better than the non-jamming case. Our paper also outlines upcoming research efforts to further explore error sensitivity and channel state temporal stability through experimentation.
In this paper, we present our study of an Eigenvector-based artificial noise-based jamming technique developed to provide increased wireless physical layer security in transmit-receive diversity systems and analyze the impact of channel estimation errors on system performance. Our simulation results showed that with knowledge of perfect channel state information, the technique provided secrecy capacity of approximately 7 bits/s/Hz for a normalized transmit power of 25 dB for a variety of transmit, receive, and eavesdropper configurations. We also describe a novel method to simulate generalized channel state information estimation errors. While other publications neglect the impact of these estimation errors, our simulations show that the secrecy capacity decreased rapidly as the channel estimation errors increased. For instance, at 25% error the secrecy capacity of the jamming technique was only slightly better than the non-jamming case. Our paper also outlines upcoming research efforts to further explore error sensitivity and channel state temporal stability through experimentation.
In this paper, we propose a novel approach for providing secure wireless communications in transmit-receive diversity systems. In this approach, we precode the information-bearing signal with a uniquely generated randomized eigenvector-based jamming signal to impair the eavesdropper's received signal, while the main channel, the link between the transmitter and the desired receiver, remains unaffected. Unlike existing methods, our approach can be applied to any antenna array configuration, even when the receiver and eavesdropper utilize more antennas than the transmitter, with no benefits to the eavesdropper's information detection capability from employing more antenna elements. Moreover, our proposed approach can provide more degrees of freedom for the jamming signal, significantly increasing the provided level of security. Additionally, our scheme does not assume any knowledge about the eavesdropper or even the number of collaborating eavesdroppers. Our simulation results show a secrecy capacity increase of about 7 bits/s/Hz for a 4 x 4 antenna configuration under typical transmit power constraints, which results in significant improvement in security performance and enables physically secure wireless communications.
Physical-layer secrecy in wireless fading channels has been studied extensively in recent years to ensure reliable communication between the transmitter and the receiver subject to constraints on the information attainable by the eavesdropper. With multiple antennas at the transmitter, Goel and Negi proposed the use of artificial noise (AN) in the null space of the receiver's channel to corrupt the eavesdropper's reception, which helps guarantee secrecy without knowledge of the eavesdropper's channel. It has been shown that the secrecy capacity can be made arbitrarily large by increasing the transmission power, when perfect knowledge of the receiver's channel direction information (CDI) is available. However, in practice, this is not possible due to rate-limitations on the feedback channel. This paper studies the impact of quantized channel feedback on the secrecy capacity achievable with artificial noise.We show that, with imperfect CDI at the transmitter, the AN that was originally intended only for the eavesdropper may leak into the receiver's channel and limit the achievable secrecy rate. To maintain a constant performance degradation, the number of feedback bits must increase at least logarithmically with the transmission power. Moreover, we observe that the portion of power allocated to the transmission of AN should decrease as the number of quantization bits decreases to alleviate the degradation due to noise leakage.
Wireless communication is highly susceptible to eavesdropping attacks where a malicious user can exploit the broadcast nature of the wireless signals to eavesdrop on confidential information. At the physical layer, there are multiple possible avenues to utilize the inherent randomness of the wireless transmission medium to achieve secure communication. One of the lucrative possibilities is to use the channel state information (CSI) to establish a secure communication link because it is vital in decoding the received signal at the transmitter. This technique is commonly referred to as discriminatory channel estimation (DCE) where the channel estimation performance is intentionally degraded at the eavesdropper as compared to the legitimate nodes to achieve secure communication.In this thesis, we capitalize on full-duplex (FD) transmissions to transmit the pilot signals to obscure the channel estimates from the eavesdropper. FD transmission severely limits the estimation performance at the eavesdropper while the legitimate nodes can acquire robust estimates. The secrecy of channel estimates from the eavesdropper provides a bandwidth-efficient security technique as the channel estimation requires less bandwidth than the data transmission. We have presented the achievable secrecy capacity analysis along with the simulation analysis to illustrate the performance improvements achieved by the proposed novel secure channel estimation. In this thesis, we also study the impact of artificial noise (AN) to improve the secrecy achieved by the use of FD transmission of pilot signals. For a strategically located eavesdropper, we have presented novel DCE techniques where AN signals are transmitted along with pilot signals using FD transmission. The AN signals confuse the nearby eavesdropper to establish a secure and robust communication link. We have also presented novel local adaptive power allocation algorithms, where each legitimate node performs power allocation in the absence of statistical channel characteristics regarding the eavesdropping channel. We have provided an in-depth simulation analysis including a location-based simulation analysis to illustrate that the secrecy performance achieved by the proposed DCE techniques. The simulation results indicate that the proposed DCE techniques achieve robust secure communication against a strategically located eavesdropper: while the other DCE techniques are unable to avoid the leakage of information to the eavesdropper
For physical layer security with multiple antennas over wireless channels, we consider an artificial noise-aided secure beamforming system. A transmitter can send the confidential information to the legitimate user more securely without eavesdropping when an artificial jamming signal interfering eavesdroppers is transmitted with the confidential information signal. The transmitter splits its transmit power for both the information and jamming signals with a power splitting factor. Under such a system model, we investigate the impacts on secrecy performance of a power splitting factor, the numbers of antennas and eavesdroppers, and noise variance at the legitimate receivers and eavesdroppers by analyzing the expected secrecy rate. The optimal power splitting factor and limiting secrecy rate with large number of antennas are also derived. Moreover, we examine the expected secrecy rate loss caused by channel variation over time. It is shown that the secrecy rate loss is independent of system parameters like a power splitting factor, the numbers of antennas and eavesdroppers in a high signal to interference plus noise ratio (SINR) region. In a low SINR region, on the other hand, the secrecy rate loss changes with system parameters. Simulation results verify these observations on ergodic secrecy rate and its loss due to time-varying channels.
In recent years, physical layer security (PLS) has emerged as a promising concept to complement cryptography solutions. Many PLS schemes require perfect knowledge of the channel state information (CSI) at the transmitter. However, in practical cases, CSI is often imperfect due to channel estimation errors, noisy feedback channels and outdated CSI. In this paper, we study the impact of imperfect CSI on an adaptive PLS scheme that combines diversity with interleaving to provide security. Particularly, we derive the secrecy capacity expressions for the legitimate receiver and the eavesdropper's channels under imperfect CSI conditions. Numerical and theoretical simulations for secrecy capacity and bit error rate (BER) are carried out for the frequency-selective Rayleigh fading wiretap channel model. The results reveal the negative impact of imperfect CSI on the secrecy and BER performance of the single input single output (SISO) orthogonal frequency division multiplexing (OFDM) system. The analysis is done under both frequency division duplex (FDD) and time division duplex (TDD) modes.