Analysis on the effects of artificial noise on physical layer security

Artificial noise (AN) is one of physical layer security techniques, which can realize secure communication. AN is a noise signal which is intentionally transmitted from transmitter along with data signals. Since AN is generated to be canceled out at legitimate receivers, it can prevent eavesdroppers from eavesdropping even if transmitters do not know the existence of eavesdroppers. In spite of its usefulness, most of the AN generation techniques cannot be applied to multiple-input multiple-output (MIMO) systems when the number of antennas at the transmitter is less than that at the legitimate receiver. In this paper, we consider time-domain AN generation techniques for MIMO orthogonal frequency division multiplexing (OFDM) systems. A time-domain AN generation technique is originally proposed for single-input single-output (SISO) OFDM systems. Thus, we first consider to apply the conventional time-domain AN generation technique to MIMO-OFDM systems, and show that this technique requires a large number of antennas at the transmitter and/or a longer cyclic prefix (CP). Next, to solve this problem, we propose another time-domain AN generation technique. Our proposed time-domain AN is generated to be canceled out at the legitimate receiver in the frequency domain, while the conventional time-domain AN is canceled out in the time domain. As a result, the proposed time-domain AN generation technique can be applied to MIMO-OFDM systems, irrespective of the number of antennas and the length of CP. Simulation results can show that the proposed AN achieves the same secrecy rate as the conventional time-domain AN. Moreover, the proposed technique achieves a higher secrecy rate when a MIMO-OFDM system is employed with the antenna configuration to which the conventional time-domain AN generation technique is hard to be applied.

In this paper, it is aimed to increase the physical layer security by optimizing the power and time parameters in two-user symbiotic radio networks. In the proposed model, the signal provided by the power station is used for both information transmission with the backscatter principle and energy harvesting. In addition, the secrecy rate of the system is maximized by preventing the eavesdropper (ED) intervention with the artificial noise technique. The system is examined under certain channel gains and artificial noise levels, and the effects of backscatter coefficients on energy harvesting and secrecy performance are analyzed. Numerical results show that channel gains are also of critical importance in addition to appropriate power and time allocation, and artificial noise offers an effective solution in physical layer security.

Random unitary beamforming (RUB) is a multiple antenna transmission scheme requiring limited channel state information (CSI) with low computational complexity. In this paper, we investigate the security performance of RUB over a multiple-input single-output single-eavesdropper (MISOSE) broadcast channel. We derive the closed-form expressions of ergodic secrecy rate and the secrecy outage probability (SOP) of the resulting design. Meanwhile, the effect of artificial noise (AN) on physical layer (PHY) security performance of RUB-based MISOSE transmission is also investigated. Numerical results are presented to illustrate the tradeoff between performance and complexity of the proposed PHY security design. We show that the deployment of RUB offers an attractive solution for enhancing the security of wireless transmission systems.

As per the conception of RF (Radio) propagation, wireless communications can be easily overheard by unauthorized users for interception and thus wireless communication are highly vulnerable to eaves dropping attacks by exploitation of physical characteristics of wireless channels. The propose work is focused on development of diversity techniques to enhance physical layer security, marking a paradigm Shift from conventional artificial noise generation and beam forming techniques. Artificial noise techniques are highly power hungry and require on additional degree of power capacity which is not suitable for better operated system. Thus work is focused at development of a new techniques using variable length cryptography in which MAC (Medium Access Control)/ address of the wireless nodes for key generation purposes. Also, it is proposed, that the keys for communication encryption are randomized by a global time source such as GPS or internal master RTC (Real Time Clock). This unique feature allows a high degree of security as keys are truly random due to Millisecond level synchronization key randomization using a global accurate time source facility highly secure communication in a closed group. Also, the author has proposed key expiry time, after elapse station of such time, all key will have to be farce fully regenerated.

Due to the constraints on power supply and limited encryption capability, data security based on physical layer security (PLS) techniques in backscatter communications has attracted a lot of attention. In this work, we propose to enhance PLS in a full-duplex symbiotic radio (FDSR) system with a proactive eavesdropper, which may overhear the information and interfere legitimate communications simultaneously by emitting attack signals. To deal with the eavesdroppers, we propose a security strategy based on pseudo-decoding and artificial noise (AN) injection to ensure the performance of legitimate communications through forward noise suppression. A novel AN signal generation scheme is proposed using a pseudo-decoding method, where AN signal is superimposed on data signal to safeguard the legitimate channel. The phase control in the forward noise suppression scheme and the power allocation between AN and data signals are optimized to maximize security throughput. The formulated problem can be solved via problem decomposition and alternate optimization algorithms. Simulation results demonstrate the superiority of the proposed scheme in terms of security throughput and attack mitigation performance.

The conventional physical-layer (PHY) security approaches, e.g., transmit beamforming and artificial noise (AN)-based design, may fail when the channels of legitimate user (LU) and eavesdropper (Eve) are close correlated. Due to the highly directional transmission feature of millimeter-wave (mmWave), this may occur in mmWave transmissions as the transmitter, Eve and LU are aligned in the same direction exactly. To handle the PHY security problem with directionally-aligned LU and Eve, we propose a novel frequency diverse array (FDA) beamforming approach to differentiating the LU and Eve. By intentionally introducing some frequency offsets across the antennas, the FDA beamforming generates an angle-range dependent beampattern. As a consequence, it can degrade the Eve's reception and thus achieve PHY security. In this paper, we maximize the secrecy rate by jointly optimizing the frequency offsets and the beamformer. This secrecy rate maximization (SRM) problem is hard to solve due to the tightly coupled variables. Nevertheless, we show that it can be reformulated into a form depending only on the frequency offsets. Building upon this reformulation, we identify some cases where the SRM problem can be optimally solved in closed form. Numerical results demonstrate the efficacy of FDA beamforming in achieving PHY security, even for aligned LU and Eve.

Physical layer security is envisaged to provide secure wireless communications. So far there exist schemes that both achieve physical layer security and maintain a reasonable level of link capacity. However, in all these schemes, capacity of a communication link depends on the channel characteristics of both the communication link and the eavesdropping links. Thus, when packets are scheduled in a wireless network with physical layer security, the most critical task is to select an appropriate link for a new transmission such that the network throughput and quality of services are properly balanced. In this paper, packet scheduling is studied for a wireless network with physical layer security considering beamforming and artificial noise. Particularly, a cross-layer scheduling scheme is developed based on the stochastic optimization theory to maximize the admission rate of all users and guarantee queue stability in each link. The scheme takes into account the constraints of physical layer security in different eavesdropping strategies: colluding and non-colluding. The effectiveness of the scheduling scheme is validated via simulations. The impact of antenna number and eavesdropping strategy to the scheduling scheme is also revealed in the performance results.

Background. Ultra-Reliable Low Latency Communication (URLLC) as a service offered by fifth and sixth generation (5G/6G) wireless systems is a technological response to the needs of various mission-critical applications that require reliable data transmission with low latency. These applications also include Intelligent Transportation Systems services, which, among other things, provide connectivity and autonomous vehicle control. The combination of high reliability and low latency requirements in URLLC usage scenarios creates a security problem for URLLC data transmission that cannot be solved using conventional complex cryptographic methods based on a secret key. The article discusses in detail the approach to using physical layer security mechanisms (physical layer security - PLS) as a powerful alternative to classical cryptographic security methods for URLLC, and also proposes the application of the wire-tap channel concept in URLLC with an analysis of the efficiency that can be achieved for physical layer security. Objective. The aim of the article is to provide an overview of information security solutions in URLLC usage scenarios, as well as to propose a constructive method for information protection for reliable data transmission with low latency without the use of cryptographic mechanisms based on a secret key. Methods. Theoretical research in the field of the branch channel concept was used to create solutions that allow data protection with information-theoretic stability in URLLC usage scenarios for providing IoT, connected car and autonomous driving services. Results. The article examines in detail the data security issues in ultra-reliable low latency communication (URLLC) as a service offered by fifth and sixth generation (5G/6G) wireless systems. It is determined that URLLC is a technological response to the needs of various critical applications that require reliable signal transmission with low latency, and among these applications are Intelligent Transportation Systems services, which, among other things, provide connectivity and autonomous vehicle control. It is shown that the combination of high reliability and low latency requirements in URLLC scenarios creates a security problem for URLLC data transmission that cannot be solved using conventional complex cryptographic methods based on a secret key. The feasibility of using physical layer security mechanisms (PLS) as a powerful alternative to classical cryptographic security methods for URLLC is substantiated. The approach to applying the concept of a wire-tap channel in URLLC is considered in detail, as well as the results that can be achieved for physical layer security, and the influence of code parameters for probabilistic cryptographic transformations in accordance with the concept of a wire-tap channel on PLS URLLC. Estimates of the effectiveness of PLS URLLC for finite block length codes are provided. Conclusions. An effective way to ensure data security for ultra-reliable low-latency physical layer link (PLS URLLC) of fifth-generation 5G wireless systems in the field of connected cars and vehicles of 4-5 levels of automation can be approaches based on the concept of a tapped channel ("wire-tap channel").

The next generation network (5G) promises to offer a wide spectrum of advantages like massive user connections and high mobility. Massive user connection is achieved by incorporating Multiple Input Multiple Output (MIMO). Securing 5G wireless networks is of greater concern because they are developed with the intention of providing exponentially increasing wireless services where a trillion of legitimate users will be involved. Data transmission in 5G networks has been exposed to various security threats such as eavesdropping, jamming, Denial of Service (DoS) attack and Man-In-The-Middle (MITM) attack. The above mentioned threats have the ability of affecting the performance of 5G wireless networks since 5G is a major support system for new use cases. Some of the existing mechanisms employed to deal with the security threats are Physical Layer Security (PLS) and cryptography. PLS is preferred since its primary focus is on physical and Media Access Control (MAC) layer where variations in security between wireless and wired networks occur. The existing PLS approach for security against single cell MIMO eavesdropper is Original Symbol Phase Rotated (OSPR) secure transmission scheme where one base station serves the user terminals in a single cell. Our paper implements OSPR for a multi cell MIMO where multiple base stations serve multiple user terminals located in different cells. This architecture will be referred to as Multi cell MIMO Eavesdropping (MME). The efficiency of multi cell OSPR will be compared with Artificial Noise (AN) generation. The extent to which OSPR gives protection against MIMO eavesdropper is measured in terms of Symbol Error Rate (SER). As SER increases, security of data transmission increases. The efficiency of multi cell OSPR over AN is expected to be 8% and it will be verified in simulation using MATLAB.

The high speed railway wireless communication system is quite different from public wireless communication system, because the service is train control message, which are closely related to the safety of train transportation. Thus it has much higher requirements for the safety and reliability. In this paper, secrecy capacity and outage probability at the high speed railway scenario with traditional MIMO and beamforming schemes are analyzed. The analytic results show that MIMO scheme can not meet the safety requirements and the beamforming scheme is also helpless while the eavesdropper is close to eNodeB. In order to guarantee the transmission safety of train control messages, a physical layer secure scheme with artificial noise (AN) is proposed for high speed railway communication system. In this proposed scheme, beamforming and AN transmitting directions are adjusted accordingly with the onboard legitimate receiver's channel state information (CSI) and eavesdropper's partial CSI to degrade the eavesdropper while maximize the system secrecy capacity. Simulation results demonstrate the proposed scheme decreases the outage probability under the secrecy capacity constraint, and can meet the safety communication requirements.

Unmanned aerial vehicle (UAV) communication using non-orthogonal multiple access-based coordinated direct and relay transmission (NOMA-CDRT) supports both massive connectivity and wide-area coverage, becoming a key technology for future emergency rescue communications. However, relay forwarding and high-quality line-of-sight links may subject UAV-aided NOMA-CDRT to multiple eavesdropping attempts by saboteurs. Therefore, we propose a multi-node joint jamming scheme using artificial noise (AN) for the UAV-assisted NOMA-CDRT to improve the system’s physical layer security. In the proposed scheme, the base station directly serves a nearby user while using a UAV relay to serve a disaster-affected user, and both the users and the UAV relay utilize AN to jointly interfere with eavesdroppers around the users. To accurately characterize and maximize the ergodic secrecy sum rate (ESSR) of the proposed scheme, we derive the corresponding closed-form expressions and design a joint power allocation and interference control (JPAIC) algorithm using particle swarm optimization. Simulations verify the correctness of the theoretical analysis, the ESSR advantage of the proposed scheme compared with the conventional NOMA-CDRT, and the effectiveness of the proposed JPAIC.

In this study, the authors secure the mixed radio frequency/free space optical (FSO) relay‐aided interference aligned system using a proposed physical layer security algorithm. This algorithm reduces the quality of the received signal at the eavesdropper through two procedures. First, it minimises the data transmission power from the legitimate users and the relays. Second, it jams the eavesdropper by broadcasting artificial noise from the users and the relays. Therefore, a joint optimisation problem is formulated to degrade the received signal at the eavesdropper from the users and the relays and to maximise the jamming artificial noise power, which is solved using an iterative optimisation algorithm beside a semi‐definitive programming algorithm. Furthermore, the pre‐coding and decoding matrices of the users and the relay are designed to enable the legitimate users to cancel the artificial noise, while the eavesdropper is disabled from distinguishing the artificial noise from the real streams. Moreover, the security performance of the proposed algorithm is analysed, and the impact of the FSO link's state on the security performance is studied. The extensive simulation results show the efficiency of the proposed algorithm and illustrate the role of the FSO link's state on the security performance.

In this study, the physical layer (PHY) security performance of orthogonal space‐time block coding (OSTBC) employing a coordinate interleaved orthogonal design (CIOD) is analysed and investigated using two metrics: average secrecy capacity and secrecy outage probability. It is shown that the CIOD system is superior than OSTBC in terms of secrecy outage probability. Closed‐form expressions for PHY security metrics in OSTBC as well as CIOD are presented and compared. Then, an extended model of CIOD with arbitrary number of antennas is considered. Furthermore, the effects of artificial noise and imperfect channel estimation on PHY security of OSTBC and CIOD systems are investigated. The validity of theoretical expressions is verified by simulation, and it is shown that in practical cases the CIOD system has a better secrecy outage performance than that of the OSTBC system.

Non-orthogonal multiple access (NOMA) has been deemed a promising technology to achieve high spectral efficiency. This paper investigates transmit power optimization for a multi-user multiple-input single-output (MISO) NOMA downlink system endowed with energy harvesting and physical layer security. More specifically, the system is designed to satisfy the data-link security requirements of its legitimate users while charging energy harvesting devices. To achieve that goal, we investigate a joint design on beamforming vectors and artificial noise (AN) covariance matrix. Then, an iterative difference-of-two-convex-function (D.C.) algorithm is proposed by applying the successive convex approximation (SCA) approach. To further reduce the computational complexity, a sub-optimal alternating D.C. (ADC) algorithm is devised by decoupling beamforming and mapping the AN to the null space of legitimate users. In the ADC algorithm, optimal null space and beamforming vectors are alternately solved by convex programming. Furthermore, the convergence of the proposed D.C. and ADC algorithms is derived. Extensive simulation results show that the two proposed AN-aided algorithms significantly reduce the transmit power cost over OMA and NOMA scheme without AN, especially when there are more eavesdroppers.

Attack from malicious access points in cell-free massive MIMO systems: Performance analysis and countermeasure