Physical layer security is an emerging security field that explores the possibilities of achieving perfect secrecy data transmission between the intended network nodes, while possible malicious nodes that eavesdrop the communication obtain zero information. In this paper, we observe how node cooperation improves the physical layer security of a simple wireless network by reducing the surface of the geographical area in which the malicious nodes can listen to the transmitted data from the source to the destination. Our analysis and simulation results show a dramatic improvement even by cooperation with only one relay node. The improvement gets better by adding more cooperating nodes. We also observe that if cooperating nodes are closer to the line that connects the source and the destination node, the region in which the malicious node can profit from the eavesdropping gets smaller.
Physical layer security is an emerging security field that explores the possibilities of achieving perfect secrecy data transmission between the intended network nodes, while possible malicious nodes that eavesdrop the communication obtain zero information. In this paper, we observe how node cooperation improves the physical layer security of a simple wireless network by reducing the surface of the geographical area in which the malicious nodes can listen to the transmitted data from the source to the destination. Our analysis and simulation results show a dramatic improvement even by cooperation with only one relay node. The improvement gets better by adding more cooperating nodes. We also observe that if cooperating nodes are closer to the line that connects the source and the destination node, the region in which the malicious node can profit from the eavesdropping gets smaller.
Security is an important aspect for the future wireless networks. Since the number of network nodes increases constantly, and, in addition, the networks are decentralized and ad-hoc in nature, it becomes more challenging to apply the current cryptographic methods that require exchange of keys between the communicating parties. Information-theoretic secrecy is an emerging security field that explores the possibility of achieving perfect secrecy data transmission between the intended network nodes, while possible malicious nodes (also called eavesdroppers) are kept ignorant of the transmitted information. In other words, that is the ability of the physical layer to provide security (beside the reliability) of the transmitted (broadcasted) data. For that reason, it is often called physical layer security. In this paper we observe how a simple cooperative network with one relay node can improve the physical layer security by decreasing the area in which the eavesdropper can reside and listen to the information transmitted to the destination. This region is called vulnerability region and we provide its characterization. Under certain conditions, the vulnerability region vanishes, which makes our wireless system perfectly secure for any position of the eavesdropper within the wireless network.
Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without upper layer data encryption. However, they are hampered by wireless channel conditions: absent feedback, they are typically feasible only when the source-destination channel is better than the source-eavesdropper channel. Node cooperation is a means to overcome this challenge and improve the performance of secure wireless communications. This paper addresses secure communications of one source-destination pair with the help of multiple cooperating relays in the presence of one or more eavesdroppers. Three cooperative schemes are considered: decode-and-forward (DF), amplify-and-forward (AF), and cooperative jamming (CJ). For these schemes, the relays transmit a weighted version of a reencoded noise-free message signal (for DF), a received noisy source signal (for AF), or a common jamming signal (for CJ). Novel system designs are proposed, consisting of the determination of relay weights and the allocation of transmit power, that maximize the achievable secrecy rate subject to a transmit power constraint, or, minimize the transmit power subject to a secrecy rate constraint. For DF in the presence of one eavesdropper, closed-form optimal solutions are derived for the relay weights. For other problems, since the optimal relay weights are difficult to obtain, several criteria are considered leading to suboptimal but simple solutions, i.e., the complete nulling of the message signals at all eavesdroppers (for DF and AF), or the complete nulling of jamming signal at the destination (for CJ). Based on the designed relay weights, for DF in the presence of multiple eavesdroppers, and for CJ in the presence of one eavesdropper, the optimal power allocation is obtained in closed-form; in all other cases the optimal power allocation is obtained via iterative algorithms. Numerical evaluation of the obtained secrecy rate and transmit power results show that the proposed design can significantly improve the performance of secure wireless communications.
Cooperative relay is considered as an efficient scheme to improve the physical layer security of a wireless relay system in the presence of eavesdroppers. In this paper, multiple-level relay scheme is proposed. We consider relay weight design for secrecy rate maximization subject to a power constraint. The results show that a higher achievable secrecy rate is achieved in the two-level relay channel than that of the one-level relay channel when the destination node is far away from the source node. Therefore, the performance of the two-level relays channel is generally better under the circumstances of the long distance transmission.
Privacy and security have an increasingly important role in wireless networks. A secure communication enables a legitimate destination to successfully retrieve information sent by a source, while it disables the eavesdropper (illegitimate destination) to interpret the intercepted information. Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without encryption. It exploits the physical characteristics of the wireless channel in order to transmit messages securely. They are typically feasible when the source-destination channel is better than the source-eavesdropper channel. Cooperative schemes are a means to improve the performance of secure wireless communications. We propose an improved relay selection scheme, based on source-eavesdropper channel SNR restriction, that will guarantee the best secrecy rate at the destination under QoS condition. Performance has been studied in terms of secrecy rate, outage probability and average error probability. Simulations shows that the proposed scheme outperforms in terms of the secrecy rate at the destination when compared to techniques in the literature.
Due to the broadcast nature of radio propagation, wireless transmission can be readily overheard by unauthorized users for interception purposes and is thus highly vulnerable to eavesdropping attacks. To this end, physical-layer security is emerging as a promising paradigm to protect the wireless communications against eavesdropping attacks by exploiting the physical characteristics of wireless channels. This article is focused on the investigation of diversity techniques to improve physical-layer security differently from the conventional artificial noise generation and beamforming techniques, which typically consume additional power for generating artificial noise and exhibit high implementation complexity for beamformer design. We present several diversity approaches to improve wireless physical-layer security, including multiple-input multiple-output (MIMO), multiuser diversity, and cooperative diversity. To illustrate the security improvement through diversity, we propose a case study of exploiting cooperative relays to assist the signal transmission from source to destination while defending against eavesdropping attacks. We evaluate the security performance of cooperative relay transmission in Rayleigh fading environments in terms of secrecy capacity and intercept probability. It is shown that as the number of relays increases, both the secrecy capacity and intercept probability of cooperative relay transmission improve significantly, implying there is an advantage in exploiting cooperative diversity to improve physical-layer security against eavesdropping attacks.
We employed node cooperation in a cooperative wireless network to achieve physical layer- based security. The case of a source-destination pair that works with the assistance of multiple cooperating nodes in the presence of an eavesdropper was considered in this study to improve the performance of secure wireless communications. A novel cooperative scheme, called the decode-and-forward plus cooperative jamming (DFCJ), was proposed. In this scheme, relay nodes transmit a weighted version of the source signals plus a common weighted jamming signal to confound the eavesdropper. The novel system design was proposed to determine cooperative node weights and transmit power allocation. In DFCJ, a closed-form solution is obtained to minimize the total transmit power that is subjected to a secrecy rate constraint under complete nulling of jamming signals at the destination. The results of the numerical evaluation of the transmit power and the obtained secrecy rate show that the proposed scheme can significantly improve the performance of wireless physical layer security compared with the original decode-and-forward scheme.