Physical layer security is an attractive security mechanism, which exploits the randomness characteristics of wireless transmission channel to achieve security. However, it is hampered by the limitation of the channel condition that the main channel must be better than the eavesdropper channel. To alleviate the limitation, cooperative communication is introduced. Few studies have investigated the physical layer security of the relay transmission model. In this paper, we performed some experiments to evaluate the physical layer security of a cooperative communication system, with a relay operating in decode-and-forward (DF) cooperative mode, selfish and malicious behavior in real non-ideal transmission environment. Security performance is evaluated in terms of the probability of non-zero secrecy capacity. Experiments showed some different results compared to theoretical simulation: (1) to achieve the maximum secrecy capacity, the optimal relay power according to the experiments result is larger than that of ideal theoretical results under both cooperative and selfish behavior relay; (2) the relay in malicious behavior who forwards noise to deteriorate the main channel may deteriorate the eavesdropper channel more seriously than the main channel; (3) the optimal relay positions under cooperative and selfish behavior relay cases are both located near the destination because of non-ideal transmission.
Physical layer security is an attractive security mechanism, which exploits the randomness characteristics of wireless transmission channel to achieve security. However, it is hampered by the limitation of the channel condition that the main channel must be better than the eavesdropper channel. To alleviate the limitation, cooperative communication is introduced. Few studies have investigated the physical layer security of the relay transmission model. In this paper, we performed some experiments to evaluate the physical layer security of a cooperative communication system, with a relay operating in decode-and-forward (DF) cooperative mode, selfish and malicious behavior in real non-ideal transmission environment. Security performance is evaluated in terms of the probability of non-zero secrecy capacity. Experiments showed some different results compared to theoretical simulation: (1) to achieve the maximum secrecy capacity, the optimal relay power according to the experiments result is larger than that of ideal theoretical results under both cooperative and selfish behavior relay; (2) the relay in malicious behavior who forwards noise to deteriorate the main channel may deteriorate the eavesdropper channel more seriously than the main channel; (3) the optimal relay positions under cooperative and selfish behavior relay cases are both located near the destination because of non-ideal transmission.
The broadcast nature of wireless communications makes it difficult to hide transmitted signals from unauthorized users. To this end, physical-layer security is emerging as a promising paradigm to protect the wireless communications against eavesdropping attacks. The fundamental principle behind physical layer security is to exploit the inherent randomness of noise and communication channels to limit the amount of information that can be extracted at the `bit' level by an unauthorized receiver. In this paper, we investigate physical layer security issues in a two-way relay network. The idea is that when the eavesdropper channel is a degraded version of the main channel, the source and the destination can exchange perfectly secure messages at a non-zero rate. Moreover, we use green base stations as relays. Conventional energy sources are a huge source of atmospheric pollution. The renewable energy sources use natural resources and do not cause any pollution, hence they are termed green energy sources. We evaluate the security performance of cooperative relay transmission in Rayleigh fading environments in terms of secrecy capacity and intercept probability.
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.
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.
In this paper, physical layer security (PLS) analysis of a cooperative wireless communication system in which the source and destination nodes communicate via a relay employing decode-and-forward protocol is performed for double Rayleigh fading channel model. For the system where the source, relay and target have single antenna, an eavesdropper with multiantenna listens the source and relay together by using maximum-ratio-combining, secrecy outage and positive secrecy capacity possibilities are obtained in closed-form. The theoretical results are verified by Monte-Carlo simulations. From the results, it is observed that as the number of antennas of the eavesdropper is increased, the PLS performance of the system worsens.
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.
Physical Layer Security (PLS) provides a promising complementary approach to cryptographic methods for protecting wireless communications from eavesdropping. This paper investigates secrecy enhancement through cooperative relaying and jamming in a wireless network with two legitimate users, one eavesdropper, and five potential relay nodes operating in amplify-and-forward mode. Three relay–jammer selection strategies are considered: random relay and jammer selection, best-SNR (signal-to-noise ratio) relay with random jammer selection, and best-SNR relay with a jammer chosen based on the strongest channel toward the eavesdropper. The secrecy performance of these strategies are evaluated in terms of secrecy rate and secrecy outage probability. The results demonstrate that intelligent relay and jammer selection can significantly improve PLS compared to random selection, highlighting the benefits of cooperation in secure wireless systems.