The significant concepts in the area of wireless communication are cooperative communication and physical layer security. Since current related research does not involve detailed performance analysis in different scenarios, the performance in different scenarios between amplify-and-forward scheme and cooperative-jamming scheme is compared. In combination with the characteristics of the both concepts, the physical layer security model based on cooperative communication, and the optimal secrecy capacity on amplify-and-forward scheme and cooperative-jamming scheme is analyzed. The number increase of antennas for relays can improve the secrecy performance, just like the number increase of relays. Simulation results show that amplify-and-forward scheme is more difficult to be effected by the scenarios and is more stable than cooperative-jamming scheme.
The significant concepts in the area of wireless communication are cooperative communication and physical layer security. Since current related research does not involve detailed performance analysis in different scenarios, the performance in different scenarios between amplify-and-forward scheme and cooperative-jamming scheme is compared. In combination with the characteristics of the both concepts, the physical layer security model based on cooperative communication, and the optimal secrecy capacity on amplify-and-forward scheme and cooperative-jamming scheme is analyzed. The number increase of antennas for relays can improve the secrecy performance, just like the number increase of relays. Simulation results show that amplify-and-forward scheme is more difficult to be effected by the scenarios and is more stable than cooperative-jamming scheme.
Collaborative communication and physical layer information security are two valuable aspects in the field of modern wireless communication. Combining the characteristics of the two, the physical layer security model based on cooperative communication is studied, and the amplification and forwarding strategy and cooperation among them in this paper, the best security capacity of congestion strategy is analyzed. In the light of the fact that related researches do not involve the analysis of performance scenarios, the comparison of security capacity performance under different scenarios is carried out for amplification forwarding strategy and collaborative congestion strategy. Simulation studies show that the amplification and forwarding strategy is more stable and less susceptible to scenario changes than the cooperative congestion strategy. In addition, the performance improvement caused by the increased number of relay antennas is also equivalent to increasing the number of trunks.
In this work, physical layer secure transmission of a cooperative wireless communication system over a three-phase amplify-and-forward (AF) two-way relaying channels is studied. A cooperative jamming and multi-antenna relay beamforming scheme that improves physical layer security of the system is proposed. Specifically, it is suggested that in the first and second timeslots when the legitimate users transmit alternatively, a jamming signal can be transmitted by the legitimate party that is not transmitting information-bearing signals This scheme, compared with the approach using a dedicated jammer, achieves a similar jamming effect with reduced complexity. In the third time slot of the protocol, the relay uses two beamforming matrices to process the bidirectional information signals. The jamming signal components at the relay are projected onto the null space of the legitimate relay-destination channels such that they do not affect legitimate communications. Through joint optimization, the sum throughput of the legitimate communication is maximized. In the numerical examples, the proposed scheme is shown to improve the system's secrecy transmission performance.
In wireless communication, physical layer security is widely used for secure communication between the transmitter and the receiver. In this paper, the secrecy performance of two cooperative schemes, decode-and-forward (DF) and amplify-and-forward (AF) relays is investigated in a single hop wireless relaying system. The achievable secrecy rate is investigated with these two types of relays under the constraint of total power transmitted. In the given jamming relay network, the relay transmits jamming signal while receiving data signal from the source. It is indicated by the resulting analysis that the AF relays have better secrecy rate as compared to the DF relays in the given condition. The secrecy rate of the AF relay is higher than that of the DF relay by 71.88% at a distance of 70 m between the relay and the eavesdropper in this jamming relay network.
Cooperative communications is obviously an evolution in wireless networks due to its noticeable advantages such as increasing the coverage as well as combating fading and shadowing effects. However, the broadcast characteristic of a wireless medium which is exploited in cooperative communications leads to a variety of security vulnerabilities. As cooperative communication networks are globally expanded, they expose to security attacks and threats more than ever. Primarily, researchers have focused on upper layers of network architectures to meet the requirements for secure cooperative transmission while the upper-layer security solutions are incapable of combating a number of security threats, e.g., jamming attacks. To address this issue, physical-layer security has been recommended as a complementary solution in the literature. In this thesis, physical layer attacks of the cooperative communication systems are studied, and corresponding security techniques including cooperative jamming, beamforming and diversity approaches are investigated. In addition, a novel security solution for a two-hop decode-and-forward relaying system is presented where the transmitters insert a random phase shift to the modulated data of each hop. The random phase shift is created based on a shared secret among communicating entities. Thus, the injected phase shift confuses the eavesdropper and secrecy capacity improves. Furthermore, a cooperative jamming strategy for multi-hop decode-and-forward relaying systems is presented where multiple non-colluding illegitimate nodes can overhear the communication. The jamming signal is created by the transmitter of each hop while being sent with the primary signal. The jamming signal is known at the intended receiver as it is according to a secret common knowledge between the communicating entities. Hence, artificial noise misleads the eavesdroppers, and decreases their signal-to-noise-ratio. As a result, secrecy capacity of the system is improved. Finally, power allocation among friendly jamming and main signal is proposed to ensure that suggested scheme enhances secrecy.
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.
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.