A distributed wireless network with one source, one destination, one eavesdropper and multiple Decode-and-Forward (DF) relays is investigated. A two-slot cooperative relaying scheme is considered, in which relays help the source transmit to the destination while keeping the message as secret as possible from the eavesdropper. To prevent the system becoming interference limited, a destination assisted jamming scheme is used, i.e., the destination transmits a jamming signal rather than listening to the source. Several relay selection methods are proposed to let the system benefit from increase of the number of relays. With the proposed transmission scheme, the system secrecy rate is shown to outperform the methods in literature and maintain a scaling law of the achievable secrecy rate of log2(1 + P0/8 log K) -1.6252, where K is the number of relays and P0is the total transmit power.
A distributed wireless network with one source, one destination, one eavesdropper and multiple Decode-and-Forward (DF) relays is investigated. A two-slot cooperative relaying scheme is considered, in which relays help the source transmit to the destination while keeping the message as secret as possible from the eavesdropper. To prevent the system becoming interference limited, a destination assisted jamming scheme is used, i.e., the destination transmits a jamming signal rather than listening to the source. Several relay selection methods are proposed to let the system benefit from increase of the number of relays. With the proposed transmission scheme, the system secrecy rate is shown to outperform the methods in literature and maintain a scaling law of the achievable secrecy rate of log2(1 + P0/8 log K) -1.6252, where K is the number of relays and P0is the total transmit power.
A wireless network with one source, one destination, one eavesdropper and multiple decode-and-forward (DF) relays is considered. A two-slot cooperative relaying scheme is proposed that targets at maximizing the secrecy rate. In the first slot, the source transmits the information bearing signal, and at the same time, it cooperates with the destination in jamming the eavesdropper without creating interference at the relay. In the second slot, one optimally selected relay retransmits the decoded source signal, and at the same time, it cooperates with the source to jam the eavesdropper without creating interference at the destination. For the beamforming, no eavesdropper channel information is required. Optimal relay selection and also optimal power allocation among the first/second slot data signal and jamming noise are proposed. It is shown that the system secrecy rate of the proposed scheme scales with the total system power, P0and the number of available relays, K, according to log2(1 + P0/8 log K) - 1.6252bps.
A distributed wireless network with one source, one destination, one eavesdropper and multiple Decode-and-Forward (DF) relays is considered. A two-slot cooperative relaying scheme is proposed, in which relays help the source transmit to the destination while keeping the message as secret as possible from the eavesdropper. In the first slot, the source transmits a weighted combination of the information bearing signal and a noise signal. At the same time, the destination cooperates with the source in transmitting a noise signal with the purpose of confounding the eavesdropper. In the second slot, the `best' relay cooperates with the source to send a jamming signal along the null space of the destination channel. Optimal relay selection and also optimal power allocation among the first/second slot data signal and jamming noise is proposed. With the proposed transmission scheme, the system secrecy rate is shown to outperform the methods in literature and always benefits from increasing total power and larger number of relays.
A wireless network with one source, one destination, one eavesdropper, and multiple decode-and-forward relays is considered. A two-slot cooperative relaying scheme is proposed that targets at maximizing the secrecy rate. In the first slot, the source transmits the information bearing signal, and at the same time, it cooperates with the destination in jamming the eavesdropper without creating interference at the relay. In the second slot, one optimally selected relay retransmits the decoded source signal, and at the same time, that particular relay cooperates with the source to jam the eavesdropper without creating interference at the destination. Optimal relay selection and also optimal power allocation among the first/second slot data signal and jamming noise are proposed. It is shown that the secrecy rate of the proposed scheme scales with the total system powerP0and the number of available relaysKaccording to 1/2log2(1 +P0/8logK) - 1.6 bits/channel use . Although the proposed power allocation and relay selection assume global CSI available, the performance under imperfect relay CSI is also investigated. Also, the performance under distributed relay selection with limited feedback is demonstrated.
To improve physical (PHY) layer security of a wireless relay system in the presence of an eavesdropper, a two-phase cooperative relaying scheme is investigated in this paper. In phase I, the source transmits confidential message, simultaneously, it cooperates with the friendly jammers and destination to create jamming signal at the eavesdropper without affecting the forwarding relay which is preselected. In phase II, the forwarding relay retransmits the decoded signal, meanwhile, the particular relay cooperates with the friendly jammers to create jamming signal at the eavesdropper without affecting the destination. We focus on the investigation of optimal power allocation for maximizing achievable secrecy rate subject to a total power constraint. Optimal relay selection and suboptimal relay selection schemes are also proposed. It is shown that as the number of relays increases, both secrecy rate and the performance of suboptimal relay selection scheme improve significantly. Numerical results are presented to validate the derived analytical results and compare them to existing work.
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.
The broadcast nature of wireless communications makes the propagation medium vulnerable to security attacks such as eavesdropping and jamming from adversarial or unauthorized users. Applying physical layer secrecy approaches will enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers, without using any secret keys. However, physical layer security approaches are typically feasible only when the source-eavesdropper channel is weaker than the source-destination channel. Cooperative jamming can be used to overcome this challenge and increase the secrecy rate. In this paper, the security of two-phase relaying system with multiple intermediate nodes and in the presence of an eavesdropper is investigated. To enhance the system secrecy rate, a joint cooperative beamforming and jamming combined with relay and jammer selections is proposed. In phase I, the source node broadcasts a signal to relays while three intermediate nodes (which act as jammers) help the source node by transmitting random jamming signals to confuse the eavesdropper. Since the friendly (cooperative) jammers create interference for both the intended relays and the eavesdropper, optimal beamforming is applied such that no interference is caused at two preselected desired relays (that are going to receive the confidential massage in phase I). In phase II, two preselected relays transmit the source message with beamforming coefficients such that the received signal at the eavesdropper is completely nulled out. Our goal in this paper is to minimize the received SNR at the eavesdropper while increasing it at the destination as much as possible by applying different methods such as cooperative beamforming, cooperative jamming and relay selection. To avoid operational complexity, we consider the minimum number of intermediate nodes that are necessary without losing the performance. Numerical results demonstrate the advantage of our proposed scheme compared with the scheme with no cooperative jamming.