A novel relay-aided physical layer security scheme is proposed in this letter. The channel model incorporates partial reflection components in the received signal according to the signal power. With this channel model, we formulate three security capacity maximization problems based on three relay-aided scenarios: cooperative jamming, decode-and-forward, and amplify-and-forward. By using an iterative algorithm, we jointly optimize the beamforming vector and two-dimensional spatial positions of relays based on the formulated problems to maximize the sum data rate while defending against eavesdropping. Numerical results show that the sum data rate for legal receivers can be improved by applying the proposed scheme.
A novel relay-aided physical layer security scheme is proposed in this letter. The channel model incorporates partial reflection components in the received signal according to the signal power. With this channel model, we formulate three security capacity maximization problems based on three relay-aided scenarios: cooperative jamming, decode-and-forward, and amplify-and-forward. By using an iterative algorithm, we jointly optimize the beamforming vector and two-dimensional spatial positions of relays based on the formulated problems to maximize the sum data rate while defending against eavesdropping. Numerical results show that the sum data rate for legal receivers can be improved by applying the proposed scheme.
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.
We propose a novel relay-aided physical layer security scheme for multi-eavesdropper visible light communication. When eavesdroppers outnumber relays, we strategically position relays to prioritize blocking line-of-sight (LoS) paths from the light source to the subset of eavesdroppers with stronger interception capabilities, ingeniously transforming potential limitations of obstacles into security advantages. Subsequently, relays are designed to broadcast jamming signals, with beamforming vector optimized to minimize the sum signal-to-interference-plus-noise-ratio at remaining eavesdroppers. Conversely, we solely determine relay placement to obstruct all LoS paths from the light source to eavesdroppers. Numerical results demonstrate that our scheme significantly outperforms traditional schemes in security capacity.
This paper proposes a new joint cooperative beamforming and jamming (JCBJ) scheme for improving the physical layer security of decode-and-forward wireless networks where a source node transmits to its destination with the aid of multiple intermediate nodes in the presence of an eavesdropper. In the proposed JCBJ scheme, we select the intermediate nodes succeeding in source decoding as the relays to forward the source transmission simultaneously by employing a beamforming weight vector, and meanwhile, use the remaining ones as the friendly jammers to disturb the eavesdropper by sending artificial noise. In order to achieve the secrecy rate maximum, we further study on the power allocation among the source, relays, and jammers under two assumptions of the wiretap link's channel state information. We derive the closed-form optimal solutions by first allocating the transmit power at the source within different ranges to consider all the possible relay selection schemes in which different numbers of relays are employed, and then transforming the multivariable power allocation problem to a set of single-variable optimization subproblems. Our numerical results show the superiority of the proposed JCBJ scheme and the proposed power allocation strategies.
A visible light communication (VLC) broadcast channel is considered, in which a transmitter communicates with two receivers in the presence of an external eavesdropper. Trusted cooperative half-duplex relays are deployed to aid with securing the transmitted data. Transmission is amplitude-constrained to maintain operation within the light emitting diodes (LEDs) dynamic range. Achievable secrecy rate regions are derived under such amplitude constraints for this multi receiver wiretap channel, first for direct transmission without the relays, and then for cooperative jamming, decode-and-forward, and amplify-and-forward relaying schemes. Superposition coding with uniform signaling is used for transmission, along with secure beamforming at the relays. Superiority of the secure relaying schemes over direct transmission is shown, with performance depending on how far the eavesdropper is from the transmitter and the relays.
A visible light communication (VLC) system with an improved noise model applied to physical layer security (PLS) is investigated, where secure beamforming signals with superposition coding are used. In the improved model, the output signal follows Gaussian distribution, but its variance is signal-dependent. Two different methods are proposed to obtain lower and upper bounds on the secrecy rate of the strong user for direct transmission. Under some constraints, closed-form expressions of the lower and upper bounds on secrecy rate regions for various (trusted cooperative half-duplex) relaying schemes are derived. Moreover, the scenarios of blockage/outside coverage are included, and the relevant security performances are discussed. Numerical results show that the lower and upper bounds on secrecy rate regions are tight enough, and the cooperative jamming is superior over other relaying schemes.
In this paper, a coordinated multiple-relays-based cooperative communication scheme is proposed to improve the physical-layer security. In order to benefit the relays in forwarding the signals for defending against the eavesdropping attacks, the interactions between the source and the multiple relays are modeled as a single-leader multiple-followers Stackelberg game. The source plays as the leader to coordinate the relays, including the phase of signals forwarded by the relays and the transmit power of the relays, for maximizing the secrecy capacity of the system. An algorithm is developed for the relays to find an optimal price allocation to achieve the fairness among the multiple relays based on the egalitarian welfare solution, and an approximate optimal strategy of source (i.e., phase coordinated vector and power allocation) is studied. The closed-form intercept probability of the proposed scheme is derived. Numerical studies demonstrate that the proposed scheme can greatly improve the utilities of both the source and multiple relays over that resulted from the Nash equilibrium scheme and rand scheme, which means that the relays are more willing to participate in the cooperative communication, and the source can achieve better secure transmission based on the proposed scheme. It is also shown that the proposed scheme performs much better in defending against the eavesdropping attacks than those existing schemes, for example, the single relay selection scheme, the opportunistic relay selection scheme, the optimal relay scheme, and cooperative jamming scheme.