This paper evaluates the secure energy efficiency (SEE) of a cooperative network subject to partial secrecy requirements, implemented through a fractional equivocation parameter θ ∈ (0, 1] that allows partial secrecy when θ <; 1. We assume that only the channel state information (CSI) of the legitimate channel is available, while the CSI with respect to the eavesdropper is unknown. Then, we propose a CSI-aided decode-and-forward (DF) scheme, in which the transmitter uses the available CSI in order to choose between direct and cooperative paths. Moreover, the relay employs either repetition coding (CSI-RC), i.e., source and relay use the same codebook, or parallel coding (CSI-PC), when different codebooks are used. By resorting to the Dinkelbach algorithm, we propose a joint power allocation scheme, which also optimizes θ to maximize the SEE. Our schemes are compared with the traditional DF, amplify- and-forward, and cooperative jamming (CJ). In most scenarios, CSI-RC performs best in terms of SEE. Nevertheless, we observe that CSI-PC achieves the highest SEE when θ → 1 and if the relay is close to either the transmitter or the receiver. Moreover, CJ also stands out to maximize the SEE if the relay is placed closer to the eavesdropper. In addition, the influence of θ in the system performance is evaluated, showing that a joint θ and power optimization considerably improves the SEE.
This paper evaluates the secure energy efficiency (SEE) of a cooperative network subject to partial secrecy requirements, implemented through a fractional equivocation parameter θ ∈ (0, 1] that allows partial secrecy when θ <; 1. We assume that only the channel state information (CSI) of the legitimate channel is available, while the CSI with respect to the eavesdropper is unknown. Then, we propose a CSI-aided decode-and-forward (DF) scheme, in which the transmitter uses the available CSI in order to choose between direct and cooperative paths. Moreover, the relay employs either repetition coding (CSI-RC), i.e., source and relay use the same codebook, or parallel coding (CSI-PC), when different codebooks are used. By resorting to the Dinkelbach algorithm, we propose a joint power allocation scheme, which also optimizes θ to maximize the SEE. Our schemes are compared with the traditional DF, amplify- and-forward, and cooperative jamming (CJ). In most scenarios, CSI-RC performs best in terms of SEE. Nevertheless, we observe that CSI-PC achieves the highest SEE when θ → 1 and if the relay is close to either the transmitter or the receiver. Moreover, CJ also stands out to maximize the SEE if the relay is placed closer to the eavesdropper. In addition, the influence of θ in the system performance is evaluated, showing that a joint θ and power optimization considerably improves the SEE.
The growing demand for wireless communications systems makes security an important and difficult design task. Therefore, in this thesis we approached different studies at physical layer security considering different scenarios of partial secrecy requirements, multiple antennas and finite blocklenghts. With respect to the partial secrecy regime, we evaluate the secure energy efficiency (SEE) of a cooperative network subject to partial secrecy requirements, implemented through a fractional equivocation parameter θ ϵ (0, 1] that allows partial secrecy when θ < 1. We assume that only the channel state information (CSI) of the legitimate channel is available, while the CSI with respect to the eavesdropper is unknown. Then, we propose a CSI-Aided Decode-and-Forward (DF) scheme, in which the transmitter uses the available CSI in order to choose between direct and cooperative paths. Moreover, the relay employs either Repetition Coding (CSI-RC), i.e., source and relay use the same codebook, or Parallel Coding (CSI-PC), when different codebooks are used. By resorting to the Dinkelbach algorithm, we propose a joint power allocation scheme, which also optimizes θ to maximize the SEE. Our schemes are compared with the traditional DF, Amplify-and-Forward (AF), and Cooperative Jamming (CJ). Extending the previous analysis, we also study the SEE in a cooperative scenario where all nodes are equipped with multiple antennas. Moreover, we employ secrecy rate and power allocation at Alice and at the relay in order to maximize the SEE, subjected to a constraint in terms of a minimal required secrecy outage probability. Considering this MIMO scenario in which only the CSI with respect to the legitimate nodes is available at Alice, we compare the Artificial-Noise (AN) scheme with CSI-Aided Decode-and-Forward (CSI-DF). Lastly, considering a more restrictive scenario with respect to the CSI, but more realistic, in which the legitimate transmitter has no knowledge of the instantaneous channel state information with respect to neither the legitimate receiver nor the eavesdropper, we investigate the secure throughput in a delay-critical scenario, such as in some applications of machine-to-machine communications, so that users communicate with a finite blocklength. In this approach, the performance of direct and selective decode-and-forward cooperative communication strategies are compared.
We investigate the secure energy efficiency of a cooperative network where two legitimate users (Alice and Bob) communicate with the help of a relay node, in the presence of a passive eavesdropper (Eve). Power is adequately allocated between Alice and the relay using a Dinkelbach-based iterative power allocation algorithm. We assume channel state information of the legitimate channel only and compare the secure energy efficiency of several cooperative schemes, namely, selective decode-and-forward (SDF), fixed decode-and-forward (DF), amplify-and-forward (AF) and cooperative jamming (CJ). Our results show that, in terms of secure energy efficiency, SDF outperforms the other cooperative schemes in many scenarios. However, when the transmit rate increases or when Eve is close to the legitimate nodes, CJ stands out as the most advantageous scheme.
In this letter, we investigate the secure energy efficiency (SEE) in a cooperative scenario where all nodes are equipped with multiple antennas. Moreover, we employ secrecy rate and power allocation at Alice and at the relay in order to maximize the SEE, subjected to a constraint in terms of a minimal required secrecy outage probability. Only the channel state information (CSI) with respect to the legitimate nodes is available. Then, we compare the artificial-noise (AN) scheme with CSI-aided decode-and-forward (CSI-DF), which exploits the CSI to choose the best communication path (direct or cooperative). Our results show that CSI-DF outperforms AN in terms of SEE in most scenarios, except when eavesdropper (Eve) is closer to the relay or with the increase of antennas at Eve. Additionally, we also show that the maximization of SEE implies in an optimal number of antennas to be used at each node, which is due to the tradeoff between secure throughput and power consumption.
This paper investigates secrecy efficiency (SE) optimization in a friendly full-duplex (FD) decode- and-forward (DF) relay network with a passive eavesdropper. Targeting on SE maximization, the power allocation is optimized subject to the total power and minimum secrecy rate constraints adapting to the assumption of unknown eavesdropper's channel state information (CSI). By exploiting the properties of fractional programming (FP) and Difference of Convex functions (DC) programming, the resulting nonconvex optimization problem can be relaxed into a more tractable equivalent problem. Simulation results demonstrate that our proposed scheme can reach a better trade-off between security performance and energy consumption.
This paper studies cooperative transmission for securing a decode-and-forward (DF) two-hop network where massive cooperative nodes coexist with a potential single eavesdropper. With only the statistical channel state information (CSIs) of the eavesdroppers, we propose an opportunistic relaying with artificial jamming secrecy scheme, where a “best” cooperative node is chosen to forward the confidential signal and the others act as jammers to send the jamming signals to confuse the eavesdropper. Utilizing the limiting distribution technique of extreme order statistics, we optimize the power allocation between the confidential information and jamming signal based on the statistical CSIs of the legitimate nodes for ergodic secrecy rate (ESR) maximization. Although the optimization problems are non-convex, we propose a sequential parametric convex approximation (SPCA) algorithm to locate the KKT solutions. Then, we derive an analytical closed-form expression of the achievable ESR, which reduces the complexity of the system analysis and design.
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.