Asma Mabrouk

Relay selection for optimized cooperative jamming scheme

In this paper, we study the problem of secure dual-hop transmission in the presence of an eavesdropper, where a secrecy-enhanced relay selection as well as a destination cooperation are presented to prevent the source information from being eavesdropped. Taking into account the total power budget, a power allocation scheme is investigated to optimize the destination contribution. We present the system performance in terms of secrecy capacity where we derive a closed form expression for its lower bound. Simulation results reveal that a higher power allocation to the jamming signal should be balanced by a closer placement of the relay to the source to get better system performance, and vice versa.

Transmission mode selection scheme for physical layer security in multi-user multi-relay systems

We study a relay and user selection scheme to improve the secrecy performance of cooperative multi-user multiple amplify-and-forward (AF) relay network. Nevertheless, relay transmission is highly susceptible to eavesdropping since confidential information is broadcasted twice, i.e., by the source and the relay. In particular, we propose a cooperative jamming aided secure transmission through the relay path. Furthermore, with the presence of the direct path, a transmission mode selection scheme is elaborated in such a way to reduce the amount of information leaked to non-selected users in the system, who may overhear the source message as eavesdroppers. Specifically, the selected relay is only activated when it has better secrecy performance than the source. We study the impact of outdated channel state information (CSI) on the system by deriving a closed-form lower bound for the secrecy outage probability (SOP). By investigating the effect of the jamming power level and the correlation coefficients imbalance, a comparison reveals that the proposed scheme outperforms the fixed transmission modes and its signal-to-noise ratio based counterpart. It is shown that the secrecy outage probability can be decreased as the number of destinations grows unless the number of relays is small. Importantly, optimal relay location and jamming power allocation significantly enhance the secrecy performance.

Adaptive Secure Transmission for RF-EH Untrusted Relaying with Alien Eavesdropping

An adaptive cooperative scheme is proposed to improve the security of a wireless-powered relay network. A source node sends data to a destination node in the presence of an amplify-and-forward untrusted relay node and an alien eavesdropper where both are assumed to attempt to decode the source’s information signal. The source uses a fraction of its transmit power to send a jamming signal to keep its information confidential. To save energy, the energy-harvesting relay node transmits with the minimum power level that ensures secure transmissions. We derive a closed-form upper bound on the system’s secrecy outage probability. The proposed cooperative scheme is more efficient than the conventional scheme, where once the relay has accumulated sufficient energy, it assists the source’s information transmission.

Secure cooperative untrusted-relay network with outdated CSI

This paper studies the secrecy performance of an untrusted amplify-and-forward relaying network where both the relaying and the direct links are used to convey the sources information. Since relays act as eavesdroppers, a source-based jamming technique is proposed to keep the sources message secret from these helper nodes. We analyze the secrecy capacity of partial relay selection based on outdated channel state information. The study is conducted analytically by deriving the lower-bound expression for the ergodic secrecy capacity (ESC). We demonstrate through the simulation results the tightness of the derived bound. The use of the direct link is shown to improve the secrecy performance of the proposed scheme. In this case, we found that ESC performance with maximum ratio combining at the destination is better than that with selection combining. The system performance worsens as the correlation coefficient decreases. Furthermore, the maximum of ESC is achieved when relays are in the middle between the source and the destination with equal power allocation between the information and the jamming signals at the source.

A Secure Relay Selection AN-Aided Scheme for Dual-Hop DF Relay Networks With Two-Sided Eavesdropping

We propose a new relay selection artificial-noise (AN)-aided scheme to enhance the security of relay networks. We assume the presence of two multi-antenna eavesdroppers where one of them is closer to the legitimate transmitter (Alice) and the other one is closer to the legitimate receiver (Bob). To improve the system’s security, we optimize the transmit power allocation factor between data and AN. Moreover, we design the data and AN precoders at Alice, the AN precoder at Bob, the AN precoder at the relays, and data receive filter at Bob. We derive closed-form expressions for the links’ rates and the instantaneous secrecy rate. Numerical results show that our proposed scheme achieves higher average secrecy rate than others in the literature.

AN-Aided Relay-Selection Scheme for Securing Untrusted RF-EH Relay Systems

Energy harvesting (EH) technology has imposed new constraints on the amount of time an energy-constrained relay node needs to use for EH and information forwarding. Moreover, EH techniques may increase vulnerability to eavesdropping, since a power receiver, as a potential eavesdropper, usually has a shorter access distance than an information receiver. Motivated by this issue, in this paper, we investigate a tradeoff between energy consumption and physical layer security in a wireless powered-untrusted cooperative communication (WPUCC) network consisting of one source-destination pair and multiple amplify-and-forward untrusted relays. To minimize the energy consumption of the network, we propose a secure adaptive relay-based cooperation approach. Moreover, a greedy battery-aware relay-selection scheme is proposed to minimize the power consumption in WPUCC systems. Using power-splitting-based energy accumulation, untrusted relays attempt to intercept the information intended to the legitimate destination while harvesting energy at the same time. To keep the information secure from potential eavesdropping, the source injects a jamming signal along with its data signal. By modeling the dynamic behavior of the relay battery as a finite-state Markov chain, we derive an analytical expression for the secrecy outage probability of our proposed secure adaptive harvest-use-store cooperative communication scheme and show that it is more secure than its direct transmission and pure two-hop transmission counterparts.

Securing Untrusted RF-EH Relay Networks Using Cooperative Jamming Signals

We propose a new scheme to secure a wireless-powered untrusted cooperative-communication network, where a legitimate source node (Alice) transmits her information messages to a legitimate destination node (Bob) through the multiple amplify-and-forward untrusted relays. The relay nodes are assumed to be honest but curious nodes; hence, they are trusted at the service level but are untrusted at the information level. To reduce the energy consumption of the network, only one relay node is selected in each time slot to forward Alice’s information signal. We assume a power-splitting-based energy-harvesting scheme, where each relay node splits its received signal into information and energy streams. Since the relay nodes are assumed to be untrusted at the information level, they attempt to decode the information intended to Bob while harvesting energy at the same time. When the relaying mode is selected, the scheme is realized over two non-overlapping time phases. To prevent any information leakage to the untrusted relay nodes, Bob and a cooperative jammer (John) inject jamming (artificial noise) signals during the first phase. During the second phase, the untrusted relay nodes that will not be forwarding the information signal must harvest energy to accumulate more energy to help Alice in future time slots. Moreover, the cooperative jammer will jam the untrusted relays to further power their batteries and prevent them from decoding the information-forwarding relay signal in case they decided to cheat and decode it. We model the battery state transitions at each relay as a finite-state Markov chain and analyze it. Our numerical results show the security gains of our proposed scheme relative to two benchmark schemes.

Performance analysis of secure AF relay networks using cooperative jamming under outdated CSI

This paper studies cooperative transmission for securing a two-hop network where the eavesdropper can wiretap the relay channels. With outdated channel state information (CSI), we propose an opportunistic relaying with destination-based jamming scheme, where one relay is chosen to forward the confidential signal and the destination sends jamming signal to confuse the eavesdropper. To reveal the capability of the proposed scheme in improving the system secrecy, we investigate the two common performance metrics under different assumptions on the eavesdropper CSI. First, lower bound on the ergodic secrecy capacity (ESC) is derived assuming perfect knowledge of the eavesdropper channel gains. We, then, extend our results to the scenario where only the legitimate channel gain is known. Here, lower bound on the secrecy outage probability (SOP) is obtained. To further improve the utility of the destination, under total power constraint, a power allocation between data signal and jamming noise is considered. Both the analysis and simulation results indicate that the system performance is significantly improved in terms of both ESC and SOP when the jamming power at the destination is adjusted according to the selected relay position. We verify that, with outdated CSI, the secrecy performance of opportunistic relaying is severely degraded.

Efficient AN-Aided Scheme to Power RF-EH Source Nodes and Secure Their Transmissions

We propose an artificial-noise (AN)-aided transmission scheme to achieve two objectives: 1) energize a single-antenna legitimate transmitter (<italic>Alice</italic>) by receiving an AN signal from a multi-antenna base-station (<italic>Bob</italic>) and 2) secure the information signal transmitted from <italic>Alice</italic> to <italic>Bob</italic> from eavesdropping by a multi-antenna eavesdropper (<italic>Eve</italic>). We assume a two-phase transmission scheme. In the first phase, <italic>Bob</italic> transmits two orthogonal precoded AN vectors to power <italic>Alice</italic> and confuse <italic>Eve</italic>. In the second phase, <italic>Alice</italic> transmits her information signal to <italic>Bob</italic> along with an amplified version of the AN signal to confuse <italic>Eve</italic>. Our numerical results show that the proposed scheme can efficiently power <italic>Alice</italic> while securing her transmissions. Moreover, we show that the achieved average secrecy rate under the proposed scheme outperforms the case when the conventional communication scheme is employed.