In this paper, we investigate the achievable secrecy rate in a relay channel where the source and the destination wish to keep the information confidential from an untrusted relay (potential eavesdropper). The relay has no energy supply, and harvests its required energy for relaying from its received signals. For radio-frequency (RF) Energy Harvesting (EH) at the relay, we adopt power splitting (PS) approach. We study the problem of achieving positive secrecy rates between the transmitter and the receiver while making use of an untrusted relay. Energy limitation at the relay makes the problem more interesting. Because, the relay must choose either to eavesdrop the signal to be able to decode or to harvest energy (from the information signal) to be able to forward the message. Our scheme to guarantee the secrecy uses cooperative jamming by either the destination or an extra jammer node. We derive the achievable secrecy rates for the compress-and-forward (CF) and amplify-and-forward (AF) relays for two different scenarios. First, we assume the destination and the jammer are two separate nodes. Then, we consider destination-assisted jamming. In addition, we let the relay to use both the sources and the jammers transmitted signals to harvest energy. Our numerical results show that our proposed schemes guarantee a positive secrecy rate by properly locating the jammer and allocating enough jamming power. However, for a given power budget (i.e., fixed total transmission and jamming power) there is an optimum amount for the jamming power.
In this paper, we investigate the achievable secrecy rate in a relay channel where the source and the destination wish to keep the information confidential from an untrusted relay (potential eavesdropper). The relay has no energy supply, and harvests its required energy for relaying from its received signals. For radio-frequency (RF) Energy Harvesting (EH) at the relay, we adopt power splitting (PS) approach. We study the problem of achieving positive secrecy rates between the transmitter and the receiver while making use of an untrusted relay. Energy limitation at the relay makes the problem more interesting. Because, the relay must choose either to eavesdrop the signal to be able to decode or to harvest energy (from the information signal) to be able to forward the message. Our scheme to guarantee the secrecy uses cooperative jamming by either the destination or an extra jammer node. We derive the achievable secrecy rates for the compress-and-forward (CF) and amplify-and-forward (AF) relays for two different scenarios. First, we assume the destination and the jammer are two separate nodes. Then, we consider destination-assisted jamming. In addition, we let the relay to use both the sources and the jammers transmitted signals to harvest energy. Our numerical results show that our proposed schemes guarantee a positive secrecy rate by properly locating the jammer and allocating enough jamming power. However, for a given power budget (i.e., fixed total transmission and jamming power) there is an optimum amount for the jamming power.
The broadcast nature of the wireless medium allows unintended users to eavesdrop on confidential information transmission. In this regard, we investigate the problem of secure communication between a source and a destination via a wireless energy harvesting untrusted node that acts as a helper to relay the information; however, the source and destination nodes wish to keep the information confidential from the relay node. To realize the positive secrecy rate, we use destination-assisted jamming. Being an energy-starved node, the untrusted relay harvests energy from the received radio-frequency (RF) signals, which include the source's information signal and the destination's jamming signal. Thus, we utilize the jamming signal efficiently by leveraging it as a useful energy source. At the relay, to enable energy harvesting and information processing, we adopt power splitting (PS) and time switching (TS) policies. To evaluate the secrecy performance of this proposed scenario, we derive analytical expressions for two important metrics, viz., the secrecy outage probability and the ergodic secrecy rate. The numerical analysis reveals design insights into the effects of different system parameters such as PS ratio, energy harvesting time, target secrecy rate, transmit signal-to-noise ratio (SNR), relay location, and energy conversion efficiency factor, on secrecy performance. Specifically, the PS policy achieves better optimal secrecy outage probability and optimal ergodic secrecy rate than that of the TS policy at higher target secrecy rate and transmit SNR, respectively.
We focus on a scenario where two wireless source nodes wish to exchange confidential information via an RF energy harvesting untrusted two-way relay. Despite its cooperation in forwarding the information, the relay is considered untrusted out of the concern that it might attempt to decode the confidential information that is being relayed. To discourage the eavesdropping intention of the relay, we use a friendly jammer. Under the total power constraint, to maximize the sum-secrecy rate, we allocate the power among the sources and the jammer optimally and calculate the optimal power splitting ratio to balance between the energy harvesting and the information processing at the relay. We further examine the effect of imperfect channel state information at both sources on the sum- secrecy rate. Numerical results highlight the role of the jammer in achieving the secure communication under channel estimation errors. We have shown that, as the channel estimation error on any of the channels increases, the power allocated to the jammer decreases to abate the interference caused to the confidential information reception due to the imperfect cancellation of jammer's signal.
Energy harvesting (EH) has attracted a lot of attention in cooperative communication networks studies for its capability of transferring energy from sources to relays. In this paper, we study the secrecy capacity of a cooperative compressed sensing amplify and forward (CCS-AF) wireless network in the presence of eavesdroppers based on an energy harvesting protocol. In this model, the source nodes send their information to the relays simultaneously, and then the relays perform EH from the received radio-frequency signals based on the power splitting-based relaying (PSR) protocol. The energy harvested by the relays will be used to amplify and forward the received information to the destination. The impacts of some key parameters, such as the power splitting ratio, energy conversion efficiency, relay location, and the number of relays, on the system secrecy capacity are analyzed through a group of experiments. Simulation results reveal that under certain conditions, the proposed EH relaying scheme can achieve higher secrecy capacity than traditional relaying strategies while consuming equal or even less power.
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.
The secrecy capacity (SC) from the source to a destination in a dual-hop amplify-and-forward (AF) relay network using cooperative jamming (CJ) is investigated. Conditions for achieving a positive SC are derived. An energy constrained untrusted cooperative relaying protocol is considered in which the relay forwards information from the source to the destination while harvesting energy from the source signal and the destination jamming signal. An optimization problem is proposed to maximize the SC subject to the energy constraints. A method is proposed to find the optimal power split ratio (PSR) which maximizes the SC. An approximate expression for the optimal PSR is also derived. Results show that a mutually beneficial relationship exists between source-destination pair and the relay. This allows the relay to achieve a net energy gain while the secrecy of the confidential message from the source to the destination is protected.
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.