This paper considers a wireless powered communication network, where a multiantenna power beacon (PB) is employed to assist an energy constrained source to establish secure communications with a destination in the presence of multiple eavesdroppers. We propose a two-phase communication protocol termed as accumulate then transmit to enhance network secrecy. In the energy harvesting phase, the PB transfers radio frequency energy to charge the source; then in the information transmission phase, the PB acts as a friendly jammer to protect the source transmission against eavesdropping. We study the dynamic energy state transitions at the source using an energy discretization method and a finite-state Markov chain. Closed-form expressions are derived for connection outage probability, secrecy outage probability, and effective secrecy throughput, with the aim to evaluate both reliability and security of the proposed protocol. Furthermore, numerical results reveal the impacts of various system parameters on the secrecy performance and demonstrate the superior performance of our proposed protocol over an existing scheme.
This paper considers a wireless powered communication network, where a multiantenna power beacon (PB) is employed to assist an energy constrained source to establish secure communications with a destination in the presence of multiple eavesdroppers. We propose a two-phase communication protocol termed as accumulate then transmit to enhance network secrecy. In the energy harvesting phase, the PB transfers radio frequency energy to charge the source; then in the information transmission phase, the PB acts as a friendly jammer to protect the source transmission against eavesdropping. We study the dynamic energy state transitions at the source using an energy discretization method and a finite-state Markov chain. Closed-form expressions are derived for connection outage probability, secrecy outage probability, and effective secrecy throughput, with the aim to evaluate both reliability and security of the proposed protocol. Furthermore, numerical results reveal the impacts of various system parameters on the secrecy performance and demonstrate the superior performance of our proposed protocol over an existing scheme.
This paper investigates secure transmission in a wireless powered communication network (WPCN) with an energy harvesting (EH) source configured with multiple antennas. In the WPCN, the EH source harvests energy from the radio frequency (RF) signals broadcasted by a power beacon (PB), and purely relies on the harvested energy to communicate with the destination in the presence of passive eavesdroppers. It is noteworthy that the RF-EH source is equipped with a finite energy storage to accumulate the harvested energy. To enhance the security, we propose an energy-aware transmit antenna selection (EATAS) scheme. According to the energy status and the channel quality, the source adaptively decides to transmit confidential information or harvest RF energy. For evaluating the secrecy performance, we first study the evolution of the energy storage, and then derive the analytical expressions of connection outage probability (COP), secrecy outage probability (SOP) and effective secrecy throughput (EST). Numerical results demonstrate that our proposed scheme outperforms the existing accumulate-then-transmit (ATT) scheme.
This paper investigates secure transmission in a wireless powered communication network (WPCN) with an energy harvesting (EH) source configured with multiple antennas. In the WPCN, the EH source harvests energy from the radio frequency (RF) signals broadcasted by a power beacon (PB), and purely relies on the harvested energy to communicate with the destination in the presence of passive eavesdroppers. It is noteworthy that the RF-EH source is equipped with a finite energy storage to accumulate the harvested energy for the future usage. Moreover, due to energy-constraint and complexity- limitation, the multi-antenna source is only configured with a single RF-chain. To enhance the security for the WPCN, we propose two adaptive transmission schemes, i.e., energy-aware transmit antenna selection (EATAS) and energy-aware differential spatial modulation (EADSM). According to the energy status and the channel quality, the source adaptively decides whether to transmit confidential information or harvest RF energy. To evaluate the secrecy performance of the proposed schemes, we first study the evolution of the energy storage, and then derive the analytical expressions of connection outage probability (COP), secrecy outage probability (SOP) and efficient secrecy throughput (EST). Numerical results demonstrate that our proposed schemes outperform the existing schemes, i.e., time-switching based TAS (TS-TAS) and accumulate-then-transmit (ATT). And, increasing the transmit power of the PB or the capacity of the source's energy storage is helpful to improve the secrecy performance. Moreover, there exists an optimal transmission rate for each proposed scheme to achieve best secrecy performance.
In this paper, we propose using a wireless-powered friendly jammer to enable secure communication between a source node and destination node, in the presence of an eavesdropper. We consider a two-phase communication protocol with fixed-rate transmission. In the first phase, wireless power transfer is conducted from the source to the jammer. In the second phase, the source transmits the information-bearing signal under the protection of a jamming signal sent by the jammer using the harvested energy in the first phase. We analytically characterize the long-term behavior of the proposed protocol and derive a closed-form expression for the throughput. We further optimize the rate parameters for maximizing the throughput subject to a secrecy outage probability constraint. Our analytical results show that the throughput performance differs significantly between the single-antenna jammer case and the multiantenna jammer case. For instance, as the source transmit power increases, the throughput quickly reaches an upper bound with single-antenna jammer, while the throughput grows unbounded with multiantenna jammer. Our numerical results also validate the derived analytical results.
In this paper, we present a secrecy outage performance analysis of wireless powered communication networks with multiple eavesdroppers, where an energy-limited information source with multiple antennas harvests the radio frequency (RF) energy from a dedicated power beacon (PB) before transmission. To exploit the benefits of multiple antennas at source, two popular multi-antenna transmission schemes, i.e., maximal ratio transmission and transmit antenna selection, are investigated for two intercepting ways at Eves, i.e., non-colluding and colluding scenarios, respectively. Specifically, adopting the time-switching protocol at PB, we derive exact and asymptotic closed-form expressions of the secrecy outage probability for both two transmission schemes taking into account the outdated channel state information (CSI). From our analysis, several important concluding remarks are obtained as follows: a) Full secrecy diversity order can be achieved by both two transmission schemes with no feedback delay, however, it reduces to zero in the presence of feedback delay; b) MRT scheme always outperforms TAS scheme with no feedback delay. However, TAS scheme achieves a similar performance as MRT scheme or even better in moderate and even serious feedback delay conditions.
This paper develops a new cooperative jamming protocol, termed accumulate-and-jam (AnJ), to improve physical layer security in wireless communications. Specifically, a full-duplex (FD) friendly jammer is deployed to secure the direct communication between source and destination in the presence of a passive eavesdropper. We consider the friendly jammer as an energy-constrained node without embedded power supply but with an energy harvesting unit and rechargeable energy storage; it can thus harvest energy from the radio frequency signals transmitted by the source, accumulate the energy in its battery, and then use this energy to perform cooperative jamming. In the proposed AnJ protocol, based on the energy status of the jammer and the channel state of source-destination link, the system operates in either dedicated energy harvesting (DEH) or opportunistic energy harvesting (OEH) mode. In DEH mode, the source sends dedicated energy-bearing signals and the jammer performs energy harvesting. In OEH mode, the source transmits an information-bearing signal to the destination. Meanwhile, using the harvested energy, the wireless-powered jammer transmits a jamming signal to confound the eavesdropper. Thanks to the FD capability, the jammer also harvests energy from the information-bearing signal that it overhears from the source. We study the complex energy accumulation and consumption procedure at the jammer by considering a practical finite-capacity energy storage, of which the long-term stationary distribution is characterized through applying a discrete-state Markov Chain. An alternative energy storage with infinite capacity is also studied to serve as an upper bound. We further derive closed-form expressions for two secrecy metrics, i.e., secrecy outage probability and probability of positive secrecy capacity. In addition, the impact of imperfect channel state information on the performance of our proposed protocol is also investigated. Numerical results validate all theoretical analyses and reveal the merits of the proposed AnJ protocol over its half-duplex counterpart.
In this work, we propose a secure communication scheme, where a source transmits information to the legitimate receiver in the presence of multiple eavesdroppers. To improve the security, single or multiple friendly jammers are deployed to confuse the eavesdroppers. Specifically, we assume that the jammers have to harvest energy from the source, thus we consider a two-phase transmission scheme where the source transmits energy to the jammers first and then transmits information to the legitimate receiver confidentially with the help of the jammers. We first give the expression of the secrecy outage probability, revealing how the secrecy performance depends on the transmission parameter tuple, and then we use the simulated annealing method to obtain the optimal transmission parameter tuple. The simulation results show the superiority of our proposed scheme.