In this work, we investigate the secrecy performance in multi-antenna untrusted relay networks, where destination-aided jamming is incorporated to help reduce the amount of confidential information leaked to an untrusted relay. We conduct a robust secrecy performance analysis for the worst-case scenario, where the antenna selection technique is performed at the untrusted relay for data reception and retransmission, and the selected antenna is the one with the highest probability of interrupting the confidential information. In addition, maximal ratio transmission is used at the source and destination for sending information and jamming signals. Under this transmission scheme, we derive the novel exact and asymptotic closed-form expressions for the secrecy outage probability (SOP) to evaluate the secrecy performance with arbitrary number of antennas. Numerical and simulation results indicate that there exists an optimal number of transmit antennas at the source to achieve the tradeoff between reliability and security.
In this work, we investigate the secrecy performance in multi-antenna untrusted relay networks, where destination-aided jamming is incorporated to help reduce the amount of confidential information leaked to an untrusted relay. We conduct a robust secrecy performance analysis for the worst-case scenario, where the antenna selection technique is performed at the untrusted relay for data reception and retransmission, and the selected antenna is the one with the highest probability of interrupting the confidential information. In addition, maximal ratio transmission is used at the source and destination for sending information and jamming signals. Under this transmission scheme, we derive the novel exact and asymptotic closed-form expressions for the secrecy outage probability (SOP) to evaluate the secrecy performance with arbitrary number of antennas. Numerical and simulation results indicate that there exists an optimal number of transmit antennas at the source to achieve the tradeoff between reliability and security.
We investigate a relay network where the source can potentially utilize an untrusted non-regenerative relay to augment its direct transmission of a confidential message to the destination. Since the relay is untrusted, it is desirable to protect the confidential data from it while simultaneously making use of it to increase the reliability of the transmission. We first examine the secrecy outage probability (SOP) of the network assuming a single antenna relay, and calculate the exact SOP for three different schemes: direct transmission without using the relay, conventional non-regenerative relaying, and cooperative jamming by the destination. Subsequently, we conduct an asymptotic analysis of the SOPs to determine the optimal policies in different operating regimes. We then generalize to the multi-antenna relay case and investigate the impact of the number of relay antennas on the secrecy performance. Finally, we study a scenario where the relay has only a single RF chain which necessitates an antenna selection scheme, and we show that unlike the case where all antennas are used, under certain conditions the cooperative jamming scheme with antenna selection provides a diversity advantage for the receiver. Numerical results are presented to verify the theoretical predictions of the preferred transmission policies.
In this paper, we investigate secure communication for an untrusted relay network, in which a source equipped with NS antennas communicates to M users with the help of an untrusted relay. To protect the data confidentially while concurrently relying on the untrusted relays, joint antenna and user selection scheme has been proposed with the aid of cooperative jamming. Furthermore, the impacts of both the number of antennas and the number of users on system performance are studied. Both the secrecy outage probability (SOP) and ergodic secrecy rate (ESR) are derived in closed form, and the secrecy diversity order of the considered networks is proved to be min(NS, M/2). Compared with the traditional single antenna and single source-destination scenario, both SOP and ESR can achieve a great improvement owing to the mutual effects of antenna diversity and user diversity. In addition, numerical results are conducted to demonstrate the validity of the proposed scheme.
We design a new relay-aided secure transmission scheme, in which a source communicates with a destination through a trusted decode-and-forward relay in the presence of spatially random-distributed non-colluding eavesdroppers. We consider a general antenna configuration, in which the source, relay, destination, and eavesdroppers are equipped with multiple antennas. We assume that both the source and the relay transmit artificial noise signals in addition to information signals. We also assume that the source and the relay adopt different codebooks, and that the transmitted signals from the source and relay are not jointly processed at each eavesdropper. We first derive a closed-form expression for the transmission outage probability and a new expression for the secrecy outage probability. Notably, these expressions are valid for an arbitrary number of antennas at the source, relay, and destination. We then derive simple yet valuable expressions for the asymptotic transmission outage probability and the asymptotic secrecy outage probability, which reveal the secrecy performance when the number of antennas at the source grows sufficiently large. Using our expressions, we quantify a practical performance metric, namely, the secrecy throughput, under a secrecy outage probability constraint. We further determine the system and channel parameters that maximize the secrecy throughput, leading to analytical security solutions suitable for real-world deployment.
This paper investigates secure communications of energy harvesting untrusted relay networks, where the destination assists jamming signal to prevent the untrusted relay from eavesdropping and to improve the forwarding ability of the energy constrained relay. Firstly, the source and the destination transmit the signals to the relay with maximal ratio transmission (MRT) technique or transmit antenna selection (TAS) technique. Then, the destination utilizes maximal ratio combining (MRC) technique or receive antenna selection (RAS) technique to receive the forwarded information. Therefore, four transmission and reception schemes are considered. For each scheme, the closed-form expressions of the secrecy outage probability (SOP) and the connection outage probability (COP) are derived. Besides, the effective secrecy throughput (EST) metric is analyzed to achieve a good tradeoff between security and reliability. In addition, the asymptotic performance of EST is also considered at the high signal-to-noise ratio (SNR). Finally, simulation results illustrate that: (1) the EST of the system with MRT and MRC scheme are superior to other schemes, however, in the high SNR regime, the EST of the system with MRT scheme is inferior to TAS; and (2) for the source node, there exists an optimal number of antennas to maximize the EST of the proposed schemes.
Abstract Secrecy performance of a cooperative communication network is analyzed in which source transmits information to a destination via multiple relays, assisted with multiple antennas, where an eavesdropper is able to eavesdrop the information signal from relay only. The direct link does not exist between source and destination due to deep fading and shadowing effect and transmission of a signal from source to destination is completed in two phases; first is the broadcasting phase and other is the relaying phase. Each relay follows decode and forward protocol and receives the information signal with multiple antennas. A selected relay harvests energy from received multiple signals through multiple antennas. Both information and jamming signals are transmitted by the selected antenna of a selected relay. It has been seen that a selected relay harvests energy 0.3706 joule with an array of 5 antennas when the source transmits the information signal with 5 dBW power. We have also observed that the performance increased by 99.24% in case of an array four antennas system with respect to an array of two antennas system when secrecy threshold is 1 bit/s/Hz . Secrecy performance is measured in terms of secrecy outage probability (SOP). A closed-form expression of the SOP is derived to analyze the secrecy performance which is verified by the simulation results.
Abstract—In this paper, the problem of secure transmission in two-hop amplify-and-forward (AF) systems with an untrusted relay is investigated. To prevent the untrusted relay from intercepting the source message and to achieve positive secrecy rate, the destination-based cooperative jamming (DBCJ) technique is used. In this method the destination sends an intended jamming signal to the relay. This jamming signal helps protecting the source message from being captured reliably at the untrusted relay, while the destination cancels itself intended jamming signal. The optimal power allocation (OPA) technique is considered for the presented system. It is observed that the objective function is a quasiconcave function at high signal-to-noise-ratio (SNR) regimes. Based on this OPA technique, we study the ergodic secrecy rate (ESR) and the secrecy outage probability (SOP) of the system when the source and relay are equipped with a single antenna while the destination is equipped with largescale antenna arrays (LSA). Using the achieved closed-form expressions, one can evaluate the performance of the secure system easily and fast and also, they provide significant insight for system design. Finally, simulation results indicate the accuracy of the derived expressions.