Wireless backhaul is a cost-effective and flexible alternative to wired backhaul, yet it suffers from unreliability. This paper studies the secrecy performance of a relay network with such unreliable wireless backhaul. Bernoulli process is adopted to model the wireless backhaul reliability. In the network, a relay employing time-switching-based radio frequency harvesting technique aids in forwarding the signal from the best transmitter. An eavesdropper, which is able to wiretap signals from both the transmitter and the relay, uses selection combining to maximize its received signal-to-noise ratio. Analytical expressions for secrecy outage probability, ergodic secrecy rate and non-zero achievable secrecy rate are derived, which can reveal the effect of the number of transmitters and backhaul reliability on the system performance. Furthermore, for the first time the impact of energy harvesting time fraction upon secrecy performances under unreliable backhaul is presented.
Wireless backhaul is a cost-effective and flexible alternative to wired backhaul, yet it suffers from unreliability. This paper studies the secrecy performance of a relay network with such unreliable wireless backhaul. Bernoulli process is adopted to model the wireless backhaul reliability. In the network, a relay employing time-switching-based radio frequency harvesting technique aids in forwarding the signal from the best transmitter. An eavesdropper, which is able to wiretap signals from both the transmitter and the relay, uses selection combining to maximize its received signal-to-noise ratio. Analytical expressions for secrecy outage probability, ergodic secrecy rate and non-zero achievable secrecy rate are derived, which can reveal the effect of the number of transmitters and backhaul reliability on the system performance. Furthermore, for the first time the impact of energy harvesting time fraction upon secrecy performances under unreliable backhaul is presented.
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.
In this paper, the secrecy performance of cooperative heterogeneous networks with unreliable backhaul over Nakagami- m fading channels is investigated. To secure the proposed system, a friendly jammer is considered to confuse eavesdroppers. To transmit the signals from the source to the destination, a two-phase transmitter/relay selection scheme is proposed. The best transmitter is selected when the signal-to-noise ratio at the relays is maximized. In the second phase, the best relay is chosen when the jamming signal-to-interference-plus-noise ratio of the eavesdroppers is minimized. To investigate the system performance, closed -form expressions are derived for the secrecy outage probability, ergodic capacity and non-zero achievable secrecy rate. In order to gain an insight into the system, asymptotic analysis is also provided. The results show that the degree of cooperative transmission and backhaul reliability are key parameters in the system and these parameters determine the secrecy performance.
In this paper, the impacts of unreliable backhaul links on the secrecy performance of cooperative single carrier heterogeneous networks in the presence of eavesdroppers are investigated. A two-phase transmitter/relay selection scheme is proposed, where the best transmitter is selected to maximize signal-to-noise ratio at the relays in the first phase and the best relay is chosen in the second phase to minimize the signal-to-interference-plus-noise ratio of the eavesdroppers with the aid of a friendly jammer. Closed-form expressions are derived for the secrecy outage probability, probability of non-zero achievable secrecy rate, and ergodic secrecy rate. The asymptotic performance analysis is furthermore performed to explicitly reveal the impacts of unreliable backhaul links on the secrecy performance. Our results show that the diversity gain cannot be achieved in the presence of imperfect backhaul links.
This paper investigates the secrecy performance of a finite-sized in-band selective relaying system with M transmitters connected via unreliable backhaul links, N decode-and-forward relays, and K collaborative eavesdroppers. To send the source message to the destination, a transmitter-relay pair that achieves the highest end-to-end signal-to-noise ratio is selected for transmissions, while the K eavesdroppers combine all the received signals from the selected transmitter and relay using maximal ratio combining. The proposed model introduces backhaul reliability and eavesdropping probability parameters to investigate practical constraints on the transmitter-relay cooperation and eavesdropper collaboration, respectively. Closed-form expressions are derived for the secrecy outage probability, probability of non-zero achievable secrecy rate, and ergodic secrecy rate for non-identical frequency-selective fading channels with robust cyclic-prefixed single carrier transmissions. These results show that the asymptotic secrecy outage probability and probability of non-zero achievable secrecy rate are exclusively determined by the number of transmitters M and their corresponding set of backhaul reliability levels. Under unreliable backhaul connections, it is found that the secrecy diversity gain is determined by M, N, and the number of multipath components in the frequency selective fading channels. Link-level simulations are conducted to verify the derived impacts of backhaul reliability and collaborative eavesdropping on the secrecy performance.
The use of multiple source nodes with wireless backhaul is considered for secrecy enhancement through source node selection in future wireless networks. The ergodic secrecy rate (ESR) of optimal source node selection in the presence of multiple eavesdroppers over independent non-identically distributed (INID) Rayleigh fading channels is evaluated in closed-form. At high signal-to-noise ratio (SNR), the ESR is expressed as a simple weighted summation where each term relates to the contribution of an individual source and eavesdropper. An asymptotic analysis shows the effect of the system parameters and backhaul reliability on the performance. The proposed method can provide a generalized solution for the ESR of optimal transmit antenna selection in multi-antenna systems, optimal source node selection, and optimal relay selection with or without unreliable backhaul.
This paper investigates the physical layer secrecy performance of radio frequency (RF) energy harvesting (EH) relaying networks based on the combination of time switching-adaptive power splitting (TSAPS) and best relay selection (BRS) schemes. Specifically, the system consists of one source, one destination and multiple energy-constrained decode-and-forward (DF) relays which help the source transmit information to the destination, in the presence of a passive eavesdropper. In this setting, the relays harvest RF energy from the source signal to power their relaying transmission, in which power splitting ratio self-adjustment policy and best relay selection scheme are utilized. To characterize the secrecy performance, the exact closed-form expressions of secrecy outage probability for random relay selection and best relay selection are derived. In addition, the comparison to random relay selection is presented to verify the efficiency in terms of secrecy outage probability of the proposed protocol. Finally, the numerical and simulation results are also provided to evaluate the impact of the key parameters on the secrecy performance and confirm the correctness of our analysis.