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This paper investigates the decode-and-forward (DF) full-duplex (FD) relaying system under the presence of an eavesdropper. Moreover, the relay node is able to harvest energy from a transmitter, and then it uses the harvested energy for conveying information to the receiver. Besides, both two-hop and direct relaying links are taking into consideration. In the mathematical analysis, we derived the exact expressions for intercept probability and outage probability (OP) by applying maximal ratio combining (MRC) and selection combining (SC) techniques at the receiver. Next, the Monte Carlo simulation is performed to validate the mathematical analysis. The results show that the simulation curves match the mathematic expressions, which confirms the analysis section.

Radio frequency- (RF-) enabled wireless power transfer (WPT) has recently become a promising technique to overcome the energy limitation for wireless communication networks [

In this paper, we consider a new system model to investigate the trade-off between physical layer security (PLS) and reliability for an energy-constrained FD relaying network. Further, the direct link between transmitter and receiver is taken into account to improve the total network performance. Moreover, the maximal ratio combining (MRC) and selection combining (SC) protocols are exploited at the eavesdropper and destination to enhance their received rate. The research contributions are summarized as follows:

We present an FD- and SWIPT-assisted relaying network in decode-and-forward (DF) under the presence of a direct link. Particularly, an eavesdropper is able to overhear the information transmission from source to destination via a relay. Moreover, an FD-enabled relay node is able to get energy from a transmitter and use it to transfer signals to the a receiver. Notably, the relay node can simultaneously receive information from the source and transmit it to the destination using the FD technique.

We derive closed-form expressions of intercept probability (IP) at the eavesdropper E and outage probability (OP) at the destination D in maximal ratio combining (MRC) and selection combining (SC) techniques.

The correctness of the developed analysis is validated through the Monte Carlo simulation. On one hand, we investigate the security perspective in terms of intercept probability. On the other hand, system reliability is also studied through outage probability. Consequently, a trade-off between IP and OP can provide many insightful and useful perspectives for system designers.

In Figure

System model.

IT and EH processes.

We assume that the channel between two users follows block Rayleigh fading, where channel coefficients are unchanged during a time frame and change independently across time frames. Moreover, let us denote

The received signal at the relay can be expressed as_{0}.

At the first phase, the harvested energy at the relay can be computed by

From (

Next, in the second phase, the eavesdropper E may intercept signals from both relay R and source S. Nevertheless, source S also generates artificial noise _{0}.

Since we adopt the decode-and-forward (DF) protocol, the signal to interference noise ratios (SINR) at the eavesdropper in the second phase from (

As mentioned in the above discussion, the destination D can cancel the artificial noise from source S. Consequently, the received signal at the destination from relay R and source S during the second phase can be expressed as_{0}.

Destination D will be intercepted if E can successfully wiretap signal; that is,

Therefore, the IP of the system can be expressed as

In this case, the end-to-end SNR at E from (

Then, the IP in (

In order to find the probability in (

By applying (Eq. 3.324.1, [

Next, the CDF of Y can be formulated as

The PDF of Y is given by

Applying (

In this case, the end-to-end SNR at E can be given by

Then, the IP can be expressed as

By applying (

The OP can be defined by

From (

From (

Equivalently, we can represent the end-to-end SINR of the relay path by

By using MRC technique, the received SINR at destination can be given as

The OP, in this case, can be expressed by

From (

Substituting (

By substituting (

Similar to MRC technique as mentioned above, the overall SNR at D can be given by

Hence, the OP can be calculated as

Finally, substituting (

The simulation results are given to validate the performance, that is, IP and OP, of our proposed schemes under maximal ratio combining (MRC) and selection combining (SC) techniques. The results are obtained by averaging 10^{5} Rayleigh channels [

In Figures

IP versus

OP versus

Figures

IP versus

OP versus

In Figures

IP versus R (bps/Hz).

OP versus R (bps/Hz).

In Figures

IP versus

OP versus

This paper investigated the decode-and-forward (DF) full-duplex (FD) relaying networks under the presence of a direct link. Specifically, the relay node can harvest energy from the source and use it to transmit information to the destination. By considering the above discussions, we derive the closed-form expressions of the intercept probability (IP) and the outage probability (OP) in both maximal ratio combining (MRC) and selection combining (SC) techniques at the receiver. Besides, the simulation results show the exactness of the mathematical results compared to simulation ones. Besides, the IP and OP of the MRC technique obtain better performance in comparison to those of the SC technique. In particular, the system security is improved significantly when the time splitting factor value is small. We can extend this work to the case where the source and eavesdropper are equipped with multiple antennas.

No data were used in this paper. The authors just proposed the system and simulated it by MATLAB.

The authors declare that they have no conflicts of interest.

Phu Tran Tin (

This research was supported by the Industrial University of Ho Chi Minh City (IUH), Vietnam, under Grant no. 72/HD-DHCN.