Hybrid TSR-PSR in nonlinear EH half duplex network: system performance analysis

ABSTRACT


INTRODUCTION
Nowadays, harvesting energy (EH) from green environmental sources and converting this energy into the electrical energy used in purpose to supply the communication network devices is considered the main research direction. Furthermore, this solution can provide not only the environmentally friendly energy supplies, but also the self-maintained, long-lived, and autonomous communication systems. In the series of the leading environmental green energy sources, such as solar, wind, geothermal, and mechanical, the radio frequency (RF) signals can be considered as the prospective energy source in the future. [1][2][3][4][5][6][7][8][9]. Wireless nodes can harvest RF energy either in the time domain before data reception, or in the power domain by dividing the received RF signals for the EH and information decoding (ID) [9][10][11][12]. In a cooperative network, authors in [13][14][15][16] developed two new relaying protocols based on the receiver structures adopted at R, termed time switching-based relaying (TSR) and power splitting-based relaying (PSR). From [14][15][16], the TSR and PSR protocols have some drawbacks; for instance, TSR has to lose some information while it switches to the harvesting mode and PSR has a low coverage area. In another way, PSR requires a complicated hardware structure to make sure that a proper portion of energy from the source signal is extracted for energy harvesting. In contrast, TSR can simplify the hardware at the expense of the throughput or achievable rate of the system. Based on the fact that both TSR and PSR protocols have their drawbacks, the prospective idea is to combine these two protocols to get the best out of them. This is a solution that can obtain in this paper by using an adaptive relaying protocol [17][18]. In this research, we investigate the hybrid TDR-PSR Nonlinear Energy Harvesting (EH) Halfduplex (HD) Relaying network in terms of the Success Probability (SP). For this purpose, we derive the integral form of the SP in connection with all primary system parameters. Also, we use the Monte Carlo simulation for verifying the correctness of the analytical expression. We can focus on the main contributions as the follows a. The hybrid TDR-PSR Nonlinear EH HD Relaying network is proposed and investigated. b. The integral-form expressions of the system SP are derived. c. The correctness of the analytical expressions are verified by the Monte Carlo simulation.

SYSTEM MODEL
In this paper, the hybrid TDR-PSR Nonlinear EH HD Relaying network is illustrated in Figure 1. In this model, the information is transferred from the source (S) to the multi-destination (Di), through relay node (R). The energy harvesting (EH) and information transmission (IT) of the system model are proposed in Figure 2. As shown in Figure 2, T is the block time. In the first interval time (αT), the relay node R harvests energy ρPs and receives the information (1-ρ)Ps from the source signal, where α is the time switching factor α ∈ (0, 1) and ρ is the power splitting factor ρ ∈ (0, 1). In the remaining interval time (1-α) T, the relay node R transfers information to the destination node D [12][13][14][15][16].

Energy harvesting (EH) phase
In this phase, the received signal at the relay R can be given as Where s x is the energy symbol and must be satisfied   Ps is the transmit power of the source. nr is the additive white Gaussian noise (AWGN) at the relay node with variance N0.
hSR is channel gain between S-R link and belongs to Rayleigh channel.
In this paper, the nonlinear transformation model proposed in reference [19] is used. The transmission power at the relay can be given as 22

Information transmission (IT) phase
The received signal at the relay R in the first time slot can be calculated as In the second time slot, after receiving the signal from the source R, the relay amplifíes with  factor as following The received signal at the destination D can be formulated as Where r x is the transmission signal at relay and must be satisfied   The end to end signal to noise ratio can be computed as ( Where th  is the threshold of the system.  (11) Here, considering that Where rd  is the mean value of the random variable (RV) 2 Now, we will find P2 from (9) as the following 2 () Substituting (15)

NUMERICAL RESULTS AND DISCUSSION
In this section, the Monte Carlo simulation is used for validating the analytical expression in the above section [20][21][22][23][24][25]. Figure 3 shows the SC versus time switching factor α with the main system parameters as η=0.4, 0.85; ψ=Pth= 5 dB; ρ=0.5 and γth=0.25. From Figure 3 we can state that the SP of the system network has a massive increase while time switching factor α varies from 0 to 0.9, and the simulation and analytical values are the same. Moreover, the effect of energy efficiency η on the system SP. Here, we set α=0.5; ρ=0.5 and γth=0.25. Similarity as Figure 4, the system SP increases significantly with the rising of energy efficiency η, and the analytical results agree with the simulation values. Furthermore, the influence of Pth and ψ on the system SP are drawn in Figures 5 and 6, respectively. From the results, we can see that the system SP increases considerably with the rising of Pth and ψ. In addition, the system SP versus the power splitting factor ρ is presented in Figure 7. From Figure 7, we can see that the system SP has a considerable increase in the first interval of ρ and the has a decease. The optimal value of the system SP can be obtained with the values of ρ from 0.5 to 0.6. In all Figures 5-7, the simulation values match well with the analytical values for verifying the correctness of the analytical expressions.

CONCLUSION
In this research, we investigate the hybrid TDR-PSR Nonlinear Energy EH HD Relaying network in terms of the SP. Firstly, we derive the integral form of the SP in connection with all primary system parameters. In addition, we use the Monte Carlo simulation for verifying the correctness of the analytical expression. From the research results, we can state that all the simulation and analytical values are the same in connection with all primary system parameters.