# Performance Analysis of a Cognitive RIS-NOMA in Wireless Sensor Network
## 4 Numerical Result and Discussion  
For the analyses in this section, the main parameters are listed in Table 1--\(\Omega_{j}=d_{j}^{\ell}\), in which \(\ell\) denotes the pass loss exponent and BPCU denotes the bit per channel use. In all figures, Sim. and Ana. are the abbreviations of Simulation and Analytical, respectively. For simulation, we apply the Monte Carlo method with a \(10^{6}\) trial to clarify the accuracy of our analysis. Figure 2 plots the outage probability of three users versus \(\eta_{S}\) in dB from varying \(N\). We can see that over the whole range of \(\eta_{S}\), outage probability curves and analytical results accord exceptionally well based on a Monte Carlo simulation. It can be seen that when \(\eta_{S}\) is from \(-20\) to \(0\) dB and the number of reflective elements \(N\) is \(15\), the OP almost reaches \(1\)It leads to the system not being able to operate and presents operational challenges. But when we increase \(\eta_{S}\) as well as \(N\), the OP will be decreased, specifically when \(\eta_{S}\) is larger than 5 dB and \(N=20\). Therefore, in reality, choosing the parameters to configure the system to operate well also plays a very important role. Furthermore, the asymptotic findings produced in (27) and (28) are extremely constrained, with the theoretical analysis at a high \(\eta_{S}\) confirming the accuracy of our developed analysis approach. In addition, observe that outage performance improved when increasing the transmit power but did not change with a high \(\eta_{S}\). The fact that OP depends on more factors than only transmitting \(\eta_{S}\) can be explained. Specifically, we can see in (1) that the transmission power of \(\eta_{S}\) in the SN is limited by \(\eta_{th}\) in the PN. Another observation is that outage performance was better when increasing the number of RIS reflective elements. This is because applying an RIS to a NOMA network offers an additional level of flexibility to improve performance for users. Figure 3 plots the outage probability of three users versus \(\eta_{S}\) in dB when varying \(\eta_{th}\). Observe that the outage performance improved when increasing \(\eta_{th}\). Furthermore, we can see that the outage performance for three users from RIS-NOMA was superior to RIS-OMA. Figures 4 and 5 plot outage probability versus \(\eta_{S}\) in dB when varying the number of primary users \(K\) and when varying interference \(\zeta\), respectively. We can see in Figure 4 that when increasing \(K\), outage performance for secondary users was reduced regardless of the increase in transmit power. Figure 5 shows that when increasing interference, \(\zeta\) outage performance for users was reduced but not significantly. That is because of interference with the secondary network from the source in the primary network. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Number of secondary users & \(M=3\) \\ Number of primary users & \(K=3\) \\ Number of reflective elements & \(N=20\) \\ Power allocation & \(\beta_{1}=0.5\), \(\beta_{2}=0.3\) and \(\beta_{3}=0.2\) \\ Scaling coefficient & \(\zeta=0.01\) \\ Target rate & \(R_{1}=0.6\), \(R_{2}=0.9\), \(R_{3}=1.6\) [BPCU] \\ Maximum interference level & \(\eta_{th}=-10\) [dB] \\ Pass loss exponent & \(\ell=2\) \\  & \(d_{\mathcal{SR}}=d_{\mathcal{SD}}=d_{\mathcal{RU}_{3}}=10\) [m], \(d_{\mathcal{RU}_{1}}=20\) [m], \\ Distance & \(d_{\mathcal{RU}_{2}}=15\) [m], \(d_{\mathcal{S}{\mathcal{U}_{1}}}=30\) [m], \(d_{\mathcal{S}{\mathcal{U}_{2}}}=25\) [m], \\  & and \(d_{\mathcal{S}{\mathcal{U}_{3}}}=20\) [m] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Table of the main parameter. Figure 2: Outage probability versus \(\eta_{S}\) in dB from varying the number of reflective elements. Figure 4: Outage probability versus \(\eta_{S}\) in dB when varying the number of primary users. Figure 5: Outage probability versus \(\eta_{S}\) in dB when varying \(\zeta\). Figure 3: Outage probability versus \(\eta_{S}\) in dB when varying \(\eta_{th}\).