## 5 Results and Discussion
At an SNR of 20 dB, the performance metrics are as follows: NN-FF, OO-EE, SW, RP-1, RP-2, RP-3, and SW-SW yields SSEs of \(\sim\)16.27, \(\sim\)16.47, \(\sim\)16.57, \(\sim\)16.63, \(\sim\)16.78, \(\sim\)16.81, and \(\sim\)16.89 \(\mathrm{bps/Hz}\), respectively. SW-SW pairing offers an SSE improvement ranging from \(\sim\)0.48% to \(\sim\)3.81% compared to other pairing schemes. Figure 14 illustrates the SSE achieved by optimizing power fractions in a SW-SW pairing scheme with \(L=256\). To account for the SIC error and variations in HWD, the SSE values for different PA schemes were evaluated. The optimal power fractions of the SUE and WUE are described in (38) and (39), respectively. Any value between \(\mathcal{A}_{s,p}^{min}\) and \(\mathcal{A}_{s,p}^{max}\) indicates sub-optimal power allocated to the SUE. In our simulations, we assign the average of the minimum and maximum limits of (37), \(\mathcal{A}_{s,p}^{min}\) and \(\mathcal{A}_{s,p}^{max}\), to the SUE, while the remaining power is designated for the WUE. To evaluate the effectiveness of these optimal power fractions, we also use the minimum value from Equation (37) for the SUE, with the leftover power allocated to the WUE. Improvements in the SSE with these optimal power fractions are illustrated in Figures 14 and 15. Simulations indicate that optimal power fractions consistently yield the highest SSE, even under conditions of HWD and SIC errors. This proves the effectiveness of optimal power fractions for maximizing the SSE, even under SIC error and HWDs. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{\(\mathbf{L}\)} & \multicolumn{3}{c}{**SNR (dB) Required to Reach a Throughput of 1 bps/Hz**} \\  & \(\mathbf{d=0.08}\) & \(\mathbf{d=0.09}\) & \(\mathbf{d=0.15}\) \\ \hline
32 & \(\sim\)\(-  
The impact of PA strategies in SSE under an SIC error of 0.01 and varying HWD is summarized in Table 8. The optimal PA produces maximum SSE compared to other PA schemes. The power fraction is the only adjustable parameter that can be optimized to maximize SSE without triggering an outage. Both the pieces of paired UE can meet their minimum QoS requirements by optimizing the power fraction while maximizing the overall system's SSE. Using sub-optimal PA, the SUE always allocated power less than the optimal PA power allotted. This indicates a degradation in performance. However, for applications that compromise performance for complexity, sub-optimal PA strategies may be considered. The minimum limit of PA used in the system evaluates the performance and significance of PA schemes. This minimum limit provides the least PA values, resulting  
Figure 14: SSE of SW-SW pairing scheme with various PA strategies considering \(\epsilon=0.01\) and varying HWD conditions. Figure 13: SSE comparison of varying pairing schemes. in the smallest power fraction for the SUE while allocating the remaining to the WUE. Consequently, the SUE's QoS requirement is not fulfilled. This infers that the optimal PA maximizes the SSE by fulfilling the QoS requirements of individual pieces of UE in the proposed IOS-aided C-HNOMA system. In Figure 15, the SSE for optimal, sub-optimal, and minimum limits is compared by varying the parameter \(L\) and introducing a 1% SIC error, along with an HWD of \(d\) = 0.08. As \(L\) increases, the SSE improves across all PA schemes. Table 9 shows the impact of optimal power values on SSE for different values of \(L\) at an SNR of 15 dB. The table clearly shows that the influence of optimal PA results in maximum SSE for larger values of \(L\). For smaller values of \(L\), the effect of optimal PA compared to other PA schemes is less pronounced. However, as \(L\) increases, optimal PA leads to a significant improvement in SSE over other PA schemes. This indicates that the optimal power fraction is ideal for achieving maximum SSE, while the sub-optimal fraction is more suitable for less complex systems. The choice between optimal and sub-optimal values reflects a trade-off between system complexity and performance.