## 4 Simulation Results, Theoretical Calculation, and Analysis  
### Performance Comparison under Different Transmission Schemes  
Unless otherwise specified, the relevant parameters of the simulation model are shown in Table 2. In addition, in order to complete the experiment successfully, we made the following assumptions:  
* \(N_{\text{U}}\) pieces of UE are randomly distributed within the region from 0 to \(R\). * \(N_{\text{C}}\) cooperation nodes are evenly distributed around R/2. * There is no interference between any two devices. Under these conditions, in order to compare the latency performance of AUA under different \(\alpha\) and \(\beta\) values compared with general relay, we set \(\alpha=\beta=2\) dB, 3 dB, 4 dB, and 6 dB. The cumulative distribution function (CDF) of the SNR between the UE and BS is shown in Figure 3. It can be noticed that the SNR between the UE and BS at 90% was below 6.2 dB. In order to test the effectiveness of AUA, we set the SNR threshold higher to obtain better performance when there were more transmissions. Furthermore, we assumed that the path loss calculation for the UE located between 0 and \(R/100\) was identical to the path loss calculation for the UE situated at \(R/100\). This assumption implies that there is no variation in the path loss experienced by the UE within the first 1% of the total radius compared with the UE precisely located at \(R/100\). In other words, the propagation characteristics, such as the signal attenuation and interference levels, remained consistent within this specific range. \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline Cell radius (\(R\)) & 1000 m \\ Cooperation node number (\(N_{\text{C}}\)) & 32 \\ UE number (\(N_{\text{U}}\)) & 10,000 \\ Distance between cooperation node and BS (\(r\)) & \(R/2\) \\ SNR threshold (\(\gamma_{\text{th}}\)) & 18 dB \\ Transmit power (\(P_{\text{t}}\)) & 3.2 mW \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation settings. Figure 2: The flowcharts. (**a**) UE aggregation. (**b**) Adaptive UE aggregation. Our first concern was the latency problem of the whole system, which is the overall transmission number of the whole system. In comparison with a general relay configuration, we computed the latency performance gains for Case 2 with the combination, multi-path transmission, and AUA schemes. Figure 4 displays the gains of different schemes when the cooperation nodes were located at \(R/3\), \(R/2\), and \(2R/3\). As shown in Figure 4b, it is certain that the latency performance of Case 2 with the combination scheme is the lower bound, which is the same as the AUA scheme when \(\alpha=\beta=0\) dB. The performance of the multi-path transmission scheme is the upper bound, which is the same as the AUA scheme when \(\alpha=\beta=\infty\). Actually, the gain of the AUA scheme when \(\alpha=\beta=6\) dB was almost the same as that of the multi-path transmission scheme. In addition, the number of transmissions from the cooperation node to the BS had a great influence on the gain value. Whenever the number of transmissions from the cooperation node to the BS increased, the gain value under \(\gamma_{\text{th}}\) would suddenly drop and then return to the normal level. However, when analyzed with Figure 4a,c, the values of \(\alpha\) and \(\beta\) for reaching the maximum performance gradually decreased as the distance between the cooperation node and the BS increased. Moreover, the CDF of the latency enhancement gain under different \(\alpha\) and \(\beta\) values is shown in Figure 5:  
Figure 4: The gain of latency performance vs. \(\gamma_{\text{th}}\) under different schemes (\(M=1\)). (**a**) Cooperation node location: R/3. (**b**) Cooperation node location: R/2. (**c**) Cooperation node location: \(2R/3\). Figure 3: CDF of SNR between UE and BS.