## 5 Experimental Results and Analysis
### Simulation Results  
#### 5.2.1 Dopra Performance Analysis  
It is assumed that six UNs are deployed in a square area of 10 m \(\times\) 10 m, as shown in Figure 5. In Figure 5, the triangle in the center represents the AP, and the red dots represent the UNs. Here, \(P_{0}=30\) dBm, and \(\alpha=3\). Figure 5 shows the results for the data forwarding paths obtained with and without the cooperation of the UNs. The number on the straight line indicates the proportion of each UN's data that is forwarded to its relay UNs. For example, the proportions of UNI's data forwarded to AP, UN0, and UN2 are 0.113, 0.874, and 0.003, respectively. The weight value is calculated based on the DOPA. In the non-cooperative transmission method, each weight is 1, indicating direct transmission to the AP. As shown in Figure 5a, the proposed method effectively balances the relationship between the transmitted information and the energy consumption. Since UN0 and UN2 are closer to the AP, they exhibit better channel quality and can harvest more energy. Therefore, UN1 and UN3 forward their information through UN0 and UN2, respectively. Since UN4 is farther from the AP, part of its data is forwarded by UN5, while the rest is transmitted directly to the AP. Figure 5b does not consider cooperative transmission. The tasks offloaded by UN 1, UN 3, and UN 4 need to be transmitted to the AP over a long distance, which causes significant signal attenuation. The data offloading path for UN 1, UN 3, and UN 4 is not optimized, which increases the latency. The long delays for UN 1, UN 3, and UN 4 have become the bottleneck of delay optimization. The data transmission delay for \"far\" UNs can be optimized through UN cooperation. The delays in Figure 5a,b are CT-t = 0.3046, CT-t = 0.7031, DT-t0 = 0.3046, and DT-t = 0.7392, respectively. Compared with the non-cooperation method, the DOPA can effectively reduce the data offloading delay while maintaining the same harvest energy time. Figure 6 illustrates the delay variation for different AP transmission power values using \(\alpha=3\) and \(N=6\). The results show that the delay of the proposed DOPA is lower compared to that of the non-cooperative method. When \(P_{0}\) is very small, the delay of both the non-cooperative method and the DOPA are similar because UNs harvest less energy, resulting in minimal data being forwarded by the relay UNs. As \(P_{0}\) increases, the UNs can use the energy harvested to forward more information. Consequently, the delay gap between the DOPA and the non-cooperative method gradually increases. As AP transmission power \(P_{0}\) continues to rise, the DOPA allows the UNs to offload more data with enhanced energy channel gains, thereby improving the overall delay performance of the system. Figure 5: Routing results for two methods: (**a**) with cooperation of UNs and (**b**) without cooperation of UNs. Figure 7 shows the delay under different path attenuation coefficients with \(P_{0}~{}=~{}30\) dBm. As the path attenuation coefficient decreases, the gap in the delay between the DOPA and non-cooperative method increases. Lower path attenuation improves the channel quality for both energy and information transmission. With better channel quality, the DOPA can utilize more of the available energy, leading to a greater reduction in delay compared to that of the non-cooperative method. As the path attenuation coefficient increases, the delay performance of both decreases. This occurs because as the channel quality deteriorates, the UNs are unable to harvest sufficient energy to both receive and forward information effectively. With reduced energy harvesting, the UNs can only sustain the transmission of their own information and are unable to effectively participate in cooperative data forwarding. Changes in the delay are observed for different numbers of UNs. As shown in Figure 8, both the DOPA and non-cooperative method exhibit increases in energy harvesting time and system delays when there is a higher number of UNs.