## 5 Simulation and Experiment
### Simulation Results and Analysis  
With the 24 bits/s generating rate of each node, the calculated throughput of link subnet_3_0-subnet_2_0 is 168 bits/s. The throughput of link subnet_2_0-subnet_1_0, including the data of subnet 3 and subnet 2, is 336 bits/s. The throughput of link subnet_1_0-subnet_0, which includes the data of all the 21 nodes, is 504 bits/s. The throughput simulation results of links subnet_3_0-subnet_2_0, subnet_2_0-subnet_1_0 and subnet_1_0-subnet_0 are shown in Figure 12a. The figure shows that the throughput simulation results of every link are identical to the theoretical calculations. According to Equation (2), the calculated transmission delay of each link is 0.07 s, 0.14 s, and 0.21 s. The simulation results of the data transmission delay between each link are shown in Figure 12b. The delay simulation results are also identical to the theoretical calculation. The simulation results indicate that with a throughput and transmission delay, the networking structure can guarantee QoS in power line communication.  
According to the simulation model shown in Figure 11, the parameters of Equations (6), (11), (15), and (20) are \(n=3\), \(j=7\), \(k=7\) and \(l=7\), and the corresponding delays are \(t_{d3}=1.55\) s, \(t_{d3}=5.15\) s, \(T_{dAll}=3.63\) s, and \(T_{dAll}=14.43\) s. The simulation result of the delay in the transmission of data from node subnet_3_2 to the BS is shown in Figure 13a. It shows that the delay is between 1.55 s and 1.56 s; this result corresponds with the theoretical calculation. In the simulation model, we select that subnet_3_2 cannot communicate with subnet_3_0, which is the central node of subnet 3. The rerouting algorithm is used, and subnet_3_3 is the relay. The simulation result of the delay in the transmission of  
Figure 11: Simulation model.  
Figure 12: Simulation results of links between centre nodes. (**a**) Throughput between central nodes; (**b**) Delay between central nodes.  
data from node subnet_3_2 to the BS is shown in Figure 13b. The delay is between 5.14 s and 5.16 s; this result corresponds with the theoretical calculations. The simulation result of the delay in the transmission of data from all the nodes to the BS is shown in Figure 13c. The delay is between 3.62 s and 3.63 s; this result is consistent with the theoretical calculations. The simulation result of the delay in the transmission of data from all the nodes to the BS when subnet_1_2, subnet_2_2 and subnet_3_2 have bad nodes and they select adjacent nodes as a relay is shown in Figure 13d. The result is consistent with the theoretical calculations. The simulation results shown in Figure 13 demonstrate the accuracy of the delay theoretical calculation previously mentioned. The simulation also shows that although the rerouting algorithm is time consuming, it increases the data collection success rate of the BS, guarantees QoS in power line communication, improves the reliability of the system and is practical.  
Figure 14a shows a comparison of the simulation results related to channel conflict between ACRA and CSP. Vertical lines represent the occurrence of channel conflict at a specific time. The figure shows that within the simulation time, conflict caused by ACRA (blue line) is far less than that caused by CSP (green line). ACRA divides the whole large network into several small networks, in which the nodes of each network send messages to a central node within a certain time. This process reduces the nodes in the channel at any one moment, which considerably reduces the conflict and improves the channel utilisation, as shown in Figure 14b.  
Figure 13: Simulation results of delay. (**a**) Simulation results of \(t_{d3}\); (**b**) Simulation results of \(t_{d3}\); (**c**) Simulation results of \(T_{dALL}\); (**d**) Simulation results of \(T_{dALL}\).