## 4 Simulation Experiments and Result Analysis
### Analysis of Simulation Experiments
#### 4.2.2 High-Speed Mobile Scenario
In addition, the ICCDRL algorithm introduces a congestion sensitivity factor \(\lambda_{ODL}\), which is used to compare the weights of the QoS parameters and the values of the threshold features to determine whether they meet the service criteria and the minimum overhead for normal network operation. ICCDRL can therefore quickly reach the maximum bandwidth and stabilize at the switching gap point by properly adjusting the size of the congestion window. In this way, frequent sharp drops in the congestion window and resulting throughput reductions can be avoided effectively. The results show that the conventional TCP algorithm cannot adapt to the characteristics of vehicular communication. On the contrary, ICCDRL has better performance with smoother throughput after a certain amount of learning and can fully utilize the network bandwidth for data transmission. (4) Comparison of RTT  
RTT represents the time it takes for a packet to be sent until an acknowledgement is received, and it directly reflects the current state of network latency. The comparison graph in RTT is shown in Figure 11. Generally, the RTT of ICCDRL and DRL-based DCC algorithms increases compared to the other three algorithms due to the fact that ICCDRL and DRL-based DCC algorithms are more aggressive, trying to utilize all available bandwidth and sending too many packets into the link, which causes network congestion and leads to an increase in RTT eventually. In addition, the ICCDRL algorithm has a smaller RTT than the DRL-based DCC algorithm because it introduces a congestion-sensitive factor to differentiate the service data weights. Moreover, the increase of RTT in ICCDRL is not significant compared with the other three algorithms. Figure 10: Comparison of throughput. From another perspective, this also reflects that the use of intelligent congestion control based on DRL has a significant impact on the transmission performance of vehicle communication. (5) Comparison of Packet Loss  
The packet loss rate during the node sending data is shown in Figure 12. It can be seen from Figure 12 that the packet loss rate of all five algorithms is close to 0.01%, which is consistent with the ns-3 parameter setting; the packet loss rate of ICCDRL is 0.124%, which is slightly higher than the other three traditional algorithms and lower than the DRL-based DCC. This is because ICCDRL sends the most packets, and some packets are dropped because the link node cache is full, which results in packet loss. (6) Evaluation of Fairness and Friendliness  
This section tests ICCDRL's good fairness and friendliness through simulation experiments. When multiple data flows compete for a bottleneck link, ICCDRL is tested for its ability to allocate bandwidth fairly. In the simulation experiment, 10 long-life FTP flows and 20 short-life FTP flows were created and tested. Each test sends data simultaneously and randomly samples 4 flows and counts the throughput of each flow. The comparison of the fairness of ICCDRL at different wireless BERs is given in Figure 13.  
Figure 11: Comparison of RTT. Figure 7:0 Comparison of Packet Loss. As can be seen from Figure 13, the throughput of each data flow is basically in the range of 0.02-0.04 Mbps, with little difference when using ICCDRL in cases of low and high BER, and each data flow can basically allocate bandwidth fairly, showing that ICCDRL has good fairness. Randomly sampled data flows get different shares of bandwidth, which is due to the ICCDRL algorithm setting congestion sensitivity factors and QoS weights to distinguish the importance of different services, so that the congestion window changes more smoothly and is not too aggressive.