# UAV-Assisted Caching Strategy Based on Content Cache Pricing in Vehicular Networks
## 5 Analysis of Simulation Results
This is because, as the Zipf distribution parameter increases, the requests of vehicle users become more and more concentrated on the content with high popularity, so the cache hit rate increases, the request latency of vehicles becomes smaller, and the success rate of vehicles to successfully obtain the content becomes larger. As the cache hit rate increases, the benefit and total utility of NO increases. From Figure 7a, the average delay decreases as the Zipf distribution parameter increases when the total number of contents is constant. This is because, as the Zipf distribution parameter increases, the request rate of vehicle users for content with low popularity decreases, which will lead to a lower degree of demand for these contents by NO, so the content rental price decreases and the total utility of CP decreases accordingly. Figure 8 gives the relationship between the performance of this paper's strategy and the vehicle speed for different total number of contents. From Figure 8a-d, it can be seen that the average delay decreases with the increase in vehicle speed, the benefit and total utility of NO increases with the increase in vehicle speed, and the total benefit of CP  
Figure 7: Performance versus Zipf distribution parameters. (**a**) Relationship between the total utility of CP and the Zipf distribution parameter; (**b**) relationship between the total utility of NO and the Zipf distribution parameter; (**c**) relationship between the benefit of NO and the Zipf distribution parameter; (**d**) relationship between the average delay and the Zipf distribution parameter. decreases with the increase in vehicle speed. This is because, as vehicle speed increases, the time vehicle users spend traveling on the roadway becomes shorter, the maximum waiting delay becomes shorter, and the average delay decreases. As the vehicle travel speed increases, the contact time between the vehicle and each cache node decreases, and the success rate of content delivery decreases, so the degree of demand for content by NO decreases and the content rental price decreases, resulting in a decrease in the total utility of CP and an increase in the benefits and total utility of NO. Figure 9 gives the relationship between the performance of this paper's strategy and the communication radius of RSU for different total number of contents. From Figure 9a-d, it can be seen that the average delay, the benefit, and the total utility of NO decreases with the increase in the communication radius of RSU and the total benefit of CP increases with the increase in the communication radius of RSU. This is because, as the communication radius of the RSU increases, the success rate of the vehicle user in obtaining content from the RSU increases; then, the average request delay of the vehicle user decreases. At the same time, the demand of NO for content becomes larger and the content rental price increases; then, the total utility of CP increases and the benefit of NO decreases. The total utility of NO is determined by both the delay and the benefit of NO and, combined, it decreases slightly with the increase in RSU communication radius. Figure 8: Performance versus vehicle speed. (**a**) Relationship between the total utility of CP and the vehicle speed; (**b**) relationship between the total utility of NO and the vehicle speed; (**c**) relationship between the benefit of NO and the vehicle speed; (**d**) relationship between the average delay and the vehicle speed.