## 5 Performance Evaluation and Simulation Results
### Simulation Results
However, due to the relaxed delay requirements of TT flows in the VPP system, the proposed SPS-RBSP scheme can still meet the transmission requirements of TT flows. The end-to-end delay of TT flows in the SPS-RBSP scheme is  
Figure 4: Comparisons of system resource utilization: (**a**) percentage of reserved RBs is 20%; (**b**) percentage of reserved RBs is 30%; (**c**) percentage of reserved RBs is 40%. Figure 5: Comparisons of average end-to-end delay (event-triggered flows): (**a**) percentage of reserved RBs is 20%; (**b**) percentage of reserved RBs is 30%; (**c**) percentage of reserved RBs is 40%. much smaller than that in the dynamic scheduling scheme. The reason is that some TT flows in SPS-RBSP scheme can be carried by idle reserved resources to reduce the access delay of TT flows. As shown in Table 1, the delay requirement of TT flows in the VPP system is longer compared with that of ET flows. Although TT flows may be pre-empted and delayed by high-priority ET flows, they can still be transmitted within the latency bound in the SPS-RBSP. To sum up, under various traffic loads, the SPS-RBSP algorithm guarantees delay performance. It achieves low delay scheduling for different types of time-critical applications in VPP systems. Comparing Figure 6a-c, when the percentage of reserved resources is only 20%, the delay of TT flows with the SPS-RBSP mechanism is much higher than that of the reserved RBs at 30% and 40%. This is because insufficient reserved RBs lead to there being no idle static resources to share with TT flows. As a result, the TT flows can only be dynamically scheduled, greatly increasing the access delay. Moreover, dynamic scheduling increases the possibility of conflicts between TT flows and other traffic. In addition, increasing the proportion of reserved RBs too much cannot significantly reduce the delay of TT flows. When the percentage of reserved RBs is 30%, SPS-RBSP has the lowest latency. Figure 7 shows the performance tradeoff between the delay and resource utilization of SPS-RBSP under different percentages of the reserved RBs with 600 flows. The resource utilization sharply decreases when the percentage of the reserved RBs exceeds 30%. The delay of TT flows in VPP declines with the percentage of reserved RBs, and it becomes stable when the percentage is larger than 30%. The delay of ET flows in VPP is stable and it is always below 50 ms under different percentages of reserved RBs. This is because non-time-critical traffic cannot use the reserved RBs. More reserved RBs (\(>\)30%) for time-critical traffic may result in a waste of resource. The reservation of RBs can reduce the handshake delay in 5G systems. When the percentage of reserved resources is less than 30%, time-critical traffic cannot be completely carried by the reserved resources. If time-critical traffic is transmitted through the dynamic scheduling method, the access delay is increased. If time-critical traffic waits for reserved resources in the next cycle, the queuing delay is increased. It is suggested that the percentage of reserved RBs should be set as 30% to optimize the performance tradeoff between the delay and resource utilization of SPS-RBSP in the VPP under the simulation parameters. Figure 6: Comparisons of average end-to-end delay (time-triggered flows): (**a**) percentage of reserved RBs is 20%; (**b**) percentage of reserved RBs is 30%; (**c**) percentage of reserved RBs is 40%.