## 4 Performance Evaluation
### Result Analysis of RMF-MVS  
The performance of RMF-MVS scheme is assessed in terms of PSNR, SSIM index, which are Quality of Experience (QoE) measure and E2 ED, which is sometimes considered as Quality of Service (QoS) metric based on different densities of vehicles and different data rates of the video streaming. The proposed scheme is benchmarked against MSLND and 3 MRP schemes. In Figure 6a, the PSNR of the video data based on different vehicle densities has been depicted. In the simulation, it is observed that the PSNR of the video increases as the number of vehicles increases, although with a small fluctuation in the increase and decrease. The PSNR of the video data starts to drop when the vehicle number is above 300. The PSNR relatively drops, but the video data still maintains reasonable value above the average value of the PSNR that is 20 dB for the various densities considered. The increase in PSNR despite the high vehicle density might be connected to the road-based multiple metrics considered. Since, the metrics employed utilizes the vehicle advancement, road density and hello message receive rate of the NFV for video transmission. In addition, the high PSNR might be due to the presence of ample amount of vehicles that are available for video forwarding. Both the 3 MRP and MSLND have lower video quality compared to the proposed RMF-MVS. Thus, RMF-MVS outperformed the two baseline schemes mentioned previously. The average percentage of video PSNR attained by 3 MRP, MSLND and RMF-MVS are 68.4%, 44.1% and 72.7%, respectively. The following are the performance improvement on PSNR of the video data delivered by RMF-MVS with 50-500 \begin{table}
\begin{tabular}{l l} \hline
**Parameters** & **Values** \\ \hline Urban simulation area & \(1000\times 1000\) m\({}^{2}\) \\ Simulation time & 600 s \\ Vehicle speed & 2.78 to 13.89 m/s (10 to 50 km/h) \\ Number of vehicles & 50 to 500 \\ MAC protocol & IEEE 802.11p \\ Video resolution & \(352\times 288\) \\ Video play duration & 139 s \\ Transmission range & 250 m \\ Frequency Bandwidth & 5.9 GHz \\ Propagation model & Shadowing \\ Antenna model & Omni-directional \\ Traffic type & Constant Bit Rate \\ Channel type & Wireless \\ Transmission Protocol & UDP \\ Hello packet timeout & 1 s \\ Scenarios & High-density urban scenario \\ Comparison protocol & MSLND, 3 MRP and 3 MRP + DSW \\ Metrics & PSNR, SSIM index, PLR and E2 ED \\ \hline \end{tabular}
\end{table} 
Table 1: Simulation Parameter. vehicles against the two baseline schemes as 4.3% and 28.6%; that is, RMF-MVS outperforms 3 MRP with 4.3% and MSLND with 28.6%. In Figure 6b, the PSNR is studied alongside the various transmitted video data rate. The result depicts that the PSNR of the video is higher when the transmitted video size is small. However, a large amount of video transmitted also achieves relatively good PSNR. The video quality, which is indicated by the PSNR value decreases as the transmitted video size increases. The result shows that RMF-MVS outperforms the 3 MRP and MSLND. The average percentage gains of the three schemes are 66.7%, 48.4% and 70.1% for 3 MRP, MSLND and RMF-MVS, respectively. The percentage of performance improvement of RMF-MVS against 3 MRP and MSLND are 3.4% and 21.7%, respectively. Figure 7a depicts the structural similarity index of the video data in relation to different vehicle densities. Considering the results, the structural quality increases with fluctuation as the number of vehicles increases. The highest SSIM index was observed when the density of vehicles is 300. However, there is a little drop in SSIM index as the number of vehicles increases above 300. Despite the drop in SSIM index, the result is still significant because it is above the average value of the SSIM index value. The high SSIM index observed at the initial stage when the number of vehicles is 50-300 might be connected to the reason that the vehicle trajectory is considered when selecting the NFV by also considering the probability of vehicle stoppage.