## 5 Performance Evaluation
### Performance Evaluation of the Buffer-Based ABR Technique Using Predicted Network Bandwidth Values
As demonstrated in Figure 14, the MOS of pedestrian scenarios 1, 2, and 7 outperforms BBA owing to accurate bandwidth prediction and the selection of appropriate video rate chunks. Consequently, the proposed scheme provides a higher QoE than BBA. Table 2 presents detailed performance indicators for scenario 2, in which the performance differences between the two methods were the most pronounced. The average video qualities were similar, with the proposed method at 2624 KB and BBA at 2615 KB. However, the proposed method yielded 22 video quality changes, approximately 26% fewer than BBA's 30 changes, and had only 15 rebuffering events, which is less than half of BBA's total. Figures 15 and 16 display the selected video quality and buffer occupancy, respectively, in response to network bandwidth changes in pedestrian scenario 2. The blue curve represents BBA, the orange curve represents the proposed technique, and the red curve represents the network bandwidth. Initially, as the network bandwidth was stable, video quality and buffer occupancy increased simultaneously. Although the network bandwidth began to decrease after approximately 100 s, the video quality remained stable because the videos were buffered. BBA began to reduce video quality at approximately 500 s, causing buffer occupancy to drop to zero temporarily. By contrast, the proposed technique managed to prevent rebuffering by lowering video quality starting at approximately 450 s.  
Figure 17 presents the MOS measurement results for each scenario when traveling by bus. The proposed technique achieved an average MOS of 76, which is approximately 5% better than the BBA's average MOS of 72. The standard deviation of the proposed method is approximately 9, and that of the BBA is approximately 10, which means that the stabilities of both schemes are similar. Although the MOS values for both techniques were similar in most of the scenarios, the proposed technique delivered a superior QoE in scenario 7. As detailed in Table 3, the average video quality selected by both techniques was comparable, but the proposed technique resulted in fewer video quality changes. The number of rebuffering events was two for the proposed technique, compared with 12 for BBA. This reduction in rebuffering contributed to the higher MOS of the proposed technique. Changes in the network environment while traveling by bus were more significant than those while walking, with the network bandwidth often converging to zero over a longer duration. Figures 18 and 19 present the selected video quality and buffer occupancy in response to network bandwidth changes in bus scenario 7. The network bandwidth approached 0 between 350 and 400 s. BBA gradually reduced the video quality to keep the buffer occupancy low for a period. In contrast, the proposed technique reduced video quality more quickly, leading to a faster increase in buffer occupancy. By swiftly responding to decreases in network bandwidth and selecting the lowest video quality as soon as a drop is detected, the proposed technique effectively minimizes rebuffering. Figure 16: Comparison of buffer occupancies in pedestrian scenario 2. Figure 15: Comparison of video quality in pedestrian scenario 2. Figure 19: Comparison of buffer occupancy in bus scenario 7. Figure 17: Comparison of mean opinion scores in bus scenarios. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Proposed Technique** & **BBA** \\ \hline Average video quality & 4060 KB & 4066 KB \\ Number of video quality changes & 16 & 20 \\ Number of rebufferings & 2 & 12 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of the proposed scheme and the buffer-based adaptive bitrate algorithm (BBA) in bus scenarios. Figure 18: Comparison of video quality in bus scenario 7. Finally, the QoE was measured in the train scenario. Figure 20 presents the MOS measurement results for each train travel scenario. The proposed technique achieved an average MOS of 65, which is significantly greater than the BBA algorithm's average MOS of 45.