# An Accurate Platform for Investigating TCP Performance in Wi-Fi Networks
## 4 Evaluation
### Comparison to the Actual Network and CCAs  
Figures 4 and 5 show the throughput and RTT results in the actual Wi-Fi network and the Mininet-WiFi emulator in the one-client scenario. In these figures, we present bar plots of the average values, with each CCA on the x-axis. Moreover, the error bars show the maximum and minimum on the y-axis. First, we compare the throughputs in Figure 4a,b, which show the values in the emulated and actual networks, respectively. The throughput values of all 14 CCAs in the two networks are similar with the two queue size settings. This means that the 10 Mbps bottleneck bandwidth is fully occupied in all cases. Second, we compare the RTT values in the two networks, as shown in Figure 5a,b. In the case of the 20-packet queue, most of the RTT values with the same CCA are comparable. However, in the 100-packet queue case, there are several exceeded values. To compare the values collected in the two environments, we use a qualitative metric that is the ratio of the emulated value and the actual one. We have calculated the ratio values for average throughput (Tx) and RTT with two queue sizes and shown them in Table 4. Regarding the throughput, most of the Tx ratio values are close to 1. Moreover, a similar observation can be seen with the RTT ratios, with few exceptions, due to the bufferploat, as presented below. In the two-client scenario, we kept all the simulation settings similar to the previous scenario. Moreover, we let the two clients simultaneously start our scripts at the same time. It is trivial to keep the simultaneity in the emulated environment. However, we may not have the same level of perfectness in the actual network due to the possibility of human operation. The comparative results for throughput and RTT are shown in Figures 6 and 7, respectively. Regarding the throughput comparison, we calculate the total throughput achieved by two clients in the different CCAs and conditions of queue sizes. Figure 6a shows that in the emulated environment, similar to the one-client scenario, the two clients can occupy all the bandwidth limited by the bottleneck link. Moreover, all CCAs achieve similar and stable values of total throughput. On the other hand, Figure 6b shows a slight difference between the reported throughput values. That may cause by uncontrolled factors in the actual environment, such as neighboring interference or human errors. However, we can see that the throughput performance values in the two networks are comparable. Regarding the RTT values, we use the cumulative distribution function (CDF) of the ratio between the emulator's RTT and the actual one, as in Figure 7. Each ratio value is calculated between two experiments with the same settings in two environments. Although RTT varies and sometimes reaches unexpected values (i.e., in the bufferploat condition), we still see that a large portion of the ratio values is close to one in both queue conditions. Therefore, we can conclude that, overall, the emulator's results are close to those in the actual network. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Section** & **Wi-Fi** & **S1–S2 Link Bandwidth** & **Queue Size** \\ \hline Section 4.2 & g & 10 Mbps & [20, 100] packets \\ \hline Section 4.3 & g, n, ax & 1000 Mbps & 100 packets \\ \hline Section 4.4 & g & \{10, 100\} Mbps & 100 packets \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Network settings in each evaluation. Figure 4: Throughput comparison. Figure 5: RTT comparison.