## 3 MOS-Aware Measurement Scheme in Mobile Networks
### Video Conference MOS Testing and Analysis  
In order to conduct a simulation environment for mobile networks, we refer to the path loss model in 3 GPP TR36.814 [27]. As shown in Equation (8), PL represents the path loss in dB. R means the eNB's signal covered radius in kilometers. The UE-measured RSRP (reference symbol received power) is given by Equation (9). The transmission power for each resource element is \(\text{P}_{\text{t}}\) (dBm), and this model is imported into Mininet-WiFi [28] to ensure that the user's performance during mobility has the characteristics of an LTE network. \[\text{PL}\ =\ 131.1+42.8\log_{10}\text{R}\ (\text{dB}) \tag{8}\]  
\[\text{RSRP}\ =\ \text{P}_{\text{t}}-\text{PL}\ (\text{dBm}) \tag{9}\]  
In addition, the effect between distance and throughput was simulated based on the characteristics of IEEE 802.11 g in the original Mininet-WiFi. However, this simulation result will be different from LTE. Therefore, we obtained the correspondence between throughput and RSRP from the UE measurements based on the results of the downlink tests for LTE from [29]. The relationship between the average downlink throughput and RSRP is shown in Table 3. \(\text{Q}_{\text{DL}}\) = 10% is used as a reference for LTE throughput performance in this paper. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**RSRP Range**} & \multicolumn{4}{c}{**Downlink Throughput (Kbps)**} \\ \cline{2-5}  & **Q\({}_{\text{DL}}\)** = 5\% & **Q\({}_{\text{DL}}\)** = 1 & **Q\({}_{\text{DL}}\)** = 20\% & **Q\({}_{\text{DL}}\)** = 50\% \\ \hline \((-130,-125)\) & 5286.42 & 4957.90 & 4511.61 & 3413.85 \\ \hline \((-125,-120)\) & 9965.03 & 8336.40 & 6276.86 & 3608.57 \\ \hline \((-120,-115)\) & 19,379.11 & 17,267.44 & 14,352.46 & 9847.88 \\ \hline \((-115,-110)\) & 31,757.07 & 27,976.82 & 23,088.08 & 16,024.25 \\ \hline \((-110,-105)\) & 45,420.39 & 39,257.92 & 31,975.05 & 22,218.22 \\ \hline \((-105,-100)\) & 57,578.17 & 48,962.60 & 39,552.47 & 27,603.03 \\ \hline \((-100,-95)\) & 59,869.94 & 49,117.72 & 38,543.68 & 26,140.81 \\ \hline \((-95,-90)\) & 69,091.76 & 57,735.74 & 46,309.86 & 32,471.78 \\ \hline \((-90,-85)\) & 69,119.64 & 57,362.81 & 45,757.79 & 31,899.25 \\ \hline \((-85,-80)\) & 73,730.66 & 62,012.55 & 50,166.78 & 35,667.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The relationship between downlink throughput and RSRP. The simulation scenario is implemented using Mininet-WiFi, which is based on the Mininet SDN network simulator with the IEEE 802.11 module for simulating the characteristics of wireless networks. Although Mininet-WiFi has the capability of SDN network simulation, in this research, we only deploy it for analysis of handover characteristics in wireless networks. A single eNB scenario has been considered in order to study the impact of transmission distance on RSRP. The topology is shown in Figure 5, and the network parameters in this simulation scenario are shown in Table 4. The eNB's transmission range is about 4200 m. During the experiment, one target UE moves from the center of the effective eNB transmission range at a speed of 20 m per second until it reaches the edge of the eNB transmission range. The total test time is 230 s. There are eight UE competing for network resources as the background traffic, while each of them uses Skype video calls with 640 \(\times\) 480 resolution. In this paper, the acceptable threshold of MOS is set to 4. When the MOS value is higher than 4, it means that the current network environment can meet the acceptable needs of users. When the MOS is lower than 4, the network resources at this time may not be able to maintain the quality of user experience for the application. Figure 5: Network topology.