# Call Model and Test-Verification Methods for PS-LTE Core Equipment
## 4 Measurement of Wireless Coverage and Quality
### Measurement of Coverage and Call Quality  
The purpose of coverage measurement is to provide stable services of DSCNs and to check the call rights necessary for immediate response in the event of a disaster. As for the coverage verification method, the RSRP value is measured at \(75\times 75\) grid units based on submunicipal administrative divisions, and RF scanners are used to verify whether an area is present whose RSRP drops below \(-117\) dBm in the coverage edge. As for coverage measurements, RF scanners installed in vehicles measure RSRP values on roads that allow vehicle entry within the measurement area. The level of frequency for PS-LTE (700 MHz band) is measured in seconds using an RF scanner and stored together with GPS coordinates. To ensure a sufficient number of inspections (four or more) per grid, the inspection is conducted within 60 km/h, and if the average of RSRP is less than \(-117\) dBm, it is judged as an area with insufficient coverage. The problem of the terminal itself should be minimized by selecting the manufacturer's terminal with the most stable operation in DSCNs. The terminal setting for the measurement is configured by dividing the terminals into those set up to communicate only via the PS-LTE (Band 28) frequency and those capable of RAN sharing. The composition of the terminals and measuring instruments for the coverage and quality of data/call tests is shown in Figure 9. For the measurement of coverage, the test should be conducted after the consultation of coverage paths for the target area so that the terminal can check the latest version of firmware and measure the signal strength for the target coverage proposed by the business carrier that built it. Quality measurement is performed by composing a scenario in the order of individual call voice \(\rightarrow\) individual call text \(\rightarrow\) individual call video (set to record call video on the receiving terminal when measuring a video call) \(\rightarrow\) voice group call \(\rightarrow\) text group call \(\rightarrow\) video group call. This scenario is repeated more than 20 times for measurement, and the composition of the measured call time for each call is shown in Table 5. Because 405 s are required for one measurement, approximately 135 min are required for 20 measurements [22; 23]. Data are measured by repeatedly uploading and downloading files 30 times or more from the NIA diagnostic monitor app installed in the terminal. The time required for one measurement is 37 s, i.e., ping measurement (11 s), upload (13 s), and download (13 s). The measurement indicators based on the use stage of service for individual and group voice calls in standards such as ITU-T, ETSI, and 3 GPP are shown in Table 6. [24; 25]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Indicators** & **Description** \\ \hline Connection & The rate at which the connection is completed within a certain base time \\ success rate & among the calls of a connection attempt. \\ \hline Dropped call rate & The rate at which the call is cut off within a certain call time among the calls of a successful connection. \\ \hline Voice quality & Measurement on a five-point scale for quality deterioration between original and received voices. \\  & (ITU-T P.862 PESQ or P.863 POLQA standard algorithm applied). \\ \hline Call success rate & Call rate of successful calls above MOS threshold among call attempts. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Verification indicators for individual/group voice calls. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Item**} & \multicolumn{3}{c}{**Private Currency (s)**} & \multicolumn{3}{c}{**Group Calls (s)**} \\  & **Voice** & **Text** & **Video** & **Voice** & **Text** & **Video** \\ \hline Idle time & 10 & 5 & 10 & 10 & 10 & 10 \\ Setup time & 20 & 10 & 20 & 30 & 30 & 30 \\ Traffic time & 65 & 10 & 65 & 30 & 10 & 30 \\ Total & 95 & 25 & 95 & 70 & 50 & 70 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Measured call time for each call.