## 4 Solution of the Fiber Optical Repeater
### Measurement of Practice
#### 4.2.3 Results of Measurement  
The measurements of acceptance entail the evaluation of a cell's coverage, which is approximated by means of the common pilot channel (CPICH) and the reference signal receiving power (RSRP) for the primary common pilot channel. The standard deviation of RSRP, as caused by free-space attenuation and slow and fast fading, conveys the evenness of RSRP throughout the network. Large variations in RSRP necessitate greater margins for slow fading. The quality of the coverage is indicated by CPICH-Ec/No, which denotes the received energy per chip on CPICH divided by the power density in the band. The CPICH-Ec/No is defined as the ratio between reference signal received quality (RSRQ) and the received signal strength indicator (RSSI) of the measured quality indicators for an SCE network system. * Station and platform  
The CPICH-RSRP metric is employed to assess the signal strength of the SCE system. Nevertheless, it ought to be observed that a high recorded value of RSRP may not necessarily indicate the presence of a strong signal but instead may result from high levels of co-channel interference. The signal strength can be exceptionally high if the interference component is in phase with the carrier. In the absence of significant interference, RSRP values of between \(-75\) dBm to \(-100\) dBm are considered acceptable for achieving a satisfactory signal quality. Meanwhile, the CPICH-Ec/No is utilized to evaluate the transmission bit error rate of the cellular system. Table 8 demonstrates the relationship between CPICH-RSRP and CPICH-Ec/No for the R4A station. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**RSRP Signal** & **Numbers** & **Percentage** & **Cumulative** & **Cumulative** \\  **Level** & & & & **Percentage** \\ \hline \(-35\leq x\) & 0 & 0 & 0 & 0 \\ \hline \(-45\leq x\leq-35\) & 127 & 13.5 & 127 & 13.5 \\ \hline \(-55\leq x<-45\) & 153 & 29.9 & 280 & 43.4 \\ \hline \(-65\leq x<-55\) & 261 & 11.5 & 541 & 54.9 \\ \hline \(-75\leq x<-65\) & 353 & 33.8 & 894 & 95.6 \\ \hline \(-85\leq x<-75\) & 33 & 2.3 & 927 & 99 \\ \hline \(-95\leq x<-85\) & 8 & 0.8 & 935 & 100 \\ \hline \(-110\leq x<-95\) & 0 & 0 & 935 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Relationship between CPICH-RSRP and CPICH-Ec/No for the R4A Station. Figure 22 shows RSRP on the second-level platform of the R4A station. The platform is covered by an antenna, which is placed downward in the center of the platform ceiling. Mobile units of RSRP and Ec/No are measured by walking around the platform on which the Multi-RAT-Layer is located in order to optimize the mobility and data efficiency [32, 33]. CPICH-Ec/No is used to evaluate the transmission bit error rate of the SCE system. Table 9 shows the R3 to R4A N Tunnel relation between CPICH-RSRP and CPICH-Ec/No. Figure 24 shows the RSRP on the second-level N Tunnel of the R3 to R4A station. The N Tunnel is covered by leakage coaxial cables, wherein a radiated-mode leakage coaxial cable (Andrew Company) was installed 25 cm from the southern wall of the tunnel and 3.5 m above the floor of the tunnel [34]. The conditions in the tunnel were as follows [35; 36]:  
* When cross-connection followed standard regulation, then CCO improved system coverage, while the throughput performance function was excellent, as shown in Figures 25 and 26. * Train tracking was carried out twice in both directions for the MLB and MRO function of each system. * Smooth signal handoff in the tunnel was observed, with there being no decline in call rate in the case of signal intensity. Figure 23: N tunnel measurement position.