# Railway Wireless Communications Channel Characterization
## 4 Communication Channel Measurement Methodology and CCT Description  
CCT is a technology-independent tool, which allows the measurement of different communication channels in terms of IP QoS parameters along a given track with a specific location. Intending to fulfill this main requirement, the methodology proposed is the following one:  
1. Installation of an on-board device in the train. 2. Configuration of the different tests to be performed in the specific track. 3. Test measurements of the different IP impairments with the need of being geolocated to obtain information on how the communication channel behaves in each location of the tack. 4. Processing of the test results. 5. Visualization in a user-friendly interface. 6. Analysis of the results of the test. In order to reach the main goal already mentioned, the development of the CCT has been carried out. The main features of this tool are explained in Table 2. \begin{table}
\begin{tabular}{c c} \hline \hline  & **CCT** \\ \hline \multirow{2}{*}{**Networks to be measured**} & Any network the user wants to monitor, the \\  & CCT is plug and play * \\ \hline \multirow{2}{*}{**Environment**} & Any environment, with railway-specific \\  & module * \\ \hline \multirow{2}{*}{**Measured parameters**} & RF and IP parameters: BW, throughput, RTT, \\  & jitter, packet loss, RSSI, RSRP, RSRQ, SINR \\ \hline \multirow{2}{*}{**Usage**} & Easy usage adapted also for \\  & non-communication expert users * \\ \hline \multirow{2}{*}{**Testing and post-processing/visualizing from**} & On-board testing equipment: CCT agent \\  & Visualizing: internet connection and web page \\  & User-friendly interface \\ \hline \multirow{4}{*}{**User-customizable**} & Any technology can be inserted * \\  & Customizable connection for any technology \\ \cline{1-1}  & (Ethernet connection) * \\ \cline{1-1}  & SMA connections for desired antenna \\ \hline \hline \end{tabular}
\end{table} 
Table 2: CCT features (innovations with respect to state of the art are marked with *). In comparison with the other tools already mentioned, this novel tool allows testing the communication channel in continuous mode along a track and not point by point like static testing. Moreover, it is a save-spacing tool in addition to being a non-intrusive system; it can work in a train in operation, not degrading its normal functioning. Hereunder, some of the benefits of CCT are detailed:  
* CCT measures the impairments defined by the user in a continuous mode with its geolocation. This feature is the most important one since the railway environment changes while the train is going from the starting point to the endpoint of the journey, affecting the communication channel. * CCT is a modular and plug-and-play tool; therefore, the CCT can be network-customized, allowing the possibility to include current technologies that are not integrated such as satellite communications or in development (e.g., 5G) or future ones such as 6G. Furthermore, other technologies which other purposes such as maintenance could be tested to know their limitations, such as LoRA which is being used in the railway domain [16]. * CCT contains information about the different network operators such as theoretical coverage (cell information), which could help in the analysis of the network performance. * CCT is railway specialized; therefore, the mapping of QoS parameters is more accurate along the track than in general applications. * This tool includes more IP impairments than the other tool in the current market: packet loss, jitter, throughput. * CCT allows an easy usage for expert and non-expert users in the communication area. * It allows for knowing the statistic results from every test and impairment, visualizing the summary of how the communication channel is based on the different tests performed in the same track. * A user-friendly interface for configuring and visualizing the tests is included, being accessible from any device with an internet connection.