## 3 Communication Technologies for Improved Energy Efficiency and Safety in Railways
### State of the Art in Communication Systems in Railways
according to [108] are summarised in Table 3. These point to the unsurpassed performance of LTE-R based communication networks in terms of throughput and communication channel availability. Other communication standards (both proprietary and open ones) have also been considered for wireless communication in railways, and their comparative features in terms of their compliance with railway communication systems are listed in Table 4. Obviously, there does not appear to be a single wireless communication standard that can fulfil all of these strict requirements, which has further strengthened the case for LTE (4G/5G)-based communications as a backbone for future smart railways and railway related the IoT paradigm of smart trains. It should also be noted that even though LTE-R can provide improved railway communication services compared to the currently used GSM-R, it cannot support certain emerging railway features such as autonomous driving and massive IoT applications. A possible solution for these issues may be through the introduction of railway-adapted 5G communication systems (5G-R), which are expected to offer highly competitive performance in terms reliability and even higher data transfer rates [109]. Figure 4: Some uses of wireless communications in future smart railways, as indicated in [26; 108]. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Parameter** & **Frequency** & \begin{tabular}{l} **Channel** \\ **Bandwidth** \\ \end{tabular} & **Peak Data Rate** & **Maturity** & **Market Support** \\ \hline GSM-R & \begin{tabular}{l} 921–925 MHz download \\ 876–880 MHz upload \\ \end{tabular} & 200 kHz & 172 kbps & **Mature** & Until 2030 \\ \hline LTE-R & \
\begin{tabular}{l} 450 MHz, 800 MHz, \\ 1.4 GHz and 2.1 GHz \\ \end{tabular} & From 1.4 to 100 MHz &
\begin{tabular}{l} 50 Mbps download \\ 10 Mbps upload \\ \end{tabular} & Emerging & Building standards \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of GSM-R and LTE-R radio communication technologies in railways [108] in terms of performance and maturity. These communication systems can be integrated with the railway traffic control system. For example, the European Rail Traffic Management System (ERTMS) is a system of standards for the management and interoperation of signalling for railways by the European Union. The ERTMS system is based on the technical specification for interoperability for \"traffic-control and signal-safety\" subsystems, which was designed by the European Union Railways Agency (ERA). The ERTMS system can be installed at several levels, depending on the equipment installed on the track and the way information is transmitted to the train. Figure 4 shows two levels of implementation of such systems:  
1. Level 1, which includes constant monitoring of the train movement and occasional communication between the train and the track (using so-called Eurobalise). Trackside signals are required at this level. 2. Level 2, which includes constant monitoring of the train movement and constant communication between the train and the track using the GSM-R system. At this level, signalling equipment is not required along the track. Fifth generation communications offer some distinct innovations and possible advantages, such as the introduction of Filter Bank Multi-Carrier (FBMC) modulation instead of the Orthogonal Frequency-Division Multiplexing (OFDM) [108]. In particular, FBMC can facilitate a higher bandwidth utilisation efficiency, and consequently, better utilisation of the existing spectrum and synchronisation for simultaneous communication between both stationary and mobile communication nodes (both V2V and V2I communications) [108]. In fact, FBMC can provide increased robustness to timing and frequency variations compared to the OFDM method with lower error probability rates [110], while also being able to provide better spectral containment of signals, thus offering increased robustness even for high-volume data rates [111].