## 3 Communication Technologies for Improved Energy Efficiency and Safety in Railways
### State of the Art in Communication Systems in Railways  
According to [108], future railways and related industries are going to be increasingly reliant on the ITS paradigm, ushering innovative integrated security services, along with improved fleet management and Industry 4.0 concepts such as the predictive maintenance of railway vehicles and infrastructure to reduce their operational costs and augment the traffic capacity. These measures are expected to improve the performance of key management systems, such as those related to traffic scheduling and transportation system capacity planning, along with railway transportation safety and energy efficiency, interoperability, and support to multimodal transportation [108]. For that to happen, communication systems supporting the smart railway paradigm should be characterised by high availability, data throughput and reliability, along with integrated software support needed to optimise the utilisation of existing fleets and energy resources within the railway network [108]. Hence, future smart railways are likely to incorporate many emerging wireless communication technologies that are capable of offering the desired level of decision-making flexibility and integrated security features needed to operate the critical infrastructure. GSM-R networks currently represent the standard paradigm in the field of railway communication systems, which are used for both voice communication and data transfer [108]. Over time, other communication technologies have been considered for this task, with the current focus being on the development of long-term evolution radio networks for railways (LTE-R), which can be broadly considered as counterparts of 4G/5G cellular communications. These communications are good candidates for the future implementation of the Industrial Internet of Things (Industrial IoT, or shortly IIoT) concept in railway transportation, where massive data communications between heterogenous nodes, such as in the case of V2I, V2V, and infrastructure-to-infrastructure (I2I) communications will be key for the effective operation of smart railway networks, as illustrated in Figure 4. The key comparative features of GSM-R and LTE-R radio communication technologies \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \begin{tabular}{c} **New** \\ **Infrastructure** \\ \end{tabular} & \
\begin{tabular}{c} **Production** \\ **Costs** \\ \end{tabular} &
\begin{tabular}{c} **Production** \\ **Efficiency** \\ \end{tabular} & **Food Price** \\ \hline Hydrogen & Yes * & High & Low ** & Not affected \\ \hline Biofuels & Not needed & Low & High & Affected \\ \hline Synthetic fuels & Not needed & High & Low & Not affected \\ \hline PV for synthetic fuels & Not needed & Low & High & Not affected \\ \hline \hline \end{tabular}  
* When distributed PV-based hydrogen production is considered, the existing power grid could be used for necessary power allocation. ** Low efficiency of the complete production cycle (well-to-wheel).  
\end{table} 
Table 1: Economic barriers for alternative fuels and hydrogen use in transport [103]. \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \begin{tabular}{c} **Fuelling** \\ **Infrastructure** \\ \end{tabular} & \begin{tabular}{c} **Supply Chain** \\ **Systems in Railways** \\ \end{tabular} & \
\begin{tabular}{c} **Land Demand** \\ **Systems in Railways** \\ \end{tabular} &
\begin{tabular}{c} **Intermittency** \\ **Friendly** \\ \end{tabular} \\ \hline Hydrogen & New & New & No concern & Yes ** \\ \hline Biofuels & Existing & Existing & Yes (arable land) & No \\ \hline Synthetic fuels & Existing & Existing & No concern & Yes ** \\ \hline PV for synthetic fuels & Existing & Existing & No concern * & Yes \\ \hline \hline \end{tabular}  
* If photovoltaic systems are located on non-arable land and buildings. ** In case of excess electricity production from renewables used for hydrogen and synthetic fuel production.  
\end{table} 
Table 2: Infrastructure barriers for alternative fuels and hydrogen use in transport [103].