# Towards the Internet of Smart Trains:
## 4 Long Term Evolution (LTE): One Step Ahead of Broadband Communication Systems  
As a narrowband system, the main GSM-R shortcoming relates to its limited provision of advanced data services due to its lack of packet-switched transmissions (Table 7). For instance, in order to deliver burst low-rate ETCS data, connections need to take network resources continually even though not \begin{table}
\begin{tabular}{l l} \hline \hline
**Requirements** & **Value** \\ \hline Connection establishment delay of mobile originated calls & \(<\) 8.5 s (95\%), \(\leq\) 10 s (100\%) \\ Connection establishment error ratio & \(<\) 10\({}^{-2}\) (100\%) \\ Connection loss rate & \(<\) 10\({}^{-2}\)/h (100\%) \\ Maximum end-to-end transfer delay (of 30 byte data block) & \(\leq\) 0.5 s (99\%) \\ Transmission interference period & \(<\) 0.8 s (95\%), \(<\) 1 s (99\%) \\ Error-free period & \(>\) 20 s (95\%), \(>\) 7 s (99\%) \\ Network registration delay & \(\leq\) 30 s (95\%), \(\leq\) 35 s (99\%), \(\leq\) 40 s (100\%) \\ Call-setup time & \(\leq\) 10 s (100\%) \\ Emergency call-setup time & \(\leq\) 2 s (100\%) \\ Duration of transmission failures & \(<\) 1 s (99\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Main GSM-R QoS requirements. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Service Group** & **Type of Service** & **Cab** & **ETCS Data Only** & **General Purpose** & **Operational** & **Shunting** \\ \hline \multirow{4}{*}{Voice-Call} & Point-to-point & MI & NA & M & M & M \\  & Public emergency & M & NA & M & M & M \\  & Broadcast & M & NA & M & M & M \\  & Group & MI & NA & M & M & M \\  & Multi-party & MI & NA & O & O & M \\ \hline \multirow{4}{*}{Data} & Text message & MI & NA & M & M & M \\  & General data applications & M & O & O & O & O \\  & Automatic fixe & O & NA & O & O & O \\  & ETCS train control & NA & MI & NA & NA & NA \\ \hline \multirow{4}{*}{Specific features} & Functional addressing (FA) & MI & NA & M & M & M \\  & Location dependent addressing (LDA) & MI & M & O & O & O \\  & Direct mode & NA & NA & NA & NA & NA \\  & Shunting mode & MI & NA & NA & NA & M \\  & Multiple driver communications within the same train & MI & NA & NA & NA & NA \\  & Railway emergency calls & MI & NA & O & M & M \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Services to be supported according to the radio type. Note that Mandatory for Interoperability (MI), Mandatory for the System (M), Optional (O) or Not Applicable (NA) [43,48]. \begin{table}
\begin{tabular}{l l} \hline \hline
**Call Type** & **Call Set-Up Time** \\ \hline Railway emergency call & \(<\)4 s (M) \\ High priority group calls & \(<\)5 s (M) \\ Group calls between drivers in the same area & \(<\)5 s (M) \\ All operational and high priority mobile-to-fixed calls not covered by the above & \(<\)5 s (O) \\ All operational and high priority fixed-to-mobile calls not covered by the above & \(<\)7 s (O) \\ All operational mobile-to-mobile calls not covered by the above & \(<\)10 s (O) \\ All other calls & \(<\)10 s (O) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: GSM-R call set-up time requirements [43,48]. being used. The maximum transmission rate of GSM-R per connection is 9.6 kbps and the packet delay is in the range of 400 ms, which is sufficient only for applications with low demands [42]. Possible solutions to enhance its limited capacity (i.e., ETCS in high traffic areas) include an LTE micro-cell deployment or the usage of the ER-GSM band (includes standard and extended GSM 900 band) and changing to ETCS over packet-switched data using GPRS, Enhanced General Packet Radio Service (EGPRS) or Enhanced GPRS Phase 2 (EGPRS2) [53]. Despite the commitment of the GSM-R Industry [54] to support GSM-R until 2030, these shortcomings are encouraging the replacement for different system architectures mainly LTE/LTE-A.