# End-to-End Delay Model for Train Messaging over Public Land Mobile Networks
## 1 Introduction  
Future railway communication systems will integrate a variety of systems, each of them specialized to specific services [1]. The communication platform for railway management will be oriented towards a unified infrastructure to increase efficiency, speed up the business processes, increase operational effectiveness, facilitate information exchange and improve the quality of decision-making. Other and new applications for railways are discussed in [2]. However, to provide broadband communication services for railways (even beyond those services supporting control and management functionalities), innovative communication systems' architectures should be considered sometimes disregarding the existing infrastructure(s) along the line [3, 4]. Moreover, recent advances on the Internet of Things (IoT) open a way to several innovative use cases and applications for creating a connected railway mainly oriented to passengers including: journey planner, social networking apps, gathering status information from diverse on-board public-facing assets, such as toilets, food carchiller, etc., real-time alarms for potential problems, allowing for more timely intervention responses and potentially reducing service outages and many others [5]. Effective management of railway operation processes will require highly reliable and stable telecommunication platforms, supporting new operational modes enabling the increasing of the railway traffic capacity while ensuring high security and safety levels. The European Rail Agency (ERA) has undertaken studies to evaluate possible options for the evolution of the Global System for Mobile Communications-Railways (GSM-R) that will have to be replaced in the next few years. However, in the definition of a viable solution, two major challenges arise: to comply with the interoperability requirement, as done by the GSM-R today, and, from the train operator side, to protect the investments on the GSM-R. In addition, a migration to full IP-based telecom systems could facilitate the evolution towards a full service-based system for all rail applications [6]. Thus, the main body of current research on railway communication is mainly focused on the application of IP-based radio networks, such as LTE (Long Term Evolution), to high speed railway lines. The problem of supporting train control services by the LTE system is considered in [7]. Authors propose solutions based on modifying QoS (Quality of Service) policies, adjusting some cell parameters with respect to cell planning performed by the operator or optimizing procedures to resolve any network issue. These solutions can be costly for the railway owner. Concerning cost reduction, a first breakthrough in economic sustainability is represented by the replacement of proprietary/dedicated networks based on GSM-R, with public networks such as the cellular and satellite networks operated by commercial operators (mobile network operator, MNO). The use of public telecommunication infrastructure(s) makes it possible to rapidly extend the existing automated train control procedures (such as the European Rail Traffic Management System/European Train Control System (ERTMS/ETCS), and communications based train control [8]) for improving rail traffic capacity for local/regional lines where the deployment of a dedicated radio infrastructure is expensive in terms of both CAPEX (Capital Expenditures) and OPEX (Operating Expenditure). Furthermore, public networks can be considered as low cost and effective enablers for the rapid deployment of the modern railway information systems such as those proposed and investigated in the InteGRail project [9]. This innovative scenario would imply a step-change in the liability process with the introduction of guaranteed QoS in the provisioning of mobile connectivity services by telecommunication operators. In the last few years, other important European research projects investigated on the railway communications.