Policy Based Railway Communications

Future Railway Mobile Communication System (FRMCS) enables the transition to railways digitalization. Defined by the International Union of Railways (UIC), it is expected to optimize the costs of infrastructure, to improve reliability, safety, and security of the railway services, and to enhance user quality of experience. FRMCS critical communication applications embed policy enabled functions which are based on operational rules. The paper presents an approach to design a service for policy management which enables railway operator to create, update and delete policy rules and to control the access to them. Using the Policy service, FRMCS applications can request policy evaluation in order to perform functions such as application authorization, communication authorization, arbitration between competing communications, and multiuser talker control. The Policy service design follows the principles of REpresentational State Transfer (REST) architectural style. Policy service resources, methods and data types are defined. The usage of the Policy service interfaces is illustrated by the FRMCS Arbitration application which makes rule based prioritization of communications competing for the attention of a FRMCS user. Call state models reflecting the application's and the FRMCS system's views are developed, formally described, and verified.