# Towards Intelligent, Programmable, and Open Railway Networks
## 4 Intelligent Railway Network Architecture  
Figure 1 shows a high-level view of the proposed open, intelligent, and programmable railway network architecture, with a focus on the separation of time-tolerant RBC functions from time-sensitive RBC functions. Radio communication modules for information exchange based on the FRMCS are not shown for simplicity. The vertical disaggregation can be achieved through the virtualization of RBC functions. The virtualization enables software to run on a standard server platform and provides greater scalability, adaptability, and agility compared to traditional proprietary RBC equipment. The virtualization of the RBC functions can provide an open architecture with flexible deployment options. Virtualized RBC functions can be implemented as software applications that deliver specific RBC functions, such as train monitoring and control, track-side monitoring and management, security, radio communications, etc. These software applications can be packaged as virtual machines or containers that run on the railway edge cloud (REC), which is deployed at the edge of the railway network. The REC is a cloud computing platform that consists of computing, storage, and networking components that meet the requirements to host the relevant RBC functions, supporting software components such as a hypervisor, container runtime, etc., as well as appropriate management and orchestration functions. The REC exports interfaces for cloud and workload management (e.g., infrastructure discovery, software and workload lifecycle management, and registration). The railway management, automation, and orchestration (RMAO) framework is responsible for the management and orchestration of virtualized RBC functions. It supports fault, configuration, performance, and software management and initial installation over the R3 interface. The RMAO hosts a time-tolerant intelligent control unit (TTICU) whose primary goal is to support intelligent railway operation optimization by providing ML model management, policy-based guidance, and supplementary information to the time-sensitive intelligent control unit (TSICU). The TTICU performs intelligent, non-real-time RBC functions, such as the first route assignment for the train, train chasing, acquisition of diagnostic information, trackside maintenance, etc. The TTICU can embed intelligence to optimize railway operation, for which it may use RMAO services for data collection and provisioning services for an onboard train control system, an interlocking system, and a control center. The TTICU contains a framework functionality, which terminates the interface towards the TSICU and  
Figure 1: High-level view of the logical architecture of the intelligent railway network. exposes the required services to ttApps. The ttApps are modular applications used for railway operation optimization. The TTICU is involved in a non-real-time control loop. The TSICU's functionality includes time-sensitive monitoring, control, and optimization of the onboard train control and trackside equipment functions. It is involved in a near-real-time control loop (e.g., responsible for setting temporary train speed limits, evaluation of potentially dangerous situations, commanding emergency stops, etc.). It hosts tsApps that use the interfaces toward the ETCS entities to collect time-sensitive information (e.g., on a train basis or a track-section basis) and provide value-added services. The TSICU control steers the ETCS entities (onboard train control system, interlockings, LEU, RIU, Eurobalise, Euroloop) through policies and enrichment information provided by the TTICU. The R1 interface is between the TTICU in the RMAO and the TSICU for railway operation optimization. It enables policy management, information provisioning, and ML model deployment and updating. It is used to provide the TSICU with enrichment information, policies, and ML model updates, as well as to provide feedback information to the TTICU on how the policy set works.