Single Network Session
One APN connection, with the associated IP address, means that the public, private and critical network data flows over a single IP connection.
Multiple PDN’s allow for enhanced network security as they are explicitly designed to separate public, private, or critical data over multiple connections, with each PDN having a unique IP Address.
Each PDN is configured independently by the 4G-LTE network. For example, the first PDN can be allocated for private communication network data and the second for critical train control systems.
Quality of Service
Traditional 4G networks offer best-effort IP connectivity for voice, video, and other real-time critical application data.
4G railway networks need to distinguish different kinds of traffic, thereby ensuring the performance of critical applications, guaranteeing enough bandwidth for their correct operation.
Dedicated bearers provide dedicated tunnels to one or more specific data traffic and include quality-of-service (QoS) for particular service flows.
The router can establish dedicated bearers, based on quality-of-service (QoS) requirements. A total of 11 dedicated bearers can be supported simultaneously per PDN.
Additionally, a Guaranteed Bit Rate (GBR) bearer means the bandwidth is guaranteed. For instance, critical network communication and voice traffic could be assigned a guaranteed bit rate
A failed router in the network can cause loss of service to data and train control systems. Therefore, it is critical to implement redundancy in the network and the onboard systems so that a loss of a link or node does not result in loss of service.
Both active and standby 4G interfaces are available in all on-board communication hardware. If then, the active link fails, the standby can take over with limited packet drops in the network. Both links can also be configured to load-balance increasing network access capacity.
In addition, railway and public transportation are likely to adopt multiple wireless technologies to support their mission-critical applications. Mobile Router Multipath (MRM) support between the railway router and automatic train control (ATC) system allows traffic to be load-balanced over all available interfaces.
When there are multiple paths, the traffic from the mobile networks that goes toward the router is generally load-balanced. Policy-based application routing allows you to identify a particular type of traffic from the mobile networks and then select the tunnel for routing this traffic.