SRCC is a link layer solution (OSI level 2). It implies that SRCC is independent from any existing IP configuration and integrates smoothly into the operator’s architecture.
Smart Redundant Carriage Coupling (SRCC) is a service that automates the wireless coupling of adjacent carriages to establish a redundant link-layer backbone, using secured WiFi connections and Ethernet links.
The wireless carriage coupling will consist on the discovery and association with the neighbouring carriage.
The neighbour discovery over wireless channels is made difficult by the broadcast nature of the wireless medium, as wireless broadcasting causes a frame to be received also by nodes that are not physical neighbours.
In order to avoid bad coupling and interferences, we have to make sure that each switch node only receives signal from the closest valid switch node.
So a first step will be to ensure that the radio design has been down in a such way that we will limit the radio cell of each radio coupler.
The following methods are available to make sure to comply with the above rule :
- Use a directional antenna in order to focus radiations on the desired coach
- Limit Transmit Power
- Use as possible low gain antenna and/or RF attenuators.
A second step will be to identify “good” and “bad” coupling.
Bad couplings are all WiFi neighbours that are :
- From the same coach and that could generate a network loop once associated
- From a distant coach on the same train with a low signal quality
- From a different train on a different track that will generate network disconnection once associated.
To avoid these bad couplings, SRCC will perform topology and neighbour discovery to identify the good neighbour to associate on:
SRCC starts by the discovery of the internal topology of each carriage, then in a second step the discovery of the neighbouring carriage. It will automatically choose the right partner for coupling among all the potential devices around.
Once the partner is elected, SRCC will automatically establish a secured link between both devices linking the internal network of both carriages.
If coaches are separated later, SRCC detects the drop of RF link, closes the link on both sides and restarts the detection process.
SRCC aims to be very simple to configure.
To go further in the train network automatization, ACKSYS has developed a layer 3 carriage coupling solution: MIR (for Inter-consist network communication module)
MIR allows, based on the IEC 61375-2-5 standard, to perform automatically a train network inauguration and to build from a linear topology of similar chained consists (with the same initial/default configuration) a full train network having different consist networks that can communicate with each other. This makes the maintenance and train re-arrangement much simpler and allows to build new applications and features for IOT and TCN (Train Communication Network).
