It is perceived that military Vetronic systems will predominantly be distributed real-time systems. For these systems to operate, a communication system is required that delivers messages with a predictable performance, specified to suit each application. This deterministic transfer behaviour requires some form of co-ordinated and scheduled message generation at each network node. The MilCAN protocol that was produced within QinetiQ (previously known as DERA) has provided Vetronic systems with an acceptable solution by using Controller Area Networks (CAN) as the basic real-time communication network. Although CAN is perfectly suited for Vetronic systems there are some drawbacks that provide limitations for future expansion. The main drawback is the limited available speed (1Mbps max), especially when different CAN segments have to be brought together into a backbone and still provide determinism. It is envisaged that the need of more powerful backbones within Vetronic systems will be a requirement for the future.
Therefore, the work introduced here aims to explore a new approach to the integration of a number of communication networks with the Vetronic systems that will operate transparently providing an additional high bandwidth backbone, while maintaining the key features of the MilCAN protocol (determinism and priority-based scheduling). The developed project is a software-based Bridge with routing capabilities (BRouter), a custom Standard Network Interface (SNI) layer, and a remote configuration/monitoring utility. It uses Ethernet as a high-speed backbone.
The main objective of the project is to provide a software platform such that the Standard Vetronic Interface (SVI) can act as the vehicle of interconnecting different Vetronic Systems using different communications networks transparently. The software is based on a generic platform that transports messages, according to their priorities, between different Network Interfaces and Applications attached on to the Bridge. The Object Oriented software modelling transfers messages via the Vetronic Standard Interface and therefore any new additions in terms of new network interfaces and applications can be easily implemented
As Vetronic Systems are predominately deterministic systems and the MilCAN was initially based on Vehicle CAN systems, the Standard Interface was designed with the MilCAN extensions of the standard CAN Frame messages in mind and extended to include dynamic.size block messages (to utilise the large MTU of modern high-speed Layer 2 protocols), and to support the required high-level Bridge-to-Bridge communication.
To provide determinism and low-latency over the Ethernet backbone the Bridges use 100Mbps point-to-point connections onto Gbit Ethernet switches. Two protocol stacks were used, a high-layer (OSI 3-7 layers) deterministic protocol called EtherNet/IP, which stands for Ethernet Networks Industrial Protocol, and standard TCP/IP. The EtherNet/IP interface was based on the open source example code, which has limited functionalities used for demonstration.
This project is in collaboration with QinetiQ and funded by the Ministry of Defence, UK.
