Timing analysis of SpaceWire using OMNeT++ based simulator

Abstract

The SpaceWire is a standard for communication for on-board spacecraft. SpaceWire is nominated by ESA and planned to be the only communication standard for spacecrafts in future. It is already in use by many missions which are currently in operation. The SpaceWire protocol is not a deterministic protocol. It supports arbitrarily large sizes of messages with possibility of different datarate. It has wormhole routing in routers which may block critical messages for larger amount of time. It also has very low buffer memory and no virtual channel support. These conditions makes SpaceWire’s timings very uncertain. Embedded system developers need realistic bound on the end-to-end delay for messages sent over the SpaceWire for a more timing predictable software. Worst-case analysis of the end-to-end delay reports very pessimistic bounds, which are not applicable for many applications. A good simulator can provide less pessimistic bounds. However, there is a few options when it comes to SpaceWire simulator. A simulator can provide accurate modelling of the network and it’s timing behavior. For these reasons in this work first a SpaceWire’s routing strategies will designed in OMNeT++. Then an implementation of wormhole routing will be done. Based on routing strategies end-to-end delay for messages considering different network scenarios will be analyzed. The blocking of packets in the router will also be demonstrated. Future work may focus on network emulation and validation process.