Analysis of worst-case delay bounds for best-effort communication in wormhole networks on chip
NOCS '09 Proceedings of the 2009 3rd ACM/IEEE International Symposium on Networks-on-Chip
Network calculus: a theory of deterministic queuing systems for the internet
Network calculus: a theory of deterministic queuing systems for the internet
Worst-case end-to-end delays evaluation for SpaceWire networks
Discrete Event Dynamic Systems
Using Network Calculus to compute end-to-end delays in SpaceWire networks
ACM SIGBED Review - Work-in-Progress (WiP) Session of the 23rd Euromicro Conference on Real-Time Systems (ECRTS 2011)
A Network Calculus Model for SpaceWire Networks
RTCSA '11 Proceedings of the 2011 IEEE17th International Conference on Embedded and Real-Time Computing Systems and Applications - Volume 01
A Sensitivity Analysis of Two Worst-Case Delay Computation Methods for SpaceWire Networks
ECRTS '12 Proceedings of the 2012 24th Euromicro Conference on Real-Time Systems
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The aim of this presentation is to provide an introduction to the communication needs on board unmanned spacecraft and to their current evolution. By nature, spacecraft are beyond any improvement or repair capability by means of physical/mechanical intervention as soon as they are launched into space. This leads to requirements for on-board communication being dominated by reliability. However, the level of autonomy required from any modern spacecraft in nominal operation mode leads to timeliness requirements as well. The combination of both properties, Reliability and Timeliness, is a common frame for communications on board unmanned spacecraft and is abbreviated in the acronym "RT" which, in this context, does not mean "real-time". Although both reliability and timeliness are the main requirements on communications on board unmanned spacecraft, this presentation done in the context of the RTS WCTT (Worst Case Traversal Time) workshop focuses mainly on the timeliness issues. We first describe the need for non-real-time and real-time communications on-board any unmanned spacecraft and then the scope of real-time communications on-board past and current spacecraft. Current and future trends are also presented for which no solution is clearly established yet. This presentation briefly describes the challenges to be addressed with respect to these trends. It then exposes short-terms solutions that have been academically investigated and are now available to spacecraft designers. Finally, the presentation provides perspectives on possible investigation lines. Overall, this presentation shows that, for the schedulability of SpaceWire traffic, both in the frame of the real-time communications only and in the more complex frame of mixed hard real-time, soft real-time and non-real-time traffic, any academic result is very welcome. In this domain, most space agencies are willing to support related academic research. There are many other parameters (mostly related to reliability) to be taken into account for the design of real-time communication protocols for spacecraft data handling, like Failure Detection, Isolation and Recovery (FDIR) issues, redundancy (cold, warm, hot, cross-strapping), Single Point of Failure (SPF), Single Fault hypothesis, availability, maintainability, determinism, babbling idiot, fails-safe, fail-operational, bus guardian, safety, security, etc. These concepts are not presented in this paper. They should be taken on board any academic research on communications on board unmanned spacecraft, and would require a dedicated paper at the same level as this presentation introduces timeliness issues.