4Links SpaceWire Bibliography
4Links staff regularly present papers on SpaceWire and related topics at conferences and technical meetings. In this section of our website, we have selected some of our favourite papers.
Our test equipment is highly effective in detecting bugs and giving you the information to fix those bugs. In these papers, we aim to give you the information that will help you to build "Networks that Work" and thus to save you stress, time and money. We hope that you find them useful, and we would appreciate your feedback or questions.
Low Latency Packet Delivery in SpaceWire Networks
This paper quantifies typical latency requirements of SpaceWire networks. It goes on to describe a simple technique that uses virtualization and priorities with dynamic, on-demand segmentation, to provide deterministic, low latency delivery of packets whilst allowing high utilisation of the network. This offers the ability to carry data with real-time and low-latency requirements, such as command and control, at the same time as, and completely fire-walled from, high-bandwidth data such as that from experiments and instruments. This paper was presented at ISC 2011.
Running a SpaceWire connection using a half-duplex variant of the protocol would result in savings of power and weight, and there would be little effect on throughput for a unidirectional data flow. This presentation was made to the SpaceWire Working Group in 2009.
Virtual SpaceWire Networks
Virtual SpaceWire Networks provide an elegant mechanism for sharing a SpaceWire platform between high-priority low-latency traffic (such as telecommand and control streams) as well as lower-priority high-throughput data streams. This paper was written in 2008. Also available are some more recent presentation slides on Virtual SpaceWire Networks.
Asynchronous Challenges for SpaceWire on FPGA
Of the many faulty SpaceWire implementations that we have seen and analysed, most were due to incorrect asynchronous interfaces. Unfortunately, asynchronous design is poorly supported by silicon design tools and simulation is particularly difficult; we have seen asynchronous errors in several designs even after extensive simulations detected no problems. This paper, from DASIA 2008, explains the issues and shows how we have implemented the whole SpaceWire CODEC in a single clock domain.
Reducing Electromagnetic Emissions from SpaceWire
This paper, presented at DASIA 2007, explains that SpaceWire can generate electromagnetic emissions both within an enclosure and from cables between enclosures. Well-shielded cables and good practice will often be adequate to control emissions, but there may be sensitive applications where further reduction is required. We show that simple techniques can be used to mitigate these undesired effects. Also available are the presentation slides.
Measuring Time and Time-related Aspects of SpaceWire
This paper, presented at the International SpaceWire Conference in 2007, presents techniques to measure timing parameters of a SpaceWire device, such as the receive link speed, the times of arrival of Time Codes, the durations and latencies of packets, and the operating margins of the SpaceWire receiver. It points to a number of design defects that have been discovered by such measurements, and how these defects often relate to asynchronous design of the SpaceWire receiver. The paper then shows how the timing measurement techniques can be expanded to cover a large SpaceWire system. Also available are the presentation slides.
Reducing Time Code Jitter on SpaceWire
SpaceWire has the very useful facility of allowing its bit period to be varied, even on-the-fly. This has been used by 4Links to reduce the jitter on time code transmissions to less than 10ns.
SpaceWire Plug-and-Play: An Early Implementation and Lessons Learned
This paper documents an early demonstration of the flexibility and resilience provided by a SpaceWire network that was built around a group of three SpaceWire routers. Also available are the presentation slides.
SpaceWire Network Topologies
This paper suggests that SpaceWire's topological flexibility can be used to optimize parameters such as performance, cost, cable-harness mass, or fault-tolerance, or to provide an optimum balance of such parameters for a particular mission. The paper introduces some simple topologies and points to work on earlier technologies such as IEEE 1355 that give useful design insights and may help to get the architecture right early in the project. Presented at the International SpaceWire Conference in 2007. Also available are the presentation slides.
SpaceWire and IEEE 1355 Revisited
Space missions need enhancements to SpaceWire, to the extent that several are already using (non-standard) adaptations of the SpaceWire standard. Some of these aspects, such as DC-balance, power down the cable, and Gbit physical layer, were handled in IEEE 1355, on which SpaceWire was based - but they were discarded in the SpaceWire standard. We suggest that, if SpaceWire is fully to meet user needs, it must evolve to take account of the needs of missions such as these. Presented at the International SpaceWire Conference in 2007. Also available are the presentation slides.
Ethernet SpaceWire Hardware Issues
The two papers on Ethernet over SpaceWire consider the opportunities for combining the best of SpaceWire, such as modularity, high speed, low latency, fault tolerance, and ease of implementation, with the vast experience of protocol design that has been implemented on Ethernet. The papers then consider how existing Ethernet-based designs can be implemented on SpaceWire networks. The papers were presented at IAC 2006 and were selected for publication in Acta Astronautica in 2007. This paper considers the hardware issues. Also available are the presentation slides.
Ethernet SpaceWire Software Issues
These two papers on Ethernet over SpaceWire consider the opportunities for combining the best of SpaceWire, such as modularity, high speed, low latency, fault tolerance, and ease of implementation, with the vast experience of protocol design that has been implemented on Ethernet. The papers then consider how existing Ethernet-based designs can be implemented on SpaceWire networks. The papers were presented at IAC 2006 and were selected for publication in Acta Astronautica in 2007. This paper considers the software issues. Also available are the presentation slides.
SpaceWire: Key principles brought out from its 40-year history
This paper used the evolution of SpaceWire over the past 40 years to describe its concepts, where they were being used, and from these suggested the opportunities that SpaceWire provides for the future. It was presented at SmallSat in 2006.
SpaceWire - Improvements in Support of Mission Requirements
This paper, presented at the first annual workshop on Spacecraft Data Systems and Software (SDSS 2005) at ESTEC, shows that 4Links was exploring potential enhancements of SpaceWire as early as 2005. At that time, this paper reported on reducing time-code jitter, some early work on virtual networks, and a faster link error recovery scheme.
These presentation slides, from 2005, give an early overview of the potential of SpaceWire.
The Origins of SpaceWire
This paper, from 2003, tells the story of serial links, from the early days of minicomputers, via the Inmos transputer, to the development of SpaceWire at ESA.
IEEE1355 at the IEE Forum
Back in 1999, Paul Walker presented an overview of the IEEE 1355 serial communication standard to a meeting of the IEEE Forum, where he compared it to serial UART data streaming.