Robust implicit EDF: A wireless MAC protocol for collaborative real-time systems

• Published in: ACM transactions on embedded computing systems 2007-09, Vol.6 (4), p.28
• Main Authors: Crenshaw, Tanya L., Hoke, Spencer, Tirumala, Ajay, Caccamo, Marco
• Format: Article
• Language: English
• ISSN: 1539-9087; 1558-3465
• DOI: 10.1145/1274858.1274866

Advances in wireless technology have brought us closer to extensive deployment of distributed real-time embedded systems connected through a wireless channel. The medium-access control (MAC) layer protocol is critical in providing a real-time guarantee. We have devised a real-time wireless MAC protocol, robust implicit earliest deadline first, or RI-EDF. Packets are transmitted according to EDF scheduling rules, offering a protocol that implicitly avoids contention. In the event of a packet loss or a node failure, every node has the opportunity to recover the schedule based on a static recovery priority, offering a protocol that is robust with no central point of failure. We demonstrate in simulations that RI-EDF provides better goodput and lower packet loss than existing protocols like 802.11 PCF and EDCF. In our implementation and distributed control test-bed, we show that RI-EDF provides better throughput than the TinyOS MAC-layer protocol. Overall, RI-EDF provides predictable temporal behavior with minimal impact on node failures, packet losses, and noise in the channel.