Responsive Link for Distributed Real-Time Processing

In this paper, we design and implement responsive link, which is a real-time communication link, for distributed real-time systems including sensor-actuator networked systems, ubiquitous computing systems, robot systems, and mechatronic systems. In order to realize flexible real-time communications, the responsive link has many unique features including priority-based packet overtaking (the packet with higher priority overtakes other packets at each node.), separation of data transmission (data link) and event transmission (event link), independent routing of the data link and the event link, packet acceleration/deceleration using priority replacement (packet priority can be replaced with a new priority level at each node to accelerate/decelerate packets under distributed control), prioritized routing (when multiple packets with different priority levels are sent to the same destination, the different route can be set to realize exclusive communication lines or detours.), dynamically variable link speed (800, 400, 200, 100, 50, 25, 12.5 Mbaud), hot-plug&play, topology transparent, etc. The responsive link is implemented on the responsive processor and a few kinds of RMT processors for distributed real-time systems. The responsive link is now under standardization at ISO/IEC JTCI SC25.