RATAD - Reliability and Timing Analysis of Distributed systems



Reliability and Timing Analysis of Distributed systems. --- Traditionally, real-time scheduling theory has targeted hard real-timesystems which are, most of the time, safety critical. Typically, thesesystems can be found as small embedded applications, operated in acontrolled environment. Since these systems are not allowed to have any flaws (in the sence of timliness), analysis thechniques need to be precise. Having precise methods, taking all possible scenarios of execution combinations and execution times into consideration, the analysis becomes very pessimistic which calls for more expensive applications in terms of resources and hardware. However, today moreand more applications have real-time demands, although not assafety-critical as traditional real-time systems, e.g. audio and video transmissions. These new applications open the door to loosen up a bit, thus allowing some deadline misses every now and then. We call this controlled optimism. By using distributions of values instead of worst-case values, designers are given more freedom in terms of arguments for making well founded trade-offs when designing anapplication. We define this as the first problem. Moreover, traditionally scheduling paradigms can be divided into 3 different groups: (1) PRIORITY DRIVEN, (2) TIME DRIVEN, and (3) SHARE DRIVEN. For the Controller Area Network, priority driven scheduling is the natural scheduling method supportedby the CAN protocol, and scheduling analysis methods have been presented. Regarding time driven sceduling, methods have also been implemented. One of those methods also supports priority driven scheduling in combination with time driven scheduling. However, yet so far, share driven scheduling has notbeen implemented. By providing the option of share driven scheduling of the CAN we believe that designers are given more freedom in designing an application. This is our second problem. Therefore, the problems that we try to solve are described in two parts: (1) Probabilistic modelling of thebit-stuffing mechanism of the Controller Area Network (CAN), and (2)Server based scheduling of CAN.

Hans Hansson, Professor

Email: hans.hansson@mdh.se
Room: U1-063
Phone: +46 21 103163