Reducing jitter in embedded systems employing a time-triggered software architecture and dynamic voltage scaling

• Main Author: Phatrapornnant, Teera
• Published: University of Leicester 2007
• Subjects: 621.381
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.697372

Following a review of previous work in this area, a presentation is made which illustrates the impact of a naive application of DVS in a system incorporating a time-triggered co-operative (TTC) scheduler. Novel algorithms (TTC-jDVS, TTC-jDVS2) and then introduced which more successfully integrate TTC and DVS techniques. These algorithms involve: (i) changes to system timer settings when the frequency is altered; (ii) use of a form of 'sandwich delay' to reduce the impact of changes to the scheduler overhead which arise as a result of frequency changes, and (iii) execution of jitter-sensitive tasks at a fixed operating frequency. The impact of these algorithms on both jitter and energy consumption is illustrated empirically on a representative hardware platform, using both 'dummy' task sets and a more realistic case study. In designs for which low jitter is an important consideration, at least a limited degree of task pre-emption may be required. A simple time-triggered hybrid (TTH) scheduler can be used to achieve such behaviour. A novel TTH secluding algorithm (TTH-jDVS) is presented and evaluated, again through use of dummy task sets and a case study. The third piece of experimental work presented in this thesis illustrates that --- in situations where minimal jitter is required --- hardware support is required. To illustrate the potential of such an approach a final case study is employed.