Extending schedulability tests of tree-shaped transactions for TDMA radio protocols

In this paper, a schedulability test is proposed for tree-shaped transactions with non-immediate tasks. A tree-shaped transaction is a group of precedence dependent tasks, partitioned on different processors, which may release several other tasks upon completion. When there are non-immediate tasks, tasks are not necessarily released immediately upon their predecessor´s completion. The schedulability test we propose is based on an existing test that does not handle non-immediate tasks directly. Simulation results show that tighter response time upper-bounds can be accessed when effects of non-immediateness are considered. Our schedulability test is motivated by real industrial TDMA systems developed at Thales, and experimental results show it provides less pessimistic schedulability results compared to current methods used by Thales system engineers.