Enhancing the end-to-end schedulability condition of EDF scheduling for real-time applications

Earliest deadline first (EDF) schedulers are known to be optimal with respect to achieving delay bounds in the single node case. For a session traversing a multi-node network, applying EDF schedulability condition at each node separately leads to very restrictive admission control policy for delay sensitive applications. Other scheduling disciplines such as PGPS, that take into account the delay dependency in the network, outperform EDF in such situations. We present a heuristic method to enhance the schedulability condition for EDF schedulers as compared to PGPS. The method is based on matching the delay bound obtained by EDF schedulers and PGPS schedulers in a homogeneous network of nodes where all sessions traverse the same number of hops and require the same maximum delay. The method leads to enhancing the performance of the EDF schedulers in a multi-node network. Our simulation results show that the method works well in practice.