An Algorithm to Avoid Power Command Jitter in Middleware-Based Distributed Embedded Systems

Middleware such as CORBA provides a software architecture that supports integration of legacy software components with new software in a way that is modular, scalable, and evolvable. However, these benefits come with high run-time overhead. In dynamic hard realtime distributed embedded systems, usually a central power manager calculates and issues all the power commands. The power manager must communicate with different modules to transparently perform mode transitions. Due to inherent communication overhead of middleware based embedded systems, issuing each power command will have considerable overhead for the power manager. This overhead limits the rate of issuing power commands and may cause a shift in their schedule. This paper has two contributions; first, it introduces the Power Command Jitter (PCJ) problem in middleware based embedded systems; second, it proposes an effective Power Command Adjustment algorithm (PCA) that re-orders and reschedules the power commands so that the correctness of the schedule is maintained while minimizing the energy loss. Our experimental results on a commercial software defined radio system (JTRS) shows PCJ can cause violation of real-time deadlines and unreliability of the system. Moreover, in presence of power command issue overhead, even as low as 3ms, the power manager can lose 25% of its energy savings.