QoS negotiation in real-time systems and its application to automated flight control

We propose a model for quality-of-service (QoS) negotiation in building real-time services to meet both predictability and graceful degradation requirements. QoS negotiation is shown to (i) outperform conventional "binary" admission control schemes (either guaranteeing the required QoS or rejecting the service request), and (ii) achieve higher application-perceived system utility. We incorporated the proposed QoS-negotiation model into an example real-time middleware service, called RTPOOL, which manages a distributed pool of shared computing resources (processors) to guarantee timeliness QoS for real-time applications. The efficacy and power of QoS negotiation are demonstrated for an automated flight control system implemented on a network of PCs running RT-POOL. This system is used to fly an F-16 fighter aircraft modeled using the Aerial Combat (ACM) F-16 Flight Simulator. Experimental results indicate that QoS negotiation, while maintaining real-time guarantees, enables graceful QoS degradation under conditions in which traditional schedulability analysis and admission control schemes fail.