Terminal QoS of adaptive applications
Pratyush Moghé, Asawaree Kalavade · Bell Labs Technical Journal · 2002
An intensive effort is under way to support networked multimedia applications on slim hosts or terminals such as personal digital assistants (PDAs) and set-top boxes. In addition to their limited processing capabilities, these terminals may use limited network bandwidth conditions — for example, wireless links. One way to implement multimedia applications on terminals is to make them adaptive. Such applications can then use bandwidth availability in the network as feedback to adapt their output packet rate. This manages the bandwidth scarcity by preventing the network congestion from worsening beyond a point. However, such an implementation imposes unique challenges. Simple task-level processing variations in audio/video applications can seriously overload a terminal. Adaptive applications impose even more variability. Consequently, the processing delay of applications can become unpredictable. We classify processing delay as a terminal quality of service (QoS) measure since it determines the overall perceptual quality of applications. We design a framework that can quantify the terminal QoS through the processing delay distribution. Our framework is broad enough to be used across several applications, terminal system architectures, and run-time schedulers. At Bell Labs, we have implemented the framework in a tool called AsaP. Its output can be used to design adaptive applications, application managers, and both software and architecture support for terminals and other networked embedded systems.