Technical Report Number
Real-time image transmission is crucial to an emerging class of distributed embedded systems operating in open network environments. Examples include avionics mission re-planning over Link-16, security systems based on wireless camera networks, and online collaboration using camera phones. Meeting image transmission deadlines is a key chal-lenge in such systems due to unpredictable network condi-tions. In this paper, we present the design, modeling, and analysis of CAMRIT, a Control-based Adaptive Middleware framework for Real-time Image Transmission in distributed real-time embedded systems. CAMRIT features a distributed feedback control loop that meets image transmission dead-lines by dynamically adjusting the quality of image tiles. We derive an analytic model that captures the dynamics of a moderately distributed middleware architecture. A control theoretic methodology is applied to systematically design a control algorithm with analytic assurance of system stability and performance, despite signiﬁcant uncertainties in network bandwidth. CAMRIT has been successfully implemented as middleware service on top of the TAO real-time CORBA ORB. Experimental results demonstrate that CAMRIT can provide robust real-time guarantees under varying bandwidth for a representative application scenario.
Wang, Xiaorui; Huang, Huang-Ming; Subramonian, Venkita; Lu, Chenyang; and Gill, Christopher, "CAMRIT: Control-based Adaptive Middleware for Real-time Image Transmission" Report Number: WUCSE-2004-4 (2004). All Computer Science and Engineering Research.