Document Type

Technical Report

Publication Date

2004-01-26

Filename

wucse-2004-4.pdf

Technical Report Number

WUCSE-2004-4

Abstract

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.

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Permanent URL: http://dx.doi.org/10.7936/K75719C7

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