A best-effort communication protocol for real-time broadcast networks

Abstract

In this paper, we present a best-effort communication protocol, called ABA, that seeks to maximize aggregate application benefit and deadline-satisfied ratio of asynchronous real-time distributed systems that use CSMA/DDCR broadcast networks. ABA considers an application model where end-to-end timeliness requirements of trans-node application tasks are expressed using Jensen's benefit functions. Furthermore, the protocol assumes that the application is designed using CSMA/DDCR feasibility conditions that is driven by a "best" possible estimate of upper bounds on message arrival densities that is possible at design-time. When such design-time postulations get violated at run-time, ABA directs message traffic so that messages that will increase applications' aggregate benefit are only transmitted, buffering others, until such time when the workloads respect their design-time postulated values. To study the performance of ABA, we consider a previously studied algorithm called RBA* as a baseline algorithm. Our experimental results indicate that ABA yields higher aggregate benefit and higher deadline-satisfied ratio than RBA* when message arrival densities increase at faster rates or at the same rates as that of process execution latencies due to the dynamics of the workload.