Mutual exclusion in cyber-physical systems

Distributed computing problems such as mutual exclusion have been studied extensively for traditional distributed systems. In traditional systems, a strict layered approach is taken wherein a set of users (application processes) U ₁; ... ;U _n is layered on top of a mutual exclusion algorithm with processes P ₁; ... ;P _n. User Ui interacts with process P _i to request access to resources which are modeled as tokens, and users rely entirely on mutual exclusion algorithm to regulate access to the resources. In a cyber-physical system, users (physical entities) may themselves possess capabilities such as sensing, observing and mobility using which they may also attempt to locate physical resources such as wheelchairs. Thus, a mutual exclusion algorithm in a cyber-physical system must contend with the behavior of users. This paper proposes a graph-based model for cyber-physical systems which is used to describe mutual exclusion algorithm as well as user behavior. Based on this model, we present several solutions for the mutual exclusion problem. We have also conducted an extensive simulation study of our algorithms using OMNeT++ discrete event simulation system.