Robust and Cost-Effective Design of Cyber-Physical Systems: An Optimal Middleware Deployment Approach

Cyber-Physical Systems (CPS) are emerging as the underpinning technology for major industries in this century. Wide-area monitoring and control is an essential ingredient of CPS to ensure reliability and security. Traditionally, a hierarchical system has been used to monitor and control remote devices deployed in a large geographical region. However, a general consensus is that such a hierarchical system can be highly vulnerable to component (i.e., nodes and links) failures, calling for a robust and cost-effective communication system for CPS. To this end, we consider a middleware approach to leverage the existing commercial communication infrastructure (e.g., Internet and cellular networks) with abundant connectivity. In this approach, a natural question is how to use the middleware to cohesively "glue" the physical system and the commercial communication infrastructure together, in order to enhance robustness and cost-effectiveness. We tackle this problem while taking into consideration two different cases of middleware deployment: single-stage and multi-stage deployments. We design offline and online algorithms for these two cases, respectively. We show that the offline algorithm achieves the best possible approximation ratio while the online algorithm attains the order-optimal competitive ratio. We also demonstrate the performance of our proposed algorithms through simulations.