CPS: Synergy: Resilient Wireless Sensor-Actuator Networks

1. Introduction: Wireless sensor-actuator networks (WSAN) are cyber-physical systems (CPS) consisting of numerous sensing and actuation devices sharing information over a wireless communication network. This project studies resilient WSANs where " resilience " means that the system maintains an awareness of surrounding threats while taking actions assuring a return to operational normalcy as quickly as possible. Building resilient WSANs is challenging due to the time-varying nature of these networks. Temporal variations in a network's quality-of-service introduce an unpredictability that appears to be inconsistent with resilience. Appearances, however, can be deceiving. Wireless networking is evolving rapidly with technologies such as IEEE 802.11n and 3GPP LTE pushing bit/rates from 10 5 bps to 10 8 bps. Moreover, recent results determining the minimum bit-rates for control stability suggest that the actual bandwidth needed for resilience is much less than previously believed. We therefore have two trends, higher achievable bit-rates from wireless technologies and lower required bit-rates for control. Exploiting these two trends will enhance our ability to achieve resilience in large-scale complex WSANs. We propose exploting these two trends through a three part effort. The first part involves the development of a hierarchical control architecture based on a sporadic " event-triggered " message passing framework in which sensors and actuators only exchange information when needed. This approach allows us to greatly reduce the peak and average bit rates required for stabilization and resilience. The second part of this project develops wireless networking technologies to support the sporadic bursty traffic generated by our controllers. This work will leverage an emerging paradigm for networking wireless devices known as machine-to-machine (M2M) communication. The third part of this project evaluates the resilience achievable with our approach using a robotic testbed consisting of unmanned ground vehicles (UGV) and air vehicles (UAV) that communicate using a USB dongle employing M2M wireless networking technologies. CPS Relevance: This effort addresses the problem of resilience in CPS. The physical component of our CPS is a multi-robot swarm and the cyber component is the M2M wireless network. The effort addresses the CPS Research Target area Science of CPS through its development of fundamental information theoretic limits and practical approaches for resilient control. It addresses the CPS Research Target area Engineering of CPS with its development of M2M technologies and layered event-triggered architectures for resilient control. The project's synergy comes from its combination of scalable methods in three distinct areas: control, communication, and computer …