Fidelity-Aware Utilization Control for Cyber-Physical Surveillance Systems

Recent years have seen the growing deployments of Cyber-Physical Systems (CPSs) in many mission-critical applications such as security, civil infrastructure, and transportation. These applications often impose stringent requirements on system sensing fidelity and timeliness. However, existing approaches treat these two concerns in isolation and hence are not suitable for CPSs where system fidelity and timeliness are dependent of each other because of the tight integration of computational and physical resources. In this paper, we propose a holistic approach called Fidelity-Aware Utilization Controller (FAUC) for Wireless Cyber-physical Surveillance (WCS) systems that combine low-end sensors with cameras for large-scale ad hoc surveillance in unplanned environments. By integrating data fusion with feedback control, FAUC can enforce a CPU utilization upper bound to ensure the system's real-time schedulability although CPU workloads vary significantly at runtime because of stochastic detection results. At the same time, FAUC optimizes system fidelity and adjusts the control objective of CPU utilization adaptively in the presence of variations of target/noise characteristics. We have implemented FAUC on a small-scale WCS testbed consisting of TelosB/Iris motes and cameras. Our extensive experiments on light and acoustic target detection show that FAUC can achieve robust fidelity and real-time guarantees in dynamic environments.

1 Introduction

Cyber-Physical System (CPS) is a new class of embedded systems that tightly integrate computational and physical resources. Recent years have seen the growing deployments of CPSs in many mission-critical applications such as security, civil infrastructure, and transportation. These applications often impose stringent performance requirements including sensing fidelity and timeliness. In this work, we define fidelity as a system's capability of reaching correct conclusions even when the sensing results from the dynamic physical environment are noisy. In addition to fidelity, timeliness is another fundamental requirement as many computational tasks in a CPS must complete within tight deadlines in order to avoid undesirable or even catastrophic consequences.