I. Introduction
The Industrial Internet of Things (IIoT), also known as Industry 4.0, has been widely considered for a variety of industry and manufacturing systems [1], [2]. In IIoT systems, massive numbers of smart sensing and actuating devices are deployed and interconnected to enable efficient and intelligent monitoring and control of systems. As smart sensing devices are deployed to monitor things/objects in the system, massive amounts of data will be collected. By analyzing collected data, the states and operational conditions of systems can be accurately estimated so that efficient monitoring and control of IIoT systems can be realized.