I. Introduction
In the past decade, networked control systems have gained attention from both the control community and the network and communication community. When compared with classical feedback control systems, networked control systems have several advantages. For example, they can reduce the system wiring, make the system easy to operate, maintain and diagnose, and increase system agility. Although networked control systems have advantages, inserting a network in between the plant and the controller can introduce many problems as well. For example, in communication networks, data packets that carry the information can be dropped, delayed or even reordered due to the network traffic conditions. When closing the control loop over such communication networks, the overall system might have poor performance or even become unstable when the aforementioned issues exist. Thus the effect that those issues have on the closed loop system performance must be fully analyzed before networked control systems become commonplace.