Optimal controller location in wireless sensor and actuator networks

In wireless sensor and actuator networks (WSAN), both sensory measurements and control signals transmitted through the wireless media are prone to packet losses. Moreover, the distance between the sender and receiver is a critical factor for the loss rate. Therefore, where to place the controller to ensure optimal control performance is an interesting problem. In this paper, we focus on WSAN with one sensor and one actuator residing at different geographic locations. If the controller is constrained at either the sensor side or actuator side, we derive the necessary and sufficient conditions under which the optimal controller location can be directly determined. For the more general case when the controller can be placed anywhere, with mild assumptions on the packet drop model, we also provide the conditions under which the optimal controller location is unique and can be determined. Numerical simulations based on a practical packet loss model verify our results.