Wireless Communication Tradeoffs in Distributed Control

We present a framework to study control systems with feedback loops closed over wireless communication links. We show the choice of communication parameters can greatly affect the performance of such systems. The trade-offs of data rate, time delay and packet loss in the communication link layer design are illustrated with a numerical example of an inverted pendulum. Packet loss is shown to signi£cantly degrade performance, which is not surprising since the controller design does not take into account random packet losses in the feedback loop. We thus propose an analog soft-decoding communication link design that does not incur any packet losses. It is shown that, for low channel gains, the control system closed over a soft-decoding communication link performs better than the same system closed over a hard-decoding communication link with optimal selection of sample period and data rate. This suggests fundamental changes in wireless link designs may be necessary to support robust distributed control systems.