Real-Time Finite-Rate Tracking: Performance Limitations

In this paper, we consider a set up in which the plant and controller are local to each other, but are together driven by a remote reference signal that is transmitted through a finite-rate noiseless channel. When control must be done over a communication channel, there is a fundamental tradeoff between allowing enough time for reconstruction of signals over the channel and achieving performance in finite-time. Most work in the area of control under communication constraints have addressed infinite- horizon control objectives (eg. stability, disturbance rejection). In this paper, we compute lower and upper bounds on worst-case performance for a finite-horizon tracking objective. We achieve the lower bound with a noncausal coding scheme and show how imposing causality on the coding scheme severely limits achievable performance. We illustrate how the bounds behave under various scenarios and show tradeoffs between time and performance accuracy.