  We focus our attention on the most common scenario in networked control
systems where the measured output from the observer is transmitted via a
communication channel to the controller. Using information theoretic results,
we studied the tradeoff between the performance and the accuracy of
observations due to communication constraints for such a scenario. We focused
on three important cases in the communication channel, the additive white
Gaussian noise (AWGN), limited data rate and systems with multiplicative
uncertainty in the system parameters. Using known theoretical results for a
rate limited communication channel, we showed the effect of entropy of the
output of quantizer on the control performance. The same was done for the case
of multiplicative uncertainty in the system . For an AWGN channel, we showed
the effect of channel SNR on the performance. For the analog joint source
channel coding approach (which works only for Gaussian disturbances in the
system), we showed that the known lower bound is tight even for non Gaussian
system disturbances. We also compared the simulated performance of a system
with known upper and lower rate distortion bounds for all the three cases. The
lower bound on the rate is closely approached by a simple uniform quantization
scheme, hence demonstrating its tightness.
