On the Performance Limits of Pilot-Based Estimation of Bandlimited   Frequency-Selective Communication Channels
  In this paper the problem of assessing bounds on the accuracy of pilot-based estimation of a bandlimited frequency selective communication channel is tackled. Mean square error is taken as a figure of merit in channel estimation and a tapped-delay line model is adopted to represent a continuous time channel via a finite number of unknown parameters. This allows to derive some properties of optimal waveforms for channel sounding and closed form Cramer-Rao bounds. 
Francesco Montorsi, Giorgio M. Vitetta
cs.IT cs.NI math.IT