ML timing estimation for generalized UWB-IR energy detection receivers

Timing estimation of the receive pulse is a crucial component for communication systems as well as localization with ultra wideband impulse radio. Standard timing estimation algorithms might not be applicable due to stringent requirements on complexity and power consumption of the receiver. Therefore, we consider maximum likelihood timing estimation at the output of a generalized energy detection receiver, that consists of a squaring device followed by an arbitrary post-detection filter and low rate sampler. Moreover, we assume only the statistics of the channel to be known at the receiver. To the best of our knowledge, this problem has not been treated so far in this generalized set up. Known approaches for specific post-detection filters rely on a Gaussian approximation of the detector output. We show that the estimation accuracy can be improved by using the exact marginal PDF of the energy detector output. This is verified by channel model and measurements. Towards reduced complexity, we approximate the ED detector output as multivariate normally or multivariate log-normally distributed. Verification based on channel model and measured channels favors the log-normal approximation and shows that the correlation is not relevant. Accuracy down to centimeter precision can be reached.