On using transmission overhead efficiently for channel estimation in OFDM

The limited time available for acquiring the channel state in mobile broadband wireless communication systems makes it crucial to count with channel estimation methods that attain the highest accuracy with a given preamble length. For the family of preambles that probe channels repeatedly at equispaced frequencies, we find that the shortest preamble that attains a given mean square error is a sequence that undersamples the channel spectrum, thereby allowing for a better mitigation of white Gaussian noise by averaging a higher number of observations.