  Radio channels are typically sparse in the delay domain, and ideal for
compressed sensing. A new compressed sensing algorithm called eX-OMP is
developed that yields performance similar to that of the optimal MMSE
estimator. The new algorithm relies on a small amount additional data. Both
eX-OMP and the MMSE estimator adaptively balance channel tracking and noise
reduction. They perform better than simple estimators such as the
linear-interpolator which fix this trade-off a priori. Some wideband
measurements are examined, and the channels are found to be represented by a
few delays.
