  The sparsity of multipaths in wideband channel has motivated the use of
compressed sensing for channel estimation. In this letter, we propose an
entirely different approach to sparse channel estimation. We exploit the fact
that $L$ taps of channel impulse response in time domain constitute a
non-orthogonal superposition of $L$ geometric sequences in frequency domain.
This converts the channel estimation problem into the extraction of the
parameters of geometric sequences. Notably, the proposed scheme achieves the
error-free estimation of the whole bandwidth with a few pilot symbols if the
excess delay is bounded to a certain value.
