  We address the perturbation power spectrum generated in the recently proposed
ekpyrotic scenario by Khoury et al. The issue has been raised recently by Lyth
who used the conventional method based on a conserved variable in the
large-scale limit, and derived different results from Khoury et al. The
calculation is straightforward in the uniform-curvature gauge where the
generated blue spectrum with suppressed amplitude survives as the final
spectrum. Whereas, although the metric fluctuations become unimportant and a
scale-invariant spectrum is generated in the zero-shear gauge the mode does not
survive the bounce, thus with the same final result. Therefore, an exponential
potential leads to a power-law expansion/contraction $a \propto |t|^p$, and the
power $p$ dictates the final power spectra of both the scalar and tensor
structures. If $p \ll 1$ as one realization of the ekpyrotic scenario suggests,
the results are $n_S -1 \simeq 2 \simeq n_T$ and the amplitude of the scalar
perturbation is suppressed relative to the one of the gravitational wave by a
factor $\sqrt{p}/2$. Both results confirm Lyth's. An observation is made on the
constraint on the dynamics of the seed generating stage from the requirement of
scale-invariant spectrum.
