  We investigate two sets of two-epoched reionization models and their
manifestation in the CMB anisotropy and polarization data of the recent WMAP
project and make some predictions for the future PLANCK missions. In the first
set of models, the universe was reionized twice, first at z~15 by population
III stars and then at z~6 by stars in large galaxies. In the second set of
models, the extra peak-like reionization at high redshifts z > 100 is induced
by the decay of unstable particles, followed by the standard picture of
reionization at z~6. We examine the general properties of these two-epoched
reionization models and their implication in the WMAP CMB temperature
anisotropy-polarization cross-correlation. We have shown that these models have
comparable likelihood values for the WMAP data and distinct characters which
can be tested with the Planck high sensitivities.
