  Following an elegant approach that merge the effects of the stringy spacetime
uncertainty relation into primordial perturbations suggested by Brandenberger
and Ho, we show the mode equation up to the first order of non-commutative
parameter.
  A new approximation is provided to calculate the mode functions analytically
in the non-commutative power-law inflation models.
  It turns out that non-commutativity of spacetime can provide small
corrections to the power spectrum of primordial fluctuations as the first-year
results of WMAP indicate. Moreover, using the WMAP data, we obtain the value of
expansion parameter, non-commutative parameter and find the approximation is
viable. In addition, we determined the string scale $l_s \simeq 2.0\times
10^{-29}{cm}$.
