The BICEP2 collaboration reports a detection of primordial cosmic microwave background ( CMB ) B-mode with a tensor-scalar ratio r = 0.20 ^ { +0.07 } _ { -0.05 } ( 68 % C.L . ) .
However , this result has a tension with the recent Planck limit , r < 0.11 ( 95 % C.L .
) , on constraining inflation models .
In this Letter we consider an inflationary cosmology with a preceding nonsingular bounce which gives rise to observable signatures on primordial perturbations .
One interesting phenomenon is that both the primordial scalar and tensor modes can have a step feature on their power spectra , which nicely cancels the tensor excess power on the CMB temperature power spectrum .
By performing a global analysis , we obtain the 68 % C.L .
constraints on the parameters of the model from the Planck+WP and BICEP2 data together : the jump scale \log _ { 10 } ( k _ { B } / { Mpc } ^ { -1 } ) = -2.4 \pm 0.2 and the spectrum amplitude ratio of bounce-to-inflation r _ { B } \equiv P _ { m } / A _ { s } = 0.71 \pm 0.09 .
Our result reveals that the bounce inflation scenario can simultaneously explain the Planck and BICEP2 observations better than the standard \Lambda CDM model , and can be verified by the future CMB polarization measurements .