Detecting relic gravitational waves in the CMB: Comparison of different
  methods
  In this paper, we discuss the constraint on the relic gravitational waves by
both temperature and polarization anisotropies power spectra of cosmic
microwave background radiation. Taking into account the instrumental noises of
Planck satellite, we calculate the signal-to-noise ratio $S/N$ by the
simulation and the analytic approximation methods. We find that, comparing with
the $BB$ channel, the value of $S/N$ is much improved in the case where all the
power spectra, $TT$, $TE$, $EE$ and $BB$, are considered. If the noise power
spectra of Planck satellite increase for some reasons, the value of $S/N$ in
$BB$ channel is much reduced. However, in the latter case where all the power
spectra of cosmic microwave background radiation are considered, the value of
$S/N$ is less influenced. We also find that the free parameters $A_s$, $n_s$
and $n_t$ have little influence on the value of $S/N$ in both cases.
