  We forecast the cosmological constraints of the neutral hydrogen (HI)
intensity mapping (IM) technique with radio telescopes by assuming 1-year of
observational time. The current and future radio telescopes we consider here
are FAST (Five hundred meter Aperture Spherical Telescope), BINGO (Baryon
acoustic oscillations In Neutral Gas Observations), and SKA-I (Square Kilometre
Array phase I) single-dish experiment. We also forecast the combined
constraints of the three radio telescopes with Planck. We find that, the $1
\sigma$ errors of $(w_{0}, w_{a})$ for BINGO, FAST and SKA-I with respect to
the fiducial values are respectively, $(0.9293, 3.5792), (0.4083, 1.5878),
(0.3158, 0.4622)$. This is equivalent to $(56.04\%, 55.64\%)$ and $(66.02\%,
87.09\%)$ improvements in constraining $(w_{0}, w_{a})$ for FAST and SKA-I
relative to BINGO. Simulations further show that SKA-I will put more stringent
constraints than both FAST and BINGO when each of the experiment is combined
with Planck measurement. For the $9$ cosmological parameters in consideration,
we find that, there is a trade-off between SKA-I and FAST in constraining
cosmological parameters, with each experiment being more superior in
constraining a particular set of parameters.
