  Ultraviolet (UV) and X-ray photons from active galactic nuclei (AGNs) can
ionize hydrogen in the intergalactic medium (IGM). We solve radiative transfer
around AGNs in high redshift to evaluate the 21-cm line emission from the
neutral hydrogen in the IGM and obtain the radial profile of the brightness
temperature in the epoch of reionization. The ionization profile extends over
10 [Mpc] comoving distance which can be observed in the order of 10 [arcmin].
From estimation of the radio galaxy number counts with high sensitivity
observation through the Square Kilometre Array (SKA), we investigate the
capability of parameter constrains for AGN luminosity function with Fisher
analysis for three evolution model through cosmic time. We find that the errors
for each parameter are restricted to a few percent when AGNs are sufficiently
bright at high redshifts. We also investigate the possibility of further
parameter constraints with future observation beyond the era of SKA.
