  In this paper we describe a method of luminosity measurement at the future
linear collider ILC that estimates and corrects for the impact of the dominant
sources of systematic uncertainty originating from the beam-induced effects and
the background from physics processes. Based on the relativistic kinematics of
the collision frame of the Bhabha process, the beam-beam related uncertainty is
reduced to a permille independently of the precision with which the beam
parameters are known. With the specific event selection, different from the
isolation cuts based on topology of the signal used at LEP, combined with the
corrective methods we introduce, the overall systematic uncertainty in the peak
region above 80% of the nominal center-of-mass energy meets the physics
requirements to be at the few permille level at all ILC energies.
