  We discuss measurability of phi, omega and rho mesons via di-electron decays
in high-temperature states produced in heavy-ion collisions, equivalently at
different pion multiplicities per heavy-ion collision dN_{pi^{0} + pi^{+-}}/dy
= 1000 and 2700 intended for the most central Au+Au collisions at sqrt(s_{NN})
= 200 GeV (RHIC) and the most central Pb+Pb collisions at sqrt(s_{NN}) = 5.5
TeV (LHC), by evaluating the signal-to-background ratios and the statistical
significance for the idealized detection system in the numerical simulation.
The simulation study provides a guideline to be applicable to a concrete
detector design by focusing on only the key experimental issues relevant to the
measurement of di-electrons. The results suggest that there are realizable
parameter ranges to measure light vector mesons via di-electrons with the
reasonable significance level, even in the highest multiplicity case.
