  The results of a full simulation of an endcap Time-of-Flight detector upgrade
based on multigap resistive plate chambers for the BESIII experiment are
presented. The simulation and reconstruction software is based on Geant4 and
has been implemented into the BESIII Offline Software System. The results of
the simulations are compared with beam test results and it is shown that a
total time resolution $\sigma$ of about 80 ps can be achieved allowing for a
pion and kaon separation up to momenta of 1.4 GeV/c at a 95% confidence level.
