Experimental result of standard time and frequency signal (STFS) dissemination system via GEO-satellite is described in this paper. We propose the differential mode STFS as the most effective calibration technique for mitigating errors in GEO-satellite based STFS dissemination system. We then use trilateration technique associated with extended Kalman filtering (EKF) to further improve the accuracy of differential mode STFS by improving the accuracy of predicted satellite position. It is found to be possible to track Korean domestic satellite KOREASAT within a few hundred meters accuracy in order to provide a reliable, extremely accurate time service through setting up domestic-only baseline. Our simulation results show that a time accuracy is a few ns and a frequency stability is better than 1 part in $10^14 for an averaging time of 7 days all over Korean peninsula.