The modernized GPS, Galileo, and BeiDou global navigation satellite system (BDS3) offers new potential for time transfer using overlap-frequency (L1/E1/B1, L5/E5a/B2a) observations. To assess the performance of frequency with observations BDS3, mathematical models single- dual-frequency carrier-phase (CP) technique are discussed presented. For single-frequency CP model, three-day average RMS va...