Assessment of Time Synchronization Error using Different GNSS Clock Products

Precise time synchronization using Global Positioning System (GPS) has been widely applied in various civil technologies, such as bank transactions, internet communication, and power grid management. Different applications require varying levels of time synchronization accuracy. This study assesses the time synchronization using the so-called precise point positioning (PPP) technique with Taiwan Radio Occultation Process System (TROPS), International GNSS Service (IGS), and Broadcast ephemeris (BRDC) orbit and clock products for a station (TLT1) located in the Telecommunication Laboratories at Chunghwa Telecom. We employ the smoothed code together with carrier phase to perform the time synchronization with the clock onboard GPS satellite. The Allan Deviation is used to assess the clock frequency stability performance. In the short term, at an average time of 30s, the IGS-derived and the TROPS-derived stability reaches 8.74×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup> and 8.96×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup>, equivalent to ~0.7 and ~0.8 cm error in range, respectively. The difference in short-term stability between IGS and TROPS is insignificant. In contrast, the BRDC-derived stability is 9.28×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup>, leading to 83.5 cm error in range. This indicates that the BRDC-derived time solution may not meet the real-time precise timing applications. For long-term stability, at an average time of 3000s, the IGS-derived, TROPS-derived and BRDC-derived stability reaches 2.00×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-14</sup>, 6.12×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-14</sup> and 1.68×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup>, respectively. This suggests that the trend of the timing solution among the three products is consistent. This work demonstrates that the TROPS product can be used for the precise timing application in real-time.