The advent of assisted GPS/GNSS can reduce the time to first fix (TTFF) dramatically and still provide sufficient positioning accuracy. However, many applications utilize GNSS for timing and assisted GPS/GNSS does not always provide the accurate nanosecond synchronization. Accurate timing is challenging for assisted GNSS due to the lack of diversity in the solution over short time periods. The relatively short ambiguities of the GPS L1 C/A code signal, one millisecond and twenty milliseconds, are too coarse to resolve accurate time reliably. In this paper, the impact of different ambiguity times has been derived/computed and validated. Experimental results show that when the ambiguity time is 200 milliseconds or longer, the least squares process will reliably converge and the typical nanosecond‐level timing can be achieved. An example shows how the GPS L1 C/A data parity word (provided every 600 milliseconds) can be used, demonstrating nanosecond‐level timing from assisted GPS.

中文翻译：

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使用扩展的歧义度解析度从辅助GNSS得出准确的时间

辅助GPS / GNSS的出现可以大大减少首次定位（TTFF）的时间，并且仍然提供足够的定位精度。但是，许多应用程序利用GNSS进行计时，辅助GPS / GNSS并不总是提供准确的纳秒同步。由于解决方案在短时间内缺乏多样性，因此对于辅助GNSS而言，准确的定时具有挑战性。GPS L1 C / A代码信号的相对较短的模糊度（分别为1毫秒和20毫秒）太粗糙而无法可靠地解析准确的时间。在本文中，已经得出/计算并验证了不同歧义时间的影响。实验结果表明，当歧义时间为200毫秒或更长时，最小二乘过程将可靠地收敛，并且可以实现典型的纳秒级时序。