Impact of a controlled GNSS Receiver Clock on GNSS Performance

Jens Henzler, Carsten Butzmühlen, Holger Krag

Abstract:	Safety critical applications place the highest requirements for accuracy, integrity, availability and continuity of serv-ice on the Global Navigation Satellite Systems (GNSS). Several integrity monitoring algorithms have been pub-lished to detect a failure and identify its source. In this way the faulty signal can be excluded from the position deter-mination algorithm in order to maintain availability and continuity of service. All these algorithms make use of the so called pseudoranges which are depending on the signal reception time. This point in time is determined by means of a local oscillator. However, many GNSS receivers are equipped with control loops that influence this oscillator in order to reduce the clock offset versus GNSS time by feeding back the clock offset that is being determined in the position solution. In the case of a satellite signal failure this feedback causes the failure to couple into the meas-urements of all other signals, which entails an additional blurring effect of the failure. The pseudorange residuals are influenced by this effect as well, which certainly has an impact on the integrity algorithms. This paper explains the interaction of receive time deter-mination and receiver clock control. A test environment will be described that allows the analysis of the mentioned effects for different failure scenarios. In this context the influence of the different parameters of the test environ-ment are pointed out. Furthermore the impact of the de-scribed effect on integrity monitoring algorithms is inves-tigated. This investigation gives information in how far a receiver clock control affects the performance of integrity monitoring algorithms.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1655 - 1663
Cite this article:	Henzler, Jens, Butzmühlen, Carsten, Krag, Holger, "Impact of a controlled GNSS Receiver Clock on GNSS Performance," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1655-1663.
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