The Multipath Estimating Delay Lock Loop - Approaching Theoretical Accuracy Limits

Richard D.J. van Nee and J. Siereveld

Abstract:	It is widely recognized that multipath propagation is the main error source in differential GPS applications. Till now, however, receivers hardly use specific countermea- sures against multipath. Decreasing the early-late spacing like Novatel and Rogue did is a step in the right direction. However, carrier range errors are not reduced at all by this techniques, while the remaining code range errors can still be considerable. This paper demonstrates that it is possible to almost completely eliminate both code and carrier multipath errors by using a specific receiver structure which simul- taneously estimates the parameters of lineof-sight plus multipath signals. The paper provides a brief description ofthetheorybehindthisnew technique,calledtheMultipath Estimating Delay Lock Loop (MEDLL). The MEDLL has been implemented in a prototype GPS receiver. Test results in various practical situations show that code and carrier errors are greatly reduced as com- pared to the errors of a standard GPS receiver, using a small early-late spacing. The MEDLL makes it possible to retain high accuracies, even in highly multipath propa- gating environments. It can therefore greatly facilitate carrier phase ambiguity resolution, since the small code range errors reduce the search volume, while the de- creased carrier range errors make it easier to reject false solutions.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	921 - 921
Cite this article:	van Nee, Richard D.J., Siereveld, J., "The Multipath Estimating Delay Lock Loop - Approaching Theoretical Accuracy Limits," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 921-921.
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