Peak Tracking Algorithm for Galileo-Based Positioning in Multipath Fading Channels

Line-of-sight (LOS) delay estimation with high accuracy is a pre-requisite for reliable location via satellite systems. The future European satellite positioning system, Galileo, uses spread-spectrum signals modulated via binary-offset-carrier (BOC) modulation. The receiver for a BOC-modulated spread spectrum signal has to cope not only with multipath effects, but also with possible lost of lock due to additional peaks in the envelope of the correlation function. Traditionally, code tracking is implemented at the receiver side via feedback delay locked loops. Feedforward methods have also been presented as alternatives for increased delay estimation accuracy, especially for short-delay multipaths. The increase in the delay estimation accuracy is typically counter-balanced by a faster mean time to lose lock (MTLL). In this paper we introduce a new algorithm, namely the peak tracking (PT) algorithm, which combines the feedback technique with the feedforward technique, in such a way that it increases the delay estimation accuracy while preserving a good MTLL.