A Novel Code Tracking Scheme using Correlation Outputs in Advanced Offset Region for GALILEO L1 Open Service

The single delta delay lock loop is the most widely used code tracking scheme for the GALILEO system that employs the binary offset carrier modulated spreading signal. When only a line-of-sight signal is received, the single delta delay lock loop is the optimal code tracking scheme. However, when the multipath signals are received, the correlation values are distorted, and thus, the tracking bias arises, which is defined as the difference between correct and estimated synchronization points. To tackle this problem, many tracking schemes have been proposed, e.g. narrow correlator DLL, high resolution correlator DLL, and so on. These schemes use the correlation values nearby the offset of the peak correlation values. However, the coherent auto-correlation function of the binary offset carrier modulated spreading signal has additionally two locally minimum correlation values whose offsets are plusmnT_c /2 , respectively, where T_c is the chip duration. In multipath environments, the correlation values nearby the locally minimum correlation value are less distorted compared with those nearby the one whose offset is plusmnT_c /2 . From this observation, we propose a novel tracking scheme, and then, its tracking accuracy is assessed using Monte-Carlo simulation.