Code Tracking Bias Compensation Scheme for the Galileo E1 OS signal

Galileo system uses direct sequence/spread spectrum (DS/SS) as its modulation method. Single delta delay lock loop (Δ-DLL), where Δ is sample duration between early and late correlation values, has been widely used for code tracking in DS/SS systems. When the Δ-DLL is used for code tracking in ideal environments, code tracking bias does not arise because the symmetry of the correlation function is not destroyed. However, in multipath (MP) environments, a large code tracking bias arises owing to the asymmetrical correlation function. An MP signal always has a propagation delay time after that of the line of sight signal. Thus, correlation values in the advanced offset region are less distorted than those in the delay offset region. From this observation, we propose an effective tracking bias compensation scheme for the Galileo E1 open service signal.