Modeling of GPS code and carrier tracking error in multipath

The code tracking error model of coherent Code tracking loop (CTL) is modified since existing model cannot accurately describe the characteristic that the code tracking error is determined by multipath and correlator spacing in multipath. The noncoherent DOT-product (DOT) power mode CTL is established as a comparison with different CTLs in multipath. Besides, the carrier tracking error model is modified based on the established code tracking error models, which indicates that the carrier tracking error is also determined by the multipath and the correlator spacing. The presented error models indicate that the correlation between the code tracking error and carrier tracking error can be decorrelated. Theoretical analysis shows that the noncoherent DOT power mode CTL is essentially coherent when the discriminator output of carrier tracking loop is zero. The influence of multipath and correlator spacing on CTL and carrier tracking loop is analyzed by simulations.