Performance comparison of multipath detection using early late phase in BPSK and BOC modulated signals

Abstract

Global navigation satellite systems are spread spectrum systems and modulation schemes used in them can be divided into two types; BPSK and BOC. This paper presents comparison of early late phase (ELP) parameter for multipath detection in BPSK and BOC(1,1) signals. ELP was recently proposed for multipath detection in GPS BPSK signals exploiting carrier phase difference between the line of sight and reflected signals. It has been shown in this paper that ELP can also be used for multipath detection in BOC(1,1) signals. In fact, in BOC(1,1) signals ELP has improved performance since for a given multipath, increase in ELP magnitude is higher in a BOC(1,1) signal as compared to a BPSK signal. Magnitude of increase in ELP for various multipath conditions at varying correlators spacing has also been compared for BPSK and BOC(1,1) signals. It has been found that in BPSK signals, ELP magnitude continually increases with increasing correlator spacing, whereas in BOC(1,1) signal it increases up to a point and then reduces. Maximum ELP is generally obtained for correlators spacing between 0.3 and 0.4 chips, depending on multipath parameters.