Unambiguous combined correlation functions for sine-BOC signal tracking

Abstract

Binary offset carrier (BOC) modulated signal has been widely employed in modern global navigation satellite system (GNSS). However, the multiple peaks auto-correlation function of BOC signal leads to tracking ambiguity problem. For high-order BOC signal, the above problem becomes more severe. We propose an unambiguous tracking method based on combined correlation functions for sine-BOC signal. The main feature of this technique is that two new local reference waveforms are used. Based on the cross-correlation functions between the BOC signal and these two local reference waveforms, unambiguous combined correlation functions without any main positive side-peaks are generated. To achieve unambiguous tracking for sine-BOC signal, we present two non-coherent discriminator functions, denoted as V1 and V2. The theoretical expressions of code tracking error in thermal noise are derived. Then, the impact of thermal noise and multipath is analyzed with the help of numerical simulations. Results show that V1 is easier to implement and has relatively better multipath mitigation performance at the expense of some performance degradation in code tracking error. V2 has better code tracking accuracy and provides the most robust code tracking process for high-order sine-BOC signal, but two additional complex correlators are required.