Efficient technique for DLL S ‐curve side zero‐crossings cancellation in global positioning system/Galileo receiver

Abstract

In this study, the authors propose a new method that eliminates ambiguity in global navigation satellite system (GNSS) code acquisition and tracking significantly. It is based on the use of a specified locally generated (SLG) pseudo‐random noise code that can be correlated with any received binary offset carrier sine‐ or cosine‐modulated signal. As a result, the correlation function (CF) together with its discriminator function (DF) at the delay locked loop (DLL) output, determined within a tracking region of (−1, 1) chips, are unambiguous and narrow, providing thus better positioning accuracy. On the other hand, the SLG‐based methods CF and DF are such as those of high‐resolution correlator and Strobe correlator, initially proposed for multipath mitigation in classical binary phase shift keying‐modulated code. In addition, their proposed SLG‐based scheme is valid for any value of the early–late chip spacing in the DLL‐DF. The computer simulation results show that the proposed scheme is unambiguous for DLL code‐tracking operation and has superior performance in the estimation of the delay of line of sight signal in GNSS applications.

Unambiguous method for DLL BOC signals tracking

“…In the absence of noise and interferences, the coherent DLL‐DF can be given as follows: where R Early ( τ ) = R ( τ +d) and R Late ( τ ) = R ( τ − d) are respectively the early and late CFs.…”

“…In the first BOCs‐PRN version, presented in Dovis et al and dedicated to BOCs(n,n)‐modulated signals, the resultant CF plays the same role as the DLL DF, which reduces the receiver complexity . However, it exhibits lower accuracy due to increased phase jitter of the code and low resistance to MP when applied to multiplexed BOC (MBOC) signal . Moreover, it does not allow the use of any one of the classical discriminators designed to improve the performances in the presence of noise and MP phenomena such as the narrow correlator (NC) .…”

“…While retaining the advantages of the BOCs‐PRN discriminator, BOCc‐PRN method also provides better resistance to MP, but only for average MP delays. Nevertheless, the decrease of the tracking error and the sensitivity cannot be guaranteed, since its implementation is restricted to a fixed and unique value of the E/L chip spacing …”

“…To remedy the problem of fixed and unique value of the E/L chip spacing in BOCc‐PRN method, Rouabah et al have proposed the specified locally generated (SLG) method with free DLL early‐late chip spacing parameter intended for BOCs/c(m,n) signals. This method eliminates completely the tracking ambiguity . Furthermore, it has the same CF and DLL DF as that of the HRC and the SC MP mitigation techniques .…”

“…Furthermore, it has the same CF and DLL DF as that of the HRC and the SC MP mitigation techniques . Consequently, it has a performance that is superior to those of BOCs/c‐PRN and DPE methods in terms of MP error effect reduction …”