Sub-carrier shaping for BOC modulated GNSS signals
- PDF / 1,342,890 Bytes
- 18 Pages / 595.28 x 793.7 pts Page_size
- 68 Downloads / 172 Views
RESEARCH
Open Access
Sub-carrier shaping for BOC modulated GNSS signals Pratibha B Anantharamu*, Daniele Borio and Gérard Lachapelle
Abstract One of the main challenges in Binary Offset Carrier (BOC) tracking is the presence of multiple peaks in the signal autocorrelation function. Thus, several tracking algorithms, including Bump-Jump, Double Estimator, Autocorrelation Side-Peak Cancellation Technique and pre-filtering have been developed to fully exploit the advantages brought by BOC signals and mitigate the problem of secondary peak lock. In this paper, the advantages of pre-filtering techniques are explored. Pre-filtering techniques based on the concepts of Zero-Forcing and Minimum Mean Square Error equalization are proposed. The BOC sub-carrier is modeled as a filter that introduces secondary peaks in the autocorrelation function. This filtering effect can be equalized leading to unambiguous tracking and allowing autocorrelation shaping. Monte Carlo simulations and real data analysis are used to characterize the proposed algorithms. Keywords: binary offset carrier, BOC, equalization, global navigation satellite system, GNSS, MMSE, sub-carrier, zeroforcing
1 Introduction Recent developments in the Galileo program have introduced a variety of new modulation schemes including the Binary Offset Carrier (BOC) [1] that has several advantages over traditional Binary Phase Shift Keying (BPSK) signals. BOC signals have increased resilience against multipath and provide improved tracking performance. However, they are characterized by autocorrelation functions (ACF) with multiple peaks that may lead to false code lock. This has led to the design of various BOC tracking algorithms such as Bump-Jump (BJ) [2], Autocorrelation Side-Peak Cancellation Technique (ASPeCT) [3] and its extensions [4], Double Estimator (DE) [5], Side Band Processing (SBP) [6] and pre-filtering [7]. In BJ, the BOC autocorrelation function is continuously monitored using additional correlators. A control logic detects and corrects false peak locks exploiting these additional correlators. In ASPeCT and its extensions, i.e., Sidelobes Cancellation Methods (SCM) [4], the BOC signal is correlated with its local replica and a modified local code. Thus, two correlation functions are computed: the first one is the ambiguous BOC autocorrelation, whereas the * Correspondence: [email protected] Department of Geomatics Engineering, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada
second only contains secondary peaks. An unambiguous cost function is determined as a linear combination of the two correlations. The DE technique maps the BOC ambiguous correlation over an unambiguous bidimensional function [5]. The sub-carrier and the Pseudo-Random Number (PRN) code, the two components of a BOC signal, are tracked independently and an additional tracking loop for the sub-carrier is required. In SBP, the spectrum of BOC signals is split into side band components through modulation and filtering. Each side band component leads t
Data Loading...
