New unambiguous BOC(n,n) tracking technique

Abstract : Galileo and Modernized GPS have included in their signal structures a new signal modulation: the Binary Offset Carrier (BOC). In the navigation field, this modulation is characterized by the chipping rate of its spreading code (m×1.023 MHz) and the frequency of its square sub-carrier (n×1.023 MHz). As a consequence, it is usually referred to as a BOC(n,m) modulation. The choice of the parameters n and m has a significant impact on the signal tracking performance and characteristics [1]. It is well known that each BOC modulation brings many improvements when compared against a classical Bi-Phase Shift Keying (BPSK) modulation with the same chipping rate [1]. Among other examples, it provides a lower code tracking error in thermal noise, better multipath mitigation, and better rejection of narrow-band interference. However, its multi-peak autocorrelation function is a major drawback. This implies that when using classical acquisition and tracking techniques, there is a possibility of detecting and tracking the signal by locking onto a side-peak. This can lead to severe undesirable measurement biases when not corrected. Several methods have been developed in order to prevent such an event to occur [2, 3, 4, and 5]. These methods are usually generic to all BOC modulations. However, they have to incorporate trade-offs, such as a degraded code tracking accuracy, or the risk of a certain period of potential false peak tracking. This research uses a different approach to the problem. Instead of trying to find a generic solution, it was decided to study this ambiguity problem on a particular signal in order to try to apply relevant methods using this specific signal?s characteristics. The BOC modulation chosen was the sine-BOC(n,n) (sine- stands for the use of a sine square as the sub-carrier). This decision was motivated by the fact a sine-BOC(1,1) will most likely be used for the Galileo civil signal on L1, and potentially on GPS III [6, 7]. Moreover, the Galileo L1 signal will constitute the main Galileo signal for mass market applications due to its narrow frequency bandwidth and low sampling frequency required for its processing. As a result, finding an optimal way to track Galileo BOC(1,1) unambiguously is critical, as well as very challenging. This paper presents a new unambiguous BOC tracking method that can be applied to any sine-BOC(n,n) signal. It consistently removes the bias threat while having a close-to-optimum tracking accuracy. Sine-BOC modulation will be referred to as BOC modulation for simplicity throughout this paper. The first part focuses on the shortcomings of traditional BOC(n,n) tracking and the second part offers a detailed description of the new proposed method. The third part then focuses on the theoretical tracking performance of the proposed method in thermal noise only. Its behaviour in a multipath environment is then investigated before some simulation results are shown in the last section.
Type de document :
Communication dans un congrès
NAVITEC 2004, ESA Workshop on Satellite Navigation User Equipment Technologies, Dec 2004, Noordwijk, Netherlands. 2004
Liste complète des métadonnées

Littérature citée [7 références]  Voir  Masquer  Télécharger

https://hal-enac.archives-ouvertes.fr/hal-01022449
Contributeur : Laurence Porte <>
Soumis le : jeudi 30 octobre 2014 - 13:42:43
Dernière modification le : vendredi 9 février 2018 - 20:36:01
Document(s) archivé(s) le : lundi 2 février 2015 - 15:37:38

Fichier

128.pdf
Fichiers produits par l'(les) auteur(s)

Identifiants

  • HAL Id : hal-01022449, version 1

Collections

Citation

Olivier Julien, Christophe Macabiau, Me Cannon, Gerard Lachapelle. New unambiguous BOC(n,n) tracking technique. NAVITEC 2004, ESA Workshop on Satellite Navigation User Equipment Technologies, Dec 2004, Noordwijk, Netherlands. 2004. 〈hal-01022449〉

Partager

Métriques

Consultations de la notice

106

Téléchargements de fichiers

97