Quality Monitoring of BOC Signals through Codeless Techniques

Coexistence between GNSS and communications services is becoming a more and more concrete issue that is gathering the attention of the scientific community. This is due, on one side, to the spectrum scarcity that is pushing communications providers to ask for frequency bands previously reserved for other services. On the other side, new GNSS signals with larger frequency occupations and with different centre frequencies are being deployed. GNSS services are thus more exposed to interference from communication services operating in the nearby frequencies. An example is the LightSquared case, which generated concern among the GNSS community. Several research groups are currently investigating the impact of LightSquared on GNSS signals. The assessment of the impact of interfering sources is however limited to Open Service (OS) GNSS signals. The analysis of encrypted modulations motivates the development of codeless techniques that enable quality monitoring of those signals. In this paper, codeless techniques are adapted to Binary Offset Carrier (BOC) modulations. In particular, a Sub-carrier Lock Loop (SLL) is implemented to wipe-off the BOC sub-carrier and implement a first filtering stage that reduces the input noise. The remaining unknown Pseudo-Random Noise (PRN) and data are removed through squaring. Simplifications based on the availability of OS signals broadcast jointly with the encrypted components are then examined. The main application of the proposed technique aims at monitoring the quality of the encrypted signal. In this respect, a C/N0 estimator is implemented and used to assess the impact of interfering signals. The proposed algorithm has been thoroughly characterized and its effectiveness has been supported through Monte Carlo simulations and real data analysis. More specifically, several interference signals mimicking the impact of telecommunications systems allocated in bands adjacent to GNSS frequencies have been broadcast in an anechoic chamber along with Galileo signals obtained from the GIOVE and IOV satellites. The technique was also applied to signals with a known PRN, thus making possible the comparison between codeless and traditional techniques. The tests confirm the effectiveness of the developed codeless technique. Analytical and experimental analysis supports the effectiveness of the proposed architecture. The considered codeless techniques are effective tools that enable quality monitoring of encrypted GNSS signals.

BORIO Daniele;  RAO Marco;  O'DRISCOLL Cillian; 

2013-01-21

European Group of Institutes of Navigation (EUGIN)

JRC69415

https://publications.jrc.ec.europa.eu/repository/handle/JRC69415,