Quantification of the potential threat to Galileo from man-made Noise sources. (QGN)
Background & Objectives
The development of the Galileo system will significantly improve the already high level of accuracy, availability, reliability and integrity provided by current satellite navigation systems. However, in urban canyon and indoor locations there is a significant performance loss due to high levels of attenuation, signal masking and multipath. Receiver design for positioning in challenging areas like this is dependent on accurate characterisation of the signal and noise environments. Effects of signal propagation into urban canyons and indoors is relatively well known. However, the noise characteristics are largely unknown in the sensitive Galileo bands, especially the effect on the noise floor, from the increasing number of electronic devices.
With the development of Galileo, there are new frequency allocations. Although there should not be any intentional interference, electronic devices could unintentionally leak into these frequency bands and therefore some investigation is needed. It is important to assess the interference situation early on before Galileo is fully operational.
The proposed characterisation of the man-made noise environment at Galileo L1 and E5 frequencies will be based upon a combination of analysis and measurements. The analysis component of this effort will characterise the radio frequency interference (RFI) expected within the Galileo frequency band, with a primary focus on the L1 and a secondary focus on the E5 bands.
The identification of potential interference sources will be an important aspect of this work. In order to validate the analysis/predictions, measurement hardware will be constructed to enable actual spectral measurements that can be taken to assess the operational environment of GNSS receivers for various locations. Such knowledge will prove invaluable, as it will provide the necessary corroborate insight into the expected operational environment and the challenges posed by specific environments.
The measurements will be thoroughly analysed to provide a detailed characterisation of the representative environments tested. An assessment will also be made of the impact of such noise conditions on a pre-defined Galileo receiver operating in such locations. Two distinct hardware development efforts will be initiated in this project.
The first will provide a high-end measurement device. The key element in this system will be a spectrum analyser. Such a device will be able to be deployed into an environment of interest, recording spectral measurements over a 24-hour period. The benefit of such an instrument will be the rapid development time (less than four months) to provide measurements into the analytic process.
The problem with such an instrument will be the high development cost and bulky size, which will prevent rapid parallel deployment. In order to improve upon these drawbacks, a second instrument will be developed which will provide a low-cost sensor module that can be deployed widely, essentially capable of establishing an RFI monitoring network. There will be an extended development time for this instrument; however the project schedule will still allow it to provide data for the analytic process, validating its performance as an instrument for low-cost, high-performance RFI monitoring.
The key objective of the proposed research is to characterise the man-made noise environment at Galileo L1 and E5 frequencies in urban and indoor locations. As GNSS received signal powers are at a very low level in these locations, minor elevations of the noise floor can be of significance. Two distinct hardware development projects will be initiated. One will provide a high-end measurement device with a spectrum analyser as the key element. The other project will provide a low-cost instrument that is more suited for parallel deployment.
Work performed & results
This project has made accurate measurements of the noise in a range of environments and this data and its interpretation is detailed in the following reports which are freely available to the public: - Report presenting the interference characteristics and levels required to disrupt the defined indoor Galileo receiver; - Report describing the expected man-made noise sources likely to impact the performance of Galileo receivers indoors; - Results from SA-based measurement campaign; - Results from front-end-based measurement campaign; - Galileo man made noise characterisation report. Additionally, small, cheap, easily deployable, monitoring equipment resulting from the project is available to users.