Detection, Location and Mitigation of GNSS Interference

N. Ward, and G. Shaw, C. Hill

Abstract:	Position input for navigation is becoming increasingly reliant on Global Navigation Satellite Systems (GNSS) across all sectors of transport. However, GNSS is vulnerable to signal interference. Deliberate and accidental jamming can render the whole system unusable at a particular time or location, while faults affecting individual signals can also arise. Under such conditions, GNSS equipment, including systems on ships’ bridges and GNSS-enabled Aids-to-Navigation (AtoN), can produce erroneous position solutions, which are then fed to safety-related systems such as electronic charts/displays and Automatic Identification Systems (AIS). In January 2012, the GNSS Research and Applications Centre (GRACE) at the University of Nottingham was tasked by the General lighthouse Authorities to investigate current trends in ‘hardening’ GNSS technology against signal interference, to support GLA policy development and research prioritisation in the context of e-Navigation which is expected to be established in the 2015 - 2022 timeframe. GNSS receivers are vulnerable to interference, due to the low received signal powers. It has been shown that unintentional radio frequency interference (RFI) is ubiquitous. In close proximity to the GNSS frequency bands, there are active services for satellite communications, TV broadcasting, radar and UWB applications. These services can cause out-of-band emissions, harmonics or inter-modulation products. The weak signal environment, presence of intentional and unintentional interference and the use of GNSS in critical applications make an impact assessment of RFI essential. Receiver manufacturers are slowly responding and improving their jamming detection and mitigation capabilities. Mid-range receivers are available that implement narrow-band RF filters, adaptive A/D, FFT (notch) filter and multipath mitigation. Adaptive antenna-arrays with spatial filtering, providing from 25 to 40dB of anti-jamming protection, are available on high-end receivers. Receivers integrated with INS solutions have prices varying according to the grade of the inertial measurement unit employed. RAIM is provided for many high-end receivers, in particular for aviation applications. There are measures that can be taken by radio regulatory bodies, navigation service providers and geodetic organisations to detect, locate and mitigate interference. The approach has generally been reactive, networks of detection probes have only been set up on a trial basis. However, there is much infrastructure already in place that can be used for this purpose and this paper looks at the requirements and possible design approaches, particularly in the maritime context.
Published in:	Proceedings of the 2014 International Technical Meeting of The Institute of Navigation January 27 - 29, 2014 Catamaran Resort Hotel San Diego, California
Pages:	304 - 310
Cite this article:	Ward, N., Shaw, G., Hill, C., "Detection, Location and Mitigation of GNSS Interference," Proceedings of the 2014 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2014, pp. 304-310.
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