Aerospace and Electronic Systems Magazine August 2017 - 74

An Approach to Detect GNSS Spoofing
tive effect on the performance of a receiver and consequently
severely affected the performance of the postdespreading detection metrics. The chirp jammer also affected the SPCA spoofing
detection metric and its behaviour on detection metrics is very
similar to that of a nonoverlapped spoofing attack. The SQM
metric was implemented to detect spoofing and multipath at the
postdespreading level. As shown in the scenarios used, the SQM
metric is not overly sensitive for short-range multipath/spoofing
signals.

REFERENCES
[1]

[2]

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Figure 12.

C/N0 and SQM metrics for data sets 3 and 13.

set 13 which may be due to multipath interference. However, the
SQM metric values in this case did not pass the detection threshold. This is likely due to signal blockages or short multipath signals
which only affects the C/N0 but have a minimal effect on the SQM
metric. Analyzing other data sets and different PRNs revealed that,
given the data utilized in this investigation, the SQM metrics are
less sensitive in dense urban environments affected by multipath.
This observation confirms the simulation results provided in the
previous section.

[5]

[6]

[7]

CONCLUSIONS
The focus here has been on correct detection of spoofing attacks
from interference sources. To this end several predespreading and
postdespreading spoofing detection metrics, namely temporal/
spectral analyses, SPCA, C/N0, and SQM, were implemented and
analysed under different interference signals, namely CW jammer, wideband noise, chirp jammer, and multipath. Considering
the real data analysis results, the predespreading detection metrics, namely variance analysis and SPCA, are not affected under multipath and hence used to discriminate between spoofing
and multipath signals based on the assumption that these metrics
are not affected in typical multipath scenarios. The assumption
was validated by collecting several data sets in dense urban environments and analysing the metric results. The temporal/spectral analyses in the presence of jamming signals were affected.
Among jamming signals, the chirp jammer had the most destruc74

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IEEE A&E SYSTEMS MAGAZINE

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AUGUST 2017

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