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Classification of GNSS interference
Zhouyi1, Xiong Wen2, Zhen Weimin2
1. Beijing Satellite Navigation Center2. China Research Institute of Radiowave Propagation
ICG Expert meeting, Vienna
Content
� Classification of interference in ICG
� Interference Events description
� Summary
Classification of interference in ICG
GNSS has been applied into almost every aspect of human lives. It would have significant impact on national defense and economic security once GNSS is interfered. People all know about the harm of interference, but
What is GNSS Interference?
GNSS applications
Classification of interference in ICG
A definition of GNSS interference has been provided in ICG-7
�Radio interference (Interference from radio systems)
� Unintentional interference
� Intentional interference
� Natural Disturbance
Definition of GNSS interference
The main reason why GNSS signal is vulnerable to interference is the weak transmit power.
Unintentional, Intentional and Natural disturbance are three aspects of interference:� Unintentional disturbance
� In-band emission� Out-of-band emission� ……
� Intentional disturbance� Spoofing� Jamming� ……
� Natural disturbance� Ionospheric scintillation� ……
Classification of interference in ICG
Classification of GNSS interference
Interference Events description
More and more interference events, not only to GPS but also to BDS, have been found. They all have great effect on the performance of GNSS. People should be aware of the harm of interference.
Unintentional interference
1) Unintentional interference to GPS
Failure of GPS time synchronization
system in mobile station
Aerial GPS signal was interrupted caused by interference in Shenzhen city
and Henan province, etc. Backup system was started as a consequence.
Failure of GPS time synchronization system in mobile station.
Source: Unknown interference.
Unintentional interference
2) Unintentional interference to BDS
Interference was found in all the three frequencies of B1,B2 and B3 in Xi’an.
Sources:
� TV/mobile transmit tower (at B1)
� microwave device (at B2)
� airport radar (at B3)
Interference at B1, B2 and B3 in Xi’an
Intentional interference
Intentional interference to BDS
A bus driver was caught at Luzhou
Passenger Transport Center with a
GNSS jammer in his bus.
The jammer was used to avoid being
tracked by the transportation manage
department.
SourceJammer available on Internet
Intentional interference with jammer
GNSS interference may also be caused by natural disturbance. Among
which ionospheric scintillation effect is most important.
Ionospheric scintillation varies with many factors such as time, season
and geomagnetic position。
Factors affecting ionospheric scintillation
Natural disturbance
Ionospheric scintillation
Distribution of S4 index Times of scintillation occurrence
Natural disturbance
Ionospheric scintillation
Ionospheric scintillation may
degrade the positioning
accuracy of GNSS and even
cause loss of lock during severe
scintillation activities, especially
in the low latitude region of
China.
Affected area of ionospheric scintillation
Loss of lock of GPS signal
caused by scintillation
20:00 20:15 20:30 20:45 21:00 21:15 21:30 21:45 22:000
10
20
30
40
50
60
时时（ ）2003-10-14
信信信（
）dB
/Hz
信信信 信变 （ ） 海海PRN 8 - 20031014
Sig
nal to
no
ise ra
tio d
egra
datio
n
Natural disturbance
Ionospheric scintillation —— 2003.10.14
� The signal to noise ratio fluctuates
rapidly while scintillation occurs.
� The track of signal may be
interrupted during intense
scintillation.
10 11 12 13 14 15 16-40
-30
-20
-10
0
10
20
30
40
50定定 定定 定 信误 时时 变 （ ， ）QION 2003-10-14
时时（ ） UT
定定
定误
（）
m
N
EU
Du
al fre
qu
en
cy p
ositio
nin
g a
ccu
racy
� The error of positioning accuracy
of dual frequency receiver
becomes large during scintillation.
� Sometimes huge slips may occur.
Dilution of Precision
Natural disturbance
Ionospheric scintillation —— 2003.10.14
10 11 12 13 14 15 160.5
1
1.5
2
2.5
3
3.5
4
时时（ ）UT
VD
OP
（ ， ）VDOP QION 2003-10-13
10 11 12 13 14 15 160.5
1
1.5
2
2.5
3
3.5
4
时时（ ）UT
VD
OP
（ ， ）VDOP QION 2003-10-14
No
Scin
tillatio
nS
cin
tillatio
n
时时（ ）UT
10 11 12 13 14 15 164
6
8
10
时时（ ）UT
可可可定定定可可
卫
站可可可定定定 可可卫 （ ）QION 2003-10-14
Number of satellites visible
10 11 12 13 14 15 16-2500
-2000
-1500
-1000
-500
0
500
1000
定定 定定 定 信误 时时 变 所所可 可见-（ 海海 ） 2003-10-14
时时（ ） UT
定定
定误
（）
m
N
E
U
Both the number of satellites visible and the dilution of precision at Qion station varied significantly with the occurrence of scintillation.
Summary
From the harm of interference study, we can realize the importance of IDM tasks, countermeasures should be implemented urgently and some recommendations can be drawn:
� To avoid unintentional interference (such as interference
between GNSS and the other services in-band or out-band),
compatibility study is of most important;
� To avoid intentional interference (such as jammers available),
legislation in spectrum protection and jammer prevention
should be promoted;
� To avoid natural disturbance (such as ionospehric
scintillation), ionospheric study was encouraged so that pre-
countermeasures could be carried out through the
prediction of spatial weather.
