ICG Expert meeting,Vienna
Classification of GNSS interference Zhouyi1, Xiong Wen2, Zhen Weimin2 1. Beijing Satellite Navigation Center 2. China Research Institute of Radiowave Propagation
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
Classification of interference in ICG 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 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 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.
Failure of GPS time synchronization system in mobile station
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. Source Jammer available on Internet Intentional interference with jammer
Natural disturbance Ionospheric scintillation 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。
Distribution of S4 index
Times of scintillation occurrence
Factors affecting ionospheric scintillation
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.
Loss of lock of GPS signal Affected area of ionospheric scintillation
caused by scintillation
Natural disturbance Ionospheric scintillation —— 2003.10.14 The signal to noise ratio fluctuates
50
rapidly while scintillation occurs.
信 信 信 （
dB/Hz）
40
30
The track of signal may be
20
10
0 20:00
interrupted during intense 20:15
20:30
20:45
21:00 21:15 时时（ 2003-10-14）
21:30
21:45
22:00
scintillation.
The error of positioning accuracy
N E U
40 30
of dual frequency receiver
20 m）
Dual frequency positioning accuracy
定定 误 定定 时 时 定 变 信（ QION， 2003-10-14） 50
定 定 误 定 （
Signal to noise ratio degradation
信信 信 变 信 （ PRN 8） -海海 20031014 60
10 0
becomes large during scintillation.
-10 -20
Sometimes huge slips may occur.
-30 -40 10
11
12
13
时时（
14 UT）
15
16
Natural disturbance Ionospheric scintillation —— 2003.10.14 Number of satellites visible
Dilution of Precision
定定 误 定定 时时 定 变 信 -所所可 见 可 （ 海海 2003-10-14）
VDOP （ QION， 2003-10-13） 4
1000
3
-500
2.5 VDOP
m） 定 定 误 定 （
3.5
0
-1000
-1500
1
13 14 15 UT）） 时时（ UT QION站可可可定定定 卫 可可 （ 2003-10-14）
11
12
0.5 10
16
时时 （
11
12
13
14
15
16
15
16
时时（ UT） VDOP （ QION， 2003-10-14）
10
4
3.5
8
Scintillation
3
2.5
6
4 10
VDOP
可可可定定定卫可可
2
1.5
-2000
-2500 10
No Scintillation
N E U
500
2
1.5
11
12
13 时时（ UT）
14
15
16 1
0.5 10
11
12
13
14
时时（ UT）
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 precountermeasures could be carried out through the prediction of spatial weather.
Thanks for your attention!
[email protected] [email protected] [email protected]
