U.S. patent number RE41,382 [Application Number 12/469,142] was granted by the patent office on 2010-06-22 for method and system for detecting interference for global positioning systems.
This patent grant is currently assigned to General Dynamics C4 Systems, Inc.. Invention is credited to Clinton Charles Hepner, David Moon Yee, Jeffrey Dean York.
United States Patent |
RE41,382 |
Yee , et al. |
June 22, 2010 |
Method and system for detecting interference for global positioning
systems
Abstract
A method and system for detecting GPS interference is disclosed.
In one exemplary embodiment, a method for detecting interference in
a Global Positioning System comprises the steps of receiving at
least one satellite signal from one or more satellites in a Global
Positioning System; identifying a noise floor value from the at
least one satellite signal; identifying an interference signal
based on the noise floor value; determining an interference value
for the interference signal from the noise floor value wherein a
level of the noise floor value corresponds to a level of
interference; and providing the interference value to at least one
user for informing the user of the interference signal.
Inventors: |
Yee; David Moon (Scottsdale,
AZ), Hepner; Clinton Charles (Chandler, AZ), York;
Jeffrey Dean (Gilbert, AZ) |
Assignee: |
General Dynamics C4 Systems,
Inc. (Scottsdale, AZ)
|
Family
ID: |
33418136 |
Appl.
No.: |
12/469,142 |
Filed: |
May 20, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
10463408 |
Jun 18, 2003 |
07221312 |
May 22, 2007 |
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Current U.S.
Class: |
342/357.23 |
Current CPC
Class: |
H04B
1/1027 (20130101); G01S 19/215 (20130101); G01S
5/02 (20130101); G01S 3/40 (20130101); G01S
19/48 (20130101) |
Current International
Class: |
G01S
5/14 (20060101) |
Field of
Search: |
;342/357.02,357.06,357.09,357.12,358 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 489 432 |
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Dec 2004 |
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EP |
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1 489 432 |
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May 2008 |
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EP |
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Other References
Fiber Optic Power Meter FPM-8200 User's Guide, ILX Lightwave,
http:www.ixlightwave.com/manuals/fiber_optic_power_meter_FPM-8200_manual.-
pdf, p. 70. cited by other .
Wikipedia, The Free Encyclopedia, "Noise floor", at
http:/en.wikipedia.org/wiki/Noise_floor. cited by other .
European Search Report dated Aug. 17, 2004, for European patent
Application No. 04102571.9-2220-. cited by other .
Thomas H. Jaeckle, "Development of Techniques to Identifying and
Locate Global Positioning System Interfering Signals, 16-9215,"
Aug. 29, 2000, Development of Techniques to Identifying and Locate
Global Positioning System Interfering Signals website, pp. 1-2.
cited by other.
|
Primary Examiner: Tarcza; Thomas H
Assistant Examiner: Mull; Fred H
Attorney, Agent or Firm: Hunton & Williams, LLP
Claims
The invention claimed is:
1. A method for detecting interference in a Global Positioning
System, the method comprising the steps of: receiving at least one
satellite signal from one or more satellites in a Global
Positioning System; measuring a noise floor value in a frequency
band of the at least one satellite signal; identifying an
interference signal based on the noise floor value wherein the
interference signal is determined by a comparison between the noise
floor value from the at least one satellite signal and a
predetermined acceptable range; determining an interference value
for the interference signal from the noise floor value wherein a
level of the noise floor value corresponds to a level of
interference; wherein the comparison between the noise floor value
and the predetermined acceptable range determines a corresponding
interference value for the interference signal; wherein if the
noise floor value is within the predetermined acceptable range, the
interference value is set at a predetermined low interference
value; wherein if the noise floor value is outside the
predetermined acceptable range, the .[.noise floor.].
.Iadd.interference .Iaddend.value is set at a predetermined high
interference value; and providing the interference value to at
least one user for informing the user of the interference
signal.
2. The method of claim 1, wherein the interference value comprises
a percentage between 0% and 100% representing a percentage of
interference of the interference signal on maintaining a GPS signal
lock.
3. The method of claim 1, wherein the interference value represents
an average interference value for the one or more satellites.
4. The method of claim 1, wherein the interference signal comprises
one or more of a jamming signal and a spoofing signal.
5. The method of claim 1, further comprising the step of: providing
the interference value to one or more recipients other than the at
least one user for informing the one or more recipients of the
interference signal via radio transmission.
6. The method of claim 5, wherein the one or more recipients
comprise one or more of a ground unit, an airborne unit, an
equipment unit, and a vehicle sensor unit.
7. The method of claim 1, further comprising the steps of:
determining an interference strength of the interference signal;
and providing the interference strength of the interference signal
to the at least one user.
8. The method of claim 1, further comprising the steps of:
determining an interference direction of the interference signal;
and providing the interference direction of the interference signal
to the at least one user.
9. The method of claim 1, wherein the step of receiving is
performed at a search and rescue radio.
10. The method of claim 1, wherein the step of providing the
interference value further comprises the step of: displaying the
interference value to the at least one user via a user
interface.
11. The method of claim 10, further comprising the step of:
displaying a graphical representation of the interference
value.
12. The method of claim 1, further comprising the step of:
triggering the user to switch to an alternative mode of position
location, in response to being informed of the interference
signal.
13. The method of claim 12, wherein the alternative mode of
operation comprises distance measuring equipment (DME) mode.
14. The method of claim 1, further comprising the step of:
triggering the user to block the interference signal, in response
to being informed of the interference signal.
15. The method of claim 1, further comprising the steps of:
transmitting the interference value to a central unit wherein the
central unit receives a plurality of interference values from a
plurality of other users; and determining a source location of the
interfering signal based at least in part on the interference value
from the user and the one or more interference values from the
plurality of other users.
16. A system for detecting interference in a Global Positioning
System, the system comprising: a receiving module for receiving at
least one satellite signal from one or more satellites in a Global
Positioning System; a noise floor module for measuring a noise
floor value in a frequency band of the at least one satellite
signal; a detection module for identifying an interference signal
based on the noise floor value wherein the interference signal is
determined by a comparison between the noise floor value from the
at least one satellite signal and a predetermined acceptable range
and determining an interference value for the interference signal
from the noise floor value wherein a level of the noise floor value
corresponds to a level of interference; wherein the comparison
between the noise floor value and the predetermined acceptable
range determines a corresponding interference value for the
interference signal; wherein if the noise floor value is within the
predetermined acceptable range, the interference value is set at a
predetermined low interference value; wherein if the noise floor
value is outside the predetermined acceptable range, the .[.noise
floor.]. .Iadd.interference .Iaddend.value is set at a
predetermined high interference value; and a notification module
for providing the interference value to at least one user for
informing the user of the interference signal.
17. The system of claim 16, wherein the interference value
comprises a percentage between 0% and 100% representing a
percentage of interference of the interference signal on
maintaining a GPS signal lock.
18. The system of claim 16, wherein the interference value
represents an average interference value for the one or more
satellites.
19. The system of claim 16, wherein the interference signal
comprises one or more of a jamming signal and a spoofing
signal.
20. The system of claim 16, wherein the interference value is
provided to one or more recipients other than the at least one user
for informing the one or more recipients of the interference signal
via radio transmission.
21. The system of claim 20, wherein the one or more recipients
comprise one or more of a ground unit, an airborne unit, an
equipment unit, and a vehicle sensor unit.
22. The system of claim 16, wherein the detection module further
determines an interference strength of the interference signal; and
the notification module further provides the interference strength
of the interference signal to the at least one user.
23. The system of claim 16, wherein the detection module further
determines an interference direction of the interference signal;
and the notification module further provides the interference
direction of the interference signal to the at least one user.
24. The system of claim 16, wherein the system comprises a search
and rescue radio.
25. The system of claim 16, further comprises a user display for
displaying the interference value to the at least one user via a
user interface.
26. The system of claim 25, wherein the user display displays a
graphical representation of the interference value.
27. The system of claim 16, wherein the user switches to an
alternative mode of position location, in response to being
informed of the interference signal.
28. The system of claim 27, wherein the alternative mode of
operation comprises distance measuring equipment (DME) mode.
29. The system of claim 16, wherein the user blocks the
interference signal, in response to being informed of the
interference signal.
30. The system of claim 16, wherein the interference value is
transmitted to a central unit wherein the central unit receives a
plurality of interference values from a plurality of other users;
and a source location of the interfering signal is determined based
at least in part on the interference value from the user and the
one or more interference values from the plurality of other
users.
31. An article of manufacture for detecting interference in a
Global Positioning System, the article of manufacture comprising:
at least one processor readable carrier; and instructions carried
on the at least one carrier; wherein the instructions are
configured to be readable from the at least one carrier by at least
one processor and thereby cause the at least one processor to
operate so as to: receive at least one satellite signal from one or
more satellites in a Global Positioning System; measure a noise
floor value in a frequency band of the at least one satellite
signal; identify an interference signal based on the noise floor
value wherein the interference signal is determined by a comparison
between the noise floor value from the at least one satellite
signal and a predetermined acceptable range; determine an
interference value for the interference signal from the noise floor
value wherein a level of the noise floor value corresponds to a
level of interference; wherein the comparison between the noise
floor value and the predetermined acceptable range determines a
corresponding interference value for the interference signal;
wherein if the noise floor value is within the predetermined
acceptable range, the interference value is set at a predetermined
low interference value; wherein if the noise floor value is outside
the predetermined acceptable range, the .[.noise floor.].
.Iadd.interference .Iaddend.value is set at a predetermined high
interference value; and provide the interference value to at least
one user for informing the user of the interference signal.
Description
FIELD OF THE INVENTION
The present invention relates generally to detecting interference
for Global Positioning Systems, and more particularly, to a method
and system for detecting interference for Global Positioning
Systems based on noise floor values corresponding to interference
levels.
BACKGROUND OF THE INVENTION
Global Positioning System generally involves a system for
determining a position on the Earth's surface by comparing radio
signals from several satellites. The system essentially comprises
24 satellites equipped with radio transmitters and atomic clocks.
Depending on a geographic location, a GPS receiver samples data
from the satellites and calculates the time for each satellite
signal to reach the GPS receiver. From the difference in time of
reception, the location may be determined. The GPS generally
represents a constellation of 24 satellites that orbit the Earth
where ground receivers are able to pinpoint a precise geographic
location. The location accuracy may range from anywhere from 10 to
100 meters.
The GPS is owned and operated by the United States Department of
Defense but is available for general use around the world. Twenty
one GPS satellites and three spare satellites are in orbit above
the Earth. The satellites are spaced so that from any point on
Earth, four satellites will be above the horizon. Each satellite
contains a computer, an atomic clock and a radio. With an
understanding of its own orbit and the clock, each satellite
continually broadcasts its changing position and time. Periodically
(e.g., daily), each satellite will checks its own time and position
with a ground station and makes any minor correction, if necessary.
On the ground, any GPS receiver may contain a computer that
triangulates its own position from information provided by a
plurality of satellites (e.g., three to four satellites). The
result is provided in the form of a geographic position (e.g.,
longitude and latitude). If the receiver is also equipped with a
display screen that shows the map, the position can be shown on the
map. In addition, an altitude reading may also be provided.
There are many instances where the GPS satellite signal may be
interfered with or otherwise compromised. Generally, the user will
experience a delay, difficulty in receiving a reading or data that
is incorrect or misleading. The user is essentially unaware of the
cause, an amount of interference or even the presence of
interference. For example, the user may be completely unaware that
the signal is being interfered with and may rely on delayed signals
or inaccurate data. Therefore, as the user is unaware of
interference detection, the user does not have the information to
compensate for the interference.
In view of the foregoing, it would be desirable to provide a
technique for detecting GPS interference which overcomes the
above-described inadequacies and shortcomings.
SUMMARY OF THE INVENTION
According to an embodiment of the present invention, a method and a
system detects interference in a Global Positioning System.
According to an exemplary embodiment of the present invention, a
method for detecting interference in a Global Positioning System
comprises the steps of receiving at least one satellite signal from
one or more satellites in a Global Positioning System; identifying
a noise floor value from the at least one satellite signal;
identifying an interference signal based on the noise floor value;
determining an interference value for the interference signal from
the noise floor value wherein a level of the noise floor value
corresponds to a level of interference; and providing the
interference value to at least one user for informing the user of
the interference signal.
According to other aspects of this particular exemplary embodiment
of the present invention, in the method described above, the
interference value comprises a percentage between 0% and 100%
representing a percentage of interference; the interference value
represents an average interference value for the one or more
satellites; the interference signal comprises one or more of a
jamming signal and a spoofing signal; the method further comprises
the step of providing the interference value to one or more
recipients other than the at least one user for informing the one
or more recipients of the interference signal via radio
transmission; the one or more recipients comprise one or more of a
ground unit, an airborne unit, an equipment unit, and a vehicle
sensor unit; the method further comprises the steps of determining
an interference strength of the interference signal and providing
the interference strength of the interference signal to the at
least one user; the method further comprises the steps of
determining an interference direction of the interference signal
and providing the interference direction of the interference signal
to the at least one user; the step of receiving is performed at a
search and rescue radio; the step of providing the interference
value further comprises the step of displaying the interference
value to the at least one user via a user interface; the method
further comprises the step of displaying a graphical representation
of the interference value; the method further comprises the step of
triggering the user to switch to an alternative mode of position
location, in response to being informed of the interference signal;
the alternative mode of operation comprises distance measuring
equipment (DME) mode; the method further comprises the step of
triggering the user to block the interference signal, in response
to being informed of the interference signal; and the method
further comprises the steps of transmitting the interference value
to a central unit wherein the central unit receives a plurality of
interference values from a plurality of other users and determining
a source location of the interfering signal based at least in part
on the interference value from the user and the one or more
interference values from the plurality of other users.
According to another exemplary embodiment of the present invention,
a system for detecting interference in a Global Positioning System
comprises a receiving module for receiving at least one satellite
signal from one or more satellites in a Global Positioning System;
a noise floor module for identifying a noise floor value from the
at least one satellite signal; a detection module for identifying
an interference signal based on the noise floor value and
determining an interference value for the interference signal from
the noise floor value wherein a level of the noise floor value
corresponds to a level of interference; and a notification module
for providing the interference value to at least one user for
informing the user of the interference signal.
According to another exemplary embodiment of the present invention,
at least one processor readable carrier for storing a computer
program of instructions configured to be readable by at least one
processor for instructing the at least one processor to execute a
computer process for performing the method as recited above.
According to another exemplary embodiment of the present invention,
at least one signal embodied in at least one carrier wave for
transmitting a computer program of instructions configured to be
readable by at least one processor for instructing the at least one
processor to execute a computer process for detecting interference
in a Global Positioning System, the computer process comprising a
receiving means for receiving at least one satellite signal from
one or more satellites in a Global Positioning System; a noise
floor identifying means for identifying a noise floor value from
the at least one interference signal; an interference identifying
means for identifying an interference signal based on the noise
floor value; an interference determining means for determining an
interference value for interference signal from the noise floor
value wherein a level of the noise floor value corresponds to a
level of interference; and a notification means for providing the
interference value to at least one user for informing the user of
the interference signal.
According to another exemplary embodiment of the present invention,
an article of manufacture for detecting interference in a Global
Positioning System, the article of manufacture comprising at least
one processor readable carrier; and instructions carried on the at
least one carrier; wherein the instructions are configured to be
readable from the at least one carrier by at least one processor
and thereby cause the at least one processor to operate so as to:
receive at least one satellite signal from one or more satellites
in a Global Positioning System; identify a noise floor value from
the at least one satellite signal; identify an interference signal
based on the noise floor value; determine an interference value for
the interference signal from the noise floor value wherein a level
of the noise floor value corresponds to a level of interference;
and provide the interference value to at least one user for
informing the user of the interference signal.
The present invention will now be described in more detail with
reference to exemplary embodiments thereof as shown in the appended
drawings. While the present invention is described below with
reference to preferred embodiments, it should be understood that
the present invention is not limited thereto. Those of ordinary
skill in the art having access to the teachings herein will
recognize additional implementations, modification, and
embodiments, as well as other fields of use, which are within the
scope of the present invention as disclosed and claimed herein, and
with respect to which the present invention could be of significant
utility.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to facilitate a fuller understanding of the present
invention, reference is now made to the appended drawings. These
drawings should not be construed as limiting the present invention,
but are intended to be exemplary only.
FIG. 1 is a diagram of a system for detecting GPS interference,
according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a method for detecting GPS
interference, according to an embodiment of the present
invention.
FIG. 3 is a flowchart illustrating a method for detecting GPS
interference, according to an embodiment of the present
invention.
FIG. 4 is an illustration of a user interface for displaying GPS
interference data, according to an embodiment of the present
invention.
FIG. 5 is an illustration of an interface for displaying GPS
interference data, according to an embodiment of the present
invention.
FIG. 6 is an illustration of an interface for displaying GPS
interference data, according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)
According to an embodiment of the present invention, a method and
system detects interference in a Global Positioning System (GPS).
In particular, a noise floor associated with a received satellite
signal may be used to determine an interference level. Further, an
interference percentage, an interference strength, an interference
source direction and/or other information associated with the
detected GPS interference may be determined. Interference may
include jamming signals, spoofing signals, other signals that may
interfere with receiving the satellite signal and/or other types of
interference. A user and other recipients may receive notification
of the GPS interference. In addition, the user may notify other
recipients when the GPS signal is being interfered with and/or when
the interference is gone.
The GPS interference detection of an embodiment of the present
invention aids the user in taking steps to address and/or minimize
the interference with such techniques as body shielding, antenna
rotation, relocation (e.g., moving behind a hill) and/or switching
to a different mode of position location or other appropriate
response. The user may also transmit the interference level to a
central location that collects interference information from a
plurality of users to determine the direction and/or location of
the interference. An embodiment of the present invention provides
data, such as mission critical data, to the user and/or other
recipients for providing the status of the GPS signal quality. This
data may be used to aid a variety of missions and applications. For
example, interference values from more than one receiver (e.g., GPS
radio, etc.) may be collected to determine the location of the
interference signal (e.g., jamming signal, etc.) through
triangulation.
FIG. 1 is a diagram of a system for detecting GPS interference,
according to an embodiment of the present invention. System 100 may
provide various functions, such as detection of interference,
calculation of interference strength, notification to the user and
notification to other recipients of the detection of interference
and other data, such as interference level. In particular, GPS
receiving unit 110 may include a correlator 112, a noise floor
module 114, an interference detection module 116, an averaging
module 118, a notification module 120 and other module 122. Other
functionality associated with GPS interference detection may also
be supported by GPS receiving unit 110.
GPS signal 102 may be received by a GPS receiver at GPS receiving
unit 110. GPS signal 102 may represent one or more GPS signals from
a satellite. GPS receiving unit 110 may represent a receiver for
continuously monitoring GPS signal quality. For example, the
receiver may include various models and types of GPS receivers,
such as a GPS radio, a search and rescue radio, a combat search and
rescue radio or other GPS receiver. When the receiver detects that
a level of interference impedes or prevents receiving valid GPS
coordinates, the receiver may automatically notify the user via an
interface (e.g., a display). For example, the interface may display
that a 2D and/or 3D position lock can no longer be achieved. The
interface may further display an indication of interference, such
as a percentage of interference or other representation or
interference. The user may also choose to send a message indicating
GPS interference to other users (e.g., ground users) with a
receiver, such as search and rescue radio, aircraft users and/or
other intended recipients. Once the interference level drops and
the GPS unit is able to obtain a 2D and/or 3D position lock, the
user may be notified via the interface and may further notify the
other recipients that interference has dissipated.
The GPS interference detection system and method of an embodiment
of the present invention may detect an interference signal and
provide data, such as an interference strength. GPS satellite
signals 102, when received by GPS receiving unit 110, may appear as
random values. These seemingly random values may be referred to as
noise. Noise values are constantly changing and may be referred to
as a noise floor. Noise values may represent interference while the
noise floor may represent increases and decreases in intensity of
the interference. A GPS receiving unit 110 of an embodiment of the
present invention may include a correlator 112 for implementing a
correlation technique for detecting a known waveform within the
noise floor. Each satellite may have an associated known waveform
where the known waveform for each satellite may be detected by
correlator 112. The noise floor may produce distinctive
characteristics when an interference signal is broadcast near a
carrier wave, such as GPS's L1 signal of 1575.42 MHz. The noise
floor of the GPS satellite signal may be identified by noise floor
module 114. According to an embodiment of the present invention,
GPS interference may be detected and calculated by characterizing
the noise floor. The noise floor may be characterized to understand
the various noise levels when varying interference signals are
present. Varying noise floor levels may be characterized to
represent varying interference levels. Thus, for a particular noise
floor, a corresponding interference level may be identified.
Interference detection module 116 may calculate an interference
percentage, an interference source direction, an interference
strength and/or other characteristics. According to an example, an
interference level may represent a percentage between 0% to 100%.
In particular, a relationship between noise floor levels and the
amount of interference may be calculated to represent a value from
0% to 100%. For example, interference levels approximately above
40% to 50% may be determined to prevent the GPS receiver from
acquiring valid satellite signals. Interference levels
approximately between 30% to 40% may allow satellites that have
already been locked to remain locked where a GPS position lock will
not be/remain acquired. The varying exemplary ranges are due to
slight differences between receivers and the differences in the GPS
satellites' signal strengths. Other ranges and representations of
interference may be implemented in accordance with an embodiment of
the present invention.
According to another embodiment of the present invention, the GPS
interference detection system and method may determine a source
direction of the detected interference. Through a rotation of a
receiver (e.g., a search and rescue radio), the user may determine
an approximate direction of an interference source. For example,
holding the receiver (e.g., a search and rescue radio) in a
vertical position with a GPS antenna pointing toward the user but
with the unit at arms reach and with the user slowly turning
360.degree. while monitoring the interference level displayed, the
user may determine an approximate direction of the GPS interference
source. Provided that the interference strength is not greater than
a threshold amount (e.g., 85%), the user may notice that the
interference strength differs depending on which direction the GPS
antenna is facing. The direction of the GPS antenna exhibiting a
maximum level of interference detected is likely the direction of
the source of interference. The receiver may provide this
capability through a metal shell acting as a shield to the GPS
interference source.
Each GPS satellite channel may be uniquely affected by the
interference signal and a percentage of interference value may be
calculated from 0% to 100%. According to another example, based on
a lack of correlation, a channel experiencing interference may be
identified. For example, if a signal is being interfered with
(e.g., jammed, spoofed, etc.), data may not be correlated. In
particular, spoofed data will not match various parameters, such as
pseudorandom noise (pn) sequence, almanac, etc. By utilizing the
lack of correlation, channels that are being interfered with (e.g.,
jammed, spoofed, etc.) may be identified.
Each satellite's percentage value may be averaged together to
produce an average percentage representation, as calculated by
averaging module 118. A user and other intended recipients may be
informed of a detected interference. For example, a final averaged
percentage of interference may be displayed to the user and other
intended recipients, via notification module 120, where an
interference percentage or other characteristic may be displayed to
a user via a user interface or user display 130. Other intended
recipients may also be notified by an interface, such as display
140, 142. Examples of recipients may include an airborne unit, a
ground unit, missiles, fuses, vehicle sensors and other recipients.
The interference detection and/or other interference data may be
communicated to the user and/or other recipients via radio
transmission. For example, this capability provides users and/or
recipients a source of information for determining tactics and
procedures.
FIG. 2 is a flowchart illustrating a method for detecting GPS
interference, according to an embodiment of the present invention.
At step 210, a receiving unit may receive a satellite signal. The
satellite signal may represent multiple frequencies or a frequency
band. At step 212, a noise floor may be identified from the
satellite signal. According to an embodiment of the present
invention, the noise floor may be characterized to represent a
level of interference. Based on the noise floor, a corresponding
level of interference may be identified. At step 214, an
interference signal may be identified by the noise floor. For
example, the interference signal may represent a jammed signal, a
spoofed signal or other type of interference signal. At step 216,
an interference value, such as an interference percentage of other
measure or representation of interference may be determined. For
example, the noise floor may be characterized to represent a
percentage of interference. At step 218, for a plurality of
satellites, an average value of the interference percentage of the
plurality of satellites may be calculated. As each satellite
provides a different perspective, an average value provides a
composite representation of the GPS interference. At step 220, the
average value may be displayed to the user. At step 222, the
average value may be displayed to other recipients.
FIG. 3 is a flowchart illustrating a method for detecting GPS
interference, according to an embodiment of the present invention.
Step 310 indicates a start of a GPS interference detection process.
At step 312, a noise floor for the satellite signal received by a
receiver may be identified. The noise floor may be read from
correlation data. For example, satellite signals from satellites in
search or acquire modes may be received. At step 314, it may be
determined whether the noise floor is within an acceptable range.
If the noise floor is within an acceptable range, an interference
level may be set to a predetermined percentage (e.g., approximately
1%) to indicate a low interference, at step 316. Other percentages
or values may be used to indicate a low interference. If the noise
floor is determined to be outside the acceptable range at step 314,
it may be determined whether the noise floor is above a
predetermined high interference level, at step 318. The high
interference level may indicate a situation where the GPS receiver
can not receive a readable signal, a situation where the signals
are substantially blocked or other similar high interference
situation. If the noise floor is determined to be above the high
interference level, the interference level may be set to a
predetermined percentage (e.g., approximately 100%) to indicate
high interference, at step 320. Other percentages or values may be
used to indicate high interference. If the noise floor is
determined to be outside the acceptable range and less than the
high interference level, the interference percentage may be
calculated from the noise floor, at step 322. The interference
percentages may be saved for each satellite, at step 324. At step
326, it may be determined whether interference detection has been
completed for all satellites. If not, the process is repeated for
each satellite, as shown by step 328. Each satellite offers a
different perspective of the position location. Therefore, an
average interference percentage may be calculated to provide a
comprehensive interference reading. At the completion of the
process for each satellite, an average interference percentage may
be calculated, at step 330. At step 332, it may be determined
whether a half (or other predetermined number or percentage) of the
satellites have a maximum interference percentage. If less than
half of the satellites have a maximum interference percentage
value, an average percentage of interference may be displayed, at
step 334. If more than half of the satellites have a maximum
interference percentage value, a predetermined interference value
(e.g., 100%) may be displayed, at step 336. In this example,
percentage values have been used to indicate interference values.
However, other representations of interference may be implemented
in accordance with an embodiment of the present invention.
FIG. 4 is an illustration of a user interface for displaying GPS
interference data, according to an embodiment of the present
invention. When the GPS interference level is detected to be
greater than or equal to a predetermined level, such as 37%, and
the receiver unit does not have a 2D or 3D GPS position lock, a GPS
interference screen may be displayed. In a particular example, the
GPS interference screen may replace a normal top level display
screen. FIG. 4 is an example of a GPS interference screen. In this
exemplary GPS interference screen, the user may be notified that
GPS signal interference is detected and 2D and 3D position is not
available. A bar graph 410 may be displayed along with a percentage
of interference (e.g., 52%) allowing the user to quickly assess GPS
interference.
To prevent the display screen from flickering back and forth
between the GPS interference screen and a normal Satellite Display
Screen when the interference level fluctuates around a
predetermined range, such as 35-37%, the GPS interference screen
may not be removed until the level drops down to a predetermined
threshold, such as 34%.
According to another example, the GPS interference screen may not
be displayed based on certain conditions, such as a 2D or 3D
position lock, regardless of the level of interference. This may be
useful because as long as there is a position lock, the GPS unit is
still operating as expected and therefore the position data is
valid.
A GPS interference gauge indicator may be displayed, as shown by
420. The GPS indicator allows the user to determine an approximate
level of GPS interference regardless of what menu or screen is
currently accessed or displayed. For example, each line of the GPS
indicator may equate to approximately 14% and may be completely
filled in once the percentage level reaches a predetermined
threshold, such as 86% or higher. Other graphical displays and
variations thereof may be implemented.
Other recipients may be notified of detected GPS interference, GPS
interference levels and/or other data. FIG. 5 is an illustration of
an interface for displaying GPS interference data, according to an
embodiment of the present invention. FIG. 6 is an illustration of
another interface for displaying GPS interference data, according
to an embodiment of the present invention. For example, the user
may send pre-programmed text messages indicating detected GPS
interference to one or more intended recipients. An exemplary
message to indicate the presence of interference is shown in FIG. 5
and another exemplary message to indicate that the interference is
gone is shown in FIG. 6.
According to another example, the percentage of GPS interference
detected may be embedded into the messages. The interference
information may be updated each time the user sends the message to
ensure accurate information is transmitted. For example, if the
user has a message stored in memory and presses a send key without
looking at the saved message, the percentage of interference will
still be updated regardless of what was saved in memory. Otherwise,
old data could be mistakenly sent.
The messages may be formatted to allow for receiver units with
older versions of software to receive the GPS interference
messages. Rather than sending a message index representing the
message to send, the actual text may be sent each time. This allows
for older receiver units that would not know about this new message
index type to receive the messages thereby preventing or minimizing
logistics problems of having to update every receiver unit.
When choosing a message, the percentage of interference may be
dynamically updated on a screen at set intervals, such as
one-second intervals. This allows for the user to cancel the
sending of the message if the interference level changes while
selecting the message to send. If the interference level were
static, the user could send an incorrect notification.
The GPS interference detection system and method of an embodiment
the present invention provides a warning of interference and
enables a user to switch to another mode of position location, such
as Distance Measuring Equipment (DME) mode. The GPS interference
detection system and method of an embodiment of the present
invention may trigger a blocking mechanism, such as body shielding
(or moving behind a tree or a hill, etc.), to block the
interference based on an indication of interference as well as the
level of interference.
The functionality associated with the GPS interference detection,
as discussed above, may be represented as software code and/or
hardware structure. Further, detecting GPS interference in
accordance with the present invention as described above typically
involves the processing of input data and the generation of output
data to some extent. This input data processing and output data
generation may be implemented in hardware of software. For example,
specific electronic components may be employed in a hardware or
similar or related circuitry for implementation the functions
associated with detecting GPS interference in accordance with the
present invention as described above. Alternatively, one or more
processors operating in accordance with stored instructions may
implement the functions associated with detecting GPS interference
in accordance with the present invention as described above. If
such is the case, it is within the scope of the present invention
that such instructions may be stored on one or more processor
readable carriers (e.g., a magnetic disk), or transmitted to one or
more processors via one or more signals.
The present invention is not to be limited in scope by the specific
embodiments described herein. Indeed, various modifications of the
present invention, in addition to those described herein, will be
apparent to those of ordinary skill in the art from the foregoing
description and accompanying drawings. Thus, such modifications are
intended to fall within the scope of the following appended claims.
Further, although the present invention has been described herein
in the context of a particular implementation in a particular
environment for a particular purpose, those of ordinary skill in
the art will recognize that its usefulness is not limited thereto
and that the present invention can be beneficially implemented in
any number of environments for any number of purposes. Accordingly,
the claims set forth below should be construed in view of the full
breath and spirit of the present invention as disclosed herein.
* * * * *
References