Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD FOR CHARACTERIZING AN RF ENVIRONMENT OF
AN AREA
TECHNICAL FIELD
This invention relates to the field of telecommunications.
More precisely, this invention pertains to a method for
characterizing an RF environment of an area in which a
plurality of obstacles is located.
BACKGROUND OF THE INVENTION
It is desirable to characterize an RF environment of an
area. Such characterizing may then be used for various
applications such as for positioning a wireless mobile unit
for instance.
Unfortunately, prior art characterizing of an RF
environment suffers from many drawbacks.
For instance, the characterizing is usually limited to a
single frequency band.
Furthermore, such characterizing usually requires to be
performed at least one of a large amount of computing
resources and a large amount of storing space which. is
costly.
Furthermore many individuals may be required in order to
perform such characterizing.
There is therefore a need for a method and apparatus that
will overcome at least one of the above-identified
drawbacks.
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SU1~IARY OF THE INVENTION
It is an object of the invention to provide a method for
characterizing an RF environment.
Yet another object of the invention is to provide a method
for generating a database characterizing an RF environment.
According to a first aspect of the invention, there is
provided a method for characterizing an RF environment of
an area in which a plurality of obstacles is located, the
method comprising providing a physical layout of the area,
the physical layout comprising an indication of physical
properties of the obstacles, positioning a plurality of
beacons in the physical layout, the beacons for emitting RF
signals, simulating an influence of the plurality of
obstacles on the RF signals, calculating an RF environment
using the RF signals and the influence and mapping onto the
physical layout the RF environment.
According to another aspect of the invention, there is
provided a method for generating a database characterizing
an RF environment of an area in which a plurality of
obstacles is located, the method comprising providing a
physical layout of the area, the physical layout comprising
an indication of physical properties of the obstacles,
positioning a plurality of beacons in the physical layout,
the beacons for emitting RF signals, simulating an
influence of the plurality of obstacles on the RF signals,
calculating an RF environment using the RF signals and the
influence and generating a database mapping the RF
environment with the physical layout.
In this specification, the term "known area" is intended to
mean "an evolving map".
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The term "obstacle" is intended to mean "an element which
is modifying the transmission path of an electromagnetic
signal".
BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the present invention
will become apparent from the following detailed
description, taken in combination with the appended
drawings, in which:
Fig. 1 is a diagram showing a plurality of wireless
transmitting units, a wireless mobile unit and a wireless
mobile unit positioning server;
Fig . 2 is a block diagram showing a f first embodiment of a
wireless mobile unit;
Fig. 3 is a block diagram showing a preferred embodiment of
the wireless mobile unit positioning server;
Fig. 4 is a flowchart showing how a mapping of an RF
environment is performed;
Fig. 5 is a flowchart showing how a physical layout of the
area is provided;
Fig. 6 is a flowchart showing how calculating an RF
environment using RF signals and the influence of obstacles
and RF sources is performed.
It will be noted that throughout the appended drawings,
like features are identified by like reference numerals.
DETAILED DESCRIPTION OF AN EMBODIMENT
Now referring to Fig. 1, there is shown a system comprising
a wireless mobile unit 10, a plurality of wireless
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transmitting units 12, 14, and 16 and a wireless mobile
positioning server 18.
The wireless mobile unit 10 is a wireless transceiver
capable of wirelessly communicating with at least one of
the plurality of wireless transmitting units 12, 14, and 16
and the wireless mobile positioning server 18 according to
a communication standard.
In an embodiment the communication standard is IEEE802.11x.
Alternatively, the communication standard is Bluetooth~TM~
or any other wireless communication standard.
Now referring to Fig. 2a, there is shown an embodiment of
the wireless mobile unit 10.
The wireless mobile unit 10 comprises a wireless port 20, a
processing unit 24 and an optional memory unit 26. The
skilled addressee will appreciate that the wireless mobile
unit 10 may further comprise various units, not shown here
for clarity purposes, such a display unit, a speaker unit,
etc. The wireless port 20 is adapted for transceiving a
wireless signal according to the communication standard. It
should be understood that while in one embodiment, the
wireless port 20 may receive and transmit a wireless
signal; in an alternative embodiment, the wireless port 20
may only transmit a wireless signal.
The processing unit 24 is used for processing the received
signal and for providing a signal to transmit to using the
wireless port 20.
The wireless mobile unit 10 further comprises the optional
memory unit 26 which is used to store data provided by the
processing unit 24. In an embodiment, the optional memory
unit 26 is a volatile-type memory.
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Now referring to Fig. 2b, there is shown another embodiment
of the wireless mobile unit 10. In this embodiment, the
wireless mobile unit 10 further comprises an inertial
sensor unit 28. The inertial sensor unit 28 provides an
inertial sensor signal to the processing unit 24. In an
embodiment of the invention, the inertial sensor unit 28 is
preferably a Micro-Electro-Mechanical Systems (MEMS)
selected from the group consisting of accelerometers,
gyroscopes, altimeters, magnetic compass, barometer, etc.
Alternatively, the inertial sensor unit 28 may comprise an
apparatus which uses a Voltage Controlled Oscillator (VCO)
or a Numerically Controlled Oscillator (NCO). As further
explained below, the inertial sensor unit 28 is used to
further enhance the provision of the estimated position of
the wireless mobile unit 10 comprising the inertial sensor
unit 28.
Now referring back to Fig. 1, the plurality of wireless
transmitting units 12, 14 and 16 may or not be adapted for
communication with the wireless mobile unit 10. The
plurality of wireless transmitting units 12, 14 and 16 may
therefore comprise base stations for communicating with the
wireless mobile unit 20 as well as any devices
transmitting/radiating a wireless signal.
The skilled addressee will appreciate that such devices
transmitting/radiating a wireless signal may be selected
from the group consisting of mobile phones, computers, TV,
satellite-transmitted signals, current/voltage
transformers, rotating machines, or the like.
Now referring to Fig. 3, there is shown an embodiment of
the wireless mobile unit positioning server 18.
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The wireless mobile unit positioning server 18 comprises a
physical layout providing unit 30, an electromagnetic
simulation unit 32, a beacon data manipulation unit, an
electromagnetic data acquisition unit 34, an
electromagnetic environment data manipulation unit 35, an
electromagnetic environment data storing unit 36, a
position detection unit 38, a position providing unit 39
and a wireless receiving unit 40.
The physical layout providing unit 30 provides a physical
layout data signal to the electromagnetic simulation unit
32.
The physical layout data relates to a given environment. It
should be understood that the environment is not limited
solely to closed or interior spaces.
The physical layout data signal comprises a physical
location indication as well as pertinent data fox each
element which may affect radio wave transmission in the
given environment. The skilled addressee will appreciate
that the elements may comprise physical structures, walls,
obstacles, objects, floor, ceiling, apparatus, or the like.
The physical location indication is preferably given
according to a 3-dimensional coordinate system while the
pertinent data comprises information such as porosity,
attenuation, loss, reflection, distortion, corruption,
angular effect and a squared providing of these values with
respect to a material and space as well as proximity or
distance effect with respect to a transmitter. It will be
appreciated that a squared value is used in order to obtain
more reliable information about the influence caused by a
material on an electromagnetic wave. In fact, the skilled
addressee will appreciate that for instance an incoming
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electromagnetic wave hitting perpendicularly a given
material will propagate less in the material than in the
case where the incoming electromagnetic wave hits the
material with an angle smaller than 90 degrees.
In an embodiment, the physical layout providing unit 30 is
implemented in the wireless mobile unit positioning server
18. Alternatively, the physical layout data signal is
provided to the electromagnetic simulation unit 32 via a
network, which is a Wide Area Network (WAN) such as the
Internet. In another embodiment, the physical layout is
provided by the wireless mobile unit 10.
The beacon data manipulation unit 33 provides a beacon data
signal to the electromagnetic simulation unit 32. The
beacon data manipulation unit 33 may be operated by a user
which selects a desired position or by using an algorithm.
The beacon data signal comprises an indication of a
position of a beacon communicating with the wireless mobile
unit 10 in the environment. In an embodiment of the
invention, the position of the beacon is a 3-dimensional
position with respect to a given reference. The beacon data
signal further comprises information pertinent to wireless
transmission such as frequency of the beacon, transmission
power of the beacon, an antenna radiation pattern, etc.
The electromagnetic data acquisition unit 34 is used for
performing an electromagnetic data acquisition at selected
places in the real environment. The selected places may be
chosen according to various criteria. The criteria may be
anyone of a signal stability, a signal quality, a signal
availability, an absence or a small movement of the
wireless mobile unit and a tuning of a reading according to
predetermined delays.
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The acquired data signal comprises an indication of a
physical location in the environment as well as an
electromagnetic measure. The electromagnetic measure
comprises for a given frequency band at least one of a
signal/noise value and a power value.
The electromagnetic environment data manipulation unit 35
receives the acquired data signal and provides a
manipulated acquired data signal to the electromagnetic
simulation unit 32.
The wireless receiving unit 40 receives a wireless signal.
It should be appreciated that the wireless signal may
comprise data related to a wireless transmission of a
plurality of devices, if applicable, and is not limited to
data related to the wireless transmission of the wireless
mobile unit 10 or to the wireless transmission of the
wireless transmitting unit communicating with the wireless
mobile unit 10 if applicable. Therefore and more precisely,
the wireless receiving unit 40 provides a detected
electromagnetic source signal to the electromagnetic
simulation unit 32. The detected electromagnetic source
signal comprises at least one of a signal/noise value and a
power value for a given frequency band.
The electromagnetic simulation unit 32 receives the
physical layout data signal provided by the physical layout
providing unit 30, the beacon data signal provided by the
beacon data manipulation unit 33, the manipulated acquired
data signal provided by the electromagnetic environment
data manipulation unit 35 and the detected electromagnetic
sources signal provided by the wireless receiving unit. The
electromagnetic simulation unit 32 may further receive a
simulated data signal provided by the electromagnetic
environment data storing unit 36. The electromagnetic
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simulation unit 32 performs .a simulation of the
electromagnetic environment using the physical layout data
signal, the beacon data signal, the manipulated acquired
data signal and the detected electromagnetic sources and
provides a simulated data signal to the electromagnetic
environment data storing unit 36. The electromagnetic
simulation unit 32 is therefore used for building the
electromagnetic environment data storing unit 36. The
skilled addressee should understand that a mapping of the
electromagnetic environment is dynamically performed by the
electromagnetic simulation unit 32 and that the
electromagnetic environment data storing unit 36 is
continuously updated. Only selected parts of the
electromagnetic environment data storing unit 36 are
preferably updated which avoid unnecessary computations.
The selected part are selected according to various
criteria such as a frequency band, a knowledge of a former
position of the wireless mobile unit 10, a level of
activity in a given part of the electromagnetic
environment, a client need, etc.
The electromagnetic environment data storing unit 36 stores
data preferably in a matrix form and comprises
electromagnetic data for the environment.
It will be appreciated that the electromagnetic environment
data manipulation unit 35 may also provide at least one
part of the acquired data signal to the electromagnetic
environment data storing unit 36.
The position detection unit 38 receives a measured data
signal provided by the wireless receiving unit 40 and uses
the electromagnetic environment data storing unit 36 to
create an estimated position signal as explained below.
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The estimated position signal is provided to the position
providing unit 39. The position providing unit 39 may
provide the estimated position signal of the wireless
mobile unit 10 to a plurality of destinations depending on
an application sought. For instance, the wireless mobile
positioning server 18 may performs a tracking of the
wireless mobile unit 10 without submitting any information
to the wireless mobile unit 10. Alternatively, it may be
desirable to provide the estimated position signal to the
wireless mobile unit 10.
Now referring to Fig. 4, there is shown how a mapping of an
RF environment is performed.
According to step 40, a physical layout of the environment
is provided.
Now referring to Fig. 5, there is shown how the physical
layout of the environment is provided.
According to step 50, a physical layout is scanned. The
physical layout may be selected from the group consisting
of floor plans, maps, architecture sketch, libraries
comprising data about materials used for at least one of
building and furnishing a place, etc. Alternatively, the
physical layout is directly provided in an electronic
format such as a binary file of a given file format such as
AutoCAD (TM) .
In an embodiment, the physical layout is scanned using the
physical layout providing unit 30.
According to step 52, obstacles and RF sources are
identified in the scanned physical layout. In fact, after
scanning the physical layout, a processing is performed in
order to detect in the scanned physical layout pertinent
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elements that may affect radiowave transmission such as
structural elements as well as RF sources. The pertinent
elements may comprise physical structures, walls,
obstacles, objects, floor, ceiling, apparatus, or the like.
The processing is performed in accordance with the type of
physical layout provided. In an embodiment of the
invention, the physical layout to scan is a plan of the
building.
Still referring to Fig. 5 and according to step 54, needs
for beacons are determined in the scanned physical layout
considering the identified obstacles.
In an embodiment, the needs for beacons are determined in
the scanned layout by providing the physical layout data
signal to the electromagnetic simulation unit 32 and
performing a simulation using the electromagnetic
simulation unit 32. The skilled addressee will appreciate
that pertinent elements may influence the propagation of
wireless signals and that accordingly it is desirable to
find out needs for beacons for communicating with a
wireless mobile unit 10 for the purpose of communicating
with the wireless mobile unit 10. Furthermore, the needs
for positioning the wireless mobile unit 10 may be achieved
using other wireless transmitting units communicating on
various frequency bands. In an embodiment, the needs for
beacons are displayed to a user via a user interface not
shown in the drawings. More precisely, the needs for
beacons are identified by marking a corresponding physical
area of the provided layout with a specific color. The
color may be used to indicate various qualities of signals
available and/or frequency bands.
Now referring back to Fig. 4 and according to step 42, a
plurality of beacons is positioned in the physical layout.
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The plurality of beacons is positioned in the physical
layout using the beacon data manipulation unit 33.
In one embodiment, the plurality of beacons is positioned
via a user interface, not shown in the figure. In such
case, the user selects a suitable position for positioning
the plurality of beacons according to the determined needs
for beacons. Alternatively, the plurality of beacons is
positioned automatically according to the determined needs
for beacons.
According to step 44, an influence of the pertinent
elements and other RF sources is simulated. More precisely,
the electromagnetic simulation unit 32 receives the
physical layout data signal provided by the physical layout
providing unit 30 and the beacon data signal provided by
the beacon data manipulation unit 33 and simulates the
influence of the pertinent elements in the propagation of
wireless signals transmitted by the other RF sources. In an
embodiment, the simulation is performed as follows.
According to a first step, a pertinent wireless
transmitting source is selected. According to a second
step, the physical layout is partitioned into a plurality
of zones which are created for each of the selected
pertinent wireless transmitting source. It will be
appreciated that each zone of the plurality of zones is
defined as a geographical zone wherein a plurality of
wireless signals transmitted by the selected pertinent
wireless transmitting source propagates in a similar way.
The skilled addressee will therefore appreciate that such
zones are 3-dimensional polygons. According to a third
step, a simulation is performed for a plurality of points
in each zone. In one embodiment the plurality of points
comprises the edges of the zone. According to a fourth
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step, an interpolation is performed for each other points
of the zone using the results of the simulation performed
for the plurality of points. The skilled addressee will
appreciate that this is of great advantage for simulating
the influence of each pertinent elements in the propagation
of wireless signals transmitted by a pertinent wireless
transmitting source.
According to step 46, an RF environment is calculated using
RF signals and the influence of pertinent elements and the
plurality of beacons.
Now referring to 6, there is shown how the RF environment
is calculated.
According to step 60, an RF environment is estimated using
the RF signals transmitted and the influence of the
pertinent elements and other RF sources.
According to step 62, a test is performed in order to find
out if the estimated RF environment is suitable for a given
application.
In the case where the estimated RF environment is not
suitable for the given application, the positioning of a
beacon is modified in the physical layout using the beacon
data manipulation unit 33.
Now referring back to Fig. 4 and according to step 48, the
RF environment is mapped using the simulated influence of
the pertinent elements and the other RF sources and further
using the calculated RF environment.
The mapped RF environment is stored in the electromagnetic
environment data storing unit 36 and may be used in order
to provide an estimated position signal of the wireless
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mobile unit 10 as shown in the co-pending patent
application that is concurrently filed and is entitled
"Method for positioning an RF transceiver in a known area".
The mapped RF environment may be provided as a matrix or as
a database. It should be understood that such mapped RF
environment comprises a plurality of entries, each
comprising data indicative of a wireless signal and a
corresponding position established preferably in a 3
dimensional coordinate system for each of at least one
frequency band.
Furthermore, it should be understood that the mapped RF
environment comprises a plurality of subsets or sub-
matrices, in the case where the mapped RF environment is
provided as a matrix. The plurality of subsets is defined
according to the plurality of zones defined herein above.
The skilled addressee will appreciate that providing such
plurality of sub-matrices is of great advantage as it
enables the updating of a limited part of the mapped RF
environment. In fact, updating a limited part of the mapped
RF environment is of great interest as it enables an
efficient use of the processing resources required to
update data.
The embodiments of the invention described above are
intended to be exemplary only. The scope of the invention
is therefore intended to be limited solely by the scope of
the appended claims.
