U.S. patent application number 14/011648 was filed with the patent office on 2013-12-26 for indoor localization using commercial frequency-modulated signals.
This patent application is currently assigned to Microsoft Corporation. The applicant listed for this patent is Microsoft Corporation. Invention is credited to Yin Chen, Jie Liu, Dimitrios Lymberopoulos, Nissanka Arachchige Bodhi Priyantha.
Application Number | 20130344892 14/011648 |
Document ID | / |
Family ID | 48610624 |
Filed Date | 2013-12-26 |
United States Patent
Application |
20130344892 |
Kind Code |
A1 |
Lymberopoulos; Dimitrios ;
et al. |
December 26, 2013 |
INDOOR LOCALIZATION USING COMMERCIAL FREQUENCY-MODULATED
SIGNALS
Abstract
A commercial frequency-modulated (FM) radio signal indoor
localization system and method for finding a location of a mobile
embedded device (such as a smartphone) within a building. Indoor
localization is performed by receiving commercial FM radio signals
on the device, analyzing the signals using signal quality metrics,
and generating signal quality vectors for each signal and signal
quality metric used for the signal. The signal quality metric can
be any physical signal quality indicator. The signal quality
vectors are added to obtain a current location fingerprint. The
current location fingerprint is compared to fingerprints stored in
a fingerprint database. The location associated with the stored
fingerprint that is the closest match to the current fingerprint
location is designated as the current location in the building of
the mobile embedded device. Locally generated radio signals can be
used in conjunction with the commercial FM radio signals to improve
localization accuracy.
Inventors: |
Lymberopoulos; Dimitrios;
(Bellevue, WA) ; Liu; Jie; (Medina, WA) ;
Priyantha; Nissanka Arachchige Bodhi; (Redmond, WA) ;
Chen; Yin; (Baltimore, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Microsoft Corporation |
Redmond |
WA |
US |
|
|
Assignee: |
Microsoft Corporation
Redmond
WA
|
Family ID: |
48610624 |
Appl. No.: |
14/011648 |
Filed: |
September 10, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13328613 |
Dec 16, 2011 |
8548497 |
|
|
14011648 |
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Current U.S.
Class: |
455/456.1 |
Current CPC
Class: |
G01S 5/0252 20130101;
H04W 4/33 20180201; H04W 4/60 20180201; H04W 64/00 20130101 |
Class at
Publication: |
455/456.1 |
International
Class: |
H04W 4/04 20060101
H04W004/04 |
Claims
1-20. (canceled)
21. A computer system comprising: one or more processing units; and
one or more computer storage media storing computer-executable
instructions which, when executed by the one or more processing
units, cause the one or more processing units to: obtain multiple
different signal indicators for a frequency-modulated signal, the
multiple different signal indicators characterizing the
frequency-modulated signal as received by a mobile device; and
compare the multiple different signal indicators to a fingerprint
database to obtain a current location of the mobile device.
22. The computer system of claim 21, embodied as the mobile
device.
23. The computer system of claim 21, wherein the
frequency-modulated signal is a commercial frequency-modulated
signal.
24. The computer system of claim 23, wherein the multiple different
signal indicators comprise: a received signal strength indicator of
the commercial frequency-modulated signal; a multipath indicator of
the commercial frequency-modulated signal; and a frequency offset
indicator of the commercial frequency-modulated signal.
25. The computer system of claim 23, wherein the commercial
frequency-modulated signal is transmitted by a radio station at a
frequency between 87.8 megahertz and 108 megahertz.
26. The computer system of claim 21, wherein the
frequency-modulated signal is a locally-generated
frequency-modulated signal.
27. The computer system of claim 26, wherein the multiple different
signal indicators comprise: a received signal strength indicator of
the locally-generated frequency-modulated signal; a multipath
indicator of the locally-generated frequency-modulated signal; and
a frequency offset indicator of the locally-generated
frequency-modulated signal.
28. A method implemented by at least one computer processing unit,
the method comprising: obtaining a current location fingerprint of
a mobile device, the current location fingerprint comprising
multiple different signal indicators for a plurality of commercial
frequency-modulated radio signals that are received by the mobile
device; and determining a current location of the mobile device
using the current location fingerprint.
29. The method of claim 28, wherein the at least one computer
processing unit is embodied in the mobile device.
30. The method of claim 29, further comprising receiving the
plurality of commercial frequency-modulated signals at the mobile
device.
31. The method of claim 28, wherein determining the current
location comprises matching the current location fingerprint to a
matching fingerprint stored in a fingerprint database that is
located remotely from the mobile device.
32. The method of claim 28, wherein the current location
fingerprint comprises one or more vectors of individual signal
indicators.
33. The method of claim 28, wherein the multiple different signal
indicators include: a received signal strength indicator of an
individual commercial frequency-modulated signal; and a multipath
indicator of the individual commercial frequency-modulated
signal.
34. The method of claim 28, wherein the multiple different signal
indicators include: a received signal strength indicator of an
individual commercial frequency-modulated signal; and a frequency
offset indicator of the individual commercial frequency-modulated
signal.
35. The method of claim 28, wherein the multiple different signal
indicators include: a multipath indicator of an individual
commercial frequency-modulated signal; and a frequency offset
indicator of the individual commercial frequency-modulated
signal.
36. One or more volatile or non-volatile storage devices storing
executable instructions which, when executed by one or more
processing units, cause the one or more processing units to perform
acts comprising: obtaining multiple different signal indicators for
a frequency-modulated signal, the multiple different signal
indicators characterizing the frequency-modulated signal as
received by a mobile device; and obtaining a current location of
the mobile device using the multiple different signal
indicators.
37. The one or more volatile or non-volatile storage devices of
claim 36, embodied in the mobile device with the one or more
processing units.
38. The one or more volatile or non-volatile storage devices of
claim 36, wherein the obtaining the multiple different signal
indicators comprises: receiving the frequency-modulated signal; and
analyzing the frequency-modulated signal to determine the multiple
different signal indicators.
39. The one or more volatile or non-volatile storage devices of
claim 36, the acts further comprising: obtaining other multiple
different signal indicators for another frequency-modulated signal;
and obtaining the current location using both the multiple
different signal indicators for the frequency-modulated signal and
the other multiple different signal indicators for the another
frequency-modulated signal.
40. The one or more volatile or non-volatile storage devices of
claim 39, wherein both the frequency-modulated signal and the
another frequency-modulated signal are commercial
frequency-modulated signals transmitted by different radio
stations.
Description
BACKGROUND
[0001] Accurately determining the location of mobile embedded
devices (such as smartphones) in indoor environments can be
difficult. A global positioning systems (GPS) cannot be used
because the needed satellite signals are hard to receive indoors
because they are blocked by the walls of the building.
[0002] There are a number of existing approaches to indoor
localization. One approach is a WiFi.RTM.-based indoor localization
(WiFi.RTM. is a registered trademark of the WiFi Alliance in
Austin, Tex.). In general, this type of approach records the signal
strength from WiFi.RTM. access points in the immediate vicinity.
Given the location of the WiFi.RTM. access points, the location of
the mobile device can be calculated. Similar approaches have also
been used where FM radio transmitters deployed in the building are
used instead of WiFi.RTM. signals.
[0003] Another approach is proximity-based indoor localization.
This type of approach uses a large number of low-power radios (such
as RFIDs, low-power Bluetooth.RTM. devices (Bluetooth.RTM. is a
registered trademark of the Bluetooth.RTM. Special Interest Group
in Kirkland, Wash.), FM radio transmitters) that are deployed in
every room or location that needs to be localized. The mobile
embedded device detects proximity to and obtains its location from
the nearest low-power radio source or sources.
[0004] Each of these approaches measure a signal strength between
the mobile embedded device and the transmitter. The indoor space of
the building then is profiled by creating a map of the signal
strength. For example, this profiling may occur by measuring the
signal strength along every meter of the indoor space and recording
each of the record wireless access points that can be connected to
at each location. This collection (or vector) of signal strengths
becomes the "fingerprint" of that indoor location. This is
performed for a large numbers of locations within the building to
create a fingerprint database that consists of pairs of ground
truth locations and signal strength vectors.
[0005] Once the fingerprint database is obtained, any user can
enter the building with his mobile embedded device and localize the
device. The mobile embedded device will determine which local radio
transmitters are within the range of the device, and will record
the signal strength from these individual transmitters at the
user's current location in the building. The fingerprint of the
mobile embedded device at the location in the building is compared
to the fingerprint database to find the closest match. The position
that is associated to the closest fingerprint match in the database
is assumed to be the location of the mobile embedded device in the
building.
[0006] One problem, however, with using local radio transmitters
(such as WiFi.RTM.) is that it operates at the 2.4 GHz range, which
means that its signal strength is susceptible to human presence,
device orientation, and presence of small objects in a room.
Additionally, these parameters change over time, further impacting
the signal strength of WiFi.RTM. signals, and leading to additional
errors in the indoor localization.
SUMMARY
[0007] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter.
[0008] Embodiments of the commercial FM radio signal indoor
localization system and method enable indoor localization of mobile
embedded devices (such as smartphones) using commercial
frequency-modulated (FM) radio signals. In other words, embodiments
of the system and method use commercial FM radio signal broadcasts
to find which room in a building the device is located. Embodiments
of the system and method use the commercial FM radio signals either
alone or in combination with one or more other types of
locally-generated radio signals. These are radio signals that are
generated locally in the close vicinity or within the building.
These other types of locally-generated radio signals include
WiFi.RTM., Bluetooth.RTM., and local FM signals.
[0009] Commercial FM radio signals are used by embodiments of the
system and method because there is an existing and large
infrastructure of commercial FM radio stations throughout the
country. This is especially true in urban areas. Moreover, because
of the low frequency at which these signals operate, they achieve
improved penetration through structures, walls and furniture over
WiFi.RTM., Bluetooth.RTM., or most other radio signals. In
addition, because of the wavelength, FM radio signals have improved
resilience to small objects, human presence, and to multipath and
fading effects. Further, a WiFi.RTM. receiver generally uses more
power on a mobile embedded device that an FM radio receiver.
[0010] Embodiments of the system and method first build a database
of commercial FM radio signal quality vectors that are used for the
indoor localization. These signal quality vectors are used to
generate a fingerprint at a specific location within the building.
The building is profiled by measuring the radio signals at set
locations in the building and obtaining fingerprints for the
locations. These fingerprints then are stored in a fingerprint
database along with the location at which they were recorded.
[0011] Later, when a user carries his mobile embedded device into a
mapped building, embodiments of the system and method use the
receiver in the device to automatically synchronize to the
different available commercial FM radio stations. In some
embodiments, other types of radio signals are also used. Next, one
or more signal quality metrics are applied to each of the radio
signals in order to construct a signal quality vector. There is a
signal quality vector for each signal quality metric associated
with a particular radio signal. Several different types of signal
quality metrics of each type of radio signal may be used, including
received signals strength indication (RSSI), signal-to-noise ratio
(SNR), multipath indicators, and frequency offset indicators. The
same process can be repeated for other available wireless signals,
such as WiFi.RTM. signals, and the resulting signal vectors from
each type of wireless signal can be combined to form a single
signature.
[0012] Embodiments of the system and method then construct a
fingerprint for the current location in the building using the
signal quality vectors. This current location fingerprint is
compared to the fingerprints in the fingerprint database. The
closest match is found between the current location fingerprint and
a fingerprints in the fingerprint database. The stored fingerprint
in the database that is the closest match to the current location
fingerprint is designated as the current location in the building
of the mobile embedded device.
[0013] It should be noted that alternative embodiments are
possible, and steps and elements discussed herein may be changed,
added, or eliminated, depending on the particular embodiment. These
alternative embodiments include alternative steps and alternative
elements that may be used, and structural changes that may be made,
without departing from the scope of the invention.
DRAWINGS DESCRIPTION
[0014] Referring now to the drawings in which like reference
numbers represent corresponding parts throughout:
[0015] FIG. 1 is a block diagram illustrating a general overview of
embodiments of the commercial FM radio signal indoor localization
system and method implemented in a computing environment.
[0016] FIG. 2 is a flow diagram illustrating the detailed operation
of embodiments of the commercial FM radio signal indoor
localization system and method shown in FIG. 1.
[0017] FIG. 3 illustrates a simplified example of a general-purpose
computer system on which various embodiments and elements of the
commercial FM radio signal indoor localization system and method,
as described herein and shown in FIGS. 1-2, may be implemented.
DETAILED DESCRIPTION
[0018] In the following description of embodiments of a commercial
FM radio signal indoor localization system and method reference is
made to the accompanying drawings, which form a part thereof, and
in which is shown by way of illustration a specific example whereby
embodiments of the commercial FM radio signal indoor localization
system and method may be practiced. It is to be understood that
other embodiments may be utilized and structural changes may be
made without departing from the scope of the claimed subject
matter.
I. Commercial Frequency-Modulated (FM) Radio Signals
[0019] Embodiments of the commercial FM radio signal indoor
localization system and method make use of commercial FM radio
signals, such as those used by commercial FM radio stations.
Currently, the FM band occupies 87.8-108 MHz, a total of 20.2 MHz
and 101 channels. There are usually multiple FM radio stations
available at a given location. In addition, some transmission
towers are shared by several FM stations.
[0020] Commercial FM broadcasting is usually strong enough for
outdoor reception. In addition, the indoor penetration of
commercial FM radio signal is also high. The wavelength of the FM
radio signals is about 3 meters. Thus indoor propagation is less
sensitive to the smaller objects, but is more determined by large
obstacles such as walls. For the same reason, FM signals are less
susceptible to human presence and orientation. This means that FM
radio signals are typically more stable in an indoor environment
than radio signals of shorter wavelength, such as WiFi.RTM. and
Bluetooth.RTM..
[0021] Moreover, FM receivers are widely available in mobile
embedded devices (such as smartphones) due to their small footprint
and low cost. As compared to Wi-Fi.RTM., FM receivers also consume
much less energy (about 15 mW versus 300 mW). Thus, compared to
other types of radio signals (such as Wi-Fi.RTM.), commercial FM
radio signals require less power, are less susceptible to human
presence and small objects, and have improved penetration.
II. System Overview
[0022] Embodiments of the commercial FM radio signal indoor
localization system and method leverage commercial FM radio signals
transmitted by already deployed FM radio towers to profile indoor
locations and perform signature-based indoor localization of a
mobile embedded device. FIG. 1 is a block diagram illustrating a
general overview of embodiments of the commercial FM radio signal
indoor localization system 100 and method implemented in a
computing environment. In particular, embodiments of the commercial
FM radio signal indoor localization system 100 and method are shown
implemented on an mobile embedded device 105 (such as a
smartphone).
[0023] Embodiments of the commercial FM radio signal indoor
localization system 100 and method include a receiver 110 that is
capable of receiving radio signals. These radio signals may be a
variety of types of radio signals. However, in each embodiment of
the system 100 and method the receiver 110 is capable of receiving
commercial FM radio signals broadcasted by FM radio transmitters.
These FM radio transmitters include N number of commercial FM radio
transmitters. As shown in FIG. 1, the N number of commercial FM
radio transmitters include commercial FM radio transmitter (1) to
commercial FM radio transmitter (N), where N can be any positive
integer from 1 or more.
[0024] It should be noted that the term "commercial" is used to
denote that the commercial FM radio transmitters (1) to (N)
broadcast their FM radio signals over a wide area. These FM radio
signals are broadcast wirelessly over the airwaves, as denoted by
the first communication link 115 from commercial FM radio
transmitter (1) to the mobile embedded device 105 and the second
communication link 120 from commercial FM radio transmitter (N) to
the mobile embedded device 105. Typically, the commercial FM radio
transmitters (1) to (N) will be associated with one or more
commercial FM radio stations. Moreover, these transmitters
typically will broadcast their FM radio signals over a wide area
involving several square miles, such as tens or hundreds of square
miles.
[0025] Moreover, a commercial FM radio signal is not dedicated only
to the indoor localization process, unlike most existing
techniques. In fact, the commercial FM radio signal's primary
intent is not for indoor localization but for carrying radio
broadcasts. Using commercial FM radio signals does not require the
deployment of any device in any building. This also limits the cost
associated with large-scale deployment of transmitters throughout a
building.
[0026] Some embodiments of the commercial FM radio signal indoor
localization system 100 and method also include using local radio
transmitters. It should be noted the term "local" is used to
indicate that the radio signals are broadcast over a short
geographic range, such as less than a half mile or so. Typically,
these local radio transmitters are designed to transmit within a
building, such as with a WiFi.RTM. network.
[0027] As shown in FIG. 1, these optional local radio transmitters
include local radio transmitter (1) to local radio transmitter (M),
where M is some positive integer that is 1 or greater. These local
radio signals are broadcast wirelessly locally over the airwaves,
as denoted by the third communication link 125 from local radio
transmitter (1) to the mobile embedded device 105 and the fourth
communication link 130 from local radio transmitter (M) to the
mobile embedded device 105. The local radio transmitter (1) to (M)
are optional, as denoted by the dotted third communication link 125
and the dotted fourth communication link 130. The local radio
transmitters (1) to (M) may be any type of radio signal, such as a
WiFi.RTM., Bluetooth.RTM., or even a local non-commercial FM radio
signal.
[0028] These local radio transmitters (1) to (M) typically have a
short geographic range, such as within an enclosed building or
structure. FIG. 1 illustrates this building 135 (or structure) as a
heavy solid line. Note that the mobile embedded device 105 and the
optional local radio transmitters (1) to (M) are located within the
building 135.
[0029] Embodiments of the commercial FM radio signal indoor
localization system 100 and method include an optional fingerprint
profiling module 140. The optionality of the module 140 is shown by
the dotted lines around the module 140. The module 140 is used
during a profiling stage of the method to profile the radio signal
fingerprints at various location in the building 135. These
fingerprints are stored in a fingerprint database 145. In some
embodiments, the fingerprint database resides on a web server 150
in a cloud computing environment 155. The cloud computing
environment is in communication with the mobile embedded device 105
over a fifth communications link 160.
[0030] The two-way communication between the fingerprint profiling
module 140 and the fifth communications link 160 is shown as a
dotted two-way arrow to indicate that this the profiling is an
optional process. In reality, the profiling is done at least once
in order to populate the fingerprint database 145. However, the
fingerprint profiling module 140 does not have to be performed on
the mobile embedded device 105 and may be performed with any other
type of devices capable of receiving the radio signals and
generating the associated fingerprints. Fingerprints can also be
automatically crowdsourced by real users as they check-in to
different business from their mobile devices. Every time a check-in
is taking place, the signal vectors are recorded on the mobile
device, annotated with the location of the business the user
checked in and uploaded to the fingerprint database.
[0031] Once the fingerprint database 145 is populated and the
building 135 is profiled, any mobile embedded device containing
embodiments of the system 100 and method can be determine a
location of the device 105 within the building 135, even without
the optional fingerprint profiling module 140. In FIG. 1, the
optional fingerprint profiling module 140 is shown on the mobile
embedded device 105 merely for ease of describing embodiments of
the system 100 and method.
[0032] Embodiments of the commercial FM radio signal indoor
localization system 100 and method include a radio signal quality
metric module 165 and a fingerprint matching module 170. In order
to find a location of the mobile embedded device 105 once the
fingerprint database 145 has been populated, embodiments of the
system 100 and method receive radio signals on the receiver 110 and
process these radio signals using the radio signal quality metric
module 165. Embodiments of the module 165 use one or more signal
quality metrics to measure a signal quality of the incoming radio
signals.
[0033] The signal quality of the incoming signals is used to
generate a location fingerprint 175 based on the signal quality
metrics. This location fingerprint 175 is used to update the
fingerprint database 145. In addition, the location fingerprint 175
is process by the fingerprint matching module 170 in order to
determine a current location 180 of the mobile embedded device 105
at the indoor location. This process is explained in more detail
below.
II.A. Fingerprint Profiling Module
[0034] Some embodiments of the commercial FM radio signal indoor
localization system 100 and method include the fingerprint
profiling module 140. The module 140 is used during a profiling
stage of the method to profile the radio signal fingerprints in the
building 135. Specifically, at a given location inside the building
135, the desired signal quality metrics are recorded using the
receiver 110 and the radio signal quality metric module 165. This
is performed at the given location for every radio signal frequency
(or radio station) that the mobile embedded device 105 can
receive.
[0035] This collection of radio signal quality metric information
across each of the plurality of radio signals becomes a "signature"
or fingerprint for the given location in the building 135. Whenever
a user is in an unknown location in the building 135, the mobile
embedded device 105 uses a current location fingerprint generated
from the plurality of radio signals to and compares it against the
fingerprint database 145 of already collected fingerprints. As
explained in detail below, the closest fingerprint from the
fingerprint database 145 is selected and its corresponding location
is assumed to be the current location of the user.
[0036] In some embodiments of the commercial FM radio signal indoor
localization system 100 and method the fingerprint profiling module
140 is not used. Instead, the GPS location of the mobile embedded
device 105 can be associated with signal quality vectors (described
below). This avoids the need to profile the entire building 135. As
the user checks into a business in the building 135 the map of the
business will be known to the mobile embedded device 105. This
means that the GPS location of the mobile embedded device 105 can
be associated with the signal quality vectors and the fingerprint
database for the business in the building. In this case, there is
longer a need to manually fingerprint the entire building. In many
cases the user's consent will be obtained prior to releasing any
user data (such as the user's location).
III. Operational Details
[0037] FIG. 2 is a flow diagram illustrating the detailed operation
of embodiments of the commercial FM radio signal indoor
localization system 100 and method shown in FIG. 1. As shown in
FIG. 2, the operation of embodiments of the commercial FM radio
signal indoor localization method begins by using the mobile
embedded device 105 to receive a plurality of radio signals at a
current indoor location (box 200). The plurality of radio signals
includes at least one commercial FM radio signal.
[0038] In some embodiments, only commercial FM radio signals are
used for the indoor localization of the mobile embedded device 105.
In other embodiments, the commercial FM radio signal and other
types of local radio signals are used. These two general
embodiments will now be discussed in further detail.
III.A. Commercial FM Radio Signals for Indoor Localization
[0039] Some embodiments of the commercial FM radio signal indoor
localization system 100 and method use only commercial FM radio
signals for the plurality of radio signals to perform indoor
localization. In these embodiments no other types of radio signals
are used. Although a single commercial FM radio signal may be used
for the indoor localization, improved results are obtained when
using a plurality of commercial FM radio signals.
[0040] One advantage to commercial FM radio signals is that they
are more robust than WiFi.RTM. radio signals. The receiver 110 on
the mobile embedded device 105 is used to collect individual
commercial FM radio signals. As explained below, the each
commercial FM radio signal received is analyzed using a signal
quality metric to obtain a signal quality vector. These vectors
together constitute a fingerprint that defines the indoor location
of the mobile embedded device 105.
[0041] The strength of the commercial FM radio signals does vary
over the course of the day. Moreover, there is some variation of
signal quality metrics over different receivers. However, it has
been shown that the variation is not that high to prevent
embodiments of the commercial FM radio signal indoor localization
system 100 and method from performing the indoor localization.
III.B. Combined Commercial FM Radio Signals and Local Radio
Signals
[0042] Some embodiments of the commercial FM radio signal indoor
localization system 100 and method pair the commercial FM radio
signals with additional local (or locally-generated) radio signals.
This allows these embodiments of the system 100 and method to
exhibit a marked improvement in indoor localization over techniques
that use the local radio signals alone.
[0043] In these combined embodiments, the plurality of radio
signals includes the commercial FM radio signals along with the
local radio signals. These local radio signals can include
WiFi.RTM. radio signals, Bluetooth.RTM. radio signals, or even
local FM radio signals from local FM radio transmitters. These
embodiments can include virtually any combination or type of radio
signals, as long as the commercial FM radio signals are
included.
[0044] In addition, signal quality metrics are used to analyze each
type of radio signal in the plurality of radio signals. Because
these embodiments have a plurality of different types of radio
signals, the fingerprints in the fingerprint database 145 have a
longer fingerprint that includes both the commercial FM radio
signal fingerprint and fingerprint from the other types of radio
signals.
[0045] These combined embodiments typically provide a higher indoor
localization accuracy that using just the local radio signals or
commercial FM radio signals alone. This means that the error is
complementary of the error that is obtained using just the local
radio signals along. Combined, the indoor localization becomes more
accurate.
[0046] Referring again to FIG. 2, one of the plurality of radio
signals is selected (box 205). Embodiments of the method then
select a signal quality metric (box 210). These signal quality
metrics include the received signals strength indication (RSSI),
signal-to-noise ratio (SNR), multipath indicators, and the offset
indicators. Each of these signal quality metrics will be discussed
below. However, it should be noted that any physical layer signal
quality indicator (or metric) can be used, besides the four listed
above. Moreover, all, one, or any combination of the signal quality
metrics may be used to analyze the plurality of radio signals.
III.C. Received Signal Strength Indication
[0047] The received signal strength indication (RSSI) is a signal
quality metric that existing receivers report. However, one problem
with the RSSI is that it is a high-level indication signal that
because it is high level it contains more noise that low-level
signals. More noise means more localization error.
[0048] It is desirable to use more low-level signal indicators in
place of or to augment a signal quality vector. By using more
indicators at the physical layer, we can generate more
discriminative signatures can be generated, which improves indoor
localization accuracy. Thus, instead of using only RSSI as the
signal quality metric for a selected radio signal, embodiments of
the system 100 and method can use other signal quality metrics in
place of or in addition to the RSSI signal quality metric. These
additional signal quality metrics include signal-to-noise ratio,
multipath indicators, and frequency offset of signal
indicators.
III.D. Signal-to-Noise Ratio
[0049] Another type of signal quality metric that can be used by
embodiments of the system 100 and method is the signal-to-noise
ratio (SNR). The SNR uses the fact that no wireless radio signal
has a perfect incoming signal. There is some noise because it is a
wireless transmission. The SNR measures the perturbation of the
incoming radio signal by indicating how strong the actual signal is
compared to the noise of the input signal. The higher the noise as
denoted by the SNR, then the lower the confidence in the quality of
the signal.
III.E. Multipath Indicators
[0050] Yet another type of signal quality metric that can be used
by embodiments of the system 100 and method is multipath
indicators. Whenever a wireless signal is transmitted, it is
reflected when it meets metallic or other types of objects. This
causes the receiver 110 to receive the original signal and a
plurality of reflected signals. The receiver 110 rarely receives a
single signal. It is usually receiving the original signal and its
reflected signals.
[0051] The multipath indicators indicate how many of these
reflected signals have been received. This is a valuable signal
quality metric because it can characterize the physical space in
which the person is occupying. This is because depending on the
space in which the person is occupying (including the walls and
furniture setup), the multipath indicators can be used to
characterize the room and therefore find the indoor location.
III.F. Frequency Offset of Signal
[0052] Still another type of signal quality metric that can be used
by embodiments of the system 100 and method is indicators of the
frequency offset of the signal. The receiver 110 receives multiple
signals at virtually the same time. These multiple signals, because
they travel different distances, usually have some delay that is
translated into frequency offset. This can be used as a signal
quality metric of the incoming signal.
[0053] Referring again to FIG. 2, once the signal quality metric is
selected, embodiments of the method then analyze the selected radio
signal using the selected signal quality metric (box 215). A signal
quality vector for the selected radio signal then is generated
using the selected signal quality metric (box 220). This signal
quality metric corresponding to the selected signal quality metric
and the selected radio signal is added to a current location
fingerprint (box 225).
[0054] A determination then is made as to whether there are
additional signal quality metrics that will be used on the selected
radio signal (box 230). If so, then embodiments of the method
select another signal quality metric (box 235). This newly selected
signal quality metric then is used to analyze the selected radio
signal (box 215) and generate a signal quality vector (box 220).
This signal quality vector for the newly selected signal quality
metric is added to the current location fingerprint (box 225).
[0055] If there are no additional signal quality metrics to be
processed for the selected radio signal, then a determination is
made as to whether there are additional radio signals to process
(box 240). If so, then embodiments of the method select another one
of the plurality of radio signal (box 245). Embodiments of the
method then process this selected radio signal as described above
in connection with boxes 210, 215, 220, 225, 230, and 235.
[0056] If there are no more radio signals to process, then
embodiments of the method compare the current location fingerprint
to fingerprints in the fingerprint database 145 (box 250). The
fingerprint in the fingerprint database 145 that most closely
matches the current location fingerprint is found. This "closest
match" means that the signal quality vectors of the current
location fingerprint and the fingerprint in the fingerprint
database 145 that is the closest match have values that are nearest
each other, as compared to the other fingerprints in the
fingerprint database 145.
[0057] Embodiments of the system 100 and method can use any one of
a variety of techniques to find the closest match between
fingerprints. In general, these techniques basically are given a
fingerprint to be localized and the fingerprint database 145, and
then find which entry in the fingerprint database 145 is the
closest to the given fingerprint. These techniques include distance
metric techniques that match the given fingerprints with the
fingerprint database 145. In addition, any type of metric, and any
type of smoothing on top of the metric can be used to compare the
signal quality vectors obtained from the mobile embedded device 105
to the fingerprint database 145.
[0058] Referring again to FIG. 2, embodiments of the method then
find a current indoor location of the mobile embedded device 105
based on the closest match in the fingerprint database 145 (box
255). In other words, the location corresponding to the fingerprint
in the fingerprint database 145 that is the closest match to the
current location fingerprint is designated as the current indoor
location of the mobile embedded device 105.
[0059] The fingerprint database 145 then is updated with the
current location fingerprint (box 260). This ensures that the
fingerprint database 145 contains current fingerprint information
about locations within the building 135. A determination then is
made as to whether the mobile embedded device 105 has moved within
the building 135 (box 265). If so, then the process described above
is repeated for the plurality of radio signals to obtain an updated
indoor location of the mobile embedded device 105. Otherwise, the
process is completed 270 until the mobile embedded device 105 is
moved again.
IV. Exemplary Operating Environment
[0060] Embodiments of the commercial FM radio signal indoor
localization system 100 and method described herein are operational
within numerous types of general purpose or special purpose
computing system environments or configurations. FIG. 3 illustrates
a simplified example of a general-purpose computer system on which
various embodiments and elements of the commercial FM radio signal
indoor localization system and method, as described herein and
shown in FIGS. 1-2, may be implemented. It should be noted that any
boxes that are represented by broken or dashed lines in FIG. 3
represent alternate embodiments of the simplified computing device,
and that any or all of these alternate embodiments, as described
below, may be used in combination with other alternate embodiments
that are described throughout this document.
[0061] For example, FIG. 3 shows a general system diagram showing a
simplified computing device 10. Such computing devices can be
typically be found in devices having at least some minimum
computational capability, including, but not limited to, personal
computers, server computers, hand-held computing devices, laptop or
mobile computers, communications devices such as cell phones and
PDA's, multiprocessor systems, microprocessor-based systems, set
top boxes, programmable consumer electronics, network PCs,
minicomputers, mainframe computers, audio or video media players,
etc.
[0062] To allow a device to implement embodiments of the commercial
FM radio signal indoor localization system 100 and method described
herein, the device should have a sufficient computational
capability and system memory to enable basic computational
operations. In particular, as illustrated by FIG. 3, the
computational capability is generally illustrated by one or more
processing unit(s) 12, and may also include one or more GPUs 14,
either or both in communication with system memory 16. Note that
that the processing unit(s) 12 of the general computing device of
may be specialized microprocessors, such as a DSP, a VLIW, or other
micro-controller, or can be conventional CPUs having one or more
processing cores, including specialized GPU-based cores in a
multi-core CPU.
[0063] In addition, the simplified computing device of FIG. 3 may
also include other components, such as, for example, a
communications interface 18. The simplified computing device of
FIG. 3 may also include one or more conventional computer input
devices 20 (e.g., pointing devices, keyboards, audio input devices,
video input devices, haptic input devices, devices for receiving
wired or wireless data transmissions, etc.). The simplified
computing device of FIG. 3 may also include other optional
components, such as, for example, one or more conventional computer
output devices 22 (e.g., display device(s) 24, audio output
devices, video output devices, devices for transmitting wired or
wireless data transmissions, etc.). Note that typical
communications interfaces 18, input devices 20, output devices 22,
and storage devices 26 for general-purpose computers are well known
to those skilled in the art, and will not be described in detail
herein.
[0064] The simplified computing device of FIG. 3 may also include a
variety of computer readable media. Computer readable media can be
any available media that can be accessed by computer 10 via storage
devices 26 and includes both volatile and nonvolatile media that is
either removable 28 and/or non-removable 30, for storage of
information such as computer-readable or computer-executable
instructions, data structures, program modules, or other data. By
way of example, and not limitation, computer readable media may
comprise computer storage media and communication media. Computer
storage media includes, but is not limited to, computer or machine
readable media or storage devices such as DVD's, CD's, floppy
disks, tape drives, hard drives, optical drives, solid state memory
devices, RAM, ROM, EEPROM, flash memory or other memory technology,
magnetic cassettes, magnetic tapes, magnetic disk storage, or other
magnetic storage devices, or any other device which can be used to
store the desired information and which can be accessed by one or
more computing devices.
[0065] Retention of information such as computer-readable or
computer-executable instructions, data structures, program modules,
etc., can also be accomplished by using any of a variety of the
aforementioned communication media to encode one or more modulated
data signals or carrier waves, or other transport mechanisms or
communications protocols, and includes any wired or wireless
information delivery mechanism. Note that the terms "modulated data
signal" or "carrier wave" generally refer to a signal that has one
or more of its characteristics set or changed in such a manner as
to encode information in the signal. For example, communication
media includes wired media such as a wired network or direct-wired
connection carrying one or more modulated data signals, and
wireless media such as acoustic, RF, infrared, laser, and other
wireless media for transmitting and/or receiving one or more
modulated data signals or carrier waves. Combinations of the any of
the above should also be included within the scope of communication
media.
[0066] Further, software, programs, and/or computer program
products embodying the some or all of the various embodiments of
the commercial FM radio signal indoor localization system 100 and
method described herein, or portions thereof, may be stored,
received, transmitted, or read from any desired combination of
computer or machine readable media or storage devices and
communication media in the form of computer executable instructions
or other data structures.
[0067] Finally, embodiments of the commercial FM radio signal
indoor localization system 100 and method described herein may be
further described in the general context of computer-executable
instructions, such as program modules, being executed by a
computing device. Generally, program modules include routines,
programs, objects, components, data structures, etc., that perform
particular tasks or implement particular abstract data types. The
embodiments described herein may also be practiced in distributed
computing environments where tasks are performed by one or more
remote processing devices, or within a cloud of one or more
devices, that are linked through one or more communications
networks. In a distributed computing environment, program modules
may be located in both local and remote computer storage media
including media storage devices. Still further, the aforementioned
instructions may be implemented, in part or in whole, as hardware
logic circuits, which may or may not include a processor.
[0068] Moreover, although the subject matter has been described in
language specific to structural features and/or methodological
acts, it is to be understood that the subject matter defined in the
appended claims is not necessarily limited to the specific features
or acts described above. Rather, the specific features and acts
described above are disclosed as example forms of implementing the
claims.
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