U.S. patent application number 14/980103 was filed with the patent office on 2017-06-29 for location-aware communication system using visible light transmission.
The applicant listed for this patent is Wisconsin Alumni Research Foundation. Invention is credited to Suman Banerjee, Chi Zhang, Jialiang Zhang, Xinyu Zhang.
Application Number | 20170187454 14/980103 |
Document ID | / |
Family ID | 59086887 |
Filed Date | 2017-06-29 |
United States Patent
Application |
20170187454 |
Kind Code |
A1 |
Zhang; Xinyu ; et
al. |
June 29, 2017 |
Location-Aware Communication System Using Visible Light
Transmission
Abstract
A visible light communication system identifies the location of
a mobile device using light intensities corrected by mobile device
orientation. This location can be used to generate a dynamic
cluster of visible light transmitters about the mobile device
providing improved "handoff" between transmitters and reduced
shadowing.
Inventors: |
Zhang; Xinyu; (Madison,
WI) ; Banerjee; Suman; (Madison, WI) ; Zhang;
Jialiang; (Madison, WI) ; Zhang; Chi;
(Madison, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wisconsin Alumni Research Foundation |
Madison |
WI |
US |
|
|
Family ID: |
59086887 |
Appl. No.: |
14/980103 |
Filed: |
December 28, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 5/16 20130101; G01S
1/7034 20190801; H04W 4/026 20130101; H05B 47/19 20200101; G01S
1/7038 20190801; H04W 4/023 20130101; H04B 10/116 20130101; G01S
1/70 20130101 |
International
Class: |
H04B 10/116 20060101
H04B010/116; H04W 4/02 20060101 H04W004/02 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] This invention was made with government support under
CNS1318292, CNS1343363, CNS1350039, and CNS1404613 awarded by the
National Science Foundation. The government has certain rights in
the invention.
Claims
1. A location-aware communication system for mobile devices
comprising: (a) a plurality of light transmission units spatially
dispersed in an area through which a mobile device may move, the
light transmission units outputting a light signal into the area
including an identifier for each given light transmission unit; (b)
a mobile device including: (i) a light sensor for receiving light
from a set of the light transmission units and processing that
light to extract the identifier of the light transmission units of
the set and an intensity of the light signal; (ii) an orientation
sensing system sensing an orientation of the mobile device; and (c)
a location server communicating with the mobile device; wherein the
mobile device and location server execute stored programs held in
non-transitory medium to: (i) for each given light transmission
unit of the set, determine an intensity of the light signal
received at the mobile device by the light sensor, (ii) identify at
least one possible location of the mobile device with respect to
the given light transmission unit of the set based on a
relationship between intensity of the light signal and location of
the mobile device corrected for orientation of the mobile device;
(iii) use the at least one possible location of the mobile device
to determine a single location of the mobile device with respect to
the light transmission units of the set; wherein the orientation
sensing system includes a sensor sensing at least one of roll and
pitch of the mobile device with respect to gravity. wherein the
orientation sensing system includes sensors sensing yaw of the
device with respect to a predefined azimuth heading. wherein the
correction of the intensity of the light signal at the mobile
device uses predetermined relationships between light dispersion
from the given light transmission unit as a function of angle and
light sensitivity of the mobile device's light sensor unit as a
function of angle and a determination of a degree of alignment
between the light transmission unit and the light sensor unit based
on the orientation of the mobile device.
2-4. (canceled)
5. The location-aware system of claim 1 wherein step (iii) uses the
at least one possible location of the mobile device for multiple
given light transmission units to determine a single location of
the mobile device with respect to the light transmission units of
the set.
6. The location-aware system of claim 1 wherein step (iii) finds an
intersection of possible locations determined among different given
light transmission units to determine the single location among an
intersection of the possible locations.
7. The location-aware system of claim 1 wherein the mobile device
further includes at least one movement sensor and wherein step
(iii) calculates movement since a last determined single location
and wherein step (iii) determines the single location by combining
the at least one possible location and the movement since the last
determined signal location.
8. The location-aware system of claim 7 wherein step (iii) finds an
intersection of possible locations determined among different given
light transmission units to determine the single location among an
intersection of the possible locations.
9. The location-aware system of claim 1 wherein the light sensor is
a single photosensing element providing an identification of the at
least one possible location with respect to the given light
transmission unit to receive a light intensity signal from only a
single light sensor.
10. A location-aware communication system for mobile devices
comprising: (a) a plurality of light transmission units spatially
dispersed in an area through which a mobile device may move, the
light transmission units outputting a light signal into the area
including an identifier for each given light transmission unit; (b)
a mobile device including: (i) a light sensor for receiving light
from a set of the light transmission units and processing that
light to extract the identifier of the light transmission units of
the set and an intensity of the light signal; (ii) an orientation
sensing system sensing an orientation of the mobile device; and (c)
a location server communicating with the mobile device; wherein the
mobile device and location server execute stored programs held in
non-transitory medium to: (i) for each given light transmission
unit of the set, determine an intensity of the light signal
received at the mobile device by the light sensor; (ii) identify at
least one possible location of the mobile device with respect to
the given light transmission unit of the set based on a
relationship between intensity of the light signal and location of
the mobile device corrected for orientation of the mobile device;
(iii) use the at least one possible location of the mobile device
to determine a single location of the mobile device with respect to
the light transmission units of the set. wherein the location
server communicates with the light transmission units over a
network to control the light transmission units and the single
location of the mobile device is used to dynamically define the set
of light transmission units to move with the mobile device as the
mobile device moves.
11. The location-aware system of claim 10 wherein the selected
light transmission units of the set of light transmission units are
selected to surround the mobile device to reduce shadowing on the
mobile device by a mobile device user.
12. The location-aware system of claim 10 wherein the network is a
powerline communication network communicating data together with
power over power lines communicating with the light transmission
units.
13. The location-aware system of claim 10 wherein the location
server further communicates data to be transmitted synchronously
from each of the light transmission units of the set of light
transmission units.
14. The location-aware system of claim 1 wherein the light signal
is visible light and the light transmission units operate to
provide ambient light to the area.
15. The location-aware system of claim 1 wherein the mobile device
and the location device both further include a wireless transceiver
for communicating therebetween and wherein data needed to determine
the location of the mobile device is communicated from the mobile
device to the location server using the wireless transceivers.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0002] --
BACKGROUND OF THE INVENTION
[0003] The present invention relates to systems for accurately
locating mobile devices, and in particular to a system providing
location-aware visible light communication.
[0004] Increased use of light emitting diodes (LEDs) to provide for
the primary environmental lighting in buildings and the like
(termed herein "ambient lighting") has raised the possibility of
using these lights for data communication. Such data communication
systems take advantage of the ability of the LEDs to switch on and
off at a high rate of speed imperceptible to human eyes but
suitable for communicating data. The IEEE 802.1 5.7 standard has
established a basis for visible light communication protocols
allowing communication of up to 96 megabits per second.
[0005] While such visible light communication is practical for
point-to-point communication with a stationary device, ideally,
such a system could supplant standard wireless radio communication
used for mobile devices such as cell phones and the like. Extending
visible light communication to such devices, however, raises a
number of problems including sharing bandwidth when multiple users
are present and shadowing of the mobile device (for example, by the
user's body).
SUMMARY OF THE INVENTION
[0006] The present invention provides a system that can determine
the location of a mobile device using the light communication
signals by analyzing the intensity of the signals from various
light fixtures (of known position) adjusted by a measured
orientation of the mobile device. This location information may be
used to generate dynamic clusters of light fixtures that follow the
user with motion of the mobile device, allowing a reduced number of
light fixtures to be dedicated to a particular user while reducing
shadowing and interruptions during handoff between light
fixtures.
[0007] The present invention generally provides a system that moves
beyond localization using radio waves, which are far less
predictable in their falloff with distance, by correcting for the
confounding problem of inherent sensitivity of light signal
measurement to mobile device orientation.
[0008] Specifically, the invention provides a location-aware
communication system for mobile devices including a plurality of
light transmission units spatially dispersed in an area through
which a mobile device may move, the light transmission units
outputting a light signal into the area including an identifier for
each given light transmission unit; a mobile device and a location
server communicating with the mobile device. The mobile device
includes a light sensor for receiving light from a set of the light
transmission units and processing that light to extract the
identifier of the light transmission units of the set and an
intensity of the light signal and an orientation sensing system
sensing an orientation of the mobile device. The mobile device and
location server execute stored programs held in non-transitory
medium to: (i) for each given light transmission unit of the set,
determine an intensity of the light signal received at the mobile
device by the light sensor, (ii) identify at least one possible
location of the mobile device with respect to the given light
transmission unit of the set based on a relationship between
intensity of the light signal and location of the mobile device
corrected for orientation of the mobile device; and (iii) use the
at least one possible location of the mobile device to determine a
single location of the mobile device with respect to the light
transmission units of the set.
[0009] It is thus a feature of at least one embodiment of the
invention to provide a system that allows mobile devices to
identify their location without the need for auxiliary location
hardware such as radio beacons or the like.
[0010] The orientation sensor system may sense roll and/or
pitch.
[0011] It is thus a feature of at least one embodiment of the
invention to make use of common orientation sensors in mobile
devices to correct for changes in light sensor sensitivity as the
light sensor moves from an optimal vertical orientation.
[0012] In addition, the orientation sensor system may sense yaw of
the device with respect to a predefined azimuth heading.
[0013] It is thus a feature of at least one embodiment of the
invention to determine a "compass bearing" direction in which the
light sensor is oriented such as preferentially may receive light
from certain directions.
[0014] The correction of the intensity of the light signal at the
mobile device may use predetermined relationships between light
dispersion from the given light transmission unit as a function of
angle and light sensitivity of the mobile device light sensor unit
as a function of angle, and a determination of a degree of
alignment between the light transmission unit and the light sensor
unit based on the orientation of the mobile device.
[0015] It is thus a feature of at least one embodiment of the
invention to correct for the primary variability in receive light
signal intensity using the known angular gain curves of the light
transmitter and light receiver thereby allowing light intensity to
be used for localization.
[0016] The system may collect possible locations of the mobile
device with respect to multiple given light transmission units to
determine a single location of the mobile device with respect to
the light transmission units of the set. In one example, the system
may find an intersection of possible locations determined among
different given light transmission units to determine the single
location among an intersection of the possible locations.
[0017] It is thus a feature of at least one embodiment of the
invention to permit a trilateralization type location using
multiple light transmitters for improved accuracy and reduced noise
influence.
[0018] The mobile device may further include at least one movement
sensor that may calculate movement since a last determined single
location. In this case, the determined single location may be
determined by locations deduced by light intensity and the movement
since the last determined signal location.
[0019] It is thus a feature of at least one embodiment of the
invention to augment light intensity-based location sensing with
dead reckoning to minimize the number of light sources necessary
for localization or to refine that localization.
[0020] The light sensor may be a single photosensing element
providing an identification of the possible location with respect
to the given light transmission unit by receiving a light intensity
signal from only a single light sensor.
[0021] It is thus a feature of at least one embodiment of the
invention to allow localization without the need to provide an
imaging system such as a camera or to use camera functionality if
it is available.
[0022] The location server may communicate with the light
transmission units over a network to control the light transmission
units, and the single location of the mobile device is used to
dynamically define the set of light transmission units to move with
the mobile device as the mobile device moves.
[0023] It is thus a feature of at least one embodiment of the
invention to improve the efficiency of allocating light
transmitters to mobile devices by following or anticipating
movement of the mobile device with a small set of transmitters.
[0024] The light transmission units of the set may be selected to
surround the mobile device to reduce shadowing on the mobile device
by a mobile device user.
[0025] It is thus a feature of at least one embodiment of the
invention to provide a mobile experience using visible light
communication that better approximates shadow-free performance
provided by wireless radio signals.
[0026] The network may be a powerline communication network
communicating data together with power over power lines
communicating with the light transmission units.
[0027] It is thus a feature of at least one embodiment of the
invention to provide for the benefits of dynamic clustering of
light transmitters without requiring extensive infrastructure
changes through the use of existing power wiring.
[0028] The location server may communicate data to be transmitted
synchronously from each of the light transmission units of the set
of light transmission units.
[0029] It is thus a feature of at least one embodiment of the
invention to provide improved signal strength and resistance to
shadowing by synchronous transmission through a cluster of light
transmitters.
[0030] The light signal maybe visible light and the light
transmission units may operate to provide ambient light to the
area.
[0031] It is thus a feature of at least one embodiment of the
invention to provide a system that is compatible with the needs for
environmental lighting and the distribution of light emitters as is
necessary for environmental lighting.
[0032] The mobile device and the location device may both further
include a wireless transceiver for communicating therebetween and
wherein data needed to determine the location of the mobile device
is communicated from the mobile device to the location server using
the wireless transceivers.
[0033] It is thus a feature of at least one embodiment of the
invention to provide a system that does not rely on light
transmissions from the wireless device requiring capabilities not
typically present in portable wireless devices such as cell
phones.
[0034] These particular objects and advantages may apply to only
some embodiments falling within the claims and thus do not define
the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a perspective view of a mobile device within an
area having multiple light transmission units providing ambient
lighting and communicating with a location server and cooperating
with the mobile device to locate the mobile device within the area
and to provide data to the mobile device;
[0036] FIG. 2 is a simplified block diagram of each light
transmission unit showing the angular dispersion pattern of the
light produced by the light transmission unit;
[0037] FIG. 3 is a figure similar to that of FIG. 2 showing a block
diagram of the mobile device and the angular sensitivity pattern of
a light sensor on the mobile device;
[0038] FIG. 4 is a simplified top plan view of the light
transmission units of FIG. 3 showing a clustering provided by one
embodiment of the invention to select light transmitting units
around the location of the mobile device to reduce shadowing and to
provide more uniform transitions as the mobile device moves and
showing an optional clustering pattern to anticipate that
movement;
[0039] FIGS. 5a and 5b are simplified top plan views of the
expected intensity detection patterns of a given light transmitting
unit with respect to two different orientations of the mobile unit,
the latter depicted in elevation;
[0040] FIG. 6 is a top plan view showing possible locations of the
mobile device with respect to two light transmitting units and
depicting the determination of a single mobile device location
using a combination of possible positions calculated with respect
to two light transmitting units and a projected trajectory
determined by dead reckoning;
[0041] FIG. 7 is a flowchart showing the operation of the light
transmitting units under control of a system typically including
the location server and at least one mobile device; and
[0042] FIG. 8 is a detailed flowchart of the calculation of
location.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0043] Referring now to FIG. 1, the present invention may provide
for a locator system 10 operating within a volume 12, for example,
the interior of a structure such as a store, office building,
hospital, airline terminal or the like, having a floor area 14 over
which users 16 may move together with the users' wireless devices
18.
[0044] Volume 12 may be illuminated, for example, by ceiling
mounted luminaires 20, in one example, each projecting a downward
cone 22 of visible light to illuminate the floor area 14 as is
generally understood in the art. The volumes of the cones 22 will
typically overlap for the purpose of providing uniform lighting;
however, overlap is not critical to the present invention. The term
cone is used generally in this application, it being understood
that the shape of the illuminated region for a given luminaire is
highly variable and that the boundaries of projected light are
generally gradated and indistinct.
[0045] Each of the luminaires 20 may communicate data with a
location server 24 over a network 23. In one embodiment, the
network 23 makes use of power line communication in which
communication signals are impressed upon standard power wiring
simultaneously used to provide power to the luminaires 20. This
powerline communication largely eliminates the need for a separate
wiring in the installation of the present invention. Commercial
powerline communication transmitter and receiver, following the
IEEE 1901 (HomePlug) standard, are already available on the
market.
[0046] The location server 24 may include a computer processor 26
communicating with a memory 28 holding a stored program and stored
data 30 for implementing the invention that will be described
below. In one embodiment, the location server 24 may also connect
with one or more wireless access points 32 which may communicate
via radio waves 34 data between the location server 24 and the
mobile devices 18, for example, using the IEEE 802.11 (Wi-Fi)
standard. In a principal embodiment, this data is largely one way,
passing from the mobile devices 18 to the location server 24 to
conserve radio wave bandwidth. The location server 24 may also
generally communicate with the Internet 25 and with various
terminals 27 providing data to individuals attached thereto as is
generally understood in the art.
[0047] Referring now to FIG. 2, each of the luminaires 20 may
connect to powerline 35 which also provides the network 23 using
powerline communication as discussed above. The powerline 35 may
connect to an internal power regulator 36 for converting
high-voltage AC power into power levels suitable for operation of
the luminaire 20 and its components and to a communication
modulator/demodulator 38 which extracts high-frequency Ethernet
protocol information from the same conductors used as the network
23. In this case, a similar modulator/demodulator 38 connects the
network 23 to the location server 24.
[0048] The modulator/demodulator 38 in each luminaire 20 may
provide unidirectional or bidirectional communication between the
location server 24 and a processor 40 in the luminaire 20. This
latter processor 40 may communicate with a memory 42 holding a
program 45 for execution, program instructions, data, and one or
more illumination models 44 that will be described below. The
program instructions may be used with the stored program and data
30 in the location server 24 and to implement the present invention
as will be discussed.
[0049] The processor 40 may also communicate with a luminaire power
control module 46 providing electrical power (for example,
controlled in-current and power) to a bank of light emitting diodes
(LED) 48, for example, positioned within a reflector/light shield
50 projecting the downward cone 22. The power control module 46 may
provide the desired operating characteristics of the LEDs 48 in
producing the desired high average power output commensurate with
providing illumination to the area 14 and may also provide for a
high-frequency modulation of the LEDs 48 above the flicker rate
perceptible to the human eye. As will be understood in the art, the
intensity of the light from the LEDs 48 as a function of the angle
of the light within the cone 22 (from a center line 53 of the
illumination, normally vertically directed) will provide an
intensity profile 52 that may be pre-characterized at the factory
and stored in a illumination model 44. This intensity profile 52 is
dependent on the arrangement and characteristics of the LEDs 48 and
the surrounding reflector/light shield 50. The LEDs 48 may be white
LEDs employing phosphors or without phosphors but using different
colored red, green and blue LEDs for higher modulation speeds.
[0050] Referring now to FIG. 3, the mobile device 18 may be, for
example, a standard smart phone, tablet or the like and provides a
housing 60 that may be conveniently carried with the user 16 having
an exposed display touch surface 62 or the like for providing input
and output communication with the user 16. A processor 63 within
the mobile device 18 may communicate with an internal memory 64
holding a stored program 67 whose operation in conjunction with
other programs discussed below implement the present invention.
[0051] Generally, as is understood in the art, the processor 63 may
also communicate with a Wi-Fi transceiver 68 allowing communication
of data by radio waves 34 with the wireless access points 32
discussed above with FIG. 1. Importantly, the processor 63 also
communicates with an orientation sensor systems 70 including but
not limited to a three-axis accelerometer, magnetometers and a
three-axis gyroscope that serve to provide an indication of the
orientation of the housing 60 with respect to gravity and the
Earth's magnetic field, as well as providing motion signals (linear
and angular accelerations) that allow for inertial-based guidance
or dead reckoning to identify the location and orientation of the
mobile device 18 for short periods of time through the multiple
integration of accelerations into positional changes.
[0052] The mobile device 18 may also include a light sensor 72
which may, for example, be a single photodiode or phototransistor
or a pixel on a CCD camera device. Notably, the present invention
does not require any characterization of the angle of the received
light with respect to other light sensors, for example, as would be
obtainable through the spatial mapping of a CCD camera with
multiple pixels.
[0053] The light sensor 72 will nevertheless have an angular
sensitivity characteristic 74 indicating its sensitivity at various
angles with respect to an axis 75 normal to the detecting surface
of the sensor 72. Generally the sensor 72 is fixed relative to the
housing 60 and thus the orientation of axis 75 may be deduced using
the orientation sensor system 70 discussed above. The sensitivity
characteristic 74 may be stored as a model 66 in the memory 64.
Desirably, the angular sensitivity characteristic 74 will be
substantially uniform over a given angular range of as much as 180
degrees; however, most light sensors 72 provide significant
sensitivity variation in as little as 60 degrees. For this reason,
a fisheye lens 73 or the like may be placed over the light sensor
72 to decrease angular sensitivity in conjunction with other
techniques described herein for managing this angular sensitivity
variation.
[0054] Referring now to FIG. 1 and FIG. 7, the location server 24
and the luminaires 20 will cooperate to control the luminaires 20,
as indicated by process block 80, to transmit, one at a time from
each luminaire 20, a beacon signal providing a luminaire
identification code uniquely indicating the identity of a given
luminaire 20. This identification code may be transmitted, for
example, with the illumination model 44 of the luminaire's
distribution pattern 52 or this latter information may be provided
only to the location server 24. During this transmission, the light
from the other luminaires 20 is held constant or may be momentarily
switched off to provide greater signal-to-noise in the transmitted
beacon signal.
[0055] In between each transmission or periodically with respect to
each transmission of process block 80, multiple luminaires 20 of a
cluster (whose identity will be described below) may operate
synchronously as indicated by process block 82 to transmit data to
one or more mobile devices 18. This data, for example, may be
streamed audio or video data or any type of data normally desired
by the user 16 of the mobile device 18 and will be obtained from
the location server 24 over the network 23, for example, as
downloaded from the Internet 25.
[0056] At process block 84 the location server 24, optionally in
conjunction with the mobile device 18 and the luminaires 20, may
calculate a location of a given mobile device 18 from data uploaded
from the mobile device 18, for example, over the radio link. This
process will be described in much greater detail below.
[0057] After the location of the mobile device 18 is determined, at
process block 86 the cluster of luminaires 20 used for the
transmission of data at process block 82 may be reformulated by the
location server 24 based on the location data derived at process
block 84. After this reformulation, the process of process blocks
80, 82, 84, and 86 may be repeated. It will be appreciated to the
extent these devices (the location server 24, luminaires 20 and the
mobile device 18) intercommunicate that these tasks of process
blocks 80, 82, 84 and 86 may be freely distributed among these
devices except as constrained by the need for specialized hardware
which will be evident from context.
[0058] Referring now to FIG. 4, as noted above with respect to
process block 80 and 86, the luminaires 20 are formed into
"clusters" 90 for the purpose of communicating with a given mobile
device 18. Generally, location data derived at process block 84
will be used to construct a cluster 90 defining a set of luminaires
20 including one luminaire 20' closest to the user 16 and other
"scout" luminaires 20 on different sides of the user 16 with
respect to the luminaire 20'. The scout luminaires 20 ideally
provide overlapping light at the location of the user 16 such as
prevents shadows 91 of the user 16 from falling on the mobile
device 18 for all luminaires 20 in the cluster 90. As the mobile
device 18 moves in the area 14, the luminaires 20 within the
cluster 90 are changed so that the center of mass of the cluster
(being the weighted distance between the mobile device 18 and each
luminaire 20 weighted according to its light output) follows the
user 16. This approach will generally surround the user 16 with
luminaires 20. As will be discussed below, tracking the location of
the mobile device 18 allows a trajectory of the device 18 to be
determined such as may permit a predicted trajectory 93 of the
device 18 to be determined. The center of mass of the cluster 90
may be shifted from the device 18 to a point along the predicted
trajectory 93 in order to anticipate movement of the mobile device
18 and to accommodate assumptions about the mobile device 18 being
in front of the user 16 as the user 16 moves. The amount of
shifting may, for example, be proportional to the speed of movement
of the user 16 and may anticipate movement in the orientation of
the mobile device 18 as well. The size of the cluster 90 may be
increased, for example, by adding frontward cluster areas 90' to
the cluster 90 addressing the greater probability of user 16
movement into these forward areas over time and may be skewed along
the predicted trajectory 93 depending on the anticipated or current
orientation of the mobile device 18.
[0059] The number of luminaires 20 in the cluster 90 may be
dynamically changed depending on bandwidth demands by a given
mobile device but will generally be far fewer than all of the
luminaires 20 and may be practically limited to the region just
around the user 16.
[0060] Determining the set of luminaires 20 in the cluster 90 may
be done by using a pre-prepared map linking luminaire identifiers
(and hence luminaires 20) to particular locations in the volume 12
that can be matched to the location of the mobile device. This map
may be held, for example, as data in the location server 24 and may
be generated either empirically by moving a photosensor with a
constant orientation through the area 14 or by mathematical
modeling using the known illumination models 44 and measured
positions of the luminaires 20. Initially, when the mobile device
18 arrives in the area 14, for example, as detected by radio waves
34 (for example, a Wi-Fi beacon signal) from the mobile device 18,
the cluster 90 may be arbitrarily large to accommodate the fact
that the location of the mobile device 18 is not yet been
determined. Once the location is determined, the size of the
cluster may be reduced. Alternatively, predetermined clusters 90
may be located at entrances to the area 14 with the expectation
that they will capture new users 16.
[0061] Referring now to FIG. 8, the process of identifying the
location of the user 16 and the mobile device 18 may begin as
indicated by process block 94 by collecting intensity information
at the mobile device 18 indicating the light intensity detected by
the mobile device 18 from particular luminaires 20. This intensity
information is collected through the light sensor 72 (shown in FIG.
3) and will generally not include any identification of the
orientation of the received light but will simply be a list of
light intensities and identifications of associated luminaries
20.
[0062] At process block 96 the orientation of the mobile device 18
is determined, for example, using the sensor system 70 as described
above. This orientation generally determines how vertical axis 75
is (altitude) and, to the extent that the axis 75 is not vertical,
in what direction it is tipping (azimuth). Altitude can be
determined from a three-axis accelerometer providing an indication
of the dominant acceleration of gravity along an x-axis (roll) and
y-axis (pitch) of the housing of the portable device 18. In the
case of a smart phone or the like where the light sensor 72 is on a
front face of the phone that also provides the touch sensing
display, the x-axis will generally be oriented along the long
dimension (height) of the housing parallel to the display and
y-axis will also be parallel to the display but perpendicular to
the x-axis. The azimuth (yaw) will generally be measured about a
z-axis perpendicular to the x-axis and y-axis and parallel to the
axis 75 using the magnetometer, when possible, augmented by
rotational motion sensing by the internal gyroscopes extrapolating
from previously determined yaw orientations.
[0063] Once the orientation of the mobile device 18 is established,
an estimate of the location of the mobile device 18 may be
determined by a variety of methods. One embodiment of the present
invention contemplates that location will be deduced by the
intensity of the light from different luminaires 20 of known
position. The raw intensity received by the light sensor 72,
however, will normally not yield an accurate location because of
the confounding effect of the orientation of the mobile device 18
on those intensities. That is, the intensity of light from a given
luminaire 20 will vary significantly depending on the orientation
of the mobile device 18 as either facing toward or away from that
luminaire 20. Accordingly, at process block 98, information
conveyed by the intensities and known locations of the associated
luminaires 20 is corrected by the information of orientation
available from process block 96.
[0064] Referring momentarily to FIGS. 5a and 5b, a given luminaire
20 may have a well-described illumination pattern described by the
illumination model 44 associated with the luminaire 20 and as
represented in FIG. 5 by the intensity iso-curves 100, each
following a path of constant intensity of received light. For a
conical light pattern, the iso-curves 100 will generally be
concentric circles about the location of the luminaire 20. The
actual light detected by the mobile device 18 will depend on its
orientation, however, so that when the mobile device 18 is oriented
so that axis 75 is substantially vertical, a given intensity
reading associated with the luminaire 20 will place the mobile
device 18 on one of the iso-curves 100 based on the received
intensity weighted by the sensitivity characteristic 74 of the
mobile device 18. This iso-curve 100 describes a locus of possible
location points.
[0065] As shown in FIG. 5b, however, if the mobile device 18 is
tipped such that axis 75 has an altitude of, say, 45 degrees
(toward the left as shown in FIG. 5b), the effective iso-curves 100
as detected by the mobile device 18 will shift rightward with
respect to the location of the luminaire 20 as a result of the
preferential sensitivity of the mobile device 18 in the left
direction. The exact amount of shifting will depend on the curve 74
which will also tend to distort the iso-curves 100.
[0066] Based on this observation, knowledge of the orientation of
the mobile device 18 derived at process block 96 may correct the
received intensity information, for example, by adjusting the
expected modeled iso-curves 100 associated with each luminaire 20.
This modification may, for example, consider hypothetical placement
of the mobile device 18 over the area of the iso-curves 100
modifying the value of the iso-curves 100 by the degree of
alignment of axis 75 of the mobile device 18 and a straight line
path between the luminaire 20 and the mobile device 18. The more
these two axes deviate, the more the intensity of the iso-curves
100 is decreased. These modified iso-curves may then be used to
determine a locus of possible locations of the mobile device 18
with respect to each luminaire 20.
[0067] It will be appreciated that an additional intensity effect
will also occur if the elevation of the mobile device 18 is
changed; however, these elevational effects will generally be small
given the range of heights of most users 16 and may be corrected
over the course of time by monitoring maximum intensity as the user
16 moves through the volume 12 which will give an idea of the
user's height.
[0068] Referring now to FIGS. 6 and 8, various loci of possible
locations for different luminaires 20 are then reconciled at
process block 106 by one of several means. If two or more luminaire
20 provide adequate signal strength to each to develop a locus 108
of possible positions, their intersections may be used to narrow
the locus to two points (in the case of two luminaires 20 or a
single-point in the case of three or more luminaires 20). Looking
at the case of one or two luminaires 20, where intersection of loci
108 do not define a single location point but rather multiple
points 114, an estimated single location point may be obtained at
process block 96, for example, from previously identified locations
110 (using the techniques described herein) by selecting the
closest point 114 from the intersection of loci 108 to that point.
Preferably, however, a dead reckoning of new position estimation
112 of the mobile device 18 will be calculated from a last
identified location of the mobile device 18, and the movement since
that time determined from elapsed time and acceleration of the
mobile device will be measured by the sensor system 70. The
intersection of this new position estimation 112, which may be, for
example, a portion of a trajectory, with the multiple points 114
may then provide for a single identified location 116.
[0069] Other location estimates may be used to resolve a single
identified location 116 in the event that the intensity of light
from three or more luminaires 20 cannot be determined. For example,
a location estimate based on a GPS signal, wireless triangulation,
or local near field beacons may be used. Mismatch between various
location measures that may not perfectly intersect can be averaged
to provide a single identified location 116. Present experiments by
the inventors indicate that resolution of less than 0.5 meters can
readily be obtained.
[0070] Referring again to FIG. 8, as indicated by process block
120, this single location value 116 may be output, for example, to
other programs, that may use the location of the mobile device 18
to provide location-based content to the user 16, for example,
information about the user's location, points of interest,
promotions in a particular part of a store or retail environment.
The location value 116 may also be provided to the server 24 to be
transmitted to others, for example, in hospitals or airports where
this location information may be provided to individuals who need
to find critical personnel quickly.
[0071] In addition, this location information may be used at
process block 86 to reform the cluster 90 as discussed above.
[0072] Certain terminology is used herein for purposes of reference
only, and thus is not intended to be limiting. For example, terms
such as "upper", "lower", "above", and "below" refer to directions
in the drawings to which reference is made. Terms such as "front",
"back", "rear", "bottom" and "side", describe the orientation of
portions of the component within a consistent but arbitrary frame
of reference which is made clear by reference to the text and the
associated drawings describing the component under discussion. Such
terminology may include the words specifically mentioned above,
derivatives thereof, and words of similar import. Similarly, the
terms "first", "second" and other such numerical terms referring to
structures do not imply a sequence or order unless clearly
indicated by the context.
[0073] When introducing elements or features of the present
disclosure and the exemplary embodiments, the articles "a", "an",
"the" and "said" are intended to mean that there are one or more of
such elements or features. The terms "comprising", "including" and
"having" are intended to be inclusive and mean that there may be
additional elements or features other than those specifically
noted. It is further to be understood that the method steps,
processes, and operations described herein are not to be construed
as necessarily requiring their performance in the particular order
discussed or illustrated, unless specifically identified as an
order of performance. It is also to be understood that additional
or alternative steps may be employed.
[0074] References to "a microprocessor" and "a processor" or "the
microprocessor" and "the processor," can be understood to include
one or more microprocessors that can communicate in a stand-alone
and/or a distributed environment(s), and can thus be configured to
communicate via wired or wireless communications with other
processors, where such one or more processor can be configured to
operate on one or more processor-controlled devices that can be
similar or different devices. Furthermore, references to memory,
unless otherwise specified, can include one or more
processor-readable and accessible memory elements and/or components
that can be internal to the processor-controlled device, external
to the processor-controlled device, and can be accessed via a wired
or wireless network.
[0075] It is specifically intended that the present invention not
be limited to the embodiments and illustrations contained herein
and the claims should be understood to include modified forms of
those embodiments including portions of the embodiments and
combinations of elements of different embodiments as come within
the scope of the following claims. All of the publications
described herein, including patents and non-patent publications are
hereby incorporated herein by reference in their entireties.
* * * * *