U.S. patent application number 15/285493 was filed with the patent office on 2018-04-05 for method and system for enhancing accuracy in location and proximity determination.
The applicant listed for this patent is Hong Kong Applied Science and Technology Research Institute Company Limited. Invention is credited to Eddy CHIU, Xinyi LIU, Chunhua SUN.
Application Number | 20180098301 15/285493 |
Document ID | / |
Family ID | 61759208 |
Filed Date | 2018-04-05 |
United States Patent
Application |
20180098301 |
Kind Code |
A1 |
SUN; Chunhua ; et
al. |
April 5, 2018 |
Method and System for Enhancing Accuracy in Location and Proximity
Determination
Abstract
A system comprising beacon-generating clusters for enabling a
mobile computing device to perform location or proximity
determination is provided. Each cluster comprises a primary station
for broadcasting a primary beacon, and an offset-assisted station,
positioned from the primary station by an offset distance along a
direction, for broadcasting a secondary beacon. The offset distance
and the direction are unique for all the clusters, causing a
jittering area, within which the mobile computing device is unable
to determine which one of adjacent primary stations is closer to
from detecting the primary beacons, to be reduced by further
utilizing the secondary beacons provided by the clusters.
Fluctuation in received signal strength indicator (RSSI) can be
reduced by having each station, primary or secondary, installed
with multiple co-located broadcasting units for utilizing space and
time diversity to reduce RSSI fluctuation. In another option,
multiple offset-assisted stations are used for each cluster.
Inventors: |
SUN; Chunhua; (Hong Kong,
HK) ; LIU; Xinyi; (Hong Kong, HK) ; CHIU;
Eddy; (Hong Kong, HK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hong Kong Applied Science and Technology Research Institute Company
Limited |
Hong Kong |
|
HK |
|
|
Family ID: |
61759208 |
Appl. No.: |
15/285493 |
Filed: |
October 5, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 64/00 20130101;
H04W 40/32 20130101; H04W 40/20 20130101; H04W 40/12 20130101; H04W
4/80 20180201; H04W 40/10 20130101; H04W 40/244 20130101 |
International
Class: |
H04W 64/00 20060101
H04W064/00; H04W 4/02 20060101 H04W004/02; H04W 4/00 20060101
H04W004/00; H04W 40/24 20060101 H04W040/24; H04W 24/10 20060101
H04W024/10 |
Claims
1. A system for enabling a mobile computing device to perform
location or proximity determination, comprising: plural
beacon-broadcasting clusters, an individual cluster comprising: a
primary station for broadcasting a primary beacon, the primary
station having a broadcasting coverage area; and an offset-assisted
station for broadcasting a secondary beacon, the offset-assisted
station having a broadcasting coverage area substantially similar
to the primary station's broadcasting coverage area in size, the
offset-assisted station being positioned from the primary station
by an offset distance along a direction; wherein: the broadcasting
coverage areas of adjacent two or more of the primary stations are
mutually partially-overlapped; and all the clusters use the same
offset distance and the same direction in defining locations of the
primary station and the offset-assisted station in the individual
cluster, causing a jittering area, within which the mobile
computing device is unable to determine which one of said adjacent
two or more primary stations is closer to from detecting the
primary beacons of said adjacent two or more primary stations, to
be reduced by further utilizing the secondary beacons provided by
the clusters having said adjacent two or more primary stations.
2. The system of claim 1, wherein the direction and the offset
distance are selected such that in the individual cluster, the
offset-assisted station is located inside the primary station's
broadcasting coverage area not overlapped with the broadcasting
coverage area of any other cluster's primary station.
3. The system of claim 1, wherein: the direction is substantially
similar to a pointing direction from a first primary station to a
second primary station, wherein the first and second primary
stations are selected from the plural primary stations in the
clusters and have overlapped broadcasting coverage areas; and the
offset distance is less than half of the distance between the first
and second primary stations.
4. The system of claim 1, wherein the primary beacon and the
secondary beacons are compliant to a Bluetooth Low Energy (BLE)
specification.
5. A method for enabling a mobile computing device to perform
location or proximity determination, comprising the steps of: (a)
providing the system of claim 1; (b) measuring, by the mobile
computing device, the primary beacon sent from the individual
cluster and received at the mobile computing device to give a first
received signal strength indicator (RSSI) value unless the primary
beacon is not detectable; (c) measuring, by the mobile computing
device, the secondary beacon sent from the individual cluster and
received at the mobile computing device to give a second RSSI value
unless the secondary beacon is not detectable; (d) repeating the
steps (b) and (c) for all the clusters; (e) according to the first
and second RSSI values obtained in the step (d), determining, by
the mobile computing device, whether the mobile computing device is
located outside an augmented coverage area formed by augmenting the
broadcasting coverage areas of the primary and offset-assisted
stations in the clusters; and (f) when it is determined in the step
(e) that the mobile computing device is not outside the augmented
coverage area, determining, by the mobile computing device, a zone
on which the mobile computing device is located according to the
first and second RSSI values obtained in the step (d), wherein the
zone is selected from a plurality of candidate zones, the candidate
zones being obtained by partitioning the augmented coverage area
along boundaries of the broadcasting coverage areas of all the
primary and offset-assisted stations in the clusters.
6. The method of claim 5, wherein: the first RSSI value is obtained
by averaging plural RSSI values of the primary beacon measured at
different time instants over a pre-defined time window; and the
second RSSI value is obtained by averaging plural RSSI values of
the secondary beacon measured at different time instants over the
pre-defined time window.
7. The system of claim 1, wherein in at least one of the clusters:
the primary station comprises a first group of plural co-located
broadcasting units, each of the broadcasting units in the first
group being configured to broadcast a component primary-beacon
signal such that the component primary-beacon signals broadcast
from all the broadcasting units in the first group collectively
form the primary beacon, wherein the component primary-beacon
signals from all the broadcasting units in the first group are
individually distinguishable at the mobile computing device to
thereby allow the mobile computing device to utilize diversity
reception of the primary beacon to enhance a received signal
strength indicator (RSSI) value thereof measured at the mobile
computing device.
8. The system of claim 7, wherein in said one of the clusters: the
offset-assisted station comprises a second group of plural
co-located broadcasting units, each of the broadcasting units in
the second group being configured to broadcast a component
secondary-beacon signal such that the component secondary-beacon
signals broadcast from all the broadcasting units in the second
group collectively form the secondary beacon, wherein the component
secondary-beacon signals from all the broadcasting units in the
second group are individually distinguishable at the mobile
computing device to thereby allow the mobile computing device to
utilize diversity reception of the secondary beacon to enhance a
RSSI value thereof measured at the mobile computing device.
9. The system of claim 1, wherein in the individual cluster: the
primary station comprises a first group of plural co-located
broadcasting units, each of the broadcasting units in the first
group being configured to broadcast a component primary-beacon
signal such that the component primary-beacon signals broadcast
from all the broadcasting units in the first group collectively
form the primary beacon, wherein the component primary-beacon
signals from all the broadcasting units in the first group are
individually distinguishable at the mobile computing device to
thereby allow the mobile computing device to utilize diversity
reception of the primary beacon to enhance a received signal
strength indicator (RSSI) value thereof measured at the mobile
computing device; and the offset-assisted station comprises a
second group of plural co-located broadcasting units, each of the
broadcasting units in the second group being configured to
broadcast a component secondary-beacon signal such that the
component secondary-beacon signals broadcast from all the
broadcasting units in the second group collectively form the
secondary beacon, wherein the component secondary-beacon signals
from all the broadcasting units in the second group are
individually distinguishable at the mobile computing device to
thereby allow the mobile computing device to utilize diversity
reception of the secondary beacon to enhance a RSSI value thereof
measured at the mobile computing device.
10. The system of claim 9, wherein each of the component
primary-beacon signals and the component secondary-beacon signals
is compliant to a Bluetooth Low Energy (BLE) specification.
11. A method for enabling a mobile computing device to perform
location or proximity determination, comprising the steps of: (a)
providing the system of claim 9; (b) measuring, by the mobile
computing device, the primary beacon sent from the individual
cluster and received at the mobile computing device to give a first
RSSI value unless the primary beacon is not detectable; (c)
measuring, by the mobile computing device, the secondary beacon
sent from the individual cluster and received at the mobile
computing device to give a second RSSI value unless the secondary
beacon is not detectable; (d) repeating the steps (b) and (c) for
all the clusters; (e) according to the first and second RSSI values
obtained in the step (d), determining, by the mobile computing
device, whether the mobile computing device is located outside an
augmented coverage area formed by augmenting the broadcasting
coverage areas of the primary and offset-assisted stations in the
clusters; and (f) when it is determined in the step (e) that the
mobile computing device is not outside the augmented coverage area,
determining, by the mobile computing device, a zone on which the
mobile computing device is located according to the first and
second RSSI values obtained in the step (d), wherein the zone is
selected from a plurality of candidate zones, the candidate zones
being obtained by partitioning the augmented coverage area along
boundaries of the broadcasting coverage areas of all the primary
and offset-assisted stations in the clusters.
12. The method of claim 11, wherein: in the step (b), the first
RSSI value is obtained by averaging plural RSSI values of the
component primary-beacon signals broadcast from all the
broadcasting units in the first group; and in the step (c), the
second RSSI value is obtained by averaging plural RSSI values of
the component secondary-beacon signals broadcast from all the
broadcasting units in the second group.
13. The method of claim 12, wherein: in the step (b), each of the
component primary-beacon signals broadcast from each broadcasting
unit is measured at different time instants over a pre-defined time
window to give more-than-one RSSI values for averaging; and in the
step (c), each of the component secondary-beacon signals broadcast
from each broadcasting unit is measured at different time instants
over the pre-defined time window to give more-than-one RSSI values
for averaging.
14. A system for enabling a mobile computing device to perform
location or proximity determination, comprising: plural
beacon-broadcasting clusters, an individual cluster comprising: a
primary station for broadcasting a primary beacon, the primary
station having a broadcasting coverage area; and plural
offset-assisted stations each for broadcasting a secondary beacon,
each of the offset-assisted stations having a broadcasting coverage
area substantially similar to the primary station's broadcasting
coverage area in size, the primary beacon and the offset-assisted
stations of the individual cluster being positioned to form an
evenly-spaced station sequence with the primary station at an end
of the sequence, wherein successive stations in the sequence are
spaced by an offset distance, and each offset-assisted station is
oriented from the primary beacon along a direction; wherein: the
broadcasting coverage areas of adjacent two or more of the primary
stations are mutually partially-overlapped; and all the clusters
use the same offset distance and the same direction in defining
locations of the primary station and the offset-assisted stations
in the individual cluster, causing a jittering area, within which
the mobile computing device is unable to determine which one of
said adjacent two or more primary stations is closer to from
detecting the primary beacons of said adjacent two or more primary
stations, to be reduced by further utilizing the secondary beacons
provided by the clusters having said adjacent two or more primary
stations.
15. The system of claim 14, wherein the direction and the offset
distance are selected such that in the individual cluster, the
offset-assisted stations are located inside the primary station's
broadcasting coverage area not overlapped with the broadcasting
coverage area of any other cluster's primary station.
16. The system of claim 14, wherein in the individual cluster: the
primary station comprises a first group of plural co-located
broadcasting units, each of the broadcasting units in the first
group being configured to broadcast a component primary-beacon
signal such that the component primary-beacon signals broadcast
from all the broadcasting units in the first group collectively
form the primary beacon, wherein the component primary-beacon
signals from all the broadcasting units in the first group are
individually distinguishable at the mobile computing device to
thereby allow the mobile computing device to utilize diversity
reception of the primary beacon to enhance a received signal
strength indicator (RSSI) value thereof measured at the mobile
computing device; and an individual offset-assisted station
comprises a second group of plural co-located broadcasting units,
each of the broadcasting units in the second group being configured
to broadcast a component secondary-beacon signal such that the
component secondary-beacon signals broadcast from all the
broadcasting units in the second group collectively form the
secondary beacon of the individual offset-assisted station, wherein
the component secondary-beacon signals from all the broadcasting
units in the second group are individually distinguishable at the
mobile computing device to thereby allow the mobile computing
device to utilize diversity reception of the secondary beacon to
enhance a RSSI value thereof measured at the mobile computing
device.
17. The system of claim 16, wherein each of the component
primary-beacon signals and the component secondary-beacon signals
is compliant to a Bluetooth Low Energy (BLE) specification.
18. A method for enabling a mobile computing device to perform
location or proximity determination, comprising the steps of: (a)
providing the system of claim 16; (b) measuring, by the mobile
computing device, the primary beacon sent from the individual
cluster and received at the mobile computing device to give a first
RSSI value unless the primary beacon is not detectable; (c)
measuring, by the mobile computing device, the secondary beacon
sent from the individual offset-assisted stations of the individual
cluster and received at the mobile computing device to give a
second RSSI value unless the secondary beacon is not detectable;
(d) repeating the steps (b) and (c) for all the clusters and all
the offset-assisted stations thereof; (e) according to the first
and second RSSI values obtained in the step (d), determining, by
the mobile computing device, whether the mobile computing device is
located outside an augmented coverage area formed by augmenting the
broadcasting coverage areas of the primary and offset-assisted
stations in the clusters; and (f) when it is determined in the step
(e) that the mobile computing device is not outside the augmented
coverage area, determining, by the mobile computing device, a zone
on which the mobile computing device is located according to the
first and second RSSI values obtained in the step (d), wherein the
zone is selected from a plurality of candidate zones, the candidate
zones being obtained by partitioning the augmented coverage area
along boundaries of the broadcasting coverage areas of all the
primary and offset-assisted stations in the clusters.
19. The method of claim 18, wherein: in the step (b), the first
RSSI value is obtained by averaging plural RSSI values of the
component primary-beacon signals broadcast from all the
broadcasting units in the first group; and in the step (c), the
second RSSI value is obtained by averaging plural RSSI values of
the component secondary-beacon signals broadcast from all the
broadcasting units in the second group.
20. The method of claim 19, wherein: in the step (b), each of the
component primary-beacon signals broadcast from each broadcasting
unit is measured at different time instants over a pre-defined time
window to give more-than-one RSSI values for averaging; and in the
step (c), each of the component secondary-beacon signals broadcast
from each broadcasting unit is measured at different time instants
over the pre-defined time window to give more-than-one RSSI values
for averaging.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to location or proximity
determination by a mobile computing device based on beacons sent
from nearby beacon-generating stations.
BACKGROUND
[0002] The following definitions are used herein in the
specification and the appended claims. "Location determination"
means determining a location of a certain device. Usually, location
determination is assisted by installing a network of
beacon-broadcasting stations at known locations over a region of
interest such that when the device listens to the beacons sent out
by these stations, the location of the device is estimable by the
signal strengths of the received beacons or by the arrival times
thereof. "Proximity determination" means determining a degree of
proximity between a device and a certain beacon-broadcasting
station. "A degree of proximity" is a descriptive qualifier for
indicating how close a device is distant from a beacon-broadcasting
station. As one example, a set of such descriptive qualifiers
includes "immediate," "near," "far" and "unknown." Note that
proximity determination does not provide a quantitative value of
distance between the device and the station. Proximity
determination may be implemented by first measuring a received
signal strength indicator (RSSI) value of the beacon sent out from
the station. Then the measured RSSI value is mapped to a
corresponding descriptive qualifier. This approach is usually
employed for a Bluetooth Low Energy-(BLE-)enabled device. "A mobile
computing device" is a portable electronic device having computing
power, and configured to provide wireless communications and to
support location or proximity determination. For example, a mobile
computing device may be a BLE-enabled smartphone, or a handheld
tablet computer equipped with BLE-compliant functionalities.
[0003] BLE signals from battery-driven beacon-broadcasting stations
are at the core of the indoor location technology. A mobile
computing device detects a beacon from one beacon-broadcasting
station and can calculate roughly the distance to this station and
hence estimate the location of the mobile computing device. The
stations are placed at known locations around an area of interest
and each station repeatedly transmits a radio beacon. When the
mobile computing device detects the beacons transmitted by the
stations, the position of the mobile computing device relative the
stations can be determined by measuring RSSI values of the
transmitted beacons. However, one practical problem encountered in
BLE location-determining system is that BLE beacons are transmitted
in an industrial, scientific and medical (ISM) band. The presence
of co-channel interference, such as WiFi signals, introduces
fluctuation of the measured RSSI values and hence reduces the
location-determining accuracy achieved by the system. Another
factor that increases RSSI fluctuation is the occurrence of
multipath fading, especially in an indoor environment where
location determination is required. It is desirable to reduce RSSI
fluctuation in order to enhance location-determining accuracy in
the presence of co-channel interference and multipath fading.
[0004] The BLE system is also useful for proximity determination.
FIG. 1 depicts a practical scheme of partitioning a broadcasting
coverage area 170 of a BLE beacon-generation station 105 into a
plurality of zones for proximity determination. A first zone 110 of
"immediate" is assigned for a region within 0.5 m from the station
105, a second zone 120 of "near" for another region between 0.5 m
and 2 m, a third zone 130 of "far" for a farther region between 2 m
to 30 m, and possibly an extra zone 140 of "unknown" classified as
a region when a mobile computing device 107 is outside the
broadcasting coverage area 170. Other partitioning schemes are also
possible. In some schemes, the third zone 130 may be extended up to
50 m or even 100 m, depending on the transmitted power. However, in
some location-based applications, the size of the third zone 130
may be considered too large. A scheme having finer zones is
desirable. If the RSSI fluctuation due to co-channel interference
and multipath fading can be reduced, the realization of such scheme
is made easier.
[0005] Apart from the need to reduce RSSI fluctuation, there is
another challenge encountered in BLE systems. For advanced
solutions to location determination, where it is desired to locate
a user of the mobile computing device accurately in a
two-dimensional region and show the user's whereabouts (zone or
position) on a map, several BLE beacon-broadcasting stations are
required. Ideally, the stations have contiguous broadcasting
coverage areas, usually the same in size, so that when the mobile
computing navigates from one broadcasting coverage area to another,
the station closest to the mobile computing device can be clearly
identified. Practically, however, the broadcasting coverage areas
of adjacent stations are usually overlapped. There is a chance that
the mobile computing device falls into a jittering area between two
or more zones. The jittering area is an area of overlap between
zones. The presence of jittering area creates uncertainty in
location determination in that the mobile computing device is
unable to determine which one of two or more adjacent stations is
closer to. It is also desirable if the jittering area can be
reduced as much as possible.
[0006] Existing techniques attempting to increase positioning
accuracy in location or proximity determination includes, for
example, the following. In a system disclosed by CN103983266,
movement directions and steps of a user are further monitored in
addition to using beacons. In another system suggested by
CN105353351, arrival times of multiple beacons are analyzed to
improve the positioning accuracy. In yet another system disclosed
by U.S. Pat. No. 8,965,411, different transmit powers for different
beacons are employed, offering additional information useful for
increasing the positioning accuracy. However, the aforementioned
three systems have a common disadvantage that system design is
significantly complicated. Applying the techniques used in these
three systems to a BLE system implies considerable modification to
the BLE system is required. In a system of US2015105099, each
beacon is associated with a group value. Grouping may be based on
multiple criteria including geographical location, work team
assignment, transceiver type or other constraining information.
Beacons with minority group values are then excluded in RSSI
determination. However, RSSI fluctuation may introduce incorrect
beacon exclusions and thus reduces the positioning accuracy.
Furthermore, grouping results are required to be adjusted when new
beacons are deployed. The latter disadvantage complicates the
system design.
[0007] In view of the above-mentioned observations, there is a need
in the art to have a technique for reducing RSSI fluctuation at a
mobile computing device in the presence of co-channel interference
and multipath fading during beacon signal measurement as well as
for reducing the jittering area. The technique is not only for BLE
systems but also useful to other wireless systems using beacons for
the mobile computing device to perform location or proximity
determination.
SUMMARY OF THE INVENTION
[0008] In a first aspect of the present invention, a system for
enabling a mobile computing device to perform location or proximity
determination is provided with an advantage of reducing a jittering
area.
[0009] The system comprises plural beacon-broadcasting clusters. An
individual cluster comprises a primary station for broadcasting a
primary beacon, and one or more offset-assisted stations each for
broadcasting a secondary beacon. Each offset-assisted station has a
broadcasting coverage area substantially similar to the primary
station's broadcasting coverage area in size. If there is only one
offset-assisted station in the individual cluster, the
offset-assisted station is positioned from the primary station by
an offset distance along a pre-determined direction. If there are
plural offset-assisted stations in the individual cluster, the
primary beacon and the offset-assisted stations of the individual
cluster are positioned to form an evenly-spaced station sequence
with the primary station at an end of the sequence. In addition,
successive stations in the sequence are spaced by the offset
distance, and each offset-assisted station is oriented from the
primary beacon along the pre-determined direction. Among the
clusters, the broadcasting coverage areas of adjacent two or more
of the primary stations are mutually partially-overlapped.
Furthermore, the offset distance and the direction used in defining
locations of the primary station and each offset-assisted station
in the individual cluster are unique for all the clusters. It
causes the jittering area, within which the mobile computing device
is unable to determine which one of said adjacent two or more
primary stations is closer to from detecting the primary beacons of
said adjacent two or more primary stations, to be reduced by
further utilizing the secondary beacons provided by the clusters
having said adjacent two or more primary stations.
[0010] The direction and the offset distance may be selected such
that in the individual cluster, each offset-assisted station is
located inside the primary station's broadcasting coverage area not
overlapped with the broadcasting coverage area of any other
cluster's primary station.
[0011] The direction may also be selected to be substantially
similar to a pointing direction from a first primary station to a
second primary station, wherein the first and second primary
stations are selected from the plural primary stations in the
clusters and have overlapped broadcasting coverage areas. The
offset distance may be selected to be less than half of the
distance between the first and second primary stations.
[0012] In a second aspect of the present invention, the system
disclosed in the first aspect is further improved for reducing RSSI
fluctuation.
[0013] In the system, the primary station of the individual cluster
comprises a first group of plural co-located broadcasting units.
Each of the broadcasting units in the first group is configured to
broadcast a component primary-beacon signal such that the component
primary-beacon signals broadcast from all the broadcasting units in
the first group collectively form the primary beacon. In addition,
the component primary-beacon signals are individually
distinguishable at the mobile computing device, thereby allowing
the mobile computing device to utilize diversity reception of the
primary beacon to enhance a RSSI value thereof measured at the
mobile computing device.
[0014] In addition, each offset-assisted station in the individual
cluster comprises a second group of plural co-located broadcasting
units. Each broadcasting unit in the second group is configured to
broadcast a component secondary-beacon signal such that the
component secondary-beacon signals broadcast from all the
broadcasting units in the second group collectively form the
secondary beacon. The component secondary-beacon signals are
individually distinguishable at the mobile computing device to
thereby allow the mobile computing device to utilize diversity
reception of the secondary beacon to enhance a RSSI value thereof
measured at the mobile computing device.
[0015] In a third aspect of the present invention, it is provided
with a method for performing location or proximity determination by
a mobile computing device when any of the embodiments of the system
disclosed above is provided.
[0016] According to the method, the primary beacon sent from the
individual cluster and received at the mobile computing device is
measured to give a first RSSI value unless the primary beacon is
not detectable. When space diversity is employed, the first RSSI
value is obtained by averaging plural RSSI values of the component
primary-beacon signals broadcast from all the broadcasting units in
the first group. When time diversity is further employed, each of
the component primary-beacon signals broadcast from each
broadcasting unit is measured at different time instants over a
pre-defined time window is measured to give more-than-one RSSI
values for averaging.
[0017] Additionally, each secondary beacon sent from the individual
cluster and received at the mobile computing device is measured to
give a second RSSI value unless the secondary beacon is not
detectable. When space diversity is employed, the second RSSI value
is obtained by averaging plural RSSI values of the component
secondary-beacon signals broadcast from all the broadcasting units
in the second group. When time diversity is further employed, each
of the component secondary-beacon signals broadcast from each
broadcasting unit is measured at different time instants over the
pre-defined time window to give more-than-one RSSI values for
averaging.
[0018] The steps of measuring the primary beacon and of measuring
each secondary beacon are repeated for all the clusters.
[0019] According to the first and second RSSI values that are
obtained, determine whether the mobile computing device is located
outside an augmented coverage area. The augmented coverage area is
formed by augmenting the broadcasting coverage areas of the primary
and offset-assisted stations in the clusters.
[0020] When it is determined that the mobile computing device is
not outside the augmented coverage area, determine a zone on which
the mobile computing device is located according to the first and
second RSSI values that are obtained. The zone is selected from a
plurality of candidate zones. The candidate zones are obtained by
partitioning the augmented coverage area along boundaries of the
broadcasting coverage areas of all the primary and offset-assisted
stations in the clusters.
[0021] Other aspects of the present invention are disclosed as
illustrated by the embodiments hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 depicts a scheme of partitioning a broadcasting
coverage area of a BLE beacon-generation station into a plurality
of zones for proximity determination.
[0023] FIG. 2A depicts a network having two primary stations for
beacon broadcasting.
[0024] FIG. 2B depicts, in accordance with an exemplary embodiment
of the present invention, the network of FIG. 2A further including
an offset-assisted station for each of the primary stations, where
the offset-assisted station is positioned from the primary station
by an offset distance along a direction the same as a pointing
direction from one primary station to another.
[0025] FIG. 2C depicts, in accordance with one embodiment of the
present invention, the network of FIG. 2A further including an
offset-assisted station for each of the primary stations, where,
different from FIG. 2B, the offset-assisted station is shifted from
the primary station in another direction different from the
aforementioned pointing direction.
[0026] FIG. 2D illustrates that an augmented coverage area is
formed by combining broadcasting coverage areas of all the primary
and offset-assisted stations, and different zones are defined by
partitioning the augmented coverage area along boundaries of the
broadcasting coverage areas.
[0027] FIG. 3 illustrates one configuration of a network of primary
stations and the resultant network after incorporating an
offset-assisted station to each primary station to form a
cluster.
[0028] FIG. 4 illustrates another configuration of a network of
primary stations and the resultant network after incorporating an
offset-assisted station to each primary station to form a
cluster.
[0029] FIG. 5 illustrates a further configuration of a network of
primary stations and the resultant network after incorporating two
offset-assisted stations to each primary station to form a
cluster.
[0030] FIG. 6 depicts (a) a station, either a primary station or an
offset-assisted station, having multiple broadcasting units for
achieving spatial diversity, and (b) a space-time representation of
component beacon signals generated by the station.
[0031] FIG. 7 depicts a flowchart of the steps in accordance with
an exemplary embodiment of a method for the mobile computing device
to perform location or proximity determination when any of the
embodiments of the disclosed system is used.
DETAILED DESCRIPTION
[0032] Herein in the specification and the appended claims, the
following definitions are also used. "A broadcasting coverage area"
of a beacon-broadcasting station means an area within which the
signal strength of a beacon sent out by the station is higher than
a pre-determined threshold signal strength, where the signal
strength of the beacon is a predicted one or an actually measured
one, whichever more appropriate as determined by those skilled in
the art according to practical situations. For example, if the
station is designed to have to a certain broadcasting coverage
area, the aforementioned signal strength is preferably a predicted
one. In case the station is in situ tuned to have a certain
broadcasting coverage area, the aforementioned signal strength is
preferably a measured one. The threshold signal strength is usually
determined according to the radio-signal detection sensitivity of a
device that intends to receive the beacon. "A primary station" in a
system used for enabling a mobile computing device to perform
location or proximity determination means a beacon-broadcasting
station that the mobile computing device references to in location
or proximity determination. For example, the primary station acts
as a reference point such that the mobile computing device
determines and reports its location as a distance from the primary
station. "An offset-assisted station" means a beacon-broadcasting
station working with a certain primary station, where the
offset-assisted station is not physically located at the same place
of the primary station, and broadcasts additional beacon(s) to a
mobile computing device to assist the mobile computing device to
determine its location or proximity from the primary station. The
offset-assisted station is said to be "associated with" the
aforesaid certain primary station. Usually, the offset-assisted
station is located nearby this primary station. "A cluster" or "a
beacon-broadcasting cluster" means a set of beacon-broadcasting
stations including one primary station and one or more
offset-assisted stations associated therewith.
[0033] Although the present invention has an obvious practical
application to a BLE system, the present invention is not limited
only to a location or proximity determining system compliant to a
BLE specification. The present invention is applicable to any
location or proximity determining system based on using beacons to
enable a mobile computing device to perform location or proximity
determination.
[0034] A first aspect of the present invention is to provide a
system for enabling a mobile computing device to perform location
or proximity determination with an advantage that a jittering area
in the presence of overlapped broadcasting coverage areas is
reduced.
[0035] The inventors have found that the jittering area can be
reduced by introducing one or more auxiliary beacon-generating
stations offset-located from each originally-used station. In this
way, location or proximity determination by a mobile computing
device is more accurate by means of additional information provided
by the auxiliary stations augmented with the information provided
by the originally-used station. For the sake of clarity, the
aforesaid station is referred to as a primary station, and each
auxiliary beacon-generating station is named as an offset-assisted
station.
[0036] Exemplarily, the system as disclosed herein comprises plural
beacon-broadcasting clusters. An individual cluster comprises a
primary station for broadcasting a primary beacon usable to the
mobile computing device in location or proximity determination. The
primary station has a broadcasting coverage area. The individual
cluster further comprises one or more offset-assisted stations each
for broadcasting a secondary beacon usable to the mobile computing
device in location or proximity determination. Each offset-assisted
station has a broadcasting coverage area substantially similar to
the primary station's broadcasting coverage area in size. The
primary beacon and each secondary beacon are configured to be
distinguishable at the mobile computing device, such that pieces of
information derived from the primary and secondary beacons are
independent and hence combinable for enhancing position accuracy in
location or proximity determination. If the primary and secondary
beacons are compliant to the BLE specification, these beacons can
be made distinguishable at the mobile computing device by coding
these beacons with different UUID, major, and minor values
according to the BLE specification, and optionally by transmitting
these beacons at different BLE-defined radio channels.
[0037] Among the clusters, the broadcasting coverage areas of
adjacent two or more of the primary stations are mutually
partially-overlapped. This condition is only a reflection of the
creation of one or more jittering areas, which the present
invention is aimed to tackle with. Clearly, it is possible that the
system includes one or more standalone primary stations each having
broadcasting coverage areas not overlapped with the broadcasting
coverage area of any other primary station in the system.
[0038] In the individual cluster, the primary station and the one
or more secondary stations are positioned in a specific way as
follows. In the simplest case that there is only one secondary
station in the individual cluster, the offset-assisted station is
positioned from the primary station by an offset distance along a
pre-determined direction. If the individual cluster has plural
offset-assisted stations, the primary beacon and the
offset-assisted stations are positioned to form an evenly-spaced
sequence of stations with the primary station at an end of the
sequence. Successive stations in the sequence are spaced by the
offset distance, and each offset-assisted station is oriented from
the primary beacon along the pre-determined direction. In
particular, the offset distance and the pre-determined direction
used in defining locations of the primary station and the one or
more offset-assisted stations in the individual cluster are unique
for all the clusters in the system. As will be demonstrated later,
this condition causes a jittering area, within which the mobile
computing device is unable to determine which one of primary
stations having overlapping broadcasting coverage areas is closer
to from detecting the primary beacons of these primary stations, to
be reduced by further utilizing the secondary beacons provided by
the clusters having these primary stations.
[0039] To demonstrate the reduction of jittering area, consider a
representative case that there are two primary stations having
partially-overlapped broadcasting coverage areas. Those skilled in
the art will appreciate that the same reasoning in jittering-area
reduction carries over to cases with more than two primary
stations.
[0040] FIG. 2A depicts a first primary station 201 (labeled as
"S1") and a second primary station 202 (labeled as "S2") having a
first broadcasting coverage area 271 and a second broadcasting
coverage area 272, respectively. The first broadcasting coverage
area 271 and the second broadcasting coverage area 272 are bounded
by a first boundary 211 and a second boundary 212, respectively.
The two broadcasting coverage areas 271, 272 are set to have the
same size for simplicity. Note that the overlapping of the two
broadcasting coverage areas 271, 272 creates a jittering area 278.
For convenience, the pointing direction from the first primary
station 201 to the second primary station 202 is referenced by the
numeral 250.
[0041] On top of FIG. 2A, FIG. 2B adds a first offset-assisted
station 206 (labeled as "S1off") to the first primary station 201
to form a first cluster 281, and a second offset-assisted station
207 (labeled as "S2off") to the second primary station 202 to from
a second cluster 282. The first and second offset-assisted stations
206, 207 are positioned from the first and second primary stations
201, 202 by a first distance 251 and a second distance 252,
respectively, along a same direction 255. The first and second
distances 251, 252 are equal. The direction 255 is set to be
aligned with the pointing direction 250 for simplicity. The first
offset-assisted station 206 has a third broadcasting coverage area
273, bounded by a third boundary 216, same in size with the first
broadcasting coverage area 271. Similarly, the second
offset-assisted station 207 has a fourth broadcasting coverage area
274, bounded by a fourth boundary 217, same in size with the second
broadcasting coverage area 272. An entirety of the four
broadcasting coverage areas 271-274 (the resultant area being
referred to an augmented coverage area 290 as shown in FIG. 2D) is
partitioned into different zones 231, 232a-c, 233, 234, 235a-b,
236, 237a-c, 238 along the four boundaries 211, 212, 216, 217.
[0042] Before analysis to the network of FIG. 2B is made, different
zone types are first defined, as listed in Table 1.
TABLE-US-00001 TABLE 1 Zone type Condition Zone A Covered by one
and only one beacon, either primary or secondary. Zone B1 Covered
by the primary and secondary beacons belonged to only one cluster.
Zone B2 Covered by three beacons, two of which are from one cluster
and the remaining one of which is from another cluster. Zone C
Covered by two beacons each from a different cluster, or covered by
all the four beacons.
[0043] In the forthcoming analysis, it is assumed that the mobile
computing device determine whether it is closer to the first
primary station 201 or the second primary station 202 by a simple
majority voting rule according to the number of beacons received
from the two clusters 281, 282. That is, the first primary station
201 is selected if the number of beacons received from the first
cluster 281 is more than from the second cluster 282. Hence, "Zone
C" is a jittering area. The majority voting rule reflects a
worst-case scenario that the mobile computing device is only able
to determine if it is inside or outside a given broadcasting
coverage area. However, this worst-case scenario is useful to
approximate practical cases when the mobile computing device is
near the perimeter of a broadcasting coverage area. It can be seen
from FIG. 1, where the third zone 130 of "far" is a large region
between 2 m to 30 m from the station 105.
[0044] The classification of the zones 231, 232a-c, 233, 234,
235a-b, 236, 237a-c, 238 into different zone types is given in
Table 2.
TABLE-US-00002 TABLE 2 Zone Beacon(s) received from Zone type 231
S1 A 232a S1, S1off B1 232b S1off A 232c S1off A 233 S1, S1off, S2
B2 234 S1, S1off, S2, S2off C 235a S1off, S2 C 235b S1off, S2 C 236
S1off, S2, S2off B2 237a S2, S2off B1 237b S2 A 237c S2 A 238 S2off
A
[0045] It is apparent that the zones 234, 235a, 235b amount to a
modified jittering area after the introduction of the first and
second offset-assisted stations 206, 207. The original jittering
area 278 is given by a combination of the zones 233, 234. Obvious
from visual inspection, the modified jittering area is smaller than
the original jittering area 278, demonstrating the advantage of
introducing the two offset-assisted stations 206, 207.
[0046] The arrangement shown on FIG. 2B is that the direction 255
of shifting the first and second offset-assisted station 206, 207
from the first and second primary stations 201, 202, respectively,
follows the pointing direction 250 directed from the first primary
station 201 to the second primary station 202. FIG. 2C depicts
another option that the shifting direction is different from the
pointing direction 250. On FIG. 2C, the numerals with apostrophes
carry the same meanings with the corresponding numerals (without
apostrophes) on FIG. 2B. It is obvious that the shifting direction
255' is not the same as the pointing direction 250. Furthermore, it
is easy to see that zones 234', 235a', 235b' are classified as Zone
C. Again, the resultant jittering area, which is a combination of
the zones 234', 235a', 235b', is smaller than the original
jittering area 278 by simple visual inspection. The result
demonstrates that a reduction of jittering area is achievable even
if the shifting direction 255' is not aligned with the pointing
direction 250.
[0047] Examples of other configurations of a network of primary
stations are given in FIGS. 3-5.
[0048] FIG. 3 depicts a network comprising a first primary station
301, a second primary station 302 and a third primary station 303,
where the three primary stations 301-303 have mutually
partially-overlapped broadcasting coverage areas. A first
offset-assisted station 311, a second offset-assisted station 312
and a third offset-assisted station 313 are positioned at the same
offset distance from the first primary station 301, the second
primary station 302 and the third primary station 303,
respectively, along an orientation 350 directed from the first
primary station 301 to the second primary station 302 (viz., along
a straight line 399 linking the first and second primary stations
301, 302). As a result, a first cluster 321, a second cluster 322
and a third cluster 323 are formed.
[0049] FIG. 4 depicts another network comprising a first primary
station 401, a second primary station 402 and a third primary
station 403, where the first primary station 401 has a broadcasting
coverage area partially overlapped with the second primary station
402's broadcasting coverage area at one end, and an opposite end
thereof is in turn partially overlapped with the third primary
station 403's broadcasting coverage area. In addition, the first,
second and third primary stations 401-403 are located on a straight
line 499. Similar to the network of FIG. 3, a first offset-assisted
station 411, a second offset-assisted station 412 and a third
offset-assisted station 413 are positioned at the same offset
distance from the first primary station 401, the second primary
station 402 and the third primary station 403, respectively, along
an orientation 450 aligned with the straight line 499. A first
cluster 421, a second cluster 422 and a third cluster 423 are then
formed.
[0050] FIG. 5 is an example of having more-than-one offset-assisted
stations in each cluster. In FIG. 5, it is depicted a network
comprising a first primary station 501 (labeled as "S1") and a
second primary station 502 (labeled as "S2") both having mutually
partially-overlapped broadcasting coverage areas. A first cluster
581 is formed by including the first primary station 501 and a pair
of first offset-assisted stations 511, 521 (respectively labeled as
"S1off1" and "S1off2"). S1off1 511 is located from S1 501 by a
first offset distance 561 along a pre-determined direction 550. In
turn, S1off2 521 is located from S1off1 511 by a second offset
distance 562 along the pre-determined direction 550. As a result, a
first sequence of stations 51, S1off1, S1off2 is formed. Similarly,
a second cluster 582 is formed by including the second primary
station 502 and a pair of second offset-assisted stations 512, 522
(respectively labeled as "S2off1" and "S2off2"). S2off1 512 is
located from S2 502 by a third offset distance 571 along the
pre-determined direction 550. S2off2 522 is located from S2off1 512
by a fourth offset distance 572 also along the pre-determined
direction 550. A second sequence of stations S2, S2off1, S2off2 is
then formed. In addition, the first, second, third and fourth
offset distances 561, 562, 571, 572 are equal.
[0051] In designing the disclosed system, it is required to
determine the offset distance and the pre-determined direction used
in defining the locations of the primary stations and the
offset-assisted stations for all the clusters. In one embodiment,
the pre-determined direction and the offset distance are selected
such that in the individual cluster, all the one or more
offset-assisted stations are located inside the primary station's
broadcasting coverage area not overlapped with the broadcasting
coverage area of any other cluster's primary station. Examples of
this selection of the pre-determined direction and the offset
distance are provided in FIGS. 2B, 2C and 3-5. In another
embodiment, the pre-determined direction is substantially similar
to a pointing direction from a first primary station to a second
primary station, where the first and second primary stations are
selected from the plural primary stations in the clusters and have
overlapped broadcasting coverage areas. This choice of the
pre-determined direction is exemplified in FIGS. 2B, 3 and 4. The
offset distance may be selected to be less than half of the
distance between the first and second primary stations. Take FIGS.
2A and 2B collectively as an example. The first primary station 201
and the second primary station 202 are separated by a distance 298.
The offset distance, i.e. the first distance 251 or the second
distance 252, is shorter than half of the distance 298.
[0052] A second aspect of the present invention is to improve the
system disclosed in the first aspect of the present invention by
reducing RSSI fluctuation. Diversity reception at the mobile
computing device is employed in the reduction of RSSI fluctuation.
In this regard, the system is configured to provide spatial
diversity transmission to primary beacons and/or secondary beacons
such that the mobile computing device can utilize spatial diversity
reception.
[0053] FIG. 6 depicts a station 610, either a primary station or an
offset-assisted station, configured to provide spatial diversity
transmission as shown in a subplot (a), and a space-time
representation of signals generated by the station 610 as shown in
a subplot (b). As depicted in the subplot (a), the station 610
comprises a group of plural co-located broadcasting units 620-1,
620-2, . . . , 620-S where S is greater than 1. As used herein,
"the broadcasting units 620-1, 620-2, . . . , 620-S being
co-located" means that the broadcasting units 620-1, 620-2, . . . ,
620-S are integrated with the station 610, or are integrated
together to form the station 610, such that the broadcasting units
620-1, 620-2, . . . , 620-S are deemed to be co-located. To achieve
spatial diversity transmission, the broadcasting units 620-1,
620-2, . . . , 620-S are sufficiently mutually-spaced apart. The
i-th broadcasting unit 620-i, 1.ltoreq.i.ltoreq.S, is configured to
broadcast an i-th component beacon signal 621-i such that the
component beacon signals 621-1, 621-2, . . . , 621-S are broadcast
from all the broadcasting units 620-1, 620-2, . . . , 620-S
collectively form a beacon (either a primary beacon or a secondary
beacon) of the station 610. In particular, the component beacon
signals 621-1, 621-2, . . . , 621-S are configured to be
individually distinguishable at the mobile computing device to
thereby allow the mobile computing device to utilize diversity
reception of the beacon to enhance a RSSI value thereof measured at
the mobile computing device. As indicated in the subplot (b), the
i-th component beacon signal 621-i broadcast from the i-th
broadcasting unit 620-i is received and measured at the mobile
computing device to give an i-th RSSI value 652-i. The S RSSI
values 652-1, 652-2, . . . , 652-S can be directly used for spatial
diversity reception. One approach is to average the RSSI values
652-1, 652-2, . . . , 652-S. As a result, the RSSI fluctuation is
reduced. Additionally, time diversity can be used to further reduce
the RSSI fluctuation. The i-th component beacon signal 621-i is
measured at different time instants over a pre-defined time window
655 to give a space-time array of RSSI values 642. Averaging the
array of RSSI values 642 gives a resultant RSSI value 643, which is
subject to less fluctuation.
[0054] To obtain the advantage of spatial and time diversity, at
least one of the primary or offset-assisted stations in the
clusters of the system is realized as the station 610.
Advantageously and more preferably, each of the primary and
offset-assisted stations in the clusters is realized as the station
610. When the station 610 is used as a primary station, the
component beacon signal is referred to as a component
primary-beacon signal, and the beacon mentioned above is a primary
beacon. When the station 610 is used as an offset-assisted station,
the component beacon signal is referred to as a component
secondary-beacon signal, and the beacon mentioned above is a
secondary beacon.
[0055] A third aspect of the present invention is to provide a
method for performing location or proximity determination when any
of the embodiments of the system disclosed above is provided. The
method is illustrated with the aid of FIG. 7, which depicts a
flowchart of steps according to an exemplary embodiment of the
method.
[0056] In a step 710, the primary beacon sent from the individual
cluster and received at the mobile computing device is measured to
give a first RSSI value unless the primary beacon is not
detectable. In case the station 610 is used as the primary station
in generating the primary beacon for utilizing spatial diversity,
the first RSSI value is obtained by averaging plural RSSI values of
the component primary-beacon signals broadcast from all the
broadcasting units at the primary station. If time diversity is
further utilized, each of the component primary-beacon signals
broadcast from each broadcasting unit is measured at different time
instants over a pre-defined time window to give more-than-one RSSI
values for averaging.
[0057] In a step 720, the secondary beacon sent from an individual
offset-assisted station in the individual cluster and received at
the mobile computing device is measured to give a second RSSI value
unless the secondary beacon is not detectable. Again, if the
station 610 is used as the individual offset-assisted station in
generating the secondary beacon for utilizing spatial diversity,
the second RSSI value is obtained by averaging plural RSSI values
of the component secondary-beacon signals broadcast from all the
broadcasting units at the individual offset-assisted station. If
time diversity is further utilized, each of the component
secondary-beacon signals broadcast from each broadcasting unit is
measured at different time instants over the pre-defined time
window to give more-than-one RSSI values for averaging.
[0058] The steps 710 and 720 are repeated for the primary stations
and the one or more offset-assisted stations of all the clusters
(step 730).
[0059] In a step 740, whether the mobile computing device is
located outside an augmented coverage area is determined according
to the first and second RSSI values obtained in the step 730. The
augmented coverage area is an area formed by augmenting the
broadcasting coverage areas of the primary and offset-assisted
stations in the clusters. FIG. 2D provides an example for
illustrating the formation of augmented coverage area based on the
network shown in FIG. 2B. The augmented coverage area 290 is the
combination of the four broadcasting coverage areas 271-274.
[0060] If it is determined in the step 740 that the mobile
computing device is not outside the augmented coverage area, a zone
on which the mobile computing device is located is determined (step
750) according to the first and second RSSI values obtained in the
step 730. In particular, the zone is selected from a plurality of
candidate zones, where the candidate zones are obtained by
partitioning the augmented coverage area along boundaries of the
broadcasting coverage areas of all the primary and offset-assisted
stations in the clusters. Take FIG. 2D as an illustrative example,
the augmented coverage area 290 is partitioned along the first
boundary 211, the second boundary 212, the third boundary 216 and
the fourth boundary 217 to give the candidate zones 231, 232a-c,
233, 234, 235a-b, 236, 237a-c, 238.
[0061] The present invention may be embodied in other specific
forms without departing from the spirit or essential
characteristics thereof. The present embodiment is therefore to be
considered in all respects as illustrative and not restrictive. The
scope of the invention is indicated by the appended claims rather
than by the foregoing description, and all changes that come within
the meaning and range of equivalency of the claims are therefore
intended to be embraced therein.
* * * * *