U.S. patent application number 13/418689 was filed with the patent office on 2012-07-05 for system and method for locating mobile device in wireless communication network.
This patent application is currently assigned to Andrew LLC. Invention is credited to Neil HARPER, Martin THOMSON.
Application Number | 20120169533 13/418689 |
Document ID | / |
Family ID | 42126444 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120169533 |
Kind Code |
A1 |
HARPER; Neil ; et
al. |
July 5, 2012 |
SYSTEM AND METHOD FOR LOCATING MOBILE DEVICE IN WIRELESS
COMMUNICATION NETWORK
Abstract
A method is provided for determining a location of a mobile
device in a wireless network. The method includes receiving global
navigation satellite system (GNSS) measurements from the mobile
device, and receiving terrestrial measurements from corresponding
transceivers in the wireless network, each terrestrial measurement
indicating a distance between the corresponding transceivers and
the mobile device. The method further includes selecting at least
one terrestrial measurement having an uncertainty value within a
predetermined accuracy threshold. The location of the mobile device
is determined as a function of the GNSS measurements and the
selected terrestrial measurement.
Inventors: |
HARPER; Neil; (Mangerton,
AU) ; THOMSON; Martin; (Keiraville, AU) |
Assignee: |
Andrew LLC
Hickory
NC
|
Family ID: |
42126444 |
Appl. No.: |
13/418689 |
Filed: |
March 13, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12406384 |
Mar 18, 2009 |
8160610 |
|
|
13418689 |
|
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Current U.S.
Class: |
342/357.29 |
Current CPC
Class: |
H04W 36/385
20130101 |
Class at
Publication: |
342/357.29 |
International
Class: |
G01S 19/46 20100101
G01S019/46 |
Claims
1. A method for determining a location of a mobile device in a
wireless network, the method comprising: receiving a plurality of
global navigation satellite system (GNSS) measurements for the
mobile device; receiving a plurality of terrestrial measurements
from a corresponding plurality of transceivers in the wireless
network, each terrestrial measurement indicating a distance between
the corresponding transceiver and the mobile device; selecting at
least one terrestrial measurement having an uncertainty value
within a predetermined accuracy threshold; and determining the
location of the mobile device as a function of the plurality of
GNSS measurements and the at least one selected terrestrial
measurement.
2. The method of claim 1, wherein the plurality of GNSS
measurements are received from the mobile device.
3. The method of claim 1, wherein the GNSS measurements comprise
measurements from one of a global positioning system (GPS), a
Global Navigation Satellite System (GLONASS), Galileo system or a
COMPASS Navigation Satellite System (BeiDou).
4. The method of claim 1, wherein the plurality of terrestrial
measurements comprise at least one of uplink-time difference of
arrival (U-TDOA) measurements, timing advance (TA) measurements,
round-trip time (RTT) measurements, enhanced observed time
difference (E-OTD) measurements, angle of arrival (AoA)
measurements, power of arrival (POA) measurements, WiFi
measurements, and DTV signals.
5. The method of claim 2, further comprising: receiving a location
request to determine an estimated location of the mobile device;
determining GNSS assistance data as a function of information in
the received request; and sending the GNSS assistance data to the
mobile device to obtain the GPS measurements.
6. A method of determining a location of a mobile device in a
wireless network, the method comprising: receiving a plurality of
global navigation satellite system (GNSS) measurements for the
mobile device; receiving a plurality of terrestrial measurements
from a corresponding plurality of transceivers in the wireless
network, each terrestrial measurement indicating a distance between
the corresponding transceiver and the mobile device, and a
corresponding uncertainty value associated with the distance;
determining a first dilution of precision (DOP) measure
corresponding to the received GNSS measurements; determining a
revised DOP measure corresponding to each terrestrial measurement
combined with the GNSS measurements; determining for each
terrestrial measurement whether a product of the corresponding
revised DOP measure and the corresponding uncertainty value is less
than a predetermined threshold; selecting at least one terrestrial
measurement as a function of the corresponding revised DOP measure;
and determining the location of the mobile device as a function of
the GNSS measurements and the selected at least one terrestrial
measurement; and wherein the selected at least one terrestrial
measurement includes all terrestrial measurements having
corresponding products less than the predetermined threshold.
7. The method of claim 6, wherein the GNSS measurements comprise
measurements from one of a global positioning system (GPS), a
Global Navigation Satellite System (GLONASS), Galileo system or a
COMPASS Navigation Satellite System (BeiDou).
8. The method of claim 6, wherein the plurality of terrestrial
measurements comprise at least one of uplink-time difference of
arrival (U-TDOA) measurements, timing advance (TA) measurements,
round-trip time (RTT) measurements, enhanced observed time
difference (E-OTD) measurements, angle of arrival (AoA)
measurements, power of arrival (POA) measurements, WiFi
measurements, and DTV signals.
9. A method for determining a location of a mobile device in a
wireless network, the method comprising: providing an initial
location estimate for the mobile device, the initial location
estimate having a corresponding initial uncertainty area;
calculating a minimum range and a maximum range between a
transceiver in the wireless network and the mobile device as a
function of a given location of the transceiver and the uncertainty
area of the initial location; receiving global navigation satellite
system (GNSS) measurements for the mobile device; receiving a
terrestrial measurement from the transceiver indicating a distance
between the transceiver and the mobile device, and accepting the
terrestrial measurement when the terrestrial measurement is between
the minimum range and the maximum range; and determining the
location of the mobile device as a function of the GNSS
measurements and the terrestrial measurement when the terrestrial
measurement is accepted.
10. The method of claim 9, further comprising: determining the
location of the mobile device as a function of the GNSS
measurements when the terrestrial measurement is not accepted.
11. The method of claim 9, wherein the initial location estimate
comprises a location of a base station in the wireless network
serving the mobile device, and the uncertainty area comprises a
coverage area of a cell corresponding to the base station.
12. The method of claim 9, wherein the initial uncertainty area
comprises one of an ellipse, a circle, an arc band or a
polygon.
13. The method of claim 9, wherein the minimum range is zero and
the maximum range is a distance between the transceiver and a
furthest point on an outer boundary of the initial uncertainty area
when the given location of the transceiver is inside the
uncertainty area.
14. The method of claim 9, wherein the minimum range is a distance
between the transceiver and a closest point on an outer boundary of
the initial uncertainty area, and the maximum range is a distance
between the transceiver and a furthest point on the outer boundary
of the initial uncertainty area when the given location of the
transceiver is outside the uncertainty area.
15. The method of claim 9, wherein the initial uncertainty area
comprises one of a WiFi hotspot or a WiMedia hotspot.
16. A method for determining a location of a mobile device in a
wireless network, the method comprising: receiving a plurality of
global navigation satellite system (GNSS) measurements for the
mobile device; calculating a first location of the mobile device
and a first error ellipse at a predetermined confidence level as a
function of the GNSS measurements; receiving a plurality of
terrestrial measurements from a plurality of transceivers in the
wireless network, each terrestrial measurement indicating a
distance between the respective transceiver and the mobile device;
calculating a plurality of second locations of the mobile device
and a plurality of second error ellipses at the predetermined
confidence level as a function of the GNSS measurements and
multiple combinations of the plurality of terrestrial measurements;
comparing the first error ellipse with each of the plurality of
second error ellipses; and determining the location of the mobile
device as either the first location or one of the second locations
as a function of the comparison of the first and second error
ellipses.
17. The method of claim 16, wherein the location of the mobile
device is determined as the first location when the first error
ellipse is smaller than each of the plurality of second error
ellipses.
18. The method of claim 16, wherein the one of the second locations
is calculated as a function of the GNSS measurements and all of the
plurality of terrestrial measurements.
Description
[0001] This application is a divisional application of application
Ser. No. 12/406,384, filed on Mar. 18, 2009, which is hereby
incorporated by reference for all purposes.
BACKGROUND AND SUMMARY
[0002] A wireless communication network typically includes multiple
cells having corresponding base stations for exchanging
communications with mobile device operating within the cell. The
base stations are connected to a centralized system, such as a
mobile location center (MLC), for coordinating the communications
and interfacing with other networks, such as the public switched
telephone network (PSTN) and/or a packet switching network, such as
the Internet.
[0003] A variety of modern wireless communication services include
the feature of determining a geographic location of a mobile
device. For example, an emergency service responsive to "911" being
initiated at the mobile device includes estimating latitude and
longitude of the mobile device in order to locate the device, which
is particularly important when a distressed caller is otherwise
unable to provide their present location. The geographic location
of the mobile device may be determined by a server or other node in
the wireless communication network, such as an MLC or a location
information server (LIS). The MLC, for example, may determine the
geographic location of a mobile device operating within the
wireless communication network using positioning measurements from
a global navigation satellite system (GNSS) or measurements from a
terrestrial positioning system.
[0004] Location determinations based on GNSS measurements are
generally more accurate than terrestrial measurements, although
there are exceptions. For example, GNSS positioning may not be
effective in urban environments or indoors, where structures
obscure access to multiple satellites, weaken signal strengths, or
introduce multi-path components to the signals. Therefore,
conventional systems for determining geographic locations of mobile
devices typically rely on GNSS measurements, and resort to
terrestrial measurements only when GNSS measurements are not
available or fail to provide reliable results. Conventional systems
may also combine GNSS and terrestrial measurements by requesting
and using them in a linear fashion. This approach is
time-consuming, and does not necessarily result in the most
accurate geographic location determination.
[0005] In a representative embodiment, a method is provided for
determining a location of a mobile device in a wireless network.
The method includes receiving global navigation satellite system
(GNSS) measurements for the mobile device, and receiving
terrestrial measurements from corresponding transceivers in the
wireless network, each terrestrial measurement indicating a
distance between the corresponding transceiver and the mobile
device. The method further includes selecting at least one
terrestrial measurement having an uncertainty value within a
predetermined accuracy threshold. The location of the mobile device
is determined as a function of the GNSS measurements and the at
least one selected terrestrial measurement.
[0006] In a representative embodiment, a method is provided for
determining a location of a mobile device in a wireless network.
The method includes receiving GNSS measurements for the mobile
device, and receiving terrestrial measurements from corresponding
transceivers in the wireless network, each terrestrial measurement
indicating a distance between the corresponding transceiver and the
mobile device. The method further includes determining a first
dilution of precision (DOP) measure corresponding to the received
GNSS measurements, and determining a revised DOP measure
corresponding to each terrestrial measurement combined with the
GNSS measurements. At least one terrestrial measurement is selected
as a function of the corresponding revised DOP measure, and the
location of the mobile device is determined as a function of the
GNSS measurements and the selected at least one terrestrial
measurement.
[0007] In a representative embodiment, a method is provided for
determining a location of a mobile device in a wireless network.
The method includes providing an initial location estimate for the
mobile device, the initial location estimate having a corresponding
initial uncertainty area, and calculating a minimum range and a
maximum range between a transceiver in the wireless network and the
mobile device as a function of a given location of the transceiver
and the uncertainty area of the initial location. The method
further includes receiving GNSS measurements for the mobile device
and receiving a terrestrial measurement from the transceiver
indicating a distance between the transceiver and the mobile
device. The terrestrial measurement is accepted when the
terrestrial measurement is between the minimum range and the
maximum range. The location of the mobile device is determined as a
function of the GNSS measurements and the terrestrial measurement
when the terrestrial measurement is accepted.
[0008] In a representative embodiment, a method is provided for
determining a location of a mobile device in a wireless network.
The method includes receiving GNSS measurements for the mobile
device and calculating a first location of the mobile device and a
first error ellipse at a predetermined confidence level as a
function of the GNSS measurements. The method further includes
receiving terrestrial measurements from transceivers in the
wireless network, each terrestrial measurement indicating a
distance between the respective transceiver and the mobile device,
and calculating second locations of the mobile device and second
error ellipses at the predetermined confidence level as a function
of the GNSS measurements and multiple combinations of the
terrestrial measurements. The first error ellipse is compared with
each of the second error ellipses. The location of the mobile
device is determined as either the first location or one of the
second locations as a function of the comparison of the first and
second error ellipses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The illustrative embodiments are best understood from the
following detailed description when read with the accompanying
drawing figures. It is emphasized that the various features are not
necessarily drawn to scale. In fact, the dimensions may be
arbitrarily increased or decreased for clarity of discussion.
Wherever applicable and practical, like reference numerals refer to
like elements.
[0010] FIG. 1 is a functional block diagram illustrating a system
for locating a mobile device in a wireless communication network,
according to a representative embodiment.
[0011] FIG. 2 is a flowchart illustrating a method for locating a
mobile device in a wireless communication network, according to a
representative embodiment.
[0012] FIG. 3 is a flowchart illustrating a method for locating a
mobile device in a wireless communication network, according to a
representative embodiment.
[0013] FIG. 4 is a flowchart illustrating a method for locating a
mobile device in a wireless communication network, according to a
representative embodiment.
[0014] FIG. 5 is a flowchart illustrating a method for locating a
mobile device in a wireless communication network, according to a
representative embodiment.
[0015] FIGS. 6a and 6b are functional block diagrams illustrating a
system for locating a mobile device in a wireless communication
network, according to a representative embodiment.
[0016] FIG. 7 is a flowchart illustrating a method for locating a
mobile device in a wireless communication network, according to a
representative embodiment.
[0017] FIG. 8 is a functional block diagram illustrating a device
for locating a mobile device in a wireless communication network,
according to a representative embodiment.
[0018] FIG. 9 is a functional block diagram illustrating a mobile
device in a wireless communication network, according to a
representative embodiment.
DETAILED DESCRIPTION
[0019] In the following detailed description, for purposes of
explanation and not limitation, illustrative embodiments disclosing
specific details are set forth in order to provide a thorough
understanding of embodiments according to the present teachings.
However, it will be apparent to one having had the benefit of the
present disclosure that other embodiments according to the present
teachings that depart from the specific details disclosed herein
remain within the scope of the appended claims. Moreover,
descriptions of well-known devices and methods may be omitted so as
not to obscure the description of the example embodiments. Such
methods and devices are within the scope of the present
teachings.
[0020] In various embodiments, the geographic location of a mobile
device is efficiently determined based on location measurements
acquired and processed over the same period of time from multiple
positioning systems, such as a global navigation satellite system
(GNSS) and a terrestrially-based range measurement system. For
example, in a representative embodiment, separate GNSS and
terrestrial measurements are acquired and substantially
simultaneously. The terrestrial measurements are selectively
combined with the GNSS measurements only when the aggregate
measurements enhance the accuracy of a hybrid location calculation.
For example, terrestrial measurements may be included in the hybrid
location calculation if they meet a predetermined uncertainty
threshold, improve dilution of precision (DOP) of the calculation
compared with using GNSS measurements alone, fall within a initial
uncertainty area and/or reduce overall uncertainty.
[0021] FIG. 1 is a functional block diagram illustrating a system
for locating a mobile device in a wireless communication network,
according to a representative embodiment. In particular, the
embodiment of FIG. 1 shows system 100, which includes wireless
communication network 110 and GNSS network 140.
[0022] The wireless communication network 110 includes
representative cell towers or base stations 111-114, mobile
location center (MLC) 120 and location server (LS) 125. An
alternative embodiment may include an LIS or other system in place
of the MLC 120, for example. Each base station 111-114 is
associated with a corresponding coverage area or "cell," although
only cell 115 associated with base station 112 is depicted for
purposes of explanation, since FIG. 1 depicts base station 112 as
the base station serving representative mobile device 130 at its
present location. The mobile device 130 may be any type of wireless
device configured for communicating over the wireless communication
network 110, including a cellular telephone, a laptop computer, a
personal computer, a personal digital assistant (PDA), a gaming
device, or the like. The wireless communication network 110 is
configured to enable wireless communications between the mobile
device 130 and the base stations 111-114 in compliance with various
wireless communications standards, including, but not limited to,
Universal Mobile Telecommunications System (UMTS) network, Global
System for Mobile communications (GSM) network, code division
multiple access (CDMA), IEEE 802.11 (WiFi), IEEE 802.16 (WiMax),
digital television (DTV) network, and the like.
[0023] In an embodiment, the MLC 120 and the LS 125 are configured
to determine geographic locations of mobile devices in the wireless
communication network 110, including the representative mobile
device 130. For example, the MLC 120 may receive a message from the
mobile device 130 through the base station 112 requesting
determination of the geographic location of the mobile device 130.
The message may be transmitted over voice/data communication
channels and/or signaling channels of the wireless communication
network 110, for example. In response, the MLC 120 forwards a
corresponding request to the LS 125, which retrieves measurements
from location measurement units (LMUs) 116-119 of a terrestrial
positioning system for determining the geographic location of the
mobile device 130. In various embodiments, the terrestrial
positioning system may be any system configured to determine the
location of a mobile device using terrestrial measurements as input
to the position calculation, which may include a trilateration
technique. The terrestrial measurements may be any type of range
measurements, including cellular network measurements, such as
uplink-time difference of arrival (U-TDOA) or timing advance (TA)
measurements (e.g., in a GSM network), round-trip time (RTT)
measurements (e.g., in a UMTS network), enhanced observed time
difference (E-OTD) measurements, angle of arrival (AoA)
measurements, power of arrival (POA) measurements, WiFi
measurements, DTV signals and the like. In addition, although one
terrestrial positioning system is shown in FIG. 1, it is understood
that multiple terrestrial positioning systems may be included in
various configurations, without departing from the scope of the
disclosure.
[0024] LMUs 116-119, depicted in FIG. 1 for purposes of discussion,
are typically associated with U-TDOA systems, in which case the LS
125 is implemented as a U-TDOA location services (ULS) server and
receives the U-TDOA measurements from the LMUs 116-119. In other
embodiments, the MLC 120 receives the terrestrial measurements
directly from the LMUs 116-119, such as embodiments using RTT
measurements. The LMUs 116-119 are positioned throughout the
wireless communication network 110. Also, for purposes of
discussion, the LMUs 116-119 are transceivers depicted as being
collocated with the base stations 111-114, although it is
understood that in alternative embodiments the LMUs 116-119 may be
positioned at different locations, and that there may be a
different number of LMUs 116-119 than base stations 111-114. The
MLC 120 is then able to calculate the location of the mobile device
130 using at least the terrestrial measurements obtained by the LS
125, as discussed below. In an embodiment, the functionality of the
LS 125 is implemented by the MLC 120, although the LS 125 may
alternatively be a separate entity connected to the MLC 120 through
an interface.
[0025] The GNSS network 140 shown in FIG. 1 includes a
constellation of positioning satellites 141-144, which provide
signals to the mobile device 130. The GNSS network 140 may include
any satellite positioning system configured to provide geographic
locations of receivers using a constellation of satellites, such as
the Global Positioning System (GPS), Global Navigation Satellite
System (GLONASS), Galileo and COMPASS Navigation Satellite System
(BeiDou), for example. The mobile device 130 includes a
corresponding mobile GNSS receiver that receives the satellite
positioning signals from the positioning satellites 141-144. The
mobile device 130 is thus able to provide GNSS measurements to the
MLC 120 over the wireless communications network 110. The MLC 120
is then able to calculate the location of the mobile device 130
using at least the GNSS measurements, as discussed below. In an
embodiment, the mobile device 130 calculates its own location based
on the GNSS measurements, and sends the calculated GNSS location to
the MLC 120. However, the MLC 120 typically has more processing
power, and the mobile device 130 saves battery power by not
performing the calculations. Also, the MLC 120 is able to perform a
hybrid location calculation because it has access to other
measurements that the mobile device 130 does not have access to,
such as U-TDOA measurements, base station timing or ranging
signals, and/or signals from other terrestrial positioning systems.
In another embodiment, the MLC 120 may receive GNSS measurements
indicating the location of the mobile device 130 from a source
other than the mobile device 130, such as a server remotely
tracking the position of mobile device 130.
[0026] In an embodiment, the GNSS network 140 also includes a wide
area reference network (WARN) 150. The WARN 150 provides a network
of fixed GNSS receivers, indicated by representative GNSS receivers
151 and 152, geographically spread over the coverage area of the
wireless communication network 110, and a central cache. Although
only two fixed GNSS receivers 151 and 152 are depicted, e.g.,
positioned at locations different from the locations of base
stations 111-114, it is understood that in various embodiments,
there may be different numbers of fixed GNSS receivers, which may
be collocated with base stations 111-114 of the wireless
communication network 110. The WARN 150 collects navigation
messages from the fixed GNSS receivers 151 and 152 broadcast by the
satellites 141-144. The navigation messages are collated and
provided to the MLC 120 for caching. The MLC 120 may then use the
cached navigation messages to provide assistance data to the mobile
device 130 over the wireless communication network 110, as
discussed below.
[0027] FIG. 2 is a flow diagram illustrating a method for locating
a mobile device in a wireless communication network, using
uncertainty determinations, according to a representative
embodiment.
[0028] Referring to FIG. 2, the MLC 120 receives a request at step
205 from the mobile device 130 over the wireless communication
network 110 to determine the geographic location of the mobile
device 130. The request may be in the form of a "911" call, for
example, dialed at the mobile device 130, which automatically
initiates the location determination process at the MLC 120, via
messaging that is received from the network node that detects the
emergency call. In addition to the "911" emergency service, the
mobile device 130 may include applications specifically directed to
determining current geographic location, such as subscriber
location services, mapping services, and the like.
[0029] In an embodiment, the location request includes a time
within which the location of the mobile device 130 is to be
determined and/or a designated accuracy of the location
determination, such as a quality of position (QoP) parameter, which
identifies the required accuracy within a specified range (e.g.,
indicated as an "error ellipse" in meters). For example, the QoP
parameter may indicate requisite horizontal accuracy, vertical
accuracy and/or age of location with respect to the mobile device
130. When no time limit or QoP parameter is provided in the
location request, the MLC 120 may provide respective default
values.
[0030] At steps 210 and 220, the MLC 120 requests location
measurements from devices in the wireless communication network 110
and the mobile device 130, so that the MLC 120 is able to calculate
the location of the mobile device 130 using a combination of
different measurement systems, such as a GNSS positioning system
and one or more terrestrial positioning systems. For purposes of
explanation, it is assumed that the satellite positioning system of
the GNSS network 140 is a GPS system, and that the corresponding
measurements are distance and/or signal transit time measurements
between the mobile device 130 and each of the GPS satellites (e.g.,
satellites 141-144) provided by the mobile device 130. However, it
is understood that other types of satellite positioning systems and
corresponding measurements may be incorporated without departing
from the scope of the disclosure. It is further understood that the
MLC 120 may request the location measurements consecutively,
concurrently or substantially concurrently without departing from
the scope of the disclosure.
[0031] Likewise, for purposes of explanation, it is further assumed
that the wireless communications network 110 includes one
terrestrial positioning system, which may be any type of
terrestrial trilateration system, as discussed above. For purposes
of discussion, it is assumed that the terrestrial positioning
system is a U-TDOA system, for example, and that the corresponding
terrestrial measurements are time-difference measurements provided
by the LMUs 116-119 based on transit time measurements of signals
received from the mobile device 130. It is understood that other
types of terrestrial positioning systems may likewise require
incorporation of system specific devices into the wireless
communication network 110, including associated hardware, software,
antennae, modulators, demodulators and the like, although not
specifically shown in FIG. 1. It is further understood that other
types of terrestrial positioning systems and corresponding
terrestrial measurements may be incorporated without departing from
the scope of the disclosure.
[0032] Accordingly, in the representative embodiment, the MLC 120
requests the GPS measurements from the mobile device 130 and the
terrestrial measurements from the LMUs 116-119 at steps 210 and
220, respectively. Notably, the GPS measurements are delivered
together as a set to the MLC 120 by the mobile device 130, while
the terrestrial measurements do not necessarily arrive at the MLC
120 from the LMUs 116-119 at the same time. Therefore, if the MLC
120 requests the GPS and terrestrial measurements at about the same
time, for example, a full set of GPS measurements typically arrives
before a full set of U-TDOA measurements, which may be spread over
a period of time. However, depending on the circumstances, the MLC
120 may receive the full set of U-TDOA measurements first, for
example, when geographical conditions make acquisition of GPS
signals difficult, such as in low signal environments like urban
canyons or indoors.
[0033] In an embodiment, the MLC 120 also provides satellite data
to the mobile device 130 over the wireless communication network
110 to aid the mobile device 130 in more quickly locating and
acquiring the satellites 141-144. For example, the mobile device
130 may be an Assisted-GPS (A-GPS) capable handset, and the MLC 120
is thus able to provide A-GPS data to the mobile device 130, along
with the request to begin providing GPS measurements. The A-GPS
data may include, for example, satellite acquisition assistance in
order to inform the mobile device 130 for which satellites to
search and where in the time and frequency domain to search. The
A-GPS data may also include other assistance data types, such as
orbital modeling information of the GPS satellites (e.g.,
satellites 141-144), including satellite ephemeris data from the
GPS satellites and/or previously stored almanac data, for
example.
[0034] The A-GPS data enables the mobile device 130 to locate and
"lock-on" to each of the GPS satellites quickly and efficiently.
The GPS assistance data may be calculated, in part, using cached
navigation messages (including ephemeris data and timing signals)
provided by the WARN 150, as discussed above. In an embodiment,
when GPS assistance data is required, the request from the mobile
device 130 includes a number or other identifier of the cell in
which it is located (e.g., cell 115). The MLC 120 may then access a
database (not shown) to determine the latitude, longitude,
orientation, opening and/or range of the cell 115, which may be
used as an initial location for calculating the GPS assistance
data. For example, the MLC 120 may calculate the GPS assistance
data using the latitude and longitude of the serving base station
112 and its coverage area as the approximate initial location of
the mobile device 130.
[0035] In an embodiment, the GPS assistance data improves the
time-to-first-fix (TTFF) and yield. For example, the orbital
modeling information of the GPS assistance data enables the mobile
device 130 to avoid demodulating navigation messages broadcast from
the GPS satellites, thus improving TTFF. Also, the search space for
locating each of the GPS satellites is narrowed by the GPS
acquisition assistance, so that the mobile device 130 can detect
weaker GPS signals, thus improving yield.
[0036] At steps 212 and 222, the MLC 120 receives and stores GPS
measurements from the mobile device 130 and the terrestrial
measurements from the LMUs 116-119, e.g., via the LS 125. Further,
the MLC 120 determines the uncertainty of the GPS measurements at
step 214 and the uncertainty of each of the terrestrial
measurements at step 224 upon receipt from the respective systems.
Notably, some measurement errors, such as troposphere and
ionosphere errors, may be removed or partially removed from GPS
measurements, which makes the GPS measurements more precise than
uncorrected measurements. Typically, GPS measurements are more
accurate than a terrestrial-based range measurement. In alternative
embodiments, the uncertainties of the GPS and terrestrial
measurements may be determined by the mobile device 130 and the LS
125, respectively.
[0037] With respect to the terrestrial measurements, for purposes
of explanation, FIG. 2 indicates a loop in which steps 226 through
230 are repeated successively for each terrestrial measurement,
each loop ending with a determination at step 230 whether
additional terrestrial measurements are available for processing.
However, it is understood that any or all terrestrial measurements
(including terrestrial measurements from multiple terrestrial
positioning systems, depending on configuration) may be processed
simultaneously or substantially simultaneously, e.g., assuming that
MLC 120 has sufficient processing power and that multiple
terrestrial measurements have been received.
[0038] At step 226, it is determined whether the uncertainty
determined in step 224, associated with each terrestrial
measurement, meets a predetermined uncertainty threshold. The
uncertainty threshold may be set by a user or network operator,
provided by a default setting, or the like. Alternatively, the MLC
120 may set the uncertainty threshold on a case-by-case basis,
depending on the uncertainty of the GPS measurements determined at
step 214. For example, when the uncertainty of the GPS measurements
is very low (indicating high accuracy), the uncertainty threshold
may be set relatively high, so that the terrestrial measurements
are largely excluded, so as not to degrade the otherwise high
accuracy of the GPS measurements, unless the terrestrial
measurements are also very accurate. Likewise, when the uncertainty
of the GPS measurements is very high (indicating low accuracy), the
uncertainty threshold may be set relatively low, so that the
terrestrial measurements are more likely to be included to help
boost overall accuracy.
[0039] When the uncertainty of the terrestrial measurement meets
the predetermined uncertainty threshold (step 226: Yes), the
terrestrial measurement is identified for inclusion in the location
calculation of step 232, discussed below. For example, the
terrestrial measurement may be stored separately, or memory
addresses of the previously stored terrestrial measurement (e.g.,
stored in step 222) may be tagged accordingly. When the uncertainty
of the terrestrial measurement does not meet the predetermined
uncertainty threshold (step 226: No), the terrestrial measurement
is not identified for inclusion in the location calculation.
[0040] In either case, the process subsequently determines at step
S230 whether there are additional terrestrial measurements to be
received, stored and processed, as discussed above. When it is
determined that there are additional terrestrial measurements (step
230: Yes), the process returns to step 226 to compare the next
terrestrial measurement to the predetermined uncertainty threshold.
In an embodiment including multiple terrestrial systems, the
additional terrestrial measurements may be from a terrestrial
system different from the terrestrial system involved in previous
processing. When it is determined that there are no further
terrestrial measurements, e.g., that a full set of terrestrial
measurements has been received (step 230: No), the process
continues to step 232 for hybrid location calculation.
[0041] At step 232, the hybrid location calculation is performed by
the MLC 120 using the set of GPS measurements and each of the
terrestrial measurements meeting the predetermined threshold, as
determined at step 226. The hybrid location calculation may include
combining the GPS measurements and selected U-TDOA measurements in
a weighted least squares process to perform the position
calculation. The MLC 120 may also calculate the uncertainty
associated with the calculated hybrid location.
[0042] For example, in an embodiment, a position calculation
function (PCF) provided by the MLC 120 implements single point
positioning (SPP), using a least squares process with a
mathematical and stochastic model. With respect to the GPS
measurements, the stochastic model "weights" the satellites 141-144
depending on their respective elevations above the horizon, such
that satellites at higher elevations are accorded greater weights
because satellites at higher elevations tend to have fewer errors,
e.g., since satellites at lower elevations are subject to more
ionosphere error, troposphere error and multipath effects.
[0043] The selected terrestrial measurements are integrated into
the stochastic model slightly differently because the various
terrestrial measurements are not subject to the clock error of the
GPS receiver (e.g., in mobile device 130). That is, the terrestrial
measurements provide "ranges" as opposed to the "pseudoranges"
provided by the GPS measurements. The terrestrial measurements are
range measurements in the form of a distance value, the uncertainty
in the distance value and the coordinates of the range sources
(e.g., LMUs 116-119). The uncertainties in the terrestrial
measurements are used to contribute to calculation of an "error
ellipse" or other area of uncertainty reported as part of the final
calculated hybrid location. As with respect to the GPS
measurements, the stochastic model weights the various sets of
terrestrial measurements, depending on respectively perceived
accuracies, e.g., identified through corresponding uncertainties
determined at step 224.
[0044] FIG. 3 is a flow diagram illustrating a method for locating
a mobile device in a wireless communication network, using dilution
of precision (DOP) determinations, according to another
representative embodiment.
[0045] Referring to FIG. 3, the MLC 120 receives a request at step
305 from the mobile device 130 over the wireless communication
network 110 to determine the geographic location of the mobile
device 130, as discussed above with respect to step 205. At steps
310 and 320, the MLC 120 requests location measurements from the
mobile device 130 and devices in the wireless communication network
110, so that the MLC 120 is able to calculate the location of the
mobile device 130 using a combination of different measurement
systems, such as a GNSS positioning system and one or more
terrestrial positioning systems. For purposes of explanation, it is
assumed that the satellite positioning system of the GNSS network
140 is a GPS system, and that the wireless communication network
110 includes one terrestrial positioning system, which may be a
U-TDOA system, for example. It is understood that other types of
satellite and/or terrestrial systems may be incorporated without
departing from the scope of the disclosure. It is further
understood that the MLC 120 may request the location measurements
consecutively, concurrently or substantially concurrently without
departing from the scope of the disclosure.
[0046] Accordingly, in the representative embodiment, the MLC 120
requests the GPS measurements from the mobile device 130 and the
terrestrial measurements from the LMUs 116-119 at steps 310 and
320, respectively. At steps 312 and 322, the MLC 120 receives and
stores GPS measurements from the mobile device 130 and terrestrial
measurements from the LMUs 116-119, e.g., via the LS 125.
[0047] The MLC 120 determines the measurement error and the DOP of
the GPS measurements at step 314. Measurement error results from
ionosphere error, troposphere error, multipath effects, and the
like. The DOP is a measurement of the geometric spread of the
measurements, for example, based on the relative positions of the
satellites 141-144 with respect to the mobile device 130.
Generally, with respect to a GPS system, the greater the spread
among the satellites 141-144, the lower the DOP. That is, a lower
DOP indicates a wider angular separation among the satellites
141-144, and thus a more accurate location calculation.
[0048] At step 326, each of the terrestrial measurements is
combined with the GPS measurements, and a new measurement error and
corresponding DOP are calculated. With respect to combining the
terrestrial measurements, for purposes of explanation, FIG. 3
indicates a loop in which steps 326 through 336 are repeated
successively for each terrestrial measurement, each loop ending
with a determination at step 336 whether additional terrestrial
measurement(s) are available for processing. However, it is
understood that any or all terrestrial measurements alternatively
may be processed simultaneously or substantially simultaneously,
e.g., assuming that MLC 120 has sufficient processing power and
that multiple terrestrial measurements have been received.
[0049] Generally, when the combined GPS and terrestrial
measurements improve the DOP without increasing measurement error,
then the resulting calculated hybrid location is more accurate.
Therefore, at step 328, it is determined whether the new
measurement error of the combined GPS and terrestrial measurements
increases over the measurement error of only the GPS measurements
determined at step 314. When the new combined measurement error has
not increased (step 328: No), it is determined at step 330 whether
the new DOP of the combined GPS and terrestrial measurements
decreases (improves) over the DOP of only the GPS measurements
determined in step 314. When the new combined DOP has decreased
(step 330: Yes), the corresponding terrestrial measurement is
included with the GPS measurements for subsequent calculation of
the hybrid location (e.g., at step 340), discussed below.
[0050] It is understood that the order of determining whether the
terrestrial measurement increases measurement error and/or
decreases DOP may vary, or the determinations may be performed
simultaneously, without departing from the scope of the disclosure.
When either the new combined measurement error is increased over
the GPS measurements error (step 328: Yes) or the new combined DOP
is increased over the GPS measurements DOP, the terrestrial
measurement is disregarded at step 334.
[0051] The process determines at step 336 whether there are
additional terrestrial measurements to be processed, as discussed
above. When it is determined that there are additional terrestrial
measurements (step 336: Yes), the process returns to step 326 to
determine the combined measurement error and DOP of the next
terrestrial measurement. In an embodiment including multiple
terrestrial systems, the additional terrestrial measurement may be
from a terrestrial system different from the terrestrial system
involved in previous processing. When there are no additional
terrestrial measurements to be obtained (step 336: No), the MLC 120
calculates the hybrid location at step 340 using the GPS
measurements and the terrestrial measurements that improved the DOP
without increasing measurement error, included in step 332. The
hybrid location calculation is performed, for example, as discussed
above with respect to step 232 of FIG. 2.
[0052] FIG. 4 is a flow diagram illustrating a method for locating
a mobile device in a wireless communication network, effectively
combining the processes depicted in FIGS. 2 and 3, so that
terrestrial measurements are selected based on their corresponding
uncertainties, as well as the effect of each terrestrial
measurement on the DOP when combined with the GPS measurements.
[0053] Referring to FIG. 4, the MLC 120 receives a request at step
405 from the mobile device 130 over the wireless communication
network 110 to determine the geographic location of the mobile
device 130, as discussed above with respect to step 205. At steps
410 and 420, the MLC 120 requests location measurements from the
mobile device 130 and devices in the wireless communication network
110, so that the MLC 120 is able to calculate the location of the
mobile device 130 using a combination of different measurement
systems, such as a GNSS positioning system and one or more
terrestrial positioning systems. For purposes of explanation, it is
assumed that the satellite positioning system of the GNSS network
140 is a GPS system, and that the wireless communication network
110 includes one terrestrial positioning system, which may be a
U-TDOA system, for example. It is understood that other types of
satellite and/or terrestrial systems may be incorporated without
departing from the scope of the disclosure. It is further
understood that the MLC 120 may request the location measurements
consecutively, concurrently or substantially concurrently without
departing from the scope of the disclosure.
[0054] Accordingly, in the representative embodiment, the MLC 120
requests the GPS measurements from the mobile device 130 and the
terrestrial measurements from the LMUs 116-119 at steps 410 and
420, respectively. At steps 412 and 422, the MLC 120 receives and
stores GPS measurements from the mobile device 130 and terrestrial
measurements from the LMUs 116-119, e.g., via the LS 125. Further,
the MLC 120 determines the uncertainty and the DOP of the GPS
measurements at step 414, as discussed above with respect to step
214 of FIG. 2. Also, the MLC 120 determines the uncertainty of each
terrestrial measurement at step 424, as discussed above with
respect to step 224 of FIG. 2.
[0055] At step 426, each of the terrestrial measurements is
combined with the GPS measurements, and a DOP is calculated. With
respect to combining the terrestrial measurements, for purposes of
explanation, FIG. 4 indicates a loop in which steps 426 through 436
are repeated successively for each terrestrial measurement, each
loop ending with a determination at step 436 whether additional
terrestrial measurement(s) are available for processing. However,
it is understood that any or all terrestrial measurements may be
processed simultaneously or substantially simultaneously, e.g.,
assuming that MLC 120 has sufficient processing power and that
multiple terrestrial measurements have been received.
[0056] At step 428, the combined DOP and the uncertainty of the
terrestrial measurement, determined at step 424, are multiplied to
provide a product indicating whether the terrestrial measurement
should be combined with GPS measurements, as a function of the
terrestrial measurement's uncertainty and the effect on the DOP of
combining the terrestrial measurement with the GPS measurements.
The product is compared to a predetermined threshold at step 430.
When the product is less than the predetermined threshold (step
430: Yes), indicating a low uncertainty of the terrestrial
measurement and/or a combined DOP lower than the DOP based only on
the GPS measurements, the terrestrial measurement is identified at
step 432 to be included in the hybrid location calculation,
discussed below with respect to step 440. When the product is
greater than or equal to the predetermined threshold (step 430:
No), indicating a high uncertainty of the terrestrial measurement
and/or a combined DOP higher than the DOP based only on the GPS
measurements, the terrestrial measurement is disregarded at step
434.
[0057] The predetermined threshold is set at a value that prevents
undesirable results based on the particular factors associated with
each terrestrial measurement. For example, when the uncertainty of
a terrestrial measurement determined at step 424 is particularly
high, the terrestrial measurement should be disregarded, even if
the terrestrial measurement would otherwise decrease the DOP when
combined with the GPS measurements. Likewise, when a terrestrial
measurement has a low uncertainty, indicating that the terrestrial
measurement is accurate, but the terrestrial measurement does not
decrease the DOP when combined with the GPS measurements, the
terrestrial measurement is still disregarded. Thus, a terrestrial
measurement is included only when the combined uncertainty and
effect of DOP provides a net improvement in the hybrid location
calculation.
[0058] Referring again to FIG. 4, after determining whether to
include or disregard the terrestrial measurement and step 432 or
step 434, the process determines at step 436 whether there are
additional terrestrial measurements to be received, stored and
processed, as discussed above. When it is determined that there are
additional terrestrial measurements (step 436: Yes), the process
returns to step 426 to determine the combined DOP using the next
terrestrial measurement. In an embodiment including multiple
terrestrial systems, the additional terrestrial measurement may be
from a terrestrial system different from the terrestrial system
involved in previous processing. When there are no additional
terrestrial measurements to be obtained (step 436: No), the MLC 120
calculates the hybrid location at step 440 using the GPS
measurements and the terrestrial measurements that provided a
product of uncertainty and DOP lower than the predetermined
threshold. The hybrid location calculation is performed, for
example, as discussed above with respect to step 232 of FIG. 2.
[0059] FIG. 5 is a flow diagram illustrating a method for locating
a mobile device in a wireless communication network, using initial
location estimates of the mobile device, according to a
representative embodiment.
[0060] Referring to FIG. 5, the MLC 120 receives a request at step
505 from the mobile device 130 over the wireless communication
network 110 to determine the geographic location of the mobile
device 130, as discussed above with respect to step 205 of FIG. 2.
At steps 510 and 520, the MLC 120 requests location measurements
from the mobile device 130 and devices in the wireless
communication network 110, so that the MLC 120 is able to calculate
the location of the mobile device 130 using a combination of
different measurement systems, such as a GNSS positioning system
and one or more terrestrial positioning systems. For purposes of
explanation, it is assumed that the satellite positioning system of
the GNSS network 140 is a GPS system, and that the wireless
communication network 110 includes one terrestrial positioning
system, which may be a U-TDOA system, for example. It is understood
that other types of satellite and/or terrestrial systems may be
incorporated without departing from the scope of the disclosure. It
is further understood that the MLC 120 may request the location
measurements consecutively, concurrently or substantially
concurrently without departing from the scope of the
disclosure.
[0061] Accordingly, in the representative embodiment, the MLC 120
requests the GPS measurements from the mobile device 130 and the
terrestrial measurements from the LMUs 116-119 at steps 510 and
520, respectively. At steps 512 and 522, the MLC 120 receives and
stores GPS measurements from the mobile device 130 and terrestrial
measurements from the LMUs 116-119, e.g., via the LS 125.
[0062] Meanwhile, at step 524, the MLC 120 initially estimates the
location of the mobile device 130, which includes an initial
uncertainty area. In an embodiment, the initial location estimate
of the mobile device 130 is the location of the base station
currently servicing the mobile device 130 (e.g., base station 112),
and the initial uncertainty area is the coverage of the
corresponding cell. For example, referring to FIG. 1, the initial
location estimate may be the longitude and latitude of the
servicing base station 112, and the initial uncertainty area may be
the area of cell 115.
[0063] At step 526, minimum and maximum ranges from each LMU
116-119 to the mobile device are determined based on the initial
uncertainty area (e.g., the area of cell 115). For example, in a
cellular network (e.g., UMTS, GSM), the initial uncertainty area
may be the servicing cell, or in a wireless broadband or local area
network (e.g., WiFi, WiMedia), the initial uncertainty area may be
the "hotspot" area corresponding to an access point. The minimum
and maximum ranges are determined differently for LMUs outside the
initial uncertainty area (e.g., LMUs 116 and 119) and LMUs inside
the initial uncertainty area (e.g., LMUs 117 and 118). FIGS. 6a and
6b are block diagrams showing the minimum and maximum ranges with
respect to LMUs 116 and 118, respectively located inside and
outside the initial uncertainty area (e.g., cell 115).
[0064] Referring to FIG. 6a, depicting representative LMU 116
located outside the initial uncertainty area (e.g., cell 115), the
minimum range is the distance between the LMU 116 and the closest
point of the initial uncertainty area, determined as the point at
which vector Vmin from the LMU 116 perpendicularly intersects a
tangent of the outer periphery of the near boundary of the initial
uncertainty area, for example. The maximum range is the distance
between the LMU 116 and the furthest point of the initial
uncertainty area, determined as the point at which vector Vmax from
the LMU 116 perpendicularly intersects a tangent of the outer
periphery of the far boundary of the initial uncertainty area, for
example. Referring to FIG. 6b, depicting representative LMU 118
located inside the initial uncertainty area (e.g., cell 115), the
minimum range is zero, and the maximum range is the distance
between the LMU 118 and the furthest point of the initial
uncertainty area, determined as the point at which vector Vmax from
the LMU 118 perpendicularly intersects a tangent of the outer
periphery of the far boundary of the uncertainty area, for
example.
[0065] Although depicted as an ellipse, it is understood that the
initial uncertainty area (e.g., cell 115) may be any other shape or
area, including a circle, a sector, an arc band, a polygon or the
like. It is further understood that the initial uncertainty area
need not match the area of the cell in which the mobile device 130
is presently located, although the initial uncertainty area would
overlap at least a portion of the cell in which the mobile device
130 is presently located.
[0066] At step 528, it is determined whether each received
terrestrial measurement is within the minimum and maximum ranges
determined with respect to the corresponding one of the LMUs
116-119. For purposes of explanation, FIG. 5 indicates a loop in
which steps 528 through 534 are repeated successively for each
terrestrial measurement, each loop ending with a determination at
step 534 whether additional terrestrial measurement(s) are
available for processing. However, it is understood that any or all
terrestrial measurements may be processed simultaneously or
substantially simultaneously. It is further understood that the MLC
120 may be receiving and storing terrestrial measurements from any
or all LMUs 116-119 as it is estimating initial locations and
determining minimum and maximum ranges for each of the LMUs
116-119, depicted in steps 524 and 526, respectively.
[0067] When the terrestrial measurement is within the minimum and
maximum ranges (step 528: Yes), indicating a valid terrestrial
measurement, the terrestrial measurement is identified at step 530
to be included in the hybrid location calculation, discussed below
with respect to step 540. When the terrestrial measurement is not
within the minimum and maximum ranges (step 528: No), indicating an
invalid terrestrial measurement, the terrestrial measurement is
disregarded at step 532.
[0068] After determining whether to include or disregard the
terrestrial measurement and step 530 or step 532, the process
determines at step 534 whether there are additional terrestrial
measurements to be processed, as discussed above. When it is
determined that there are additional terrestrial measurements (step
534: Yes), the process returns to step 528 to compare the next
terrestrial measurement with the minimum and maximum ranges. In an
embodiment including multiple terrestrial systems, the additional
terrestrial measurement may be from a terrestrial system different
from the terrestrial system involved in previous processing. When
there are no additional terrestrial measurements (step 534: No),
the MLC 120 calculates the hybrid location at step 540 using the
GPS measurements and the valid terrestrial measurements, identified
in step 530. The hybrid location calculation is performed, for
example, as discussed above with respect to step 232 of FIG. 2.
[0069] FIG. 7 is a flow diagram illustrating a method for locating
a mobile device in a wireless communication network, considering
all terrestrial measurements in combination with GPS
measurements.
[0070] Referring to FIG. 7, the MLC 120 receives a request at step
705 from the mobile device 130 over the wireless communication
network 110 to determine the geographic location of the mobile
device 130, as discussed above with respect to step 205 of FIG. 2.
At steps 710 and 720, the MLC 120 requests location measurements
from the mobile device 130 and devices in the wireless
communication network 110, so that the MLC 120 is able to calculate
the location of the mobile device 130 using a combination of
different measurement systems, such as a GNSS positioning system
and one or more terrestrial positioning systems. For purposes of
explanation, it is assumed that the satellite positioning system of
the GNSS network 140 is a GPS system, and that the wireless
communication network 110 includes one terrestrial positioning
system, which may be a U-TDOA system, for example. It is understood
that other types of satellite and/or terrestrial systems may be
incorporated without departing from the scope of the disclosure. It
is further understood that the MLC 120 may request the location
measurements consecutively, concurrently or substantially
concurrently without departing from the scope of the
disclosure.
[0071] Accordingly, in the representative embodiment, the MLC 120
requests the GPS measurements from the mobile device 130 and the
terrestrial measurements from the LMUs 116-119 at steps 710 and
720, respectively. At steps 712 and 722, the MLC 120 receives and
stores GPS measurements from the mobile device 130 and terrestrial
measurements from the LMUs 116-119, e.g., via the LS 125. Further,
the MLC 120 calculates and stores the location of the mobile device
130 using only the GPS measurements at step 714. At step 716, the
MLC 120 determines and stores the uncertainty of the location
calculated at step 716, using only GPS measurements. The
uncertainty of the GPS calculated location may be expressed as an
error ellipse (or other shape) at a given confidence level. An area
of the error ellipse varies directly with respect to the given
confidence level, such that a greater given confidence level
results in a larger corresponding error ellipse.
[0072] Meanwhile, at step 724, the MLC 120 calculates and stores
hybrid locations using every combination of terrestrial
measurements with the GPS measurements. For example, when four
terrestrial measurements are received from the LMUs 116-119,
respectively, hybrid locations are calculated as a function of the
GPS measurements combined with each one of the terrestrial
measurements, as well as with every possible combination of two or
more terrestrial measurements, including all terrestrial
measurements.
[0073] The uncertainty of each location calculated at step 724 is
determined at step 726, e.g., resulting in corresponding error
ellipses at the same given confidence level used to determine the
error ellipse of the GPS location calculation at step 716. At step
730, one of the calculated GPS location or calculated hybrid
locations is selected as the location of the mobile device 130,
based on the lowest corresponding uncertainty. In other words, the
GPS location calculation or the one of the hybrid location
calculations based on a combination of GPS and terrestrial
measurements having the smallest error ellipse at the give
confidence level is selected. In an embodiment, a location and
corresponding error ellipse determined as a function of only the
terrestrial measurement may also be calculated and compared to the
GPS location calculation.
[0074] Each of the representative embodiments thus improves
efficiency and accuracy in determining the geographic location of a
mobile device, selectively using the best GPS and terrestrial
measurements available, while disregarding the others.
[0075] FIG. 8 is a functional block diagram illustrating an MLC 820
for calculating locations of mobile devices in a wireless
communication network, according to representative embodiments.
Although the MLC 820 is shown and discussed in detail, it is
understood that other servers in the system 100, such as the LS 125
in the wireless communication network 110, may be configured in a
similar manner as the MLC 820, at least with respect to processing
and storage functionality.
[0076] In the depicted embodiment, the MLC 820 includes central
processing unit (CPU) 821, internal memory 822, bus 829 and various
interfaces 825-828. The CPU 821 is configured to execute one or
more software algorithms, including the mobile device location
determination process and PCF of the embodiments described herein.
In various embodiments, the CPU 821 may include its own memory
(e.g., nonvolatile memory) for storing executable software code
that allows it to perform various functions, including the location
determination process. Alternatively, the executable code may be
stored in designated memory locations within internal memory 822.
The CPU 821 may execute an operating system, such as a Windows.RTM.
operating system available from Microsoft Corporation, a Linux
operating system, a Unix operating system (e.g., Solaris.TM.
available from Sun Microsystems, Inc.), or a NetWare.RTM. operating
system available from Novell, Inc.
[0077] The internal memory 822 includes at least nonvolatile read
only memory (ROM) 823 and volatile random access memory (RAM) 824,
although it is understood that internal memory 822 may be
implemented as any number, type and combination of ROM and RAM, and
may provide look-up tables and/or other relational functionality.
In various embodiments, the internal memory 822 may include a disk
drive or flash memory, for example. Further, the internal memory
822 may store program instructions and results of calculations or
summaries performed by CPU 821.
[0078] In an embodiment, a user and/or other computers may interact
with the MLC 820 using various input device(s) through I/O
interface 825. The input devices may include a keyboard, a track
ball, a mouse, a touch pad or touch-sensitive display, and the
like. Also, information may be displayed on a display through a
display interface (not shown), which may include any type of
graphical user interface (GUI). For example, as a result of the
location determination process, the geographic location of the
mobile device 130 or an indication of failure, e.g., in the event
that no calculation location meets predetermined accuracy criteria,
may be visually displayed.
[0079] Other interfaces include the WARN interface 826, the network
interface 827 and the ULS interface 828. The WARN interface 826
enables the MLC 820 to receive GPS information, such as navigation
messages, from fixed GPS receivers 151 and 152, e.g., of the GNSS
network 140. The network interface 827 enables data communications
and control signaling between the MLC 820 and other network nodes,
such as the base stations 111-114. The LS interface 828 enables the
MLC 820 to communicate with the LS 125 and to receive U-TDOA
measurements collected by the LS 125 from the LMUs 116-119, for
example. The various interfaces may be a universal serial bus (USB)
interface, an IEEE 1394 interface, or a parallel port interface,
for example. As stated above, it will be understood that, although
depicted separately, the MLC 820 may include the functionality of
various entities with which it is depicted as interfacing,
including the LS 125 and WARN 150, in various embodiments.
[0080] The various "parts" shown in the MLC 820 may be physically
implemented using a software-controlled microprocessor, hard-wired
logic circuits, or a combination thereof. Also, while the parts are
functionally segregated in the MLC 820 for explanation purposes,
they may be combined variously in any physical implementation.
[0081] FIG. 9 is a functional block diagram of representative
mobile device 930, configured to communicate with an MLC (e.g., MLC
120 of FIG. 1 or MLC 820 of FIG. 8), over a wireless communication
network, according to various embodiments. The mobile device 930
includes transceiver 924, antenna system 922, GPS receiver 934, GPS
antenna system 932, processor 926 and memory 928.
[0082] The transceiver 924 includes a receiver 923 and a
transmitter 925, and provides functionality for the mobile device
930 to communicate with base stations in the wireless communication
network (e.g., base stations 111-114), according to appropriate
standard protocols, such UMTS, GSM, CDMA, WiFi, WiMax, DTV, and the
like. The transceiver 924 sends and received voice/data and control
signals through the antenna system 922, which may include an
omni-directional antenna, a steerable antenna, an antenna array or
other compatible antenna. The GPS receiver 934 receives positioning
signals from GPS satellites (e.g., satellites 141-144), including
navigation messages providing ephemeris data and timing signals.
The GPS receiver 934 receives GPS positioning signals through the
GPS antenna system 932, which may be a stub antenna, for
example.
[0083] The processor 926 is configured to execute one or more
software algorithms, including the location determination algorithm
of the embodiments described herein, in conjunction with memory 928
to provide the functionality of mobile device 930. The processor
926 may include its own memory (e.g., nonvolatile memory) for
storing executable software code that allows it to perform the
various functions of the mobile device 930, discussed herein.
Alternatively, the executable code may be stored in designated
memory locations within memory 928. The processor 926 may also
provide a clock for determining timing for the mobile device 930.
In an embodiment, the processor 926 is configured to derive GPS
measurements from received GPS ranging signals. The GPS
measurements may then be forwarded to an MLC (e.g., MLC 120, MLC
820) through the transmitter 925 over a wireless communication
network (e.g., wireless communication network 110). Also, in
another embodiment, the processor 926 may calculate the location of
the mobile device 930 using the GPS measurements, and forward the
calculated GPS location to the MLC 120.
[0084] The various "parts" shown in the mobile device 930 may be
physically implemented using a software-controlled microprocessor,
hard-wired logic circuits, or a combination thereof. Also, while
the parts are functionally segregated in the mobile device 930 for
explanation purposes, they may be combined variously in any
physical implementation.
[0085] While specific embodiments are disclosed herein, many
variations are possible, which remain within the concept and scope
of the invention. Such variations would become clear after
inspection of the specification, drawings and claims herein. The
invention therefore is not to be restricted except within the scope
of the appended claims.
* * * * *