U.S. patent application number 14/207651 was filed with the patent office on 2014-09-18 for directional pruning of transmitters to improve position determination.
This patent application is currently assigned to NEXTNAV, LLC. The applicant listed for this patent is NEXTNAV, LLC. Invention is credited to Andrew Sendonaris.
Application Number | 20140266912 14/207651 |
Document ID | / |
Family ID | 50625100 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140266912 |
Kind Code |
A1 |
Sendonaris; Andrew |
September 18, 2014 |
DIRECTIONAL PRUNING OF TRANSMITTERS TO IMPROVE POSITION
DETERMINATION
Abstract
Described are systems and methods for identifying transmitters
that adversely affect a trilateration result.
Inventors: |
Sendonaris; Andrew; (Los
Gatos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEXTNAV, LLC |
SUNNYVALE |
CA |
US |
|
|
Assignee: |
NEXTNAV, LLC
SUNNYVALE
CA
|
Family ID: |
50625100 |
Appl. No.: |
14/207651 |
Filed: |
March 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61786556 |
Mar 15, 2013 |
|
|
|
Current U.S.
Class: |
342/458 |
Current CPC
Class: |
G01S 5/0045 20130101;
G01S 11/04 20130101; G01S 5/0242 20130101; G01S 5/10 20130101; G01S
19/28 20130101 |
Class at
Publication: |
342/458 |
International
Class: |
G01S 5/10 20060101
G01S005/10 |
Claims
1. A method for estimating a position of a receiver using a network
of transmitters, the method comprising: identifying a set of
transmitters from the network of transmitters; associating each
transmitter from the set of transmitters with at least one of three
or more groups of transmitters based on geographic information
associated with of that transmitter; and determining an estimated
position of the receiver using at least one range measurement
corresponding to at least one transmitter in each of the three or
more groups that includes a transmitter from the set of
transmitters.
2. The method of claim 1, wherein the geographic information
associated with include an estimated azimuth relating to a location
of the transmitter.
3. The method of claim 2, wherein each of the three or more groups
corresponds to a different range of azimuths, and each transmitter
is associated with a particular group of the three or more groups
when the azimuth relating to that transmitter falls within the
range of azimuths corresponding to that particular group.
4. The method of claim 1, wherein the geographic information
associated with include a location of the transmitter.
5. The method of claim 4, wherein each of the three or more groups
corresponds to a different geographic region, and each transmitter
is associated with a particular group of the three or more groups
when the location relating to that transmitter falls within the
geographic region corresponding to that particular group.
6. The method of claim 1, wherein each of the three or more groups
corresponds to a different geographic region in the network of
transmitters.
7. The method of claim 1, the method comprising: determining, for
each of the three or more groups, the number of transmitters
associated with each group; determining, when the number is less
than the integer M, the estimated position using range measurements
corresponding to each of the transmitters in that group; and
determining, when the number is equal to or greater than an integer
M, the estimated position using at least M range measurements
corresponding to at least M of the transmitters in that group.
8. The method of claim 1, the method comprising: determining, for
each of the three or more groups, the number of transmitters
associated with each group; determining, when the number is equal
to or less than an integer M, the estimated position using range
measurements corresponding to each of the transmitters in that
group; and determining, when the number is greater than the integer
M, the estimated position using a selection of M range measurements
corresponding to a selection of M transmitters in that group,
wherein a value of a quality metric for each of the M transmitters
is at least equal to each value of the quality metric for the
unselected transmitters in that group.
9. The method of claim 8, wherein each value of the quality metric
relates to at least one of: an estimated range error related to
that transmitter; a trilateration weight related to that
transmitter; an estimated distance between the transmitter and an
initial estimate of the receiver's position; and an angle of
incidence related to that transmitter.
10. The method of claim 1, wherein the method comprises:
identifying one or more preferred transmitters with a value of a
quality metric that is above a threshold level of the quality
metric; and determining the estimated position of the receiver
using a range measurement corresponding to a preferred transmitter
from each of the three or more groups that includes at least one of
the preferred transmitters.
11. The method of claim 10, wherein the method comprises:
identifying each non-preferred transmitter with a value of the
quality metric that is below the threshold level of the quality
metric, wherein the estimated position of the receiver is
determined without using range measurements corresponding to any of
the non-preferred transmitters from each of the three or more
groups that includes at least one of the preferred
transmitters.
12. A system comprising one or more processors that perform the
method of claim 1.
13. A non-transitory machine-readable medium embodying program
instructions adapted to be executed to implement the method of
claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to co-pending U.S. Provisional Patent Application Ser.
No. 61/786,556, filed Mar. 15, 2013, entitled DIRECTIONAL PRUNING
OF TRANSMITTERS To IMPROVE POSITION DETERMINATION, the content of
which is hereby incorporated by reference herein in its entirety
for all purposes.
FIELD
[0002] Various embodiments relate selecting transmitters in a way
to improve trilateration performance.
BACKGROUND
[0003] There is a need for improved techniques for improving
trilateration results based on analysis of transmitters.
SUMMARY
[0004] Certain embodiments of this disclosure relate generally to
removing transmitters that adversely affect a trilateration
result.
DRAWINGS
[0005] FIG. 1A depicts aspects of a terrestrial positioning
system.
[0006] FIG. 1B depicts two sets of transmitters in a terrestrial
positioning system.
[0007] FIG. 2A depicts equal numbers of transmitters in different
regions.
[0008] FIG. 2B depicts different regions of unequal numbers of
transmitters.
[0009] FIG. 3 illustrates a process for pruning transmitters.
[0010] FIG. 4A and FIG. 4B illustrate how division of transmitters
may be carried out.
DESCRIPTION
[0011] Various aspects of the invention are described below. It
should be apparent that the teachings herein may be embodied in a
wide variety of forms and that any specific structure, function, or
both, being disclosed herein is merely representative. Based on the
teachings herein one skilled in the art should appreciate that any
aspect disclosed may be implemented independently of any other
aspects and that two or more of these aspects may be combined in
various ways. For example, a system may be implemented or a method
may be practiced using any number of the aspects set forth
herein.
[0012] As used herein, the term "exemplary" means serving as an
example, instance or illustration. Any aspect and/or embodiment
described herein as "exemplary" is not necessarily to be construed
as preferred or advantageous over other aspects and/or
embodiments.
[0013] In the following description, numerous specific details are
introduced to provide a thorough understanding of, and enabling
description for, the systems and methods described. One skilled in
the relevant art, however, will recognize that these embodiments
can be practiced without one or more of the specific details, or
with other components, systems, and the like. In other instances,
well-known structures or operations are not shown, or are not
described in detail, to avoid obscuring aspects of the disclosed
embodiments.
Overview
[0014] Various aspects, features, and functions are described below
in conjunction with the appended Drawings. While the details of the
embodiments of the invention may vary and still be within the scope
of the claimed invention, one of skill in the art will appreciate
that the Drawings described herein are not intended to suggest any
limitation as to the scope of use or functionality of the inventive
aspects. Neither should the Drawings and their description be
interpreted as having any dependency or requirement relating to any
one or combination of components illustrated in those Drawings.
[0015] Aspects of the disclosure generally relate to positioning
systems with satellites and/or terrestrial transmitters positioned
at various locations. By way of example, FIG. 1A depicts a
positioning system 100A that includes a plurality of transmitters
110 and a receiver 120. "Range" signals 115 transmitted from each
of the transmitters 110 may be collected by the receiver 120, and
later used to estimate the receiver 120's position relative to the
position of transmitters 110. The process of estimating a receiver
120's position is often referred to as "trilateration", which is
the process of using geometry to determine a location of an
intersection point where transmitted signals from known locations
of transmitters converge, where each signal specifies a distance
from the respective transmitter to the intersection point.
[0016] In order to precisely determine the location of the
intersection point, signals must specify accurate distance
measurements. In "time-of-arrival" positioning systems, a signal's
travel time can be measured and converted to a distance or "range"
using the speed of light. Unfortunately, positing systems like the
system 100A shown in FIG. 1A are often built in urban environments
where buildings and other obstructions block "range" or
"pseudorange" signals, and then reflect those range signals in a
manner so that their overall travel time is increased, which
results in inaccurate distance measurements. Inaccurate distance
measurements, along with other characteristics are often
undesirable because they adversely affect the estimate of a
receiver's position after trilateration processing. Accordingly, it
is often desirable to identify inaccurate range signal
measurements, and then filter or "prune" those measurements during
trilateration processing (e.g., by removing the measurements or
adjusting the measurements to decrease their effect on the
trilateration result).
[0017] However, pruning transmitter range signal measurements that
exhibit undesirable characteristics may result in a remaining set
of range signal measurements from respective transmitters that
exhibits poor relative transmitter-receiver geometry, which
ultimately impairs the precision of position measurements with
respect to any of latitude, longitude, altitude and time (x, y, z,
t).
[0018] FIG. 1B illustrates a system 100B with such a remaining set
111a of transmitters after another set 111b of transmitters has
been pruned from trilateration processing. As shown, transmitter
set 111a includes transmitters that are clustered around each other
in generally the same radial direction from the receiver 120.
Ideally, trilateration processing would use range signal
measurements from transmitters 110 that are collectively
distributed around the receiver 120 (as shown in FIG. 1A) as
compared to a group of transmitters 111a that lacks such
distribution around the receiver 120 (as shown in FIG. 1B). This is
because using only transmitter set 111a provides geometric position
error referred to as "dilution of precision" (DOP), which refers to
uneven distribution of transmitters with respect to a receiver.
[0019] Accordingly, other approaches are needed to avoid "over
pruning" of range signal measurements. One such approach, as
illustrated by FIGS. 2A-2B, identifies transmitters 110 of a
transmitter system 200 for inclusion into different transmitter
sets 211a-n based on transmitter regions. Each transmitter set 211
may then be individually analyzed to select the best range signals
from that transmitter set 211. Division of transmitters 110 into
transmitter sets 211 may be accomplished using various techniques,
including dividing based on the general radial direction of each
transmitter 110 from the current estimated location of the receiver
120.
[0020] Another approach may involve firmware-based or
software-based calculations of DOP with all transmitters except a
candidate transmitter. However, consideration of many candidate
transmitters can lead to a computationally complex load that
increases time to first fix (TTIF).
Methodologies
[0021] As discussed above, in order to improve trilateration
performance, transmitters that adversely affect the trilateration
result (i.e. the position estimate) may be removed or devalued. One
way of achieving this is to remove transmitters that are "bad"
according to some metric (e.g. estimated range error, estimated
distance to receiver, weight applied to range measurement, and
other metrics, or a combination of these metrics). However, as
previously noted, if we simply remove transmitters that have an
undesired metric among all visible transmitters, the remaining set
of transmitters that exhibit good metrics may result in poor
Dilution of Precision (DOP) at the receiver location, which will
adversely affect the position estimate after trilateration.
[0022] Accordingly, candidate transmitters that adversely affect
the trilateration result may be identified and removed in such a
way as to ensure a reasonable DOP after those candidate
transmitters are removed. One approach involves removing one of a
sub-set of candidate transmitters to avoid removing all candidate
transmitters that are positioned in the same general radial
direction from an estimated position of a receiver. By way of
example, the area around an estimated position of the receiver may
be divided into N transmitter "regions" (e.g., 4 quadrants, 8
half-quadrants, or non-uniform division depending on density of
transmitters). Transmitters in each region may then be analyzed to
identify poorer performing transmitters, or conversely, better
performing transmitters. A minimum number of transmitters may be
selected as the better performing transmitters (e.g., 1 or 2
transmitters from each region). It is further contemplated that
only a subset of transmitters may be divided into regions for
pruning, where another subset of transmitters that exhibit
preferred characteristics may not be pruned.
[0023] Attention is drawn to FIG. 3, which illustrates a
methodology 300 for identifying poorer performing transmitters
using transmitter regions that define a set of transmitters (e.g.,
transmitter sets 211 of FIGS. 2A-B).
[0024] At Step 310, transmitters are divided into transmitter sets
(e.g., based on radial regions). FIG. 4A and FIG. 4B illustrate how
division of transmitters may be carried out. As shown, the number
of regions may be 8 (as depicted by the rectangles), while the
number of transmitters per region may be 2 (as depicted by
different clusters of dots within each rectangle). By comparison,
the number of transmitters in a region may not be fixed, where two
transmitter sets may have two transmitters, while another
transmitter set may have three transmitters. For example, one way
of determining the number of transmitters in a region may involve
usage of terrain and building map obstruction information in the
direction of a transmitter region from the approximate receiver
location in such a way that regions that have a lot of terrain or
building clutter may have a lesser number of transmitters or a
greater number of transmitters.
[0025] In FIG. 4A, for example, the two charted measurements
designated by 410(a)(i) (e.g., the lighter dots) may relate to one
transmitter of a region 411a that is "in view" of the receiver 120,
while the charted measurement designated by 410(a)(ii) (e.g., the
darker dots) may relate to another transmitter of the region 411a
that is "in view" of the receiver 120. In region 411b, no
transmitters are "in view" of the receiver 120, and there are
consequently no measurements shown. In region 411c, only one
transmitter is "in view" of the receiver 120.
[0026] At step 320, a pruning metric is calculated. The overall
metric used to determine which transmitters to prune may include a
combination of the following sub-metrics: estimated range error
(e.g., the smaller the range error, the better the transmitter);
trilateration weight, which results from an estimate of ranging
error standard deviation (e.g., the higher the weight the better
the transmitter (lower estimated ranging error standard
deviation)); range quality metric (e.g., the range quality metric
may be determined using terrain and/or building map information in
the direction of the transmitters or from the set of range
measurements or signals themselves); estimated distance to
transmitter (e.g., it is possible that the smaller the distance to
the transmitter, the better the transmitter (less likelihood of
multipath)); angle of incidence of transmitter (e.g., the higher
the angle of incidence from a transmitter, the better the
transmitter (less likelihood of multipath)); and others. A
resultant pruning metric may be a function of any sub-metric, where
the function is some function that takes in a set of sub-metrics
and calculates a final metric that can be used for pruning some of
the transmitters.
[0027] One example of a pruning metric would be:
pruning_metric=.SIGMA..sub.k=1-nalpha[k]*sub_metric[k],
where alpha[k] is a positive or negative "weight" associated with a
particular sub-metric depending on the nature of the k.sup.th
sub-metric and whether it makes the transmitter more or less
desirable, among other considerations.
[0028] At Step 330, sets of transmitters are sorted and pruned so
the a selected subset exhibits better trilateration performance.
Step 320 may result in an array of pruning metrics, where each
pruning metric corresponds to one transmitter in a given region.
Transmitters may be sorted based on their pruning metrics, and one
or more transmitters with the least preferred pruning metric may
pruned. Transmitters with more preferred pruning metrics may then
be used during trilateration processing.
[0029] As previously described, certain aspects relate to creating
radial sections (e.g., that are equal in number of degrees) around
the estimated receiver location, and then, for each section, pick
the best M transmitters, where "best" can be defined by any number
of metrics. One of the metrics can be the density of terrain and
manmade objects in the direction of a particular transmitter.
[0030] The number of transmitters in each radial direction may be a
factor of geometry (i.e. where the receiver is and where the
transmitters are), so that in one particular receiver location
there may be many transmitters in one quadrant (e.g., a northeast
quadrant 211c of FIG. 2B) and few transmitters in another quadrant
(e.g., a northwest quadrant 211d of FIG. 2B). Thus, the number of
transmitters in each direction is somewhat fixed to division of
quadrants or other types of regions or areas where transmitters
reside with respect to the estimated position. Then, at least M
transmitters in each such region may need to be selected to avoid
poor DOP characteristics.
[0031] For example, if M is 2, and one direction has 8
transmitters, the best 2 transmitters may be selected, or at least
two transmitters may be selected where others are pruned. Where
regions have less than M transmitters, each transmitter in that
region may be selected without pruning.
[0032] Regions may be based on the number of radial directions
(e.g., ranges of azimuth angles with respect to an estimated
receiver position as indicated by 211c, 211a, 211b and 211d of FIG.
2B, which show azimuth ranges of 0 to 90.degree., 90 to
180.degree., 180 to 270.degree. and 270 to 360.degree.), or other
configurations (e.g., as shown in FIG. 2A). The number of regions,
the number of transmitters (e.g., the value of M, which may depend
on the number of transmitters per region), and the metrics may be
used to determine the quality of the transmitter with respect to a
candidate position estimate.
Algorithms
[0033] The following sample code describes various approaches
associated with various aspects disclosed herein.
TABLE-US-00001 function [new_pranges, new_weights, new_tx_enu,
new_tx_idx] = prune_txs(pranges, weights, tx_enu, rx_enu_hat,
prune_method, settings) % This function attempts to prune Tx's so
that the remaining set of Tx's has better % trilateration
performance % The first prune_method implemented is a radial
pruning, i.e. dividing the area around % the rx_enu_hat into
''slices'' (e.g. quadrants) and selecting a certain subset from
each slice % More prune_method's can be implemented in the future.
% % Usage: % prune_method = 0; % settings = struct('num_slices',8,
'max_num_tx_per_slice', 2); % [new_pranges, new_weights,
new_tx_enu, new_tx_idx] = % prune_txs(pranges, weights, tx_enu,
rx_enu_hat, prune_method, settings); % % new_pranges, new_weights,
and new_tx_enu can now be used to trilaterate % Also, new_tx_idx
can be used to find out the names of the remaining Tx's: %
new_tx_names = tx_names(new_tx_idx); % % More complex usage: %
prune_method = 0; % settings = struct('num_slices',8,
'max_num_tx_per_slice', 2, 'alpha',[1 -0.2 0.1 -0.1]); %
[new_pranges, new_weights, new_tx_enu, new_tx_idx] = %
prune_txs(pranges, weights, tx_enu, rx_enu_hat, prune_method,
settings); prune_method = input_arg_check('prune_method', 0);
settings = input_arg_check('settings', struct('num_slices',8,
'max_num_tx_per_slice', 2, 'alpha',[1 0 0 0])); if
~isfield(settings,'alpha') settings.alpha = [1 0 0 0]; end if
~isfield(settings,'min_num_total_tx') settings.min_num_total_tx =
4; end if prune_method == 0 num_slices = settings.num_slices;
max_num_tx_per_slice = settings.max_num_tx_per_slice; alpha =
settings.alpha; min_num_total_tx = settings.min_num_total_tx; end
num_tx = size(tx_enu,1); switch prune_method %
------------------------------------------------------------------------
- case 0 slices = linspace(0,360,num_slices+1); theta =
atan2(tx_enu(:,2) - rx_enu_hat(2), tx_enu(:,1) -
rx_enu_hat(1))*180/pi; theta(theta<0) = theta(theta<0) + 360;
rx_tx_distance_hat = distance(tx_enu, repmat(rx_enu_hat, num_tx,1),
2)'; pranges_adj = pranges - rx_tx_distance_hat; phi =
atan2(tx_enu(:,3) - rx_enu_hat(3),
sqrt((tx_enu(:,1)-rx_enu_hat(1)).{circumflex over ( )}2 +
(tx_enu(:,2)- rx_enu_hat(2)).{circumflex over ( )}2))'*180/pi;
new_pranges = [ ] ; new_weights = [ ]; new_tx_enu = [ ]; new_tx_idx
= [ ]; num_tx_per_slice = zeros(1,num_slices); for Is=1:num_slices
idx = find((theta >= slices(Is) & theta < slices(Is+1))
& (weights' ~= 0) & (pranges_adj' > median(pranges_adj)
-1e3)); num_tx_per_slice(Is) = length(idx); end if
isnan(max_num_tx_per_slice) max_num_tx_per_slice =
ceil(median(num_tx_per_slice)); end % Ensure that the total number
of remaining Tx's (after pruning) is >= min_num_total_tx (e.g.
4) if ~isnan(min_num_total_tx) if sum(num_tx_per_slice) >=
min_num_total_tx while
sum(min(num_tx_per_slice,max_num_tx_per_slice)) <
min_num_total_tx, max_num_tx_per_slice = max_num_tx_per_slice+1;
end end end for Is=1:num_slices idx = find((theta >= slices(Is)
& theta < slices(Is+1)) & (weights' ~= 0) &
(pranges_adj' > median(pranges_adj) -1e3)); if ~isempty(idx)
pranges_adj_tmp = pranges_adj(idx); [junk,idxidx] =
sort(alpha(1)*pranges_adj_tmp + alpha(2)*weights(idx) +
alpha(3)*rx_tx_distance_hat(idx) + alpha(4)*phi(idx)); if
max_num_tx_per_slice > 0 idx_select =
idxidx(1:min(max_num_tx_per_slice,length(idxidx))); else idx_select
= idxidx(1:max(length(idxidx)-abs(max_num_tx_per_slice),
min(2,length(idxidx)))); end else pranges_adj_tmp = [ ]; idx_select
= [ ]; end new_pranges = [new_pranges pranges(idx(idx_select))];
new_weights = [new_weights weights(idx(idx_select))]; new_tx_enu =
[new_tx_enu; tx_enu(idx(idx_select),:)]; new_tx_idx = [new_tx_idx
idx(idx_select)']; end otherwise error('Unsupported value for
prune_method') end
Supporting Aspects
[0034] Various aspects relate to disclosures of other patent
applications, patent publications, or issued patents. For example,
each of the following applications, publications, and patents are
incorporated by reference in their entirety for any and all
purposes: United States Utility patent application Ser. No.
13/412,487, entitled WIDE AREA POSITIONING SYSTEMS, filed on Mar.
5, 2012; U.S. Utility patent Ser. No. 12/557,479 (now U.S. Pat. No.
8,130,141), entitled WIDE AREA POSITIONING SYSTEM, filed Sep. 10,
2009; United States Utility patent application Ser. No. 13/412,508,
entitled WIDE AREA POSITIONING SYSTEM, filed Mar. 5, 2012; United
States Utility patent application Ser. No. 13/296,067, entitled
WIDE AREA POSITIONING SYSTEMS, filed Nov. 14, 2011; Application
Serial No. PCT/US12/44452, entitled WIDE AREA POSITIONING SYSTEMS
(WAPS), filed Jun. 28, 2011); U.S. patent application Ser. No.
13/535,626, entitled CODING IN WIDE AREA POSITIONING SYSTEMS
(WAPS), filed Jun. 28, 2012; U.S. patent application Ser. No.
13/565,732, entitled CELL ORGANIZATION AND TRANSMISSION SCHEMES IN
A WIDE AREA POSITIONING SYSTEM (WAPS), filed Aug. 2, 2012; U.S.
patent application Ser. No. 13/565,723, entitled CELL ORGANIZATION
AND TRANSMISSION SCHEMES IN A WIDE AREA POSITIONING SYSTEM (WAPS),
filed Aug. 2, 2012; U.S. patent application Ser. No. 13/831,740,
entitled SYSTEMS AND METHODS CONFIGURED TO ESTIMATE RECEIVER
POSITION USING TIMING DATA ASSOCIATED WITH REFERENCE LOCATIONS IN
THREE-DIMENSIONAL SPACE, filed Mar. 14, 2013. The above
applications, publications and patents may be individually or
collectively referred to herein as "incorporated reference(s)",
"incorporated application(s)", "incorporated publication(s)",
"incorporated patent(s)" or otherwise designated. The various
aspect, details, devices, systems, and methods disclosed herein may
be combined with disclosures in any of the incorporated references
in accordance with various embodiments.
[0035] This disclosure relates generally to positioning systems and
methods for providing signaling for position determination and
determining high accuracy position/location information using a
wide area transmitter array of transmitters in communication with
receivers such as in cellular phones or other portable devices with
processing components, transceiving capabilities, storage,
input/output capabilities, and other features.
[0036] Positioning signaling services associated with certain
aspects may utilize broadcast-only transmitters that may be
configured to transmit encrypted positioning signals. The
transmitters (which may also be denoted herein as "towers" or
"beacons") may be configured to operate in an exclusively licensed
or shared licensed/unlicensed radio spectrum; however, some
embodiments may be implemented to provide signaling in unlicensed
shared spectrum. The transmitters may transmit signaling in these
various radio bands using novel signaling as is described herein or
in the incorporated references. This signaling may be in the form
of a proprietary signal configured to provide specific data in a
defined format advantageous for location and navigation purposes.
For example, the signaling may be structured to be particularly
advantageous for operation in obstructed environments, such as
where traditional satellite position signaling is attenuated and/or
impacted by reflections, multipath, and the like. In addition, the
signaling may be configured to provide fast acquisition and
position determination times to allow for quick location
determination upon device power-on or location activation, reduced
power consumption, and/or to provide other advantages.
[0037] The receivers may be in the form of one or more user
devices, which may be any of a variety of electronic communication
devices configured to receive signaling from the transmitters, as
well as optionally be configured to receive GPS or other satellite
system signaling, cellular signaling, Wi-Fi signaling, Wi-Max
signaling, Bluetooth, Ethernet, and/or other data or information
signaling as is known or developed in the art. The receivers may be
in the form of a cellular or smart phone, a tablet device, a PDA, a
notebook or other computer system, and/or similar or equivalent
devices. In some embodiments, the receivers may be a standalone
location/positioning device configured solely or primarily to
receive signals from the transmitters and determine
location/position based at least in part on the received signals.
As described herein, receivers may also be denoted herein as "User
Equipment" (UE), handsets, smart phones, tablets, and/or simply as
a "receiver."
[0038] The transmitters may be configured to send transmitter
output signals to multiple receiver units (e.g., a single receiver
unit is shown in certain figures for simplicity; however, a typical
system will be configured to support many receiver units within a
defined coverage area) via communication links). The transmitters
may also be connected to a server system via communication links,
and/or may have other communication connections to network
infrastructure, such as via wired connections, cellular data
connections, Wi-Fi, Wi-Max, or other wireless connections, and the
like.
[0039] Various embodiments of a wide area positioning system
(WAPS), described herein or in the incorporated references, may be
combined with other positioning systems to provide enhanced
location and position determination. Alternately, or in addition, a
WAPS system may be used to aid other positioning systems. In
addition, information determined by receivers of WAPS systems may
be provided via other communication network links, such as
cellular, Wi-Fi, pager, and the like, to report position and
location information to a server system or systems, as well as to
other networked systems existing on or coupled to network
infrastructure.
[0040] For example, in a cellular network, a cellular backhaul link
may be used to provide information from receivers to associated
cellular carriers and/or others via network infrastructure. This
may be used to quickly and accurately locate the position of
receiver during an emergency, or may be used to provide
location-based services or other functions from cellular carriers
or other network users or systems.
[0041] It is noted that, in the context of this disclosure, a
positioning system is one that localizes one or more of latitude,
longitude, and altitude coordinates, which may also be described or
illustrated in terms of one, two, or three dimensional coordinate
systems (e.g., x, y, z coordinates, angular coordinates, vectors,
and other notations). In addition, it is noted that whenever the
term `GPS` is referred to, it is done so in the broader sense of
Global Navigation Satellite Systems (GNSS) which may include other
satellite positioning systems such as GLONASS, Galileo and
Compass/Beidou. In addition, as noted previously, in some
embodiments other positioning systems, such as terrestrially based
systems, may be used in addition to or in place of satellite-based
positioning systems.
[0042] Embodiments of WAPS include multiple transmitters configured
to broadcast WAPS data positioning information, and/or other data
or information, in transmitter output signals to the receivers. The
positioning signals may be coordinated so as to be synchronized
across all transmitters of a particular system or regional coverage
area, and may use a disciplined GPS clock source for timing
synchronization. WAPS data positioning transmissions may include
dedicated communication channel resources (e.g., time, code and/or
frequency) to facilitate transmission of data required for
trilateration, notification to subscriber/group of subscribers,
broadcast of messages, and/or general operation of the WAPS system.
Additional disclosure regarding WAPS data positioning transmissions
may be found in the incorporated references.
[0043] In a positioning system that uses time difference of arrival
or trilateration, the positioning information typically transmitted
includes one or more of precision timing sequences and positioning
signal data, where the positioning signal data includes the
location of transmitters and various timing corrections and other
related data or information. In one WAPS embodiment, the data may
include additional messages or information such as
notification/access control messages for a group of subscribers,
general broadcast messages, and/or other data or information
related to system operation, users, interfaces with other networks,
and other system functions. The positioning signal data may be
provided in a number of ways. For example, the positioning signal
data may be modulated onto a coded timing sequence, added or
overlaid over the timing sequence, and/or concatenated with the
timing sequence.
[0044] Data transmission methods and apparatus described herein may
be used to provide improved location information throughput for the
WAPS. In particular, higher order modulation data may be
transmitted as a separate portion of information from pseudo-noise
(PN) ranging data. This may be used to allow improved acquisition
speed in systems employing CDMA multiplexing, TDMA multiplexing, or
a combination of CDMA/TDMA multiplexing. The disclosure herein is
illustrated in terms of WAPS in which multiple towers broadcast
synchronized positioning signals to UEs and, more particularly,
using towers that are terrestrial. However, the embodiments are not
so limited, and other systems within the spirit and scope of the
disclosure may also be implemented.
[0045] In an exemplary embodiment, a WAPS system uses coded
modulation sent from a tower or transmitter, such as transmitter,
called spread spectrum modulation or pseudo-noise (PN) modulation,
to achieve wide bandwidth. The corresponding receiver unit, such as
receiver, includes one or more modules to process such signals
using a despreading circuit, such as a matched filter or a series
of correlators. Such a receiver produces a waveform which, ideally,
has a strong peak surrounded by lower level energy. The time of
arrival of the peak represents the time of arrival of the
transmitted signal at the receiver. Performing this operation on a
multiplicity of signals from a multiplicity of towers, whose
locations are accurately known, allows determination of the
receivers location via trilateration. Various additional details
related to WAPS signal generation in a transmitter, along with
received signal processing in a receiver are described herein or in
the incorporated references.
[0046] Transmitters may include various blocks for performing
associated signal reception and/or processing. For example, a
transmitter may include one or more GPS modules for receiving GPS
signals and providing location information and/or other data, such
as timing data, dilution of precision (DOP) data, or other data or
information as may be provided from a GPS or other positioning
system, to a processing module. Other modules for receiving
satellite or terrestrial signals and providing similar or
equivalent output signals, data, or other information may
alternately be used in various embodiments. GPS or other timing
signals may be used for precision timing operations within
transmitters and/or for timing correction across the WAPS
system.
[0047] Transmitters may also include one or more transmitter
modules (e.g., RF transmission blocks) for generating and sending
transmitter output signals as described subsequently herein. A
transmitter module may also include various elements as are known
or developed in the art for providing output signals to a transmit
antenna, such as analog or digital logic and power circuitry,
signal processing circuitry, tuning circuitry, buffer and power
amplifiers, and the like. Signal processing for generating the
output signals may be done in the a processing module which, in
some embodiments, may be integrated with another module or, in
other embodiments, may be a standalone processing module for
performing multiple signal processing and/or other operational
functions.
[0048] One or more memories may be coupled with a processing module
to provide storage and retrieval of data and/or to provide storage
and retrieval of instructions for execution in the processing
module. For example, the instructions may be instructions for
performing the various processing methods and functions described
subsequently herein, such as for determining location information
or other information associated with the transmitter, such as local
environmental conditions, as well as to generate transmitter output
signals to be sent to the user devices.
[0049] Transmitters may further include one or more environmental
sensing modules for sensing or determining conditions associated
with the transmitter, such as, for example, local pressure,
temperature, or other conditions. In an exemplary embodiment,
pressure information may be generated in the environmental sensing
module and provided to a processing module for integration with
other data in transmitter output signals as described subsequently
herein. One or more server interface modules may also be included
in a transmitter to provide an interface between the transmitter
and server systems, and/or to a network infrastructure.
[0050] Receivers may include one or more GPS modules for receiving
GPS signals and providing location information and/or other data,
such as timing data, dilution of precision (DOP) data, or other
data or information as may be provided from a GPS or other
positioning system, to a processing module (not shown). Of course,
other Global Navigation Satellite Systems (GNSS) are contemplated,
and it is to be understood that disclosure relating to GPS may
apply to these other systems. Of course, any location processor may
be adapted to receive and process position information described
herein or in the incorporated references.
[0051] Receivers may also include one or more cellular modules for
sending and receiving data or information via a cellular or other
data communications system. Alternately, or in addition, receivers
may include communications modules for sending and/or receiving
data via other wired or wireless communications networks, such as
Wi-Fi, Wi-Max, Bluetooth, USB, or other networks.
[0052] Receivers may include one or more position/location modules
for receiving signals from terrestrial transmitters, and processing
the signals to determine position/location information as described
subsequently herein. A position module may be integrated with
and/or may share resources such as antennas, RF circuitry, and the
like with other modules. For example, a position module and a GPS
module may share some or all radio front end (RFE) components
and/or processing elements. A processing module may be integrated
with and/or share resources with the position module and/or GPS
module to determine position/location information and/or perform
other processing functions as described herein. Similarly, a
cellular module may share RF and/or processing functionality with
an RF module and/or processing module. A local area network (LAN)
module may also be included.
[0053] One or more memories may be coupled with processing module
and other modules to provide storage and retrieval of data and/or
to provide storage and retrieval of instructions for execution in
the processing module. For example, the instructions may perform
the various processing methods and functions described herein or in
the incorporated references.
[0054] Receivers may further include one or more environmental
sensing modules (e.g., inertial, atmospheric and other sensors) for
sensing or determining conditions associated with the receiver,
such as, for example, local pressure, temperature, movement, or
other conditions, that may be used to determine the location of the
receiver. In an exemplary embodiment, pressure information may be
generated in such an environmental sensing module for use in
determining location/position information in conjunction with
received transmitter, GPS, cellular, or other signals.
[0055] Receivers may further include various additional user
interface modules, such as a user input module which may be in the
form of a keypad, touchscreen display, mouse, or other user
interface element. Audio and/or video data or information may be
provided on an output module (not shown), such as in the form or
one or more speakers or other audio transducers, one or more visual
displays, such as touchscreens, and/or other user I/O elements as
are known or developed in the art. In an exemplary embodiment, such
an output module may be used to visually display determined
location/position information based on received transmitter
signals, and the determined location/position information may also
be sent to a cellular module to an associated carrier or other
entity.
[0056] The receiver may include a signal processing block that
comprises a digital processing block configured to demodulate the
received RF signal from the RF module, and also to estimate time of
arrival (TOA) for later use in determining location. The signal
processing block may further include a pseudorange generation block
and a data processing block. The pseudorange generation block may
be configured to generate "raw` positioning pseudorange data from
the estimated TOA, refine the pseudorange data, and to provide that
pseudorange data to the position engine, which uses the pseudorange
data to determine the location of the receiver. The data processing
block may be configured to decode the position information, extract
packet data from the position information and perform error
correction (e.g., CRC) on the data. A position engine of a receiver
may be configured to process the position information (and, in some
cases, GPS data, cell data, and/or LAN data) in order to determine
the location of the receiver within certain bounds (e.g., accuracy
levels, etc.). Once determined, location information may be
provided to applications. One of skill in the art will appreciate
that the position engine may signify any processor capable of
determining location information, including a GPS position engine
or other position engine.
Variations of Implementation
[0057] Methods may: identify a first set of two or more
transmitters from the network of transmitters; and evaluate the
first set of transmitters to determine which transmitters associate
with one or more characteristics; and refine the estimated position
of the receiver based on the transmitters that exhibit the one or
more characteristics.
[0058] In accordance with certain aspects, a first number of
transmitters in the first set depends on a density of terrain and
manmade objects. In accordance with certain aspects, the first
number and the first density are inversely proportional. In
accordance with certain aspects, the first number and the first
density are proportional.
[0059] Methods may: identify a second set of two or more other
transmitters from the network of transmitters. In accordance with
certain aspects, the number of transmitters in the first set
differs from the number of transmitters in the second set. In
accordance with certain aspects, the numbers of transmitters in all
sets, including the first set and the second set, are equal.
[0060] In accordance with certain aspects, a first number of
transmitters in the first set depends on a first density of terrain
and manmade objects near the transmitters in the first set, and a
second number of transmitters in the second set depends on a second
density of terrain and manmade objects near the transmitters in the
second set. In accordance with certain aspects, the first set of
transmitters includes transmitters that are within a first
transmission region with respect to an estimated position of the
receiver. In accordance with certain aspects, the size of the first
transmission region is based on a spatial mapping of natural
terrain or manmade structures nearby the transmitters of the
network.
[0061] Methods may: calculate a first quality metric corresponding
to a first transmitter in the first set, wherein the estimated
position is refined based on a first range measurement
corresponding to the first transmitter when the first quality
metric meets a threshold condition.
[0062] Methods may: calculate a first quality metric corresponding
to a first transmitter in the first set; and calculate a second
quality metric corresponding to a second transmitter in the first
set, wherein the estimated position is refined based on a first
range measurement corresponding to the first transmitter when the
first quality metric is preferred over the second quality metric,
and the estimated position is refined based on a second range
measurement corresponding to the second transmitter when the second
quality metric is preferred over the first quality metric.
[0063] In accordance with certain aspects, the first quality metric
is based on a calculation of one or more weighted sub metrics
selected from the group consisting of: estimated range error,
weight applied to the first range measurement during trilateration,
estimated distance between the estimated position and the first
transmitter, quantification of probable multipath effect associated
with obstructions in the direction of the first transmitter from
the estimated position; and angle of incidence of first
transmitter. In accordance with certain aspects, only a subset of
transmitters from the first set of transmitters associate with the
one or more characteristics.
[0064] In accordance with certain aspects, the one or more
characteristics include one or more of low estimated range error,
high weight applied to range measurement of the respective
transmitters during trilateration, shorter estimated distance
between the estimated position and the respective transmitter with
respect to estimated distances for other transmitters, low
estimated multipath effect associated with obstructions in the
direction of the respective transmitter from the estimated
position, and high angle of incidence of the respective
transmitter.
[0065] The various components, modules, and functions described
herein can be located together or in separate locations.
Communication paths couple the components and include any medium
for communicating or transferring files among the components. The
communication paths include wireless connections, wired
connections, and hybrid wireless/wired connections. The
communication paths also include couplings or connections to
networks including local area networks (LANs), metropolitan area
networks (MANs), wide area networks (WANs), proprietary networks,
interoffice or backend networks, and the Internet. Furthermore, the
communication paths include removable fixed mediums like floppy
disks, hard disk drives, and CD-ROM disks, as well as flash RAM,
Universal Serial Bus (USB) connections, RS-232 connections,
telephone lines, buses, and electronic mail messages.
[0066] Aspects of the systems and methods described herein may be
implemented as functionality programmed into any of a variety of
circuitry, including programmable logic devices (PLDs), such as
field programmable gate arrays (FPGAs), programmable array logic
(PAL) devices, electrically programmable logic and memory devices
and standard cell-based devices, as well as application specific
integrated circuits (ASICs). Some other possibilities for
implementing aspects of the systems and methods include:
microcontrollers with memory (such as electronically erasable
programmable read only memory (EEPROM)), embedded microprocessors,
firmware, software, etc. Furthermore, aspects of the systems and
methods may be embodied in microprocessors having software-based
circuit emulation, discrete logic (sequential and combinatorial),
custom devices, fuzzy (neural) logic, quantum devices, and hybrids
of any of the above device types. The underlying device
technologies may be provided in a variety of component types, e.g.,
metal-oxide semiconductor field-effect transistor (MOSFET)
technologies like complementary metal-oxide semiconductor (CMOS),
bipolar technologies like emitter-coupled logic (ECL), polymer
technologies (e.g., silicon-conjugated polymer and metal-conjugated
polymer-metal structures), mixed analog and digital, etc.
[0067] It should be noted that any system, method, and/or other
components disclosed herein may be described using computer aided
design tools and expressed (or represented), as data and/or
instructions embodied in various computer-readable media, in terms
of their behavioral, register transfer, logic component,
transistor, layout geometries, and/or other characteristics.
Computer-readable media in which such formatted data and/or
instructions may be embodied include, but are not limited to,
non-volatile storage media in various forms (e.g., optical,
magnetic or semiconductor storage media) and carrier waves that may
be used to transfer such formatted data and/or instructions through
wireless, optical, or wired signaling media or any combination
thereof. Examples of transfers of such formatted data and/or
instructions by carrier waves include, but are not limited to,
transfers (uploads, downloads, e-mail, etc.) over the Internet
and/or other computer networks via one or more data transfer
protocols (e.g., HTTP, HTTPs, FTP, SMTP, WAP, etc.). When received
within a computer system via one or more computer-readable media,
such data and/or instruction-based expressions of the above
described components may be processed by a processing entity (e.g.,
one or more processors) within the computer system in conjunction
with execution of one or more other computer programs.
[0068] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise," "comprising,"
and the like are to be construed in an inclusive sense as opposed
to an exclusive or exhaustive sense; that is to say, in a sense of
"including, but not limited to." Words using the singular or plural
number also include the plural or singular number respectively.
Additionally, the words "herein," "hereunder," "above," "below,"
and words of similar import, when used in this application, refer
to this application as a whole and not to any particular portions
of this application. When the word "or" is used in reference to a
list of two or more items, that word covers all of the following
interpretations of the word: any of the items in the list, all of
the items in the list and any combination of the items in the
list.
[0069] The above description of embodiments of the systems and
methods is not intended to be exhaustive or to limit the systems
and methods to the precise forms disclosed. While specific
embodiments of, and examples for, the systems and methods are
described herein for illustrative purposes, various equivalent
modifications are possible within the scope of the systems and
methods, as those skilled in the relevant art will recognize. The
teachings of the systems and methods provided herein can be applied
to other systems and methods, not only for the systems and methods
described above. The elements and acts of the various embodiments
described above can be combined to provide further embodiments.
These and other changes can be made to the systems and methods in
light of the above detailed description.
[0070] One of skill in the art will appreciate that the processes
shown in the Drawings and described herein are illustrative, and
that there is no intention to limit this disclosure to the order of
stages shown. Accordingly, stages may be removed and rearranged,
and additional stages that are not illustrated may be carried out
within the scope and spirit of the invention.
[0071] In one or more exemplary embodiments, the functions, methods
and processes described may be implemented in whole or in part in
hardware, software, firmware, or any combination thereof. If
implemented in software, the functions may be stored on or encoded
as one or more instructions or code on a computer-readable medium.
Computer-readable media includes computer storage media. Storage
media may be any available media that can be accessed by a
computer.
[0072] By way of example, and not limitation, such
computer-readable media can include RAM, ROM, EEPROM, CD-ROM or
other optical disk storage, magnetic disk storage or other magnetic
storage devices, or any other medium that can be used to carry or
store desired program code in the form of instructions or data
structures and that can be accessed by a computer. Disk and disc,
as used herein, includes compact disc (CD), laser disc, optical
disc, digital versatile disc (DVD), floppy disk and Blu-ray disc
where disks usually reproduce data magnetically, while discs
reproduce data optically with lasers. Combinations of the above
should also be included within the scope of computer-readable
media.
[0073] Those of skill in the art would understand that information
and signals may be represented using any of a variety of different
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that may
be referenced throughout the above description may be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
[0074] Those of skill in the art would further appreciate that the
various illustrative logical blocks, modules, circuits, and
algorithm steps described in connection with the embodiments
disclosed herein may be implemented as electronic hardware,
computer software, or combinations of both. To clearly illustrate
this interchangeability of hardware and software, various
illustrative components, blocks, modules, circuits, and steps have
been described above generally in terms of their functionality.
Whether such functionality is implemented as hardware or software
depends upon the particular application and design constraints
imposed on the overall system. Skilled artisans may implement the
described functionality in varying ways for each particular
application, but such implementation decisions should not be
interpreted as causing a departure from the scope of the
disclosure.
[0075] The various illustrative logical blocks, modules, processes,
and circuits described in connection with the embodiments disclosed
herein may be implemented or performed with a general purpose
processor, a digital signal processor (DSP), an application
specific integrated circuit (ASIC), a field programmable gate array
(FPGA) or other programmable logic device, discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions described herein. A
general purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0076] The steps or stages of a method, process or algorithm in
connection with the embodiments disclosed herein may be embodied
directly in hardware, in a software module executed by a processor,
or in a combination of the two. A software module may reside in RAM
memory, flash memory, ROM memory, EPROM memory, EEPROM memory,
registers, hard disk, a removable disk, a CD-ROM, or any other form
of storage medium known in the art. An exemplary storage medium is
coupled to the processor such that the processor can read
information from, and write information to, the storage medium. In
the alternative, the storage medium may be integral to the
processor. The processor and the storage medium may reside in an
ASIC. The ASIC may reside in a user terminal. In the alternative,
the processor and the storage medium may reside as discrete
components in a user terminal.
[0077] The claims are not intended to be limited to the aspects
shown herein, but is to be accorded the full scope consistent with
the language of the claims, wherein reference to an element in the
singular is not intended to mean "one and only one" unless
specifically so stated, but rather "one or more." Unless
specifically stated otherwise, the term "some" refers to one or
more. A phrase referring to "at least one of" a list of items
refers to any combination of those items, including single members.
As an example, "at least one of: a, b, or c" is intended to cover:
a; b; c; a and b; a and c; b and c; and a, b and c.
[0078] The previous description of the disclosed aspects is
provided to enable any person skilled in the art to make or use the
present disclosure. Various modifications to these aspects will be
readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other aspects without
departing from the spirit or scope of the disclosure. Thus, the
disclosure is not intended to be limited to the aspects shown
herein but is to be accorded the widest scope consistent with the
appended claims and their equivalents.
[0079] As used herein, computer program products comprising
computer-readable media including all forms of computer-readable
medium except, to the extent that such media is deemed to be
non-statutory, transitory propagating signals.
[0080] While various embodiments of the present invention have been
described in detail, it may be apparent to those skilled in the art
that the present invention can be embodied in various other forms
not specifically described herein. Therefore, the protection
afforded the present invention should only be limited in accordance
with the following claims.
* * * * *