U.S. patent application number 10/729049 was filed with the patent office on 2004-06-17 for rapid acquisition and system selection of mobile wireless devices using a system map.
Invention is credited to Hunzinger, Jason F., Yamaguchi, Robert.
Application Number | 20040116132 10/729049 |
Document ID | / |
Family ID | 23891303 |
Filed Date | 2004-06-17 |
United States Patent
Application |
20040116132 |
Kind Code |
A1 |
Hunzinger, Jason F. ; et
al. |
June 17, 2004 |
Rapid acquisition and system selection of mobile wireless devices
using a system map
Abstract
The present invention enhances service system selection by a
mobile unit in a wireless communication system. The mobile unit
determines its geographic position, and based on that position
selects the proper service system. The geographic position may be
determined using a global position system, deck reckoning, or
estimated from a last known position. The distance of varying
service systems from the mobile station can then be calculated and
a service system selected based on this distance. The mobile
station may also use the position information in combination with a
database including position information of service systems to
select the proper service system. The position information of the
service systems can be included in the system selection database.
The mobile station may also map service systems based on position
information and service availability. The mobile station can then
subsequently refer to these maps to estimate available service.
Inventors: |
Hunzinger, Jason F.;
(Carlsbad, CA) ; Yamaguchi, Robert; (San Diego,
CA) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
23891303 |
Appl. No.: |
10/729049 |
Filed: |
December 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10729049 |
Dec 5, 2003 |
|
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|
09476301 |
Dec 30, 1999 |
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Current U.S.
Class: |
455/456.1 ;
455/404.2; 455/432.1; 455/435.1; 455/456.3 |
Current CPC
Class: |
H04W 48/18 20130101 |
Class at
Publication: |
455/456.1 ;
455/456.3; 455/404.2; 455/432.1; 455/435.1 |
International
Class: |
H04Q 007/00 |
Claims
What is claimed is:
1. A method of prioritizing a plurality of service systems in a
wireless communication system comprising: determining a reference
location; calculating a distance from the reference location to
each of the plurality of service systems; and prioritizing the
plurality of service systems based on the distance from the
reference location.
2. The method of claim 1, wherein the reference location is
determined using a global positioning system.
3. The method of claim 1, wherein the reference location is
determined using dead reckoning.
4. The method of claim 1, wherein the reference location is a last
known location of a mobile station.
5. The method of claim 1, wherein the calculating step further
comprises: determining a drift term; and adjusting the reference
location based on the drift term.
6. The method of claim 5, wherein the drift term is determined
using the equation: radius.sub.d=(t-t.sub.last-system)V.sub.max
where t is a current time, t.sub.last-system is a time that service
was last available on a last known system, and V.sub.max is a
maximum expected velocity that a mobile station would travel during
the period without service.
7. The method of claim 6, wherein the distance is calculated using
the equation: 2 d sys ( n ) = ( latitude s - latitude r ) + (
longitude s - longitude r ) radius s + radius d .
8. A method of prioritizing a plurality of service systems in a
wireless communication system comprising: determining a reference
location; and obtaining a prioritized list of service systems based
on the reference location.
9. The method of claim 8, wherein the reference location is
determined using a global positioning system.
10. The method of claim 8, wherein the reference location is
determined using dead reckoning.
11. The method of claim 1, wherein the prioritized list of service
systems based on the reference location is obtained from stored
data within a mobile station.
12. The method of claim 11, wherein the data is stored in the
system selection database.
13. The method of claim 12, wherein the system selection database
includes a position reference for each of the plurality of service
systems.
14. A mobile station for use in a wireless communication system
comprising: a position determination device; and a database of
system providers based on position information.
15. The mobile station of claim 14, wherein the position
determination device is a global positioning system.
16. The mobile station of claim 14, wherein the database is
included in the system selection database.
17. The mobile station of claim 14, wherein the mobile station
selects one of the system providers based on the database
information.
18. A mobile station for use in a wireless communication system
comprising: a position determination device; a service detector
which determines if service is available at any given position; and
memory locations for storing data regarding service availability
for a plurality of locations, wherein the grouping of the memory
locations provides a map of a service area showing service
availability.
19. The mobile station of claim 18, wherein the position
determination device is a global positioning system.
20. The mobile station of claim 18, wherein a grouping of memory
locations containing position information can be converted to a
formula defining a service area.
21. The mobile station of claim 18, wherein each memory location
stores both a latitude and a longitude of a position along with
information indicating whether service was available at the
position.
22. A method of mapping a service system for a wireless
communication system comprising: establishing a reference location;
determining service availability for the reference location; and
storing the information on service availability for the reference
location.
23. The method of claim 22, wherein the reference location is
established using a global positioning system.
24. The method of claim 22, wherein the reference location is
determined using dead reckoning.
25. The method of claim 22, further comprising: collecting data on
service information for a plurality of reference locations; and
combining the data to provide a map of a service area showing
service availability.
26. The method of claim 25, further comprising converting the
combined data into a formula defining a service area.
27. The method of claim 22, wherein the stored information includes
both a latitude and a longitude of the reference location along
with information indicating whether service was available at the
reference location.
Description
TECHNICAL FIELD
[0001] This invention relates to wireless communication systems,
and more particularly to cellular carrier selection within wireless
communication systems.
BACKGROUND
[0002] The use of wireless communication systems is growing with
users now numbering well into the millions. One of the popular
wireless communications systems is the cellular telephone, having a
mobile station (or handset) and a base station. Cellular telephones
allow a user to talk over the telephone without having to remain in
a fixed location. This allows users to, for example, move freely
about the community while talking on the phone.
[0003] Cellular telephones may operate under a variety of standards
including the code division multiple access (CDMA) cellular
telephone communication system as described in TIA/EIA, IS-95,
Mobile station-Base Station Compatibility Standard for Dual-Mode
Wideband Spread Spectrum Cellular System, published July 1993. CDMA
is a technique for spread-spectrum multiple-access digital
communications that creates channels through the use of unique code
sequences. In CDMA systems, signals can be and are received in the
presence of high levels of interference. The practical limit of
signal reception depends on the channel conditions, but CDMA
reception in the system described in the aforementioned IS-95
Standard can take place in the presence of interference that is 18
dB larger than the signal for a static channel. Typically, the
system operates with a lower level of interference and dynamic
channel conditions.
[0004] A cellular telephone communication system typically provides
services to an area by dividing the area into many smaller
geographic areas, known as cells, each of which is serviced by a
transmitter-receiver station, known as a cell site. The cell sites
are connected through landlines, or other communication links, to
so-called mobile telephone switching offices (MTSO's) which are, in
turn, connected to the public switched telephone network (PSTN).
According to current FCC rules, any given area is serviced by up to
two competing providers of cellular airtime communication services
(i.e., cellular carriers). The two service providers in any given
geographic area, commonly referred to as "A" and "B" carriers, are
assigned different groups of frequencies, or frequency sets,
through which services are provided along paging, control, access,
and voice channels, as would be understood by those reasonably
skilled in the industry and as dictated by technical standards of
appropriate regulatory agencies.
[0005] When a mobile station first activates in a particular area,
the mobile station searches for available service systems. Based on
the service subscription and other factors, the mobile station has
a preference when selecting a service system. The mobile station
generally looks for a system supported by the subscriber, and if
none if available the mobile system searches for a compatible
system. At present, the mobile station simply searches for
systems-regardless of the geographic location of the mobile
station. What is desired is a system where the mobile station can
limit the number of systems required for searching based on the
geographic position of the mobile station.
SUMMARY
[0006] The present invention enhances service system selection by a
mobile unit in a wireless communication system. The mobile unit
determines its geographic position, and based on that position
selects the proper service system. The geographic position may be
determined using a global position system, deck reckoning, or
estimated from a last known position. The distance of varying
service systems from the mobile station can then be calculated and
a service system selected based on this distance. The mobile
station may also use the position information in combination with a
database including position information of service systems to
select the proper service system. The position information of the
service systems can be included in the system selection database.
The mobile station may also map service systems based on position
information and service availability. The mobile station can then
subsequently refer to these maps to estimate available service.
[0007] One aspect of the invention is a method of prioritizing a
plurality of service systems in a wireless communication system.
The method comprises determining a reference location and
calculating a distance from the reference location to each of the
plurality of service systems. The method the prioritizes the
plurality of service systems based on the distance from the
reference location. The reference location may be determined using
a global positioning system or dead reckoning, among other
techniques. The calculating step further comprises determining a
drift term and adjusting the reference location based on the drift
term.
[0008] Another aspect of the invention is a method of prioritizing
a plurality of service systems in a wireless communication system.
The method comprises determining a reference location and obtaining
a prioritized list of service systems based on the reference
location. The reference location may be determined using a global
positioning system or dead reckoning. The prioritized list of
service systems based on the reference location is obtained from
stored data within a mobile station. The data may be stored in the
system selection database. The system selection database includes a
position reference for each of the plurality of service
systems.
[0009] Another aspect of the invention is a mobile station for use
in a wireless communication system. The mobile station comprises a
position determination device and a database of system providers
based oh position information. The position determination device
may be a global positioning system. The database is included in the
system selection database, and the selects one of the system
providers based on the database information.
[0010] Another aspect of the invention is a mobile station for use
in a wireless communication system. The mobile station comprises a
position determination device and a service detector. The service
detector determines if service is available at any given position.
The mobile station includes memory locations for storing data
regarding service availability for a plurality of locations. A
grouping of the memory locations provides a map of a service area
showing service availability. The grouping of memory locations
containing position information can be converted to a formula
defining a service area. Each memory location stores both a
latitude and a longitude of a position along with information
indicating whether service was available at the position.
[0011] Another aspect of the invention is a method of mapping a
service system for a wireless communication system. The method
comprises establishing a reference location and determining service
availability for the reference location. Information on service
availability for the reference location is then stored. The method
further comprises collecting data on service information for a
plurality of reference locations and combining the data to provide
a map of a service area showing service availability. The combined
data may be converted into a formula defining a service area.
DESCRIPTION OF DRAWINGS
[0012] These and other features and advantages of the invention
will become more apparent upon reading the following detailed
description and upon reference to the accompanying drawings.
[0013] FIG. 1 illustrates the components of an exemplary wireless
communication system used by the present invention.
[0014] FIG. 2 illustrates the system selection map structure
according to the present invention.
[0015] FIG. 3 is a flowchart illustrating the system selection
process according to the present invention.
[0016] FIG. 4A illustrates a first system map according to the
present invention.
[0017] FIG. 4B illustrates a second system map according to the
present invention.
[0018] FIG. 5 illustrates an exemplary system map having an
exclusion area according to the present invention.
[0019] FIG. 6 illustrates an exemplary system map showing a
coverage boundary which is mapped according to the present
invention.
DETAILED DESCRIPTION
[0020] FIG. 1 illustrates components of an exemplary wireless
communication system. A mobile switching center 102 communicates
with base stations 104a-104k (only one connection shown). The base
stations 104a-104k (generally 104) broadcasts data to and receives
data from mobile stations 106 within cells 108a-108k (generally
108). The cell 108 is a geographic region, roughly hexagonal,
having a radius of up to 35 kilometers or possibly more.
[0021] A mobile station 106 is capable of receiving data from and
transmitting data to a base station 104. In one embodiment, the
mobile station 106 receives and transmits data according to the
Code Division Multiple Access (CDMA) standard. CDMA is a
communication standard permitting mobile users of wireless
communication devices to exchange data over a telephone system
wherein radio signals carry data to and from the wireless
devices.
[0022] Under the CDMA standard, additional cells 108a, 108c, 108d,
and 108e adjacent to the cell 108b permit mobile stations 106 to
cross cell boundaries without interrupting communications. This is
so because base stations 104a, 104c, 104d, and 104e in adjacent
cells assume the task of transmitting and receiving data for the
mobile stations 106. The mobile switching center 102 coordinates
all communication to and from mobile stations 106 in a multi-cell
region. Thus, the mobile switching center 102 may communicate with
many base stations 104.
[0023] Mobile stations 106 may move about freely within the cell
108 while communicating either voice or data. Mobile stations 106
not in active communication with other telephone system users may,
nevertheless, scan base station 104 transmissions in the cell 108
to detect any telephone calls or paging messages directed to the
mobile station 106.
[0024] One example of such a mobile station 106 is a cellular
telephone used by a pedestrian who, expecting a telephone call,
powers on the cellular telephone while walking in the cell 108. The
cellular telephone scans certain frequencies (frequencies known to
be used by CDMA) to synchronize communication with the base station
104. The cellular telephone then registers with the mobile
switching center 102 to make itself known as an active user within
the CDMA network.
[0025] When detecting a call, the cellular telephone scans data
frames broadcast by the base station 104 to detect any telephone
calls or paging messages directed to the cellular telephone. In
this call detection mode, the cellular telephone receives, stores
and examines paging message data, and determines whether the data
contains a mobile station identifier matching an identifier of the
cellular telephone. If a match is detected, the cellular telephone
establishes a call with the mobile switching center 102 via the
base station 104. If no match is detected, the cellular telephone
enters an idle state for a predetermined period of time, then exits
the idle state to receive another transmission of paging message
data.
[0026] When a mobile station 106 activates, the mobile station 106
searches for an active and desirable wireless communication system.
Different areas may be served by multiple wireless communication
systems, and depending on the selected service provider and other
factors, the mobile station 106 selects which system to operate
within. The present invention provides a means to use location
information to enhance proper system selection. The invention
defines a system selection map and system selection algorithm that
use the map to optimize the service acquisition process.
[0027] The area covered by a wireless communication system can
generally be approximated with system circles or other shapes. Each
system may be defined by one or more circles which, when combined,
approximate the general service area of the system. Each of the
system circles may be defined by a data set containing the system
circle latitude (latitude.sub.s), the system circle longitude
(longitude.sub.s), and the radius of the system circle
(radius.sub.s). As shown in FIG. 2, a system selection map may
contain varying levels, and the varying levels may be diagramed in
a system tree 200. The system tree 200 shows a system selection map
having two levels (level N and level N+1). In level N, the system
tree 200 has a system group M.sub.i 205. In level N+1, the system
group M.sub.i 205 of FIG. 2 has a plurality of child system nodes
including a child system {N+1.1} 210, a child system {N+1.2} 215,
and other child systems until child system {N+1.n.sub.N+1} 220. The
system group M.sub.i 205 of FIG. 2 also has a plurality of child
system group nodes including a child system group {N+1.1} 225, a
child system group {N+1.2} 230, and other child systems groups
until child system group {N+1.M.sub.N+1} 220. Each of the child
systems groups may have its own child systems or child system
groups. Of course, the system group M.sub.i 205 may also have no
child systems or no child system groups.
[0028] The system group M.sub.i 205, each of the child systems 210,
215, 220, and each of the child system groups 225, 230, 235 are
generally defined as a circle having a centerpoint and a radius.
The centerpoint of each circle may be defined by a corresponding
set of coordinate points {latitude.sub.s, longitude.sub.s}. As
depicted in FIG. 2, the radius of each system and system group may
vary. The system group M.sub.i 205 encompasses, at a minimum, the
centerpoint of each child node. The system group M.sub.i 205 may
also encompass the majority of the child nodes, or completely
encompass the child nodes.
[0029] The present invention uses a reference location
{latitude.sub.r, longitude.sub.r} for the mobile station 106 to
enhance the system selection process. The process 300 of using
position information to enhance system selection is shown in FIG.
3. The process begins at a start state 305. Proceeding to state
310, the mobile station 106 determines if the position information
is available. The position information may be available to the
mobile station 106 from a variety of sources, including a global
positioning system (GPS), base station triangulation, dead
reckoning, and any other positioning system that is well known in
the art. If the position information is available, the process 300
proceeds along the YES branch to state 315. At state 315, the
mobile station 106 obtains the position information. The position
information is stored as the reference location {latitude.sub.r,
longitude.sub.r}.
[0030] Proceeding to state 320, the mobile station 106 determines
if the system selection database contains position information. The
system selection database provides the mobile station 106 with
information for the user zones to which the mobile station 106 is
subscribed. The system selection database contains information on
user zone priority, user zone identification, user zone system
identification, user zone name, active flag, priority control
field, notification flag, user zone revision, and overhead
parameters. According to the present invention, an additional field
is inserted into the system selection database containing position
information. The position information can be listed with each entry
in the system selection database, or may be included only for each
group of listings. By including position information in the system
selection database, the mobile station 106 can use the position
information of the mobile station 106 combined with the position
information in the system selection database to determine the most
desirable system. If the system selection database does not contain
any position information, the process 300 proceeds along the NO
branch to state 345, which will be described below. If the system
selection database does contain position information, the process
300 proceeds to state 325.
[0031] In state 325, the mobile station 106 retrieves the system
listings from the system selection database. Based on the position
information, the mobile station 106 can classify each of the
systems with a priority level, with the system having the highest
priority being the most desirable system and the first system with
which the mobile station 106 attempts to connect.
[0032] Returning to state 310, if position information is not
available, the process 300 proceeds along the NO branch to state
335. In state 335, the mobile station 106 determines a reference
location {latitude.sub.r, longitude.sub.r}. The reference location
is an approximation of the position of the mobile station 106, and
may be the last known position available, any nearby or recently
communicated infrastructure location, the last known system circle
centerpoint, or any other position information that may be
available to the mobile station 106.
[0033] Proceeding to state 340, the mobile station 106 determines
an estimated drift factor (radius.sub.d). The drift factor is used
when timing information is available and no system has been
available for a significant amount of time. If timing information
is not available, the drift factor (radius.sub.d) is set to 0. The
drift factor can be calculated using the formula:
radius.sub.d=(t-t.sub.last-system)V.sub.max
[0034] where t is the current time, t.sub.last-system is the time
that service was last available on the last known system, and
V.sub.max is the maximum expected velocity that the mobile station
106 would travel during the period without service.
[0035] Proceeding to state 345, the mobile station 106 calculates
the distance to each available system (d.sub.sys(n)). As stated
above, the location of each system is defined by a set of
coordinate points {latitude.sub.s, longitude.sub.s}. The mobile
station 106 uses the reference location and the drift factor to
determine the distance to each available system (d.sub.sys(n))
according to the following formula: 1 d sys ( n ) = ( latitude s -
latitude r ) + ( longitude s - longitude r ) radius s + radius
d
[0036] The distance (d.sub.sys(n)) is calculated for each available
system.
[0037] Proceeding to state 350, the mobile station 106 disregards
any systems located beyond a threshold distance
(d.sub.sys(n)>d.sub.thresh- old). The threshold distance
(d.sub.threshold) may be predetermined or the mobile station 106
may calculate the threshold distance (d.sub.threshold) based on
prior performance. Of course, if it is desired for the mobile
station 106 to consider all available systems, the threshold
distance may be ignored. After any systems beyond the threshold
distance are removed, the mobile station 106 prioritizes the
remaining systems. Prioritization of the systems is well known in
the art and will not be described herein.
[0038] Proceeding to state 330, the mobile station selects the
highest priority system and attempts to connect to that system. The
system is chosen from either the list generated from the system
selection database information or the list calculated by the mobile
station 106.
[0039] Proceeding to state 355, the mobile station 106 determines
if service is available on the selected system. If service is
available, the mobile-unit 106 connects with the service and the
process 300 proceeds along the YES branch to an end state 360.
Returning to state 355, if service is not available, the process
300 proceeds along the NO branch back to state 330, where the next
highest priority system is selected and connection attempted. This
process is repeated until the mobile station 106 connects to a
system, at which point the process 300 terminates in the end state
360.
[0040] The present invention may also use the position information
to create a map of serving systems within the mobile station 106.
The map may be used to determine the likelihood of service being
available from any particular system at any geographic location.
When a mobile station 106 obtains service, it can begin to map the
service area. The current position information (which may be stored
as a {latitude, longitude}), along with the service information is
recorded within the mobile station 106. The more a mobile station
106 travels within a service area, the more detailed the map.
[0041] FIG. 4A illustrates a map 400 according to one embodiment of
the present invention. The map 400 illustrates a service area 402
defined by a series of points 405, 410, 415, 420, 425, 430, 435,
and 440. Each of the series of points 405, 410, 415, 420, 425, 430,
435, and 440 is recorded by the mobile station 106 by recording the
{latitude, longitude} of each point along with the information that
service is available at that point. In general, it is not necessary
to map points inside the service area, as those points would be
assumed to have service. However, if an area inside a service area
does not have service, that information may also be mapped as will
be discussed below. After a service area is mapped, it may be
possible to condense the map 400 down from a number of points to an
equation defining the map 400. For example, if the service area
generally defined a circular area, the map 400 may be condensed to
a centerpoint and a radius. By condensing the map 400 to an
equation, the amount of memory required to store the map 400 within
the mobile station 106 is reduced.
[0042] As shown in FIG. 4, there may be areas within a service map
400 such as a point 450 that are within the service area, but the
map 400 may not completely define. For example, in FIG. 4, the
point 450 is within the service area 402, but because only the
points 420 and 425 define the outer perimeter of the service area,
the mobile station 106 cannot accurately predict whether service is
available at the point 450. One technique that may be used to
enhance the accuracy of the mobile station 106 is to include a
confidence factor. The confidence factor is a measure of how
definite the mobile station 106 is that the current location has
service, and may range for example from 0 (not confident) to 1
(extremely confident). If a mobile station 106 is in an area that
has not been mapped, the confidence factor for that area would be
0. If the mobile station 106 looks for service in at an exact
location it had service before, the confidence factor would be
1.
[0043] In FIG. 4A, the series of points 405, 410, 415, 420, 425,
430, 435, and 440 define the service area 402. However, because no
points have been recorded at the top of the arc, that shape can
only be approximated. Therefore, if service is desired at the point
450, the mobile station 106 would assign a relatively low
confidence factor that service is available at that point. However,
if the mobile station 106 records data at an additional point 445
as shown in FIG. 4B, the service area 402 becomes better defined.
Therefore, the mobile station 106 can now assign a higher
confidence factor to the point 450.
[0044] Some areas located within a service area may not have
coverage available or may have poor coverage. This may happen for a
variety of reasons, including entering a tunnel, encountering
natural obstacles such as hills, or entering the basement of a
building. FIG. 5 illustrates a service map 500 having a service
area 505. The service area 505 generally defines the geographic
area where service may be expected to be available. In general, any
points within the service area 505 would have a high confidence
factor. However, the service area 505 may include an exclusion area
510. The exclusion area 510 defines an area within the service area
505 where the mobile station 106 has determined that either no
service is available, or the service is weak. The exclusion area
510 may also define that service is only available for a certain
operating mode. For example, digital service may not be available
in the exclusion area 510 but service may be available on an analog
network.
[0045] The use of mapping and the confidence factor may be used to
predict the availability of service when the mobile station 106
moves a long distance between measured points. FIG. 6 illustrates a
service map 600 having a point 605 where service is available. The
service boundary is indicated by a line 610. If the mobile station
106 is turned off at the point 605, no further mapping occurs. As
the mobile station 106 travels east from the point 605, the mobile
station 106 will pass the service boundary. If the mobile station
106 is turned on again at a point 615 where no service is
available, the mobile station 106 will not know at what point
service is lost. However, the mobile station 106 does know that
service is available at the point 605, so as the mobile station
travels west, the confidence factor is increased. Of course, the
mobile station 106 is continually mapping new points to enhance the
mapping area stored in memory.
[0046] Numerous variations and modifications of the invention will
become readily apparent to those skilled in the art. Accordingly,
the invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. The
detailed embodiment is to be considered in all respects only as
illustrative and not restrictive and the scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
* * * * *