(12) United States Patent
`(10) Patent N0.:
`US 6,321,092 B1
`
`Fitch et al.
`(45) Date of Patent:
`Nov. 20, 2001
`
`USOO6321092B1
`
`(54) MULTIPLE INPUT DATA MANAGEMENT
`FOR WIRELESS LOCATION—BASED
`APPLICATIONS
`
`(75)
`
`Inventors: James Fitch, Edmonds, WA (US);
`.
`.
`.
`,
`.
`Dav1d L. Hose, Boulder, Michael
`MCKnlght> WeStmmSteL bOth 0f CO
`(US)
`
`.
`(73) ASSIgneeI Signal Soft Corporation, Boulder, CO
`(US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`Patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.2 09/396,235
`.
`.
`(22) Flled'
`
`(60)
`
`Sep. 15’ 1999
`Related US. Application Data
`Provisional application No. 60/106,816, filed on NOV. 3,
`1998
`Int. Cl.7 ....................................................... H04Q 7/20
`(51)
`(52) US. Cl.
`............................................. 455/456; 342/357
`.
`(58) Field of Search ..................................... 455/456, 422,
`455/457, 517; 342/357, 450, 457
`
`(56)
`
`.
`References Clted
`U.S. PATENT DOCUMENTS
`.
`10/1998 Dennison et a1.
`................... 455/456
`10/1987
`...... 379/60
`
`8/1991 Darnell et a1.
`....................... 342/357
`5/1993 Song .................................... 364/449
`6/1993 Mansell et a1.
`455/456
`
`.
`..... 379/60
`8/1993 Dennison et a1.
`
`
`..
`5/1994 Kennedy et a1.
`342/457
`........................... 342/457
`7/1994 Sillp et a1.
`2/1995 Grimes ................................... 379/59
`
`""" 379/59
`12/1995 Gnmes
`5/1996 Sheffer ..............
`.. 379/58
`7/1996 Holliday, Jr. et a1.
`.
`.. 379/59
`
`.. 379/60
`8/1996 Dennison et a1.
`.......................... 342/450
`2/1997 Dunn et a1.
`
`Re. 35,916
`4,700,374
`5,043,736
`5 208 756
`5,223,844 *
`5,235,633
`5,317,323
`5,327,144 *
`5,388,147
`574797482
`5,515,419
`5,537,460
`5,546,445
`5,600,706 *
`
`5,608,410 *
`5,625,668
`5,673,322
`5,724,660 *
`
`........................... 342/457
`3/1997 Stilp et a1.
`4/1997 Loomis et a1.
`......................... 379/58
`9/1997 Pepe et a1.
`.......
`380/49
`3/1998 Kauser et a1.
`..... 455/456
`
`5,732,354 *
`3/1998 MacDonald ........... 455/456
`5,754,955
`.............................. 455/422
`5/1998 Ekbatani
`,
`,
`................... 455/456
`/1998 Dennison et a1.
`5 815 814
`9
`.
`5,835,907 * 11/1998 Newman ............... 455/456
`
`5,844,522 * 12/1998 Sheffer et a1.
`..... 342/457
`
`
` 5,999,126 * 12/1999 Ito ..................... 455/456
`
`8/2000 Bergen .................. 455/456
`6,097,958 *
`8/2000 Maloney et a1.
`..................... 455/456
`6,108,555 *
`
`FOREIGN PATENT DOCUMENTS
`W0 98/10307
`3/1998 (W0) ............................... GO1S/3/02
`W0 98/10538
`3/1998 (W0) .............................. H04B/7/26
`.
`*
`.
`cued by exammer
`Primary Examiner—Nay Maung
`Assistant Examiner—Quochien B. Vuong
`(74) Attorney, Agent, or Firm—Marsh Fischmann &
`Breyfogle LLP
`ABSTRACT
`(57)
`d
`LFE .
`.
`fi d'
`.
`1
`1
`M 1.
`)“IP‘HS are “.56
`‘1th 6 0cm“ I? mg equlpmem
`to enhance the location information made available to Wire-
`less location-based applications. In one implementation the
`.
`.
`.
`.
`.
`.
`.
`.
`’
`invention is implemented in a Wireless network including an
`MSC (112) for use in routing communications to or from
`Wireless stations (102), a network platform (114) associated
`With the MSC (112), and a variety of LFE systems (104, 106,
`108 and 110). A Location Finding System (LFS) (116) in
`-
`-
`-
`-
`-
`accordance With the present invention is reSident on the
`.
`.
`.
`.
`Platform (114) The LFS (116) recelves locanon.lnf°rmat¥°n
`from the LFES(104>106>103 and 110) and Pr0V1d6510<=athH
`information to Wireless location based applications (118). In
`this regard, the LFS (116) can receive input information at
`varying time intervals of varying accuracies and in various
`formats, and can provide standardized outputs to the apph-
`cations (118), for example, depending on the needs of the
`applications (118). Multiple inputs may also be co-processed
`for enhanced accurac
`
`y‘
`
`20 Claims, 8 Drawing Sheets
`
`
`CELL/SECTOR
`(LFE SYSTEM n+1)
`
`
`
`114
`
`EXHIBIT 1004
`
`IIIIIIIII1I|IIIIIIII
`
`102
`
`WIRELESS
`
`
`“5
`LOCATION
`FINDING
`
`SYSTEM
`
`
`WIRELESS
`
`LOCATION
`APPLICATIONS
`
`
`118
`
`
`F 77777777777 L 7777777
`INTELLIGENT
`NETWORK
`PLATFORM
`
`104
`
`LFE
`SYSTEM 1
`
`E1
`
`106
`
`LFE
`SYSTEM 2
`
`LFE
`SYSTEM n
`
`
` :L I
`
`
`STATION "9
`
`EXHIBIT 1004
`
`

`

`US. Patent
`
`Nov. 20, 2001
`
`Sheet170f8
`
`US 6,321,092 B1
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`US. Patent
`
`Nov. 20, 2001
`
`Sheet 3 0f 8
`
`US 6,321,092 B1
`
`14"
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`
`
`318
`
`FIG.3C
`
`

`

`US. Patent
`
`Nov. 20, 2001
`
`Sheet 4 0f 8
`
`US 6,321,092 B1
`
`326
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`330
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`324
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`328
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`332
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`
`

`

`US. Patent
`
`Nov. 20, 2001
`
`Sheet 5 0f 8
`
`US 6,321,092 B1
`
`
`
`FI G .5
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`
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`
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`
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`
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`
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`MEASUREMENT
`INFO
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`
`FIG.6
`
`

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`US. Patent
`
`Nov. 20, 2001
`
`Sheet 7 0f 8
`
`US 6,321,092 B1
`
`WLA
`
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`
`WLA REQUEST
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`RETURN RESULT
`
`FIG.8
`
`

`

`US. Patent
`
`Nov. 20, 2001
`
`Sheet 8 0f 8
`
`US 6,321,092 B1
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`

`US 6,321,092 B1
`
`1
`MULTIPLE INPUT DATA MANAGEMENT
`FOR WIRELESS LOCATION-BASED
`APPLICATIONS
`
`This applications claims benefit of Prov. No. 60/106,816
`filed Nov. 3, 1998.
`FIELD OF THE INVENTION
`
`to wireless
`invention relates in general
`The present
`location-based applications and, in particular, to a method
`and apparatus for use in processing multiple location finding
`equipment inputs and making the resulting location infor-
`mation available to wireless location-based applications.
`BACKGROUND OF THE INVENTION
`
`Wireless communications networks generally allow for
`voice and/or data communication between wireless stations,
`e.g., wireless telephones (analog, digital cellular and PCS),
`pagers or data terminals that communicate using RF signals.
`In recent years, a number of location-based service systems
`have been implemented or proposed for wireless networks.
`Such systems generally involve determining location infor-
`mation for a wireless station and processing the location
`information to provide an output desired for a particular
`application.
`Examples of such existing or proposed applications
`include emergency or “911” applications, location depen-
`dent call billing, cell-to-cell handoff and vehicle tracking. In
`911 applications, the location of a wireless station is deter-
`mined when the station is used to place an emergency call.
`The location is then transmitted to a local emergency dis-
`patcher to assist in responding to the call. In typical location
`dependent call billing applications, the location of a wireless
`station is determined, for example, upon placing or receiving
`a call. This location is then transmitted to a billing system
`that determines an appropriate billing value based on the
`location of the wireless station. In handoff applications,
`wireless location is determined in order to coordinate hand-
`
`off of call handling between network cells. Vehicle tracking
`applications are used, for example, to track the location of
`stolen vehicles. In this regard, the location of a car phone or
`the like in a stolen vehicle can be transmitted to the
`
`appropriate authorities to assist in recovering the vehicle.
`From the foregoing, it will be appreciated that location-
`based service systems involve location finding equipment
`(LFE) and location-related applications. To some extent, the
`LFEs and applications have developed independently. In this
`regard, a number of types of LFEs exist and/or are in
`development. These include so-called angle of arrival
`(AOA) time difference of arrival (TDOA), handset global
`positioning system (GPS) and the use of cell/sector location.
`The types of equipment employed and the nature of the
`information received from such equipment vary in a number
`of ways. First, some of these equipment types, like GPS, are
`wireless station-based whereas others are “ground-based”,
`usually infrastructure-based. Some can determine a wireless
`station’s location at any time via a polling process, some
`require that the station be transmitting on the reverse traffic
`channel (voice channel), and others can only determine
`location at call origination, termination, and perhaps regis-
`tration. Moreover, the accuracy with which location can be
`determined varies significantly from case to case.
`Accordingly, the outputs from the various LFE’s vary in a
`number of ways including data format, accuracy and time-
`liness.
`
`10
`
`15
`
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`2
`such as 911, accuracy and timeliness are important. For the
`applications such as vehicle tracking, continuous or frequent
`monitoring independent of call placement is a significant
`consideration. For other applications, such as call billing,
`location determination at call initiation and call termination
`
`or during handoff is generally sufficient.
`Heretofore, developers have generally attempted to match
`available LFEs to particular applications in order to obtain
`the location information required by the application. This
`has not always resulted in the best use of available LFE
`resources for particular applications. Moreover, applications
`designed to work with a particular LFE can be disabled
`when information from that LFE is unavailable, e.g., due to
`limited coverage areas, malfunctions or local conditions
`interfering with a particular LFE modality. In addition, the
`conventional query and response mode of operation between
`applications and the associated LFEs has resulted in the use
`by applications of LFE dependent data formats, LFE limited
`data contents, and single LFE input location determinations.
`
`SUMMARY OF THE INVENTION
`
`The present invention is directed to a method and appa-
`ratus for using multiple LFE inputs to enhance the location
`information made available to wireless location-based appli-
`cations. The invention allows wireless location-based appli-
`cations access to information based inputs from LFEs of
`different types, thereby enhancing the timeliness, accuracy
`and/or reliability of the requested location information.
`Moreover, in accordance with the present invention, appli-
`cations are independent of particular LFEs and can access
`location information from various LFE sources without
`
`indeed
`requiring specific adaptations, data formats, or
`knowledge of the LFE sources employed, in order to access
`and use such location information. By virtue of such
`independence, new location finding technologies can be
`readily deployed and existing applications can exploit such
`new technologies without compatibility issues. The inven-
`tion also allows multiple LFE inputs, from one or more
`LFEs, to be used to allow for wireless station tracking and
`reduced location uncertainty.
`invention, a
`According to one aspect of the present
`method is provided for using multiple (i.e., two or more)
`LFEs to support a wireless location application. The method
`involves receiving first and second inputs from first and
`second LFEs, storing location information based on the
`inputs in memory, receiving a location request regarding a
`wireless station from a wireless location application, selec-
`tively retrieving the location information from memory, and
`outputting a response to the location request to wireless
`location application.
`The first and second LFEs preferably may employ differ-
`ent location finding technologies, e.g, GPS, AOA, TDOA,
`and cell/sector technologies. The stored location information
`preferably includes at least location information and corre-
`sponding time information for particular wireless stations,
`and may further include location uncertainty information,
`travel speed information and travel direction information. In
`response to the location request from the wireless location
`application,
`location information may be retrieved from
`memory or, alternatively, one or more of the LFEs may be
`prompted to obtain location information. In this regard, the
`location request may include a specification regarding the
`desired location information, for example, indicating how
`recent or how accurate the information should be. If the
`
`The nature of the information desired for particular appli-
`cations also varies. For example, for certain applications
`
`memory includes information conforming to the
`specification, then such information is retrieved and output
`
`

`

`US 6,321,092 B1
`
`3
`to the requesting application. Otherwise, appropriate infor-
`mation may be obtained by prompting one or more LFEs to
`locate the wireless station of interest.
`
`In accordance with another aspect of the present
`invention, a processing system is interposed between the
`LFEs and the wireless location applications such that the
`applications can access location information in a manner
`that
`is independent of the location finding technology
`employed by the LFEs. The corresponding process imple-
`mented by the processing system involves: receiving LFE
`dependent location data (i.e., location data having a content
`and/or format dependent on the location finding technology
`employed) from multiple LFEs receiving a location request
`from a wireless location application seeking LFE indepen-
`dent location data (i.e., location data having a content and
`format
`independent of any particular location finding
`technology) and responding to the location request based on
`LFE dependent location data. The process implemented by
`the processing system may further involve generating and
`storing LFE independent location data based on the LFE
`dependent data. The processing system may be resident on
`the location finding controllers associated with each LFE, on
`a separate platform and/or the processing system function-
`ality may be distributed over multiple platforms.
`According to a still further aspect of the present invention,
`multiple LFE inputs, are utilized to make a location deter-
`mination regarding a wireless station. The corresponding
`method involves the steps of receiving a first location input
`from a first LFE including first location information and first
`uncertainty information, receiving a second location input
`from a second LFE including second location information
`and second uncertainty information and combining the first
`and second location inputs to provide a combined location
`input including combined location information and uncer-
`tainty information based on the first and second inputs.
`Preferably, the first and second inputs include raw location
`and uncertainty information obtained from LFE measure-
`ments prior to aggregation and related processing. One or
`both of the first and second inputs may constitute partial
`information, insufficient on its own to yield a location and
`uncertainty regarding the wireless station within the require-
`ments of the wireless location application. For example, in
`the case of LFEs that determine location based on readings
`obtained relative to two or more cell sites, a reading from
`one of the cell sites may be used in conjunction with other
`location information, e.g., cell sector information, to make a
`location determination.
`
`invention,
`According to another aspect of the present
`multiple LFE inputs, obtained at different times from the
`same or different LFEs, are utilized to derive tracking
`information such as for obtaining improved location deter-
`mination accuracy. The associated method includes the steps
`of receiving a first LFE input including first location infor-
`mation and first corresponding time information for a par-
`ticular wireless station, receiving a second LFE input includ-
`ing second location information and second time
`information for the wireless station, and using the first and
`second inputs to derive tracking information for the wireless
`station. The tracking information preferably includes infor-
`mation regarding the mobile station’s speed of travel and
`direction of travel. This tracking information can be used in
`conjunction with subsequent LFE inputs for the wireless
`station to improve location determination accuracy and can
`also be used to interpolate wireless station location between
`location determinations, or to project future wireless station
`locations as may be desired for some applications. It will be
`appreciated that this tracking function and other functions
`
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`4
`are facilitated by the provision of a system for receiving
`inputs from one or more LFEs, standardizing such inputs
`with regard to data content and format, and storing such
`information.
`In particular, such standardized and stored
`information can be readily analyzed to yield derivative
`information regarding wireless station position as well as
`statistical information for wireless stations of interest in the
`service area.
`
`A system constructed in accordance with the present
`invention includes an input facility for receiving inputs from
`multiple LFEs, a memory such as a cache for storing
`information from the LFE inputs (e.g., a wireless station
`identification, a location, a time associated with that
`location, an uncertainty for that location, and travel speed
`and bearing), an interface for receiving location requests
`from wireless location applications and providing responses
`to such requests, and a processing subsystem for processing
`the LFE inputs and location requests. The apparatus may
`also include a facility for prompting LFEs to make location
`measurements in response to location requests. Among other
`things,
`the processing subsystem may convert
`the LFE
`inputs into a standard format, direct storage of data in the
`memory, derive tracking or other derivative information
`from multiple inputs, analyzing stored information relative
`to received location requests to determine whether the stored
`information includes information responsive to the requests
`and selectively directing the LFEs to make location mea-
`surements. The system may be resident on a single or
`multiple platform and the functionality may be spread
`among multiple applications.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`For a more complete understanding of the present inven-
`tion and further advantages thereof, reference is now made
`to the following detailed description taken in conjunctions
`with the drawings in which:
`FIG. 1 is a schematic diagram of a wireless network
`implementing a location finding system in accordance with
`the present invention;
`FIG. 2 is a schematic diagram illustrating a wireless
`location-based services system in accordance with the
`present invention;
`FIGS. 361—36 illustrate various location finding technolo-
`gies that may be utilized in the context of the present
`invention;
`FIG. 4 is a graphical illustration of the use of multiple
`LFE inputs to reduce location uncertainty in accordance
`with the present invention;
`FIG. 5 is a graphical depiction of a location uncertainty
`analysis in accordance with the present invention; and
`FIGS. 6—9 illustrate various wireless location interface
`
`signaling sequences in accordance with the present inven-
`tion.
`
`DETAILED DESCRIPTION
`
`In the following description, particular embodiments and
`implementations of the present invention are set forth in the
`context of a telecommunications network. It will be appre-
`ciated however, that various aspects of the invention are
`more broadly applicable to other location based services
`environments.
`
`Referring to FIG. 1, an wireless telecommunications
`network implementing the present invention is generally
`identified by the reference numeral 100. Generally,
`the
`network includes a mobile switching center (MSC) 112 for
`
`

`

`US 6,321,092 B1
`
`5
`use in routing wireless communications to or from wireless
`stations 102, a network platform 114 associated with the
`MSC 112 for implementing a variety of subscriber or
`network service functions, and a variety of location finding
`equipment (LFE) systems 104, 106, 108 and 110. In the
`illustrated embodiment, the network platform is used to run
`a Location Manager (LM) 16 in accordance with the present
`invention and a number of wireless location applications
`118. Although the illustrated location finding system 116 and
`wireless location applications 118 are illustrated as being
`resident on the network platform 114, it will be appreciated
`that the elements 116 and 118 may be located elsewhere in
`the network 100, may be resident on separate platforms, or
`the functionality of each of these elements 116 and 118 may
`be spread over multiple platforms. In addition, other appli-
`cations not depicted in FIG. 1 may be resident on the
`platform 114.
`As shown in FIG. 1, multiple LFE systems 104, 106, 108
`and 110 may be associated with the network 100. These LFE
`systems 104, 106, 108 and 110 may employ any of a variety
`of location finding technologies such as AOA, TDOA, GPS
`and cell/sector technologies and the various system 104,
`106, 108 and 110 may be the same as or different from one
`another. It will be appreciated that the nature of the data
`obtained from the LFE systems 104, 106, 108 and 110 as
`well as the path by which the data is transmitted varies
`depending on the type of LFE employed, and the ability to
`accommodate a variety of LFEs is an important advantage of
`the present invention. Some types of LFEs include LFE
`equipment in the handset. Examples include certain GPS
`and TDOA systems. In such cases, location information may
`be encoded into signals transmitted from the handset to a cell
`site or other receiver, and the information may then be
`transferred to the platform 114 via the MSC 112 or other-
`wise. Other LFE systems, i.e., embedded systems use equip-
`ment associated with individual cell sties such as specialized
`antennae to make location determinations such as by trian-
`gulation and, again, the resulting location information may
`be transferred to the platform 114 via the MSC 112 or
`otherwise. Still other LFE systems employ a network of
`dedicated LFE equipment that is overlayed relative to the
`wireless network. Such systems may communicate location
`information to the platform 114 independent of the MSC 112
`and network cell site equipment. In addition, some LFE
`technologies can be implemented via equipment resident in
`the handset, in cell sites or other network locations and/or in
`dedicated LFE sites such that
`the data pathway of the
`location information may vary even for a given LFE tech-
`nology.
`Three of the illustrated systems 104, 106 and 108 operate
`separate from the MSC 112. For example, such systems may
`include network based systems ADA and TDOA systems
`and external systems such as GPS. Generally, the illustrated
`network based system such as ADA and TDOA systems
`determine the location of a wireless station 102 based on
`communications between the wireless station and the cell
`
`site equipment of multiple cell sites. For example, and as
`will be described in more detail below, such systems may
`receive information concerning a directional bearing of the
`wireless station 102 or a distance of the wireless station 102
`
`relative to each of multiple cell sites. Based on such
`information, the location of the wireless station 102 can be
`determined by triangulation or similar geometric/
`mathematic techniques. External systems such as GPS
`systems, determine the wireless station location relative to
`an external system. In the case of GPS systems, the wireless
`station 102 is typically provided with a GPS receiver for
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`determining geographic position relative to the GPS satellite
`constellation. This location information is then transmitted
`across an air interface to the network 100.
`
`The illustrated cell sector system 110 may be associated
`with cell site equipment for communicating with the wire-
`less station 102. In this regard, the cell site equipment may
`include three or more directional antennas for communicat-
`
`ing with wireless stations within subsections of the cell area.
`These directional antennas can be used to identify the
`subsection of a cell where the wireless station 102 is located.
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`In addition, ranging information obtained from signal timing
`information may be obtained to identify a radius range from
`the cell site equipment where the wireless station 102 is
`located, thereby yielding a wireless station location in terms
`of a range of angles and a range of radii relative to the cell
`site equipment. This cell/sector location information can be
`transmitted to the LM 116 via the MSC 112 or possibly via
`other network information or structure.
`
`As shown, the LM 116 receives location information from
`the various LFE systems 104, 106, 108 and 110. The nature
`of such information and handling of such information is
`described in more detail below. Generally, however, such
`information is processed by the LM 116 to provide location
`outputs for use by any of various wireless location applica-
`tions 118 in response to location requests from the applica-
`tion 118. Such applications may include any wireless loca-
`tion services applications such as 911, vehicle tracking and
`location-based billing programs.
`FIG. 2 illustrates a location-based services system 200 in
`accordance with the present invention. An important aspect
`of the present invention relates to the operation of the LM
`214 to receive inputs from multiple LFEs 202, 204 and 206
`and provide location outputs to multiple applications 226,
`228 and 230. In accordance with the present invention, the
`LFEs 202, 204 and 206 may be based on different
`technologies, and may therefore provide different types of
`location information, in different data formats, with different
`accuracies based on different signals.
`A number of different location finding technologies are
`depicted in FIGS. 3a—3d for purposes of illustration. FIG. 3a
`generally shows the coverage area 300 of a cell sector. As
`noted above, the cell site equipment for a particular cell of
`a wireless telecommunications system may include a
`number, e.g., three or more, of directional antennas. Each
`antenna thus covers an angular range relative to the cell site
`bounded by sides 302. In the case of a three sector cell, each
`antenna may cover about 120°—150° relative to the cell site.
`In addition the coverage range for the antenna defines an
`outer perimeter 304 of the coverage area 300. As shown, the
`range varies with respect to angle defining a somewhat
`jagged outer perimeter 304. Accordingly, the actual uncer-
`tainty regarding the location of a wireless station located in
`the illustrated cell sector is defined by the coverage area 300.
`The location determination output from a cell/sector LFE is
`therefore effectively defined by the coordinates of the cov-
`erage area 300.
`the
`FIG. 3b depicts a TOA based LFE. In this case,
`wireless station’s range from a cell sector antenna is
`determined, based on time of signal arrival or signal transit
`time to within a radius range, e.g., about 1000 meters.
`Accordingly, the wireless station’s location can be deter-
`mined to be within an area bounded by sides 306 (based on
`the angular range of the cell sector antenna) and inner 308
`and outer 310 arcs (defined by the ranging uncertainty). The
`output from a TOA based LFE is effectively defined by the
`coordinates of the sides 306 and the axes 308 and 310.
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`US 6,321,092 B1
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`An AOA based LFE is generally illustrated in FIG. 3c.
`AOA based LFEs determine the location of a wireless
`
`station based on the angle of arrival of signals, generally
`indicated by rays 312 and 314, from the wireless station as
`measured by two or more cell sites 316 and 318. Each angle
`measurement has an angular uncertainty generally indicated
`by line segments 320 and 322. Consequently, the uncertainty
`region for a given location determination is defined by a
`polygon having 2n sides, where n is the number of cell sites
`316 and 318 involved in the measurement.
`
`FIG. 3d illustrates a TDOA based LFE although the
`illustrated system is cell site based, the TDOA system may
`alternatively be handset based. In TDOA systems, multiple
`cell sites measure the time of arrival of signals from a
`wireless station. Based on such measurements, each cell site
`can provide information regarding wireless station location
`in terms of a hyperbola 324 or 326 and an uncertainty,
`generally indicated by segments 328 and 330. The resulting
`uncertainty region is defined by a multi-sided region (where
`each wall is curved) having 2n walls, where n is the number
`of cell sites involved in the determination.
`
`FIG. 36 illustrates a GPS based LFE. In GPS systems, the
`wireless station includes a GPS transceiver for receiving
`signals indicating the wireless station’s location relative to
`multiple satellites in the GPS constellation. Based on these
`signals, the geographic coordinates of the wireless station’s
`location is determined to an accuracy of perhaps 20 meters
`as generally indicated by circle 332. This information is then
`transmitted to the wireless network across an air interface.
`
`Referring again to FIG. 2, each of the LFEs 202, 204 or
`206 outputs location information to its respective LFC 208,
`210 or 212. The nature of this “raw” LFE output depends in
`part on the type of LFE involved. For example, in the case
`of a cell sector system the output may be a sector identifier
`or coordinates; in the case of a TOA system, the output may
`be a sector identifier or coordinates and a radius; in an AOA
`system the output may be angular measurements and cor-
`responding cell site identifiers/coordinates; in TDOA sys-
`tems the output may define multiple hyperbolae; and in GPS
`systems the output may be geographic coordinates.
`The LFCs 208, 210 and 212 collect and aggregate the
`“raw” location into a standard format which is then sent to
`
`the location cache (LC) 220 of the LM 214 for storage.
`Aggregation involves using the raw data to determine a
`wireless station location and uncertainty. For some LFE
`systems, such as GPS systems,
`this process is simple
`because location coordinates are reported and the uncer-
`tainty is known. For other LFE systems, aggregation is more
`involved. For example, in the case of TDOA, aggregation
`may involve receiving multiple hyperbola definitions and
`using these definitions to define a wireless station location
`and a multi-sided uncertainty region. The LFCs 208, 210 and
`212 may be provided by the LFE vendors or their function-
`ality may be incorporated into a subsystem of the LM 214.
`In the context of the present invention, it is useful to
`express the location information in a standard format.
`Accordingly, the LFCs 208, 210 and 212 or a cooperating
`subsystem of the LM 214 associated with the LC 220, may
`implement a conversion facility for converting the deter-
`mined (processed) location information of the LFCs 208,
`210 and 212 into standardized location information
`
`expressed, for example, as geographical location coordi-
`nates and a region of uncertainty. The uncertainty region
`may be of any shape (e.g., polygonal) depending, for
`example, on the nature of the LFE(s) employed. Once such
`type of uncertainty region is a circular region that can be
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`characterized by an uncertainty radius. In the illustrated
`embodiment,
`two dimensional
`location coordinates are
`defined (e.g., latitude and longitude) together with an uncer-
`tainty radius applied relative to the location coordinates. It
`will be appreciated that the standard format may allow for
`altitude coordinates, non-circular uncertainty regions and
`other parameters.
`Referring again to FIGS. 3a—3e, examples of these coor-
`dinates and circular uncertainty regions are graphically
`depicted. In particular, in each case, a location “L” and
`standardized uncertainty region “C” are geometrically
`defined such that
`the standardized uncertainty region C
`circumscribes the actual uncertainty region associated with
`that location finding technology. In this regard, the location
`L may be defined first (e.g., as the intersection of rays 312
`and 314 in FIG. 3c) and then the minimum radius circle C
`may be defined to circumscribe the actual uncertainty
`region;
`the standardized uncertainty r