,
`Direct all correspondence to:
`
`
`
`Customer Number
`
`.. OR
`V Firm or
`M Individual Name Holme Roberts & Owen LLP
`1700 Lincoln Street, Suite 4100
`
`D Yes, the name ofthe US Government agency and the Government contract number are:
`
`1.
`
`
`
`
`Please type a plus sign (+) inside this box —> +
`
` DocketNumber:]
`
`42365-00050
`
`' / %
`
`lNVENTOR(S)/APPLICANT(S)
`
`Family Name or Surname
`
`Resrdence (City and either State or Foreign Country)
`
`Fitch
`Hose
`
`McKnight
`
`Edmonds, Washington
`Boulder, Colorado
`
`Westminster, Colorado
`
`||l|ll|lll||l~92
`
`=\
`159 —=—_n
`——a
`
`“'8
`
`I Additional inventors are being named on page 2 attached hereto
`
`TITLE OF THE INVENTION (280 characters max)
`
`"DATA FUSION FOR WIRELESS LOCATION-BASED APPLICATIONS"
`
`CORRESPONDENCE ADDRESS
`
`
`
`
`Place Customer Number
`Bar Code Label here
`
`
`
` State
`
`Colorado
`
`Telephone
`
`(303) 861-7000
`
`(303) 866-0200
`
`ENCLOSED APPLICATION PARTS (check all that apply)
`
`Specification
`’1‘
`E Drawing(s)
`
`Number ofPages
`NumberofSheets
`
`34
`
`D Small Entity Statement
`
`
`D Other (specify)
`
`V
`M A check or money order is enclosed to cover the filing fees
`
`The Commissioner is hereby authorized to charge filing fees or
`credit any overpayment to Deposit Account Number:
`
`
`
`
`
`FILING FEE
`AMOUNT
`
`
`
`Respectfully submitted '
`
`
`SIGNATURE w a 9%,.
`Date
`11/03/1998
`TYPED or PRINTED NAME Kent A. Fischmann, Esq.
`REG'STRAT'ON NO
`
`(If appropriate)
`
`
`
`
`TELEPHONE
`
`(303) 861-7000
`
`
`USE ONLY FOR FILING A PROVISIONAL APPLICATION FOR PA TENT
`SEND TO: Box Provisional Application, Assistant Commissionerfor Patents, Washington, DC 20231
`[Page Inf
`2
`]
`P19$MALLIREVO4
`
`EXHIBIT 1007
`
`35,511
`
`i
`
`EXHIBIT 1007
`
`

`

`PROVISIONAL APPLICATION FOR PA TENT COVER SHEET (Small Entity)
`
`
`
`Given Name (first and middle [if any])
`
`lNVENTOR(S)/APPLICANT(S)
`Family Name or Surname
`
`Residence (city and either State or Foreign Country)
`
`
`
`r
`
`II'1HtH
`
`
`
`
`
`
`
`Certificate ofMailing by Express Mail
`
`
`
`this provisional patent application cover sheet,
`I certify that
`provisional patent application and fee is being deposited on
`November 3, 1998
`with the US. Postal Service as
`"Express Mail Post Office to Addressee" service under 37
`CF.
`. 1.10 and is addre
`to the Assistant Commissioner
`
`. 20231.
`‘ents, Washingt
`
`
`Typed or Printed Name ofPerson Mailing Correspondence
`Connie Larson
`
`Signature ofPerson Mailing Correspondence
`
`USE ONLY FOR FILING A PROVISIONAL APPLICATION FOR PATENT
`SEND TO: Box Provisional Application, Assistant Commissionerfor Patents, Washington, DC 20231
`P1 QSMALL/REVO4
`
`[Page 2 of 2]
`
`

`

`DATA FUSION FOR WIRELESS LOCATION—BASED APPLICATIONS
`
`FIELD OF THE INVENTION
`
`The present invention relates in general to wireless 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 information available to wireless
`
`location-based applications.
`
`BACKGROUND OF THE INVENTION
`
`Wireless communications networks generally allow for 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 information 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 dependent call billing and vehicle tracking. In 911 applications, the
`
`location of a wireless station is determined when the station is used to place an emergency
`
`call. The location is then transmitted to a local emergency dispatcher 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. 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
`
`delay of arrival (TDOA), handset global positioning system (GPS) and cell/sector equipment.
`
`
`
`
`
`
`
`
`
`10
`
`15
`
`20
`
`25
`
`#3 8849
`
`

`

`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 registration.
`
`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 timeliness.
`
`The nature of the information desired for particular applications also varies. For
`
`example, for certain applications 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 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 apparatus for using multiple LFE
`
`inputs to enhance the location information made available to wireless location-based
`
`applications.
`
`The invention allows wireless location-based applications 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, applications are independent of particular LFEs and can access
`
`_2_
`
`10
`
`15
`
`20
`
`25
`
`30
`
`#38849
`
`
`
`

`

`multiple LFEs receiving a location request from a wireless location application seeking LFE
`
`independent 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 functionality may be
`
`distributed over multiple platforms.
`
`According to a still further aspect of the present invention, multiple LFE inputs, are
`
`10
`
`utilized to make a location determination regarding a wireless station. The corresponding
`
`15
`
`20
`
`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 uncertainty information based on the first and
`
`second inputs. Preferably, the first and second inputs include raw location and uncertainty
`
`information obtained from LFE measurements 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
`
`requirements of the wireless location application. For example, in the case of LFEs that
`
`determine location based on readings obtained from two or more cell sites, a reading from
`
`one of the cell sites may be used in conjunction with, e.g., cell sector information to make
`
`a location determination.
`
`According to another aspect of the present invention, multiple LFE inputs, obtained
`
`25
`
`at different times from the same or different LFEs, are utilized to derive tracking information
`
`improved location determination accuracy. The associated method includes the steps of
`
`receiving a first LFE input including first location information and first corresponding time
`
`information for a particular wireless station, receiving a second LFE input including 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 information regarding the mobile station's speed of travel
`
`_4_
`
`30
`
`#38849
`
`

`

`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 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
`
`10
`
`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 measurements. 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 invention and further advantages
`
`thereof, reference is now made to the following detailed description taken in conjunctions
`
`with the drawings in which:
`
`Figure 1 is a schematic diagram of a wireless network implementing a location
`
`finding system in accordance with the present invention;
`
`_5_
`
`
`
`15
`
`20
`
`25
`
`3O
`
`#38349
`
`

`

`Figure 2 is a schematic diagram illustrating a wireless location—based services system
`
`in accordance with the present invention;
`
`Figures 3a—3e illustrate various location finding technologies that may be utilized in
`
`the context of the present invention;
`
`Figure 4 is a graphical illustration ofthe use ofmultiple LFE inputs to reduce location
`
`uncertainty in accordance with the present invention;
`
`Figure 5 is a graphical depiction of a location uncertainty analysis in accordance with
`
`the present invention; and
`
`Figures 6—9 illustrate various wireless location interface signaling sequences in
`
`10
`
`accordance with the present invention.
`
`DETAILED DESCRIPTION
`
`In the following description, particular embodiments and implementations of the
`
`present invention are set forth in the context of an intelligent telecommunications network.
`
`It will be appreciated however, that various aspects of the invention are more broadly
`
`applicable to other location based services environments.
`
`Referring to Figure 1, an intelligent 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 use in routing
`
`wireless communications to or from wireless stations 102, an intelligent 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 intelligent network platform is used to run a
`
`Location Finding System (LFS)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 intelligent 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
`
`
`
`
`15
`
`20
`
`25
`
`#38849
`
`

`

`these elements 116 and 118 may be spread over multiple platforms.
`
`In addition, other
`
`applications not depicted in Figure 1 may be resident on the platform 114.
`
`As shown in Figure 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 a
`
`variety of location finding technologies such as AOA, TDOA, GPS and cell/sector
`
`technologies. Three of the illustrated systems 104, 106 and 108 operate separate from the
`
`MSC. Examples of such systems include infrastructure based systems such as AOA and
`
`TDOA and external systems such as GPS. Generally, infrastructure based system such as
`
`AOA and TDOA 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 transceiver for 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 wireless station 102.
`
`In this regard, the cell site equipment may
`
`include three or more directional antennas for communicating with wireless stations within
`
`subsections ofthe cell area. These directional antennas can be used to identify the subsection
`
`of a cell where the wireless station 102 is located. In addition, ranging 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 LFS 116 via the MSC 112.
`
`As shown, the LFS 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
`
`-7-
`
`10
`
`15
`
`20
`
`25
`
`30
`
`#3 8849
`
`
`
`

`

`LFS 116 to provide location outputs for use by any of various wireless location applications
`
`1 18 in response to location requests fiom the application 1 18. Such applications may include
`
`any Wireless location services applications such as 911, vehicle tracking and location-based
`
`billing programs.
`
`Figure 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 LFS 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 Figures 3a—3d for
`
`purposes of illustration. Figure 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 uncertainty 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
`
`coverage area 300.
`
`Figure 3b depicts a TOA based LFE. In this case, the 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 determined 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
`
`
`
`
`
`10
`
`15
`
`20
`
`25
`
`30
`
`and the axes 308 and 310.
`
`#38849
`
`

`

`An AOA based LFE is generally illustrated in Figure 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.
`
`Figure 3d illustrates a TDOA based LFE.
`
`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.
`
`Figure 3e 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 Figure 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 corresponding cell site identifiers/coordinates; in TDOA systems
`
`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 LFS 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
`
`_9_
`
`
`
`
`
`
`
`10
`
`15
`
`20
`
`25
`
`30
`
`#3 8849
`
`

`

`location coordinates are reported and the uncertainty 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 functionality may be incorporated into a subsystem of
`
`the LFS 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 LFS 214 associated with the LC 220, may implement a conversion facility for
`
`converting the determined (processed) location information of the LFCs 208, 210 and 212
`
`into standardized location information expressed, for example, as geographical location
`
`coordinates and an uncertainty radius.
`
`In the illustrated embodiment, two dimensional
`
`location coordinates are defined (e.g., latitude and longitude) together with an uncertainty
`
`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 Figures 3a—3e, examples of these coordinates 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 Figure 3c) and then the minimum radius circle C may be
`
`defined to circumscribe the actual uncertainty region; the standardized uncertainty region C
`
`may be defined first (e. g., as the minimum radius circle required to circumscribe the actual
`
`uncertainty region) and then L be defined as the center of the circle C; or any other
`
`appropriate geometric solutions/approximations may be employed.
`
`This standardized location information is then stored in a database in LC 220.
`
`Specifically, the location coordinates for a wireless station and corresponding uncertainties
`
`can be stored in a field, in a relational database, or can otherwise be indexed to a wireless
`
`station identifier, e. g., a cellular telephone Electronic Serial Number/Mobile Identification
`
`Number (ESN/MIM. The coordinates and uncertainty may be expressed in terms of any
`
`_10_
`
`10
`
`15
`
`20
`
`25
`
`30
`
`#38849
`
`
`
`

`

`appropriate units. For example, the coordinates may be expressed as latitude and longitude
`
`values in units of 10'6 degrees and the uncertainty may be expressed in units of meters.
`
`The stored, standardized information can be used to perform a number of multiple
`
`input analyses. Three examples of such facilities are generally indicated by the velocity 216,
`
`multi-input processing 217 and tracking 218 facilities of LFS 214. The velocity facility 216
`
`involves determining and storing speed information and direction (bearing) information for
`
`a wireless station based on multiple LFE inputs for the station. Because of the standardized
`
`format, such determinations can be easily made relative to inputs from the same or different
`
`LFEs 104, 106 and/or 108. The velocity information can be obtained based on knowledge
`
`of the change in position and the change in time (determined by way of the time stamps
`
`associated with the location information) and may be expressed in terms of latitudinal and
`
`longitudinal velocity components in units of meters per second, together with velocity
`
`uncertainty terms. The direction information can be directly obtained from the location
`
`information, or can be based on a ratio of the velocity components, using standard
`
`trigonometric principles. It will be appreciated that such speed and direction information
`
`may be useful for a variety of applications such as vehicle tracking.
`
`The multi-input processing facility 217 can be used to improve location accuracy
`
`based on multiple inputs from the same or, more preferably, different LFEs 202, 204 and/or
`
`206. That is, if two locations with two uncertainties can be obtained for a given wireless
`
`station at a given time, a reduced uncertainty can be calculated as the overlap of the two
`
`original uncertainties. A complicating factor is that the locations and uncertainties stored in
`
`the LC 220 for a given wireless station will typically not represent location determinations
`
`for the same time. Because wireless stations are generally mobile, an additional element of
`
`uncertainty is introduced.
`
`The illustrated multi-input processing facility 217 takes time into account. This is
`
`accomplished by:
`
`l.
`
`accessing the LC 220 to obtain two (or more) sets of location information for
`
`a given Wireless station;
`
`2.
`
`3.
`
`identifying a location, uncertainty and time for each set of information;
`
`determining a time difference between the times of the information sets;
`
`-11-
`
`
`
`10
`
`15
`
`20
`
`25
`
`30
`
`#38849
`
`

`

`4.
`
`calculating an element of location uncertainty associated with the time
`
`difference; and
`
`5 .
`
`applying the calculated element of location uncertainty to the earlier location
`
`information to obtain time translated location information.
`
`This time translated location information can then be compared to the later location
`
`information in an uncertainty overlap analysis, as described below, to obtain a reduced
`
`uncertainty.
`
`Various processes can be employed to calculate the additional, time—related element
`
`of location uncertainty. A simple case involves assuming a maximum rate of travel. For
`
`example, a maximum rate of travel of 70 miles per hour may be assumed to account for
`
`travel of a mobile phone in a vehicle. The uncertainty associated with an earlier location
`
`determination may then be expanded by a value determined by multiplying the maximum
`
`rate of travel by the time difference between the two measurements to be compared.
`
`Different maximum travel rates may be assumed for different conditions, for example, a
`
`lower rate may be assumed for city locations than for suburban locations, a lower rate may
`
`be assumed for peak traffic periods, or a lower rate may be assumed for mobile stations that
`
`are not generally used on fast moving vehicles. Also, wireless station speed and direction
`
`information as described above or other tracking information as described below may be
`
`used to reduce the time—related element of uncertainty.
`
`Once such a time translation process has been employed to normalize multiple LFE
`
`inputs relative to a given time, an uncertainty overlap analysis can be implemented. Such
`
`an analysis is graphically illustrated in Figures 4 and 5. Referring first to Figure 4, the
`
`smaller circle represents a location and uncertainty associated with a later LFE input taken
`
`to be at time t]. The larger circle 402 represents a location and uncertainty associated with
`
`a time translated location information based on an earlier LFE input taken to be at time to.
`
`Circle 402 is illustrated as having a larger uncertainty than circle 400 to account for the
`
`additional time and travel related element of uncertainty associated with the time translation.
`
`The shaded overlap area 404 represents the reduced uncertainty achieved by using multiple
`
`inputs. That is, statistically, if circle 400 represents a 95% confidence level regarding the
`
`position of the station at t1 and circle 402 represents a nearly 95% confidence level regarding
`
`-12_
`
`
`
`10
`
`15
`
`20
`
`25
`
`30
`
`#38849
`
`

`

`the position of the station at t1, the position of the station can be determined to be in the
`
`shaded area 404 with a high level of confidence.
`
`Figure 5 illustrates a mathematical process for combining the original uncertainties
`
`to obtain a more accurate position and uncertainty. Mathematically, the problem is to
`
`compute the intersection of the circular uncertainty regions, and express the result as a
`
`location with an uncertainty (e.g., a circular uncertainty circumscribing the intersection
`
`region). To simplify the mathematics, the geometric arrangement of Figure 4 is translated
`
`to provide a first axis (x in Figure 5) that extends through the centerpoints of the circular
`
`uncertainty regions 500 and 502 (generally, the coordinates of the originally determined
`
`10
`
`locations) and an orthogonal axis (y) intersecting the center of the larger (in this case later)
`
`circular uncertainty region 502. The mathematical equations for the boundaries of circular
`
`uncertainty regions 500 and 502 are:
`
`fi+¢=fi
`
`(n
`
`(X-Xo)2 + Y2 = r22
`
`(2)
`
`15
`
`2O
`
`25
`
`It will be appreciated that the values of r1, r2 and x0 are known as these are the uncertainty of
`
`the time translated information, the uncertainty of the later LFE input and the difference
`
`between I1 and r2, respectively. Equations (1) and (2) can then be simultaneously solved to
`
`obtain x and y, where x is the new location and y is the radius of the new uncertainty region.
`
`Finally, these values can be translated back into Earth coordinates. This mathematical
`
`analysis can be used for cases where x S x0 and x0 5 r1 + r2. In other cases, the most recent
`
`or most accurate of the LFE inputs can be utilized.
`
`The illustrated LFS 214 also includes a tracking facility 218. Such tracking involves
`
`using historical information (at least two sets of location information) and using such
`
`information to reduce the uncertainty associated with current measurements. That is, by
`
`tracking movement of a wireless station, information can be obtained that is useful in
`
`analyzing the uncertainty of current measurements.
`
`In a simple case, where tracking
`
`information indicates that a wireless station is moving in a straight line (or otherwise on a
`
`definable course) or at a constant speed, then curve fitting techniques or other simple
`
`#38849
`
`_l3_
`