(12) United States Patent
`US 6,466,788 B1
`(10) Patent N0.:
`Carlsson
`
`(:45) Date of Patent: Oct. 15, 2002
`
`USOO6466788B1
`
`4/1997 Loomis et al.
`5,625,668 A
`............... 455/456
`3/1998 Emery et a1.
`5,727,057 A *
`9/1998 Valentine .................... 455/435
`5,815,808 A *
`5,822,418 A * 10/1998 Yacenda et a1.
`............ 379/198
`. 455/432
`6,002,932 A * 12/1999 Kingdon et al.
`.
`
`6,014,102 A
`1/2000 Mitzlaff et a].
`..
`. 342/457
`
`. 342/457
`6,374,098 B1
`4/2002 Raith et a1.
`
`**
`
`METHODS AND APPARATUS FOR
`TRANSFERRING POSITION DATA
`BETWEEN TERMINALS IN WIRELESS
`COMMUNICATIONS SYSTEMS
`
`Inventor: Ove Carlsson, Linkoping (SE)
`
`Assignee: Telefonaktiebolaget LM EI'ICSSOII
`(publ), Stockholm (SE)
`
`WO
`
`FOREIGN PATENT DOCUMENTS
`WO9725828
`11/1997
`
`(54)
`
`(75)
`
`(73)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.s.C. 154(b) by 0 days.
`
`“709852379
`W0
`.
`*
`,
`cued by exammer
`
`11/1998
`
`Primary Examiner—Dwayne Bost
`Assistant Examiner—L West
`(74) Attorney, Agent, or Firm—Burns, Doane, Swecker &
`Mathis, LLP.
`
`<21)
`
`<22)
`
`<51)
`(52)
`(58)
`
`(so)
`
`.
`Appl. No" 09/216’830
`Filed:
`Dec. 21, 1998
`
`7
`
`Int. Cl.
`.................................................. H04Q 7/20
`US. Cl.
`........................ 455/435; 455/461; 701/213
`
`Field Of Search ““““““““““ 455/435> :86’
`455/404’ 414’ 433’ 456’ 458’ 461’ 701' 213
`References Cited
`
`~~~~~~~~~~~ 455/403
`
`(57)
`ABSTRACT
`Techniques for ascertaining the geographic position of users
`and terminals in a Wireless communications system are used,
`fortexample, by operations personnel in performing system
`maintenance and by emergency personnel in locatmg lost or
`injured individuals. According to an exemplary method of
`requesting and obtaining user position information, user
`terminals in a Wireless communications system routinely
`.
`.
`.
`.
`.
`.
`.
`.
`.
`glans“:POSItloréuitflormmg’? to In??? SWHChtmg “mg: 1n
`e Sys em, an.
`6 I90 1,6 “V191“? cell 51.5 mam .am
`up-to-date terminal posrtion informatlon 1n Visiting location
`registers. Requests for user position information are routed
`to a home location register Which in turn routes terminal
`position requests to mobile switching centers With which the
`target users are registered. Terminal position information is
`retrieved from the appropriate visiting location registers and
`sent back to the requesting parties with a minimum of
`5 stem traffic
`y
`
`‘
`
`US. PATENT DOCUMENTS
`*
`.
`:figg’ggg : *
`igfiggg 3211131 it all. “““““““““ 255/438
`e a. ......
`,
`,
`u
`
`..
`342/3571
`5,235,633 A *
`8/1993 Dennison et a1.
`379/11427
`5,251,248 A * 10/1993 Tokunaga etal.
`5,315,636 A a.
`5/1994 Patel
`..................... 379/20107
`5,369,684 A 4 11/1994 Buhl et a].
`.................. 455/432
`5,485,163 A *
`1/1996 Singer et a1.
`............... 455/435
`5,502,758 A
`3/1996 Tsuzuki et a1.
`5,513,242 A *
`4/1996 Mukerjee et a1.
`55157419 A
`5/1996 Sheff“
`,
`575157426 A
`541996, Yaceflda CF al‘
`5,519,760 A *
`5/1996 Borkowskl .................. 455/456
`5,548,822 A
`8/1996 Yogo
`5,577,264 A * 11/1996 Tuohino ..................... 455/432
`5,621,783 A *
`4/1997 Lantto et al.
`............... 455/433
`20 Claims, 3 Drawing Sheets
`
`
`Message
`,
`Para/717 Para/712 Para/n3 Para/r14
`Para/775
`
`Pas/flan
`Termld
`X
`Y
`Z
`
`Information
`copra/hate word/hate word/hate
`UserPosm'o/I
`Feature Ussrld
`
`Request
`Coda
`
`Orly/hat/ug/
`USE/Position
`Tar/771d
`X
`Y
`Z
`
`RequestAo/r
`_ coordinate word/hate word/hate firm/nanny
`UserPDs/Won
`
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`Term/ua/PoS/t/‘an Feature Userld
`
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`. Code
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`Term/ua/Posmon Termld
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`Z
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`
`Request/40k
`word/hate coordinate ward/hate
`
`Eurr/ugflequest Feature
`
` Code
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`UnBarr/hgfieques/ Feature
`
`Code
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`
`LYFT 1014
`
`LYFT 1014
`
`1
`
`

`

`US. Patent
`
`Oct. 15, 2002
`
`Sheet 1 0f3
`
`US 6,466,788 B1
`
`FIG. /
`
`
`
`2
`
`

`

`US. Patent
`
`Oct. 15, 2002
`
`Sheet 2 0f3
`
`US 6,466,788 B1
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`f/M’
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`
`
`fill?
`
`
`
`3
`
`

`

`US. Patent
`
`Oct. 15, 2002
`
`Sheet 3 0f 3
`
`US 6,466,788 B1
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`FIG. 4
`
`
`Poe/Won ‘
`.I'nformaf/on
`
`Message
`
`Param /
`
`
`
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`Y
`X
`word/hare word/hare coord/nafe
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`IIIII
`
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`
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`Requesf
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`User/003M017
`RequesrAc/c
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`UserPos/fl'on
`Request/Wok
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`
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`
`----
`
`
`Feature
`Code
`
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`
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`
`4
`
`

`

`US 6,466,788 B1
`
`1
`METHODS AND APPARATUS FOR
`TRANSFERRING POSITION DATA
`BETWEEN TERMINALS IN WIRELESS
`COMMUNICATIONS SYSTEMS
`
`FIELD OF THE INVENTION
`
`The present invention relates to communications systems,
`and more particularly,
`to the transfer of data regarding
`geographic positions of mobile terminals and mobile termi-
`nal users in wireless communications systems.
`BACKGROUND OF THE INVENTION
`
`Wireless communications systems are pervasive in the
`world today. For example, a significant percentage of indi—
`viduals in developed nations already personally own at least
`one cellular telephone for use with well established land-
`based and satellite-based systems. Furthermore, a growing
`number of developing nations are now bringing wireless
`systems on line. This insatiable global appetite for wireless
`technology will only intensify in the foreseeable future.
`FIG. 1 depicts an exemplary wireless communications
`system 100 including ten cells or coverage areas C1—C10,
`ten base stations B17B10, a Mobile Switching Center MSC
`and ten mobile stations M1—M10. Such a wireless system
`100 can be constructed, for example, in accordance with any
`of the well known wireless communications standards,
`including the European Global System for Mobile (GSM)
`cellular standard or the United States Digital Cellular
`(USDC) standard (i.e., the Electronic Industry Association
`Interim Standard IS-54). While such a system 100 typically
`includes far more than ten cells, ten base stations and ten
`mobile stations,
`ten of each component is sufficient for
`illustrative purposes.
`As shown, one or more base stations can be situated in
`each of the cells. Although FIG. 1 shows the base stations
`located toward the cell centers, each base station can instead
`be located anywhere within a cell. Base stations located
`toward a cell center
`typically employ omni-directional
`antennas, whereas base stations located toward a cell bound-
`ary typically employ directional antennas. Those skilled in
`the art will also appreciate that each individual base station
`shown in FIG. 1 can, in practice, comprise a base station
`controller in communication with a number of separate base
`station units, each unit providing coverage for a cell sector.
`Typically, each base station and each mobile station
`includes a radio transceiver for transmitting and receiving
`communications signals over the air interface (as defined,
`for example, by one of the known standards, GSM, IS-54,
`etc.). More specifically, the base and mobile stations com-
`municate using a form of time, frequency or code division
`multiple access (i.e., TDMA, FDMA or CDMA) as is known
`in the art. As the mobile stations move within a cell and from
`cell to cell, communication with at least one base station is
`always possible. As a result, mobile station users are able to
`place, receive and conduct calls from anywhere within the
`overall system coverage area.
`As shown, the base stations are also in communication
`with the MSC. Though only one MSC is shown in FIG. 1,
`those of skill in the art will appreciate that an overall system
`typically includes multiple MSCs, each MSC being coupled
`(e.g., by radio or hard-wire link) to a unique subset of the
`base stations in the overall system, and each MSC being
`capable of communicating with the other MSCs in the
`system (e.g., via the US. Signaling System No. 7, or SS7,
`protocol). As is known in the art, the MSCs keep track of
`which cells the mobile stations are registered in and provide
`
`10
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`2
`a link between the wireless system 100 and the Public
`Switched Telephone Network (PSTN).
`To keep track of which cells the mobile stations are
`registered in, each MSC typically maintains a Visiting
`Location Register (VLR) which provides a list of mobile
`stations presently registered within the coverage area of the
`MSC (i.e., in the coverage area serviced by all of the base
`stations which are coupled to the MSC). Furthermore, at
`least one Home Location Register (HLR) is typically main-
`tained for an overall system, the HLR conventionally pro-
`viding a list of all local subscribers based within the system
`coverage area and also providing, for each local subscriber,
`a description of the various features available to the sub-
`scriber. When a mobile station moves into a new coverage
`area and registers with a new MSC (via a coupled base
`station),
`the visited MSC updates its VLR to reflect the
`presence of the mobile station and also contacts the HLR to
`obtain subscription information for the mobile station. In
`this way, mobile stations can seamlessly roam from cover-
`age area to coverage area while maintaining the ability to
`place and receive calls in accordance with their base sub-
`scription.
`there has been a strong connection
`Conventionally,
`between a wireless subscription and a particular mobile
`terminal and a particular mobile user. In other words, an
`individual user conventionally purchases a subscription with
`which a particular terminal is associated (e.g., by Mobile
`Identification Number, or MIN), and the individual user is
`charged for calls placed from the particular terminal.
`Additionally, calls are conventionally placed by dialing a
`number associated with a particular terminal, and thus
`varying numbers are used to reach an individual, depending
`upon which of many terminals the individual happens to be
`near.
`
`More recently, however, the growing demand for wireless
`technology has required a more sophisticated approach to
`system management. In particular, there has been a recent
`push toward a global system in which calls are made, not
`from terminal to terminal, but from user to user. In other
`words, a system in which each user has a unique identifi-
`cation number by which all calls to that user are placed,
`irrespective of which terminal the user happens to be using.
`Toward that end, the concepts of user, terminal and sub-
`scription are beginning to diverge. See,
`for example,
`co—pending US. patent application Ser. No. 08/585,149,
`filed Jan. 10, 1996 and entitled Cellular Telecommunication
`Systems having Selectively Associatable Usage Parameters,
`which is incorporated herein by reference. Consequently, the
`above described Home and Visiting Location Registers can
`now include distinct user, terminal and subscription data-
`bases.
`
`Recently (e.g., with the advent of the Global Positioning
`System, or GPS), there has also been a push toward enabling
`a wireless communications system to provide detailed infor-
`mation regarding the geographic position of users and
`terminals. However, while the MSCs in a conventional
`wireless system can determine the cell in which a mobile
`terminal is located, they typically cannot provide the more
`precise location information which is often necessary or
`desirable in practice (e.g., when an individual must be
`located in an emergency situation or when system operations
`personnel wish to locate a particular terminal for mainte-
`nance or repair). Further, known methods for providing
`more precise location information (see, c.g., US. Pat. No.
`5,727,057 to Emery et al.) do not account for the recent
`divergence of the concepts of user, terminal and subscrip-
`tion.
`
`5
`
`

`

`US 6,466,788 B1
`
`3
`Consequently, there is a need for improved techniques for
`ascertaining the geographic location of a mobile terminal in
`a wireless communications system.
`
`SUMMARY OF THE INVENTION
`
`The present invention fulfills the above-described and
`other needs by providing methods and apparatus for ascer-
`taining the geographic position of users and terminals in a
`wireless communications system. Embodiments of the
`invention enable system users to easily request the position
`of a terminal (e.g., when operations personnel wish to locate
`a terminal in order to perform maintenance of traffic system
`performance or to determine the reasons for lost calls) or the
`position of a user (e.g., when emergency personnel wish to
`locate a lost or injured individual). Further, embodiments of
`the invention permit mobile terminals to be used as navi-
`gation instruments and open the door to more sophisticated
`supervision of taxis, buses and other transport vehicles.
`Advantageously, aspects of the invention can be readily
`incorporated within a wireless communications protocol
`which contemplates the distinct concepts of user, terminal
`and subscription.
`An exemplary method for requesting and obtaining user
`position information in a wireless communications system
`includes the steps of: sending terminal position information
`from user terminals to mobile switching centers with which
`the user terminals are registered; storing the terminal posi-
`tion information in visiting location registers of the receiv-
`ing mobile switching centers; entering a feature code and a
`user identification code at a requesting terminal (the feature
`code and user identification code indicating a request for
`position information regarding a remote system user asso-
`ciated with the user identification code); sending a user
`position request message and the user identification code
`from the requesting terminal to a mobile switching center
`with which the requesting terminal is registered; forwarding
`the user position request message from the mobile switching
`center to a home location register in the system; determining
`(at the home location register) which user terminals the
`remote system user is registered with; sending a terminal
`position request message and the user identification code to
`each mobile switching center where the remote user is
`registered on a terminal; retrieving (for each terminal with
`which the remote user is registered) terminal position infor-
`mation from a visiting location register; sending (for each
`terminal with which the remote user is registered) a terminal
`position request acknowledged message, a terminal identi-
`fication code and retrieved terminal position information to
`the home location register; and forwarding at least one of the
`terminal position request acknowledged messages from the
`home location register to the requesting terminal.
`Prior to determining which user terminals the remote
`system user is registered with, a determination can be made
`(e.g., at the home location rcgistcr) whcthcr position infor-
`mation requests for the remote user are barred. If so, a user
`position request not acknowledged message can be sent
`from the home location register to the mobile switching
`center with which the requesting terminal is registered, and
`then back to the requesting terminal.
`According to exemplary embodiments, a user terminal
`can include a global positioning system receiver for deter-
`mining position coordinates. Alternatively, the user terminal
`can compute position coordinates based on at
`least one
`timing advance parameter received from at least one base
`station in the wireless communications system. In either
`case, the user terminal can periodically transmit position
`
`10
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`coordinates to a mobile switching center with which it is
`registered. Alternatively,
`the mobile switching center can
`periodically poll the user terminal for position coordinates,
`or wait and request the position coordinates when a request
`for position information regarding the user terminal is made.
`An exemplary wireless communications system accord-
`ing to the invention includes a plurality of user terminals, at
`least one mobile switching center (each mobile switching
`ccntcr including a visiting location register), and at least one
`home location register. According to exemplary
`embodiments, each user terminal is configured to transmit
`terminal position information to a mobile switching center
`with which the user terminal is registered, and each mobile
`switching center is configured to store received terminal
`position information in a corresponding visiting location
`register. Additionally, the home location register is config-
`ured to receive requests for position information relating to
`target users registered in the system and, for each received
`request, to send a terminal position request to each mobile
`switching center where a target user is registered on a
`terminal. Upon receiving terminal position requests,
`the
`mobile switching centers can retrieve terminal position
`information from their visiting location registers and trans-
`mit the retrieved terminal position information to the home
`location register.
`The above-described and other features and advantages of
`the invention are explained in detail hereinafter with refer—
`ence to the illustrative examples shown in the accompanying
`drawings. Those of skill in the art will appreciate that the
`described embodiments are provided for purposes of illus-
`tration and understanding and that numerous equivalent
`embodiments are contemplated herein.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 depicts an exemplary wireless communications
`system in which the teachings of the present invention can
`be implemented.
`FIG. 2 is a flow diagram depicting steps in an exemplary
`method of obtaining user and terminal position data accord-
`ing to the invention.
`FIG. 3 is a flow diagram depicting steps in an exemplary
`method of blocking and unblocking user position requests
`according to the invention.
`FIG. 4 is a table listing exemplary control messages and
`associated mcssagc paramctcrs according to the present
`invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`FIG. 2 depicts steps in an exemplary method for request-
`ing and obtaining, from a terminal (e.g., from a telephone or
`a computer coupled to a Public Land Mobile Network, or
`PLMN),
`the geographic position of other terminals with
`which a particular user has registered. Exemplary methods
`by which a user can register with (and de-register from) a
`terminal are described in the above cited US. patent appli—
`cation Ser. No. 08/585,149. Those of skill in the art will
`appreciate that the functionality of the system components
`described with respect to FIG. 2 can be implemented using,
`for example, known digital signal processing components or
`digital computers.
`As is indicated by arrows labclcd S1 in FIG. 2, all
`registered mobile terminals MA, MB, MC can, according to
`the invention, regularly send position information to their
`visited switching centers MSCA, MSCB, MSCC.
`
`6
`
`

`

`US 6,466,788 B1
`
`10
`
`15
`
`5
`the switching centers can periodically poll
`Alternatively,
`registered terminals for current position information.
`Further, the switching centers can request current position
`information from terminals whenever position requests are
`made. Thus, according to the invention, each MSC can store
`up-to-date position information for each registered terminal
`in its respective Visiting Location Register.
`Each terminal can, for example, be equipped with a GPS
`receiver and can therefore provide the position information
`in the form of X-Y—Z Cartesian coordinates (i.e., longitude-
`latitude-altitude). Alternatively, each terminal can compute
`its own position using the timing advance parameter which
`is typically transmitted from the base stations in a wireless
`system. The timing advance parameter indicates to a mobile
`station the appropriate timing to be used in transmitting data
`in TDMA time slots (i.e., to compensate for delays due to the
`physical separation between the base station and the mobile
`terminal) and thus provides the mobile station with an
`indication of the distance between the mobile station and the
`base station. The timing advance parameter from one base '
`station can therefore be used to pinpoint the position of the
`terminal within a fixed radius of the base station, and timing
`advance parameters from two or more base stations can be
`used to further narrow the position of the terminal.
`To initiate a user location request, a first user registered on
`a first terminal MA enters (i.e., by pushing buttons on a
`telephone keypad or keys on a computer keyboard of
`terminal MA) an appropriate feature code (e.g., a character
`sequence indicating that the first user wishes to make a
`location request) and an identification code, or user ID,
`corresponding to the remote user the first user wishes to
`locate. Thereafter, as is indicated by arrows labeled S2 in
`FIG. 2, a User Position Request code is sent from the
`terminal MA to the local switching center MSCA. As is
`shown by additional arrows labeled S2 in the figure, a
`similar request can also be made from either a fixed terminal
`in the PSTN or from a fixed terminal
`in an Operations
`Support System OSS (which can, for example, be used to
`respond to alarms indicating that certain system equipment
`has failed or to adjust various system parameters, such as
`base station transmit frequencies).
`Upon receiving the User Position Request from the first
`mobile terminal MA, the local switching center MSCA for-
`wards the request to the system HLR (as is indicated by an
`arrow labeled S3 in FIG. 2). Thereafter,
`the HLR uses
`information in the user and terminal registers within the
`HLR (again, see the above cited US. patent application Ser.
`No. 08/585,149) to determine which terminals the user is
`registered with. Assuming the user has not barred position
`requests (’see the detailed discussion below with respect to
`barring and unbarring of position requests by a user or by an
`OSS), the IILR sends a Terminal Position Request to each of
`the mobile switching centers MSCB, MSCC where the user
`is presently registered on a terminal. Transmission of the
`Terminal Position Requests is indicated by arrows labeled
`S4 in FIG. 2.
`
`40
`
`45
`
`Upon receiving a Terminal Position Request, each queried
`switching center MSCB, MSCC answers the HLR with one
`Terminal Position Request Acknowledgment (including
`position information data) for each terminal with which the
`user is actually currently registered. Transmission of the
`Terminal Position Request Acknowledgments is indicated
`by arrows labeled SS in FIG. 2.
`Upon receiving each Terminal Position Request
`Acknowledgment, the HLR transmits a corresponding User
`Position Request Acknowledgment (including the position
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`60
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`6
`information and an indication, as determined by the HLR, of
`whether the remote user is an originating or terminating user
`on the corresponding remote terminal) to the originating
`switching center MSCA. Transmission of the User Position
`Request Acknowledgements is indicated by an arrow labeled
`S6 in FIG. 2. However, if the original User Position Request
`was barred for the remote user, the HLR instead transmits a
`single User Position Request Not Acknowledged back to the
`originating switching center MSCA without sending any
`Terminal Position Requests to the remote switching centers
`MSCB, MSC“.
`Upon receiving each User Position Request Acknowledg—
`ment (i.e., one Acknowledgment for each remote terminal
`with which the remote user is registered), the originating
`switching center MSCA forwards the Acknowledgment on to
`the originating terminal MA, OSS or PSTN, as appropriate.
`Forwarding of the Acknowledgements is indicated by
`arrows labeled S7 in FIG. 2. Alternatively, if the originating
`switching center MSCA receives a User Position Request
`Not Acknowledged message from the HLR (indicating that
`position requests are barred for the remote user), that mes-
`sage is sent (one time only) back to the originating terminal
`MA, OSS or PSTN.
`By maintaining current position data in the VLRs, and by
`monitoring registrations and request barring/unbarring at the
`HLR, the above described technique provides efficient trans-
`mission of position data, on a per request basis, with a
`minimum of system traffic. As noted above, the technique
`can be used, for example, to quickly locate terminals for
`purposes of system maintenance or to find lost or injured
`individuals in emergency situations.
`According to embodiments of the invention, a system user
`can (e.g., for purposes of security or privacy) bar position
`requests by others. FIG. 3 depicts steps in an exemplary
`method by which a system user can do so.
`A user registered as an originating user on the mobile
`terminal MA inputs an appropriate feature code (e.g., a
`character sequence)
`indicating whether User Position
`Requests shall be barred or unbarred for his own User ID.
`Thereafter, a Barring Request or an Unbarring Request, as
`appropriate, is sent to the local switching center MSCA, as
`is indicated by an arrow labeled $10 in FIG. 3.
`Upon receiving the Barring or Unbarring Request from
`the mobile terminal MA, the switching center MSCA for-
`wards the Request on to the system HLR. Forwarding of the
`request to the HLR is indicated by an arrow labeled $20 in
`FIG. 3. Upon receiving the Request, the HLR updates the
`User Register within the HLR for the user who is registered
`as originating user on the terminal (again, see the above
`cited US. patent application Ser. No. 08/585,149) and sends
`a Barring or Unbarring Request Acknowledgment, as
`appropriate, back to the originating switching center MSCA
`(as is indicated by an arrow labeled S30 in FIG. 3).
`Thereafter, the switching center MSCA forwards the Request
`Acknowledgment to the terminal MA (as indicated by an
`arrow labeled S40 in FIG. 3), and the Barring or Unbarring
`Request process is complete.
`In addition to a user being able to Bar and Unbar Position
`Requests, an OSS system can also be used to Bar and Unbar
`Position Requests for system users. To do so, an OSS
`operator can input a command or feature code indicating that
`position requests for a particular riser ID are to be barred or
`unbarred, as desired. An OSS Barring Request or OSS
`Unbarring Request, as appropriate, is sent to the switching
`center to which the OSS is connected, and the switching
`center forwards the request on to the system HLR. Upon
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`US 6,466,788 B1
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`receiving the request, the HLR updates the User Register in
`the HLR for the user indicated in the request and sends an
`OSS Barring or Unbarring Request Acknowledgment back
`to the switching center. Thereafter,
`the switching center
`forwards the Request Acknowledgment back to the OSS,
`and the OSS Barring/Unbarring Request process is com-
`plete.
`FIG. 4 provides a table listing each of the various
`messages, and associated parameters, which is described
`above with respect
`to the exemplary embodiments. As
`shown, the Position Information message includes a Termi-
`nal ID and a set of X—Y—Z location coordinates. The User
`
`Position Request message includes a Feature Code and a
`User ID, and the User Position Request Acknowledged
`message includes a Terminal ID, a set of X-Y—Z coordinates
`and an Originating/Terminating caller indicator or flag. The
`Terminal Position Request message includes a Feature Code
`and a User ID, and the Terminal Position Request Acknowl-
`edged message includes a Terminal ID and a set of X-Y-Z
`coordinates. The OSS Barring Request and the OSS Unbar-
`ring Request messages include a Feature Code and a User
`ID, whereas the Barring Request and Unbarring Request
`messages (from a user) include a Feature Code only (the
`User ID is presumed to be that of the requester). As shown
`in FIG. 4, the User Position Request Not Acknowledged,
`Barring Request Acknowledged, Unbarring Request
`Acknowledged, OSS Barring Request Acknowledged and
`OSS Unbarring Request Acknowledged messages do not
`require parameters.
`The above described embodiments of the invention pro-
`vide efficient transmission of position data, on a per request
`basis, with a minimum of system traffic. The disclosed
`techniques can be used, for example,
`to quickly locate
`terminals for purposes of system maintenance or to find lost
`or injured individuals in emergency situations.
`Those skilled in the art will appreciate that the present
`invention is not limited to the specific exemplary embodi-
`ments which have been described herein for purposes of
`illustration and that numerous alternative embodiments are
`
`also contemplated. The scope of the invention is therefore
`defined by the claims appended hereto, rather than the
`foregoing description, and all equivalents which are consis-
`tent with the meaning of the claims are intended to be
`embraced therein.
`What is claimed is:
`
`1. A method of requesting and obtaining user position
`information in a wireless communications system, the sys-
`tem including a plurality of user terminals, at least one
`mobile switching center and a home location register, and
`the method comprising the steps of:
`sending terminal position information from the riser ter-
`minals to mobile switching centers with which the user
`terminals are registered;
`storing the terminal position information in visiting loca-
`tion registers of the receiving mobile switching centers;
`entering a feature code and a user identification code at a
`requesting terminal, the feature code and user identi-
`fication code indicating a request for position informa-
`tion regarding a remote system user associated with the
`user identification code;
`sending a user position request message and the user
`identification code from the requesting terminal to a
`mobile switching center with which the requesting
`terminal is registered;
`forwarding the user position request message from the
`mobile switching center to the home location register;
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`determining, at the home location register, which user
`terminals the remote system user is registered with;
`sending a terminal position request message and the user
`identification code to each mobile switching center
`where the remote user is registered on a terminal;
`retrieving, for each terminal with which the remote user
`is registered,
`terminal position information from a
`visiting location register;
`sending, for each terminal with which the remote user is
`registered, a terminal position request acknowledged
`message, a terminal identification code and retrieved
`terminal position information to the home location
`register; and
`forwarding at least one of the terminal position request
`acknowledged messages from the home location reg-
`ister to the requesting terminal.
`2. The method of claim 1, wherein, prior to determining
`which user terminals the remote system user is registered
`with, a determination is made, at the home location register,
`whether position information requests for the remote user
`are barred.
`3. The method of claim 2, wherein, for barred position
`information requests, a user position request not acknowl-
`edged message is sent from the home location register to the
`mobile switching center with which the requesting terminal
`is registered, and wherein the user position request not
`acknowledged message is forwarded from the mobile
`switching center to the requesting terminal.
`4. The method of claim 1, wherein said step of sending a
`terminal position request acknowledged message from the
`home location register to the requesting terminal includes
`the steps of:
`supplementing the terminal position request acknowl-
`edged message by adding, at the home location register,
`a parameter indicating whether the remote user is
`registered as an originating or a terminating user on the
`terminal
`to which the terminal position request
`acknowledged message corresponds;
`forwarding the supplemented terminal position request
`acknowledged message from the home location register
`to the mobile switching center with which the request-
`ing terminal is registered; and
`forwarding the supplemented terminal position request
`acknowledged message from the mobile switching cen-
`ter to the requesting terminal.
`5. The method of claim 1, wherein a user terminal
`includes a global positioning system receiver, and wherein
`said step of sending terminal position information includes
`the step of periodically transmitting position coordinates
`from the user terminal to a mobile switching center with
`which the user terminal is registered.
`6. The method of claim 1, wherein a user terminal
`computes position coordinates based on at least one timing
`advance parameter received from at least one base station in
`the wireless communications system, and wherein said step
`of sending terminal position information includes the step of
`periodically transmitting position coordinates from the user
`terminal to a mobile switching center with which the user
`terminal is registered.
`7. The method of claim 1, wherein said step of sending
`terminal position informati