United States Patent [19]
`Houde et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US005623532A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,623,532
`Apr. 22, 1997
`
`[54] HARDWARE AND DATA REDUNDANT
`ARCHITECTURE FOR NODES IN A
`COMMUNICATIONS SYSTEM
`
`[75]
`
`Inventors: Michel Houde, St. Laurent; Luc
`Mayrand, Pierrefouds, both of Canada
`
`[73] Assignee: Telefonaktiebolaget LM Ericsson,
`Stockholm, Sweden
`
`[21] Appl. No.: 372,074
`
`[22] Filed:
`
`Jan. 12, 1995
`
`Int. Cl.6
`................................ H04Q 7/24; H04Q 7/34
`[51]
`[52] U.S. Cl .................................. 379/58; 379/59; 379/60;
`455/33.1
`[58] Field of Search .................................. 379/58, 59, 60,
`379/221, 207, 317; 455/33.1, 33.2; 395/441,
`439, 200.05, 200.15; 3641228.3
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,278,890
`5,289,179
`5,406,504
`5,526,507
`5,555,430
`
`1/1994 Beeson, Jr. et al. ...................... 379/57
`2/1994 Beeson, Jr. et al. .................... 340/826
`4/1995 Denisco et al .......................... 364/580
`6/1996 Hill ......................................... 395/441
`9/1996 Gephardt et al ........................ 395/800
`
`FOREIGN PATENT DOCUMENTS
`
`W093/25051 12/1993 Sweden .
`W094/23506 10/1994 Sweden .
`
`OTHER PUBLICATIONS
`
`Satyanarayanan, Accessing information on demand at any
`location mobile information access, IEEE. Feb. 1996.
`
`Primary Examiner-Dwayne D. Bost
`Assistant Examiner-Nay Aung Mavng
`Attorney, Agent, or Firm-Jenkins & Gilchrist, P.C.
`
`[57]
`
`ABSTRACT
`
`A mobile switching center including multiple home location
`register platforms presented in varying configurations and
`connected to a network through a set of signal transfer
`points. In a master/slave configuration, a master platform is
`given primary responsibility for handling network service
`request messages, and dynamic data affecting messages are
`copied to a slave platform in order to maintain data integrity
`therein in the event the master fails and the slave must take
`over for the master. In a load sharing configuration, each
`platform is given primary responsibility for handling net(cid:173)
`work service request messages of its "own" subscribers, and
`dynamic data affecting messages are copied between the
`platforms in order to maintain data integrity therein in the
`event one of the platforms fails and the remaining functional
`platforms must take over for the failed platform in addition
`to serving its own subscribers. The signal transfer points
`function to automatically and transparently route service
`requests to the platforms for handling in accordance with the
`configurations and platform operating status. The disclosed
`platform configurations are applicable to data base systems
`in particular and, in general, to any node of a data commu(cid:173)
`nications system.
`
`40 Claims, 5 Drawing Sheets
`
`44
`
`62
`
`50 ------------------------1
`.,._......._-H~ MASTER ~......&...----4~
`HLR
`32.
`
`STP
`3IJ.
`
`NElWORK
`3.6.
`
`48
`
`46
`
`STP
`~
`
`56
`
`64
`
`48
`
`52
`SLAVE
`HLR
`34.
`____________________ __j.r1B'
`
`I
`
`Pet., Exh. 1009, p. 1
`
`

`
`U.S. Patent
`
`Apr. 22, 1997
`
`Sheet 1of5
`
`5,623,532
`
`22
`
`PSTN a..--...i
`
`12.
`
`H
`
`Fig.1
`
`(PRIORART)
`
`10
`
`44
`
`NElWORK
`36_
`
`48
`
`46
`
`50 r------------------------
`62
`M-1.-...i MASTER __._..__a.i
`HLR
`32
`
`48
`
`52
`
`64
`
`56
`
`'
`_____________________ j_r-18'
`
`Fig.2
`
`44
`
`50 ;------------------------;
`.
`.
`:
`:
`:
`:
`1
`..i FIRST W-i-
`~---+-1
`.L..-..i
`HLR
`32!.
`
`STP1
`3fl
`
`NElWORK
`36_
`
`48
`
`46
`
`120
`52
`
`64
`
`STP2
`4ll
`
`Fig.6
`
`Pet., Exh. 1009, p. 2
`
`

`
`U.S. Patent
`
`Apr. 22, 1997
`
`Sheet 2 of 5
`
`5,623,532
`
`END
`Fig.3
`
`Pet., Exh. 1009, p. 3
`
`

`
`U.S. Patent
`
`Apr. 22, 1997
`
`Sheet 3 of 5
`
`5,623,532
`
`98
`
`100
`
`102
`
`104
`
`106
`
`108
`
`110
`
`112
`
`114
`
`116
`
`118
`
`Disconnect
`HLR
`
`Reload With Last
`Back-up and Dur11J
`
`Transfer Dynanic
`Data
`
`Reconfigure HLRs
`
`Reconnect HLR
`
`( END )
`Fig.SA
`
`Flag Interim ijynamic
`Data
`
`Reload With Last
`Back-up and Dur11J
`
`Handle Messages During
`Back-up HLR Faaure
`
`Transfer Flagged
`Dynanic Data Only
`
`Reconfigure HLRs
`
`Reconnect HLR
`
`END
`Fig.58
`
`156
`
`158
`
`160
`
`162
`
`164
`
`166
`
`168
`
`170
`
`172
`
`174
`
`176
`
`Disconnect
`HLR
`
`Reload With Last
`Back-up
`
`Connect HLRs
`Together
`
`Transfer Dynanic Data
`
`Reconnect HLRs
`to Network
`
`END
`Fig.SA
`
`Disconnect
`HLR
`
`Reload Wdh Last
`Back-up
`
`Transfer Subscri>er
`Data
`
`Connect HLRs
`T99ether
`
`Transfer Ont/ M>dified
`Dyananic Data
`
`Reconnect HLRs
`
`END
`Fig.SB
`
`Pet., Exh. 1009, p. 4
`
`

`
`U.S. Patent
`
`Apr. 22, 1997
`
`Sheet 4 of 5
`
`5,623,532
`
`EstabflSh Load Sharilg
`Configuration
`
`Route lnconing Messages
`to Designated HLR
`
`Forward Received Message
`to Appropriate Application
`
`Generate Response
`
`Forward Response Back
`, to Network
`
`NO
`
`Copy Message
`
`Direct Copied Message
`to OtherHLR
`
`Forward Copied Message
`to Appropriate Application
`
`Update Data
`
`124
`
`126
`
`128
`
`130
`
`132
`
`136
`
`138
`
`140
`
`Acknowledge Message
`
`144
`
`END
`Fig.7
`
`146
`
`148
`
`150
`
`152
`
`154
`
`Detedion of HLR Fail11e
`
`Route lnconing Messages
`to Back-up HLR
`
`Forward Received Message
`to Appropriate Application
`
`Generate Response
`
`Forward Response Back
`to Network
`
`END
`Fig.8
`
`Pet., Exh. 1009, p. 5
`
`

`
`U.S. Patent
`
`Apr. 22, 1997
`
`Sheet 5 of 5
`
`5,623,532
`
`r------............. _ .. ___ ............. -
`
`'
`
`~
`
`- Jill - 68.
`
`~
`
`38!.
`
`..
`'·
`
`-
`
`'
`
`..
`
`NETWORK
`
`!
`! .
`! .
`!
`!
`as!. ~
`!
`I . . ~
`
`12Di
`
`£r. ~ 121i
`
`-"'-"' ~ -
`
`Fig.10
`
`! 122~
`I
`·------·--·---·---....................... .
`
`I
`
`'
`
`Pet., Exh. 1009, p. 6
`
`

`
`5,623,532
`
`1
`HARDWARE AND DATA REDUNDANT
`ARCIDTECTURE FOR NODES IN A
`COMMUNICATIONS SYSTEM
`
`BACKGROUND OF THE INVENTION
`
`1. Technical Field of the Invention
`The present invention relates to communications systems
`and, in particular, to an architecture for providing both
`hardware and data redundancy to individual nodes in a
`communications system. The present invention is particu(cid:173)
`larly applicable to providing such redundancy for system
`nodes utilizing data bases, for example, mobile telephone
`network home or visitor location registers.
`2. Description of Related Art
`The mobile switching center of a mobile telephone net(cid:173)
`work includes a plurality of data bases which are consulted
`by the center during the establishment of a telephone con(cid:173)
`nection within the mobile telephone network. These data
`bases include a home location register and a visitor location
`register which comprise platforms for storing in a data base
`format both static (i.e., non-changing) and dynamic (i.e.,
`changing) data related to the subscribers.
`The static data stored in the registers includes, for
`example, a list of identifiers for cooperating exchanges
`interconnected with the mobile switching center, an identi(cid:173)
`fication of the services (like transfer on busy) permitted for
`use by each subscriber, and the parameters associated with
`such services (like a fixed C number). The foregoing
`examples of data, as well as other types of static data, are
`entered into the data base and may be modified only by the
`administrator for the registers. The dynamic data on the
`other hand includes, for example, subscriber defined service
`data (like a variable C number), mobile station location data
`(with respect to both the mobile switching center and the
`base station), and mobile station activity data (like mobile
`station on/off status). This data, as well as other types of
`dynamic data, are entered into the data base and may be
`modified at any time by the subscriber, by the mobile station,
`or by the network in a manner that is transparent to the
`subscriber.
`Because the home location register contains the data
`needed to establish a telephone connection within the mobile
`telephone network, the failure of the platform for the home
`location register will deprive a substantial number of sub(cid:173)
`scribers of the capability of receiving or originating a
`telephone call. It is further important to remember that it is
`not only the platform, but also the static and dynamic data
`stored thereon, that are critical to the establishment of the
`telephone connection. Accordingly, there is a need for a
`system capable of handling a home location register plat(cid:173)
`form failure from not only the hardware point of view, but
`also with respect to maintaining the integrity of the static and
`dynamic data stored thereon. Such a system will have
`applications in any data base system or communications
`system node wherein redundancy is required.
`
`SUMMARY OF THE INVENTION
`
`10
`
`25
`
`2
`with the multiple platforms being presented in varying
`configurations.
`In one embodiment of the present invention, the multiple
`platforms are paired in a master/slave relationship and
`connected to a network. All network users are redundantly
`connected for communications to both platforms through
`signal routers that render the existence of the multiple
`platforms transparent to the network. The master platform is
`given the primary responsibility for handling (i.e., process-
`ing and responding to) data communications. Thus, all data
`communications are routed by the signal routers to the
`master platform. The slave platform is copied to by the
`master platform with the communications that when pro(cid:173)
`cessed result in the modification of data stored in the master
`15 platform. Copying of such communications to the slave
`platform maintains data integrity across the data communi(cid:173)
`cations system and gives the slave platform the information
`necessary to take over processing tasks from the master
`platform in the event of a failure. When a master platform
`20 failure occurs and is detected, the signal routers automati(cid:173)
`cally and transparently route data communications to the
`slave platform instead of to the master platform for handling.
`In another embodiment of the present invention, each one
`of a number of included platforms is assigned responsibility
`for only a portion of the total user population. Thus, the
`multiple platforms share processing load responsibilities for
`the overall user load. At the same time, however, all network
`users are redundantly connected for communications
`through the signal routers to each of the platforms. The data
`communications that when processed result in the modifi(cid:173)
`cation of data stored in a platform are copied between the
`platforms. Copying of such communications between plat(cid:173)
`forms maintains data integrity across the data communica-
`tions system and gives each platform access to the informa(cid:173)
`tion necessary to take over processing tasks from another
`platform in the event of a platform failure. When a platform
`failure occurs and is detected, the signal routers automati(cid:173)
`cally and transparently route data communications instead to
`one of the remaining functional platforms for handling.
`The system and method of the pre~ent invention are
`especially useful in providing hardware and data redundancy
`for the data bases comprising the location registers (home or
`visitor) maintained in the mobile switching center of a
`45 mobile telephone system. It is in connection with this
`particular application that the preferred embodiments of the
`present invention will be described. However, as the system
`and method of the present invention are applicable to any
`node in a data communications system and/or to any data
`50 base system wherein redundancy as to both hardware and
`data is needed or useful, it will be understood that the
`description of present invention in the context of redundant
`home location registers provided herein is by way of expla(cid:173)
`nation of the invention rather than of limitation of the scope
`55 of the invention.
`
`30
`
`35
`
`40
`
`An architecture is presented for providing hardware and
`data redundancy to individual nodes in a data communica(cid:173)
`tions system, along with a method for redundant data
`handling communications by the individual nodes. The
`method further provides for the restoration of accurate·data 65
`following a node failure. This architecture utilizes multiple
`platforms in each node of the data communications system,
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A more complete understanding of the method and appa-
`60 ratus of the present invention may be had by reference to the
`following Detailed Description when taken in conjunction
`with the accompanying Drawings wherein:
`FIG. 1 is a block diagram of a conventional mobile
`switching center including a home location register;
`FIG. 2 is a block diagram of a first embodiment of the
`present invention comprising redundant home location reg(cid:173)
`ister platforms presented in a master/slave configuration;
`
`Pet., Exh. 1009, p. 7
`
`

`
`5,623,532
`
`3
`FIG. 3 is a flow diagram illustrating the processing steps
`for handling received service request messages in the system
`of FIG. 2;
`FIG. 4 is a flow diagram illustrating the processing steps
`for handling a master home location register platform failure
`and any service request messages received thereafter in the
`system of FIG. 2;
`FIGS. SA and SB are flow diagrams illustrating the
`processing steps of two methods for restoring subscriber
`data in a failed home location register platform in the system
`of FIG. 2;
`FIG. 6 is a block diagram of a second embodiment of the
`present invention comprising redundant home location reg(cid:173)
`ister platforms presented in a load sharing configuration;
`FIG. 7 is a flow diagram illustrating the processing steps
`for handling received service request messages in the system
`of FIG. 6;
`FIG. 8 is a flow diagram illustrating the processing steps
`for handling a home location register platform failure and
`any service request messages received thereafter in the
`system of FIG. 6;
`FIGS. 9A and 9B are flow diagrams illustrating the
`processing steps for restoring subscriber data in a failed
`home location register platform in the system of FIG. 6; and
`FIG. 10 is a block diagram of a load sharing configuration
`for linking more than two redundant home location register
`platforms.
`
`DETAILED DESCRIPTION OF EMBODIMENTS
`
`Referring now to FIG. 1, there is shown a block diagram
`of a conventional mobile switching center 10 comprising an
`exchange 12 and a mobile telephony subsystem 14. The
`mobile telephony subsystem 14 includes a plurality of data
`bases 16 for storing both static (i.e., non-changing) and
`dynamic (i.e., changing) data related to the subscribers of the
`mobile telephone system. These data bases comprise a home
`location register 18 and a visitor location register 20 that are
`consulted by the center during the establishment of a tele(cid:173)
`phone connection within the mobile telephone network and
`through a base station 26 to a subscriber mobile station 24.
`The exchange 12 is further connected to the public switched
`telephone network 22. The home location register 18 and
`visitor location register 20 also process service request
`messages from the components of the telephone system.
`Examples of commonly responded to service request mes(cid:173)
`sages are: Registration-Notification; Registration-Cancella(cid:173)
`tion; and Service-Profile-Request.
`The static data stored in the data bases 16 includes, for
`example, a list of identifiers for cooperating exchanges
`interconnected with the mobile switching center 10, an
`identification of the services (like transfer on busy) permit(cid:173)
`ted for use by each subscriber, and the parameters associated
`with such services (like a fixed C number). This data, as well
`as other types of static data known to those skilled in the art,
`is entered into the data bases 16 and may be modified only
`by a data base administrator 28 provided within the mobile
`switching center 10. The dynamic data, on the other hand,
`includes, for example, subscriber defined service data (like
`a variable C number), mobile station 24 location data (with
`respect to both the mobile switching center 10 and the base
`station 26), and mobile station activity data (like mobile
`station on/off status). This data, as well as other types of 65
`dynamic data known to those skilled in the art, is entered
`into the data bases 16 and may be modified at any time by
`
`25
`
`30
`
`4
`the subscriber, by the mobile station 24, or by the network
`22 in a manner transparent to (i.e., without the knowledge or
`participation of) the subscriber.
`The mobile telephony subsystem 14 further includes an
`authentication center 30 that provides authentication param(cid:173)
`eters for preventing subscribers from falsely assuming the
`identity of another subscriber, and encryption parameters for
`encrypting transmitted information when necessary. Further
`detailed description of the functional operation and configu-
`10 ration of the conventional mobile switching center 10 or its
`component parts is deemed unnecessary as such information
`is well known to those skilled in the art.
`Referring now to FIG. 2, there is shown a block diagram
`of a first embodiment of the present invention wherein the
`15 mobile switching center includes redundant home location
`register (HLR) platforms 18' comprising a master home
`location register platform 32 and a slave home location
`register platform 34. The home location register platforms
`32 and 34 include alarms 42 and interface with the network
`20 36 of the mobile switching center through a pair of signal
`transfer points (STPs) 38 and 40. It should be recognized
`that the signal transfer points 38 and 40 render the existence
`of multiple home location register platforms 32 and 34
`transparent to the network 36. By "transparent" it is meant
`that the network 36 is unaware of either the existence of
`multiple home location register platforms 32 or 34 or of
`which platform is responding to network service request
`messages.
`The network 36 is connected to the first signal .transfer
`point 38 via communications link 44, and is connected to the
`second signal transfer point 40 via communications link 46.
`Another communications link 48 is provided between the
`first and second signal transfer points 38 and 40. The master
`35 home location register platform 32 is connected to the first
`signal transfer point 38 via communications link SO, and is
`connected to the second signal transfer point 40 via com(cid:173)
`munications link S2. Similarly, the slave home location
`register platform 34 is connected to the first signal transfer
`40 point 38 via communications link S4, and is connected to the
`second signal transfer point 40 via communications link S6.
`The master home location register platform 32 and the slave
`home location register platform 34 are further connected to
`a home location register administrator S8 through an inter-
`45 face 60 and a pair of communications links 62 and 64. The
`interface 60 facilitates concurrent administrator S8 commu(cid:173)
`nications access to both the master and slave home location
`register platforms 32 and 34. Although shown as single
`links, the communications links shown in FIG. 2 may
`50 comprise multiple parallel links as necessary.
`The master home location register platform 32 is given
`the primary responsibility for handling (i.e., processing and
`responding to) network communications service request
`messages. In operation of the system, as will be described in
`55 more detail herein, all service request messages are routed
`by the signal transfer points 38 and 40 to the master home
`location register platform 32. The slave home location
`register platform 34 is copied to by the master home location
`register platform 32 using the signal transfer points 38 or 40
`60 with relevant messages in order to maintain dynamic data
`integrity and give the slave platform access to the informa(cid:173)
`tion necessary to take over from the master platform in the
`event of a platform failure.
`Reference is now made to FIGS. 2 and 3, wherein FIG. 3
`is a flow diagram illustrating the processing steps for han(cid:173)
`dling received service request messages by the master and
`slave home location register platforms 32 and 34, respec-
`
`Pet., Exh. 1009, p. 8
`
`

`
`5,623,532
`
`5
`tively, in the system of FIG. 2. Each service request message
`includes a direct point code identifying the home location
`register platform 32 or 34 designated for handling the
`message. In the master/slave configuration of FIG. 2, the
`master home location register platform 32 preferably
`handles all messages unless it is determined that the master
`platform is not serving the network 36 (i.e., there is a
`platform failure). Accordingly, in step 66, the network
`administrator S8 configures the home location register plat-
`~~:~ ~e :~s~! ~~~e~:~!~[~~~~~i~t~~~f~~~:n3~~odse:~~ 10
`
`all network service request messages.
`In response to the receipt of a message from the network
`36, the signal transfer points 38 and 40 then route the
`message via alternate routing paths only to the master home
`location register platform 32 (step 68). For example, when 15
`the first signal transfer point 38 receives the message over
`link 44, it first attempts to route the message over commu(cid:173)
`nications link SO. If this fails, the first signal transfer point
`38 passes the message to the second signal transfer point 40
`via link 48 for transmission to the master home location 20
`register platform 32 over communications link S2. Two
`paths are similarly provided to the master home location
`register platform 32 from the second signal transfer point 40
`(link S2 or links 48 and SO) for carrying messages received
`over link 46. Thus, redundant/alternate communications 25
`paths are provided from the signal transfer points 38 and 40
`for carrying messages to the master home location register
`platform 32. This data link redundancy provides alternative
`message paths and addresses concerns over potential com(cid:173)
`munications link failures that would otherwise prevent the 30
`network 36 from accessing an operating master home loca(cid:173)
`tion register platform 32.
`Upon receipt of the message, the master home location
`register platform 32 forwards the message to the appropriate
`application for processing (step 70). The application pro(cid:173)
`cesses the message and generates an appropriate response
`(step 72). This response is then forwarded by the master
`home location register platform 32 back to the network 36
`via the signal transfer points 38 or 40 (step 74).
`The master home location register platform 32 further
`makes a determination as to whether the received message
`should also be sent to the slave home location register
`platform 34 (step 76). This decision is made based on
`whether the processing of the message in the application will
`result in a modification of the stored dynamic data. If a 45
`modification in the stored dynamic data will occur, the
`master home location register platform 32 copies the mes(cid:173)
`sage (step 78) and directs the copied message back through
`the signal transfer points 38 or 40 in accordance with routing
`instructions to the slave home location register platform 34 50
`(step 80). The slave home location register platform 34 then
`responds like the master register platform by forwarding the
`message to the appropriate application (step 82) resulting in
`a modification of the dynamic data stored therein and the
`generation of a response (step 83). In this case, however, the 55
`generated response is ignored (step 84) by the slave platform
`and not sent to the network 36 because the slave home
`location register platform 34 has not been designated by the
`administrator S8 to service network requests.
`Following processing of the received message in accor(cid:173)
`dance with the steps described above, both home location
`register platforms 32 and 34 include the same stored
`dynamic data. In the event the master home location register
`platform 32 should thereafter fail, the slave home location
`register platform 34 possesses all the dynamic data neces(cid:173)
`sary to transparently take over responding to network ser(cid:173)
`vice requests.
`
`6
`Reference is now made to FIGS. 2 and 4, wherein FIG. 4
`is a flow diagram illustrating the processing steps for han(cid:173)
`dling the failure of a master home location register platform
`32, and for the handling by the slave home location register
`platform 34 of any service requests received thereafter.
`Following detection of a failure of the master home location
`register platform 32 by either or both the administrator S8 or
`the signal transfer points 38 and 40 (step 86), the adminis-
`trator reconfigures the home location register platforms 32
`and 34 by now designating the slave home location register
`platform 34 to serve all network requests (step 88).
`In response to the receipt of a message from the network
`36, the signal transfer points 38 and 40 automatically and
`transparently route the message to the slave home location
`register platform 32 (step 90). In this connection, "transpar(cid:173)
`ently" again means that the network 36 is unaware of either
`the existence of multiple home location register platforms 32
`or 34 or of which platform is responding to the message.
`Upon receipt of the message, the slave home location
`register platform 34 forwards the message to the appropriate
`application (step 92). The application then generates a
`response (step 94), and the response is forwarded back to the
`network 36 via the signal transfer points 38 and 40 (step 96).
`With respect to the handling of a received message by the
`signal transfer points 38 and 40 after a failure of the master
`home location register platform 32, if the first signal transfer
`point 38 receives the message over link 44, it first attempts
`to route the message over communications link 54. If this
`fails, the first signal transfer point 38 passes the message to
`the second signal transfer point 40 via link 48 for transmis(cid:173)
`sion to the slave home location register platform 34 over
`communications link S6. Two paths are similarly provided to
`the slave home location register platform 34 from the second
`signal transfer point 40 (link S6 or links 48 and S4) for
`carrying messages received over link 46. Thus, redundant/
`35 alternate communications paths are provided from the signal
`transfer points 38 and 40 for carrying messages to the 'slave
`home location register platform 34 following master plat(cid:173)
`form failure. This data link redundancy provides alternate
`message paths and addresses concerns over potential com-
`40 munications link failures that would otherwise prevent the
`network 36 from accessing an operating slave home location
`register platform ~4.
`It is possible for messages to be received from the
`network 36 and transmitted automatically by the signal
`transfer points 38 and 40 to the slave home location register
`platform 34 (following master platform failure) before the
`administrator S8 has had a chance to reconfigure the system.
`In that case, the messages are discarded by the slave home
`location register platform 34 upon receipt because the slave
`platform has not yet been designated to handle network
`service requests. These discarded messages must be retrans(cid:173)
`mitted by the network 36. Discovery of the discarded
`messages is generally made when the designated time-out
`for the message expires without network reception of a
`response from the home location register.
`Reference is now made to FIGS. 2 and SA, wherein FIG.
`SA is a flow diagram illustrating the processing steps of one
`method for restoring accurate and up-to-date subscriber data
`in the failed master home location register platform 32 in the
`system of FIG. 2. The subscriber data that is updated in the
`master home location register platform 32 comprises prima(cid:173)
`rily the dynamic data which was affected by the interim
`handling of service requests by the slave home location
`register platform 34.
`The master home location register platform 32 is first
`disconnected from the signal transfer points 38 and 40 (step
`
`65
`
`60
`
`Pet., Exh. 1009, p. 9
`
`

`
`5,623,532
`
`10
`
`40
`
`8
`7
`in the system of FIG. 2. The home location register plat(cid:173)
`98). The master home location register platform 32 is then
`forms 32' and 34' include alarms 42 and interface with the
`reloaded with its last back-up and subscriber data dump
`network 36 of the mobile switching center through a pair of
`(step 100). Next, dynamic data is transferred from the slave
`signal transfer points 38 and 40. Thus, even though they are
`home location register platform 34 to the master home
`normally serviced by only a designated one of the platforms
`location register platform 32 (step 102) by loading the slave
`32' or 34', all subscribers are connected to both platforms
`platform's last subscriber data dump into the master plat(cid:173)
`through the signal transfer points 38 and 40. In this connec(cid:173)
`form, dumping the slave platform's dynamic data, and
`tion, it should be recognized that the signal transfer points 38
`loading the dumped data into the master platform. The
`and 40 render the existence of multiple home location
`administrator 58 then reconfigures the home location regis(cid:173)
`ter platforms 32 and 34 by again designating the master
`register platforms 32' and 34' transparent to the network 36.
`home location register platform 32 to service all network
`By "transparent" it is meant that the network 36 is unaware
`request messages (step 104). Restoration concludes when
`of either the existence of multiple home location register
`the master home location register platform 32 is reconnected
`platforms 32' or 34' or of which platform is responding to
`network service request messages.
`to the signal transfer points 38 and 40 (step 106). Preferably,
`at a time prior to beginning platform handling of network
`The network 36 is connected to the first signal transfer
`15 point (STPl) 38 via communications link 44, and is con(cid:173)
`service requests, the master home location register platform
`nected to the second signal transfer point (STP2) 40 via
`32 propagates an "Unreliable-Roamer-Data-Directive" to
`communications link 46. Another communications link 48 is
`acquire and store accurate mobile station 24 locations. A
`provided between the first and second signal transfer points
`data dump from the master home location register platform
`38 and 40. The first home location register platform 32' is
`32 may also be performed at this time in case the platform
`20 connected to the first signal transfer point 38 via commu(cid:173)
`should immediately fail again.
`nications link SO, and is connected to the second signal
`In FIG. SB, another method for restoring the subscriber
`transfer point 40 via communications link S2. Similarly, the
`data of the failed master home location register platform 32
`second home location register platform 34' is connected to
`is shown. This method is particularly applicable.to handling
`the first signal transfer point 38 via communications link S4,
`situations where the slave home location register platform 25
`and is connected to the second signal transfer point 40 via
`34 fails before the restoration of the master platform 32 is
`communications link S6. The first home location register
`completed. In accordance with this method, when the slave
`platform 32' and the second home location register platform
`home location register platform 34 takes over for a failed
`34' are further connected to a home location register admin(cid:173)
`master home location register platform 32, all dynamic data
`istrator S8 through an interface 60 and a pair of communi(cid:173)
`in the slave platform modified by the processing of a 30
`cations links 62 and 64. The interface 60 facilitates concur-
`network service request during the interim period is marked
`rent administrator S8 communications access to both the
`(flagged) as new data (step 108). When the master home
`home location register platforms 32' and 34'. A pair of
`location register platform 32 is brought back on-line, the
`communications links 120 and 122 connect between the first
`master platform is reloaded with its last back-up and sub(cid:173)
`and second home location register platforms 32' and 34'.
`scriber data dump (step 110). If the slave platform 34 then 35
`Although shown as single links, the communications links
`fails prior to restoration of dynamic data, the master plat(cid:173)
`shown in FIG. 6 may comprise multiple links as necessary.
`form 32 handles service request messages as best as possib