United States Patent [19]
`La Porta et al.
`
`[54] METHOD AND SYSTEM FOR DISTRIBUTED
`CONTROL IN WIRELESS CELLULAR AND
`PERSONAL COMMUNICATION SYSTEMS
`_
`[75] Inventors‘ gr‘h?smi'alc‘z Pam’ Tlzloniwood’
`Matawan' Malgltlhirz’lcleeraarzjigvan
`Atlantic
`ghlands both of?“ ’
`’
`'
`'
`.
`_
`.
`.
`[73] Asslgnec' lb‘l'ujcent Technologles Inc" Murray H111’
`'
`'
`
`[21] Appl. No.: 324,427
`[22] Filed_
`Oct 17 1994
`I 6
`’
`[51] Int. Cl. ........................... .. H04M 11/00; H04Q 7/22
`[52] US. Cl. ........................ .. 370/312; 370/331; 370/338;
`370/390; 370/396; 370/522; 455/433
`[58] Field of Search ................................ .. 379/58. 59. 60.
`379/63. 93~ 94_ 157_ 158‘ 165_ 201; 455/33_1_
`33.2’ 531~ 541‘ 54_2_ 561; 370/289_ 270.
`312_ 328_ 329_ 331; 338‘ 357_ 360’ 384;
`385; 389_ 390_ 395_ 396; 400; 401_ 428'~
`'
`'
`522'
`
`[5 6]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`1/1993 Harrison ............................... .. 370/95.1
`5,1s1,200
`1,1994 Beesom In et a1.
`5,278,890
`6,1994 Ken-hue] et a1_ __
`5,319,699
`7/1994 Chang et a1.
`5,329,573
`8/1994 Wang et al. ..
`5,343,512
`5,353,340 10/1994 Kunz .......... ..
`
`
`
`
`
`5,361,396 11/1994 Onoe et al. 5,434,852 7/1995 La Porta et a1. ..
`
`5,473,679 12/1995 La Pona et a1. ..
`5,497,412
`3/1996 Lannen et a1.
`
`US005659544A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,659,544
`Aug. 19, 1997
`
`OTHER PUBLICATIONS
`-
`~
`..
`La Porta, T.F.. and Veeraraghavan. M.. Descriptlon of a
`Functional Signaling Architecture for Broadband Net
`works,” Re rinted from IEEE Communication Society IEEE
`Global Telellommunications Society. Nov. 29-Dec. 2, 1993.
`pp' 10124016
`Mohan, S., and Jain, K. “North American and European
`Standards for Mobile Cormnunications. 'IXvo User Location
`Strategies for Personal Communications Services,” IEEE
`Personal Communications. First Quarter 1994. pp. 42-50.
`Veeraraghavan. M.. and La Porta. T.F.. “Object-oriented
`Analysis of Signalling and Control in Broadband Net
`works,” International Journal of Communication Systems.
`vol. 7, 1994, by John Wiley & Sons. Ltd., pp. 131-147.
`Primary Examiner-—Alpus H. Hsu
`[57]
`ABSTRACT
`
`A system for distributed control in Wireless cellular and
`pcrsonal communication system includes separate Servers
`for performing callcontrol and connection control functions.
`thereby obviating the need for a mobile switching or other
`switch to be anchored for the duration of a call. During a
`registration procedure, visiting location servers track only
`roaming mobiles, rather than tracking both roaming mobiles
`as well as mobiles located in their home network. Direct
`signalling links between servers and base stations. or other
`servers, located in different networks allow roaming mobiles
`to contact their home networks for service at all times.
`thereby obviating the need for passing signalling informa
`mm for imbue? Whe? they .are not involved in a can‘ The use
`of multrcast signalling with asynchronous transfer mode
`sw1tches, perrmts speci?ed channel control functions to take
`place concurrently in channel servers associated with base
`station and switches that form a segment of the route for a
`call. Similarly. speci?ed call control functions are performed
`concurrently with mobile location functions. thereby
`decreasing the delays in setting up a call.
`
`20 Claims, 12 Drawing Sheets
`
`100
`\
`
`NErwoRK1
`
`RoAMER
`170/ CALL
`sERvER
`
`1 01
`\
`180 \
`HOME
`LOCATION
`sERvER
`
`visiToR
`LOCATION /190
`sERvER
`
`110
`
`cLusTER1
`
`CALL
`SERVER
`
`130, CONNECTION
`SERVER
`
`111
`
`150 -’ BASE
`STATION 1
`
`160
`\
`
`END
`
`SYSTEM,
`
`BASE r159
`STATION,
`
`169
`/
`
`_ . _
`
`102
`\
`
`103
`\
`
`NETWORK2 . . NETWOHKmH)
`
`Bright House Networks - Ex. 1042, Page 1
`
`

`
`Bright House Networks - Ex. 1042, Page 2
`
`

`
`U.S. Patent
`
`Aug. 19, 1997
`
`Sheet 2 0f 12
`
`5,659,544
`
`200 -’
`
`MOBILE GENERATES
`REGISTRATION MESSAGE
`I
`20 , BASE STATION RECEIVES
`5
`REGISTRATION MESSAGE
`
`210
`
`IS
`MOBILE LOCATED
`IN ITS HOME
`NETWORK ?
`
`V
`FORWARD REGISTRATION
`INFORMATION TO MOBILE’S
`230 J
`VISITOR LOCATION SERVER
`
`240
`
`DOES
`REGISTRATION
`
`YES
`
`CLUSTER
`CHANGE ‘.7
`
`FORWARD REGISTRATION
`INFORMATION TO MOBILE’S
`220 -/
`HOME LOCATION SERVER
`I
`STORE MOBILE
`225"
`CLUSTER MAPPING
`
`NO
`
`STORE MOBILE
`/ 245
`CLUSTER MAPPING
`
`FORWARD REGISTRATION
`INFORMATION TO MOBILE’S
`250 f
`HOME LOCATION SERVER
`I
`STORE NETWORK
`IDENTIFIER AND VISITOR
`LOCATION SERVER
`255 f
`CORRESPONDING TO
`MOBILE LOCATION
`
`FIG. 2
`
`Bright House Networks - Ex. 1042, Page 3
`
`

`
`US. Patent
`
`Aug. 19,1997
`
`Sheet 3 0f 12
`
`5,659,544
`
`CALLING END SYSTEM
`300/ GENERATES CALL
`ORIGINATION MESSAGE
`I
`305/. BASE STATION RECEIVES
`CALL ORIGINATION MESSAGE
`
`310
`
`IS
`CALLING END
`SYSTEM A
`MOBILE '?
`YES
`
`FIG- 3
`
`}315
`SEND SETUP CALL
`MESSAGE TO CALL
`SERVER IN BASE
`STATION’S CLUSTER
`
`NO
`
`v
`|s
`CALLING
`MOBILE LOCATED
`IN ITS HOME
`NETWORK '2
`
`320
`
`YES
`
`325
`I
`‘
`I
`SEND SETUP CALL
`MESSAGE TO CALL
`SERVER IN BASE
`STATION’S CLUSTER
`.
`
`330
`/
`‘
`SEND SETUP CALL
`AND UPDATE MESSAGES
`TO ROAMER CALL
`SERVER IN MOBILE’S
`HOME NETWORK
`
`335
`I
`STORE MOBILE-TO
`L CALL SERVER MAPPING ‘
`IN BASE STATION FOR
`CALLING MOBILE
`
`Bright House Networks - Ex. 1042, Page 4
`
`

`
`Bright House Networks - Ex. 1042, Page 5
`
`

`
`US. Patent
`
`Aug. 19, 1997
`
`Sheet 5 of 12
`
`5,659,544
`
`CALL SERVER FOR OALLING END SYSTEM
`500/ SENDS A FIND REQUEST TO HOME
`LOCATION SERVER FOR CALLED MOBILE
`+
`J HOME LOCATION SERVER FOR OALLED
`505
`MOBILE REOEIVES FIND REQUEST
`
`507
`
`IS
`CALLED MOBILE
`LOCATED IN ITS HOME
`NETWORK '2
`
`TO FIG- 5B
`
`HOME LOCATION SERVER
`FOR CALLED MOBILE SENDS
`A FIND RESPONSE
`(SPECIFYING THE CALL
`520 _, SERVER, CONNECTION
`SERVER AND GATEWAY
`SWITCH FOR THE CALLED
`MOBILE) TO THE CALL
`SERVER FOR THE
`CALLING END SYSTEM
`
`HOME LOCATION SERVER FOR
`CALLED MOBILE SENDS PAGE
`522 _, REQUEST AND UPDATE MESSAGE
`TO ALL BASE STATIONS IN THE
`CLUSTER IN WHICH CALLED
`MOBILE IS LOCATED
`I,
`EACH BASE STATION IN
`THE OLuSTER GENERATES
`523 ’ PAGE ORDER TO LOCATE
`THE OALLED MOBILE
`I
`IF A BASE STATION REOEIVES
`PAGE RESPONSE, IT SENDS
`PAGE RESPONSE TO HOME
`524 / LOCATION SERVER AND
`STORES MOBILE-TO-OALL
`SERVER MAPPING FOR THE
`OALLED MOBILE
`I
`HOME LOCATION SERVER FOR
`CALLED MOBILE SENDS AN
`526 / UPDATE MESSAGE TO THE
`CONNECTION SERVER FOR
`THE CALLED MOBILE
`
`521
`/
`I
`COMMUNICATE WITH CALL
`SERVER IDENTIFIED IN
`STEP 520 TO INVOKE
`IMPLICIT SERVICES FOR
`THE CALLED END SYSTEM
`
`FIG‘ 5A
`
`Bright House Networks - Ex. 1042, Page 6
`
`

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`Bright House Networks - Ex. 1042, Page 7
`
`

`
`Bright House Networks - Ex. 1042, Page 8
`
`

`
`U.S. Patent
`
`Aug. 19, 1997
`
`Sheet 8 of 12
`
`5,659,544
`
`CONNECTION SERVER RECEIVES A
`700“ SETUP CONNECTIONS MESSAGE
`+
`FIND AN
`705/
`END-TO-END ROUTE
`i
`I
`CONNECTION SERVER SENDS \
`RESERVE CHANNEL
`MESSAGE TO CHANNEL
`710 / SERVERS ASSOCIATED WITH
`BASE STATIONS AND
`SWITCHES IN THE ROUTE
`AND WITHIN ITS DOMAIN
`I
`CHANNEL SERVERS PERFORM '
`712 / CHANNEL RESERVATION
`FUNCTIONS CONCURRENTLY
`I
`SEND RESERVE CHANNEL
`714 I RESPONSES TO THE
`CONNECTION SERVER
`
`720
`f
`/
`CONNECTION SERVER SENDS
`A RESERVE SEGMENT MESSAGE
`TO THE NEXT CONNECTION
`SERVER IN THE ROUTE
`I
`FIND THE SWn-OHES
`REQUIRED TO
`>CONNECTION
`ESTABLISH THE
`ADMISSION
`SEGMENT OF
`ROUTINE
`, THE ROUTE
`722
`I,
`PERFORM THE CONNECTION
`ADMISSION ROUTINE WITH
`RESPECT TO NEXT CONNECTION
`SERVER AND THE ASSOCIATED I
`CHANNEL SERVERS
`{I
`
`I
`_,
`724
`
`FIG. 7
`
`f SEND RESERVE
`726 SEGMENT RESPONSES
`I
`
`‘I
`730* ACCEPT
`CONNECTION
`CONNECTION SERVER SENDS \
`740 / SETUP TRANSLATION
`MESSAGE TO THE
`CHANNEL SERVERS
`I
`CHANNEL SERVERS PERFORM COQEESITJON
`742 , SETUP TRANSLATION
`ROUTINE
`FUNCTIONS CONCURRENTLV
`I
`SEND SETUP
`744 /
`TRANSLATION RESPONSE
`S I
`
`SEND SETUP SEGMENT
`750 / MESSAGE TO THE NEXT
`CONNECTION SERVER
`IN THE ROUTE
`I
`PERFORM THE
`CONNECTION
`SETUP ROUTINE
`WITH RESPECT
`752 CONNE-ICQTEJTNXSERVER
`AND THE
`ASSOCIATED
`CHANNEL SERVERS
`+
`SEND SETUP SEGMENT RESPONSE
`754 -’ TO THE CONNECTION SERVER THAT
`SENT THE SETUP SEGMENT MESSAGE
`I
`
`_/
`
`‘II
`760 _,- SEND SETUP CONNECTIONS RESPONSE TO
`CALL SERVER FOR THE CALLING END SYSTEM
`
`Bright House Networks - Ex. 1042, Page 9
`
`

`
`Bright House Networks - Ex. 1042, Page 10
`
`

`
`US. Patent
`
`Aug. 19, 1997
`
`Sheet 10 Of 12
`
`5,659,544
`
`/ END SYSTEM SENDS A
`900
`RELEASE-ORDER MESSAGE
`V
`BASE STATION SENDS A
`905/ RELEASE-CALL MESSAGE TO
`THE END SYSTEM’S CALL SERVER
`'6
`CALL SERVER SENDS RELEASE-
`910/ CALL MESSAGES TO OTHER CALL
`SERVERS INVOLVED IN THE CALL
`
`'
`
`+
`
`FIG- 9
`
`ONE OF THE CALL SERVERS SENDS
`915/ A RELEASE-CONNECTION MESSAGE TO
`CORRESPONDING CONNECTION SERVER
`I.
`'
`CONNECTION SERVER SENDS \
`DROP-CHANNEL
`920 , MESSAGE TO CHANNEL
`SERVERS IN THE
`SEGMENT OF THE ROUTE
`W'TH'N ‘TS DOM/“N
`+
`CHANNEL SERVERS RELEASE
`922 / RESOURCES CONCURRENTLY
`I
`CHANNEL DROPPED
`924 / RESPONSES SENT BY
`CHANNEL SERVERS
`
`]
`
`930
`/
`+
`CONNECTION SERVER SENDS
`DROP-SEGMENT MESSAGE
`TO NEXT CONNECTION
`SERVER IN THE ROUTE
`I,
`PERFORM RELEASE
`RELEASE-
`CONNECTION CONNECTION ROUTINE
`ROUTINE
`WITH RESPECT TO
`NEXT CONNECTION
`i‘éé‘éi'im‘”
`ATED
`CHANNEL SERVER
`+
`SEND SEGMENT
`DROPPED RESPONSE TO
`934/ CONNECTION SERVER
`THAT SENT DROP
`SEGMENT MESSAGE
`
`932/
`
`i
`
`'
`_, SEND CONNECTIONS-RELEASED
`94°
`RESPONSE TO CALL SERVER
`
`FIG. 10
`
`//
`1010\//
`L/
`CURRENT f1
`BASE STATION
`
`1021
`SWITCH
`
`K
`1012 \
`
`1
`
`_/—
`
`NEW
`BASE STATION
`
`Bright House Networks - Ex. 1042, Page 11
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`

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`Bright House Networks - Ex. 1042, Page 12
`
`

`
`Bright House Networks - Ex. 1042, Page 13
`
`

`
`5 ,659,544
`
`1
`METHOD AND SYSTEM FOR DISTRIBUTED
`CONTROL IN WIRELESS CELLULAR AND
`PERSONAL COMMUNICATION SYSTEMS
`
`FIELD OF THE INVENTION
`The present invention relates generally to communication
`systems using wireless cellular and personal communication
`networks, and. in particular, to methods and apparatus for
`distributed control in such networks.
`
`BACKGROUND OF THE INVENTION
`
`10
`
`20
`
`In current cellular networks, three functions are per
`formed in order to establish a call or connection to a mobile
`unit or mobile in such a network: (1) locating the mobile; (2)
`handling any implicit services to which a user may have
`subscribed; and (3) establishing the connection. These
`functions. may be referred to, respectively, as mobile
`location. call control. and connection control. In some
`networks. authentication functions are also performed
`During registration of a mobile in current cellular
`networks, a user pro?le is sent from a home network to a
`Visitors’ Location Register (VLR) in the network in which
`the mobile user is currently located A Mobile Switching
`Center (MSC) then obtains the user’s pro?le from the VLR
`25
`either during registration or during call delivery in order to
`provide signalling services for the mobile user. One disad
`vantage of this technique is that sending the user pro?le
`requires the sharing of competitive information between
`different networks. A second disadvantage is that signalling
`tra?ic is generated even when the mobile is not involved in
`a call.
`Also, in typical current cellular networks, the function of
`locating the mobile is performed, in a sequential manner,
`prior to the function of performing call control and estab
`lishing the connection. The sequential nature of current
`procedures leads to long setup delays.
`Finally, in typical current cellular networks. the MSC, is
`required to be an anchor for the duration of the call. The
`MSC thus remains involved for the duration of a call even
`if there exists a more e?icient route for the user information
`path.
`
`35
`
`2
`location server, a visitor location server. a roamer call server,
`and a plurality of clusters. Each cluster may comprise a call
`server, a connection server, a plurality of base stations each
`having a channel server associated with it. a plurality of
`switches each of which has a channel server associated with
`it, and a plurality of signalling transfer points. The system
`also may comprise a plurality of end systems, including a
`plurality of mobiles, where each mobile has a home net
`work
`Other features and advantages of the present invention
`will be readily apparent by reference to the following
`detailed description and accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram illustrating a cluster-based
`multi-network system for the transfer of data or voice.
`FIG. 2 is a ?ow diagram showing the steps of a mobile
`location tracking routine for use in the present invention.
`FIG. 3 is a flow diagram illustrating the initial steps of a
`call control routine for a call originating in a mobile.
`FIG. 4 is a ?ow diagram showing further steps in the call
`control routine.
`FIGS. 5A and 5B are a ?ow diagram illustrating in greater
`detail several of the steps of the call control routine and a
`base station location routine.
`FIG. 6 illustrates the use of several direct signalling links
`used in the call control routine of FIGS. 4 and 5 for a
`roaming mobile according to the principles of the present
`invention.
`FIG. 7 is a ?ow diagram showing the steps of a connection
`establishment routine according to the principles of the
`present invention.
`FIG. 8 illustrates an exemplary route for connecting a call
`from one end system to another end system.
`FIG. 9 is a ?ow diagram showing the steps of a release
`call routine according to the principles of the present inven
`tion.
`FIG. 10 illustrates a hando?c routine according to the
`principles of the present invention.
`FIGS. 11A, 11B and 11C show exemplary values of input
`parameters used in an analysis of the system of FIG. 1.
`FIG. 12 shows exemplary resulting values of certain
`parameters based upon the exemplary input values in FIGS.
`11A-11C.
`
`45
`
`SUMMARY OF THE INVENTION
`The present invention comprises a system and methods
`for distributed control in wireless cellular and personal
`communication systems. The system includes separate serv
`ers for performing call control and connection control
`functions, thereby obviating the need for a mobile switching
`or other switch to be anchored for the duration of a call.
`During a registration procedure, visiting location servers
`track only roaming mobiles, rather than tracking both roam
`ing mobiles as well as mobiles located in their home
`network. Direct signalling links between servers and base
`stations, or other servers. located in di?erent networks allow
`roaming mobiles to contact their home networks for service
`at all times, thereby obviating the need for passing signalling
`information for mobiles when they are not involved in a call.
`The use of multicast signalling with asynchronous transfer
`mode switches. permits speci?ed channel control functions
`to take place concurrently in channel servers associated with
`base station and switches that form a segment of the route
`for a call. Similarly, speci?ed call control functions are
`performed concurrently with I mobile location functions.
`thereby decreasing the delays in setting up a call.
`The system of the present invention may suitably com
`prise a plurality of networks each of which includes a home
`
`DETAILED DESCRIPTION
`FIG. 1 is a block diagram illustrating a cluster-based
`multi-network system 100 for the transfer of data or voice.
`FIG. 1 shows (G+1) networks 101. 102 and 103. each having
`at least one and as many as 11 clusters, where G and n are
`positive integers. For example. networkl 101 has 11 clusters.
`three of which are labelled clusters 110. 111 and 112. Each
`cluster. such as cluster1 110 has a call server 120. a con
`nection server 130. and a plurality of base stations. For
`example, cluster1 110 has I base stations. two of which are
`labelled in FIG. I with reference numbers 150 and 159. In
`FIG. 1. the subscript r is a positive integer. Although only
`one call server 120 and one connection server 130 are shown
`in cluster1 110 of FIG. 110. it should be understood that each
`cluster may have multiple call servers and multiple connec
`tion servers. In any event. each cluster has at least one call
`server and at least one connection server.
`Each cluster. such as the cluster1 110. also has a plurality
`of switches for establishing a voice or data path between two
`
`55
`
`65
`
`Bright House Networks - Ex. 1042, Page 14
`
`

`
`5,659,544
`
`10
`
`15
`
`25
`
`3
`end systems. Cluster1 110, for example. has m switches, two
`of which are labelled in FIG. 1 with reference numbers 140
`and 149. In FIG. 1, the subscript m is a positive integer. In
`a preferred embodiment of the present invention the
`switches, such as the switches 140, 149 are asynchronous
`transfer mode (ATM) switches. Alternatively. however, they
`may be synchronous transfer mode (STM) switches.
`Within each cluster, such as cluster1 110. there also may
`be one or more end systems, including ?xed and mobile end
`systems. FIG. 1, for example, shows s end systems currently
`located within cluster1 110, where the subscript s is a
`positive integer. Three of the end systems currently located
`in cluster1 110 of network1 101 are labelled with reference
`numbers 160. 161 and 169. For exemplary purposes, the end
`systems 160 and 161 are mobile end systems or mobiles.
`such as cellular telephones, and the end system 169 is a ?xed
`end system. Each mobile end system is assigned a home
`network, so that, at any given time, a particular mobile end
`system either may be located in its home network or may be
`roaming in another network. In addition. each mobile is
`assigned an address, which uniquely identi?es it. The end
`systems, such as the end systems 160, 161 and 169, and the
`base stations. such as the base stations 150, 159, use wireless
`or wired transfer of voice or data.
`The transfer of inter-node signalling messages, such as
`messages or signals sent between a base station and a server
`or between servers. takes place via either ATM switches,
`which may by any of the switches 140, 141 or 149 imple
`mented as ATM switches. or signalling transfer points
`(STPs) 135. Each cluster has a plurality of signalling transfer
`points. The links interconnecting the nodes or servers in
`FIG. 1, such as the servers 120, 130, 170, 180 and 190,
`therefore. may be, for example, connection-oriented ATM
`signalling virtual channel connections (V CCs) or datagram
`oriented links interconnecting servers through routers.
`Additionally, at least some of the signalling links are mul
`ticast signalling links.
`In a preferred embodiment of the present invention,
`provisioned direct signalling or ATM virtual channel con
`nections (VCCs) provide the links between base stations and
`servers in the same network, whereas datagram-oriented
`links are used for the connections between nodes, or servers,
`and base stations located in different networks wherever
`needed. An exception is made for the links from base
`stations and connection servers of one network to roamer
`call servers in all other networks, in which case A'IM VCCs
`are also used in the preferred embodiment.
`The functions performed by a call server, such as the call
`server 120, are cumulatively referred to as call control. For
`cellular phone and data applications, the call control func
`tions include maintaining a basic call state model for a call,
`de?ned as a communication session involving users and
`servers. and triggering implicit services subscribed to by the
`users in the call. The call control functions also include
`handling multiple connections, or end-to-end user informa
`tion paths. per call, such as multiple audio connections,
`multiple data connections. or a mixture of audio and data
`connections.
`The functions performed by a connection server, such as
`the connection server 130, are cumulatively referred to as
`connection control. The connection control functions
`include ?nding routes to establish an end-to-end connection,
`computing end-to-end quality of service measurements for
`the connection. establishing, modifying and releasing
`connections, and handling segments of a connection. A
`65
`segment is de?ned as any part of the connection, in other
`words. a concatenation of channels.
`
`4
`Each switch, such as the switch 140, and each base
`station, such as the base station 150, has an associated
`channel server (not shown in FIG. 1). The functions of a
`channel server include managing channels or user informa
`tion links on a physical interface of a base station or switch.
`The functions of a channel server further include setting up
`translation tables to enable the proper routing of user infor
`mation across the base station or switch with which the
`channel server is associated A channel server associated
`with a base station also maps virtual channel identi?ers
`(VCIs) to the next switch in the connection to air interface
`resources, such as frequency, time-slot or code, depending
`upon the wireless access scheme used.
`Each network, such as networkl, also has a roamer call
`server 170. a home location server 180, and a visitor location
`server 190. The functions of the location servers 180 and 190
`include tracking the location of an assigned set of mobile
`users and responding to requests for the location of these
`users. The home location server 180 tracks the cluster for its
`mobiles located in the home network and tracks the visiting
`network for its mobiles that are roaming. The visitor location
`server 190 tracks the cluster in which each visiting mobile
`is located. in contrast to existing networks, in which a VLR
`tracks both home and visiting mobiles. The roamer call
`server 170 handles calls for users of network1 101 which are
`roaming or visiting another network. Although only one
`roamer call server 170, one home location server 180, and
`one visitor location server 190 are shown in cluster1 110 of
`FIG. 1, it should be understood that some networks may
`have multiple roamer call servers, home location servers or
`visitor location servers. In any event, each network prefer
`ably has at least one roamer call server, at least one home
`location server. and at least one visitor location server.
`The location server responsible for tracking the location
`of a particular mobile is identi?ed by the address of the
`mobile. The call server handling the calls for a mobile
`located in its home network and the connection server
`handling the connections for a particular mobile are identi
`?ed by the cluster in which the mobile is located. The call
`server handling the calls for a mobile visiting another
`network is identi?ed by the network in which the mobile is
`visiting. In a preferred embodiment of the present invention,
`the servers 120, 130, 170, 180 and 190 occur in pairs in order
`to increase reliability.
`FIG. 2 is a ?ow diagram showing the steps of a mobile
`location tracking routine in accordance with the present
`invention. As shown in step 200, a mobile, such as the
`mobile end system 160, generates a registration message
`identifying itself when it turns its power on or off, or when
`it changes clusters by moving from one cluster to another
`cluster. Each base station, such as the base station 150,
`periodically transmits a message identifying the cluster in
`which it is located. These messages transmitted by the base
`stations allow a mobile to determine when it changes
`clusters. Upon receiving a registration message from a
`mobile as indicated by step 205, a determination is made as
`to whether the mobile that generated the registration mes
`sage is located in its home network, as indicated by 210.
`As shown in step 220, if the mobile that generated the
`registration message is in its home network, then the base
`station that received the registration message forwards the
`registration information to the home location server for that
`mobile. Next. as indicated in step 225, the home location
`server would then store information indicating the cluster in
`which the mobile is currently located by storing the mobile
`to-cluster mapping.
`If on the other hand. the mobile that generated the
`registration message is not located in its home network,
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`then. as shown in step 230, the base station that received the
`registration message forwards the registration information
`visitor location server located in the same network as the
`base station and currently tracking the mobile. As indicated
`by 240, the next step depends upon whether the registration
`message indicates a cluster change, in other words. that the
`mobile has moved from one cluster to another cluster within
`the network. If the registration message indicates a cluster
`change. then. as shown in step 245. the visitor location
`server, to which the registration information was forwarded,
`stores the cluster in which the mobile is currently located by
`storing the mobile-to-cluster mapping. If the registration
`message indicates that the mobile is powering up or pow
`ering down. then. as indicated in step 250, the visitor
`location server that received the registration information
`forwards the registration information to the home location
`server in the mobile’s home network. Finally, as shown in
`step 255, the home location server in the mobile’s home
`network would store a network identi?er and visitor location
`server identi?er corresponding to the location of the mobile.
`The steps illustrated in FIG. 2 thus represent the mobile
`location tracking routine.
`In a preferred embodiment of the present invention. the
`base station that received the registration message from a
`mobile uses bicast signalling VCCs to update both location
`servers in the pair assigned to the mobile. Also. a timer
`based registration occurs in addition to the registration
`procedures explained above. Timer-based registration mes
`sages are generated at a relatively slow rate. for example
`once each day, and are processed by the visitor location
`servers for roaming mobiles and by the home location
`servers for mobiles located in their respective home net
`works. If. for example. a visitor location server does not
`receive a timer-based registration from a mobile that previ
`ously was roaming within its domain. it deletes the entry for
`the previously registered mobile. This timer-based registra
`tion procedure obviates the need for a registration cancel
`lation procedure from the home location server to a previous
`visitor location server, as is presently done in the current
`18-41 and GSM standards.
`FIGS. 3 and 4 are ?ow diagrams illustrating the steps of
`a call control routine for use in conjunction with the present
`invention. As shown in step 300 of FIG. 3. a calling end
`system. such as the mobile 160 or the ?xed end system 169,
`generates a call origination message indicating that it wishes
`to call a particular called end system. The remaining steps of
`FIG. 3 and FIG. 4. with the exception of step 422 in FIG. 4.
`illustrate the call control routine. As illustrated in step 305.
`the base station covering the area in which the end system
`is located receives the call origination message. A determi
`nation is made as to whether the end system that generated
`the call origination message is a mobile, as shown by 310.
`If the calling end system is not a mobile, but rather is ?xed.
`then, as indicated in step 315, the base station sends a setup
`call message to the call server covering the cluster in which
`the base station is located. If. on the other hand. the calling
`end system is a mobile, then a determination is made as to
`whether the calling mobile is located in its home network. as
`indicated by 320. A setup call message is sent to the call
`server serving the calling mobile. More particularly. if the
`calling mobile is located in its home network, then. as
`illustrated in step 325. the base station sends a setup call
`message to the call server covering the cluster in which the
`base station and mobile are located. In contrast, if the calling
`mobile is not located in its home network. then the base
`station sends a setup call message to the roamer call server
`located in the mobile’s home network as shown in step 330.
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`6
`In this latter situation, the base station also sends an update
`message to the roamer call server indicating the identity of
`the connection server in the cluster where the mobile is
`presently located. The identity of the connection server
`received in the update message is used by the roamer call
`server. as explained further below. to request that the con
`nections needed to connect the call be set up. Finally. as
`indicated in step 335. when the calling end system is a
`mobile, the base station stores the mobile-to-call server
`mapping needed to handle subsequent requests from the
`mobile.
`FIG. 4 illustrates additional steps which are performed as
`part of the call control routine. As indicated in step 400, a
`call server for the calling end system receives the setup call
`message. As explained above. this call server will be either
`the call server in the cluster in which the base station is
`located or the roamer call server that is associated with the
`end system’s home network. Upon receiving the setup call
`message. a call server instantiates or creates a state machine
`for the call, as shown in step 410. Next. as indicated in step
`411. the call server invokes implicit services for the calling
`end system. Then. the call server creates a record for
`mapping connections to the call as shown in step 412.
`The call server that received the setup call message
`additionally performs several steps concurrently with the
`steps 410-412. Speci?cally. as indicated by step 420. the call
`server that received the setup message identi?es the call
`server, the connection server and the gateway switch for the
`called end system. A gateway switch is the switch that
`interconnects two networks. When the called end system is
`a ?xed end system. then this information may be retrieved
`from a database. When the called end system, however. is a
`mobile, then further processing is required to obtain this
`information. as explained below with reference to FIG. 5.
`Next. as indicated in step 421, the call server that received
`the setup message communicates with the call server iden
`ti?ed in step 420 to invoke implicit services for the called
`end system.
`According to the principles of the present invention. if the
`called end system is a mobile, then a base station location
`routine is performed concurrently or in parallel with step
`421. as indicated by step 422. The base station location
`routine, as explained further below. determines which base
`station. within the cluster where the called mobile is cur
`rently located. is serving the called mobile. This information
`is subsequently used when the connections for the call are
`established. By performing the base station location routine
`in parallel with the call control functions of step 421 the
`delays in establishing the connections for the call are
`decreased.
`Once the steps 410-412 and 420-421 have been
`performed. the call server that received the setup message
`sends a setup connections message to the connection server
`for the calling end system, as shown in step 430. The
`connection server for the calling end system is the connec
`tion server covering the cluster in which the calling end
`system is currently located. In a setup connections message.
`the call server sending the message speci?es the connection
`server and gateway switch for the called end system which
`were identi?ed in the step 420.
`FIGS. 5A and 5B are a ?ow diagram illustrating in greater
`detail several of the steps of the call control routine and the
`base station location routine. In particular. FIGS. 5A and 5B
`illustrate the details of the steps 420 and 422 when the called
`end system is a mobile. First. as shown in step 500. the call
`server for the calling end system. sends a ?nd request to the
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`home location server for the called mobile. The call server
`for the calling end system is the call server that received the
`setup call message in the step 400. In step 505, the home
`location server for the called mobile receives the ?nd
`request. As indicated by 507, a determination is made as to
`whether the called mobile is located in its home network.
`If the called mobile is located in its home network, then,
`as indicated by step 520, the home location server for the
`called mobile sends a ?nd response to the call server for the
`calling end system. This ?nd response would specify the call
`server, the connection server and the gate