(12) United States Patent
`US 6,868,272 B1
`(10) Patent N0.:
`Berkowitz et al.
`(45) Date of Patent:
`Mar. 15, 2005
`
`USOO6868272B1
`
`(54)
`
`(75)
`
`METHOD AND APPARATUS FOR ROAMING
`IN HIERARCHICAL MOBILE
`COMMUNICATIONS NETWORK
`
`Inventors: Paul Berkowitz, Little Silver, NJ (US);
`Chauncey Shey, East Brunswick, NJ
`(US); Jan Vancraeynest, White Plains,
`NY (US); Jose Vasconcellos, Lincroft,
`NJ (US)
`
`(73)
`
`Assignee: UTStarcom, Inc., Alameda, CA (US)
`
`( * )
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21)
`
`(22)
`
`(51)
`(52)
`(58)
`
`(56)
`
`Appl. No.: 09/328,306
`
`Filed:
`
`Jun. 8, 1999
`
`Int. Cl.7 .................................................. H04Q 7/20
`US. Cl.
`................... 455/445; 455/433; 379/201.02
`Field of Search .............................. 455/432.1, 433,
`455/445, 552.1, 406, 432.2, 432, 552; 379/201.02,
`211, 211.01; 709/106; 725/106
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,670,905 A
`4,833,701 A
`5,345,498 A
`5,353,340 A
`5,434,854 A *
`5,497,412 A
`5,526,400 A
`5,629,974 A
`5,659,544 A
`5,666,107 A
`5,724,658 A
`
`6/1987 Sandvos et a1.
`.............. 455/33
`
`5/1989 Comroe et a1. ........... 379/60
`9/1994 Mauger .................... 379/58
`
`10/1994 Kunz ....................... 379/60
`
`7/1995 Focarile et a1.
`.....
`370/335
`
`................ 379/60
`3/1996 Lannen et a1.
`6/1996 Nguyen ....................... 379/59
`............. 379/58
`5/1997 Rajala et a1.
`
`8/1997 La Porta et a1.
`370/312
`
`9/1997 Lockhart ct a1.
`340/827
`3/1998 Hasan ........................ 455/445
`
`11/1998 Alperovich ................. 455/433
`5,832,382 A
`
`.. 455/432.2
`1/1999 Kulkarni et a1.
`5,862,481 A *
`............... 455/433
`5,978,678 A * 11/1999 Houde et a1.
`
`6,104,915 A *
`8/2000 Zhang et a1.
`....... 455/76
`.................. 455/450
`6,385,454 B1 *
`5/2002 Bahl et a1.
`FOREIGN PATENT DOCUMENTS
`
`W0
`W0
`W0
`W0
`W0
`
`............ H04Q/7/38
`11/1996
`WO 96/35309
`............ H04Q/7/24
`2/1997
`WO 97/04611
`H04Q/7/38
`5/1998
`WO 98/23123
`H04Q/7/24
`12/1998
`WO 98/56198
`
`............ H04Q/7/38
`5/2000
`WO 00/28772
`OTHER PUBLICATIONS
`
`US 5,282,240, 1/1994, Buhl et al. (withdrawn)
`Newton’s Telecom Dictionary, 15th Edition, Feb. 1999, pp.
`272, 762, 763*
`
`* cited by examiner
`
`Primary Examiner—Nay Maung
`Assistant Examiner—Edan Orgad
`(74) Attorney, Agent, or Firm—George A. Willman; Felix
`L. Fischer
`
`(57)
`
`ABSTRACT
`
`Communications system comprising a set of interface
`devices adapted to be coupled to a public switch telephone
`network (PSTN) and radio transceivers. The interface
`devices are configured to serve in various geographic
`regions. The radio transceivers are coupled to the interface
`devices in the set of interface devices. The radio transceivers
`are for communication with mobile subscribers. The mobile
`
`subscribers each have a home region. The circuitry coupled
`to the set of interfaces routes a call through a path including
`an interface device that serves the mobile subscriber’s home
`
`region, for a call involving the PSTN and a mobile sub-
`scriber located outside the mobile subscriber’s home region.
`
`27 Claims, 9 Drawing Sheets
`
`312
`310
`311
`
`
`
`
`319
`
`f originating
`Nail
`320KAT
`
`Ps,
`
`\ 322
`
`APPLE 1012
`
`APPLE 1012
`
`1
`
`

`

`US. Patent
`
`Mar. 15,2005
`
`Sheet 1 0f 9
`
`US 6,868,272 B1
`
`116
`
` I
`
`I
`RPCAI—Ell'i‘lf
`
`/"‘]l7
`
`119
`
`“3
`
`f
`
`120
`
`I
`I
`5-11»
`‘-
`
`-E% .23.,
`
`l2]
`
`.
`
`*1
`
`P8n
`
`110
`
`1“
`
`11:;
`
`ATCl
`
`,
`
`NIU
`
`B
`
`‘ 112
`nuamflrm
`Rpm-12% [”7
`
`FIG. 1
`
`ATC1
`
`‘ 112
`
`
`
`/
`
`”3
`
`124
`
`mm 3% r'”
`
`
`125
`
`Rpccz —
`
`[27
`
`/"
`
`FIG. 2
`
`2
`
`

`

`US. Patent
`
`Mar. 15, 2005
`
`Sheet 2 0f 9
`
`US 6,868,272 B1
`
`
`
`
`
`
`f3l9
`originating
`call
`
`3
`
`

`

`US. Patent
`
`Mar. 15, 2005
`
`Sheet 3 0f 9
`
`US 6,868,272 B1
`
`410
`
`PSTN
`
`location registration
`
`4”
`NIU-x
`
`412
`qua 413
`NIU
`C
`
`414
`RPCB]
`41.5
`C324”
`ATC
`
`417
`
`PsA
`
`418
`
`— 419
`
`420
`
`(421 /
`
`
`
`
`
`426
`
`/2
`uthentication request
`authentication response
`k 427
`
`FIG. 4
`
`4
`
`

`

`US. Patent
`
`Mar. 15, 2005
`
`Sheet 4 0f 9
`
`US 6,868,272 B1
`
`510
`
`PSTN
`
`originating call
`
`511
`NIUA51
`
`2
`
`Nut 513
`NI
`
`9:
`
`514
`
`RPCB]
`515
`
`I I%2
`
`516
`
`517
`
`PS
`
`518
`
`setup
`
`525
`authentication requegt/R
`authentication response
`
`526
`
`530
`
`setu n
`
`' connect
`
`531
`
`
`
`Ill‘
`
`535
`
`communication in r0; 655
`L 536
`
`FIG. 5
`
`5
`
`

`

`US. Patent
`
`Mar. 15,2005
`
`Sheet 5 0f 9
`
`US 6,868,272 B1
`
`610
`
`PSTN
`
`terminating call
`
`511
`NIUA612
`qus 613
`
`614
`RPCBI
`615
`
`618RP
`Q2
`
`517
`
`setup
`
`
`
`
`
`650
`
`640
`
`
`
`
`
`
`
`6
`
`

`

`US. Patent
`
`Mar. 15, 2005
`
`Sheet 6 0f 9
`
`US 6,868,272 B1
`
`710
`PSTN
`
`inter—NIU handover
`
`711
`
`mg
`
`13%
`
`713
`NIUC
`
`718
`714
`RP
`Mm
`0%:5
`' CBZ716 RPCC‘
`ATC
`
`719
`
`PSA
`
`
`
`C0
`
`[111
`
`cation in my es
`
`720 D
`
`
`
`\
`
`-..
`
`:Iu’u
`729
`
`cation 1n 0.1‘0 eSS
`
`FIG. 7
`
`7
`
`

`

`US. Patent
`
`h4ar.15,2005
`
`Sheet7 0f9
`
`US 6,868,272 B1
`
`FIG. 8
`
`
`
`FIG. 9
`
`ATC block
`
`H9
`
`
`
`Oufiofim.movmam8580
`
`8
`
`
`
`

`

`US. Patent
`
`Mar. 15,2005
`
`Sheet 8 0f 9
`
`US 6,868,272 B1
`
`1019
`
`1020
`
`_QIIJ
`
`1015
`
`0‘0
`
`RATC/a
`
`
`
`1018 10”f}--ATC
`\/
`
`m
`
`M-ATC
`
`R—ATC
`
`-
`
`[017
`
`/\
`
`C-ATC cloud
`
`.ATC
`
`FIG. 10
`
`9
`
`

`

`US. Patent
`
`Mar. 15,2005
`
`Sheet 9 0f 9
`
`US 6,868,272 B1
`
`Roaming
`
`Gateway
`
` 1112
`
`
`
`
`
` ControlBus(e.g.Bhternet)
`
`PSTN
`1125
`
`1127
`
`V
`
`1126
`
`’\
`
`\
`
`M
`
`\‘
`
`1 1 10
`
`1121
`
`m,
`
`‘123
`
`f‘
`
`‘
`
`1124
`
`////*—1111
` 1114
`\ 1116
`
`////——1115
`
`Roaming
`Gateway
`
`1117
`
`1113
`
`1118
`
`
`
`Gateway
`
`Roaming
`
`FIG. 1 l
`
`10
`
`10
`
`

`

`US 6,868,272 B1
`
`1
`METHOD AND APPARATUS FOR ROAMING
`IN HIERARCHICAL MOBILE
`COMMUNICATIONS NETWORK
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates to the field of communication
`
`networks. In particular, the invention relates to a method and
`apparatus for roaming in a mobile communications network.
`2. Description of the Related Art
`A mobile communications system may include various
`systems between which a subscriber may wish to travel.
`Often a subscriber is associated with a particular system and
`when the subscriber is present
`in a region serviced by
`another system, the subscriber is considered to be roaming.
`A subscriber’s home system is typically a system for which
`the subscriber is registered. Several techniques allow mobile
`subscribers to roam into systems different from the subscrib-
`er’s home system. An example is the IS-41 based system.
`Some prior art systems use home location and Visited
`location registers (HLR/VLR) and even dedicated switching
`networks for mobile subscribers. A disadvantage of some
`prior systems is the possibility of single point of failure, the
`need for a dedicated signaling network, the need for central
`coordination between entities entering into roaming agree-
`ments and difficulties in billing.
`Some methods in the prior art rely on explicit rules for
`determining the home location of a roaming subscriber and
`how to handle a call to and from such a subscriber. Typically
`in such applications these functions are carried out by
`interrogation of an HLR. Such an approach introduces
`complexity and delay. Prior art methods also may require
`additional signaling traffic to establish correct billing for
`each call since the path may go through a different exchange
`than the subscriber’s home exchange. Such additional sig-
`naling may be complex.
`
`SUMMARY OF THE INVENTION
`
`One aspect of the invention is directed to a method of
`modifying an existing telephone network. Interface deVices
`serve various geographic regions of the telephone network.
`The interface devices are coupled to the telephone network.
`The interface devices are coupled to circuitry coupled to
`radio transceivers that service mobile subscribers that may
`be located in one of the geographic regions. The mobile
`subscribers are each assigned to a respective geographic
`region. When a subscriber is located in a region other than
`the geographic region to which the subscriber is assigned,
`circuitry coupled to the interface devices routes a call with
`a mobile subscriber through a path including a radio trans-
`ceiver that serves the region in which the mobile subscriber
`is currently located and an interface device that serves the
`region to which the subscriber is assigned.
`One embodiment of the present invention is directed to a
`communications system that includes a first network dis-
`persed throughout a national area. The communications
`system also includes a second network coupled to the first
`network by interfaces in a plurality of geographic regions in
`the national area. The second network includes radio trans-
`
`ceivers for communicating with subscribers located in the
`plurality of geographic regions. Each subscriber has a home
`region, and various subscribers are located outside of their
`home regions. The system includes circuitry that routes all
`communication between a subscriber and the first network
`
`2
`through an interface between the first network and the
`second network in the subscriber’s home region.
`Another embodiment of the present invention is directed
`to a communications system that includes a set of interfaces
`adapted to be coupled to a public switched telephone net-
`work (PSTN). The interfaces ar configured to serve various
`geographic regions. For communication between the PSTN
`and a subscriber located in a region other than a region in
`which an interface to which the subscriber is assigned is
`located, circuitry included by the system and coupled to the
`set of interfaces causes the communication to take place Via
`the interface to which the subscriber is assigned. According
`to one embodiment of the invention, the circuitry coupled to
`the set of interfaces is coupled to the interfaces Via an E1
`interface. According to one embodiment of the invention
`communication between a circuitry coupled to the set of
`interfaces and the subscriber takes place entirely over a land
`line system.
`Yet another embodiment to the invention is directed to a
`communications system comprising radio transceivers and a
`set of interface devices adapted to be coupled to a PSTN.
`The interface devices are configured to serve various geo-
`graphic regions. The radio transceivers are coupled to the
`interface devices in the set of interface devices. The radio
`transceivers are for communication with mobile subscribers.
`The mobile subscribers each have a home region. The
`circuitry coupled to the set of interfaces routes a call through
`a path including an interface device that serves the mobile
`subscriber’s home region, for a call involving the PSTN and
`a mobile subscriber located outside the mobile subscriber’s
`home region.
`Another aspect of the invention is directed to a method of
`modifying an existing telephone network in which interface
`devices are located in various geographic regions of the
`telephone network. The interface devices are coupled to the
`telephone network in the various geographic regions. The
`interface devices are coupled to circuitry coupled to radio
`transceivers that service mobile subscribers that may be
`located in one of the geographic regions. The mobile sub-
`scribers are each assigned to a respective geographic region.
`When a subscriber is located in a region other than the
`geographic region to which the subscriber is assigned,
`circuitry coupled to the interface devices routes a call with
`a mobile subscriber through a path including a radio trans-
`ceiver in the region in which the mobile subscriber is
`currently located and an interface device in the region to
`which the subscriber is assigned.
`In yet another embodiment of the invention, each sub-
`scriber is associated with one or more directory numbers.
`Routing of incoming calls is conditioned upon a subscriber
`profile when the subscriber is out of the subscriber’s home
`geographic region. Incoming calls may be routed to the
`subscriber in the subscriber’s new location or to another
`
`subscriber or to voice mail depending on the subscriber’s
`feature profile and which directory number with which the
`call is associated. If a subscriber has for example directory
`numbers 1, 2, 3 assigned, the subscriber may set up the
`subscriber profile to cause the interface device to act as
`follows when the subscriber is out of the area:
`
`for incoming calls associated with number 1, route to the
`subscriber’s new location (“follow-me” number);
`for incoming calls associated with number 2,
`route
`another directory number; or
`for incoming calls associated with number 3, route to
`voice mail.
`
`BRIEF DESCRIPTION OF THE FIGURES
`
`FIG. 1 is a block diagram of a telephone communications
`system, according to an embodiment of the invention.
`
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`11
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`

`

`US 6,868,272 B1
`
`3
`FIG. 2 is a block diagram illustrating circuitry acting as a
`proxy for radio ports belonging to other interface devices for
`terminating calls, according to an embodiment of the inven-
`tion.
`
`FIG. 3 is a block diagram illustrating circuitry acting as a
`proxy for network ports for a first interface for calls origi-
`nating from mobile subscribers assigned to another region,
`according to an embodiment of the invention.
`FIG. 4 is a flow diagram of location registration, accord-
`ing to an embodiment of the invention.
`FIG. 5 is a flow diagram of an originating call process,
`according to an embodiment of the invention.
`FIG. 6 is a flow diagram of a terminating call process,
`according to an embodiment of the invention.
`FIG. 7 is a flow diagram of an interface handover process,
`according to an embodiment of the invention.
`FIG. 8 is a block diagram illustrating the circuitry that
`routes calls configured as regional circuitry interconnected
`centrally, according to an embodiment of the invention.
`FIG. 9 is a block diagram illustrating expanded circuitry
`for routing calls connected by a local or distributed control
`bus, according to an embodiment of the invention.
`FIG. 10 is a block diagram illustrating circuitry that routes
`calls implemented in a mesh configuration, according to an
`embodiment of the invention.
`
`FIG. 11 is a block diagram showing circuitry that routes
`calls configured to route calls to home interfaces through the
`public switched telephone network (PSTN) by including a
`gateway functionality inside interface devices, according to
`an embodiment of the invention.
`
`DETAILED DESCRIPTION
`
`One embodiment of the invention is directed to a system
`for routing calls when subscribers are located outside of the
`coverage area of an interface to the public network in their
`home area. When such a subscriber wants to make a call, the
`circuitry routes the call to an interface to the public network
`that serves the home area. Similarly, incoming calls from the
`public network are routed through the interface that services
`the home region, to equipment in the region outside of the
`home region where the subscriber is currently located. Such
`an arrangement has an advantage of, according to one
`embodiment, making roaming transparent
`to the public
`network and billing systems.
`FIG. 1 is a block diagram of a telephone communications
`system, according to an embodiment of the invention. The
`system includes interface devices that are coupled to the
`public network (NIUA 111, NIUBl 112, and NIUC 113).
`Radio port controllers are coupled to the various
`interfaces—as shown, NIUA 111 is coupled to RPCA1 115
`and RPCA2 117, NIUB 112 is coupled to RPCB1 119 and
`RPCB2 121, and NIUC 113 is coupled to RPCCl 124 and
`RPCC2 125. The radio port controllers are coupled to radio
`transmitters —RPCA1 115 is coupled to radio transceivers
`116, RPCA2 117 to radio transceivers 118, RPCBl 119 is
`coupled to radio transceivers 120, RPCB2 121 is coupled to
`radio transceivers 122, RPCCl 124 is coupled to radio
`transceivers 126, and RPCC2 125 is coupled to radio trans-
`ceivers 127. Radio transceivers are used to communicate
`
`for example, PSA 123. Radio
`with mobile subscribers,
`transceivers include radio ports and appropriate transceiver
`circuitry.
`The interfaces each serve a different geographic region by
`being coupled, through the radio port controllers, to radio
`transmitters that serve the respective geographic region.
`
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`60
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`65
`
`4
`According to one embodiment of the invention, such inter-
`faces are located in the respective regions that they serve.
`According to another embodiment of the invention, such
`interfaces are not necessarily located in the respective
`regions that they serve. For example, the interfaces may be
`co-located.
`
`Circuitry ATC1 114 couples the various interface devices
`(NIUA 111, NIUB 112, and NIUC 113. Circuitry ATC1 114
`may be implemented in the form of dedicated circuits, or a
`computerized system. Typically, circuitry ATC1 114 includes
`bearer channels and control channels. E1 links are provided
`to interconnect the various interface devices via ATC1 114.
`Circuitry that routes calls between interface devices, cir-
`cuitry ATC as shown in FIG. 1, may be implemented as a
`computer system. The ATC circuitry acts as a controller and
`includes an E1 interface. The circuitry ATC includes bearer
`and control circuitry. The bearer circuitry provides a path for
`transmission of information, such as voice from a subscriber,
`to the correct interface. Such transmission typically occurs
`over an E1 interface. The circuitry that routes between the
`interfaces (e.g., ATC) includes a cross connect, which is a
`split
`that maps between various incoming and outgoing
`lines. An ATC may have, in one example, 30 multiplexed
`lines.
`
`An interface device, shown in FIG. 1 as, for example,
`NIUA 111, may be implemented as a computer with con-
`trollers. The interface device includes interface boards for
`
`interfacing with radio port controllers (e.g., RPCAl 115).
`Such interfacing takes place typically via an E1 standard.
`The interface from the interface device to the PSTN (PSTN
`110) may take place via an analog. T1 interface, or other
`interface. The interface device is typically coupled to a class
`5 switch in the PSTN. The system may include circuitry
`coupled to the set of interfaces that converts a signal from
`the subscriber to packets before passing the signal to the
`PSTN.
`
`According to one embodiment of the invention, an inter-
`face device can have a large number of subscribers assigned
`to it, e.g., 10,000 subscribers, and a large number of roaming
`subscribers. According to one embodiment of the invention,
`subscribers are registered in a particular home interface
`device for billing purposes and because of telephone number
`assignment to the particular PSTN ports to which the home
`interface device is connected. The sizing of connectivity
`between interface devices and circuitry ATCs is determined
`by the amount of roaming traffic between respective inter-
`face devices and the desired grade of service for such
`roaming traffic. According to one embodiment of the
`invention, for calls with the subscriber located in a region
`other than the geographic region to which the subscriber is
`assigned, billing information is passed to the existing net-
`work regarding location of the subscriber only through the
`interface that serves the region to which is assigned.
`When a subscriber, for example, PSA 123 is located out of
`the subscriber’s home area,
`the following may occur,
`according to an embodiment of the invention. Radio ports
`under a network interface emit a paging area identifier
`unique for each network interface. This paging area identi-
`fier is received by subscribers in the network interface’s
`coverage area. As a subscriber moves away from the region
`served by the subscriber’s home network interface device,
`say, NIUA 111,
`it notices that the paging area identifier
`changes. The subscriber then knows that it has moved into
`the coverage area of a new network interface device. At this
`point,
`the subscriber, say PSA 123, sends a registration
`message including its own identification to the new network
`interface device, say NIUB 112. NIUB 122 receives the
`
`12
`
`12
`
`

`

`US 6,868,272 B1
`
`5
`registration request and notices from the subscriber identi-
`fication that PSA 123 is not assigned in an NIUB’s 112
`database.
`
`to circuitry
`NIUB 112 forwards a registration request
`ATC1 114. ATC1 114 either knows about the subscriber PSA
`123 (through previous registration or calls made by a
`subscriber PSA 123) or does not know about subscriber PSA
`123. If ATC1 114 knows about subscriber PSA 123, then
`circuitry ATC1 114 updates the location entry in its database
`for subscriber PSA 123 to indicate that the subscriber PSA
`123 is located in the area covered by interface device NIUB
`112 and sends the registration request on to interface device
`NIUA 111. If circuitry ATC1 114 does not know about
`subscriber PSA 123,
`then circuitry ATC1 114 sends the
`registration request on to NIUs connected to ATC1 114
`except to the interface device that originated the request. In
`this case, for example, the registration request is sent to
`interface device NIUA 111 and interface device NIUC 113
`but not to interface device NIUB 112. The one interface
`device recognizes the subscriber PSA 123 from the sub-
`scriber identification contained in the registration message.
`Such interface device recognizes subscriber PSA 123 as
`assigned to that interface device’s database and responds to
`the registration request. The circuitry ATC1 114 then updates
`its table to reflect
`that subscriber PSA 123 belongs to
`interface device NIUA 111 and is currently assigned to NIUB
`112.
`
`In another embodiment of the invention, subscriber PSA
`123 is programmed with the identity of its assigned or home
`region, or is programmed with the identity of the assigned or
`home network interface device. According to one embodi-
`ment of the invention, such assignment is made at the time
`the subscriber is activated for service and has the ability to
`inform the network about
`the subscriber’s home region
`and/or corresponding interface device. Upon receipt of such
`notification, an interface device serving each visited region
`can directly forward the registration to the proper home
`interface device through the circuitry ATC.
`In another embodiment of the invention, each interface
`device and circuitry ATC can deduce from the construction
`of the subscriber identification to which region the sub-
`scriber belongs. The registration is then forwarded to the
`proper home interface device corresponding to the region
`through the circuitry ATC. An example of such subscriber
`identification structuring is the use of prefixes unique to each
`interface device.
`
`When a call comes in for subscriber PSA 123 from the
`public network (terminating call), interface device NIUA 111
`sends a page request to radio port controllers under NIUA
`111 and also to circuitry ATC1 114. Because subscriber PSA
`123 is outside of the coverage of network interface NIUA
`111, none of the radio port controllers under interface device
`NIUA 111 respond with a positive page acknowledgement. If
`circuitry ATC1 114 knows about subscriber PSA 123,
`it
`forwards the page to NIU under whose coverage it knows
`subscriber PSA 123 to have most recently been in (for
`example, to interface device NIUB 112). If circuitry ATC1
`114 does not know about subscriber PSA 123, circuitry ATC1
`114 sends the page to all
`interface devices coupled to
`circuitry ATC1 114, except
`to the originating interface
`device (in this case,
`to interface device NIUB 112 and
`interface device NIUC 113, but not to interface device NIUA
`111). The interface device that has subscriber PSA 123 under
`its coverage responds to the page. Circuitry ATC1 114
`forwards the page response to the home interface device and
`establishes a call path between a home interface device,
`through circuitry ATC1 114,
`through a visited interface
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`device and to subscriber PSA 123. Authentication and alert-
`ing are also performed. An advantage of such a configuration
`is that a call may be delivered to subscriber PSA 123 without
`the home interface device,
`interface device NIUA 111,
`explicitly knowing the location of subscriber PSA 123.
`In another embodiment to of the invention,
`the home
`interface device keeps track of the location of each sub-
`scriber assigned to it by communication from circuitry ATC
`and therefore can directly page the correct radio port con-
`troller for a terminating call without having the circuitry
`ATC broadcast the page to all interface devices connected to
`it. Because the home interface device updates its database as
`the location is updated in the circuitry ATC, an advantage is
`gained that the interface device does not need to query the
`circuitry ATC.
`Having the home interface device keep track of the
`location of each subscriber assigned to it also allows the
`home interface to make different routing decisions when the
`subscriber is out of the subscriber’s home coverage area,
`according to one embodiment of the invention. When a
`single subscriber is associated with multiple directory
`numbers, such an approach may provide an advantage.
`Incoming calls associated with each of the directory num-
`bers may be routed differently depending on instructions in
`the subscriber’s service profile. For instance, calls associated
`with (directed to) the subscriber’s first directory number
`may be routed to the subscriber’s new location (“follow-me”
`service), calls associated with a subscriber’s second direc-
`tory number may be sent to voice mail, and calls associated
`with a subscriber’s third directory number may be routed to
`another subscriber.
`
`When subscriber PSA 123 wants to originate a call from
`the coverage area of a visited region covered by interface
`device NIUB 112, subscriber PSA 123 sends a set-up mes-
`sage to interface device NIUB 112. Then NIUB 112 recog-
`nizes that subscriber PSA 123 is not assigned in the database
`of interface device NIUB 112. Call handling proceeds as in
`the case of registration and the call path is established
`between subscriber PSA 123 through the interface device
`NIUB 112 in the visited region, through circuitry ATC1 114
`and home interface device NIUA 111. An advantage of such
`a configuration is that the call from subscriber PSA 123 is
`delivered to the network without the interface device which
`
`makes contact with subscriber PSA 123 necessarily knowing
`which interface device is the home interface device for
`
`subscriber PSA 123.
`According to one embodiment of the invention, the same
`messages are exchanged between the interface device and
`the circuitry ATC for traveling subscribers as are exchanged
`between the interface device and radio port controllers for a
`home subscriber.
`
`In another embodiment of the invention, subscriber PSA
`123 is programmed with the identity of its home region or
`corresponding home interface device at the time the sub-
`scriber is activated for a service. The subscriber has the
`
`its home region or
`ability to inform the network about
`interface device. Upon receipt of such notification with a call
`set-up message, each visited region’s interface device can
`directly forward the call to the proper home interface device
`through the circuitry ATC.
`In another embodiment to the invention, each interface
`device and circuitry ATC can deduce from the construction
`of a subscriber identifier which region or interface device the
`subscriber belongs to and directly forward the registration to
`the proper home interface device through the circuitry ATC.
`An example of such subscriber ID structuring is the use of
`prefixes unique to each interface device or region.
`
`13
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`13
`
`

`

`US 6,868,272 B1
`
`7
`When a subscriber moves from the coverage of a radio
`port belonging to a first interface device to the coverage of
`another radio port belonging to an interface device different
`from the first interface device,
`the subscriber initiates a
`handover by dropping the connection to the old radio port
`and requesting a new connection to the new radio port. The
`circuitry ATC processes the set-up messages similarly to a
`regular originating call, with the exception that authentica-
`tion steps are skipped to reduce the time to set the new
`handover call and with the exception that the circuitry ATC
`retains any parts of the existing call that are common to the
`handover call.
`Since calls enter or leave the mobile communications
`network through the home interface device of a subscriber
`even when the subscriber is located outside of the subscrib-
`er’s home region, according to one embodiment of the
`invention, no change is needed in the billing methods of the
`public switched telephone network (PSTN) to which the
`mobile communications network connects. If an operator
`optionally wishes to bill differently for roaming calls, this
`flexibility is provided through separate call detail records
`which record call information such as which radio port and
`interface devices are involved in each call.
`
`FIG. 2 is a block diagram illustrating circuitry acting as a
`proxy for radio ports belonging to other interface devices for
`terminating calls, according to an embodiment of the inven-
`tion. Thus, this shows that circuitry ATC may act logically
`like another radio port controller coupled to an interface
`device. For example, here interface device NIUA 211 is
`coupled to radio port controller RPCAl 212 and radio port
`controller RPCA2 214. Circuitry ATC 216 routes calls to
`respective interface devices (not shown)
`thus logically
`allowing access through interface device NIUA 211 to radio
`port controllers RPCCl 221, RPCC2 223, RPCB1 217, and
`RPCB2 219. Thus, subscriber PSA 230, whose home inter-
`face device is interface device NIU A 211, is provided access
`to PSTN 210 via remote radio ports serving a region outside
`of subscriber’s PSA 230 home region. Thus, logically, the
`ATC 216 circuitry makes radio ports 222, 224, 218, and 220,
`which serve a remote region, appear like local radio ports
`coupled to home interface device NIUA 211.
`FIG. 3 is a block diagram illustrating circuitry acting as a
`proxy for network ports for a first interface for calls origi-
`nating from mobile subscribers assigned to another region,
`according to an embodiment of the invention. An originating
`call is placed from subscriber PSA 320, currently located in
`the region of network interface NIUB 317. This call
`is
`received by a radio port among radio ports 319, which are
`coupled to radio port controller RPCB1 318. Radio port
`controller RPCB1 318 is coupled to interface device NIUB
`317, which is coupled to PSTN 310. However, the call is
`routed through an ATC to interface device NIUA 311 through
`which the call is then routed to the PSTN 310. Thus, a virtual
`connection exists from interface device NIUB 317 into a
`portion of the PSTN to which interface device NIUA 311 is
`coupled. This is shown in the figure as the connection
`between interface device NIUB 317 and PSTN 316.
`Similarly, connection is provided virtually from interface
`device NIUC 323 to PSTN 310. This connection takes place
`physically through a connection between interface device
`NIUC 323 and interface device NIUA 311. However
`logically, it is as if there is a connection between interface
`device NIUC 323 at
`the portion of the PSTN to which
`interface device NIUA 311 is connected. This is shown here
`as a connection between interface device NIUC 323 and
`PSTN 324.
`
`FIG. 4 is a flow diagram of the location registration
`process, according to an embodiment of the invention. FIG.
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`4 has various lines representing communication with the
`following entities: PSTN 410, NIUA 411, NIUB 412, NIUC
`413, RPCBl 414, RPCB2 415, ATC 416, and PSA 417. First
`a registration message is received by a radio port and
`forwarded to the radio port controller. As shown here,
`location registration 418 is sent from subscriber PSA 417 to
`radio port RPCB1 414. In this case, subscriber PSA 417 is
`located in the coverage area of radio port controller RPCB1
`414, which is not the home location of subscriber PSA 417.
`Radio port controller RPCB1 414 sends a message to its
`respective interface device, interface device NIUB 412 (line
`419). Interface device NIUB 412 does not recognize sub-
`scriber PSA 417. Thus interface NIUB 412 sends a message
`to the circuitry ATC 416 (line 420). Assuming that ATC 416
`has not yet stored PSA 417 in its database, then ATC 416
`queries other interface devices to determine the home loca-
`tion for subscriber PSA 417 (lines 421 and 422, which are
`sent to interface device 411 NIUA and interface device NIUC
`413, but not interface device NIUB 412).
`In this example, subscriber PSA 417 belongs to interface
`device NIUA 411. Thus, interface device NIUA 411 responds
`(authorization request 423). ATC 416 forwards this response
`to interface device NIUB 412. Interface device NIUB 412
`then sends the authorization request 428 to interface device
`NIUB 412. An authorization response is sent back (429)
`from interface device NIUB 412 to circuitry ATC 416. The
`authorization response is then sent from circuitry ATC 416
`back to interface device NIUA 411. Interface device NIUA
`411 determines whether the subscriber PSA 417 should be
`authenticated, and can then make future deter