US006980801B1
`
`(12) United States Patent
`Soininen et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,980,801 B1
`Dec. 27, 2005
`
`(54) SELECTION MOBILITY AGENT IN ACCESS
`
`6,104,929 A *
`
`8/2000 Josse et al. ............... .. 455/445
`
`(75) Inventors; Jonne soininen, Mountain View, CA
`(Us); Ahti Muhonen, Hirvihaara (F1)
`
`(73) Assignee: Nokia Corporation, Espoo (FI)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 403 days.
`
`(21) Appl. No.:
`
`09/980,781
`
`(22) PCT Filed:
`
`Jun. 6, 2000
`
`(86) PCT No.:
`
`PCT/FI00/00504
`
`§ 371 (6X1),
`(2), (4) Date:
`
`Dec. 6, 2001
`
`(87) PCT Pub. N0.: W000/76234
`
`PCT Pub. Date: Dec. 14, 2000
`
`6,137,791 A * 10/2000 Frid et al. . . . . . .
`
`. . . . .. 370/352
`
`455/426.1
`6,151,495 A * 11/2000 Rune ....... ..
`6,195,705 B1 *
`2/2001 Leung ...................... .. 709/245
`6,256,300 B1 *
`7/2001 Ahmed 618.1. ............ .. 370/331
`6,442,616 B1 *
`8/2002 Inoue et a1. .... ..
`.. 455/433
`6,606,501 B1 *
`8/2003 Saha et a1. ...... ..
`.... .. 342/450
`6,622,016 B1 *
`9/2003 Sladek et al. .......... .. 455/414.1
`6,628,943 B1 *
`9/2003 Agrawal et al. ....... .. 455/432.1
`6,643,511 B1 * 11/2003 Rune et a1. ............... .. 455/433
`6,711,147 B1 *
`3/2004 Barnes et a1.
`370/338
`6,725,038 B1 *
`4/2004 Subbiah .......... ..
`455/436
`2003/0190915 A1 * 10/2003 Rinne et a1. .............. .. 455/436
`
`FOREIGN PATENT DOCUMENTS
`
`W0
`W0
`W0
`
`10/1998
`W0 8943446
`W0 9843446 A2 * 10/1998
`WO 98/59468
`12/1998
`
`* cited by examiner
`
`Primary Examiner—William Trost
`Assistant Examiner—Sharad Rampuria
`(74) Attorney, Agent, or Firm—Pillsbury Winthrop ShaW
`Pittman LLP
`
`(30)
`
`Foreign Application Priority Data
`
`(57)
`
`ABSTRACT
`
`Jun. 7, 1999
`
`(Fl)
`
`.................................... .. 991297
`
`(51) Int. Cl.7 .............................................. .. H04Q 7/20
`(52) US. Cl. .............. .. 455/435.1; 455/433; 455/432.1;
`455/445; 370/228; 370/328; 370/329; 370/331;
`370/338; 370/401; 709/220; 709/222; 709/223;
`709/224; 709/225
`(58) Field of Search ........................... .. 455/445, 435.1,
`455/4321, 436, 439, 433; 370/338, 349,
`370/352—356, 27s, 328, 329; 709/220, 222
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,793,762 A
`
`8/1998 Penners et al.
`
`In an access network Which supports macro mobility man
`agement, an access node checks during an attach procedure
`of a mobile station Whether the mobile has macro mobility
`capability, i.e., Whether there is a potential need for a macro
`mobility services. If there is no macro mobility capability, a
`normal attach procedure is preformed. HoWever, if there is
`macro mobility capability, the access node selects a suitable
`mobility entity to the mobile station, sends the identity of the
`selected mobility entity to the mobile station and requests
`the initiation of a packet protocol context activation in the
`system.
`
`20 Claims, 2 Drawing Sheets
`
`HPLMN
`
`Urn /
`
`VPLMN
`
`Petitioner's Exhibit 1006
`Page 1 of 9
`
`

`

`U.S. Patent
`
`Dec. 27,2005
`
`Sheet 1 of2
`
`US 6,980,801 B1
`
`VPLMN
`
`Fig, l
`
`2 N A R
`
`SGSN1
`
`Inter-op.
`network
`
`56
`
`BG
`
`SGSN2
`
`HA
`
`Internet
`
`GGSN1
`
`GGSN2
`
`Petitioner's Exhibit 1006
`Page 2 of 9
`
`

`

`U.S. Patent
`
`Dec. 27,2005
`
`Sheet 2 of2
`
`US 6,980,801 B1
`
`MS
`
`SGSN
`
`GGSNIFAZ
`
`HA
`
`Fig, 2
`
`V
`
`1 ESPRS Attach
`2 Routing Area Update
`i
`4 EDP Context Activation Request
`
`Activate PDP Context Request
`
`7
`
`tees
`
`6 Create PDP Context Request ;
`7 <Create PDP Context Response
`
`& ftctivate PDP Context Accept
`
`9 I
`
`10 ‘
`
`MiP AgentAdvertisement (COA)
`
`Mobile IP Registration
`
`4
`
`7
`
`FA Selection
`
`g o 5
`
`SeIectaFA
`
`K’
`tr
`/
`]
`I Complete the Attach procedure 1
`
`55
`/
`
`r
`Send a PCP context Activation
`Request to the MS
`Identify the seiected FA
`in the request.
`
`End
`
`Petitioner's Exhibit 1006
`Page 3 of 9
`
`

`

`US 6,980,801 B1
`
`1
`SELECTION MOBILITY AGENT IN ACCESS
`NETWORK
`
`This is the US. National Stage of International Applica
`tion PCT/F100/00504 Which Was ?led on Jun. 6, 2000 and
`published in the English language.
`
`FIELD OF THE INVENTION
`
`The invention relates to a mechanism for the selection of
`a mobility agent for routing of higher protocol layer traf?c,
`such as an Internet-type protocol traffic, in an access net
`Work.
`
`10
`
`BACKGROUND OF THE INVENTION
`
`15
`
`Mobile communications system refers generally to any
`telecommunications system Which enables a Wireless com
`munication When users are moving Within the service area of
`the system. A typical mobile communications system is a
`Public Land Mobile NetWork (PLMN). Often the mobile
`communications netWork is an access netWork providing a
`user With a Wireless access to eXternal networks, hosts, or
`services offered by speci?c service providers.
`The general packet radio service GPRS is a neW service
`in the GSM system (Global System for Mobile Communi
`cation). A subnetWork comprises a number of packet data
`service nodes SN, Which in this application Will be referred
`to as serving GPRS support nodes SGSN. Each SGSN is
`connected to the GSM mobile communication netWork
`(typically to a base station controller BSC or a base station
`BTS in a base station system) so that the SGSN can provide
`a packet service for mobile data terminals via several base
`stations, i.e. cells. The intermediate mobile communication
`netWork provides radio access and packet-sWitched data
`transmission betWeen the SGSN and mobile data terminals.
`Different subnetWorks are in turn connected to an eXternal
`data netWork, eg to a public sWitched data netWork
`PSPDN, via GPRS gateWay support nodes GGSN. The
`GPRS service thus alloWs to provide packet data transmis
`sion betWeen mobile data terminals and eXternal data net
`Works When the GSM netWork functions as a radio access
`netWork RAN.
`Third generation mobile systems, such as Universal
`Mobile Communications system (UMTS) and Future Public
`Land Mobile Telecommunications system (FPLMTS), later
`renamed as IMT-2000 (International Mobile Telecommuni
`cation 2000), are being developed. In the UMTS architec
`ture, a UMTS terrestrial radio access netWork, UTRAN,
`consists of a set of radio access netWorks RAN (also called
`radio netWork subsystem RNS) connected to the core net
`Work (CN). Each RAN is responsible for the resources of its
`set of cells. For each connection betWeen a mobile station
`MS and the UTRAN, one RAN is a serving RAN. A RAN
`consists of a radio netWork controller RNC and a multiplic
`55
`ity of base stations BTS. One core netWork Which Will be
`using the UMTS radio access netWork is the GPRS.
`One of the main targets in the development of mobile
`communication netWorks is to provide an IP (Internet Pro
`tocol) service With a standard IP backbone Which Would use
`a combination of a Mobile IP and mobile netWork mobility
`management in the mobile netWorks. The basic IP concept
`does not support the mobility of the user: IP addresses are
`assigned to netWork interfaces in dependence on their physi
`cal location. In fact, the ?rst ?eld of an IP address (the
`NETID) is common to all interfaces that are linked to the
`same Internet subnet. This scheme prevents the user (the
`
`2
`mobile host) from keeping its address While moving over
`different Internet subnets, i.e. While changing the physical
`interface.
`In order to enhance mobility in the Internet, a Mobile IP
`protocol for IP version 4 has been introduced by the Internet
`Engineering Task Force (IETF) in the standard RFC2002. A
`Mobile IP enables the routing of IP datagrams to mobile
`hosts, independently of the point of attachment in the
`subnetWork. The Mobile IP protocol introduces folloWing
`neW functional or architectural entities.
`‘Mobile Node MN’ (also called Mobile Host MH) refers
`to a host that changes its point of attachment from one
`netWork or subnetWork to another. A mobile node may
`change its location Without changing its IP address; it may
`continue to communicate With other Internet nodes at any
`location using its (constant) IP address. ‘Mobile Station
`(MS)’ is a mobile node having a radio interface to the
`netWork. ‘Tunnel’ is the path folloWed by a datagram When
`it is encapsulated. The encapsulated datagram is routed to a
`knoWn decapsulation agent, Which decapsulates the data
`gram and then correctly delivers it to its ultimate destination.
`Each mobile node is connected to a home agent over a
`unique tunnel, identi?ed by a tunnel identi?er Which is
`unique to a given Foreign Agent/Home Agent pair.
`‘Home NetWork’ is the IP netWork to Which a user
`logically belongs. Physically, it can be eg a local area
`netWork (LAN) connected via a router to the Internet.
`‘Home Address’ is an address that is assigned to a mobile
`node for an eXtended period of time. It may remain
`unchanged regardless of Where the MN is attached to the
`Internet. Alternatively, it could be assigned from a pool of
`addresses.
`‘Mobility Agent’ is either a home agent or a foreign agent.
`‘Home Agent HA’ is a routing entity on a mobile node’s
`home netWork Which tunnels packets for delivery to the
`mobile node When it is aWay from home, and maintains
`current location information for the mobile node. It tunnels
`datagrams for delivery to a mobile node, and, optionally,
`detunnels datagrams from it, When the mobile node is aWay
`from home. ‘Foreign Agent FA’ refers to a routing entity in
`a mobile node’s visited netWork Which provides routing
`services to the mobile node While registered, thus alloWing
`a mobile node to utilise its home netWork address. The
`foreign agent detunnels and delivers packets to the mobile
`node that Were tunnelled by the mobile node’s home agent.
`For datagrams sent by a mobile node, the foreign agent may
`serve as a default router for registered mobile nodes.
`RFC2002 de?nes ‘Care-of Address’ (COA) as the termi
`nation point of a tunnel toWard a mobile node, for datagrams
`forWarded to the mobile node While it is aWay from home.
`The protocol can use tWo different types of care-of
`addresses: a “foreign agent care-of address” is an address
`announced by a foreign agent With Which the mobile node is
`registered, and a “co-located care-of address” is an exter
`nally obtained local address Which the mobile node has
`acquired in the netWork. An MN may have several COAs at
`the same time. An MN’s COA is registered With its HA. The
`list of COAs is updated When the mobile node receives
`advertisements from foreign agents. If an advertisement
`expires, its entry or entries should be deleted from the list.
`One foreign agent can provide more than one COA in its
`advertisements. ‘Mobility Binding’ is the association of a
`home address With a care-of address, along With the remain
`ing lifetime of that association. An MN registers its COA
`With its HA by sending a Registration Request. The HA
`replies With a Registration Reply and retains a binding for
`the MN.
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`Petitioner's Exhibit 1006
`Page 4 of 9
`
`

`

`US 6,980,801 B1
`
`3
`Asingle generic mobility handling mechanism that allows
`roaming between all types of access networks would allow
`the user to conveniently move between ?xed and mobile
`networks, between public and private networks as well as
`between PLMN’s with different access technologies. There
`fore, mechanisms supporting the Mobile IP functionality are
`being developed also in mobile communication systems,
`such as UMTS and GPRS.
`It is desired that the Mobile IP will be implemented as an
`overlay of the UMTS/GPRS network while maintaining
`backwards compatibility with present systems, assuming
`minimal modi?cations in the GPRS standards and on net
`works whose operators do not want to support the MIP. FIG.
`1 illustrates the minimum con?guration for a GPRS operator
`who wishes to offer the mobile IP service. The current GPRS
`structure is kept and it handles the mobility within the
`PLMN, while MIP allows the user to roam between other
`systems, such as LAN ’s, and the UMTS without loosing an
`ongoing session. In FIG. 1 the foreign agents FA are located
`at GGSN’s. All GGSN’s may not have FA’s. The SGSN and
`the GGSN may also be co-located. One FA in a PLMN is
`sufficient for offering MIP service, but for capacity and
`ef?ciency reasons, more than one FA may be desired. This
`means that the MS must request a PDP conteXt to be set up
`with a GGSN that offers FA functionality. While setting up
`the PDP conteXt, the MS is informed about network param
`eters of the FA, eg the care-of address.
`The problem is to know whether the SGSN has an
`associated GGSN with Foreign Agent (FA) capabilities and
`to open a PDP address to the correct one of several FAs, such
`as the nearest one.
`Similar problems may be encountered in any mobility
`management and routing on a system level overlaying the
`mobility management of an access network. These various
`overlaying mobility managements are commonly referred to
`as macro mobility management herein.
`
`SUMMARY OF THE INVENTION
`
`An object of the present invention is to overcome or
`alleviate the above described problems.
`The object is achieved with a method, a system and an
`access node characteriZed by what is disclosed in the
`attached independent claims. Preferred embodiments of the
`invention are disclosed in the attached dependent claims.
`In the present invention a support node, or more generally
`any access node, checks preferably during an attach proce
`dure of a mobile station whether the mobile concerned has
`macro mobility capability, ie whether a potential need for
`a mobility entity or a macro mobility capability can be
`assumed. Mobility entity may be any entity which provides
`a point of attachment on the macro mobility level, such as
`a mobility agent in the mobile IP type mobility management.
`If there is no mobility capability, a normal attach procedure
`is performed. However, if there is a macro mobility capa
`bility, the access node selects a suitable mobility entity to the
`mobile station and sends the identity of the selected mobility
`entity to the mobile station in association with an access
`conteXt establishment. The access context establishment
`may be, for example, the creation of a packet protocol (PDP)
`conteXt, and the access node may request the mobile station
`to initiate an activation of a packet protocol (PDP) conteXt
`in the system. The mobility entity identity is preferably sent
`in the PDP conteXt activation request so that no eXtra
`message is required. Also other mobility entity attributes
`may be sent to the mobile station. If the mobile station really
`is interested in using the macro mobility, it performs a PDP
`conteXt activation immediately so that a connection is set up
`to the selected mobility entity.
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`In the preferred embodiment of the invention the macro
`mobility management is Mobile IP type mobility manage
`ment. A typical feature of the mobility agent in the Mobile
`IP is that it periodically transmits agent advertisement mes
`sages to the mobile nodes in order to advertise its services.
`The mobile nodes use these advertisements to determine the
`current point of attachment to the Internet. The connection
`established to the selected mobility agent allows the agent
`advertisement messages sent by the selected mobility agent
`to be received by the mobile node, and thereby the mobile
`node is able to initiate a standard mobile IP registration.
`In an embodiment of the invention, when the mobile
`station is not interested in using the macro mobility, eg
`because it has no associated mobile node (e.g application or
`device using mobile IP) at the moment, it may ignore the
`PDP activation request. The mobile station may further store
`the received mobility entity information to be used later.
`When the mobile station at a later stage wishes to make the
`registration according to the speci?c macro mobility man
`agement, it can the use the stored information.
`The selection of the mobility entity may be based on any
`suitable criterion. For example, a mobility entity associated
`with the nearest gateway node may be selected in order to
`optimiZe the routing of the macro layer traf?c. Another
`criterion may be a current loading of the mobility entities so
`that mobility entity with a light traf?c load is preferred to
`heavily loaded mobility agents in order to distribute the
`traffic in the network. Selection may be based on mobility
`entity data stored in the access node, or on information or an
`overriding command received from another network ele
`ment, or on a combination of these.
`The checking of the macro mobility capability may be
`based on subscriber data stored in a subscriber data base or
`on information provided by said mobile station in said attach
`procedure. For eXample, the mobile station may indicate the
`Mobile IP capability in the attach request, eg by means of
`a Mobile Station Classmark. As a further eXample, the
`Mobile IP capability may be checked by interrogating a
`home subscriber data base. Generally, the checking includes
`all measures which indicate the Mobile IP capability of the
`mobile station to the access node.
`One of the bene?ts of the invention is that the mobile
`station does not need to know the mobility agents before
`hand but it is informed of a suitable one when accessing the
`network. Afurther advantage of the invention is that the new
`inventive functionality at the access node enables to detect
`the need for a mobility entity, to select the most optimal
`mobility entity in each part of the network and to change it,
`without any non-standard signalling or procedure being
`needed in other elements of the packet radio network or on
`the Mobile IP level. The optimal selection of the mobility
`entity may further result in more optimal routing which
`allows transmission mobility entity resources to be saved or
`used more effectively in the packet radio system, and
`possibly also to make the connection faster as the connection
`leg between the access node and the mobility entity is
`shorter.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`In the following, the invention will be described in greater
`detail by means of preferred embodiments with reference to
`the accompanying drawings, in which
`FIG. 1 illustrates GPRS network architecture,
`FIG. 2 is a signalling diagram illustrating the method
`according to the invention, and
`FIG. 3 is a How diagram illustrating the function of a
`support node.
`
`Petitioner's Exhibit 1006
`Page 5 of 9
`
`

`

`US 6,980,801 B1
`
`5
`PREFERRED EMBODIMENTS OF THE
`INVENTION
`
`The present invention can be applied to any packet mode
`communications requiring a macro mobility management
`Which overlays the mobility management of an access
`netWork. The invention is especially Well suited for support
`ing a Mobile IP type mobility management in an access
`netWork. The access netWork may be any access network,
`such as a radio access netWork. The invention can be
`particularly preferably used for providing a general packet
`radio service GPRS in the pan-European digital mobile
`communication system GSM (Global System for Mobile
`Communication) or in corresponding mobile communica
`tion systems, such as DCS1800 and PCS (Personal Com
`munication System), or in third generation (3G) mobile
`systems, such as UMTS, implementing a GPRS-type packet
`radio. In the folloWing, the preferred embodiments of the
`invention Will be described With reference to a GPRS packet
`radio netWork formed by the GPRS service and the 3G or
`GSM system, Without limiting the invention to this particu
`lar packet access system.
`A GPRS architecture utiliZing 3G radio access (such as
`UMTS) or 2G radio access (such as GSM) is illustrated in
`FIG. 1. The GPRS infrastructure comprises support nodes
`such as a GPRS gateWay support node (GGSN) and a GPRS
`serving support node (SGSN). The main functions of the
`GGSN nodes involve interaction With an external data
`netWork. The GGSN updates a location directory using
`routing information supplied by the SGSNs about an MS’s
`path and routes the encapsulated external data netWork
`protocol packet over the GPRS backbone to the SGSN
`currently serving the MS. It also decapsulates and forWards
`external data netWork packets to the appropriate data net
`Works and handles the billing of data traf?c.
`The main functions of the SGSN are to detect neW GPRS
`mobile stations in its service area, to handle the process of
`registering the neW MSs along With the GPRS registers, to
`send/receive data packets to/from the GPRS MS, and to keep
`a record of the location of the MSs Within its service area.
`The subscription information is stored in a GPRS register
`(HLR) Where the mapping betWeen a mobile’s identity (such
`as MS-ISDN or IMSI) and the PSPDN address is stored. The
`GPRS register serves as a database from Which the SGSNs
`can ask Whether a neW MS in its area is alloWed to join the
`GPRS netWork.
`The GPRS gateWay support nodes GGSN connect an
`operator’ s GPRS netWork to external systems, such as other
`operators’ GPRS systems, to data netWorks 11, such as an IP
`netWork (Internet) or an X25 netWork, and to service
`centres. Fixed hosts 14 can be connected to the data netWork
`11 eg through a local area netWork LAN and a router 15.
`A border gateWay BG provides access to an inter-operator
`GPRS backbone netWork 12. The GGSN may also be
`connected directly to a private corporate netWork or a host.
`The GGSN includes GPRS subscribers’ PDP addresses and
`routing information, i.e. SGSN addresses. Routing informa
`tion is used for tunnelling protocol data units PDU from the
`data netWork 11 to the current sWitching point of the MS, i.e.
`to the serving SGSN. The functionalities of the SGSN and
`GGSN can be connected to the same physical node
`(SGSN+GGSN).
`The home location register HLR of the GSM netWork
`contains GPRS subscriber data and routing information, and
`it maps the subscriber’ s IMSI into one or more pairs of the
`PDP type and PDP address. The HLR also maps each PDP
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`type and PDP address pair into a GGSN node. The SGSN
`has a Gr interface to the HLR (a direct signalling connection
`or via an internal backbone netWork 13). The HLR of a
`roaming MS and its serving SGSN may be in different
`mobile communication netWorks.
`The intra-operator backbone netWork 13, Which intercon
`nects an operator’s SGSN and GGSN equipment can be
`implemented, for example, by means of a local netWork,
`such as an IP netWork. It should be noted that an operator’s
`GPRS netWork can also be implemented Without the intra
`operator backbone netWork, eg by providing all features in
`one computer.
`NetWork access provides the means for connecting a user
`to a telecommunication netWork in order to use the services
`and/or facilities of that netWork. An access protocol is a
`de?ned set of procedures that enables the user to employ the
`services and/or facilities of the netWork. The SGSN, Which
`is at the same hierarchical level as the mobile sWitching
`centre MSC, keeps track of the individual MSs’ locations
`and performs security functions and access control. GPRS
`security functionality is equivalent to the existing GSM
`security. The SGSN performs authentication and cipher
`setting procedures based on the same algorithms, keys, and
`criteria as in the existing GSM. The GPRS uses a ciphering
`algorithm optimised for packet data transmission.
`In order to access the GPRS services, an MS shall ?rst
`make its presence knoWn to the netWork by performing a
`GPRS attach. This operation establishes a logical link
`betWeen the MS and the SGSN, and makes the MS available
`for the SMS over the GPRS, for paging via the SGSN, and
`for noti?cation of incoming GPRS data. More particularly,
`When the MS attaches to the GPRS netWork, i.e. in a GPRS
`attach procedure, the SGSN creates a mobility management
`context (MM context), and a logical link LLC (Logical Link
`Control) is established betWeen the MS and the SGSN in a
`protocol layer. MM contexts are stored in the SGSN and MS.
`The MM context of the SGSN may contain subscriber data,
`such as the subscriber’s IMSI, TLLI and location and
`routing information, etc.
`In order to send and receive GPRS data, the MS shall
`activate the packet data address that it Wants to use by
`requesting a PDP activation procedure. This operation
`makes the MS knoWn in the corresponding GGSN, and
`interWorking With external data netWorks can commence.
`More particularly, one or more PDP contexts are created in
`the MS, the GGSN and the SGSN, and stored in the serving
`SGSN in connection With the MM context. The PDP context
`de?nes different data transmission parameters, such as the
`PDP type (eg X25 or IP), PDP address (eg IP address),
`quality of service QoS and NSAPI (NetWork Service Access
`Point Identi?er). The MS activates the PDU context With a
`speci?c message, Activate PDP Context Request, in Which
`it gives information on the TLLI, PDP type, PDP address,
`the required QoS and NSAPI, and optionally the access
`point name APN. The SGSN sends a Create PDP Context
`message to the GGSN Which creates the PDP context and
`sends it to the SGSN. The SGSN sends the PDP context to
`MS in an Activate PDP Context Response message, and a
`virtual connection or link betWeen the MS and the GGSN is
`established. As a result, the SGSN forWards all the data
`packets from the MS to the GGSN, and the GGSN forWards
`to the SGSN all data packets received form the external
`netWork and addressed to the MS. The PDP context is stored
`in the MS, the SGSN and the GGSN. When the MS roams
`to the area of a neW SGSN, the neW SGSN requests MM and
`PDP contexts from the old SGSN.
`
`Petitioner's Exhibit 1006
`Page 6 of 9
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`US 6,980,801 B1
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`FIG. 1 illustrates the implementation of a Mobile IP in the
`GPRS/3G environment.
`The MS can be a laptop computer PC connected to a
`cellular telephone enabling packet radio transmission. Alter
`natively, the MS can be an integrated combination of a small
`computer and a packet radio telephone, similar in appear
`ance to the Nokia Communicator 9000 series. Yet further
`embodiments of the MS include various pagers, remote
`control, surveillance and/or data-acquisition devices, etc.
`The user of a mobile station MS subscribes to a special
`Mobile IP service. The subscription information is stored in
`the Home Location Register HLR together With the user’s
`home IP address.
`In FIG. 1 the foreign agents FA are located at (integrated
`into) GGSN’S. An alternative is that the SGSN and the
`GGSN are co-located, and the FAs are located at
`SGSN+GGSNs. It should be noted that there may be more
`than one SGSN and GGSN in one netWork. All GGSNs may
`not have FAs. Each FA has an IP address in the Internet and
`in the operator’s oWn private GPRS/3G backbone netWork.
`More precisely, the FA’s IP address is such that IP packets
`destined to that address are routed in the Internet to the
`GGSN associated With the FA. When the MN leaves its
`home subnet and registers to a neW FA, it can no longer be
`reached on the basis of its home IP address alone, but must
`be assigned an address belonging to the visited netWork,
`called the care-of address (COA). The care-of address
`positively identi?es the instantaneous location of the mobile
`terminal and may be: 1) the IP address of the FA belonging
`to the visited netWork, or 2) an IP address acquired directly
`by the mobile terminal through an autocon?guration mecha
`nism from the local IP address space, in Which case the term
`co-located care-of address is used. Upon registering to a neW
`FA and obtaining a COA, the MN then registers With a home
`agent HA in its home netWork and informs the latter of its
`COA. In FIG. 1 a home agent HA is located in the data
`netWork 11 Which is the home netWork of the mobile node
`MN associated With the mobile station MS. Asecond host 14
`Wishing to communicate With the MN need not knoW that
`the MN has moved: it simply sends IP packets addressed to
`the MN’s home IP address. These packets are routed via
`normal IP routing to the MN’s home netWork, there they are
`intercepted by the HA. The HA encapsulates each such
`packet into another IP packet Which contains the MN’s COA
`as these packets are thus delivered to the FA (a process called
`45
`tunneling). The FA forWards the IP packet to the GGSN. The
`GGSN forWards the IP packet (Which may be encapsulated
`for transmission over the GPRS backbone) to the serving
`SGSN Which further forWards the IP packet to the MS/MN.
`Packets from the MN to the second host 14 need not
`necessarily be tunneled: the MN may simply send them to
`the GGSN Which directly forWards the packets to the second
`host 14, Without interception by the FA or the HA.
`As noted above, according to the present invention the
`SGSN selects the mobility agent and indicates it to the
`mobile station during the GPRS attach. Apreferred embodi
`ment of the invention Will be noW described With reference
`to FIGS. 1, 2, 3 and 4.
`Areference is noW made to FIG. 1. The home netWork of
`the mobile station MS is the GPRS/3G netWork 1. The user
`of the mobile station MS subscribes to a special Mobile IP
`service, and an IP application in the MS or in a separate data
`terminal is a mobile node MN in the Mobile IP communi
`cation.
`Let us noW assume that the MS/MN is located in the
`service area of another GPRS/3G netWork 2 Which is served
`by a support node SGSN2. The MS part listens to radio
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`broadcast messages, Which contain information about radio
`parameters, netWork and cell identity, etc. as Well as eg
`information about available core netWork, service providers,
`service capabilities etc. Then the MS sends a GPRS attach
`request to the SGSN2, as shoWn in step 1 in FIG. 2. The
`SGSN2 creates a mobility management conteXt (MM con
`teXt), and a logical link LLC (Logical Link Control) is
`established betWeen the MS and the SGSN in a protocol
`layer. MM conteXts are stored in the SGSN and MS. The
`MM conteXt of the SGSN may contain subscriber data, such
`as the subscriber’s IMSI, TLLI and location and routing
`information, etc. The authentication, ciphering and location
`updating procedures, as Well as an interrogation to the HLR
`of the MS/MN in order to obtain the subscriber data, may
`typically be involved With the creation of the MM conteXt,
`as shoWn in steps 2. In the preferred embodiments the
`procedures involved in steps 1 and 2 are in accordance With
`the basic GPRS attach de?ned in the current GPRS/UMTS
`speci?cations.
`During the GPRS attach procedure, preferably after the
`MM conteXt is created, the SGSN2 eXecutes the Mobile IP
`capability check and the FA selection procedure according to
`the present invention, step 3.
`The check and selection procedure according to the
`preferred embodiment of the present invention is illustrated
`in FIG. 3.
`In step 31 the SGSN2 checks Whether the MS/MM has a
`Mobile IP capability. For eXample, the SGSN2 may check
`Whether the subscriber data obtained from the HLR indicates
`that the mobile station MS subscribes to a special Mobile IP
`service. Alternatively or in addition, the SGSN2 may check
`Whether the Mobile Station Classmark Information element
`received in the attached request message from the MS
`indicates that the MS has the Mobile IP capability. The
`Mobile Station Classmark Information element is used to
`indicate the general characteristics of the mobile station
`equipment to the netWork in order to affect the manner in
`Which the netWork handles the operation of the mobile
`station. If the Mobile IP capability is indicated in the
`classmark, this can be utiliZed in the present invention.
`HoWever, it should be noted that the recognition of the
`Mobile IP capability can be based on any information
`received from the MS, another netWork element (such as
`HLR) or stored locally in the SGSN2.
`If the Mobile IP capability of the MS is found in step 31,
`the SGSN2 selects a suitable foreign agent (FA) for the MS,
`step 32. The selection of the mobile agent may be based on
`any suitable criterion. For eXample, the address of the FA
`associated With the nearest GGSN, ie a FA2 at the GGSN2,
`may be stored in SGSN2 for selection purposes. In that case,
`the SGSN2 may alWays select the FA2. Normally this
`approach also provides the most optimal routing, i.e. mini
`miZes the length of the routing path through the netWork. In
`another embodiment of the invention, the selection is based
`on the traf?c load at the foreign agents FA1 and FA2. The
`traffic load may be monitored by the operation and mainte
`nan