United States Patent
`US 7,280,505 B2
`(10) Patent No.:
`(12)
`Chaskaret al.
`(45) Date of Patent:
`Oct. 9, 2007
`
`
`US007280505B2
`
`(54) METHOD AND APPARATUS FOR
`PERFORMING INTER-TECHNOLOGY
`HANDOFF FROM WLAN TO CELLULAR
`NETWORK
`Inventors: Hemant Chaskar, Woburn, MA (US),
`Govind Krishnamurthi, Arlington, MA
`(US); Dirk Trossen, Cambridge, MA
`(US)
`
`(75)
`
`(73) Assignee: Nokia Corporation, Espoo (FI)
`(*) Notice:
`Subject to any disclaimer, the term ofthis
`.
`,
`patent is extended or adjusted under 35
`US.C. 154(b) by 15 days.
`
`.
`(21) Appl. No.: 10/600,156
`(22)
`Filed:
`Jun. 19, 2003
`(65)
`Prior Publication Data
`US 2004/0090937 Al
`May 13, 2004
`
`Related U.S. Application Data
`ee
`(60) nal application No. 60/425,801, filed on Nov.
`°
`.
`(51)
`Int. Cl
`(2006.01)
`H040 7100
`,
`370/331; 370/401
`US. Cl
`52)
`370/331
`oe Fi ld f aue.feativeeSoe1.
`(58)
`Fie
`*370/338 359.356,401: 455/432.1 436 ‘439.
`200A
`OOM
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`i
`TOO
`79
`lication
`file
`£
`let
`hen 171
`tor complete search
`ile
`ee application
`References Cited
`U.S. PATENT DOCUMENTS
`
`S
`
`(56)
`
`Austory.
`
`6,137,791 A * 10/2000 Frid et al... 370/352
`6,243,581 B1*
`6/2001 Jawanda..........
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`
`
`6,708,031 B2*
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`
`............... 370/467
`6/2005 Pichnaet al.
`(Continued)
`FOREIGN PATENT DOCUMENTS
`2003-333639
`11/2003
`(Continued)
`
`JP
`
`OTHER PUBLICATIONS
`Perkins et al, Mobile IP Joins Forces with AAA, IEEE, pp. 59-61,
`Aug. 2000.
`.
`(Continued)
`Primary Examiner—Frank Duong
`(74) Attorney, Agent, or Firm—Harrington & Smith, PC
`(57)
`ABSTRACT
`A method, system and computer program are disclosed to
`perform a low latency inter-technology handoff of a MN
`from a WLANto a cellular network. The method includes
`transmitting a Bearer Context from the MN for use by the
`cellular network, the Bearer Context containing information
`required to establish access network bearers in the cellular
`network for an ongoing Internet session of the MN; and
`responding to the Bearer Context with a Router Advertise-
`ment that is forwarded to the MN. The Bearer Context may
`be piggybacked on another message, or it may be sent as a
`Presy
`8
`y
`separate message. The Bearer Context includes information
`expressive of: (a) a QoS requirement of an ongoing appli-
`cation or applications of the MN; (b) a uniqueidentity of the
`MN that is recognizable by the cellular network; (c) param-
`eters to facilitate the creation of a Point-to-Point Protocol
`state in the cellular network; and (d) parameters to enable
`establishment of packetfilters in the cellular network. The
`method also includes authenticating and authorizing with the
`target cellular network for the purpose of executing handoff.
`
`43 Claims, 4 Drawing Sheets
`
`
` AAA IN HONE
`
`OPERATOR NETWORK
`
`
`
`
`SECURITY ASSOCIATION
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`
`LOCAL AAA IN VISITED
`CDMA 2000 NETWORK
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`

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`US 7,280,505 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`1/2007 Shoaib et al. ........0.... 370/331
`7,161,914 B2
`2/2007 Shaheen et al.
`............ 370/338
`7,173,924 B2*
`1/2004 Janevski etal.
`. 370/331
`2004/0008645 Al*
`
`4/2004 Koodli et al... 370/329
`2004/0081122 Al
`6/2004 Jiang et al. ow. 370/328
`2004/0114553 Al*
`FOREIGN PATENT DOCUMENTS
`
`Malki et al (Low Latency Handoff in Mobile IPv4, Internet Draft,
`pp. 1-65, May 2001.*
`Pahlavan et al, Handoff in Hybrid Mobile Data Networks, IEEE,pp.
`34-47, 2000.*
`Tsao et al (Design and Evaluation of UMTS-WLANInterworking
`Strategies, IEEE, pp. 777-781, Sep. 2002).*
`Salberg, WLAN-GPRSInterworking, Graduate Thesis, pp. 1-50,
`May 2001.*
`34 Generation Partnership Project 2; “Wireless IP Network Stan-
`WoO WO-03/101025 A2=12/2003
`
`dard” (3G PP2 P.SO001-A,version 3.0), Jul. 2001.
`WO
`WO 2004/023249
`3/2004
`3" Generation Partnership Project 2; “Wireless IP Architecture
`Based on IETF Protocols” (3G PP2 P.ROOOI, version 1.0.0), Jul.
`2000.
`IETF Mobile IP Working Group; “Low Latency Handoffs in Mobile
`IPv4”, Jun. 2002.
`IETF Mobile IP Working Group; “Fast Handovers for Mobile
`IPv6”, Mar. 2003.
`IETF Seamoby Working Group; “Issues in Candidate Access Router
`Discovery for Seamless IP-level Handoffs”, Oct. 2002.
`Malki et al., “Low Latency Handoff in Mobile [Pv4”, Internet Draft,
`May 2001, pp. 1-65.
`Wuet al., “MIRAI Architecture for Heterogeneous Network,” IEEE
`Communications Magazine, Feb. 2002, vol. 40, No. 2, pp. 126-134.
`Watanabe et al., “Multimedia Integrated network by radio Access
`Innovation (MIRAI), A Combined WLAN and PHS Multi-service
`User Terminal,” 2002 IEICE General Conference B-5-15.
`
`Srikaya et al, Packet Mode in Wireless Network : Overview of
`Transition to Third Generation, IEEE, pp. 164-172, Sep. 2000.*
`3GPP2P.S0001, Wireless IP Network Standard, 3GPP2 Project, pp.
`1-52, 1999.*
`Karagiannis, Mobility Support for Ubiquitous Internet Access,
`ERICSSON,pp. 1-70, 2000.*
`Xu et al, Mobile IP Based Micro Mobility Management Protocol in
`The Third Generation Wireless Network, Internet Draft, pp. 1-16,
`Nov. 2000.*
`Choi et al, A Fast Handoff Scheme for Packet Data Service in the
`CDMA 2000 System, IEEE, pp. 1747-1753, 2001.*
`Parikh et al, Seamless Handoff of Mobile Terminal from WLAN to
`cdma2000 Network, download at http:/‘www.nokia.com/library/
`
`files/docs/Seamless__Handoff_of_Mobile_Terminal_ from
`WLAN_to__cdma2000_Network.pdf.*
`
`OTHER PUBLICATIONS
`
`* cited by examiner
`
`

`

`U.S. Patent
`
`Oct. 9, 2007
`
`Sheet 1 of 4
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`US 7,280,505 B2
`
`1
`METHOD AND APPARATUS FOR
`PERFORMING INTER-TECHNOLOGY
`HANDOFF FROM WLAN TO CELLULAR
`NETWORK
`
`CLAIM OF PRIORITY TO PROVISIONAL
`PATENT APPLICATION
`
`This patent application claims priority under 35 U.S.C.
`119(e)
`from U.S. Provisional Patent Application No.:
`60/425,801, filed Nov. 13, 2002, incorporated by reference
`herein in its entirety.
`
`
`
`TECHNICAL FIELD
`
`This invention relates generally to wireless communica-
`tions systems and methods and, more specifically, relate to
`techniques for handing off a Mobile Node (MN) between
`wireless network providers that operate with different tech-
`nologies, such as wireless local area network (WLAN) and
`a cellular network.
`
`BACKGROUND
`
`Cellular wireless technologies, such as cdma2000 and
`Universal Mobile Telecommunication System (UMTS),are
`expected to provide high speed wireless Internet connectiv-
`ity to mobile users over a wide coverage area. At the same
`time, WLANtechnologies, such as IEEE 802.11 and Euro-
`pean HiperLAN,are becoming increasingly popular, as they
`provide a low cost and high speed wireless access solution
`for localized “hot spots”. According to one prediction
`regarding the future of mobile networking, wide area cel-
`lular networks and WLANswill complement each other to
`provide mobile users with ubiquitous high-speed wireless
`Internet connectivity. In such an environment the mobile
`users can be expected to experience a need to seamlessly
`switch between the WLAN and the cellular network, even
`during an ongoing Internet session.
`Mobile terminals, also referred to herein as mobile nodes,
`that combine different radio interfaces, such as cellular and
`WLAN,in one device will be available soon. Further, the
`developmentof mobility aware Internet protocols has picked
`up pacein recent years. These and other factors will combine
`and converge in the near future to provide enhanced mobile
`user features and connectivity. This will, however, require
`that the inter-technology handoff issues and problems be
`addressed and resolved., such as the inter-technology hand-
`off from a WLANto a cellular network. In particular, when
`the mobile node moves from WLANto cellular network
`coverageit has been found that the WLANsignal fades very
`fast. As a result, the time and signal margin available for
`execution of handoff or handover procedures is very small.
`The Internet Engineering Task Force (IETF) has devel-
`oped a Mobile IP protocol to enable IP-layer handoffs during
`an ongoing Internet session. To minimize disruption to the
`mobile node’s Internet connectivity during such handoffs,
`protocols such as Fast Handoff and Context Transfer are also
`under development. While these protocols provide the core
`framework for seamless inter-technology handoffs, addi-
`tional effort is required to apply them to specific environ-
`ments. Further, these protocols assume the existence of a
`“trusting” relationship between the source (e.g., WLAN)
`and destination (e.g., cdma2000) access networks, which is
`not alwaysthe case.
`
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`15
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`2
`SUMMARY OF THE PREFERRED
`EMBODIMENTS
`
`The foregoing and other problems are overcome, and
`other advantages are realized, in accordance with the pres-
`ently preferred embodiments of these teachings.
`This invention provides a method for inter-technology
`handoff of a mobile node from, in the preferred but not
`limiting environment, a WLANto a cellular network. The
`handoff procedure incorporates enhancements to basic IP-
`layer handoff techniques in the following areas: (i) rapid set
`up of access network bearers in the cellular access network;
`and (ii) a dynamic authentication and authorization with the
`cellular network at the time of handoff.
`
`The method advantageously requires no significant modi-
`fication to existing cellular network protocol architectures.
`Further,
`the method is compatible with IP-layer handoff
`techniques such as low-latency Mobile IPv4 and fast Mobile
`IPv6.
`
`A method, system and computer program are disclosed to
`perform a low latency inter-technology handoff of a MN
`from a WLANto a cellular network. The method includes
`transmitting a Bearer Context from the MN for use by the
`cellular network, the Bearer Context containing information
`required to establish access network bearers in the cellular
`network for an ongoing Internet session of the MN; and
`responding to the Bearer Context with a Router Advertise-
`mentthat is forwarded to the MN. The Bearer Context may
`be piggybacked on another message, or it may be sent as a
`separate message. The Bearer Context includes information
`expressive of: (a) a QoS requirement of an ongoing appli-
`cation or applications of the MN; (b) a uniqueidentity of the
`MN that is recognizable by the cellular network; (c) param-
`eters to facilitate the creation of a Point-to-Point Protocol
`state in the cellular network; and (d) parameters to enable
`establishment of packetfilters in the cellular network. The
`methodalso includes authenticating and authorizing with the
`target cellular network for the purpose of executing handoff.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The foregoing and other aspects of these teachings are
`made moreevident in the following Detailed Description of
`the Preferred Embodiments, when read in conjunction with
`the attached Drawing Figures, wherein:
`FIG. 1 is a simplified block diagram of a first, most
`preferred, embodimentof a reference network architecture,
`and is illustrative of one suitable type of multi-technology
`wireless system architecture in which this invention can be
`deployed to advantage;
`FIG. 2 is a simplified block diagram of a second, less
`preferred, embodimentof a reference network architecture,
`and is illustrative of another suitable type of multi-technol-
`ogy wireless system architecture in which this invention can
`be deployed to advantage;
`FIG.3 illustrates a typical indoor WLAN environment
`that lies within the coverage area of a cellular network; and
`FIG. 4 is a message diagram showing MN, WLANand
`cellular network inter-technology handoff signal flow in
`accordance with an aspect of this invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`Those skilled in the art may appreciate that the following
`publications contain information related to this invention,
`and may be incorporated as necessary into this Patent
`
`

`

`US 7,280,505 B2
`
`3
`Application in whole or in part: IETF MobileIP Working
`Group (www.ietf.org): Low Latency Mobile IPv4 and Fast
`Mobile IPv6 specifications; IETF Seamoby Working Group
`(www.ictf.org): Context Transfer Framework specification;
`3GPP2 Specifications: “Wireless IP architecture based on
`IETF protocols” (3GPP2#P.R0001) and “Wireless IP Net-
`work Standard (3GPP2#P.S0001-A v3.0)”, www.3gpp2.org;
`3GPP2 Specification: “Access Network Interfaces Interop-
`erability
`Specification”, Revision A (G-IOSv4.1),
`3GPP2#A.S0001-A, www.3gpp2.org; 3GPP Specification:
`“QoS
`Concept
`and Architecture’,
`TS
`23.107,
`www.3gpp.org; and 3GPP Specification: “General Packet
`Radio
`Service:
`Service Description”,
`TS
`03.60,
`www.3gpp.org.
`FIG. 1 shows a reference network deployment embodi-
`ment, also referred to as an independent AAA (Authentica-
`tion, Authorization, Accounting) embodiment. For the pur-
`poseof illustration, and not by wayoflimitation, in FIG. 1
`the cdma2000 specification is used as a representative
`cellular network 2 architecture. In the architecture of FIG.1,
`the WLAN 1 access and cdma2000 network 2 access are
`
`10
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`15
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`4
`it should be noted that the handoff method of this
`ever,
`invention can be adapted for use as well
`in the shared
`deployment model of FIG. 2.
`Referring again to FIG. 1, consider a handoff from the
`WLAN network 1 to the cdma2000 network 2. In this
`environment, assumethat the mobile user initiates an Inter-
`net 4 session, such as a voice over IP (VoIP) call or a
`multimedia conferencing call, from the WLAN1, andlater
`moves away from the WLANhotspot coverage area. Before
`attempting an inter-technology handoff from the WLAN1 to
`the wide area cdma2000 network 2, the MN 3 should first
`perform authentication and authorization procedures with
`the cdma2000 network 2. Note that the home agent 6 for MN
`3 mayreside in the same realm as that of the WLAN 1 (e.g.,
`in the enterprise case), or in the same realm as that of the
`homeoperator network 2, or in a completely different realm
`(e.g., in the bookstore or free access case).
`In addition, a numberof procedures, including those for
`IP access and quality of service (QoS) setup, should be
`performed before the MN 3 can exchange IP packets with
`the Internet 4 via the cdma2000 access network 2. These
`
`include procedures for setting up a PPP (Point to Point
`Protocol) connection with the PDSN 12, Mobile IP proce-
`dures, and procedures for setting up access network bearers
`with appropriate QoS characteristics in the cdma2000 net-
`work 2.
`
`The latency in performing these procedures should be
`minimized to avoid a service disruption at
`the time of
`handoff from the WLAN1 to the cdma2000 network 2, such
`as a handoff that occurs during an ongoing session, such as
`a VoIP session, or a multimedia streaming session, or a
`gaming session. This invention provides a technique to
`efficiently and quickly perform an inter-technology handoff
`that avoids the problems inherent in the priorart.
`In general, the performance of the handoff can be con-
`siderably improvedif at least some of the handoff messaging
`is performed proactively, i.e., while the MN3 still sees a
`strong signal from the WLAN Access Point 9. These pro-
`actively performed steps may include, for example, fast
`handoff signaling, authenticating with the cellular network
`2, and informing the cellular network 2 about QoS and other
`requirements of current MN 3 application(s). Then, as soon
`as the WLAN signal strength diminishes,
`the MN 3 is
`enabled to send a final trigger to the cellular network 2 to
`complete the handoff process (i.e., to actually commit the
`radio resources, arrange for packet rerouting, and perform
`any other necessary procedures to complete the handoff).
`It should be noted that it
`is generally not possible to
`FIG. 2 shows another network deployment embodiment,
`reliably perform this task based on MN3signal strength
`50
`referred to as a shared AAA architecture. Here, a trusted
`measurements alone. For example, if the proactive handoff
`relationship is assumed to exist between the WLAN 1 and
`procedures are initiated after the WLAN signal strength
`the cdma2000 network 2. Note in this embodiment
`the
`begins to decline noticeably, the MN 3 Internet connectivity
`overlapping domains 5A and 5B. This embodiment may
`may be disrupted before these steps are completed. On the
`exist, for example, if WLAN hotspot access is operated by
`other hand, if the handoff proceduresare initiated too early
`the cdma2000operator. Alternatively, a roaming agreement
`(when the WLANsignalis still strong), it may result in large
`may exist between the WLAN1 operator and the cdma2000
`numberoffalse starts. In other words, the mobile user may
`network 2 operator. Thus, at the time of inter-technology
`actually never leave the coverage area of the WLAN1, even
`handoff,
`the authentication and authorization performed
`though the proactive handoff steps have begun. This may
`with the WLAN1 can be reused for the cdma2000 2 access
`create an unnecessary signaling burden on the cellular
`network 2.
`as well. Further, a security association 5C may exist between
`the AR 8 in the WLAN1 and the PDSN 12 in the cdma2000
`Reference is made to FIG. 3 for showing an exemplary
`WLAN/cellular network environment, such as may be
`encountered within a hotel or other type of building. In FIG.
`3 is can be seen that a cellular network (e.g., a cdma2000
`network) base station coverage area (footprint) 20 encom-
`passesa structure 22 containing a plurality of WLAN access
`point (AP) coverage areas (footprints) 24.
`
`independently managed, and no peering relationship (such
`as common ownership or roaming agreement) is assumed to
`exit between them. A non-limiting example of this type of
`arrangement is a WLANhotspot in a bookstore that charges
`access fees to a user readership account. Another example
`would be an enterprise WLAN, which only employeesof the
`enterprise are authorized to access(i.e., there are no access
`fees for the employees). Or, in some cases, WLANaccess at
`a hot spot could be free of charge, and hence, no localAAA
`functionality is required at the WLAN. This could be the
`case for a WLAN hot spot
`in, as an example, a small
`restaurant. On the other hand, cdma2000 cellular access
`would typically always be charged to a user’s subscription
`account with the (home) cellular operator.
`In the illustrated example there are a plurality of domains
`5 in each of the WLAN1 andthe cdma2000 network 2. For
`
`example, the WLAN 1 includes a home agent domain 6, and
`a WLAN AAA function 7 connected via an access router
`(AR) 8 to WLAN Access Points 9. The cdma2000 network
`2 can include an AAA function 10 located in the Home
`Operator Network, as well as a local AAA function 11 in a
`Visited cdma2000 network, connected via a PDSN (Packet
`Data Support Node) 12 to an IMT-2000 Radio Network 13.
`The MN 3 is assumed to handoff from the WLAN1 to the
`cdma2000 network 2 via the WLAN Access Points 9 and the
`IMT-2000 Radio Network 13.
`
`network 2. For completeness, there is shown outside of the
`trusted WLAN/cellular network arrangement another opera-
`tor 14 having an access router 15 connected to the WLAN
`Access Points 9.
`
`Of most interest to the teachings of this invention is the
`independent network architecture shown in FIG. 1. How-
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`US 7,280,505 B2
`
`10
`
`6
`5
`First described is a handoff procedure that is adapted to
`In addition to providing an inter-technology handoff tech-
`Low Latency Mobile IPv4 (ETF MobileIP Working Group:
`nique that can be cleanly partitioned into proactive and
`reactive steps, this invention provides a method to anticipate
`“Low latency Mobile IPv4 and Fast Mobile IPv6 specifica-
`the need for a handoff from the WLAN1to the cellular
`tions”, www.ietf.org) in a “pre-registration” mode. This
`modeis useful, as Mobile IPv4 has been incorporated in the
`cdma2000 specifications. The corresponding signaling
`schemeis shownin FIG. 4. The adaptation of the invention
`to Fast Mobile IPvé6 (in the “anticipated handoff’ mode) is
`conceptually similar, and a description for this embodiment
`is also provided below.
`Referring now also to FIG.4, after the MN 3 determines
`to initiate an inter-technology handoff from the WLAN 1 to
`the cdma2000 network 2 (based on whatever suitable param-
`eter(s) are employed, such as signal strength and/or signal
`quality and/or the use of borderbits), it sends, by a wireless
`connection, a Proxy Router Solicitation (ProxyRtSol) to an
`AR 8, which in turn sends, via the Internet 4, a Router
`Solicitation to the PDSN 12. In addition, the MN 3 arranges
`to transfer what is referred to herein as a “Bearer Context”
`
`network 2, with sufficient time for the execution of proactive
`handoff steps. In this regard handoff trigger mechanismsare
`desired for initiating Phase 1 and Phase 2 aspects of the
`handoff technique (the Phase 1 and Phase 2 operations are
`described in detail below).
`A signal strength criterion, among others, can be used to
`generate handoff triggers, and the signal strength criterion
`may be employed to generate the ultimate handoff trigger.
`However, in the context of WLAN to cdma2000 handoff,
`this approach provides an opportunity for generating spuri-
`ous handoff triggers. To further explain, consider the handoff
`scenario depicted in FIG. 3, which shows the WLAN
`footprint in a hot spot, which in this case is the indoor
`environment such as a hotel (structure 22). The areas 24A
`and 24B indicate strong signal footprints of different WLAN
`message to the PDSN 12 via the AR 8. The Bearer Context
`APs located at the hot spot. Note that the WLAN 1 geo-
`message contains parameters for use in establishing access
`graphical coverage area is subsumed in cdma2000 network
`network bearers in the cdma2000 network 2 for the ongoing
`2 geographical coverage area, as typically is the case.
`Assume that a mobile user having a multi-radio (e.g.,
`Internet session(s) of the MN 3. The Bearer Context mes-
`
`dual-mode WLAN and cdma2000) MN3initiates an Inter- sage can be sent from the MN 3 to the AR 8 piggybacked on
`25
`net session over the WLANaccess, and then walks along the
`the ProxyRtSol, or piggybacked on another message,orit
`path 26. Along the path 26, whenthe userarrives at locations
`can be sent as a separate message. From the AR 8 to the
`where WLANsignal strength drops due to local factors such
`PDSN 12 the Bearer Context message can be piggybacked
`as metal objects, walls, etc., the MN 3 detects a drop in
`on a Router Solicitation message, or it can be sent in a
`WLANsignal strength, but still detects a strong cellular
`separate message. The Bearer Context message includes at
`signal. In these cases the MN 3 would attempt to initiate a
`least one or more of the following, or similar or equivalent
`handoff from the WLAN 1 to the cellular network 2.
`information:
`
`20
`
`30
`
`35
`
`40
`
`45
`
`However, seconds or moments later the MN 3 again detects
`the QoS requirement of the MN’s ongoing application(s),
`such as one or more of the desired bandwidth, reliabil-
`
`a strong signal from the WLAN1and, hence, initiates
`handoff back to the WLAN network 1. Such a ping-pong
`ity and latency characteristics,
`effect
`is undesirable as it causes unnecessary signaling
`the MSID: Mobile Station Identity recognizable by the
`traffic, as well as possibly causing more disruption to the
`cdma2000 network 2, e.g.,
`the IMSI (International
`user’s service than what would have been caused due to a
`Mobile Subscriber Identity) of the MN 3,
`momentary lack of the WLANsignal. Of course, the MN 3
`LCP (Link Control Protocol) configuration parameters
`could wait for a short time after the loss of the WLANsignal
`such as MRU (Maximum Receive Unit), ACCM
`before initiating handoff to the cellular network 2. However,
`(Asyne Character Control Map) and a link quality
`this approach degrades the (latency) performance of the
`monitoring protocol to be used,to facilitate the creation
`of PPP state in the PDSN 12,
`handoff when the user actually exits from the structure 22
`through the door 22A and, hence, actually loses connectivity
`TFT (Traffic Flow Templates) to enable establishment of
`to the WLAN network 1.
`packet filters in the PDSN 12, and any other desired
`strength criterion may be
`As
`such, while a signal
`service parameters, such as a requested security level.
`employed to initiate the inter-technology handoff, and to
`The foregoing parameters that comprise the Bearer Con-
`generate the final WI,AN/cellular network handoff, those
`text message are not to be read in a limiting sense. For
`skilled in the art should realize that other considerations and
`example, it is also within the scope of this invention to also
`criteria, such as packet error rate and/or the number of
`provide, or to provide in lieu of one of the foregoing
`requests for retransmission generated per unit of time, as
`parameters, other parameters that request resources from the
`well as other signal quality-related parameters, may be
`cellular network 2, such as a location tracking service and/or
`employed instead of, or in conjunction with, the use of the
`a transcoding service for use in certain packet sessions.
`signal strength received at the MN 3.
`The PDSN 12 responds to the Bearer Context message
`Another technique that is more presently preferred for
`with a Router Advertisement message that is forwarded to
`performing proactive handoff control relies on the use of
`the MN 3 via the Internet 4 and the AR 8 (as a Proxy Router
`“border bits”, i.e., information provided by border access
`Advertisement or ProxyRtAdv). The ProxyRtAdv contains,
`nodes that provide geographical coverage or region infor-
`among other items, a challenge (e.g., a Mobile Node-
`mation for use by a mobile nodein controlling the initiation
`Foreign Agent (MN-FA) challenge extension) for authenti-
`of a handoff from one technology network to another tech-
`cation and authorization purposes.
`nology network. Reference in this regard can be made to
`The MN 3 responds by sending a Registration Request
`U.S. Provisional Patent Application No.: 60/426,385,
`(RegReq) message to the PDSN 12 via the AR 8 (shown as
`entitled “Smart Inter-Technology Handover Control”, by H.
`step 2 in FIG. 4). This message contains, among other items,
`Chaskar et al.,
`incorporated by reference herein in its
`the MN 3 network address identifier (MN-NAJ) that iden-
`tifies the home AAA 10 of the MN 3, authentication data to
`entirety.
`Described now is a handoff procedure, with specific
`be used for registering with the HA 6, and the response
`reference to the cdma2000 network 2 architecture,
`that
`(MN-Radius extension) calculated over the MN-FA chal-
`operates in accordance with this invention.
`lenge received in the ProxyRtAdvfor the purpose of authen-
`
`50
`
`55
`
`60
`
`65
`
`

`

`US 7,280,505 B2
`
`7
`tication and service authorization with the cdma2000 net-
`work 2. It should be noted that the Bearer Context message
`can be piggybacked on this message as well, if it is not sent
`earlier.
`
`Upon the receipt of the Registration Request, the PDSN
`12 uses the NAI extension to determine the home AAA
`domain of the MN 3, and issues a query to the identified
`home AAA 10 of the MN 3. In the preferred embodimentthe
`PDSN 12 actually queries the local (visited) AAA 11 in the
`cdma2000 access network 2. The visited AAA 11 then
`
`8
`12 and AR 8). The MN 3 may then use this key to
`authenticate or encrypt future message transactions with the
`PDSN12 (e.g., ACK).
`Now described is a technique to adapt the foregoing
`handoff embodiments to the Fast Mobile IPv6 environment
`
`(ETF MobileIP Working Group: “low latency Mobile IPv4
`and Fast Mobile IPv6 specifications”, www.ietf.org). In this
`approach communication between the AR 8 and the PDSN
`12 in step 1 of FIG. 4 is performed via a HI/HACK
`(Handover Initiate/Handover ACK) message exchange, and
`in this embodimentit is desirable to piggyback the Bearer
`forwards the query to the home AAA 10 of the MN 3,
`Context message and the MN-FA challenge on the HI and
`possibly via one or more intermediate broker AAAs. The
`the HACK messages, respectively. In this case a new mes-
`PDSN 12 supplies the home AAA 10 with the challenge
`sage may be used to implement step 2, wherein the MN 3
`issued by the PDSN 12 in the MN-FAchallenge extension,
`sends responses for authenticating and authorizing with the
`and the reply of the MN 3 to it obtained in the MN-Radius
`cdma2000 network 2. Such a message is not specified as yet
`extension. The PDSN 12 also provides the home AAA 10
`in the Fast Mobile IPv6 protocol, as the design of this
`with the description of the access service (e.g., the QoS)
`protocol assumes a solid security association between the
`requested by the MN 3. Upon a successful authentication
`AR 8 and the PDSN 12. In step 4, another new message may
`and service authorization, the home AAA 10 sends to the
`be used to send the ticket to the MN 3, while the ACKin step
`PDSN 12 (this response would typically follow the same
`5 can be sent to the AR 8 using a F-BU (Fast Binding
`path asthatof the query, but in a reverse direction) a success
`Update) message with the ticket piggybacked on it. Another
`indication authorizing the access by the MN 3. The home
`new message can be used the AR 8 to sendthe indication to
`AAA 10 also sends a “ticket” to the PDSN 12 in clear text,
`the PDSN 12 tostart step 6. In step 6, the PDSN 12 does not
`as well as in encrypted form. Theticket is encrypted using
`the shared secret between the home AAA 10 and the MN 3.
`perform registration with the HA 6. Further, a temporary
`tunnel is preferably established between the AR 8 and the
`These procedures are shown as step 3 in FIG.4.
`PDSN 12 until the MN 3 performs a binding update.
`As shown in step 4, the PDSN 12 stores the ticket in a
`While described above in the context of certain presently
`clear text form and sends the encrypted copy to the MN 3 via
`preferred embodiments, it should be realized that the prac-
`the AR. The PDSN 12 also sends in this message any
`tice of this invention is not limited to only these embodi-
`configuration parameters for the MN 3. At this point one
`ments. For example, the Bearer Context can be sent by the
`may consider that a first phase (Phase 1) of the inter-
`MN 3 in context transfer signaling. Further by example, and
`technology handoff process is completed.
`as was mentioned above, other service specification param-
`The second phase (Phase 2) of the inter-technology hand-
`eters, in addition to those mentioned above, may be included
`off process is initiated when the MN3sends an acknowl-
`in the Bearer Context message, such as location tracking
`edgment (ACK) to the PDSN 12 via the AR 8, and includes
`services and transcoding services for certain packet sessions.
`the ticket in clear text form with the ACK(step 5 of FIG.4),
`Further by example, the Bearer Context message can be
`thereby proving to the PDSN 12 that
`the ACK indeed
`encrypted using the shared secret between the MN 3 andthe
`originated from the MN 3. This is a security measure thatis
`home AAA 10. This maybe useful to prevent compromising
`useful
`to avoid denial of service (DOS) attacks where
`privacyover the AR 8 to PDSN 12 path. When the PDSN 12
`malicious nodes spoof the ACK, causing the burden offalse
`receives the encrypted Bearer Context, it passes it on to the
`bearer set up on the cdma2000 network 2.
`home AAA 10 in a query. The home AAA10 deciphers the
`Tt should be noted that there can be a time delay between
`encrypted Bearer Context and sendsit to the PDSN 12 ina
`the completion of Phase 1 and the start of Phase 2. This
`response.
`would occur if the MN 3 begins Phase 1 while the WLAN
`Also, it should be appreciated that this invention encom-
`signal
`is still quite strong (but fading)
`in the hope of
`passes computer program code embodiedonor in a tangible
`completing Phase 1 before losing connectivity with the
`medium for directing one or more data processors to imple-
`Internet 4. Phase 2 would typically begin when the MN3is
`ment the various steps of the methods discussed above.
`about to leave the WLAN coverage area 24. After sending
`These data process