Note: Within nine months of the publication of the mention of the grant of the European patent in the European PatentBulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with theImplementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has beenpaid. (Art. 99(1) European Patent Convention).

Printed by Jouve, 75001 PARIS (FR)

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(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention of the grant of the patent: 07.09.2016 Bulletin 2016/36

(21) Application number: 10707139.1

(22) Date of filing: 12.02.2010

(51) Int Cl.:H04W 36/00 (2009.01) H04W 92/14 (2009.01)

(86) International application number: PCT/JP2010/052481

(87) International publication number: WO 2010/150568 (29.12.2010 Gazette 2010/52)

(54) MANAGING CS IRAT HANDOVER FROM 2G/3G NETWORK TO LTE NETWORK

HANDHABUNG EINER CS-IRAT-ÜBERGABE VON EINEM 2G/3G-NETZ ZU EINEM LTE-NETZ

GESTION DE TRANSFERT INTERCELLULAIRE CS IRAT D’UN RÉSEAU 2G/3G À UN RÉSEAU LTE

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

(30) Priority: 25.06.2009 EP 09163817

(43) Date of publication of application: 02.05.2012 Bulletin 2012/18

(73) Proprietor: Lenovo Innovations Limited (Hong Kong)Quarry Bay, Hong Kong (HK)

(72) Inventors: • SHINTANI, Tatsuyuki

Tokyo 108-8001 (JP)• LAMPURE, Marianne

ReadingBerkshire RG2 0TD (GB)

• ROGER, VincentReadingBerkshire RG2 0TD (GB)

• DAVIT, LucReadingBerkshire RG2 0TD (GB)

(74) Representative: MacDougall, Alan John Shaw et alMathys & Squire LLP The Shard 32 London Bridge StreetLondon SE1 9SG (GB)

(56) References cited: WO-A1-2008/038949 WO-A1-2008/081310WO-A1-2008/148429 WO-A1-2009/121745

• 3GPP: "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 3GPP System Architecture Evolution: Report on Technical Options and Conclusions (Release 7)" 3GPP DRAFT; 23882-1D1-CLEAN, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCE, vol. SA WG2, no. Marina del Rey; 20080109, 9 January 2008 (2008-01-09), XP050262528

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Description

TECHNICAL FIELD

[0001] The invention pertains to telecommunicationfield and concerns a method to manage a CS IRAT (Cir-cuit Switch Inter RAT (Radio Access technology)) hando-ver of a user Equipment from a 2G/3G network to a LTE(Long Term Evolution) network wherein at least two dif-ferent routing paths depending on at least two differenthandover technologies are possible for transferringHandover messages from a BSC/RNC (Base StationController/Radio Network Controller) node of said 2G/3Gnetwork to a target eNodeB of said LTE network.[0002] The invention also concerns a 2G/3G networkBSC/RNC node comprising means for selecting a routingpaths for transmitting a Handover message from aMSC/VLR node in a 2G/3G network to a target eNodeBin an LTE network, in order to handover a user Equipmentperforming a CS call in said 2G/3G network.[0003] The invention also concerns a 2G/3G networkMSC node comprising means for routing the handovermessage to a target eNodeB in a LTE network accordingto the selected path indicated by the RNC/BSC node.[0004] The invention also concerns a User Equipmentcomprising means for indicating its CS IRAT handovercapabilities to a 2G/3G RNC/BSC node.

BACKGROUND ART

[0005] 3GPP has defined two technologies to manageCS calls (e.g. voice calls) in EUTRAN: CS over PS(CSoPS) and Voice over IMS (VoIMS over LTE). Eachof these two technologies requires a specific handoverprocedure from EUTRAN to GERAN/LJTRAN, i.e.,CSoPS handover for CSoPS, or Single-Radio Voice CallContinuity (SRVCC) for handover from VoIMS over LTEto CS GERAN/LTTRA.[0006] For both SRVCC and CSoPS technologies, theCS IRAT handover from GERAN/UTRAN to EUTRAN isnot defined and is considered as for further study in thestandard. It can be assumed that, similarly to any otherhandover technologies (like CS 2G/3G, PS 2G/3G, LTE,CS GAN (Generic Access Network)), the CS IRAThandover from GERAN/LTTRAN to EUTRAN will be us-ing a reverse sequence than the CS IRAT handover fromEUTRAN to GERAN/IJTRAN. This means that, for bothcases, the RNC/BSC initiates the handover by sendinga "Handover Required" message to the MSC/VLR tomanage the handover.[0007] FIG. 1 illustrates different routing paths fortransmitting a handover message from the Radio AccessNetwork of the 2G/3G Network (GERAN/UTRAN: GSMRadio Access Network-UMTS Terrestrial Radio AccessNetwork) to Radio Access Network of the LTE Network(EUTRAN- Evolved Universal Terrestrial Radio AccessNetwork).[0008] It is then expected that for SRVCC, the

MSC/VLR triggers the Handover by sending a messageto MME (Mobility Management Entity), via the Sv inter-face (MME-MSC/VLR) which is the reference point de-fined for handling the SRVCC handover between 3GPPE-UTRAN/UTRAN (HSPA) and 3GPP UTRAN/GERAN,and for CSoPS, the MSC/VLR triggers the Handover bysending a message to IWF, via the A/Iu interface whichis known to support the handover in GERAN/UTRAN andwhich is reused by CSoPS technology.[0009] Consequently, for a network supporting bothSRVCC and CSoPS IRAT handover from GER-AN/UTRAN to EUTRAN, two different routing paths arepossible in MSC/VLR for transferring the Handover Re-quired message. So there is a need to identify to whichtarget node (IWF for CSoPS or MME for SRVCC) theMSC/VLR shall transfer the "Handover Required (targeteNodeB cell ID)" message received from RNCBSC.[0010] 3GPP: "3rd Generation Partnership Project;Technical Specification Group Services and System As-pects; 3GPP System Architecture Evolution: Report onTechnical Options and Conclusions (Release 7) "3GPPDRAFT; 23882-1D1-CLEAN, 3RD GENERATIONPARTNERSHIP PROJECT (3GPP), MOBILE COMPE-TENCE CENTRE; 650, ROUTE DES LUCIOLES; F-06921 SOPHIA-ANTIPOLIS CEDEX; FRANCE, vol. SAWG2, no. Marina del Rey; 20080109, 9 January 2008(2008-01-09), XP050262528 discloses a number of al-ternatives for performing circuit switched inter RAThandover of a user equipment from a 2G/3G network toan LTE network. WO 2008/148429 A1 discloses a meth-od for initiating handover of a circuit switched serviceusing a packet switched bearer of a mobile station froma packet switched domain to a circuit switched domainin a mobile communications network comprising a radionetwork and a core network. The method comprises com-municating to the mobile station that a circuit switchedhandover procedure is to be initiated, including sendinga circuit switched handover required message to the mo-bile station, which circuit switched handover requiredmessage comprising identification of a circuit switchedhandover target cell. The mobile station then sends acircuit switched handover required message to the corenetwork that includes identification of the handover targetcell.[0011] WO 2008/081310 A1 discloses a method thatincludes, during an ongoing call of a wireless user termi-nal in one of a circuit switched domain or a packetswitched domain, initiating a handover procedure; settingparameters allowing the other domain to determine theactual resources needed to continue the call in the otherdomain, sending an indication of these parameters to-wards a network element of the other domain and com-pleting the handover procedure. When the ongoing callis in the circuit switched domain completing the handoverprocedure results in handing over the ongoing call to thepacket switched domain, and when the ongoing call is inthe packet switched domain completing the handoverprocedure results in handing over the ongoing call to the

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circuit switched domain. For example, the circuitswitched domain may be a GERAN network and thepacket switched domain may be an E-UTRAN (LTE) net-work. In the GERAN network the handover proceduremay be accomplished at least in part through a Gs inter-face between a mobile switching center and a servinggeneral packet radio system support node and/or througha Gb interface between a base station system and theserving general packet radio system support node. Thehandover procedure is accomplished at least in part bysignaling conducted over an S3 interface between theserving general packet radio system support node of theGERAN network and the mobility management entity ofthe E-UTRAN network.

DISCLOSURE OF INVENTION

[0012] The invention is based on the fact that for thenew expected CS IRAT handover sequence from a2G/3G network to a LTE network, two different routing,corresponding respectively to a SRVCC IRAT handoverpath and a CSoPS IRAT handover path, are possible inthe MSC/VLR node (Mobile services Switching Center)of said 2G/3G for transferring the Handover Requiredmessage from GERAN/UTRAN to EUTRAN.[0013] The invention enables a correct routing ofhandover required message by MSC/VLR to either IWF(CSoPS) or MME (SRVCC).[0014] The present invention provides a method tomanage a Circuit Switch Inter RAT, CS IRAT, handoverof a user equipment, UE, from a 2G/3G network to a LongTerm Evolution, LTE, network wherein at least two dif-ferent routing paths corresponding to at least two differ-ent handover technologies are possible for transferringthe Handover messages from a BSC/RNC node of said2G/3G network to a target eNodeB of said LTE network,said method comprising: transmitting, by the UE, its CSIRAT handover from 2G/3G to LTE capabilities to theBSC/RNC node; selecting, by the BSC/RNC node, a rout-ing path among said different routing paths based on theUE capabilities for CS IRAT handover from 2G/3G to LTEand transmitting to a MSC/VLR node of said 2G/3G net-work a Handover message comprising information indic-ative of the selected path corresponding to the selectedCS handover technology; and transferring, by theMSC/VLR node, said Handover message to said targeteNodeB through a MME node or through an IWF nodedepending on said information indicative of the selectedpath corresponding to the selected CS handover tech-nology.[0015] In a first embodiment, said information indica-tive of the selected path is a target cell identifier.[0016] In a second embodiment of the invention, saidinformation indicative of the selected path is a supple-mentary parameter associated with an identifier of theselected CS handover technology.[0017] The method according to the invention is imple-mented for managing a CS IRAT handover when the dif-

ferent handover technologies consist of the CS handovertechnologies SRVCC (Single Radio Voice Call Continu-ity) and CSoPS (Circuit switched over Packet Switched).[0018] The method according to the invention whereinsaid UE capabilities for CS IRAT handover include thesupport of SRVCC handover from 2G/3G to LTE, or thesupport of CSoPS handover from 2G/3G to LTE or thesupport of both SRVCC and CSoPS handovers from2G/3G to LTE.[0019] In a first variant, when the RNC/BSC node de-tects the need to handover the UE to the LTE networkfor a CS call, it sends to the MSC/VLR a Handover mes-sage including the target LTE cell ID (eNodeB CGI), incase of SRVCC handover, or a virtual 2G/3G cell ID, incase of CSoPS handover, said IDs are pre-configured inthe mapping and routing tables of BSC/RNC node,MSC/VLR node and the IWF node to allow the associa-tion of the LTE cell ID with the virtual 2G/3G cell ID.[0020] In a second variant, when RNC/BSC detectsthe need to handover the UE to the LTE network for theCS call, it sends a Handover message including the targetLTE cell ID and an indicator informing the MSC/VLRwhether the handover is a SRVCC or a CSoPS handover.[0021] The invention also provides a 2G/3G networkBSC/RNC node comprising means for selecting, basedon received UE capabilities for CS IRAT handover, a rout-ing path for transmitting a Handover message from aMSC/VLR node in a 2G/3G network to a target eNodeBin a LTE network, in order to handover a user equipmentperforming a CS call in said 2G/3G network, said Hando-ver message comprising information indicating the se-lected routing path, and means for transmitting to theMSC/VLR node said Handover message comprising theinformation indicating the selected routing path.[0022] The invention also provides an MSC/VLR nodeconfigured to communicate with a RNC/BSC in a 2G/3Gnetwork in order to manage a Circuit Switch Inter RAT,CS IRAT, handover of a user equipment from said 2G/3Gnetwork to a Long Term Evolution, LTE, network whereinat least two different routing paths corresponding to atleast two different handover technologies are possiblefor transferring the Handover messages from theBSC/RNC node of said 2G/3G network to a target eNo-deB of said LTE network via said MSC/VLR node, theMSC/VLR node comprising an analyzing unit configuredto analyze indicators received from said RNC/BSC nodeto indicate which handover technology is to be used, anda routing unit configured to route said Handover messag-es depending on the analyzed indicators.[0023] The invention also provides a communicationsystem as set forth in claim 12.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The forgoing summary, as well as the followingdetailed description, will be better understood when readin conjunction with the appended figures illustrating anexemplary embodiment of the invention in which:

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FIG. 1 schematically illustrates different routingpaths between for a CS handover from GER-AN/UTRAN to EUTRAN;FIGS. 2A, 2B and 2C represent tables illustrating theconfiguration of network routing and mapping of theRNC/BSC node, the MSC/VLR node and the IWFnode during the handover according to a first em-bodiment of the invention;FIGS. 2D and 2E represent tables illustrating theconfiguration of network routing and mapping of theRNC/BSC node, the MSC/VLR node during thehandover according to a second embodiment of theinvention;FIG. 3 illustrates the preparation of CS IRAT hando-ver for a UE supporting SRVCC and a UE supportingCSoPS;FIG. 4 illustrates the CS IRAT handover via SRVCCand CSoPS according to a first embodiment of theinvention; andFIG. 5 illustrates the CS IRAT handover via SRVCCand CSoPS according to a second embodiment ofthe invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] The invention will be described in the case of aCS IRAT handover of two User Equipments/ UE1 andUE2, camping in a cell of a 2G/3G Network to a cell in aLTE Network supporting both SRVCC (Single RadioVoice Call Continuity) and CSoPS (Circuit switched overPacket Switched).[0026] It is assumed that UE1 is CSoPS capable andsupports CSoPS-based CS IRAT handover from GER-AN/UTRAN to EUTRAN during a CS call established inthe UTRAN/GERAN, and UE2 is SRVCC capable andsupports SRVCC-based CS IRAT handover from GER-AN/UTRAN to EUTRAN during the CS call establishedin the UTRAN/GERAN[0027] It is assumed that UE1 and UE2 are initially at-tached to a BTS/NodeB 2 in a 2G/3G cell and transmittheir capabilities to a BSC/RNC 4 (Base Station Control-ler/Radio Network Controller) in the 2G/3G network.[0028] When the BSC/RNC node 4 detects the needto handover (HO) the UEs to the LTE network for the CScall, it sends a Handover message including the targetLTE cell ID and an indicator informing the MSC/VLR 8whether the handover is a SRVCC or a CSoPS handover.[0029] If the indicator received by the MSC/VLR 8 fromRNC/BSC 4 indicates SRVCC handover, the MSC/VLR8 sends the handover message to a Mobility Manage-ment Entity (MME node) 10 located in the LTE network.Else; if the indicator received by the MSC/VLR 8 fromRNC/BSC 4 indicates CSoPS handover, the MSC/VLR8 sends the handover message to a Interworking Func-tion node 12 (IWF node) located in the LTE network.[0030] The invention will be explained in details by ref-erence to the tables of FIGS. 2A-2E illustrating the con-figuration of network mapping and routing of the RNCB-

SC 4, the IWF 12 and the MSC/VLR 8 during the hando-ver.[0031] Referring now to FIG. 3, at step 20, UE1 trans-mits its capabilities to the BSC/RNC 4 and receives aconfirmation message from said BSC/RNC 4 at step 22.[0032] At step 24, BSC/RNC 4, transmits to UE1 infor-mation indicating the neighbor cells along with target eN-odeB (ARFCN, BSIG).[0033] A similar exchange is performed between UE2and BSC/RNC 4 at steps 26 to 30.[0034] At step 32, UE2 transmits to BSC/RNC 4 meas-urement report that allows BSC/RNC 4 to make a deci-sion regarding UE2 handover at step 34.[0035] FIG. 4 illustrates the steps of the method ac-cording to a first embodiment of the invention when theBSC/RNC 4 detects the need of a CS IRAT handover toLTE for UE2 (respectively UE1) in which RNC/BSC 4provides MSC/VLR 8 with a target cell ID indicatingwhether the handover is a SRVCC or CSoPS handover.[0036] At step 34 the BSC/RNC 4 initiates a CS IRAThandover to LTE for UE2, using SRVCC.[0037] At step 36, the eNodeB ARFCN (Absolute Ra-dio Frequency Channel Number) and the eNodeB BSIC(Base Station Identity Code) are mapped to eNodeB CGI(Cell Global Identity) as illustrated in the RNC/BSC map-ping table of FIG. 2A.[0038] At step 38, the BSC/RNC 4 transmits to theMSC/VLR/VLR 8 a handover request message compris-ing UE2 and eNodeB CGI.[0039] At step 40, the MSC/VLR 8 retrieves the targetnode address (MME address) associated to the eNodeBusing its routing table as illustrated at figure 2B and trans-mits said handover request message to the MME node10 at step 42.[0040] At step 44, the MME node 10 forwards saidhandover request message to the target eNodeB 6.[0041] At step 46, the target eNodeB 6 sends an ac-knowledgement to the MME node 10.[0042] At step 48, the MME node 10 transmits toMSC/VLR 8 a message comprising a response to thehandover request of UE2 from CS to PS.[0043] At step 50, MSC/VLR 8 requests the 3GPP IMS(IP Multimedia Subsystem) to initiate a Session transfer.[0044] At step 52, the MSC/VLR 8 sends to theBSC/RNC 4 a Handover Command.[0045] At step 54, BSC/RNC 4 forwards HandoverCommand to UE2.[0046] At step 56, UE2 tunes to E-UTRAN.[0047] At step 58, the BSC/RNC 4 initiates a CS IRAThandover to LTE, using CSoPS.[0048] At step 60, the eNodeB ARFCN (Absolute Ra-dio Frequency Channel Number) and the eNodeB BSIC(Base Station Identity Code) are mapped to 2G/3G virtualCGI (Cell Global Identity) as illustrated in the RNC/BSCmapping table of FIG 2A.[0049] At step 62, the BSC/RNC 4 transmits to theMSC/VLR/VLR 8 a handover request message compris-ing UE1 and 2G/3G virtual CGI mapping.

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[0050] At step 64, the MSC/VLR 8 retrieves the targetnode address (IWF address) associated to the 2G/3Gvirtual CGI using its routing table as illustrated at FIG. 2Band transmits said handover request message to the IWFnode 12 at step 66.[0051] At step 67, the 2G/3G virtual CGI (Cell GlobalIdentity) is mapped to the eNodeB CGI as illustrated inthe RNC/BSC mapping table of FIG. 2C.[0052] At step 68, the IWF node 12 transmits to theMME node 10 a message comprising a request to switchthe DEI from CS to PS and the target eNodeB CGI.[0053] At step 70, the MME node 10 transmits to thetarget eNodeB the handover request for UE1.[0054] At step 12, the target eNodeB sends an ac-knowledgement to the MME node 10.[0055] At step 74 the MME node 10 transmits to theIWF node 12 a response concerning the handover re-quest for UE1.[0056] At step 76, the IWF node 12 forwards said re-sponse to the MSC/VLR 8. The later sends, at step 78 aHandover Command to the BSC/RNC 4 which executesaid handover at step 80.[0057] At step 82, UE1 tunes to E-UTRAN.[0058] FIG. 5 illustrates the steps of the method ac-cording to a second embodiment of the invention whenthe BSC/RNC 4 detects the need of a CS IRAT handoverto LTE for UE2 (respectively Ul) in which RNC/BSC 4provides MSC/VLR 8 with a indicator (SRVCC/CSoPS)according to whether the call is SRVCC or CSoPS.[0059] At step 99, the BSC/RNC 4 takes a decision tohandover UE2 to eNodeB 6.[0060] At step 100, the eNodeB ARFCN (Absolute Ra-dio Frequency Channel Number) and the eNodeB BSIC(Base Station Identity Code) are mapped to eNodeB CGI(Cell Global Identity) for UE2 as illustrated in theRNC/BSC mapping table of FIG. 2D.[0061] At step 102, BSC/RNC 4 maps the UE capabil-ities to the CS IRAT handover indicator according to itsmapping table as illustrated in FIG. 2D and transmits toMSC/VLR 8 a message requesting an SRVCC handoverto eNodeB 6 for UE2.[0062] At step 104, the MSC/VLR 8 retrieves the targetnode address (MME address) associated to the SRVCCindicator using its routing table as illustrated at FIG. 2Eand the MSC/VLR 8 forwards said SRVCC handover re-quest to the MME node 10.[0063] At step 106, the MME node 10 forwards saidhandover request message to the target eNodeB 6.[0064] At step 108, the target eNodeB 6 sends an ac-knowledgement to the MME node 10.[0065] At step 110, the MME node 10 transmits toMSC/VLR 8 a message comprising a response to thehandover request of UE2 from CS to PS.[0066] At step 112, the MSC/VLR 8 sends to theBSC/RNC 4 a Handover Command.[0067] At step 114, BSC/RNC 4 forwards HandoverCommand to UE2.[0068] At step 116, UE2 tunes to E-UTRAN.

[0069] At step 118, the BSC/RNC 4 initiates a CS IRAThandover to LTE for UE1, using CSoPS.[0070] At step 120, the eNodeB ARFCN (Absolute Ra-dio Frequency Channel Number) and the eNodeB BSIC(Base Station Identity Code) are mapped to eNodeB CGIfor UE2 as illustrated in the RNC/BSC mapping table ofFIG. 2D.[0071] At step 122, the BSC/RNC 4 maps the UE ca-pabilities to the CS IRAT handover indicator accordingto its mapping table as illustrated in FIG. 2D and transmitsto the MSC/VLR/VLR 8 a CSoPS handover request mes-sage comprising UE1 ID, eNodeB CGI.[0072] At step 124, the MSC/VLR 8 retrieves the targetnode address (IWF address) associated to the CSoPSindicator using its routing table as illustrated at FIG. 2Eand the MSC/VLR/VLR 8 transmits to the IWF 12 ahandover request message comprising UE1 ID and eN-odeB CGI.[0073] At step 126, the IWF node 12 forwards thehandover request from CS to PS to the MME node 10with the UE1 and the target eNodeB CGI.[0074] At step 128, the MME node 10 transmits to thetarget eNodeB the handover request for UE1.[0075] At step 130, the target eNodeB sends an ac-knowledgement to the MME node 10.[0076] At step 132, the MME node 10 transmits to theIWF node 12 a response concerning the handover re-quest for UE1.[0077] At step 134, the IWF node 12 forwards said re-sponse to the MSC/VLR 8. The later sends, at step 138a Handover Command to the BSC/RNC 4.[0078] At step 140, the BSC/RNC 4 forwards theHandover Command to UE1 which execute said hando-ver at step 142.

INDUSTRIAL APPLICABILITY

[0079] The invention is applicable to telecommunica-tion field and a method to manage a CS IRAT (CircuitSwitch Inter RAT (Radio Access technology)) handoverof a user Equipment from a 2G/3G network to a LTE(Long Term Evolution) network. The invention is also ap-plicable to a 2G/3G network BSC/RNC node, a 2G/3Gnetwork MSC node, and a User Equipment, and so on.

Claims

1. A method to manage a Circuit Switch Inter RAT, CSIRAT, handover of a user equipment, UE, from a2G/3G network to a Long Term Evolution, LTE, net-work wherein at least two different routing paths cor-responding to at least two different handover tech-nologies are possible for transferring the Handovermessages from a BSC/RNC node (4) of said 2G/3Gnetwork to a target eNodeB (6) of said LTE network,said method comprising:

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transmitting (20), by the UE, its CS IRAT hando-ver from 2G/3G to LTE capabilities to theBSC/RNC node (4);selecting (36, 60, 102, 122), by the BSC/RNCnode (4), a routing path among said differentrouting paths based on the UE capabilities forCS IRAT handover from 2G/3G to LTE andtransmitting (38, 62, 102, 122) to a MSC/VLRnode (8) of said 2G/3G network a Handovermessage comprising information indicative ofthe selected path corresponding to the selectedCS handover technology; andtransferring (42, 66, 104, 134), by the MSC/VLRnode (8), said Handover message to said targeteNodeB (6) through a MME node (10) or throughan IWF node (12) depending on said informationindicative of the selected path corresponding tothe selected CS handover technology.

2. A method according to claim 1, wherein said infor-mation indicative of the selected path is a target cellidentifier.

3. A method according to claim 1, wherein said infor-mation indicative of the selected path is a supple-mentary parameter associated with an identifier ofthe selected CS handover technology.

4. A method according to claim 1, wherein the differenthandover technologies include the CS handovertechnologies Single Radio Voice Call Continuity,SRVCC, and Circuit switched over Packet Switched,CSoPS.

5. A method according to claim 4, wherein the UE ca-pabilities for CS IRAT handover consist of the sup-port of SRVCC handover from 2G/3G to LTE, or thesupport of CSoPS handover from 2G/3G to LTE orthe support of both SRVCC and CSoPS handoverfrom 2G/3G to LTE.

6. A method according to claim 2, wherein, when theRNC/BSC node (4) detects the need to handoverthe UE to the LTE network for a CS call, it sends (38,62) to the MSC/VLR (8) a Handover message includ-ing the target LTE cell ID, in case of SRVCC hando-ver, or a virtual 2G/3G cell ID, in case of CSoPShandover, said IDs are pre-configured in the map-ping and routing tables of BSC/RNC node, MSC/VLRnode (8) and the IWF node (12) to allow the associ-ation of the LTE cell ID with the virtual 2G/3G cell ID.

7. A method according to claim 3, wherein, when theRNC/BSC node (4) detects the need to handoverthe UE to the LTE network for a CS call, it sends(102, 122) a Handover message including the targetLTE cell ID and an indicator informing the MSC/VLR(8) whether the handover is a SRVCC or a CSoPS

handover.

8. A method according to claim 6, wherein, if the targetcell ID received by the MSC/VLR (8) from RNC/BSC(4) indicates a LTE cell, the MSC/VLR node (8) sends(42) the handover message to a MME node (10) ofthe LTE network, else if the target cell ID receivedby the MSC/VLR node (8) from RNC/BSC node (4)indicates a 2G/3G cell, the MSC/VLR (8) sends (66)the handover message to a IWF node (12).

9. A method according to claim 7, wherein, if the indi-cator received by the MSC/VLR (8) from RNC/BSC(4) indicates SRVCC handover, the MSC/VLR node(8) sends (104) the handover message to the MMEnode (10) of the LTE network, else if the indicatorreceived by the MSC/VLR node (8) from RNC/BSCnode (4) indicates CSoPS handover, the MSC/VLR(8) sends (134) the handover message to the IWFnode (12).

10. A 2G/3G network BSC/RNC node (4) comprisingmeans for selecting, based on received UE capabil-ities for CS IRAT handover, a routing path for trans-mitting a Handover message from a MSC/VLR node(8) in a 2G/3G network to a target eNodeB (6) in aLTE network, in order to handover a user equipmentperforming a CS call in said 2G/3G network, saidHandover message comprising information indicat-ing the selected routing path, and means for trans-mitting to the MSC/VLR node (8) said Handovermessage comprising the information indicating theselected routing path.

11. A MSC/VLR node (8) configured to communicatewith a RNC/BSC (4) in a 2G/3G network in order tomanage a Circuit Switch Inter RAT, CS IRAT, hando-ver of a user equipment from said 2G/3G network toa Long Term Evolution, LTE, network wherein atleast two different routing paths corresponding to atleast two different handover technologies are possi-ble for transferring the Handover messages from theBSC/RNC node (4) of said 2G/3G network to a targeteNodeB (6) of said LTE network via said MSC/VLRnode (8), the MSC/VLR node (8) comprising an an-alyzing unit configured to analyze indicators re-ceived from said RNC/BSC node (4) to indicatewhich handover technology is to be used, and a rout-ing unit configured to route said Handover messagesdepending on the analyzed indicators.

12. A communications system comprising a 2G/3G net-work BSC/RNC node (4) according to claim 10, anMSC/VLR node (8) according to claim 11 and a userequipment (UE) configured to roam between an areacovered by the 2G/3G network and an area coveredby a Long Term Evolution, LTE, network, said UEbeing configured to transmit its capabilities to the

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BSC/RNC node (4) of said 2G/3G network in orderto manage a Circuit Switch Inter RAT, CS IRAT,handover of said UE from said 2G/3G network to theLTE network.

Patentansprüche

1. Verfahren zum Verwalten einer CS-IRAT-(CircuitSwitch Inter RAT)-Übergabe eines Benutzergeräts(UE) von einem 2G/3G-Netzwerk auf ein LTE-(LongTerm Evolution)-Netzwerk, wobei wenigstens zweiunterschiedliche Routing-Pfade entsprechend we-nigstens zwei unterschiedlichen Übergabetechnolo-gien zum Übertragen der Übergabenachrichten voneinem BSC/RNC-Knoten (4) des genannten 2G/3G-Netzwerks auf einen Ziel-eNodeB (6) des genanntenLTE-Netzwerks möglich sind, wobei das genannteVerfahren Folgendes beinhaltet:

Senden (20), durch das UE, von dessen CS-IRAT-Übergabe von 2G/3G- auf LTE-Fähigkei-ten zum BSC/RNC-Knoten (4);Auswählen (36, 60, 102, 122), durch denBSC/RNC-Knoten (4), eines Routing-Pfads ausden genannten unterschiedlichen Routing-Pfa-den auf der Basis der UE-Fähigkeiten für eineCS-IRAT-Übergabe von 2G/3G auf LTE undSenden (38, 62, 102, 122), zu einem MSC/VLR-Knoten (8) des genannten 2G/3G-Netzwerks,einer Übergabenachricht, die Informationen be-inhaltet, die den gewählten Pfad anzeigen, ent-sprechend der gewählten CS-Übergabetechno-logie; undÜbertragen (42, 66, 104, 134), durch denMSC/VLR-Knoten (8), der genannten Überga-benachricht zu dem genannten Ziel-eNodeB (6)durch einen MME-Knoten (10) oder durch einenIWF-Knoten (12) je nach den genannten Infor-mationen, die den gewählten Pfad anzeigen,entsprechend der gewählten CS-Übergabe-technologie.

2. Verfahren nach Anspruch 1, wobei die genanntenInformationen, die den gewählten Pfad anzeigen, einZielzellenidentifikator sind.

3. Verfahren nach Anspruch 1, wobei die genanntenInformationen, die den gewählten Pfad anzeigen, einmit einem Identifikator der gewählten CS-Übergabe-technologie assoziierter ergänzender Parameter ist.

4. Verfahren nach Anspruch 1, wobei die unterschied-lichen Übergabetechnologien die CS-Übergabe-technologien SRVCC (Single Radio Voice Call Con-tinuity) und CSoPS (Circuit switched over PacketSwitched) beinhalten.

5. Verfahren nach Anspruch 4, wobei die UE-Fähigkei-ten für eine CS-IRAT-Übergabe aus der Unterstüt-zung von SRVCC-Übergabe von 2G/3G auf LTEoder der Unterstützung von CSoPS-Übergabe von2G/3G auf LTE oder die Unterstützung von SRVCC-und CSoPS-Übergabe von 2G/3G auf LTE beste-hen.

6. Verfahren nach Anspruch 2, wobei der RNC/BSC-Knoten (4), wenn er die Notwendigkeit für eine Über-gabe des UE auf das LTE-Netzwerk für einen CS-Anruf erkennt, eine Übergabenachrichteinschließlich der Ziel-LTE-Zellen-ID, im Falle einerSRVCC-Übergabe, oder einer virtuellen 2G/3G-Zel-len-ID, im Falle einer CSoPS-Übergabe, zumMSC/VLR (8) sendet (38, 62), die genannten IDssind in den Mapping- und Routing-Tabellen desBSC/RNC-Knotens, des MSC/VLR-Knotens (8) unddes IWF-Knotens (12) vorkonfiguriert, um die Asso-ziation der LTE-Zellen-ID mit der virtuellen 2G/3G-Zellen-ID zuzulassen.

7. Verfahren nach Anspruch 3, wobei der RNC/BSC-Knoten (4), wenn er die Notwendigkeit für eine Über-gabe des UE auf das LTE-Netzwerk für einen CS-Anruf erkennt, eine Übergabenachrichteinschließlich der Ziel-LTE-Zellen-ID und eines In-dikators sendet (102, 122), der den MSC/VLR (8)darüber informiert, ob die Übergabe eine SRVCC-oder eine CSoPS-Übergabe ist.

8. Verfahren nach Anspruch 6, wobei der MSC/VLR-Knoten (8), wenn die durch den MSC/VLR (8) vomRNC/BSC (4) empfangene Zielzellen-ID eine LTE-Zelle anzeigt, die Übergabenachricht zu einemMME-Knoten (10) des LTE-Netzwerks sendet (42),und der MSC/VLR (8) ansonsten, wenn die durchden MSC/VLR-Knoten (8) vom RNC/BSC-Knoten(4) empfangene Zielzellen-ID eine 2G/3G-Zelle an-zeigt, die Übergabenachricht zu einem IWF-Knoten(12) sendet (66).

9. Verfahren nach Anspruch 7, wobei der MSC/VLR-Knoten (8), wenn der durch den MSC/VLR (8) vomRNC/BSC (4) empfangene Indikator eine SRVCC-Übergabe anzeigt, die Übergabenachricht zumMME-Knoten (10) des LTE-Netzwerks sendet (104),und der MSC/VLR (8) ansonsten, wenn der durchden MSC/VLR-Knoten (8) vom RNC/BSC-Knoten(4) empfangene Indikator eine CSoPS-Übergabeanzeigt, die Übergabenachricht zum IWF-Knoten(12) sendet (134).

10. 2G/3G-Netzwerk-BSC/RNC-Knoten (4), der Folgen-des umfasst: Mittel zum Auswählen, auf der Basisvon empfangenen UE-Fähigkeiten für eine CS-IRAT-Übergabe, eines Routing-Pfades zum Sendeneiner Übergabenachricht von einem MSC/VLR-Kno-

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ten (8) in einem 2G/3G-Netzwerk zu einem Ziel-eNo-deB (6) in einem LTE-Netzwerk, um ein Benutzer-gerät zu übergeben, das einen CS-Anruf in dem ge-nannten 2G/3G-Netzwerk durchführt, wobei die ge-nannte Übergabenachricht die Informationen um-fasst, die den gewählten Routing-Pfad anzeigen,und Mittel zum Senden der genannten Übergabe-nachricht, die die Informationen umfasst, die den ge-wählten Routing-Pfad anzeigen, zum MSC/VLR-Knoten (8).

11. MSC/VLR-Knoten (8), konfiguriert zum Kommuni-zieren mit einem RNC/BSC (4) in einem 2G/3G-Netzwerk, um eine CS-IRAT-(Circuit Switch InterRAT)-Übergabe eines Benutzergerätes von dem ge-nannten 2G/3G-Netzwerk auf ein LTE-(Long TermEvolution)-Netzwerk zu verwalten, wobei wenigs-tens zwei unterschiedliche Routing-Pfade entspre-chend wenigstens zwei unterschiedlichen Überga-betechnologien zum Übertragen der Übergabe-nachrichten vom BSC/RNC-Knoten (4) des genann-ten 2G/3G-Netzwerks zu einem Ziel-eNodeB (6) desgenannten LTE-Netzwerks über den genanntenMSC/VLR-Knoten (8) möglich sind, wobei derMSC/VLR-Knoten (8) eine Analyseeinheit umfasst,die zum Analysieren von Indikatoren konfiguriert ist,die von dem genannten RNC/BSC-Knoten (4) emp-fangen werden, um anzuzeigen, welche Übergabe-technologie zu verwenden ist, und eine Routing-Ein-heit, die zum Routen der genannten Übergabenach-richten je nach den analysierten Indikatoren konfi-guriert ist.

12. Kommunikationssystem, das einen 2G/3G-Netz-werk-BSC/RNC-Knoten (4) nach Anspruch 10, ei-nen MSC/VLR-Knoten (8) nach Anspruch 11 und einBenutzergerät (UE) umfasst, konfiguriert zum Roa-men zwischen einem von dem 2G/3G-Netzwerk ver-sorgten Bereich und einem von einem LTE-(LongTerm Evolution)-Netzwerk versorgten Bereich, wo-bei das genannte UE zum Senden seiner Fähigkei-ten zum BSC/RNC-Knoten (4) des genannten2G/3G-Netzwerks konfiguriert ist, um eine CS-IRAT-(Circuit Switch Inter RAT)-Übergabe des ge-nannten UE von dem genannten 2G/3G-Netzwerkzum LTE-Netzwerk zu verwalten.

Revendications

1. Procédé de gestion d’un transfert intercellulaire in-ter-RAT à commutation de circuits (CS IRAT) d’unéquipement d’utilisateur (UE) d’un réseau 2G/3G àun réseau à technologie d’évolution à long terme(LTE), dans lequel au moins deux chemins de rou-tage différents correspondant à au moins deux tech-nologies de transfert intercellulaire différentes sontpossibles pour transférer les messages de transfert

intercellulaire d’un noeud BSC/RNC (4) dudit réseau2G/3G à un eNoeudB cible (6) dudit réseau LTE,ledit procédé consistant à :

transmettre (20), par l’UE, son transfert CS IRATde capacités 2G/3G à des capacités LTE aunoeud BSC/RNC (4) ;sélectionner (36, 60, 102, 122), par le noeudBSC/RNC (4), un chemin de routage parmi les-dits chemins de routage différents sur la basedes capacités de l’UE pour un transfert intercel-lulaire CS IRAT d’un réseau 2G/3G à un réseauLTE, et transmettre (38, 62, 102, 122) à unnoeud MSC/VLR (8) dudit réseau 2G/3G unmessage de transfert intercellulaire comprenantune information révélatrice du chemin sélection-né correspondant à la technologie de transfertintercellulaire CS sélectionnée ; ettransférer (42, 66, 104, 134), par le noeudMSC/VLR (8), ledit message de transfert inter-cellulaire audit eNoeudB cible (6) par l’intermé-diaire d’un noeud MME (10) ou par l’intermédiai-re d’un noeud IWF (12) selon ladite informationrévélatrice du chemin sélectionné correspon-dant à la technologie de transfert intercellulaireCS sélectionnée.

2. Procédé selon la revendication 1, dans lequel laditeinformation révélatrice du chemin sélectionné est unidentifiant de cellule cible.

3. Procédé selon la revendication 1, dans lequel laditeinformation révélatrice du chemin sélectionné est unparamètre supplémentaire associé à un identifiantde la technologie de transfert intercellulaire CS sé-lectionnée.

4. Procédé selon la revendication 1, dans lequel lestechnologies de transfert intercellulaire différentesincluent les technologies de transfert intercellulaireCS à continuité d’appel vocal radio unique (SRVCC)et à commutation de circuits sur commutation de pa-quets (CSoPS).

5. Procédé selon la revendication 4, dans lequel lescapacités de l’UE pour un transfert intercellulaire CSIRAT consistent en la prise en charge d’un transfertintercellulaire SRVCC d’un réseau 2G/3G à un ré-seau LTE, ou en la prise en charge d’un transfertintercellulaire CSoPS d’un réseau 2G/3G à un ré-seau LTE, ou en la prise en charge d’un transfertintercellulaire SRVCC et CSoPS d’un réseau 2G/3Gà un réseau LTE.

6. Procédé selon la revendication 2, dans lequel, quandle noeud RNC/BSC (4) détecte la nécessité de trans-férer intercellulairement l’UE sur le réseau LTE pourun appel CS, il envoie (38, 62) au noeud MSC/VLR

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(8) un message de transfert intercellulaire compre-nant l’ID de cellule LTE cible, en cas de transfertintercellulaire SRVCC, ou un ID de cellule 2G/3Gvirtuelle, en cas de transfert intercellulaire CSoPS,lesdits ID étant préconfigurés dans les tables demappage et de routage du noeud BSC/RNC, dunoeud MSC/VLR (8) et du noeud IWF (12) pour per-mettre l’association de l’ID de cellule LTE à l’ID decellule 2G/3G virtuelle.

7. Procédé selon la revendication 3, dans lequel, quandle noeud RNC/BSC (4) détecte la nécessité de trans-férer intercellulairement l’UE sur le réseau LTE pourun appel CS, il envoie (102, 122) un message detransfert intercellulaire comprenant l’ID de celluleLTE cible et un indicateur informant le noeudMSC/VLR (8) de si le transfert intercellulaire est untransfert intercellulaire SRVCC ou CSoPS.

8. Procédé selon la revendication 6, dans lequel, si l’IDde cellule cible reçu par le noeud MSC/VLR (8) dunoeud RNC/BSC (4) indique une cellule LTE, lenoeud MSC/VLR (8) envoie (42) le message detransfert intercellulaire à un noeud MME (10) du ré-seau LTE, sinon si l’ID de cellule cible reçu par lenoeud MSC/VLR (8) du noeud RNC/BSC (4) indiqueune cellule 2G/3G, le noeud MSC/VLR (8) envoie(66) le message de transfert intercellulaire à unnoeud IWF (12).

9. Procédé selon la revendication 7, dans lequel, si l’in-dicateur reçu par le noeud MSC/VLR (8) du noeudRNC/BSC (4) indique un transfert intercellulaire SR-VCC, le noeud MSC/VLR (8) envoie (104) le mes-sage de transfert intercellulaire au noeud MME (10)du réseau LTE, sinon si l’indicateur reçu par le noeudMSC/VLR (8) du noeud RNC/BSC (4) indique untransfert intercellulaire CSoPS, le noeud MSC/VLR(8) envoie (134) le message de transfert intercellu-laire au noeud IWF (12).

10. Noeud BSC/RNC de réseau 2G/3G (4) comprenantun moyen permettant de sélectionner, sur la basedes capacités de l’UE reçues pour un transfert inter-cellulaire CS IRAT, un chemin de routage pour trans-mettre un message de transfert intercellulaire d’unnoeud MSC/VLR (8) sur un réseau 2G/3G à uneNoeudB cible (6) sur un réseau LTE, afin de trans-férer intercellulairement un équipement d’utilisateureffectuant un appel CS sur ledit réseau 2G/3G, leditmessage de transfert intercellulaire comprenant uneindication révélatrice du chemin de routage sélec-tionné, et un moyen permettant de transmettre auditnoeud MSC/VLR (8) ledit message de transfert in-tercellulaire comprenant l’information révélatrice duchemin de routage sélectionné.

11. Noeud MSC/VLR (8) configuré pour communiquer

avec un noeud RNC/BSC (4) sur un réseau 2G/3Gafin de gérer un transfert intercellulaire inter-RAT àcommutation de circuits (CS IRAT) d’un équipementd’utilisateur d’un réseau 2G/3G à un réseau à tech-nologie d’évolution à long terme (LTE), dans lequelau moins deux chemins de routage différents cor-respondant à au moins deux technologies de trans-fert intercellulaire différentes sont possibles pourtransférer les messages de transfert intercellulairedu noeud BSC/RNC (4) dudit réseau 2G/3G à uneNoeudB cible (6) dudit réseau LTE par l’intermé-diaire dudit noeud MSC/VLR (8), le noeud MSC/VLR(8) comprenant une unité d’analyse conçue pouranalyser des indicateurs reçus dudit noeudRNC/BSC (4) afin d’indiquer la technologie de trans-fert intercellulaire qui doit être utilisée, et une unitéde routage conçue pour router lesdits messages detransfert intercellulaire selon les indicateurs analy-sés.

12. Système de communication comprenant un noeudBSC/RNC de réseau 2G/3G (4) selon la revendica-tion 10, un noeud MSC/VLR (8) selon la revendica-tion 11, et un équipement d’utilisateur (UE) conçupour être en itinérance entre une zone couverte parle réseau 2G/3G et une zone couverte par un réseauà technologie d’évolution à long terme (LTE), leditUE étant configuré pour transmettre ses capacitésau noeud BSC/RNC (4) dudit réseau 2G/3G afin degérer un transfert intercellulaire inter-RAT à commu-tation de circuits (CS IRAT) dudit équipement d’uti-lisateur dudit réseau 2G/3G au réseau LTE.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the Europeanpatent document. Even though great care has been taken in compiling the references, errors or omissions cannot beexcluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• WO 2008148429 A1 [0010] • WO 2008081310 A1 [0011]

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• 3GPP: ’’3rd Generation Partnership Project; Techni-cal Specification Group Services and System As-pects; 3GPP System Architecture Evolution: Reporton Technical Options and Conclusions (Release 7).3GPP DRAFT; 23882-1D1-CLEAN, 3RD GENERA-TION PARTNERSHIP PROJECT (3GPP). MOBILECOMPETENCE CENTRE, 09 January 2008 [0010]