Method for managing CS IRAT handover from 2G/3G network to LTE network

1. A method to manage a Circuit Switch Inter Radio Access Technology (CS IRAT) handover of a user equipment (UE) from a 2G/3G network to a Long Term Evolution (LTE) network wherein at least two different routing paths corresponding to at least two different handover technologies are possible for transferring handover messages from a Base Station Controller/Radio Network Controller (BSC/RNC) node of said 2G/3G network to a target eNodeB of said LTE network, said method comprising:

transmitting, by the UE, CS IRAT handover from 2G/3G to LTE capabilities to the BSC/RNC node;

selecting, by the BSC/RNC node, a routing paths among said different routing paths based on the UE capabilities for CS IRAT handover from 2G/3G to LTE and transmitting to a Mobile Switching Center/Visitor Location Register (MSC/VLR) node of said 2G/3G network a message comprising information indicative of the selected path corresponding to the selected CS handover technology; and

transferring, by the MSC/VLR node, said handover message to said target eNodeB through a Mobility Management Entity (MME) node or through an Interworking Function (IWF) node depending on said information of the selected path corresponding to the selected CS handover technology;

wherein said information indicative of the selected path is a target cell identifier and

when the RNC/BSC node detects the need to handover the UE to the LTE network for a CS call, the RNC/BSC node sends to the MSC/VLR a handover message including a target LTE cell ID (eNodeB CGI), in case SRVCC handover, or a virtual 2G/3G cell ID, in case of CSoPS handover, said IDs are pre-configured in the mapping and routing tables of BSC/RNC node, MSC/VLR node and the IWF node to allow the association of the LTE cell ID with the virtual 2G/3G cell ID.

2. A method according to claim 1 , wherein said information indicative of the selected path is a supplementary parameter associated with an identifier of the selected CS handover technology.

3. A method according to claim 1 , wherein the different handover technologies include the CS handover technologies Single Radio Voice Call Continuity (SRVCC) and Circuit switched over Packet Switched (CSoPS).

4. A method according to claim 3 , wherein the UE capabilities for CS IRAT handover consist of the support of SRVCC handover from 2G/3G to LTE, or the support of CSoPS handover from 2G/3G to LTE or the support of both SRVCC and CSoPS handover from 2G/3G to LTE.

5. A method according to claim 2 , wherein, when the RNC/BSC node detects the need to handover the UE to the LTE network for a CS call, the RNC/BSC node sends a handover message including a target LTE cell ID and an indicator informing the MSC/VLR whether the handover is a SRVCC or a CSoPS handover.

6. A method according to claim 1 , wherein, if the target cell ID received by the MSC/VLR from RNC/BSC indicates a LTE cell, the MSC/VLR node sends the handover message to a MME node of the LTE network, else if the target cell ID received by the MSC/VLR node from RNC/BSC node indicates a 2G/3G cell, the MSC/VLR sends the handover message to a IWF node.

7. A method according to claim 5 , wherein, if the indicator received by the MSC/VLR from RNC/BSC indicates SRVCC handover, the MSC/VLR node sends the handover message to the MME node of the LTE network, else if the indicator received by the MSC/VLR node from RNC/BSC node indicates CSoPS handover, the MSC/VLR sends the handover message to the IWF node.