Interworking function using untrusted network

Abstract

The invention provides a method of registering an access in a network, the method comprising receiving in a second network a request to register a user equipment, UE, device over a second access network, the request including first information that the UE device is registered in a first network over a first access network; receiving in the second network second information regarding the UE device from the first network; establishing in the second network a security association with the UE device over the second access network; forwarding third information regarding the UE device to the first network by the second network; and registering in the first network the UE over the second access network while maintaining the registration of the UE in the first network over the first access network.

1 . A method of registering an access in a network, the method comprising:
 receiving in a second network a request to register a user equipment, UE, device over a second access network, the request including first information that the UE device is registered in a first network over a first access network;   receiving in the second network second information regarding the UE device from the first network; establishing in the second network a security association with the UE device over the second access network;   forwarding third information regarding the UE device to the first network by the second network; and   registering in the first network the UE over the second access network while maintaining the registration of the UE in the first network over the first access network.   
     
     
         2 . The method according to  claim 1 , wherein the first network is a visited public land mobile network and the second network is a home public land mobile network. 
     
     
         3 . The method according to  claim 1 , wherein the first access network is a trusted access network and the second access network is an untrusted access network. 
     
     
         4 . The method according to  claim 1 , wherein the first information from the UE device is one of a flag in an attach message, a secondary attach request message, a secondary registration message and a flag, an information field, a parameter and an identity in a message according to an internet key exchange protocol. 
     
     
         5 . The method according to  claim 1 , wherein the second information regarding the UE device includes a permanent identity of the UE device. 
     
     
         6 . The method according to  claim 1 , wherein the third information regarding the UE device includes one of an address of the second access network and security parameters of the security association. 
     
     
         7 . A user equipment, UE, device adapted to register with a first network to obtain a first access with a first security association and thereafter to request a second access to a second network, the second access including establishing a second security association over the second access while maintaining the first access, whereby the UE device is arranged to provide information about the first access during an establishment of the second access, and wherein the UE device is arranged to access the first network via the first access and via the second access after the second access is registered. 
     
     
         8 . The UE device according to  claim 7 , wherein the UE device includes stored information for identifying an interworking function entity of a home network of the UE device, the stored information being sufficient for the UE device to discover an IP-address of the interworking function entity. 
     
     
         9 . The UE device according to  claim 7 , wherein the UE device is arranged to provide information to the second network that it already has an access to the first network as part of an establishment of the second access. 
     
     
         10 . A public land mobile network, PLMN, arranged to receive from a user equipment, UE, device a request for a first registration of a first access, the request comprising information about a second registration with a second network, wherein the PLMN is arranged to perform a mutual authentication between the UE device and the PLMN and establish a secure connection over the first access and forward information about the first access to the second network, the information being such as to enable the second network to register the first access and use the secure connection over the first access to exchange registration with the UE device while maintaining the second registration of the UE device in the second network. 
     
     
         11 . The PLMN according to  claim 10 , wherein the PLMN is a home network of the UE device. 
     
     
         12 . The PLMN according to  claim 10 , wherein the second access is over a 3GPP radio access network and the first access is over a non-3GPP access network. 
     
     
         13 . The PLMN according to  claim 10 , wherein the second access is over a trusted access network and the first access is over a non-trusted access network. 
     
     
         14 . A first node of a first network arranged to receive from a user equipment, UE, device a request for registration of a first access, the request comprising information about a second registration with a second node of a second network, the first node being arranged:
 to request and receive first context information of the UE device from the second node;   to establish a secure connection to the UE device over the first access;   to provide second context information to the second node, the second context information comprising information about the first access and the secure connection; and   to delete a UE device context in the first node in response to receiving an acknowledgement of successful reception of the second context information by the second node.   
     
     
         15 . A public land mobile network, PLMN, arranged to register a first access of a user equipment, UE, device, the registering comprising requesting authentication of the UE device from a second network, wherein the PLMN is arranged to receive from the second network a request for registration of a second access of the UE device, the second access including an established security association between the UE device and an entity providing the second access, the request comprising information used by the PLMN to connect to the UE device over the second access, wherein the PLMN is arranged to register the second access for the UE device while maintaining the registration of the first access of the UE device.