Interconnections between the core networks

A node for a first type of core network in a wireless communication system, the wireless communications system comprising the first type of core network, a second type of core network and terminal devices, the node comprising:

• circuitry configured to
• transmit, in a first cell, an identifier to the terminal devices, the identifier comprising a first identifier of the node or a group of nodes in the first type of core network;
• transmit system information indicating whether service via the first type of core network is available in the first cell;
• establish a connection via the first cell with a first terminal device by receiving a message based on at least a portion of the identifier;
• and
• receive from the first terminal device a first indication in the message indicating whether the identifier was received from the first type of core network, wherein
• the identifier is a 5G globally unique temporary identity (5G GUTI), and
• the identifier comprises an Access and Mobility Management Function (AMF) region ID, an AMF set ID, and an AMF pointer.

A node for a second type of core network in a wireless communication system, the wireless communications system comprising the first type of core network, the second type of core network and terminal devices, the node comprising:

• circuitry configured to
• transmit system information in a second cell indicating whether service via the first type core network is available in the second cell;
• establish a connection via the second cell with a first terminal device by receiving a message based on at least a portion of an identifier assigned by another node in the first type of core network;
• and
• receive from the first terminal device a second indication in the message indicating that the second identifier is mapped from the identifier assigned by the another node in the first type of core network, the identifier assigned by the another node comprising a first identifier of the node or a group of nodes in the first type core network.