Optimized deregistration of user equipment

A method comprising:

• receiving, at an Access and Mobility Management Function (AMF) node of a second type of telecommunication network, a notification identifying that a User Equipment (UE) has transmitted a registration request to the second type of telecommunication network from a Mobility Management Entity (MME) node of a first type of telecommunication network;
• and
• when the UE is associated with a single registration mode, transmitting, by the AMF node of the second type of telecommunication network to a Unified Data Management (UDM) node, a singleRegIndication attribute introduced in the registration request of the UE,
• wherein a drFlag attribute associated with the registration request of the AMF node to the second type of telecommunication network is set to false or absent, and
• wherein the transmitting of the singleRegIndication attribute between the AMF node and the UDM node enables receiving a deregister-sn communication at a Home Subscriber Server (HSS) node from the UDM node initiates a deregistration process between the HSS node and the MME node of the first type of telecommunication network.

An Access and Mobility Management Function (AMF) node of a second type of telecommunication network, the AMF node comprising:

• a memory;
• and
• one or more processors that are configured to execute machine readable instructions stored in the memory for performing the method comprising:
• receiving a notification identifying that a User Equipment (UE) has transmitted a registration request to the second type of telecommunication network from a Mobility Management Entity (MME) node of a first type of telecommunication network;
• and
• when the UE is associated with a single registration mode, enabling a transmission by the AMF node of the second type of telecommunication network to a Unified Data Management (UDM) node, a singleRegIndication attribute associated with the UE,
• wherein a drFlag attribute associated with the registration request of the UE to the second type of telecommunication network is set to false or absent, and
• wherein the transmitting of the singleRegIndication attribute between the AMF node and the UDM node enables receiving a deregister-sn communication at a Home Subscriber Server (HSS) node from the UDM initiates a deregistration process between the HSS node and the MME node of the first type of telecommunication network.