On-demand circuit-switched (CS) network registration

A system comprising:

• one or more processors;
• and
• memory storing computer-executable instructions that, when executed by the one or more processors, cause the system to:
• receive a combined attach request from a user equipment (UE);
• determine that the UE is presently registered with a first circuit-switched (CS) network;
• de-register, at least in part in response to receiving the combined attach request, the UE from the first CS network;
• send, to the UE, a message indicating that the combined attach request is accepted;
• receive a service request from the UE, the service request having been sent using Non-Access Stratum (NAS) protocol;
• and
• in response to receiving the combined attach request and the service request from the UE, register the UE with a second circuit-switched (CS) network.

A method comprising:

• receiving, by a mobility management entity (MME) node of a telecommunications network, a combined attach request from a first user equipment (UE);
• sending, by the MME node, to the first UE, a message indicating that the combined attach request is accepted;
• refraining, at least in part in response to receiving the combined attach request, from registering the UE with a circuit-switched (CS) network;
• receiving, by the MME node, from a Home Subscriber Server (HSS), a notification of an incoming session request originating from a second UE to establish a communication session over the CS network with the first UE;
• and
• in response to receiving the attach request and the notification from the HSS, registering, by the MME node, the first UE with the CS network.