Ims pdn/pdu for emergency call

A method of placing an emergency call over a wireless network, the method comprising:

• establishing, between a user equipment (UE) and an internet protocol (IP) multimedia subsystem (IMS) packet data network (PDN) or protocol data unit (PDU) network (IMS PDN/PDU), an IMS PDN/PDU session over the wireless network;
• and
• initiating, by the UE, the emergency call over the wireless network, wherein initiating the emergency call comprises:
• initiating, between the UE and an emergency PDN/PDU network (EPDN/EPDU), an EPDN/EPDU session over the wireless network;
• and
• detecting a failure of the emergency call over the EPDN/EPDU session, and in response to detecting the failure, re-initiating the emergency call using the IMS PDN/PDU session over the wireless network.

A system comprising:

• a processor;
• and
• a memory storing programming instructions for execution by the processor, the programming instructions, upon execution by the processor, causing the system to perform the following operations:
• establishing, between a user equipment (UE) and an internet protocol (IP) multimedia subsystem (IMS) packet data network (PDN) or protocol data unit (PDU) network (IMS PDN/PDU), an IMS PDN/PDU session over a wireless network;
• and
• initiating, by the UE, an emergency call over the wireless network, wherein initiating the emergency call comprises:
• initiating, between the UE and an emergency PDN/PDU network (EPDN/EPDU), an EPDN/EPDU session over the wireless network;
• and
• detecting a failure of the emergency call over the EPDN/EPDU session, and in response to detecting the failure, re-initiating the emergency call using the IMS PDN/PDU session over the wireless network.

A method comprising:

• establishing, by a user equipment (UE), an internet protocol (IP) multimedia subsystem (IMS) packet data network (PDN) or protocol data unit (PDU) network (IMS PDN/PDU) session over a wireless network;
• transmitting, by the UE, an SOS Invite requesting an emergency call over an emergency PDN/PDU (EPDN/EPDU) session over the wireless network;
• receiving, by the UE, a session initiation protocol (SIP) error indicating that an attempt at establishing the emergency call over the EPDN/EPDU session has failed;
• transmitting, by the UE, an SOS Invite requesting establishment of the emergency call over the IMS PDN/PDU session in response to the SIP error;
• connecting, by the UE, to the emergency call using the IMS PDN/PDU over the wireless network.