A server of a fifth generation (5G) network can provide substantially real-time charges for a UE during fallback to another network. A Telephony Application Server (TAS) in an IP Multimedia Subsystem (IMS) can identify Evolved Packet System Fallback (EPSFB) and report the EPSFB to a charging system to cause the charging system to generate accurate charges for user equipment communicating over the 5G network and the other network. The TAS can comprise logic to identify a change in P-Access-Network-Information associated with each network, and generate a call detail records for billing, or real-time communication via an online charging and/or offline charging for the served UE. Information (a user profile, call detail records, instance of EPSFB, etc.) associated with the TAS can be used to make network improvements that decrease instances of EPSFB and increase an amount of new radio services available to UEs.

An apparatus for wireless communication of a UE is disclosed. The apparatus may initiate, at a new radio (NR) serving cell, a voice session with an IMS. The apparatus may perform, in response to determining that voice over NR (VoNR) is not supported by the first NR cell, an EPS fallback procedure to establish the voice session with the IMS. The apparatus may update a whitelist of NR cells that support VoNR to include the first NR cell when it is determined that the first NR cell supports VoNR.

A service registration method, a terminal, and a network side device are provided. The terminal includes a first subscriber identity card module associated with a first subscriber identity card and a second subscriber identity card module associated with a second subscriber identity card. The method includes: accessing a first mobile network based on the first subscriber identity card; and transmitting a voice over wireless fidelity (VoWiFi) registration message of the second subscriber identity card based on the first mobile network.

A server of a fifth generation (5G) network can provide substantially real-time charges for a UE during fallback to another network. A Telephony Application Server (TAS) in an IP Multimedia Subsystem (IMS) can identify Evolved Packet System Fallback (EPSFB) and report the EPSFB to a charging system to cause the charging system to generate accurate charges for user equipment communicating over the 5G network and the other network. The TAS can comprise logic to identify a change in P-Access-Network-Information associated with each network, and generate a call detail records for billing, or real-time communication via an online charging and/or offline charging for the served UE. Information (a user profile, call detail records, instance of EPSFB, etc.) associated with the TAS can be used to make network improvements that decrease instances of EPSFB and increase an amount of new radio services available to UEs.

This invention is a system and method for implementing a VoLTE and circuit switched voice and SMS interworking function to provide voice and SMS service to roaming mobile devices at visiting network based on Circuit-switched (CS) roaming towards VPLMN, and VoLTE voice and SMS roaming towards HPLMN. The interworking function translates CS signaling with VPLMN into IMS signaling towards IMS core at HPLMN. The interworking function also performs location-update registration at HSS at HPLMN for receiving mobile-terminated voice calls and SMS.

A method and apparatus for processing a call initiation anomaly are disclosed in this application. The method includes: sending a first call request message through a first PS domain; performing a first operation in a case that a first call initiation anomaly occurs, where the first operation includes any one of the following: sending the first call request message through a second PS domain; disabling a VoLTE function, and sending the first call request message through a CS domain; registering in the second PS domain again, and sending the first call request message through the second PS domain; and sending a second call request message to a first account through a target application program, where the first account corresponds to an account indicated by the first call request message.

Systems and methods are provided for improving quality and coverage of a VoNR session on a user device. When a user device is currently engaged in a VoNR session having a voice signal and a data signal, at least one KPI is monitored. The KPI is an indicator that can indicate the quality of the VoNR session, such as RSRP, RSRQ, SINR, or the like. A threshold for the KPI is determined. Once the threshold is met, a handover is initiated for the voice signal without initiating a handover for the data signal.

The voice call device includes a processor, and a memory having instructions stored thereon, which, when executed by the processor, cause the processor to perform operations as follows. After a voice call is initiated via a user equipment (UE) device over 5G NR, a status of an IMS registration (e.g., failed, in progress, etc.) for the UE is identified. For example, in response to determining that the status of IMS registration for the UE is in-progress, the voice call can be held, and a wait timer initiated. If the IMS registration completes prior to the wait timer expiring, the voice call is conducted over 5G NR or 4G Long-term Evolution (LTE).

An example electronic device includes at least one processor, wherein the at least one processor can be configured to confirm an event associated with an emergency service while registered to a first communication system, transmit a service request, corresponding to the event, to a network on the basis of the confirmation of the event, start, on the basis of the transmission of the service request, a timer having an end time that is shorter than the end time of a T3517 timer, search for and select, on the basis of failing to receive a response corresponding to the service request until the timer ends, a cell corresponding to a PLMN of a second communication system that excludes the first communication system, perform at least one operation for registration to the second communication system on the basis of the selected cell, and perform the emergency service corresponding to the event in the second communication system on the basis of the registration to the second communication system.

A user equipment (UE) can determine when to send an initial request for a voice communication to an Internet Protocol (IP) Multimedia Subsystem (IMS) core of a telecommunication network. For instance, the UE can identify when a call setup instruction should be sent to the IMS to cause a communication channel to be established. The UE can determine whether the UE will experience a change to another radio frequency band or radio technology based on test data, and delay sending the call setup instruction for a time period during which the test data can be analyzed.