Embodiments of the present invention include a method for enhanced indication of network support of SRVCC and/or Voice-over-IMS for an User Equipment UE in an Evolved Packet System EPS network, said method comprising at least one step based on taking into account support of SRVCC and/or Voice-over-IMS by Radio Access Network RAN nodes and/or by Radio Access Technologies RATs available for SRVCC for said UE in said EPS network.

Methods and apparatuses are provided for controlling a voice call at a user equipment (UE) in a wireless network. A method includes transmitting, to a network entity, a tracking area update (TAU) service request for a subsystem (IMS) initiation; receiving, from the network entity, a TAU service reject message; and in response to the TAU service reject message, stopping a circuit switch (CS) fall back call in at least one legacy radio technology (RAT).

Systems and methods for reducing fall back from long term evolution voice calls (VoLTE) to legacy systems. The system can include one or more lookup tables including ranges of internet protocol (IP) addresses for a plurality of user equipment (UE). The lookup tables can be stored on one or more network entities, such as on a proxy call session control function (PCSCF). In the event that a policy charging rules function (PCRF) is unable to establish a Gx session with the relevant packet gateway (PGW), the PCSCF can provide the name and/or the IP address for the appropriate PGW to the PCRF. The PCRF can then send a session request AVP to the IP address to cause the PGW to initiate Gx binding. The system enables VoLTE calls to be established despite problems with the PCRF and reduces fallback to legacy systems.

Methods, systems, and devices for wireless communications are described. An access and mobility management function (AMF) associated with a first radio access network (RAN) may identify a user equipment (UE) connected to a source base station of the first RAN. The AMF may receive a handover message including a voice call continuity handover trigger message indicating a handover of the UE to a target base station associated with a second RAN. In some examples, the AMF may transmit a bypass handover message to a second network device based a on the received handover message. In some cases, the bypass handover message may include the voice call continuity handover trigger message. In some examples, the second network device is a mobility management entity (MME) associated with an Evolved Universal Terrestrial Radio Access Network (E-UTRAN).

Embodiments of the present disclosure provide method and apparatus for handover management. A method performed by a first mobility management function in a first system comprises obtaining mobility management context for single radio voice call continuity (SRVCC). The method further comprises sending a forward relocation request to a second mobility management function in a second system during a handover from the first system to the second system. The forward relocation request comprises mobility management context for the SRVCC.

The techniques include receiving a handover request from a user device connected to a first access network and identifying a Non-3GPP Interworking Function (N3IWF) serving the user device. The user device provides to the N3IWF, measurement report indicating network conditions. The techniques further include receiving the measurement report from the N3IWF and determining whether a measurement in the measurement report is above a predetermined threshold. If the measurement is above the predetermined threshold, the handover request is accepted to enable the user device to connect to a second access network.

The present disclosure relates to a communication method and system for converging a 5.sup.th-Generation (5G) communication system for supporting higher data rates beyond a 4.sup.th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services.

Apparatuses, methods, and systems are disclosed for providing fallback assistance information to a RAN node. One apparatus includes a transceiver that sends a service request, wherein the service request requires fallback to at least one of: a different radio access technology and a different core network (CN) and receives a connection release message, where the connection release message includes redirection information for the service fallback, the redirection information including the target CN. The apparatus includes a processor that selects a non-access stratum (NAS) procedure based on the target CN and connects to the target CN using the selected NAS procedure.

A communication system is provided that includes a network node, a first terminal which supports an EVS (Enhanced Voice Service) codec, and a second terminal. The EVS codec supports an AMR-WB (Adaptive Multi Rate Wideband) codec compatible mode and an AMR-WB codec non-compatible mode, the AMR-WB codec having a dedicated payload format, where the AMR-WB codec compatible mode is compatible with an AMR-WB codec and the AMR-WB codec non-compatible mode is non-compatible with the AMR-WB codec. The first terminal and the second terminal negotiate the AMR-WB codec non-compatible mode in a session negotiation to select the AMR-WB codec non-compatible mode to be used for the communication between the first terminal and the second terminal when the communication starts.

An embodiment of the present specification provides a method for acquiring an identifier of a visited public land mobile network (V-PLMN), in which a user equipment is roaming, by a proxy-call session control function (P-CSCF) of a home public land mobile network (H-PLMN). The method may comprise the steps of: receiving a register message from the user equipment; generating a first V-PLMN identifier on the basis of the register message; and transferring the first V-PLMN identifier to a home subscriber server (HSS), wherein whether the first V-PLMN identifier corresponds to an identifier of the V-PLMN which is serving the user equipment is verified by the HSS through comparison with a second V-PLMN identifier acquired in an initial attach procedure for an evolved packet core (EPC) of the user equipment.