A method of performing CSFB in an IMS comprises receiving, at a TAS, an incoming voice call for a UE attached to an EPS; paging the UE by the first ICS GW; receiving, by a second ICS GW associated with a second CS RAN currently connected to the UE, a Location Update message from the UE, the Location Update message containing a first CSFB indicator; transmitting, by the second ICS GW, a Registration message to the TAS, the Registration message containing a second CSFB indicator in response to the first CSFB indicator in the Location Update message; transmitting, by the TAS, a Cancel message to the first ICS GW; and transmitting, by the TAS, an Invite message to the second ICS GW to complete the voice call with the UE.

A portable communication system (100) maintains mission critical functionality. An accessory (120) and a handset (130) are tethered and interoperate such that the accessory operates as the primary controlling device and the handset operates as a secondary device. The accessory (120) contains a main applications processor (102) that handles non-mission critical functions. The accessory further contains a mission critical processor (104) for handling mission critical functions of transmit and receive audio as well as PTT and emergency. In response to a failure of the mission critical processor (104), the mission critical functions are maintained by handing over the mission critical functions to the non-controlling device in a manner transparent to the user. The handover is triggered in response to status changes of the mission critical processor or as a result of battery depletion. Audio paths are re-routed through backup paths (146b, 148) negating reliance on processors of the accessory (120).

A user equipment (UE), which is able to use a plurality of different wireless access technologies, receives a request to establish a voice call. In response to the request, the UE determines whether voice over a first wireless access technology of the different wireless access technologies is supported, and responsive to determining that voice over the first wireless access technology is not supported, the UE attempts to establish the voice call over a second wireless access technology of the different wireless access technologies.

Provided are a method and an apparatus for identifying a pseudo base-station, and a terminal and the method includes the follows. A terminal is redirected to a target cell supporting the circuit domain business when receiving a first call request in a first serving cell not supporting circuit domain business. A location area update request is sent to a base-station where the target cell is located when a popularity of LAIs stored do not include a LAI of the target cell. The popularity of LAIs is received from a base-station where the first serving cell is located. The base-station where the target cell is located is identified as a pseudo base-station when a location area update reject information carrying a cause value is received from the base-station where the target cell is located. There is also provided an apparatus for identifying a pseudo base-station and a terminal.

A method includes receiving a request to initiate an emergency call, directing, the mobile device to initiate the emergency call using a cellular network, receiving a network not available indication that the emergency call cannot be completed using the cellular network, selecting location information of the mobile device and requesting the emergency call be initiated by a VoIP client on the mobile device using the location information obtained from the selecting step.

Internet protocol session continuity can be achieved via an access point registration process. Mobile devices near an access point device that has registered with a base station device can offload wireless communication from the base station device to the access point device. The access point device can be a known access point device that can be secured and subject to session continuity policies of a service provider. The session continuity policies can be stored at a content handover processor, which can oversee the handover processes between the base station device and the mobile device.

In a wireless system in which a base station provides a time division duplex (TDD) air interface having a TDD frame configuration, a method and system for controlling whether a user equipment device (UE) operates in a first mode in which the UE sets up and engages in voice call communication via the base station or rather operates in a second mode in which the UE tunes away from the base station to set up and engage in voice call communication via another base station, such as under a different air interface protocol. The method involves determining whether traffic demand for the air interface exceeds a threshold level, and if so, causing the UE to operate in the second mode rather than in the first mode. Further, the method involves setting the threshold level based on the TDD frame configuration of the air interface.

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).

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may use the techniques described herein to reattempt a video telephony (VT) call after receiving a rejection message indicating that a prior attempt at the VT call failed. In some cases, the UE may have a first configuration indicating that the UE is to redial VT calls exclusively using packet-switched (PS) networks. In other cases, the UE may have a second configuration indicating that the UE is to switch to a circuit-switched (CS) network after one or more failed attempts at the VT call using PS networks. In any case, once the UE receives a rejection message in response to a prior attempt at a VT call, the UE may reattempt the VT call based on a rejection cause in the rejection message and whether the UE has the first configuration or the second configuration.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine, during an active call on a first radio access technology (RAT), that a first condition for performing a handover from the first RAT to a second RAT is satisfied. The UE may determine that the second RAT would trigger a fallback to a third RAT after the handover from the first RAT to the second RAT and that a second condition for performing a handover from the third RAT to the first RAT is satisfied. The UE may refrain from performing the handover from the first RAT to the second RAT based at least in part on the determination that the second RAT would trigger the fallback and the determination that the second condition is satisfied. Numerous other aspects are provided.