Improved handling of timer expiry for mt csfb

A computer-readable storage medium of a user equipment (UE), the computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions configured to instruct processing circuitry to:

• decode a paging received from an evolved NodeB (eNB), the paging indicating a mobile terminated circuit-switched fallback (MT CSFB) call;
• generate an extended service request message indicating acceptance of the MT CSFB call to be sent to the eNB;
• start a T3417 extended service request for mobile terminated services (T3417ext-mt) timer when the extended service request message is sent;
• and
• attempt to select Global System for Mobile communications (GSM) Enhanced Data Rates for GSM Evolution (EDGE) Radio Access Network (RAN) (GERAN) or Universal Mobile Telecommunications Service (UMTS) Terrestrial RAN (UTRAN) radio access technology if the T3417ext-mt timer expires before the UE successfully performs inter-system change from S1 mode to A/Gb mode or Iu mode and a circuit-switched (CS) fallback cancellation request was not received.

An apparatus of a visitor location register (VLR), comprising:

• a data storage device configured to store a value of a first timer for use in guarding a mobile terminated (MT) user equipment (UE) fallback procedure to Global System for Mobile communications (GSM) Enhanced Data Rates for GSM Evolution (EDGE) Radio Access Network (RAN) (GERAN) or Universal Mobile Telecommunications Service (UMTS) Terrestrial RAN (UTRAN);
• and
• one or more processors operably coupled to the data storage device, the one or more processors configured to:
• generate a paging request to be transmitted to a mobile management entity (MME), the paging request indicating a mobile terminated circuit-switched fallback (MT CSFB) call directed to the UE;
• decode a Short Message Service (SMS) over evolved Gs Application Part (SGsAP) service request message received from the MME, the SGsAP service request message indicating that the UE accepted the MT CSFB call;
• start the first timer responsive to receiving the SGsAP service request message;
• and
• set up the MT CSFB call directly with the UE responsive to an attempt by the UE to select GERAN or UTRAN after expiration of a second timer on a side of the UE corresponding to an extended service request for mobile terminated services, wherein a value of the first timer is greater than a value of the second timer.