Methods and apparatus to handle bearers during circuit switched fallback operation

Abstract

Methods and apparatus to provide packet switched service continuity during circuit switched fallback operation are described. One example method includes determining that a target system does not support packet switched handover; determining if non-3GPP access for packet switched service is available; and triggering handover to the non-3GPP access.

1 . A method in user equipment (UE), the method comprising:
 determining that the UE is attached to a circuit switched (CS) domain; and   sending an information element (IE) to indicate bearers to be maintained by an MME, wherein such bearers shall not be handed over to GERAN/UTRAN.   
     
     
         2 . (canceled) 
     
     
         3 . The method of  claim 1 , wherein the IE comprises a preserved evolved packet system (EPS) bearers IE. 
     
     
         4 . The method of  claim 1 , wherein sending the IE comprises sending the IE in an extended service request. 
     
     
         5 - 21 . (canceled) 
     
     
         22 . The method of  claim 1 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in 3GPP access. 
     
     
         23 . The method of  claim 1 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in non-3GPP access. 
     
     
         24 . The method of  claim 1 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in GERAN or UTRAN access. 
     
     
         25 . The method of  claim 1 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in GERAN access. 
     
     
         26 . The method of  claim 1 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in UTRAN access. 
     
     
         27 - 32 . (canceled) 
     
     
         33 . The method of  claim 1 , further comprising receiving a preserved bearers list indicating that bearers identified by the UE in the IE have been or have not been transferred to GERAN/UTRAN as part of a PS HO. 
     
     
         34 . The method of  claim 33 , wherein bearers which are not in the preserved bearers list and not been handed over to a target system have been dropped. 
     
     
         35 . The method of  claim 33 , wherein if the preserved bearers list is empty the UE determines that no bearers have been preserved. 
     
     
         36 . The method of  claim 33 , wherein if the preserved bearers list is not empty the UE determines that the bearers in the preserved bearers list have been preserved and that the UE can handover the preserved bearers to non-3GPP. 
     
     
         37 . The method of  claim 1 , further comprising receiving indications from a lower layer of a network that a Preserved Bearers List has been received as part of an inter-system packet switched (PS) Handover to GERAN or UTRAN. 
     
     
         38 . The method of  claim 37 , further comprising considering the indications from the lower layer as acknowledgement that an MME has preserved within an E-UTRAN system the bearers identified in the Preserved Bearers List. 
     
     
         39 . An apparatus in user equipment (UE), the apparatus comprising a processor configured to:
 determine that the UE is attached to a circuit switched (CS) domain; and   sending an information element (IE) to indicate bearers to be maintained by an MME, wherein such bearers shall not be handed over to GERAN/UTRAN.   
     
     
         40 . (canceled) 
     
     
         41 . The apparatus of  claim 39 , wherein the IE comprises a preserved evolved packet system (EPS) bearers IE. 
     
     
         42 . The apparatus of  claim 39 , wherein sending the IE comprises sending the IE in an extended service request. 
     
     
         43 - 59 . (canceled) 
     
     
         60 . The apparatus of  claim 39 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in 3GPP access. 
     
     
         61 . The apparatus of  claim 39 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in non-3GPP access. 
     
     
         62 . The apparatus of  claim 39 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in GERAN or UTRAN access. 
     
     
         63 . The apparatus of  claim 39 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in GERAN access. 
     
     
         64 . The apparatus of  claim 39 , wherein the IE comprises a circuit switched fallback (CSFB) packet switched (PS) handover (HO) preference IE that comprises a preference to keep an EPS bearer in UTRAN access. 
     
     
         65 - 70 . (canceled) 
     
     
         71 . The apparatus of  claim 39 , wherein the processor is further configured to receive a preserved bearers list indicating that bearers identified by the UE in the IE have been or have not been transferred to GERAN/UTRAN as part of a PS HO. 
     
     
         72 . The apparatus of  claim 71 , wherein bearers which are not in the preserved bearers list and not been handed over to a target system have been dropped. 
     
     
         73 . The apparatus of  claim 71 , wherein if the preserved bearers list is empty the UE determines that no bearers have been preserved. 
     
     
         74 . The apparatus of  claim 71 , wherein if the preserved bearers list is not empty the UE determines that the bearers in the preserved bearers list have been preserved and that the UE can handover the preserved bearers to non-3GPP. 
     
     
         75 . The apparatus of  claim 39 , wherein the processor is further configured to receive indications from a lower layer of a network that a Preserved Bearers List has been received as part of an inter-system packet switched (PS) Handover to GERAN or UTRAN. 
     
     
         76 . The apparatus of  claim 75 , wherein the processor is further configured to consider the indications from the lower layer as acknowledgement that an MME has preserved within an E-UTRAN system the bearers identified in the Preserved Bearers List. 
     
     
         77 . The method of  claim 1 , further comprising determining that the UE cannot initiate an Internet Protocol Multimedia Subsystem (IMS) voice session. 
     
     
         78 . The apparatus of  claim 1 , wherein the processor is further configured to determine that the UE cannot initiate an Internet Protocol Multimedia Subsystem (IMS) voice session.