公开(公告)号：US11019538B2

公开(公告)日：2021-05-25

申请号：US16489279

申请日：2018-06-12

Applicant: APPLE INC.

Inventor： Alexandre Saso Stojanovski ,  Sudeep Palat ,  Pingping Zong

IPC: H04W36/00 ,  H04W76/25 ,  H04W76/50 ,  H04W8/08 ,  H04W60/00 ,  H04W80/10

Abstract: User equipment (UEs) can fallback to a legacy system, such as an evolved packet system (EPS), from a fifth generation system (5GS). For example, a UE camps on the 5GS network by default. When an indicator of a voice call is detected, the UE performs a fallback to EPS for a duration of the voice call. After the voice call, the UE can return to the 5GS. In another example, the UE detects an emergency session request (e.g., internet protocol multimedia subsystem (IMS) emergency session request). The UE performs a fallback to EPS for a duration of the emergency session. After the emergency session is complete, the UE can return to the 5GS. The solution can operate with UEs that operate in either Single Registration (SR) mode embodiments or Dual Registration (DR) mode embodiments. Depending on the embodiment, the UE can perform a handover or redirection to the legacy system (such as E-UTRAN).