US 12,477,414 B2
Voice over internet protocol multimedia subsystem
Nitin Kuppelur, Bangalore (IN); Anish George, Bangalore (IN); Karthik Anantharaman, Cupertino, CA (US); and Deepak Dash, Bangalore (IN)
Assigned to Apple Inc., Cupertino, CA (US)
Filed by Apple Inc., Cupertino, CA (US)
Filed on Jun. 22, 2022, as Appl. No. 17/847,124.
Claims priority of application No. 202141036332 (IN), filed on Aug. 11, 2021.
Prior Publication US 2023/0049004 A1, Feb. 16, 2023
Int. Cl. H04W 36/00 (2009.01); H04L 65/1016 (2022.01); H04L 65/1073 (2022.01)
CPC H04W 36/0079 (2018.08) [H04L 65/1016 (2013.01); H04L 65/1073 (2013.01); H04W 36/00226 (2023.05)] 17 Claims
OG exemplary drawing
 
1. A user equipment device (UE), comprising:
one or more antennas;
one or more radios configured to perform cellular communication using a plurality of radio access technologies (RATs) that support voice over an Internet protocol (IP) multimedia subsystem (IMS); and
one or more processors coupled to the one or more radios, wherein the one or more processors are configured to cause the UE to perform operations comprising:
sending, to a communications network associated with a first RAT of the plurality of RATs, a first request for IMS registration, wherein the UE is camped on a first cell of the first RAT;
determining, based on an IMS rejection message, that an IMS registration failure is due to a temporary radio failure; and
in response to determining that the IMS registration failure is due to the temporary radio failure, attempting to perform the IMS registration on at least one other cell associated with the first RAT, wherein the attempting to perform the IMS registration on the at least one other cell associated with the first RAT comprises:
identifying the at least one other cell associated with the first RAT, wherein the at least one other cell shares a public land mobile network (PLMN) with the first cell;
sending a second request for IMS registration to the communications network via the at least one other cell; and
receiving, from the communications network and via the at least one other cell, an IMS approval message indicating that the IMS registration is successful.