US 11,700,290 B1Granted

Silent retry in a legacy system

AssigneeT-Mobile USA, Inc.

InventorsHsin Fu Henry Chiang, Joel Arends

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Abstract

Techniques and systems for selectively implementing a silent retry procedure after a voice session has moved from a preferred IP-based system (e.g., 5GS) to a legacy IP-based system (e.g., EPS) are disclosed. The silent retry procedure may be implemented by a UE and/or by a TAS using one or more specific error codes and/or timeouts. In this manner, after a voice session has been redirected or handed over from a preferred system (e.g., 5GS) to a legacy system (e.g., EPS), and based on an issue arising that prevents the voice session from being successfully established thereafter, the UE or the TAS may reattempt to establish the voice session directly in the legacy system, instead of allowing the UE to transition back to the preferred system (e.g., 5GS) after a session failure in the legacy system, which increases the overall success rate of establishing voice sessions.

Claims20

Dependent claims

A method comprising:

sending, by a user equipment (UE), a first request to establish a first voice session in a fifth generation system (5GS);
determining, by the UE, that the first voice session is to be redirected or handed over to an evolved packet system (EPS);
continuing, by the UE, to establish the first voice session in the EPS;
receiving, by the UE, a message indicating that establishment of the first voice session in the EPS has failed, the message including an error code of a plurality of error codes, the plurality of error codes including at least one error code associated with associated with automatically retrying in the EPS and at least one error code associated with transiting back to the 5GS;
determining, based on the error code, to retry in the EPS, wherein the error code is one of the at least one error code associated with automatically retrying in the EPS;
and
sending, by the UE, and based at least in part on the determining to retry in the EPS, a second request to establish a second voice session in the EPS, wherein the second request is a request to establish the second voice session directly in the EPS, without redirection or handover from 5GS.

4 more elements

A user equipment (UE) comprising:

a processor;
and
memory storing computer-executable instructions that, when executed by the processor, cause the UE to:
send a first request to establish a first voice session in a fifth generation system (5GS);
determine that the first voice session is to be redirected or handed over to an evolved packet system (EPS);
continue to establish the first voice session in the EPS;
receive a message indicating that establishment of the first voice session in the EPS has failed, the message including an error code of a plurality of error codes, the plurality of error codes including at least one error code associated with associated with automatically retrying in the EPS and at least one error code associated with transiting back to the 5GS;
determining, based on the error code, to retry in the EPS, wherein the error code is one of the at least one error code associated with automatically retrying in the EPS;
and
send, based at least in part on the determining to retry in the EPS, a second request to establish a second voice session in the EPS, wherein the second request is a request to establish the second voice session directly in the EPS, without redirection or handover from 5GS.

7 more elements

Dependencies are inferred from the claim text.