VoLTE Performance Issue
VoLTE Performance Issue
VoLTE Performance Issue
Detailed flow
- When the UE is performing the S1 handover while the user is trying to make the volte call.
- PGW initiated bearer related requests
- MME may reject the request with the cause-id of reason unspecified. (lead to the ripple effect
towards the upstream forcing each node on the path to release the corresponding resources).
- Handover is successful.
- CCR-U with RESOURCE ALLOCATION FAILURE -> PCRF ->ASR with RESOURCE NOT
AVAILABLE.
- The process ends up with sending the 503 Service Unavailable by the P-CSCF.
- Upon receiving the 503 Service Unavailable, the UE releases all the resources for the call.
In the 3GPP TS29.274(r9), the 3GPP has specified the proper cause value of
"Temporarily rejected due to handover in progress" and in the 3GPP
TS29.274(r11), "Temporarily rejected due to handover/TAU/RAU procedure in
progress". This cause-id value is used by the MME rejecting the bearer related
request when the handover results in the relocation of the Serving GW and/or
MME. The PDN GW which initiated the bearer related request will be able to
consider this error cause value to handle the rejection.