In 3GPP TS 29.212 V13.5.0 (2016-03) As mentioned in section 3.6, Request of IP-CAN Bearer Termination If the IP-CAN bearer termination is caused by the PS to CS handover, the PCEF shall report related PCC rules for this IP-CAN bearer by including the Rule-Failure-Code AVP set to the value PS_TO_CS_HANDOVER.
In 3GPP TS 29.212 V14.3.0 (2017-03) As mentioned in section 4.5.6 Indication of IP-CAN Bearer Termination Implications When the PCEF detects that a dedicated IP-CAN bearer could not be activated or has been terminated it shall remove the affected PCC rules and send a CCR command to the PCRF with CC-Request-Type AVP set to the value "UPDATE_REQUEST", including the Charging-Rule-Report AVP specifying the affected PCC rules with the PCC-Rule-Status set to inactive and including the Rule-Failure-Code AVP assigned to the value RESOURCE_ALLOCATION_FAILURE.
SRVCC PS-to-CS Handover Indication Support in starOS This feature helps in notifying the PCRF about the exact reason for PCC rule deactivation on Voice bearer deletion. This exact cause will help PCRF to then take further action appropriately. This feature ensures complete compliance for SRVCC, including support for PS-to-CS handover indication when voicebearers are released. If the IP-CAN bearer termination is caused by the PS to CS handover, the PCEF may report related PCC rules for thisIP-CAN bearer by including the Rule-Failure-Code AVP set to the value PS_TO_CS_HANDOVER.