diagram depicts the call flow when a UE loses radio access, and then later
regains access, as it relates to overcharging protection.
Figure 1. Overcharging
Protection Call Flow
protection in MME is triggered by a UE Context Release Request from the eNodeB.
This request can come to MME when UE is in EMM connected/connecting mode.
On receiving the UE
Context Release Request, the MME checks the radio cause in the received message
against the configured overcharging protection cause code.
If the configured
cause code matches the received cause code, the MME sends Loss of Radio Contact
using ARRL (Abnormal Release of Radio Link) bit in the Release Access Bearer
Request (GTPv2 message) to the S-GW. The ARRL (Abnormal Release of Radio Link)
is bit 7 in the 8th Octet of Indication IE of Release Access Bearer Req
On Receiving ARRL
indication in Release Access Bearer Request , the S-GW will inform the P-GW to
When the radio
contact is resumed in the 4G network, the Modify Bearer Req will enable the
P-GW to start charging again.
The ARRL bit is
supported only in Release Access Bearer Request message by MME.