For Non-GBR (Guaranteed Bit Rate) 4G bearers, the P-GW is not aware when the UE loses radio coverage, and will continue to forward and charge downlink packets, which can result in overcharging of subscribers. 3GPP does not specify a standard solution to deal with such scenarios.
A typical example is when a subscriber drives into a tunnel while having an active download session. Downlink packets will be counted in P-GW before discarded later in S-GW due to the UE not responding to paging.
The subscriber may lose coverage while connected to a particular MME/S-GW and later regain coverage in the same or diiferent MME/S-GW.
The subscriber may lose coverage in 4G and regain coverage in 2G/3G, or vice versa.
Gn and S3/S4 based network architecture may be used in the case of Loss of Radio Coverage.
A valid license key is required to enable Overcharge Protection on the MME. Contact your Cisco Account or Support representative for information on how to obtain a license.
Relationships to Other Features
Overcharging protection on the MME requires separate overcharging protection licenses on the S-GW and P-GW.