LTE: How does charging work when an UE handover to wifi network from LTE network ?

Question

During the Handover from LTE to WiFi, how an UE is authenticated at WiFi network ?
Is there any difference in authentication procedure when UE is handed over to un-trusted or trusted WiFi network ?

Answer 1

The charging mechanism would be similar as Harshita mentioned. However in some cases, Rating-Group could be changed by PCRF and hence the user might be charged in a different way.
One more thing which I would like to add here that as Charging-ID that PGW forwards to Online Charging and ePDG will change for dedicated bearer as per spec 23.402. For default bearer, it would be kept same.

Regards,
Peeyush Sharma

Answer 2

I don't think so it will impact charging mechanism at all. When an UE handed over from LTE to trusted/un-trusted wifi network, as part of handover signalling, connections are established between wifi and PGW. Now consider the un-trusted wifi network, in this case Wifi access point makes connection with ePDG which in turn makes connection with PGW.
PGW forwards charging id along with other information to ePDG. As per my understanding on call flows, PGW and ePDG both can collect charging data record since data will still flow from PGW, ePDG , Wifi AP and UE in downlink direction.

Since I am not sure 100% so please correct me if my thought process on this topic is wrong.

Answer 3

A slight update on my previous answer. The charging ID for dedicated bearer will also be same for GTP based S5/S8