What is the role of charging gateway function in lte ?

Question

For me, the role of SGW is packet forwarding w.r.t user plane ? Is it possible MME interacts with PGW directly ?

Answer 1

Charging gateway function i.e. CGF is one of the nodes involve in offline charging model. Charging data function generates charging data records and sends to charging gateway function. There is m:1 mapping between CDFs and CGF. I mean to say, multiple charging data functions can feed CDRs to same gateway.
CGF acts as a gateway between 3GPP and billing domain.

Following are the actions taken by CGF.
1. CDR pre-processing: Validation, Consolidation and Re-formatting of CDRs.
2. Persistent storage for CDRs.
3. CDR routing and filtering.
4. CDR file management and transfer to it to billing domain.

Reference:
3GPP TS 32.240