Question

Why PCRF is separately in LTE Core network, can’t we provision the whole function and features in P-GW itself, what is the exact need of PCRF rather than PCC?

Answer 1

More then the technical reason it is more for the convenience. A PCRF is the Policy Decision Point virtually cut-and-pasted into IMS and afterwards taken by the 3GPP who awarded it with a new acronym. It is a place where business rules are merged with network actor information (in the case of mobile, subscribers). It acts as a centralized engine for deploying policy to enforcement points in a specific, limited domain (usually a MSC/MME, APN, or geographic region).

PCRF the business rules themselves are stored in a rules base (the SPR), and the user information is stored in a directory (the HSS) and the execution of the policy is done by PCEF.