Policy and Charging Rules Function
The major improvement provided in Release 7 of 3GPP in terms of policy and charging is the definition of a new converged architecture to allow the optimization of interactions between the Policy and Rules functions.
The R7 evolution involves a new network node, Policy and Charging Rules Function (PCRF), which is a concatenation of Policy Decision Function (PDF) and Charging Rules Function (CRF).
Release 8 further enhances PCRF functionality by widening the scope of the Policy and Charging Control (PCC) framework to facilitate non-3GPP access to the network (for example, WiFi or fixed IP broadband access). In the generic policy and charging control 3GPP model, the Policy and
Charging Enforcement Function (PCEF) is the generic name for the functional entity that supports service data flow detection, policy enforcement and flow-based charging.
The Application Function (AF) here represents the network element that supports applications that require dynamic policy and/or charging
control. In the IMS model, the AF is implemented by the Proxy Call Session Control Function (P-CSCF).
This architecture specifies several interfaces – Gx, Gy or Gz – to online (OCS) and offline charging systems (OFCS) through the policy and charging enforcement function (PCEF). However, the 3GPP doesn’t define how to implement this integration, and vendors and service providers have pursued a variety of approaches.
Integration between policy and charging systems is required to charge for services based on subscriber entitlements. Both multi- and single-vendor implementations can support this integration. However, a single-vendor platform that pre-integrates policy and charging functions can ultimately limit a service provider’s choices, signaling efficiency and time-to-market for new services.