The Application Function (AF) is an element offering applications that require the control of IP bearer resources or the control of flow based bearer charging. The AF is capable of communicating with the PCRF to transfer dynamic QoS-related service information and/or dynamic charging-related service information.
One example of an AF is the P CSCF of the IM CN subsystem.
A WLAN UE is the User Equipment using a UICC card utilized by a 3GPP subscriber to access the WLAN network for 3GPP interworking purpose.
The 3GPP AAA Proxy in case of I-WLAN access as specified in TS 23.234
represents a AAA proxying and filtering function and resides in the visited 3GPP network. It is involved in access and service authentication and authorization procedures of a WLAN UE.
The 3GPP AAA server resides in the 3GPP network and in case of I-WLAN access as specified in TS 23.234
is responsible for access and service authentication and authorization of a WLAN UE.
The WLAN access gateway is a gateway between WLAN and 3GPP network. In the roaming case it resides in the visited 3GPP network, otherwise in the home 3GPP network. It provides filtering, policing and charging functionality for the traffic between WLAN UE and 3GPP network.
The Packet Data Gateway provides access to PS based services for a WLAN UE. It resides either in the home (for access to home services) or in the visited 3GPP network (for access to local services).
The HA provides control and mobility function for service continuity between 3GPP WLAN Interworking system and 3GPP Systems. The HA terminates the HGi reference point towards the PDN as defined in TS 23.327
The GUP Server is a functional entity providing a single point of access to the Generic User Profile data of a particular subscriber. The architecture does not specify or limit the physical location of the GUP Server enabling flexibility in the implementations. For further details of the GUP Server, see TS 23.240
The Policy and Charging Rules Function (PCRF) acts as a policy decision point for policy and charging control of service data flows/applications and IP bearer resources. The PCRF selects and provides the applicable policy and charging control decision to the PCEF and, if applicable, application detection and control decision to the TDF or PCEF with application detection and control feature. When the Gxx interface applies, the PCRF maintains the correlation between the GW control session over Gxx interface and the IP-CAN session over Gx. The PCRF also acts as an information exchange relay between BBERF and PCEF to forward event triggers, which can't be transferred directly.
When the Sd interface applies, the PCRF maintains the correlation between the IP-CAN session and the TDF session. Events subscribed by the TDF are reported by the PCRF.
When S9a interface applies, the PCRF provides to the BPCF the UE/H(e)NB local IP address and UDP port number, the QoS rules and PCC rules over S9a interface. PCRF maintains the correlation between the GW control session over S9a interface and the IP-CAN session over Gx interface (if IP-CAN session over Gx interface is available).
When S15 interface applies, the PCRF provides dynamic QoS control policies to the BPCF for the purpose of allocation of QoS resources in the Fixed Broadband Access Network for HNB CS traffic.
PCRF is the policy and charging control element. PCRF functions are described in more detail in TS 23.203
In non-roaming scenario, there is only a single PCRF in the HPLMN associated with one UE's IP-CAN session.
In a roaming scenario with local breakout of traffic and/or when a Gxx interface applies there are two PCRFs associated with one UE's IP-CAN session:
H-PCRF that resides within the H-PLMN;
V-PCRF that resides within the V-PLMN.
A single logical PCRF entity may be deployed by means of multiple and separately addressable PCRFs in the PLMN. In this case, the PCRF discovery and selection is enabled by Diameter Routing Agency (DRA).