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Mobile in Minute papers

 IMS Network Elements

The major IMS network elements include:

Source: IMS: Driving New Business Models and Opportunities

• Access Gateway (AG): This network element provides an interface between the radio network (Access Network) and the IP-based network.

• Access Network (AN): This is the radio portion of the network.

• Breakout Gateway Control Function (BGCF): Controls resources allocation to IP sessions

• Call Session Control Function (CSCF): Provides control and routing function for IP sessions.

• Foreign Agent (FA): Advertises itself to mobile stations in serving area.  Provides registration information to Home Agent.  Forwards packets from mobile to Home Agent.

• Home Agent (HA): Tracks current Foreign Agent serving the mobile.  Forwards packets to current FA.

• Home Subscriber Server (HSS): Can take the place of a HLR in all-IP network.  Contains AAA function and other databases

• Media Gateway (MGW): Provides interface for bearer traffic between IP and PSTN

• Media Gateway Control Function (MGCF): Provides signaling interoperability between IP and PSTN domains – SIP to ISUP and vice versa

• Policy Decision Function (PDF): As IP networks, unlike TDM networks, assign network bandwidth and resources in real-time, the PDF’s role is to assign resources according to demand and QoS requirements.

• Position Determining Entity (PDE): While some mobiles can determine position independently, the PDE can provide assistance by way of location determination algorithms

• SIP Application Server: Represents a platform for SIP application development and operation.

by David Mangini Author of IP Multimedia Subsystem (IMS): Driving New Business Models & Opportunities