Presence in IMS

The presence service provides the ability for the home network to manage presence information of a user’s device, service or service media even whilst roaming. A user’s presence information may be obtained through input from the user, information supplied by network entities or information supplied by elements external to the home network. Consumers of presence information, watchers, may be internal or external to the home network. The architecture for the 3GPP presence service is specified in 3GPP TS 23.141.

Presence Definitions 

Presentity: Entity providing presence information

Presence Server (PS): An entity that accepts, stores, and distributes presence information. 

Watcher: A watcher is an entity that subscribes to or requests presence information about a presentity from the PS. 

Presence User Agent (PUA): An entity that provides presence information to a PS. When the PUA intends to publish its own view of the presentity’s presence information, it shall generate a PUBLISH request by acting as an Event Publication Agent (EPA) 

Resource List Server (RLS): An implementation of the presence list server. The RLS is an entity that accepts subscriptions to resource lists and sends notifications to update subscribers of the state of the resources in a resource list. 

Presence Network Agent (PNA): Collects presence information about the presentity from a number of core network entities. The PNA can combine information from various core network entities to form more complete presence information. 

For more information, see:

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