Evolved Packet System (EPS): The LTE and SAE Evolution of 3G UMTS

6.3 Presence

The Presence service's purpose is to allow a subscriber to make its Presence information available to other users of Application Servers in the network. By extension, the Presence service is not limited to user availability information. During the past few years, there have been lots of new extensions brought to this service, coming from IETF activities or OMA specifications. These may also include lots of different information being defined by IETF documents, or by the OMA Presence specifications. These extensions provide richer information about the subscriber status, such as:

• The current activity (travelling, sleeping, …).
• The current location (at home, in office, …).
• The mood (afraid, hungry, …).
• Time offset (specifies the current time zone of the person).
• Contact address (an address in the form of a URL to which the user can be joined).
• The services the user has access to, e.g. PoC, Instant Messaging, ….
• The list of devices and network connectivity the user has access to (802.11, GPRS, IMS, …).

The rest of the section describes the service architecture as well as the relations with other parts of the Evolved UMTS network, and an example of Presence service usage.

6.3.1 Service Architecture

Figure 6.11 is a simplified overview of the Presence service architecture, as described in OMA specifications. The service itself relies on a central node – the Presence Server – in charge of storing and distributing Presence information. From the IMS perspective, the Presence ...