Chapter 19 gave an overview of the presence service on the Internet, as defined by the IETF. This chapter focuses on the use of the presence service in the IMS. We explore the IMS architecture that supports the presence service and the applicability of presence to the IMS. 3GPP has defined, in 3GPP TS [51], a presence service that runs over IMS, but mostly, 3GPP is just maintaining the specification, not actively progressing it. | Chapter 20 The Presence Service in the IMS Chapter 19 gave an overview of the presence service on the Internet as defined by the IETF. This chapter focuses on the use of the presence service in the IMS. We explore the IMS architecture that supports the presence service and the applicability of presence to the IMS. 3GPP has defined in 3GPP TS 51 a presence service that runs over IMS but mostly 3GPP is just maintaining the specification not actively progressing it. The presence service in IMS has since moved to OMA. OMA considers the presence service as an enabler . the set of specifications that enables a service. The main specification of the OMA Presence SIMPLE enabler is the OMA Presence SIMPLE specification 246 . This chapter describes this OMA Presence SIMPLE enabler. The Foundation of Services When we described the presence service on the Internet we unveiled a few of the powerful and rich possibilities that the presence service can offer to both end-users and other services. On the one hand end-users benefit from the presence service since they decide what information related to presence they want to provide to a list of authorized watchers. Presentities can decide the information they want to publish such as communication address capabilities of the terminals or availability to establish a communication. Watchers receive that information in real time and decide how and when to interact with the presentity. All of these features enrich the end-user communication experience. On the other hand presence information is not only available to end-users but also to other services. These other services can benefit from the presence information supplied. For instance an answering machine server is interested in knowing when users are online to send them an instant message announcing that they have pending voicemails stored in the server. A video server can benefit by adapting the bandwidth of the streaming video to the characteristics of the network .
