The 3GPP Technical Specifications TS 22.340 and TS 22.141 define the requirements for the 3GPP IP Multimedia Subsystem (IMS) based messaging and presence services. This Technical Specification takes the requirements into account when defining the minimal baseline and optional media codecs and message container format to be used by IMS Messaging and associated Presence service, when supported. IMS Messaging services incorporate one or more of the following messaging types Immediate messaging, Deferred delivery messaging, and Session based messaging. With Immediate messaging the sender expects immediate message delivery in what is perceived as real time compared with Deferred messaging where the sender expects the network to deliver the message as soon as the recipient becomes available. With Session based messaging a communications association is established between two or more users before communication can take place. In the simplest form Session based messaging may be a direct communication between two users. This specification defines the media types and container formats for both the Immediate message type and the Session based message type. The specification provides the ability to have an interoperable baseline set of media types for messaging and presence services, that will simultaneously maximise the technology re-use of the already existing 3GPP services with media types, defined in TS 26.140 and TS 26.234. Simultaneously, the specification will provide the ability to indicate the IMS system about the complete set of UE media and storage capabilities relevant for the IMS messaging and presence service. For IMS terminals capable of Combined CS and IMS (CSI) operation [59][60], the specification provides an Annex with guidelines on how to combine IMS media with CS calls.

The present document specifies the basic media formats and codecs to be used in the IMS Messaging and Presence services, including CSI. It defines the mandatory 'baseline' set of media types for the services. Additionally, it also targets to allow possible message content type enhancements, either 3GPP-standardized or other generally used media types, in a flexible way.