During Release 12, use cases and requirements on IMS-based telepresence were introduced by SA1 into TS 22.228 to enable telepresence support in IMS applications. In TS 22.228, telepresence is defined as a conference with interactive audio-visual communications experience between remote locations, where the users enjoy a strong sense of realism and presence between all participants (i.e. as if they are in same location) by optimizing a variety of attributes such as audio and video quality, eye contact, body language, spatial audio, coordinated environments and natural image size. A telepresence system is defined as a set of functions, devices and network elements which are able to capture, deliver, manage and render multiple high quality interactive audio and video signals in a telepresence conference. An appropriate number of devices (e.g. cameras, screens, loudspeakers, microphones, codecs) and environmental characteristics are used to establish telepresence. The core network aspects of IMS-based telepresence have been addressed by the CT groups (CT1, CT3, CT4), including incorporation of new tools into IMS as defined by IETF's ControLling mUltiple streams for tElepresence (CLUE) WG (see more from: https://datatracker.ietf.org/wg/clue/charter/) that achieves media advertisement and configuration to facilitate controlling and negotiating multiple spatially related media streams in an IMS conference supporting telepresence, taking into account capability information, e.g. screen size, number of screens and cameras, codecs, etc., so that sending system, receiving system, or intermediate system can make decisions about transmitting, selecting, and rendering media streams. This present document provides a study of media handling aspects of IMS-based telepresence in 3GPP services. This includes identification of codec-level technical gaps for a telepresence UE (TP UE), which is expected to not only support Multimedia Telephony Service for IMS (MTSI) UE media handling capabilities [2], but also more advanced media handling capabilities. Other SA4-level media handling aspects such as media configuration and session control, data transport, media adaptation, QoS handling and interworking with MTSI are also studied.

The present document provides a study on the media handling aspects of IMS-based telepresence in 3GPP services. This includes the investigation of the following areas:

• Media codecs (speech, video, real-time text) for IMS-based telepresence.
• Media configuration including session setup and control procedures for IMS-based telepresence, and media provisioning aspects of capability negotiation based on SDP and CLUE protocols, etc.
• Set-up and control of the individual media streams between clients including interactivity, such as adding and dropping of media components, as well as end-to-end QoS handling, etc. for IMS-based telepresence.
• Data transport including usage of RTP / RTCP protocols, RTP profiles, RTP payload formats, RTP mapping, media synchronization, etc. for IMS-based telepresence, e.g. in relation to negotiation and establishment of the CLUE data channel, and exchange of CLUE ADVERTISEMENT and CONFIGURE messages.
• Requirements and guidelines for media adaptation in IMS-based telepresence, for example in response to changes of network bandwidth.
• Media handling requirements and guidelines for fixed-mobile interworking as well as interworking with MTSI and with GSMA's IMS profile on High-Definition Video Conference (HDVC) service in IR.39.

The gap analysis of the above areas and associated recommendations and conclusions for the proposed improvements are documented in the present document. Study and evaluation of end-to-end quality of experience (QoE) for IMS-based telepresence use cases for various codec, media handling and QoS configurations are also presented.