Method, apparatus and computer program

Abstract

There is provided an apparatus configured to perform: receiving, in a Session Initiation Protocol, SIP, request message from an application server comprised in an Internet Protocol Multimedia Subsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream; selecting a subset of the plurality of avatar identifiers; and signalling an indication of the subset to the application server in a SIP response.

Description

METHOD, APPARATUS AND COMPUTER PROGRAMRELATED APPLICATIONS

[0001] This patent application claims the benefit of priority of Indian Provisional Patent Application No. 202341073360 filed October 27, 2023, which is hereby incorporated by reference as if reproduced in its entirety.FIELD

[0002] The present application relates to a method, apparatus, system and computer program and in particular but not exclusively to receiving, from an application server, a plurality of avatar identifiers, and signalling an indication of a selected subset of the plurality of avatars to the application server.BACKGROUND

[0003] A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and / or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and / or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0004] In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Some wireless systems can be divided into cells, and are therefore often referred to as cellular systems.

[0005] A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided withan appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and / or receive communications on the carrier.

[0006] The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and / or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (3G radio). Other examples of communication systems are the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radioaccess technology and so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3GPP).SUMMARY

[0007] According to a first aspect, there is provided a communication device comprising means for performing: receiving, in a Session Initiation Protocol, SIP, request message from an application server comprised in an Internet Protocol Multimedia Subsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream; selecting a subset of the plurality of avatar identifiers; and signalling an indication of the subset to the application server in a SIP response or in an application layer protocol.

[0008] The means may be further for: downloading the selected subset of avatars via an internet protocol multimedia subsystem data channel connection or other Hypertext Transfer Protocol, HTTP, based mechanism.

[0009] The means may be further for: receiving a video stream from the another communication device, the video stream comprising an avatar representation of a user of the another communication device that corresponds to an avatar identifier comprised in the subset.

[0010] The means may be further for: determining to downgrade an avatar call to a call comprising an audio and / or video stream that does not comprise an avatar; signalling an indication of said determination to downgrade to an IMS network entity; and subsequently receiving a call associated to a same session as the avatar using an audio stream and / or a video stream that does not comprise an avatar.

[0011] The means may be further for: determining at least one avatar identifier that identifies an avatar to be used for representing a user of the communication device in a video stream transmitted by the communication device; and signalling the at least one avatar identifier to the Internet Protocol Multimedia Subsystem, IMS, application server.

[0012] The means for selecting the subset may comprise means for: obtaining metadata that defines at least one property of avatar identified by said plurality of avatar identifiers; and selecting the subset using the obtained metadata.

[0013] The metadata may associate an avatar identifier to at least one of: a language, voice, or video.

[0014] The application server may comprise an extended Reality application server.

[0015] According to a second aspect, there is provided an extended Reality application server comprising means for performing: receiving, via a hypertext transfer protocol, HTTP, or any other application layer protocol, at least one avatar identifier that identifies at least one avatar to be used to represent a user of another communication device within an avatar call received by a communication device via an internet protocol multimedia subsystem, IMS, network or via an application layer protocol; and causing another apparatus to render said at least one avatar within the avatar call.

[0016] The means for causing may comprise means for performing at least one of: signalling a media function to trigger the media function to render said at least one avatar within the avatar call; or signalling the another communication device to trigger the another communication device to render said at least one avatar within the avatar call; or signalling the communication device to trigger the communication device to render said at least one avatar within the avatar call.

[0017] The means may be further for: receiving said at least one avatar identifier; and retrieving avatar data and metadata associated with the at least one avatar identifier from a digital access container function by signalling an identifier of the another communication device and the at least one avatar identifier to the digital access container function.

[0018] According to a third aspect, there is provided an internet protocol multimedia subsystem, IMS, application server comprising means for performing: signalling, to a communication device using a session initiation protocol, SIP, request, a plurality of avatar identifiers that identifies at a plurality of avatars that can be used to represent a user of another communication device within an avatar call received by the communication device; receiving, from the communication device using a SIP response, an indication of a selected subset of said plurality of avatar identifiers; and causing the selected subset to be provided to the another communication device and / or an extended Reality application server.

[0019] The means may be further caused to perform: causing another apparatus to render at least one avatar of said selected subset within the avatar call.

[0020] Where mentioned above, the SIP request may comprise a session initiation protocol invite message or a session initiation protocol registration message.

[0021] Where mentioned above, the SIP response may comprise a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

[0022] According to a fourth aspect, there is provided an apparatus for a communication device, the apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receiving, in a Session Initiation Protocol, SIP, request message from an application server comprised in an Internet Protocol Multimedia Subsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream; selecting a subset of the plurality of avatar identifiers; and signalling an indication of the subset to the application server in a SIP response or in an application layer protocol.

[0023] The at least one processor may be configured to cause the apparatus to perform: downloading the selected subset of avatars via an internet protocol multimedia subsystem data channel connection or other Hypertext Transfer Protocol, HTTP, based mechanism.

[0024] The at least one processor may be configured to cause the apparatus to perform: receiving a video stream from the another communication device, the video stream comprising an avatar representation of a user of the another communication device that corresponds to an avatar identifier comprised in the subset.

[0025] The at least one processor may be configured to cause the apparatus to perform: determining to downgrade an avatar call to a call comprising an audio and / or video stream that does not comprise an avatar; signalling an indication of said determination to downgrade to an IMS network entity; and subsequently receiving a call associated to a same session as the avatar using an audio stream and / or a video stream that does not comprise an avatar.

[0026] The at least one processor may be configured to cause the apparatus to perform: determining at least one avatar identifier that identifies an avatar to be used for representing a user of the communication device in a video stream transmitted by the communication device; and signalling the at least one avatar identifier to the Internet Protocol Multimedia Subsystem, IMS, application server.

[0027] The selecting the subset may comprise: obtaining metadata that defines at least one property of avatar identified by said plurality of avatar identifiers; and selecting the subset using the obtained metadata.

[0028] The metadata may associate an avatar identifier to at least one of: a language, voice, or video.

[0029] The application server may comprise an extended Reality application server.

[0030] According to a fifth aspect, there is provided an apparatus for an extended Reality application server, the apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receiving, via a hypertext transfer protocol, HTTP, or any other application layer protocol, at least one avatar identifier that identifies at least one avatar to be used to represent a user of another communicationdevice within an avatar call received by a communication device via an internet protocol multimedia subsystem, IMS, network or via an application layer protocol; and causing another apparatus to render said at least one avatar within the avatar call.

[0031] The causing may comprise performing at least one of: signalling a media function to trigger the media function to render said at least one avatar within the avatar call; or signalling the another communication device to trigger the another communication device to render said at least one avatar within the avatar call; or signalling the communication device to trigger the communication device to render said at least one avatar within the avatar call.

[0032] The at least one processor may be configured to cause the apparatus to perform: receiving said at least one avatar identifier; and retrieving avatar data and metadata associated with the at least one avatar identifier from a digital access container function by signalling an identifier of the another communication device and the at least one avatar identifier to the digital access container function.

[0033] According to a sixth aspect, there is provided an apparatus for an internet protocol multimedia subsystem, IMS, application server, the apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: signalling, to a communication device using a session initiation protocol, SIP, request, a plurality of avatar identifiers that identifies at a plurality of avatars that can be used to represent a user of another communication device within an avatar call received by the communication device; receiving, from the communication device using a SIP response, an indication of a selected subset of said plurality of avatar identifiers; and causing the selected subset to be provided to the another communication device and / or an extended Reality application server.

[0034] The at least one processor may be configured to cause the apparatus to perform: causing another apparatus to render at least one avatar of said selected subset within the avatar call.

[0035] According to a seventh aspect, there is provided a method for a communication device, the method comprising: receiving, in a Session Initiation Protocol, SIP, request message from an application server comprised in an Internet Protocol MultimediaSubsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream; selecting a subset of the plurality of avatar identifiers; and signalling an indication of the subset to the application server in a SIP response or in an application layer protocol.

[0036] The method may further comprise: downloading the selected subset of avatars via an internet protocol multimedia subsystem data channel connection or other Hypertext Transfer Protocol, HTTP, based mechanism.

[0037] The method may further comprise: receiving a video stream from the another communication device, the video stream comprising an avatar representation of a user of the another communication device that corresponds to an avatar identifier comprised in the subset.

[0038] The method may further comprise: determining to downgrade an avatar call to a call comprising an audio and / or video stream that does not comprise an avatar; signalling an indication of said determination to downgrade to an IMS network entity; and subsequently receiving a call associated to a same session as the avatar using an audio stream and / or a video stream that does not comprise an avatar.

[0039] The method may further comprise: determining at least one avatar identifier that identifies an avatar to be used for representing a user of the communication device in a video stream transmitted by the communication device; and signalling the at least one avatar identifier to the Internet Protocol Multimedia Subsystem, IMS, application server.

[0040] The selecting the subset may comprise: obtaining metadata that defines at least one property of avatar identified by said plurality of avatar identifiers; and selecting the subset using the obtained metadata.

[0041] The metadata may associate an avatar identifier to at least one of: a language, voice, or video.

[0042] The application server may comprise an extended Reality application server.

[0043] According to an eighth second aspect, there is provided a method for an extended Reality application server, the method comprising: receiving, via a hypertext transfer protocol, HTTP, or any other application layer protocol, at least one avataridentifier that identifies at least one avatar to be used to represent a user of another communication device within an avatar call received by a communication device via an internet protocol multimedia subsystem, IMS, network or via an application layer protocol; and causing another apparatus to render said at least one avatar within the avatar call.

[0044] The causing may comprise performing at least one of: signalling a media function to trigger the media function to render said at least one avatar within the avatar call; or signalling the another communication device to trigger the another communication device to render said at least one avatar within the avatar call; or signalling the communication device to trigger the communication device to render said at least one avatar within the avatar call.

[0045] The method may further comprise: receiving said at least one avatar identifier; and retrieving avatar data and metadata associated with the at least one avatar identifier from a digital access container function by signalling an identifier of the another communication device and the at least one avatar identifier to the digital access container function.

[0046] According to a ninth aspect, there is provided a method for an internet protocol multimedia subsystem, IMS, application server, the method comprising: signalling, to a communication device using a session initiation protocol, SIP, request, a plurality of avatar identifiers that identifies at a plurality of avatars that can be used to represent a user of another communication device within an avatar call received by the communication device; receiving, from the communication device using a SIP response, an indication of a selected subset of said plurality of avatar identifiers; and causing the selected subset to be provided to the another communication device and / or an extended Reality application server.

[0047] The method may further comprise: causing another apparatus to render at least one avatar of said selected subset within the avatar call.

[0048] According to a tenth aspect, there is provided a computer readable medium comprising instructions which, when executed by an apparatus for a communication device, cause the apparatus to perform at least the following: receiving, in a Session Initiation Protocol, SIP, request message from an application server comprised in anInternet Protocol Multimedia Subsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream; selecting a subset of the plurality of avatar identifiers; and signalling an indication of the subset to the application server in a SIP response or in an application layer protocol.

[0049] The apparatus may be caused to perform: downloading the selected subset of avatars via an internet protocol multimedia subsystem data channel connection or other Hypertext Transfer Protocol, HTTP, based mechanism.

[0050] The apparatus may be caused to perform: receiving a video stream from the another communication device, the video stream comprising an avatar representation of a user of the another communication device that corresponds to an avatar identifier comprised in the subset.

[0051] The apparatus may be caused to perform: determining to downgrade an avatar call to a call comprising an audio and / or video stream that does not comprise an avatar; signalling an indication of said determination to downgrade to an IMS network entity; and subsequently receiving a call associated to a same session as the avatar using an audio stream and / or a video stream that does not comprise an avatar.

[0052] The apparatus may be caused to perform: determining at least one avatar identifier that identifies an avatar to be used for representing a user of the communication device in a video stream transmitted by the communication device; and signalling the at least one avatar identifier to the Internet Protocol Multimedia Subsystem, IMS, application server.

[0053] The selecting the subset may comprise: obtaining metadata that defines at least one property of avatar identified by said plurality of avatar identifiers; and selecting the subset using the obtained metadata.

[0054] The metadata may associate an avatar identifier to at least one of: a language, voice, or video.

[0055] The application server may comprise an extended Reality application server.

[0056] According to an eleventh aspect, there is provided a computer readable medium comprising instructions which, when executed by an apparatus for an extended Realisty application server, cause the apparatus to perform at least thefollowing: receiving, via a hypertext transfer protocol, HTTP, or any other application layer protocol, at least one avatar identifier that identifies at least one avatar to be used to represent a user of another communication device within an avatar call received by a communication device via an internet protocol multimedia subsystem, IMS, network or via an application layer protocol; and causing another apparatus to render said at least one avatar within the avatar call.

[0057] The causing may comprise performing at least one of: signalling a media function to trigger the media function to render said at least one avatar within the avatar call; or signalling the another communication device to trigger the another communication device to render said at least one avatar within the avatar call; or signalling the communication device to trigger the communication device to render said at least one avatar within the avatar call.

[0058] The apparatus may be caused to perform: receiving said at least one avatar identifier; and retrieving avatar data and metadata associated with the at least one avatar identifier from a digital access container function by signalling an identifier of the another communication device and the at least one avatar identifier to the digital access container function.

[0059] According to a twelfth aspect, there is provided a computer readable medium comprising instructions which, when executed by an apparatus, for an internet protocol multimedia subsystem, IMS, application server cause the apparatus to perform at least the following: signalling, to a communication device using a session initiation protocol, SIP, request, a plurality of avatar identifiers that identifies at a plurality of avatars that can be used to represent a user of another communication device within an avatar call received by the communication device; receiving, from the communication device using a SIP response, an indication of a selected subset of said plurality of avatar identifiers; and causing the selected subset to be provided to the another communication device and / or an extended Reality application server.

[0060] The apparatus may be caused to perform: causing another apparatus to render at least one avatar of said selected subset within the avatar call.

[0061] According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, causethe apparatus to perform at least the method according to any of the preceding aspects.

[0062] Where mentioned above, the SIP request may comprise a session initiation protocol invite message or a session initiation protocol registration message.

[0063] Where mentioned above, the SIP response may comprise a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

[0064] In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above.DESCRIPTION OF FIGURES

[0065] Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

[0066] Fig. 1 shows a schematic representation of an originating user equipment communicating with a terminating user equipment via a communication network comprising two internet protocol multimedia subsystem networks in accordance with an example embodiment;

[0067] Fig. 2 shows a schematic representation of an apparatus implementing one or more network functions of an internet protocol multimedia subsystem network;

[0068] Fig. 3 shows a schematic representation of a user equipment;

[0069] FIGS. 4 to 7 illustrate example procedures; and

[0070] FIGS. 8 to 10 illustrate operations that may be performed by apparatus described herein.DETAILED DESCRIPTION

[0071] Avatar calling relates to the ability of an internet protocol multimedia subsystem (IMS) network (and / or a communication device communicating via the IMS network) to modify and / or generate a video stream being provided from a communication device associated with a first participant (a.k.a. a first party, UE-A), via the IMS network, to a communication device associated with a second participant (a.k.a. a second party,UE-B) such that at least one object being depicted in the video stream is replaced by an alternative representation (a.k.a., by an avatar) in the video stream that is rendered at the communication device (e.g., UE) associated with the second participant. The object may be, for example, a person.

[0072] Stated differently, an avatar call is a call that comprises an audio stream and a video stream that has been at least partially generated (e.g., formed) by rendering an artificial object therein such that a real-life object is represented by the artificial object.

[0073] The avatar may be two dimensional and / or three dimensional. The avatar may have a range of physical characteristics. The replacement of at least one person in a video stream by a communication device (e.g., a UE) may be performed by, at least in part, detecting motion (e.g., gestures) of the at least one person in a video (e.g., by processing the video, using, for examples an AI / ML model configured for gesture detection or gesture recognition)and matching the motions (e.g., gestures) of the at least one person to avatar actions such that the motion of the avatar in the modified video stream mimics the motions (e.g., gestures) that of the at least one person in the video stream. The avatar may be associated with metadata that describe the avatar. As described further herein, the metadata of the presently described avatar may include, for example, whether the avatar is associated with a specific language to be used in the audio stream of the avatar call.

[0074] Clause 5.2.2 of 3GPP TS 22.156 describes several features for avatar calling. For example, 5G system that includes an IMS network should support (e.g., be capable of or configured for) multimedia communications, including the transfer of realtime avatar media and audio media. An IMS call or IMS session that uses avatar media is referred to herein as an IMS avatar call and / or an avatar call. The 5G system that includes the IMS network should also support the encoding of sensor data (and transmission thereof) that includes for example a facial expression, pose and movement, and body movement and gestures of a participant in an avatar call.

[0075] In relation to this, avatar metadata and avatar media has been defined. For example, an avatar that is identified by an avatar identifier may be associated with respective avatar metadata and avatar media. Stated differently, each avatar identifier (and hence avatar identified by the avatar identifier) is associated with respective avatar metadata and / or respective avatar media. Avatar metadata comprises the 2Dand / or 3D representational content of an Avatar. The representational content may also be referred to as a model. The avatar metadata can be stored in a file that can be addressed via a URL. Avatar media (used synonymously herein with “gesture media”) comprises user plane and / or media plane data related to an Avatar. This avatar media information is transmitted between two UEs and can be used to animate an avatar. Stated differently, avatar metadata information relates to information that defines the appearance and / or representation of an avatar, while avatar media information relates to information for animating of the avatar.

[0076] Several different use contexts in the context of avatar calls in a 5G system comprising an IMS network have been considered.

[0077] As a first use case, a calling party (also referred to as an originating party, first party, and / or UE-A) that is served by the IMS network can preselect 2 or more avatars to be represented as to a receiving party (also referred to as a terminating party, second party, and / or UE-B). These 2 or more avatars may be provided in a second step to UE-B, and UE-B may select the avatar that it wants to use in the conversation. This may be useful, for example, when different avatars are used to represent different languages and / or different genders. In such a situation, an automated customer care calling UE-A could propose at least two avatars, each corresponding to a different audio language or voice, and UE-B could select the language / avatar it wants to use during the conversation. UE-A may subsequently interact with UE-B using the selected avatar / language.

[0078] In a second example use case, the avatar represented call may be downgraded (e.g., converted from an audio-visual call comprising the avatar to simply an audio call).

[0079] In a third example use case, the terminating UE-B may elect to switch from one Avatar to another avatar or the originating UE-A in the middle of a session. This change, when notified to UE-A, may result in changing the language being used in the audio part of the call.

[0080] Mechanisms for effecting the above-mentioned use cases have not been described. The following describes at least one feature for addressing the above- mentioned issues.

[0081] Throughout the following, it will be assumed that “Party-A”, “participant-A”, and / or IIE-A refers to the originating (e.g., calling) party, and that “Party-B”, “participant-B”, and / or IIE-B refers to the terminating (e.g., receiving) party.

[0082] The following illustrates mechanisms for enabling IIE-A and / or the originating IMS network to propose, to IIE-B, multiple avatars that can be used in an IMS session for representing IIE-A in a video stream being displayed by IIE-B. In response to receipt of the proposed multiple avatars, IIE-B can accept a subset (one or more) of the avatars offered by IIE-A or reject them all. IIE-B may download and / or use any of the proposed avatar representation / metadata received from IIE-A. This can be achieved over the session initiation protocol (SlP)ZSession description protocol (SDP) or via the IMS Data Channel (DC).

[0083] In the following certain examples are explained with reference to mobile communication devices capable of communication via a wireless cellular system and mobile communication systems serving such mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system, access systems thereof, and mobile communication devices are briefly explained with reference to FIGS. 1 , 2 and 3 to assist in understanding the technology underlying the described examples.

[0084] FIG. 1 shows a schematic representation of a first user equipment (denoted IIE-A) communicating with a second user equipment comprising a communication network that includes two IMS networks. The communication network may comprise a public land mobile network (PLMN). A communication network may comprise a (radio) access network ((R)AN) (not illustrated), a core network (5GC) (not illustrated) in addition to the two internet protocol multimedia subsystem (IMS) networks shown. The IMS network serving the first user equipment (e.g., IIE-A) may be referred to as an originating IMS network and the IMS network servicing the second user equipment (e.g., IIE-B) may be referred to as a terminating IMS network.

[0085] In this disclosure, the expressions “internet protocol multimedia subsystem” and “internet protocol multimedia subsystem network” may be used interchangeably.

[0086] The (R)AN (not illustrated) may comprise one or more base stations. A base station may be an evolved NodeB (eNB) or a gNodeB (gNB). A gNB may comprisedistributed units connected to one or more centralized units. A (base station may be configured to provide wireless connectivity between the first user equipment and a base station and wired and / or wireless connectivity between the base station and the IMS network via the 5GC. and between the second user equipment and the 5GC.

[0087] The 5GC may comprise an access and mobility management function (AMF), a session management function (SMF), an authentication server function (ALISF), a user data management (UDM), a network exposure function (NEF), a unified data repository (UDR), a network repository function (NRF) and / or a network data analytics function (NWDAF), and a user plane comprising a user plane function (UPF). The 5GC may be connected to an IMS network (e.g., the originating IMS network or the terminating IMS network). The 5GC may be to manage traffic and routing from a UE via the (R)AN towards an IMS network (e.g., from the first UE towards the originating IMS network or the second UE towards the terminating IMS network).

[0088] An IMS network (e.g., the originating IMS network or the terminating IMS network) may comprise a proxy call session control function (P-CSCF), a serving call session control function (S-CSCF), an interrogating call session control function (I- CSCF), an IMS application level gateway (IMS-AGW), an IMS home subscriber server (IMS HSS), an IMS application server (IMS AS), a media function (MF) or media repository function (MRF), a transition gateway (TrGW), an interconnection border control function (IBCF), a terminating IMS core, a data channel signalling function (DCSF), an XR application server (AS), a digital asset container (DAC) or a web server (not represented).

[0089] The DAC may be separate from other network functions of the originating IMS network or may be integrated with other network functions of the originating IMS network. For example, the DAC may be integrated within the IMS HSS or the XR AS.

[0090] Although the DAC is illustrated in Figure 1 as being part of the originating IMS network, it will be understood that the DAC is not necessarily part of the originating IMS network, let alone the communication network (e.g., PLMN). The DAC may be part of the 5GC. The DAC may be separate from other network functions of the 5GC or may be integrated with other networks functions of the 5GC. For example, the DAC may be integrated within the UDM. Alternatively, the DAC may not be part of the communication network (e.g., PLMN). For example, the DAC may be part of a webserver or a computing system of a cloud provider that is connected to the communication network (e.g., PLMN).

[0091] The DAC may be separate from other functions of the IMS or may be integrated with other functions of the IMS. For example, the DAC may be integrated within the IMS HSS or the XR AS. The DAC stores digital assets of a user. Digital assets of a user may comprise digital representations of, for example, user information and / or user documents such as e.g. passport, social security number, avatar, driving license, insurance policy etc. Any signalling provided to the XR AS may be provided using application-layer signalling, such as hypertext transfer protocol signalling.

[0092] It will be understood that the DAC is not necessarily part of the IMS, let alone the PLMN. The DAC may be part of the 5GC. The DAC may be separate from other functions of the 5GC or may be integrated with other functions of the 5GC. For example, the DAC may be integrated within the UDN. Alternatively, the DAC may not be part of the PLMN. The DAC may be part of a web server or a cloud provider outside the PLMN.

[0093] A user equipment (UE) can connect and register to the IMS network in various ways through an access network (such as through a 5G and / or 6G access network). Registration with the IMS network currently uses Session Initiation Protocol (SIP) signalling mechanisms, which are defined by the Internet Engineering Task Force (IETF). A home subscriber server (HSS) and / or unified data management (UDM) located in the core network contains subscription-related information for users, performs authentication and / or authorisation of the user for the IMS network. An IMS subscriber comprises a user and / or user equipment that has an IMS subscription stored in the HSS. Each IMS subscription is linked to a single IP multimedia private user identity (IMP I), which is discussed further below.

[0094] The IMS network further comprises a plurality of IMS network-based identifies. For example, IMS user identities include at least IP multimedia private user identity (IMPI), IP multimedia public user identity (IMPU), globally routable user agent URI (GRUU), wildcarded public user identity. Both IMPI and IMPU are uniform resource identifiers (URIs), that can be digits or alphanumeric identifiers.

[0095] The IMPI is a unique permanently allocated global identity assigned by the home network operator. It has the form of a Network Access Identifier (NAI) (e.g., user.name@domain), and is used, for example, for Registration, Authorization, Administration, and Accounting purposes.

[0096] The IMPU is used by any user for requesting communications to other users (e.g. this might be included on a business card). There can be multiple IMPU per IMPI.

[0097] In the IP Multimedia Subsystem (IMS), the Session Description Protocol (SDP) is used to describe and negotiate the parameters of multimedia sessions, such as voice and video calls. The SDP offer includes information about the user's capabilities and preferences for the session. For example, it may specify supported audio and video codecs, IP addresses, and port numbers for media transmission. SDP allows the inclusion of various media attributes, such as bandwidth constraints, media type (audio, video, etc.), codec selection, and encryption preferences.

[0098] FIG. 2 illustrates an example of a control apparatus 200 for controlling a function of the IMS as illustrated in FIG. 1. The control apparatus may comprise at least one random access memory (RAM) 211 a, at least on read only memory (ROM) 211 b, at least one processor 212, 213 and an input / output interface 214. The at least one processor 212, 213 may be coupled to the RAM 211 a and the ROM 211 b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215. The software code 215 may for example allow to perform one or more steps to perform one or more of the present aspects. The software code 215 may be stored in the ROM 211 b. The control apparatus 200 may be interconnected with another control apparatus 200 controlling another function of the 5GRAN or the 5GC. In some embodiments, each function of the 5GRAN or the 5GC comprises a control apparatus 200. In alternative embodiments, two or more functions of the 5GRAN or the 5GC may share a control apparatus.

[0099] FIG. 3 illustrates an example of a terminal 300, such as the terminal illustrated on FIG. 1. The terminal 300, which is also referred to herein as a user equipment (UE) and / or communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a user equipment, a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interfacefacility (e.g., USB dongle), a personal data assistant (PDA) or a tablet provided with wireless communication capabilities, a machine-type communications (MTC) device, an Internet of things (loT) type communication device or any combinations of these or the like. The terminal 300 may provide, for example, communication of data for carrying communications. The communications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on.

[0100] The terminal 300 may receive signals over an air or radio interface 307 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In FIG. 3 transceiver apparatus is designated schematically by block 306. The transceiver apparatus 306 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0101] The terminal 300 may be provided with at least one processor 301 , at least one memory ROM 302a, at least one RAM 302b and other possible components 303 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The at least one processor 301 is coupled to the RAM 302b and the ROM 302a. The at least one processor 301 may be configured to execute an appropriate software code 308. The software code 308 may for example allow to perform one or more of the present aspects. The software code 308 may be stored in the ROM 302a.

[0102] The processor, storage and other relevant control apparatus can be provided on an appropriate circuit board and / or in chipsets. This feature is denoted by reference 304. The device may optionally have a user interface such as key pad 305, touch sensitive screen or pad, combinations thereof or the like. Optionally one or more of a display, a speaker and a microphone may be provided depending on the type of the device.

[0103] As mentioned above, the following illustrates procedures for enabling UE-A and / or the originating IMS network to propose, to UE-B, multiple avatars that can be used in an IMS session for representing a person in a video stream associated with UE-A that is being (or is to be) displayed by UE-B. In response to receipt of the proposed multiple avatars (e.g., by signalling multiple avatar identifiers that areassociated with the proposed multiple avatars), IIE-B can accept a subset (zero / reject, one or more) of the avatars offered by IIE-A. IIE-B may download and / or use any of the proposed avatar metadata received from IIE-A. This can be achieved over the session initiation protocol (SlP)ZSession description protocol (SDP) or via the IMS Data Channel (DC).

[0104] Although these concepts are illustrated with reference to the signalling examples of FIGS. 4 to 7, several general principles may be considered.

[0105] For example, there is disclosed the provision of multiple avatar identifiers (and any associated avatar metadata that describes properties associated therewith (e.g., language)) in signaling of an IMS session. The avatar identifiers and associated avatar metadata may be used by the terminating party for autonomously selecting an avatar representation to be used for this IMS session, e.g., over the session initiation protocol (SlP)ZSession description protocol (SDP) or the IMS Data Channel (DC), which is an Extended reality (XR)-specific IMS data channel.

[0106] IIE-A and / or the originating IMS network may be able to select and / or propose multiple avatars to IIE-B that could be displayed at IIE-B during IMS calling.

[0107] IIE-B can select a subset (e.g., one or more, up to all of the multiple avatars) of the avatars offered by IIE-A or reject them all. This selection may be based on user input and / or on the associated avatar metadata and / or avatar media. The avatar metadata and / or avatar media associated with the selected avatar(s) may be used to animate the selected avatar(s) when rendering the selected avatar(s) into a video stream. The entity that modifies the video stream to comprise the selected avatar(s) may be authorised to download / use any of the proposed avatar metadata and / or avatar media from IIE-A.

[0108] IIE-B may be able to switch locally at any time between different avatars without signalling towards IIE-A.

[0109] Avatar identifiers of the avatars selected by IIE-B can be relayed back to the IMS network and IIE-A (e.g., as part of a Session Description Protocol (SDP) answer and / or some other application layer protocol). However, IIE-B may choose not to inform IIE-A of which avatar(s) IIE-B intends to use (or which one IIE-B is currently using when IIE-B switches freely between multiple avatars). In an alternativeembodiment, IIE-A and / or the originating IMS network may be able to request in the signaling to be informed about any switch of avatar performed by IIE-B, as this may impact the overall session.

[0110] UE-B may switch to another avatar indicated by IIE-A and / or the IMS network in the middle of the IMS session by selecting the appropriate Avatar and corresponding avatar identifier. The avatar identifier that identifies the another avatar may be provided to IIE-A and / or the originating IMS network. The IIE-A or the originating IMS network will switch to the another avatar based on the received avatar identifier in the middle of the IMS session.

[0111] UE-B and / or IIE-A may trigger to switch the avatar session to a simple audio session in the middle of the IMS session by updating the media of the ongoing IMS session (media re-negotiation). This update can also be triggered by the XR AS via IMS AS. IMS AS triggers update of the session at IIE-A, UE-B, MF / MRF.

[0112] The following illustrates the above-mentioned features in a plurality of different call flows.

[0113] In the below call flows, UE-A avatar(s) are transmitted to UE-B by a network media function (NMF). It is assumed that UE-A does not send avatar media (animated gesture and avatar representation altogether), as this would imply that UE-A has selected a single avatar to be used.

[0114] A first call flow is illustrated with respect to FIG. 4. Referring to FIG. 4, a procedure in shown in which a terminating party selects at least one avatar to represent a calling party during an IMS avatar call from multiple avatars preferred by the calling party. In more detail, the calling party may indicate the calling party’s preferred avatars to an IMS network, which provides avatar identifiers of the preferred avatars to the terminating party. These preferred avatars correspond to the multiple avatars mentioned above. The at least one avatar subsequently selected by the terminating party is provided to the IMS network and / or calling party. The IMS network of FIG. 4 is configured to generate a video stream and / or to modify an existing video stream to represent a video stream provided from the calling party to the terminating party during an avatar call.

[0115] FIG. 4 illustrates signalling that may be performed between UE-A 401 , a CSCF 402, a DAC 403, an IMS application server (AS) 404, a data channel signalling function (DCSF) 405, a media function and / or media repository function (MF / MRF) 406, and extended reality (XR) AS 407, a terminating IMS core 408, and a IIE-B 409. The terminating IMS core 408 and the IIE-B are on the terminating call side of the IMS network, while the remaining entities are associated with an originating call side of the IMS network. This example signalling of FIG. 4 relates to a network-based avatar rendering example that uses an IMS data channel.

[0116] During 4001 , an audio and / or video (A / V) session is established, and an IMS bootstrap data channel is established for both IIE-A and IIE-B.

[0117] During 4002, UE-A401 determines to request network-based avatar rendering. This determination may be based on a current status and / or capabilities of IIE-A. For example, this determination may be based on IIE-A having at least a threshold amount of power left (e.g., a UE may determine not to perform avatar rendering itself when that UE has a low power). As another example, UE-A may be incapable of generating and / or modifying a video for avatar calling. In such a case, the IMS network may be requested to perform this function as network-based avatar rendering.

[0118] During 4003, UE-A 401 performs an avatar rendering negotiation between UE- A and the IMS network. As part of this negotiation, UE-A 401 negotiates with the XR AS 407 the avatar identifiers to be used by the UE-A for the session. The avatars identified by these avatar identifiers are avatars that are authorised for use by the UE- A.

[0119] During 4004, application data channels are established between UE-A and the IMS network.

[0120] During 4005, UE-A and the IMS network renegotiate media in order to anchor UE’s A / V to MF 406.

[0121] During 4006, media renegotiation between UE-B 409 and the IMS network (which may be triggered by UE-B) is performed for anchoring UE-B’s A / V to MF 406. As part of this, UE-B 409 may be provided with UE-As avatar identifiers of 4003 via the originating and terminating IMS networks. Optionally, UE-B may be provided with a request to select a single one of UE-As avatar identifiers and to indicate the selectedsingle avatar identifier back to the originating IMS network. This optional request may be sent to IIE-B from the originating IMS network based on an indication from IIE-A that this selection indication of UE-B’s avatar selection for IIE-A is to be obtained from UE-B.

[0122] Stated differently, UE-B may receive, in session initiation protocol signalling (e.g., a SIP request message) and / or application-layer signalling from an application server comprised in an IMS network), a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream. UE-B selects a subset of the plurality of avatar identifiers. The subset may comprise only a single avatar identifier of the plurality of avatar identifiers. The subset may comprise more than one avatar identifier of the plurality of avatar identifiers. The subset may be selected, at least in part, based on receipt of a user input that selects one or more avatar identifier from the plurality of avatar identifiers.

[0123] Stated differently, based on the received avatar identifiers and avatar metadata associated with the identified avatars, and optionally based on displayed representation (either downloaded or previously cached) at the UE-B, UE-B has the option to select one or more (if allowed) avatar(s) using the provided avatar identifiers of UE-A, reject other avatar identifiers of UE-A, or to terminate the session. The avatar metadata may comprise, for example, a human readable name. The avatar metadata may comprise, for example, a representation format. The avatar metadata may comprise, for example, a minimum and / or maximum and / or requested resolution for an avatar call to be rendered.

[0124] For example, if the avatar identifiers provided to UE-B for UE-A are avatar-A1 and avatar-A2, and are linked with English and German audio language respectively, then avatar-A1 may be presented to the user of UE-B with the description “English language” and avatar-A2 may be presented to the user of UE-B with the description “German language”. The user of UE-B can select one of these identified (e.g., Avatar- A2) and UE-B can send an indication that avatar-A2 is selected.

[0125] In another example, UE-B selects an avatar identifier based on at least one avatar metadata parameter defining a capability of UE-B to format and / or render image data. Stated differently, UE-B selects an avatar identifier that identifies an avatarassociated with IIE-A based on the format and / or resolution of the avatar in line with its local computing and rendering capabilities.

[0126] It is useful for the IIE-B to send to the terminating and / or originating IMS network an indication of the avatar identifier selected by IIE-B. Stated differently, the IIE-B signals an indication of the selected subset to the application server in a SIP response signalling and / or an application protocol signalling (e.g., HTTP). This may assist the MF / MRF in the originating and / or terminating network (MF / MRF in the terminating network is not shown) in adapting the media sent to IIE-B by IIE-A during the avatar call as part of network-based avatar rendering. The IMS network that comprises the MF / MRF that is to perform network-based avatar rendering may be the IMS.

[0127] During 4007, the XR AS 407 signals the DAC 403. This signalling may comprise a request for avatar data (e.g., avatar metadata and / or avatar media) associated with the avatar representation selected during 4006 (e.g., avatar-A2). The avatar data may comprise binary and / or textual data. The textual data may comprise, for example, Extensible Markup Language (XML) and / or JavaScript Object Notation (JSON).

[0128] The avatar data may comprise avatar media and / or avatar metadata, as described above.

[0129] During 4008, the DAC 403 signals the XR AS 407. This signalling may comprise the avatar data requested during 4007.

[0130] During 4009, the XR AS determines that avatar rendering should start for the selected avatar.

[0131] During 4010, the XR-AS 407 signals the MF / MRF 406. This signalling may comprise the avatar data and / or the necessary data for the IMS network-based avatar rendering. Stated differently, this signalling may comprise avatar media and / or avatar metadata for enabling the MF / MRF to modify a video stream originating from UE-A for an avatar call between UE-A and UE-B, and / or for enabling the MF / MRF to generate a video stream based on sensor information provided by UE-A for an avatar call between UE-A and UE-B.

[0132] During 4011 , UE-A 401 signals the MF / MRF 406 a video stream and / or sensor information that indicates gestures, pose and / or movements performed by a person(referred to as “gesture media”). This video stream and / or sensor information does not comprise any avatar.

[0133] During 4012, the MF / MRF 406 receives the traditional video stream from IIE-A and replaces a face and / or body rendered therein with the selected avatar. This may be performed, for example, using face detection and / or other computer vision mechanisms.

[0134] In another example, depending on their capabilities as per regular IMS media negotiation, IIE-A could send “gesture media” during 4011. In this case, during 4012, the MR / MRF uses the gesture media from IIE-A and avatar media to animate the selected avatar metadata retrieved during 4010. The resulting stream is sent as regular video media or avatar media to IIE-B during 4013 (not shown). During 4014, the rendered avatar video is sent back to IIE-A as feedback (same content as the one sent to IIE-B during 4013). This may be useful for UE-A to display a thumbnail view of their avatar to IIE-A in the IMS session.

[0135] It is understood that the signalling of FIG. 4 may be further modified in any of a plurality of different ways.

[0136] For example, IIE-B may initiate the avatar media data during 4002 by providing potential IIE-B avatar identifiers to the IMS AS 504 (e.g., B1 and B2). These may be provided to IIE-A for selection between.

[0137] As a further example, IIE-B may be enabled to downgrade the avatar session to an audio session during the session. This may be achieved by, for example, using the RE-INVITE / UPDATE SIP signalling mechanism with “removing Avatar” signalled in the m-line in the SDP content. The originating or terminating IMS network will remove the avatar towards the IIE-B in response to this signalling.

[0138] As a further example, IIE-B may be enabled to switch the avatar during the session. This may be performed by, for example, using Re-INVITE / UPDATE signalling mechanisms. Changing the avatar may for example result in a change of audio language or voice used in the avatar session.

[0139] Referring to FIG. 5, a procedure in shown in which a terminating party selects at least one avatar to represent a calling party during an IMS avatar call from multiple avatars preferred by the calling party. In more detail, the calling party may indicate thecalling party’s preferred avatars to an IMS network, which provides identifiers of the preferred avatars (e.g., preferred avatar identifiers) to the terminating party. These preferred avatar identifiers correspond to the multiple avatars. The terminating party selects at least one of the preferred avatar identifiers. The at least one avatar identifier selected by the terminating party is provided to the IMS network and / or calling party. The IMS network of FIG. 4 is configured to generate a video stream and / or to modify an existing video stream to represent a video stream provided from the calling party to the terminating party during an avatar call. It is understood that where similar language to FIG. 4 is used in FIG. 5, the description provided above in respect of FIG. 4 may be used to understand FIG. 5.

[0140] Referring to FIG. 5, FIG. 5 illustrates example signalling that may be performed for a second example. In this second example, there is provided an IMS avatar call with network centric call flow using an avatar identifier within the Session Description Protocol (SDP).

[0141] FIG. 5 illustrates signalling that may be performed between a IIE-A 501 , a CSCF 502, a DAC 503, an IMS AS 504, an MF / MRF 505, an XR AS 506, a terminating IMS core 507, and a IIE-B 508.

[0142] During 5001 , IIE-A 501 determines to request a network avatar rendering based on its status.

[0143] During 5002, IIE-A 502 signals IMS AS 504 via the CSCF 502. This signalling may comprise an invitation to initiate an audio-video call with IIE-B 508. This signalling may comprise a plurality of avatar identifiers (e.g., two of more avatar identifiers). In the present example, the provided avatar identifiers are A1 and A2. The avatars identifiers may be stored in a local cache of IIE-A and / or provided to IMS AS 504 via previous signalling (e.g., by the DAC 503 and / or XR AS 506). The avatar identifiers may be comprised in, for example, an m- (media description) or a- (attributes) line in the SDP.

[0144] Optionally, the signalling of 5002 may comprise respective information for at least one identifier avatar. For example, the signalling may comprise, for a specific avatar identifier, an indication of a related representation format, and / or resolution,and / or a human readable description of the avatar (including its language). Stated differently, the signalling of 5002 may comprise avatar metadata.

[0145] During 5003, the IMS AS 504 signals the XR AS. This signalling may comprise information relating to the provided avatar identifiers. Stated differently, the IMS AS 504 may read the avatar identifiers’ (A1 and A2) information and request the XR Application Server to retrieve the avatar metadata (e.g., the related representations) of those avatar identifiers from the DAC.

[0146] During 5004, the IMS AS 504 signals the IIE-B 508 via the terminating IMS core 507. This signalling may comprise an invitation to an audio-video call. This signalling may comprise an indication of avatar identifiers A1 and A2. The signalling of 5004 may be performed using a SIP and / or SDP signalling. The signalling of 5004 may comprise an indication indicating an explicit request for IIE-B to send back a single choice amongst the proposed avatars. Stated differently, IIE-B receives, in a Session Initiation Protocol, SIP, request message and / or HTTP-based signalling (or other application protocol layer signalling) from an application server comprised in an Internet Protocol Multimedia Subsystem, IMS, network (originating or terminating IMS network), a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream.

[0147] When the XR-AS does not comprise the information associated with the avatar rendering for rendering both A1 and A2 within a video stream (e.g., because this information is inaccessible in a local cache of the XR-AS), the XR-AS proceeds to 5005. Otherwise, the mechanism proceeds to 5007.

[0148] During 5005, the XR-AS 506 signals the DAC 503. This signalling may comprise a request to receive information for implementing avatars A1 and / or A2. Stated differently, this signalling may comprise a request for avatar media and / or avatar metadata associated with avatars A1 and A2. This signalling may comprise an identifier of IIE-A. It is understood that 5005 may be performed at any time between 5003 and 5008 (e.g., after IIE-B 508 has selected a specific avatar identifier associated with IIE-A). In this case, only avatar information for the avatar selected by IIE-B may be requested, which may help save system signalling resources).

[0149] During 5006, the DAC 503 signals the requested information of 5005 to the XR- AS 506. This signalling may be performed based on the DAC 503 verifying that IIE-A is authorized to use avatars A1 and A2.

[0150] During 5007, IIE-B 508 signals IMS-AS 504. This signalling may comprise an acceptance of the signalling of 5004. This signalling may indicate which avatar has been selected by IIE-B 504 for use in representing IIE-A 501 during the requested A / V call. This signalling may be provided in a SIP response and / or an application protocol layer signalling (such as HTTP).

[0151] The selection of the avatar identiifer made by IIE-B may optionally be based on a displayed representation (either downloaded or previously cached) at the IIE-B to the user of IIE-B. The displayed representation may display at least some of the avatar metadata associated with the avatar identifiers being selected between by the IIE-B. The user of IIE-B may thus be presented with an option to select one (or more, if allowed) avatar identifier(s), reject other avatar identifier(s), and / or terminate the session.

[0152] For example, if avatar-A1 is presented with description “English language” and Avatar-A2 is presented with description “German language”, IIE-B can select Avatar- A2, and subsequently send an indication to the IMS-AS that Avatar-A2 is selected.

[0153] As another example, IIE-B may select an avatar identifier based on the format / resolution associated with each avatar identifier such that the selected avatar identifier is in line with UE-B’s local computing and rendering capabilities. IIE-B sending back an indication of the selected avatar identifier to the terminating IMS network and / or the originating IMS network may assist entities in the IMS network (e.g., MF / MRF) in adapting the media sent to IIE-B (as described above in relation to FIG. 4).

[0154] During 5008, the IMS-AS 504 signals IIE-A 501. This signalling may comprise an indication that the AV session is being established. This signalling may comprise an indication that avatar A2 has been selected by IIE-B (e.g., the avatar identifier of avatar A2 may be signalled by the IMS-AS). This selection may be comprised in an m-line of the signalling. This signalling may comprise SIP signalling.

[0155] During 5009, the IMS-AS 504 signals the XR-AS 506. This signalling may comprise an indication that a specific session is to be rendered using a specified avatar. Therefore, the signalling may comprise an identifier of a specific session, and at least one specific avatar identifier (e.g., A2).

[0156] During 5010, the XR AS 506 determines that avatar rendering should be performed based on the signalling of 5009.

[0157] During 5011 , the XR AS 506 signals the MF / MRF 505. This signalling may comprise avatar rendering data (e.g., avatar data for avatar A2) to be used by the MF / MRF in rendering media such that calling party IIE-A is represented by the identifier avatar A2.

[0158] It is understood that when the IMS AS does not receive an indication of at least one selected avatar ID(s) from IIE-B during 5007, then IMS AS 5006 can optionally insert the initial set of avatar ID(s) received in 5002 into the signalling of 5009. Further, when the XR AS does not receive avatar ID(s) from IMS AS during 5009, then the XR AS can select at least one avatar identifier to be used by the MF / MRF amongst the one(s) received during 5003.

[0159] During 5012, IIE-A 501 signals a plain video stream (e.g., without any avatar information) to MF / MRF 505.

[0160] During 5013, the MF / MRF 505 replaces a face / body comprised in the video stream of 5012 with the selected avatar signalling during 5011 . This may be performed using, for example, face detection and / or gesture recognition mechanism employed by the MF / MRF.

[0161] In an example, depending on their capabilities, IIE-A could send “gesture media” during 5012. In this case, during 5013, the MR / MRF uses the gesture media from IIE-A to animate the selected avatar representation retrieved during 5011 as described above in relation to FIG. 4.

[0162] In all scenarios, the video stream formed by the MF / MRF 505 by inserting at least one avatar is labelled as a modified video stream.

[0163] During 5014, the modified video stream is signalled from the MF / MRF to IIE-B 508.

[0164] During 5015, the modified video stream is signalled from the MF / MRF to IIE-A 501 . This signalling may be used by IIE-A to display (e.g., as a thumbnail) to the user of UE-A.

[0165] It is understood that 5014 and 5015 may be sent as avatar media depending on the capabilities of UE-A and / or UE-B. Properties of avatar media is largely described in clause 5.2.2.1 of 3GPP TS 22.156.

[0166] It is understood that the example signalling of FIG. 5 may be modified in any of a plurality of different respects.

[0167] For example, UE-B may initiate the signalling during 5007 by providing potential UE-B avatar identifiers to the IMS AS 504 (e.g., B1 and B2). These may be provided to UE-A for selection between.

[0168] As a further example, UE-B may be enabled to downgrade the avatar session to an audio session during the session. This may be achieved by, for example, using the RE-INVITE / UPDATE SIP signalling mechanism with “removing Avatar” signalled in the m-line in the SDP. The IMS network will remove the avatar comprised in video signalling and / or remove video signalling towards the UE-B in response to this “removing Avatar” signalling.

[0169] As a further example, UE-B may be enabled to switch the avatar during the session. This may be performed by, for example, using Re-INVITE / UPDATE signalling mechanisms. Changing the avatar may also result in a change of language used in the session, based on the language category associated with the avatar switched from and the language of the avatar switched to. Stated differently, the UE-B may trigger a re-negotiation by sending a new session description offer in a SIP relNVITE or SIP UPDATE message to UE-A. UE-A may reply to this with an SDP answer in a SIP 200 OK message.

[0170] Referring to FIG. 6, a procedure is shown in which a terminating party selects at least one avatar identifier that identifies an avatar to represent a calling party during an IMS avatar call from multiple avatar identifiers preferred by the calling party. In more detail, the calling party may indicate the calling party’s preferred avatars to an IMS network, which provides identifiers of the preferred avatars to the terminating party. These preferred avatars correspond to the multiple avatars. The at least one avatarselected by the terminating party is provided to the IMS network and / or calling party. The IMS network of FIG. 6 is configured to generate a video stream and / or to modify an existing video stream to represent a video stream provided from the calling party to the terminating party during an avatar call. It is understood that where similar language to FIG. 4 is used in FIG. 6, the description provided above in respect of FIG.4 may be used to understand FIG. 6.

[0171] FIG. 6 illustrates signalling associated with a UE-based avatar call using a data channel.

[0172] FIG. 6 illustrates signalling that may be performed between a IIE-A 601 , a CSCF 602, a DAC 603, an MF / MRF 604, an XR-AS 605, an Interconnection Border Control Functions (IBCF) 606, a terminating IMS core 607, and a IIE-B 608.

[0173] During 6001 , an IMS session is established, including establishing a bootstrap data channel.

[0174] During 6002, real-time transport protocol (RTP) and / or application data channel establishment is performed for both IIE-A and IIE-B. The Real-time Transport Protocol (RTP) is a network protocol for delivering audio and video over IP networks. As part of this process, IIE-A 601 may indicate a plurality of avatar identifiers (A1 , A2) that are available for use to IIE-B 608 for representing IIE-A 601 , and IIE-B 608 may select at least one of these avatar identifiers (e.g., A2) for use in representing IIE-A 601. This may be as performed above in relation to FIG. 4 and / or FIG. 5.

[0175] When IIE-A 601 does not have the avatar metadata / representation associated with the selected avatar identifier(s) available in a local cache, then 6003-6006 are performed.

[0176] During 6003, the XR-AS 605 signals the DAC 602. This signalling may comprise a request for metadata associated with at least one of the indicated available avatar identifiers (e.g., A1 , A2), or the avatar identifier(s) selected by IIE-B (e.g., A2). This signalling may comprise an identifier of IIE-A 601 .

[0177] During 6004, the DAC 602 signals at least some of the requested avatar metadata of 6003 to the XR-AS 605.

[0178] During 6005, the XR-AS 605 signals the avatar metadata received during 6004 to IIE-A 601 . The message may be sent over a data channel (DC), hypertext transportprotocol (HTTP), websocket, or Session Initiation Protocol (SIP). In case of SIP, IMS call flow between XR application server and IIE-A may follow.

[0179] During 6006, IIE-A 601 indicates to the XR-AS whether the avatar metadata was received correctly during 6005.

[0180] During 6007, IIE-A 601 locally mixes an avatar representation derived using the avatar metadata received during 6005 (or previously locally cached) together with gesture data received from local sensors (e.g., a camera) to animate an avatar that represents a user of IIE-A within a video stream. The resulting video data is labelled herein as a modified video stream.

[0181] During 6008, IIE-A signals the modified video stream to IIE-B 608 as regular video media and / or as avatar media (depending on capabilities of IIE-A 601 and / or UE-B 608).

[0182] When IIE-A 601 and UE-B have agreed during session setup or update that UE-B uses (mixed) avatar media, then 6009 to 6010 are performed. These signalling elements relate to UE-B 608 providing avatar media representing a user in a video stream associated with UE-B to UE-A and UE-A displaying the avatar media at UE-A.

[0183] During 6009, UE-B 608 signals avatar data (e.g., avatar metadata and / or avatar media) to UE-A 601 .

[0184] During 6010, UE-A decodes the avatar data received during 6009, renders the avatar for UE-B within the video stream received from UE-B, and displays the rendered avatar to the user of UE-A. The signalling of 6009 to 6010 may be based on, for example, an SDP offer / answer mechanism, in which the type of media exchanged from B to A (e.g., avatar media, gesture media, plain video media) is independent from the one from A to B.

[0185] It is understood that although this signalling of FIG. 6 is illustrated from the originating UE to the terminating UE, that similar principles may be performed in the opposite direction.

[0186] For example, during 6001 , UE-A 601 may indicate in its SDP offer that the avatar media will comprise gesture information, and that rendering of the avatar within the video stream from UE-A is to be performed at UE-B.

[0187] In such an example, 6005 and 6006 may be performed between the XR-AS and UE-B instead of between XR-AS and IIE-A, with rendering of 6007 being performed at UE-B 608 instead of UE-Afor each of the avatar representations selected by UE-B. Subsequently, 6008 would comprise UE-A signalling audio and “gesture media” to UE-B (e.g., using RTP). The audio and gesture media is rendered at UE-B for display using the avatar metadata associated with A1 and / or A2 depending on UE- B’s autonomous choice of preferred avatar. 6008 to 6009 may be unchanged and relate to UE-B’s media.

[0188] It is understood that the signalling of FIG. 6 may be further modified in any of a plurality of different ways.

[0189] For example, UE-B may initiate the avatar media data during 6002 by providing potential UE-B avatar identifiers to the IMS AS 604 (e.g., B1 and B2). These may be provided to UE-A for selection between.

[0190] As a further example, UE-B may be enabled to downgrade the avatar session to an audio or video session during the session. This may be achieved by, for example, using the RE-INVITE / UPDATE SIP signalling mechanism with “removing Avatar” signalled in the m-line in the SDP. The IMS network will remove the avatar towards the UE-B in response to this signalling. The IMS network may downgrade the avatar call to an AV call, or an audio call, or a video call.

[0191] As a further example, UE-B may be enabled to switch the avatar during the session. This may be performed by, for example, using Re-INVITE / UPDATE signalling mechanisms. Changing the avatar may also result in a change of audio language or voice used in the session.

[0192] Referring to FIG. 7, a procedure in shown in which a terminating party selects at least one avatar to represent a calling party during an IMS avatar call from multiple avatars preferred by the calling party. In more detail, the calling party may indicate the calling party’s preferred avatars to an IMS network, which provides identifiers of the preferred avatars to the terminating party. These preferred avatars correspond to the multiple avatars. The at least one avatar selected by the terminating party is provided to the IMS network and / or calling party. The IMS network of FIG. 7 is configured to generate a video stream and / or to modify an existing video stream to represent a videostream provided from the calling party to the terminating party during an avatar call. It is understood that where similar language to FIG. 4 is used in FIG. 7, the description provided above in respect of FIG. 4 may be used to understand FIG. 7.

[0193] FIG. 7 illustrates signalling that may be performed in an example in which an originating UE performs avatar rendering (e.g., using SIP and / or SDP signalling).

[0194] FIG. 7 illustrates signalling that may be performed between a IIE-A 701 , an CSCF 702, a DAC 703, an IMS-AS 704, an MF / MRF 705, an XR-AS 706, a terminating IMS core 707, and UE-B 708.

[0195] During 7001 , IIE-A 701 determines to request a network avatar rendering based on its status.

[0196] During 7002, IIE-A 701 signals IMS AS 704 via the CSCF 702. This signalling may comprise an invitation to initiate an audio-video call with UE-B 708. This signalling may comprise a plurality of avatar identifiers (e.g., two of more avatar identifiers). In the present example, the provided avatar identifiers are A1 and A2. The avatars may be stored in a local cache of UE-A and / or provided to IMS AS 704 via previous signalling (e.g., by the DAC 703 and / or XR AS 706). The avatar identifiers may be comprised in, for example, an m-line in the SDP.

[0197] Optionally, the signalling of 7002 may comprise respective information for at least one identifier avatar. For example, the signalling may comprise, for a specific avatar identifier, an indication of a related representation format, and / or resolution, and / or a human readable description of the avatar (including its language).

[0198] During 7003, the IMS AS 704 signals the XR AS. This signalling may comprise information relating to the provided avatar identifiers. Stated differently, the IMS AS 704 may read the avatar identifiers’ (A1 and A2) information and request the XR Application Server to retrieve the related representations of those identified avatars from the DAC.

[0199] During 7004, the IMS AS 704 signals the UE-B 708 via the terminating IMS core 707. This signalling may comprise an invitation to an audio-video call. This signalling may comprise an indication of avatar identifiers A1 and A2. The signalling of 7004 may be performed using a SIP / SDP signalling, (e.g., SDP content transmitted inside SIP signalling messages). The signalling of 7004 may comprise an indicationindicating an explicit request for IIE-B to send back a single choice amongst the proposed avatars.

[0200] When the XR-AS does not comprise the information associated with the XR for implementing both A1 and A2 (e.g., because this information is accessible in a local cache of the XR-AS), the XR-AS proceeds to 7005. Otherwise, the mechanism proceeds to 7007.

[0201] During 7005, the XR-AS 706 signals the DAC 703. This signalling may comprise a request to receive information for implementing A1 and A2. This signalling may comprise an identifier of IIE-A. It is understood that 7005 may be performed at any time between 7003 and 7008 (e.g., after IIE-B 708 has selected a specific avatar. In this case, only avatar information for the avatar selected by IIE-B may be requested, which may help save system signalling resources).

[0202] During 7006, the DAC 703 signals the requested information of 7005 to the XR- AS 506. This signalling may be performed based on the DAC 703 verifying that IIE-A is authorized to use avatars A1 and A2.

[0203] During 7007, IIE-B 708 signals IMS-AS 704. This signalling may comprise an acceptance of the signalling of 7004. This signalling may indicate which avatar has been selected by IIE-B 704 for use in representing IIE-A 701 during the requested A / V call.

[0204] The selection of the avatar made by IIE-B may optionally be based on a displayed representation (either downloaded or previously cached) at the IIE-B to the user of IIE-B. The user of IIE-B may thus be presented with an option to select one [or more, if allowed] avatar(s), reject others, and / or terminate the session.

[0205] For example, if avatar-A1 is presented with description “English language” and Avatar-A2 is presented with description “German language”, IIE-B can select Avatar- A2, and subsequently send an indication to the IMS-AS that Avatar-A2 is selected.

[0206] As another example, IIE-B may select an avatar based on the format / resolution associated with each avatar such that the selected avatar is in line with UE-B’s local computing and rendering capabilities. IIE-B sending back its choice may assist entities in the IMS network (e.g., MF / MRF) in adapting the media sent to IIE-B.

[0207] During 7008, the IMS-AS 704 signals IIE-A 701 . This signalling may comprise an indication that the A-V session is being established. This signalling may comprise an indication that avatar A2 has been selected by IIE-B. This selection may be comprised in an m-line (media description) of the SDP signalling.

[0208] During 7009, IIE-A 701 signals the XR-AS 706. This signalling may comprise an indication that a specific session is to be rendered using a specified avatar. Therefore, the signalling may comprise an identifier of a specific session, and at least one specific avatar identifier (e.g., A2). The signalling may comprise an identifier of UE-A 701.

[0209] During 7010, the XR AS 706 determines that avatar rendering should be performed based on the signalling of 7009.

[0210] During 7011 , the XR AS 506 signals IIE-A 701 . This signalling may comprise avatar data (e.g., avatar data, such as avatar media and / or avatar metadata, for avatar A2) to be used by IIE-A 701 in rendering media such that calling party IIE-A is represented by the identifier avatar A2 in the video data subsequently signalled by UE- A.

[0211] It is understood that when the IMS AS does not receive an indication of at least one selected avatar ID(s) from IIE-B during 7007, then IIE-A can optionally insert the initial set of avatar ID(s) signalled during 7002 into the signalling of 7009. Further, when the XR AS does not receive avatar ID(s) from IIE-A during 7009, then the XR- AS can select at least one avatar identifier to be used by IIE-A amongst the one(s) received during 7003.

[0212] During 7012, IIE-A 701 replaces a face / body comprised in a video stream to be transmitted by IIE-A with the selected avatar metadata signalled during 7008. This may be performed using, for example, face detection and / or gesture recognition mechanism employed by IIE-A. The video stream formed by IIE-A 701 by inserting at least one avatar is labelled herein as a modified video stream.

[0213] During 7013, the modified video stream is signalled from IIE-A 701 to IIE-B 708.

[0214] During 7014, IIE-B 708 signals IIE-A 701. This signalling may comprise an indication and / or an identifier of an avatar to be used for modifying and / or generating a video representing IIE-B 708 in the avatar call.

[0215] In this example of FIG. 7, Avatar ID A1 and A2 are exchanged with the IMS network for getting the avatar rmetadata. During 7003, the IMS AS reads the avatar ID A1 and A2 information and requests the XR Application Server to retrieve the related avatar metadata from DAC (7005 to 7006). Alternatively, this step can be performed after IIE-B provides an indication of at least one selected avatar during 7007. In such a case, only avatar metadata and / or avatar media related to the selected avatar(s) is sent to the XR application server.

[0216] When IIE-A and IIE-B have agreed during session setup or update that IIE-B uses plain video media, IIE-B provides plain audio / video media during 7014. This plain A / V data may be signalled using, for example, RTP.

[0217] It is understood that although the example of FIG. 7 is framed in the context of IIE-A, that IIE-B may instead be configured to perform the rendering of the avatar of IIE-A within the video stream.

[0218] For example, during 7002, UE-A’s SDP offer indicates that the avatar media will only include gesture information and / or that rendering of UE-A’s avatar within a video stream is to be performed by UE-B. 7009 and 7011 will then be performed between the XR-AS and UE-B instead of between XR-AS and UE-A. Further, during 7013, UE-A would send audio and “gesture media” to UE-B (e.g., over RTP). This audio and gesture media may be rendered into a displayable video stream by UE-B using the avatar representation(s) A1 and / or A2 autonomously selected by UE-B. 7014 is unchanged and relates to UE-B’s media.

[0219] It is understood that the signalling of FIG. 7 may be further modified in any of a plurality of different ways.

[0220] For example, UE-B may initiate the avatar media obtaining during 7002 by providing potential UE-B avatar identifiers to the IMS AS 704 (e.g., B1 and B2). These may be provided to UE-A for selection between.

[0221] As a further example, UE-B may be enabled to downgrade the avatar session to an audio session during the session. This may be achieved by, for example, usingthe RE-INVITE / UPDATE SIP signalling mechanism with “removing Avatar” signalled in the m-line (media description) in the SDP. The IMS network will remove the avatar towards the IIE-B in response to this signalling. Based on this removal, the avatar call will be converted into an audio-only call (e.g., there will be no video component).

[0222] As a further example, IIE-B may be enabled to switch the avatar during the session. This may be performed by, for example, using Re-INVITE / UPDATE signalling mechanisms. Changing the avatar may also result in a change of audio language or voice used in the session.

[0223] Features of the above examples of illustrated below with reference to FIGS. 8 to 10. It is therefore understood that features mentioned below may find functional correspondence to features mentioned above, and that the above-described examples provide an illustration of additional features that may supplement the following described procedures.

[0224] FIG. 8 illustrates operations that may be performed by a communication device. The communication device may perform at least one feature described above in relation to IIE-B.

[0225] During 801 , the communication device receives, in a Session Initiation Protocol, SIP, request message from an application server comprised in an Internet Protocol Multimedia Subsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream.

[0226] During 802, the communication device selects a subset of the plurality of avatar identifiers. The subset may comprise only a single avatar identifier of the plurality of avatar identifiers. The subset may comprise more than one avatar identifier of the plurality of avatar identifiers. The subset may be selected, at least in part, based on receipt of a user input that selects one or more avatar identifier from the plurality of avatar identifiers.

[0227] During 803, the communication device signals an indication of the subset to the application server in a SIP response.

[0228] The communication device may download the selected subset of avatars via an internet protocol multimedia subsystem data channel connection or other Hypertext Transfer Protocol, HTTP, based mechanism.

[0229] The communication device may receive a video stream from the another communication device, the video stream comprising an avatar representation of a user of the another communication device that corresponds to an avatar identifier comprised in the subset. Stated differently, the communication device may receive a video stream that comprises a rendering of an avatar, said avatar corresponding to an avatar of the selected subset.

[0230] The communication device may determine to downgrade an avatar call to a call comprising an audio and / or video stream that does not comprise an avatar. The communication device may signal an indication of said determination to downgrade to an IMS network entity, and subsequently receive a call associated to a same session as the avatar using an audio stream and / or a video stream that does not comprise an avatar. The IMS network entity may comprise the IMS application server. The IMS network entity may comprise an MF and / or MRF. The IMS network entity may comprise an extended Reality application server.

[0231] The communication device may select at least one avatar to represent a user within a video stream originated from the communication device. For example, the communication device may determine at least one avatar identifier that identifies an avatar to be used for representing a user of the communication device in a video stream transmitted by the communication device, and signal the at least one avatar identifier to an Internet Protocol Multimedia Subsystem, IMS, application server.

[0232] The communication device may select the subset by obtaining metadata that defines at least one property of avatar identified by said plurality of avatar identifiers, and select the subset using the obtained metadata. The obtained metadata may comprise information associating a specified avatar identifier to at least one of: a language, voice, or video.

[0233] The application server may comprise an extended Reality application server.

[0234] The SIP request may comprise a session initiation protocol invite message or a session initiation protocol registration message.

[0235] The SIP response may comprise a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

[0236] FIG. 9 illustrates operations that may be performed by an extended Reality application server.

[0237] During 901 , the extended Reality application server receives, via a hypertext transfer protocol, HTTP, or any other application layer protocol, at least one avatar identifier that identifies at least one avatar to be used to represent a user of another communication device within an avatar call received by a communication device via an internet protocol multimedia subsystem, IMS, network or via an application layer protocol.

[0238] During 902, the extended Reality application server causes another apparatus to render said at least one avatar within the avatar call.

[0239] The rendering of the at least one avatar within the avatar call (e.g., within a video stream of an avatar call) may be performed in any of a plurality of different ways.

[0240] For example, the extended Reality application server may signal a media function to trigger the media function to render said at least one avatar within the avatar call. The extended Reality application server may signal the another communication device to trigger the another communication device to render said at least one avatar within the avatar call. The extended Reality application server may signal the communication device to trigger the communication device to render said at least one avatar within the avatar call.

[0241] The extended Reality application server may obtain avatar data and / or metadata about the at least one avatar identifier from a DAC.

[0242] For example, the extended Reality application server may receive said at least one avatar identifier, and retrieve avatar data and metadata associated with the at least one avatar identifier from a digital access container function by signalling an identifier of the another communication device and the at least one avatar identifier to the digital access container function.

[0243] FIG. 10 illustrates operations that may be performed by an internet protocol multimedia subsystem, IMS, application server.

[0244] During 1001 , the IMS AS signals, to a communication device using a session initiation protocol, SIP, request, a plurality of avatar identifiers that identifies at a plurality of avatars that can be used to represent a user of another communication device within a avatar call received by the communication device.

[0245] During 1002, the IMS AS receives, from the communication device using a SIP response, an indication of a selected subset of said plurality of avatar identifiers.

[0246] During 1003, the IMS AS causes the selected subset to be provided to the another communication device and / or an extended Reality application server.

[0247] The IMS AS may cause another apparatus to render at least one avatar of said selected subset within the avatar call. For example, the IMS application server may signal a media function to trigger the media function to render said at least one avatar within the avatar call. The IMS AS may signal the another communication device to trigger the another communication device to render said at least one avatar within the avatar call. The IMS application server may signal the communication device to trigger the communication device to render said at least one avatar within the avatar call.

[0248] The SIP request may comprise a session initiation protocol invite message or a session initiation protocol registration message.

[0249] The SIP response may comprise a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

[0250] It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and / or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

[0251] It is noted that whilst some embodiments have been described in relation to 5G networks, similar principles can be applied in relation to other networks and communication systems. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

[0252] It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0253] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0254] In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0255] As used in this application, the term “circuitry” may refer to one or more or all of the following:(a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):1. (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and2. (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions); and3. (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.”

[0256] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0257] The embodiments of this disclosure may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

[0258] Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

[0259] The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal ) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0260] The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and maycomprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

[0261] Embodiments of the disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0262] The scope of protection sought for various embodiments of the disclosure is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the disclosure.

[0263] The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this disclosure will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

CLAIMS1. A communication device comprising: means for receiving, in a Session Initiation Protocol, SIP, request message from an application server comprised in an Internet Protocol Multimedia Subsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream; means for selecting a subset of the plurality of avatar identifiers; and means for signalling an indication of the subset to the application server in a SIP response or in an application layer protocol.

2. The communication device as claimed in claim 1 , further comprising: means for downloading the selected subset of avatars via an internet protocol multimedia subsystem data channel connection or other Hypertext Transfer Protocol, HTTP, based mechanism.

3. The communication device as claimed in claim 1 , further comprising: means for receiving a video stream from the another communication device, the video stream comprising an avatar representation of a user of the another communication device that corresponds to an avatar identifier comprised in the subset.

4. The communication device as claimed in claim 3, further comprising: means for determining to downgrade an avatar call to a call comprising an audio and / or video stream that does not comprise an avatar; means for signalling an indication of said determination to downgrade to an IMS network entity; and means for subsequently receiving a call associated to a same session as the avatar using an audio stream and / or a video stream that does not comprise an avatar.

5. The communication device as claimed in any of claims 1 to 4, further comprising: means for determining at least one avatar identifier that identifies an avatar to be used for representing a user of the communication device in a video stream transmitted by the communication device; and means for signalling the at least one avatar identifier to the Internet Protocol Multimedia Subsystem, IMS, application server.

6. The communication device as claimed in any of claims 1 to 5, wherein the means for selecting the subset comprises means for: means for obtaining metadata that defines at least one property of avatar identified by said plurality of avatar identifiers; and means for selecting the subset using the obtained metadata.

7. The communication device as claimed in claim 6, wherein the metadata associates an avatar identifier to at least one of: a language, voice, or video.

8. The communication device as claimed in any of claims 1 to 7, wherein the application server comprises an extended Reality application server.

9. The communication device as claimed in any of claims 1 to 8, wherein the SIP request comprises a session initiation protocol invite message or a session initiation protocol registration message.

10. The communication device as claimed in any of claims 1 to 9, wherein the SIP response comprises a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

11. An extended Reality application server comprising: means for receiving, via a hypertext transfer protocol, HTTP, or any other application layer protocol, at least one avatar identifier that identifies at least one avatar to be used to represent a user of another communication device within anavatar call received by a communication device via an internet protocol multimedia subsystem, IMS, network or via an application layer protocol; and means for causing another apparatus to render said at least one avatar within the avatar call.

12. The extended Reality application server as claimed in claim 11 , wherein the means for causing comprises at least one of: means for signalling a media function to trigger the media function to render said at least one avatar within the avatar call; or means for signalling the another communication device to trigger the another communication device to render said at least one avatar within the avatar call; or means for signalling the communication device to trigger the communication device to render said at least one avatar within the avatar call.

13. The extended Reality application server as claimed in any of claims 11 to 12, further comprising: means for receiving said at least one avatar identifier; and means for retrieving avatar data and metadata associated with the at least one avatar identifier from a digital access container function by signalling an identifier of the another communication device and the at least one avatar identifier to the digital access container function.

14. An internet protocol multimedia subsystem, IMS, application server comprising: means for signalling, to a communication device using a session initiation protocol, SIP, request, a plurality of avatar identifiers that identifies at a plurality of avatars that can be used to represent a user of another communication device within a avatar call received by the communication device; means for receiving, from the communication device using a SIP response, an indication of a selected subset of said plurality of avatar identifiers; andmeans for causing the selected subset to be provided to the another communication device and / or an extended Reality application server.

15. The IMS application server as claimed in claim 14, further comprising: means for causing another apparatus to render at least one avatar of said selected subset within the avatar call.

16. The IMS application server as claimed in any of claims 14 to 15, wherein the SIP request comprises a session initiation protocol invite message or a session initiation protocol registration message.

17. The IMS application server as claimed in any of claims 14 to 16, wherein the SIP response comprises a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

18. A method of a communication device, the method comprising: receiving, in a Session Initiation Protocol, SIP, request message from an application server comprised in an Internet Protocol Multimedia Subsystem, IMS, network, a plurality of avatar identifiers, each avatar identifier identifying a respective avatar that can be used to represent a user of another communication device during an audio-video stream; selecting a subset of the plurality of avatar identifiers; and signalling an indication of the subset to the application server in a SIP response.

19. The method as claimed in claim 18, further comprising: downloading the selected subset of avatars via an internet protocol multimedia subsystem data channel connection or other Hypertext Transfer Protocol, HTTP, based mechanism.

20. The method as claimed in claim 18, further comprising: receiving a video stream from the another communication device, the video stream comprising an avatar representation of a user of the another communication device that corresponds to an avatar identifier comprised in the subset.

21. The method as claimed in claim 20, further comprising: determining to downgrade an avatar call to a call comprising an audio and / or video stream that does not comprise an avatar; signalling an indication of said determination to downgrade to an IMS network entity; and subsequently receiving a call associated to a same session as the avatar using an audio stream and / or a video stream that does not comprise an avatar.

22. The method as claimed in any of claims 18 to 21 , further comprising: determining at least one avatar identifier that identifies an avatar to be used for representing a user of the communication device in a video stream transmitted by the communication device; and signalling the at least one avatar identifier to the Internet Protocol Multimedia Subsystem, IMS, application server.

23. The method as claimed in any of claims 18 to 22, wherein the selecting the subset comprises: obtaining metadata that defines at least one property of avatar identified by said plurality of avatar identifiers; and selecting the subset using the obtained metadata.

24. The method as claimed in claim 23, wherein the metadata associates an avatar identifier to at least one of: a language, voice, or video.

25. The method as claimed in any of claims 18 to 24, wherein the application server comprises an extended Reality application server.

26. The method as claimed in any of claims 18 to 25, wherein the SIP request comprises a session initiation protocol invite message or a session initiation protocol registration message.

27. The method as claimed in any of claims 18 to 26, wherein the SIP response comprises a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

28. A method of an extended Reality application server, the method comprising: receiving, via a hypertext transfer protocol, HTTP, or any other application layer protocol, at least one avatar identifier that identifies at least one avatar to be used to represent a user of another communication device within an avatar call received by a communication device via an internet protocol multimedia subsystem, IMS, network or via an application layer protocol; and causing another apparatus to render said at least one avatar within the avatar call.

29. The method as claimed in claim 28, wherein the causing comprises at least one of: signalling a media function to trigger the media function to render said at least one avatar within the avatar call; or signalling the another communication device to trigger the another communication device to render said at least one avatar within the avatar call; or signalling the communication device to trigger the communication device to render said at least one avatar within the avatar call.

30. The method as claimed in 28 or 29, further comprising: receiving said at least one avatar identifier; and retrieving avatar data and metadata associated with the at least one avatar identifier from a digital access container function by signalling anidentifier of the another communication device and the at least one avatar identifier to the digital access container function.

31. A method for an internet protocol multimedia subsystem, IMS, application server, the method comprising: signalling, to a communication device using a session initiation protocol, SIP, request, a plurality of avatar identifiers that identifies at a plurality of avatars that can be used to represent a user of another communication device within a avatar call received by the communication device; receiving, from the communication device using a SIP response, an indication of a selected subset of said plurality of avatar identifiers; and causing the selected subset to be provided to the another communication device and / or an extended Reality application server.

32. The method as claimed in claim 31 , further comprising: means for causing another apparatus to render at least one avatar of said selected subset within the avatar call.

33. The method as claimed in claim 31 or 32, wherein the SIP request comprises a session initiation protocol invite message or a session initiation protocol registration message.

34. The method as claimed in any of claims 31 to 33, wherein the SIP response comprises a session initiation protocol 200 OK message or a session initiation protocol provisional acknowledgement message.

35. A computer program comprising instructions, wherein when the computer program is executed by a communication device the communication device is caused to perform the method of any of claims 18 to 27.

36. A computer program comprising instructions, wherein when the computer program is executed by an extended Reality application server, the extended Reality application server is caused to perform the method of any of 28 to 30.

37. A computer program comprising instructions, wherein when the computer program is executed by an internet protocol multimedia subsystem, IMS, application server, IMS application server is caused to perform the method of any of claims 31 to 34.

38. A computer-readable medium comprising instructions which, when executed by at least one processor of a communication device, cause the communication device to perform the method of any of claims 18 to 27.

39. A computer-readable medium comprising instructions which, when executed by at least one processor of an extended Reality application server, cause the extended Reality application server to perform the method of any of 28 to 30.

40. A computer-readable medium comprising instructions which, when executed by at least one processor of an internet protocol multimedia subsystem, IMS, application server, cause the IMS application server to perform the method of any of claims 31 to 34.

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