EP1938550A1

EP1938550A1 - Signalling for establishing an h.324 videotelefony connection between a media gateway and a controller

Info

Publication number: EP1938550A1
Application number: EP06793344A
Authority: EP
Inventors: Andreas Trapp; Thomas Belling; Franz Kalleitner; Hans-Jürgen HANISCH; Norbert Seitter
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2005-10-21
Filing date: 2006-09-08
Publication date: 2008-07-02
Also published as: DE102005050588A1; US9614714B2; US20090116477A1; WO2007045526A1; CN101292495A; CN101292495B; DE102005050588B4

Abstract

The invention relates to a e and method for setting up a telecommunication connection, in particular a video telecommunication connection, which after being established, is carried out by means of a line-bound telecommunications network (CS) and an IP multimedia subsystem telecommunications network (IMS), wherein a media gateway control function device (MGCF) of said IP multimedia subsystem telecommunications network (IMS) comprises at least one Internet multimedia-media gateway device (IM-MGW). The inventive method consists in exposing an H.223 multiplex level usable for a telecommunication connection to an H.223 protocol negotiation, in carrying out an H.245 protocol negotiation for setting up the H.223 protocol negotiation connection for a telecommunication connection and in informing the media gateway control function device (MGCF) when the H.223 logic channels are open by means of a H.245 signalling, thereby enabling the Internet multimedia-media gateway device (IM-MGW) of the IP multimedia subsystem telecommunications network (IS) to carry out at least one of said three steps.

Description

"Signaling regarding the structure of H.324 video telephony between a media gateway and a controller"

The invention relates to methods and apparatus for call setup a telecommunications connection.

In addition to the so-called "Circuit Switched (CS) Domain" of a based on the 3rd Generation Partnership Project (3GPP) mobile network, the so-called "IP Multimedia Subsystem" (IMS) for voice and video telephony can be used, and a so-called Interworking of the services concerned, d. H. it is necessary to connect the services by means of a suitable conversion of the signaling used and the transport format of the data used, between the IMS and the CS domain. The IMS is used in addition to the 3GPP "Global System for Mobile Communications" (GSM) and "Universal Mobile Telecommunications System" (UMTS) access networks for other access networks, such as "Wireless Local Area Network" (WLAN) and "Digital Subscriber Line" ( DSL). Especially in these scenarios, it can first be expected that voice and video telephony will take place via the IMS. Video telephony can also be used in a public telephone network, i. a public switched telephone network (PSTN), whereby the same inband video telephony-specific protocols as in the 3GPP CS domain are generally used for transport and signaling, and the PSTN also requires interworking with the IMS.

So far, only an interworking between IMS and CS Domain or PSTN for voice telephony is described in the standard. The present invention relates to the corresponding interworking of video telephony. A need for this is foreseen, as both in the 3GPP CS domain and in IMS, here Especially for access networks such as WLAN or DSL, or emerging network access options (eg, Worldwide Interoperability for Microwave Access (WiMAX), video telephony gains in importance.

The interworking between IMS and a CS network, ie a PSTN or a 3GPP CS domain, is specified as of 3GPP Release 6 only for pure voice telephony in 3GPP TS 29.163.

According to TS 29.163 the interworking of the so-called

"Call-Control" signaling in the so-called "Media Gateway Control Function" (MGCF). The interworking of the user connection, ie the handover and repackaging as well as, if necessary, the transcoding of the user data, takes place in the so-called "Internet Multimedia - Media Gateway" (IM-MGW.) The MGCF controls the IM-MGW by means of the ITU software. T standardized H.248 protocol over the so-called "Mn" interface, as further described in 3GPP TS 29.332.

In the CS network, Bearer Independent Call Control (BICC) or

ISDN User Part (ISUP) used for call control signaling. In this case, if the call-control signaling is kept separate from the transport connections, this method is also referred to as "out-of-band" signaling. Subsequently, it is also possible within the transport connection exchange signaling messages, which are referred to as "in-band" signaling. In the case of ISUP, Time Division Multiplex (TDM) is used as transport in the CS network, and in the case of BICC, packet transport via Internet Protocol (IP) or asynchronous

Transfer Mode (ATM). The negotiation of whether pure voice telephony or video telephony is used can be used by ISUP during call-control signaling to set up the call using the so-called ISUP "UDI fallback" procedure. For BICC, this negotiation can be carried out using the service change and UDI fallback (SCUDIF) standardized in 3GPP TS 23.172, which also allows a change between voice telephony and video telephony during the call. "Both UDI fallback and SCUDIF benefit out-of -band signaling. In addition, it is possible for ISUP, such as BICC, not to use the procedures mentioned, and to try to set up a call only for video telephony, and in the event that video telephony is not supported, to abort the call setup. In contrast to the optional negotiation between voice and video, the negotiation of the voice and video codecs used for video telephony is carried out "in-band" after video telephony has already been selected and a corresponding transport connection ("bearer") has been set up for video telephony In the CS network, a so-called BS30 data connection with 64 kbyte / s bandwidth is used.This data connection uses the ITU-T standardized protocol suite H.324, whereby in the 3GPP CS domain the mobile-adapted variant H. After setting up the data connection, the configuration of the inband multimedia connection is negotiated via the H.245 protocol standardized by the ITU-T, in particular the video codec and voice codec used and the details of the respective codec configuration. Speech and video are multiplexed into the same transport connection using the H.223 protocol, for the 3GP P TS domain TS 26.110 further describes the use of the H.245 protocol suite, in particular the so-called H.324M configuration is selected.

The most important processes when building a 3G-324M connection are the following: 1. After the start of the ISUP or BICC call setup signaling, the reservation of the necessary resources which are required for the desired "bearer" takes place and, subsequently, the establishment of the transport connection.

2. Start of the "in-band" negotiation. First, negotiate which H.223 "Multiplexer Level" to use for this transport connection.

3. Detection of the conductive terminal which opens the multi-stream connection by means of H.245 negotiation, if necessary. This function is only necessary if there is a conflict in the context of opening a bi-directional logical channel (= logical channel). This feature is called Master or Slave Determination (MSD)

4. The so-called "Terminal Capability Set" H.245 messages are used to transmit the capabilities of the terminal transmitting the message.These messages are sent independently of both terminals.These described capabilities include the following information: Audio and video codec and their specific characteristics Functional scope of the multiplexer, in detail which adaptation layer is supported (eg "simple" or "nested" multiplexing) and its mobile-specific extensions.

5. Construction of "logical" channels per media stream by means of

H.245 signaling. From this point in time, either with MSD or without, the terminal or the IM-MGW is prepared to open "logical channels" in order to enable the exchange of voice and / or video payload data. When creating a bidirectional "logical channel" defines the channel number and the final "media capabilities" to be used.

6. Definition of multiplex properties using H.245.

7. Start transmission of video, audio / voice or data

In the IMS, the negotiation for video telephony is carried out "out-of-band" with the aid of the so-called "Session Description Protocol" (SDP), IETF RFC 2327, which uses the so-called "Session Initiation Protocol" (SIP), IETF RFC 3261, is transported. Here, the negotiation of whether voice telephony or video telephony is used is connected to the negotiation of the codecs used, and occurs before or during the structure of the bearer. The so-called SDP "offer-answer" mechanism according to RFC 3264 is used, whereby the provider sends a list of supported codecs in the SDP "offer" message. After receiving this message, the respondent sends an SDP "Answer" message that contains the codecs from the list that he also wants to support and use.The respondent is not allowed to specify codecs that are not in the SDP "offer" list were. In contrast to the CS domain, voice and video use two separate transport links ("bearers"), each of which uses the so-called "Real Time Transport Protocol" (RTP), IETF RFC 3550. For the 3GPP IMS over the General Packet Radio Service (GPRS) access network, 3GPP TS 26.235 describes the codecs to be used for video telephony.

In the following, the protocols and codecs used for video telephony on the CS Domain side and on the IMS side are summarized again:

CS network (especially 3GPP CS domain): Call Control BICC or ISUP.

Negotiation between pure voice telephony and video telephony can be done for ISUP by means of "UDI fallback" and for BICC by means of "SCUDIF".

Multimedia Protocol suite: H.324M (H.324 Annex C): Codec Negotiation: H.245 inband Negotiation over the established CS bearer with 64 kbps video codec: Required support of H.263

H.261 optional

MP4V-ES (simple video profile level 0) optional

Voice Codec: Support of NB-AMR prescribed WB-AMR optional

G.723.1 recommended

Transport: multiplexing voice and video into a bearer according to H.223 Annex A + B

IMS (Codecs for GPRS access network): Call Control: SIP

Includes both negotiation between pure voice telephony and video calling, as well as codec negotiation. Codec Negotiation: Before setting up the bearer out-of-band using SDP, which is transported in SIP. Video codec: support required by H.263,

H.264 optional, MP4V-ES (simple video profile level 0) optional

Voice Codec: Compulsory NB-AMR and WB-AMR support. Transport: Two separate RTP bearers for voice and video using different so-called RTP payload formats: Language: Nb-AMR + WB-AMR: IETF RFC 3267 Video: H.263: IETF RFC 2429

H.264 (AVC): IETF RFC 3984 MPEG-4: IETF RFC 3016

Synchronization of parallel RTP media streams takes place by means of so-called RTP timestamps, which are provided by the Real Time Control Protocol.

(RTCP, see IETF RFC 3550).

In addition to or instead of the codecs specified here, other codecs can also be supported by the terminals, in particular if the CS terminals are located in the PSTN or the IMS terminals do not use GPRS as the access network.

It is desirable to use the same video codec and, if possible, the same speech codec on the CS side and in the IMS in order to avoid transcoding. Transcoding of the video codec in particular, but to a lesser extent of the speech codec, would require significant processing power and resources in the IM-MGW. In addition, the transmission was delayed and the quality of the image or the language deteriorated. If the required bandwidth for the codecs on the CS domain side and the IMS side is different, additional bandwidth was used on one side without improving image or voice quality.

For this it is necessary that the MGCF and the IM-MGW exchange appropriate information regarding the negotiation of the Speech and video codecs using H.245 and SIP / SDP and regarding the structure of the transport connection using H.223.

A procedure for exchange of information relating to the negotiation of voice and video codecs

H.245 and the construction of the transport connection by means of H.223 between MGCF and IM-MGW is the subject of the present invention. This largely avoids transcoding video calls. The MGCF and the IM-MGW connect a CS network, ie a PSTN or a 3GPP CS domain, as well as an IP network that SIP and SDP use to negotiate the codecs, eg the IMS.

An object of the invention is as efficiently as possible to support the establishment of a suitable telecommunications connection via a circuit-switched network and an IMS network and to avoid video telephony transcoding as far as possible. The object is solved by the independent claims. Advantageous embodiments are specified in the subclaims.

According to the invention, the so-called "H.245 client", ie the functional unit terminating the H.245 protocol, is located in the IM-MGW The H.245 client exchanges information regarding the selection of the codecs and the sequence of the call setup with the functional components in the MGCF responsible for the so-called "call control", preferably with the functional component or components that are responsible for handling the SIP and the SDP on the IMS side. For this purpose, the protocol of the "Mn" interface is extended appropriately. The gist of the invention is the following:

For example, if the MGCF recognizes or suspects call signaling on the CS side according to the H.324, the MGCF instructs the IM-MGW:

• Perform the H.223 negotiation of the so-called "multiplex leech" on its own, and

• To perform the H.245 negotiation necessary for the establishment of H.324 video telephony, and • To inform the MGCF as soon as logical H.223 channels are opened by means of H.245, and the IM-MGW executes the corresponding instructions.

The MGCF preferably configures the IM-MGW accordingly by means of so-called H.248 "Add" or "Modify" messages, for example if it sets up the so-called "termination" responsible for the handling of the multiplexed H.223 protocol MGCF included in these messages one or more H.248 "signals" to be re-standardized, which print out that the H.223 and / or H.245 negotiation should be performed.

In order to request a notification about the construction of logical H.223 channels, the MGCF preferably uses a so-called H.248 "Event" to be re-standardized, which preferably inserts the MGCF into the same H.248 message H.223 channel is opened by means of H.245 signaling, the IM-MGW uses according to the invention a so-called H.248 "Notify" message, in which it specifies the newly defined "Event".

It is advantageous if the IM-MGW indicates in the notification about the opening of a logical H.223 channel the selected codec as well as the so-called "logical channel number", preferably as a parameter of the event used in the notification. The MGCF provides this information in accordance with the invention to configure the IM MGW to pass through the media stream between the CS network side and the IMS side. The MGCF indicates for both sides, which codecs were chosen. On the side of the CS network, according to the existing H.248 standard, the specification "logical channel number" is required If the same codec in the same configuration has been selected on both sides, the IM-MGW does not need to use a transcoder.

It is advantageous if the IM-MGW also notifies the MGCF when the H.223 Negotiation of the Multiplex Level "has ended or if this negotiation has failed.The MGCF can determine the absence of the notification or with the help of an error message that the CS-side transport connection is not or not yet used for video telephony and respond to it in the call control signaling, for example by reconfiguring the call to another service such as voice telephony or terminate the connection.

In order to request a notification of the result of the multiplex level H.223 negotiation, the MGCF preferably uses a so-called H.248 "event" which is to be newly standardized, which the MGCF preferably also includes in the H.248 message for starting the multiplexing H.223 negotiation inserts. If, in the following, the negotiation is ended, the IM-MGW uses according to the invention a so-called H.248 "Notify" message, in which it specifies the newly defined "event".

In the case of a call setup on the part of the CS network in the direction of the IMS, it may happen that the connection is forwarded by the IMS to another MGCF. In this In this case, it is advantageous for the MGCF to configure the IM-MGW in such a way that it transparently forwards the BS30 data service, for example using the so-called "Clearmode" codec, IETF RFC 4040. The MGCF acts by means of the SIP exchanged with the other MGCF In one embodiment, the MGCF first configures the IM MGW only for the BS30 service, and does not yet power off the data connection, as soon as the MGCF receives signaling from the IMS side regarding the selected codecs the MGCF detects if it is video calling and in this case configures the IM-MGW to start in-band H.223 negotiation, however, if a transparent transport is selected, no reconfiguration of the IM-MGW is required.

The IM-MGW preferably carries out the H.245 procedures for the so-called "master slave determination" independently.

In a simple embodiment, it sends and receives the

IM-MGW also includes the so-called H.245 "Terminal-Capability Set" messages, which contain information about supported audio and video codecs and their specific properties as well as about the functional scope of the multiplexer (eg which adaptation layer) The supported nesting depth of the multiplexing, ie so-called "simple" or "nested" multiplexing and information about mobile-specific extensions, is given. The IM-MGW specifies preconfigured values in the sent "Terminal-Capability Set" message that reflect their own abilities. In a simpler embodiment, the transmission of codecs between the MGCF and the IM-MGW is omitted, and MGCF and IM-MGW are configured to handle the same voice-and-video codecs in the SIP / SDP out-of-band negotiation on the part of the IMS or in the H.245 in-band negotiation on the part of the CS Networks. This embodiment may be sufficient because, according to 3GPP TS 26.235 and TS 26.110, the same voice and video codecs in the CS domain and the IMS must be supported.

In an alternative embodiment, however, the IM-MGW exchanges information regarding the supported codecs with the MGCF:

In an advantageous embodiment, the MGCF of the IM-MGW communicates which codecs the IM-MGW should specify in the transmitted "Terminal-Capability Set" message, and in each case also communicates the details of the codec configuration For this purpose, the MGCF also considers in the selection which codecs are supported at the IM-MGW The MGCF has either configured knowledge about these capabilities, or it queries these capabilities with a so-called H.248 "AuditCapabilities" message at the IM-MGW. In an alternative embodiment, the IM-MGW removes those of the codecs received from the MGCF which it does not support itself before sending the codecs in a "Terminal-Capability Set" message.The MGCF preferably outputs the codecs in an "Add" or "Modify" message as a parameter of the "Signal" instructing the IM-MGW to perform the H.245 transaction. The MGCF can already specify the codecs if it instructs the IM-MGW to start the H.245 negotiation, or in a separate H.248 message at a later time, for example if it receives corresponding information in a SIP message. If the MGCF does not want to specify the codecs until later, it preferably instructs the MGCF to wait for this message. To do this, the MGCF preferably uses a special parameter of the "signal" instructing the IM-MGW to perform the H.245 negotiation.If the MGCF has not sent codecs and the MGCF has not requested to wait, the IM-MGW sends a " Terminal-Capability Set "message with preconfigured values

In an advantageous embodiment, the IM-MGW of the MGCF also informs which codecs they have in a "terminal

However, the MGCF does not notify the MGCF of received codecs which it does not support, but the MGCF preferably passes this information by means of SIP / SDP to the terminal on the side of IMS.

In order to request notification of the received codecs, the MGCF preferably uses a so-called H.248 "event" to be standardized, which preferably inserts the MGCF into the same H.248 message in which it instructs the IM-MGW According to the invention, when the IM-MGW receives message in the following "Terminal-Capability Set" message, the IM-MGW uses according to the invention a so-called H.248 "Notify" message in which it receives the newly defined "H.245" message. Event "and specifies the codecs as parameters of this event.

In one embodiment, after replacing the H.245 "Terminal-Capability Set", the IM-MGW opens messages and completes the H.245 "Master Slave Determination" independently logical H.223 channels, if it is responsible for the output of the Master Slave Determination, whereby the IM-MGW selects suitable codecs from the intersection of the codecs transmitted in the "Terminal-Capability Set" messages , preferably each a voice codec and a video codec, and then opens the channels by means of so-called H.245 "Open Logical Channel" messages As described above, the IM-MGW informs the MGCF of the opening of the channels.

In an alternative embodiment, the MGCF instructs the IM-MGW to set up the logical channels for certain codecs, preferably by specifying the codecs as special parameters of a suitable signal to be re-standardized within a H.248 "Modify" message If it wants to use such a signal, it preferably instructs the MGCF to wait for that message, for which the MGCF preferably uses a special parameter of the "signal" instructing the IM-MGW to perform the H.245 negotiation.

In a preferred embodiment, the IM-MGW also informs the MGCF when in-band negotiation has failed by means of H.245, for example, because no matching capabilities were found that allowed the transmission of video telephony. If the inband negotiation was unsuccessful, the MGCF can either reduce the call or initiate a fallback to voice, whereby the MGCF on the CS side can use the so-called "Service Change and UDI Fallback" (SCUDIF), 3GPP TS 23.172 , and also on the IMS side of a SIP / SDP codec renegotiation using a SIP re-INVITe message. The MGCF may instruct the IM-MGW either to initiate the connection the first time it configures so-called "terminations" or after notification of a successful in-band negotiation, as soon as the MGCF instructs the IMS-MGW to toggle the video call the IMS-MGW determines the settings for the video codec and the speech codec to decide whether transcoding is required for the video signal and / or the voice signal Further features and advantages of the invention will be apparent from the claims and the following description of an embodiment with reference to the drawing, in which: Fig. 1 shows a network configuration,

Fig. 2 is a block diagram of the key components, Fig. 3 shows the principle of interworking to an embodiment and

4 shows the context for a video call.

Figure 1 shows a typical network configuration. The network configuration required for a mobile terminal MS1 connected to the 3GPP CS domain to communicate with a mobile terminal MS2 connected to the IMS is illustrated. The CS domain is connected to the IMS by means of a "Media Gateway Control Function" (MGCF) and an IMS Media Gateway (IM-MGW) .The MGCF controls the IM-MGW by means of the ITU-T standardized H. 248 protocol via the so-called "Mn" interface. On the CS domain side, there are so-called "Mobile Switching Center" (MSC) servers in the core network, which communicate with each other and with the MGCF via BICC signaling.They monitor CS MGWs, the CS MGWs are above each other and with the IMS MGW connected to the so-called "Nb" interface. For video telephony, the so-called "BS30" data transport service ("bearer service") is used. MSl is by means of such a radio access network, such as a UTRAN, connect to an MSC server of a CS MGW. From the side of the IMS, the MGCF communicates with the help of the SIP call control protocol with so-called "call session control functions" (CSCF), the signaling via the Gatewy GPRS support node "(GGSN) and a radio access network, for example a UTRAN, to the mobile Hand over the MS2 device. Data is transported by the IMS Media Gateway via the Mb interface to the GGSN, which also passes it on to the MS via the radio access network.

Figure 2 shows a block diagram of the key components. Functional key components are shown in MGCF and IM-MGW. According to the invention, the so-called "H.245 client", ie the functional unit which terminates the H.245 protocol, is located in the IM-MGW and exchanges information concerning the selection of the codecs by means of the H.248 protocol via the "Mn" interfaces and the flow of call setup with the functional components in the MGCF responsible for the so-called "call control", preferably with the functional component (s) responsible for handling the SIP and the SDP on the IMS side According to the invention, H.245 messages received from the CS side within the H.223 protocol are forwarded from the H.223 multiplexer to the "H.245 client". According to the invention, the H.245 client also exchanges information regarding the H.223 protocol with the H.223 multiplexer / demultiplexer. In the IM-MGW, so-called "media streams" for audio and video are treated separately Depending on the selected on IMS side and CS side audio and video codecs and the details of their transport format in these networks can optionally a transparent handing the data, a so-called "re-framing", ie a simple change of the transport format tes, or a complete conversion of the data between different codecs by means of a so-called transcoder be required. The present invention aims to largely avoid transcoding, especially for video codecs.

FIG. 3 (principle of interworking) illustrates the principle of interworking between the H.245 signaling and on the CS side and the H.248 signaling between MGCF and IM-MGW with the aid of the signaling process.

The signaling steps are as follows:

1. The MGCF decides to set up an H.324 connection for video telephony on the CS side. First, the MGCF configures the physical so-called "termination" on the side of the CS network For packet transport, the MGCF generates a new termination in a new so-called H.248 "context" with the help of an H.248 "Add" command Instead, the MGCF can shift an existing termination, which represents a fixed time slot in a physical line, into a new context, which is assigned a so-called H.248 "stream".

2. The IM-MGW sets up the termination accordingly and returns the identifiers of the Tl for the termination and Cl for the context.

3. The CS-side transport connection is established.

4. The MGCF establishes according to existing H.248.1 and H.248.20 standard a special logical H.248 termination for describing the multiplexing in the same context Cl and expresses by the so-called "mux" parameter that the multiplexing in Termination Tl is written and done according to the H.223 standard, which describes the logical channel of the H.223 protocol used for H.245 signaling is to be assigned by means of its own "streams" of the so-called "logical channel number" (LCN) with a value of 0. According to the invention, the MGCF instructs the IM-MGW to begin the H.223 negotiation of the so-called "multiplexing level", preferably by means of a new so-called H.248 "signal", which is here called "H223negotiation" MGCF then instructs the IM-MGW to begin the H.245 negotiation, preferably by means of a new so-called H.248 "signal", here called "H245Negotiation." In one variant of the invention, "H223Negotiation" and "H245Negotiation" are used. According to the invention, the MGCF preferably also instructs the IM-MGW to send a message to the MGCF as soon as the H.223 negotiation of the so-called "multiplexing level" is completed, preferably by means of a new so-called H. 248 "events", which is here called "H223Establishment". According to the invention, the MGCF also instructs the IM-MGW to send a message with codecs supported on the CS side to the MGCF as soon as the IM-MGW receives an H.245 "Terminal Capability Set" message, in which case the MGCF preferably uses a new one According to the invention, the MGCF also instructs the IM-MGW to send a message to the MGCF with the selected codec and the associated H.245 "logical channel number" as soon as it is called "H.245" H.245 is used to open a logical H.223 "channel." The MGCF preferably uses a new H.248 "e-vent", which is called "H245Channel" here.

5. The IM-MGW sets up the new termination accordingly and returns the identifier T2.

6. The IM-MGW establishes the H.223 connection while negotiating the multiplexing level, in example 2. 7. According to the invention, the IM-MGW notifies the MGCF that the negotiation of the H.223 multiplexing level has been completed. Preferably, the IM-MGW uses a so-called H.248 "Notify" message to notify the MGCF with the new event "H223 Establishment.

The MGCF can use the information obtained to determine whether an inband H.245 negotiation is possible at the given time, which is advantageous because, for example, so-called "early media" before the completion of the call setup by the call control signaling on the CS If no H.223 signaling is received over a long period of time, the MGCF may also detect the failure to expect video calling by mistake.

8. The MGCF confirms receipt of the "Notify" message.

9. The IM-MGW receives a so-called "Terminal Capability Set" H.245 message, which can be combined with a so-called "Master-Slave Determination" H.245 message. The "Terminal Capability Set" H.245 message contains under

Other information about the voice and video codecs supported by the terminal on the CS network side and the details of their configuration.

10. According to the invention, the IM-MGW passes on the information obtained via the codecs. The IM-MGW preferably uses a so-called H.248 "Notify" message with the new event "H245Capabilities", which contains suitable parameters for specifying the codecs, for example as SDP or in the form of the so-called H.248 "SDP equivalents". In an advantageous variant of the invention, the IM-MGW deletes its unsupported codecs before it forwards the information to the MGCF.

11. The MGCF confirms receipt of the "Notify" message. 12. The IM-MGW confirms the "Terminal Capability Set" H.245 message and the "Master-Slave Determination" H.245 message.

13. The MGCF instructs the IM-MGW to offer certain codecs in the H.245 negotiation, for example because the MGCF has received corresponding information within SIP / SDP messages on the IMS side. It is advantageous if the MGCF also takes into account the codecs supported by the IM-MGW. The MGCF either has configured knowledge of these capabilities, or polls those capabilities using a so-called H.248 "AuditCapabilities" message at the IM-MGW In an advantageous variant of the invention, the MGCF considers the codecs supported by the IM-MGW not itself, but all applicable codecs to the IM-MGW.The IM-MGW then deletes even unsupported codecs before it passes the information in H.245 signaling.

Preferably, the MGCF uses the new so-called H.248 "sig- nal" "H245Negotiation" within an H.248 "Modify" digest, and specifies the codecs as suitable parameters of the "sig- nal", for example as SDP or encoded in the form of the so-called H.248 "SDP equivalents".

14. The IM-MGW sends out a "Terminal Capability Set" H.245 message, in which you provide information on capabilities supported on the IM-MGW, for example regarding H.223 protocol options, as reported by the MGCF in message 13 In this example, the IM-MGW combines this information with a "Master-Slave Determination" H.245 message.

15. The IM-MGW sends a confirmation of the H.248 "Modify" message. 16. The IM-MGW receives a confirmation of the "Terminal Capability Set" H.245 message and the "Master-Slave Determination" H.245 message.

17. The MGCF selects codecs for video telephony, taking into account information from the SIP / SDP signaling on the IMS side as well as the information regarding the CS-side terminal contained in message 10. Preferably, the MGCF according to the invention selects codecs which are supported on both the IMS and the CS network sides in order to avoid transcoding.

According to the invention, the MGCF instructs the IM-MGW to configure logical channels for this codec (s).

Preferably, the MGCF uses the new so-called H.248 "sig- nal" "H245Selection" within a H.248 "Modify" digest, and specifies the codecs as suitable parameters of the "sig- nal", for example as SDP or encoded in the form of the so-called H.248 "SDP equivalents".

In a variant of the invention not shown here, the MGCF dispenses with the final selection of the codecs and leaves this decision to the IM-MGW. According to the invention, the IM-MGW would then select from the intersection of the codecs obtained in messages 9 and 13 and the codecs supported by them.

18. The MGCF sends for the codecs obtained in message 17 a so-called "Open Logical Channel" H.245 message in which it uses the H.223 "logical channel number" (LCN) corresponding to the selected codec, which previously by means of the Terminal Capability Set "H.245 messages 9 or 14. In a case not shown here it can also happen that the IM-MGW receives an" Open Logical Channel "H.245 message from the CS network. In this case was in the CS Network selected from the capabilities offered in the "Terminal Capability Set" message 14.

19. The IM-MGW confirms the "Modify" message If the IM-MGW is not able to set up the required logical "channels", for example because it is the H.245 "slave", it preferably shares that in this Message with.

20. The IM-MGW receives a so-called "Open Logical Channel Ack" H.245 message 21. According to the invention, the IM-MGW informs the MGCF as soon as a logical channel has been opened by means of H.245 and gives the H used .223 "logical channel number" and the corresponding codec. The IMGM determines the codec with the aid of the logical channel number signaled in the ensuing "Open Logical Channel" message and the information assigned to it in the "Terminal Capability Set" H.245 messages 9 or 14.

The IM-MGW preferably uses a so-called H.248 "Notify" message with the new event "H245Channel", the suitable parameters for specifying the codecs and the "logical

Channel number ", for example, encoded as SDP or in the form of the so-called H.248" SDP equivalents ".

22. The MGCF confirms receipt of the "Notify" message.

23. The MGCF instructs the IM-MGW to set up the logical H.223 channel, which has already been negotiated by means of messages 21 to 26 via H.245 signaling. For this, the IM-MGW sends a H.248 "Modify" message regarding the multiplexing termination T2 in which it describes a new "stream 3", where it specifies the LCN and the codec as in message 21.

24. The IM-MGW sends a confirmation of the H.248 "Modify" message. 25. The MGCF instructs the IM-MGW to establish a termination on the IMS side, to which stream 3 is to be connected, so that the IM-MGW receives the data assigned to it on the IMS or CS network side other side passes on. For this, the IM-MGW sends an H.248 "Add" message regarding Context Cl, indicating that "stream 3" is to be carried and which codec to use for it. If the same codec is specified in messages 23 and 25, the IM-MGW recognizes that no transcoding is required.

26. The IM-MGW confirms the "Modify" message.

27. Steps 17 through 26 are also performed to configure the stream 4 for the bearer to transport the speech and the corresponding speech codec for a termination T4.

The H.248 context for a video call thus looks like FIG. 4.

Claims

claims

1. A method for establishing a video or multimedia telecommunication connection, which after construction via a wired

("Circuit switched", CS) telecommunications network and via another telecommunications network (IMS) that uses SIP for signaling leads, with a "Media Gateway Control Function" - device (MGCF) an "Internet Multimedia - Media Gateway" device (IM-MGW) of a telecommunication network (CS, IMS) at least instructs to establish the video or multimedia telecommunication connection inband negotiations on the part of the wireline telecommunication network with respect to the codecs to be used for the video or multimedia connection, according to which the Internet Multimedia - Media Gateway "device (IM-MGW) at least executes the negotiations assigned to it.

2. The method according to claim 1, characterized in that the telecommunication connection according to the structure via a wired telecommunication network (CS) which is or contains a 3GPP CS domain or a PSTN, and via a telecommunication network, the SIP is used for signaling and the an "IP Multimedia Subsystem "- Telecommunications Network (IMS) is or contains leads.

3. The method according to claim 1 or 2 for establishing a video telecommunication connection, which after setup via a wired telecommunication network (CS) and an "IP Multimedia Subsystem" - telecommunications network (IMS) leads, wherein a "Media Gateway Control Function" - device (MGCF) of the "IP Multimedia Subsystem" - telecommunications network (IMS ) at least instructs an "Internet Multimedia - Media Gateway" device (IM-MGW):

• first, to perform an H.223 protocol negotiation of the "H.223 Multiplex Levels" to be used for the video telecommunication connection in the "IP Multimedia Subsystem" telecommunication network (IMS), and

• secondly, for establishing a H.324 video telecommunication connection in the wireline

Telecommunications network (CS) to perform an H.245 protocol negotiation regarding codecs to be used for the telecommunication connection, and

• thirdly, to inform the "Media Gateway Control Function" device (MGCF) as soon as H.223-

Transport channels for the video telecommunication connection have been opened by means of H.245 signaling, according to which the "Internet Multimedia Media Gateway" device (IM-MGW) of the "IP Multimedia Subsystem" telecommunication network (IMS) at least these three mentioned Executes statements.

4. The method according to any one of the preceding claims, characterized in that the instructions are given when the one "Media Gateway Control Function" device (MGCF) recognizes the call structure due to the Call Control or assumes that video-telephony according to the H.324 protocol is desired on the circuit-switched (CS) side.

5. The method according to any one of the preceding claims, characterized in that the "Media Gateway Control Function" means (MGCF) the "Internet Multimedia - Media Gateway" device (IM-MGW) by means of so-called H.248 "Add" or Configure "Modify" messages, especially if it sets up the so-called "Termination" responsible for handling the multiplexed H.223 protocol.

6. The method according to any one of the preceding claims, characterized in that the the "Media Gateway

Control Function "device (MGCF) inserts in messages to the IM-MGW one or more newly standardized H.248" signals "that express that the H.223 and / or H.245 negotiation is to be performed.

7. The method according to any one of the preceding claims, characterized in that the "Media Gateway Control Function" means (MGCF) to a notification about the structure of logical H.223

Requiring channels to re-standardize to a so-called H.248 "Event", which inserts the "Media Gateway Control Function" device (MGCF) into an H.248 message to the MGW, and that if logical H.223 channel is opened by H.245 signaling, the Media Gateway "device (IM-MGW) for notifying the MGCF according to the invention a so-called H.248" No- tify "message using the redefined" event ".

8. The method according to any one of the preceding claims, characterized in that the Media Gateway "-

Means (IM-MGW) in the notification of the opening of a logical H.223 channel indicating the selected codec and the so-called "logical channel number", preferably as a parameter of the event used in the notification.

A method according to any one of the preceding claims, characterized in that the Media Gateway "device (IM-MGW) also notifies the MGCF when the H.223 negotiation of the" Multiplex Level "has ended or when this negotiation has failed.

10. The method according to any one of the preceding claims, characterized in that the "Media Gateway

Control Function "device (MGCF) to request notification of the H.223 negotiation of the" Multiplex Level "to use a newly standardized H.248" Event "that uses the" Media Gateway Control Function "facility

(MGCF) inserts into an H.248 message to the MGW, and that when in the following the H.223 negotiation of the "Multiplex Level" is finished, the Media Gateway "device (IM-MGW) according to the invention for notifying the MGCF uses a so-called H.248 "Notify" message, in which it specifies the newly defined "Event".

11. The method according to any one of the preceding claims, characterized in that when in the case of a call setup on the part of the circuit-switched (CS) network through a first MGCF in the direction of the "IP Multimedia subsystem" - telecommunications network (IMS), the connection from the "IP Multimedia subsystem "- telecommunications network (IMS) is forwarded to another" Media Gateway Control Function "device (MGCF), the first MGCF instructs the controlled by her Media Gateway" device (IM-MGW) to pass the data channel transparent ,

12. The method according to any one of the preceding claims, characterized in that the "Internet Multimedia - Media Gateway" device (IM-MGW) preferably performs the H.245 procedures for the so-called "Master Slave Determination" independently.

13. The method according to any one of the preceding claims, characterized in that the "Internet Multimedia

- Media Gateway "device (IM-MGW) also sends and receives the so-called H.245" Terminal-Capability Set "messages independently.

14. Method according to one of the preceding claims, characterized in that the transmission of codecs between the "Media Gateway Control Function" device (MGCF) and the "Internet Multimedia Media Gateway" device (IM-MGW) is dispensed with, and "Media Gateway Control Function" device (MGCF) and "Internet Multimedia - Media Gateway" device (IM-MGW) are configured to share the same voice and video codecs in the SIP / SDP Select out-of-band negotiation on the IP Multimedia Subsystem (IMS) or H.245 inband negotiation on the circuit-switched (CS) network side

15. The method according to any one of the preceding claims, characterized in that the "Internet Multimedia - Media Gateway" device (IM-MGW) exchanges information regarding the supported codecs with the "Media Gateway Control Function" device (MGCF).

16. The method according to any one of the preceding claims, characterized in that the "Media Gateway Control Function" - device (MGCF) of the "Internet

Multimedia - Media Gateway "device (IM-MGW) instructs which codecs the Internet Multimedia - Media Gateway device (IM-MGW) should specify in the sent" Terminal-Capability Set "message.

17. The method according to claim 15, wherein the "Media Gateway Control Function" device (MGCF) transmits codecs to the "Media Gateway Control Function", which transmits them on the side of the "IP Multimedia Subsystem" (IMS) in the SIP / SDP signaling had received.

18. The method according to claim 15, wherein the "Media Gateway Control Function" device (MGCF) only sends codecs to the "Media Gateway Control Function" which is connected to the "Internet Multimedia - Media Gateway".

Facility (IM-MGW).

19. Method according to claim 15, characterized in that the "Internet Multimedia - Media Gateway" device (IM-MGW) removes those of the codecs received from the "Media Gateway Control Function" device (MGCF), which themselves not supported before sending the codecs in a "Terminal-Capability Set" message.

20. The method according to any one of the preceding claims, characterized in that the "Media Gateway

Control Function "device (MGCF) indicating codecs in an" Add "or" Modify "message as parameters of the" Signal "instructing the" Internet Multimedia - Media Gateway "device (IM-MGW), the H.245 Negotiation.

21. The method according to any one of the preceding claims, characterized in that "Media Gateway Control Function" means (MGCF) indicates the codecs, if they the "Internet Multimedia - Media Gateway" -

Setup (IM-MGW) instructs to start the H.245 transaction.

22. The method according to any one of the preceding claims, characterized in that "Media Gateway Control

Function "means (MGCF) indicating the codecs in an H.248 message that the" Media Gateway Control Function "device (MGCF) sends when it receives information regarding the codecs in a SIP lookup.

23. The method according to any one of the preceding claims, characterized in that the "Internet Multimedia Media Gateway Control Facility (IM-MGW) tells the Media Gateway Control Function Facility (MGCF) which codecs it has received in a Terminal Capability Set message,

24. Method according to the preceding claim, characterized in that the "Internet Multimedia - Media Gateway" device (IM-MGW) only those of the received in a "Terminal-Capability Set" message codecs of the "Media Gateway Control Function "-

Device (MGCF) that supports the Internet Multimedia - Media Gateway (IM-MGW) device.

25. Method according to one of the preceding claims, characterized in that in order to request a notification about the codecs received from the "Internet Multimedia - Media Gateway" device (IM-MGW) in a "Terminal-Capability Set" message, the "Media Gateway Control Function" device (MGCF) uses a so - called H.248 "Event" which is to be newly standardized, which preferably inserts the "Media Gateway Control Function" device (MGCF) into the same H.248 message, in they use the "Internet Multimedia - Media Gateway" facility

(IM-MGW) instructs to start the H.245 negotiation, and that if in the following the "Internet Multimedia

- Media Gateway "device (IM-MGW) receives a" Terminal Capability Set "message, the Media Gateway device (IM-MGW) according to the invention for notifying the MGCF a so-called H.248" Notify " Message in which she redefined the "Event" indicates.

26. The method according to any one of the preceding claims, characterized in that the "Internet Multimedia - Media Gateway" device (IM-MGW) after replacing the H.245 "Terminal-Capability Set" messages and completion of the H.245 "Master Slave Determination "automatically opens logical H.223 channels, if it is responsible for the output of the Master Slave Determination.

27. Method according to one of the preceding claims, characterized in that the "Media Gateway Control Function" device (MGCF) instructs the "Internet Multimedia - Media Gateway" device (IM-MGW) to set up the logical channels for specific codecs.

28. Method according to the preceding claim, characterized in that the "Media Gateway Control Function" device (MGCF) which specifies specific codecs and logical channels as special parameters of a suitable signal to be re-standardized within a H.248 "Modify" message ,

29. Method according to one of the preceding claims, characterized in that the "Internet Multimedia - Media Gateway" device (IM-MGW) also informs the "Media Gateway Control Function" device (MGCF) if the inband negotiation failed with H.245, for example, because no matching capabilities were found, the one Transmission of video telephony

30. The method according to any one of the preceding claims, characterized in that the "Media Gateway Control Function" means (MGCF) the "Internet

Multimedia - Media Gateway "device (IM-MGW) either switches on the connection the first time the so-called" terminations "are configured or after notification of a successful inband negotiation.

31. 'Media Gateway Control Function' device (MGCF), in particular for carrying out the method according to one of the preceding claims, which is designed such that it has an 'Internet Multimedia - Media Gateway' device (IM-MGW) at least instructs:

• first, an H.223 protocol negotiation of the protocol to be used for the telecommunication connection

"H.223 Multiplex Levels", and

Secondly, to perform an H.245 protocol negotiation for the establishment of an H.324 protocol connection for the telecommunication connection, and thirdly, the "Media Gateway Control Function"

Device (MGCF) as soon as logical H.223 channels are opened by means of H.245 signaling.

32. 'Internet Multimedia - Media Gateway' device (IM-MGW), in particular for carrying out the method according to one of the preceding claims, which is designed so that it is instructed by a Media Gateway Control Function "(MGCF):

• first, to carry out an H.223 protocol negotiation of the "H.223 multiplex level" to be used for the telecommunication connection, and secondly, to establish an H.324 protocol

Connection for the telecommunications connection performs an H.245 protocol negotiation, and

• Thirdly, the "Media Gateway Control Function" device (MGCF) informs as soon as logical H.223 channels are opened by means of H.245 signaling.

33. Telecommunications network, in particular for carrying out the method according to one of the preceding claims,

with a "Media Gateway Control Function" device (MGCF), in particular for use in an "IP Multimedia Subsystem" telecommunication network (IMS), which is designed such that it has an "Internet Multimedia - Media Gateway" device (IMM). MGW) at least instructs:

First, to perform an H.223 protocol negotiation of the "H.223 multiplex level" to be used for the telecommunication connection, and

Second, to perform H.245 protocol negotiation to establish an H.324 protocol connection for the telecommunications connection, and

• third, to inform the "Media Gateway Control Function" device (MGCF) as soon as logical

H.223 channels are opened by H.245 signaling, and an "Internet Multimedia - Media Gateway" device (IM-MGW), in particular for use in an "IP Multimedia Subsystem" telecommunication network (IMS) which is designed to be used on the instructions of a Media Gateway Control Function " Facility (MGCF):