Title of Invention	METHOD, COMMUNICATIONS SYSTEM AND COMMUNICATIONS TERMINAL FOR ESTABLISHING COMMUNICATION
Abstract	The invention relates to a method for establishing communication in a packet-oriented communications network (IPN) between a calling (EG1) and a called terminal (EG2). In the method, before a call-accepted signal by the called terminal (EG2), triggered by a message (MSIG, M3) within the framework of call set-up signaling (SIG), a direct, first payload connection (ND) is established and maintained between the calling (EG1) and the called terminal (EG2). As a direct result of the call-accepted signal of the called terminal (EG2) communication is triggered between the calling (EG1) and called terminal (EG2) by means of the established first payload connection (ND). The invention also relates to a communications system and to a terminal for carrying out the method.

Title of Invention

METHOD, COMMUNICATIONS SYSTEM AND COMMUNICATIONS TERMINAL FOR ESTABLISHING COMMUNICATION

Abstract

The invention relates to a method for establishing communication in a packet-oriented communications network (IPN) between a calling (EG1) and a called terminal (EG2). In the method, before a call-accepted signal by the called terminal (EG2), triggered by a message (MSIG, M3) within the framework of call set-up signaling (SIG), a direct, first payload connection (ND) is established and maintained between the calling (EG1) and the called terminal (EG2). As a direct result of the call-accepted signal of the called terminal (EG2) communication is triggered between the calling (EG1) and called terminal (EG2) by means of the established first payload connection (ND). The invention also relates to a communications system and to a terminal for carrying out the method.

Full Text	Description In modern communications systems it is known to transmit payload via packet-oriented networks. Payloads are, for example, digitized voice data, with the term "Voice over IP", or VoIP for short, being common for transmission of voice data via packet-oriented networks. The use of packet-oriented data transmission methods often results in losses in the quality of the payload being transmitted and these are often caused by conversions, delays or loss of payload packets in network nodes. Based on the often used, so-called internet protocol, also abbreviated to IP, reference will be made hereinafter using the term "IP terminal" to communication terminals that operate on the basis of a packet-oriented transmission method. In packet-oriented networks a connection between IP terminals can conventionally be routed via network nodes, such as what are known as routers, switches or gateways. In this connection routers switch data between packet-oriented sub-networks, while gateways can also provide a junction between different types of 1 irie-switched and/or packet-oriented networks. With a connection between two IP terminals the payloads may be routed in particular via a plurality of gateways, it being possible for each additional gateway in a transmission path of the payloads to have an adverse effect on the payload quality - i.e. for example a voice quality. Furthermore, a distinction is often made with packet-oriented connections between signaling connections and payload connections, it being possible for signaling and payload connections between two IP terminals to have different connection paths in the network. To improve the voice quality IP terminals, which endorse the ITU-T recommendation H.323 (ITU-T: International Telecommunication Union - Telecommunications Standardizations Sector) and what is referred to as the Direct Media Connection (DMC), communication payloads can be transmitted directly between the IP terminals while avoiding the gateways and thereby avoiding additional conversions and delays. In some cases it has continued to prove problematical that, with conventional DMC methods, when switching through the payload connection there is a delay before a definitive end-to-end connection is produced between the IP terminals, so with voice connections the start of a call is potentially not transmitted to a conversation partner. The object of the invention is to disclose a method in which establishing of communication between two communication terminals in a packet-oriented communications network is improved. It is a further object of the invention to disclose a communications system and a communications terminal for carrying out the method. This object is achieved by a method with the features of claim I and by a communications system according to claim 11 and a communications terminal according to claim 12. Advantageous embodiments and developments of the invention are disclosed in the dependent claims. In the method ciccording to the invention, to establish communication, in particular of media such as voice, video, photos, fax or multimedia, in a packet-oriented communications network between a calling and a called terminal, before a call-accepted signal by the called terminal, triggered by a message within the framework of call set-up signaling, a direct, first payload connection is established between the calling and the called terminal. This accordingly established, first payload connection is maintained. As a direct result of the call-accepted signal of the called terminal communication is triggered between the calling and called terminals by means of the established first payload connection. In the method according to the invention it is particularly advantageous that following initiation of a call set-up, the direct, first payload connection is established even before the call-accepted signal by the called terminal, so protracted establishment of a payload connection only when there is a call-accepted signal between the called and the calling terminals can be omitted. Since the first payload connection established for transmission of payload - for example a djgitized and encoded voice - is on standby it may be ensured that the payload can be transmitted simultaneous with the call-accepted signal without there being any connection delays. In particular the method according to the invention can ensure that, by way of the called device, the supplied communication can be processed without delay with the callaccepted signal and can be transmitted to the calling terminal via the first: payload connection already established, so the calling terminal can reach all of the communication incoming at the called terminal, without loss of an initial communication portion in an otherwise conventional time slot: between call-.accepted signal and switching-through of a payload connection. A gap in transmission of this kind or an excessive switch-through delay in payload transmission may therefore be avoided. When applying the invention to a voice connection via telephone, immediately after the receiver of a called telephone, as the called terminal, is picked up therefore, the sounds arriving at the microphone are processed - i.e. are in particular encoded - by the called telephone, as communication according to the invention, and transmitted to a calling telephone as the calling terminal via the payload connection already maintained. An otherwise frequently occurring loss of a voice portion immediately after the receiver has been picked up is thereby avoided. The call-accepted signal is in particular taken to mean actions which bring about acceptance of the signaled call setup signaling for switching through the payload connection. With telephones this is in particular the action of taking up a receiver or pressing of a key. Alternatively acceptance of the incoming connection can be automatically triggered, without manual intervention, in other terminals such as fax machines. A direct, first payload connection can be taken to mean a connection between two terminals which consists in particular in avoiding connection controllers such as gateways and/or gate keepers, tri an advantageous embodiment of the invention this is for example a direct media connection, in particular according to Direct Media Connection (DMC) specifications. A connection via network elements which only carry out transportation of data at a low level of the OSI-reference model (OSI: Open. Systems Interconnection) standardized by the ISO (International Organization for Standardization) - for example bridges, switches, routers, are'to be regarded as a direct connection according to the invention. Depending on the embodiment it may also be provided, in addition to the direct, first payload connection, that an additional payload connection routed via connection controllers is established between the terminals. In an advantageous development of the invention a connection controller, in particular a gatekeeper and/or a gateway, can be associated with the called and the calling terminals. Connection controllers of this type are for example provided to provide allocation of call numbers to IP addresses, with a respective connection controller only managing the terminals associated with it. The connection controllers may also be involved in signaling and in particular in call set-up signaling according to the invention. Within the framework of call set-up signaling the connection controllers can be involved in determining the codec (encoder/decoder) of the terminals and connection controllers that is to be used, the signaling path and the payload path in the communications network, encoding and/or further transmission parameters for the subsequent; payload connection. A call set-up signaling path can run via a plurality of connection controllers as a function of the network structure and grouping of the terminal. In a further advantageous development of the invention, before the call-accepted signal by the called terminal, triggered by a message within the framework of call set-up signaling, a second payload connection can be established between the called terminal and a connection controller - in particular a connection controller involved in call set-up signaling. The payload entering the calling terminal via the second payload connection is preferably processed at the calling terminal if there has been no call-accepted signal by the called terminal. With voice connections of the calling terminal this second payload connection can be used to transmit the ringing tone to indicate a clear or busy signal as an audible representation of the call status of the called terminal. The second payload connection can moreover be used to transmit announcements, option and/or input menus, generated by the connection controller or a further network node, to the calling terminal. In generalized terms and independently of the transmitted media type for the payload communication the second payload connection can be provided for transmission of additional communication between a connection controller and the calling terminal before the call-accepted signal by the called terminal, it being possible for the additional communication to be audio, video and/or multimedia information provided in a call set-up state, i.e. during call set-up and before the called terminal is answered, if generated by any desired network node that is different from the calling device. In an advantageous embodiment, before the call-accepted signal between the calling terminal and the called terminal a direct signaling connection associated with the first payload connection can be established between the calling terminal and the called terminal, in particular via the same data path in the communications network as the first payload connection. This can be established in addition to further signaling actions running via connection controllers and can advantageously be used for signaling for a direct connection according to DMC (Direct Media Connection), the direct signaling connection and the direct, first payload connection representing the DMC connection after the call-accepted signal. According to a further advantageous development of the invention, before the call-accepted signal by the called terminal, measures for call clearing suppression can be implemented by the calling terminal and/or the called terminal. This can therefore advantageously prevent/the first payload connection from being cleared, even before the callaccepted signal owing to a conventional time allowance being exceeded - for example a maximum period -of inactivity at a connection -, and therefore no longer being available for transmission of communication. In particular maintenance messages or packets, triggered by the call set-up signaling from the calling terminal to the called terminal, can be transmitted from the called terminal via the first payload connection to the calling terminal. A trigger time until a connection is cleared is also called a connection "time out" or is designated as the attainment of the maximum allowed "idle" time. The maintenance packets can be called "dummy", "keep alive" or "idle" packets and are transmitted by the called and/or the calling terminal. The respective receiving terminal can advantageously recognize on the basis of the content of an incoming packet whether it is a maintenance packet and in this case ignore or reject the contents. In an advantageous embodiment of the invention the calling terminal, induced by receipt of a maintenance packet, can transmit an additional maintenance packet or an acknowledgement conforming to protocol. The calling device can preferably transmit maintenance packets to the called terminal via the first payload connection provided only maintenance packets are received by the calling terminal via the first payload connection. By recognizing a payload packet that differs from the maintenance packets and/or a payload packet implicitly indicating a call-accepted signal, owing to the start of a transmission of communication contents, at the called terminal, in an advantageous embodiment of the invention the calling terminal can recognize and/or determine the'callaccepted signal of the called terminal with the aid of incoming payload packets via the first payload connection. This preferably takes place via a signaling connection without additional signaling, so advantageously only the first payload connection has to be monitored without additional connections of the calling terminal having to be observed. Since no separate signaling of the call-accepted signal is required existing protocols that are used do not need to be expanded for the invention. Delays through to transmission of the first payload packet to the calling terminal are also avoided, in particular if transmission of.maintenance packets is terminated by the called terminal when it recognizes the callaccepted signal, and the pending payloads are transmitted immediately - in particular without further delay or explicit signaling - via the first payload connection. Triggered by reception of a payload packet, indicating the call-accepted signal, at the calling terminal via the first payload connection, in an advantageous embodiment of the invention the call-accepted signal of the called terminal can be accepted by the calling terminal without acknowledgement by the payloads received via the first payload connection being processed in the calling terminal and being output at an output unit and in response thereto a message that is conventional in the connected state being transmitted to the called terminal. The calling terminal can also reject payload entering via the second payload connection and payload at the calling terminal can accordingly be transmitted via the first payload connection and no longer via the second payload connection. There is thus a changeover at the calling terminal from the second to the first payload connection without explicit signaling messages for announcing or triggering this changeover being sent or received via a signaling connection. The above advantages, developments and embodiments apply analogously to the communications system according to the invention and to the communications terminal according to the invention in addition to applying to the method according to the invention. An exemplary embodiment of the invention will be described in more detail hereinafter with reference to the drawings, in which schematically: Fig. 1 shows a communications system and a message flow and essential method steps within the framework of establishing communication in the communications system, and Fig. 2 shows a flow diagram of a calling and a called terminal in the communications system for establishing communication. Fig. 1A to 1C schematically show the components of a packetoriented communications system. The components are, in particular, a calling first terminal EG1, a called second terminal EG2 and three connection controllers GW1, GW2 and GW3. Said components are coupled via an IP network IPN as a packet-oriented communications network according to the invention, the messages and connections mentioned below being based on IP-based concepts. The terminals EG1 and EG2 are IPbased voice terminals and are visualized in figures 1A to 1C as telephones. The connection controllers GW1, GW2, GW3 are shown as rectangles and in the present exemplary embodiment fulfill gateway and gatekeeper functionalities. This means in particular that, owing to the gatekeeper functionality, the respective terminals EG1, EG2 are allocated to a specific connection controller and, furthermore, the respective connection controller, owing to its gateway functionality, allows a transition between sub-networks of the packetoriented communications system and a transition to lineoriented or other packet-oriented communications systems. The communications system is configured in such a way that the first terminal EG1 is registered with the first connection controller GW1 and the second terminal EG2 with the second connection controller GW2. The first connection controller GW1 can moreover route connections to the third connection controller GW3 and this, owing to its configuration, can in turn transmit messages and connections to the second connection controller GW2 and to the first connection controller GW1. The second connection controller GW2 is configured in such a way that it can transmit messages to the third connection controller GW3. Direct communication between the first connection controller GW1 and the second connection controller GW2 should be possible via the IP network IPN, although it is assumed that the two connection controllers GW1 and GW2 are not reciprocally known, so a connection is in each case made via an intermediate connection controller - the third connection controller GW3 in this case. IP addresses are allocated to all terminals and connection controllers shown in figures 1A to 1C, with only the first IP address IP1 associated with the first terminal EG1 and the second IP address IP2 associated with the second terminal EG2 being shown. Furthermore the two terminals EG1 and EG2 have a call number for addressing in the voice communications system, only the call number RUN02 associated with the second terminal EG2 being shown in Fig. 1. Directed messages are shown in Fig. 1 as directed arrows with arrow tip in the transmission direction and non-directed messages and connections are shown in the figures as double arrows. Signaling connections are shown in broken lines and payload connections in solid lines. Establishment of voice communication between the calling first terminal EG1 and the called second terminal EG2 will be described hereinafter with reference to Fig. 1. Initial triggers in this connection are the lifting of the telephone receiver and dialing of the call number RUNO2 at the first terminal EG1. Triggered thereby between the first terminal EG1 and the first connection controller GW1 is a signaling connection SIG for the purpose of setting up a call, within the framework of which a signaling message MSIG is transmitted from the first terminal EG1 to the first connection controller GW1. In particular the target call number RUNO2 of the second called terminal EG2 and the transmission IP address IP1 of the first terminal EG1 are transmitted as the parameters. A signaling message MSIG of this type could for example be a setup message according to the ITU-T recommendation H.323 (ITU-T: : International Telecommunication Union - Telecommunications Standardizations Sector) or an invite message according to the SIP protocol (SIP: Session Initiation Protocol) of the IETF workgroup (IETF: Internet Engineering Task Force). The first connection controller GW1 then checks whether a terminal with the second call number RUN02 is registered with it. It is not in the present embodiment.. The first connection controller GW1 then routes the call set-up signaling to the next configured routing node. This is the third connection controller GW3 in the present embodiment. In turn a signaling message MSIG is transmitted together with the target call number RUNO2 and the transmission IP address IP1. In the present exemplary embodiment the target call number RUN02 is not registered with the third connection controller GW3 either. The third connection controller.GW3 then transmits a query to further connection controllers and this includes in particular a query to the second connection controller GW2 (Fig. 1A shows only the query to the second connection controller GW2 by a signaling message MSIG) • A signaling connection is therefore established between the third connection controller GW3 and the second connection controller GW2 via which a signaling message MSIG is transmitted with said parameters. The second connection controller GW2 checks the terminals registered with it and recognizes that, associated with call number RUNG2, the second device EG2 is registered with it. The second connection controller GW2 determines the second IP address IP2 of the second terminal EG2 with the aid of call number RUNO2 arid internal configuration data. A signaling message MSIG is then sent to this IP address IP2 with the IP address IP1 of the first terminal EG1 as parameters. Signaling SIG is therefore continuously established from the first terminal EG1 via the connection controllers GW1, GW3 and GW2 to the second called terminal EG2. Fig. 1A does not show acknowledgements within the framework of signaling SIG for reasons of clarity. Owing to the incoming signaling SIG an incoming call is visually or acoustically signaled to a user of terminal EG2 at the second terminal EG2, in particular by ringing of the phone. Fig. IB indicates -this by a star next to the telephone receiver of the second terminal EG2. A first payload connection Nl between the calling first terminal EG1 and the - from the perspective of the first terminal EG1 - last, gateway in the chain of signaling SIG, i.e. the second connection controller GW2, and a payload connection N2 between the second connection controller GW2 and the called terminal EG2 will be established hereinafter. Both payload connections are active, and this is indicated in the drawings by a subscripted "A". The payload connection Nl as the second payload connection according to the invention is used in particular in this connection to generate and transmit to the first terminal EG1 the ringing tone in the receiver, so a user at the first terminal EG1 recognizes that the call request has been signaled through to the second terminal EG2. The payload connection Ni can, moreover, be used to transmit automatic announcements, to provide call centre option menus - for example by IVR systems (IVR: Interactive Voice Response), voice and/or key actions carried out at the first terminal EG1 being transmitted to the connection controller GW2 via the payload connection Nl. Also triggered by the signaling message MSiG entering within the framework of call set-up signaling at the called second terminal EG2, even before the call-accepted signal by the called terminal EG2, is the establishment of a direct signaling connection SIGD and a direct payload connection ND as the first payload connection according to the invention, in each case as a direction connection to the first terminal EG1. A direct connection in this connection is a connection which is not routed via the connection controllers GW1, GW2, GW3, it being possible however to provide known network nodes such as routers, switches, bridges and firewalls., in the transmission path of the direct connections SIGD, ND for packet-oriented transmission if they do not carry out any kind of voice conversions or other time-consuming processing operations of data packets of the connections SIGD, ND. The direct connection is established in this case with the aid of the first IP address IP1 transferred to the second terminal EG2, network address conversions between various sub-networks being ignored in the present exemplary embodiment. The direct connection may also be established by depending on or using known DMC method steps for direct media communication. The established connections SIGD, ND are maintained for subsequent, rapid switching-through of the communication between the second terminal EG2 and the first terminal EG1 after the call has been accepted by the second terminal EG2. Time-consuming connection establishment steps, such as the exchange of codes and/or certificates for secured, subsequent communication, are carried out as early as when the signaling connection SIGD and the direct payload connection ND are established. The first terminal EG1 is actively involved in the direct establishment of the signaling connection SIGD and payload connection ND, data transmission via the connections SIG and Nl already established not being affected thereby. Maintenance packets IDLE conforming to protocol will be transmitted hereinafter between the called second terminal EG2 and the calling terminal EG1 via the direct payload connection ND, so the direct payload connection ND, despite apparent inactivity, is not automatically cleared but is maintained. The calling first: terminal EG1 is accordingly configured in such a way that, while it manages the payload connection Nl it analyses incoming data packets via the direct payload connection ND. The incoming data packets are analyzed in this connection such that the first terminal EG1, with the aid of the incoming packets, recognizes whether the incoming data packets are still maintenance packets IDLE for call clearing suppression or are already valid payload packets following a call-accepted signal by the second terminal EG2. Reception of maintenance packets IDLE in the first terminal EG1 means that the received maintenance-packets IDLE are ignored and/or maintenance packets IDLE are also transmitted via the direct payload connection ND to the called terminal EG2. A call-accepted signal by the called terminal EG2 would, moreover, be recognized at the first calling terminal EG1 by a data packet, which differs from a maintenance message or a maintenance packet IDLE, arriving via the direct payload connection ND, This is described in more detail hereinafter with reference to Fig. 1C. Lifting of the telephone receiver of the second terminal EG2, indicated in Fig. 1C, causes acceptance of the call by the second terminal EG2. As a direct result of this call-accepted signal at the second terminal EG2 the communication pending at the microphone of the telephone receiver of the second terminal EG2 is processed in the second terminal EG2. Without explicit signaling via one of the signaling connections SIG or SIGD - wherein explicit signaling of the call-accepted signals by means of SIG and/or SIGD may also be provided in alternative embodiments to communicate the call-accepted signal of the second terminal EG2 even if the microphone of the first terminal EG1 is muted, or to ensure correct detection for determining call charges - the incoming communication is digitized by the second terminal EG2 and transmitted via the direct payload connection ND to the calling first terminal EGl, with transmission of maintenance packets IDLE to the second terminal EG2 being terminated. The arrival of a payload packet of this type, which differs from maintenance packets IDLE, at the calling first terminal EGl means that the call-accepted signal of the second terminal is recognized by the first. This call-accepted signal Is, moreover, implicitly accepted, i.e. without transmission of an acknowledgement or confirmation, by the first terminal EGl in that the payload incoming via the direct- payload connection ND is processed immediately - without any further signaling -, and is output via the associated telephone receiver of the first terminal EGl. The payload connection Nl between the calling terminal EGl and the second connection controller GW2 is furthermore switched so as to be inactive in that no further packets that differ from maintenance packets IDLE are transmitted by the calling terminal EGl via this connection. Sounds and/or speech received via the telephone receiver of the first terminal EGl are no longer transmitted via the payload connection Nl from this point in time either but via the direct payload connection ND, without additional signaling having been carried out. Payload packets entering via the payload connection Nl are rejected by the first terminal EGl. Rapid switching-through of a communication is thus possible via a direct payload connection ND. A loss of payload packets or a communication at a telephone receiver can thus be avoided. This is particularly advantageous if the second terminal EG2 is a device for automatic announcements or is a fax machine or modem. The latter devices conventionally have the property of transmitting payloads very quickly after signaled call acceptance, so logs of these payloads would have an adverse effect. In particular the loss of fax or modem payloads could prevent connection establishment or make it impossible. This may be prevented by the, presented method because directly after the call-accepted signal the pending communication is transmitted without losses and without delay to the calling terminal EG1. The existing payload connections Nl and N2 and the signaling connections SIG which run via the connection controllers GW1, GW2, GW3, can continue to be maintained or alternatively (not shown) be cleared within the framework -of further signaling messages. If these connections are not cleared it is provided in the case of both terminals EG1 and EG2 that packets entering via these connections are ignored. The terminals EG1, EG2 shown in Fig. 1 and the illustrated communications system structure should be regarded merely as examples in this connection. A generalization compared with any desired terminals and any desired topology as well as any desired communications protocol is easily possible without limiting the disclosure of the invention. Fig. 2 will hereinafter describe a respective state transmission diagram for the calling terminal EG1 and the called terminal EG2 according to the method steps illustrated with reference to Fig. 1. The state transitions are described, with reference to their course over time, jointly for the calling and the called terminal EG1, EG2, respective state transition diagrams being shown separately from each other for the calling terminal EG1 in Fig. 2A and for the called terminal EG2 in Fig. 2B. The starting situation for the calling terminal EG1 is a rest state 0EG1 and likewise a rest state 0EG1 for the called terminal EG2. Triggered by dialing of the call number RUNO2 at the first terminal EG1, the first terminal EG1 changes into an initialization state for the connection to be established (state 1EG1) . Triggered as a result, a signaling message Ml is transmitted to the called terminal EG2 . The transmission takes place in particular via a plurality of connection controllers, with these not being shown in Fig. 2. Receipt of the signaling message Ml causes the called terminal EG2 to leave its rest state and to change into the state 1EG2 in which steps are carried out which are executed in the case of an incoming connection request. In state 2EG2 the called terminal EG2 transmits a response belonging to message Ml via the same signaling path with the aid of signaling message M2. The calling terminal EG1 then changes its state to the state 2EGi which establishes a payload connection to a connection controller involved in message traffic. The called terminal EG2 passes immediately from state 2EG2 to state 3EG2 in that an additional direct signaling and payload connection is established. For this purpose a signaling message M3 is transmitted to the calling terminal EG1 and first packets via the direct payload connection (hereinafter designated "ND" according to the designation in Fig. 1). In a modification of the method the first terminal EG1 could also initiate the direct payload connection ND. This is especially possible if an IP address of the second terminal EG2 is transmitted as a parameter of the signaling message M2. Triggered by reception of this signaling message M3, the calling terminal EG1 changes its state (new state 3EG1) and accepts the incoming direct connections - the direct signaling connection SIGD and the direct payload connection ND - from the called terminal EG2. The calling terminal EG1 also immediately changes to state 4Eca in which incoming packets, which arrive via the direct payload connection ND at the calling terminal EG1, are analyzed. The called terminal EG2 changes owing to timer expiry from the state 3EG2 to the state 4EG2 and in this state sends a maintenance packet as a payload packet PIDLE with only "dummy" content to the calling terminal EG1 via the direct payload connection ND. In the still active state 4Eci the calling terminal EG1 analyses this incoming payload packet. If it is a maintenance packet the calling terminal EG1 changes to state 5EG1 and as a result causes the direct payload connection ND to continue not to be activated, and instead maintenance payload packets PIDLE are transmitted via the direct payload connection ND, starting from the calling terminal EG1. With renewed timer expiry at the called terminal EG2 this procedure is repeated again, so a maintenance payload packet PIDLE is transmitted again to the calling terminal EG1 and is analyzed therein analogously to the above-mentioned steps. This process is repeated until either the calling terminal EG1 terminates its call set-up request, until there is a call-accepted signal at the called terminal EG2 - in particular by lifting of a telephone receiver - or until one of the connection contx'ollers involved initiates termination of the connection. Triggered by a call-accepted signal of this type, the called terminal EG2 changes from the state 4EG2 to state 5EG2 - In this state pending communication data is converted directly into payload and transmitted via the direct payload connection ND to the calling terminal EG1 by means of filled payload packets PNUTZ • Sending of: filled payload packets PNUTZ is continued until the call is terminated in a known manner - for example by replacing the receiver. Before arrival of the first filled payload packet Ptnnz the calling terminal ,EG1 is still in the state 4EG1 in which incoming payload packets are analyzed via the direct payload connection ND. If a filled payload packet PNUTZ accordingly reaches the calling terminal EG1, this recognizes the receipt of a valid payload packet PNUTZ that describes a call-accepted signal and changes to state 6EG1 in which the connection, and therefore the communication to be transmitted, is switched through to the input/output device (i.e. the telephone receiver) of the calling device EG1. In this state the calling terminal EG1 processes incoming payload packets PNUTZ which arrive via the direct payload connection ND and sends its own payload packets to the called terminal EG2 via this direct payload connection ND. Both terminals EG1, EG2 can therefore change over into a connected state - states 7EG1 or 6EG2 - in which a payload stream NDS of payload packets is exchanged via the direct payload connection ND. Further steps, such as execution of specific features or, subsequently, call clearing, are accordingly possible. These steps are not described in more detail in the illustrated figures 2A and 2B, however. The states shown in Fig. 2 illustrate a largely simplified depiction of a connection establishment according to the invention. For example communication between a connection controller and the first terminal EG1 has been omitted for reasons of clarity. Observation of this connection would therefore have led to payload packets arriving at the first terminal EG1 being rejected by a connection controller in state SEGI - In states 2EG1 to 5EG1 on the other hand incoming payload packets would be processed by a connection controller via the first terminal EG1. The method steps shown with reference to figures 1 and 2 are advantageous insofar as the method allows rapid and loss-free changeover between an existing payload connection and an already established, but not yet active payload connection. This is particularly advantageous if, owing to time-consuming and complex call set-up methods a connection establishment of a payload connection is completed comparatively slowly, so without employing the invention recommended maximum switchthrough delays - for example 250 ms maximum delay - recommended by the ITU-T, cannot be observed. It is also advantageous that integration in existing implementations of protocols and transmission methods is easily possible since only minor modifications are necessary. Known methods may also be used for signaling and the payload connection. These are, in particular, method steps according to H.323, SIP, a transmission of payload packets according to RTF (Real-time Transport Protocol) and/or other standards or implementations. The method can advantageously be applied to all IP-based communications systems which are provided for real-time-critical transmission of flows of media - for example within the framework of Voice-over-IP or Multimediaover- IP. Although in the present exemplary embodiment only packet-based connections are used, individual signaling portions between the connection controllers for example can also be carried out by line-based communication segments. We Claim: 1. A method for establishing a communication in a packet-oriented communications network (IPN) between a calling (EG1) and a called terminal (EG2) , comprising a plurality of connection controllers for connecting the calling terminal to the called terminal, provided with a first connection controller and a second connection controller, comprising the following steps- - initiating a sending of a signaling message from the first connection controller of the calling terminal to the called terminal to establish a first payload connection between the called terminal and the first connection controller such that data is transmittable between the calling terminal and the called terminal via a communication path defined by at least the first and second connection controllers; - sending the signaling message comprising a parameter identifying an address of the calling terminal by the first controller to the called terminal; - receiving the signaling message from the first connection controller; - establishing a direct payload connection not including any connection controller within a path of communication defined by the direct payload connection between the called terminal and the calling terminal, before generating a call-accepted signal - communicating between the calling (EG1) and called terminal (EG2) by means of the established direct, first payload connection (ND) as a direct result of the call-accepted signal. 2. A method as claimed in claim 1, wherein - a direct signaling connection associated with the direct payload connection is established between the calling terminal and the called terminal prior to sending the call-accepted signal, - maintenance packets are transmitted between the called terminal and the calling terminal to maintain the direct payload connection prior to the transmitting of data packets between the calling terminal and the called terminal; and - data packets are transmitted between the calling terminal and the called terminal enabling the direct payload connection to be in an active state 3. A method as claimed in claim 1, wherein before the call-accepted signal by the called terminal (EG2), triggered by a message (MSIG) within the framework of call set-up signaling (SIG), a second payload connection (Nl) is established between the called terminal (EG1) and a connection controller (GW2). A. A method as claimed in claim 1, wherein the called terminal implements a call clearing suppression prior to transmitting the call-accepted signal. 5. A method as claimed in claim 1, wherein the call clearing suppression is configured such 'that maintenance packets are transmitted between the calling and the called terminal. 6. A method as claimed in claim 1, wherein the calling terminal recognizes the call-accepted signal of the called terminal by a first reception of data packets comprising contents of the communication via the direct payload connection. 7. A method as claimed any of the preceding claims, wherein the calling terminal checks, until the call-accepted signal of the called terminal is recognized at the calling terminal, whether a packet entering via the direct payload connection is one of the maintenance packets and the data packets. 8. A method as claimed any of the preceding claims, wherein triggered by the call-accepted signal, the called terminal terminates transmission of the maintenance packets in response to recognizing the call accepted signal. 9. A method as claimed any of the preceding claims, wherein in response to the call-accepted signal by the called terminal a payload is transmitted for the communication in data packets via the direct payload connection or stopping a signaling of the call-accepted signal. 10. A method as claimed any of the preceding claims, wherein the calling terminal accepting the call- accepted signal of the called terminal without acknowledgement, or the calling terminal rejecting data arriving via a-second payload connection formed between the calling terminal and a second one of the connection controllers, the second payload connection formed such that data is transmittable between the calling terminal and the called terminal via the communication path defined by at least the first and second connection controllers. 11. A communication system for establishing communication in a packet-oriented communications network comprising: - a calling terminal; - a called terminal; - a plurality of connection controllers comprising a first connection controller and a second connection controller, the first connection controller having a first payload connection to the calling terminal and the second connection controller having a second payload connection to the called terminal, the first and second payload connections at least in part defining a communication path through which data for a communication is transmittable between the calling terminal and the called terminal; - the second connection controller sending a signalling message to the called terminal to establish the second payload connection, the signaling message comprising a parameter identifying an address of the calling terminal; - the called terminal receiving the signaling message from the second connection controller; - before generating a call-accepted signal, the called terminal establishing a direct payload connection between the called terminal and the calling terminal, the direct payload connection not including any of the connection controllers within a path of communication defined by the direct payload connection; and - data packets for the communication being sent via the direct payload connection between the called terminal and the calling terminal. 12. The communications system of claim 11, wherein the called terminal establishes a direct signaling connection between the calling terminal and the called terminal prior to sending the call-accepted signal, the direct signaling connection associated with the direct payload connection. 13. A communications terminal for establishing communication in a packet-oriented communications network, comprising: - a direct payload connection established between the terminal and a calling terminal in response to receiving a call set-up signaling message and prior to sending a call-accepted signal, the direct payload connection not including any connection controller within a path of communication between the terminal and the calling terminal defined by the direct payload connection; a communication between the terminal and the calling terminal via of the established direct payload connection triggered in response to the call-accepted signal; and a direct signaling connection between the calling terminal and the terminal prior to sending the call-accepted signal, the direct signaling connection associated with the direct payload connection.

Full Text

Description
In modern communications systems it is known to transmit
payload via packet-oriented networks. Payloads are, for
example, digitized voice data, with the term "Voice over IP",
or VoIP for short, being common for transmission of voice data
via packet-oriented networks. The use of packet-oriented data
transmission methods often results in losses in the quality of
the payload being transmitted and these are often caused by
conversions, delays or loss of payload packets in network
nodes.
Based on the often used, so-called internet protocol, also
abbreviated to IP, reference will be made hereinafter using
the term "IP terminal" to communication terminals that operate
on the basis of a packet-oriented transmission method.
In packet-oriented networks a connection between IP terminals
can conventionally be routed via network nodes, such as what
are known as routers, switches or gateways. In this connection
routers switch data between packet-oriented sub-networks,
while gateways can also provide a junction between different
types of 1 irie-switched and/or packet-oriented networks.
With a connection between two IP terminals the payloads may be
routed in particular via a plurality of gateways, it being
possible for each additional gateway in a transmission path of
the payloads to have an adverse effect on the payload quality
- i.e. for example a voice quality. Furthermore, a distinction
is often made with packet-oriented connections between
signaling connections and payload connections, it being
possible for signaling and payload connections between two IP
terminals to have different connection paths in the network.
To improve the voice quality IP terminals, which endorse the
ITU-T recommendation H.323 (ITU-T: International
Telecommunication Union - Telecommunications Standardizations
Sector) and what is referred to as the Direct Media Connection
(DMC), communication payloads can be transmitted directly
between the IP terminals while avoiding the gateways and
thereby avoiding additional conversions and delays. In some
cases it has continued to prove problematical that, with
conventional DMC methods, when switching through the payload
connection there is a delay before a definitive end-to-end
connection is produced between the IP terminals, so with voice
connections the start of a call is potentially not transmitted
to a conversation partner.
The object of the invention is to disclose a method in which
establishing of communication between two communication
terminals in a packet-oriented communications network is
improved. It is a further object of the invention to disclose
a communications system and a communications terminal for
carrying out the method.
This object is achieved by a method with the features of claim
I and by a communications system according to claim 11 and a
communications terminal according to claim 12.
Advantageous embodiments and developments of the invention are
disclosed in the dependent claims.
In the method ciccording to the invention, to establish
communication, in particular of media such as voice, video,
photos, fax or multimedia, in a packet-oriented communications
network between a calling and a called terminal, before a
call-accepted signal by the called terminal, triggered by a
message within the framework of call set-up signaling, a
direct, first payload connection is established between the
calling and the called terminal. This accordingly established,
first payload connection is maintained. As a direct result of
the call-accepted signal of the called terminal communication
is triggered between the calling and called terminals by means
of the established first payload connection.
In the method according to the invention it is particularly
advantageous that following initiation of a call set-up, the
direct, first payload connection is established even before
the call-accepted signal by the called terminal, so protracted
establishment of a payload connection only when there is a
call-accepted signal between the called and the calling
terminals can be omitted. Since the first payload connection
established for transmission of payload - for example a
djgitized and encoded voice - is on standby it may be ensured
that the payload can be transmitted simultaneous with the
call-accepted signal without there being any connection
delays. In particular the method according to the invention
can ensure that, by way of the called device, the supplied
communication can be processed without delay with the callaccepted
signal and can be transmitted to the calling terminal
via the first: payload connection already established, so the
calling terminal can reach all of the communication incoming
at the called terminal, without loss of an initial
communication portion in an otherwise conventional time slot:
between call-.accepted signal and switching-through of a
payload connection. A gap in transmission of this kind or an
excessive switch-through delay in payload transmission may
therefore be avoided.
When applying the invention to a voice connection via
telephone, immediately after the receiver of a called
telephone, as the called terminal, is picked up therefore, the
sounds arriving at the microphone are processed - i.e. are in
particular encoded - by the called telephone, as communication
according to the invention, and transmitted to a calling
telephone as the calling terminal via the payload connection
already maintained. An otherwise frequently occurring loss of
a voice portion immediately after the receiver has been picked
up is thereby avoided.
The call-accepted signal is in particular taken to mean
actions which bring about acceptance of the signaled call setup
signaling for switching through the payload connection.
With telephones this is in particular the action of taking up
a receiver or pressing of a key. Alternatively acceptance of
the incoming connection can be automatically triggered,
without manual intervention, in other terminals such as fax
machines.
A direct, first payload connection can be taken to mean a
connection between two terminals which consists in particular
in avoiding connection controllers such as gateways and/or
gate keepers, tri an advantageous embodiment of the invention
this is for example a direct media connection, in particular
according to Direct Media Connection (DMC) specifications. A
connection via network elements which only carry out
transportation of data at a low level of the OSI-reference
model (OSI: Open. Systems Interconnection) standardized by the
ISO (International Organization for Standardization) - for
example bridges, switches, routers, are'to be regarded as a
direct connection according to the invention. Depending on the
embodiment it may also be provided, in addition to the direct,
first payload connection, that an additional payload
connection routed via connection controllers is established
between the terminals.
In an advantageous development of the invention a connection
controller, in particular a gatekeeper and/or a gateway, can
be associated with the called and the calling terminals.
Connection controllers of this type are for example provided
to provide allocation of call numbers to IP addresses, with a
respective connection controller only managing the terminals
associated with it. The connection controllers may also be
involved in signaling and in particular in call set-up
signaling according to the invention. Within the framework of
call set-up signaling the connection controllers can be
involved in determining the codec (encoder/decoder) of the
terminals and connection controllers that is to be used, the
signaling path and the payload path in the communications
network, encoding and/or further transmission parameters for
the subsequent; payload connection. A call set-up signaling
path can run via a plurality of connection controllers as a
function of the network structure and grouping of the
terminal.
In a further advantageous development of the invention, before
the call-accepted signal by the called terminal, triggered by
a message within the framework of call set-up signaling, a
second payload connection can be established between the
called terminal and a connection controller - in particular a
connection controller involved in call set-up signaling. The
payload entering the calling terminal via the second payload
connection is preferably processed at the calling terminal if
there has been no call-accepted signal by the called terminal.
With voice connections of the calling terminal this second
payload connection can be used to transmit the ringing tone to
indicate a clear or busy signal as an audible representation
of the call status of the called terminal. The second payload
connection can moreover be used to transmit announcements,
option and/or input menus, generated by the connection
controller or a further network node, to the calling terminal.
In generalized terms and independently of the transmitted
media type for the payload communication the second payload
connection can be provided for transmission of additional
communication between a connection controller and the calling
terminal before the call-accepted signal by the called
terminal, it being possible for the additional communication
to be audio, video and/or multimedia information provided in a
call set-up state, i.e. during call set-up and before the
called terminal is answered, if generated by any desired
network node that is different from the calling device.
In an advantageous embodiment, before the call-accepted signal
between the calling terminal and the called terminal a direct
signaling connection associated with the first payload
connection can be established between the calling terminal and
the called terminal, in particular via the same data path in
the communications network as the first payload connection.
This can be established in addition to further signaling
actions running via connection controllers and can
advantageously be used for signaling for a direct connection
according to DMC (Direct Media Connection), the direct
signaling connection and the direct, first payload connection
representing the DMC connection after the call-accepted
signal.
According to a further advantageous development of the
invention, before the call-accepted signal by the called
terminal, measures for call clearing suppression can be
implemented by the calling terminal and/or the called
terminal. This can therefore advantageously prevent/the first
payload connection from being cleared, even before the callaccepted
signal owing to a conventional time allowance being
exceeded - for example a maximum period -of inactivity at a
connection -, and therefore no longer being available for
transmission of communication. In particular maintenance
messages or packets, triggered by the call set-up signaling
from the calling terminal to the called terminal, can be
transmitted from the called terminal via the first payload
connection to the calling terminal. A trigger time until a
connection is cleared is also called a connection "time out"
or is designated as the attainment of the maximum allowed
"idle" time. The maintenance packets can be called "dummy",
"keep alive" or "idle" packets and are transmitted by the
called and/or the calling terminal. The respective receiving
terminal can advantageously recognize on the basis of the
content of an incoming packet whether it is a maintenance
packet and in this case ignore or reject the contents. In an
advantageous embodiment of the invention the calling terminal,
induced by receipt of a maintenance packet, can transmit an
additional maintenance packet or an acknowledgement conforming
to protocol. The calling device can preferably transmit
maintenance packets to the called terminal via the first
payload connection provided only maintenance packets are
received by the calling terminal via the first payload
connection.
By recognizing a payload packet that differs from the
maintenance packets and/or a payload packet implicitly
indicating a call-accepted signal, owing to the start of a
transmission of communication contents, at the called
terminal, in an advantageous embodiment of the invention the
calling terminal can recognize and/or determine the'callaccepted
signal of the called terminal with the aid of
incoming payload packets via the first payload connection.
This preferably takes place via a signaling connection without
additional signaling, so advantageously only the first payload
connection has to be monitored without additional connections
of the calling terminal having to be observed. Since no
separate signaling of the call-accepted signal is required
existing protocols that are used do not need to be expanded
for the invention. Delays through to transmission of the first
payload packet to the calling terminal are also avoided, in
particular if transmission of.maintenance packets is
terminated by the called terminal when it recognizes the callaccepted
signal, and the pending payloads are transmitted
immediately - in particular without further delay or explicit
signaling - via the first payload connection.
Triggered by reception of a payload packet, indicating the
call-accepted signal, at the calling terminal via the first
payload connection, in an advantageous embodiment of the
invention the call-accepted signal of the called terminal can
be accepted by the calling terminal without acknowledgement by
the payloads received via the first payload connection being
processed in the calling terminal and being output at an
output unit and in response thereto a message that is
conventional in the connected state being transmitted to the
called terminal. The calling terminal can also reject payload
entering via the second payload connection and payload at the
calling terminal can accordingly be transmitted via the first
payload connection and no longer via the second payload
connection. There is thus a changeover at the calling terminal
from the second to the first payload connection without
explicit signaling messages for announcing or triggering this
changeover being sent or received via a signaling connection.
The above advantages, developments and embodiments apply
analogously to the communications system according to the
invention and to the communications terminal according to the
invention in addition to applying to the method according to
the invention.
An exemplary embodiment of the invention will be described in
more detail hereinafter with reference to the drawings, in
which schematically:
Fig. 1 shows a communications system and a message flow and
essential method steps within the framework of establishing
communication in the communications system, and
Fig. 2 shows a flow diagram of a calling and a called terminal
in the communications system for establishing communication.
Fig. 1A to 1C schematically show the components of a packetoriented
communications system. The components are, in
particular, a calling first terminal EG1, a called second
terminal EG2 and three connection controllers GW1, GW2 and
GW3. Said components are coupled via an IP network IPN as a
packet-oriented communications network according to the
invention, the messages and connections mentioned below being
based on IP-based concepts. The terminals EG1 and EG2 are IPbased
voice terminals and are visualized in figures 1A to 1C
as telephones. The connection controllers GW1, GW2, GW3 are
shown as rectangles and in the present exemplary embodiment
fulfill gateway and gatekeeper functionalities. This means in
particular that, owing to the gatekeeper functionality, the
respective terminals EG1, EG2 are allocated to a specific
connection controller and, furthermore, the respective
connection controller, owing to its gateway functionality,
allows a transition between sub-networks of the packetoriented
communications system and a transition to lineoriented
or other packet-oriented communications systems.
The communications system is configured in such a way that the
first terminal EG1 is registered with the first connection
controller GW1 and the second terminal EG2 with the second
connection controller GW2. The first connection controller GW1
can moreover route connections to the third connection
controller GW3 and this, owing to its configuration, can in
turn transmit messages and connections to the second
connection controller GW2 and to the first connection
controller GW1. The second connection controller GW2 is
configured in such a way that it can transmit messages to the
third connection controller GW3. Direct communication between
the first connection controller GW1 and the second connection
controller GW2 should be possible via the IP network IPN,
although it is assumed that the two connection controllers GW1
and GW2 are not reciprocally known, so a connection is in each
case made via an intermediate connection controller - the
third connection controller GW3 in this case.
IP addresses are allocated to all terminals and connection
controllers shown in figures 1A to 1C, with only the first IP
address IP1 associated with the first terminal EG1 and the
second IP address IP2 associated with the second terminal EG2
being shown. Furthermore the two terminals EG1 and EG2 have a
call number for addressing in the voice communications system,
only the call number RUN02 associated with the second terminal
EG2 being shown in Fig. 1.
Directed messages are shown in Fig. 1 as directed arrows with
arrow tip in the transmission direction and non-directed
messages and connections are shown in the figures as double
arrows. Signaling connections are shown in broken lines and
payload connections in solid lines.
Establishment of voice communication between the calling first
terminal EG1 and the called second terminal EG2 will be
described hereinafter with reference to Fig. 1. Initial
triggers in this connection are the lifting of the telephone
receiver and dialing of the call number RUNO2 at the first
terminal EG1. Triggered thereby between the first terminal EG1
and the first connection controller GW1 is a signaling
connection SIG for the purpose of setting up a call, within
the framework of which a signaling message MSIG is transmitted
from the first terminal EG1 to the first connection controller
GW1. In particular the target call number RUNO2 of the second
called terminal EG2 and the transmission IP address IP1 of the
first terminal EG1 are transmitted as the parameters. A
signaling message MSIG of this type could for example be a
setup message according to the ITU-T recommendation H.323
(ITU-T: : International Telecommunication Union -
Telecommunications Standardizations Sector) or an invite
message according to the SIP protocol (SIP: Session Initiation
Protocol) of the IETF workgroup (IETF: Internet Engineering
Task Force).
The first connection controller GW1 then checks whether a
terminal with the second call number RUN02 is registered with
it. It is not in the present embodiment.. The first connection
controller GW1 then routes the call set-up signaling to the
next configured routing node. This is the third connection
controller GW3 in the present embodiment. In turn a signaling
message MSIG is transmitted together with the target call
number RUNO2 and the transmission IP address IP1. In the
present exemplary embodiment the target call number RUN02 is
not registered with the third connection controller GW3
either. The third connection controller.GW3 then transmits a
query to further connection controllers and this includes in
particular a query to the second connection controller GW2
(Fig. 1A shows only the query to the second connection
controller GW2 by a signaling message MSIG) • A signaling
connection is therefore established between the third
connection controller GW3 and the second connection controller
GW2 via which a signaling message MSIG is transmitted with said
parameters.
The second connection controller GW2 checks the terminals
registered with it and recognizes that, associated with call
number RUNG2, the second device EG2 is registered with it. The
second connection controller GW2 determines the second IP
address IP2 of the second terminal EG2 with the aid of call
number RUNO2 arid internal configuration data. A signaling
message MSIG is then sent to this IP address IP2 with the IP
address IP1 of the first terminal EG1 as parameters. Signaling
SIG is therefore continuously established from the first
terminal EG1 via the connection controllers GW1, GW3 and GW2
to the second called terminal EG2. Fig. 1A does not show
acknowledgements within the framework of signaling SIG for
reasons of clarity. Owing to the incoming signaling SIG an
incoming call is visually or acoustically signaled to a user
of terminal EG2 at the second terminal EG2, in particular by
ringing of the phone. Fig. IB indicates -this by a star next to
the telephone receiver of the second terminal EG2.
A first payload connection Nl between the calling first
terminal EG1 and the - from the perspective of the first
terminal EG1 - last, gateway in the chain of signaling SIG,
i.e. the second connection controller GW2, and a payload
connection N2 between the second connection controller GW2 and
the called terminal EG2 will be established hereinafter. Both
payload connections are active, and this is indicated in the
drawings by a subscripted "A". The payload connection Nl as
the second payload connection according to the invention is
used in particular in this connection to generate and transmit
to the first terminal EG1 the ringing tone in the receiver, so
a user at the first terminal EG1 recognizes that the call
request has been signaled through to the second terminal EG2.
The payload connection Ni can, moreover, be used to transmit
automatic announcements, to provide call centre option menus -
for example by IVR systems (IVR: Interactive Voice Response),
voice and/or key actions carried out at the first terminal EG1
being transmitted to the connection controller GW2 via the
payload connection Nl.
Also triggered by the signaling message MSiG entering within
the framework of call set-up signaling at the called second
terminal EG2, even before the call-accepted signal by the
called terminal EG2, is the establishment of a direct
signaling connection SIGD and a direct payload connection ND
as the first payload connection according to the invention, in
each case as a direction connection to the first terminal EG1.
A direct connection in this connection is a connection which
is not routed via the connection controllers GW1, GW2, GW3, it
being possible however to provide known network nodes such as
routers, switches, bridges and firewalls., in the transmission
path of the direct connections SIGD, ND for packet-oriented
transmission if they do not carry out any kind of voice
conversions or other time-consuming processing operations of
data packets of the connections SIGD, ND. The direct
connection is established in this case with the aid of the
first IP address IP1 transferred to the second terminal EG2,
network address conversions between various sub-networks being
ignored in the present exemplary embodiment. The direct
connection may also be established by depending on or using
known DMC method steps for direct media communication.
The established connections SIGD, ND are maintained for
subsequent, rapid switching-through of the communication
between the second terminal EG2 and the first terminal EG1
after the call has been accepted by the second terminal EG2.
Time-consuming connection establishment steps, such as the
exchange of codes and/or certificates for secured, subsequent
communication, are carried out as early as when the signaling
connection SIGD and the direct payload connection ND are
established. The first terminal EG1 is actively involved in
the direct establishment of the signaling connection SIGD and
payload connection ND, data transmission via the connections
SIG and Nl already established not being affected thereby.
Maintenance packets IDLE conforming to protocol will be
transmitted hereinafter between the called second terminal EG2
and the calling terminal EG1 via the direct payload connection
ND, so the direct payload connection ND, despite apparent
inactivity, is not automatically cleared but is maintained.
The calling first: terminal EG1 is accordingly configured in
such a way that, while it manages the payload connection Nl it
analyses incoming data packets via the direct payload
connection ND. The incoming data packets are analyzed in this
connection such that the first terminal EG1, with the aid of
the incoming packets, recognizes whether the incoming data
packets are still maintenance packets IDLE for call clearing
suppression or are already valid payload packets following a
call-accepted signal by the second terminal EG2.
Reception of maintenance packets IDLE in the first terminal
EG1 means that the received maintenance-packets IDLE are
ignored and/or maintenance packets IDLE are also transmitted
via the direct payload connection ND to the called terminal
EG2. A call-accepted signal by the called terminal EG2 would,
moreover, be recognized at the first calling terminal EG1 by a
data packet, which differs from a maintenance message or a
maintenance packet IDLE, arriving via the direct payload
connection ND, This is described in more detail hereinafter
with reference to Fig. 1C.
Lifting of the telephone receiver of the second terminal EG2,
indicated in Fig. 1C, causes acceptance of the call by the
second terminal EG2. As a direct result of this call-accepted
signal at the second terminal EG2 the communication pending at
the microphone of the telephone receiver of the second
terminal EG2 is processed in the second terminal EG2. Without
explicit signaling via one of the signaling connections SIG or
SIGD - wherein explicit signaling of the call-accepted signals
by means of SIG and/or SIGD may also be provided in
alternative embodiments to communicate the call-accepted
signal of the second terminal EG2 even if the microphone of
the first terminal EG1 is muted, or to ensure correct
detection for determining call charges - the incoming
communication is digitized by the second terminal EG2 and
transmitted via the direct payload connection ND to the
calling first terminal EGl, with transmission of maintenance
packets IDLE to the second terminal EG2 being terminated. The
arrival of a payload packet of this type, which differs from
maintenance packets IDLE, at the calling first terminal EGl
means that the call-accepted signal of the second terminal is
recognized by the first. This call-accepted signal Is,
moreover, implicitly accepted, i.e. without transmission of an
acknowledgement or confirmation, by the first terminal EGl in
that the payload incoming via the direct- payload connection ND
is processed immediately - without any further signaling -,
and is output via the associated telephone receiver of the
first terminal EGl. The payload connection Nl between the
calling terminal EGl and the second connection controller GW2
is furthermore switched so as to be inactive in that no
further packets that differ from maintenance packets IDLE are
transmitted by the calling terminal EGl via this connection.
Sounds and/or speech received via the telephone receiver of
the first terminal EGl are no longer transmitted via the
payload connection Nl from this point in time either but via
the direct payload connection ND, without additional signaling
having been carried out. Payload packets entering via the
payload connection Nl are rejected by the first terminal EGl.
Rapid switching-through of a communication is thus possible
via a direct payload connection ND. A loss of payload packets
or a communication at a telephone receiver can thus be
avoided. This is particularly advantageous if the second
terminal EG2 is a device for automatic announcements or is a
fax machine or modem. The latter devices conventionally have
the property of transmitting payloads very quickly after
signaled call acceptance, so logs of these payloads would have
an adverse effect. In particular the loss of fax or modem
payloads could prevent connection establishment or make it
impossible. This may be prevented by the, presented method
because directly after the call-accepted signal the pending
communication is transmitted without losses and without delay
to the calling terminal EG1.
The existing payload connections Nl and N2 and the signaling
connections SIG which run via the connection controllers GW1,
GW2, GW3, can continue to be maintained or alternatively (not
shown) be cleared within the framework -of further signaling
messages. If these connections are not cleared it is provided
in the case of both terminals EG1 and EG2 that packets
entering via these connections are ignored.
The terminals EG1, EG2 shown in Fig. 1 and the illustrated
communications system structure should be regarded merely as
examples in this connection. A generalization compared with
any desired terminals and any desired topology as well as any
desired communications protocol is easily possible without
limiting the disclosure of the invention.
Fig. 2 will hereinafter describe a respective state
transmission diagram for the calling terminal EG1 and the
called terminal EG2 according to the method steps illustrated
with reference to Fig. 1. The state transitions are described,
with reference to their course over time, jointly for the
calling and the called terminal EG1, EG2, respective state
transition diagrams being shown separately from each other for
the calling terminal EG1 in Fig. 2A and for the called
terminal EG2 in Fig. 2B. The starting situation for the
calling terminal EG1 is a rest state 0EG1 and likewise a rest
state 0EG1 for the called terminal EG2.
Triggered by dialing of the call number RUNO2 at the first
terminal EG1, the first terminal EG1 changes into an
initialization state for the connection to be established
(state 1EG1) . Triggered as a result, a signaling message Ml is
transmitted to the called terminal EG2 . The transmission takes
place in particular via a plurality of connection controllers,
with these not being shown in Fig. 2. Receipt of the signaling
message Ml causes the called terminal EG2 to leave its rest
state and to change into the state 1EG2 in which steps are
carried out which are executed in the case of an incoming
connection request. In state 2EG2 the called terminal EG2
transmits a response belonging to message Ml via the same
signaling path with the aid of signaling message M2. The
calling terminal EG1 then changes its state to the state 2EGi
which establishes a payload connection to a connection
controller involved in message traffic. The called terminal
EG2 passes immediately from state 2EG2 to state 3EG2 in that an
additional direct signaling and payload connection is
established. For this purpose a signaling message M3 is
transmitted to the calling terminal EG1 and first packets via
the direct payload connection (hereinafter designated "ND"
according to the designation in Fig. 1).
In a modification of the method the first terminal EG1 could
also initiate the direct payload connection ND. This is
especially possible if an IP address of the second terminal
EG2 is transmitted as a parameter of the signaling message M2.
Triggered by reception of this signaling message M3, the
calling terminal EG1 changes its state (new state 3EG1) and
accepts the incoming direct connections - the direct signaling
connection SIGD and the direct payload connection ND - from
the called terminal EG2. The calling terminal EG1 also
immediately changes to state 4Eca in which incoming packets,
which arrive via the direct payload connection ND at the
calling terminal EG1, are analyzed. The called terminal EG2
changes owing to timer expiry from the state 3EG2 to the state
4EG2 and in this state sends a maintenance packet as a payload
packet PIDLE with only "dummy" content to the calling terminal
EG1 via the direct payload connection ND.
In the still active state 4Eci the calling terminal EG1
analyses this incoming payload packet. If it is a maintenance
packet the calling terminal EG1 changes to state 5EG1 and as a
result causes the direct payload connection ND to continue not
to be activated, and instead maintenance payload packets PIDLE
are transmitted via the direct payload connection ND, starting
from the calling terminal EG1. With renewed timer expiry at
the called terminal EG2 this procedure is repeated again, so a
maintenance payload packet PIDLE is transmitted again to the
calling terminal EG1 and is analyzed therein analogously to
the above-mentioned steps. This process is repeated until
either the calling terminal EG1 terminates its call set-up
request, until there is a call-accepted signal at the called
terminal EG2 - in particular by lifting of a telephone
receiver - or until one of the connection contx'ollers involved
initiates termination of the connection.
Triggered by a call-accepted signal of this type, the called
terminal EG2 changes from the state 4EG2 to state 5EG2 - In this
state pending communication data is converted directly into
payload and transmitted via the direct payload connection ND
to the calling terminal EG1 by means of filled payload packets
PNUTZ • Sending of: filled payload packets PNUTZ is continued until
the call is terminated in a known manner - for example by
replacing the receiver. Before arrival of the first filled
payload packet Ptnnz the calling terminal ,EG1 is still in the
state 4EG1 in which incoming payload packets are analyzed via
the direct payload connection ND. If a filled payload packet
PNUTZ accordingly reaches the calling terminal EG1, this
recognizes the receipt of a valid payload packet PNUTZ that
describes a call-accepted signal and changes to state 6EG1 in
which the connection, and therefore the communication to be
transmitted, is switched through to the input/output device
(i.e. the telephone receiver) of the calling device EG1. In
this state the calling terminal EG1 processes incoming payload
packets PNUTZ which arrive via the direct payload connection ND
and sends its own payload packets to the called terminal EG2
via this direct payload connection ND.
Both terminals EG1, EG2 can therefore change over into a
connected state - states 7EG1 or 6EG2 - in which a payload
stream NDS of payload packets is exchanged via the direct
payload connection ND. Further steps, such as execution of
specific features or, subsequently, call clearing, are
accordingly possible. These steps are not described in more
detail in the illustrated figures 2A and 2B, however.
The states shown in Fig. 2 illustrate a largely simplified
depiction of a connection establishment according to the
invention. For example communication between a connection
controller and the first terminal EG1 has been omitted for
reasons of clarity. Observation of this connection would
therefore have led to payload packets arriving at the first
terminal EG1 being rejected by a connection controller in
state SEGI - In states 2EG1 to 5EG1 on the other hand incoming
payload packets would be processed by a connection controller
via the first terminal EG1.
The method steps shown with reference to figures 1 and 2 are
advantageous insofar as the method allows rapid and loss-free
changeover between an existing payload connection and an
already established, but not yet active payload connection.
This is particularly advantageous if, owing to time-consuming
and complex call set-up methods a connection establishment of
a payload connection is completed comparatively slowly, so
without employing the invention recommended maximum switchthrough
delays - for example 250 ms maximum delay -
recommended by the ITU-T, cannot be observed.
It is also advantageous that integration in existing
implementations of protocols and transmission methods is
easily possible since only minor modifications are necessary.
Known methods may also be used for signaling and the payload
connection. These are, in particular, method steps according
to H.323, SIP, a transmission of payload packets according to
RTF (Real-time Transport Protocol) and/or other standards or
implementations. The method can advantageously be applied to
all IP-based communications systems which are provided for
real-time-critical transmission of flows of media - for
example within the framework of Voice-over-IP or Multimediaover-
IP. Although in the present exemplary embodiment only
packet-based connections are used, individual signaling
portions between the connection controllers for example can
also be carried out by line-based communication segments.

We Claim:
1. A method for establishing a communication in a packet-oriented communications network (IPN) between a calling (EG1) and a called terminal (EG2) , comprising a plurality of connection controllers for connecting the calling terminal to the called terminal, provided with a first connection controller and a second connection controller, comprising the following steps-
- initiating a sending of a signaling message from the first connection controller of the calling terminal to the called terminal to establish a first payload connection between the called terminal and the first connection controller such that data is transmittable between the calling terminal and the called terminal via a communication path defined by at least the first and second connection controllers;
- sending the signaling message comprising a parameter identifying an address of the calling terminal by the first controller to the called terminal;
- receiving the signaling message from the first connection controller;
- establishing a direct payload connection not including any connection controller within a path of communication defined by the direct payload connection between the called terminal and the calling terminal, before generating a call-accepted signal
- communicating between the calling (EG1) and called
terminal (EG2) by means of the established direct,
first payload connection (ND) as a direct result of the call-accepted signal.
2. A method as claimed in claim 1, wherein
- a direct signaling connection associated with the direct payload connection is established between the calling terminal and the called terminal prior to sending the call-accepted signal,
- maintenance packets are transmitted between the called terminal and the calling terminal to maintain the direct payload connection prior to the transmitting of data packets between the calling terminal and the called terminal; and
- data packets are transmitted between the calling terminal and the called terminal enabling the direct payload connection to be in an active state
3. A method as claimed in claim 1, wherein before the
call-accepted signal by the called terminal (EG2),
triggered by a message (MSIG) within the framework of
call set-up signaling (SIG), a second payload
connection (Nl) is established between the called
terminal (EG1) and a connection controller (GW2).
A. A method as claimed in claim 1, wherein the called terminal implements a call clearing suppression prior to transmitting the call-accepted signal.
5. A method as claimed in claim 1, wherein the call clearing suppression is configured such 'that maintenance packets are transmitted between the calling and the called terminal.
6. A method as claimed in claim 1, wherein the calling terminal recognizes the call-accepted signal of the called terminal by a first reception of data packets comprising contents of the communication via the direct payload connection.
7. A method as claimed any of the preceding claims, wherein the calling terminal checks, until the call-accepted signal of the called terminal is recognized at the calling terminal, whether a packet entering via the direct payload connection is one of the maintenance packets and the data packets.
8. A method as claimed any of the preceding claims, wherein triggered by the call-accepted signal, the called terminal terminates transmission of the maintenance packets in response to recognizing the call accepted signal.
9. A method as claimed any of the preceding claims, wherein in response to the call-accepted signal by the called terminal a payload is transmitted for the communication in data packets via the direct payload connection or stopping a signaling of the call-accepted signal.
10. A method as claimed any of the preceding claims, wherein
the calling terminal accepting the call-
accepted signal of the called terminal without acknowledgement, or
the calling terminal rejecting data arriving via a-second payload connection formed between the calling terminal and a second one of the connection controllers, the second payload connection formed such that data is transmittable between the calling terminal and the called terminal via the communication path defined by at least the first and second connection controllers.
11. A communication system for establishing communication in a packet-oriented communications network comprising:
- a calling terminal;
- a called terminal;
- a plurality of connection controllers comprising a first connection controller and a second connection controller, the first connection controller having a first payload connection to the calling terminal and the second connection controller having a second payload connection to the called terminal, the first and second payload connections at least in part defining a communication path through which data for a communication is transmittable between the calling terminal and the called terminal;
- the second connection controller sending a signalling message to the called terminal to establish the second payload connection, the signaling message comprising a parameter identifying an address of the calling terminal;
- the called terminal receiving the signaling message from the second connection controller;
- before generating a call-accepted signal, the called terminal establishing a direct payload connection between the called terminal and the calling terminal, the direct payload connection not including any of the connection controllers within a path of communication defined by the direct payload connection; and
- data packets for the communication being sent via the direct payload connection between the called terminal and the calling terminal.

12. The communications system of claim 11, wherein the called terminal establishes a direct signaling connection between the calling terminal and the called terminal prior to sending the call-accepted signal, the direct signaling connection associated with the direct payload connection.
13. A communications terminal for establishing communication in a packet-oriented communications network, comprising:
- a direct payload connection established between the
terminal and a calling terminal in response to
receiving a call set-up signaling message and prior
to sending a call-accepted signal, the direct payload
connection not including any connection controller
within a path of communication between the terminal
and the calling terminal defined by the direct
payload connection;
a communication between the terminal and the calling terminal via of the established direct payload connection triggered in response to the call-accepted signal; and a direct signaling connection between the calling terminal and the terminal prior to sending the call-accepted signal, the direct signaling connection associated with the direct payload connection.

Documents:

740-del-2007-abstract.pdf

740-del-2007-Assignment-(15-11-2012).pdf

740-DEL-2007-Claims-(08-05-2012).pdf

740-del-2007-claims.pdf

740-del-2007-Correspondence Others-(05-07-2013).pdf

740-DEL-2007-Correspondence Others-(08-05-2012).pdf

740-DEL-2007-Correspondence Others-(09-07-2012).pdf

740-del-2007-Correspondence Others-(15-11-2012).pdf

740-del-2007-correspondence-others 1.pdf

740-del-2007-correspondence-others.pdf

740-del-2007-description (complete).pdf

740-del-2007-Drawings-(05-07-2013).pdf

740-del-2007-drawings.pdf

740-del-2007-Form-1-(05-07-2013).pdf

740-del-2007-form-1.pdf

740-del-2007-form-18.pdf

740-del-2007-Form-2-(05-07-2013).pdf

740-del-2007-form-2.pdf

740-del-2007-Form-3-(05-07-2013).pdf

740-DEL-2007-Form-3-(08-05-2012).pdf

740-del-2007-form-3.pdf

740-DEL-2007-Form-5-(05-07-2013).pdf

740-del-2007-form-5.pdf

740-del-2007-GPA-(05-07-2013).pdf

740-DEL-2007-GPA-(08-05-2012).pdf

740-DEL-2007-GPA-(09-07-2012).pdf

740-del-2007-GPA-(15-11-2012).pdf

740-del-2007-gpa.pdf

740-DEL-2007-Petition-137-(08-05-2012).pdf

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Patent Number

256860

Indian Patent Application Number

740/DEL/2007

PG Journal Number

32/2013

Publication Date

09-Aug-2013

Grant Date

05-Aug-2013

Date of Filing

02-Apr-2007

Name of Patentee

SIEMENS ENTERPRISE COMMUNICATIONS GMBH & CO. KG

Applicant Address

HOFMANNSTRASSE 51, 81379 MUNCHEN, GERMANY

Inventors:

#	Inventor's Name	Inventor's Address
1	KENNEDY;STEPHEN	EGELSEESTR. 10,86949, WINDACH, GERMANY
2	STACH; THOMAS	HERMESSTR.199, 1130, WIEN, AUSTRIA

PCT International Classification Number

H04Q7/20

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	EP06008955	2006-04-28	EUROPEAN UNION