CN101803332B - Method for setting up a call in a communication network - Google Patents

Abstract

A method for establishing a call in a communications network by selecting a media gateway to be used for the call is disclosed. The media gateway is in a user plane, and the method includes a negotiation process provided by at least the following steps: a first call control node in a control plane sends a message to a second call control node in the control plane identifying a list of at least two media gateways considered suitable for the call to be established. A call control node and a computer program are also disclosed.

Description

Method for setting up a call in a communication network

technical field

The invention relates to a method for setting up a call in a communication network. It also relates to a call control node configured to participate in setting up a call in a communication network, and to a computer program comprising instructions configured to, when executed on a call control node, cause the call control node to execute a The method by which calls are established in the network.

Background technique

In a communication network, such as a telecommunications network, a call usually involves a control or signaling plane on the one hand and a user plane on the other hand. The control or signaling plane is responsible for establishing and managing the connection between two points on the network. The user plane is responsible for transmitting user data.

Setting up a call on the user plane involves selecting a node called a Media Gateway (MG or MGW) through which data will be routed or exchanged. The media gateway is a node on the user plane. The selection of a media gateway is performed by a node called a Call Control Node (CCN). The call control node is on the control plane. Call Control Nodes act as Media Gateway Controllers (MGC) in that they control which media gateways are used for calls. The Media Gateway is responsible for exchanging user plane data and providing in-band facilities if required.

An exemplary communication network including a call control node and a media gateway is 3GPPTS 23.205 V7.5.0 (2007-06), 3rd Generation Partnership Project, Technical Specification Group Core Network and Terminals, Bearer - independent circuit-switched core network, a bearer-independent circuit switched (CS) core network described in Stage 2 (Release 7) (available from 3GPP, Sophia Antipolis, France). The core network of Ref. [1] uses on the one hand Media Switching Center (MSC) servers, both called call control nodes (eg described in Ref. [1] section 5.1.1.1) and (eg in Ref. [1] described in section 5.1.1.2) Gateway Media Switching Center (GMSC) server and on the other hand use a media gateway (eg described in reference [1] section 5.1.1.3). The GMSC server and MSC server provide call control and mobility management functions, and the media gateway provides bearer control and transport resource functions. A media gateway may include stream manipulation functionality and may perform media conversion and framing protocol conversion.

Other exemplary call control nodes include transit switching centers (TSCs) and media gateway control functions (MGCFs). Exemplary in-band devices (eg, media handling devices) of a media gateway include transcoder devices, echo cancellers, or tone and announce devices.

Several call control nodes may be involved in setting up a call. Call setup information can be signaled between call control nodes using a call control protocol such as ISUP (ISDN User Part or Integrated Services Digital Network User Part), BICC (Bearer Independent Call Control) or SIP (Session Initiation Protocol). In the case that a call control node selects a media gateway, a call control protocol may be provided such that the call control node sends the identifier of the selected media gateway to another call control node (see for example reference [1] section 6.1.1.1 , where MGW selection may be based on MGW-ids likely to be received from subsequent nodes). The other call control nodes then have the opportunity to select the same media gateway for user plane switching. The choice of a media gateway has an impact on node and resource utilization in the communication network.

Therefore, it is desirable to provide methods and call control nodes that solve or partially solve the above-mentioned problem of selecting a media gateway in order to optimize resource utilization.

Contents of the invention

Such a method and call control node are defined in the independent claims. Advantageous embodiments are defined in the dependent claims.

In one embodiment, the method is to set up a call in a communication network by selecting a media gateway to be used for the call. The media gateway is in the user plane. The method comprises at least a negotiation process provided by the steps in which a first call control node in the control plane sends an identification to a second call control node in the control plane which is considered eligible for A message with a list of at least two media gateways for a call to be established.

In this embodiment, the first call control node sends information to the second call control node about which media gateways the first call control node was able to successfully select to establish a call in the communication network. Rather than having the second call control node select among all the media gateways a media gateway that the second call control node can use to set up the call, the second call control node receives from the first call control node the media gateway from which to select. A list of gateways. The method adds constraints to media gateway selection on the side of the second call control node. In this case it helps to select an appropriate media gateway which can normally be used by both the first and the second call control node if possible.

Such selection of a common media gateway for the call to be established enables an efficient use of network resources, since the second call control node receives a priori information about the capabilities of the first call control node.

A communication network may here be any network used for data communication, for example a core network in a mobile communication network, or a fixed telephone communication network. A media gateway constitutes a node through which data packets or flows are routed or switched. In one embodiment, the communication network is a circuit switched core network, a bearer independent circuit switched core network, a packet switched core network, a circuit switched core network for ATM and/or IP transport, a circuit in a GSM and/UMTS environment Switched core network and any of the circuit switched core networks described in reference [1].

The control plane is the protocol and the set of protocols and mechanisms and, by extension, the network nodes implementing these mechanisms for establishing and managing connections, eg for providing mobility management.

The user plane is the protocol and the set of protocols and mechanisms and, by extension, the network nodes for transporting user data that implement these mechanisms. In one embodiment, the user plane implements bearer functions, such as providing bearer control and transmission resource functions.

A call is a connection between at least two parties, such as a calling party and a called party. The connection may be established to transmit voice, data, voice frames, or any other type of data.

The call control node may be a server computer configured to perform functions related to the establishment and management of media gateway nodes in the user plane. The call control node may comprise a processor, a memory unit, and software arranged to execute on the call control node to enable it to perform its functions. In one embodiment, each of the first and second call control nodes is any one of a media switching center server, a gateway media switching center server and a media gateway control function (MGCF).

The media gateway may be a server computer configured at least to perform transmission of user data on the user plane. The media gateway may comprise a processing unit, a memory unit and software configured to execute on the media gateway to enable it to perform its functions.

In one embodiment, a media gateway is considered suitable for a call to be established by the call control node if the call control node knows about the media gateway and is able to command the media gateway to function in the call to be established.

In one embodiment, the message identifying the list contains an identifier of the list, wherein the list itself is stored at a location accessible by the call control node. In one embodiment, the message identifying the list contains the identifiers of the media gateways in the list. These two embodiments are not exclusive and may be combined. In other words, the message may contain an unambiguous identifier of at least one media gateway and an identifier of a list stored outside the message, so that the message identifies a list of at least two media gateways as a result.

This method realizes media gateway negotiation (namely, common media gateway negotiation) between call control nodes, for example, forwarding bearer establishment is applied therein. Forwarding bearer establishment is a setup where a bearer is established on the user plane in the same direction as the call (ie from calling party to called party). The selection of a common media gateway node improves resource utilization in the network. The method can be applied to existing protocols, such as standard BICC or SIP protocols, without any impact on them.

In one embodiment, the first call control node sends a message identifying the list of at least two media gateways to the second call control node in forward direction. The forward direction is the direction in which the call connection is established.

By sending a message identifying the list in the forward direction (ie, from the calling party to the called party), efficient utilization of network resources is provided when setting up the call. The messages used in existing protocols for establishing connections and sent in the forward direction may be used to send the list or an identifier identifying the list.

In one embodiment, the negotiation process is further provided with steps in which the second call control node receives a message from the first call control node. The second call control node then removes media gateways that the second call control node cannot select for the call from the list identified by the received message. The second call control node then selects from the list a media gateway to be used for the call to be established and sends a message identifying the selected media gateway to the first call control node.

In this embodiment, the second call control node takes into account the constraints applicable to the first call control node. This is done by taking into account the list of media gateways which the first call control node considers suitable for the call to be established. The second call control node also takes into account its own constraints. This is done by removing from the list identified by the received message the media gateways that the second node cannot select for the call.

The second call control node, after taking into account the constraints of the first call control node as well as its own constraints, selects from the list, if possible, the media gateway to be used for the call to be established. It then sends a message identifying the selected media gateway back to the first call control node. The first call control node can then select the same media gateway for the call to be established, ie the media gateway that has been agreed upon by the first and second call control node.

This embodiment provides an efficient implementation for minimizing the number of media gateways used for a call, so that network resources are used efficiently.

In this embodiment, the second call control node removes the media gateway that the second call control node cannot select for the call from the list identified by the received message, and selects from the list to be used for the call to be established media gateway. However, such a removal step may result in an empty list. If so, it is not possible to select from this list. However, the process can continue as follows. The second call control node selects a media gateway according to its local constraints and sends a message identifying the selected media gateway to the first call control node. The first call control node recognizes that the selected media gateway does not belong to the originally transmitted list and selects a media gateway from the originally transmitted list. This situation does not cause the first and second node to use a common media gateway.

In one embodiment, the negotiation process is provided with steps in which the first call control node receives a message identifying the selected media gateway. Upon receipt of said message, said first call control node completes or attempts to complete the call to be established using the selected media gateway identifier in the received message. This provides efficient utilization of network resources. Using eg the teachings of reference [1], a person skilled in the art will understand how to use a Media Gateway Identifier to complete or attempt to complete a call.

In one embodiment, the negotiation process is further provided with the steps in which the third call control node receives a message sent by the first call control node to the second call control node. This third call control node is therefore called an intermediate call control node. As mentioned above, this message identifies a list of at least two media gateways that the first call control node considers suitable for the call to be established. Upon receipt of this message, said third call control node removes from the list identified by the received message the media gateways which it cannot select for the call. It then forwards to the second call control node a message identifying this list, ie a message identifying a possibly modified list from which media gateways that the third call control node cannot select for the call have been removed. In other words, the list identified in the message forwarded from the third node to the second node is the list of media gateways that the first and third nodes together consider to be suitable for the call to be established.

This embodiment further enables to take into account the constraints of the intermediate call control node (ie the third call control node) when selecting the media gateway for the call to be established.

The processing of the third call control node may produce an unmodified list that is kept as received (as received) (in the case that all media gateways of the list are considered suitable by the third call control node), produce a list that is kept in modified form but is not empty A modified list of (in case the third call control node considers some media gateways to be suitable and other media gateways are not suitable), or an empty list (in case all media gateways are considered to be unsuitable). In case of the third case (obtaining an empty list), the following can happen. The third call control node may create a new list and start a new media gateway negotiation to a subsequent call control node (eg to the second call control node). In this case, the list identified in the message forwarded from the third node to the second node is not a list of media gateways that the first and third nodes consider together to be suitable for the call to be established, but is only used by the second node A list of media gateways that the three peers consider suitable. Alternatively (still in the third case), the third call control node may select a media gateway according to its local constraints, and send a message to the second call control node identifying the selected media gateway as being to be used by the third and the proposed common media gateway used by the second call control node. In another alternative (still in the third case), the third call control node may request the second call control node to select a media gateway according to its local constraints and send a message identifying the selected media gateway as the Messages of the proposed common media gateway used by the third and second call control nodes.

This embodiment is applied to an intermediate call control node capable of controlling media gateways. Signaling plane nodes that do not control media gateways (eg call mediation nodes) should not participate in media gateway negotiations, should not interfere with the negotiations, and should only forward messages without removing entries from the list.

In one embodiment, the negotiation process is further provided with steps in which the third call control node receives a message identifying the selected media gateway from the second call control node. The third call control node then selects the media gateway identified in the received message as the media gateway to be used for the call to be established. The third call control node then forwards a message identifying the selected media gateway to the first call control node.

This embodiment enables to order the intermediate call control node to use the media gateway selected by the second call control node.

The invention also relates to a method performed by each call control node in the control plane to participate in setting up a call in a communication network by selecting a media gateway to be used for the call. That is, the invention relates to a method performed by the first call control node initially sending a message identifying a list of at least two media gateways considered suitable for the call to be established. The method also relates to a method in which the second call control node receives a message identifying a list of at least two media gateways considered suitable by the first call control node for the call to be established; a media gateway for the call to be established; and sending a message identifying the selected media gateway back to the first call control node. The invention also relates to a method performed by forwarding, by a third call control node (i.e. an intermediate call control node), a message identifying the above-mentioned list in the direction of the second call control node, or in the direction of the first call control node The message identifying the selected media gateway is forwarded.

The invention also relates to the call control node itself configured to operate in the operation of the method described above. The invention also relates to a computer program comprising instructions configured to, when executed on a call control node, cause the call control node to perform any one of the methods described above or a part thereof.

Description of drawings

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figures 1 and 2 schematically illustrate two exemplary call setup scenarios to help understand some of the problems addressed by the present invention;

Figures 3a and 3b respectively illustrate a method and a network configuration according to an embodiment of the present invention, wherein a first call control node sends a message to a second call control node during the process of establishing a call within the communication network;

Figures 4a and 4b illustrate respectively a method and a network configuration according to an embodiment of the present invention, wherein a first call control node sends a message to a second call control node which receives the message, processes the message and sending a message back to said first call control node;

Figures 5a and 5b respectively illustrate a method and a network configuration according to an embodiment of the present invention, wherein a first call control node sends a message to a second call control node which receives the message, processes the message and sending a message back to said first call control node, which then receives the message and completes or attempts to complete the call;

Figures 6a and 6b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention, wherein a first call control node and an intermediate call control node participate in setting up a call in a communication network;

Figures 7a and 7b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention, wherein first, second and third call control nodes participate in setting up a call in a communication network;

Figures 8a and 8b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention, wherein first, intermediate and second call control nodes participate in setting up a call in a communication network;

Figure 9 illustrates three call control nodes participating in setting up a call in a communication network according to one embodiment of the present invention; and

Figures 10a, 10b, 11, 12a and 12b illustrate a call control node according to an embodiment of the invention.

detailed description

The invention will now be described with reference to specific embodiments. It is noted that three specific examples are provided to provide a good understanding to those skilled in the art, but are not intended to limit the scope of the invention in any way, which is defined by the appended claims.

Figure 1 schematically represents an exemplary call setup scenario to help understand some of the problems underlying the present invention.

The illustrated scenario applies to a telephone call (mobile or fixed), or more generally to a telecommunications connection, and uses a forwarding bearer setup procedure. Here, a bearer from the calling party to the called party is established. On the left hand side of the diagram, the originating radio access network (RAN, eg GERAN for GSMEDGE radio access network) is illustrated (calling party ie calling party side). On the right-hand side of the diagram, the (called party ie called party side) remote radio access network (RAN, eg GERAN) is illustrated.

The previous call control node CNN-1 and the subsequent call control node CNN-2 are part of the control plane, and each controls a media gateway node (respectively media gateway node MG-1 and media gateway node MG-2) to use exchanged at the user plane. To achieve forwarding bearer setup, the subsequent call control node CCN-2 first selects a media gateway (MG) and then sends the media gateway identifier and bearer address information back to the previous call control node CNN-1. The previous call control node CNN-1 then selects a media gateway and initiates the bearer setup procedure.

More particularly, Fig. 1 illustrates the principles behind the establishment of forwarding bearers using the BICC protocol as an exemplary call control protocol, to help understand some of the potential problems of the present invention. The steps leading to the establishment of a call are as follows:

(1) An Initial Addressing Message (IAM) is sent from the previous call control node CNN-1 to the subsequent call control node CNN-2 to provide call setup information. This step is illustrated by the arrow associated with the encircled reference number 1 and the notation "IAM<>".

(2) Then the call control node CNN-2 selects the media gateway node (here, the media gateway node MG-2), and occupies the media gateway resources for connecting the endpoints. This step is illustrated by the arrow associated with the encircled reference number 2 and the label "Select MG resource".

(3) Reversely send the identifier of the media gateway MG-2 (ie BCU-ID2) from the subsequent call control node CCN-2 to the previous call control node CCN-1. This step is illustrated by the arrow associated with the encircled reference number 3 and the label "APM(BCU-ID2)".

(4) The previous call control node CCN-1 selects the media gateway node MG-1, and occupies the media gateway resource for connecting the endpoints. This step is illustrated by the arrow associated with the encircled reference number 4 and the label "Select MG resource".

(5) The previous call control node CCN-1 triggers the start of the bearer establishment process through the media gateway MG-1. This step is illustrated by the arrow associated with the encircled reference number 5 and the label "Establishment of bearer in forward direction". When the Internet Protocol (IP) is used as the user plane transport protocol and BICC is used as the call control protocol, the bearer setup message is tunneled via the call control nodes CCN-1 and CCN-2 (not shown in Figure 1 Show).

In fact, it frequently happens that the subsequent call control node CCN-2 has the opportunity to select from multiple sets of media gateway nodes without knowing which media gateway nodes can be selected in the preceding call control node CCN-1. Therefore, there is no guarantee that a media gateway node selected in the subsequent call control node CCN-2 can also be selected in the preceding call control node CCN-1. If the preceding call control node CCN-1 and the following call control node CCN-2 do not select the common media gateway node MG, unnecessarily long user plane routes may be obtained. This results in inefficient use of network resources.

Figure 2 shows one possible exemplary situation that may arise. The illustrated exemplary situation helps to understand some potential problems of the present invention in more detail. In this case, it is assumed that call control node CCN-2 must then play an announcement ( See for example reference [1] section 14.1.1). At the end of call setup, media gateway nodes MG at three sites are involved in the call.

In Figure 2, dashed lines depict signaling or control plane data transmissions. A plain line depicts user plane data transmission.

The steps leading to the establishment of a call are as follows:

(1) A setup message is sent from the mobile terminal (illustrated in the radio access network RAN on the left hand side of the illustration) to the previous call control node CCN-1 in station 1. A site is a physical location where the functionality associated with one or more nodes is aggregated. This step is illustrated by the arrow associated with the encircled reference number 1 and the label "build()".

(2) The previous call control node CCN-1 sends a BICCIAM message to the subsequent call control node CCN-2 in station 2. This step is illustrated by the arrow associated with the encircled reference number 2 and the notation "IAM()".

(3) The Call Control Node CCN-2 must then play an announcement, for example because of Intelligent Network (IN) interworking. This step is illustrated by a balloon containing a circled reference number 3 and a text prompt marked "CCN sign must play announcement".

(4) Then the call control node CCN-2 selects a media gateway node to establish a bearer (user plane) and play an announcement. In this example, the call control node CCN-2 then selects the media gateway MG-3 in site-3. This step is illustrated by the arrow associated with the encircled reference number 4 and the label "Select MG resource and play announcement".

(5) The call control node CCN-2 subsequently sends the identifier of the media gateway MG-3 back to the previous call control node CCN-1. This step is illustrated by the arrow associated with the encircled reference number 5 and the label "APM(BCU-ID3)".

(6) In this example, it is assumed that the previous call control node CCN-1 cannot select the media gateway node MG-3. Therefore, the preceding call control node CCN-1 selects another media gateway node, eg media gateway node MG-1 in site-1. This step is illustrated by the arrow associated with the encircled reference number 6 and the label "Select MG Node".

(7) Establish a bearer between the media gateway node MG-1 in site 1 and the media gateway node MG-3 in site 3 and play the announcement. This step is illustrated by the arrow associated with the encircled reference number 7 and the label "Establish Bearer; MG-3 Play Announcement".

(8) Then the call control node CCN-2 continues the call setup. It identifies that the call must be routed to the Public Switched Telephone Network (PSTN) illustrated on the bottom right corner of Figure 2 . This step is illustrated by a balloon containing the encircled reference number 8 and the text "Continue call setup, route call to PSTN".

(9) Then the call control node CCN-2 selects the media gateway node MG capable of connecting the user plane to the public switched telephone network (PSTN). Here, the call control node CCN-2 then selects the media gateway node MG-4 in site-4. This step is illustrated by the arrow associated with the encircled reference number 9 and the label "Select MG resources interworking with PSTN".

(10) Finally, a bearer is established between the media gateway node MG-3 and the media gateway node MG-4. This step is illustrated by the arrow associated with the encircled reference numeral 10 and the label "Establish Bearer".

It follows that call setup involves three sites, namely site 1 (where media gateway node MGW-1 is located), site 3 (where media gateway node MGW-3 is located), and site 4 (where media gateway node MGW-3 is located). node MGW-4).

Figures 3a and 3b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention. The first call control node (CCN) 6 starts the negotiation process S100. Part S600 of the negotiation process S100 performed by the call control node 6 includes sending S102 a list identifying at least two media gateways 4 (not shown in Figures 3a and 3b) to a second call control node (CCN) 8 over the communication network 2 message steps.

This enables the first call control node 6 to inform the second call control node 8 which media gateway 4 the first call control node 6 can select for the call to be established. The second call control node 8 then has the opportunity to consider the proposed list of media gateways 4 for the call to be set up.

The embodiment illustrated in Figures 3a and 3b includes in particular a sub-embodiment in which the second call control node 8 is not provided with the ability to make it understand the message identifying the list of at least two media gateways . From the second call control node 8, which is not provided with the ability to make it understand the message identifying the list of at least two media gateways, to provide it with the ability to understand without the need to modify the first call control node 6 The smooth transition of the second call control node 8 of the messaging capability.

Figures 4a and 4b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention. The negotiation process S100 includes a part S600 performed by the first call control node 6 and a part S800 performed by the second call control node 8 . The first call control node 6 sends S102 a message identifying a list of at least two media gateways 4 that the first call control node 6 can select for the call to be established to the second call control node 8 via the communication network 2 .

In part S800 of the negotiation process S100, the second call control node 8 receives S104 a message identifying a list of at least two media gateways 4 that the first call control node 6 considers suitable for the call to be established. The second call control node 8 is removed from the list S106 The node 8 cannot select the media gateway(s) for the call. The second call control node 8 then selects S108 the media gateway 4 to be used for the call to be established from the possibly modified list. Finally, the second call control node 8 sends S110 a message identifying the selected media gateway 4 to the first call control node 6 .

For step S106, the expression "(one or more) media gateways" here means one media gateway or multiple media gateways. However, if all media gateways of the list identified by the message are determined to be selectable for the call, the call control node is not required to remove the media gateway identifier. Therefore, although the negotiation process S100 includes, i.e. provides for, the removal step S106, the removal step S106 is optional when the process S100 is actually performed, and may be equivalent to Verification steps. In one embodiment, the negotiation process S100 includes a determination process (not shown), which is used to determine whether each media gateway 4 identified by the received message can be selected for the call, and if not, This determination process is used to eliminate which media gateways 4 are not selectable. This also applies to step S118 described later.

Figures 5a and 5b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention. Compared with Figures 4a and 4b, the method and configuration of Figures 5a and 5b additionally illustrate the step of receiving S112 a message identifying the selected media gateway by the first call control node 6, and using the The selected media gateway completes S114 or attempts to complete the steps of the call to be established. Figures 5a and 5b illustrate a negotiation process S100 comprising a bidirectional control plane exchange of information from the first call control node 6 to the second call control node 8 and then from the second node 8 back to the first node 6.

Figures 6a and 6b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention. In particular, the negotiation process S100 includes a part S600 performed by the first call control node 6 and a part S700 performed by the third call control node 7 or an intermediate call control node for participating in call establishment.

The first call control node 6 sends a message to the second call control node 8 via the first part 2a of the communication network 2 identifying a list of at least two media gateways 4 which the first node 6 considers suitable for the call to be established. When sending a message to the second call control node 8, the message is transmitted via the third call control node 7 which receives S116 the message. The third call control node 7 is then removed from the list S118 it cannot select the media gateway(s) 4 for the call. If all media gateways 4 of the list are suitable for the call to be set up by the third node 7, no media gateway 4 is removed from the list. Therefore, this removing step S118 is a verifying step. The third node 7 then forwards S120 a message identifying the list that may have been modified to the second call control node 8 via the second part 2b of the communication network 2 .

As explained similarly with reference to Figures 3a and 3b, the embodiment illustrated in Figures 6a and 6b includes in particular a sub-embodiment in which no provision is made for the second call control node 8 to enable it to understand Ability to identify a message for a list of at least two media gateways. In the case that there is no need to modify the first call control node 6 and the third call control node 7 (both of which are ready to carry out the negotiation process S100), it is provided from the non-enabled (non-enabled) second call control node 8 to use Smooth transition of node 8 is enabled.

Figures 7a and 7b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention. In this embodiment, the negotiation process S100 includes a part S600 performed by the first call control node 6 , a part S700 performed by the third call control node 7 and a part S800 performed by the second call control node 8 .

That is, the first call control node 6 sends a message to the second call control node 8 via the third call control node 7 in the manner illustrated with particular reference to Figures 6a and 6b. For the sake of clarity, the transition through the third call control node 7 in the forward direction is not illustrated in Fig. 7a and is indicated only by three dots "...". As explained above, this message identifies a list of at least two media gateways 4 considered by the first node 6 and the third node 7 together to be suitable for the call to be established. The second call control node 8 receives S104 and processes S106, S108 the list before sending S110 a message identifying the selected media gateway 4 back to the first call control node 6. When the second node 8 sends a message identifying the selected media gateway 4 to the first node 6, the message is transmitted via the third call control node 7 . The third node 7 receives S122 a message identifying the selected media gateway 4 . The third call control node selects S124 the media gateway 4 identified by the message sent from the second node 8 as the media gateway 4 to be used for the call to be established. Then, forward S126 the message to the first call control node 6.

Figures 8a and 8b illustrate a method and a network configuration, respectively, according to an embodiment of the present invention. FIG. 8b illustrates in particular a series of exemplary media gateways 4 .

The method comprises a protocol procedure S100 comprising a part S600 performed by the first call control node 6 , a part S700 performed by the third call control node 7 , and a part S800 performed by the second call control node 8 . Each call control node (ie the first call control node 6, the second call control node 8 and the third call control node 7) participates in setting up the call by performing their respective parts S600, S700 and S800 of the negotiation process S100.

In more detail, the first call control node 6 sends S102 a message identifying a list of at least two media gateways 4 considered suitable for the call to be established. The message is sent S102 by the first node 6 over the part 2a of the communication network 2 . The message sent from the first node 6 to the second call control node 8 is received S116 by the third call control node 7 . The third node 7 removes S118 from the list identified by the received message that it cannot select media gateway(s) 4 for the call (as explained above, if all media gateways can be selected then no remove the media gateway). It then forwards S120 to the second call control node 8 a message identifying the list that may have been modified. The message is sent S120 by the third node 7 over the part 2b of the communication network 2 .

The second call control node 8 receives S104 the message from the first call control node 6 via the third call control node 7 . The second node 8 removes S106 from the list identified by the received message it cannot select the media gateway(s) 4 for the call (as explained above, if at this stage it is also possible to select all media gateway, the media gateway is not removed). It then selects S108 from this list the media gateway 4 to be used for the call to be established. The second call control node 8 then sends S110 to the first call control node 6 a message identifying the selected media gateway 4 . The message is sent S110 by the second node 8 over the part 2b of the communication network 2 .

When the second call control node 8 sends a message identifying the selected media gateway 4 to the first call control node 6, the message is first received by the third call control node 7 . The third node 7 receives S122 the message identifying the selected media gateway 4 and selects S124 the media gateway 4 identified in the received message as the media gateway to be used for the call to be established. It then forwards S126 to the first call control node 6 a message identifying the selected media gateway 4 . The message is sent on part 2a of the communication network 2 .

The first call control node 6 receives S112 the message identifying the selected media gateway 4 and uses the selected media gateway 4 identified in the received message to complete S114 or attempt to complete the call to be established.

Thus, the call can be set up by taking into account the constraints on the first, second and third call control nodes 6,8,7. Although Figures 8a and 8b illustrate an embodiment in which one intermediate call control node 7 is used, more than one intermediate call control node may be involved in setting up the call. First intermediate call control node (wherein there is no intermediate call control node on the path between first and second call control node 6,8) or additional intermediate call control node (wherein first and second call control node 6, 8 there are already one or more intermediate call control nodes on the path) can be added to the communication network 2 at any time without modifying the first or second call control nodes (or any existing intermediate call control nodes) call control node, if any).

As used herein, the word "to" in expressions such as "to send a message to a destination node" etc. does not exclude one or more transitions of the message through intermediate nodes before reaching the destination node. Although the message is sent to the destination node, it is not excluded that the message does not reach the destination node for any reason such as communication failure. Likewise, the word "from" in expressions such as "receive a message from a source node" etc. does not exclude one or more transitions of the message through intermediate nodes between the step of transmitting the message by the source node and receiving the message.

Figure 9 illustrates a method according to one embodiment of the invention.

This embodiment of the invention provides a procedure for negotiation between the call control node and the media gateway nodes that can be used in the call. The negotiation process S100 provides an opportunity for one or more subsequent call control nodes to agree on a common media gateway node. Such a choice improves resource usage in the network.

The call control node 6 sending a call setup message (eg IAM in BICC) in forward direction adds to the message a list of at least two media gateway nodes 4 suitable for the call.

Any subsequent call control node 7, 8 that removes the call control node 7, 8 from the list cannot select the media gateway node 4 for the call. If they can all be selected, the media gateway node 4 is not removed. Call control nodes which do not control any media gateways (eg call mediation nodes) also transmit this list transparently.

For example, a call control node that has to establish a user plane because an announcement has to be played selects a media gateway node from the media gateway node's negotiated list. The identifier of the selected media gateway node 4 is sent in the reverse direction to give subsequent call control nodes 6, 7 the opportunity to select the same media gateway node 4.

More specifically, Figure 9 illustrates media gateway node selection or negotiation.

Instead of sending a list of media gateway node identifiers, it is also possible to send identifiers for a group of media gateway nodes 4 . In case an intermediate node 7 wants to remove an identifier BCU-ID from this list, it must choose a new identifier representing this modified list of identifiers BCU-ID, wherein in this case said identifier BCU-ID The ID is actually an identifier for a group of media gateway nodes 4 .

In one embodiment, the method of the present invention can be applied when the call control node 4 first selects the media gateway node 4 subsequently, for example in a BICC using a forwarding bearer setup procedure. For the following discussion with reference to Figure 9, it is assumed that a forwarding bearer setup is used.

The nomenclature of nodes 4, lists and other items is derived from Figure 1.

The call control node CCN _org 6, here referred to as the originating call control node CCN _org 6 (which corresponds to the first call control node 6 described earlier), starts media gateway node negotiation or selection, and is configured to perform the following steps :

Step (1): The originating call control node CCN _org 6 constructs a list of identifiers of media gateway (MG) nodes that can be used to set up the call. The list is referred to here as the BCU-IDlist _org . This is illustrated by the text balloon associated with the encircled reference number 1 and the label "Construct a list of identifiers associated with MG nodes applicable to the call (BCU-IDlist _org )". This list is added to the call setup message sent to the next Call Control Node (CCN). This is illustrated by the arrow associated with the encircled reference number 2 and the label "IAM (BCU-IDlist _org )". The next call control node is either an intermediate call control node CCN _tran or a terminating call control node CCN _term .

Step (2): As illustrated by the arrow associated with the circled reference number 9 and the label "APM(BCU-ID _back-2 )", when the originating call control node CCN _org 6 receives the response When sending a message, then:

Step (2.1): If the message includes a media gateway node identifier BCU-ID _back-2 , the originating call control node CCN _org 6 verifies whether this identifier is specified in the original list BCU-IDlist _org ).

Step (2.1.1): If the received identifier is specified in the original list, the originating call control node CCN _org 6 selects this media gateway node 4 for call setup. This is illustrated by the text balloon associated with the encircled reference number 10 and the note "Accept BCU-ID _back if sent in BCU- _{IDlist org} ".

Step (2.1.2): Otherwise, the originating call control node CCN _org 6 selects any media gateway node 4 for call setup from the original list BCU-IDlist _org .

Step (2.2): If the message does not include a media gateway node identifier, the originating call control node CCN _org 6 selects any one media gateway node 4 for call setup from the original list BCU-IDlist _org . In one embodiment, reception of reverse messages without a media gateway identifier is not allowed and would result in a setup failure.

For example, if the BICC protocol is used as a call control protocol, a list BCU-IDlist _org is added to an Initial Addressing Message (IAM) message. The received identifier BCU-ID _back is received in an Acknowledgment Path Message (APM) message.

In one embodiment, a call control node (call mediation node, not shown) that does not control the media gateway node transparently transmits the list of media gateway node identifiers.

The call control node that transmits the call setup message but has to select a media gateway node for the call is called an intermediate call control node CCN _trans (which corresponds to the third call control node 7 as described above). Such call control node 7 performs the following steps:

Step (1): The intermediate call control node CCN _trans 7 receives a call setup message (eg Initial Addressing Message (IAM) message in BICC). This is illustrated by the arrow associated with the encircled reference number 2 and the label "IAM (BCU-IDlist _org )".

Step (1.1): If the message includes a list BCU-IDlist _org of media gateway node identifiers, the intermediate call control node CCN _trans 7 performs the following steps:

Step (1.1.1): The intermediate call control node CCN _trans 7 removes any unknown identifier BCU-ID from the list. If all media gateway node identifiers BCU-ID are known, no identifiers are removed.

Step (1.1.2): The intermediate call control node CCN _trans 7 removes from the list any identifier BCU-ID associated with a media gateway node 4 that cannot be used by the intermediate call control node CCN _trans 7 for the call. If all media gateway node identifiers BCU-ID can be used, no identifiers are removed.

Step (1.1.1) and step (1.1.2) are denoted by the enclosed reference number 3 and the label "Remove any unknown identifiers. Remove any identifiers associated with MG nodes not applicable for this call" The associated text balloon icon.

Step (1.1.3): The intermediate call control node CCN _trans 7 processes the remaining list BCU-IDlist _trans in the following manner:

Step (1.1.3.1): If at least one element remains in the list, the intermediate call control node CCN _trans 7 forwards the list BCU-IDlist _trans in a call setup message IAM sent to the subsequent call control node. This is illustrated by the arrow associated with the encircled reference number 4 and the label "IAM(BCU-IDlist _trans )".

Step (1.1.3.2): If the list is empty, the intermediate call control node CCN _trans 7 starts negotiating with the media gateway node pointing to the subsequent call control node. As described for the originating call control node CCN _org , the intermediate call control node CCN _trans 7 constructs and transmits the BCU-ID list. In other words, in this case the intermediate call control node CCN _trans 7 acts as the originating call control node CCN _org .

Step (1.2): If the received call setup message does not include the list BCU-IDlist _org of media gateway node identifiers, the intermediate call control node CCN _trans 7 starts as described for the originating call control node CCN _org 6 Media gateway node negotiation. In other words, also in this case, the intermediate call control node CCN _trans 7 behaves as if it were the originating call control node CCN _org .

Step (2): As illustrated by the arrow associated with the circled reference number 7 and the label "APM(BCU-ID _back-1 )", when the intermediate call control node CCN _trans 7 receives When reversing a message, it performs the following steps:

Step (2.1): If the message includes a media gateway node identifier BCU-ID _back-1 , the intermediate call control node CCN _trans 7 verifies whether this identifier is specified in the previously forwarded list (BCU-IDlist _trans ).

Step (2.1.1): If the received identifier is specified in the forwarded list BCU-ID list _trans , the intermediate call control node CCN _trans 7 selects the media gateway node 4 for call setup. This is illustrated by the text balloon associated with the encircled reference number 8 and the note "Accept BCU-ID _back if sent in BCU- _{IDlist org} ".

Step (2.1.2): Otherwise, the intermediate call control node CCN _trans 7 selects for call setup any one of the media gateway nodes 4 listed in the previously sent list of media gateways BCU-IDlist _trans . In one embodiment, this also applies to the case where the media gateway returned is an element in the list BCU-IDlist-tran, and step 2.1.1 is performed, but it is not possible to select this media gateway for some reason (i.e. in the media There was an error during gateway seizure).

Step (2.2): If the reverse message does not include the media gateway node identifier,

Step (2.2.1): The intermediate call control node CCN _trans 7 selects for call setup any media gateway node 4 listed in the previously sent list BCU-ID"st _trans .

In one embodiment, if the reverse message does not identify a media gateway, then the call setup fails (ie, cannot be successfully completed).

Step (2.3): Transmitting the BCU-ID of the selected media gateway node in the reverse direction, as indicated by the arrow associated with the circled reference number 9 and the label "APM(BCU-ID _back-2 )" icon.

The call control node terminating the media gateway node negotiation is called the terminating call control node CCN _term 8 (which corresponds to the second call control node 8 as previously described), and it performs the following steps:

Step (1): The terminating call control node CCN _term 8 receives a call setup message (eg Initial Addressing Message (IAM) message in BICC). This is illustrated by the arrow associated with the encircled reference number 4 and the label "IAM(BCU-IDlist _tran )".

Step (1.1): If the message includes a list of media gateway node identifiers, the terminating call control node CCN _term 8 performs the following steps:

Step (1.1.1): The terminating call control node CCN _term 8 removes any unknown media gateway node identifier BCU-ID from the list. If all media gateway identifiers BCU-ID are known, no identifiers are removed.

Step (1.1.2): The terminating call control node CCN _term 8 removes from the list any media gateway node identifiers BCU-ID associated with media gateway nodes 4 that are not available for the call. If all media gateway node identifiers BCU-ID can be used, no identifiers are removed.

Step (1.1.1) and step (1.1.2) are denoted by the enclosed reference number 5 and the label "Remove any unknown identifiers. Remove any identifiers associated with MG nodes not applicable for this call" The associated text balloon icon.

Step (1.1.3): The terminating call control node CCN _term 8 processes the remaining list BCU-ID list _trans in the following manner:

Step (1.1.3.1): If there is at least one element left in the list, the terminating call control node CCN _term 8 selects one of them and uses the associated media gateway node 4 to establish the user plane. This is illustrated by the text balloon associated with the encircled reference number 6 and the label "Select any MG from the remaining list (BCU-IDlist _term )".

Step (1.1.3.2): If the list is empty, the terminating call control node CCN _term 8 selects any media gateway node 4 suitable for the call.

Step (1.1.4): The terminating call control node CCN _term 8 sends back the BCU-ID of the selected media gateway node (BCU-ID _back-1 ). This is shown by the arrow associated with the encircled reference number 7 and the label "APM(BCU-ID _back-1 )".

Step (1.2): If the received call setup message does not include a list of media gateway node identifiers, the terminating call control node CCN _tern 8 selects any media gateway node suitable for the call.

In one embodiment, instead of sending a list of media gateway identifiers BCU-ID, identifiers BCU-ID _MGG for a group or group of media gateway nodes are sent. The group or group of media gateways may be defined somewhere else. In other words, in this embodiment, the media gateway group identifier is a placeholder for a list of media gateways defined elsewhere. This means:

a) will know the definition for each media gateway in the call control node;

b) there is one or more definitions of media gateway groups when each media gateway in the media gateway group belongs to a group of media gateways known in the call control node (defined in a)); and

c) Each media gateway group has an associated group identifier.

Such a group of media gateways may be referred to as a well-defined media gateway group (MGG).

For example, let us assume that media gateways MGw-1, MGw-2, MGw-3...MGw-7 are defined in the call control node. Then, for example, the following media gateway group can be defined:

MGG-1={MGw-1, MGw-2, MGw-3};

MGG-2 = {MGw-1, MGw-4, MGw-5}; and

MGG-3={MGw-5, MGw-6}.

Such media gateway node negotiation can be introduced into BICC in the following manner. If BICC is used as a call control protocol, the identifier BCU-ID _MGG is defined with the same data format as BCU-ID (5 octets) defined for the BICC protocol. This value can be conveyed by standard BICC messages without any modification. Any node that does not know this value MUST ignore this parameter (BICC standard). In nodes supporting the use of BCU-ID _MGG , this value is regarded as an identifier for a group of media gateway nodes, and media gateway node negotiation is performed.

Figure 10a illustrates a call control node according to an embodiment of the invention. A call control node, referred to herein as an originating or first call control node 6, is configured to take part in setting up a call in the communication network 2 and in negotiating a media gateway 4 to be used for the call. The call control node 6 is configured to operate in a control plane and includes a call control node 8 (not shown in FIG. Sender 62 of a message of a list of at least two media gateways 4 for an established call.

Figure 10b illustrates a call control node according to an embodiment of the invention. In addition to comprising the sender 62 described with reference to Figure 10a, the call control node 6 also comprises: a receiver 64 configured to receive a message identifying the selected media gateway 4; and a completer 66 , which is configured to complete or attempt to complete the call to be established using the selected media gateway 4 identified in the received message.

Fig. 11 illustrates a call control node according to an embodiment of the present invention. This call control node is referred to herein as terminating or second call control node 8 . It is configured to participate in setting up calls in the communication network 2 . The terminating call control node 8 is configured to operate in a control plane and comprises a receiver 82 , a remover 84 , a selector 86 and a sender 88 . The receiver 82 is configured to receive a message identifying a list of at least two media gateways 4 from another call control node 6 or 7 in the control plane (not illustrated in Fig. 11). The remover 84 is configured to remove from the list identified by the received message the media gateways 4 which the call control node 8 cannot select for the call. The selector 86 is configured to select from a list the media gateway to be used for the call to be established. The sender 88 is configured to send a message identifying the selected media gateway 4 to the other call control node 6 or 7 .

Figure 12a illustrates a call control node according to an embodiment of the invention. This call control node is referred to herein as an intermediate or third call control node 7 . The call control node 7 includes a receiver 72 , a remover 73 and a repeater 74 . The receiver 72 is configured to receive calls to the control plane from a first other call control node 6 (not shown in FIG. 12 a ) or another intermediate call control node 7 (not shown in FIG. 12 a ) in the control plane. A message sent by a second other call control node 8 (not shown in Fig. 12a) or another intermediate call control node 7 (not shown in Fig. 12a ), wherein the message identifies a list of at least two media gateways . The remover 73 is configured to remove from the list identified by the received message the media gateways 4 which the call control node 7 cannot select for the call. If all media gateways can be selected, the media gateway identifier is not removed from the list. If only one media gateway can be selected from the list, the list is left with one element. If a media gateway cannot be selected from the list, the list is empty and a new list of media gateways can be created based on the constraints of the call control node 7 . Finally, the repeater 74 is configured to forward the message identifying the list to the second other call control node 8 .

Figure 12b illustrates an intermediate call control node 7 comprising the functionality of the call control node of Figure 12a together with receiver 75, selector 76 and repeater 77. The receiver 75 is configured to receive a call to the control node 8 from a second other call control node 8 (not shown in FIG. 12 b ) in the control plane or from another intermediate call control node 7 (not shown in FIG. 12 a ). A message sent by the first other call control node 6 (not shown in Fig. 12b) or another intermediate call control node 7 (not shown in Fig. 12b) in the plane. This message identifies the selected media gateway. The selector 76 is configured to select the media gateway 4 identified in the received message as the media gateway to be used for the call to be established. Finally, this repeater 77 is configured to forward the message identifying the selected media gateway 4 towards the first other call control node 6 .

A physical entity comprising a call control node and a media gateway according to the invention may comprise or store a computer program comprising instructions such that, when said computer program is executed on the physical entity, the steps and process. The invention also relates to such a computer program for carrying out the method according to the invention and to any computer-readable medium storing the computer program for carrying out the method according to the invention.

Where the terms "sender", "receiver", "completer", "remover", "selector" and "transponder" are used herein, there are no How to aggregate elements for constraints. That is, constituent elements of a unit may be distributed among different software or hardware components or devices for bringing about intended functions. Multiple distinct elements can also be aggregated to provide these intended functions.

Any of the above-mentioned elements of a call control node may be implemented in hardware, software, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), firmware, or the like.

In other embodiments of the present invention, the sending means, the receiving means, the completing means, the removing means, the selecting means or the forwarding means are used respectively, or the sending unit, the receiving unit, the completing unit, the removing unit, the selecting unit or the forwarding unit are respectively used to In lieu of any of the above-mentioned and/or claimed senders, receivers, completers, removers, selectors, and transponders to perform the sender, receiver, completer, remover, selector, respectively and transponder functions.

In other embodiments of the invention, computer-readable instructions may be used, for example in the form of computer-understandable procedures, methods, etc., in any kind of computer language, and/or in the form of Any one of the above-described processes, parts of processes, and/or steps may be implemented in the form of software.

Although the present invention has been described on the basis of the detailed examples, the detailed examples are only for providing better understanding to those skilled in the art and are not intended to limit the scope of the present invention. Rather, the scope of the invention is defined by the appended claims.

Claims (8)

1. A method for setting up a call in a communication network (2) by selecting a media gateway (4) to be used for the call, said media gateway (4) being in a user plane, said method comprising having at least The negotiation process (S100) of the following steps, wherein: A first call control node (6) in the control plane sends (S102) to a second call control node (8) in the control plane identifying at least two media gateways (4) that are considered suitable for the call to be established ) for the list of messages, Wherein the negotiation process (S100) also includes the following steps, wherein the second call control node (8) receiving (S104) said message from said first call control node (6); removing (S106) from the list identified by the received message that said second call control node (8) cannot select a media gateway (4) for said call; Selecting (S108) from said list the media gateway (4) to be used for the call to be established; and A message identifying the selected media gateway (4) is sent (S110) to said first call control node (6). 2. The method according to claim 1, wherein said message is sent (S102) by said first call control node (6) to said second call control node (8) in forward direction, said The forward direction is the direction in which the call connection is established. 3. The method according to claim 1, wherein said negotiation process (S100) is further provided with the following steps, wherein said first call control node (6) receiving (S112) a message identifying the selected media gateway (4); and The call to be established is completed (S114) or attempted to be completed using the selected media gateway (4) identified in the received message. 4. The method according to claim 1 or 2, wherein said negotiation process (S100) is also provided with the following steps, wherein the third call control node (7) receiving (S116) a message sent by said first call control node (6) to said second call control node (8); removing (S118) from the list identified by the received message that said third call control node (7) cannot select a media gateway (4) for said call; and A message identifying said list is forwarded (S120) to said second call control node (8). 5. A method performed by a call control node (8) in a control plane for participating in setting up a call in a communication network (2) by selecting a media gateway (4) to be used for the call, said media gateway ( 4) In the user plane, the method includes a negotiation process (S800) with at least the following steps, wherein: the call control node (8) receiving (S104) a message identifying a list of at least two media gateways (4) from another call control node (6) in said control plane; removing (S106) from the list identified by the received message that said call control node (8) cannot select a media gateway (4) for said call; Selecting (S108) from said list the media gateway (4) to be used for the call to be established; and A message identifying the selected media gateway (4) is sent (S110) to said further call control node (6). 6. A method performed by a call control node (7) in a control plane for participating in setting up a call in a communication network (2) by selecting a media gateway (4) to be used for the call, said media gateway ( 4) In the user plane, the method includes a negotiation process (S710) with at least the following steps, wherein: the call control node (7) receiving (S116) a message sent from a first other call control node (6) in said control plane to a second other call control node (8) in said control plane, said message identifying at least two media gateways ( 4) list; removing (S118) said call control node (7) from the list identified by the received message not being able to select a media gateway (4) for said call; and A message identifying said list is forwarded (S120) to said second other call control node (8). 7. A call control node (8) configured to participate in setting up a call in the communication network (2) and negotiating a media gateway (4) to be used for said call, said media gateway (4) being in the user plane, said Said call control node (8) is configured to operate in a control plane and comprises: a receiver (82) configured to receive a message identifying a list of at least two media gateways (4) from another call control node (6) in said control plane; a remover (84) configured to remove from the list identified by the received message the media gateways (4) that the call control node (8) cannot select for the call; a selector (86) configured to select from said list a media gateway to be used for the call to be established; and A sender (88) configured to send a message identifying the selected media gateway (4) to said further call control node (6). 8. A call control node (7) configured to participate in setting up a call in a communication network (2) and negotiating a media gateway (4) to be used for said call, said media gateway (4) being in the user plane, said Said call control node (7) is configured to operate in a control plane and comprises: a receiver (72) configured to receive a message sent from a first other call control node (6) in said control plane to a second other call control node (8) in said control plane, said message identifying a list of at least two media gateways (4); a remover (73) configured to remove from the list identified by the received message the media gateways (4) that the call control node (7) cannot select for the call; and A repeater (74) configured to forward a message identifying said list to said second further call control node (8).