MERGING OF CALLS

Abstract: Conference call set-up is conventionally controlled with special keys # and * of a telephone set. Today these functions are performed by means of intelligent network technology. A problem with standard CS-1 and CS-2 intelligent network architectures is that they do not allow merging of call segments initiated by a Service Control Point (SCP). According to the invention: in response to the messages from the service control function (SCF), the service switching point (SSP) creates a separate call segment for each B subscriber; in response to the creation of a call segment (CS1 - CS3), the service switching point (SSP) sends a message about this to the service control function (SCF); in response to a message confirming the creation of at least two call segments (CS1 - CS3), the service control function (SCF) orders the service switching point (SSP) to merge the call segments created.

Description: MERGING OF CALLS The invention relates to a mechanism improving the operations of an Intelligent Network (IN) for merging calls initiated by the intelligent network and for producing services to subscribers. An intelligent network allows providing a subscriber of a telecommunication network - such as a wired network or a mobile telephone network - with a host of different services. These services include e.g. a Private Numbering Plan (PNP), enabling the use of private numbers, and a Personal Number which allows the users to call a specific person using the same number, irrespective of the person's location and the subscriber connection used for receiving calls. A specific numbering block is defined for PBX subscribers in the numbering domain of the exchange. One example of this kind of an intelligent network is described in the recommendations of ITU-T Q-1200 series, of which Q-1210 - Q-1219 define the set of features known as CS-1 (Capability Set 1) and, correspondingly, Q-1220 - Q-1229 define the set of features CS-2. The present invention suggests an improvement to the call set-up mechanism presented in recommendation Q-1214. This recommendation defines functions such as Service Control Function (SCF) and Service Switching Function (SSF). A network element performing the SCF is called a Service Control Point (SCP). Similarly, a network element performing the SSF is called a Service Switching Point (SSP). A Basic Call State Model BCSM defined in connection with an intelligent network describes the different stages of call control and includes the points where call control can be interrupted for initiating an intelligent network service. It identifies those Event Detection Points in the call and the connection process where service logic entities of the intelligent network can have an interactive relationship with basic call and connection management features. One of the services offered by telecommunication operators is conference call. The problem with the general mechanisms for setting up a conference call is that they require considerable skill and care from the subscriber, because conference call set-up must be controlled using special keys # and * of the telephone set. Such problems relating to the convenience of use are often solved by means of an intelligent network architecture. The problem with CS-1 and CS-2 intelligent network architectures is that they do not include the possibility of merging call segments initiated by a Service Control Function SCF. For instance, CS-2 architecture entities CallSegmentAssociation, Call- Segment, SSF FSM and the MergeCallSegments operation in the BCSM SDL -model are not possible for calls which the service control function SCF has initiated with the operation InitiateCallAttempt. In other words, within the ITU-T and ETSI draft recommendations this operation is not allowed, but the draft recommendations define the states in which the MergeCallSegments operation is allowed, and this situation is not one of them. The object of the present invention is thus to provide a method for producing services in such a way that the above-mentioned problems relating to production of services can be solved. The objects of the invention are achieved with a method which is characterized by what is stated in the characterizing parts of the independent claims. The dependent claims relate to the preferred embodiments of the invention. The invention is based on complementing an intelligent network ar- chitecture so as to enable automatic merging of calls, without the subscriber controlling the merging with the keys of a terminal. At a predetermined time, the exchange sets up a conference call by calling the conference participants, i.e. the B subscribers. The answer-signal received from the telephone network about the call being connected to each B subscriber serves as a signal for the service control point SCP of the intelligent network. On the basis of the answer-signal, the SCP commands the SSP to merge the calls. The invention will now be described in more detail, in connection with a preferred embodiment, with reference to the attached drawing in which Figure 1 provides an example of a signalling diagram illustrating the invention. Figure 1 illustrates a method for setting up a conference call between three B subscribers. The events in the figure proceed from top to bottom and they are described accordingly. The service control point SCP commands the service switching point SSP to set up a first call segment to a first B subscriber. Parameters CSA1 , CS1 and LEG1 have been appended to this InitiateCallAttempt message by way of an example. A leg is a connection to the subscriber. A CS (CallSegment) corresponds to one call. A CSA (CallSegmentAssociation) is logical joining of two or more call segments. Other messages and parameters can be used as well. The symbols placed to the left of the SSP illustrate setting up and connecting of calls. A sur- rogate leg S means that there is no connection to a real subscriber. A call segment indicated by a dashed line means that the connection is being ere- ated, and a call segment shown with a continuous line means that the connection has been established. In connection with an InitiateCallAttempt message, the SCP also sends a RequestReportBCSMEvent message by which it asks the SSP to report when the event detection point has been reached (the con- nection has been established). With a Continue message, the SCP commands the SSP to initiate the defined events. As a result of this, the SSP sends an Initial Address Message 1AM to the telephone network for setting up a call to a first B subscriber. The events are repeated for a second and a third B subscriber, after which three logical connections to three B subscribers have been established in the SSP call model. The B subscribers 1 , 2 and 3 each answer the call and the network submits for each B subscriber first an Address Complete Message (ACM) and then an ANswer Message (ANM). In connection with the latter, the event detection point mentioned above is triggered, and the SSP reports this to the SCP. The establishment of a conference call can be informed to B subscribers in such a way that the SCP sends the messages ConnectToResource, Play- Announcement and DisconnectForwardConnection to the SSP. The first one of these messages defines the resources needed for transmitting an announcement, the second one causes the announcement to be read to a B subscriber and the third one releases the resources reserved for the announcement. For each of these three messages, the SSP sends the SSP/IP (IP = Intelligent Peripheral) a corresponding command on the basis of which the SSP/IP reads an audio announcement to the B subscriber. The phases indicated by a brace in Figure 1 are repeated for each B subscriber with n values 1 ,2 and 3. After receiving an ANswer Message and the subsequent notification of the triggering of the event detection point from all B subscribers 1 , 2 and 3, the SCP commands the SSP to merge the call segments two at a time. The figure shows an example where segments 2 and 3 are merged first and then segments 1 and 2. The result is a single call seg- ment with no A subscriber, but a Surrogate Leg S in place of the A subscriber, and with three B subscribers. The reason for merging call segments two at a time is that known intelligent network messages (in this case MergeCallSegments) include two call segments as parameters, so n call segments may be merged by performing n-1 MergeCallSegment operations. If the intelligent network used recognises a message allowing several call segments to be merged by a single operation, such a message can naturally be employed. The invention therefore requires for instance the following deviations from the ITU-T and ETSI draft recommendations. When two call segments initiated by the SCP (for example CS2 and CS3) are merged, the passive legs (the connections set up to real subscribers) are transferred from one call segment (CS3) to the target call segment (CS2) and the surrogate legs S in the source call segment (CS3) are deleted so that only one surrogate leg S will be left in the target call segment (CS2). The embodiment described above is only one example of implementing the invention. For instance, it is not technically necessary to have all the call segments created before their merging begins. However, it is more convenient for the subscribers that the merging of the call segments only starts after they all have been created. Hearing a ringing tone during the call will thus be avoided. It is also technically possible to merge the call segments without an audio announcement (PlayAnnouncement) to the B subscribers. However, in this case the B subscribers would need to constantly ask who are presently connected to the conference. The method of the invention only requires fairly minor changes to a previously known intelligent network architecture. Although the described conference call is between three parties, it is apparent that the technology can be applied to an arbitrary number of conference parties. The invention is therefore not restricted to the preferred embodiments described above but it may vary within the scope of the claims.

Claims: Claims 1. Method for merging call segments (CS1 - CS3) of several B subscribers in a telecommunication network including a service control point (SCP) and a service switching point (SSP), characterized in that - in response to messages from the service control point(SCP), the service switching point (SSP) creates a separate call segment (CS1 - CS3) for each B subscriber; - in response to the creation of a call segment (CS1 - CS3), the service switching point (SSP) sends a message about this to the service con- trol point (SCP); - in response to a message confirming the creation of at least two call segments (CS1 - CS3), the service control point (SCP) orders the service switching point (SSP) to merge the call segments created. 2. Method according to claim 1, characterized in that the service control function (SCF) orders the service switching point (SSP) to only merge the call segments (CS1 - CS3) created after having received a message about the creation of call segments to all B subscribers. 3. Method according to claim 1 or 2, characterized in that before merging call segments (CS1 - CS3), the service switching point (SSP) produces an audio announcement about this to the B subscribers. 4. Method according to any one of claims 1 to 3, character- i z e d in that the call segments (CS1 - CS3) are merged two at a time. 5. Method according to any one of claims 1 to 3, characterized in that all the call segments (CS1 - CS3) are merged by the same operation. 6. Method according to any one of the preceding claims, wherein said call segments (CS1 - CS3) may comprise actual connections to real subscribers and surrogate legs (S), characterized in that said merging of the call segments (CS2, CS3) comprises transferring the actual connections from a source call segment (CS3) to a target call segment (CS2) and deleting the surrogate legs (S) of the source call segment (CS3), which only leaves a single surrogate leg (S) in the target call segment (CS2). 7. Method according to any one of the preceding claims, characterized in that the message from the service control point (SCP) to the service switching point (SSP) for creating a call segment (CS1 - CS3) is an InitiateCallAttempt message. 8. Method according to any one of the preceding claims, characterized in that the message from the service control point (SCP) to the service switching point (SSP) for merging call segments (CS1 - CS3) is a MergeCallSegments message. 9. An arrangement for merging call segments (CS1 - CS3) of several B subscribers in a telecommunication network comprising a service con- trol point(SCP) and a service switching point (SSP), characterized in that - the service switching point (SSP) is arranged to create a separate call segment (CS1 - CS3) for each B subscriber, in response to messages from the service control point(SCP); - the service switching point (SSP) is arranged to send a message to the service control point(SCP), in response to the creation of a call segment (CS1 - CS3); - the service control point (SCP) is arranged to command the service switching point (SSP) to merge the call segments created, in response to a message informing of the creation of at least two call segments (CS1 - CS3).

Inventors: WALLENIUS JUKKA, WALLENIUS, JUKKA
Applicants: NOKIA TELECOMMUNICATIONS OY, WALLENIUS JUKKA, WALLENIUS, JUKKA
Application year: 1997
Main classification: H04Q3
IPC codes: H04M3, H04Q3