Abstract:
In the framework of a conversion of a feature control signaling, an item of feature control information is extracted from a protocol-specific feature control message of a communication network and is transmitted to a feature-neutral coordination module. The coordination module then relays the item of feature control information to a feature-specific conversion module, which converts the relayed item of feature control information into an item of feature control information, which is subsequently inserted into another protocol-specific feature control message and is transmitted therewith into another communication network.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is based on and hereby claims priority to PCT Application No. PCT/DE01/03491 filed on 11 Sep. 2001 and German Patent Application No. 100 48 484.0 filed on 29 Sep. 2000, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   In contemporary communications systems, connections, e.g. for voice, video, multimedia and/or data communication, which are traditionally routed via circuit-switched communications networks, are to an increasing extent also being switched via packet-switched communications networks, such as e.g. so-called local area networks (LANs) or the Internet. For example, Internet telephony, frequently also referred to as “Voice over Internet Protocol” (VoIP), is based on this technology. 
   At the point of transition of a connection between a circuit-switched and a packet-switched communications network, it is usually necessary, owing to the differing transmission and signaling protocols, to convert control signaling information provided for connection control. As well as an implementation of cross-network setup and cleardown of connections, the principal problem that poses itself here is also to ensure cross-network control and interworking of service features in the communications system. 
   SUMMARY OF THE INVENTION 
   According to an aspect of the present invention, there is provided a method and a gateway device for converting service feature control signaling information at the point of transition between communications networks using different signaling protocols. 
   According to an aspect, the present invention permits service feature control signaling information for controlling service features such as e.g. call forwarding—all calls, conferencing, call forwarding—no answer, callback, etc., to be efficiently converted at the point of transition (gateway) between communications networks using different signaling protocols. Toward that end, an item of service feature control information is extracted from a service feature control message of a communications network, the message being specific to the respective signaling protocol of the communications network in question, and transmitted to a service feature-neutral coordination module. The service feature-neutral coordination module assigns the transmitted service feature control information to a service feature-specific conversion module, i.e. a module specifically responsible for a particular service feature, and relays the service feature control information to this conversion module. The assigned conversion module then converts the relayed service feature control information into service feature control information that is specific to another of the communications networks. The converted service feature control information is then inserted into a further protocol-specific service feature control message and transmitted with this into the other communications network. 
   Because the service feature-specific conversion module is logically separated from the service feature-neutral coordination module and from the protocol-specific access modules, the functionality of a gateway device according to the invention can be extended in a very simple way. Thus, for example, processing of an additional service feature can be implemented simply by adding a further conversion module specific to this additional service feature. Furthermore, the gateway device can be adapted to different signaling protocols by modification, replacement or addition of a protocol-specific access module. Such extensibility achievable by adding function modules is frequently also referred to as “plug &amp; play” capability. 
   According to an aspect of the present invention, there is provided service feature control information between the access modules, the coordination module and a conversion module can be transferred by asynchronous messages. Such an asynchronous information exchange reduces the dependencies between the individual function modules, resulting in a considerable improvement in the extensibility and maintainability of the gateway device. 
   According to an aspect of the present invention, there is provided a service feature-specific conversion module can register with the coordination module by transmitting an item of service feature information. At the same time the service feature information can specify which service feature control information is to be assigned to the conversion module concerned. The service feature information can preferably comprise a service feature code identifying the particular service feature and the particular conversion device as well as a set of operation codes. Here, each of the operation codes identifies a service feature control operation from the set of control operations provided for controlling the respective service feature. Each of the operation codes can preferably be assigned to at least one conversion module in an assignment table of the coordination module. A conversion module can be registered for example at system start, at the time that the respective conversion module is generated as an instance of a programmed object class and/or at the time that a service feature assigned to the respective conversion module is requested. By an assignment table of this type, service feature control information can be assigned to the respective conversion module responsible on the basis of operation codes contained in the table by simple table access. 
   The coordination module also enables status information about the status of a connection to be assigned to at least one conversion module and to be relayed to this module. In this way the conversion of the service feature control information can be performed as a function of the status of a connection to which the respective service feature is assigned. 
   Furthermore, according to an aspect of the present invention, a connection can also be controlled as a function of an item of service feature control information or status information transmitted in the course of a connection by a service feature-specific conversion module. To this end, connection control information generated by the conversion module can be relayed by the coordination module to an access module, which forwards the connection control information to a connection controller. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  shows a gateway device interposed between a circuit-switched and a packet-switched communications network; and 
       FIG. 2  shows a connection setup message containing an item of service feature control information. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     FIG. 1  shows a schematic representation of a gateway device GW according to the invention, the gateway device being interposed as a switching element between a circuit-switched communications network SCN (Switched Circuit Network) and a packet-switched communications network LAN implemented as a local area network (LAN). For the present example embodiment it is assumed that the QSIG protocol stack conforming to the ETSI/ECMA standard for signaling at the Q reference point is provided for connection signaling in the circuit-switched communications network SCN. In order to control service features, service feature control signaling based on the QSIG-GFT protocol (QSIG Generic Functional Transport) is also supported in the circuit-switched communications network SCN. In the local area network LAN, connection signaling is performed according to ITU-T recommendation H.323, with service features being controlled according to ITU-T recommendations H.450 and H.450.1. 
   As functional components, the gateway device GW comprises a connection controller VS, a protocol controller QSIG-PS for the QSIG protocol stack, a protocol controller H.323-PS for H.323 signaling, a protocol-specific, service feature-neutral access module QSIG-ZM for accessing the QSIG-GFT signaling, a protocol-specific, service feature-neutral access module H.450.1-ZM for accessing the H.450.1 signaling framework, a central, service feature- and protocol-neutral coordination module KM, as well as multiple conversion modules UM 1 , . . . , UMN. Each of the conversion modules UM 1 , . . . , UMN is specifically responsible for one of several different service features, such as e.g. call forwarding—all calls, conferencing, call forwarding—no answer, etc. 
   The connection controller VS is linked to the circuit-switched communications network via the protocol controller QSIG-PS and to the local area network LAN via the protocol controller H.323-PS. The connection controller VS is further linked to the coordination module KM on the one hand via the access module QSIG-ZM and on the other hand via the access module H.450.1-ZM. Also linked to the coordination module KM are the service feature-specific conversion modules UM 1 , . . . , UMN as well as a control module QSIG-ROSE specifically provided for the QSIG protocol and a control module H.450.1-ROSE (ROSE: Remote Operation Service Entity) specifically provided for the H.450.1 protocol. 
   The functional components of the gateway device GW are separated into different logical layers, namely a connection controller layer VSS, a service feature transport layer LMTS and a service feature conversion layer LMUS. The boundaries between these logical layers are indicated by dotted lines in  FIG. 1 . The connection controller VS as well as the protocol controllers QSIG-PS and H.323-PS are assigned here to the connection controller layer VSS. The coordination module KM, the control modules QSIG-ROSE and H.450.1-ROSE as well as the access modules QSIG-ZM and H.450.1-ZM are further associated with the service feature transport layer LMTS. The access modules QSIG-ZM and H.450.1-ZM act among other things as a logical link and synchronization device between the connection signaling and the service feature signaling. The control modules QSIG-ROSE and H.450.1-ROSE serve to monitor the transactions initiated by the service feature control messages in the service feature transport layer LMTS. Finally, the conversion modules UM 1 , . . . , UMN are assigned to the service feature conversion layer LMUS. Owing to the separation of the functional components into individual logical layers, the functionality of the gateway device GW can be extended in a very simple manner. For example, the processing of an additional service feature can be implemented simply by adding an additional conversion module specific to this service feature. Furthermore, the gateway device GW can be adapted to different signaling protocols in the connected communication networks by modification, replacement or addition of a protocol-specific access module. The modular layer architecture further supports an interaction between the service features in a generic manner. 
   The central coordination module KM, the access modules QSIG-ZM and H.450.1-ZM, the control modules QSIG-ROSE and H.450.1-ROSE, and the conversion modules UM 1 , . . . , UMN are in each case preferably implemented as an instance of a programmed object class. An information exchange between the instances takes place by asynchronous messages. While the coordination module KM is preferably initialized as a class instance at system start time, the remaining class instances are preferably initialized the first time a service feature control message is received by the connection controller VS. 
   During the initialization of the conversion modules UM 1 , . . . , UMN, these register themselves with the coordination module KM. In the course of the registration of a conversion module UM 1 , . . . , UMN, this transmits a registration message (not shown) to the coordination module KM. The registration message preferably contains a service feature code LMIDI, . . . , LMIDN which identifies the corresponding conversion module or the service feature to be processed by this module, as well as a set of operation codes OIDI,OID 2 ,OID 3 , . . . , by which those service feature control operations are identified which are provided for controlling the corresponding service feature. The set of operation codes and the service feature code of a registration message are stored assigned to each other in an assignment table ZT of the coordination module KM. For the present example embodiment it is assumed that the conversion module UM 1  with the service feature code LMID 1  and the operation codes OID 1 , OID 3  and the conversion module UMN with the service feature code LMIDN and the operation code OID 2  are registered in the assignment table ZT. 
   In the following, consideration is given to conversion of a service feature control signaling information of the circuit-switched communications network SCN into functionally equivalent service feature control signaling information for the local area network LAN. The chosen direction of the conversion should be understood here only as an example. Accordingly, the following statements apply analogously also for a conversion in the opposite direction. 
   In the present example embodiment, a QSIG connection setup message SETUP is transmitted in the course of the service feature control signaling as a protocol-specific service feature control message to the gateway device GW by the circuit-switched communications network SCN. 
   As shown schematically in  FIG. 2 , the connection setup message SETUP contains—apart from its message header MK—a generic data container for accepting signaling elements that are formed in the present example embodiment by protocol-specific coded service feature control information LO 1 , LO 2 , LO 3 , . . . . Each service feature control information LO 1 ,LO 2 ,LO 3 , . . . is composed of an operation code OIDI,OID 2 ,OID 3 , . . . identifying a service feature control operation and an associated set of operation parameters OP 1 ,OP 2 ,OP 3 , . . . . 
   Other QSIG signaling messages that possess a generic data container can also be used as service feature control messages instead of the connection setup message SETUP. 
   The connection setup message SETUP received by the gateway device GW is forwarded by the protocol controller QSIG-PS to the connection controller VS and recognized by this as a service feature control message. As a result, the connection controller VS initiates an initialization of the access modules QSIG-ZM and H.450.1-ZM, the control modules QSIG-ROSE and H.450.1-ROSE, as well as the conversion modules UM 1 , . . . , UMN as instances of programmed object classes. 
   The protocol-specific access module QSIG-ZM then extracts the service feature control information LO 1 , LO 2  and LO 3  from the protocol-specific connection setup message SETUP and decodes this into a protocol-neutral format. The decoded service feature control information LO 1 , LO 2  and LO 3  is then transferred separately within asynchronous messages to the coordination module KM. A connection code (not shown) identifying the connection to be set up is also transmitted to the coordination module KM, the service feature control information LO 1 , LO 2  and LO 3  being assigned to the connection to be set up on the basis of the connection code. 
   The operation codes OID 1 , OID 2  and OID 3  contained in the service feature control information LO 1 , LO 2  and LO 3  are read out together with the respective set of operation parameters OP 1 , OP 2  or OP 3  in the coordination module KM. Next, the service feature code, in this case LMID 1  or LMIDN, assigned to a respective operation code OID 1 , OID 2  or OID 3 , and hence the respective conversion module responsible, in this case UM 1  or UMN, is determined by accessing the assignment table ZT. Accordingly, the operation code OID 1  with the operation parameters OPI and the operation code OID 3  with the operation parameters OP 3  are relayed to the conversion module UM 1 . Analogously, the operation code OID 2  and the operation parameters OP 2  transmitted with this operation code OID 2  are relayed to the conversion module UMN. In the conversion module UM 1 , the service feature control operation with the operation parameters OP 1  identified by the operation code OID 1  and the service feature control operation with the operation parameters OP 3  identified by the operation code OID 3  are then converted into one or more functionally equivalent items of service feature control information ULO 1  for the local area network LAN. In the same way, the service feature control operation identified by the operation code OID 2  is converted together with its operation parameters OP 2  into one or more functionally equivalent items of service feature control information ULO 2  for the local area network in the conversion module UMN. 
   The converted service feature control information ULOI and ULO 2  is transferred to the coordination module KM by asynchronous messages. The service feature control information ULO 1  and ULO 2  of the connection identified by the connection code is assigned by the coordination module KM and thus relayed to the access module H.450.1-ZM. The access module H.450.1-ZM then codes the converted service feature control information ULO 1  and ULO 2  into a H.450.1-specific format. In this format, the converted service feature control information ULO 1  and ULO 2  is inserted into a connection setup message SETUP specific to the local area network LAN, the connection setup message finally being transmitted via the protocol controller H.323-PS into the local area network LAN by the connection controller VS. 
   The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.