Patent Publication Number: US-2005129003-A1

Title: Call control method for IP based telephone services

Description:
The invention is based on a priority application EP 03293082.8 which is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to a call control method for IP based telephone services and to a call control server for providing IP based telephone services within a communication network.  
      Existing PSTN telecommunication systems (PSTN=Public Switched Telecommunication Network) provides various services performing a kind of redirection or call forwarding of calls, directed to a telephone number. Further, services in private telephone systems are known which assigns different telephones to a user group, wherein each of the telephones of the user group will ring, when an incoming call to one of the telephones of the user group is detected. Also in this case, there is a one to one mapping between the terminal and telephone number.  
      In contrast to existing PSTN telecommunication systems, next generation networks will consist out of many new devices, like Soft Switches, media gateway controllers, media gateways, SIP-phones, SIP-proxies and so on (SIP=Session Initiation Protocol). From an end-user point of view we have in such kind of environment various scenarios which applies here. Some end-users will reuse their analogue telephone set of digital ISDN appliance (ISDN=Integrated Services Digital Network). Such end-users can be connected by means of legacy PSTN network. Further, they can be connected by residential gateways, access gateways or integrated access devices to the next generation networks. Some end-users will use or buy new equipment like SIP-phones, SIP-clients and so on. Such equipment can be connected by means of broadband access CPE (CPE=Customer Premise Equipment) like HFC, DSL or WLAN (HFC=Hybrid Fiber Coax; DSL=Digital Subscriber Line; WLAN=Wireless LAN).  
      Users connected via legacy PSTN network to new generations networks are simply connected from operators craftsmen at central office side. Such users do not see any difference. In contrast to this, users by means of residential gateways, access gateway, integrated access devices and SIP-phones have to configure the new devices by themselves.  
     SUMMARY OF THE INVENTION  
      It is the object of the present invention to improve the call control within a next generation network environment.  
      The object of the present invention is achieved by a call control method for IP based telephone services, wherein two or more IP telephone terminals are assigned to a telephone number commonly shared by said IP telephone terminals and IP address data of said IP telephone terminals are stored in the registry of a call control server responsible for control of VoIP calls directed to this telephone number, wherein one of these IP telephone terminals transmits a presence message to said call control server, when a presence button of this IP telephone terminal is pressed, and wherein a VoIP call directed to the telephone number is routed to that one of the IP telephone terminals assigned to the telephone number, from that the call control server has received the presence message (VoIP=Voice over IP; IP=Internet Protocol).  
      The object of the present invention is further achieved by a call control server for providing IP based telephone services within a communication network, wherein the call control server is responsible for controlling VoIP calls directed to a telephone number and wherein the call control server comprises a communication unit for receiving presence messages from IP telephone terminals and a call control unit adapted to assign two or more IP telephone terminals to that telephone number commonly shared by said IP telephone terminals, to store IP addressed data of said IP telephone terminals in a registry of the call control server and to route a VoIP call directed to the telephone number to that one of the IP telephone terminals assigned to the telephone number, the call control server received a presence message from.  
      The invention makes it possible for a user to use various, different telephone sets and remain still available via one single telephone number. When the end user presses a kind of presence button, the intelligent in the network takes care that only some of the end-equipment devices will ring. Only one or more of the end-equipment devices are in a actuated state once there is an incoming call. Further, the invention supports a smooth evolution of existing PSTN networks to next generation network and the coexistence of the above-specified scenarios.  
      Further advantages are achieved by the embodiments indicated by the dependent claims.  
      A powerful way of sharing multiple telephone sets can be achieved by the usage of configuration cards assigned to clients. IP telephone configuration data stored on such a configuration card are transferred from the configuration card to one or several of the IP telephone terminals. One configuration card can be used for several different type of IP telephone terminals. But, it is also possible to assign multiple configuration cards to a subscriber. The IP telephone configuration data stored on the configuration card includes address data of the call control server. The respective IP telephone terminal contacts the call control server by means of this transferred address data. Further, it transfers terminal data to the call control server. The call control server registers the IP telephone terminal by means of the received terminal data. Further, the transferred IP telephone configuration data includes subscriber data and the IP telephone terminal transfers the received subscriber data to the call control server. The assignment of IP telephone terminals to telephone numbers is executed by help of such transferred subscriber data. IP telephone terminals assigned to the same subscriber are assigned to the same telephone number.  
      For example, the configuration card subscriber has the following couple of telephone sets: a fixed telephone set with loudspeaker/microphone, display and better voice quality; a small mobile with low weight, small dimension—which fits in every pocket—for riding a bicycle; and a multimedia mobile with a camera, higher weight, and bigger dimension for usage at events to transmit pictures on the spot. All these telephone sets have the same configuration card and will be used at different opportunities, while the telephone sets have different settings (codex, voice quality . . . ).  
      This approach provides a high degree of user friendliness and flexibility.  
      Further advantages are achieved when the IP telephone configuration data stored on the configuration card include a quality of service profile specifying the quality of service assigned to the subscriber. Further, the terminal data can include terminal descriptors specifying the type of terminal and the communication protocols which have to be used for communicating with the respective IP terminal. Such kind of data is used by the IP telephone terminal and a call control server to provide a telephone service to the subscriber which is well adapted to the needs of the subscriber and the capabilities of the respective IP telephone terminal.  
      Preferably, an authentisation procedure is executed between the IP telephone terminal and the call control server during the registering process. Thereby, safety, security and privacy of communication is guaranteed.  
      To improve user friendliness, it is proposed to automatically execute the registering process as soon as the configuration card is connected with the IP telephone terminal. The subscriber has not to take care of the registering process and can immediately use his IP telephone terminal as soon as such connection is established.  
      According to a preferred embodiment of the invention, the call control server supports all the IP telephone terminals assigned to the telephone number in the establishment of VoIP calls. Therefore, it is possible for the user to initiate an outgoing call from each and all of its IP telephone terminals. In contrast to this, the call control server directs incoming VoIP calls to that one of the IP telephone terminals assigned to the subscriber, from that it at least received a presence message.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These as well as other features and advantages of the invention will be better appreciated by reading the following detailed description of presently preferred exemplary embodiments taken in conjunction with accompanying drawings of which:  
       FIG. 1  is a block diagram showing several components of a communication system with a call control server according to the present invention.  
       FIG. 2  is a functional view showing the call control server of  FIG. 1 , an IP telephone terminal and a configuration card. 
    
    
       FIG. 1  shows a communication network  1 , a call control server  2 , several IP telephone terminals  31 ,  32 ,  33  and  35 , a configuration card  4 , several subscribers  51  and  52  and a service provider  53 . The IP telephone terminals  31 ,  32  and  33  are assigned to the subscriber  51  and the IP telephone terminal  53  is assigned to the subscriber  52 .  
      The communication network  1  is a NGN communication network (NGN=Next Generation Network) which is based on a distributed IP network (IP=Internet Protocol). The architecture of this communication network is split into two main sections, the control plane, which is responsible for controlling the communication connection between users of the communication system, and the transport plane, which is responsible for the transportation of the associated media streams. The transport plane can be formed by various different types of physical networks, for example ATM networks or MPLS networks (ATM=Asynchroune Transfer Mode; MPLS=Multiprotocol Lables Switching), which are linked via a common level 3 IP protocol layer. Further, the transport plane may comprise one or several telephone networks, for example PSTN or ISDN-networks (PSTN=Public Switched Telecommunication network; ISDN=Integrated Service Digital Network). Further, the communication network  1  may include fixed and mobile communication networks, for example GSM, UMTS or CDMA  2000  cellular networks (GSM=Global System for Mobile Communication; UMTS=Universal Mobile Telecommunications System).  
      The control plane of the communication network  1  contains various media gateways, access gateways and switching nodes responsible for the switching and routing of the media streams through the communication network  1 . Such media gateways support stream-like communication as voice, fax or video-communication between two or more terminals linked to the communication network  1 . Further, such media gateways may provide seamless working of voice and fax connections between public switched telephone networks and IP based networks.  
      The call control serve  2  is part of the control plane of the communication network  1 . It provides all control functions for network elements of the transport layer of the communication network  1 . For example, the call control server  2  is a media gateway controller which is within an NGN architecture the centralized intelligent instance for providing new VoIP or multimedia services (VoIP=Voice over IP). A media gateway controller is a single entity which controls several media gateway via a specific interface (for example H.248) for the sake of providing an access point for subscribers of telecommunication networks. The media gateway controller provides independent call functionalities together with switching functions for basic-and supplementary-services in addition with, for example, billing-, routing- and measurement capabilities for network operators and telecommunication service providers.  
      Within such context, the call control server  2  provides the functionality of a SIP-server (SIP=Session Initiation Protocol).  
      But, it is also possible that the communication network  1  is a pure IP network and the call control server  2  is a SIP-server supporting the establishment of VoIP connections through the IP network constituted by the communication network  1 .  
      The IP telephone terminals  31 ,  32 ,  33  and  35  are IP-phones or computers executing an IP phone client. For example, these terminals are SIP-phones or computers executing a SIP client. Further, the IP telephone terminal  31 ,  32 ,  33  and  35  can be terminals connected via a residential gateway, integrated access device (IAD) or embedded media termination device (eMTD) with the communication network  1 . Such residential gateways provide a connection between a LAN or wireless LAN environment and an ISDN interface. Such integrated access devices or embedded media termination devices providing a connection between a LAN or wireless LAN environment and a DSL cable modem (DSL=Digital Subscriber Line). Further, the IP phone terminals  31 ,  32 ,  33  and  35  can be connected via an access node or access gateway of a private network to the communication network  1 .  
      According to an embodiment of this invention, the IP phone terminal  33  is a fixed terminal, for example a computer with a SIP-client, the IP telephone terminal  32  is a small mobile terminal with low weight, small dimension and reduced functionalities, and the IP telephone terminal  31  is a multimedia mobile with a camera and enhanced input and output facilities.  
      To enable the establishment of VoIP communications to his IP telephone terminals  31 ,  32  and  33 , the subscriber  51  has to choose a service provider, sign a contract and configurate his IP telephone terminals  31 ,  32  and  33 . For example, the subscriber  51  chooses the service provider  53 , which is the service provider operating the call control server  2 . The network operator  53  delivers the configuration card  4  to the subscriber  51 . This is, for example, done via postal mail. IP telephone configuration data are stored on the configuration card  4 . This data contain the necessary information which makes it possible to the IP telephone terminals  31 ,  32  and  33  to enroll themselves within the call control server  2  and make the VoIP telephone service provided by the call control server  2  available to the subscriber  51 .  
      The subscriber  51  uses the configuration card  4  to transfer the IP telephone configuration data stored on the configuration card  4  to his IP telephone terminals  31 ,  32  and  33 . But, it is also possible that the subscriber  51  receives from the service provider  53  several configuration cards, each for one of the IP telephone terminals  31 ,  32  and  33 . Such configuration cards can contain different sets of configuration data, which makes it, for example, possible to configure different services and quality of services at different IP telephone terminals of the subscriber  51 .  
      The IP telephone terminals  31 ,  32  and  33  are registered within the call control server  2  by means of IP telephone configuration data downloaded from the configuration card  4 . The call control server  2  assigns the IP telephone terminals  31 ,  32  and  33  of the subscriber  51  to a single telephone number commonly shared by these IP telephone terminals. Further, it stores IP address data of the IP telephone terminals  31 ,  32  and  33  in its registry.  
      In the following, the call control server  2  monitors whether it receives a presence message from one of the IP telephone terminals  31 ,  32  and  33 . For example, the IP telephone terminal  31  transmits such a presence message to the call control server  2 , when detecting that a presence button  34  is pressed by the subscriber  51 . In the following, incoming VoIP calls directed to the telephone number of the subscriber  51  are routed to that one of the IP telephone terminals  31 ,  32  and  33 , the call control server  2  has received the presence message from. If, for example, the subscriber  52  tries to set up a phone call to the subscriber  51  via an IP telephone terminal  35 , the call control server  2  routes this call to the IP telephone terminal  31 , from which it has received a presence message.  
      In the following, the details of the invention are described by hand of  FIG. 2 .  
       FIG. 2  shows the IP telephone terminal  31 , the configuration card  4 , the subscriber  51  and the call control server  2 .  
      The configuration card  4  is a smart card, chip card or plane memory card. Different IP telephone configuration data are stored in the memory means of the configuration card  4 . The IP telephone configuration data include address data of the call control server that is responsible for serving the telephone number assigned to the subscriber  51 , for example, the IP address of the call control server  2 . Further, it includes subscriber data which makes it possible to identify the subscriber  51  towards the responsible call control server. In addition, the IP telephone configuration data can include a quality of service profile specifying the quality of services assigned to the subscriber. Such quality of service parameter may be delay time, packet size (e.g. six packets containing 5 ms, one packet containing 30 ms), fixed route or secure route, use of a secured, encrypted connection or not, codec used for the communication and/or codec selection strategy. For example, the IP telephone configuration data may contain a G.729, a G.726 and a G.711 codec. The IP telephone terminal configured by help of the configuration card  4  chooses first the G.729 codec. If the voice quality does not fit with preset quality level, it changes to the G.726 codec or G.711 codec.  
      The IP telephone terminal  31  comprises, from functional point of view, two memory units  37  and  39 , a configuration card reader  36  and a control unit  38 .  
      The call control server  2  is constituted by one or several interconnected computers, a software platform running on this hardware platform and several application programs executed by the system platform formed by the hardware and software platform. The functionalities of the call control server  2  are provided by the execution of these software components on the hardware platform of the call control server  2 . From functional point of view, the call control server comprises a communication unit  22 , two control units  21  and  24  and a memory unit  23 .  
      The configuration card reader  36  of the IP phone terminal  31  is, for example, a connector which is galvanically coupled with the configuration card  4  when the configuration card  4  is inserted into the IP telephone terminal  31 . But, it is also possible that the configuration card reader  36  is connected to the configuration card  4  in a wireless way. For example, the configuration card reader  36  exchanges data with the configuration card  4  via an infrared or radio interface, for example a bluetooth or wireless LAN interface. That makes it possible that the configuration card  4  has solely to be hold in the neighborhood of the IP telephone terminals  31  to enable the download of IP telephone configuration data to the IP telephone terminal  31 .  
      The downloaded IP telephone configuration data are stored in the memory unit  37 , which holds in the following a copy of the IP telephone configuration data stored on the configuration card  4 .  
      The memory unit  39  holds terminal specific data, for example the type of the IP telephone terminal  31 , and the communication protocol supported by the IP telephone terminal  31 . For example, the telephone terminal  31  supports the SIP, the MGCP, the MEGACO, H.323, and/or the H.248 protocol used for a VoIP communication via the communication network  1 . (MGCP=Media Gateway Control Protocol; MEGACO=Media Gateway Control Protocol). Further, the IP telephone terminal  31  may support further proprietary protocols, for example SKINI.  
      To initiate the registering of the IP telephone terminal  31  in the registry of the call control server  2 , the control unit  38  determines the IP address of the IP telephone terminal  31  and sends a registration request message to the call control server specified in the IP telephone configuration data received from the configuration card  4 . Within the context of this registration request message, it transfers terminal data to this call control server. These terminal data includes at least the IP address of the IP telephone terminal  31 . Preferably, this data contains in addition various of the data stored in the memory units  37  and  39 . For example, this terminal data include terminal descriptors specifying the type of terminal and the communication protocol which has to be used for communicating with the IP telephone terminal  31 . Further, it transmits subscriber data to the call control server.  
      Optionally, the control unit  38  executes in the following an authentisation procedure. For example, it requests the subscriber  51  to input a PIN code which is transferred to the call control server for authentication purpose (PIN=Personal Identification Code). Further, also a PIN/TAN based authentication procedure or an encryption key based authentication procedure can be executed between the IP telephone terminal  31  and the call control server (TAN=Transaction Number).  
      After registration, the control unit  38  monitors whether the subscriber  51  presses the presence button  34 . This presence button may be a programmable key of the IP telephone terminal  31 . Further, several or all of the keys of the IP telephone terminal  31  can be defined as presence button. When the control unit  38  detects the pressing of the presence button, it sends a presence message  63  to the call control server addressed in the IP telephone configuration data.  
      The communication unit  22  of the call control server  22  provides an interface to the terminal registration function of the call control server  2 . It makes it possible for this function to receive messages from terminals connected to the communication network  1 , for example from the IP telephone terminals  31 ,  32 ,  33  and  35 .  
      The control unit  21  provides the terminal registration function of the call control server  2 . When receiving a registration request message, for example from the control unit  38  of the IP telephone terminal  31 , it executes by means of the terminal data submitted in the context of this request a terminal registration process. By means of the submitted IP address and subscriber data of the requesting terminal, it establishes the registration of this terminal in the registry of the call control server  2 , which is formed by the memory unit  23 . Thereby, it is possible that the control unit  21  assigns two or more IP telephone terminals to a single telephone number commonly shared by said IP telephone terminals. For example, if the control unit  21  detects that the subscriber data of the IP telephone terminals  31 ,  32  and  33  assigns these IP telephone terminals to one and same subscriber, it assigns all these IP telephone terminals to the same telephone number, which is the telephone number of the subscriber  51 . Further, it stores the IP address data of each of these IP telephone terminals as well as the other terminal data submitted by these IP phone terminals within the memory unit  23 .  
      If it receives a presence message from one of the IP telephone terminals, it locates the data set assigned to this terminal within the memory unit  23  and stores an indication indicating that the presence button of this terminal is pressed. Further, the date of receipt may in addition be stored in this data set.  
      The control unit  24  controls by help of the data stored in the memory  23  the routing of incoming calls. If a incoming VoIP call is directed to a telephone number to which two or more IP telephone terminals are assigned, it checks whether a presence message is received from one of these IP telephone terminals. If several of such messages are received for several terminals, it selects the IP telephone terminal at last received a presence message. But, it is also possible to perform some different strategies:  
      For example, it directs the call to all of the IP telephone terminals in parallel, which has sent a present message. Further, it can direct the VoIP call to these IP telephone terminals which has sent a presence message within a sliding time frame, for example within the last five hours.