Abstract:
A method is disclosed for the optimization of a BICC (Bearer Independent Call Control) IP Bearer Support in a WCDMA R4 Telecommunication system, and provides for exchange of IPAddress and Port Id between two MGWs by avoiding tunneling between two MSCs, reducing the number of message exchanges, and reducing the message sizes.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention in general relates to the telecommunication technology. More particularly, the present invention relates to optimization of BICC (Bearer Independent Call Control) IP Bearer Support in a WCDMA R4 Telecommunication system. 
         [0003]    2. Description of the Related Art 
         [0004]    IP networks are fundamentally different from connection-oriented networks such as those based on TDM or ATM, in that signaling messages do not need to be acted upon by all the network elements for User Plane communication to take place. If the Gateways or Inter-working points can exchange information, then the IP network can route the user plane packets between the gateways. The exchange of information is simple and consists of IP address, port numbers and some information on the type of media required. 
         [0005]    In IP networks utilizing SIP as the call control protocol, the information concerning the media is defined in the Session Description Protocol (SDP). SDP specifies the definition of the data format and its meaning. 
         [0006]    For the UMTS Core Network, ATM is used in the transport network user plane and the transport network control plane with BICC as the call control protocol on the Nb interface. As BICC call control procedures are independent of the bearer technology, these protocols can also be used over the IP networks. 
         [0007]    IP Bearer Control Protocol (IPBCP) is suitable for use in IP network environments where the Bearer Independent Call Control (BICC) is deployed. The purpose of IPBCP is to exchange information between the two BIWFs. BICC IPBCP is used for the exchange of media stream characteristics, port numbers and IP addresses of the source and sink of media stream to establish and allow the modification of IP bearers. The exchange of information with IPBCP is done during the BICC call establishment and after a call has been established. IPBCP uses the Session Description Protocol to encode this information. 
         [0008]    The IPBCP makes use of the BICC Bearer Control Tunneling Protocol which provides a tunneling mechanism over the “horizontal” BICC interface between CCUs and the “vertical” CBC interface between CCU and the BCU. 
         [0009]    This operates as follows: (Refer  FIG. 3 ): 
         [0010]    Note: To explain the invention Forward Bearer Delayed Tunneling Technique is used.
       1. MSC-A (also referred to as Originating Mobile Switching Centre from now on) initiates bearer establishment procedure by sending BICC IAM message with BNC Characteristics set to IP/RTP indicating IP Bearer needs to be established, codec list indicating that codes negotiation is required, Tunneling Indicator set to tunneling to be used and no tunnel data indicating that bearer establishment type is Delayed tunneling.   2. MSC-B (also referred to as Terminating Mobile Switching Centre from now on) after processing IAM, performs Prepare Bearer procedure by sending AddRequest message to MGW-B (also referred to as Terminating Media Gateway from now on). AddRequest contains the selected codec for bearer establishment. BNC Characteristics set to IP/RTP and tunneling option set to delayed tunneling indicating that MGW needs to wait for IPBCTP Request message.   3. MGW-B responds with AddReply message that contains the BIWF Address and BCNId.   4. MSC-B indicates to MSC-A the selected codec for bearer establishment, tunneling indicator that is set to tunneling used, BIWF Address and the BNCId through BICC APM message.   5. MSC-A now performs Establish Bearer procedure by sending AddRequest message containing the Codec type that needs to be used for bearer establishment and the tunneling option set.   6. MGW-A (also referred to as Originating Media Gateway from now on) responds with AddReply message. MSC-A waits for tunnel data.   7. MGW-A sends NotifyMessage with IPBCTP Request message containing the MGW&#39;s IPAddress and PortId information.   8. MSC-A responds with NotifyReply confirming the receipt of tunnel data.   9. MSC-A now responds to MSC-B the IPBCTP Request message as the tunnel data through BICC APM message.   10. MSC-B sends a ModifyRequest message to MGW-B containing the IPBCTP Request message as tunnel data received in the APM message.   11. MGW-B responds with ModifyReply message. MSC-B waits to receive the tunnel data.   12. MGW-B sends the NotifyRequest message containing the IPBCTP Accept message with its own IPAddress and PortId as tunnel data.   13. MSC-B responds with NotifyReply confirming the receipt of the tunnel data.   14. MSC-B sends the IPBCTP Accept message as tunnel data to MSC-A in the APM message.   15. MSC-A sends ModifyRequest message to MGW-A with tunnel data.   16. MGW-A responds with ModifyReply. At this point in time, both the MGWs are aware of each others IPAddress and PortId.   17. After RabAssignment procedures are successful on MSC-A towards the source RNC, it sends COT message to MSC-B to indicate that bearer establishment is successful on the originating side.   18. MSC-B after successful bearer establishment on terminating side, sends the ACM message to MSC-A.   19. And when terminating party answers, MSC-B sends the BICC ANM message to MSC-A.       
 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 Sample IPBCTP Message 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 v=0 
               
               
                   
                 o=−0 4727641859017609960 IN IP4 60.20.1.200 
               
               
                   
                 s=IPBCP Message 
               
               
                   
                 c=IN IP4 60.20.1.200 
               
               
                   
                 t=0 0 
               
               
                   
                 a=ipbcp:1 Request 
               
               
                   
                 m=audio 5098 RTP/AVP 97 
               
               
                   
                 a=rtpmap:97 VND.3GPP.IUFP/16000 
               
               
                   
                   
               
             
          
         
       
     
         [0030]    In the above data, only IP Address (60.20.1.200 in the above example data) and Port Number (5098 in the above example data) fields are of significance for an MGW. Since all other information is redundant, the required information namely the IP Address and Port Id can be communicated between MGWs through the BICC Call Control Protocol in the form of BIWF Address and BNCId fields provided by BICC. 
         [0031]    All other fields are either unused or have predefined values which are not interpreted by the MGW receiving the IPBCP message. 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 Sample APM Message Carrying IPBCTP Data 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 APM 
                 --&gt;1f 00 00 00 41 01 78 bb 85 81 c0 00 00 01 82 81 02 07 82 81 
               
               
                   
                 04  08 2b 81 81 22 20 20 76 3d 30 0a 6f 3d 2d 20 30 20 34 30   
               
               
                   
                 
                   36 36 31 31 33 38 34 36 32 38 33 31 31 32 38 36 38 20 49 4e 
                 
               
               
                   
                 
                   20 49 50 34 20 36 30 2e 32 30 2e 31 2e 32 30 30 0a 73 3d 49 
                 
               
               
                   
                 
                   50 42 43 50 20 4d 65 73 73 61 67 65 0a 63 3d 49 4e 20 49 50 
                 
               
               
                   
                 
                   34 20 36 30 2e 32 30 2e 31 2e 32 30 30 0a 74 3d 30 20 30 0a 
                 
               
               
                   
                 
                   61 3d 69 70 62 63 70 3a 31 20 52 65 71 75 65 73 74 0a 6d 3d 
                 
               
               
                   
                 
                   61 75 64 69 6f 20 35 30 38 32 20 52 54 50 2f 41 56 50 20 39 
                 
               
               
                   
                 
                   37 0a 61 3d 72 74 70 6d 61 70 3a 39 37 20 56 4e 44 2e 33 47 
                 
               
               
                   
                   50 50 2e 49 55 46 50 2f 31 36 30 30 30 0a 22  00 
               
               
                   
               
             
          
         
       
     
         [0032]    In the above APM data, the highlighted portions indicate an IPBCTP request being tunneled though BICC. 
         [0033]    The following are the problems in the existing system:
       1. Large and Redundant messages (Extra H.248.1 Notifies and Modifies) exchanged over Mc and Nc Interfaces thereby increasing the processing time at MGW in terms of encoding and decoding of these messages.   2. Delayed Call Setup.   3. Support for IPBCTP in MSC Server and IPBCP in MGW in order to support IP Bearer.       
 
       SUMMARY OF THE INVENTION 
       [0037]    The invention deals with optimization of BICC procedures for IP Bearer support. The invented method is to provide for exchange of IPAddress and Port Id between two MGWs by:
       1. Avoiding tunneling between two MSCs.   2. Reducing the number of message exchanges.   3. Reducing the message sizes.       
 
         [0041]    UMTS Core Networks employ ATM in transport network user plane and transport network control plane with BICC as the call control protocol on the Nb interface. As BICC call control procedures are independent of the bearer technology, BICC can be used over the IP networks. 
         [0042]    IP Bearer Control Protocol (IPBCP) is used over IP network environments where BICC is deployed. BICC IPBCP is used for exchange of media stream characteristics, port numbers and IP addresses of the source and sink of media stream to establish and allow the modification of IP bearers. The exchange of this information with IPBCP is done during the BICC call establishment and after a call has been established. 
         [0043]    The current invention proposes an optimization technique for the exchange of such information over BICC protocol without necessarily using IPBCP. 
         [0044]    Accordingly the present invention relates to IP Bearer Support in a WCDMA system without using IPBCTP and IPBCP protocols wherein only interpretation of existing procedures is changed and not messages and parameters. 
         [0045]    Accordingly, this invention explains a method for Bearer Independent Call Control (BICC) optimization for IP bearer support wherein a Originating Mobile Switching Centre initiates bearer establishment procedure by sending BICC IAM message with BNC characteristics set to IP/RTP indicating the need of IP Bearer establishment and codec list indicating the codec negotiation requirement. 
         [0046]    A Terminating Mobile Switching Centre after processing IAM, performs Prepare Bearer procedure by sending AddRequest message to a Terminating Media Gateway where AddRequest contains the selected codec for bearer establishment and BNC Characteristics set to IP/RTP. For the said request a Terminating Media Gateway responds with AddReply message that contains the IPAddress which is in BIWF Address and PortId which is in BCNId. Terminating Mobile Switching Centre indicates to Originating Mobile Switching Centre the selected codec for bearer establishment, BIWF Address and the BNCId through BICC APM message. Originating Mobile Switching Centre performs Prepare Bearer procedure by sending AddRequest message containing the Codec type that is used for bearer establishment, remote IPAddress and the PortId. A Originating Media Gateway responds with AddReply with its own IPAddress and PortId. Originating Mobile Switching Centre responds to Terminating Mobile Switching Centre with Originating Media Gateway&#39;s IPAddress and PortId through BICC APM message. Terminating Mobile Switching Centre sends a ModifyRequest message to Terminating Media Gateway containing the originating sides IPAddress and PortId. 
         [0047]    Terminating Media Gateway responds with ModifyReply where, both the MGWs are aware of each other&#39;s IPAddress and PortId. After RabAssignment procedures are successful on Originating Mobile Switching Centre towards the source RNC, it sends COT message to Terminating Mobile Switching Centre to indicate that bearer establishment is successful on the originating side. Terminating Mobile Switching Centre, after successful bearer establishment on terminating side, sends the ACM message to Originating Mobile Switching Centre. When terminating party answers, Terminating Mobile Switching Centre sends the BICC ANM message to Originating Mobile Switching Centre. BICC for IP Bearer support performs Prepare Bearer Procedure to retrieve IPAddress and PortId from its associated MGW whenever an AddRequest message is received by MGW from an MSC Server over the Mc Interface and if the procedure type is Prepare Bearer and BNC Characteristics is IP/RTP, MGW responds with an AddReply message containing its own IPAddress and PortId. 
         [0048]    These and other objects, features and advantages of the present invention will become more readily apparent from a reading of the following detailed description taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         [0049]      FIG. 1  illustrates the tunneling mechanism. 
           [0050]      FIG. 2  illustrates IPBCP data being tunneled though BICC messages using IPBCTP protocol. 
           [0051]      FIG. 3  illustrates existing bearer establishment procedures between two WCDMA R4 systems using Forward Bearer Delayed Tunneling approach that provides for Codec Negotiation between the systems. 
           [0052]      FIG. 4  illustrates the proposed optimized bearer establishment procedures between two WCDMA R4 systems. IPAddress and Port Numbers are communicated using the existing BIWFAddress and BNCId fields respectively, thereby negating the usage of the IPBCTP and IPBCP protocols. The result is reduced interactions between MSC Servers as well as between the MSC Server and the Media Gateway thereby providing a faster call setup. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0053]    The preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail. 
         [0054]    BICC Bearer Control Tunnelling Protocol (Q.1990) assumes a reliable, sequenced, point-to-point signalling transport service between peer Tunnelling PDU Generating and Receiving Entities. 
         [0055]    Q.1990 supports the tunnelling of bearer control protocols (BCP) over the following protocols:
       BICC protocol. BICC tunnelling makes use of BICC APM mechanism, as defined in Q.765.5 (Signalling system No. 7—Application transport mechanism: Bearer Independent Call Control) and Q.1902.4 (Bearer Independent Call Control Protocol—Capability Set 2—Basic Call Procedures)   CBC protocol. CBC tunnelling makes use of the H.248 Tunnelling package, as defined in Q.1950 (Bearer Independent Call Bearer Control Protocol).       
 
         [0058]    The operation of the tunnelling mechanism is illustrated in  FIG. 1  and the transport of IPBCP messages is illustrated in  FIG. 2 . 
         [0059]    To overcome the drawbacks of the IP Bearer support that uses IPBCTP and IPBCP, the relevant IP Address and Port Numbers are carried in BICC&#39;s BIWF Address and BNCId protocol fields over the Nc Interface. This helps in overcoming the need for IPBCTP and IPBCP. 
         [0060]    Due to this technique the changes that are required as part of Megaco (H.248.1) and BICC Protocol (Q.1902.4). Procedures for which are as follows:
       1. BICC Protocol for IP Bearer Support will always need to perform Prepare Bearer Procedure (Steps  2  and  5  in  FIG. 4 ) in order to retrieve IPAddress and PortId from its associated MGW. Currently the originating side performs an Establish Bearer Procedure (Step  5  in  FIG. 3 ).   2. Whenever an AddRequest message is received by MGW (Steps  2  and Steps  5  in  FIG. 4 ) from an MSC Server over the Mc Interface, if the procedure type is Prepare Bearer and BNC Characteristics is IP/RTP, MGW should respond with an AddReply message containing its own IPAddress (in BIWF Address) and PortId (in BNCId).   3. On the originating side, MSC Server sends the remote MGW&#39;s IP Address (in BIWF Address) and PortId (in BNCId) as part of Remote Descriptor in the AddRequest message (Step  5  in  FIG. 4 ).   4. On the terminating side, MSC Server needs to send ModifyRequest message with Remote Descriptor containing the originating side&#39;s IPAddress (in BIWF Address) and PortId (in BNCID) (Step  8  in  FIG. 4 ).   5. Notify messages (Steps  7  and  8 ) are not required as IPAddress and PortId are retrieved from AddReply (Step  6  in  FIG. 4 ) itself.   6. Notify messages (Steps  12  and  13  in  FIG. 3 ) are not required as IPAddress and PortId are retrieved in AddReply (Step  3  in  FIG. 4 ).   7. APM message (in Step  14  in  FIG. 3 ) is not required since the IPAddress and PortId has already been conveyed in the previous APM message (Step  4  in  FIG. 4 ).   8. Modify Request (in Steps  15  and  16  in  FIG. 3 ) are not required since IPAddress and PortId of peer has already been conveyed as part of AddRequest message (Step  5  in  FIG. 4 ).       
 
         [0069]    From the protocol perspective, when IP Bearer needs to be used, the optional BIWF Address and BNCId need to be made as mandatory as part of APM message. 
         [0070]    The above optimization procedure constitutes the invention. 
         [0071]    This section continues to outline the procedure proposed and the concrete benefits that would be arrived at. 
         [0072]      FIG. 4  illustrates proposed optimized bearer establishment procedures between two WCDMA R4 systems:
       1. MSC-A initiates bearer establishment procedure by sending BICC IAM message with BNC Characteristics set to IP/RTP indicating IP Bearer needs to be established and codec list indicating that codec negotiation is required.   2. MSC-B after processing IAM, performs Prepare Bearer procedure by sending AddRequest message to MGW-B. AddRequest contains the selected codec for bearer establishment and BNC Characteristics set to IP/RTP.   3. MGW-B responds with AddReply message that contains the IPAddress (in BIWF Address) and PortId (in BCNId).   4. MSC-B indicates to MSC-A the selected codec for bearer establishment, BIWF Address and the BNCId through BICC APM message.   5. MSC-A now performs Prepare Bearer procedure by sending AddRequest message containing the Codec type that needs to be used for bearer establishment, remote IPAddress and the PortId.   6. MGW-A responds with AddReply with its own IPAddress and PortId.   7. MSC-A now responds to MSC-B with MGW-A&#39;s IPAddress and PortId through BICC APM message.   8. MSC-B sends a ModifyRequest message to MGW-B containing the originating sides IPAddress and PortId.   9. MGW-B responds with ModifyReply. At this point in time, both the MGWs are aware of each other&#39;s IPAddress and PortId.   10. After RabAssignment procedures are successful on MSC-A towards the source RNC, it sends COT message to MSC-B to indicate that bearer establishment is successful on the originating side.   11. MSC-B after successful bearer establishment on terminating side, sends the ACM message to MSC-A.   12. And when terminating party answers, MSC-B sends the BICC ANM message to MSC-A.         
         [0085]    The following advantages are secured by following the invented method:
       1. Protocols involved (namely Q.1902.x and H.248.1) are not changed in terms of addition or removal of parameters, but only interpretation of existing procedures.   2. Support of IP Bearer by a WCDMA R4 system without using IPBCTP and IPBCP protocols.   3. Faster Call Setup due to the minimization and optimal usage of MGW procedures.   4. Processing power saved due to the absence of IPBCP strings and reduced message interactions. This will result in higher BHCA in the WCDMA system.   5. Reduced message sizes over the Nc (APM Message in BICC Protocol) and Mc (Add Request and Add Reply Messages in H.248.1) interfaces thereby providing for an effective utilization of the signaling resources.   6. The Forward Bearer Delayed Tunneling with Codec Negotiation that is detailed could be extended for Forward Bearer and Backward Bearer establishment procedures with or without Codec Negotiation between the two systems achieving the same set of advantages as detailed above.       
 
         [0092]    It will also be obvious to those skilled in the art that other control methods and apparatuses can be derived from the combinations of the various methods and apparatuses of the present invention as taught by the description and the accompanying drawings and these shall also be considered within the scope of the present invention. Further, description of such combinations and variations is therefore omitted above. It should also be noted that the host for storing the applications include but not limited to a microchip, microprocessor, handheld communication device, computer, rendering device or a multi function device. 
         [0093]    Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom. 
       REFERENCES 
       [0000]    
       
         
           
             1. ITU-T Recommendation Q.1902.4 (07/2001)—Bearer Independent Call Control Protocol. 
             2. ITU-T Recommendation Q.1970 (07/2001)—BICC IP Bearer Control Protocol. 
             3. ITU-T Recommendation Q.1990—BICC Bearer Control Tunneling Protocol. 
             4. ITU-T Recommendation H.248.1—(05/2002) Gateway Control Protocol. 
             5. 3GPP TS 29.414 V4.4.0 (2002-03)—Core Networlk Nb Data Transport and Transport Signaling. 
             6. ITU-T Recommendation Q.765.5—Signalling System No. 7—Application Transport Mechanism: Bearer Independent Call Control