Abstract:
A method and apparatus for transmitting User Equipment (UE) capability information required for provisioning of a service to a network before a UE requests the service are provided. Before an outgoing or incoming call setup is requested for the UE, a signaling connection is established between the UE and a core network (CN) node to which the UE belongs. After the signaling connection is established, a message including UE capability information of the UE is received and stored for use when the call setup is requested.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit under 35 U.S.C. § 119(a) of a Korean patent application entitled “Method and Apparatus for Acquiring UE Capability Information in a Communication Network”, filed in the Korean Intellectual Property Office on Mar. 18, 2005 and assigned Serial No. 2005-22614, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to a communication system. In particular, the present invention relates to a method and apparatus for transmitting information about the capabilities of a User Equipment (UE) to a network before a call setup in the UE.  
         [0004]     2. Description of the Related Art  
         [0005]     In a conventional call setup procedure, a UE transmits information about the UE capabilities in relation to call data processing to a network during requesting a call setup. The UE capability information comprises the phone number and supported CODEC list of the UE. The capability information of the calling UE is transferred to and stored in a called network node. The called network node then forwards the call setup request from the calling UE to a called UE. The called UE transmits its capability information to the called network node, such as Mobile Switching Center (MSC), by a response message. The called network node, which has acquired the UE capability information from both the calling UE and the called UE, forwards corresponding information to the calling UE based on the UE capability information, thereby establishing a bearer.  
         [0006]      FIG. 1  is a diagram illustrating a signal flow for a conventional call setup procedure. UE capability information provides supported CODECs herein, by way of example. The conventional call setup procedure will be described in the context of Tandem Free Operation (TFO) or Transcoding Free Operation (TrFO), a technique that obviates the need for additional CODEC translation during a call by finishing negotiations on CODECs during establishing a bearer for the call. CODEC information used to deliver voice information during a TrFO-supporting Circuit Switched (CS) call setup is determined at a CS connection setup.  
         [0007]     Referring to  FIG. 1 , a calling UE  101  (UE- 1 ) transmits a SETUP message to a Core Network (CN)  103  (CN- 1 ) via a Radio Network Controller (RNC)  102  (RNC- 1 ) in order to request a call setup in step  107 . The SETUP message comprises a supported CODEC list of UE- 1  which lists CODEC indexes x, y, z and w.  
         [0008]     In step  108 , CN- 1  stores the supported CODEC list and transmits a CALL PROCEEDING message to UE- 1 . CN- 1  then translates the SETUP message to an Initial Address Message (IAM) message by the System Signaling No. 7 (SS7) ISDN User Part (ISUP) protocol and transmits the supported CODEC list by the IAM message to a CN  104  (CN- 2 ) to which a called UE  106  (UE- 2 ) belongs in step  110 .  
         [0009]     CN- 2  stores the supported CODEC list of UE- 1 . To place UE- 2  to a connected mode, CN- 2  pages UE- 2 , sets up a Radio Resource Control (RRC) connection with UE- 2 , and receives a response for the paging from UE- 2  in step  112 .  
         [0010]     In step  114 , CN- 2  translates the IAM message received from CN- 1  to the SETUP message and forwards it as a call setup request from UE- 1  to UE- 2 . UE- 2  transmits a CALL CONFIRMED message containing its supported CODEC list with y, z, w and v to CN- 2  via an RNC  105  (RNC- 2 ) in step  115 . CN- 2  selects a CODEC to be used from the supported CODEC lists of UE- 1  and UE- 2  and transmits a Bearer Information message comprising the selected CODEC and an Available CODEC List to CN- 1  in step  117 . The selected CODEC is y and the available CODEC list has y, z and w, for example.  
         [0011]     In step  119 , CN-  1  establishes a data bearer with CN- 2  based on the Bearer Information message. After the bearer setup, a Radio Access Bearer (RAB)/Radio Bearer (RB) for the caller is established between UE- 1  and CN- 1  in step  121 . CN- 1  then notifies CN- 2  of completion of the RAB/RB setup by a Continuity message in step  123 .  
         [0012]     In step  125 , an RAB/RB for the called is established between UE- 2  and CN- 2 . After the RAB/RB setup, UE- 2  transmits to CN- 2  an Alerting message as ringing information indicating that it is prepared for a call setup in step  127 . CN- 2  translates the Alerting message to an ISUP Address Complete Message (ACM) message and transmits the ISUP ACM message to CN- 1  in step  129 . CN- 1  recovers the ACM message to the Alerting message and transmits the Alerting message to UE- 1  in step  131 .  
         [0013]     In step  133 , as the called lifts his receiver (Hook-Off) and thus a call starts, UE- 2  transmits a Connect message to CN- 2 . CN- 2  translates the Connect message to an ISUP Answer Message (ANM) message and transmits the ISUP ANM message to CN- 1  in step  135 . In step  138 , CN- 1  recovers the ANM message to the Connect message indicating the call connection and forwards the Connect message to UE- 1 . In steps  134  and  139 , CN- 1  and CN- 2  transmit Connect Ack messages to UE- 1  and UE- 2 , respectively. Thus, the call setup is completed.  
         [0014]     As described above, UE capability information related to UEs and a service is exchanged between CNs during a call service request from a calling UE and a bearer setup for the call service. This capability information exchange triggers capability negotiation, and an end-to-end bearer, that is, a bearer for the call between the caller and the called is established based on the capability negotiation. Therefore, the end-to-end call setup leads to degraded service quality and an increased latency due to additional time delay.  
       SUMMARY OF THE INVENTION  
       [0015]     An object of the present invention is to substantially solve at least the above problems and/or disadvantages and to provide at least the advantages below. Accordingly, the present invention provides a method and apparatus for reducing an overall latency in providing a fast end-to-end call service to a user.  
         [0016]     Exemplary implementation of the present invention provides a method and apparatus for transmitting UE capability information required for provisioning of a user-requested service to a network before the service request in order to provide the service fast to a user.  
         [0017]     According to one aspect of the present invention, a method of acquiring UE capability information in a communication network is provided. Before an outgoing or incoming call setup is requested for a User Equipment (UE), a signaling connection is established between the UE and a Core Network (CN) node to which the UE belongs. After the signaling connection is established, a message comprising UE capability information of the UE is received and stored in the CN node for use when the call setup is requested.  
         [0018]     According to another aspect of the present invention, a UE apparatus for transmitting UE capability information to a network in a communication network is provided. A message transmitter transmits a message comprising UE capability information of a UE through a signaling connection established between the UE and a CN node to which the UE belongs, before an outgoing or incoming call setup is requested for the UE. A message receiver receives a response message indicating whether the UE capability information has been stored from the CN node. A call processor determines whether to include the UE capability information in a confirmed message in response to a setup message or a call setup request message for requesting a call setup according to whether the UE capability information has been stored in the CN node.  
         [0019]     According to a further aspect of the present invention, an apparatus for acquiring UE capability information in a communication network is provided. A message transmitter and receiver establish a signaling connection with a UE and receive a message comprising UE capability information of the UE, before an outgoing or incoming call setup is requested for the UE. A UE capability information storage stores the UE capability information for use when the call setup is requested. A call processor acquires the UE capability information from the message and stores the UE capability information in the UE capability information storage. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:  
         [0021]      FIG. 1  is a diagram illustrating a signal flow for a conventional call setup procedure;  
         [0022]      FIG. 2  is a diagram illustrating a signal flow for a call setup procedure according to a first exemplary embodiment of the present invention;  
         [0023]      FIG. 3  is a diagram illustrating a signal flow for a call setup procedure according to a second exemplary embodiment of the present invention;  
         [0024]      FIG. 4  is a diagram illustrating a signal flow for a call setup procedure according to a third exemplary embodiment of the present invention;  
         [0025]      FIG. 5  is a block diagram of a User Equipment (UE) according to a preferred exemplary embodiment of the present invention; and  
         [0026]      FIG. 6  is a block diagram of a Core Network (CN) according to a preferred exemplary embodiment of the present invention. 
     
    
       [0027]     Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures.  
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0028]     Exemplary embodiments of the present invention will be described in greater details herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions will be omitted for clarity and conciseness.  
         [0029]     The subject matter of the present invention is to transmit User Equipment (UE) capability information required for providing a user-requested service to a network before the service request in order to provide the service fast to a user.  
         [0030]     The UE capability information is transmitted to the network during the UE&#39;s attaching to the network in an exemplary embodiment of the present invention. In an exemplary embodiment, the UE capability information transmitted to a Home Location Register (HLR) during registration is acquired from the HLR. After registration and attachment, the UE capability information is transmitted to the network by a new defined message in an exemplary embodiment of the present invention.  
         [0031]     For better understanding of an exemplary embodiment of the present invention, a UE-requested service is assumed to be a Tandem Free Operation (TFO) or Transcoding Free Operation (TrFO)-based end-to-end call service, and the UE capability information is described as CODEC information for a call service, that is, the UE&#39;s supported CODEC list. While detailed procedures, their names, and the definition of UE capability information may vary depending on the type of a service that a UE receives, the concepts are the same on the whole. The UE capability information can be the types of services available to the UE according to a network the UE has subscribed or is connected to, the UE&#39;s radio related information, identity information, charging information, authentication information, the phone number of the UE, a supported CODEC list, etc. While the present invention will be described below in the context of detailed message formats and signaling procedures used for a (CS) call, the subject matter of the present invention is not limited to the specific message names and signaling procedures.  
         [0032]     Embodiment 1  
         [0033]     The supported CODEC lists of UE- 1  and UE- 2  are transmitted to and stored in their corresponding Core Networks (CNs) during a Location Update procedure, i.e. an International Mobile System Identifier (IMSI) Attach procedure. The supported CODEC lists indicate CODEC types or CODEC modes.  
         [0034]      FIG. 2  is a diagram illustrating a signal flow for a call setup procedure according to an exemplary embodiment of the present invention. A calling UE  201  (UE- 1 ) is attached to a calling CN  203  (CN- 1 ) via a calling RNC  202  (RNC- 1 ), and a called UE  206  (UE- 2 ) is attached to a called CN  204  (CN- 2 ) via a called RNC  205  (RNC- 2 ). An HLR  207  (HLR- 1 ) and an HLR  208  (HLR- 2 ) to which CN- 1  and CN- 2  are respectively connected are the same entity or different entities.  
         [0035]     Referring to  FIG. 2 , UE- 1  and UE- 2  establish RRC connections for signaling in steps  210   a  and  210   b  and transmit Location Update Request messages to CN- 1  and CN- 2 , respectively in steps  212   a  and  212   b.  Each of the Location Update Request messages comprises the supported CODEC list of UE- 1  or UE- 2 . The supported CODEC list comprises CODEC indexes supported by the UE and is stored in the CN of the UE, for later use in selecting a CODEC.  
         [0036]     Upon receipt of the Location Update Request messages, CN- 1  and CN- 2  register the locations of UE- 1  and UE- 2  to HLR- 1  and HLR- 2 , respectively by Update Location messages in steps  213   a  and  213   b  and receive Update Location Ack messages from HLR- 1  and HLR- 2  in steps  214   a  and  214   b.  After the location registration, CN- 1  and CN- 2  transmit Location Update Accept messages to UE- 1  and UE- 2 , respectively in steps  215   a  and  215   b.    
         [0037]     To set up a call connection at a desired time point, UE- 1  transmits a SETUP message to CN- 1  in step  216 . While the SETUP message may not have the supported CODEC list of UE- 1 , it can comprise the supported CODEC list, considering ‘Backward Compatibility’.  
         [0038]     In step  218 , CN- 1  translates the SETUP message to an IAM message by the SS 7  ISUP protocol and transmits the IAM message to CN- 2 . The IAM message contains the supported CODEC list of UE- 1  that CN- 1  received and stored in step  212   a.  In step  220 , CN- 2  selects a CODEC from the supported CODEC list of UE- 1  and the stored supported CODEC list of UE- 2 . CN- 2  then transmits a Bearer Information message comprising the selected CODEC and an Available CODEC List to CN- 1  in step  222 .  
         [0039]     After paging UE- 2  in step  224 , CN- 2  establishes a bearer with CN- 1  based on the selected CODEC and the Available CODEC List in step  226   a.  When UE- 2  responds to the paging, CN- 2  forwards the SETUP message to UE- 2  in step  226   b  and receives a CALL CONFIRMED message from UE- 2  in step  229 . The CALL CONFIRM message may or may not comprise the supported CODEC list of UE  2 .  
         [0040]     As done in step  220 , CN- 2  can select a CODEC to be used between UE- 1  and UE- 2  before steps  224  through  229 . The selected CODEC and the Available CODEC List is transferred backward, that is, to CN- 1  by the Bearer Information message, thereby supporting fast setup of a data bearer required for transmitting a call.  
         [0041]     In step  230 , an RAB/RB for the caller is established between UE- 1  and CN- 1  based on the selected CODEC and the Available CODEC List. CN- 1  then notifies CN- 2  of completion of the RAB/RB setup by a Continuity message in step  231 .  
         [0042]     In step  232 , an RAB/RB for the called is established between UE- 2  and CN- 2  based on the selected CODEC and the Available CODEC List. After the RAB/RB setup, UE- 2  transmits to CN- 2  an Alerting message as ringing information indicating that it is prepared for a call setup in step  234   a.  CN- 2  translates the Alerting message to an ISUP ACM message and transmits the ISUP ACM message to CN- 1  in step  234   b.  CN- 1  recovers the ACM message to the Alerting message and transmits the Alerting message to UE- 1  in step  234   c.    
         [0043]     In step  236   a,  as the called lifts his receiver (Hook-Off) and thus the call starts, UE- 2  transmits a Connect message to CN- 2 . CN- 2  translates the Connect message to an ISUP ANM message and transmits the ISUP ANM message to CN- 1  in step  236   b.  In step  236   c,  CN- 1  recovers the ANM message to the Connect message indicating the call connection and forwards the Connect message to UE- 1 . In steps  238   a  and  238   b,  CN- 1  and CN- 2  transmit Connect Ack messages to UE- 1  and UE- 2 , respectively. Thus, the call setup is completed.  
         [0044]     Embodiment 2  
         [0045]     A calling CN and a called CN acquire the CODEC information of UEs from their subscriber information stored in HLRs during registration. Upon receipt a Location Update Request message from a UE within its coverage, a CN registers the location of the UE to an HLR and the HLR forwards the subscriber information of the UE to the CN. The subscriber information comprises a supported CODEC list as UE capability information registered to the HLR during subscription. During a Location Update procedure, the HLR transmits the supported CODC list along with the subscriber information of the UE to the CN, for use in a later CODEC negotiation.  
         [0046]      FIG. 3  is a diagram illustrating a signal flow for a call setup procedure according to an exemplary embodiment of the present invention. An HLR transmits the supported CODEC list of a UE together with the subscriber information of the UE. A calling UE  301  (UE- 1 ) is attached to a calling CN  303  (CN- 1 ) via a calling RNC  302  (RNC- 1 ), and a called UE  306  (UE- 2 ) is attached to a called CN  304  (CN- 2 ) via a called RNC  305  (RNC- 2 ). An HLR  307  (HLR- 1 ) and an HLR  308  (HLR- 2 ) to which CN- 1  and CN- 2  are respectively connected are the same entity or different entities.  
         [0047]     Referring to  FIG. 3 , UE- 1  and UE- 2  establish RRC connections in steps  310   a  and  31   b  and transmit Location Update Request messages to CN- 1  and CN- 2 , respectively in steps  312   a  and  312   b.  Each of the Location Update Request messages does not comprise the supported CODEC list of UE- 1  or UE- 2 .  
         [0048]     Upon receipt of the Location Update Request messages, CN- 1  and CN- 2  transmit Update Location messages to HLR- 1  and HLR- 2  in order to update the location information of UE- 1  and UE- 2  stored in HLR- 1  and HLR- 2 , respectively in steps  314   a  and  314   b.  After registering the location information of UE- 1  and UE- 2  in the Mobility Management (MM) contexts of UE- 1  and UE- 2 , HLR- 1  and HLR- 2  transmit the subscriber information and supported CODEC lists of UE- 1  and UE- 2  to CN- 1  and CN- 2 , respectively in steps  316   a  and  316   b.    
         [0049]     After storing the subscriber information and the supported CODEC lists, CN- 1  and CN- 2  transmit Location Update Ack messages to HLR- 1  and HLR- 2 , respectively, to notify successful reception of the subscriber information and the supported CODEC lists, in steps  318   a  and  318   b.  Upon receipt of Update Location Ack messages from HLR- 1  and HLR- 2  in steps  320   a  and  320   b,  CN- 1  and CN- 2  transmit Location Update Accept messages to UE- 1  and UE- 2 , respectively in steps  322   a  and  322   b.    
         [0050]     Because the supported CODEC lists of UE- 1  and UE- 2  are delivered to CN- 1  and CN- 2  before transmitting and receiving the call setup request in steps  312  through  320 , UE- 1  and UE- 2  do not need to transmit their supported CODEC lists later by a SETUP message and a CALL CONFIRMED message.  
         [0051]     When a user intends to set up a call connection, CN- 1  receives the SETUP message from UE- 1 , translates the SETUP message to an IAM message, and transmits the IAM message to CN- 2  in steps  324   a  and  324   b.  The SETUP message may or may not contain the supported CODEC list of UE- 1 , for ‘Backward Compatibility’. The IAM message comprises the supported CODEC list of UE- 1  that CN- 1  received and stored in step  316   a.  In step  326 , CN- 2  selects a CODEC from the supported CODEC list of UE- 1  acquired by the IAM message and the stored supported CODEC list of UE- 2 . CN- 2  then transmits a Bearer Information message comprising the selected CODEC and an Available CODEC List to CN- 1  in step  328 .  
         [0052]     As described above, since CN- 2  preliminarily stores the subscriber information and supported CODEC list of UE- 2  before UE- 1  requests the call setup to UE- 2 , it can select a CODEC without awaiting receipt of the CALL CONFIRMED message from UE- 2 .  
         [0053]     After paging UE- 2  in step  330 , CN- 2  establishes a bearer with CN- 1  based on the selected CODEC and the Available CODEC List in step  332 . When UE- 2  responds to the paging, CN- 2  forwards the SETUP message to UE- 2  in step  336  and receives the CALL CONFIRMED message from UE- 2  in step  338 . The CALL CONFIRM message may comprise the supported CODEC list of UE  2 , for ‘Backward Compatibility, or may not.  
         [0054]     In step  334 , an RAB/RB for the caller is established between UE- 1  and CN- 1  based on the selected CODEC and the Available CODEC List. CN- 1  then notifies CN- 2  of completion of the RAB/RB setup by a Continuity message in step  340 .  
         [0055]     In step  342 , an RAB/RB for the called is established between UE- 2  and CN- 2  based on the selected CODEC and the Available CODEC List. After the RAB/RB setup, UE- 2  transmits to CN- 2  an Alerting message as ringing information indicating that it is prepared for a call setup in step  344   a.  CN- 2  translates the Alerting message to an ISUP ACM message and transmits the ISUP ACM message to CN- 1  in step  344   b.  CN- 1  recovers the ACM message to the Alerting message and transmits the Alerting message to UE- 1  in step  344   c.    
         [0056]     In step  346   a,  when the called lifts his receiver (Hook-Off) and thus the call starts, UE- 2  transmits a Connect message to CN- 2 . CN- 2  translates the Connect message to an ISUP ANM message and transmits the ISUP ANM message to CN- 1  in step  346   b.  In step  346   c,  CN- 1  recovers the ANM message to the Connect message indicating the call connection and forwards the Connect message to UE- 1 . In steps  348   a  and  348   b,  CN- 1  and CN- 2  transmit Connect Ack messages to UE- 1  and UE- 2 , respectively. Thus, the call setup is completed.  
         [0057]     In accordance with the second exemplary embodiment of the present invention, the time delay of selecting a CODEC can be reduced by as much as the processing time of establishment of the RRC connection between UE- 2  and RNC- 2  by paging UE- 2  by CN- 2 , transmission of the SETUP message, and acquisition of the supported CODEC list from UE- 2  by the CALL CONFIRMED message.  
         [0058]     Embodiment 3  
         [0059]     A UE transmits its supported CODEC list to the CN to which it belongs by a new defined message. This message is called a ‘Capability Information’ message in the present invention. The Capability Information message comprises information about all CODECs supported by the UE. The Capability Information message can notify of the supported CODEC, i.e. UE capability information at any time before the UE requests a call as well as during a Location Update procedure.  
         [0060]      FIG. 4  is a diagram illustrating a signal flow for a call setup procedure according to a third exemplary embodiment of the present invention. A calling UE  401  (UE- 1 ) is attached to a calling CN  403  (CN- 1 ) via a calling RNC  402  (RNC- 1 ), and a called UE  406  (UE- 2 ) is attached to a called CN  404  (CN- 2 ) via a called RNC  405  (RNC- 2 ). An HLR  407  (HLR- 1 ) and an HLR  408  (HLR- 2 ) to which CN- 1  and CN- 2  are respectively connected are the same entity or different entities.  
         [0061]     Referring to  FIG. 4 , UE- 1  and UE- 2  establish RRC connections in steps  410   a  and  410   b  and transmit their supported CODEC lists to CN- 1  and CN- 2 , respectively by Capability Information messages at a particular time point before a call setup in steps  412   a  and  412   b.  CN- 1  and CN- 2  acquire and store the supported CODEC lists from the Capability Information messages and transmit Capability Information Ack messages to UE- 1  and UE- 2 , respectively in steps  414   a  and  414   b.  While not shown, in the case where CN- 1  and CN- 2  cannot process the supported CODEC lists, they transmit Error messages instead of the Capability Information Ack messages.  
         [0062]     In step  412   a  through step  414   b,  CN- 1  and CN- 2  acquire the supported CODEC lists of UE- 1  and UE- 2  by receiving the Capability Information messages and the Capability Information Ack messages and UE- 1  and UE- 2  perform the call setup by receiving the Capability Information Ack messages.  
         [0063]     When the user intends to set up a call connection, UE- 1  transmits a SETUP message to CN- 1 , for the call setup in step  416 . If UE- 1  and UE- 2  confirm by the Capability Information Ack messages that CN- 1  and CN- 2  have stored the supported CODEC lists in steps  414   a  and  414   b,  the SETUP message may not comprise the supported CODEC list of UE- 1 .  
         [0064]     In step  418 , CN- 1  translates the SETUP message to an IAM message and transmits the IAM message with the supported CODEC list of UE- 1  to CN- 2 .  
         [0065]     CN- 2  selects a CODEC from the supported CODEC list of UE- 1  acquired by the IAM message and the stored supported CODEC list of UE- 2  in step  420  and then transmits a Bearer Information message comprising the selected CODEC and an Available CODEC List to CN- 1  in step  422 .  
         [0066]     While not shown, if CN- 2  does not have the supported CODEC list of UE- 2  by the time when receiving the IAM message, CN- 2  pages UE- 2 , establishes an RRC connection, and acquires the supported CODEC list of UE- 2  by exchanging a SETUP message and a CALL CONFIRMED message, as done conventionally.  
         [0067]     After paging UE- 2  in step  424 , CN- 2  establishes a bearer with CN- 1  based on the selected CODEC and the Available CODEC List in step  426   a.  When UE- 2  responds to the paging, CN- 2  forwards the SETUP message to UE- 2  in step  428  and receives the CALL CONFIRMED message from UE- 2  in step  430 .  
         [0068]     Since CN- 1  and CN- 2  have already stored the supported CODEC lists of UE- 1  and UE- 2  by the CODEC Information messages and CODEC Information Ack messages, the CALL CONFIRMED message may not comprise the supported CODEC list of UE- 2  but may comprise it for ‘Backward Compatibility’.  
         [0069]     In step  432 , an RAB/RB for the caller is established between UE- 1  and CN- 1  based on the selected CODEC and the Available CODEC List. CN- 1  then notifies CN- 2  of completion of the RAB/RB setup by a Continuity message in step  434 .  
         [0070]     In step  436 , an RAB/RB for the called is established between UE- 2  and CN- 2  based on the selected CODEC and the Available CODEC List. After the RAB/RB setup, UE- 2  transmits to CN- 2  an Alerting message as ringing information indicating that it is prepared for a call setup in step  438   a.  CN- 2  translates the Alerting message to an ISUP ACM message and transmits the ISUP ACM message to CN- 1  in step  438   b.  CN- 1  recovers the ACM message to the Alerting message and transmits the Alerting message to UE-  1  in step  438   c.    
         [0071]     In step  440   a,  when the called lifts his receiver (Hook-Off) and thus the call starts, UE- 2  transmits a Connect message to CN- 2 . CN- 2  translates the Connect message to an ISUP ANM message and transmits the ISUP ANM message to CN- 1  in step  440   b.  In step  440   c,  CN- 1  recovers the ANM message to the Connect message indicating the call connection and forwards the Connect message to UE- 1 . In steps  442   a  and  442   b,  CN- 1  and CN- 2  transmit Connect Ack messages to UE- 1  and UE- 2 , respectively. Thus, the call setup is completed.  
         [0072]     With reference to  FIGS. 5 and 6 , the configurations of a UE and a CN for implementing the above exemplary embodiments of the present invention will be described below.  
         [0073]      FIG. 5  is a block diagram of a UE according to a preferred exemplary embodiment of the present invention. Referring to  FIG. 5 , a UE  500  comprises a message transmitter  502 , a call processor  504 , and a message receiver  506 .  
         [0074]     The message transmitter  502  generates a message comprising UE capability information such as a supported CODEC list and transmits the message to a CN that the UE  500  belongs to. The message is a Location Update Request message or a Capability Information message according to one of the first, second and third exemplary embodiments. The message transmitter  502  also transmits messages for a call setup with the other party and transmits the messages to the CN via an RNC, under the control of the call processor  504 . After the call setup, the message transmitter  502  transmits call data.  
         [0075]     The message receiver  506  receives a response message indicating whether the UE capability information has been stored from the CN to which the UE  500  belongs, and transmits the response message to the call processor  504 . The message receiver  506  also receives message for the call setup with the other party, interprets the received messages, and receives call data after the call setup, under the control of the call processor  504 .  
         [0076]     The call processor  504  establishes a radio bearer for a call service with the other party by controlling the message transmitter  502  and the message receiver  506 . Particularly, the call processor  504  controls the message transmitter  502  to transmit the UE capability information before the call setup, receives the response message indicating whether the UE capability information has been stored in a corresponding CN through the message receiver  506 , and determines whether to comprise the UE capability information in a SETUP message or a CALL CONFIRM message generated from the message transmitter  502  according to the response message. If the UE capability information has already been stored in the CN, the SETUP message or the CALL CONFIRM message may not comprise the UE capability information.  
         [0077]      FIG. 6  is a block diagram of a CN according to a preferred exemplary embodiment of the present invention.  
         [0078]     Referring to  FIG. 6 , a CN  600  comprises a message receiver  604  (message receiver  1 ) and a message transmitter  606  (message transmitter  1 ) for transmitting/receiving messages to/from a UE within its coverage and an HLR, a message transmitter  610  (message transmitter  1 ) and a message receiver  612  (message receiver  2 ) for transmitting/receiving messages to/from another CN, a UE capability information storage  602 , and a call processor  608 .  
         [0079]     The message receivers  604  and  612  receive a message comprising UE capability information from a UE irrespective of whether the UE within the coverage of the CN  600  is a caller or a called and provide the received message to the call processor  608 . The message is a Location Update Request message or a Capability Information message according to one of the first, second and third exemplary embodiments. The UE capability information storage  602  stores the UE capability information acquired through the message receivers  604  and  612  by the call processor  608 .  
         [0080]     In the case where the UE is a caller, the message receiver  604  provides a SETUP message for requesting a call service received from the UE to the call processor  608 . The SETUP message may comprise the supported CODEC list of the UE, for ‘Backward Compatibility’, or may not. The call processor  608  translates the SETUP message to an IAM message, comprises the UE capability information read from the UE capability information storage  602  in the IAM message, and transmits the IAM message to a called CN through the message transmitter  610 .  
         [0081]     In response to the IAM message, the message receiver  612  receives a Bearer Information message comprising a selected CODEC and an Available CODEC list for the call service from the called CN and provides the received message to the call processor  608 .  
         [0082]     The call processor  608  acquires the selected CODEC and the Available CODEC list from the Bearer Information message. Based on the selected CODEC and the Available CODEC list, the call processor  608  establishes a radio bearer for the call service with the UE by controlling the message transmitter  606  and the message receiver  604 , and establishes a data bearer with the called CN by controlling the message transmitter  610  and the message receiver  612 .  
         [0083]     In the case where the UE is a called, the message receiver  605  receives an IAM message comprising the supported CODEC list of a calling UE from a calling CN and provides the IAM message to the call processor  608 . The call processor  608  reads the supported CODEC list of the UE from the UE capability information storage  602  and acquires the supported CODEC list of the calling UE from the IAM message. It then selects a CODEC commonly existing in both the supported CODEC lists, for the call service, and generates an Available CODEC List. The call processor  608  transmits the selected CODEC and the Available CODEC List by a BEARER Information message to the calling CN through the message transmitter  601 .  
         [0084]     Meanwhile, the call processor  608  establishes a radio bearer for the call service with the UE by controlling the message transmitter  606  and the message receiver  604 , and establishes a data bearer with the called CN by controlling the message transmitter  610  and the message receiver  612 .  
         [0085]     The UE and the CN configured as illustrated in  FIGS. 5 and 6  acquire the capability information of a corresponding UE before a call setup. The resulting decrease of a latency involved in a UE capability information acquisition procedure during the call setup allows for a more efficient call service procedure.  
         [0086]     In accordance with the present invention as described above, since a UE registers information destined for a network to a provider network or transmits the information to the network at a later specific time during requesting a particular service, the latency of the call setup can be reduced when a user wants the service.  
         [0087]     While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.