Patent Publication Number: US-2013250748-A1

Title: Apparatus and method for providing multi-rab service in communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     The present application is related to and claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Mar. 26, 2012 and assigned Serial No. 10-2012-0030430, the entire disclosure of which is hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a communication system. More particularly, the present disclosure relates to an apparatus and a method for providing a multi-Radio Access Bearer (multi-RAB) service in a communication system. 
     BACKGROUND 
     As a communication technology develops, various wireless communication services using a wireless network are provided. For example, a wireless communication system provides a voice communication service between users via a communication electronic device. For another example, a wireless communication system provides a data service such as a wireless Internet service in order to meet a user&#39;s demand for a multimedia service. 
     The wireless communication system provides a multi-RAB service for connecting, a voice call and a data call together between nodes in order to swiftly provide a voice communication service and a data service. 
     In the case where an error of a data call occurs during a multi-RAB state, the wireless communication system releases both a data call and a voice call between nodes due to the error of the data call. That is, a user of an electronic device cannot use even a voice communication service due to the error of the data call. 
     SUMMARY 
     To address the above-discussed deficiencies, embodiments of the present disclosure provide an apparatus and a method for providing a multi-RAB service in a communication system. 
     Certain embodiments of the present disclosure include an apparatus and a method for maintaining a voice call connection when an error of a data call occurs in a communication system providing a multi-RAB service. 
     Certain embodiments of the present disclosure include an apparatus and a method for releasing a data call while maintaining a voice call when an error of the data call occurs in a communication system providing a multi-RAB service. 
     Certain embodiments of the present disclosure include an apparatus and a method for releasing a data call while maintaining a voice call when an error of the data call occurs based on the number of retransmissions in a communication system providing a multi-RAB service. 
     Certain embodiments of the present disclosure include an apparatus and a method for releasing a data call while maintaining a voice call when an error of the data call occurs depending on a wireless network state in a communication system providing a multi-RAB service. 
     Certain embodiments of the present disclosure include a method for maintaining a voice call in an electronic device providing a multi-Radio Access Bearer (RAB). The method includes connecting a data call and a voice call with a wireless network, and when an error of the data call is detected, releasing the connection of the data call with the wireless network. 
     Certain embodiments of the present disclosure include a method for maintaining a voice call in a base station providing a multi-Radio Access Bearer (RAB). The method includes connecting a data call and a voice call with an electronic device, and when an error of the data call is detected, releasing the connection of the data call with the electronic device. 
     Certain embodiments of the present disclosure include an apparatus for maintaining a voice call in an electronic device providing a multi-Radio Access Bearer (RAB). The apparatus includes a receiver for receiving a signal, a transmitter for transmitting a signal, and a controller for connecting a data call and a voice call with a wireless network using the receiver and the transmitter. When an error of the data call is detected, the controller releases the connection of the data call with the wireless network. 
     Certain embodiments of the present disclosure include an apparatus for maintaining a voice call in a base station providing a multi-Radio Access Bearer (RAB). The apparatus includes a transmitter for transmitting a signal, a receiver for receiving a signal, and a controller for connecting a data call and a voice call with an electronic device using the transmitter and the receiver. When an error of the data call is detected, the controller releases the connection of the data call with the electronic device. 
     Other aspects, advantages and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses embodiments of the disclosure. 
     Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or: the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings: 
         FIG. 1  illustrates a procedure for maintaining a voice call in a communication system according to embodiments of the present disclosure; 
         FIG. 2  illustrates a procedure for maintaining a voice call with a base station in an electronic device according to embodiments of the present disclosure; 
         FIG. 3  illustrates a procedure for maintaining a voice call with an electronic device in a base station according to embodiments of the present disclosure; 
         FIG. 4  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions of an electronic device according, to embodiments of the present disclosure; 
         FIG. 5  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions of a base station according to embodiments of the present disclosure; 
         FIG. 6  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions of an electronic device according to embodiments of the present disclosure; 
         FIG. 7  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions of a base station according to embodiments of the present disclosure; 
         FIG. 8  illustrates a procedure for maintaining a voice call with a base station based on a wireless network state of an electronic device according to embodiments of the present disclosure; 
         FIG. 9  illustrates a procedure for maintaining a voice call in a communication system according to embodiments of the present disclosure; 
         FIG. 10  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions of a base station according to embodiments of the present disclosure; 
         FIG. 11  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions of an electronic device according to embodiments of the present disclosure; 
         FIG. 12  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions of a base station according to embodiments of the present disclosure; 
         FIG. 13  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions of an electronic device according to embodiments of the present disclosure; 
         FIG. 14  illustrates a base station according to embodiments of the present disclosure; and 
         FIG. 15  illustrates an electronic device according to embodiments of the present disclosure. 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures. 
     DETAILED DESCRIPTION 
       FIGS. 1 through 15 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication device or wireless communication system. The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of embodiments of the present disclosure as defined by the claims and their equivalents. The present disclosure includes various specific details to assist in that understanding but these embodiments of the present disclosure are to be regarded as mere examples. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of embodiments of the present disclosure is provided for illustration purposes only and not for the purpose of limiting the appended claims and their equivalents. 
     Embodiments of the present disclosure provide a technology for maintaining a voice call when an error of a data call occurs in a communication system providing a multi-RAB service. 
     In the following description, a base station can represent a wireless network providing a wireless communication service to an electronic device. 
     In the following description, examples of the electronic device include a mobile communication terminal, a Personal Digital Assistant (PDA), a laptop computer, a smart phone, a netbook, a television, a Mobile Internet Device (MID), an Ultra Mobile Personal Computer (UMPC), a tablet Personal Computer (PC), a navigation, and an MP3. 
       FIG. 1  illustrates a procedure for maintaining a voice call in a communication system according to embodiments of the present disclosure. 
     As illustrated in  FIG. 1 , an electronic device  100  and a base station  110  set a voice call and a data call (step  121 ). That is, the electronic device  100  and the base station  110  set a multi-RAB state. 
     In the case where an error of a data call is detected during the multi-RAB state (step  123 ), the electronic device  100  requests the base station  110  to release the data call in order to prevent both the connections of the data call and the voice call from being released due to the error of the data call with the base station  110  (step  125 ). For example, in step  125 , the electronic device  100  transmits Signaling Connection Release Indication (SCRI) to the base station  110 . 
     The base station  110  performs a data call release procedure with the electronic device  100  as a result of receiving the data call release request of the electronic device  100  (step  127 ). For example, the base station  110  performs the data call release procedure with the electronic device  100  via a Radio Bearer Release. Specifically, the base station  110  sets a domain to a Packet Switched (PS) domain and transmits the same to the electronic device  100 . The electronic device  100  releases the data call with the base station  110  according to the PS domain provided from the base station  110 . At this point, the electronic device  100  maintains a Packet Data Protocol (PDP) context with the base station  110 . 
     Accordingly, the electronic device  100  and the base station  110  can maintain the voice call and provide a voice service even when an error of the data call occurs (step  129 ). 
     When an error of a data call between nodes is detected, a wireless communication system providing a multi-RAB service releases connections of the data call and a voice call between nodes via cell update. Accordingly, to prevent a connection release of the voice call, the wireless communication system can release a data call connection between the electronic device  100  and the base station  110  before cell update occurs, thereby maintaining, the voice call. At this point, the electronic device  100  operates as illustrated in  FIG. 2 . 
       FIG. 2  illustrates a procedure for maintaining a voice call with a base station  110  in an electronic device  100  according to embodiments of the present disclosure. 
     Referring to  FIG. 2 , the electronic device sets a multi-RAB with the base station in block  201 . That is, the electronic device  100  connects a voice call and a data call with the base station  110 . 
     After that, the electronic device proceeds to block  203  to determine whether an error of the data call is detected. For example, the electronic device  100  determines whether a data transmission error (Radio Link Control (RLC)-unrecoverable error) or a radio link error is detected. 
     When the error of the data call is not detected, the electronic device proceeds to block  201  to maintain the multi-RAB state with the base station. 
     In contrast, when the error of the data call is detected, the electronic device proceeds to block  205  to request the base station to release the data call. For example, the electronic device  100  transmits a SCRI to the base station  110 . 
     After that, the electronic device proceeds to block  207  to determine whether a response signal to the data call release request has been received from the base station. 
     When the response signal to the data call release request has been received from the base station, the electronic device proceeds to block  209  to release the data call connection with the base station. For example, in case of receiving a domain set to a PS domain from the base station  110 , the electronic device  100  releases the data call connection with the base station. At this point, the electronic device  100  maintains PDP context with the base station. 
     After that, the electronic device  100  ends the present algorithm. 
       FIG. 3  illustrates a procedure for maintaining a voice call with an electronic device in a base station according to embodiments of the present disclosure. 
     Referring to  FIG. 3 , the base station sets a multi-RAB with the electronic device in block  301 . That is, the base station  110  connects a voice call and a data call with the electronic device  100 . 
     After that, the base station  110  proceeds to block  303  to determine whether the electronic device  100  requests a release of the data call. For example, the base station  110  determines whether a SCRI has been received from the electronic device  100 . 
     When the electronic device  100  does not request the release of the data call, the base station  110  proceeds to block  301  to maintain the multi-RAB state with the electronic device. 
     In contrast, when the electronic device  100  requests the release of the data call, the base station  110  proceeds to block  305  to transmit a response signal to the data call release request to the electronic device. For example, the base station  110  sets a domain to a PS domain according to a radio bearer release and transmits the same to the electronic device  100 . 
     After that, the base station proceeds to block  307  to release the data call connection with the electronic device. At this point, the base station  110  maintains the voice call connection with the electronic device and provides a voice service to the electronic device. 
     After that, the base station  110  ends the present algorithm. 
     As described above, when detecting an error of a data call before cell update by the error of the data call occurs, the electronic device  110  releases the data call connection with the base station as illustrated in  FIG. 2 . Accordingly, the electronic device  100  can maintain the voice call connection with the base station to receive the voice service from the base station. 
     The electronic device  100  can determine whether an error of a data call occurs with consideration of a data transmission error as illustrated in  FIG. 4 . 
       FIG. 4  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions by an electronic device according to embodiments of the present disclosure. 
     Referring to  FIG. 4 , the electronic device sets a multi-RAB with the base station in block  401 . That is, the electronic device  100  connects a voice call and a data call with the base station  110 . 
     After that, the electronic device  100  proceeds to block  403  to determine whether data has been received from the base station. For example, the electronic device  100  determines whether data has been received from the base station  110  via the data call connected with the base station. 
     When data has been received from the base station, the electronic device  100  proceeds to block  405  to determine whether an error of the data received from the base station occurs. 
     When the error of the data received from the base station does not occur, the electronic device proceeds to block  403  to determine whether the next data has been received from the base station. At this point, the electronic device  100  transmits an acknowledgment message ACK for error-free data to the base station  110 . 
     In contrast, when the error of the data received from the base station occurs, the electronic device proceeds to block  407  to determine the number of retransmission requests for the error-occurred data. 
     After that, the electronic device proceeds to block  409  to determine whether the number of retransmission requests is equal to or greater than a reference request frequency in order to determine whether retransmission of the error-occurred data is requested. The reference request frequency is set to a value equal to or less than a maximum request frequency by which the electronic device  100  can request the base station to retransmit data. That is, in the case where the electronic device  100  has requested retransmission of data as many as the maximum request frequency, but failed to receive the data, the wireless communication system performs a cell update, so that connections of the data call and the voice call between the base station and the electronic device are released. Accordingly, the reference request frequency is set to a value equal to or less than the maximum request frequency. At this point, the electronic device  100  receives the reference request frequency from the base station  110 . 
     When the number of retransmission requests is less than the reference request frequency, the electronic device  100  recognizes that a retransmission request of the error-affected data is possible. Accordingly, the electronic device  100  proceeds to block  417  to request the base station to retransmit the error-occurred data. For example, the electronic device  100  transmits a NACK message for the error-affected data to the base station  110 . 
     In contrast, when the number of retransmission requests is equal to or greater than the reference request frequency, the electronic device  100  determines that an error of data has occurred. Accordingly, the electronic device  100  proceeds to block  411  to request the base station  110  to release the data call. For example, the electronic device  100  transmits a SCRI to the base station  110 . 
     After that, the electronic device  100  proceeds to block  413  to determine whether a response signal to the data call release request has been received from the base station. 
     When the response signal to the data call release request has been received from the base station, the electronic device  100  proceeds to block  415  to release the data call connection with the base station. For example, when receiving a domain set to a PS domain from the base station, the electronic device  100  releases the data call connection with the base station. At this point, the electronic device maintains the voice call connection with the base station  110  and receives a voice service from the base station. 
     After that, the electronic device  100  ends the present algorithm. 
       FIG. 5  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions by a base station according, to embodiments of the present disclosure. 
     Referring to  FIG. 5 , the base station sets a multi-RAB with the electronic device in block  501 . That is, the base station  110  connects a voice call and a data call with the electronic device. 
     After that, the base station proceeds to block  503  to transmit data to the electronic device. For example, the base station  110  transmits data to the electronic device  100  via the data call connected with the electronic device. 
     After transmitting data to the electronic device, the base station  110  proceeds to block  505  to determine whether the electronic device  100  requested a release of the data call. For example, the base station  110  determines whether a SCRI has been received from the electronic device  110 . 
     When the electronic device  100  does not request the release of the data call, the base station  110  proceeds to block  511  to determine whether a retransmission request signal has been received from the electronic device. For example, the base station  110  determines whether a NACK for data transmitted to the electronic device has been received. 
     When receiving an ACK for data transmitted to and received by the electronic device, the base station  110  recognizes that data transmission to the electronic device has been completed. Accordingly, the base station  110  ends the present algorithm. At this point, the base station  110  proceeds to block  503  to transmit the next data to the electronic device. 
     In contrast, when receiving a NACK for the data transmitted to and received by the electronic device, the base station  110  proceeds to block  513  to retransmit, to the electronic device, the data for which the NACK was received. 
     After that, the base station  110  proceeds to block  505  to determine whether the electronic device requests a release of the data call. 
     When the electronic device  100  requests the release of the data call, the base station  110  proceeds to block  507  to transmit a response signal to the data call release request by the electronic device to the electronic device. For example, the base station sets a domain to a PS domain according to a radio bearer release and transmits the same to the electronic device. 
     After that, the base station  110  proceeds to block  509  to release the data call connection with the electronic device. At this point, the base station  110  maintains the voice call connection with the electronic device and provides a voice service to the electronic device. 
     After that, the base station  110  ends the present algorithm. 
     In certain embodiments, the electronic device  100  determines whether an error of the data call occurs based on the number of retransmission requests for data that have been provided from the base station. 
     In certain embodiments, the electronic device  100  determines whether an error of the data call occurs based on the number of retransmissions of the data as illustrated in  FIG. 6 . 
       FIG. 6  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions by an electronic device according to embodiments of the present disclosure. 
     Referring to  FIG. 6 , the electronic device sets a multi-RAB with the base station in block  601 . That is, the electronic device  100  connects a voice call and a data call with the base station  110 . 
     After that, the electronic device  100  proceeds to block  603  to transmit data to the base station. For example, the electronic device  100  transmits data to the base station  110  via the data call connected with the electronic device. 
     After transmitting the data to the base station, the electronic device  100  proceeds to block  605  to determine whether a NACK associated with the data transmitted in block  603  has been received from the base station  110 . 
     When receiving an ACK for the data transmitted in block  603  from the base station, the electronic device  100  recognizes that the data transmission is successful. Accordingly, the electronic device  100  proceeds to block  603  to transmit the next data to the base station. 
     In contrast, when receiving a NACK associated with the data transmitted in block  603  from the base station, the electronic device  100  proceeds to block  607  to determine the number of retransmissions of the data for the NACK. 
     After that, the electronic device  100  proceeds to block  609  to determine whether the number of retransmissions is equal to or greater than a reference frequency in order to determine whether a retransmission of the data associated with the NACK is possible. The reference frequency is set to a value equal to or less than a maximum transmission frequency by which the electronic device can retransmit data. That is, in the case where the electronic device  100  has retransmitted data as many as the maximum transmission frequency but failed to successfully transmit the data, the wireless communication system performs cell update, so that connections of the data call and the voice call between the base station and the electronic device are released. Accordingly, the reference frequency is set to a value equal to or less than the maximum transmission frequency. The electronic device  100  can receive the reference frequency from the base station. 
     When the number of retransmissions is less than the reference frequency, the electronic device  100  determines that retransmission of the data associated with the NACK is possible. Accordingly, the electronic device  100  proceeds to block  617  to retransmit the data associated with the NACK to the base station. 
     In contrast, when the number of retransmissions is equal to or greater than the reference frequency, the electronic device  100  determines that an error of the data call occurred. Accordingly, the electronic device  100  proceeds to block  611  to request the base station to release the data call. For example, the electronic device  100  transmits a SCRI to the base station  110 . 
     After that, the electronic device  100  proceeds to block  613  to determine whether a response signal to the data call release request has been received from the base station. 
     When receiving the response signal associated with the data call release request from the base station, the electronic device  100  proceeds to block  615  to release the data call connection with the base station. For example, when receiving a domain set to a PS domain from the base station, the electronic device  100  releases the data call connection with the base station. At this point, the electronic device maintains the voice call connection with the base station  110  and continues to receive a voice service from the base station. 
     After that, the electronic device  100  ends the present algorithm. 
       FIG. 7  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions by a base station according to embodiments of the present disclosure. 
     Referring to  FIG. 7 , the base station sets a multi-RAB with the electronic device in block  701 . That is, the base station  110  connects a voice call and a data call with the electronic device  100 . 
     After that, the base station  110  proceeds to block  703  to determine whether data has been received from the electronic device. For example, the base station  110  determines whether data is received from the electronic device  100  via the data call connected with the electronic device. 
     When receiving data from the electronic device, the base station  110  proceeds to block  705  to determine whether an error of the data received from the electronic device occurs. 
     When the error of the data received from the electronic device does not occur, the base station  100  determines that the data reception from the electronic device is successful. Accordingly, the base station  110  proceeds to block  709  to transmit an ACK associated with the error-free data to the electronic device. 
     After that, the base station  110  proceeds to block  703  to determine whether the next data has been received from the electronic device. 
     In contrast, when the error of the data received from the electronic device occurs, the base station  110  proceeds to block  707  to transmit a NACK associated with the error-occurred data to the electronic device. 
     After that, the base station  110  proceeds to block  711  to determine whether the electronic device requests release of the data call. For example, the base station  110  determines whether a SCRI has been received from the electronic device  100 . 
     When the electronic device  100  does not request the release of the data call, the base station  110  proceeds to block  703  to determine whether the next data has been received from the electronic device. 
     In contrast, when the electronic device  100  requests the release of the data call, the base station  110  proceeds to block  713  to transmit a response signal associated with the data call release request to the electronic device. For example, the base station  110  sets a domain to a PS domain according to a radio bearer release and transmits the same to the electronic device  100 . 
     After that, the base station  110  proceeds to block  715  to release the data call connection with the electronic device. At this point, the base station maintains the voice call connection with the electronic device and continues to provide a voice service to the electronic device. 
     After that, the base station  110  ends the present algorithm. 
     In certain embodiments, the electronic device  100  determines whether an error of the data call occurs based on a data transmission error. 
     In certain embodiments, the electronic device  100  determines whether the error of the data call occurs based on a wireless network error as illustrated in  FIG. 8 . 
       FIG. 8  illustrates a procedure for maintaining a voice call with a base station based on a wireless network state of an electronic device according to embodiments of the present disclosure. 
     Referring to  FIG. 8 , the electronic device  100  sets a multi-RAB with the base station in block  801 . That is, the electronic device  100  connects a voice call and a data call with the base station  110 . 
     After that, the electronic device  100  proceeds to block  803  to determine whether an error of a wireless network with the base station has occurred. For example, the electronic device  100  determines whether the error of the wireless network with the base station occurs based on wireless channel estimate information with the base station. For another example, the electronic device  100  compares intensity of a signal provided from the base station  110  with a reference intensity to determine whether the error of the wireless network with the base station has occurred. 
     When the error of the wireless network does not occur, the electronic device  100  determines that an error of the data call has not occurred. Accordingly, the electronic device  100  proceeds to block  801  to maintain the multi-RAB with the base station. 
     In contrast, when the error of the wireless network occurs, the electronic device  100  determines that the error of the data call has occurred. Accordingly, the electronic device  100  proceeds to block  805  to request the base station  110  to release the data call. For example, the electronic device  100  transmits a SCRI to the base station  110 . 
     After that, the electronic device  100  proceeds to block  807  to determine whether a response signal associated with the data call release request has been received from the base station. 
     When the response signal associated with the data call release request has been received from the base station, the electronic device  100  proceeds to block  809  to release the data call connection with the base station. For example, when receiving a domain set to a PS domain from the base station, the electronic device  100  releases the data call connection with the base station. At this point, the electronic device maintains the voice call connection with the base station and continues to receive a voice service from the base station. 
     After that, the electronic device  100  ends the present algorithm. 
     In certain embodiments, when an error of a data call occurs in the wireless communication system providing the multi-RAB service, the electronic device  100  requests the base station to release the connection of the data call. 
     In certain embodiments, when an error of a data call occurs in the wireless communication system, the base station  110  requests the electronic device to release the connection of the data call as illustrated in  FIG. 9 . 
       FIG. 9  illustrates a procedure for maintaining a voice call in a communication system according to embodiments of the present disclosure. 
     As illustrated in  FIG. 9 , an electronic device  900  and a base station  910  set a voice call and a data call (step  921 ). That is, the electronic device  900  and the base station  910  set the multi-RAB state. 
     When detecting an error of the data call of the multi-RAB state (step  923 ), the base station  910  requests the electronic device  900  to release the data call in order to prevent both connections of the data call and the voice call from being released due to the error of the data call with the electronic device  900  (step  925 ). 
     After that, the base station  910  performs a data call release procedure with the electronic device  900 . For example, the base station  910  performs the data call release procedure with the electronic device  900  via a radio bearer release (step  927 ). Specifically, the base station  910  sets a domain to a PS domain and transmits the same to the electronic device  900 . The electronic device  900  releases the data call according to the PS domain provided from the base station  910 . At this point, the electronic device  900  maintains Packet Data Protocol (PDP) information with the base station  910 . 
     Accordingly, the electronic device  900  and the base station  910  maintain a voice call and continue to provide a voice service (step  929 ). 
     In certain embodiments, when detecting the error of the data call (step  923 ), the base station  910  requests the electronic device  900  to release the data call (step  925 ), and then performs the data call release procedure with the electronic device  900  (step  927 ). 
     In certain embodiments, when detecting the error of the data call (step  923 ), the base station  910  performs the data call release procedure with the electronic device  900  (step  927 ). 
     As described above, when detecting the error of the data call, the base station  910  of the wireless communication system requests the electronic device  900  to release the data call before cell update occurs in order to prevent the connections of the data call and the voice call from being released by the cell update. For example, the base station determines whether the error of the data call occurs based on a data transmission error as illustrated in  FIG. 10 . 
       FIG. 10  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions in a base station  910  according to embodiments of the present disclosure. 
     Referring to  FIG. 10 , the base station  910  sets a multi-RAB with the electronic device in block  1001 . That is, the base station  910  connects a voice call and a data call with the electronic device  900 . 
     After that, the base station  910  proceeds to block  1003  to transmit data to the electronic device  900 . For example, the base station  910  transmits data to the electronic device  900  via the data call connected with the electronic device. 
     After transmitting the data to the electronic device, the base station  910  proceeds to block  1005  to determine whether a retransmission request signal has been received from the electronic device  900 . For example, the base station  910  determines whether a NACK associated with the data transmitted to the electronic device has been received. 
     When receiving an ACK associated with the data transmitted to the electronic device, the base station  910  determines that data transmission to the electronic device has been completed. Accordingly, the base station  910  proceeds to block  1003  to transmit data to the next electronic device  900 . 
     In contrast, when receiving a NACK associated with the data transmitted to the electronic device, the base station  910  proceeds to block  1007  to determine the number of retransmissions of the data associated with NACK. 
     After that, the base station  910  proceeds to block  1009  to determine the number of retransmissions is equal to or greater than a reference frequency in order to determine whether retransmission of the data associated with the NACK is possible. The reference frequency is set to a value equal to or less than a maximum transmission frequency by which the base station can retransmit data. That is, when the base station  910  has retransmitted data as many as the maximum retransmission frequency, but failed to transmit the data, the wireless communication system performs cell update, so that connections of the data call and the voice call between the base station and the electronic device are released. Accordingly, the reference frequency is set to a value equal to or less than the maximum transmission frequency. 
     When the number of retransmissions is less than the reference frequency, the base station  910  determines that retransmission of the data associated with the NACK is possible. Accordingly, the base station  910  proceeds to block  1013  to retransmit the data associated with the NACK to the electronic device  900 . 
     In contrast, when the number of retransmissions is equal to or greater than the reference frequency, the base station  910  determines that an error of the data call has occurred. Accordingly, the base station  910  proceeds to block  1011  to perform a data call release procedure with the electronic device  900 . For example, the base station  910  sets a domain to a PS domain according to a radio bearer release and transmits the same to the electronic device  900  to release the data call connection with the electronic device. At this point, the base station  910  maintains the voice call connection with the electronic device and continues to provide a voice service to the electronic device. 
     After that, the base station  910  ends the present algorithm. 
       FIG. 11  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions by an electronic device  900  according to embodiments of the present disclosure. 
     Referring to  FIG. 11 , the electronic device  900  sets a multi-RAB with the base station in block  1101 . That is, the electronic device  900  connects a voice call and a data call with the base station  910 . 
     After that, the electronic device  900  proceeds to block  1103  to determine whether data has been received from the base station. For example, the electronic device  900  determines whether data has been received from the base station  910  via the data call connected with the base station. 
     When receiving the data from the base station, the electronic device  900  proceeds to block  1105  to determine whether an error of the data received from the base station has occurred. 
     When the error of the data received from the base station does not occur, the electronic device  900  proceeds to block  1103  to determine whether the next data has been received from the base station  910 . At this point, the electronic device  900  transmits an ACK associated with the error-free data to the base station  910 . 
     In contrast, when the error of the data received from the base station occurs, the electronic device  900  proceeds to block  1107  to request the base station  910  to retransmit the error-occurred data. For example, the electronic device  900  transmits a NACK f associated with or the error-occurred data to the base station  910 . 
     After that, the electronic device  900  proceeds to block  1109  to determine whether a release signal for the data call has been received from the base station  910 . For example, the electronic device  900  determines whether a signal set to a PS domain has been received from the base station  910 . 
     When receiving a data call release signal from the base station, the electronic device  900  proceeds to block  1111  to release the data call connection with the base station. At this point, the electronic device  900  maintains the voice call connection with the base station  910  and continues to receive a voice service from the base station. 
     After that, the electronic device  900  ends the present algorithm. 
     In certain embodiments, the base station  910  determines whether an error of the data call occurs based on the number of retransmissions of data to the electronic device. 
     In certain embodiments, the base station  910  determines whether the error of the data call occurs based on the number of retransmission requests sent to the electronic device  900  as illustrated in  FIG. 12 . 
       FIG. 12  illustrates a procedure for maintaining a voice call with an electronic device based on the number of data retransmissions by a base station according to embodiments of the present disclosure. 
     Referring to  FIG. 12 , the base station  910  sets a multi-RAB with the electronic device in block  1201 . That is, the base station  910  connects a voice call and a data call with the electronic device  900 . 
     After that, the base station  910  proceeds to block  1203  to determine whether data has been received from the electronic device  900 . 
     When receiving the data from the electronic device, the base station  910  proceeds to block  1205  to determine whether an error of the data received from the electronic device has occurred. 
     When the error of the data received from the electronic device does not occur, the base station  910  proceeds to block  1215  to transmit an ACK associated with the error-free data to the electronic device. 
     After that, the base station  910  proceeds to block  1203  to determine whether the next data has been received from the electronic device  900 . 
     In contrast, when the error of the data received from the electronic device occurs, the base station  910  proceeds to block  1207  to determine the number of retransmission requests. 
     After that, the base station  910  proceeds to block  1209  to determine whether the number of retransmission requests is equal to or greater than the reference request frequency in order to determine whether the base station  910  can request the electronic device  900  to retransmit data. The reference request frequency is set to a value equal to or less than a maximum request frequency by which the base station  910  can request the electronic device  900  to retransmit data. That is, when the base station  910  has requested retransmission of data as many as the maximum request frequency, but failed to receive the data, the wireless communication system performs cell update, so that connections of a data call and a voice call between the base station and the electronic device are released. Accordingly, the reference request frequency is set to a value equal to or less than the maximum request frequency. 
     When the number of retransmission requests is less than the reference request frequency, the base station  910  determines that a retransmission request of the error-occurred data is possible. Accordingly, the base station  910  proceeds to block  1211  to request the electronic device  900  to retransmit the error-affected data. For example, the base station  910  transmits a NACK associated with the error-occurred data to the electronic device  900 . 
     After that, the base station  910  proceeds to block  1203  to determine whether retransmission data has been received from the electronic device  900 . 
     In contrast, when the number of retransmission requests is equal to or greater than the reference request frequency, the base station  910  determines that the error of the data call has occurred. Accordingly, the base station  910  proceeds to block  1213  to perform a data call release procedure with the electronic device. For example, the base station  910  sets a domain to a PS domain according to a radio bearer release and transmits the same to the electronic device  900  to release the data call connection with the electronic device  900 . At this point, the base station maintains a voice call connection with the electronic device and continues to provide a voice service to the electronic device  900 . 
     After that, the base station  910  ends the present algorithm. 
       FIG. 13  illustrates a procedure for maintaining a voice call with a base station based on the number of data retransmissions by an electronic device according to embodiments of the present disclosure. 
     Referring to  FIG. 13 , the electronic device  900  sets a multi-RAB with the base station in block  1301 . That is, the electronic device  900  connects a voice call and a data call with the base station  910 . 
     After that, the electronic device  900  proceeds to block  1303  to transmit data to the base station  910 . For example, the base station  910  transmits data to the electronic device  900  via the data call connected with the electronic device. 
     After transmitting data to the base station, the electronic device  900  proceeds to block  1305  to determine whether a NACK associated with the data transmitted in block  1303  has been received from the base station  910 . 
     When receiving a NACK associated with the data transmitted in block  1303  from the base station, the electronic device  900  proceeds to block  1313  to retransmit data associated with the NACK to the base station  910 . 
     In contrast, when not receiving a NACK associated with the data transmitted in block  1303  from the base station, the electronic device  900  proceeds to block  1307  to determine whether an ACK associated with the data transmitted in block  1303  has been received. 
     When receiving an ACK associated with the data transmitted in block  1303  from the base station, the electronic device  900  proceeds to block  1303  to transmit data to the base station  910 . 
     In contrast, when not receiving an ACK associated with the data transmitted in block  1303  from the base station, the electronic device  900  proceeds to block  1309  to determine whether a release signal for the data call has been received from the base station  910 . For example, the electronic device  900  determines whether a signal set to a PS domain has been received from the base station  910 . 
     After transmitting data to the base station, when not receiving one of a NACK, an ACK, and a release signal for the data call for a reference time, the electronic device  900  determines that transmission of the data transmitted to the base station in block  1303  has failed. Accordingly, the electronic device  900  proceeds to block  1313  to retransmit, to the base station, data transmitted to the base station in block  1303 . 
     In contrast, when receiving a data call release signal from the base station, the electronic device  900  proceeds to block  1311  to release the data call connection with the base station. At this point, the electronic device  900  maintains the voice call connection with the base station and continues to receive a voice service from the base station. 
     After that, the electronic device  900  ends the present algorithm. 
       FIG. 14  illustrates a base station  1410  according to embodiments of the present disclosure. 
     As illustrated in  FIG. 14 , the base station  1410  includes a duplexer  1401 , a reception modem  1403 , a controller  1405 , and a transmission modem  1407 . 
     The duplexer  1401  connects the reception modem  1403  and the transmission modem  1407  with an antenna  1409  so that the reception modem  1403  and the transmission modem  1407  share one antenna to transmit/receive a signal. For example, during a reception section, the duplexer  1401  connects the reception modem  1403  with the antenna  1409 . In contrast, during a transmission section, the duplexer  1401  connects the transmission modem  1407  with the antenna  1409 . 
     The reception modem  1403  converts a Radio Frequency (RF) signal received via the antenna  1409  to a baseband signal and demodulates the baseband signal. For example, the reception modem  1403  includes an RF process block, a demodulation block, a channel decoding block, and a message process block. The RF process block converts an RF signal received via a channel for receiving a signal from a reception end via a reception antenna to a baseband signal under control of the controller  1405 . The demodulation block includes a Fast Fourier Transform (FFT) operator for extracting data conveyed on each subcarrier from a signal provided from the RF process block. The channel decoding block includes a demodulator, a deinterleaver, and a channel encoder, and demodulates and decodes a signal provided from the demodulation block. The message process block detects an ACK/NACK message provided from the reception end and provides the same to the controller  1405 . 
     The controller  1405  controls an overall operation of the base station  1410 . Particularly, the controller  1405  controls to set and maintain a multi-radio access link with an electronic device  1400 . When an error of a data call with the electronic device occurs, the controller  1405  releases the data call in order to prevent connections of the data call and a voice call from being released due to the error of the data call with the electronic device. For example, when the electronic device  1400  requests release of the data call connection, the controller  1405  instructs the electronic device to release the data call connection as illustrated in  FIG. 3 ,  5 , or  7 . For another example, when determining an error of the data call with the electronic device, the controller  1405  controls or instructs the electronic device to release the data call connection as illustrated in  FIG. 10  or  12 . 
     The transmission modem  1407  encodes data and a control signal to transmit to a reception end and converts them to RF signals to transmit the same to the reception end via a transmission antenna. For example, the transmission modem  1407  includes a message generate block, a channel encoding block, a modulation block, and an RF process block. The message generate block generates channel information for transmitting data or channel information for retransmitting data. For example, in case of releasing the connection of the data call with the electronic device, the message generate block generates a data call release signal that has set a domain to a PS domain under control of the controller  1405 . The channel encoding block includes a modulator, an interleaver, and a channel encoder to encode and modulate a transmission signal. The modulation block includes an IFFT operator for mapping a signal provided from the channel encoding block to each subcarrier. The RF process block converts a baseband signal provided from the modulation block to an RF signal and transmits the same to the reception end via a transmission antenna. 
     Though not shown, the base station can further include an error determination unit for determining whether an error of data provided from the electronic device occurs. 
     In certain embodiments, the reception modem  1403  and the transmission modem  1407  of the base station  1410  share one antenna  1409  to transmit/receive a signal. In certain embodiments, the reception modem  1403  and the transmission modem  1407  of the base station transmit/receive a signal via different antennas, respectively. 
     In certain embodiments, the base station  1410  connects the voice call and the data call with the electronic device together using one reception modem  1403  and one transmission modem  1407 . In certain embodiments, the base station  1410  can include a reception modem and a transmission modem for a voice call, and include a reception modem and a transmission modem for a data call. 
       FIG. 15  is a block diagram illustrating an electronic device  1400  according to embodiments of the present disclosure. 
     As illustrated in  FIG. 15 , the electronic device  1400  includes a duplexer  1501 , a reception modem  1503 , a controller  1505 , a link state determine unit  1507 , and a transmission modem  1509 . 
     The duplexer  1501  connects the reception modem  1503  and the transmission modem  1509  with an antenna  1511  so that the reception modem  1503  and the transmission modem  1509  can share one antenna  1511  to transmit/receive a signal. For example, during, a reception section, the duplexer  1501  connects the reception modem  1503  with the antenna  1511 . In contrast, during a transmission section, the duplexer  1501  connects the transmission modem  1509  with the antenna  1511 . 
     The reception modem  1501  converts an RF signal received via the antenna  1511  to a baseband signal, and demodulates the same. For example, the reception modem  1501  includes an RF process block, a demodulation block, a channel decoding block, and a message process block. The RF process block converts an RF signal received via a channel for receiving a signal from a transmission end via a reception antenna to a baseband signal under control of the controller  1505 . The demodulation block includes an FFT operator for extracting data conveyed on each subcarrier from a signal provided from the RF process block. The channel decoding block includes a demodulator, a deinterleaver, and a channel decoder to demodulate and decode a signal provided from the demodulation block. The message process block detects channel information for data transmission and channel information for data retransmission provided from the transmission end and provides the same to the controller  1503 . 
     The controller  1503  controls an overall operation of the electronic device  1400 . Particularly, the controller  1503  controls to set and maintain a multi-radio access link with the base station. In the case where the link state determine unit  1507  determines that an error of a data call with the base station occurs, the controller  1505  releases the data call in order to prevent connections of the data call and a voice call from being released due to the error of the data call with the base station. For example, in the case where the link state determine unit  1507  determines that an error of a data call with the base station occurs, the controller  1505  requests the base station  1410  to release connection of the data call as illustrated in  FIG. 2 ,  4 ,  6 , or  8 . For another example, in the case where the base station  1410  instructs to release of the data call, the controller  1505  releases the data call with the base station as illustrated in  FIG. 11  or  13 . 
     The link state determination unit  1507  determines the state of a radio link with the base station. 
     The transmission modem  1509  encodes data and a control signal to transmit to the base station  1410  and converts them to RF signals, and transmits the same to a transmission end via a transmission antenna. For example, the transmission modem  1509  includes a message generate block, a channel encoding block, a modulation block, and an RF process block. The message generate block generates a control signal to transmit to the base station. For example, the message generate block generates a SCRI in order to request release of a data call connection under control of the controller  1505 . For another example, the message generate block generates an ACK/NACK associated with the data provided from the base station  1410 . The channel encoding block includes a modulator, an interleaves, and a channel encoder to encode and modulate a transmission signal. The modulation block includes an IFFT operator for mapping a signal provided from the channel encoding block to each subcarrier. The RF process block converts a baseband signal provided from the modulation block to an RF signal and transmits the same to the base station via the antenna  1511 . 
     Though not shown, the electronic device  1400  can further include an error determination unit for determining whether an error of data provided from the base station  1410  occurs. 
     In certain embodiments, the reception modem  1503  and the transmission modem  1509  of the electronic device share one antenna  1511  to transmit/receive a signal. In another embodiment, the reception modem  1503  and the transmission modem  1509  of the electronic device transmit/receive a signal via different antennas, respectively. 
     In certain embodiments, the electronic device  1400  connects a voice call and a data call with the base station  1410  together using one reception modem  1503  and one transmission modem  1509 . In certain embodiments, the electronic device  1400  includes a reception modem and a transmission modem for a voice call, and includes a reception modem and a transmission modem for a data call. 
     As described above, when an error of a data call occurs in a communication system providing a multi-RAB service, the embodiments of present disclosure can release the data call while maintaining the voice call connection, thereby maintaining the voice call even when the error of the data call occurs to improve communication quality. 
     Although the invention has been shown and described with reference to certain 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 appended claims and their equivalents. Therefore, the scope of the present disclosure is not be limited to the above-described embodiments but should be determined by not only the appended claims but also the equivalents thereof.