Abstract:
Provided is a method of transmitting and receiving data using a persistent allocation scheme in order to effectively support a voice service between a base station and a mobile terminal in a packet based mobile communication system. When an error occurs in transmitting control information that indicates whether to use a radio resource using the persistent allocation scheme, the base station may retransmit the control information and thereby maintain a communication quality.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/996,927, filed Dec. 8, 2010, which claims the benefit under 35 U.S.C. §371, of International Application No. PCT/KR09/03254, filed Jun. 17, 2009, which claimed priority to Korean Application No. 10-2009-0052760, filed Jun. 15, 2009, and Korean Application No. 10-2008-0058425, filed Jun. 20, 2008, in the Korean Intellectual Property Office, all of the disclosures of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    (1) Field 
         [0003]    The present invention relates to a method of transmitting and receiving data in a packet based mobile communication system, and more particularly, to a method of recovering from a reception error of a control message, which occurs when transmitting and receiving data using a persistent allocation scheme, in order to effectively support a voice service between a base station and a mobile terminal in a next generation packet mobile communication system, which is under discussion for a standardization. 
         [0004]    (2) Discussion of the Background 
         [0005]    3rd Generation Partnership Project (3GPP), one of a number of mobile communication standardization organizations, is engaging in a Long Term Evolution (LTE) standardization process and an advanced LTE standardization process in order to develop a packet based mobile communication system standardization. A mobile communication system generally includes a base station constituting a cell, and a mobile terminal used by a user. A plurality of mobile terminals may transmit and receive packet data to and from the base station via a radio channel. 
       SUMMARY 
       [0006]    An aspect of the present invention provides a method of effectively controlling an activation and a deactivation of a persistent allocation scheme when transmitting and receiving packet data using the persistent allocation scheme, and a method of transmitting and receiving a control message for an error recovery. 
         [0007]    According to an aspect of the present invention, there is provided a base station including: a radio resource allocation unit to allocate a radio resource to a terminal; a control information generation unit to generate control information based on the allocated radio resource; a transmitter to transmit the control information to the terminal; and a receiver to receive an acknowledgement (ACK) message with respect to the control information. 
         [0008]    According to another aspect of the present invention, there is provided a terminal including: a receiver to receive, from a base station, control information associated with data; and a transmitter to transmit, to the base station, an ACK message with respect to the control information. The receiver may receive the data based on the control information. 
         [0009]    According to still another aspect of the present invention, there is provided a base station including: a transmitter to transmit, to a terminal, control information associated with first data, and to transmit the first data to the terminal using the control information; and a receiver to receive an ACK message with respect to the control information. When the ACK message with respect to the control information is not received, the transmitter may retransmit the control information. 
         [0010]    According to embodiments of the present invention, when an error occurs wherein the error is an activation message not received by a terminal transmitted from a base station in a persistent allocation scheme, it is possible to quickly recover from the error. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a diagram illustrating an example of recovering from a transmission error according to an embodiment of the present invention; 
           [0012]      FIG. 2  is a diagram illustrating an operation of a base station recovering from a transmission error according to an embodiment of the present invention; 
           [0013]      FIG. 3  is a diagram illustrating an operation of a terminal recovering from a transmission error according to an embodiment of the present invention; 
           [0014]      FIG. 4  is a block diagram illustrating a structure of a base station according to an embodiment of the present invention; 
           [0015]      FIG. 5  is a block diagram illustrating a structure of a terminal according to an embodiment of the present invention; and 
           [0016]      FIG. 6  is a block diagram illustrating a structure of a base station according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Exemplary embodiments are described below to explain the present invention by referring to the figures. 
         [0018]      FIG. 1  is a diagram illustrating an example of recovering from a transmission error according to an embodiment of the present invention. Although  FIG. 1  shows an embodiment where a base station transmits downlink data to a terminal, the present invention may be applicable to an embodiment where the terminal transmits uplink data to the base station. 
         [0019]    Generally, an amount of the downlink data may be too great to be transmitted from the base station to the terminal at once. Therefore, the base station may divide the downlink data into a plurality of data blocks, and sequentially transmit the divided data blocks to the terminal. Hereinafter, the divided data blocks are referred to as first data, second data, and the like, respectively. 
         [0020]    Referring to  FIG. 1 , the base station may transmit first data  120  to the terminal. The base station may transmit control information  110  associated with the first data  120  prior to transmitting the first data  120 . According to an embodiment of the present invention, the control information  110  may include information associated with a radio resource used to transmit the first data  120 . The terminal may receive information associated with the radio resource, and receive the first data  120  by referring to the received information associated with the radio resource. For example, the terminal may be aware of information associated with a time domain or a frequency domain where the first data  120  is transmitted, by referring to information associated with the radio resource. The terminal may receive the first data  120  in the time domain or the frequency domain where the first data  120  is transmitted. 
         [0021]    The control information  110  may include modulation and coding scheme information associated with the first data  120  or error control scheme information associated with the first data  120 . The terminal may receive the modulation and coding scheme information or the error control scheme information, and receive the first data  120  using the modulation and coding scheme information or the error control scheme information. 
         [0022]    When the present invention is applied to a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system, control information may be transmitted using a Physical Downlink Control Channel (PDCCH). Also, first data or second data may be transmitted using a Physical Downlink Shared Channel (PDSCH). 
         [0023]    Referring again to  FIG. 1 , the base station may transmit data every persistent allocation interval  190 . After transmitting the first data  120 , the base station may transmit second data  140  to the terminal. When control information  130  associated with the second data  140  is different from the control information  110  associated with the first data  120 , the base station may transmit the control information  130  associated with the second data  140  to the terminal. 
         [0024]    The terminal may receive information associated with a radio resource to transmit the second data  140 , and modulation and coding scheme information or error control scheme information associated with the second data  140 , which are included in the control information  130 . The terminal may receive the second data  140  using the control information  130 . 
         [0025]    A case where the control information  110  associated with the first data  120  is different from the control information  130  associated with the second data  140  is referred to as a variable allocation scheme. The variable allocation scheme may need to transmit control information with respect to every piece of data. 
         [0026]    In the case of a service with a low data transmission rate such as a voice service, when control information is additionally transmitted with respect to every piece of data, it may be ineffective. The base station may apply the same modulation and coding scheme or the same error control scheme to every piece of data. In this case, the control information  110  associated with the first data  120  may be the same as the control information  130  associated with the second data  140 . Accordingly, only when initially transmitting data, the base station may transmit the control information  110 . After transmitting the control information  110 , the base station may not transmit additional control information. Since a transmission of control information decreases, a radio resource utilization efficiency may be enhanced, which is referred to as a persistent allocation scheme or a semi-persistent scheduling scheme. 
         [0027]    In the case of the persistent allocation scheme, an activation message included in the control information  110  may be transmitted prior to data transmission. The activation message indicates a start of use of the radio resource. Also, a deactivation message included in control information  170  may be transmitted after the data transmission. The deactivation message indicates a suspension of use of the radio resource. 
         [0028]    Since a status of a radio channel formed between the base station and the terminal may be unstable, the terminal may not receive control information. When the terminal does not receive the control information, the terminal may not receive first data and second data. 
         [0029]    Referring to  FIG. 1 , in the variable allocation scheme, the control information  110 ,  130 , and  150  may be transmitted with respect the first data  120 , the second data  140 , and third data  160 , respectively. Therefore, when the terminal does not receive the control information  110  associated with the first data  120 , the terminal may abandon receiving of the first data  120 . When the terminal receives the control information  130  associated with the second data  140 , the terminal may receive the second data  140  using the control information  130 . 
         [0030]    In the persistent allocation scheme, the control information  110  and  130  may be transmitted at particular points in time. When the terminal does not receive the control information  110  and  130 , the terminal may not receive the first data  120  and the second data  140 . 
         [0031]    According to an embodiment of the present invention, when a terminal receives a control information, the terminal may transmit, to a base station, an acknowledgement (ACK) message with respect to the control information. When the base station receives, from the terminal, the ACK message with respect to the control information, it may be known that the base station successfully receives the control information. 
         [0032]    Conversely, when the base station does not receive the ACK message with respect to the control information, whether the terminal successfully receives the control information may be uncertain. In preparation for a case where the terminal does not receive the control information, the base station may retransmit the control information to the terminal. 
         [0033]      FIG. 2  is a diagram illustrating an operation of a base station recovering from a transmission error according to an embodiment of the present invention. The base station may transmit first data  242  and  252 , second data  262 , and control information  241 ,  251 , and  261  using a downlink channel  210 . 
         [0034]    The control information  241  may include an activation message with respect to a radio resource. The terminal may receive the first data  242  using the radio resource. The transmission error may be defined as the control information  241  or the first data  242  transmitted from the base station is not received by the terminal. 
         [0035]    When the transmission error occurs, the terminal may not recognize that the radio resource is activated. Also, since the terminal may be unaware of that the control information  241  or the first data  242  is transmitted, the terminal may not transmit a NACK message  243 . 
         [0036]    When the base station does not receive an ACK message from the terminal, the base station may retransmit the first data  252 . Also, the base station may retransmit the control information  251  associated with the first data  252 . The retransmitted control information  251  may include an activation message with respect to the radio resource, and modulation and coding scheme information or error control scheme information associated with the first data  252 . 
         [0037]    When the terminal receives the retransmitted control information  251  and transmits an ACK message  253  to the base station using an uplink channel  220 , the base station may no longer transmit additional control information. The base station may transmit the second data  262  to the terminal but may not transmit control information  261  associated with the second data  262 . The terminal may receive the second data  262  using the control information  251  with respect to the second data  262 . 
         [0038]    When the terminal does not receive, from the base station, a deactivation message with respect to a radio resource, the base station may retransmit the deactivation message to the terminal, which is similar to an embodiment of checking on ACK message and retransmitting an activation message with respect to the radio resource. 
         [0039]      FIG. 3  is a diagram illustrating an operation of a terminal recovering from a transmission error according to an embodiment of the present invention. A base station may transmit first data  342  and  352 , and second data  362  using a downlink channel  310 . Also, the base station may transmit control information  341 ,  351 , and  361  using the downlink channel  310 . 
         [0040]    Here, it is assumed that the base station transmits the control information  341  associated with the first data  342  but a transmission error occurs. 
         [0041]    When the transmission error occurs, the terminal may not receive an ACK message and may not transmit a NACK message  343 . When the base station does not receive the ACK message from the terminal, the base station may retransmit the first data  352 . The retransmitted control information  351  may include modulation and coding scheme information or error control scheme information associated with the first data  352 . 
         [0042]    The terminal may receive the first data  352  using the retransmitted control information  351 . An activation message with respect to a radio resource may not be received yet at the terminal. The terminal may retransmit an error recovery request  354  using an uplink channel  320 . 
         [0043]    The base station may retransmit an activation message  361 , in response to the error recovery request  354 . 
         [0044]    When the terminal does not receive, from the base station, a deactivation message with respect to a radio message, the base station may retransmit the deactivation message to the terminal, which is similar to an embodiment of retransmitting an activation message with respect to the radio resource. 
         [0045]      FIG. 4  is a block diagram illustrating a structure of a base station  400  according to an embodiment of the present invention. The base station  400  may include a radio resource allocation unit  410 , a control information generation unit  420 , a transmitter  430 , and a receiver  440 . 
         [0046]    The radio resource allocation unit  410  may allocate a radio resource to a terminal  450 . 
         [0047]    The control information generation unit  420  may generate control information by referring to the allocated radio resource. The control information may include information associated with the radio resource. 
         [0048]    The transmitter  430  may transmit the control information to the terminal  450 . According to an embodiment of the present invention, the transmitter  430  may transmit first data to the terminal  450  using the radio resource. The terminal  450  may receive information associated with the radio resource, included in the control information, and receive the first data using information associated with the radio resource. 
         [0049]    According to an embodiment of the present invention, control information may include an activation message or a deactivation message with respect to a radio resource. The activation message with respect to the radio resource indicates that a previously unused radio resource is allocated to a particular terminal and is used to transmit first data. The deactivation message with respect to the radio resource indicates that a radio resource used to transmit the first data is released. In a 3GPP LTE system, the activation message and the deactivation message may be indicated as a field of a PDCCH, for example, one bit, or may be indicated as a terminal identifier for a voice service, for example, a semi-persistent scheduling C-RNTI, and the like. 
         [0050]    Accordingly, the terminal  450  may receive the activation message with respect to the radio resource, and transmit the first data using the radio resource associated with the activation message. The terminal  450  may receive the deactivation message with respect to the radio resource and may suspend a transmission of the first data using the radio resource. 
         [0051]    When the terminal  450  does not receive the activation message with respect to the radio resource, the terminal  450  may not receive the first data. Also, when the terminal  450  does not receive the deactivation message with respect to the radio resource, the radio resource may not be retrieved. Accordingly, the base station  400  may need to verify whether the terminal  450  receives the activation message or the deactivation message with respect to the radio resource. The terminal  450  may receive the control information, and may transmit, to the base station  400 , an ACK message with respect to the received control information. 
         [0052]    The receiver  440  may receive the ACK message with respect to the control information. When the receiver  440  does not receive the ACK message with respect to the control information, the base station  400  may not verify whether the terminal  450  does not receive the control information. In this case, the transmitter  430  may retransmit the control information to the terminal  450 . 
         [0053]    When the present invention is applied to the 3GPP LTE system, the ACK message may be transmitted using a Physical Uplink Control Channel (PUCCH). A content of the ACK message may include a Hybrid ARQ Positive Acknowledgement (HARQ ACK). A content of a NACK message may include a HARQ NACK. 
         [0054]    According to an embodiment of the present invention, the control information may include modulation and coding scheme information associated with the first data or error control scheme information associated with the first data. 
         [0055]    The transmitter  430  may transmit, to the terminal  450 , the modulation and coding scheme information or the error control scheme information associated with the first terminal. The terminal  450  may receive the first data based on the modulation and coding scheme information or the error control scheme information. 
         [0056]    According to an embodiment of the present invention, the transmitter  430  may transmit, to the terminal  450 , second data using modulation and coding scheme information associated with the first data or error control scheme information associated with the first data. Specifically, control information transmitted from the transmitter  430  may be applicable to a plurality of data as well as particular data. 
         [0057]    Also, the transmitter  430  may transmit the first data or the second data using the radio resource associated with the activation message. 
         [0058]      FIG. 5  is a block diagram illustrating a structure of a terminal  500  according to an embodiment of the present invention. The terminal  500  may include a receiver  510  and a transmitter  520 . 
         [0059]    The receiver  510  may receive, from a base station  530 , control information associated with data. 
         [0060]    When the receiver  510  successfully receives the control information, the transmitter  520  may transmit, to the base station  530 , an ACK message with respect to the control information. According to an embodiment of the present invention, the control information may include information regarding a radio resource associated with first data. The receiver  510  may receive the first data by referring to information associated with the radio resource. 
         [0061]    According to an embodiment of the present invention, the control information may include modulation and coding scheme information associated with the first data or error control scheme information associated with the first data. 
         [0062]    According to an embodiment of the present invention, the control information may include an activation message or a deactivation message with respect to the radio resource. The activation message with respect to the radio resource indicates that a previously unused radio resource is allocated to a particular terminal and is used to transmit the first data. The deactivation message with respect to the radio resource indicates that the radio resource used to transmit the first data is released. The receiver  510  may receive the first data using the activated radio resource. 
         [0063]      FIG. 6  is a block diagram illustrating a structure of a base station  600  according to another embodiment of the present invention. The terminal  600  may include a transmitter  610  and a receiver  620 . 
         [0064]    The transmitter  610  may transmit, to a terminal  630 , control information associated with first data. According to an embodiment of the present invention, the control information may include information associated with a radio resource that is allocated for the first data. Specifically, the control information may include information associated with a time domain or a frequency domain where the first data is transmitted. 
         [0065]    According to an embodiment of the present invention, the control information may include an activation message with respect to the radio resource. The activation message with respect to the radio resource indicates that a previously unused radio resource is allocated to a particular terminal and is used to transmit the first data. The terminal  630  may receive the activation message and receive the first data using the activated radio resource. 
         [0066]    Also, the deactivation message with respect to the radio resource indicates that the radio resource used to transmit the first data is released. The terminal  630  may receive the deactivation message and suspend the data transmission using the radio resource. 
         [0067]    The control information may include at least one of modulation and coding scheme information associated with the first data and error control scheme information associated with the first data. The terminal  630  may receive the first data using the modulation and coding scheme information or the error control scheme information. 
         [0068]    The control information is required for the terminal  630  to receive the first data. Accordingly, the base station  600  may verify whether the terminal  630  receives the control information. According to an embodiment of the preset invention, when the terminal  630  receives the control information, the terminal  630  may transmit, to the base station  600 , an ACK message with respect to the control information. The receiver  620  may receive the ACK message with respect to the control information. 
         [0069]    When the receiver  620  does not receive the ACK message with respect to the control information, it is uncertain whether the terminal  630  receives the control information. Accordingly, the transmitter  610  may retransmit the control information to the terminal  630 . 
         [0070]    According to an embodiment of the present invention, the control information may be applicable to second data as well as the first data. In this case, the transmitter  610  may also transmit the second data using the control information. 
         [0071]    Although a few exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described exemplary embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.