Patent Publication Number: US-8972813-B2

Title: Apparatus and method for automatic repeat request (ARQ) feedback in wireless communication system

Description:
PRIORITY 
     This application is a continuation application of U.S. patent application Ser. No. 12/544,851 filed Aug. 20, 2009 in the U.S. Patent and Trademark Office, which claims the benefit of Korean Patent Application No. 10-2008-0081125, filed on Aug. 20, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus and a method for Automatic Repeat reQuest (ARQ) in a wireless communication system. More particularly, the present invention relates to an apparatus and a method for performing effective ARQ feedback in the wireless communication system. 
     2. Description of the Related Art 
     A wireless communication system can encounter data error according to the channel condition of the radio resource. In this regard, the wireless communication system controls and recovers the data error using an Automatic Repeat reQuest (ARQ) scheme to increase the transmission reliability. 
     Using the ARQ scheme, a receiving end informs a transmitting end of success or failure of the packet reception from the transmitting end. For example, when the packets received from the transmitting end have no error, the receiving end may send ACKnowledgement (ACK) information to the transmitting end. In contrast, when the packets received from the transmitting end have error, the receiving end sends Non-ACKnowledgement (NACK) information to the transmitting end. Herein, a series of the operations for the receiving end to transmit the success or the failure of the packet reception to the transmitting end is referred to as an ARQ feedback. 
     Based on the ARQ feedback, the transmitting end can determine whether the packets transmitted to the receiving end are successfully received. When determining that there has been successful packet reception at the receiving end based on the ARQ feedback, the transmitting end deletes the packets successfully received at the receiving end from its transmission buffer. When determining that there has been packet reception failure at the receiving end through the ARQ feedback, the transmitting end retransmits the original packets of the reception failure of the receiving end to the receiving end for the data error recovery at the receiving end. 
     The receiving end performs the ARQ feedback in various manners according to a communication standard. For example, the receiving end may perform the ARQ feedback only when the received packets are corrupted. Alternatively, the receiving end can perform the ARQ feedback according to ARQ feedback indication information in data received from the transmitting end. Alternatively, without determining whether to perform the ARQ feedback or defining the ARQ feedback time, the receiving end itself may determine and carry out the ARQ feedback. 
     When the receiving end performs the ARQ feedback according to the ARQ feedback indication information provided from the transmitting end, the transmitting end, which has to include an ARQ feedback request indicator into every ARQ block, is subject to regular overhead. In addition, since the receiving end cannot perform the ARQ feedback without the ARQ feedback indication of the transmitting end, the degree of freedom in the ARQ feedback operation of the receiving end deteriorates. 
     When the receiving end itself determines and performs the ARQ feedback, the transmitting end cannot know the ARQ feedback time of the receiving end. As a result, the transmitting end cannot smoothly allocate the resource for the ARQ feedback of the receiving end. In addition, since the transmitting end performs the ARQ depending on the ARQ feedback of the receiving end, the ARQ performance disadvantageously degrades. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an apparatus and a method for performing an Automatic Repeat reQuest (ARQ) feedback at a receiving end without the control of a transmitting end in a wireless communication system. 
     Another aspect of the present invention is to provide an apparatus and a method for reducing overhead according to ARQ feedback in a wireless communication system. 
     Yet another aspect of the present invention is to provide an apparatus and a method for recovering ARQ feedback information when the ARQ feedback information is corrupted in a wireless communication system. 
     Still another aspect of the present invention is to provide an apparatus and a method for recovering an ARQ feedback indicator when an ARQ feedback request indicator is corrupted in a wireless communication system. 
     In accordance with an aspect of the present invention, a method for performing ARQ feedback to transmit an indication of one of success and failure of reception of at least one ARQ block to a transmitting end at a receiving end in a wireless communication system is provided. The method includes when receiving an ARQ block from the transmitting end, checking for error in the ARQ block, when the ARQ block has no error, initializing and driving a timer used for determining whether to perform the ARQ feedback according to reception of a next ARQ block, when receiving the next ARQ block without error before the timer expires, initializing and driving the timer, and when the timer expires, performing the ARQ feedback in relation to at least one ARQ block received without error. 
     In accordance with another aspect of the present invention, a method for confirming ARQ feedback information indicative of one of reception success and failure of at least one ARQ block transmitted from a receiving end, at a transmitting end in a wireless communication system is provided. The method includes, to transmit the ARQ block, initializing and driving a first timer to determine reception of the ARQ feedback information, when a next ARQ block is transmitted or the ARQ feedback information is received before the first timer expires, initializing and driving the timer, and when the first timer expires, requesting the ARQ feedback from the receiving end. 
     In accordance with yet another aspect of the present invention, an apparatus for performing ARQ feedback to transmit an indication of one of success and failure of reception of at least one ARQ block to a transmitting end at a receiving end in a wireless communication system is provided. The apparatus includes a receiver for receiving the ARQ block, a timer controller for, every time the ARQ block is received without error, initializing and driving a timer for determining whether to perform the ARQ feedback according to reception of a next ARQ block, and for providing expiration information of the timer to an ARQ controller, the timer driven under control of the timer controller that expires when a preset driving time elapses, the ARQ controller for checking for error in the ARQ block received through the receiver, and for controlling to perform the ARQ feedback in relation to at least one ARQ block received without error when the expiration information of the timer is provided from the timer controller, and a transmitter for transmitting the ARQ feedback information to the transmitting end under control of the ARQ controller. 
     In accordance with still another aspect of the present invention, an apparatus for confirming ARQ feedback information indicative of one of reception success or failure of at least one ARQ block transmitted from a receiving end, at a transmitting end in a wireless communication system is provided. The apparatus includes an ARQ controller for generating one or more ARQ blocks, for assigning a sequence to the ARQ blocks, and for controlling to request ARQ feedback from the receiving end when expiration information of a first timer is provided from a timer controller, a transmitter for transmitting the ARQ blocks, the timer controller for initializing and driving the first timer to confirm reception of the ARQ feedback information every time the transmitter transmits the ARQ blocks, and for providing the expiration information of the first timer to the ARQ controller when the first timer expires, and the first timer driven under control of the timer controller that expires when a preset driving time elapses. 
     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 exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of certain exemplary embodiments the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an Automatic Repeat reQuest (ARQ) feedback condition at a receiving end in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 2  illustrates an ARQ feedback condition at a receiving end in a wireless communication system according to another exemplary embodiment of the present invention; 
         FIG. 3  illustrates an ARQ feedback condition at a receiving end in a wireless communication system according to yet another exemplary embodiment of the present invention; 
         FIG. 4  illustrates an ARQ feedback method of a receiving end in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 5  illustrates a method of a transmitting end for an ARQ feedback in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 6  illustrates a structure of a transmitting end for an ARQ feedback in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 7  illustrates a structure of a receiving end for an ARQ feedback in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 8  illustrates an ARQ feedback condition at a receiving end in a wireless communication system according to still another exemplary embodiment of the present invention; 
         FIG. 9  illustrates an ARQ feedback method of a receiving end in a wireless communication system according to another exemplary embodiment of the present invention; and 
         FIG. 10  illustrates a method of a transmitting end for an ARQ feedback in a wireless communication system according to an exemplary embodiment of the present invention; 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. 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 invention. 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 used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. 
     Exemplary embodiments of the present invention provide a technique for performing effective Automatic Repeat reQuest (ARQ) feedback in a wireless communication system. Herein, the ARQ feedback indicates a series of operations for a receiving end in the wireless communication system using an ARQ scheme to inform a transmitting end of success or failure of packet reception from the transmitting end. 
     Hereinafter, the transmitting end and the receiving end include all of transmitting and receiving nodes constituting the wireless communication system, such as base station controller, base station, mobile station, and relay station. 
     The receiving end of the wireless communication system executes the ARQ feedback by taking into account a number of successfully received ARQ blocks as illustrated in  FIG. 1 . Herein, the ARQ block indicates a fundamental unit of data transmitted from the transmitting end to the receiving end for the ARQ scheme. 
       FIG. 1  depicts an ARQ feedback condition at a receiving end in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , when the transmitting end  100  transmits 18 ARQ blocks to the receiving end  110  and the receiving end  110  successfully receives N ARQ     —     feedback     —     block  ARQ blocks  120 , the receiving end  110  sends ARQ feedback information to the transmitting end  100 . For example, N ARQ     —     feedback     —     block    120  is set to 10 and the receiving end  110  successfully receives 10 ARQ blocks in succession, the receiving end  110  may send the ARQ feedback information of the first through 10 th  ARQ blocks successfully received to the transmitting end  100 . In so doing, the receiving end  110  initializes N ARQ     —     feedback     —     block    120 , which is the criterion for determining whether to perform the ARQ feedback. 
     When receiving the 18 th  ARQ block and not receiving new ARQ blocks within a T new     —     packet     —     arrival     —     timer  time  130 , the receiving end  110  performs the ARQ feedback. That is, when not receiving new ARQ blocks within the T new     —     packet     —     arrival     —     timer  time  130  after receiving the 18 th  ARQ block, the receiving end  110  recognizes that the transmitting end  100  did not additionally transmit ARQ packets. Thus, the receiving end  110  sends ARQ feedback information of the 11 th  through 18 th  ARQ blocks successfully received to the transmitting end  100 . When the 19 th  and 20 th  ARQ blocks are received within T new     —     packet     —     arrival     —     timer  time  130  but are corrupted, the receiving end  110  recognizes that no new ARQ blocks are received. 
     The receiving end  110  resets a T new     —     packet     —     arrival     —     timer  timer, which expires after operating for the T new     —     packet     —     arrival     —     timer  time  130 , every time the ARQ block is received. Herein, when the receiving end  110  sends the ARQ feedback information, the T new     —     packet     —     arrival     —     timer  timer stops to prevent the receiving end  110  from conducting the ARQ feedback while new ARQ packets are not received. The T new     —     packet     —     arrival     —     timer  timer is reset and driven when the receiving end  110  sends the ARQ feedback information and the reception of the new ARQ packets is successful. 
     As stated above, the receiving end sends the ARQ feedback information by taking into account the number of the successfully received ARQ blocks N ARQ     —     feedback     —     block  and T new     —     packet     —     arrival     —     timer  time  130 . Accordingly, within a certain time after transmitting the ARQ blocks, the transmitting end may receive the feedback of the ARQ blocks from the receiving end. Hence, the transmitting end can avoid the data transfer efficiency degradation caused by the ARQ feedback delay or the transmission delay in consideration of the ARQ feedback. 
     Since the receiving end performs the ARQ feedback by taking into consideration the number of the successfully received ARQ blocks, the transmitting end is able to predict the ARQ feedback time of the receiving end by considering the number of the ARQ blocks transmitted to the receiving end. Hence, the transmitting end can allocate the resource for the ARQ feedback to the receiving end by taking into account its predicted ARQ feedback time of the receiving end. That is, the transmitting end can allocate the resource for the ARQ feedback to the receiving end without the request of the receiving end. 
       FIG. 2  depicts an ARQ feedback condition at a receiving end in a wireless communication system according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 2 , when the transmitting end  200  transmits 18 ARQ blocks to the receiving end  210  and the receiving end  210  successfully receives N ARQ     —     feedback     —     block  ARQ blocks  220  as illustrated in  FIG. 2 , the receiving end  210  sends ARQ feedback information to the transmitting end  200 . For example, when N ARQ     —     feedback     —     block    220  is set to 10 and the receiving end  210  successfully receives 10 ARQ blocks in succession, the receiving end  210  may send the ARQ feedback information of the first through 10 th  ARQ blocks successfully received to the transmitting end  200 . In so doing, the receiving end  210  initializes N ARQ     —     feedback     —     block    220 , which is the criterion for determining whether to perform the ARQ feedback. 
     In every transmission of the N ARQ     —     feedback     —     block  ARQ blocks  220 , the transmitting end  200  can expect that the receiving end  210  will conduct the ARQ feedback. For the accurate reception of the ARQ feedback information from the receiving end  210 , the transmitting end  200  transmits the N ARQ     —     feedback     —     block  ARQ bocks  220  and then resets a T new     —     packet     —     arrival     —     timer  timer, which expires after operating for a T ARQ     —     feedback     —     arrival     —     timer  time  230 . When receiving the ARQ feedback information before the T ARQ     —     feedback     —     arrival     —     timer  timer expires, the transmitting end  200  aborts the operation of the T ARQ     —     feedback     —     arrival     —     timer  timer to avoid the transmission of an ARQ feedback request message. 
     Meanwhile, if the ARQ feedback information is not received before the T ARQ     —     feedback     —     arrival     —     timer  timer expires, the transmitting end  200  sends the ARQ feedback request message to the receiving end  210 . Herein, the ARQ feedback request message includes ID information of the receiving end to which the transmitting end  200  requests the ARQ feedback, the last ARQ block information acknowledged by the transmitting end  200 , and ARQ block information completely transmitted by the transmitting end  200 . The transmitting end  200  generates the ARQ feedback request message in the form of a control message applying a coding that is robust to the radio channel. 
     After sending the ARQ feedback request message, the transmitting end  200  resets a T message     —     timer  timer, which expires after operating for a T message     —     timer  time  240 . The transmitting end  200  resets the T message     —     timer  timer in order to determine whether the ARQ feedback request message has error or whether the ARQ feedback information transmitted by the receiving end  210  according to the ARQ feedback request message has error. 
     Upon receiving the ARQ feedback request message from the transmitting end  200 , the receiving end  210  sends the ARQ feedback information to the transmitting end  200 . In doing so, the receiving end  210  recognizes that the transmitting end  200  did not receive the previous ARQ feedback information. Thus, the receiving end  210  sends the previous ARQ feedback information and the ARQ feedback information up to the ARQ blocks successfully received to the transmitting end  200  until the ARQ feedback request message is received. For example, when the transmitting end  200  fails to receive the ARQ feedback information of the first through 10 th  ARQ blocks successfully received at the receiving end  210 , the receiving end  210  may transmit the ARQ feedback information of the first through the 17 th  ARQ blocks successfully received until the ARQ feedback request message is received, to the transmitting end  200 . 
     When receiving no new ARQ blocks during a T new     —     packet     —     arrival     —     timer  time  250  after receiving the 18 th  ARQ block, the receiving end  210  performs the ARQ feedback. More specifically, when not receiving new ARQ blocks during the during a T new     —     packet     —     arrival     —     timer  time  250 , the receiving end  210  recognizes that the transmitting end  200  did not transmit additional packets. Hence, the receiving end  210  sends the ARQ feedback information up to the 18 th  ARQ blocks successfully received to the transmitting end  200 . When the 19 th  and 20 th  ARQ blocks are received within the T new     —     packet     —     arrival     —     timer  time  250  but are corrupted, the receiving end  210  recognizes that new ARQ blocks are not received. 
     To accurately receive the ARQ feedback information from the receiving end  210 , the transmitting end  200  resets a T ARQ     —     feedback     —     arrival     —     timer     —     2  timer, which expires after operating for a T ARQ     —     feedback     —     arrival     —     timer     —     2  time  260 , in every transmission of the ARQ block. When receiving the ARQ feedback information before the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer expires, the transmitting end  200  stops the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer to block the transmission of the ARQ feedback request message. When not receiving the ARQ feedback information before the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer expires, the transmitting end  200  sends the ARQ feedback request message to the receiving end  210 . After sending the ARQ feedback request message, the transmitting end  200  resets a T message     —     timer  timer, which expires after operating for a T message     —     timer  time  240 . 
     As such, the transmitting end  200  can recover the error of the ARQ feedback using the T ARQ     —     feedback     —     arrival     —     timer  timer and the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer. Thus, it is possible to rapidly exchange the accurate information relating to the reception status of the ARQ blocks between the transmitting end  200  and the receiving end  210 . 
     As illustrated in  FIGS. 1 and 2 , the receiving end carries out the ARQ feedback by taking into account the number of the successfully received ARQ blocks and the T new     —     packet     —     arrival     —     timer  time. The transmitting end considers the T ARQ     —     feedback     —     arrival     —     timer  time, the T ARQ     —     feedback     —     arrival     —     timer     —     2  time, and the T message     —     timer  time for the sake of the accurate reception of the ARQ feedback information. The transmitting end and the receiving end determine variables for the ARQ feedback and variables for the accurate reception of the feedback information under the mutual agreement. For example, in case of a base station, a mobile station, and a relay station, the mobile station and the relay station may determine the variables for the ARQ feedback and the variables for the accurate reception of the ARQ feedback information in the process of the registration with the base station. In compliance with the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, the base station, the mobile station, and the relay station determine the variables for the ARQ feedback and the variables for the accurate reception of the ARQ feedback information using REG-REQ messages and REG-RSP messages. 
     Alternatively, the transmitting end and the receiving end determine the variables for the ARQ feedback and the variables for the accurate reception of the ARQ feedback information in the process of the connection initial setup or the service initial setup. In compliance with the IEEE 802.16 standard, the transmitting end and the receiving end determine the variables for the ARQ feedback and the variables for the accurate reception of the ARQ feedback information using Dynamic Service Addition (DSA)-REQ messages and DSA-RSP messages. In addition, the transmitting end and the receiving end can modify the variables for the ARQ feedback and the variables for the accurate reception of the ARQ feedback information using Dynamic Service Change (DSC)-REQ messages and DSC-RSP messages. 
     The determination and the modification of the variables through the connection initial setup or the service initial setup are related to Quality of Service (QoS) of a connection between the transmitting end and the receiving end. 
       FIG. 3  depicts an ARQ feedback condition at a receiving end in a wireless communication system according to yet another exemplary embodiment of the present invention. 
     Referring to  FIG. 3 , when the transmitting end  300  transmits 18 ARQ blocks to the receiving end  310  as illustrated in  FIG. 3  and the receiving end  310  encounters reception error in the ARQ blocks, the receiving end  310  sends ARQ feedback information to the transmitting end  300  regardless of N ARQ     —     feedback     —     block  and T new     —     packet     —     arrival     —     timer  values. For example, when N ARQ     —     feedback     —     block  is set to 10 and the receiving end  310  successfully receives 10 ARQ blocks in a row, the receiving end  310  may send the ARQ feedback information of the first through 10 th  ARQ blocks successfully received to the transmitting end  300 . 
     However, when encountering the reception error in the 5 th  ARQ block or not receiving the 5 th  ARQ block at all, the receiving end  310  sends the ARQ feedback information to the transmitting end  300  to inform of the error of the 5 th  ARQ block. The receiving end  310  initializes N ARQ     —     feedback     —     block  and terminates the T new     —     packet     —     arrival     —     timer  timer. 
     An ARQ feedback method of the receiving end is described below. 
       FIG. 4  illustrates an ARQ feedback method of a receiving end in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , in step  401 , the receiving end determines whether the ARQ blocks are received from the transmitting end. 
     When no ARQ blocks are received, the receiving end determines whether the T new     —     packet     —     arrival     —     timer  timer, which expires after operating for the T new     —     packet     —     arrival     —     timer  time, expires in step  411 . 
     When the T new     —     packet     —     arrival     —     timer  timer expires, the receiving end generates and transmits the ARQ feedback information to the transmitting end in step  415 . 
     When the T new     —     packet     —     arrival     —     timer  timer is not being operated or has not expired in step  411 , the receiving end returns to step  401  and determines whether the ARQ blocks are received from the transmitting end. 
     When receiving the ARQ blocks in step  401 , the receiving end examines whether the received ARQ blocks have error or not in step  403 . 
     When the ARQ blocks have error, the receiving end stops the operation of the T new     —     packet     —     arrival     —     timer  timer to perform the ARQ feedback in step  413 . 
     In contrast, when the ARQ blocks have no error, the receiving end resets the T new     —     packet     —     arrival     —     timer  timer in step  405 . Herein, the resetting of the T new     —     packet     —     arrival     —     timer  timer indicates the initialization and the driving of the timer. 
     After resetting the T new     —     packet     —     arrival     —     timer  timer, the receiving end increases the number of the successfully received ARQ blocks N ARQ     —     block  by one (N ARQ     —     block =N ARQ     —     block +1) in step  407 . 
     In step  409 , the receiving end determines whether to conduct the ARQ feedback by taking into account the number of the successfully received ARQ blocks N ARQ     —     block . That is, the receiving end carries out the ARQ feedback when the N ARQ     —     feedback     —     block  ARQ blocks are successfully received in a row. To determine whether to conduct the ARQ feedback, the receiving end compares the updated N ARQ     —     block  with N ARQ     —     feedback     —     block  in step  409 . 
     When the updated N ARQ     —     block  is less than N ARQ     —     feedback     —     block , the receiving end determines not to perform the ARQ feedback. Accordingly, the receiving end proceeds to step  411  and determines whether the T new     —     packet     —     arrival     —     timer  timer reset in step  405  expires. 
     When the T new     —     packet     —     arrival     —     timer  timer has not expired, the receiving end returns to step  401  and determines whether ARQ blocks are received from the transmitting end. 
     In contrast, when T new     —     packet     —     arrival     —     timer  timer expires, the receiving end generates and transmits the ARQ feedback information to the transmitting end in step  415 . 
     Returning to step  409 , when the N ARQ     —     block  updated in step  407  is greater than or equal to N ARQ     —     feedback     —     block , the receiving end determines to conduct the ARQ feedback. Accordingly, in step  413 , the receiving end stops the operation of the T new     —     packet     —     arrival     —     timer  timer reset in step  405 . That is, the receiving end stops the operation of the T new     —     packet     —     arrival     —     timer  timer to prevent the ARQ feedback other than the ARQ feedback determined in step  409 . 
     After stopping the operation of the T new     —     packet     —     arrival     —     timer  timer, the receiving end generates and transmits the ARQ feedback information to the transmitting end in step  415 . 
     In step  417 , the receiving end initializes N ARQ     —     block  indicative of the number of the successfully received ARQ blocks. 
     Next, the receiving end finishes this process. 
     In this exemplary embodiment, the receiving end stops the operation of the T new     —     packet     —     arrival     —     timer  timer before generating the ARQ feedback information. In addition, the receiving end initializes N ARQ     —     block  after transmitting the ARQ feedback information. 
     Alternatively, the receiving end may stop the operation of the T new     —     packet     —     arrival     —     timer  timer and initialize N ARQ     —     block  before generating the ARQ feedback information. 
     When the ARQ blocks are corrupted, the receiving end stops the operation of the T new     —     packet     —     arrival     —     timer  timer in step  413 . 
     Alternatively, when the ARQ blocks are corrupted, the receiving end may proceed to step  415 . 
     Now, a description is provided for a method of the transmitting end to accurately receive the ARQ feedback information by taking into consideration the T ARQ     —     feedback     —     arrival     —     timer  time, the T ARQ     —     feedback     —     arrival     —     timer     —     2  time, and the T message     —     timer  time. 
       FIG. 5  illustrates a method of a transmitting end for an ARQ feedback in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , in step  501 , the transmitting end determines whether there are ARQ blocks to transmit to the receiving end. 
     When there are no ARQ blocks to transmit to the receiving end, the transmitting end determines whether the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer, which expires after operating for the T ARQ     —     feedback     —     arrival     —     timer     —     2  time, expires in step  511 . 
     When the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer expires, the transmitting end sends the ARQ feedback request message to the receiving end in step  523 . Herein, the ARQ feedback request message includes ID information of the receiving end to which the transmitting end requests the ARQ feedback, the last ARQ block information acknowledged by the transmitting end, and the ARQ block information completely transmitted by the transmitting end. 
     When the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer is not being operated or has not expired, the transmitting end returns to step  501  and determines whether there exist ARQ blocks to transmit to the receiving end. 
     When there exist the ARQ blocks to transmit to the receiving end in step  501 , the transmitting end transmits the ARQ blocks to the receiving end in step  503 . 
     In step  505 , the transmitting end resets the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer. Herein, the resetting of the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer initializes and drives the timer. 
     In step  507 , the transmitting end increases the number of the ARQ blocks N ARQ     —     block  transmitted to the receiving end by one (N ARQ     —     block =N ARQ     —     block +1). 
     In step  509 , the transmitting end predicts whether the receiving end will perform the ARQ feedback, by taking into account the number of the ARQ blocks N ARQ     —     block  transmitted to the receiving end. In more detail, upon successfully receiving the N ARQ     —     feedback     —     block  ARQ blocks, the receiving end performs the ARQ feedback. To predict whether the receiving end will perform the ARQ feedback, the transmitting end compares the N ARQ     —     block  updated in step  507  with N ARQ     —     feedback     —     block . 
     When the updated N ARQ     —     block  is less than N ARQ     —     feedback     —     block , the transmitting end predicts that the receiving end does not perform the ARQ feedback. Accordingly, the transmitting end proceeds to step  511  and determines whether the T new     —     packet     —     arrival     —     timer     —     2  timer reset in step  505  expires. 
     When the T new     —     packet     —     arrival     —     timer     —     2  timer has not expired, the transmitting end returns to step  501  and determines whether there exist ARQ blocks to transmit to the receiving end. 
     When the T new     —     packet     —     arrival     —     timer     —     2  timer expires, the transmitting end sends the ARQ feedback request message to the receiving end in step  523 . 
     When the N ARQ     —     block  updated in step  507  is greater than or equal to N ARQ     —     feedback     —     block  in step  509 , the transmitting end predicts that the receiving end will conduct the ARQ feedback. In step  513 , the transmitting end resets the T ARQ     —     feedback     —     arrival     —     timer  timer, which expires after operating for the T ARQ     —     feedback     —     arrival     —     timer  time. 
     In step  515 , the transmitting end stops the operation of the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer reset in step  505 . 
     In step  517 , the transmitting end determines whether the ARQ feedback information is received. 
     When not receiving the ARQ feedback information, the transmitting end determines whether the T ARQ     —     feedback     —     arrival     —     timer  timer reset in step  513  expires in step  521 . 
     When the T ARQ     —     feedback     —     arrival     —     timer  timer has not expired, the transmitting end once again determines whether the ARQ feedback information is received in step  517 . 
     When the T ARQ     —     feedback     —     arrival     —     timer  timer expires in step  521 , the transmitting end sends the ARQ feedback request message to the receiving end in step  523 . 
     In step  525 , the transmitting end resets the T message     —     timer  timer, which expires after operating for the T message     —     timer  time. 
     In step  527 , the transmitting end determines whether the ARQ feedback information is received from the receiving end. 
     Upon receiving the ARQ feedback information, the transmitting end stops the T ARQ     —     feedback     —     arrival     —     timer  timer and the T message     —     timer  timer in step  519 . 
     When not receiving the ARQ feedback information, the transmitting end determines whether the T message     —     timer  timer reset in step  525  expires in step  529 . 
     When the T message     —     timer  timer has not expired, the transmitting end returns to step  527  and determines whether the ARQ feedback information is received from the receiving end. 
     In contrast, when the T message     —     timer  timer expires, the transmitting end returns to step  523  and transmits the ARQ feedback request message to the receiving end. 
     When receiving the ARQ feedback information in step  517 , the transmitting end stops the T ARQ     —     feedback     —     arrival     —     timer  timer and the T message     —     timer  timer in step  519 . 
     Next, the transmitting end finishes this process. 
     Hereafter, a description is provided for a structure of the transmitting end that receives the ARQ feedback information by taking into consideration the T ARQ     —     feedback     —     arrival     —     timer  time, the T ARQ     —     feedback     —     arrival     —     timer     —     2  time, and the T message     —     timer  time. 
       FIG. 6  depicts a structure of a transmitting end for an ARQ feedback in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 6 , the transmitting end includes a data storage  601 , a data constitutor  603 , an ARQ controller  605 , a transmitter  607 , a receiver  609 , a duplexer  611 , an ARQ timer controller  613 , an ARQ variable controller  615 , and an ARQ control message generator  617 . 
     The data storage  601  stores data generated by an application program. For example, the data storage  601  may be constituted in the form of a data queue. 
     The data constitutor  603  converts the data stored in the data storage  601  into a size to be transmitted by splitting or combining the data according to scheduling information. 
     The ARQ controller  605  generates ARQ blocks with the data provided from the data constitutor  603 , and assigns sequence numbers to the ARQ blocks respectively. 
     The ARQ controller  605  controls the ARQ operations according to control information provided from the ARQ timer controller  613  and the ARQ variable controller  615 . 
     The ARQ timer controller  613  manages the operation of the T ARQ     —     feedback     —     arrival     —     timer  timer, the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer, the T message     —     timer  timer, and T ARQ     —     feedback      —     time  timer, which are driven to accurately receive the ARQ feedback information. For instance, the ARQ timer controller  613  resets the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer every time the ARQ controller  605  transmits new ARQ blocks. 
     The ARQ timer controller  613  resets the T ARQ     —     feedback     —     arrival     —     timer  timer every time the ARQ controller  605  transmits new N ARQ     —     feedback     —     block  ARQ blocks. 
     The ARQ timer controller  613  resets the T ARQ     —     feedback     —     arrival     —     timer  timer every time the ARQ controller  605  terminates the T ARQ     —     feedback     —     time  timer, which expires after operating for the T ARQ     —     feedback     —     time  time. 
     The ARQ timer controller  613  resets the T message     —     timer  timer every time the ARQ controller  605  sends the ARQ feedback request message. 
     When the timer expires, the ARQ timer controller  613  sends expiration information of the corresponding timer to the ARQ controller  605 . Based on the expiration information of the T ARQ     —     feedback     —     arrival     —     timer  timer and the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer provided from the ARQ timer controller  613 , the ARQ controller  605  recognizes that the ARQ feedback from the receiving end is compromised. The ARQ controller  605  controls the ARQ control message generator  617  to send the ARQ feedback request message. Although it is not illustrated, the transmitting end includes at least one timer driven under the control of the ARQ timer controller  613 . 
     Based on the expiration information of the T message     —     timer  timer provided from the ARQ timer controller  613 , the ARQ controller  605  recognizes that the ARQ feedback request message sent to the receiving end is corrupted or the ARQ feedback transmitted from the receiving end is corrupted. The ARQ controller  605  controls the ARQ control message generator  617  to send the ARQ feedback request message. 
     Based on the expiration information of the T ARQ     —     feedback     —     time  timer provided from the ARQ timer controller  613 , the ARQ controller  605  can predict the ARQ feedback time of the receiving end. 
     The ARQ variable controller  615  controls the variables for the ARQ execution. For example, the ARQ variable controller  615  may store the N ARQ     —     feedback     —     block  information agreed with the receiving end for the ARQ. In so doing, the ARQ variable controller  615  predicts the ARQ feedback time of the receiving end according to the number of the ARQ blocks transmitted to the receiving end at the ARQ controller  605 , and provides the predicted ARQ feedback time to the ARQ controller  605 . 
     The ARQ control message generator  617  generates the ARQ feedback request message to transmit to the receiving end under the control of the ARQ controller  605 . The ARQ control message generator  617  generates the ARQ feedback request message including the ID information of the receiving end to which the transmitting end requests the ARQ feedback, the last ARQ block information acknowledged by the transmitting end, and the ARQ block information completely transmitted by the transmitting end. 
     The transmitter  607  includes a channel coding block, a modulation block, and a Radio Frequency (RF) processing block. The transmitter  607  converts the ARQ blocks and the ARQ feedback request message fed from the ARQ controller  605  into an RF signal and transmits the RF signal to the receiving end via the duplexer  611 . For example, the channel coding block may include a channel encoder, an interleaver, and a modulator. The modulation block includes an Inverse Fast Fourier Transform (IFFT) operator in a case of an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and includes a code spread modulator in a case of a Code Division Multiple Access (CDMA) scheme. The RF processing block converts the baseband signal output from the modulation block into an RF signal and outputs the RF signal over an antenna. 
     The receiver  609  includes an RF processing block, a demodulation block, and a channel decoding block. The receiver  609  converts and demodulates an RF signal output from the duplexer  611  into a baseband signal. The demodulation block includes an FFT operator for extracting data carried by subcarriers from the signal output from the RF processing block. The channel decoding block includes a demodulator, a deinterleaver, and a channel decoder. 
     The duplexer  611  transmits the transmit signal output from the transmitter  607  over an antenna and provides a signal received via the antenna to the receiver  609  according to a duplex manner. 
     As constructed above, the ARQ controller  605  can function as the ARQ timer controller  613 , the ARQ variable controller  615 , and the ARQ control message generator  617 . Herein, they are separately provided to distinguish their functions. In the actual implementation, the ARQ controller  605  can process all or part of the functions of the ARQ timer controller  613 , the ARQ variable controller  615 , and the ARQ control message generator  617 . 
     A description is provided below for a structure of the receiving end for the ARQ feedback by taking into account the number of the successfully received ARQ blocks and the T ARQ     —     feedback     —     arrival     —     timer  time. 
       FIG. 7  illustrates a structure of a receiving end for an ARQ feedback in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 7 , the receiving end includes a duplexer  701 , a receiver  703 , a transmitter  705 , an ARQ controller  707 , a data restorer  709 , a data storage  711 , an ARQ timer controller  713 , an ARQ variable controller  715 , and an ARQ control message generator  717 . 
     The duplexer  701  transmits a transmit signal output from the transmitter  705  over an antenna and forwards a signal received via the antenna to the receiver  703  according to a duplex manner. 
     The receiver  703  includes an RF processing block, a demodulation block, and a channel decoding block. The receiver  703  converts and demodulates the RF signal output from the duplexer  701  into a baseband signal. The demodulation block includes an FFT operator for extracting data carried by the subcarriers from the signal output from the RF processing block. The channel decoding block includes a demodulator, a deinterleaver, and a channel decoder. 
     The ARQ controller  707  confirms the sequence of the ARQ blocks output from the receiver  703  and checks for error in the ARQ blocks. 
     The ARQ controller  707  controls the ARQ operations according to the control information provided from the ARQ timer controller  713  and the ARQ variable controller  715 . 
     Upon receiving the ARQ feedback request message transmitted by the transmitting end from the receiving end  703 , the ARQ controller  707  recognizes that the transmitting end fails to receive the ARQ feedback. Thus, the ARQ controller  707  controls the ARQ control message generator  717  to generate the ARQ feedback message relating to the previous ARQ feedback information and the ARQ feedback information of the ARQ blocks successfully received until the ARQ feedback request message is received. 
     The data restorer  709  restores the original data of the data split or combined by the data generator  603  of the transmitting end, using the ARQ blocks successfully received at the ARQ controller  707  without error. 
     The data storage  711  stores the data restored by the data restorer  709 , and provides the data to an application program. For example, the data storage  711  may be constructed in the form of a data queue. 
     The ARQ timer controller  713  manages the T new     —     packet     —     arrival     —     timer  timer and the T ARQ     —     feedback     —     time  timer to confirm the ARQ feedback time. For example, the ARQ timer controller  713  may reset the T new     —     packet     —     arrival     —     timer  timer every time the ARQ controller  707  successfully receives the new ARQ blocks without error. 
     When the ARQ controller  707  succeeds to receive the ARQ blocks for the first time after the ARQ feedback, the ARQ timer controller  713  resets the T ARQ     —     feedback     —     time  timer. 
     When the timer expires, the ARQ timer controller  713  transmits the expiration information of the corresponding timer to the ARQ controller  707 . Based on the expiration information of the timer provided from the ARQ timer controller  713 , the ARQ controller  707  controls the ARQ control message generator  717  to conduct the ARQ feedback. Although it is not illustrated, the receiving end includes at least one timer which is driven under the control of the ARQ timer controller  713 . 
     The ARQ control message generator  717  generates the ARQ feedback message to transmit to the transmitting end under the control of the ARQ controller  707 . 
     The ARQ variable controller  715  controls the variables for the ARQ execution. For example, the ARQ variable controller  715  may store the N ARQ     —     feedback     —     block  information agreed with the transmitting end for the ARQ. The ARQ variable controller  715  determines the ARQ feedback time according to the number of the ARQ blocks successfully received at the ARQ controller  707 , and provides the determined ARQ feedback time to the ARQ controller  707 . 
     The transmitter  705  includes a channel coding block, a modulation block, and an RF processing block. The transmitter  705  converts the ARQ feedback message output from the ARQ controller  707  into an RF signal and transmits the RF signal to the transmitting end via the duplexer  701 . For example, the channel coding block may include a channel encoder, an interleaver, and a modulator. The modulation block includes an IFFT operator in a case of the OFDM scheme, and includes a code spread modulator in a case of the CDMA scheme. The RF processing block converts the baseband signal output from the modulation block into an RF signal and outputs the RF signal via an antenna. 
     As constructed above, the ARQ controller  707  can function as the ARQ timer controller  713 , the ARQ variable controller  715 , and the ARQ control message generator  717 . Herein, they are separately provided to distinguish their functions. In the actual implementation, the ARQ controller  707  can process all or part of the functions of the ARQ timer controller  713 , the ARQ variable controller  715 , and the ARQ control message generator  717 . 
     In this exemplary embodiment, the receiving end executes the ARQ feedback by taking into account the number of the successfully received ARQ blocks. 
     Alternatively, the receiving end may fulfill the ARQ feedback by considering the reception time of the ARQ blocks as illustrated in  FIG. 8 . 
       FIG. 8  depicts an ARQ feedback condition at a receiving end in a wireless communication system according to still another exemplary embodiment of the present invention. 
     Referring to  FIG. 8 , when the transmitting end  800  transmits 18 ARQ blocks to the receiving end  810 , the receiving end  810  sends ARQ feedback information to the transmitting end  800  after the lapse of the T ARQ     —     feedback     —     time  time  820 . For instance, when successfully receiving the first ARQ block, the receiving end  810  resets the T ARQ     —     feedback     —     time  timer, which expires after operating for the T ARQ     —     feedback      —     time  time  820 . Next, when successfully receiving up to the 10 th  ARQ block before the T ARQ     —     feedback     —     time  timer expires, the receiving end  810  sends the ARQ feedback information of the first through 10 th  ARQ blocks to the transmitting end  800 . 
     When receiving the 18 th  ARQ block and not receiving new ARQ blocks for the T new     —     packet     —     arrival     —     timer  time  830 , the receiving end  810  performs the ARQ feedback. More specifically, when not receiving new ARQ blocks for the T new     —     packet     —     arrival     —     timer  time  830 , the receiving end  810  recognizes that the transmitting end  800  did not additionally transmit ARQ packets. Hence, the receiving end  810  sends the ARQ feedback information relating to the 11 th  through 18 th  ARQ blocks successfully received to the transmitting end  800 . At this time, when the 19 th  and 20 ARQ blocks are received within the T new     —     packet     —     arrival     —     timer  time  830  but are corrupted, the receiving end  810  recognizes that new ARQ blocks are not received at all. 
     The receiving end  810  resets the T new     —     packet     —     arrival     —     timer  timer, which expires after operating for the T new     —     packet     —     arrival     —     timer  time  830 , every time the ARQ block is successfully received. Herein, the T new     —     packet     —     arrival     —     timer  timer is aborted when the receiving end  810  sends the ARQ feedback information so as to prevent the receiving end  810  from conducting the ARQ feedback while new ARQ packets are not received. The T new     —     packet     —     arrival     —     timer  timer is reset and operated when new ARQ packets are successfully received after the receiving end  810  sends the ARQ feedback information. 
     A description is provided below for a method for the ARQ feedback of the receiving end. 
       FIG. 9  illustrates the ARQ feedback method of a receiving end in a wireless communication system according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 9 , in step  901 , the receiving end determines whether ARQ blocks are received from the transmitting end. 
     If the ARQ blocks are not received, the receiving end determines whether the T new     —     packet     —     arrival     —     timer  timer, which expires after operating for the T new     —     packet     —     arrival     —     timer  time, expires in step  909 . 
     When the T new     —     packet     —     arrival     —     timer  timer expires, the receiving end generates and transmits the ARQ feedback information to the transmitting end in step  913 . 
     When the T new     —     packet     —     arrival     —     timer  timer is not operating or has not expired, the receiving end returns to step  901  to determine whether ARQ blocks are received from the transmitting end. 
     Upon receiving the ARQ blocks in step  901 , the receiving end checks for error in the received ARQ blocks in step  903 . 
     When the ARQ blocks are corrupted, the receiving end stops the T new     —     packet     —     arrival     —     timer  timer in step  911 . 
     In contrast, when the ARQ blocks are free from error, the receiving end resets the T new     —     packet     —     arrival     —     timer  timer in step  905 . Herein, the resetting of the T new     —     packet     —     arrival     —     timer  timer indicates the initialization and the operation of the timer. 
     In step  907 , the receiving end determines whether to perform the ARQ feedback by taking into account the ARQ elapsed time T ARQ     —     time . More specifically, when the ARQ elapsed time exceeds the T ARQ     —     feedback     —     time  time, the receiving end performs the ARQ feedback. To determine whether to perform the ARQ feedback, the receiving end compares T ARQ     —     time  and T ARQ     —     feedback     —     time . Herein, the ARQ elapsed time indicates the time taken from the first reception time of the ARQ blocks after the ARQ feedback to the reception time of the current ARQ blocks. 
     When T ARQ     —     time  is less than T ARQ     —     feedback     —     time , the receiving end determines not to execute the ARQ feedback. Thus, the receiving end proceeds to step  909  and determines whether the T new     —     packet     —     arrival     —     timer  timer reset in step  905  expires. 
     When the T new     —     packet     —     arrival     —     timer  timer has not expired, the receiving end returns to step  901  to determine whether ARQ blocks are received from the transmitting end. 
     In contrast, when the T new     —     packet     —     arrival     —     timer  timer expires, the receiving end generates and transmits the ARQ feedback information to the transmitting end in step  913 . 
     When T ARQ     —     time  is equal to or greater than T ARQ     —     feedback     —     time  in step  907 , the receiving end determines to carry out the ARQ feedback. Hence, the receiving end stops the T new     —     packet     —     arrival     —     timer  timer reset in step  903 , in step  911 . In other words, the receiving end stops the T new     —     packet     —     arrival     —     timer  timer in order to avoid the ARQ feedback other than the ARQ feedback determined in step  907 . 
     In step  913 , the receiving end generates and transmits the ARQ feedback information to the transmitting end. 
     In step  915 , the receiving end initializes T ARQ     —     time  indicative of the transmission time of the successfully received ARQ blocks. 
     Next, the receiving end finishes this process. 
     In this exemplary embodiment, before generating the ARQ feedback information, the receiving end stops the T new     —     packet     —     arrival     —     timer  timer. The receiving end initializes T ARQ     —     time  after sending the ARQ feedback information. 
     Alternatively, the receiving end may stop the T new     —     packet     —     arrival     —     timer  timer and initialize T ARQ     —     time  before generating the ARQ feedback information. 
     When the ARQ blocks are corrupted, the receiving end stops the T new     —     packet     —     arrival     —     timer  timer in step  911 . 
     Alternatively, when the ARQ blocks are corrupted, the receiving end may proceed to step  913 . 
     Now, a description is provided for a method of the transmitting end to receive the ARQ feedback information by considering the T ARQ     —     feedback     —     arrival     —     timer  time, the T ARQ     —     feedback     —     arrival     —     timer     —     2  time, and the T message     —     timer  time. 
       FIG. 10  illustrates a method of a transmitting end for an ARQ feedback in a wireless communication system according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 10 , in step  1001 , the transmitting end determines whether there exist ARQ blocks to transmit to the receiving end. 
     When there are no ARQ blocks to transmit to the receiving end, the transmitting end determines whether the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer, which expires after operating for the T ARQ     —     feedback     —     arrival     —     timer     —     2  time, expires in step  1009 . 
     When the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer expires, the transmitting end sends the ARQ feedback request message to the receiving end in step  1021 . 
     When the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer is not operating or has not expired, the transmitting end returns to step  1001  and determines whether there exist ARQ blocks to transmit to the receiving end. 
     When there exist the ARQ blocks to transmit to the receiving end in step  1001 , the transmitting end transmits the ARQ blocks to the receiving end in step  1003 . 
     In step  1005 , the transmitting end resets the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer. Herein, the resetting of the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer initializes and drives the timer. 
     In step  1007 , the transmitting end predicts whether the receiving end will perform the ARQ feedback, by taking into account the transmission time of the ARQ blocks T ARQ     —     time  to the receiving end. In more detail, when the T ARQ     —     feedback      —     time  time elapses, the receiving end performs the ARQ feedback. To predict whether the receiving end will conduct the ARQ feedback, the transmitting end compares T ARQ     —     time  with T ARQ     —     feedback     —     time . 
     When T ARQ     —     time  is less than T ARQ     —     feedback     —     time , the transmitting end predicts that the receiving end does not perform the ARQ feedback. Accordingly, the transmitting end proceeds to step  1009  and determines whether the T new     —     packet     —     arrival     —     timer     —     2  timer reset in step  1005  expires. 
     When the T new     —     packet     —     arrival     —     timer     —     2  timer has not expired, the transmitting end returns to step  1001  and determines whether there exist ARQ blocks to transmit to the receiving end. 
     When the T new     —     packet     —     arrival     —     timer     —     2  timer expires, the transmitting end sends the ARQ feedback request message to the receiving end in step  1021 . Herein, the ARQ feedback request message includes the ID information of the receiving end to which the transmitting end requests the ARQ feedback, the last ARQ block information acknowledged by the transmitting end, and the ARQ block information completely transmitted by the transmitting end. 
     When T ARQ     —     time  is greater than or equal to T ARQ     —     feedback      —     time  in step  1007 , the transmitting end predicts that the receiving end will conduct the ARQ feedback. In step  1011 , the transmitting end resets the T ARQ     —     feedback     —     arrival     —     timer  timer, which expires after operating for the T ARQ     —     feedback     —     arrival     —     timer  time. 
     In step  1013 , the transmitting end stops the operation of the T ARQ     —     feedback     —     arrival     —     timer     —     2  timer reset in step  1005 . 
     In step  1015 , the transmitting end determines whether the ARQ feedback information is received. 
     When receiving no ARQ feedback information, the transmitting end determines whether the T ARQ     —     feedback     —     arrival     —     timer  timer reset in step  1011  expires in step  1019 . 
     When the T ARQ     —     feedback     —     arrival     —     timer  timer has not expired, the transmitting end returns to step  1015  and determines whether the ARQ feedback information is received. 
     When the T ARQ     —     feedback     —     arrival     —     timer  timer expires, the transmitting end sends the ARQ feedback request message to the receiving end in step  1021 . 
     In step  1023 , the transmitting end resets the T message     —     timer  timer, which expires after operating for the T message     —     timer  time. 
     In step  1025 , the transmitting end determines whether the ARQ feedback information is received from the receiving end. 
     Upon receiving the ARQ feedback information, the transmitting end stops the T ARQ     —     feedback     —     arrival     —     timer  timer and the T message     —     timer  timer in step  1017 . 
     When receiving no ARQ feedback information, the transmitting end determines whether the T message     —     timer  timer reset in step  1023  expires in step  1027 . 
     When the T message     —     timer  timer has not expired, the transmitting end returns to step  1025  and determines whether the ARQ feedback information is received from the receiving end. 
     In contrast, when the T message     —     timer  timer expires, the transmitting end returns to step  1021  and sends the ARQ feedback request message to the receiving end. 
     When receiving the ARQ feedback information in step  1015 , the transmitting end stops the T ARQ     —     feedback     —     arrival     —     timer  timer and the T message     —     timer  timer in step  1017 . 
     Next, the transmitting end finishes this process. 
     As set forth above, the ARQ feedback is carried out by taking into consideration the number of the ARQ blocks successfully received at the receiving end of the wireless communication system, and the timer for transmitting and receiving the ARQ feedback is driven to reduce the loss of the ARQ feedback information. Therefore, the shift of the transmit window of the transmitting can be accurately accomplished and the transmission reliability can be raised. 
     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 and their equivalents.