KR20070003274A - Apparatus and method for retransmitting packet data in wireless communication system - Google Patents

Abstract

An apparatus and a method for retransmitting packet data in a wireless communication system are provided to request retransmission of an ARQ block with an error, by detecting the ARQ block with an error in a packet data unit received in the wireless communication system. In a transmitter apparatus of a broadband wireless communication system, a first generation part divides a data unit from an upper layer into ARQ(Automatic Repeat reQuest) blocks and then adds an error check code to each ARQ block, when an ARQ mode is a first mode. A second generation part collects ARQ blocks from the first generation part, and generates a packet data unit by adding a header in front of the collected data. A control part determines the ARQ mode according to feedback information from a receiver.

Description

Packet data retransmission apparatus and method in a wireless communication system {APPARATUS AND METHOD FOR RETRANSMITTING PACKET DATA IN WIRELESS COMMUNICATION SYSTEM}

1 is a diagram illustrating a packet data unit (PDU) format of a medium access control (MAC) layer in an 802.16 based system.

2 is a diagram illustrating a process of generating a MAC PDU in a wireless communication system according to the prior art.

3 is a diagram illustrating a process of generating a MAC PDU when performing an extended ARQ mode according to an embodiment of the present invention.

4 illustrates the format of a MAC header according to an embodiment of the present invention.

5 is a detailed functional block diagram of a MAC layer according to an embodiment of the present invention.

6 is a diagram illustrating a procedure of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

7 illustrates a procedure of a receiver in a broadband wireless communication system according to an embodiment of the present invention.

8 is a diagram for explaining an extended ARQ mode according to the present invention;

The present invention relates to an apparatus and method for retransmitting packet data in a wireless communication system. In particular, an error detection code is added to each ARQ block in a packet data unit (PDU) to add an ARQ block unit. The present invention relates to an apparatus and a method for performing retransmission.

In wireless data communication, data transmission between a transmitting side and a receiving side may cause an error in specific data according to a channel state of a radio resource section. Control and recovery techniques for such errors can be largely divided into ARQ (Automatic Repeat ReQuest) and FEC (Forward Error Check). The ARQ is a technique for requesting retransmission for the lost data at the receiver, and the FEC is a technique for correcting an error for the lost data at the receiver.

In particular, in the ARQ scheme, an error checking result (eg, CRC result) for packets received at a receiving end should be transmitted to the transmitting end. First, when the transmitter initially transmits a packet, the demodulator and the channel decoder decode the packet received at the receiver. At this time, if an error does not occur, an ACK signal is transmitted to the transmitting end. If an error occurs, the NACK signal is transmitted to the transmitting end. The transmitting end retransmits the previous packet or transmits a new packet according to the ACK / NACK signal from the receiving end.

1 illustrates a packet data unit (PDU) format of a medium access control (MAC) layer in an 802.16-based system.

As shown, in the packet data unit (PDU) of the MAC layer transmitted through the radio section, a generic MAC header 101 is added in front of the payload 103, followed by a CRC (Cyclic). Redundancy Checking 105 is added. Therefore, when the ARQ mode is performed, retransmission is performed in units of PDUs.

2 is a diagram illustrating a process of generating a MAC PDU in a wireless communication system according to the prior art.

Referring to FIG. 2, the MAC layer receives MAC SDUs (MAC SDUs) in the form of IP packets from an upper layer in step 201. In step 203, the MAC layer divides the received IP packets into ARQ block units and adds a block sequence number (BSN) to each ARQ block. In step 205, after collecting a plurality of ARQ blocks, the MAC layer adds a PSH (Packing Sub Header) or FSH (Fragmentation Sub Header) in front, and then adds a general MAC header in front of the sub header. After generating MAC PDU, transfer it to lower layer (eg, physical layer).

As shown, each MAC PDU is added with a MAC header and a subheader (FSH / PSH) before the payload. In the Type field of the MAC header, a value of '001110b' is set and the subheader is set. Fragment Count (FC), Block Sequence Number (BSN), Length (Length) information, and the like are set. The enlarged illustrated MAC PDU is composed of five ARQ blocks from BSN 6 to BSN 10. Cyclic redundancy checking (CRC) may be added to the MAC PDU as described with reference to FIG. 1.

That is, according to the prior art, the transmitter calculates a CRC for the entire MAC PDU, and transmits the CRC after the MAC PDU. Meanwhile, the receiver calculates a CRC for the received packet (MAC PDU) and checks whether the calculated CRC is the same as the received CRC. At this time, if the two values are different, the receiver determines that an error has occurred in the received packet and requests retransmission of the packet (MAC PDU) through the feedback channel.

As described above, in the 802.16 based system (eg, WiBro system), the ARQ method includes one packet data unit (PDU) including a plurality of blocks, but there is no method of detecting an error of a specific block. Even if an error occurs in the block, the entire PDU must be retransmitted. As such, when retransmitting the entire PDU, there is a problem in that the radio section is inefficiently used and the data transmission delay is worsened.

Accordingly, an object of the present invention is to provide an apparatus and method for retransmitting packet data in a wireless communication system.

Another object of the present invention is to provide an apparatus and method for communicating a packet data unit including a plurality of ARQ blocks to which an error detection code is added in a wireless communication system.

Another object of the present invention is to provide an apparatus and method for detecting an ARQ block in which an error occurs in a packet data unit received in a wireless communication system and requesting retransmission of the ARQ block in which the error occurs.

Another object of the present invention is to add an error detection code to each of the Automatic Repeat reQuest (ARQ) blocks carried in a packet data unit (PDU) in a wireless communication system for performing retransmission in units of ARQ block And providing a method.

It is still another object of the present invention to adapt an ARQ mode according to a channel state in a wireless communication system supporting a first ARQ mode for retransmitting the entire packet data unit and a second ARQ mode for retransmitting an ARQ block having an error in the packet data unit. In another aspect, there is provided an apparatus and method for switching.

According to an aspect of the present invention for achieving the above object, in the transmitter device of a broadband wireless communication system, when the ARQ (Automatic Repeat reQuest) mode is the first mode, ARQ data unit from the upper layer ARQ A first generation unit for dividing into blocks and adding an error check code to each of the ARQ blocks, and collecting ARQ blocks from the first generation unit, and adding a header to the collected data to add a packet. And a second generator for generating a data unit.

According to another aspect of the present invention, in the receiver device of a broadband wireless communication system, when the ARQ (Automatic Repeat ReQuest) mode is the first mode, the first to decompose and output the packet data unit from the physical layer into ARQ blocks Compute an error check code for each of the ARQ blocks from the first and second decomposition units, and compares the calculated error check code with the received error check code to check for errors, and generates an ARQ block. And a control unit for generating a feedback message for requesting retransmission of the ARQ block (s) in which the error has occurred, and a second decomposition unit for notifying the control unit (s).

According to still another aspect of the present invention, in a transmission method of a broadband wireless communication system, when transmission data is generated, a process of checking a current Automatic Repeat Request (ARQ) mode, and an upper layer (upper) when the ARQ mode is the first mode dividing a data unit from the layer into ARQ blocks, adding an error check code to each of the ARQ blocks, collecting ARQ blocks to which the error check code is added, and collecting the collected data. And transmitting a packet data unit added with a header to the receiver.

According to still another aspect of the present invention, in a reception method of a broadband wireless communication system, a process of checking a current ARQ mode when receiving a packet, and a packet data unit from a physical layer when the ARQ mode is a first mode. Decomposing the ARQ blocks, calculating an error check code for each of the ARQ blocks, comparing the calculated error check code with the received error check code, and checking the error; And transmitting a feedback message requesting retransmission of the block (s) to the transmitter.

According to still another aspect of the present invention, in the ARQ mode switching method in a wireless communication system supporting a first ARQ mode for retransmitting the entire packet data unit and a second ARQ mode for retransmitting an ARQ block in which the error occurs in the packet data unit Calculating a mean value of the number of retransmissions during a predetermined period, checking a current mode, comparing the calculated mean value with a first threshold value when the current mode is the first ARQ mode, and the average value When the current threshold value is greater than the first threshold value, converting the current mode to a second ARQ mode; when the current mode is the second ARQ mode, comparing the calculated average value with a second threshold value; If the average value is less than the second threshold value, it comprises the step of switching the current mode to the first ARQ mode.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, when an error control through ARQ (Automatic Repeat ReQuest) is performed in an 802.16 based system or a 4th generation system, an error detection code is assigned to each of ARQ blocks carried in a MAC PDU at a transmitter. In addition, the method for transmitting and requesting retransmission of the ARQ block (s) having an error at the receiving side will be described.

In addition, a first ARQ mode (or Normal ARQ mode) for retransmitting the entire packet data unit and a second ARQ mode (Extended ARQ mode: Extended ARQ mode) for retransmitting an ARQ block having an error in the packet data unit are provided. If all of them are supported, the scheme for adaptively switching the ARQ mode according to the channel state will be described.

3 is a diagram illustrating a process of generating a MAC PDU when performing an extended ARQ mode according to an embodiment of the present invention.

Referring to FIG. 3, the MAC layer receives MAC Service Data Units (MAC SDUs) in the form of IP packets from an upper layer in step 301. In step 303, the MAC layer divides the received IP packets in units of ARQ blocks, and adds a sequence number (BSN: Block Sequence Number) and CRC 8 (or CRC 12 or CRC 16) to each ARQ block. In step 305, the MAC layer collects a plurality of ARQ blocks, adds a PSH (Packing Sub Header) or FSH (Fragmentation Sub Header) to the front, and then adds a MAC Header before the sub header. Create MAC PDUs. The MAC PDUs thus generated are delivered to lower layers (eg, physical layers).

When performing the extended ARQ mode, the MAC PDU includes an error detection code in each of the ARQ blocks carried in the payload as shown. The error detection code may use one of CRC-8, CRC-12, and CRC-16. As described above, the extended ARQ mode in which CRC is added to each ARQ block may be performed when the radio channel is in a bad state and an error rate is high. In this case, since the receiver can detect an error in units of ARQ blocks and retransmit only an ARQ block in which an error occurs, the receiver can use radio resources more efficiently and reduce transmission delay than when retransmitting the entire MAC PDU.

According to the present invention, when both the normal ARQ mode and the extended ARQ mode are used, the mode change should be notified to the counterpart. To do this, use the following MAC header:

4 illustrates a format of a MAC header according to an embodiment of the present invention.

As shown, the generic MAC header includes a field for recording header type information (HT: Header Type), a field for recording encryption control information (EC: Encryption Control), and payload identification information. Field to record (Type), field to record ARQ mode (Mode), field to record CRC presence (CI: CRC Indicator), field to record encryption key sequence (EKS: Encryption Key Sequence), reservation Field (Rsv: Reserved), field for recording the length of the MAC PDU (LEG: Length), field for recording the connection identification information (CID: Connection ID), field for recording the header error check code (HCS: Header Check Sequence).

The Mode field according to the present invention indicates a normal ARQ mode when '0' is set, and indicates an extended ARQ mode when '1' is set. The receiver determines the ARQ mode based on the average number of retransmissions during the predetermined period, and sets the mode field of the MAC header to '0' or '1' according to the determined mode, and transmits it to the transmitter.

5 is a detailed functional block diagram of a MAC layer according to an embodiment of the present invention. The MAC layer illustrated in FIG. 5 is common to both the transmitter and the receiver. Hereinafter, the transmission and reception operations will be described. Here, the transmitter and the receiver may be relative to each other, depending on whether a terminal or a base station transmits or receives data, or may be a receiver.

First, referring to the transmission operation of the transmitter, the protocol control unit 500 generates and analyzes the MAC header according to the prescribed protocol, and controls the overall operation of the MAC layer including ARQ control. According to the present invention, the protocol controller 500 determines an ARQ mode by examining a mode field value of an ARQ feedback message received from a receiver. For example, if the mode field value is '0', the current mode is set to the normal ARQ mode, and if it is '1', the current mode is set to the extended ARQ mode.

The buffer management unit 503 includes a plurality of transmit buffers and receive buffers, and temporarily buffers MAC SDUs (Service Data Units) in the form of IP packets received from an upper layer in a transmit buffer (Tx Buffer). The ARQ block generation and decomposition unit 505 divides MAC SDUs from the buffer management unit 503 into ARQ block units (or sizes), and adds a sequence number (BSN: Block Sequence Number) to each ARQ block. At this time, when the current mode is the extended ARQ mode, an error detection code (eg CRC) is added to each ARQ block and output.

The PDU generation and decomposition unit 507 collects the ARQ blocks from the ARQ block generation and decomposition unit 505 and then adds a Packing Sub Header (PSH) or a Fragmentation Sub Header (FSH) in front of the ARQ block. MAC header is added by adding a MAC header before the sub header, and then transferred to a lower layer (physical layer). The MAC PDU delivered to the physical layer is mapped to a corresponding time-frequency resource (area) and transmitted to the receiver.

Next, referring to the reception operation of the receiver, the PDU generation and decomposition unit 507 decomposes the received MAC PDU received from the lower physical layer into ARQ blocks and delivers the ARQ block generation and decomposition unit 505. If the current mode is a normal ARQ mode, the PDU generation and decomposition unit 507 calculates a CRC for the entire PDU before decomposing the ARQ blocks, and adds the calculated CRC and the CRC added to the received PDU. Perform error checking by comparing Then, the error check result is transmitted to the protocol controller 500. Then, the protocol controller 500 generates an ARQ feedback message including the error check result and transmits it to the counterpart.

The ARQ block generation and decomposition unit 505 assembles the ARQ blocks from the PDU generation and decomposition unit 507 into a MAC service data unit (SDU) and delivers them to the buffer management unit 503. If the current mode is the extended ARQ mode, the ARQ block generation and decomposition unit 505 calculates a CRC for each ARQ block and compares the calculated CRC with the received CRC before assembling the SDU. Perform the test. The error check result is transmitted to the protocol controller 500. Then, the protocol controller 500 generates an ARQ feedback message including the error check result and transmits it to the counterpart.

The buffer manager 503 temporarily buffers the MAC SDU from the ARQ block generation and decomposition unit 505 in an Rx buffer and transfers the MAC SDU to an upper layer.

Meanwhile, the protocol controller 500 determines the ARQ mode based on the average number of retransmissions for a predetermined period every time the PDU is received, and sets the mode field of the ARQ feedback message according to the determined mode to '0 (normal ARQ mode). ) Or '1 (extended ARQ mode)' to send to the transmitter.

6 illustrates a procedure of a transmitter in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 6, first, in step 601, a transmitter checks a transmission buffer (or a transmission queue) to check whether data to be transmitted exists. If there is data to be transmitted, the transmitter checks the ARQ mode value (specific flag value) in step 603 to determine whether the current mode is a normal ARQ mode.

If in normal ARQ mode, the transmitter proceeds to step 605 to generate a PDU according to the normal ARQ mode and transmit it to the receiver. In other words, an error detection code (eg, CRC-8, CRC-12, CRC-16) for the entire PDU is added to the receiver. If in the extended ARQ mode, the transmitter proceeds to step 607 and generates a PDU according to the extended ARQ mode and transmits it to the receiver. That is, an error detection code is added to each of the ARQ blocks carried in the payload of the PDU and transmitted to the receiver.

After transmitting the PDU as described above, the transmitter checks whether an ARQ feedback message (or packet) for the transmitted PDU is received in step 609. Upon reception of the ARQ feedback message, the transmitter checks the mode field of the header of the received ARQ feedback message and updates the ARQ mode value in step 611.

In operation 613, the transmitter analyzes the ARQ feedback message to determine whether an ACK is received for the transmitted PDU. Here, in normal ARQ mode, ACK / NACK for all of the transmitted PDUs is received, and in extended ARQ mode, ACK / NACK for each of ARQ blocks carried in the transmitted PDU is received.

If the NACK is received for the transmitted PDU, the transmitter returns to step 603 to perform retransmission of the packet (PDU or ARQ block) in which the NACK has occurred. In this case, the PDU is retransmitted in the normal ARQ mode, and only the ARQ block (s) in which an error occurs is transmitted again in the extended ARQ mode.

If an ACK is received for the transmitted PDU, the transmitter proceeds to step 615 and discards the temporarily buffered PDU and returns to step 601.

7 illustrates a procedure of a receiver in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 7, first, a receiver checks whether a MAC PDU is received from a transmitter in step 701. Upon reception of the PDU, the receiver proceeds to step 703 in which an ARQ mode value (specific flag value) is checked to determine whether the current mode is a normal ARQ mode.

If the normal ARQ mode, the receiver calculates a CRC for the entire received PDU in step 705, and performs an error check by comparing the calculated CRC and the received CRC. In operation 707, the receiver determines whether an error occurs in the received PDU. If no error has occurred, the receiver proceeds directly to step 713. If an error occurs, the receiver proceeds to step 709 to increase the number of retransmissions for the PDU. In step 711, the receiver updates the average number of retransmissions corresponding to the predetermined period from the present time, and then proceeds to step 713.

In step 713, the receiver checks whether an average value of the number of retransmissions during the predetermined period is greater than a first threshold value TH1. If the average value is less than or equal to the first threshold value, the receiver proceeds directly to step 717. If the average value is larger than the first threshold value, the receiver proceeds to step 715 to switch the current mode to the extended ARQ mode and proceeds to step 717. Thereafter, in step 717, the receiver generates an ARQ feedback message including ACK / NACK information and ARQ mode indication information for the received PDU, transmits the ARQ feedback message to the transmitter, and returns to step 701.

If it is determined in step 703 that the current mode is the extended ARQ mode, the receiver proceeds to step 719 to calculate a CRC for each of the ARQ blocks included in the received PDU, and calculates the calculated CRC and the received CRC. In comparison, an error check is performed for each ARQ block. In operation 721, the receiver determines whether an error occurs in the received PDU according to the error check result. If no error has occurred, that is, no error is detected in all ARQ blocks, the receiver proceeds directly to step 727. If an error has occurred, that is, if an error is detected in at least one ARQ block, the receiver proceeds to step 723 to increase the number of retransmissions for the corresponding ARQ block. The receiver proceeds to step 725 to update the average number of retransmissions corresponding to the predetermined period from the present time and proceeds to step 727.

In step 727, the receiver checks whether an average value of the number of retransmissions during the predetermined period is smaller than a second threshold value TH2. If the average value is greater than or equal to the second threshold value, the receiver immediately proceeds to step 731. If the average value is smaller than the second threshold value, the receiver proceeds to step 729 to switch the current mode to a normal ARQ mode and proceeds to step 731. Thereafter, in step 731, the receiver generates an ARQ feedback message including ACK / NACK information and ARQ mode indication information for the received PDU, transmits the ARQ feedback message to the transmitter, and returns to step 701. In the above-described embodiment, the first threshold value and the second threshold value may be determined through an experiment or the like.

As described above, the receiver retains the number of retransmissions for a predetermined period regardless of the ARQ mode, and calculates an average value by averaging the number of retransmissions for the predetermined period each time a PDU is received. If the current mode is the normal ARQ mode, the mode change is determined by comparing the average value with the first threshold value. If the current mode is the extended ARQ mode, the mode value is determined by comparing the average value with the second threshold value.

Meanwhile, the above-described embodiment performs counting of the number of retransmissions in the normal ARQ mode on the basis of the PDU, and counts the number of retransmissions in the ARQ mode on the ARQ block basis. In another embodiment, when the receiver requests retransmission for a specific ARQ block in extended ARQ mode, if the transmitter retransmits the specific ARQ block alone without rearranging the specific ARQ block with other ARQ blocks (see FIG. 8C). In the extended ARQ mode, the number of retransmissions can be counted based on the PDU. In this case, the number of retransmissions for the corresponding PDU may be initialized or maintained as '0' when switching modes.

In addition, although the above-described embodiment is described as determining the mode change at the receiver and notifying the transmitter, the transmitter may also count the number of retransmissions for the corresponding transmission packet (PDU or ARQ block). The mode switch may be determined and the receiver may be notified.

8 is a diagram for explaining an extended ARQ mode according to the present invention.

Referring to FIG. 8, 801 and 803 show two consecutive Service Data Units (SDUs) appearing on the same connection. The first SDU 801 is composed of seven ARQ blocks of sequence numbers 5 to 11. The second SDU 803 is composed of five ARQ blocks of sequence numbers 12 to 16.

805 and 807 represent two PDUs (Packet Data Units) configured with the two SDUs 801 and 803. The first PDU 805 is composed of the zeroth fragment of the first SDU 801, that is, the ARQ blocks 5 through 7. The second PDU 807 may include the first fragment (ARQ blocks 8 through 11 ARQ blocks) of the first SDU 801 and the zero fragment (ARQ blocks 12 through 14 ARQs) of the second SDU 803. Block). The transmitter transmits the two PDUs 805 and 807 configured as described above to the receiver.

Then, when the retransmission request for the ARQ block 9 is received, for example, as shown in (b), the transmitter transmits the first fragment of the ARQ block 9 and the second SDU 803 (ARQ 15). Block and ARQ block 16) may be rearranged in one PDU and retransmitted to the transmitter. As another example, the transmitter may retransmit the ARQ block # 9 into one PDU, as shown in (c). As described above, the present invention can reduce bandwidth waste and transmission delay in the radio section since only the ARQ block having an error is retransmitted.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, according to the present invention, when performing error control through ARQ (Automatic Repeat ReQuest) in a wireless communication system, an ARQ is added to an ARQ block by adding an error detection code to each of ARQ blocks carried in a MAC PDU. An error can be detected in units of blocks and retransmission can be requested. That is, the present invention has an advantage of reducing the waste of radio resources and the transmission delay by performing retransmission in units of ARQ blocks. In addition, the present invention has the advantage that the error control can be adaptively performed according to the channel state by using the extended ARQ mode according to the state of the radio section.

Claims (27)

In the transmitter device of a broadband wireless communication system, When the ARQ mode is the first mode, the first generator divides a data unit from an upper layer into ARQ blocks, and adds an error check code to each of the ARQ blocks to output the first unit. Wow, And a second generator for collecting ARQ blocks from the first generator and generating a packet data unit by adding a header to the collected data. The method of claim 1, And a controller configured to determine the ARQ mode in accordance with feedback information from a receiver. The method of claim 1, And a controller configured to determine the automatic repeat request (ARQ) mode according to the average number of retransmissions during a predetermined period. The method according to claim 2 or 3, When the ARQ mode is the second mode, the first generator divides and outputs a data unit from the upper layer into ARQ blocks. And the second generation unit collects ARQ blocks from the first generation unit and adds a header and an error check code to the collected data to generate the packet data unit. The method of claim 1, The packet data unit is a packet data unit of a medium access control (MAC) layer. The method of claim 1, Wherein the error check code is one of cyclic redundancy checking (CRC) -8, CRC-12, and CRC-16. In the receiver device of a broadband wireless communication system, A first decomposition unit for decomposing and outputting the packet data unit from the physical layer into ARQ blocks when the ARQ mode is the first mode; An error check code is calculated for each of the ARQ blocks from the first decomposition unit, the error is checked by comparing the calculated error check code with the received error check code, and the ARQ block (s) in which the error is generated are checked. A second decomposition unit notifying the control unit; And the controller generating a feedback message requesting retransmission of the ARQ block (s) in which the error occurred. The method of claim 7, wherein The controller determines the ARQ mode according to the average number of retransmissions during a predetermined period, and sets the determined ARQ mode value in a predetermined field of the feedback message. The method of claim 7, wherein The controller determines the ARQ mode according to the control information received from the transmitter. The method according to claim 8 or 9, When the ARQ mode is the second mode, the first decomposition unit calculates an error check code for the packet data unit from the physical layer, compares the calculated error check code with the received error check code, and determines whether there is an error. Notify the control unit, The control unit, characterized in that for generating the feedback message including error information of the packet data unit. The method of claim 7, wherein The packet data unit is a packet data unit of a medium access control (MAC) layer. The method of claim 7, wherein Wherein the error check code is one of cyclic redundancy checking (CRC) -8, CRC-12, and CRC-16. In the transmission method of a broadband wireless communication system, The process of checking the current ARQ (Automatic Repeat ReQuest) mode when transmission data is generated, When the ARQ mode is the first mode, dividing a data unit from an upper layer into ARQ blocks, and adding an error check code to each of the ARQ blocks; And collecting the ARQ blocks to which the error check code has been added, and transmitting a packet data unit having a header added to the collected data to a receiver. The method of claim 13, When the ARQ mode is the second mode, dividing a data unit from the upper layer into ARQ blocks; Collecting the ARQ blocks and transmitting a packet data unit to which the header and an error check code are added to the collected data to the receiver. The method of claim 13, The ARQ mode is determined according to feedback information from a receiver. The method of claim 13, The ARQ mode is determined according to the average value of the number of retransmissions during a predetermined period. The method of claim 13, The packet data unit is a packet data unit of a medium access control (MAC) layer. The method of claim 13, The error check code is characterized in that one of CRC-8, CRC-12, CRC-16. The method of claim 14, Discarding the temporarily buffered packet data unit upon receiving a success (ACK) message for the transmitted packet data unit. In the reception method of a broadband wireless communication system, When the packet is received, checking the current ARQ mode; Decomposing the packet data unit from the physical layer into ARQ blocks when the ARQ mode is the first mode; Calculating an error check code for each of the ARQ blocks, comparing the calculated error check code with a received error check code, and checking an error; And transmitting a feedback message to the transmitter requesting retransmission of the failed ARQ block (s). The method of claim 20, When the ARQ mode is the second mode, calculating an error check code for the packet data unit from the physical layer, comparing the calculated error check code with the received error check code, and checking an error; And transmitting the feedback message including error information of the packet data unit to the transmitter. The method of claim 20, The ARQ mode is determined according to the control information received from the transmitter. The method of claim 20, The ARQ mode is determined according to an average number of retransmissions during a predetermined period, and the determined ARQ mode value is set in a predetermined field of the feedback message. The method of claim 20, The packet data unit is a packet data unit of a medium access control (MAC) layer. The method of claim 20, The error check code is characterized in that one of CRC-8, CRC-12, CRC-16. An ARQ mode switching method in a wireless communication system supporting a first ARQ mode for retransmitting an entire packet data unit and a second ARQ mode for retransmitting an ARQ block having an error in the packet data unit, Calculating an average value of the number of retransmissions for a predetermined period of time; Checking the current mode, Comparing the calculated average value with a first threshold value when the current mode is a first ARQ mode; And switching the current mode to a second ARQ mode if the average value is greater than the first threshold value. The method of claim 26, Comparing the calculated average value with a second threshold value when the current mode is a second ARQ mode; And if the average value is less than the second threshold value, switching the current mode to the first ARQ mode.

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