KR101467764B1 - Method for packet retransmission employing feedback information - Google Patents

Abstract

A packet retransmission method according to feedback information is disclosed. The method of retransmitting packets according to the feedback information according to an embodiment of the present invention is characterized in that after transmitting a packet, the packet retransmission method receives from the receiving terminal the channel status information and acknowledgment information indicating whether the packet is successfully decoded, Changing the retransmission scheme according to the channel status information and transmitting a retransmission packet for the packet according to the changed retransmission scheme when the information indicates decoding failure. According to the embodiments of the present invention, there is an effect that the transmitting terminal changes the retransmission method according to the information fed back from the receiving end and retransmits the packet, thereby improving the decoding probability at the receiving end and thereby increasing the retransmission efficiency.

HARQ, packet retransmission, feedback information, 3GPP LTE, IEEE 802.16m

Description

[0001] The present invention relates to a packet retransmission method,

The present invention relates to a packet retransmission method, and more particularly, to a packet retransmission method in accordance with feedback information for changing a retransmission method and retransmitting a packet at a transmitting end so as to increase the decoding probability of a received packet according to information fed back from a receiving end.

The next generation communication system is designed to use a wide frequency band and increase the data rate between the transmitter and the receiver. For such a system configuration, an OFDM-based modulation scheme is mainly adopted. The wireless communication standard using the OFDM modulation scheme includes 3GPP LTE (+), 3GPP2 UMB (+), IEEE 802.16 (d, e, m), IEEE 802.11, IEEE 802.20, IEEE 802.22 and HiperLAN. In such a communication system, a method of distinguishing between users can be exemplified by FDMA for dividing into frequency axes and TDMA for dividing into time axes. In a system configured at a low cost such as a wireless LAN (wireless LAN, HiperLAN, etc.), CSMA, which is a TDMA, is mainly used. On the other hand, systems such as 3GPP LTE, 3GPP2 UMB, and IEEE 802.16, which support commercial voice communication, are configured to transmit and receive traffic of each terminal in FDM manner in order to maximize frequency efficiency. Accordingly, the data is transmitted under the control of the base station, and the information for the control is transmitted to the terminal through the scheduling information.

Scheduling for maximizing frequency efficiency and obtaining multi-user diversity is mainly used in the communication process between the UE and the BS. That is, a frequency resource is allocated to a specific terminal so as to achieve maximum throughput with a minimum frequency resource, and the scheduling result is transmitted with a setting such that the terminal can be decoded without most errors.

However, if the state of the channel of the terminal is not good, the packet transmission between the base station and the terminal is carried out without ending the re-transmission. Packets transmitted in retransmission can simultaneously achieve time diversity and transmission energy boosting effects. Retransmission is a good way to construct a reliable channel, although it does reduce maximum performance. A Hybrid Automatic Repeat Request (HARQ) scheme is mainly used as a method of constructing the initial transmission and retransmission packets. A packet transmitted between the UE and the BS is encoded through a channel code, and various HARQ modes are generated according to a scheme of converting the packet into various types. The simplest retransmission scheme is to use the entire encoded code word for all packet transmission, and the receiving end generally performs decoding using chase combining. Another method is an Incremental Redundancy (IR) technique in which a codeword is divided and transmitted every transmission. When new code bit information is received in the retransmitted packet, additional information is received. When existing bits are received in the retransmitted packet, bit combining is performed.

FIG. 1 illustrates that when a packet is transmitted through HARQ, the configuration of a transmission packet may be changed at each retransmission.

In the case of using the chase combination, the retransmitted packets are all the same, but if the IR is used, the configuration of each packet may be changed at each retransmission.

FIG. 2 shows a decoding process of a receiving end.

In case of using IR, when a receiver receives a retransmission packet, the part not transmitted at each codeword bit position is set to reliability 0 to perform soft decision decoding or assume decoding (erasure) hard decision decoding.

Also, in the case of the codeword bits transmitted in multiple, the transmitted bits are used in combination, and it is possible to distinguish the case of merging by soft decision and the case of merging by hard decision. When merging into a soft decision, the received signal is summed in analog form or combined and averaged with multi-bit precision under the assumption that the channel is corrected. In this process, weighting combining is possible according to the accuracy of the received bits. On the other hand, when only 0 and 1 status of bits are required, as in hard decision decoding, 0 and 1 based on majority are selected when merging for each bit.

The following equation (1) represents soft combining when soft decision is performed and Equation (2) represents a majority selection when hard decision decoding is performed. Actually, these configurations can be changed according to the decoding method.

Here, R (k) is the soft decision / hard decision information of the received bit, r (k, i) is the soft decision / hard decision value in the reception of the i-th HARQ packet, and w Value is a weight to be applied to the corresponding bit of each transmission packet.

This transmission / decoding scheme is suitable for general blind channels, and may have ideal performance in situations where the channel has the same uncertainty of all bits, such as AWGN. The actual radio channel has mostly frequency selective characteristics, which makes it ideal for an existing IR or Chase combination approach. To improve this, if the blindness of the channel is maintained, it is possible to change the interleaver or select the subpacket of the IR assuming independent subcarrier characteristics.

However, in order to properly obtain the diversity of the actual channel, it is possible to obtain better performance by adding some additional channel information bits.

In the case where a resource is allocated to the entire system bandwidth for packet transmission without knowing the channel information, that is, a part of the entire resources in all subcarriers, a distributed mode, a localized allocation scheme, In the case of a resource structure that goes beyond the coherence band, such as an area exceeding the coherence bandwidth, the transmission method needs to be improved so that the receiving end can more effectively utilize the channel bandwidth. In this case, the number of packet retransmissions is reduced, and the overall transmission latency can be reduced.

However, in a state in which the transmitter does not know the channel information, there is a limitation in properly obtaining the diversity of the actual channel.

SUMMARY OF THE INVENTION The present invention is directed to a method and apparatus for retransmitting a packet using feedback information from a receiving end to improve a decoding probability of a receiving end.

According to an aspect of the present invention, there is provided a method of retransmitting packets according to feedback information, the method comprising: after transmitting a packet, transmitting packet status information and acknowledgment information indicating whether a packet is successfully decoded, Changing a retransmission scheme according to the channel status information and transmitting a retransmission packet for the packet according to the changed retransmission scheme when the reception confirmation information indicates decoding failure.

Advantageously, the channel state information may include a CQI value of subbands divided into one or more subcarrier units.

Preferably, the channel state information may include a maximum CQI value and a minimum CQI value of the subbands divided by one or more subcarrier units, and a reliability order of the subbands.

Advantageously, the channel state information may include a CQI average value of subbands divided by one or more subcarrier units and a reliability order of the subbands.

Preferably, the channel state information may include a CQI average value of the channel measured by the receiver.

Preferably, the channel state information may include information on a band other than a resource region in which the receiver has received the packet.

Preferably, in the process of transmitting the retransmission packet, the sub-carrier mapping scheme may be changed according to the channel state information, and the retransmission packet for the packet may be transmitted by applying the modified sub-carrier mapping scheme.

Preferably, in the process of transmitting the retransmission packet, the deteriorated channel may be compensated by applying a power enhancement technique according to the channel status information, and the retransmission packet for the packet may be transmitted using the compensated channel.

Preferably, in the process of transmitting the retransmission packet, the redundancy rate for a specific portion of the incremental redundancy packet to be retransmitted according to the channel status information may be adjusted, and the incremental redundancy packet may be retransmitted.

Preferably, in the process of transmitting the retransmission packet, the MIMO operation mode is changed according to the channel state information, and the retransmission packet for the packet is transmitted by applying the changed MIMO operation mode.

According to another aspect of the present invention, there is provided a method of retransmitting packets according to feedback information, the method comprising: after a transmitting end transmits a packet, Changing the retransmission scheme according to the reliability information when the reception acknowledgment information indicates decoding failure, and transmitting a retransmission packet for the packet according to the changed retransmission scheme.

Advantageously, the reliability information may include reliability of blocks defined in a codeword bit unit or a subcarrier symbol unit in the packet.

Advantageously, the reliability information may include a reliability maximum and minimum value of blocks defined in a codeword bit unit or a subcarrier symbol unit in the packet, a reliability order of the blocks.

Advantageously, the reliability information may include a reliability mean value of blocks defined in a codeword bit unit or a subcarrier symbol unit in the packet and a reliability order of the blocks.

Advantageously, the reliability information may include a reliability average value of all symbols received at the receiving end.

Preferably, in transmitting the retransmission packet, the sub-carrier mapping scheme may be changed according to the reliability information, and the retransmission packet for the packet may be transmitted by applying the modified sub-carrier mapping scheme.

Preferably, in the process of transmitting the retransmission packet, the deteriorated channel may be compensated by applying a power enhancement technique according to the reliability information, and the retransmission packet for the packet may be transmitted using the compensated channel.

Preferably, in the process of transmitting the retransmission packet, the redundancy rate for a specific part of the incremental redundancy packet to be retransmitted according to the reliability information may be adjusted, and the incremental redundancy packet may be retransmitted.

Preferably, in the process of transmitting the retransmission packet, the MIMO operation mode is changed according to the reliability information, and the retransmission packet for the packet is transmitted by applying the changed MIMO operation mode.

According to the embodiments of the present invention, there is an effect that the transmitting terminal changes the retransmission method according to the information fed back from the receiving end and retransmits the packet, thereby improving the decoding probability at the receiving end and thereby increasing the retransmission efficiency.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the following embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

When determining the modulation order or coding rate of the first packet in the wireless system, the channel quality information or the channel state information at the position where the packet is to be transmitted is required, which is transmitted through feedback.

There are various ways to transmit channel information. A commonly used method is to transmit a single CQI value calculated with a certain measurement rule for the entire system bandwidth, or to indicate a part where the channel state of the receiving end is best judged within a certain band to which the transmitting end transmits the packet Is a method. This is usually called the best M method. The transmitted information indicates that the UE can show optimal reception performance within a specific band. The transmitting terminal can transmit a packet using the specific band as much as possible and allocate another band to another receiver, Multi-user diversity can be obtained as a whole system.

However, if the first transmission packet fails, the transmitter must retransmit the packet. If the state of the subcarrier on which the packet is transmitted can not be clearly known, the time diversity expected at retransmission can not be optimally obtained. Particularly, when the transmitting terminal or the receiving terminal moves at high speed, the state of the channel is completely changed due to the time difference between the previous packet transmission time and the packet retransmission time. In this case, it is impossible to make an estimation on the state of the channel, so time diversity is obtained passively. In other words, no matter which technique is used in the transmitter, the effect is obtained only when the change of the channel is changed according to the technique. On the contrary, the channel may change in the direction of giving the minimum diversity gain at a specific retransmission time. Therefore, in order to overcome such a disadvantage, the transmitter needs to know the state of the receiver more specifically, so that the time diversity gain can be maximized.

3 is a schematic signal flow diagram of a packet retransmission method according to feedback information according to the present invention.

When receiving the channel information from the receiving end 320 before transmitting the first packet at the transmitting end 310, the packet is transmitted according to the channel information. When there is no channel information in the transmitter 310, a Modulation Coding Scheme (MCS) is determined using basic algorithms such as the strongest modulation and coding scheme and the last successful mode. When the packet arrives at the receiving end 320, the receiving end 320 performs channel estimation when the packet is to be decoded in a coherent manner, and performs packet decoding based on the channel estimation. In the case of a non-coherent detection scheme such as a differential modulation scheme, although the channel information is not estimated, the reliability of each code word bit is still influenced by the channel state. If the decoding is successful, the packet transmission procedure is completed. Otherwise, the transmission terminal 310 should be informed of packet decoding failure. For this, a signal such as ACK / NACK may be used. Actually, there may be a way of transmitting them by using a coherent response or a signal on / off function. However, it is impossible to determine a packet configuration capable of increasing the decoding probability in the next retransmission by simply detecting whether or not the packet has failed to be decoded.

Therefore, the transmitter 310 retransmits the packet using the feedback information transmitted from the receiver 320.

The information that can be transmitted from the receiving end 320 to the transmitting end 310 can inform the ACK / NACK indicating the decoding success / failure of the packet, the reliability information of the packet, the channel state information, and the like. Here, the reliability information of the packet may include reliability for each codeword, reliability for each received symbol, reliability for each subcarrier segment of the received signal, reliability for each bit group, reliability for each symbol group, and the like. Here, the channel state information may indicate the channel state or reliability of the received band of the packet, the channel state or reliability of the subbands usable by the terminal, the channel state or reliability of the entire system band, have.

The transmitting end 310 determines an option to be taken at retransmission based on the information of the receiving end 320 or according to an inherent basic algorithm. When the feedback information is not used, a packet is generated on the assumption of randomness. In the case of using the feedback information, reliability can be set by adding an error probability to the feedback information. Accordingly, it is possible to select an incremental redundancy version of HARQ or to select a location of a resource to be retransmitted or to map to a subcarrier so that the decoding probability at the receiver 320 becomes optimal.

4 is a flowchart of a packet retransmission method according to feedback information according to the present invention.

First, the transmitting terminal transmits a packet to the receiving terminal (S410). The receiving end decides the decoding success / failure of the packet and generates acknowledgment information, that is, an ACK or a NACK. The receiving end determines channel state information or reliability information, and feeds back the information together with the acknowledgment information to the transmitting end.

Next, the transmitting end receives channel state information, reliability information, and acknowledgment information from the receiving end (S420). At this time, if a NACK is not received or an ACK is received at the transmitting end, the following procedure is skipped and a normal packet transmission procedure is performed.

If the NACK is received or the ACK is not received, i.e., the acknowledgment information indicates decoding failure, the transmitting terminal changes the retransmission method according to the channel status information at step S440.

Finally, the transmitting end transmits a retransmission packet for the packet transmitted first according to the changed retransmission method to the receiving end (S450).

If the receiving end transmits only the ACK / NACK as in the conventional case, the receiving end decodes the packet into one or more decoding methods based on the resource allocation area and the packet configuration information that the transmitting end notifies by transmitting the corresponding packet, .

As an example of a feedback scheme applied to the present invention, a receiver may decode a packet and transmit channel state information together with an ACK / NACK according to the result.

The channel state information may be channel information in the resource area in which the packet is received at the receiving end.

As shown in FIGS. 5 and 6, a resource type used for transmitting a packet at a transmitter may be a localized allocation scheme, a localized-distributed allocation scheme, or a distributed allocation scheme.

In the case of the local allocation method, the location of the resource is changed each time of transmission. When additional information is fed back to the resource block, the transmitting end can be used as a clue to determine the reliability with which particular symbols are received. The area allocation scheme corresponds to the case of one allocation block in FIG. In FIG. 5, the receiving end divides one local resource block into two subbands, and determines channel state information of each subbands.

As shown in FIG. 5, in the case of the local distributed allocation method, when a resource allocation unit is defined as a constant L _b sub-carrier, and a resource is allocated by a transmitter, L _b is allocated locally, Position to obtain a frequency gain. In this case, the resources are not changed at the time of retransmission, or are configured so that they are spread evenly in the system band. Therefore, not only can the receiving end notify the transmitting end of the symbol reliability of the received packet by transmitting the channel state of each sub-band, but also informs the channel to transmit the packet later. In FIG. 5, the receiving end divides each local resource block into two subbands, and determines channel state information of each subbands.

As shown in FIG. 6, in the case of the distributed allocation scheme, since all the sub-carriers within the operating bandwidth are used, the resources of the same type are allocated in the retransmission as long as the bandwidth is not changed to completely different RF carriers. Therefore, the receiving end transmits the channel information to notify the reliability of the received packet symbols and inform the channel state at the retransmission. In FIG. 6, the receiving end divides one distributed resource block into four subbands, and determines channel state information of each subbands.

Among the methods of transmitting the channel state information to the transmitting end, in the array type reporting method, the channel state values corresponding to the divided subbands are calculated as shown in FIG. 5 or 6, and the values of the respective blocks are directly encoded , And can be encoded in a differential format as shown in FIGS. 8 and 9.

7, the values of each block are Val A, Val B, Val C, Val D, and the like.

In case of differential encoding, as shown in FIG. 8, it is possible to consider a form of transmitting a value of a specific block as a reference value and a remaining value as a differential value of the reference value. 8, Val A is the reference value, and the remaining dVal B, dVal C, and dVal D are the difference values with respect to the reference value.

Alternatively, as shown in FIG. 9, the average value may be calculated and a value difference of each block may be defined based on the average value. In Fig. 8, Val Avarage is the average value, and the remaining dVal A, dVal B, dVal C, and dVal D are the difference values with respect to the average value.

Among the methods of transmitting the channel state information to the transmitting end, the method of reporting the CQI and the profile of the channel reports the maximum / minimum CQI value and the ordering information of each subband, for example, in the form of labeling . Here, labeling refers to a method of numbering each permutation pattern of a block obtained by sorting values of each block and expressing the value in bits. For example, if there are four blocks, the number of possible sort orders is 4 * 3 * 2 * 1 = 24, so it can be transmitted using 5 bits. Here, it is possible to use only permutations smaller than the permutations. That is, instead of sending alignment information in N (= 5) bits earlier, it can be expressed using N-1 or fewer bits and mapped to some of the permutations.

Among methods of transmitting channel state information to a transmitter, a mean value and a profile of a channel may be reported in the form of labeling, and the average value may be reported instead of the maximum / minimum of the CQI value of the channel.

In the method of transmitting the channel state information to the transmitting end only the average value of the channel, only the average CQI value of the used resource allocated subcarriers can be reported without considering the profile.

In the case where the receiver unit constructs the channel information for all or part of the system bandwidth out of the resource area in which the packet is received, the resource blocks of FIGS. 5 and 6 may refer only to a specific band of the system band, . The feedback to this channel is to facilitate the packet mapping by considering the channel state at the next retransmission to the transmitting end.

Meanwhile, as another embodiment of the present invention, the receiving end may transmit the ACK / NACK and the packet reliability information to the transmitting end. The reliability can be estimated through the channel state before decoding the received packet or by using the soft output value after decoding. The receiver divides the codeword into blocks or divides the blocks into OFDM symbols, and feeds back the reliability of the block.

FIG. 10 illustrates an example of a method for defining a block for feedback information in a codeword order in FIG.

One block may be divided into the code bit order of the actual code word or the combination state in the received signal. As shown in FIG. 10, the block classification can be divided into values before and after the arrangement for the codeword is performed, and before and after packet decoding. In Fig. 10, blocks 1 to 4 may correspond to the block values in Figs. 7 to 9.

FIG. 11 shows an example of a method for defining a block for feedback information in the order of OFDM symbols in FIG.

The receiving end may feed back the average value or the maximum / minimum value of the reliability of the code bits or symbols in the corresponding block to the transmitting end according to the block definition of the symbol unit. In FIG. 11, the blocks of OFDM 1 to OFDM 4, a info, b info, c info, d info may correspond to the block values in FIGS. 7 to 9.

In this case, when the reliability is fed back in an array form on the basis of the above-defined blocks, the coding scheme may include an average reliability value and an array of reliability information between the blocks when the maximum / minimum reliability and the reliability array information between the blocks are fed back. The case of feeding back the average of the total reliability, and the like. When the reliability is fed back in the form of an array, the configurations of Figs. 7 to 9 can be used.

On the other hand, when the channel status information and the reliability information of the codeword are fed back to the transmitter at the same time, the feedback overhead is greatest, but the retransmission probability can be minimized.

Based on various kinds of feedback information, various methods can be applied to the transmitting end to improve the decoding probability at the receiving end.

First, in the case of improving the mapping method to a subcarrier in a transmitter, a method of modifying a process of mapping a generated codeword or subpacket to a subcarrier may be modified so that a specific part of the codeword And the like. To this end, the transmitting end may select and apply a sub-carrier mapper set or an interleaver set according to the reliability information. In this case, sub-hypotheses about the mapper or the interleaver are transmitted together to inform the receiving end of the method applied at the transmitting end. The additional information is preferably transmitted to the receiving end together with the resource allocation information.

Second, the transmitter can adjust the power based on the reliability or the channel information. That is, when a channel is deteriorated in a specific code word region or a sub-carrier region in a receiving end, a power boosting technique may be applied to compensate for the deteriorated channel. At this time, additional information about the power enhancement is transmitted to the receiving end. In the case of omitting the additional information on the power enhancement, a dedicated pilot (Dedicated Pilot) is included in the retransmission packet. Since the dedicated pilot is reinforced in the same way as the transmission symbol, the receiver can perform channel compensation without receiving information on the power enhancement. In the case of downlink, a dedicated pilot can also be applied.

Thirdly, when the transmitting terminal uses incremental redundancy, a redundancy packet can be generated according to the feedback information, and additional information on the redundant packet is transmitted to the receiving terminal together with the resource allocation information. A method of increasing the redundancy rate of a specific block part of a codeword when generating a redundant packet at a transmitting end can be used. In addition, a set of various possible methods for generating duplicate packets can be defined, and a redundant packet can be generated by selecting the most suitable version.

When a MIMO antenna is used, a MIMO mode can be selected to improve the reliability according to the feedback information. That is, the specific MIMO mode can be applied when the packet is retransmitted, and information on the applied MIMO mode can be transmitted to the receiving end together with the resource allocation information. Even if the same mode is used, the symbol mapping order in the MIMO input can be changed to emphasize the reliability uniformity at the receiving end.

One or more of the improvement methods described above may be applied in combination. Also, in the packet transmission process, if the receiving end fails to decode, the receiving end can recommend an option that can be selected by the transmitting end. The transmitting end can retransmit the packet based on this. In this case, information on the selected option may be transmitted to the receiving end together with the resource allocation information. In this case, while being robust to the feedback channel, the overhead increases. On the other hand, if the information about the selected option is not transmitted to the receiving end, the reliability of the feedback channel should be further increased to lower the error probability to prevent the protocol from being broken.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that such modifications are within the technical scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

The present invention relates to a packet retransmission method in accordance with feedback information for changing a retransmission method and retransmitting a packet in a transmitting terminal so as to increase a decoding probability of a received packet according to information fed back from a receiving end, The present invention can be applied to an apparatus such as a base station or a terminal using a packet retransmission method.

1 illustrates a coding process of a transmitter and a retransmission packet structure of an HARQ scheme.

FIG. 2 shows a decoding process of a receiving end.

3 is a schematic signal flow diagram of a packet retransmission method according to feedback information according to the present invention.

4 is a flowchart of a packet retransmission method according to feedback information according to the present invention.

FIG. 5 illustrates an example of a method of dividing a block for feedback information in the case of the local distributed resource allocation scheme in FIG.

FIG. 6 shows an example of a method for dividing a block for feedback information in the case of the distributed resource allocation scheme in FIG.

FIGS. 7 to 9 illustrate examples of constructing channel state information or reliability information in FIG.

FIG. 10 illustrates an example of a method for defining a block for feedback information in a codeword order in FIG.

FIG. 11 shows an example of a method for defining a block for feedback information in the order of OFDM symbols in FIG.

Claims (19)

A method for retransmitting a packet according to feedback information of a receiving end in a transmitting end, Receiving, from the receiving end, acknowledgment information indicating channel state information, reliability information on the packet, and success or failure of decoding of the packet after the transmitting end transmits the packet; And Changing the retransmission scheme according to the channel state information and the reliability information when the acknowledgment information indicates decoding failure and transmitting a retransmission packet for the packet according to the changed retransmission scheme, Wherein the reliability information comprises reliability of blocks defined by one or more OFDM symbol intervals in a codeword bit unit or a subcarrier symbol unit in the packet. The method according to claim 1, Wherein the reliability information comprises: A reliability maximum value and a minimum value of blocks defined by one or more OFDM symbol intervals in a code word bit unit or a subcarrier symbol unit in the packet, and a reliability order of the blocks. The method according to claim 1, Wherein the reliability information comprises: A reliability average value of blocks defined by one or more OFDM symbol intervals in a codeword bit unit or a subcarrier symbol unit in the packet, and a reliability order of the blocks. The method according to claim 1, Wherein the reliability information comprises: And a reliability average value of all symbols received at the receiving end. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Changing a subcarrier mapping scheme according to the reliability information; And And transmitting a retransmission packet for the packet by applying the modified subcarrier mapping scheme. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Compensating a degraded channel by applying a power enhancement technique according to the reliability information; And And transmitting a retransmission packet for the packet using the compensated channel. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Adjusting an overlap ratio for a specific portion of an Incremental Redundancy packet to be retransmitted according to the reliability information; And And retransmitting the incremental redundancy packet according to the feedback information. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Changing a MIMO operation mode according to the reliability information; And And transmitting a retransmission packet for the packet by applying the changed MIMO operation mode. The method according to claim 1, The channel state information includes: A method of retransmitting packets according to feedback information, the method comprising a CQI value of subbands divided by subcarrier units. The method according to claim 1, The channel state information includes: A maximum CQI value and a minimum CQI value of subbands divided on a subcarrier basis, and a reliability order of the subbands. The method according to claim 1, The channel state information includes: A CQI average value of subbands divided on a subcarrier basis, and a reliability order of the subbands. The method according to claim 1, The channel state information includes: And a CQI average value of the channel measured by the receiver. The method according to claim 1, The channel state information includes: And information on bands other than the resource region in which the receiving terminal has received the packet. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Changing a subcarrier mapping scheme according to the channel state information; And And transmitting a retransmission packet for the packet by applying the modified subcarrier mapping scheme. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Compensating a degraded channel by applying a power enhancement technique according to the channel state information; And And transmitting a retransmission packet for the packet using the compensated channel. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Adjusting an overlap ratio for a specific portion of an Incremental Redundancy packet to be retransmitted according to the channel status information; And And retransmitting the incremental redundancy packet according to the feedback information. The method according to claim 1, Wherein the step of transmitting the retransmission packet comprises: Changing a MIMO operation mode according to the channel state information; And And transmitting a retransmission packet for the packet by applying the changed MIMO operation mode. delete delete

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