KR101426956B1 - Method for transmitting data using HARQ - Google Patents

Abstract

A method for transmitting data using HARQ includes transmitting a first bit string that is a part of a codeword, and modulating the first bit string in the first bit string according to a retransmission request for the codeword, And transmitting a second bit string to which a modulation order smaller than a modulation order is applied. The non-adaptive HARQ scheme of the proposed IR mode can increase the efficiency of the retransmission data by changing the modulation order of the retransmission data based on the modulation order applied to the initial data. Since the modulation order and the number of subchannels allocated are determined in advance according to the number of retransmissions, the size of the retransmission data can be known in advance, and continuous retransmission data is transmitted to the previously transmitted data to maximize the coding gain of the IR mode Can be obtained.

Description

[0001] The present invention relates to a method for transmitting data using HARQ,

The present invention relates to wireless communication, and more particularly, to a data transmission method using HARQ.

The Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard provides techniques and protocols for supporting broadband wireless access. Standardization progressed from 1999 and IEEE 802.16-2001 was approved in 2001. It is based on a single carrier physical layer called 'Wirelssman-SC'. In the IEEE 802.16a standard approved in 2003, 'Wirelssman-OFDM' and 'Wirelssman-OFDMA' were added to the physical layer in addition to 'Wirelssman-SC'. The IEEE 802.16-2004 standard was revised in 2004 after the IEEE 802.16a standard was completed. IEEE 802.16-2004 / Cor1 was completed in 2005 in the form of 'corrigendum' to correct bugs and errors in the IEEE 802.16-2004 standard.

As an error compensation scheme for ensuring the reliability of communication, there are a forward error correction (FEC) scheme and an automatic repeat request (ARQ) scheme. In the FEC scheme, an extra error correcting code is added to the information bits, thereby correcting the error at the receiving end. The ARQ scheme corrects errors by retransmitting data, and includes SAW (stop and wait), GBN (Go-back-N), and SR (selective repeat). The SAW method is a method of transmitting the next frame after confirming whether the transmitted frame is correctly received or not. The GBN scheme transmits N consecutive frames, and if not successfully transmitted, retransmits all frames transmitted after an erroneous frame. The SR scheme is a scheme for selectively retransmitting only frames in which an error has occurred.

The FEC scheme has an advantage in that there is no time delay and no information is exchanged between the transmitting and receiving ends, but there is a disadvantage in that system efficiency is poor in a good channel environment. Although the ARQ scheme can increase transmission reliability, there is a disadvantage in that time delay occurs and system efficiency drops in a poor channel environment. To solve these drawbacks, a hybrid automatic repeat request (HARQ) scheme combining FEC and ARQ is proposed. According to the HARQ scheme, whether or not the data received by the physical layer includes an error that can not be decoded is confirmed, and when an error occurs, performance is improved by requesting retransmission.

The mode of HARQ can be divided into chase combining and incremental redundancy (IR). Chase combining is a method of obtaining a signal-to-noise ratio (SNR) gain by combining error-detected data with retransmitted data without discarding the data. IR is a method of incrementally transmitting additional redundant information to retransmitted data to reduce the burden of retransmission and obtain coding gain.

If no error is detected in the received data, the receiver transmits an ACK (acknowledgment) signal as a response signal to inform the transmitter of the success of the reception. When an error is detected in the received data, the receiver transmits a negative acknowledgment (NACK) signal to the acknowledgment signal to inform the transmitter of the error detection. The transmitter can retransmit the data when the NACK signal is received.

A receiver based on a Hybrid Auto Repeat Request (HARQ) basically attempts error correction on received data and determines whether to retransmit the data using an error detection code. The CRC (Cyclic Redundancy Check) can be used for the error detection code. Upon detecting an error in the received data through the CRC detection process, the receiver sends a NACK signal to the transmitter. The transmitter that receives the NACK signal transmits the appropriate retransmission data according to the HARQ mode (Chase combining or IR). The receiver receiving the retransmission data combines and decodes the previous data and the retransmission data, thereby improving reception performance.

The HARQ retransmission scheme can be divided into synchronous and asynchronous. Synchronous HARQ is a method of retransmitting data at a point in time when both the transmitter and the receiver are aware, thereby reducing signaling required for data transmission such as an HARQ processor number. Asynchronous HARQ allocates resources at an arbitrary time for retransmission and requires signaling for data transmission, resulting in overhead.

HARQ can be classified into adaptive HARQ and non-adaptive HARQ according to transmission attributes such as resource allocation, modulation scheme, and transport block size. The adaptive HARQ is a method of changing the transmission attributes used for the retransmission according to the change of the channel condition, by comparing the transmission attributes with the initial transmission and changing the transmission attributes in whole or in part. Non-adaptive HARQ is a scheme in which transmission attributes used for initial transmission are continuously used irrespective of changes in channel conditions.

In the IR mode, the retransmission data indicates additional information incrementally added to the previously transmitted data. As in the non-adaptive HARQ, it is not necessary to transmit the retransmission data at the same size as the initial transmission data, Transmitting data is a waste of radio resources. If the modulation scheme or resource allocation used for the initial transmission is used as it is in the retransmission data, the channel state changed at the time of transmission of the retransmission data can not be properly reflected.

Generally, the necessity of retransmission indicates that the channel condition is not good, and it is necessary to transmit retransmission data using a modulation scheme having a good decoding performance. There is a need for a method for increasing the efficiency of retransmission data in non-adaptive HARQ in which retransmission data is transmitted in the IR mode.

SUMMARY OF THE INVENTION The present invention provides a data transmission method using adaptive HARQ.

According to an aspect of the present invention, there is provided a data transmission method using HARQ, the method comprising: transmitting a first bit string, which is a part of a codeword, to a first bit string in response to a retransmission request for the codeword; And transmitting a second bit stream to which a modulation order smaller than a modulation order applied to the first bit stream is applied.

According to another aspect of the present invention, there is provided a method for transmitting data using HARQ, the method including transmitting initial data and transmitting retransmission data according to a retransmission request for the initial data, A number of subchannels greater than the number of subchannels is allocated and a modulation scheme applied to the retransmission data is determined according to the number of allocated subchannels.

The non-adaptive HARQ scheme of the proposed IR mode can increase the efficiency of the retransmission data by changing the modulation order of the retransmission data based on the modulation order applied to the initial data. Since the modulation order and the number of subchannels allocated are determined in advance according to the number of retransmissions, the size of the retransmission data can be known in advance, and continuous retransmission data is transmitted to the previously transmitted data to maximize the coding gain of the IR mode Can be obtained.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station (BS) 20. The terminal 10 may be fixed or mobile and may be referred to by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, The base station 20 generally refers to a fixed station that communicates with the terminal 10 and may be referred to in other terms such as a Node-B, a Base Transceiver System (BTS), an Access Point Can be called. One base station 20 may have more than one cell.

Hereinafter, downlink (DL) means communication from the base station 20 to the terminal 10, and uplink (UL) means communication from the terminal 10 to the base station 20. In the downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In the uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20.

The wireless communication system may be an Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) based system. OFDM uses multiple orthogonal subcarriers. OFDM utilizes the orthogonality property between IFFT (inverse fast Fourier transform) and FFT (fast Fourier transform). In the transmitter, data is transmitted by performing IFFT. The receiver performs an FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

Fig. 2 shows an example of a frame structure. A frame is a data sequence for a fixed time that is used by a physical specification. Reference may be made to Section 8.4.4.2 of the IEEE Standard 802.16-2004 "Part 16: Air Interface for Fixed Broadband Wireless Access Systems" (hereinafter referred to as Reference 1).

Referring to FIG. 2, a frame includes a downlink (DL) frame and an uplink (UL) frame. Time Division Duplex is a scheme in which uplink and downlink transmissions share the same frequency but occur at different times. The DL frame is temporally ahead of the UL frame. The DL frame starts in the order of a preamble, a frame control header (FCH), a downlink (DL) -MAP, an uplink (UL) -MAP, and a burst area. A guard time for distinguishing the UL frame from the DL frame is inserted in the middle part of the frame (between the DL frame and the UL frame) and the last part (after the UL frame). The transmit / receive transition gap (TTG) is the gap between the downlink burst and the subsequent uplink burst. A receive / transmit transition gap (RTG) is a gap between an uplink burst and a subsequent downlink burst.

The preamble is used for initial synchronization, cell search, frequency offset, and channel estimation between the base station and the terminal. The FCH includes the length of the DL-MAP message and the coding scheme information of the DL-MAP.

The DL-MAP is an area to which the DL-MAP message is transmitted. The DL-MAP message defines a downlink channel connection. The DL-MAP message includes a configuration change count of DCD (Downlink Channel Descriptor) and a base station ID. The DCD describes a downlink burst profile applied to the current map. The downlink burst profile refers to the characteristics of the downlink physical channel, and DCD is periodically transmitted by the base station through the DCD message.

The UL-MAP is an area in which a UL-MAP message is transmitted. The UL-MAP message defines the uplink channel connection. The UL-MAP message includes a configuration change count of a UCD (Uplink Channel Descriptor), and an effective start time of UL allocation defined by UL-MAP. The UCD describes an uplink burst profile. The uplink burst profile refers to the characteristics of the uplink physical channel, and the UCD is periodically transmitted by the base station through the UCD message.

In the following, a slot is defined as a time and a subchannel with a minimum possible data allocation unit. The number of subchannels depends on the FFT size and time-frequency mapping. The subchannel includes a plurality of subcarriers, and the number of subcarriers per subchannel follows a permutation scheme. A permutation is a mapping of a logical subchannel to a physical subcarrier. In FUSC (Full Usage of Subchannels), the subchannel includes 48 subcarriers. In PUSC (Partial Usage of Subchannels), the subchannel includes 24 or 16 subcarriers. A segment is a set of at least one subchannel.

In order to map the data to the physical subcarriers in the physical layer, it is generally divided into two steps. In a first step, data is mapped onto at least one data slot on at least one logical subchannel. In the second stage, each logical subchannel is mapped to a physical subcarrier. This is called permutation. Reference 1 discloses a permutation scheme such as FUSC, PUSC, O-FUSC, O-PUSC, AMC and the like. A set of OFDM symbols using the same permutation scheme is referred to as a permutation zone, and one frame includes at least one permutation area.

FUSC and O-FUSC are used only for downlink transmission. The FUSC consists of one segment including all subchannel groups. Each subchannel is mapped to a physical subcarrier distributed over the entire physical channel. This mapping is changed for each OFDM symbol. A slot is composed of one subchannel on one OFDM symbol. O-FUSC differs from FUSC in the way pilots are assigned.

PUSC is used for both downlink transmission and uplink transmission. In the downlink, each physical channel is divided into clusters consisting of 14 contiguous subcarriers on two OFDM symbols. The physical channels are mapped into six groups. Within each group, pilots are assigned to each cluster in a fixed location. In the uplink, subcarriers are divided into tiles composed of four adjacent physical subcarriers on 3 OFDM symbols. The subchannel includes 6 tiles. Pilot is assigned to each corner of each tile. O-PUSC is used for uplink transmission only, and the tile is composed of 3 adjacent physical subcarriers on 3 OFDM symbols. The pilot is assigned to the center of the tile.

Hereinafter, a resource allocation structure and an information block process for performing HARQ will be described.

3 is an exemplary diagram illustrating a resource allocation structure for HARQ.

Referring to FIG. 3, a data region is a logical two-dimensional resource allocation region including at least one sub-channel and at least one OFDM symbol. The data area may correspond to one burst on the frame. The information on the data area in the downlink transmission can be transmitted from the BS to the MS through the HARQ DL MAP message. The information on the data area in the UL transmission can be transmitted from the BS to the MS through the HARQ UL MAP message.

The data area is partitioned into at least one subburst according to the HARQ process for each user. In one sub-burst, an HARQ process for one information block is performed. One sub-burst may be assigned a CID (connection identifier). The CID is a value for confirming the connection between the BS and the MAC of the UE. All sub-bursts belonging to one data area operate in the same HARQ mode (Chase combining or IR).

Each sub-burst is allocated on a slot-by-slot basis, and the slots may be allocated in a frequency-first order. That is, starting from the slot having the smallest OFDM symbol and the smallest subchannel, the subchannel is increased and the slot is allocated. And increases the number of OFDM symbols by the slot duration again in the last subchannel.

One burst is allocated to a data stream using a HARQ process operating in the same mode, and each burst is sub-divided into sub-bursts per user (or CID).

4 is a diagram illustrating an example of processing of an information block for performing HARQ.

Referring to FIG. 4, all or a part of an information block is sent to a transport block for transmission to a physical layer, and a CRC (error detection code) is added to one transport block (CRC attachment) . The information block may be called PDU (Protocol Data Unit) of MAC (Medium Access Control). The MAC PDU is a data unit transmitted from the MAC layer, which is the upper layer, to the physical layer when a layer for performing HARQ is referred to as a physical layer.

The transport block to which the CRC is added is divided into a code block segmentation for channel encoding. The divided blocks are called code blocks. An encoder performs channel encoding on a code block and outputs coded bits. The encoder may apply a turbo code, one of the error correction codes. A turbo code is a structured code that includes information bits as systematic bits. In the case of a turbo code with a code rate of 1/3, two parity bits are assigned to one structured bit. However, the error correction code is not limited to the turbo code, and the technical idea of the present invention can be applied to low density parity check code (LDPC) or other convolutional codes.

One HARQ function is performed in units of transport blocks. The HARQ processor performs an HARQ mode (chase combining or IR) and an HARQ method (adaptive HARQ or non-adaptive HARQ) according to a retransmission environment in order to retransmit a packet in which an error has occurred.

The channel interleaver mixes the encoded bits on a bit-by-bit basis to distribute transmission errors according to the channel. A physical resource mapper converts the interleaved coded bits into data symbols and maps them to subburs of the data area.

Now, HARQ data retransmission will be described. Data retransmission of HARQ can be performed synchronously or asynchronously according to stop and wait (SAW), go-back-N (GBN), and selective repeat (SR) methods.

5 shows data retransmission in the stop and wait (SAW) scheme.

Referring to FIG. 5, in the SAW scheme, the transmitter Tx transmits a next frame or a retransmission frame after a round trip time (RTT) in which an ACK / NACK signal for a transmission frame is received from a receiver Rx send. In the non-adaptive HARQ of the IR mode, when the transmitter receives the NACK signal from the receiver, the transmitter transmits incremental retransmission data to the retransmitted frame and transmits the incremented retransmission data to the previously transmitted data. At this time, the transmitter can change the modulation scheme and the radio resource applied to the retransmission data according to a predetermined rule. The transmitter can transmit the retransmission data by applying a modulation scheme and a radio resource determined for each transmission count of the retransmission data.

In the SAW scheme, since the transmission of the data frame is delayed during the RTT, the transmission efficiency is degraded.

6 shows data retransmission of the N-channel stop and wait (SAW) scheme.

Referring to FIG. 6, in the N-channel SAW scheme, the transmitter Tx performs independent SAW HARQ until one frame is transmitted and an ACK / NACK signal is received from the receiver Rx. That is, in the N-channel SAW scheme, the transmitter transmits N frames during RTT, and the receiver transmits an ACK / NACK signal independently for each frame. In the non-adaptive HARQ of the IR mode, the transmitter transmits incremental retransmission data to the previously transmitted data in the retransmission frame for the frame received the NACK signal from the receiver. At this time, the transmitter can transmit the retransmission data by applying a modulation scheme and a radio resource determined for each transmission number of the retransmission data.

The N-channel SAW scheme compensates for the disadvantage of the SAW scheme in which data frames are not transmitted during RTT, thereby enhancing transmission efficiency.

7 shows data retransmission of a multi-stop and wait (SAW) scheme.

Referring to FIG. 7, when a bandwidth available for a wireless communication system is wide or multiple antennas are used, a plurality of HARQ processors are performed in parallel and several (m) transmission blocks are transmitted through one frame . The receiver can respond with m ACK / NACK signals for m transport blocks included in one frame. In the non-adaptive HARQ of the IR mode, the transmitter transmits incremental retransmission data to the previously transmitted data in the retransmission frame for the frame received the NACK signal from the receiver. At this time, the transmitter can transmit the retransmission data by applying a modulation scheme and a radio resource determined for each transmission number of the retransmission data.

The transmission efficiency of the system can be further improved by applying the N-channel SAW method based on the multi-SAW method.

Now, the non-adaptive HARQ of the IR mode will be described.

FIG. 8 shows an example in which non-adaptive HARQ in the IR mode is performed. The modulation scheme and the radio resource applied at the time of the initial data transmission are directly applied to the retransmission data.

Referring to FIG. 8, the retransmission data in the non-adaptive HARQ scheme of the IR mode can be incrementally transmitted after the data transmitted earlier. In the non-adaptive HARQ, the retransmission data is transmitted with the same size as the original (first transmission) data. Retransmission data can be transmitted cyclically if the index of the retransmission data becomes equal to the length (R _m · N _EP ) of the mother codeword. R _m is the reciprocal of the mother code rate 1 / R _m , and N _EP is the size of the code block entering the encoder. The mother codeword may be composed of systematic bits having a bit string having the same size as a code block and at least one parity bit which is a bit string related thereto. When the mother coding rate is 1/3, the mother codeword consists of one structured bit and two parity bits. The mother codeword may be a turbo codeword. The length of the mother codeword is R _m · N _EP .

In the IR mode, some bit strings including the structured bits of the mother codeword are transmitted in the initial transmission, and some other bit strings are incrementally transmitted in response to the retransmission request for the mother codeword. That is, part of the bit stream of the mother codeword is transmitted on an initial transmission and retransmission basis on a block-by-block basis.

In the non-adaptive HARQ scheme of the IR mode, when retransmission data is transmitted with the same modulation technique and radio resource as the original data, it is advantageous to transmit successive bit streams without overlapping with the transmitted bit sequence. That is, since the sizes of the initial data and the retransmission data are the same, the start point of the bit stream to be transmitted can be accurately found according to the number of transmissions. Thus, the coding gain of the IR mode can be maximized. However, since the retransmission data is transmitted with the same size as the original data, many radio resources are used, and the scheduling efficiency of the radio resources is not good. Generally, the retransmission data incrementally transmitted to the initial data in the IR mode can obtain a sufficient coding gain even if it is smaller than the original data. In the non-adaptive HARQ scheme, since the same modulation technique as the initial data is applied to the retransmission data without applying the channel state, the data transmission efficiency is decreased due to an increase in the number of retransmissions under a bad channel environment.

Hereinafter, the non-adaptive HARQ scheme of the IR mode capable of maximizing the coding gain of the IR mode and increasing the data transmission efficiency will be described.

FIG. 9 shows an example in which non-adaptive HARQ of the IR mode is performed according to an embodiment of the present invention.

Referring to FIG. 9, a modulation scheme and a radio resource (subchannel) applied at the time of initial data transmission are changed according to a predetermined rule to transmit retransmission data. That is, the modulation order is changed according to a certain rule according to the number of retransmission, and the retransmission data is transmitted. The size of the retransmission data is changed according to the number of retransmissions and is transmitted. The non-adaptive HARQ scheme of the proposed IR mode can be applied to both downlink and uplink data transmission.

First, downlink data transmission will be described. Assume that the modulation schemes supported in the IR mode non-adaptive HARQ scheme are Quadrature-Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and 64 QAM. Given N _EP and the number of subchannels (N _SCH ), the modulation order (MOD) is determined by the Modulation order Product code Rate (MPR) value. MPR means the number of information bits efficiently transmitted on one subcarrier. MPR is defined as Equation (1). The range of the MPR value can be changed according to the kind of the channel code or the user's arbitrary criterion.

At this time, the MPR value

When 0 < MPR < 1.5, QPSK is used, and the modulation order of QPSK is 2.

If 1.5 < MPR &lt; 3.0, 16 QAM is used, and the modulation order of 16 QAM is 4. [

If 3.0 < MPR &lt; 5.4, 64 QAM is used, and the modulation order of 64 QAM is 6. [

The effective coding rate is the MPR divided by the modulation order.

Table 1 shows the number of subchannels (N _SCH ), MPR, modulation order (MOD) and coding rate according to N _EP in the downlink. 'Sch' denotes the number of subchannels, and 'Rate' denotes the code rate.

In the same N _EP , the modulation order (MOD) may be applied differently depending on the number of subchannels (Sch). That is, the modulation technique applied to the same N _EP changes. For example, in the case of N _EP = 144, a 64 QAM modulation scheme is used with a modulation order of 6 for a subchannel of 1, a 16 QAM modulation scheme is used with a modulation order of 4 for a subchannel of 2, Is 3 or more, the modulation order is 2, and a QPSK modulation scheme is used.

The modulation order to be applied may be gradually decreased according to the number of retransmissions. Decoding performance is improved if the modulation order is lowered. The change of the modulation order according to the number of retransmissions can be indicated by the number of subchannels allocated to the retransmission data based on Table 1. [ The number of subchannels allocated to the retransmission data can be known from the radio resource scheduling information.

Table 2 shows an example of the number of subchannels in initial transmission and retransmission for each N _EP in the downlink. It is assumed that the maximum number of retransmissions is 4 (2nd to 5th trans.), And the modulation order can be changed in retransmission.

N _EP 1st trans. 2nd trans. 3rd trans. 4th trans. 5th trans. sch sch sch sch sch 144 One 3 3 3 3 144 One One 3 3 3 144 One One One 3 3 144 One One One One 3 144 2 3 3 3 3 144 2 2 3 3 3 144 2 2 2 3 3 144 2 2 2 2 3 192 One 3 3 3 3 192 One One 3 3 3 192 One One One 3 3 192 One One One One 3 192 2 3 3 3 3 192 2 2 3 3 3 192 2 2 2 3 3 192 2 2 2 2 3 288 2 3 5 5 5 288 2 3 3 5 5 288 2 3 3 3 5 288 2 2 3 5 5 288 2 2 3 3 5 288 2 2 2 3 5 288 2 5 5 5 5 288 2 2 5 5 5 288 2 2 2 5 5 288 2 2 2 2 5 288 2 3 3 3 3 288 2 2 3 3 3 288 2 2 2 3 3 288 2 2 2 2 3 288 3 5 5 5 5 288 3 3 5 5 5 288 3 3 3 5 5 288 3 3 3 3 5 288 3 6 6 6 6 288 3 3 6 6 6 288 3 3 3 6 6 288 3 3 3 3 6 384 2 3 6 6 6 384 2 3 3 6 6 384 2 3 3 3 6 384 2 2 3 6 6 384 2 2 3 3 6 384 2 2 2 3 6 384 2 6 6 6 6 384 2 2 6 6 6 384 2 2 2 6 6 384 2 2 2 2 6 384 2 3 3 3 3 384 2 2 3 3 3 384 2 2 2 3 3 384 2 2 2 2 3 384 3 6 6 6 6 384 3 3 6 6 6 384 3 3 3 6 6 384 3 3 3 3 6 384 4 6 6 6 6 384 4 4 6 6 6 384 4 4 4 6 6 384 4 4 4 4 6 384 4 8 8 8 8 384 4 4 8 8 8 384 4 4 4 8 8 384 4 4 4 4 8 480 2 8 8 8 8 480 2 2 8 8 8 480 2 2 2 8 8 480 2 2 2 2 8 480 3 4 8 8 8 480 3 4 4 8 8 480 3 4 4 4 8 480 3 3 4 8 8 480 3 3 4 4 8 480 3 3 3 4 8 480 3 8 8 8 8 480 3 3 8 8 8 480 3 3 3 8 8 480 3 3 3 3 8 480 3 4 4 4 4 480 3 3 4 4 4 480 3 3 3 4 4 480 3 3 3 3 4 480 4 8 8 8 8 480 4 4 8 8 8 480 4 4 4 8 8 480 4 4 4 4 8 480 5 10 10 10 10 480 5 5 10 10 10 480 5 5 5 10 10 480 5 5 5 5 10 480 6 8 8 8 8 480 6 6 8 8 8 480 6 6 6 8 8 480 6 6 6 6 8 480 6 10 10 10 10 480 6 6 10 10 10 480 6 6 6 10 10 480 6 6 6 6 10 960 5 15 15 15 15 960 5 5 15 15 15 960 5 5 5 15 15 960 5 5 5 5 15 960 6 8 15 15 15 960 6 8 8 15 15 960 6 8 8 8 15 960 6 6 8 15 15 960 6 6 8 8 15 960 6 6 6 8 15 960 6 15 15 15 15 960 6 6 15 15 15 960 6 6 6 15 15 960 6 6 6 6 15 960 6 8 8 8 8 960 6 6 8 8 8 960 6 6 6 8 8 960 6 6 6 6 8 960 8 15 15 15 15 960 8 8 15 15 15 960 8 8 8 15 15 960 8 8 8 8 15 1920 10 15 30 30 30 1920 10 15 15 30 30 1920 10 15 15 15 30 1920 10 10 15 30 30 1920 10 10 15 15 30 1920 10 10 10 15 30 1920 10 30 30 30 30 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4800 26 26 26 26 38 4800 32 38 76 76 76 4800 32 38 38 76 76 4800 32 38 38 38 76 4800 32 32 38 76 76 4800 32 32 38 38 76 4800 32 32 32 38 76 4800 32 76 76 76 76 4800 32 32 76 76 76 4800 32 32 32 76 76 4800 32 32 32 32 76 4800 32 38 38 38 38 4800 32 32 38 38 38 4800 32 32 32 38 38 4800 32 32 32 32 38 4800 50 76 76 76 76 4800 50 50 76 76 76 4800 50 50 50 76 76 4800 50 50 50 50 76 4800 50 100 100 100 100 4800 50 50 100 100 100 4800 50 50 50 100 100 4800 50 50 50 50 100 4800 64 76 76 76 76 4800 64 64 76 76 76 4800 64 64 64 76 76 4800 64 64 64 64 76 4800 64 100 100 100 100 4800 64 64 100 100 100 4800 64 64 64 100 100 4800 64 64 64 64 100

The number of subchannels increases according to the number of retransmissions, which means that the modulation order is lowered. When a specific N _EP is applied, the UE can know the modulation order through the number of subchannels allocated in the downlink based on Table 1, and thus can know the used modulation scheme. If the number of subchannels allocated according to the number of retransmissions is determined to be a predetermined rule, the UE can know the modulation order applied in the retransmission without additional signaling from the number of subchannels allocated in the initial transmission.

Table 3 shows an example in which the number of subchannels in the initial transmission and retransmission for each N _EP in the downlink is fixed to a certain rule.

N _EP 1st trans. 2nd trans. 3rd trans. 4th trans. 5th trans. sch sch sch sch sch 144 One 3 3 3 3 144 2 3 3 3 3 192 One 3 3 3 3 192 2 3 3 3 3 288 2 3 5 5 5 288 3 5 5 5 5 384 2 3 6 6 6 384 3 6 6 6 6 384 4 6 6 6 6 480 2 8 8 8 8 480 3 4 8 8 8 480 4 8 8 8 8 480 5 10 10 10 10 480 6 8 8 8 8 960 5 15 15 15 15 960 6 8 15 15 15 960 8 15 15 15 15 1920 10 15 30 30 30 1920 13 15 30 30 30 1920 15 30 30 30 30 1920 20 30 30 30 30 1920 26 30 30 30 30 2880 15 22 44 44 44 2880 20 22 44 44 44 2880 30 44 44 44 44 3840 20 30 60 60 60 3840 26 30 60 60 60 4800 26 38 76 76 76 4800 32 38 76 76 76 4800 50 76 76 76 76 4800 64 76 76 76 76

The UE can know the modulation order applied to the initial data from the number of subchannels allocated in the first transmission. The UE can know the modulation order applied to the retransmission data in the retransmission from the number of subchannels allocated in the initial transmission. For example, if the number of subchannels allocated in the initial transmission in N _EP 144 is 1, then the modulation order applied to the initial data is 6 from Table 1. Also, the UE can know in advance that the number of subchannels allocated in retransmission (2nd through 5th trans.) Is 3, and can know in advance that the applied modulation order is 2. If the base station does not allocate the subchannel according to the predetermined rule, the terminal can find the applied modulation order with reference to Table 1. [ The change in modulation order according to the number of retransmissions can be determined from the number of allocated sub-channels, i.e., radio resource scheduling information.

Uplink data transmission will now be described. Assume that the modulation schemes supported in the non-adaptive HARQ scheme of the IR mode are Quadrature-Phase Shift Keying (QPSK) and Quadrature Amplitude Modulation (QAM).

Table 4 shows the number of subchannels (N _SCH ), MPR, modulation order (MOD) and coding rate according to N _EP in the uplink. 'Sch' denotes the number of subchannels, and 'Rate' denotes the code rate.

In the same N _EP , the modulation order (MOD) may be applied differently depending on the number of subchannels (Sch). The number of subchannels allocated in the retransmission may be different and the modulation order to be applied may be gradually decreased according to the number of retransmissions.

Table 5 shows an example of the number of subchannels in the initial transmission and retransmission for each N _EP in the uplink. Assuming that the maximum number of retransmissions is 4 (2nd to 5th trans.), It is shown that the modulation order can be changed in retransmission based on Table 4. [

N _EP 1st trans. 2nd trans. 3rd trans. 4th trans. 5th trans. sch sch sch sch sch 96 One 2 2 2 2 96 One One 2 2 2 96 One One One 2 2 96 One One One One 2 144 2 3 3 3 3 144 2 2 3 3 3 144 2 2 2 3 3 144 2 2 2 2 3 192 2 3 3 3 3 192 2 2 3 3 3 192 2 2 2 3 3 192 2 2 2 2 3 192 2 4 4 4 4 192 2 2 4 4 4 192 2 2 2 4 4 192 2 2 2 2 4 192 2 4 3 3 3 192 2 2 4 3 3 192 2 2 4 4 3 192 2 2 2 4 3 192 2 4 4 3 3 192 2 4 4 4 4 288 3 5 5 5 5 288 3 3 5 5 5 288 3 3 3 5 5 288 3 3 3 3 5 288 3 6 6 6 6 288 3 3 6 6 6 288 3 3 3 6 6 288 3 3 3 3 6 288 3 6 5 5 5 288 3 3 6 5 5 288 3 3 6 6 5 288 3 3 3 6 5 288 3 6 6 5 5 288 3 6 6 6 5 288 4 5 5 5 5 288 4 4 5 5 5 288 4 4 4 5 5 288 4 4 4 4 5 288 4 6 6 6 6 288 4 4 6 6 6 288 4 4 4 6 6 288 4 4 4 4 6 288 4 6 5 5 5 288 4 4 6 5 5 288 4 4 6 6 5 288 4 4 4 6 5 288 4 6 6 5 5 288 4 6 6 6 5 384 3 6 6 6 6 384 3 3 6 6 6 384 3 3 3 6 6 384 3 3 3 3 6 384 4 6 6 6 6 384 4 4 6 6 6 384 4 4 4 6 6 384 4 4 4 4 6 384 4 8 8 8 8 384 4 4 8 8 8 384 4 4 4 8 8 384 4 4 4 4 8 384 4 8 6 6 6 384 4 4 8 6 6 384 4 4 8 8 6 384 4 4 4 8 6 384 4 8 8 6 6 384 4 8 8 8 6 384 5 6 6 6 6 384 5 5 6 6 6 384 5 5 5 6 6 384 5 5 5 5 6 384 5 8 8 8 8 384 5 5 8 8 8 384 5 5 5 8 8 384 5 5 5 5 8 384 5 8 6 6 6 384 5 5 8 6 6 384 5 5 8 8 6 384 5 5 5 8 6 384 5 8 8 6 6 384 5 8 8 8 6 480 4 8 8 8 8 480 4 4 8 8 8 480 4 4 4 8 8 480 4 4 4 4 8 480 5 8 8 8 8 480 5 5 8 8 8 480 5 5 5 8 8 480 5 5 5 5 8 480 5 10 10 10 10 480 5 5 10 10 10 480 5 5 5 10 10 480 5 5 5 5 10 480 5 10 8 8 8 480 5 5 10 8 8 480 5 5 10 10 8 480 5 5 5 10 8 480 5 10 10 8 8 480 5 10 10 10 8 480 6 8 8 8 8 480 6 6 8 8 8 480 6 6 6 8 8 480 6 6 6 6 8 480 6 10 10 10 10 480 6 6 10 10 10 480 6 6 6 10 10 480 6 6 6 6 10 480 6 15 15 15 15 480 6 6 15 15 15 480 6 6 6 15 15 480 6 6 6 6 15 480 6 15 10 10 10 480 6 6 15 10 10 480 6 6 15 15 10 480 6 6 6 15 10 480 6 15 15 10 10 480 6 15 15 15 10 480 6 10 8 8 8 480 6 6 10 8 8 480 6 6 10 10 8 480 6 6 6 10 8 480 6 10 10 8 8 480 6 10 10 10 8 480 6 15 8 8 8 480 6 6 15 8 8 480 6 6 15 15 8 480 6 6 6 15 8 480 6 15 15 8 8 480 6 15 15 15 8 480 6 15 10 8 8 480 6 15 10 10 8 480 6 15 15 10 8 960 8 15 15 15 15 960 8 8 15 15 15 960 8 8 8 15 15 960 8 8 8 8 15 960 10 15 15 15 15 960 10 10 15 15 15 960 10 10 10 15 15 960 10 10 10 10 15 960 10 20 20 20 20 960 10 10 20 20 20 960 10 10 10 20 20 960 10 10 10 10 20 960 10 20 15 15 15 960 10 10 20 15 15 960 10 10 20 20 15 960 10 10 10 20 15 1920 15 30 30 30 30 1920 15 15 30 30 30 1920 15 15 15 30 30 1920 15 15 15 15 30 1920 20 30 30 30 30 1920 20 20 30 30 30 1920 20 20 20 30 30 1920 20 20 20 20 30 1920 20 40 40 40 40 1920 20 20 40 40 40 1920 20 20 20 40 40 1920 20 20 20 20 40 1920 20 40 30 30 30 1920 20 20 40 30 30 1920 20 20 40 40 30 1920 20 20 20 40 30 1920 20 40 40 30 30 1920 20 40 40 40 30 2880 24 45 45 45 45 2880 24 24 45 45 45 2880 24 24 24 45 45 2880 24 24 24 24 45 2880 30 45 45 45 45 2880 30 30 45 45 45 2880 30 30 30 45 45 2880 30 30 30 30 45 2880 30 60 60 60 60 2880 30 30 60 60 60 2880 30 30 30 60 60 2880 30 30 30 30 60 2880 30 60 45 45 45 2880 30 30 60 45 45 2880 30 30 60 60 45 2880 30 30 30 60 45 2880 30 60 60 45 45 2880 30 60 60 60 45 2880 40 45 45 45 45 2880 40 40 45 45 45 2880 40 40 40 45 45 2880 40 40 40 40 45 2880 40 60 60 60 60 2880 40 40 60 60 60 2880 40 40 40 60 60 2880 40 40 40 40 60 2880 40 60 45 45 45 2880 40 40 60 45 45 2880 40 40 60 60 45 2880 40 40 40 60 45 2880 40 60 60 45 45 2880 40 60 60 60 45 3840 30 60 60 60 60 3840 30 30 60 60 60 3840 30 30 30 60 60 3840 30 30 30 30 60 3840 40 60 60 60 60 3840 40 40 60 60 60 3840 40 40 40 60 60 3840 40 40 40 40 60 3840 40 80 80 80 80 3840 40 40 80 80 80 3840 40 40 40 80 80 3840 40 40 40 40 80 3840 40 80 60 60 60 3840 40 40 80 60 60 3840 40 40 80 80 60 3840 40 40 40 80 60 4800 38 76 76 76 76 4800 38 38 76 76 76 4800 38 38 38 76 76 4800 38 38 38 38 76 4800 50 76 76 76 76 4800 50 50 76 76 76 4800 50 50 50 76 76 4800 50 50 50 50 76 4800 50 100 100 100 100 4800 50 50 100 100 100 4800 50 50 50 100 100 4800 50 50 50 50 100 4800 50 100 76 76 76 4800 50 50 100 76 76 4800 50 50 100 100 76 4800 50 50 50 100 76

The number of subchannels increases according to the number of retransmissions, which means that the modulation order is lowered. If the number of subchannels allocated according to the number of retransmissions is set to a predetermined rule, the base station does not need to inform the terminal about the modulation order to be applied in retransmission.

Table 6 shows an example in which the number of subchannels in the initial transmission and retransmission for each N _EP in the uplink is fixed to a certain rule.

N _EP 1st trans. 2nd trans. 3rd trans. 4th trans. 5th trans. sch sch sch sch sch 96 One 2 2 2 2 144 2 3 3 3 3 192 2 3 3 3 3 288 3 5 5 5 5 288 4 5 5 5 5 384 3 6 6 6 6 384 4 6 6 6 6 384 5 6 6 6 6 480 4 8 8 8 8 480 5 8 8 8 8 480 6 8 8 8 8 960 8 15 15 15 15 960 10 15 15 15 15 1920 15 30 30 30 30 1920 20 30 30 30 30 2880 24 45 45 45 45 2880 30 45 45 45 45 2880 40 45 45 45 45 3840 30 60 60 60 60 3840 40 60 60 60 60 4800 38 76 76 76 76 4800 50 76 76 76 76

If the number of subchannels in the initial transmission and retransmission in the uplink is fixed to a predetermined rule, the base station can notify the modulation order to be applied to the initial data from the number of subchannels allocated in the first transmission. The UE can know in advance the modulation order to be applied to the retransmission data in the retransmission from the number of subchannels allocated in the initial transmission. If the base station does not allocate the subchannel according to the predetermined rule, the terminal can transmit the data by determining the modulation order with reference to Table 4. The change in modulation order according to the number of retransmissions can be determined from the number of allocated sub-channels, i.e., radio resource scheduling information.

As described above, in the non-adaptive HARQ scheme of the proposed IR mode, efficiency of the retransmission data can be improved by changing the modulation order of the retransmission data based on the modulation order applied to the initial data. Since the modulation order and the number of allocated subchannels are determined in advance according to the number of retransmissions, the size of the retransmission data can be known in advance. Therefore, since the continuous retransmission data can be transmitted to the previously transmitted data, the coding gain of the IR mode can be maximized.

In the above description, it is assumed that the modulation schemes used in the downlink are QPSK, 16 QAM, and 64 QAM, and the modulation scheme used in the uplink is QPSK and 16 QAM, but this is not a limitation. Various modulation techniques such as BPSK (Binary Phase Shift Keying) and 8 PSK can be applied to the downlink and uplink modulation schemes. And the maximum number of retransmissions is 4, the maximum number of retransmissions may be variously determined according to the system, and Tables 2 and 3 and Tables 5 and 6 may be changed and used in a self-evident manner.

All of the functions described above may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), etc. according to software or program code or the like coded to perform the function. The design, development and implementation of the above code will be apparent to those skilled in the art based on the description of the present invention.

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. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

1 is a block diagram illustrating a wireless communication system.

2 shows an example of a frame structure.

3 is an exemplary diagram illustrating a resource allocation structure for HARQ.

4 is a diagram illustrating an example of processing of an information block for performing HARQ.

5 shows data retransmission in the stop and wait (SAW) scheme.

6 shows data retransmission of the N-channel stop and wait (SAW) scheme.

7 shows data retransmission of a multi-stop and wait (SAW) scheme.

FIG. 8 shows an example in which non-adaptive HARQ in the IR mode is performed.

FIG. 9 shows an example in which non-adaptive HARQ of the IR mode is performed according to an embodiment of the present invention.

Claims (5)

In a data transmission method using HARQ, Transmitting a first bit stream that is part of a codeword; And And transmits a second bit sequence that continues to the first bit string and is applied with a modulation order smaller than a modulation order applied to the first bit string according to the number of retransmissions in response to a retransmission request for the codeword, In the case of downlink transmission, data is transmitted from a base station to a mobile station, And transmitting data from the UE to the Node B in case of UL transmission. 2. The method of claim 1, wherein the modulation order is determined by the number of subchannels allocated according to the number of retransmissions. The method of claim 1, wherein the codeword is composed of systematic bits and at least one parity bits by applying a turbo code. 4. The method of claim 3, wherein when the size of the structured bits is N _EP and the number of subchannels is N _SCH , a modulation order product code rate (MPR)

ego, Wherein the modulation order is determined according to the MPR. In a data transmission method using HARQ, Transmitting initial data; And And transmitting retransmission data in response to a retransmission request for the initial data, wherein the retransmission data includes a number of subchannels greater than the number of subchannels allocated to the initial data, and the number of allocated subchannels The modulation scheme applied to the retransmission data is determined according to the modulation scheme, In the case of downlink transmission, data is transmitted from a base station to a mobile station, And transmitting data from the UE to the Node B in case of UL transmission.

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