WO2011008048A2 - Method and apparatus for performing harq in multiple carrier system - Google Patents

Abstract

A method and an apparatus for performing HARQ in a multiple carrier system are provided. A terminal generates an ACK/NACK (Acknowledgement/Non-acknowledgement) signal for a codeword that is transmitted via each component carrier out of plural component carriers (CCs), and transmits the ACK/NACK signal. Each ACK/NACK signal indicates one of an ACK state which indicates that the codeword is decoded, a NACK state which indicates that the codeword is not decoded and a discontinuous transmission (DTX) state which indicates that transmission of each component carrier is not acknowledged.

Description

Method and apparatus for performing HARQ in multi-carrier system

The present invention relates to wireless communication, and more particularly, to a method and apparatus for performing a hybrid automatic repeat request (HARQ) in a multi-carrier system.

In the case of broadband wireless communication systems, effective transmission and reception techniques and utilization methods have been proposed to maximize the efficiency of limited radio resources. One of the systems considered in the next generation wireless communication system is an Orthogonal Frequency Division Multiplexing (OFDM) system that can attenuate inter-symbol interference (ISI) effects with low complexity. OFDM converts serially input data symbols into N parallel data symbols and carries them on N subcarriers, respectively. The subcarriers maintain orthogonality in the frequency dimension. Each orthogonal channel experiences mutually independent frequency selective fading, thereby reducing complexity at the receiving end and lengthening the interval of transmitted symbols, thereby minimizing inter-symbol interference.

Orthogonal Frequency Division Multiple Access (OFDMA) refers to a multiple access method for realizing multiple access by independently providing each user with a portion of available subcarriers in a system using OFDM as a modulation method. OFDMA provides each user with a frequency resource called a subcarrier, and each frequency resource is provided to a plurality of users independently so that they do not overlap each other. Eventually, frequency resources are allocated mutually exclusively for each user. In an OFDMA system, frequency diversity scheduling can be obtained through frequency selective scheduling, and subcarriers can be allocated in various forms according to permutation schemes for subcarriers. In addition, the spatial multiplexing technique using multiple antennas can increase the efficiency of the spatial domain.

Multiple-Input Multiple-Output (MIMO) technology uses multiple transmit and multiple receive antennas to improve data transmission and reception efficiency. Techniques for implementing diversity in MIMO systems include Space Frequency Block Code (SFBC), Space Time Block Code (STBC), Cyclic Delay Diversity (CDD), frequency switched transmit diversity (FSTD), time switched transmit diversity (TSTD), Precoding Vector Switching (PVS) and Spatial Multiplexing (SM). The MIMO channel matrix according to the number of receive antennas and the number of transmit antennas may be decomposed into a plurality of independent channels. Each independent channel is called a layer or stream. The number of layers is called rank.

In the LTE-A system, a bandwidth extension technique in which a terminal may use a plurality of component carriers (CC) may be applied. However, as a plurality of component carriers are configured, the terminal needs to transmit a plurality of feedback information. For example, when there are N component carriers used for downlink transmission, the terminal should transmit ACK / NACK (Acknowledgment / Non-acknowledgement) information corresponding to each downlink component carrier. Accordingly, there is a need for an uplink control channel that can accommodate both the ACK / NACK information. However, in the control channel structure of the LTE Rel-8 system, it is difficult to transmit all ACK / NACK information for a plurality of component carriers using only one control channel. In addition, when ACK / NACK information is transmitted at a time by using a plurality of control channels, a single carrier property of a single carrier frequency division multiple access (SC-FDMA) is not only destroyed, but also a PAPR of a transmitted signal. Peak-to-Average Power Ratio (CPM) and Cubic Metric (CM) characteristics deteriorate, thereby reducing uplink coverage of the terminal. On the other hand, if a control channel of a new structure capable of transmitting more control information is introduced in the LTE-A system, a decrease in cell coverage is inevitable due to an increase in control information.

Therefore, a method of reducing the amount of feedback information transmitted is required. Accordingly, a method of reducing the number of information states related to uplink feedback information such as ACK / NACK may be proposed.

An object of the present invention is to provide a method and apparatus for performing a hybrid automatic repeat request (HARQ) in a multi-carrier system.

In one aspect, a method and apparatus for performing HARQ in a multi-carrier system is provided. The method generates an ACK / NACK (Acknowledgement / Non-acknowledgement) signal for a codeword transmitted through each component carrier among a plurality of component carriers (CCs), and each of the ACK / NACK signals. Wherein each ACK / NACK signal includes an ACK state indicating that the codeword has been decoded, a NACK state indicating that the codeword has not been decoded, and a discontinuous transmission indicating that transmission of each component carrier has not been recognized. ) To indicate any one of the states. The number of codewords transmitted through each component carrier is one, respectively, and the ACK / NACK signal for one codeword may indicate any one of ACK, NACK, and DTX states. The length of the ACK / NACK signal for the one codeword may be 2 bits. Alternatively, the number of codewords transmitted through each component carrier is two, and ACK / NACK signals for the two codewords are respectively ACK / ACK, ACK / NACK, NACK / NACK, and NACK / NACK or DTX states. Either one can be indicated. The length of the ACK / NACK signal for the two codewords may be 2 bits. Each ACK / NACK signal may include DTX information for at least one component carrier group including a plurality of component carriers. A plurality of component carriers included in the at least one component carrier group may be predefined or signaled. The DTX information for the at least one component carrier group may be generated by calculating DTX information of each of the plurality of component carriers by a predetermined operation method, and the predetermined operation method may be a logical AND operation or a logical operation. It may be one of the OR operations. Each of the ACK / NACK signals may be generated by combining a plurality of the basic units based on a basic unit determined according to a predetermined number of component carriers. The plurality of basic units may be separately coded. The number of the predetermined configuration carrier may be any one of one to three. Among the ACK / NACK signals, an ACK / NACK signal for a codeword transmitted through a primary component carrier (PCC) may be generated based on an independent basic unit.

In another aspect, an apparatus for performing HARQ in a wireless communication system is provided. The apparatus is connected to an ACK / NACK signal generator for generating an ACK / NACK signal for a codeword transmitted through each component carrier among a plurality of component carriers, and the ACK / NACK signal generator, An RF unit (RF unit) for transmitting a NACK signal, each ACK / NACK signal is an ACK state indicating that the codeword is decoded, the NACK state indicating that the codeword was not decoded and the transmission of each component carrier is recognized It is characterized by indicating any one of the DTX state indicating that the failure.

By supporting the separate transmission of DTX (Discontinuous Transmission) status information, it is possible to efficiently transmit the DTX signal using a constant size bit regardless of the operation mode. In addition, by using the additional DTX signal, it is possible to transmit the DTX state information for the primary component carrier (PCC) and non-PC (non-PC).

1 is a wireless communication system.

2 shows a structure of a radio frame in 3GPP LTE.

3 shows an example of a resource grid for one downlink slot.

4 shows a structure of a downlink subframe.

5 shows a structure of an uplink subframe.

6 shows an uplink HARQ.

7 is an embodiment of a proposed method of performing HARQ.

8 to 15 are examples of ACK / NACK configuration according to the proposed method of performing HARQ.

16 is a block diagram of a DFT-s OFDM system.

17 is a block diagram of a base station and a terminal in which an embodiment of the present invention is implemented.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various wireless communication systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA), or the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of Evolved UMTS (E-UMTS) using Evolved-UMTS Terrestrial Radio Access (E-UTRA), which employs OFDMA in downlink and SC in uplink -FDMA is adopted. LTE-A (Advanced) is the evolution of 3GPP LTE.

For clarity, the following description focuses on LTE-A, but the technical spirit of the present invention is not limited thereto.

1 is a wireless communication system.

The wireless communication system 10 includes at least one base station (BS) 11. Each base station 11 provides a communication service for a particular geographic area (generally called a cell) 15a, 15b, 15c. The cell can in turn be divided into a number of regions (called sectors). The UE 12 may be fixed or mobile, and may include a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a PDA. (Personal Digital Assistant), a wireless modem (wireless modem), a handheld device (handheld device) may be called other terms. The base station 11 generally refers to a fixed station communicating with the terminal 12, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like. have.

A terminal typically belongs to one cell, and a cell to which the terminal belongs is called a serving cell. A base station that provides a communication service for a serving cell is called a serving BS. Since the wireless communication system is a cellular system, there are other cells adjacent to the serving cell. Another cell adjacent to the serving cell is called a neighbor cell. A base station that provides communication service for a neighbor cell is called a neighbor BS. The serving cell and the neighbor cell are relatively determined based on the terminal.

This technique can be used for downlink or uplink. In general, downlink means communication from the base station 11 to the terminal 12, and uplink means communication from the terminal 12 to the base station 11. In downlink, the transmitter may be part of the base station 11 and the receiver may be part of the terminal 12. In uplink, the transmitter may be part of the terminal 12 and the receiver may be part of the base station 11.

2 shows a structure of a radio frame in 3GPP LTE. This is described in Section 5 of 3rd Generation Partnership Project (3GPP) TS 36.211 V8.2.0 (2008-03) "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation (Release 8)". Reference may be made.

Referring to FIG. 2, a radio frame consists of 10 subframes, and one subframe consists of two slots. Slots in a radio frame are numbered with slots # 0 through # 19. The time taken for one subframe to be transmitted is called a Transmission Time Interval (TTI). TTI may be referred to as a scheduling unit for data transmission. For example, one radio frame may have a length of 10 ms, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

One slot includes a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in the time domain and a plurality of subcarriers in the frequency domain. The OFDM symbol is used to represent one symbol period since 3GPP LTE uses OFDMA in downlink, and may be called a different name according to a multiple access scheme. For example, when SC-FDMA is used as an uplink multiple access scheme, it may be referred to as an SC-FDMA symbol. A resource block (RB) includes a plurality of consecutive subcarriers in one slot in resource allocation units. The structure of the radio frame is merely an example. Accordingly, the number of subframes included in the radio frame, the number of slots included in the subframe, or the number of OFDM symbols included in the slot may be variously changed.

3GPP LTE defines that one slot includes 7 OFDM symbols in a normal cyclic prefix (CP), and one slot includes 6 OFDM symbols in an extended CP. .

3 shows an example of a resource grid for one downlink slot.

The downlink slot includes a plurality of OFDM symbols in the time domain and N _RB resource blocks in the frequency domain. The number N _RB of resource blocks included in the downlink slot depends on the downlink transmission bandwidth set in the cell. For example, in the LTE system, N _RB may be any one of 60 to 110. One resource block includes a plurality of subcarriers in the frequency domain. The structure of the uplink slot may also be the same as that of the downlink slot.

Each element on the resource grid is called a resource element. Resource elements on the resource grid may be identified by an index pair (k, l) in the slot. Where k (k = 0, ..., N _RB × 12-1) is the subcarrier index in the frequency domain, and l (l = 0, ..., 6) is the OFDM symbol index in the time domain.

Here, an exemplary resource block includes 7 × 12 resource elements including 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain, but the number of OFDM symbols and the number of subcarriers in the resource block is equal to this. It is not limited. The number of OFDM symbols and the number of subcarriers can be variously changed according to the length of the CP, frequency spacing, and the like. For example, the number of OFDM symbols is 7 for a normal CP and the number of OFDM symbols is 6 for an extended CP. The number of subcarriers in one OFDM symbol may be selected and used among 128, 256, 512, 1024, 1536 and 2048.

4 shows a structure of a downlink subframe.

The downlink subframe includes two slots in the time domain, and each slot includes seven OFDM symbols in the normal CP. The leading up to 3 OFDM symbols (up to 4 OFDM symbols for 1.4Mhz bandwidth) of the first slot in the subframe are the control regions to which control channels are allocated, and the remaining OFDM symbols are the PDSCH (Physical Downlink Shared Channel). Becomes the data area to be allocated.

PDCCH is a resource allocation and transmission format of downlink-shared channel (DL-SCH), resource allocation information of uplink shared channel (UL-SCH), paging information on PCH, system information on DL-SCH, random access transmitted on PDSCH Resource allocation of upper layer control messages such as responses, sets of transmit power control commands for individual UEs in any UE group, activation of Voice over Internet Protocol (VoIP), and the like. A plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH is transmitted on an aggregation of one or several consecutive CCEs. CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

The base station determines the PDCCH format according to the DCI to be sent to the terminal, and attaches a CRC (Cyclic Redundancy Check) to the control information. In the CRC, a unique identifier (RNTI: Radio Network Temporary Identifier) is masked according to an owner or a purpose of the PDCCH. If the PDCCH is for a specific terminal, a unique identifier of the terminal, for example, a C-RNTI (Cell-RNTI) may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier, for example, P-RNTI (P-RNTI), may be masked to the CRC. If the PDCCH is for a System Information Block (SIB), the system information identifier and the System Information-RNTI (SI-RNTI) may be masked to the CRC. A random access-RNTI (RA-RNTI) may be masked to the CRC to indicate a random access response that is a response to the transmission of the random access preamble of the UE.

5 shows a structure of an uplink subframe.

The uplink subframe may be divided into a control region and a data region in the frequency domain. The control region is allocated a Physical Uplink Control Channel (PUCCH) for transmitting uplink control information. The data region is allocated a physical uplink shared channel (PUSCH) for transmitting data. In order to maintain the characteristics of a single carrier, the UE does not simultaneously transmit the PUCCH and the PUSCH.

PUCCH for one UE is allocated to an RB pair in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers in each of the first slot and the second slot. The frequency occupied by the resource block belonging to the resource block pair allocated to the PUCCH is changed based on a slot boundary. This is called that the RB pair allocated to the PUCCH is frequency-hopped at the slot boundary. The terminal may obtain a frequency diversity gain by transmitting uplink control information through different subcarriers over time. m is a location index indicating a logical frequency domain location of a resource block pair allocated to a PUCCH in a subframe.

The uplink control information transmitted on the PUCCH includes a hybrid automatic repeat request (HARQ) acknowledgment (ACK) / non-acknowledgement (NACK), a channel quality indicator (CQI) indicating a downlink channel state, and an SR that is an uplink radio resource allocation request. (Scheduling Request).

PUSCH is mapped to an uplink shared channel (UL-SCH) which is a transport channel. The uplink data transmitted on the PUSCH may be a transport block which is a data block for the UL-SCH transmitted during the TTI. The transport block may be user information. Alternatively, the uplink data may be multiplexed data. The multiplexed data may be a multiplexed transport block and control information for the UL-SCH. For example, control information multiplexed with data may include CQI, PMI (Precoding Matrix Indicator), HARQ, RI (Rank Indicator), and the like. Alternatively, the uplink data may consist of control information only.

 3GPP LTE-A system may support a carrier aggregation (carrier aggregation) system. The carrier aggregation system may refer to 3GPP TR 36.814 V9.0.0 (2010-3).

The carrier aggregation system refers to a system in which one or more component carriers (CCs) having a smaller bandwidth than a target broadband when a wireless communication system tries to support a broadband constitute a broadband. The carrier aggregation system may be called another name such as a bandwidth aggregation system.

The carrier aggregation system may be classified into a contiguous carrier aggregation system in which each carrier is continuous and a non-contiguous carrier aggregation system in which each carrier is separated from each other. In the continuous carrier aggregation system, a guard band may exist between each carrier. In the continuous carrier aggregation system, the spacing between the center frequencies of each carrier may be a multiple of 300 kHz. The size of each carrier may be limited to a maximum of 110 resource blocks in the frequency domain. When collecting one or more carriers, a target carrier may use the bandwidth used by the existing system as it is for backward compatibility with the existing system. For example, the 3GPP LTE system supports bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz, and the 3GPP LTE-A system may configure a bandwidth of 20 MHz or more using only the bandwidth of the 3GPP LTE system. A plurality of component carriers may be used to support a bandwidth of up to 100 MHz, and the maximum number of component carriers that can be used may be five. Alternatively, broadband can be configured by defining new bandwidth without using the bandwidth of the existing system.

In the carrier aggregation system, the terminal may simultaneously transmit or receive one or a plurality of carriers according to capacity. The LTE-A terminal may simultaneously transmit or receive a plurality of carriers. The LTE Rel-8 terminal may transmit or receive only one carrier when each carrier constituting the carrier aggregation system is compatible with the LTE Rel-8 system. Therefore, when at least the same number of carriers used in uplink and downlink, all the configuration carriers need to be configured to be compatible with the LTE Rel-8 system. In addition, the terminal may configure different bandwidths in uplink and downlink using different numbers of component carriers originating from the same base station. In a typical TDD system, the number of component carriers and the size of bandwidth are the same in uplink and downlink. In addition, carriers originating from the same base station need not provide the same coverage.

Since the existing LTE Rel-8 system is designed based on a single layer or a single carrier, a method for effectively supporting multiple carriers and / or multiple transport blocks and / or multiple codewords is needed.

The wireless communication system may support uplink or downlink Hybrid Automatic Repeat Request (HARQ).

6 shows an uplink HARQ.

The base station receiving the uplink data 50 on the PUSCH from the terminal transmits an ACK / NACK signal 51 on the PHICH after a predetermined subframe has elapsed. The ACK / NACK signal 51 becomes an ACK signal when the uplink data 50 is successfully decoded, and becomes an NACK signal when the decoding of the uplink data 50 fails. When the NACK signal is received, the UE may transmit retransmission data 60 for the uplink data 50 until ACK information is received or up to a maximum number of retransmissions. The base station may transmit the ACK / NACK signal 61 for the retransmission data 60 on the PHICH.

HARQ of FIG. 6 assumes a single carrier system, and in a multi-carrier system, a Discontinuous Transmission (DTX) state may occur in addition to ACK / NACK. For example, when N component carriers are configured and data is scheduled only for N 'component carriers smaller than N as a base station, the remaining N-N' component carriers may be placed in a DTX state. Alternatively, even when the terminal does not detect the downlink transmission in a specific component carrier to which the downlink transmission is allocated, the corresponding component carrier may be placed in the DTX state. If the DTX state is not distinguished from the NACK, the criteria for the selection of the HARQ method for retransmission and the selection of the Modulation and Coding Scheme (MCS) cannot be determined, and thus the HARQ performance may be deteriorated. Therefore, in a multi-carrier system, it is preferable to transmit a DTX signal in addition to the ACK / NACK signal. In this case, the DTX signal may be explicitly defined separately from the NACK, or may be defined without being distinguished from the NACK. When the DTX signal is defined separately from the NACK, the ACK / NACK information on the component carrier is a non-binary ACK / NACK codebook. When the DTX signal is defined in combination with the NACK, the ACK / NACK information on the component carrier is binary. It may be represented by an ACK / NACK codebook. Codebook refers to source coding of a plurality of pieces of information. The codebook goes through channel coding such as Reed-Muller (RM) coding, and goes through a modulation scheme such as Quadrature Phase Shift Keying (QPSK) and an access scheme such as SC-FDMA. Is sent. The present invention relates to a construction technique or source coding technique of a codebook.

Accordingly, the present invention proposes an ACK / NACK signal and a DTX signal transmission method for effectively supporting a plurality of component carriers in a wireless communication system. However, the present invention may include not only a case of transmitting the ACK / NACK signal and the DTX signal together, but also a case of omitting the DTX signal or sharing the DTX signal with the NACK signal. When the DTX signal is shared with the NACK signal When the ACK / NACK signal and the DTX signal are represented at the bit level, it may be assumed that 1 indicates ACK, and 0 indicates NACK and DTX.

In addition, in the following description, for convenience of description, the present invention is described without description of a specific access method, but for various access methods such as OFDMA, Discrete Fourier Transform (DFT) -precoding OFDMA, clustered DFT-s OFDM, etc. It is possible to apply the present invention, and the various connection methods are not a limitation of the present invention. The present invention may be applied to a response to a PDCCH or a PDSCH, or may be applied to a response to a PUCCH or a PUSCH. The channel on which the ACK / NACK or DTX according to the present invention is transmitted may also be a PDCCH or a PUSCH, or may be transmitted through a PUCCH or a PUSCH.

In the following description, it is assumed that one codeword is transmitted or two codewords are transmitted at the same time and ACK / NACK signals for each codeword are transmitted.However, for convenience, the number of codewords and ACK / NACK that can be simultaneously transmitted are assumed. The transmission unit of the signal does not limit the present invention. That is, the ACK / NACK signal may be transmitted for each codeword, for each component carrier, or for each subframe. Alternatively, a plurality of ACK / NACK signals may be bundled or punctured in a spatial domain / frequency domain / time domain. Although the present invention assumes five configured CCs, the number of configuration CCs is not a limitation of the present invention. The present invention will be described assuming joint source coding of ACK / NACK information of a plurality of component CCs. In addition, for convenience, it is assumed that the feedback on the configuration CC is described, but the application of the present invention also applies to feedback on the active CC, the scheduled CC, and the detected CC in addition to the configuration CC. This is possible and is not a limitation of the present invention as the object of feedback.

7 is an embodiment of a proposed method of performing HARQ.

In step S100, the terminal generates an ACK / NACK signal for a code word transmitted through each component carrier of the plurality of component carriers. In step S110, the terminal transmits each of the ACK / NACK signal to the base station.

By using the proposed method of performing HARQ, a DTX signal may be combined with an ACK / NACK signal and transmitted.

8 is an example of ACK / NACK configuration according to a proposed method of performing HARQ.

When performing HARQ on two codewords, five states of ACK / ACK, ACK / NACK, NACK / ACK, NACK / NACK, or DTX, respectively, in response to the first codeword and in response to the second codeword Can be considered. Since DTX is a state indicating whether a downlink control channel is received, the DTX can be expressed in one state without distinguishing two codewords. As described above, three bits are required to perform HARQ in consideration of five states, and when a plurality of CCs exist, the required number of bits increases in proportion to the number of CCs. Therefore, in order to reduce signaling overhead or to reduce coding gain, NACK / NACK and DTX may be expressed without being distinguished. That is, when a control signal or data is not detected or a detection is incorrect in a specific CC, the terminal may transmit a representative value sharing the NACK / NACK and the DTX to the base station.

Referring to FIG. 8, a response to a codeword may be expressed as four states (A / A, A / N, N / A, N / N or DTX) instead of five states by the proposed method of performing HARQ. . By expressing the four states by 2 bits, signaling overhead can be reduced. Thereafter, the UE may perform HARQ using information of 2 bits in length for each CC.

9 is another example of ACK / NACK configuration according to the proposed method of performing HARQ.

When performing HARQ for one codeword, three states of ACK, NACK or DTX may be considered. That is, two bits are required to perform HARQ in consideration of three states, and when a plurality of CCs are present, the number of bits required increases in proportion to the number of CCs. However, since the number of states is smaller than in the case of supporting two code words, it is possible to express all three states using two bits of information. Referring to FIG. 9, a response to a codeword may be expressed in three states (A, N, and DTX) by the proposed method of performing HARQ. The UE may perform HARQ by using information of 2 bits in length for each CC. Alternatively, HARQ may be performed using 1 bit length information by expressing the NACK and DTX states as one value in the same manner as in FIG. 8.

When the two codewords are supported as shown in the embodiments of FIGS. 8 and 9, HARQ is performed in a total of four states without distinguishing between N / N and DTX, and N and DTX are supported when one codeword is supported. HARQ may be performed in total by three states. Accordingly, HARQ can be performed using the same structure regardless of the number of codewords. When the number of codewords is small, more information can be transmitted. That is, when performing a HARQ for each CC, if more than the number of states that can be represented by a fixed bit (2 bits in Figs. 1 and 2) is required, HARQ is performed without distinguishing or using DTX. If only, otherwise, HARQ may be performed by distinguishing DTX. Therefore, it is possible to efficiently transmit the DTX signal.

Alternatively, by using the proposed method of performing HARQ, a DTX signal indicating DTX information may be added to ACK / NACK information for each existing CC. However, adding a DTX signal increases signaling overhead, so it is necessary to minimize the number.

In order to classify the DTX state into as few bits as possible, the present invention proposes to transmit a DTX signal using a CC group including one or more CCs. Each CC group may include different numbers of CCs. That is, the terminal may be configured to transmit the DTX signal for one or more CC groups. The configuration of the CC group may be predefined or may be signaled. For example, the plurality of CCs may be divided into primary CCs (PCCs) and non-primary CCs. Alternatively, the plurality of CCs may be divided into scheduled CCs and non-scheduled CCs. The DTX information for each CC group may be configured by bundling DTX information of CCs in the CC group. By bundling DTX information of CCs in the CC group, the size of the DTX signal for the CC group can be reduced. For example, when the CC group is composed of three CCs, bundling may be performed by an AND operation on the three DTX information. When the DTX information for all three CCs is DTX / DTX / DTX, the DTX signal for the CC group may indicate the DTX state, and in other cases, the DTX signal may indicate the non-DTX state. Alternatively, bundling by OR operation may be performed on three pieces of DTX information. If at least one of the DTX information for the three CCs is DTX, the DTX signal for the CC group indicates the DTX state, and if the DTX information for all three CCs are all non-DTX state, the DTX signal indicates the non-DTX state. Can be directed. When configuring a CC group according to a predetermined rule, CCs having the same characteristics may be organized in the same CC group according to the characteristics of the CC. In addition, when the terminal measures and transmits the downlink CC, CC according to the transmission / measurement / reporting mode can be grouped. It is also possible to consider all CCs as independent groups.

The present invention proposes a method of transmitting a DTX signal by dividing a plurality of CCs into PCCs and non-major CCs. Here, the PCC may mean a UE-specific CC in downlink or uplink. The downlink PCC may refer to a CC which always operates without changing activation / deactivation among configuration CCs in a specific terminal, and the uplink PCC may refer to a terminal specific CC configured for transmitting ACK / NACK information from a specific terminal. . In general, the PCC may be a CC in which important information is transmitted and / or received from other CCs from the viewpoint of a specific terminal. Alternatively, the downlink PCC may be a downlink CC initially accessed by the UE for initial network access or a CC determined through signaling (cell-specific or UE-specific RRC signaling). The uplink PCC is a CC that is UE-specifically determined through signaling (cell-specific or UE-specific RRC signaling) or a CC that is determined by a DL-UL relationship in a System Information Block 2 (SIB2) transmitted by the downlink PCC. Can be. Alternatively, the uplink PCC may be a specific CC on which PUCCH or Uplink Control Information (UCI) is transmitted. The downlink PCC or the uplink PCC may be configured with at least one, and the CC other than the PCC may be referred to as a downlink secondary CC (SCC) or an uplink SCC.

In the following description, the present invention will be described without distinguishing the downlink or the uplink, but the present invention may be applied to the downlink PCC or the uplink PCC by a predetermined rule. In addition, it is assumed that one downlink PCC and an uplink PCC exist for convenience, and when there are a plurality of PCCs, the present invention may be applied by bundling the plurality of PCCs or by setting priorities within the plurality of PCCs. .

10 is another example of ACK / NACK configuration according to the proposed method of performing HARQ.

Referring to FIG. 10, DTX information of a PCC may be transmitted by adding a 1-bit long DTX signal after an ACK / NACK signal according to each component carrier having a 1-bit, 2-bit, or 4-bit length. In FIG. 10, when the value of the DTX signal is '0b0', the PCC may be in a non-DTX state, and when it is '0b1', it may indicate that the PCC is in the DTX state. That is, the terminal may transmit a DTX signal for a relatively important PCC among the plurality of CCs to the base station. The location of the PCC among the plurality of CCs may be different for each terminal and may be predetermined or signaled by the base station.

Meanwhile, in FIG. 10, it is assumed that the DTX state is possible only when all the responses to the plurality of codewords of a specific PCC are NACK. That is, when a response of a plurality of codewords of a specific PCC includes one or more ACKs, the PCC is in a non-DTX state. Therefore, if the DTX signal is a NACK response to a plurality of codewords of the PCC all indicate a DTX state for the PCC, and if the response to the plurality of codewords of the PCC includes one or more ACK, other information is provided. Can be directed. Table 1 shows an example of 1-bit DTX signal configuration. In Table 1, when ACK / NACK information of a response to a codeword of a specific PCC is transmitted, it is assumed that each UE transmits NACK instead of a DTX signal.

By configuring the DTX signal as shown in Table 1, the terminal transmits the DTX state by using the DTX signal when the responses to the plurality of codewords of the PCC are all NACK or the PCC is in the DTX state, and the plurality of codewords of the PCC are transmitted. If the response includes more than one ACK, assuming that the PCC is in a non-DTX state, the DTX information for non-major CCs may be indicated using a DTX signal. Therefore, since the DTX state information for the PCC and the DTX state information for the non-PCC can be indicated through the same signal, a lot of information can be indicated using a small number of bits. In the above embodiment, a case in which all non-PCCs are in a non-DTX state or at least one non-PCC in a DTX state has been described through the DTX signal, but may be differently applied. For example, the DTX signal may be used to indicate whether all non-PCCs are in the DTX state or one or more non-PCCs are in the DTX state.

11 is another example of ACK / NACK configuration according to a proposed method of performing HARQ. Referring to FIG. 11, DTX information of a PCC may be transmitted by adding a 2-bit length DTX signal after an ACK / NACK signal according to each component carrier having a 1-bit, 2-bit, or 4-bit length. The 2-bit long DTX signal may be configured through various methods. Table 2 shows an example of a 2-bit DTX signal configuration. In Table 2, it is assumed that each UE transmits NACK instead of DTX signal when ACK / NACK information of a response to a codeword of a specific PCC is transmitted.

According to Table 2, when all the responses to the plurality of codewords of the PCC are NACK or the PCC is in the DTX state, the UE informs the DTX state of the PCC through one bit of the added DTX signal, and uses the remaining one bit. It can inform the status of non-PCC DTX. In the above embodiment, a case in which all non-PCCs are in a non-DTX state or at least one non-PCC in a DTX state has been described through the DTX signal, but may be differently applied. For example, the DTX signal may be used to indicate whether all non-PCCs are in the DTX state or one or more non-PCCs are in the DTX state.

When a response to a plurality of codewords of the PCC includes one or more ACKs, the PCC may inform the DTX information of a specific CC group in the non-PCC in addition to the DTX information for the non-PCC group on the assumption that the state is non-DTX. . For example, when there are five component CCs as shown in FIG. 11, except for one PCC, the remaining four CCs may be divided into groups by a predetermined rule. When dividing the remaining four CCs into two groups including two CCs in order except for the PCC, the DTX information for the CCs belonging to the first group can be informed through the DTX signal, and the base station receives '0b1'. Thus, it can be seen that the CC belonging to the first group is not in the DTX state, and the CC belonging to the second group is in the DTX state.

The proposed HARQ execution method can be further extended and applied. When all CCs in a specific CC or a specific CC group are not in the DTX state (or all are not NACK), the DTX signal may be used to indicate the DTX information for the next CC or the next CC group. In addition, the DTX information may be indicated for two or more CCs or two or more CC groups as well as the next CC or the next CC group. This can be applied regardless of the number of CCs or CC groups. Table 3 shows an example of a 2-bit DTX signal configuration. In Table 3, it is assumed that one PCC and two or more non-PCCs exist for convenience.

According to Table 3, when the response to the plurality of codewords of the PCC are all NACK or the PCC is in the DTX state, the UE informs the DTX state of the PCC through one bit of the added DTX signal, and uses the remaining one bit. It can inform the status of non-PCC DTX. In the above embodiment, a case in which all non-PCCs are in a non-DTX state or at least one non-PCC in a DTX state has been described through the DTX signal, but may be differently applied. For example, the DTX signal may be used to indicate whether all non-PCCs are in the DTX state or one or more non-PCCs are in the DTX state.

When a response to a plurality of codewords of the PCC includes one or more ACKs, the PCC may inform the DTX information of a specific CC group in the non-PCC in addition to the DTX information for the non-PCC group on the assumption that the state is non-DTX. . For example, when there are five component CCs as shown in FIG. 11, except for one PCC, the remaining four CCs may be divided into groups by a predetermined rule. In the case of dividing the remaining four CCs into two groups including two CCs in order except for the PCC, the DTX information for the CCs belonging to the first group may be indicated through '0b0' or '0b1'. If the CCs belonging to the first group include one or more DTX states, the information is transmitted. If all CCs belonging to the first group are not in the DTX state, the DTX information is transmitted for CCs belonging to the second group. do. If the base station receives '0b1' and the CCs belonging to the first group are not all NACK, '0b0' is interpreted as information about the second group, and since the '0b1' is transmitted, the CC belonging to the second group is also in the DTX state. I can see that it is not. In addition, when all CCs belonging to the first group of non-PCC are not NACK, a 2-bit DTX signal may indicate a DTX state for each CC of the second group. That is, when both the PCC and the response to the first non-PCC are not NACK, and the CCs of the second CC group are all NACKs, the DTX state may be indicated for each CC in the second group through the DTX signal. By using the above method, it is possible to know whether one CC or two or more CCs in the DTX state among all the CCs.

As another embodiment, when the ACK / NACK information for the PCC includes one or more ACKs, the DTX signal for the PCC may be used for other purposes. That is, if the PCC is not in the DTX state, all of the DTX signals may be used to indicate the DTX state for the non-PCC. That is, when 2 bits are used to transmit the DTX state, at least two CCs of the non-PCCCs may be independently informed of the DTX state. At this time, it can be defined as being in the DTX state only when the response to the CC is NACK / NACK. The order of mapping to NACK / NACK among the information indicating the DTX state and the ACK / NACK information for the non-PCC may be predetermined or determined by signaling.

When the number of DTX is larger than the length of the DTX signal, the DTX signal may indicate that the CC in actual DTX state among the CCs marked NACK / NACK in the non-PCC. For example, when scheduling the CCs in a certain order by performing scheduling, the terminal may transmit the number of CCs that have not received the scheduling information. In this case, the UE may count the number of CCs in the DTX state while transmitting upside down from the last CC in the scheduled order and transmit the same through the DTX signal. When counting only consecutive numbers when counting the number of CCs in the DTX state, the UE may efficiently transmit ACK / NACK information for unscheduled CCs. When counting the number of all non-contiguous CCs when counting the number of CCs in the DTX state, the base station may estimate the DTX state of a specific CC considering the unscheduled CCs and all CCs with NACKs.

The method of transmitting the number of DTX through the above-described DTX signal may be combined with the proposed method of performing HARQ or may be performed independently. For example, a new bit may be added to the DTX signal of FIG. 11 to transmit the number of DTXs.

In addition, the above-described method of performing HARQ may be applied differently according to the number of configuration CCs. For example, DTX information may be transmitted by varying the length of the DTX signal of FIGS. 10 and 11 and the method of analyzing the same according to the number of configuration CCs.

In the following description, a method of minimizing an ACK / NACK reception error when receiving an ACK / NACK signal is described.

As described above, in the multi-carrier system, ACK / NACK information for each CC may be expressed in three to five states, and ACK / NACK information for a plurality of CCs may be transmitted by being joint source coded. Can be. In this case, if an error occurs when the base station receives and detects ACK / NACK information for a plurality of CCs, an error may occur not only for the CC but also for other CCs by joint source coding. For example, one bit or four states (A / A, A / N, N / A, N / N) where the ACK / NACK signal for each CC represents two states (A, N) without consideration of the DTX state. In the case of 2 bits representing), one bit indicates specific information independently without affecting the other bit. However, if the ACK / NACK signal represents three or five states, the independence of each bit is not maintained. Therefore, when an error occurs for one bit of the ACK / NACK signal at the receiving end, an error for a plurality of bundled information may occur together with an error for the information indicated by the corresponding ACK / NACK signal. Such an error may become more severe when an ACK / NACK signal is generated in consideration of ACK / NACK information for a plurality of CCs simultaneously.

Therefore, in order to minimize the effect of error between a plurality of CCs, it is necessary to specify the maximum number of CCs supported by joint source coding, and to use separate source coding for each CC group to support more CCs. Can be suggested. In this case, the CC group may be divided into the maximum number of CCs that can be jointly source coded or divided into PCC and non-PCC. In the following description, combined source coding and separated source coding refer to source coding, not channel coding. Source coded information or bits by the application of the present invention may be channel coded by the RM code.

There are three states of ACK, NACK, and DTX as ACK / NACK information for each CC. When the number of CCs is 1, 2, 3, 4, or 5, the total number of states to be expressed is (3 ¹ -1), (3 ² -1), (3 ³ -1), (3 ⁴ -1), and (3 ⁵ -1). When all CCs are in the DTX state, it is assumed that there is no response signal thereto. At this time, in order to express the number of states of the ACK / NACK information ACK / NACK signal is

It may have a size of. That is, the ACK / NACK signal should have a size of 1, 3, 5, 7, 8 bits when the number of CCs is 1, 2, 3, 4, or 5, respectively, and accordingly, the ACK / NACK signal 0 may represent 0, 0, 6, 48, and 14 pieces of information more than the total number of states to be actually expressed. There are four states of ACK / ACK, ACK / NACK, NACK / ACK and NACK / NACK or DTX as ACK / NACK information for each CC, and the number of CCs is 1, 2, 3, 4 or When five, the total number of states to be expressed is (4 ¹ -1), (4 ² -1), (4 ³ -1), (4 ⁴ -1), and (4 ⁵ -1). When all CCs are in the DTX state, it is assumed that there is no response signal thereto. In order to express the number of states of ACK / NACK information, the size of the ACK / NACK signal is 2, 4, 6, 8, 10 bits when the number of CCs is 1, 2, 3, 4, or 5, respectively. Therefore, the ACK / NACK signal may represent one more information than the total number of states to be actually expressed. Similarly, there are five states of ACK / ACK, ACK / NACK, NACK / ACK, NACK / NACK, and DTX as ACK / NACK information for each CC, and the number of CCs is 1, 2, 3, and 4, respectively. Or five, the total number of states to be expressed is (5 ¹ -1), (5 ² -1), (5 ³ -1), (5 ⁴ -1), (5 ⁵ -1). When all CCs are in the DTX state, it is assumed that there is no response signal thereto. In order to express the number of states of ACK / NACK information, the size of the ACK / NACK signal is 2, 5, 7, 10, and 12 bits when the number of CCs is 1, 2, 3, 4, or 5, respectively. Therefore, the ACK / NACK signal may represent 0, 8, 4, 400, and 972 pieces of information more than the total number of states to be actually expressed. That is, the number of information that can be represented by the size of the ACK / NACK signal required when the ACK / NACK information for each CC is expressed in three or five states is more than necessary. In addition, errors for one CC may affect other CCs. Therefore, a method of designating a maximum number of CCs that can be supported and transmitting ACK / NACK information using a plurality of pieces of information for a larger number of CCs needs to be proposed.

12 is another example of ACK / NACK configuration according to a proposed method of performing HARQ.

The base unit configuring the ACK / NACK signal can be defined only for up to three CCs. If the system includes more CCs than this, the base units may be placed in succession. In order to support four CCs, a structure for three CCs and a structure for one CC may be sequentially arranged, and in order to support five Cs, a structure for three CCs and a structure for two CCs may be consecutive. Can be arranged. In order to support more than the number of CCs supported by the base unit, a method of arranging the base unit may be predefined or signaled. For example, when combining base units to support a specific CC, the base units may be arranged in order of a base unit supporting a large number of CCs from a base unit supporting a small number of CCs.

In FIG. 12, the maximum number of supported configuration CCs is set to three. That is, the maximum number of CCs that can be combined source coded is three, and thus the basic unit configuring the ACK / NACK signal includes only ACK / NACK information for one to three CCs. The ACK / NACK signal for more than one CC is configured by combining the base unit. For example, if five CCs are present, the ACK / NACK signal for five CCs may include a base unit including ACK / NACK information for three CCs of five CCs and ACK / NACK information for two CCs. It can be configured by combining the base unit including. In this case, the basic unit for three CCs is 7 bits when representing 5 states, and 5 bits when expressing 3 states, and the basic unit for 2 CCs is 5 bits when expressing 5 states and 3 states when expressing 5 states. Has 4 bits. Therefore, the ACK / NACK signal can be transmitted using the same number of bits as compared to the case of combining source coding the ACK / NACK information for five CCs, and the influence of the error between CCs can be reduced by using separate source coding. If there are four CCs, the ACK / NACK signal for four CCs is a combination of a basic unit including ACK / NACK information for three CCs and a basic unit including ACK / NACK information for one CC. Can be configured. In this case, the basic unit for three CCs is 7 bits when representing 5 states, and 5 bits when expressing 3 states, and the basic unit for 1 CC is 3 bits when expressing 5 states and 3 states when expressing 5 states. When it has 2 bits. Compared to the case of combining source coding the ACK / NACK information for four CCs, when the number of states represented is five, the ACK / NACK signal can be transmitted using the same number of bits, and the number of states represented is 3 In the individual case, one more bit is needed. However, there is an advantage that the influence of the error between CCs can be reduced by separate source coding. In the present embodiment, when grouping CCs, similar CCs may be grouped according to characteristics of the CCs.

12- (a) shows an example of configuring an ACK / NACK signal for four CCs using a base unit when four CCs exist. In FIG. 12- (a), the ACK / NACK signal for four CCs is composed of a combination of a basic unit constituting ACK / NACK information for three CCs and a basic unit for ACK / NACK information for one CC. Can be. 12- (b) shows an example of configuring an ACK / NACK signal for four CCs by using a base unit when five CCs exist. In FIG. 12- (b), the ACK / NACK signal for five CCs is composed of a combination of a basic unit constituting ACK / NACK information for three CCs and a basic unit for ACK / NACK information for two CCs. Can be.

13 is another example of ACK / NACK configuration according to a proposed method of performing HARQ.

In FIG. 13, the maximum supportable configuration CC is determined as one. That is, the maximum number of CCs that can be combined source coded is one. Accordingly, the basic unit constituting the ACK / NACK signal includes ACK / NACK information for one CC. The ACK / NACK signals for four CCs are configured by combining the base units. Accordingly, the ACK / NACK signal for each CC is separated and source coded, and the influence of the error between CCs can be minimized.

14 is another example of ACK / NACK configuration according to a proposed method of performing HARQ.

In FIG. 14, the maximum number of supported CCs is set to two. That is, the maximum number of CCs that can be combined source coded is two, and thus, the basic unit configuring the ACK / NACK signal includes only ACK / NACK information for one CC or ACK / NACK information for two CCs. . The ACK / NACK signal for more than one CC is configured by combining the base unit. For example, when three CCs exist, ACK / NACK information for two CCs of the three CCs may use the base unit, and ACK / NACK for the remaining one CC may be configured through additional bits. . The additional bits may be 2 bits when the number of states represented is 3, or 3 bits when 5 bits are represented. Compared to the case of combining source coding the ACK / NACK information for three CCs, when the number of states represented is five, the ACK / NACK signal can be transmitted using the same number of bits, and the number of states represented is 3 In the individual case, one more bit is needed. However, there is an advantage that the influence of the error between CCs can be reduced by separate source coding.

14- (a) and 14- (b) show different examples of configuring ACK / NACK signals for four CCs by using a base unit when four CCs exist. In FIG. 14- (a), ACK / NACK information for a first CC, a second CC, a third CC, and a fourth CC is transmitted using two basic units transmitting ACK / NACK information for two CCs, respectively. Can be. In FIG. 14- (b), the ACK / NACK signal for the first CC and the second CC may be transmitted using a basic unit for transmitting ACK / NACK information for two CCs. The ACK / NACK information for the third CC and the fourth CC may be transmitted using another basic unit for transmitting ACK / NACK information for one CC, respectively.

In applying separate source coding between CC groups as described above, PCC may be considered first.

15 is another example of ACK / NACK configuration according to a proposed method of performing HARQ. The terminal first generates ACK / NACK information regarding the PCC. In the present embodiment, it is assumed that the number of PCCs is one. However, when a plurality of PCCs exists, a base unit for a plurality of CCs may be used. After generating ACK / NACK information for the PCC, the order of the remaining CCs may be rearranged to configure ACK / NACK information. This can reduce the effects of errors between PCC and non-PCC.

As shown in FIG. 15, if there is a basic unit that preferentially considers the PCC and supports the number of CCs less than the maximum number supported by the system, only the ACK / NACK information for the PCC is separately coded and for the remaining non-PCCs. ACK / NACK information can be seen that two separate source coding is applied to the combined source coding.

In addition, the HARQ performing method described in FIG. 10 or FIG. 11 may be combined with the HARQ performing method described in FIGS. 12 to 15. That is, the method of indicating the DTX state may be applied to separate source coding of ACK / NACK information for a plurality of component carriers.

Meanwhile, in the above embodiment, the basic unit is configured by CC, but the basic unit may be configured by bit. That is, the base unit is configured in units of bits, and the base unit may be used in combination when supporting more than the base unit.

For example, assuming that a base unit including 2 bits and a base unit including 5 bits exist, the terminal generates ACK / NACK information to be transmitted for each CC. In this case, the 2-bit base unit and the 5-bit base unit may be used in combination according to the number of bits to be transmitted. If the number of bits of the ACK / NACK signal to be transmitted by the UE is 7 bits, the ACK / NACK signal may be generated by combining one 2-bit basic unit and one 5-bit basic unit one by one. If the number of bits of the ACK / NACK signal to be transmitted by the UE is 12 bits, the ACK / NACK signal may be generated by combining one 2-bit basic unit and two 5-bit basic units. In addition, the base unit may have a length of 2 bits, 5 bits, or 7 bits. Three basic units may be combined to generate an ACK / NACK signal according to the total number of bits of the ACK / NACK information to be transmitted. If the number of bits of the ACK / NACK signal to be transmitted by the UE is 12 bits, the ACK / NACK signal may be generated by combining one 5-bit basic unit and one 7-bit basic unit.

Meanwhile, in the application of the present invention, when fewer CCs than the predetermined number of CCs are allocated, the DTX state may be distinguished from the NACK and transmitted. Otherwise, the DTX state and the NACK may be regarded as NACK without being distinguished from each other. . In this case, different channel structures may be used when the number of CCs is less than or equal to the number of CCs based on the predetermined number of CCs.

For example, let n be the number of predetermined CCs. If the number of CCs constituting the system is less than n, the ACK / NACK information for each CC includes three states of ACK, NACK, and DTX for one codeword, and ACK / ACK, ACK / NACK, and NACK for two codewords. It can be represented by five states of / ACK, NACK / NACK, and DTX. In this case, one of the PUCCH structures of the LTE Rel-8 system may be used as the channel structure. If the number of CCs constituting the system is greater than n, the ACK / NACK information for each CC includes ACK for one codeword, two states of NACKX, ACK / ACK, ACK / NACK, NACK / ACK, and two codewords. It can be represented by four states of NACK / NACK. That is, if the number of CCs in the system is greater than n, NACK is transmitted without distinguishing between NACK and DTX. In this case, the channel structure may be the same as the channel structure used when the number of CCs is smaller than n, or may use another channel structure. For example, PUCCH format 1 / 1a / 1b may be used when the number of CCs is smaller than n, and PUCCH format 2 / 2a / 2b may be used when the number of CCs is larger than n. Alternatively, the DFT-s OFDM system may be used instead of the PUCCH format 2 / 2a / 2b. In addition, channel selection or enhanced channel selection may be used to transmit more bits on one or both sides with respect to n.

16 is a block diagram of a DFT-s OFDM system. A transmission scheme in which IFFT is performed after DFT spreading is called DFT-s OFDM. In the LTE-A system, uplink uses a DFT-s OFDM transmission scheme. DFT-s OFDM may also be referred to as Single Carrier-Frequency Division Multiple Access (SC-FDMA). DFT is performed on the input symbols, and the complex symbols output may be mapped to resource elements corresponding to the resource block allocated for data transmission. In addition, IFFT is performed on the input symbol to output a baseband signal for data, which is a time domain signal. In DFT-s OFDM, peak-to-average power ratio (PAPR) or cubic metric (CM) may be lowered. When the DFT-s OFDM transmission scheme is used, non-linear distortion intervals of a power amplifier may be avoided, thereby increasing transmission power efficiency in a terminal with limited power consumption. Accordingly, user throughput may be high.

17 is a block diagram of a base station and a terminal in which an embodiment of the present invention is implemented.

The base station 800 includes a processor 810, a memory 820, and an RF unit 830. Processor 810 implements the proposed functions, processes, and / or methods. Layers of the air interface protocol may be implemented by the processor 810. The memory 820 is connected to the processor 810 and stores various information for driving the processor 810. The RF unit 830 is connected to the processor 810 to transmit and / or receive a radio signal.

The terminal 900 includes an ACK / NACK signal generator 910, a memory 920, and an RF unit 930. The ACK / NACK signal generator 910 implements the proposed function, process, and / or method. The ACK / NACK signal generator 910 generates an ACK / NACK signal for a codeword transmitted through each component carrier among a plurality of component carriers. The ACK / NACK signal may indicate any one of an ACK state, a NACK state, and a DTX state. The memory 920 is connected to the ACK / NACK signal generator 910 and stores various information for driving the ACK / NACK signal generator 910. The RF unit 930 is connected to the ACK / NACK signal generator 910 to transmit and / or receive a radio signal and to transmit the respective ACK / NACK signals to the base station 800.

The processor 810 and the ACK / NACK signal generator 910 may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and / or a data processing device. The memory 820, 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and / or other storage device. The RF unit 830 and 930 may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in the memories 820 and 920 and executed by the processor 810 and the ACK / NACK signal generator 910. The memories 820 and 920 may be inside or outside the processor 810 and the ACK / NACK signal generator 910, and may be connected to the processor 810 and the ACK / NACK signal generator 910 by various well-known means. Can be.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Claims (14)

1. In a method of performing HARQ in a multi-carrier system, an ACK / NACK (Acknowledgement / Non-acknowledgement) signal for a codeword transmitted through each component carrier among a plurality of component carriers (CC) is generated. And transmitting the respective ACK / NACK signals, wherein each ACK / NACK signal includes an ACK state indicating that the codeword has been decoded, a NACK state indicating that the codeword has not been decoded, and a transmission of each component carrier is not recognized. HARQ performing method, characterized in that indicating any one of the discontinuous transmission (DTX) state.
2. The method according to claim 1, wherein the number of codewords transmitted through each component carrier is one, respectively, and an ACK / NACK signal for the one codeword indicates one of ACK, NACK, and DTX states. HARQ performing method.
3. The method of claim 2, wherein the length of the ACK / NACK signal for the one codeword is 2 bits.
4. The method of claim 1, wherein the number of codewords transmitted through each component carrier is two, and ACK / NACK signals for the two codewords are respectively ACK / ACK, ACK / NACK, NACK / NACK, and NACK /. Method for performing HARQ, characterized in that indicating either the NACK or DTX state.
5. The method of claim 4, wherein the length of the ACK / NACK signal for the two codewords is 2 bits.
6. The method of claim 1, wherein each ACK / NACK signal includes DTX information for at least one component carrier group including a plurality of component carriers.
7. The method of claim 6, wherein a plurality of component carriers included in the at least one component carrier group are previously designated or signaled.
8. The method of claim 6, wherein the DTX information of the at least one component carrier group is generated by calculating DTX information of each of the plurality of component carriers by a predetermined calculation method.
9. The method of claim 8, wherein the predetermined operation method is one of a logical AND operation and a logical OR operation.
10. The method of claim 1, wherein each of the ACK / NACK signals is generated by combining a plurality of the basic units based on a basic unit determined according to a predetermined number of component carriers.
11. The method of claim 10, wherein the plurality of basic units are separately coded.
12. The method of claim 10, wherein the number of the predetermined configuration carriers is any one of one to three.
13. The HARQ of claim 10, wherein an ACK / NACK signal for a codeword transmitted through a primary component carrier (PCC) among the ACK / NACK signals is generated based on an independent basic unit. Way.
14. An apparatus for performing HARQ in a wireless communication system, the apparatus comprising: generating an ACK / NACK (Acknowledgement / Non-acknowledgement) signal for a codeword transmitted through each component carrier among a plurality of component carriers (CC) An ACK / NACK signal generator; And an RF unit (RF unit) connected to the ACK / NACK signal generator and transmitting the respective ACK / NACK signals, wherein each ACK / NACK signal includes an ACK state indicating that the codeword has been decoded, and the codeword is An apparatus for performing HARQ, characterized in that one of the NACK state indicating that it was not decoded and the discontinuous transmission (DTX) state indicating that the transmission of each component carrier is not recognized.

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