KR101799595B1 - Method and apparatus of performing harq in wireless communication system - Google Patents

Abstract

A method and apparatus for performing HARQ by a terminal in a wireless communication system are provided. In the HARQ method, a UE transmits uplink data on a Physical Uplink Shared Channel (PUSCH), and receives uplink data through a plurality of layers on a physical hybrid-ARQ indicator channel (PHICH) (Acknowledgment / Non-Acknowledgment) signal indicating whether the ACK / NACK signal is received. In this case, downlink resources to which PHICHs are mapped to each of the plurality of layers do not overlap each other, and downlink resources to which PHICHs are mapped to each of the plurality of layers are cyclically shifted to different cyclic shifts ) ≪ / RTI > value.

Description

TECHNICAL FIELD [0001] The present invention relates generally to a HARQ in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 wireless communication system.

In the case of a broadband wireless communication system, 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 capable of attenuating the inter-symbol interference (ISI) effect with low complexity. OFDM converts serial data symbols into N parallel data symbols, and transmits the data symbols on N separate subcarriers. The subcarriers maintain orthogonality at the frequency dimension. Each of the orthogonal channels experiences mutually independent frequency selective fading, thereby reducing the complexity at the receiving end and increasing the interval of transmitted symbols, thereby minimizing intersymbol interference.

Orthogonal frequency division multiple access (OFDMA) refers to a multiple access method in which a part of subcarriers available in a system using OFDM as a modulation scheme is independently provided to each user to realize multiple access. OFDMA provides a frequency resource called a subcarrier to each user, and each frequency resource is provided independently to a plurality of users and is not overlapped with each other. Consequently, frequency resources are allocated mutually exclusively for each user. Frequency diversity for multiple users can be obtained through frequency selective scheduling in an OFDMA system and subcarriers can be allocated in various forms according to a permutation scheme for subcarriers. And the efficiency of spatial domain can be improved by spatial multiplexing technique using multiple antennas.

Multiple-input multiple-output (MIMO) technology improves data transmission and reception efficiency by using multiple transmit antennas and multiple receive antennas. Techniques for implementing diversity in a MIMO system include space frequency block codes (SFBC), space time block codes (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 reception antennas and the number of transmission antennas can be decomposed into a plurality of independent channels. Each independent channel is called a layer or a stream. The number of layers is called a rank.

3rd Generation Partnership Project (3GPP) TS 36.211 V8.8.0 (2009-09) " Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); (PDCCH), Physical Hybrid-ARQ Indicator (PHICH), and Physical Uplink Control Channel (PDCH) as shown in Section 6 of 3GPP LTE, Channel). The PCFICH transmitted in the first OFDM symbol of the subframe carries information on the number of OFDM symbols (i.e., the size of the control region) used for transmission of the control channels in the subframe. The control information transmitted through the PDCCH is referred to as downlink control information (DCI). DCI refers to uplink or downlink scheduling information and uplink transmission power control commands for certain UE groups. The PHICH carries an ACK (Acknowledgment) / NACK (Non-Acknowledgment) signal for an uplink HARQ (Hybrid Automatic Repeat Request). That is, the ACK / NACK signal for the uplink data transmitted by the UE is transmitted on the PHICH.

A plurality of PHICHs may be allocated according to the system environment. In particular, a plurality of PHICHs need to be simultaneously allocated in a carrier aggregation system, a MIMO system, or the like that transmits data using a plurality of carriers. The base station allocates resources to a plurality of PHICHs and transmits ACK / NACK through the PHICH.

There is a need for a resource allocation method for preventing PHICH resources from colliding in a multi-user MIMO (MU-MIMO) environment.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for performing Hybrid Automatic Repeat Request (HARQ) in a wireless communication system.

In one aspect, a method for performing HARQ by a terminal in a wireless communication system is provided. The HARQ method includes transmitting uplink data on a Physical Uplink Shared Channel (PUSCH), determining whether to receive the uplink data on a physical hybrid-ARQ indicator channel (PHICH) corresponding to the PUSCH through a plurality of layers, Wherein the downlink resources to which the PHICHs are mapped to each of the plurality of layers do not overlap with each other and the PHICHs of the plurality of layers are mapped to each other The downlink resources are determined based on different cyclic shift values allocated to each of the plurality of layers.

If the number of the plurality of layers is two, the cyclic shift value allocated to each of the plurality of layers may differ by four.

If the number of the plurality of layers is four, the cyclic shift value allocated to each of the plurality of layers may differ by two.

The cyclic shift value assigned to each of the plurality of layers may be any one of 0 to 7.

One of the cyclic shift values allocated to each of the plurality of layers may be determined by a cyclic shift field in a downlink control information (DCI) transmitted through a physical downlink control channel (PDCCH).

을 기반으로 결정될 수 있다. 단, n_PHICH ^group는 PHICH 그룹 인덱스, n_PHICH ^seq는 PHICH 그룹 내의 직교 시퀀스 인덱스, I_{PRB_RA} ^lowest_index는 상기 PUSCH가 맵핑된 PRB(Physical Resource Block) 중 가장 작은 PRB의 인덱스, n_DMRS는 상향링크 DMRS(Demodulation Reference Signal) 순환 쉬프트 파라미터, N_PHICH ^group은 PHICH 그룹의 개수 및 N_SF ^PHICH는 스프레딩 인자(SF; Spreading Factor)이다. 상기 N_PHICH ^group=4이며, 2N_SF ^PHCIH=4일 수 있다.The downlink resources to which the PHICHs are mapped for each of the plurality of layers is expressed by Equation

As shown in FIG. N _PHICH ^group is the PHICH group index, n _PHICH ^seq is the orthogonal sequence index in the PHICH group, I _{PRB_RA} ^lowest index is the index of the smallest PRB among the PRBs mapped to the PUSCH, and _DMRS is the uplink DMRS Demodulation Reference Signal) cyclic shift parameter, N _PHICH ^group is the number of PHICH groups, and N _SF ^PHICH is the spreading factor (SF). The N _PHICH ^group = 4 and the 2N _SF ^PHCIH = 4.

The HARQ method may further include transmitting retransmission data of the uplink data based on the ACK / NACK signal.

In another aspect, a method for performing HARQ by a terminal in a wireless communication system is provided. In the HARQ method, a first terminal and a second terminal transmit first uplink data and second uplink data to a base station on a PUSCH, respectively, and the base station transmits, on a PHICH corresponding to the PUSCH, And transmitting a first ACK / NACK signal and a second ACK / NACK signal indicating whether to receive the first uplink data and the second uplink data, respectively, to the first terminal and the second terminal, A downlink resource to which a PHICH is mapped for each of the plurality of layers is determined based on a cyclic shift value allocated to each of the plurality of layers.

If the number of the plurality of layers is two, the cyclic shift value allocated to each of the plurality of layers may differ by four.

If the number of the plurality of layers is four, the cyclic shift value allocated to each of the plurality of layers may differ by two.

The cyclic shift value assigned to each of the plurality of layers may be any one of 0 to 7.

을 기반으로 결정될 수 있다. 단, n_PHICH ^group는 PHICH 그룹 인덱스, n_PHICH ^seq는 PHICH 그룹 내의 직교 시퀀스 인덱스, I_{PRB_RA} ^lowest_index는 상기 PUSCH가 맵핑된 PRB 중 가장 작은 PRB의 인덱스, n_DMRS는 상향링크 DMRS 순환 쉬프트 파라미터, n_OCC는 상기 OCC 인덱스, N_PHICH ^group은 PHICH 그룹의 개수 및 N_SF ^PHICH는 스프레딩 인자이다.The downlink resources to which the PHICHs are mapped to each of the plurality of layers may be determined based on an OCC (Orthogonal Code Covering) index. Different OCC indices may be assigned to the first terminal and the second terminal. The downlink resources to which the PHICHs are mapped for each of the plurality of layers is expressed by Equation

As shown in FIG. Stage, n _PHICH ^group is a PHICH group index, n _PHICH ^seq is the orthogonal sequence index within the PHICH group, I _{PRB_RA} ^lowest_index is the index of the smallest PRB in which the PUSCH mapped to a PRB, n _DMRS is UL DMRS cyclic shift parameter, n _OCC Is the OCC index, N _PHICH ^group is the number of PHICH groups, and N _SF ^PHICH is the spreading factor.

It is possible to effectively perform HARQ (Hybrid Automatic Repeat Request) by preventing collision of resources mapped by a plurality of PHICHs.

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 sub-frame.
5 shows a structure of an uplink sub-frame.
6 shows an example of a transmitter structure in an SC-FDMA system.
FIG. 7 shows an example of a scheme in which a subcarrier mapper maps complex symbols to subcarriers in the frequency domain.
8 is an example of a transmitter applying the clustered DFT-s OFDM transmission scheme.
9 is another example of a transmitter applying the clustered DFT-s OFDM transmission scheme.
10 is another example of a transmitter applying the clustered DFT-s OFDM transmission scheme.
11 shows an example of a structure of a reference signal transmitter for demodulation.
12 is an example of a structure of a subframe in which a reference signal is transmitted.
13 shows an example in which OCC is applied to the reference signal.
FIG. 14 shows an example in which reference signals transmitted from two terminals having different bandwidths are multiplexed by applying OCC.
15 is a block diagram illustrating an example of a PARC technique.
16 is a block diagram showing an example of the PU2RC technique.
17 shows an uplink HARQ.
18 is a block diagram showing that an ACK / NACK signal is transmitted on the PHICH.
19 is a block diagram illustrating a MIMO transmission process in an uplink using an SC-FDMA transmission scheme.
20 is an example of a PHICH resource allocation.
FIG. 21 shows an example of allocation of a cyclic shift value for two UEs according to the proposed HARQ performing method.
FIG. 22 shows an example of allocation of a cyclic shift value for two UEs according to the proposed HARQ performing method.
FIG. 23 is a block diagram illustrating an embodiment of a method for performing the HARQ.
24 shows an embodiment of the proposed downlink control signal transmission method.
25 is a block diagram illustrating a base station and a terminal in which an embodiment of the present invention is implemented.

The following description will be made on the assumption that the present invention is applicable to a CDMA system such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and Single Carrier Frequency Division Multiple Access And can be used in various wireless communication systems. CDMA may be implemented in radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. The TDMA may be implemented in a wireless technology 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 wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). IEEE 802.16m is an evolution of IEEE 802.16e, providing backward compatibility with systems based on IEEE 802.16e. UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) LTE (Long Term Evolution) is a part of E-UMTS (Evolved UMTS) using Evolved-UMTS Terrestrial Radio Access (E-UTRA). It adopts OFDMA in downlink and SC -FDMA is adopted. LTE-A (Advanced) is the evolution of 3GPP LTE.

For the sake of clarity, LTE-A is mainly described, but the technical idea 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 11 (BS). Each base station 11 provides a communication service to a specific geographical area (generally called a cell) 15a, 15b, 15c. The cell may again be divided into multiple regions (referred to as sectors). A user equipment (UE) 12 may be fixed or mobile and may be a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, (Personal Digital Assistant), a wireless modem, a handheld device, and the like. The base station 11 generally refers to a fixed station that communicates with the terminal 12 and may be referred to by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point have.

A terminal usually belongs to one cell, and a cell to which the terminal belongs is called a serving cell. A base station providing a communication service to 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 services to neighbor cells is called a neighbor BS. The serving cell and the neighboring cell are relatively determined based on the terminal.

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

The wireless communication system may be any one of a multiple-input multiple-output (MIMO) system, a multiple-input single-output (MISO) system, a single-input single-output (SISO) system, and a single- Lt; / RTI > A MIMO system uses a plurality of transmit antennas and a plurality of receive antennas. The MISO system uses multiple transmit antennas and one receive antenna. The SISO system uses one transmit antenna and one receive antenna. The SIMO system uses one transmit antenna and multiple receive antennas. Hereinafter, a transmit antenna means a physical or logical antenna used to transmit one signal or stream, and a receive antenna means a physical or logical antenna used to receive one signal or stream.

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

This is described in Section 5 of the 3rd Generation Partnership Project (3GPP) TS 36.211 V8.2.0 (2008-03) "Technical Specification Group Radio Access Network (E-UTRA), Physical channels and modulation Can be referenced. Referring to FIG. 2, a radio frame is composed of 10 subframes, and one subframe is composed of two slots. Slots in radio frames are numbered from # 0 to # 19. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). TTI is a scheduling unit for data transmission. For example, the length of one radio frame is 10 ms, the length of one subframe is 1 ms, and the length of one slot may be 0.5 ms.

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

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

The wireless communication system can be roughly divided into a Frequency Division Duplex (FDD) system and a Time Division Duplex (TDD) system. According to the FDD scheme, uplink transmission and downlink transmission occupy different frequency bands. According to the TDD scheme, uplink transmission and downlink transmission occupy the same frequency band and are performed at different times. The channel response of the TDD scheme is substantially reciprocal. This is because the downlink channel response and the uplink channel response are almost the same in a given frequency domain. Therefore, in the TDD-based wireless communication system, the downlink channel response has an advantage that it can be obtained from the uplink channel response. The TDD scheme can not simultaneously perform downlink transmission by a base station and uplink transmission by a UE because the uplink transmission and the downlink transmission are time-divided in the entire frequency band. In a TDD system in which uplink transmission and downlink transmission are divided into subframe units, uplink transmission and downlink transmission are performed in different subframes.

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 an LTE system, N _RB may be any of 60 to 110. One resource block includes a plurality of subcarriers in the frequency domain. The structure of the uplink slot may be the same as the structure of the downlink slot.

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

Here, one resource block exemplarily 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 are But is not limited to. The number of OFDM symbols and the number of subcarriers can be changed variously according to the length of CP, frequency spacing, and the like. For example, the number of OFDM symbols in a normal CP is 7, and the number of OFDM symbols in an extended CP is 6. The number of subcarriers in one OFDM symbol can be selected from one of 128, 256, 512, 1024, 1536, and 2048.

4 shows a structure of a downlink sub-frame.

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

The PDCCH includes a resource allocation and transmission format of a downlink-shared channel (DL-SCH), resource allocation information of an uplink shared channel (UL-SCH), paging information on a PCH, system information on a DL- Resource allocation of upper layer control messages such as responses, collection of transmission power control commands for individual UEs in any UE group, and activation of VoIP (Voice over Internet Protocol). A plurality of PDCCHs can be transmitted in the control domain, and the UE can monitor a plurality of PDCCHs. The PDCCH is transmitted on an aggregation of one or several consecutive CCEs (Control Channel Elements). The CCE is a logical allocation unit used to provide the PDCCH with the coding rate according to the state of the radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of bits of the possible PDCCH are determined according to the relationship 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 transmitted to the UE, and attaches a CRC (Cyclic Redundancy Check) to the control information. The CRC is masked with a Radio Network Temporary Identifier (RNTI) according to the owner or use of the PDCCH. If the PDCCH is for a particular UE, the unique identifier of the UE, e.g., C-RNTI (Cell-RNTI), may be masked in the CRC. Alternatively, if the PDCCH is a PDCCH for a paging message, a paging indication identifier, e.g., P-RNTI (P-RNTI), may be masked on the CRC. If the PDCCH is for a system information block (SIB), a system information identifier (SI-RNTI) may be masked in the CRC. Random Access-RNTI (RA-RNTI) may be masked in the CRC to indicate a random access response that is a response to the transmission of the UE's random access preamble.

5 shows a structure of an uplink sub-frame.

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

A PUCCH for one UE is allocated as a resource block pair (RB pair) in a subframe. The resource blocks belonging to the resource block pair occupy different subcarriers in the first slot and the second slot. The frequency occupied by the resource blocks belonging to the resource block pair allocated to the PUCCH is changed based on the slot boundary. It is assumed that the RB pair allocated to the PUCCH is frequency-hopped at the slot boundary. The UE transmits the uplink control information through different subcarriers according to time, thereby obtaining a frequency diversity gain. and m is a position index indicating the logical frequency domain position of the resource block pair allocated to the PUCCH in the subframe.

The uplink control information transmitted on the PUCCH includes a Hybrid Automatic Repeat reQuest (ACK) acknowledgment / non-acknowledgment (NACK), a CQI (Channel Quality Indicator) indicating a downlink channel state, (Scheduling Request).

The 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 that 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, the control information multiplexed on the data may include a CQI, a Precoding Matrix Indicator (PMI), a HARQ, a Rank Indicator (RI), and the like. Alternatively, the uplink data may be composed of only control information.

In the LTE-A system, the uplink uses the SC-FDMA transmission scheme. The transmission scheme in which IFFT is performed after DFT spreading is referred to as SC-FDMA. SC-FDMA may be referred to as DFT-s OFDM (DFT-spread OFDM). In SC-FDMA, the peak-to-average power ratio (PAPR) or the cubic metric (CM) may be lowered. In the case of using the SC-FDMA transmission scheme, the non-linear distortion period of the power amplifier can be avoided, so that the transmission power efficiency can be increased in a terminal with limited power consumption. Accordingly, the user throughput can be increased.

6 shows an example of a transmitter structure in an SC-FDMA system.

Referring to FIG. 6, the transmitter 50 includes a Discrete Fourier Transform (DFT) unit 51, a subcarrier mapper 52, an IFFT (Inverse Fast Fourier Transform) unit 53, and a CP inserting unit 54. The transmitter 50 may include a scrambler unit, a modulation mapper, a layer mapper, and a layer permutator (not shown) , Which can be arranged in advance of the DFT unit 51. [

The DFT unit 51 performs DFT on the input symbols to output complex-valued symbols. For example, when N _tx symbols are input (where N _tx is a natural number), the DFT size (size) is N _tx . The DFT unit 51 may be referred to as a transform precoder. The subcarrier mapper 52 maps the complex symbols to subcarriers in the frequency domain. The complex symbols may be mapped to resource elements corresponding to resource blocks allocated for data transmission. The subcarrier mapper 52 may be referred to as a resource element mapper. The IFFT unit 53 performs IFFT on the input symbol and outputs a baseband signal for data, which is a time domain signal. The CP inserting unit 54 copies a part of the rear part of the base band signal for data and inserts it in the front part of the base band signal for data. Inter-symbol interference (ISI) and inter-carrier interference (ICI) are prevented through CP insertion, and orthogonality can be maintained in a multi-path channel.

FIG. 7 shows an example of a scheme in which a subcarrier mapper maps complex symbols to subcarriers in the frequency domain.

Referring to FIG. 7A, a subcarrier mapper maps complex symbols output from the DFT unit to consecutive subcarriers in the frequency domain. A '0' is inserted in a sub-carrier for which complex symbols are not mapped. This is called localized mapping. In the 3GPP LTE system, a concentrated mapping method is used. Referring to FIG. 7B, the subcarrier mapper inserts L-1 '0' s between two consecutive complex symbols outputted from the DFT unit (L is a natural number). That is, the complex symbols output from the DFT unit are mapped to subcarriers dispersed at equal intervals in the frequency domain. This is called distributed mapping. When the subcarrier mapper uses the concentrated mapping method as shown in FIG. 7A or the distributed mapping method as shown in FIG. 7B, the single carrier characteristic is maintained.

The clustered DFT-s OFDM transmission scheme is a modification of the existing SC-FDMA transmission scheme, in which data symbols that have passed the precoder are divided into a plurality of subblocks, and the divided data symbols are mapped in the frequency domain.

8 is an example of a transmitter applying the clustered DFT-s OFDM transmission scheme.

Referring to FIG. 8, the transmitter 70 includes a DFT unit 71, a subcarrier mapper 72, an IFFT unit 73, and a CP inserting unit 74. The transmitter 70 may further include a scrambler unit (not shown), a modulation mapper (not shown), a layer mapper (not shown) and a layer permuter (not shown), which are arranged before the DFT unit 71 .

The complex symbols output from the DFT unit 71 are divided into N subblocks (N is a natural number). N subblocks can be represented by subblock # 1, subblock # 2, ..., subblock #N. The subcarrier mapper 72 maps N subblocks to subcarriers in a frequency domain. NULL can be inserted between two consecutive subblocks. The complex symbols in one subblock can be mapped to consecutive subcarriers in the frequency domain. That is, a concentrated mapping method can be used in one sub-block.

The transmitter 70 of FIG. 8 may be used for either a single carrier transmitter or a multi-carrier transmitter. When used in a single carrier transmitter, N subblocks all correspond to one carrier. When used in a multi-carrier transmitter, each sub-block of the N sub-blocks may correspond to one carrier. Alternatively, even when used in a multi-carrier transmitter, a plurality of sub-blocks among the N sub-blocks may correspond to one carrier. On the other hand, in the transmitter 70 of FIG. 8, a time domain signal is generated through one IFFT unit 73. Therefore, in order for the transmitter 70 of FIG. 8 to be used in a multi-carrier transmitter, adjacent carrier-to-carrier subcarrier spacings must be aligned in a contiguous carrier allocation situation.

9 is another example of a transmitter applying the clustered DFT-s OFDM transmission scheme.

9, the transmitter 80 includes a DFT unit 81, a subcarrier mapper 82, a plurality of IFFT units 83-1, 83-2, ..., 83-N (N is a natural number) And a CP insertion unit 84. The transmitter 80 may further include a scrambler unit (not shown), a modulation mapper (not shown), a layer mapper (not shown) and a layer permuter (not shown) .

An IFFT is performed individually for each sub-block among the N sub-blocks. The nth IFFT unit 83-N performs IFFT on the sub-block #n to output the n-th baseband signal (n = 1, 2, ..., N). An n-th baseband signal is multiplied by an n-th carrier signal to produce an n-th radio signal. The N radio signals generated from the N subblocks are added, and then the CP is inserted by the CP inserting unit 84. The transmitter 80 of FIG. 9 may be used in a non-contiguous carrier allocation situation where the carriers allocated by the transmitter are not adjacent.

10 is another example of a transmitter applying the clustered DFT-s OFDM transmission scheme.

10 is a chunk specific DFT-s OFDM system that performs DFT precoding on a chunk basis. This may be referred to as Nx SC-FDMA. 10, the transmitter 90 includes a code block dividing unit 91, a chunk dividing unit 92, a plurality of channel coding units 93-1 to 93-N, A plurality of DFT units 95-1 to 95-N, a plurality of subcarrier mappers 96-1 to 96-N, a plurality of modulators 94-1 to 94- , A plurality of IFFT units (97-1, ..., 97-N), and a CP inserting unit (98). Here, N may be the number of multi-carriers used by the multi-carrier transmitter. Each of the channel coding units 93-1, ..., 93-N may include a scrambler unit (not shown). Modulators 94-1, ..., 94-N may also be referred to as modulation maps. The transmitter 90 may further include a layer mapper (not shown) and a layer permuter (not shown), which may be disposed in advance of the DFT units 95-1 to 95-N.

The code block dividing unit 91 divides the transport block into a plurality of code blocks. The chunk divider 92 divides the code block into a plurality of chunks. Here, the code block may be data transmitted from a multi-carrier transmitter, and the chunk may be a data fragment transmitted through one carrier among multiple carriers. The transmitter 90 performs DFT on a chunk basis. The transmitter 90 may be used both in a discontinuous carrier allocation situation or in a continuous carrier allocation situation.

The uplink reference signal will be described below.

The reference signal is typically transmitted in a sequence. The reference signal sequence may be any sequence without any particular limitation. The reference signal sequence may use a PSK-based computer generated sequence (PSK) -based computer. Examples of PSKs include Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK). Alternatively, the reference signal sequence may use a Constant Amplitude Zero Auto-Correlation (CAZAC) sequence. Examples of the CAZAC sequence include a ZC-based sequence, a ZC sequence with a cyclic extension, a truncation ZC sequence (ZC sequence with truncation), and the like . Alternatively, the reference signal sequence may use a PN (pseudo-random) sequence. Examples of PN sequences include m-sequences, computer generated sequences, Gold sequences, and Kasami sequences. Also, the reference signal sequence may use a cyclically shifted sequence.

The uplink reference signal may be divided into a demodulation reference signal (DMRS) and a sounding reference signal (SRS). The DMRS is a reference signal used for channel estimation for demodulating a received signal. The DMRS may be combined with the transmission of the PUSCH or PUCCH. The SRS is a reference signal transmitted from a mobile station to a base station for uplink scheduling. The base station estimates the uplink channel through the received sounding reference signal and uses the estimated uplink channel for uplink scheduling. The SRS is not combined with the transmission of the PUSCH or PUCCH. Basic sequences of the same kind may be used for DMRS and SRS. On the other hand, the precoding applied to the DMRS in the uplink multi-antenna transmission may be the same as the precoding applied to the PUSCH. Cyclic shift separation is a primary scheme for multiplexing DMRS. In the LTE-A system, the SRS may not be precoded and may also be an antenna specific reference signal.

The reference signal sequence r _{u, v} ^(α) (n) can be defined based on the basic sequence b _{u, v} (n) and the cyclic shift α according to equation (1).

<Number 1>

In Equation (1), M _sc ^RS (1? M? N _RB ^{max, UL} ) is the length of the reference signal sequence and M _sc ^RS = m * N _sc ^RB . N _sc ^RB denotes the size of a resource block expressed by the number of subcarriers in the frequency domain, and N _RB ^{max and UL} denote the maximum value of the uplink bandwidth represented by a multiple of N _sc ^RB . The plurality of reference signal sequences may be defined by applying a cyclic shift value a differently from one base sequence.

The basic sequence b _{u, v} (n) is divided into a plurality of groups, where _u ∈ {0, 1, ... , 29} denotes a group index, and v denotes a basic sequence index in the group. The base sequence depends on the length of the base sequence (M _sc ^RS ). Each group and for the 1≤m≤5 m length contains one base sequence (v = 0) of M _sc ^RS, the length for 6≤m≤n _RB ^{max, UL,} m, the M _sc ^RS And contains two basic sequences (v = 0, 1). The sequence group index u and the basic sequence index v in the group may change over time, such as group hopping or sequence hopping, which will be described later.

Further, when the length of the reference signal sequence is 3N _sc ^RB or more, the basic sequence can be defined by Equation (2).

<Number 2>

In Equation (2), q represents a root index of a ZC (Zadoff-Chu) sequence. N _ZC ^RS is the length of the ZC sequence and can be given as a prime number less than M _sc ^RS . The ZC sequence with root index q can be defined by Equation (3).

<Number 3>

q can be given by Equation (4).

<Number 4>

If the length of the reference signal sequence is 3N _sc ^RB or less, the basic sequence can be defined by Equation (5).

<Number 5>

Table 1 is an example of defining φ (n) when M _sc ^RS = N _sc ^RB .

φ (0), ... , φ (11) 0 -One One 3 -3 3 3 One One 3 One -3 3 One One One 3 3 3 -One One -3 -3 One -3 3 2 One One -3 -3 -3 -One -3 -3 One -3 One -One 3 -One One One One One -One -3 -3 One -3 3 -One 4 -One 3 One -One One -One -3 -One One -One One 3 5 One -3 3 -One -One One One -One -One 3 -3 One 6 -One 3 -3 -3 -3 3 One -One 3 3 -3 One 7 -3 -One -One -One One -3 3 -One One -3 3 One 8 One -3 3 One -One -One -One One One 3 -One One 9 One -3 -One 3 3 -One -3 One One One One One 10 -One 3 -One One One -3 -3 -One -3 -3 3 -One 11 3 One -One -One 3 3 -3 One 3 One 3 3 12 One -3 One One -3 One One One -3 -3 -3 One 13 3 3 -3 3 -3 One One 3 -One -3 3 3 14 -3 One -One -3 -One 3 One 3 3 3 -One One 15 3 -One One -3 -One -One One One 3 One -One -3 16 One 3 One -One One 3 3 3 -One -One 3 -One 17 -3 One One 3 -3 3 -3 -3 3 One 3 -One 18 -3 3 One One -3 One -3 -3 -One -One One -3 19 -One 3 One 3 One -One -One 3 -3 -One -3 -One 20 -One -3 One One One One 3 One -One One -3 -One 21 -One 3 -One One -3 -3 -3 -3 -3 One -One -3 22 One One -3 -3 -3 -3 -One 3 -3 One -3 3 23 One One -One -3 -One -3 One -One One 3 -One One 24 One One 3 One 3 3 -One One -One -3 -3 One 25 One -3 3 3 One 3 3 One -3 -One -One 3 26 One 3 -3 -3 3 -3 One -One -One 3 -One -3 27 -3 -One -3 -One -3 3 One -One One 3 -3 -3 28 -One 3 -3 3 -One 3 3 -3 3 3 -One -One 29 3 -3 -3 -One -One -3 -One 3 -3 3 One -One

Table 2 is an example of defining φ (n) when M _sc ^RS = 2 * N _sc ^RB .

φ (0), ... ,? (23) 0 -One 3 One -3 3 -One One 3 -3 3 One 3 -3 3 One One -One One 3 -3 3 -3 -One -3 One -3 3 -3 -3 -3 One -3 -3 3 -One One One One 3 One -One 3 -3 -3 One 3 One One -3 2 3 -One 3 3 One One -3 3 3 3 3 One -One 3 -One One One -One -3 -One -One One 3 3 3 -One -3 One One 3 -3 One One -3 -One -One One 3 One 3 One -One 3 One One -3 -One -3 -One 4 -One -One -One -3 -3 -One One One 3 3 -One 3 -One One -One -3 One -One -3 -3 One -3 -One -One 5 -3 One One 3 -One One 3 One -3 One -3 One One -One -One 3 -One -3 3 -3 -3 -3 One One 6 One One -One -One 3 -3 -3 3 -3 One -One -One One -One One One -One -3 -One One -One 3 -One -3 7 -3 3 3 -One -One -3 -One 3 One 3 One 3 One One -One 3 One -One One 3 -3 -One -One One 8 -3 One 3 -3 One -One -3 3 -3 3 -One -One -One -One One -3 -3 -3 One -3 -3 -3 One -3 9 One One -3 3 3 -One -3 -One 3 -3 3 3 3 -One One One -3 One -One One One -3 One One 10 -One One -3 -3 3 -One 3 -One -One -3 -3 -3 -One -3 -3 One -One One 3 3 -One One -One 3 11 One 3 3 -3 -3 One 3 One -One -3 -3 -3 3 3 -3 3 3 -One -3 3 -One One -3 One 12 One 3 3 One One One -One -One One -3 3 -One One One -3 3 3 -One -3 3 -3 -One -3 -One 13 3 -One -One -One -One -3 -One 3 3 One -One One 3 3 3 -One One One -3 One 3 -One -3 3 14 -3 -3 3 One 3 One -3 3 One 3 One One 3 3 -One -One -3 One -3 -One 3 One One 3 15 -One -One One -3 One 3 -3 One -One -3 -One 3 One 3 One -One -3 -3 -One -One -3 -3 -3 -One 16 -One -3 3 -One -One -One -One One One -3 3 One 3 3 One -One One -3 One -3 One One -3 -One 17 One 3 -One 3 3 -One -3 One -One -3 3 3 3 -One One One 3 -One -3 -One 3 -One -One -One 18 One One One One One -One 3 -One -3 One One 3 -3 One -3 -One One One -3 -3 3 One One -3 19 One 3 3 One -One -3 3 -One 3 3 3 -3 One -One One -One -3 -One One 3 -One 3 -3 -3 20 -One -3 3 -3 -3 -3 -One -One -3 -One -3 3 One 3 -3 -One 3 -One One -One 3 -3 One -One 21 -3 -3 One One -One One -One One -One 3 One -3 -One One -One One -One -One 3 3 -3 -One One -3 22 -3 -One -3 3 One -One -3 -One -3 -3 3 -3 3 -3 -One One 3 One -3 One 3 3 -One -3 23 -One -One -One -One 3 3 3 One 3 3 -3 One 3 -One 3 -One 3 3 -3 3 One -One 3 3 24 One -One 3 3 -One -3 3 -3 -One -One 3 -One 3 -One -One One One One One -One -One -3 -One 3 25 One -One One -One 3 -One 3 One One -One -One -3 One One -3 One 3 -3 One One -3 -3 -One -One 26 -3 -One One 3 One One -3 -One -One -3 3 -3 3 One -3 3 -3 One -One One -3 One One One 27 -One -3 3 3 One One 3 -One -3 -One -One -One 3 One -3 -3 -One 3 -3 -One -3 -One -3 -One 28 -One -3 -One -One One -3 -One -One One -One -3 One One -3 One -3 -3 3 One One -One 3 -One -One 29 One One -One -One -3 -One 3 -One 3 -One One 3 One -One 3 One 3 -3 -3 One -One -One One 3

The hopping of the reference signal can be applied as follows.

The sequence group index u of the slot index n _s can be defined based on the group hopping pattern f _gh (n _s ) and the sequence shift pattern f _ss by Equation (6).

<Number 6>

Seventeen different group hopping patterns and thirty different sequence shift patterns may exist. Whether group hopping is applied can be indicated by an upper layer.

PUCCH and PUSCH may have the same group hopping pattern. The group hopping pattern f _gh (n _s ) can be defined by Equation (7).

<Number 7>

In Equation (8), c (i) is a pseudo-random sequence that is a PN sequence and can be defined by a Gold sequence of length -31. Equation (9) shows an example of the gold sequence c (n).

<Number 8>

로 초기화될 수 있다.And Nc = 1600 on the Equation 8, x ₁ (i) is the m- sequence of claim 1, x ₂ (i) is the m- sequence of claim 2. For example, the first m-sequence or the second m-sequence may be initialized according to a cell ID, a slot number in one radio frame, an OFDM symbol index in a slot, a CP type, and the like for every OFDM symbol. The imitation random sequence generator generates a random sequence at the beginning of each radio frame

Lt; / RTI &gt;

PUCCH and PUSCH may have different sequence shift patterns. The sequence shift pattern f _ss ^PUCCH = N _ID ^cell mod 30 of the ^PUCCH . PUSCH sequence shift pattern f _ss ^PUSCH = (f _ss ^PUCCH + _ss ) mod 30, and Δ _ss ∈ {0, 1, ..., , 29} can be configured by an upper layer.

Sequence hopping can be applied only to reference signal sequences longer than 6N _sc ^RB . At this time, the basic sequence index v in the basic sequence group of the slot index n _s can be defined by Equation (9).

<Number 9>

로 초기화될 수 있다.c (i) can be represented by the example of Equation (8), and the application of the sequence hopping can be indicated by an upper layer. The imitation random sequence generator generates a random sequence at the beginning of each radio frame

Lt; / RTI &gt;

The DMRS sequence for the PUSCH can be defined by Equation (10).

<Number 10>

In Equation (10), m = 0, 1, ... , N = 0, ... , And M _sc ^RS- 1. M _sc ^RS = M _sc ^PUSCH .

Is given as a cyclic shift value? = 2? N _cs / 12 in the slot, and n _cs can be defined by Equation (11).

<Number 11>

In Equation (11), n _DMRS ⁽¹⁾ is indicated by a parameter transmitted in an upper layer, and Table 3 shows an example of a correspondence relationship between the parameter and n _DMRS ⁽¹⁾ .

Parameter n _DMRS ⁽¹⁾ 0 0 One 2 2 3 3 4 4 6 5 8 6 9 7 10

N _DMRS ⁽²⁾ in Equation (11 ⁾ can be defined by a cyclic shift field in DCI format 0 for the transport block corresponding to the PUSCH transmission. The DCI format is transmitted on the PDCCH. The cyclic shift field may have a length of 3 bits.

Table 4 is an example of the correspondence relationship between the cyclic shift field and n _DMRS ⁽²⁾ .

Cyclic shift field in DCI format 0 n _DMRS ⁽²⁾ 000 0 001 6 010 3 011 4 100 2 101 8 110 10 111 9

Table 5 is another example of the correspondence relationship between the cyclic shift field and n _DMRS ⁽²⁾ .

Cyclic shift field in DCI format 0 n _DMRS ⁽²⁾ 000 0 001 2 010 3 011 4 100 6 101 8 110 9 111 10

In the case where the PDCCH including the DCI format 0 is not transmitted in the same transport block, the first PUSCH is scheduled semi-persistently in the same transport block, or the first PUSCH in the same transport block is random access n _DMRS ⁽²⁾ may be zero if it is scheduled by a response grant.

n _PRS (n _s ) can be defined by equation (12).

<Number 12>

로 초기화될 수 있다.c (i) can be represented by the example of equation (8) and can be applied cell-specfic of c (i). The imitation random sequence generator generates a random sequence at the beginning of each radio frame

Lt; / RTI &gt;

The DMRS sequence r ^PUSCH is multiplied with an amplitude scaling factor? _PUSCH and mapped to a sequence starting from r ^PUSCH (0) to the physical transport block used for the corresponding PUSCH transmission. The DMRS sequence is mapped to a fourth OFDM symbol (OFDM symbol index 3) for a normal CP and a third OFDM symbol (OFDM symbol index 2) for an extended CP in one slot.

11 shows an example of a structure of a reference signal transmitter for demodulation.

11, the reference signal transmitter 60 includes a subcarrier mapper 61, an IFFT unit 62, and a CP inserting unit 63. Unlike the transmitter 50 of FIG. 6, the reference signal transmitter 60 is directly generated in the frequency domain without passing through the DFT unit 51, and is mapped to subcarriers through the subcarrier mapper 61. At this time, the subcarrier mapper can map the reference signal to the subcarrier using the centralized mapping method of FIG. 7 (a).

12 is an example of a structure of a subframe in which a reference signal is transmitted.

The structure of the subframe in FIG. 12- (a) shows the case of a normal CP. The subframe includes a first slot and a second slot. Each of the first slot and the second slot includes 7 OFDM symbols. The 14 OFDM symbols in the subframe are indexed from 0 to 13 symbols. A reference signal can be transmitted through an OFDM symbol having symbol indices 3 and 10. The data can be transmitted through the remaining OFDM symbols except for the OFDM symbol to which the reference signal is transmitted. The structure of the subframe in Fig. 12- (b) shows the case of the extended CP. The subframe includes a first slot and a second slot. Each of the first slot and the second slot includes 6 OFDM symbols. The 12 OFDM symbols in the subframe are indexed from 0 to 11 symbols. A reference signal is transmitted through an OFDM symbol having symbol indices 2 and 8. Data is transmitted through the remaining OFDM symbols except for the OFDM symbol to which the reference signal is transmitted. Although not shown in FIG. 12, a sounding reference signal (SRS) may be transmitted through an OFDM symbol in a subframe.

13 shows an example in which OCC is applied to the reference signal.

The reference signal sequence for layer 0 and the reference signal sequence for layer 1 in one subframe are all mapped to the 4 th OFDM symbol of the 1st slot and the 4 th OFDM symbol of the 2nd slot. The same sequence is mapped to two OFDM symbols in each layer. At this time, the reference signal sequence for layer 0 is multiplied by the orthogonal sequence of [+1 +1] and mapped to the OFDM symbol. The reference signal sequence for layer 1 is multiplied by an orthogonal sequence of [+1 -1] and mapped to an OFDM symbol. That is, when the reference signal sequence for layer 1 is mapped to the second slot in one subframe, -1 is multiplied and mapped.

When the OCC is applied as described above, the base station receiving the reference signal can estimate the channel of layer 0 by adding the reference signal sequence transmitted in the first slot and the reference signal sequence transmitted in the second slot. Also, the BS can estimate the channel of the layer 1 by subtracting the reference signal sequence transmitted in the second slot from the reference signal sequence transmitted in the first slot. That is, the base station can distinguish reference signals transmitted from each layer by applying OCC. Therefore, a plurality of reference signals can be transmitted using the same resources. If the possible cyclic shift value is 6, the number of layers or users that can be multiplexed by applying the OCC can be increased to 12. [

In this example, it is assumed that a binary format of [+1 +1] or [+1 or -1] is used as the OCC, but various types of orthogonal sequences can be used as the OCC. For example, orthogonal sequences such as Walsh codes, DFT coefficients, CAZAC sequences, and the like may be applied to the OCC.

Also, by applying OCC, reference signals can be more easily multiplexed between users having different bandwidths.

FIG. 14 shows an example in which reference signals transmitted from two terminals having different bandwidths are multiplexed by applying OCC.

The first terminal and the second terminal transmit reference signals with different bandwidths. The first terminal UE # 0 transmits the reference signal through the first bandwidth BW0 and the second terminal UE # 1 transmits the reference signal through the second bandwidth BW1. The reference signal transmitted by the first mobile station is multiplied by the orthogonal sequence of [+1 +1] in the first slot and the second slot, respectively. The reference signal transmitted by the second UE is multiplied by the orthogonal sequence of [+1 -1] in the first slot and the second slot, respectively. Accordingly, the base station receiving the reference signal from the first terminal and the second terminal can perform channel estimation by separating the two terminals.

Hereinafter, MIMO (Multiple-Input Multiple-Output) will be described. The MIMO scheme can be divided into two methods, Per-Antenna Rate Control (PARC) and Per-User Unitary Rate Control (PU2RC).

15 is a block diagram illustrating an example of a PARC technique.

PARC is a technique for performing MIMO using a basic spatial multiplexing method. Space resources may be allocated to one terminal or may be allocated to a plurality of terminals through the PARC scheme. When a spatial resource is allocated to one terminal, it is referred to as a single user (SU) MIMO, and when allocated to a plurality of terminals, it is referred to as a multi-user (MU) MIMO.

FIG. 15 shows a case where the PARC scheme is applied to SU-MIMO. Assuming three terminals, the base station selects one of the three terminals to which data is to be transmitted by a plurality of antennas. When a first terminal is selected, a Modulation and Coding Scheme (MCS) level for a stream of each of a plurality of antennas is determined, and data is transmitted to a first terminal through a plurality of antennas via an OFDMA modulator. Each terminal transmits a CQI (Channel Quality Indicator) for a plurality of antennas of the corresponding terminal to the base station.

16 is a block diagram showing an example of the PU2RC technique.

PU2RC performs MIMO by precoding data based on a codebook to reduce interference of multiple users. In step S100, the base station groups the streams for a plurality of terminals (100) to generate a plurality of group streams, and schedules and multiplexes (101) the group streams generated in step S101. The base station precodes (102) each group stream using a precoding matrix corresponding to the group, and transmits the group stream through a plurality of antennas. In precoding, a unitary codebook based precoding can be used. Each terminal feeds back a preferred precoding matrix, a transmission antenna, and a CQI corresponding to each transmission antenna to the base station, and the base station can use feedback information in scheduling. By performing MIMO using precoding as described above, spatial multi-user interference can be reduced, and high performance gain can be obtained in an MU-MIMO environment.

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

17 shows an uplink HARQ.

The base station receiving the uplink data 110 on the PUSCH from the terminal transmits the ACK / NACK signal 111 on the PHICH after a certain subframe has elapsed. The ACK / NACK signal 111 becomes an ACK signal when the uplink data 110 is successfully decoded and becomes a NACK signal when decoding of the uplink data 110 fails. When a NACK signal is received, the UE can receive ACK information or transmit retransmission data 120 for the uplink data 110 up to the maximum number of retransmissions. The base station may transmit an ACK / NACK signal 121 for retransmission data 120 on the PHICH.

The PHICH will be described below.

18 is a block diagram showing that an ACK / NACK signal is transmitted on the PHICH.

Since the LTE system does not support SU-MIMO in the uplink, one PHICH transmits only one bit ACK / NACK for a PUSCH of a single terminal, i.e., a single stream. In step S130, a 1-bit ACK / NACK is coded into 3 bits using a repetition code having a code rate of 1/3. In step S131, the coded ACK / NACK is modulated by BPSK (Binary Phase Key-Shifting) to generate three modulation symbols. In step S132, the modulation symbol is spread using spreading factor SF = 4 in the normal CP structure and SF = 2 in the extended CP structure. An orthogonal sequence is used for spreading the modulation symbols, and the number of orthogonal sequences used is SF * 2 to apply I / Q multiplexing. SF * Spreaded PHICHs using two orthogonal sequences can be defined as one PHICH group. In step S133, layer mapping is performed on the spread symbols. In step S124, the layer mapped symbols are mapped and transmitted.

The PHICH carries HARQ ACK / NACK according to the PUSCH transmission. A plurality of PHICHs mapped to the same set of resource elements form a PHICH group, and each PHICH in the PHICH group is divided by a different orthogonal sequence. In the FDD system, the N _PHICH ^{group, which} is the number of _PHICH ^groups, is constant in all subframes and can be determined by Equation (13).

<Number 13>

In Equation (13), Ng is transmitted from an upper layer through a PBCH (Physical Broadcast Channel), and Ng? {1/6, 1/2, 1, 2}. The PBCH carries the system information necessary for the terminal to communicate with the base station, and the system information transmitted through the PBCH is called the master information block (MIB). In comparison, the system information transmitted through the Physical Downlink Control Channel (PDCCH) is referred to as SIB (System Information Block). N _RB ^DL is a downlink bandwidth configuration expressed by a multiple of N _sc ^RB , which is the size of a resource block in the frequency domain. The PHICH group index n _PHICH ^group is an integer from 0 to N _PHICH ^group -1.

The resources used for the PHICH may be determined based on the smallest PRB index at the time of PUSCH resource allocation and the cyclic shift value of DMRS (Demodulation Reference Signal) transmitted in the UL grant. The PHICH resource mapping (the PHICH resources) may be represented by the index pair (n _PHICH ^group, n _PHICH ^seq), n _PHICH ^group is a PHICH group index, n _PHICH ^seq denotes an orthogonal sequence index within the PHICH group. (N _PHICH ^group , n _PHICH ^seq ) can be determined by Equation (14).

<Number 14>

n _DMRS can be determined based on the Cyclic Shift for DMRS field in DCI format 0 according to Table 6. &lt; tb &gt;&lt; TABLE &gt;

Cyclic Shift for DMRS Field in DCI format 0 n _DMRS 000 0 001 One 010 2 011 3 100 4 101 5 110 6 111 7

Also, when the PDCCH including the DCI format 0 is not transmitted in the same transport block, the first PUSCH is scheduled semi-persistently in the same transport block, or the first PUSCH is scheduled in the same transport block as a random access grant n _DMRS may be zero if it is scheduled by a response grant.

N _SF ^PHICH in Equation (14) is a spreading factor (SF) used for PHICH modulation in FIG. I _{PRB_RA The} ^lowest index is the smallest PRB index among the PRBs of the slot to which the PUSCH corresponding to the corresponding PHICH is transmitted. I _PHICH is a value of 0 or 1.

The orthogonal sequence used for the PHICH can be determined according to Table 7. The orthogonal sequence used may vary depending on the n _PHICH ^seq value or the CP structure.

Sequence index (n _PHICH ^seq ) Orthogonal sequence Normal CP (N _SF ^PHICH = 4) Extended CP (N _SF ^PHICH = 2) 0 [+1 +1 +1 +1] [+1 +1] One [+1 -1 +1 -1] [+1 -1] 2 [+1 +1 -1 -1] [+ j + j] 3 [+1 -1 -1 +1] [+ j-j] 4 [+ j + j + j + j] - 5 [+ j - j + j - j] - 6 [+ j + j - j - j] - 7 [+ j-j-j + j] -

A plurality of PHICHs can be allocated at the same time. In particular, a plurality of PHICHs can be allocated in a system such as a carrier aggregation system, an MU-MIMO, and a cooperative multi-point (CoMP) transmission scheme.

19 is a block diagram illustrating a MIMO transmission process in an uplink using an SC-FDMA transmission scheme.

A plurality of codewords may be used to perform the MIMO transmission. Assuming that the number of codewords is two, each codeword is scrambled in step S140, the codeword is mapped to a modulation symbol in step S141, and each symbol is mapped to each layer in step S142. In step S143, the layers are DFT spread, and in step S144, the respective layers are precoded. The stream precoded in step S145 is mapped to the resource element and transmitted through each antenna through the SC-FDMA signal generator generated in step S146. In order to facilitate HARQ for the uplink, two independent ACK / NACK signals are required for each codeword.

20 is an example of a PHICH resource allocation.

20, the horizontal axis represents the PHICH group index, and the vertical axis represents the orthogonal sequence index in the PHICH group. The PHICH resource corresponding to the smallest PRB index and the n _DRMS value to which the PUSCH is allocated is determined in each terminal. For example, the PHICH resource can be determined by Equation (23). n _DMRS can distinguish PHICH resources for up to 8 users in MU-MIMO environment. Thus, it is possible to prevent the PHICH resources from colliding with each other when a plurality of PHICHs are transmitted.

A resource element (resource element # 0) having an index (0,0) and a resource element (resource element # 1) having an index (1, 0) includes a PHICH corresponding to two PUSCHs transmitted through two antennas Resources are allocated. At this time, the smallest PRB index to which the PUSCH is transmitted may be the same and n _DMRS may be different from each other. Also, a PHICH resource corresponding to the PUSCH transmitted from the second terminal is allocated to the resource element (resource element # 2) having the index (2,0). Likewise, a PHICH resource corresponding to the PUSCH transmitted from the third terminal and the fourth terminal, respectively, is allocated to the resource element (resource element # 3) having the index (0,1) and the resource element (resource element # Respectively.

However, when data is multiplexed by applying OCC, it is possible to transmit a plurality of data or a plurality of reference signals using the same resource by applying different _OCCs with the same PRB index and n _DMRS . At this time, the corresponding plurality of PHICHs use the same resources in Equation (14), and PHICH resources collide. Therefore, a method for preventing collision of PHICH resources when a plurality of PHICHs are allocated is required.

Hereinafter, a method for solving the collision problem of the PHICH resource will be described. The present invention proposes a method of assigning a cyclic shift value for DMRS to a plurality of antennas in each terminal so that each terminal does not collide PHICH resources transmitting ACK / NACK signals in an uplink MU-MIMO environment .

As mentioned in Equation (14), the PHICH resource can be assigned by Equation (15).

<Number 15>

Assuming that 2N _SF ^PHICH = 4 and N _PHICH ^group = 4 when the extended CP structure has n _DMRS = 0 and n _DMRS = 4, n _PHICH ^group indicating location where PHICH resources are allocated and n _PHICH ^seq can be equal. That is, even when different n _DMRSs are allocated, PHICH resources may collide with each other. For example, PHICH resources may collide with each other if the first terminal uses n _DMRS = 0 and the second terminal uses n _DMRS = 4. Also, when n _DMRS allocated to each terminal is 1 and 5, 2 and 6 or 3 and 7, respectively, PHICH resource collisions may occur as well. At this time, if each terminal has a single antenna, the cyclic shift value of the DMRS on the DCI format 0 can be flexibly allocated in the scheduler so that the base station does not collide with PHICH resources. However, when each terminal has a plurality of antennas, a different cyclic shift value is assigned to each terminal, and a different cyclic shift value needs to be assigned to each antenna in a terminal. Therefore, A method is needed to reduce the probability of collision of resources.

Therefore, in the present invention, when a cyclic shift value is assigned to a plurality of layers in one terminal, a cyclic shift value capable of causing collision of PHICH resources to each layer is assigned to each layer, We propose a method to prevent collision. That is, for example, a method of reducing the collision probability of PHICH resources among a plurality of terminals by assigning n _DMRS = 0 and n _DMRS = 4, as described above, to a plurality of layers in one terminal is proposed.

The present invention will be described by way of various examples. In the following description, different cyclic shift values are allocated to a plurality of layers, respectively, but different cyclic shift values may be assigned to a plurality of antennas. In addition, the different cyclic shift values assigned to the plurality of layers can be implicitly assigned based on the cyclic shift value of the DMRS transmitted through the DCI format 0. In the following description, the cyclic shift value of DMRS transmitted through DCI format 0 is set to n _DMRS = A.

First, the case where the present invention is applied when a single codeword or ACK / NACK signals for a plurality of codewords are transmitted on one PHICH will be described.

A different cyclic shift value may be allocated to each of the MSs performing uplink MU-MIMO transmission.

FIG. 21 shows an example of allocation of a cyclic shift value for two UEs according to the proposed HARQ performing method. FIG. 21 shows a case where each terminal has rank-2 transmission with two transmit antennas. That is, two different cyclic shift values are required for each terminal.

Referring to FIG. 21, A and (A + 4) mod8 are assigned as cyclic shift values to the two layers of the first UE 1, respectively. In addition, B and (B + 4) mod8 are assigned to the two layers of the second terminal UE2 as cyclic shift values, respectively. A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. For example, the cyclic shift values for the respective antennas of the first terminal are assigned 0 and 4, respectively, and the cyclic shift values for the antennas of the second terminal are assigned 1 and 5, respectively. Accordingly, the probability of collision of the PHICH resources between the terminals can be reduced. In addition, the cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed. For example, (A + 4) mod8 may be assigned as the cyclic shift value to the first layer of the first terminal, and A may be assigned to the second layer as the cyclic shift value.

In addition, when each terminal has rank-2 transmission with two transmit antennas, the cyclic shift value according to the present invention can be assigned to four terminals. Since each terminal transmits rank-2, two different cyclic shift values are required for each terminal. Table 8 shows an example in which a cyclic shift value is assigned to each of two layers in four terminals.

[0035] The second terminal The third terminal The fourth terminal First layer A B C D Second layer (A + 4) mod8 (B + 4) mod8 (C + 4) mod8 (D + 4) mod8

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. C is a different value from A, (A + 4) mod8, B and (B + 4) mod8, and can have any one of 0 to 7. D is a different value from A, (A + 4) mod8, B, (B + 4) mod8, C and (C + 4) mod8 and can have any one of 0 to 7. In addition, the cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

In addition, when each terminal has rank-4 transmission with four transmission antennas, the cyclic shift value according to the present invention can be allocated to two terminals. Since each terminal transmits rank-4, four different cyclic shift values are required for each terminal. Table 9 and Table 10 show examples in which a cyclic shift value is assigned to each of four layers in two terminals.

[0035] The second terminal [0035] The second terminal First layer A C A C Second layer (A + 4) mod8 (C + 4) mod8 B D Third layer B D (A + 4) mod8 (C + 4) mod8 Fourth layer (B + 4) mod8 (D + 4) mod8 (B + 4) mod8 (D + 4) mod8

[0035] The second terminal [0035] The second terminal First layer A B A B Second layer (A + 2) mod8 (B + 2) mod8 (A + 4) mod8 (B + 4) mod8 Third layer (A + 4) mod8 (B + 4) mod8 (A + 2) mod8 (B + 2) mod8 Fourth layer (A + 6) mod8 (B + 6) mod8 (A + 6) mod8 (B + 6) mod8

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. C is a different value from A, (A + 4) mod8, B and (B + 4) mod8, and can have any one of 0 to 7. D is a different value from A, (A + 4) mod8, B, (B + 4) mod8, C and (C + 4) mod8 and can have any one of 0 to 7. In addition, the cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

In addition, when each terminal has rank-4 transmission with four transmit antennas, a cyclic shift value according to the present invention can be assigned to four terminals. Since each terminal transmits rank-4, four different cyclic shift values are required for each terminal. Tables 11 and 12 show examples in which a cyclic shift value is assigned to each of four layers in four terminals.

[0035] The second terminal The third terminal The fourth terminal First layer A A C D Second layer (A + 2) mod8 (B + 2) mod8 (C + 2) mod8 (D + 2) mod8 Third layer (A + 4) mod8 (B + 4) mod8 (C + 4) mod8 (D + 4) mod8 Fourth layer (A + 6) mod8 (B + 6) mod8 (C + 6) mod8 (D + 6) mod8

[0035] The second terminal The third terminal The fourth terminal First layer A A C D Second layer (A + 4) mod8 (B + 4) mod8 (C + 4) mod8 (D + 4) mod8 Third layer (A + 2) mod8 (B + 2) mod8 (C + 2) mod8 (D + 2) mod8 Fourth layer (A + 6) mod8 (B + 6) mod8 (C + 6) mod8 (D + 6) mod8

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. C is a different value from A, (A + 4) mod8, B and (B + 4) mod8, and can have any one of 0 to 7. D is a different value from A, (A + 4) mod8, B, (B + 4) mod8, C and (C + 4) mod8 and can have any one of 0 to 7. In addition, the cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

Alternatively, it is possible to allocate the same cyclic shift value to each of the MSs performing uplink MU-MIMO transmission, and distinguish each MS using different OCC indexes for reference signal multiplexing.

Equation (16) is an example of a formula for assigning a PHICH resource by applying an OCC index.

<Number 16>

N _OCC indicating the OCC index in Equation (16) can have a length of up to 3 bits. That is, the maximum number of terminals that can be classified based on the OCC index in the MU-MIMO transmission environment is 8. In the following description, it is assumed that n _OCC has a length of 1 bit and has a value of either 0 or 1. It is also assumed that a DMRS is transmitted in two SC-FDMA symbols in a subframe.

FIG. 22 shows an example of allocation of a cyclic shift value for two UEs according to the proposed HARQ performing method. FIG. 22 shows a case where each terminal has rank-2 transmission with two transmit antennas.

Referring to FIG. 22, A and (A + 4) mod8 are assigned cyclic shift values to two layers of the first UE 1, respectively. Likewise, A and (A + 4) mod8 are assigned to the two layers of the second terminal UE2 as cyclic shift values, respectively. However, OCC indices are assigned to the first terminal and the second terminal differently from 0 to 1, respectively. Accordingly, the first terminal and the second terminal can be distinguished from each other. A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. Accordingly, the probability of collision of the PHICH resources between the terminals can be reduced. In addition, the cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed. For example, (A + 4) mod8 may be assigned as the cyclic shift value to the first layer of the first terminal, and A may be assigned to the second layer as the cyclic shift value.

In addition, when each terminal has rank-2 transmission with two transmit antennas, the cyclic shift value according to the present invention can be assigned to four terminals. Table 13 shows an example in which a cyclic shift value is assigned to each of two layers in four terminals.

[0035] The second terminal The third terminal The fourth terminal First layer A B A B Second layer (A + 4) mod8 (B + 4) mod8 (A + 4) mod8 (B + 4) mod8 OCC Index 0 One 0 One

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed. Also, the OCC index may be changed in the UE to which the same cyclic shift value is assigned.

In Table 13, it is assumed that the OCC index has a length of 1 bit and has a value of either 0 or 1. However, the length of the OCC index can be increased up to 3 bits. If the OCC index is 2 bits, the OCC index may be assigned to 0 to 3 for the first to fourth terminals. Table 14 shows another example in which a cyclic shift value is assigned to each of two layers in four terminals.

[0035] The second terminal The third terminal The fourth terminal First layer A A A A Second layer (A + 4) mod8 (A + 4) mod8 (A + 4) mod8 (A + 4) mod8 OCC Index 0 One 2 3

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed. Also, the OCC index may be changed in the UE to which the same cyclic shift value is assigned.

In addition, when each terminal has rank-4 transmission with four transmission antennas, the cyclic shift value according to the present invention can be allocated to two terminals. Table 15 shows an example in which a cyclic shift value is assigned to each of four layers in two terminals.

[0035] The second terminal First layer A A Second layer (A + 2) mod8 (A + 2) mod8 Third layer (A + 4) mod8 (A + 4) mod8 Fourth layer (A + 6) mod8 (A + 6) mod8 OCC Index 0 One

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed. Also, the OCC index may be changed in the UE to which the same cyclic shift value is assigned.

In addition, when each terminal has rank-4 transmission with four transmit antennas, a cyclic shift value according to the present invention can be assigned to four terminals. Table 16 shows an example in which a cyclic shift value is assigned to each of four layers in four UEs. At this time, the OCC index has a length of 1 bit and can have either 0 or 1 value.

[0035] The second terminal The third terminal The fourth terminal First layer A A B B Second layer (A + 2) mod8 (A + 2) mod8 (B + 2) mod8 (B + 2) mod8 Third layer (A + 4) mod8 (A + 4) mod8 (B + 4) mod8 (B + 4) mod8 Fourth layer (A + 6) mod8 (A + 6) mod8 (B + 6) mod8 (B + 6) mod8 OCC Index 0 One 0 One

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed. Also, the OCC index may be changed in the UE to which the same cyclic shift value is assigned.

Table 17 shows another example in which a cyclic shift value is assigned to each of four layers in four terminals. In this case, the OCC index has a length of 2 bits and can have any one of 0 to 3.

[0035] The second terminal The third terminal The fourth terminal First layer A A A A Second layer (A + 2) mod8 (A + 2) mod8 (A + 2) mod8 (A + 2) mod8 Third layer (A + 4) mod8 (A + 4) mod8 (A + 4) mod8 (A + 4) mod8 Fourth layer (A + 6) mod8 (A + 6) mod8 (A + 6) mod8 (A + 6) mod8 OCC Index 0 One 2 3

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed. Also, the OCC index may be changed in the UE to which the same cyclic shift value is assigned.

The present invention can also be applied to a case where ACK / NACK signals for a plurality of codewords are transmitted on a plurality of PHICHs. As in the case where ACK / NACK signals for a plurality of codewords are transmitted on one PHICH, by allocating a cyclic shift value that can cause PHICH resources to collide with a plurality of layers in one terminal, The probability of collision of PHICH resources can be reduced. However, in order to allocate a plurality of PHICHs to each terminal, it is necessary to set at least two different cyclic shift values so that collision of resources allocated to each PHICH does not occur.

A different cyclic shift value may be allocated to each of the MSs performing uplink MU-MIMO transmission.

When each terminal has rank-2 transmission with two transmit antennas, a cyclic shift value according to the present invention can be assigned to two terminals. Since each terminal performs rank-2 transmission, two different cyclic shift values are required for each terminal, and it is assumed that two PHICH resources are allocated to each terminal. Table 18 shows an example in which a cyclic shift value for the first PHICH is allocated to two layers in two terminals.

First layer Second layer [0035] A (A + 4) mod8 The second terminal B (B + 4) mod8

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

If the rule to which the PHICH resource is allocated and the rule to which the cyclic shift value between each layer is allocated are different, the second PHICH resource in the first terminal may be allocated based on n _DMRS = (A +?) Mod8. Also, the second PHICH resource at the second terminal may be allocated based on n _DMRS = (B +?) Mod8. a may have a value of any one of 1 to 8, and may have the same value when applied to the first terminal and the second terminal.

In addition, in the case where the rule to which the PHICH resource is allocated and the rule to which the cyclic shift value between each layer is allocated are identical, in order to prevent collision of PHICH resources among different codewords in one UE, Shift values can be assigned to each layer. That is, a cyclic shift value can be assigned to each layer as shown in Table 19.

First layer Second layer [0035] A (A +?) Mod8 The second terminal B (B +?) Mod8

alpha may have a value of any one of 1 to 8. A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and can have any one of 0 to 7 as in A. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

In the case where each terminal has rank-2 transmission while having two transmission antennas, a cyclic shift value according to the present invention can be assigned to four terminals. Since each terminal performs rank-2 transmission, two different cyclic shift values are required for each terminal, and it is assumed that two PHICH resources are allocated to each terminal. Table 20 shows an example in which a cyclic shift value for the first PHICH is allocated to two layers in four UEs.

First layer Second layer [0035] A (A + 4) mod8 The second terminal B (B + 4) mod8 The third terminal C (C + 4) mod8 The fourth terminal D (D + 4) mod8

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. C is a different value from A, (A + 4) mod8, B and (B + 4) mod8, and can have any one of 0 to 7. D is a different value from A, (A + 4) mod8, B, (B + 4) mod8, C and (C + 4) mod8 and can have any one of 0 to 7. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

The second PHICH resources in the first to fourth UEs are n _DMRS = (A + α) mod8, n _DMRS = ( B +?) Mod8, n _DMRS = (C +?) Mod8 and n _DMRS = (D +?) Mod8. alpha may have a value from 1 to 8, and may have the same value when applied to the first to fourth terminals.

In addition, in the case where the rule to which the PHICH resource is allocated and the rule to which the cyclic shift value between each layer is allocated are identical, in order to prevent collision of PHICH resources among different codewords in one UE, Shift values can be assigned to each layer. That is, a cyclic shift value can be assigned to each layer as shown in Table 21.

First layer Second layer [0035] A (A +?) Mod8 The second terminal B (B +?) Mod8 The third terminal C (C +?) Mod8 The fourth terminal D (D +?) Mod8

alpha may have a value of any one of 1 to 8. A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and can have any one of 0 to 7 as in A. C is a different value from A and B, and can have any one of 0 to 7. D is a value different from A, B, and C, and can have any one of 0 to 7. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

When each terminal has rank-4 transmission with four transmit antennas, the cyclic shift value according to the present invention can be assigned to two terminals. Since each terminal transmits rank-4, it is assumed that four cyclic shift values are required for each terminal, and two PHICH resources are allocated to each terminal. Table 22 shows an example in which a cyclic shift value for the first PHICH is allocated to four layers in two UEs.

First layer Second layer Third layer Fourth layer [0035] A (A + 4) mod8 (A + 2) mod8 (A + 6) mod8 The second terminal B (B + 4) mod8 (B + 2) mod8 (B + 6) mod8

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

The second PHICH resources in the first and second terminals are n _DMRS = (A + α) mod8 and n _DMRS = ((A + α) mod8), respectively, when the rule to which the PHICH resource is allocated and the rule to which the cyclic- B + a) mod8. a may have a value of any one of 1 to 8, and may have the same value when applied to the first terminal and the second terminal.

In addition, in the case where the rule to which the PHICH resource is allocated and the rule to which the cyclic shift value between each layer is allocated are identical, in order to prevent collision of PHICH resources among different codewords in one UE, Shift values can be assigned to each layer. That is, a cyclic shift value can be assigned to each layer as shown in Table 23.

First layer Second layer Third layer Fourth layer [0035] A (A +?) Mod8 (A + 4) mod8 (A +? + 4) mod8 The second terminal B (B +?) Mod8 (B + 4) mod8 (B +? + 4) mod8

alpha may have a value of any one of 1 to 8. A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and can have any one of 0 to 7 as in A. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

When each terminal has rank-4 transmission with four transmit antennas, a cyclic shift value according to the present invention can be assigned to four terminals. Since each terminal transmits rank-4, it is assumed that four cyclic shift values are required for each terminal, and two PHICH resources are allocated to each terminal. Table 24 shows an example in which a cyclic shift value for the first PHICH is allocated to four layers in four UEs.

First layer Second layer Third layer Fourth layer [0035] A (A + 4) mod8 (A + 2) mod8 (A + 6) mod8 The second terminal B (B + 4) mod8 (B + 2) mod8 (B + 6) mod8 The third terminal C (C + 4) mod8 (C + 2) mod8 (C + 6) mod8 The fourth terminal D (D + 4) mod8 (D + 2) mod8 (D + 6) mod8

A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and (A + 4) mod8, and can have any one of 0 to 7 similarly to A. C is a different value from A, (A + 4) mod8, B and (B + 4) mod8, and can have any one of 0 to 7. D is a different value from A, (A + 4) mod8, B, (B + 4) mod8, C and (C + 4) mod8 and can have any one of 0 to 7. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

The second PHICH resources in the first to fourth UEs are n _DMRS = (A + α) mod8, n _DMRS = ( B +?) Mod8, n _DMRS = (C +?) Mod8 and n _DMRS = (D +?) Mod8. alpha may have a value from 1 to 8, and may have the same value when applied to the first to fourth terminals.

In addition, in the case where the rule to which the PHICH resource is allocated and the rule to which the cyclic shift value between each layer is allocated are identical, in order to prevent collision of PHICH resources among different codewords in one UE, Shift values can be assigned to each layer. That is, a cyclic shift value can be assigned to each layer as shown in Table 25.

First layer Second layer Third layer Fourth layer [0035] A (A +?) Mod8 (A + 4) mod8 (A +? + 4) mod8 The second terminal B (B +?) Mod8 (B + 4) mod8 (B +? + 4) mod8 The third terminal C (C +?) Mod8 (C +?) Mod8 (C +? + 4) mod8 The fourth terminal D (D +?) Mod8 (D +?) Mod8 (D +? + 4) mod8

alpha may have a value of any one of 1 to 8. A is a cyclic shift value of the DMRS transmitted on DCI format 0, and may have a value of 0 to 7. B is a different value from A and can have any one of 0 to 7 as in A. C is a different value from A and B, and can have any one of 0 to 7. D is a value different from A, B, and C, and can have any one of 0 to 7. The cyclic shift value assigned to each layer in each terminal or the order of the cyclic shift value assigned between the terminals may be changed.

On the other hand, since the number of PHICH sequences that can be allocated to one PHICH group is four in the extended CP structure, a plurality of PHICHs for a plurality of codewords can not be supported when the number of terminals is four or more. Therefore, when the number of terminals is four or more, the number of PHICH sequences in one PHICH group can be increased to support a plurality of PHICHs. Alternatively, a plurality of PHICHs may be supported by applying new parameters not defined in LTE rel-8. The new parameter may be a static, semi-static or dynamic parameter and may be signaled on the PDCCH via Radio Resource Control (RRC) signaling or via DCI format.

Also, when a plurality of PHICH resources are allocated, the same cyclic shift value is allocated to each UE performing uplink MU-MIMO transmission as shown in FIG. 22, and different OCC indexes are used for reference signal multiplexing Each terminal can be distinguished.

FIG. 23 is a block diagram illustrating an embodiment of a method for performing the HARQ. In step S100, the terminal transmits the uplink data on the PUSCH to the base station. In step S110, the UE receives an ACK / NACK signal indicating the reception of the uplink data on the PHICH corresponding to the PUSCH from the base station through a plurality of layers. In this case, the PHICH resources for the plurality of layers do not overlap with each other, and the PHICH resources may have different cyclic shift values.

24 shows an embodiment of the proposed downlink control signal transmission method.

In step S300, the base station generates a plurality of PHICH sequences for a plurality of terminals. In step S310, the base station maps the generated plurality of PHICH sequences to downlink resources. At this time, the resources to which the plurality of PHICH sequences are mapped in the respective terminals do not overlap with each other. In step S320, the base station transmits the mapped PHICH sequences to the UE.

25 is a block diagram illustrating 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 a radio frequency unit 830. Processor 810 implements the proposed functionality, process and / or method. The layers of the air interface protocol may be implemented by the processor 810. Processor 810 allocates a PHICH resource for ACK / NACK signaling. The memory 820 is coupled to the processor 810 and stores various information for driving the processor 810. [ The RF unit 830 is connected to the processor 810 and transmits and / or receives a radio signal and transmits an ACK / NACK signal through the allocated PHICH resource.

The terminal 900 includes a processor 910, a memory 920, and an RF unit 930. The RF unit 930 is connected to the processor 910 and transmits uplink data on the PUSCH. Processor 910 implements the proposed functionality, process and / or method. The layers of the air interface protocol may be implemented by the processor 910. Processor 910 processes the received ACK / NACK signal. The memory 920 is coupled to the processor 910 and stores various information for driving the processor 910. [

Processors 810 and 910 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. Memory 820 and 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage media, and / or other storage devices. The RF units 830 and 930 may include a baseband circuit for processing radio signals. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The modules may be stored in memories 820 and 920 and executed by processors 810 and 910. The memories 820 and 920 may be internal or external to the processors 810 and 910 and may be coupled to the processors 810 and 910 in various well known means.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (15)

A method for performing HARQ by a terminal in a wireless communication system,
Transmits uplink data on a Physical Uplink Shared Channel (PUSCH)
Receiving an acknowledgment / non-acknowledgment (ACK / NACK) signal indicating a reception of the uplink data through a plurality of layers on a Physical Hybrid-ARQ Indicator Channel (PHICH) corresponding to the PUSCH,
The downlink resources to which the PHICHs are mapped for each of the plurality of layers do not overlap with each other,
Wherein a downlink resource to which a PHICH is mapped for each of the plurality of layers is determined based on a different cyclic shift value allocated to each of the plurality of layers,
The downlink resource to which the PHICH is mapped to each of the plurality of layers is determined based on the following equation,

N _PHICH ^group is the PHICH group index, n _PHICH ^seq is the orthogonal sequence index in the PHICH group, I _{PRB_RA} ^lowest index is the index of the smallest PRB among the PRBs mapped to the PUSCH, and _DMRS is the uplink DMRS A demodulation reference signal cyclic shift parameter, an N _PHICH ^group , a number of PHICH groups, an N _SF ^PHICH , a spreading factor (SF), and an I _PHICH value of 0 or 1. The method according to claim 1,
When the number of the plurality of layers is two,
Wherein the cyclic shift value allocated to each of the plurality of layers is different by 4. The method according to claim 1,
When the number of the plurality of layers is four,
Wherein the cyclic shift value allocated to each of the plurality of layers is different by 2. &lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein one of the cyclic shift values allocated to each of the plurality of layers is determined by a cyclic shift field in a downlink control information (DCI) transmitted through a physical downlink control channel (PDCCH). A terminal for performing HARQ in a wireless communication system,
A radio frequency (RF) unit for transmitting and receiving a radio signal;
And a processor coupled to the RF unit,
Transmits uplink data on a Physical Uplink Shared Channel (PUSCH) through the RF unit,
Receiving an acknowledgment / non-acknowledgment (ACK / NACK) signal through the plurality of layers on an PHICH (Physical Hybrid-ARQ Indicator Channel) corresponding to the PUSCH through the RF unit,
The downlink resources to which the PHICHs are mapped for each of the plurality of layers do not overlap with each other,
Wherein a downlink resource to which a PHICH is mapped for each of the plurality of layers is determined based on a different cyclic shift value allocated to each of the plurality of layers,
The downlink resource to which the PHICH is mapped to each of the plurality of layers is determined based on the following equation,

N _PHICH ^group is the PHICH group index, n _PHICH ^seq is the orthogonal sequence index in the PHICH group, I _{PRB_RA} ^lowest index is the index of the smallest PRB among the PRBs mapped to the PUSCH, and _DMRS is the uplink DMRS Demodulation reference signal cyclic shift parameter, N _PHICH ^group is the number of PHICH groups, N _SF ^PHICH is a spreading factor (SF), and I _PHICH is a value of 0 or 1. delete delete delete delete delete delete delete delete delete delete

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