KR20110069735A - Method and apparatus of performing harq in wireless communication system - Google Patents

Abstract

PURPOSE: A HARQ implementing method in a wireless telecommunication system and an apparatus thereof are provided to perform HARQ efficiently, by preventing collision of resources including a plurality of mapped PHICH(Physical Hybrid-ARQ Indicator Channel). CONSTITUTION: Upward link data is transmitted on a PUSCH(Physical Uplink Shared Channel). An ACK/NACK(Acknowledgement/Non-Acknowledgement) signal is received through a plurality of layers on a PHICH corresponding to the PUSCH. The ACK/NACK signal indicates the receiving of the upward link data. PHICH for each of a plurality of layers is mapped to downward link resources. The downward link resources are not overlapped with each other.

Description

Method and apparatus for performing HARQ in wireless communication system {METHOD AND APPARATUS OF PERFORMING HARQ IN WIRELESS COMMUNICATION SYSTEM}

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

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

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

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

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); As shown in section 6 of “Physical channels and modulation (Release 8)”, the downlink control channels used in 3GPP LTE are the Physical Control Format Indicator Channel (PCFICH), the Physical Downlink Control Channel (PDCCH), and the Physical Hybrid-ARQ Indicator (PHICH). Channel). The PCFICH transmitted in the first OFDM symbol of the subframe carries information about the number of OFDM symbols (that is, the size of the control region) used for transmission of control channels in the subframe. Control information transmitted through the PDCCH is called downlink control information (DCI). DCI indicates uplink or downlink scheduling information and uplink transmission power control command for certain UE groups. The PHICH carries ACK (Acknowledgement) / NACK (Non-Acknowledgement) signals for 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, it is necessary to simultaneously allocate a plurality of PHICHs in a carrier aggregation system or a MIMO system for transmitting data using a plurality of carriers. The base station allocates resources to the 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.

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

In one aspect, a method of performing HARQ by a terminal in a wireless communication system is provided. The method of performing HARQ transmits uplink data on a physical uplink shared channel (PUSCH) and receives the uplink data through a plurality of layers on a physical hybrid-ARQ indicator channel (PHICH) corresponding to the PUSCH. Receiving an indicating ACK / NACK (Acknowledgement / Non-Acknowledgement) signal, wherein downlink resources to which PHICHs are mapped for each of the plurality of layers do not overlap each other, and PHICHs for each of the plurality of layers are mapped Downlink resources are determined based on different cyclic shift values allocated to each of the plurality of layers.

When 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.

When 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 allocated to each of the plurality of layers may be any one of 0 to 7.

Any one of the cyclic shift values allocated to each of the plurality of layers may be determined by a cyclic shift field in downlink control information (DCI) transmitted through 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 resource to which the PHICH for each of the plurality of layers is mapped is represented by equation

It can be determined based on. Where n _PHICH ^group is the 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 of the ^PUBs to which the PUSCH is mapped, and n _DMRS is an uplink DMRS ( Demodulation Reference Signal) The cyclic shift parameter, N _PHICH ^group is the number of PHICH groups, and N _SF ^PHICH is a spreading factor (SF). The N _PHICH ^group = 4 and 2N _SF ^PHCIH = 4 may be.

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

In another aspect, a method of performing HARQ by a terminal in a wireless communication system is provided. In the method for performing HARQ, the first terminal and the second terminal transmit the first uplink data and the second uplink data to the base station on the PUSCH, respectively, and the base station transmits the plurality of layers on the PHICH corresponding to the PUSCH. And transmitting the first ACK / NACK signal and the 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. The downlink resource to which the 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.

When 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.

When 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 allocated 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 resource to which the PHICH is mapped for each of the plurality of layers may be further determined based on an orthogonal code covering (OCC) index. Different OCC indexes may be allocated to the first terminal and the second terminal. The downlink resource to which the PHICH for each of the plurality of layers is mapped is represented by equation

It can be determined based on. Where n _PHICH ^group is the 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 among the PRBs to which the PUSCH is mapped, n _DMRS is an uplink DMRS cyclic shift parameter, n _OCC Is the OCC index, N _PHICH ^group is the number of PHICH groups, and N _SF ^PHICH is a spreading factor.

By preventing a plurality of PHICH mapped resources from colliding with each other, it is possible to efficiently perform a hybrid automatic repeat request (HARQ).

1 is a wireless communication system.
2 shows a structure of a radio frame in 3GPP LTE.
3 shows an example of a resource grid for one downlink slot.
4 shows a structure of a downlink subframe.
5 shows a structure of an uplink subframe.
6 shows an example of a transmitter structure in an SC-FDMA system.
7 shows an example of a method in which the subcarrier mapper maps complex symbols to each subcarrier in the frequency domain.
8 is an example of a transmitter to which the clustered DFT-s OFDM transmission scheme is applied.
9 is another example of a transmitter using the clustered DFT-s OFDM transmission scheme.
10 shows another example of a transmitter using 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 an OCC is applied to a reference signal.
14 illustrates an example in which reference signals transmitted from two terminals having different bandwidths are multiplexed by applying an OCC.
15 is a block diagram illustrating an example of a PARC technique.
16 is a block diagram illustrating an example of a PU2RC technique.
17 shows an uplink HARQ.
18 is a block diagram illustrating that an ACK / NACK signal is transmitted on a PHICH.
19 is a block diagram illustrating a MIMO transmission process in uplink using the SC-FDMA transmission scheme.
20 is an example of PHICH resource allocation.
21 shows an example of allocation of cyclic shift values to two terminals according to the proposed method of performing HARQ.
22 shows an example of allocation of cyclic shift values for two terminals according to the proposed method of performing HARQ.
23 is a block diagram illustrating an embodiment of a proposed method of performing HARQ.
24 shows an embodiment of a proposed method for transmitting a downlink control signal.
25 is a block diagram showing a base station and a terminal in which an embodiment of the present invention is implemented.

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

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

1 is a wireless communication system.

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

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

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

The wireless communication system is any one of a multiple-input multiple-output (MIMO) system, a multiple-input single-output (MIS) system, a single-input single-output (SISO) system, and a single-input multiple-output (SIMO) system. Can be. The 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, the transmit antenna means a physical or logical antenna used to transmit one signal or stream, and the 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 3rd Generation Partnership Project (3GPP) TS 36.211 V8.2.0 (2008-03) "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation (Release 8)". Reference may be made. Referring to FIG. 2, a radio frame consists of 10 subframes, and one subframe consists of two slots. Slots in a radio frame are numbered with slots # 0 through # 19. The time taken for one subframe to be transmitted is called a Transmission Time Interval (TTI). TTI may be referred to as a scheduling unit for data transmission. For example, one radio frame may have a length of 10 ms, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

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

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

A wireless communication system can be largely 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 are performed while occupying different frequency bands. According to the TDD scheme, uplink transmission and downlink transmission are performed at different times while occupying the same frequency band. The channel response of the TDD scheme is substantially reciprocal. This means that the downlink channel response and the uplink channel response are almost the same in a given frequency domain. Therefore, in a TDD based wireless communication system, the downlink channel response can be obtained from the uplink channel response. In the TDD scheme, the uplink transmission and the downlink transmission are time-divided in the entire frequency band, and thus the downlink transmission by the base station and the uplink transmission by the terminal cannot be simultaneously performed. 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 the LTE system, N _RB may be any one of 60 to 110. One resource block includes a plurality of subcarriers in the frequency domain. The structure of the uplink slot may also be the same as that of the downlink slot.

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

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

4 shows a structure of a downlink subframe.

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

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

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

5 shows a structure of an uplink subframe.

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

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

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

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

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

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 inverse fast fourier transform (IFFT) unit 53, and a CP insertion unit 54. The transmitter 50 may include a scramble unit (not shown), a modulation mapper (not shown), a layer mapper (not shown), and a layer permutator (not shown). This may be arranged before the DFT unit 51.

The DFT unit 51 performs a DFT on the input symbols and outputs complex-valued symbols. For example, when N _tx symbols are input (where N _tx is a natural number), the DFT size is N _tx . The DFT unit 51 may be called a transform precoder. The subcarrier mapper 52 maps the complex symbols to each subcarrier 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 called a resource element mapper. The IFFT unit 53 performs an IFFT on the input symbol and outputs a baseband signal for data which is a time domain signal. The CP inserter 54 copies a part of the rear part of the baseband signal for data and inserts it in the front part of the baseband signal for data. Inter-symbol interference (ISI) and inter-carrier interference (ICI) can be prevented through CP insertion to maintain orthogonality even in multipath channels.

7 shows an example of a method in which the subcarrier mapper maps complex symbols to each subcarrier in the frequency domain.

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

The clustered DFT-s OFDM transmission scheme is a variation of the conventional SC-FDMA transmission scheme. The clustered DFT-s OFDM transmission scheme divides the data symbols passed through the precoder into a plurality of sub-blocks and maps the data symbols separated from each other in the frequency domain.

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

Referring to FIG. 8, the transmitter 70 includes a DFT unit 71, a subcarrier mapper 72, an IFFT unit 73, and a CP insertion unit 74. The transmitter 70 may further include a scrambled unit (not shown), a modulation mapper (not shown), a layer mapper (not shown), and a layer permutator (not shown), which may be disposed before the DFT unit 71. Can be.

The complex symbols output from the DFT unit 71 are divided into N subblocks (N is a natural number). N subblocks may be represented by subblock # 1, subblock # 2, ..., subblock #N. The subcarrier mapper 72 distributes N subblocks in the frequency domain and maps them to subcarriers. NULL may be inserted between every two consecutive subblocks. Complex symbols in one subblock may be mapped to consecutive subcarriers in the frequency domain. That is, a centralized mapping scheme may be used in one subblock.

The transmitter 70 of FIG. 8 may be used for both a single carrier transmitter or a multi-carrier transmitter. When used in a single carrier transmitter, all N subblocks correspond to one carrier. When used in a multi-carrier transmitter, one subcarrier may correspond to each subblock among N subblocks. Alternatively, even when used in a multi-carrier transmitter, a plurality of sub blocks among the N sub blocks may correspond to one carrier. Meanwhile, in the transmitter 70 of FIG. 8, a time domain signal is generated through one IFFT unit 73. Accordingly, in order for the transmitter 70 of FIG. 8 to be used for a multi-carrier transmitter, subcarrier spacing between adjacent carriers must be aligned in a continuous carrier allocation situation.

9 is another example of a transmitter using 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 CP insertion part 84 is included. The transmitter 80 may further include a scrambled unit (not shown), a modulation mapper (not shown), a layer mapper (not shown), and a layer permutator (not shown), which may be disposed before the DFT unit 71. Can be.

IFFT is performed separately for each subblock among the N subblocks. The nth IFFT unit 83-N performs an IFFT on subblock #n and outputs an nth base band signal (n = 1, 2,..., N). The n th baseband signal is multiplied by the n th carrier signal to generate an n th radio signal. After the N radio signals generated from the N subblocks are added, a 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 in which carriers allocated by the transmitter are not adjacent to each other.

10 shows another example of a transmitter using 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 called Nx SC-FDMA. Referring to FIG. 10, the transmitter 90 includes a code block divider 91, a chunk divider 92, a plurality of channel coding units 93-1,. Modulators 94-1, ..., 94-N, a plurality of DFT units 95-1, ..., 95-N, a plurality of subcarrier mappers 96-1, ..., 96-N And a plurality of IFFT units 97-1,..., 97-N and a CP insertion unit 98. Here, N may be the number of multicarriers used by the multicarrier transmitter. Each of the channel coding units 93-1,..., 93 -N may include a scrambled unit (not shown). The modulators 94-1, ..., 94-N may be referred to as modulation mappers. The transmitter 90 may further include a layer mapper (not shown) and a layer permutator (not shown), which may be disposed before the DFT units 95-1,..., 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 referred to as data transmitted from the multicarrier transmitter, and the chunk may be referred to as a piece of data transmitted through one carrier of the multicarrier. The transmitter 90 performs a DFT in chunks. The transmitter 90 may be used both in a discontinuous carrier allocation situation or in a continuous carrier allocation situation.

Hereinafter, the uplink reference signal will be described.

Reference signals are generally transmitted in sequence. As the reference signal sequence, any sequence may be used without particular limitation. The reference signal sequence may use a PSK-based computer generated sequence. 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 CAZAC sequences are ZC-based sequences, ZC sequences with cyclic extensions, ZC sequences with truncation, etc. There is this. Alternatively, the reference signal sequence may use a pseudo-random (PN) sequence. Examples of PN sequences include m-sequences, computer generated sequences, Gold sequences, and Kasami sequences. In addition, the reference signal sequence may use a cyclically shifted sequence.

The uplink reference signal may be classified into a demodulation reference signal (DMRS) and a sounding reference signal (SRS). DMRS is a reference signal used for channel estimation for demodulation of a received signal. DMRS may be combined with transmission of PUSCH or PUCCH. The SRS is a reference signal transmitted by the terminal to the base station for uplink scheduling. The base station estimates an uplink channel based on the received sounding reference signal and uses the estimated uplink channel for uplink scheduling. SRS is not combined with transmission of PUSCH or PUCCH. The same kind of base sequence can be used for DMRS and SRS. Meanwhile, precoding applied to DMRS in uplink multi-antenna transmission may be the same as precoding applied to PUSCH. Cyclic shift separation is a primary scheme for multiplexing DMRS. In an LTE-A system, the SRS may not be precoded and may also be an antenna specified reference signal.

The reference signal sequence r _{u, v} ^(α) (n) may 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 a length of a reference signal sequence, and M _sc ^RS = m * N _sc ^RB . N _sc ^RB represents the size of a resource block represented by the number of subcarriers in the frequency domain, and N _RB ^{max, UL} represents the maximum value of an uplink bandwidth expressed in multiples of N _sc ^RB . The plurality of reference signal sequences may be defined by differently applying a cyclic shift value α from one basic 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 within a 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 It 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.

In addition, when the length of the reference signal sequence is 3N _sc ^RB or more, the base sequence may be defined by equation (2).

<Joe 2>

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

<Number 3>

q can be given by equation (4).

<Joe 4>

When the length of the reference signal sequence is 3N _sc ^RB or less, the base sequence may be defined by Equation 5.

<Joe 5>

Table 1 shows 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),... , φ (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

Hopping of the reference signal may be applied as follows.

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

<Joe 6>

There may be 17 different group hopping patterns and 30 different sequence shift patterns. Whether to apply group hopping may be indicated by a higher layer.

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

<Seven 7>

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

<Joe 8>

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

Can be initialized to

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

Sequence hopping can be applied only to a reference signal sequence whose length is longer than 6N _sc ^RB . In this case, the basic sequence index v in the basic sequence group of the slot index n _s may be defined by Equation 9.

<Joe 9>

로 초기화될 수 있다.c (i) may be represented by the example of Equation 8, and whether or not to apply sequence hopping may be indicated by a higher layer. A pseudo random sequence generator is used at the beginning of each radio frame

Can be initialized to

The DMRS sequence for the PUSCH may be defined by Equation 10.

<Joe 10>

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

A cyclic shift value α = 2πn _cs / 12 in a slot is given, and n _cs may be defined by Equation 11.

<Wed 11>

In Equation 11, n _DMRS ⁽¹⁾ is indicated by a parameter transmitted in a higher layer, and Table 3 shows an example of a corresponding 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

In Equation 11, n _DMRS ⁽²⁾ may be defined by a cyclic shift field in DCI format 0 for a transport block corresponding to a 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

When a PDCCH including DCI format 0 is not transmitted in the same transport block, when the first PUSCH is semi-persistently scheduled in the same transport block, or the first PUSCH is random access response grant in the same transport block. n _DMRS ² may be 0 when scheduled by a response grant).

n _PRS (n _s ) may be defined by Equation 12.

<Joe 12>

로 초기화될 수 있다.c (i) may be represented by the example of Equation 8, and may be applied to each cell of c (i). A pseudo random sequence generator is used at the beginning of each radio frame

Can be initialized to

The DMRS sequence r ^PUSCH is multiplied by an amplitude scaling factor β _PUSCH and mapped to a sequence starting from r ^PUSCH (0) to a physical transport block used for transmission of the corresponding PUSCH. 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.

Referring to FIG. 11, the reference signal transmitter 60 includes a subcarrier mapper 61, an IFFT unit 62, and a CP insertion unit 63. Unlike the transmitter 50 of FIG. 6, the reference signal transmitter 60 is generated directly in the frequency domain without passing through the DFT unit 51 and is mapped to the subcarrier through the subcarrier mapper 61. In this case, the subcarrier mapper may map the reference signal to the subcarrier using the concentrated 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 of FIG. 12- (a) shows a 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. 14 OFDM symbols in a subframe are symbol indexed from 0 to 13. Reference signals may be transmitted through OFDM symbols having symbol indices of 3 and 10. Data may be transmitted through the remaining OFDM symbols except for the OFDM symbol on which the reference signal is transmitted. The structure of the subframe of FIG. 12- (b) shows a case of an 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. 12 OFDM symbols in a subframe are indexed from 0 to 11 symbols. Reference signals are transmitted over OFDM symbols with 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 an OCC is applied to a reference signal.

In one subframe, the reference signal sequence for layer 0 and the reference signal sequence for layer 1 are both mapped to the fourth OFDM symbol of the first slot and the fourth OFDM symbol of the second slot. The same sequence is mapped to two OFDM symbols in each layer. In this case, the reference signal sequence for layer 0 is multiplied by an orthogonal sequence of [+1 +1] and mapped to an 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 the 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 may estimate the channel of the layer 0 by adding the reference signal sequence transmitted in the first slot and the reference signal sequence transmitted in the second slot. In addition, the base station 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, by applying the OCC, the base station can distinguish the reference signal transmitted in each layer. Therefore, a plurality of reference signals can be transmitted using the same resource. If the number of possible cyclic shifts is six, the number of layers or users that can be multiplexed by applying the above OCC can be increased up to twelve.

In this example, it is assumed that a binary format of [+1 +1] or [+1 or -1] is used as the OCC, but is not limited thereto. Various orthogonal sequences may be used as the OCC. For example, orthogonal sequences such as Walsh codes, DFT coefficients, and CAZAC sequences may be applied to the OCC.

In addition, by applying the OCC, reference signals can be more easily multiplexed among users having different bandwidths.

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

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

Hereinafter, MIMO (Multiple-Input Multiple-Output) will be described. The MIMO scheme can be largely classified 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. The spatial resource may be allocated to one terminal or a plurality of terminals through the PARC scheme. When allocating spatial resources to one terminal, it is referred to as single-user (SU) MIMO, and when allocating to a plurality of terminals is referred to as multi-user (MU) MIMO.

15 illustrates a case where the PARC technique is applied to SU-MIMO. Assuming three terminals, the base station selects one terminal from which the plurality of antennas are to transmit data. When the first terminal is selected, the modulation and coding scheme (MCS) level for each stream of the plurality of antennas is determined, and data is transmitted to the first terminal through the plurality of antennas through an OFDMA modulator. Each terminal transmits channel quality indicators (CQIs) for a plurality of antennas of the corresponding terminal to the base station.

16 is a block diagram illustrating an example of a 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 100 streams for a plurality of terminals to generate a plurality of group streams, and schedules and multiplexes 101 the group streams generated in step S101. The base station precodes each group stream using a precoding matrix corresponding to the corresponding group, and transmits the plurality of antennas through a plurality of antennas. In precoding, unitary codebook based precoding may be used. Each terminal feeds back a preferred precoding matrix, a transmit antenna, and a CQI corresponding to each transmit antenna to the base station, and the base station may use the feedback information in scheduling. In this way, by performing MIMO using precoding, spatial multi-user interference can be reduced, so that a high performance gain can be obtained in an MU-MIMO environment.

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

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

Hereinafter, the PHICH will be described.

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

Since the LTE system does not support SU-MIMO in uplink, one PHICH transmits only 1-bit ACK / NACK for a PUSCH, that is, a single stream of one UE. In step S130, 1 bit ACK / NACK is coded into 3 bits using a repetition code having a code rate of 1/3. The ACK / NACK coded in step S131 is modulated by a binary phase key-shifting (BPSK) scheme 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 when spreading the modulation symbols, and the number of orthogonal sequences used is SF * 2 to apply I / Q multiplexing. PHICHs spread using SF * 2 orthogonal sequences may 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 resource mapped and transmitted.

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

(13)

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

The resource used for the PHICH may be determined based on a cyclic shift value of a demodulation reference signal (DMRS) transmitted through a smallest PRB index and an UL grant when a PUSCH resource is allocated. A resource to which a PHICH is mapped (hereinafter, referred to as a PHICH resource) may be expressed as an index pair (n _PHICH ^group , n _PHICH ^seq ), n _PHICH ^group indicates a PHICH group index, and n _PHICH ^seq indicates an orthogonal sequence index within the PHICH group. The (n _PHICH ^group , n _PHICH ^seq ) may be determined by Equation 14.

(Jos 14)

n _DMRS may be determined based on the DMRS Cyclic Shift for DMRS field in DCI format 0 according to Table 6.

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

In addition, when the PDCCH including 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 random access response grant is assigned to the first PUSCH in the same transport block. n _DMRS may be 0 when scheduled by a response grant).

In Equation 14, N _SF ^PHICH is a spreading factor (SF) used for the PHICH modulation of FIG. I _{PRB_RA} ^lowest_index is the smallest PRB index among the PRBs of the slots in which the PUSCH corresponding to the corresponding PHICH is transmitted. I _PHICH is a value of zero or one.

The orthogonal sequence used for the PHICH may be determined by 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] -

Multiple PHICHs may be assigned at the same time. In particular, a plurality of PHICHs may be allocated in a system such as a carrier aggregation system, MU-MIMO, and Cooperative Multi-Point (CoMP) transmission scheme.

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

A plurality of codewords may be used to perform 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. Each layer is DFT spread in step S143, and each layer is precoded in step S144. The stream pre-coded and generated in step S145 is mapped to resource elements, and is transmitted through each antenna through the SC-FDMA signal generator generated in step S146. In order to facilitate HARQ for uplink, two independent ACK / NACK signals are required for each codeword.

20 is an example of PHICH resource allocation.

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

A PHICH corresponding to two PUSCHs transmitted through two antennas at a first terminal is included in a resource element (resource element # 0) having an index (0,0) and a resource element (resource element # 1) having an index (1,0). Each resource is allocated. In this case, the smallest PRB index on which the PUSCH is transmitted may be the same and n _DMRS may be different. In addition, a resource element (resource element # 2) having an index (2,0) is allocated a PHICH resource corresponding to the PUSCH transmitted from the second terminal. Similarly, the PHICH resource corresponding to the PUSCH transmitted from the third terminal and the fourth terminal is included in the resource element (resource element # 3) having the index (0,1) and the resource element (resource element # 4) having the index (1,1). Are each assigned.

However, in case of multiplexing data by applying OCC, it is possible to transmit a plurality of data or a plurality of reference signals using the same resource by applying the same OCC with the smallest PRB index and n _DMRS . In this case, the corresponding plurality of PHICHs use the same resources according to Equation 14, and the PHICH resources collide. Therefore, when a plurality of PHICHs are allocated, a method for preventing a collision of PHICH resources is required.

Hereinafter, a method for solving a collision problem of PHICH resources will be described. The present invention proposes a method for allocating a cyclic shift value for a DMRS for a plurality of antennas in each terminal so that PHICH resources in which each terminal transmits ACK / NACK signals do not collide with each other in an uplink MU-MIMO environment. .

As mentioned in equation (14), the PHICH resource may be allocated by equation (15).

<Joe 15>

In case of having an extended CP structure, assuming 2N _SF ^PHICH = 4 and N _PHICH ^group = 4, n _PHICH ^group and n indicating a location where PHICH resources are allocated when n _DMRS = 0 and n _DMRS = 4 _PHICH ^seq may be equal. That is, even when different n _DMRSs are allocated, PHICH resources may collide with each other. For example, when the first terminal uses n _DMRS = 0 and the second terminal uses n _DMRS = 4, PHICH resources may collide with each other. In addition, when n _DMRSs allocated to each UE are 1 and 5, 2 and 6, or 3 and 7, respectively, similarly, a collision of PHICH resources may occur. In this case, if each UE has a single antenna, the BS may flexibly allocate a cyclic shift value of DMRS on DCI format 0 in the scheduler so that a collision of PHICH resources does not occur. However, when each terminal has a plurality of antennas, since different cyclic shift values need to be assigned to each antenna within each terminal as well as different cyclic shift values, the PHICH between the terminals What is needed is a method to reduce the probability of resource conflicts.

Therefore, in the present invention, when assigning a cyclic shift value to a plurality of layers (layer) in one terminal, by assigning a cyclic shift value that can conflict with the PHICH resource to each layer of the PHICH resources for the plurality of terminals Suggest ways to prevent collisions. That is, for example, by allocating the above-described n _DMRS = 0 and n _DMRS = 4 to a plurality of layers in one terminal, a method of reducing the collision probability of PHICH resources between the plurality of terminals is proposed.

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

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

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

21 shows an example of allocation of cyclic shift values to two terminals according to the proposed method of performing HARQ. 21 shows a case in which each terminal performs rank-2 transmission while having two transmit antennas. That is, two different cyclic shift values are required for each terminal.

Referring to FIG. 21, two layers of the first UE UE 1 are assigned A and (A + 4) mod 8 as cyclic shift values. In addition, B and (B + 4) mod8 are allocated to two layers of the second UE UE 2 as cyclic shift values. A is a cyclic shift value of DMRS transmitted on DCI format 0 and may have a value of 0 to 7. B is different from A and (A + 4) mod8 and may have a value from 0 to 7, like A. For example, 0 and 4 may be allocated as cyclic shift values for each antenna of the first terminal, and 1 and 5 may be allocated as cyclic shift values for each antenna of the second terminal. Accordingly, it is possible to reduce the probability of collision of PHICH resources between the respective terminals. In addition, the order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated between each terminal may be changed. For example, (A + 4) mod8 may be allocated to the first layer of the first terminal as a cyclic shift value, and A may be allocated to the second layer.

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

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

In addition, when each terminal has four transmit antennas and performs rank-4 transmission, a cyclic shift value according to the present invention may be allocated to the two terminals. Since each UE performs rank-4 transmission, four different cyclic shift values are required for each UE. Table 9 and Table 10 show an example in which a cyclic shift value is allocated to each of four layers in two terminals.

First terminal Second terminal First terminal 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 4th layer (B + 4) mod8 (D + 4) mod8 (B + 4) mod8 (D + 4) mod8

First terminal Second terminal First terminal 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 4th layer (A + 6) mod8 (B + 6) mod8 (A + 6) mod8 (B + 6) mod8

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

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

First terminal Second terminal Third terminal 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 4th layer (A + 6) mod8 (B + 6) mod8 (C + 6) mod8 (D + 6) mod8

First terminal Second terminal Third terminal 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 4th layer (A + 6) mod8 (B + 6) mod8 (C + 6) mod8 (D + 6) mod8

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

Alternatively, the same cyclic shift value may be allocated to each of UEs performing uplink MU-MIMO transmission, and each UE may be distinguished by using different OCC indexes for reference signal multiplexing.

Equation 16 is an example of an equation for allocating PHICH resources by applying an OCC index.

<Joe 16>

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

22 shows an example of allocation of cyclic shift values for two terminals according to the proposed method of performing HARQ. 22 shows a case in which each terminal performs rank-2 transmission while having two transmit antennas.

Referring to FIG. 22, A and (A + 4) mod 8 are allocated to two layers of the first UE UE 1 as cyclic shift values. Similarly, A and (A + 4) mod 8 are allocated to two layers of the second UE UE 2 as cyclic shift values, respectively. However, OCC indexes are differently assigned to 0 and 1 to the first terminal and the second terminal, respectively. Accordingly, the first terminal and the second terminal can be distinguished. A is a cyclic shift value of DMRS transmitted on DCI format 0 and may have a value of 0 to 7. Accordingly, it is possible to reduce the probability of collision of PHICH resources between the respective terminals. In addition, the order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated between each terminal may be changed. For example, (A + 4) mod8 may be allocated to the first layer of the first terminal as a cyclic shift value, and A may be allocated to the second layer.

In addition, when each terminal has two transmit antennas and performs rank-2 transmission, a cyclic shift value according to the present invention may be allocated to four terminals. Table 13 shows an example in which cyclic shift values are allocated to two layers in four terminals.

First terminal Second terminal Third terminal 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 DMRS transmitted on DCI format 0 and may have a value of 0 to 7. B is different from A and (A + 4) mod8 and may have a value from 0 to 7, like A. The order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated among the terminals may be changed. In addition, the OCC index may be changed in the terminal to which the same cyclic shift value is assigned.

In Table 13, it is assumed that an OCC index has a value of 1 bit or 0 or 1, but the length of the OCC index may be increased up to 3 bits. When the OCC index is 2 bits, the OCC index may be allocated from 0 to 3 for the first to fourth terminals. Table 14 shows another example in which cyclic shift values are allocated to two layers in four terminals.

First terminal Second terminal Third terminal 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 DMRS transmitted on DCI format 0 and may have a value of 0 to 7. The order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated among the terminals may be changed. In addition, the OCC index may be changed in the terminal to which the same cyclic shift value is assigned.

In addition, when each terminal has four transmit antennas and performs rank-4 transmission, a cyclic shift value according to the present invention may be allocated to the two terminals. Table 15 shows an example in which cyclic shift values are allocated to four layers in two terminals.

First terminal Second terminal First layer A A Second layer (A + 2) mod8 (A + 2) mod8 Third layer (A + 4) mod8 (A + 4) mod8 4th layer (A + 6) mod8 (A + 6) mod8 OCC index 0 One

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

In addition, when each terminal has four transmit antennas and performs rank-4 transmission, a cyclic shift value according to the present invention may be allocated to four terminals. Table 16 shows an example in which cyclic shift values are allocated to four layers in four terminals. In this case, the OCC index has a length of 1 bit and may have any one of 0 or 1.

First terminal Second terminal Third terminal 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 4th 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 DMRS transmitted on DCI format 0 and may have a value of 0 to 7. B is different from A and (A + 4) mod8 and may have a value from 0 to 7, like A. The order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated among the terminals may be changed. In addition, the OCC index may be changed in the terminal to which the same cyclic shift value is assigned.

Table 17 shows another example in which cyclic shift values are allocated to four layers in four terminals. In this case, the OCC index has a length of 2 bits and may have any one of 0 to 3.

First terminal Second terminal Third terminal 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 4th 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 DMRS transmitted on DCI format 0 and may have a value of 0 to 7. The order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated among the terminals may be changed. In addition, the OCC index may be changed in the terminal to which the same cyclic shift value is assigned.

On the other hand, the present invention can be applied even when the ACK / NACK signal for a plurality of code words are transmitted on a plurality of PHICH. As in the case where ACK / NACK signals for a plurality of codewords are transmitted on one PHICH, a cyclic shift value for collision of PHICH resources may be allocated to a plurality of layers in one terminal for each of the plurality of terminals. The collision probability of PHICH resources can be reduced. However, in order to allocate a plurality of PHICHs to each UE, it is necessary to set at least two different cyclic shift values so that there is no collision of resources allocated to each PHICH.

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

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

First layer Second layer First terminal A (A + 4) mod8 Second terminal B (B + 4) mod8

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

When a rule for assigning PHICH resources and a rule for assigning a cyclic shift value between layers are different, the second PHICH resource in the first terminal may be allocated based on n _DMRS = (A + α) mod8. In addition, the second PHICH resource in the second terminal may be allocated based on n _DMRS = (B + α) mod8. α 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, when a rule for assigning PHICH resources and a rule for assigning cyclic shift values between layers are the same, in order to prevent collision of PHICH resources between different codewords in one UE, a PHICH resource collision does not occur. Shift values can be assigned to each layer. That is, as shown in Table 19, a cyclic shift value can be assigned to each layer.

First layer Second layer First terminal A (A + α) mod 8 Second terminal B (B + α) mod 8

α may have a value of any of 1 to 8. A is a cyclic shift value of DMRS transmitted on DCI format 0 and may have a value of 0 to 7. B is different from A and may have a value from 0 to 7, like A. The order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated among the terminals may be changed.

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

First layer Second layer First terminal A (A + 4) mod8 Second terminal B (B + 4) mod8 Third terminal C (C + 4) mod8 Fourth terminal D (D + 4) mod8

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

When the rule for assigning PHICH resources and the rule for assigning cyclic shift values between layers are different, the second PHICH resources in the first to fourth terminals are respectively n _DMRS = (A + α) mod 8 and n _DMRS = ( B + α) mod8, n _DMRS = (C + α) mod8 and n _DMRS = (D + α) mod8. α may have any one value from 1 to 8, and may have the same value when applied to the first to fourth terminals.

In addition, when a rule for assigning PHICH resources and a rule for assigning cyclic shift values between layers are the same, in order to prevent collision of PHICH resources between different codewords in one UE, a PHICH resource collision does not occur. 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 First terminal A (A + α) mod 8 Second terminal B (B + α) mod 8 Third terminal C (C + α) mod 8 Fourth terminal D (D + α) mod 8

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

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

First layer Second layer Third layer 4th layer First terminal A (A + 4) mod8 (A + 2) mod8 (A + 6) mod8 Second terminal B (B + 4) mod8 (B + 2) mod8 (B + 6) mod8

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

When the rule for assigning PHICH resources and the rule for assigning cyclic shift values between layers are different, the second PHICH resources in the first terminal and the second terminal are respectively n _DMRS = (A + α) mod8 and n _DMRS = ( Can be assigned based on B + α) mod8. α 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, when a rule for assigning PHICH resources and a rule for assigning cyclic shift values between layers are the same, in order to prevent collision of PHICH resources between different codewords in one UE, a PHICH resource collision does not occur. Shift values can be assigned to each layer. That is, cyclic shift values may be assigned to each layer as shown in Table 23.

First layer Second layer Third layer 4th layer First terminal A (A + α) mod 8 (A + 4) mod8 (A + α + 4) mod8 Second terminal B (B + α) mod 8 (B + 4) mod8 (B + α + 4) mod8

α may have a value of any of 1 to 8. A is a cyclic shift value of DMRS transmitted on DCI format 0 and may have a value of 0 to 7. B is different from A and may have a value from 0 to 7, like A. The order of the cyclic shift value allocated to each layer in each terminal or the cyclic shift value allocated among the terminals may be changed.

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

First layer Second layer Third layer 4th layer First terminal A (A + 4) mod8 (A + 2) mod8 (A + 6) mod8 Second terminal B (B + 4) mod8 (B + 2) mod8 (B + 6) mod8 Third terminal C (C + 4) mod8 (C + 2) mod8 (C + 6) mod8 Fourth terminal D (D + 4) mod8 (D + 2) mod8 (D + 6) mod8

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

When the rule for assigning PHICH resources and the rule for assigning cyclic shift values between layers are different, the second PHICH resources in the first to fourth terminals are respectively n _DMRS = (A + α) mod 8 and n _DMRS = ( B + α) mod8, n _DMRS = (C + α) mod8 and n _DMRS = (D + α) mod8. α may have any one value from 1 to 8, and may have the same value when applied to the first to fourth terminals.

In addition, when a rule for assigning PHICH resources and a rule for assigning cyclic shift values between layers are the same, in order to prevent collision of PHICH resources between different codewords in one UE, a PHICH resource collision does not occur. Shift values can be assigned to each layer. That is, as shown in Table 25, a cyclic shift value can be assigned to each layer.

First layer Second layer Third layer 4th layer First terminal A (A + α) mod 8 (A + 4) mod8 (A + α + 4) mod8 Second terminal B (B + α) mod 8 (B + 4) mod8 (B + α + 4) mod8 Third terminal C (C + α) mod 8 (C + α) mod 8 (C + α + 4) mod8 Fourth terminal D (D + α) mod 8 (D + α) mod 8 (D + α + 4) mod8

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

Meanwhile, since the number of PHICH sequences that can be allocated to one PHICH group in the extended CP structure is four, it is not possible to support a plurality of PHICHs for a plurality of codewords 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 may be increased to support a plurality of PHICHs. Alternatively, a plurality of PHICHs may be supported by applying a new parameter not defined in LTE rel-8. The new parameter may be a static, semi-static or dynamic parameter and may be signaled on the RDC (Radio Resource Control) signal or on the PDCCH via DCI format.

In addition, even when a plurality of PHICH resources are allocated, the same cyclic shift value is allocated to each of UEs 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.

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

24 shows an embodiment of a proposed method for transmitting a downlink control signal.

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, resources to which a plurality of PHICH sequences are mapped in each terminal do not overlap each other. In step S320, the base station transmits the mapped plurality of PHICH sequences to the terminal.

25 is a block diagram showing 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 (RF) 830. Processor 810 implements the proposed functions, processes, and / or methods. Layers of the air interface protocol may be implemented by the processor 810. The processor 810 allocates PHICH resources for ACK / NACK signal transmission. The memory 820 is connected to the processor 810 and stores various information for driving the processor 810. The RF unit 830 is connected to the processor 810 to transmit and / or receive a radio signal and to transmit 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 functions, processes, and / or methods. Layers of the air interface protocol may be implemented by the processor 910. The processor 910 processes the received ACK / NACK signal. The memory 920 is connected 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. The memory 820, 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and / or other storage device. The RF unit 830 and 930 may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module may be stored in the memory 820, 920 and executed by the processor 810, 910. The memories 820 and 920 may be inside or outside the processors 810 and 910, and may be connected to the processors 810 and 910 by various well-known means.

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

The above-described embodiments include examples of various aspects. While 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)

In a method of performing HARQ by a terminal in a wireless communication system,
Transmit uplink data on a PUSCH (Physical Uplink Shared Channel),
Receiving an acknowledgment / non-acknowledgement (ACK / NACK) signal indicating whether the uplink data is received through a plurality of layers on a physical hybrid-ARQ indicator channel (PHICH) corresponding to the PUSCH,
Downlink resources to which PHICHs for each of the plurality of layers are mapped do not overlap each other.
The downlink resource to which the PHICH is mapped for each of the plurality of layers is determined based on different cyclic shift values allocated to each of the plurality of layers. The method of claim 1,
When the number of the plurality of layers is two,
The cyclic shift value allocated to each of the plurality of layers differs by four. The method of claim 1,
When the number of the plurality of layers is four,
The cyclic shift value assigned to each of the plurality of layers differs by two. The method of claim 1,
The cyclic shift value assigned to each of the plurality of layers is HARQ method, characterized in that any one of 0 to 7. The method of claim 1,
Any one of the cyclic shift values assigned to each of the plurality of layers is determined by a cyclic shift field in downlink control information (DCI) transmitted through physical downlink control chann (PDCCH). The method of claim 1,
The downlink resource to which the PHICH is mapped for each of the plurality of layers is determined based on the following equation.

Where n _PHICH ^group is the 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 of the ^PUBs to which the PUSCH is mapped, and n _DMRS is an uplink DMRS ( Demodulation Reference Signal) The cyclic shift parameter, N _PHICH ^group is the number of PHICH groups, and N _SF ^PHICH is a spreading factor (SF). The method according to claim 6,
The method of performing HARQ, characterized in that the N _PHICH ^group = 4 and 2N _SF ^PHCIH = 4. The method of claim 1,
And retransmitting data of the uplink data based on the ACK / NACK signal. In a method of performing HARQ by a terminal in a wireless communication system,
The first terminal and the second terminal transmits the first uplink data and the second uplink data to the base station on the physical uplink shared channel (PUSCH), respectively,
The base station indicates a first acknowledgment (ACK / NACK) indicating whether the first uplink data and the second uplink data are received through a plurality of layers on a physical hybrid-ARQ indicator channel (PHICH) corresponding to the PUSCH. / Non-Acknowledgement) and the second ACK / NACK signal to the first terminal and the second terminal, respectively,
The downlink resource to which the PHICH is mapped for each of the plurality of layers is determined based on a cyclic shift value assigned to each of the plurality of layers. The method of claim 9,
When the number of the plurality of layers is two,
The cyclic shift value allocated to each of the plurality of layers differs by four. The method of claim 9,
When the number of the plurality of layers is four,
The cyclic shift value assigned to each of the plurality of layers differs by two. The method of claim 9,
The cyclic shift value assigned to each of the plurality of layers is HARQ method, characterized in that any one of 0 to 7. The method of claim 9,
The downlink resource to which the PHICH is mapped for each of the plurality of layers is determined based on an Orthogonal Code Covering (OCC) index. The method of claim 13,
The method of performing HARQ, characterized in that different OCC indexes are allocated to the first terminal and the second terminal. The method of claim 13,
The downlink resource to which the PHICH is mapped for each of the plurality of layers is determined based on the following equation.

Where n _PHICH ^group is the 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 of the ^PUBs to which the PUSCH is mapped, and n _DMRS is an uplink DMRS ( Demodulation Reference Signal) A cyclic shift parameter, n _OCC is the OCC index, N _PHICH ^group is the number of PHICH groups, and N _SF ^PHICH is a spreading factor (SF).

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