KR20110097235A - Method and apparatus for transmitting and receiving a signal in wireless communication system - Google Patents

Abstract

The present invention discloses a method and apparatus for transmitting and receiving signals in a wireless communication system. A user equipment (UE) according to the present invention is a physical HARQ (PHHY) allocated using a plurality of physical resource block (PRB) indexes, a plurality of PHICH group indexes, and a plurality of PHICH sequence indexes. Automatic Repeat Request) signal, and the plurality of PHICH group indexes include a CSO PHICH group index group corresponding to a cyclic shift offset (CSO) used by the UE. The PHICH group index group includes at least one PHICH group index, wherein the at least one PHICH group index is included by a CSO PHICH group index group corresponding to any of the CSOs different from the CSO used by the UE. Mapped to a PRB index in the same order as one PHICH group index, and the plurality of PHICH sequence indexes are used by the UE. A CSO PHICH sequence index group corresponding to a CSO, wherein the CSO PHICH sequence index group comprises at least one PHICH sequence index, wherein the at least one PHICH sequence index is a CSO PHICH sequence index group corresponding to the CSO This is characterized in that the mapping to the PRB index so as not to overlap with at least one PHICH sequence index.

Description

METHOD AND APPARATUS FOR TRANSMITTING AND RECEIVING A SIGNAL IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a method and apparatus for transmitting and receiving signals in a wireless communication system.

Currently, the 3rd Gerneration Partnership Project (3GPP), an asynchronous cellular mobile communication standard organization, is standardizing the next generation mobile communication system, the Long Term Evolution (LTE) communication system based on a multiple access method. Orthogonal Frequency-Division Multiplexing (OFDM) is a method of transmitting data using a multi-carrier. In detail, the OFDM scheme performs parallel conversion of serially input symbol strings and modulates each of them into a plurality of subcarriers having a mutual orthogonality, that is, a plurality of subcarrier channels. -Carrier Modulation (MCM).

Hereinafter, an orthogonal frequency division multiple access (OFDMA) based subframe structure used in an LTE communication system will be described with reference to FIG. 1.

1 is a diagram illustrating a structure of an OFDMA based subframe used in a conventional LTE communication system.

Referring to FIG. 1, radio resources of the LTE communication system may be represented by a two-dimensional array of time and frequency domains. In FIG. 1, the horizontal axis represents the time domain 100 and the vertical axis represents the frequency domain 101. In addition, one square in a frequency domain represents one subcarrier 103, and one square in a time domain represents one OFDM symbol 104. Accordingly, one resource element 102 may be represented by one rectangular figure consisting of one subcarrier and one OFDM symbol.

Seven OFDM symbols constitute one slot 105 and two slots constitute one subframe 106. The subframe 106 is a basic transmission unit of a downlink signal transmitted from a base station (eNodeB) to a user equipment (UE).

Meanwhile, one block including seven OFDM symbols (ie, one slot) and twelve subcarriers is called a resource block (RB). The RB represents a physical resource block (PRB) 107 which is an allocation unit for physical resources allocated by the base station to the UE.

Physical Downlink Control Channel (PDCCH) is a physical downlink control channel transmitted from the base station to the UE. The PDCCH is resource allocation information for transmitting a downlink signal from the base station to the UE and an uplink signal from the UE to the base station. The scheduling information (Downlink / Uplink grant) including resource allocation information for transmitting the data is transmitted.

An ACK (Acknowledgement) / NACK (Negative ACK) signal, which is a response signal of data transmitted in uplink, may be transmitted from the base station to the UE through the resource region through which the PDCCH signal is transmitted. The PDCCH signal is transmitted in subframe units, and may be transmitted through first or fewer OFDM symbols (eg, n = 3) in each subframe. For example, as shown in FIG. 1, when each slot includes seven symbols, the PDCCH signal may be transmitted using the first three or less OFDM symbols in the first slot. That is, up to three OFDM symbols initially located in each subframe are used to transmit the PDCCH signal. The remaining OFDM symbols other than the OFDM symbols used to transmit the PDCCH signal in one subframe are used for data transmission.

A downlink ACK / NACK signal, which is a response signal for uplink data, is generally used to increase the reliability and data throughput of a data transmission in a packet-based communication system. In addition, the ACK / NACK signal represents control information transmitted in a system using a hybrid automatic repeat request (HARQ) technique. The ACK / NACK signal is transmitted through the radio resource region 108 through which the PDCCH signal is transmitted, and a channel for transmitting the ACK / NACK signal is called a physical HARQ indicator channel (PHICH).

Radio resources (hereinafter, referred to as 'PHICH resources') required for transmitting the ACK / NACK signal may be used as much as the total PRB allocable to the uplink.

However, in this case, although the uplink can directly receive a response signal for the transmitted data, there is an advantage that the restriction due to the data transmission is eliminated, but there is a problem that resources are wasted in the downlink.

On the other hand, when a multiuser multiple input multiple output (MU-MIMO) scheme is used in the uplink, since the ACK / NACK signals of downlinks for multiple users must be transmitted, PHICH resources are twice as many as the total number of PRBs that can be allocated to the uplink. This must exist.

If the PHICH resource is allocated less than the maximum required amount corresponding to the data transmitted in the uplink, it is necessary to determine whether the PHICH resource for transmitting the corresponding ACK / NACK signal is available every time the uplink resource is allocated. There is a problem of increasing complexity.

The present invention proposes a signal transmission / reception method and apparatus for transmitting and receiving an ACK (Acknowledgement) / NACK (Negative ACK) signal which is a response signal to uplink data in a wireless communication system.

The present invention proposes a method and apparatus for transmitting and receiving signals for transmitting and receiving ACK / NACK signals using PHICH resources efficiently allocated in a wireless communication system.

According to the present invention, even when a multiuser multiple input multiple output (MU-MIMO) scheme is used in a wireless communication system, a PHICH group index and a PHICH sequence index corresponding to one UE do not overlap with a PHICH group index and a PHICH sequence index of another UE. The present invention proposes a method and apparatus for preventing a problem of deterioration of uplink capacity due to limitation of uplink resource allocation by PHICH.

The method proposed by the present invention for achieving the above-mentioned; In a method for receiving a signal of a user equipment (UE) in a wireless communication system, a plurality of physical resource block (PRB) indexes, a plurality of PHICH group index and a plurality of PHICH sequence index assigned And receiving a signal through a physical hybrid automatic repeat request (HARICH) indicator channel (PHICH), wherein the plurality of PHICH group indexes correspond to a CSO corresponding to a cyclic shift offset (CSO) used by the UE. A PHICH group index group, wherein the CSO PHICH group index group includes at least one PHICH group index, wherein the at least one PHICH group index corresponds to any of the CSOs different from the CSO used by the UE The CSO PHICH group index is mapped to the PRB index in the same order as the at least one PHICH group index included in the group. The plurality of PHICH sequence index includes a CSO PHICH sequence index group corresponding to the CSO used by the UE, wherein the CSO PHICH sequence index group includes at least one PHICH sequence index, wherein the at least one PHICH sequence index The CSO PHICH sequence index group corresponding to any CSO is characterized in that it is mapped to the PRB index so as not to overlap with at least one PHICH sequence index.

Another method proposed by the present invention; A signal transmission method of a base station in a wireless communication system, comprising: a plurality of physical resource block (PRB) indexes, a plurality of PHICH group indexes and a plurality of PHICH sequence indexes to a user equipment (UE) Transmitting a signal through an assigned Physical Automatic Repeat Request (HARQ) Indicator Channel (PHICH), wherein the plurality of PHICH group indexes correspond to a cyclic shift offset (CSO) used by the UE. And a CSO PHICH group index group, wherein the CSO PHICH group index group includes at least one PHICH group index, wherein the at least one PHICH group index is assigned to any one of the CSOs different from the CSO used by the UE. At least one PHICH group index included in the corresponding CSO PHICH group index group is included in the PRB index in the same order. The plurality of PHICH sequence indexes includes a CSO PHICH sequence index group corresponding to a CSO used by the UE, the CSO PHICH sequence index group includes at least one PHICH sequence index, and the at least one PHICH The sequence index may be mapped to a PRB index such that the sequence index does not overlap with at least one PHICH sequence index included in the CSO PHICH sequence index group corresponding to the CSO.

And the device proposed in the present invention; A signal receiving apparatus in a wireless communication system, comprising: a transceiver for performing wireless communication, a control unit for controlling the transceiver, and a plurality of physical resource block (PRB) indexes, a plurality of PHICH group indexes, and a plurality of PHICH sequences And a control unit for receiving a signal through a physical hybrid automatic repeat request (HICH) indicator channel (PHICH) allocated using an index, wherein the plurality of PHICH group indexes include a cyclic shift offset used by the signal receiving apparatus. Offset: CSO PHICH group index group corresponding to (CSO), wherein the CSO PHICH group index group includes at least one PHICH group index, wherein the at least one PHICH group index and the CSO used by the signal receiving device At least one PHICH, included in the CSO PHICH group index group corresponding to any of the different CSOs The plurality of PHICH sequence indexes may be mapped to PRB indexes in the same order as a group index, and the plurality of PHICH sequence indexes may include a CSO PHICH sequence index group corresponding to a CSO used by the signal reception apparatus, and the CSO PHICH sequence index group may include at least one And a PHICH sequence index, wherein the at least one PHICH sequence index is mapped to a PRB index so as not to overlap with at least one PHICH sequence index included in the CSO PHICH sequence index group corresponding to the CSO. .

Another apparatus proposed by the present invention; In the apparatus for transmitting a signal in a wireless communication system, a transceiver for performing wireless communication, and a controller for controlling the transceiver, a plurality of physical resource block (PRB) index, a plurality of PHICH group index and a plurality of PHICH sequences And a controller for transmitting a signal through a physical HARQ indicator channel (PHICH) allocated to a signal receiving apparatus using an index, wherein the plurality of PHICH group indexes are cyclic shifts used by the signal receiving apparatus. And a CSO PHICH group index group corresponding to an cyclic shift offset (CSO), wherein the CSO PHICH group index group includes at least one PHICH group index, wherein the at least one PHICH group index is determined by the signal receiving apparatus. The CSO PHICH group index group corresponding to any of the CSOs different from the CSO to be used includes And mapped to a PRB index in the same order as at least one PHICH group index, wherein the plurality of PHICH sequence indexes include a CSO PHICH sequence index group corresponding to a CSO used by the signal receiving apparatus, and the CSO PHICH sequence index The group includes at least one PHICH sequence index, and the at least one PHICH sequence index is included in the PRB index such that it does not overlap with at least one PHICH sequence index included in the CSO PHICH sequence index group corresponding to the CSO. Characterized in that it is mapped.

In the present invention, even when the PHICH resources are smaller than the number of uplink resources, there is an advantage that the PHICH does not need to be checked every time the uplink resources are allocated. In addition, in the present invention, even when a multiuser multiple input multiple output (MU-MIMO) scheme is used in a wireless communication system, an assignable cyclic shift offset to be used for an uplink demodulation reference signal by PHICH resources may be allocated. There is an advantage in that the reception performance is not reduced since the number of h) is not reduced.

1 is a view showing a structure of an OFDMA-based subframe used in a conventional LTE communication system,
2 illustrates a downlink resource map of a conventional wireless communication system;
3 illustrates an example of PRB mapping between a PHICH group index and a PHICH sequence index in a conventional wireless communication system;
4 is a view showing a wireless communication system according to an embodiment of the present invention;
5 is an internal configuration diagram of a base station according to an embodiment of the present invention;
6 is an internal configuration diagram of a UE according to an embodiment of the present invention;
7 illustrates an example of PRB mapping between a PHICH group index and a PHICH sequence index in a wireless communication system according to an embodiment of the present invention;
8 is a flowchart illustrating the operation of a base station according to an embodiment of the present invention;
9 is a flowchart illustrating the operation of a UE according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

The present invention proposes a method and apparatus for transmitting and receiving signals in a wireless communication system, for example, a Long Term Evolution (LTE) communication system. Specifically, in the present invention, an ACK (Acknowledgement) / NACK (Negative ACK) signal that is a response signal for uplink data is physical downlink control (PDCCH) in downlink based on an orthogonal frequency division multiple access (OFDMA). A method and apparatus for transmitting / receiving over a channel are provided.

In the present invention, for convenience of description, an LTE communication system is described as an example, but the signal transmission and reception method and apparatus proposed by the present invention can be applied not only to the LTE communication system but also to other communication systems.

The ACK / NACK signal is one of downlink control information (DCI) signals of a system in which a hybrid automatic repeat request (HARQ) is used, and refers to a signal for responding to successful reception of uplink data.

When the eNodeB receives uplink data through a PUSCH (Physical Uplink Shared Channel) from a user equipment (UE), the base station (eNodeB) through a physical HARQ indicator channel (PHICH) according to a decoding result of the uplink data. Send one of an ACK and a NACK signal to the UE. The ACK / NACK signal is transmitted using a resource element (RE) included in a radio resource region (hereinafter, referred to as a 'PDCCH region') in which a PDCCH signal is transmitted.

Hereinafter, a downlink resource map (MAP) of a conventional wireless communication system will be described with reference to FIG. 2.

2 illustrates a downlink resource map of a conventional wireless communication system. For example, FIG. 2 shows that the PDCCH region 200 is allocated during one symbol period.

The ACK / NACK signal is a reference signal (RS) (for example, a reference symbol T ₁ for a Tx antenna ₁ and a reference symbol T ₂ for a Tx antenna 2 in the PDCCH region 200. ), A control channel format indicator (CCFI) and a control channel element (CCE) can be transmitted using the remaining REs other than the REs used to transmit.

Since the transmission of the ACK / NACK signal aims at high reliability, the ACK / NACK signal is transmitted through a code division multiplexing (CDM) scheme. The CDM scheme mitigates interference by randomizing interference between channels transmitting ACK / NACK signals of different users.

For example, when using a Walsh sequence with a Spreading Factor (SF) of 4, four REs available among the available REs are used as shown in FIG. 2 to transmit an ACK / NACK signal and each to an I / Q signal. Other signals can be transmitted.

That is, one ACK / NACK signal is spread by a Walsh sequence having a length of 4, and as the same resource (ie, 4 REs) is used, ACK / NACK signals corresponding to up to 8 users can be transmitted.

Meanwhile, in order to obtain diversity gain in the frequency domain, the ACK / NACK signal may be transmitted repeatedly. In the current LTE communication system, since three repetitive transmissions are possible, a total of 12 REs are required to transmit an actual ACK / NACK signal.

Thus, 12 REs are grouped into one group, and four Walsh sequences on the I-axis and four Walsh sequences on the Q-axis are combined to refer to a normal cyclic prefix (normal CP) per group. ) Is defined as 8 sequences, and in the case of Extended Cyclic Prefix (hereinafter referred to as 'extented CP'), it is defined as 4 sequences. Accordingly, one CP may be used for eight users and one CP may be used for four users.

The radio resource for transmitting the ACK / NACK signal of the downlink, that is, the PHICH resource is referred to as a physical resource block (PRB) index and a demodulation reference signal (DMRS), which are physical resources of the uplink. It may be defined as a PHICH group index and a PHICH sequence index according to the cyclic shift offset (cyclic shift offset) to be used.

The PHICH group index indicates a number of a PHICH group, and the PHICH sequence index indicates an orthogonal sequence index within the PHICH group. In detail, the PHICH group index and the PHICH sequence index may be calculated by using Equation 1 at the base station and the UE, respectively.

는 상기 PHICH 그룹 인덱스를 나타내고,

는 상기 PHICH 시퀀스 인덱스를 나타낸다. 그리고,

는 UE가 할당받은 DM RS에 사용될 순환 쉬프트 오프셋을 나타내고,

는 PHICH에 대한 확산 지수(normal CP일 때 4, extended CP일 때 2)를 나타내고,

는 할당받은 상향링크 자원(PRB)들 중 가장 작은 인덱스를 나타낸다. 그리고,

는 다음 수학식 2를 사용하여 설정되며, TDD(Time Division Duplex) 방식이 사용될 때, 하향링크 전송 슬롯(slot)보다 상향링크 전송 슬롯이 더 많은 경우(즉, configuration 0인 경우), 서로 다른 상향링크 슬롯에서의 PHICH를 구분하기 위한 식별자를 나타낸다.In Equation (1)

Represents the PHICH group index,

Represents the PHICH sequence index. And,

Denotes a cyclic shift offset to be used for the DM RS allocated to the UE,

Denotes the spreading index for the PHICH (4 for normal CP, 2 for extended CP),

Denotes the smallest index among the allocated uplink resources (PRBs). And,

Is set using Equation 2 below, when TDD (Time Division Duplex) is used, when there are more uplink transmission slots than downlink transmission slots (that is, configuration 0), different uplinks are used. Represents an identifier for identifying a PHICH in a link slot.

는 PHICH 그룹의 개수로 다음 수학식 3과 같이 산출될 수 있다. Also,

May be calculated as shown in Equation 3 as the number of PHICH groups.

In Equation 3, N _g is 2-bit information transmitted on a broadcast channel and has one of 1/6, 1/2, 1, and 2, and indicates the maximum number of ACK / NACK signals that can be transmitted. Used to determine. The number of ACK / NACK is calculated as N _g times the total number of PRBs in the downlink.

In the current wireless communication system, the number of PHICH resources may be represented as a ratio of the total number of PRBs (hereinafter, referred to as the total number of PRBs) that can be allocated to the uplink according to the N _g value. Can be set.

The number of PHICH resources is set to 1/6 of the total number of PRBs when N _g is 0, and is set to 1/2 of the total number of PRBs when N _g is 1. The number of PHICH resources is set by the total number of PRBs when N _g is 2, and is set by twice the total number of PRBs when N _g is 3.

As described above, the PHICH group index and the PHICH sequence index according to Equations 1 to 3 may be mapped to the PRB as shown in FIG. 3.

3 is a diagram illustrating an example of PRB mapping between a PHICH group index and a PHICH sequence index in a conventional wireless communication system. In FIG. 3, for example, when N _g is 2 at 5 MHz, that is, a PHICH group index and a PHICH sequence index are mapped by the total number of PRBs.

First, a PRB mapping method of a PHICH group index will be described by taking a case where a PHICH group index of 0 to 6 is present as an example.

When the cyclic shift offset is 0, the PHICH group index is repeatedly mapped in order of 0,1,2,3,4,5,6 to PRB indexes 0 to 24. When the cyclic shift offset is 1, the PHICH group index is repeatedly mapped in order of 1,2,3,4,5,6,0 to PRB indexes 0 to 24. In this way, when the cyclic shift offset is n (n = 0 ~ 6), seven PHICH group indexes including n starting from n are repeated in PRB indexes 0 ~ 24 as one set. Mapped in sequence. In exceptional cases, when the cyclic shift offset is 7, the PHICH group index is sequentially mapped to the PRB indexes 0 to 24 in the form of repeating 0 to 6 starting from 0 as in the case of the cyclic shift offset to 0.

On the other hand, the PHICH sequence index is mapped to PRB indexes 0 to 24 in a form in which values are increased one by one according to the number of PHICH group indexes constituting one set.

In FIG. 3, since the PHICH group indexes 0 to 6 constitute one set, the number of PHICH group indexes constituting one set becomes seven. Therefore, the PHICH sequence index is mapped to PRB indexes 0 to 24 in a form in which values are increased by one in units of seven PRB indexes.

In detail, when the cyclic shift offset is 0, corresponding to the first PHICH group indexes 0 to 6 sequentially mapped to the PRB indexes 0 to 6, 0 is mapped to the PHICH sequence index corresponding to the PRB indexes 0 to 6. In addition, corresponding to the second PHICH group indexes 0 to 6 sequentially mapped to the PRB indexes 7 to 13, 1 is mapped to the PHICH sequence index corresponding to the PRB indexes 7 to 13.

In this manner, when the cyclic shift offset is n, the PHICH sequence index is mapped to PRB indexes 0 to 24 in a form in which values are increased by one in units of seven PRB indexes starting from n.

For example, when the cyclic shift offset is 0, the PHICH sequence index is mapped to the PRB index in increments of one by one from 0 to 7 PRB index units. When the cyclic shift offset is 1, the PHICH sequence index is 1 to 7 The value is mapped to the PRB index in increments of one PRB index unit, and when the cyclic shift offset is 2, the PHICH sequence index is mapped to the PRB index in increments of one to two PRB index units.

If the PHICH sequence index is to be mapped to the PRB index with a value greater than the number of PHICH group indexes, the PHICH group index is mapped to 0.

For example, when the cyclic shift offset is 7, PHICH sequence index 7 is mapped to PRB indexes 0 to 6, and then 0, which is increased by 1 from 7, is mapped to PRB indexes 7 to 13.

As described above, when both the PHICH group index and the PHICH sequence index are mapped to the PRB index, the base station may transmit one of the ACK / NACK signals using the PHICH group index and the PHICH sequence index corresponding to each UE.

In detail, when a PRB corresponding to PRB indexes 0, 1, 2, and 3 is allocated with a cyclic shift offset of 0, a PHICH having a PHICH group index of 0 and a PHICH sequence index of 0 is used corresponding to the first UE of the plurality of UEs. Can be.

In addition, when a PRB corresponding to PRB indexes 8, 9, 10, 11, 12, and 13 is allocated with a cyclic shift offset of 0, a PHICH having a PHICH group index of 1 and a PHICH sequence index of 1 is assigned to a second UE of a plurality of UEs. Can be used correspondingly.

Meanwhile, the MU-MIMO scheme is used for the PRBs corresponding to the PRB indexes 0, 1, 2, and 3, so that the PRBs corresponding to the PRB indexes 0, 1, 2, and 3 may be allocated to the third UE. In this case, the PHICH group index and the PHICH sequence index when the cyclic shift offset is assigned 1 may be used as the most optimal performance. The combination of the PHICH group index and the PHICH sequence index according to the cyclic shift offset used as the most optimal performance may be preset in advance.

When cyclic shift offset 1 is assigned, the PHICH group index corresponding to PRB indexes 0, 1, 2, and 3 is 1 and the PHICH sequence index is 1. This is the same as the PHICH group index and the PHICH sequence index used by the second UE. Therefore, since the third UE cannot use PHICH group index 1 and PHICH sequence index 1, cyclic shift offset 1 cannot be used and cyclic shift offset 2 should be used instead.

This is because when the cyclic shift offset 2 is used, since the PHICH group index corresponding to PRB indexes 0, 1, 2, and 3 is 2 and the PHICH sequence index is 2, it does not overlap with the PHICH group index and PHICH sequence index of another UE. .

As such, when the MU-MIMO method using different cyclic shift offsets is used in the same PRB, there is a problem that the PHICH group index and the PHICH sequence index corresponding to one UE overlap with the PHICH group index and the PHICH sequence index of the other UE. May occur. Accordingly, the PHICH group index and the PHICH sequence index that optimize the reception performance cannot be used, which causes a limitation in cyclic shift offset allocation, and also causes a problem that the MU-MIMO scheme cannot be used or the reception performance of corresponding UEs is degraded.

Accordingly, the present invention solves the above problems, and proposes a PRB mapping method of PHICH group index and PHICH sequence index to efficiently perform downlink PHICH resource and uplink resource allocation.

Hereinafter, a wireless communication system according to an exemplary embodiment of the present invention will be described with reference to FIG. 4.

4 is a diagram illustrating a wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the wireless communication system includes a base station 400 and a plurality of UEs 410 and 420.

When the base station 400 receives data from the UEs 410 and 420 through the PUSCH, one of the ACK and NACK signals is transmitted to the UEs 410 and 420 through the PHICH according to the data decoding result. Send.

Then, each of the UEs 410 and 420 transmits data to be transmitted next to the base station 400 when an ACK signal is received, and transmits previously transmitted data to the base station 400 when a NACK signal is received. Resend to 400).

Hereinafter, internal configurations of the base station 400 and the UEs 410 and 420 will be described in detail with reference to FIGS. 5 and 6.

5 is an internal configuration diagram of a base station according to an embodiment of the present invention.

Referring to FIG. 5, the base station includes a transceiver 500, a decoder 510, and a controller 520.

The transceiver 500 performs a wireless communication function of the base station. For example, the transceiver 500 receives data from the UE and transmits an ACK or NACK signal corresponding to the received data to the UE.

The decoder 510 decodes the received data and outputs the decoded data to the controller 520.

The controller 520 controls the transceiver 500 and the decoder 510 and manages overall operations of the base station.

The controller 520 generates UL grant information including UL resource allocation information and transmits the UL grant information to the UE through the transceiver 500. When the data is received from the UE, the controller 520 transmits the received data to the decoder 510. Subsequently, the controller 520 transmits one of the ACK / NACK signals to the UE 410 through a PHICH corresponding to a PHICH group index and a PHICH sequence index according to the data decoding result of the decoder 510. .

In detail, the controller 520 decodes the received data through a reverse error correction (FEC) reverse process, and then determines whether there is an error through a cyclic redundancy check (CRC) check on the decoded data. When there is no error in the decoded data as a result of the CRC test, the controller 520 feeds back an ACK signal to the UE so that the UE can transmit the next data. In contrast, when there is an error in the decoded data as a result of the CRC test, the controller 520 feeds back a NACK signal to the UE to retransmit previously transmitted data.

6 is a diagram illustrating an internal configuration of a UE according to an embodiment of the present invention.

Referring to FIG. 6, the UE includes a transceiver 600, an encoder 610, and a controller 620.

The transceiver 600 performs a wireless communication function of the UE. For example, the transceiver 600 transmits data to a base station and receives an ACK or NACK signal corresponding to the transmitted data from the base station.

The encoder 610 encodes data to be transmitted, and outputs the encoded data to the controller 620.

The controller 620 controls the transceiver 600 and the encoder 610 and manages the overall operation of the UE.

The controller 620 receives uplink grant information including uplink resource allocation information from the base station through the transceiver 600. The controller 620 generates data to be transmitted to the base station using the uplink grant information, and transmits the generated data to the base station through a PUSCH. The controller 620 receives one of the ACK / NACK signals from the base station in response to the transmitted data using a corresponding PHICH group index and a PHICH sequence index.

The UE configured as described above receives the ACK / NACK signal using the determined PHICH group index and the PHICH sequence index after determining the PHICH group index and the PHICH sequence index in the following manner.

값을 알려주는 phich_Resource 정보를 수신한다.

는 1/6, 1/2, 1, 2 와 같은 4가지의 값 중 하나로 설정될 수 있으며, phich_Resource는 상기 4가지 값 중 하나에 대응하는 인덱스(index)를 나타낸다. 일 예로, phich_Resource가 0이면 phich_Resource는 1/6의 값을 갖는

에 대응하며, phich_Resource가 3이면 phich_Resource는 2의 값을 갖는

에 대응할 수 있다. The UE determines from the base station to determine the PHICH group index and PHICH sequence index corresponding to the UE

Receive phich_Resource information indicating a value.

May be set to one of four values such as 1/6, 1/2, 1, and 2, and phich_Resource represents an index corresponding to one of the four values. For example, if phich_Resource is 0, phich_Resource has a value of 1/6.

If phich_Resource is 3, phich_Resource has a value of 2.

It can correspond to.

값을 상기 기지국으로부터 수신하거나 기존의 phich-Resource값으로부터 획득한다. 상기

값은 MU-MIMO 방식이 사용되는지 여부를 나타내는 파라미터로서, 일 예로 1의 값으로 설정된 경우 MU-MIMO 방식이 사용되고 있음을 나타내며 0의 값으로 설정된 경우 MU-MIMO 방식이 사용되지 않음을 나타낸다.The UE is a parameter proposed by the present invention

A value is received from the base station or obtained from an existing phich-resource value. remind

The value is a parameter indicating whether the MU-MIMO method is used. For example, when the value is set to 1, the value indicates that the MU-MIMO method is used. If the value is set to 0, the value indicates that the MU-MIMO method is not used.

값을 수신할 수 있다. 이와 달리, 상기 UE는 2 비트로 구성된 기존의 phich_Resource값의 상위 비트를

값을 나타내는 지시자(indicator)로서 이용한다. 따라서,

값은 phich_Resource값의 상위 비트가 1이 되는 경우 즉, phich_Resource값이 2나 3인 경우에 MU-MIMO 방식이 사용됨을 나타낼 수 있다.The UE has one bit applicable to all existing phich_Resource values from the base station.

Can receive a value. In contrast, the UE sends a higher bit of the existing phich_Resource value composed of 2 bits.

Used as an indicator of values. therefore,

The value may indicate that the MU-MIMO method is used when the upper bit of the phich_Resource value is 1, that is, when the phich_Resource value is 2 or 3.

값이 사용되어 다음 수학식 4를 통해 산출될 수 있다.The PHICH group index and the PHICH sequence index proposed by the present invention are as described above.

The value may be used to calculate the following equation (4).

는 기지국으로부터 수신되거나, 기존의 phich_Resource값이 사용되어

로 계산된다. 그리고,

는 현재 할당된 DM RS 인덱스에 따라 사용되는 순환 쉬프트 오프셋을 나타낸다.

,

,

,

,

,

및

는 수학식 1~3에서 이미 설명하였으므로 상세한 설명은 생략하도록 한다. In Equation 4

Is received from the base station, or the existing phich_Resource value is used.

. And,

Denotes a cyclic shift offset used according to a currently allocated DM RS index.

,

,

,

,

,

And

Has already been described in Equations 1 to 3, so a detailed description thereof will be omitted.

Meanwhile, the PHICH group index and the PHICH sequence index determination scheme of the UE may be used correspondingly to the corresponding UE in the base station.

7 illustrates an example of PRB mapping between a PHICH group index and a PHICH sequence index in a wireless communication system according to an embodiment of the present invention. In FIG. 7, for example, when N _g is 2 at 5 MHz, that is, the PHICH group index and the PHICH sequence index are mapped by the total number of PRBs.

First, a PRB mapping method of a PHICH group index will be described by taking a case where a PHICH group index of 0 to 6 is present as an example.

When the cyclic shift offset is 0 or 1, the PHICH group index is repeatedly mapped in order of 0, 1, 2, 3, 4, 5, 6 to PRB indexes 0 to 24. When the cyclic shift offset is 2 or 3, the PHICH group index is repeatedly mapped in order of 1,2,3,4,5,6,0 to PRB indexes 0 to 24. Also, when the cyclic shift offset is 4 or 5, the PHICH group index is repeatedly mapped in order of 2,3,4,5,6,0,1 to the PRB indexes 0 to 24, and the cyclic shift offset. When this is 6 or 7, the PHICH group index is repeatedly mapped in order of 3,4,5,6,0,1,2 to PRB indexes 0-24.

On the other hand, the PHICH sequence index is mapped to the PRB indexes 0 to 24 in a form in which a value increases by 2 in units of PRB indexes according to the number of PHICH group indexes forming one set.

In detail, the PHICH sequence index 0 is mapped to the PRB indexes 0 to 6 corresponding to the first PHICH group indexes 0 to 6 sequentially mapped to the PRB indexes 0 to 6. The PHICH sequence index 2 is mapped to the PRB indexes 7 to 13 corresponding to the second PHICH group indexes 0 to 6 sequentially mapped to the PRB indexes 7 to 13.

In this manner, when the cyclic shift offset is n, the PHICH sequence index is mapped to PRB indexes 0 to 24 in a form in which a value increases by 2 in units of 7 PRB indexes starting from n.

For example, when the cyclic shift offset is 0, the PHICH sequence index is mapped to the PRB index in increments of 2 by 0 in units of 7 PRB indexes. When the cyclic shift offset is 1, the PHICH sequence index is 1 to 7 If the cyclic shift offset is 2, the PHICH sequence index is mapped to the PRB index in increments of 2 to 7 PRB index units. do.

When the PHICH sequence index is to be mapped to the PRB index with a value larger than the number of PHICH group indexes, the PHICH group index is mapped to 0 or 1.

For example, when the cyclic shift offset is 6, PHICH sequence index 6 is mapped to PRB indexes 0 to 6, and then 8 is increased from 6 to 2, and 0 is mapped to PRB indexes 7 to 13. And, if the cyclic shift offset is 7, PHICH sequence index 7 is mapped to PRB indexes 0 to 6, and then 1 is mapped to 9 instead of 9, which is increased from 2 to PRB indexes 7 to 13.

As described above, when both the PHICH group index and the PHICH sequence index are mapped to the PRB index, even if a MU-MIMO method using different cyclic shift offsets is used for the same PRB, the PHICH group index corresponding to one UE and The problem that the PHICH sequence index overlaps with the PHICH group index and the PHICH sequence index of another UE does not occur. In addition, since the PHICH group index and the PHICH sequence index may be combined according to the cyclic shift offset for optimizing the reception performance, the duplication of the PHICH group index and the PHICH sequence index may limit the allocation of the cyclic shift offset. Can be.

Hereinafter, an operation of a base station according to an embodiment of the present invention will be described with reference to FIG. 8.

8 is a flowchart illustrating the operation of a base station according to an embodiment of the present invention.

Referring to FIG. 8, the base station receives uplink data through the PUSCH from the UE in step 800. The base station decodes the data received in step 802 and determines whether decoding is successful in step 804.

If the decoding is successful, the base station proceeds to step 806 to generate an ACK signal, and if the decoding is not successful, proceeds to step 808 to generate a NACK signal.

After determining whether to use the MU-MIMO scheme in step 810, the base station determines the PHICH group index and the PHICH sequence index corresponding to the corresponding UE by using Equation 4 described above. In this case, when the MU-MIMO scheme is used, the base station may determine the PHICH group index and the PHICH sequence index of each UE to use different cyclic shift offsets in the same PRB.

The base station may select the PHICH group index and the PHICH sequence index according to the cyclic shift offset to maximize the reception performance of each UE according to the mapping method as shown in FIG. 7 without overlapping each other.

That is, the base station corresponds to each UE at least one PHICH group index determined corresponding to the cyclic shift offset of each UE among the PHICH group indexes mapped in the same order for the at least two cyclic shift offsets PHICH group index to be selected. The base station determines, for each of the at least two cyclic shift offsets, corresponding to the cyclic shift offsets of each UE among the plurality of PHICH sequence indexes mapped to the plurality of PRB indexes such that the at least two cyclic shift offsets do not overlap each other. At least one PHICH sequence index is selected as a PHICH sequence index corresponding to each UE.

In step 812, the base station transmits one of the generated ACK / NACK signals for each UE by using the selected PHICH group index and PHICH sequence index.

Next, the operation of the UE according to an embodiment of the present invention will be described with reference to FIG. 9.

9 is a flowchart illustrating the operation of a UE according to an embodiment of the present invention.

Referring to FIG. 9, the UE generates data using uplink resources allocated from the base station in operation 900. In operation 902, the UE encodes the generated data and transmits the encoded data to the base station.

를 수신하고, 상기 수신된

를 사용하여 앞서 설명한 수학식 4에 따라 PHICH 그룹 인덱스 및 PHICH 시퀀스 인덱스를 선택한다. Next, the UE is a parameter indicating whether the MU-MIMO scheme is used from the base station in step 904.

Receive the received

The PHICH group index and the PHICH sequence index are selected using Equation 4 described above.

That is, the UE corresponds to the UE by at least one PHICH group index determined corresponding to the cyclic shift offset of the UE among the PHICH group indexes mapped in the same order for the at least two cyclic shift offsets. PHICH group index to be selected. The UE is determined corresponding to the cyclic shift offset of the UE among the PHICH sequence indexes mapped to the plurality of PRB indexes so that the at least two cyclic shift offsets do not overlap each other. At least one PHICH sequence index is selected as the PHICH sequence index corresponding to the UE.

를 기지국으로부터 수신하지 않고, 기존의 N_g 값의 상위 비트로부터

를 획득하는 것도 가능하다.Meanwhile, the UE

Without receiving from the base station, and from the higher bits of the existing N _g value.

It is also possible to obtain.

In step 906, the UE receives one of ACK / NACK signals from the base station using the selected PHICH group index and PHICH sequence index.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

Claims (20)

In the method of receiving a signal of a user equipment (UE) in a wireless communication system,
Receives a signal through a Physical Hybrid Repeat Repeat (HICH) Indicator Channel (PHICH) allocated using a plurality of Physical Resource Block (PRB) indexes, a plurality of PHICH group indexes, and a plurality of PHICH sequence indexes Process,
The plurality of PHICH group index includes a CSO PHICH group index group corresponding to a cyclic shift offset (CSO) used by the UE,
The CSO PHICH group index group includes at least one PHICH group index, and the at least one PHICH group index includes a CSO PHICH group index group corresponding to any CSO among CSOs different from the CSO used by the UE. Map to PRB indexes in the same order as at least one PHICH group index,
The plurality of PHICH sequence index includes a CSO PHICH sequence index group corresponding to the CSO used by the UE,
The CSO PHICH sequence index group includes at least one PHICH sequence index, and the at least one PHICH sequence index overlaps with at least one PHICH sequence index included in the CSO PHICH sequence index group corresponding to the CSO. Signal reception method, characterized in that mapped to the PRB index.
The method of claim 1,
The plurality of PHICH group index and the plurality of PHICH sequence index,
It is determined using a parameter received from a base station, wherein the parameter indicates whether the base station uses a multi-user multiple input multiple output (MU-MIMO) scheme.
The method of claim 2,
The plurality of PHICH group index and the plurality of PHICH sequence index is determined using the following equation (5).
<Equation 5>

In Equation 5,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes the cyclic shift offset to be used for the demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the base station uses the MU-MIMO scheme.
The method of claim 1,
The plurality of PHICH group index and the plurality of PHICH sequence index,
Determined using a parameter used to determine the maximum number of ACK / NACK signals that a base station can transmit, wherein a part of the parameter is whether the base station uses a multiuser multiple input multiple output (MU-MIMO) scheme. Signal receiving method characterized in that.
The method of claim 4, wherein
The plurality of PHICH group index and the plurality of PHICH sequence index is determined using the following equation (6).
&Quot; (6) &quot;

In Equation 6,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes the cyclic shift offset to be used for the demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the base station uses the MU-MIMO scheme.
A signal transmission method of a base station in a wireless communication system,
Physical Hybrid Repeat Request (PHICH) assigned to user equipment (UE) using a plurality of physical resource block (PRB) indexes, a plurality of PHICH group indexes, and a plurality of PHICH sequence indexes An indicator channel).
The plurality of PHICH group index includes a CSO PHICH group index group corresponding to a cyclic shift offset (CSO) used by the UE,
The CSO PHICH group index group includes at least one PHICH group index, and the at least one PHICH group index includes a CSO PHICH group index group corresponding to any CSO among CSOs different from the CSO used by the UE. Map to PRB indexes in the same order as at least one PHICH group index,
The plurality of PHICH sequence index includes a CSO PHICH sequence index group corresponding to the CSO used by the UE,
The CSO PHICH sequence index group includes at least one PHICH sequence index, and the at least one PHICH sequence index overlaps with at least one PHICH sequence index included in the CSO PHICH sequence index group corresponding to the CSO. Signal transmission method characterized in that it is mapped to the PRB index.
The method of claim 6,
The plurality of PHICH group index and the plurality of PHICH sequence index,
And determining by using a parameter indicating whether the base station uses a multi-user multiple input multiple output (MU-MIMO) scheme.
The method of claim 7, wherein
The plurality of PHICH group index and the plurality of PHICH sequence index is determined using the following equation (7).
&Quot; (7) &quot;

In Equation 7,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes a cyclic shift offset to be used by the UE for demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the base station uses the MU-MIMO scheme.
The method of claim 6,
The plurality of PHICH group index and the plurality of PHICH sequence index,
It is determined using a parameter used to determine the maximum number of ACK / NACK signals that can be transmitted. A part of the parameter indicates whether the base station uses a multiuser multiple input multiple output (MU-MIMO) scheme. Signal transmission method characterized in that.
10. The method of claim 9,
The plurality of PHICH group index and the plurality of PHICH sequence index is determined using the following equation (8).
<Equation 8>

In Equation 8,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes a cyclic shift offset to be used by the UE for demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the base station uses the MU-MIMO scheme.
A signal receiving apparatus in a wireless communication system,
A transceiver for performing wireless communication,
The physical HARQ indicator channel (PHICH) allocated using a plurality of physical resource block (PRB) indexes, a plurality of PHICH group indexes, and a plurality of PHICH sequence indexes by controlling the transceiver. It includes a control unit for receiving a signal through,
The plurality of PHICH group indexes include a CSO PHICH group index group corresponding to a cyclic shift offset (CSO) used by the signal receiving apparatus.
The CSO PHICH group index group includes at least one PHICH group index, wherein the at least one PHICH group index is a CSO PHICH group index group corresponding to any CSO among CSOs different from the CSO used by the signal receiving apparatus. Including, at least one PHICH group index mapped to the PRB index in the same order mutually,
The plurality of PHICH sequence index includes a CSO PHICH sequence index group corresponding to the CSO used by the signal receiving apparatus,
The CSO PHICH sequence index group includes at least one PHICH sequence index, and the at least one PHICH sequence index overlaps with at least one PHICH sequence index included in the CSO PHICH sequence index group corresponding to the CSO. Signal receiving apparatus, characterized in that mapped to the PRB index so as not to be.
The method of claim 11,
The plurality of PHICH group index and the plurality of PHICH sequence index,
The signal receiving apparatus is determined using a parameter received from a signal transmitting apparatus, wherein the parameter indicates whether the signal transmitting apparatus uses a multiuser multiple input multiple output (MU-MIMO) scheme.
The method of claim 12,
The plurality of PHICH group index and the plurality of PHICH sequence index is determined using the following equation (9).
<Equation 9>

In Equation 9,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes the cyclic shift offset to be used for the demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the signal transmission device uses the MU-MIMO method.
The method of claim 11,
The plurality of PHICH group index and the plurality of PHICH sequence index,
The signal transmitting apparatus is determined using a parameter used to determine the maximum number of ACK / NACK signals that can be transmitted, and a part of the parameter is determined by the signal transmitting apparatus in a multiuser multiple input multiple output (MU-MIMO) scheme. Signal receiving device, characterized in that indicating whether or not to use.
The method of claim 14,
The plurality of PHICH group index and the plurality of PHICH sequence index is determined using the following equation (10).
<Equation 10>

In Equation 10,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes the cyclic shift offset to be used for the demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the signal transmission apparatus uses the MU-MIMO scheme.
In the signal transmission apparatus in a wireless communication system,
A transceiver for performing wireless communication,
By controlling the transceiver, a physical hybrid repeat request (PHICH) assigned to a signal receiving apparatus using a plurality of physical resource block (PRB) indexes, a plurality of PHICH group indexes, and a plurality of PHICH sequence indexes A control unit transmitting a signal through an indicator channel),
The plurality of PHICH group indexes include a CSO PHICH group index group corresponding to a cyclic shift offset (CSO) used by the signal receiving apparatus.
The CSO PHICH group index group includes at least one PHICH group index, wherein the at least one PHICH group index is a CSO PHICH group index group corresponding to any CSO among CSOs different from the CSO used by the signal receiving apparatus. Including, at least one PHICH group index mapped to the PRB index in the same order mutually,
The plurality of PHICH sequence index includes a CSO PHICH sequence index group corresponding to the CSO used by the signal receiving apparatus,
The CSO PHICH sequence index group includes at least one PHICH sequence index, and the at least one PHICH sequence index overlaps with at least one PHICH sequence index included in the CSO PHICH sequence index group corresponding to the CSO. Signal transmitting apparatus, characterized in that mapped to the PRB index so as not to be.
The method of claim 16,
The plurality of PHICH group index and the plurality of PHICH sequence index,
And the signal transmitter is determined using a parameter indicating whether the signal transmitter uses a multiuser multiple input multiple output (MU-MIMO) scheme.
The method of claim 17,
The plurality of PHICH group index and the plurality of PHICH sequence index is determined using the following equation (11).
<Equation 11>

In Equation 11,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes a cyclic shift offset to be used by the signal receiving apparatus for demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the signal transmission apparatus uses the MU-MIMO scheme.
The method of claim 16,
The plurality of PHICH group index and the plurality of PHICH sequence index,
It is determined using a parameter used to determine the maximum number of ACK / NACK signals that can be transmitted, and part of the parameter is whether the signal transmission apparatus uses a multiuser multiple input multiple output (MU-MIMO) scheme. Signal transmission apparatus characterized in that.
The method of claim 19,
And the plurality of PHICH group indexes and the plurality of PHICH sequence indexes are determined using Equation 12 below.
<Equation 12>

In Equation 12,

Represents one of the plurality of PHICH group indexes,

Represents one of the plurality of PHICH sequence indexes,

Denotes a cyclic shift offset to be used by the signal receiving apparatus for demodulation reference signal,

Denotes the diffusion index for the PHICH (set to 4 for the Normal Cyclic Prefix and set to 2 for the Extended Cyclic Prefix),

Represents the smallest PRB index among the plurality of allocated PRB indexes,

When the time division duplex (TDD) scheme is used, when there are more uplink transmission slots than downlink transmission slots, the ID indicates an identifier for distinguishing PHICHs from different uplink slots.

Represents the number of PHICH groups,

The value indicates whether the signal transmission apparatus uses the MU-MIMO scheme.

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