KR102204200B1 - Apparatus and method for transmitting and receiving reference signal on small cells environment - Google Patents

Abstract

Disclosed is a method and apparatus for transmitting and receiving a reference signal in a small cell environment. In a wireless communication system, a method of transmitting a reference signal of a terminal is a step of determining whether uplink transmission based on a reduced DM-RS is possible based on an overhead reduction activation field received by the terminal from the base station, and the reduced DM-RS is performed. When the uplink transmission based on the base is possible, the terminal may include the step of determining whether to perform the uplink transmission based on the reduced DM-RS based on the uplink-related DCI received from the base station, The overhead reduction activation field is a field indicating whether the UE is capable of uplink transmission based on the reduced DM-RS, and the reduced DM-RS may be allocated to one orthogonal frequency division multiplexing (OFDM) symbol per subframe. .

Description

Method and apparatus for transmitting and receiving a reference signal in a small cell environment {APPARATUS AND METHOD FOR TRANSMITTING AND RECEIVING REFERENCE SIGNAL ON SMALL CELLS ENVIRONMENT}

The present invention relates to wireless communication, and more particularly, to a method and apparatus for transmitting and receiving a reference signal in a wireless communication system supporting a small cell.

In next-generation communication systems such as LTE-A (Advanced), not only a macro cell (F1) based on a high-power node, but also a small cell (F2) based on a low-power node. ), a study is in progress to provide wireless communication services to indoors and outdoors.

The small cell may be considered in both a frequency band that is the coverage of the macro cell and a frequency band other than the coverage of the macro cell, and may be provided in both an indoor environment (inside the cube) and an outdoor environment (outside the cube). In addition, an ideal or non-ideal backhaul network may be supported between a macro cell and a small cell and/or between the small cells. In addition, the small cell may be provided in both a sparse deployment environment and/or a dense deployment environment of a low density.

An object of the present invention is to provide a method of transmitting a reference signal in a wireless communication system supporting a small cell.

Another object of the present invention is to provide an apparatus for transmitting a reference signal in a wireless communication system supporting a small cell.

In a wireless communication system according to an aspect of the present invention for achieving the above-described object of the present invention, a method for transmitting a reference signal by a terminal includes a reduction uplink DM (demodulation) based on an overhead reduction activation field received by the terminal from the base station. -Determining whether uplink transmission based on a reference signal (RS) is possible, and when uplink transmission based on the reduced uplink DM-RS is possible, the uplink received by the terminal from the base station And determining whether to perform uplink transmission based on the reduced uplink DM-RS based on uplink related downlink control information (DCI). The overhead reduction activation field is a field indicating whether the terminal is capable of uplink transmission based on the reduced uplink DM-RS, and the reduced uplink DM-RS may be allocated to one symbol per subframe. have. In addition, the step of determining whether to perform uplink transmission based on the reduced uplink DM-RS may include, when the format of the uplink-related DCI is DCI format 0, the terminal performs the reduced uplink DM-RS. Performing uplink transmission based on, and when the format of the uplink-related DCI is DCI format 4, it is determined whether the number of layers allocated for uplink transmission of the terminal is less than or equal to the number of threshold layers, and the The terminal may include performing uplink transmission based on the reduced uplink DM-RS. Here, the number of threshold layers is the number of layers serving as a criterion for determining whether to perform uplink transmission based on the reduced uplink DM-RS. On the other hand, the step of determining whether to perform uplink transmission based on the reduced uplink DM-RS may include, if the format of the uplink-related DCI is DCI format 0, the terminal performs the reduced uplink DM-RS. Performing uplink transmission based on, and when the format of the uplink-related DCI is DCI format 4, the terminal reduces the uplink DM-RS based on an overhead reduction field included in the DCI format 4 It may include the step of determining whether to perform uplink transmission based on. The overhead reduction field may be a field indicating whether the terminal uses the reduced uplink DM-RS. In addition, the step of determining whether to perform uplink transmission based on the reduced uplink DM-RS includes a reduction in uplink transmission resources allocated based on the uplink-related DCI. Uplink DM-RS transmission available resources Determining whether to be associated with, and when the uplink transmission resource is associated with the reduced uplink DM-RS transmission available resource, performing uplink transmission based on the reduced uplink DM-RS Can include. The information on the available resources for the reduced uplink DM-RS transmission may be included in the overhead reduction activation field so that the UE receives it from the base station or may be predefined between the UE and the base station. The step of determining whether to perform uplink transmission based on the reduced uplink DM-RS may include, if the format of the uplink-related DCI is DCI format 0, the terminal is based on the reduced uplink DM-RS. Performing uplink transmission with the uplink, if the format of the uplink-related DCI is DCI format 4, whether the uplink transmission resource allocated based on the DCI format 4 is associated with the reduced uplink DM-RS transmission available resource Determining, and when the uplink transmission resource is associated with the reduced uplink DM-RS transmission available resource, performing uplink transmission based on the reduced uplink DM-RS, the The information on the available resources for reduced uplink DM-RS transmission is included in the overhead reduction activation field and may be received by the terminal from the base station or may be predefined between the terminal and the base station. And the step of determining whether to perform uplink transmission based on the reduced uplink DM-RS includes the reduced uplink based on information on a cyclic shift field included in the uplink-related DCI. This may be a step of determining whether to perform uplink transmission using the DM-RS. On the other hand, the step of determining whether to perform uplink transmission based on the reduced uplink DM-RS may include, if the format of the uplink-related DCI is DCI format 0, the terminal performs the reduced uplink DM-RS. Performing uplink transmission based on, and when the format of the uplink-related DCI is DCI format 4, the reduction uplink is based on information on a cyclic shift field included in the uplink-related DCI This may be a step of determining whether to perform uplink transmission using the link DM-RS.

In a terminal for transmitting a reference signal in a wireless communication system according to another aspect of the present invention for achieving the object of the present invention, the terminal is an RF (radio frequency) unit for transmitting and receiving a radio signal, and the RF And a processor selectively connected to the unit, wherein the processor determines whether uplink transmission is possible based on a reduction DM (demodulation)-RS (reference signal) based on an overhead reduction activation field received from the base station, and , When uplink transmission based on the reduced uplink DM-RS is possible, uplink based on the reduced uplink DM-RS based on uplink related downlink control information (DCI) received from the base station It is implemented to determine whether to perform link transmission, and the overhead reduction activation field is a field indicating whether the terminal is capable of uplink transmission based on the reduced uplink DM-RS, and the reduced uplink DM- RS may be allocated to one symbol per subframe. Here, when the format of the uplink-related DCI is DCI format 0, the processor performs uplink transmission based on the reduced uplink DM-RS, and when the format of the uplink-related DCI is DCI format 4 , Is implemented to perform uplink transmission based on the reduced uplink DM-RS by determining whether the number of layers allocated for uplink transmission of the terminal is less than or equal to the number of critical layers, wherein the number of critical layers is reduced It may be the number of layers serving as a reference for determining whether to perform uplink transmission based on the uplink DM-RS. When the format of the uplink-related DCI is DCI format 0, the processor performs uplink transmission based on the reduced uplink DM-RS, and when the uplink-related DCI format is DCI format 4, the Implemented to determine whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction field included in DCI format 4, wherein the overhead reduction field indicates that the terminal is the reduced uplink DM May be a field indicating whether to use -RS. Meanwhile, the processor determines whether an uplink transmission resource allocated based on the uplink-related DCI is associated with a reduced uplink DM-RS transmission available resource, and the uplink transmission resource is reduced to the reduced uplink DM- When associated with an available RS transmission resource, it is implemented to perform uplink transmission based on the reduced uplink DM-RS, but the information on the reduced uplink DM-RS transmission available resource is in the overhead reduction activation field. It may be included and the terminal may receive from the base station or may be predefined between the terminal and the base station. When the format of the uplink-related DCI is DCI format 0, the processor performs uplink transmission based on the reduced uplink DM-RS, and when the uplink-related DCI format is DCI format 4, the Determine whether an uplink transmission resource allocated based on DCI format 4 is a reduced uplink DM-RS transmission available resource, and if the uplink transmission resource is the reduced uplink DM-RS transmission available resource, the reduced uplink It is implemented to perform uplink transmission based on link DM-RS, and the information on the available resources for the reduced uplink DM-RS transmission is included in the overhead reduction activation field so that the terminal receives it from the base station or It may be predefined between the terminal and the base station. Meanwhile, the processor may be implemented to determine whether to perform uplink transmission using the reduced uplink DM-RS based on information on a cyclic shift field included in the uplink-related DCI. have. In addition, when the format of the uplink-related DCI is DCI format 0, the processor performs uplink transmission based on the reduced uplink DM-RS, and when the format of the uplink-related DCI is DCI format 4 , May be implemented to determine whether to perform uplink transmission using the reduced uplink DM-RS based on information on a cyclic shift field included in the uplink-related DCI.

In a small cell environment, the UE may perform uplink transmission by newly defining a resource allocated for transmitting a reference signal. By adjusting the resources allocated to the uplink DM (demodulation)-RS (reference signal) in consideration of the channel environment of the small cells, the overhead of the uplink DM-RS can be reduced, thereby increasing the data transmission efficiency of the terminal in the small cell. have.

1 is a block diagram showing a wireless communication system to which the present invention is applied.
2 and 3 schematically show the structure of a radio frame to which the present invention is applied.
4 is a conceptual diagram illustrating transmission of an uplink DM-RS when a PUSCH is transmitted.
5 is a conceptual diagram illustrating that one basic reference signal sequence is generated as a plurality of reference sequences according to cyclic shift.
6 shows an uplink DM-RS generated using an orthogonal cover code.
7 is a conceptual diagram showing a small cell environment.
8 is a conceptual diagram showing that an uplink DM-RS is allocated from an existing resource block.
9 is a conceptual diagram showing resource allocation of an uplink DM-RS according to an embodiment of the present invention
10 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.
11 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.
12 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.
13 is a flowchart showing a method for selecting an uplink DM-RS according to an embodiment of the present invention.
14 shows a method of defining available resources for reduced uplink DM-RS transmission according to an embodiment of the present invention.
15 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.
16 is a flowchart showing a method for selecting an uplink DM-RS according to an embodiment of the present invention.
17 is a flowchart showing a method for selecting an uplink DM-RS according to an embodiment of the present invention.
18 is a block diagram showing a wireless communication system according to an embodiment of the present invention.

Hereinafter, some embodiments will be described in detail through exemplary drawings in the present specification. In adding reference numerals to constituent elements in each drawing, it should be noted that the same constituent elements are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in describing an embodiment of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present specification, a detailed description thereof will be omitted.

This specification describes a communication network, and operations performed in the communication network are performed in the process of controlling the network and transmitting data in a system (for example, a base station) that governs the communication network, or a terminal linked to the corresponding network. Work can be done in

1 is a block diagram showing a wireless communication system to which the present invention is applied.

Referring to FIG. 1, a wireless communication system 10 is widely deployed to provide various communication services such as voice and packet data. The wireless communication system 10 includes at least one base station (BS). Each base station 11 provides a communication service for a specific geographic area or frequency area, and may be referred to as a site. A site may be divided into a plurality of areas 15a, 15b, and 15c, which may be referred to as sectors, and each of the sectors may have different cell IDs.

The terminal 12 (user equipment, UE) may be fixed or mobile, and may be a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a PDA. (personal digital assistant), wireless modem (wireless modem), handheld device (handheld device) can be referred to as other terms. Base station 11 generally refers to a station communicating with the terminal 12, eNodeB (evolved-NodeB), BTS (Base Transceiver System), access point (Access Point), femto base station (Femto eNodeB), in-home Base station (Home eNodeB: HeNodeB), relay (relay), remote radio head (Remote Radio Head: RRH) may be referred to as other terms. Cells (15a, 15b, 15c) should be interpreted in a comprehensive meaning indicating a partial area covered by the base station 11, and encompass all various coverage areas such as megacells, macrocells, microcells, picocells, and femtocells. to be.

Hereinafter, downlink refers to a communication or communication path from the base station 11 to the terminal 12, and uplink refers to a communication or communication path from the terminal 12 to the base station 11 . In downlink, the transmitter may be a part of the base station 11 and the receiver may be a part of the terminal 12. In the uplink, the transmitter may be a part of the terminal 12 and the receiver may be a part of the base station 11. There is no limitation on a multiple access technique applied to the wireless communication system 10. Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA (SC-FDMA), OFDM-FDMA, OFDM-TDMA , OFDM-CDMA, such as various multiple access techniques can be used. These modulation techniques increase the capacity of the communication system by demodulating signals received from multiple users of the communication system. Uplink transmission and downlink transmission may use a Time Division Duplex (TDD) scheme transmitted using different times or a Frequency Division Duplex (FDD) scheme transmitted using different frequencies.

The layers of the radio interface protocol between the terminal and the base station are based on the lower three layers of the Open System Interconnection (OSI) model, which is widely known in communication systems. It may be divided into a second layer (L2) and a third layer (L3). Among them, a physical layer belonging to the first layer provides an information transfer service using a physical channel.

There are several physical channels used in the physical layer. The physical downlink control channel (PDCCH) is a resource allocation and transmission format of a downlink shared channel (DL-SCH), and a resource of an uplink shared channel (UL-SCH). Allocation information, resource allocation of upper layer control messages such as random access response transmitted on a physical downlink shared channel (PDSCH), transmission power control for individual terminals within a terminal group : TPC) Can carry a set of commands. A plurality of PDCCHs may be transmitted within the control region, and the UE may monitor the plurality of PDCCHs.

Control information of the physical layer mapped to the PDCCH is referred to as downlink control information (DCI). That is, DCI is transmitted through the PDCCH. The DCI may include an uplink or downlink resource allocation field, an uplink transmission power control command field, a control field for paging, a control field for indicating a random access response (RA response), and the like.

2 and 3 schematically show the structure of a radio frame to which the present invention is applied.

2 and 3, a radio frame includes 10 subframes. One subframe includes two slots. The time (length) for transmitting one subframe is called a transmission time interval (TTI). Referring to FIG. 2, for example, a length of one subframe may be 1 ms, and a length of one slot may be 0.5 ms.

One slot may include a plurality of symbols in the time domain. For example, in the case of a wireless system using Orthogonal Frequency Division Multiple Access (OFDMA) in a downlink (DL), the symbol may be an Orthogonal Frequency Division Multiplexing (OFDM) symbol, and SC in uplink (UL). -In the case of a wireless system using Single Carrier-Frequency Division Multiple Access (FDMA), the symbol may be a Single Carrier-Frequency Division Multiple Access (SC-FDMA) symbol. Meanwhile, the expression of the symbol period in the time domain is not limited by the multiple access method or the name.

The number of symbols included in one slot may vary according to the length of a cyclic prefix (CP). For example, in the case of a normal CP, 1 slot may include 7 symbols, and in the case of an extended CP, 1 slot may include 6 symbols.

A resource block (RB) is a resource allocation unit and includes a time-frequency resource corresponding to 180 kHz on a frequency axis and 1 slot on a time axis. A resource element (RE) represents the smallest time-frequency unit to which a modulation symbol of a data channel or a modulation symbol of a control channel is mapped.

In a wireless communication system, it is necessary to estimate an uplink channel or a downlink channel for data transmission/reception, system synchronization acquisition, and channel information feedback. A process of restoring a transmission signal by compensating for distortion of a signal caused by a sudden change in a channel environment is called channel estimation. In addition, it is necessary to measure a channel state of a cell to which the UE belongs or another cell. In general, a reference signal (RS) known to each other between a UE and a transmission/reception point is used for channel estimation or channel state measurement.

)를 추정할 수 있다.In the case of downlink channel estimation, since the terminal knows the information of the reference signal, it can estimate the channel based on the received reference signal and compensate the channel value to accurately obtain data sent from the base station. If p is the reference signal sent from the base station, h is the channel information experienced by the reference signal during transmission, n is the thermal noise generated by the terminal, and y is the signal received by the terminal, it can be expressed as y = h·p + n. . At this time, since the reference signal p is already known by the terminal, when using the LS (Least Square) method, channel information (

) Can be estimated.

<Equation 1>

는

값에 의존하게 되므로, 정확한 h값의 추정을 위해서는

이 0에 수렴시킬 필요가 있다. Here, the channel estimate value estimated using the reference signal p

Is

Depends on the value, so for accurate estimation of h

We need to converge to this zero.

In the case of uplink channel estimation, it can be described similarly to the aforementioned downlink channel estimation, except that the transmitting subject of the reference signal is the terminal and the receiving subject is the base station.

Reference signals are generally transmitted by generating signals from a sequence of reference signals. As the reference signal sequence, one or more of various sequences having excellent correlation properties may be used. For example, constant Amplitude Zero Auto-Correlation (CAZAC) sequences such as ZC (Zadoff-Chu) sequences, pseudo-noise (PN) sequences such as m-sequence, Gold sequence, and Kasami sequence, etc. This reference signal sequence may be used. In addition, various other sequences having excellent correlation characteristics may be used depending on the system situation. In addition, the reference signal sequence may be used after cyclic extension or truncation to adjust the length of the sequence, and various types such as binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK). It may be modulated and mapped to a resource element (RE).

The downlink reference signal includes a cell-specific reference signal (CRS), a multimedia broadcast and multicast single frequency network (MBSFN) reference signal, a UE-specific reference signal (UE-specific RS), and a position reference signal (PRS: Positioning). RS) and channel state information (CSI) reference signals (CSI-RS).

A terminal-specific reference signal is a reference signal received by a specific terminal or a specific terminal group in a cell, and is mainly used for data demodulation of a specific terminal or a specific terminal group, so it can be called a demodulation reference signal (Demodulation RS: DM-RS). have.

Similar to the downlink, the reference signal is transmitted in the LTE uplink. In LTE uplink, uplink DM-RS and SRS may be used. The uplink DM-RS can be used by a base station to estimate a channel for coherent demodulation of uplink physical channels (physical uplink shared channel (PUSCH) and physical uplink control channel (PUCCH)). . Therefore, the uplink DM-RS is always transmitted with the PUSCH or PUCCH and may be transmitted with the same bandwidth as the corresponding physical channels.

The uplink SRS can be used by the base station for channel dependent scheduling and channel estimation for link adaptation according to an uplink channel. The SRS can also be used to estimate the downlink channel state when sufficient reciprocity exists between uplink/downlink, that is, when uplink and downlink channels exhibit sufficiently similar characteristics.

Hereinafter, in an embodiment of the present invention, an uplink DM-RS is additionally disclosed.

The uplink DM-RS is used for channel estimation for coherent demodulation of the PUSCH to which the UL-SCH transport channel is mapped, and is also required for coherent demodulation of the PUCCH carrying various types of L1/L2 control signaling. Do. There are some differences, but the basic uplink DM-RS structure may be the same for PUSCH and PUCCH. The difference is that OFDM symbols for transmitting a reference signal may be different.

4 is a conceptual diagram illustrating transmission of an uplink DM-RS when a PUSCH is transmitted.

Referring to FIG. 4, specific symbols may be used to transmit an uplink DM-RS entirely. Therefore, the uplink reference signal is time multiplexed with other uplink transmissions from the same terminal. More specifically, in the case of PUSCH transmission, the uplink DM-RS may be transmitted in the fourth symbol from the back of each uplink slot. That is, in the case of a normal CP, the fourth symbol (l = 3) may be transmitted from the front of each uplink slot, and in the case of an extended CP, the third symbol (l = 2) can be transmitted.

Therefore, in each subframe, there may be a total of two transmissions of the reference signal, once per slot.

In the case of PUCCH transmission, the number of symbols used for reference signal transmission and the exact positions of symbols used for reference signal transmission within a slot may vary according to the PUCCH format. Regardless of whether the type of uplink transmission is PUCCH or PUSCH, the basic structure of each reference signal transmission may be a reference signal in a frequency domain mapped to a continuous input (continuous subcarrier) of a signal generator. The bandwidth of the reference signal corresponding to the sequence length of the reference signal may be the same as the transmission bandwidth of the PUSCH/PUCCH measured by the number of subcarriers. This may mean that, in the case of PUSCH transmission, as the possible PUSCH transmission bandwidth changes, reference signal sequences of different lengths corresponding thereto must be generated. Since uplink resource allocation for PUCSH transmission is always performed in units of resource blocks having 12 subcarriers, the number of reference signals may always be a multiple of 12.

Hereinafter, in an embodiment of the present invention, a method of generating a reference signal sequence of an uplink demodulation reference signal for PUSCH (DM-RS) for PUCSH will be described in detail. That is, the uplink DM-RS disclosed in the embodiment of the present invention may indicate the uplink DM-RS for the PUSCH.

로서 레이어

에 따라 아래의 수학식 2와 같이 정의될 수 있다. The sequence of the uplink DM-RS for PUSCH is

As layer

It can be defined as in Equation 2 below.

<Equation 2>

는 참조 신호 시퀀스의 길이를 나타낸다.

로 정의될 수 있고,

는 하나의 자원 블록에 포함되는 부반송파(subcarrier)의 개수이다. m은

의 범위의 값으로 정의될 수 있다. 전술한 바와 같이 참조 신호 시퀀스의 길이는 하나의 자원 블록에 포함되는 부반송파 개수의 배수로 정의될 수 있다.

로써 참조 신호 시퀀스의 길이와 PUSCH에 할당된 부반송파의 개수가 동일함을 알 수 있다. Referring to Equation 2,

Represents the length of the reference signal sequence.

Can be defined as,

Is the number of subcarriers included in one resource block. m is

It can be defined as a range of values. As described above, the length of the reference signal sequence may be defined as a multiple of the number of subcarriers included in one resource block.

As a result, it can be seen that the length of the reference signal sequence and the number of subcarriers allocated to the PUSCH are the same.

는

로 정의될 수 있다. Disclosed in Equation 2

Is

Can be defined as

는 순환 쉬프트(cyclic shift)

및 기본 시퀀스

에 의해 정의될 수 있다. 아래의 수학식 3은

을 나타낸다.

Is a cyclic shift

And basic sequence

Can be defined by Equation 3 below is

Represents.

<Equation 3>

는 참조 신호 시퀀스의 길이이다. 순환 쉬프트

에 따라 하나의 기본 시퀀스

가 복수의 참조 신호 시퀀스로 정의될 수 있다. As described above

Is the length of the reference signal sequence. Cyclic shift

Based on one basic sequence

May be defined as a plurality of reference signal sequences.

는 자드오프-추(Zadoff-Chu) 시퀀스에 의해 정의될 수 있다. 이러한 기본 시퀀스의 정의에 대해서는 2013년 9월에 개시된 ‘3GPP TS36.211 V11.4.0, 3rd Generation Partnership Project Technical Specification Group Radio Access Network Evolved Universal Terrestrial Radio Access (E-UTRA) Physical Channels and Modulation(Release 11)’(이하, 3GPP TS36.211)의 5.5.1 절에 개시되어 있다.
Basic sequence

May be defined by a Zadoff-Chu sequence. For the definition of such a basic sequence, '3GPP TS36.211 V11.4.0, 3rd Generation Partnership Project Technical Specification Group Radio Access Network Evolved Universal Terrestrial Radio Access (E-UTRA) Physical Channels and Modulation (Release 11) disclosed in September 2013. '(Hereinafter, 3GPP TS36.211) is disclosed in Section 5.5.1.

5 is a conceptual diagram illustrating that one basic reference signal sequence is generated as a plurality of reference sequences according to cyclic shift.

의 값이

과 같은 값을 같게 되면 하나의 기본 시퀀스를 기반으로 순환 쉬프트의 변화에 따라 서로 직교하는 참조 신호 시퀀스를 생성할 수 있다. 즉, 하나의 기본 시퀀스로부터 최대 12개까지의 직교 참조 신호를 정의할 수 잇다. Uplink DM-RSs defined from different reference signal sequences generally have a relatively low, but non-zero, mutual correlation. On the other hand, the reference signals defined by different phase rotations of the same basic reference signal sequence are completely orthogonal to each other, so that there is no interference between them. For example, if m changes from 0 to 11, cyclic shift

The value of

When the same value is equal to, reference signal sequences that are orthogonal to each other may be generated according to a change in cyclic shift based on one basic sequence. That is, up to 12 orthogonal reference signals can be defined from one basic sequence.

는 직교 시퀀스(orthogonal sequence)(또는 직교 커버 코드(OCC, orthogonal cover code))를 나타낸다. 직교 시퀀스는 상향링크 다중 안테나 전송, 구체적으로는 공간 다중화를 포함한 다중 안테나 프리코딩 방식에서 사용될 수 있다. 공간 다중화를 수행하는 경우 레이어(layer) 당 별도의 상향링크 DM-RS가 필요하다. 예를 들어, 4개의 공간적으로 다중화되는 레이어를 동시에 전송하는 것을 지원해야 하는 경우, 하나의 단말은 4개의 서로 다른 상향링크 DM-RS를 전송할 수 있어야 한다. 이러한 서로 다른 상향링크 DM-RS를 생성하기 위해서는 전술한 바와 같이 서로 다른 순환 시퀀스를 사용하여 복수개의 상호 직교하는 참조 신호를 생성하거나 또는 서브프레임 내의 2개의 참조 신호 전송에 대하여 직교 커버 코드(orthogonal cover code)와 같은 상호 직교 패턴을 적용함으로써 2개의 서로 다른 참조 신호를 생성할 수 있다. Referring back to Equation 2,

Represents an orthogonal sequence (or an orthogonal cover code (OCC)). The orthogonal sequence may be used in uplink multi-antenna transmission, specifically, a multi-antenna precoding scheme including spatial multiplexing. When performing spatial multiplexing, a separate uplink DM-RS is required per layer. For example, when it is necessary to support simultaneous transmission of four spatially multiplexed layers, one UE must be able to transmit four different uplink DM-RSs. In order to generate these different uplink DM-RSs, as described above, a plurality of mutually orthogonal reference signals are generated using different cyclic sequences, or orthogonal cover codes for transmission of two reference signals in a subframe. Two different reference signals can be generated by applying a mutually orthogonal pattern such as code).

6 shows an uplink DM-RS generated using an orthogonal cover code.

The top of FIG. 6 is an uplink DM-RS generated when the orthogonal cover code is [+1, +1], and the bottom of FIG. 6 is an uplink DM-RS generated when the orthogonal cover code is [+1, -1]. -RS. The generated plurality of orthogonal reference signals may be used, for example, when performing an uplink multi-user (MU)-multiple input multiple output (MIMO).

는 DCI(downlink control information) 포맷(format)이 0에 대해,

로 정의될 수 있다. If the upper layer parameter Activate-DMRS-with OCC is not set or is a temporary C- to transmit the most recent uplink-related DCI for the transport block related to the corresponding PUSCH transmission When RNTI (temporary cell radio network identifier) is used, an orthogonal sequence

Is for a DCI (downlink control information) format of 0,

Can be defined as

는 상응하는(corresponding) PUSCH 전송과 관련된 전송 블록에 대한 가장 최근의 상향링크 관련 DCI의 순환 쉬프트 필드를 사용하여 아래의 표 1에 의해 주어질 수 있다. Otherwise, the orthogonal sequence

May be given by Table 1 below using a cyclic shift field of the most recent uplink-related DCI for a transport block related to a corresponding PUSCH transmission.

<Table 1>

를 결정하기 위한 순환 쉬프트(cyclic shift)

는 슬롯

에서

로 정의될 수 있고

는 아래의 수학식 4와 같이 정의될 수 있다.In Equation 2

Cyclic shift to determine

The slot

in

Can be defined as

May be defined as in Equation 4 below.

<Equation 4>

는 아래의 표 2와 같이 순환 쉬프트의 값에 따라 결정될 수 있다. In Equation 4

May be determined according to the value of the cyclic shift as shown in Table 2 below.

<Table 2>

는 전술한 표 1에서와 같이 상향링크 관련 DCI 포맷에서 순환 쉬프트 필드에 의해 결정될 수 있다.

May be determined by a cyclic shift field in an uplink-related DCI format as shown in Table 1 above.

는 아래의 수학식 5에 의해 결정될 수 있다.

May be determined by Equation 5 below.

<Equation 5>

In Equation 5, a pseudo-random sequence c(i) is defined by a Gold sequence of length 31 as follows.

<Equation 6>

을 기반으로 초기화될 수 있다. 만약, 상위 계층에서

에 대한 값이 설정되지 않는 경우, 또는 랜덤 액세스 승인(grant) 또는 경쟁 기반의 랜덤 액세스 절차의 일부로써 동일한 전송 블록의 재전송이 PUSCH 전송과 관련된 경우

는

로 초기화될 수 있다.

는 셀의 PCI(physical cell identifier)이다. 그 외의 경우에는

로 초기화될 수 있다. Here, N _c =1600, the first m-sequence is initialized to x ₁ (0)=1, x ₁ (n)=0, n=1,2,...,30. The second m-sequence is at the beginning of each radio frame.

Can be initialized based on. If, in the upper layer

When the value for is not set, or when retransmission of the same transport block as part of a random access grant or contention-based random access procedure is related to PUSCH transmission

Is

Can be initialized to

Is the cell's physical cell identifier (PCI). In other cases

Can be initialized to

Hereinafter, an uplink-related DCI format is disclosed in an embodiment of the present invention.

DCI format 0 or DCI format 4 may be used for PUSCH scheduling in one uplink cell. DCI format 4 was added in release 10 to support UL spatial multiplexing. The basic uplink resource allocation scheme is a single cluster scheme in which all resource blocks are contiguous in the frequency domain, but in Release 10, transmission to a maximum of two clusters per component carrier is supported. A multi-cluster method was added.

DCI format 0 can be used to schedule uplink transmission when spatial multiplexing is not used on the component carrier, and has the same size as the control signaling message of compact downlink allocation (DCI format 1A). A flag on the message may inform the terminal of information on whether uplink scheduling approval (DCI format 0) or downlink scheduling assignment (DCI format 1A).

Information included in DCI format 0 and DCI format 4 is described in '3GPP TS36.212 V11.3.0, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding (Release 11)' (hereinafter, 3GPP TS36.212) is disclosed in 5.3.3.1.1 FORMAT 0 and 5.3.3.1.8 FORMAT 4. The information included in each DCI format is as follows.

DCI format 0 is a carrier indicator, a DCI format classification flag (flag for format 0/format 1A differentiation), a frequency hopping flag, resource block assignment and hopping resource allocation information (resource block assignment and hopping resource). allocation), modulation and coding scheme (MCS) and redundancy version (RV) information, new data indicator (NDI), PUSCH power information (TPC command for scheduled PUSCH), cyclic shift for DM-RS and OCC index), uplink index information (UL index), downlink assignment index information (downlink assignment index), CSI request information (CSI request), SRS request information (SRS request), resource allocation type information (resource allocation type), etc. It may include.

DCI format 4 may be used in the case of uplink transmission using spatial multiplexing on one component carrier.

DCI format 4 is a carrier indicator (carrier indicator), resource block assignment (resource block assignment), PUSCH power information (TPC command for PUSCH), cyclic shift and orthogonal code information (cyclic shift for DM-RS and OCC index), uplink It may include index information (UL index), downlink assignment index information (downlink assignment index), CSI request information (CSI request), SRS request information (SRS request), resource allocation type information (resource allocation type), and the like.

In addition, DCI format 4 may include precoding information, and the precoding information may include information on the number of transmitted precoding matrix indicators (TPMI) and layers.

Table 3 below shows the number of bits allocated to precoding information according to the number of antenna ports of the terminal.

<Table 3>

Information included in the precoding information may be defined differently according to the number of the transmitted precoding matrix indicator and the number of layers according to the number of antenna ports of the terminal.

Table 4 below shows the number of precoding matrix indicators and layers included in precoding information when there are two antenna ports.

<Table 4>

Table 5 below shows the number of precoding matrix indicators and layers included in precoding information when there are 4 antenna ports.

<Table 5>

Referring to Tables 4 and 5, a precoding matrix indicator and the number of layers may be determined according to a value of a bit mapped to precoding information.

7 is a conceptual diagram showing a small cell environment.

In FIG. 7, in 3GPP, a feasibility study for technology improvement for a small eNodeB that can be used to cover a small area compared to the existing macro base station among various work items is in progress. have.

Referring to FIG. 7, a base station may be classified into a macro, pico, and femto base station according to the size of a covered area. The macro base station is a base station that is generally used and may be a base station that covers a wide area compared to a pico base station. Accordingly, the macro base station can use relatively stronger power during transmission than the pico base station. The pico base station covers a small area for a hotspot or a coverage hole. In addition, in general, a pico base station can use relatively less power than a macro base station. Accordingly, the pico base station may have lower connection reliability than the macro base station. In 3GPP, a cell provided by a base station smaller than a macro base station, such as a pico base station, is referred to as a small cell 750. Research is underway on various methods to enable more efficient use of the network in a situation where the macro cell 700 by the macro base station and the small cell 750 by the small base station are mixed. For example, a macro cell The efficiency can be increased by controlling the load of the network by offloading traffic to the small cell 750 according to the load situation of 700. In addition, different types of QoS traffic can be handled by using a difference in connection conditions between the macro cell 700 and the small cell 750. In terms of the terminal, research on dual connectivity is also underway so that the macro cell 700 and the small cell 750 can be simultaneously accessed to transmit and receive traffic.

In an embodiment of the present invention, a resource allocated for a UE to transmit a reference signal in such a small cell environment may be newly defined. According to an embodiment of the present invention, the UE may perform uplink transmission using a reference signal newly defined according to a transmission environment of a cell. For example, when the channel environment of the small cells 750 has low frequency-selective and low time-selective fading, the overhead of the uplink DM-RS is reduced. Thus, data transmission efficiency in the small cell 750 can be improved.

8 is a conceptual diagram showing that an uplink DM-RS is allocated from an existing resource block.

Referring to FIG. 8, in the uplink DM-RS associated with the current PUSCH, for each slot, in the case of a normal CP, a fourth symbol of each slot, and in the case of an extended CP, a PUSCH is transmitted in the third symbol. Each subcarrier may be mapped and transmitted.

That is, the uplink DM-RS may be mapped and transmitted for every subcarrier in a resource block allocated from two symbols of one subframe.

According to an embodiment of the present invention, when a specific condition is satisfied, the UE uses the uplink DM-RS of the new format for uplink transmission, thereby reducing the resources allocated to the uplink DM-RS in the small cell. The resources allocated to the uplink DM-RS are used for PUSCH transmission, thereby increasing data transmission efficiency of the terminal.

The overhead reduction of the uplink DM-RS can be achieved in the time and/or frequency domain by the following two main methods. In the time domain, the number of symbols allocated for uplink DM-RS per subframe can be reduced. For example, in one subframe, the uplink DM-RS may not be allocated to two symbols, but may be allocated to only one symbol. In the frequency domain, the number of subcarriers transmitting the reference signal may be reduced. For example, a reference signal is not mapped and transmitted for each subcarrier in which PUSCH is transmitted, but an uplink DM-RS may be mapped and transmitted for some subcarriers among subcarriers in which PUSCH is transmitted.

Among them, the embodiment of the present invention discloses a method for the UE to transmit by reducing the overhead of the uplink DM-RS in the time domain when a specific condition is satisfied for convenience of description.

9 is a conceptual diagram showing resource allocation of an uplink DM-RS according to an embodiment of the present invention.

In FIG. 9, a resource allocation method for reducing overhead of an uplink DM-RS is disclosed.

Referring to FIG. 9, an uplink DM-RS may be allocated and transmitted only in one symbol of an even-numbered slot. The uplink DM-RS may be allocated only in one symbol of odd-numbered slots other than even-numbered slots. That is, the uplink DM-RS is not currently allocated to two symbols for one subframe, but the uplink DM-RS may be allocated and transmitted for only one symbol.

When using such an uplink DM-RS transmission method, an orthogonal code used to generate an uplink DM-RS may change or may not be used.

를 사용할 수 있다. As described above, in the uplink DM-RS, uplink DM-RSs generated based on different cyclic shifts are used to ensure orthogonality between layers and terminals. In addition, the uplink DM-RS may guarantee orthogonality by additionally using different orthogonal cover codes (OCC). As described above, the uplink DM-RS is an orthogonal sequence, which is an OCC of length 2

You can use

As disclosed in Table 1, for uplink DM-RS, one of two OCCs of length [1 1] and [1 -1] may be used. As shown in Table 1, the current cyclic shift value and OCC may be indicated as a 3-bit value in a cyclic shift field of uplink-related downlink control information (DCI).

의 값으로 ‘+1’이 적용되고, 상기 하나의 서브프레임에서 상향링크 DM-RS가 매핑된 두 번째 심볼에서도 ‘+1’이 적용된다. OCC가 [1 -1]인 경우 도 8에서 보는 것과 같은 하나의 서브프레임에서 상향링크 DM-RS가 매핑된 첫 번째 심볼에

의 값으로 ‘+1’이 적용되고, 상기 하나의 서브프레임에서 상향링크 DM-RS가 매핑된 두 번째 심볼는 ‘-1’이 적용된다. The OCC defined in Table 1 is an OCC of length 2 mapped to two symbols in consideration of transmission of the existing uplink DM-RS. When the OCC is [1 1], the uplink DM-RS is mapped to the first symbol in one subframe as shown in FIG.

'+1' is applied as the value of'+1', and'+1' is also applied to the second symbol to which the uplink DM-RS is mapped in the one subframe. When the OCC is [1 -1], the uplink DM-RS is mapped to the first symbol in one subframe as shown in FIG.

'+1' is applied as a value of, and'-1' is applied to the second symbol to which the uplink DM-RS is mapped in the one subframe.

OCC may play a role of guaranteeing orthogonality according to a transmission method. OCC may not be essential to ensure orthogonality between uplink DM-RSs depending on the transmission method and the number of total layers used.

For example, in the case of single user (SU)-MIMO, when the total number of layers is 3 or more, the OCC assists cyclic shift to further ensure orthogonality between layers. In SU-MIMO, when the number of layers is less than two, the OCC is applied equally to the two layers, so there is no effect of orthogonality due to OCC. In addition, even when the number of layers in SU-MIMO is three or more, OCC can guarantee orthogonality between layers only with different cyclic shift values. In this case, the OCC may serve to further guarantee orthogonality between layers by assisting cyclic shifting.

In the case of MU-MIMO, OCC can be used to guarantee not only orthogonality between layers, but also between terminals. In MU-MIMO, when the total number of layers (sum of the number of layers used for each terminal) is 4 or less, even if there is no OCC, orthogonality between layers and terminals can be guaranteed to some extent with only different cyclic shift values. Even in this case, the OCC can serve to further guarantee orthogonality between the layer and the terminal by supporting cyclic shift. In SU-MIMO, even when the total number of layers (the sum of layers used for each terminal) is 5 or more, there is a limit to guaranteeing orthogonality between layers only with different cyclic shift values. Therefore, it may be necessary to apply different OCCs between layers and/or terminals.

를 의미할 수 있다. 여기서, 레이어 및/또는 단말 간에 순환 쉬프트의 값은 최소한 2 이상 차이가 나는 경우를 고려할 수 있다 왜냐하면, 그 이상 차이가 나지 않을 경우 순환 쉬프트를 적용한 경우에도 시스템 상황에 따라 직교성의 보장이 힘들 수도 있다.Here, the cyclic shift value is indicated based on the 3-bit cyclic shift field disclosed in Table 1 above.

Can mean Here, it may be considered that the value of the cyclic shift between the layers and/or the terminal differs by at least 2 or more. .

OCC can be classified whether or not it is essential to guarantee orthogonality according to the transmission method and the number of layers, and the necessity of OCC can be divided into three types as follows.

In the first case, even without OCC, orthogonality can be guaranteed between uplink DM-RSs based on cyclic shift. This case can be satisfied when the total number of layers is one or two. For example, when performing rank 1 transmission or performing rank 2 SU-MIMO transmission, the total number of layers may be one or two.

In the second case, even without OCC, a certain degree of orthogonality can be maintained due to cyclic shift, but in the presence of OCC, it is possible to have more orthogonality as an auxiliary means of cyclic shift. This case may be satisfied when the total number of layers is 3 or 4. For example, when SU-MIMO of rank 3 is performed or SU-MIMO of rank 4 is performed, the total number of layers may be 3 or 4.

In the third case, it is difficult to guarantee orthogonality only by cyclic shift, so OCC is absolutely necessary. This case may be satisfied when the total number of layers is 5 or more. For example, when performing MU-MIMO greater than rank 5, the total number of layers may be 5 or more.

As described above, the first case is a case where the number of layers is one or two for one terminal. In the second case, in the case of SU-MIMO, the number of layers for one terminal is 3 or 4, but in the case of MU-MIMO, the number of layers for each terminal is mostly 1 or 2. . The third case is MU-MIMO, and it is common that the number of layers of each terminal is three or more. Of course, even in the third case, MU-MIMO may be configured in a case where the number of layers is one or two for each UE, but in this case, MU-MIMO between a large number of UEs is not common.

In other words, when the number of layers for each terminal is 1 or 2 (especially, as in the case of Rel-8/9 where only 1 layer is supported), it corresponds to the first or second case, so even if there is no OCC, cyclic shift Only a certain degree of orthogonality can be obtained for the uplink DM-RS.

When the overhead of the uplink DM-RS is reduced as shown in FIG. 9, since the uplink DM-RS is allocated and transmitted to one symbol in one subframe, the OCC cannot be applied as in the past. Therefore, a new method such as not applying OCC or applying OCC in another way may be required.

In the present invention, configurations of the following two types of uplink DM-RS can be considered in a small cell environment.

In the first case, the overhead reduction of the uplink DM-RS is not applied. Hereinafter, in the embodiment of the present invention, a case in which the overhead reduction of the uplink DM-RS is not applied is referred to as a'default uplink DM-RS'. As shown in FIG. 8 described above, the UL DM-RS may be mapped and transmitted in two symbols within one subframe, as in the conventional case.

이 새롭게 정의될 수 있다. 표 1에서 OCC와 관련된 표의 오른쪽의

과 관련된 열들은 OCC가 적용되지 않을 수 있다. 따라서, 수학식 7과 같이 그 값이 항상 1인

부분만 사용되거나 수학식 8과 같이 아예 사용되지 않을 수 있다. In the second case, uplink DM-RS overhead reduction is applied. Hereinafter, in the embodiment of the present invention, a case in which the overhead reduction of the uplink DM-RS is applied is referred to as'reduced uplink DM-RS'. As shown in FIG. 9, the uplink DM-RS can be mapped and transmitted in only one symbol within one subframe. When the uplink DM-RS overhead reduction is applied, the conventional OCC may not be applied. In this case, related to the sequence of the uplink DM-RS for the PUSCH described above in Equation 2

Can be newly defined. In Table 1, on the right side of the table related to OCC

OCC may not be applied to the columns related to. Therefore, the value is always 1 as in Equation 7

Only a portion may be used or may not be used at all as shown in Equation 8.

<Equation 7>

<Equation 8>

Hereinafter, according to an embodiment of the present invention, a case where a default uplink DM-RS is used and a case where a reduced uplink DM-RS is used may be selectively determined. For example, it is possible to selectively determine whether to use a default uplink DM-RS or a reduced uplink DM-RS in an uplink subframe in consideration of the number of layers used for uplink transmission in each terminal. .

For example, as described above, when the number of layers of each terminal is one or two, even without OCC, it is possible to obtain some degree of orthogonality only by cyclic shift. In this case, the UE may use the reduced uplink DM-RS as the uplink DM-RS during uplink transmission. Conversely, if the OCC is required to obtain orthogonality between uplink DM-RSs, the terminal may use the default uplink DM-RS as the uplink DM-RS during uplink transmission.

Hereinafter, in an embodiment of the present invention, a specific method of selecting whether to use a default uplink DM-RS or a reduced uplink DM-RS in an uplink subframe will be described.

10 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.

In FIG. 10, a method for selecting an uplink DM-RS by a terminal is disclosed. 10 discloses a method of determining whether to use a default uplink DM-RS or a reduced uplink DM-RS based on a DCI format and the number of layers.

Referring to FIG. 10, the terminal may determine whether overhead reduction is possible (step S1000).

The UE may obtain information on whether to use the reduced uplink DM-RS based on a higher layer signal transmitted from an upper layer (eg, radio resource control (RRC)). Information on whether the reduced uplink DM-RS can be used based on the higher layer signal may be transmitted based on, for example, an overhead reduction enabling field. The overhead reduction activation field may be transmitted semi-statically in consideration of a small cell arrangement environment. The overhead reduction activation field may serve to indicate a mode in which overhead reduction is possible.

As a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is not possible to use the reduced uplink DM-RS in the terminal, the terminal performs uplink transmission based on the default uplink DM-RS. Can be performed (step S1010).

Or, if a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is not configured (thus, if the UE does not receive an upper layer signal related to overhead reduction), the UE defaults to uplink DM Uplink transmission may be performed based on -RS (step S1010).

Conversely, as a result of receiving a higher layer signal, if it is possible for the terminal to use the reduced uplink DM-RS, the terminal determines whether to use the reduced uplink DM-RS based on the DCI format related to the uplink allocated from the base station. I can.

Or, when a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is configured (thus, when the UE receives a higher layer signal related to overhead reduction), the UE is associated with uplink allocated from the base station. It may be determined whether to use the reduced uplink DM-RS based on the DCI format.

It is determined whether the DCI format is 0 (step S1020).

The terminal may determine the DCI format for transmitting the control signal. For convenience of description, the step of determining whether the DCI format is 0 is described in step S1020, but it may be determined whether the DCI format is 4 in step S1020.

If DCI format 0 is determined based on step S1020, a reduced uplink DM-RS may be applied (step S1030).

According to an embodiment of the present invention, it is possible to determine whether to preferentially use the reduced uplink DM-RS based on the DCI format. As described above, in DCI format 0, the number of transport layers for the PUSCH of the UE and the UL DM-RS linked to the PUSCH may be one. That is, in the case of DCI format 0, it is possible to guarantee some degree of orthogonality only by cyclic shift without applying OCC. Therefore, when the UE receives an uplink control signal of DCI format 0 from the base station, the UE can perform uplink transmission using the reduced uplink DM-RS, which can reduce the overhead of the uplink DM-RS without applying OCC. have.

As a result of the determination based on step S1020, in case of DCI format 4, it may be determined whether the number of layers is less than or equal to a threshold number (step S1040).

In the case of DCI format 4 as a result of the determination based on step S1020, it is possible to determine whether to use the reduced uplink DM-RS by additionally determining whether the number of layers is less than or equal to a threshold number (eg, 1). .

For example, when uplink-related control information is transmitted in DCI format 4 and the number of layers is one, uplink transmission may be performed by applying a reduced uplink DM-RS (step S1030). Conversely, when the number of layers is greater than one, uplink transmission may be performed using the default uplink DM-RS without applying the reduced uplink DM-RS (step S1010).

That is, when the number of layers is larger than a certain number, OCC must be used to secure orthogonality. In this case, uplink transmission may be performed using a default uplink DM-RS using OCC without using a reduced uplink DM-RS in which OCC cannot be used.

Information on the number of layers may be obtained based on precoding information defined in Tables 4 and 5 and information on the number of layers. As disclosed in Table 3, when the bits included in the precoding information field transmitted based on DCI format 4 are 3 bits, they are for two antenna ports, and when the bits included in the precoding information field are 6 bits. May be for 4 antenna ports.

Referring to Tables 4 and 5, in the precoding information fields for two antenna ports, all cases in which one codeword is used is a case in which the number of layers is one. In the precoding information field for 4 antenna ports, when one codeword is used, a case in which a 6-bit bit value is 0 to 23 may be a case in which the number of layers is 1.

That is, when uplink-related control information is transmitted through DCI format 4, the terminal defaults to uplink data transmission based on information on the number of layers acquired based on the precoding information field included in DCI format 4 It can be determined whether to use the link DM-RS or the reduced uplink DM-RS.

11 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.

In FIG. 11, a method for selecting an uplink DM-RS of a terminal is disclosed. In FIG. 11, as in FIG. 10, the UE determines whether to use a default uplink DM-RS or a reduced uplink DM-RS based on the DCI format and the number of layers, but the reduced uplink DM-RS is The number of critical layers for determining whether to use may be differently set.

Referring to FIG. 11, the terminal may determine whether overhead reduction is possible (step S1100).

The UE may obtain information on whether to use the reduced uplink DM-RS based on a higher layer signal transmitted from an upper layer (eg, radio resource control (RRC)). Information on whether the reduced uplink DM-RS can be used based on the higher layer signal may be transmitted, for example, based on an overhead reduction enabling field. The overhead reduction activation field may be transmitted semi-statically in consideration of a small cell arrangement environment and the like. The overhead reduction activation field may serve to indicate a mode in which overhead reduction is possible.

As a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is not possible to use the reduced uplink DM-RS in the terminal, the terminal performs uplink transmission based on the default uplink DM-RS. Can be performed (step S1110).

Or, if a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is not configured (thus, if the UE does not receive an upper layer signal related to overhead reduction), the UE defaults to uplink DM Uplink transmission may be performed based on -RS (step S1110).

Conversely, as a result of receiving a higher layer signal, if it is possible for the terminal to use the reduced uplink DM-RS, the terminal determines whether to use the reduced uplink DM-RS based on the DCI format related to the uplink allocated from the base station. I can.

Or, when a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is configured (thus, when the UE receives a higher layer signal related to overhead reduction), the UE is associated with uplink allocated from the base station. It may be determined whether to use the reduced uplink DM-RS based on the DCI format.

It is determined whether the DCI format is 0 (step S1120).

The terminal may determine the DCI format for transmitting the control signal. For convenience of explanation, the step of determining whether the DCI format is 0 is described in step S1120, but it may be determined whether the DCI format is 4 in step S1120.

If DCI format 0 is determined based on step S1120, a reduced uplink DM-RS may be applied (step S1130).

According to an embodiment of the present invention, it is possible to determine whether to preferentially use the reduced uplink DM-RS based on the DCI format. As described above, in DCI format 0, the number of transport layers for the PUSCH of the UE and the UL DM-RS linked to the PUSCH may be one. That is, in the case of DCI format 0, it is possible to guarantee some degree of orthogonality only by cyclic shift without applying OCC. Accordingly, the UE may perform uplink transmission based on a reduced uplink DM-RS in which OCC is not applied and the overhead of the uplink DM-RS can be reduced.

As a result of the determination based on step S1120, in case of DCI format 4, it may be determined whether the number of layers is less than or equal to a threshold number (step S1140).

As a result of the determination based on step S1120, in case of DCI format 4, it may be determined whether to use the reduced uplink DM-RS by additionally determining whether the number of layers is less than or equal to a threshold number (eg, 2). .

For example, when uplink-related control information is transmitted in DCI format 4 and the number of layers is 2 or less, uplink transmission may be performed by applying a reduced uplink DM-RS (step S1130). Conversely, when the number of layers is greater than two, uplink transmission may be performed using the default uplink DM-RS without applying the reduced uplink DM-RS (step S1110).

That is, when the number of layers is larger than a certain number, OCC must be used to secure orthogonality, and in this case, the default uplink DM-RS is used instead of the reduced uplink DM-RS in which OCC cannot be used. Uplink transmission can be performed.

Information on the number of layers may be obtained based on precoding information defined in Tables 4 and 5 and information on the number of layers. As disclosed in Table 3, when the bits included in the precoding information field transmitted based on DCI format 4 are 3 bits, they are for two antenna ports, and when the bits included in the precoding information field are 6 bits. May be for 4 antenna ports.

Referring to Tables 4 and 5, in the precoding information field for two antenna ports, all cases of using one codeword are cases in which the number of layers is one or two. In the precoding information field for 4 antenna ports, in all cases of using one codeword and in case of using two codewords, when the bit value of 6 bits is 0 to 15, the number of layers is 1 or There may be two cases.

That is, when the uplink-related control information is transmitted through DCI format 4, the terminal defaults uplink when transmitting uplink data based on information on the number of layers acquired based on precoding field information included in DCI format 4 It can be determined whether to use the link DM-RS or the reduced uplink DM-RS.

12 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.

12 discloses a method of selecting an uplink DM-RS of a terminal. In FIG. 12, it may be determined whether to use a default uplink DM-RS or a reduced uplink DM-RS based on a field defined in DCI format 4.

Referring to FIG. 12, the terminal may determine whether overhead reduction is possible (step S1200).

The UE may obtain information on whether to use the reduced uplink DM-RS based on a higher layer signal transmitted from an upper layer (eg, radio resource control (RRC)). Information on whether the reduced uplink DM-RS can be used based on the higher layer signal may be transmitted based on, for example, an overhead reduction enabling field. The overhead reduction activation field may be transmitted semi-statically in consideration of a small cell arrangement environment. The overhead reduction activation field may serve to indicate a mode in which overhead reduction is possible.

As a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is not possible to use the reduced uplink DM-RS in the terminal, the terminal performs uplink transmission based on the default uplink DM-RS. Can be performed (step S1210).

Or, if a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is not configured (thus, if the UE does not receive an upper layer signal related to overhead reduction), the UE defaults to uplink DM Uplink transmission may be performed based on -RS (step S1210).

Conversely, as a result of receiving a higher layer signal, if it is possible for the terminal to use the reduced uplink DM-RS, the terminal determines whether to use the reduced uplink DM-RS based on the DCI format related to the uplink allocated from the base station. I can.

Or, when a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is configured (thus, when the UE receives a higher layer signal related to overhead reduction), the UE is associated with uplink allocated from the base station. It may be determined whether to use the reduced uplink DM-RS based on the DCI format.

It is determined whether the DCI format is 0 (step S1220).

The terminal may determine the DCI format for transmitting the control signal. For convenience of description, the step of determining whether the DCI format is 0 is described in step S1220, but it may be determined whether the DCI format is 4 in step S1220.

If the DCI format is 0 as a result of the determination based on step S1220, a reduced uplink DM-RS may be applied (step S1230).

According to an embodiment of the present invention, it is possible to determine whether to preferentially use the reduced uplink DM-RS based on the DCI format. As described above, in DCI format 0, the number of transport layers for the PUSCH of the UE and the UL DM-RS linked to the PUSCH may be one. That is, in the case of DCI format 0, it is possible to guarantee some degree of orthogonality only by cyclic shift without applying OCC. Accordingly, a reduced uplink DM-RS capable of reducing the overhead of the uplink DM-RS without applying OCC may be used.

As a result of the determination based on step S1220, in case of DCI format 4, it may be determined whether the overhead reduction field indicates the use of the reduced uplink DM-RS (step S1240).

As a result of the determination based on step S1220, in case of DCI format 4, a value of the overhead reduction field transmitted through DCI format 4 may be determined. The overhead reduction field may include information indicating whether to apply the reduced uplink DM-RS. For example, when the value of the overhead reduction field is 0, the reduced uplink DM-RS is used, and when the value of the overhead reduction field is 1, the reduced uplink DM-RS is not used and the default uplink DM-RS is Can be used. Conversely, when the value of the overhead reduction field is 1, the reduced uplink DM-RS is used, and when the value of the overhead reduction field is 0, the reduced uplink DM-RS is not used and the default uplink DM-RS may be used. have.

In the case of DCI format 4, since there is no strict limitation to have the same payload size as other DCI formats, a new 1-bit field such as an overhead reduction field can be additionally set. However, in the case of DCI format 0 used for UL grant in addition to DCI format 4, there is a constraint that must have the same payload size as DCI format 1A used for downlink assignment (DL assignment). Therefore, in the case of DCI format 0, it may be difficult to additionally set a field having a size of a new 1-bit. As described above, when overhead reduction is activated based on the overhead reduction activation field and uplink approval is granted in DCI format 0, the UE performs uplink transmission based on the reduced uplink DM-RS without additional determination. can do.

In addition, according to an embodiment of the present invention, it is possible to indicate whether or not the reduced uplink DM-RS is used based on existing field information of the DCI format. For example, it may indicate whether the reduced uplink DM-RS is used based on information on the RB allocation field of the DCI format or the cyclic shift field included in the uplink-related DCI format. Hereinafter, an embodiment of the present invention discloses a method of indicating whether a reduced uplink DM-RS is used based on existing field information of a DCI format.

13 is a flowchart showing a method for selecting an uplink DM-RS according to an embodiment of the present invention.

13 discloses a method for a UE to select an uplink DM-RS based on information on an overhead reduction enabling field and an available resource for reduced uplink DM-RS transmission. When the information on the available resource for the reduced uplink DM-RS transmission is pre-defined according to the specification, the overhead reduction activation field is the overhead mentioned in the embodiments according to FIGS. It may be the same as the reduction activation field. On the other hand, when the information on the available resource for the reduced uplink DM-RS transmission is included in the overhead reduction activation field and signaled from a higher layer, the overhead reduction activation field is a resource-based overhead reduction activation field. reduction enabling field).

In FIG. 13, when uplink resources are scheduled to transmit uplink data and uplink DM-RS and allocated to a terminal is reduced uplink DM-RS transmission, when associated with available resources, uplink transmission based on reduced uplink DM-RS Can be done. For example, the resource block corresponding to the lowest resource block index among the uplink resource blocks allocated to the terminal by being scheduled to transmit uplink data and uplink DM-RS belongs to the reduced uplink DM-RS transmission available resource. In this case, the terminal may perform uplink transmission based on the reduced uplink DM-RS.

Referring to FIG. 13, the terminal may determine whether overhead reduction is possible (step S1300).

The UE may obtain information on whether to use the reduced uplink DM-RS based on a higher layer signal transmitted from an upper layer (eg, radio resource control (RRC)). Information on whether the reduced uplink DM-RS can be used based on the higher layer signal may be transmitted, for example, through an overhead reduction enabling field. As mentioned, the overhead reduction activation field may be the same as the overhead reduction activation field mentioned in the embodiments according to FIGS. 10 to 12, and a resource including information on available resources for reduced uplink DM-RS transmission. It may be a base overhead reduction activation field. The overhead reduction activation field may be transmitted semi-statically in consideration of a small cell arrangement environment. The overhead reduction activation field may serve to indicate a mode in which overhead reduction is possible.

As a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is not possible to use the reduced uplink DM-RS in the terminal, the terminal performs uplink transmission based on the default uplink DM-RS. Can be performed (step S1310).

Or, if a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is not configured (thus, if the UE does not receive an upper layer signal related to overhead reduction), the UE defaults to uplink DM Uplink transmission may be performed based on -RS (step S1310).

Conversely, as a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is possible to use the reduced uplink DM-RS in the terminal, the terminal is allocated to the terminal through the uplink-related DCI format allocated from the base station. It is possible to determine whether to transmit the reduced uplink DM-RS by determining whether the uplink resource is associated with the available resource for transmission of the reduced uplink DM-RS.

Or, when a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is configured (thus, when the UE receives a higher layer signal related to overhead reduction), the UE is associated with uplink allocated from the base station. It is possible to determine whether to transmit the reduced uplink DM-RS by determining whether the uplink resource allocated to the terminal through the DCI format is associated with the reduced uplink DM-RS transmission available resource.

It is determined whether an uplink allocation resource allocated to a terminal through an uplink-related DCI format is associated with a reduced uplink DM-RS transmission available resource (step S1320).

The terminal may determine whether to transmit the reduced uplink DM-RS by determining whether the allocated uplink resource is associated with the reduced uplink DM-RS transmission available resource.

Resource blocks allocated to the terminal are reduced based on resource block allocation information allocated to transmit uplink data and uplink DM-RS in uplink-related DCI format (DCI format 0 or DCI format 4). Uplink DM-RS It can be determined whether or not it is associated with the available resources for transmission. For example, among the resource blocks allocated to the terminal, the resource block allocated to the terminal is reduced by determining whether the resource block with the lowest resource block index belongs to the reduced uplink DM-RS transmission available resource. Uplink DM-RS transmission It can be determined whether or not it is linked to available resources.

When the uplink resource allocated to the terminal is associated with the available resource for reduced uplink DM-RS transmission, for example, it corresponds to the lowest resource block index among uplink resource blocks allocated to the terminal through an uplink-related DCI format. When the resource block belongs to the available resource for the reduced uplink DM-RS transmission, the terminal may perform uplink transmission based on the reduced uplink DM-RS (step S1330).

Conversely, if the uplink resource allocated to the terminal is not associated with the uplink DM-RS transmission available resource, for example, the lowest resource block index among the uplink resource blocks allocated to the terminal through an uplink-related DCI format. When the corresponding resource block does not belong to the available resource for the reduced uplink DM-RS transmission, the terminal may perform uplink transmission based on the default uplink DM-RS (step S1310).

That is, in an embodiment of the present invention, an uplink DM-RS to be used by a terminal allocated with the corresponding resource may be determined by classifying uplink resources. The terminal may receive information on whether any of the uplink resources is an available resource for reduced uplink DM-RS transmission from the base station. Alternatively, an available resource for reduced uplink DM-RS transmission may be previously defined between the terminal and the base station.

14 shows a method of defining available resources for reduced uplink DM-RS transmission according to an embodiment of the present invention.

14, among the uplink resources, a first uplink resource 1400 is used as a reduced uplink DM-RS transmission available resource, and a second uplink resource 1450 is used as a reduced uplink DM-RS transmission unavailable resource. Can be used. In FIG. 14, it is assumed that resources available for reduced uplink DM-RS transmission are allocated over a plurality of subframes, but available resources for reduced uplink DM-RS transmission may be defined for each subframe.

)를 기반으로 감소 상향링크 DM-RS 전송 가용 자원을 정의할 수 있다. 감소 상향링크 DM-RS 전송 가용 자원은 아래의 수학식 9와 같이 자원 지시 값(resource indication value)으로 정의될 수 있다.In order to transmit information on the available resources for reduced uplink DM-RS transmission, for example, information on the starting resource block from which the reduced uplink DM-RS transmission available resources start and the number of consecutive resource blocks from the starting resource block Information about can be used. Specifically, information on the start resource block (RB _start ), information on the resource block consecutive from the start resource block (

), the available resources for reduced uplink DM-RS transmission can be defined. The reduced uplink DM-RS transmission available resource may be defined as a resource indication value as shown in Equation 9 below.

<Equation 9>

는 상향링크에서 설정된 자원 블록의 개수에 대한 정보를 나타낸다.

Represents information on the number of resource blocks configured in uplink.

As another method, in the existing uplink and downlink, such as existing uplink resource allocation 0, existing uplink resource allocation 1 and existing downlink resource allocation 0, existing downlink resource allocation 1, or existing downlink resource allocation 2 The allocation scheme used to allocate resources may be used to transmit information on available resources for reduced uplink DM-RS transmission. Information on the available resources for such reduced uplink DM-RS transmission may be transmitted through an upper layer (eg, RRC). For example, as mentioned above, information on available resources for reduced uplink DM-RS transmission may be included in an overhead reduction activation field and signaled from an upper layer and transmitted.

Meanwhile, as mentioned above, information on available resources for reduced uplink DM-RS transmission may be pre-defined according to the specification. For example, information on a pre-defined (pre-define) reduced uplink DM-RS transmission available resource, RB index is odd-numbered RBs or even-numbered RBs are reduced as uplink DM-RS transmission available resources RBs that are used or (RB index) mod N=0 (where N is an integer greater than or equal to 2) can be used as resources available for reduced uplink DM-RS transmission.

15 is a flowchart illustrating a method for selecting an uplink DM-RS according to an embodiment of the present invention.

In FIG. 15, the UE is uplinked by additionally considering information on the DCI format as well as information on the overhead reduction enabling field and the reduced uplink DM-RS transmission available resource mentioned in the embodiment according to FIG. A method of selecting a link DM-RS is disclosed.

Referring to FIG. 15, it may be determined whether or not overhead reduction is possible (step S1500).

The UE may obtain information on whether to use the reduced uplink DM-RS based on a higher layer signal transmitted from an upper layer (eg, radio resource control (RRC)). Information on whether the reduced uplink DM-RS can be used based on the higher layer signal may be transmitted, for example, through an overhead reduction enabling field. As mentioned, the overhead reduction activation field may be the same as the overhead reduction activation field mentioned in the embodiments according to FIGS. 10 to 12, and a resource including information on available resources for reduced uplink DM-RS transmission. It may be a base overhead reduction activation field. The overhead reduction activation field may be transmitted semi-statically in consideration of a small cell arrangement environment. The overhead reduction activation field may serve to indicate a mode in which overhead reduction is possible.

As a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is not possible to use the reduced uplink DM-RS in the terminal, the terminal performs uplink transmission based on the default uplink DM-RS. Can be performed (step S1510).

Or, if a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is not configured (thus, if the UE does not receive an upper layer signal related to overhead reduction), the UE defaults to uplink DM Uplink transmission may be performed based on -RS (step S1510).

Conversely, as a result of receiving a higher layer signal, if it is possible for the terminal to use the reduced uplink DM-RS, the terminal should use the reduced uplink DM-RS based on the information on the DCI format and the uplink resources allocated to the terminal. You can decide whether or not.

Or, when an upper layer signal related to overhead reduction (for example, an overhead reduction activation field) is configured (thus, when the terminal receives an upper layer signal related to overhead reduction), information on the DCI format and allocation to the terminal The UE may determine whether to use the reduced uplink DM-RS based on the uplink resource.

It is determined whether the DCI format is 0 (step S1520).

When the UE can use the reduced uplink DM-RS, it may additionally determine whether the DCI format is 0 or 4 to determine whether to use the reduced uplink DM-RS.

According to an embodiment of the present invention, when the DCI format is 0, a reduced uplink DM-RS may be used (step S1540).

Conversely, when the DCI format is not 0, that is, when the DCI format is 4, it is determined whether the resource allocated by the terminal is associated with the available resource for reduced uplink DM-RS transmission, and whether to use the reduced uplink DM-RS. You can judge about

It is determined whether the uplink allocation resource is associated with the reduced uplink DM-RS transmission available resource (step S1530).

When the terminal is uplink scheduled based on DCI format 4, the terminal determines whether to transmit the reduced uplink DM-RS by determining whether the allocated uplink resource is associated with the reduced uplink DM-RS transmission available resource. I can.

In DCI format 4, it can be determined whether the resource block allocated to the terminal is associated with the available resource for the reduced uplink DM-RS transmission based on the resource block allocation information allocated for transmitting the uplink data and the uplink DM-RS. have. For example, among the resource blocks allocated to the terminal, the resource block allocated to the terminal is reduced by determining whether the resource block with the lowest resource block index belongs to the reduced uplink DM-RS transmission available resource. Uplink DM-RS transmission It can be determined whether or not it is linked to available resources.

When the UE is associated with an available resource for reduced uplink DM-RS transmission based on the DCI format 4, the uplink resource is the lowest among the uplink resource blocks allocated to the UE through DCI format 4, for example. When the resource block corresponding to the resource block index belongs to the available resource for the reduced uplink DM-RS transmission, the terminal may perform uplink transmission based on the reduced uplink DM-RS (step S1540).

On the contrary, if the UE is not associated with the available resources for uplink DM-RS transmission when the uplink resource allocated to the UE is reduced based on DCI format 4, for example, among the uplink resource blocks allocated to the UE through DCI format 4 If the resource block corresponding to the lowest resource block index does not belong to the available resource for the reduced uplink DM-RS transmission, the terminal may perform uplink transmission based on the default uplink DM-RS (step S1510). ).

That is, in an embodiment of the present invention, information on a DCI format used to transmit uplink-related control information and an uplink resource may be classified to determine an uplink DM-RS to be used by a terminal allocated the corresponding resource. The terminal may receive information on whether any of the uplink resources is an available resource for reduced uplink DM-RS transmission from the base station. Alternatively, an available resource for reduced uplink DM-RS transmission may be previously defined between the terminal and the base station.

16 is a flowchart showing a method for selecting an uplink DM-RS according to an embodiment of the present invention.

In FIG. 16, a method for a UE to select an uplink DM-RS in consideration of information on an overhead reduction activation field and a cyclic shift field is disclosed.

Referring to FIG. 16, it may be determined whether or not overhead reduction is possible (step S1600).

The UE may obtain information on whether to use the reduced uplink DM-RS based on a higher layer signal transmitted from an upper layer (eg, radio resource control (RRC)). Information on whether the reduced uplink DM-RS can be used based on the higher layer signal may be transmitted based on, for example, an overhead reduction enabling field. The overhead reduction activation field may be transmitted semi-statically in consideration of a small cell arrangement environment. The overhead reduction activation field may serve to indicate a mode in which overhead reduction is possible.

As a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is not possible to use the reduced uplink DM-RS in the terminal, the terminal performs uplink transmission based on the default uplink DM-RS. Can be performed (step S1610).

Or, if a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is not configured (thus, if the UE does not receive an upper layer signal related to overhead reduction), the UE defaults to uplink DM Uplink transmission may be performed based on -RS (step S1610).

Conversely, as a result of receiving a higher layer signal, if it is possible for the UE to use the reduced uplink DM-RS, it may be determined whether to use the reduced uplink DM-RS based on the cyclic shift field information included in the DCI format. .

Or, when an upper layer signal related to overhead reduction (for example, an overhead reduction activation field) is configured (thus, when the terminal receives an upper layer signal related to overhead reduction), cyclic shift field information included in the DCI format It may be determined whether to use the reduced uplink DM-RS based on.

It is determined whether the cyclic shift field belongs to the first cyclic shift group (step S1620).

In an uplink-related DCI format (DCI format 0 or DCI format 4), it is determined whether to apply uplink DM-RS overhead reduction through a cyclic shift field.

As shown in Table 1 above, eight 3-bit values indicated by the cyclic shift field are divided into two groups (a first cyclic shift group and a second cyclic shift group), and the 3-bit value of the cyclic shift field is the first cyclic When belonging to the shift group, overhead reduction may be applied, and when belonging to the second cyclic shift group, overhead reduction may not be applied.

For example, a field value of 3 bits corresponding to a cyclic shift field belonging to the first cyclic shift group and a field value of 3 bits corresponding to the cyclic shift field belonging to the second cyclic shift group may be variously set. Hereinafter, in the embodiment of the present invention, for convenience of description, it is assumed that 4 of the 8 cyclic shift field values are included in the first cyclic shift group and the remaining 4 are included in the second cyclic shift group. A first cyclic shift group and a second cyclic shift group may be classified.

Referring to Table 1, a cyclic shift field having the same OCC mapping value for each layer may be paired with two field values as follows.

The first set is 000, 111, and may have ([1 1], [1 1], [1 -1], [1 -1]) as OCC values. The second set may have ([1 -1], [1 -1], [1 1], [1 1]) as OCC values of 001 and 010. The third set may have ([1 1], [1 1], [1 1], [1 1]) as OCC values of 011 and 100. The fourth set is 101 and 110, and may have ([1 -1], [1 -1], [1 -1], [1 -1]) as OCC values.

Among the first to fourth sets, one cyclic shift field value among two cyclic shift field values included in each set may be classified as a first cyclic shift group, and the other may be classified as a second cyclic shift group. For example, '111, 010, 100, 110' may be classified as a first cyclic shift group, and '000, 001, 011, 101' may be classified as a second cyclic shift group. As another example, '001, 100, 101, 111' may be classified as a first cyclic shift group, and '000, 010, 011, 110' may be classified as a second cyclic shift group.

In addition, various methods of dividing one cyclic shift field value among two cyclic shift field values included in the first to fourth sets into a first cyclic shift group and the other into a second cyclic shift group may be used.

Based on the cyclic shift field included in the DCI format, when the value of the cyclic shift is the first cyclic shift group, transmission is performed using the reduced uplink DM-RS and the second cyclic shift group is the default uplink DM-RS You can use to perform the transfer. That is, in the case of the first cyclic shift group, since the reduced uplink DM-RS is not used, the OCC may not be separately defined. Tables 6 and 7 below are tables defined by classifying a first cyclic shift and a second cyclic shift. Table 6 or Table 7 may be used instead of Table 1 when overhead reduction is activated based on the overhead reduction activation field.

<Table 6>

<Table 7>

As a result of the determination in step S1620, in the case of the first cyclic shift group, uplink transmission may be performed by using the reduced uplink DM-RS (step S1630).

As a result of the determination of step S1620, in the case of the second cyclic shift group, uplink transmission may be performed using the default uplink DM-RS (step S1610).

17 is a flowchart showing a method for selecting an uplink DM-RS according to an embodiment of the present invention.

In FIG. 17, a method for a UE to select an uplink DM-RS in consideration of information on an overhead reduction activation field, a DCI format, and a cyclic shift field is disclosed.

Referring to FIG. 17, the terminal may determine whether overhead reduction is possible (step S1700).

The UE may obtain information on whether to use the reduced uplink DM-RS based on a higher layer signal transmitted from an upper layer (eg, radio resource control (RRC)). Information on whether the reduced uplink DM-RS can be used based on the higher layer signal may be transmitted based on, for example, an overhead reduction enabling field. The overhead reduction activation field may be transmitted semi-statically in consideration of a small cell arrangement environment. The overhead reduction activation field may serve to indicate a mode in which overhead reduction is possible.

As a result of receiving a higher layer signal (for example, an overhead reduction activation field), if it is not possible to use the reduced uplink DM-RS in the terminal, the terminal performs uplink transmission based on the default uplink DM-RS. Can be performed (step S1710).

Or, if a higher layer signal (e.g., an overhead reduction activation field) related to overhead reduction is not configured (thus, if the UE does not receive an upper layer signal related to overhead reduction), the UE defaults to uplink DM Uplink transmission may be performed based on -RS (step S1710).

Conversely, as a result of receiving the higher layer signal, if it is possible to use the reduced uplink DM-RS in the terminal, the base station determines the information on the DCI format used to transmit the uplink-related control information to the terminal and reduces the uplink DM- Whether to use RS can be determined.

Or, when a higher layer signal related to overhead reduction (for example, an overhead reduction activation field) is configured (thus, when the UE receives a higher layer signal related to overhead reduction), uplink-related control information from the base station to the terminal It is possible to determine whether or not to use the reduced uplink DM-RS by determining information on the DCI format used to transmit the signal.

It is determined whether the DCI format is 0 (step S1720).

When the UE can use the reduced uplink DM-RS, it may be determined whether the DCI format is 0 or 4. When the DCI format is 0, uplink transmission may be performed based on the reduced uplink DM-RS (step S1740).

When the DCI format is 4, it may be determined whether to use the reduced uplink DM-RS based on information on the cyclic shift field included in the DCI format 4.

It is determined whether it is included in the first cyclic shift group (step S1740).

When included in the first cyclic shift group, the UE may perform uplink transmission by applying the reduced uplink DM-RS.

When not included in the first cyclic shift group, that is, included in the second cyclic shift group, the UE performs uplink transmission by applying the default uplink DM-RS without applying the reduced uplink DM-RS. Yes (step S1710).

18 is a block diagram showing a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 18, a base station 1800 includes a processor 1810, a memory 1820, and a radio frequency (RF) unit 1830. The memory 1820 is connected to the processor 1810 and stores various information for driving the processor 1810. The RF unit 1820 is connected to the processor 1810 and transmits a radio signal (for example, an upper layer signal related to overhead reduction disclosed herein, an uplink-related control signal according to DCI format 0 or DCI format 4). Transmit and/or receive a radio signal (for example, an uplink DM-RS disclosed herein). The processor 1810 configures settings for an upper layer signal related to overhead reduction disclosed in this specification and an uplink-related control signal according to DCI format 0 or DCI format 4, and uplink from the received uplink DM-RS. Channel estimation is performed. In the above-described embodiment, the operation of the base station of the serving cell may be implemented by the processor 1810.

The wireless device (or terminal) 1850 includes a processor 1860, a memory 1870, and an RF unit 1880. The memory 1870 is connected to the processor 1860 and stores various information for driving the processor 1860. The RF unit 1880 is connected to the processor 1860 and transmits a radio signal (for example, an upper layer signal related to overhead reduction disclosed in this specification, an uplink-related control signal based on DCI format 0 or DCI format 4). It receives or transmits a radio signal (eg, an uplink DM-RS disclosed herein). The processor 1860 implements the functions, processes, and/or methods proposed in the embodiments according to FIGS. 10 to 17 of the present invention. The operation of the terminal in all the embodiments disclosed in this specification may be implemented by the processor 1860.

The processor may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and/or a data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and/or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the embodiment is implemented as software, the above-described technique may be implemented as a module (process, function, etc.) that performs the above-described functions. The modules are stored in memory and can be executed by the processor. The memory may be inside or outside the processor, and may be connected to the processor through various well-known means.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims (14)

In a method for transmitting a reference signal of a terminal in a wireless communication system,
Determining whether uplink transmission is possible based on a reduced uplink demodulation (DM)-RS (reference signal) based on an overhead reduction activation field received from the base station by the terminal; And
When uplink transmission based on the reduced uplink DM-RS is possible, based on the reduced uplink DM-RS based on uplink related downlink control information (DCI) received from the base station by the terminal Including the step of determining whether to perform one uplink transmission,
The overhead reduction activation field is a field indicating whether the UE is capable of uplink transmission based on the reduced uplink DM-RS,
The step of determining whether to perform uplink transmission based on the reduced uplink DM-RS,
When the format of the uplink-related DCI is DCI format 0, performing, by the terminal, uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field; And
If the format of the uplink-related DCI is DCI format 4, determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information. But,
The reduced uplink DM-RS is a method of transmitting a reference signal of a terminal in a wireless communication system in which one symbol is allocated per subframe. The method of claim 1,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
Determining whether the number of layers allocated for uplink transmission of the terminal is less than or equal to a threshold number of layers, and performing, by the terminal, uplink transmission based on the reduced uplink DM-RS,
The number of threshold layers is the number of layers serving as a criterion for determining whether to perform uplink transmission based on the reduced uplink DM-RS. The method of claim 1,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
Including the step of determining, by the terminal, whether to perform uplink transmission based on the reduced uplink DM-RS based on an overhead reduction field included in the DCI format 4,
The overhead reduction field is a field indicating whether the terminal uses the reduced uplink DM-RS. A method of transmitting a reference signal by a terminal in a wireless communication system. delete The method of claim 1,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
Determining whether an uplink transmission resource allocated based on the DCI format 4 is associated with a reduced uplink DM-RS transmission available resource; And
If the uplink transmission resource is associated with the reduced uplink DM-RS transmission available resource, comprising the step of performing uplink transmission based on the reduced uplink DM-RS,
The information on the available resources for the reduced uplink DM-RS transmission is included in the overhead reduction activation field so that the terminal receives from the base station or can be predefined between the terminal and the base station. Reference signal transmission method. delete The method of claim 1,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
Reference of the terminal in a wireless communication system, which is a step of determining whether to perform uplink transmission using the reduced uplink DM-RS based on information on a cyclic shift field included in the uplink-related DCI Signal transmission method. In a terminal for transmitting a reference signal in a wireless communication system, the terminal
A radio frequency (RF) unit for transmitting and receiving radio signals; And
Including a processor that is selectively connected to the RF unit,
The processor determines whether uplink transmission is possible based on a reduced uplink demodulation (DM)-RS (reference signal) based on an overhead reduction activation field received from the base station,
When uplink transmission based on the reduced uplink DM-RS is possible, uplink based on the reduced uplink DM-RS based on uplink related downlink control information (DCI) received from the base station Is implemented to determine whether to perform the transfer,
The overhead reduction activation field is a field indicating whether the UE is capable of uplink transmission based on the reduced uplink DM-RS,
Implementation to determine whether to perform uplink transmission based on the reduced uplink DM-RS,
When the format of the uplink-related DCI is DCI format 0, the terminal performs uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field,
When the format of the uplink-related DCI is DCI format 4, it is determined whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
The reduced uplink DM-RS is assigned to one symbol per subframe. The method of claim 8,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
It is implemented to perform uplink transmission based on the reduced uplink DM-RS by determining whether the number of layers allocated for uplink transmission of the terminal is less than or equal to a threshold number of layers,
The number of critical layers is the number of layers serving as a criterion for determining whether to perform uplink transmission based on the reduced uplink DM-RS. The method of claim 8,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
It is implemented to determine whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction field included in the DCI format 4,
The overhead reduction field is a field indicating whether the terminal uses the reduced uplink DM-RS. delete The method of claim 8,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
Determine whether an uplink transmission resource allocated based on the DCI format 4 is a reduced uplink DM-RS transmission available resource,
When the uplink transmission resource is the reduced uplink DM-RS transmission available resource, it is implemented to perform uplink transmission based on the reduced uplink DM-RS,
The information on the available resources for the reduced uplink DM-RS transmission is included in the overhead reduction activation field so that the terminal receives from the base station or can be predefined between the terminal and the base station. . delete The method of claim 8,
Determining whether to perform uplink transmission based on the reduced uplink DM-RS based on the overhead reduction activation field and DCI-related information,
A terminal implemented to determine whether to perform uplink transmission using the reduced uplink DM-RS based on information on a cyclic shift field included in the uplink-related DCI.

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