KR102094419B1 - Method and apparatus for transmitting reference signal in wireless communication system - Google Patents

Abstract

A method and apparatus for transmitting a reference signal in a wireless communication system is provided. A user equipment (UE) generates a reference signal sequence according to whether an orthogonal sequence indicated by a base station is applied, and transmits it by mapping it to a resource element according to whether the orthogonal sequence is applied. When application of the orthogonal sequence is indicated, the reference signal sequence is mapped to the resource element included in two single carrier frequency division multiple access (SC-FDMA) symbols in one subframe. In addition, when it is indicated that the orthogonal sequence is not applied, the reference signal sequence is mapped to the resource element included in one SC-FDMA symbol in one subframe.

Description

Method and device for transmitting a reference signal in a wireless communication system {METHOD AND APPARATUS FOR TRANSMITTING REFERENCE SIGNAL IN WIRELESS COMMUNICATION SYSTEM}

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

Universal mobile telecommunications system (UMTS) is a third generation (3rd) operating in wideband code division multiple access (WCDMA) based on European systems such as global system for mobile communications (GSM) and general packet radio services (GPRS). generation) It is an asynchronous mobile communication system. As a 4th generation mobile communication system, long-term evolution (LTE) and advanced (LTE-A) are being discussed by a 3rd generation partnership project (3GPP) that standardizes UMTS.

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. In a wireless communication system environment, fading occurs due to multipath time delay. The process of restoring a transmission signal by compensating for distortion of a signal caused by a rapid environmental change due to fading is called channel estimation. In addition, it is necessary to measure the channel state (channel state) for the cell or other cell to which the terminal belongs. For channel estimation or channel state measurement, channel estimation is generally performed using a reference signal (RS) that transceivers know each other.

A subcarrier used for transmitting a reference signal is referred to as a reference signal subcarrier, and a resource element used for data transmission is referred to as a data subcarrier. In an orthogonal frequency division multiplexing (OFDM) system, there is a method of allocating a reference signal to all subcarriers and a data subcarrier. The method of allocating a reference signal to all subcarriers uses a signal consisting of only a reference signal, such as a preamble signal, in order to obtain a channel estimation performance gain. When this is used, since the density of the reference signal is generally high, channel estimation performance may be improved compared to a method of allocating a reference signal between data subcarriers. However, since the data transmission amount is reduced, a method of allocating a reference signal between data subcarriers is used to increase the data transmission amount. When this method is used, since the density of the reference signal is reduced, deterioration of channel estimation performance occurs and an appropriate arrangement to minimize it is required.

1 shows an example of a communication system in which a high power node and a low power node are arranged.

In a next-generation communication system such as 3GPP LTE-A, as shown in FIG. 1, not only a macro cell (F1) based on a high-power node, but also a small cell based on a low-power node (low-power node). , F2), research is being conducted to provide wireless communication services to indoors and outdoors.

The small cell can be considered in both the frequency band F1 which is the coverage of the macro cell and the frequency band F2 other than the coverage of the macro cell. Further, the small cell may be provided in both an indoor environment (shown as a cube in FIG. 1) and an outdoor environment (shown outside a cube in FIG. 1). Also, an ideal or non-ideal backhaul network may be supported between a macro cell and a small cell, and / or between small cells. Further, the small cell may be provided in both a low-density deployment environment and / or a high-density deployment environment.

Small cells aim to improve spectral efficiency through efficient deployment and operation. To this end, various techniques may be proposed, and as one of them, a technique for reducing overhead for a UE (user equipment) specific reference signal such as a demodulation reference signal (DMRS) may be proposed. .

The technical problem of the present invention is to provide a method and apparatus for transmitting a reference signal in a wireless communication system. The present invention provides a method and apparatus for configuring and transmitting an uplink (UL) demodulation reference signal (DMRS) in a small cell environment. In particular, the present invention provides a method and apparatus for configuring and transmitting UL DMRS through only one single carrier frequency division multiple access (SC-FDMA) symbol in one subframe in a small cell environment.

In one aspect, a method for transmitting a reference signal by a user equipment (UE) in a wireless communication system is provided. The method includes generating a reference signal sequence according to whether an orthogonal sequence indicated from a base station is applied, performing precoding on the generated reference signal sequence, orthogonalizing the precoded reference signal sequence Mapping to a resource element according to whether a sequence is applied, and transmitting a single carrier frequency division multiple access (SC-FDMA) signal generated based on the mapped reference signal sequence to the base station, wherein the orthogonal sequence When the application of is indicated, the precoded reference signal sequence is mapped to the resource element included in two SC-FDMA symbols in one subframe, and when it is indicated that the application of the orthogonal sequence is not applied, the free The coded reference signal sequence is included in one SC-FDMA symbol in one subframe. Is mapped to an existing resource element.

Whether to apply the orthogonal sequence may be indicated by a 3-bit cyclic shift field in downlink control information (DCI) transmitted from the base station.

When the value of the 3-bit cyclic shift field is included in the first group, application of the orthogonal sequence may be indicated.

The first group may include cyclic shift fields having values of 011, 100, 101, and 110.

When the value of the 3-bit cyclic shift field is included in the second group, it may be indicated that the orthogonal sequence is not applied.

The second group may include cyclic shift fields having values of 000, 001, 010, and 111.

When it is indicated that the orthogonal sequence is not applied, the precoded reference signal sequence may be mapped to the resource element included in one SC-FDMA symbol of the first slot in one subframe.

Whether to apply the orthogonal sequence may be indicated by 1 bit defined additionally in DCI transmitted from the base station.

In another aspect, a user equipment (UE) is provided in a wireless communication system. The terminal is a reference signal generator configured to generate a reference signal sequence according to whether an orthogonal sequence indicated by a base station is applied, and performs precoding on the generated reference signal sequence, and the precoded reference signal A resource mapper configured to map a sequence to a resource element according to whether the orthogonal sequence is applied, and a single carrier frequency division multiple access (SC-FDMA) signal generated based on the mapped reference signal sequence is configured to be transmitted to the base station When the application of the orthogonal sequence is indicated, the precoded reference signal sequence is mapped to the resource element included in two SC-FDMA symbols in one subframe, and the application of the orthogonal sequence If not indicated, the precoded reference signal sequence is one It is mapped to the resource elements included in one SC-FDMA symbol in the subframe.

In another aspect, a method for demodulating a physical uplink shared channel (PUSCH) by a base station in a wireless communication system is provided. The method includes transmitting the indication information indicating whether an orthogonal sequence is applied to a user equipment (UE), and generating based on the reference signal sequence generated according to the indication information indicating whether the orthogonal sequence is applied. Receiving a reference signal and a PUSCH from the terminal, and demodulating the received reference signal to perform channel estimation, and demodulating the PUSCH based on the estimated channel, wherein the generated reference signal sequence Is mapped to a resource element according to whether the orthogonal sequence is applied through precoding, and when the application of the orthogonal sequence is indicated, the precoded reference signal sequence is two single carrier frequencies (SC-FDMA) in one subframe. division multiple access) is mapped to the resource element included in the symbol, and is not applied to the orthogonal sequence. When the precoded reference signal sequence is mapped to the resource elements included in one SC-FDMA symbols within one subframe.

In a small cell environment, the overhead of UL DMRS can be reduced.

1 shows an example of a communication system in which a high power node and a low power node are arranged.
2 shows a wireless communication system to which an embodiment of the present invention can be applied.
3 shows a structure of a radio frame in 3GPP LTE.
4 shows an example of a resource grid for one uplink slot.
5 shows an example of a conventional UL DMRS transmission method.
6 shows an example of a PUSCH DMRS transmission method according to an embodiment of the present invention.
7 shows an embodiment of a method for transmitting a reference signal according to an embodiment of the present invention.
8 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

Hereinafter, some embodiments will be described in detail through exemplary drawings. It should be noted that in adding reference numerals to the components of each drawing, the same components have the same reference numerals as possible even though they are displayed on different drawings. In addition, in describing the embodiments of the present specification, when it is determined that detailed descriptions of related well-known configurations or functions may obscure the subject matter of the present specification, detailed descriptions 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) in charge of the communication network, or a terminal linked to the network Can be done in

The following technologies include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access (SC-FDMA). It can be used in various wireless communication systems. CDMA may be implemented by radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with radio technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA can be implemented with wireless technologies such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). IEEE 802.16m is an evolution of IEEE 802.16e, and provides backward compatibility with a system based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is part of evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access (E-UTRA), employing OFDMA in the downlink and SC in the uplink -Adopt FDMA. LTE-A (advanced) is an evolution of 3GPP LTE.

For clarity, LTE-A is mainly described, but the technical spirit of the present invention is not limited thereto.

2 shows a wireless communication system to which an embodiment of the present invention can be applied.

Referring to FIG. 2, the 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) 11. Each base station 11 provides a communication service for a specific geographic area or frequency domain, and may be called a site. A site may be divided into a plurality of areas 15a, 15b, and 15c, which may be called sectors, and the sectors may have different cell IDs.

The mobile station (MS) 12 may be fixed or mobile, and user equipment (UE), mobile terminal (MT), user terminal (UT), subscriber station (SS), wireless device (PDA), PDA (personal digital assistant), wireless modem (wireless modem), handheld device (handheld device) can be called in other terms. The base station 11 generally refers to a station communicating with the terminal 12, evolved-NodeB (eNodeB), base transceiver system (BTS), access point, femto eNB, home The base station (HeNB; home eNodeB), relay (relay), a remote radio head (RRH) may be called in other terms. Cells (15a, 15b, 15c) should be interpreted in a comprehensive sense indicating a part of the area covered by the base station 11, mega cell (mega cell), macro cell (macro cell), micro cell (micro cell), pico It means to cover all the various coverage areas such as pico cell and femto cell.

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

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

The wireless communication system includes any one of a multiple-input multiple-output (MIMO) system, a multiple-input single-output (MISO) system, a single-input single-output (SISO) system, and a single-input multiple-output (SIMO) system. Can be The MIMO system uses a plurality of transmit antennas and a plurality of receive antennas. The MISO system uses multiple transmit antennas and one receive antenna. The SISO system uses one transmit antenna and one receive antenna. The SIMO system uses one transmit antenna and multiple receive antennas. Hereinafter, the transmit antenna means a physical or logical antenna used to transmit one signal or stream, and the receive antenna means a physical or logical antenna used to receive one signal or stream.

The wireless communication system can be roughly divided into a frequency division duplex (FDD) method and a time division duplex (TDD) method. According to the FDD method, uplink transmission and downlink transmission are performed while occupying different frequency bands. According to the TDD method, uplink transmission and downlink transmission are performed at different times while occupying the same frequency band. The channel response of the TDD scheme is substantially reciprocal. This means that the downlink channel response and the uplink channel response are almost the same in a given frequency domain. Therefore, in a TDD-based wireless communication system, a downlink channel response has an advantage that can be obtained from an uplink channel response. In the TDD scheme, since uplink transmission and downlink transmission are time-divided over the entire frequency band, downlink transmission by the base station and uplink transmission by the terminal cannot be simultaneously performed. In a TDD system in which uplink transmission and downlink transmission are divided into subframe units, uplink transmission and downlink transmission are performed in different subframes.

3 shows a structure of a radio frame in 3GPP LTE. This may refer to 3GPP TS 36.211 V11.2.0 (2013-02).

Referring to FIG. 3, a radio frame is composed of 10 subframes, and one subframe is composed of two slots. Slots in the radio frame are numbered from # 0 to # 19. The transmission time interval (TTI) is a basic scheduling unit for data transmission. In 3GPP LTE, one TTI may be equal to the time it takes for one subframe to be transmitted. The length of one radio frame may be 10 ms, the length of one subframe may be 1 ms, and the length of one slot may be 0.5 ms.

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

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

The downlink subframe includes 2 slots in the time domain, and each slot includes 7 OFDM symbols in the normal CP. Up to 3 OFDM symbols in the first slot in a subframe (up to 4 OFDM symbols for 1.4 MHz bandwidth) are control regions to which control channels are allocated, and the remaining OFDM symbols are physical downlink shared channel (PDSCH). Becomes the data area to be allocated.

4 shows an example of a resource grid for one uplink slot.

The uplink slot includes a plurality of SC-FDMA symbols in the time domain and N _RB resource blocks in the frequency domain. The number of resource blocks N _RB included in the uplink slot depends on the uplink transmission bandwidth set in the cell. For example, in 3GPP LTE, N _RB may be any one of 6 to 110. One resource block includes a plurality of subcarriers in the frequency domain. The structure of the downlink slot may be the same as that of the uplink slot.

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

Here, one resource block corresponds to one slot in 0.5 ms in the time domain, and corresponds to a total of 12 subcarriers when the frequency spacing between each subcarrier is 15 KHz in 180 KHz in the frequency domain. In FIG. 4, it is exemplarily described that one resource block includes 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain, but the number of OFDM symbols and the number of subcarriers in the resource block are illustrated. Is not limited thereto. The number of OFDM symbols and the number of subcarriers may be variously changed according to the length of CP, frequency interval, and the like. For example, the number of OFDM symbols is 7 for a normal CP and the number of OFDM symbols is 6 for an extended CP.

In addition, two resource blocks physically allocated in one subframe on the time axis may be referred to as a pair of physical resource blocks (PRBs).

The reference signal (RS) is generally transmitted in sequence. As the reference signal sequence, a sequence having excellent correlation properties may be used. As an example, a reference signal sequence may use a constant amplitude zero auto-correlation (CAZAC) sequence. The CAZAC sequence includes a ZC-based sequence (Zadoff-Chu based sequence), and the ZC-based sequence may be used by being cyclically extended or truncated depending on the purpose. As another example, a reference signal sequence may use a pseudo-noise (PN) sequence. The PN sequence includes an m-sequence, a computer generated PN sequence, a Gold sequence, and a Kasami sequence.

The uplink reference signal may be divided into a demodulation reference signal (DMRS) and a sounding reference signal (SRS). DMRS is a reference signal used for channel estimation for demodulation of the received signal. DMRS is associated with transmission of PUSCH or PUCCH. SRS is a reference signal that the UE transmits to the base station for uplink scheduling. The base station estimates an uplink channel through the received sounding reference signal, and uses the estimated uplink channel for uplink scheduling. SRS is not associated with the transmission of PUSCH or PUCCH. The same kind of basic sequence can be used for DMRS and SRS. Meanwhile, in uplink multi-antenna transmission, precoding applied to DMRS may be the same as precoding applied to PUSCH. Cyclic shift separation is a primary scheme for multiplexing DMRS. In 3GPP LTE-A system, SRS may not be precoded and may also be an antenna-specific reference signal.

The reference signal sequence will be described.

의 순환 쉬프트(CS; cyclic shift) α를 기반으로 정의될 수 있다.The reference signal sequence r _{u, v} ^(α) (n) is a basic sequence by Equation (1).

It may be defined based on the cyclic shift (CS) α of.

<Equation 1>

In Equation 1, M _sc ^RS = m × N _sc ^RB (1 ≦ m ≦ N _RB ^{max, UL} ) is the length of the reference signal sequence. N _sc ^RB represents the number of subcarriers in one resource block in the frequency domain. For example, when the frequency interval between each subcarrier is 15 KHz, N _SC ^RB = 12. N _RB ^{max, UL} indicates the maximum value of the uplink bandwidth as the number of resource blocks. For example, N _RB ^{max, UL} = 110. A plurality of reference signal sequences may be defined by differently applying a cyclic shift value α from one basic sequence.

는 복수의 그룹으로 나누어지며, 이때 u∈{0,1,…,29}는 시퀀스 그룹 번호를, v는 시퀀스 그룹 내에서 기본 시퀀스 번호를 나타낸다. 각 그룹은 1≤m≤5인 m에 대해서 길이가 M_sc ^RS 인 하나의 기본 시퀀스(v=0)를 포함하며, 6≤m≤n_RB ^max,UL인 m에 대해서는 길이가 M_sc ^RS 인 2개의 기본 시퀀스(v=0,1)를 포함한다. 시퀀스 그룹 번호 u와 그룹 내의 기본 시퀀스 번호 v는 후술할 그룹 홉핑(group hopping) 또는 시퀀스 홉핑(sequence hopping)에 의하여 시간에 따라 변할 수 있다. 기본 시퀀스는 기본 시퀀스의 길이 M_sc ^RS에 의존한다.Basic sequence

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

The sequence group number u of the slot n _s may be defined based on the group hopping pattern f _gh (n _s ) and the sequence shift pattern f _ss by Equation 2.

<Equation 2>

Referring to Equation 2, the sequence group number u can be obtained by adding a group hopping pattern f _gh (n _s ) and a sequence shift pattern f _ss and performing a modular 30 operation. Through this, the sequence group number u can have a total of 30 values from 0 to 29.

There may be 17 different group hopping patterns and 30 different sequence shift patterns. Group hopping may be enabled (enable) or disabled (disable) by the cell-specific parameter Group-hopping-enabled provided by the upper layer. In addition, even if the group hopping for PUSCH is configured to be activated on a cell basis, it may be deactivated for a specific UE by the terminal specific parameter Disable-sequence-group-hopping .

The group hopping pattern f _gh (n _s ) may be different for PUSCH, PUCCH, and SRS, and may be given by Equation 3.

<Equation 3>

로 초기화될 수 있다. 수학식 3을 참조하면, 그룹 홉핑 패턴 f_gh(n_s)는 그룹 홉핑이 비활성화 되었을 때는 0의 값을 가진다. 그룹 홉핑 패턴 f_gh(n_s)는 그룹 홉핑이 활성화 되었을 때는 상향링크 참조 신호를 위한 식별자 n_ID ^RS와 슬롯 번호 n_s에 따라 정해진다.In Equation 3, c (i) is a pseudo-random sequence, and may be defined by a Gold sequence of length-31. Pseudo random sequence generator at the start of each radio frame

Can be initialized to Referring to Equation 3, the group hopping pattern f _gh (n _s ) has a value of 0 when group hopping is deactivated. The group hopping pattern f _gh (n _s ) is determined according to an identifier n _ID ^RS and a slot number n _s for an uplink reference signal when group hopping is activated.

n _ID ^RS may be determined according to the transmission type. In transmission associated with PUSCH, n _ID ^PUSCH is not configured by the upper layer or PUSCH transmission is the same transport block as part of a random access response grant or contention-based random access procedure. When it corresponds to the retransmission of n _ID ^RS = n _ID ^cell may be determined. That is, n _ID ^RS may be determined as a physical cell identifier. Otherwise, N _ID ^RS = n _ID ^PUSCH may be determined. That is, n _ID ^RS may be determined as a virtual cell identifier (virtual cell identifier). In transmission associated with ^PUCCH, when n _ID ^PUCCH is not configured by an upper layer, n _ID ^RS = n _ID ^cell may be determined. That is, n _ID ^RS may be determined as a physical cell identifier. Otherwise, N _ID ^RS = n _ID ^PUCCH may be determined. That is, n _ID ^RS may be determined as a virtual cell identifier.

The sequence shift pattern f _ss may be different for PUCCH, PUSCH and SRS. The sequence shift pattern f _ss ^{PUCCH of PUCCH} = N _ID ^RS mod 30 may be given. If the sequence shift pattern f _ss ^PUSCH of the ^PUSCH is n _ID ^PUSCH is not configured by the upper layer or the PUSCH transmission corresponds to retransmission of the same transport block as part of a random access response grant or contention-based random access procedure, f _ss ^PUSCH = (N _ID ^cell + Δ _ss ) Can be given as mod 30, Δ _ss ∈ {0,1,… , 29} may be configured by a higher layer. Otherwise, f _ss ^PUSCH = n _ID ^RS mod 30 may be given.

Sequence hopping can be applied only to a reference signal sequence whose length is longer than 6N _sc ^RB . For reference signal sequences shorter than 6N _sc ^RB , the basic sequence number v = 0 in the basic sequence group is given. For a reference signal sequence having a length longer than 6N _sc ^RB , the basic sequence number v in the basic sequence group in slot n _s may be defined by Equation (4).

<Equation 4>

로 초기화될 수 있다. 수학식 4를 참조하면, 기본 시퀀스 번호 v는 그룹 홉핑이 비활성화 되고 시퀀스 홉핑이 활성화 되었을 때에만 상향링크 참조 신호를 위한 식별자 n_ID ^RS, 슬롯 번호 n_s, 및 f_ss ^PUSCH에 따라 정해진다. 나머지 경우에서 기본 시퀀스 번호 v의 값은 0이다.In Equation 4, c (i) is a pseudo-random sequence and may be defined by a gold sequence of length-31. For PUSCH, the pseudo-random sequence generator is at the start of each radio frame.

Can be initialized to Referring to Equation 4, the basic sequence number v is determined according to the identifiers n _ID ^RS , slot numbers n _s , and f _ss ^PUSCH for the uplink reference signal only when group hopping is deactivated and sequence hopping is activated. In the rest of the cases, the value of the base sequence number v is 0.

Sequence hopping may be activated or deactivated by the cell-specific parameter Sequence-hopping-enabled provided by the upper layer. In addition, even if the sequence hopping for PUSCH is configured to be activated on a cell basis, it may be deactivated for a specific UE by the terminal specific parameter Disable-sequence-group-hopping .

DMRS transmission for PUSCH and / or PUCCH will be described.

5 shows an example of a conventional UL DMRS transmission method.

Referring to FIG. 5, UL DMRS may be transmitted for every slot in every subframe in which PUSCH or PUCCH is transmitted. In addition, since UL DMRS is associated with PUSCH transmission or PUCCH transmission, information on UL DMRS transmission bandwidth expressed in resource block (RB) units may be determined based on previously transmitted signaling information. For example, in the case of DMRS associated with PUSCH (hereinafter, PUSCH DMRS), since PUSCH DMRS is transmitted to RBs to which PUSCH is allocated, the PUSCH DMRS transmission bandwidth may be determined based on information on RBs to which PUSCH is allocated. . In this case, RBs to which PUSCH is allocated for each UE may be determined based on a resource block assignment field of downlink control information (DCI).

The UL DMRS sequence may be transmitted by being mapped to all subcarriers in the RB used for DMRS transmission. The PUSCH DMRS sequence r _PUSCH ^(λ) (.) Linked to the layer λ ∈ {0,1, ..., v-1} may be defined by Equation 5.

<Equation 5>

At this time, m = 0,1, and n = 0, ..., M _sc ^RS -1. M _SC ^RS = M _SC ^PUSCH .

를 순환 쉬프트(CS; cyclic shift)하고, PUSCH DMRS 전송을 위해 사용되는 RB에 해당하는 길이 M_SC ^RS(사용되는 RB의 개수×RB 내의 부반송파의 개수(보통 12))를 가지고 생성된다. 기본 시퀀스는 앞에서 설명한 수학식 1 내지 수학식 4를 기반으로 정의될 수 있다. 즉, 기본 시퀀스는 각 상향링크 참조 신호를 위한 식별자 N_ID ^RS 및 슬롯 별로 서로 다르게 결정될 수 있다. 상기 각 상향링크 참조 신호를 위한 식별자는 물리 셀 식별자일 수도 있고, 가상 셀 식별자일 수도 있다. 기본 시퀀스의 시퀀스 그룹 번호 u 및 기본 시퀀스 번호 v는 서브프레임 내의 슬롯 번호에 따라 달라질 수 있다. 또한, 순환 쉬프트 α_λ는 각 UE 및 레이어(layer)마다 서로 다르게 할당될 수 있다. Referring to Equation 5, the PUSCH DMRS sequence is a basic sequence based on a ZC (Zadoff-Chu) sequence.

Cyclic shift (CS), and is generated with a length M _SC ^RS (number of RBs used × number of subcarriers in the RB (usually 12)) corresponding to the RB used for PUSCH DMRS transmission. The basic sequence may be defined based on Equations 1 to 4 described above. That is, the basic sequence may be determined differently for each identifier N _ID ^RS and slot for each uplink reference signal. The identifier for each of the uplink reference signals may be a physical cell identifier or a virtual cell identifier. The sequence group number u and the basic sequence number v of the basic sequence may vary depending on the slot number in the subframe. In addition, the cyclic shift α _λ may be allocated differently for each UE and layer.

An orthogonal sequence (orthogonal sequence or orthogonal cover code (OCC)) w ^(λ) (m) is a 3-bit cyclic shift field in the most recent uplink DCI for a transport block associated with a corresponding PUSCH transmission. It can be determined according to Table 1 using. That is, the orthogonal sequence w ^(λ) (m) can be dynamically determined through DCI.

Cyclic Shift Field in
uplink-related DCI format n _{DMRS, λ} ⁽²⁾ [w ^(λ) (0) w ^(λ) (1)] λ = 0 λ = 1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3 000 0 6 3 9 [1 1] [1 1] [1 -1] [1 -1] 001 6 0 9 3 [1 -1] [1 -1] [1 1] [1 1] 010 3 9 6 0 [1 -1] [1 -1] [1 1] [1 1] 011 4 10 7 One [1 1] [1 1] [1 1] [1 1] 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1] 101 8 2 11 5 [1 -1] [1 -1] [1 -1] [1 -1] 110 10 4 One 7 [1 -1] [1 -1] [1 -1] [1 -1] 111 9 3 0 6 [1 1] [1 1] [1 -1] [1 -1]

Referring to Table 1, n _{DMRS, λ} ⁽²⁾ is indicated by a 3-bit cyclic shift field signaled through DCI. At this time, n _{DMRS, 0} ⁽²⁾ , n _{DMRS, 1} ⁽²⁾ , n _{DMRS, 2} ⁽²⁾ and n _{DMRS, 3} ⁽²⁾ are the first layer (λ = 0) and the second layer (λ =) 1), n _{DMRS, λ} ⁽²⁾ of the third layer (λ = 2) and the fourth layer (λ = 3). Also, as described later, the cyclic shift value may be determined specifically for the terminal according to n _{DMRS, λ} ⁽²⁾ .

The cyclic shift α _λ = 2πn _{cs, λ} / 12 in slot n _s is given, and n _{cs, λ} can be defined by Equation 6.

<Equation 6>

Referring to Equation 6, n _{cs, λ} used to calculate the cyclic shift α _λ can be obtained by modulating 12 sums of three parameters.

In Equation 6, n _DMRS ⁽¹⁾ may be determined according to the parameter cyclicShift provided by the upper layer. The _DMRS ⁽¹⁾ may be assigned cell-specific. Table 2 shows the mapping relationship between cyclic shift and n _DMRS ⁽¹⁾ .

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

Again, in Equation 6, n _{DMRS, λ} ⁽²⁾ is given by a cyclic shift field in the most recent uplink DCI for a transport block associated with a corresponding PUSCH transmission, as described in Table 1. _{DMRS, λ} ⁽²⁾ may be allocated differently for each UE.

The parameter n _PN (n _s ) related to cyclic shift hopping (CSH) may be defined by Equation (7).

<Equation 7>

로 결정될 수 있다. 그렇지 않은 경우,

로 결정될 수 있다.In Equation 7, c (i) is a pseudo-random sequence and may be defined by a gold sequence of length-31. c (i) can be applied cell-specific. The pseudo-random sequence generator can be initialized with c _init at the start of each radio frame. c _init is when N _ID ^csh_DMRS is not configured by the upper layer or PUSCH transmission corresponds to retransmission of the same transport block as part of a random access response grant or contention-based random access procedure,

Can be determined as. If not,

Can be determined as.

A vector of reference signals may be precoded by Equation (8).

<Equation 8>

In Equation 8, P is the number of antenna ports used for PUSCH transmission. W is a precoding matrix. P = 1, W = 1, and γ = 1 for PUSCH transmission using a single antenna port. Also, P = 2 or 4 for spatial multiplexing.

는 진폭 스케일링 인자(amplitude scaling factor) β_PUSCH와 곱해지고,

부터 순서대로 자원 블록에 맵핑될 수 있다. 맵핑에 사용되는 물리 자원 블록의 집합 및 인덱스

와 안테나 포트 번호 p의 관계는 대응되는 PUSCH 전송과 동일할 수 있다. 서브프레임 내에서 상기 DMRS 시퀀스는 먼저 주파수 영역에서 증가하는 방향으로, 그리고 슬롯 번호가 증가하는 방향으로 자원 요소에 맵핑될 수 있다. DMRS 시퀀스는 일반 CP인 경우 4번째 SC-FDMA 심볼(SC-FDMA 심볼 인덱스 3), 확장 CP인 경우 3번째 SC-FDMA 심볼(SC-FDMA 심볼 인덱스 2)에 맵핑될 수 있다.For each antenna port used for PUSCH transmission, DMRS sequence

Is multiplied by the amplitude scaling factor β _PUSCH ,

From the can be mapped to the resource block in order. Set and index of physical resource blocks used for mapping

And the antenna port number p may be the same as the corresponding PUSCH transmission. In the subframe, the DMRS sequence may be mapped to a resource element in an increasing direction in the frequency domain and an increasing slot number. The DMRS sequence may be mapped to the fourth SC-FDMA symbol (SC-FDMA symbol index 3) in the case of a normal CP and the third SC-FDMA symbol (SC-FDMA symbol index 2) in the case of the extended CP.

As described above, the existing PUSCH DMRS is transmitted through one SC-FDMA symbol for each slot. That is, PUSCH DMRS is transmitted through a total of two SC-FDMA symbols, one for each of two slots in one subframe. Meanwhile, in a small cell environment, a method of reducing the overhead of a time-frequency resource for PUSCH DMRS to improve spectrum efficiency may be proposed. For example, PUSCH DMRS may be transmitted only in one of two slots in one subframe. That is, PUSCH DMRS is transmitted through only one SC-FDMA symbol in one subframe. In a small cell environment, since the channel state is not significantly changed, the number of SC-FDMA symbols allocated to PUSCH DMRS can be reduced. However, when PUSCH DMRS is transmitted through only one SC-FDMA symbol, since the OCC applied to two SC-FDMA symbols of two slots within one subframe cannot be applied, a specific MU-MIMO environment Can cause problems.

Therefore, when transmitting the PUSCH DMRS in a small cell environment, when it is necessary to apply the OCC, the PUSCH DMRS is configured and transmitted through two SC-FDMA symbols in one subframe in the same way as the conventional method, and the application of the OCC is applied. If this is not required, a method of configuring and transmitting PUSCH DMRS through only one SC-FDMA symbol in one subframe may be proposed. In addition, a signaling method for indicating this to the UE may be proposed.

According to an embodiment of the present invention, a method of configuring a PUSCH DMRS based on whether application of an OCC is necessary may vary. First, the case where the application of the OCC is necessary will be described. OCC can be applied in the following cases.

-OCC may be applied when the allocated bandwidth is different between at least two UEs among UEs constituting MU-MIMO. For example, PUSCH and PUSCH DMRS for UE A are allocated to RB # 4, # 5, # 6, and # 7, and PUSCH and PUSCH DMRS for UE B are allocated to RB # 6, # 7, and # 8. Assume that MU-MIMO is configured because UE A and UE B transmit PUSCH and PUSCH DMRS through RB # 6 and # 7. At this time, since the PUSCH DMRS for MU-MIMO UEs allocated to different bandwidths cannot be distinguished only by cyclic shift, OCC may be applied to distinguish MU-MIMO UEs.

-Even if the bandwidth allocated to UEs constituting MU-MIMO is the same, OCC may be applied when the total number of layers used by UEs is 5 or more. For example, if PUSCH and PUSCH DMRS for UE A are allocated to RB # 4, # 5, and # 6, and PUSCH and PUSCH DMRS for UE B are allocated to RB # 4, # 5, and # 6, UE A And UE B transmit PUSCH and PUSCH DMRS through RB # 4, # 5, and # 6, so MU-MIMO is configured. In addition, when UE A transmits PUSCH DMRS using two layers and UE B transmits PUSCH DMRS using four layers, the total number of layers is six. Or, if UE A transmits PUSCH DMRS using two layers, UE B uses two layers, and UE C uses one layer, the total number of layers is five. When five or more layers used by MU-MIMO UEs are divided into different cyclic shift values, deterioration of performance may occur. Therefore, in this case, OCC can be applied.

When the application of the OCC is necessary, PUSCH DMRS may be configured and transmitted through two SC-FDMA symbols in one subframe, as in the case of conventional PUSCH DMRS transmission. That is, in order to configure the PUSCH DMRS, the contents of Equations 1 to 7, and Tables 1 and 2 described above may be applied as they are.

Describes the case where the application of OCC is not necessary. If OCC application is not required, it is as follows.

-Single antenna transmission or SU-MIMO, that is, PDSCH and DMRS are transmitted only for one UE in an allocated RB of a specific bandwidth, and when the number of layers used for this is 4 or less, application of OCC is not required. At this time, even if OCC is not applied, each layer can be classified through up to four cyclic shifts.

For example, when the number of layers of UE A is 1, n _DMRS for layer 0 _{, 0} ⁽²⁾ = 0, may be determined. For example, when the number of layers of UE A is 2, it may be determined that n _{DMRS, 0} ⁽²⁾ = 0 for layer 0 and n _{DMRS, 1} ⁽²⁾ = 6 for layer 1. For example, if the number of layers of UE A is 3, n _DMRS for layer 0 _{, 0} ⁽²⁾ = 0, n _DMRS for layer 1 _{, 1} ⁽²⁾ = 6, n _DMRS for layer 2 _{, It} can be determined as ₂ ⁽²⁾ = 3. For example, if the number of layers of UE A is 4, n _DMRS for layer 0 _{, 0} ⁽²⁾ = 0, n _DMRS for layer 1 _{, 1} ⁽²⁾ = 6, n _DMRS for layer 2 _{, 2} ⁽²⁾ = 3, n _DMRS for layer 3 _{, 3} ⁽²⁾ = 9 may be determined.

-When the bandwidth allocated to UEs constituting MU-MIMO is the same and the total number of layers used by UEs is 4 or less, application of OCC is not required. For example, if PUSCH and PUSCH DMRS for UE A are allocated to RB # 4, # 5, and # 6, and PUSCH and PUSCH DMRS for UE B are allocated to RB # 4, # 5, and # 6, UE A And UE B transmit PUSCH and PUSCH DMRS through RB # 4, # 5, and # 6, so MU-MIMO is configured. At this time, even if OCC is not applied, the UE and the layer can be distinguished through up to four cyclic shifts.

For _example, n _{DMRS, 0} ⁽²⁾ to the UE A and the case where the number of layers of the UE B each one ^{_{individual, n DMRS, 0 (2)}} = 0, layer 0 of UE B to the layer 0 of the UE A = 6, respectively. For example, UE A, UE B and when the number of layers in the UE C, each one individual, n on the layer 0 of the ^{_{UE A DMRS, 0 (2)}} = 0, n DMRS, 0 of the layer 0 of the UE B ⁽²⁾ = 6, n _DMRS for layer 0 of UE C _{, 0} ⁽²⁾ = 3, respectively. For example, if the number of layers of UE A and UE B is 2 and 1, respectively, n _{DMRS, 0} ⁽²⁾ = 0 for layer 0 of UE A, n _{DMRS, 1} for layer 1 of UE A ⁽²⁾ = 6, n _DMRS for layer 0 of UE B _{, 0} ⁽²⁾ = 3, respectively. For example, the number of layers of UE A, UE B, UE C, and UE D is 1, respectively. when individual, n _DMRS for the layer 0 of the ^{_{UE a, 0 (2) =}} 0, n DMRS for the layer 0 of the ^{_{UE B, 0 (2) =}} 6, n for the layer 0 of the UE C _{DMRS, 0} ^{(2 )} = 3, n _DMRS for layer 0 of UE D _{, 0} ⁽²⁾ = 9, respectively. For example, if the number of layers of UE A, UE B, and UE C is 2, 1, and 1, respectively, n _{DMRS, 0} ⁽²⁾ = 0 for layer 0 of UE A, layer 1 of UE A N _{DMRS for 1,} ⁽²⁾ = 6, n _DMRS for layer 0 of UE B _{, 0} ⁽²⁾ = 3, n _DMRS for layer 0 of UE C _{, 0} ⁽²⁾ = 9, respectively. . For example, if the number of layers of UE A and UE B is 2, n _{DMRS, 0} ⁽²⁾ = 0 for layer 0 of UE A, and n _{DMRS, 1} ⁽²⁾ for layer 1 of UE A = 6, n _DMRS for layer 0 of UE B _{, 0} ⁽²⁾ = 3, n _DMRS for layer 1 of UE B _{, 1} ⁽²⁾ = 9, respectively. For example, if the number of layers of UE A and UE B is 3 and 1, respectively, n _{DMRS, 0} ⁽²⁾ = 0 for layer 0 of UE A, n _{DMRS, 1} for layer 1 of UE A ⁽²⁾ = 6, n _DMRS for layer 2 of UE A _{, 2} ⁽²⁾ = 3, n _DMRS for layer 0 of UE B _{, 0} ⁽²⁾ = 9, respectively.

6 shows an example of a PUSCH DMRS transmission method according to an embodiment of the present invention.

Referring to FIG. 6, unlike the conventional method, PUSCH DMRS may be configured and transmitted through only one SC-FDMA symbol in one subframe. That is, PUSCH DMRS is transmitted by occupying one SC-FDMA symbol only in the first slot in the subframe, and is not transmitted in the second slot in the subframe. The SC-FDMA symbol of the second slot in the subframe used for the transmission of the PUSCH DMRS can be used for the transmission of data. Accordingly, throughput may increase.

If OCC need not be applied, PUSCH DMRS may be transmitted through only one SC-FDMA symbol in one subframe, and accordingly, one or more of Equations 1 to 7 described above may be changed accordingly.

When the application of the OCC is not required, first, the PUSCH DMRS sequence r _PUSCH ^(λ) (.) Associated with the layer λ ∈ {0,1, ..., v-1} may be defined by Equation (9). Equation 9 is a modified form of Equation 5.

<Equation 9>

In Equation 9, m = 0, n = 0, ..., M _sc ^RS -1, and M _SC ^RS = M _SC ^PUSCH . That is, while Equation 5 expresses two slots in one subframe as m = 0 and 1, Equation 9 can express one slot in one subframe as m = 0.

Alternatively, the PUSCH DMRS sequence r _PUSCH ^(λ) (.) May be defined by Equation (9). Equation 10 is a modified form of Equation 5 or Equation 9.

<Equation 10>

In Equation 10, n = 0, ..., M _sc ^RS -1, and M _SC ^RS = M _SC ^PUSCH . Equation 10 is obtained by removing m from Equation 9.

In addition, when application of the OCC is not required, the group hopping pattern f _gh (n _s ) used to determine the sequence group number u of the slot n _s may be determined by Equation 3 as it is. However, in Equation 3, the group hopping pattern f _gh (n _s ) is determined for each slot. When OCC is not required, Equation 3 is a group hopping pattern for only one of the two slots in one subframe. f _gh (n _s ) can be interpreted to be determined.

Alternatively, when application of the OCC is not required, the group hopping pattern f _gh (n _s ) may be determined by Equation (11). Equation 11 is a modified form of Equation 3.

<Equation 11>

로 변경된 것이다. 즉, 수학식 11에 의해서 그룹 홉핑 패턴 f_gh(n_s)가 서브프레임 단위로 결정될 수 있다.In Equation 11, slot number n _s in Equation 3 indicates a subframe number.

It has been changed to. That is, the group hopping pattern f _gh (n _s ) may be determined in units of subframes by Equation (11).

In addition, when application of the OCC is not required, the basic sequence number v in the basic sequence group in slot n _s may be determined by Equation (4). However, in Equation 4, the basic sequence number v in the basic sequence group is determined for each slot. If OCC is not required, Equation 4 is the basic sequence for only one of the two slots in one subframe. It can be interpreted to determine the base sequence number v within the group.

Alternatively, when the application of the OCC is not required, the basic sequence number v in the basic sequence group in slot n _s may be determined by Equation (12). Equation 12 is a modified form of Equation 4.

<Equation 12>

로 변경된 것이다. 즉, 수학식 12에 의해서 슬롯 n_s에서 기본 시퀀스 그룹 내에서의 기본 시퀀스 번호 v가 서브프레임 단위로 결정될 수 있다.In Equation 12, slot number n _s in Equation 4 indicates a subframe number.

It has been changed to. That is, the basic sequence number v in the basic sequence group in slot n _s may be determined in units of subframes by Equation (12).

In addition, when the application of the OCC is not required, the parameter n _PN (n _s ) related to CSH may be determined by Equation (7). However, in Equation 7, the parameter n _PN (n _s ) related to CSH is determined for each slot, and when OCC is not required, Equation 7 is CSH only for one of the two slots in one subframe. It can be interpreted that the related parameter n _PN (n _s ) is determined.

Or, when the application of the OCC is not required, the parameter n _PN (n _s ) related to CSH may be determined by Equation (13). Equation 13 is a modified form of Equation 7.

<Equation 13>

로 변경된 것이다. 즉, 수학식 13에 의해서 CSH과 관련된 파라미터 n_PN(n_s)가 서브프레임 단위로 결정될 수 있다.In Equation 13, slot number n _s in Equation 7 indicates a subframe number.

It has been changed to. That is, the parameter n _PN (n _s ) related to CSH may be determined in units of subframes by Equation (13).

In addition, when the application of the OCC is not required, Table 1 showing the cyclic shift field in the uplink DCI and n _{DMRS, λ} ⁽²⁾ of each layer and the mapping relationship of the OCC applied to each layer may be used as it is. However, in Table 1, OCC is applied to each slot, and when it is not necessary to apply OCC, OCC may be applied to only one of two slots in one subframe. Can be used, for example, manyi w ^{(λ) (0)} of w ^{(λ) (0)} and w ^{(λ) (1)} in Table 1. In Table 1, the value of w ^(λ) (0) is always 1, and the value of w ^(λ) (1) is either 1 or -1, because only w ^(λ) (0) is used. The value can always be 1.

Or, when the application of the OCC is not required, the mapping relationship between the cyclic shift field in the uplink DCI and n _{DMRS, λ} ⁽²⁾ of each layer may be determined by Table 3. Table 3 is a modified form of Table 1.

Cyclic Shift Field in
uplink-related DCI format n _{DMRS, λ} ⁽²⁾ λ = 0 λ = 1 λ = 2 λ = 3 000 0 6 3 9 001 6 0 9 3 010 3 9 6 0 011 4 10 7 One 100 2 8 5 11 101 8 2 11 5 110 10 4 One 7 111 9 3 0 6

Table 3 is a table showing only the mapping relationship between cyclic shift fields in uplink DCI and n _{DMRS, λ} ⁽²⁾ in each layer, except for OCC in Table 1. That is, when the application of the OCC is not required, since the OCC of the same value can be always applied _, only the mapping relationship between the cyclic shift field in the uplink DCI and n _{DMRS, λ} ⁽²⁾ of each layer may be required.

Or, considering both the case where the application of the OCC is required and the case where the application of the OCC is not required, the cyclic shift field in the uplink DCI and n _{DMRS, λ} ⁽²⁾ of each layer and the mapping relationship of the OCC applied to each layer Table 4 may be applied. Table 4 will be described later.

Hereinafter, according to an embodiment of the present invention, a signaling method for informing whether a base station needs to apply OCC to a UE will be described. From the UE's point of view, it is not known whether or not it is a MU-MIMO UE constituting a MU-MIMO environment. That is, the UE is transparent about whether it is a MU-MIMO UE. As described above, the configuration method of the PUSCH DMRS may vary according to whether OCC is applied. Therefore, the base station needs to inform the UE whether or not the application of the OCC is necessary.

The base station determines whether application of the OCC is necessary and signals it to the UE, and the UE configures PUSCH DMRS according to whether the application of the OCC is required and transmits it to the base station. The base station estimates a channel using the received PUSCH DMRS, and demodulates the PUSCH based on the estimated channel.

1) The base station can explicitly inform the UE whether or not the OCC is applied. That is, the base station may signal to the UE whether or not OCC is applied through 1 bit added in DCI. Accordingly, the UE can dynamically know whether OCC is applied.

For example, if the value of 1 bit added in DCI is 0 (or 1), it may indicate a case where OCC is applied. Accordingly, PUSCH DMRS may be configured and transmitted through two SC-FDMA symbols in one subframe as in the prior art. That is, Equation 1, Equation 2, Equation 3, Equation 4, Equation 5, Equation 6, Equation 7, Table 1, etc. may be used to construct the PUSCH DMRS.

Alternatively, if the value of 1 bit added in DCI is 1 (or 0), the OCC may not be applied. Accordingly, PUSCH DMRS may be configured and transmitted through only one SC-FDMA symbol in one subframe, as in the prior art. That is, in order to configure the PUSCH DMRS, Equation 1, Equation 2, Equation 3 (or Equation 11), Equation 4 (or Equation 12), Equation 9 (or Equation 10), Equation 6, Equation 7 (or Equation 13), Table 1 (or Table 3), etc. may be used.

2) The base station may implicitly inform the UE whether or not OCC is applied. That is, the base station can implicitly signal whether the OCC is applied through the 3-bit cyclic shift field currently defined in DCI. More specifically, some of the eight values indicated by the 3-bit cyclic shift field (first group) are used for the case where the OCC is applied, and the other part (second group) is for the case where the OCC need not be applied. Can be used. That is, the UE reads the cyclic shift field in DCI, and when the value belongs to the first group, it can be seen that OCC is applied. In addition, the UE reads the cyclic shift field in DCI, and when the value belongs to the second group, it can be seen that OCC is not applied.

For example, the first group indicating that OCC is applied may include a cyclic shift field whose values are 011, 100, 101, and 110. As shown in Table 1, the cyclic shift fields having values 011, 100, 101, and 110 indicate n _{DMRS, 0} ⁽²⁾ = 4, 2, 8, 10, respectively. The UE reads the cyclic shift field in DCI, and when the value is one of 001, 100, 101, and 110, it can be seen that OCC is applied. Accordingly, PUSCH DMRS may be configured and transmitted through two SC-FDMA symbols in one subframe as in the prior art. That is, Equation 1, Equation 2, Equation 3, Equation 4, Equation 5, Equation 6, Equation 7, Table 1 (or Table 4 to be described later) may be used to construct the PUSCH DMRS. .

The second group indicating that OCC is not applied may include a cyclic shift field whose values are 000, 001, 010, 111. As shown in Table 1, cyclic shift fields having values of 000, 001, 010, and 111 indicate n _{DMRS, 0} ⁽²⁾ = 0, 6, 3, 9, respectively. The UE reads the cyclic shift field in DCI, and when the value is one of 000, 001, 010, 111, it can be seen that OCC is not applied. Accordingly, PUSCH DMRS may be configured and transmitted through only one SC-FDMA symbol in one subframe, as in the prior art. That is, in order to configure the PUSCH DMRS, Equation 1, Equation 2, Equation 3 (or Equation 11), Equation 4 (or Equation 12), Equation 9 (or Equation 10), Equation 6, Equation 7 (or Equation 13), Table 1 (or Table 3, or Table 4 to be described later) may be used.

Or, considering both the case where the application of the OCC is required and the case where the application of the OCC is not required, a cyclic shift field in the uplink DCI and n _{DMRS, λ} ⁽²⁾ of each layer and each layer are applied according to Table 4 It can indicate the mapping relationship of OCC.

Cyclic Shift Field in
uplink-related DCI format n _{DMRS, λ} ⁽²⁾ [w ^(λ) (0) w ^(λ) (1)] λ = 0 λ = 1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3 000 0 6 3 9 N / A 001 6 0 9 3 N / A 010 3 9 6 0 N / A 011 4 10 7 One [1 1] [1 1] [1 1] [1 1] 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1] 101 8 2 11 5 [1 -1] [1 -1] [1 -1] [1 -1] 110 10 4 One 7 [1 -1] [1 -1] [1 -1] [1 -1] 111 9 3 0 6 N / A

Referring to Table 4, N / A (non-available) indicates that OCC is not applied. That is, according to Table 4, when the value of the cyclic shift field is one of 011, 100, 101, or 110, it is indicated that OCC is applied, and the value of the cyclic shift field is any of 000, 001, 010, 111 It may be indicated that OCC does not apply.

In the above description, it is assumed that the first group includes a cyclic shift field whose values are 011, 100, 101, and 110, and the second group includes a cyclic shift field whose values are 000, 001, 010, 111. The first group and the second group configured according to an embodiment of the present invention are not limited thereto and may be configured in various ways. However, the first group and the second group exemplified above may be preferred examples. This is a combination that can maintain the largest orthogonality with only cyclic shift without OCC for up to 4 layers among 8 n _{DMRS, 0} ⁽²⁾ {0,6,3,4,2,8,10,9} that can be indicated. This is because n _{DMRS, 0} ⁽²⁾ = {0,6,3,9}.

Meanwhile, that the OCC is not applied when transmitting the PUSCH DMRS described above may be considered only in a small cell environment. Accordingly, 1 bit indicating whether a small cell environment may be additionally signaled to the UE. That is, in consideration of an environment in which a small cell is not applied or compatibility with an existing system, 1 bit may be additionally signaled to the UE. One bit indicating whether a small cell environment is transmitted through higher layer signaling such as radio resource control (RRC) signaling, or may be included in DCI. Whether the base station and the UE are in the small cell environment may be indicated through 1 bit indicating whether the small cell environment is present. Alternatively, a small cell environment may be implicitly determined according to a transmission mode or the like instead of a 1-bit indicating a small cell environment.

In the case of a small cell environment, the PUSCH DMRS configuration and transmission method may be different depending on whether application of the OCC is necessary as mentioned in the above description. When it is not a small cell environment or operates like an existing system, as in the conventional method, OCC is always applied and PUSCH DMRS can be configured and transmitted.

7 shows an embodiment of a method for transmitting a reference signal according to an embodiment of the present invention.

Referring to FIG. 7, in step S100, the base station may explicitly signal the indication information indicating whether or not the orthogonal sequence is applied, or implicitly signal according to a cyclic shift field in DCI.

In step S110, the UE generates a reference signal sequence. The reference signal sequence may be configured through two SC-FDMA symbols in one subframe, or one SC-FDMA symbol in one subframe, depending on whether an orthogonal sequence is applied. That is, when an orthogonal sequence is applied, a reference signal sequence may be generated by Equation 1, Equation 2, Equation 3, Equation 4, Equation 5, Equation 6, Equation 7, Table 1, or the like. When the orthogonal sequence is not applied, equation 1, equation 2, equation 3 (or equation 11), equation 4 (or equation 12), equation 9 (or equation 10), equation 6, A reference signal sequence may be generated by Equation 7 (or Equation 13), Table 1 (or Table 3), or the like. The base station can explicitly signal whether the orthogonal sequence is applied to the UE or implicitly signal it according to a cyclic shift field in DCI.

In step S120, the UE performs precoding on the generated reference signal sequence.

In step S130, the UE maps the precoded reference signal sequence to a resource element. When an orthogonal sequence is applied, the reference signal sequence may be mapped to two SC-FDMA symbols in one subframe. When the orthogonal sequence is not applied, the reference signal sequence may be mapped to one SC-FDMA symbol in one subframe.

In step S140, the UE transmits the SC-FDMA signal generated based on the reference signal sequence mapped to the resource element to the base station.

In step S150, the base station receives the SC-FDMA signal, demodulates it, and performs channel estimation. The base station demodulates the PUSCH based on the estimated channel. The procedure for demodulating the SC-FDMA signal may be in the reverse order of the procedure for generating the SC-FDMA signal. For example, the base station detects a reference signal sequence by de-mapping the received SC-FDMA signal to a resource element. The base station performs channel estimation by comparing the detected reference signal sequence with the reference signal sequence generated by the base station itself.

8 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

The terminal 800 includes a processor 810, a transmitter 820, and a receiver 830. The processor 810 includes a reference signal generator 811 and a resource mapper 812.

The reference signal generator 811 is configured to generate a reference signal sequence. The reference signal sequence may be configured through two SC-FDMA symbols in one subframe, or one SC-FDMA symbol in one subframe, depending on whether an orthogonal sequence is applied. That is, when an orthogonal sequence is applied, a reference signal sequence may be generated by Equation 1, Equation 2, Equation 3, Equation 4, Equation 5, Equation 6, Equation 7, Table 1, or the like. When the orthogonal sequence is not applied, equation 1, equation 2, equation 3 (or equation 11), equation 4 (or equation 12), equation 9 (or equation 10), equation 6, A reference signal sequence may be generated by Equation 7 (or Equation 13), Table 1 (or Table 3), or the like. The base station can explicitly signal whether the orthogonal sequence is applied to the UE or implicitly signal it according to a cyclic shift field in DCI.

The resource mapper 812 is configured to precode the generated reference signal sequence and map the precoded reference signal sequence to the resource element. When an orthogonal sequence is applied, the reference signal sequence may be mapped to two SC-FDMA symbols in one subframe. When the orthogonal sequence is not applied, the reference signal sequence may be mapped to one SC-FDMA symbol in one subframe.

The transmitter 820 is configured to transmit the SC-FDMA signal generated based on the reference signal sequence mapped to the resource element to the base station 900.

The receiving unit 830 is configured to receive the indication information indicating whether the orthogonal sequence is applied from the base station 900. The indication information indicating whether or not the orthogonal sequence is applied may be explicitly signaled or implicitly signaled according to a cyclic shift field in DCI.

The base station 900 includes a PUSCH demodulator 910, a transmitter 920, and a receiver 930.

The receiving unit 930 is configured to receive the SC-FDMA signal from the terminal 800.

The PUSCH demodulator 910 is configured to demodulate the received SC-FDMA signal to perform channel estimation and demodulate the PUSCH based on the estimated channel. The procedure for demodulating the SC-FDMA signal may be in the reverse order of the procedure for generating the SC-FDMA signal. For example, the base station detects a reference signal sequence by de-mapping the received SC-FDMA signal to a resource element. The base station performs channel estimation by comparing the detected reference signal sequence with the reference signal sequence generated by the base station itself.

The transmitting unit 920 is configured to transmit the indication information indicating whether to apply the orthogonal sequence to the terminal 800.

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

Claims (20)

A method for transmitting a reference signal by a user equipment (UE) in a wireless communication system,
Generating a reference signal sequence according to whether an orthogonal sequence indicated from the base station is applied;
Performing precoding on the generated reference signal sequence;
Mapping the precoded reference signal sequence to a resource element according to whether the orthogonal sequence is applied; And
Transmitting a single carrier frequency division multiple access (SC-FDMA) signal generated based on the mapped reference signal sequence to the base station,
When application of the orthogonal sequence is indicated, the precoded reference signal sequence is mapped to the resource element included in two SC-FDMA symbols in one subframe,
When it is indicated that the orthogonal sequence is not applied, the precoded reference signal sequence is mapped to the resource element included in one SC-FDMA symbol in one subframe. delete delete delete delete delete delete delete delete In a user equipment (UE) in a wireless communication system,
A reference signal generator configured to generate a reference signal sequence according to whether an orthogonal sequence indicated from the base station is applied;
A resource mapper configured to perform precoding on the generated reference signal sequence and map the precoded reference signal sequence to a resource element according to whether the orthogonal sequence is applied; And
And a transmitter configured to transmit a single carrier frequency division multiple access (SC-FDMA) signal generated based on the mapped reference signal sequence to the base station,
When application of the orthogonal sequence is indicated, the precoded reference signal sequence is mapped to the resource element included in two SC-FDMA symbols in one subframe,
If it is indicated that the orthogonal sequence is not applied, the precoded reference signal sequence is mapped to the resource element included in one SC-FDMA symbol in one subframe. The method of claim 10,
Whether the orthogonal sequence is applied is a terminal characterized by being indicated by a 3-bit cyclic shift field in downlink control information (DCI) transmitted from the base station. The method of claim 11,
When the value of the 3-bit cyclic shift field is included in the first group, the terminal is characterized in that the application of the orthogonal sequence is indicated. The method of claim 12,
The first group is a terminal characterized in that it comprises a cyclic shift field of the values 011, 100, 101, 110. The method of claim 11,
When the value of the 3-bit cyclic shift field is included in the second group, it is indicated that the application of the orthogonal sequence is not applied. The method of claim 14,
The second group is a terminal characterized in that it includes a cyclic shift field having a value of 000, 001, 010, 111. A method for demodulating a physical uplink shared channel (PUSCH) by a base station in a wireless communication system,
Transmitting indication information indicating whether an orthogonal sequence is applied to a user equipment (UE);
Receiving a reference signal and a PUSCH generated based on a reference signal sequence generated according to indication information indicating whether to apply the orthogonal sequence from the terminal; And
And demodulating the received reference signal to perform channel estimation and demodulating the PUSCH based on the estimated channel.
The generated reference signal sequence is mapped to a resource element according to whether the orthogonal sequence is applied through precoding, and when application of the orthogonal sequence is indicated, the precoded reference signal sequence is two SCs in one subframe. -Is mapped to the resource element included in a single carrier frequency division multiple access (FDMA) symbol,
When it is indicated that the orthogonal sequence is not applied, the precoded reference signal sequence is mapped to the resource element included in one SC-FDMA symbol in one subframe. delete delete delete delete

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