KR102136812B1 - Apparatus and method for configuring reference signal in wireless communication system supporting small cells - Google Patents

Abstract

The present invention relates to an apparatus and method for configuring a reference signal in a wireless communication system supporting a small cell.
In this specification, the channel state information (channel state information (CSI))-RS CRS-RS configuration information (configuration) to generate a configuration that enables transmission according to a long period (period) or a certain muting pattern, Transmitting the CSI-RS configuration information to the terminal, and transmitting the CSI-RS to the terminal when the transmission of the CSI-RS is possible based on the CSI-RS configuration information. A method for transmitting a reference signal (RS) by a station (BS).

Description

Device and method for configuring a reference signal in a wireless communication system supporting a small cell {APPARATUS AND METHOD FOR CONFIGURING REFERENCE SIGNAL IN WIRELESS COMMUNICATION SYSTEM SUPPORTING SMALL CELLS}

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

In a next-generation communication system such as LTE (A-Advanced), as shown in FIG. 1, a macro-cell (F1) based on a high-power node, as well as a small cell based on a low-power node ( Research is being conducted to provide wireless communication services to indoors and outdoors through small cells (F2).

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 (in a cube) and an outdoor environment (outside a cube). Also, an ideal or non-ideal backhaul network may be supported between a macro cell and a small cell, and/or between small cells. In addition, the small cell may be provided in both a low-density deployment environment and/or a high-density deployment environment.

The terminal may search among a plurality of small cells distributed in a macro cell to see if there is a small cell capable of providing a service to itself. The operation of finding a small cell is also referred to as small cell discovery. For small cell discovery, the small cell transmits a discovery signal to the terminal, and the terminal can find the small cell using the discovery signal. However, when the transmission periods of the discovery signals transmitted by a plurality of small cells are short or the transmission period is long and the duty cycle is high, interference between the discovery signals occurs and accurate small cell discovery is possible. It can be difficult. Furthermore, power may be wasted in a small cell that is sensitive to power.

An object of the present invention is to provide an apparatus and method for configuring a reference signal in a wireless communication system supporting a small cell.

Another technical problem of the present invention is to provide an apparatus and method for variably configuring the period and duration of a reference signal for small cell discovery.

Another technical problem of the present invention is to provide an apparatus and method for transmitting a reference signal having a long transmission period and a short transmission period for small cell discovery.

According to an aspect of the present invention, there is provided a method for transmitting a reference signal (RS) by a base station (BS) in a wireless communication system. The method includes generating CSI-RS configuration information that enables channel state information (CSI)-RS to be transmitted according to a long period or a certain muting pattern. And transmitting the RS configuration information to the terminal, and transmitting the CSI-RS to the terminal when the transmission of the CSI-RS is possible based on the CSI-RS configuration information.

According to another aspect of the present invention, a base station (BS) for transmitting a reference signal (RS) by a wireless communication system is provided. The base station is a channel state information (CSI)-RSC RRS control unit for generating CSI-RS configuration information (configuration information) to enable the transmission according to a long period (periodicity) or a certain muting pattern, and And a transmitting unit that transmits the CSI-RS configuration information to the terminal and transmits the CSI-RS to the terminal when the CSI-RS transmission is possible based on the CSI-RS configuration information.

According to another aspect of the present invention, there is provided a method for receiving a reference signal (RS) by a user equipment (UE) in a wireless communication system. The method includes receiving CSI-RS configuration information from a base station to enable channel state information (CSI)-RS to be transmitted according to a long period (periodicity) or a certain muting pattern, And receiving the CSI-RS from the base station at a time when transmission of the CSI-RS is possible based on the CSI-RS configuration information, and performing small cell discovery using the CSI-RS.

According to another aspect of the present invention, a user equipment (UE) for receiving a reference signal (RS) in a wireless communication system is provided. The terminal receives channel state information (CSI)-CSI-RS configuration information from the base station to enable the RS to be transmitted according to a long period (periodicity) or a certain muting pattern, and the It includes a receiver for receiving the CSI-RS from the base station when the transmission of the CSI-RS is possible based on the CSI-RS configuration information, and an RRC control unit for performing small cell discovery using the CSI-RS.

When a discovery signal having a long transmission period and a short transmission duration is transmitted, inter-cell interference from dormant small cells is minimized and an off state ( In the off-state), power saving of the base station can be achieved.

1 is a view showing a communication system in which a high-power node and a low-power node are arranged according to the prior art.
2 is a block diagram showing a wireless communication system to which the present invention is applied.
3 and 4 schematically show the structure of a radio frame to which the present invention is applied.
5 shows an example of a CSI-RS configuration and a CSI-RS pattern according to the number of CSI-RS antenna ports in a general CP.
6 shows an example of a CSI-RS configuration and a CSI-RS pattern according to the number of CSI-RS antenna ports in an extended CP.
7 is a flowchart illustrating a configuration and transmission method of CSI-RS according to an example of the present invention.
8 is an exemplary view to which CSI-RS muting information according to an embodiment of the present invention is applied.
9 is a block diagram showing a terminal and a base station according to an example of the present invention.

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 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

2 is a block diagram showing a wireless communication system to which the present invention is 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 number of areas 15a, 15b, and 15c, which may be called sectors, and each sector may have a different cell ID.

User equipment (UE) 12 may be fixed or mobile, and may be mobile station (MS), 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. Base station 11 generally refers to a station (station) that communicates with the terminal 12, eNodeB (evolved-NodeB), BTS (Base Transceiver System), access point (Access Point), femto base station (Femto eNodeB), home The base station (Home eNodeB: HeNodeB), relay (relay), remote radio head (Remote Radio Head: RRH) can be called in other terms. Cells (15a, 15b, 15c) should be interpreted in a comprehensive sense indicating some areas covered by the base station 11, meaning to cover all of the various coverage areas such as megacell, macrocell, microcell, picocell, femtocell to be.

Hereinafter, a downlink means a communication or communication path from the base station 11 to the terminal 12, and an uplink means a communication or communication path 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. There is no limitation in the 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 can use various multiple access techniques. These modulation techniques demodulate signals received from multiple users of the communication system to increase the capacity of the communication system. For uplink transmission and downlink transmission, a time division duplex (TDD) method that is transmitted using different times or a frequency division duplex (FDD) method that is transmitted using different frequencies may be used.

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, the 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 (hereinafter referred to as PDCCH) is a resource allocation and transmission format of a downlink shared channel (DL-SCH), a resource of an uplink shared channel (UL-SCH). Resource allocation of upper layer control messages such as allocation information, random access response transmitted on a physical downlink shared channel (PDSCH), and transmission power control for individual terminals in an arbitrary terminal group : TPC) Can carry a set of commands. A plurality of PDCCHs can be transmitted within a control region, and the terminal can monitor a plurality of PDCCHs.

Control information of the physical layer mapped to the PDCCH is called downlink control information (DCI). That is, DCI is transmitted on 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, and a control field for indicating a random access response (RA response).

3 and 4 schematically show the structure of a radio frame to which the present invention is applied.

3 and 4, a radio frame includes 10 subframes. One subframe includes two slots. The time (length) for transmitting one sub-frame is called a transmission time interval (TTI). Referring to FIG. 2, for example, the length of one subframe may be 1 ms, and the 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 an orthogonal frequency division multiple access (OFDMA) in a downlink (DL), the symbol may be an orthogonal frequency division multiplexing (OFDM) symbol. Meanwhile, the expression of the symbol period in the time domain is not limited by the multiple access scheme or name. For example, a plurality of symbols in the time domain may be SC-FDMA (Single Carrier-Frequency Division Multiple Access) symbols, symbol periods, etc. in addition to OFDM symbols.

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

The resource block (RB) is a resource allocation unit, and includes a time-frequency resource corresponding to 180 kHz on the frequency axis and 1 slot on the time axis. The 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. The 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 also necessary to measure the channel state of the cell to which the UE belongs or another cell. In general, a reference signal (RS) that is known between a UE and a transmission/reception point is used for channel estimation or channel state measurement.

)를 추정할 수 있다.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 transmission/reception point. If the reference signal sent by the transmission/reception point is p, the channel information experienced by the reference signal during transmission is h, the thermal noise generated by the terminal is n, and the signal received by the terminal is y, y = h·p + n. have. In this case, since the reference signal p is already known to the UE, channel information (Equation 1) when using the LS (Least Square) method

) Can be estimated.

는

값에 의존하게 되므로, 정확한 h값의 추정을 위해서는

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

The

Since it depends on the value, for accurate h value estimation

It is necessary to converge to this zero.

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

Examples of the downlink reference signal include a cell-specific RS (CRS), a multimedia broadcast and multicast single frequency network (MBSFN) reference signal, a UE-specific RS (UE-specific RS), and a position reference signal (PRS) RS) and channel state information (CSI) reference signal (CSI-RS).

The 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, and thus may be called a demodulation reference signal (Demodulation RS: DM-RS). have.

CSI-RS is used for channel estimation for a physical downlink shared channel (PDSCH) of the LTE-A terminal. The CSI-RS is relatively sparse in the frequency domain or time domain. When necessary through estimation of CSI, a channel quality indicator (CQI), a precoding matrix indicator (PMI), and a rank indicator (RI) may be reported from the UE.

CSI-RS may be transmitted through 1, 2, 4 or 8 antenna ports. At this time, the antenna ports used may be p=15, p=15,16, p=15,...,18 and p=15,...,22, respectively. CSI-RS can be defined only when the frequency interval Δf between subcarriers is 15 kHz. The CSI-RS sequence r _{l , ns} (m) may be defined as in Equation 2.

In Equation 2, n _s is a slot number in a radio frame, and l is an OFDM symbol number in a slot. Referring to Equation 2, the m-th CSI-RS sequence is generated by constructing a real part and an imaginary part through a pseudo-random sequence c(i), and then normalizing them. c(i) may be defined by a Gold sequence of length-31. c(i) is a binary pseudo-random sequence and may have a value of 0 or 1. Accordingly, as shown in Equation 2, 1-2·c(i) may represent a value of 1 or -1, and a 2m-th sequence corresponding to an even number in the real part and an odd number (2m) in an imaginary part. Use the +1)th sequence. The output sequence c(n) of length M _PN (n=0,1,...,MPN-1) may be defined as in Equation 3.

로 표현될 수 있다. In Equation 3, N _C =1600, and the first m-sequence x ₁ (i) is x ₁ (0)=1, x ₁ (n)=0, (n=1,2,...,30) Can be initialized to The initialization of the second m-sequence x ₂ (i) can be initialized to different values according to the system parameter values used in the channel or signal to which the sequence is applied, which

Can be expressed as

The pseudo-random sequence c(i) may be initialized by Equation 4 at the beginning of each OFDM symbol.

In Equation 3, N _CP has a value of 1 in the general CP and 0 in the extended CP. The N _ID ^CSI may have any value from 0 to 503. The N _ID ^CSI may be a virtual cell ID (VCID) for CSI-RS when signaled from a higher layer. The N _ID ^CSI may be the same as a physical cell ID (PCI) if there is no signaling from a higher layer.

In a subframe configured for transmission of CSI-RS, the CSI-RS sequence r _{l , ns} (m) is a complex-valued modulation symbol a _k used as a reference symbol on antenna port p according to Equation (5). _,l ^(p) .

Referring to Equation 5, a _{k ,l} ^(p) are complex modulation symbols mapped to the k-th subcarrier and the l-th OFDM symbol of the p-th antenna port. a _{k ,l} ^(p) are mapped by multiplying the CSI-RS sequence r _{l , ns} (m') and orthogonal sequence w _l'' .

Each parameter of Equation 5 may be defined by Equation 6.

Referring to Equation 6, the requirements for (k',l') and n _s can be given by Tables 1 and 2 described later.

The CSI-RS configuration includes a non-zero transmission power (CSI-RS) configuration indicating a pattern in which the CSI-RS is transmitted to a UE of each cell (or a transmission point (TP)), and an adjacent cell (or TP) may be classified into a zero transmission power CSI-RS configuration for muting the PDSCH region corresponding to CSI-RS transmission. 0 or 1 CSI-RS configuration per CSI process for a terminal assuming non-zero power CSI-RS, and 0 or multiple CSI RS configurations for a terminal assuming zero power CSI-RS may be used.

Information on one or more non-zero power CSI-RS configurations (hereinafter, CSI-RS configurations) may be transmitted to each terminal of a corresponding cell. The CSI-RS configuration information includes 2-bit information indicating whether the number of antenna ports (hereinafter referred to as CSI-RS antenna ports) for transmitting non-zero power CSI-RS is one of 1, 2, 4, and 8, It may include 5 bit information indicating a configurable CSI-RS pattern for each number of CSI-RS antenna ports.

Table 1 shows CSI-RS configuration in general CP and (k',l') in Equation 6, that is, mapping of CSI-RS pattern, and Table 2 shows CSI-RS configuration in extended CP and (k in Equation 6). ',l'), that is, the mapping of the CSI-RS pattern.

CSI-RS configuration Number of composed CSI-RS 1 or 2 4 8 (k',l') n _s mod 2 (k',l') n _s mod 2 (k',l') n _s mod 2 Frame structure types 1 and 2 0 (9,5) 0 (9,5) 0 (9,5) 0 One (11,2) One (11,2) One (11,2) One 2 (9,2) One (9,2) One (9,2) One 3 (7,2) One (7,2) One (7,2) One 4 (9,5) One (9,5) One (9,5) One 5 (8,5) 0 (8,5) 0 6 (10,2) One (10,2) One 7 (8,2) One (8,2) One 8 (6,2) One (6,2) One 9 (8,5) One (8,5) One 10 (3,5) 0 11 (2,5) 0 12 (5,2) One 13 (4,2) One 14 (3,2) One 15 (2,2) One 16 (1,2) One 17 (0,2) One 18 (3,5) One 19 (2,5) One Frame structure type 2 only 20 (11,1) One (11,1) One (11,1) One 21 (9,1) One (9,1) One (9,1) One 22 (7,1) One (7,1) One (7,1) One 23 (10,1) One (10,1) One 24 (8,1) One (8,1) One 25 (6,1) One (6,1) One 26 (5,1) One 27 (4,1) One 28 (3,1) One 29 (2,1) One 30 (1,1) One 31 (0,1) One

CSI-RS configuration Number of composed CSI-RS 1 or 2 4 8 (k',l') n _s mod 2 (k',l') n _s mod 2 (k',l') n _s mod 2 Frame structure types 1 and 2 0 (11,4) 0 (11,4) 0 (11,4) 0 One (9,4) 0 (9,4) 0 (9,4) 0 2 (10,4) One (10,4) One (10,4) One 3 (9,4) One (9,4) One (9,4) One 4 (5,4) 0 (5,4) 0 5 (3,4) 0 (3,4) 0 6 (4,4) One (4,4) One 7 (3,4) One (3,4) One 8 (8,4) 0 9 (6,4) 0 10 (2,4) 0 11 (0,4) 0 12 (7,4) One 13 (6,4) One 14 (1,4) One 15 (0,4) One Frame structure type 2 only 16 (11,1) One (11,1) One (11,1) One 17 (10,1) One (10,1) One (10,1) One 18 (9,1) One (9,1) One (9,1) One 19 (5,1) One (5,1) One 20 (4,1) One (4,1) One 21 (3,1) One (3,1) One 22 (8,1) One 23 (7,1) One 24 (6,1) One 25 (2,1) One 26 (1,1) One 27 (0,1) One

In Table 1 and Table 2, frame structure type 1 means FDD, and frame structure type 2 means TDD.

Referring to Table 1, in the case of general CP, when the number of antenna ports is 1 or 2, a total of 32 CSI-RS configurations, and when the number of antenna ports is 4, a total of 16 CSI-RS configurations, the number of antenna ports When there are 8, a total of 8 CSI-RS configurations exist. Referring to Table 2, in the case of the extended CP, when the number of antenna ports is 1 or 2, a total of 28 CSI-RS configurations, and when the number of antenna ports is 4, a total of 14 CSI-RS configurations, the number of antenna ports When there are 8, a total of 7 CSI-RS configurations exist.

Referring to Table 1 and Table 2, for a CSI-RS configuration, the location of one specific resource element to which CSI-RS is mapped for each number of CSI-RS antenna ports may be indicated. That is, the position of the remaining resource elements to which CSI-RS is mapped may be determined by Equation 6 based on the location of the specific one resource element, and accordingly, the entire CSI-RS that can be configured for each number of CSI-RS antenna ports. The pattern is known.

For example, if the number of CSI-RS antenna ports is 8 and the value of the CSI-RS configuration is 2 (=00010), corresponding (k',l')=(9,2) according to Table 1 And n _s mod 2=1. Accordingly, it can be seen that within a subframe configured for CSI-RS transmission, CSI-RS is mapped to a resource element having a subcarrier index of 9 and an OFDM symbol index of 2 in the second slot. The resource element indicated by Table 1 may be one of the positions of the resource element to which the CSI-RS transmitted through the first CSI-RS antenna port is mapped. The positions of the remaining resource elements to which the CSI-RSs transmitted through the first CSI-RS antenna port are mapped and the positions of the resource elements to which the CSI-RSs transmitted through the remaining CSI-RS antenna ports are mapped are represented by Equation (6). It can be located at regular intervals from the resource element indicated by 1.

5 shows an example of a CSI-RS configuration and a CSI-RS pattern according to the number of CSI-RS antenna ports in a general CP.

FIG. 5-(a) shows a CSI-RS pattern in the case of FDD+TDD, and FIG. 5-(b) shows a case of TDD. In FIG. 5, the number indicated on each resource element indicates a CSI-RS configuration number. a is CSI-RS antenna port {15, 16}, b is CSI-RS antenna port {17, 18}, c is CSI-RS antenna port {19, 20}, d is CSI-RS antenna port {19, 20 } It indicates that CSI-RS is transmitted. A represents the DMRS antenna ports {7, 8, 11, 13}, and B represents the transmission of DMRS over the DMRS antenna ports {9, 10, 12, 14}. C represents a resource element to which CRS is mapped. In addition, it is assumed that the number of CRS antenna ports in FIG. 5 is two, and a control region (shaded portion) is allocated to the first three OFDM symbols of the subframe.

The CSI-RS pattern of FIG. 5 may be applied even when the number of CRS antenna ports is 1 or 4 or CRS is not transmitted. In addition, the CSI-RS pattern of FIG. 5 can be applied even when a control region is allocated to OFDM symbols in the first 1 to 4 of a subframe, or a control region is not allocated. In addition, in FIG. 5, DMRS uses two code division multiplexing (CDM) groups (A: DMRS antenna ports {7, 8, 11, 13}, B: DMRS antenna ports {9, 10, 12, 14}). It is assumed, but the CSI-RS pattern of FIG. 5 can be applied even when one CDM group is used.

6 shows an example of a CSI-RS configuration and a CSI-RS pattern according to the number of CSI-RS antenna ports in an extended CP.

As in FIG. 5, the number indicated in each resource element in FIG. 6 represents a CSI-RS configuration number. a is CSI-RS antenna port {15, 16}, b is CSI-RS antenna port {17, 18}, c is CSI-RS antenna port {19, 20}, d is CSI-RS antenna port {19, 20 } It indicates that CSI-RS is transmitted. E indicates that DMRS is transmitted on the DMRS antenna ports {7, 8}. C represents a resource element to which CRS is mapped. In addition, it is assumed that the number of CRS antenna ports in FIG. 6 is two, and a control region (shaded portion) is allocated to the first three OFDM symbols of the subframe.

The CSI-RS pattern of FIG. 6 may be applied even when the number of CRS antenna ports is 1 or 4 or CRS is not transmitted. In addition, the CSI-RS pattern of FIG. 6 can be applied even when a control region is allocated to OFDM symbols in the first 1 to 4 of a subframe or a control region is not allocated.

Table 3 shows an example of a subframe configuration (subframe config) in which CSI-RS is transmitted.

CSI-RS-subframe configuration
I _{CSI - RS} CSI-RS cycle
T _{CSI - RS} (subframe) CSI-RS subframe offset
Δ _{CSI - RS} (subframes) 0-4 5 I _{CSI - RS} 5-14 10 I _{CSI - RS} -1 15-34 20 I _{CSI - RS} -15 35-74 40 I _{CSI - RS} -35 75-154 80 I _{CSI - RS} -75

Referring to Table 3, the period (CSI-RS period, T _{CSI - RS} ) and the offset (Δ _{CSI - RS} ) of the subframe in which CSI-RS is transmitted according to the CSI-RS subframe configuration (I _{CSI - RS} ) Can be determined. The CSI-RS subframe configuration may be configured separately for the non-zero power CSI-RS and the zero power CSI-RS. Meanwhile, the subframe transmitting the CSI-RS needs to satisfy Equation (7).

The zero-power CSI-RS configuration may be composed of a 16-bit bitmap corresponding to a CSI-RS pattern when each number of CSI-RS antenna ports is four. That is, for a bit set to 1 in a 16-bit bitmap constituted by an upper layer, the UE indicates a resource element corresponding to the case where the number of CSI-RS antenna ports is 4 in Tables 1 and 2 is zero power CSI- RS can be set. More specifically, the most significant bit (MSB) of the 16-bit bitmap corresponds to the first CSI-RS configuration index when the number of CSI-RS antenna ports is 4 in Tables 1 and 2. The following bits of the 16-bit bitmap correspond to the direction in which the CSI-RS configuration index increases in the case where the number of CSI-RS antenna ports is 4 in Tables 1 and 2. In the resource element set to zero power CSI-RS, a PDSCH corresponding to CSI-RS transmission of an adjacent cell or TP is muted, and a PDSCH can be transmitted in a resource element not set to zero power CSI-RS.

The parameters transmitted in the RRC layer for the zero power CSI-RS are as follows.

1) Zero-power CSI-RS configuration list: 16-bit bitmap composed of each CSI-RS configuration as one bit when the number of CSI-RS antenna ports is four in Table 1 or Table 2.

2) Zero Power CSI-RS Subframe Configuration (I _{CSI - RS} ): Like the subframeConfig parameter transmitted for non-zero power CSI-RS, which will be described later, indicates a subframe configuration for zero power CSI-RS. The zero power CSI-RS subframe configuration has a length of 8 bits, and the period (T _{CSI - RS} ) and offset of the subframe used by the zero power CSI-RS for transmission according to the zero power CSI-RS subframe configuration ( Δ _{CSI - RS} ) can be determined.

The terminal may search among a plurality of small cells distributed in a macro cell to see if there is a small cell capable of providing a service to itself. The operation of finding a small cell is also referred to as small cell discovery. For small cell discovery, the small cell transmits a discovery signal to the terminal, and the terminal can find the small cell using the discovery signal. In this embodiment, the discovery signal may include CSI-RS. Of course, one or more of physical signals such as CRS, PSS/SSS, modified CRS, modified PSS/SSS, CSI-RS or PRS may be used as the discovery signal, but CSI-RS is used in this embodiment. It will be described as a case. When CSI-RS is a discovery signal, a new transmission period and/or transmission duration for CSI-RS is required. Hereinafter, a subframe in which the actual CSI-RS is transmitted by the CSI-RS subframe configuration is referred to as a CSI-RS subframe, and a subframe in which the CSI-RS is not transmitted is referred to as a non-CSI-RS subframe. In addition, although the technical features of the present invention will be described below using CSI-RS as a discovery signal, all of the technical features based on CSI-RS can be applied in the same way when different physical signals are used as discovery signals.

7 is a flowchart illustrating a configuration and transmission method of CSI-RS according to an example of the present invention.

Referring to FIG. 7, the base station generates CSI-RS configuration information (S700). The CSI-RS configuration information provides a modified CSI-RS period and/or offset such that the CSI-RS has a long transmission period or a short transmission duration.

To this end, CSI-RS configuration information may have various embodiments.

One. CSI - RS Muting Informative CSI - RS Composition information

The CSI-RS configuration information may include CSI-RS muting information. CSI-RS muting information may be included in CSI-RS configuration information as shown in Table 4, and may be signaling of a higher layer such as RRC. The CSI-RS muting information may be included in existing CSI-RS configuration information (in this case, CSI-RS for channel estimation and channel measurement is also used for small cell signal discovery), and existing CSI-RS configuration information It may be included in the new CSI-RS configuration information for small cell signal discovery separate from (in this case, CSI-RS for small cell signal discovery is transmitted separately from the existing CSI-RS for channel estimation and channel measurement). .)

CSI-RS-Config ::= SEQUENCE { csi-RS CHOICE { release NULL, setup SEQUENCE { CSI-RS-mutingInfo antennaPortsCount ENUMERATED {an1, an2, an4, an8}, resourceConfig INTEGER (0..31), subframeConfig INTEGER (0..154), p-C INTEGER (-8..15) } }

For CSI-RS, the parameters shown in Table 4 may be signaled from a higher layer such as RRC (radio resource control), and including these parameters is referred to as CSI-RS configuration information. CSI-RS configuration information may include at least one of CSI-RS muting information (CSI-RS-mutingInfo), antenna port count (antennaPortsCount) information, resource configuration (resourceConfig) information, subframe configuration (subframeConfig) information, and Pc information. Can.

The antenna port count (antennaPortsCount) information has a length of 2 bits, and indicates the number of CSI-RS antenna ports in Table 1 or Table 2. Resource configuration (resourceConfig) information has a length of 5 bits, CSI-RS configuration in Table 1 or Table 2 and the corresponding resource element, that is, indicates a CSI-RS pattern. The subframe configuration information has a length of 8 bits and indicates the CSI-RS subframe configuration in Table 3. That is, regarding the CSI-RS subframe configuration, Table 3 may be equally applied to the present embodiment. The Pc information indicates a value related to CSI-RS transmission power.

In addition, when considering a coordinated multi point (CoMP) transmission environment (eg, transmission mode 10), N _ID ^CSI of Equation 3 is shown in Table 4 and Tables 5, 6, and 7 and Table 9 to be described later. As an example, it may be included in the CSI-RS configuration information and signaled from a higher layer. In addition, other parameters may be additionally included when considering various situations. For example, in the case of the existing CSI-RS used for channel estimation and channel measurement, CSI-RS is transmitted for the entire system bandwidth. In the case of CSI-RS for a small cell discovery signal, CSI-RS is used only for a specific bandwidth. It may be transmitted, the bandwidth information for this (for example, the bandwidth is expressed as the number of RB (resource block) number of RB 6, 15, 25, 50, 75, 100, information on which one of Table 4) And CSI-RS configuration information exemplified in Tables 5, 6, 7 and 9, which will be described later, may be signaled from a higher layer.

CSI-RS muting information (CSI-RS-mutingInfo) is information indicating whether or not CSI-RS is actually transmitted or not in every CSI-RS period. That is, even if CSI-RS transmission is scheduled by CSI-RS subframe configuration, when CSI-RS muting information indicates'muting', CSI-RS is not transmitted in the corresponding CSI-RS period. . On the other hand, when the CSI-RS muting information indicates'non-muting', the CSI-RS is transmitted in the corresponding CSI-RS period. As described above, the CSI-RS muting information defines'muting' or'non-muting' for each of N given CSI-RS periods.

As an example, the CSI-RS muting information may be a bitmap of N bits. In other words, the CSI-RS muting information may consist of a bit string of size N. At this time, the CSI-RS muting information indicates'muting' or'non-muting' for each of N consecutive CSI-RS periods. For example, the k-th bit from the MSB (or LSB) in the N-bit bitmap corresponds to the k-th CSI-RS period. Here, if the k-th bit is 0, CSI-RS transmission is'non-muted' in the corresponding CSI-RS period, and 1 is'muted' in the corresponding CSI-RS period. In other words, if the bit value is 0, even if a CSI-RS transmission subframe in a corresponding CSI-RS period is configured and the generation of CSI-RS is indicated, the base station actually mutes without transmitting CSI-RS, and the bit value is If 1, a CSI-RS transmission subframe within a corresponding CSI-RS period is configured so that the base station transmits CSI-RS as CSI-RS generation is indicated. Of course, the points indicated by the k-th bit values 0 and 1 may be reversed.

As such, the CSI-RS muting information is represented by a pattern in which CSI-RS is muted or non-muted in every CSI-RS period. For example, as shown in FIG. 8, CSI-RS period T _{CSI - RS} =40ms, CSI-RS subframe offset = 10ms (or 10 subframes), CSI-RS subframe configuration is given, and N=8 . In this case, the CSI-RS muting information indicates CSI-RS muting or non-muting for a total of 8 CSI-RS periods. And a pattern of'muting'/'non-muting' is formed every 40 ms within 320 ms as shown in FIG. 8. Therefore, the length of the pattern is 320 ms, and is defined as N*T _{CSI - RS} .

8 is a case where CSI-RS muting information = '10001000'. Each bit from MSB to LSB in turn corresponds to a first CSI-RS period (first 40 ms), a second CSI-RS period (next 40 ms), ..., and an eighth CSI-RS period (last 40 ms). Since MSB=1, since CSI-RS is'non-muting' in the first CSI-RS period, the base station transmits CSI-RS to the terminal within the first CSI-RS period. Since the next bit = 0, since the CSI-RS is'muted' in the second CSI-RS period, the base station does not transmit the CSI-RS to the terminal within the second CSI-RS period. Similarly, since the bit corresponding to the fifth CSI-RS period is 1, since the CSI-RS is'non-muting' in the fifth CSI-RS period, the base station transmits the CSI-RS to the terminal within the fifth CSI-RS period. do.

If muting/non-muting is defined as a pattern of length 8 by CSI-RS muting information in this way, these patterns can be applied repeatedly. In addition, since only the base station actually transmits the CSI-RS 2 times instead of 8 times for every pattern (320ms), the CSI-RS period and offset of Table 3 can have a lower duty cycle than before. do. Therefore, inter-cell interference from dormant small cells is minimized, and power saving of the base station can be achieved in an off-state.

In the following, examples of the size of N are described.

As an example, N may be defined as one fixed value by a system or communication protocol. For example, CSI-RS muting information (CSI-RS-mutingInfo) may be defined as shown in Table 5.

CSI-RS-Config ::= SEQUENCE { csi-RS CHOICE { release NULL, setup SEQUENCE { CSI-RS-mutingInfo BIT STRING (SIZE(4)) antennaPortsCount ENUMERATED {an1, an2, an4, an8}, resourceConfig INTEGER (0..31), subframeConfig INTEGER (0..154), p-C INTEGER (-8..15) } }

Referring to Table 5, the size of CSI-RS muting information is N=4. Of course, in addition to N=4, N=2, N=8, N=16, N=32,... etc. may be fixed to a value corresponding to a multiple of 2.

As another example, the length of the pattern (ie N*T _{CSI - RS} ) may be defined as a fixed value by a system or communication protocol. And the N value is set to fit the length of the fixed pattern. For example, suppose that the length of the pattern is fixed at 160 ms. If the CSI-RS period of Table 3 is determined to be 5ms, 10ms, 20ms, 40ms, or 80ms, N may be 32, 16, 8, 4, or 2, respectively, depending on the CSI-RS period. Or, for example, suppose that the length of the pattern is fixed at 240 ms. If the CSI-RS period of Table 3 is determined to be 5ms, 10ms, 20ms, 40ms, or 80ms, respectively, N may be 48, 24, 12, 6, or 3, respectively, according to the CSI-RS period. Or, for example, suppose that the length of the pattern is fixed at 320 ms. If the CSI-RS period of Table 3 is determined to be 5ms, 10ms, 20ms, 40ms, or 80ms, respectively, N may be 64, 32, 16, 8, 4, respectively, according to the CSI-RS period.

As another example, N may be selected by a base station among a plurality of values determined by a system or communication protocol. According to this, CSI-RS muting information (CSI-RS-mutingInfo) may be defined as shown in Table 6.

CSI-RS-Config ::= SEQUENCE { csi-RS CHOICE { release NULL, setup SEQUENCE { CSI-RS-mutingInfo CHOICE { po2 BIT STRING (SIZE(2)), po4 BIT STRING (SIZE(4)), po8 BIT STRING (SIZE(8)), po16 BIT STRING (SIZE(16)), ... } antennaPortsCount ENUMERATED {an1, an2, an4, an8}, resourceConfig INTEGER (0..31), subframeConfig INTEGER (0..154), p-C-r10 INTEGER (-8..15) } }

Referring to Table 6, the N value can be selected from one of four types: 2, 4, 8, and 16.

2. Modified CSI - RS Subframe configuration (1)

First, CSI-RS configuration information according to this embodiment is shown in Table 7.

CSI-RS-Config ::= SEQUENCE { csi-RS CHOICE { release NULL, setup SEQUENCE { antennaPortsCount ENUMERATED {an1, an2, an4, an8}, resourceConfig INTEGER (0..31), subframeConfig INTEGER (0..154), p-C INTEGER (-8..15) } }

Referring to Table 7, compared to Table 4, the CSI-RS configuration information has only CSI-RS muting information (CSI-RS-mutingInfo), antenna port count (antennaPortsCount) information, resource configuration (resourceConfig) information, and subframe It may include configuration (subframeConfig) information and Pc information. The subframe configuration information is 8 bits long and is the same as Table 4, but regarding the CSI-RS subframe configuration, Table 8 instead of Table 3 may be applied to the present embodiment.

CSI-RS-subframe configuration
I _{CSI - RS} CSI-RS cycle
T _{CSI - RS} (subframe) CSI-RS subframe offset
Δ _{CSI - RS} (subframes) 0-4 160 I _{CSI - RS} *K 5-14 320 (I _{CSI - RS} -5)*K 15-34 640 (I _{CSI - RS} -15)*K 35-74 1280 (I _{CSI - RS} -35)*K 75-154 2560 (I _{CSI - RS} -75)*K

The CSI-RS subframe configuration of Table 8 is indicated from the CSI-RS period (160 ms) twice the longest CSI-RS period (80 ms) that can be indicated from Table 3. At this time, the CSI-RS subframe configuration according to Table 8 can be represented up to 32 times longer CSI-RS period compared to Table 3.

At this time, the offset (Δ _{CSI - RS} ) may be the same as Table 3 or as large as K times (for example, K=32) as shown in Table 8.

In this embodiment, in order to inform whether the CSI-RS subframe configuration according to Table 3 or the CSI-RS subframe configuration according to Table 8 is applied in determining the CSI-RS period and offset, the base station Signaling (for example, 1 bit) of a higher layer such as RRC may be transmitted to the terminal.

3. Modified CSI - RS Subframe configuration (2)

First, CSI-RS configuration information according to this embodiment is shown in Table 9.

CSI-RS-Config ::= SEQUENCE { csi-RS CHOICE { release NULL, setup SEQUENCE { antennaPortsCount ENUMERATED {an1, an2, an4, an8}, resourceConfig INTEGER (0..31), subframeConfig INTEGER (0..X), p-C INTEGER (-8..15) } }

Referring to Table 9, compared to Table 4, the CSI-RS configuration information has only CSI-RS muting information (CSI-RS-mutingInfo), antenna port count (antennaPortsCount) information, resource configuration (resourceConfig) information, and subframe It may include configuration (subframeConfig) information and Pc information.

With regard to the CSI-RS subframe configuration, a new CSI-RS subframe configuration may be added. For example, the CSI-RS transmission period to be added may be an exponential multiplier (eg, 160 ms, 320 ms, etc.) of the longest 80 ms among the existing CSI-RS transmission cycles. To this end, the bit length of subframe configuration information may be maintained as 8, and 1 to 2 bits may be further added.

As an example, a CSI-RS subframe configuration according to Table 10 below instead of Table 3 may be applied to this embodiment.

CSI-RS-subframe configuration
I _{CSI - RS} CSI-RS cycle
T _{CSI - RS} (subframe) CSI-RS subframe offset
Δ _{CSI - RS} (subframes) 0-4 5 I _{CSI - RS} 5-14 10 I _{CSI - RS} -5 15-34 20 I _{CSI - RS} -15 35-74 40 I _{CSI - RS} -35 75-154 80 I _{CSI - RS} -75 155-254 160 I _{CSI - RS} -155

Referring to Table 10, the CSI-RS period is 160 ms, and the offset is an embodiment in which ICSI-RS-155 is added. Since the new CSI-RS subframe configuration 155-254 can be expressed as 8 bits, the subframe configuration information has a length of 8 bits as in Table 4. At this time, the X value in'subframeConfig INTEGER (0..X)' of Table 9 may be 254 when following the example of Table 10.

As another example, a CSI-RS subframe configuration according to Table 11 may be applied to this embodiment.

CSI-RS-subframe configuration
I _{CSI - RS} CSI-RS cycle
T _{CSI - RS} (subframe) CSI-RS subframe offset
Δ _{CSI - RS} (subframes) 0-4 5 I _{CSI - RS} 5-14 10 I _{CSI - RS} -5 15-34 20 I _{CSI - RS} -15 35-74 40 I _{CSI - RS} -35 75-154 80 I _{CSI - RS} -75 155-194 160 (I _{CSI - RS} -155)*K1 195-234 320 (I _{CSI - RS} -195)*K2

Referring to Table 11, i) CSI-RS period 160ms, offset (ICSI-RS-155)*K1, ii) CSI-RS period 320ms, offset (ICSI-RS-195)*K2 is an embodiment added. Here, K1∈{1, 2, 3, 4}, and K2∈{1, 2, 3, 4, 5, 6, 7, 8}. Since the new CSI-RS subframe configuration (155-194, 195-234) can be expressed as 8 bits, the subframe configuration information has a length of 8 bits as in Table 4. At this time, the X value in'subframeConfig INTEGER (0..X)' of Table 9 may be 234 when following the example of Table 11.

As another example, a CSI-RS subframe configuration according to Table 12 may be applied to this embodiment.

CSI-RS-subframe configuration
I _{CSI - RS} CSI-RS cycle
T _{CSI - RS} (subframe) CSI-RS subframe offset
Δ _{CSI - RS} (subframes) 0-4 5 I _{CSI - RS} 5-14 10 I _{CSI - RS} -5 15-34 20 I _{CSI - RS} -15 35-74 40 I _{CSI - RS} -35 75-154 80 I _{CSI - RS} -75 155-314 160 I _{CSI - RS} -155

Referring to Table 12, a new CSI-RS subframe configuration 155-314 is added. That is, the CSI-RS period 160ms, the offset (ICSI-RS-155) is an embodiment added. Since the new CSI-RS subframe configuration 155-234 can be expressed as 9 bits, the subframe configuration information has a length of 9 bits unlike Table 4. At this time, the X value in'subframeConfig INTEGER (0..X)' of Table 9 may be 314 according to the example of Table 12.

As another example, a CSI-RS subframe configuration according to Table 13 may be applied to this embodiment.

CSI-RS-subframe configuration
I _{CSI - RS} CSI-RS cycle
T _{CSI - RS} (subframe) CSI-RS subframe offset
Δ _{CSI - RS} (subframes) 0-4 5 I _{CSI - RS} 5-14 10 I _{CSI - RS} -5 15-34 20 I _{CSI - RS} -15 35-74 40 I _{CSI - RS} -35 75-154 80 I _{CSI - RS} -75 155-314 160 I _{CSI - RS} -155 315-634 320 I _{CSI - RS} -315

Referring to Table 13, i) CSI-RS period 160ms, offset (ICSI-RS-155), ii) CSI-RS period 320ms, offset (ICSI-RS-315) is an embodiment added. Since the new CSI-RS subframe configurations 155-314 and 315-634 can be expressed as 10 bits, the subframe configuration information has a length of 10 bits unlike Table 4. At this time, the value of X in'subframeConfig INTEGER (0..X)' in Table 9 may be 634 according to the example in Table 13.

As another example, a CSI-RS subframe configuration according to Table 14 may be applied to this embodiment.

CSI-RS-subframe configuration
I _{CSI - RS} CSI-RS cycle
T _{CSI - RS} (subframe) CSI-RS subframe offset
Δ _{CSI - RS} (subframes) 0-X X+1 I _{CSI - RS}

비트로서 표현 가능하기 때문에, 서브프레임 구성(subframeConfig) 정보는 표 4와는 같은 비트 길이를 가질 수도 있고 다른 비트 길이를 가질 수도 있다. 예를 들어, X+1=160, X+1=200 또는 X+1=240일 경우 8비트의 길이를 가지며, X+1=320 또는 X+1=480일 경우 9비트의 길이를 가진다. 표 14의 경우 표 10 내지 표 13과는 달리 기존 CSI-RS-서브프레임 구성에 새로운 CSI-RS-서브프레임 구성이 추가되는 것이 아니라, 기존 CSI-RS-서브프레임 구성 대신에 새로운 CSI-RS-서브프레임 구성(오직 하나의 고정된 CSI-RS 전송 주기(이 때, 전송 주기는 X+1)와 그에 따른 오프셋)만 쓰는 경우이다. 따라서, 표 10 내지 표 13이 아래 2가지 방식 모두에 적용될 수 있는데 반해, 표 14는 2가지 방식 중 후자의 방식에서만 적용될 수가 있다.Referring to Table 14, the existing CSI-RS transmission period and offset are not transmitted, and only CSI-RS period (X+1) ms, offset I _{CSI - RS} is transmitted in a CSI-RS-subframe configuration. When a new CSI-RS-subframe configuration (I _{CSI - RS} , 0-X) is added like this

Since it can be expressed as bits, the subframe configuration information may have the same bit length as Table 4 or different bit lengths. For example, when X+1=160, X+1=200 or X+1=240, it has a length of 8 bits, and when X+1=320 or X+1=480, it has a length of 9 bits. In the case of Table 14, unlike Tables 10 to 13, a new CSI-RS-subframe configuration is not added to the existing CSI-RS-subframe configuration, but a new CSI-RS- instead of the existing CSI-RS-subframe configuration. This is a case in which only a subframe configuration (only one fixed CSI-RS transmission period (in this case, a transmission period is X+1) and an offset accordingly) is used. Therefore, while Tables 10 to 13 can be applied to both of the following methods, Table 14 can be applied only to the latter method among the two methods.

Method 1: The CSI-RS-subframe configuration is changed and included in the existing CSI-RS configuration information (in this case, CSI-RS for channel estimation and channel measurement is also used for small cell signal discovery)

Method 2: The CSI-RS-subframe configuration is included in new CSI-RS configuration information for discovering a small cell signal separate from the existing CSI-RS configuration information (in this case, CSI- for existing channel estimation and channel measurement) Apart from RS, CSI-RS for small cell signal discovery is transmitted)

Referring back to FIG. 7, the base station transmits CSI-RS configuration information to the terminal (S705). The CSI-RS configuration information may be transmitted to the terminal through higher layer signaling (eg, RRC message).

The base station transmits the CSI-RS to the terminal at a predetermined time point based on the CSI-RS configuration information (S710). At this time, CSI-RS may or may not be transmitted in the CSI-RS subframe according to the indication of the CSI-RS muting information. Alternatively, the CSI-RS may be transmitted based on a long period indicated by the modified CSI-RS subframe configuration and an offset accordingly.

The UE receives the CSI-RS configuration information, and performs small cell discovery according to the CSI-RS configuration information (S715). For small cell discovery, the UE can find a time point at which the CSI-RS will be transmitted using the CSI-RS configuration information. As an example, the terminal may receive the CSI-RS at the time when the CSI-RS can be found, according to the indication of the CSI-RS muting information. As another example, the UE may receive the CSI-RS at a time point determined based on a long period indicated by the modified CSI-RS subframe configuration and an offset accordingly.

9 is a block diagram showing a terminal and a base station according to an example of the present invention.

Referring to FIG. 9, the base station 950 includes a transmitter 955, a receiver 960, and a base station processor 970. The base station processor 970 includes a reference signal generator 971 and an RRC controller 972.

The RRC control unit 972 generates CSI-RS configuration information as described in step S700. The CSI-RS configuration information provides a modified CSI-RS period and/or offset such that the CSI-RS has a long transmission period or a short transmission period. Here, the generated CSI-RS configuration information may include all embodiments described throughout this specification. In addition, the CSI-RS subframe configuration applied by the RRC control unit 972 may include those defined in Tables 3, 8, and 10 to 14.

The reference signal generator 971 generates CSI-RSs as described in Equations 2 to 6 and Tables 1 to 2 and sends them to the transmitter 955.

The transmission unit 955 transmits the CSI-RS configuration information received from the RRC control unit 972 to the terminal 900. Also, the transmitter 955 transmits the CSI-RS received from the reference signal generator 971 to the terminal 900. In particular, the transmission unit 955 transmits the CSI-RS to the terminal 900 at a predetermined time point based on the CSI-RS configuration information. For example, the transmission unit 955 may or may not transmit CSI-RS in the CSI-RS subframe (non-muting) or not according to the indication of the CSI-RS muting information (muting). Alternatively, the transmitter 955 may transmit the CSI-RS based on the long period indicated by the modified CSI-RS subframe configuration and the offset accordingly.

The receiving unit 960 receives a corresponding message or an uplink signal from the terminal 900 that has received CSI-RS configuration information and CSI-RS.

The terminal 900 performing wireless communication with the base station 950 includes a receiver 950, an RRC controller 910, and a transmitter 915.

The receiving unit 950 receives the CSI-RS configuration information and/or CSI-RS from the base station 950.

The RRC control unit 910 interprets the CSI-RS configuration information and performs a configuration for receiving the CSI-RS as indicated by the CSI-RS configuration information. Thereafter, the RRC control unit 910 performs small cell discovery according to the CSI-RS configuration information. For small cell discovery, the RRC control unit 910 may use CSI-RS configuration information to find a time point at which the CSI-RS will be transmitted. As an example, the RRC control unit 910 may control the receiving unit 905 to receive the CSI-RS at the time when the CSI-RS can be found, according to the indication of the CSI-RS muting information. As another example, the RRC control unit 910 controls the receiving unit 905 to receive the CSI-RS at a time determined based on a long period indicated by the modified CSI-RS subframe configuration and an offset accordingly. can do.

The transmission unit 915 transmits the CSI-RS configuration information, a message corresponding to the reception of the CSI-RS, or an uplink signal to the base station 950.

The above description is merely illustrative of the technical spirit of the present invention, and those of ordinary skill in the art to which the present invention pertains will be capable of 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 following claims, and all technical spirits within the equivalent range should be interpreted as being included in the scope of the present invention.

Claims (10)

A method for transmitting a reference signal (RS) by a base station (BS) in a wireless communication system,
Generating CSI-RS configuration information to enable channel state information (CSI)-RS to be transmitted according to a long period or a certain muting pattern;
Transmitting the CSI-RS configuration information to a terminal; And
And transmitting the CSI-RS to the terminal at a time when the CSI-RS can be transmitted based on the CSI-RS configuration information.
The CSI-RS configuration information includes CSI-RS muting information defining the predetermined muting pattern,
The CSI-RS muting information is a bitmap of length N, each bit of the bitmap muting or non-muting the transmission of the CSI-RS for each of N consecutive periods. -muting), a method of transmitting a reference signal. delete delete In a base station (BS) for transmitting a reference signal (RS) in a wireless communication system,
An RRC control unit that generates CSI-RS configuration information that enables channel state information (CSI)-RS to be transmitted according to a long period or a certain muting pattern; And
And a transmitting unit that transmits the CSI-RS configuration information to the terminal and transmits the CSI-RS to the terminal at a time when the CSI-RS transmission is possible based on the CSI-RS configuration information.
The CSI-RS configuration information includes CSI-RS muting information defining the predetermined muting pattern,
The CSI-RS muting information is a bitmap of length N, each bit of the bitmap muting or non-muting the transmission of the CSI-RS for each of N consecutive periods. -muting), the base station. delete delete In a method for receiving a reference signal (RS) by a user equipment (UE) in a wireless communication system,
Receiving CSI-RS configuration information from the base station to enable channel state information (CSI)-RS to be transmitted according to a long period or a certain muting pattern;
Receiving the CSI-RS from the base station at a time when transmission of the CSI-RS is possible based on the CSI-RS configuration information; And
And performing small cell discovery using the CSI-RS,
The CSI-RS configuration information includes CSI-RS muting information defining the predetermined muting pattern,
The CSI-RS muting information is a bitmap of length N, each bit of the bitmap muting or non-muting the transmission of the CSI-RS for each of N consecutive periods. -muting), a method of receiving a reference signal. delete delete In a user equipment (UE) for receiving a reference signal (RS) in a wireless communication system,
CSI-RS configuration information that enables channel state information (CSI)-RS to be transmitted according to a long period (periodicity) or a certain muting pattern is received from a base station, and the CSI-RS A receiver configured to receive the CSI-RS from the base station at a time when the CSI-RS can be transmitted based on configuration information; And
It includes an RRC control unit for performing small cell discovery using the CSI-RS,
The CSI-RS configuration information includes CSI-RS muting information defining the predetermined muting pattern,
The CSI-RS muting information is a bitmap of length N, and each bit of the bitmap mutes or non-mutes the transmission of the CSI-RS for each of N consecutive periods. -muting) indicating that the terminal.

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