KR20130020487A - Control signals transmitting method and apparatus and data receiving method and apparatus thereof - Google Patents

Abstract

The present invention relates to a method and apparatus for transmitting control information in downlink CoMP, and a method and apparatus for receiving data using the same. The method for transmitting control information according to the present invention is the same in a CoMP (Coordinated Multi Point) system. Controlling data channels transmitted from transmission points of a CoMP cooperative set with respect to control channels and reference signals transmitted from transmission points in a subframe of a transmission time interval and information of the controlled data channel. And configuring downlink control information to be included. According to the present invention, in a CoMP environment, control information for avoiding interference between the data channel and the control channel transmitted from each transmission point and control information for avoiding the interference of the data channel and the reference signal are transmitted to the UE at one time and delivered to the UE. The overhead of control information can be reduced.

Description

Method and apparatus for transmitting control information and method and apparatus for receiving data using same {Control Signals Transmitting Method And Apparatus And Data Receiving Method And Apparatus Thereof}

The present invention relates to CoMPed Multi Points (CoMP) in a wireless communication system, and more particularly, to a method and apparatus for transmitting control information in downlink CoMP, and a data receiving method and apparatus using the same.

High-speed, high-capacity data transmission is achieved using a multi-antenna system. In addition, CoMP technology based on Multi-Input Multi-Output (MIMO) has been discussed.

CoMP is a technology for adjusting or combining signals transmitted from multiple points. CoMP can be applied to increase data rate and to obtain high quality and high throughput.

As a terminal supporting CoMP, a terminal to which CoMP is applied in a CoMP environment to which CoMP is applied (hereinafter referred to as a 'CoMP environment' for convenience of description). For convenience, the term "terminal operating in CoMP mode") may receive data simultaneously from the CoMP cooperative set or influence the interference between CoMP cooperative sets in consideration of the channel environment of each cell constituting the CoMP cooperative set. Since the purpose is to minimize and receive the transmission, it is necessary to measure the channel information for each cell and report it to the serving cell of the corresponding terminal. CoMP Cooperated Set (CoMP Cooperated Set) is a set of (geographically separated) transmission and reception points (geographically separated) to directly or indirectly participate in data transmission on a time-frequency resource for a user equipment (UE). Here, the direct participation in the data transmission means that the transmitting and receiving end actually transmits data to the UE in the corresponding time-frequency resource, and the indirect participation in the data transmission means that the transmitting and receiving end does not actually transmit data in the corresponding time-frequency resource. It does mean, however, that it contributes to making decisions about user scheduling / beamforming.

Meanwhile, reference information for generating channel information, such as a reference signal, is determined in a CoMP cooperative set composed of various cells, and information about the same needs to be shared between the terminal and the base station.

An object of the present invention is to provide a method in which a UE can correctly receive data in a CoMP environment.

One object of the present invention is to provide a method in which a UE correctly receives data even when a cell ID of each transmission point is different in a CoMP environment.

An object of the present invention is to provide a method for preventing interference between a data channel and a control channel transmitted from each transmission point even when a cell ID of each transmission point is different in a CoMP environment.

An object of the present invention is to provide a method for preventing interference between a data channel transmitted from each transmission point and a reference signal even when a cell ID of each transmission point is different in a CoMP environment.

The present invention provides a method of transmitting control information for avoiding interference between a data channel and a control channel transmitted from each transmission point and control information for avoiding interference between a data channel and a reference signal at one time in a CoMP environment. For work purposes.

An object of the present invention is to provide a method for reducing overhead of control information transmitted to a UE in a CoMP environment.

(1) An embodiment of the present invention is a method for transmitting downlink control information in a CoMP (Coordinated Multi Point) system, wherein the transmission points of a CoMP cooperative set are transmitted in subframes of the same transmission time interval. Controlling the transmitted data channels with respect to control channels and reference signals transmitted from the transmission points and constructing downlink control information including information of the controlled data channel.

(2) In (1), in the controlling the data channels, in the subframe, start points of data channels transmitted from the transmission points are aligned, and reference signals transmitted from the transmission points are mapped. A symbol of a data channel may be mapped to avoid a resource, and the information of the controlled data channel may be an indicator indicating a resource region where the start point of the data channel and the data channel are not mapped in the subframe.

(3) The index according to (2), wherein the indicator indicates an area in which the start point of the data channel and the data channel are not mapped in the subframe on a table composed of information on the start points of the data channel and the mapping of the data channel. Can be.

(4) In (1), in the controlling the data channels, in the subframe, symbols of the data channel are mapped by avoiding a resource to which symbols of control channels transmitted from the transmission points are mapped. A symbol of a data channel can be mapped by avoiding a resource to which reference signals transmitted from transmission points are mapped, and the information of the controlled data channel is an indicator indicating a resource region to which a data channel is not mapped in the subframe. Can be.

(5) In (4), the indicator may be an index indicating an area in which the data channel is not mapped in the subframe on a table configured with information on resources to which a symbol of the data channel is not allocated.

(6) In (1), the different transmission points may have different cell IDs.

(7) Another embodiment of the present invention is a data reception method of a UE in a Coordinated Multi Point (CoMP) system, wherein a data channel from transmission points of a CoMP cooperative set in subframes of the same transmission time interval Receiving data on a field; and combining the received data based on information on a data channel included in downlink control information received from a control information transmission point among the transmission points, wherein the data channel is combined. The information about includes information on control of a data channel made in the subframe with respect to control channels and reference signals transmitted from the transmission points.

(8) In (7), in the combining of the data, the starting point of the data channel in the subframe, indicated by the information on the data channel and control format information received from a serving point among the transmission points. And combining data received from the transmission points based on information on resources to which symbols of the data channel are not mapped in the subframe, indicated through the information about the data channel, and controlling the control format information. Indicates an area of a control channel in the subframe.

(9) In (8), the information about the data channel is a region composed of information about the mapping of the start points of the data channel and the data channel. It may be an index indicating.

(10) In (7), in the combining of the data, based on the information about resources to which symbols of the data channel are not mapped in the subframe indicated by the information about the data channel, Data received from the transmission points may be combined.

(11) The method of (10), wherein the information about the data channel may be an index indicating an area in which the data channel is not mapped in the subframe on a table composed of information on resources to which symbols of the data channel are not allocated. have.

(12) In (7), cell IDs of the transmission points may be different from each other.

According to the present invention, in the CoMP environment, even when the cell ID of each transmission point is different, the UE can correctly receive data.

According to the present invention, even when the cell ID of each transmission point is different in the CoMP environment, it is possible to prevent interference between the data channel and the control channel transmitted from each transmission point.

According to the present invention, even when the cell ID of each transmission point is different in the CoMP environment, it is possible to prevent interference between the data channel transmitted from each transmission point and the reference signal.

According to the present invention, in a CoMP environment, control information for avoiding interference between the data channel and the control channel transmitted from each transmission point and control information for avoiding the interference of the data channel and the reference signal can be transmitted to the UE at once.

According to the present invention, in the CoMP environment, the overhead of control information transmitted to the UE can be reduced.

1 schematically shows an example of a radio frame structure in a system to which the present invention is applied.
2 is a flowchart schematically illustrating an example of data processing between an eNodeB and a UE in a multi-antenna system.
3 schematically illustrates an example in which a CRS is mapped to an RE in the case of a normal CP.
4 schematically illustrates an example in which a CRS is mapped to an RE in the case of an extended CP.
5 is a diagram schematically illustrating a first CoMP scenario.
6 is a diagram schematically illustrating a second CoMP scenario.
FIG. 7 is a diagram schematically illustrating third and fourth CoMP scenarios.
8 is a diagram schematically illustrating an example in which positions of OFDM symbols at which a PDSCH region starts in the case of JT CoMP are shifted between cells.
FIG. 9 is a diagram schematically illustrating an example in which interference (collision) occurs between PDSCHs and CRSs transmitted in different cells in the case of JT-CoMP.
FIG. 10 is a diagram schematically illustrating puncturing and muting.
FIG. 11 schematically illustrates possible muting cases within one subframe for a normal CP.
12 schematically illustrates possible cases of muting in one subframe in an extended CP.
13 is a flowchart schematically illustrating an operation of an eNodeB in a system to which the present invention is applied.
14 is a diagram schematically illustrating an operation of a UE in a system to which the present invention is applied.
15 is a diagram schematically illustrating a structure of a UE in a system to which the present invention is applied.
16 is a diagram schematically illustrating the operation of an eNodeB in a system to which the present invention is applied.

Hereinafter, some embodiments will be described in detail with reference to the accompanying drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In addition, in describing the embodiments of the present specification, when it is determined that the detailed description of the related well-known configuration or function may obscure the subject matter of the present specification, the detailed description thereof will be omitted.

The present specification describes a wireless communication network, and the work performed in the wireless communication network is performed in the process of controlling the network and transmitting data in a system (for example, a base station) that manages the wireless communication network, or the corresponding wireless network. Work can be done in the terminal coupled to.

A user equipment (UE) may be fixed or mobile, and may include a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a personal digital assistant (PDA). It may be called other terms such as digital assistant, wireless modem, handheld device.

A base station generally refers to a fixed station communicating with a terminal, and may be referred to as other terms such as an evolved-NodeB (eNodeB), a base transceiver system (BTS), and an access point.

Each base station provides communication services for a particular geographic area (commonly called a cell). The base station may in turn be divided into a number of areas (called sectors). In addition, multiple transmission terminals may configure one cell.

1 schematically shows an example of a radio frame structure in a system to which the present invention is applied. A radio frame is composed of 20 slots (# 0 to # 19). One subframe consists of two slots. The time (length) of transmitting one subframe is called a transmission time interval (TTI). Referring to FIG. 1, for example, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

One slot may include a plurality of symbols in the time domain. For example, when Orthogonal Frequency Division Multiple Access (OFDMA) is used in downlink (DL), the symbol may be an Orthogonal Frequency Division Multiplexing (OFDM) symbol. Meanwhile, the representation of the symbol period in the time domain is not limited by the multiple access scheme or the name. For example, the plurality of symbols in the time domain may be a Single Carrier-Frequency Division Multiple Access (SC-FDMA) symbol, a symbol interval, or the like in addition to the OFDM symbol.

The number of symbols included in one slot may vary depending on the length of a cyclic prefix (CP). For example, one slot may include 7 symbols in the case of a normal CP, and one slot may include 6 or 3 symbols in the case of an extended CP.

A resource block (RB) is a resource allocation unit and is defined as a time-frequency domain represented by one slot in the time domain and a plurality of subcarriers corresponding to 180 kHz in the frequency domain. For example, if one slot includes seven symbols in the time domain, and the plurality of subcarriers corresponding to 180 kHz in the frequency domain total 12, one resource block may contain 7 ㅧ 12 = 84 resource elements (Resource). Element, RE).

'RE' (Resource Element) represents the smallest frequency-time unit to which the modulation symbol of the data channel or the modulation symbol of the control channel is mapped. If there are M subcarriers on one symbol, and one slot includes N symbols, one slot includes M × N REs.

'PRB' (Physical Resource Block) represents a unit time-frequency resource for transmitting data. One PRB is composed of a plurality of consecutive REs in the time-frequency domain, and a plurality of PRBs are defined in one subframe. 'VRB' (Virtual Resource Block) represents a virtual unit resource for transmission of a data channel or a control channel. The number of REs included in one VRB is equal to the number of REs included in one PRB. For transmission of a data channel or control channel, one VRB may be mapped to one PRB or one VRB may be distributed and mapped to a plurality of PRBs.

The downlink subframe may be divided into a control region and a data region in the time domain. The control region may include up to four OFDM symbols in front of the first slot in the subframe. The number of OFDM symbols included in the control region may be changed. A control channel such as PDCCH is allocated to the control region, and a data transmission channel such as PDSCH is allocated to the data region.

The PCFICH transmitted in the first OFDM symbol of the subframe carries a Control Format Indicator (CFI) indicating the number of OFDM symbols (that is, the size of the control region) used for transmission of control channels in the subframe. For example, the terminal may first receive the CFI on the PCFICH and then monitor the PDCCH. The PCFICH is transmitted using fixed PCFICH resources of a subframe without using blind decoding.

PHICH carries a positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for uplink HARQ (Hybrid Automatic Repeat reQuest). The ACK / NACK signal for the uplink data on the PUSCH transmitted from the UE is transmitted on the PHICH.

The Physical Broadcast Channel (PBCH) is transmitted as four OFDM symbols in front of the second slot of the first subframe of the radio frame. The PBCH carries system information necessary for the terminal to communicate with the base station. System information transmitted through the PBCH is called a master information block (MIB). On the other hand, the system information transmitted on the PDSCH indicated by the PDCCH is called a system information block (SIB).

Control information transmitted through the PDCCH is called downlink control information (DCI). DCI is the resource allocation of PDSCH (also called DL grant), the PUSCH resource allocation (also called UL grant), and a set of transmit power control commands for individual UEs in any UE group. And / or activation of Voice over Internet Protocol (VoIP).

The control region in the subframe includes a plurality of control channel elements (CCEs). The CCE is a logical allocation unit used to provide a coding rate according to the state of a radio channel to a PDCCH and corresponds to a plurality of resource element groups (REGs). The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

It is possible to aggregate the RE to configure the REG, and to aggregate the REG to configure the CCE. For example, one REG may include four REs, and one CCE may include nine REGs. {1, 2, 4, 8} CCEs may be used to configure one PDCCH, and each element in the set {1, 2, 4, 8} is called a CCE aggregation level.

A control channel composed of one or more CCEs performs interleaving in units of REGs and is mapped to a physical resource after a cyclic shift based on a cell ID.

In order to detect the PDCCH, blind decoding may be used. Blind decoding is also referred to as blind detection. Blind decoding is a method of descrambling a desired identifier to a CRC of a received PDCCH (which is called a candidate PDCCH) and checking a CRC error to determine whether the corresponding PDCCH is its control channel.

A plurality of PDCCHs may be transmitted in one subframe. The UE monitors a plurality of PDCCHs in every subframe. Here, monitoring means that the UE attempts to decode the PDCCH according to the format of the target PDCCH.

Meanwhile, a multi-input multi-output (MIMO) system, also called a multi-antenna system, improves transmission and reception data transmission efficiency by using a multi-transmission antenna and a multi-reception antenna.

 MIMO techniques include transmit diversity, spatial multiplexing, and beamforming.

Transmit diversity is a technique of increasing transmission reliability by transmitting the same data in each antenna constituting a multiple transmit antenna. Spatial multiplexing is a technology that allows high-speed data transmission without increasing the bandwidth of the system by simultaneously transmitting different data using multiple transmit antennas. Beamforming is used to increase the signal to interference plus noise ratio (SINR) of a signal by applying weights according to channel conditions for each antenna constituting the multiple antenna. In this case, the weight may be expressed by a weight vector or a weight matrix, which is referred to as a precoding vector or a precoding matrix.

Spatial multiplexing includes spatial multiplexing for a single user and spatial multiplexing for multiple users. Spatial multiplexing for a single user is also referred to as SU-MIMO (Single User MIMO), and spatial multiplexing for multiple users is called Spatial Division Multiple Access (SDMA) or Multi User MIMO (MU-MIMO).

On the other hand, the capacity of the MIMO channel increases in proportion to the number of antennas. The MIMO channel may be decomposed into independent channels. When the number of transmitting antennas is Nt and the number of receiving antennas is Nr, the number Ni of independent channels is Ni? Min {Nt, Nr}. Each independent channel is referred to as a spatial layer. The rank is the number of non-zero eigenvalues of the MIMO channel matrix and can be defined as the number of spatial streams that can be multiplexed.

MIMO technology includes a codebook based precoding technique. The codebook based precoding scheme is a method of preprocessing data using a precoding matrix most similar to a MIMO channel among predetermined precoding matrices. Using a codebook-based precoding scheme, the overhead can be reduced because the precoding matrix indicator (PMI) can be transmitted as feedback data as feedback data. Codebooks consist of a set of codebooks that can represent spatial channels. In order to increase the data transmission rate, the number of antennas must be increased. As the number of antennas increases, a codebook must be configured with a larger codebook set.

2 is a flowchart schematically illustrating an example of data processing between an eNodeB and a UE in a multi-antenna system.

Referring to FIG. 2, the eNodeB transmits data to the UE (S210). The eNodeB may perform precoding of an input symbol by using a precoding matrix composed of a plurality of rows and columns, and transmit a symbol that is precoded, that is, data. In this case, the eNodeB may select the precoding matrix by using a codebook including at least one precoding matrix.

The eNodeB may include a scheduler, channel encoder / mapper, MIMO encoder and OFDM modulator. The eNodeB may include Nt (Nt> 1) transmit antennas.

The scheduler receives data from N users and outputs K streams to be transmitted at one time. The scheduler uses the channel information sent to or from each user to determine the user and transmission rate to send to available radio resources. The scheduler extracts channel information from the fed back information and selects a code rate, a modulation and coding scheme (MCS), and the like.

Information fed back for the operation of the MIMO system may include control information such as channel quality indicator (CQI), channel state information (CSI), channel covariance matrix (CCM), precoding weight (PW), channel rank (CR), and the like. .

The CSI may include a channel matrix between transceivers, a channel correlation matrix, a quantized channel matrix or a quantized channel correlation matrix, and a PMI. The CQI may be a Signal to Noise Ratio (SNR), a Signal to Interference and Noise Ratio (SINR), or the like, between the transceivers.

The channel encoder / mapper encodes the input stream according to a predetermined coding scheme to form coded data and maps the coded data to symbols representing positions on a signal constellation.

The MIMO encoder performs precoding on the input symbol. Precoding is a technique for performing preprocessing on a symbol to be transmitted. Among the precoding techniques, there is a random beamforming (RBF), a zero forcing beamforming (ZFBF), and the like, which generate a symbol by applying a weight vector or a precoding matrix.

The OFDM modulator assigns incoming symbols to the appropriate subcarriers and transmits them through the transmit antenna.

The UE transmits feedback on data received from the eNodeB (S220). The UE may include an OFDM demodulator, a channel estimator, a MIMO decoder, a channel decoder / demapper and a feedback information obtainer. The UE may include Nr (Nr> 1) receive antennas.

The signal received from the receive antenna is demodulated by the OFDM demodulator, the channel estimator estimates the channel, and the MIMO decoder performs post processing corresponding to the MIMO encoder. The decoder / demapper demaps the input symbol into encoded data and decodes the encoded data to restore the original data. The feedback information obtainer generates user information including CSI, CQI, PMI, and the like. The generated user information is composed of feedback data and transmitted to the eNodeB.

Control information such as a CQI, a CSI, a channel covariance matrix, a precoding weight, a channel rank, and the like may be required for the operation of the MIMO-OFDM system. Such control information may be reported through a feedback channel as feedback information.

As described above, the precoding scheme is a MIMO technique that preprocesses and transmits a transmission data string using preprocessing weights. Equation 1 shows a precoding scheme for preprocessing a transmission data string x using preprocessing weights.

Where W (i) represents the precoding matrix.

In the case of codebook based precoding, the UE may have a codebook containing a predetermined precoding matrix with the eNodeB. The UE can estimate the channel and determine the most suitable precoding matrix. The UE may select and report a precoding matrix that maximizes channel performance, and select an indicator (PMI) for the selected precoding matrix. For example, a precoding matrix capable of maximizing the average throughput of a certain band of resources may be selected from among the precoding matrices defined in the codebook. In addition, a precoding matrix maximizing the reception power at the receiver may be selected. Can be selected. In addition, a precoding matrix that maximizes the Signal to Interference plus Noise Ratio (SINR) may be selected.

The UE feeds back an index (PMI) indicating the determined precoding matrix to the eNodeB. The eNodeB may select a precoding matrix indicated by the fed back PMI from a codebook and use it for data transmission.

The method of using the precoding weight according to the channel state is called a closed-loop (MIMO) method. In the CL MIMO scheme, a transmitting side, for example, an eNodeB, uses channel state information (CSI) as feedback information transmitted from a receiving side, eg, a UE, to correspond to a channel condition. CSI may be transmitted including the PMI. The method of using precoding weights according to a certain rule regardless of the channel state is called OL (Open-Loop) MIMO method.

In FIG. 2, for convenience of description, the eNodeB performs the operation described in step S210 and the UE performs the operation described in step S220. However, the present disclosure is not limited thereto, and the UE performs the operation described in step S210. The eNodeB may perform the operation described in step S220.

Meanwhile, in a wireless communication system, it is necessary to estimate an uplink channel or a downlink channel for data transmission / reception, system synchronization acquisition, channel information feedback, and the like, and compensates for a distortion of a signal caused by a sudden environmental change. The process of restoring the signal is called channel estimation. It is also necessary to measure the channel state of the cell or other cell to which the terminal belongs. In general, a reference signal (RS) known to each other is used by a transceiver for channel estimation or channel state measurement.

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 transmission signal is compensated by compensating for a distortion of a signal caused by a sudden environmental change. The reconstruction process is called channel estimation. It is also necessary to measure the channel state of the cell or other cell to which the terminal belongs. In general, a reference signal (RS) known to each other is used by a transceiver for channel estimation or channel state measurement.

)를 추정할 수 있다.Since the receiver knows the information of the reference signal, the receiver can estimate the channel based on the reference signal of the received signal and compensate the channel value to accurately obtain the data sent from the transmitter. If p is the reference signal transmitted from the transmitter, channel information that the reference signal undergoes during transmission, h is thermal noise generated at the receiver, and n is the signal received at the receiver, it can be expressed as y = h · p + n . . In this case, since the reference signal p is already known to the receiver, when the LS (Least Square) method is used, channel information (

) Can be estimated.

는

값에 의존하게 되므로, 정확한 h값의 추정을 위해서는

을 0에 수렴시켜 영향을 최소화 할 필요가 있다. Here, the channel estimation value estimated using the reference signal p

The

Value, so for accurate estimation of the h value

We need to minimize the effect by converging to 0.

In an OFDM system, a reference signal is allocated to all subcarriers and between data subcarriers for transmitting data. The method of allocating a reference signal to all subcarriers uses a signal consisting of only the reference signal in order to obtain a gain of channel estimation performance. In this case, since the density of the reference signal is high, the channel estimation performance can be improved as compared with the method of allocating the reference signal between data subcarriers. However, since allocating reference signals to all subcarriers reduces the amount of data transmission, a method of increasing the amount of data transmission by allocating reference signals between data subcarriers may be used.

The reference signal is generally transmitted by generating a signal from a sequence of reference signals. In the 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 Zadoff-Chu (ZC) sequences, pseudo-noise (PN) sequences such as m-sequences, Gold sequences, and Kasami sequences. This reference signal may be used as a sequence, and various other sequences having 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 may be various forms such as binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK). May be modulated and mapped to a resource element (RE).

The downlink reference signal may include a cell-specific RS (CRS), a multimedia broadcast and multicast single frequency network (MBSFN) reference signal, a UE-specific RS, and a position reference signal (PRS). : Positioning RS and Channel State Information (CSI) reference signal (CSI-RS).

The CRS is a reference signal transmitted to all terminals in a cell and used for channel estimation. The CRS may be transmitted in all downlink subframes in a cell supporting PDSCH transmission.

The MBSFN reference signal is a reference signal for providing a multimedia broadcast multicast service (MBMS) and may be transmitted in a subframe allocated for MBSFN transmission.

The PRS may be used for location measurement of the terminal. The PRS may be transmitted only through resource blocks in a downlink subframe allocated for PRS transmission.

CSI-RS may be used for estimation of channel state information. The CSI-RSs are relatively sparse in the frequency domain or the time domain and are transmitted in subframes having a constant period. A channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and the like may be reported from the terminal when necessary through the estimation of the CSI.

The UE-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 referred to as DM-RS.

The CRS of the reference signal may be transmitted in all downlink subframes in a cell supporting PDSCH transmission. In addition, the CRS may be transmitted through at least one antenna port among the antenna ports 0 through 3.

는 수학식 3과 같이 정의된다.Reference signal sequence used to generate CRS

Is defined as Equation (3).

하향링크 자원 블록의 최대 개수를 나타낸다. Where n _S is a slot number in the radio frame and l is an OFDM symbol number in the slot. Also,

This indicates the maximum number of downlink resource blocks.

In Equation 2, c (i) is a pseudo random sequence generated from a gold sequence defined from two m-sequences of m = 31, and is initialized as shown in Equation 4 at the beginning of each OFDM symbol.

In this case, N _CP has a value of 1 in the case of a normal cyclic prefix (CP) and a value of 0 in the case of an extended CP. In addition, N ^cell _ID indicates a cell ID (physical layer cell ID) in the physical layer.

는, 슬롯 n_S의 안테나 포트 p에 대한 복소 변조 심볼

에 매핑된다. 이때,

와

의 매핑 관계는 수학식 5와 같다. Reference signal sequence

Is a complex modulation symbol for antenna port p of slot n _S

Is mapped to. At this time,

Wow

The mapping relationship of is as shown in Equation 5.

In Equation 5, N ^DL _RB represents the number of downlink resource blocks. In addition, the v value and the v _shift value can be obtained as shown in Equation 6.

As described in the process of calculating the sequence of the CRS, the CRS is generated based on the cell ID.

Resource element (RE, hereinafter referred to as 'RE') (k, l) used to transmit the generated CRS to the antenna port in the slot is not used for transmission made in another antenna port in the same slot.

3 schematically shows that the CRS is mapped to the RE in the case of a normal CP, as described above. In FIG. 3, R _p represents an RE used for CRS transmission at the antenna port P. In FIG. 4 schematically shows that the CRS is mapped to the RE in the case of an extended CP. As shown in Figures 3 and 4, the CRS is mapped to the RE in a certain pattern.

Meanwhile, in a MIMO system, a CoMP (Coordinated Multi Point) scheme may be applied to transmit and receive between a UE and a multi cell and / or a multi point. CoMP system is also called a cooperative multiplex transmission and reception system.

In a CoMP system to which CoMP is applied, a point represents a set of transmit antennas that are geographically co-located. Even sectors of the same site may correspond to different points.

The serving point is a point at which the UE receives the PBCH and may exist in plural. If there are a plurality of serving points, these serving points may be aggregated. The serving point may be said to include the concept of a serving cell. The control signaling point is a point at which the UE receives a UE specific control signal and may exist in plural. In the case where there are a plurality of control signaling points, these control signaling points may form an aggregation. The control signaling point can also be said to include the concept of a serving cell. The points used to send the PDSCH to a particular UE may or may not be the serving point and / or control signaling point of the UE.

Examples of CoMP scenarios include the following first CoMP scenarios and fourth CoMP scenarios.

5 is a diagram schematically illustrating a first CoMP scenario. The first CoMP scenario relates to a homogeneous network with intra-site CoMP. For example, in the first CoMP scenario, a CoMP cooperation set is configured between three different cells (or sectors) of one eNodeB.

CoMP Cooperated Set refers to a set of (geographically separated) points that directly / indirectly participate in data transmission for a UE in a time-frequency resource. The CoMP cooperative set may or may not be transparent to the UE. In this case, participating directly in data transmission means that the point actually transmits data in the corresponding time-frequency resource. Indirect participation in data transmission means that the point is a candidate point for data transmission and does not actually transmit data, but contributes to determining scheduling / beamforming or the like in the corresponding time-frequency resource.

Referring to FIG. 5, for a cooperative region 501 to which CoMP is applied, a CoMP cooperative set includes three sectors 503, 504, and 505 that are configured by one eNodeB 402.

6 is a diagram schematically illustrating a second CoMP scenario. The second CoMP scenario relates to a homogeneous network with high Tx Power RRHs. RRH (Remote Radio Head) is a device composed of RF part by separating eNodeB equipment into RF (Radio Frequency) part and baseband part. Accordingly, the RRH may include an A / D converter, an up / down converter, etc. in addition to the RF circuitry. By separating and miniaturizing the RF part, coverage can be extended without installing a base station. The RRH may be connected to the eNodeB through an optical fiber or the like.

In the second CoMP scenario, for example, a CoMP cooperation set is configured between eNodeBs, and data required to operate a CoMP system through a wired or wireless network (eg, optical fiber) connecting between the eNodeBs may be shared between the eNodeBs. For convenience of description, the eNodeB is taken as an example, but the points constituting the CoMP cooperation set in the second CoMP scenario may include not only the eNodeB but also the RRH. Referring to FIG. 6, a wired network is established between an eNodeB and an RRH constituting a CoMP cooperation set, and information necessary to operate a CoMP system may be shared through a wired network.

FIG. 7 is a diagram schematically illustrating third and fourth CoMP scenarios.

The third CoMP scenario relates to heterogeneous networks with low power RRHs within the macro cell coverage, where the transmission and reception points generated by the RRH are transmitted. / reception points) have different cell IDs than macro cells. The fourth CoMP scenario also relates to a heterogeneous network including low power RRHs within the range of the macro cell. However, unlike the third CoMP scenario, the transmission / reception points generated by the RRH have the same cell ID as the macro cell. Here, CoMP transmission point (s) refers to a point or set of points for transmitting data to a certain UE, such that CoMP receiving point (s) refers to a point or set of points for receiving data from any one UE.

The categories of CoMP include Joint Processing (JP) and Coordinated Scheduling / Beamforming (CS / CB). It is also possible to mix CS and CB.

In the case of JP, data for the UE is available at at least one point of the CoMP cooperation set in some time-frequency resource. JP includes Joint Transmission (JT, hereinafter referred to as 'JT') and Dynamic Point Selection (DPS, hereinafter referred to as 'DPS'). JT means that data transmission is performed together from a multi point belonging to a CoMP cooperative set to one UE or a plurality of UEs in time-frequency resources. In the DPS, data transmission is performed from one point of a CoMP cooperative set in time-frequency resources. The transmission point may change from subframe to subframe, and includes change over an RB pair (Resource Block Pair) in the subframe. The data to be transmitted is available simultaneously at multiple points. DPS includes Dynamic Cell Selection (DCS).

In the case of CS / CB, data is sent from a point in a CoMP collaboration set for time-frequency resources, and user scheduling / beamforming is determined by coordination between the points of that CoMP collaboration set. The points used are then selected dynamically or semi-statically. In the case of dynamically selecting points, the transmission is performed only one point at a time, which may be changed from subframe to subframe, and includes changing over an RB pair within a subframe. In the case of semi-statically selecting points, only one point at a time is transmitted, and the transmission point can be changed only in a semi-static manner.

As mentioned above, it is also possible to mix JP and CS / CB. For example, some points in the CoMP cooperation set may send data to the target UE according to JP, and other points in the CoMP cooperation set may perform CS / CB.

On the other hand, in the case of JT, as described above, REs used for signal transmission by different transmission points should be identical. That is, the same signal is transmitted on the same time-frequency resource region.

For example, the PDCCH may be transmitted in the first one to three OFDM symbols, up to four OFDM symbols in general in the downlink subframe. In this case, when transmission points, for example, RRHs have different cell IDs, different cells may have different PDCCH regions, and thus, REs that cannot be used for downlink JT-CoMP may occur. For example, when the PDCCH of the first cell is transmitted in one OFDM symbol in front of a downlink subframe, and the PDCCH of the second cell is transmitted in three OFDM symbols in front of a downlink subframe, each cell is downlinked. Since the starting point of the PDSCH region, for example PDSCH, is different in link transmission, it is difficult to combine the signals received by the UE.

8 is a diagram schematically illustrating an example in which positions of OFDM symbols at which a PDSCH region starts in the case of JT CoMP are shifted between cells. Referring to FIG. 8, in the case of JP-CoMP, the first OFDM symbol of a subframe is used for PDCCH transmission in the case of the first cell among the cells constituting the CoMP cooperative set, and the cell ID is different from the first cell. In the case of a different second cell, the first three OFDM symbols are used for PDCCH transmission in a subframe.

If the cell IDs of transmission points, for example, RRHs are different from each other, as shown in FIG. 8, the number of OFDM symbols used for PDCCH transmission in different cells is changed. Therefore, in the case of JP-CoMP, a starting position of PDSCHs transmitted from CoMP transmission points in a corresponding subframe may not be aligned.

In addition, even in the case of the CRS described above, since the reference signal sequence is generated based on the cell ID, if the cell ID is different, the pattern of the CRS transmitted in the downlink is different. In this case, a collision may occur between CSR and PDSCH transmitted from different transmission points in the corresponding subframe, and there may be REs that cannot be used for downlink JT-CoMP.

FIG. 9 is a diagram schematically illustrating an example in which interference (collision) occurs between PDSCHs and CRSs transmitted in different cells in the case of JT-CoMP. 9, in the case of JP-CoMP, a pattern of CRSs transmitted by a first cell among cells constituting a CoMP cooperation set, and a pattern of CRSs transmitted by a second cell having a different cell ID from the first cell. This is different.

If the cell IDs of transmission points, e.g., RRHs are different, as shown in Fig. 9, since cell-specific CRS frequency shift, i.e., v _shift in Equation 6, is different from each other, The patterns of the transmitted CRSs are different from each other. In the case of JP CoMP, interference may occur between PDSCH and CRS transmitted from different transmission points.

As described above in the case of JP-CoMP, if the starting point is not aligned or ignores or neglects an interference state between PDSCHs from different transmission points in one subframe, communication performance is greatly degraded. Therefore, information about this situation needs to be transmitted to the UE, and control such as muting PDSCH and / or CRS or recovering the PDCCH region in downlink transmission is necessary.

Hereinafter, when the RRH constituting the CoMP transmission point, for example, the CoMP cooperation set has different cell IDs in the system to which the present invention is applied, interference coordination and / or PDSCH starting point between PDSCHs and CRSs transmitted from different transmission points A method of aligning will be described with reference to the drawings and tables.

As described above, in CoMP downlink transmission, when cell IDs of transmission points, for example, RRHs are different, PDCCHs from each RRH may have different areas. That is, PDCCHs from each RRH may be transmitted using different numbers of OFDM symbols. The PDCCH region, i.e., how many OFDM symbols are used for PDCCH transmission, may be dynamically changed by the value of a control format indicator (CFI) transmitted on a physical control format indicator channel (PCFICH).

Table 1 shows an example of a CFI value and a CFI codeword.

Referring to Table 1, the CFI value represents the number of OFDM symbols used for PDCCH transmission. For example, when the number of downlink RBs is more than 10, one OFDM symbol is used to transmit the PDCCH when the CFI value is 1, and two OFDM symbols are used to transmit the PDCCH when the CFI value is 2, When the value of CFI is 3, three OFDM symbols are used to transmit the PDCCH. In addition, when the number of downlink RBs is 10 or less, when the CFI value is 1, two OFDM symbols are used to transmit the PDCCH. When the CFI value is 2, three OFDM symbols are used to transmit the PDCCH. When is 3, four OFDM symbols are used to transmit the PDCCH. The CFI value 4 is not used here and is reserved.

Meanwhile, even in the case of CRS, as described above, CRSs transmitted from cells having different cell IDs may have different CRS patterns due to different frequency transitions. Therefore, the mapping of data to resource elements (REs) in the PDSCH region may also vary between transmission points having different cell IDs due to the CRS pattern.

To solve these problems, as described above, control such as muting the PDSCH or recovering the PDSCH region to the PDCCH region in downlink transmission is necessary.

Referring to FIG. 8, in order to align the PDSCH region starting at S1 in the downlink transmission of the first cell and the PDSCH region starting at S2 in the downlink transmission of the second cell, the second and third cells of the first cell are aligned. The PDSCH may be muted in the first OFDM symbol. This may be said that the PDSCH is muted in view of the first cell where the PDSCH start point is changed.

In addition, the alignment of the PDSCH start point may be performed by matching the PDSCH start point S2 of the second cell with the PDSCH start point S1 of the first cell. This may be expressed from the viewpoint of the second cell in which the PDSCH start point is changed, that the PDSCH is recovered in the PDCCH region.

Here, 'mute' or 'muting' refers to a resource to be muted, unlike puncturing, which maps data to a resource and then extracts the symbols assigned to that resource. This means not mapping data (symbols).

10 is a diagram schematically illustrating puncturing and muting. In the case of puncturing, puncturing is performed after allocating symbols S1, S2, ... to each RE (Resource). For example, referring to FIG. 10A, when the symbol to be punctured is a symbol mapped to RE2, the symbol S2 is punctured after being mapped to RE2. On the other hand, in the case of muting, the symbol is not mapped to the RE to be muted. Referring to FIG. 10B, when the RE to be muted is RE2, the symbol is not mapped to RE2 and the symbol is mapped to the next RE.

Hereinafter, for convenience of explanation, not allocating PDSCH data to a specific RE is referred to as 'muting the PDSCH (for the corresponding RE)'.

Referring to FIG. 9, in order to prevent data transmission of the CSI-RS and the PDSCH from colliding (interfering) between downlink transmission of the first cell and downlink transmission of the second cell, transmission from the first cell may be performed. It can be seen that muting the PDSCH for the part corresponding to the CSI-RS of two cells, and muting the PDSCH for the part corresponding to the CSI-RS of the first cell in transmission from the second cell. Accordingly, in the case of the CRS, when a collision occurs with the CRS transmitted from different transmission points, the collision can be prevented by muting the PDSCH for the corresponding regions (REs).

In order to perform the control as described above, information about the muting needs to be transmitted to the UE. In this case, if the muting information of the PDSCH related to the PDCCH and the muting information of the PDSCH related to the CRS are transferred, the overhead of information transmission increases. The present invention discloses a method of transmitting both muting information of a PDSCH associated with a PDCCH and muting information of a PDSCH associated with a CRS.

FIG. 11 schematically illustrates possible muting cases in one subframe for a normal CP. Referring to FIG. 11, when a transmission point transmits 2Tx (transmission) downlink in a MIMO system, when 4Tx transmission is performed with OFDM symbols 1110, 1140, 1150, and 1170 in which a CRS is located with respect to a normal CP. In addition, the positions of the OFDM symbols 1120 and 1160 where the CRS is located may be checked.

12 schematically illustrates possible cases of muting in one subframe in an extended CP. Referring to FIG. 12, when a transmission point transmits 2Tx (transmission) downlink in a MIMO system, 4Tx transmission is performed with OFDM symbols 1210, 1240, 1250, and 1270 in which a CRS is located for an extended CP. In this case, the positions of the OFDM symbols 1220 and 1260 where the CRS is located may be additionally checked.

Hereinafter, the present invention will be described for the case of normal CP for convenience of explanation. The content of the present invention described with respect to the normal CP can be applied equally to the case of the extended CP.

Referring to FIG. 11, it can be seen that when CoMP is applied, the following collision (interference) may occur between channels and / or reference signals transmitted from each transmission point in one subframe: 1) collision between PDCCH and PDSCH, (2) collision between PDSCH and CRS.

(1) When PDCCH and PDSCH Conflict

In the case of JP (Joint Process) -CoMP, the same transmission time interval (TTI) is used for downlink transmission transmitted from the transmission point of the first cell and the transmission point of the second cell, as in the example of FIG. 8. The number of OFDM symbols used for PDCCH transmission in each subframe, i.e., the starting point of the PDSCH region may be different. Therefore, a problem in which a UE to which JP-CoMP is applied cannot accurately combine information received from each transmission point may occur.

In this case, the collision problem can be solved by aligning the transmission time points of the PDSCHs transmitted from the transmission points constituting the CoMP cooperation set. For example, in downlink transmission transmitted from transmission points constituting a CoMP cooperative set, a PDSCH start point (OFDM symbol at which PDSCH transmission is started) in the same subframe may be matched with the latest PDSCH start point. Referring to the example of FIG. 8, PDSCH transmission is started in the second OFDM symbol of the subframe in transmission from the transmission point of the first cell, and fourth OFDM symbol of the same subframe in the transmission from the transmission point of the second cell. PDSCH transmission is initiated at. At this time, in the transmission from the first cell, by muting the PDSCH in the second and third OFDM symbols, that is, by not mapping the PDSCH symbol to the second and third OFDM symbols, the transmission from the second cell and the PDSCH You can align the starting point.

In addition, the PDSCH start point may be aligned with the fastest PDSCH start point in downlink transmission transmitted from the transmission points. For example, referring to the example of FIG. 8, by changing the starting point of the PDSCH to the second OFDM symbol in the transmission from the second cell, the starting point of the PDSCH in the transmission from the first cell and the transmission from the second cell is determined. You can sort. In this case, in the case of the second cell, the PDSCH may be recovered from the PDCCH region.

In this case, for transmission from each of the transmission points, the PDSCH starting point may be determined through the wired or wireless network between each transmission point constituting the CoMP cooperation set. A point for transmitting control information, for example, the above-described control signaling point, informs the UE of the start point of the PDSCH or downlinks in the downlink control channel, that is, through the downlink control information (DCI). I can tell you.

(2) when PDSCH and CRS collide

In the case of Joint Process (JP) -CoMP, if the cell IDs of the transmission points constituting the CoMP cooperation set are different, the pattern of the CRS is different in downlink transmission transmitted from each transmission point. In this case, a collision between the CRS and the PDSCH may occur at the same resource location, and a problem in which a UE to which JP-CoMP is applied may not accurately combine information received from each transmission point may occur.

Referring to the example of FIG. 9, it can be seen that the RE of the fifth OFDM symbol allocated for transmitting the CRS is allocated to the transmission of the PDSCH in the second cell. In this case, the collision between the PDSCH and the CRS may be prevented by muting the PDSCH for the OFDM symbol where the collision between the PDSCH and the CRS transmitted from different transmission points occurs. For example, in the example of FIG. 9, the collision between the CRS and the PDSCH can be resolved by muting the PDSCH on the fifth OFDM symbol in both the transmission from the first cell and the transmission from the second cell.

In this case, the OFDM symbol to which the PDSCH is muted in transmission from each transmission point may be determined through the wired / wireless network between each transmission point constituting the CoMP cooperative set. A point for transmitting control information, for example, the above-described control signaling point or serving point, may inform the UE of an OFDM symbol to which the PDSCH is muted on the downlink control channel, that is, through the DCI.

In order to reduce the transmission overhead, it is preferable to transmit the muting information of the PDSCH to the UE together or simultaneously for the above two cases of collision in one subframe (collision between PDCCH and PDSCH, collision between PDSCH and CRS). If the point for transmitting the control information transmits the muting information of the PDSCH to avoid the collision of the PDCCH and the PDSCH and the muting information of the PDSCH to avoid the collision of the CRS and the PDSCH, respectively, the overhead in transmission will be greater.

Therefore, by encoding and transmitting the muting information of the PDSCHs for the PDCCH and the CRS, overhead can be greatly reduced. Referring to FIG. 9, it can also be confirmed that there is a PDSCH symbol commonly muted with respect to the PDCCH and the CRS. Since there is an area where PDSCH can be muted in common for PDCCH and CRS, the overhead can be further reduced by encoding the muting information of PDSCH for PDCCH and the muting information of PDSCH for CRS together.

On the other hand, by adding a muting information index indicating the muting information of the PDSCH for the PDCCH and the CRS to the downlink control information (DCI), a method of dynamically signaling the muting information to the UE can be considered. The muting information index indicates muting information of the PDSCH for the PDCCH and the CRS in the muting information table. As a muting information table that may use the muting information index, a table indicating the start point of the PDSCH of the corresponding subframe and the muting information of the PDSCH for the CRS may be configured in downlink transmissions from the transmission points. In addition, as a muting information table, a table indicating information of an OFDM symbol muted in a PDSCH in a downlink subframe from transmission points can be configured without distinguishing whether the PDCCH or the CRS.

Hereinafter, a method of delivering muting information to a UE in a system to which the present invention is applied will be described.

<Delivery information about PDSCH start point and CRS muted to CRS>

In the case of JP-CoMP, a muting information table may be used to avoid collision between PDCCH and PDSCH transmitted from different transmission points and collision between PDSCH and CRS. The muting information table shows (1) the number of OFDM symbols available for the PDCCH, that is, the OFDM symbols that can be the PDSCH starting point, and (2) the OFDM symbols where the CRS can be located, i.e., 2Tx and 4Tx. OFDM symbols may be located, and (3) a muting information index indicating a combination of (1) and (2).

Table 2 is an example of a muting information table for simultaneously transmitting information about a PDSCH start point and information about a PDSCH muted with respect to a CRS in three bits in a corresponding subframe.

In Table 2, information about the starting point of the PDSCH in the corresponding subframe and information about the PDSCH muted for the CRS are indicated together. Table 2 may be stored in advance in the UE and the transmission point, or may be determined between the transmission points and delivered to the UE through an upper layer message. In addition, the index indicating the starting point of the PDSCH and the PDSCH muted with respect to the CRS may be delivered to the UE through DCI on the physical control channel. At this time, the start point of the PDSCH indicated by the muting information index and the muted PDSCH may be a PDSCH muted with the start point of the PDSCH in a subframe in which the corresponding muting information index is transmitted.

The information about the starting point of the PDSCH is information indicating an OFDM symbol at which the PDSCH starts in downlink transmission from each transmission point. In other words, as described in the case of (1) PDCCH and PDSCH collide, PDSCH for OFDM faster than the reference OFDM symbol according to the transmission point starting PDSCH transmission from the latest OFDM symbol (reference OFDM symbol). May be information indicating that muted. In addition, as mentioned in the description of PDSCH recovery, a part of PDSCHs from another transmission point is muted in accordance with a PDSCH from one transmission point, or a PDSCH is restored in a PDCCH region to be transmitted from each transmission point. It may be information indicating that the PDSCH starts from the indicated one OFDM symbol within the subframe.

In addition, PDSCH muting for 2Tx indicates that the PDSCH is muted for the OFDM symbol where the CRS is located in the case of 2Tx, and PDSCH muting for 4Tx indicates that the PDSCH is muted for the OFDM symbol where the CRS is located in the case of 4Tx. To indicate that

For example, in the example of Table 2, if the muting information index delivered to DCI is 000, the PDSCH transmitted from each transmission point in the corresponding subframe to the UE starts at the second OFDM symbol, and there is no PDSCH muted for CRS. To instruct.

In the example of Table 2, if the muting information index delivered to the DCI is 100, the PDSCH transmitted from each transmission point to the UE in the corresponding subframe starts at the third OFDM symbol, and the CRS transmitted at 2Tx from each transmission point. Only indicates that the PDSCH is muted. Referring to the example of FIG. 11, the first OFDM symbol is always used for PDCCH transmission, and the PDSCH is muted in other OFDM symbols 1140, 1150, and 1170 in which 2Tx CRSs are located.

In the example of Table 2, if the muting information index delivered to the DCI is 111, the PDSCH transmitted from each transmission point to the UE in the corresponding subframe starts at the fourth OFDM symbol, and the CRS transmitted at 4Tx from each transmission point. Indicates that the PDSCH is muted. Referring to the example of FIG. 11, in the 4Tx case, the CRSs are located in the OFDM symbols 1120 and 1160 in addition to the pattern of the 2Tx CRS. Thus, the PDSCH is muted at OFDM symbols 1120, 1140, 1150, 1160, 1170.

Table 2 may also be dynamically switched and applied between all CoMP schemes, ie between Joint Processing (JP) and Coordinated Scheduling / Beamforming (CS / CB). For example, since the muting of PDSCH for CRS is applied in the case of JP, the muting information indexes 000, 011, and 101 may be applied to a scheme other than JP, that is, CS / CB.

Table 2 may also be applied to PDSCH recovery in the PDCCH region in the case of DPS CoMP. For example, transmission is performed from a first transmission point in a first subframe, and PDSCH transmission is performed from a fourth OFDM symbol with a CFI of 3, but as a result of DPS, transmission is performed from a second transmission point in a second subframe. When PDSCH transmission is performed from the third OFDM symbol, for example, a muting information index of 011 may be transmitted to the UE in the second subframe to indicate that the PDSCH is transmitted from the third OFDM symbol. Although the CFI is 3 in the second subframe, it can be seen that the PDSCH is reconstructed in the PDCCH region.

The overhead can be greatly reduced by transmitting information about the PDSCH start point and the muted PDSCH together.

Meanwhile, in Table 2, there is no muting information about 4Tx CRS when 2 OFDM symbols are used for PDCCH transmission, that is, when PDSCH transmission starts with a third OFDM symbol. Referring to FIG. 11, the muting regarding 4Tx CRS when PDSCH transmission is started in the third OFDM symbol is the same muting result as that for 4Tx CRS when PDSCH transmission is started in the second OFDM symbol, that is, the same muting pattern. Has Therefore, the muting information about the 4Tx CRS when the PDSCH transmission starts in the third OFDM symbol and the muting information about the 4Tx CRS when the PDSCH transmission starts in the second OFDM symbol may be indicated by the same index. For example, in the example of Table 2, the information of both cases is indicated by the same index 010.

<Deliver information about all muted PDSCHs>

In the case of JP-CoMP, another muting information table can be used to avoid collision between PDCCH and PDSCH and collision between PDSCH and CRS. The muting information table used in this case may be composed of each case that can be derived from FIG. 11 and a muting information index indicating the same as in the embodiment of Table 2, but unlike the case of Table 2, the muting information index is The PDSCH is configured to indicate only the OFDM symbols to be muted.

Table 3 is an example of a muting information table for transferring information about a muted PDSCH in 3 bits. As described above, in Table 3, the muting information of the PDSCH to avoid collision with the PDCCH and the muting information of the PDSCH to avoid the collision with the CRS are transmitted together, but the UE distinguishes whether the PDSCH muting is related to the PDCCH or the CRS. There is no need to do it. Therefore, in Table 3, only the information of the muted PDSCH is transmitted without distinguishing whether it is related to PDCCH or CRS.

Table 3 shows an example of a case in which the total number of normal CPs and downlink total RBs is greater than 10. OFDM symbols in which PDSCHs are muted among the 0th (# 0) OFDM symbols and the 13th (# 13) OFDM symbols of one subframe. To indicate. In this case, the OFDM symbol indicated that the PDSCH is muted by the muting information index may be an OFDM symbol of a subframe in which the corresponding muting information index is transmitted.

Unlike Table 2, Table 3 directly indicates the OFDM symbol number to which the PDSCH is muted, but the muting information means substantially the same. For example, as shown in Table 4 below, each muting information index of Table 4 is the same as that of each muting information index of Table 2. In addition, as shown in Table 5 below, Table 5 summarizes the OFDM symbol numbers that are substantially PDSCH muting according to each case, as the respective muting information index means, Table 3 is derived based on this Can be. Accordingly, Table 3 may be seen as an example of representing the OFDM symbol number in which the PDSCH is muted substantially in accordance with each muting information index.

Meanwhile, in Tables 2 to 5, the present invention has been described with reference to FIG. 11, which is a case of a normal CP, for convenience of description. However, the above description may be equally applied to FIG. .

In addition, in Tables 2 to 5, the case in which the total number of downlink RBs is greater than 10 has been described as an example. For example, in Table 2, when the total number of downlink RBs is 10 or less, the starting PDSCH start point may be changed from the second, third, and fourth symbols to the third, fourth, and fifth symbols, respectively.

13 is a flowchart schematically illustrating an operation of a transmission point for transmitting control information, for example, a control signaling point, in a system to which the present invention is applied.

In a system to which JP-CoMP is applied, when a cell ID of each transmission point constituting a CoMP cooperation set is different, a point for transmitting control information determines a PDSCH muted in a corresponding subframe (S1310). In this case, the muted PDSCH may be specified by the start point of the PDSCH (the OFDM symbol at which the PDSCH starts) and the OFDM symbol at which the PDSCH is muted with respect to the CRS. In addition, the muted PDSCH may be specified only with OFDM symbols with muted PDSCH. The muted PDSCH has been described above in detail.

On the other hand, with respect to the starting point of the PDSCH in the subframe, a point for transmitting control information or a serving point may determine a CFI. As described above, the CFI indicates the number of OFDM symbols used for PDCCH transmission, and the starting point of the actual PDSCH may be determined according to the number of OFDM symbols indicated by the CFI and the OFDM symbol to which the PDSCH is muted.

In addition, regarding the start point of the PDSCH in the subframe, the point for transmitting control information may determine recovery of the PDSCH in the PDCCH region in the case of Dynamic Cell Selection (DCS) as described above.

In this case, the PDSCH muted in the corresponding subframe may be determined through a wired or wireless network between transmission points constituting a CoMP cooperative set.

The point for transmitting the control information configures downlink control information (DCI) including muting information of the PDSCH determined in step S1310 (S1320). The muting information included in the DCI may be a muting information index indicating a muting state of a corresponding subframe on the muting information table. In this case, the muting information table may be a table consisting of an OFDM symbol at which the PDSCH is muted with respect to the start point of the PDSCH and the CRS, for example, a table shown in Table 2. In addition, the muting information table may be a table consisting of OFDM symbols muted PDSCH, for example, a table such as Table 3. The muting information table may be previously stored in the point for transmitting the control information and the UE, or may be delivered to the UE through higher layer signaling from the point for transmitting the control information.

The point or the serving point for transmitting the control information transmits the DCI including the muting information of the PDSCH to the UE to which CoMP is applied (S1330). In this case, the UE may be a UE to which JP-CoMP is applied or a UE to which CS / CB other than JP is applied. The mute information table according to the present invention can support dynamically indicating a CoMP scheme other than JP-CoMP, as described in the examples of Tables 2 and 3. Therefore, the mute information index included in the DCI is not limited to JP-CoMP, and can also be dynamically indicated in the case of CS / CB.

14 is a diagram schematically illustrating an operation of a UE in a system to which the present invention is applied.

Referring to FIG. 14, in an environment in which CoMP is applied, the UE receives downlink transmission from each transmission point and receives a DCI from a point or serving point for transmitting control information (S1410). If the cell ID of each transmission point constituting the CoMP cooperation set is different, when JP-CoMP is performed, it is necessary to align the starting points of PDSCHs transmitted from each transmission point in the same subframe, or to prevent collision between the CRS and the PDSCH. There is.

The UE checks the muting information of the PDSCH included in the received DCI (S1420). As described above, the DCI received by the UE includes muting information of the PDSCH.

The muting information of the PDSCH included in the DCI may be a muting information index indicating a muting state of a corresponding subframe on the muting information table. In this case, the muting information table may be a table consisting of an OFDM symbol at which the PDSCH is muted with respect to the start point of the PDSCH and the CRS, for example, a table shown in Table 2. In addition, the muting information table may be a table consisting of OFDM symbols muted PDSCH, for example, a table such as Table 3. The muting information table may be previously stored in the point for transmitting the control information and the UE, or may be delivered to the UE through higher layer signaling from the point for transmitting the control information.

The UE combines the data received in the downlink (S1430). The UE may align the starting point of the PDSCH received from each transmission point of the CoMP cooperative set in the corresponding subframe and avoid collision of the CRS and the PDSCH based on the muting information of the PDSCH. Thus, the UE can successfully combine the data received from each transmission point.

15 is a diagram schematically illustrating a configuration of a UE in a system to which the present invention is applied.

Referring to FIG. 15, the UE 1510 includes an RF unit 1520, a memory 1530, and a processor 1540.

The UE 1510 performs communication through the RF unit 1520. The RF unit 1520 may be configured with multiple antennas, may support MIMO (Multi Input Multi Output), or may support CoMP.

The memory 1530 may store information necessary for the UE to perform communication. For example, the memory 1530 may store channel measurement information, a precoding matrix indicator, a codebook, and the like. In addition, the memory 1530 may store the above-described muting information table.

The processor 1540 implements the functions, processes, and / or methods proposed herein. For example, as described above, the processor 1540 may combine data received from each transmission point of the CoMP cooperation set based on the muting information received through the DCI.

In more detail, the processor 1540 may include a muting information detector 1550 and a data combiner 1560. The muting information detector 1550 may detect muting information for the corresponding subframe from the received DCI. The data combiner 1560 may successfully combine data received from each transmission point in the corresponding subframe based on the detected muting information.

16 is a block diagram schematically illustrating a configuration of a point for transmitting control information in a system to which the present invention is applied.

Referring to FIG. 16, a point 1610 that transmits control information includes a communication unit 1620, a memory 1630, and a processor 1640.

The point 1610 that transmits control information performs necessary communication through the communication unit 1620. The communication unit 1620 includes multiple antennas, and may communicate with the UE through this. The multiple antennas of the communication unit 1620 may support MIMO and CoMP. In addition, the communication unit 1620 may be connected to a transmission point constituting a CoMP cooperation set, for example, RRHs through a wired or wireless network, and may transmit and receive necessary information.

The memory 1630 may store information necessary for communication. For example, the memory 1630 may store measurement information received from the UE and a codebook for determining a precoding matrix. In addition, the memory 1630 may store the muting information table as described above.

The processor 1640 implements the functions, processes, and / or methods proposed herein. For example, as described above, the processor 1640 may determine the muting information, configure a DCI including the same, and transmit the muting information to the UE.

In detail, the processor 1640 may include a muting information determiner 1650 and a DCI component 1660. The muting information determiner 1650 may determine a PDSCH muted in a corresponding subframe as described above. The information on the muted PDSCH includes information about the starting point of the PDSCH and / or information about the recovery of the PDSCH in the PDCCH region. As described above, the muting information may be an index indicating a corresponding muting state in the muting information table. In addition, the DCI configuration unit 1660 may configure a DCI including the muting information determined by the muting information determiner 1650.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (9)

In a wireless communication system,
Controlling data channels transmitted from transmission points of a CoMP cooperative set with respect to control channels and reference signals transmitted from the transmission points in each subframe; And
Configuring downlink control information including information of the controlled data channel;
The controlling of the data channels may include: aligning start points of data channels transmitted from the transmission points in the subframe and mapping symbols of the data channel avoiding resources to which reference signals transmitted from the transmission points are mapped. ,
The information of the controlled data channel is an indicator indicating a resource region where the start point of the data channel and the data channel are not mapped in the subframe.
The indicator is an index indicating the start point of the data channel corresponding to the sub-frame and the region in which the data channel is not mapped on the table consisting of information on the start points of the data channel and the data channel mapping. Way. The method of claim 1, wherein the different transmission points have different cell identities. In a wireless communication system,
Controlling data channels transmitted from transmission points of a CoMP cooperative set with respect to control channels and reference signals transmitted from the transmission points in each subframe; And
Configuring downlink control information including information of the controlled data channel;
In the controlling of the data channels, a symbol of a data channel is mapped by avoiding a resource to which symbols of control channels transmitted from the transmission points are mapped in the subframe, and reference signals transmitted from the transmission points are mapped. Map the symbols of the data channel, avoiding the resources
The information of the controlled data channel is an indicator indicating a resource region to which a data channel is not mapped in the subframe.
And the indicator is an index indicating an area in which a data channel is not mapped in the subframe on a table configured with information on resources to which a symbol of a data channel is not allocated. 4. The method of claim 3, wherein the different transmission points have different cell IDs. In a wireless communication system,
Receiving data on data channels from the transmission points of the CoMP cooperative set in each subframe; And
Combining the received data based on information on a data channel included in downlink control information received from a control information transmission point among the transmission points,
The information about the data channel is an index indicating a region in which a data channel is not mapped and a start point of a data channel corresponding to the subframe on a table composed of data channel start points and data channel mapping.
In the step of combining the data,
A starting point of a data channel in the subframe, indicated by the index; And
Resources to which no symbol of the data channel is mapped in the subframe, indicated by the index;
And combining the data received from the transmission points based on the information about. The method of claim 5, wherein the cell IDs of the transmission points are different from each other. In a wireless communication system,
Receiving data on data channels from the transmission points of the CoMP cooperative set in each subframe; And
Combining the received data based on information on a data channel included in downlink control information received from a control information transmission point among the transmission points,
The information about the data channel is an index indicating an area in which a data channel is not mapped in the subframe on a table configured with information about resources to which symbols of the data channel are not allocated.
In the combining of the data, combining the data received from the transmission points based on information on resources to which the symbol of the data channel is not mapped in the subframe indicated by the index. The data reception method. 8. The method of claim 7, wherein the cell IDs of the transmission points are different from each other. In a wireless communication system, in the control information transmission method,
Generating control information indicating whether to mute the resource block occupied by the downlink data of the second cell corresponding to the start point of the downlink data region and the resource block occupied by the CRS of the first cell; and,
Transmitting the generated control information;
The start point of the downlink data region is designated by an OFDM symbol, the resource block occupied by the CRS is occupied corresponding to the number of antennas.

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