KR20100113040A - Method for transmitting downlink reference signal and appratus for the same - Google Patents

Abstract

PURPOSE: A downlink reference signal transmission method and an apparatus thereof are provided to improve the channel estimation performance by exclusively transmitting the exclusive reference signal with various control channels. CONSTITUTION: The data for less than two layers is transmitted through the data area of the downlink subframe. The reference signal arranged in the time-frequency domain is transmitted according to a first pattern in the first OFDM symbol group of the down link subframe(3112). The reference signal arranged in the time-frequency domain is transmitted according to the second pattern on the second OFDM symbol group of the down link subframe.

Description

TECHNICAL FOR TRANSMITTING DOWNLINK REFERENCE SIGNAL AND APPRATUS FOR THE SAME}

The following description relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting a downlink reference signal in a wireless communication system.

A multiple input multiple output (MIMO) system refers to a system that improves transmission and reception efficiency of data using multiple transmission antennas and multiple reception antennas. MIMO technology includes a spatial diversity technique and a spatial multiplexing technique. The spatial diversity scheme can increase transmission reliability or widen a cell radius through diversity gain, which is suitable for data transmission for a mobile terminal moving at high speed. Spatial multiplexing can increase the data rate without increasing the bandwidth of the system by simultaneously transmitting different data.

In the MIMO system, each transmit antenna has an independent data channel. Therefore, the receiver estimates a channel for each of the transmitting antennas and receives data transmitted from each transmitting antenna. Channel estimation refers to a process of restoring a received signal by compensating for distortion of a signal caused by fading. Here, fading refers to a phenomenon in which the strength of a signal is rapidly changed due to multipath-time delay in a wireless communication system environment. For channel estimation, a reference signal known to both the transmitter and the receiver is required. In addition, the reference signal may simply be referred to as a reference signal (RS) or a pilot according to the applied standard.

The downlink reference signal is a coherent such as a Physical Downlink Shared CHannel (PDSCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid Indicator CHannel (PHICH), and a Physical Downlink Control CHannel (PDCCH). Pilot signal for demodulation. The downlink reference signal includes a common reference signal (CRS) shared by all terminals in a cell and a dedicated reference signal (DRS) only for a specific terminal. The common reference signal may be called a cell-specific reference signal. The dedicated reference signal may also be called a UE-specific reference signal.

The dedicated reference signal is used to provide coherent demodulation of the terminal that performs beamforming. Channel estimation by the common reference signal is performed by interpolating and averaging reference signals in frequency domain and time domain other than the allocated bandwidth. The terminal measures the common reference signal and informs the base station of feedback information such as channel quality information (CQI), precoding matrix indicator (PMI), and rank indicator (RI). The base station may perform downlink frequency domain scheduling using the feedback information. Pseudo-random sequences may be used as the dedicated and common reference signals.

In arranging a dedicated reference signal and a common reference signal, there are various things to consider. The amount of radio resources to be allocated to the reference signal, the exclusive arrangement of the dedicated reference signal and the common reference signal, the location of the synchronization channel (hereinafter referred to as SCH) and broadcast channel (hereinafter referred to as BCH), the density of the dedicated reference signal, etc. This is it.

If a lot of resources are allocated to the reference signal, high channel estimation performance can be obtained because the density of the reference signal is high, while the data rate can be relatively low. If a small amount of resources are allocated to the reference signal, a high data rate can be obtained, but the density of the reference signal can be lowered, resulting in degradation of channel estimation performance.

In the case of beamforming transmission, since both the dedicated reference signal and the common reference signal are transmitted, there is a need for a method of arranging them so as not to overlap them. In addition, when a specific OFDM symbol is allocated for the transmission of the SCH and the BCH, the dedicated reference signal may not be transmitted. If the dedicated RS is not transmitted exclusively with the common RS or overlaps with the SCH or BCH, the UE may not be able to recover data.

Accordingly, there is a need for a method capable of efficiently transmitting a dedicated reference signal.

The present invention is to provide a method of transmitting a dedicated reference signal to reduce the loss caused during data recovery by efficiently placing the dedicated reference signal in a subframe.

In order to solve the above technical problem, the base station transmits a reference signal to the terminal using two or less layers according to an embodiment of the present invention. Transmitting data for the reference signal, transmitting the reference signal disposed in a time-frequency domain according to a first pattern on a first OFDM symbol group of the downlink subframe, and a second OFDM symbol of the downlink subframe Transmitting the reference signal arranged in a time-frequency domain according to a second pattern on a group, wherein the reference signal is a dedicated reference signal (DRS) for demodulating data for the two or less layers. The first OFDM symbol group is O where physical downlink control channel (PDCCH), cell-specific reference signal (CRS), synchronization channel (SCH) and broadcast channel (BCH) are located. OFDM symbols including the FDM symbols and the last OFDM symbol of the downlink subframe, wherein the second OFDM symbol group is the remaining OFDM symbols except for the OFDM symbols belonging to the first OFDM symbol group among the OFDM symbols included in the downlink subframe Can include them.

In addition, the first and second patterns may define that the reference signals are arranged at uniform subcarrier intervals on an OFDM symbol.

In addition, the first and second patterns may define that the reference signals are arranged at uniform OFDM symbol intervals.

In addition, the first and second patterns may define that more reference signals are disposed in the second OFDM symbol group than the first OFDM symbol group.

In addition, the first pattern may define that the reference signal is disposed in OFDM symbols in which the synchronization channel (SCH) and the broadcast channel (BCH) are located among the first OFDM symbol group.

In addition, the first pattern may define that the reference signal is not disposed on the first OFDM symbol group, and the second pattern may define that one or more reference signals are disposed on the second OFDM symbol group. Can be.

In addition, the first and second patterns are resource mapping in two resource blocks (RBs) contiguous in time of one subframe of the downlink subframe, that is, one TTI (or first and second slots of a subframe). The reference signal may be defined in 12 resource elements RE on an RB pair which may be a unit of.

In addition, the reference signals for the two layers may be multiplexed using one or more of a time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) scheme.

In order to solve the above technical problem, a method of processing a reference signal received from a base station by a terminal using two or less layers according to another embodiment of the present invention, the two or less through the data area of the downlink subframe Receiving data for a layer, receiving the reference signal disposed in a time-frequency domain according to a first pattern on a first OFDM symbol group of the downlink subframe, and a second OFDM of the downlink subframe Receiving the reference signal disposed in a time-frequency domain according to a second pattern on a symbol group, and estimating a channel to demodulate data for the two or less layers using the received reference signal. The first OFDM symbol group includes a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), a synchronization channel (SCH), and OFDM symbols including a broadcast channel (BCH) and a last OFDM symbol of the downlink subframe, wherein the second OFDM symbol group is the first OFDM symbol group among the OFDM symbols included in the downlink subframe It may include the remaining OFDM symbols except the OFDM symbols belonging to.

In order to solve the above technical problem, a base station for transmitting a reference signal to a terminal using two or less layers according to another embodiment of the present invention, a receiving module for receiving an uplink signal from the terminal, the downlink to the terminal A transmission module for transmitting a link signal, and a processor connected to the reception module and the transmission module and controlling the base station including the reception module and the transmission module, wherein the processor includes: Transmit data for the two layers or less through a data region of a downlink subframe, and transmit the reference signal arranged in a time-frequency region according to a first pattern on a first OFDM symbol group of the downlink subframe. In the time-frequency domain according to a second pattern on a second OFDM symbol group of the downlink subframe The reference signal is controlled to be transmitted, wherein the reference signal is a dedicated reference signal (DRS) for demodulating data for the two or less layers, and the first OFDM symbol group is a physical downlink control channel (PDCCH). And OFDM symbols in which a cell-specific reference signal (CRS), a synchronization channel (SCH) and a broadcast channel (BCH) are located, and a last OFDM symbol of the downlink subframe, wherein the second OFDM symbol group is The OFDM symbols included in the downlink subframe may include the remaining OFDM symbols except for the OFDM symbols belonging to the first OFDM symbol group.

In order to solve the above technical problem, a terminal for processing a reference signal received from a base station using two or less layers according to another embodiment of the present invention, a receiving module for receiving control information and data from the base station, the A transmission module for transmitting control information and data to a base station, and a processor connected to the reception module and the transmission module and controlling the terminal including the reception module and the transmission module. A module for receiving data for the two or less layers through a data region of a downlink subframe, and arranged in a time-frequency region according to a first pattern on a first OFDM symbol group of the downlink subframe Receive a reference signal, and a second on the second OFDM symbol group of the downlink subframe Control to receive the reference signal arranged in the time-frequency domain according to a pattern, and control the terminal to estimate a channel to demodulate data for the two or less layers using the received reference signal, The first OFDM symbol group includes OFDM symbols in which a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), a synchronization channel (SCH) and a broadcast channel (BCH) are located, and the last of the downlink subframe. The OFDM symbol group may include the remaining OFDM symbols except for the OFDM symbols belonging to the first OFDM symbol group among the OFDM symbols included in the downlink subframe.

According to the present invention, in a wireless communication system, a dedicated reference signal can be transmitted exclusively with various control channels, thereby improving channel estimation performance. In addition, by efficiently disposing within the subframe of the dedicated reference signal it is possible to reduce the loss caused during data recovery.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

1 is a block diagram showing the structure of a transmitter having multiple antennas.
2 illustrates a structure of a downlink radio frame.
3 is an exemplary diagram illustrating an example of a resource grid for one downlink slot.
4 is a diagram illustrating a subframe structure according to a general CP configuration.
5 to 30 illustrate embodiments of a pattern of a dedicated reference signal according to the present invention.
31 is a diagram showing the configuration of a preferred embodiment of a wireless communication system including a terminal apparatus and a base station apparatus according to the present invention.

The following embodiments are a combination of elements and features of the present invention in a predetermined form. Each component or feature may be considered to be optional unless otherwise stated. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some of the elements and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

In the present specification, embodiments of the present invention will be described based on a relationship between data transmission and reception between a base station and a terminal. Here, the base station has a meaning as a terminal node of the network that directly communicates with the terminal. The specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases.

That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. A 'base station (BS)' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point (AP), and the like. The repeater may be replaced by terms such as relay node (RN) and relay station (RS). In addition, the term “terminal” may be replaced with terms such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), a subscriber station (SS), and the like.

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802 system, 3GPP system, 3GPP LTE and LTE-Advanced (LTE-A) system and 3GPP2 system. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various radio access systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (Advanced) is the evolution of 3GPP LTE. WiMAX can be described by the IEEE 802.16e standard (WirelessMAN-OFDMA Reference System) and the advanced IEEE 802.16m standard (WirelessMAN-OFDMA Advanced system). For clarity, the following description focuses on the 3GPP LTE standard, but the technical spirit of the present invention is not limited thereto.

1 is a block diagram showing the structure of a transmitter having multiple antennas.

Referring to FIG. 1, the transmitter 100 includes an encoder (110-1, ..., 110-K), a modulation mapper (120-1, ..., 120-K) (or a modulator, Modulator, layer mapper 130, precoder 140, resource element mapper 150-1, ..., 150-K (or subcarrier mapper) and OFDM Signal generators 160-1, ..., 160-K. The transmitter 100 includes Nt transmit antennas 170-1,..., 170 -Nt.

The encoders 110-1, ..., 110-K encode the input data according to a predetermined coding scheme to form coded data. The modulation mapper 120-1, ..., 120-K maps the coded data to modulation symbols representing positions on the signal constellation. The modulation scheme is not limited and may be m-Phase Shift Keying (m-PSK) or m-Quadrature Amplitude Modulation (m-QAM). For example, m-PSK may be BPSK, QPSK or 8-PSK. m-QAM may be 16-QAM, 64-QAM or 256-QAM.

The layer mapper 130 defines a layer of modulation symbols so that the precoder 140 can distribute antenna-specific symbols to the paths of the respective antennas. The layer is defined as an information path input to the precoder 140. The information path before the precoder 140 may be referred to as a virtual antenna or a layer.

The precoder 140 outputs an antenna specific symbol by processing the modulation symbol by a MIMO scheme according to the multiple transmit antennas 170-1,..., 170 -Nt. The precoder 140 distributes the antenna specific symbol to the resource element mappers 150-1,..., 150 -K of the path of the corresponding antenna. Each information path sent by the precoder 140 to one antenna is called a stream. This may be referred to as a physical antenna.

The resource element mapper 150-1,..., 150 -K allocates an antenna specific symbol to an appropriate resource element and multiplexes according to a user. The OFDM signal generators 160-1,..., 160 -K output an OFDM symbol by modulating the antenna specific symbol by the OFDM scheme. The OFDM signal generators 160-1, ..., 160-K may perform an inverse fast fourier transform (IFFT) on an antenna specific symbol, and a cyclic prefix (CP) is inserted into the time domain symbol on which the IFFT is performed. Can be. The CP is a signal inserted in a guard interval to remove inter-symbol interference due to multiple paths in the OFDM transmission scheme. The OFDM symbol is transmitted through each transmit antenna 170-1,..., 170 -Nt.

2 shows a structure of a downlink radio frame.

Referring to FIG. 2, a downlink radio frame consists of 10 subframes, and one subframe consists of two slots. The downlink radio frame may be configured by frequency division duplex (FDD) or time division duplex (TDD). The time it takes for one subframe to be transmitted is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms. One slot includes a plurality of OFDM symbols in the time domain and includes a plurality of resource blocks (RBs) in the frequency domain.

The number of OFDM symbols included in one slot may vary depending on the configuration of the CP. CP has an extended CP (normal CP) and a normal CP (normal CP). For example, when an OFDM symbol is configured by a general CP, the number of OFDM symbols included in one slot may be seven. When the OFDM symbol is configured by an extended CP, since the length of one OFDM symbol is increased, the number of OFDM symbols included in one slot is smaller than that of the normal CP. In the case of an extended CP, for example, the number of OFDM symbols included in one slot may be six. If the channel state is unstable, such as when the terminal moves at a high speed, an extended CP may be used to further reduce intersymbol interference.

When a general CP is used, since one slot includes 7 OFDM symbols, one subframe includes 14 OFDM symbols. In this case, the first two or three OFDM symbols of each subframe may be allocated to a physical downlink control channel (PDCCH), and the remaining OFDM symbols may be allocated to a physical downlink shared channel (PDSCH).

The structure of the radio frame is only an example, and the number of subframes included in the radio frame or the number of slots included in the subframe and the number of symbols included in the slot may be variously changed.

3 is an exemplary diagram illustrating an example of a resource grid for one downlink slot. This is the case in which an OFDM symbol consists of a normal CP. Referring to FIG. 3, the downlink slot includes a plurality of OFDM symbols in the time domain and includes a plurality of resource blocks (RBs) in the frequency domain. Here, one downlink slot includes 7 OFDM symbols and one resource block includes 12 subcarriers, but is not limited thereto. Each element on the resource grid is called a resource element (RE). For example, the resource element a (k, l) becomes a resource element located in the k-th subcarrier and the l-th OFDM symbol. One resource block includes 12 × 7 resource elements. Since the interval of each subcarrier is 15 kHz, one resource block includes about 180 kHz in the frequency domain. N ^DL is the number of resource blocks included in the downlink slot. The value of N ^DL may be determined according to a downlink transmission bandwidth set by scheduling of the base station.

4 is a diagram illustrating a resource element to which a reference signal, a synchronization channel, and a broadcast channel are mapped when a general CP is used. In FIG. 4, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. 4 corresponds to two slots constituting one subframe in the time domain, and corresponds to subcarriers constituting a resource block of one slot in the frequency domain. For example, two resource blocks (resource block pairs) contiguous in time of one subframe of FIG. 4 may consist of 14 OFDM symbols in the time domain and 12 subcarriers in the frequency domain. The smallest rectangular area in the time-frequency domain shown in FIG. 4 is an area corresponding to one OFDM symbol in the time domain and one subcarrier in the frequency domain.

Referring to FIG. 4, Rp indicates a resource element used for transmitting a reference signal on a pth antenna port. For example, R0 to R3 represent resource elements to which common reference signals transmitted from the 0 to third antenna ports are mapped, and R5 represents resource elements to which dedicated reference signals transmitted to the fifth antenna port are mapped. The common reference signals transmitted by the zeroth and first antenna ports are transmitted at six subcarrier intervals (based on one antenna port) on the zeroth, fourth, seventh, and eleventh OFDM symbols. The common reference signals transmitted by the second and third antenna ports are transmitted at six subcarrier intervals (based on one antenna port) on the first and eighth OFDM symbols. The dedicated reference signal is transmitted in four subcarrier intervals on the third, sixth, ninth and twelfth OFDM symbols of every subframe. Accordingly, 12 dedicated reference signals are transmitted in two consecutive resource blocks (resource block pairs) in time of one subframe.

In addition, although not shown in FIG. 4, R4 may indicate a resource element used for transmitting a reference signal of a multicast broadcast single frequency network (MBSFN) in a fourth antenna port. The positions of each of R0 to R5 are arranged not to overlap.

On the other hand, the synchronization signal is a physical layer signal used for cell-search (cell-search), there is a primary synchronization signal (primary synchronization signal) and the secondary synchronization signal (secondary synchronization signal). The physical channel through which the primary synchronization signal is transmitted is called a primary-synchronization channel (P-SCH), and the physical channel through which the secondary synchronization signal is transmitted is called a secondary-synchronization channel (S-SCH).

The main synchronization signal is a signal used for the terminal to synchronize slot synchronization during initial cell search and may be generated by a ZADoff-Chu sequence in the frequency domain. If the downlink radio frame is a structure supporting FDD, the main synchronization signal is the last OFDM symbol of the 0th and 10th slots of every radio frame (i.e., the 6th subframe at 5 subframe periods) as shown in FIG. May be mapped to an OFDM symbol). If the downlink radio frame has a structure supporting TDD, the main synchronization signal may be mapped to third OFDM symbols of the first and sixth subframes (not shown).

The auxiliary synchronization signal is a signal used for frame synchronization after the terminal synchronizes slot synchronization, and may be defined as a combination of two 31-bit sequences. As shown in FIG. 4 of each radio frame, the auxiliary synchronization signal may be mapped to fifth OFDM symbols of the 0th and 10th slots of the radio frame (that is, the fifth OFDM symbol of the subframe in 5 subframe periods).

The physical broadcast channel (P-BCH) is a channel for transmitting system information of a cell. As illustrated in FIG. 4, the P-BCH may be mapped to seventh through ninth OFDM symbols in one subframe and transmitted in a period of 10 subframes. However, it is mapped only to subcarriers at positions other than R0 to R3 which are resource elements allocated as the common reference signal.

Here, the resource element to which the SCH and the P-BCH are mapped may overlap with the resource element to which data is transmitted or the resource element to which a dedicated reference signal is transmitted. For example, when the downlink radio frame has a structure supporting FDD, the fifth to ninth OFDM symbols are occupied by SCHs or P-BCHs, and are dedicated reference signals mapped to R5 on the sixth and ninth OFDM symbols. Overlap Therefore, the dedicated reference signal is punctured and not transmitted in the OFDM symbol of this period. Similar problems may occur when the downlink radio frame has a structure supporting TDD. Therefore, when the dedicated reference signal is disposed, the positions of the SCH and the P-BCH should be taken into consideration, and the dedicated reference signal may be positioned in at least one symbol period in symbols other than the OFDM symbols in which the SCH and the P-BCH are transmitted. In addition, considerations in the arrangement of dedicated reference signals include PDSCH decoding, transmission density of dedicated reference signals, robustness in a high-speed mobile environment, frequency selective channel, support for distributed mode, and PDCCH. Number of OFDM symbols; In addition, since FIG. 4 is a case of a general CP, how to arrange a dedicated reference signal in case of an extended CP.

The aforementioned cell-specific reference signal is used for estimating a channel of a physical antenna terminal and is a reference signal commonly transmitted to all UEs in a cell. The channel information estimated by the UE through the cell-specific reference signal includes single antenna transmission, transmit diversity, closed-loop spatial multiplexing, and open-loop spatial multiplexing. (Open-loop Spatial multiplexing), it can be used for demodulation of data transmitted by a transmission scheme such as multi-user MIMO (MU-MIMO), and the terminal measures the channel and reports to the base station Can be used as In order to improve channel estimation performance through the cell-specific reference signal, the cell-specific reference signal may be shifted by shifting the position in the subframe of the cell-specific reference signal. For example, when the reference signal is located every three subcarriers, one cell may be arranged at a subcarrier spacing of 3k and another cell at a subcarrier spacing of 3k + 1.

The dedicated reference signal is a terminal-specific reference signal used for data demodulation. When a multi-antenna transmission is performed, a precoding weight used for a specific terminal is also used for the reference signal. Equivalent channel combined with the transmitted precoding weight and the transmission channel can be estimated. Since the dedicated reference signal requires orthogonality between the transport layers, the pattern of the reference signal may be defined differently according to the transmission rank.

Existing 3GPP LTE systems support transmission of up to 4 transmit antennas, and cell-specific reference signals for supporting a single transmit antenna, 2 transmit antennas, and 4 transmit antennas are defined, and dedicated reference signals for rank 1 beamforming are defined. Meanwhile, in the LTE-A (Advanced) system, which is the evolution of 3GPP LTE, high order MIMO, multi-cell transmission, and advanced multi-user-MIMO are considered, which supports efficient reference signal operation and advanced transmission scheme. In order to solve this problem, data demodulation based on a dedicated reference signal is considered. In the LTE-A system, an 8 transmit antenna RS structure is provided to support an 8 transmit antenna MIMO scheme, and a measurement reference signal and a dedicated reference signal may be separated and transmitted to reduce RS overhead. In the case of the dedicated reference signal, the reference signal structure may be optimized by further reducing the reference signal overhead by using the precoded reference signal and transmitting the measurement reference signal in a low duty cycle. In addition, the dedicated reference signal is preferably set to exist only in the resource block and layer scheduled downlink transmission by the base station.

In order to satisfy the above requirements, the newly defined dedicated reference signal can support rank 8 and support dual stream beamforming, cooperative multi-point transmission, and advanced multi-user-MIMO together. To this end, the following may be considered.

Transmitting a reference signal with a high density to improve channel estimation performance may satisfy a target performance of a user who requires high channel estimation performance, but in some users, a wasteful pilot may occur. On the contrary, when a low density reference signal is transmitted to increase system yield, a user may have a high data rate but an increased bit error. For example, a user with a fast moving speed experiences a rapidly changing channel, and since the correlation time is short, a narrow reference signal structure is suitable to obtain a desired channel estimation performance. However, some users may be stationary, and in this case, since the correlation time is long, excellent channel estimation performance can be obtained even with wide reference signal intervals. Therefore, in consideration of the reference signal density and the channel estimation performance, a method of transmitting a reference signal having a proper reference signal density and a pattern on the time domain and the frequency domain should be considered.

In the LTE-A system, a cell-specific reference signal needs to be always transmitted so that an existing LTE system can operate. The cell-specific reference signal may be a reference signal for a single transmit antenna, 2 transmit antennas, and 4 transmit antennas. In designing a dedicated reference signal, a frequency shift of a cell-specific reference signal may be considered. The dedicated reference signal may be located on the same OFDM symbol as the cell-specific reference signal or may be located on an OFDM symbol that does not include the cell-specific reference signal.

In the LTE-A system, it is required to support two types of reference signals: a reference signal for PDSCH demodulation and a reference signal for channel state information (CSI) measurement. The above-mentioned dedicated reference signal (DRS) may also be referred to as a demodulation reference signal (DM RS) and is distinguished from a reference signal for CSI measurement. One or two reference signals for the CSI measurement may exist in one subframe, and the reference signal and the dedicated reference signal for the CSI measurement may be designed not to be located together on one OFDM symbol.

In consideration of the puncturing of data and dedicated reference signals to resource elements to which SCHs and BCHs are mapped, a dedicated reference signal may be included in at least one OFDM symbol except for OFDM symbols to which SCHs and BCHs are mapped. In addition, in the backhaul link between the repeater and the base station, a transition of subframe timing may be required for timing alignment and the like, and for this purpose, the last OFDM symbol of the subframe may be punctured. Therefore, it is possible to design such that a dedicated reference signal is not disposed at the position of the last OFDM symbol of the subframe.

In dual stream beamforming, a dedicated reference signal for rank 2 beamforming may be designed to reuse a dedicated reference signal pattern for rank 1 beamforming. In this case, the two layers can be multiplexed using code division multiplexing (CDM), time division multiplexing (TDM) or frequency division multiplexing (FDM). In addition, when transmitting a reference signal of rank 2 or more using two or more layers, reference signals through each layer may be multiplexed using a CDM in a specific time-frequency domain, or additionally, TDM or FDM between time-frequency domains. It is also possible to transmit a dedicated reference signal by multiplexing using.

In addition, demodulation may be performed on a frequency domain and a time domain to which the dedicated reference signal is not allocated by interpolating or extrapolating the dedicated reference signal. Channel estimation by extrapolation may have lower channel estimation performance than the case of interpolation. Therefore, it may be considered to reduce the extrapolated channel estimation by placing a dedicated reference signal at the end of the time-frequency domain of two consecutive resource blocks (resource block pairs) in time of one subframe.

Thus, in the case of a general CP configuration in which one subframe includes 14 OFDM symbols (0 th to 13 th OFDM symbols), the PDCCH region is located in the 0 th to 2 nd OFDM symbols, and the cell-specific reference signal is generated by the first CP. Located in 0, 1, 4, 7, 8, and 11 OFDM symbols, SCH is located in the fifth and sixth OFDM symbol, BCH may be located in the seventh, eighth and ninth OFDM symbol. . In addition, the thirteenth OFDM symbol may be punctured according to the subframe timing shift. Therefore, the dedicated reference signal needs to be designed to be located in at least one of the third, tenth and twelfth OFDM symbols.

In consideration of the above, it is necessary to design a pattern of the dedicated reference signal so that demodulation of data by channel estimation using the dedicated reference signal is efficiently performed.

In the following embodiments, a general CP configuration that configures one subframe using 14 OFDM symbols will be mainly described. However, when one subframe is configured with fewer than 14 OFDM symbols as in the case of an extended CP configuration in which one subframe includes 12 OFDM symbols, a dedicated reference signal is described in the following embodiments. The OFDM symbol including the cell-specific reference signal and the reference signal for CSI measurement is included in a subframe, and in the following embodiments, the OFDM symbol including only data without reference signal is allocated is excluded from the subframe. One subframe may be configured.

The present invention proposes a dedicated reference signal pattern for each layer (antenna port) up to rank 2 as described in the following embodiments.

Regarding the dedicated reference signal pattern according to FDM or TDM in the case of rank 2 transmission, the position indicated by 'A' in the time-frequency domain in the figure and related description showing the resource element RE to which the present invention is applied is The position of the dedicated reference signal with respect to one layer (antenna port) is shown, and the position marked with 'B' indicates the position of the dedicated reference signal with respect to the second layer (antenna port). Alternatively, 'A' may indicate the position of the dedicated reference signal for the layer (antenna port) and 'B' may indicate the position of the dedicated reference signal for the second layer (antenna port).

In the case of rank 2 transmission, a dedicated reference signal for two layers multiplexed using the CDM may be multiplexed using various codes. For example, Hadamard, Discrete Fourier Transform (DFT), Walsh, Constant Amplitude Zero Autocorrelation Waveform (CAZAC), Pseudo Noise (PN) sequence, and the like may be used. In the drawings and related description, the position indicated as 'A / B' on one resource element indicates the position of the dedicated reference signal for the first and second layers multiplexed using the CDM.

In the case of rank 1 transmission, both A and B positions may be used as positions of reference signals for one layer (antenna port).

In the following embodiments, a dedicated reference signal pattern may be configured in consideration of the following matters.

In order to reduce the occurrence of symbol power fluctuation during power boosting of the dedicated reference signal, the dedicated reference signal for each antenna port may be equally allocated in one subframe. Meanwhile, in order to further improve channel estimation performance for one layer, more dedicated reference signals for one layer may be allocated in one subframe than other layers.

In order to make the channel estimation performance through the dedicated reference signal robust to the time-selective characteristic, the symbol interval may be narrowly arranged in a manner that encompasses the time domain of one subframe. Alternatively, the subcarrier spacing may be narrowly arranged in such a manner as to cover the frequency domain of one subframe such that channel estimation performance through the dedicated reference signal is robust to the frequency selective characteristic.

In consideration of low mobility, the positions of the dedicated reference signals may be densely arranged in a specific time domain. On the other hand, in consideration of high mobility, the position of the dedicated reference signal may be widely arranged in a manner that encompasses the time domain of one subframe.

In designing a dedicated reference signal pattern, in consideration of the frequency shift of the cell-specific reference signal, a margin for the dedicated reference signal is not disposed on a subcarrier may be provided to increase scalability with respect to the frequency shift. Alternatively, the dedicated reference signal may be positioned in the first and last subcarriers as much as possible to prevent degradation of channel estimation performance caused by extrapolating the dedicated reference signal to estimate the channel.

In the following embodiments, 14 OFDM symbols are classified into two groups in the case of a general CP configuration. The first OFDM symbol group includes the 0th to 2nd OFDM symbols to which the PDCCH region is allocated, the 0th, 1st, 4th, 7th, 8th, and 11th OFDM symbols where the cell-specific reference signal is located, and the SCH is located. A fifth and sixth OFDM symbol, a seventh, eighth and ninth OFDM symbol in which a BCH is located, and a thirteenth OFDM symbol punctured according to a subframe timing transition. That is, the first OFDM symbol group includes the 0 to 2nd, 4th to 9th, 11th, and 13th OFDM symbols.

Meanwhile, the third, tenth, and twelfth OFDM symbols not included in the first OFDM symbol group are included in the second OFDM symbol group. In order to guarantee transmission of the dedicated reference signal, at least one dedicated reference signal should be allocated to the second OFDM symbol group, and as many dedicated reference signals as possible should be allocated.

In this regard, as described above, by extrapolating / extrapolating the dedicated reference signal to the resource element to which the dedicated reference signal is not allocated, the channel for the corresponding resource element is estimated to restore the data. Therefore, if all dedicated reference signals are allocated only to the second OFDM symbol group, there is a possibility that the channel estimation performance becomes inefficient. Therefore, there is a need to properly arrange the dedicated reference signal in the first OFDM symbol group in some cases.

In addition, the SCH and the BCH are transmitted in 5 subframe and 10 subframe periods, respectively, so that the dedicated reference signals are not punctured on the fifth to ninth OFDM symbols in all subframes. The pattern may be designed by placing a part of the dedicated reference signal on the fifth to ninth OFDM symbols.

In the following embodiments, a dedicated reference signal is not disposed in the first to second OFDM symbols allocated to the PDCCH and the thirteenth OFDM symbol that may be punctured according to the subframe timing transition. Design. A dedicated reference signal may not be disposed in the remaining OFDM symbols (fourth through ninth and eleventh OFDM symbols) of the first OFDM symbol group, and a portion of the dedicated reference signal may be disposed. At least one dedicated reference signal is disposed on the second OFDM symbol.

5 to 30 of various embodiments of the present invention, a resource element to which the dedicated reference signal is mapped in one subframe according to the general CP configuration is shown, the horizontal axis is a time domain, the vertical axis is a frequency domain Indicates. The smallest rectangular area in the time-frequency domain shown in FIGS. 5 to 30 is an area corresponding to one OFDM symbol in the time domain and one subcarrier in the frequency domain. In addition, the position of the dedicated reference signal may be represented by (OFDM symbol index l, subcarrier index k).

Example  1 (Figure 5)

A (l, k) = {(3,3), (3,7), (3,11), (6,1), (6,5), (6,9)}

B (l, k) = {(9,3), (9,7), (9,11), (12,1), (12,5), (12,9)}

With reference to FIG. 5, an embodiment in which an existing dedicated reference signal pattern for rank 1 beamforming is reused is proposed. In FIG. 4, the dedicated reference signal A for the first layer and the dedicated reference signal B for the second layer are distributed at equal ratios at positions R5 in FIG. 4. Dedicated reference signals A and B supporting maximum rank 2 transmission in two consecutive resource blocks (resource block pairs) in time of one subframe are arranged in 12 resource elements.

Regarding the meanings of A and B indicating dedicated reference signals for this embodiment and the following embodiments, in case of rank 2 transmission, A corresponds to the first layer and B corresponds to the first layer in the dedicated reference signal pattern according to FDM or TDM. It should be noted that may correspond to the second layer, A may correspond to the second layer and B may correspond to the first layer. In addition, it should be noted that A and B may be multiplexed by the CDM method in each of the illustrated dedicated reference signal positions, and in the case of rank 1 transmission, both A and B positions may be used as reference signal positions for one layer. do.

Dedicated reference signals are allocated to two (sixth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. Three dedicated reference signals are allocated to one OFDM symbol at equal intervals of four subcarrier intervals. The dedicated reference signal is not disposed in the OFDM symbol where the cell-specific reference signal is located.

Example  2 (Figure 6)

A (l, k) = {(3,3), (3,7), (3,11), (9,1), (9,5), (9,9)}

B (l, k) = {(6,3), (6,7), (6,11), (12,1), (12,5), (12,9)}

Referring to FIG. 6, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (sixth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. Three dedicated reference signals are allocated to one OFDM symbol at equal intervals of four subcarrier intervals.

Example  3 (FIG. 7)

A (l, k) = {(3,0), (3,5), (3,10), (9,0), (9,5), (9,10)}

B (l, k) = {(5,0), (5,5), (5,10), (12,1), (12,5), (12,9)}

Referring to FIG. 7, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (fifth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. Three dedicated reference signals are allocated to one OFDM symbol at equal intervals of five subcarrier intervals. By covering the range of the third to twelfth OFDM symbols and the range of the zeroth to tenth subcarriers, channel estimation due to extrapolation of a dedicated reference signal can be reduced, thereby improving channel estimation performance.

Example  4 (FIG. 8)

A (l, k) = {(3,0), (3,2), (3,10), (10,1), (10,9), (10,11)}

B (l, k) = {(3,1), (3,9), (3,11), (10,0), (10,2), (10,10)}

Referring to FIG. 8, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is not allocated to the first OFDM symbol group, and a dedicated reference signal is allocated to two (third and tenth) OFDM symbols of the second OFDM symbol group. In one OFDM symbol, six dedicated reference signals are allocated at intervals of 1 or 7 subcarriers for rank 1 transmission, and three dedicated reference signals are allocated for each layer at intervals of 2 or 8 subcarriers for rank 2 transmission. The dedicated reference signal is not disposed at the OFDM symbol position where the cell-specific reference signal, SCH and BCH exist.

Example  5 (Fig. 9)

A (l, k) = {(3,0), (3,5), (3,10), (10,1), (10,6), (10,11)}

B (l, k) = {(3,1), (3,6), (3,12), (10,0), (10,5), (10,10)}

Referring to FIG. 9, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is not allocated to the first OFDM symbol group, and a dedicated reference signal is allocated to two (third and tenth) OFDM symbols of the second OFDM symbol group. Six dedicated reference signals are allocated to one OFDM symbol at intervals of 1 or 4 subcarriers for rank 1 transmission, and three dedicated reference signals are allocated for each layer at equal intervals of 5 subcarrier intervals for rank 2 transmission.

Example  6 (Figure 10)

A (l, k) = {(3,0), (3,10), (5,5), (8,6), (10,1), (10,11)}

B (l, k) = {(3,1), (3,11), (5,6), (8,5), (10,0), (10,10)}

Referring to FIG. 10, in the present embodiment, A and B are disposed in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (fiveth and eighth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and tenth) OFDM symbols of the second OFDM symbol group. Two dedicated reference signals are allocated to one OFDM symbol belonging to the first OFDM symbol group at one subcarrier interval for rank 1 transmission, and one dedicated reference signal for each layer is allocated to rank 2 transmission. One dedicated OFDM symbol belonging to the second OFDM symbol group is allocated four dedicated reference signals at intervals of 1 or 9 subcarriers for rank 1 transmission, and two dedicated signals per layer at equal intervals of 10 subcarrier intervals for rank 2 transmission. The reference signal is assigned.

Example  7 (FIG. 11)

A (l, k) = {(3,0), (3,4), (3,8), (10,3), (10,7), (10,11)}

B (l, k) = {(5,0), (5,4), (5,8), (12,3), (12,7), (12,11)}

Referring to FIG. 11, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to one (fifth) OFDM symbol of the first OFDM symbol group, and dedicated reference signals are allocated to three (third, tenth, and twelfth) OFDM symbols of the second OFDM symbol group. Dedicated reference signals are allocated to three subcarrier positions at equal intervals of four subcarrier intervals in one OFDM symbol.

Example  8 (Figure 12)

A (l, k) = {(3,0), (3,4), (3,8), (10,2), (10,6), (10,10)}

B (l, k) = {(5,0), (5,4), (5,8), (12,2), (12,6), (12,10)}

Referring to FIG. 12, in the present embodiment, A and B are disposed in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to one (fifth) OFDM symbol of the first OFDM symbol group, and dedicated reference signals are allocated to three (third, tenth, and twelfth) OFDM symbols of the second OFDM symbol group. Three dedicated reference signals are allocated to one OFDM symbol at equal intervals of four subcarrier intervals.

Example  9 (Fig. 13)

A (l, k) = {(3,0), (3,6), (5,3), (5,9), (10,0), (10,6), (12,3), (12,9)}

B (l, k) = {(3,3), (3,6), (12,0), (12,6)}

Referring to FIG. 13, A is arranged in eight resource elements and B is arranged in four resource elements within two consecutive resource blocks (resource block pairs) in time of one subframe. By varying the density of the dedicated reference signal for each layer, channel estimation performance of a layer having a high density dedicated reference signal can be improved. Dedicated reference signals are allocated to one (fifth) OFDM symbol of the first OFDM symbol group, and dedicated reference signals are allocated to three (third, tenth, and twelfth) OFDM symbols of the second OFDM symbol group. Only two dedicated reference signals for one layer are arranged in one OFDM symbol belonging to the first OFDM symbol group at equal intervals of six subcarrier intervals. One dedicated OFDM symbol belonging to the second OFDM symbol group is allocated four dedicated reference signals at equal intervals of three subcarrier intervals for rank 1 transmission, and two dedicated at equal intervals of six subcarrier intervals for rank 2 transmission. The reference signal is assigned.

Example  10 (FIG. 14)

A (l, k) = {(3,0), (3,7), (8,1), (8,8), (12,4), (12,10)}

B (l, k) = {(3,4), (3,10), (6,1), (6,8), (12,0), (12,7)}

Referring to FIG. 14, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (sixth and eighth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. For rank 1 transmission, two dedicated reference signals are allocated to one OFDM symbol belonging to the first OFDM symbol group at seven subcarrier intervals. For rank 2 transmission, two dedicated reference signals for one layer are allocated to one OFDM symbol belonging to the first OFDM symbol group at seven subcarrier intervals, and the other OFDM symbol is allocated to another layer at seven subcarrier intervals. Two dedicated reference signals are allocated. One dedicated OFDM symbol belonging to the second OFDM symbol group is allocated four dedicated reference signals at intervals of three or four subcarriers for rank 1 transmission, and two dedicated references for each layer at six or seven subcarrier intervals for rank 2 transmission. The signal is assigned.

Example  11 (Fig. 15)

A (l, k) = {(3,0), (3,6), (8,3), (8,9), (12,0), (12,6)}

B (l, k) = {(3,3), (3,9), (8,0), (8,6), (12,3), (12,9)}

Referring to FIG. 15, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is allocated to one (eighth) OFDM symbol of the first OFDM symbol group, and a dedicated reference signal is allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. Four dedicated reference signals are allocated to one OFDM symbol at equal intervals of three subcarrier intervals for rank 1 transmission, and two dedicated reference signals are allocated for each layer at equal intervals of six subcarrier intervals for rank 2 transmission.

Example  12 (FIG. 16)

A (l, k) = {(3,0), (3,6), (6,3), (6,9), (9,0), (9,6), (12,3), (12,9)}

B (l, k) = {(3,3), (3,9), (6,3), (6,9), (9,0), (9,6), (12,0), (12,6)}

Referring to FIG. 16, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (sixth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group.

One OFDM symbol belonging to the first OFDM symbol group is allocated a dedicated reference signal A / B multiplexed by CDM at two subcarrier positions at intervals of six subcarriers. In this regard, the resource element positions {(6,3), (6,9), (9,0), and (9,6)} are denoted by A / B, which is a single CDM scheme as described above. This means that two dedicated reference signals are multiplexed using an orthogonal code in a resource element. Accordingly, eight dedicated reference signals are allocated to each of the first and second layers in two consecutive resource blocks (resource block pairs) in time of one subframe.

Four dedicated reference signals are allocated to one OFDM symbol belonging to the second OFDM symbol group at equal intervals of three subcarrier intervals for rank 1 transmission, and two each for each layer at equal intervals of six subcarrier intervals for rank 2 transmission. A dedicated reference signal is assigned.

Example  13 (Fig. 17)

A (l, k) = {(3,0), (3,9), (6,3), (9,6), (12,0), (12,9)}

B (l, k) = {(5,0), (5,9), (6,6), (9,3), (10,0), (10,9)}

Referring to FIG. 17, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to three (5th, 6th, and 9th) OFDM symbols of the first OFDM symbol group, and dedicated to three (3rd, 10th, and 12th) OFDM symbols of the second OFDM symbol group. The reference signal is assigned. Two dedicated reference signals for one layer are allocated at intervals of nine subcarriers in one OFDM symbol belonging to the first OFDM symbol group, or one dedicated reference signal is allocated for each layer at three subcarrier intervals. Two dedicated reference signals for one layer are allocated to one OFDM symbol belonging to the second OFDM symbol group at nine subcarrier intervals.

Example  14 (Fig. 18)

A (l, k) = {(3,0), (3,9), (6,3), (9,6), (12,0), (12,9)}

B (l, k) = {(3,0), (3,9), (6,3), (9,6), (12,0), (12,9)}

Referring to FIG. 18, A and B are arranged in six resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (sixth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. A single OFDM symbol belonging to the first OFDM symbol group is allocated a dedicated reference signal (A / B) multiplexed in the CDM scheme to one subcarrier position. One OFDM symbol belonging to the second OFDM symbol group is allocated a dedicated reference signal (A / B) multiplexed by the CDM method at two subcarrier positions at intervals of nine subcarriers. Accordingly, six dedicated reference signals are allocated to each of the first and second layers in two consecutive resource blocks (resource block pairs) in time of one subframe.

Example  15 (FIG. 19)

A (l, k) = {(3,0), (3,9), (6,3), (9,6), (12,0), (12,9)}

B (l, k) = {(3,0), (3,9), (6,6), (9,3), (12,0), (12,9)}

Referring to FIG. 19, A and B are arranged in eight resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (sixth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. Two dedicated reference signals are allocated to one OFDM symbol belonging to the first OFDM symbol group at three subcarrier intervals, and each of the two dedicated reference signals is allocated to each layer for rank 2 transmission. One OFDM symbol belonging to the second OFDM symbol group is allocated a dedicated reference signal (A / B) multiplexed by the CDM method at two subcarrier positions at intervals of nine subcarriers. Accordingly, six dedicated reference signals are allocated to each of the first and second layers in two consecutive resource blocks (resource block pairs) in time of one subframe.

Example  16 (Fig. 20)

A (l, k) = {(3,0), (3,6), (6,3), (9,6), (12,2), (12,8)}

B (l, k) = {(3,3), (3,9), (6,6), (9,9), (12,5), (12,11)}

Referring to FIG. 20, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (sixth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. Two dedicated reference signals are allocated to one OFDM symbol belonging to the first OFDM symbol group at three subcarrier intervals, and each of the two dedicated reference signals is allocated to each layer for rank 2 transmission. Four dedicated reference signals are allocated to one OFDM symbol belonging to the second OFDM symbol group at equal intervals of three subcarrier intervals for rank 1 transmission, and two dedicated reference signals for each layer at six subcarrier intervals for rank 2 transmission. Is assigned.

Example  17 (Figure 21)

A (l, k) = {(3,0), (3,6), (6,4), (6,10), (12,3), (12,9)}

B (l, k) = {(3,3), (3,9), (6,1), (6,7), (12,0), (12,6)}

Referring to FIG. 21, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is allocated to one (sixth) OFDM symbol of the first OFDM symbol group, and a dedicated reference signal is allocated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. Four dedicated reference signals are allocated to one OFDM symbol belonging to the first OFDM symbol group at equal intervals of three subcarrier intervals for rank 1 transmission, and two dedicated reference signals for each layer at six subcarrier intervals for rank 2 transmission. Is assigned. Four dedicated reference signals are allocated to one OFDM symbol belonging to the second OFDM symbol group at equal intervals of three subcarrier intervals for rank 1 transmission, and two dedicated reference signals for each layer at six subcarrier intervals for rank 2 transmission. Is assigned.

Example  18 (Fig. 22)

A (l, k) = {(4,1), (4,7), (8,4), (8,10), (12,1), (12,7)}

B (l, k) = {(4,4), (4,10), (8,1), (8,7), (12,4), (12,10)}

In the present embodiment with reference to FIG. 22, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (fourth and eighth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to one (twelfth) OFDM symbol of the second OFDM symbol group. Four dedicated reference signals are allocated to one OFDM symbol at equal intervals of three subcarrier intervals for rank 1 transmission, and two dedicated reference signals are allocated for each layer at six subcarrier intervals for rank 2 transmission.

In the present embodiment, in consideration of the case where the dedicated reference signal is power boosted, the dedicated reference signal ratio is equally arranged for each layer (antenna port or stream) in the symbol where the dedicated reference signal is located. In addition, since the dedicated reference signals are arranged at intervals of 4 OFDM symbols on the basis of the third OFDM symbol to which data is transmitted, it has a characteristic that is robust to Doppler Spread. Channel selection by maintaining 3 subcarrier spacing for dedicated reference signal of Rank 1 or 2 of FDM scheme and 6 subcarrier spacing for Rank 2 dedicated reference signal of FDM scheme It has characteristics that are strong in characteristic. In addition, frequency shift is supported by designing a margined interlaced pattern in which the dedicated reference signal is not disposed at the first and last subcarrier positions of the OFDM symbol to which the dedicated reference signal is allocated.

Example  19 (Figure 23)

A (l, k) = {(10,0), (10,4), (10,8), (12,2), (12,6), (12,10)}

B (l, k) = {(10,1), (10,5), (10,9), (12,3), (12,7), (12,11)}

Referring to FIG. 23, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is not allocated to the first OFDM symbol group, and a dedicated reference signal is allocated to two (10th and 12th) OFDM symbols of the second OFDM symbol group. Six dedicated reference signals are allocated to one OFDM symbol at one or three subcarrier intervals for rank 1 transmission, and three dedicated reference signals are assigned to each layer at four subcarrier intervals for rank 2 transmission.

In the present embodiment, when the downlink subframe is configured in the TDD scheme, it is proposed not to allocate a dedicated reference signal in an area in which data does not exist but to arrange a dedicated reference signal in a compact area in which data exists. In addition, in the present embodiment, in consideration of the case in which the dedicated reference signal is power boosted, the dedicated reference signal ratio is equally set for each layer in the symbol where the dedicated reference signal is located. In addition, the dedicated reference signals are located in the 10th and 12th OFDM symbols of the second OFDM symbol group so that the dedicated reference signals are not affected by the SCH and the BCH (located in the fifth to ninth OFDM symbols). do. In this embodiment, the dedicated reference signal is designed to be concentrated in a specific part in the time domain in consideration of relatively low mobility, but the interval is less than 4 subcarriers in the OFDM symbol to which the dedicated reference signal is allocated to be robust to the frequency selective characteristic. do. By contiguously arranging dedicated reference signals for the first and second layers, it is possible to have the same channel estimation performance and to support the dedicated reference signals of the CDM scheme. In addition, a frequency shift is supported by giving a margin of 2 subcarriers in an OFDM symbol to which a dedicated reference signal is allocated.

Example  20 (Fig. 24)

A (l, k) = {(10,0), (10,2), (10,7), (12,1), (12,3), (12,8)}

B (l, k) = {(10,1), (10,3), (10,8), (12,0), (12,2), (12,7)}

Referring to FIG. 24, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is not allocated to the first OFDM symbol group, and a dedicated reference signal is allocated to two (10th and 12th) OFDM symbols of the second OFDM symbol group. Six dedicated reference signals are allocated to one OFDM symbol at intervals of 1 or 4 subcarriers for rank 1 transmission, and three dedicated reference signals are allocated to each layer at 2 or 5 subcarrier intervals for rank 2 transmission.

In the present embodiment, in consideration of the case where the dedicated reference signal is boosted by power, the dedicated reference signal ratio is equally set for each layer in the symbol where the dedicated reference signal is located. In addition, the dedicated reference signals are located in the 10th and 12th OFDM symbols of the second OFDM symbol group so that the dedicated reference signals are not affected by the SCH and the BCH (located in the fifth to ninth OFDM symbols). do. In this embodiment, the dedicated reference signal is designed to be concentrated in a specific part in the time domain in consideration of relatively low mobility, but the interval is less than 5 subcarriers in the OFDM symbol to which the dedicated reference signal is allocated to be robust to the frequency selective characteristic. do. By concatenating and arranging dedicated reference signals for the first and second layers, it is possible to have the same channel estimation performance and to support the dedicated reference signal of the CDM scheme. In addition, a frequency shift is supported by giving a margin of three subcarriers in an OFDM symbol to which a dedicated reference signal is allocated.

Example  21 (Figure 25)

A (l, k) = {(3,1), (4,10), (5,4), (6,7), (9,1), (9,7), (12,4), (12,10)}

B (l, k) = {(3,10), (4,1), (5,9), (6,2), (9,4), (9,10), (12,1), (12,7)}

Referring to FIG. 25, A and B are arranged in 16 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to four (fourth, fifth, sixth, and ninth) OFDM symbols of the first OFDM symbol group, and dedicated to two (third and twelfth) OFDM symbols of the second OFDM symbol group. The reference signal is assigned. Two dedicated reference signals are allocated to the third to sixth OFDM symbols at intervals of 5 or 9 subcarriers for rank 1 transmission, and one dedicated reference signal is allocated to each layer for rank 2 transmission. In the ninth and twelfth OFDM symbols, four dedicated reference signals are allocated for rank 1 transmission at equal intervals of three subcarrier intervals, and two dedicated reference signals are allocated for each layer at six subcarrier intervals for rank 2 transmission.

In the present embodiment, in the case of subframes in which SCHs and BCHs are not located (SCH is transmitted in 5 subframe periods and BCH in 10 subframe periods), a dedicated reference signal is arranged at intervals of 1 to 3 OFDM symbols so that high mobility ( High Mobility), a dedicated reference signal is arranged in a manner of covering the entire RB at intervals of 3 or less subcarriers or at maximum 9 subcarrier intervals to correspond to frequency selective characteristics. In the case of subframes in which SCHs and BCHs are located, channel estimation performance can be maintained as a whole by allocating a dedicated reference signal that is not affected to the second OFDM symbol group. In the frequency domain, a margin for each one of the first and the last subcarriers is provided to support the cross pattern for the frequency shift, and the same reference signal ratio for each layer in all OFDM symbols into which the dedicated reference signal is inserted is used for power boosting. Design so that no power fluctuations occur.

Example  22 (Figure 26)

A (l, k) = {(10,0), (10,4), (10,8), (12,0), (12,4), (12,8)}

B (l, k) = {(10,1), (10,5), (10,9), (12,1), (12,5), (12,9)}

Referring to FIG. 26, in the present embodiment, A and B are disposed in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is not allocated to the first OFDM symbol group, and a dedicated reference signal is allocated to two (10th and 12th) OFDM symbols of the second OFDM symbol group. Six dedicated reference signals are allocated in one or three subcarrier intervals for rank 1 transmission in one OFDM symbol, and three dedicated reference signals are allocated in four subcarrier intervals for each layer for rank 2 transmission.

In the present embodiment, in consideration of the case in which the dedicated reference signal is boosted by power, the dedicated reference signal ratio is equally set for each antenna in the OFDM symbol to which the dedicated reference signal is allocated. In addition, the dedicated reference signal is arranged in the tenth and twelfth OFDM symbols so that the dedicated reference signal is not affected by the SCH and the BCH. In the present embodiment, the dedicated reference signals are concentrated in a specific region in the time domain in consideration of relatively low mobility, and are designed to have a spacing of up to 4 subcarriers or less to be robust to the frequency selective characteristic. By concatenating and arranging dedicated reference signals for the first and second layers, the same channel estimation performance can be achieved and the support of the dedicated reference signal of the CDM method can be facilitated. In addition, by improving the position of the dedicated reference signal in the frequency domain for each OFDM symbol layer, the performance improvement for the case of using 1-dimensional channel estimation can be additionally obtained. In addition, a margin of three subcarriers may be provided in each OFDM symbol to support scalability of frequency shift.

Example  23 (Figure 27)

A (l, k) = {(12,0), (12,2), (12,4), (12,6), (12,8), (12,10)}

B (l, k) = {(12,1), (12,3), (12,5), (12,7), (12,9), (12,11)}

Referring to FIG. 27, in the present embodiment, A and B are disposed in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is not allocated to the first OFDM symbol group, and a dedicated reference signal is allocated to one (twelfth) OFDM symbol of the second OFDM symbol group. Twelve dedicated reference signals are allocated at intervals of one subcarrier for rank 1 transmission in one OFDM symbol, and six dedicated reference signals are allocated at intervals of two subcarriers for each layer for rank 2 transmission.

In the present embodiment, in consideration of the case where the dedicated reference signal is boosted by power, the ratio of the dedicated reference signal for each layer in the symbol where the DRS is located is equally set. In addition, the dedicated reference signal may not be affected by the SCH and the BCH, and may be applied regardless of how the radio frame is configured (FDD or TDD), and the same dedicated reference signal pattern may be used even when the extended CP is considered. A dedicated reference signal is located in the twelfth OFDM symbol so that it is located. In this embodiment, while designed in consideration of the relatively low mobility, it is designed to have a maximum of two sub-carrier spacing to be robust to the frequency selective characteristics. By concatenating and placing dedicated reference signals for the first and second layers, the same channel estimation performance can be achieved and the dedicated reference signals of the CDM scheme can be easily supported.

Example  24 (Figure 28)

A (l, k) = {(8,3), (9,6), (10,0), (10,8), (12,1), (12,9)}

B (l, k) = {(8,6), (9,3), (10,1), (10,9), (12,0), (12,8)}

Referring to FIG. 28, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (eighth and ninth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (tenth and twelfth) OFDM symbols of the second OFDM symbol group. In one OFDM symbol belonging to the first OFDM symbol group, two dedicated reference signals are allocated at intervals of three subcarriers for rank 1 transmission, and one dedicated reference signal is allocated for each layer for rank 2 transmission. In one OFDM symbol belonging to the second OFDM symbol group, four dedicated reference signals are allocated at intervals of 1 or 7 subcarriers for rank 1 transmission, and two dedicated reference signals for each layer at 8 subcarrier intervals for rank 2 transmission. Is assigned.

In this embodiment, the dedicated reference signal is arranged in consideration of low mobility. In consideration of the case where the dedicated reference signal is boosted by power, the ratio of the dedicated reference signal for each layer in the OFDM symbol where the dedicated reference signal is located is equally set. In addition, the dedicated reference signal is not disposed in the OFDM symbol where the SCH can be located, thereby eliminating the influence of the SCH. Two-dimensional channel estimation performance in the case of a subframe in which the BCH is not located by placing a dedicated reference signal in an intermediate region in the frequency domain on the eighth and ninth OFDM symbols for the seventh to ninth OFDM symbols where the BCH may be located. In the case of the subframe in which the BCH is located, good channel estimation performance can be ensured through a dedicated reference signal having 7 subcarrier spacing or less in the 10th and 12th OFDM symbols. In addition, a margin of two subcarriers may be provided in each OFDM symbol to support scalability of frequency shift.

Example  25 (Figure 29)

A (l, k) = {(5,6), (8,3), (10,1), (10,9), (12,0), (12,8)}

B (l, k) = {(5,3), (8,6), (10,0), (10,8), (12,1), (12,9)}

Referring to FIG. 29, in the present embodiment, A and B are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals are allocated to two (fiveth and eighth) OFDM symbols of the first OFDM symbol group, and dedicated reference signals are allocated to two (tenth and twelfth) OFDM symbols of the second OFDM symbol group. In one OFDM symbol belonging to the first OFDM symbol group, two dedicated reference signals are allocated at intervals of three subcarriers for rank 1 transmission, and one dedicated reference signal is allocated for each layer for rank 2 transmission. In one OFDM symbol belonging to the second OFDM symbol group, four dedicated reference signals are allocated at intervals of 1 or 7 subcarriers for rank 1 transmission, and two dedicated reference signals for each layer at 8 subcarrier intervals for rank 2 transmission. Is assigned.

In this embodiment, in consideration of the case in which the dedicated reference signal is boosted by power, the ratio of the dedicated reference signal for each layer in the symbol where the dedicated reference signal is located is equally set. In addition, by arranging one or two dedicated reference signals in OFDM symbols in which SCHs and BCHs can be located, minimum channel estimation performance is ensured for a corresponding region, and tenth and twelfth generations are not affected by SCHs and BCHs. Good channel estimation performance can be ensured even in a subframe in which SCHs and BCHs exist through dedicated reference signals having 7 subcarrier intervals or less in an OFDM symbol. In addition, a margin of two subcarriers may be provided in each OFDM symbol to support scalability of frequency shift.

Example  26 (Fig. 30)

A (l, k) = {(10,0), (10,4), (10,8), (12,1), (12,5), (12,9)}

B (l, k) = {(10,1), (10,5), (10,9), (12,0), (12,4), (12,8)}

Referring to FIG. 30, in the present embodiment, A and B are disposed in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. A dedicated reference signal is not allocated to the first OFDM symbol group, and a dedicated reference signal is allocated to two (10th and 12th) OFDM symbols of the second OFDM symbol group. Six dedicated reference signals are allocated in one or three subcarrier intervals for rank 1 transmission in one OFDM symbol, and three dedicated reference signals are allocated for each layer in four subcarrier intervals for rank 2 transmission.

In the present embodiment, in consideration of the case in which the dedicated reference signal is boosted by power, the ratio of the dedicated reference signal for each layer in the OFDM symbol in which the dedicated reference signal is located is equally set. In addition, the dedicated reference signal is arranged in the tenth and twelfth OFDM symbols so that the dedicated reference signal is not affected by the SCH and the BCH. In this embodiment, it is designed to have a spacing of up to 4 subcarriers or less so as to be robust to frequency selective characteristics while considering relatively low mobility. By concatenating and arranging dedicated reference signals for the first and second layers, it is possible to have the same channel estimation performance and to support the dedicated reference signal of the CDM scheme. In addition, it is possible to improve the estimation performance of the frequency selective characteristic for the case of using 2D channel estimation by reversing the position of the dedicated reference signal for each OFDM symbol for each layer. In addition, a margin of three subcarriers may be provided in each OFDM symbol to support scalability of frequency shift.

31 is a diagram showing the configuration of a preferred embodiment of a wireless communication system including a terminal apparatus and a base station apparatus according to the present invention.

Referring to FIG. 31, the terminal UE1 and UE2 apparatuses may include receiving modules 3111 and 3121, transmitting modules 3112 and 3122, processors 3113 and 3123, and memories 3114 and 3124, respectively. The receiving modules 3111 and 3121 may receive various signals, data, information, and the like from the base station. The transmission modules 3112 and 3122 may transmit various signals, data, information, and the like to the base station.

The processors 3113 and 3123 receive data for two or less layers through the data regions of the downlink subframe through the receiving modules 3111 and 3121, and receive the first data on the first OFDM symbol group of the downlink subframe. Receiving a reference signal arranged in the time-frequency domain according to the pattern, controlling to receive the reference signal arranged in the time-frequency domain according to the second pattern on the second OFDM symbol group of the downlink subframe, and receiving By using the received reference signal, it is possible to control to estimate a channel in order to demodulate data for two or less layers. Herein, the first OFDM symbol group includes OFDM symbols and downlink subframes in which a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), a synchronization channel (SCH), and a broadcast channel (BCH) are located. The second OFDM symbol group may include the last OFDM symbol, and the second OFDM symbol group may include the remaining OFDM symbols except for the OFDM symbols belonging to the first OFDM symbol group among the OFDM symbols included in the downlink subframe.

In addition, the processors 3113 and 3123 perform a function of processing the information received by the terminal device, information to be transmitted to the outside, and the memory 3114 and 3124 may store the processed information for a predetermined time, It may be replaced by a component such as a buffer (not shown).

Meanwhile, the base station (eNB) device may include a receiving module 3131, a transmitting module 3132, a processor 3133, and a memory 3134. The receiving module 3131 may receive various signals, data, information, and the like from the terminal. The transmission module 3132 may transmit various signals, data, information, and the like to the terminal.

The processor 3133 transmits data for two or less layers through the data region of the downlink subframe through the transmission module 3132, and transmits time according to the first pattern on the first OFDM symbol group of the downlink subframe. A reference signal arranged in the frequency domain may be transmitted, and a reference signal arranged in the time-frequency domain may be controlled according to a second pattern on the second OFDM symbol group of the downlink subframe. Here, the reference signal is a dedicated reference signal (DRS) for demodulating data for two or less layers, and the first OFDM symbol group is a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), and a synchronization channel. (SCH) and a broadcast channel (BCH) include OFDM symbols and the last OFDM symbol of the downlink subframe, the second OFDM symbol group is a first OFDM symbol group of the OFDM symbols included in the downlink subframe It may include the remaining OFDM symbols except the OFDM symbols belonging to.

In addition, the processor 3133 performs a function of processing information received by the terminal device, information to be transmitted to the outside, and the like. The memory 3134 may store the processed information and the like for a predetermined time and may include a buffer (not shown). May be replaced by a component such as).

Embodiments of the present invention described above may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

For implementation in hardware, a method according to embodiments of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), and Programmable Logic Devices (PLDs). It may be implemented by field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of the preferred embodiments of the invention disclosed herein has been presented to enable any person skilled in the art to make and use the present invention. While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, those skilled in the art can utilize each of the configurations described in the above-described embodiments in a manner of mutually combining them. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The invention can be embodied in other specific forms without departing from the spirit and essential features of the invention. Accordingly, the above detailed description should not be interpreted as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship or may be incorporated as new claims by post-application correction.

3131 Receive Module 3132 Receive Module
3133 Processor 3134 Memory

Claims (11)

A method for transmitting a reference signal to a terminal by a base station using two or less layers,
Transmitting data for the two or less layers through a data region of a downlink subframe;
Transmitting the reference signal arranged in a time-frequency domain according to a first pattern on a first OFDM symbol group of the downlink subframe; And
Transmitting the reference signal disposed in a time-frequency domain according to a second pattern on a second OFDM symbol group of the downlink subframe,
The reference signal is a dedicated reference signal (DRS) for demodulating data for two or less layers.
The first OFDM symbol group includes OFDM symbols in which a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), a synchronization channel (SCH) and a broadcast channel (BCH) are located, and the downlink subframe. Includes the last OFDM symbol,
The second OFDM symbol group includes remaining OFDM symbols except for OFDM symbols belonging to the first OFDM symbol group among the OFDM symbols included in the downlink subframe. The method of claim 1,
Wherein the first and second patterns define that the reference signals are arranged at uniform subcarrier intervals on an OFDM symbol. The method of claim 1,
And the first and second patterns define that the reference signals are arranged at uniform OFDM symbol intervals. The method of claim 1,
The first and second patterns define that more reference signals are arranged in the second OFDM symbol group than the first OFDM symbol group. The method of claim 1,
The first pattern defines that the reference signal is disposed in OFDM symbols in which the synchronization channel (SCH) and the broadcast channel (BCH) are located in the first OFDM symbol group. The method of claim 1,
The first pattern defines that the reference signal is not disposed on the first OFDM symbol group.
And the second pattern defines that at least one reference signal is disposed on the second OFDM symbol group. The method of claim 1,
The first and second patterns define that the reference signal is disposed in 12 resource elements (RE) on a resource block pair (RB Pair) of one subframe of the downlink subframe. The method of claim 1,
A reference signal for two layers is multiplexed using one or more of a time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) scheme. A method of processing a reference signal received from a base station by a terminal using two or less layers,
Receiving data for the two or less layers through a data region of a downlink subframe;
Receiving the reference signal disposed in a time-frequency domain according to a first pattern on a first OFDM symbol group of the downlink subframe;
Receiving the reference signal arranged in a time-frequency domain according to a second pattern on a second OFDM symbol group of the downlink subframe; And
Estimating a channel to demodulate data for the two or less layers using the received reference signal,
The first OFDM symbol group includes OFDM symbols in which a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), a synchronization channel (SCH) and a broadcast channel (BCH) are located, and the downlink subframe. Includes the last OFDM symbol,
The second OFDM symbol group includes remaining OFDM symbols except for OFDM symbols belonging to the first OFDM symbol group among the OFDM symbols included in the downlink subframe. A base station for transmitting a reference signal to a terminal using two or less layers,
A receiving module for receiving an uplink signal from the terminal;
A transmission module for transmitting a downlink signal to the terminal; And
A processor connected to the receiving module and the transmitting module and controlling the base station including the receiving module and the transmitting module,
The processor comprising:
Through the transmission module, data for the two or less layers are transmitted through a data region of a downlink subframe, and arranged in a time-frequency region according to a first pattern on a first OFDM symbol group of the downlink subframe. Transmitting the reference signal, and transmitting the reference signal arranged in a time-frequency domain according to a second pattern on a second OFDM symbol group of the downlink subframe,
The reference signal is a dedicated reference signal (DRS) for demodulating data for two or less layers.
The first OFDM symbol group includes OFDM symbols in which a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), a synchronization channel (SCH) and a broadcast channel (BCH) are located, and the downlink subframe. Includes the last OFDM symbol,
The second OFDM symbol group includes the remaining OFDM symbols except for the OFDM symbols belonging to the first OFDM symbol group of the OFDM symbols included in the downlink subframe, the base station. A terminal for processing a reference signal received from a base station using two or less layers,
A receiving module for receiving control information and data from the base station;
A transmission module for transmitting control information and data to the base station; And
A processor connected to the receiving module and the transmitting module and controlling the terminal including the receiving module and the transmitting module,
The processor comprising:
Receiving data for the two layers or less through the data region of the downlink subframe through the receiving module, and arranged in the time-frequency region according to the first pattern on the first OFDM symbol group of the downlink subframe Receiving the received reference signal, and receiving the reference signal arranged in a time-frequency domain according to a second pattern on a second OFDM symbol group of the downlink subframe,
Controlling the terminal to estimate a channel in order to demodulate data for the two or less layers using the received reference signal,
The first OFDM symbol group includes OFDM symbols in which a physical downlink control channel (PDCCH), a cell-specific reference signal (CRS), a synchronization channel (SCH) and a broadcast channel (BCH) are located, and the downlink subframe. Includes the last OFDM symbol,
The second OFDM symbol group includes remaining OFDM symbols except for OFDM symbols belonging to the first OFDM symbol group among the OFDM symbols included in the downlink subframe.

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