KR20100113042A - 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 four layers is transmitted through the data area of the down link subframe(1412). The reference signal for the first and second layers respective arranged on two OFDM symbols adjacent to the down link subframe is transmitted. The reference signal for the third and fourth layers respective arranged on two OFDM symbols adjacent to the downlink subframes is transmitted.

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, a method of transmitting a reference signal to a terminal by a base station using a layer of 4 or less according to an embodiment of the present invention is provided to the layer of 4 or less through a data region of a downlink subframe. Transmitting data for the first and second layers arranged on contiguous two OFDM symbols of the downlink subframe, and concatenating two OFDM symbols of the downlink subframe Transmitting reference signals for the third and fourth layers respectively disposed on the reference signal, wherein the reference signal is a dedicated reference signal (DRS) for demodulating data for the four layers or less, and the first reference signal; And a reference signal for the second layer or a reference signal for the third and fourth layers may be disposed at the same subcarrier position on the concatenated 2 OFDM symbols. There.

In addition, reference signals for the first to fourth layers may be disposed at the same subcarrier positions on contiguous 4 OFDM symbols.

In addition, the reference signals for the first to fourth layers are respectively disposed on concatenated four OFDM symbols of the first slot of the downlink subframe, and concatenated four OFDM symbols of the second slot of the downlink subframe. Can be placed in each symbol.

In addition, two resource blocks (RB) consecutive in time of one subframe of the downlink subframe, that is, a resource block that can be a unit of resource mapping in one TTI (or first and second slots of a subframe). Reference signals for the first to fourth layers in a pair may be disposed on 16 resource elements at the same ratio.

In addition, the reference signals for the four layers or less 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 a layer of 4 or less according to another embodiment of the present invention, the 4 or less through the data area of the downlink subframe Receiving data for a layer, receiving reference signals for first and second layers disposed on two concatenated OFDM symbols of the downlink subframe, and concatenating two OFDM of the downlink subframe Receiving reference signals for the third and fourth layers respectively disposed on the symbol, and estimating a channel to demodulate data for the four layers or less using the received reference signals; The reference signals for the first and second layers or the reference signals for the third and fourth layers are on the concatenated two OFDM symbols. It may be located in the same sub-carrier position.

In addition, reference signals for the first to fourth layers may be disposed at the same subcarrier positions on contiguous 4 OFDM symbols.

In addition, the reference signals for the first to fourth layers are respectively disposed on concatenated four OFDM symbols of the first slot of the downlink subframe, and concatenated four OFDM symbols of the second slot of the downlink subframe. Can be placed in each symbol.

In addition, in two consecutive resource blocks (resource block pairs) in time of one subframe of the downlink subframe, reference signals for the first to fourth layers may be disposed on 16 resource elements at the same ratio.

In addition, the reference signals for the four layers or less 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 base station for transmitting a reference signal to a terminal using 4 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 is downward through the transmission module. Transmits data for the four layers or less through a data region of a link subframe, transmits reference signals for the first and second layers disposed on two concatenated OFDM symbols of the downlink subframe, Reference signals for third and fourth layers disposed on two concatenated OFDM symbols of the downlink subframe, respectively, The reference signal is a dedicated reference signal (DRS) for demodulating data for the 4 or less layers, and the reference signal for the first and second layers or for the third and fourth layers. The reference signal may be arranged in the same subcarrier position on the contiguous 2 OFDM symbols.

In order to solve the above technical problem, a terminal for processing a reference signal received from a base station using 4 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. Receiving data for the four layers or less through the data region of the downlink subframe through the module, and referring to the first and second layers disposed on two concatenated OFDM symbols of the downlink subframe, respectively. A third receiving signal and disposed on contiguous 2 OFDM symbols of the downlink subframe And control to receive a reference signal for a fourth layer, and control the terminal to estimate a channel to demodulate data for the layer 4 or less using the received reference signal. A reference signal for a layer or a reference signal for the third and fourth layers is disposed in the same subcarrier position on the concatenated 2 OFDM symbols.

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 13 illustrate embodiments of a pattern of a dedicated reference signal according to the present invention.
14 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 signal, 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 RS 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.

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 4 as described through 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). 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 4 transmission, in addition to the above-described display method in rank 2 transmission, the position indicated by 'C' indicates a dedicated reference signal for the third layer, and the position indicated by 'D' is dedicated to the fourth layer. Indicates a reference signal. In the case of rank 8 transmission, in addition to the display method of rank 4 transmission, the position indicated by 'E' indicates a dedicated reference signal for the fifth layer, and the position indicated by 'F' indicates a dedicated reference signal for the sixth layer. The position indicated by 'G' indicates a dedicated reference signal for the seventh layer, and the position indicated by 'H' indicates a dedicated reference signal for the eighth layer.

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.

Meanwhile, in the case of rank 1 transmission, all positions in which a dedicated reference signal for rank 2 transmission is displayed 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, the dedicated reference signal may be configured not to be disposed in the 0 to 2 OFDM symbols to which the PDCCH region is allocated. In addition, since the dedicated reference signal may be punctured in the OFDM symbol in which the CRS, the SCH, and the BCH are located, and the last OFDM symbol of one subframe, in order to guarantee transmission of the dedicated reference signal in every subframe, the third and tenth signals may be used. And at least one dedicated reference signal should be allocated to the twelfth OFDM symbol, 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 the dedicated reference signals are allocated only to the third, tenth and twelfth OFDM symbols, there is a possibility that the channel estimation performance becomes inefficient. Therefore, in some cases, there is a need to properly allocate the dedicated reference signals to the remaining OFDM symbols. do.

In addition, since the SCH and the BCH are transmitted in 5 subframe and 10 subframe periods, the dedicated reference signals are not punctured on the fifth to ninth OFDM symbols in all subframes, and thus, on the fifth to ninth OFDM symbols. A pattern can also be designed by placing a portion of the dedicated reference signal at.

In addition, in the following various embodiments, one OFDM symbol among OFDM symbols in which a dedicated reference signal is disposed may be used for a reference signal for CQI.

5 to 13 of various embodiments of the present invention, a resource element to which a dedicated reference signal is mapped in one subframe according to a general CP configuration is shown, with the horizontal axis representing the time domain and the vertical axis representing the frequency domain. Indicates. The smallest rectangular area in the time-frequency domain corresponds 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  A (FIG. 5)

(One) A (l, k) = {(3,0), (3,6), (8,2), (8,8), (12,4), (12,10)} B (l, k) = {(3,1), (3,7), (8,3), (8,9), (12,5), (12,11)} (2) A (l, k) = {(3,0), (3,6), (8,4), (8,10), (12,2), (12,8)} B (l, k) = {(3,1), (3,7), (8,5), (8,11), (12,3), (12,9)} (3) A (l, k) = {(3,0), (3,6), (8,2), (8,8), (12,0), (12,6)} B (l, k) = {(3,3), (3,9), (8,5), (8,11), (12,3), (12,9)} (4) 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)} (5) A (l, k) = {(3,2), (3,8), (8,5), (8,11), (12,2), (12,8)} B (l, k) = {(3,5), (3,11), (8,2), (8,8), (12,5), (12,11)}

Referring to FIG. 5, in this embodiment, dedicated reference signals for the first and second layers 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 for the first and second layers may be multiplexed by the FDM scheme, and positions in the frequency domain may be changed from each other. In Embodiments A (1) to A (5), the dedicated reference signal is illustrated as being disposed on the third, eighth and twelfth OFDM symbols, but the first pattern is the third or fifth OFDM symbol and the second pattern is the same. In the eighth or ninth OFDM symbol, a third pattern may be disposed in the tenth or twelfth OFDM symbol.

In Embodiments A (1) and A (2), the dedicated reference signals for the first and second layers are arranged at contiguous subcarrier positions to have the same channel estimation performance, and at the same time, the dedicated reference signals of the CDM scheme. Support is easy. In Embodiments A (3) to A (5), the dedicated reference signals for the first and second layers are spaced apart at equal subcarrier intervals on one OFDM symbol.

Example  B (Figure 6)

(One) P (l, k) = {(3,1), (3,5), (3,9), (6,1), (6,5), (6,9), (9,1), (9,5), ( 9,9), (12,1), (12,5), (12,9)} (2) P (l, k) = {(3,1), (3,5), (3,9), (6,2), (6,6), (6,10), (9,1), (9,5), ( 9,9), (12,2), (12,6), (12,10)} (3) P (l, k) = {(3,0), (3,4), (3,8), (6,3), (6,7), (6,11), (9,0), (9,4), ( 9,8), (12,3), (12,7), (12,11)} (4) P (l, k) = {(3,0), (3,3), (3,6), (3,9), (8,2), (8,5), (8,8), (8,11), ( 12,0), (12,3), (12,6), (12,9)} (5) P (l, k) = ((3,0), (3,3), (3,6), (3,9), (8,0), (8,3), (8,6), (8,9), ( 12,0), (12,3), (12,6), (12,9)} (6) P (l, k) = {(3,2), (3,5), (3,8), (3,11), (8,2), (8,5), (8,8), (8,11), ( 12,2), (12,5), (12,8), (12,11)}

The position on the time-frequency domain indicated by "P" in FIG. 6 indicates that dedicated reference signals for the first and second layers are multiplexed in the CDM scheme and arranged in one resource element.

In Embodiments B (1) to B (3), the dedicated reference signals for the first and second layers are equally divided into 16 resource elements in two resource blocks (resource block pairs) contiguous in time in one subframe. Is placed on. Dedicated reference signals for the first and second layers are multiplexed by the CDM scheme and arranged at equal intervals at three subcarrier positions on the third, sixth, ninth, and twelfth OFDM symbols. Alternatively, the first pattern may be disposed on the third OFDM symbol, the second pattern on the fifth or sixth OFDM symbol, the third pattern on the eighth or ninth OFDM symbol, and the fourth pattern on the tenth or twelfth OFDM symbol. have.

In Embodiments B (4) to B (6), the dedicated reference signals for the first and second layers within 12 resource blocks (resource block pairs) contiguous in time of one subframe have 12 resource elements at an equal ratio. Is placed on. Dedicated reference signals for the first and second layers are multiplexed by the CDM scheme and arranged at equal intervals at four subcarrier positions on the third, eighth, and twelfth OFDM symbols. Alternatively, the first pattern may be disposed in the third or fifth OFDM symbol, the second pattern in the eighth or ninth OFDM symbol, and the third pattern in the tenth or twelfth OFDM symbol.

Example  C (FIGS. 7 and 8)

(One) A (l, k) = {(3,0), (3,7), (7,3), (7,10), (11,0), (11,7)} B (l, k) = {(4,0), (4,7), (8,3), (8,10), (12,0), (12,7)} C (l, k) = {(3,3), (3,10), (7,0), (7,7), (11,3), (11,10)} D (l, k) = {(4,3), (4,10), (8,0), (8,7), (12,3), (12,10)} (2) A (l, k) = {(3,0), (3,4), (3,10), (9,0), (9,6), (9,10)} B (l, k) = {(4,0), (4,4), (4,10), (10,0), (10,6), (10,10)} C (l, k) = {(5,0), (5,4), (5,10), (11,0), (11,6), (11,10)} D (l, k) = {(6,0), (6,4), (6,10), (12,0), (12,6), (12,10)} (3) A (l, k) = {(3,0), (3,10), (5,6), (9,0), (9,10), (11,6)} B (l, k) = {(4,0), (4,10), (6,6), (10,0), (10,10), (12,6)} C (l, k) = {(3,4), (5,0), (5,10), (9,4), (11,0), (11,10)} D (l, k) = {(4,4), (6,0), (6,10), (10,4), (12,0), (12,10)} (4) A (l, k) = {(3,0), (3,10), (5,4), (9,0), (9,10), (11,6)} B (l, k) = {(4,0), (4,10), (6,4), (10,0), (10,10), (12,6)} C (l, k) = {(3,4), (5,0), (5,10), (9,6), (11,0), (11,10)} D (l, k) = {(4,4), (6,0), (6,10), (10,6), (12,0), (12,10)} (5) A (l, k) = {(3,0), (3,4), (3,10), (9,0), (9,6), (9,10)} B (l, k) = {(4,0), (4,4), (10,0), (4,10), (10,6), (10,10)} C (l, k) = {(5,0), (5,6), (5,10), (11,0), (11,4), (11,10)} D (l, k) = {(6,0), (6,6), (6,10), (12,0), (12,4), (12,10)} (6) A (l, k) = {(3,1), (3,7), (7,4), (7,10), (11,1), (11,7)} B (l, k) = {(4,1), (4,7), (8,4), (8,10), (12,1), (12,7)} C (l, k) = {(3,4), (3,10), (7,1), (7,7), (11,4), (11,10)} D (l, k) = {(4,4), (4,10), (8,1), (8,7), (12,4), (12,10)} (7) A (l, k) = {(3,1), (3,4), (3,10), (9,1), (9,7), (9,10)} B (l, k) = {(4,1), (4,4), (4,10), (10,1), (10,7), (10,10)} C (l, k) = {(5,1), (5,4), (5,10), (11,1), (11,7), (11,10)} D (l, k) = {(6,1), (6,4), (6,10), (12,1), (12,7), (12,10)} (8) A (l, k) = {(3,1), (3,4), (3,10), (9,1), (9,4), (9,10)} B (l, k) = {(4,1), (4,4), (4,10), (10,1), (10,4), (10,10)} C (l, k) = {(5,1), (5,7), (5,10), (11,1), (11,7), (11,10)} D (l, k) = {(6,1), (6,7), (6,10), (12,1), (12,7), (12,10)} (9) A (l, k) = {(3,1), (5,7), (5,10), (9,4), (9,10), (11,1)} B (l, k) = {(4,1), (6,7), (6,10), (10,4), (10,10), (12,1)} C (l, k) = {(3,4), (3,10), (5,1), (9,1), (11,7), (11,10)} D (l, k) = {(4,4), (4,10), (6,1), (10,1), (12,7), (12,10)} 10 A (l, k) = {(3,1), (3,10), (5,4), (9,1), (9,10), (11,7)} B (l, k) = {(4,1), (4,10), (6,4), (10,1), (10,10), (12,7)} C (l, k) = {(3,4), (5,1), (5,10), (9,7), (11,1), (11,10)} D (l, k) = {(4,4), (6,1), (6,10), (10,7), (12,1), (12,10)} (11) A (l, k) = {(3,1), (3,10), (5,7), (9,1), (9,10), (11,4)} B (l, k) = {(4,1), (4,10), (6,7), (10,1), (10,10), (12,4)} C (l, k) = {(3,4), (5,1), (5,10), (9,7), (11,1), (11,10)} D (l, k) = {(4,4), (6,1), (6,10), (10,7), (12,1), (12,10)} (12) A (l, k) = {(3,1), (3,10), (5,7), (9,4), (11,1), (11,10)} B (l, k) = {(4,1), (4,10), (6,7), (10,4), (12,1), (12,10)} C (l, k) = {(3,4), (5,1), (5,10), (9,1), (9,10), (11,7)} D (l, k) = {(4,4), (6,1), (6,10), (10,1), (10,10), (12,7)} (13) A (l, k) = {(3,1), (5,4), (5,10), (9,7), (9,10), (11,1)} B (l, k) = {(4,1), (6,4), (6,10), (10,7), (10,10), (12,1)} C (l, k) = {(3,4), (3,10), (5,1), (9,1), (11,7), (11,10)} D (l, k) = {(4,4), (4,10), (6,1), (10,1), (12,7), (12,10)} (14) A (l, k) = {(3,1), (5,7), (5,10), (9,7), (9,10), (11,1)} B (l, k) = {(4,1), (6,7), (6,10), (10,7), (10,10), (12,1)} C (l, k) = {(3,4), (3,10), (5,1), (9,1), (11,4), (11,10)} D (l, k) = {(4,4), (4,10), (6,1), (10,1), (12,4), (12,10)} (15) A (l, k) = {(3,1), (3,10), (5,4), (9,7), (11,1), (11,10)} B (l, k) = {(4,1), (4,10), (6,4), (10,7), (12,1), (12,10)} C (l, k) = {(3,4), (5,1), (5,10), (9,1), (9,10), (11,7)} D (l, k) = {(4,4), (6,1), (6,10), (10,1), (10,10), (12,7)} (16) A (l, k) = {(3,1), (3,10), (5,7), (9,7), (11,1), (11,10)} B (l, k) = {(4,1), (4,10), (6,7), (10,7), (12,1), (12,10)} C (l, k) = {(3,4), (5,1), (5,10), (9,1), (9,10), (11,4)} D (l, k) = {(4,4), (6,1), (6,10), (10,1), (10,10), (12,4)}

7 and 8, in the present embodiment, for the rank 4 transmission, the dedicated reference signals for the first and second layers are equally proportional in two consecutive resource blocks (resource block pairs) in time in one subframe. 12 resource elements are allocated, and dedicated reference signals for the third and fourth layers are arranged in 12 resource elements at an equal ratio.

In this embodiment, the dedicated reference signals for the first and second layers / third and fourth layers are multiplexed by the TDM scheme, or the dedicated reference signals for the first to fourth layers are multiplexed by the TDM scheme.

In this embodiment, dedicated reference signals for the first and second layers / third and fourth layers are respectively disposed on two OFDM symbols concatenated at the same subcarrier index, or on four OFDM symbols concatenated at the same subcarrier index. Dedicated reference signals for the first to fourth layers are disposed, respectively, so that multiplexing by the CDM scheme can be easily applied. In addition, dedicated reference signals for the first to fourth layers are disposed on contiguous four OFDM symbols of the first slot of the subframe, respectively, and the first to the fourth contiguous symbols on the contiguous four OFDM symbols of the second slot of the subframe. Dedicated reference signals for four layers may be disposed respectively.

Example  D (FIG. 9)

(One) A (l, k) = {(3,0), (3,10), (7,3), (7,7), (11,0), (11,10)} B (l, k) = {(4,0), (4,10), (8,3), (8,7), (12,0), (12,10)} (2) A (l, k) = {(3,0), (4,10), (7,3), (8,7), (11,0), (12,10)} B (l, k) = {(3,10), (4,0), (7,7), (8,3), (11,10), (12,0)} (3) A (l, k) = {(3,1), (3,10), (7,4), (7,7), (11,1), (11,10)} B (l, k) = {(4,1), (4,10), (8,4), (8,7), (12,1), (12,10)} (4) A (l, k) = {(3,1), (4,10), (7,4), (8,7), (11,1), (12,10)} B (l, k) = {(3,10), (4,1), (7,7), (8,4), (11,10), (12,1)} (5) A (l, k) = {(3,0), (3,3), (3,7), (3,10), (11,0), (11,3), (11,7), (11,10)} B (l, k) = {(4,0), (4,3), (4,7), (4,10), (12,0), (12,3), (12,7), (12,10)} (6) A (l, k) = {(3,0), (3,7), (4,3), (4,10), (11,0), (11,7), (12,3), (12,10)} B (l, k) = {(3,3), (3,10), (4,0), (4,7), (11,3), (11,10), (12,0), (12,7)} (7) A (l, k) = {(3,1), (3,4), (3,7), (3,10), (11,1), (11,4), (11,7), (11,10)} B (l, k) = {(4,1), (4,4), (4,7), (4,10), (12,1), (12,4), (12,7), (12,10)} (8) A (l, k) = {(3,1), (3,7), (4,4), (4,10), (11,1), (11,7), (12,4), (12,10)} B (l, k) = {(3,4), (3,10), (4,1), (4,7), (11,4), (11,10), (12,1), (12,7)}

With reference to FIG. 9, in embodiments D (1) to D (4), the dedicated reference signals for the first and second layers are equally proportional in two contiguous resource blocks (resource block pairs) of one subframe in time. This is arranged in 12 resource elements.

In Embodiments D (5) to D (8), the dedicated reference signals for the first and second layers within two consecutive resource blocks (resource block pairs) of one subframe in time are equal to 16 resource elements at an equal ratio. Is placed on.

In Embodiments D (1) to D (8), dedicated reference signals for the first and second layers are multiplexed by the TDM scheme. In addition, since a dedicated reference signal for the first and second layers is disposed on two OFDM symbols concatenated at the same subcarrier index, multiplexing by the CDM scheme can be easily applied. In addition, since the dedicated reference signal is disposed at the end of two consecutive resource blocks (resource block pairs) in time of one subframe, channel estimation due to extrapolation of the dedicated reference signal can be reduced.

Example  E (Fig. 10)

(One) A (l, k) = ((3,0), (3,10), (4,0), (4,10), (7,3), (7,7), (8,3), (8,7), ( 11,0), (11,10), (12,0), (12,10)} (2) A (l, k) = {(3,1), (3,10), (4,1), (4,10), (7,4), (7,7), (8,4), (8,7), ( 11,1), (11,10), (12,1), (12,10)} (3) A (l, k) = {(3,0), (3,3), (3,7), (3,10), (4,0), (4,3), (4,7), (4,10), ( 11,0), (11,3), (11,7), (11,10), (12,0), (12,3), (12,7), (12,10)} (4) A (l, k) = {(3,1), (3,4), (3,7), (3,10), (4,1), (4,4), (4,7), (4,10), ( 11,1), (11,4), (11,7), (11,10), (12,1), (12,4), (12,7), (12,10)}

Referring to FIG. 10, the present invention proposes a correlation reference signal (pilot) effective for a time domain change. In Embodiments E (1) and E (2), dedicated reference signals for one layer are arranged in 12 resource elements in two resource blocks (resource block pairs) contiguous in time in one subframe, and Embodiment E In (3) and E (4), dedicated reference signals for one layer are arranged in 16 resource elements in two consecutive resource blocks (resource block pairs) in time of one subframe. Dedicated reference signals for the same layer are disposed on concatenated OFDM symbols at the same subcarrier location, thereby reducing the influence of changes in the time domain.

Example  F (FIG. 11)

(One) A (l, k) = {(3,1), (3,9), (6,5), (9,1), (9,9), (12,5)} B (l, k) = {(3,5), (6,1), (6,9), (9,5), (12,1), (12,9)} (2) A (l, k) = {(3,0), (3,8), (6,4), (9,0), (9,8), (12,4)} B (l, k) = {(3,4), (6,0), (6,8), (9,4), (12,0), (12,8)} (3) A (l, k) = {(3,2), (3,10), (6,6), (9,2), (9,10), (12,6)} B (l, k) = {(3,6), (6,2), (6,10), (9,6), (12,2), (12,10)} (4) A (l, k) = {(3,0), (3,8), (6,6), (9,0), (9,8), (12,6)} B (l, k) = {(3,4), (6,2), (6,10), (9,4), (12,2), (12,10)} (5) A (l, k) = {(3,2), (3,10), (6,4), (9,2), (9,10), (12,4)} B (l, k) = {(3,6), (6,0), (6,8), (9,6), (12,0), (12,8)} (6) A (l, k) = {(3,3), (3,11), (6,5), (9,3), (9,11), (12,5)} B (l, k) = {(3,7), (6,1), (6,9), (9,7), (12,1), (12,9)} (7) A (l, k) = {(3,3), (3,11), (6,7), (9,3), (9,11), (12,7)} B (l, k) = {(3,7), (6,3), (6,11), (9,7), (12,3), (12,11)} (8) A (l, k) = {(3,1), (3,9), (6,4), (9,1), (9,9), (12,4)} B (l, k) = {(3,5), (6,0), (6,8), (9,5), (12,0), (12,8)}

Referring to FIG. 11, in this embodiment, dedicated reference signals for the first and second layers are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. . The first and second dedicated reference signals are arranged at three subcarrier positions on four OFDM symbols.

The dedicated reference signals for the first and second layers are intersected at equal intervals of four subcarrier intervals in one OFDM symbol. If the dedicated reference signal for the first layer and the dedicated reference signal for the second layer are disposed 2: 1 in one OFDM symbol, the dedicated reference signal for the second layer is 1: 2 in the next OFDM symbol. By the dedicated reference signal pattern, the dedicated reference signal for each layer is uniformly distributed in the time-frequency domain, thereby providing channel estimation performance robust to the time-selective and / or frequency-selective characteristics.

Example  G (Figure 12)

(One) A (l, k) = {(3,2), (3,8), (9,5), (9,11), (12,2), (12,8)} B (l, k) = {(3,5), (3,11), (9,2), (9,8), (12,5), (12,11)} (2) A (l, k) = {(3,0), (3,6), (9,4), (9,10), (12,2), (12,8)} B (l, k) = {(3,3), (3,9), (9,1), (9,7), (12,5), (12,11)} (3) A (l, k) = {(3,2), (3,8), (9,4), (9,10), (12,0), (12,6)} B (l, k) = {(3,5), (3,11), (9,1), (9,7), (12,3), (12,9)}

Referring to FIG. 12, in this embodiment, dedicated reference signals for the first and second layers are arranged in 12 resource elements at equal ratios in two consecutive resource blocks (resource block pairs) in time of one subframe. . The first and second dedicated reference signals are arranged at four subcarrier positions on three OFDM symbols.

The dedicated reference signals for the first and second layers are intersected at equal intervals of four subcarrier intervals in one OFDM symbol. By the dedicated reference signal pattern, the dedicated reference signal for each layer is uniformly distributed in the time-frequency domain, thereby providing channel estimation performance robust to the time-selective and / or frequency-selective characteristics. In addition, since more dedicated reference signals are disposed in third and twelfth OFDM symbols in which CRSs, SCHs, and BCHs are not located, transmission of dedicated reference signals is guaranteed in every subframe, thereby providing better channel estimation performance. .

Example  H (Fig. 13)

(One) A (l, k) = {(3,0), (3,4), (3,8), (10,0), (10,4), (10,8)} B (l, k) = {(3,2), (3,6), (3,10), (10,2), (10,6), (10,10)} (2) A (l, k) = {(3,0), (3,4), (3,8), (10,1), (10,5), (10,9)} B (l, k) = {(3,2), (3,6), (3,10), (10,3), (10,7), (10,11)} (3) A (l, k) = {(3,0), (3,4), (3,8), (10,2), (10,6), (10,10)} B (l, k) = {(3,2), (3,6), (3,10), (10,0), (10,4), (10,8)} (4) A (l, k) = {(5,0), (5,4), (5,8), (10,3), (10,7), (10,11)} B (l, k) = {(5,2), (5,6), (5,10), (10,1), (10,5), (10,9)} (5) A (l, k) = {(5,0), (5,4), (5,8), (10,1), (10,5), (10,9)} B (l, k) = {(5,2), (5,6), (5,10), (10,3), (10,7), (10,11)} (6) A (l, k) = {(3,0), (3,4), (3,8), (10,3), (10,7), (10,11)} B (l, k) = {(3,2), (3,6), (3,10), (10,1), (10,5), (10,9)}

Referring to FIG. 13, in this embodiment, dedicated reference signals for the first and second layers 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 for the first and second layers are arranged at six subcarrier positions on two OFDM symbols. Dedicated reference signals for the first and second layers in one OFDM symbol are intersected at two subcarrier intervals.

In the embodiments H (1), H (2), H (3), and H (6), all dedicated reference signals are arranged in the third and tenth OFDM symbols, so that even when CRS, SCH, and BCH are transmitted, dedicated reference All signal transmissions can be guaranteed to provide good channel estimation performance.

14 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. 14, the terminal UE1 and UE2 devices may include receiving modules 1411 and 1421, transmitting modules 1412 and 1422, processors 1413 and 1423, and memories 1414 and 1424, respectively. The reception modules 1411 and 1421 may receive various signals, data, information, and the like from the base station. The transmission modules 1412 and 1422 may transmit various signals, data, information, and the like to the base station.

The processors 1413 and 1423 receive data for 4 or less layers through the data regions of the downlink subframe through the receiving modules 1411 and 1421, respectively, on two concatenated OFDM symbols of the downlink subframe. Receives reference signals for the arranged first and second layers, controls to receive the reference signals for the third and fourth layers disposed on two concatenated OFDM symbols of the downlink subframe, respectively, and is received by the terminal. By using the received reference signal, it is possible to control to estimate a channel in order to demodulate data for 4 or less layers. Here, the reference signal for the first and second layers or the reference signal for the third and fourth layers may be disposed at the same subcarrier location on two concatenated OFDM symbols.

In addition, the processor 1423 and 1423 perform a function of arithmetic processing information received from the terminal device, information to be transmitted to the outside, and the memory 1414 and 1424 may store the arithmetic 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 1431, a transmitting module 1432, a processor 1433, and a memory 1434. The receiving module 1431 may receive various signals, data, information, and the like from the terminal. The transmission module 1432 may transmit various signals, data, information, and the like to the terminal.

The processor 1433 transmits data for four or less layers through the data region of the downlink subframe through the transmission module, and includes first and second signals disposed on two concatenated OFDM symbols of the downlink subframe, respectively. A reference signal for the layer may be transmitted and control may be performed to transmit the reference signals for the third and fourth layers disposed on two concatenated OFDM symbols of the downlink subframe, respectively. Here, the reference signal is a dedicated reference signal (DRS) for demodulating data for a layer of 4 or less, and the reference signal for the first and second layers or the reference signal for the third and fourth layers are concatenated with 2 OFDM. It may be located in the same subcarrier position on the symbol.

In addition, the processor 1433 performs a function of processing the information received by the terminal device, information to be transmitted to the outside, and the like, and the memory 1434 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.

1431 Receive Module 1432 Transmit Module
1433 Processor 1434 Memory

Claims (12)

A method of transmitting a reference signal to a terminal by a base station using 4 or less layers,
Transmitting data for the four layers or less through a data region of a downlink subframe;
Transmitting reference signals for first and second layers disposed on two concatenated OFDM symbols of the downlink subframe; And
Transmitting reference signals for third and fourth layers disposed on two concatenated OFDM symbols of the downlink subframe, respectively;
The reference signal is a dedicated reference signal (DRS) for demodulating data for the layer 4 or less.
The reference signal for the first and second layers or the reference signal for the third and fourth layers are arranged in the same subcarrier position on the concatenated two OFDM symbols. The method of claim 1,
The reference signals for the first to fourth layers are arranged in the same subcarrier position on contiguous 4 OFDM symbols, respectively. The method of claim 1,
Reference signals for the first to fourth layers are respectively disposed on contiguous four OFDM symbols of a first slot of the downlink subframe, and concatenated to four OFDM symbols of a second slot of the downlink subframe. Respectively disposed. The method of claim 1,
The reference signal for the first to fourth layers in an RB pair of one subframe of the downlink subframe is disposed on 16 resource elements at the same rate. The method of claim 1,
The reference signal for the layer 4 or less 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 4 or less layers,
Receiving data for the 4 layers or less through a data region of a downlink subframe;
Receiving reference signals for first and second layers respectively disposed on two concatenated OFDM symbols of the downlink subframe;
Receiving reference signals for third and fourth layers disposed on two concatenated OFDM symbols of the downlink subframe, respectively; And
Estimating a channel to demodulate data for the 4 or less layers using the received reference signal;
The reference signal for the first and second layers or the reference signal for the third and fourth layers are disposed at the same subcarrier position on the concatenated two OFDM symbols. The method according to claim 6,
The reference signals for the first to fourth layers are arranged in the same subcarrier position on contiguous 4 OFDM symbols, respectively. The method according to claim 6,
Reference signals for the first to fourth layers are respectively disposed on contiguous four OFDM symbols of a first slot of the downlink subframe, and concatenated to four OFDM symbols of a second slot of the downlink subframe. Respectively disposed. The method according to claim 6,
The reference signal for the first to fourth layers in an RB pair of one subframe of the downlink subframe is disposed on 16 resource elements at the same rate. The method according to claim 6,
The reference signal for the layer 4 or less is multiplexed using one or more of a time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) scheme. A base station for transmitting a reference signal to a terminal using a layer of 4 or less,
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 layer 4 or less is transmitted through the data region of the downlink subframe, and for the first and second layers respectively disposed on two concatenated OFDM symbols of the downlink subframe. Transmits a reference signal and controls to transmit reference signals for third and fourth layers disposed on two concatenated OFDM symbols of the downlink subframe,
The reference signal is a dedicated reference signal (DRS) for demodulating data for the layer 4 or less.
And a reference signal for the first and second layers or a reference signal for the third and fourth layers are disposed at the same subcarrier position on the concatenated two OFDM symbols. A terminal for processing a reference signal received from a base station using 4 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 4 or lower layers through the data region of the downlink subframe through the receiving module, and receiving the data for the first layer and the second layer disposed on two concatenated OFDM symbols of the downlink subframe, respectively. Receive a reference signal, and control to receive reference signals for third and fourth layers disposed on two concatenated OFDM symbols of the downlink subframe, respectively,
Controlling the terminal to estimate a channel in order to demodulate data for the layer 4 or less using the received reference signal,
The reference signal for the first and second layers or the reference signal for the third and fourth layers are disposed in the same subcarrier position on the concatenated two OFDM symbols.

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