KR20140122530A - Apparatus and method for configuring reference signal in wireless communication system supporting small cells - Google Patents

Abstract

The present invention relates to a device and a method for configuring a reference signal in a wireless communications system to support a small cell. A terminal of the present invention comprises: a receiving unit to receive an OFDM signal and to demap a resource element included in the OFDM signal to a modulation symbol of a complex value; and a channel estimating unit to extract a reference signal sequence by multiplying an orthogonal cover code (OCC), which is defined by each antenna port for a demodulation reference signal (DM-RS), and the modulation symbol of the complex value, to generate an actual reference signal sequence on the DM-RS, and to compare the actual reference signal sequence and the extracted reference signal sequence to estimate a channel. According to the present invention, a regulation for mapping the OCC is clarified in consideration of a power balance in resource configuration for the modified DM-RS to reduce overheads of the DM-RS, thereby solving various communications problems that may occur due to a power unbalance.

Description

TECHNICAL FIELD [0001] The present invention relates to an apparatus and a method for configuring a reference signal in a wireless communication system supporting a small-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to an apparatus and method for configuring a reference signal in a wireless communication system supporting small cells.

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

The small cell can be considered in both the frequency band F1, which is the coverage of the macrocell, and the frequency band F2, except the coverage of the macrocell, and it can be provided both in the indoor environment (in the cube) and in the outdoor environment have. Ideal or non-ideal backhaul networks may also be supported between macrocells and small cells, and / or between small cells. And small cells can be provided both in a low density sparse deployment environment and / or a dense deployment environment.

Small cells aim to increase spectrum efficiency with efficient placement and operation. Several techniques have been proposed for this purpose, one of which is to reduce the overhead for a UE-specific reference signal such as a demodulation reference signal (DM-RS) .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for configuring a reference signal in a wireless communication system supporting small cells.

According to an aspect of the present invention, there is provided a method for transmitting a DM-RS, the method comprising: generating a reference signal sequence for a demodulation reference signal (DM-RS) Generating at least one complex valued modulation symbol based on a reference signal sequence and an orthogonal covering code (OCC), generating a modulation symbol of at least one complex value from the antenna Mapping a resource element of the resource element to a resource element of the port, and transmitting an OFDM signal including the resource element to the terminal.

Herein, the antenna port is included in one of two antenna port groups using different resource elements for transmission of the DM-RS, and the OCC applied to the two antenna port groups is determined according to the index of the PRB pair And the number of the resource elements to which the at least one complex-valued modulation symbol is mapped may be one pair of physical resource block (PRB) and less than six per antenna port group.

According to another aspect of the present invention, a method is provided for generating a sequence of reference signals for a demodulation reference signal (DM-RS) and generating an orthogonal cover code a reference signal generator for generating at least one complex valued modulation symbol based on the orthogonal covering code (OCC) and the reference signal sequence, A resource mapper for mapping the at least one complex-valued modulation symbol to a resource element of the antenna port, and a resource mapper for mapping the at least one complex-valued modulation symbol to a resource element of the antenna port, And a transmitter for transmitting the OFDM signal to the mobile station.

The reference signal generator maps the modulation symbols of the at least one complex value to one physical resource block pair and less than six resource elements per antenna port group, The OCCs applied to the two antenna port groups can be individually determined according to the index.

According to another aspect of the present invention, there is provided a method for demodulating a signal, comprising: receiving an OFDM signal; demapping a resource element included in the OFDM signal to a modulation symbol of a complex value; Extracting a reference signal sequence by multiplying a modulation symbol of the complex value by an orthogonal covering code (OCC) defined for each antenna port, generating an actual reference signal sequence for the DM-RS And performing channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence.

Herein, the antenna port is included in one of two antenna port groups using different resource elements for transmission of the DM-RS, and the OCC applied to the two antenna port groups is included in the index of the PRB pair And the number of the resource elements to which the complex-valued modulation symbols are mapped may be less than six per one physical resource block pair and antenna port group.

According to another aspect of the present invention, there is provided a receiver for receiving an OFDM signal, demultiplexing a resource element included in the OFDM signal into a modulation symbol of a complex value, and a demodulation reference signal (DM-RS) Extracting a reference signal sequence by multiplying a modulation symbol of the complex value by an orthogonal covering code (OCC) defined for each antenna port, generating an actual reference signal sequence for the DM-RS, And a channel estimator for performing channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence.

Here, the antenna port is included in one group of two antenna port groups using different resource elements for transmission of the DM-RS, and the channel estimator may include one or more modulation symbols of the at least one complex value (PRB) pairs and less than six resource elements per antenna port group, and determine OCCs to be applied to the two antenna port groups according to the index of the PRB pair .

In order to reduce the overhead of the DM-RS, in the resource configuration for the modified DM-RS, various communication problems that may arise due to power imbalance are solved by clarifying the rule for mapping orthogonal cover codes considering power balance .

1 is a diagram illustrating a conventional communication system in which a high-power node and a low-power node are disposed.
2 is a block diagram illustrating a wireless communication system to which the present invention is applied.
3 and 4 schematically show the structure of a radio frame to which the present invention is applied.
5A and 5B are diagrams illustrating a pattern in which a downlink DM-RS is mapped to a resource element when an OFDM symbol is composed of a normal CP (Cyclic Prefix).
FIG. 6 is a diagram illustrating a state in which the same OCC is not mapped to one OFDM symbol according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a resource configuration for a DM-RS according to an embodiment.
8 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
9 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
10 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
11 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
12 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
FIG. 13 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
14 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
FIG. 15 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
16 is a diagram illustrating a resource configuration for a DM-RS according to yet another embodiment.
FIG. 17 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
18 is a view showing a resource configuration for a DM-RS according to yet another embodiment.
19 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
20 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
FIG. 21 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.
22 is a flowchart illustrating a method of transmitting a reference signal between a terminal and a base station according to an embodiment of the present invention.
23 is a block diagram illustrating a terminal and a base station according to an embodiment.

Hereinafter, some embodiments will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

The present invention will be described with reference to a communication network. The work performed in the communication network may be performed in a process of controlling the network and transmitting data by a system (e.g., a base station) that manages the communication network, The work can be done.

2 is a block diagram illustrating a wireless communication system to which the present invention is applied.

Referring to FIG. 2, the wireless communication system 10 is widely deployed to provide various communication services such as voice, packet data, and so on. The wireless communication system 10 includes at least one base station 11 (BS). Each base station 11 provides communication services for a particular geographical area or frequency domain and may be referred to as a site. A site may be divided into a plurality of areas 15a, 15b, and 15c, which may be referred to as sectors, and the sectors may have different cell IDs.

A mobile station (MS) 12 may be fixed or mobile and may be a user equipment (UE), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, (personal digital assistant), a wireless modem, a handheld device, and the like. The base station 11 generally refers to a station that communicates with the terminal 12 and includes an evolved-NodeB (eNodeB), a base transceiver system (BTS), an access point, a femto base station (Femto eNodeB) (ENodeB), a relay, a remote radio head (RRH), and the like. The cells 15a, 15b and 15c should be interpreted in a comprehensive sense to indicate a partial area covered by the base station 11 and include all coverage areas such as megacell, macrocell, microcell, picocell, femtocell to be.

Hereinafter, a downlink refers to a communication or communication path from the base station 11 to the terminal 12, and an uplink refers to a communication or communication path from the terminal 12 to the base station 11 . In the downlink, the transmitter may be part of the base station 11, and the receiver may be part of the terminal 12. In the uplink, the transmitter may be part of the terminal 12, and the receiver may be part of the base station 11. There is no limit to the multiple access scheme applied to the wireless communication system 10. [ (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA , OFDM-CDMA, and the like. These modulation techniques increase the capacity of the communication system by demodulating signals received from multiple users of the communication system. The uplink transmission and the downlink transmission may be performed using a time division duplex (TDD) scheme transmitted at different times or a frequency division duplex (FDD) scheme using different frequencies.

The layers of the radio interface protocol between the terminal and the base station are divided into a first layer (L1), a second layer (L1), and a second layer (L2) based on the lower three layers of an Open System Interconnection A second layer (L2), and a third layer (L3). Among them, the physical layer belonging to the first layer provides an information transfer service using a physical channel.

There are several physical channels used in the physical layer. The physical downlink control channel (PDCCH) includes a resource allocation and transmission format of a downlink shared channel (DL-SCH), a resource of an uplink shared channel (UL-SCH) Resource allocation of an upper layer control message such as allocation information, a random access response transmitted on a physical downlink shared channel (PDSCH), transmission power control for individual terminals in an arbitrary terminal group : TPC) commands, and so on. A plurality of PDCCHs can be transmitted in the control domain, and the UE can monitor a plurality of PDCCHs.

The control information of the physical layer mapped to the PDCCH is referred to as downlink control information (DCI). That is, the DCI is transmitted on the PDCCH. The DCI may include an uplink or downlink resource allocation field, an uplink transmission power control command field, a control field for paging, a control field for indicating a random access response (RA response), and the like.

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

Referring to FIGS. 3 and 4, a radio frame includes 10 subframes. One subframe includes two slots. The time (length) for transmitting one subframe is called a transmission time interval (TTI). Referring to FIG. 2, for example, the length of one subframe (1 subframe) may be 1 ms and the length of one slot may be 0.5 ms.

A slot may contain a plurality of symbols in the time domain. For example, in the case of a radio system using OFDMA (Downlink Frequency Division Multiple Access) in a downlink (DL), the symbol may be an Orthogonal Frequency Division Multiplexing (OFDM) symbol. On the other hand, the representation of the symbol period of the time domain is not limited by the multiple access scheme or the name. For example, in a time domain, a plurality of symbols may be a single-carrier-frequency division multiple access (SC-FDMA) symbol, a symbol period, etc. in addition to an OFDM symbol.

The number of OFDM symbols included in one slot may vary according to the length of a CP (Cyclic Prefix). For example, one slot includes seven OFDM symbols in case of a normal CP, and one slot may include six OFDM symbols in case of an extended CP.

A resource block (RB) is a resource allocation unit, which includes time-frequency resources corresponding to 180 kHz on the frequency axis and 1 slot on the time axis. A resource element (RE) represents a smallest time-frequency unit to which a modulation symbol of a data channel or a modulation symbol of a control channel is mapped.

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

Since the terminal knows the information of the reference signal, the terminal estimates the channel based on the received reference signal and compensates the channel value, so that the data sent from the transmission / reception point can be accurately obtained. Let p be the reference signal sent from the transmitting / receiving point, h be the channel information experienced by the reference signal during transmission, n be the thermal noise generated by the terminal, and y be the signal received by the terminal y = h p + n have. Since the reference signal p is already known by the UE, if the LS (Least Square) scheme is used, the channel information

) Can be estimated.

Here, the channel estimation value estimated using the reference signal p

The

Value, so for accurate estimation of the h value

It is necessary to converge to zero.

The reference signal is typically generated by generating a signal from a sequence of reference signals. The reference signal sequence may be one or more of several sequences having superior correlation characteristics. For example, a Constant Amplitude Zero Auto-Correlation (CAZAC) sequence such as a Zadoff-Chu (ZC) sequence or a PN (pseudo-noise) sequence such as an m-sequence, a Gold sequence or a Kasami sequence May be used as a sequence of reference signals, and various other sequences having superior correlation characteristics may be used depending on system conditions. The reference signal sequence may be cyclic extension or truncation to adjust the length of the sequence or may be used in various forms such as binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) And may be mapped to RE (Resource element).

The downlink reference signal includes a cell-specific RS, a MBSFN reference signal, a UE-specific RS, a position reference signal PRS, RS) and a CSI (Channel State Information) reference signal (CSI-RS).

The UE-specific reference signal is a reference signal received by a specific UE or a specific UE group in a cell and can be called a Demodulation RS (DM-RS) since it is mainly used for data demodulation of a specific UE or a specific UE group. have.

5A and 5B are diagrams illustrating a pattern in which a downlink DM-RS is mapped to a resource element when an OFDM symbol is composed of a normal CP (Cyclic Prefix).

5A and 5B, there is a specific antenna port defined to transmit the downlink DM-RS. This is called an antenna port for DM-RS. For example, a DM-RS may be transmitted using up to eight antenna ports, and the number of these antenna ports may be 7, 8, 9, 10, 11, 12, 13, The DM-RS transmitted from the antenna port x is denoted by Rx, and for example, the DM-RS transmitted from the antenna port 7 is denoted by R7.

When one layer is used for transmission of the PDSCH, antenna port 7 or 8 is used for transmission of the DM-RS. When v layers are used for transmission of the PDSCH, antenna ports 7, 8, ... , v + 6 are used. A total of 12 resource elements are mapped per antenna port for DM-RS in one physical resource block (PRB) on the frequency axis and one PRB pair defined as one subframe on the time axis.

Antenna ports 7, 8, 11, and 13 are mapped to the same resource elements on time-frequency and may be referred to as code division multiplexing (CDM) group 1. That is, R7, R8, R11, and R13 are all mapped to resource elements at the same position. Although antenna ports 11 and 13 are not shown in FIG. 5, R11 and R13 are all mapped to resource elements at the same positions as R7 and R8. Also, antenna ports 9, 10, 12, and 14 are mapped to the same resource elements on a time-frequency basis and can be referred to as CDM group 2. That is, R9, R10, R12, and R14 are all mapped to resource elements at the same position. Although antenna ports 12 and 14 are not shown in FIG. 5, R12 and R14 are all mapped to resource elements at the same positions as R9 and R10.

The resource elements to which the DM-RS is mapped on different time-frequency are different between different CDM group 1 and CDM group 2. Therefore, CDM group 1 and CDM group 2 can be distinguished by the location of the resource element. This is called the division based on frequency division muting (FDM) and time division multiplexing (TDM). This is because the location of the resource element is located by frequency and time.

The antenna ports in the CDM group that are mapped to the same resource elements in time-frequency are classified by an orthogonal sequence such as Orthogonal Cover Code (OCC) as shown in Table 1 below. This is called CDM-based classification.

OCC (length = 4) [a b c d] OCCA [+1 +1 +1 +1] OCC B [+1 -1 +1 -1] OCC C [+1 +1 -1 -1] OCC D [+1 -1 -1 +1]

Referring to Table 1, the antenna ports 7, 8, 11 and 13 in the CDM group 1 are divided into OCC A, B, C and D, respectively, and antenna ports 9, 10, 12 and 14 in the CDM group 2 are also divided into OCC A, B, C and D.

The length of the OCC depends on how many OFDM symbols are applied in one subframe. For example, a four-channel OCC is applied across four OFDM symbols in one subframe on the time axis. For example, when a normal CP is used in a normal subframe, four OFDM symbols to which OCC is applied among a total of 14 OFDM symbols are indexes # 5, # 6, # 7, 12, # 13. The OFDM symbol indexes # 0, # 1, # 2, # 3, # 4, # 5 and # 6 in the first slot and the OFDM symbol indexes # # 5 and # 6 are OFDM indices # 0, # 1, # 2, # 3, # 4, # 5, # 6, # 7, # 8, # 9 , # 10, # 11, # 12, and # 13.

In a time division duplex (TDD) system, each subframe may be composed of a downlink subframe, an uplink subframe, and a special subframe. The special subframe includes three fields such as DwPTS, GP, and UpPTS, and the TDD configuration of the special subframe may be defined as nine as shown in Table 2 according to the length of each field.

TDD configuration of special subframe Normal CP Expanded CP DwPTS UpPTS DwPTS UpPTS In the uplink, the normal CP In the uplink, the extended CP In the uplink, the normal CP In the uplink, the extended CP 0 6592Ts 2192Ts 2560Ts 7680Ts 2192Ts 2560Ts One 19760Ts 20480Ts 2 21952Ts 23040Ts 3 24144Ts 25600Ts 4 26336Ts 7680Ts 4384Ts 5120Ts 5 6592Ts 4384Ts 5120Ts 20480Ts 6 19760Ts 23040Ts 7 21952Ts 12800Ts 8 24144Ts - - - 9 13168Ts - - -

Referring to Table 2, when a normal CP is used in a special subframe in which the TDD configuration is 3, 4, or 8, four OFDM symbols to which OCC is applied among a total of 14 OFDM symbols are indexes # 2, # 3, 9, # 10. As another example, when a normal CP is used in a special subframe in which the TDD configuration is 1, 2, 6, or 7, four OFDM symbols to which OCC is applied among the total 14 OFDM symbols are indexes # 2, # 3, 5, # 6.

On the other hand, a 2-length OCC is applied over two OFDM symbols in one subframe on the time axis. For example, when a normal CP is used in a special subframe in which the TDD configuration is 9, two OFDM symbols to which OCC is applied among a total of 6 OFDM symbols may be indexes # 2 and # 3.

When mapping a 4-length OCC to 4 OFDM symbols in the order of a, b, c, and d in Table 1, only one of a, b, c, and d may be intensively mapped to a specific resource element . This is also true when two OCCs of length 2 are mapped to two OFDM symbols in the order of a and b in Table 1. [ That is, in the case of an OFDM symbol to which only a is mapped, only +1 is mapped, which may cause power balancing with other OFDM symbols to which +1 and -1 can be mapped. Therefore, it is necessary to distribute the same OCC to one OFDM symbol as shown in FIG.

FIG. 6 is a diagram illustrating a state in which the same OCC is not mapped to one OFDM symbol according to an embodiment of the present invention.

Referring to FIG. 6, there are a total of six DM-RS mappings per each CDM group over two PRBs over frequency. Each mapping can start counting from the bottom of the PRB, or from the top of the PRB, starting with 0, 1, 2, ... , 6th mapping (0 ^th , 1 ^st , 2 ^nd , ..., 6 ^th ) mapping. At this time, the OCC is mapped so that a, b, c, and d are distributed as evenly as possible over a plurality of subcarriers on one OFDM symbol, so that the power balance between the OFDM symbols can be balanced. To achieve this, the power is balanced in terms of two PRB units over frequency. Hereinafter, in the present invention, each index such as a PRB index, an OFDM symbol index, and a subcarrier index is assigned from 0th. That is, the even number is 0, 2, 4, 6, ... And an odd number means 1, 3, 5, 7, ....

First, OCCs in the order of a, b, c, and d are applied to the CDM group 1 in the order of 0, 2, and 4 (that is, 3, and 5 (that is, odd-numbered starting from 0), OCC is applied in the order of d, c, b, a in the reverse order.

Next, in the CDM group 2, a cyclic delay of CDM groups 1 and 2 is performed on the frequency axis from 0, 2, and 4 (that is, starting from 0) The OCC is applied in order of d, a, and b, and OCC in the order of b, a, d, and c in the reverse order of 1, 3, and 5 (ie, do.

In this case, there are 12 OCC mappings in total for the entire CDM group and 6 times for each CDM group in the two PRBs on the frequency, and the OCC sequence values a, b, c, and d are mapped three times, respectively.

Hereinafter, an OCC mapping rule applicable in a resource configuration for a DM-RS of a modified type to reduce the overhead of a DM-RS in order to increase spectral efficiency, and a reference signal sequence mapping . The mapping pattern of the DM-RS in the resource configuration for the modified DM-RS may be a subset of the mapping pattern of the DM-RS as shown in FIG.

1. OCC mapping rules

7 is a diagram illustrating a resource configuration for a modified DM-RS according to an embodiment of the present invention.

Referring to FIG. 7, a resource configuration for a modified DM-RS transmits a DM-RS as a set of power balance between PRB pairs A, B, C, and D corresponding to four PRBs on the frequency axis. In the resource configuration for the modified DM-RS, antenna ports 7, 8, 9, and 10 out of 7, 8 belong to CDM group 1, and 9, 10 belong to CDM group 2.

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of this embodiment are transmitted on the OFDM symbols of the indexes # 5 and # 6 of the even slot in the time axis and the indexes # 5 and # 6 OFDM symbols.

On the other hand, in the frequency axis, the DM-RS of the CDM group 1 transmits the subcarriers of the indexes # 1 and # 11 of the PRB A and the subcarriers of the subcarrier # When a subcarrier index is defined from the bottom to # 0, # 1, ..., # 11 on the frequency axis for 12 subcarriers in the PRB, it means that the subcarrier corresponds to the ath subcarrier starting from 0, And PRB B, D in the sub-carrier of index # 6. Conversely, the DM-RS of the CDM group 1 is transmitted in the subcarriers of the index # 6 of the PRB A and the subcarriers of the index # 1 and # 11 of the PRB B and D in the odd numbered slot.

In the even-numbered slot, the DM-RS of the CDM group 2 is transmitted in the subcarriers of the indexes # 0 and # 10 of subcarriers PRB A and C, and subcarriers of index # 5 of PRB B and D in the even-numbered slot. Conversely, the DM-RS of the CDM group 2 is transmitted in the subcarriers of index # 5 of PRB A and PRB B, and indexes # 0 and # 10 of D in odd numbered slots.

According to the resource configuration for the modified DM-RS of FIG. 7, since the number of resource elements to which the DM-RS is mapped per CDM group in one PRB pair is 6, it is reduced to 1/2 of the existing 12, DM-RS overhead is reduced in half.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over two OFDM symbols on each carrier wave, the OCC length is 2. That is, as shown in Table 1, only a and b are used as OCC, not a, b, c, and d, when OCC length is 4.

When the OCC mapping rule is defined in units of two PRBs on a frequency basis, the OCC mapping is applied repeatedly or equally to every two PRBs. In this case, OCC a and b exist at a ratio of 2: 1 or 1: 2 on one OFDM symbol for each CDM group, resulting in a power imbalance. Therefore, the embodiment of FIG. 7 defines the OCC mapping rule in units of four PRBs in terms of frequency. That is, the OCC mapping is applied repeatedly or equally to every four PRBs. In this case, PRB A, B, C, and D correspond to _{PRBs in} which the rest of the modulo operation (n _PRB mod 4) is 0, 1, 2, and 3 respectively when n _PRB is divided by 4 . Here, n _PRB is the PRB index on the frequency axis.

For each CDM group, OCCs are mapped six times from the bottom along the frequency axis in one slot and four PRBs, with the even-mapped OCCs being a, b and the odd-mapped OCCs being b, a. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

The OCC mapping rules are expressed as follows.

Referring to Equation (2 ⁾ , a ^(p) _{k, l} is a modulation symbol of a demodulation value, and is expressed as a product of w _p (i) and r (m). p is an antenna port number, k is an index of a subcarrier for all subcarriers, and l is an index of OFDM symbols in a single slot. That is, a ^(p) _{k, l} denotes a modulation symbol of a demodulation value mapped to a resource element whose index of the sub-carrier is k and the index of the OFDM symbol is l when the antenna port number is p.

l 'is a value indicating the order of OFDM symbols to which the OCC is mapped along the time axis in the subframe. Or l 'means the l'th sequence of the OCC. For example, if l '= 0, the OCC indicates the OFDM symbol to be mapped to the 0th, and if l' = 1, the OCC indicates the first mapped OFDM symbol.

w _p (i) is the i-th sequence of OCC for antenna port p. For i = 0, 1, 2, 3, the OCC is

to be. Then, w _p (i) is calculated according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

Referring to Equation (3), m 'is a value indicating the order or the number of times the OCC is mapped along the frequency axis in the two PRBs. In the case of FIG. 7, for each CDM group, m '= 0, 1, 2 since a total of 3 OCC mappings are made along the frequency axis within one slot and two PRBs.

Is a PRB offset to the order m 'are two of the OCC PRB mapped to be counted over (from n _PRB index of the PRB index PRB _(PRB n +1)). For example, m '= 0, 1, 2 exists over PRB A, B, and m' = 0, 1, 2 over PRB C, D.

On the other hand, according to the modulo operation of Equation (3), w _p (i), when the integer obtained by dividing n _PRB by 2 and m '

, And the remainder is 1, w _p (i)

to be. For example, let w _P (i) be defined as the following table.

Antenna port p

7 [+1 +1] 8 [+1 -1] 9 [+1 +1] 10 [+1 -1]

Referring to Table 3, w ₇ (0) is a value of the 0th sequence of the OCC applied to the antenna port 7, and w ₈ (1) is a value of the first sequence of the OCC applied to the antenna port 8 -1.

p = 8, and CDM group 1, and applying Equations 3 and 3 to FIG. 7, the following OCC mapping rule is derived. Based on the even-numbered slot (even slot), PRB, so the sub-carrier index OCC mapping # 1 in the zeroth A generated m '= 0, and, since this is the result of the operation zero modulo of Equation 3 w _p (i) The

to be. Therefore, OCC mapped to CDM group 1 at PRB A is [+1 -1] according to Table 3, which is referred to as [ab]. Next, since OCC mapping occurs first in subcarrier index # 11 in PRB A, m '= 1 and the result of modulo operation in Equation (3) becomes 1, so w _p (i)

to be. Therefore, the OCC mapped first in CDM group 1 in PRB A is [-1 +1] according to Table 3 and is represented by [ba]. That is, the OCC applied to m '= 0 and the OCC applied to m' = 1 are in reverse order. In addition, the OCC B PRB mapped to the second sub-carrier indexes # 6 in it occurs in m '= 2, and so is the result of the calculation modulo 0 of Equation 3 w _p (i) is

to be. Therefore, the OCC that is mapped second to CDM group 1 in PRB B is [+1 -1] according to Table 3 and is represented by [ab].

The embodiment of FIG. 7 discloses that the same OCC mapping rule as that of CDM group 1 is applied to CDM group 2 as well. That is, in PRB A and B, the OCC mapping rule for CDM group 2 is the same as the OCC mapping rule for CDM group 1, which is repeatedly applied to PRB C and D in the same manner. For example, assuming that p = 9 and CDM group 2, an OCC mapping result as shown in FIG. 7 can be obtained.

As a result, referring to the OCC sequences of the CDM groups 1 and 2 mapped along the frequency axis on the OFDM symbol # 5 in FIG. 7, PRBs A, B, C, , b, a, a, b, b. Since a is mapped six times and b is mapped six times, the OCC sequences a and b are mapped the same number of times as a whole. Thus, the DM-RSs on OFDM symbol # 5 can be seen as power balanced.

Table 3 may be replaced by the following Table 4.

Antenna port p

7 [+1 +1] 8 [-1 +1] 9 [+1 +1] 10 [-1 +1]

Table 4 shows the order of the OCC sequences [a b] in Table 3.

On the other hand, r (m) is a reference signal sequence. One part of the reference signal sequence r (m) is mapped to a ^(p) _{k, l} in one subframe within a PRB (index = n _PRB ) allocated for PDSCH transmission. For example, r (m) may be calculated by the pseudo-random sequence c (i) based on a gold sequence as follows:

Here, when a total of X resource elements are used in one PRB pair (X = 2, 4, 6, 8, etc.), the total length of the reference signal sequence r (m) becomes 12 N N _RB ^{max, DL} . Therefore, m = 0, 1, ..., XN _RB ^{max, DL} -1. For example, when a normal CP is used, a total of 12 resource elements in one PRB pair are used for DM-RS transmission, so that the total length of the reference signal sequence r (m) _RB ^{max, DL} . Therefore, m = 0, 1, ..., 12N _RB ^{max, DL} -1. As another example, when an extended CP is used, a total of 16 resource elements in one PRB pair are used for transmission of the DM-RS, so that the total length of the reference signal sequence r (m) required over the entire band is 16 N _RB ^{max , DL} . Thus, m = 0, 1, ..., 16N _RB ^{max , DL} -1.

N _RB ^{max, DL} represents the maximum number of RBs in the downlink. N _RB ^{max, DL} is not the case in an even number, the equation 2 N _RB ^{max, DL} / 2 is

≪ / RTI > n _PRB corresponds to the PRB index on the frequency ^, and has an integer value between 0 and N _RB ^{max, DL} -1.

The subcarrier index k may be defined in various forms. As an example, the subcarrier index k may be determined according to the following equation.

Referring to Equation (5), N _sc ^RB is the number of subcarriers in one RB, usually 12. And k 'can be determined by the following equation.

As another example, the subcarrier index k may be determined according to the following equation (7).

As another example, the subcarrier index k may be determined according to the following equation (8).

As another example, the subcarrier index k may be determined according to the following equation (9).

In the case of a special subframe in which the DM-RS is transmitted i) TDD configuration 1, 2, 6, 7, i = (1 'mod 2) of w _p (i) and ii) a subframe other than the special subframe of TDD configuration 1, 2, 6, 7. For example, i 'can be defined as the following equation.

When the special subframe TDD configuration is 1, 2, 6, or 7, all DM-RSs are distributed in even-numbered slots as shown in FIG. 5, and are not distributed in odd-numbered slots. This is because GP and UpPTS may exist in odd numbered slots. That is, since the distribution of the DM-RS varies depending on the configuration of the special subframe TDD, the order 1 'of the OFDM symbol to which the OCC is mapped must be changed. For example, in a special subframe of TDD configuration 1, 2, 6 and 7 as shown in Equation 10, OCC is (n _s mod 2) = 0 slot that satisfies n _s, i.e., four OFDM symbols of the even-numbered time slot (L '= 0, 1, 2, 3). On the other hand, in a special sub-frames or regular subframes instead of TDD configuration 1, 2, 6, 7, OCC is (n _s mod 2) = 2 in the even-numbered time slot that satisfies 0 OFDM symbol (l '= 0, 1) or (n _s mod 2) = 1 are sequentially mapped to the two OFDM symbols (l '= 2, 3) of the odd numbered slot.

The index 1 of the OFDM symbol to which the actual OCC is mapped according to l 'is determined. An example of this is shown in Equation (11).

Table 3 and Equations (2) to (11) are merely one embodiment expressing the OCC mapping rule of FIG. 7 according to the present embodiment. All of which are included in the technical idea of the present invention.

8 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.

Referring to FIG. 8, the resource configuration for the modified DM-RS according to FIG. 8 is the same as the resource configuration for the modified DM-RS according to FIG. However, in the OCC mapping rule, FIG. 8 differs from FIG. 7 in that different OCC mapping rules are applied between the CDM group 1 and the CDM group 2. This is because the same OCC mapping rule is applied to the CDM groups 1 and 2 in FIG.

More specifically, in the embodiment of FIG. 8, OCC is cyclically shifted and mapped by 1 at the same m 'among different CDM groups. For example, in the case of CDM group 1, the even-numbered OCCs are [a, b] from the bottom along the frequency axis in the PRB and the odd-mapped OCCs are [b, a]. On the other hand, in the case of CDM group 2, the even-numbered OCCs are [b, a] from the bottom along the frequency axis in the PRB, and the odd-mapped OCCs are [a, b]. That is, the OCC is circularly shifted and mapped between different CDM groups.

To implement this embodiment, the i-th sequence w _p (i) of the OCC for the antenna port p can be defined as shown in the following table.

Antenna port p

7 [+1 +1] 8 [+1 -1] 9 [+1 +1] 10 [-1 +1]

Table 3 and Table 5 are compared with Table 3 in that OCC of antenna port 10 in Table 5 is [-1 +1]. That is, Table 5 shows the result of cyclically shifting the OCC of Table 3 by 1. In this way, OCC can be mapped by cyclic shifting by 1 between CDM groups.

According to the present embodiment, the following OCC mapping rules are applied to CDM group 1 and CDM group 2. OCC mapping is performed at the 0th position in the subcarrier index # 1 of the PRB A with respect to the even slot in the CDM group 1, so that m '= 0 and OCC mapped to the CDM group 1 as the 0th [ ab]. Meanwhile, according to the present embodiment, OCC mapped to the 0th CDM group 2 is cyclically shifted by 1 compared to the CDM group 1, so that [b a] is obtained.

Next, OCC mapping is performed first in the subcarrier index # 11 on the PRB A for the CDM group 1, m '= 1, and the OCC mapped first to the CDM group 1 according to Equation (3) . Meanwhile, according to the present embodiment, OCC mapped first in the CDM group 2 is cyclically shifted by one compared to the CDM group 1, so that [a b] is obtained.

Next, for the CDM group 1, m '= 2 since OCC mapping occurs secondly in the subcarrier index # 6 on the PRB B, and the OCC, which is mapped second to the CDM group 1 according to Equation (3) . Meanwhile, according to the present embodiment, the OCC mapped second to the CDM group 2 is cyclically shifted by one compared with the CDM group 1, and therefore, [b a] is obtained.

B, a, a, b, b, a, and b in sequence from PRB A, B, C, and D in the OCC sequences of CDM groups 1 and 2 mapped along the frequency axis on OFDM symbol # , b, b, a, a, b. Since a is mapped six times and b is mapped six times, the OCC sequences a and b are mapped the same number of times as a whole. Thus, the DM-RSs on OFDM symbol # 5 can be seen as power balanced.

On the other hand, Table 5 may be replaced by Table 6.

Antenna port p

7 [+1 +1] 8 [-1 +1] 9 [+1 +1] 10 [+1 -1]

Table 6 shows the order of the OCC sequences [a b] in Table 5.

9 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 9, a resource configuration for a modified DM-RS transmits a DM-RS as a set of power balance between PRB pairs A, B, C, and D on a frequency axis. Among the antenna ports 7, 8, 9 and 10, the resource configuration for the modified DM-RS belongs to the CDM group 1, and the CDM group 2 belongs to the CDM group 1,

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of the present embodiment are transmitted on the OFDM symbols of the indexes # 5 and # 6 of the even-numbered slot in the time axis and are transmitted on the OFDM symbols of the indexes # 5 and # 6 of the odd-numbered slot.

On the other hand, in the frequency axis, the DM-RSs of the CDM groups 1 and 2 are transmitted only in the even-numbered PRBs (i.e., PRB A and C) D). In particular, the DM-RS of the CDM group 1 is transmitted on the subcarriers of the indexes # 1, # 6 and # 11 in the PRBs A, B, C and D while the DM- D on subcarriers of indexes # 0, # 5, and # 10.

According to the resource configuration for the modified DM-RS of FIG. 9, since the number of resource elements to which the DM-RS is mapped per CDM group in one PRB pair is six, DM-RS overhead is reduced in half.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

Similarly, for all CDM groups, the OCC is mapped six times along the frequency axis in one slot and four PRBs, where the even-numbered OCCs from the bottom are mapped a and b, and the odd-mapped OCCs are b, a to be. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

An example for implementing this OCC mapping rule is shown in Equation (12).

Equation 2 is the same as Equation 2 except that in order to give an offset to map the OCC to the PRB of the even index in the even number slot and to map the OCC to the PRB of the odd index in the odd number slot, Can be defined together.

Here, k 'is expressed by Equation (6). As another example, k may be defined more precisely as shown in the following Equation (14).

The reason that N ^RB _sc is included in equations (13) and (14) is that the PRB transmitting the DM-RS exists one by one, i.e., gives an offset of one PRB. w _p (i) can be defined in Table 3 or Table 4.

The OCC mapping rules of FIG. 9 according to the present embodiment are merely one embodiment, and the OCC mapping rules of FIG. All of which are included in the technical idea of the present invention.

10 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 10, the resource configuration for the modified DM-RS according to FIG. 10 is the same as the resource configuration for the modified DM-RS according to FIG. However, in the OCC mapping rule, FIG. 10 differs from FIG. 9 in that different OCC mapping rules are applied between CDM group 1 and CDM group 2. This is because the same OCC mapping rule is applied to the CDM groups 1 and 2 in FIG.

More specifically, in the embodiment of FIG. 10, OCCs are cyclically shifted and mapped by 1 at the same m 'among different CDM groups. For example, in the case of CDM group 1, the even-numbered OCCs are [a, b] from the bottom along the frequency axis in the PRB and the odd-mapped OCCs are [b, a]. On the other hand, in the case of CDM group 2, the even-numbered OCCs are [b, a] from the bottom along the frequency axis in the PRB, and the odd-mapped OCCs are [a, b]. That is, the OCC is circularly shifted and mapped between different CDM groups.

In order to implement this embodiment, the i-th sequence w _p (i) of the OCC for the antenna port p may be defined as shown in Table 5 or 6. That is, Tables 5 and 6 are the results of cyclically shifting OCCs of Table 3 and Table 4, respectively. In this way, OCC can be mapped by cyclic shifting by 1 between CDM groups.

The OCC mapping rules of FIG. 10 according to the present embodiment are merely one embodiment, and the OCC mapping rules of FIG. All of which are included in the technical idea of the present invention.

11 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment.

Referring to FIG. 11, a resource configuration for a modified DM-RS transmits a DM-RS as a set of power balance between PRB pairs A and B corresponding to two PRBs on a frequency axis. Among the antenna ports 7, 8, 9 and 10, the resource configuration for the modified DM-RS belongs to the CDM group 1, and the CDM group 2 belongs to the CDM group 1,

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of this embodiment are transmitted only on the OFDM symbols of the indexes # 5 and # 6 of the even slot in the time axis, and are not transmitted in the odd slot.

On the other hand, when viewed from the frequency axis, the DM-RS of the CDM group 1 is transmitted on the subcarriers of the indexes # 1, # 6 and # 11 of each PRB. The DM-RS of the CDM group 2 is transmitted on the subcarriers of indexes # 0, # 5, and # 10 of each PRB.

According to the resource configuration for the modified DM-RS of FIG. 11, since the number of resource elements to which the DM-RS is mapped per CDM group in one PRB pair is 6, DM-RS overhead is reduced in half.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over two OFDM symbols of each carrier wave, the OCC length is 2. That is, as shown in Table 1, only a and b are used as OCC, not a, b, c, and d, when OCC length is 4.

Similarly, for all CDM groups, the OCC is mapped six times along the frequency axis in one slot and two PRBs, where the even-numbered OCCs from the bottom are mapped a and b, and the odd-mapped OCCs are b, a to be. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

An example for implementing this OCC mapping rule is shown in Equation (15).

In order to implement the same OCC mapping for all the CDM groups as described above, the i-th sequence w _p (i) of the OCC for the antenna port p can be defined as shown in Table 3 or 4.

And the value of k can be defined as the following equation (16).

Here, k 'is expressed by Equation (6). w _p (i) can be defined in Table 3 or Table 4. w _p (i) can be expressed by the following equation (17) according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

Also, l '= 0, 1, m' = 0, 1, 2, and 1 is defined by the following equation (18).

Or l may be defined more concisely as: " (19) "

Table 3, Table 4, and Equations 15 to 19 represent only one embodiment expressing the OCC mapping rule of FIG. 11 according to the present embodiment, and may be expressed by other formulas or tables that implement the OCC mapping rule of FIG. All of which are included in the technical idea of the present invention.

12 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 12, the resource configuration for the modified DM-RS according to FIG. 12 is the same as the resource configuration for the modified DM-RS according to FIG. However, in the OCC mapping rule, FIG. 12 differs from FIG. 11 in that different OCC mapping rules are applied between the CDM group 1 and the CDM group 2. This is because the same OCC mapping rule is applied to the CDM groups 1 and 2 in FIG.

More specifically, in the embodiment of FIG. 12, OCC is cyclically shifted and mapped by 1 at the same m 'among different CDM groups. For example, in the case of CDM group 1, the even-numbered OCCs are [a, b] from the bottom along the frequency axis in the PRB and the odd-mapped OCCs are [b, a]. On the other hand, in the case of CDM group 2, the even-numbered OCCs are [b, a] from the bottom along the frequency axis in the PRB, and the odd-mapped OCCs are [a, b]. That is, the OCC is circularly shifted and mapped between different CDM groups.

In order to implement this embodiment, the i-th sequence w _p (i) of the OCC for the antenna port p may be defined as shown in Table 5 or 6. That is, Tables 5 and 6 are the results of cyclically shifting OCCs of Table 3 and Table 4, respectively. In this way, OCC can be mapped by cyclic shifting by 1 between CDM groups.

Table 5, Table 6, and Equations 15 to 19 are merely one embodiment for expressing the OCC mapping rule of FIG. 12 according to the present embodiment, and may be applied to other formulas or expressions for implementing the OCC mapping rule of FIG. All of which are included in the technical idea of the present invention.

13 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 13, a resource configuration for a modified DM-RS transmits a DM-RS by balancing power on only one PRB pair on a frequency axis. Among the antenna ports 7, 8, 9 and 10, the resource configuration for the modified DM-RS belongs to the CDM group 1, and the CDM group 2 belongs to the CDM group 1,

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of this embodiment are transmitted only on the OFDM symbols of the indexes # 5 and # 6 of the even slot in the time axis, and are not transmitted in the odd slot.

On the other hand, when viewed from the frequency axis, the DM-RS of the CDM group 1 is transmitted on the subcarriers of the indexes # 1 and # 11 of each PRB. The DM-RS of the CDM group 2 is transmitted on the subcarriers of indexes # 0 and # 10 of each PRB. That is, the DM-RS is transmitted on the subcarriers at both edges of the PRB.

According to the resource configuration for the modified DM-RS of FIG. 13, since the number of resource elements to which the DM-RS per CDM group is mapped in one PRB pair is four, it is reduced to 1/3 of the existing 12, DM-RS overhead is reduced to 1/3.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over two OFDM symbols of each carrier wave, the OCC length is 2. That is, as shown in Table 1, only a and b are used as OCC, not a, b, c, and d, when OCC length is 4.

According to this embodiment, the OCCs are mapped twice in total in the same frequency axis in one slot and one PRB for all the CDM groups. The even-numbered OCCs from the bottom are mapped to a and b, OCC is b, a. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

An example for implementing such an OCC mapping rule is shown in Equation 20 below.

In order to implement the same OCC mapping for all the CDM groups as described above, the i-th sequence w _p (i) of the OCC for the antenna port p can be defined as shown in Table 3 or 4.

And the value of k can be defined by the following equation (21).

Here, k 'is expressed by Equation (6). w _p (i) can be defined in Table 3 or Table 4. w _p (i) can be expressed by the following equation (22) according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

Referring to Equation (22), since the OCC mapping rule is applied in units of one PRB, there is no need to set a separate PRB offset with n _PRB values. Also, l '= 0,1, m' = 0,1, and 1 is defined as the following equation (23).

Or l may be defined more concisely as in Equation 24 below.

Table 3, Table 4, and Equations 20 to 24 represent only one embodiment expressing the OCC mapping rule of FIG. 13 according to the present embodiment, and may be expressed by other formulas or tables that implement the OCC mapping rule of FIG. All of which are included in the technical idea of the present invention.

FIG. 14 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 14, the resource configuration for the modified DM-RS according to FIG. 14 is the same as the resource configuration for the modified DM-RS according to FIG. However, in the OCC mapping rule, FIG. 14 differs from FIG. 13 in that different OCC mapping rules are applied between the CDM group 1 and the CDM group 2. This is because the same OCC mapping rule is applied to the CDM groups 1 and 2 in FIG.

More specifically, in the embodiment of FIG. 14, OCCs are cyclically shifted and mapped by 1 at the same m 'among different CDM groups. For example, in the case of CDM group 1, the even-numbered OCCs are [a, b] from the bottom along the frequency axis in the PRB and the odd-mapped OCCs are [b, a]. On the other hand, in the case of CDM group 2, the even-numbered OCCs are [b, a] from the bottom along the frequency axis in the PRB, and the odd-mapped OCCs are [a, b]. That is, the OCC is circularly shifted and mapped between different CDM groups.

In order to implement this embodiment, the i-th sequence w _p (i) of the OCC for the antenna port p may be defined as shown in Table 5 or 6. That is, Tables 5 and 6 are the results of cyclically shifting OCCs of Table 3 and Table 4, respectively. In this way, OCC can be mapped by cyclic shifting by 1 between CDM groups.

Table 5, Table 6, and Equations 20 to 24 are merely one embodiment expressing the OCC mapping rule of FIG. 14 according to the present embodiment, and may be applied to other formulas or expressions for implementing the OCC mapping rule of FIG. All of which are included in the technical idea of the present invention.

15 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 15, a resource configuration for a modified DM-RS transmits a DM-RS by balancing power on two PRB pairs on a frequency axis. Among the antenna ports 7, 8, 9 and 10, the resource configuration for the modified DM-RS belongs to the CDM group 1, and the CDM group 2 belongs to the CDM group 1,

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of this embodiment are transmitted only on the OFDM symbols of the indexes # 5 and # 6 of the even slot in the time axis, and are not transmitted in the odd slot.

On the other hand, when viewed from the frequency axis, the DM-RS of CDM group 1 is transmitted on the subcarrier of index # 6 in each PRB. And the DM-RS of CDM group 2 is transmitted on the sub-carrier of index # 5 in each PRB. That is, the DM-RS is transmitted in the sub-carrier of the middle part in each PRB.

According to the resource configuration for the modified DM-RS of FIG. 15, since the number of resource elements to which the DM-RS is mapped per CDM group in one PRB pair is two, the number is reduced to 1/6 of that of the existing twelve, DM-RS overhead is reduced to 1/6.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over two OFDM symbols of each carrier wave, the OCC length is 2. That is, as shown in Table 1, only a and b are used as OCC, not a, b, c, and d, when OCC length is 4.

According to this embodiment, the OCCs are mapped twice in total in the same frequency axis within one slot and two PRBs for all the CDM groups. The even-numbered OCCs from the bottom are mapped to a and b, OCC is b, a. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

An example for implementing this OCC mapping rule is shown in Equation 25 below.

Referring to equation (25), the variable m 'is not included because OCC is mapped only once in one PRB, so that it is not necessary to identify the number of mappings by m'.

In order to implement the same OCC mapping for all the CDM groups as described above, the i-th sequence w _p (i) of the OCC for the antenna port p can be defined as shown in Table 3 or 4.

Then, the value of k can be defined as shown in Equation 26 below.

Here, k 'is expressed by Equation (6). w _p (i) can be defined in Table 3 or Table 4. w _p (i) may be expressed by the following equation (27) according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

Referring to Equation 27, since the OCC mapping rule is applied in units of two PRBs, the PRB offset is set to n _PRB values. Also, l '= 0,1, and l is defined as the following equation (28).

Or l may be defined more concisely as the following equation (29).

Table 3, Table 4, and expressions 25 to 29 are only one embodiment expressing the OCC mapping rule of FIG. 15 according to the present embodiment. All of which are included in the technical idea of the present invention.

16 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 16, the resource configuration for the modified DM-RS according to FIG. 16 is the same as the resource configuration for the modified DM-RS according to FIG. However, in the OCC mapping rule, FIG. 16 differs from FIG. 15 in that different OCC mapping rules are applied between the CDM group 1 and the CDM group 2. This is because the same OCC mapping rule is applied to the CDM groups 1 and 2 in FIG.

More specifically, the embodiment of FIG. 16 cyclically shifts OCC by 1 at the same m 'among different CDM groups. For example, in the case of CDM group 1, the even-numbered OCCs are [a, b] from the bottom along the frequency axis in the two PRBs, and the odd-mapped OCCs are [b, a]. On the other hand, in the case of CDM group 2, the even-numbered OCCs are [b, a] from the bottom along the frequency axis in the two PRBs, and the odd-mapped OCCs are [a, b]. That is, the OCC is circularly shifted and mapped between different CDM groups.

In order to implement this embodiment, the i-th sequence w _p (i) of the OCC for the antenna port p may be defined as shown in Table 5 or 6. That is, Tables 5 and 6 are the results of cyclically shifting OCCs of Table 3 and Table 4, respectively. In this way, OCC can be mapped by cyclic shifting by 1 between CDM groups.

Table 5, Table 6, and Expressions 25 to 29 represent only one embodiment expressing the OCC mapping rule of FIG. 16 according to the present embodiment, and may be expressed by other formulas or expressions for implementing the OCC mapping rule of FIG. All of which are included in the technical idea of the present invention.

17 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 17, a resource configuration for a modified DM-RS transmits a DM-RS with power balance to two PRB pairs on a frequency axis. Among the antenna ports 7, 8, 9 and 10, the resource configuration for the modified DM-RS belongs to the CDM group 1, and the CDM group 2 belongs to the CDM group 1,

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of this embodiment are transmitted on the OFDM symbols of the indexes # 5 and # 6 of the even slot in the time axis and the indexes # 5 and # 6 OFDM symbols.

On the other hand, in the frequency axis, the DM-RS of the CDM group 1 is transmitted in the sub-carrier of the index # 1 in the PRB on the even-numbered slot and in the sub-carrier of the index # 11 in the PRB on the odd-numbered slot. And the DM-RS of CDM group 2 is transmitted in the sub-carrier of index # 0 within the PRB on the even-numbered slot. And is transmitted in the subcarrier of Index # 10 within the PRB on the odd numbered slot.

According to the resource configuration for the modified DM-RS of FIG. 17, since the number of resource elements to which the DM-RS is mapped per CDM group in one PRB pair is four, it is reduced to 1/3 of the existing 12, DM-RS overhead is reduced to 1/3.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over two OFDM symbols of each carrier wave, the OCC length is 2. That is, as shown in Table 1, only a and b are used as OCC, not a, b, c, and d, when OCC length is 4.

According to this embodiment, the OCCs are mapped twice in total in the same frequency axis within one slot and two PRBs for all the CDM groups. The even-numbered OCCs from the bottom are mapped to a and b, OCC is b, a. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

An example for implementing such an OCC mapping rule is shown in Equation 30 below.

Referring to Equation (30), the variable m 'is not included because the OCC is mapped only once within one PRB, one slot, so that it is not necessary to identify the mapping frequency as m'.

In order to implement the same OCC mapping for all the CDM groups as described above, the i-th sequence w _p (i) of the OCC for the antenna port p can be defined as shown in Table 3 or 4.

Then, the value of k can be defined as the following equation (31).

Here, k 'is expressed by Equation (6). w _p (i) can be defined in Table 3 or Table 4. w _p (i) can be expressed by the following equation (32) according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

Referring to Equation 32, since the OCC mapping rule is applied in units of two PRBs, the PRB offset is set to n _PRB values. Also, l 'is defined as the following equation (33).

And l is defined by the following equation (34).

Table 3, Table 4, and Equations 30 to 34 are merely one embodiment for expressing the OCC mapping rule of FIG. 17 according to the present embodiment, and other formulas or expressions for implementing the OCC mapping rule of FIG. All of which are included in the technical idea of the present invention.

18 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 18, the resource configuration for the modified DM-RS according to FIG. 18 is the same as the resource configuration for the modified DM-RS according to FIG. However, FIG. 18 differs from FIG. 17 in that different OCC mapping rules are applied between the CDM group 1 and the CDM group 2 in the OCC mapping rule. This is because the same OCC mapping rule is applied to the CDM groups 1 and 2 in FIG.

More specifically, in the embodiment of FIG. 18, the OCC is cyclically shifted and mapped by 1 at the same m 'among different CDM groups. For example, in the case of CDM group 1, the even-numbered OCCs are [a, b] from the bottom along the frequency axis in the two PRBs, and the odd-mapped OCCs are [b, a]. On the other hand, in the case of CDM group 2, the even-numbered OCCs are [b, a] from the bottom along the frequency axis in the two PRBs, and the odd-mapped OCCs are [a, b]. That is, the OCC is circularly shifted and mapped between different CDM groups.

In order to implement this embodiment, the i-th sequence w _p (i) of the OCC for the antenna port p may be defined as shown in Table 5 or 6. That is, Tables 5 and 6 are the results of cyclically shifting OCCs of Table 3 and Table 4, respectively. In this way, OCC can be mapped by cyclic shifting by 1 between CDM groups.

Table 5, Table 6, and Equations 30 to 34 are merely one embodiment expressing the OCC mapping rule of FIG. 18 according to the present embodiment, and other formulas or expressions for implementing the OCC mapping rule of FIG. 18 All of which are included in the technical idea of the present invention.

19 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 19, a resource configuration for a modified DM-RS transmits a DM-RS by balancing power on only one PRB pair on the frequency axis. Among the antenna ports 7, 8, 9, 10, 11, 12, 13 and 14, the resource configuration for the modified DM-RS belongs to CDM group 1, 14 belong to CDM group 2.

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of the present embodiment are OFDM symbols of the indexes # 5 and # 6 of the even slot and the OFDM symbols of the indexes # 5 and # 6 of the odd slot, Symbol.

On the other hand, when viewed from the frequency axis, the DM-RS of the CDM group 1 is transmitted on the subcarriers of the indexes # 1 and # 11 of each PRB. The DM-RS of the CDM group 2 is transmitted on the subcarriers of indexes # 0 and # 10 of each PRB.

According to the resource configuration for the modified DM-RS of FIG. 19, since the number of resource elements to which the DM-RS is mapped per CDM group in one PRB pair is 8, it is reduced to 2/3 of the existing 12, DM-RS overhead is reduced to 2/3.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over four OFDM symbols of each carrier wave, the OCC length becomes 4. That is, the case where the OCC length is 4 as shown in Table 1 can be applied as it is.

According to the present embodiment, different OCC mapping rules are applied to each CDM group. For example, an OCC is mapped twice in total in a slot and a PRB along the frequency axis. For CDM group 1, the even-numbered OCC mapped from the bottom are a, b, c, OCC is d, c, b, a. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order. On the other hand, for CDM group 2, the even-numbered OCCs are c, d, a, b from the bottom, and the odd-mapped OCCs are b, a, d and c. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

Comparing the OCC mapping rules of CDM group 1 and CDM group 2, there are again two circular shifts between the OCC of CDM group 1 and the OCC of CDM group 2.

As a result, the OCC sequences of the CDM groups 1 and 2 mapped along the frequency axis on the OFDM symbol # 5 in FIG. 19 are sequentially c, a, b, and d in the PRB. That is, since all of a, b, c, and d are mapped once, OCC sequences are mapped the same number of times as a whole. Thus, the DM-RSs on OFDM symbol # 5 can be seen as power balanced. This power balance is the same in other OFDM symbols.

An example for implementing such an OCC mapping rule is shown in Equation (35).

w _p (i) may be expressed by the following equation (36) according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

To implement different OCC mappings between CDM groups according to this embodiment, the i-th sequence of OCCs for antenna port p

Can be defined as shown in the following table.

Antenna port p

7 [+1 +1 +1 +1] 8 [+1 -1 +1 -1] 9 [+1 +1 +1 +1] 10 [+1 -1 +1 -1] 11 [+1 +1 -1 -1] 12 [-1 -1 +1 +1] 13 [+1 -1 -1 +1] 14 [-1 +1 +1 -1]

On the other hand, the value of k can be defined by the following equation (37).

here,

to be.

Referring to Equation (37), since the OCC mapping rule is applied in units of one PRB, there is no need to set a separate PRB offset with n _PRB values. Also, l '= 0,1, m' = 0,1, and l 'is defined as the following equation (38).

Also, l may be defined by the following equation (39).

The formulas and tables of the other form that implement the OCC mapping rule of FIG. 19 are the same as those of the present invention And is included in the technical idea of.

20 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 20, a resource configuration for a modified DM-RS transmits a DM-RS on a frequency axis with a power balance to two PRB pairs (an even PRB and an odd PRB). Among the antenna ports 7, 8, 9, 10, 11, 12, 13 and 14, the resource configuration for the modified DM-RS belongs to CDM group 1, 14 belong to CDM group 2.

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of the present embodiment are OFDM symbols of the indexes # 5 and # 6 of the even slot and the OFDM symbols of the indexes # 5 and # 6 of the odd slot, Symbol.

On the other hand, when viewed from the frequency axis, the DM-RS of CDM group 1 is transmitted on the subcarrier of index # 6 in each PRB. And the DM-RS of CDM group 2 is transmitted on the sub-carrier of index # 5 in each PRB.

According to the resource configuration for the modified DM-RS of FIG. 20, since the number of resource elements to which the DM-RS is mapped per CDM group in one PRB pair is four, the number is reduced to 1/3 of the existing twelve, DM-RS overhead is reduced to 1/3.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over four OFDM symbols of each carrier wave, the OCC length becomes 4. That is, the case where the OCC length is 4 as shown in Table 1 can be applied as it is.

According to the present embodiment, different OCC mapping rules are applied to each CDM group. For example, within the two PRBs, OCCs are mapped twice in total for each CDM group along the frequency axis. For CDM group 1, the even-numbered OCCs are a, b, c, and d from the bottom, and the odd-mapped OCCs are d, c, b, a. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order. For CDM group 2, the even-numbered OCCs are c, d, a, and b from the bottom, and the odd-mapped OCCs are b, a, d, and c. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

Comparing the OCC mapping rules of CDM group 1 and CDM group 2, there are again two circular shifts between the OCC of CDM group 1 and the OCC of CDM group 2.

As a result, the OCC sequences of the CDM groups 1 and 2 mapped along the frequency axis on the OFDM symbol # 5 in FIG. 20 are sequentially c, a, b, and d in two PRBs. That is, since all of a, b, c, and d are mapped once, OCC sequences are mapped the same number of times as a whole. Therefore, the DM-RSs on OFDM symbol # 5 can be seen to be power balanced on two PRBs.

An example for implementing this OCC mapping rule is shown in Equation 40 below.

Referring to Equation 40, the variable m 'is not included because OCC is mapped only once in one PRB, so it is not necessary to identify the number of mappings by m'.

w _p (i) can be expressed by the following equation (41) according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

Referring to Equation 41, since the OCC mapping rule is applied in units of two PRBs, the PRB offset is set to n _PRB values.

The i-th sequence w _p (i) of the OCC for the antenna port p can be defined as shown in Table 7 so as to implement the cyclic-shifted OCC mapping for each CDM group as described above.

And the value of k can be defined by the following equation (42).

here,

Also, l may be defined as the following equation (44).

Table 7, Equation 40 to Equation 44 are merely one embodiment expressing the OCC mapping rule of FIG. 20 according to the present embodiment, and all other equations and tables of the form implementing the OCC mapping rule of FIG. And is included in the technical idea of.

21 is a diagram illustrating a resource configuration for a DM-RS according to another embodiment of the present invention.

Referring to FIG. 21, the resource configuration for the modified DM-RS transmits the DM-RS with power balance to four PRB pairs (PRB pair A, B, C, D) on the frequency axis. Among the antenna ports 7, 8, 9, 10, 11, 12, 13 and 14, the resource configuration for the modified DM-RS belongs to CDM group 1, 14 belong to CDM group 2.

Both the CDM group 1 of the CDM group 1 and the DM-RS of the CDM group 2 of the present embodiment are OFDM symbols of the indexes # 5 and # 6 of the even slot and the OFDM symbols of the indexes # 5 and # 6 of the odd slot, Symbol.

On the other hand, in view of the frequency axis, the DM-RS of the CDM group 1 is transmitted in subcarriers of indexes # 1 and # 11 in each PRB or in subcarriers of index # 6 (that is, Numbered PRBs are transmitted in subcarriers of indexes # 1 and # 11 and are transmitted in subcarriers of index # 6 in odd-numbered PRBs. May be transmitted in the subcarriers of indexes # 1 and # 11). The DM-RS of the CDM group 2 is transmitted on the subcarriers of the indexes # 0 and # 10 in each PRB or on the subcarriers of the index # 5 (that is, the indexes # 0 and # 10 in the even- And in the odd-numbered PRBs, the subcarriers of the indexes # 0 and # 10 are transmitted in the subcarriers of the index # Lt; / RTI > According to the resource configuration for the modified DM-RS of FIG. 21, since the number of resource elements to which the DM-RS is mapped per CDM group in the two PRB pairs is 12, DM-RS overhead is reduced to 1/2.

In this resource configuration for the modified DM-RS, the OCC mapping rule for providing the power balance of the DM-RS is as follows.

First, since the DM-RS is transmitted over four OFDM symbols of each carrier wave, the OCC length becomes 4. That is, the case where the OCC length is 4 as shown in Table 1 can be applied as it is.

According to the present embodiment, different OCC mapping rules are applied to each CDM group. For example, within the four PRBs, OCCs are mapped six times for each CDM group along the frequency axis. For CDM group 1, the even-numbered OCCs are a, b, c, and d from the bottom, and the odd-mapped OCCs are d, c, b, a. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order. On the other hand, for CDM group 2, the even-numbered OCCs are c, d, a, b from the bottom, and the odd-mapped OCCs are b, a, d and c. That is, in the odd-numbered OCC, the odd-numbered OCC is in the reverse order.

Comparing the OCC mapping rules of CDM group 1 and CDM group 2, there are again two circular shifts between the OCC of CDM group 1 and the OCC of CDM group 2.

As a result, referring to the OCC sequences of the CDM groups 1 and 2 mapped along the frequency axis on the OFDM symbol # 5 in FIG. 21, the OCC sequences are sequentially mapped three times in the order of c, a, b and d in the four PRBs, The sequences are mapped the same number of times. Therefore, the DM-RSs on the OFDM symbol # 5 can be seen as power balanced on the four PRBs.

An example for implementing such an OCC mapping rule is shown in Equation (45).

Referring to Equation 45, m '= 0, 1, 2 since a total of 3 OCC mappings are made along the frequency axis in two PRBs for each CDM group.

Is a PRB offset to the order m 'are two of the OCC PRB mapped to be counted over (from n _PRB index of the PRB index PRB _(PRB n +1)). For example, m '= 0, 1, 2 exists over PRB A, B, and m' = 0, 1, 2 over PRB C, D.

w _p (i) may be expressed by the following equation (46) according to the order on the frequency axis to which the OCC is mapped

or

Lt; / RTI >

Referring to Equation 46, since the OCC mapping rule is applied in units of four PRBs,

After adding the value and m 'value, the OCC mapping rule changes depending on whether this value is even or odd.

The i-th sequence w _p (i) of the OCC for the antenna port p can be defined as shown in Table 7 so as to implement the cyclic-shifted OCC mapping for each CDM group as described above.

Then, the value of k can be defined by the following equation (47) or (48).

or

here,

or

here,

Also, l may be defined as the following equation (50).

21 and FIG. 21 are only one embodiment expressing the OCC mapping rule of FIG. 21 according to this embodiment, and all the other formulas and tables implementing the OCC mapping rule of FIG. And is included in the technical idea of.

22 is a flowchart illustrating a method of transmitting a reference signal between a terminal and a base station according to an embodiment of the present invention.

Referring to FIG. 22, the base station generates a reference signal sequence r (m) to be used in a resource configuration for a modified DM-RS for a DM-RS (S2200). The method of calculating r (m) may be as shown in Equation (4). In the resource configuration for the modified DM-RS, there may be more than one antenna port, and the number may be determined according to the number of layers used for transmission of the PDSCH. And each antenna port may belong to CDM group 1 or CDM group 2.

The base station transmits a sequence of an orthogonal cover code (OCC) defined for each antenna port

Is multiplied by the reference signal sequence r (m) to generate a modulation symbol a ^(p) _{k, l} of the demodulation value (S2205). The OCC has a certain length according to the configuration of the antenna port. For example, the resource configuration for the modified DM-RS may be any one of FIG. 7 to FIG. 21, and for each resource configuration for the DM- The lengths can be defined individually. For example, the resource configuration for the DM-RS according to FIG. 12 is OCC length 2 (i.e., i = 0, 1), and the OCC can be selected based on any one of Tables 3 to 6.

The sequence of the OCC multiplied by the reference signal sequence r (m)

May be determined according to the OCC mapping rules based on various embodiments of the present disclosure. For example, CDM group 1 and CDM group 2 have the same OCC mapping rules

Or according to OCC mapping rules cyclically shifted by 1 or 2 between CDM group 1 and CDM group 2

Respectively. Or different OCC mapping rules may be applied to each CDM group. For example, OCC mapping in CDM group 2 may be in the reverse order of OCC mapping in CDM group 1. The OCC mapping rules may include the OCC mapping rules in Figs. 7 to 21 disclosed herein.

The base station maps the modulation symbol a ^(p) _{k, l} of the demodulation value to a resource element RE defined by a subcarrier of an index k in each PRB and an OFDM symbol of an index l (S2210).

The base station generates an OFDM signal including the mapped resource element of the modulation symbol a ^(p) _{k, l} of the demodulation value _, and transmits the OFDM signal to the terminal (S2215).

The terminal receiving the OFDM signal decodes the OFDM signal in the reverse order of the procedure for the base station to generate the OFDM signal.

For example, the UE demaps a received OFDM signal to a resource element, extracts a modulation symbol of a demodulation value, and multiplies the received modulation symbol by the OCC sequence to extract an estimated reference signal sequence r '(m) (S2220). The terminal generates a reference signal sequence r (m) in the same manner as the base station (S2225), and performs channel estimation by comparing r (m) and r (m) (S2230).

23 is a block diagram illustrating a terminal and a base station according to an embodiment.

23, the terminal 2300 includes a receiving unit 2305, a channel estimating unit 2310, and a transmitting unit 2315.

The receiving unit 2305 receives the OFDM signal from the base station 2350. The receiving unit 2305 decodes the OFDM signal in the reverse order of the procedure in which the base station 2350 generates the OFDM signal. For example, the receiver 2305 demaps a received OFDM signal to a resource element, extracts a modulation symbol of a demodulation value, and sends the modulation symbol to the channel estimation unit 2310.

The channel estimation unit 2310 extracts the estimated reference signal sequence r '(m) by multiplying the modulation symbol of the demodulation value by the sequence of the OCC. The channel estimation unit 2310 generates the reference signal sequence r (m) in the same manner as the base station, and performs channel estimation by comparing r (m) and r '(m).

The transmitting unit 2315 transmits the uplink signal to the base station 2350.

The base station 2350 includes a transmitting unit 2355, a receiving unit 2360, and a base station processor 2370. The base station processor 2370 again includes a reference signal generator 2371 and a resource mapper 2372.

The reference signal generator 2371 generates the reference signal sequence r (m) to be used in the resource configuration for the modified DM-RS for the DM-RS. The reference signal generator 2371 can calculate r (m) using the same method as Equation (4). In the resource configuration for the modified DM-RS, there may be more than one antenna port, and the number may be determined according to the number of layers used for transmission of the PDSCH. And each antenna port may belong to CDM group 1 or CDM group 2.

The reference signal generator 2371 generates a sequence of an orthogonal cover code (OCC) defined for each antenna port

Is multiplied by the reference signal sequence r (m) to generate a modulation symbol a ^(p) _{k, l} of the demodulation value. The OCC has a certain length according to the resource configuration for the modified DM-RS. For example, the resource configuration for the DM-RS may be any one of the configurations shown in FIG. 7 to FIG. 21, . ≪ / RTI > For example, the resource configuration for the DM-RS according to FIG. 12 is such that the OCC length is 2 (i = 0, 1) and the reference signal generator 2371 assigns the OCC to any one of Tables 3 to 6 As shown in FIG.

The reference signal generation unit 2371 generates a reference signal

May be determined according to the OCC mapping rules based on various embodiments of the present disclosure. For example, CDM group 1 and CDM group 2 have the same OCC mapping rules

Or according to OCC mapping rules cyclically shifted by 1 or 2 between CDM group 1 and CDM group 2

Respectively. Alternatively, the reference signal generator 2371 may apply different OCC mapping rules to each CDM group. For example, in the OCC mapping rule for each CDM group applied in the reference signal generation unit 2371, the OCC mapping in the CDM group 2 may be in the reverse order as compared with the OCC mapping in the CDM group 1. The OCC mapping rules may include the OCC mapping rules in Figs. 7 to 21 disclosed herein.

The resource mapper 2372 maps the modulation symbol a ^(p) _{k, l} of the demodulation value to the resource element RE defined by the subcarrier of the index k in each PRB and the OFDM symbol of the index l.

The transmission unit 2355 generates an OFDM signal including the mapped resource element with the modulation symbol a ^(p) _{k, l} of the demodulation value, and transmits the OFDM signal to the terminal 2300.

The receiving unit 2360 can receive the uplink signal from the terminal 2300.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

Claims (16)

Generating a reference signal sequence for a demodulation reference signal (DM-RS);
A complex valued modulation symbol based on the orthogonal covering code (OCC) defined for each antenna port for DM-RS transmission and the reference signal sequence, ;
Mapping the at least one complex-valued modulation symbol to a resource element of the antenna port; And
And transmitting an OFDM signal including the resource element to a terminal,
Wherein the antenna port is included in one of two antenna port groups using different resource elements for transmission of the DM-RS, and the OCC applied to the two antenna port groups is individually , And the number of the resource elements to which the at least one complex-valued modulation symbol is mapped is less than six per pair of physical resource blocks (PRBs) and each antenna port group. Transmission method. The method according to claim 1,
And the length of the OCC is 2. 3. The method of claim 2,
A sequence of a first OCC is applied to a first group of the two antenna port groups, a sequence of a second OCC is applied to a second group, and a sequence of the second OCC is applied to a sequence of the first OCC And the reference signal is shifted. The method according to claim 1,
Wherein in each antenna port group, a sequence of OCCs is sequentially cyclically shifted and applied along a frequency axis on the same OFDM symbol. A sequence of reference signals for a demodulation reference signal (DM-RS), orthogonal covering codes (OCC) defined for each antenna port for the DM-RS, A reference signal generator for generating at least one complex valued modulation symbol based on the reference signal sequence, wherein the antenna port uses different resource elements for transmission of the DM-RS; Wherein the antenna port group comprises:
A resource mapper for mapping the at least one complex-valued modulation symbol to a resource element of the antenna port; And
And a transmitter for transmitting an OFDM signal including the resource element to a terminal,
Wherein the reference signal generator maps the modulation symbols of the at least one complex value to one physical resource block pair and less than six resource elements per antenna port group, And determines an OCC applied to the two antenna port groups individually. 6. The method of claim 5,
Wherein the OCC has a length of 2. The method according to claim 6,
Wherein the reference signal generator comprises:
Applying a sequence of a first OCC to a first group of the two antenna port groups, applying a sequence of a second OCC to a second group, cyclically shifting the sequence of the first OCC by one, Wherein the base station determines a sequence. 6. The method of claim 5,
Wherein the reference signal generator comprises:
Characterized in that in each antenna port group, a sequence of OCCs is sequentially cyclically shifted and applied along the frequency axis on the same OFDM symbol. Receiving an OFDM signal;
Demapping a resource element included in the OFDM signal to a modulation symbol of a complex value;
Extracting a reference signal sequence by multiplying a modulation symbol of the complex value by an orthogonal covering code (OCC) defined for each antenna port for a demodulation reference signal (DM-RS) ;
Generating an actual reference signal sequence for the DM-RS; And
Performing channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence,
Wherein the antenna port is included in one of two antenna port groups using different resource elements for transmission of the DM-RS, and the OCC applied to the two antenna port groups is individually Wherein the number of resource elements to which the complex-valued modulation symbols are mapped is less than six per pair of physical resource blocks (PRBs) and antenna port groups. 10. The method of claim 9,
And the length of the OCC is 2. 11. The method of claim 10,
A sequence of a first OCC is applied to a first group of the two antenna port groups, a sequence of a second OCC is applied to a second group, and a sequence of the second OCC is applied to a sequence of the first OCC And the reference signal is shifted. 10. The method of claim 9,
Wherein in each antenna port group, a sequence of OCCs is sequentially cyclically shifted and applied along a frequency axis on the same OFDM symbol. A receiver for receiving an OFDM signal and demapping a resource element included in the OFDM signal to a modulation symbol of a complex value; And
Extracting a reference signal sequence by multiplying a modulation symbol of the complex value by an orthogonal covering code (OCC) defined for each antenna port for a demodulation reference signal (DM-RS) And a channel estimator for generating an actual reference signal sequence for the DM-RS, and performing channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence,
The antenna port is included in one of two antenna port groups using different resource elements for transmission of the DM-RS,
Wherein the channel estimator maps the modulation symbols of the at least one complex value to one physical resource block pair and less than six resource elements per antenna port group, And determines an OCC applied to the two antenna port groups individually. 14. The method of claim 13,
Wherein the OCC has a length of 2. 15. The method of claim 14,
Wherein the channel estimator comprises:
Applying a sequence of a first OCC to a first group of the two antenna port groups, applying a sequence of a second OCC to a second group, cyclically shifting the sequence of the first OCC by one, Wherein the sequence is determined by the terminal. 14. The method of claim 13,
Wherein the channel estimator comprises:
And sequentially applying an OCC sequence cyclically shifted along a frequency axis on the same OFDM symbol in each antenna port group.

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