KR20150018301A - Method and apparatus for transmitting reference signal in wireless communication system - Google Patents

Abstract

Disclosed is a method for transmitting a reference signal, which comprises: a step of generating a reference signal sequence for a DMRS; a step of generating at least one complex-valued modulation symbol based on the reference signal sequence and an orthogonal covering code defined for each antenna port to transmit the DMRS; a step of mapping the complex-valued modulation symbol onto a resource element for the antenna port; and a step of transmitting an OFDM signal containing the resource element to a terminal.

Description

Field of the Invention [0001] The present invention relates to a method and apparatus for transmitting a reference signal in a wireless communication system,

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

The universal mobile telecommunications system (UMTS) is a third generation (3rd) mobile communication system operating on wideband code division multiple access (WCDMA) based on European systems such as global system for mobile communications (GSM) and general packet radio services generation asynchronous mobile communication system. Long-term evolution (LTE) and LTE-advanced (LTE-advanced) are being discussed by the 3rd generation partnership project (3GPP), which standardized UMTS as a 4th generation mobile communication system.

Component carriers (CCs) used in a conventional multiple carrier system emphasize the versatility of the physical layer, and redundancy of control areas and common signal overhead exist. Therefore, there is a problem that resources for the data signal are reduced and there is unnecessary loss in terms of spectrum efficiency. Accordingly, in order to efficiently operate a multi-carrier system, introduction of a new carrier type (NCT) constituting a multi-carrier system is required. In the NCT, a reference signal (RS) for downlink control channel or channel estimation is used in comparison with a conventional carrier type (LCT) Can be removed or reduced. This is to obtain maximum data transmission efficiency. The existing conventional carrier wave type (LCT) is also called a backward compatible carrier type (BCCT) by distinguishing it from the NCT.

The NCT may include a non-standalone NCT and a standalone NCT. A non-exclusive NCT is an NCT that can not exist in a single cell form and can exist in the form of a secondary serving cell (SCell) when a primary cell (PCell) exists. On the other hand, a single NCT is an NCT that can exist in a single cell form. For example, a standalone NCT can exist in the form of a PCell. In a single NCT and a non-exclusive NCT, a cell-specific RS (CRS) may not be transmitted. Accordingly, the existing control channel (PDCCH), the physical HARQ indicator channel (PHICH), and the physical control format indicator channel (PCFICH), which are control channels based on the CRS, can be removed or replaced with other types of channels.

In the NCT environment, a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) are transmitted to a UE (user equipment) such as a downlink demodulation reference signal (DMRS) May overlap in a particular OFDM (orthogonal frequency division multiplexing) symbol with a particular reference signal. In this case, the DMRS can be punctured.

In this case, when the orthogonal cover code (OCC) is mapped to the DMRS as in the conventional case, the number of layers for the DMRS transmission is limited, and various communication faults are caused due to the power imbalance in the OFDM symbol . Accordingly, there is a need for an OCC mapping method and a DMRS transmission method and apparatus that solve the limitation of the number of layers for DMRS transmission as much as possible and consume power balance.

It is a technical object of the present invention to provide a method and apparatus for transmitting a reference signal in a wireless communication system.

It is another object of the present invention to provide a method and apparatus for configuring and transmitting a downlink (DL) demodulation reference signal (DMRS) in an NCT environment.

According to an aspect of the present invention, there is provided a method for transmitting a DMRS, the method comprising: generating a reference signal sequence for a demodulation reference signal (DMRS); generating orthogonal cover codes comprising: generating at least one complex valued modulation symbol based on the reference signal sequence and a covering code (OCC), generating a modulation symbol of at least one complex value from a resource associated with the antenna port And transmitting an Orthogonal Frequency Division Multiplexing (OFDM) signal including the resource element to a mobile station. In this method, at least one DMRS is punctured in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), and the length of the OCC is 3 or less .

According to another aspect of the present invention, there is provided a method of generating a reference signal sequence for a demodulation reference signal (DMRS) and orthogonal covering codes defined for antenna ports for the DMRS transmission, a reference signal generator for generating at least one complex valued modulation symbol based on the reference signal sequence and a reference signal sequence, And a transmitter for transmitting an Orthogonal Frequency Division Multiplexing (OFDM) signal including the resource element to a mobile station. In the base station, in at least one OFDM symbol used for transmission of the DMRS in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), a DMRS Punctured, and the length of the OCC may be 3 or less.

According to still another aspect of the present invention, there is provided a method for demodulating an OFDM signal, comprising: receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal from a base station; demapping a resource element included in the OFDM signal to a complex valued modulation symbol; 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 (DMRS) And performing a channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence. The present invention also provides a method for receiving a reference signal. In the above method, in at least one of OFDM symbols used for transmission of the DMRS in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), a DMRS Punctured, and the length of the OCC may be 3 or less.

According to another aspect of the present invention, there is provided an OFDM receiver comprising: a receiver for receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal from a base station, demapping a resource element included in the OFDM signal to a modulation symbol of a complex value, extracts a reference signal sequence by multiplying the modulation symbol of the complex value by an orthogonal covering code (OCC) defined for each antenna port for the DM-RS, And a channel estimator for generating an actual reference signal sequence and performing channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence. In the AT, a DMRS is transmitted from at least one OFDM symbol among OFDM symbols used for transmission of the DMRS in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) Punctured, and the length of the OCC may be 3 or less.

In the resource configuration for the DMRS when the DMRS is punctured, by clarifying the rule for mapping the orthogonal cover codes considering the power balance, the limitation of the number of layers for the DMRS transmission and the power imbalance Various possible communication deficiencies can be solved.

1 is a block diagram illustrating a wireless communication system to which the present invention is applied.
2 and 3 schematically show the structure of a radio frame to which the present invention is applied.
4 and 5 are diagrams illustrating a pattern in which a downlink DMRS 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.
7 is a diagram illustrating a situation in which the SSS and the DMRS overlap in the normal CP and the normal subframe.
FIGS. 8 and 9 are diagrams illustrating a situation where PSS and DMRS overlap in a general CP and a special subframe.
10 is a diagram illustrating a rule for mapping an OCC to a DMRS according to an embodiment of the present invention.
11 is a diagram illustrating a rule for mapping an OCC to a DMRS according to another embodiment of the present invention.
12 is a diagram illustrating a rule for mapping an OCC to a DMRS according to another embodiment of the present invention.
13 to 15 are diagrams illustrating a method of generating DMRS by mapping the DMRS sequences A and B to two OFDM symbols.
16 is a flowchart of DMRS transmission between a terminal and a base station according to an example of the present invention.
17 is a block diagram illustrating a terminal and a base station according to an embodiment of the present invention.

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.

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

Referring to FIG. 1, a wireless communication system 10 is widely deployed to provide various communication services such as voice, packet data, and the like. 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.

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

Referring to FIGS. 2 and 3, 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.

)를 추정할 수 있다.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.

는

값에 의존하게 되므로, 정확한 h값의 추정을 위해서는

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

The

Value, so for accurate estimation of the h value

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 in a cell or a specific UE group, and may be referred to as a Demodulation RS (DMRS) since it is mainly used for data demodulation of a specific UE or a specific UE group.

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

Referring to FIGS. 4 and 5, there is a specific antenna port defined to transmit the downlink DMRS. This is called antenna port for DMRS. For example, a DMRS can be transmitted using up to eight antenna ports, and the number of these antenna ports can be 7, 8, 9, 10, 11, 12, 13, The DMRS transmitted from the antenna port x is denoted by Rx, for example, the DMRS transmitted from the antenna port 7 is denoted by R7.

When one layer is used for transmission of PDSCH, antenna port 7 or 8 is used for transmission of DMRS. When v layer is used for transmission of PDSCH, antenna port 7, 8, ... , v + 6 are used. A total of 12 resource elements are mapped per antenna port for DMRS 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 DMRS is mapped on the 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] OCC (length = 2)  [a b] OCCA [+1 +1] OCC B [+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 the antenna ports 9, 10, 12 and 14 in the CDM group 2 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, In the uplink, the extended CP In the uplink, 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, the configuration of the special subframe in the TDD frame is composed of 9 in the normal CP (cyclic prefix) and 7 in the extended CP. Among the orthogonal frequency division multiplexing (OFDM) symbols of a particular subframe (DwPTS, guard period, etc.), 0, 1, 2, 3, 4, 5, 6, 7, 8, 1, 1), (10, 3, 1), (11, 2, 1), (12, 1, 1) (3, 9, 2), (9, 3, 2), (10, 2, 2), (11, 1, 2), (6, 6, 2). In the case of the extended CP, the number of OFDM symbols for the (DwPTS, guard period, UpPTS) of the twelve OFDM symbols of one special subframe is 0, 1, 2, 3, 4, 5, (8, 3, 1), (9, 2, 1), (10, 1, 1), (3, 7, 2) , 1, 2), (5, 5, 2).

With respect to the mapping of the OCC, for example, in a special subframe, when a special subframe configuration is 3, 4, or 8 and a normal CP is used, four OFDM symbols to which OCC is applied among a total of 11 or 12 OFDM symbols are 3 (OFDM symbol indexes # 2 and # 3 of the first slot and # 2 and # 3 of the second slot).

As another example, when a special subframe is 1, 2, 6, or 7 in a special subframe and a normal CP is used, four OFDM symbols to which OCC is applied among the total 9 or 10 OFDM symbols are the third and fourth , 6th, and 7th OFDM symbols (the indexes of # 2, # 3, # 5, and # 6 of the first slot are OFDM symbols).

If a length 2 OCC is used, OCC is applied across two OFDM symbols in one subframe on the time axis. For example, in a special subframe, when a special subframe configuration is 9 and a normal CP is used, OCC is applied to the third and fourth OFDM symbols of a total of six OFDM symbols (the index of the OFDM symbol includes the first slot # 2 and # 3).

When a 4-length OCC is mapped 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 have. 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 DMRS maps per 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, ... , 5 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 (ie, 3, and 5 (that is, odd number starting from 0), OCC is applied in the order of d, c, b, a in the reverse order.

Next, in the CDM group 2, the CDM groups 1 and 2 are cyclically delayed by 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.

On the other hand, in the NCT environment and TDD (frame structure type 2), a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) are transmitted as a downlink demodulation reference signal (DMRS (UE) specific reference signal, such as a demodulation reference signal, in a particular orthogonal frequency division multiplexing (OFDM) symbol. FIG. 7 is a diagram illustrating a situation in which the SSS and the DMRS overlap in the normal CP and the normal subframe, and FIGS. 8 and 9 are views showing a situation in which the PSS and the DMRS overlap in the normal CP and the special subframe.

Referring to FIG. 7, in a general CP and a general subframe, a DMRS is mapped to resource elements corresponding to A and B, respectively. And the SSS is mapped to the center 6 PRBs in the last OFDM symbol of subframe indices 0 and 5 (slot indices 1 and 11). In this case, the SSS overlaps the DMRS in the last OFDM symbol.

Referring to FIG. 8, in the general CP and the special subframe configurations 3, 4, and 8, the DMRS is mapped to resource elements corresponding to A and B, respectively. According to the special subframe configurations 3, 4 and 8, the OFDM symbol (s) of the last two or three OFDM symbols in the special subframe are guard period (GP) and the remaining OFDM symbol (s) Can be used. And the PSS is mapped to the central six PRBs in the third OFDM symbol of subframe indices 1 and 6 (slot indices 2 and 12). Therefore, the PSS overlaps with the DMRS in the third OFDM symbol.

Referring to FIG. 9, in the general CP and special subframe configurations 1, 2, 6, and 7, the DMRS is mapped to resource elements corresponding to A and B, respectively. According to the special subframe constructions 1, 2, 6 and 7, some OFDM symbol (s) of last 4 or 5 OFDM symbols in a special subframe may be used as GP and remaining OFDM symbols may be used as UpPTS. And the PSS is mapped to the six central PRBs in the third OFDM symbol of subframe indices 1 and 6 (slot indices 2 and 12). Therefore, the PSS overlaps with the DMRS in the third OFDM symbol.

In Figures 7 to 9, the DMRS overlapping the PSS or SSS can be punctured. In this case, the OFDM symbol to which the DMRS is mapped becomes three in one PRB pair. When the DMRS is mapped through three OFDM symbols, it is not possible to distinguish each antenna port within one CDM group through the existing four-length OCC. Since this means that only one antenna port can be supported, it is difficult to transmit a DMRS of rank 2 or more through two or more layers.

Hereinafter, the present specification discloses an OCC that can be applied when the overhead of DMRS is reduced by puncturing or the like, a rule for mapping OCC, and an apparatus and method for transmitting DMRS. When the OCC of length 4 is mapped to the DMRS, there arises a problem that it is impossible to support a plurality of antenna ports as described above.

According to an embodiment of the present invention, a terminal and a base station distinguish a maximum of three antenna ports in one CDM group through an OCC having a length of three. For example, an OCC of length 3 as shown in Table 3 may be used.

OCC (length 3) [a b c] OCCA [1 1 1] OCC B ^{[1 e j2 π / 3 e} j4 π / 3] OCC C ^{[1 e j4 π / 3 e} j2 π / 3]

Referring to Table 1, antenna ports 7, 8, and 11 in CDM group A (or CDM group 1) can be distinguished by OCC A, OCC B, and OCC C. In CDM group B (or CDM group 2), antenna ports 9, 10, and 12 can be distinguished by OCC A, OCC B, and OCC C. According to this, in the case of a general CP, it is possible to transmit DMRS up to rank 6 through a maximum of six layers.

OCC mapping should be performed so that power balance is achieved within one OFDM symbol even when 3-length OCC is used.

10 is a diagram illustrating a rule for mapping an OCC to a DMRS according to an embodiment of the present invention.

Referring to FIG. 10, CDM group A (antenna ports 7, 8, 11) and CDM group B (antenna ports 9, 10, 12) in a single PRB on the frequency have three OCC mappings in total. Let us call the mapping 0, the mapping 1, and the mapping 2 sequentially from the bottom of the frequency axis. In the case of the CDM group A, b, c, and a are mapped in the order of a, b, and c in the mapping 0 (subcarrier # 1) The OCCs can be mapped (or applied) in the order a and b. Similarly, in the case of the CDM group B, mapping is performed in the order of a, b and c in the 0 mapping (subcarrier # 0), in the order of b, c and a in the 1 mapping (subcarrier # 5) ), OCCs can be mapped (or applied) in the order of c, a, b.

The rules of OCC mapped to each CDM group are shown in the following table.

Antenna port p

7 [1 1 1] 8 ^{[1 e j2 π / 3 e} j4 π / 3] 9 [1 1 1] 10 ^{[1 e j2 π / 3 e} j4 π / 3] 11 ^{[1 e j4 π / 3 e} j2 π / 3] 12 ^{[1 e j4 π / 3 e} j2 π / 3]

는 각각 DMRS가 맵핑되는 첫 번째 OFDM 심볼, 두 번째 OFDM 심볼, 세 번째 OFDM 심볼에 적용되는 직교 시퀀스 값에 해당한다. 이는 CDM 그룹 A의 경우 표 3에서 언급한 시퀀스 a, b, c에 해당한다. Referring to Table 4,

Corresponds to an orthogonal sequence value applied to the first OFDM symbol, the second OFDM symbol, and the third OFDM symbol to which the DMRS is mapped, respectively. This corresponds to the sequence a, b, c mentioned in Table 3 for CDM group A.

11 is a diagram illustrating a rule for mapping an OCC to a DMRS according to another embodiment of the present invention.

Referring to FIG. 11, there are a total of 3 OCC mappings for CDM group A (antenna ports 7, 8, 11) and CDM group B (antenna ports 9, 10, 12) in one PRB on frequency. Let us call the mapping 0, the mapping 1, and the mapping 2 sequentially from the bottom of the frequency axis. In the case of the CDM group A, b, c, and a are mapped in the order of a, b, and c in the mapping 0 (subcarrier # 1) The OCCs can be mapped (or applied) in the order a and b. In the case of the CDM group B, OCCs cyclically shifted by 1 in the CDM group A can be mapped. For example, in the mapping 0 (subcarrier # 0), c, a and b in the mapping 1 (subcarrier # 5) The OCC can be mapped (or applied) in the order c.

The table of OCC rules mapped to each CDM group is as follows.

Antenna port p

7 [1 1 1] 8 ^{[1 e j2 π / 3 e} j4 π / 3] 9 [1 1 1] 10 ^{[e j2 π / 3 e j4} π / 3 1] 11 ^{[1 e j4 π / 3 e} j2 π / 3] 12 ^{[e j4 π / 3 e j2} π / 3 1]

12 is a diagram illustrating a rule for mapping an OCC to a DMRS according to another embodiment of the present invention.

Referring to FIG. 12, there are a total of 3 OCC mappings for CDM group A (antenna ports 7, 8, 11) and CDM group B (antenna ports 9, 10, 12) in one PRB on the frequency. Let us call the mapping 0, the mapping 1, and the mapping 2 sequentially from the bottom of the frequency axis. In the case of the CDM group A, b, c, and a are mapped in the order of a, b, and c in the mapping 0 (subcarrier # 1) The OCCs can be mapped (or applied) in the order a and b. In the case of the CDM group B, OCCs cyclically shifted by 2 in the CDM group A can be mapped. For example, in a mapping 0 (subcarrier # 0), a, b, c in 1 mapping (subcarrier # 5), b, c, The OCC can be mapped (or applied) in a order.

The table of OCC rules mapped to each CDM group is as follows.

Antenna port p

7 [1 1 1] 8 ^{[1 e j2 π / 3 e} j4 π / 3] 9 [1 1 1] 10 ^{[e j4 π / 3 1 e} j2 π / 3] 11 ^{[1 e j4 π / 3 e} j2 π / 3] 12 ^{[e j2 π / 3 1 e} j4 π / 3]

When the OCC mapping rule is implemented in the same manner as in FIGS. 10 to 12, there are a total of 3 times for each CDM group and 6 times for the entire CDM group in one PRB on the frequency, and the sequence values of a, b, and c are applied to the OFDM symbol twice in the PRB in the frequency domain. In addition to the embodiments shown in Figs. 10 to 12, OCC mapping can be performed in various ways in a line for maintaining power balance, and these will be included in the technical idea of the present invention.

10 to 12 illustrate OCC mapping rules only in the case of a general subframe having a general CP as shown in FIG. However, the rule of mapping an OCC of length 3 to another case (for example, in the case of a special subframe having a general CP as shown in FIG. 8 or 9) in which three OFDM symbols are used to map the DMRS is also applied .

The OCC mapping rules described above are expressed mathematically 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 an orthogonal sequence value w _p (i) such as OCC and a reference signal sequence r (m). p is an antenna port number, k is an index of a subcarrier, and l is an index of an OFDM symbol 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 first OFDM symbol to be mapped (0 mapped), and if l' = 1, the OCC indicates the OFDM symbol to be mapped to the second (1 mapped).

이다. i=0, 1, 2인 경우에는,

이다. 그리고 w_p(i)는 OCC가 맵핑되는 주파수 축상의 순서 m'에 따라 다음의 수학식 3과 같은 값을 가질 수 있다. 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. When i = 0, 1, 2,

to be. And w _p (i) may have the following Equation 3 according to the order m 'on the frequency axis to which the OCC is mapped.

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 PRB. In the case of FIGS. 10 to 12, m '= 0, 1, 2 because three OCC mappings are performed along the frequency axis in two slots and one PRB for each CDM group. That is, m '= 0, m' = 1, and m '= 2 correspond to 0 mapping, 1 mapping and 2 mapping sequentially from the bottom of the frequency axis as mentioned above.

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. That is, the antenna port p = 7, p = 8, or p = 7, 8, ..., v + with respect to 6, having an index n _PRB on the frequency domain assigned to the corresponding PDSCH transmission (transmission) one Within the PRB, a portion of the reference signal sequence is mapped into complex-valued modulation symbols in one subframe. For example, r (m) may be calculated by the pseudo-random sequence c (i) based on a gold sequence as follows:

Here, m = 0,1, ..., 9N _RB ^{max , DL} -1 (in the case of a general CP) or m = 0,1, ..., 12N _RB ^{max , DL} -1.

Here, when a total of X resource elements are used for one DMRS CDM group in one PRB pair (X = 6, 8, 9, 12, 16, etc.), the total length of the reference signal sequence r X · 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 for one DMRS CDM group in one PRB pair are used for transmission of the DMRS, so that the total number of reference signal sequences r (m) The length is 12 · N _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 for one DMRS CDM group in one PRB pair are used for transmission of the DMRS, so that the total number of reference signal sequences r (m) The length is 16 · N _RB ^{max , DL} . Thus, m = 0, 1, ..., 16N _RB ^{max , DL} -1.

Therefore, as shown in Equation (4), a total of 9 resource elements for one DMRS CDM group in one PRB pair are used for transmission of the DMRS, as shown in FIG. 10 to FIG. 12, You can use X = 12 as well as some of them.

N _RB ^{max , DL} represents the maximum number of RBs in the downlink. 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.

Next, the index l of the OFDM symbol in a single slot and the sequence l 'of the OFDM symbols to which the OCC is mapped along the time axis in the subframe can be defined by the following equations, respectively.

According to another embodiment of the present invention, the DMRS is not transmitted in the slot where the PSS or SSS is transmitted. That is, in the slot where the PSS or SSS is transmitted, the DMRS is punctured. In this case, the base station can generate the DMRS by mapping the DMRS sequences A and B to two OFDM symbols as shown in FIGS. 13 to 15, and transmit the generated DMRS to the terminal. In this case, the variables of the equations (2) to (8) can be modified as shown in the following equation.

The OCC sequence values for each antenna port 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]

중 2개만 실질적으로 사용된다. Since only two of the four OFDM symbols are used as the DMRS, the length of the OCC of Table 4 is used as it is, but the four sequence values of the OCC of length 4

Only two of them are actually used.

16 is a flowchart of DMRS transmission between a terminal and a base station according to an example of the present invention.

Referring to FIG. 16, a base station generates a reference signal sequence r (m) to be used in a resource configuration for a DMRS (S1600). The method of calculating r (m) may be the same as Equation 4 or 9 described above. In the resource configuration for the DMRS, 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.

를 참조 신호 시퀀스 r(m)에 곱하여 복조 값의 변조 심볼 a^(p) _k,l을 생성한다(S1605). OCC는 안테나 포트의 구성에 따라 길이 2 내지 4 중 하나의 길이를 가진다. 예를 들어, DMRS를 위한 자원 구성에서 길이가 4인 OCC를 적용하는 경우에는 도 4 내지 도 5를 따를 수 있고, 길이가 3인 OCC를 적용하는 경우에는 도 7 내지 도 9를 따를 수 있고, 길이가 2인 OCC를 적용하는 경우에는 도 13 내지 도 15를 따를 수가 있다. 참조 신호 시퀀스 r(m)에 곱하여지는 OCC의 시퀀스

는 본 명세서의 다양한 실시예들에 기반한 OCC 맵핑 규칙에 따라 결정될 수 있다. 예를 들어, OCC 맵핑 규칙은 길이가 3인 OCC를 적용하는 경우에는 도 10 내지 도 12를 따를 수 있고, 길이가 4 또는 2인 OCC를 적용하는 경우에는 도 6을 따를 수가 있다, 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 (S1605). The OCC has a length of one of 2 to 4 in length depending on the configuration of the antenna port. For example, in the case of applying the OCC having the length of 4 in the resource configuration for the DMRS, FIG. 4 to FIG. 5 may be applied. In the case of applying the OCC having the length of 3, 13 to 15 in the case of applying the OCC having the length of 2. 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, the OCC mapping rule may follow FIGS. 10 to 12 when OCC of length 3 is applied, and FIG. 6 when OCC of length 4 or 2 is applied.

If the base station needs to puncture the DMRS in some OFDM symbols in consideration of the PSS or the SSS, the base station may transmit to the terminal a signaling indicating that the DMRS is punctured (or indicating that the length of the OCC is not 4) have. The signaling may be one bit RRC signaling or may be implicitly transmitted in a specific transceiving mode.

Here, if the DMRS is not instructed to be punctured, the OCC with a length of 4 is applied as in the conventional case (if the special subframe is 9 in the special subframe and the normal CP is used, the OCC with the length 2 is applied being). However, when DMRS is indicated to be punctured, the length of the OCC and the OCC sequence value may be defined in several cases.

First, the length of the OCC can be defined regardless of the number of transport layers.

As an example, a 3-length OCC sequence to be applied to 3 OFDM symbols may be used regardless of the number of transmission layers (i.e., for all cases where the transmission layer = 1 to 6) (see, for example, And an OCC mapping rule as shown in FIGS. 10 to 12). Then, the base station can multiply the reference signal sequence by the OCC sequence of length 3. At this time, the value of the OCC sequence of the third of the road is determined by Tables 4 to 6.

As another example, for all cases where the transmission layer = 1 to 4, a 2-length OCC sequence to be applied to two OFDM symbols may be used (e.g., the DMRS resource configuration as shown in FIGS. OCC mapping rules). The base station may multiply the OCC sequence of length 2 by the reference signal sequence. At this time, the value of the OCC sequence is determined by Table 7, and only two of the four OCC sequence values in Table 7 are used.

Second, the length of the OCC can be defined taking into account the number of transport layers. As an example, the length of the OCC can be defined by the criteria shown in the following table.

Transport Layer = 1 Transmission layer = 2 to 4 OCC length 3 2 Configuring DMRS Resources 7 to 9 13 to 15 OCC mapping rules 6 6 OCC sequence value

중에서 3개만 사용Table 7

Use only 3 of them Table 7

Use only 2 of them

Referring to Table 8, the length of the OCC is changed to 3 or 2 depending on the number of transmission layers. That is, when the number of transmission layers is 1 (Rank 1 transmission), the DMRS sequence is mapped to three OFDM symbols as shown in FIG. 7 to FIG. At this time, DMRS is generated by applying OCC of length 4 as shown in Table 7 as before. Here, only three of the four sequence values of the 4-length OCC are actually used. When the number of transmission layers is 2 to 4 (Rank 2 to 4 transmission), the DMRS sequence is mapped to two OFDM symbols as shown in FIG. 13 to FIG. At this time, DMRS is generated by applying OCC of length 4 as shown in Table 7. Here, only two of the four sequence values of the 4-length OCC are actually used.

As another example, the length of the OCC can be defined by the criteria shown in the following table.

Transport Layer = 1 Transmission layer = 2 to 4 OCC length 3 3 Configuring DMRS Resources 7 to 9 7 to 9 OCC mapping rules 6 10 to 12 OCC sequence value

중에서 3개만 사용Table 7

Use only 3 of them Using OCC sequence values according to Tables 4 to 6

Referring to Table 9, regardless of the number of transmission layers, the OCC length is equal to 3 and the OCC mapping rule is the same. However, if the number of transmission layers is 1, only three of the four sequence values of the OCC of length 4 in Table 7 are used as OCC sequence values, and if the number of transmission layers is 2 to 4, the OCC sequence values of Table 4 to Table 6 OCC of length 3 is used as it is.

When step S1605 is completed, the base station maps the modulation symbol a ^(p) _{k, l} of the demodulation value to the resource element RE defined by the subcarrier of index k in each PRB and the OFDM symbol of index l (S1610).

The base station 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 mobile station in operation S1615.

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 a sequence of OCC to extract an estimated reference signal sequence r '(m) (S1620). The terminal generates a reference signal sequence r (m) in the same manner as the base station (S1625), and performs channel estimation by comparing r (m) with r (m) (S1630).

17 is a block diagram illustrating a terminal and a base station according to an embodiment of the present invention.

17, the terminal 1700 includes a receiving unit 1705, a channel estimating unit 1710, and a transmitting unit 1715.

The receiving unit 1705 receives the OFDM signal from the base station 1750. The receiving unit 1705 decodes the OFDM signal in the reverse order of the procedure in which the base station 1750 generates the OFDM signal. For example, the receiver 1705 demaps a received OFDM signal to a resource element, extracts a modulation symbol of a demodulation value, and sends the extracted modulation symbol to the channel estimation unit 1710.

The channel estimation unit 1710 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 1710 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 1715 transmits the uplink signal to the base station 1750.

The base station 1750 includes a transmitter 1755, a receiver 1760, and a base station processor 1770. The base station processor 1770 again includes a reference signal generator 1771 and a resource mapper 1772.

The reference signal generator 1771 generates a reference signal sequence r (m) to be used in the resource configuration for the DMRS. For example, the reference signal generator 1771 can generate the reference signal sequence r (m) by a method similar to Equation (4) or (9). In the resource configuration for the DMRS, 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.

를 참조 신호 시퀀스 r(m)에 곱하여 복조 값의 변조 심볼 a^(p) _k,l을 생성한다. OCC는 안테나 포트의 구성에 따라 길이 2 내지 4 중 하나의 길이를 가진다. 예를 들어, DMRS를 위한 자원 구성에서 길이가 4인 OCC를 적용하는 경우에는 도 4 내지 도 5를 따를 수 있고, 길이가 3인 OCC를 적용하는 경우에는 도 7 내지 도 9를 따를 수 있고, 길이가 2인 OCC를 적용하는 경우에는 도 13 내지 도 15를 따를 수가 있다. 참조 신호 시퀀스 r(m)에 곱하여지는 OCC의 시퀀스

는 본 명세서의 다양한 실시예들에 기반한 OCC 맵핑 규칙에 따라 결정될 수 있다. 예를 들어, OCC 맵핑 규칙은 길이가 3인 OCC를 적용하는 경우에는 도 10 내지 도 12를 따를 수 있고, 길이가 4 또는 2인 OCC를 적용하는 경우에는 도 6을 따를 수가 있다,The reference signal generator 1771 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 length of one of 2 to 4 in length depending on the configuration of the antenna port. For example, in the case of applying the OCC having the length of 4 in the resource configuration for the DMRS, FIG. 4 to FIG. 5 may be applied. In the case of applying the OCC having the length of 3, 13 to 15 in the case of applying the OCC having the length of 2. 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, the OCC mapping rule may follow FIGS. 10 to 12 when OCC of length 3 is applied, and FIG. 6 when OCC of length 4 or 2 is applied.

When the reference signal generator 1771 has to puncture the DMRS in some OFDM symbols in consideration of the PSS or the SSS, the transmitter 1755 instructs the DMRS to be punctured (or to indicate that the length of the OCC is not 4) ) To the mobile station in advance. The signaling may be one bit RRC signaling or may be implicitly transmitted in a specific transceiving mode.

Here, if the DMRS is not instructed to be punctured, the reference signal generator 1771 uses an OCC having a length of 4 as in the conventional case (if the special sub-frame configuration is 9 in the special sub-frame and the general CP is used The OCC of length 2 is used). However, when the DMRS is instructed to be punctured, the length of the OCC and the OCC sequence value used by the reference signal generator 1771 can be defined in various ways.

First, the reference signal generator 1771 can use a fixed OCC length irrespective of the number of transmission layers. As an example, the reference signal generator 1771 uses a 3-length OCC sequence to be applied to 3 OFDM symbols, irrespective of the number of transmission layers (i.e., for all transmission layers = 1 to 6) For example, the DMRS resource configuration as shown in FIGS. 7 to 9 and the OCC mapping rule as shown in FIG. 10 to FIG. 12). Then, the OCC sequence of length 3 can be multiplied by the reference signal sequence. At this time, the values of the OCC sequence are determined by Tables 4 to 6. As another example, the reference signal generator 1771 uses a 2-length OCC sequence to be applied to two OFDM symbols for all cases in which transmission layers = 1 to 4 (for example, a DMRS Resource configuration and OCC mapping rules as shown in FIG. 6). And the OCC sequence of length 2 can be multiplied by the reference signal sequence. At this time, the value of the OCC sequence is determined by Table 7, and only two of the four OCC sequence values in Table 7 are used.

Second, the reference signal generator 1771 may use a variable OCC length in consideration of the number of transmission layers. As an example, the reference signal generator 1771 can use the OCC length according to the following table.

Transport Layer = 1 Transmission layer = 2 to 4 OCC length 3 2 Configuring DMRS Resources 7 to 9 13 to 15 OCC mapping rules 6 6 OCC sequence value

중에서 3개만 사용Table 7

Use only 3 of them Table 7

Use only 2 of them

Referring to Table 10, depending on the number of transmission layers, the length of the OCC is changed to 3 or 2.

As another example, the reference signal generator 1771 can use the OCC length according to the following table.

Transport Layer = 1 Transmission layer = 2 to 4 OCC length 3 3 Configuring DMRS Resources 7 to 9 7 to 9 OCC mapping rules 6 10 to 12 OCC sequence value

중에서 3개만 사용Table 7

Use only 3 of them Using OCC sequence values according to Tables 4 to 6

Referring to Table 11, regardless of the number of transmission layers, the OCC length is equal to 3 and the DMRS resource configuration is the same. However, if the number of transmission layers is 1, only three of the four OCC sequence values in Table 7 are used as OCC sequence values, and if the number of transmission layers is 2 to 4, the OCC sequence values are divided into three OCC sequences in Tables 4 to 6 Value.

The resource mapper 1772 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 transmitting unit 1755 generates an OFDM signal including the resource element mapped with the modulation symbol a ^(p) _{k, l} of the demodulation value, and transmits the OFDM signal to the terminal 1700. The transmitting unit 1755 transmits signaling to the terminal 1700 indicating that the DMRS is punctured (or indicates that the length of the OCC is not 4).

The receiving unit 1760 can receive the uplink signal from the terminal 1700.

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 (DMRS);
A complex valued modulation symbol is generated based on the orthogonal covering code (OCC) defined for each antenna port for the DMRS transmission and the reference signal sequence ;
Mapping the at least one complex-valued modulation symbol to a resource element for the antenna port; And
And transmitting an Orthogonal Frequency Division Multiplexing (OFDM) signal including the resource element to the UE,
At least one DMRS is punctured in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), and the length of the OCC is 3 or less , A reference signal transmission method. The method according to claim 1,
Further comprising transmitting to the terminal a signaling indicating that the DMRS is punctured in at least one OFDM symbol among OFDM symbols used for transmission of the DMRS in the subframe. The method according to claim 1,
Wherein the length of the OCC is set to 2 or 3 irrespective of the number of transmission layers. The method of claim 1,
3 when the number of transmission layers is 1,
And when the number of transmission layers is 2 to 4, the reference signal is transmitted. A reference signal sequence for a demodulation reference signal (DMRS) is generated and an orthogonal covering code (OCC) defined for each antenna port for the DMRS transmission and a reference signal A reference signal generator for generating at least one complex valued modulation symbol based on the sequence;
A resource mapper for mapping the modulation symbols of the at least one complex value to resource elements for the antenna port; And
And a transmitter for transmitting an Orthogonal Frequency Division Multiplexing (OFDM) signal including the resource element to a mobile station,
A DMRS is punctured in at least one OFDM symbol among OFDM symbols used for transmission of the DMRS in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) ), And the length of the OCC is 3 or less. 6. The method of claim 5,
Wherein the transmitting further comprises transmitting to the terminal a signaling indicating that the DMRS in the at least one OFDM symbol is punctured. 6. The method of claim 5,
Wherein the length of the OCC is set to 2 or 3 regardless of the number of transmission layers. 6. The method of claim 5,
3 when the number of transmission layers is 1,
And 2 when the number of transmission layers is 2 to 4. Receiving an OFDM (Orthogonal Frequency Division Multiplexing) signal from a base station;
Demapping a resource element included in the OFDM signal to a complex valued modulation symbol;
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 (DMRS);
Generating an actual reference signal sequence for the DMRS; And
Performing channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence,
A DMRS is punctured in at least one OFDM symbol among OFDM symbols used for transmission of the DMRS in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) ), And the length of the OCC is 3 or less. 10. The method of claim 9,
Further comprising receiving from the base station signaling that the DMRS in the at least one OFDM symbol is to be punctured. 10. The method of claim 9,
Wherein the length of the OCC is set to 2 or 3 irrespective of the number of transmission layers. 10. The method of claim 9,
3 when the number of transmission layers is 1,
And when the number of transmission layers is 2 to 4, the reference signal is received. A receiver for receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal from a base station 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,
A DMRS is punctured in at least one OFDM symbol among OFDM symbols used for transmission of the DMRS in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) ), And the length of the OCC is 3 or less. 14. The method of claim 13,
Wherein the receiving further comprises receiving from the base station signaling that the DMRS is punctured in the at least one OFDM symbol. 14. The method of claim 13,
Wherein the length of the OCC is set to 2 or 3 irrespective of the number of transmission layers. 14. The method of claim 13,
3 when the number of transmission layers is 1,
And 2 when the number of transmission layers is 2 to 4.

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