KR102155090B1 - Method and apparatus for transmitting reference signal in wireless communication system - Google Patents

Abstract

Generating a reference signal sequence for DMRS, generating at least one complex-valued modulation symbol based on the reference signal sequence and an orthogonal cover code defined for each antenna port for DMRS transmission, the at least one complex Disclosed is a method of transmitting a reference signal including mapping a modulation symbol of a value to a resource element related to the antenna port, and transmitting an OFDM signal including the resource element to a terminal.

Description

Method and apparatus for transmitting a reference signal in a wireless communication system {METHOD AND APPARATUS FOR TRANSMITTING REFERENCE SIGNAL IN WIRELESS COMMUNICATION SYSTEM}

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.

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

A component carrier (CC) used in a conventional multiple carrier system emphasizes the versatility of the physical layer, and thus overlaps the control region and common signal overhead. Accordingly, there is a problem in that resources for data signals are reduced, and thus unnecessary losses exist in terms of spectrum efficiency. Accordingly, in order to efficiently operate the multi-carrier system, it is required to introduce a new carrier type (NCT) constituting the multi-carrier system. In NCT, a reference signal (RS) for downlink control channel or channel estimation compared to a conventional carrier type (LCT) within a range that does not degrade or minimizes performance. Can be eliminated or reduced. This is to obtain maximum data transmission efficiency. The conventional conventional carrier type (LCT) is also referred to as a backward compatible carrier type (BCCT) by distinguishing it from NCT.

NCT may include non-standalone NCT and standalone NCT. Non-single NCT is an NCT that cannot exist in the form of a single cell and can exist in the form of a secondary serving cell (SCell) when a primary serving cell (PCell) is present. On the other hand, single NCT is an NCT that can exist in the form of a single cell. For example, a single NCT may exist in the form of a PCell. Cell-specific reference signals (CRSs) may not be transmitted in single NCT and non-alone NCT. Accordingly, a conventional physical downlink control channel (PDCCH), a physical HARQ indicator channel (PHICH), and a physical control format indicator channel (PCFICH), which are control channels based on CRS, may 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 a user equipment (UE) such as a downlink demodulation reference signal (DMRS). A specific reference signal and a specific orthogonal frequency division multiplexing (OFDM) symbol may overlap. In this case, the DMRS may be punctured.

In this case, if the orthogonal cover code (OCC) is mapped to the DMRS as before, the number of layers for DMRS transmission is limited, and various communication defects occur due to power imbalance within the OFDM symbol. I can. Accordingly, there is a need for a method for mapping an OCC and a method and an apparatus for transmitting the DMRS in consideration of power balance and solving the limit on the number of layers for DMRS transmission as much as possible.

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

Another technical problem of the present invention is 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, generating a reference signal sequence for a demodulation reference signal (DMRS), an orthogonal cover code defined for each antenna port for DMRS transmission. covering code: OCC) and generating at least one complex valued modulation symbol based on the reference signal sequence, the at least one complex valued modulation symbol as a resource for the antenna port It provides a method of transmitting a reference signal comprising the step of mapping an element and transmitting an Orthogonal Frequency Division Multiplexing (OFDM) signal including the resource element to a terminal. In the above 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. I can.

According to another aspect of the present invention, a reference signal sequence for a demodulation reference signal (DMRS) is generated, and an orthogonal covering code is defined for each antenna port for DMRS transmission. code: OCC) and a reference signal generator for generating at least one complex valued modulation symbol based on the reference signal sequence, and the at least one complex valued modulation symbol to the antenna port It provides a base station including a resource mapper that maps to a related resource element, and a transmission unit that transmits an OFDM (Orthogonal Frequency Division Multiplexing) signal including the resource element to a terminal. In the base station, in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), the DMRS in at least one of the OFDM symbols used for transmission of the DMRS is It is punctured, and the length of the OCC may be 3 or less.

According to another aspect of the present invention, receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal from a base station, demapping a resource element included in the OFDM signal into a complex valued modulation symbol, see demodulation. Extracting a reference signal sequence by multiplying an orthogonal covering code (OCC) defined for each antenna port for a demodulation reference signal (DMRS) by the complex-valued modulation symbol, the DMRS It provides a method for receiving a reference signal, comprising: generating an actual reference signal sequence related to the reference signal sequence, and performing channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence. In the method, in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), a DMRS is performed in at least one OFDM symbol among OFDM symbols used for transmission of the DMRS. It is punctured, and the length of the OCC may be 3 or less.

According to another aspect of the present invention, a receiver for receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal from a base station and demaps a resource element included in the OFDM signal into a complex-valued modulation symbol, and a demodulation reference signal. signal: a reference signal sequence is extracted by multiplying the complex-valued modulation symbol by an orthogonal covering code (OCC) defined for each antenna port (DM-RS), and the DM-RS It provides a terminal including a channel estimation unit that generates an actual reference signal sequence and performs channel estimation by comparing the actual reference signal sequence with the extracted reference signal sequence. In the terminal, in a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), the DMRS in at least one of the OFDM symbols used for transmission of the DMRS is It is punctured, and the length of the OCC may be 3 or less.

In the resource configuration for the DMRS when the DMRS is puncturing, by clarifying the rule for mapping the orthogonal cover code in consideration of power balance, due to the limitation of the number of layers for DMRS transmission and power imbalance. Various communication defects that may occur can be solved.

1 is a block diagram showing 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 configured with a normal CP (Cyclic Prefix).
6 is a diagram for explaining a state in which the same OCC is distributed so that 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 SSS and DMRS overlap in a general CP and a general subframe.
8 and 9 are diagrams illustrating a situation in which 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 a DMRS by mapping 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 showing a terminal and a base station according to an embodiment of the present invention.

Hereinafter, some embodiments will be described in detail through exemplary drawings in the present specification. In adding reference numerals to constituent elements in each drawing, it should be noted that the same constituent elements are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in describing an embodiment of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present specification, a detailed description thereof will be omitted.

This specification describes a communication network, and operations performed in the communication network are performed in the process of controlling the network and transmitting data in a system (for example, a base station) that governs the communication network, or a terminal linked to the corresponding network. Work can be done in

1 is a block diagram showing 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 and packet data. The wireless communication system 10 includes at least one base station (BS). Each base station 11 provides a communication service for a specific geographic area or frequency area, 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 each of the sectors may have different cell IDs.

The terminal 12 (mobile station, MS) 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, and a PDA. (personal digital assistant), wireless modem (wireless modem), handheld device (handheld device) can be referred to as other terms. Base station 11 generally refers to a station communicating with the terminal 12, eNodeB (evolved-NodeB), BTS (Base Transceiver System), access point (Access Point), femto base station (Femto eNodeB), in-home Base station (Home eNodeB: HeNodeB), relay (relay), remote radio head (Remote Radio Head: RRH) may be referred to as other terms. Cells (15a, 15b, 15c) should be interpreted in a comprehensive meaning indicating a partial area covered by the base station 11, and encompass all various coverage areas such as megacells, macrocells, microcells, picocells, femtocells to be.

Hereinafter, downlink refers to a communication or communication path from the base station 11 to the terminal 12, and uplink refers to a communication or communication path from the terminal 12 to the base station 11 . In downlink, the transmitter may be a part of the base station 11 and the receiver may be a part of the terminal 12. In the uplink, the transmitter may be a part of the terminal 12 and the receiver may be a part of the base station 11. There is no limitation on a multiple access technique applied to the wireless communication system 10. Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA (SC-FDMA), OFDM-FDMA, OFDM-TDMA , OFDM-CDMA, such as various multiple access techniques can be used. These modulation techniques increase the capacity of the communication system by demodulating signals received from multiple users of the communication system. Uplink transmission and downlink transmission may use a Time Division Duplex (TDD) scheme transmitted using different times or a Frequency Division Duplex (FDD) scheme transmitted using different frequencies.

The layers of the radio interface protocol between the terminal and the base station are based on the lower three layers of the Open System Interconnection (OSI) model, which is widely known in communication systems. It may be divided into a second layer (L2) and a third layer (L3). Among them, a 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) is a resource allocation and transmission format of a downlink shared channel (DL-SCH), and a resource of an uplink shared channel (UL-SCH). Allocation information, resource allocation of upper layer control messages such as random access response transmitted on a physical downlink shared channel (PDSCH), transmission power control for individual terminals within a terminal group : TPC) Can carry a set of commands. A plurality of PDCCHs may be transmitted within the control region, and the UE may monitor the plurality of PDCCHs.

Control information of the physical layer mapped to the PDCCH is referred to as downlink control information (DCI). That is, DCI is transmitted through 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.

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, a length of one subframe may be 1 ms, and a length of one slot may be 0.5 ms.

One slot may include a plurality of symbols in the time domain. For example, in the case of a wireless system using Orthogonal Frequency Division Multiple Access (OFDMA) in a downlink (DL), the symbol may be an Orthogonal Frequency Division Multiplexing (OFDM) symbol. Meanwhile, the expression of the symbol period in the time domain is not limited by the multiple access method or the name. For example, in the time domain, the plurality of symbols may be SC-FDMA (Single Carrier-Frequency Division Multiple Access) symbols, symbol intervals, etc. in addition to OFDM symbols.

The number of OFDM symbols included in one slot may vary according to the length of a cyclic prefix (CP). For example, in the case of a normal CP, 1 slot may include 7 OFDM symbols, and in the case of an extended CP, 1 slot may include 6 OFDM symbols.

A resource block (RB) is a resource allocation unit and includes a time-frequency resource corresponding to 180 kHz on a frequency axis and 1 slot on a time axis. A resource element (RE) represents the 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, and channel information feedback. The process of restoring a transmission signal by compensating for distortion of a signal caused by a sudden change in a channel environment is called channel estimation. In addition, it is necessary to measure a channel state of a cell to which the UE belongs or another cell. In general, a reference signal (RS) known to each other 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, it can estimate the channel based on the received reference signal and compensate for the channel value to accurately obtain data sent from the transmission/reception point. If p is the reference signal transmitted from the transmission/reception point, h is the channel information experienced by the reference signal during transmission, n is the thermal noise generated by the terminal, and y is the signal received by the terminal, it can be expressed as y = h·p + n. have. At this time, since the reference signal p is already known by the terminal, when using the LS (Least Square) method, channel information (

) Can be estimated.

는

값에 의존하게 되므로, 정확한 h값의 추정을 위해서는

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

Is

Depends on the value, so for accurate estimation of h

Need to converge to zero.

Reference signals are generally transmitted by generating signals from a sequence of reference signals. As the reference signal sequence, one or more of various sequences having excellent correlation properties may be used. For example, CAZAC (Constant Amplitude Zero Auto-Correlation) sequences such as ZC (Zadoff-Chu) sequences, or pseudo-noise (PN) sequences such as m-sequence, Gold sequence, and Kasami sequence, etc. This reference signal sequence may be used. In addition, various other sequences having excellent correlation characteristics may be used depending on the system situation. In addition, the reference signal sequence may be used after cyclic extension or truncation to adjust the length of the sequence, and various types such as binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK). It may be modulated and mapped to a resource element (RE).

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

The terminal-specific reference signal is a reference signal received by a specific terminal or a specific terminal group in a cell, and is mainly used for data demodulation of a specific terminal or a specific terminal group, and thus may be referred to as a demodulation RS (DMRS).

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

4 and 5, there is a specific antenna port defined to transmit a downlink DMRS. This is called an antenna port for DMRS. For example, the DMRS may be transmitted using up to 8 antenna ports, and the number of these antenna ports may be 7, 8, 9, 10, 11, 12, 13, 14. The DMRS transmitted from the antenna port x is denoted as Rx, and for example, the DMRS transmitted from the antenna port 7 is denoted as R7.

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

Antenna ports 7, 8, 11, and 13 are mapped to the same resource elements on time-frequency, and this 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 location. In FIG. 5, antenna ports 11 and 13 are not shown, but both R11 and R13 are mapped to resource elements at the same location as R7 and R8. In addition, antenna ports 9, 10, 12, and 14 are also mapped to the same resource elements on time-frequency, and this may be referred to as CDM group 2. That is, R9, R10, R12, and R14 are all mapped to the resource element at the same location. In FIG. 5, antenna ports 12 and 14 are not shown, but both R12 and R14 are mapped to resource elements at the same location as R9 and R10.

Resource elements to which the DMRS is mapped on a time-frequency are different between different CDM group 1 and CDM group 2. Accordingly, CDM group 1 and CDM group 2 can be classified by the location of the resource element. This is called frequency division mutiplexing (FDM) and time division multiplexing (TDM) based division. This is because the location of the resource element is divided by frequency and time.

And the antenna ports in the CDM group mapped to the same resource elements on time-frequency are classified by an orthogonal sequence such as an orthogonal cover code (OCC) as shown in Table 1 below. This is called CDM-based division.

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

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

The length of the OCC varies depending on how many OFDM symbols are applied in one subframe. For example, an OCC of length 4 is applied over 4 OFDM symbols within one subframe on the time axis. As an 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 index #5, #6, and # May be 12 or #13. OFDM symbol indices #0, #1, #2, #3, #4, #5 and #6 in the first slot and OFDM symbol indices #0, #1, #2, #3, #4 in the second slot, #5 and #6 are OFDM indexes #0, #1, #2, #3, #4, #5, #6, #7, #8, #9 for 14 OFDM symbols of one subframe, respectively. , #10, #11, #12, and #13 may also be expressed.

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

TDD configuration of special subframe General CP Extended CP DwPTS UpPTS DwPTS UpPTS Normal CP in uplink Extended CP in uplink Normal CP in uplink Extended CP in uplink 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 special subframes in a TDD frame is composed of 9 in a normal cyclic prefix (CP) and 7 in an extended CP. In the case of a general CP, configurations 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 are each of 14 orthogonal frequency division multiplexing (OFDM) symbols of one special subframe (DwPTS, guard period, The number of OFDM symbols for UpPTS) is (3, 10, 1), (9, 4, 1), (10, 3, 1), (11, 2, 1), (12, 1, 1), respectively, (3, 9, 2), (9, 3, 2), (10, 2, 2), (11, 1, 2), (6, 6, 2). In the case of extended CP, configurations 0, 1, 2, 3, 4, 5, 6 and 7 each have the number of OFDM symbols for (DwPTS, guard period, UpPTS) among 12 OFDM symbols of one special subframe, respectively (3, 8, 1), (8, 3, 1), (9, 2, 1), (10, 1, 1), (3, 7, 2), (8, 2, 2), (9 , 1, 2), (5, 5, 2).

Regarding the mapping of OCC, for example, when a special subframe configuration is 3, 4 or 8 in a special subframe and a general CP is used, 4 OFDM symbols to which OCC is applied among a total of 11 or 12 OFDM symbols are 3 It may be a fourth, fourth, tenth, and eleventh OFDM symbol (OFDM symbol indexes are #2 and #3 in the first slot and #2 and #3 in the second slot).

As another example, when a special subframe configuration is 1, 2, 6, or 7 in a special subframe and a general CP is used, 4 OFDM symbols to which OCC is applied among a total of 9 or 10 OFDM symbols are 3rd, 4th , 6th, 7th OFDM symbol (OFDM symbol indexes are #2, #3, #5, and #6 of the first slot).

If an OCC of length 2 is used, the OCC is applied over two OFDM symbols within one subframe as a time axis. For example, when a special subframe configuration is 9 and a general CP is used in a special subframe, OCC is applied to the 3rd and 4th OFDM symbol among a total of 6 OFDM symbols (the first slot as the index of the OFDM symbol #2 and #3).

When mapping an OCC of length 4 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 the same even when OCC of length 2 is mapped to two OFDM symbols in the order a and b in Table 1. That is, in the case of an OFDM symbol to which only a is mapped, since only +1 is mapped, a problem may occur in power balancing with other OFDM symbols to which +1 and -1 can be mapped. Therefore, it is necessary to distribute the same OCC as shown in FIG. 6 so that the same OCC is not mapped to one OFDM symbol.

6 is a diagram for explaining a state in which the same OCC is distributed so that 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 6 DMRS mappings per CDM group across two PRBs on a frequency. Each mapping can start counting from the bottom of the PRB, or from the top of the PRB, and starting from either side, 0 times, 1 times, 2 times,... , Is defined as mapping #5. In this case, the OCC is mapped so that a, b, c, and d are distributed as evenly as possible across a plurality of subcarriers on one OFDM symbol, so that power balance between each OFDM symbol can be adjusted. To do this, the power is balanced by two PRB units in terms of frequency. Hereinafter, in the present invention, each index such as a PRB index, an OFDM symbol index, and a subcarrier index is assigned from 0. That is, even number means 0, 2, 4, 6,... Means, and the odd number means 1, 3, 5, 7,..

First, for CDM group 1, OCC in the order of a, b, c, d is applied when mapping 0, 2, and 4 from the bottom on the frequency axis (i.e., even numbers starting from 0), When mapping 3 and 5 (i.e. starting from 0 and odd), the OCC in the reverse order of d, c, b, a is applied.

Next, in CDM group 2, when mapping 0 times, 2 times, and 4 times from the bottom on the frequency axis (i.e., even numbers starting from 0), c, through a cyclic delay of CDM groups 1 and 2, OCC in the order of d, a, b is applied, and when mapping 1, 3, 5 (i.e., odd number starting from 0), OCC in the reverse order of b, a, d, c is applied do.

In this case, in terms of frequency, there are a total of 6 OCC mappings for each CDM group in two PRBs, and a total of 12 OCC mappings for all CDM groups. The sequence values a, b, and OCC over two PRBs on one OFDM symbol It can be seen that c and d are mapped three times each.

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

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

Referring to FIG. 8, in general CP and special subframe configurations 3, 4, and 8, DMRSs are mapped to resource elements corresponding to A and B. Depending on the special subframe configuration 3, 4, 8, some of the last 2 or 3 OFDM symbols in the special subframe are used as a guard period (GP) and the remaining OFDM symbol(s) are used as UpPTS. Can be used. In addition, the PSS is mapped to 6 central PRBs in the third OFDM symbol of subframe indexes 1 and 6 (slot indexes 2 and 12). Therefore, the PSS overlaps 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. Depending on the special subframe configurations 1, 2, 6, and 7, some OFDM symbol(s) of the last 4 or 5 OFDM symbols in the special subframe may be used as GP and the remaining OFDM symbols may be used as UpPTS. In addition, the PSS is mapped to six central PRBs in the third OFDM symbol of subframe indexes 1 and 6 (slot indexes 2 and 12). Therefore, the PSS overlaps the DMRS in the third OFDM symbol.

In FIGS. 7 to 9, the DMRS overlapping the PSS or SSS may be punctured. In this case, there are three OFDM symbols to which the DMRS is mapped within one PRB pair. When the DMRS is mapped through three OFDM symbols, each antenna port cannot be distinguished within one CDM group through the existing OCC of length 4. 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 the DMRS is reduced due to puncturing or the like, a rule for mapping the OCC, and an apparatus and method for transmitting the DMRS. When the OCC of length 4 is mapped to the DMRS, there arises a problem that it cannot support multiple antenna ports as described above.

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

OCC (length 3) [a b c] OCC A [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) may be classified by OCC A, OCC B, and OCC C. In CDM group B (or CDM group 2), antenna ports 9, 10, and 12 may be classified by OCC A, OCC B, and OCC C. According to this, in the case of a general CP, DMRS transmission up to rank 6 through up to 6 layers is possible.

Even when an OCC of length 3 is used, OCC mapping must be performed to balance power within one OFDM symbol.

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, there are three OCC mappings for CDM group A (antenna ports 7, 8, and 11) and CDM group B (antenna ports 9, 10, and 12) in one PRB on a frequency basis. Let's say mapping #0, mapping #1, and mapping #2 sequentially from the bottom of the frequency axis. In the case of CDM group A, mapping #0 (subcarrier #1) in the order of a, b, c, mapping #1 (subcarrier #6) in order of b, c, a, mapping #2 (subcarrier #11) in order of c, OCCs may be mapped (or applied) in the order of a and b. In the case of CDM group B, mapping number 0 (subcarrier #0) in the order of a, b, c, mapping number 1 (subcarrier #5) in order of b, c, a, and mapping number 2 (subcarrier #10) ), OCC may be mapped (or applied) in the order of c, a, and b.

Accordingly, the rules of OCC mapped to each CDM group are as follows.

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,

Each 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. This corresponds to the sequences a, b, and c mentioned in Table 3 in the case of 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 three OCC mappings for CDM group A (antenna ports 7, 8, and 11) and CDM group B (antenna ports 9, 10, and 12) in one PRB on a frequency basis. Let's say mapping #0, mapping #1, and mapping #2 sequentially from the bottom of the frequency axis. In the case of CDM group A, mapping #0 (subcarrier #1) in the order of a, b, c, mapping #1 (subcarrier #6) in order of b, c, a, mapping #2 (subcarrier #11) in order of c, OCCs may be mapped (or applied) in the order of a and b. In addition, in the case of CDM group B, OCCs cyclically shifted by 1 in CDM group A may be mapped. For example, mapping #0 (subcarrier #0) in the order of b, c, a, mapping #1 (subcarrier #5) in order of c, a, b, mapping #2 (subcarrier #10) in order of a, b, OCCs may be mapped (or applied) in c order.

The rules of OCC mapped to each CDM group are 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 three OCC mappings for CDM group A (antenna ports 7, 8, and 11) and CDM group B (antenna ports 9, 10, and 12) in one PRB on a frequency basis. Let's say mapping #0, mapping #1, and mapping #2 sequentially from the bottom of the frequency axis. In the case of CDM group A, mapping #0 (subcarrier #1) in the order of a, b, c, mapping #1 (subcarrier #6) in order of b, c, a, mapping #2 (subcarrier #11) in order of c, OCCs may be mapped (or applied) in the order of a and b. Also, in the case of CDM group B, OCCs cyclically shifted by 2 in CDM group A may be mapped. For example, mapping #0 (subcarrier #0) in the order of c, a, b, mapping #1 (subcarrier #5) in order of a, b, c, mapping #2 (subcarrier #10) in order of b, c, OCCs may be mapped (or applied) in the order of a.

The rules of OCC mapped to each CDM group are 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 mappings for each CDM group in one PRB and a total of 6 mappings for all CDM groups. It can be seen that b and c are applied twice in each PRB on a frequency for one OFDM symbol. In addition to the embodiments shown in FIGS. 10 to 12, OCC mapping may be possible in various ways while maintaining power balance, and these will be included in the technical idea of the present invention.

In addition, FIGS. 10 to 12 have described OCC mapping rules limited to the case of a general subframe having a general CP as shown in FIG. 7. However, for other cases in which DMRS is mapped using 3 OFDM symbols (for example, in the case of a special subframe having a general CP as in FIG. 8 or 9), the same rule for mapping an OCC of length 3 is applied. I can.

When the above-described OCC mapping rule is expressed mathematically, it is as follows.

Referring to Equation 2, a ^(p) _k,l is modulation symbols of a demodulation value, which 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 subcarrier index is k and OFDM symbol index is l when the antenna port number is p.

l'is a value indicating the order of OFDM symbols to which OCCs are mapped along a time axis within a subframe. Alternatively, l'means the l'th sequence of the OCC. For example, if l'=0, the OCC indicates an OFDM symbol mapped first (mapped No. 0), and if l'=1, the OCC indicates an OFDM symbol mapped second (mapped No. 1).

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 the OCC for the antenna port p. For i=0, 1, 2, 3, OCC is

to be. If i=0, 1, 2,

to be. In addition, w _p (i) may have a value as shown in Equation 3 below according to the order m'on the frequency axis to which the OCC is mapped.

Referring to Equation 3, m'is a value representing the order or number of times that OCCs are mapped along the frequency axis in the PRB. In the case of FIGS. 10 to 12, for each CDM group, since OCC mapping is performed three times along the frequency axis in two slots and one PRB, m'=0, 1, 2. That is, as mentioned above, mapping number 0, mapping number 1, and mapping number 2 sequentially from the bottom of the frequency axis correspond to m'=0, m'=1, and m'=2, respectively.

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 in a PRB (index = n _PRB ) allocated for PDSCH transmission. In other words, for antenna ports p=7, p=8 or p=7, 8,..., v+6, one having an index n _PRB in the frequency domain allocated for corresponding PDSCH transmission In the PRB, a part of the reference signal sequence is mapped to complex-valued modulation symbols in one subframe. For example, r(m) may be calculated by the following equation by a pseudo-random sequence c(i) based on a gold sequence.

Here, m=0,1,...,9N _RB ^{max , DL} -1 (for general CP) or m=0,1,...,12N _RB ^{max , DL} -1.

Here, when using a total of X resource elements for one DMRS CDM group within one PRB pair (X=6, 8, 9, 12, 16, etc.), the total length of the reference signal sequence r(m) is It becomes X·N _RB ^{max and DL} . Therefore, it has a range of m=0, 1, ..., XN _RB ^{max , DL} -1. As an example, when a general CP is used, a total of 12 resource elements are used for DMRS transmission for one DMRS CDM group within one PRB pair, so the total of the required reference signal sequence r(m) over the entire band The length is 12·N _RB ^{max and DL} . Therefore, it has a range of m=0, 1, ..., 12N _RB ^max,DL -1. As another example, when the extended CP is used, since a total of 16 resource elements are used for DMRS transmission for one DMRS CDM group in one PRB pair, the total number of reference signal sequences r(m) required over the entire band The length is 16·N _RB ^{max and DL} . Therefore, it has a range of m=0, 1, ..., 16N _RB ^{max , DL} -1.

Therefore, as mentioned in Equation 4, since a total of 9 resource elements are used for DMRS transmission for one DMRS CDM group within one PRB pair as in FIGS. 10 to 12, considering this, X=9 You can do it, or you can use only some of them after setting X=12 as before.

N _RB ^{max and DL} represent the maximum number of RBs in downlink. n _PRB corresponds to a PRB index on a frequency ^, and has an integer value between 0 and N _RB ^{max and DL} -1.

The subcarrier index k can 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, and is usually 12. And k'can be determined by the following equation.

Next, an index l of an OFDM symbol in a single slot and an order l'of OFDM symbols to which OCCs are mapped along a time axis in a subframe may be defined by the following equations, respectively.

According to another embodiment of the present invention, DMRS is not transmitted in a slot in which PSS or SSS is transmitted. That is, all DMRSs are punctured in a slot in which PSS or SSS is transmitted. In this case, the base station may generate a DMRS by mapping the DMRS sequences A and B to the two OFDM symbols as shown in FIGS. 13 to 15 and transmit the DMRS to the terminal. In this case, the variables of Equations 2 to 8 may be modified as shown in the following Equation.

In addition, the OCC sequence value for each antenna port may 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. However, since only two of the four OFDM symbols are used as DMRSs, the four-length OCC in Table 7 is used as it is, but the four sequence values of the four-length OCC

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, the base station generates a reference signal sequence r(m) to be used in resource configuration for DMRS (S1600). A method of calculating r(m) may be the same as in Equation 4 or 9 described above. In the resource configuration for DMRS, there may be one or more antenna ports, and the number may be determined according to the number of layers used for transmission of the PDSCH. In addition, 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 is a sequence of orthogonal cover codes (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 2 to 4 depending on the configuration of the antenna port. For example, in the case of applying an OCC of length 4 in the resource configuration for DMRS, it may follow FIGS. 4 to 5, and when applying an OCC of length 3 may follow FIGS. 7 to 9, When an OCC of length 2 is applied, FIGS. 13 to 15 may be followed. Sequence of OCC multiplied by reference signal sequence r(m)

May be determined according to an OCC mapping rule based on various embodiments of the present specification. For example, the OCC mapping rule may follow FIGS. 10 to 12 when an OCC of length 3 is applied, and may follow FIG. 6 when an OCC of length 4 or 2 is applied.

When the base station needs to puncture the DMRS in some OFDM symbols in consideration of the PSS or SSS, the base station may transmit signaling indicating that the DMRS is punctured (or indicating that the length of the OCC is not 4) to the terminal in advance. have. The signaling may be 1-bit RRC signaling, or may be implicitly transmitted in a specific transmission/reception mode.

Here, if it is not indicated that the DMRS is punctured, the OCC of length 4 is applied as before (however, if the special subframe configuration is 9 in the special subframe and the general CP is used, the OCC of length 2 is applied. being). However, when it is indicated that the DMRS is punctured, the length of the OCC and the value of the OCC sequence may be defined in various cases.

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

As an example, regardless of the number of transport layers (i.e., for all cases of transport layers = 1 to 6), an OCC sequence of length 3 to be applied to three OFDM symbols may be used (for example, Figs. 7 to 9 DMRS resource configuration and OCC mapping rules as shown in FIGS. 10 to 12). In addition, the base station may multiply the reference signal sequence by the OCC sequence of length 3. At this time, the value of the OCC sequence of Gil 3 is determined by Tables 4 to 6.

As another example, for all cases of transport layer = 1 to 4, an OCC sequence of length 2 to be applied to two OFDM symbols may be used (for example, a DMRS resource configuration as shown in FIGS. 13 to 15 and OCC mapping rules). In addition, 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 may be defined in consideration of the number of transport layers. As an example, the length of the OCC may be defined by the criteria shown in the table below.

Transport layer=1 Transport layer=2~4 OCC length 3 2 DMRS resource configuration 7 to 9 13-15 OCC mapping rules Fig. 6 Fig. 6 OCC sequence value

중에서 3개만 사용Of table 7

Use only 3 out of Of 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 transport layers. That is, when the number of transport layers is 1 (Rank 1 transmission), the DMRS sequence is mapped to three OFDM symbols as shown in FIGS. 7 to 9. At this time, DMRS is generated by applying the OCC of length 4 as shown in Table 7. Here, only three of the four sequence values of a length 4 OCC are actually used. When the number of transport layers is 2 to 4 (Rank 2 to 4 transmission), the DMRS sequence is mapped to two OFDM symbols as shown in FIGS. 13 to 15. At this time, DMRS is generated by applying the OCC of length 4 as shown in Table 7. Here, only two of the four sequence values of the OCC of length 4 are actually used.

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

Transport layer=1 Transport layer=2~4 OCC length 3 3 DMRS resource configuration 7 to 9 7 to 9 OCC mapping rules Fig. 6 10-12 OCC sequence value

중에서 3개만 사용Of table 7

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

Referring to Table 9, regardless of the number of transport layers, the OCC length is the same as 3 and the OCC mapping rules are the same. However, if the number of transport layers is 1, only three of the four sequence values of OCC of length 4 in Table 7 are used as the OCC sequence value, and if the number of transport layers is 2 to 4, the OCC sequence values in Tables 4 to 6 are used. 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 a resource element (RE) defined by an index k subcarrier and an index l OFDM symbol in each PRB (S1610).

The base station generates an OFDM signal including a resource element to which a modulation symbol a ^(p) _{k, l} of the demodulation value is mapped and transmits it to the terminal (S1615).

Upon receiving the OFDM signal, the UE decodes the OFDM signal in the reverse order of the procedure for generating the OFDM signal by the base station.

For example, the UE extracts a modulation symbol of a demodulation value by demapping the received OFDM signal to a resource element, and extracts the estimated reference signal sequence r'(m) by multiplying this by the sequence of OCC (S1620). The UE generates a reference signal sequence r(m) in the same manner as the base station (S1625) and compares r(m) with r'(m) to perform channel estimation (S1630).

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

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

The receiver 1705 receives an OFDM signal from the base station 1750. In addition, 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 receiving unit 1705 demaps the received OFDM signal to a resource element, extracts a modulation symbol of a demodulation value, and sends it to the channel estimating unit 1710.

The channel estimating unit 1710 extracts the estimated reference signal sequence r'(m) by multiplying the modulation symbol of the demodulation value by the sequence of OCC. In addition, the channel estimation unit 1710 generates a reference signal sequence r(m) in the same manner as the base station, and performs channel estimation by comparing r(m) with r'(m).

The transmission unit 1715 transmits an uplink signal to the base station 1750.

The base station 1750 includes a transmission unit 1755, a reception unit 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 resource configuration for DMRS. For example, the reference signal generator 1771 may generate the reference signal sequence r(m) by a method such as Equation 4 or 9. In the resource configuration for DMRS, there may be one or more antenna ports, and the number may be determined according to the number of layers used for transmission of the PDSCH. In addition, 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 is a sequence of orthogonal cover codes (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 2 to 4 depending on the configuration of the antenna port. For example, in the case of applying an OCC of length 4 in the resource configuration for DMRS, it may follow FIGS. 4 to 5, and when applying an OCC of length 3 may follow FIGS. 7 to 9, When an OCC of length 2 is applied, FIGS. 13 to 15 may be followed. Sequence of OCC multiplied by reference signal sequence r(m)

May be determined according to an OCC mapping rule based on various embodiments of the present specification. For example, the OCC mapping rule may follow FIGS. 10 to 12 when an OCC of length 3 is applied, and may follow FIG. 6 when an OCC of length 4 or 2 is applied.

When the reference signal generation unit 1771 needs to puncture the DMRS in some OFDM symbols in consideration of PSS or SSS, the transmission unit 1755 indicates that the DMRS is punctured (or indicates that the length of the OCC is not 4) Signaling) can be transmitted to the terminal in advance. The signaling may be 1-bit RRC signaling, or may be implicitly transmitted in a specific transmission/reception mode.

Here, if it is not indicated that the DMRS is punctured, the reference signal generation unit 1771 uses an OCC having a length of 4 as in the past (however, if a special subframe configuration is 9 and a general CP is used in a special subframe OCC of length 2 is used). However, when it is indicated that the DMRS is punctured, the length of the OCC and the OCC sequence value used by the reference signal generator 1771 may be defined in various ways.

First, the reference signal generator 1771 may use a fixed OCC length regardless of the number of transport layers. As an example, the reference signal generator 1771 uses an OCC sequence of length 3 to be applied to three OFDM symbols, regardless of the number of transport layers (ie, for all cases of transport layers = 1 to 6) ( For example, a DMRS resource configuration as shown in FIGS. 7 to 9 and an OCC mapping rule as shown in FIGS. 10 to 12). In addition, the OCC sequence of length 3 may be multiplied by the reference signal sequence. At this time, the value of the OCC sequence is determined by Tables 4 to 6. As another example, the reference signal generation unit 1771 uses an OCC sequence of length 2 to be applied to two OFDM symbols in all cases of transport layer = 1 to 4 (for example, DMRS as shown in Figs. 13 to 15). Resource configuration and OCC mapping rule as shown in FIG. 6). In addition, the OCC sequence of length 2 may 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 length of OCC in consideration of the number of transport layers. As an example, the reference signal generator 1771 may use the length of the OCC according to the criteria shown in the table below.

Transport layer=1 Transport layer=2~4 OCC length 3 2 DMRS resource configuration 7 to 9 13-15 OCC mapping rules Fig. 6 Fig. 6 OCC sequence value

중에서 3개만 사용Of table 7

Use only 3 out of Of table 7

Use only 2 of them

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

As another example, the reference signal generator 1771 may use the length of the OCC according to the criteria shown in the table below.

Transport layer=1 Transport layer=2~4 OCC length 3 3 DMRS resource configuration 7 to 9 7 to 9 OCC mapping rules Fig. 6 10-12 OCC sequence value

중에서 3개만 사용Of table 7

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

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

The resource mapper 1772 maps a modulation symbol a ^(p) _k,l of a demodulation value to a resource element (RE) defined by a subcarrier of index k and an OFDM symbol of index _l in each PRB.

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

The reception unit 1760 may receive an uplink signal from the terminal 1700.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, 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 interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims (16)

delete delete delete delete delete delete delete delete Receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal from a base station;
Demapping a resource element included in the OFDM signal into a complex valued modulation symbol;
Extracting a reference signal sequence by multiplying an orthogonal covering code (OCC) defined for each antenna port for a demodulation reference signal (DMRS) by the complex-valued modulation symbol;
Generating an actual reference signal sequence for the DMRS; And
Comprising the step of performing channel estimation by comparing the actual reference signal sequence and the extracted reference signal sequence,
In a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), DMRS is punctured in at least one OFDM symbol among OFDM symbols used for transmission of the DMRS. ),
The OCC sequence value for each antenna port is defined as shown in the table below,
The length of the OCC is,
3 when the number of transport layers is 1, 2 when the number of transport layers is 2 to 4,
The OCC sequence value used for the OCC is,
When the number of transport layers is 1,

3 of them are used,
When the number of transport layers is 2 to 4,

A method for receiving a reference signal, characterized in that two of them are used.

At this time, w _p (i) is the i-th sequence of the OCC for the antenna port p The method of claim 9,
And receiving, from the base station, signaling indicating that the DMRS is punctured in the at least one OFDM symbol. delete delete A receiver for receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal from a base station and demaps a resource element included in the OFDM signal into a complex-valued modulation symbol; And
A reference signal sequence is extracted by multiplying an orthogonal covering code (OCC) defined for each antenna port for a demodulation reference signal (DMRS) by the complex-valued modulation symbol, and the DMRS Comprising a channel estimation unit for generating an actual reference signal sequence for, and performing channel estimation by comparing the actual reference signal sequence and the extracted reference signal sequence,
In a subframe including a primary synchronization signal (PSS) or a secondary synchronization signal (SSS), DMRS is punctured in at least one OFDM symbol among OFDM symbols used for transmission of the DMRS. ),
The OCC sequence value for each antenna port is defined as shown in the table below,
The length of the OCC is,
3 when the number of transport layers is 1, 2 when the number of transport layers is 2 to 4,
The OCC sequence value used for the OCC is,
When the number of transport layers is 1,

3 of them are used,
When the number of transport layers is 2 to 4,

The terminal, characterized in that two are used.

At this time, w _p (i) is the i-th sequence of the OCC for the antenna port p The method of claim 13,
The receiving unit further comprises receiving, from the base station, signaling indicating that the DMRS is punctured in the at least one OFDM symbol. delete delete

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