KR20120023635A - Method and apparatus for transmitting/receiving a sounding reference signal in a wireless communication system - Google Patents

Abstract

PURPOSE: A method and an apparatus for transmitting/receiving sounding reference signals in a wireless communication system are provided to efficiently transmit sounding reference signals through terminals operated by CoMP by the efficient transmission of sounding reference signals through relay nodes. CONSTITUTION: Sounding reference signals toward a plurality of transmission antennae of a relay node are allocated to a first OFDM symbol from a relay node. The multiplexed first OFDM symbol is received. The sounding reference signals toward a plurality of transmission antennae of the terminal are allocated to the second OFDM symbol from the terminal. The multiplexed second OFDM symbol is received. The second OFDM symbol is the final OFDM symbol of a subframe. The first OFDM symbol one of the rest OFDM symbols except for the final OFDM symbol among the symbols of the subframe.

Description

METHOD AND APPARATUS FOR TRANSMITTING / RECEIVING A SOUNDING REFERENCE SIGNAL IN A WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting and receiving a sounding reference signal in a wireless communication system.

As an example of a mobile communication system to which the present invention can be applied, a 3GPP LTE (3rd Generation Partnership Project Long Term Evolution (LTE)) communication system will be described schematically.

1 is a diagram schematically illustrating an E-UMTS network structure as an example of a mobile communication system. The Evolved Universal Mobile Telecommunications System (E-UMTS) system evolved from the existing Universal Mobile Telecommunications System (UMTS), and is currently undergoing basic standardization work in 3GPP. In general, E-UMTS may be referred to as an LTE (Long Term Evolution) system. For details of the technical specifications of UMTS and E-UMTS, refer to Release 7 and Release 8 of "3rd Generation Partnership Project (Technical Specification Group Radio Access Network)" respectively.

1, an E-UMTS is located at the end of a user equipment (UE) 120, an eNode B (eNode B) 110a and 110b, and a network (E-UTRAN) And an access gateway (AG). The base station may transmit multiple data streams simultaneously for broadcast service, multicast service and / or unicast service.

One or more cells exist in one base station. The cell is set to one of the bandwidths of 1.25, 2.5, 5, 10, 15, 20Mhz and the like to provide downlink or uplink transmission service to a plurality of UEs. Different cells may be configured to provide different bandwidths. The base station controls data transmission and reception for a plurality of terminals. The base station transmits downlink scheduling information for downlink (DL) data and informs the user equipment of time / frequency domain, encoding, data size, and HARQ (Hybrid Automatic Repeat and reQuest) related information. In addition, the base station transmits uplink scheduling information to uplink UL data for uplink (UL) data and informs the user equipment of time / frequency domain, encoding, data size, HARQ related information, and the like. An interface for transmitting user traffic or control traffic may be used between base stations. The Core Network (CN) can be composed of an AG and a network node for user registration of the UE. The AG manages the mobility of the UE in units of a tracking area (TA) composed of a plurality of cells.

Wireless communication technologies have been developed to LTE based on WCDMA, but the demands and expectations of users and operators are continuously increasing. In addition, as other radio access technologies continue to be developed, new technological evolution is required to be competitive in the future. Reduced cost per bit, increased service availability, the use of flexible frequency bands, simple structure and open interface, and adequate power consumption of the terminal are required. Recently, 3GPP is working on standardization of subsequent technologies for LTE (Release 8/9). The technique is referred to herein as "LTE-Advanced" or "LTE-A" (Release 10 or later).

Next, a wireless communication system including a relay node will be described with reference to FIG. 2.

2 is a diagram schematically illustrating a network for performing wireless communication using a relay node.

The wireless communication system using the relaying method can quickly reconfigure the network in response to changes in the communication environment, and operate the entire wireless network more efficiently. For example, a wireless communication system using a relaying scheme may expand a cell service area and increase system capacity. That is, when the channel state between the base station and the terminal is poor, a relay node may be installed between the base station and the terminal to configure a relaying path through the relay node, thereby providing a wireless channel having a better channel state to the terminal.

As such, the relay node is widely used as a technology introduced to solve the radio shade area in a mobile communication system. In the past, it has evolved into a more intelligent form, compared to the ability of repeaters to simply amplify and transmit signals.

In FIG. 2, a link between a base station and a relay node is called a backhaul link, and a link established between the relay node and the terminal is called an access link.

Next, a coordinated multi-point (hereinafter referred to as "CoMP") system will be described with reference to FIG. 3.

3 is a diagram conceptually illustrating CoMP (Coordinated Multi-Point) of an existing intra eNB and an inter eNB.

Referring to FIG. 3, intra base stations 110 and 120 and inter base stations 130 exist in a multi-cell environment. In Long Term Evolution (LTE), an intra base station consists of several cells (or sectors). Cells belonging to a base station to which a specific terminal belongs have a relationship with a specific terminal and an intra base station (110, 120). That is, cells sharing the same base station as its own cell to which the terminal belongs are cells corresponding to the intra base stations 110 and 120, and cells belonging to other base stations are cells corresponding to the inter base station 130. As such, cells based on the same base station as a specific UE exchange information (eg, data, channel state information (CSI)) through an x2 interface, but cells based on other base stations Information may be exchanged between cells through the backhaul 140 and the like. As shown in FIG. 1, a single cell MIMO user 140 within a single cell communicates with one serving base station in one cell (sector), and the multi cell MIMO user 150 located at the cell boundary is a multi cell (sector). Can communicate with multiple serving base stations.

The CoMP system is a system for improving throughput of a user at a cell boundary by applying improved MIMO transmission in a multi-cell environment. Application of the CoMP system can reduce inter-cell interference in a multi-cell environment. Using this CoMP system, the terminal can be jointly supported data from the multi-cell base station (Multi-cell base-station). In addition, each base station can improve the performance of the system by simultaneously supporting one or more terminals (MS1, MS2, ... MSK) using the same Radio Frequency Resource. Also, the base station may perform a space division multiple access (SDMA) method based on channel state information between the base station and the terminal.

An object of the present invention is to provide a method for a relay node to transmit a sounding reference signal in a wireless communication system.

Another object of the present invention is to provide a sounding reference signal transmission method of a terminal operating in CoMP.

Technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

In one aspect of the present invention, in a method for receiving a sounding reference signal at a base station of a wireless communication system, a first OFDM in which sounding reference signals for a plurality of transmission antennas of the relay node are multiplexed and allocated from a relay node Receiving a symbol; And receiving, from the terminal, a second OFDM symbol in which sounding reference signals for the plurality of transmission antennas of the terminal are multiplexed and allocated, wherein the second OFDM symbol is the last OFDM symbol of a subframe. One OFDM symbol is provided with a sounding reference signal receiving method, characterized in that one of the remaining OFDM symbols except the last OFDM symbol among the symbols of the subframe.

In another aspect of the present invention, a method of transmitting a plurality of sounding reference signals in a relay node of a wireless communication system, the method comprising: multiplexing sounding reference signals for a plurality of transmission antennas and assigning them to OFDM symbols; And transmitting the OFDM symbol to a base station, wherein the OFDM symbol is one of the remaining OFDM symbols except the last OFDM symbol among the symbols of the subframe.

In this case, the first OFDM symbol may be the last OFDM symbol of the first slot of the subframe.

In addition, sounding reference signals for a plurality of transmission antennas of the relay node may be multiplexed by a code division multiplexing (CDM) scheme.

In another aspect of the present invention, in a method of transmitting a plurality of sounding reference signals in a terminal of a wireless communication system that supports coordinated multi-point (hereinafter referred to as "CoMP"), a plurality of transmission antennas Transmitting a first OFDM symbol allocated by multiplexing sounding reference signals for the first base station to the first base station; And transmitting a second OFDM symbol allocated to multiplexing sounding reference signals for the plurality of transmission antennas to a second base station.

In another aspect of the present invention, a method for receiving a plurality of sounding reference signals at a base station of a wireless communication system supporting a coordinated multi-point (hereinafter referred to as "CoMP"), operating in CoMP Receiving an allocated OFDM symbol by multiplexing sounding reference signals for a plurality of transmission antennas from a terminal; And acquiring downlink channel information by using the sounding reference signals.

In another aspect of the present invention, in a method for receiving a sounding reference signal at a base station of a wireless communication system, the first sounding reference signals for a plurality of transmission antennas of the relay node from a relay node are multiplexed and allocated. A receiving module for receiving a first OFDM symbol and receiving, from a terminal, a second OFDM symbol in which second sounding reference signals for a plurality of transmission antennas of the terminal are multiplexed and allocated; And a processor for acquiring backhaul uplink channel information using the first sounding reference signals, and acquiring uplink channel information using the second sounding reference signals, wherein the second OFDM symbol is a subframe. And a first OFDM symbol is one of the remaining OFDM symbols except for the last OFDM symbol among the symbols of the subframe.

In still another aspect of the present invention, there is provided a processor, comprising: a processor for multiplexing sounding reference signals for a plurality of transmission antennas and assigning them to OFDM symbols; And a transmission module for transmitting the OFDM symbol to a base station, wherein the OFDM symbol is one of the remaining OFDM symbols except the last OFDM symbol among the symbols of the subframe.

In another aspect of the present invention, in a terminal of a wireless communication system supporting coordinated multi-point (hereinafter referred to as "CoMP"), by multiplexing the first sounding reference signals for a plurality of transmission antennas A processor for allocating a first OFDM symbol and multiplexing second sounding reference signals for a plurality of transmission antennas to the second OFDM symbol; And a transmission module configured to transmit the first OFDM symbol to a first base station and to transmit the second OFDM symbol to a second base station.

According to embodiments of the present invention, a relay node can efficiently transmit a sounding reference signal, and a terminal operating in CoMP can efficiently transmit a sounding reference signal.

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

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included as part of the detailed description in order to provide a thorough understanding of the present invention, provide an embodiment of the present invention and together with the description, illustrate the technical idea of the present invention.
1 illustrates an E-UMTS network structure as an example of a mobile communication system.
2 is a diagram schematically illustrating a network for performing wireless communication using a relay node.
FIG. 3 is a diagram conceptually illustrating CoMP (Coordinated Multi-Point) of an existing intra eNB and an inter eNB.
4 illustrates a structure of a radio frame used in an LTE system.
5 illustrates a structure of an uplink subframe used in an LTE system.
6 illustrates a process of performing channel sounding when applying a closed-loop antenna selection in an LTE system.
FIG. 7 illustrates a method of multiplexing a sounding reference signal (SRS) using a code division multiplexing (CDM) method according to an embodiment of the present invention.
8 illustrates a method of multiplexing SRS in a frequency division multiplexing (FDM) scheme according to an embodiment of the present invention.
9 illustrates a method of multiplexing SRS in a CDM / FDM scheme according to an embodiment of the present invention.
10 and 11 illustrate an example of configuring a plurality of SRS transmission symbols in a subframe according to an embodiment of the present invention.
12 illustrates a process of performing channel sounding according to an embodiment of the present invention.
13 illustrates a block diagram of a base station and a terminal according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details. For example, the following detailed description will be described in detail on the assumption that the mobile communication system is a 3GPP LTE-A system, but is applicable to any other mobile communication system except for the specific matters of the 3GPP LTE-A system. .

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

In addition, in the following description, it is assumed that a terminal collectively refers to a mobile or fixed user terminal device such as a user equipment (UE), a mobile station (MS), a relay node, and the like. In addition, it is assumed that the base station collectively refers to any node of the network side that communicates with the terminal such as a Node B, an eNode B, a Base Station, and a relay node.

4 is a diagram illustrating a structure of a radio frame used in an LTE system.

Referring to FIG. 4, a radio frame has a length of 10 ms (327200? Ts) and consists of 10 equally sized subframes. Each subframe has a length of 1 ms and consists of two slots. Each slot has a length of 0.5ms (15360? Ts). Here, Ts represents a sampling time and is represented by Ts = 1 / (15 kHz x 2048) = 3.2552 x 10 -8 (about 33 ns). The slot includes a plurality of OFDM symbols in the time domain and includes a plurality of resource blocks (RBs) in the frequency domain. In the LTE system, one resource block includes 12 subcarriers x 7 (6) OFDM symbols. Transmission time interval (TTI), which is a unit time for transmitting data, may be determined in units of one or more subframes. The structure of the radio frame described above is merely an example, and the number of subframes included in the radio frame, the number of slots included in the subframe, and the number of OFDM symbols included in the slot may be variously changed.

5 is a diagram illustrating a structure of an uplink subframe used in an LTE system.

Referring to FIG. 5, a subframe 500 having a length of 1 ms, which is a basic unit of LTE uplink transmission, is composed of two 0.5 ms slots 501. Assuming the length of a normal cyclic prefix (CP), each slot is composed of seven symbols 502 and one symbol corresponds to one SC-FDMA symbol. The resource block (RB) 503 is a resource allocation unit corresponding to 12 subcarriers in the frequency domain and one slot in the time domain. The structure of the uplink subframe of LTE is largely divided into a data region 504 and a control region 505. Here, the data area means a series of communication resources used in transmitting data such as voice and packet transmitted to each terminal, and corresponds to the remaining resources except for the control area in the subframe. The control region means a series of communication resources used for transmitting downlink channel quality reports from each terminal, reception ACK / NACK for downlink signals, and uplink scheduling requests.

As in the example shown in FIG. 5, the time at which a Sounding Reference Signal (SRS) can be transmitted in one subframe is a period in which a SC-FDMA symbol located last on the time axis in one subframe. It is transmitted through the data transmission band on the frequency. SRSs of multiple terminals transmitted in the last SC-FDMA of the same subframe can be distinguished according to frequency location / sequence. Hereinafter, generation of SRS, physical resource mapping, multiplexing scheme, resource allocation, etc. will be described in detail with reference to 3GPP LTE (Release 8).

)이다.The sounding reference signal is composed of a constant amplitude zero auto correlation (CAZAC) sequence, and the sounding reference signals transmitted from various terminals have different cyclic shift values ( α ) according to Equation 1 below. sequence(

)to be.

[Equation 1]

는 상위 계층에 의하여 각 단말에 설정되는 값으로, 0 내지 7 사이의 정수 값을 갖는다.here

Is a value set for each terminal by a higher layer and has an integer value between 0 and 7.

CAZAC sequences generated through cyclic shifts from one CAZAC sequence are characterized by having zero-correlation with sequences having cyclic shift values different from themselves. Using this property, sounding reference signals in the same frequency domain may be classified according to the CAZAC sequence cyclic shift value. The sounding reference signal of each terminal is allocated on the frequency according to the parameter set in the base station. The terminal performs frequency hopping of the sounding reference signal to transmit the sounding reference signal over the entire uplink data transmission bandwidth.

Hereinafter, a specific method of mapping a physical resource for transmitting a sounding reference signal in an LTE system will be described.

The sounding reference signal sequence r ^SRS ( n ) is the first transmit power P _SRS Amplitude scaling factor β _SRS to satisfy After multiplying, r ^SRS (0) is mapped to a resource element (RE) having an index of ( k, l ) by Equation 2 below.

[Equation 2]

는 아래 수학식 3과 같이 정의된 부반송파 단위로 표현된 사운딩 참조 신호 시퀀스의 길이, 즉 대역폭이다.Where k ₀ Refers to the frequency domain starting point of the sounding reference signal,

Is the length, i.e. bandwidth, of the sounding reference signal sequence expressed in subcarrier units defined as in Equation 3 below.

&Quot; (3) "

에 따라 기지국으로부터 시그널링 되는 값이다.In Equation 3, m _{SRS , b} is the uplink bandwidth as shown in Tables 1 to 4 below.

According to the value signaled from the base station.

Cell specific parameter C _{SRS, which} is an integer value from 0 to 7 _, to obtain m _{SRS , b} And terminal specific parameter B _{SRS which} is an integer value of 0 to 3. Is needed. These C _SRS The values of and B _SRS are given by higher layers.

[Table 1]

TABLE 2

[Table 3]

[Table 4]

As described above, the terminal may perform frequency hopping of the sounding reference signal to transmit the sounding reference signal over the entire uplink data transmission bandwidth, and the frequency hopping may be performed by the 0 to 3 given from the higher layer. Parameter b _hop with value Is set by.

If the frequency hopping of the sounding reference signal is disabled, that is, if b _hop ≥ B _SRS , the frequency position index n _b Has a constant value as shown in Equation 4 below. Here n is a parameter given in the _RRC upper layer.

&Quot; (4) "

On the other hand, when the frequency hopping of the sounding reference signal is activated, that is, when b _hop < B _SRS , the frequency position index n _b Is defined by Equations 5 and 6 below.

[Equation 5]

&Quot; (6) &quot;

Where n _SRS Is a parameter that calculates the number of times the sounding reference signal is transmitted, and is represented by Equation 7 below.

[Equation 7]

T _SRS in Equation 7 Is the period of the sounding reference signal, and T _offset Refers to the subframe offset of the sounding reference signal. Also, n _s Is the slot number, n _f Refers to the frame number.

Period of Sounding Reference Signal T _SRS The UE-specific sounding reference signal configuration index ( I _SRS ) for setting the subframe offset T _offset is shown in Tables 5 and 6 below according to FDD and TDD.

TABLE 5

TABLE 6

TABLE 7

FIG. 6 illustrates an SRS transmission method for each antenna when antenna selection is applied in an LTE system. In a conventional LTE system, a UE transmits a single antenna transmission or a single power amplifier output based on a single RF power amp chain to uplink transmission to a plurality of physical antennas (eg, two) during uplink transmission. An open-loop antenna selection or closed-loop antenna selection scheme for switching in the time resource domain is applied.

Specifically, FIG. 6 shows an example of transmitting an SRS using a closed-loop selection transmission method. 6 illustrates a method of allocating a frequency resource region to an SRS for each antenna at the time of SRS transmission when an SRS band smaller than the entire system band is applied and SRS hopping is applied. If the SRS hopping is not applied, the SRS is transmitted using alternating antennas on the same SRS band and transmission position for each individual SRS transmission time point. Alternatively, an uplink transmission entity (ie, a terminal or a relay node) such as an LTE-A terminal may have a plurality of transmit antennas and a plurality of RF power amplifier chains and transmit the uplink to a plurality of antennas simultaneously. In this situation, assuming that the SRS transmission scheme of the individual antennas described above is applied as the SRS transmission scheme, any LTE-A system to which a simultaneous transmission scheme using a plurality of RF power amplifier chains and a plurality of antennas is applied may be applied. One or more SRS transmission symbols (eg, OFDM symbols or SC-FDMA symbols) in a subframe may cause a problem in that a power amplifier of an antenna that does not transmit SRS should be turned off. In addition, a problem may occur in that the transmit power of the antenna for transmitting the SRS is limited to 1 / (number of transmit antennas) compared to a single antenna transmission. In case of LTE, any terminal uses the last symbol on a subframe at the time of SRS transmission for SRS transmission. In the LTE-A system, the same number and / or location of SRS transmission symbols as in LTE may be applied, but a plurality of symbols may be used for SRS transmission and their positions on subframes may also be different from those of LTE. In addition, in the LTE-A uplink transmission scheme in which non-contiguous RB transmission and thus PUSCH / PUCCH and PUCCH / PUCCH decoupling (simultaneous transmission of distinct channels) are allowed, uplink different from SRS transmission Configuration schemes between transmissions of link channels may also be applied differently from the case of LTE, which requires a single carrier characteristic. Based on this, in the LTE-A system, an SRS transmission method of an individual antenna different from the existing one may be defined.

According to the present invention, a situation in which an uplink transmission entity (ie, a terminal or a relay node) in the LTE-A system may have a plurality of transmit antennas and a plurality of RF power amplifier chains and simultaneously transmit the uplink to a plurality of antennas. In this paper, we propose an SRS transmission scheme for channel sounding for performing measurement related to state information of channel (s) configured for uplink transmission. For the purpose of explanation, all the mobile communication systems described in the first half of the present invention based on the LTE-A system but simultaneously perform uplink transmission through separate antennas based on a plurality of transmit antennas and a plurality of RF power / signal amplifiers. The suggestions of the present invention can be applied to.

Next, the information related to the SRS transmission resource allocation for any terminal in the prior art will be described.

Transmission comb k _TC

k _TC is a parameter used to derive the frequency domain starting point of the SRS. Use one of the values 0 and 1 as the offset value associated with the "transmission comb". Defined with UE-specific RRC parameters and indicated by UE-specific RRC signaling. K _TC in section 5.5.3.2 of the 3GPP Technical Specification (TS) 36.211 See the definition of.

Allocating a starting physical resource block n _RRC n _RRC Is indicated by the UE-specific RRC signaling as a UE-specific RRC parameter value indicating the frequency domain location of the SRS. N _RRC in section 5.5.3.2 of the 3GPP TS 36.211 document See the definition of.

SRS Duration: Single or Infinite (Unavailable)

Information defined by UE-specific RRC parameters and transmitted through UE-specific RRS signaling. In case of single transmission, the SRS is transmitted only once, and if it is set to indefinite, the transmission continues according to the configured configuration unless a situation in which the SRS transmission is disabled or a signaling is disabled.

SRS configuration index ISRS and SRS subframe offset T _offset for SRS periodicity

Information defined by UE-specific RRC parameters and transmitted through UE-specific RRC signaling. Information indicating a transmission period of the SRS and an arbitrary subframe offset. Information configured as shown in Table 5 for FDD and table 6 as for TDD. See section 8.2 of the 3GPP TS 36.211 document.

SRS Bandwidth B _SRS

Information defined by UE-specific RRC parameters and transmitted through UE-specific RRS signaling. Index information used to define an SRS band, which is specified as one of 0, 1, 2, and 3. It is utilized for physical resource mapping through the description of 3GPP TS36.211 section 5.5.3.2 in the prior art.

Frequency hopping bandwidth, b _hop

Information defined by UE-specific RRC parameters and transmitted through UE-specific RRS signaling. Index information used to configure frequency hopping of the SRS, which is specified as one of 0, 1, 2, and 3. It is utilized for physical resource mapping through the description of 3GPP TS36.211 section 5.5.3.2 in the prior art.

Cyclic shift

Information defined by UE-specific RRC parameters and transmitted through UE-specific RRS signaling. As index information of a cyclic shift for a sequence used when generating an SRS sequence, the cyclic shift is used as an orthogonal resource in code multiplexing of SRSs for various terminals. The prior art described in section 5.5.3.2 of 3GPP TS36.211 in the prior art is used to generate SRS code sequences.

Base sequence index

This information is information characterizing the SRS sequence with cyclic shift in generating the SRS sequence. Information derived from the base sequence index of the PUCCH.

Based on the above-listed parameters, physical resource mapping and resource allocation for SRSs of individual terminals are performed in the LTE system. On the other hand, the most important point in considerations in the design of physical resource mapping and resource allocation for the uplink SRS transmission in the LTE-A system is that the LTE terminal uses a single power amplifier at any moment using a single transmit antenna The LTE-A terminal performs uplink transmission using a plurality of transmit antennas at any instant using a plurality of power amplifiers and RF chains. Focusing on this, the important design considerations in the main proposals in the present invention are summarized as follows.

In order for an arbitrary LTE-A terminal to transmit uplink channel information for resource allocation and transmission mode setting for a corresponding terminal of a cell / base station scheduler, the terminal has a physical (physical) bandwidth over an entire system band as compared to an existing LTE terminal. In order to perform channel sounding for both antennas, there is a high probability that the frequency (number of transmissions) of SRS transmission attempts will increase. As a result, a delay may occur in terms of overall band channel sounding for the uplink full (physical) antenna, and different delay conditions may be applied to individual antennas or when SRS transmission for each layer is applied. This may limit the optimum throughput gain acquisition when the Doppler frequency is present in view of channel-dependent scheduling of the base station.

For the purpose of channel sounding, PUSCH or PUCCH may be applied to the case where the SRS inherits the LTE scheme that defines the SRS transmission symbol in a TDM scheme in which a SRS is transmitted in a time domain of a certain subframe as it is in LTE-A. Symbols that transmit and symbol (s) that transmit SRS may be distinguished within any subframe. In this situation, if the PUSCH or PUCCH is transmitted using multiple transmit antennas, if the SRS is transmitted using a different number of antennas, turn-on / turn of some transmit antennas at the boundary between the PUSCH / PUCCH transmit symbol and the SRS transmit symbol A power pooling situation may occur where the power of a transmitting antenna that is turned off and possibly a series of turn-offs is distributed to the transmitting antenna (s) in the turned-on state. Time is required for the / OFF transition. In order to support this, if a boundary is moved according to the importance of symbols at a boundary on a symbol (eg, OFDM symbol, SC-FDMA symbol) between PUSCH or PUCCH transmission symbols and SRS transmission symbol (s) in a symbol period or a subframe A series of guard times may be defined as a series of time sample regions at the beginning of the symbols after the last time sample interval or boundary of the symbol (in the latter case, if a time sample region of guard time is defined within the symbol's circular transpose region) You may not define a separate guard time). However, this scheme is a scheme that can lead to an overall uplink throughput deterioration. If possible, this scheme is applied without defining guard time, and the number of transmit antennas used for SRS transmission on any LTE-A terminal is different from each other. In SSCH resource multiplexing allocation scheme of the type to be equal to the number of transmit antennas when the PUSCH or PUCCH is transmitted can be considered. In the proposal of some SRS transmission resource allocation or multiplexing scheme proposed in the present invention, this may be considered as one of important considerations.

-Basically, when any UE transmits SRS with the proposed UE transmission power, one of the important points in performing uplink channel measurement with the cell / base station receiver is the frequency domain for the SRS transmission signal. The transmission power spectral density (PSD) level at. The settings associated with allocating power for individual SRS transmissions, taking into account the output power on any symbol in SRS transmission resource allocation, include the SRS transmission band and also code division multiplexing (CDM) and / or FDM on any frequency resource region. (Frequency Division Multiplexing) has to be implemented with a degree of multiplexing. In addition, the consideration on the LTE-A terminal is the number of uplink transmission antennas used at the same time. That is, when the LTE-A terminal supports the transmission through the multi-antenna at an arbitrary transmission time point, as the SRS transmission process increased compared to the existing, when the total number of SRS transmissions required in any cell increases, SRS perspective There is a need for multiplexing and power allocation schemes to provide comparable coverage to LTE systems and to support reliable measurement of individual SRS transmissions. In addition, as described above, it is also important to consider whether the LTE-A UE can perform antenna power pooling during multi-antenna transmission.

Basic SRS multiplexing and resource allocation methods are proposed as follows to support important considerations in SRS design of LTE-A described in the specification of the present invention.

Embodiment 1: Physical Resource Multiplexing for SRS in SRS Transmission Subframe

In case of transmitting another series of PUSCHs or PUCCHs on a subframe including SRS transmission symbols in an LTE-A system supporting multiple antenna transmissions based on a configuration of a multiple power amplifier and an RF chain, SRS transmission symbol (s) assigned to a subframe, such as those channels (ie, PUSCH or PUCCH), in which SRS transmissions for physical or logical antennas (or antenna ports) or layers (or streams) used for PUSCH or PUCCH are assigned. To make it happen. As an SRS multiplexing scheme for supporting this, CDM, FDM, or CDM / FDM may be considered on SRS transmission symbols in any subframe.

The factor that determines the basic multiplexing capacity for a CDM is the number of available cyclic shifts on the SRS sequence. The number of available cyclic shifts can be determined by the relationship between the cyclic prefix length (CP) interval length of a transmission symbol (eg, OFDM symbol or SC-FDMA symbol) and the delay spread value of the channel. have. As an example, the number of available cyclic shifts is an RRC parameter that is explicit at the higher layer (ie, RRC) for all or some of the cyclic shifts required for SRS transmission on any LTE-A terminal. It may be configured to be UE-specific RRC signaling. Some cyclic shifts may be set implicit without separate explicit signaling. In some cases, the base sequence index (aka root index) on the SRS sequence may also be an element for determining the multiplexing capacity together with the cyclic shift as a resource division unit. In applying the present scheme, it may be selectively applied according to a transmission mode or channel environment of a corresponding UE and indicating this may be set implicitly or indirectly through a series of other signaling information. An explicit signaling parameter may be defined.

7 shows an example of a CDM for a case in which an SRS transmission symbol is a last transmission symbol of a subframe in a subframe in which an LTE-A terminal transmits an SRS. 7 illustrates a situation in which SRSs of arbitrary LTE-A terminals multiplexed by CDM are transmitted in a limited SRS transmission band, but the size of the SRS transmission band may have various sizes including the entire system band.

As a specific example, a favorable environment for the application of the CDM is high power Coordinated multiple point transmission and reception (UL CoMP), UL / DL CoMP, geometry (power-limited) from the viewpoint of the terminal transmission power through power control (power-limited) It is preferable to apply to the case of LTE-A terminals, not the situation. Application of code segmentation in applying CDM or CDM / FDM to SRSs to be transmitted by any terminal having multiple antenna transmissions applying multiple power amplifier / RF chains (e.g., using several code resources to transmit It may be further explicitly defined as an SRS-related RRC parameter to indicate cyclic shifts for the value of whether or not (in addition to the value of its indices for the total or partial number of numbers for which the base sequence indes is required). have. In addition, the number of code resources used according to the UE MIMO transmission mode is defined as a predetermined value or an explicit RRC parameter, and cyclic shift indices (or base sequence indexes) of individual code resources thereto are defined. You can also implicitly specify the rest of the values using a series of offsets or rules, via one explicitly specified value.

Discrete comb mapping ratio (comb division) that determines the subcarrier spacing, or density, used for transmission in any frequency domain as a factor that determines the degree of multiplexing on any SRS transmission symbol in the FDM scheme. And also a band for unit SRS transmission allocated to an arbitrary terminal. For example, in LTE, the discrete comb mapping ratio is set to 2 to serve as a resource division between full-band sounding and sub-band sounding or as a resource separation between sub-band soundings. Resource allocation is divided between even subcarrier indexes and odd subcarrier indexes on the frequency subcarrier. SRS transmission bands are also defined in tables as values for various system bands. In LTE-A, considering the conditions of multi-antenna transmission, an increased discrete comb mapping ratio may be applied. For example, 2 * (number of transmit antennas) or 2 * (number of transmit layers) may have a comb split ratio of 2 or 4 for 2Tx, and 2, 4, 6, or 8 comb split for 4Tx. Can have a ratio. All or some of the comb frequency offsets may be used for multiplexing of antenna-specific SRS sequences for the situation in which the increased comb splitting ratio or the comb splitting ratio is 2. In view of the SRS transmission band, a situation occurs in which power of each antenna of an arbitrary terminal supporting multi-antenna transmission is reduced by the number of antennas compared to a single antenna or an antenna selection. This further defines a smaller value of SRS transmission band on any system band as compared to the case of LTE terminal with single antenna transmission to support coverage or reliable measurement of SRS transmission of individual antennas (or individual layers). Can be applied. That is, smaller SRS transmission bands may be defined for any possible case of the SRS transmission band of the existing LTE on any system band and candidates of the SRS transmission band may be added with more granularity. As an independent or additional method, candidates to be applied in the form of a subset of the entire set of SRS transmission-related parameters (including transmission bands) configured through RRC parameters for multi-antenna transmission may be designated. It can be specified through assignment (terminal-specific RRC signaling or L1 / L2 control signaling). A separate RRC parameter may be defined and signaled for this purpose. Through the above schemes, a subcarrier power speactral density (PS) level required in terms of coverage or measurement quality may be maintained in SRS transmission for each antenna or layer. As a method that can be applied in parallel or independently, there is a method of increasing the discrete comb mapping ratio for a terminal having a plurality of transmission antennas or for all terminals in a cell (base station) having these terminals. This approach reduces the density of physical resources in the frequency domain to which power is allocated to any antenna in a given SRS transmission band, thereby reducing the power spectral density (PSD) on the physical resources (i.e., subcarriers or resource elements). Can increase. In addition, a series of FDM multiplexing may be implemented by mapping SRS sequences transmitted through different (physical) transmit antennas to comb frequency offsets (ie, unit comb patterns) derived through an increase in the abnormal comb mapping ratio. As the abnormal comb mapping ratio is increased, measurement performance degradation of the channel may occur. In order to prevent this, the abnormal comb mapping ratio may be set to 3 in a situation of two or four terminal (physical) transmission antennas. In this case, one comb pattern may be allocated for overall or wider channel sounding of a designated range, and in case of two transmit antennas, an SRS sequence of each antenna may be differently mapped to the remaining two comb patterns. On the other hand, if the number of UE transmit antennas is 4, two antenna groups may be defined by grouping two transmit antennas in an arbitrary manner, and each antenna group may be differently mapped to the remaining two comb patterns. In addition, two transmit antennas in the antenna group may be multiplexed by allocating different frequency bands or code resources (that is, cyclic shifts).

8 shows an example of FDM for a case where an SRS transmission symbol is a last transmission symbol of a subframe in a subframe in which an LTE-A terminal transmits an SRS. In FIG. 8, the SRSs of arbitrary LTE-A terminals multiplexed by FDM are transmitted in a limited SRS transmission band, but the size of the SRS transmission band may have various sizes including the entire system band. The representation of the SRS transmission bands indicated by bands separated from each other in FIG. 8 specifies that the FDM scheme for the discrete physical comb patterns described in the present invention is also covered.

The FDM or CDM / FDM scheme of the SRS proposed by the present invention is preferably applied to a UE in a non power-limited situation. For example, the FDM or CDM / FDM scheme of the SRS is a non-contiguous RB (Discrete Fourier Transform-spread-Orthogonal Frequency Division Multiple Access (DFT-s-OFDMA)) clustered uplink. It is preferable to apply to a terminal capable of performing Resource Block (ABS) allocation or using a multi-component carrier (CC). To this end, an indication indicating the application of clustered DFT-s-OFDMA is made explicitly or implicitly from the base station, or an indication indicating the application of an uplink multi-component carrier. In the case where is performed explicitly or implicitly from the base station, a multiplexing scheme in which FDM or CDM / FDM is applied to SRS multiplexing may be applied based on these indication signaling. A parameter for instructing the SRS configuration to be changed according to the uplink transmission mode or the power-limit of the UE may be defined and may be indicated through UE-specific RRC signaling or L1 / L2 control signaling.

In the application of the CDM / FDM scheme, rather than a simple combination of the two multiplexing techniques, there is a correlation between the parameters that determine the multiplex granularity and dose of the CDM and the parameters that determine the multiplex granularity and dose of the FDM. Consideration is needed. As an example, in defining the available number of cyclic shifts associated with CDM capacity, the setting of the discrete comb mapping ratio, which determines the frequency component density and multiplexing level of the SRS signal on the FDM, influences. Specifically, as the value of the discrete comb mapping ratio is increased, the number of available cyclic shifts in the CDM is reduced. In addition, when the base sequence index is set to the code resource region of the CDM, the size of the available base sequence index pool is determined in proportion to the size of the SRS transmission band on the FDM. Considering this situation, if CDM / FDM is applied to SRS transmission multiplexing of LTE-A terminals that support multiple antenna transmission using multiple power amplifier / RF chain, the efficiency of channel sounding itself will be basically based. As an additional aspect, the detailed scheme of CDM / FDM can be defined based on aspects such as reduction of signaling overhead or backward compatibility. As an example, when considering the multiplexing with the PUSCH or the PUCCH while pursuing a design of a direction in which the capacity of the cyclic shift is small or minimizes additional indication overhead for the cyclic shift used, the configuration antenna or MIMO of the corresponding UE is considered. SRS resource allocation / multiplexing may be configured as shown in FIG. 9 under the premise that all SRSs are transmitted in the SRS transmission symbol according to the transmission mode.

9 shows an example of CDM / FDM in an uplink subframe of a terminal (eg, LTE-A terminal) transmitting SRS. 9 illustrates a situation in which SRSs of arbitrary LTE-A terminals multiplexed by CDM / FDM are transmitted in a limited SRS transmission band, but the size of the SRS transmission band may have various sizes including the entire system band. In more detail, the example illustrated in FIG. 9 shows that when there are M (> 0) SRSs that an LTE-A terminal needs to transmit in an arbitrary subframe, M SRS resources are allocated for transmission thereof. As a method, a method of allocating the number of cyclic shifts and indices to be used for each of the N SRS transmission bands used for optimizing resource usage can be used. Alternatively, as illustrated in FIG. 9 for signaling overhead or configuration simplification, the number and location index information of the N SRS transmission bands and the P available cyclic shifts (or the base sequence are also referred to as resource allocation elements). A method of specifying the number of resources and index information may be used. At this time, the designation of N and P may consider that N * P is greater than or equal to M. Individual resource allocation for each of the M SRSs may use a band-first assignment scheme for the SRS transmission band and a code-first assignment scheme for cyclic shifts. You may.

A series of SRS resource multiplexing and configuration including CDM / TDM, FDM / TDM, CDM / FDM / TDM, etc., including the CDM, FDM, or CDM / FDM schemes mentioned above, may be used. Applicable for Hereinafter, a method of changing the configuration of the SRS will be described based on the LTE-A. Conventional LTE continues to transmit SRS until separate termination occurs (ie, disable) when SRS transmission is enabled, and separate RRC for SRS transmission release The parameter is not defined. However, it may be considered to additionally set the SRS transmission release parameter for the LTE-A terminal, and after the SRS transmission is enabled by the UE-specific RRC signaling, the number of transmissions or the transmission time of the SRS may be set according to the period configuration information. have. In addition, it may be considered to deliver the SRS transmission configuration information using L1 / L2 control signaling (eg, PDCCH, MAC messaging). For example, SRS transmission may be triggered by L1 / L2 control signaling. In this case, in order to efficiently reduce signaling overhead, the L1 / L2 control signaling carrying SRS transmission configuration information may be event-triggered or have a periodic nature. Although not limited thereto, for example, the effective number of transmissions, transmission periods, period configuration information, and the like may be included in the L1 / L2 control information for signaling. In this case, the periodic SRS transmission may use one subframe per transmission period, and use S subframes continuously from the transmission period time point, or give a series of offsets and drop them by an offset. The method can be applied. The periodic configuration information includes a transmission start point, a period, and subframe group allocation information (in case of periodic transmission in a specific subframe group unit). The information about the transmission start point does not need to be defined separately in accordance with the conventional grant-to-uplink timing relationship. Meanwhile, in the case of configuring SRS transmission with UE-specific RRC signaling, all or part of the L1 / L2 control information defined above according to the present invention may also be defined as an RRC parameter. In addition, when enabling or triggering SRS transmission through L1 / L2 control signaling, an SRS transmission release parameter (or message) may be further defined in L1 / L2 control signaling.

Embodiment 2: A plurality of SRS transmission symbols are defined in an SRS transmission subframe

LTE-A can support a multi-antenna or multi-layer transmission based on it by applying a multi-power amplifier / RF chain in the uplink, and can be connected to a plurality of UL component carriers independently or in parallel, and through UL CoMP Communication with a plurality of points may be performed. Accordingly, a plurality of SRS transmissions may be configured for multiplexing capacity, coverage, and measurement reliability guarantee on channel sounding for each antenna (or layer), UL component carrier, or UL CoMP unit transmission point in a multi-antenna configuration. . To this end, the present invention proposes to define a plurality of SRS transmission symbols in an uplink subframe of a terminal (eg, LTE-A terminal). For convenience of description, in the case where the number of SRS transmission symbols is defined as two, two configuration schemes for positions in a subframe are described in detail.

10 illustrates a first scheme of designating two SRS transmission symbols in an uplink subframe according to an embodiment of the present invention. Referring to FIG. 10, the position of the SRS transmission symbol, which is defined as one more in comparison with the existing LTE, is the last transmission symbol (eg, OFDM symbol, SC-FDMA symbol) of the first slot of the subframe in which the SRS of the UE is transmitted. Can be defined in To this end, shortened PUCCH formats used when the SRS is transmitted through the second slot in the conventional LTE may be defined to be used in the first slot according to the present invention. This approach has the advantage of being able to induce minimal standard specification changes.

11 shows a second scheme of designating two SRS transmission symbols in an uplink subframe according to an embodiment of the present invention. Referring to FIG. 11, the position of the SRS transmission symbol, which is defined as one more in comparison with the existing LTE, is determined from the last transmission symbol (eg, OFDM symbol, SC-) at the end of the second slot of the subframe in which the SRS of the UE is transmitted. FDMA symbol). This scheme has the advantage that the power transition between the SRS transmission symbol and the data transmission symbol appears at the same frequency as when defining one SRS transmission symbol in a subframe as in the conventional LTE. In order to apply the present scheme, an additional definition of a shortened PUCCH format in which the last two transmission symbols are punctured in any slot is required based on the existing LTE standard. In addition, the control information transmission scheme through the PUSCH of the existing LTE involves rate matching for data, and maps rank information (RI) to physical frequency resources of four transmission symbols on a subframe. For example, in case of normal CP, RI is mapped to second and fifth transmission symbols on each slot of a subframe. In this case, the fifth transmission symbol of the second slot to which the rank information is mapped overlaps with the position of the additional SRS transmission symbol proposed in this scheme. Therefore, in order to apply the present scheme, an RI transmission scheme using three transmission symbols may be considered, excluding a transmission symbol defined last on a second slot among four transmission symbols used for RI transmission. In addition, a method of mapping the RI from the first physical resource of the subframe or backward from the last physical resource may be considered in a time-first format. In this case, the RI is mapped in a time-first manner in a state in which the transmission symbols to which the SRS is mapped are avoided or the transmission symbols to which the SRS is mapped are avoided. In addition, by applying the multiplexing method of data and CQI defined in the existing LTE in addition to the RI may consider a method of transmitting the RI in a multiplexed form with the data. In this case, the RI is mapped to the physical resource of the subframe in the time-first form.

In the first proposal scheme and the second proposal scheme, the burden of signaling by separately defining configuration parameters for the SRS transmission symbol for each slot can be reduced. In addition, M SRS required for the corresponding LTE-A terminal for the purpose of not causing a transient operation of the power amplifier (and / or signal amplifier) of the individual antenna at the boundary between the SRS transmission symbol and the data symbol. The power allocated to each of the individual S SRSs is transmitted by applying the scheme of configuring the allocation on the individual symbols instead of dividing the symbols on the plurality of SRS transmission symbols by symbols and repeating the SRS transmission symbols defined for each slot. It is possible to make the sum of the allocated powers on the symbol. In the two SRS transmission symbols, the same SRS resource allocation is taken for each slot as described above, and the positions of the individual SRS bands are set differently for each slot, thereby enabling two uplink channel soundings in an arbitrary uplink subframe. . The same or different SRS transmission bands, or the case of using two SRS transmission symbols and the case of using one SRS transmission symbol may be selectively or individually applied according to the UE situation. In this case, the indication information for SRS configuration may be explicitly signaled by using a separately defined RRC parameter or may be applied explicitly or implicitly by using L1 / L2 control signaling. It may be implicitly applied depending on the state or setting information of the transmission mode. The transmission mode may include whether to transmit MIMO and whether to transmit based on non-consecutive RB allocation.

Alternatively, in order to reduce the channel sounding time for the entire scheduling band, the M SRSs that need to be transmitted by an arbitrary LTE-A terminal for two SRS transmission symbols on an arbitrary SRS transmission subframe are transmitted in the present invention. The entire multiplexing scheme may be configured by applying M SRSs separately for each SRS transmission symbol by further applying the TDM format to the embodiments of the CDM, FDM, and CDM / FDM described. In this case, code resources of an SRS band and / or a cyclic shift (which may additionally include a base sequence index) applied to two SRS transmission symbols may be independently designated in individual SRS transmission symbols. It can also be distinguished by arbitrarily setting different resource values arbitrarily. To this end, in consideration of the signaling overhead of SRS-related RRC parameters (or control information on L1 / L2 control signaling) that must be further defined, the SRS transmission band and code resources applied to the two SRS transmission symbols are commonly allocated; The same configuration is possible in terms of RRC parameters, control information, code and frequency resource allocations), and additionally, indication information for distinguishing resource allocations for individual SRSs in two SRS transmission symbols may be included in the RRC parameter or L1 / L2. It can be defined in addition to the control information on the control signaling.

All the proposed multiplexing schemes associated with the TDM scheme for defining a plurality of SRS transmission symbols on any subframe among the multiplexing schemes proposed in the present invention are relayed regardless of the number of transmit antennas and radio frequency power amplifier chains. It can be applied when SRS transmission of a relay node in the backhaul uplink. In addition, it can be applied to SRS transmission of the relay node in the relay backhaul uplink irrespective of the number of transmission antennas and radio frequency power amplifier chains applied to all other types of multiplexing schemes.

As an additional solution to this, a position in a subframe of a transmission OFDM or DFT-s-OFDM symbol may be changed during relay node SRS transmission in the relay backhaul uplink. As an example, the last transmission symbol on a subframe to which the series of multiplexing schemes and the SRS multiplexing scheme applied on the LTE Rel-8 (also including Rel-9) is applied is a transition gap or a guard time. SRS transmission for a situation that is difficult to use for relay node transmission due to time)? The position of the symbol may be changed to the last transmitted symbol of the first slot. In this case, an uplink shared channel in an arbitrary relay node may be punctured in consideration of the position of the SRS symbol. In addition, the SRS and the data uplink common channel between different terminals or relay nodes may basically overlap within a subframe.

Alternatively, instead of transmitting SRS separately, SRS transmission is performed in one of the following two schemes on one DM-RS transmission symbol for PUSCH transmission per slot (fourth symbol for general CP and third symbol for extended CP). Can replace

In the corresponding subframe determined by the cell-specific and relay node (or terminal) -specific RRC parameters, not the frequency domain mapped by the corresponding DM-RS sequence is allocated through the uplink grant PDCCH for PUSCH transmission. It is possible to set the frequency band transmission band consisting of the transmission band and the frequency domain position, the offset value of.

In the case where the scheme transmits RS out of the PUSCH transmission frequency region allocated through the uplink grant PDCCH or in a frequency region larger than this region, the minimum RB allocation size of the scheduler is larger than the configured SRS transmission band size. Accordingly, the PUSCH resource allocation on the uplink grant may be configured to include the corresponding SRS frequency domain location.

Example 3: Precoded SRS Configuration

Solving the problem of power amplifier turn-on / off for SRS transmission and reducing the number of SRS required for the terminal for LTE-A terminals supporting multi-antenna transmission through the application of multiple power amplifier / RF chain As a scheme, precoded SRS transmission may be considered. According to the present embodiment, even in a situation where a plurality of terminal transmission antennas are configured, in case of rank-1 MIMO transmission in UL MIMO (Uplink Multiple Input Multiple Output) transmission, one SRS resource may be defined and used. In case of rank MIMO transmission, the same number of SRS resources as the corresponding rank value may be defined and used. Precoding matrices used for precoding of the SRS may apply the corresponding precoding matrix according to the precoding matrix index (PMI) information specified in the most recent uplink grant information (the PMI (or TPMI) Precoding Matrix Indication) means that the same codebook as the codebook defined for uplink data transmission is used for SRS transmission.) Alternatively, separate PMI information for SRS transmission is determined by UE-specific RRC signaling or UL grant. In addition, a method of separately signaling through a series of L1 / L2 control signaling including a case may be considered.In addition, PMIs applied to both SRS or DeModulation Reference Signal (DM-RS) / SRS may be considered. In case of separate L1 / L2 control which is composed of codebook different from existing data transmission codebook and indicates PMI to be applied Signaling information may be defined by channeling or UE-specific RRC signaling As another method, rank for both SRS, DM-RS, or SRS / DM-RS for uplink data transmission using TxD (Transmit Diversity) As in the case of 1, a method of allocating one SRS and / or DM-RS resource and transmitting a corresponding RS based on the PMIs described above of the present invention can be applied. As described above, it may be one of the PMIs for a single layer on a data transmission codebook or a codebook defined separately for RS transmission, considering that TxD is an open-loop transmission. It is also possible to consider a method in which the base station indicates to the UE through specific RRC signaling or L1 / L2 control signaling. Alternatively, a single ray according to the open-loop characteristic can be considered. For example, a series of cycling, shifting, or permutation schemes may be used for a whole set or a subset of PMIs at a transmission symbol or slot level. It can be applied differently in domain. When considering the operating range of TxD, the PMI can be selected and configured in consideration of the Cubic Metric / Peak to Average Power Ratio (CM / PAPR) characteristics corresponding to the single antenna transmission, or it does not form a beam. It may also be configured as PMIs in the form of antenna selection in order not to.

According to the present embodiment, any scheme of applying precoding to an SRS (or DM-RS) may be selectively applied to any LTE-A terminal together with a scheme of not applying precoding. In this case, as a criterion of the selective application, whether the terminal is in a power-limited state or UL MIMO transmission mode (rank or TxD / precoding) may be considered. As a specific example, a precoded SRS (or DM-RS) is transmitted for rank-1 with or without TxD, and a non-precoded SRS (or DM-RS) for rank values above. ) Is a method of transmitting. Alternatively, transmit precoded SRS (or DM-RS) for rank-1 and rank-2 transmissions, with or without TxD, and non-precoded SRS (or DM-RS) for higher rank values. There is a way to transmit. As another specific embodiment, the DM-RS considers a method of applying precoding at rank-1 or precoding for rank-1 and rank-2 for data transmission on a corresponding subframe, and independently of the SRS. For P, there is a method of precoding with rank-1 based PMI only in a power-limited situation or regardless of a UE channel situation. As another method, a PMI may be defined as an orthogonal resource divided in a spatial domain for any one of all types of SRS transmission resource allocation and multiplexing schemes defined above. have. In this case, a method of precoding SRS with a rank-2 PMI in a codebook for data transmission or a codebook for separate SRS transmission is always applied selectively or irrespective of the UE channel situation according to the power-limited UE situation. can do. In this case, PMIs used are PMIs that provide CM / PAPR based on a single antenna and may define UE-specific signaling or control information of L1 / L2 control signaling for an indication of PMI to be used for SRS precoding. Alternatively, a series of cycling at the transmit symbol or slot level for a set of PMIs (which can be defined as a whole PMI or a set of subsets) applied according to the present invention to any criteria in an open-loop fashion. Cycling, shifting or permutation schemes may be applied differently in the time domain or the frequency domain.

Example 4 SRS Transmission Scheme in UL Carrier Aggregation

When an arbitrary LTE-A UE is allocated multiple component component carriers (multiple uplink component carriers) from the cell base station, SRS transmission is basically RRC for configuration information such as SRS resource allocation and transmission time for the corresponding carrier on the individual UL component carrier Parameters may be identified through UE-specific RRC signaling as independent control information for each carrier, and an independent SRS transmission scheme may be implemented in each UL component carrier. Alternatively, SRS resource allocation and transmission scheme configuration can be related to each other. In order not to increase CM / PAPR for uplink SRS transmission using multiple component carriers, the SRS transmission period is the same for each carrier. In order to configure a subframe to be transmitted in the form of staggering on a component carrier basis, a scheme of granting an associated offset value between UL component carriers set at a transmission start point by an explicit or implicit rule Applicable

Embodiment 5: SRS Transmission Scheme for Antenna Transmission Mode

According to the LTE-A technology (for example, relay backhaul uplink or uplink CoMP) that is newly introduced regardless of the number of applications or the number of antennas and a plurality of radio frequency power amplifier chains mentioned in the present invention. Covering all the proposals related to the configuration and multiplexing scheme for SRS transmission, the frequency band applying channel sounding through uplink SRS transmission is limited to a smaller band than the entire system band, and the channel sounding is applied to this band. The SRS transmission configuration scheme and the multiplexing scheme can be applied. This can reduce the latency required for the entire sounding and in some cases reduce the SRS transmission band based on the same sounding latency, thereby reducing the SRS transmission frequency resource element (RE, ie subcarrier) on the SRS sounding. It is also possible to increase the power spectral density.

As another example of LTE-A technology, when downlink CoMP is applied in a TDD mode system, a cell base station receives an uplink channel sounding signal based on reciprocity between uplink and downlink channels, and coordinates the corresponding coordinate of the corresponding CoMP. It can be applied as downlink channel measurement information for coordinated beamforming or joint transmission. In this case, all the proposed schemes of all SRS transmission configurations and multiplexing schemes proposed in the present invention can be applied regardless of the number of transmit antennas and radio frequency power amplifier chains. In this case, the channel-specific sounding of the corresponding terminal or relay node is performed so that the channel sounding for the frequency domain or the sounding in the entire system band is performed frequently so that the frequency of channel sounding for the DL CoMP frequency domain is frequent. A method of configuring an SRS transmission scheme and a multiplexing scheme by UE or relay node-specific RRC parameter setting may be applied.

The proposed schemes for channel sounding according to a plurality of uplink transmission antenna configurations proposed by the present invention are applied to uplink multiple antennas applied to PUSCH or PUCCH transmission symbols except SRS symbol (s) in an SRS transmission subframe. The transmission scheme mainly considers a situation in which a signal is transmitted using all the (physical) transmit antennas (that is, a power is loaded into all the (physical) transmit antennas). However, depending on the application of technology on the system, for example in the case of uplink precoding, an antenna selection precoder is defined on the codebook and applied to the corresponding data transmission symbols, or a closed-loop scheme (e.g., long-term ( There is a possibility that an uplink transmission diversity mode of an antenna selection or an antenna group selection scheme of a long-term or short-term selection scheme is applied. When such transmission modes are introduced, the multi-antenna channel sounding method proposed by the present invention can be basically applied. In addition, in implementing the detailed operation and process of the multi-antenna channel sounding method in the transmission mode of the characteristic, turn-on / turn-on of a series of antenna power amplifiers and / or signal amplifiers between data transmission symbols and SRS transmission symbols Measures can be applied to minimize the occurrence of off. Hereinafter, the present invention proposes methods for applying channel sounding when only specific (physical) antennas among the entire (physical) transmit antennas of the UE participate in uplink signal transmission.

Example 5-1: Channel Sounding When Applying Antenna Turn-on / Turn-Off Precoder

When the terminal performs uplink transmission using multiple antennas, an antenna gain imbalance (AGI) may occur due to hand gripping of a user. In this case, the transmission signal actually radiated from all or some of the transmission antennas causes loss of about 6 dB or more in terms of output power. When the base station observes a signal (eg, DM-RS, SRS) transmitted from the terminal and recognizes that AGI has occurred on the transmission antenna signal of the terminal, the base station turns on some transmit antennas to prevent unnecessary transmission antenna power consumption of the terminal. You can signal it to be off. On the other hand, the base station needs to signal to turn on some transmit antennas. To this end, the base station applies the turn-on / turn-off precoders for the antennas on which the AGI occurs to the codebook and assigns its designation to a series of terminal-specific L1 / L2 control signaling (e.g., free on DCI format on the UL grant). Coder instructions). In another alternative, turn-on / turn on the output power of a transmission antenna in which AGI occurs directly through UE-specific L1 / L2 control signaling in a form of separate UE-specific RRC signaling or a separate control channel DCI format. -Can be off. The present proposal is "1" when the power control mechanism is defined separately for each transmit antenna (or layer) in the PUSCH power control mechanism of the terminal or one power control mechanism is defined for each terminal, and is turned on as a signaling parameter. If it is off, it may be defined in the form of having a value of "0" and multiplying the entire power control mechanism equation. Of course, it is also possible to comprehensively include a form of a detailed formula that may implement turn-on / turn-off by using the present signaling parameter. When the precoding transmission mode having this characteristic is applied to the data transmission symbol, the schemes for preventing the turn-on / turn-off transition of the power amplifier and / or the signal amplifier at the boundary with the SRS transmission symbol are summarized as follows. . The schemes proposed below can be applied as a method of SRS transmission even when a series of antennas or antenna-group selection precoders are used, rather than the antenna turn-on / turn-off precoder introduced due to reasons such as AGI. . First, an embodiment of the present invention will be described based on the antenna turn-on / turn-off precoder.

Considering that the AGI occurs in a semi-static state, the base station transmits the SRS according to the application time of the precoder for the antenna turn-on / turn-off or the application of power control through separate signaling. Antennas (or power amplifiers, signal amplifiers) turned on among all the (physical) transmit antennas of the terminal by reconfiguring the detailed configuration (eg, SRS transmission timing, multiplexing scheme, SRS band, etc.) SRS signals for the uplink transmission are multiplexed to the SRS transmission symbol by any of the multiplexing schemes proposed by the present invention or in another form of multiplexing. Through this, generation of turn-on / off transitions of the power amplifier and / or the signal amplifier may be prevented at the boundary between the data transmission symbol and the SRS transmission symbol.

In the situation where the channel sounding is limited to some antennas among all the antennas (or layers, power amplifiers, or signal amplifiers) of the terminal as described above, according to the generation of AGI, the cell or the base station is half of the AGI situation. In order to monitor the static change, the UE periodically performs channel sounding for all antennas so that the cell or the base station can measure the change in the AGI situation. To this end, the SRS transmission detailed configuration may be reconfigured through UE-specific RRC signaling to perform channel sounding on some or all system bands for all antennas for a time interval sufficient for measurement every appropriate period. UE-specific RRC signaling for reconfiguring the SRS transmission detailed configuration may be performed in a periodic or event-triggered manner.

12 illustrates an example in which a terminal performs channel sounding through multiple antennas according to an embodiment of the present invention. 12 shows that an AGI situation has already occurred and some antennas (or layers, power amplifiers, or signal amplifiers) of the UE are turned off and the SRS transmission detailed configuration is applied to the (physical) transmit antennas in the turned-on state. Assume a finite situation. The antenna turn-off situation may apply only to a particular frequency band, a particular (physical) channel (eg, SRS transmit symbol). If at least some of the transmit antennas are set to the turn-off state, the base station should observe the signal transmitted from the terminal to confirm whether the terminal is out of the AGI situation. To this end, the terminal may perform channel sounding by periodically turning on or off the transmit antenna set to the turn-off state or in an event-triggering manner. That is, when at least some transmit antennas are set to the turn-off state in the terminal, the terminal basically turns the corresponding transmit antennas temporarily according to a specific period or a specific event while maintaining the turn-off state for the corresponding transmit antenna. It can be turned on to perform channel sounding. For example, every (or some of) (physical) transmit antennas of the terminal are turned on during a time interval called B for all the time intervals of all A, and some or all system bands for all (physical) transmit antennas are turned on. Channel sounding may be performed. To this end, the turn-on precoder may be applied to the SRS transmission symbol in the B section, and the turn-off precoder may be applied to the SRS transmission symbol in the subsequent section. The time interval A corresponds to a channel sounding transmission period applied to the antenna in the turn-off state, and the time interval A may be set longer than the channel sounding transmission period set for the antenna in the turn-on state. In particular, the time interval A may be set as a multiple of the channel sounding transmission period set for the antenna of the turn-on state. When channel sounding through time interval B is performed by event-triggering (eg, L1 / L2 control signaling), time interval A may not be defined / signaled separately.

In parallel, when the transmit antenna is temporarily turned on (time interval B) for channel sounding, it is used by precoders other than the antenna turn-on / turn-off precoder with respect to the data transmission symbol. Or if the antenna turn-off situation is implemented through a power control mechanism, either through separate UE-specific RRC signaling of the cell or base station, UE-specific UL grant PDCCH, or separate UE-specific L1 / L2 control signaling. Some of which may cause the (physical) transmit antennas to be turned on to prevent the occurrence of turn-on / off transitions of the power amplifier and / or signal amplifier at the boundary between the data transmission symbol and the SRS transmission symbol on that subframe. have. In the present scheme, the time intervals A and B may be defined as direct time and may be set in units of subframes (eg, corresponding to 1ms) or radio frames (eg, corresponding to 10ms).

If the base station wants measurement to check whether the AGI of the UE changes in the event-triggered method, the L1 / L2 control signaling (eg, UL grant PDCCH, power control PDCCH, separate) Channel sounding for all (or part thereof) (physical) transmit antennas of the UE through a dedicated PDCCH of the UE), for a time interval (eg, time interval B) that is predetermined, implied or explicitly signaled. can do. When channel sounding is performed during time interval B, the precoder on the data transmission symbol may additionally be designated as a precoder other than the antenna turn-on / turn-off precoder. Such event-triggered signaling may also be designated as UE-specific RRC signaling. This event-triggering scheme may be implemented by reconfiguration of the SRS transmission detailed configuration as well as data transmission symbols as precoder designation on the UL grant DCI format.

In this scheme, when precoding is applied to the SRS and the precoder designation on the UL grant is applied not only to the data transmission symbol but also to the precoder on the SRS transmission symbol, antenna turns of (physical) transmission antennas naturally transmitting the SRS on the codebook. On / turn-off may be implemented. Of course, the proposal according to the present embodiment may be applied even when the SRS is precoded.

Embodiment 5-2: Channel Sounding When the Transmit Diversity Scheme of the Antenna (Group) Selection Method is Applied

In this embodiment, any channel sounding schemes proposed in Embodiment 5-1 may be applied. The only difference is that the SRS transmission details are tailored to the point in time when the antenna selection specification for a series of AGI or other specific channel information is made through UE-specific RRC signaling, UE-specific UL grant PDCCH or other form of UE-specific dedicated PDCCH. In this case, terminal-specific / cell-specific RRC control signaling for SRS reconfiguration is performed for channel sounding for corresponding (physical) transmit antennas in an antenna (or power amplifier or signal amplifier) turn-off situation. to be. In addition, with respect to the antenna turn-off / turn-on on the terminal, the above-described embodiment may be used for parameters signaled through a power control mechanism for the terminal or a power control mechanism separately defined for the (physical) transmission antenna. The same method as the details in 5-1 can be applied.

Example 5-3 Channel Sounding When Applying a Dynamic Antenna Selection Precoder

Considering that the basic configuration of the SRS in the case of applying the antenna selection precoder dynamically or semi-statically is semi-static, any of all the detailed proposals for the SRS transmission of the above embodiment 5-1 The scheme can be applied. In addition, the proposed scheme of applying the precoded SRS according to the embodiment 5-1 may also be applied, and the use of the event-triggered SRS may also be considered.

13 illustrates a base station and a terminal applicable to an embodiment of the present invention.

Referring to FIG. 13, a wireless communication system includes a base station (BS) 110 and a terminal (UE) 120. In downlink, the transmitter is part of the base station 110 and the receiver is part of the terminal 120. In uplink, the transmitter is part of the terminal 120 and the receiver is part of the base station 110. Base station 110 includes a processor 112, a memory 114, and a radio frequency (RF) unit 116. The processor 112 may be configured to implement the procedures and / or methods suggested by the present invention. The memory 114 is connected to the processor 112 and stores various information related to the operation of the processor 112. The RF unit 116 is coupled to the processor 112 and transmits and / or receives wireless signals. The terminal 120 includes a processor 122, a memory 124 and an RF unit 126. The processor 122 may be configured to implement the procedures and / or methods proposed by the present invention. The memory 124 is connected with the processor 122 and stores various information related to the operation of the processor 122. The RF unit 126 is coupled to the processor 122 and transmits and / or receives radio signals. The base station 110 and / or the terminal 120 may have a single antenna or multiple antennas.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

In this document, the embodiments of the present invention have been mainly described with reference to the data transmission / reception relationship between the terminal and the base station. The specific operation described herein as being performed by the base station may be performed by its upper node, in some cases. That is, it is apparent that various operations performed for communication with a terminal in a network including a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A base station may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. In addition, the terminal may be replaced with terms such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), and the like.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

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

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit of the invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

[Industry availability]

The present invention can be applied to a wireless communication system. Specifically, the present invention can be applied to a channel sounding method using a plurality of antennas and an apparatus therefor.

Claims (13)

A method of receiving a sounding reference signal at a base station of a wireless communication system,
Receiving, from a relay node, a first OFDM symbol to which sounding reference signals for a plurality of transmission antennas of the relay node are multiplexed and allocated; And
Receiving from the terminal a second OFDM symbol to which sounding reference signals for the plurality of transmission antennas of the terminal are multiplexed and allocated;
The second OFDM symbol is the last OFDM symbol of the subframe, and the first OFDM symbol is one of the remaining OFDM symbols except the last OFDM symbol among the symbols of the subframe. . The method of claim 1,
The first OFDM symbol is a sounding reference signal receiving method, characterized in that the last OFDM symbol of the first slot of the subframe. The method of claim 1,
A sounding reference signal receiving method, characterized in that sounding reference signals for a plurality of transmission antennas of the relay node are multiplexed by a code division multiplexing (CDM) method. In the method for transmitting a plurality of sounding reference signals in a relay node of a wireless communication system,
Multiplexing sounding reference signals for a plurality of transmission antennas and assigning them to OFDM symbols; And
Transmitting the OFDM symbol to a base station,
The OFDM symbol is a sounding reference signal transmission method, characterized in that one of the remaining OFDM symbols except the last OFDM symbol among the symbols of the subframe. The method of claim 4, wherein
The OFDM symbol is a sounding reference signal transmission method, characterized in that the last OFDM symbol of the first slot of the subframe. The method of claim 1,
Sounding reference signal transmission method for the plurality of transmission antennas, characterized in that the multiplexed by code division multiplexing (code division multiplexing, CDM) method. In the method of transmitting a plurality of sounding reference signals in a terminal of a wireless communication system that supports coordinated multi-point (hereinafter referred to as "CoMP"),
Transmitting, to the first base station, an allocated first OFDM symbol by multiplexing sounding reference signals for the plurality of transmission antennas; And
And transmitting a second OFDM symbol allocated to multiplexing sounding reference signals for the plurality of transmission antennas to a second base station. The method of claim 7, wherein
Sounding reference signal transmission method for the plurality of transmission antennas, characterized in that the multiplexed by code division multiplexing (code division multiplexing, CDM) method. In the method of receiving a plurality of sounding reference signals at a base station of a wireless communication system that supports coordinated multi-point (hereinafter referred to as "CoMP"),
Receiving an allocated OFDM symbol by multiplexing sounding reference signals for a plurality of transmission antennas from a terminal operating in CoMP; And
And acquiring downlink channel information using the sounding reference signals. 10. The method of claim 9,
Sounding reference signal receiving method for the plurality of transmission antennas characterized in that the multiplexed by code division multiplexing (code division multiplexing, CDM) method. A method of receiving a sounding reference signal at a base station of a wireless communication system,
A first sounding reference signal for a plurality of transmission antennas of the relay node is multiplexed and allocated from a relay node, and a first sounding reference signal for the plurality of transmission antennas of the terminal is received from the terminal. A receiving module for receiving the second OFDM symbol to which the multiplexing is allocated; And
A processor for acquiring backhaul uplink channel information using the first sounding reference signals and acquiring uplink channel information using the second sounding reference signals;
And the second OFDM symbol is the last OFDM symbol of a subframe, and the first OFDM symbol is one of the remaining OFDM symbols except the last OFDM symbol among the symbols of the subframe. A processor for multiplexing sounding reference signals for a plurality of transmission antennas and assigning them to OFDM symbols; And
A transmission module for transmitting the OFDM symbol to a base station,
And the OFDM symbol is one of the remaining OFDM symbols except the last OFDM symbol among the symbols of the subframe. In a terminal of a wireless communication system that supports coordinated multi-point (hereinafter referred to as "CoMP"),
A processor for multiplexing first sounding reference signals for the plurality of transmission antennas and assigning the first sounding reference signals to the first OFDM symbol, multiplexing the second sounding reference signals for the plurality of transmission antennas and assigning the second sounding reference signals to the second OFDM symbol; And
And a transmission module for transmitting the first OFDM symbol to a first base station and transmitting the second OFDM symbol to a second base station.

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