KR20100056962A - Method for transmitting referece signal for downlink channel measurement - Google Patents

Abstract

PURPOSE: A method for transmitting reference signal in order to measure a downlink channel is provided to transmit the reference signal which is dedicated for a base station if the number of transmission antenna is increased. CONSTITUTION: A base state maps reference signal, which is related to N to M-1 transmission antenna port, to a physical hybrid-automatic repeat request indicator channel(PHICH) groups in a sub-frame. The PHICH groups are used for transmitting acknowledgement/negative acknowledgement information with respect to an uplink data channel in the sub-frame. The base station transmits the sub-frame in which the reference signal is mapped.

Description

Reference signal transmission method for downlink channel measurement in wireless communication system {METHOD FOR TRANSMITTING REFERECE SIGNAL FOR DOWNLINK CHANNEL MEASUREMENT}

The present invention relates to a wireless communication system, and more particularly, to a method of transmitting a reference signal using a specific downlink control channel in order to perform efficient downlink channel estimation in a wireless communication system.

LTE ( Long Term Evolution Slot structure

In a cellular OFDM wireless packet communication system, uplink / downlink data packet transmission is performed in subframe units, and one subframe includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols. time duration).

3GPP (3 ^rd Generation Partnership Project) is a FDD (Frequency Division Duplex) available type 1 (type 1) the radio frame structure (Radio Frame Structure) and TDD (Time Division Duplex) possible type 2 radio frame structure (Radio of the application on the application in Frame Structure).

1 shows a structure of a type 1 radio frame. Type 1 radio frame consists of 10 subframes, one subframe consists of two slots (Slot).

2 shows a structure of a type 2 radio frame. Type 2 radio frames consist of two half frames, each of which has five subframes, a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). One subframe consists of two slots. DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. The guard period is a period for removing interference generated in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink. That is, regardless of the type of radio frame, one subframe consists of two slots.

개의 부반송파(subcarrier)와

개의 OFDM(Orthogonal Frequency Division Multiplexing) 심볼(symbol)로 구성되는 자원 격자 (Resource Grid)에 의해 묘사될 수 있다. 여기서,

은 하향링크에서의 자원 블록 (Resource Block; RB)의 개수를 나타내고,

는 하나의 RB을 구성하는 부반송파의 개수를 나타내고,

는 하나의 하향링크 슬롯에서의 OFDM 심볼의 개수를 나타낸다.3 shows a slot structure of an LTE downlink. As shown in FIG. 3, a signal transmitted in each slot is

Subcarriers and

It may be depicted by a resource grid composed of four Orthogonal Frequency Division Multiplexing (OFDM) symbols. here,

Represents the number of resource blocks (RBs) in downlink,

Represents the number of subcarriers constituting one RB,

Denotes the number of OFDM symbols in one downlink slot.

A resource element (RE) represents one subcarrier and one OFDM symbol in a resource unit defined by indexes (a, b) in the uplink slot and the downlink slot. Where a is an index on the frequency axis and b is an index on the time axis.

3 GPP LTE  Reference Signal Allocation Method for Base Station in Downlink System

For efficient communication, the receiving side should feed back channel information to the transmitting side. In general, the downlink channel information is transmitted by the terminal to the base station through the uplink, and the uplink channel information is transmitted by the base station through the downlink to the terminal. Such channel information is called a channel quality indicator (CQI). Channel quality indicators can be generated in several ways.

4 is a diagram illustrating generation and transmission of a channel quality indicator.

The terminal measures the quality of the downlink channel and reports the selected channel quality indicator value to the base station through the uplink control channel. The base station performs downlink scheduling (terminal selection, resource allocation, etc.) according to the reported channel quality indicator.

That is, in the wireless communication system, when the base station allocates radio resources to the terminal, the base station uses the channel quality indicator received from the terminal.

The terminal receives a pilot channel from the base station, measures channel quality information such as a signal to interference ratio (SIR), and reports the measured channel quality information to the base station. Then, the base station allocates radio resources to each of the base stations by using the channel quality information received from each of the terminals.

When transmitting a packet in a mobile communication system, since the transmitted packet is transmitted through a wireless channel, signal distortion may occur during the transmission process. In order to receive such a distorted signal correctly, the receiver must find out the channel information and correct the distortion of the transmission signal by the channel information in the received signal. In order to find out the information of the channel, it is mainly used to find out the information of the channel with the degree of distortion of the signal when the signal is transmitted from both the transmitting side and the receiving side. The signal known to both the transmitting side and the receiving side is called a pilot signal or a reference signal (RS).

Looking at the frame structure used in the system, one frame is transmitted at a time of 10msec, which is composed of 10 subframes over a period of 1msec. One subframe consists of 14 or 12 OFDM symbols, and the number of subcarriers in one OFDM symbol is selected from 128, 256, 512, 1024, 1536, and 2048.

5 to 7 each show an example of a downlink reference signal structure for a system having 1, 2, and 4 transmission antennas when one transmission time interval (TTI) has 14 OFDM symbols. Where R0 represents a pilot symbol for transmit antenna 0, R1 represents a pilot symbol for transmit antenna 1, R2 represents a pilot symbol for transmit antenna 2, and R3 represents a pilot symbol for transmit antenna 3, respectively. A subcarrier using a pilot symbol does not transmit a signal for all other transmit antennas except for a transmit antenna for transmitting a pilot symbol to eliminate interference.

8 is a diagram illustrating an example of a downlink pilot symbol structure according to frequency shift of a pilot symbol according to a cell when one transmission time interval (TTI) has 14 OFDM symbols.

Assuming that the structure of the pilot symbol for the system having one transmit antenna of FIG. 5 is used for cell 1 of FIG. 8, in cell 2 and cell 3, the collision of the pilot symbol between cells does not occur in the frequency domain or In the time domain, pilot symbols may be protected by a transition of a subcarrier unit or an OFDM symbol unit. For example, in the case of a system having one transmitting antenna, it can be seen that each pilot symbol is located at six subcarrier intervals in the frequency domain. Accordingly, at least five neighboring cells may be located at different positions through the transition of the frequency domain subcarrier unit. FIG. 8 is a diagram corresponding to the above example, and shows that a plurality of cells avoid collision of pilot symbols through frequency shift.

Additionally, by multiplying a pseudo-random (PN) sequence by a downlink reference signal for each cell, the receiver may reduce interference of a signal of a pilot symbol received from an adjacent cell at a receiver, thereby improving channel estimation performance. This PN sequence is applied in units of OFDM symbols in one subframe, and the PN sequence may have a different sequence according to the cell ID, the number of subframes, and the position of the OFDM symbol.

When the number of transmit antennas that can be supported in a system having N antennas to support up to M (M> N) transmit antennas, UE (User Equipment) that can recognize only N transmit antennas and UEs that can recognize up to M transmit antennas coexist. In this case, transmission of additional M-N RSs is required in addition to RS for supporting existing N antennas. At this time, efficient transmission of data and RS is required in an environment in which a UE recognizing M antennas is added.

An object of the present invention is to provide a method for transmitting an RS dedicated to a base station when the number of transmit antennas increases in a communication system.

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.

An object of the present invention is to provide a method for transmitting an RS dedicated to a base station when the number of transmit antennas increases in a communication system.

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 order to achieve the above object, a first user equipment (UE) for recognizing N (M> N) transmit antennas among a total of M transmit antennas according to an aspect of the present invention and the M transmit antennas are recognized. In a downlink system supporting a second user equipment, a reference signal transmission method includes a physical hybrid-ARQ indicator channel (PHICH) used by a base station to transmit ACK / NACK information for an uplink data channel in a subframe. Mapping reference signals for the N to M-1 < th > transmit antenna ports to a predetermined number of PHICH groups among groups; And transmitting a subframe in which the reference signal is mapped, wherein each of the PHICH groups includes a predetermined number of resource elements (REs) concatenated on the frequency domain of the subframe. ) A predetermined number.

According to another aspect of the present invention, a first user equipment (UE) recognizing N (M> N) transmit antennas among a total of M transmit antennas and a second user equipment recognizing the M transmit antennas are supported. A system for feeding back channel quality information, the method comprising: receiving, by a user equipment, a subframe in which a reference signal is mapped from a base station; And feeding back channel quality information between the base station and the user equipment using a reference signal included in the received subframe, and acknowledging ACK / NACK information on an uplink data channel in a subframe transmitted by the base station. Reference signals for the N to M-1th transmit antenna ports are mapped to a predetermined number of PHICH groups among PHICH groups used for transmitting the PICH groups, and each of the PHICH groups A predetermined number includes a Resoruce Element Group (REG) including a predetermined number of Resource Elements (REs) concatenated on the frequency domain of the subframe.

In this case, the number of PHICH groups may be larger than the number of PHICH groups required for transmitting the ACK / NACK information.

In this case, the method may further include transmitting the index of the PHICH group in which the reference signal is mapped through a broadcast channel (BCH).

In this case, the index of the PHICH group in which the reference signal is mapped may be transmitted through a physical downlink control channel (PDCCH) on the subframe.

In this case, reference signals for the N to M-1 < th > transmit antenna ports are mapped to a predetermined number of control channel elements (CCEs) constituting a PDCCH on the subframe, and the CCE is composed of a predetermined number of REGs. The number of CCEs used to map the reference signal may be proportional to the number of PHIC groups used to use the reference signal.

According to an embodiment of the present invention, efficient downlink channel estimation is possible in a wireless communication system.

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

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted for simplicity of explanation, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

First, the configuration of a control channel in the 3GPP LTE downlink system will be described.

The basic downlink control channel is transmitted in the first three OFDM symbols of each subframe. In this case, the number of OFDM symbols for the downlink control channel may be adjusted to one to three according to the overhead of the downlink control channel. A channel used to adjust the number of OFDM symbols for the downlink control channel for each subframe is a physical control format indicator channel (PCFICH). In addition, a channel for transmitting ACK / NACK (ACKnowledgement / Negative ACKnowledgement) information on the uplink data channel is a PHICH (Physical Hybrid-ARQ Indicator Channel). In addition, a control channel for transmitting control information for downlink data transmission or uplink data transmission is a physical downlink control channel (PDCCH).

9 is a diagram illustrating a resource configuration of a control channel in a system having one or two transmit antennas. FIG. 10 is a diagram illustrating a configuration of resources of a control channel in a system having four transmit antennas. Resources may be configured as shown in FIGS. 9 and 10 to allocate the above-described control channel to each subframe. As shown in FIG. 9, the basic resource configuration of the control channel is composed of a resource element group (REG). The REG is composed of resource elements (REs) concatenated in four frequency domains except for pilot symbols, and a specific number of REGs may be used as a control channel according to a situation. Here, RE is used as one subcarrier.

Hereinafter, the PCFICH will be described in more detail.

In each subframe, PDCCH (Physical Downlink Control Channel) is transmitted between 0 and 2 OFDM symbols for resource allocation information of each subframe, and 0, 0, 1, 0 according to the amount of control channel. Control channel information may be sent to the OFDM symbol two times. In this way, the number of OFDM symbols used by the control channel can be changed in every subframe, and the information about this is indicated by a physical control format indicator channel (PCFICH). Therefore, the PCFICH should be transmitted every subframe and has a total of three pieces of information.

Table 1 below shows CFI (Control Format Indicator) of the PCFICH.

In Table 1, when CFI = 1, the PDCCH is transmitted only to the 0 th OFDM symbol. In the case of CFI = 2 and CFI = 3, the PDCCH is 0 th to 1 th OFDM symbol and 0 th to 2 th OFDM symbol. Indicates that it is sent.

Of course, such information may be defined differently according to bandwidth. For example, when the bandwidth of the system is smaller than a specific threshold, CFI = 1, 2, and 3 may indicate that 2, 3, and 4 OFDM symbols are used for the PDCCH.

11 is a diagram illustrating a transmission form of a PCFICH. In FIG. 11, the REG consists of four subcarriers, and consists only of data subcarriers excluding RS, and generally uses a transmit diversity scheme. In addition, the frequency shift is used so that the location of the REG does not interfere with the cells. Since the PCFICH is always transmitted in the first OFDM symbol of the subframe, the receiver first checks the information of the PCFICH after receiving the subframe and then receives the information of the PDCCH.

Ah, the PHICH will be described in detail.

12 is a diagram illustrating a transmission form of a general PCFICH and a Physical Hybrid-ARQ Indicator Channel (PHICH) in a specific bandwidth. The PHICH is a channel for transmitting ACK / NACK information on an uplink data channel. Several PHICH groups may be created in one subframe, and one PHICH group may include several PHICHs. Therefore, one PHICH group may include PHICHs for a plurality of user equipments (UEs).

와 같은 인덱스 쌍(index pair)로 알려진다. 상기 인덱스 쌍

에서

는 PHICH 그룹 번호,

는 해당 PHICH 그룹안에서의 직교 시퀀스 인덱스(orthogonal sequence index)를 나타낸다.As shown in FIG. 12, PHICH allocation for each UE in a plurality of PHICH groups is transmitted in a lowest PRB index and an uplink grant of PUSCH resource allocation. It allocates using frequency shift (cyclic shift) of DMRS. PHICH resources

It is known as an index pair such as The index pair

in

PHICH group number,

Denotes an orthogonal sequence index in the PHICH group.

An example of an orthogonal sequence used in a 3GPP LTE system is shown in Table 2 below.

Sequence index Orthogonal sequence

Normal cyclic prefix

Extended cyclic prefix

0

One

2

3

4

- 5

- 6

- 7

-

와

는 아래의 수학식 1에 의해 구할 수 있다.remind

Wow

Can be obtained by Equation 1 below.

는 PHICH와 관련된 상향링크 전송에서 사용되는 DMRS의 주파수 천이를,

는 PHICH에 사용되는 확산 계수(spreading factor) 크기를,

는 상향링크 자원할당의 가장 낮은 PRB 인덱스를, 는 PHICH 그룹의 수를 나타낸다.In Equation 1,

The frequency shift of the DMRS used in uplink transmission associated with PHICH,

Is the spreading factor size used in PHICH,

Is the lowest PRB index of uplink resource allocation, Represents the number of PHICH groups.

는 아래의 수학식 2에 의해 구할 수 있다.remind

Can be obtained by Equation 2 below.

는 PBCH(Physical Broadcast Channel)로 전송되는 2 비트(

)로 표현되는 PHICH 자원의 양과 관련된 정보를 나타내고,

은 하향링크에서의 자원 블록 (Resource Block; RB)의 개수를 나타낸다. 도 13은 PHICH 기간(duration)에 따른 서브프레임 내에서 PHICH 그룹의 구성을 나타내는 도면이다. 도 13에 도시된 바와 같이, PHICH 그룹은 PHICH 기간에 따라 하나의 서브프레임안에서 다른 시간영역으로 구성될 수 있다.In Equation 2,

Is 2 bits transmitted over the PBCH (Physical Broadcast Channel).

Information relating to the amount of PHICH resources represented by

Denotes the number of resource blocks (RBs) in downlink. FIG. 13 is a diagram illustrating a configuration of a PHICH group in a subframe according to a PHICH duration. As shown in FIG. 13, the PHICH group may be configured as different time domains in one subframe according to the PHICH period.

Hereinafter, the PDCCH will be described in detail.

The physical downlink control channel (PDCCH) has different sizes and uses of control information according to a downlink control indicator (DCI) format, and may vary in size depending on a coding rate. For example, the DCI format may be defined as shown in Table 3 below.

DCI format Objectives 0 Scheduling of PUSCH One Scheduling of one PDSCH codeword 1A Compact scheduling of one PDSCH codeword 1B Closed-loop single-rank transmission 1C Paging, RACH response and dynamic BCCH 1D MU-MIMO 2 Scheduling of rank-adapted closed-loop spatial multiplexing mode 2A Scheduling of rank-adapted open-loop spatial multiplexing mode 3 TPC commands for PUCCH and PUSCH with 2bit power adjustments 3A TPC commands for PUCCH and PUSCH with single bit power adjustments

The DCI format may be applied independently for each UE, and PDCCHs of multiple UEs may be multiplexed simultaneously in one subframe. Channel coding is performed independently on the PDCCH of each multiplexed UE and CRC is applied. The unique ID of each UE is masked in the CRC so that the UE can receive its own PDCCH. However, since the UE does not know the location of its PDCCH, the UE should blindly detect all PDCCHs of the corresponding DCI format until receiving a PDCCH having its ID in every subframe. The basic resource allocation unit of PDCCH is CCE (Control Channel Element), and one CCE is composed of 9 REGs. One PDCCH may consist of one, two, four or eight CCEs depending on the situation. The PDCCH configured according to each UE is interleaved and mapped to the control channel region of each subframe by a CCE-to-RE mapping rule. The location of the PDCCH may vary depending on the number of OFDM symbols, the number of PHICH groups, the transmission antenna, and the frequency shift for the control channel of each subframe.

Hereinafter, a method of transmitting a pilot symbol dedicated to a base station when the number of transmission antennas increases to eight using the above-described control channel will be described.

Example  One

In this embodiment, PHICH-based CRS transmission will be described.

In the case of the standard CP, each PHICH group consists of three resource element groups (REGs), and each REG consists of four REs. Therefore, when one PHICH group is used as a CRS for transmission antennas 4 to 7, three pilot symbols for each antenna may be allocated to the total used bandwidth. In this case, the PHICH group may be defined in other terms, and in the following description of the present invention, the name of the PHICH group may also be defined in other terms.

14 illustrates a structure of a PHICH-based CRS according to an embodiment of the present invention. At this time, as shown in FIG. 14, each REG may be configured to have one pilot symbol of transmission antennas 4 to 7 times.

In FIG. 14, even if the order of the REG mapping of the pilot symbols of each transmission antenna is changed, the performance is irrelevant. In addition, the mapping form of the pilot symbol of the transmit antenna may be changed according to the REG. In addition, although the method described in FIG. 13 may be applied to the mapping method of the REG according to the CFI index and the PHICH duration of the PCFICH, other types of mapping methods may be applied.

값에 의하여 결정된다. 이때,

값은 PBCH를 통하여 전송되며 셀 고유한(cell specific) 정보이다. 따라서 필요한 PHICH 그룹보다

값을 크게 구성하여 특정 개수의 PHICH 그룹을 CRS를 위해 사용할 수 있다. 이때 지정되는 CRS 용 PHICH 그룹의 개수는 시스템 대역폭(system BW)과 관련하여 정의된 서브밴드 크기(subband size)와 전체 서브밴드의 개수 등의 파라미터에 따라 결정될 수 있다. 즉, CRS 용 PHICH 그룹의 개수는 수학식에 의해 정의된 규칙에 의해 결정될 수 있다. 또한, 임의의 서브밴드 내 최소 R(≥1)개 이상의 CRS가 매핑될 수 있도록 CRS 용 PHICH 그룹의 개수를 지정하는 방식을 독립적으로 또는 상기 방식과 함께 적용할 수 있다.As shown in Equation 2, the total number of PHICH groups is equal to the number of RBs corresponding to a specific bandwidth.

Determined by the value. At this time,

The value is transmitted via PBCH and is cell specific information. Therefore than the required PHICH group

By configuring a large value, a certain number of PHICH groups can be used for the CRS. At this time, the number of PHICH groups for CRS may be determined according to parameters such as the subband size defined in relation to the system bandwidth and the number of total subbands. That is, the number of PHICH groups for CRS may be determined by a rule defined by the equation. In addition, a method of designating the number of PHICH groups for CRSs may be applied independently or in combination with the above schemes so that at least R (≥1) CRSs in any subband can be mapped.

Since the performance of channel estimation is proportional to the number of pilot symbols, it is advantageous to use as many PHICH groups for CRS as possible. The index of the PHICH group used for the CRS may notify the UE in the following manner.

The index of the PHICH group for CRS may be informed by using a bitmap or a specific bit field on a broadcasting channel.

에 따라 미리 CRS 용 PHICH 그룹 인덱스를 정해놓은 형태로 사용할 수 있다.Or, for each subframe, PCFICH, PHICH duration, RB number,

In this case, the PHICH group index for the CRS may be used in the form of a predetermined form.

Alternatively, a specific PDCCH for a UE that wants to use a CRS for each subframe is transmitted, and the PDCCH may be used after being CRC masked with a specific ID. The PDCCH may be configured to include a PHICH group index for the CRS. Therefore, the UE reads the CRC masked PDCCH with the specific ID and performs channel estimation in the specific PHICH group.

The CRS transmitted using this PHICH group may be used for all subframes, but may be transmitted only at a specific position of one radio frame according to a channel quality indicator (CQI) feedback period. Alternatively, a CRS transmitted using a PHICH group may be configured to be used only in a subframe including a PDCCH transmitting a PHICH group index using a CRS.

Alternatively, the PHICH group index (or indexes) for transmitting the CRS may be differently set in units of N (≥1) subframes transmitted, where the PHICH group index may be shifted by a specific offset value on the index or may be arbitrarily defined. You can also hop to an established rule (which can be defined as an expression). This is because it may be difficult to measure the entire desired band if one or more PHICH group indexes are fixedly allocated. Therefore, it is necessary to distribute one or more PHICH group indexes allocated for CRS in the time domain.

Alternatively, the PHICH duration value on the PBCH of the cell or eNB where the PHICH group for CRS is configured may be defined as 3 and a certain number or more of PHICH group indexes may be allocated to the PHICH group for CRS to provide a sufficient frequency interval for measurement. Can be.

값과

을 더한 후

으로 모듈로 연산하여 결정된다. 상기 설명된 방법을 이용하여 CRS를 포함시키면 특정 UE의 PHICH가 CRS로 사용되는 PHICH 그룹에 포함될 수 있다. 기지국의 스케줄러가 이와 같은 상황을 피하도록 할 수 있지만, 한계가 있다. 따라서, PHICH로 전송되는 CRS를 이용하는 UE(예를 들어, LTE-A UE)는 다른 형태의 PHICH 그룹 할당을 사용하도록 구성하고 해당 UE가 상기 수학식 1로 PHICH 그룹을 할당하는 경우 CRS 전송을 위해 사용되는 PHICH 그룹에 CRS가 할당되도록 구성할 수 있다.As can be seen in Equation 1, the allocation of the PHICH group

Value and

After adding

Is determined by modulo operation. If the CRS is included using the above-described method, the PHICH of the specific UE may be included in the PHICH group used as the CRS. The scheduler of the base station can avoid this situation, but there are limitations. Therefore, a UE (eg, an LTE-A UE) using CRS transmitted to PHICH is configured to use a different form of PHICH group allocation and for CRS transmission when the UE allocates PHICH group by Equation 1 above. CRS may be allocated to the PHICH group to be used.

In this case, the LTE-A UE may allocate a PHICH group in the form of Equation 3 below. Alternatively, to avoid collisions, the unused value of the DM-RS cyclic shift or the unused value on the PRB index is intentionally set, or if there is a value that is not originally used in the system, the value is used as it is. As a setting form, a method of avoiding collision may be applied.

는 CRS 전송을 위하여 사용되는 PHICH 그룹의 개수를 나타낸다. 상기 수학식 3은 추가적으로

값을 정의하고 0부터

까지는 일반적인 PHICH 할당을 위해 사용되고 나머지

부터

까지는 CRS를 위해 할당되는 경우를 의미한다. CRS를 위해 사용되는 PHICH 그룹 인덱스가 하나 이상의 임의의 개수로 연속적으로 할당되는 경우 상기에서 기술한 시간 영역에서 N(≥1) 서브프레임 단위로 PHICH 그룹 인덱스를 다르게 설정하는 방식을 논리 영역에 적용하여 실제 물리 자원에 맵핑하는 방식을 적용할 수 있다.In Equation 3

Denotes the number of PHICH groups used for CRS transmission. Equation 3 is additionally

Define the value and start at 0

Is used for general PHICH allocation

from

Means the case allocated for CRS. If the PHICH group index used for CRS is continuously allocated to one or more arbitrary numbers, the method for setting the PHICH group index differently in units of N (≥1) subframes in the time domain described above is applied to the logical domain. You can apply the mapping to the actual physical resources.

값에 의하여 결정되는 것을 알 수 있다. 하지만

의 경우 총 4가지의 값으로 되어 있고 각 값에 따라서 배수의 형태로 구성되므로 유연하게(flexible) PHICH 그룹 개수를 결정할 수 없다. 따라서, 아래의 수학식 4와 같은 형태로 구성하면 PHICH 그룹의 개수를 유연하게 구성할 수 있다.In Equation 2, the number of PHICH groups is equal to the number of RBs of the corresponding bandwidth.

It can be seen that it is determined by the value. However

In the case of 4 values in total and each value is configured in the form of multiples, it is impossible to determine the number of flexible PHICH groups. Therefore, the configuration as shown in Equation 4 below can flexibly configure the number of PHICH groups.

은 특정 집합(set)으로 구성될 수 있으며, 일례로

의 형태로 '0'을 포함하는 정수의 집합으로 집합을 구성할 수 있다. 다른 형태로서 아래의 수학식 5와 같은 형태로 유연하게 할당할 수 있다. In the above equation

May consist of a specific set, for example

The set may be composed of a set of integers including '0' in the form of. As another form, it may be flexibly allocated in the form of Equation 5 below.

의 값은 상기 예에서 보듯이 양의 정수와 음의 정수로 대칭적 또는 비대칭적으로 구성된 집합으로 정의될 수도 있으며 양의 정수 또는 음의 정수로만 구성될 수도 있다.in this case

The value of may be defined as a set symmetrically or asymmetrically composed of positive and negative integers as shown in the above example, and may be composed of only positive or negative integers.

Equations 4 and 5 may be described as Equations 6 and 7 below.

The PHICH-based CRS transmission scheme proposed by the present invention needs to be embodied as a scheme for supporting backward compatibility with an existing LTE UE. CCEs defined by any CCE aggregation level unique to the UE once a UE has been assigned to a common search space among all total logical CCEs and a hashing function It may be considered to perform blind decoding with respect to the candidate region for.

In this case, if the existing LTE UEs know only the number of PHICH groups originally used for downlink PHICH transmission as the total PHICH group number, physical resources to which PHICH group indexes additionally allocated for CRS are mapped for CCE are allocated. In the situation of interpreting as the physical support, the PHICH group index for the CRS may be allocated so that the physical resources to which the PHICH group indexes are mapped do not collide with the common search space recognized by existing LTE UEs and / or LTE-A UEs. . In addition, the base station scheduler (scheduler) through the remaining candidate CCE region excluding the CCE PHICH group index for the CRS and the CCEs collide on the physical resource on the PDCCH transmission candidate CCE index region on the individual UE search space of the existing LTE UEs By allocating a PDCCH of the UE, it is possible to minimize a collision problem during PDCCH transmission for existing LTE UEs according to the PHICH index setting for the CRS.

값을 정의되어 있는 값과 다르게 해석하여 원래의

를 이용한 경우보다 더 많은 개수의 PHICH 그룹을 할당할 수 있다. 하향링크 RB의 수가 10개 이하인 시스템 대역폭에 대해서 PCFICH가 전송된 값에 +1된 값으로 CFI를 해석하는 것과 같이 전송된

값에 1을 더하거나

값을 두배로 하는 방법 등을 이용하여 더 많은 PHICH 그룹을 할당할 수 있다. In addition, in case of LTE-A UE, it is transmitted through PBCH.

Interpret the value differently from the defined value

More PHICH groups can be allocated than when using. For system bandwidths with 10 or fewer downlink RBs, the PCFICH is interpreted as interpreting CFI as a value +1 to the transmitted value.

Add 1 to the value

More PHICH groups can be allocated, for example, by doubling the value.

값을 그대로 이용하면 LTE-A UE와 LTE Rel. 8 UE가 서로 다르게 해석한

값에 의해 PHICH 그룹 수의 차이가 발생할 수 있다. LTE-A UE가 계산한 PHICH 그룹의 수에서 LTE Rel. 8 UE가 계산한 PHICH 그룹의 수를 뺀 만큼의 PHICH 그룹을 CRS 할당에 사용할 수 있다. 이런 경우에 LTE-A UE의 PHICH 할당은 상기의 수학식 3을 이용할 수 있다.At this time, LTE Rel. 8 terminals existing

If the value is used as it is, LTE-A UE and LTE Rel. 8 UEs interpret differently

Values may cause a difference in the number of PHICH groups. LTE Rel in the number of PHICH groups calculated by the LTE-A UE. As many as PHICH groups subtracting the number of PHICH groups calculated by the 8 UE may be used for CRS allocation. In this case, the PHICH allocation of the LTE-A UE may use Equation 3 above.

Hereinafter, a PDCCH-based CRS transmission method according to an embodiment of the present invention will be described.

Example  2

The CRS allocation described in the PHICH-based CRS transmission of the first embodiment may also be applied when transmitting the CRS using the PDCCH. Since one PDCCH consists of one or more CCEs and one CCE consists of nine REGs, the CRS allocation described in Embodiment 1 can be applied, and one PHICH group is used for CRS transmission. Using one PDCCH for CRS transmission can transmit three times as many CRSs.

Since the PDCCH has a different size and location of the CCE according to the UE for each subframe, and information on the CCE is not notified to the UE, the UE should find its PDCCH through blind detection.

15 is a diagram illustrating a method of blind detection of a CCE according to an embodiment of the present invention. As shown in FIG. 15, a search space is determined according to the size of each CCE, and blind detection is performed from logical CCE index 0. FIG.

라면 논리적 CCE의 인덱스는 {0,....,

} 로 구성될 수 있으며, 상기 도 15에 도시된 바와 같은 같은 형태로 특정 횟수의 블라인드 디텍션(blind detection)을 수행할 수 있다. 따라서, CRS 전송을 위하여 특정 논리적 CCE 인덱스를 지정(reservation)하면 기존 UE의 불필요한 블라인드 디텍션(blind detection)을 줄일 수 있다. The total number of logical CCEs in any subframe depends on the number of CFI indexes, PHICH groups, and transmit antennas of the PCFICH. For example, if the number of CCEs

If the index of the logical CCE is {0, ....,

} Blind detection may be performed a specific number of times in the form as shown in FIG. 15. Therefore, if a specific logical CCE index is reserved for CRS transmission, unnecessary blind detection of an existing UE can be reduced.

부터 x개 지정하여 x개의 CCE를 CRS 전송에 사용할 수 있다. 즉, UE가 블라인드 디텍션하는 CCE 인덱스의 역순으로 지정하면 기존 UE의 불필요한 블라인드 디텍션을 줄일 수 있다. In one embodiment, the logical CCE index is

X CCEs can be used for CRS transmission. That is, unnecessary blind detection of the existing UE can be reduced by specifying the reverse order of the CCE index that the UE detects blind.

,

}가 되며 해당 CCE는 4번부터 7번 송신안테나를 위한 CRS 전송에 사용된다. 지정하는 논리적 CCE의 인덱스는 CCE 열 중에서 첫 번째 CCE인 0번 CCE 인덱스, 마지막 CCE인

번 CCE 인덱스, 또는 UE 고유한 검색 공간(UE-specific search space)의 첫 번째 CCE 인덱스등과 같이 다양한 방법으로 설정할 수 있다.For example, if two CCEs are used for CRS transmission, the logical index of the specified CCE is {

,

} And the CCE is used for CRS transmission for transmission antennas 4 to 7. The index of the logical CCE that you specify is the first CCE in the CCE column, index 0 CCE, and the last CCE.

The CCE index may be set in various ways, such as the first CCE index or the first CCE index of the UE-specific search space.

The CCE designation for CRS transmission described above may be used only for every subframe or a specific subframe. Information on this may inform only the number information of CCEs used for CRS transmission using a broadcast channel, or may inform a bitmap or a corresponding CCE index according to circumstances. In addition, the CCE may be used for CRS transmission in a predetermined form. In this case, a predetermined pattern may be used according to the CFI index of the PHICH, the number of PHICH groups, and the number of transmission antennas.

Hereinafter, a method of transmitting a CRS by combining a PHICH and a PDCCH according to an embodiment of the present invention will be described.

Example  3

The CRS may be transmitted by using both of the above-described channels PHICH and PDCCH. In case of transmitting CRS using only PHICH, channel estimation performance may be reduced due to the limitation of the number of PHICH groups and the lack of the number of REGs in one PHICH group. Therefore, channel estimation performance can be improved by simultaneously using the PHICH and the PDCCH. It can be configured and used according to the situation.

First, the number of CCEs may be determined differently according to the number of PHICH groups used as the CRS. For example, the number of CCEs for the CRS may decrease when the number of CICH PHICH groups is increased, and the number of CCEs may be increased in advance when the number of CICHs for the CRS is decreased.

Second, the number of CCE logical indexes for CRS may be mapped to the number of PHICH groups for CRS, and may be used in advance. That is, the number of CICH PHICH groups and the number of CCE logical indexes may be set to be linearly proportional to each other. FIG. 16 illustrates a method of mapping a PHICH group index and a logical CCE index according to an embodiment of the present invention. As shown in FIG. 16, an index of one PHICH group may indicate several CCE logical indexes. Therefore, by notifying the number of PHICH groups used for the CRS, the logical index of the CCE used for the CRS can be determined. The logical CCE index can be expressed as a function of the PHICH group index. For example, it may be expressed by a function such as Logical_CCE_index = F (PHICH_group_index).

Hereinafter, a method of transmitting a CRS by combining a PDCCH and a PDSCH according to an embodiment of the present invention will be described.

Example  4

In the present embodiment, as the base station allocates downlink data to the UE, the PDCCH notifies the RB including pilot symbols of 4 to 7 transmission antennas. In this case, the position may shift by a fixed offset value or a value according to a constant law derived as an equation in units of N (≥1) subframes, and the changed position may be designated by PDCCH. In particular, when a PDCCH is designated, a change time point may be variably applied. The PDCCH may be configured by using CRC masking with a predetermined ID or configured as a PDCCH fixed at a predetermined position. In this case, it is preferable that the pilot symbols of the 4 to 7 transmit antennas are transmitted by avoiding the pilot symbol positions of the 0 to 3 transmit antennas. Such a method may be additionally used when the CRS cannot be sent to the above-described PHICH and PDCCH regions, or may be used separately from the above-described scheme.

However, in this method, since the pilot symbols of the transmission antennas 4 to 7 cannot be transmitted to all RBs, channel estimation performance may be different according to frequency bands. Therefore, it is desirable to configure the pilot symbol to be spread as much as possible using frequency hopping for each slot. In order to further solve this problem, the RB transmitting the CRS may be configured to perform data transmission depending on the situation. In this case, the UE assigned the RB knows the position of the pilot symbol in advance, and the transmitted data may be configured to be rate matched and transmitted, or may be implemented by puncturing the data symbol coming to the pilot position. This is possible.

Hereinafter, a control channel based CRS transmission power control method according to an embodiment of the present invention will be described.

Example  5

When the CRS is transmitted through the control channel, power control different from the CRS of the 0 to 3 transmitting antennas may be required. In general, power level information of a control channel is not informed to the terminal, so power information is essential to calculate an accurate CQI. If P_CRS_a is information on transmission power of transmission antennas 0 to 3 and P_CRS_b is information on transmission power of transmission antennas 4 to 7 transmitted through the control channel, the power ratio P_c = P_CRS_a / P_CRS_b The value can be informed to the terminal. At this time, P_c may be configured to include '0dB' to have the same size as the CRS of the 0 to 3 transmission antennas.

In addition, the power ratio with the data RE can provide information on this. The P_c may be transmitted in the same cycle as the power information of the 0 to 3 transmission antennas or may be configured to transmit more frequently than P_CRS_a to enable fast power adaptation.

The schemes for transmitting the CRS proposed by the present invention may be applied to all subframes of all carriers without distinction and are designated as LTE-A dedicated carriers or LTE-A dedicated subframes in an arbitrary carrier. It may be applied to a subframe only. In this case, the content of the subframe unit setting in the present invention may be interpreted as being applied to the column of the LTE-A dedicated subframe.

The UE, which has received the CRS from the base station by the above-described method, may generate channel information using the received CRS and feed back to the base station.

17 is a block diagram showing a configuration of a device applicable to a user equipment or a base station and capable of carrying out the present invention. As shown in FIG. 17, the device 170 includes a processing unit 171, a memory unit 172, a radio frequency (RF) unit 173, a display unit 174, and a user interface unit 175. . The layer of physical interface protocol is performed in the processing unit 171. The processing unit 171 provides a control plane and a user plane. The functions of each layer may be performed in the processing unit 171. The memory unit 172 is electrically connected to the processing unit 171 and stores an operating system, an application, and a general file. If the device 170 is a user device, the display unit 174 may display a variety of information, and may be implemented using a known liquid crystal display (LCD), an organic light emitting diode (OLED), or the like. The user interface unit 175 can be configured in combination with a known user interface such as a keypad, touch screen, or the like. The RF unit 173 is electrically connected to the processing unit 171 and transmits or receives a radio signal.

In the present specification, embodiments of the present invention have been described based on data transmission / reception relations between a base station and a terminal. Here, the base station has a meaning as a terminal node of a network that directly communicates with the terminal. The specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases.

That is, various operations performed for communication with a terminal in a network consisting of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. In this case, the base station may be replaced by terms such as an evolved Node B (eNB), a fixed station, a Node B, and an access point. In addition, in the present invention, a 'mobile terminal' corresponds to a user equipment (UE), and a 'mobile terminal' corresponds to a 'mobile station (MS)', a subscriber station (SS), or an MSS. (Mobile Subscriber Station) ".

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

In the case of the implementation by firmware or software, the method for reporting channel quality information in a wireless communication system according to 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 the memory unit and driven by the 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 can be embodied in other specific forms without departing from the spirit and essential features of the present 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.

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.

The present invention can be used in a terminal, base station, or other equipment of a wireless mobile communication system.

1 shows a structure of a type 1 radio frame.

2 shows a structure of a type 2 radio frame.

3 shows a slot structure of an LTE downlink.

4 is a diagram illustrating generation and transmission of a channel quality indicator.

5 to 7 each show an example of a downlink reference signal structure for a system having 1, 2, and 4 transmission antennas when one transmission time interval (TTI) has 14 OFDM symbols.

8 illustrates an example of a downlink pilot symbol structure according to frequency shift of a pilot symbol according to a cell when one transmission time interval (TTI) has 14 OFDM symbols.

9 is a diagram illustrating a resource configuration of a control channel in a system having one or two transmit antennas.

FIG. 10 is a diagram illustrating a configuration of resources of a control channel in a system having four transmit antennas.

11 is a diagram illustrating a transmission form of a PCFICH.

12 is a diagram illustrating a transmission form of a general PCFICH and a Physical Hybrid-ARQ Indicator Channel (PHICH) in a specific bandwidth.

FIG. 13 is a diagram illustrating a configuration of a PHICH group in a subframe according to a PHICH duration.

14 illustrates a structure of a PHICH-based CRS according to an embodiment of the present invention.

15 is a diagram illustrating a method of blind detection of a CCE according to an embodiment of the present invention.

FIG. 16 illustrates a method of mapping a PHICH group index and a logical CCE index according to an embodiment of the present invention.

17 is a block diagram showing a configuration of a device applicable to a user equipment or a base station and capable of carrying out the present invention.

Claims (10)

A downlink system supporting a first user equipment (UE) that recognizes N (M> N) transmit antennas among a total of M transmit antennas and a second user equipment that recognizes the M transmit antennas, As a reference signal transmission method, In the base station, the N-th M-1 th transmit antenna port in a predetermined number of PHICH groups among PHICH groups used for transmitting ACK / NACK information for an uplink data channel in a subframe Mapping a reference signal for; And Transmitting a subframe in which the reference signal is mapped; Each of the PHICH groups includes a predetermined number of Resoruce Element Groups (REGs) including a predetermined number of resource elements (REs) concatenated on the frequency domain of the subframe. How to send reference signal. The method of claim 1, The number of PHICH groups is larger than the number of PHICH groups required for transmitting the ACK / NACK information. How to send reference signal. The method of claim 1 wherein the method is Transmitting the index of the PHICH group in which the reference signal is mapped through a broadcast channel (BCH); How to send reference signal. The method of claim 1, The index of the PHICH group in which the reference signal is mapped is transmitted through a physical downlink control channel (PDCCH) on the subframe. How to send reference signal. The method of claim 1, In the step of mapping the reference signal, a reference signal for the N to M−1 th transmission antenna ports is mapped to a predetermined number of CCEs (Control Channel Elements) constituting a PDCCH on the subframe. The CCE consists of a predetermined number of REGs, and the number of CCEs used to map the reference signal is proportional to the number of PHIC groups used to use the reference signal. How to send reference signal. In a system supporting a first user equipment (UE) that recognizes N (M> N) transmit antennas among a total of M transmit antennas and a second user equipment that recognizes the M transmit antennas, a channel quality As a method of feeding back information, Receiving, by the user equipment, a subframe in which a reference signal is mapped from the base station; Feeding back channel quality information between the base station and the user equipment using a reference signal included in the received subframe; In the subframe transmitted by the base station, the Nth to M-1th transmissions are performed to a predetermined number of PHICH groups among PHICH groups used for transmitting ACK / NACK information for an uplink data channel. A reference signal for an antenna port is mapped, and each of the PHICH groups has a predetermined number of Resoruce Element Groups (REGs) including a predetermined number of Resource Elements (REs) concatenated on the frequency domain of the subframe. Included, How to feedback channel quality information. The method of claim 6, The number of PHICH groups is larger than the number of PHICH groups required for transmitting the ACK / NACK information. How to feedback channel quality information. The method of claim 6, wherein the method Receiving the index of the PHICH group in which the reference signal is mapped via a broadcast channel (BCH), How to feedback channel quality information. The method of claim 6, The index of the PHICH group in which the reference signal is mapped is determined through a physical downlink control channel (PDCCH) on the subframe. How to feedback channel quality information. The method of claim 6, A reference signal for the N to M-1 < th > transmit antenna ports is mapped to a predetermined number of CCEs (Control Channel Element) constituting a PDCCH on the subframe, and the CCE is composed of a predetermined number of REGs. The number of CCEs used to map the reference signal is proportional to the number of PHIC groups used to use the reference signal. How to feedback channel quality information.

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