WO2010104321A2

WO2010104321A2 - Method for transmitting a reference signal in a downlink mimo system

Info

Publication number: WO2010104321A2
Application number: PCT/KR2010/001474
Authority: WO
Inventors: 이문일; 구자호; 정재훈; 임빈철; 고현수
Original assignee: 엘지전자 주식회사
Priority date: 2009-03-09
Filing date: 2010-03-09
Publication date: 2010-09-16
Also published as: WO2010104321A3

Abstract

The present invention relates to a method for transmitting a CRS (Common Reference Signal) for channel measurement in a downlink MIMO (Multi Input Multi Output) system which supports first user equipment that supports N transmitting antennas from among M transmitting antennas in total, and second user equipment that supports said M (wherein, M>N) transmitting antennas. The method comprises: a step in which a base station maps the CRS (Common Reference Signal) for said M transmitting antennas to a RE (Resource Element) of a subframe; and a step in which the base station transmits the subframe. The position of the RE to which the CRS for said M transmitting antennas is mapped in the subframe falls within the random even-numbered REs which are consecutively arranged in a frequency domain, excluding the RE to which a DRS (dedicated reference signal) for the first user equipment is mapped.

Description

Method for transmitting a reference signal in a downlink MIMO system

The present invention relates to a method for efficiently providing a reference signal in an environment in which an antenna is added to an existing system in a multiple antenna (MIMO) communication system.

LTE physical structure

^{3GPP (3 rd Generation Project Partnership)} LTE (Long Term Evolution) is a FDD (Frequency Division Duplex) can be applied to type 1 (type 1) the radio frame structure (Radio Frame Structure) and TDD (Time Division Duplex) possible type 2 applied to the It supports the Radio 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.

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.

4 shows an LTE uplink slot structure. As shown in FIG. 8, a signal transmitted in each slot is

Subcarriers

It may be depicted by a resource grid consisting of OFDM symbols. here,

Represents the number of RBs in the uplink,

Represents the number of subcarriers constituting one RB,

Denotes the number of OFDM symbols in one uplink slot.

A resource element 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.

5 is a diagram illustrating a structure of a downlink subframe. In FIG. 5, at most three OFDM symbols located at the front of the first slot in one subframe correspond to the control region allocated to the control channel. The remaining OFDM symbols correspond to data regions allocated to a physical downlink shared channel (PDSCH). Examples of downlink control channels used in 3GPP LTE include a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), and a physical hybrid ARQ indicator channel (PHICH).

Definition of Multiple Antenna (MIMO) Technology

MIMO stands for Multiple-Input Multiple-Output, and it is a method that can improve the transmission / reception data efficiency by adopting multiple transmission antennas and multiple reception antennas, away from the use of one transmission antenna and one reception antenna. . That is, a technique of increasing capacity or improving performance by using multiple antennas in a transmitter or receiver in a wireless communication system. MIMO will be referred to herein as multiple antennas.

Multi-antenna technology is an application of a technique of gathering and completing fragmented pieces of data received from multiple antennas without relying on a single antenna path to receive a message. The multi-antenna technology is a next generation mobile communication technology that can be widely used in a mobile communication terminal and a repeater because it can improve the data transmission speed in a specific range or increase the system range for a specific data transmission speed. The technology is attracting attention as a next generation technology capable of overcoming the transmission limitation of mobile communication, which has reached a limit situation due to the expansion of data communication.

6 is a configuration diagram of a general multiple antenna (MIMO) communication system. As shown in FIG. 6, when the number of transmitting antennas is increased to N _{T and the} number of receiving antennas is increased to N _R at the same time, unlike a case where only a plurality of antennas are used in a transmitter or a receiver, the number of channels is theoretically proportional to the number of antennas. The transmission capacity is increased. Therefore, it is possible to improve the transmission rate and to significantly improve the frequency efficiency. According to the increase in channel transmission capacity, theoretically, the maximum transmission rate when using one antenna is

Increase rate of the following equation (1)

Can be multiplied by

Equation 1

For example, in a MIMO communication system using four transmit antennas and four receive antennas, a theoretical transmission rate of four times can be obtained for a single antenna system. Since the theoretical capacity increase of the multi-antenna system was proved in the mid-90s, various technologies have been actively studied to lead to substantial data rate improvement. Some of these technologies have already been developed for 3G mobile communication and next generation WLAN. Is reflected in the various standards of wireless communication.

The research trends related to multi-antennas to date include information theory aspects related to calculation of multi-antenna communication capacity in various channel environments and multi-access environments, research on wireless channel measurement and model derivation of multi-antenna systems, and improvement of transmission reliability and transmission rate. Active research is being conducted from various viewpoints, such as the study of space-time signal processing technology.

UE-specific reference signal allocation scheme in 3GPP LTE downlink system

Looking at the structure of a radio frame applicable to FDD among the radio frame structures supported by 3GPP LTE described above in detail, one frame is transmitted at a time of 10 msec. The frame is divided into 10 subframes composed of 1 msec intervals. It is composed. 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.

FIG. 7 is a diagram illustrating a downlink reference signal structure dedicated to a terminal in a subframe in which 1TTI (transmission time interval) uses a normal cyclic prefix (normal CP) having 14 OFDM symbols. In FIG. 7, R5 represents a UE-specific reference signal.

Denotes the position of the OFDM symbol on the subframe.

FIG. 8 is a diagram illustrating a structure of a downlink reference signal dedicated to a terminal in a subframe in which 1TTI uses an extended cyclic prefix (extended CP) having 12 OFDM symbols.

9 is a diagram illustrating a structure of a CRS according to an antenna port. As shown in FIG. 9, the CRS pattern for each antenna port is orthogonal to each other in a time and frequency domain. If the LTE system has one antenna port, only the CRS for antenna port 0 in FIG. 3 is used. Also, if 4Tx MIMO transmission is applied to the LTE downlink, CRSs for antenna ports 0 to 3 are used simultaneously. In this case, R0 represents a pilot symbol for transmission antenna 0, R1 represents a transmission antenna 1, R2 represents a transmission antenna 2 and R3 represents a pilot symbol for transmission antenna 3, respectively. A subcarrier using a pilot symbol of each transmit antenna does not transmit a signal to eliminate interference with all other transmit antennas except the transmit antenna transmitting the pilot symbol.

Meanwhile, by multiplying a predetermined sequence (eg, Pseudo-random (PN), m-sequence, etc.) by a downlink reference signal for each cell, the receiver reduces the interference of a signal of a pilot symbol received from an adjacent cell at a receiver and estimates a channel. It can improve performance. The PN sequence is applied in units of OFDM symbols in one subframe, and different PN sequences may be applied according to a cell ID, a subframe number, an OFDM symbol position, and an ID of a UE.

As an example, in the structure of the 4Tx pilot symbol of FIG. 9, it can be seen that two pilot symbols of one transmission antenna are used for a specific OFDM symbol including a pilot symbol. In the case of 3GPP LTE system, there are systems composed of several types of bandwidths, which range from 6 RB (Resource Block) to 110 RB. Therefore, the number of pilot symbols of one transmit antenna in one OFDM symbol including pilot symbols

The sequence used by multiplying the downlink reference signal for each cell is

It must have a length of. At this time,

Denotes the number of RBs according to the bandwidth, and the sequence may use a binary sequence or a complex sequence. Equation 2 below

Shows one example of a complex sequence.

Equation 2

In Equation 2 above

Since is the number of RBs corresponding to the maximum bandwidth, it can be determined as 110 according to the above description.

May be defined as a Gold sequence of length-31 as a PN sequence. In case of the UE-specific downlink reference signal, Equation 2 may be expressed as Equation 3 below.

Equation 3

Equation 3 above,

Denotes the number of RBs corresponding to downlink data allocated by a specific terminal. Therefore, the length of the sequence may vary according to the amount of UE assignment.

Meanwhile, the LTE-Advanced (LTE-A) system supports a larger number of transmit antennas in the existing LTE system. Hereinafter, a terminal supported by the new LTE-A system is called an LTE-A terminal and is supported by the existing LTE system. A terminal to be referred to as an LTE terminal.

When the base station transmits a reference signal to the LTE-A terminal, since the terminal operating in the existing LTE system recognizes the reference signal as data, the reference signal transmitted to the LTE-A terminal is the performance of the existing LTE terminal Will affect. Therefore, when the base station transmits a reference signal to the LTE-A terminal, a method of designing a reference signal that can minimize the impact on the performance of the LTE terminal is required.

The problem to be solved by the present invention is to provide a reference signal design method for the LTE-A terminal to minimize the impact on the performance of the existing LTE terminal.

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

To solve the above problems, a first user device supporting N transmit antennas out of a total of M transmit antennas and a second user device supporting M (M> N) transmit antennas according to an aspect of the present invention. In a downlink MIMO system, a method of transmitting a common reference signal (RS) for channel measurement may be performed by a base station in a common reference signal for the M transmit antennas. Mapping a Signal (CRS) to a Resource Element (RE) on a subframe; And transmitting the subframe, wherein the location of the RE where the CRSs for the M transmission antennas are mapped in the subframe is mapped by a dedicated dedicated reference signal (DRS) for the first user. Any even number of REs contiguous on the frequency axis except for REs.

In the subframe, the RE included in the OFDM symbol in which the reference signals for the N transmit antennas are mapped may be excluded from the RE in which the CRSs for the M transmit antennas are mapped.

In the subframe, an RE included in an OFDM symbol in which a synchronization channel (SCH) for the N transmission antennas is transmitted may be excluded from an RE in which CRSs of the M transmission antennas are mapped.

In the subframe, an RE included in an OFDM symbol in which a broadcasting channel (BCH) for the N transmission antennas is transmitted may be excluded from an RE in which CRSs of the M transmission antennas are mapped.

The arbitrary even number may be any one of 2, 4, 6, and 8.

M and N may be 8 and 4, respectively.

According to another aspect of the present invention, a downlink MIMO supporting a first user device supporting N transmit antennas among a total of M transmit antennas and a second user device supporting M (M> N) transmit antennas is provided. In an input multi output) system, a channel information feedback method includes: receiving, from a base station, a subframe on which a common reference signal (CRS) for the M transmit antennas is mapped; Generating channel information using the CRS included in the subframe; And feeding back the generated channel information, wherein a location of a resource element (RE) in which CRSs for the M transmission antennas are mapped in the subframe is a user-specific reference signal for the first user. (Dedicated Reference Signal (DRS)) is any even number of REs contiguous on the frequency axis except for the RE to which it maps.

The arbitrary even number may be any one of 2, 4, 6, and 8.

M and N may be 8 and 4, respectively.

According to an embodiment of the present invention, the reference signal can be efficiently transmitted to both the user device of the existing system and the user device newly added to the system. In particular, the influence on the performance of the existing LTE terminal by the reference signal transmitted to the LTE-A terminal can be minimized.

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.

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 shows an LTE uplink slot structure.

5 is a diagram illustrating a structure of a downlink subframe.

6 is a configuration diagram of a general multiple antenna (MIMO) communication system.

FIG. 7 is a diagram illustrating a downlink reference signal structure dedicated to a UE in a subframe in which 1TTI uses a normal cyclic prefix (normal CP) having 14 OFDM symbols.

9 is a diagram illustrating a structure of a CRS according to an antenna port.

10 illustrates the structure of a multi-antenna transmitter when precoded RS is used.

11 is a diagram illustrating the structure of a multi-antenna transmitter when CRS is used.

12 is a diagram illustrating an LTE radio frame structure.

FIG. 13 illustrates an example of an RS structure when a CRS and a DRS for a single stream beamforming are used at the same time.

FIG. 14 is a diagram illustrating a resource element for transmitting LTE-A C_port # 0 to 7 to one resource block (RB) in a normal cyclic prefix (normal CP) according to an embodiment of the present invention; Resource Element) location.

FIG. 15 is a diagram illustrating a location of an RE capable of transmitting LTE-A C_ports # 0 to 7 except for an RE that may be affected by interference from another cell.

FIG. 16 is a diagram illustrating a location of an RE capable of transmitting LTE-A C_port # 0 to 7 except for the SCH region in FIG. 15.

FIG. 17 is a diagram illustrating a location of an RE capable of transmitting LTE-A C_port # 0 to 7 except for the BCH region in FIG. 16.

18 is a diagram illustrating a case in which a plurality of component carriers are used for a terminal when each component carrier is regarded as an independent physical or LTE channel according to an embodiment of the present invention.

19 is a block diagram illustrating a configuration of a device applicable to a base station and a user equipment and capable of performing the above-described method.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description set forth below in conjunction with the appended drawings is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details to assist in a thorough understanding of the present invention. However, those skilled in the art will appreciate that the invention may be practiced without these specific details. For example, the following description will focus on certain terms, but need not be limited to these terms and may refer to the same meaning even when referred to as any term. In addition, the same or similar components throughout the present specification will be described using the same reference numerals.

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 type of the reference signal will be described before explaining the structure of the reference signal.

A dedicated reference signal (DRS) is used only for a specific terminal and no other terminal can use the DRS. The DRS is mainly used for demodulation, and may be classified into a precoded RS and a non-precoded RS. 10 illustrates the structure of a multi-antenna transmitter when precoded RS is used. The precoded RS is precoded with the same precoding as the precoding used for data symbols. In FIG. 10, Nt represents the number of physical antennas, and K represents a spatial multiplexing rate. K is less than or equal to Nt.

As shown in FIG. 10, K streams may be allocated to one terminal or multiple terminals. If a plurality of terminals share K streams, 1 to K terminals may simultaneously share the same time and frequency resources.

The common reference signal (CRS) may be used for demodulation or measurement, and all terminals share a CRS in one cell. In this case, the measurement includes the behavior of all terminals including channel state information feedback, synchronization, and the like. 11 is a diagram illustrating the structure of a multi-antenna transmitter when CRS is used. As shown in FIG. 11, the RS is transmitted to the antenna as it is without being affected by the multiple antenna scheme. Therefore, Nt RSs are always transmitted regardless of the spatial multiplexing rate of the terminal. However, if there is a cell specific precoder in a particular system, the precoder is considered virtualization and not precoder. The RS sequences should be transmitted for all antenna ports regardless of the number of streams.

In order to support 8Tx MIMO transmission in LTE-Advanced (LTE-A) downlink, an RS structure must be designed so that the LTE terminal supports the LTE-A terminal together with the LTE-A terminal. In particular, the RS structure for the LTE-A terminal should be designed in view of performance, RS overhead, and backward compatibility with the LTE terminal.

Hereinafter, the optimum design of the RS from the above point of view will be described.

12 is a diagram illustrating an LTE radio frame structure. As shown in FIG. 12, one radio frame consists of ten subframes and one subframe consists of 1 ms. In the LTE system, CRSs of 0th transmission antennas, 0th and 1st transmission antennas, and 0th to 3rd transmission antennas are transmitted in all transmission antennas according to the number of transmission antennas, respectively, and the CRS is used for measurement or demodulation purposes. Can be used. However, since the CRS does not include terminal specific information such as PMI (Precoding Matrix Index) and rank, the information must be transmitted through a control channel.

FIG. 13 illustrates an example of an RS structure when a CRS and a DRS for a single stream beamforming are used at the same time. CRS may be applied as shown in FIG. 13 to improve performance using non-coddebook based precoding. However, since DRS supports single stream transmission in LTE, CRS should be used for larger rank transmission. In FIG. 13, for example, even if the CRS supports 4Tx, there may be another case where it is possible to transmit DRS such as 2Tx and 1Tx. In FIG. 13, DRS means the same as a User Equipment-Specific Reference Signal (UE-specific RS), and R5 means DRS of antenna port 5 in the LTE system.

As described above, in the LTE system, antenna ports are defined from 0 to 5, antenna ports 0 to 3 are defined for the CRS, and antenna port 4 is an antenna port for a multi-media broadcast over a single frequency network (MBSFN) subframe. And another type of RS structure for antenna port 4 is defined. Therefore, when a combination of CRS and DRS is introduced for measurement and demodulation purposes in the LTE-A system, DRS antenna ports 0 to 7 and CRS antenna ports 0 to 7 should be further defined.

Hereinafter, antenna ports 0 to 5 of the LTE system are for convenience, LTE ports # 0 to 5, and CRS and DRS of the LTE-A system are divided into LTE-A C_port # 0 to 7 and D_port # 0 to 7, respectively. Shall be. In addition, the fact that LTE port # 5 and LTE-A D_port # 0 are the same means that the position of RS for each antenna port is the same.

First, a method of transmitting LTE-A C_port # 0 to 7 through PDSCH (Physical Downlink Shared Channel) will be described. LTE-A C_port # 0 ~ 7 should be transmitted for measurement in LTE-A system.

A certain number of LTE-A CRS can be shared with the LTE antenna port. For example, LTE-A C_port # 0 may be the same as LTE antenna port 0. One method of transmitting the LTE-A C_port # 0-7 is a method of allowing the transmission of the LTE-A C_port # 0-7 to the PDSCH region regardless of whether the LTE-A C_port # 0 ~ 7 is allocated. If the CRS is transmitted in the PDSCH region allocated to the LTE terminal, since the CRS is regarded as interference to the LTE terminal, performance of the LTE terminal may be degraded. Therefore, LTE-A C_port # 0 ~ 7 should be properly designed so as not to degrade the performance of the LTE terminal.

In FIG. 14, it is assumed that the first three OFDM symbols are used for physical downlink control channel (PDCCH) transmission and four antenna ports are used. However, the possible positions are the same regardless of the number of antenna ports for the LTE terminal. In this case, as shown in FIG. 14, a total of 104 RE locations for transmission of LTE-A C_port # 0-7 may be defined. In FIG. 14, various numbers of REs may be separately provided for transmission of LTE-A C_port # 0 to 7 as shown in Table 1 below.

Table 1

	Reserved RE sets for LTE-A C_port in figure 14
2 REs	Any of two possible RE position
4 REs	Any of four possible RE position
6 REs	Any of six possible RE position
8 REs	Any of eight possible RE position

In order to transmit LTE-A C_port # 0-7, an even number of REs are used as shown in Table 1 in order not to deteriorate the performance of the LTE terminal due to Space Frequency Block Coding (SFBC).

In FIG. 14, the location of an RE capable of transmitting LTE-A C_port # 0-7 in an OFDM symbol including RSs (R0 to R3) of the LTE system may be affected by interference from other cells. Accordingly, the location of the RE capable of transmitting LTE-A C_port # 0-7 in the OFDM symbol including RS (R0 to R3) of the LTE system may transmit LTE-A C_port # 0-7 shown in Table 1 above. May be excluded from a candidate RE. FIG. 15 is a diagram illustrating a location of an RE capable of transmitting LTE-A C_ports # 0 to 7 except for an RE that may be affected by interference from another cell.

In FIG. 15, it is assumed that the first three OFDM symbols are used for physical downlink control channel (PDCCH) transmission and four antenna ports are used. In this case, 72 RE locations for transmission of LTE-A C_port # 0-7 may be defined as shown in FIG. 15. In FIG. 15, various numbers of REs for transmitting LTE-A C_port # 0 to 7 may be separately provided as shown in Table 2 below.

TABLE 2

	Reserved RE sets for LTE-A C_port in figure 15
2 REs	{10 + n, 16 + n}, {40 + n, 46 + n}, {61 + n, 67 + n} where {1 + n, 6 + n}, {10 + n, 15 + n}, where {10 + n, 14 + n}, {40 + n, 44 + n}, where {10 + n, 16 + n}, {31 + n, 36 + n}, where {10 + n, 14 + n}, where {19 + n, 24 + n}, where
4 REs	{1 + n, 5 + n, 22 + k, 25 + k}, where and {1 + n, 6 + n, 22 + k, 26 + k}, where and {1 + n, 5 + n, 10 + k, 15 + k}, where and {1 + n, 5 + n, 31 + k, 35 + k}, where and {1 + n, 5 + n, 40 + k, 46 + k}, where and {10 + n, 15 + n, 10 + k, 15 + k}, where and {10 + n, 13 + n, 16 + n, 19 + n}, where
6 REs	{1 + n, 4 + n, 7 + n, 10 + k, 13 + k, 16 + k}, where where and {1 + n, 4 + n, 7 + n, 19 + k, 22 + k, 25 + k}, where where and {10 + n, 13 + n, 16 + n, 19 + k, 22 + k, 25 + k}, where where and {1 + n, 4 + n, 10 + k, 13 + k, 19 + m, 23 + m}, where where , and {1 + n, 6 + n, 11 + k, 15 + k, 20 + m, 26 + m}, where where , and
8 REs	{1 + n, 5 + n, 10 + k, 16 + k, 24 + m, 29 + m, 32 + j, 36 + j}, where , , and {1 + n, 5 + n, 10 + k, 16 + k, 24 + m, 29 + m, 40 + j, 46 + j}, where , , and {1 + n, 5 + n, 10 + k, 16 + k, 24 + m, 29 + m, 54 + j, 59 + j}, where , , and {1 + n, 5 + n, 10 + k, 16 + k, 24 + m, 29 + m, 64 + j, 70 + j}, where , , and

If the LTE-A CRS is transmitted through a subframe including a synchronization channel (SCH), another restriction may be added to avoid collision of the LTE-A CRS and the SCH. That is, the LTE-A CRS may not be allocated to the OFDM symbol including the SCH. This restriction can be accomplished in two ways. For example, when the SCH is transmitted in a subframe, the LTE-A CRS located in the SCH region may be punched or the LTE-A CRS pattern may be designed to avoid the SCH region at all times. FIG. 16 is a diagram illustrating a location of an RE capable of transmitting LTE-A C_port # 0 to 7 except for the SCH region in FIG. 15. When the LTE-A CRS pattern is designed to always avoid the SCH region, the location of the RE for transmitting the LTE-A C_port # 0 to 7 may be defined as shown in FIG. 16.

In FIG. 16, it is assumed that the first three OFDM symbols are used for physical downlink control channel (PDCCH) transmission and four antenna ports are used. In this case, 51 RE positions for transmission of LTE-A C_port # 0-7 may be defined as shown in FIG. 16. In FIG. 16, various numbers of REs for transmitting LTE-A C_port # 0 to 7 may be separately provided as shown in Table 3 below.

TABLE 3

	Reserved RE sets for C_port in figure 10
2 REs	{1+ n , 5+ n }, {10+ n , 14+ n }, where {1+ n , 6+ n }, {10+ n , 15+ n }, where {10+ n , 14+ n }, {31+ n , 35+ n }, where {10+ n , 15+ n }, {31+ n , 36+ n }, where {19+ n , 25+ n }, where {19+ n , 24+ n }, where
4 REs	{1+ n , 5+ n , 10+ k , 14+ k }, where and {1+ n , 6+ n , 10+ k , 15+ k }, where and {1+ n , 5+ n , 10+ k , 15+ k }, where and {1+ n , 5+ n , 19+ k , 25+ k }, where and {1+ n , 5+ n , 19+ k , 24+ k }, where and {1+ n , 6+ n , 10+ k , 15+ k }, where and {1+ n , 6+ n , 19+ k , 25+ k }, where and {1+ n , 6+ n , 19+ k , 24+ k }, where and {10+ n , 14+ n , 19+ k , 25+ k }, where and {10+ n , 14+ n , 19+ k , 24+ k }, where and {10+ n , 15+ n , 10+ k , 15+ k }, where and {10+ n , 15+ n , 19+ k , 25+ k }, where and {10+ n , 15+ n , 19+ k , 24+ k }, where and {10+ n , 14+ n , 19+ k , 25+ k }, where and {19+ n, 22+ n, 25+ n, 28+ n}, where {40+ n , 43+ n , 46+ n , 49+ n }, where
6 REs	{1+ n , 4+ n , 7+ n , 10+ k , 13+ k , 16+ k }, where where and {1+ n , 4+ n , 7+ n , 19+ k , 22+ k , 25+ k }, where where and {10+ n , 13+ n , 16+ n , 19+ k , 22+ k , 25+ k }, where where and {1+ n , 4+ n , 10+ k , 13+ k , 19+ m , 23+ m }, where where , and {1+ n , 6+ n , 11+ k , 15+ k , 20+ m , 26+ m }, where where , and
8 REs	{1+ n , 5+ n , 10+ k , 16+ k , 19+ m , 25+ m, 40 + j, 46 + j }, where , , and {1+ n , 5+ n , 12+ k , 16+ k , 19+ m , 25+ m, 33 + j, 38 + j }, where , , and {10+ n , 15+ n , 19+ k , 25+ k, 32 + m, 36 + m, 40 + j, 46 + j }, where , , and {19+ n, 22+ n, 25+ n, 28+ n, 40+ k, 43+ k, 46 + k, 49 + k}, where and

If the LTE-A CRS is transmitted through a subframe including a broadcasting channel (BCH), another restriction may be added to avoid collision of the LTE-A CRS and the BCH. That is, the LTE-A CRS may not be allocated to the OFDM symbol including the BCH. FIG. 17 is a diagram illustrating a location of an RE capable of transmitting LTE-A C_port # 0 to 7 except for the BCH region in FIG. 16.

In FIG. 17, it is assumed that the first three OFDM symbols are used for physical downlink control channel (PDCCH) transmission and four antenna ports are used. In this case, 30 RE locations for transmission of LTE-A C_port # 0-7 may be defined as shown in FIG. 17. In FIG. 17, various numbers of REs for transmitting LTE-A C_port # 0 to 7 may be separately provided as shown in Table 4 below.

Table 4

	Reserved RE sets for C_port in figure 11
2 REs	{1+ n , 5+ n }, {10+ n , 14+ n }, where {1+ n , 6+ n }, {10+ n , 15+ n }, where {19+ n , 25+ n }, where {19+ n , 24+ n }, where
4 REs	{1+ n , 5+ n , 10+ k , 14+ k }, where and {1+ n , 6+ n , 10+ k , 15+ k }, where and {1+ n , 5+ n , 10+ k , 15+ k }, where and {1+ n , 5+ n , 19+ k , 25+ k }, where and {1+ n , 5+ n , 19+ k , 24+ k }, where and {1+ n , 6+ n , 10+ k , 15+ k }, where and {1+ n , 6+ n , 19+ k , 25+ k }, where and {1+ n , 6+ n , 19+ k , 24+ k }, where and {10+ n , 14+ n , 19+ k , 25+ k }, where and {10+ n , 14+ n , 19+ k , 24+ k }, where and {10+ n , 15+ n , 19+ k , 25+ k }, where and {10+ n , 15+ n , 19+ k , 24+ k }, where and {19+ n, 22+ n, 25+ n, 28+ n}, where
6 REs	{1+ n , 4+ n , 7+ n , 10+ k , 13+ k , 16+ k }, where where and {1+ n , 4+ n , 7+ n , 19+ k , 22+ k , 25+ k }, where where and {10+ n , 13+ n , 16+ n , 19+ k , 22+ k , 25+ k }, where where and {1+ n , 4+ n , 10+ k , 13+ k , 19+ m , 23+ m }, where where , and {1+ n , 6+ n , 11+ k , 15+ k , 20+ m , 26+ m }, where where , and
8 REs	{1+ n , 5+ n , 10+ k , 14+ k , 19+ m , 22+ m, 25 + m, 28 + m }, where , and {1+ n , 4+ n , 10+ k , 13+ k , 19+ m , 22+ m, 25 + m, 28 + m }, where , and

Hereinafter, the CRS pattern that can be determined by the base station will be described. LTE-A CRS overhead and pattern may be determined by the base station in the cell, time and component carrier (Component Carrier). The component carrier CC refers to an element carrier constituting a multicarrier. That is, the plurality of component carriers configure a multicarrier through carrier aggregation. The component carrier includes a plurality of lower bands. In this case, when the term multicarrier is replaced with the term full band, the component carrier may be replaced with a subband and the lower band may be replaced with a partial band. Carrier aggregation is also referred to as bandwidth aggregation. Carrier aggregation is to expand the bandwidth by collecting a plurality of carriers in order to increase the data rate (data rate). For example, in LTE system, one carrier is 20MHz, and LTE-A system gathers five 20Mhz carriers to expand the bandwidth to 100MHz. And, carrier aggregation includes aggregating carriers in different frequency bands.

In this case, the plurality of CRS patterns may be predefined and selected by the base station. Or it may be fully defined by the base station. 18 is a diagram illustrating a case in which a plurality of component carriers are used for a terminal when each component carrier is regarded as an independent physical or LTE channel according to an embodiment of the present invention. In FIG. 18, each component carrier (indicated by PHY # in FIG. 18) or a group of component carriers has a different number of space frequency block code (SFBC) blocks per RB, and each of the component carriers or component carrier groups Is configured by the base station.

On the other hand, with respect to the design of the LTE-A DRS, LTE-A DRS should be mutually orthogonal (orthogonal) with the LTE-A CRS. In addition, since LTE-A DRS does not degrade the performance of the LTE terminal, LTE-A D_port # 0-7 need not be designed based on the SFBC block.

19 is a block diagram illustrating a configuration of a device applicable to a base station and a user equipment and capable of performing the above-described method. As shown in FIG. 25, the device 100 includes a processing unit 101, a memory unit 102, a radio frequency (RF) unit 103, a display unit 104, and a user interface unit 105. . The layer of physical interface protocol is performed in the processing unit 101. The processing unit 101 provides a control plane and a user plane. The function of each layer may be performed in the processing unit 101. The memory unit 102 is electrically connected to the processing unit 101 and stores an operating system, an application, and a general file. If the device 100 is a user device, the display unit 104 may display a variety of information, and may be implemented by using a known liquid crystal display (LCD), an organic light emitting diode (OLED), or the like. The user interface unit 105 can be configured in combination with known user interfaces such as keypads, touch screens, and the like. The RF unit 103 is electrically connected to the processing unit 101 and transmits or receives a radio signal.

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 embodied 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 components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. 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 the present invention, a user equipment (UE) may be replaced with terms such as a mobile station (MS), a subscriber station (SS), a mobile subscriber station (MSS), or a mobile terminal.

Meanwhile, the UE of the present invention includes a PDA (Personal Digital Assistant), a cellular phone, a Personal Communication Service (PCS) phone, a Global System for Mobile (GSM) phone, a Wideband CDMA (WCDMA) phone, a Mobile Broadband System (MBS) phone, and the like. Can be used.

Embodiments of the invention may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

In the case of a hardware implementation, the method according to embodiments 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). Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function 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.

The invention can be embodied in other specific forms without departing from the spirit and essential features 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. It is also possible to form embodiments by combining claims that do not have an explicit citation in the claims or to include them 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.

Claims

In a downlink multi-input multi-output (MIMO) system supporting a first user equipment supporting N transmit antennas out of a total of M transmit antennas and a second user equipment supporting M (M> N) transmit antennas. As a method of transmitting a common reference signal (RS) for channel measurement,

Mapping, at a base station, a common reference signal (CRS) for the M transmit antennas to a resource element (RE) on a subframe; And

Transmitting the subframe;

The position of the RE where the CRSs are mapped to the M transmit antennas in the subframe may be any consecutive on the frequency axis except for the RE where a dedicated dedicated reference signal (DRS) for the first user is mapped. Even number of REs,

How to send reference signal.
The method of claim 1,

In the subframe, an RE included in an OFDM symbol in which reference signals for the N transmit antennas are mapped is excluded from an RE in which CRSs for the M transmit antennas are mapped.

How to send reference signal.
The method of claim 2,

In the subframe, an RE included in an OFDM symbol in which a synchronization channel (SCH) for the N transmit antennas is transmitted is excluded from an RE in which CRSs for the M transmit antennas are mapped.

How to send reference signal.
The method of claim 3,

In the subframe, an RE included in an OFDM symbol in which a broadcasting channel (BCH) for the N transmission antennas is transmitted is excluded from an RE in which CRSs of the M transmission antennas are mapped.

How to send reference signal.
The method of claim 1,

The arbitrary even number is any one of 2, 4, 6, and 8

How to send reference signal.
The method of claim 1,

M and N are 8 and 4, respectively

How to send reference signal.
In a downlink multi-input multi-output (MIMO) system supporting a first user equipment supporting N transmit antennas out of a total of M transmit antennas and a second user equipment supporting M (M> N) transmit antennas. As a channel information feedback method,

Receiving, from a base station, on a subframe in which a common reference signal (CRS) for the M transmit antennas is mapped;

Generating channel information using the CRS included in the subframe; And

Feeding back the generated channel information;

The location of a resource element (RE) in which CRSs of the M transmission antennas are mapped in the subframe is a frequency other than an RE in which a dedicated reference signal (DRS) for the first user is mapped. Any even number of REs contiguous on the axis,

Channel information feedback method.
The method of claim 7, wherein

In the subframe, an RE included in an OFDM symbol in which reference signals for the N transmit antennas are mapped is excluded from an RE in which CRSs for the M transmit antennas are mapped.

Channel information feedback method.
The method of claim 8,

In the subframe, an RE included in an OFDM symbol in which a synchronization channel (SCH) for the N transmit antennas is transmitted is excluded from an RE in which CRSs for the M transmit antennas are mapped.

Channel information feedback method.
The method of claim 9,

In the subframe, an RE included in an OFDM symbol in which a broadcasting channel (BCH) for the N transmission antennas is transmitted is excluded from an RE in which CRSs of the M transmission antennas are mapped.

Channel information feedback method.
The method of claim 7, wherein

The arbitrary even number is any one of 2, 4, 6, and 8,

Channel information feedback method.
The method of claim 7, wherein

M and N are 8 and 4, respectively

Channel information feedback method.