KR101641956B1 - METHOD OF CoMP REFERENCE SIGNAL TRANSMITTING AND RECEIVING IN THE MULTIPLE-CELL SITUATION - Google Patents

Abstract

A channel estimation method using a CoMP reference signal in a multi-cell environment is disclosed. In the reception of the CoMP reference signal, the UE receives a CoMP reference signal to which an orthogonal code orthogonal to each cell is applied, from each cell that performs Cooperative Multi-Point (CoMP) operation. In the channel estimation step, the UE estimates a channel of each cell performing the CoMP operation using the CoMP reference signal. In the channel status feedback information transmission step, the UE transmits channel status feedback information to each of the cells.

CoMP reference signal, multi-cell, MIMO

Description

TECHNICAL FIELD [0001] The present invention relates to a CoMP reference signal transmission method and a CoMP reference signal transmission / reception method in a multi-

The present invention relates to a method of transmitting and receiving a reference signal, and more particularly, to a method of transmitting and receiving a CoMP reference signal from each cell that performs Cooperative Multi-Point (CoMP) operation in a multi-cell environment.

Recently, a multiple input multiple output (MIMO) system has attracted attention as a broadband wireless mobile communication technology. A MIMO system refers to a system that increases data communication efficiency by using a plurality of antennas. The MIMO system can be implemented using a MIMO scheme such as a spatial multiplexing scheme and a spatial diversity scheme according to the same data transmission.

Spatial multiplexing refers to a method of transmitting data at high speed without increasing the bandwidth of the system by simultaneously transmitting different data through a plurality of transmission antennas. The spatial diversity scheme refers to a scheme in which transmission diversity can be achieved by transmitting the same data in a plurality of transmission antennas. One example of such a space diversity technique is space time channel coding.

In addition, the MIMO technique can be divided into an open loop method and a closed loop method depending on whether feedback of channel information from a receiving side to a transmitting side is performed. In the open-loop method, information is transmitted in parallel at the transmitting end. In the receiving end, a blast (BLAST) capable of detecting signals by repeatedly using ZF (Zero Forcing) and MMSE (Minimum Mean Square Error) And a space-time trellis code (STTC) scheme in which transmission diversity and coding gain can be obtained by using a new space area. And a closed antenna scheme is a TxAA (Transmit Antenna Array) scheme.

In a wireless channel environment, a fading phenomenon occurs in which the channel state varies irregularly in the time domain and the frequency domain. Therefore, the receiver corrects the received signal using the channel information to recover the data transmitted from the transmitter and to find the correct signal.

A wireless communication system transmits a signal known to both a transmitter and a receiver and detects channel information using a degree of distortion when the signal is transmitted through a channel. The signal is referred to as a reference signal (or a pilot signal) Finding information is called channel estimation. The reference signal does not contain actual data and has a high output. In the case of transmitting / receiving data using multiple antennas, since a channel condition between each transmission antenna and a reception antenna needs to be known, a reference signal exists for each transmission antenna.

A cooperative MIMO system is proposed to reduce inter-cell interference in a multi-cell environment. With a cooperative MIMO system, a terminal can receive data jointly from a multi-cell base-station. Also, each base station can simultaneously support one or more MSs MS1, MS2, ..., MSK using the same frequency resource (Same Radio Frequency Resource) to improve the performance of the system. Also, the base station can perform a space division multiple access (SDMA) method based on channel state information between the base station and the terminal.

In a cooperative MIMO system, a serving base station and one or more cooperative base stations are connected to a scheduler through a backbone network. The scheduler can operate by receiving feedback on channel information about channel states between the MSs MS1, MS2, ..., MSK and the cooperative BSs measured by the BSs BS1, BS2, ..., BSM through the backbone network. For example, the scheduler schedules information for cooperative MIMO operations for a serving base station and one or more cooperative base stations. That is, the scheduler directly directs the cooperative MIMO operation to each base station.

CoMP is proposed to reduce inter-cell interference in a multi-cell environment and improve the performance of a UE at the cell boundary. That is, by using the CoMP system, it is possible to improve the communication performance of a terminal at a cell boundary under a multi-cell environment. For this, accurate channel estimation based on a reference signal (reference signal) from multiple base stations is required.

However, when the number of cells performing CoMP increases, the existing CoMP reference signal becomes shorter in PN (Pseudo Noise) code length in a resource block, and in the case of channel estimation, ), The channel estimation performance is deteriorated. Therefore, a new CoMP reference signal pattern is required for a UE performing a CoMP operation to ensure accurate channel estimation of an adjacent cell.

In addition, the CoMP reference signal for LTE-A (Long Term Evolution-Advanced) has not been defined to date.

SUMMARY OF THE INVENTION The present invention provides a method for receiving a CoMP reference signal in a multi-cell environment.

The technical problems to be solved by the present invention are not limited to the technical problems and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a method for receiving a CoMP reference signal according to the present invention, the method comprising: receiving, from each cell in which the UE performs the CoMP operation, orthogonality between reference signals of each cell performing the CoMP operation; Receiving a CoMP reference signal to which an orthogonal code of a slot unit or a symbol unit is applied; And processing the received CoMP reference signal for each cell performing the CoMP operation, using the orthogonal code applied by the terminal in the slot unit or the symbol unit.

According to an aspect of the present invention, there is provided a method for receiving a CoMP reference signal, the method comprising: receiving orthogonal code resources orthogonal to each other in a slot unit or a symbol unit, Assigning; And transmitting the CoMP reference signal using an orthogonal code resource having orthogonal codes orthogonal to each other in the slot unit or the symbol unit between the base station reference signals.

The method of receiving a CoMP reference signal according to the present invention has various advantages.

First, the accuracy of the channel estimation can be improved by demodulating the CoMP reference signal received from each cell of the UE.

Second, there is an advantage that the communication performance of the UE at the cell boundary can be improved by using the CoMP in the multi-cell environment.

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

Hereinafter, preferred embodiments according to 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 illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details for a better understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. For example, in the following description, certain terms are mainly described, but they need not be limited to these terms, and they may have the same meaning when they are referred to as arbitrary terms. In addition, the same or similar components throughout the present specification will be described using the same reference numerals.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

In order to effectively perform channel estimation at the receiver, the following conditions are required for allocation of the reference signal transmitted from the transmission antenna.

First, since a reference signal is used for channel estimation by a receiver, a reference signal must be allocated so that a receiver can distinguish a reference signal transmitted from a transmission antenna. The reference signal is allocated not to overlap in the time and / or frequency domain for each transmission antenna so that the receiver can distinguish the reference signal. In addition, even if the reference signal is assigned redundantly in the time and / or frequency domain, orthogonality must be obtained in the code domain. For this purpose, the reference signal can use an orthogonal code having excellent autocorrelation or cross-correlation characteristics. For example, Constant Amplitude Zero AutoCorrelation (CAZAC), Walsh code, or the like can be used.

Next, it is preferable that the channel change is as short as possible in the region where the reference signal is located. This is because, if the channel change is large in the region to which the reference signal is allocated, the channel estimation error may increase. And the data around the reference signal is decoded using the channel in the region where the reference signal is located.

The frame may include a plurality of subframes. The subframe includes a plurality of OFDM symbols in the time domain and a plurality of subcarriers in the frequency domain. For example, one subframe may contain 14 or 28 OFDM symbols. When one subframe includes 14 OFDM symbols, for convenience of explanation, 14 OFDM symbols are divided into a first OFDM symbol, a second OFDM symbol, and a second OFDM symbol of a transmission time interval (TTI) ...., the 14th OFDM symbol.

A subframe corresponds to one resource grid defined for each transmission antenna. A Transmission Time Interval (TTI) can be defined as a time when one subframe is transmitted. Each element on the resource grid that constitutes a subframe represents a resource element. For example, the resource element (k, l) corresponds to the kth OFDM symbol and the resource element located in the lth subcarrier.

A method of allocating a reference signal on a resource block includes a method of allocating a reference signal over all bands and a method of allocating a reference signal over a certain band. Compared with the method of allocating all bands over a certain band, a high channel estimation performance can be obtained because the density of the reference signal is high. However, when allocating over some bands, a high data rate can be obtained, but the density of the reference signal may be low and the channel estimation performance may be degraded.

Coordinated Multi-Point (CoMP) system (hereinafter referred to as CoMP system) is a system for improving the throughput of a user at a cell boundary by applying improved MIMO transmission in a multi-cell environment. The CoMP system can reduce inter-cell interference in a multi-cell environment. With the CoMP system, a UE can receive data jointly from a multi-cell base station. In addition, each base station can simultaneously support one or more MSs MS1, MS2,... MSK using the same radio frequency resource, thereby improving the performance of the system. Also, the base station can perform a space division multiple access (SDMA) method based on channel state information between the base station and the terminal.

Hereinafter, a method for a cooperative MIMO system capable of minimizing inter-cell interference in a multi-cell environment will be described, and a method for improving channel estimation performance from multiple base stations will be described. A method for transmitting a reference signal with a preferable reference signal pattern capable of improving channel estimation performance regardless of a reference signal position for performing cooperative multi-point (CoMP) in a multi-cell environment will be described .

Currently, the CoMP reference signal for LTE-A (Long Term Evolution-Advanced) is not defined. Generally, a reference signal for performing CoMP includes a common reference signal (CRS) for use in channel state measurement such as channel state information of multiple cells and a dedicated reference signal for demodulation DRS: Dedicated Reference Signal).

A dedicated reference signal sequence (DRS sequence) that can be used for the CoMP reference signal can be mapped in one resource block, unlike the common reference signal. As an example, a dedicated reference signal sequence of length 12 may be mapped in a resource block. However, when the number of cells performing CoMP increases, the PN code length becomes short in one resource block, and channel estimation performance due to lack of a dispreading sample may be deteriorated in channel estimation. As a method for solving this problem, it may be considered to allocate a CoMP reference signal using an orthogonal code resource.

<Code Resources (Code resources)  Used CoMP  Reference signal assignment (same time And frequency  Area)>

First, it can be considered that a plurality of cells performing CoMP allocate a CoMP reference signal in the same time and frequency domain. A code resource corresponding to the number of CoMP-performing cells can be generated to perform channel estimation. Then, each cell can allocate a CoMP reference signal based on the allocated code resources.

The set of cells performing CoMP can be largely determined by three methods. First, the base station can determine a cell to perform CoMP from the beginning and generate a code resource for the CoMP reference signal. Second, the UE may determine the number of cells performing the CoMP based on a threshold (the base station advertises or a predetermined interference level). Third, the maximum number of cells in which the base station can perform the CoMP may be predetermined, and the number of cells performing the CoMP may be determined based on a predetermined threshold value such as the maximum number of cells and the interference level. In this case, when the number of CoMP cells exceeding the threshold value exceeds the predetermined maximum number of cells, the CoMP set can be configured only for a predetermined maximum number of cells to perform CoMP.

In this manner, the cell determined to perform the CoMP may be composed of intra-eNB cells, cells of the inter base station (inter eNB), or cells belonging to the intra base station and the inter base station. Here, the cells of the intra base station can be defined as cells based on the same base station, and the cells of the inter base station can be defined as cells based on different base stations.

The terminal can know information about what kind of code resources each cell uses by the following method.

First, the serving cell can inform the UE of all information. The serving cell may inform the terminal of the code resource information through a broadcast channel (BCH) or higher layer signaling. In addition, a predefined value can be used to inform the cell ID information that performs CoMP. That is, the code resources can be defined in advance for the cell IDs by allocating the code resources in order from the IDs of the remaining cells except for the serving cell in order, or conversely allocating the code resources in a large order. Therefore, the UE can know the code resource information corresponding to the cell only with the cell ID information.

Second, the serving cell can inform only the number of cells that perform CoMP and its code resource information. The information of the remaining cells performing CoMP excluding the serving cell can be identified in a predetermined order. In this case, the terminal does not need to know the cell ID information of the remaining cells, and can distinguish the adjacent cells performing the CoMP according to the determined ID. The serving cell can identify the ID information of the remaining cells through a predetermined ID.

Third, there may be a super cell that manages cells performing CoMP, and a super cell may broadcast information capable of distinguishing cells performing CoMP to the UE.

In the case of CoMP for soft combining, a reference signal having the same sequence can be assigned to the same time and frequency domain. In this case, CoMP reference signal allocation using code resources is not performed. On the other hand, in the case of other CoMP scenarios except for soft combining, a code resource (for example, transmit diversity (TxD), spatial multiplexing (SM), precoding matrix indication And allocates CoMP reference signals to facilitate multi-cell based channel estimation. When a CoMP reference signal of a multi-cell performing CoMP is allocated to the same time and frequency domain even if the same sequence is used or another sequence is used, a CoMP reference signal is allocated and transmitted using a code resource, Channel estimation.

The code resources may include all orthogonal codes such as Walsh / Hadamard or Discrete Fourier transform orthogonal codes (Circular shift).

In the present invention, one subframe may be composed of two slots or four slots having seven OFDM symbols in each slot. And one subframe may have a transmission time interval (TTI) of 1 msec. However, the present invention is not limited thereto, but the subframe and the TTI may be implemented in various forms.

1. If each cell is the same PN ( Pseudo Noise ) Using the code CoMP  When a reference signal is allocated

Now consider the case where each cell that performs CoMP generates the same PN code for the CoMP reference signal and assigns it to the same time and frequency domain.

First, suppose there are two cells. Let us consider the following 2 × 2 Walsh-Adamar matrix equation.

If you define a code resource in each column order, then code 1 = {1, 1}, code 2 = {1, -1}. For example, in code 2, 1 and -1 correspond to code resource elements, respectively.

At this time, cell 1 is assigned code 1 for transmission of the CoMP reference signal, and cell 2 is assigned code 2. Each cell can assign a reference signal on a time or frequency axis based on the allocated code resources. In this example, a reference signal is allocated on the time axis for transmission.

FIG. 1 is a diagram illustrating an example of a reference signal pattern for allocating a reference signal in a slot unit by using a code resource in two multiple cells. FIG. FIG. 8 is a diagram illustrating an example of a reference signal pattern for allocation in symbol units. FIG.

Referring to FIG. 1, a cell 1 allocated a code 1 can allocate R0 in the first slot and allocate R0 in the second slot. Alternatively, cell 2 assigned code 2 may allocate R0 to the first slot and -R0 to the second slot.

Here, R0 and -R0 indicate the positions of reference signals, and -R0 indicates reference signals to which phase shift or the like is applied to R0 by code resources. R0 can be mapped with a reference signal sequence length assigned to one resource block or one symbol.

Referring back to FIG. 1, it can be seen that R0, which is one resource block length 4, is mapped on a resource block basis. When the cell 1 and the cell 2 allocate a reference signal by using a code resource and transmit it by a slot unit, the reference signal can be transmitted until two slots are transmitted.

The terminal receives the reference signal through the channel h1 formed with cell 1 and the channel h2 formed with cell 2. As an example, the terminal may receive (h1 + h2) · R0 in the first transmission by the code resource and (h1-h2) · R0 in the second transmission. At this time, the terminal can estimate each channel using the received signal. As another example, the UE can obtain channel 2 · h1 · R0 by adding the first transmission (h1 + h2) · R0 and the second transmission (h1-h2) · R0. In a similar manner, the terminal can obtain channel 2 · h2 · R0 using the difference between the first transmission (h1 + h2) · R0 and the second transmission (h1-h2) · R0.

A terminal performing CoMP has a frequency diversity channel characteristic and a high gain can be obtained when moving at low speed. However, when intra base station cells are used to perform CoMP, frequency diversity is small, but it is possible to move at a relatively high speed. In this case, since the channel becomes more sensitive to time, the reference signal pattern shown in Fig. 1 can be replaced with the reference signal pattern as shown in Fig.

Referring to FIG. 2, a code resource (code 1 = {1, 1}, code 2 = {1, -1},) may be allocated on a symbol basis. That is, in one slot, the code resource elements 1 and 1 may be allocated to one OFDM symbol, and the code resource elements 1 and -1 may be allocated to one OFDM symbol, respectively. When cell 1 and cell 2 allocate reference signals on a symbol basis by using code resources, they can transmit all reference signals even if one slot is transmitted. In this case, .

The reference signal patterns shown in FIGS. 1 and 2 may vary in performance depending on channel characteristics. Therefore, it is possible to construct both patterns and use a structure of a proper type according to the situation of the cell. That is, when the cell has a small frequency diversity and moves at a relatively high speed, it is preferable to configure the reference signal pattern as shown in FIG. In this manner, the reference signal can be transmitted based on the code resource allocated to each cell in units of slots or symbols. A reference signal allocated to a code resource may be a slot or a symbol unit in a time domain and may be allocated in a resource block or a subcarrier unit in a frequency domain in a slot or a frequency axis within a symbol. The code resource may include an orthogonal code such as a Walsh ADAMAR or a discrete Fourier transform (DFT) orthogonal code (circular shift).

Next, it is assumed that there are three cells. For odd CoMP cells, it is somewhat difficult to support orthogonality with the Walsh / Adamar matrix. Therefore, it is preferable to use a DFT orthogonal code (time-domain cyclic shift) to support an odd number of CoMP cells. The DFT orthogonal code is useful for supporting an odd number of CoMP cells as well as an even number of CoMP cells.

Hereinafter, a method of performing CoMP operation using three DFT orthogonal codes (time-domain cyclic shift) will be described. A DRS symbol extension method based on a Code Division Multiplexing (CDM) scheme uses a cyclic shift of a PN sequence multiplied by a symbol to generate a reference signal symbol of each cell constituting CoMP Code division multiplexing. For example, the dedicated reference signal can be expressed by Equation (2).

로부터 얻어지는 하나의 직교시퀀스

은 수학식 3과 같이 표현할 수 있다. 여기서

의 값에 따라, N개의 직교 시퀀스를 생성할 수 있으며, N값은 채널상황에 따라 달라질 수 있다.The orthogonal sequence can be generated by cyclically shifting the sequence used for the reference signal symbol of Equation (2) in the time domain, and orthogonal sequences can be generated by assigning different orthogonal sequences to the generated orthogonal sequences for each CoMP cell, Can be simultaneously allocated and transmitted. For example, when the PN sequence used in the reference signal symbol of Equation (2) is cyclically shifted in the time domain, it may be configured by multiplying the phase shift sequence in the frequency domain. At this time,

One orthogonal sequence &lt; RTI ID = 0.0 &gt;

Can be expressed by Equation (3). here

N orthogonal sequences can be generated according to the value of N, and the value of N may vary depending on the channel condition.

일 수 있다.here,

Lt; / RTI &gt;

3 is a diagram illustrating an example of a reference signal pattern for allocating reference signals in a slot unit by using DFT orthogonal codes in three multiple cells, FIG. 2 is a diagram illustrating an example of a reference signal pattern for assigning signals on a symbol basis. FIG.

Referring to FIG. 3 and FIG. 4, when three cells perform CoMP, three orthogonal sequences can be formed with N = 3. Each orthogonal sequence is assigned to each cell, which may be mapped to a dedicated reference signal (DRS) on a slot or symbol basis. The orthogonal sequences assigned to each CoMP cell are orthogonal to each other. At this time, the cyclic shift values &thgr; _i constituting the different orthogonal sequences must have sufficient intervals to distinguish the impulse responses of the channels for each CoMP cell. That is, for example, if the system has an effective OFDM symbol length with a symbol length of 66.7 μsec and operates in a channel environment with a maximum delay spread of 5 μsec, it must have a shift value of at least 5 μsec Therefore, up to 12 cyclic shifts can be distinguished.

In addition, as shown in FIG. 3, the OFDM symbols may be allocated at four subcarrier intervals so that the reference signal Rd is not overlapped for each OFDM symbol in two OFDM symbols within one slot for each cell. Also, the reference signal Rd may be allocated in another slot in the same manner. At this time, since each cell uses different orthogonal codes, the UE can distinguish which cell the reference signal is transmitted from. In this manner, when the reference signal is inserted at four subcarrier intervals in the frequency domain, the number of available shifts decreases by four times. That is, it can have 12/4 = 3 cyclic shift values. However, if the cyclic shift is applied in combination with the reference signal symbols of a plurality of OFDM symbols, it can be used in the form that a dedicated reference signal is inserted at two subcarrier intervals. In this case, it can be configured to have 12/2 = 6 cyclic shift values. However, this case can also be applied under the condition that the channel hardly changes during the corresponding period.

Referring back to FIG. 3, the cyclic shift can be applied using two OFDM symbols including a pilot symbol. In this case, the cyclic shift of Equation (3) can apply linear phase increments alternately to two paired OFDM symbols. This method is advantageous in that a larger number of cyclic shifts can be applied because the frequency spacing of the pilot symbols becomes smaller.

Referring again to FIG. 4, by applying a cyclic shift to each OFDM symbol, a high performance gain can be obtained in a high-speed mobile environment where a channel changes rapidly. However, since the number of cyclic shifts is small, the number of CoMP cells that can be transmitted at the maximum can be reduced.

As described above, the orthogonal sequences can be mapped in units of slots and symbols in FIG. 3 and FIG. 4, respectively. However, orthogonal sequence mapping in units of subframes is also possible to support more CoMP multi-cells. Or, orthogonal sequence mapping for a plurality of subframe units is also possible.

Next, assume that there are four cells. Consider the following 4 × 4 Walsh-Adamar matrix equation.

Define a code resource in each column. That is, the code 1 = {1, 1, 1, 1}, the code 2 = {1, -1, 1, -1}, the code 3 = {1, , -1, -1, 1}.

5 is a diagram illustrating an example of a reference signal pattern for allocating reference signals in a slot unit by using code resources in four multiple cells. FIG. 6 is a diagram illustrating a reference signal pattern using code resources in four multi- FIG. 8 is a diagram illustrating an example of a reference signal pattern for allocation in symbol units. FIG.

Referring to FIGS. 5 and 6, a cell 1 is assigned a code 1 for transmitting a CoMP reference signal, a cell 2 is assigned a code 2, a cell 3 is assigned a code 3, and a cell 4 is assigned a code 4. Each cell can allocate a reference signal on a time or frequency axis based on the allocated code resources. In this example, a reference signal is allocated on the time axis for transmission. R0, which is one resource block length 4, is mapped on a resource block basis. Here, one subframe may be composed of four slots having 7 OFDM symbols for each slot.

Referring to FIG. 5, the cell 1 allocated the code 1 can allocate R0 to the first slot, allocate R0 to the second slot, allocate R0 to the third slot, and allocate R0 to the fourth slot. Cell 2 assigned code 2 can assign R0 to the first slot, -R0 to the second slot, R0 to the third slot, and -R0 to the fourth slot. Cell 3 allocated with code 3 can allocate R0 to the first slot, allocate R0 to the second slot, -R0 to the third slot, and -R0 to the fourth slot. In addition, the cell 4 allocated with code 4 can allocate R0 to the first slot, -R0 to the second slot, -R0 to the third slot, and R0 to the fourth slot. The reference signals R0 and -R0 can be allocated on a slot-by-slot basis based on the code resources allocated to the cells 3 and 4 in a manner similar to the method of allocating the reference signals R0 and -R0 in the cells 1 and 2. [

In this manner, when the reference signals are allocated in units of slots in the cells 1 to 4 using the code resources, all of the reference signals can be transmitted by transmitting four slots.

Referring to FIG. 5 again, the UE can receive a reference signal through the channel h1 formed in the cell 1, the channel h2 formed in the cell 2, the channel h3 formed in the cell 3, the cell 4, and the formed channel h4. (H1 + h2 + h3 + h4) · R0 in the first transmission, h1-h2 + h3-h4 in the second transmission, R0 in the first transmission, h4) · R0, and (h1-h2-h3 + h4) · R0 in the fourth transmission. The received signal can be used to estimate each channel.

Hereinafter, an example in which the UE estimates each channel will be described. (H1 + h2 + h3 + h4) · R0 in the first transmission, (h1-h2 + h3-h4) in the second transmission · R0, , And (h1-h2-h3 + h4) R0 in the fourth transmission are all summed to obtain the channel h1. In a similar manner, values for the remaining channels h2, h3, h4 can also be obtained, respectively. The code resources may include Walsh-Adamar or DFT orthogonal codes (Circular Shift), and the like.

Referring again to FIG. 6, reference signals may be allocated in symbol units in one slot. Code 1 = {1, 1, 1, 1}, Code 2 = {1, -1, 1, -1}, Code 3 = {1, 1, -1, -1, 1}) can be allocated in symbol units. That is, for example, 1, -1 in the first part among the code resource elements 1, -1, -1 and 1 can be allocated to different OFDM symbols in one slot, and the remaining code resource elements -1, 1 may be allocated to different OFDM symbols within another slot. The code resources corresponding to the remaining codes 1, 2 and 3 may be allocated in a similar manner. In the case of allocating in symbol units, when two slots are transmitted, all of the reference signals can be transmitted. This is different from the allocation of reference signals in the slot unit in which all the reference signals are transmitted in order to transmit four slots.

The reference signal allocation pattern shown in FIG. 5 has a channel characteristic of high frequency diversity in a terminal performing CoMP. And, when moving at low speed, there is a high gain. However, when the cells of the intra base station are used to perform the CoMP, relatively high speed movement is possible with a small frequency diversity. In this case, since the channel is more sensitive to time, it is possible to configure a reference signal pattern for allocation in slot units shown in FIG. 5 as a reference signal pattern for allocation in symbol units in FIG.

The reference signal patterns shown in FIGS. 5 and 6 may vary in performance depending on channel characteristics. Therefore, it is possible to construct both patterns and use a structure of a proper type according to the situation of the cell. That is, when the cell has a small frequency diversity and moves at a relatively high speed, it is preferable to configure the reference signal pattern as shown in FIG. As such, each cell may transmit a reference signal based on a code resource allocated on a slot or symbol basis. A reference signal allocated to a code resource may be a slot or a symbol unit in a time domain and may be allocated in a resource block or a subcarrier unit in a frequency domain in a slot or a frequency axis within a symbol. Where the code resource may be a Walsh-Adamar or Discrete Fourier Transform (DFT) orthogonal code (Circular Shift).

2. If the cell is different PN code use with CoMP  When a reference signal is transmitted

It can be considered that each cell that performs CoMP generates different PN codes for CoMP reference signals and allocates them to the same time / frequency domain. Here, it is assumed that two cells perform CoMP as shown in FIG. 1 and FIG.

7 is a diagram illustrating an example of a reference signal pattern for generating a different PN code in two multiple cells and allocating a reference signal on a slot basis using code resources, And a reference signal pattern for allocating a reference signal on a symbol basis using a code resource.

Referring to FIG. 7, one subframe may be composed of two slots each having seven OFDM symbols. At this time, the cell 1 and the cell 2 can respectively assign reference signals (for example, R0 and R1) based on different PN codes. In the case of the cell 1, the reference signal RO can be allocated in the same manner as the allocation pattern of the reference signal shown in FIG. In the case of the cell 2, the reference signal is changed from RO to R1 and can be assigned the same as the allocation pattern of the reference signal R0 shown in FIG. In the case where the reference signals are allocated in the cell 1 and the cell 2 using the code resources, the reference signals may be transmitted in two slots.

Referring to FIGS. 7 and 8, R0 and R1 denote the positions of reference signals, and -R0 and -R1 denote reference signals to which phase shift, etc. are applied by code resources. R0, R1 can be mapped with a reference signal sequence length assigned to one resource block or one symbol.

The terminal receives the reference signal that has passed through the channel h1 formed in the cell 1 and the channel h2 formed in the cell 2. The terminal can receive (h1 · R0 + h2 · R1) in the first transmission by the code resource and (h1 · R0-h2 · R1) in the second transmission. The terminal can estimate each channel using the received signal.

An example in which the UE estimates each channel will be described. The channel 2 · h1 · R0 can be obtained by adding the first transmission (h1 · R0 + h2 · R1) and the second transmission (h1 · R0-h2 · R1) In a similar manner, channel 2 · h2 · R1 can be obtained using the difference between the first transmission (h1 · R0 + h2 · R1) and the second transmission (h1 · R0-h2 · R1). Using this method, the UE can accurately estimate the channel using the reference signal.

Referring again to FIG. 8, the reference signals R0 and R1 are assigned to the cell 1 and the cell 2, respectively, on a symbol basis, which can be allocated in the same pattern as in the case where the cell 1 and the cell 2 allocate the reference signal on a symbol basis have. In the case where the cell 1 and the cell 2 allocate the reference signal on a symbol basis by using the code resource, the cell 1 and the cell 2 can transmit all the reference signals even if one slot is transmitted. This is different from the reference signal allocation.

In the reference signal structure defined in 3GPP LTE (Release 3, 3GPP LTE) release 8, a UE-specific antenna port 5 for performing CoMP is divided into multiple cells in the same time / frequency domain Consider the case of allocation. The antenna port 5 may be used for beamforming, which is a technique for increasing the throughput of terminals. Also, port 5 can be used to perform CoMP to improve cell boundary performance.

9 is a diagram illustrating an example of a reference signal pattern (terminal-specific antenna port 5) for allocating reference signals in multiple cells using code resources.

Referring to FIG. 9, cell 1 allocates a CoMP reference signal to two subframes using a code resource {1,1}, and cell 2 allocates CoMP reference signals to two subframes using code resources {1, It is possible to estimate each channel by allocating and transmitting a CoMP reference signal. That is, the cell 1 allocates the CoMP reference signal using the code resource element 1 in the subframe 1 and the code resource element 1 in the subframe 2, and the cell 2 allocates the code resource element 1 in the subframe 1 and the code resource element 1 in the subframe 2 The CoMP reference signal can be allocated using the code resource element-1. In this case, each cell must transmit two subframes to transmit all of the CoMP reference signals.

The cell-specific reference signal is a reference signal shared by all terminals in the cell, and the terminal-specific reference signal is a reference signal used only by a specific terminal. A plurality of cells may transmit a common reference signal through cell-specific ports (0-3). The cell may then transmit a dedicated reference signal via the terminal-specific port. The common reference signal can be shifted according to the cell, but in the case of a dedicated reference signal, multiple cells can be transmitted to the same location for CoMP.

The UE-specific reference signal may be transmitted through a physical downlink shared channel (PDSCH) to a single-antenna port. The UE can know whether a UE-specific reference signal exists for demodulating the physical downlink shared channel through the upper layer and whether the UE-specific reference signal is a valid reference signal. The UE-specific reference signal is transmitted only on the resource block to which the corresponding physical downlink shared channel is mapped. Hereinafter, a resource element mapping when a single-specific reference signal is transmitted will be described.

에 매핑한다고 가정하면, 다음과 같이 셀-특정 주파수 천이(cell-specific frequency shift)

을 제외한 식을 생각해 볼 수 있다.As an example, consider the following resource element mapping. An antenna port 5 is used to convert the reference signal sequence r (m) into a complex-value modulation symbol

Cell-specific frequency shift &lt; RTI ID = 0.0 &gt;

Can be considered.

은 주파수 영역 인덱스가 k이고 시간 영역 인덱스 j인 자원 요소를 나타내고,

는 안테나 포트 P에 대한 자원 요소

의 값이며,

는 부반송파의 개수로 표현된 주파수 영역에서의 자원 블록의 크기를 나타내고,

는 물리 자원 블록 수를 나타내고,

는 하나의 무선 프레임 내의 슬롯 수를 나타내고,

는 PDSCH를 위한 자원 블록의 수를 나타낸다.here,

Denotes a resource element with a frequency domain index k and a time domain index j,

RTI ID = 0.0 &gt; P &lt; / RTI &gt;

Lt; / RTI &gt;

Represents the size of the resource block in the frequency domain expressed by the number of subcarriers,

Represents the number of physical resource blocks,

Represents the number of slots in one radio frame,

Represents the number of resource blocks for the PDSCH.

Referring back to FIG. 9, the common reference signals allocated to the plurality of cell-specific ports 0 to 3 in subframe 1 and subframe 2 may be allocated so that cell 1 and cell 2 do not overlap with each other. At this time, the dedicated reference signal may be allocated so as not to overlap with the common reference signal. Also, a dedicated reference signal may be assigned to the same position in cell 1 and cell 2.

Multiple antennas using code resources CoMP  Reference signal transmission

Now consider the case where each cell that performs CoMP uses multiple antennas. In the case of transmitting a common reference signal, each cell can transmit a reference signal through the currently defined antenna ports 0 to 3, thereby performing a measurement such as a channel state (for example, CSI). Alternatively, when transmitting a dedicated reference signal, only reference signals are transmitted to one antenna port in one slot or subframe. However, it is necessary to support multiple antennas even in the case of dedicated reference signal transmission for demodulation. The CoMP reference signal transmission using the orthogonal code resources of the above embodiments can be extended until the CoMP performing cells perform with multiple antennas.

Assume that two cells each carry two CoMPs with two transmit antennas.

10 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using code resources in two cells having two transmission antennas.

Referring to FIG. 10, one subframe may be composed of two slots each having 7 OFDM symbols. When a CoMP reference signal is transmitted through a dedicated reference signal, each cell can transmit a reference signal corresponding to each antenna, alternating in slot or symbol units. Cell-specific ports 0 to 3 (cell-specific ports 0 to 3) can transmit a common reference signal. A common reference signal is assigned to the cell-specific ports 0 to 3, and the common reference signals of the cell 1 and the cell 2 within one subframe can be allocated so as not to overlap each other.

As shown in the matrix equation (1), the serving cell 1 is allocated a code resource 1 and the neighboring cell 2 is allocated a code resource 2. Each cell can transmit a reference signal on a time or frequency axis based on the allocated code resources. In this example, the reference signal is transmitted on the time axis.

The cell 1 allocated with the code 1 allocates the CoMP reference signal Ra for the first antenna to the first slot of the two slots in the first subframe of the code resource element and the CoMP reference signal Rb for the second antenna to the second slot can do. That is, two CoMP reference signals for the first and second antennas may be transmitted before two slots are transmitted. CoMP reference signals for the first and second antennas may be assigned to the second subframe in the same manner. The remaining slots of each subframe may be similarly allocated. At this time, the dedicated reference signal may be allocated so as not to overlap with the common reference signal. Also, dedicated reference signals of cells 1 and 2 can be assigned to the same position.

On the other hand, in the cell 2 allocated with the code 2, the CoMP reference signal Ra for the first antenna is assigned to the first one of the two slots in the first subframe, and the CoMP reference signal Rb for the second antenna is assigned to the second slot can do. For the two slots in the second subframe, -Ra and -Rb may be assigned to the first slot and the second slot, respectively. At this time, if two slots are to be transmitted, all reference signals for two antennas can be transmitted.

Here, the reference signal of the CoMP multiple antenna may be transmitted first, and then the CoMP reference signal may be transmitted using the code resource.

11 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using code resources in two cells having four transmission antennas.

Referring to FIG. 11, four subframes may be used for each cell to allocate four antenna CoMP reference signals.

In the case of the cell 1, the CoMP reference signal Ra for the first antenna and the CoMP reference signal Rb for the second antenna may be allocated to the first slot of the two slots in the first subframe. A CoMP reference signal Rc for the third antenna and a CoMP reference signal Rd for the fourth antenna may be allocated to the first slot of the two slots in the second subframe. A CoMP reference signal may be allocated to the first subframe in the third subframe and to the second subframe in the fourth subframe. At this time, the two OFDM symbols in one slot of each subframe may be allocated at four subcarrier intervals so that the dedicated reference signal is not overlapped for each OFDM symbol. A dedicated reference signal allocated in each slot can be allocated so as not to overlap with the common reference signal.

For Cell 2, a CoMP reference signal for four antennas can be allocated over four subframes in a manner similar to Cell 1. The common reference signals assigned to cell 1 and cell 2 can be allocated so that they do not overlap with each other.

Assuming that a UE located at the edge of a cell performing CoMP moves at a low speed, a multi-antenna reference signal of each cell can be transmitted on a symbol, slot or subframe basis. In the above embodiments, the CoMP multi-antenna reference signal transmission in the slot unit and the orthogonal code covering in the subframe unit are used. This unit is based on the number of multiple antennas in each cell and the number of cells performing CoMP It can be different. In addition to the above embodiments, transmission of a CoMP multiple antenna reference signal on a symbol or subframe basis may also be considered, and accordingly orthogonal code covering may be considered.

A new reference signal can be added in addition to the currently defined dedicated reference signal. The reference signal resource can be allocated to the CoMP reference signal in addition to the currently defined dedicated reference signal. When each cell carrying CoMP transmits a CoMP reference signal using multiple antennas, more reference signals can be allocated according to the number of antennas of each cell.

12 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using reference signal extension and code resources in two cells having two transmission antennas.

Referring to FIG. 12, one subframe may be composed of two slots each having 7 OFDM symbols. If the number of multiple antennas used in each cell further increases, reference signal resources may be further allocated, or reference signal resources for additional antennas may be allocated through time domain expansion. FIG. 12 corresponds to a case where reference signal resources are additionally allocated.

In the case of cell 1, a CoMP reference signal for the first antenna is allocated in one slot, and further a reference signal resource is allocated for a CoMP reference signal for the second antenna, Can be assigned. At this time, the CoMP reference signal and the common reference signal for the antenna may be allocated so as not to overlap each other.

In the case of cell 2, a CoMP reference signal for multiple antennas may be allocated in the same manner as in cell 1 described above. The CoMP reference signals of Cell 1 and Cell 2 can be assigned to the same position. And, in the case of cell-specific ports 0 to 3, the common reference signal can be allocated so that cell 1 and cell 2 do not overlap.

FIG. 13 is a diagram showing an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal on a slot basis by expanding a reference signal in two cells having four transmitting terminals Tx and using code resources.

Referring to FIG. 13, one subframe may be composed of two slots each having 7 OFDM symbols. The cell 1 and the cell 2 can allocate a reference signal by a slot unit by using a code resource, respectively. When there are four multiple antennas, the reference signal resources for the two antennas can be doubled while the reference signal resources for the remaining two antennas can be allocated to the slots or subframes. In this case, a slot unit may be applied to a unit using a code resource.

In the case of the cell 1, the CoMP reference signal Ra for the first antenna and the CoMP reference signal Rb for the second antenna may be adjacent to the first slot of the two slots in the first subframe. The remaining slots of the first subframe may be allocated in the same manner. In a similar manner, the CoMP reference signal Rc for the third antenna and the CoMP reference signal Rd for the fourth antenna may be allocated within each slot in the second subframe, respectively.

In the case of cell 2, a CoMP reference signal for multiple antennas may be allocated in the same manner as in cell 1 described above. The CoMP reference signals of Cell 1 and Cell 2 can be assigned to the same position. And, in the case of cell-specific ports 0 to 3, the common reference signal can be allocated so that cell 1 and cell 2 do not overlap. In this way, two subframes must be transmitted before all of the CoMP reference signals for the first to fourth antennas can be transmitted.

14 is a diagram showing an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal on a sub-frame basis by expanding a reference signal in two cells having four transmitting terminals Tx and using code resources .

Referring to FIG. 14, one subframe may be composed of two slots each having seven OFDM symbols, as in FIG. Cell 1 and cell 2 can transmit a reference signal on a sub-frame basis using code resources, respectively. Here, the allocation of the reference signal indicates allocation of all the CoMP reference signals for the four multiple antennas in the subframe. At this time, the code resource can be applied in units of subframes.

In the case of the cell 1, the CoMP reference signal Ra for the first antenna and the CoMP reference signal Rb for the second antenna may be adjacent to the first slot of the two slots in the first subframe. For the remaining slots of the first subframe, the CoMP reference signal Rc for the third antenna and the CoMP reference signal Rd for the fourth antenna may be allocated adjacent to each other, similar to the scheme allocated to the first slot. The assignment scheme of the second subframe is the same as that of the CoMP reference signal for each antenna in the first subframe.

In the case of cell 2, a CoMP reference signal for each antenna can be allocated in the same manner as cell 1. However, the common reference signals (cell-specific ports 0 to 3) may be allocated so as not to overlap between cell 1 and cell 2. According to this method, if one subframe is transmitted, all the CoMP reference signals for the first to fourth antennas can be transmitted.

As described above, FIG. 12 and FIG. 13 are respectively the case where reference signal resources are allocated in each cell, or reference signal resources are allocated by extending the time domain, in comparison with FIG. 10 and FIG. When the reference signal resource is extended and transmitted, the CoMP reference signal transmission time is shorter than the pattern without the reference signal resource extension, but the data efficiency may be lower.

On the other hand, multiple cells performing CoMP can transmit CoMP reference signals on the time axis as well as on the frequency axis. That is, a channel of a multi-cell can be estimated by transmitting a CoMP reference signal using a code resource in a resource block unit or a subcarrier unit on the frequency axis within the same slot or symbol. As the number of cells performing CoMP increases, corresponding code resources are generated and assigned to each cell, thereby enabling channel estimation in a multi-cell environment.

4. Grouping  Code division multiplexing ( CDM )

It is possible to group each cell that performs CoMP and allocate a CoMP reference signal using orthogonal code resources. That is, the positions of dedicated reference signals may be different for each group, or CoMP reference signals may be allocated to different time and frequency resource regions. As described above, when the cells are grouped and the CoMP reference signals of the multiple cells are allocated, the reference signals can be efficiently allocated and transmitted to more CoMP cells.

Consider the case where four cells each having two transmit antennas are assigned CoMP reference signals with two groups.

FIG. 15 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using four groups of two transmission antennas, which are grouped into two groups, using grouping and code resources.

Referring to FIG. 15, one slot may include 7 OFDM symbols. An orthogonal code resource may be applied between cells in each group. Each group can transmit a CoMP reference signal by assigning a dedicated reference signal to the same time and frequency domain. Each cell in each group alternates in slot or symbol units and can assign a CoMP reference signal corresponding to each antenna. In the first cell group, if the CoMP reference signal is allocated to the first antenna in the first slot, the CoMP reference signal for the second antenna can be assigned to the second slot. In this way, the CoMP can allocate the reference signals of multiple antennas and then allocate the CoMP reference signals using the code resources.

In the matrix equation (1), a cell 1 serving as a serving cell of the first cell group is allocated a code resource 1, and a cell 2 serving as a neighboring cell is assigned a code 2. Each cell can transmit a reference signal on the time and frequency axis based on the allocated code resources. In this example, the reference signal is transmitted on the time axis. Cell group 1 may include cell 1 and cell 2, and cell group 2 may include cell 3 and cell 4.

The cell 1 assigned the code 1 can allocate the CoMP reference signals Ra and Rc corresponding to the first and second antennas of the cell group 1 corresponding to the code resource element 1 to each slot in the first subframe, The CoMP reference signals Ra and Rc corresponding to the first and second antennas of the cell group 1 corresponding to the code resource element 1 can be allocated to each slot in the second subframe. In the cell 2 to which the code 2 is allocated, the CoMP reference signals Ra and Rc corresponding to the first and second antennas of the cell group 1 corresponding to the code resource element 1 can be allocated to each slot in the first subframe, The CoMP reference signals -Ra and -Rc corresponding to the first and second antennas of the cell group 1 corresponding to the resource element-1 can be allocated to each slot in the second subframe, respectively.

The cell 3 belonging to the cell group 2 transmits the CoMP reference signal corresponding to the first and second antennas of the cell group 2 to the first subframe and the second subframe using the code resource 1 in the time and frequency regions different from the cell group 1, Rb, and Re. Similarly to the cell 3, the cell 4, which is an adjacent cell, allocates the CoMP reference signals -Rb and -Re corresponding to the first and second antennas of the cell group 2 using the code resource 2 in the time and frequency regions different from the cell group 1 can do.

Then, the common reference signals (cell-specific ports 0 to 3) can be allocated so as not to overlap between cell 1 and cell 2, and between cell 3 and cell 4. The dedicated reference signal may be mapped with a reference signal sequence length assigned to one resource block or one symbol.

Each group can be formed with the same or different number of cells constituting the CoMP. That is, when four cells form a CoMP, as in the case of FIG. 15, two cells may be paired and formed into two groups, and one serving cell and three remaining cells forming a group It is possible. Such CoMP cell grouping can be changed according to circumstances.

As another example, two of the four cells performing CoMP (cell 1 and cell 2) share the same data and are transmitted to perform soft combining for macro diversity And the cells of the remaining two (cells 3 and 4) can be considered in other CoMP scenario cases (for example, transmit diversity, spatial multiplexing (SM), etc.) except for soft combining. In this case, cell 1 and cell 2 can be regarded as one reference signal assigned to the same sequence and the same time and frequency domain. Therefore, the same CoMP reference signal as that when the cell performs CoMP can be allocated.

That is, the first group for soft combining and the remaining two neighbor cells respectively allocate CoMP reference signals using orthogonal code resources, or the remaining two adjacent cells form a group, and the first group for soft combining Groups can be assigned differently. Also, when the second group composed of the cell 3 and the cell 4 is subjected to soft combining, which is different from the first group, like the first group, the first group and the second group are as if two cells perform CoMP The CoMP reference signal can be allocated using two orthogonal code resources as in the case of FIG.

The joint processing method refers to a cooperative MIMO type scheme by sharing data among cells in the CoMP execution method. In a case where multiple cells perform joint processing, a resource zone for transmitting CoMP data and a reference signal may be dedicated. If a resource area for performing CoMP is allocated exclusively, a CoMP reference signal does not need to be allocated to a resource outside the CoMP resource area. That is, resources can be efficiently used by freely using the resources of the portion as reference signals or data for other purposes without having to keep the positions of the CoMP reference signals between the cells for performing CoMP.

This CoMP resource area allocation can be semi-static allocated by higher layer signaling. The CoMP resource area physical resource block (PRB) may be allocated to the same physical resource block among the cells or may be allocated to another physical resource block. When a CoMP resource area is allocated to the same physical resource block among cells performing CoMP, the UE can correctly estimate channels of other cells using CoMP reference signal transmission based on code resources. In this case, only the information about the CoMP resource area physical resource block of the serving cell is notified to the UE. On the other hand, when CoMP resource areas are assigned to different physical resource blocks among the cells performing CoMP, the UE can effectively estimate channels of other cells without an additional transmission method for CoMP reference signal transmission. However, the UE must receive location information of the CoMP resource region physical resource block of the neighboring cell performing the CoMP from the serving cell.

As described above, the present invention relates to reference signal allocation and transmission of multiple cells performing CoMP. The present invention is particularly useful for joint processing based on multiple cells. In addition, the technique of the present invention can be applied not only to a multi-cell environment, but also to a reference signal transmission technique for a higher-order MIMO with a single cell.

That is, it is possible to map each cell that performs multi-cell based CoMP to each antenna port based on a single cell and transmit the same. For example, in FIG. 5, when four cells transmit a CoMP reference signal to one virtual antenna, this may be matched with the case where four antennas transmit data to rank four in a single cell. In a similar manner, for example, if two cells in FIG. 10 transmit a CoMP reference signal to two virtual antennas, then four antennas in a single cell may be matched with the case of transmitting data to rank four. Also, it can be matched with the case where eight antennas in a single cell transmit data to rank 8 in FIG.

The CoMP reference signal pattern proposed by the present invention is useful for the LTE-A terminal. A subframe for LTE-A (LTE-Advanced) can be defined for backward compatibility with existing LTE terminals. That is, the reference signal pattern for performing CoMP proposed in the present invention is useful in a subframe defined as a subframe for LTE-A.

Also, in the present invention, the CoMP reference signal is mainly described from the viewpoint of the dedicated reference signal for demodulation, but the same can be applied to the common reference signal for measuring the channel state and the like. For convenience of explanation, a reference signal structure in which multiple cells are mapped to the same position is taken as an example. However, a frequency shift or a time shift is performed for each cell, and each reference signal pattern includes interference .

The embodiments described above are those in which the elements and features of the present invention are combined in a predetermined form. Each component or feature shall be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to construct embodiments of the present invention by combining some of the elements and / or features. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

Embodiments in accordance with the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of hardware implementation, an embodiment of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs) Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, a procedure, a function, or the like which performs the functions or operations described above. The software code can be stored in a 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 well-known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

1 is a diagram illustrating an example of a reference signal pattern for assigning a reference signal on a slot-by-slot basis using code resources in two multiple cells,

2 is a diagram illustrating an example of a reference signal pattern for allocating reference signals on a symbol basis using code resources in two multiple cells,

3 is a diagram illustrating an example of a reference signal pattern for assigning a reference signal on a slot-by-slot basis using DFT orthogonal codes in three multi-cells,

4 is a diagram illustrating an example of a reference signal pattern for assigning reference signals on a symbol basis using DFT orthogonal codes in three multiple cells,

5 is a diagram illustrating an example of a reference signal pattern for assigning a reference signal on a slot basis using code resources in four multiple cells;

6 is a diagram illustrating an example of a reference signal pattern for assigning reference signals on a symbol basis using code resources in four multiple cells,

FIG. 7 is a diagram illustrating an example of a reference signal pattern for generating different PN codes in two multiple cells and assigning reference signals on a slot basis using code resources;

8 is a diagram illustrating an example of a reference signal pattern for generating different PN codes in two multiple cells and assigning reference signals on a symbol basis using code resources,

9 is a diagram illustrating an example of a reference signal pattern (terminal-specific antenna port 5) for allocating reference signals in multiple cells using code resources,

10 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using code resources in two cells having two transmission antennas,

11 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using code resources in two cells having four transmission antennas,

12 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using reference signal extension and code resources in two cells having two transmission antennas,

13 and 14 are diagrams showing an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using a code resource and a reference signal extended in two cells having four transmitting terminals Tx, and FIG. ,

FIG. 15 is a diagram illustrating an example of a reference signal pattern for allocating a multi-antenna CoMP reference signal using four groups of two transmission antennas, which are grouped into two groups, using grouping and code resources.

Claims (8)

A method for receiving a CoMP reference signal from each cell in a multi-cell environment in which a UE performs Cooperative Multi-Point (CoMP) Receiving a CoMP reference signal in which orthogonal codes of a slot unit or a symbol are applied to orthogonality between reference signals of cells for performing the CoMP operation from each cell in which the UE performs the CoMP operation; And Wherein the UE identifies and processes the received CoMP reference signal for each cell performing the CoMP operation using an orthogonal code applied in the slot unit or the symbol unit, And the orthogonal code of the slot unit or the symbol unit is determined based on the moving speed of the terminal. The method according to claim 1, Wherein the CoMP reference signal is applied to the CoMP reference signal in units of slots on a resource block, one orthogonal code resource element corresponding to the CoMP reference signal. The method according to claim 1, Wherein the CoMP reference signal is applied on a symbol block basis on a resource block, each orthogonal code resource element corresponding to the CoMP reference signal. The method according to claim 1, Wherein the UE receives information of an orthogonal code resource used by each cell that performs CoMP through a broadcast channel or a higher layer signaling from a cell to which the UE belongs. The method according to claim 1, The orthogonal code resource elements corresponding to the first antenna and the second antenna of the cell performing the CoMP are applied in slot units in the first subframe and the orthogonal code resource elements corresponding to the third antenna and the fourth antenna respectively In the second sub- A method for receiving a CoMP reference signal applied in units of blocks. The method according to claim 1, The orthogonal code resource elements corresponding to the first antenna and the second antenna of the cell performing the CoMP are included in the same slot in the first subframe and are applied in slot units, and orthogonal code resources corresponding to the third antenna and the fourth antenna, And the resource element is included in the same slot in the second subframe and applied in a slot unit. The method according to claim 1, Wherein orthogonal code resource elements corresponding to a first antenna and a second antenna of a cell performing CoMP are applied to a first slot of a first subframe and orthogonal code resource elements corresponding to a third antenna and a fourth antenna are applied to the first slot of the first subframe, And applying the CoMP reference signal to the second slot of the first subframe. A method for transmitting a CoMP reference signal from each base station that performs Cooperative Multi-Point (CoMP) operation in a multi-cell environment, Allocating orthogonal code resources to which orthogonal codes are applied so as to have orthogonality with respect to each other in a slot unit or a symbol unit among reference signals of each base station performing a CoMP operation; And And transmitting a CoMP reference signal using an orthogonal code resource having orthogonal codes orthogonal to each other in the slot unit or the symbol unit among the base station reference signals, And the orthogonal code of the slot unit or the symbol unit is determined based on a moving speed of the terminal.

Images