KR101526996B1 - Method of transmitting and receiving pilot signal in a system with Multiple Input Multiple Output - Google Patents

Abstract

The present invention discloses an efficient data transmission and reception method in a wireless access system and a pilot allocation structure therefor. The method may include transmitting data using a resource block configured in consideration of a channel estimation performance and a data rate, and receiving data using a resource block. At this time, the resource block includes pilot symbols composed of a predetermined number and a predetermined pattern.

Resource block, pilot symbol, OFDM symbol, subcarrier

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of transmitting and receiving pilot signals in a system having multiple transmission antennas,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of efficiently transmitting and receiving data in a wireless access system. Embodiments of the present invention also disclose a pilot allocation structure for efficient data transmission.

Hereinafter, the channel estimation method and the pilot signal will be briefly described.

To detect the synchronization signal, the receiver must know the information of the radio channel (attenuation, phase shift or time delay, etc.). At this time, channel estimation refers to estimating the size and the reference phase of the carrier wave. The wireless channel environment has a fading characteristic in which the channel state changes irregularly in time in the frequency domain. Estimating the amplitude and phase for these channels is called channel estimation. That is, the channel estimation is to estimate the frequency response of the radio section or the radio channel.

As a channel estimation method, there is a method of estimating a reference value based on pilot symbols of several base stations using a two-dimensional channel estimator. At this time, the pilot symbol refers to a symbol having high output although it does not have actual data to help carrier phase synchronization and acquisition of base station information. The transmitter and receiver can perform channel estimation using the pilot symbols as described above. The channel estimation by the pilot symbol estimates a channel through a pilot symbol commonly known to the transmitting and receiving end, and restores the data by using the estimated value.

1 is a diagram showing an example of a general pilot structure used in a single transmission antenna structure.

1 shows a case of one transmission antenna. In the case of one antenna, two pilot sub-carriers are used in an even symbol and an odd symbol. In this case, the overhead due to the pilot subcarrier may be approximately 14.28%.

2 is a diagram illustrating an example of a general pilot structure used in two transmission antenna structures.

Space-Time Coding (STC) is used in the downlink to provide high-order transmit diversity. At this time, two or more transmission antennas are required to support STC.

Referring to FIG. 2, two transmit antennas (a first antenna and a second antenna) can simultaneously transmit two different data symbols. At this time, it is repeatedly transmitted in the time domain (space-time) and the frequency domain (space-frequency). Therefore, there is a problem of increased complexity of the receiver, but it can provide better performance in data transmission.

The method of allocating data in FIG. 2 may be modified to use two antennas with the same channel estimation capability. Each pilot symbol is transmitted twice at each antenna. The position of the pilot symbol is changed in four symbol intervals. The symbol is calculated from the start of the current area, and the number of the first symbol is even.

In Fig. 2, pilot subcarriers are used for channel estimation. At this time, the overhead due to the pilot subcarrier may be approximately 14.28%.

3 is a diagram showing an example of a general pilot structure used in four transmission antenna structures.

Transmit diversity can be enhanced when four antennas (a first antenna, a second antenna, a third antenna, and a fourth antenna) are used than two antennas. Also, even if four antennas are used, there is a characteristic that the channel estimation process of the user is not changed.

Referring to FIG. 3, a pilot channel for each antenna is allocated for each symbol. For example, in the case where one symbol is composed of 14 subchannels, the four antennas allocate one pilot to each subcarrier for each symbol. Therefore, the overhead due to the pilot subcarrier can be approximately 28.57%.

As described above, when one transmission antenna and two transmission antennas are used, the pilot overhead due to the pilot subcarrier is 14.28%. In addition, when four transmission antennas are used, pilot overhead of 28.57% may occur due to pilot subcarriers.

In the prior art IEEE 802.16e system, different permutation schemes such as PUSC / FUSC / AMC have different pilot subcarrier allocation structures for each permutation scheme. In addition, as described above, the overhead of the pilot is considerably large in the MIMO system. The prior art pilot subcarrier allocation structure is specified in IEEE 802.16e.

Common permutation methods include Partial Usage of Subchannel (PUSC), Full Usage of Subchannel (FUSC), and Adaptive Modulation and Coding (AMC). At this time, in the prior art, different pilot subcarrier allocation structures are provided for each permutation method (distributed / AMC).

This is because the permutation method is separated in time, so that different optimized structures can be designed for each permutation. If permutation methods coexist in time, a unified basic data allocation structure is needed. In addition, the prior art has a problem that the pilot overhead is serious and the data rate is lowered. In the present invention, a pilot signal transmission / reception method using an efficient pilot structure for a new system, for example, an IEEE 802.16 system, is presented.

Referring to FIGS. 1 to 3, it can be seen that the overhead due to the pilot subcarrier is considerably large in a commonly used Orthogonal Frequency Division Multiplexing (OFDM) system. Such pilot overhead may reduce link throughput and may result in degradation of the system performance. Also, a commonly used pilot structure has a disadvantage in that the commonality among a plurality of antennas is not maintained in a multi-antenna system. That is, if the pilot overhead is serious, a problem of a decrease in the transmission rate may arise.

Disclosure of Invention Technical Problem [8] The present invention has been made to solve the above-mentioned problems of the related art, and an object of the present invention is to provide an efficient data signal transmission method.

It is another object of the present invention to provide a pilot subcarrier allocation structure applicable to a system having a plurality of transmit antennas to increase a data rate.

It is another object of the present invention to provide a unified data allocation structure for various permutation methods.

In order to solve the above technical problems, embodiments of the present invention disclose a data transmission method in an efficient wireless access system. Embodiments of the present invention also disclose a pilot subcarrier allocation structure for efficient data transmission.

According to an aspect of the present invention, there is provided a method of transmitting and receiving data in a wireless access system, comprising: transmitting data using a resource block configured in consideration of a channel estimation performance and a data rate; And receiving data using the above resource block, wherein the above resource block includes pilot symbols composed of a predetermined number and a predetermined pattern. At this time, the above resource block may have one of the subcarrier and OFDM symbol configurations of 18x3, 18x6, 9x6, 9x12, and 26x2. At this time, the above resource block is configured such that the configuration of subcarriers and OFDM symbols is one of 18x6, 9x6, 9x12, and 26x2, the number of OFDM symbols is n, and the number of subcarriers is m (I, j) th resource element of the above resource block having a structure of m * n (where i = 0, 1, ..., m-1; j = 1, ..., n-1) and (m-1-i, n-1-j) th resource elements may be allocated pilot symbols. In this case, four antennas are used, and P (i, j) is defined as P (i, j) among antenna numbers assigned to the OFDM symbol index j and subcarrier index i among the above four antenna numbers. = P (m-1-i, n-1-j). Alternatively, one pilot symbol allocated to four antennas may be allocated to each of the four resource elements at the outer edge of the above resource block.

In the data transmission / reception method in the wireless access system according to an aspect of the present invention, the pilot symbols may be assigned to the same number of subcarriers included in the resource block. Alternatively, the above pilot symbols may be allocated to the same number of OFDM symbols included in the above resource block. Or, to boost the power of the above pilot symbols, the above pilot symbols can borrow power from the data symbols contained in the assigned OFDM symbol. Alternatively, the above transmit antennas may support at least one of space and frequency block coding (SFBC), space and time block coding (STBC) and spatial multiplexing (SM), which are multiple antenna transmission techniques. In this case, if the above transmission antennas support SFBC, the above pilot symbols are located in concatenation in the frequency domain. If the above transmission antenna supports STBC, the above pilot symbols are concatenated in the time domain, can do.

According to embodiments of the present invention, using the air-initiated pilot allocation scheme of embodiments of the present invention, a unified data allocation scheme can be used for various permutation methods. The use of the pilot allocation structure disclosed in the embodiments of the present invention allows a system using the same permutation mode at the same time to use a single pilot allocation scheme without using a separate pilot allocation scheme according to a resource allocation scheme Structure can be utilized. The technical idea of the present invention can be applied to a system using multiple transmission / reception antennas.

Embodiments of the present invention disclose data transmission methods using a pilot allocation structure in a wireless access system.

The following embodiments are a combination of elements and features of the present invention in a predetermined form. Each component or characteristic may 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. In addition, some of the elements and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

In the description of the drawings, there is no description of procedures or steps that may obscure the gist of the present invention, nor is any description of steps or steps that can be understood by those skilled in the art.

Herein, the embodiments of the present invention have been described with reference to the data transmission / reception relationship between the base station and the terminal. Herein, the base station is a terminal node of a network that directly communicates with the terminal. The specific operation described herein as performed by the base station may be performed by an upper node of the base station, as the case may be.

That is, various operations performed for communication with a terminal in a network consisting of a plurality of network nodes including a base station can be performed by a base station or other network nodes other than the base station. At this time, the 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. In addition, 'Mobile Station (MS)' may be replaced with terms such as User Equipment (UE), Subscriber Station (SS), Mobile Subscriber Station (MSS) or Mobile Terminal.

Also, the transmitting end refers to a node that transmits data or voice service, and the receiving end refers to a node that receives data or voice service. Therefore, in the uplink, the terminal may be the transmitting end and the base station may be the receiving end. Similarly, in the downlink, the terminal may be the receiving end and the base station may be the transmitting end.

Meanwhile, the mobile terminal of the present invention may be a PDA (Personal Digital Assistant), a cellular phone, a PCS (Personal Communication Service) phone, a GSM (Global System for Mobile) phone, a WCDMA (Wideband CDMA) Etc. may be used.

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

For a hardware implementation, the method according to embodiments of the present invention may be implemented in 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 embodiments of the present invention may be implemented in the form of a module, a procedure or a function for performing 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.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the IEEE 802 systems, 3GPP systems, 3GPP LTE systems and 3GPP2 systems, which are wireless access systems. That is, the steps or portions of the embodiments of the present invention that are not described in order to clearly illustrate the technical idea of the present invention can be supported by the documents. In addition, all terms disclosed in this document may be described by the standard document. In particular, embodiments of the present invention may be supported by the standard document P802.16e-2005 or P802.16Rev2 / D4 (April 2008) of the IEEE 802.16 system.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention, and are not intended to limit the scope of the invention.

The pilot allocation structure disclosed in the embodiments of the present invention can be designed in consideration of various factors. In addition, the pilot allocation structure disclosed in the embodiments of the present invention can be repeatedly applied in a time domain and a frequency domain within a frame or a subframe.

For example, the pilot allocation structure can be designed in consideration of a time and frequency interval between pilot symbols, a data transfer amount with respect to pilot density, and a power ratio per symbol considering power boosting. Further, in the case of using multiple antennas, the power ratio between the antennas considering the power boosting and whether or not it can efficiently support the multi-antenna transmission technique can be additionally considered.

A resource block (RB) used in embodiments of the present invention is a set of REs (Resource Elements), and one resource block is composed of m subcarriers and n OFDM symbols. At this time, the resource element RE may represent a resource allocation unit composed of one subcarrier and one OFDM symbol. The resource block (RB) and the resource element (RE) are terms for appropriately describing the technical idea of the present invention and can be used corresponding to all the resource allocation units performing the same function.

Hereinafter, important elements considered in designing the pilot allocation structure will be described in detail.

1. Pilot symbol allocation interval

In the pilot allocation schemes according to the technical concept of the present invention, it is preferable that the interval between the pilot symbols is maintained at 2 to 3 symbol intervals in consideration of the coherent time for the moving speed (for example, 120 Km) Do. Also, considering the frequency-selective characteristics, it is desirable to have an effective coherence bandwidth within 8 to 9 subcarriers. However, these conditions can be adjusted according to the trade-off between the channel estimation capability of the pilot and the data transmission rate.

2. Power boosting

Power boosting can be considered to improve the channel estimation performance of the UE. For example, in order to boost the pilot symbol, clipping or back-off may be considered based on the boosted pilot power. If clipping or backoff is considered, the power loss may cause degradation of the terminal performance.

The data power can be steered or punctured to boost the power of the pilot symbol. In this case, although the channel estimation performance increases, if the channel condition is poor, the data processing capability may be degraded due to power loss of the data area. Among the methods for boosting power, various factors such as channel environment or overall performance can be considered in various ways to select the most appropriate method. If the power of the data symbol is borrowed when the power of the pilot symbol is boosted, a power difference may not occur for each OFDMA symbol.

However, if only the power of the pilot symbol is boosted without borrowing the power of the data symbol, a power difference may occur between OFDMA symbols to be transmitted. In this case, the maximum available power of the power amplifier (PA) is set based on the power of the boosted pilot. Therefore, it is necessary to use a relatively expensive PA having a relatively wide power range, or the power efficiency of the PA may be deteriorated.

Therefore, in order to avoid power unevenness among OFDM symbols, it is desirable to steer or puncture the power of the data area or to have the same number of pilots for each OFDMA symbol to match the power level of each symbol.

Embodiments of the present invention disclose a pilot allocation structure for multiple transmit antennas. The pilot allocation scheme for multiple transmit antennas may cause power level differences between transmit antennas per OFDMA symbol. Therefore, in order to reduce the power difference between the antennas, it is desirable to design the antenna to have pilot symbols for all antennas in each OFDMA symbol.

3. Multi-antenna transmission scheme

The pilot allocation structures disclosed in the embodiments of the present invention should be able to efficiently support multi-antenna transmission schemes. For example, assuming that four transmit antennas are assumed, a spatial frequency block coding (SFBC), a spatial time block coding (STBC), and a spatial multiplexing (SM) ) Can be considered.

Considering the channel estimation performance, the channel between two subcarriers which are coded in four transmission antennas must be flat in the case of SFBC, and the data transmission performance is better as the channel between the two symbols, which are coded in STBC, good. Therefore, when SFBC is supported in the communication system, it is preferable that the pilots for the four transmission antennas are located in a concatenated manner in the frequency domain. Further, when STBC is supported in the communication system, it is preferable that the pilots for the four transmit antennas are located in a concatenated manner in the time domain.

The pilot allocation structure shown in the present invention basically considers the case where four transmit antennas are used. In addition, when a collaborative transmission (Collaborative SM) is assumed, a pilot allocation structure can be distinguished using a specific code for different users in order to distinguish different users.

In the embodiments of the present invention, the pilot allocation structure can be applied to both uplink and downlink. In addition, the pilot allocation structure can be used only as a common pilot, and can be used only as a dedicated pilot. In addition, the pilot structure may be used together as a public pilot and a dedicated pilot.

A signal such as a control channel or preamble may be embedded in the pilot structure disclosed in the embodiments of the present invention. At this time, the pilot may not be loaded only at the position where the control channel or the preamble is allocated. Also, a dedicated pilot used only for a position to which a control channel or preamble is allocated may be allocated. Embodiments of the present invention can also be applied to a pilot allocation structure of Multicast and Broadcast Service (MBS) data transmission.

The pilot allocation structure used in the embodiments of the present invention described below can be represented by one resource block (RB) unit. At this time, the vertical axis is represented by a subcarrier index (m) as a frequency domain, and the horizontal axis is represented as an OFDM symbol index (n) as a time domain. Embodiments of the present invention may support multiple antenna systems.

The pilot allocation structure of the present invention is repeatedly applied in time domain and frequency domain within a frame or subframe. The structure of the pilot of each antenna can be applied mutually by changing the antenna. The pilot allocation structure of the present invention can be applied to both the uplink and the downlink, and can be used only as a common pilot, as a dedicated pilot, or as a common pilot and a dedicated pilot Can also be used together. When a signal such as a control channel or a preamble is loaded, the pilot may not be loaded in the signal, or another pilot dedicated to the signal may be loaded. The present invention can also be applied to a pilot allocation structure of MBS (Multicast Broadcast Service) data transmission.

Although the pilot allocation method of the present invention is expressed by the reference unit resource allocation structure, it is not necessarily limited, and the same can be applied to other unit resource allocation structure. In other words, it should be understood that the important pilot allocation criteria are the pilot spacing of the frequency axis and the time axis.

The abscissa of each of the accompanying drawings represents a set of time-domain OFDM symbols and the ordinate represents subcarriers in the frequency domain. The pilot index for each antenna is as follows. This index applies equally to all pilot allocation structures herein. The pilot symbol of the first transmission antenna Tx # 1 is denoted as '1' in the resource element RE and the pilot symbol of the second transmission antenna Tx # 2 is denoted as the resource element RE. The pilot symbol of the third transmission antenna Tx # 3 is denoted as' 3 'in the resource element RE and the pilot symbol of the fourth transmission antenna Tx # 4 is denoted as' And '4' in the element RE. A resource element with no indication is a resource element for data transmission.

Hereinafter, the embodiments of the present invention according to Figs. 4 to 18 all show the case where there are four transmission antennas.

4 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

4, the resource block (RB) is a method for allocating pilots based on a unit resource allocation structure composed of 26 subcarriers x 2 OFDM symbols. And the pilots of four antennas are allocated uniformly for each OFDM symbol to minimize the per antenna power fluctuation.

Referring to FIG. 4A, in the first OFDM symbol (n = 0), pilot symbols of Tx # 3 (third transmission antenna) are allocated where m is 0, and Tx # 1 (Fourth transmission antenna) is assigned, m is 16, a pilot symbol of Tx # 2 (second transmission antenna) is assigned, m is 25, and Tx # 4 (fourth transmission antenna) Of the pilot symbols are allocated. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 2 is allocated in a place where m is 0, a pilot symbol of Tx # 4 is allocated in a place where m is 7, 3 pilot symbols are allocated, and the pilot symbols of Tx # 1 are allocated where m is 25.

Referring to FIG. 4B, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 2 is allocated in a location where m is 0, and a pilot symbol of Tx # 4 is allocated in a location where m is 7 , a pilot symbol of Tx # 2 is allocated in a location where m is 16, and a pilot symbol of Tx # 1 is allocated in a location where m is 25. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 3 is allocated where m is 0, a pilot symbol of Tx # 1 is allocated where m is 7, and Tx A pilot symbol of # 2 is allocated, and a pilot symbol of Tx # 4 is allocated where m is 25.

Referring to FIG. 4C, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 2 is assigned where m is 0, and a pilot symbol of Tx # 1 is allocated A pilot symbol of Tx # 3 is allocated where m is 8, a pilot symbol of Tx # 4 is allocated where m is 15, a pilot symbol of Tx # 1 is allocated where m is 16, and a pilot symbol of Tx # 2 is allocated in a location where m is 25. [ In the second OFDM symbol (n = 1), a pilot symbol of Tx # 1 is allocated where m is 0, a pilot symbol of Tx # 2 is allocated where m is 7, and Tx A pilot symbol of Tx # 3 is allocated to a pilot symbol of # 4, a pilot symbol of Tx # 2 is assigned to a pilot symbol of m # 16, and a pilot symbol of Tx # 1 Of the pilot symbols are allocated.

Referring to FIG. 4 (d), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0, and a pilot symbol of Tx # 2 is allocated A pilot symbol of Tx # 3 is allocated to a location where m is 8, a pilot symbol of Tx # 4 is allocated to a location where m is 15, and a pilot symbol of Tx # 2 is allocated to a location where m is 16 , and a pilot symbol of Tx # 1 is allocated in a location where m is 25. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 2 is allocated where m is 0, a pilot symbol of Tx # 1 is allocated where m is 7, and Tx A pilot symbol of Tx # 3 is assigned to a pilot symbol of # 4, a pilot symbol of Tx # 1 is assigned to a pilot symbol of m # 16, and a pilot symbol of Tx # 2 Of the pilot symbols are allocated.

In the configurations of Figs. 4 (a) and 4 (b), the pilots of the four antennas are allocated evenly for each OFDM symbol. Further, the pilots of the same antenna are not allocated to the same subcarrier in two adjacent OFDM symbols.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

5 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

5, the resource block RB is a method for allocating pilots on the basis of a unit resource allocation structure composed of 18 subcarriers x 3 OFDM symbols. And the pilots of four antennas are allocated uniformly for each OFDM symbol to minimize the per antenna power fluctuation. And shifted by a predetermined frequency offset interval every OFDM symbol.

Referring to FIG. 5, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0, a pilot symbol of Tx # 3 is allocated where m is 1, The pilot symbol of Tx # 4 is allocated to the pilot symbol # 8, and the pilot symbol of Tx # 2 is assigned to the pilot symbol of m # 9. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated at m = 4, the pilot symbol of Tx # 4 is allocated at m = 5, A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 1 is allocated where m is 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 1 is assigned at m = 8, a pilot symbol of Tx # 3 is assigned at m = 9, and Tx A pilot symbol of # 4 is allocated, and a pilot symbol of Tx # 3 is allocated where m is 17.

In this configuration, the position where the pilot symbol is allocated when the unit resource allocation structure having the 18x3 structure is rotated 180 degrees on the plane shown in this structure is the same as the original structure. In other words, when a pilot symbol is assigned to a resource element of (m, n) in an 18 × 3 structure, a pilot symbol is also allocated to resource elements of (17-m, 2-n). For example, in this embodiment, a pilot symbol is assigned to a (0, 0) resource element, and therefore a pilot symbol is also assigned to (17, 2).

Also, in this configuration, the resource element to which the pilot symbol is allocated at the index n = 1 has a symmetric structure with respect to the frequency axis based on the center frequency of the 18 × 3 unit resource allocation structure. In this embodiment, the center frequency is the boundary frequency between the resource elements with m = 8 and m = 9.

In this configuration, the allocation structure of the index n = 2 is a structure in which the allocation structure at the index n = 0 is shifted by 8 resource elements.

Also, in this configuration, the pilots of the four antennas are equal for each OFDM symbol.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

6 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 6 illustrates a method of allocating a pilot according to a unit resource allocation structure including 18 subcarriers × 3 OFDM symbols.

Referring to FIG. 6A, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 3 is assigned where m is 0, and a pilot symbol of Tx # 1 is allocated A pilot symbol of Tx # 1 is allocated in a location where m is 10, and a pilot symbol of Tx # 4 is allocated in a location where m is 11. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated at m = 4, and the pilot symbol of Tx # 2 is allocated at m = 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 4 is allocated where m is 6, a pilot symbol of Tx # 1 is allocated where m is 7, and a pilot symbol of Tx A pilot symbol of # 1 is allocated, and a pilot symbol of Tx # 3 is allocated where m is 17.

Referring to FIG. 6B, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0, and a pilot symbol of Tx # 3 is allocated And a pilot symbol of Tx # 4 is allocated to a location where m is 8, and a pilot symbol of Tx # 1 is allocated to a location where m is 9. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated at m = 4, and the pilot symbol of Tx # 2 is allocated at m = 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 1 is allocated at m = 8, a pilot symbol of Tx # 4 is allocated at m = 9, and Tx A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 1 is allocated where m is 17.

Referring to FIG. 6 (c), in the first OFDM symbol (n = 0), the pilot symbol of Tx # 1 is allocated at m = 1 and the pilot symbol of Tx # 4 is allocated at m = A pilot symbol of Tx # 1 is allocated in a location where m is 10, and a pilot symbol of Tx # 3 is allocated in a location where m is 16. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated at m = 4, and the pilot symbol of Tx # 2 is allocated at m = 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 3 is allocated where m is 1, a pilot symbol of Tx # 1 is allocated where m is 7, and Tx A pilot symbol of Tx # 1 is assigned to a pilot symbol of # 4, and a pilot symbol of Tx # 1 is assigned to a pilot symbol of m #

In this configuration, the position where the pilot symbol is allocated when the unit resource allocation structure having the 18x3 structure is rotated 180 degrees on the plane shown in this structure is the same as the original structure. In other words, when a pilot symbol is assigned to a resource element of (m, n) in an 18 × 3 structure, a pilot symbol is also allocated to resource elements of (17-m, 2-n). For example, in this embodiment, a pilot symbol is assigned to a (0, 0) resource element, and therefore a pilot symbol is also assigned to (17, 2).

In this configuration, P (m, n) = P (17-m, 2) is defined as P (m, n) when an antenna number assigned to an OFDM symbol index n and a subcarrier index m is defined as P -n). For example, the number of transmit antennas allocated to P (0, 0) and P (17, 2) is the same.

Also, in this configuration, the resource element to which the pilot symbol is allocated at the index n = 1 has a symmetric structure with respect to the frequency axis based on the center frequency of the 18 × 3 unit resource allocation structure. In this embodiment, the center frequency is the boundary frequency between the resource elements with m = 8 and m = 9.

Further, in this configuration, only pilot symbols for one antenna are allocated at the OFDM index n = 1.

6 (c), the resource elements to which the pilot symbols are allocated in the index n = 0, 1, and 2 are symmetric with respect to the frequency axis on the basis of the center frequency of the 18 × 3 unit resource allocation structure .

In this configuration, the pilots of four antennas are allocated evenly for each OFDM symbol.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

7 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 7 is a flowchart illustrating a method of allocating a pilot according to a unit resource allocation structure including 18 subcarriers by 3 OFDM symbols.

Referring to FIG. 7A, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 3 is allocated where m is 0, and a pilot symbol of Tx # 1 is allocated A pilot symbol of Tx # 2 is allocated in a location where m is 10, and a pilot symbol of Tx # 4 is allocated in a location where m is 11. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is assigned in the case of m = 4, and the pilot symbol of Tx # 1 is assigned in the place of m = 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 4 is allocated where m is 6, a pilot symbol of Tx # 1 is allocated where m is 7, and a pilot symbol of Tx A pilot symbol of # 2 is allocated, and a pilot symbol of Tx # 3 is allocated where m is 17.

Referring to FIG. 7 (b), in the first OFDM symbol (n = 0), the pilot symbol of Tx # 1 is allocated where m is 0, and the pilot symbol of Tx # 3 is allocated A pilot symbol of Tx # 4 is allocated at a location where m is 10, and a pilot symbol of Tx # 2 is allocated at a location where m is 11. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is assigned in the case of m = 4, and the pilot symbol of Tx # 1 is assigned in the place of m = 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 1 is allocated at m = 6, a pilot symbol of Tx # 4 is allocated at m = 7, and Tx A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 2 is allocated where m is 17.

In this configuration, the position where the pilot symbol is allocated when the unit resource allocation structure having the 18x3 structure is rotated 180 degrees on the plane shown in this structure is the same as the original structure. In other words, when a pilot symbol is assigned to a resource element of (m, n) in an 18 × 3 structure, a pilot symbol is also allocated to resource elements of (17-m, 2-n). For example, in this embodiment, a pilot symbol is assigned to a (0, 0) resource element, and therefore a pilot symbol is also assigned to (17, 2).

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

8 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

8 is a method for allocating a pilot based on a unit resource allocation structure composed of 18 subcarriers x 6 OFDM symbols in a resource block (RB). Only pilots of two antennas among the four antennas are allocated for each OFDM symbol. This allocation method allocates first and third pilot symbols in an OFDM symbol having an even numbered index and allocates second and fourth pilot symbols in an OFDM symbol having an odd index. Alternatively, the allocation by antennas may be interchanged between the odd and even indexes above.

In the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is assigned where m is 0, a pilot symbol of Tx # 3 is allocated where m is 1, and Tx A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 1 is allocated where m is 9. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 2 is allocated where m is 0, a pilot symbol of Tx # 4 is allocated where m is 1, and Tx A pilot symbol of # 4 is allocated, and a pilot symbol of Tx # 2 is allocated where m is 9. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 1 is allocated at m = 4, a pilot symbol of Tx # 3 is allocated at m = 5, Tx A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 1 is allocated where m is 13. In the fourth OFDM symbol (n = 3), a pilot symbol of Tx # 2 is allocated at m = 4, a pilot symbol of Tx # 4 is allocated at m = 5, and Tx A pilot symbol of # 4 is allocated, and a pilot symbol of Tx # 2 is allocated where m is 13. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 1 is assigned in a place where m is 8, a pilot symbol of Tx # 3 is allocated in a place where m is 9, A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 1 is allocated where m is 17. In the sixth OFDM symbol (n = 5), a pilot symbol of Tx # 2 is assigned where m is 8, a pilot symbol of Tx # 4 is allocated where m is 9, and a pilot symbol of Tx A pilot symbol of # 4 is allocated, and a pilot symbol of Tx # 2 is allocated where m is 17.

In this configuration, the position where the pilot symbol is allocated when the unit resource allocation structure having the 18x6 structure is rotated 180 degrees on the plane shown in this structure is the same as the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in an 18 × 6 structure, a pilot symbol is also allocated to resource elements of (17-m, 5-n). For example, in this embodiment, a pilot symbol is assigned to a (0, 0) resource element, and therefore a pilot symbol is also assigned to (17, 5).

In this configuration, the pilot symbols allocated to the four antennas are gathered in four adjacent resource elements to form clusters. That is, for example, symbols allocated to four antennas are allocated to four adjacent resource elements having indices (0, 0), (0, 1), (1, 0), and (1, 1).

The above-described cluster structure is shifted on the frequency axis by four resource elements for each set of OFDM symbol groups composed of two adjacent OFDM symbols and repeated.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

9 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 9 shows a method of applying FIG. 8 in a different manner, and a resource block (RB) is a method of allocating pilots on the basis of a unit resource allocation structure composed of 18 subcarriers × 6 OFDM symbols.

Referring to FIG. 9A, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 3 is allocated where m is 0, and a pilot symbol of Tx # 1 is allocated A pilot symbol of Tx # 2 is allocated in a location where m is 10, and a pilot symbol of Tx # 4 is allocated in a location where m is 11. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is assigned in the case of m = 4, and the pilot symbol of Tx # 1 is assigned in the place of m = 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 4 is allocated where m is 6, a pilot symbol of Tx # 1 is allocated where m is 7, and a pilot symbol of Tx A pilot symbol of # 2 is allocated, and a pilot symbol of Tx # 3 is allocated where m is 17. The fourth OFDM symbol (n = 3) to the sixth OFDM symbol (n = 5) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the third OFDM symbol (n = 2) .

Referring to FIG. 9 (b), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 3 is allocated where m is 0, and a pilot symbol of Tx # 1 is allocated A pilot symbol of Tx # 2 is allocated in a location where m is 10, and a pilot symbol of Tx # 4 is allocated in a location where m is 11. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated at m = 4, the pilot symbol of Tx # 4 is allocated at m = 5, A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 1 is allocated where m is 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 3 is allocated where m is 6, a pilot symbol of Tx # 1 is allocated where m is 7, and Tx A pilot symbol of # 2 is allocated, and a pilot symbol of Tx # 4 is allocated where m is 17. The fourth OFDM symbol (n = 3) to the sixth OFDM symbol (n = 5) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the third OFDM symbol (n = 2) .

Referring to FIG. 9C, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0, and a pilot symbol of Tx # 3 is allocated A pilot symbol of Tx # 4 is allocated in a location where m is 8, and a pilot symbol of Tx # 2 is allocated in a location where m is 9. In the second OFDM symbol (n = 1), the Tx # 2 pilot symbol is allocated at m = 4, and the pilot symbol at Tx # 1 is allocated at m = 13. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 1 is allocated at m = 8, a pilot symbol of Tx # 4 is allocated at m = 9, and Tx A pilot symbol of # 3 is allocated, and a pilot symbol of Tx # 2 is allocated where m is 17. The fourth OFDM symbol (n = 3) to the sixth OFDM symbol (n = 5) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the third OFDM symbol (n = 2) .

Referring to FIG. 9D, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0, and a pilot symbol of Tx # 3 is allocated A pilot symbol of Tx # 4 is allocated in a location where m is 8, and a pilot symbol of Tx # 2 is allocated in a location where m is 9. In the second OFDM symbol (n = 1), the Tx # 2 pilot symbol is allocated at m = 4, the pilot symbol at Tx # 4 is allocated at m = 5, 3 pilot symbols are assigned, and where m is 13, the pilot symbols of Tx # 1 are allocated. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 1 is assigned at m = 8, a pilot symbol of Tx # 3 is assigned at m = 9, and Tx A pilot symbol of # 4 is allocated, and a pilot symbol of Tx # 2 is allocated where m is 17. The fourth OFDM symbol (n = 3) to the sixth OFDM symbol (n = 5) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the third OFDM symbol (n = 2) .

In this configuration, the position where the pilot symbol is allocated when the unit resource allocation structure having the 18x6 structure is rotated 180 degrees on the plane shown in this structure is the same as the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in an 18 × 6 structure, a pilot symbol is also allocated to resource elements of (17-m, 5-n). For example, in this embodiment, a pilot symbol is assigned to a (0, 0) resource element, and therefore a pilot symbol is also assigned to (17, 5).

In this configuration, the structure of the OFDM symbol index n = 0, 1, 2 is repeated as it is at the indices 3, 4,

In this configuration, the pilot allocation structure of the OFDM symbol index n = 2 in FIG. 9 (b) is a structure in which the structure of n = 0 is shifted downward by six resource elements in the frequency axis.

9 (b) and 9 (d) of this configuration, the pilots of the four antennas are allocated evenly for each OFDM symbol.

9 (a) and 9 (c), in this configuration, the pilots of four antennas are uniformly allocated at OFDM symbol index 0, 2, 3,

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

10 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

10, a resource block (RB) is a method of allocating pilots based on a unit resource allocation structure composed of 9 subcarriers x 6 OFDM symbols.

Referring to FIG. 10 (a), in the first OFDM symbol (n = 0), pilot symbols of Tx # 1 are allocated where m is 0. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated where m is 0. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 3 is allocated where m is 0, a pilot symbol of Tx # 1 is allocated where m is 4, and Tx # 4 < / RTI > In the fourth OFDM symbol (n = 3), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 2 is allocated where m is 4, and Tx # 3 < / RTI > In the fifth OFDM symbol (n = 4), pilot symbols of Tx # 1 are allocated where m is 8. In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 2 are allocated where m is 8.

Referring to FIG. 10 (b), in the first OFDM symbol (n = 0), pilot symbols of Tx # 1 are allocated where m is 1. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated where m is 1. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 3 is allocated where m is 1, a pilot symbol of Tx # 1 is allocated where m is 4, and Tx # 4 < / RTI > In the fourth OFDM symbol (n = 3), a pilot symbol of Tx # 4 is allocated where m is 1, a pilot symbol of Tx # 2 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI > In the fifth OFDM symbol (n = 4), the pilot symbol of Tx # 1 is allocated where m is 7. In the sixth OFDM symbol (n = 5), the pilot symbol of Tx # 2 is allocated where m is 7.

In this configuration, when a unit resource allocation structure having a 9 × 6 structure is rotated 180 degrees on the plane shown in this structure, the positions where the pilot symbols are allocated are the same as the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 6 structure, a pilot symbol is also allocated to resource elements of (8-m, 5-n). For example, in this embodiment, a pilot symbol is assigned to a (0, 0) resource element, and therefore a pilot symbol is also assigned to (8, 5).

In this configuration, the pilot symbols allocated to the same antenna are allocated for the OFDM symbol indexes n = 0 and n = 4, and so on for n = 1 and n = 5.

In FIG. 10A of this configuration, pilot symbols for four antennas are uniformly allocated in subcarrier indices 0 and 8. The same holds true for the subcarrier indices 1 and 7 in Fig. 10 (b).

In the OFDM symbol indexes n = 0 and n = 4, pilot symbols allocated to the same antenna are allocated, and also for n = 1 and n = 5.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

11 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 11 illustrates a method of allocating pilots on the basis of a unit resource allocation structure composed of 9 subcarriers × 6 OFDM symbols.

Referring to FIG. 11A, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 2 is allocated where m is 0, a pilot symbol of Tx # 3 is allocated where m is 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 8. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 1 is allocated where m is zero. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 3 is allocated where m is 4, and a pilot symbol of Tx # 2 < / RTI > In the sixth OFDM symbol (n = 5), the pilot symbol of Tx # 1 is allocated where m is 8.

Referring to FIG. 11 (b), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 2 is allocated where m is 1, a pilot symbol of Tx # 3 is allocated where m is 4, and a pilot symbol of Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 7. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 1 is allocated where m is 1. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 1, a pilot symbol of Tx # 3 is allocated where m is 4, and Tx # 2 < / RTI > In the sixth OFDM symbol (n = 5), the pilot symbol of Tx # 1 is allocated where m is 7.

Referring to FIG. 11 (c), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 2. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated at m = 2, the pilot symbol of Tx # 3 is allocated at m = 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 6. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 1 is allocated where m is 2. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 2, a pilot symbol of Tx # 3 is allocated where m is 4, and a pilot symbol of Tx # 2 < / RTI > In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 1 are allocated where m is 6.

In this configuration, when the unit resource allocation structure having the 9 × 6 structure is rotated 180 degrees on the plane shown in the figure, the position where the pilot symbols are allocated is the same as the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 6 structure, a pilot symbol is also allocated to resource elements of (8-m, 5-n). For example, in this embodiment, a pilot symbol is assigned to a (0, 0) resource element, and therefore a pilot symbol is also assigned to (8, 5).

P (m, n) = P (8-m, 5) where P (m, n) is an antenna number assigned to an OFDM symbol index n and a subcarrier index m, -n). For example, the numbers of transmit antennas allocated to P (0, 0) and P (8, 5) are the same.

In this configuration, only pilot symbols for one antenna are allocated in the OFDM symbol indexes 0, 2, 3, and 5. In the indexes 1 and 4, pilot symbols for the three antennas except for the above one antenna are uniformly allocated .

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

12 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 12 illustrates a method of allocating pilots based on a unit resource allocation structure composed of 9 subcarriers × 6 OFDM symbols.

Referring to FIG. 12 (a), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 3. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 3 is allocated at m = 3, the pilot symbol of Tx # 2 is allocated at m = 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 5. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 1 is allocated where m is 3. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 3, a pilot symbol of Tx # 2 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI > In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 1 are allocated where m is 5.

Referring to FIG. 12 (b), in the first OFDM symbol (n = 0), pilot symbols of Tx # 3 are allocated where m is 0 and pilot symbols of Tx # 1 are allocated And a pilot symbol of Tx # 4 is allocated where m is 8. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated where m is 4. In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 4. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 1 is allocated where m is 4. In the fifth OFDM symbol (n = 4), the pilot symbol of Tx # 2 is allocated where m is 4. In the sixth OFDM symbol (n = 5), a pilot symbol of Tx # 4 is assigned where m is 0, a pilot symbol of Tx # 1 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI >

Referring to FIG. 12C, in the first OFDM symbol (n = 0), a pilot symbol of Tx # 3 is allocated where m is 0, and a pilot symbol of Tx # 1 is allocated And a pilot symbol of Tx # 4 is allocated where m is 8. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated where m is 4. In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 4. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 4. In the fifth OFDM symbol (n = 4), pilot symbols of Tx # 1 are allocated where m is 4. In the sixth OFDM symbol (n = 5), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 2 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI >

In this configuration, when a unit resource allocation structure having a 9 × 6 structure is rotated 180 degrees on the plane shown in this structure, the positions where the pilot symbols are allocated are the same as the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 6 structure, a pilot symbol is also allocated to resource elements of (8-m, 5-n). For example, in this embodiment, a pilot symbol is assigned to a (4, 1) resource element, and therefore a pilot symbol is also assigned to (4, 4).

12 (a) and 12 (b), when an antenna number allocated to a pilot signal at an OFDM symbol index n and a subcarrier index m is defined as P (m, n), P m, n) = P (8-m, 5-n). For example, the numbers of transmit antennas allocated to P (0, 0) and P (8, 5) are the same.

12 (b) and 12 (c) of this configuration have a structure in which pilot symbols allocated to four antennas are evenly allocated to four resource elements at the outermost corner.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

13 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 13 illustrates a method of allocating pilots on the basis of a unit resource allocation structure composed of 9 subcarriers × 6 OFDM symbols.

Referring to FIG. 13 (a), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 3 is allocated where m is 0, the pilot symbol of Tx # 2 is allocated where m is 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 8. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 0. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 1 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI > In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 2 are allocated where m is 8.

Referring to FIG. 13 (b), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 1. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 3 is allocated where m is 1, a pilot symbol of Tx # 2 is allocated where m is 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 7. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 1. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 1, a pilot symbol of Tx # 1 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI > In the sixth OFDM symbol (n = 5), the pilot symbol of Tx # 2 is allocated where m is 7.

Referring to FIG. 13 (c), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 2. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 3 is allocated at m = 2, the pilot symbol of Tx # 2 is allocated at m = 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 6. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 2. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is assigned where m is 2, a pilot symbol of Tx # 1 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI > In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 2 are allocated where m is 6.

In this configuration, when a unit resource allocation structure having a 9 × 6 structure is rotated 180 degrees on the plane shown in this structure, the positions where the pilot symbols are allocated are the same as the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 6 structure, a pilot symbol is also allocated to resource elements of (8-m, 5-n). For example, in this embodiment, a pilot symbol is assigned to a (4, 1) resource element, and therefore a pilot symbol is also assigned to (4, 4).

In Fig. 13 (a) of this configuration, pilot symbols for four antennas are uniformly allocated in subcarrier indices 0 and 8. The same holds for the index subcarrier indexes 1 and 7 in FIG. 13 (b) and the index subcarrier indexes 2 and 6 in FIG. 13 (c).

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

14 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 14 illustrates a method of allocating a pilot on the basis of a unit resource allocation structure composed of 9 subcarriers × 6 OFDM symbols.

Referring to FIG. 14 (a), in the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 3. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 2 is allocated at m = 3, a pilot symbol of Tx # 3 is allocated at m = 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 5. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 3. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is assigned where m is 3, a pilot symbol of Tx # 1 is allocated where m is 4, and Tx # 3 < / RTI > In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 2 are allocated where m is 5.

14 (b), in the first OFDM symbol (n = 0), the pilot symbol of Tx # 3 is assigned where m is 0, and the pilot symbol of Tx # 1 is allocated And a pilot symbol of Tx # 4 is allocated where m is 8. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated where m is 4. In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 4. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 4. In the fifth OFDM symbol (n = 4), pilot symbols of Tx # 1 are allocated where m is 4. In the sixth OFDM symbol (n = 5), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 2 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI >

In this configuration, when a unit resource allocation structure having a 9 × 6 structure is rotated 180 degrees on the plane shown in this structure, the positions where the pilot symbols are allocated are the same as the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 6 structure, a pilot symbol is also allocated to resource elements of (8-m, 5-n). For example, in this embodiment, a pilot symbol is assigned to a (4, 1) resource element, and therefore a pilot symbol is also assigned to (4, 4).

In Fig. 14 (a) of this configuration, pilot symbols for four antennas are uniformly allocated in the subcarrier indexes 3 and 6.

14 (b) of this configuration has a structure in which pilot symbols allocated to four antennas are uniformly allocated to four resource elements at the outermost corner.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

15 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

15 is a method for allocating a pilot based on a unit resource allocation structure composed of 9 subcarriers x 12 OFDM symbols. Fig. 15 shows a configuration in which the configuration according to Fig. 10 is repeated on the time axis.

In the first OFDM symbol (n = 0), the pilot symbol of Tx # 1 is allocated where m is 0. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated where m is 0. In the third OFDM symbol (n = 2), a pilot symbol of Tx # 3 is allocated where m is 0, a pilot symbol of Tx # 1 is allocated where m is 4, and Tx # 4 < / RTI > In the fourth OFDM symbol (n = 3), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 2 is allocated where m is 4, and Tx # 3 < / RTI > In the fifth OFDM symbol (n = 4), pilot symbols of Tx # 1 are allocated where m is 8. In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 2 are allocated where m is 8. The seventh OFDM symbol (n = 6) to the twelfth OFDM symbol (n = 11) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the sixth OFDM symbol (n = 5) .

In this configuration, when a unit resource allocation structure having a 9 × 12 structure is rotated 180 degrees on the plane shown in the figure, the positions where the pilot symbols are allocated are the same as in the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 12 structure, a pilot symbol is also allocated to resource elements of (8-m, 11-n). For example, in this embodiment, a pilot symbol is assigned to a (4, 2) resource element, and thus a pilot symbol is also assigned to (4, 9).

In this configuration, the structure of the OFDM symbol indexes 0 to 5 is repeated at the indices 6 to 11 as they are.

In this configuration, the pilot symbols for the four antennas are allocated evenly at the subcarrier index 0, 8.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

16 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

16 is a method for allocating pilots on the basis of a unit resource allocation structure composed of 9 subcarriers x 12 OFDM symbols. Fig. 16 is an example in which Fig. 15 is applied in a different manner.

In the first OFDM symbol (n = 0), a pilot symbol of Tx # 1 is allocated where m is 0, a pilot symbol of Tx # 3 is allocated where m is 4, and a pilot symbol of Tx # 4 < / RTI > In the second OFDM symbol (n = 1), the pilot symbol of Tx # 2 is allocated where m is 0. In a third OFDM symbol (n = 2), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 1 is allocated where m is 4, and Tx # 3 < / RTI > In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 4. In the fifth OFDM symbol (n = 4), pilot symbols of Tx # 1 are allocated where m is 8. In the sixth OFDM symbol (n = 5), a pilot symbol of Tx # 3 is allocated where m is 0, a pilot symbol of Tx # 4 is allocated where m is 4, and a pilot symbol of Tx # 2 < / RTI > The seventh OFDM symbol (n = 6) to the twelfth OFDM symbol (n = 11) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the sixth OFDM symbol (n = 5) .

In this configuration, when a unit resource allocation structure having a 9 × 12 structure is rotated 180 degrees on the plane shown in the figure, the positions where the pilot symbols are allocated are the same as in the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 12 structure, a pilot symbol is also allocated to resource elements of (8-m, 11-n). For example, in this embodiment, a pilot symbol is assigned to a (4, 2) resource element, and thus a pilot symbol is also assigned to (4, 9).

In this configuration, the structure of the OFDM symbol indexes 0 to 5 is repeated at the indices 6 to 11 as they are.

In this configuration, a 9 × 6 structure in which pilot symbols allocated to four antennas are uniformly allocated to four resource elements at the outermost edges is repeated on the time axis.

In this configuration, the pilot symbols for the four antennas are allocated evenly at the subcarrier index 0, 8.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

17 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 17 shows a method of allocating a pilot on the basis of a unit resource allocation structure composed of 9 subcarriers 占 12 OFDM symbols as a resource block (RB). 17 is an example in which FIG. 15 is applied in a different manner

In the first OFDM symbol (n = 0), the pilot symbol of Tx # 1 is allocated where m is 0. In the second OFDM symbol (n = 1), the pilot symbol of Tx # 3 is allocated where m is 0, the pilot symbol of Tx # 2 is allocated where m is 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 8. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 0. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 0, a pilot symbol of Tx # 1 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI > In the sixth OFDM symbol (n = 5), pilot symbols of Tx # 2 are allocated where m is 8. The seventh OFDM symbol (n = 6) to the twelfth OFDM symbol (n = 11) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the sixth OFDM symbol (n = 5) .

In this configuration, the pilot symbols for the four antennas are allocated evenly at the subcarrier index 0, 8.

In this configuration, when a unit resource allocation structure having a 9 × 12 structure is rotated 180 degrees on the plane shown in the figure, the positions where the pilot symbols are allocated are the same as in the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 12 structure, a pilot symbol is also allocated to resource elements of (8-m, 11-n). For example, in this embodiment, a pilot symbol is assigned to a (4, 2) resource element, and thus a pilot symbol is also assigned to (4, 9).

In this configuration, the structure of the OFDM symbol indexes 0 to 5 is repeated at the indices 6 to 11 as they are.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

18 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

FIG. 18 shows a method of allocating a pilot based on a unit resource allocation structure consisting of 9 subcarriers 占 12 OFDM symbols in a resource block (RB). 17 is an example in which FIG. 15 is applied in a different manner

In the first OFDM symbol (n = 0), the pilot symbol of Tx # 1 is allocated where m is 1. In the second OFDM symbol (n = 1), a pilot symbol of Tx # 3 is allocated where m is 1, a pilot symbol of Tx # 2 is allocated where m is 4, and Tx # 4 < / RTI > In the third OFDM symbol (n = 2), the pilot symbol of Tx # 1 is allocated where m is 7. In the fourth OFDM symbol (n = 3), the pilot symbol of Tx # 2 is allocated where m is 1. In the fifth OFDM symbol (n = 4), a pilot symbol of Tx # 4 is allocated where m is 1, a pilot symbol of Tx # 1 is allocated where m is 4, and a pilot symbol of Tx # 3 < / RTI > In the sixth OFDM symbol (n = 5), the pilot symbol of Tx # 2 is allocated where m is 7. The seventh OFDM symbol (n = 6) to the twelfth OFDM symbol (n = 11) are allocated pilot symbols in the same manner as the first OFDM symbol (n = 0) to the sixth OFDM symbol (n = 5) .

In this configuration, the pilot symbols for the four antennas are uniformly allocated in subcarrier indices 1 and 7.

In this configuration, when a unit resource allocation structure having a 9 × 12 structure is rotated 180 degrees on the plane shown in the figure, the positions where the pilot symbols are allocated are the same as in the original structure. In other words, when a pilot symbol is allocated to a resource element of (m, n) in a 9 × 12 structure, a pilot symbol is also allocated to resource elements of (8-m, 11-n). For example, in this embodiment, a pilot symbol is assigned to a (4, 1) resource element, and therefore a pilot symbol is also assigned to (4, 10).

In this configuration, the structure of the OFDM symbol indexes 0 to 5 is repeated at the indices 6 to 11 as they are.

This pilot pattern in one resource block is used repeatedly in all the remaining subframes and frames.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of embodiments of the invention, For example, in the pilot symbol structure in which the technical idea of the present invention is reflected, drawings are not created reflecting the cyclic transition for all the drawings. However, by combining the technical ideas shown in the above-mentioned drawings, it is possible to confirm the number of all cases.

That is, the present specification discloses pilot symbol structures capable of cyclically shifting pilot symbols included in each pilot symbol structures into one or more OFDM symbol units and / or one or more subcarrier units.

In this specification, in addition to the above-described pilot allocation scheme and pilot allocation scheme, the present invention proposes a method of using a pilot allocation scheme in which four transmission antennas are used and four or more transmission antennas are used for one or more UEs sharing resources.

In general, the pilot division of an antenna or a terminal (user) for spatial multiplexing is performed in the time / frequency domain. In this case, as the number of antennas or the number of terminals (users) sharing resources increases, the pilot overhead increases. If the number of antennas or the number of terminals (users) sharing resources is increased, the channel estimation performance may be lowered if a relatively low pilot overhead is maintained. The present invention proposes an antenna allocation scheme having the same channel estimation performance while maintaining a relatively low pilot overhead in such trade-off.

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. In addition, claims that do not have an explicit citation in the claims may be combined to form an embodiment or included in a new claim by amendment after the application.

INDUSTRIAL APPLICABILITY The present invention can be applied to a terminal or a network device used in a wireless access system.

1 is a diagram showing an example of a general pilot structure used in a single transmission antenna structure.

2 is a diagram illustrating an example of a general pilot structure used in two transmission antenna structures.

3 is a diagram showing an example of a general pilot structure used in four transmission antenna structures.

4 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

5 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

6 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

7 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

8 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

9 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

10 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

11 is a diagram illustrating a pilot allocation structure according to an embodiment of the present invention.

12 is a diagram showing one of the methods of cyclically transiting the pilot allocation structure as another embodiment of the present invention.

13 is a diagram showing another method of cyclically transiting the pilot allocation structure according to another embodiment of the present invention.

14 is a diagram illustrating another method of cyclically transiting the pilot allocation structure according to another embodiment of the present invention.

15 is a diagram illustrating another method of cyclically transiting the pilot allocation structure according to another embodiment of the present invention.

16 is a diagram illustrating another method of cyclically transiting the pilot allocation structure according to another embodiment of the present invention.

17 is a diagram showing another method of cyclically transiting the pilot allocation structure according to another embodiment of the present invention.

18 is a diagram showing another method of cyclically transiting the pilot allocation structure according to another embodiment of the present invention.

Claims (10)

In a wireless access system, when a transmitter having four transmit antennas transmits a pilot for data transmission, Transmitting the data using a resource block comprised of a plurality of subcarriers and a plurality of successive orthogonal frequency division multiplexing (OFDM) symbols; And Transmitting a first pilot via a first transmit antenna, a second pilot via a second transmit antenna, a third pilot via a third transmit antenna, and a fourth pilot via a fourth transmit antenna, Wherein the resource block includes the first pilot, the second pilot, the third pilot, and the fourth pilot allocated in a predetermined pilot pattern, The predetermined pilot pattern is repeatedly applied in a subframe, The third and the second pilot are allocated to the same subcarrier (hereinafter referred to as a first pilot subcarrier) in two adjacent OFDM symbols, and the first and fourth pilots are allocated in the adjacent two OFDM symbols (Hereinafter referred to as " second pilot subcarrier ") different from the subcarriers to which the third and second pilots are allocated, The third pilot in the predetermined pilot pattern is allocated to the first pilot subcarrier in one OFDM symbol of the adjacent two OFDM symbols and in the other OFDM symbol in the adjacent two OFDM symbols, (Hereinafter, referred to as " third pilot subcarrier "), Wherein the second pilot in the predetermined pilot pattern is allocated to the third pilot subcarrier in the one OFDM symbol among the adjacent two OFDM symbols and the second pilot in the other OFDM symbol is allocated to the third pilot subcarrier in the one OFDM symbol, Subcarriers, Wherein the first pilot in the predetermined pilot pattern is allocated to the second pilot subcarrier in the one OFDM symbol among the two neighboring OFDM symbols and in the other OFDM symbol in the adjacent two OFDM symbols, (Hereinafter referred to as " fourth pilot subcarrier ") that is separated from the subcarrier by a second predetermined number, The fourth pilot in the predetermined pilot pattern is allocated to the fourth pilot subcarrier in the one OFDM symbol among the two neighboring OFDM symbols and in the other OFDM symbol in the adjacent two OFDM symbols, ≪ / RTI > Data transmission method. The method according to claim 1, The predetermined pilot pattern in the resource block is given according to the following table n n + 1 m P2 P3 m ' P4 P1 m + a P3 P2 m '+ b P1 P4 , Where P1 denotes the first pilot, P2 denotes the second pilot, P3 denotes the third pilot P4 denotes the fourth pilot, n and n + 1 are the numbers of OFDM symbols in the resource block, m denotes Where a is the first predetermined number, b is a second predetermined number indicating the second predetermined number of pilot subcarriers in the resource block, m is the number of the first pilot subcarriers in the resource block, m 'is the number of the second pilot subcarriers in the resource block, Data transmission method. The method according to claim 1, The predetermined pilot pattern in the resource block is given according to the following table n n + 1 m P2 P3 m ' P4 P1 m + a P3 P2 m '+ b P1 P4 , Where P1 denotes the first pilot, P2 denotes the second pilot, P3 denotes the third pilot P4 denotes the fourth pilot, n and n + 1 are the numbers of OFDM symbols in the resource block, m denotes Where a is the first predetermined number, b is a second predetermined number indicating the second predetermined number of pilot subcarriers in the resource block, m is the number of the first pilot subcarriers in the resource block, m 'is the number of the second pilot subcarriers in the resource block, Data transmission method. The method according to claim 2 or 3, m = 0, a = 16, m '= 7, b = 18, Data transmission method. In receiving a pilot for data reception from a transmitter having four transmit antennas in a wireless access system, Receiving the data using a resource block comprised of a plurality of subcarriers and a plurality of successive orthogonal frequency division multiplexing (OFDM) symbols; And Receiving a first pilot via a first transmit antenna, a second pilot via a second transmit antenna, a third pilot via a third transmit antenna, and a fourth pilot via a fourth transmit antenna, Wherein the resource block includes the first pilot, the second pilot, the third pilot, and the fourth pilot allocated in a predetermined pilot pattern, The predetermined pilot pattern is repeatedly applied in a subframe, Wherein the third and the second pilot are allocated to the same subcarrier (hereinafter referred to as a first pilot subcarrier) in two adjacent OFDM symbols, and the first and fourth pilots are allocated in the adjacent two OFDM symbols (Hereinafter referred to as a second pilot subcarrier) different from the subcarriers to which the third and second pilots are allocated, The third pilot in the predetermined pilot pattern is allocated to the first pilot subcarrier in one OFDM symbol of the adjacent two OFDM symbols and the second pilot subcarrier in another OFDM symbol in the adjacent two OFDM symbols, (Hereinafter, referred to as " third pilot subcarrier ") spaced apart from the carrier by a first predetermined number, The second pilot in the predetermined pilot pattern is allocated to the third pilot subcarrier in the one OFDM symbol among the two adjacent OFDM symbols and the first pilot in the other OFDM symbol is allocated to the third pilot subcarrier in the one OFDM symbol, Is assigned to a pilot subcarrier, Wherein the first pilot in the predetermined pilot pattern is allocated to the second pilot subcarrier in the one OFDM symbol among the two adjacent OFDM symbols and the second pilot subcarrier is allocated in the other OFDM symbol in the second pilot subcarrier, (Hereinafter, referred to as " fourth pilot subcarrier ") that is separated from the pilot subcarrier by a second predetermined number, The fourth pilot in the predetermined pilot pattern is allocated to the fourth pilot subcarrier in the one OFDM symbol among the two adjacent OFDM symbols and the second pilot subcarrier in the other OFDM symbol is allocated to the second pilot subcarrier in the one OFDM symbol, Lt; RTI ID = 0.0 > subcarrier, < / RTI > A method for receiving data. 6. The method of claim 5, The predetermined pilot pattern in the resource block is given according to the following table n n + 1 m P2 P3 m ' P4 P1 m + a P3 P2 m '+ b P1 P4 , Where P1 denotes the first pilot, P2 denotes the second pilot, P3 denotes the third pilot P4 denotes the fourth pilot, n and n + 1 are the numbers of OFDM symbols in the resource block, m denotes Where a is the first predetermined number, b is a second predetermined number indicating the second predetermined number of pilot subcarriers in the resource block, m is the number of the first pilot subcarriers in the resource block, m 'is the number of the second pilot subcarriers in the resource block, A method for receiving data. 6. The method of claim 5, The predetermined pilot pattern in the resource block is given according to the following table n n + 1 m P2 P3 m ' P4 P1 m + a P3 P2 m '+ b P1 P4 , Where P1 denotes the first pilot, P2 denotes the second pilot, P3 denotes the third pilot P4 denotes the fourth pilot, n and n + 1 are the numbers of OFDM symbols in the resource block, m denotes Where a is the first predetermined number, b is a second predetermined number indicating the second predetermined number of pilot subcarriers in the resource block, m is the number of the first pilot subcarriers in the resource block, m 'is the number of the second pilot subcarriers in the resource block, A method for receiving data. 8. The method according to claim 6 or 7, m = 0, a = 16, m '= 7, b = 18, A method for receiving data. delete delete

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