KR100895049B1 - Apparatus and Method for Estimating Channel based on OFDM/OFDMA system - Google Patents

Abstract

Provided are a channel estimation method and apparatus for an uplink partial usage of subchannels (PUSC) mode in a wireless communication system having a MIMO structure supporting OFDM / OFDMA. To this end, the channel estimation method includes extracting a plurality of pilots from a received signal transformed into a frequency domain, and copying the channel estimates of the extracted pilots to data and null of the same subcarrier index as the pilots in units of tiles. copying; and estimating the channel by performing interpolation on a symbol index axis using the copied channel estimate, thereby transmitting an uplink PUSC mode in a high level MCS in a low speed mobile environment. For the signal of, the base station can effectively estimate the channel.

Description

Apparatus and Method for Estimating Channel based on OFDM / OFDMA system in wireless communication system supporting OPDM or OPDMA

1 is a diagram illustrating an example of a frame structure used in an IEEE 802.16d / e based portable Internet system.

2 is a diagram illustrating a part of subcarrier allocation structure according to Table 1;

3 is a view for explaining an outline of a SISO system, a MIMO system, and a cooperative MIMO system.

4 is a diagram illustrating a pilot pattern in a tile when an uplink PUSC mode applied by a first transmission antenna and a second transmission antenna is transmitted.

5 is a diagram illustrating a configuration of a channel estimating apparatus according to an embodiment of the present invention.

6 is a flowchart illustrating a channel estimation method according to an embodiment of the present invention.

FIG. 7 is a diagram for describing channel estimation using an average in an uplink PUSC mode having a 2 × 2 MIMO structure. FIG.

8 illustrates channel estimation using interpolation in an uplink PUSC mode of a 2 × 2 MIMO structure according to an embodiment of the present invention.

9 is a diagram for explaining interpolation using a difference between symbol indices.

10 illustrates MSE of channel estimates versus SNR in different mobile channel environments.

FIG. 11 is a diagram illustrating a packet error rate (PER) versus an SNR measured at different modulation and coding scheme (MCS) levels. FIG.

Explanation of symbols on the main parts of the drawings

510: FFT unit 520: offset estimation unit

530: offset compensator 540: channel estimator

The present invention relates to channel estimation in an orthogonal frequency division multiplexing system. More particularly, the present invention relates to a channel estimation method and apparatus in an uplink partial usage of subchannels (PUSC) mode in a wireless communication system having a MIMO structure supporting OFDM / OFDMA. It is about.

Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) is a transmission method that transmits data in parallel using multiple subcarriers having orthogonality to each other instead of a single wide carrier. In a frequency selective fading channel having Inter-Symbol Interference, each subchannel in a narrow band has a flat fading characteristic.

Such an OFDM / OFDMA system has higher frequency efficiency and transmission rate than a communication system using a single carrier. However, even in such an OFDM / OFDMA system, the reception side requires distortion compensation according to a channel environment for the received OFDM / OFDMA symbol (hereinafter, referred to as a 'symbol'). In particular, when an OFDM / OFDMA system is a system that guarantees mobility, such as a portable Internet service, the wireless channel environment is time-varying. Accordingly, channel estimation should also be designed to keep track of changing channels. For channel estimation for the time-varying channel, the transmitting side transmits a pilot signal known to the receiving side to the pilot subcarrier allocated to some subcarriers in the symbol. Then, the receiver performs channel estimation on a subcarrier through which data is actually transmitted using a pilot.

On the other hand, MIMO (Multiple Input Multiple Output) system, unlike the SISO (Single Input Single Output) system in which the transmitting side and the receiving side communicate with one antenna, respectively, the number of antennas on the transmitting side and the receiving side is increased to multiple data. It is a technology that can transmit the path, reduce the interference by detecting the signal received on each path at the receiving side, and improve the transmission efficiency through space-time diversity and spatial multiplexing at the transmitting side.

When the MIMO structure is applied to an OFDM or OFDMA system, since a pilot pattern for channel estimation transmitted from a transmitter side depends on the MIMO structure, a channel estimation technique suitable for the above-described MIMO structure is needed, and in particular, OFDM / A channel estimation technique suitable for the Partial Usage of Sub-Carrier (PUSC) mode preferentially adopted in an OFDMA system is required.

The present invention was devised to meet the above requirements, and an object of the present invention is to provide a high-level MCS (Modulation and Subsequence) mode when using an uplink partial usage of subchannels (PUSC) mode in a MIMO-structured wireless communication system supporting OFDM / OFDMA. The present invention provides a channel estimation method and apparatus suitable for a coding scheme.

For this purpose, an apparatus for estimating a channel in a wireless communication system supporting OFDM or OFDMA of one embodiment of the present invention includes: an FFT unit for converting a received signal in a time domain into a received signal in a frequency domain; And extracting pilots from the received signal in the frequency domain and estimating the channel in tile units using the extracted pilots, wherein a channel estimate for the pilot in the tile is set to the same subcarrier index as the pilot in the tile. And a channel estimator for copying each of the symbols in the tile to be positioned, and performing interpolation using the channel estimates copied to the symbols in the tile, respectively.

On the other hand, in a wireless communication system supporting OFDM or OFDMA of one embodiment of the present invention, a method for estimating a channel includes: (a) extracting a plurality of pilots from a received signal converted into a frequency domain; (b) copying channel estimates for the pilots in the tiles into nulls and data located at the same subcarrier index as the pilots in the tiles, in units of tiles for the extracted pilots; And (c) estimating the channel by performing interpolation on a symbol index axis using the copied channel estimate.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments. For reference, in the following description, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention are omitted.

1 is a diagram illustrating an example of a frame structure used in an IEEE 802.16d / e-based portable Internet system. A portable Internet system using the TDD method divides one frame in time and uses it for transmission and reception. .

Referring to FIG. 1, one frame is divided into a downlink frame for transmitting data from a base station to a terminal and an uplink frame for transmitting data from a terminal to a base station, with TTG ( Transmit / receive transition gap and RTG (receive / transmit transition gap) are inserted. In the illustrated example, the downlink frame includes at least a preamble section, a partial usage of subchannels (PUSC) subchannel section, a full usage of subchannels (FUSC) subchannel section, an adaptive modulation & coding (AMC) subchannel section, and the like. One uplink frame includes at least one uplink symbol interval, a PUSC subchannel interval, an AMC subchannel interval, and the like.

In particular, in the context of the present invention, when using 1024 fast fourier transform (FFT) of the subcarrier allocation method for the uplink PUSC subchannel interval, it can be allocated as shown in Table 1 below, Figure 2 is a subcarrier allocation according to Table 1 A part of the structure is shown.

 TABLE 1

Referring to Tables 1 and 2, in the uplink PUSC subchannel section using 1024 FFT, 92 and 91 subcarriers, respectively, of left and right sides of the total 1024 subcarriers are used as protection intervals to mitigate interference between adjacent channels. Is used as the DC subcarrier. Since 840 subcarriers other than these are used as effective subcarriers and provide 210 tiles in the entire allocated frequency band, each of the six sub-carriers allocated to each tile supports 35 subchannels.

In addition, the basic unit constituting the uplink PUSC subchannel is a tile, and the tile is composed of three OFDMA symbols × four subcarriers in a two-dimensional plane of an OFDMA symbol-subcarrier, and includes four pilots and eight data. Includes subcarriers Accordingly, one uplink PUSC subchannel consists of six tiles, and provides a total of 24 pilots and 48 data subcarriers.

Meanwhile, the present invention is also applied to a MIMO system or a cooperative MIMO system that performs multiple input / output transmissions using a plurality of transmit antennas and a plurality of receive antennas. Hereinafter, the MIMO system or the cooperative MIMO system will be described with reference to FIGS. 3 to 4. It demonstrates.

First, FIG. 3 is a diagram illustrating an overview of a general SISO system, a MIMO system, and a collaborative MIMO system.

As shown in FIG. 3 (a), a single input single output (SISO) system is a technology in which one antenna (Base_Ant, Terminal_Ant) is used at a receiving side and a transmitting side, respectively, in a transmitting side and a receiving side in wireless communication. In case of communication with each one antenna, multipath phenomenon occurs due to obstacles in the propagation path such as hills and steel towers, which causes problems due to fading. do.

Multiple Input Multiple Output (MIMO) system transmits data through multiple paths by increasing the number of antennas of the base station and the terminal, reduces interference by detecting signals received on each path at the receiving end, and performs space-time diversity and spatial multiplexing at the transmitting end. Through this, transmission efficiency can be increased. For example, FIG. 3 (b) illustrates a 2 × 2 MIMO system using a base station having two receive antennas Base_Ant0 and Base_Ant1 and a terminal having two transmit antennas Terminal_Ant0 and Terminal_Ant1. As shown in b), four channels, that is, the first channel H00, are provided between the first and second reception antennas Base_Ant0 and Base_Ant1 of the base station and the first and second transmission antennas Terminal_Ant0 and Terminal_Ant1 of the terminal. The second channel H01, the third channel H10, and the fourth channel H11 are formed.

The cooperative MIMO system performs MIMO transmission through a plurality of channels formed between a base station having a plurality of antennas and a plurality of terminals each having a single antenna. 3 (c) shows a base station having two receive antennas Base_Ant0 and Base_Ant1, a first terminal having a single transmit antenna Terminal_Ant, and a second terminal having a single transmit antenna Terminal_Ant, respectively. As an example of a 2x2 cooperative MIMO system, as shown in FIG. 3 (c), the first and second reception antennas Base_Ant0 and Base_Ant1 of the base station, the transmission antennas (Terminal_Ant) and the second terminal of the first terminal are illustrated. Four channels, that is, a first channel H 0 0, a second channel H 0 1, a third channel H 1 0, and a fourth channel H 1 1 are formed between the transmitting antennas of the terminal_ant. do. In addition, the received signals of the first and third channels transmitted from the first terminal and the received signals of the second and fourth channels transmitted from the second terminal are spatial multiplexed through the same subcarriers in different pilot patterns. are multiplexed and transmitted to the base station. For reference, in channel notation H00, the first index 0 is related to the index of the receiving antenna, and the second index 0 is related to the index of the transmitting antenna.

In addition, in the uplink PUSC section related to the present invention, in the case of MIMO, a terminal (Mobile Station / Portable Subscriber Station) transmits signals to two transmission antennas (Terminal_Ant0 and Terminal_Ant1), and a base station (Base Station / Radio Access Station) Receives a signal with two receiving antennas Base_Ant0 and Base_Ant1. In addition, in the case of cooperative MIMO, a signal is transmitted from a transmitting antenna (Terminal_Ant) of a first terminal and a transmitting antenna (Terminal_Ant) of a second terminal, respectively, and the base station transmits signals to the first and second receiving antennas (Base_Ant0, Base_Ant1). Receive.

Meanwhile, FIG. 4 is a diagram illustrating a pilot pattern in an uplink PUSC mode, in which pilots disposed in one tile are divided into SISO and MIMO. At this time, Figure 4 (a) shows a pilot pattern of the uplink PUSC mode in the SISO system, Figures 4 (b) and 4 (c) is an example of the pilot pattern of the uplink PUSC mode in a 2 × 2 MIMO system It is shown.

Referring to FIG. 4, in the case of SISO, pilot and data are transmitted from a transmission antenna (Terminal_Ant) of a terminal in the pattern shown in FIG. In this case, four pilots are included in one tile, and the four pilots may be used or two pilots may be used for channel estimation at the base station.

In the case of MIMO, the first transmission antenna (Terminal_Ant0) of the terminal transmits pilot and data in the pattern shown in Figure 4 (b), the second transmission antenna (Terminal_Ant1) of the terminal is the pattern shown in Figure 4 (c) Send pilot and data. In addition, in the case of cooperative MIMO, the transmit antenna (Terminal_Ant) of the first terminal transmits pilot and data in the pattern shown in FIG. 4 (b), and the transmit antenna (Terminal_Ant) of the second terminal is transmitted to FIG. 4 (c). Send pilot and data in the pattern shown.

Then, the first receiving antenna Base_Ant0 is connected to the first and second receiving signals (ie, the first channel and the second channel) through the first and second channels H00, H01, or H 0 0, H 0 1, respectively. Receive signal), and the second receive antenna Base_Ant1 transmits the third and fourth receive signals (ie, the third channel) through the third and fourth channels H10, H11, or H 1 0, H 1 1, respectively. And a received signal of a fourth channel), and receive both signals (uplink frame) transmitted by two receive antennas. For example, the pilot and data patterns transmitted when the PUSC mode is used for the uplink in a 2x2 MIMO system or a 2x2 cooperative MIMO system supporting the OFDM / OFDMA method are shown in FIGS. 4 (b) and 4 (c). . In this case, each tile includes two pilots, two null subcarriers, and eight data, and the base station uses these two pilots for channel estimation. When these signals are transmitted, they are carried on different subcarriers in units of tiles. In particular, in the present invention, for convenience of description, it is assumed that subchannel rotation is performed at the time of tile allocation, but it should be noted that the same result is performed even if the above-described rotation is not performed.

As described above, since two or four pilots are used for SISO and two for each pattern for MIMO, a different channel estimation scheme is used for MIMO or cooperative MIMO to which the present invention is applied. In particular, a new channel estimation scheme according to a pilot pattern is required in the uplink PUSC mode.

Hereinafter, a channel estimation apparatus in a 2x2 MIMO system when using an uplink PUSC mode to which the present invention is applied will be described with reference to the accompanying drawings. Naturally, the same technical concept applies to 2 × 2 cooperative MIMO systems.

FIG. 5 is a diagram illustrating a configuration of a channel estimator according to an embodiment of the present invention, and is received through a first channel H00, a second channel H01, a third channel H10, and a fourth channel H11. A channel estimating device for a given signal is shown.

As shown in FIG. 5, the channel estimating apparatus includes an FFT unit 510, an offset estimating unit 520, an offset compensating unit 530, and a channel estimating unit 540.

The FFT unit 510 converts a signal in the time domain, which is received through the first and second receive antennas of the terminal and converted into a baseband signal, into a signal in the frequency domain. The FFT unit 510 may include a first FFT unit 510a and a second FFT unit 510b. In this case, the first FFT unit 510a may include a first FFT unit 510a of the time domain received through the first receiving antenna. The received signals of the first and second channels are converted into signals in the frequency domain, and the second FFT unit 510b converts the received signals of the third and fourth channels in the time domain received through the second receive antenna into the frequency domain. Convert to the signal of. Of course, the FFT unit 510 may be divided into four to convert the time domain signals received through the respective channels H00, H01, H10, and H11 into signals in the frequency domain, and conversely, all the time in one FFT unit. It may be implemented to convert a signal in the region to a signal in the frequency domain.

The offset estimator 520 estimates a time offset (TO) and / or a carrier frequency offset (CFO) using a pilot from at least one received signal of each channel. The offset compensator 530 compensates for errors generated when the channel passes by using the time offset or the carrier frequency offset estimated by the offset estimator 520.

The channel estimator 540 estimates the entire channel by interpolating the offset-compensated pilots for each of the four channels H00, H01, H10, and H11. For example, in FIG. 5, the channel estimator 540 includes a first channel estimator 540a for estimating the first channel H00 and the second channel H01 associated with the first receive antenna and a second receiver antenna associated with the second receive antenna. Separately implemented by the second channel estimator 540b for estimating the three channels H10 and the fourth channel H11, the channel estimator 540 estimates each channel H00, H01, H10, H11. It can be implemented in four to separate, and conversely can be implemented to estimate all the channels in one channel estimator.

A channel estimation method according to the present invention configured as described above will be described with reference to FIG. 6 is a flowchart illustrating a channel estimation method according to an embodiment of the present invention.

First, the FFT unit 510 converts a signal in the time domain, which is received through the first and second receiving antennas and converted into a baseband signal, into a signal in the frequency domain (S610). Subsequently, the offset estimator 520 estimates a time offset and / or a carrier frequency offset generated when the channel passes, and compensates an error according to the estimated offset (S620-S630). This offset is usually represented by a phase error, and it is common for the offset compensator 530 to compensate for this phase error.

Subsequently, the channel estimator 540 estimates the channel using the pilot whose offset is compensated in step S630. That is, the channel estimator 540 copies the channel estimates of the corresponding pilots for symbols located on the same subcarrier index as the pilots in each tile (S640). Here, the symbols located on the same subcarrier index as the aforementioned pilot include a null subcarrier and a data subcarrier. Then, in symbols having the same symbol index in the tile, interpolation is performed by using a subcarrier having a minimum subcarrier index and a subcarrier having a maximum subcarrier index (S650). This channel estimation method is described in more detail with reference to FIGS. 7 to 9 to be described later.

Hereinafter, a channel estimation method according to a predetermined pilot pattern when receiving an uplink frame in a 2x2 MIMO based base station supporting OFDM / OFDMA according to an embodiment of the present invention will be described with reference to the accompanying drawings. do. Here, the predetermined pilot pattern means two pilot patterns as shown in FIGS. 4 (b) and 4 (c) in the case of an uplink frame having a 2 × 2 MIMO structure supporting OFDM / OFDMA. For convenience of explanation, only the pilot pattern of FIG. 4B will be described. However, even when the pilot pattern of FIG.

[1] Channel Estimation Using Means

FIG. 7 is a diagram for describing channel estimation using an average in an uplink PUSC mode having a 2 × 2 MIMO structure, and includes an average of pilots in one tile (that is, a pilot of a minimum symbol index and a pilot of a maximum symbol index). And apply this average result to the data subcarriers d in the tile as channel estimates. For example, FIG. 7 (a) shows that the averaging is performed on two pilots P in one tile, and FIG. 7 (b) uses this average result as a channel estimate for all data subcarriers 8 in the tile. It applies to dog).

As described above, the pilot-based averaging method can be implemented relatively simply and has a merit of reducing the computation amount for the channel estimation. However, since the accuracy of the channel estimation is somewhat lower than that of the interpolation method, a higher level of modulation and coding scheme (MCS) is used. There are inadequate disadvantages. Accordingly, the present embodiment proposes a channel estimation method in an uplink PUSC mode of a 2 × 2 MIMO structure suitable for a high level MCS.

[2] Channel Estimation Using Interpolation

8 is a diagram for explaining channel estimation using interpolation in an uplink PUSC mode of a 2x2 MIMO structure according to an embodiment of the present invention, in which symbols of channel estimates for pilots in a tile have the same subcarrier index Respectively, and perform interpolation on a symbol index axis using the copied channel estimates for the symbols.

First, referring to FIG. 8 (a), the channel estimate of the pilot in a tile is copied to symbols of the same subcarrier index. By copying in this way, channel estimation of null subcarriers and data subcarriers located at the same subcarrier index (for example, subcarrier indexes 0 and 3) is determined.

Next, referring to FIG. 8 (b), interpolation is performed on symbol index axes for the symbols having the same symbol index in the tile by using the channel estimate determined in FIG. 8 (a). By performing the interpolation in this way, as shown in Fig. 8C, all channel estimates for the data subcarriers in the aforementioned tile are determined. Here, although the above-described interpolation may use a difference between symbol indices or a difference between distances between indices, according to the present embodiment, the difference between symbol indices and the distance between indices is the same. Listen and explain.

9 is a diagram for explaining interpolation using the difference in symbol index described above.

FIG. 9 (a) shows the pilot pattern according to FIG. 8 (a) as a numerical value, in which the pilot, null subcarrier, and data subcarrier before copying the pilot channel estimate are digitized. Here, P denotes a channel estimate of the pilot, h denotes a channel estimate of the data subcarrier, i denotes a subcarrier index of the tile start position, and j denotes a symbol index of the tile start position.

FIG. 9 (b) shows the after copying the pilot of FIG. 9 (a) to symbols located at the same subcarrier index. The pilot channel estimates P _{i, j + 2} and P _i at subcarrier indices i and i + 3. _{+3 and j} are copied as they are.

FIG. 9 (c) shows channel estimates of the respective data subcarriers after interpolation is performed on the symbol index axes with respect to the copied symbols as described above. FIG.

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Will have a channel estimate of.

Simulation results according to the channel estimation method described above are illustrated in FIGS. 10 and 11.

FIG. 10 illustrates a mean square error (MSE) of a channel estimate to a signal to noise ratio (SNR) in a different mobile channel environment, and FIG. 10 (a) illustrates a mobile channel of 3 km / h per hour. 11B shows a mobile channel environment at 10 km / h. Here, SNR is a ratio of signal power to noise power, and the larger the value, the higher the signal power. The MSE is a squared difference between the actual channel and the estimated channel. High.

First, in FIG. 10 (a), in a mobile channel environment of 3 k / m / h, when the SNR of each receiving antenna is 20 dB or less, the MSE of the average method is lower than that of the interpolation method described above. However, as the signal power is increased, the MSE has a lower interpolation method according to an embodiment of the present invention. For example, it can be said that the channel estimation performance is superior when the SNR is 20 dB or more. On the other hand, in the case of SNR of 30dB in Fig. 10 (a), each MSE corresponds to an average method of -30.5dB, the above-described interpolation method corresponds to -35.5dB.

In FIG. 10 (b), when the signal-to-noise ratio of each receiving antenna is 17 dB or less in a mobile channel environment of 10 k / m / h, the MSE has a low channel estimation performance because the average method is superior. MSE is lower in the case of the interpolation method described above, for example, it can be said that the channel estimation performance is superior when the SNR is 17dB or more. On the other hand, when the SNR is 30dB, each MSE has an average method of -29.5dB and the above-described interpolation method corresponds to -35dB. As described above, the overall performance decreases as the speed of the mobile channel environment increases. It can be seen that the performance difference deepens for each method. Accordingly, it can be seen that the channel estimation performance using the interpolation method described above is superior to the channel estimation performance using the average method in a low speed mobile channel environment.

Meanwhile, FIG. 11 is a diagram illustrating a packet error rate (PER) compared to a SNR measured by a minimum mean squared error (MMSE) -Ordered Successive Interference Cancellation (OSIC) decoding method at various modulation and coding scheme (MCS) levels. .

FIG. 11 (a) shows the PER performance measured using the MMSE-OSIC decoding method when the MCS level of QPSK 3/4 is used in a mobile channel environment of 3 km / h, and FIG. 11 (b) shows 3 km / h. PER performance measured using the MMSE-OSIC decoding method in the case of having an MCS level of 16 QAM 3/4 in a mobile channel environment of / h. Here, the PER represents an error rate according to the above-described data detection method in actual packet transmission, and the lower the value, the better the performance.

Referring to FIG. 11 (a), when the MCS level of QPSK 3/4 is used, for example, when the SNR is 20 dB, the PER of the average method corresponds to 1 / 93,000, and the interpolation method described above corresponds to approximately 1 / 94,000. In addition, it can be seen that the channel estimation performance does not differ significantly between the average method and the interpolation method.

Referring to FIG. 11 (b), when the MCS level of 16 QAM 3/4 is used, for example, when the SNR is 20 dB or less, the performance of both methods is not significantly different. However, when the SNR is 27 dB due to the increase in signal power, the PER is average. The method corresponds to approximately 1/8700, and the above-described interpolation method corresponds to approximately 1 / 1,000,000, indicating that the interpolation method is superior to the PER compared to the average method. As a result, the channel estimation using the interpolation method according to an embodiment of the present invention, it can be seen that the channel estimation performance is superior to the channel estimation using the average method in the case of high-level MCS.

Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art to which the present invention pertains can implement the present invention in other specific forms without changing the technical spirit or essential features, The examples are to be understood in all respects as illustrative and not restrictive. For example, in the present embodiment, for the convenience of description, the description will focus on a 2 × 2 MIMO system. However, if the pilot pattern is similar to the present embodiment in a wireless communication system having various MIMO structures, the technical idea according to the present invention can be easily applied. Able to know.

In addition, the scope of the present invention is specified by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. Should be interpreted as

According to the present invention, by providing a channel estimation method and apparatus suitable for an uplink PUSC mode in a wireless communication system having a MIMO structure supporting OFDM / OFDMA, an uplink PUSC transmitted to a high level MCS in a low speed mobile environment Even for the signal in the mode, the base station can effectively perform the estimation on the corresponding channel.

Claims (12)

An apparatus for estimating a channel in a wireless communication system supporting OFDM or OFDMA, An FFT unit converting the received signal in the time domain into the received signal in the frequency domain; And Extract pilots from the received signal in the frequency domain, and estimate the channel in tile units using the extracted pilots, wherein channel estimates for the pilots in the tile are located at the same subcarrier index as the pilots in the tile. And a channel estimator for copying each of the symbols in the tile, and performing interpolation using the channel estimate copied for each of the symbols in the tile. The method of claim 1, wherein the interpolation, And interpolating using an index difference or a distance difference with respect to the pilot in the tile. The method of claim 1, And the symbols in the tile are data and null. The method of claim 3, wherein the pilot and null in the tile, And symmetrically positioned within the tile. The method according to any one of claims 1 to 4, wherein the received signal, The first channel received through the first receiving antenna, the second channel received through the first receiving antenna, the third channel received through the second receiving antenna, and the fourth channel received through the second receiving antenna. Channel estimation apparatus, characterized in that any one of the received signal. The method of claim 5, wherein And the received signals of the first and third channels and the received signals of the second and fourth channels are transmitted from different terminals. The method according to any one of claims 1 to 4, An offset estimator estimating at least one of a time offset and a carrier frequency offset using pilots included in the received signal transmitted from the FFT unit; And And an offset compensator for compensating for errors generated when a channel passes through the received signal using the estimated offset and transmitting the compensation to the channel estimator. A method of estimating a channel in a wireless communication system supporting OFDM or OFDMA, (a) extracting a plurality of pilots from the received signal converted into the frequency domain; (b) copying channel estimates for the pilots in the tiles into nulls and data located at the same subcarrier index as the pilots in the tiles, in units of tiles for the extracted pilots; And (c) estimating the channel by performing interpolation on a symbol index axis using the copied channel estimate. The method of claim 8, wherein step (c) comprises: And interpolating using an index difference or a distance difference with respect to the pilot in the tile. The method of claim 8 or 9, wherein the received signal, The first channel received through the first receiving antenna, the second channel received through the first receiving antenna, the third channel received through the second receiving antenna, and the fourth channel received through the second receiving antenna. Channel estimation method, characterized in that any one of the received signal. The method of claim 10, The received signal of the first and third channels and the received signal of the second and fourth channels are transmitted from different terminals. The method according to claim 8 or 9, wherein, between steps (a) and (b), Estimating at least one of a time offset and a carrier frequency offset using pilots included in the received signal; And And using the estimated offset to compensate for errors generated when the channel passes through the received signal.

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