KR100880894B1 - Apparatus and method for estimating time offset and channel in MOM wireless communication system supporting OPMM / OFFDMA scheme - Google Patents

Abstract

The present invention relates to an apparatus and method for estimating a time offset and a channel in a MIMO wireless communication system supporting the OFDM / OFDMA scheme.

According to an embodiment of the present invention, at least one of a received signal of a first channel and a second channel received through a first receive antenna and a received signal of a third channel and a fourth channel received through a second receive antenna among a plurality of receive antennas. In estimating a channel by using two or more pilots included in the received signal of, determining a subchannel mapping rule for the received signals of the first to fourth channels, and in a different manner according to the determined subchannel mapping rule. Estimating a channel. That is, when there is no subchannel rotation in the subchannel mapping rule, after calculating channel estimates of adjacent tiles in the OFDMA symbol axis direction, the calculated channel estimates of the adjacent tiles are reflected in the channel estimates of the corresponding tiles. The channel is estimated by calculating the channel correction value of the corresponding tile. If there is a subchannel rotation in the subchannel mapping rule, the channel is estimated for each tile using two pilots included in the individual tiles.

Description

Apparatus and Method for Estimating Time Offset and Channel in MIMO System based OFDM / OFDMA for Estimating Time Offset and Channel in MIMO Wireless Communication System Supporting OPDM / OFDMA Method

The present invention relates to an apparatus and method for estimating a time offset and a channel in a MIMO wireless communication system supporting the OFDM / OFDMA scheme. More specifically, the present invention conforms to the standards of IEEE 802.16d / e, Wibro, WiMAX, and the like. An apparatus and method for estimating a time offset and a channel in different ways according to a subchannel mapping rule for an uplink PUSC mode in a MIMO wireless communication system supporting the OFDMA scheme are provided.

Wireless Broadband Internet (Wibro), a Korean wireless mobile Internet standard, uses OFDM (Orthogonal Frequency Division Multiplexing) as a signal transmission method to enable high-speed data service even when a user is moving in a wireless environment. In addition, OFDMA (Orthogonal Frequency Division Multiple Access) based on OFDM is used as a multiple access method to allow multiple users to simultaneously receive Internet services. Downlink and uplink are used as duplexing methods. Use Time Division Duplexing (TDD) to separate the time by time.

In a wireless communication system supporting the OFDM and / or OFDMA scheme, in order to perform smooth communication between a base station and a terminal, it is necessary to know characteristics of channels formed between each other. To do this, synchronization must first be achieved, and the oscillator must be accurate. However, in the case of the receiving side, a time offset may be generated due to various factors such as multipath characteristics between the transmitting side and the receiving side, and time-varying characteristics generated as the terminal or the radio interference is moved. Therefore, the receiving side needs to continuously estimate the time offset and compensate for it, and ultimately it is necessary to estimate and compensate the mutually formed channels based on this.

On the other hand, in a multiple input multiple output (MIMO) system using multiple transmit antennas and multiple receive antennas, a plurality of channels exist between a transmitting side and a receiving side. Even in the channel formed between the side and the receiving side, a subcarrier used according to a subchannel mapping rule may change according to time (specifically, an OFDMA symbol). Therefore, in the uplink PUSC mode of the MIMO system, the base station (receiving side) needs to receive a signal transmitted in a different pilot pattern from each terminal (transmitting side) and fluidly estimate and compensate the channel according to the situation of the base station. Do.

The present invention has been made to solve the above-described needs, and an object of the present invention is to provide a time based on a subchannel mapping rule for an uplink PUSC mode in a MIMO wireless communication system supporting an OFDM / OFDMA scheme. An apparatus and method for estimating and compensating an offset and estimating a channel based thereon are provided.

Another object of the present invention is to provide an apparatus and method for estimating channels in different ways according to a subchannel mapping rule for an uplink PUSC mode in a MIMO wireless communication system supporting an OFDM / OFDMA scheme.

Still another object of the present invention is a case in which a collaborative MIMO in which a plurality of terminals transmit respective signals using different pilot patterns in an uplink PUSC mode in a MIMO wireless communication system supporting the OFDM / OFDMA scheme. An apparatus and method for efficiently estimating time offset and channel are provided.

For this purpose, the channel estimating apparatus of one embodiment of the present invention includes a reception signal of a first channel and a second channel received through a first reception antenna and a second reception antenna among a plurality of reception antennas. An FFT unit converting the received signals of the third and fourth channels from the time domain to the frequency domain; A subchannel mapping rule determiner which determines a subchannel mapping rule for each of the received signals of the first to fourth channels; A plurality of tiles or slots adjacent to each other in the OFDMA symbol axis direction are selected for a received signal having no subchannel rotation in a subchannel mapping rule among the received signals of the first to fourth channels converted into the frequency domain. A time offset processor which estimates a time offset for the corresponding received signal by using; And a channel estimator for estimating a channel of each received signal by using a plurality of pilots included in each received signal with respect to the received signals of the first to fourth channels transmitted from the time offset processor. It features.

In addition, the channel estimating apparatus according to another aspect of the present invention includes, among a plurality of receiving antennas, a received signal of a first channel and a second channel received through a first receiving antenna and a third channel received through a second receiving antenna. And an FFT unit converting the received signal of the fourth channel from the time domain to the frequency domain. A subchannel mapping rule determiner which determines a subchannel mapping rule for each of the received signals of the first to fourth channels; A time offset processor configured to estimate a time offset for the corresponding received signal using at least two pilots included in at least one received signal among the received signals of the first to fourth channels converted into the frequency domain; And a channel of tiles adjacent in the OFDMA symbol axis direction with respect to a received signal having no subchannel rotation in a subchannel mapping rule among the received signals of the first to fourth channels transmitted from the time offset processor. And a channel estimator for estimating a channel of each received signal by calculating a channel correction value of the corresponding tile by calculating an estimated value and reflecting the calculated channel estimate of the adjacent tile to the channel estimate of the corresponding tile.

In addition, the time offset estimation device of one embodiment of the present invention includes a received signal of a first channel and a second channel received through a first receive antenna, and a third received through a second receive antenna, among a plurality of receive antennas. An FFT unit for converting the received signals of the channel and the fourth channel from the time domain to the frequency domain; A subchannel mapping rule determiner which determines a subchannel mapping rule for each of the received signals of the first to fourth channels; And a plurality of tiles adjacent in the OFDMA symbol axis direction for a received signal having no subchannel rotation in a subchannel mapping rule among the received signals of the first to fourth channels converted into the frequency domain. And a time offset processor for estimating a time offset for at least one corresponding received signal using a plurality of pilots included or a plurality of pilots included in each of the plurality of slots.

On the other hand, the channel estimation method of one embodiment of the present invention comprises: a) spatially multiplexed through the same subcarriers in different pilot patterns from a first terminal and a second terminal each having one transmit antenna; Receiving the transmitted signals with a first receive antenna and a second receive antenna; b) For a signal having no subchannel rotation in the subchannel mapping rule among the received signals, a time offset for at least one corresponding received signal is determined using a plurality of slots adjacent in the OFDMA symbol axis direction. Estimating and compensating; And c) estimating a channel of each received signal with respect to the received signal whose time offset is compensated, using a plurality of pilots included in each received signal.

In addition, a channel estimation method according to another aspect of the present invention includes: a) spatial multiplexing through the same subcarrier in different pilot patterns from a first terminal and a second terminal each having one transmitting antenna; Receiving the received signals with the first receiving antenna and the second receiving antenna; b) estimating and compensating a time offset for a corresponding received signal using two or more pilots included in at least one received signal of the received signals; And c) calculating a channel estimate of each tile adjacent to the OFDMA symbol axis direction for a signal having no subchannel rotation in a subchannel mapping rule among the signals whose time offset is compensated. Estimating a channel of the received signal by calculating a channel correction value of the tile by reflecting the channel estimate of the tile to the channel estimate of the tile.

In addition, the time offset estimation method of one embodiment of the present invention includes: a) spatial multiplexing through the same subcarrier in different pilot patterns from a first terminal and a second terminal each having one transmit antenna; Receiving the received signals with the first receiving antenna and the second receiving antenna; And b) at least one of a plurality of pilots included in a plurality of slots adjacent to each other in the OFDMA symbol axis direction for a signal having no subchannel rotation in a subchannel mapping rule among the received signals. Estimating a time offset with respect to the received signal.

According to the present invention, according to the present invention, in the MIMO wireless communication system supporting the OFDM / OFDMA scheme, the channel performance is estimated by efficiently using the pilot pattern for the uplink PUSC mode to improve the reception performance of the terminal. Have

In addition, according to the present invention, in the MIMO wireless communication system supporting the OFDM / OFDMA scheme, the base station is flexible in accordance with the situation by estimating the time offset and the channel in different ways according to the subchannel allocation scheme for the uplink PUSC mode. Has the effect of estimating.

In addition, according to the present invention, in the MIMO wireless communication system supporting the OFDM / OFDMA scheme, even in the case of collaborative MIMO in which a plurality of terminals transmit respective signals using different pilot patterns for the uplink PUSC mode This has the effect of estimating the channel.

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

1 illustrates a frame structure used in a portable Internet system supporting IEEE 802.16d / e.

A portable Internet system using the TDD scheme 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.

The present invention relates to an uplink PUSC subchannel period in the above-described frame structure. Meanwhile, when using 1024 fast fourier transforms (FFTs) among subcarrier allocation schemes for the uplink PUSC mode, the allocation may be allocated as shown in Table 1 below, and FIG. 2 illustrates a part of the subcarrier allocation structure according to Table 1 below.

TABLE 1

Parameter Value Comments Number of DC Subcarriers One Index 512 Number of Guard Subcarriers, Left 92 Number of Guard Subcarriers, Right 91 Number of Used Subcarriers 840 Number of all subcarriers used within a symbol Number of Subchannels 35 Number of Tiles 210 Number of Tiles per Subchannel 6 Number of Subcarriers per Tile 12 Number of all subcarriers used within tile

Referring to Table 1 and FIG. 2, in the uplink PUSC mode using 1024 FFT, 92 and 91 subcarriers, respectively, on the left and right sides of the total 1024 subcarriers are used as protection intervals to mitigate interference between adjacent channels. Used as a DC subcarrier. In addition, 840 subcarriers except these are used as an effective subcarrier, which is based on a tile composed of four consecutive subcarriers in three consecutive symbol intervals. One tile includes four pilot subcarriers and eight data subcarriers.

Meanwhile, the present invention is also applied to a MIMO system that performs multiple input / output transmission using a plurality of transmit antennas and a plurality of receive antennas. Hereinafter, the MIMO system will be described with reference to FIGS. 3 to 6.

First, FIG. 3 is a diagram for explaining an outline of a SISO system and a MIMO system.

As shown in FIG. 3A, a single input single output (SISO) system performs single input and output transmission through one channel H formed between one transmit antenna TxAnt and one receive antenna RxAnt.

In contrast, a multiple input multiple output (MIMO) system performs multiple input / output transmission through a plurality of channels formed between a plurality of transmit antennas and a plurality of receive antennas. FIG. 3B illustrates a 2x2 MIMO system using two transmit antennas and two receive antennas of which, as shown, the first and second transmit antennas TxAnt0 and TxAnt1 and the first and second Four channels, that is, a first channel H00, a second channel H01, a third channel H10, and a fourth channel H11 are formed between the reception antennas RxAnt0 and RxAnt1. For reference, in the channel notation, the first index is related to the index of the receiving antenna, and the second index is related to the index of the transmitting antenna for each transmitter (ie, the terminal).

4 illustrates an uplink collaborative MIMO system performed between two mobile stations / portable subscriber stations and one base station / radio access station in a 2 × 2 MIMO system. . In brief, the first terminal transmits through a different pilot pattern through the first transmission antenna TxAnt0 and the second terminal through the second transmission antenna TxAnt1. Then, 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. The base station having multiplexing and transmitting the first and second receiving antennas RxAnt0 and RxAnt1 receives signals transmitted from the first terminal and the second terminal, respectively. For reference, FIG. 5 illustrates an example of a resource allocation method for the case of non-MIMO (FIG. 5A) and the case of cooperative MIMO (FIG. 5B). Referring to FIG. 5, more data is defined as limited resources in case of cooperative MIMO. It can be seen that it can be transmitted.

In this regard, FIG. 6 illustrates pilot patterns transmitted by the first transmit antenna TxAnt0 and the second transmit antenna TxAnt1 for the uplink PUSC mode of the 2 × 2 MIMO system. Referring to FIG. 6, the first transmit antenna TxAnt0 transmits pilot and data in the pattern shown in FIG. 6A, and the second transmit antenna TxAnt1 transmits pilot and data in the pattern shown in FIG. 6B. Then, the first reception antenna RxAnt0 receives the first and second reception signals (that is, the reception signals of the first channel and the second channel) through the first and second channels H00 and H01, respectively. The two reception antennas RxAnt1 receive the third and fourth reception signals (that is, the reception signals of the third channel and the fourth channel) through the third and fourth channels H10 and H11, respectively. Receives all signals (uplink frames) transmitted by.

Meanwhile, FIG. 7 shows an example of subchannel mapping for an uplink PUSC period. Here, FIG. 7A illustrates a case where there is no subchannel rotation in the uplink PUSC mode, and FIG. 7B illustrates a case where there is subchannel rotation. When subchannel rotation is not performed in subchannel mapping as shown in FIG. 7A (that is, when a slot allocated to each UE does not rotate according to an OFDMA symbol), each UE uses the same subcarrier for successive OFDMA symbols. By transmitting the signal (ie, without changing the subcarrier), the base station may estimate the corresponding channel using pilots included in two or more adjacent tiles transmitted through the same subcarrier for each terminal. On the contrary, when subchannel rotation is performed in subchannel mapping as shown in FIG. 7B (that is, when a slot allocated to each UE rotates according to an OFDMA symbol), the base station is included in a subsequent tile in the OFDMA symbol axis direction. The pilot is not available and therefore the channel is estimated using only the pilots contained in the individual tiles. For reference, FIG. 7 uses a logical map rather than an actual physical map to explain the concept of subchannel rotation in subchannel mapping.

Hereinafter, a channel estimation apparatus and method according to the present invention will be described with reference to FIGS. 8 to 14. For reference, this embodiment relates to a channel estimation apparatus and method applied to a 2x2 MIMO system. In the uplink PUSC mode used in the present embodiment, the aforementioned pilot pattern is applied.

As shown in FIG. 8, the apparatus for estimating a channel according to the present invention includes a fast fourier transform (FFT) unit 100, a sub-channel mapping rule determiner 200, a time offset processor 300, and a channel estimator 400. And the like.

The FFT unit 100 performs a function of converting a signal in a time domain, which is received through a first and a second receiving antenna of a base station and converted into a signal in a baseband, to a signal in a frequency domain. In this case, the FFT unit 100 may include a first FFT unit 110 and a second FFT unit 120, in which case, the first FFT unit 110 may include the first FFT unit 110. The received signals of the first and second channels are converted into signals in the frequency domain, and the second FFT unit 120 receives the received signals of the third and fourth channels in the time domain received through the second receive antenna. Convert to the signal of. Of course, the FFT unit 100 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 subchannel mapping rule determiner 200 determines a subchannel mapping rule for the OFDMA symbol in the uplink PUSC period and transmits the subchannel mapping rule to the time offset processor 300 and / or the channel estimator 400. Do this. For example, the subchannel mapping rule determiner 200 may refer to UL_ZONE_IE (specifically, disable subchannel rotation bit: 0 = subchannel rotation enable, 1 = subchannel rotation disable) included in the UL_MAP of the downlink frame, so that the rotation of the subchannel may be reduced. It is determined whether there is or not, and the result is transmitted to the time offset processor 300 and / or the channel estimator 400.

The time offset processor 300 performs a function of estimating and compensating a time offset (TO) in a different manner according to the subchannel mapping rule transmitted from the subchannel mapping rule determiner 200. To this end, the time offset processor 300 includes a time offset estimator 310 for estimating a time offset and a time offset compensator 320 for compensating the estimated time offset (see FIG. 8).

Hereinafter, the time offset processor 300 will be described in detail with reference to FIGS. 9 to 11.

As shown in FIG. 9, the time offset estimator 310 includes a phase difference calculator 311, a phase difference accumulator 312, a linear phase calculator 313, a time offset (TO) calculator 314, and the like.

The phase difference calculator 311 is configured to receive at least one of a received signal of a first channel and a second channel received through a first receive antenna and a received signal of a third channel and a fourth channel received through a second receive antenna. The phase difference according to the time offset is calculated using two or more included pilots. The phase difference calculator may be implemented in the form of a multiplier that performs conjugate multiplication operations on two complex numbers, for example, to calculate the phase difference according to a time offset.

The phase difference accumulator 312 accumulates the phase difference according to each time offset calculated by the phase difference calculator 311 to generate a phase difference accumulation value. The phase difference accumulator 312 can estimate a more accurate time offset by accumulating the calculated phase difference for a larger number of pilots. For reference, the phase difference accumulator may be implemented in the form of an adder.

The linear phase calculator 313 converts the phase difference accumulator accumulated in the phase difference accumulator 312 into a linear phase according to a time offset. The phase difference cumulative value exists in a complex form, and thus, an arctan operation is performed on a form having a real part as a denominator and an imaginary part as a numerator in the phase difference cumulative value, and this By dividing by the difference, we can find the linear phase according to the time offset. Here, the arc tangent operation can be performed using a look-up table that inputs a ratio of a complex real part and an imaginary part as an input, and outputs an arc tangent calculated value. You can also find the linear phase. The linear phase with respect to the time offset obtained as described above represents an average phase difference according to a time offset occurring between adjacent subcarriers (that is, subcarriers having a difference of subcarrier indices of 1).

The time offset calculator 314 converts the linear phase according to the time offset calculated by the linear phase calculator 313 into a time offset (TO).

Hereinafter, a time offset estimation method for a case where there is no subchannel rotation will be described with reference to FIGS. 10 and 11. For reference, in this embodiment, the linear phases according to time offsets are obtained for each slot, and then the linear phases according to time offsets are averaged for slots corresponding to the same OFDMA slot section index (same OFDMA slot section). After calculating the average of the linear phase according to the time offset, and finally calculating the linear phase correction value according to the time offset of the individual slot section by reflecting the linear phase average according to the time offset of the adjacent slot section, the time offset for each slot section. To calculate.

In detail, as illustrated in FIGS. 10 and 11, signals (data and pilots) transmitted between the terminal and the base station are allocated and transmitted in units of slots. In the uplink PUSC mode, one slot includes three OFDMAs. It consists of a symbol and one subchannel. The subchannel consists of six tiles, and one tile includes four pilots and eight data.

)을 나타내며, 수학식 1-2는 제2 단말에 대한 시간 오프셋에 따른 선형위상(

)을 나타낸다. 참고로, 하기 수학식 2에 있어 m은 수신 안테나 인덱스를, t는 타일 인덱스를, w는 웨이트(weight)를 나타낸다.In the 2x2 cooperative MIMO system, when the first terminal and the second terminal transmit signals in different pilot patterns as shown in FIG. 11B, the time offsets for the first and third received signals have a subcarrier index k and a symbol index l. It can be estimated using pilot pairs of pilot P _m (3,2, t) having pilot P _m (0,0, t), subcarrier index k + 3 and symbol index l + 2, and the second and fourth The time offset for the received signal is pilot P _m (0,2, t) with subcarrier index k and symbol index l + 2 and pilot P _m (3,0, t) with subcarrier index k + 3 and symbol index l. It can be estimated using a pilot pair of. Equation 1 below shows an example of calculating a linear phase according to time offsets for individual slots by accumulating phase differences according to time offsets calculated for each tile, and Equation 1-1 shows a time offset for a first terminal. Linear phase according to

), Equation 1-2 represents the linear phase according to the time offset for the second terminal (

). For reference, in Equation 2, m denotes a reception antenna index, t denotes a tile index, and w denotes a weight.

[Equation 1]

(1-1)

(1-2)

)를 산출하는 예를 나타낸 것인데, 이는 하나의 슬롯 구간(3개의 심볼로 구성됨)에 포함된 N_s+1개의 슬롯들에 대한 시간 오프셋에 따른 선형위상들을 평균한 것이다. 참고로, 수학식 2에서 x는 OFDMA 슬롯구간 인덱스(OFDMA 심볼축 방향으로 위치하는 슬롯의 구간을 표시하는 인덱스)를 나타내고, slot는 슬롯 인덱스를 나타낸다(도 10 참조).Meanwhile, the linear phases according to the time offsets for the individual slots calculated as described above are averaged for each slot section to calculate the linear phase averages according to the time offsets for each slot section. Equation 2 is an average value of the linear phases according to the time offset of each slot section for the first terminal (

), Which is an average of linear phases according to time offsets for N _s +1 slots included in one slot section (three symbols). For reference, in Equation 2, x represents an OFDMA slot section index (index indicating a section of a slot located in the OFDMDMA symbol axis direction), and slot represents a slot index (see FIG. 10).

 [Equation 2]

)를 산출한 예를 나타낸 것인데, 수학식 3-1은 x=0인 경우이며, 수학식 3-2는 x=1,2,3,... 인 경우이다.The linear phase average value according to the time offset calculated for each slot section may be corrected by reflecting the linear phase average value according to the time offset of adjacent slot sections. Equation 3 is a linear phase correction value according to a time offset for each OFDMA slot section index (ie, slot section).

) Is calculated, where Equation 3-1 is x = 0, and Equation 3-2 is x = 1,2,3, ....

[Equation 3]

(3-1)

(3-2)

Equation 3 may be generalized as in Equation 4 below. Similarly, Equation 4-1 is a case where x = 0, and Equation 4-2 is a case where x = 1, 2, 3, .... And w is weight.

[Equation 4]

(4-1)

(4-2)

Finally, the linear phase correction value according to the time offset for each slot section is converted into a time offset. For example, when using a 1024 FFT as in the present embodiment, the time offset TO may be calculated by Equation 5 below.

[Equation 5]

On the other hand, when there is a subchannel rotation, as described above, adjacent tiles or slots cannot be used in the OFDMA symbol axis direction, and thus, a time offset is obtained by using tiles or slots corresponding to the same slot period.

For example, in the case of a time offset to the first terminal, the pilot with the pilot P _m (0,0, t) and a sub-carrier index k + 3 and the symbol index l + 2 having a subcarrier index k and the symbol index P l _m (3 A pilot offset of (2, t) is used, and a time offset can be calculated by the following Equations 6 to 8. Detailed description thereof will be omitted (refer to the description of Equations 1, 2, and 5 described above).

[Equation 6]

[Equation 7]

[Equation 8]

Referring back to FIG. 8, the channel estimator 400 estimates the first to fourth channels in different ways according to the subchannel mapping rule with respect to the first to fourth received signals whose time offset is compensated. For reference, in FIG. 8, the channel estimator 400 relates to the first channel estimator 410 and the second receiver antenna for estimating the first channel H00 and the second channel H01 associated with the first receiving antenna. Separately implemented by the second channel estimator 420 estimating the third channel H10 and the fourth channel H11, of course, the channel estimator 400 separates each of the channels H00, H01, H10, and H11. It may be implemented in four separate parts to estimate, and conversely, it may be implemented to estimate all channels in one channel estimator.

)는 하기 수학식 9-2와 같이 산출될 수 있다.Hereinafter, a channel estimation method according to the present invention will be described in detail with reference to FIG. 12. For reference, FIG. 12 shows four tiles adjacent in the OFDMA symbol axis direction, and they have a tile index t and an OFDMA slot section index x = 0,1,2,3. Meanwhile, the channel estimates for each tile are h _{m , n} (t, 0), h _{m , n} (t, 1), h _{m, n} (t, 2), h _{m , n} (t, 3), respectively. Where m is a receive antenna index and n is a transmit antenna index. For example, the tile-specific channel estimates of the received signals of the first and third channels transmitted through the first transmit antenna TxAnt0 may be calculated as shown in Equation 9-1 below, and the second transmit antenna TxAnt1 may be calculated. Channel estimates for each tile for the received signals of the second and fourth channels transmitted through

) May be calculated as in Equation 9-2.

[Equation 9]

(9-1)

(9-1)

)를 산출하는데, 이는 예컨대 하기 수학식 10과 같이 산출할 수 있다.On the other hand, if there is no subchannel rotation, the channel estimator 400 corresponds to the same subcarrier and reflects the channel estimates of adjacent tiles in the OFDMA symbol axis direction to reflect the channel correction values for the individual tiles (

), Which can be calculated as shown in Equation 10 below.

[Equation 10]

(10-1)

(10-2)

(10-3)

(10-4)

Equation 10 may be generalized as in Equation 11 below. Here, Equation 11-1 is a case where x = 0, and Equation 11-2 is a case where x = 1, 2, 3, .... And w is weight.

[Equation 11]

(11-1)

(11-2)

)를 이용할 수 없으며, 각 타일의 채널 추정치(

)를 산출하여 채널을 추정한다.On the other hand, when there is a subchannel rotation, as described above, adjacent tiles cannot be used in the OFDMA symbol axis direction, and therefore, a channel is estimated using only pilots included in individual tiles. That is, the channel correction value (

) Is not available, and each tile's channel estimate (

) To estimate the channel.

The channel estimation apparatus according to the embodiment of the present invention has been described so far. According to another embodiment of the present invention, as shown in FIG. 13, the subchannel mapping rule determination unit 200 is an FFT unit 100. And the time offset processor 300 to determine a subchannel mapping rule for the first to fourth received signals, and then time offset the subchannel mapping rule together with the first to fourth received signals. It may be implemented to transmit to the processor 300.

Hereinafter, a channel estimation method according to the present invention will be described with reference to FIG. 14. For reference, a detailed process or operation principle of the channel estimation method according to the present invention may refer to the description of the channel estimation apparatus described above, and thus, detailed descriptions thereof will be omitted, and the following briefly focuses on steps that occur in time series. Explain.

Referring to FIG. 14, in step S110, a base station receives a received signal of a first channel and a second channel through a first receive antenna among a plurality of receive antennas, and receives a third channel and a fourth through a second receive antenna. Receive the received signal of the channel. Here, the received signals of the first channel and the third channel are signals transmitted from a first transmit antenna, and the received signals of the second channel and fourth channel are signals transmitted from a second transmit antenna. The first transmitting antenna and the second transmitting antenna may be provided in different terminals, and the received signals of the first and third channels and the received signals of the second and fourth channels may be different pilot patterns. Is sent to.

In step S120, the subchannel mapping rule is determined for the received signals of the first to fourth channels, respectively. As a result of the determination in step S120, if there is no subchannel rotation in the subchannel mapping rule, the process proceeds to step S130 where channel estimation is performed after estimating and compensating a time offset using adjacent tiles or slots in the OFDMA symbol axis direction. . On the contrary, if there is a subchannel rotation in the subchannel mapping rule, the process proceeds to step S150 where channel estimation is performed after estimating and compensating a time offset using a tile or a slot corresponding to the same slot period.

In detail, in the case of a received signal having no subchannel rotation in the subchannel mapping rule, in step S130, a time offset is estimated and compensated using adjacent tiles or slots in the OFDMA symbol axis direction. In this case, as described above with reference to Equations 1 and 2, the linear phases of the time offsets are obtained for each slot corresponding to the same OFDMA slot section, and then averaged to the linear phases according to the time offsets for each slot section. Calculate the average value. As described with reference to Equations 3 and 4, the linear phase correction value according to the time offset of the slot section to be calculated is calculated by reflecting the linear phase average value according to the time offset of the adjacent slot section. Thereafter, as described with reference to Equation 5, the time offset is estimated by converting the calculated linear phase correction value according to the time offset for each slot section to a time offset.

If the time offset is estimated and compensated in step S130, the channel for each received signal is estimated in step S140. For a received signal having no subchannel rotation in the subchannel mapping rule, as described with reference to Equations 9 to 11, a channel correction value of a tile to be obtained by reflecting a channel estimate of adjacent tiles in the OFDMA symbol axis direction By calculating, the channel of the received signal is estimated.

On the other hand, if the received signal does not have the sub-channel rotation in the sub-channel mapping rule, in step S150, the time offset is estimated and compensated using a tile or slot corresponding to the same slot interval. This may be described with reference to Equations 6 to 8. In step S160, the channel of the corresponding received signal is estimated by calculating the channel estimate of the individual tile for each received signal.

The channel estimation method according to an embodiment of the present invention described above illustrates a preferred form of estimating a time offset and a channel in different ways according to the subchannel mapping rule, and if there is a subchannel rotation in the subchannel mapping rule, step S130. And of course, it is also possible to implement in the form of a combination of S160 or a combination of step S150 and step S140.

Finally, with respect to the apparatus and method for time offset estimation according to the present invention, since the technique for estimating a channel is omitted in the above-described channel estimation apparatus and method, the time offset is estimated in substantially the same manner, and thus, the repeated description Omit.

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.

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

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

FIG. 2 is a detailed structural diagram of an uplink PUSC subchannel section of the frame shown in FIG. 1.

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

4 is a diagram illustrating a signal transmission method between two terminals and one base station in a 2x2 collaborative MIMO system.

5 is a diagram illustrating a resource allocation scheme for the case of non-MIMO and cooperative MIMO.

FIG. 6 is a diagram illustrating a pilot pattern in a PUSC mode transmitted by a first transmit antenna and a second transmit antenna in a 2x2 MIMO system.

FIG. 7 illustrates a case in which there is no subchannel rotation and a subchannel rotation in a subchannel mapping rule.

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

9 is a detailed configuration diagram of the time offset estimator of FIG. 8.

FIG. 10 is a diagram for explaining that signals are allocated and transmitted in units of slots in the uplink PUSC mode.

11 is a detailed structural diagram of slots and tiles used in an uplink PUSC mode.

12 illustrates four tiles having the same tile index and adjacent in the OFDMA symbol axis direction.

13 is a configuration diagram of a channel estimating apparatus according to another embodiment of the present invention.

14 is a flowchart of a channel estimation method according to the present invention.

Explanation of symbols on the main parts of the drawings

100: FFT part

110: first FFT unit

120: second FFT unit

200: subchannel mapping rule determination unit

300: time offset processing unit

310: time offset estimation unit

320: time offset compensation unit

400: channel estimator

410: First channel estimator

420: second channel estimator

Claims (25)

A channel estimation apparatus in a MIMO wireless communication system supporting OFDM or OFDMA scheme, Among the plurality of receiving antennas, received signals of the first and second channels received through the first receiving antenna and received signals of the third and fourth channels received through the second receiving antenna from the time domain to the frequency domain. A FFT unit to convert; A subchannel mapping rule determiner which determines a subchannel mapping rule for each of the received signals of the first to fourth channels; A plurality of tiles or slots adjacent to each other in the OFDMA symbol axis direction are selected for a received signal having no subchannel rotation in a subchannel mapping rule among the received signals of the first to fourth channels converted into the frequency domain. A time offset processor which estimates a time offset for the corresponding received signal by using; And And a channel estimator for estimating a channel of each received signal using a plurality of pilots included in each received signal with respect to the received signals of the first to fourth channels transmitted from the time offset processor. Channel estimation apparatus. The method of claim 1, The channel estimator calculates a channel estimate of each tile adjacent to the OFDMA symbol axis direction with respect to a signal having no subchannel rotation in the subchannel mapping rule, and then calculates the channel estimate of the adjacent tile. And estimating a channel using the channel correction value of the corresponding tile calculated by reflecting the estimated value. The method of claim 2, And the channel correction value of the corresponding tile is calculated by multiplying a channel estimate of a tile adjacent to the OFDMA symbol axis direction and a channel estimate of the corresponding tile by a weight. The method of claim 1, The channel estimator estimates a channel by calculating a channel estimate of a corresponding tile by averaging the pilots included in each received signal in units of tiles with respect to the signal having the subchannel rotation in the subchannel mapping rule. Channel estimation apparatus. The method according to any one of claims 1 to 4, The time offset processor calculates a linear phase average value according to time offsets of each slot section by averaging the linear phases according to time offsets for individual slots for each slot section, and then applies the linear phase average value according to time offsets of adjacent slot sections. And estimating the time offset by reflecting the linear phase average value according to the time offset of the slot section and calculating the linear phase correction value according to the time offset of the slot section. The method of claim 5, The linear phase correction value according to the time offset of the corresponding slot section is calculated by multiplying the linear phase average value according to the time offset of the adjacent slot section and the linear phase average value according to the time offset of the corresponding slot section. Characterized in that the channel estimation device. The method according to any one of claims 1 to 4, The time offset processing unit, A phase difference calculator for calculating a phase difference according to a time offset with respect to two or more pilots included in each tile; A phase difference accumulator for accumulating the phase difference according to the calculated time offset; A linear phase calculator configured to calculate a linear phase according to a time offset for each slot section by using the phase difference according to the accumulated time offset; And And a time offset estimator configured to calculate a time offset based on the linear phase according to the time offset. The method according to any one of claims 1 to 4, And the time offset processor estimates a time offset of a signal having a subchannel rotation in the subchannel mapping rule by using a tile or a slot corresponding to the same slot period. The method according to any one of claims 1 to 4, And receiving signals of the first and third channels are transmitted from a first terminal, and receiving signals of the second and fourth channels are transmitted from a second terminal. The method according to any one of claims 1 to 4, And the channel estimating apparatus supports at least one of IEEE 802.16d / e, Wibro, and WiMAX standards. A channel estimation apparatus in a MIMO wireless communication system supporting OFDM or OFDMA scheme, Among the plurality of receiving antennas, received signals of the first and second channels received through the first receiving antenna and received signals of the third and fourth channels received through the second receiving antenna from the time domain to the frequency domain. A FFT unit to convert; A subchannel mapping rule determiner which determines a subchannel mapping rule for each of the received signals of the first to fourth channels; A time offset processor configured to estimate a time offset for the corresponding received signal using at least two pilots included in at least one received signal among the received signals of the first to fourth channels converted into the frequency domain; And A channel estimate of each tile adjacent in the OFDMA symbol axis direction for a received signal having no subchannel rotation in a subchannel mapping rule among the received signals of the first to fourth channels transmitted from the time offset processor. And a channel estimator for estimating a channel of each of the received signals using the channel correction value of the corresponding tile calculated by calculating the channel estimate of the adjacent tile to the channel estimate of the corresponding tile after calculating. Channel estimation device. The method of claim 11, The time offset processor calculates a linear phase average value according to time offsets of each slot section by averaging the linear phases according to time offsets for individual slots for each slot section, and then applies the linear phase average value according to time offsets of adjacent slot sections. And estimating a time offset by calculating a linear phase correction value according to the time offset of the corresponding slot section by reflecting the linear phase average value according to the time offset of the slot section. An apparatus for estimating time offset in a MIMO wireless communication system supporting OFDM or OFDMA scheme, Among the plurality of receiving antennas, received signals of the first and second channels received through the first receiving antenna and received signals of the third and fourth channels received through the second receiving antenna from the time domain to the frequency domain. A FFT unit to convert; A subchannel mapping rule determiner which determines a subchannel mapping rule for each of the received signals of the first to fourth channels; And A plurality of tiles adjacent to each other in the OFDMA symbol axis direction are included in a received signal having no subchannel rotation in a subchannel mapping rule among the received signals of the first to fourth channels converted into the frequency domain. And a time offset processing unit for estimating a time offset of at least one corresponding received signal by using the plurality of pilots or the plurality of pilots included in the plurality of slots, respectively. The method of claim 13, The time offset processor calculates a linear phase average value according to time offsets of each slot section by averaging the linear phases according to time offsets for individual slots for each slot section, and then applies the linear phase average value according to time offsets of adjacent slot sections. Time offset estimating apparatus characterized by estimating the time offset by reflecting the linear phase average value according to the time offset of the slot section by calculating the linear phase correction value according to the time offset of the slot section. The method of claim 14, The linear phase correction value according to the time offset of the corresponding slot section is calculated by multiplying the linear phase average value according to the time offset of the adjacent slot section and the linear phase average value according to the time offset of the corresponding slot section. Characterized in that the time offset estimation device. The method according to claim 13 or 14, The time offset processing unit, A phase difference calculator for calculating a phase difference according to a time offset with respect to two or more pilots included in each tile; A phase difference accumulator for accumulating the phase difference according to the calculated time offset; A linear phase calculator configured to calculate a linear phase according to a time offset for each slot section by using the phase difference according to the accumulated time offset; And And a time offset estimator configured to calculate a time offset based on the linear phase according to the time offset. The method according to claim 13 or 14, And the time offset processor estimates a time offset with respect to a signal having a subchannel rotation in the subchannel mapping rule by using a tile or a slot corresponding to the same slot period. The method according to claim 13 or 14, The received signals of the first and third channels are transmitted from a first terminal, and the received signals of the second and fourth channels are transmitted from a second terminal. The method according to claim 13 or 14, The apparatus for estimating time offset according to claim 1, wherein the channel estimating apparatus supports at least one of IEEE 802.16d / e, Wibro, and WiMAX standards. A channel estimation method for an uplink PUSC mode in a MIMO wireless communication system supporting OFDM or OFDMA scheme, a) Spatial multiplexed signals transmitted from the first terminal and the second terminal each having one transmitting antenna in different pilot patterns through the same subcarrier to the first receiving antenna and the second receiving antenna; Receiving; b) For a signal having no subchannel rotation in the subchannel mapping rule among the received signals, a time offset for at least one corresponding received signal is determined using a plurality of slots adjacent in the OFDMA symbol axis direction. Estimating and compensating; And and c) estimating a channel of each received signal with respect to the received signal whose time offset is compensated for, using a plurality of pilots included in each received signal. The method of claim 20, Step b) is b-1) calculating a linear phase average value according to time offsets for each slot section by averaging the linear phases according to time offsets for individual slots for each slot section; b-2) calculating a linear phase correction value according to the time offset of the corresponding slot section by reflecting the linear phase average according to the time offset of the adjacent slot section to the linear phase average according to the time offset of the corresponding slot section; And b-3) estimating a time offset using the linear phase correction value of the corresponding slot section. The method of claim 20 or 21, Step c) is c-1) calculating channel estimates of tiles adjacent to each other in the OFDMA symbol axis direction; c-2) calculating a channel correction value of the corresponding tile by reflecting the calculated channel estimate of the adjacent tile to the channel estimate of the corresponding tile; And c-3) estimating a channel of the received signal using a channel correction value of the corresponding tile. A channel estimation method for an uplink PUSC mode in a MIMO wireless communication system supporting OFDM or OFDMA scheme, a) Spatial multiplexed signals transmitted from the first terminal and the second terminal each having one transmitting antenna in different pilot patterns through the same subcarrier to the first receiving antenna and the second receiving antenna; Receiving; b) estimating and compensating a time offset for a corresponding received signal using two or more pilots included in at least one received signal of the received signals; And c) calculating the channel estimate of each tile adjacent to the OFDMA symbol axis direction with respect to a signal having no subchannel rotation in the subchannel mapping rule among the signals whose time offset is compensated, and then calculating the adjacent tiles Estimating a channel of the received signal by calculating a channel correction value of the tile by reflecting a channel estimate of the tile to a channel estimate of the tile. A time offset estimation method for an uplink PUSC mode in a MIMO wireless communication system supporting OFDM or OFDMA scheme, a) Spatial multiplexed signals transmitted from the first terminal and the second terminal each having one transmitting antenna in different pilot patterns through the same subcarrier to the first receiving antenna and the second receiving antenna; Receiving; And b) at least one corresponding signal using a plurality of pilots included in a plurality of slots adjacent to each other in the OFDMA symbol axis direction for a signal having no subchannel rotation in the subchannel mapping rule among the received signals; Estimating a time offset with respect to the received signal. The method of claim 24, Step b) is b-1) calculating a linear phase average value according to time offsets for each slot section by averaging the linear phases according to time offsets for individual slots for each slot section; b-2) calculating a linear phase correction value according to the time offset of the corresponding slot section by reflecting the linear phase average according to the time offset of the adjacent slot section to the linear phase average according to the time offset of the corresponding slot section; And b-3) estimating a time offset using the linear phase correction value of the corresponding slot section.

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