KR101626673B1 - Method for synchronization using mimo-ofdm system and apparatus thereof - Google Patents

Abstract

The present invention relates to a synchronization method and apparatus using a MIMO-OFDM system, and a synchronization method using a MIMO-OFDM system according to an embodiment of the present invention includes a step of performing CDD on a plurality of transmission antennas, Calculating a reception power for each of the plurality of reception antennas and selecting a reception antenna among the plurality of reception antennas using the magnitude of the reception power; Detecting a maximum peak value by cross-correlating a preamble and a predetermined correlation window received by the selected Rx antennas; determining a maximum peak value based on the maximum peak value, Accumulating the cross-correlation values by the number of the cross-correlation values, And determining a final synchronization point by adding a maximum CDD value according to the number of the plurality of transmission antennas at a point of time of detection.
According to the present invention, the power of the received signal is measured for each of the receive antennas, and the power of the signal obtained by measuring a smaller number of antennas than that of the available antennas is sequentially selected, thereby reducing the amount of operation of the synchronization unit performed for each antenna. In addition, according to the present invention, the synchronization point is determined by accumulating cross-correlation values for a plurality of transmission antennas, so time synchronization can be performed with high accuracy even in multipath.

Description

TECHNICAL FIELD [0001] The present invention relates to a synchronization method using a MIMO-OFDM system,

The present invention relates to a synchronization method and apparatus using a MIMO-OFDM system, and more particularly, to a synchronization method using a MIMO-OFDM system capable of performing a synchronization operation with high accuracy on multipath caused by multiple antennas And a device therefor.

BACKGROUND ART As the use of portable devices has become commonplace due to the development of communication technology and the demand for convenience, development of technology for concentrating the technology in portable devices is required. In particular, the development of an IEEE 802.11ac wireless LAN system for wireless connection between various wireless multimedia devices by configuring a home network has continued.

The IEEE 802.11ac system adopts MIMO-OFDM (Orthogonal Frequency Division Multiplexing) scheme combined with OFDM scheme with high transmission efficiency and relatively good channel compensation, and MIMO scheme which is advantageous for improving data transmission rate or reliability. . However, since MIMO technology supports up to 8 antennas, consideration should be given to antenna placement, operation speed, and power consumption.

OFDM scheme is very robust to multi-path fading environments and narrowband interference. However, due to the constraint that mutual orthogonality between sub-carriers must be maintained, synchronization error It is very sensitive. When a synchronization error occurs, inter-symbol interference and inter-subcarrier interference appear, which leads to serious performance degradation or packet loss.

Since the performance of the entire system depends on the performance of the synchronization part, accurate synchronization becomes a necessary requirement of the WLAN system. Furthermore, since the cyclic delay diversity (CDD) technique is applied to the MIMO scheme, a problem of "pseudo multipath" occurs when the conventional cross-correlation algorithm based time synchronization scheme is applied. Also, when the CDD technique is applied to the MIMO scheme, the synchronization accuracy is lowered and the calculation using the maximum likelihood (ML) algorithm increases the calculation amount and power consumption. Also, considering the computational complexity of each algorithm in the WLAN modem, it is necessary to develop a technique to reduce the computational complexity of the synchronization part because the synchronization part occupies a large proportion in the entire modem.

The technology of the background of the present invention is disclosed in Korean Patent No. 10-1341202 (published on Dec. 12, 2013).

1 is a diagram for explaining a synchronization method of a MIMO-OFDM system according to the related art.

Cross in the prior art, according to Registered Patent No. 10-1341202, W = which also corresponds to the first peak occurred near the time (t _T1) of the cross-correlation value, such as _{1 [t T1 -Lg, t T1} + Lg] Range The maximum peak value? _Max at which the correlation sum value? (W)) becomes the maximum is searched for and the threshold value? _Thr is set as shown in Equation (1) based on the detected maximum peak value? _Max .

Here,? Is an increment value, and t is a subtraction number of?. That is, the synchronizer obtains the threshold value? _Thr by subtracting over the t number of times until the condition is satisfied with the magnitude of? On the basis of the maximum peak value? _Max detected.

Then, the synchronizing device calculates the time point of occurrence of the cross-correlation peak, which causes the cross-correlation summation value? (W) to be equal to or greater than the threshold value? _Thr and the interval between the cross- _f ).

However, in the method of searching for the synchronization point using the threshold value as in the prior art (Korean Patent No. 10-1341202), when the peak value due to error is larger than the last CDD peak due to multipath, the maximum peak value ( _max ) It is discriminated and the accuracy of the motive is deteriorated. In particular, since the threshold value is used, there is a problem that the value of one point of multipath is greatly affected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a synchronization method and apparatus using a MIMO-OFDM system capable of performing a synchronization operation with high accuracy on multipath caused by multiple antennas.

A synchronization method using a MIMO-OFDM system according to an embodiment of the present invention includes a step of receiving an OFDM symbol transmitted by CDD through a plurality of transmission antennas using a plurality of reception antennas, Calculating a reception power for each of the plurality of antennas, selecting a part of the plurality of reception antennas using the magnitude of the reception power, correlating the preamble received by each of the plurality of reception antennas with a predetermined correlation window The method includes the steps of: detecting a maximum peak value; accumulating a cross-correlation value by the number of transmit antennas at CDD sample intervals in a region including a certain range based on the maximum peak value; Detects a time point at which the maximum number of transmission antennas is detected, In addition to the maximum value corresponding to the CDD determining a last synchronization time.

The step of receiving the OFDM symbol using a plurality of reception antennas may receive a signal in which transmission signals transmitted from the plurality of transmission antennas are mixed as shown in the following equation.

Here, y _j (n) is the signal received through the j-th receive antenna, h _{i, j} (l) is the l-th channel response pulse that is passed between the i-th transmit antenna and j th receive antennas, N _TX is L is the length of the channel pulse response pulse, and w _j (n) represents AWGN.

)을 연산하는 단계, 상기 수신 안테나의 수신 전력(

)을 M개의 샘플에 대하여 누적하여 누적 전력(

)를 획득하는 단계, 그리고 상기 누적 전력(

)의 크기가 상위 일정 비율 내에 포함되는 상기 일부 수신 안테나를 선택하는 단계를 포함할 수 있다. Wherein the step of selecting some of the plurality of reception antennas comprises the step of calculating a reception power of each of the plurality of reception antennas

), Calculating a reception power of the reception antenna (

) Are accumulated for M samples to obtain cumulative power (

), ≪ / RTI >

) May be included within a higher constant ratio.

는 j 번째 수신 안테나의 수신 전력이며, D는 CDD 지연 값이고, k는 상관 윈도우 길이이다. here,

Is the received power of the j-th receive antenna, D is the CDD delay value, and k is the correlation window length.

The step of cross-correlating and summing the preamble and the predetermined correlation window received by the selected Rx antennas may include calculating a correlation window from the start of the L-LTF of the preamble received through the selected Rx antenna, Obtaining a cross-correlation value of the preamble using the L-LTS, and summing cross-correlation values of the preambles received by the selected Rx antenna.

Here, S _LTS (k) is a time domain value of a predetermined correlation window (L-LTS), and? (N) represents a sum of cross-correlation values of preambles calculated from selected Q reception antennas.

의 윈도윙 구간에서 다음의 수학식과 같이 CDD 샘플 간격으로 상기 복수의 송신 안테나의 개수만큼 상호 상관 값을 누적시킬 수 있다. Wherein the step of accumulating the cross-correlation values by the number of transmit antennas comprises:

It is possible to accumulate the cross-correlation values by the number of the plurality of transmit antennas at intervals of CDD samples as shown in the following equation.

는 상기 최대 피크 값을 나타내며, CDD_max는 상기 최대 CDD 값을 나타내고, CDD_sample은 상기 CDD 샘플 간격이고, i는 송신 안테나의 인덱스이다. here,

Denotes the maximum peak value, CDD _max denotes the maximum CDD value, CDD _sample denotes the CDD sample interval, and i denotes an index of the transmitting antenna.

The step of determining the final synchronization point may be expressed by the following equation.

는 상기 최종 동기화 시점이고,

는 검출된 상기 상호 상관의 누적 값이 최대가 되는 시점을 나타낸다. here,

Is the last synchronization point,

Represents a time point at which the cumulative value of the detected cross-correlation becomes the maximum.

A synchronization apparatus using a MIMO-OFDM system according to another embodiment of the present invention includes a data receiving unit that receives an OFDM symbol transmitted through a CDD through a plurality of transmit antennas using a plurality of receive antennas, An antenna selector for calculating reception power for each of the reception antennas and selecting a part of the plurality of reception antennas using the magnitude of the reception power; Correlated values of the plurality of transmission antennas are accumulated in a CDD sample interval in an area including a certain range based on the maximum peak value, When a time point at which the maximum value of the transmission signal is detected is detected, In addition to the maximum value corresponding to the number of CDD and including a synchronization determining a last synchronization time.

As described above, according to the present invention, the power of the received signal is measured for each of the receive antennas, and the power of the signals obtained by measuring a smaller number of antennas than that of the available antennas are sequentially selected.

Also, according to the related art, accurate synchronization can not be detected due to the influence of multipath in the MIMO-OFDM system, but according to the present invention, the synchronization point is determined by accumulating cross-correlation values for a plurality of transmission antennas Time synchronization can be performed with high accuracy even in multipath.

1 is a diagram for explaining a synchronization method of a MIMO-OFDM system according to the related art.
2 is a diagram for explaining a transmission method of a general MIMO-OFDM system.
3 is a diagram illustrating a configuration of a MIMO-OFDM system according to an embodiment of the present invention.
4 is a diagram for explaining a data stream transmitted through a MIMO-OFDM system.
5 is a diagram illustrating a configuration of a reception apparatus using MIMO-OFDM according to an embodiment of the present invention.
6 is a flowchart showing the operation of the MIMO-OFDM receiving apparatus according to FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms used are terms selected in consideration of the functions in the embodiments, and the meaning of the terms may vary depending on the user, the intention or the precedent of the operator, and the like. Therefore, the meaning of the terms used in the following embodiments is defined according to the definition when specifically defined in this specification, and unless otherwise defined, it should be interpreted in a sense generally recognized by those skilled in the art.

FIG. 2 illustrates a transmission scheme of a general MIMO-OFDM system, in which a transmitter including two transmit antennas TX1 and TX2 transmits OFDM symbol data using CDD.

As shown in FIG. 2, the L-LTS transmits an OFDM symbol data stream in a state where the transmission antenna TX1 is not CDD delayed (CDD sample = 0), and the L-LTS transmits 64 symbols (S ₀ , S ₁ , S ₂ , S ₃ , ..., S ₆₃ ). It is assumed that the transmission antenna TX2 transmits an OFDM symbol data stream in a CDD-shifted state (CDD sample = -2) forward by two symbols.

The receiving apparatus 2 transmit antennas pilot symbols _{(S 0, S 1, S} 2, S 3, ..., S 63) contained in the sliding window upon receiving the OFDM symbol data stream from (TX1, TX2), such as the And cross-correlates the received signal with a cross-correlation window.

A cross-correlation output results in a peak at the start of the corresponding OFDM symbol. That is, when multiple transmission antennas are used, different CDDs are applied to each of the transmission antennas TX1 and TX2, and peaks are generated by the number of CDDs in the signal that has passed through the Rx1 and RX2 and the cross- do.

As described above, in the MIMO-OFDM system, since CDD is applied, a large number of peaks are generated, and since the peak size varies depending on the state of the channel, it is hard to know how many peaks become the synchronization point, (Pseudo multipath problem). That is, since a peak of the cross-correlation value occurs at the sample position to which the CDD is applied, it is difficult to determine the synchronization point.

FIG. 3 illustrates a structure of a MIMO-OFDM system according to an embodiment of the present invention, and FIG. 4 illustrates a data stream transmitted through a MIMO-OFDM system. 3, a MIMO-OFDM system according to an embodiment of the present invention includes an OFDM transmission apparatus 100 and an OFDM reception apparatus 200. As shown in FIG.

The OFDM transmission apparatus 100 and the OFDM reception apparatus 200 constituting the MIMO-OFDM system according to the embodiment of the present invention each include a plurality of transmission antennas TX1, TX2, ..., TXn and reception antennas RX1, RX2, ..., and RXn. The OFDM transmission apparatus 100 transmits OFDM symbol data to which the CDD scheme is applied to the OFDM reception apparatus 200 through different channels CH.

The OFDM receiving apparatus 200 receives the signals transmitted from the mixed signals through the channel estimation, and the OFDM receiving apparatus 200 receives the signals transmitted from the mixed signals through the channel estimation, Remove it.

The data stream shown in FIG. 4 is for explaining the PPDU format of the IEEE 802.11a standard. The data stream transmitted through the MIMO-OFDM communication system includes a legacy preamble as shown in FIG. 4, and the legacy preamble includes an L-STF (Legacy short training field) and an L-LTF (Legacy long training field) And has backward compatibility.

Here, L-STF of the preamble is made up of 10 STS (short training symbol) and consists of (t ₁ to t _10), L-LTF is a guard interval (GI1) and two LTS (long training symbol) (T ₁ and T ₂ ). Time synchronization by the OFDM receiving apparatus 200 is performed in the legacy preamble section.

The transmission antenna TX and the reception antenna RX can be configured up to a maximum of eight, and the CDD technique is applied to the signals transmitted from the respective antennas. CDD prevents unintentional beamforming from being generated, and allows diversity gain to be obtained for the transmit antenna.

For example, if the i-th transmission antenna has a cyclic delay of delta _i , the OFDM symbol transmitted from the transmission antenna can be expressed by Equation (2).

는 부반송파(서브캐리어)의 개수이고,

은 CDD가 적용되기 전의 i번째 송신 안테나(TX)로부터 송신되는 OFDM 심볼,

은 CDD가 적용된 i번째 송신 안테나(TX)로부터 송신되는 OFDM 심볼, mod(a,b)는 변조 함수를 나타낸다. 그리고 각각의 송신 안테나(TX)는 기 설정된 CDD 지연 값(Cyclic shift value)을 가진다. L-SFT와 L-LTF에 적용되는 송신 안테나 수(N_TX) 별 CDD 지연 값은 다음의 표 1과 같다. here,

Is the number of subcarriers (subcarriers)

Is an OFDM symbol transmitted from an i < th > transmit antenna (TX) before CDD is applied,

Is an OFDM symbol transmitted from an i < th > transmit antenna (TX) to which CDD is applied, and mod (a, b) represents a modulation function. Each transmit antenna TX has a predetermined CDD delay value. The CDD delay values for the number of transmit antennas (N _TX ) applied to L-SFT and L-LTF are shown in Table 1 below.

As shown in Table 1, when the number of transmit antennas (N _TX ) increases, the OFDM symbol data is cyclically delayed corresponding to the increased number of transmit antennas. For example, when the number of transmit antennas (N _TX ) is 3, symbol data is transmitted from each antenna to a receive antenna RX through a multipath channel at a time corresponding to 0 ns, 100 ns, and 200 ns .

Also, as shown in Table 1, it can be seen that CDD sample intervals are different from each other depending on the number of transmission antennas. For example, if there are three transmit antennas, the CDD sample interval is 100 ns, and if there are four transmit antennas, the CDD sample interval is 50 ns.

Hereinafter, an operation of the OFDM receiving apparatus 200 for selecting a part of a plurality of reception antennas and synchronizing OFDM symbol data received after CDD delay will be described with reference to FIGs. 5 and 6. FIG.

5 is a diagram illustrating a configuration of a reception apparatus using MIMO-OFDM according to an embodiment of the present invention.

The MIMO-OFDM receiving apparatus 200 includes a data receiving unit 210, an antenna selecting unit 220, and a synchronizing unit 230, which are MIMO-OFDM systems according to an embodiment of the present invention.

The data receiving unit 210 receives CDD transmitted OFDM symbols through a plurality of transmit antennas using a plurality of receive antennas. The antenna selector 220 calculates reception power for each of a plurality of reception antennas, and selects some reception antennas among the plurality of reception antennas using the magnitude of the reception power.

The synchronization unit 230 detects a maximum peak value by cross-correlation processing of the preamble received by the selected reception antenna and a predetermined correlation window, and outputs the maximum peak value as a CDD sample interval in a region including a predetermined range based on the maximum peak value. A cross-correlation value is accumulated by the number of transmit antennas, and a time point at which the cumulative value of the cross-correlation becomes the maximum is detected. Then, a maximum CDD value according to the number of the plurality of transmission antennas is added at the time of detection to determine a final synchronization point.

6 is a flowchart showing the operation of the MIMO-OFDM receiving apparatus according to FIG.

First, when the OFDM transmitting apparatus 100 transmits a plurality of CDD-delayed symbol data as shown in Equation (2) to the receiving apparatus 200 using a plurality of transmitting antennas, the OFDM receiving apparatus 200 transmits (N (n)) in which signals transmitted by CDD are mixed as shown in Equation (2) through RX1, RX2, ..., RXn at step S610.

That is, the signal y _j (n) received by the jth receive antenna RX of the receiving apparatus 200 is expressed by Equation (3) as follows: Additive White Gaussian Noise (AWGN) ) Is represented by the sum of the added signals.

Here, h _{i , j} ( 1 ) is the l- th channel response pulse transmitted between the i-th transmit antenna and the j-th receive antenna, L is the length of the channel pulse response pulse, and w _j (n) represents AWGN.

Then, the antenna selector 420 selects some reception antennas among the plurality of reception antennas RX1, RX2, ..., RXn in order to reduce the amount of computation to be processed (S620). That is, since the cross-correlation processing must be performed for each reception antenna in order to synchronize the received signals, the calculation complexity is very large and the power consumption is very serious.

Therefore, the antenna selector 420 selects only a part of all the reception antennas using the following Equations (4) to (6), thereby reducing the calculation amount and power consumption. In particular, the antenna selector 420 uses a delay and a correlate algorithm, which is one of the algorithms used for signal detection, as shown in Equations (4) to (6).

는 지연(delay) 값(D)와 상관 윈도우 길이(K)를 가지는 자기상관의 결과 값이고, 지연(delay) 값(D)은 프리앰블의 반복 주기와 동일하다.here,

Is a result of autocorrelation with a delay value D and a correlation window length K, and the delay value D is the same as the repetition period of the preamble.

)을 연산한다. Then, using the following Equation (5), the antenna selection unit 420 selects the reception power of the j < th >

).

는 [0,1] 사이의 값을 가지는 정규화된 자기 상관 결과(normalized Auto-correlation)이고, 기준값 이상의 값이 되면 패킷 수신이 시작된 것으로 판단한다. here,

Is a normalized autocorrelation result having a value between [0, 1], and it is judged that packet reception is started when the value is equal to or larger than a reference value.

)을 M개의 샘플에 대하여 누적함으로써 수학식 7과 같은 M개의 샘플에 대한 누적 전력(

)를 획득한다. Thus, each receiving antenna RX detects the received signal and accumulates the power of the received signal calculated over the M samples. That is, the reception power of each reception antenna calculated through Equation (5)

≪ / RTI > is accumulated for M samples to obtain the cumulative power < RTI ID = 0.0 >

).

)을 이용하여 누적 전력이 큰 순서대로 수신 안테나를 선택하게 되는데, 안테나 선택부(420)는 가용 수신 안테나 개수(N_RT)보다 적은 Q개의 수신 안테나를 선택함으로써, 각 안테나마다 수행되는 동기화부(440)의 연산량을 줄일 수 있다. The cumulative power obtained in this manner (

The antenna selecting unit 420 selects Q receiving antennas that are smaller than the available number of receiving antennas N _RT so that the number of receiving antennas can be reduced by using a synchronization unit 440) can be reduced.

는 누적 전력(

)이 큰 순서대로 Q개의 수신 안테나를 선택하기 위한 함수이며, 안테나 선택부(420)는 가용 수신 안테나 개수(N_RT) 중에서 누적 전력(

)이 상위 일정 비율(%) 내에 포함되는 수신 안테나를 선택할 수 있으며, 일정 비율 내에 포함되더라도 누적 전력(

)이 기준 값보다 적으면 선택하지 않을 수 있다. here,

Is the cumulative power (

Is a function for selecting Q reception antennas in a descending order, and the antenna selector 420 selects a number of available reception antennas (N _RT )

) Can select the reception antennas included in the upper constant ratio (%), and even if they are included within a certain ratio, the cumulative power

) Is less than the reference value, it may not be selected.

Next, the synchronization unit 530 detects a correlation window from a time point at which the L-LTF of the preamble received through each selected reception antenna starts, as shown in Equation (7) L-LTS), the cross-correlation of the preamble is calculated as shown in Equation (9) (S630).

Where S _LTS (k) is the time domain value of a known correlation window (L-LTS) and K 'is the length of the correlation window.

When the cross-correlation value of the preamble received by each of the Rx antennas is calculated as shown in Equation (9), the synchronization unit 530 accumulates the cross-correlation values calculated from the Q receive antennas, as shown in Equation (10) .

Since the L-LTF has two identical LTSs, a cross-correlation value occurs at a point (t _T1 , t _T2 ) where LTS T1 and T2 in Fig. 3 start. In this case, if correct synchronization is performed at t _T1 , synchronization can be applied at the same position at t _T2 .

)을 검출한다(S650).Synchronization unit 530 has the cross-correlation, such as _{W = [t T1 -Lg, t} T1 + Lg] Equation (11) in the range corresponding to the first peak occurred near the time (t _T1) of the cross-correlation value in order to improve the synchronizing efficiency The maximum peak value (? (W)) at which the sum value?

(S650).

의 윈도윙 구간에서 수학식 12와 같이 CDD 샘플 간격으로 송신 안테나의 개수만큼 상호 상관 값을 누적시킨다(S660). Next, the synchronization unit 530

The cross-correlation values are accumulated in the windowing interval of the transmission antennas in the CDD sample intervals as shown in Equation (12) (S660).

)이 0이고, 안테나의 개수가 4개이면, 윈도우(W)의 범위는 표 1과 수학식 11에 의하여 [-300. 300]이 된다. 윈도우의 이동 간격 샘플이 1이라고 가정하면, 동기화부(530)는 수학식 12를 이용하여 Wr이 -300일 때의

값을 계산하고, 다시 윈도우를 1샘플 이동시켜 Wr이 -299일 때의

값을 계산한다. 이와 같이, 윈도우를 1샘플씩 이동시켜가면서 동기화부(530)는 Wr이 300일 때까지의

값을 계산하며, 총 601개의 누적 값(

)이 산출된다. For example, the maximum peak value (

Is 0 and the number of antennas is 4, the range of the window W is [-300. 300]. Assuming that the movement interval sample of the window is 1, the synchronization unit 530 uses the equation (12)

And moves the window by one sample again to obtain the value of Wr at -299

Calculate the value. In this way, while moving the window by one sample, the synchronizing unit 530 sets the window Wr to 300

And a total of 601 cumulative values (

) Is calculated.

)이 산출되면, 동기화부(530)는 다음의 수학식 13과 같이 누적 값(

)의 최대값(

)을 검출한다(S670). Then, a plurality of accumulated values (

), The synchronization unit 530 calculates the cumulative value < RTI ID = 0.0 > (

) ≪ / RTI >

(Step S670).

)이 산출되면, 동기화부(530)는 601개의 누적 값(

) 중에서 최대값이 되는 Wr 지점을 시간 동기 시점(

)으로 검출한다. In the above example, 601 cumulative values (

), The synchronization unit 530 outputs 601 accumulated values (

) Is a time synchronization point (

).

)을 수학식 13과 같이 결정될 수 있다. That is, on the assumption that there is a correlation peak at each CDD time point, the synchronization unit 530 sets the time synchronization point (

) Can be determined as shown in Equation (13).

)으로 결정한다(S680). Since the CDD value is 0 at the original time synchronization point, the synchronization unit 530 determines that the last peak occurrence point is within the range in which CDD appears as shown in Equation (14) (

) (S680).

)에 CDD_max 값을 더해줌으로써, 보정된 최종 시간 동기 시점(

)을 획득할 수 있다. That is, since the first sample is located at the rightmost position in the synchronization unit 530,

) By adding the CDD _max value to the corrected final time synchronization point (

Can be obtained.

As described above, according to the embodiment of the present invention, the power of the received signal is measured for each of the receive antennas, and the powers of the signals obtained by measuring a smaller number of antennas than the available antennas are sequentially selected.

According to the related art, accurate synchronization can not be detected due to the influence of multipath in the MIMO-OFDM system. However, according to the embodiment of the present invention, a synchronization point is determined by accumulating cross-correlation values for a plurality of transmission antennas It is possible to perform time synchronization with high accuracy even in multipath.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, Therefore, the present invention should be construed as a description of the claims which are intended to cover obvious variations that can be derived from the described embodiments.

100: OFDM transmitting apparatus, 200: OFDM receiving apparatus,
210: data reception unit, 220: antenna selection unit,
230: synchronization unit

Claims (12)

Receiving an OFDM symbol transmitted through a plurality of transmission antennas by a CDD scheme using a plurality of reception antennas,
Calculating reception power for each of the plurality of reception antennas and selecting a reception antenna among the plurality of reception antennas using the magnitude of the reception power;
Correlating the preamble received by the selected reception antenna with a predetermined correlation window to detect a maximum peak value,
Accumulating cross-correlation values by the number of transmit antennas at CDD sample intervals in a region including a certain range based on the maximum peak value; and
And determining a final synchronization point by adding a maximum CDD value according to the number of the plurality of transmission antennas at a point in time at which the correlation value is maximized,
Wherein the step of accumulating the cross-correlation values by the number of transmit antennas comprises:

Correlation values are accumulated in the windowing interval of the transmission antenna by the number of transmission antennas at CDD sample intervals as shown in the following equation,

here,

CDD _max denotes the maximum CDD value, CDD _sample denotes the CDD sample interval, i denotes an index of a transmitting antenna,
The method of claim 1,
A synchronization method using a MIMO-OFDM system represented by the following equation:

here,

Is the last synchronization point,

Represents a time point at which the cumulative value of the detected cross-correlation becomes the maximum. The method according to claim 1,
Wherein the step of receiving the OFDM symbol using a plurality of receive antennas comprises:
A synchronization method using a MIMO-OFDM system that receives a signal mixed with transmission signals transmitted from the plurality of transmission antennas as shown in the following equation:

Here, y _j (n) is the signal received through the j-th receive antenna, h _{i, j} (l) is the l-th channel response pulse that is passed between the i-th transmit antenna and j th receive antennas, N _TX is L is the length of the channel pulse response pulse, and w _j (n) represents AWGN. 3. The method of claim 2,
Wherein the step of selecting some of the plurality of reception antennas comprises:
The reception power of each of the plurality of reception antennas ((

),
The reception power of the reception antenna (

) Are accumulated for M samples to obtain cumulative power (

), And
The cumulative power (

Selecting a part of the receive antennas in which the size of the receive antennas is within a predetermined constant ratio;

here,

Is the received power of the j-th receive antenna, D is the CDD delay value, and k is the correlation window length. The method of claim 3,
Wherein the step of cross-correlating and summing the preamble and the predetermined correlation window,
Obtaining a cross-correlation value of the preamble using the correlation window (L-LTS) from a time point at which L-LTF of a preamble received through the selected RX antenna starts,
And summing cross-correlation values of the preambles received by the selected Rx antennas.

Here, S _LTS (k) is a time domain value of a predetermined correlation window (L-LTS), and? (N) represents a sum of cross-correlation values of preambles calculated from selected Q reception antennas. delete delete A data receiving unit for receiving an OFDM symbol transmitted by CDD through a plurality of transmit antennas using a plurality of receive antennas,
An antenna selector for calculating reception power for each of the plurality of reception antennas and selecting a reception antenna among the plurality of reception antennas using the magnitude of the reception power;
A plurality of transmit antennas are arranged at intervals of a CDD interval in a region including a predetermined range based on the maximum peak value, And a synchronization unit for determining a final synchronization point by adding a maximum CDD value according to the number of the plurality of transmission antennas at a point of time of detecting a time point at which the accumulated value of the cross- In addition,
Wherein the synchronization unit comprises:

Correlation values are accumulated in the windowing interval of the transmission antenna by the number of transmission antennas at CDD sample intervals as shown in the following equation,

here,

CDD _max denotes the maximum CDD value, CDD _sample denotes the CDD sample interval, i denotes an index of a transmitting antenna,
Wherein the last synchronization point is represented by the following equation: < EMI ID =

here,

Is the last synchronization point,

Represents a time point at which the cumulative value of the detected cross-correlation becomes the maximum. 8. The method of claim 7,
Wherein the data receiver comprises:
A synchronization apparatus using a MIMO-OFDM system that receives a signal mixed with transmission signals transmitted from a plurality of transmission antennas as shown in the following equation:

Here, y _j (n) is the signal received through the j-th receive antenna, h _{i, j} (l) is the l-th channel response pulse that is passed between the i-th transmit antenna and j th receive antennas, N _TX is L is the length of the channel pulse response pulse, and w _j (n) represents AWGN. 9. The method of claim 8,
Wherein the antenna selector comprises:
The reception power of each of the plurality of reception antennas (

), And calculates the reception power of the reception antenna (

) Are accumulated for M samples to obtain cumulative power (

), And the cumulative power (

) Is included within an upper predetermined ratio. The synchronization device using the MIMO-OFDM system according to claim 1,

here,

Is the received power of the j-th receive antenna, D is the CDD delay value, and k is the correlation window length. 10. The method of claim 9,
Wherein the synchronization unit comprises:
(L-LTS) from a time point at which L-LTF of a preamble received through the selected RX antenna starts, as shown in the following equation, and calculates a cross-correlation value of the preamble A synchronization apparatus using a MIMO-OFDM system for summing cross-correlation values of the preamble;

Here, S _LTS (k) is a time domain value of a predetermined correlation window (L-LTS), and? (N) represents a sum of cross-correlation values of preambles calculated from selected Q reception antennas. delete delete

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