KR101294721B1 - Channel estimation apparatus and method using short and long training symbols - Google Patents

Abstract

PURPOSE: A least square (LS) channel estimating method using long training symbols and short training symbols is provided to estimate a channel more accurately than the existing LS channel estimating method. CONSTITUTION: A preamble is equipped with short training symbols and long training symbols. For sub-carriers where a symbol value exists, a first channel estimation part obtains a channel estimation value for the corresponding sub-carrier from a reception terminal based on short training symbols known in advance. For the rest of sub-carriers where a symbol value does not exist, a second channel estimation part obtains a channel estimation value from the reception terminal based on long training symbols known in advance. A third channel estimation part adds the channel estimation values of individual sub-carriers obtained by the first and second channel estimation parts, divides it by the number of sub-carriers, and obtains an average value of the channel estimation values for each sub-carrier.

Description

Channel estimation apparatus and method using short and long training symbols

The present invention relates to a LS channel estimation method using a long training symbol and a short training symbol. More specifically, the present invention relates to an LS channel estimation method using a short training symbol and a long training symbol that can estimate a channel more accurately than the conventional LS channel estimation method by applying a short training symbol as well as a long training symbol. .

Telematics is a compound word of communication and information technology that provides a new additional service that sends and receives information to a vehicle by using voice and data communication through a wireless network. In order to provide telematics services, various wireless communication technologies such as dedicated short range communication (DSRC), wireless LAN, and ultra wideband (UWB) have been proposed, and the dual UWB system is a connection between a terminal device in home networking and a telematics terminal device in a vehicle. Much research has been conducted to meet the needs of services and the need for high-speed data transmission in vehicles.

The UWB system is suitable for supplying a wireless PAN having a high data rate and defining a channel frequency bandwidth of 500 MHz or more in a spectrum mask of the 3.1 to 10.6 GHz band specified by the FCC.

Since the UWB system uses low power, the UWB system can provide a maximum transmission rate of about 1Gbps without affecting automobiles and other electronic products in the vehicle, and thus has various advantages as an in-vehicle wireless network application technology.

The OFDM method is a wireless access technology used in both a wireless LAN system and a UWB system and has a strong advantage against multipath interference causing performance degradation in a mobile reception environment.

In addition, in the mobile reception environment, effective channel estimation is needed to reduce the Doppler effect due to the multipath interference and mobility and to improve performance. A typical OFDM system includes a transmitter of an OFDM system and a receiver of an OFDM system.

On the transmitting side, the input data to be transmitted is channel coded by the convolutional encoder, and then modulated by the modulation unit in a quadrature phase shift keying (QPSK) method through an interleaving unit. After modulation, a training symbol (Preamble) for channel estimation is inserted in the training symbol inserter, serial data is converted into parallel data through the S / P converter, and then an inverse fast fourie transform (IFFT) and a guard interval inserter are inserted. IFFT and a guard time is inserted to prevent inter symbol interference (ISI) due to multipath delay.

Thereafter, the digital signal is converted into an analog signal through a D / A converter and transmitted to the receiving side through a channel through an antenna. The receiving side processes the data in the reverse order of the transmitting side.

That is, it receives the signal transmitted from the transmitting side through the antenna, converts the received signal into a digital signal through the A / D converter, FFTs the FFT and the protection interval removing unit, and removes the protection interval inserted at the transmitting side. .

Thereafter, parallel data is converted into serial data through a P / S converter, and a channel estimator recovers a signal by estimating a channel. The training symbol is removed from the training symbol removal unit, demodulated by the demodulation unit, and then decoded into the original signal by the Viterbi decoder via the deinterleaving unit.

In general, a channel estimator using a training symbol on one subcarrier is known to the receiver before data information at the transmitter side (In an OFDM system, a packet system has a pilot symbol defined in a preamble structure, and these symbols are transmitted before the data symbol. And the channel changes are applied to other information data Payload by the initial channel estimator.

In general, OFDM consists of a symbol on a time side and a subcarrier on a frequency side, where a preamble refers to all subcarriers of an initial symbol, and each subcarrier of an initial preamble consists of pilots in the same form as data.

In the conventional channel estimation method, an LS channel estimation technique for estimating a channel using a training symbol known in advance at a receiver is used. In the conventional LS channel estimation technique using the training symbols, since the received signal for each subchannel is represented by the product of the channel and the transmission signal in the OFDM system, the LS channel estimation technique using two long training symbols and the two long training symbols There is a method of estimating a channel by calculating an average value of channel estimation values for each long training symbol by using (averaged LS channel estimation).

However, this channel estimation technique uses only long training symbols, so it shows high second in non-frequency selective environment, but as the system bandwidth increases, it becomes severe frequency selective fading environment, resulting in error reliability due to low reliability of data. There is this.

Therefore, LS channel estimation method using not only long training symbols but also short training symbols was required.

The present invention is derived to solve the above problems, according to an embodiment of the present invention by applying a short training symbol as well as a long training symbol to estimate the channel more accurately than the conventional LS channel estimation method It provides a method for estimating LS channel using long training symbols and short training symbols.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings.

In the LS channel estimating apparatus for estimating a channel by analyzing a preamble received signal after passing through a wireless channel, when the preamble signal is transmitted through a wireless channel, the preamble is a short training symbol. And a first channel estimator having a long training symbol and estimating a channel of the corresponding subcarrier based on a short training symbol known in advance in the case of a subcarrier having a symbol value; A second channel estimator for estimating a channel based on a long training symbol previously known at a receiver in case of other subcarriers without a symbol value; And a third channel estimator for adding channel estimation values of the subcarriers obtained from the first channel estimator and the second channel estimator, and dividing them by the number of subcarriers to obtain an average value of channel estimates for each subcarrier. It can be achieved as an LS channel estimator using training symbols and long training symbols.

In the first channel estimation subcarrier, symbols exist at 12 positions, and a channel estimation value estimated by a short training symbol is represented by Equation 1 below.

[Equation 1]

는 짧은 훈련심볼에 의해 추정되는 채널추정값이며,

는 FFT 이후 주파수 영역에의 수신신호이고,

는 짧은훈련심볼이다.).It can be characterized by that (k is -24, -20, -16, -12, -8, -4, 4, 8, 12, 16, 20, 24,

Is the channel estimate estimated by the short training symbol,

Is the received signal in the frequency domain after FFT,

Is a short training symbol).

The long training symbol of the second channel estimation unit is composed of two equations (2) and (3) below.

&Quot; (2) "

&Quot; (3) "

은 제1긴훈련심볼에 대한 채널추정값이고, 상기

는 FFT 이후 주파수 영역에의 수신신호이며,

는 제1긴훈련심볼이고, 상기

은 제2긴훈련심볼에 대한 채널추정값이고, 상기

는 FFT 이후 주파수 영역에의 수신신호이며,

는 제2긴훈련심볼이다.).It can be characterized by obtaining a channel estimation value for each long training symbol by (

Is the channel estimation value for the first long training symbol,

Is the received signal in the frequency domain after FFT,

Is the first long training symbol, said

Is the channel estimation value for the second long training symbol,

Is the received signal in the frequency domain after FFT,

Is the second long training symbol.).

The second channel estimation unit may obtain an average value of the channel estimation value for the first long training symbol and the channel estimation value for the second long training symbol.

The third channel estimation unit is expressed by the following equation (4).

&Quot; (4) "

는 각 부반송파에 대한 채널추정값들의 평균값이고,

는 짧은훈련심볼에 의한 채널추정값이고,

제1긴훈련심볼에 의한 채널추정값이며,

는 제2긴훈련심볼에 의한 채널추정값이다.).It may be characterized by obtaining the average value of the channel estimates for each subcarrier (

Is the average of the channel estimates for each subcarrier,

Is the channel estimation value from the short training symbol,

Channel estimation value by the first long training symbol,

Is the channel estimation value by the second long training symbol.).

Another object of the present invention is to provide an LS channel estimation method for estimating a channel by analyzing a preamble received signal after passing through a wireless channel when the preamble signal is transmitted through a wireless channel. In the case of a subcarrier having a short training symbol and a long training symbol, and having a symbol value, obtaining a channel estimation value for the corresponding subcarrier based on a short training symbol previously known by the receiver by the first channel estimation unit; Obtaining a channel estimate based on a long training symbol previously known at a receiving end by a second channel estimator in case of other subcarriers without a symbol value; And adding a channel estimation value of each subcarrier obtained by the first channel estimation unit and the second channel estimation unit by the third channel estimation unit, and dividing it by the number of subcarriers to obtain an average value of channel estimation values for each subcarrier. It can be achieved as an LS channel estimation method using a short training symbol and a long training symbol.

Therefore, according to the embodiment of the present invention as described, according to the embodiment of the present invention by applying a short training symbol as well as a long training symbol can estimate the channel more accurately than the conventional LS channel estimation method In addition, it is independent of the transmission rate and the number of multipaths related to the reliability of the data, and thus can be obtained even in a wide bandwidth system in which the error flow of the DDCE occurs, which is useful in severe frequency selective fading environments.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it will be appreciated by those skilled in the art that various other modifications and variations can be made without departing from the spirit and scope of the invention, All fall within the scope of the appended claims.

1 is a partial configuration diagram showing a physical layer convergence procedure (PLCP) preamble structure used in IEEE 802.11a / g / n;
2 is a diagram illustrating some components of a PLCP preamble structure used in IEEE 802.11p;
3 is a frequency domain signal of a short training symbol using 12 subcarriers among 52 subcarriers,
4 is a block diagram showing an OFDM transmission system model according to an embodiment of the present invention;
5 is a graph schematically showing an LS channel estimation method using a short training symbol and a long training symbol according to an embodiment of the present invention;
6 is a graph showing a simulation result of the LS channel estimation method using a short training symbol and a long training symbol according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the detailed description of known functions and configurations incorporated herein will be omitted when it may unnecessarily obscure the subject matter of the present invention.

The same reference numerals are used for portions having similar functions and functions throughout the drawings. Throughout the specification, when a part is connected to another part, this includes not only the case where it is directly connected, but also the case where it is indirectly connected with another element in between. In addition, the inclusion of an element does not exclude other elements, but may include other elements, unless specifically stated otherwise.

Hereinafter, an LS channel estimation method using a long training symbol and a short training symbol according to an embodiment of the present invention will be described. First, FIG. 1 illustrates some configuration diagrams illustrating a physical layer convergence procedure (PLCP) preamble structure used in IEEE 802.11a / g / n. And, Figure 2 shows a part of the configuration diagram showing the PLCP preamble structure used in IEEE 802.11p.

1 and 2, the PLCP preamble includes 10 short training symbols consisting of t ₁ to t ₁₀ and a long training symbol consisting of _two T ₁ and T ₂ . It can be seen that. And, as shown in Figure 1a, the total period of the training symbol included in the PLCP preamble used in IEEE 802.11a / g / n is 16 ms, as shown in Figure 1b, used in IEEE 802.11p It can be seen that the total period of the training symbols included in the PLCP preamble corresponds to 32 ms.

Hereinafter, a short training symbol used in the channel estimation method according to an embodiment of the present invention will be described in more detail. Short training symbols are generally used to achieve automatic gain control, diversity selection, timing synchronization, and coarse frequency synchronization at the receiving end. In addition, the short training symbol is composed of 12 subcarriers phase-modulated in the frequency domain as shown in Equation 1 below.

[Equation 1]

×

×

{0,0,1 + j, 0,0,0-1-j, 0,0,0,1 + j, 0,0,0, -1-j, 0,0,0, -1-j , 0,0,0,1 + j, 0,0,0,0,0,0,0, -1-j, 0,0,0, -1-j, 0,0,0,1 + j , 0,0,0,1 + j, 0,0,0,1 + j, 0,0,0,1 + j, 0,0}

은 52개의 부반송파 중에 12개의 부반송파 만을 사용하는 OFDM 심볼의 평균전력을 정규화하기 위해서 곱해진다. 그리고, 도 3은 52개의 부반송파 중에서 12개의 부반송파를 이용하는 짧은 훈련심볼의 주파수 영역신호를 도시한 것이다. In Equation (1)

Is multiplied to normalize the average power of an OFDM symbol using only 12 subcarriers out of 52 subcarriers. 3 illustrates a frequency domain signal of a short training symbol using 12 subcarriers among 52 subcarriers.

As shown in FIG. 3, twelve positions in which a subcarrier is carried on a short training symbol according to an embodiment of the present invention are -24, -20, -16, -12, -8, -4, 4, 8, It can be seen that it corresponds to 12, 16, 20, 24. In addition, the short training symbol has a period corresponding to 1/4 of the FFT period and is repeated 10 times because a non-zero signal is carried only on a subcarrier corresponding to 4 times the frequency domain.

Therefore, this short training symbol is the same as repeating the IFFT taking the short training symbol of Equation 1 twice and cyclically extending the last 32 samples of the IFFT output. Therefore, as shown in Equation 2 below, the same two short training symbols in the frequency domain may be represented as transmitted in two OFDM symbols.

&Quot; (2) "

l = 0,1

k = -24, -20, -16, -12, -8, -4,4,8,12,16,20,24

는 l번째 OFDM의 k번째 부반송파에 실려 전송되는 짧은훈련심볼을 나타낸다. 그리고, 상기 수학식 2에 대하여 이하의 수학식 2에서와 같이 IFFT를 취하고 2번 반복한 후 IFFT 출력의 마지막 32개의 샘플을 순환확장하게 되면 이하의 수학식 4와 같은 짧은훈련심볼이 만들어 지게 된다. In Equation 2,

Denotes a short training symbol carried on the k-th subcarrier of the l-th OFDM. Then, the IFFT is taken with respect to Equation 2 as shown in Equation 2 below, and after repeating twice, the last 32 samples of the IFFT output are cyclically expanded, and a short training symbol as shown in Equation 4 is generated. .

&Quot; (3) "

n = 0,1,2,3,4, .... N-1

&Quot; (4) "

Hereinafter, a long training symbol according to an embodiment of the present invention will be described in more detail. As shown in FIGS. 1 and 2, the long training symbol according to an embodiment of the present invention can be seen that it is used for channel estimation and fine frequency synchronization. As shown in Equation 5 below, the long training symbols include 53 phase-modulated subcarriers in the frequency domain.

&Quot; (5) "

={1,1,-1,-1,1,1,-1,1,-1,1,1,1,1,1,1,-1,-1,1,1-1,1,-1,1,1,1,1,0,1,-1,-1,1,1,-1,1,-1,1,-1,-1,-1,-1,1,1,-1,-1,1,-1,1,-1,1,-1,1,1,1,1}

= {1,1, -1, -1,1,1, -1,1, -1,1,1,1,1,1,1, -1, -1,1,1-1,1, -1,1,1,1,1,0,1, -1, -1,1,1, -1,1, -1,1, -1, -1, -1, -1,1,1 , -1, -1,1, -1,1, -1,1, -1,1,1,1,1}

)이 두개의 OFDM 심볼(

)로 전송되는 것과 같이 나타낼 수 있다. The long training symbol according to an embodiment of the present invention also repeats the IFFT taken twice in the long training symbol of Equation 5 in the same manner as the short training symbol mentioned above, and cyclically expands the last 32 samples of the IFFT output. As shown in Equation 6 of the two long training symbols in the frequency domain (

Two OFDM symbols (

May be sent as

&Quot; (6) "

l = 2,3

k = -26-26

After taking the IFFT for Equation 6 above and repeating it twice, cyclically extending the last 32 samples of the IFFT output produces a long training symbol as shown in Equation 7 below.

[Equation 7]

={x₃[n]/2, x₂[n], x₃[n]}

= {x ₃ [n] / 2, x ₂ [n], x ₃ [n]}

n = 0,1,2,3,4 ,,,,, N-1

Therefore, the preamble signal consisting of the short training symbol and the long training symbol mentioned above can be expressed as Equation 8 below.

[Equation 8]

={x₁[n]/2, x₀[n], x₁[n], x₃[n]/2, x₂[n], x₃[n]}

= {x ₁ [n] / 2, x ₀ [n], x ₁ [n], x ₃ [n] / 2, x ₂ [n], x ₃ [n]}

When the preamble signal of Equation 8 is transmitted through the wireless channel, the preamble signal received after passing through the wireless channel may be represented by Equation 9 below.

&Quot; (9) "

={x₁[n]/2, x₀[n], x₁[n], x₃[n]/2, x₂[n], x₃[n]}*h_l[n]+w_l[n]

= {x ₁ [n] / 2, x ₀ [n], x ₁ [n], x ₃ [n] / 2, x ₂ [n], x ₃ [n]} * h _l [n] + w _l [n]

In Equation 9, h _l [n] represents a radio channel impulse response of the l-th OFDM symbol, and w _l [n] represents Additive White Gaussian (AWGN) noise. That is, the preamble signal (y = {y ^S , y ^L }) received after passing through the radio channel is a radio channel impulse in the transmitted preamble signal (x = {x ^S , x ^L }) according to Equation (8). It can be expressed as the product of the response h _l [n] plus the AWGN noise w _l [n].

In addition, under the assumption that OFDM symbol synchronization is performed, the received signal Y _l [k] in the frequency domain after the FFT may be expressed by Equation 10 below.

&Quot; (10) "

4 is a block diagram illustrating an OFDM transmission system model according to an embodiment of the present invention. As shown in Equations 10 and 4, H _l [k] is the channel frequency response at the k-th subcarrier of the l-th OFDM symbol, and W _l [k] is the channel at the k-th subcarrier of the l-th OFDM symbol. It corresponds to frequency noise, and X _l [k] corresponds to the l th input symbol on the k th subcarrier.

Therefore, as shown in FIG. 4, the received signal in the frequency domain after the FFT in the OFDM system is represented by adding the frequency noise of the channel to the product of the frequency response of the input symbol and the channel in each subcarrier.

LS (Least Squre) channel estimation method is a method for estimating the channel using a training symbol known in advance at the receiving end. In the conventional LS channel estimation technique using a training symbol, one long training symbol is used, and each long training symbol is independently applied to each long training symbol using two long training symbols, and then the channel is estimated and averaged. There is a way.

Using one long training symbol is a channel estimated by the LS channel estimation method using one long training symbol since the received signal Yl [k] is expressed as a product of a channel and a transmission signal for each subchannel in the OFDM system. May be represented by Equation 11 below.

&Quot; (11) "

l = 2 or 3

In addition, in the preamble structure, since the preamble is transmitted to two long training symbols, each of the two long training symbols can be independently estimated by applying an LS channel estimation technique, as shown in Equation 12 below.

&Quot; (12) "

l=2 인 경우

if l = 2

l=3 인 경우

if l = 3

As shown in Equation 12, the conventional method of estimating the channel by applying the LS channel estimation method to the case of l = 2 and l = 3 independently and taking the average value as shown in Equation 13 below There is a method (averaged LS channel estimation).

&Quot; (13) "

The channel estimation method according to an embodiment of the present invention is characterized by estimating a channel by applying both the long training symbol and the short training symbol described above, instead of using the conventional long training symbol.

That is, as mentioned above, the short training symbol may also be regarded as two OFDM symbols like the long training symbol. As shown in FIG. 3, the subcarriers have 12 positions of -24, -20, -16, Since symbols exist only at -12, -8, -4, 4, 8, 12, 16, 20, and 24, in one embodiment of the present invention, not only the Kim training symbol but also the short training symbol are used together with the LS estimation method. Estimate. 5 is a graph schematically showing an LS channel estimation method using a short training symbol and a long training symbol according to an embodiment of the present invention.

In the LS channel estimation method using the short training symbol and the long training symbol according to an embodiment of the present invention, after applying three independent channel estimation techniques, the channel values are estimated by estimating these channels. First, the channel for the long training symbol when l = 2 in Equation 12 mentioned above is estimated. Second, ② estimates the channel for the long training symbol when l = 3 in Equation 12 mentioned above. In addition, the third is to estimate the channel using the ③ short training symbols.

First, in case of 12 subcarriers having a symbol value, a channel for a corresponding subcarrier is estimated (H ₁ [k]) using a short training symbol as shown in Equation 14 below.

&Quot; (14) "

k = -24, -20, -16, -12, -8, -4, 4, 8, 12, 16, 20, 24

In the case of other subcarriers without a symbol value, channel values are estimated using long training symbols independently when l = 2 and l = 3 (H ₂ [k], H ₃ [k]. ]) And the average value of the two channel values thus estimated is used as in Equation 15 below.

&Quot; (15) "

Finally, the channel estimation value using the short training symbol independently and the channel estimation value using the long training symbol when l = 2 and l = 3 are averaged as shown in Equation 16 below to finally estimate the channel. Done.

&Quot; (16) "

Hereinafter, a simulation result for examining the performance of the LS channel estimation method using a short training symbol and a long training symbol according to an embodiment of the present invention will be described. 6 is a graph showing a simulation result of the LS channel estimation method using a short training symbol and a long training symbol according to an embodiment of the present invention.

As shown in FIG. 6, it can be seen that simulation results for examining the performance of channel estimation methods using mean square error (MSE) are shown. MSE can be represented by Equation 17 below.

&Quot; (17) "

는 정확한 채널값에 해당하고,

은 추정된 채널값을 나타낸다. 도 6에 도시된 바와 같이, 검정색선(LTS1)과 빨간색선(LTS2)은 각각 하나의 긴훈련심볼을 이용하여 추정된 채널값과 정확한 채널값에 대한 MSE이고, 연두색선(LTS12)은 2개의 긴훈련심볼을 이용하여 추정된 채널값의 평균값과 정확한 채널값에 대한 MSE이고, 파란색선(LTS12+STS)는 본 발명의 일실시예에 따른 짧은훈련심볼과 긴훈련심볼을 이용한 LS채널추정방법에 의해 추정된 채널값과 정확한 채널값에 대한 MSE를 나타내고 있음을 알 수 있다. In equation (17)

Corresponds to the correct channel value,

Represents an estimated channel value. As shown in FIG. 6, the black line LTS1 and the red line LTS2 are MSEs for the channel value and the correct channel value, respectively, estimated using one long training symbol, and the yellow green line LTS12 is divided into two lines. LS channel estimation method using a short training symbol and a long training symbol according to an embodiment of the present invention, and the blue line (LTS12 + STS) is an MSE for an average channel value and an accurate channel value estimated using a long training symbol. It can be seen that it represents the MSE for the channel value and the correct channel value estimated by.

In addition, as shown in Figure 6, when applying the LS channel estimation method using a short training symbol and a long training symbol according to an embodiment of the present invention to reduce the MSE value compared to the conventional method to estimate the channel more accurately It can be seen that.

Claims (6)

In the LS channel estimation apparatus for estimating the channel by analyzing the preamble received signal after passing through the wireless channel, when the preamble signal is transmitted through a wireless channel,
The preamble is provided with a short training symbol and a long training symbol,
A first channel estimator for estimating a channel of the corresponding subcarrier based on the short training symbols known in advance in the case of a subcarrier having a symbol value;
A second channel estimator for estimating a channel based on the long training symbol previously known at a receiver in case of other subcarriers in which the symbol value does not exist; And
And a third channel estimator for adding channel estimation values of the subcarriers obtained from the first channel estimator and the second channel estimator, and dividing them by the number of subcarriers to obtain an average value of channel estimates for each subcarrier. LS channel estimation device using short training symbols and long training symbols.
The method of claim 1,
In the first channel estimation subcarrier, a symbol exists at 12 positions, and a channel estimation value estimated by a short training symbol is represented by Equation 1 below.
[Equation 1]

LS channel estimation apparatus using short and long training symbols, characterized in that obtained by:
K is -24, -20, -16, -12, -8, -4, 4, 8, 12, 16, 20, 24, and

Is a channel estimation value estimated by a short training symbol,

Is a received signal in the frequency domain after the FFT, and

Is a short training symbol.
The method of claim 1,
The long training symbol of the second channel estimation unit is composed of two,
Equations 2 and 3 below
&Quot; (2) "

&Quot; (3) "

LS channel estimation apparatus using short training symbols and long training symbols, characterized by obtaining the channel estimation value for each long training symbol by:
remind

Is the channel estimation value for the first long training symbol,

Is a received signal in the frequency domain after FFT, and

Is the first long training symbol,
remind

Is the channel estimation value for the second long training symbol,

Is a received signal in the frequency domain after FFT, and

Is the second long training symbol.
The method of claim 3,
The second channel estimation unit
LS channel estimation apparatus using a short training symbol and a long training symbol, characterized in that to obtain an average value of the channel estimation value for the first long training symbol and the channel estimation value for the second long training symbol.
The method of claim 1,
The third channel estimation unit,
By Equation 4 below
&Quot; (4) "

LS channel estimation apparatus using a short training symbol and a long training symbol, characterized in that the average value of the channel estimation values for each subcarrier is obtained;
remind

Is an average of channel estimates for each subcarrier,

Is the channel estimation value from the short training symbol,

Channel estimation value according to the first long training symbol,

Is the channel estimation value by the second long training symbol.
In the LS channel estimation method for estimating the channel by analyzing the preamble received signal after passing through the wireless channel, when the preamble signal is transmitted through a wireless channel,
The preamble is provided with a short training symbol and a long training symbol,
In the case of a subcarrier having a symbol value, obtaining a channel estimate value for the corresponding subcarrier based on the short training symbol previously known to the receiver by a first channel estimator;
Obtaining a channel estimation value based on the long training symbol previously known at a receiving end by a second channel estimator in case of other subcarriers in which the symbol value does not exist; And
Adding channel estimation values of the respective subcarriers obtained by the first channel estimation unit and the second channel estimation unit by a third channel estimation unit, and dividing them by the number of subcarriers to obtain an average value of channel estimation values for each subcarrier. LS channel estimation method using a short training symbol and a long training symbol, characterized in that.

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