KR20110135661A - Ofdm receiver being capable of estimating timing in multi-path fading channel, ofdm system having the same and timing estimation method thereof - Google Patents

Abstract

PURPOSE: An orthogonal frequency division multiplexing(OFDM) receiver which estimates timing in a multi-path fading channel, an OFDM system including the same, and a timing estimation method thereof are provided to improve timing estimation performance by eliminating timing errors. CONSTITUTION: A first timing estimation part(110) calculates a timing metric value based on an autocorrelation function of a received signal including a baseband orthogonal frequency division multiplexing(OFDM) sample signal. The first timing estimation part calculates a first timing estimation value based on the calculated timing metric value. A second timing estimation part(120) calculates a filtered timing metric value based on a cross-correlation function between the received signal and a preamble signal in a first timing estimation range based on the first timing estimation value. The second timing estimation part calculates a second timing estimation value based on the filtered timing metric value. An optimum-timing estimation part(130) calculates an optimum-timing estimation value by comparing an amplification amount.

Description

OPDM RECEIVER BEING CAPABLE OF ESTIMATING TIMING IN MULTI-PATH FADING CHANNEL, OFDM SYSTEM HAVING THE SAME AND TIMING ESTIMATION METHOD THEREOF}

The present invention relates to an OFDM system and a timing estimation method capable of timing estimation. More specifically, an OFDM receiver capable of timing estimation in a multipath fading channel, which uses an autocorrelation technique of a received signal and a cross-correlation technique of a preamble, and obtains an optimal timing estimate by calculating a stepwise timing estimate through a timing metric. The present invention relates to an OFDM system and a timing estimation method thereof.

Orthogonal Frequency Division Multiplexing (OFDM) systems are robust to impulse noise and multi-path fading channel environments, and can be used in wireless LANs such as IEEE 802.11a because of their efficient spectrum usage. Wireless standard modulation methods such as WLANs, Wireless Local Area Networks, Digital Audio Broadcasting (DAB), and Digital Video Broadcasting-Terrestrial (DVB-T) are used.

However, despite these advantages, the OFDM system has a problem in that it is very sensitive to carrier frequency errors and timing errors. In particular, the timing error affects the determination of the starting point at the time of the fast Fourier transform (FFT) input of the OFDM signal, and thus has a continuous influence on the processing after the FFT.

Schmidl (T. Schmidl and DC Cox, “Robust frequency and timing synchronization for OFDM systems,” IEEE Trans. Commun., Vol. 45, no. 12, pp. 1613-1621, Dec. 1997.) Proposed a timing estimation technique that uses a preamble consisting of two repetitive parts and autocorrelation between repetitive parts.

However, in this technique, the timing metric for timing estimation is difficult to find the exact timing point even if there is a flat part around the exact timing point without the influence of noise and channel.

To address this problem, Park (B. Park, H. Cheon, C. Kang, and D. Hong, “A novel timing estimation method for OFDM systems,” IEEE Commun. Lett., Vol. 7, no. 5 , pp. 239-241, May 2003.) proposed a technique to remove the flat part of the existing timing metric and to make it appear sharp by using a new type of preamble.

However, since these techniques do not consider the multipath fading channel environment, there is a problem that the estimation performance is lowered when timing is estimated in the multipath fading channel environment. Therefore, there is a need for a receiver and a timing estimation method that can improve timing estimation even in a multipath fading channel environment.

SUMMARY OF THE INVENTION The present invention has been made in view of the above necessity, and an object of the present invention is to estimate timing in a multipath fading channel that can improve the performance of timing estimation by eliminating timing errors that may occur in an OFDM system in a multipath fading channel. The present invention provides an OFDM receiver, an OFDM system including the same, and a timing estimation method thereof.

An object of the present invention as described above, the baseband OFDM sample signal (CP) with a cyclic prefix (CP, Cyclic Prefix) is inserted to remove the inter-symbol interference and the preamble signal generated for the timing error estimation of the receiver In an OFDM receiver capable of timing estimation in a multipath fading channel, a timing metric value is calculated based on an autocorrelation function of a received signal located at a receiver and including a baseband OFDM sample signal and based on the calculated timing metric value. A first timing estimator for calculating a primary timing estimate; Calculate a filtered timing metric value based on a cross-correlation function between the received signal and the preamble signal in a first timing estimation range based on the first timing estimate, and calculating the second timing estimate based on the filtered timing metric value. A second timing estimator for calculating; And an optimum timing estimator configured to calculate an optimum timing estimate by comparing an amplification amount based on a cross-correlation function between successive timings in a second timing estimation range based on a second timing estimate based on a second timing estimate. It can be achieved by providing an OFDM receiver capable of estimation.

The preamble signal is preferably a repetitive structure of a random sequence.

The baseband OFDM sample signal with the cyclic prefix inserted is expressed as

,

,

Where x (k) is the baseband OFDM sample signal, N is the total number of subcarriers, X (n) is the modulated symbol sample at the nth subcarrier, and N _G is the length of the cyclic prefix.

It is preferable to represent by.

The preamble signal is represented by the following equation

Where S is a preamble, A _{N / 2} is a random sequence of length N / 2, and N is the total number of subcarriers

It is preferable to represent by.

The autocorrelation function is

Where Ra (d) is the autocorrelation function, N is the total number of subcarriers, r (d + k) is the complex value of the received signal, and r (d + k + N / 2) is the N / 2 delay of the received signal. Complex, * is a conjugate complex operation)

It is preferable to represent by.

The timing metric value is preferably a summation window applied to the autocorrelation function by the width of the autocorrelation function.

The timing metric value is expressed as

Where Ma (d) is the timing metric value, Ra (dkN / 2-N _G +1) is the autocorrelation function, N + N _G -1 is the width of the autocorrelation function, N is the total number of subcarriers, N _G Is the length of the cyclic prefix)

It is preferable to represent by.

The first timing estimate is

는 1차 타이밍 추정치, Ma(d)는 타이밍 메트릭값임)(here,

Is the primary timing estimate, Ma (d) is the timing metric)

It is preferable to represent by.

The cross-correlation function is

,

,

는 1차 타이밍 추정치, N은 총 부반송파의 개수임)Where Rc (d) is a cross-correlation function, r (d + k) is a received signal, S (k) is a preamble, * is a conjugate complex operation, d is a first timing estimation range,

Is the primary timing estimate, N is the total number of subcarriers)

It is preferable to represent by.

The filtered timing metric value is expressed as

,

,

는 1차 타이밍 추정치, N은 총 부반송파의 개수임)Where Mc (d) is a filtered timing metric value, Rc (d) is a cross-correlation function, Ma (d) is a timing metric value, d is a first timing estimation range,

Is the primary timing estimate, N is the total number of subcarriers)

It is preferable to represent by.

The second-order timing estimate is

,

,

는 2차 타이밍 추정치, Mc(d)는 필터링된 타이밍 메트릭값, d는 제 1타이밍 추정범위,

는 1차 타이밍 추정치, N은 총 부반송파의 개수임)(here,

Is the secondary timing estimate, Mc (d) is the filtered timing metric value, d is the first timing estimate range,

Is the primary timing estimate, N is the total number of subcarriers)

It is preferable to represent by.

The optimal timing estimate is

,

,

,

,

는 최적 타이밍 추정치, Rc(d)는 상호상관 함수, d는 제 2타이밍 추정범위, L은 채널의 탭 수, N_G는 순환 전치의 길이임)(here,

Is the optimal timing estimate, Rc (d) is the cross-correlation function, d is the second timing estimate range, L is the number of taps in the channel, and N _G is the length of the cyclic prefix)

It is preferable to represent by.

On the other hand, an object of the present invention comprises a sample generator for generating a baseband OFDM sample signal including an OFDM receiver, the baseband OFDM sample signal is located at the transmitting end and inserted with a cyclic prefix; And a preamble generator positioned at a transmitter and generating a preamble signal. The OFDM system may further include an OFDM system capable of timing estimation in a multipath fading channel.

Meanwhile, an object of the present invention is another category, which is a timing of an OFDM receiver in a multipath fading channel using a baseband OFDM sample signal having a cyclic prefix pre-inserted for inter-symbol interference cancellation and a preamble signal generated for timing error estimation of a receiver. A method of estimating, comprising: calculating, by a first timing estimator, a timing metric value based on an autocorrelation function of a received signal including a baseband OFDM sample signal (S300); Calculating a first timing estimate based on the calculated timing metric value by the first timing estimator (S400); Calculating a filtered timing metric value based on a cross-correlation function between a received signal and a preamble signal in a first timing estimation range based on a first timing estimate by a second timing estimator of the receiving end (S500); Calculating a second timing estimate based on the filtered timing metric value by the second timing estimator (S600); And calculating, by the optimum timing estimator of the receiver, an optimum timing estimate through an amplification comparison based on a cross-correlation function between successive timings in the second timing estimation range based on the second timing estimate (S700). It can be achieved by providing a method for timing estimation of an OFDM receiver in a channel.

The timing metric value calculating step (S300) of the first timing estimator may be a step of applying the summation window to the autocorrelation function by the width of the autocorrelation function.

Preferably, the first timing estimation unit calculating step (S400) of the first timing estimator is a step of estimating a timing at which the timing metric becomes the maximum as the primary timing estimate.

In operation S500 of filtering timing metric values of the second timing estimator, the preamble signal preferably has a repetitive structure of a random sequence.

In operation S600, the second timing estimation unit may estimate the timing at which the filtered timing metric becomes the maximum as the second timing estimate.

The optimum timing estimation value calculating step S700 of the optimum timing estimating unit is preferably a step of estimating the timing with the largest amplification amount as the optimum timing.

On the other hand, an object of the present invention includes a timing estimation method of an OFDM receiver,

Generating a baseband OFDM sample signal in which a cyclic prefix is inserted before the timing metric value calculating step S300 of the first timing estimator (S300); And a step of generating a preamble signal by the preamble generator of the transmitter (S200). The method may be achieved by providing a timing estimation method of an OFDM system in a multipath fading channel.

According to one embodiment of the present invention as described above, the timing error that may occur in the OFDM system in the multipath fading channel may be removed to improve the performance of the timing estimation.

In addition, in an OFDM system in a multipath fading channel, in order to accurately demodulate a transmission signal, not only the frequency error but also the symbol synchronization should be taken into consideration. There is an effect that can restore the signal correctly.

1 is a block diagram illustrating a configuration of an OFDM system capable of timing estimation in a multipath fading channel according to the present invention;
2A is a graph illustrating the absolute value of an autocorrelation function for timing in a multipath fading channel, in accordance with an embodiment of the present invention;
FIG. 2B is a graph showing timing metric values for timing using a saturation window applied to an autocorrelation function in a multipath fading channel according to an embodiment of the present invention; FIG.
3A and 3B are graphs showing correlation values with respect to timing through a timing estimation technique of the conventional park;
4 is a graph illustrating a correlation value with respect to timing according to an embodiment of an OFDM system capable of timing estimation in a multipath fading channel of the present invention;
5 is a flowchart sequentially showing an embodiment of a timing estimation method of an OFDM system in a multipath fading channel of the present invention.

< OFDM  System Configuration>

1 is a block diagram illustrating a configuration of an OFDM system capable of timing estimation in a multipath fading channel according to the present invention. As shown in FIG. 1, one embodiment of an OFDM system includes an OFDM receiver 10 and an OFDM transmitter 20. In addition, the OFDM receiver 10 includes a first timing estimator 110, a second timing estimator 120, and an optimum timing estimator 130, and also includes an RF receiver 140 and an FFT ( Fast Fourier Transform) unit 150 may be configured. In addition, the OFDM transmitter 20 may include a sample generator 210 and a preamble generator 220, and may further include an RF transmitter 230.

Briefly describing the operation of the OFDM system of the present invention, when a baseband OFDM sample signal and a preamble signal in which a cyclic prefix (CP, Cyclic Prefix) is inserted in the transmitter 20 are transmitted and are transmitted by the RF transmitter 230, The receiver 10, which is a receiving end, obtains accurate symbol timing of an OFDM system in a multipath fading channel by calculating a first timing estimate, a second timing estimate, and an optimum timing estimate based on a received signal including an OFDM sample signal and a preamble signal. Done.

First, the configuration of the OFDM transmitter 20 will be described with reference to FIG.

The sample generator 210 generates a baseband OFDM sample signal in which a cyclic prefix is inserted in order to remove intersymbol interference (ISI). The sample generator 210 may include an encoding means (not shown), an encoding means (not shown), and a modulation means (not shown), etc. of the data source, but are outside the gist of the present invention or are known components. Detailed description will be omitted. Here, the OFDM sample signal is represented by Equation 1 below.

Where x (k) is the baseband OFDM sample signal, N is the total number of subcarriers, X (n) is the modulated symbol sample at the nth subcarrier, and N _G is the length of the cyclic prefix.

Can be represented by

The cyclic prefix acts as an inter-symbol interference protection section in the OFDM sample signal, and is inserted or copied in the last or first interval of the effective symbol interval to prevent the destruction of orthogonality between subcarriers. Signal.

The preamble generator 220 generates a preamble signal for timing error estimation, where the preamble signal is composed of a signal sequence having a repetitive structure of a random sequence. In particular, in the present embodiment, the following equation (2)

Where S is a preamble, A _{N / 2} is a random sequence of length N / 2, and N is the total number of subcarriers

Can be represented by

The RF transmitter 230 is a configuration for transmitting the baseband OFDM sample signal and the preamble signal in which the cyclic prefix is inserted.

In addition, the basic configuration of the OFDM transmitter may include Serial to Paralle (S / P), Inverse Fast Fourier Transform (IFFT), and Digital Analogue Converter (DAC). These configurations are the same as the known configurations. Detailed description will be omitted.

Hereinafter, the configuration of the OFDM receiver 10 will be described with reference to FIG. 1.

The first timing estimator 110 calculates a timing metric value based on an autocorrelation function of a received signal including a baseband OFDM sample signal and calculates a first timing estimate based on the calculated timing metric value. .

The received signal may be represented as a complex value including Additive White Gaussian Noise (AWGN). The complex value of the received signal is expressed by the following equation (3).

Where r (k) is the complex value of the received signal, ε is the integer timing offset, w (k) is the complex additive white normal noise with an average of 0, h (m) is the impulse response of the frequency-selective channel, and L is the channel. Number of taps, N _G is the length of the cyclic prefix)

It is represented by

Therefore, the autocorrelation function is a complex sample and

Where Ra (d) is the autocorrelation function, N is the total number of subcarriers, r (d + k) is the complex value of the received signal, and r (d + k + N / 2) is the N / 2 delay of the received signal. Complex, * is a conjugate complex operation)

Can be represented by

The timing metric value is obtained by applying a summation window to the autocorrelation function by the width of the autocorrelation function.

Where Ma (d) is the timing metric value, Ra (dkN / 2-N _G +1) is the autocorrelation function, N + N _G -1 is the width of the autocorrelation function, N is the total number of subcarriers, N _G Is the length of the cyclic prefix)

Can be represented by

The first timing estimate is obtained by calculating the timing at which the timing metric value Ma (d) is maximized.

는 1차 타이밍 추정치, Ma(d)는 타이밍 메트릭값임)(here,

Is the primary timing estimate, Ma (d) is the timing metric)

Can be represented by

)에 기초한 제 1타이밍 추정범위에서 수신 신호와 프리앰블 신호 사이의 상호상관(cross-correlation) 함수에 기반한 필터링된 타이밍 메트릭값을 연산하고, 필터링된 타이밍 메트릭값을 기초로 2차 타이밍 추정치를 연산하는 역할을 한다.Meanwhile, the second timing estimator 120 estimates the first timing estimate (

Calculating a filtered timing metric value based on a cross-correlation function between the received signal and the preamble signal in the first timing estimation range, and calculating a second timing estimate based on the filtered timing metric value. Play a role.

Here, the cross-correlation function is

는 1차 타이밍 추정치, N은 총 부반송파의 개수임)Where Rc (d) is a cross-correlation function, r (d + k) is a received signal, S (k) is a preamble, * is a conjugate complex operation, d is a first timing estimation range,

Is the primary timing estimate, N is the total number of subcarriers)

Can be represented by

The filtered timing metric value is represented by Equation 8 below.

는 1차 타이밍 추정치, N은 총 부반송파의 개수임)Where Mc (d) is a filtered timing metric value, Rc (d) is a cross-correlation function, Ma (d) is a timing metric value, d is a first timing estimation range,

Is the primary timing estimate, N is the total number of subcarriers)

Can be represented by

The second timing estimate calculated based on the filtered timing metric value Mc (d) is expressed by the following equation (9).

는 2차 타이밍 추정치, Mc(d)는 필터링된 타이밍 메트릭값, d는 제 1타이밍 추정범위,

는 1차 타이밍 추정치, N은 총 부반송파의 개수임)(here,

Is the secondary timing estimate, Mc (d) is the filtered timing metric value, d is the first timing estimate range,

Is the primary timing estimate, N is the total number of subcarriers)

Can be obtained.

Meanwhile, the optimum timing estimator 130 calculates an optimal timing estimate by comparing an amplification amount based on a cross-correlation function between successive timings in the second timing estimation range based on the second timing estimate.

Here, the optimum timing estimate is expressed by Equation 10 below.

는 최적 타이밍 추정치, Rc(d)는 상호상관 함수, d는 제 2타이밍 추정범위, L은 채널의 탭 수, N_G는 순환 전치의 길이임)(here,

Is the optimal timing estimate, Rc (d) is the cross-correlation function, d is the second timing estimate range, L is the number of taps in the channel, and N _G is the length of the cyclic prefix)

Can be obtained.

RF receiver (140) serves to receive the received signal including the baseband OFDM sample signal and the preamble signal described above, FFT (Fast Fourier Transform) unit 150 is the input start point based on the optimum timing estimate A fast Fourier transform of the received signal is performed based on the information.

Of course, the fast Fourier transformed input signal symbol is restored to a data symbol which is a signal transmitted through the data symbol recovery unit 160. For this purpose, the data symbol recovery unit 160 of the OFDM receiver 10 may include decoding means of a data source ( Not shown), decoding means (not shown), P / S (Paralle to Serial (not shown)) and ADC (Analogue Digital Converter, not shown), etc. may be further included, these configurations are the same as the known configuration Therefore, detailed description is omitted.

<Experiment graph>

FIG. 2A is a graph illustrating an absolute value of an autocorrelation function for timing in a multipath fading channel according to an embodiment of the present invention, and FIG. 2B is a graph of an autocorrelation function in a multipath fading channel according to an embodiment of the present invention. The timing metric value to which the summing window is applied is a graph showing the timing. In each graph, the vertical axis is the absolute value of the autocorrelation function and the timing metric value, and the horizontal axis is the timing axis.

2A and 2B are graphs of three experiments under conditions of SNR (Signal to Noise Ratio) = 0 dB and the total number of subcarriers N = 256. FIG. As shown in FIG. 2B, it can be seen that the timing metric value Ma (d), which is a result of applying the summation window equal to the width of the autocorrelation function to the autocorrelation function, has a large value around timing 0.

3A and 3B are graphs showing correlation values with respect to timings through conventional timing estimation techniques of parks with and without multipath fading, respectively. The vertical axis of each graph represents the correlation value axis and the horizontal axis represents the timing axis.

As shown in FIG. 3B, unlike the graph of FIG. 3A when there is no multipath fading, a non-zero timing is estimated as an optimal timing.

4 is a graph illustrating a correlation value with respect to timing according to an embodiment of an OFDM system capable of timing estimation in a multipath fading channel according to the present invention. The vertical axis of the graph represents the correlation value axis and the horizontal axis represents the timing axis.

)는 제 2 타이밍 추정범위인

에서 0을 최적 타이밍으로 추정한다.
As shown in Fig. 4, the optimum timing estimate (

) Is the second timing estimation range

Estimates 0 as the best timing.

Timing Estimation Method

5 is a flowchart sequentially showing an embodiment of a timing estimation method of an OFDM system in a multipath fading channel of the present invention. As described above, since the OFDM system includes the OFDM receiver 10 and the OFDM transmitter 20, the following description includes all of the steps performed in each configuration.

Referring to FIG. 5, the embodiment of the present invention will first generate a baseband OFDM sample signal in which a cyclic prefix is inserted by the sample generator 210 of the transmitter in the OFDM transmitter 20 (S100).

Next, the preamble generator 220 of the transmitter generates a preamble signal (S200).

Next, the first timing estimator 110 of the receiver in the OFDM receiver 10 calculates a timing metric value based on an autocorrelation function of a received signal including a baseband OFDM sample signal (S300). In particular, the timing metric value calculating step S300 is performed by applying the summation window to the autocorrelation function by the width of the autocorrelation function.

Next, the first timing estimator 110 calculates a first timing estimate based on the calculated timing metric value (S400). Here, the timing at which the timing metric value is maximized is calculated as the primary timing estimate.

Next, the second timing estimator 120 of the receiver calculates a filtered timing metric value based on a cross-correlation function between the received signal and the preamble signal in the first timing estimation range based on the first timing estimate (S500). Here, the preamble signal preferably has a repetitive structure of a random sequence.

Next, the second timing estimator 120 calculates a second timing estimate based on the filtered timing metric value (S600). Here, a timing at which the filtered timing metric value is maximized is calculated as a secondary timing estimate.

Finally, the optimal timing estimation unit 130 of the receiving end calculates the optimal timing estimate by comparing the amplification amount based on the cross-correlation function between successive timings in the second timing estimation range based on the secondary timing estimate (S700). An embodiment of a timing estimation method of may be performed. Here, the optimum timing estimate calculation step S700 may be a step of estimating the timing with the largest amplification amount as the optimum timing.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. In addition, the scope of the present invention is indicated by the appended claims rather than the detailed description above. Also, it is to be construed that 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.

10: OFDM receiver
20: OFDM transmitter
110: first timing estimation unit
120: second timing estimation unit
130: optimal timing estimation unit
140: RF receiver
150: FFT part
160: data symbol recovery unit
210: sample generator
220: preamble generation unit
230: RF transmitter

Claims (20)

An OFDM receiver capable of timing estimation in a multipath fading channel using a baseband OFDM sample signal having a cyclic prefix pre-inserted for inter-symbol interference cancellation and a preamble signal generated for timing error estimation of a receiver,
A first timing estimator for calculating a timing metric value based on an autocorrelation function of a received signal located at the receiving end and including the baseband OFDM sample signal and calculating a first timing estimate based on the calculated timing metric value;
Calculate a filtered timing metric value based on a cross-correlation function between the received signal and the preamble signal in a first timing estimation range based on the first timing estimate, based on the filtered timing metric value A second timing estimator for calculating a second timing estimate; And
A multipath fading channel including a multipath fading channel located at the receiving end and calculating an optimum timing estimate by comparing an amplification amount based on the cross-correlation function between successive timings in a second timing estimation range based on the second timing estimate; An OFDM receiver capable of timing estimation at.
The method of claim 1,
The preamble signal is an OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that the repetitive structure of a random sequence.
The method of claim 1,
The baseband OFDM sample signal with the cyclic prefix inserted is represented by the following equation

,

Where x (k) is the baseband OFDM sample signal, N is the total number of subcarriers, X (n) is the modulated symbol sample at the nth subcarrier, and N _G is the length of the cyclic prefix.
And an OFDM receiver capable of timing estimation in a multipath fading channel.
The method of claim 1,
The preamble signal is represented by the following equation

Where S is a preamble, A _{N / 2} is a random sequence of length N / 2, and N is the total number of subcarriers
And an OFDM receiver capable of timing estimation in a multipath fading channel.
The method of claim 1,
The autocorrelation function is

Where Ra (d) is the autocorrelation function, N is the total number of subcarriers, r (d + k) is the complex value of the received signal, and r (d + k + N / 2) is the N / 2 delay of the received signal. Complex, * is a conjugate complex operation)
And an OFDM receiver capable of timing estimation in a multipath fading channel.
6. The method of claim 5,
The timing metric value is an OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that the summation window is applied to the autocorrelation function by the width of the autocorrelation function.
The method of claim 6,
The timing metric value is represented by the following equation

Where Ma (d) is the timing metric value, Ra (dkN / 2-N _G +1) is the autocorrelation function, N + N _G -1 is the width of the autocorrelation function, N is the total number of subcarriers, N _G Is the length of the cyclic prefix)
OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that represented by.
The method of claim 7, wherein
The first timing estimate is represented by the following equation

(here,

Is the primary timing estimate, Ma (d) is the timing metric)
OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that represented by.
The method of claim 8,
The cross-correlation function is

,

Where Rc (d) is a cross-correlation function, r (d + k) is a received signal, S (k) is a preamble, * is a conjugate complex operation, d is a first timing estimation range,

Is the primary timing estimate, N is the total number of subcarriers)
OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that represented by.
The method of claim 9,
The filtered timing metric value is represented by the following equation

,

Where Mc (d) is a filtered timing metric value, Rc (d) is a cross-correlation function, Ma (d) is a timing metric value, d is a first timing estimation range,

Is the primary timing estimate, N is the total number of subcarriers)
OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that represented by.
The method of claim 10,
The second timing estimate is represented by the following equation

,

(here,

Is the secondary timing estimate, Mc (d) is the filtered timing metric value, d is the first timing estimate range,

Is the primary timing estimate, N is the total number of subcarriers)
OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that represented by.
12. The method of claim 11,
The optimal timing estimate is

,

,

(here,

Is the optimal timing estimate, Rc (d) is the cross-correlation function, d is the second timing estimate range, L is the number of taps in the channel, and N _G is the length of the cyclic prefix)
OFDM receiver capable of timing estimation in a multipath fading channel, characterized in that represented by.
13. An OFDM receiver according to any one of the preceding claims,
A sample generation unit positioned at a transmitter and generating a baseband OFDM sample signal having the cyclic prefix inserted therein; And
And a preamble generator positioned at the transmitting end to generate the preamble signal.
A method for estimating timing of an OFDM receiver in a multipath fading channel using a baseband OFDM sample signal having a cyclic prefix pre-inserted for inter-symbol interference and a preamble signal generated for timing error estimation of a receiver,
Calculating, by the first timing estimator of the receiver, a timing metric value based on an autocorrelation function of the received signal including the baseband OFDM sample signal (S300);
Calculating, by the first timing estimator, a first timing estimate based on the calculated timing metric value (S400);
Calculating, by the second timing estimator, the filtered timing metric value based on a cross-correlation function between the received signal and the preamble signal in a first timing estimation range based on the first timing estimate;
Calculating, by the second timing estimator, a second timing estimate based on the filtered timing metric value (S600); And
Calculating, by the optimum timing estimator of the receiving end, an optimum timing estimate through an amplification comparison based on the cross-correlation function between successive timings in a second timing estimation range based on the second timing estimate (S700); Timing Estimation Method of an OFDM Receiver in a Path Fading Channel.
The method of claim 14,
The timing metric value calculating step (S300) of the first timing estimator,
And applying a summing window to the autocorrelation function by the width of the autocorrelation function.
The method of claim 14,
The first timing estimation value calculating step (S400) of the first timing estimator,
Estimating a timing at which the timing metric is maximized as a primary timing estimate.
The method of claim 14,
In operation S500 of filtering timing metric values of the second timing estimator,
The preamble signal has a repetitive structure of a random sequence, the timing estimation method of the OFDM receiver in a multipath fading channel.
The method of claim 14,
In operation S600, the second timing estimation unit calculates the second timing estimation unit.
Estimating a timing at which the filtered timing metric is maximized as a second timing estimate.
The method of claim 14,
The optimum timing estimate calculation step (S700) of the optimum timing estimator,
And estimating the timing with the largest amount of amplification as an optimal timing.
20. A method for estimating timing of an OFDM receiver according to any one of claims 14 to 19,
Before the timing metric value calculating step (S300) of the first timing estimator,
Generating a baseband OFDM sample signal to which the cyclic prefix is inserted (S100); And
And a step (S200) of generating a preamble signal by the preamble generator of the transmitter. The timing estimation method of an OFDM system in a multipath fading channel, characterized in that it further comprises.

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