KR20070117793A - Apparatus and method for estimating noise power on received signal - Google Patents

Abstract

A noise power estimating apparatus and a noise power estimating method are provided to correct correlation jitter generated in obtaining a correlation value to estimate noise included in a received signal. A channel estimating unit(110) receives a data including a training sequence through a communication channel, and outputs the N number of correlation values obtained for the reception data while moving the training sequence by N times as an estimated channel signal which has estimated the channel. In this case, if the absolute value of the correlation values is smaller than a certain masking reference value, the channel estimating unit outputs '0' as an estimated channel signal instead of the corresponding correlation value. A noise power estimating unit(130) obtains estimated noise by subtracting the estimated channel signal from the correlation value, obtains power of the estimated noise, and outputs the same.

Description

Apparatus and method for estimating noise power on received signal

1 is a block diagram of a noise power estimation apparatus according to an embodiment of the present invention;

2 is a view provided for explaining the operation of the mobile correlator according to an embodiment of the present invention;

3 is a flowchart provided to explain an operation of a noise masking unit according to an embodiment of the present invention;

4 is a conceptual diagram provided to explain an operation of a noise masking unit according to an embodiment of the present invention;

5 is a detailed block diagram of an estimated noise generation unit according to an embodiment of the present invention;

6 is a diagram for explaining jitter occurring during motion correlation according to random data;

7 is a block diagram of a data jitter compensation unit according to an embodiment of the present invention;

8 is a block diagram of an average noise power generation unit according to an embodiment of the present invention, and

9 is a block diagram of a receiving circuit including a noise power estimation apparatus according to an embodiment of the present invention.

The present invention estimates a channel from a signal received through a communication channel in which fading by a predetermined multipath exists, and estimates noise based on the estimated channel, thereby including noise included in the received signal. The present invention relates to a noise power estimator and a method for calculating the power of.

The transmission signal of the communication system is transmitted from the transmitter and transmitted to the receiver by air or wire. When a signal from a transmission system is transmitted over the air or by wire, the transmitted signal combines the signals reflected by various reflectors, such as buildings, trees, mountains, or wired cables. The receiver receives this distorted signal. The reflected components have a time difference along the time path from the original transmitted signal, and the reflected signal distorts the original signal transmitted without time delay, so that the receiver cannot obtain the original signal only by the received signal. The restoration process will be performed.

The process of restoring the signal passing through the channel includes carrier recovery, timing recovery, and channel equalization. In particular, when the receiver sets the initial equalization coefficient during the equalization process, the receiver can obtain a more optimized equalization coefficient by knowing the signal to noise ratio of the channel. Therefore, there is a need for a method of obtaining noise power of a channel by using an unequalized signal.

Summary of the Invention An object of the present invention is to estimate a channel from a signal received through a communication channel in which fading by a predetermined multipath exists, and to estimate the noise based on the estimated channel and to include it in the received signal. The present invention provides a noise power estimating device and a method for calculating the power of noise.

Another object of the present invention is to provide a method for compensating correlation jitter occurring in a process of obtaining a correlation value for estimating noise included in a received signal.

In order to achieve the above object, the noise power estimation apparatus according to the present invention includes a channel estimation and a noise power estimation.

The channel estimator receives data including a predetermined training sequence through a predetermined communication channel, and moves N training sequences previously known N times to obtain N correlation values obtained for the received data. The channel is output as an estimated channel signal. When the magnitude of the absolute value of the correlation value is equal to or less than a predetermined masking reference value, '0' is output as the estimated channel signal instead of the correlation value.

The noise power estimator obtains estimated noise by subtracting the estimated channel signal from the correlation value, and calculates and outputs the power of the estimated noise.

Here, the training sequence may be a PN sequence (Pseudo Noise Sequence), and the received data may correspond to a terrestrial or satellite digital broadcast signal received in symbol units.

Here, the channel estimator may be the estimated channel signal if the absolute value is greater than the masking reference value within a predetermined range from the correlation value even if the absolute value of the correlation value is equal to or less than the masking reference value. It is preferable to output the correlation value without outputting '0'.

In addition, the noise power estimation unit may obtain the average of the noise power by dividing the power of the estimated noise by the number of times the estimated channel signal is '0'.

According to an embodiment, the channel estimator may further include a mask flag register in which a corresponding flag is displayed when the value of the estimated channel signal is '0'. The noise power estimation unit reads the mask flag register and calculates the number of times the estimated channel signal is '0'.

According to another embodiment, the noise power estimator obtains a distance from a channel impulse response among the correlation values for each of the estimated noises, and divides the estimated noise by a weight corresponding to the distance to be included in the correlation value. Data jitter can be compensated for.

In accordance with another aspect of the present invention, a noise power estimation method includes receiving data including a predetermined training sequence through a predetermined communication channel, and obtaining the received data while moving the previously known training sequence N times. Outputting N correlation values as an estimated channel signal in which the channel is estimated, and outputting '0' as the estimated channel signal in place of the corresponding correlation value when the magnitude of the absolute value of the correlation value is equal to or less than a predetermined masking reference value. And subtracting the estimated channel signals from the N correlation values to obtain N estimated noises, and calculating and adding powers of the N estimated noises to obtain estimated noise powers.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a block diagram of a noise power estimation apparatus according to an embodiment of the present invention.

A transmitter (not shown) for transmitting a predetermined digital signal maps the corresponding digital signal into a symbol, converts each mapped symbol into a predetermined analog signal, and transmits the converted analog signal to a receiver (not shown) through a wired or wireless transmission channel. . The noise power estimation apparatus 100 of the present invention may be included in such a receiving circuit (not shown) and used to recover the original signal from the received signal.

When a predetermined signal is received from a transmitting device (not shown) through a wired or wireless channel in which a signal is distorted by a predetermined interference or fading and a ghost signal may be generated, the noise power estimating device ( 100 estimates noise power included in the received signal.

The noise power estimated by the noise power estimator 100 may be used to obtain an optimal initial coefficient for an equalizer (not shown) that may be connected to the noise power estimator 100. It may also be used to control the step size (not shown).

The noise power estimator 100 estimates a channel and a noise component based on a training sequence included in the received signal, and estimates the noise power based on the estimated noise. The noise power estimation apparatus 100 may output a channel impulse response (CIR) for a channel estimated in this process.

Referring to FIG. 1, the noise power estimating apparatus 100 includes a channel estimator 110 and a noise power estimator 130.

The signal input to the noise power estimator 100 is preferably a digital signal that is compensated for after receiving a communication channel through a basic frequency error or a sampling time error. The transmission data transmitted by the transmitter (not shown) includes data already known by the noise power estimation apparatus 100. Such data is referred to as a 'training sequence', and the training sequence may correspond to a pseudo noise sequence (PN). Hereinafter, data other than the training sequence as data included in the received signal is referred to as 'random data'. When training string data is periodically included in the received signal and transmitted, the received signal is a combination of training sequence data and random data.

The channel estimator 110 includes a moving correlation block 111 and a noise masking block 113 to estimate a channel through which the received signal has passed.

The mobile correlation unit 111 estimates a channel by performing a predetermined moving correlation on the received data by using a training train that is already known. In this case, the channel impulse response may be estimated when the mobile sequence includes the training sequence included in the received data.

The mobile correlation unit 111 obtains a correlation value by sequentially multiplying corresponding symbols from each other in the received training data Rx data as many as the number of symbols in the training sequence and the previously known training sequence. The mobile correlation unit 111 obtains a correlation value with a training train known by applying a correlation window of a training train length to the received data. At this time, the mobile correlation unit 111 outputs N moving correlation values by continuously obtaining a correlation value while moving the correlation window by at least one symbol until the desired number of moving correlations N is reached. Here, the number of movement correlations (N) can be variously selected, but, for example, a value larger than the maximum delay such as ghost estimated to be possible in the communication channel can be selected.

The noise masking unit 113 compares an absolute value of each of the N outputs of the mobile correlator 111 with a predetermined masking threshold to mask N estimated channel signals (hereinafter, referred to as an “estimated channel signal”). Channel). The masking reference value may be a reference value that distinguishes noise from a signal.

As a result of comparison, the noise masking unit 113 disregards the output of the mobile correlation unit 111, assuming that a signal that does not exceed the masking reference value among the outputs of the mobile correlation unit 111 is noise, and is output in response to the corresponding signal. Force the value of the estimated channel signal to a value of '0'.

The noise masking unit 113 outputs the output signal of the mobile correlation unit 111 belonging to a predetermined range (on the signal output order) as the estimated channel signal when the signal exceeds the masking reference value as a result of the comparison. To this end, the noise masking unit 113 may set and apply a pass window that is a window having a predetermined range around a signal exceeding a masking reference value. The passing window will be described again below.

The noise masking unit 113 includes a predetermined mask flag register (MFR) for storing information on whether or not masking is performed, and a signal (hereinafter, referred to as a signal that is determined to be equal to or less than a masking reference value among the outputs of the mobile correlation unit 111). Set a flag for the masked signal. For example, for the output signal of the mobile correlator 111 determined as noise without exceeding the masking reference value, the corresponding flag in the mask flag register is set to '1' to process it as a 'masked signal'.

The noise power estimation unit 130 may include an estimated noise generation block 131, a masking counter 133, a data jitter correction block 135, and an average noise power generation unit. An average power of noise is estimated based on the output of the channel estimator 110, including an averaged noise power generation block 137.

The estimation noise generator 131 receives the output signal of the mobile correlation unit 111 and the estimated channel signal as a block for estimating the initial noise signal, obtains a difference value between the two signals, and outputs the difference value as estimated noise.

The masking counter 133 calculates the number of masked signals using the mask flag register information received from the noise masking unit 113 and outputs the number of masked signals to the average noise power generation unit 137.

The data jitter compensator 135 calculates a data jitter generated by random data when obtaining a moving correlation value between a training signal mixed with a training sequence and a training sequence already known by the channel estimation unit 110. To compensate.

The average noise power generation unit 137 squares each estimated noise signal compensated by the data jitter compensator 135 to obtain power, adds each power value, and divides the number of masked signals received from the masking counter 133. Find the average estimated noise power.

As described above, the average estimated noise power generated by the average noise power generation unit 137 is obtained once at the beginning of receiving data from a transmitter (not shown) to obtain an initial coefficient such as an equalizer (not shown). It can be used to periodically obtain the average estimated noise power to control the step size of the equalizer (not shown).

The noise power estimation apparatus 100 includes the channel estimation unit 110 and the noise power estimation unit 130, and the channel estimation unit 110 and the noise power estimation unit 130 include different detailed configurations. Was explained. However, the noise power estimator 100 is not necessarily based on this division, and may be described as another configuration that performs the same function. For example, the noise masking unit 113 may be included in the noise power estimation unit 130 and described.

Hereinafter, the operation of the mobile correlator 111 will be described in more detail with reference to FIG. 2. 2 is a view provided for explaining the operation of the mobile correlator according to an embodiment of the present invention.

2A illustrates an example of a profile of a channel in which fading exists, and an impulse of a channel including one ghost signal 2a-2 together with a main signal 2a-1. Show the response.

Referring to (b) of FIG. 2, the transmission data (Tx data) is an original signal transmitted by a transmitter (not shown). The random data and the training sequence (here, the PN sequence), which are known signals, are used. It is a combination.

The reception data Rx data is a signal when the transmission data Tx data is received by the reception circuit 900 through one fading channel as shown in FIG. The received data thus consists of the sum of the original transmission data 2b-1 and the transmission data 2b-2 time-delayed over the fading channel.

The mobile correlation unit 111 moves the correlation window 2b-3, multiplies each symbol of the PN column 2b-4, which is a known signal, and the received data Rx data one-to-one, and adds the result of the multiplication ( correlation).

The operation of the mobile correlation unit 111 may be expressed by Equation 1 below.

,

,

Here, 'MC (i)' represents the i-th output of the mobile correlator 111. N is the number of correlations to be obtained, and M is the number of symbols included in the training sequence 2b-4, that is, the length of the correlation window 2b-3. P (k) is the kth data (symbol) of the training sequence 2b-4, and R (k) is the kth received data (symbol) among the received data included in the correlation window 2b-3. .

The moving correlation unit 111 obtains each correlation value with respect to M, which is the length of the correlation window 2b-3, among the received data Rx data while moving according to i as shown in Equation (1).

Hereinafter, the operation of the noise masking unit 113 will be described in more detail with reference to FIGS. 3 and 4. 3 is a flowchart provided to explain the operation of the noise masking unit according to an embodiment of the present invention, and FIG. 4 is a conceptual diagram provided to explain the operation of the noise masking unit according to an embodiment of the present invention.

Before describing the operation of the noise masking unit 113 on the basis of FIG. 3, referring to FIG. 4A, the noise masking unit 113 includes the entire width (L ㅧ L) including the width L from the left and right, respectively. A pass window 4a-1 or 4a-2 having a size of +1 is set.

Where L is for proper channel estimation. Referring to the channel profile of FIG. 2A, only the main signal 2a-1 and the ghost signal 2a-2 are displayed, but in reality, the main signal 2a-1 and the ghost signal 2a-2 are shown. It is common for small signals to be included around each other, and these signals should be included in the channel estimation. Such a signal may be generated by fading on a channel or may be generated by changing a phase of a signal during processing of a receiver before being input to the noise power estimator 100. The size of L can be obtained experimentally.

The output of the mobile correlator 111 is shown in FIG. 4A, and two passage windows 4a-1 and 4a-2 are displayed for convenience of description, but at the same time, two passage windows 4a are shown. -1) (4a-2) does not indicate that the operation.

4A, masking reference values 4a-3 and 4a-4 used by the noise masking unit 113 are shown. Since the masking reference values 4a-3 and 4a-4 are compared with the absolute values of the output MC (i) of the mobile correlator 111, the '+' side 4a-3 and the '-' side 4a-4 Are set to).

The noise masking unit 113 may correspond to the centers of the pass windows 4a-3 and 4a-4 to the output MC (i) of the mobile correlator 111 in the masking process and pass up to L signals to the left and right. have.

Referring to FIG. 3 again, the operation of the noise masking unit 113 will be described.

 The noise masking unit 113 initializes all values of the mask flag resist corresponding to the outputs of the N mobile correlation units 111 to 1 (S301).

When the noise masking unit 113 receives the i-th output MC (i) from the mobile correlation unit 111 (S303), the noise masking unit 113 determines whether the absolute value of the corresponding MC (i) is greater than the masking reference value (S305).

In operation S305, when the absolute value of the output MC (i) of the mobile correlation unit 111 is greater than the masking reference value, the noise masking unit 113 includes MC (i), which is an output included in the front and rear L regions. The value of the mask flag register corresponding to iL) to MC (i + L) is changed to '0'. Thus, the noise masking unit 113 indicates that the outputs MC (i-L) to MC (i + L) of the mobile correlation unit 111 are not masked in the mask flag register. Therefore, when the absolute value of the output MC (i) of the mobile correlation unit 111 is greater than the masking reference value, the value of the mask flag register MFR may be represented by Equation 2 below (S307).

Here, j is an integer and MFR (j) represents the j-th flag of the mask flag register. If the absolute value of the output MC (i) of the mobile correlator 111 is not greater than the masking reference value as a result of the determination in step S305, the noise masking unit 113 maintains the value of the corresponding flag of the mask flag register as it is. As a result, the output MC (i) of the mobile correlator 111 is masked.

The noise masking unit 113 increments i by 1 (S309) and repeats operations S303 to S309 until the increased i is equal to N (S311).

The noise masking unit 113 outputs an estimated channel signal based on the information stored in the mask flag register after the processing to the Nth output MC (N) of the mobile correlation unit 111 is completed. If the value written in the corresponding flag of the mask flag register is '1', the MC (i) is masked, and thus the value of the estimated channel signal is '0'. In addition, when the value written in the corresponding flag of the mask flag register is '0', the MC (i) is not masked, and therefore, the output MC (i) of the mobile correlation unit 111 is applied as it is to the value of the estimated channel signal. . Even if the absolute value of MC (i-1) is masked because it is smaller than the masking reference value as a result of step S307, if the value of MC (i) is larger than the masking reference value, MC (i-1) is not masked but is estimated as an estimated channel signal. Can be output. The masking counter 133 reads information stored in the mask flag register to calculate the number of masked signals (S313).

4B and 4C show an estimated channel signal and estimated noise based on FIG. 4A. However, the estimated noise in FIG. 4C is a result of the operation of the estimated noise generator 131 to be described below.

5 is a detailed block diagram of an estimated noise generator according to an exemplary embodiment of the present invention. As described above, the estimation noise generator 131 corresponds to the subtractor 131-1, and detects and outputs the difference between the output of the mobile correlation unit 111 and the estimated channel signal as estimated noise. Since the estimated channel signal is a combination of the main signal 2a-1 and the fading signal 2a-2, the estimated channel signal is subtracted from the output of the mobile correlation unit 111 during noise estimation.

Hereinafter, the data jitter compensation unit 135 will be described in more detail with reference to FIGS. 6 to 7.

FIG. 6 is a diagram for explaining jitter generated during movement correlation according to random data, and shows movement correlation with data received through a channel without ghost.

The correlation value between the training sequence 6b included in the received data 6a and the training sequence 6c known by the mobile correlator 111 in the state where no ghost is generated due to no fading is represented by the main signal of FIG. This results in an impulse response like (2a-1). However, as the correlation window 6d leaves the training sequence of the received data, the correlation between the two signal sequences becomes smaller and the jitter becomes larger. In other words, the jitter generated when the mobile correlation unit 111 obtains a correlation value increases linearly as the random data is included in the received data.

To compensate for the jitter by the random data, the data jitter compensator 135 divides the estimated noise by a predetermined weighting factor according to the distance between the output signal of the estimated noise generator 131 and the main signal.

7 is a block diagram of a data jitter compensation unit according to an exemplary embodiment of the present invention.

The distance extracting unit 135-1 receives N estimated noises in sequence from the estimated noise generating unit 131, calculates and outputs a distance between the main signal and the input signal.

The distance value output from the distance extractor 135-1 is multiplied by the weight a in the multiplier 135-3, 1 is added to the adder 135-5, and then input to the divider 135-7. The accumulator 135-7 compensates jitter by dividing the estimated noise input from the estimated noise generator 131 by the output of the adder 135-5.

8 is a block diagram of an average noise power generation unit according to an embodiment of the present invention.

The average noise power generation unit 137 includes a power calculation unit 137-1, a summation unit 137-3, and an average power calculation unit 137-5, and estimates compensated by the data jitter compensator 135. The average estimated noise power is obtained by receiving the output of the masking counter 133 that counts the number of the noise signal and the masked signal.

The power calculator 137-1 obtains power by squaring each of the N compensated estimated noises input from the data jitter compensator 135.

The adder 137-3 adds all the N power values obtained by the power calculator 137-1, and the average power calculator 137-5 adds the N estimated noise signals obtained by the adder 137-3. The average estimated noise power is calculated by dividing the sum of the power by the number of masked signals input from the masking counter 133.

9 is a block diagram of a receiving circuit including a noise power estimation apparatus according to an embodiment of the present invention.

The receiving circuit 900 according to an embodiment of the present invention may receive and process a wired or wireless signal transmitted by a transmitting device (not shown) through at least one communication channel. The wireless signal output from the transmitter (not shown) may be distorted by predetermined fading or interference in the course of passing through various wired or wireless channels. The receiving circuit 900 equalizes and distorts the distorted signal in receiving and processing the wired or wireless signal.

The receiving circuit 900 of the present invention may be included in a broadcast receiving device for receiving a terrestrial or satellite broadcast signal. The broadcast receiving device includes a set top box (STB), a digital television (DTV), and the like. Corresponding.

The receiving circuit 900 includes a tuner 901, an AGC unit (Automatic Gain Control Block) 903, a CR unit (Carrier Recovery Block) 905, a TR unit (Timing Recovery Block) 907, a channel estimation unit 911 ), A noise power estimation unit 913, an equalizer 915, and a forward error correction (FEC) unit 917. The channel estimation unit 911 and the noise power estimation unit 913 correspond to the channel estimation unit 110 and the noise power estimation unit 130 of FIG. 1 and operate in the same manner.

The signal transmitted from the transmitter (not shown) is input to the tuner 901 of the receiver circuit 900 through a channel where fading occurs and an area generating AWGN (Additive White Gaussian Noise).

The tuner 901 tunes the channel frequency and detects only a desired signal by a band pass filter or the like. The signal detected by the tuner 901 is input to the AGC unit 903, which makes the signal constant, and amplified.

Since a frequency error and a sampling time error exist in the signal output from the AGC unit 903, the signal passes through the CR unit 905 that compensates for the frequency error and the TR unit 907 that compensates for the sampling time error.

Since the signal passing through the CR unit 905 and the TR unit 907 is a signal having fading by the channel and AWGN, it is input to the equalizer 915 to compensate for fading.

In addition, a signal passing through the CR unit 905 and the TR unit 907 is input to the channel estimator 911 to estimate the channel and to the noise power estimation unit 913 to obtain an optimal initial coefficient of the equalizer. To obtain the average estimated noise power. The estimated channel and noise power are then used to find the initial coefficients of the equalizer.

The equalizer 915 equalizes the channel by obtaining an optimal initial coefficient for channel equalization based on the signal-to-noise power ratio.

The equalized signal is input to the FEC unit 917 to compensate for the residual signal error.

The invention can be implemented in methods, devices and systems. In addition, when the present invention is implemented in computer software, the components of the present invention may be replaced with code segments necessary for performing necessary operations. The program or code segment may be stored in a medium that can be processed by a microprocessor and transmitted as computer data coupled with carrier waves via a transmission medium or communication network.

The media that can be processed by the microprocessor include electronic circuits, semiconductor memory devices, ROMs, flash memory, electrically erasable programmable read-only memory (EEPROM), floppy disks, optical disks, and hard disks. (Hard) Includes the ability to transmit and store information such as disks, fiber optics, wireless networks, and the like. Computer data also includes data that can be transmitted over electrical network channels, optical fibers, electromagnetic fields, wireless networks, and the like.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the above-described specific embodiment, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

As described in detail above, the noise power estimation apparatus according to the present invention estimates a channel from a signal received through a communication channel in which fading due to a predetermined multipath exists, and based on the estimated channel. The noise is estimated to find the power of the noise included in the received signal.

The noise power thus obtained may be used to obtain an initial coefficient of an equalizer for recovering distortion of the signal due to fading. It can also be used to control the step size of the equalizer.

The noise power estimation apparatus of the present invention may compensate for correlation jitter caused by arbitrary data in the process of obtaining a correlation value for estimating noise included in a received signal.

Claims (12)

Estimated channel that receives data including a predetermined training sequence through a predetermined communication channel and estimates the N correlation values obtained for the received data while moving the previously known training sequence N times. A channel estimator outputting a signal and outputting '0' as the estimated channel signal in place of the correlation value when the magnitude of the absolute value of the correlation value is equal to or less than a predetermined masking reference value; And And a noise power estimator for subtracting the estimated channel signal from the correlation value to obtain estimated noise, and calculating and outputting power of the estimated noise. The method of claim 1, Noise training apparatus, characterized in that the training sequence is a PN (Pseudo Noise Sequence). The method of claim 1, And the received data is a terrestrial digital broadcast or satellite digital broadcast signal received in symbol units. The method of claim 1, The channel estimation unit, Even if the magnitude of the absolute value among the correlation values is equal to or less than the masking reference value, if there is a correlation value larger than the masking reference value within a predetermined range from the correlation value, '0' is not outputted to the estimated channel signal. Noise power estimation apparatus, characterized in that for outputting the correlation value. The method of claim 1, The noise power estimation unit, And estimating the average noise power by dividing the estimated noise power by the number of times the estimated channel signal is '0'. The method of claim 5, The channel estimation unit, And a mask flag register in which a corresponding flag is displayed when the value of the estimated channel signal is '0'. The noise power estimation unit, And calculating the number of times that the estimated channel signal is '0' by reading the mask flag register. The method of claim 1, The noise power estimation unit, For each of the estimated noises, a distance from a channel impulse response of the correlation values is obtained, and the estimated noise is divided by a weight corresponding to the distance to compensate for data jitter included in the correlation values. Noise power estimation device. Receiving data including a predetermined training sequence through a predetermined communication channel; N-correlation values obtained for the received data are moved as the estimated channel signals estimated by the channel while moving the training sequence known N times, and the magnitude of the absolute value of the correlation value is equal to or less than a predetermined masking reference value. Outputting '0' as the estimated channel signal in place of a correlation value; Obtaining N estimated noises by subtracting the estimated channel signals from the N correlation values; And And calculating and summing the powers of the N estimated noises to obtain an estimated noise power. The method of claim 8, And the training sequence is a PN sequence. The method of claim 8, The received data is a noise power estimation method, characterized in that the terrestrial digital broadcast or satellite digital broadcast signal received in units of symbols. The method of claim 8, The outputting as the estimated channel signal may include: Even if the magnitude of the absolute value among the correlation values is equal to or less than the masking reference value, if there is a correlation value larger than the masking reference value within a predetermined range from the correlation value, '0' is not outputted to the estimated channel signal. Outputting a corresponding correlation value. The method of claim 8, The estimating noise power may include obtaining an average noise power by dividing the estimated noise power by the number of times the estimated channel signal is '0'.

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