CN100508512C - Pulse noise suppression device and method applied to orthogonal frequency division multiplexing system - Google Patents

Abstract

An impulse noise suppression device and an impulse noise suppression method applied to an orthogonal frequency division multiplexing system are used for suppressing impulse noise in a first time domain signal to generate an output signal. The impulse noise suppression device comprises: a impulse noise eliminating unit for processing the first time domain signal to generate a second time domain signal and controlling the second time domain signal to make its absolute value not larger than a predetermined value; a first Fourier transform unit for transforming the second time domain signal to generate a second frequency domain signal; an equalization module for equalizing the subcarrier signals in the second frequency domain signal to generate an equalized signal; a decision unit for generating a decision signal according to the equalized signal; and a compensation module for detecting a difference between the equalized signal and the decision signal and correcting the equalized signal according to the difference to generate the output signal.

Description

Impulse noise suppression device and method applied to OFDM system

technical field

The present invention discloses an impulse noise suppression device and an impulse noise suppression method, especially an impulse noise suppression device and an impulse noise suppression method utilizing a decision-making reconstruction mechanism.

Background technique

Generally speaking, radio frequency communication systems are subject to more noise interference than wired communication systems, such as: atmospheric interference or man-made interference, some of which interfere with Gaussian patterns, while others , for example: the noise caused by electric self-starter (electric self-starter), power line, high current switch, etc. has a very high energy in a very short time, and this type of noise is called impulse noise ( impulse noise). Since impulse noise is a high-energy interference noise, it has a more serious impact on the received signal than other forms of noise. Therefore, how to detect and effectively suppress impulse noise has always been a very important issue for the receiving end.

Take the radio frequency communication system applied to video and audio transmission as an example, such as Digital Video Broadcasting-Terrestrial (DVB-T), due to the high-energy impulse noise, it may cause the audio output device at the receiving end to generate buzzing sound or make the Image display devices output image noise, which will cause discomfort to users. Therefore, when considering system design, designers often prefer to sacrifice part of the signal quality to suppress the impact of impulse noise on the received signal. A common impulse noise suppression method is to compare a critical value with the strength of the received signal. When the strength of the received signal is greater than the critical value, the system will determine that the received signal at this sampling point is interfered by impulse noise, and force the setting The value of the received signal at this sampling time point is assumed to be zero. Please refer to FIG. 1A . FIG. 1A is an operation schematic diagram of an input signal and sampling timing of a known impulse noise suppression mechanism. As shown in the figure, since the input signal is a digital signal, each sampling time point of the input signal corresponds to a value, which is used to represent the signal strength of the input signal at each sampling time point. In Figure 1A, the solid line represents the actual value of the input signal, that is, the signal strength of the input signal, while the dotted line represents the strength of the impulse noise, for example: at the sampling time point t _b , the signal strength of the input signal is "3", but because of the impact of an impulse noise with an intensity of "6", the received signal actually detected by the receiving end at the sampling time point t _b becomes "9". At this time, if the above-mentioned critical value is set to "8", the receiving end will determine that the signal at the sampling time point t _b is interfered by impulse noise, so it is mandatory to set the output signal corresponding to the sampling time point t _b The value is "0"; similarly, the receiving end will forcefully set the value of the output signal corresponding to the sampling time points t _a , t _c , t _d to "0". As shown in Figure 1B. It can be seen that although the known impulse noise suppression mechanism suppresses the impulse noise at the sampling time points t _a , t _b , t _c , and t _d (for example, the impulse noise intensity at the sampling time point t _b is "6"), but at the same time The original input signal at the sampling time point t _a , t _b , t _c , and t _d is also sacrificed (for example, the input signal strength at the sampling time point t _b is "3") to cause signal distortion.

For some application systems, due to the limitations of human senses, this distortion may not be noticed. For example, for image transmission systems, users usually do not perceive the difference of a certain pixel on the screen, so if The signal at only a few sampling points is slightly distorted, which will not have a great impact on the viewing users, and this feature is also applicable to the situation of the audio transmission system. However, due to the increasing quality of audio-visual equipment, users have higher and higher requirements for image quality and sound quality. Although the above-mentioned impulse noise suppression mechanism can effectively suppress impulse noise, it will sacrifice part of the signal quality. Unable to faithfully present the audiovisual data originally intended to be transmitted.

Contents of the invention

Therefore, one of the main objectives of the present invention is to provide an impulse noise suppression device and impulse noise suppression method using a decision reconstruction mechanism to solve the above problems.

According to the patent application scope of the present invention, it discloses an impulse noise suppression (impulsenoise suppression) device. The impulse noise suppressing device is applied to an Orthogonal Frequency Division Multiplexing (OFDM) communication system, and is used to suppress impulse noise in a first time domain signal to generate an output signal, wherein the first time domain The domain signal is an OFDM time-domain signal, the OFDM time-domain signal can be converted to an OFDM frequency-domain signal, and the OFDM frequency-domain signal The signal is composed of multiple sub-carrier signals. The impulse noise suppression device includes: an impulse noise elimination unit (noiseblanker), used to process the first time-domain signal to generate a second time-domain signal, wherein if at a point in time, the first time-domain signal value is greater than a first critical value, then the impulse noise elimination unit is to control the second time domain signal so that its absolute value is not greater than a predetermined value, the predetermined value can be zero, and if at a point in time, the first If the value of the time domain signal is not greater than the first critical value, then the impulse noise elimination unit sets the value of the second time domain signal according to the value of the first time domain signal; a first Fourier transform unit is electrically connected to The impulse noise elimination unit is used to convert the second time-domain signal to generate a second frequency-domain signal; the equalization module is electrically connected to the first Fourier transform unit and is used to correspond to the OFDM equalizing each subcarrier signal in the second frequency domain signal by using a channel estimation value of each subcarrier channel of the communication system to generate an equalized signal, wherein the equalized signal is composed of a plurality of equalized signal values, And each equalization signal value corresponds to a subcarrier respectively; a decision unit is electrically connected to the equalization module, and is used to generate a decision signal according to the equalization signal, wherein the decision signal is composed of a plurality of decision signal values, and Each decision signal value corresponds to a subcarrier respectively, and the decision unit can decode the equalization signal value corresponding to a subcarrier channel according to at least one critical value, so as to generate the decision signal value corresponding to the subcarrier channel, and the decision The unit can also generate the decision signal value corresponding to a subcarrier channel according to a known value; and a compensation module, electrically connected to the equalization module and the decision unit, is used to detect the equalization signal and the decision unit A time domain compensation signal corresponding to the difference of the decision signal, and correcting the equalization signal according to a frequency domain compensation signal corresponding to the time domain compensation signal to generate the output signal, wherein the output signal is composed of a plurality of output signal values composed, and each output signal value corresponds to a subcarrier. The impulse noise suppression device can be applied to a digital television system.

In addition, according to the patent application scope of the present invention, it also discloses an impulse noise suppression (impulse noise suppression) method. The impulsive noise suppression method is applied to an Orthogonal Frequency Division Multiplexing (OFDM) communication system, and is used to suppress the impulsive noise in a first time domain signal to generate an output signal, wherein the first time domain The domain signal is an OFDM time domain signal, the OFDM time domain signal can be converted into an OFDM frequency domain signal, and the OFDM frequency domain signal The signal is composed of a plurality of sub-carrier signals, and the first time domain signal is processed by pulse elimination noise to obtain a second time domain signal. The impulse noise suppression method includes: (a) if at a time point, the value of the first time domain signal is greater than a first critical value, then controlling the second time domain signal so that its absolute value is not greater than a predetermined value , and if at a point in time, the value of the first time domain signal is not greater than the first critical value, then the value of the second time domain signal is set according to the value of the first time domain signal; (b) Fourier transform The second time-domain signal is used to generate a second frequency-domain signal; (c) equalizing the second frequency-domain signal according to a channel estimation value corresponding to each subcarrier channel of the OFDM communication system Each subcarrier signal of each equalization signal is used to generate an equalization signal, wherein the equalization signal is composed of a plurality of equalization signal values, and each equalization signal value corresponds to a subcarrier respectively; (d) making a decision on the equalization signal processing to generate a decision signal, wherein the decision signal is composed of a plurality of decision signal values, and each decision signal value corresponds to a subcarrier; and (e) detecting the difference between the equalization signal and the decision signal a corresponding time domain compensation signal, and correct the equalization signal according to a frequency domain compensation signal corresponding to the time domain compensation signal to generate the output signal, wherein the output signal is composed of a plurality of output signal values, and each output The signal values correspond to one subcarrier respectively.

The impulse noise suppression device and impulse noise suppression method of the present invention use a compensation module to calculate a frequency domain compensation signal to correct the equalization signal to generate an output signal, that is, a decision reconstruction signal. Therefore, the impulse noise suppression device and impulse noise suppression method of the present invention can make the output signal a frequency domain signal corresponding to a first time domain signal, but it will not be affected by the impulse noise in the first time domain signal . In addition, the impulse noise suppression device and impulse noise suppression method of the present invention can repeatedly adjust the estimated channel value used by the OFDM system, so as to further make the OFDM system have better signal quality.

Description of drawings

1A is a schematic diagram of the operation of the input signal and the sampling timing of the known impulse noise suppression mechanism;

1B is a schematic diagram of the operation of the output signal and sampling timing of the known impulse noise suppression mechanism;

Fig. 2 is the functional block schematic diagram of an embodiment of the impulse noise suppressing device of the present invention;

Fig. 3 is a schematic functional block diagram of the compensation module shown in Fig. 2;

FIG. 4 is a flow chart of adjusting the estimated channel value and generating an output signal by the impulse noise suppression device shown in FIG. 2 .

Description of main component symbols:

10 Impulse noise elimination unit 30, 108 Fourier transform unit

50 Equalization Module 52 Equalization Unit

54 Channel estimation unit 70 Decision-making unit

90 Compensation module 100 Impulse noise suppression device

102 Error operation unit 104 Inverse Fourier transform unit

106 Compensation Estimation Unit 110 Correction Unit

Detailed ways

Please refer to FIG. 2 . FIG. 2 is a functional block diagram of an embodiment of the impulse noise suppression device 100 of the present invention. The impulse noise suppression device 100 is used for suppressing the impulse noise (impulse noise) of the received signal in an Orthogonal Frequency Division Multiplexing (OFDM) communication system, and according to the suppressed signal part in the received signal in the time domain The frequency-domain signal corresponding to the received signal is compensated to generate a decision-aided reconstruction signal. As shown in the figure, in this embodiment, the impulse noise suppression device 100 includes an impulse noise elimination unit 10 , a Fourier transform unit 30 , an equalization module 50 , a decision unit 70 and a compensation module 90 . The impulse noise elimination unit 10 is used to process a time-domain received signal r to generate another time-domain signal _rs , wherein the impulse noise elimination unit 10 compares the signal strength of the time-domain signal r with a critical value V at each sampling time point _TH , when the signal strength of the time-domain signal r is greater than the critical value V _TH , the impulse noise elimination unit 10 forces the value of the time-domain signal r _s output at the sampling time point to be zero; otherwise, directly based on the sampling time point The value of the time domain signal r is used to set the value of the output time domain signal _rs at the sampling time point. Please refer to the following equation for the operation of the impulse noise canceling unit 10:

$r_{\mathrm{the\; s}}\left[i\right]=\left\{\begin{array}{cc}0,& \mathrm{if}\left|r\right[i\left]\right|>V_{\mathrm{TH}}\\ r\left[i\right],& \mathrm{otherwise}\end{array}\right.$ Equation (1)

In equation (1), r[i] represents the value of the time-domain signal at the i-th sampling time point, and the absolute value of r[i] is recorded as |r[i]|, which is the signal strength of r[i].

The Fourier transform unit 30 performs Fourier transform on the time-domain signal _rs according to the frequency of each subcarrier in the OFDM system to generate a frequency-domain signal R. Since the OFDM system uses multiple (for example: N) subcarriers to transmit data, each frequency domain signal R will contain N subcarrier signals. The equalization module 50 is provided with an equalization unit 52 and a channel estimation unit 54, wherein the channel estimation unit 54 will calculate the channel estimation value _He of each subcarrier, and the equalization unit 52 is electrically connected to the channel An estimation unit, which equalizes the corresponding subcarrier signal in the frequency domain signal R according to the channel estimation value He _e of each subcarrier, and generates an equalized signal S _eq , therefore, each equalized signal S Each of _eq includes N equalized signal values corresponding to different subcarriers; the channel estimation unit calculates an update value for each subcarrier to update the channel estimation value corresponding to the subcarrier, wherein the The update value is multiplied by the output signal value corresponding to the subcarrier by the channel estimation value corresponding to the subcarrier, and then divided by the decision signal value corresponding to the subcarrier. The decision-making unit 70 performs hard-decision processing (hard-decision) on the equalization signal S _eq generated by the equalization module 50 to generate a decision signal S _d . Similarly, each decision signal S _d also includes information corresponding to different N decision signal values for subcarriers. It should be noted that because some subcarriers in the OFDM system have defaulted as pilot channels to transmit so-called pilot symbols, where the pilot symbols are known value, so the part corresponding to these guiding channels in the equalization signal _Seq , the decision-making unit 70 does not need to actually perform decision-making processing, but directly sets the value corresponding to these guiding channels in the decision signal S _d is defined as the known leading symbol value. Then, the compensation module 90 calculates a frequency domain compensation signal S _c according to the equalization signal S _eq , the decision signal S _d and the N channel estimation values _He , and compensates the equalization signal S according to the frequency domain compensation signal S _{c eq} to generate an output signal S _out , wherein the detailed operation of the compensation module 90 will be described in detail below.

Please refer to FIG. 3 , which is a functional block diagram of the compensation module 90 shown in FIG. 2 . As shown in the figure, the compensation module 90 is provided with an error calculation unit 102 , an inverse Fourier transform unit 104 , a compensation estimation unit 106 , a Fourier transform unit 108 and a correction unit 110 . The error calculation unit 102 is electrically connected to the equalization module and the decision unit, which is used to detect the difference between the equalization signal _Seq and the decision signal _Sd , and utilize the channel outputted by the aforementioned channel estimation unit 54 Estimated value _He to adjust this difference to generate a frequency domain error signal _Seir The operation of the error calculation unit 102 please refer to the following equation:

$S_{\mathrm{err}}^{\left(m\right)}\left[i\right]=(S_{\mathrm{eq}}^{\left(m\right)}\left[i\right]-S_d^{\left(m\right)}\left[i\right])\&Center\; Dot;h_e^{\left(m\right)}\left[i\right],m=\mathrm{1,2},...,N$ Equation (2)

When there is ideally no noise or impulse noise interference in the communication channel, that is, the time-domain signal rs _should be equal to the time-domain signal r, and the channel estimation value _He is also ideally 1, the channel response is also It will not have any impact on the frequency domain signal R, at this time, the value of the decision signal S _d should be equal to the value of the equalization signal _Seq . However, the actual situation is not the case, so the error calculation unit 102 must first calculate the difference between the equalization signal S _eq and the decision signal S _d , and multiply the difference by the estimated channel value _He to generate a frequency domain error signal _Serr . Next, the inverse Fourier transform unit 104 further converts the frequency-domain error signal S _err into a time-domain error signal s _err , and the inverse Fourier transform unit is electrically connected to the error calculation unit. At this time, the time-domain error signal S _err is equal to the pulse The data signal component in the time-domain signal r additionally suppressed by the noise elimination unit 10 while suppressing the impulse noise is related. In order to estimate the data signal component in the time-domain signal r additionally suppressed by the impulse noise elimination unit 10 while suppressing the impulse noise, the compensation estimation unit 106 uses another critical value V _TH2 to determine the time-domain error signal s _err to A time-domain compensation signal _sc is generated. The compensation estimation unit 106 is electrically connected to the inverse Fourier transform unit, which compares the critical value V _TH2 and the time-domain error signal s _err at each sampling time point, if the absolute value of the time-domain error signal s _err is greater than the critical value V When _TH2 , then set the value of the time domain compensation signal s _c at the sampling time point according to the value of the time domain error signal S _err , if the absolute value of the time domain error signal S _err is not greater than the critical value V _TH2 then set The domain compensation signal s _err has a value of zero. In this way, the time-domain compensation signal s _err can be regarded as the impact of the impulse noise elimination unit 10 on the time-domain signal r, that is, the signal component of the time-domain signal r suppressed by the impulse noise elimination unit 10 . Please refer to the following equation for the operation of the compensation estimation unit 106:

${\mathrm{the\; s}}_c^{\left(m\right)}\left[i\right]=\left\{\begin{array}{cc}{\mathrm{the\; s}}_{\mathrm{err}}^{\left(m\right)}\left[i\right],& \mathrm{if}\left|{\mathrm{the\; s}}_{\mathrm{err}}^{\left(m\right)}\right[i\left]\right|>V_{\mathrm{TH}2}\\ 0,& \mathrm{otherwise}\end{array}\right.,m=\mathrm{1,2},...,N$ Equation (3)

Next, the Fourier transform unit 108 converts the time-domain compensation signal _sc into a preliminary frequency-domain compensation signal _Sc . The Fourier transform unit 108 is electrically connected to the compensation estimation unit. Finally, the correction unit 110 can use the estimated channel value _He to adjust the preliminary frequency domain compensation signal _Sc to generate a frequency domain compensation signal, and compensate the equalized signal _Seq according to the frequency domain compensation signal to generate an output signal S _out , at this time, the output signal S _out is the decision reconstruction signal of the equalization signal S _eq . The correction unit is electrically connected to the decision unit and the second Fourier transform unit, and uses the equalization signal to subtract the frequency domain compensation signal to generate the output signal. Please refer to the following equation for the operation of the calibration unit 110:

$S_{\mathrm{om}}^{\left(m\right)}\left[i\right]=S_{\mathrm{eq}}^{\left(m\right)}\left[i\right]-\frac{S_c^{\left(m\right)}\left[i\right]}{h_e^{\left(m\right)}\left[i\right]},m=\mathrm{1,2},...,N$ Equation (4)

In addition, according to Equation (4), the value of S _out can be set to S _eq , and then put back into Equation (2) to perform the second round of calculations. Doing so many rounds of calculations can further achieve Better impulse noise suppression.

Since many of the above calculations are related to the channel estimation value _He , the accuracy of the channel estimation value _He is very important. According to the present invention, the accuracy of the channel estimation value _He can be further improved. Using the known characteristics of the pilot symbols transmitted by the pilot channel, the channel estimation value _He can be updated according to the following equation:

$\frac{S_{\mathrm{out}}^{\left(m\right)}\&Center\; Dot;h_e^{\left(m\right)}}{S_d^{\left(m\right)}}\&Right\; Arrow;h_e^{\left(m\right)}$ Equation (5)

为该引导信道所传送的引导符元。信道估测值H_e的更新可配合上述每个轮回的运算，如此循环数次后，可更进一步达到更好的脉冲噪声抑制效果。请注意，本发明中调整信道估测值H_e的方法并不以本实施例所述的利用引导符元为限，其它提高决策信号S_d准确度的方法也可以依据方程式(五)调整信道估测值H_e。Among them, m is the label of a certain guiding channel, at this time,

Pilot symbols transmitted for the pilot channel. The update of the estimated channel value _He can cooperate with the calculation of each cycle mentioned above, and after several cycles like this, a better impulse noise suppression effect can be further achieved. Please note that the method for adjusting the estimated channel value _He in the present invention is not limited to the use of pilot symbols described in this embodiment, and other methods for improving the accuracy of the decision signal _Sd can also adjust the channel according to equation (5) Estimated value _He .

To describe the operation process of the impulse noise suppression device 100 of the present invention, please refer to FIG. 4 , which is a flow chart of the impulse noise suppression device 100 shown in FIG. 2 adjusting the estimated channel value _He and generating the output signal S _nut . The operation of the impulse noise suppression device 100 includes the following steps:

Step 200: start;

Step 202: performing impulse blanking processing on the time-domain signal r to generate a time-domain signal r _s ;

Step 204: Fourier transform the time domain signal r _b to generate a frequency domain signal R;

Step 206: Equalize the frequency-domain signal R according to the estimated channel value _He to generate an equalized signal _Seq ;

Step 208: Perform decision processing on the equalized signal _Seq to generate a decision signal S _d ;

Step 212: Calculate a frequency-domain error signal S _err between the decision signal S _d and the equalization signal S _eq ;

Step 214: Inverse Fourier transform the frequency-domain error signal S _err to generate a time-domain error signal S _err ;

Step 216: Estimate a time domain compensation signal _sc according to the time domain error signal s _err ;

Step 218: Fourier transform the time domain compensation signal _sc to generate a preliminary frequency domain compensation signal _Sc ;

Step 222: Compensate the equalization signal S _eq according to the preliminary frequency domain compensation signal S _c to generate an output signal S _out ;

In addition to generating the correct output signal S _out , this embodiment further discloses the method of setting the value of the output signal S _out to the equalization signal _Seq (step 224), and then repeatedly executes steps 208-222, so Doing more rounds of calculations can further achieve a better impulse noise suppression effect. In addition, the estimated channel value _He can be updated in conjunction with the above-mentioned operations of each cycle, and after several cycles, a better impulse noise suppression effect can be further achieved. The steps of setting the equalization signal S _eq and updating the channel estimation value _He are as follows:

)、及目前的信道估测值H_e对应该引导信道的值(即

)，来更新该信道估测值值。Step 224: Use the value of the output signal S _out to set the equalization signal S _eq , and for each pilot channel (such as the pilot channel labeled m), according to the value of the output signal S _out corresponding to the pilot channel (ie The known pilot symbol value transmitted by the pilot channel (i.e.

), and the value of the current channel estimate _He corresponding to the guide channel (ie

), to update the channel estimate value.

The impulse noise suppression method of this embodiment of the present invention is as follows:

The impulsive noise suppression method is applied to an OFDM communication system for suppressing impulsive noise in a first time-domain signal to generate an output signal, wherein the first time-domain signal is an OFDM Using a time-domain signal, the OFDM time-domain signal is converted to obtain an OFDM frequency-domain signal, and the OFDM frequency-domain signal is composed of a plurality of subcarrier signals, The impulse noise suppression method includes:

(a) if at a point in time, the value of the first time domain signal is greater than a first critical value, then controlling the second time domain signal so that its absolute value is not greater than a predetermined value, and if at a point in time, The value of the first time domain signal is not greater than the first critical value, then setting the value of the second time domain signal according to the value of the first time domain signal;

(b) Fourier transforming the second time domain signal to generate a frequency domain signal;

(c) equalizing each subcarrier signal in the frequency domain signal according to a channel estimation value corresponding to each subcarrier channel of the OFDM communication system to generate an equalized signal, wherein the equalized signal It is composed of a plurality of equalized signal values, and each equalized signal value corresponds to a subcarrier respectively;

(d) generating a decision signal, wherein the decision signal is composed of a plurality of decision signal values, and each decision signal value corresponds to a subcarrier; and

(e) detecting a time domain compensation signal corresponding to the difference between the equalization signal and the decision signal, and correcting the equalization signal according to a frequency domain compensation signal corresponding to the time domain compensation signal to generate the output signal , wherein the output signal is composed of a plurality of output signal values, and each output signal value corresponds to a subcarrier respectively.

The step (d) is to decode the equalized signal value corresponding to a subcarrier channel according to at least one critical value, so as to generate the decision signal value corresponding to the subcarrier channel.

The step (d) is to generate the decision signal value corresponding to a subcarrier channel according to a known value.

Wherein step (e) includes:

(f) calculating a difference between the equalization signal and the decision signal according to the estimated channel value to generate a frequency domain error signal;

(g) inverse Fourier transforming the frequency-domain error signal to generate a time-domain error signal;

(h) estimating a time domain compensation signal according to the time domain error signal;

(i) Fourier transforming the time domain compensation signal to generate a preliminary frequency domain compensation signal; and

(j) calculating the preliminary frequency-domain compensation signal to generate the frequency-domain compensation signal according to the channel estimation value, and using the frequency-domain compensation signal to correct the equalized signal to generate the output signal.

Wherein step (h) is to compare this time domain error signal and a second critical value, if at a point in time, the value of this time domain error signal is greater than this second critical value, then set according to the value of this time domain error signal The value of the time domain compensation signal is determined, and if the value of the time domain error signal is not greater than the second critical value, the value of the time domain compensation signal is set to zero.

Wherein step (j) is to subtract the frequency domain compensation signal from the equalized signal to generate the output signal.

Wherein step (c) includes:

(k) calculating the channel estimate; and

(1) Equalize the frequency domain signal according to the estimated channel value to generate the equalized signal.

After the output signal is generated in step (e), step (k) is to update the channel according to the output signal generated in step (e), the decision signal generated in step (d), and the current estimated value of the channel Estimated value.

Wherein step (k) is to calculate an update value for each subcarrier to update the channel estimation value corresponding to the subcarrier, wherein the update value is multiplied by the output signal value corresponding to the subcarrier The estimated channel value of the subcarrier is divided by the value of the decision signal corresponding to the subcarrier.

The impulse noise suppression method can be applied to a digital television system.

The predetermined value of the impulsive noise suppression method may be zero.

Compared with the known technology, the impulse noise suppression device and impulse noise suppression method of the present invention use a compensation module to estimate a frequency domain compensation signal to compensate the equalization signal to generate a decision reconstruction signal, and at the same time gradually adjust the quadrature frequency The estimated channel value used by the OFDM system enables the OFDM system to have better signal quality.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (22)

1. An impulse noise suppression device applied to an OFDM system, characterized in that it is applied to an OFDM communication system to suppress the impulse noise in a first time domain signal to generating an output signal, wherein the first time-domain signal is an OFDM time-domain signal, and the OFDM time-domain signal is converted to obtain an OFDM frequency-domain signal, And the OFDM frequency domain signal is composed of a plurality of subcarrier signals, and the impulse noise suppression device includes: an impulse noise elimination unit for processing the first time-domain signal to generate a second time-domain signal, wherein if at a time point, the value of the first time-domain signal is greater than a first critical value, the The impulse noise elimination unit is to control the second time-domain signal so that its absolute value is not greater than a predetermined value, and if at a time point, the value of the first time-domain signal is not greater than the first critical value, the impulse noise elimination The unit sets the value of the second time domain signal according to the value of the first time domain signal; a first Fourier transformation unit, electrically connected to the impulse noise elimination unit, for converting the second time domain signal to generate a second frequency domain signal; The equalization module is electrically connected to the first Fourier transform unit, and is used to equalize the signal in the second frequency domain according to a channel estimation value corresponding to each subcarrier channel of the OFDM communication system Each subcarrier signal is used to generate an equalized signal, wherein the equalized signal is composed of a plurality of equalized signal values, and each equalized signal value corresponds to a subcarrier respectively; a decision unit, electrically connected to the equalization module, for generating a decision signal according to the equalization signal, wherein the decision signal is composed of a plurality of decision signal values, and each decision signal value corresponds to a subcarrier; and A compensation module, electrically connected to the equalization module and the decision-making unit, used to detect a time-domain compensation signal corresponding to the difference between the equalization signal and the decision-making signal, and according to a corresponding time-domain compensation signal A frequency domain compensation signal is used to correct the equalized signal to generate the output signal, wherein the output signal is composed of a plurality of output signal values, and each output signal value corresponds to a subcarrier respectively. 2. The impulse noise suppression device according to claim 1, wherein the decision-making unit decodes the equalized signal value corresponding to a subcarrier channel according to at least one critical value to generate a signal corresponding to the subcarrier The value of the decision signal for the channel. 3. The impulse noise suppression device as claimed in claim 1, wherein the decision unit generates the decision signal value corresponding to a subcarrier channel according to a known value. 4. The impulse noise suppression device according to claim 1, wherein the compensation module includes: An error calculation unit, electrically connected to the equalization module and the decision unit, used to calculate the difference between the equalization signal and the decision signal, and calculate the difference according to the estimated channel value to generate a frequency domain error signal ; an inverse Fourier transform unit electrically connected to the error calculation unit for inverse Fourier transforming the frequency domain error signal to generate a time domain error signal; a compensation estimation unit, electrically connected to the inverse Fourier transform unit, for estimating a time domain compensation signal according to the time domain error signal; a second Fourier transform unit, electrically connected to the compensation estimation unit, for Fourier transforming the time domain compensation signal to generate a preliminary frequency domain compensation signal; and a correction unit, electrically connected to the decision-making unit and the second Fourier transform unit, used to calculate the preliminary frequency-domain compensation signal according to the channel estimation value to generate the frequency-domain compensation signal, and use the frequency-domain compensation signal to correct The signal is equalized to generate the output signal. 5. The impulse noise suppression device as claimed in claim 4, wherein the compensation estimation unit compares the time-domain error signal with a second critical value, if at a point in time, the time-domain error signal value is greater than the second critical value, the compensation estimation unit sets the value of the time domain compensation signal according to the value of the time domain error signal, and if at a point in time, the value of the time domain error signal is not greater than For the second critical value, the compensation estimation unit sets the value of the time domain compensation signal to zero. 6. The impulse noise suppressing device as claimed in claim 4, wherein the correction unit subtracts the frequency domain compensation signal from the equalization signal to generate the output signal. 7. The impulse noise suppression device according to claim 1, wherein the equalization module includes: a channel estimation unit, used to calculate the channel estimation value; and The equalization unit is electrically connected to the channel estimation unit, and is used for equalizing the second frequency domain signal according to the channel estimation value to generate the equalized signal. 8. The impulse noise suppression device according to claim 7, wherein the channel estimation unit is further electrically connected to the compensation module and the decision-making unit, and the channel estimation unit is based on the output generated by the compensation module signal, the decision signal generated by the decision unit, and the current channel estimation value to update the channel estimation value. 9. The impulse noise suppression device according to claim 8, wherein the channel estimation unit calculates an update value for each subcarrier to update the channel estimation value corresponding to the subcarrier, wherein the The update value is multiplied by the output signal value corresponding to the subcarrier by the channel estimation value corresponding to the subcarrier, and then divided by the decision signal value corresponding to the subcarrier. 10. The impulse noise suppressing device as claimed in claim 1, wherein it is applied to a digital television system. 11. The impulse noise suppressing device as claimed in claim 1, wherein the predetermined value is zero. 12. A method for suppressing impulse noise applied to an OFDM system, characterized in that it is applied to an OFDM communication system for suppressing impulse noise in a first time-domain signal to generating an output signal, wherein the first time-domain signal is an OFDM time-domain signal, and the OFDM time-domain signal is converted to obtain an OFDM frequency-domain signal, And the OFDM frequency domain signal is composed of a plurality of subcarrier signals, the first time domain signal is processed by pulse noise elimination to obtain a second time domain signal, and the pulse noise suppression method includes: (a) if at a point in time, the value of the first time domain signal is greater than a first critical value, then controlling the second time domain signal so that its absolute value is not greater than a predetermined value, and if at a point in time, The value of the first time domain signal is not greater than the first critical value, then setting the value of the second time domain signal according to the value of the first time domain signal; (b) Fourier transforming the second time domain signal to generate a second frequency domain signal; (c) equalizing each subcarrier signal in the second frequency domain signal according to a channel estimation value corresponding to each subcarrier channel of the OFDM communication system to generate an equalized signal, wherein the The equalization signal is composed of a plurality of equalization signal values, and each equalization signal value corresponds to a subcarrier respectively; (d) performing decision processing on the equalization signal to generate a decision signal, wherein the decision signal is composed of a plurality of decision signal values, and each decision signal value corresponds to a subcarrier; and (e) detecting a time domain compensation signal corresponding to the difference between the equalization signal and the decision signal, and correcting the equalization signal according to a frequency domain compensation signal corresponding to the time domain compensation signal to generate the output signal , wherein the output signal is composed of a plurality of output signal values, and each output signal value corresponds to a subcarrier respectively. 13. The impulsive noise suppression method according to claim 12, wherein step (d) is to decode the equalized signal value corresponding to a subcarrier channel according to at least a critical value, so as to generate a signal corresponding to the subcarrier channel The decision signal value of the carrier channel. 14. The impulsive noise suppression method as claimed in claim 12, wherein step (d) is based on a known value to generate the decision signal value corresponding to a subcarrier channel. 15. The impulse noise suppression method according to claim 12, wherein step (e) includes: (f) calculating a difference between the equalization signal and the decision signal according to the estimated channel value to generate a frequency domain error signal; (g) inverse Fourier transforming the frequency-domain error signal to generate a time-domain error signal; (h) estimating a time domain compensation signal according to the time domain error signal; (i) Fourier transforming the time domain compensation signal to generate a preliminary frequency domain compensation signal; and (j) calculating the preliminary frequency-domain compensation signal to generate the frequency-domain compensation signal according to the channel estimation value, and using the frequency-domain compensation signal to correct the equalized signal to generate the output signal. 16. The impulsive noise suppression method as claimed in claim 15, wherein step (h) is to compare the time domain error signal with a second critical value, if at a time point, the value of the time domain error signal greater than the second critical value, then set the value of the time domain compensation signal according to the value of the time domain error signal, and if the value of the time domain error signal is not greater than the second critical value, then set the time domain The value of the compensation signal is zero. 17. The impulse noise suppression method as claimed in claim 15, wherein step (j) is to subtract the frequency-domain compensation signal from the equalized signal to generate the output signal. 18. The impulse noise suppression method according to claim 13, wherein step (c) comprises: (k) calculating the channel estimate; and (1) Equalize the second frequency domain signal according to the estimated channel value to generate the equalized signal. 19. The impulse noise suppression method according to claim 18, wherein after the output signal is generated in step (e), step (k) is based on the output signal generated in step (e) and the output signal in step (d) The generated decision signal and the current channel estimation value are used to update the channel estimation value. 20. The impulse noise suppression method according to claim 19, wherein step (k) is to calculate an update value for each subcarrier to update the channel estimation value corresponding to the subcarrier, wherein the update value The output signal value corresponding to the subcarrier is multiplied by the estimated channel value corresponding to the subcarrier, and then divided by the decision signal value corresponding to the subcarrier. 21. The impulsive noise suppression method as claimed in claim 12, wherein it is applied to a digital television system. 22. The impulsive noise suppression method according to claim 12, wherein the predetermined value is zero.

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