KR20050000748A - equalizer of digital broadcasting signal receiving system and a method thereof - Google Patents

Abstract

PURPOSE: An equalizer of a digital broadcast receiver and an equalizing method thereof are provided to equalize a channel efficiently by selectively using a proper algorithm of a filter tap coefficient after determining a state of the channel. CONSTITUTION: A filter part(205), comprised of a plurality of filter taps, removes channel interference of a digital broadcast signal. An error calculation part(260) calculates an error value on a basis of a reference signal and the signal from which the channel interference has been removed. An update part(200) includes a plurality of update portions each of which corresponds to each of the filter taps. An update portion selects one of the first and second algorithms according to a channel state inputted to a corresponding filter tap. The update portion updates a coefficient of the corresponding filter tap on the basis of the selected algorithm and the error value.

Description

Equalization of digital broadcasting receiver and method of equalization

The present invention relates to an equalizer and a method of the digital broadcast receiver, and more particularly, to an equalizer and a method for optimizing the filter tap coefficient update method of the equalizer according to the estimated channel state.

The equalizer is a device for correcting attenuation during transmission of a signal or distortion occurring during transmission, and uniformizing the characteristics thereof. A digital feedback signal receiver generally uses a decision feedback equalizer. Least Mean Squire (LMS) algorithm, Recursive Least Squire (RLS) algorithm, or Kalman algorithm are used.

1 is a block diagram of an equalizer of a conventional digital broadcast receiver. The equalizer according to FIG. 1 includes a feed forward (FF) unit 100, a feed back unit 110, an adder 120, a determiner 130, a selector 140, and an error calculator 150. ), And an update unit 160. The FF unit 100, which compensates in the form of a finite impulse response (FIR), receives and filters a digital broadcast signal. In this case, the received digital broadcast signal may be a single carrier signal including a time domain signal or a time domain synchronous-orthogonal frequency division multiplexing (TDS-OFDM) signal that is a multi-carrier signal. The FB unit 110, which compensates in the form of an infinite impulse response (IIR), receives and filters a signal from the selector 140. The adder 120 adds the outputs of the FF unit 100 and the FB unit 110. The determiner 130 determines the output signal of the adder 120 as a signal of quadrature amplitude modulation (QAM), and outputs the determined value. The selector 140 receives the determination value and the reference signal which is the same signal as the synchronization signal inserted before the transmission of the digital broadcast signal, and determines the reference signal in the training mode and the blind signal in the blind mode according to the mode of the digital broadcast signal. The value is transmitted to the FB unit 110 and the error calculator 150. The error calculator 150 receives the signals of the adder 120 and the selector 140 to calculate an error value. At this time, as an algorithm for calculating an error value, sato algorithm, CMA, modified CMA, Decision Direct algorithm, Stop and Go algorithm, Benveniste-Goursat algorithm, etc. may be used.

The updater 160 updates the filter tap coefficients of the FF unit 100 and the FB unit 110. As an algorithm for updating the filter tap coefficients of the FF unit 100 and the FB unit 110, a Least Mean Squire (LMS) algorithm, a Recursive Least Squire (RLS) algorithm, and a Kalman algorithm similar to the RLS algorithm may be used. have.

The tap coefficient update formula using the LMS algorithm is as follows.

The tap coefficient update formula using the RLS algorithm is as follows.

here, , , , , y (n) is equalizer output, e (n) is error value, Is the step size constant, H is the Hermitian transform, x (n) is the FF part input signal, f (n) is the filter tap coefficient of the FF part, d (n) is the selector output signal, and the FB part input signal, b (n Is the filter tap coefficient of the FB portion.

Referring to [Equation 1], the LMS algorithm is relatively simple to calculate the tap coefficient value to be updated. Therefore, there is an advantage that the calculation amount is small, but there is a problem that it is difficult to estimate the dynamic channel.

Meanwhile, referring to Equation 2, the RLS algorithm can equalize even a dynamic channel accurately, but there is a problem in that the complexity of the calculation process is increased, and the Kalman algorithm also has characteristics similar to those of the RLS algorithm.

Conventionally, only one of the LMS algorithm, the RLS algorithm, or the Kalman algorithm was used to equalize all dynamic and static signals. However, as mentioned above, when the LMS algorithm is used, equalization deteriorates in a dynamic channel, and when the RLS algorithm or the Kalman algorithm is used, the performance of the equalization is improved, but there is a problem in that the amount of computation is greatly increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an equalization apparatus for a digital broadcast receiver that equalizes a channel efficiently by selectively determining a state of a channel and selectively using a suitable filter tap coefficient algorithm. To provide a method.

1 is a block diagram showing an example of an equalizer of a conventional digital broadcast signal receiver;

2 is a block diagram of an equalizer of a digital broadcast signal receiver according to the present invention; and

3 is a flowchart provided to explain the operation of the equalizer of the digital broadcast signal receiver according to the present invention.

Explanation of symbols on the main parts of the drawings

200: update unit 205: filter unit

210: FF part 220: FB part

230: addition unit 240: determination unit

250: selection unit 260: error calculation unit

An equalization apparatus of a digital broadcast signal receiver according to the present invention for achieving the above object comprises a filter tab for removing channel interference of the digital broadcast signal, a signal from which the channel interference is removed, and a predetermined An error calculator configured to calculate an error value based on a reference signal and corresponding to each filter tap, wherein one of a first algorithm and a second algorithm is selected according to a state of the channel input to the corresponding filter tap. Selects and updates the corresponding filter tap coefficients based on the selected algorithm and the error value.

The updater updates the tap coefficients using the first algorithm when the channel state is static or when the channel estimate is smaller than a predetermined threshold value, and the filter taps using the second algorithm when the state of the channel is dynamic. Update the coefficients. In this case, the first algorithm is a Least Mean Squire (LMS) algorithm, and the second algorithm is any one of a recursive least required (RLS) algorithm and a kalman algorithm.

The filter unit includes a predetermined number of filter taps among the filter taps, a feedforward filter unit configured to receive a digital broadcast signal and compensate in the form of a finite impulse response (FIR). It is possible to include a feedback filter unit for receiving the reference signal and compensating in the form of an infinite impulse response (IIR), and an adder for calculating the sum of the feed forward filter unit output and the feedback filter unit output and outputting the filter unit.

The equalizer includes a decision unit for determining the output of the filter unit as a signal of a certain constellation and outputting the determined value, and a synchronization signal inserted before transmission of the determination value or the digital broadcast signal in accordance with the digital broadcast signal. And a selector for transmitting a reference signal which is the same signal, wherein the reference signal is a signal transmitted from the selector, and the constant constellation signal is a quadrature amplitude modulation (QAM) constellation signal. And outputting the reference signal in response to receiving a synchronization signal region signal, which is a signal transmitted to synchronize the digital broadcast signal with a receiver, and outputting the determination value in response to receiving the user region signal of the digital broadcast signal. do.

Preferably, the error calculator uses one of a sato algorithm, a CMA, a modified CMA, a decision direct algorithm, a stop and go algorithm, and a Benveniste-Goursat algorithm. The digital broadcast signal includes a single signal having a synchronization signal in a time domain. It may be any one of a carrier signal and a multi-carrier signal, and preferably further includes a channel estimator for estimating a channel of the transmitted digital broadcast signal and transmitting it to the updater.

In the equalization method of the digital broadcast signal receiver according to the present invention, a filtering step of removing channel interference of the digital broadcast signal using a plurality of filter taps, an error based on the signal from which the channel interference is removed and a predetermined reference signal Calculating a value and corresponding to each of the filter taps, selecting one of a first algorithm and a second algorithm according to a state of the channel input to the corresponding filter tap, and selecting the selected algorithm and the Updating the corresponding filter tap coefficient based on the error value.

The updating may include updating the tap coefficients using the first algorithm when the channel state is static or when the channel estimate is smaller than a predetermined threshold value, and using the second algorithm when the channel state is dynamic. The tap coefficient is updated, and the first algorithm is a Least Mean Squire (LMS) algorithm, and the second algorithm is any one of a recursive least demand (RLS) algorithm and a kalman algorithm.

The filtering step may include a predetermined number of filter taps among the filter taps, a feedforward filtering step of receiving a digital broadcast signal and compensating for the FIR form, and the remaining predetermined number of filter taps among the plurality of filter taps. It is possible to include a feedback filtering step of receiving and compensating in the form of an IIR, and an addition step of calculating a sum of an output of the feedforward filtering step and an output of the feedback filtering step.

In addition, the equalization method includes the step of determining the output of the filtering step as a signal of a certain constellation and outputting the determined value, and optionally inserting the determined value or the digital broadcast signal before transmission according to the digital broadcast signal. It is possible to further include a selecting step of transmitting a reference signal which is the same signal as the synchronized signal, wherein the reference signal is a signal transmitted in the selecting step. In the determining step, the constant constellation signal is preferably a quadrature amplitude modulation (QAM) constellation signal. The selecting may include outputting the reference signal in response to receiving a synchronization signal region signal, which is a signal transmitted to synchronize the transmitter and receiver of the digital broadcast signal, and in response to receiving the user region signal of the digital broadcast signal. Output the decision value.

In the error calculating step, the error value may be calculated using any one of a sato algorithm, a CMA, a modified CMA, a decision direct algorithm, a stop and go algorithm, and a Benveniste-Goursat algorithm. Any one of a single carrier signal and a multi-carrier signal having a synchronization signal of, it is preferable to further include a channel estimation step of estimating the channel of the transmitted digital broadcast signal and transmits to the update step.

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

2 is a block diagram according to an embodiment of an equalization device of a digital broadcast signal receiver according to the present invention. Referring to the drawings, the equalizer includes a plurality of update units 200-1, 200-2, 200-3, 200-4, ..., a filter unit 205, an error calculator 260, and a determiner 240. ), And a selection unit 250. The filter unit may include an FF unit 210, a plurality of filter taps 215-1, 215-2, 215-3,..., And a plurality of delay units 217-1, which compensate in an FIR form. 217-2, 217-3…), and an FF adder 219 for calculating the sum of the output values of the respective filter taps 215-1, 215-2, 215-3. 220, a plurality of filter taps 225-1, 225-2, 225-3... Inside the FB unit 220, a plurality of delay units 227-1, 227-2, 227-3. An FB adder 229 and an adder 230 for calculating the sum of the output values of the respective filter taps 225-1, 225-2, 225-3 ... are included.

The plurality of update units 200-1, 200-2, 200-3, 200-4 receive the channel estimation result and the error value, and each filter tap 215-1, 215-2, of the FF unit 210. 215-3... And coefficients of the filter taps 225-1, 225-2, 225-3. That is, when the channel corresponding to the first FF filter tap 215-1 is static or is less than or equal to a predetermined threshold, the first updater 200-1 may LMS the coefficient of the first FF filter tap 215-1. If the channel state is dynamic, the coefficient of the first FF filter tap 215-1 is updated using the RLS algorithm or the Kalman algorithm. The update unit 200-1, 200-2, 200-3, 200-provided in correspondence with the respective filter taps 215-1, 215-2, 215-3. 4, ...) updates the coefficients of the filter taps 215-1, 215-2, 215-3, ..., using the LMS algorithm or the RLS algorithm according to the channel state. Also, as described above, the Kalman algorithm can be used instead of the RLS algorithm. The coefficients of the filter taps 225-1, 225-2, 225-3... Constituting the FB unit 220 are also updated in the same manner as the update method of the filter tap of the FF unit 210. In other words, the coefficients of the first FB filter tap 225-1 are updated using the RLS, Kalman algorithm, or LMS algorithm according to the state of the channel corresponding to the first FB filter tap 225-1. The filter tap coefficients are also updated in the same manner as the coefficient update method of the first FB filter tap 225-1. That is, all filter tap coefficients constituting the FF unit 210 and the FB unit 220 are updated with an optimized algorithm according to the state of the channel corresponding to the filter. The channel estimation result can be received from a channel estimator (not shown).

The FF unit 210, which compensates in the FIR form, receives the digital broadcast signal and calculates the sum of the outputs of the respective filter taps 215-1, 215-2, ... through the FF adder 219 to output the process. Filtering is performed to remove channel interference. The FB compensating in the form of IIR receives the output signal of the selector and performs filtering to remove channel interference by calculating the sum of the outputs of the respective FB filter taps 225-1, 225-2, ... through the FB adder. The addition unit calculates the sum of the outputs of the FF unit and the FB unit, outputs the equalizer, and transmits them to the determination unit and the error calculation unit. The determination unit 240 outputs a determination value obtained by converting an input signal into a signal of quadrature amplitude modulation (QAM). The selector 250 receives the determination value and the reference signal and selectively outputs one signal. Specifically, when the currently input digital broadcast signal is a sync signal portion, the same reference signal as the sync signal inserted at the time of transmission is output, and when the received signal is a general user data signal, a determination value is output.

The error calculator 260 calculates an error based on the output of the selector 250 and the output of the adder 230 which is the output of the equalizer. In this case, the error calculation algorithm may include a sato algorithm for calculating an error value using the average size of the equalized output signal and a pre-calculated average size, and an error value using the average power and the pre-calculated average power of the equalized output signal. Decision Direct algorithm that calculates error using constant modulus algorithm (CMA), modified CMA, equalized output signal and decision value, and reliability obtained by Decision Direct method. If the error is determined to be unreliable, the Stop and Go algorithm that determines the error value as 0, the error value obtained from the CMA method, and the error value obtained from the Decision Direct algorithm are appropriately added to recalculate the error value for the tap coefficient update. It is possible to use the Benveniste-Goursat algorithm, etc.

The error calculated in this way is input to each update unit 200-1, 200-2, 200-3, 200-4... And the update unit 200-1, 200-2, 200-3, 200-4... Calculates filter tap coefficients to be updated by the RLS algorithm, the Kalman algorithm or the LMS algorithm according to the channel state based on the calculated error value. In the present embodiment, the update unit is configured to correspond to each filter tap, but it is possible to configure the update unit in units of a predetermined number of filter taps.

3 is a flowchart illustrating an equalization method according to the present invention. 2 and 3, a channel estimation result is input (S300). The filter taps of the FF unit 210 and the FB unit 220 are updated according to the state of the channel corresponding to each tap. First, it is determined whether a state of a channel corresponding to each filter tap in the FF unit 210 and the FB unit 220 is equal to or less than a predetermined value or a static state (S310). The coefficient of the filter tap satisfying the condition of S310 is updated using the LMS algorithm (S320). If the step S310 is not satisfied, check whether the state of the channel corresponding to each filter tap in the FF unit 210 and the FB unit 220 is dynamic (S330), and if the channel state is dynamic, the FF unit 210 is dynamic. And the coefficient of the filter tap in the FB unit 220 is updated by using the RLS algorithm (S340). The FF receives and filters the digital broadcast signal to remove channel interference, and the FB unit 220 receives and filters the output of the selector 250 (S350). Then, the outputs of the FF unit 210 and the FB unit 220 are added up (S360). This summed signal is an equalized signal.

The determination value is calculated using this signal (S370). If the received signal is in the synchronization signal region, the same reference signal as the inserted synchronization signal is transmitted before the received signal is transmitted, and in the case of the general data region, the determination value calculated in step S370 is calculated (S380). The error value is calculated using the determined value and the equalized signal output in step S360 (S390). As the algorithm for calculating the error value, sato algorithm, CMA, modified CMA, Decision Direct algorithm, Stop and Go algorithm, Benveniste-Goursat algorithm can be used. This calculated error value is sent to steps S320 and S330 and used to calculate the tap coefficient to be updated by the LMS algorithm and the RLS or Kalman algorithm.

By the method as described above, it is possible to equalize more accurately and effectively the channel that changes dynamically or statically.

As described above, according to the present invention, by using the optimized filter tap coefficient update algorithm by determining the state of the channel through the estimated channel, it is possible to equalize the changing channel more accurately and quickly. Equalization performance is superior to the conventional LMS algorithm alone, and the equalization speed is faster than the RLS algorithm alone.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but 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 idea or the prospect of the present invention.

Claims (20)

A channel equalizer of a digital broadcast signal receiver, A filter unit comprising a plurality of filter taps and removing channel interference of the digital broadcast signal; An error calculator configured to calculate an error value based on the signal from which the channel interference is removed and a predetermined reference signal; And A one of a first algorithm and a second algorithm is selected according to the state of the channel input to the corresponding filter tap, and based on the selected algorithm and the error value, And an updater for updating the corresponding filter tap coefficients. The method of claim 1, wherein the update unit, Updating the tap coefficients using the first algorithm when the channel state is static or the channel estimate is smaller than a predetermined threshold, and updating the filter tap coefficients using the second algorithm when the state of the channel is dynamic. Digital broadcast receiver equalization device, characterized in that. The method of claim 2, Wherein the first algorithm is a Least Mean Squire (LMS) algorithm, and the second algorithm is any one of a recursive least required (RLS) algorithm and a kalman algorithm. The method of claim 1, wherein the filter unit A feedforward filter unit comprising a predetermined number of filter taps of the filter taps and receiving a digital broadcast signal to compensate in the form of a finite impulse response (FIR); A feedback filter unit including a predetermined number of filter taps among the plurality of filter taps, and receiving the reference signal to compensate in the form of an infinite impulse response (IIR); And And an adder which calculates a sum of the feedforward filter unit output and the feedback filter unit output and outputs the filter unit. The method of claim 1, A decision unit which determines the output of the filter unit as a signal of a certain constellation and outputs the determined value; And And a selector for selectively transmitting a reference signal which is the same signal as the synchronization signal inserted before transmission of the determination value or the digital broadcast signal according to the digital broadcast signal. And the reference signal is a signal transmitted from the selector. The method of claim 5, wherein the determining unit, And said constant constellation signal is a quadrature amplitude modulation (QAM) constellation signal. The method of claim 5, wherein the selection unit, Outputting the reference signal in response to receiving a synchronization signal region signal, which is a signal transmitted to synchronize the digital broadcast signal with a transmitter and a receiver, And outputting the determined value in response to receiving the user area signal of the digital broadcast signal. The method of claim 1, wherein the error calculator, and an error value is calculated using any one of a sato algorithm, a CMA, a modified CMA, a decision direct algorithm, a stop and go algorithm, and a Benveniste-Goursat algorithm. The method of claim 1, wherein the digital broadcast signal, Equalizer of the digital broadcast signal receiver, characterized in that any one of a single carrier signal and a multi-carrier signal having a synchronization signal in the time domain. The method of claim 1, And a channel estimator for estimating a channel of the transmitted digital broadcast signal and transmitting the estimated channel to the updater. In the channel equalization method of the digital broadcast signal receiver, Filtering a channel interference of the digital broadcast signal using a plurality of filter taps; Calculating an error value based on the signal from which the channel interference is removed and a predetermined reference signal; And A one of a first algorithm and a second algorithm is selected according to the state of the channel input to the corresponding filter tap, and based on the selected algorithm and the error value, Updating the corresponding filter tap coefficients. The method of claim 11, wherein the updating step, Updating the tap coefficients using the first algorithm when the channel state is static or the channel estimate is smaller than a predetermined threshold, and updating the filter tap coefficients using the second algorithm when the state of the channel is dynamic. Digital broadcast receiver equalization method, characterized in that. The method of claim 12, The first algorithm is a Least Mean Squire (LMS) algorithm, and the second algorithm is any one of a Recursive Least Squire (RLS) algorithm and a Kalman algorithm. The method of claim 11, wherein the filtering step A feedforward filtering step comprising: a predetermined number of filter taps among the filter taps, and receiving a digital broadcast signal to compensate in the form of a finite impulse response (FIR); A feedback filtering step comprising: a predetermined number of filter taps remaining among the plurality of filter taps, and receiving the reference signal and compensating it in the form of an infinite impulse response (IIR); And And an adding step of calculating a sum of the output of the feedforward filtering step and the output of the feedback filtering step. The method of claim 11, A determination step of determining the output of the filtering step as a signal of a certain constellation and outputting the determination value; And And selectively transmitting, according to the digital broadcast signal, a reference signal which is the same signal as the synchronization signal inserted before transmission of the determination value or the digital broadcast signal. And said reference signal is a signal transmitted in said selecting step. The method of claim 15, wherein the determining step, Wherein said constant constellation signal is a quadrature amplitude modulation (QAM) constellation signal. The method of claim 15, wherein the selecting step, Outputting the reference signal in response to receiving a synchronization signal region signal, which is a signal transmitted to synchronize the digital broadcast signal with a transmitter and a receiver, And outputting the determined value in response to receiving the user area signal of the digital broadcast signal. The method of claim 11, wherein the error calculating step, An equalization method of a digital broadcasting receiver, wherein the error value is calculated using any one of a sato algorithm, a CMA, a modified CMA, a decision direct algorithm, a stop and go algorithm, and a Benveniste-Goursat algorithm. The method of claim 11, wherein the digital broadcast signal, And a single carrier signal or a multicarrier signal having a synchronization signal in the time domain. The method of claim 11, And a channel estimating step of estimating a channel of the transmitted digital broadcasting signal and transmitting the estimated channel to the updating step.