JP2002300094A - Broadcast relay station device and sneak path cancellation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadcast relay station device and a sneak path cancellation method that can enhance the follow up ability of a sneak path transmission line characteristic due to temporal fluctuations by reducing a cancellation residue so as to stably attain cancellation. SOLUTION: A transmission line characteristic prediction section 331 estimates the characteristic of a transmission line when a signal sent from a transmission antenna 5 is sneaked to a reception antenna 1 and the characteristic of the transmission line in a succeeding control unit is predicted on the basis of the result of estimate. A filter coefficient generating section 334 generates a filter coefficient on the basis of the result of prediction and a FIR filter 35 filters the filter coefficient to generate a copy signal of the signal sneaked to the reception antenna 1. A subtractor 31 subtracts the copy signal from the received signal to eliminate the interference due to the sneak path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an SFN (Single F
In configuring a requency network (single-frequency network), the present invention relates to a relay station that performs single-frequency relay, and in particular, is installed in this relay station and uses OFDM (Orthogonal Network).
The present invention relates to a wraparound canceller having a circuit configuration for estimating transmission path characteristics such as multipath and wraparound from a frequency division multiplexing (orthogonal frequency division multiplexing) signal and canceling the transmission path characteristics.

[0002]

2. Description of the Related Art In an OFDM transmission system, a large number of orthogonal carriers are allocated to digital data to be transmitted, and IFFT (Inverse Fast Fourier Transform)
rm: a transmission system that performs batch modulation by performing inverse fast Fourier transform. Therefore, the OFDM transmission method is
Compared with the conventional FDM (Frequency Division Multiplexing) transmission method, there is an advantageous effect that the frequency use efficiency is high.

Further, in the OFDM transmission system, the symbol time can be made extremely long by increasing the number of allocated carriers, for example, from several hundreds to several thousands. Furthermore, by adding a copy of the signal after the effective symbol period as a guard period signal before the effective symbol period, it is characterized in that it is hardly affected by a delayed wave. As described above, the OFDM transmission method has a strong resistance to a delayed wave, and is a transmission method suitable for constructing a broadcast network using a single frequency, that is, an SFN. Under the above circumstances, the OFDM transmission system is receiving attention as a transmission system for digital terrestrial broadcasting.

[0004] In SFN, for example, a dedicated line such as an optical fiber or a microwave is provided separately from a broadcast wave between a master station and a relay station and between the relay stations. , And finally each relay station transmits this signal on the same frequency. However, constructing an SFN using an optical fiber causes a problem that the line cost becomes high, and constructing an SFN using a microwave necessitates securing new frequency resources. For this reason, the SF which is advantageous in cost and does not require a new frequency resource
N is desired to be realized.

Therefore, as a SFN relay system, a broadcast relay system for rebroadcasting a received signal without providing a dedicated relay line is being studied. According to this broadcast relay system, costs can be reduced at each stage as compared with a system in which a dedicated relay line is provided. However, when rebroadcasting is performed, there is a problem that a loop-back occurs between a transmitting antenna and a receiving antenna in a relay station, causing oscillation of an amplifier and deterioration of transmission path characteristics.

The following technique has been proposed as a countermeasure for this wraparound. First, a technique has been proposed in which a receiving antenna is separated and arranged in a relay station to reduce the sneak path by using shielding by mountains or buildings. Secondly, there has been proposed a technique for improving the directional characteristics of the transmitting / receiving antenna to reduce the wraparound. Thirdly, there has been proposed a technique for canceling a wraparound by a circuit technique.

However, since the conditions of mountains and buildings are various, there is a case where it is not possible to sufficiently suppress the wraparound by the above first technique. Further, it is not possible to expect a sufficient effect of suppressing the wraparound only by taking measures against the directivity characteristics of the antenna, which is the second technique. Therefore, in the relay station using the first technology (the technology using the cutoff) and the second technology (the technology for improving the directivity), a wraparound canceller is further constructed using the third technology (the circuit technology). Meanwhile, a technique for suppressing interference due to a sneak wave by using the sneak canceller has been proposed as an effective technique for suppressing the sneak wave.

[0008] As the circuit technique described above, the received OF
The frequency characteristics of the loop-in transmission line are estimated from the DM signal, and the estimated frequency characteristic data of the loop-in transmission line is inverse fast Fourier transformed (IFFT).
m) to convert the impulse response data into time-axis data, set the impulse response data as a filter coefficient in a transversal filter, create a duplicate signal of the wraparound signal, and subtract the duplicate signal from the received signal. A method has been devised to cancel the wraparound. Such a circuit technology is described in, for example, IEICE Technical Report, EMCJ98-111, pp. 49-56, and ITE Technical Report, Vol. 23, 39.
No. 1, pp. 1-6.

[0009]

In terrestrial digital broadcasting using the OFDM transmission system, the symbol time is increased (that is, the number of carriers used is increased) in order to ease the station setting conditions when constructing the SFN. ) To reduce the effects of delayed waves having a large delay time.

However, as the number of carriers increases, the number of points of the frequency characteristic data input to the IFFT circuit increases, and the time required for calculating the impulse response data increases. For this reason, at the time when the transfer function is estimated from the received symbol data and the filter coefficient of the transversal filter is updated, there is a time lag between the estimated transmission path characteristic and the actual loop transmission path characteristic due to the time variation of the loop transmission path characteristic. Differences occur by the amount of change,
This difference remains as a cancellation residual. Due to this cancellation error, the conventional loop canceller has a problem that interference due to the loop wave cannot be sufficiently removed. This problem appears remarkably when the fluctuation of the loop transmission line characteristics is large.

The present invention has been made in view of the above-mentioned point of view, and by reducing the cancellation residual, it is possible to improve the followability of the loop-around transmission path characteristic with respect to time variation,
An object of the present invention is to provide a wraparound canceller that can perform a cancel operation stably.

[0012]

According to the present invention, there is provided a broadcast relay station apparatus comprising: a transmission antenna for transmitting a transmission signal; a reception antenna for receiving a reception signal; and a signal transmitted from the transmission antenna wrapping around the reception antenna. Estimating means for estimating the characteristics of the transmission path at the time of transmission, estimating means for estimating the characteristics of the transmission path in the next control unit based on the estimation result of the estimating means, and And a removing means for removing a signal that has entered the antenna.

According to this configuration, the channel characteristics of the loop-back transmission line in the next control unit are predicted, and a signal wrapping around from the transmission antenna to the reception antenna is removed based on the prediction result. , It is possible to accurately cancel a signal wrapping around the receiving antenna.

[0014] In the broadcast relay station apparatus of the present invention, in the broadcast relay station apparatus, the removing means may include a filter coefficient for filtering a duplicate signal of the signal wrapped around the receiving antenna based on a result of prediction by the predicting means. And a subtractor for subtracting the duplicated signal from the received signal.

According to this configuration, the channel characteristics of the loop-back transmission line in the next control unit are predicted, and the filter coefficient is calculated based on the prediction result. Can also calculate a filter coefficient close to the actual transmission path characteristics. Therefore,
By subtracting the duplicated signal filtered using the filter coefficient from the received signal, it is possible to accurately remove the interference caused by the loop interference.

A broadcast relay station apparatus according to the present invention includes a transmission antenna for transmitting a transmission signal, a reception antenna for receiving a reception signal, and an impulse of a transmission line when the signal transmitted from the transmission antenna goes around the reception antenna. Means for calculating a response, calculating means for calculating a filter coefficient when filtering a duplicate signal of the signal wrapped around the receiving antenna based on the impulse response, and calculating the following based on the filter coefficient calculated by the calculating means. And a removing unit that removes a signal wrapped around the receiving antenna based on a prediction result of the predicting unit.

According to this configuration, the filter coefficient in the next control unit is predicted, and the signal wrapping around from the transmitting antenna to the receiving antenna is removed based on the prediction result. It is possible to accurately cancel a signal that has entered the receiving antenna.

The wraparound cancellation program according to the present invention comprises: a computer for estimating a characteristic of a transmission path when a signal transmitted from a transmission antenna wraps around to a reception antenna; A configuration is adopted that functions as a prediction unit that predicts the characteristics of the transmission path in units and a removal unit that removes a signal that has wrapped around the receiving antenna based on the prediction result of the prediction unit.

According to this configuration, the transmission path characteristics of the loop transmission path in the next control unit are predicted, and a signal wrapped around from the transmission antenna to the reception antenna is removed based on the prediction result. , It is possible to accurately cancel a signal wrapping around the receiving antenna.

[0020] The wraparound canceling method of the present invention comprises: an estimation step of estimating a characteristic of a transmission path when a signal transmitted from a transmission antenna wraps around a reception antenna; and a control unit for the next control unit based on the estimation result of the estimation step. The method includes a prediction step of predicting the characteristics of the transmission path, and a step of removing a signal wrapped around the receiving antenna based on a prediction result of the prediction step.

According to this method, the channel characteristics of the loop-back transmission line in the next control unit are predicted, and the signal wrapping around from the transmission antenna to the reception antenna is removed based on the prediction result. , It is possible to accurately cancel a signal wrapping around the receiving antenna.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The essence of the present invention is to provide a wraparound canceller for removing a wraparound signal duplicate signal from a received signal, by using the transmission path characteristics of the wraparound transmission path estimated based on the received signal, for the next control unit. Is extrapolated to the transmission path characteristics, a filter coefficient is calculated based on the prediction result, and a duplicated signal of the wraparound signal is generated using a digital filter in which the filter coefficient is set.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. (Embodiment 1) In the description of signals and transfer functions in the following description, uppercase letters represent complex numbers, and lowercase letters represent real numbers. Further, ω represents an angular frequency, and t represents time.

FIG. 1 is a block diagram showing a configuration of a broadcast relay station according to Embodiment 1 of the present invention. The broadcast relay station shown in FIG. 1 is equipped with a loop canceller 3 for removing a loop signal from a received signal.

In FIG. 1, X (ω) is a desired signal from the master station or the preceding relay station, R (ω) is an input signal of the reception converter 2,
S (ω) is an input signal of the transmission conversion unit 4, G1 (ω) is a transfer function of the reception conversion unit 2, G2 (ω) is a transfer function of the transmission conversion unit 4,
C (ω) is the transfer function of the loop transmission path 6, and C ′ (ω) is FI
The transfer functions of an R (Finite Impulse Response) filter 35 are respectively represented.

In the broadcasting relay station shown in FIG. 1, a receiving antenna 1 is provided with a desired wave X from a master station or a preceding broadcasting relay station.
(ω) and the wraparound wave C (ω) G2 (ω) from the wraparound transmission line
A composite wave with S (ω) is received. The reception signal R (ω) is supplied to the reception conversion unit 2.

The reception conversion unit 2 performs a reception conversion process such as a filtering process and a frequency conversion process on the received signal R (ω), and wraps around the processed signal G 1 (ω) R (ω) to generate an internal signal of the canceller 3. Output to the subtractor 31. In the output signal G1 (ω) R (ω) of the reception conversion unit 2, the component of the wraparound wave is C
(ω) G1 (ω) G2 (ω) S (ω). In the present specification, the wraparound wave component of the received signal is referred to as a "wraparound signal".
It may be called.

Inside the wraparound canceller 3, the subtractor 31 converts the output G 1 (ω) R (ω) of the reception conversion unit 2 into F
The wraparound observation signal S (ω) is generated by subtracting the duplicate signal C ′ (ω) S (ω) of the wraparound signal filtered by the IR filter 35, and the generated wraparound observation signal S (ω) is subjected to an FFT circuit. 32 and the FIR filter 35. The wraparound observation signal S (ω) is output to the transmission conversion section 4 as an output of the wraparound canceller 3, and is subjected to predetermined transmission conversion processing such as filter processing and frequency conversion processing in the transmission conversion section 4, and relayed. Broadcast signal G2 (ω)
S (ω) is obtained. This relay broadcast signal G2 (ω) S (ω)
Is supplied to the input of the transmitting antenna 5. The transmitting antenna 5 radiates the relay broadcast signal G2 (ω) S (ω).

An FFT (Fast Fourier Transform) circuit 32 performs a fast Fourier transform process on the wraparound observation signal S (ω), and converts the wraparound observation signal S (ω), which is data on the time axis, on the frequency axis. To carrier data. The converted signal is output to the transmission path characteristic prediction unit 331 and the delay circuit 337.

The delay circuit 337 delays the output signal of the FFT circuit 32 by a predetermined symbol time. The output signal of the delay circuit 337 is supplied to the transmission path characteristic prediction unit 331.

The transmission line characteristic predicting section 331 includes the FFT circuit 3
2 and the respective carrier data included in the output of the delay circuit 337, each frequency characteristic data (transmission path characteristic of the loop transmission path) is calculated, and the frequency characteristic in the next control unit is calculated using the calculated frequency characteristic data. The data F ′ (ω) (that is, the frequency characteristic data F ′ (ω) at the time when the coefficient of the FIR filter 35 is updated next time) is predicted. The time at which the coefficient of the FIR filter 35 is updated next time is, in other words, the time at which the FIR filter 35 generates the next duplicated signal.

In the FIR filter 35, the filter coefficient is usually updated for each symbol. The control unit in this case is one symbol.

The frequency characteristic data F ′ (ω) at the time of the next update of the filter coefficient, which is the prediction result, is output to the cancellation residual estimator 332.

When calculating F '(ω), extrapolation prediction may be performed using a polar coordinate system. Also, the delay circuit 3
37, a plurality of delay circuits having different delay times are provided in parallel, and extrapolation prediction of F ′ (ω) is performed in the transmission line characteristic circuit 331 based on the outputs of the plurality of delay circuits. May be performed.

The cancellation residual estimating unit 332 calculates the actual transfer function C (ω) G1 (ω) G2 (ω) and the FIR filter 35 from the output F ′ (ω) of the transmission path characteristic predicting unit 331.
The transfer function E (ω) which is a difference from the transfer function C ′ (ω) is calculated. The calculated transfer function E (ω) is
3 is output.

The IFFT circuit 333 calculates the differential transfer function E
inverse fast Fourier transform (IFFT) for (ω)
Fast Fourier Transform) to convert the difference transfer function E (ω) into impulse response data H (t). The obtained impulse response data H (t) is output to the filter coefficient generator 334.

The filter coefficient generator 334 calculates a filter coefficient W (t) based on an output H (t) of the IFFT circuit 333 and an output W '(t) of a delay circuit 338 described later. The calculated filter coefficient W (t) is supplied to the coefficient update circuit 34 as an output of the update coefficient generation unit 33.

The coefficient updating circuit 34 adjusts the filter coefficient W (t) in accordance with the reception symbol timing of the subtractor 31.
Is output to the FIR filter 35 and the delay circuit 338.

The delay circuit 338 delays the output W (t) of the coefficient update circuit 34 by a time corresponding to the time from the input of the FFT circuit 32 to the update of the filter coefficient of the transversal filter (that is, the update coefficient (The same delay as the processing delay until the filter coefficient is generated by the generation unit 33). This delayed filter coefficient W '(t)
Is output to the filter coefficient generation unit 334.

The FIR filter 35 filters the wraparound observation signal S (ω) output from the subtractor 31 with a filter coefficient W (t) (the transfer function is C ′).
(ω)), and a duplicate signal C ′ (ω) S (ω) of the wraparound signal
Generate In the present specification, a duplicate signal of a wraparound signal may be simply referred to as a “wraparound duplicate signal”. The wraparound duplicate signal C '(ω) S thus generated
(ω) is output to the subtractor 31.

Next, the operation of the broadcast relay station having the above configuration will be described. Desired wave X (ω) from master station or preceding broadcast relay station and wraparound wave C (ω) G2 from wraparound transmission path
The combined wave with (ω) S (ω) is received from antenna 1. The reception signal R (ω) is subjected to a predetermined reception conversion process in the reception conversion unit 2, and the subtraction unit 31 reduces the wraparound duplicate signal C ′ (ω) S (ω) generated by the FIR filter 35. As a result, a wraparound observation signal S (ω) is obtained.

This wraparound observation signal S (ω) is output to the transmission conversion section 4 as an output of the wraparound canceller 3, and the transmission conversion section 4 performs predetermined transmission conversion processing such as filtering and frequency conversion. Relay broadcast signal G2 (ω)
It is transmitted from the transmitting antenna 5 as S (ω). The relay broadcast signal G2 (ω) S (ω) transmitted from the transmitting antenna 5 is
While being received by another broadcast relay station, a part of it is wrapped around the receiving antenna 1. That is, the relay broadcast signal G2
A part of (ω) S (ω) passes through the loop transmission line 6 to become a loop wave C (ω) G2 (ω) S (ω), and this loop wave C
(ω) G2 (ω) S (ω) is received from the receiving antenna 1.

The wraparound observation signal S (ω) is obtained by FFT
(Fast Fourier Transform) Circuit 3
2, a fast Fourier transform process is performed. In the transmission path characteristic prediction section 331, frequency characteristic data is calculated from the carrier data output from the FFT circuit 32 and the delay circuit 337. Then, the transmission path characteristic prediction unit 331
In this case, using the calculated frequency characteristic data, the frequency characteristic data F ′ (ω) at the time when the coefficient of the FIR filter 35 is updated next time (ie, the time when the next duplicated signal is generated in the FIR filter 35). ) Is expected.

Here, the frequency characteristic data calculated based on the output signal from the FFT circuit 32 is F1 (ω), the frequency characteristic data calculated based on the output signal from the delay circuit 337 is F2 (ω), N interval, delay circuit 3
Assuming that the delay at 37 is one symbol and linear extrapolation is used as the prediction method, the frequency characteristic data F ′ (ω) at the time of the next filter coefficient update can be obtained by, for example, equation (1).

[0045]

(Equation 1) In the cancellation residual estimating unit 332, the transfer function C (ω) G1 (ω) G2 (ω) of the actual wraparound and the transfer function C of the FIR filter 35 are obtained from the output F ′ (ω) of the transmission path characteristic predicting unit 331. The transfer function E (ω), which is the difference from '(ω), is calculated. This E (ω) is obtained, for example, by equation (2).

[0046]

(Equation 2) The IFFT circuit 333 performs an inverse fast Fourier transform (IFFT) on the differential transfer function E (ω).
ourier Transform) and impulse response data H
(t) is obtained.

In the filter coefficient generator 334, I
Filter coefficient W (t) is calculated based on output H (t) of FFT circuit 333 and output W ′ (t) of delay circuit 338.

Here, W (t) indicates that the update coefficient is “μ” (μ
Is usually a real number satisfying 0 <μ ≦ 1), and the FIR filter 35
The offset value taking into account the feedback delay of
If it is set to 0 ", it is obtained, for example, by the equation (3). The number of data of W (t) is equal to the number of taps in the FIR filter 35 and is smaller than the number of data of the output H (t) of the IFFT circuit 333. , Filter coefficient generator 3
Numeral 34 extracts data corresponding to the number of taps of the FIR filter 35 from the output H (t) of the IFFT circuit 333 and updates the coefficient as shown in the equation (3).

[0049]

(Equation 3) The filter coefficient W (t) calculated in this way is supplied to a coefficient update circuit 34, and the coefficient update circuit 34 outputs the filter coefficient W (t) in accordance with the reception symbol timing of the subtractor 31.
The signal is output to the FIR filter 35 and the delay circuit 338.

In the delay circuit 338, the output W (t) of the coefficient update circuit 34 is delayed by the time from the input of the FFT circuit 32 to the update of the filter coefficient of the transversal filter. This delayed filter coefficient W ′ (t) is output to filter coefficient generating section 334.

In the FIR filter 35, the subtractor 3
1 is subjected to a filtering process using a filter coefficient W (t) (the transfer function is C ′ (ω)), and the wraparound duplicate signal C ′ (ω) S is output.
(ω) is generated. The wraparound duplicate signal C ′ (ω) S (ω) thus generated is output to the subtractor 31.

The arithmetic unit 31 converts the received signal into FI
The wraparound duplicate signal output from the R filter 35 is reduced, and interference of the wraparound signal with respect to the received signal is removed.

In the feedback control described above, the update coefficient generation unit 33 generates the filter coefficient W (t) so as to remove the sneak signal from the received signal, so that the transfer function C ′ (ω) of the FIR filter 35 is Converge to the actual wraparound transfer function C (ω) G1 (ω) G2 (ω),
As a result, the wraparound transfer function C (ω) G1 (ω) G2
The difference transfer function E (ω) between (ω) and the transfer function C ′ (ω) of the FIR filter 35 converges to “0”. Considering the amount of change in each frequency characteristic over time and expressing the amount of change in each frequency characteristic as Δ, the wraparound observation signal S (ω) is expressed as shown in equation (4). As described above, C '
Since (ω) converges to C (ω) G1 (ω) G2 (ω) (ie, since the difference transfer function E (ω) converges to “0”),
Only the desired wave component from the master station appears in the wraparound observation signal S (ω) shown in equation (4).

[0054]

(Equation 4) As described above, according to the present embodiment, the transmission path characteristic at the next coefficient update time is predicted by the transmission path characteristic prediction section 331 provided in the update coefficient generation section 33, and the FIR is calculated based on the prediction result. Since the filter coefficients to be written to the filter 35 are updated (generated), the cancellation residual remaining between the actual transmission path characteristics and the estimated transmission path characteristics of the filter coefficients written to the FIR filter 35 is reduced. It can be accurately removed.

Further, since the cancellation residual is reduced, the time required for the difference transfer function to converge to 0 can be shortened, and the interference due to the loop interference can be eliminated at a higher speed.

Further, since the filter coefficient to be written to the FIR filter 35 is updated (generated) based on the prediction result of the transmission path characteristic at the next coefficient update time, the interference due to the wraparound wave having a long fluctuation period and a large fluctuation amount can be reduced. It is possible to remove well.

In this embodiment, a transversal filter for generating a copy of a wraparound signal is
Although the FIR filter 35 was used, an IIR (Infinite Imp
The same principle can be applied using an ulseResponse) filter.

Further, in the present embodiment, the wraparound is canceled in the signal after the frequency conversion by the reception conversion unit 2, but in the present invention, the signal before the frequency conversion by the reception conversion unit 2 is performed. The wraparound may be canceled for any frequency signal, such as canceling the wraparound for a signal. Such deformation can be easily performed.

Although not shown in FIG. 1, an AD (Analog to Digital) converter for digital signal processing and a DA (D
It goes without saying that the insertion position of the (digital to analog) converter is irrelevant to the principle of the present invention, and the same principle can be applied regardless of the insertion position of the AD converter and the DA converter.

(Embodiment 2) This embodiment is a modification of Embodiment 1 and differs from Embodiment 1 in that a filter coefficient W (t) at the time of the next filter coefficient update is predicted. FIG. 2 is a block diagram showing a configuration of the wraparound canceller 3 according to Embodiment 2 of the present invention. This figure 2
In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

In FIG. 2, the cancel residual estimator 332 provided in the update coefficient generator 33 is
From the output F (ω), the actual transfer function C (ω) G
1 (ω) G2 (ω) and the transfer function C ′ of the FIR filter 35
The transfer function E (ω) of the difference from (ω) is calculated, and the calculated difference transfer function (ω) is output to the IFFT circuit 333.

The filter coefficient generator 334 outputs the output H (t) of the IFFT circuit 333 and the output W 'of the delay circuit 338.
(T), the filter coefficient Wp (t) is calculated, and the calculated filter coefficient Wp (t) is calculated by the filter coefficient prediction unit 335.
And output to the delay circuit 339. Here, Wp (t) is
Assuming that the update coefficient is “μ” (μ is a real number that normally satisfies 0 <μ ≦ 1) and the offset value in consideration of the feedback delay of the FIR filter 35 is “t0”, it is obtained by, for example, equation (5). The number of data of this Wp (t) is expressed by FIR
Equal to the number of taps of the filter 35, and the IFFT circuit 333
Is smaller than the number of data of the output H (t). That is, the filter coefficient generation unit 334 outputs the output H of the IFFT circuit 333.
Data corresponding to the number of taps of the FIR filter 35 is cut out from (t) to update the coefficient of the equation (5).

[0063]

(Equation 5) When calculating F ′ (ω), extrapolation prediction may be performed using a polar coordinate system. Further, a plurality of delay circuits having the same operation as the delay circuit 339 and having different delay times are provided in parallel.
Based on the outputs of the plurality of delay circuits, a filter coefficient W (t)
May be extrapolated.

The delay circuit 339 delays the output Wp (t) of the filter coefficient generation section 334 by a predetermined symbol time, and outputs the delayed filter coefficient Wp ′ (t) to the filter coefficient prediction section 335. .

The filter coefficient prediction unit 335 calculates the filter coefficient at the time when the coefficient of the FIR filter 35 is updated next time from the output Wp (t) of the filter coefficient generation unit 334 and the output Wp ′ (t) of the delay circuit 339. W (t) is predicted, and the prediction result is output to the coefficient updating circuit 34. Where W
(T) indicates that the update coefficient is ν (ν is usually a real number satisfying 0 <ν ≦ 1), the delay in the delay circuit 339 is one symbol, and F
Assuming that the coefficient update interval of the IR filter 35 is N symbols and linear extrapolation is used as a prediction method, the filter coefficient W (t) can be obtained by, for example, equation (6).

[0066]

(Equation 6) The coefficient updating circuit 34 outputs the filter coefficient W (t) to the FIR filter 35 and the delay circuit 338 in accordance with the reception symbol timing of the subtractor 31.

In the wraparound canceller 3 having the above configuration, the wraparound transfer functions C (ω) G1 (ω) G2 (ω) and FI
Difference transfer function E from transfer function C '(ω) of R filter 35
Feedback control is performed so that (ω) converges to zero.

As described above, according to the present embodiment, filter coefficient prediction section 335 predicts the filter coefficient at the next coefficient update time, and updates the filter coefficient written to FIR filter 35 based on the prediction result. (Generate), so the actual wraparound transmission path characteristics and FI
The cancellation residual remaining between the estimated transmission path characteristics of the filter coefficients written in the R filter 35 is reduced, and interference due to a sneak wave can be accurately removed.

In the second embodiment, the filter coefficient generation section 334 is inserted before the filter coefficient prediction section 335. However, the filter coefficient generation section 334 is inserted after the filter coefficient prediction section 335. , IFFT
The channel characteristics may be estimated using extrapolation prediction for the output H (t) of the circuit 333.

(Embodiment 3) This embodiment is a modification of Embodiment 2 and differs from Embodiment 2 in that extrapolation prediction of filter coefficients is performed for each symbol. FIG. 3 is a block diagram showing a configuration of the wraparound canceller 3 according to Embodiment 3 of the present invention. 3, the same components as those in FIG. 2 are denoted by the same reference numerals as those in FIG. 2, and detailed description thereof will be omitted.

In FIG. 3, a filter coefficient generating section 334
Is the output H (t) of the IFFT circuit 333 and the delay circuit 33
8, the filter coefficient Wp (t) is calculated from the output W ′ (t), and the calculated filter coefficient Wp (t) is output to the filter coefficient extrapolation unit 336 and the delay circuit 339. Where W
p (t) is calculated in the same manner as in equation (5).

The delay circuit 339 includes the filter coefficient generator 3
The Wp (t) output from 34 is delayed by a certain symbol time. This delayed filter coefficient Wp '
(t) is output to the filter coefficient extrapolation unit 336.

When Wp (t) is received from filter coefficient generating section 334, filter coefficient extrapolating section 336 receives the Wp (t).
And FI based on the output Wp '(t) of the delay circuit 339.
The filter coefficient W (t) of the R filter 35 is extrapolated and predicted. The filter coefficient extrapolation unit 336 performs this extrapolation prediction for all symbols from the reception of Wp (t) to the reception of the next Wp (t).

Here, W (t) is an update coefficient ν (ν is usually a real number satisfying 0 <ν ≦ 1), the delay of the delay circuit 339 is one symbol, and the output Wp (t) of the filter coefficient generator 334.
Is input to the filter coefficient extrapolation unit 336, the symbol time and symbol interval are I and N, respectively, and when the filter coefficient at the time of extrapolation is predicted by linear extrapolation, it can be obtained by equation (7).

[0075]

(Equation 7) When calculating W (t) in the filter coefficient extrapolation unit 336, extrapolation prediction may be performed using a polar coordinate system. Further, the same operation as the delay circuit 339 is performed, and
A plurality of delay circuits having different delay times are provided in parallel,
The filter coefficient extrapolation unit 336 may perform extrapolation prediction of the filter coefficient W (t) based on the outputs of the plurality of delay circuits.

The coefficient updating circuit 34 controls the filter coefficient extrapolation section 33 in accordance with the reception symbol timing of the subtractor 31.
6, the filter coefficient W (t) calculated in FIR
Output to the filter 35 and the delay circuit 338.

With the above configuration, the difference transfer function E (ω) between the transfer function C (ω) G1 (ω) G2 (ω) and the transfer function C ′ (ω) of the FIR filter 35 converges to zero. The feedback control operates so that

In the wraparound canceller 3 having the above configuration, the filter coefficient Wp (t) of the FIR filter 35 is used until the output Wp (t) of the filter coefficient generation section 334 is input to the filter coefficient extrapolation section 336 next time. Is calculated for each symbol, so that the follow-up performance with respect to the time variation of the actual loop-back transmission path is improved. That is, by calculating the filter coefficient Wp (t) for each symbol in the filter coefficient extrapolation section 336, it is possible to suppress the occurrence of a large cancellation residual. As a result, fluctuations in the transmission line characteristics can be reduced inside the loop canceller 3, so that an advantageous effect of suppressing an unstable operation such as oscillation can be obtained. Further, by calculating the filter coefficient Wp (t) for each symbol, the time required for the difference transfer function to converge to 0 can be further reduced. Further, it is possible to accurately remove interference caused by a loop wave having a long fluctuation period and a large fluctuation amount.

In the third embodiment, filter coefficient generating section 334 is inserted before filter coefficient extrapolating section 336. However, filter coefficient generating section 334 is inserted after filter coefficient extrapolating section 336. The filter coefficient extrapolation unit 336 may perform prediction on the output H (t) of the IFFT circuit 333 for each symbol.

(Embodiment 4) FIG. 4 is a schematic diagram showing an example of the configuration of an SFN broadcast wave relay system according to Embodiment 4 of the present invention. F1 shown in FIG. 4 is the transmission frequency of the broadcasting station, the transmission frequency of the relay station, and the desired reception frequency of each home.

In FIG. 4, broadcasting station 7 as a master station is an OF station.
The digital broadcast wave is broadcast at the transmission frequency f1 using the DM transmission method. The relay broadcast station 8 and the relay broadcast station 9 are the relay broadcast stations described in any of the above embodiments, and reduce the cancellation residual by setting a filter coefficient using extrapolation prediction. Interference due to a loop wave can be accurately removed.

The relay broadcast station 8 at the first stage receives, at the receiving antenna, a wave obtained by adding the broadcast wave of the master station's broadcast station 7 and the wraparound wave of the own station, and from the received wave, the wraparound wave of the wraparound wave is obtained. After the cancellation, the broadcast (rebroadcast) is performed again at the transmission frequency of f1.

The relay broadcast station 9 at the second stage receives the wave obtained by adding the broadcast wave from the relay broadcast station 8 at the first stage and the wraparound wave of its own station, and After canceling the looping wave, broadcasting (rebroadcasting) is performed again at the transmission frequency of f1.

As described above, according to the present embodiment, the SFN broadcast wave relay system includes the relay broadcast stations that reduce the cancellation residual by using extrapolation prediction. It is possible to suppress the oscillation phenomenon and the deterioration of the transmission path characteristics in the relay station. Thus, the broadcast is not interrupted in each home, and the broadcast wave can be stably received.

As will be apparent to those skilled in the art, the present invention can be implemented using a general commercially available digital computer and microprocessor incorporating a program for causing the technology described in the above embodiment to function. Can be. Further, as will be apparent to those skilled in the art, the present invention includes a computer program created by those skilled in the art based on the technology described in the above embodiment.

A computer program product, which is a computer-readable recording medium on which a program for causing the technology described in the above-described embodiments to function, is included in the scope of the present invention. This recording medium is a disk such as a floppy (registered trademark) disk, an optical disk, a CDROM and a magnetic disk, a ROM, a RAM, an EPRO, and the like.
M, EEPROM, magneto-optical card, memory card, DVD, or the like, but is not limited thereto.

The present invention is not limited to the above embodiments, but can be implemented by, for example, appropriately combining the above embodiments.

[0088]

As described above, the loop canceller according to the present invention, by adding means for estimating a time variation to the estimation of a loop wave, cancels out between the loop transmission path characteristic and the estimated transmission path characteristic. The residual can be reduced, and the wraparound can be accurately canceled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a broadcast relay station according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of a wraparound canceller according to Embodiment 2 of the present invention;

FIG. 3 is a block diagram showing a configuration of a wraparound canceller according to Embodiment 3 of the present invention;

FIG. 4 is a schematic diagram showing an example of a configuration of an SFN broadcast wave relay system according to Embodiment 4 of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reception antenna 3 loop canceller 5 transmission antenna 6 loop transmission path 31 subtractor 35 FIR filter 331 transmission path characteristic prediction section 334 filter coefficient generation section 335 filter coefficient prediction section 336 filter coefficient extrapolation section

Continued on the front page (72) Inventor Sadaji Kageyama 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kenichiro Hayashi 1006 Oji Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Kentoku Kunieda 3-10-1 Higashi-Mita, Tama-ku, Kawasaki City, Kanagawa Prefecture F-term in Matsushita Giken Co., Ltd. (Reference) 5K022 DD01 DD13 DD19 DD23 DD24 DD33 DD34 5K046 AA05 BB03 HH02 KK06 YY01

Claims (5)

[Claims] 1. A transmitting antenna for transmitting a transmitting signal, a receiving antenna for receiving a receiving signal, an estimating means for estimating a characteristic of a transmission path when a signal transmitted from the transmitting antenna goes around the receiving antenna, Prediction means for predicting the characteristics of the transmission path in the next control unit based on the estimation result of the estimation means, and removal means for removing a signal wrapped around the receiving antenna based on the prediction result of the prediction means, A broadcast relay station device comprising: 2. A removing means, comprising: a calculating means for calculating a filter coefficient for filtering a duplicate signal of a signal wrapped around a receiving antenna based on a prediction result of the predicting means; and subtracting the duplicate signal from the received signal. 2. The broadcast relay station device according to claim 1, further comprising a subtraction unit that performs subtraction. 3. A transmission antenna for transmitting a transmission signal, a reception antenna for receiving a reception signal, and means for calculating an impulse response of a transmission path when a signal transmitted from the transmission antenna goes around the reception antenna. Calculating means for calculating a filter coefficient when filtering a duplicate signal of the signal wrapped around the receiving antenna based on the impulse response; anda filter coefficient in a next control unit based on the filter coefficient calculated by the calculating means. A broadcast relay station apparatus, comprising: a prediction unit for performing prediction; and a removing unit configured to remove a signal that has entered the receiving antenna based on a prediction result of the prediction unit. 4. Estimating means for estimating a characteristic of a transmission path when a signal transmitted from a transmitting antenna goes around a receiving antenna, based on an estimation result of the estimating means, A wraparound canceling program functioning as prediction means for predicting characteristics, and removing means for removing a signal wrapped around to the receiving antenna based on a prediction result of the prediction means. 5. An estimating step of estimating a characteristic of a transmission path when a signal transmitted from a transmitting antenna goes around to a receiving antenna; and estimating a characteristic of the transmission path in a next control unit based on an estimation result of the estimating step A wraparound canceling method comprising: a prediction step of predicting; and a step of removing a signal wrapped around to the receiving antenna based on a prediction result of the prediction step.