JP2003298548A - Sneak path canceller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sneak path canceller having compatibility between enhanced tracking performance and a cancellation possible extended delay time. <P>SOLUTION: The sneak path canceller is provided with: a subtractor 31 for decreasing a copy of a sneak path signal from an input signal; an FIR filter 32 for producing the copy of the sneak path signal; and a filter coefficient generating section 33b for generating a coefficient of the FIR filter 32, and the filter coefficient generating section 33b calculates a characteristic of a transmission line by using a data carrier subjected to hard decision and re- modulation for a reference, calculates a cancellation residue from the characteristic of the transmission line, and updates the coefficient of the FIR filter on the basis of the result of applying IFFT processing to the cancellation residue. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to broadcast wave relay SFN (Single Frequency Network) in terrestrial digital broadcasting.
k: OFDM (Orthogonal Frequency Division) installed in a relay broadcasting station that realizes a single frequency network
Multiplexing: A wraparound canceller that cancels wraparound using transmission path characteristics estimated from orthogonal frequency division multiplexing signals, and in particular, using hard-decision results of data carriers to estimate transmission path characteristics improves tracking performance. The present invention relates to a wraparound canceller that achieves both an increase in a cancelable delay time and a canceller.

[0002]

2. Description of the Related Art The OFDM transmission system is a system in which a large number of carriers which are orthogonal to each other are modulated by digital data to be transmitted and the modulated waves are multiplexed and transmitted. O
In the FDM transmission system, if the number of carriers to be used is increased from several hundreds to several thousands, the symbol time becomes extremely long, and a duplication of the signal after the effective symbol period is added as a guard period signal before the effective symbol period. By doing so, there is a feature that it is less likely to be affected by the delayed wave. Due to this feature, there is a possibility that a broadcasting network with a single frequency, that is, an SFN can be constructed. Therefore, the OFDM transmission system is receiving attention as a transmission system for terrestrial digital broadcasting.

As a method of realizing SFN, it is technically easy to transmit a signal to each relay broadcasting station by using a line different from a broadcasting wave such as an optical fiber and a microwave, and transmitting at the same frequency. is there. However, in the method using the optical fiber, the line cost becomes a problem, and in the method using the microwave, it is necessary to secure new frequency resources. Therefore, it is desirable to realize SFN by broadcast wave relay, which is cost-effective and does not require new frequency resources. However, in the realization of the broadcast wave relay SFN, there is a concern that radio waves emitted from the transmission antenna may sneak into the reception antenna, causing problems such as deterioration of transmission line characteristics and oscillation of an amplifier.

As measures against the wraparound of the broadcast wave relay SFN, (1) the transmitting and receiving antennas are arranged separately, and the wraparound is reduced by using shielding by mountains or buildings, (2)
It is possible to reduce the wraparound by improving the directional characteristics of the transmitting and receiving antennas, (3) cancel the wraparound by using circuit technology, etc., but there are various situations in mountains and buildings, and the directional characteristics of the antenna are improved. Since it is not possible to expect sufficient suppression of the wraparound only by the measures described above, it is effective to use the wraparound canceller using the circuit technology of (3) in addition to (1) and (2).

As such a circuit technology, the received O
Estimating the frequency characteristics of the sneak path from the FDM signal,
The estimated frequency characteristic data of the wraparound transmission line is IFFT
(Inverse Fast Fourier Transform) is performed to convert to impulse response data on the time axis, and the impulse response data is set as a filter coefficient in the transversal filter to create a wraparound duplicated signal. A method has been devised to cancel the wraparound by subtracting from the received signal.
(For example, IEICE Technical Report, EMCJ98-
111, p. 49-56. )

A conventional technique according to the present invention will be described below with reference to the drawings. FIG. 9 is a schematic diagram showing a pilot signal arrangement of a transmission system which is premised on the above literature and the present invention, and is DVB-T (Digital Video Broadcasting-Terrestria) which is a terrestrial digital broadcasting system in Europe.
l) system and ISD, which is Japanese terrestrial digital broadcasting system
BT (Integrated Services Digital Broadcasting-
Terrestrial) method corresponds to this.

White circles in FIG. 9 indicate control information (TPS (Transmission Parameter Signaling) in DVB-T).
And TMCC (Transmission Mul in ISDB-T
tiplexing Configuration Control)) and additional information (IS
It is a data carrier including AC (Auxiliary Channel) in DB-T, and black circles are pilot carriers (SP (Scattered Pilot)) arranged in a distributed manner.

Further, in FIG. 9, k on the horizontal axis (frequency axis)
Represents a carrier index, and i on the vertical axis (time axis) represents a symbol index. At this time, the SP signal is transmitted using the carrier of index k = kp that satisfies the following (formula 1). (However, mod in the formula represents a remainder operation, and p is a non-negative integer.)

[0009]

[Equation 1] Further, the SP signal is modulated based on a pseudo-random code sequence, and its amplitude and phase are determined only by the index k of the arranged carrier and do not depend on the symbol index i.

FIG. 10 shows an S using a wraparound canceller.
It is a block diagram which shows the model of a FN relay system. Hereinafter, unless otherwise specified, symbols starting with a lowercase letter represent signals and responses in the time domain, symbols beginning with a capital letter represent signals and responses in the frequency domain, and uppercase and lowercase symbols represented by the same letter , Show that they are Fourier transform pairs. The symbol "*" represents a convolution operation. Further, these signals and responses are treated as complex numbers unless otherwise specified.

The receiving unit 2 in FIG.
o Frequency: Converts a signal in the radio frequency band into a signal in the base band (hereinafter, base band), and the transmission unit 4 reversely
Although the baseband signal is converted into the RF band, since these frequency conversions do not have an essential effect on the present invention, the frequency conversions will not be mentioned unless otherwise specified below.

In FIG. 10, x (t) is a master station signal, r
(T) is the input signal of the receiver 2, s (t) is the input signal of the transmitter 4, W_in (ω) is the transfer function of the receiver 2, and W_o
ut (ω) is the transfer function of the transmitter 4, and W_loop (ω)
Is a transfer function of the sneak path 6, and W_fir (ω) is a FIR (Finite Impulse Res) inside the sneak canceller 3.
ponse: Finite impulse response) Represents the transfer function of the filter 32.

In FIG. 10, the receiving antenna 1 has a master station signal x (t) and a sneak signal w_ from a sneak path.
A combined signal with loop (t) * w_out (t) * s (t) is received, and its output r (t) is supplied to the receiving unit 2. The receiving unit 2 performs filter processing, frequency conversion processing, gain adjustment, etc. on the received signal r (t), and its output w_in (t) * r (t) is the sneak-canceller 3
It is supplied to the first input of the internal subtractor 31.

Inside the wrap-around canceller 3, the subtractor 31 outputs the output w_in (t) * r (t) of the receiver 2.
To the output of the FIR filter 32 w_fir (t) * s
(T) is subtracted, and its output s (t) is supplied to the first input of the FIR filter 32 and the filter coefficient generation unit 33, and at the same time as the output of the detour canceller 3.
It is supplied to the transmission unit 4.

The filter coefficient generator 33 estimates the characteristics of the transmission line from the output s (t) of the subtractor 31 and generates a filter coefficient, and its output w_fir (t) is FIR.
It is supplied to the second input of the filter 32.

The FIR filter 32 outputs the output w_f of the filter coefficient generator 33 with respect to the output s (t) of the subtractor 31.
The convolution operation is performed by ir (t) to generate a wraparound replica signal w_fir (t) * s (t), the output of which is supplied to the second input of the subtractor 31.

The transmission unit 4 performs a filtering process, a frequency conversion process, a gain adjustment, etc. on the output s (t) of the subtractor 31 to generate a relay signal w_out (t) * s (t). The output is supplied to the input of the transmitting antenna 5.

The transmitting antenna 5 outputs the output w_ou of the transmitting unit 4.
It radiates t (t) * s (t), and a part of the output passes through the sneak path 6 and becomes a sneak signal w_loop (t) * w_out (t) * s (t). Go around the receiving antenna 1.

FIG. 11 shows a conventional wraparound canceller 3a.
3 is a block diagram showing the configuration of FIG. In FIG. 11, FF
A T (First Fourier Transform) circuit 3301 extracts an effective symbol period from the output s (t) of the subtractor 31 and performs FFT to convert s (t), which is a signal in the time domain, into a signal in the frequency domain. The output S (ω) is supplied to the first input of the complex division circuit 3303.

The pilot generation circuit 3302 generates a specified SP signal whose amplitude and phase are known in synchronization with the output S (ω) of the FFT circuit 3301, and its output Xp (ω) is a complex division. It is supplied to the second input of the circuit 3303.

The complex division circuit 3303 is an FFT circuit 33.
01 output S (ω) received SP signal Sp (ω)
Is divided by the output Xp (ω) of the pilot generation circuit 3302 to obtain the transmission line characteristic Fp (ω) for the pilot carrier, and the output is the interpolation circuit 330.
4 is supplied.

The interpolator 3304 dispersively obtains the transmission line characteristic Fp (ω) for only the pilot carrier.
And the transmission line characteristic F0 (ω) for the entire signal band
Is estimated, and its output is input to the residual calculation circuit 3305.

The residual calculation circuit 3305 includes an interpolation circuit 330.
The cancellation residual E (ω) is calculated from the output F0 (ω) of No. 4 and the output is supplied to the IFFT circuit 3306.

The IFFT circuit 3306 transforms the residual E (ω) in the frequency domain into the residual e (t) in the time domain by IFFTing the output E (ω) of the residual calculation circuit. , Its output is supplied to the coefficient updating circuit 3307.

The coefficient updating circuit 3307 is the IFFT circuit 3
The filter coefficient w_new (t) is calculated from the output e (t) of 306 based on a predetermined coefficient update formula, and the output thereof is the output w_fire of the filter coefficient generation unit 33a.
It is supplied to the second input of the FIR filter 32 as (t).

Next, the conditions under which the detouring canceller 3a cancels the detouring signal will be described. First, the subtractor 31
The transfer function F (ω) of the system at the output of is expressed by (Equation 2).

[0027]

[Equation 2] Therefore, the condition that the detour signal is canceled by the subtractor 31 is expressed by (Equation 3).

[0028]

[Equation 3] Here, the cancellation residual E (ω) is defined as in (Equation 4),

[0029]

[Equation 4] By transforming (Equation 2), (Equation 5) is obtained.

[0030]

[Equation 5] Here, the model is simplified and the transfer function W_in of the receiving unit 2 is
When (ω) = 1, the cancellation residual E (ω) is expressed by (Equation 6).

[0031]

[Equation 6] Further, the coefficient updating formula in the coefficient updating circuit 3307 is defined by (Formula 7).

[0032]

[Equation 7] However, w_old (t) in (Equation 7) is a coefficient before update,
μ is a constant of 1 or less.

With the above configuration, the cancellation residual E (ω), which is the difference between the wraparound transfer function W_loop (ω) W_out (ω) and the transfer function W_fir (ω) of the FIR filter 32, converges to zero. The feedback control is activated to the output s of the detour canceller 3a.
At (t), only the master station signal component is output.

[0034]

In order to make the canceling operation follow the temporal fluctuation of the sneak path, it is desirable that the filter coefficient update interval be as short as possible. on the other hand,
In the detour canceller as described above, since the FFT is used to estimate the transmission path characteristic from the received OFDM symbol, at least the time for the signal for one effective symbol to arrive is required. Also, updating the coefficient during the effective symbol period may adversely affect the operation of the detour canceller itself and the operation of the device that receives the relay signal, so update the coefficient during the guard period near the beginning of the symbol. Is desirable.

FIG. 12 shows a timing relationship in the case where the above-described conventional wrap-around canceller estimates a transmission path characteristic using only SP signals included in one symbol. Here, the calculation time from the arrival of the required signal to the calculation of the coefficient is set to 1 symbol period or less.

In FIG. 12, time slot (i)
Using the SP signal included in the symbol arrived at, the transmission path characteristic is estimated and the coefficient is calculated in the time slot (i + 1), and the coefficient is updated at the head of the time slot (i + 2). Then, the next coefficient is calculated from the symbol reflecting this update, that is, the symbol arriving at the time slot (i + 2), and the coefficient is updated at the beginning of the time slot (i + 4). Therefore, in this case, the coefficient update interval is two symbol periods, which is the minimum update interval under the above-mentioned conditions.

However, when the transmission path characteristic is estimated using only the SP signal included in one symbol, SP
Since pilot carriers for transmitting signals are arranged every 12 carriers, according to the Nyquist sampling theorem,
Only the transmission path characteristics included in the range of 1/12 or less of one effective symbol period can be estimated. Therefore, it is not possible to cancel a sneak signal having a delay time exceeding 1/12 of one effective symbol period. On the other hand, when the transmission path characteristics are estimated using the SP signals for 4 symbols, the carrier interval for transmitting the SP signals is 3 carriers, and even a sneak signal having a delay time of 1/3 of one effective symbol period is canceled. It becomes possible to do.

FIG. 13 shows a timing relationship in the case where the above-described conventional sneak-canceller cancels the transmission path characteristics by using SP signals for four symbols. Also here, the calculation time from the arrival of the required signal to the calculation of the coefficient is set to one symbol period or less.

In FIG. 13, time slot (i)
Using the SP signal included in the symbol arriving at the time slot (i + 3) from, the transmission path characteristic is estimated and the coefficient is calculated at the time slot (i + 4), and the coefficient is updated at the head of the time slot (i + 5). Then, the symbol reflecting this update, that is, the time slot (i +
The next coefficient is calculated from the symbols arriving at time slot (i + 9) from 6), and the coefficient is updated at the beginning of time slot (i + 10).

Therefore, in this case, the coefficient update interval is 5 symbol periods, which is 2.5 times the update interval compared to the case where the transmission path characteristics are estimated using only the SP signal for one symbol described above, and the wraparound transmission is performed. The tracking of the temporal fluctuations of the road deteriorates.

As described above, in the conventional detour canceller as described above, when priority is given to the followability with respect to the temporal variation of the detour transmission path, the range of the delay time that can be canceled is narrowed, and conversely, the delay that can be cancelled. If priority is given to the expansion of time, the followability to the temporal variation of the sneak path is deteriorated.

The present invention has been made in view of the above points, and an object of the present invention is to solve the above-mentioned problems and to provide a wraparound canceller that achieves both improved followability and extended delay time that can be canceled. .

[0043]

In order to solve the above problems, a wraparound canceller according to the present invention is constructed as follows.

The wrap-around canceller of the present invention is a wrap-around canceller for eliminating wrap-around between transmitting and receiving antennas that occurs when a received signal is retransmitted at the same frequency, and a subtractor for subtracting a copy of the wrap-around signal from an input signal. , The estimated wraparound impulse response as a tap coefficient, and convolution of the tap coefficient with the output of the subtractor,
An FIR filter for generating a duplicate of a sneak signal, and a filter coefficient generation unit for estimating a transmission path characteristic of the sneak path by using an output of the subtractor and generating a coefficient of the FIR filter. The filter coefficient generation unit includes FFT means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means, a pilot signal having a prescribed amplitude and phase. By dividing by, the first complex division means for estimating the transmission line characteristic for the pilot carrier, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Second complex division means for compensating the influence of transmission path distortion by dividing the output of the interpolating means and the FFT means by the output of the first interpolating means Determination means for discriminating the output of the second complex division means by a threshold value group according to the modulation method of each carrier, and modulation means for re-modulating the output of the determination means with the modulation method according to each carrier , The FFT
By dividing the output of the means by the output of the modulating means,
Using a third complex division means for estimating the transmission path characteristics for the entire signal band, and the output of the third complex division means,
Residual calculation means for calculating the cancellation residual, IFFT means for converting the output of the residual calculation means into a signal in the time domain, and coefficient updating means for generating the coefficient of the FIR filter from the output of the IFFT means. And a configuration including

According to this structure, the wraparound transfer function W
The feedback control operates so that the cancellation residual E (ω), which is the difference between _loop (ω) W_out (ω) and the transfer function W_fir (ω) of the FIR filter, converges to 0, and the output s ( In t), only the master station signal component is output.

The wrap-around canceler of the present invention is a wrap-around canceller for removing wrap-around between transmitting and receiving antennas that occurs when a received signal is retransmitted at the same frequency, and a subtractor for subtracting a copy of the wrap-around signal from an input signal. , The estimated wraparound impulse response as a tap coefficient, and convolution of the tap coefficient with the output of the subtractor,
An FIR filter for generating a duplicate of a sneak signal, and a filter coefficient generation unit for estimating a transmission path characteristic of the sneak path by using an output of the subtractor and generating a coefficient of the FIR filter. The filter coefficient generation unit includes FFT means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means, a pilot signal having a prescribed amplitude and phase. By dividing by, the first complex division means for estimating the transmission line characteristic for the pilot carrier, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Second complex division means for compensating the influence of transmission path distortion by dividing the output of the interpolating means and the FFT means by the output of the first interpolating means Determination means for discriminating the output of the second complex division means by a threshold value group according to the modulation method of each carrier, and modulation means for re-modulating the output of the determination means with the modulation method according to each carrier , The FFT
By dividing the output of the means by the output of the modulating means,
Third complex division means for estimating transmission path characteristics for the entire signal band, and for pilot carriers, selects the output of the first complex division means, and for other carriers, the third complex division means Output for selecting and outputting the output, a residual calculation unit for calculating a cancellation residual using the output of the selection unit, and an IFFT for converting the output of the residual calculation unit into a signal in the time domain. Means and said I
A configuration including a coefficient updating means for generating a coefficient of the FIR filter from an output of the FFT means is adopted.

According to this structure, the selecting means outputs the output Fp (ω) of the first complex dividing means for the carrier transmitting the SP signal and the third output for the other data carrier. By outputting the output F2 (ω) of the complex division means, it becomes possible to estimate the correct transmission line characteristic for the pilot carrier even in an environment where the judgment means makes a wrong judgment, and the stability of the cancel operation is improved. It becomes possible to do.

The wrap-around canceller of the present invention is a wrap-around canceller for removing wrap-around between transmitting and receiving antennas that occurs when a received signal is retransmitted at the same frequency, and a subtractor for subtracting a copy of the wrap-around signal from an input signal. , The estimated wraparound impulse response as a tap coefficient, and convolution of the tap coefficient with the output of the subtractor,
An FIR filter for generating a duplicate of a sneak signal, and a filter coefficient generation unit for estimating a transmission path characteristic of the sneak path by using an output of the subtractor and generating a coefficient of the FIR filter. The filter coefficient generation unit includes FFT means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means, a pilot signal having a prescribed amplitude and phase. By dividing by, the first complex division means for estimating the transmission line characteristic for the pilot carrier, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Second complex division means for compensating the influence of transmission path distortion by dividing the output of the interpolating means and the FFT means by the output of the first interpolating means Determination means for discriminating the output of the second complex division means by a threshold value group according to the modulation method of each carrier, and modulation means for re-modulating the output of the determination means with the modulation method according to each carrier , The FFT
By dividing the output of the means by the output of the modulating means,
Third complex division means for estimating the transmission line characteristics for the entire signal band, and interpolating the output of the first complex division means,
Second interpolating means for estimating the transmission path characteristics for the entire signal band, reliability calculating means for calculating the reliability of the transmission path characteristics output by the third complex dividing means, and output of the reliability calculating means Accordingly, the cancel residual is calculated by using the output of the second interpolating means and the output of the third complex dividing means by weighted addition, and the output of the synthesizing means. Difference calculating means, and IFFT means for converting the output of the residual calculating means into a time domain signal,
And a coefficient updating means for generating a coefficient of the FIR filter from an output of the IFFT means.

According to this structure, in an environment in which the determination unit makes a wrong determination, the stability of the cancel operation can be improved by using the transmission path characteristic estimated from only the pilot carrier for updating the coefficient. Becomes

The sneak-canceller of the present invention is a sneak-canceller which removes sneak between transmitting and receiving antennas which occurs when a received signal is retransmitted at the same frequency, and a subtracter which subtracts a duplicate of the sneak-signal from an input signal. , The estimated wraparound impulse response as a tap coefficient, and convolution of the tap coefficient with the output of the subtractor,
An FIR filter for generating a duplicate of a sneak signal, and a filter coefficient generation unit for estimating a transmission path characteristic of the sneak path by using an output of the subtractor and generating a coefficient of the FIR filter. The filter coefficient generation unit includes FFT means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means, a pilot signal having a prescribed amplitude and phase. By dividing by, the first complex division means for estimating the transmission line characteristic for the pilot carrier, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Second complex division means for compensating the influence of transmission path distortion by dividing the output of the interpolating means and the FFT means by the output of the first interpolating means Determination means for discriminating the output of the second complex division means by a threshold value group according to the modulation method of each carrier, and modulation means for re-modulating the output of the determination means with the modulation method according to each carrier , The FFT
By dividing the output of the means by the output of the modulating means,
Third complex division means for estimating the transmission line characteristics for the entire signal band, and interpolating the output of the first complex division means,
Second interpolating means for estimating the transmission path characteristics for the entire signal band, reliability calculating means for calculating the reliability of the transmission path characteristics output by the third complex dividing means, and output of the reliability calculating means Accordingly, a synthesizing unit that weights and outputs the output of the second interpolating unit and the output of the third complex dividing unit, a smoothing unit that smoothes the output of the synthesizing unit, and the smoothing unit. Using the output of the conversion unit, a residual calculation unit for calculating a cancellation residual, an IFFT unit for converting the output of the residual calculation unit into a signal in the time domain, and an output of the IFFT unit for the FIR filter. And a coefficient updating means for generating the coefficient of.

According to this structure, the smoothing means has the transmission line characteristic F0 obtained by two methods having different combining means.
By canceling the discontinuity caused by combining (ω) and F2 (ω), cancellation is performed even when the coefficient is updated using the transmission path characteristics obtained by different methods for each carrier or each symbol. It is possible to improve the stability of operation.

In the wrap-around canceller of the present invention, in the above structure, the reliability calculating means is based on a difference between the output of the modulating means and the output of the second complex dividing means,
A configuration is adopted in which the reliability of the transmission path characteristic output by the third complex division means is calculated.

According to this structure, it is possible to improve the stability of the cancel operation.

In the wrap-around canceller of the present invention, in the above configuration, the reliability calculating means determines the transmission line characteristic output by the third complex dividing means based on the magnitude of the output of the first interpolating means. Use a configuration that calculates reliability.

According to this structure, the stability of the cancel operation can be improved.

In the wrap-around canceller of the present invention, in the above configuration, the output of the reliability calculating means is binary information, and the output of the second interpolating means and the output of the second interpolating means are output according to the output of the reliability calculating means. The selecting means for selecting and outputting the output of the third complex dividing means is provided instead of the combining means.

According to this structure, the stability of the cancel operation can be improved, and the processing can be simplified by the selecting means equivalent to the synthesizing means.

[0058]

BEST MODE FOR CARRYING OUT THE INVENTION The essence of the present invention is to use both the hard-decision result of a data carrier for the estimation of transmission line characteristics to achieve both improved followability and expanded cancelable delay time.

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

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a wraparound canceller 3b according to Embodiment 1 of the present invention. In FIG. 1, the subtractor 31 includes a receiving unit 2
Output w_in (t) * r (t) of the FIR filter 3
2 output w_fir (t) * s (t) is subtracted,
The output s (t) is supplied to the first input of the FIR filter 32 and the filter coefficient generation unit 33b, and is also supplied to the transmission unit 4 as the output of the detour canceller 3b.

The filter coefficient generator 33b includes a subtractor 31.
Is estimated from the output s (t) of the transmission line s (t) to generate a filter coefficient.
It is supplied to the second input of the R filter 32.

The FIR filter 32 outputs the output w_ of the filter coefficient generator 33b with respect to the output s (t) of the subtractor 31.
A convolution operation is performed by fir (t) to generate a wraparound duplicate signal w_fir (t) * s (t).
Its output is supplied to the second input of the subtractor 31.

The configuration and operation of the filter coefficient generator 33b inside the wrap-around canceller 3b will be described below.

The FFT circuit 3301 converts the time-domain signal s (t) into a frequency-domain signal by extracting the effective symbol period from the output s (t) of the subtractor 31 and performing FFT. The output S (ω) is supplied to the first input of the complex division circuit 3303, the first input of the complex division circuit 3309, and the first input of the complex division circuit 3312.

The pilot generation circuit 3302 generates a specified SP signal whose amplitude and phase are known in synchronization with the output S (ω) of the FFT circuit 3301, and its output Xp (ω) is a complex division. It is supplied to the second input of the circuit 3303.

The complex division circuit 3303 is an FFT circuit 33.
01 output S (ω) received SP signal Sp (ω)
Is divided by the output Xp (ω) of the pilot generation circuit 3302 to obtain the transmission line characteristic Fp (ω) for the pilot carrier, and the output is the interpolation circuit 330.
8 are supplied.

The interpolating circuit 3308 dispersively obtains the transmission line characteristics Fp (ω) only for the pilot carrier.
Of the transmission line characteristic F1 (ω) for the entire signal band
, Whose output is fed to the second input of the complex division circuit 3309.

The complex division circuit 3309 is the FFT circuit 33.
The output S (ω) of 01 is the output Fp of the interpolation circuit 3308.
By dividing by (ω), the amplitude and phase distortion received by the signal is compensated, and the output Xr (ω) is supplied to the determination circuit 3310.

The decision circuit 3310 is a complex division circuit 330.
The output Xr (ω) of 9 is discriminated by a threshold value group corresponding to the modulation method of each carrier, and its output is supplied to the modulation circuit 3311.

The modulation circuit 3311 modulates the output of the determination circuit 3310 again by the modulation method of each carrier, and its output Xd (ω) is supplied to the second input of the complex division circuit 3312.

In the above-mentioned DVB-T and ISDB-T, as a modulation method of each carrier, BPSK (Binary Phase Shir) is used for pilot signals, control information, and additional information.
ft Keying: 2-phase modulation, QPSK (Quarternary Phase Shift Keying), 16QAM (Quadrature Amplitude Modulatio) for general data
n: quadrature amplitude modulation), 64QAM, etc. are applied.

As an example of the threshold value group used in the determination circuit example 3310, a threshold value group for 16QAM is shown in FIG.
Lines (I (In phase) axis and Q (Qu
adrature phase: including the axis) corresponds to the threshold group. For example, the complex division circuit 33 for a certain carrier
When the output Xr (ω) of 09 is represented by a white circle in the figure, the white circle is included in the hatched area in the figure, and therefore the determination circuit 3310 and the modulation circuit 3311 are
(Ω) X represented by a black circle representing the area
Convert to d (ω).

Although not shown in FIG. 1, the modulation method of each carrier used in the determination circuit 3310 can be easily determined because the arrangement of pilot signals, control information, and additional information is known. As for general data, it can be obtained by demodulating control information (TPS in DVB-T or TMCC in ISDB-T) included in the received signal.

Particularly in the case of ISDB-T, a frequency division type hierarchical transmission system is adopted, and it is possible to multiplex up to three types of modulation systems in one OFDM symbol for general data transmission. Furthermore, in order to prevent the occurrence of burst errors due to frequency-selective interference (multipath interference, co-channel interference, etc.), the carrier arrangement in the frequency direction, called frequency interleaving, is swapped. The modulation method is transmitted in a disordered state. Therefore, when the present invention is applied to the ISDB-T system, it is necessary to rearrange the modulation system for each carrier according to the frequency interleaving pattern.

The complex division circuit 3312 is the FFT circuit 33.
The output S (ω) of 01 is the output Xd of the modulation circuit 3311.
The transmission path characteristic F2 (ω) for all carriers is obtained by dividing by (ω), and the output is input to the residual calculation circuit 3305.

The residual calculation circuit 3305 is a complex division circuit 3
The cancellation residual E (ω) is calculated from the output F2 (ω) of the 312, and its output is supplied to the IFFT circuit 3306.

The IFFT circuit 3306 transforms the residual E (ω) in the frequency domain into the residual e (t) in the time domain by IFFTing the output E (ω) of the residual calculation circuit. , Its output is supplied to the coefficient updating circuit 3307.

The coefficient updating circuit 3307 is the IFFT circuit 3
The filter coefficient w_new (t) is calculated from the output e (t) of 306 based on a predetermined coefficient update formula, and the output is the output w_fire of the filter coefficient generation unit 33b.
It is supplied to the second input of the FIR filter 32 as (t).

Next, the conditions under which the detouring canceller 3b cancels the detouring signal will be described. First, the subtractor 31
The transfer function F (ω) of the system at the output of is expressed by (Equation 8).

[0080]

[Equation 8] Therefore, the condition that the detour signal is canceled by the subtractor 31 is expressed by (Equation 9).

[0081]

[Equation 9] Here, the cancellation residual E (ω) is defined as in (Equation 10),

[0082]

[Equation 10] By transforming (Equation 8), (Equation 11) is obtained.

[0083]

[Equation 11] Here, the model is simplified and the transfer function W_in of the receiving unit 2 is
If (ω) = 1, the cancellation residual E (ω) becomes (Equation 1
It is represented by 2).

[0084]

[Equation 12] Furthermore, the coefficient updating formula in the coefficient updating circuit 3307 is expressed by (Formula 1)
Defined in 3).

[0085]

[Equation 13] However, w_old (t) in (Equation 13) is a coefficient before update, and μ is a constant of 1 or less.

With the above configuration, the cancellation residual E (ω), which is the difference between the wraparound transfer function W_loop (ω) W_out (ω) and the transfer function W_fir (ω) of the FIR filter 37, converges to zero. The feedback control is activated on the output s of the detour canceller 3b.
At (t), only the master station signal component is output.

FIG. 3 shows the timing relationship in this embodiment.

The wrap-around canceller according to the present embodiment requires at least a time for a signal for one effective symbol to arrive because FFT is used to estimate the transmission path characteristic from the received OFDM symbol.

If the coefficient is updated during the effective symbol period, the operation of the detour canceller itself or the operation of the device that receives the relay signal may be adversely affected. Therefore, the coefficient is updated during the guard period near the beginning of the symbol. It is desirable to update.

Here, the calculation time from the arrival of the required signal to the calculation of the coefficient is set to one symbol period or less.

The pilot generation circuit 3302, the complex division circuit 3303, and the interpolation circuit 3308 use the SP signals included in the symbols arriving from time slot (i) to time slot (i + 3) to determine the transmission path characteristics for the entire signal band. Estimate F1 (ω).

Complex division circuit 3309, determination circuit 331
0, and the modulation circuit 3311 uses time slots (i +
3) S (ω) of the symbols arriving at 3) and the above-mentioned F1 (ω)
And are used to calculate the remodulated signal Xd (ω) corresponding to the symbol arriving at the time slot (i + 3).

The complex division circuit 3312 divides the S (ω) of the symbol arriving at the time slot (i + 3) by the remodulated signal Xd (ω) corresponding to the symbol arriving at the time slot (i + 3) to obtain the time. Slot (i
Channel characteristic F2 for the symbol arriving at +3)
Calculate (ω).

Residual calculation circuit 3305 and IFFT circuit 33
06, and the coefficient update circuit 3307, the transmission path characteristic F2 for the symbol arrived at the time slot (i + 3)
A new coefficient w_new (t) is calculated from (ω) and output as the output w_fir (t) of the filter coefficient generation unit 33b.

The FIR filter 32 calculates w_ calculated for the symbol arriving at the time slot (i + 3).
fir (t) is reflected in the coefficient at the beginning of the time slot (i + 5).

Similarly, the following coefficient is calculated for the symbol reflecting this update, that is, the symbol arriving at the time slot (i + 5), and the time slot (i + 7) is calculated.
Update the coefficient at the beginning of.

Therefore, in this case, the coefficient update interval is two symbol periods, which is the same as the case where the transmission path characteristic is estimated using only the SP signal for one symbol in the conventional method, and under the above-mentioned conditions. Is the minimum update interval in.

Further, in the wrap-around canceller according to the present embodiment, in order to estimate the sneak path transmission line characteristics by using not only the SP signal but all the data carriers, in principle, there is a delay time equal to one effective symbol period. It is possible to cancel even the turning signal.

At the timing of FIG. 3, the coefficient calculated for the symbol arriving at the time slot (i + 3) is reflected in the coefficient at the beginning of the time slot (i + 5), and the next coefficient is calculated. , The transmission path characteristic F1 (ω) for the entire signal band is estimated using the SP signal included in the symbol that arrived from time slot (i + 2) to time slot (i + 5). At first glance, it seems that the continuity of the transmission path characteristics is impaired, which causes a problem, but this F1 (ω) is used for compensating the amplitude and phase of the data carrier, and some discontinuity due to coefficient updating, etc. Even if occurs, the influence is eliminated by the non-linear processing of determination by the threshold value.

As described above, according to the sneak-canceller of the present embodiment, it is possible to improve both the follow-up performance and the cancelable delay time.

(Embodiment 2) FIG. 4 is a block diagram showing the structure of a wraparound canceller 3c according to Embodiment 2 of the present invention. 4, the same parts as those in FIG. 1 are designated by the same reference numerals. The wraparound canceller shown in FIG.
The selection circuit 3313a is included in the loop canceller in FIG.
This selection circuit 3313a uses the output Fp (ω) of the complex division circuit 3303 as a first input, the output F2 (ω) of the complex division circuit 3312 as a second input, and its output F3 ( ω) is supplied to the residual calculation circuit 3305. Other configurations and operations are the same as those in FIG.

The selection circuit 3313a outputs the output Fp (ω) of the complex division circuit 3303 for the carrier transmitting the SP signal, and the output F2 (ω) of the complex division circuit 3312 for the other data carriers. Is output.

As described above, according to the detour canceller of the present embodiment, even in an environment where the decision circuit 3310 makes an erroneous decision, it becomes possible to estimate the correct transmission line characteristic for the pilot carrier, and the cancel operation is performed. It is possible to improve stability.

(Third Embodiment) FIG. 5 is a block diagram showing the structure of a wraparound canceller 3d according to a third embodiment of the present invention. 5, the same parts as those in FIG. 1 are designated by the same reference numerals. The wraparound canceller shown in FIG.
An interpolating circuit 330 is added to the wraparound canceller in FIG.
4, combination circuit 3313b, and reliability calculation circuit 3314
Is added.

The interpolation circuit 3304 is a complex division circuit 330.
The output Fp (ω) of 3 is input, and the output F0 (ω) is supplied to the first input of the combining circuit 3313b. The reliability calculation circuit 3314 outputs the output Xr of the complex division circuit 3309.
(Ω) is the first input, and the output Xd of the modulation circuit 3311
(Ω) is the second input, and its output α is the combining circuit 331.
Supply to the third input of 3b. The synthesis circuit 3313b is
The output F0 (ω) of the interpolation circuit 3304 is the first input, the output F2 (ω) of the complex division circuit 3312 is the second input, the output α of the reliability calculation circuit 3314 is the third input, and its output F4 ( ω) is supplied to the residual calculation circuit 3305. Other configurations and operations are the same as those in FIG.

The interpolation circuit 3304 has a transmission line characteristic Fp (ω) obtained dispersively only for pilot carriers.
And the transmission line characteristic F0 (ω) for the entire signal band
To estimate. The reliability calculation circuit 3314 calculates the reliability α of the transmission path characteristic F4 (ω) estimated by using the determination.
Based on the output α of the reliability calculation circuit 3314, the synthesis circuit 3313b outputs the output F0 (ω) of the interpolation circuit 3304,
The combined transmission line characteristic F4 (ω) is calculated by weighted addition with the output F2 (ω) of the complex division circuit 3312. When this is expressed by a mathematical expression, it becomes as shown in (Expression 14).

[0107]

[Equation 14] FIG. 6 is a block diagram showing a first internal configuration example of the reliability calculation circuit. In FIG. 6, the subtractor 33141 is configured to output the output Xr (ω) of the complex division circuit 3309 and the modulation circuit 331.
The difference from the output Xd (ω) of 1 is calculated, and the output is supplied to the power calculation circuit 33142. Power calculation circuit 33142
Calculates the power of the output of the subtractor 33141 and supplies the output to the intra-symbol averaging circuit 33143a. The in-symbol averaging circuit 33143a is used by the power calculating circuit 33142.
Are averaged in the carrier direction within the symbol, and the output is supplied to the conversion circuit 33144. Conversion circuit 3314
In No. 4, when the output of the intra-symbol averaging circuit 33143a is large, the output α is decreased, and conversely, when the output of the intra-symbol averaging circuit 33143a is small, the output α is increased, and the result is Reliability calculation circuit 3
It is output as the output of 314a. Where α is 0 ≦ α ≦
1 should be satisfied.

FIG. 7 is a block diagram showing a second internal configuration example of the reliability calculating circuit. The reliability calculation circuit 3314b shown in FIG. 7 is the reliability calculation circuit 3314a shown in FIG.
The intra-symbol averaging circuit 33143a is replaced with an inter-symbol averaging circuit 33143b, and the inter-symbol averaging circuit 33143b includes a power calculating circuit 33142.
The carriers of the same frequency are averaged in the symbol output in the symbol direction. Other configurations and operations are the same as those in FIG.

As the reliability calculation circuit 3314, the reliability α in the case of using the configuration of FIG. 6 represents the reliability of each symbol, and the reliability α in the case of the configuration of FIG. 7 represents the reliability of each carrier. Represent

As the reliability calculation circuit 3314,
The power of the output F1 (ω) of the interpolation circuit 3308 is calculated and averaged within a symbol or between symbols. If the average value is large, the output α is increased, and conversely, if the average value is small, the output is obtained. A configuration that makes α small is possible.

Further, the output Xr of the complex division circuit 3309
The reliability based on the difference between (ω) and the output Xd (ω) of the modulation circuit 3311 and the reliability based on the power of the output F1 (ω) of the interpolation circuit 3308 are calculated. It is also possible to use both of them together, for example, the lower one is adopted as the reliability α.

Alternatively, the intra-symbol average and the inter-symbol average may be used together, and the combining circuit 3313b may perform weighted addition based on the reliability α for each symbol and each carrier.

If the reliability α is binary information of 0 or 1, the synthesizing circuit 3313b becomes equivalent to the selecting circuit,
The process can be simplified.

Further, in the present embodiment, the interpolating circuit 3304 for calculating F0 (ω) and the interpolating circuit 3308 for calculating F1 (ω) are individually provided. If the methods are the same, it is possible to realize these in one circuit.

As described above, according to the detour canceller of the present embodiment, in an environment where the decision circuit 3310 makes a wrong decision, the transmission path characteristic estimated from only the pilot carrier is used to update the coefficient, thereby canceling. It is possible to improve the stability of operation.

(Fourth Embodiment) FIG. 8 is a block diagram showing the structure of a wraparound canceller 3e according to a fourth embodiment of the present invention. 8, the same parts as those in FIG. 5 are designated by the same reference numerals. The detour canceller shown in FIG. 8 is
The smoothing circuit 3315 is added to the detour canceller in FIG.
This smoothing circuit 3315 receives the output F4 (ω) of the synthesis circuit 3313b as an input, and supplies the output F5 (ω) to the residual calculation circuit 3305. Other configurations and operations are the same as those in FIG.

The smoothing circuit 3315 is a synthesis circuit 3313.
Transmission path characteristics F0 obtained by two methods with different b
It is intended to reduce the discontinuity caused by combining (ω) and F2 (ω), and is configured as a general filter.

As described above, according to the wraparound canceller of the present embodiment, the stability of the cancel operation is improved even when the coefficient is updated using the transmission path characteristics obtained by the different method for each carrier or each symbol. It becomes possible to do.

In all the embodiments of the present invention, the wraparound is canceled in the signal after the frequency conversion is performed in the receiving unit 2, but the wraparound is canceled in the signal before the frequency conversion is performed in the receiving unit 2. Such as canceling
The wraparound may be canceled in the signal of any frequency, and these modifications can be easily configured as long as the superordinate concept is based on the same principle as the present invention.

Further, in the above description, the calculation time from the arrival of the required signal to the calculation of the coefficient is set to one symbol period or less, but the principle of the present invention may be applied regardless of this time. It goes without saying that you can do it.

Further, although not shown in the figure, AD (Analog to Ditital) for digital signal processing used in the detour canceller.
Converter and DA (Digital to Analog)
It goes without saying that the insertion position of the (analog) converter is irrelevant to the principle of the present invention, and the same principle can be applied regardless of the insertion positions of the AD converter and the DA converter.

Finally, in the embodiment of the present invention,
Although each component has been described as embodying a unique function as individual hardware, such an implementation method is irrelevant to the principle of the present invention, and the DSP (Digital
It goes without saying that it may be embodied as software that is executed alone or on a small number of general-purpose hardware by using Signal Processor) or the like.

[0123]

As described above, according to the present invention,
By using the hard decision result of the data carrier for the estimation of the transmission path characteristics, it is possible to improve both the follow-up performance and the cancelable delay time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a detour canceller according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing the operation of a determination circuit and a modulation circuit in the wraparound canceller of the present invention.

FIG. 3 is a timing chart showing the operation timing of the present invention.

FIG. 4 is a block diagram showing a configuration of a detour canceller according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a detour canceller according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a first internal configuration example of a reliability calculation circuit in FIGS. 5 and 8;

FIG. 7 is a block diagram showing a second internal configuration example of the reliability calculation circuit in FIGS. 5 and 8;

FIG. 8 is a block diagram showing a configuration of a detour canceller according to a fourth embodiment of the present invention.

FIG. 9 is a schematic diagram showing an example of pilot signal arrangement according to the present invention.

FIG. 10 is a block diagram showing an example of a principle configuration of a relay station system using a detour canceller, which is a premise of the present invention.

FIG. 11 is a block diagram showing a configuration example of a conventional wraparound canceller.

FIG. 12 is a timing chart in the case of estimating the transmission path characteristic using only the SP signal for one symbol in the conventional wrap-around canceller.

FIG. 13 is a timing chart in the case of estimating transmission path characteristics by using SP signals for 4 symbols in a conventional wraparound canceller.

[Explanation of symbols]

1 receiving antenna 2 Receiver 3 wraparound canceller 4 transmitter 5 transmitting antenna 6 Roundabout transmission line 31 Subtractor 32 FIR filter 33 Filter Coefficient Generation Unit 3301 FFT circuit 3302 Pilot generation circuit 3303 Complex division circuit 3304 Interpolation circuit 3305 Residual calculation circuit 3306 IFFT circuit 3307 coefficient update circuit 3308 Interpolation circuit 3309 Complex division circuit 3310 judgment circuit 3311 Modulation circuit 3312 Complex division circuit 3313a selection circuit 3313b Synthesis circuit 3314 Reliability calculation circuit 33141 Subtractor 33142 Power calculation circuit 33143a Intra-symbol averaging circuit 33143b Inter-symbol averaging circuit 33144 conversion circuit 3315 Smoothing circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Suzuki Ichi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Sadaji Kageyama             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Kennori Kunieda             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5K022 DD01 DD13 DD18 DD19 DD23                       DD33                 5K046 AA05 BB00 HH18 HH42 HH47                       HH53 HH76

Claims (7)

[Claims] 1. A detouring canceller for removing a detouring between a transmitting antenna and a receiving antenna, which occurs when a received signal is retransmitted at the same frequency, and a subtractor for subtracting a duplicated signal from an input signal, and an estimated detouring method. Is used as a tap coefficient, and the tap coefficient is convoluted with the output of the subtractor to generate a replica of the wraparound signal.
esponse: finite impulse response) filter, using the output of the subtractor, to estimate the transmission path characteristics of the wraparound, a filter coefficient generation unit for generating the coefficient of the FIR filter, the filter coefficient generation unit, FFT (Fast Fourier Transform) means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means with a specified amplitude and phase. First complex division means for estimating the transmission line characteristic for the pilot carrier by dividing by the pilot signal, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Compensating the influence of the transmission line distortion by dividing the output of the first interpolating means and the FFT means by the output of the first interpolating means. A second complex division means, a determination means for discriminating the output of the second complex division means by a threshold value group corresponding to the modulation method of each carrier, and the output of the determination means is modulated according to each carrier. A modulation unit that re-modulates by a method, a third complex division unit that estimates the transmission path characteristic for the entire signal band by dividing the output of the FFT unit by the output of the modulation unit, and the third complex division unit Using the output of the means, residual calculation means for calculating the cancellation residual, IFFT (Inverse Fast Fourier Transform) means for converting the output of the residual calculation means into a signal in the time domain, A wrap-around canceller, comprising: coefficient updating means for generating a coefficient of the FIR filter from an output of the IFFT means. 2. A wrap-around canceller for removing wrap-around between transmitting and receiving antennas that occurs when a received signal is retransmitted at the same frequency, and a subtractor for subtracting a duplicate of the wrap-around signal from an input signal, and an estimated wrap-around. Is used as a tap coefficient, and the tap coefficient is convoluted with the output of the subtractor to generate a replica of the wraparound signal.
esponse: finite impulse response) filter, using the output of the subtractor, to estimate the transmission path characteristics of the wraparound, a filter coefficient generation unit for generating the coefficient of the FIR filter, the filter coefficient generation unit, FFT (Fast Fourier Transform) means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means with a specified amplitude and phase. First complex division means for estimating the transmission line characteristic for the pilot carrier by dividing by the pilot signal, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Compensating the influence of the transmission line distortion by dividing the output of the first interpolating means and the FFT means by the output of the first interpolating means. A second complex division means, a determination means for discriminating the output of the second complex division means by a threshold value group corresponding to the modulation method of each carrier, and the output of the determination means is modulated according to each carrier. A modulation means for re-modulating by a method, a third complex division means for estimating the transmission path characteristic for the entire signal band by dividing the output of the FFT means by the output of the modulation means, and for the pilot carrier , Selecting the output of the first complex division means, selecting the output of the third complex division means for other carriers and outputting the same, and using the output of the selection means, cancel residual An IFFT (Inverse Fast Fourier Transform) means for converting the output of the residual calculation means into a signal in the time domain, and an output of the IFFT means. Et al., Wraparound canceller characterized by comprising a coefficient updating means for generating the coefficients of the FIR filter. 3. A detouring canceller for removing a detouring between a transmitting antenna and a receiving antenna, which occurs when a received signal is retransmitted at the same frequency, and a subtractor for subtracting a copy of the detouring signal from an input signal, and an estimated detouring. Is used as a tap coefficient, and the tap coefficient is convoluted with the output of the subtractor to generate a replica of the wraparound signal.
esponse: finite impulse response) filter, using the output of the subtractor, to estimate the transmission path characteristics of the wraparound, a filter coefficient generation unit for generating the coefficient of the FIR filter, the filter coefficient generation unit, FFT (Fast Fourier Transform) means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means with a specified amplitude and phase. First complex division means for estimating the transmission line characteristic for the pilot carrier by dividing by the pilot signal, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Compensating the influence of the transmission line distortion by dividing the output of the first interpolating means and the FFT means by the output of the first interpolating means. A second complex division means, a determination means for discriminating the output of the second complex division means by a threshold value group corresponding to the modulation method of each carrier, and the output of the determination means is modulated according to each carrier. A modulation unit that re-modulates by a method, a third complex division unit that estimates the transmission path characteristic for the entire signal band by dividing the output of the FFT unit by the output of the modulation unit, and the first complex division unit Second interpolating means for interpolating the output of the means and estimating the transmission path characteristics for the entire signal band; reliability calculating means for calculating the reliability of the transmission path characteristics output by the third complex division means; Depending on the output of the reliability calculation means, the output of the second interpolation means, the combining means for weighted addition of the output of the third complex division means, and output, by using the output of the combining means, Cancel residual Output residual calculation means, output of the residual calculation means, IFFT (Inverse Fast Fourier Transform: Inverse Fast Fourier Transform) means for converting the signal in the time domain, and the output of the IFFT means, from the output of the FIR filter A wraparound canceller, comprising: coefficient updating means for generating a coefficient. 4. A detouring canceller for removing a detouring between a transmitting antenna and a receiving antenna, which occurs when a received signal is retransmitted at the same frequency, and a subtractor for subtracting a duplicated signal from an input signal, and an estimated detouring method. Is used as a tap coefficient, and the tap coefficient is convoluted with the output of the subtractor to generate a replica of the wraparound signal.
esponse: finite impulse response) filter, using the output of the subtractor, to estimate the transmission path characteristics of the wraparound, a filter coefficient generation unit for generating the coefficient of the FIR filter, the filter coefficient generation unit, FFT (Fast Fourier Transform) means for converting the output of the subtractor, which is a signal in the time domain, into a signal in the frequency domain, and a pilot carrier included in the output of the FFT means with a specified amplitude and phase. First complex division means for estimating the transmission line characteristic for the pilot carrier by dividing by the pilot signal, and the output of the first complex division means is interpolated to estimate the transmission line characteristic for the entire signal band. Compensating the influence of the transmission line distortion by dividing the output of the first interpolating means and the FFT means by the output of the first interpolating means. A second complex division means, a determination means for discriminating the output of the second complex division means by a threshold value group corresponding to the modulation method of each carrier, and the output of the determination means is modulated according to each carrier. A modulation unit that re-modulates by a method, a third complex division unit that estimates the transmission path characteristic for the entire signal band by dividing the output of the FFT unit by the output of the modulation unit, and the first complex division unit Second interpolating means for interpolating the output of the means and estimating the transmission path characteristics for the entire signal band; reliability calculating means for calculating the reliability of the transmission path characteristics output by the third complex division means; In accordance with the output of the reliability calculation means, the output of the second interpolation means and the output of the third complex division means are weighted and added, and the combined means is output, and the output of the combined means is smoothed. Smoothing means, Using the output of the smoothing means, a residual calculation means for calculating a cancellation residual, and an IFFT (Inverse Fast Fourier Transform) for converting the output of the residual calculation means into a signal in the time domain. And a coefficient updating means for generating a coefficient of the FIR filter from an output of the IFFT means. 5. The reliability calculation means calculates the reliability of the transmission line characteristic output by the third complex division means based on the difference between the output of the modulation means and the output of the second complex division means. The detour canceller according to claim 3 or 4, wherein the detour canceller is calculated. 6. The reliability calculation means calculates the reliability of the transmission path characteristic output by the third complex division means, based on the magnitude of the output of the first interpolation means. The wraparound canceller according to claim 3 or 4. 7. The output of the reliability calculation means is binary information, and the output of the second interpolation means and the output of the third complex division means are output according to the output of the reliability calculation means. The wraparound canceller according to claim 3 or 4, further comprising: a selecting unit that selects and outputs, instead of the combining unit.