JP2012222487A - Transmission path characteristic estimation device, transmission path characteristic estimation method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of noise, and also to improve the time followability of a transmission path characteristic.SOLUTION: Infinite impulse response (IIR) filters 109, 110 calculate the movement average values of transmission path characteristics estimated by a current transmission path characteristic estimation part. A next transmission path characteristic estimation part estimates a next-time transmission path characteristic based on the outputs of the IIR filters 109, 110 and a coefficient stored by a coefficient storage part 114. The coefficient stored by the coefficient storage part 114 is the coefficient which is calculated based on a difference between the outputs of the movement average values of transmission path characteristics previously calculated by the IIR filters 109, 110 with different oblivion coefficients and also a transmission path characteristic estimated by a pilot complex division part 101.

Description

  The present invention relates to a transmission line characteristic estimation apparatus, a transmission line characteristic estimation method, and a program for estimating a transmission line characteristic of a next reception symbol from a plurality of consecutive reception symbols.

In OFDM (Orthogonal Frequency Division Multiplexing) communication in which continuous communication is performed, a transmitter apparatus inserts pilot symbols at predetermined intervals, and a receiver apparatus estimates channel characteristics based on the pilot symbols. A method of performing demodulation is used. A pilot symbol is a signal pattern that is known in the transmission apparatus and the reception apparatus.
As a simple method for channel estimation, a method is used in which pilot symbols are linearly interpolated in the time direction (see, for example, Patent Document 1).

JP 2002-374418 A

However, the method of linearly interpolating between pilot symbols in the time direction has a large influence of noise, and as shown in FIG. 7, the channel characteristics are IQ (In-phase-Quadrature phase) planes. In the case of changing so as to draw a curve, there is a problem that a deviation occurs between the estimated transmission line characteristic and the actual transmission line characteristic. FIG. 7 is a diagram illustrating the estimation result of the transmission path characteristics by interpolation.
In addition, when this method is used, a data symbol in between cannot be demodulated until a pilot symbol and the next pilot symbol are received, so a memory for storing received data is required, and the processing delay time is further increased. There is a problem.

As a transmission path characteristic estimation method that reduces the influence of noise, there is a method of estimating transmission path characteristics by taking an average of a plurality of pilot symbols. When this method is used, the influence of noise can be reduced as compared with the method using linear interpolation. However, when this method is used, it is necessary to average the transmission path characteristics obtained from the pilot symbols in the range before and after the data symbol to be demodulated. Therefore, there is a problem that it becomes more difficult to follow the curve variation of the transmission path characteristics as compared with the method using linear interpolation. Further, the capacity of the memory for storing the received data is increased as compared with the method using linear interpolation, and there is a problem that the processing delay time is increased.
In order to reduce memory capacity and reduce delay time, there is a method of averaging only pilot symbols past data symbols to be demodulated. In this case, the follow-up of the estimated value with respect to temporal fluctuations in the channel characteristics is possible. There is a problem of getting worse.

  The present invention has been made in order to solve the above-described problem, and is a transmission path characteristic estimation apparatus that estimates a transmission path characteristic of a next reception symbol from a plurality of consecutive reception symbols. A current channel characteristic estimation unit for estimating the current channel characteristic, and a moving average value of the channel characteristic estimated by the current transmission characteristic estimation unit using a predetermined smoothing coefficient for each reception of the received symbol. And a channel characteristic estimated by the current transmission characteristic estimation unit using a smoothing coefficient different from the smoothing coefficient of the first smoothing unit for each reception of the received symbol. A second smoothing unit that calculates a moving average value of the first channel, a transmission channel characteristic estimated by the current transmission channel characteristic estimation unit, and a moving average value calculated by the first smoothing unit at the previous reception of the received symbol The difference between A division unit that divides by the difference between the moving average value calculated by the first smoothing unit at the time of reception and the moving average value calculated by the second smoothing unit at the previous reception of the received symbol; The difference between the moving average value calculated by the first smoothing unit and the moving average value calculated by the second smoothing unit is multiplied by the calculation result of the dividing unit, and the value is calculated by the first smoothing unit. And a next transmission path characteristic estimation unit that estimates the transmission path characteristic of the next received symbol by adding the calculated moving average value.

  The present invention also provides a transmission path characteristic estimation method using a transmission path characteristic estimation apparatus that estimates a transmission path characteristic of a next reception symbol from a plurality of consecutive reception symbols, and each time a reception symbol is received, The transmission line characteristic estimation unit estimates a current transmission line characteristic, and the first smoothing unit calculates a moving average value of the transmission line characteristic estimated by the current transmission characteristic estimation unit using a predetermined smoothing coefficient. The second smoothing unit uses the smoothing coefficient different from the smoothing coefficient of the first smoothing unit for each reception of the received symbol, to determine the channel characteristic estimated by the current transmission characteristic estimating unit. A moving average value is calculated, and the division unit calculates a difference between the transmission path characteristic estimated by the current transmission path characteristic estimation unit and the moving average value calculated by the first smoothing unit at the previous reception of the received symbol. The first smoothing unit at the previous reception of the received symbol Dividing by the difference between the calculated moving average value and the moving average value calculated by the second smoothing unit at the previous reception of the received symbol, the next transmission path characteristic estimating unit is configured by the first smoothing unit. The difference between the calculated moving average value and the moving average value calculated by the second smoothing unit is multiplied by the calculation result of the dividing unit, and the moving average value calculated by the first smoothing unit is multiplied by the value. The transmission path characteristics of the next received symbol are estimated by addition.

  In addition, the present invention provides a transmission path characteristic estimation device that estimates a transmission path characteristic of a next reception symbol from a plurality of consecutive reception symbols, and a current transmission path characteristic that estimates a current transmission path characteristic for each reception of the reception symbol. An estimation unit, a first smoothing unit that calculates a moving average value of a transmission path characteristic estimated by the current transmission characteristic estimation unit using a predetermined smoothing coefficient for each reception of the reception symbol, and for each reception of the reception symbol A second smoothing unit for calculating a moving average value of the transmission path characteristics estimated by the current transmission characteristic estimation unit using a smoothing coefficient different from the smoothing coefficient of the first smoothing unit, and the current transmission path The difference between the transmission path characteristic estimated by the characteristic estimation unit and the moving average value calculated by the first smoothing unit at the previous reception of the received symbol is expressed as the first smoothing at the previous reception of the received symbol. The moving average value calculated by the A division unit that divides by a difference from the moving average value calculated by the second smoothing unit at the previous reception of a reception symbol, the moving average value calculated by the first smoothing unit, and the second smoothing unit Is multiplied by the calculation result of the division unit, and the moving average value calculated by the first smoothing unit is added to the value, whereby the transmission path characteristic of the next received symbol is calculated. Is a program for operating as a next transmission path characteristic estimation unit.

  According to the present invention, the coefficient used for estimating the channel characteristic in the next received symbol is calculated by the processing of the division unit, and the next channel characteristic estimating unit uses the coefficient to calculate the channel characteristic in the next received symbol. presume. Thereby, the transmission path characteristic estimation apparatus can estimate the transmission path characteristic in the next received symbol with high accuracy based on the moving average value of the current transmission path characteristic and the past transmission path characteristic.

It is a schematic block diagram which shows the structure of the demodulation apparatus carrying the transmission line characteristic estimation apparatus by one Embodiment of this invention. It is a figure which shows an example of the pattern of the transmission frame of OFDM. It is a flowchart which shows operation | movement of the demodulation apparatus with respect to a data symbol. It is a flowchart which shows operation | movement of the demodulation apparatus with respect to a pilot symbol. It is a figure which shows the estimation result of the transmission line characteristic by the demodulation apparatus by this embodiment. It is a figure which shows the other example of the pattern of the transmission frame of OFDM. It is a figure which shows the estimation result of the transmission line characteristic by interpolation.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic block diagram showing a configuration of a demodulation device 100 equipped with a transmission path characteristic estimation device according to an embodiment of the present invention.
The demodulator 100 is an apparatus that receives input of FFT output data (received symbols) from a receiver that receives an OFDM frame and performs FFT (Fast Fourier Transform) processing, and performs demodulation processing on each subcarrier. is there. Demodulator 100 includes pilot complex division unit 101, transmission path characteristic storage unit 102, phase amplitude compensation unit 103, demapping unit 104, remapping unit 105, complex division unit 106, slope correction unit 107, switch unit 108, IIR (infinite impulse). Response: Infinite Impulse Response) filter 109 (second smoothing unit), IIR filter 110 (first smoothing unit), moving average value buffers 111 and 112, coefficient calculation unit 113 (division unit), coefficient storage unit 114 , A next transmission path characteristic estimation unit 115 and a transmission path characteristic buffer 116 are provided.

When the received symbol is a pilot symbol, pilot complex division section 101 performs complex division on the received pilot symbol by a known pilot symbol model to calculate transmission path characteristics. In the present embodiment, the complex number calculation for the received symbol is performed by treating the I component of the received symbol as a real component and the Q component as an imaginary component.
The transmission path characteristic storage unit 102 stores the transmission path characteristic calculated by the pilot complex division unit 101. Note that the transmission path characteristics stored in the transmission path characteristics storage unit 102 are updated each time the transmission path characteristics are calculated by the pilot complex division unit 101.

When the received symbol is a data symbol, the phase / amplitude compensation unit 103 reproduces the transmission symbol by dividing the received data symbol by the transmission path characteristic stored in the transmission path characteristic buffer 116. The transmission path characteristic stored in the transmission path characteristic buffer 116 is the transmission path characteristic at the time of the next reception of the received symbol, which is estimated by the next transmission path characteristic estimation unit 115 when the received symbol is received last time, that is, the current Transmission path characteristics.
The demapping unit 104 outputs bit data of “0” or “1” from the transmission symbol reproduced by the phase amplitude compensation unit 103 according to a predetermined phase amplitude modulation method. Examples of the phase amplitude modulation method include QPSK (Quadrature Phase Shift Keying) and 16QAM (16-Quadrature Amplitude Modulation).

The remapping unit 105 generates a transmission symbol from the bit data output from the demapping unit 104 based on a predetermined phase amplitude modulation method. The transmission symbol reproduced by the phase amplitude compensation unit 103 includes an estimation error of transmission path characteristics, but the transmission symbol generated by the remapping unit 105 does not include an error.
When the received symbol is a data symbol, the complex division unit 106 calculates transmission path characteristics by performing complex division on the transmission symbol generated by the remapping unit 105 by the received data symbol.

  The inclination correction unit 107 corrects the transmission path characteristics so that the constellation is aligned based on the transmission path characteristics stored in the transmission path characteristic buffer 116 and the transmission path characteristics stored in the transmission path characteristic storage unit 102. In other words, the tilt correction unit 107 corrects the transmission line characteristics so that, when the constellation is caught in a state tilted at any one of 90 degrees, 180 degrees, and 270 degrees during the initial operation of the receiver, it is corrected. Correct. Specifically, the inclination correction unit 107 uses the following equation (1) to determine the complex conjugate of the transmission path characteristic stored in the transmission path characteristic storage unit 102 and the transmission path characteristic stored in the transmission path characteristic buffer 116. Calculate the time average of complex multiplication.

Here, h _p (n) is a transmission path characteristic stored in the transmission path characteristic storage unit 102 at the nth symbol of the received symbol. The superscript side line is a symbol indicating the complex conjugate of the value. H (n) is a transmission path characteristic stored in the transmission path characteristic buffer 116 at the nth symbol of the received symbol.

Then, when the angle between the complex number calculated by the equation (1) and the real number axis is within a range of ± 45 degrees (when the constellation inclination is correct), the inclination correcting unit 107 Is output to the switch unit 108, and when it is out of the range of ± 45 degrees, the transmission channel characteristic stored in the transmission channel characteristic storage unit 102 is output to the switch unit 108 (correcting the transmission channel characteristic is corrected). To do).
When the received symbol is a pilot symbol, the switch unit 108 selects the calculation result of the pilot complex division unit 101 and outputs it to the IIR filters 109 and 110. When the received symbol is a data symbol, the switch 108 corrects the inclination. Is output to the IIR filters 109 and 110.
Pilot complex division section 101, transmission path characteristic storage section 102, complex division section 106, slope correction section 107, and switch section 108 cooperate to estimate the current transmission path characteristics every time a received symbol is received. It operates as a current transmission path characteristic estimation unit.

The IIR filters 109 and 110 are first-order IIR filters that calculate an exponential moving average value of input values using a predetermined forgetting factor. The IIR filter 109 and the IIR filter 110 calculate exponential moving average values using different forgetting factors. Two different values of 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, and 1/128 are used as the forgetting coefficients of the IIR filters 109 and 110.
Specifically, the IIR filter 109 calculates an exponential moving average value by the following equation (2), and the IIR filter 110 calculates an exponential moving average value by the following equation (3).

Here, h _a (n) is an exponential moving average value of transmission path characteristics calculated by the IIR filter 109 at the nth symbol of the received symbol. Further, a is a forgetting factor used by the IIR filter 109. Further, h is a transmission path characteristic output from the switch unit 108. Here, h _a (n−1) is an exponential moving average value of the transmission path characteristic calculated by the IIR filter 109 at the n−1th symbol of the received symbol, and is stored in the moving average value buffer 111 at the nth symbol of the received symbol. It is a stored value.

Further, h _b (n) is an exponential moving average value of transmission path characteristics calculated by the IIR filter 110 at the nth symbol of the received symbol. B is a forgetting factor used by the IIR filter 110. Note that h _b (n−1) is an exponential moving average value of the channel characteristics calculated by the IIR filter 110 at the n−1th symbol of the received symbol, and is stored in the moving average value buffer 112 at the nth symbol of the received symbol. It is a stored value.
Moving average value buffers 111 and 112 store exponential moving average values of transmission path characteristics calculated by IIR filters 109 and 110, respectively, at the previous reception of received symbols.

Coefficient calculation unit 113, a transmission path characteristic _h p for the pilot complex division section 101 is calculated (n), exponential moving average of the channel characteristics moving average buffer 111 stores values _h a (n-1) and Based on h _b (n−1), a coefficient α used to estimate the transmission path characteristics in the next received symbol is calculated. Specifically, the coefficient calculation unit 113 calculates the values of the following expressions (4) and (5).

  And the coefficient calculation part 113 calculates the time average value of the calculation result of Formula (4) and Formula (5), and calculates coefficient (alpha) based on Formula (6).

  However, average {} is a time average value of the values in parentheses. Note that the time average value calculation method includes a simple moving average, a weighted moving average (FIR (Finite Impulse Response) filter average), an exponential moving average (IIR filter average), and the like. Is used, the coefficient α can be calculated by the following equation (7).

The coefficient storage unit 114 stores the coefficient α calculated by the coefficient calculation unit 113. The coefficient stored in the coefficient storage unit 114 is updated every time the coefficient α is calculated by the coefficient calculation unit 113.
The next transmission line characteristic estimation unit 115 is based on the coefficient α stored in the coefficient storage unit 114 and the exponential moving average values h _a (n) and h _b (n) of the transmission line characteristics calculated by the IIR filters 109 and 110. Thus, the transmission path characteristic in the next received symbol is estimated. Specifically, the next transmission path characteristic estimation unit 115 estimates the transmission path characteristic H (n + 1) in the next received symbol by calculating the following equation (8).

  The transmission path characteristic buffer 116 stores the transmission path characteristic estimated by the next transmission path characteristic estimation unit 115.

  With the above-described configuration, the demodulator 100 can accurately estimate the transmission path characteristic of the next received symbol based on the moving average value of the current transmission path characteristic and the past transmission path characteristic.

Here, the reason why the coefficient calculation unit 113 calculates the coefficient α using Expression (6) will be described.
When the transmission path characteristic H (n + 1) in the next received symbol is expressed by Expression (8), the transmission path characteristic h _p (n) obtained from a known pilot symbol can be expressed by Expression (9) shown below. it can.

  Here, the coefficient α can be expressed by the following equation (10) by performing equation transformation on the equation (9).

  Incidentally, in order to reduce the influence of noise included in the estimated transmission path characteristics, it is preferable to calculate the coefficient α using a time average value. Therefore, in order to prevent the denominator of Equation (10) from becoming 0, the denominator and numerator of Equation (10) are each multiplied by a complex conjugate of the denominator value so that the denominator becomes a positive real number. Thereby, Formula (6) is obtained.

Hereinafter, the operation of the demodulation device 100 will be described.
FIG. 2 is a diagram illustrating an example of an OFDM transmission frame pattern.
As shown in FIG. 2, in the present embodiment, when transmitting a transmission frame, the transmission apparatus inserts one pilot signal for every 12 data symbols. Therefore, demodulating apparatus 100 performs channel characteristic estimation based on pilot symbols for every 12 received symbols received from the receiving apparatus, and otherwise performs data symbol demodulation processing and channel characteristic estimation.

First, data symbol demodulation processing and transmission path characteristic estimation processing by the demodulator 100 will be described.
FIG. 3 is a flowchart showing the operation of the demodulator 100 for data symbols.
First, when receiving an input of a data symbol from the receiving device, the phase amplitude compensation unit 103 reproduces the transmission symbol by dividing the data symbol that has received the input by the transmission path characteristic stored in the transmission path characteristic buffer 116 ( Step S1). Next, the demapping unit 104 performs a hard decision from the transmission symbol reproduced by the phase amplitude compensation unit 103 according to a predetermined amplitude phase modulation method, and generates bit data (step S2). The bit data is output to the processing device as a demodulation result.

  Next, the remapping unit 105 generates a transmission symbol from the bit data generated by the demapping unit 104 based on a predetermined amplitude phase modulation method (step S3). Next, the complex division unit 106 estimates transmission path characteristics by performing complex division on the data symbol that has received the input by the transmission symbol generated by the remapping unit 105 (step S4). Next, the inclination correction unit 107 calculates the above equation (1) using the transmission path characteristics stored in the transmission path characteristics storage section 102 and the transmission path characteristics stored in the transmission path characteristics buffer 116 (step S5). Next, the inclination correction unit 107 determines whether or not the angle formed by the calculation result of Expression (1) and the real number axis is within a range of ± 45 degrees (step S6).

  When the angle formed by the calculation result of Expression (1) and the real axis is within a range of ± 45 degrees (step S6: YES), the inclination correction unit 107 calculates the transmission path characteristics calculated by the complex division unit 106. It outputs to the switch part 108 (step S7). On the other hand, when the angle formed by the calculation result of Expression (1) and the real number axis is outside the range of ± 45 degrees (step S6: NO), the inclination correction unit 107 stores the transmission path characteristic storage unit 102. The transmission path characteristics are output to the switch unit 108 (step S8).

When the switch unit 108 receives the input of the transmission path characteristic in step S7 or step S8, the switching unit 108 outputs the transmission path characteristic to the IIR filters 109 and 110. The IIR filters 109 and 110 calculate the exponential moving average value of the transmission path characteristics based on the expressions (2) and (3), respectively (step S9). At this time, the IIR filters 109 and 110 record the exponential moving average values of the transmission path characteristics calculated at the previous reception of the received symbols in the moving average value buffers 111 and 112, respectively (step S10).
Then, the next transmission path characteristic estimation unit 115 uses the exponential moving average value of the transmission path characteristics calculated by the IIR filters 109 and 110 and the coefficient α stored in the coefficient storage unit 114 based on the equation (8). The transmission path characteristics in the received symbols are estimated (step S11). The next transmission line characteristic estimation unit 115 records the estimated transmission line characteristic in the transmission line characteristic buffer 116 (step S12). The transmission path characteristic is used when the next data symbol is received.

First, transmission path characteristic estimation processing based on pilot symbols by demodulator 100 will be described.
FIG. 4 is a flowchart showing the operation of the demodulation apparatus 100 for pilot symbols.
First, upon receiving an input of a pilot symbol from the receiving apparatus, pilot complex division section 101 estimates a transmission path characteristic by dividing the pilot symbol that has received the input by a predetermined pilot symbol model (step S13). . The pilot complex division unit 101 records the estimated transmission path characteristic in the transmission path characteristic storage unit 102 (step S14).

  Pilot complex division section 101 also outputs the estimated transmission path characteristics to switch section 108. When receiving an input of the transmission path characteristic, the switch unit 108 outputs the transmission path characteristic to the IIR filters 109 and 110. The IIR filters 109 and 110 calculate the exponential moving average value of the transmission path characteristics based on the equations (2) and (3), respectively (step S15). At this time, the IIR filters 109 and 110 record the exponential moving average values of the transmission path characteristics calculated at the previous reception of the received symbols in the moving average value buffers 111 and 112, respectively (step S16).

  Further, the coefficient calculation unit 113 uses the transmission path characteristic estimated by the pilot complex division unit 101 and the exponential moving average value of the transmission path characteristic at the previous reception time of the received symbol stored in the moving average value buffers 111 and 112. Based on the equation (6), the coefficient α used for estimating the channel characteristics in the next received symbol is calculated (step S17). The coefficient calculation unit 113 records the calculated coefficient α in the coefficient storage unit 114 (step S18).

  Then, the next transmission path characteristic estimation unit 115 uses the exponential moving average value of the transmission path characteristics calculated by the IIR filters 109 and 110 and the coefficient α stored in the coefficient storage unit 114 based on the equation (8). The transmission path characteristics in the received symbols are estimated (step S19). The next transmission line characteristic estimation unit 115 records the estimated transmission line characteristic in the transmission line characteristic buffer 116 (step S20). The transmission path characteristic is used when the next data symbol is received.

  Thus, according to the present embodiment, the influence of noise is reduced by providing the IIR filters 109 and 110. Furthermore, according to the present embodiment, the transmission path by the IIR filters 109 and 110 is performed by performing the process of estimating the current transmission path characteristics from the difference between the outputs of the IIR filters 109 and 110 having different forgetting coefficients (smoothing coefficients). It is possible to improve the deterioration of the time followability of characteristics.

FIG. 5 is a diagram illustrating the estimation result of the transmission path characteristics by the demodulator 100 according to the present embodiment.
According to the present embodiment, as shown in FIG. 5, even when the transmission path characteristic draws a curved locus on the complex plane, the transmission path characteristic is adjusted by appropriately adjusting the imaginary part of the coefficient α. Is accurately estimated.

  Further, according to the present embodiment, when the data symbol is received, the transmission path characteristics at that time are already estimated, and thus the demodulator 100 does not need to include a storage unit for accumulating data of the FFT output signal. .

  As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

FIG. 6 is a diagram illustrating another example of an OFDM transmission frame pattern.
For example, in the present embodiment, a case has been described where an OFDM transmission frame in which pilot symbols and data symbols are repeated at the same timing in each subcarrier as shown in FIG. 2 is not limited to this. For example, as an OFDM transmission frame, as shown in FIG. 6A, a pilot symbol and a data symbol are repeated at different timings in each subcarrier, or as shown in FIG. One in which pilot symbols are arranged only on the carrier can be mentioned.

  When pilot symbols are arranged only on specific subcarriers as shown in FIG. 6B, subcarriers without pilot symbols are interpolated in the frequency direction or frequency-time direction (FIG. 6B). By using as a substitute for a pilot symbol, the present invention can be implemented.

In this embodiment, the case where the coefficient α is calculated using the equation (6) has been described. However, the present invention is not limited to this. It may be calculated. However, in this case, it is more susceptible to noise as compared to the case of using Equation (6).
Also, by preparing an exception process when the denominator becomes 0, the coefficient α can be calculated using Expression (10) instead of Expression (6).

  Further, in the present embodiment, the case where the coefficient calculation unit 113 calculates the coefficient α only at the time of receiving a pilot symbol has been described. However, the present invention is not limited to this, and the coefficient is calculated using the output of the switch unit 108 when receiving a data symbol. α may be calculated. However, since the channel characteristics estimated from the pilot symbols have higher accuracy than the channel characteristics estimated from the data symbols, the accuracy of the coefficient α is higher when the coefficient α is calculated only when the pilot symbols are received.

  The demodulator 100 described above has a computer system therein. The operation of each processing unit described above is stored in a computer-readable recording medium in the form of a program, and the above processing is performed by the computer reading and executing this program. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  DESCRIPTION OF SYMBOLS 100 ... Demodulator 101 ... Pilot complex division part 102 ... Transmission path characteristic memory | storage part 103 ... Phase amplitude compensation part 104 ... Demap part 105 ... Remap part 106 ... Complex division part 107 ... Inclination correction part 108 ... Switch part 109, 110 ... IIR Filters 111, 112 ... Moving average value buffer 113 ... Coefficient calculation unit 114 ... Coefficient storage unit 115 ... Next transmission line characteristic estimation part 116 ... Transmission line characteristic buffer

Claims (6)

A transmission path characteristic estimation device that estimates a transmission path characteristic of a next reception symbol from a plurality of consecutive reception symbols,
A current channel characteristic estimator for estimating a current channel characteristic every time the received symbol is received;
A first smoothing unit that calculates a moving average value of transmission path characteristics estimated by the current transmission characteristic estimation unit using a predetermined smoothing coefficient for each reception of the received symbol;
Second smoothing for calculating a moving average value of the transmission path characteristic estimated by the current transmission characteristic estimation unit using a smoothing coefficient different from the smoothing coefficient of the first smoothing unit for each reception of the received symbol And
The difference between the transmission path characteristic estimated by the current transmission path characteristic estimation unit and the moving average value calculated by the first smoothing unit at the previous reception of the received symbol is expressed as the first time at the previous reception of the reception symbol. A division unit that divides by the difference between the moving average value calculated by one smoothing unit and the moving average value calculated by the second smoothing unit at the previous reception of the received symbol;
The difference between the moving average value calculated by the first smoothing unit and the moving average value calculated by the second smoothing unit is multiplied by the calculation result of the dividing unit, and the value is multiplied by the first smoothing value. A transmission path characteristic estimation device, comprising: a next transmission path characteristic estimation unit that estimates a transmission path characteristic of a next received symbol by adding the moving average values calculated by the unit. The transmission path characteristic estimation apparatus according to claim 1, wherein the division unit performs calculation when the received symbol received is a pilot symbol. The division unit is configured to calculate a difference between a transmission path characteristic estimated by the current transmission path characteristic estimation unit and a moving average value calculated by the first smoothing unit at the previous reception of the reception symbol, from a previous time of the received symbol. The value obtained by multiplying the difference between the moving average value calculated by the first smoothing unit at the time of reception and the moving average value calculated by the second smoothing unit at the previous reception of the received symbol is the value of the received symbol. Divide by the square of the absolute value of the difference between the moving average value calculated by the first smoothing unit at the previous reception and the moving average value calculated by the second smoothing unit at the previous reception of the received symbol. The transmission path characteristic estimation apparatus according to claim 1 or 2, characterized by the above.   4. The transmission path characteristic estimation apparatus according to claim 1, wherein the first smoothing unit and the second smoothing unit are first-order IIR filters. 5. A transmission path characteristic estimation method using a transmission path characteristic estimation device that estimates a transmission path characteristic of a next reception symbol from a plurality of consecutive reception symbols,
Every time the received symbol is received,
The current channel characteristics estimation unit estimates the current channel characteristics,
The first smoothing unit calculates a moving average value of the transmission path characteristics estimated by the current transmission characteristic estimation unit using a predetermined smoothing coefficient,
The second smoothing unit is a moving average of the transmission path characteristics estimated by the current transmission characteristic estimation unit using a smoothing coefficient different from the smoothing coefficient of the first smoothing unit for each reception of the reception symbol. Calculate the value,
The division unit calculates a difference between the transmission path characteristic estimated by the current transmission path characteristic estimation unit and the moving average value calculated by the first smoothing unit at the previous reception of the received symbol, from the previous reception symbol. Dividing by the difference between the moving average value calculated by the first smoothing unit at the time of reception and the moving average value calculated by the second smoothing unit at the previous reception of the received symbol;
The next transmission path characteristic estimation unit multiplies the difference between the moving average value calculated by the first smoothing unit and the moving average value calculated by the second smoothing unit by the calculation result of the division unit, A transmission path characteristic estimation method, wherein the transmission path characteristic of the next received symbol is estimated by adding the moving average value calculated by the first smoothing unit to the value. A transmission path characteristic estimation device that estimates a transmission path characteristic of a next reception symbol from a plurality of consecutive reception symbols,
A current channel characteristic estimator for estimating a current channel characteristic every time the received symbol is received;
A first smoothing unit that calculates a moving average value of transmission path characteristics estimated by the current transmission characteristic estimation unit using a predetermined smoothing coefficient for each reception of the received symbol;
Second smoothing for calculating a moving average value of the transmission path characteristic estimated by the current transmission characteristic estimation unit using a smoothing coefficient different from the smoothing coefficient of the first smoothing unit for each reception of the received symbol Part,
The difference between the transmission path characteristic estimated by the current transmission path characteristic estimation unit and the moving average value calculated by the first smoothing unit at the previous reception of the received symbol is expressed as the first time at the previous reception of the reception symbol. A division unit that divides by the difference between the moving average value calculated by one smoothing unit and the moving average value calculated by the second smoothing unit at the previous reception of the received symbol;
The difference between the moving average value calculated by the first smoothing unit and the moving average value calculated by the second smoothing unit is multiplied by the calculation result of the dividing unit, and the value is multiplied by the first smoothing value. A program for operating as a next channel characteristic estimation unit that estimates the channel characteristic of the next received symbol by adding the moving average values calculated by the unit.

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