JP2006101020A - Ofdm receiver and ofdm relay apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an OFDM receiver and an OFDM relay apparatus with a simple configuration capable of executing phase correction processing of a transmission path characteristics, without being affected by an interpolation pattern of the transmission path characteristics. <P>SOLUTION: A transmission path characteristic estimate unit 110 is configured to obtain the transmission path characteristics of all carriers by employing: a phase correction section 101 that uses an accumulated FFT window position deviation, resulting from accumulating a difference of an FFT window position signal between OFDM symbols from a reference time by each symbol to correct the phase of the transmission path characteristics of a pilot carrier into a phase of the reference time; a time axis interpolation section 12 that carries out time axis interpolation of the transmission path characteristics by using the transmission path characteristic after the phase correction; a phase correction section 102 that corrects the transmission path characteristic, obtained by the time axis interpolation into a phase of a symbol time of a correction object through the use of the accumulated FFT window position deviation with respect to the symbol of the correction object; and a frequency axis interpolation section 13 that corrects the result above in the frequency axis direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention estimates transmission path characteristics based on pilot signals arranged at predetermined positions in the time axis direction and frequency axis direction, and OFDM (Orthogonal Frequency) adapted to equalize a data signal based on the estimation result. The present invention relates to a (Division Multiplexing) receiving apparatus and an OFDM relay apparatus.

  Conventionally, OFDM has been studied as a digital signal transmission method. OFDM is a system in which a plurality of carriers orthogonal to each other are digitally modulated by PSK (Phase Shift Keying), QAM (Quadrature Amplitude Modulation), etc., and has a characteristic of being resistant to multipath.

  Examples of systems that employ the OFDM transmission method include terrestrial digital broadcasts and wireless LANs in Japan and Europe. In these systems, a known signal called a pilot signal is transmitted using a predetermined carrier, and on the receiving side, the channel characteristic is estimated using the pilot signal, and this channel characteristic estimation value is used to influence the effect of the channel distortion. The received signal is equalized.

  A pilot signal used for transmission path characteristic estimation is called SP (Scattered Pilot) in ISDB-T (Integrated Services Digital Broadcasting for Terrestrial), which is a standard for digital terrestrial broadcasting in Japan. As shown in FIG. 4, this is a known signal that is distributed and arranged on different carriers at intervals of 4 symbols every 12 carriers (see Non-Patent Document 1). Note that CP (Continual Pilot) is also a kind of pilot signal, and is a known signal continuously arranged for every symbol on the rightmost carrier of the signal band. The transmission path characteristics of a carrier in which a pilot signal is arranged (pilot carrier) can be obtained from a pilot signal that is a known signal, but a carrier carrying an unknown data signal (data carrier) is determined from the data of that carrier. Cannot directly calculate the transmission line characteristics.

  Therefore, in general, a method is used in which the transmission channel characteristics of pilot carriers arranged in a distributed manner are obtained, and the transmission channel characteristics of the data carrier are obtained by interpolating them in the time axis direction and the frequency axis direction.

  FIG. 5 shows a time axis interpolation method for pilot carrier transmission path characteristics. FIG. 5A shows a system in which transmission channel characteristics of past pilot carriers are zero-order held, and FIG. 5B shows a system in which linear interpolation is performed using transmission channel characteristics of past and future pilot carriers.

  In the 0th-order hold method, the interpolation process is performed using only the transmission path characteristics of the pilot carrier of the past OFDM symbol, so that the processing delay can be reduced. On the other hand, in the linear interpolation method, it is necessary to wait for the arrival of a future OFDM symbol and the calculation of the transmission channel characteristics of the pilot carrier, so that the processing delay increases. However, the linear interpolation method is better for tracking the transmission path characteristics over time.

  FIG. 6 shows a configuration of a conventional OFDM receiving apparatus 600 that performs channel characteristic estimation using a pilot signal and equalizes a received signal using the channel estimation result (see, for example, Patent Document 1).

  An RF (Radio Frequency) band signal received by the receiving antenna 1 is converted into a baseband (hereinafter referred to as baseband) signal in the receiving unit 2. The receiving unit 2 further performs a synchronization process for obtaining OFDM symbol data.

  The OFDM symbol output from the receiver 2 is converted into a frequency domain signal by Fourier transform processing in the FFT unit 3. Note that the FFT processing of the FFT unit 3 is performed on the effective symbol specified by the FFT window position signal fftw (i) obtained by the synchronization processing of the receiving unit 2. That is, the receiving unit 2 always detects the optimum symbol timing from the received signal, and changes the FFT window position signal fftw (i) according to the result.

で表される。 The transmission path characteristic estimation unit 20 uses the OFDM symbol after FFT and the FFT window position signal fftw (i) (actually, the FFT window position deviation signal dw (i), which will be described later), Estimate the road characteristics. Here, the data transmitted from the transmission side is X (i, k), the transmission path characteristic is H (i, k), the data received on the reception side is Y (i, k), and the noise component is N (i , K), i: symbol number, k: carrier number,

It is represented by

で表される。 Therefore, the pilot carrier transmission path characteristic estimation unit 21 of the transmission path characteristic estimation unit 20 uses the received OFDM symbol Y (i, k) converted into the frequency domain signal by the FFT unit 3 via the delay unit 4 from the pilot carrier. Data Y (i, kp) is extracted (kp: pilot carrier number) and divided by the regular pilot data X (i, kp) generated by the pilot signal generator 8 by the divider 9 to obtain X The transmission line characteristic H ′ (i, kp) acting on (i, kp) is estimated. These relationships are given by

It is represented by

  On the other hand, the transmission line characteristic of the data carrier is obtained by interpolating the transmission line characteristic H ′ (i, kp) of the pilot carrier in the time axis direction and the frequency axis direction. In the following, the method will be described by taking as an example a case where time axis interpolation is performed by a linear interpolation method.

  As described above, when time axis interpolation is performed by the linear interpolation method, the transmission channel characteristics of the pilot carrier of the current symbol, the past 3 symbols, and the future 3 symbols are used. Therefore, the pilot carrier transmission line characteristic H ′ (i, kp) obtained by the dividing unit 9 is accumulated in the accumulating unit 10, and the pilot carrier transmission line characteristic of a necessary symbol is called as needed to perform time axis interpolation. Do.

  Here, as described above, since the FFT window position signal fftw (i) varies depending on the symbol synchronization result, the phase of the symbol data output from the FFT unit 3 differs between symbols. Therefore, it is necessary to correct a phase difference caused by a difference in FFT window position between symbols (hereinafter referred to as FFT window position deviation) before time axis interpolation.

で示すＦＦＴ窓位置偏差ｃｄｗ（ｉ−６，ｉ），ｃｄｗ（ｉ−２，ｉ）が存在する。 This phase correction will be described with reference to FIG. FIG. 7 shows a past symbol (symbol number i-4, i-5, i-6) and a future symbol (symbol number i-2, i-1, This is an example of performing linear interpolation using i). The FFT window position deviation between the symbol i and the symbol i-1 is represented by dw (i) as shown in FIG. There are four types of time axis interpolation patterns (carriers k, k + 3, k + 6, k + 9) including patterns that do not actually require interpolation processing, such as carrier k. For example, in the interpolation process in carrier k + 3, the transmission path characteristics of symbols i-6 and i-2 are used for interpolation. Since there is a phase difference due to the FFT window position deviation between the two symbols, it is necessary to correct it. In Patent Document 1, the reference for phase correction is the current symbol (symbol i in FIG. 7), which will be described as an example. Symbols i-6 and i-2 are expressed as follows with respect to the phase reference symbol i.

FFT window position deviations cdw (i−6, i) and cdw (i−2, i) indicated by

に示すとおりである。なお（４）式、（５）式においてＮｕはＦＦＴポイント数を示す。 Therefore, it is necessary to correct the phase rotation caused by the FFT window position deviation for the transmission path characteristics of the symbols i-6 and i-2. The amount of phase correction for symbols i-6 and i-2 is

As shown in In Equations (4) and (5), Nu represents the number of FFT points.

  In order to perform the above phase correction, the OFDM receiver 600 calculates the window position deviation dw (i) between symbols by the FFT window position deviation calculation unit 30. Then, the transmission path characteristic estimation unit 20 calls the transmission path characteristic of the pilot carrier of the symbol necessary for the time axis interpolation from the storage unit 10 and corrects the phase rotation caused by the FFT window position deviation dw (i). After that, the time axis interpolation unit 12 performs time axis interpolation. Further, this is interpolated in the frequency axis direction by the frequency axis interpolating unit 13 to obtain the transmission path characteristics of all carriers.

  On the other hand, the OFDM symbol data Y (i, k) after the FFT processing on the main line side is delayed by the delay unit 4 by the processing delay (3 symbols) in the transmission channel characteristic estimation unit 20, and then the transmission channel described above. Similarly to the phase correction for the characteristics, the phase correction unit 5 corrects the phase difference caused by the FFT window position deviation cdw (i-3, i) between the current symbol i and the delayed symbol i-3. The result is input to the equalization unit 6.

The equalization unit 6 equalizes the received OFDM symbol using the transmission path characteristics obtained by the transmission path characteristic estimation unit 20 and then passes the equalized data to the determination unit 7 that determines the equalized data.
Japanese Patent No. 3335933 (FIG. 5) The Japan Radio Industry Association, “Transmission Method for Digital Terrestrial Television Broadcasting”, ARIB STD-B31 1.5 Edition, revised on July 29, 2003, p. 46

  By the way, as described above, the phase correction amount corresponding to the FFT window position deviation differs depending on the time axis interpolation pattern. Accordingly, the FFT window position deviation amount needs to be stored for each symbol as well as the transmission path characteristics of the pilot carrier, and the phase correction processing unit takes into account that these need to be switched and read by the time axis interpolation pattern. Implementation is complicated.

  Further, the OFDM symbol data after the FFT processing needs to be delayed by the time axis interpolation process, and the time for the time axis interpolation process always occurs after the reception signal is received until the equalization process is completed. End up. This delay becomes a problem particularly in a relay apparatus that is severe in delay time.

  The present invention has been made in view of the above points, and can perform phase correction processing of a transmission path characteristic with a simple configuration without being affected by an interpolation pattern of the transmission path characteristic, and the corrected transmission path characteristic. An object of the present invention is to provide an OFDM receiving apparatus and an OFDM relay apparatus capable of performing equalization processing using a signal with reduced processing delay.

  In order to solve such a problem, the OFDM receiving apparatus and OFDM relay apparatus of the present invention includes an accumulated FFT window position deviation calculating means for obtaining an accumulated FFT window position deviation by accumulating an FFT window position difference every symbol from a reference time, First phase correction means for correcting the phase of the channel characteristic of the pilot carrier to the phase of the reference time using the accumulated FFT window position deviation of the corresponding symbol, and the phase of the channel characteristic subjected to time axis interpolation, A configuration is provided that includes second phase correction means that corrects the phase of the symbol time to be interpolated using the accumulated FFT window position deviation corresponding to the symbol to be interpolated.

  According to this configuration, even when the time-axis interpolation pattern differs depending on the pilot carrier arrangement position, phase correction can be performed using one type of accumulated FFT window position deviation. Thus, the phase correction process of the transmission path characteristics can be performed.

  An OFDM receiving apparatus and an OFDM relay apparatus according to the present invention include an accumulated FFT window position deviation calculating means for obtaining an accumulated FFT window position deviation by accumulating a difference in FFT window position every symbol from a reference time, and a transmission path characteristic of a pilot carrier. First phase correcting means for correcting the phase of the OFDM symbol to the phase of the reference time using the accumulated FFT window position deviation of the corresponding symbol, and the phase of the FFT-symbol OFDM symbol to the accumulated FFT window position of the corresponding symbol A configuration is adopted that includes second phase correction means that corrects the phase of the reference time using the deviation.

  According to this configuration, phase correction can be performed using one type of accumulated FFT window position deviation, so that phase correction processing of transmission path characteristics can be performed with a simple configuration. In addition, it is possible to match the phase of the OFDM symbol to be equalized and the transmission path estimation result without delaying the OFDM symbol on the main line side. Can be reduced.

  As described above, according to the present invention, it is possible to perform the phase correction process of the transmission path characteristic with a simple configuration without being affected by the interpolation pattern of the transmission path characteristic, and equalization using the corrected transmission path characteristic. An OFDM receiving apparatus and OFDM relay apparatus that can perform processing with reduced processing delay can be realized.

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

(Embodiment 1)
FIG. 1 in which the same reference numerals are assigned to corresponding parts as in FIG. 6 shows the configuration of the OFDM receiver of this embodiment. Here, the same components as those in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted.

  The OFDM receiving apparatus 100 includes a cumulative FFT window position deviation calculation unit 120. The accumulated FFT window position deviation calculation unit 120 inputs the FFT window position difference dw (i) between the symbols, which is obtained by the FFT window position deviation calculation unit 30, and uses the FFT window position difference dw (i). Accumulated window position deviation aw (i) is calculated by accumulating every symbol from the reference time.

  FIG. 2A shows the relationship between the FFT window position deviation dw (i) and the accumulated FFT window position deviation aw (i). As can be seen from this figure, the accumulated FFT window position deviation aw (i) is an accumulated value of the FFT window position deviation from a past reference time i_0 to the symbol i.

  The accumulated FFT window position deviation calculation unit 120 sends the calculated accumulated window position deviation aw (i) to the first and second phase correction units 101 and 102 provided in the transmission path characteristic estimation unit 110.

のようになる。ここでＮｕはＦＦＴポイント数を示す。 The first phase correction unit 101 uses the phase of the pilot carrier transmission line characteristic H ′ (i, kp) obtained by the pilot carrier transmission line characteristic estimation part 21 as the accumulated FFT window position deviation aw (i) of the corresponding symbol. Is used to correct the phase of the reference time. That is, the phase of the pilot carrier transmission channel characteristic used for time interpolation is corrected to the phase of the reference time i_0. In practice, the phase correction amount that the first phase correction unit 101 gives to the pilot carrier transmission line characteristics of the symbol i and the carrier k + 3 is

become that way. Here, Nu represents the number of FFT points.

  The reference time i_0 may be arbitrary. For example, the reference time i_0 may be a device mounting time or a circuit reset time.

  The transmission path characteristic estimation unit 110 accumulates the transmission path characteristics of pilot carriers of a plurality of symbols, which have been phase-corrected by performing such phase correction, in the accumulating section 10, and calculates the transmission path characteristics of the pilot carrier necessary for interpolation as time. Called at any time by the axis interpolation unit 12 to perform time axis interpolation.

のようになる。 The second phase correction unit 102 corrects the phase of the time axis interpolation result obtained by the time axis interpolation unit 12 by the accumulated FFT window position deviation aw (i-3) for the symbol i-3 to be interpolated, The time axis interpolation result is corrected to the phase of the symbol time to be interpolated. Actually, the phase correction amount that the second phase correction unit 102 gives to the transmission path characteristics of the interpolation target symbol i-3 and the carrier k + 3 is given by

become that way.

  This phase correction corresponds to a process of matching the transmission path characteristics after time axis interpolation with the phase of the main line side OFDM symbol time which is the output of the delay unit 4.

  The transmission path characteristic estimation unit 110 obtains the transmission path characteristics of all carriers by interpolating the transmission path characteristics corrected by the second phase correction unit 102 in the frequency axis direction by the frequency axis interpolation unit 13. On the other hand, the OFDM symbol data Y (i, k) after the FFT processing on the main line side is delayed by the delay unit 4 by the processing delay (3 symbols) in the transmission path characteristic estimation unit 110, and then the equalization unit 6 Is input. The equalization unit 6 equalizes the OFDM symbol by using the transmission path characteristics obtained by the frequency axis interpolation unit 13.

  Next, the operation of OFDM receiving apparatus 100 according to the present embodiment will be described.

  The first phase correction unit 101 corrects the phase of the transmission path characteristic obtained by the pilot carrier transmission path characteristic estimation unit 21 to the phase of the reference time using the accumulated FFT window position deviation of the corresponding symbol. This process is a simple process of correcting the phase of the channel characteristic of the input pilot carrier by the accumulated FFT window position deviation of the corresponding symbol out of the input accumulated FFT window position deviation. The process of the second phase correction unit 102 is also a simple process of correcting the transmission path characteristics after time axis interpolation to the phase of the symbol time to be interpolated.

  That is, since only one type of cumulative FFT window position deviation is used in each of the first phase correction unit 101 and the second phase correction unit 102, according to the time axis interpolation pattern as in the conventional device of FIG. It is not necessary to consider switching of the phase correction amount (FFT window position deviation), and the apparatus can be configured simply.

  For example, consider the interpolation target symbol i-3 shown in FIG. 2B. In addition, the black circle in FIG. 2B shows a pilot carrier. For example, for the correction of the transmission path characteristic of the carrier k + 3 performed by the first phase correction unit 101, aw (i-3) / Nu in the equation (6) is fixed, and the value of k + 3 is changed as appropriate according to the carrier number. Therefore, it is only necessary to use one type of cumulative FFT window position deviation aw (i-3) corresponding to the accumulation target symbol i-3.

  Further, for example, for correction of transmission path characteristics performed by the second phase correction unit 102, since aw (i−3) / Nu in the equation (7) is fixed and the value of k + 3 is changed as appropriate according to the carrier number, It is only necessary to use one type of accumulated FFT window position deviation aw (i-3) corresponding to the accumulation target symbol i-3, and two pilots used for interpolation as in the conventional time axis interpolation processing shown in FIG. Accordingly, it is not necessary to use different FFT window position deviations as shown in the equations (4) and (5).

  As described above, according to the present embodiment, the cumulative FFT window position deviation calculation unit 120 and the first phase correction unit that corrects the phase of the pilot carrier transmission path characteristics to the phase of the reference time using the cumulative FFT window position deviation. 101, and a second phase correction unit 102 that corrects the phase of the transmission path characteristic obtained by the time axis interpolation unit 12 to the phase of the symbol time to be interpolated using the accumulated FFT window position deviation corresponding to the symbol to be interpolated. Thus, even when the time axis interpolation pattern differs depending on the pilot carrier arrangement position, phase correction can be performed using one type of accumulated FFT window position deviation. As a result, even when the interpolation pattern of the transmission path characteristics is different, it is not necessary to use an FFT window position deviation corresponding to the interpolation pattern, so that the phase correction processing of the transmission path characteristics can be performed with a simple configuration.

  In the present embodiment, an example of an OFDM receiving apparatus has been described, but the same effect can be obtained even when applied to an OFDM relay apparatus. For example, the OFDM relay apparatus may have a configuration in which a mapping unit, an IFFT unit, and a transmission unit are sequentially provided after the determination unit 7. By adopting such a configuration, it is possible to realize an OFDM relay apparatus capable of performing phase correction processing of transmission path characteristics with a simple configuration even when the interpolation pattern of transmission path characteristics is different.

  Further, in this embodiment, an example in which time axis interpolation is performed on the symbol to be interpolated in the transmission path characteristics using the transmission path characteristics of the past and future symbols, but the time axis using a plurality of past symbols is described. Even when interpolation is performed, the above-described phase correction processing can be applied.

(Embodiment 2)
FIG. 3, in which the same reference numerals are assigned to corresponding parts in FIG. 1 and FIG. 6, shows the configuration of the OFDM receiving apparatus of this embodiment. Here, the same components as those in FIGS. 1 and 6 are denoted by the same reference numerals, and the description thereof is omitted.

  The OFDM receiving apparatus 300 according to the present embodiment is similar to the OFDM receiving apparatus 100 of FIG. 1 described in the first embodiment until the time-axis interpolation is performed on the transmission path characteristics that have been subjected to phase correction corresponding to the accumulated FFT window position deviation. It is the same configuration.

  The channel characteristic estimation unit 310 of the OFDM receiver 300 according to the present embodiment uses the channel characteristic after time axis interpolation corrected to the phase of the reference time i_0 by the first phase correction unit 101 as it is as the frequency axis interpolation unit. 13 to obtain the transmission path characteristics of all carriers.

のようになる。 On the other hand, on the main line side, the OFDM symbol data after the FFT processing is not delayed as in the first embodiment, and the second phase correction unit 301 performs processing to correct the phase at the reference time i_0. The phase correction amount at this time is a phase with respect to the accumulated FFT window position deviation with respect to the symbol i in FIG.

become that way.

  In this way, the phase of the current OFDM symbol data on the main line side can be obtained by the transmission path characteristic estimation unit 310 by the second phase correction unit 301 without delaying the OFDM symbol data on the main line side. It becomes possible to match the phase of the transmission line characteristics of the symbols.

  For example, when linear interpolation as shown in FIG. 2B is performed by the transmission path estimation unit 310, the transmission path characteristics for the current symbol i are obtained for the past symbol i-3. The second phase correction unit 301 performs phase correction so that the phase of the current symbol i matches the phase of the past symbol i-3. As a result, it is not necessary to perform a delay for three symbols.

  As described above, in the OFDM receiver 300, the equalization unit 6 performs equalization using the main line side OFDM symbol data whose phase is corrected at the reference time i_0 and the transmission path characteristic whose phase is corrected at the reference time i_0. .

  Next, the operation of OFDM receiving apparatus 300 according to the present embodiment will be described.

  The processing of the first and second phase correction units 101 and 301 includes the phase of the channel characteristics of the input pilot carrier by the amount corresponding to the cumulative FFT window position deviation of the corresponding symbol out of the input cumulative FFT window position deviation. It is a simple process of correcting.

  That is, since only one type of cumulative FFT window position deviation is used for phase correction in the first and second phase correction units 101 and 301, the phase is changed according to the time axis interpolation pattern as in the conventional apparatus of FIG. It is not necessary to consider switching of the correction amount (FFT window position deviation), and the apparatus can be configured simply.

  In addition, in the OFDM receiver 300, a second second phase correction unit 301 is provided on the main line side, and phase correction is performed by the second phase correction unit 301 so that the phase of the current symbol matches the past symbol. Therefore, the phase of the symbol input to the equalization unit 6 and the transmission path estimation result can be matched without delaying the main line side symbol. As a result, the delay on the main line side due to the transmission path characteristic estimation process can be reduced.

  As described above, according to the present embodiment, the cumulative FFT window position deviation calculation unit 120 and the first phase correction unit that corrects the phase of the pilot carrier transmission path characteristics to the phase of the reference time using the cumulative FFT window position deviation. 101 and a second phase correction unit 301 that corrects the phase of the OFDM symbol obtained by the FFT unit 3 to the phase of the reference time using the accumulated FFT window position deviation of the corresponding symbol, thereby providing a pilot carrier. Even when the time-axis interpolation pattern differs depending on the arrangement position, phase correction can be performed using one type of accumulated FFT window position deviation. As a result, even when the interpolation pattern of the transmission path characteristics is different, it is not necessary to use an FFT window position deviation corresponding to the interpolation pattern, so that the phase correction processing of the transmission path characteristics can be performed with a simple configuration.

  In addition, the phase of the symbol input to the equalization unit 6 and the transmission path estimation result can be matched without delaying the main line side symbol. Can reduce the delay.

  In the present embodiment, an example of an OFDM receiving apparatus has been described, but the same effect can be obtained even when applied to an OFDM relay apparatus. For example, the OFDM relay apparatus may be configured by sequentially providing a mapping unit, an IFFT unit, and a transmission unit after the determination unit 7. By adopting such a configuration, it is possible to realize an OFDM relay apparatus capable of performing phase correction processing of transmission path characteristics with a simple configuration even when the interpolation pattern of transmission path characteristics is different. In particular, since an OFDM relay apparatus is required to have a low delay, good performance can be obtained by applying the configuration of this embodiment.

  The present invention can perform phase correction processing of transmission path characteristics using a pilot carrier with a simple configuration, and can also perform low delay equalization processing using the transmission path characteristics, for example, digital terrestrial broadcasting The present invention is useful when applied to OFDM receivers and OFDM repeaters. The present invention can also be applied to other communication apparatuses that estimate transmission path characteristics using a pilot carrier.

FIG. 1 is a block diagram showing a configuration of an OFDM receiving apparatus according to Embodiment 1 of the present invention. The figure for demonstrating the time-axis interpolation process of the transmission line characteristic in Embodiment 1,2. FIG. 3 is a block diagram showing a configuration of an OFDM receiving apparatus according to the second embodiment. The figure which shows the signal format of ISDB-T Diagram for explaining time-axis interpolation of transmission path characteristics The block diagram which shows the structure of the conventional OFDM receiver Diagram for explaining time axis interpolation of transmission path characteristics and FFT window position deviation

Explanation of symbols

3 FFT unit 6 Equalization unit 12 Time axis interpolation unit 13 Frequency axis interpolation unit 21 Pilot carrier channel characteristic estimation unit 30 FFT window position deviation calculation unit 100, 300 OFDM receiver 101 First phase correction unit 102, 301 Second Phase corrector 110, 310 Transmission path characteristic estimator 120 Cumulative FFT window position deviation calculator

Claims (3)

An OFDM receiver that receives an OFDM symbol including an OFDM symbol obtained by modulating carriers arranged at predetermined intervals in a frequency axis direction and a time axis direction with a pilot signal having a known amplitude and phase,
FFT means for converting the received OFDM symbol into a frequency domain signal;
FFT window position signal generating means for generating an FFT window position signal for designating a position of an OFDM symbol to be subjected to FFT processing in the FFT means;
FFT window position deviation calculating means for obtaining a difference in the FFT window position between each symbol;
Accumulated FFT window position deviation calculating means for obtaining an accumulated FFT window position deviation by accumulating the difference of the FFT window positions every symbol from a reference time;
Pilot carrier channel characteristic estimating means for estimating channel characteristics acting on the pilot carrier based on the received pilot signal;
First phase correction means for correcting the phase of the transmission path characteristic obtained by the pilot carrier transmission path characteristic estimation means to the phase of the reference time using the accumulated FFT window position deviation of the corresponding symbol;
A time axis interpolation means for interpolating the transmission path characteristics obtained by the first phase correction means in the time direction;
Second phase correction means for correcting the phase of the transmission path characteristic obtained by the time axis interpolation means to the phase of the symbol time to be interpolated using the accumulated FFT window position deviation corresponding to the interpolation target symbol;
Frequency axis interpolation means for interpolating the transmission path characteristics obtained by the second phase correction means in the frequency direction;
An OFDM receiver comprising: equalization means for equalizing the OFDM symbol obtained by the FFT means using the transmission path characteristics obtained by the frequency axis interpolation means. An OFDM receiver that receives an OFDM symbol including an OFDM symbol obtained by modulating carriers arranged at predetermined intervals in a frequency axis direction and a time axis direction with a pilot signal having a known amplitude and phase,
FFT means for converting the received OFDM symbol into a frequency domain signal;
FFT window position signal generating means for generating an FFT window position signal for designating a position of an OFDM symbol to be subjected to FFT processing in the FFT means;
FFT window position deviation calculating means for obtaining a difference in the FFT window position between each symbol;
Accumulated FFT window position deviation calculating means for obtaining an accumulated FFT window position deviation by accumulating the difference of the FFT window positions every symbol from a reference time;
Pilot carrier channel characteristic estimating means for estimating channel characteristics acting on the pilot carrier based on the received pilot signal;
First phase correction means for correcting the phase of the transmission path characteristic obtained by the pilot carrier transmission path characteristic estimation means to the phase of the reference time using the accumulated FFT window position deviation of the corresponding symbol;
A time axis interpolation means for interpolating the transmission path characteristics obtained by the first phase correction means in the time direction;
Frequency axis interpolation means for interpolating the transmission line characteristics obtained by the time axis interpolation means in the frequency direction;
Second phase correcting means for correcting the phase of the OFDM symbol obtained by the FFT means to the phase of a reference time using the accumulated FFT window position deviation of the corresponding symbol;
An OFDM receiver comprising: equalization means for equalizing the OFDM symbol obtained by the second phase correction means using the transmission path characteristics obtained by the frequency axis interpolation means.   An OFDM relay apparatus comprising the OFDM receiver according to claim 1.

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