JP2006101019A - Ofdm receiver and ofdm relay apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an OFDM receiver and an OFDM relay apparatus capable of reducing the deterioration in accuracy, in interpolating transmission path characteristics obtained by a pilot signal in the frequency axis direction. <P>SOLUTION: When a time axis interpolation section 40 interpolates the transmission path characteristic H'(i, kp) of an SP/CP carrier obtained from the pilot signal (SP: Scattered Pilot, and CP: Continual Pilot) extracted from a received OFDM signal in the time axis direction and a frequency axis interpolation section 120 interpolates data Hc'(i-3, k), after the time axis interpolation obtained from the result in a frequency direction to obtain the transmission path characteristic Hd'(i, k) of the entire OFDM signal band, a copy section 101 copies the SP carrier and CP carrier transmission path characteristics at the end of the signal band to a position keeping the relation of an equal interval from the SP carrier in the signal band, with respect to a predetermined interval at the outside of the signal band, before interpolation in the frequency axis direction by a frequency axis interpolation filter (FIR filter section )11. Thus, ripples caused at the end of the signal band as a result of the frequency interpolation processing result can be reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) receiving apparatus and an OFDM relay apparatus that estimate transmission path characteristics based on pilot signals arranged at predetermined positions in a time axis direction and a frequency axis direction.

  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, for example, SP (Scattered Pilot) in ISDB-T (Integrated Services Digital Broadcasting for Terrestrial), which is a Japanese terrestrial digital broadcasting standard. 7 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, generally, a technique is used in which the transmission channel characteristics of the data carrier are obtained by obtaining the transmission path characteristics of the SPs arranged in a distributed manner and interpolating them in the time axis direction and the frequency axis direction.

  FIG. 8 shows a configuration of a conventional OFDM receiving apparatus that performs channel characteristic estimation using a pilot signal and equalizes a received signal using the channel estimation result.

  The OFDM receiver 800 converts a signal in an RF (Radio Frequency) band received by the receiving antenna 1 into a signal in a base band (hereinafter referred to as a baseband) 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 receiving unit 2 is converted into a frequency domain signal by Fourier transform processing in the FFT unit 3, delayed by the processing delay in the transmission path characteristic estimation unit 20 in the delay unit 4, etc. Input to the conversion unit 5. The equalization unit 5 equalizes the received OFDM symbol using the transmission path characteristics obtained by the transmission path characteristic estimation unit 20 and passes the equalized data to the determination unit 6.

で表される。 Next, the transmission line characteristic estimation processing in the transmission line characteristic estimation unit 20 will be described. Data transmitted from the transmission side is X (i, k), transmission path characteristics are H (i, k), data received on the reception side is Y (i, k), and noise components are N (i, k). , I: symbol number, k: carrier number, these relations are given by

It is represented by

で表される。 Therefore, in the SP / CP division unit 8 provided in the pilot carrier transmission line characteristic estimation unit 30 of the transmission line characteristic estimation unit 20, the received OFDM symbol Y (i, k) converted into a frequency domain signal by the FFT unit 3 is used. ) To extract SP or CP carrier data Y (i, kp) (kp: SP carrier number or CP carrier number), and SP / CP generation unit 7 generates the normal SP or CP data X (i, kp). ) To estimate the transmission line characteristic H ′ (i, kp) acting on X (i, kp). These relationships are given by

It is represented by

  On the other hand, the transmission path characteristic of the data carrier is interpolated in the time axis direction by the time axis interpolation unit 40 using the transmission path characteristic H ′ (i, kp) of the SP / CP carrier (Hc ′ (i−3, k )), And this is obtained by further interpolating in the frequency direction by the frequency axis interpolation unit 50. The transmission path characteristic Hd ′ (i−3, k) of the entire signal band obtained in this way is output to the equalization unit 5. FIG. 8 shows an example in which the processing delay in the time axis interpolation unit 40 is 3 symbols.

  When the time axis interpolation and the frequency axis interpolation are performed in this way, the accuracy of the transmission path characteristics that can be estimated is 4Δf when the carrier interval is Δf. Further, a method of performing only frequency interpolation processing without performing time axis interpolation on the SP / CP transmission path characteristics H ′ (i, kp) after SP / CP division is also conceivable. In this case, the estimation accuracy of the transmission path characteristic is 12Δf.

  Here, the time direction interpolation method is described in, for example, Patent Document 1, but as shown in FIG. 9, zero-order hold is performed in the time axis direction using SPs of past and future symbols. The method (FIG. 9A) or the method of linear interpolation (FIG. 9B) is taken.

  This will be described based on the configuration of the time axis interpolation unit 40 shown in FIG. FIG. 8 shows a method using linear interpolation. The time axis interpolation unit 40 converts the SP and CP transmission path characteristics H ′ (i, kp) obtained from the SP / CP division section 8 into 7 symbols necessary for linear interpolation in the SP / CP transmission path characteristics storage section 9. accumulate. Then, the interpolation unit 10 sends the necessary 1-symbol or 2-symbol SP data Ha ′ (i, kp), from the SP / CP transmission path characteristic storage unit 9 according to the four linear interpolation patterns shown in FIG. 9B. Call Hb ′ (i, kp) and perform linear interpolation. Since the CP is inserted in the right end carrier of each symbol, the called CP data may be used as it is without performing the time axis interpolation.

On the other hand, regarding the interpolation method in the frequency axis direction, as shown in FIG. 8, by configuring the FIR filter of the FIR filter unit 11 to function as a frequency axis interpolation filter, the data after time axis interpolation is arranged in the frequency direction. The method of interpolation is taken.
JP 2002-344411 A (page 9, table 3) 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, since there is no signal on the left and right of the OFDM signal band, when performing interpolation in the frequency direction using an interpolation filter as in the conventional transmission line characteristic method as described above, the transmission line characteristic estimation results at both ends of the signal band There was a problem that ripples were generated and the estimation accuracy deteriorated.

  The present invention has been made in view of such points, and it is an object of the present invention to provide an OFDM receiver and an OFDM relay apparatus that can reduce deterioration in accuracy when the transmission path characteristics obtained from a pilot signal are interpolated in the frequency axis direction. And

  In order to solve such a problem, the present invention provides a pilot carrier channel characteristic estimation unit for estimating a channel characteristic acting on a pilot carrier based on a received pilot signal, and a pilot carrier obtained by the pilot carrier channel characteristic estimation unit. Among the transmission path characteristics, a predetermined length outside the OFDM signal band is set so that the pilot carrier transmission path characteristic closest to the band edge in the OFDM signal band is equal to the pilot carrier interval in the OFDM signal band. And a pilot carrier copy means for inserting 0 between the copied pilot carriers, and a frequency axis interpolation means for interpolating the data obtained by the pilot carrier copy means in the frequency axis direction. The structure to do is taken.

  According to this configuration, the pilot carrier copy means causes the pilot carrier transmission line characteristics closest to the band edge in the OFDM signal band to be equal to the pilot carrier interval in the OFDM signal band on the left and right sides of the OFDM signal band. In addition, since 0 is inserted between the pilot carriers and copied, the ripple of the channel characteristic estimation results at both ends of the signal band is reduced even if frequency interpolation is performed by the frequency axis interpolation means. As a result, it is possible to reduce deterioration in transmission path characteristic estimation accuracy caused by interpolating the transmission path characteristics obtained from the pilot signal in the frequency axis direction.

  ADVANTAGE OF THE INVENTION According to this invention, the degradation of the transmission path characteristic estimation precision resulting from interpolating the transmission path characteristic calculated | required with the pilot signal to a frequency-axis direction can be reduced, and the OFDM receiver and OFDM relay apparatus which employ | adopt a pilot carrier are reduced. The transmission path characteristic estimation accuracy can be improved.

  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. 8, shows the configuration of the OFDM receiver of this embodiment. Here, the same components as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted.

  The OFDM receiving apparatus 100 of the present embodiment differs from the OFDM receiving apparatus 800 of FIG. 8 in the configuration of the frequency axis interpolation unit 120 of the transmission path characteristic estimation unit 110. The frequency axis interpolation unit 120 performs a copy process to be described later on both ends of the OFDM signal band with respect to the data Hc ′ (i−3, k) after the time axis interpolation, and the output He ′ of the copy unit 101. The FIR filter unit 11 interpolates (i-3, k) in the frequency axis direction.

  Hereinafter, a copy process at both ends of the signal band by the copy unit 101 will be described in detail.

  FIG. 2 shows the copy processing results for both ends of the OFDM signal band by the copy unit 101. FIG. 2A shows the entire OFDM signal band, FIG. 2B shows the left end of the OFDM signal band, and FIG. 2C shows the copy processing of the right end of the OFDM signal band. Each result is shown.

  As shown in FIG. 2A, the copy unit 101 applies SP or CP at the left end of the OFDM signal band to both ends of the data Hc ′ (i−3, k) after time axis interpolation, and the FIR filter unit 11 (frequency axis interpolation filter). ) Copy only the interval for the number of half taps.

  Here, on the left end side of the OFDM signal band, as shown in FIG. 2B, the SP at the left end of each OFDM symbol is copied every three carriers outside the left end band so as to maintain the SP interval in the OFDM signal band. , 0 is inserted between the copied SPs.

  On the other hand, on the right end side of the OFDM signal band, the CP that is always arranged at the right end of the band is copied every three carriers outside the right end band so as to maintain the SP interval in the OFDM signal band, and 0 between the copied CPs. Insert.

  In this way, by adding the data corresponding to the half-tap number of the frequency interpolation filter to both ends of the OFDM signal band, the data is input to the frequency interpolation filter, whereby the output Hd of the frequency interpolation filter (FIR filter unit 11). '(I-3, k), that is, ripples at both ends of the signal band of the transmission path characteristic estimation result are reduced.

  Thus, according to the present embodiment, the pilot carrier transmission line characteristic closest to the band edge in the OFDM signal band is provided on the upstream side of the frequency interpolation filter (in this embodiment, the FIR filter 11). In addition to copying to a pilot carrier copy section having a predetermined length outside the OFDM signal band (in this embodiment, the number of half taps of the frequency interpolation filter) so as to be equal to the pilot carrier interval of OFDM that can reduce degradation of transmission path characteristic estimation accuracy due to frequency axis interpolation of pilot carrier transmission path characteristic data by a frequency interpolation filter by providing a copy unit 101 that inserts 0 between copied pilot carriers The receiving device 100 can be realized.

  In this embodiment, the case where the SP interval after the time axis interpolation process is every three carriers has been described as an example. However, the present invention is not limited to this, and the same effect can be obtained in the case of other SP intervals. Obtainable.

  In the present embodiment, the copy interval of the number of half taps of the frequency interpolation filter is provided outside the both end bands. However, the copy interval may be adjusted according to the influence of ripple.

  Furthermore, although an example of an OFDM receiving apparatus has been described in the present embodiment, 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 6. By adopting such a configuration, it is possible to realize an OFDM relay apparatus that can reduce deterioration in accuracy when frequency axis interpolation is performed on pilot carrier transmission path characteristic data using a frequency interpolation filter.

(Embodiment 2)
FIG. 3, in which the same reference numerals are assigned to corresponding parts as in FIG. 8, shows the configuration of the OFDM receiver of this embodiment. Here, the same components as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted.

  The transmission path characteristic estimation unit 310 of the OFDM receiver 300 is provided with a 0 insertion unit 302. Then, the SP / CP transmission line characteristic H ′ (i, kp) obtained by the pilot carrier transmission line characteristic estimation unit 30 is input to the 0 insertion unit 302. The 0 insertion unit 302 sets the SP / CP transmission path characteristic H ′ (i, kp), which is the output of the SP / CP division unit 8, at the position of the SP / CP carrier of the OFDM signal, and sets 0 at the position of the data carrier. Perform the insertion process. The data Hf ′ (i, k) after 0 insertion obtained in this way has a different SP arrangement depending on the symbol number, as will be described later.

  The frequency axis interpolation unit 320 includes a copy unit 301 that performs copy processing, which will be described later, at both ends of the OFDM signal band, and an FIR filter unit 11 that performs interpolation processing on the output He ′ (i, k) of the copy unit 301 in the frequency axis direction. It is comprised by.

  Hereinafter, the copy process at both ends of the signal band by the copy unit 301 will be described in detail.

  FIG. 4 shows the copy processing results for both ends of the OFDM signal band by the copy unit 301, FIG. 4A shows the entire OFDM signal band, FIG. 4B shows the left end of the OFDM signal band, and FIG. 4C shows the copy processing of the right end of the OFDM signal band. Each result is shown.

  As shown in FIG. 4A, the copy unit 301 applies the SP or CP at the left end of the OFDM signal band to both ends of the data Hf ′ (i, k) obtained from the 0 insertion unit 302, and the FIR filter unit 11 (frequency axis interpolation). Copy only the interval for the number of half taps of (Filter).

  Here, on the left end side of the OFDM signal band, as shown in FIG. 4B, the left end SP of each OFDM symbol is copied every 12 carriers outside the left end band so as to maintain the SP interval in the OFDM signal band. , 0 is inserted between the copied SPs. Since the arrangement of SPs in the OFDM signal band differs depending on the symbol number, the SP copy position also differs depending on the symbol number.

  On the other hand, on the right end side of the OFDM signal band, the CP that is always placed at the right end of the band is copied every 12 carriers outside the right end band so as to maintain the SP interval in the OFDM signal band, and 0 between the copied CPs. Insert. Since the SP arrangement differs depending on the symbol number, when symbol number% 4 = 1, 2, 3 as shown in FIG. 2C, the CP position at the right end of the signal band (carrier number Nc-1) is CP. Instead, 0 is replaced and arranged.

  In this way, by adding the data corresponding to the half-tap number of the frequency interpolation filter to both ends of the OFDM signal band, the data is input to the frequency interpolation filter, whereby the output Hd of the frequency interpolation filter (FIR filter unit 11). '(I, k), that is, ripples at both ends of the signal band of the transmission path characteristic estimation result are reduced.

  Thus, according to the present embodiment, the SP / CP transmission line characteristic H ′ (i) is placed at the position of the SP / CP carrier of the OFDM signal on the upstream side of the frequency interpolation filter (in this embodiment, the FIR filter 11). , Kp), a 0 insertion unit 302 for inserting 0 at the position of the data carrier, and a pilot carrier transmission path characteristic closest to the band edge in the OFDM signal band, with an interval equal to the pilot carrier interval in the OFDM signal band. By providing a copy unit 301 for copying in a pilot carrier copy section of a predetermined length outside the OFDM signal band (in this embodiment, the number of half taps of the frequency interpolation filter), OFDM receiver capable of reducing accuracy degradation when frequency axis interpolation of pilot carrier channel characteristic data is performed by interpolation filter 00 can be realized.

  Incidentally, compared with the configuration of the first embodiment, the configuration of the present embodiment does not perform time-axis interpolation, so in practice it is slightly more accurate than the transmission path characteristic estimation result obtained by the configuration of the first embodiment. Decreases. However, in the present embodiment, since time axis interpolation is not performed, there is no need to accumulate SP / CP transmission path characteristics H ′ (i, kp), and transmission path characteristics estimation results can be obtained in real time. In addition, there is an advantage that the circuit scale can be reduced.

  In the present embodiment, the case where the 0 insertion unit 302 is provided on the upstream side of the copy unit 301 has been described. However, the 0 insertion unit 302 may be provided on the downstream side of the copy unit 301. In short, the feature of this embodiment is that the pilot carrier transmission path characteristic closest to the band edge in the OFDM signal band is set in advance outside the OFDM signal band so as to be equal to the pilot carrier interval in the OFDM signal band. That is, a copy unit that copies to a pilot carrier copy section of a predetermined length and inserts 0 between the copied pilot carriers is configured by the copy unit 301 and the 0 insertion unit 302.

  In this embodiment, the case where the SP interval of the data after SP / CP division is every 12 carriers has been described as an example. However, the present invention is not limited to this, and the same applies to other SP intervals. An effect can be obtained.

  In the present embodiment, the copy interval of the number of half taps of the frequency interpolation filter is provided outside the both end bands. However, the copy interval may be adjusted according to the influence of ripple.

  Furthermore, although an example of an OFDM receiving apparatus has been described in the present embodiment, 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 6. By adopting such a configuration, it is possible to realize an OFDM relay apparatus that can reduce deterioration in accuracy when frequency axis interpolation is performed on pilot carrier transmission path characteristic data using a frequency interpolation filter.

(Embodiment 3)
FIG. 5, in which parts corresponding to those in FIGS. 3 and 8 are assigned the same reference numerals, shows the configuration of the OFDM receiver of this embodiment. Here, the same components as those in FIGS. 3 and 8 are denoted by the same reference numerals, and the description thereof is omitted.

  The channel characteristic estimation unit 510 of the OFDM receiver 500 is provided with a band edge data storage unit 501 and an overwrite unit 502 in addition to the configuration of the channel characteristic estimation unit 310 of FIG. Hereinafter, the processing of the band edge data storage unit 501 and the overwrite unit 502 will be described in detail.

  The band edge data accumulating unit 501 has a symbol number% 4 = 0 of the transmission path characteristics Hd ′ (i, k) obtained from the frequency axis interpolating unit 320 and a predetermined carrier component from both ends of the OFDM signal band. Are stored for one latest symbol (j: symbol number where symbol number% 4 = 0).

  As shown in FIG. 6, when the symbol number of the transmission path characteristic Hd ′ (i, k) obtained from the frequency axis interpolation unit 320 is symbol number% 4 = 1, 2, 3, The transmission line characteristic Hd ′ (j, k) at the band edge of symbol number 4 = 0 accumulated in the band edge data accumulation unit 501 is used as the transmission line characteristic Hd ′ (i, k) obtained from the frequency axis interpolation unit 320. Overwrite. Then, the data Hg ′ (i, k) obtained in this way is sent to the equalization unit 5 as a transmission path characteristic.

  Thus, in the case of symbol number% 4 = 1, 2, 3, the transmission path characteristics at both ends of the OFDM signal band are obtained by using the transmission path characteristics of symbol number% 4 = 0 at both ends of the OFDM signal band. Degradation of estimation accuracy is reduced.

  That is, the overwrite unit 502 sets the transmission path characteristics for the predetermined carrier at the OFDM signal band edge that is interpolated in the frequency axis direction based on the OFDM symbol in which the pilot carrier is not arranged at the band edge of the OFDM signal, to the OFDM signal. The processing is performed to replace the channel characteristic with a predetermined carrier at the OFDM signal band edge subjected to frequency axis interpolation based on the OFDM symbol in which the pilot carrier is arranged at the band edge.

  As a result, the pilot carrier transmission line characteristic closest to the band edge in the OFDM signal band among the pilot carrier transmission line characteristics is preliminarily placed outside the OFDM signal band so as to be equal to the pilot carrier interval in the OFDM signal band. Even when processing such as copying to a pilot carrier copy section of a predetermined length and inserting 0 between the copied pilot carriers without performing time axis interpolation, both ends of the OFDM signal band after frequency axis interpolation are performed. It is possible to reduce the degradation of the transmission path characteristic estimation accuracy.

  Thus, according to the present embodiment, in addition to the configuration of the second embodiment, an overwrite unit 502 is provided, and the OFDM interpolated in the frequency axis direction based on the OFDM symbol in which the pilot carrier is not arranged at the band edge of the OFDM signal. The transmission path characteristics for a predetermined carrier at the signal band edge are determined for the predetermined carrier at the OFDM signal band edge subjected to frequency axis interpolation based on an OFDM symbol in which a pilot carrier is arranged at the band edge of the OFDM signal. In addition to the effects of the second embodiment, an OFDM receiving apparatus 500 that can reduce degradation of transmission path characteristic estimation accuracy at both ends of the OFDM signal band can be realized.

  In this embodiment, the case where the SP interval of the data after SP / CP division is every 12 carriers has been described as an example. However, the present invention is not limited to this, and the same applies to other SP intervals. An effect can be obtained.

  Further, although an example of an OFDM receiving apparatus has been described in this embodiment, 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 6. By adopting such a configuration, it is possible to realize an OFDM relay apparatus that can reduce deterioration in accuracy when frequency axis interpolation is performed on pilot carrier transmission path characteristic data using a frequency interpolation filter.

  The present invention can reduce degradation of transmission path characteristic estimation accuracy caused by interpolating transmission path characteristics obtained from pilot signals in the frequency axis direction, and is applied to, for example, an OFDM receiver and an OFDM relay apparatus for terrestrial digital broadcasting. And useful. 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. FIG. 5 is a diagram for explaining transmission path characteristic data copy processing according to the first embodiment. FIG. 3 is a block diagram showing a configuration of an OFDM receiving apparatus according to the second embodiment. FIG. 10 is a diagram for explaining transmission path characteristic data copy processing according to the second embodiment. FIG. 9 is a block diagram showing a configuration of an OFDM receiving apparatus according to the third embodiment. The figure for demonstrating the overwrite process of the transmission line characteristic data in Embodiment 3 The figure which shows the signal format of ISDB-T The block diagram which shows the structure of the conventional OFDM receiver Diagram for explaining time-axis interpolation processing of transmission line characteristics

Explanation of symbols

11 FIR filter unit 30 Pilot carrier channel characteristic estimation unit 40 Time axis interpolation unit 100, 300, 500 OFDM receiver 101, 301 Copy unit 110, 310, 510 Channel characteristic estimation unit 120, 320 Frequency axis interpolation unit 302 0 insertion 501 Band edge data storage unit 502 Overwrite unit

Claims (6)

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,
Pilot carrier channel characteristic estimating means for estimating channel characteristics acting on the pilot carrier based on the received pilot signal;
Of the pilot carrier transmission line characteristics obtained by the pilot carrier transmission line characteristic estimation means, the pilot carrier transmission line characteristic closest to the band edge in the OFDM signal band is equal to the pilot carrier interval in the OFDM signal band. And a pilot carrier copy means for copying to a pilot carrier copy section of a predetermined length outside the OFDM signal band and inserting 0 between the copied pilot carriers,
An OFDM receiver comprising: frequency axis interpolation means for interpolating data obtained by the pilot carrier copy means in the frequency axis direction. The time-axis interpolation means provided in the front | former stage side of the said pilot carrier copy means and interpolating the pilot carrier transmission line characteristic obtained by the said pilot carrier transmission line characteristic estimation means to a time-axis direction is further provided. The OFDM receiver according to the description. The pilot carrier copy means includes
A pilot carrier transmission path characteristic at the pilot carrier position, a 0 insertion section for inserting 0 at the data carrier position,
The pilot carrier transmission path characteristic closest to the band edge in the OFDM signal band is set to a pilot carrier copy section of a predetermined length outside the OFDM signal band so that the pilot carrier transmission path characteristic is equal to the pilot carrier interval in the OFDM signal band. The OFDM receiver according to claim 1, further comprising: a copy unit that performs copying. A transmission path for a predetermined carrier at the OFDM signal band edge that is provided on the rear side of the frequency axis interpolation means and is interpolated in the frequency axis direction based on an OFDM symbol in which no pilot carrier is arranged at the band edge of the OFDM signal Overwriting means for replacing the characteristic with a transmission path characteristic for a predetermined carrier at the OFDM signal band edge that is frequency-axis interpolated based on an OFDM symbol in which a pilot carrier is arranged at the band edge of the OFDM signal is further provided. The OFDM receiver according to claim 1 or 3. The frequency axis interpolation means is constituted by an FIR filter,
The OFDM receiver according to claim 1, wherein the pilot carrier copy section by the pilot carrier copy means is half the number of taps of the FIR filter.   An OFDM relay apparatus comprising the OFDM receiver according to any one of claims 1 to 5.

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