WO2009125501A1 - Receiver and receiving method - Google Patents

Abstract

[PROBLEMS] To solve a problem that although a conventional receiver is capable of accurately calculating an estimated transfer characteristic with respect to specific carrier amplitude, it does not take the amount of operation in a 2D (2D-inverse) Fourier transform processing into consideration. [MEANS FOR SOLVING PROBLEMS] An SP transfer characteristic calculation circuit (21a) calculates a pilot signal transfer characteristic with respect to a pilot signal located in a two-dimensional data area. An SP transfer characteristic extraction circuit (21b) extracts the pilot signal transfer characteristic at the position at which the pilot signals are superposed on one another except the carrier in which the pilot signals are not superposed on one another to supply it to a two-dimensional Fourier transform section (22).

Description

Receiving apparatus and receiving method

The present invention relates to a receiver for terrestrial digital broadcasting, for example.

Generally, in terrestrial digital broadcasting using the OFDM system, a pilot carrier signal for facilitating estimation of transmission path transmission characteristics is used together with a data carrier signal for transmitting information data such as video and audio. For example, in the above-mentioned standards such as ISDB-T and DVB-T, a pilot carrier signal called a distributed pilot (SP) signal (hereinafter referred to as “SP signal”) is defined. The SP signal is known to be superimposed at a specific position in the same space when assuming an OFDM symbol space consisting of two dimensions of carrier frequency and symbol time, and its complex amplitude, that is, the absolute value of the SP signal. The amplitude and phase are also predetermined. Therefore, in a receiving apparatus that receives digital broadcasting according to these standards, the SP signal is used to estimate the transfer characteristics for each carrier of the radio wave propagation path, and based on such estimation results, correction processing related to the received signal, etc. Can be performed.

In order to improve that the estimation accuracy of the transfer characteristic for each carrier is low, the conventional receiver calculates the transfer function for each detection signal of the pilot carrier signal arranged in the OFDM signal symbol space, and the transfer function A two-dimensional data space is generated by performing a two-dimensional Fourier transform on the impulse delay time and the symbol frequency. Further, the conventional receiving apparatus extracts a predetermined region of the two-dimensional data space by a filter extraction region, performs a two-dimensional inverse Fourier transform on the carrier frequency and symbol time for the data included in the extraction region, and obtains an estimated transfer function. It was generated (see Patent Document 1).
Japanese Patent No. 3820311

In such a conventional receiving apparatus, although it is possible to accurately calculate an estimated transfer characteristic with respect to a specific carrier amplitude, the amount of calculation is not taken into consideration in the 2D (2D inverse) Fourier transform processing. It was.

The problems to be solved by the present invention include the above-mentioned problems as an example.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a pilot signal having a specific known complex amplitude is transmitted using a transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data as a transmission unit. A received signal obtained by receiving an OFDM signal superimposed on a predetermined carrier in a symbol and detecting a carrier group included in a plurality of consecutive transmission symbols is converted into a two-dimensional space corresponding to the carrier frequency and symbol time. A signal detector arranged in a two-dimensional data region, a transfer characteristic estimator for estimating a received signal transfer characteristic for each of the received signals based on a pilot signal arranged in the two-dimensional data region, and the received signal And a data decoding unit that decodes the transmission data based on the reception signal transfer characteristics, the reception device comprising: The characteristic estimation unit is configured to calculate a pilot signal transmission characteristic for a pilot signal arranged in the two-dimensional data region, and to perform a two-dimensional Fourier transform on the pilot signal transmission characteristic to obtain a transmission line delay time and a transmission line Transform means for generating two-dimensional Fourier transform data in a two-dimensional space corresponding to the fluctuation frequency, and supply means for calculating a two-dimensional filter window for allowing a group of data in a specific region of the two-dimensional Fourier transform data to pass through Filter means for selectively extracting a data group in the specific region determined based on the two-dimensional filter window, and performing a two-dimensional inverse Fourier transform on the selected and extracted data group, Generate two-dimensional inverse Fourier transform data in a two-dimensional space corresponding to the symbol time, and based on the generated data Generating means for generating a received signal transfer characteristic, wherein the calculating means superimposes the pilot signal on a transfer characteristic calculating means for calculating a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region. Excluding a carrier that is not used, the pilot signal transmission characteristic at a position where the pilot signal is superimposed is extracted, and is provided with a transmission characteristic extraction means for use in the conversion means.

In order to solve the above-mentioned problem, the invention according to claim 6 is characterized in that a pilot signal having a specific known complex amplitude is transmitted with a transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data. A received signal obtained by receiving an OFDM signal superimposed on a predetermined carrier in a symbol and detecting a carrier group included in a plurality of consecutive transmission symbols is converted into a two-dimensional space corresponding to the carrier frequency and symbol time. A signal detection step arranged in a two-dimensional data region, a transmission characteristic estimation step for estimating a reception signal transmission property for each of the reception signals based on a pilot signal arranged in the two-dimensional data region, and the reception signal And a data decoding step for decoding the transmission data based on the reception signal transfer characteristics. The transfer characteristic estimation step includes: a calculation step for calculating a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region; and a two-dimensional Fourier transform is performed on the pilot signal transfer characteristic to perform transmission. A transform step for generating two-dimensional Fourier transform data in a two-dimensional space corresponding to a path delay time and a transmission path fluctuation frequency, and a two-dimensional filter for passing a data group in a specific region of the two-dimensional Fourier transform data A supply step for calculating a window; a filter step for selectively extracting a data group in the specific region determined based on the two-dimensional filter window; and a two-dimensional inverse Fourier transform for the selected and extracted data group 2D inverse Fourier transform data in 2D space corresponding to carrier frequency and symbol time Generating a reception signal transfer characteristic based on the generated data, wherein the calculation step calculates a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region A transfer characteristic calculating step for extracting the pilot signal transfer characteristic at a position where the pilot signal is superposed, excluding a carrier on which the pilot signal is not superposed, and a transfer characteristic extracting step for use in the conversion step Is provided.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In all the embodiments described below, description will be made by taking as an example a partial receiver for terrestrial digital broadcasting by ISDB-T. In the case of the ISDB-T standard, the OFDM symbol is composed of 13 segments as shown in FIG. 1, and each segment includes, for example, a carrier of 108 waves in the case of transmission mode 1. Yes. The partial receiving apparatus is a receiving apparatus that demodulates only the carrier included in segment 0 located in the center of the 13 segments.

In the following case, the case of the transmission mode 1 among a plurality of transmission modes defined in the ISDB-T standard will be described as an example. The values of each modulation parameter in the transmission mode 1 are shown in FIG. 2, and the values of each constant parameter used in the description are shown in FIG.

<First Embodiment>
FIG. 4 is a block diagram illustrating a configuration example of the receiving device 1 according to the first embodiment. The receiving apparatus 1 mainly includes a symbol detection unit 11, a symbol storage unit 12, a frequency domain processing unit 13, a transfer characteristic estimation unit 20, and a data decoding unit 30. In addition, the arrow which shows the flow of a signal in a figure shows the flow of the main signals between each component, For example, regarding signals, such as a response signal and a monitoring signal accompanying such a main signal, a figure. Including the case of transmission in the direction opposite to the arrow in the middle. Furthermore, the arrows in the figure conceptually indicate the flow of signals between the components, and in an actual device, it is not necessary for each signal to be faithfully exchanged along the path indicated by the arrows. . Moreover, in an actual apparatus, it is not necessary that each component is divided faithfully as shown in FIG.

The symbol detection unit 11 detects a carrier group included in each symbol with respect to sequentially transmitted symbols, and obtains complex amplitudes (hereinafter referred to as “carrier amplitudes”) _{Sp, k} of these carriers. . Here, S _{p, k} represents the p-th carrier amplitude of the k-th symbol, and the carrier index p is allocated so that the carrier in the center of the channel corresponds to the index p = 0 as shown in FIG. Shall. That is, the carrier at the center of the channel corresponds to S _{0, k} , and the carrier group of segment 0 corresponds to S _{−54, k} to S _{53, k} . The symbol detection unit 11 is configured by each component circuit such as a tuner, an A / D converter, a transmission mode / guard interval ratio detector, a guard interval removal circuit, and an FFT circuit. It is not limited to cases.

Next, the symbol storage unit 12 is a circuit that selects nX carrier amplitudes output from the symbol detection unit 11 and stores them for nY symbol times in the symbol time direction. . That is, for the carrier group of (2D region carrier width nX × 2D region symbol width nY) in the OFDM symbol space shown in FIG. 6, the carrier amplitude S _{p, q} (−nX / 2 ≦ p <nX / 2) , K−nY <q ≦ k). In the following description, these stored and held carrier amplitudes are considered as a two-dimensional array {S _{p, q} : (p, q) εZ _2D } in the (p, q) space.

As shown in FIG. 6, p is a carrier index, q is a symbol index, and each index corresponds to a carrier frequency and a symbol time. Also, the Z _2D range is in the carrier frequency direction,
−nX / 2 ≦ p <nX / 2
And in the symbol time direction:
k−nY <q ≦ k
Is defined as

The relationship between each carrier amplitude information two-dimensionally arranged in the (p, q) space that is the OFDM symbol space and the attribute of each carrier (the attribute that the carrier is an SP signal or a data carrier signal) As shown in FIG. As is clear from the figure, the SP signal is superposed at a rate of one on 12 carriers, and the superposition position cyclically changes by 3 carriers for each symbol.

The frequency domain processing unit 13 performs frame synchronization processing, TMCC demodulation processing, etc., generates symbol count values from 0 to 203 for each symbol, and stores them in the symbol storage unit 12. The symbol storage unit 12 stores the symbol count value provided from the frequency domain processing unit 13 in association with each symbol provided from the symbol detection unit 11.

The data decoding unit 30 further includes an estimation region Z _EST (−wX / 2 ≦ p <wX / 2, k−nY / 2) shown in FIG. 6 from the carrier amplitude data group stored in the symbol storage unit 12. The carrier amplitude {S _{p, q} : (p, q) εZ _EST } within −wY / 2 ≦ q <k−nY / 2 + wY / 2) is extracted, and this is subjected to decoding processing.

Further, the transfer characteristic estimation unit 20 calculates an estimated transfer characteristic with respect to the carrier amplitude in the estimation region Z _EST based on the carrier amplitude stored in the symbol storage unit 12, and _supplies this to the data decoding unit 30 It is.

The data decoding unit 30 performs processing such as equalization, deinterleaving, and Reed-Solomon decoding based on the carrier amplitude from the symbol storage unit 12 and the estimated transfer characteristic from the transfer characteristic estimation unit 20, and is obtained as a result. Output received data. The transfer characteristic estimation unit 20 estimates transfer characteristics for consecutive wY symbol intervals, so it does not need to operate at the timing of each received symbol, and is once per wY symbol reception. Should work. Such operation timing is the same for the operation timing of the data decoding unit 30.

Next, the configuration and operation of the transfer characteristic estimation unit 20 will be described.

First, the configuration of the transfer characteristic estimation unit 20 is shown in FIG. As shown in the figure, the transfer characteristic estimation unit 20 mainly includes an SP transfer characteristic calculation unit 21, a two-dimensional Fourier transform unit 22, a two-dimensional filter circuit 23, a two-dimensional inverse Fourier transform circuit 24, and an estimated transfer characteristic output. The circuit 25 and the filter coefficient determination circuit 26 are included. In the following description, these circuits are referred to as a calculation unit 21, a conversion unit 22, a filter circuit 23, an inverse conversion unit 24, an output circuit 25, and a determination circuit 26, respectively, in order to simplify the description. In the detailed description of the circuit configuration below, the calculation unit 21 and the inverse conversion unit 24, which are specific configurations in the present embodiment, will be mainly described, and other circuit configurations will be described in the operation description.

As shown in FIG. 9, the calculation circuit 21 includes an SP transfer characteristic calculation circuit 21a and an SP transfer characteristic extraction circuit 21b. Among these, the SP transfer characteristic extraction circuit is referred to as an “extraction circuit”. The SP transfer characteristic calculation circuit 21a extracts only the carrier amplitude related to the SP signal from the carrier amplitude supplied from the symbol storage unit 12, and divides this by the known transmission complex amplitude value. As a result, the SP transfer characteristic calculation circuit 21a can obtain the transfer characteristic {H _{p, q} : (p, q) εZ _2D } for the SP signals scattered in the (p, q) space. The extraction circuit 21b provides the conversion unit 22 with SP signal transfer characteristics for every three carrier indexes except for a carrier index on which no SP signal is superimposed.

As shown in FIG. 10, the inverse transform unit 24 includes an inverse Fourier transform circuit 24a, a multiplier circuit 24b, and a Fourier transform circuit 24c. The inverse Fourier transform circuit 24a performs an inverse Fourier transform process on the data in the symbol index direction over all carrier indexes. The multiplication circuit 24b multiplies each carrier by a complex twiddle factor coefficient (exp (−jω _o t)). Note that j represents an imaginary unit, and exp (x) represents a complex function. The Fourier transform circuit 24 c calculates an estimated transfer characteristic by performing a Fourier transform process on the data in the carrier index direction over all symbol indexes, and provides it to the output circuit 25. That is, the multiplication circuit 24b and the Fourier transform circuit 24c perform the calculation in the carrier index direction.

Next, the operation of the transfer characteristic estimation unit 20 will be described. As described above, in the terrestrial digital broadcasting of the ISDB-T standard, the position of the SP signal in the carrier arrangement in the OFDM symbol space and the complex amplitude value of the SP signal at the time of transmission are determined in advance. Therefore, the calculation unit 21 extracts only the carrier amplitude related to the SP signal from the carrier amplitudes supplied from the symbol storage unit 12, and divides this by the known transmission complex amplitude value. Thereby, the transfer characteristics {H _{p, q} : (p, q) εZ _2D } can be obtained for the SP signals scattered in the (p, q) space. Such a calculation procedure is as follows.

In the calculation unit 21, the SP transfer characteristic calculation circuit 21a shown in FIG. 9 extracts only the carrier amplitude related to the SP signal from the carrier amplitude supplied from the symbol storage unit 12, and this is extracted as a known transmission complex amplitude value. Divide by.

SP transfer characteristic calculation circuit 21a, all the elements (p, q) in the area _{Z 2D} shown in FIG. 6 for _the case _{where S p, q} corresponds to the SP signal,
H _{p, q} = S _{p, q} / R _{p, q}
Then, transfer characteristics H _{p, q} relating to the SP signal are obtained. Here, R _{p, q} is a known transmission complex amplitude value of the SP signal.

On the other hand, the SP transfer characteristic calculation circuit 21a performs the following operation on data carrier signals other than SP signals.
H _{p, q} = 0
The transfer function {H _{p, q} } is defined as follows.

As a result, the SP transfer characteristic calculation circuit 21a can obtain the transfer characteristic {H _{p, q} : (p, q) εZ _2D } for the SP signals scattered in the (p, q) space.

The extraction circuit 21 b supplies the SP signal transfer characteristic {H _{p, q} } for each three carrier index to the conversion unit 22 except for the carrier index on which no SP signal is superimposed.

That is, the SP signal superposed at a rate of 1 on 12 carriers is present only every 3 carriers as shown in FIG. The SP signal in which the superposition position has been cyclically changed by three carriers for each symbol has its superposition position cyclically changed by one carrier for each symbol.

That is, for the carrier group in the OFDM symbol space shown in FIG. 11, the SP signal transfer characteristic {H of 2D-FFT region Z ′ _2D (−mX / 2 ≦ p <mX / 2, k−nY <q ≦ k) ' _{p, q} : (p, q) εZ' _2D } is provided to the conversion unit 22. In the figure, the range of the estimation region Z ′ _EST is (−vX / 2 ≦ p <vX / 2, k−nY / 2−wY / 2 ≦ q <knY / 2 + wY / 2).

The transform unit 22 performs a two-dimensional Fourier transform on the SP signal transfer characteristic {H ′ _{p, q} } in the (p, q) space, and performs this on the SP signal transfer characteristic {h in the (m, n) space. _{m, n} : (m, n) εZ ′ _TRA } That is, for the carrier frequency direction (p direction) in (p, q) space, IFFT (Inverse Fast Fourier Transform) processing is performed to convert the frequency domain to the time domain, and for the symbol time direction (q direction), The time domain is converted into the frequency domain by performing FFT (Fast Fourier Transform) processing.

As a result, in the (m, n) space after the two-dimensional Fourier transform, the m-axis direction corresponds to the time dimension, and the n-axis direction corresponds to the frequency dimension. Further, the region Z ′ _2D in the (p, q) space corresponds to the region Z ′ _TRA converted in the (m, n) space, and this region is
-MX / 2 ≦ m <mX / 2
And in the n-axis direction,
−nY / 2 ≦ n <nY / 2
Is defined as

The determination circuit 26 calculates a two-dimensional filter window {W _{m, n} } based on the data group that has been Fourier-transformed in the (m, n) space by the conversion unit 22. As described in Patent Document 1, the power spectrum distribution of the transmission path transfer characteristic tends to be concentrated in a specific region on the (m, n) space according to the nature of the transmission path. Therefore, the decision circuit 26 calculates a real coefficient two-dimensional filter window {W _{m, n} } having a pass band covering this area, and supplies it to the filter circuit 23. As an example, a two-dimensional filter window may be set so that a region A shown in FIG. 14 to be described later is used as a passband and other regions are used as a stopband. That is, in the region A, the two-dimensional filter window {W _{m, n} } is W _{m, n} = 1.
W _{m, n} = 0 for other areas
Set as

Needless to say, as such a two-dimensional filter window, window functions having various shapes such as a rectangular window and a cosine descent window can be applied. Needless to say, the decision circuit 26 should set the passband of the two-dimensional filter window adapted to the reception environment.

The filter circuit 23 is a circuit that performs a predetermined filtering process on the data group that has been Fourier-transformed in the (m, n) space by the conversion unit 22.

The filter circuit 23 multiplies the SP signal transfer characteristic {h _{m, n} } in the (m, n) space by the real coefficient two-dimensional filter window {W _{m, n} } provided by the decision circuit 26 ( m, n) Calculate the estimated transfer characteristic {g _{m, n} } in space. The estimated transfer characteristic {g _{m, n} } calculated by the filter circuit 23 is output to the inverse conversion unit 24 in the next stage.

The inverse transform unit 24 performs a two-dimensional inverse Fourier transform, which is an inverse process of the two-dimensional Fourier transform, on the estimated transfer characteristic {g _{m, n} } provided from the filter circuit 23, and from {g _{m, n} } to ( p, q) Estimated transfer characteristic {Gp _{, q} : (p, q) εZ _2D } in space is calculated.

The inverse transform unit 24 performs transform from the frequency domain to the time domain by performing an inverse Fourier transform process over the entire carrier index in the symbol index direction (n-axis direction) by the inverse Fourier transform circuit 24a shown in FIG.

The multiplication circuit 24b multiplies the complex twiddle factor coefficient (exp (−jω _o t)) so that a predetermined phase rotation occurs in the mX section in the time domain in the carrier index direction (m-axis direction). Note that j represents an imaginary unit, and exp (x) represents a complex exponential function.

The Fourier transform circuit 24c performs transform from the time domain to the frequency domain by performing a Fourier transform process in the carrier index direction (m-axis direction).

When the inverse transform unit 24 is configured by only the inverse Fourier transform circuit 24a and the Fourier transform circuit 24c as in the above-described Patent Document 1, the estimated transfer characteristic calculated by the inverse transform unit 24 is {G ′ _{p, q} : (P, q) εZ ′ _2D } and the estimated region is Z ′ _EST . The region where the transfer characteristic estimation unit 20 should estimate the transfer characteristic is Z _EST , whereas the estimated region Z ′ _EST is a region of 1/3 with respect to the carrier direction. This is because the SP transfer characteristic {H ′ _{p, q} : (p, q) ∈ where the SP transfer characteristic {H _{p, q} : (p, q) ∈Z _2D } is extracted every three carriers by the SP transfer characteristic extraction circuit 21 b. This is because Z ′ _2D } is supplied to the conversion unit 22, and the calculated transfer characteristic is also obtained for each three carrier index.

Therefore, the inverse transform unit 24 of the present embodiment performs an inverse Fourier transform process in the symbol direction (n-axis direction) in the inverse Fourier transform circuit 24a. Next, using the frequency shift theorem described later, the multiplication circuit 24b multiplies the carrier direction by a complex twiddle factor coefficient, and the Fourier transform circuit 24c performs Fourier transform in the carrier direction three times for each symbol. Then, the estimated transfer characteristic {G _{p, q} : (p, q) εZ _2D } including the range of the estimated region Z _EST is calculated. The estimated transfer characteristic {G _{p, q} } calculated by the inverse conversion unit 24 is provided to the output circuit 25.

For example, specifically, by applying a Fourier transform after multiplying complex twiddle factors such that the phase rotates 0Π, 2 / 3Π, and 4 / 3Π in the mX interval on the time axis, respectively, the carrier index t = The estimated transfer characteristic at the position of 3 · p, t = 3 · p + 1, t = 3 · p + 2 (−mX ≦ p <mX) can be calculated, and the estimated transfer characteristic in the region Z _2D is calculated.

<About the frequency shift theorem>
If F (ω) and f (t) are a Fourier transform pair, the following equation holds.
f (t) × exp (jω ₀ t) ⇔ F (ω−ω ₀ )
The above equation shows the theorem that “movement of ω _{0 in} the frequency domain is equivalent to multiplying exp (jω ₀ t) in the time domain”.

The output circuit 25 extracts the estimated transfer characteristic {G _{p, q} : (p, q) εZ _EST } corresponding to the carrier amplitude of the estimation region Z _EST extracted by the data decoding unit 30 and extracts such extracted data. Is provided to the data decoding unit 30.

The reason _why the estimated transfer characteristic for the entire Z _2D region is not output from the transfer characteristic estimating unit 20 to the data decoding unit 30 is that the estimated transfer characteristic is changed due to the influence of the end of the region in the peripheral part of the (p, q) space. This is because an error occurs. In order to reduce the influence of such an end, for example, as the specific values of the two-dimensional region carrier width nX and the two-dimensional region symbol width nY, values larger than those in the present embodiment may be used. In this embodiment, a value of wY = 204 is used as the estimated area symbol width wY, but the estimated area symbol width wY is not limited to such a value. Similarly, for the estimated region carrier width wX, in the present embodiment, a value of wX = 108 corresponding to the number of carriers included in the same segment is used in consideration of the configuration of the one-segment partial receiving apparatus. It is not limited to such a value. For example, in the case of a receiving apparatus that receives and demodulates three segments arranged in the center of the transmission band, wX = 324 may be set.

FIG. 13 is a diagram showing a power spectrum distribution of the transmission path transfer characteristic of the SP signal described in FIG. 9 of Patent Document 1.

Since this power spectrum distribution has been subjected to 2D Fourier transform processing, the m-axis direction is time, and represents the delay time to the effective symbol length Te. The n-axis direction is a frequency and represents a Doppler frequency up to the symbol transmission frequency Fa.

However, since the SP signal is superposed only for every three carriers, it can be confirmed that the transmission path transmission characteristic is repeated in the m-axis direction in 1/3 period of the effective symbol length Te. For example, when there is a delay wave exceeding 1/3 of the effective symbol length Te, the SP signal transfer characteristic can be observed only in a form that is folded back to 1/3 period of the effective symbol length Te. Therefore, the effective SP signal transfer characteristic is only the Te / 3 section with respect to the m-axis direction.

On the other hand, in the first embodiment, since the calculation unit 21 provides the conversion unit 22 with the SP signal transfer characteristic {H ′ _{p, q} } for every three carrier indexes, the SP signal transfer characteristic {h _m that is the output of the conversion unit 22. _{, N} } power spectrum distribution {| h _{m, n} | ² } represents a delay time up to 1/3 of the effective symbol length Te in the m-axis direction, as shown in FIG. For the n-axis direction, the frequency of the symbol transmission frequency Fa is shown as in the case shown in FIG.

As described above, in the first embodiment, since the transfer characteristic is calculated over the Te / 3 width that is an effective section in the time direction (m-axis direction) of the SP signal transfer characteristic, the accuracy of the estimated transfer characteristic is calculated. The estimated transfer characteristic can be calculated with a smaller amount of calculation processing without lowering the.

Next, only the processing of the inverse transform unit 24 whose operation is complicated in the first embodiment will be specifically described using a flowchart. FIG. 15 is a flowchart illustrating a procedure example of 2D inverse Fourier transform processing. The inverse Fourier transform process is executed by the inverse Fourier transform unit 24.

Symbol direction inverse Fourier transform processing (also referred to as S-IFFT processing) indicates processing for performing inverse Fourier transform in the symbol direction for the (p, q) space (step S100). The carrier direction Fourier transform process (also referred to as C-IFFT process) indicates a process of performing a Fourier transform in the carrier direction for the (p, q) space (step S200).

In the following explanation, each calculation formula is expressed as follows. In the following formula, “FFT” indicates a function for performing Fourier transform, and “IFFT” indicates a function for performing inverse Fourier transform.

1. 1D (one-dimensional) Fourier transform processing for n F (p, q) = FFT (f (p, n)) dn

2. 1D (one-dimensional) inverse Fourier transform processing for q f (m, n) = IFFT (F (m, q)) dq

FIG. 16 is a flowchart showing a procedure example of the symbol direction inverse Fourier transform process shown in FIG. In the following flowcharts, the symbol “←” indicates that the value or expression on the right side is set to the variable on the left side.

In step S102, an inverse Fourier transform process is performed on the symbol direction counter value n. The step S102 is repeated in the carrier direction two-dimensional region carrier width mX times (steps S101, S103, S104).

FIG. 17 is a flowchart showing a procedure example of the carrier direction Fourier transform process shown in FIG.

In step S300, a twiddle factor multiplication process is executed. In this twiddle factor multiplication process, a twiddle factor coefficient based on the repetition index k and the carrier index m is multiplied in the carrier direction. Details of the twiddle factor multiplication process will be described later.

In step S203, a Fourier transform process is performed on the carrier index m. In step S400, an estimated area extraction process is executed. This estimated area extraction process extracts estimated transfer characteristics of the estimated area. In this estimated area extraction processing, only the estimated transfer characteristic of the estimated area width vX (corresponding to the estimated area carrier width wX / 3 in FIG. 6) shown in FIG. 11 is extracted and stored in a memory (not shown). These steps S300, S203, and S400 are repeated three times for each symbol as an example (steps S202, S204, and S205). In the flowchart, the Fourier transform process in the carrier direction is repeatedly executed over the two-dimensional area symbol width nY (steps S201, S206, S207), but is repeatedly executed over the estimated area symbol width wY. Also good.

FIG. 18 is a flowchart showing a specific procedure example of the twiddle factor multiplication process shown in FIG.

In step S302, the complex exponent ph of the twiddle factor coefficient is calculated based on the repetition count index k and the carrier index m. In step S303, the variable z is calculated. The symbol “&” represents, for example, that a logical product operation is performed on a variable or the like described on the left and right of each bit. In step S304, the twiddle factor exp (ph) is multiplied using the complex exponent ph calculated in step S302. These steps S302, S303, and S304 are repeatedly executed over the estimated region carrier width wX / 2 (steps S301, S305, and S306).

FIG. 19 is a flowchart showing a specific procedure example of the estimation region extraction process shown in FIG. Note that nT represents a carrier direction calculation range parameter, and in the first embodiment, nT = wX / 3 is set (step S401). The target carrier calculation variable c represents a calculation variable for specifying a carrier to be processed.

In step S404, a variable z is set. In step S405, the estimated transfer characteristic calculated for each carrier direction Fourier transform is stored in a memory (not shown) for each three carrier index. In step S406, the target carrier calculation variable c is incremented by 3 so that the carrier to be targeted is every three carriers.

Steps S404, S405, and S406 as described above are executed as an example from −nT / 2 to nT / 2 every three carriers (steps S401, S402, S403, S407, and S408).

As described above, the receiving apparatus 1 according to the present embodiment is configured so that a pilot signal having a specific known complex amplitude with the transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data as a transmission unit is the transmission symbol. 2 received in a two-dimensional space corresponding to the carrier frequency and symbol time. The received signal obtained by receiving the OFDM signal superimposed on a predetermined carrier and detecting the carrier group included in a plurality of consecutive transmission symbols. A signal detector 11 (symbol detector) arranged in the two-dimensional data region, and a transfer characteristic estimator for estimating a received signal transfer characteristic for each of the received signals based on a pilot signal arranged in the two-dimensional data region 20 and a data decoding unit 30 for decoding the transmission data based on the reception signal and the reception signal transfer characteristic, The transfer characteristic estimation unit 20 includes a calculation unit 21 (SP transfer characteristic calculation unit) that calculates a pilot signal transfer characteristic with respect to a pilot signal arranged in the two-dimensional data region; A conversion means 22 (2D Fourier transform unit) that performs two-dimensional Fourier transform on the pilot signal transfer characteristics to generate two-dimensional Fourier transform data in a two-dimensional space corresponding to the transmission line delay time and the transmission line fluctuation frequency; Supply means 26 (filter coefficient setting circuit) for calculating a two-dimensional filter window for passing a data group in the specific area of the two-dimensional Fourier transform data, and the specific area determined based on the two-dimensional filter window Filter means 23 (2D filter circuit) for selecting and extracting a data group in the second order, and second order for the data group selected and extracted A generating unit 24 that performs inverse Fourier transform to generate two-dimensional inverse Fourier transform data in a two-dimensional space corresponding to the carrier frequency and symbol time, and generates the reception signal transfer characteristic based on the generated data. 2D inverse Fourier transform unit), and the calculating means 21 includes a transfer characteristic calculating means 21a (SP transfer characteristic calculating circuit) for calculating a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region, The pilot signal transmission characteristic for every three carriers is extracted except for the carrier on which the pilot signal is not superimposed, and is provided with transmission characteristic extraction means 21b (SP transmission characteristic extraction circuit) for use in the conversion means 22. To do.

In the receiving method in the present embodiment, a pilot signal having a specific known complex amplitude is superimposed on a predetermined carrier in the transmission symbol with a transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data as a transmission unit. A received signal obtained by receiving a received OFDM signal and detecting a carrier group included in a plurality of consecutive transmission symbols is arranged in a two-dimensional data region on a two-dimensional space corresponding to the carrier frequency and symbol time. Based on the signal detection step, the transfer characteristic estimation step for estimating the received signal transfer characteristic for each of the received signals based on the pilot signal arranged in the two-dimensional data region, the received signal and the received signal transfer characteristic And a data decoding step for decoding the transmission data. The characteristic estimation step includes a calculation step for calculating a pilot signal transmission characteristic for a pilot signal arranged in the two-dimensional data region, and a two-dimensional Fourier transform is performed on the pilot signal transmission characteristic to obtain a transmission line delay time and a transmission line A conversion step for generating two-dimensional Fourier transform data in a two-dimensional space corresponding to a variable frequency, and a supply step for calculating a two-dimensional filter window for allowing a group of data in a specific region to pass through the two-dimensional Fourier transform data. A filter step for selectively extracting a data group in the specific region determined based on the two-dimensional filter window, and performing a two-dimensional inverse Fourier transform on the selected and extracted data group, Generate two-dimensional inverse Fourier transform data in a two-dimensional space corresponding to the symbol time, and generate the data Generating a reception signal transfer characteristic based on the received data, wherein the calculation step calculates a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region And a transfer characteristic extracting step for extracting the pilot signal transfer characteristic for every three carriers except for a carrier on which the pilot signal is not superimposed and for use in the process of the conversion step.

In this way, the estimated transfer characteristic can be calculated with a smaller amount of calculation processing without lowering the accuracy of the estimated transfer characteristic.

<Second Embodiment>
Incidentally, FIG. 20 shows the power spectrum distribution {| h _{m, n} | ² } of the SP signal transfer characteristic {h _{m, n} } _, which is the output of the conversion unit 22, and is a diagram showing a property A described later. The (m, n) space corresponds to the OFDM symbol space.

The SP signal transfer characteristic {hm _{, n} } calculated by performing the 2D Fourier transform process in the conversion unit 22 has the following properties due to the regular arrangement of the SP signals. The SP signal transfer characteristic {h _{m, n} } corresponds to h (m, n).
h (m (mX-1), n & (nY-1))
= H (m & (kX-1), (n + k × nY / 4) & (nY-1))
× exp (−j × 2π / 4 × (k × co4)) (1)
co4 = (symco + (2 << mode)) & 3
k = (4-floor (((m & (mX-1) + (kX / 2)) / kX)) & 3
kX = mX / 4

The variable mode represents the transmission mode, for example, 0 for mode 1, 1 for mode 2, and 2 for mode 3. The variable symco is a symbol count value associated with the symbol arranged and stored at the q-axis origin, that is, q = k-255 symbol in FIG. The function floor (x) is a function for calculating the maximum integer value less than or equal to x.

In FIG. 20, the (m, n) space is expressed in the range of (−mX / 2 ≦ m <mX / 2, −nY / 2 ≦ n <nY), but in the expression (1), (0 ≦ m <MX, 0 ≦ n <nY). That is, in the (m, n) space in FIG. 20, m = −1 is defined as m = mX−1 in the equation (1).

That is, the first item h (m & (kX−1), (n + k × nY / 4) & (nY−1)) on the right side of the equation (1) shows only the region H in FIG. Therefore, equation (1) shows that an arbitrary SP signal transfer characteristic {h _{m, n} } in the (m, n) space can be easily calculated from the SP signal transfer characteristic of the region H. Therefore, equation (1) means that the SP signal transfer characteristic {hm _{, n} } is composed of one independent variable group and three dependent variable groups in the (m, n) space. This property is referred to as property A as a name.

In short, it can be expected that the calculation processing amount of the conversion unit 22 can be further reduced by devising only the SP signal transfer characteristic corresponding to the region H in FIG. The second embodiment described below is intended to further reduce the amount of calculation processing of the conversion unit 22 by using the property A.

FIG. 21 is a block diagram illustrating a configuration example of the receiving device 1a according to the second embodiment. The receiving device 1a according to the second embodiment has substantially the same configuration as the receiving device 1 according to the first embodiment and performs substantially the same operation. For this reason, in the second embodiment, the same configurations and operations are denoted by the same reference numerals as in FIGS. 1 to 19 in the first embodiment, and the description thereof is omitted. In the following description, differences will be mainly described. .

The receiving device 1a according to the second embodiment includes a transfer characteristic estimation unit 20a having substantially the same function as the transfer characteristic estimation unit 20 instead of the transfer characteristic estimation unit 20 according to the first embodiment.

FIG. 22 is a block diagram showing a configuration example of the transfer characteristic estimation unit 20a shown in FIG. The transfer characteristic estimation unit 20a according to the second embodiment mainly differs from the transfer characteristic estimation unit 20 according to the first embodiment mainly in a part of the function of the calculation unit 21 and the configuration and function of the conversion unit 22. .

In the first embodiment, the SP transfer characteristic calculation circuit 21a of the calculation unit 21 extracts the transfer characteristic {H _{p, q} } of the SP signal for every three carrier indexes, for example, but this is the second embodiment. Then, the SP transfer characteristic extraction circuit 21a extracts the transfer characteristic {H _{p, q} } of only the SP signal for every 12 carrier indexes, for example.

The calculating unit 21 extracts only the carrier amplitude related to the SP signal from the carrier amplitude supplied from the symbol storage unit 12 by the SP transfer characteristic calculating circuit 21a shown in FIG. Divide by value.

SP transfer characteristic calculation circuit 21a, all the elements (p, q) in the area _{Z 2D} shown in FIG. 6 for _the case _{where S p, q} corresponds to the SP signal,
H _{p, q} = S _{p, q} / R _{p, q}
Then, transfer characteristics {H _{p, q} } regarding the SP signal are obtained. Here, {R _{p, q} } is a known transmission complex amplitude value of the SP signal.

On the other hand, the SP transfer characteristic calculation circuit 21a performs the following operation on data carrier signals other than SP signals.
H _{p, q} = 0
The transfer function {H _{p, q} } is defined as follows.

As a result, the SP transfer characteristic calculation circuit 21a can obtain the transfer characteristic {H _{p, q} : (p, q) εZ _2D } for the SP signals scattered in the (p, q) space.

The extraction circuit 21b extracts only the SP signal transfer characteristic {H _{p, q} } at the SP signal position and supplies it to the converter 22x. Specifically, the extraction circuit 21b extracts the SP signal transfer characteristic only at the SP signal position shown in FIG. 24, and supplies the SP signal transfer characteristic to the conversion unit 22x in the form of packing in the carrier direction as shown in FIG.

Thus, by limiting the SP signal transfer characteristics provided to the conversion unit 22x to the carrier at the SP signal position, it is possible to further reduce the calculation processing amount of the conversion unit 22x.

As described above, the SP signal transfer characteristics {H ″ _{p, q} } provided to the conversion unit 22x are arranged in the OFDM space as shown in Fig. 23. Range of 2D Fourier transform region in the second embodiment Z " _2D is
−kX / 2 ≦ p <kX / 2; k−nY <q ≦ k
Is defined. Also, the estimated area Z " _EST is
−uX / 2 ≦ p <uX / 2; k−nY / 2−wY / 2 <q ≦ k−nY / 2 + wY / 2
Is defined.

The conversion unit 22x performs a two-dimensional Fourier transform on the SP signal transfer characteristic {H " _{p, q} } in the (p, q) space provided from the SP transfer characteristic calculation unit 21, and converts this to (m, n ) SP signal transfer characteristics in space {h _{m, n} : (m, n) εZ ′ _TRA } The conversion unit 22 x outputs this to the filter circuit 23 and the decision circuit 26.

That is, in the transform unit 22x, the inverse Fourier transform circuit 22a and the multiplier circuit 22b shown in FIG. 26 perform processing in the carrier index direction, and the Fourier transform circuit 22c performs processing in the symbol index direction.

That is, the SP signal transfer characteristic provided to the converter 22x is degenerated in the carrier direction as shown in FIG. 25, and is different from the superimposed position in the (p, q) space as originally shown in FIG. The SP signal superposition position is not shifted in the carrier direction every time. Therefore, the transform unit 22x performs the inverse Fourier transform process in the carrier direction for each symbol by the inverse Fourier transform circuit 22a using the frequency shift theorem described above, and then multiplies a predetermined complex twiddle factor coefficient in the multiplier circuit 22b. As a result, a result that is relatively shifted by a desired position on the time axis before the inverse Fourier transform processing is calculated.

Specifically, the complex twiddle factor coefficient is determined based on the symbol count value and transmission mode associated with each symbol provided from the symbol storage unit 12. Therefore, the complex factor coefficient is updated for each symbol, and in the case of the present embodiment, the cycle is 4 symbols.

Next, in the Fourier transform circuit 22c, the SP signal transfer characteristic {h ′ _{m, n} } in the (m, n) space is calculated by performing Fourier transform processing in the symbol direction.

As shown in FIG. 27, the power spectrum distribution {| h ′ _{m, n} | ² } of the SP signal transfer characteristic {h ′ _{m, n} } calculated by the converter 22x is the effective symbol length Te in the m-axis direction. The delay time is up to 1/12, and in the n-axis direction, the frequency is equal to the symbol transmission frequency Fa. Further, the SP signal transfer characteristic {h ′ _{m, n} } calculated by the conversion unit 22x corresponds to the area H of FIG. 20 used in the description of the property A described above. By utilizing the above properties A, conversion unit SP signal transfer characteristic calculated in 22x {h _{'m, n}} from the calculated conversion unit 22 in the first embodiment SP signal transfer characteristic _{{h m, n}} easily Can be converted. That is, the converter 22x outputs the SP signal transfer characteristic {h _{m, n} } to the filter circuit 23 and the determination circuit 26.

Therefore, the determination circuit 26, the filter circuit 23, the inverse conversion unit 24, and the output circuit 26 may be processed in the same manner as in the first embodiment. Since the determination circuit 26, the filter circuit 23, the inverse conversion unit 24, and the output circuit 25 are the same as those in the first embodiment, description thereof is omitted.

FIG. 28 is a flowchart showing a procedure example of 2D Fourier transform processing. This 2D Fourier conversion process represents a process performed by the conversion unit 22x. The 2D Fourier transform process includes a carrier direction inverse Fourier transform process (corresponding to step S500) and a symbol direction Fourier transform process (corresponding to step S600). In the carrier direction inverse Fourier transform process, as shown in FIG. 29, the Fourier transform process (step S501) is repeatedly performed along the symbol direction (steps S502 and S503).

FIG. 30 is a flowchart showing a procedure example of the carrier direction inverse Fourier transform process shown in FIG. In step S602, the shift amount s in the carrier direction for each symbol is calculated based on the transmission mode mode and the symbol count value symco. The transmission mode mode is a variable that is, for example, 0 in mode 1, 1 in mode 2, and 2 in mode 3. The symbol count value symco is a symbol count value associated with a symbol arranged and stored at the q-axis origin in the symbol group provided to the conversion unit 22x, that is, q = k-255 symbol in FIG. In step S603, a Fourier transform process in the carrier direction is performed.

In step S605, the complex exponent ph of the twiddle factor coefficient is calculated based on the shift amount s calculated in step S602 and the carrier index m. In step S607, {H " _{z, q} } (corresponding to H" (z, q)) subjected to the Fourier transform is multiplied by a twiddle factor exp (ph). The above process is repeated kX times in the carrier direction and nY times in the symbol direction.

As described above, according to the second embodiment, the SP signal transfer characteristic {H _{p, q} } provided to the conversion unit 22x is limited in the calculation unit 21, and the calculation is devised in the conversion unit 22x. As compared with the above, the amount of calculation can be further reduced without degrading the accuracy of the estimated transfer characteristic.

As described above, the receiving apparatus 1a according to the present embodiment uses the transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data as a transmission unit, and a pilot signal having a specific known complex amplitude is the transmission symbol. 2 received in a two-dimensional space corresponding to the carrier frequency and symbol time. The received signal obtained by receiving the OFDM signal superimposed on a predetermined carrier and detecting the carrier group included in a plurality of consecutive transmission symbols. A signal detector 11 (symbol detector) arranged in the two-dimensional data region, and a transfer characteristic estimator for estimating a received signal transfer characteristic for each of the received signals based on a pilot signal arranged in the two-dimensional data region 20 and a data decoding unit 30 for decoding the transmission data based on the received signal and the received signal transfer characteristic The transfer characteristic estimation unit 20 includes a calculation unit 21 (SP transfer characteristic calculation unit) that calculates a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region; A conversion unit 22x (2D Fourier transform unit) that performs two-dimensional Fourier transform on the pilot signal transfer characteristics to generate two-dimensional Fourier transform data in a two-dimensional space corresponding to the transmission line delay time and the transmission line fluctuation frequency; Supply means 26 (filter coefficient setting circuit) for calculating a two-dimensional filter window for passing a data group in the specific area of the two-dimensional Fourier transform data, and the specific area determined based on the two-dimensional filter window Filter means 23 (2D filter circuit) for selectively extracting a data group within the data group, and for the data group selected and extracted Generation means 24 for performing two-dimensional inverse Fourier transform to generate two-dimensional inverse Fourier transform data in a two-dimensional space corresponding to the carrier frequency and symbol time, and generating the reception signal transfer characteristic based on the generated data (2D inverse Fourier transform unit), and the calculation unit 21 includes a transfer characteristic calculation unit 21a (SP transfer characteristic calculation circuit) that calculates a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region. The pilot signal transmission characteristic at the position where the pilot signal is superimposed is extracted except for the carrier on which the pilot signal is not superimposed, and the transmission characteristic extraction means 21b (SP transmission characteristic extraction circuit) provided to the conversion means 22x It is characterized by providing.

In the receiving method in the present embodiment, a pilot signal having a specific known complex amplitude is superimposed on a predetermined carrier in the transmission symbol with a transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data as a transmission unit. A received signal obtained by receiving a received OFDM signal and detecting a carrier group included in a plurality of consecutive transmission symbols is arranged in a two-dimensional data region on a two-dimensional space corresponding to the carrier frequency and symbol time. Based on the signal detection step, the transfer characteristic estimation step for estimating the received signal transfer characteristic for each of the received signals based on the pilot signal arranged in the two-dimensional data region, the received signal and the received signal transfer characteristic And a data decoding step for decoding the transmission data. The characteristic estimation step includes a calculation step for calculating a pilot signal transmission characteristic for a pilot signal arranged in the two-dimensional data region, and a two-dimensional Fourier transform is performed on the pilot signal transmission characteristic to obtain a transmission line delay time and a transmission line A conversion step for generating two-dimensional Fourier transform data in a two-dimensional space corresponding to a variable frequency, and a supply step for calculating a two-dimensional filter window for allowing a group of data in a specific region to pass through the two-dimensional Fourier transform data. A filter step for selectively extracting a data group in the specific region determined based on the two-dimensional filter window, and performing a two-dimensional inverse Fourier transform on the selected and extracted data group, Generate two-dimensional inverse Fourier transform data in a two-dimensional space corresponding to the symbol time, and generate the data Generating a reception signal transfer characteristic based on the received data, wherein the calculation step calculates a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region And a transfer characteristic extracting step for extracting the pilot signal transfer characteristic at a position where the pilot signal is superimposed, except for a carrier on which the pilot signal is not superimposed, and for performing the process of the conversion step. And

In this way, the estimated transfer characteristic can be calculated with a smaller amount of calculation processing without lowering the accuracy of the estimated transfer characteristic as compared with the first embodiment.

In the receiving apparatus 1a in the above embodiment, in addition to the above-described configuration, the converting means 22x (2D Fourier transform unit) further uses the frequency shift theorem and is based on the pilot signal transmission characteristics for every 12 carriers. The two-dimensional Fourier transform data is generated, and the generation means 24 (2D inverse Fourier transform circuit) uses a frequency shift theorem, and based on the data group selected and extracted, A reception signal transfer characteristic is calculated.

In the receiving apparatus 1a in the above embodiment, in addition to the above-described configuration, the converting means 22x (2D Fourier converter) further multiplies the pilot signal transmission characteristics for every 12 carriers by a twiddle factor to The dimensional Fourier transform data is generated, and the generation means 24 (2D inverse Fourier transform circuit) multiplies the selected and extracted data group by a twiddle factor to calculate the reception signal transfer characteristic in the two-dimensional data area. To do.

In addition, this embodiment is not restricted above, Various deformation | transformation are possible. Hereinafter, such modifications will be described in order.

<Method without using twiddle factor coefficient>
In the second embodiment, in the configuration shown in FIG. 22, when only the SP signal is supplied to the converter 22x, the converter 22x does not need to multiply the twiddle factor coefficient after the inverse Fourier transform in the carrier direction. A desired calculation result can be obtained as follows.

The calculation unit 21 calculates the SP signal transfer characteristic {H _{p, q} } in the (p, q) space as in the above embodiment. Then, the SP transfer characteristic extraction circuit 21b extracts the SP signal transfer characteristic {H " _{p, q} } only for the carrier position of the SP signal (see FIG. 24), and SP signal transfer characteristics (see FIG. 25) packed in the carrier direction. Is provided to the converter 22x.

The conversion unit 22x performs 2D Fourier transform processing on the SP signal transfer characteristics provided from the calculation unit 21. As an example, FIG. 31 shows a flowchart of the conversion unit 22x when an SP signal exists at the origin (0, 0) in the (p, q) space. The 2D Fourier transform processing indicates carrier direction inverse Fourier transform processing (corresponding to the illustrated C-IFFT processing step S500) and symbol direction Fourier transform processing (corresponding to the illustrated S-IFFT processing step S600).

FIG. 32 is a flowchart showing a procedure example of the inverse Fourier transform process (step S500) in the carrier direction. This flowchart is executed by the conversion unit 22x.

In step S522, a value that is incremented by 1 every time the index is incremented by 4 in the symbol index q-axis direction is calculated. In step S524, an index to be circulated in the carrier index p-axis direction is calculated based on the value calculated in step S522. In step S525, the data that has been circulated in the carrier index p-axis direction is stored in the temporary storage area temp (pa). The process of step S525 is a process of changing the top address (origin) of data used for inverse Fourier transform, and does not necessarily require the temporary storage area temp (pa).

These steps S524 and S525 are repeatedly executed over the two-dimensional region carrier width kX (S526 and S527). In step S528, an inverse Fourier transform process is performed in the carrier direction. These steps S522 to S528 are repeatedly executed over the two-dimensional symbol width nY (S529, S530).

FIG. 33 is a flowchart showing an example of the procedure of Fourier transform processing in the symbol direction. This flowchart is executed by the conversion unit 22.

First, in step S621, the carrier index m is initialized. In step S622, a Fourier transform process in the symbol direction is performed. In step S623, an offset value ma for circulating data in the symbol index q-axis direction is calculated. In step S625, the index na to which data is circulated in the symbol index q-axis direction is calculated. In step S626, the data after Fourier transformation in the symbol direction is circulated in the symbol index q-axis direction to calculate the SP signal transfer characteristic {hm _{, na} }. These steps S625 and S626 are repeatedly executed over the two-dimensional area symbol width nY (S627, S628). These steps S622 to S628 are executed over the two-dimensional region carrier width mX (S629, S630).

As described above, there is an arithmetic method that does not need to multiply the complex twiddle factor coefficient by performing an index (address) operation before the inverse Fourier transform in the carrier direction and an index (address) operation after the Fourier transform in the symbol direction. . The calculation can be performed only when the value of nY / mX becomes an integer of 1 or more.

On the other hand, when the two-dimensional region carrier width mX / 2-dimensional region symbol width nY is an integer of 1 or more, the SP transfer characteristic extracting circuit 21b first extracts the SP signal transfer characteristic only at the SP carrier signal position, and the symbol direction To the conversion unit 22. Next, when the transform unit 22 performs the Fourier transform process in the symbol direction first, it is possible to perform the 2D Fourier transform only by the index (address) operation without multiplying the complex twiddle factor coefficient as described above. .

<Modification>
FIG. 34 is a block diagram illustrating a configuration example of a receiving device 1x configured to divide the symbol storage unit 12 into a data carrier storage unit 12a and an SP carrier storage unit 12b in the receiving device 1 illustrated in FIG. The receiving apparatus 1x shown in FIG. 34 has substantially the same configuration as that of the receiving apparatus 1 shown in FIG. 4 and the receiving apparatus 1a shown in FIG. Note that the data carrier storage unit 12a and the SP carrier storage unit 12b may be two storage regions secured by dividing the storage region of the symbol storage unit 12, or may be physically separated storage regions.

In each embodiment described above, the symbol storage unit 12 may be divided into a data carrier storage unit 12a and an SP carrier storage unit 12b. Since other configurations are almost the same as those in the above embodiment, the following description will mainly focus on the data carrier storage unit 12a and the SP carrier storage unit 12b.

First, the configuration will be described. The frequency domain processing unit 13 performs frame synchronization processing, TMCC demodulation processing, and the like, and generates symbol count values from 0 to 203 for each symbol. The symbol count value is provided to the data carrier storage unit 12a and the SP carrier storage unit 12b.

In the data carrier storage unit 12a, only the carrier sequence used in the data decoding unit 30 is selected for each symbol and stored as a two-dimensional space in the carrier frequency direction and the symbol time direction. Further, the data carrier storage unit 12 a stores the symbol count value provided from the frequency domain processing unit 13 in association with each symbol provided from the symbol detection unit 11. The stored carrier group is provided to the data decoding unit 30.

The SP carrier storage unit 12a selects only the SP carrier sequence used by the transfer characteristic estimation unit 20 for each symbol and stores it as a two-dimensional space in the carrier frequency direction and the symbol time direction. Further, the symbol count value provided from the frequency domain processing unit 13 is stored in a form associated with each symbol provided from the symbol detection unit 11. The stored subcarrier group is provided to the transfer characteristic estimation unit 20.

The data decoding unit 30 performs processes such as equalization, deinterleaving, and Reed-Solomon decoding based on the carrier complex amplitude from the data carrier storage unit 12a and the estimated transfer characteristic from the transfer characteristic estimation unit 20, and outputs TS data. .

The SP carrier storage unit 12a selects only the SP carrier from the nX carriers in the channel center portion of the symbol comprising the carrier sequence provided from the symbol detection unit 11, and stores this for nY symbols in the symbol time direction. . That is, in the SP carrier storage unit 12a, the carrier amplitude {S _{p, q} } of only the SP carrier in the hatched portion (−nX / 2 ≦ p <nX / 2, k−nY <q ≦ k) in the OFDM space of FIG. Is retained. As shown in FIG. 35, the carrier index in the carrier frequency direction is p, and the symbol index in the symbol time direction is q.

In the data carrier storage unit 12a, only the data carrier is selected from the wX carriers in the channel center portion of the symbol composed of the carrier sequence provided from the symbol detection unit 11, and this is selected in the symbol time direction (two-dimensional region symbol width nY). / 2 + estimated area symbol width wY / 2) Stores over symbols. That is, the carrier amplitude {SD _{p, q} } of only the data carrier of the lattice portion (−wX / 2 ≦ p <wX / 2, k−nY / 2−wX / 2 <q ≦ k) in the OFDM space of FIG. Retained.

As described above, in addition to the above-described configuration, the receiving device 1x in the embodiment further includes storage means for sequentially storing carrier amplitudes output from the signal detection means 11 (symbol detection unit), and the storage The means selects only the carrier sequence used in the data decoding means 30 (data decoding section) for each symbol, and stores it as a two-dimensional space in the carrier frequency direction and symbol time direction, the first storage means 12a (data carrier storage section) And a second storage unit 12b (SP carrier storage unit) for storing the symbol count value provided from the frequency domain processing unit 13 (frequency domain processing unit) for each symbol provided from the signal detection unit 11 ).

<Technology to make the storage area constant regardless of the transmission mode>
In the above embodiment, a specific transmission mode has been described as an example. However, the two-dimensional area carrier nX is set so that the total storage area of the data carrier storage unit 12a and the SP carrier storage unit 14 is constant regardless of the transmission mode. The two-dimensional area symbol width nY may be variable with respect to the transmission mode.

First, since the receiving device 1x has a limited storage area, the storage area should be used effectively. Therefore, it is desirable that the storage areas used in the data carrier storage unit 12a and the SP data storage unit 12b are constant regardless of the transmission mode. Therefore, the transfer characteristic estimation unit 20 variably sets each parameter depending on the transmission mode so that the storage capacity is constant regardless of the transmission mode.

In each of the above embodiments, the transfer characteristic estimation unit 20 prevents the estimated area carrier width wX × estimated area symbol width WY, 2D carrier width nX × 2D area symbol width nY from changing even if the transmission mode changes. . As an example, each parameter is set as shown in FIG.

The relationship between the two-dimensional area carrier wX and the two-dimensional area carrier width nX is expressed by the following equation. Note that ceil_pow (x) represents a function that returns the minimum factorial value of 2 that is greater than or equal to the value x.
nX = (ceil_pow (wX / 3)) × 3

In the receiving apparatus 1x, in addition to the above-described configuration, the supply unit 26 (filter coefficient determination circuit) further includes a carrier frequency width wX, nX and a symbol time width wY, nY as the two-dimensional filter window according to a transmission mode. It is characterized by providing.

Thus, by setting the carrier width wX, nX and the symbol width wY, nY according to the transmission mode, the total storage area used in the data carrier storage unit 12a and the SP carrier storage unit 12b is made constant regardless of the transmission mode. can do.

In addition to those already described above, the methods according to the above-described embodiments and modifications may be used in appropriate combination.

It is a figure which shows the structure of the OFDM symbol by ISDB-T standard. It is a figure which shows treatment of each modulation parameter by the transmission mode 1 by ISDB-T standard. It is a figure which shows treatment of each constant parameter used in 1st Embodiment. It is a block diagram which shows the structural example of the receiver by 1st Embodiment. It is explanatory drawing which shows the relationship between a segment and a carrier index. It is explanatory drawing which shows the structural example of OFDM symbol space. It is explanatory drawing which shows the attribute of the carrier arrange | positioned in OFDM symbol space. It is a block diagram which shows the structural example of the transfer characteristic estimation part shown in FIG. It is a block diagram which shows the structural example of the calculation circuit shown in FIG. It is a block diagram which shows the specific structural example of the inverse transformation part shown in FIG. It is explanatory drawing which shows the structure of OFDM symbol space. It is explanatory drawing which shows the attribute of the carrier arrange | positioned in OFDM symbol space. It is explanatory drawing which shows the power spectrum distribution on the (m, n) space in a 1st receiving environment. It is a figure which shows the power spectrum distribution of SP signal transmission characteristic which is an output of a 2D Fourier-transform part. It is a flowchart which shows the example of a procedure of 2D inverse Fourier transform processing. It is a flowchart which shows the example of a procedure of the symbol direction inverse Fourier transform process shown in FIG. It is a flowchart which shows the example of a procedure of the carrier direction Fourier-transform process shown in FIG. It is a flowchart which shows the specific example of a procedure of the twiddle factor multiplication process shown in FIG. It is a flowchart which shows the specific example of a procedure of the estimation area | region extraction process shown in FIG. It is an example of the power spectrum distribution of the SP signal transmission characteristic that is the output of the conversion unit. It is a block diagram which shows the structural example of the receiver by 2nd Embodiment. It is a block diagram which shows the structural example of the transfer characteristic estimation part shown by FIG. It is explanatory drawing which shows the structure of OFDM symbol space. It is explanatory drawing which shows the attribute of the carrier arrange | positioned in OFDM symbol space. It is explanatory drawing which shows the attribute of the carrier arrange | positioned in OFDM symbol space. It is a block diagram which shows a 2D Fourier-transform part. It is a figure which shows the power spectrum distribution of SP signal transmission characteristic output from the conversion part in 2nd Embodiment. It is a flowchart which shows the example of a procedure of 2D Fourier-transform processing. It is a flowchart which shows the example of a procedure of the symbol direction Fourier-transform process shown by FIG. It is a flowchart which shows the example of a procedure of the carrier direction inverse Fourier transform process shown by FIG. It is a flowchart which shows the example of a procedure of the 2D Fourier-transform part which does not use a twiddle factor coefficient. It is a flowchart which shows the example of a procedure of the inverse Fourier transform process step of a carrier direction. It is a flowchart which shows the example of a procedure of the Fourier-transform process of a symbol direction. FIG. 5 is a block diagram illustrating a configuration example of a receiving device in which a symbol storage unit is divided into a data carrier storage unit and an SP carrier storage unit in the receiving device shown in FIG. 4. It is explanatory drawing which shows the structural example of OFDM symbol space. It is explanatory drawing which shows the structural example of OFDM symbol space. It is a figure which shows an example of each parameter set according to the transmission mode.

Explanation of symbols

1 receiver 1a receiver 1x receiver 11 symbol detector (signal detector)
12 symbol storage section 12a data carrier storage section (first storage means, storage means)
12b SP carrier storage section (second storage means, storage means)
20 transfer characteristic estimation unit 20a transfer characteristic estimation unit 21 SP transfer characteristic calculation unit (calculation means)
21a SP transfer characteristic calculation circuit (transfer characteristic calculation means)
21b SP transfer characteristic extraction circuit (transfer characteristic extraction means)
22 Two-dimensional Fourier transform circuit (conversion means)
23 Two-dimensional filter circuit (filter means)
24 Two-dimensional inverse Fourier transform circuit (generation means)
24a Inverse Fourier Transform Circuit 24b Multiplier Circuit 24c Fourier Transform Circuit 25 Estimated Transfer Characteristic Output Circuit 26 Filter Coefficient Determination Circuit (Supply Unit)
30 Data decoding unit

Claims (6)

1. Receiving an OFDM signal in which a pilot signal having a specific known complex amplitude is superimposed on a predetermined carrier in the transmission symbol with a transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data as a transmission unit; A signal detector that arranges a received signal obtained by detecting a carrier group included in a plurality of consecutive transmission symbols in a two-dimensional data region on a two-dimensional space corresponding to a carrier frequency and a symbol time;
   A transfer characteristic estimator for estimating a received signal transfer characteristic for each of the received signals based on a pilot signal arranged in the two-dimensional data region;
   A data decoding unit that decodes the transmission data based on the received signal and the received signal transfer characteristic,
   The transfer characteristic estimator is
   Calculating means for calculating a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region;
   Conversion means for performing two-dimensional Fourier transform on the pilot signal transfer characteristic to generate two-dimensional Fourier transform data in a two-dimensional space corresponding to a transmission line delay time and a transmission line fluctuation frequency;
   Supply means for calculating a two-dimensional filter window for allowing a data group in a specific region to pass through the two-dimensional Fourier transform data;
   Filter means for selectively extracting a data group in the specific area determined based on the two-dimensional filter window;
   Two-dimensional inverse Fourier transform is performed on the selected and extracted data group to generate two-dimensional inverse Fourier transform data in a two-dimensional space corresponding to a carrier frequency and a symbol time, and based on the generated data Generating means for generating the received signal transfer characteristic,
   The calculating means includes
   Transfer characteristic calculation means for calculating a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region;
   A receiving apparatus comprising: a transfer characteristic extracting unit that extracts the pilot signal transfer characteristic at a position where the pilot signal is superimposed, except for a carrier on which the pilot signal is not superimposed, and provides the converted signal to the conversion unit .
2. The receiving device according to claim 1,
   The transforming means uses the frequency shift theorem to generate the two-dimensional Fourier transform data based on the pilot signal transfer characteristics for every 12 carriers, and the generating means uses the frequency shift theorem to perform the selective extraction. A reception apparatus that calculates the reception signal transfer characteristic in the two-dimensional data region based on the data group that has been set.
3. The receiving device according to claim 2,
   The conversion means generates the two-dimensional Fourier transform data by multiplying the pilot signal transmission characteristic for every 12 carriers by a twiddle factor, and the generation means
   The receiving apparatus, wherein the reception signal transfer characteristic in the two-dimensional data area is calculated by multiplying the selected and extracted data group by a twiddle factor.
4. The receiving device according to claim 1,
   Storage means for sequentially storing carrier amplitudes output from the signal detection means;
   The storage means
   First storage means for selecting only a carrier sequence used by the data decoding means for each symbol and storing it as a two-dimensional space in the carrier frequency direction and symbol time direction;
   And a second storage means for storing the symbol count value provided by the frequency domain processing means in association with each symbol provided by the signal detection means.
5. The receiving device according to claim 1,
   The receiving device provides a carrier frequency width and a symbol time width as the two-dimensional filter window according to a transmission mode.
6. Receiving an OFDM signal in which a pilot signal having a specific known complex amplitude is superimposed on a predetermined carrier in the transmission symbol with a transmission symbol generated by orthogonally modulating a plurality of carriers based on transmission data as a transmission unit; A signal detection step of arranging a received signal obtained by detecting a carrier group included in a plurality of continuous transmission symbols in a two-dimensional data region on a two-dimensional space corresponding to a carrier frequency and a symbol time;
   A transfer characteristic estimating step for estimating a received signal transfer characteristic for each of the received signals based on a pilot signal arranged in the two-dimensional data region;
   A data decoding step of decoding the transmission data based on the received signal and the received signal transfer characteristics, comprising:
   The transfer characteristic estimation step includes:
   A calculation step of calculating a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region;
   A transforming step of performing a two-dimensional Fourier transform on the pilot signal transfer characteristic to generate two-dimensional Fourier transform data in a two-dimensional space corresponding to a transmission path delay time and a transmission path fluctuation frequency;
   A supply step of calculating a two-dimensional filter window for allowing a data group in a specific region to pass through the two-dimensional Fourier transform data;
   A filter step of selectively extracting a data group in the specific region determined based on the two-dimensional filter window;
   Two-dimensional inverse Fourier transform is performed on the selected and extracted data group to generate two-dimensional inverse Fourier transform data in a two-dimensional space corresponding to a carrier frequency and a symbol time, and based on the generated data Generating to generate the received signal transfer characteristics;
   With
   The calculating step includes:
   A transfer characteristic calculating step for calculating a pilot signal transfer characteristic for a pilot signal arranged in the two-dimensional data region;
   And a transfer characteristic extracting step for extracting the pilot signal transfer characteristic at a position where the pilot signal is superimposed, except for a carrier on which the pilot signal is not superimposed, and for providing to the process of the conversion step. Reception method.

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