JP2001313627A - Ofdm transmitter and ofdm transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform waveform equalization with high accuracy when connecting and transmitting ISDB-Ts. SOLUTION: Information for discriminating whether an adjacent segment is a synchronous segment or a differential segment is described in TMCC information at the time of performing connection transmission. A receiver refers to the TMCC information, and when the adjacent segment is the synchronous segment, the receiver estimates the transmission characteristic of a transmission path and performs waveform equalization by using an SP signal including an adjacent channel, too. Specifically, a timing control circuit 59 decides whether the SP signal is included in the adjacent channel, and when the SP signal is included, a frequency direction filter 56 performs FIR filtering and corrects a signal of a frequency direction by using not only the SP signal inserted into a frequency channel to be a demodulation channel but also the SP signal of the adjacent channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to orthogonal frequency division multiplexing transmission (OFDM).
The present invention relates to an OFDM transmission apparatus and an OFDM transmission method applied to digital broadcasting or the like using a multiplexing method.

[0002]

2. Description of the Related Art In recent years, as a system for transmitting digital signals, an orthogonal frequency division multiplexing system (OFDM) has been proposed.
A modulation method called "requency division multiplexing" has been proposed. In this OFDM system, a number of orthogonal subcarriers (subcarriers) are provided in a transmission band, data is allocated to the amplitude and phase of each subcarrier, and PSK (Phase Shift Keying) and QAM (Quad) are provided.
ratture Amplitude Modulati
on), which is a digital modulation method.

In this OFDM system, since the transmission band is divided by a large number of subcarriers, the band per subcarrier wave becomes narrow and the modulation speed becomes slow, but the total transmission speed is different from that of the conventional modulation system. There is no feature. Further, the OFDM scheme has a feature that the symbol rate is reduced because a large number of subcarriers are transmitted in parallel. Therefore, in the OFDM system, the time length of the multipath relative to the time length of the symbol can be shortened, and multipath interference is reduced. Further, in the OFDM system, data is allocated to a plurality of subcarriers, so that an IFFT (Inverse FFT) that performs an inverse Fourier transform at the time of modulation.
as a Fourier Transform (FFT) arithmetic circuit, which performs a Fourier transform at the time of demodulation.
er Transform) has a feature that a transmission / reception circuit can be configured by using an arithmetic circuit.

[0004] From the above characteristics, the OFDM system is widely studied for application to terrestrial digital broadcasting which is strongly affected by multipath interference. Such OF
As terrestrial digital broadcasting adopting the DM system, for example, ISDB-T (Integrated Services Digital Br
oadcasting-Terrestrial) has been proposed for adoption in Japan.

Next, a description will be given of a frame configuration defined in the ISDB-T standard (in the case of mode 1), which is one of the digital terrestrial broadcasting systems.

In the ISDB-T standard, FIGS. 15 and 16
As shown in (1), a data structure of transmission data called an OFDM frame is defined. FIG. 15 shows differential modulation (D
FIG. 16 shows a frame configuration when an information signal is modulated by QPSK, and FIG. 16 shows a synchronous modulation (QPSK).
K, 16QAM, 64QAM) when the information signal is modulated.

As shown in FIGS. 15 and 16, the number of data transmitted in one symbol is 108 (carrier numbers # 0 to # 107). The data unit of one symbol is called an OFDM symbol. Also, 204 OFD
1 OFD with M symbols (symbol numbers # 0 to # 203)
M frames are formed.

[0008] In one OFDM frame, QPSK,
An information signal (S _{0,0 to} S _95,203 ) orthogonally modulated by 16QAM, 64QAM or the like is included, and a CP (Conti
nual pilot) signal, TMCC (Transmission and Multi)
plexing Configuration Control), AC (Auxiliary C
hannel) and various control signals such as SP (Scattered Pilot) signals.

The CP signals are all signals having a fixed phase and amplitude. When the information signal is modulated by differential modulation, the CP signal is arranged at the head carrier (the position with the lowest frequency) of each OFDM symbol. In the case of performing concatenated transmission, the CP signal is arranged at the right end (highest frequency) of the concatenated transmission band.

As shown in FIG. 16, the SP signal is arranged so as to be inserted once every 12 carriers in the frequency direction and once every four symbols in the symbol direction. This SP signal is used for estimating propagation path characteristics when waveform equalization is performed on the receiving side. Therefore, in the ISDB-T standard,
Synchronous modulation that requires waveform equalization (QPSK, 16QA
M, 64QAM). This SP
Details of the signal will be described later.

[0011] The AC signal is a signal used for transmitting additional information.

[0012] TMCC signal is a signal used for transmission of the transmission control information is information 204 bits to complete in 1OFDM frame (B ₀ ~B _203). TMC
FIG. 17 shows the information content assigned to the C signal.

A signal indicating the reference of the amplitude and phase of the differential demodulation is assigned to B ₀ .

A sync code (synchronous signal) that is inverted every frame is assigned to B _{1 to} B ₁₆ . The receiving side detects the bit pattern of the sync code and detects the synchronization of the TMCC signal and the synchronization of the OFDM frame.

To B _{17 to} B ₁₉ , a segment identification signal for identifying whether the frame is a frame for synchronous modulation or a frame for differential modulation is assigned.

[0016] The B ₂₀ ~B _121, TMCC information (120
Bit) is assigned. The TMCC information includes a carrier modulation scheme of an information signal, a convolutional coding rate,
An interleave length, the number of segments, and the like are described.

Parity bits are assigned to B _{122 to} B ₂₀₃ .

In the ISDB-T standard (mode 1), an OFDM signal is generated with the above-described frame configuration.

Next, the SP signal will be further described.

As a modulation method for each subcarrier, Q
In the OFDM system using the modulation of the AM system, if different distortions occur for each subcarrier due to the influence of multipath or the like during transmission, the characteristics of the amplitude and phase for each subcarrier will be different. Therefore, on the receiving side, it is necessary to equalize (correct) the waveform of the received signal so that the amplitude and phase of each subcarrier become equal. In the OFDM system, an SP signal having a predetermined amplitude and a predetermined phase is scattered in a transmission symbol in a transmission signal on a transmission side, and the amplitude and phase of the pilot signal are monitored on a reception side, thereby forming a transmission path. The characteristic is estimated, and the received signal is equalized based on the estimated characteristic of the transmission path.

In the ISDB-T standard, as shown in FIG.
The signal is inserted, and the insertion position of the SP signal is shifted by three subcarriers for each OFDM symbol.

By shifting the insertion position of the SP signal for each OFDM symbol, the redundancy of the SP signal with respect to the original data is reduced.

Such an SP signal is, for example, an ISDB
According to the -T standard, output bits of a pseudo-random code sequence (PRBS) represented by the following equation are data obtained by BPSK modulation.

G (x) = x ¹¹ + x ⁹ +1

On the other hand, the receiving side uses the SP signals scattered in the OFDM symbol to determine the propagation characteristic H of the transmission path.
By estimating (ω) and complexly dividing the estimated propagation characteristic H (ω) into the received OFDM symbol, waveform equalization of the received signal is performed. In this way, on the receiving side, the transmission characteristic of the transmission path given to each subcarrier is removed by estimating the transmission characteristic of the transmission path using the SP signal and performing waveform equalization, and thereby eliminating multipath and the like during transmission. The effect can be eliminated.

[0026]

When the propagation characteristic H (ω) of the transmission line is obtained, SP signals discretely arranged in the frequency direction are interpolated in the frequency direction using, for example, an FIR filter. , The propagation characteristic H (ω) covering all the subcarriers is obtained.

However, the subcarriers located at both ends (or in the vicinity thereof) of the OFDM symbol have a small number of SP signals to be sampled, so that the interpolation accuracy is deteriorated.

The present invention has been made in view of such a situation, and an OFDM transmitting an OFDM signal that enables the receiving side to accurately estimate the transmission characteristics of a transmission path.
An object is to apply a DM transmitting apparatus and method.

[0029]

SUMMARY OF THE INVENTION OFDM according to the present invention
The transmission apparatus and method include orthogonal frequency division multiplexing (OFDM).
An OFDM transmitting apparatus for transmitting a signal, the OFDM signal being transmitted to a plurality of information channels, the OFDM signal being transmitted to each information channel when connected transmission is performed by multiplexing in the frequency direction while maintaining orthogonality. The signal is characterized by describing information indicating that a pilot signal for waveform equalization exists in an OFDM signal transmitted to an adjacent information channel.

In the OFDM transmission apparatus and method according to the present invention, when the OFDM signals to be transmitted to a plurality of information channels are multiplexed in the frequency direction while maintaining orthogonality, and concatenated transmission is performed, each of the information channels is transmitted. OF to be transmitted
OFD transmitted to adjacent information channel in DM signal
Information indicating that a pilot signal for waveform equalization exists in the M signal is described.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as an embodiment of the present invention, an OFD adapted to the ISDB-T standard (mode 1) will be described.
OFDM transmitter for transmitting M signal, and OF
An OFDM receiver that receives a DM signal will be described.

First, the configuration on the transmitting side will be described.

An OFDM transmitting apparatus to which the present invention is applied performs a concatenated transmission in which OFDM signals transmitted to a plurality of information channels are multiplexed in the frequency direction while maintaining orthogonality. The concatenated transmission of OFDM signals is, for example,
The center frequencies of the OFDM signals in the frequency domain of the plurality of information channels are respectively changed, and these are multiplexed and connected in the frequency direction, and the OFD signals in the frequency domain of the plurality of information channels are connected.
This is performed by performing an inverse Fourier transform on the M signals collectively.

According to this concatenated transmission, for example, when transmitting information sequences (Ch1, Ch2, Ch3) of three information channels, as shown in FIG. The three information channels can be connected in the frequency axis direction and transmitted.

FIG. 2 shows a block diagram of an OFDM transmitting apparatus to which the present invention is applied.

The OFDM transmitting apparatus shown in FIG. 2 is an apparatus for connecting and transmitting three information channels. The center frequency of each information channel in the RF band is, as shown in FIG.
The information channel is f ₁ , the second information channel is f ₂ ,
Information channel is assumed to be f _3.

The OFDM transmitting apparatus 1 includes a first channel encoder 2-1 and a second channel encoder 2-2.
A third channel encoder 2-3, a synchronization control unit 3,
A first frequency converter 4-1 and a second frequency converter 4-2
, A third frequency conversion unit 4-3, a multiplexing unit 5, an IF
It comprises an FT calculation unit 6, a guard interval addition unit 7, a quadrature modulation unit 8, a frequency conversion unit 9, and an antenna 10.

An information sequence of a first information channel is input to the first channel encoder 2-1. The first channel encoder 2-1 performs a Reed-Solomon encoding process,
It performs energy diffusion processing, interleaving processing, convolutional coding processing, mapping processing, OFDM frame configuration processing, and the like. This first channel encoder 2-1 has O
Frame configuration unit 2 for performing frame configuration of FDM frame
-1a is provided. This frame component 2-1a
Represents a CP signal, an AC signal, T
15 and 16 by adding an MCC signal, an SP signal, and the like.
As shown in (1), one OFDM symbol is composed of 108 samples, and further, an OFDM frame composed of 204 OFDM symbols is composed. When configuring the OFDM frame, the frame configuration unit 2-1 controls the synchronization timing of the frame by the synchronization control unit 3. That is, the synchronization control unit 3 controls the frame cutout symbol and the frame cutout timing. The first channel encoder 2-1 performs the processing described above to generate first channel data that is an OFDM signal in the frequency domain. OF in this frequency domain
The center frequency of the first channel data, which is a DM signal, is 0.

The second channel encoder 2-2 and the third channel encoder 2-3 respectively correspond to the information sequence of the second information channel and the information sequence of the third information channel by the first channel encoder 2-2. Performs the same processing as -1. Similarly, a frame configuration unit 2-2a and a frame configuration unit 2-3 that perform the frame configuration of the OFDM frame
a is provided. In addition, these frame components 2-
The synchronization control unit 3 also controls the synchronization timing of the OFDM frames constituting the frame 2a and the frame configuration unit 2-3a. These second channel encoders 2-2,
The center frequency of the OFDM signal (the second channel data and the third channel data) output from the third channel encoder 2-3 in the frequency domain is also set to zero.

The synchronization control unit 3 controls the synchronization timing of the OFDM frame with respect to the first channel encoder 2-1, the second channel encoder 2-2, and the third channel encoder 3-1. Here, the synchronization control unit 3 performs the OFDM of the first to third channel data.
Frame synchronization control is performed so that all frames coincide in time. Specifically, the timing of the first OFDM symbol (# 0) of each OFDM frame is matched with the timing of the first symbol of another channel.
Controls the synchronization timing of the frame configuration.

The first frequency conversion section 4-1 performs frequency conversion for shifting the center frequency of the first channel data (OFDM signal in the frequency domain) output from the first channel encoder 2-1. First frequency converter 4-1
Sets the center frequency of the first channel data from 0 to (f
₁₋ f ₂ ).

The second frequency converter 4-2 performs frequency conversion for shifting the center frequency of the second channel data (the OFDM signal in the frequency domain) output from the second channel encoder 2-2. Second frequency converter 4-2
Sets the center frequency of the second channel data from 0 to (f
_2- f ₂ ) is frequency-converted.

The third frequency converter 4-3 performs frequency conversion for shifting the center frequency of the third channel data (the OFDM signal in the frequency domain) output from the third channel encoder 2-3. Third frequency converter 4-3
Sets the center frequency of the third channel data from 0 to (f
_The frequency is converted to _3- f ₂ ).

FIG. 3 shows an example of a circuit configuration of the first frequency converter 4-1, the second frequency converter 4-2, and the third frequency converter 4-3.

The frequency conversion circuit includes a phase shifter 11, a phase angle generator 12, and a cumulative adder 13.

The phase shifter 11 includes, for example, BPSK, DQ
A complex signal mapped according to a modulation scheme such as PSK, QPSK, 16QAM, or 64QAM is input. The signal point of the input complex signal is represented as (I, Q). The phase angle generator 12 has a frequency shift amount Δf
And the guard interval length ΔT. The frequency shift amount Δf is a value obtained by calculating a difference between the center frequency in the RF frequency band of each information channel and the center frequency in the RF frequency band of the multiplexed signal to be connected and transmitted. That is, the frequency shift amount Δf of the first information channel is (f ₁ −f ₂ ), the frequency shift amount Δf of the second information channel is (f ₂ −f ₂ ), and the frequency shift amount of the third information channel is The quantity Δf is (f ₃ −f ₂ ).

The phase angle generator 12 generates the phase angle θ according to the following equation.

Θ = f (Δf, ΔT) = 2πΔf (T + ΔT) T is the effective symbol period of the baseband OFDM signal.

The phase angle θ generated by the phase angle generator 12 is input to the accumulator 12.

The accumulator 12 receives the input phase angle θ
Are cumulatively added for each symbol, and a cumulative addition result θ ′ is output. The cumulative addition result θ ′ is input to the phase shifter 11.

The phase shifter 11 performs a frequency shift on the signal point (I, Q) by substituting the input cumulative addition result θ ′ into the following equation.

[0052]

(Equation 1)

The first frequency converter 4-1, the second frequency converter 4-2, and the third frequency converter 4-3 provide the signal points (I ', Q') obtained as described above. ) Is output to the multiplexer 5.

In the second channel data, the frequency conversion is not substantially performed because the second information channel is located at the center of the three channels that are connected and transmitted.

The multiplexing unit 5 includes a first frequency conversion unit 4-
1. Each channel data output from the second frequency converter 4-2 and the third frequency converter 4-3 is multiplexed in the frequency direction to generate a multiplexed signal. As shown in FIG. 4, a multiplexed signal obtained by multiplexing has a first information channel, a second information channel, and a third information channel multiplexed in the frequency direction and also has a multiplexed signal in the time axis direction. Are in a state where frames are synchronized. When such multiplexing and concatenation is performed, in the case of the ISDB-T standard (mode 1), each channel includes 108 subcarriers.

The IFFT operation unit 6 performs an inverse Fourier transform on the multiplexed signals for the three channels multiplexed by the multiplexing unit 5 at a time to generate a time-domain baseband OFDM signal. As shown in FIG. 5, the frequency characteristic of the generated baseband OFDM signal is such that the center frequency of the first information channel is (f ₁ −f ₂ ) and the center frequency of the second information channel is 0, and the center frequency of the third information channel is (f ₃ −f ₂ ). In the baseband OFDM signal, information of the first to third information channels is frequency division multiplexed, and orthogonality is maintained so that intersymbol interference does not occur between all carriers.

The guard interval adding unit 7
A guard interval is added to the baseband OFDM signal from the operation unit 6.

The orthogonal modulation section 8 orthogonally modulates the baseband OFDM signal to which the guard interval is added with respect to the carrier in the intermediate frequency band of the frequency _fIF , and outputs an IF signal.

The frequency converter 9 multiplies the IF signal output from the quadrature modulator 8 by a carrier signal of frequency f ₂ + f _IF to generate a transmission signal in the RF signal band.

The transmission signal generated by the frequency converter 9 is transmitted via the antenna 10.

As described above, in the OFDM transmitting apparatus 1, 3
Data of two information channels (OF in the frequency domain)
The center frequency of each of the DM signals can be changed, these can be multiplexed in the frequency direction, and the OFDM signals in the frequency domain of a plurality of information channels can be collectively subjected to inverse Fourier transform to perform a concatenated transmission of the OFDM signals.

When such a concatenated transmission is performed, IFFT is performed on the three channels at a time, so that intersymbol interference between subcarriers does not occur and the orthogonality is maintained and modulated. Therefore, no interference occurs in the three connected channels. Therefore, the OFDM transmission apparatus 1 can transmit information for three channels without providing a guard band for preventing interference from an adjacent channel.

In the OFDM transmission apparatus 1, OFDM frames of a plurality of information channels that have been connected and transmitted are synchronized and transmitted.

Further, in the OFDM transmitting apparatus 1, when connected and transmitted, an information channel (adjacent channel) adjacent to the receiving channel for the information channel (receiving channel) to which the RF frequency is set is set as a receiving object. Synchronization identification information indicating whether the modulation scheme of the transmitted OFDM signal is a synchronous modulation scheme is described. The synchronization identification information is described by the channel encoder 2 in the TMCC information.

FIG. 6 shows specific description contents. TMCC
The B ₁₁₈ in the information, is described segments form of lower adjacent segments, the B ₁₁₉ in TMCC information segment form of the upper adjacent segments is described.

The lower adjacent segment means an adjacent channel (segment) on the low frequency side with respect to the reception channel (segment). For example, in the example shown in FIG. 1, the lower adjacent segment of the second information channel (CH2) becomes the first information channel (CH1). In addition, the lower adjacent segment of the third information channel (CH3) becomes the second information channel (CH2).

The upper adjacent segment means an adjacent channel (segment) on the high frequency side with respect to the reception channel (segment). For example, in the example shown in FIG.
The upper adjacent segment of the information channel (CH1) of the second
(CH2). Further, the upper adjacent segment of the second information channel (CH2) becomes the third information channel (CH3).

In the segment type identification, as shown in FIG. 7, the adjacent channel (segment) is a synchronous segment, or the adjacent channel (segment) is a differential segment or there is no adjacent channel connected and transmitted. Or information that identifies The synchronous segment means that the modulation scheme of the adjacent channel (segment) is a synchronous modulation scheme (QPSK, 16QAM, 64QAM). The absence of the differential segment or the adjacent segment means that the modulation method of the adjacent channel (segment) is the differential modulation method (DQPSK) or that there is no adjacent channel (segment) because the link transmission is not performed. Or mean.

In the case of the ISDB-T standard (audio broadcasting), 6
A maximum of 13 segments can be connected and transmitted in the MHz bandwidth (that is, up to 13 information channels can be connected and transmitted).

For example, as shown in FIG.
Assume that five segments are connected and transmitted such that 0 is 64QAM, segment # 1 is 64QAM, segment # 2 is QPSK, segment # 3 is DQPSK, and segment # 4 is DQPSK. In the case of the ISDB-T standard, the segment number is set to 0 for the center segment connected and transmitted, and thereafter, the segment numbers are alternately assigned to the left and right in ascending order.

In this case, since the lower adjacent segment is 64 QAM and the upper adjacent segment is QPSK, B ₁₁₈ and B ₁₁₉ of the TMCC information of segment # 0
Is described. In B ₁₁₈ and B ₁₁₉ of the TMCC information of the segment # 1, since the lower adjacent segment is DQPSK and the upper adjacent segment is 64QAM, 1,0
Is described. In B ₁₁₈ and B ₁₁₉ of the TMCC information of segment # 2, since the lower adjacent segment is 64QAM and the upper adjacent segment is DQPSK,
Is described. In B ₁₁₈ and B ₁₁₉ of the TMCC information of the segment # 3, 1 and 0 are described because there is no lower adjacent segment and the upper adjacent segment is 64QAM. B ₁₁₈ and B ₁₁₉ of TMCC information of segment # 4
, 0 and 1 are described because the lower adjacent segment is QPSK and the upper adjacent segment is absent.

As described above, adjacent channels (segments)
By describing whether the modulation scheme of the OFDM signal to be transmitted is the synchronous modulation scheme, the receiving apparatus recognizes whether the adjacent channel is connected and transmitted and whether the SP signal is included in the adjacent channel. Can be done. In the case of the ISDB-T standard, as shown in FIGS. 15 and 16, a frame configuration when an information signal is modulated by a differential modulation (DQPSK) method and a synchronous modulation (Q
The structure is different from the frame structure when modulating the information signal by the PSK, 16QAM, 64QAM) system. In particular, in the case of the synchronous modulation method, the SP signal is included, but in the case of the differential modulation method, the SP signal is not included. Therefore, by describing whether the adjacent channel (segment) is the synchronous modulation system or the differential modulation system, it can be indicated whether the adjacent channel (segment) includes the SP signal.

It is conceivable that only a part of the information channels (segments) may be stopped during the connection transmission. For example, for example, as shown in FIG.
It is conceivable that only one information channel (segment) stops when the segments are connected and transmitted.

In such a case, for example, the state of the interruption of the adjacent segment is determined by the synchronization identification information (B
₁₁₈ , B ₁₁₉ ). For example,
When the adjacent segment stops, the value of the synchronization identification information may be set to “1”.

Even when the segment is stopped, for example, the TMCC signal, the CP signal, the SP signal, the A
Only the control signal such as the C signal may be continuously transmitted. In this case, the state of the interruption of the adjacent segment is
It may not be so as to reflect the synchronous-specific information in the _{TMCC (B 118, B 119)} .

The synchronization identification information indicating whether the modulation method of the adjacent channel (segment) is the synchronous modulation method is described in bit B of the TMCC information in the ISDB-T standard.
_{Although the} example described in ₁₁₈ and bit B ₁₁₉ has been described, the description position is merely an example and may be any position.
Further, the synchronization identification information may be described in, for example, an AC signal or NIT in MPEG-2 systems instead of the TMCC information.

Next, the configuration of the receiving side will be described.

FIG. 10 is a block diagram of an OFDM receiver according to the present invention.

As shown in FIG. 10, the OFDM receiver 21 includes an antenna 22, a tuner 23, a band pass filter (BPF) 24, an A / D converter 25, a digital quadrature demodulator 26, and an fc correction unit. Unit 27, FFT operation unit 28, narrow-band fc error calculation / window sync (FA
FC / W-Sync) unit 29, wideband fc error calculation (WAFC) unit 30, and numerical control oscillator (NC)
O) 31, an equalizer 32, a frequency direction deinterleaver 33, a time direction deinterleaver 34, a demapping unit 35, an error correction unit 36, and a TMCC decoding unit 3
7, a control unit 38, and a memory 39.

The broadcast wave transmitted from the OFDM transmitter 1 is received by the antenna 22 of the OFDM receiver 21 and supplied to the tuner 23 as an RF signal.

The RF signal received by the antenna 22 is frequency-converted into an IF signal by a tuner 23 including a local oscillator and a multiplier, and is supplied to the BPF 4.
As the local oscillation frequency of the tuner 23, a local oscillation frequency according to the channel selected by the user is set by the control unit 38. For example, the first information channel (CH1)
, The local oscillation frequency is tuned to (f ₁ ), and when the second information channel (CH2) is received, the local oscillation frequency is tuned to (f ₂ ). when performing reception channel (CH3) is tuned to the local oscillation frequency (f _3).
After being filtered by the BPF 4, the IF signal output from the tuner 23 is digitized by the A / D converter 25 and supplied to the digital quadrature demodulation unit 26.

The digital quadrature demodulator 26 quadrature demodulates the digitized IF signal using a carrier signal of a predetermined frequency (f _C : carrier frequency), and outputs a baseband OFDM signal. This digital quadrature demodulation unit 26
The baseband OFDM signal output from
This is a so-called time-domain signal before being calculated. As a result of the quadrature demodulation, the baseband OFDM signal in the time domain becomes a complex signal including a real axis component (I channel signal) and an imaginary axis component (Q channel signal). The baseband OFDM signal output by the digital quadrature demodulation unit 26 is supplied to the fc correction unit 27.

The fc correction unit 27 performs a complex multiplication of the fc error correction signal output from the NCO 31 and the baseband OFDM signal, and corrects the carrier frequency error of the baseband OFDM signal. The carrier frequency error is an error in the center frequency position of the baseband OFDM signal caused by, for example, a shift in the reference frequency output from the local oscillator. When the error increases, the error rate of the output data increases. The baseband OFDM signal whose carrier frequency error has been corrected by the fc correction unit 27 is supplied to the FFT calculation unit 28 and the FAFC / W-Sync unit 29.

The FFT operation unit 28 has a baseband OFD
An FFT operation is performed on the M signal to extract and output data orthogonally modulated on each subcarrier. This FF
The signal output from the T operation unit 28 is a so-called frequency domain signal after the FFT.

The FFT operation unit 28 extracts a signal within the effective symbol length range (256 samples) from one OFDM symbol, that is, removes the range of the guard interval from one OFDM symbol into the extracted baseband OFDM signal. Then, an FFT operation is performed. Specifically, the calculation start position is determined from the boundary of the OFDM symbol.
Any position before the end position of the guard interval. This calculation range is called an FFT window.

Then, the FFT operation unit 28
As shown in (1), the center frequency of the reception channel (for example, CH2) is set as a DC component, and the signal components of each subcarrier in the reception channel are output. Here, ISDB-T
In the case of (mode 1), since the number of subcarriers in each information channel is 108, when the FFT operation of 256 samples is performed, signal components included in adjacent channels are also output. As described above, the FFT operation unit 28 performs a Fourier transform on a frequency region wider than the signal band of the reception channel, and the operation range of the FFT operation unit 28 is such that a signal component of an adjacent channel outside the band of the reception channel can be output. It is larger than the number of subcarriers.

The FFT operation unit 28 sets the center frequency component of the reception channel to subcarrier number 0. Hereinafter, with the subcarrier number 0 as the center, the subcarrier number becomes negative in the low frequency direction and positive in the high frequency direction. Outputs data with carrier number.

The frequency domain OFDM signal output from the FFT operation unit 28 as described above is a real axis component (I channel signal) like the time domain baseband OFDM signal.
And an imaginary axis component (Q channel signal). The OFDM signal in the frequency domain is supplied to the WAFC unit 30 and the equalizer 32.

FAFC / W-Sync 29 and WAF
The C unit 30 calculates a carrier frequency error included in the output signal of the fc correction unit 27. FAFC / W-Syn
The c unit 29 calculates a narrow band fc error with an accuracy of ± 1/2 or less of the frequency interval of the subcarrier. WAFC unit 30
Calculates the wideband fc error of the subcarrier frequency interval accuracy. The carrier frequency errors obtained by the FAFC unit 29 and the WAFC unit 30 are supplied to the NCO 31 respectively.

The FAFC / W-Sync unit 29
The start timing of the FFT operation by the FFT operation unit 28 is obtained, and the operation range (FFT window) of the FFT is controlled. The control of the FFT window is based on OFDM symbol boundary position information obtained when calculating a narrowband carrier frequency error with an accuracy of ± 1/2 or less of the subcarrier frequency interval, and the length of the guard interval of the OFDM signal. It is done based on. According to the ISDB-T standard, four guard interval lengths are defined. When expressed as a length ratio with the effective symbol, 1
/ 4, 1/8, 1/16, and 1/32. The length of the guard interval of the received OFDM signal is set by the control unit 38.

The NCO 31 adds the narrowband carrier frequency error of ± 1/2 precision of the subcarrier frequency interval calculated by the FAFC section 29 and the wideband fc error of subcarrier frequency interval precision calculated by the WAFC section 30. Then, an fc error correction signal whose frequency increases or decreases according to the carrier frequency error obtained by the addition is output. This fc
The error correction signal is a complex signal and is supplied to the fc correction unit 27. The fc error correction signal is subjected to complex multiplication of the baseband OFDM signal by the fc correction unit 27, and the carrier frequency error component of the baseband OFDM signal is removed.

The equalizer 32 performs phase equalization and amplitude equalization of the OFDM frequency domain signal using, for example, a scattered pilot signal (SP signal). The frequency domain OFDM signal on which the phase equalization and the amplitude equalization have been performed is supplied to the frequency direction deinterleaver 33 and the TMCC decoding unit 37. Note that the transmitted signal is a differential demodulated signal (DQ
PSK), the processing of the equalizer 32 is not performed.

[0093] Frequency direction deinterleaver 33 deinterleaves the data interleaved in the frequency direction on the transmitting side according to the interleave pattern. The data subjected to the frequency-direction deinterleaving process is supplied to the time-direction deinterleaver 34.

The time direction deinterleaver 34 deinterleaves the data interleaved in the time direction on the transmission side in accordance with the interleave pattern. ISDB-T
In the standard, five interleave patterns are defined in each mode. For example, in mode 1, five patterns are defined such that the number of delay correction symbols is 0, 28, 56, 112, 224. The interleave pattern used for deinterleaving is set under the control of the control unit 38. The data on which the deinterleaving process in the time direction is performed is supplied to the demapping unit 35.

The demapping unit 35 performs a demapping process according to a predetermined carrier modulation method, and demodulates data that is orthogonally modulated on each subcarrier of the OFDM frequency domain signal. According to the ISDB-T standard, DQPSK, QPSK, 16QAM, 64Q
An AM modulation method is specified. Demapping unit 35
In, a mapping pattern and the like necessary for demapping are set under the control of the control unit 38. The data demodulated by the demapping unit 35 is supplied to an error correction unit 36.

The error correction unit 36 performs Viterbi decoding on the data encoded by the punctured convolutional code on the transmission side, and further performs error correction processing using the Reed-Solomon code added as the outer code. In the ISDB-T standard, the coding rate of a punctured convolutional code is set to 1/2, 2/3, 3/4, 5/6, and 7/8. The error correction unit 36 sets the coding rate of a convolutional code used for Viterbi decoding by the control unit 38.

The data corrected by the error correction unit 36 is supplied to a subsequent stage, for example, an MPEG decoding unit.

[0098] TMCC decoding section 37 extracts a TMCC signal inserted at a predetermined subcarrier position in a symbol, and decodes information described in the TMCC. T
The MCC includes system identification information of the television broadcasting system, countdown information for switching the TMCC information, an emergency warning broadcast activation flag, a segment format identification flag, a carrier modulation scheme, a convolutional coding rate, a time-direction interleave pattern, and the like. Is described. The TMCC decoding unit 37 sends the decoded information to the control unit 3
8

Further, the TMCC decoding unit 37
A sync code (synchronization signal) of the C signal is detected to generate a frame synchronization signal. This frame synchronization signal is
This signal defines one frame period of the received OFDM signal and the head position of the frame, which is turned ON at a predetermined position (for example, the head position of the frame) of the DM frame. The TMCC decoding unit 37 generates this frame synchronization signal by, for example, applying a PLL or the like based on a sync code of the TMCC signal and performing synchronous clock reproduction or the like. The frame synchronization signal is supplied to, for example, the equalizer 32, the error correction unit 36, the control unit 38, and the like.
It is used for controlling the synchronization timing of the P signal, the punctured switching timing, and the like.

Further, the TMCC decoding unit 27
Analyzes the synchronization identification information described in B ₁₁₈ and B ₁₁₉ of the TMCC information, and supplies the analyzed information to the equalizer 32.

The control section 38 controls each section and the entire apparatus. In addition, the control unit 38 includes
The information decoded by the TMCC decoding unit 37 is input, and control of each unit and setting of parameters are performed based on the information. Further, the control unit 38 reads information stored in the memory 39, and controls each unit and sets parameters based on the read information.

The memory 39 stores, for each information channel for broadcasting contents, the RF frequency of the information channel, the guard interval length of the OFDM signal of the information channel, the interleave pattern in the time direction, the carrier modulation method, the convolutional coding rate, and the like. The information contents described in TMCC such as are preset. Also, in the memory 39,
The initial value of the fc error correction signal supplied to the fc correction circuit 27 (the correction value of the accuracy in units of carrier intervals output from the WAFC unit 36, and the initial value of the clock frequency of the sampling clock supplied to the A / D converter 25) Is preset.

A remote controller (remote controller) 40
Is input by the user to select an information channel providing a program to be viewed, and the selected information is transmitted to the control unit 38 by, for example, infrared communication or the like. The user selects an information channel by referring to, for example, a program guide or the like described on the paper, or, for example, an EPG (Electric Program G) displayed on a monitor.
The information channel may be selected by selecting ide).

Next, the equalizer 32 will be described in more detail.

A signal broadcast from a broadcast station is distorted by a transmission path. Assuming that a transmission signal broadcast from a broadcasting station is X (ω) and a frequency characteristic of a transmission path is H (ω), a reception signal received by the OFDM receiver is X (ω).
H (ω). The equalizer 32 extracts, from each of the subcarriers after the FFT operation, an SP signal having a specific power level and a specific phase. , It detects how much the SP signal fluctuates from the original power level, and from this information, the frequency characteristic H of the transmission path.
(Ω) is estimated. Then, the reciprocal 1 / H (ω) of the estimated frequency characteristic of the transmission path is calculated as the received signal X (ω) · H (ω).
Multiply by. As a result, the equalizer 32 removes distortion due to the influence of the transmission path and restores the originally transmitted signal.

The equalizer 32 of the OFDM receiver 32 according to the present invention has a circuit configuration as shown in FIG.

More specifically, the equalizer 32 has a PRBS
Generation circuit 51, multiplication circuit 52, phase correction circuit 53
, SP signal extraction circuit 54, and time direction filter 55
, A frequency direction filter 56, a 1 / X circuit 57, a complex multiplication circuit 58, and a timing control circuit 59.

The PRBS generation circuit 51 generates a pseudo random code sequence (PRBS: x ¹¹ +
x ⁹ +1). The value of this PRBS is updated by the data clock of the data output from the FFT operation unit 28. The PRBS generation circuit 51 is controlled by a timing control section 59 at the reset timing of the generated PRBS (timing at which an initial value is given). P generated from PRBS generation circuit 51
The RBS is supplied to the multiplication circuit 52.

The multiplication circuit 52 generates the frequency domain OFDM signal sent from the FFT operation unit 28 and the generated PRB signal.
Multiply by S. In this way, the PRBS is changed to O in the frequency domain.
By multiplying the FDM signal, PRBS gives B
The PSK modulated SP signal is demodulated, and the original SP
The signal components of the signal (eg, phase 0, amplitude 1) are restored. Of course, signals other than the SP signal (for example, the information signal and the TMCC signal) are also multiplied by the PRBS. Absent. Multiplication circuit 52
Is supplied to the phase correction circuit 53.

The phase correction circuit 53 corrects the phase of the signal component of the adjacent channel. As shown in FIG.
The FFT operation unit 28 receives the reception channel (108 samples)
The FFT operation is performed so as to cover a wider band than the frequency band of and the signal components of adjacent channels are also demodulated. However, the signal component of the adjacent channel is read at a position different from the original subcarrier position when the center frequency of the reception channel is read as a DC component.
The signal component rotates in phase. Therefore, the phase correction circuit 53 performs phase correction on signal components outside the signal band of the reception channel.

FIG. 13 shows a circuit configuration of the phase correction circuit 53.

This phase correction circuit 53 has almost the same configuration as the frequency conversion circuit on the transmission side.
1, a phase angle generator 62, and a cumulative adder 63.

A complex signal is input to the phase shifter 61.
The signal point of the input complex signal is represented as (I, Q).
The phase angle generator 62 has a frequency shift amount Δf,
The guard interval length ΔT is input. The frequency shift amount Δf is a value obtained by calculating a difference between the center frequency in the RF frequency band of the receiving channel and the center frequency in the RF frequency band of the adjacent channel. For example, if both the receiving channel and the adjacent channel are transmitted in the one-segment format, the frequency shift amount Δf is 430 kHz.
Becomes The phase angle generator 62 generates the phase angle θ according to the following equation.

Θ = f (Δf, ΔT) = 2πΔf (T + ΔT) T is the effective symbol period of the baseband OFDM signal.

The phase angle θ generated by the phase angle generator 62 is input to the accumulator 62.

The accumulator 62 receives the input phase angle θ
Are cumulatively added for each symbol, and a cumulative addition result θ ′ is output. The cumulative addition result θ ′ is input to the phase shifter 61.

The phase shifter 61 performs a frequency shift on the signal point (I, Q) by substituting the input cumulative addition result θ ′ into the following equation.

[0118]

(Equation 2)

The phase shifter 61 corrects the frequency shift for the signal component of the adjacent channel, but does not perform the phase correction for the signal component of the reception channel.
That is, for the signal component in the band of the reception channel, the above-mentioned θ ′ is set to 0. Control of the switching timing of the operation of the phase shifter 61 is performed by the timing control circuit 59.

The SP signal extraction circuit 54 includes a phase correction circuit 5
3, only the SP signal is extracted from the output data from # 3. S
The P signal is discretely inserted into each OFDM symbol, and the insertion position is determined in advance by a standard. S
Since the SP signal is inserted at a different subcarrier position for each symbol, the P signal extraction circuit 54 refers to the symbol number of the supplied OFDM frequency domain signal, and determines the index number of the subcarrier from the symbol number. Whether the SP signal is inserted is calculated based on the standard, and the SP signal is extracted. The SP signal extraction circuit 54 extracts not only the SP signal included in the reception channel but also the SP signal included in the adjacent channel.
The SP signal extraction circuit 54 supplies the extracted SP signal to the time direction filter 55.

The time direction filter 55 is an IIR (Infini
te Impulse Response) filter, and filters the SP signal in the time axis direction to remove noise included in the SP signal. The SP signal filtered by the time direction filter 55 is supplied to the frequency direction filter 56 in OFDM symbol units.

The frequency direction filter 56 has an FIR (Fini
te Impulse Response) filter, interpolates the SP signal in the subcarrier direction, and estimates the amplitude and phase frequency characteristics for all subcarriers of the OFDM symbol. That is, the frequency characteristic H (ω) of the transmission path is estimated. For example, in the ISDB-T standard, one SP signal is supplied from the time direction filter 56 to three subcarriers. Therefore, the frequency direction filter 56 obtains by interpolating the characteristics of the frequency in which the SP signal is not inserted by using a triple interpolation filter or the like.
The transfer characteristics for all eight subcarriers are obtained.

Here, when performing such frequency interpolation, the frequency direction filter 56 sets the SP to the adjacent channel.
If a signal is included, the SP of this adjacent channel
The signal is also used to perform frequency interpolation. The range in which the frequency interpolation is performed is controlled by the timing control circuit 59. The frequency characteristics H (ω) of the transmission path for all subcarriers obtained by the frequency direction filter 56 are supplied to a 1 / X circuit 57.

The 1 / X circuit 57 performs a reciprocal operation on the estimated frequency characteristic H (ω) of the transmission path. The frequency characteristic 1 / H (ω) of the transmission line on which the reciprocal operation has been performed is supplied to the complex multiplication circuit 58.

The complex multiplication circuit 58 performs a complex multiplication of the OFDM frequency domain signal from the FFT operation circuit 6 and the frequency characteristic 1 / H (ω) of the transmission line on which the inverse operation has been performed, and performs waveform equalization.

Next, control contents of the timing control circuit 59 and operation contents of each circuit will be described with reference to a timing chart shown in FIG.

First, FIG. 14A shows the FFT operation unit 28.
5 shows the data timing output from. FFT
The operation unit 28 outputs data of 256 samples for one symbol. The FFT operation unit 28 serially outputs data of 256 samples from, for example, low frequency components. That is, when the sample number of the data at the center frequency position of the reception channel to be demodulated is set to 0, the FFT operation unit 28 sets the sample number to -128 to 127
Output data up to.

At this time, the data to be demodulated is data of 108 samples centered on the data of sample number 0. That is, data of sample numbers −54 to 53 is data to be demodulated. In addition, other data (that is, sample numbers −128 to −55)
Data and data of sample numbers 54 to 127)
This is data of an adjacent channel adjacent to the reception channel.

FIG. 14B shows the timing of the FFT start pulse supplied from the FFT operation unit 28. The FFT start flag indicating the start position of the FFT operation is input from the FFT operation circuit 28 to the timing control circuit 59. This FFT start flag is output in synchronization with the position of the sample number -128. The timing control circuit 59 performs the following timing control based on the FFT start flag and the data clock.

FIG. 14C shows the PRBS reset flag. This PRBS reset flag is supplied from the timing control circuit 59 to the PRBS generation circuit 51. The timing control circuit 59 outputs a PRBS reset flag at the same timing as the FFT start flag. When the PRBS reset flag is supplied, the PRBS generation circuit 51 resets the generated PRBS to an initial value. The timing control circuit 59 does not change its generation timing even if the filter operation range of the frequency direction filter 56 described later is switched. this is,
This is because, in ISDB-T, when the link transmission is performed, the continuously generated PRBS is given to all the connected segments, so that it is not necessary to initialize the PRBS value at the beginning of each segment. However, when the connection transmission is not performed, the PR at the head data of the reception channel is used.
A PRBS reset pulse is generated at the timing of sample number -54 so that the BS is initialized.

FIG. 14D shows the phase correction enable flag. This phase correction enable flag is supplied from the timing control circuit 59 to the phase correction circuit 53. This phase correction enable flag is a flag indicating that the data is out of the band of the reception channel. That is, it indicates that it is data of an adjacent channel. This phase correction enable flag has a sample number of -128 to -5.
5, and a flag that is turned ON at sample numbers 54 to 127. The phase correction circuit 53 operates to perform phase correction at the timing when the phase correction EN flag is turned ON.

FIG. 14E shows a time direction filter (II
R) Indicates a start flag. The IIR start flag is sent from the timing control circuit 59 to the time direction filter 5.
5 is supplied. The timing control circuit 59 outputs an IIR start flag at the same timing as the FFT start timing. The time direction filter 55 filters the SP signal having the same sample number of each symbol in the time direction, and interpolates the SP signal in the time direction. When the IIR start flag is supplied, the time direction filter 55 starts processing for the next symbol.

FIGS. 14 (f), (g), (h), (i)
Indicates a frequency direction filter (FIR) enable flag. This FIR enable flag is supplied from the timing control circuit 59 to the frequency direction filter 56.

The frequency direction filter 56 interpolates the SP signal supplied from the time direction filter using, for example, a three-fold interpolation filter or the like to obtain the characteristics of the subcarrier into which the SP signal is not inserted. The transfer characteristics for all subcarriers in the book are determined.

At this time, the frequency direction filter 56
Only when the R enable flag is ON,
The P signal is input to the delay tap to perform interpolation.

The ON timing of the FIR enable flag is switched based on the synchronization identification information described in B ₁₁₈ and B ₁₁₉ of the TMCC information. For example, when the SP signal is not included in both the adjacent channels in the high frequency direction and the low frequency direction (that is, when both the adjacent channels are of the differential modulation system), as shown in FIG. The FIR enable flag is turned on between sample numbers -54 to 53. That is, it is turned ON only at the timing of the signal of the receiving channel to be demodulated. Therefore, the equalizer 32 performs interpolation in the frequency direction using only the SP signal inserted in the reception channel to be demodulated.

Further, for example, when the SP signal is included in both of the adjacent channels in the high frequency direction and the low frequency direction (that is, when both adjacent channels are of the synchronous modulation system), FIG. As shown in the sample number-
FIR enable flag is ON between 102 and 101
Becomes That is, the signal is turned on at both the signal timing of the receiving channel to be demodulated and the signal timing of the adjacent channel. Therefore, interpolation in the frequency direction is performed using the SP signal inserted in the adjacent channel in the high frequency direction and the low frequency direction together with the SP signal inserted in the information channel to be demodulated.

Further, for example, when the SP signal is included in the adjacent channel in the high frequency direction (that is, when the adjacent channel in the high frequency direction is of the synchronous modulation system), FIG.
As shown in (h), the FIR enable flag is turned on between sample numbers -102 to 53. for that reason,
The interpolation in the frequency direction is performed using the SP signal inserted in the adjacent channel in the high frequency direction together with the SP signal inserted in the information channel to be demodulated.

Further, for example, when the SP signal is included in the adjacent channel in the low frequency direction (that is, when the adjacent channel in the low frequency direction is of the synchronous modulation system), FIG.
As shown in (i), the FIR enable flag is turned on between sample numbers -54 to 101. for that reason,
The interpolation in the frequency direction is performed using the SP signal inserted in the adjacent channel in the low frequency direction together with the SP signal inserted in the information channel to be demodulated.

The timing of turning on the enable flag when the SP signal of the adjacent channel is used and the OF timing
The timing of F may be such that an SP signal of an adjacent channel equal to or more than サ ン プ ル of the number of samples of the delay tap of the FIR filter is input to the delay tap of the FIR filter. That is, S which is a sample for interpolating the signal at the extreme end of the information channel to be demodulated is used.
The P signal may be provided from an adjacent channel.

FIG. 14 (j) shows a multiplication enable flag. The multiplication enable flag is supplied from the timing control circuit 59 to the complex multiplication circuit 58.

The complex multiplying circuit 58 operates only when the multiplication enable flag is ON, and performs an operation of masking data when the multiplication enable flag is OFF. As a result, only data required for demodulation can be transferred. Instead of masking in this way, the flag may be set in synchronization with the leading data of the valid data.

As described above, when the SP signal is included in the adjacent information channel, the equalizer 32 performs the interpolation process in the frequency direction using the SP signal of the adjacent channel, and estimates the propagation characteristic of the transmission path. I do. Therefore, it is possible to highly accurately estimate the propagation characteristics of the transmission path at the end portion of the information channel to be demodulated, that is, at the low frequency portion and the high frequency portion of the information channel.

The ISDB-T television broadcasting standard specifies that one information channel is transmitted using a 6 MHz bandwidth. In this case, similarly, the 6 MHz bandwidth is divided into 13 segments. Here, according to the ISDB-T television standard, the data format of the center segment of the 13 segments is set so that the audio broadcast receiver can partially receive, for example, only the audio portion of such a television broadcast. Is generated with compatibility with the audio broadcast standard. This is called partial reception. That is, R
By tuning the F frequency to the frequency band of television broadcasting, the digital radio receiver can receive the sound of digital television broadcasting. Reception is possible.).

Accordingly, the segment for audio defined in the ISDB-T television broadcasting standard is also added to the TMCC information as described above in the synchronous type information (B
By describing ₁₁₈ , ₁₁₉ ), when the adjacent segment is of the synchronous modulation system, waveform equalization can be performed using the SP signal of the adjacent segment.

[0146] Partial reception is realized not only by television broadcasting but also by audio broadcasting. For example, audio broadcasting is 3
This is realized when the transmission is performed in segments and all three segments may be demodulated collectively, or only the center segment of the three segments may be partially received.

In the above description of the concatenated transmission, it has been explained that the OFDM signals transmitted to a plurality of channels are collectively subjected to the IFFT conversion. For example, after the OFDM signals transmitted to each channel are individually subjected to the IFFT conversion, May be multiplexed by performing frequency conversion in the frequency direction. In this case, when performing frequency conversion, IFFT
The operation clocks of the converters are synchronized in all the channels, and the oscillators used in the frequency converters of all the channels are operated in synchronization.

[0148]

According to the OFDM transmitting apparatus and method of the present invention, when the OFDM signals to be transmitted to a plurality of information channels are multiplexed in the frequency direction while maintaining the orthogonality, each information is transmitted. O to transmit to channel
OF transmitted to adjacent information channel in FDM signal
Information indicating that a pilot signal for waveform equalization exists in the DM signal is described.

As a result, in the present invention, waveform equalization can be performed with high accuracy by using a pilot signal for waveform equalization of an OFDM signal transmitted to an adjacent information channel.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a signal that has been connected and transmitted.

FIG. 2 is a block diagram of an OFDM transmitting apparatus to which the present invention is applied.

FIG. 3 is a block diagram of a frequency conversion unit.

FIG. 4 is a diagram illustrating frame synchronization of a multiplexed OFDM signal.

FIG. 5 is a frequency characteristic diagram of a baseband OFDM signal obtained by performing IFFT conversion on three channels at once.

FIG. 6 is a diagram for describing information by synchronization type described in TMCC information.

FIG. 7 is a diagram for explaining the specific contents of the above-mentioned synchronous type information.

FIG. 8 is a diagram illustrating a case where five segments are connected and transmitted.

FIG. 9 is a diagram for explaining a case where a part of a segment is stopped;

FIG. 10 is a block diagram of an OFDM receiver according to the present invention.

FIG. 11 is a diagram illustrating a range in which an FFT operation is performed.

FIG. 12 is a block diagram of an equalizer.

FIG. 13 is a block diagram of a phase correction circuit.

FIG. 14 is a timing chart showing the generation timing of each flag of the equalizer.

FIG. 15 shows TMCC in an OFDM frame for differential modulation.
FIG. 3 is a diagram for explaining an arrangement of a signal and an AC signal in a symbol.

FIG. 16 shows TMCC in an OFDM frame for synchronous modulation.
FIG. 3 is a diagram for explaining an arrangement of a signal and an AC signal in a symbol.

FIG. 17 is a diagram for explaining the content of information included in a TMCC signal.

[Explanation of symbols]

0 OFDM transmitter, 2-1, 2-2, 2-3 channel encoder, 2-1a, 2-2a, 2-3a frame configuration unit, 3-1 4-2, 4-3 frequency conversion unit, 5 Multiplexing section, 6 IFFT calculation section, 7 guard interval addition section, 8 orthogonal modulation section, 9 frequency conversion section, 10 antennas, 21 OFDM receiver, 23 tuner, 24
BPF, 25 A / D conversion unit, 26 digital quadrature demodulation, 27 fc correction unit, 28 FFT operation unit, 29 FA
FC / W-Sync, 30 WAFC, 31 NCO,
32 equalizer, 33 frequency direction deinterleaver,
34 time direction deinterleaver, 35 demapping unit, 36 error correction unit, 37 TMCC decoding unit, 38
Control unit, 39 memory, 40 remote controller, 51 PRBS generation circuit, 53 phase correction circuit, 5
4 SP signal extraction circuit, 55 time direction filter, 56
Frequency direction filter, 57 1 / x circuit, 58 complex multiplication circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshikazu Miyado 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Yasunari Ikeda 7-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 5K022 DD01 DD13 DD18 DD19 DD23 5K041 AA02 BB10 CC04 FF01 FF27 FF32 HH07 HH24

Claims (10)

[Claims] 1. An OFDM transmitting apparatus for transmitting an orthogonal frequency division multiplexing (OFDM) signal, in which the OFDM signals to be transmitted to a plurality of information channels are multiplexed in the frequency direction while maintaining orthogonality to perform concatenated transmission. In this case, an OFDM transmitting apparatus characterized in that information indicating that a pilot signal for waveform equalization exists in an OFDM signal transmitted to an adjacent information channel is described in an OFDM signal transmitted to each information channel. 2. OFDM for transmitting to a plurality of information channels
2. The OFDM transmission apparatus according to claim 1, wherein concatenated transmission is performed by performing an inverse Fourier transform on the signals collectively. 3. The OFDM transmitting apparatus according to claim 1, wherein the OFDM signal of each information channel is inversely Fourier transformed and then multiplexed in the frequency direction while maintaining orthogonality. 4. An information indicating that a pilot signal for waveform equalization is present in an OFDM signal transmitted to an information channel adjacent to a low frequency side, and an OFDM signal transmitted to an information channel adjacent to a high frequency side. 2. The OFDM transmission apparatus according to claim 1, wherein information indicating that a pilot signal for waveform equalization exists is described. 5. The plurality of OFDM signals to be connected and transmitted,
2. The OFDM transmission apparatus according to claim 1, wherein the transmission frame is multiplexed in the frequency direction in a synchronized state. 6. An OFDM transmission method for transmitting an orthogonal frequency division multiplexing (OFDM) signal, wherein the OFDM signals transmitted to a plurality of information channels are multiplexed in the frequency direction while maintaining orthogonality to perform a concatenated transmission. In this case, an OFDM signal transmitted to each information channel includes information indicating that a pilot signal for waveform equalization exists in an OFDM signal transmitted to an adjacent information channel. 7. OFDM for transmitting to a plurality of information channels
7. The OFDM transmission method according to claim 6, wherein concatenated transmission is performed by subjecting the signals to inverse Fourier transform at once. 8. The OFDM transmission method according to claim 1, wherein after performing an inverse Fourier transform on the OFDM signal of each information channel, the OFDM signal is multiplexed in the frequency direction while maintaining orthogonality. 9. An information indicating that a pilot signal for waveform equalization is present in an OFDM signal transmitted to an information channel adjacent to a low frequency side, and an OFDM signal transmitted to an information channel adjacent to a high frequency side. 2. The OFDM transmission method according to claim 1, wherein information indicating that a pilot signal for waveform equalization exists is described. 10. The OFDM signal according to claim 1, wherein a plurality of OFDM signals to be connected and transmitted are multiplexed in a frequency direction in a state where transmission frames are synchronized.
Transmission method.