JP2000209180A - Ofdm decoder, decoder, bit rate converter and ofdm data recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate decoding of a code series transmitted with an OFDM with a bandwidth narrower than a reference bandwidth. SOLUTION: A frame storage section 30 of a frame format conversion section 16 stores a code series recovered by an OFDM signal demodulation section 13 for each transmission frame according to a clock signal frequency-divided by a 1/2 frequency divider section 11. A frame adjustment section 31 reads the code series stored in the frame storage section 30 to convert the bit rate according to the clock signal generated by a clock signal generating section 10. A frame adjustment section 31 inserts a PRBS signal generated by a PRBS signal generating section 32 to each CIF data section in a transmission frame to adjust the frame length. Thus, a data selection section 20, an audio signal decoding section 21, and a multiplex information data decoding section 22 of a signal recovery section 15 decode the frame similarly to the case with the code series transmitted by the OFDM with a reference bandwidth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to OFDM (Orth
The present invention relates to an OFDM decoding device, a bit rate conversion device, and an OFDM data reproduction method for decoding a code sequence transmitted by an Ogonal Frequency Division Multiplex, and particularly to an ODM having a bandwidth narrower than a reference bandwidth.
O for decoding a code sequence transmitted by FDM
FDM decoding device, bit rate conversion device and OFD
The present invention relates to an M data reproducing method.

[0002]

2. Description of the Related Art As a technology for digital broadcasting, I.
TU-R (International Telecommunication Union-Ra
diocommunication sector). 1114 Syst
DAB (Digital Audio Broa) standardized by emA
dcasting). In this DAB, O is used as a transmission method.
FDM (Orthogonal Frequency Division Multiplex) is adopted, and four transmission modes as shown in FIG. 5 are defined, and the number of carriers and the frame length are different depending on the transmission mode. In DAB, a unit of 24 ms is defined as a logical frame.

FIG. 4A shows a transmission frame according to a transmission mode IV. As shown in the figure, this transmission frame has a frame length of 48 ms, and has a FIC (Fast Information Format).
on Channel) data part FIC (1), FIC (2),
CIF (Common Interleaved Frame) data section CIF
(1) and CIF (2). here,
Service data such as an audio signal to be transmitted and received is MP
The data is compressed by the EG (Moving Picture Experts Group) method and included in the MPEG data portions M (1) and M (2).

On the other hand, the bandwidth of OFDM conforming to the DAB standard is defined as a reference bandwidth (reference bandwidth), and a code sequence is reproduced from a signal in which OFDM having a narrower bandwidth is performed, and decoding is performed. As shown in FIG. 3, an OFDM decoding device that performs service data (such as an audio signal) and multiplex information data has been proposed.

[0005] The OFDM decoding apparatus 200 converts an audio signal and multiplexed information data from a code sequence transmitted by OFDM with a reference bandwidth and a code sequence transmitted by OFDM with the bandwidth being １ ／ of the reference bandwidth. It is for reproduction. The OFDM decoding device 200
As shown in FIG. 3, the clock signal generator 201 and 1 /
Switches 203a and 203 interlocked with the frequency dividing unit 202
b, OFDM signal demodulation unit 204, signal reproduction unit 205
It is composed of Further, the signal reproducing unit 205 includes a data selecting unit 210, an audio signal decoding unit 211,
And a multiplex information data decoding unit 212.

[0006] In such a configuration, the OFDM decoding apparatus 200 switches the switches 203a and 203b according to the bandwidth of the signal to be received. That is, when decoding a code sequence transmitted by OFDM of the reference bandwidth, the clock signal generated by the clock signal generation unit 201 is supplied to the OFDM signal demodulation unit 204 and the signal reproduction unit 205. Further, when decoding a code sequence transmitted by OFDM having a bandwidth of １ ／ of the reference bandwidth, the clock signal divided by the 分 divider 202 is divided into an OFDM signal demodulator 204 and a signal reproducer. 205.

The OFDM signal demodulation unit 204 performs sampling and demodulation of an IF (Intermediate Frequency) signal sent from a down converter or the like based on the supplied clock signal, reproduces a code sequence, and sends the code sequence to the signal reproduction unit 205. . The signal reproducing unit 205 includes an OFDM signal demodulating unit 204
, The data selection unit 210 performs data selection, and the audio signal decoding unit 211 and the multiplex information data decoding unit 212 perform decoding, thereby outputting service data (audio signal) and multiplex information data, respectively. I do. This makes it possible to decode the code sequence transmitted by the OFDM of the reference bandwidth and the code sequence transmitted by the OFDM of the half bandwidth, and reproduce the service data and the multiplexed information data.

[0008] This conventional OFDM decoding apparatus 200
Is set to 1.536 MHz corresponding to the DAB transmission mode I shown in FIG.
When decoding a code sequence transmitted by OFDM having a bandwidth of kHz, a transmission frame as shown in FIG. 4B is used. This transmission frame is
It is created for communication using OFDM having a bandwidth of 基準 of the reference bandwidth based on the transmission frame of the transmission mode IV shown in FIG.

In the transmission frame shown in FIG. 4B, since the bandwidth is transmitted by OFDM whose bandwidth is の of the reference bandwidth,
The bit rate of the code sequence is の of the code sequence transmitted by OFDM of the reference bandwidth. Accordingly, in such a system, in order to maintain the transmission speed of service data, the CIF data section CIF (1) includes two MPEG data sections M (1) and M (2), and the CIF data section CI (2).
For F (2), it is necessary to perform data transmission by connecting two MPEG data sections M (3) and M (4).

However, in the transmission frame shown in FIG. 4B, the logical frame length is 48 ms, which is inconsistent with the DAB standard. Therefore, special encoding processing and decoding processing corresponding to this method are separately performed. Required. In order to solve this problem, an encoder for generating a code sequence having a transmission frame configuration corresponding to the DAB standard (in this case, transmission mode I) as shown in FIG. It is considered.

[0011]

In the above-mentioned prior art, even if an encoding apparatus for creating a code sequence having a transmission frame structure as shown in FIG. Communication cannot be performed without a decoding device capable of decoding a code sequence.

The present invention has been made in view of the above situation, and has as its object to provide an OFDM decoding device for easily decoding a code sequence transmitted by OFDM with a reduced bandwidth.

[0013]

An OFDM decoding apparatus according to a first aspect of the present invention includes an OFDM (Orthogonal FDM).
demodulation means for demodulating the signal transmitted by the (Requency Division Multiplex) to reproduce a code sequence, conversion means for converting the bit rate of the code sequence reproduced by the demodulation means, and the code sequence reproduced by the demodulation means. A code sequence selecting unit that selects and outputs one of a code sequence whose bit rate has been converted by the conversion unit, and decodes a code sequence output by the code sequence selecting unit to obtain multiplexed information data or service data (audio data). Signal means) for reproducing an information sequence.

In such a configuration, in the OFDM decoding apparatus, the converting means converts the bit rate of the code sequence transmitted by the OFDM having the reduced bandwidth, and the reproducing means transmits the bit stream by the OFDM having the reference bandwidth. Decoding by the same processing as that of the decoded code sequence. This makes it possible to easily decode a code sequence transmitted by OFDM with a reduced bandwidth.

The code sequence selecting means selects and outputs the code sequence reproduced by the demodulating means when the demodulating means performs demodulation corresponding to OFDM of the reference bandwidth and reproduces the code sequence in accordance with the control signal. And when the demodulation means performs demodulation corresponding to OFDM having a bandwidth different from the reference bandwidth to reproduce a code sequence, the conversion means selects and outputs a code sequence whose bit rate has been converted. Is desirable.

Further, the OFDM decoding apparatus generates a first clock signal generating means for generating a clock signal having a reference frequency, and generates a clock signal having a frequency different from that of the clock signal generated by the first clock signal generating means. A second clock signal generating means for converting the code sequence reproduced by the demodulating means into a rising or falling edge of the clock signal generated by the second clock signal generating means. Etc.
Storage means for storing in accordance with the clock signal generated by the second clock signal generation means, and a code sequence stored by the storage means for storing a rising or falling edge of the clock signal generated by the first clock signal generation means. It is preferable that the first clock signal generation unit includes a readout unit that reads out the readout timing according to the clock signal generated by the first clock signal generation unit. As a result, the bit rate of the code sequence can be converted. Further, the second clock signal generation means may divide the frequency of the clock signal generated by the first clock signal generation means by half. As a result, decoding can be easily performed by converting the bit rate of the code sequence transmitted by OFDM whose bandwidth is の of the reference bandwidth.

The conversion means may be a PRBS (Pseudo Rando
a plurality of CIFs (Common Interleaved Framing) from a PRBS signal generating means for generating an m Binary Sequence (RS) signal and a transmission frame structure of a code sequence read from the storage means.
me) Detect the data part and add the PRB to each CIF data part.
It is desirable to have means for inserting the PRBS signal generated by the S signal generation means. This adjusts the changed frame length by converting the bit rate,
A transmission frame structure similar to a transmission frame formed by a code sequence transmitted by OFDM having a reference bandwidth can be used, and decoding can be facilitated.

The demodulation means reproduces a code sequence having a transmission frame structure including four 24 ms logical frames, and the conversion means reproduces the code sequence reproduced by the demodulation means.
The PRBS signal generated by the PRBS signal generating means is inserted into each logical frame by converting the bit rate of a code sequence having a transmission frame structure including two logical frames, and the frame length is 96 ms and the bit rate is doubled. It is desirable to convert to a code sequence having a frame structure. As a result, the code sequence reproduced by the demodulating means is
A transmission frame structure conforming to the B standard can be used, and decoding becomes easy.

[0019] The reproducing means may be an ITU-R BS. 11
14 DAB (Division) standardized by System A
It may be possible to perform decoding of a code sequence having a transmission frame structure corresponding to the transmission mode I of digital audio broadcasting.

A decoder according to a second aspect of the present invention comprises:
A first OFDM signal transmitted with a reference bandwidth and a second OFDM signal transmitted with a bandwidth smaller than the reference bandwidth
And a demodulator for demodulating the received first and second OFDM signals to reproduce first and second code sequences, respectively, and reproducing by the demodulator. The stored second code sequence is stored in accordance with the bit rate of the second code sequence, and the stored code sequence is stored in the first code sequence.
Bit rate conversion means for reading pad data such as a PRBS signal or the like in a data deficient area at the bit rate of the coded sequence and the first signal in accordance with the control signal.
When decoding from the OFDM signal, the code sequence output by the demodulation means is selected, and when decoding from the second OFDM signal, the code sequence output by the bit rate conversion means is selected. And decoding means for decoding the code sequence selected by the selecting means.

A decoder according to a third aspect of the present invention comprises:
A demodulation means for decoding an OFDM signal transmitted in a bandwidth narrower than a reference bandwidth, demodulating the received OFDM signal to reproduce a code sequence, and decoding the code sequence reproduced by the demodulation means. A storage unit for storing the code sequence according to the bit rate of the code sequence, and reading the code sequence stored in the storage unit at the bit rate of the code sequence reproduced from the OFDM signal of the reference bandwidth, , PRBS signal or the like, and a decoding unit for decoding a code sequence to which the pad data is added and the bit rate is converted.

Preferably, the decoding means includes means for extracting and decoding data related to a service such as an audio signal, and means for decoding data related to multiplexing such as multiplexed information data. .

A bit rate conversion apparatus according to a fourth aspect of the present invention receives a code sequence according to a clock signal having a certain frequency, outputs the code sequence according to a clock signal having a frequency higher than the clock signal, and outputs the code sequence according to the code sequence. Each CIF (Common Interleaved Framing) of the configured transmission frame
me) PRBS (Pseudo Random Binary Seque)
nce) for inserting a signal to adjust a frame length, for decoding code sequences transmitted by OFDM having different bandwidths in the same procedure and enabling reproduction of multiplexed data. It is.

An OFD according to a fifth aspect of the present invention
The M data reproduction method is based on OFDM (Orthogonal Frequency).
Division Multiplex), a code sequence is reproduced by demodulating according to a clock signal of a lower frequency than a reference frequency, the reproduced code sequence is recorded according to the low frequency clock signal, and the recorded code sequence is converted to a reference frequency. The bit rate of the code sequence is converted by reading in accordance with the clock signal, and the multiplexed information data and service data are reproduced by decoding the code sequence with the converted bit rate.

Also, each CIF (Common Interframe) of a transmission frame composed of a code sequence whose bit rate has been converted.
A PRBS (Pseudo Random Bi
narySequence) signal may be inserted to adjust the frame length.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An OFDM decoding apparatus according to an embodiment of the present invention will be described below in detail with reference to the drawings. Here, in particular, an OFDM that enables decoding of a code sequence transmitted by OFDM having a reference bandwidth and OFDM having a bandwidth 1/2 of the reference bandwidth.
The decoding device will be described.

FIG. 1 shows an OF according to an embodiment of the present invention.
3 is a configuration diagram illustrating a configuration of a DM decoding device 100. FIG. As shown in the figure, the OFDM decoding apparatus 100 includes a clock signal generation unit 10, a 1/2 frequency division unit 11, a clock selection unit 12, an OFDM signal demodulation unit 13, a sequence selection unit 14, a signal reproduction unit 15 and a frame format converter 16.

The clock signal generator 10 is composed of an oscillator and the like, and generates a clock signal of a reference frequency used for decoding a code sequence transmitted by OFDM of a reference bandwidth.

The 分 frequency divider 11 is composed of a frequency divider or the like, and divides the frequency of the clock signal generated by the clock signal generator 10 into 周波 数.

The clock selection unit 12 is composed of a selector or the like. The clock selection unit 12 receives a switching signal from the outside and generates a clock signal for demodulation to be supplied to the OFDM signal demodulation unit 13 by the clock signal generation unit 10. / 2 frequency divider 11
Is switched with the frequency-divided one. Clock selector 12
Indicates that the OFDM signal demodulation unit 13 determines that the OFDM signal demodulation unit 13
When performing demodulation corresponding to the clock signal generation unit 1
0 outputs the generated clock signal. Further, when the OFDM signal demodulation unit 13 performs the demodulation corresponding to the OFDM having a bandwidth of の of the reference bandwidth, the clock selection unit 12 divides the clock signal divided by the 分 frequency division unit 11. Output.

The OFDM signal demodulation unit 13 includes an A / D (analog / digital) converter, an OFDM demodulator, a frequency deinterleaver, and the like, and an IF (Intermediate Frequency) signal (OFDM) in which OFDM is performed.
Signal) and demodulate it to reproduce a code sequence having a transmission frame structure.

The reproduced code sequence forms a transmission frame as exemplified in FIG. The transmission frame is composed of FIC (Fast Information Channel) data units FIC (1) to FIC (4) including information about multiplexing necessary for reproduction of service data and a plurality of CIFs for multiplexing and transmitting service data. (Common InterleavedFr
ame) Data part CIF (1) to CIF (4). Each of the CIF data units CIF (1) to CIF (4) includes MPEG data units M (1) to M (4) which encode service data compressed by the MPEG (Moving Picture Experts Group) method.

The sequence selecting section 14 is composed of a selector and the like, and is for selecting input data to the signal reproducing section 15. The sequence selecting section 14 receives the code sequence received from the OFDM signal demodulating section 13 and the code sequence received from the frame adjusting section 31. A code sequence is selectively switched and output, and sent to the data selection unit 20. Sequence selector 14 performs OFDM signal demodulation 13 in accordance with a switching signal, which is an external control signal, when the OFDM signal demodulator 13 performs demodulation corresponding to OFDM of the reference bandwidth to reproduce a code sequence.
A code sequence received from the DM signal demodulation unit 13 is selected and output. Further, the sequence selection unit 14 is configured to output the OFDM signal demodulation unit 1
3 reproduces a code sequence by performing demodulation corresponding to OFDM having a bandwidth of １ ／ of the reference bandwidth, and outputs the code sequence received from the frame adjustment unit 31.

The signal reproducing section 15 decodes a code sequence to reproduce multiplexed information data and service data (audio signal), which are information sequences, and includes a data selection section 20 and an audio signal decoding section. And a multiplexed information data decoding unit 22.

The data selection unit 20 is composed of a demultiplexer and the like.
This is for selecting the data part. The data selection unit 20 receives the code sequence from the sequence selection unit 14,
The code sequence of the data part is sent to the multiplexed information data decoding part 22, and the code sequence of the CIF data part is sent to the audio signal decoding part 21.

The audio signal decoding unit 21 includes a service data selector, a time deinterleaver, a Viterbi decoder,
It is composed of an energy descrambler, an MPEG audio decoder, a D / A (digital / analog) converter, etc., for decoding CIF data received from the data selection unit 20 to reproduce service data (audio signal). . The audio signal decoding unit 21
The code sequence corresponding to the service selected by the user is extracted and decoded from the code sequence of the CIF data portion.

The multiplexed information data decoding unit 22 is composed of a Viterbi decoder, an energy descrambler, and the like, and decodes the code sequence of the FIC data received from the data selection unit 20.

The frame format converter 16 converts the bit rate so that a code sequence transmitted by OFDM having a bandwidth of の of the reference bandwidth can be decoded at the reference frequency. 30
, A frame adjustment unit 31, and a PRBS signal generation unit 32.

The frame storage section 30 is composed of a semiconductor memory or the like, and is for recording the transmission frame data demodulated by the OFDM signal demodulation section 13 by the clock signal output from the 1/2 frequency dividing section 11. The frame storage unit 30 can read data written one frame before while writing data for one transmission frame. When the writing of the data for one transmission frame is completed, the frame storage unit 30 notifies the frame adjustment unit 31 to that effect.

The frame adjusting section 31 is provided with a DSP (Digital
This is for adjusting a transmission frame formed by a code sequence, which is configured by a signal processor. The frame adjustment unit 31 receives the notification from the frame storage unit 30 that the storage of the data for one transmission frame is completed, and generates the clock signal for the data for one transmission frame stored in the frame storage unit 30. Reading is performed by the clock signal output from the unit 10. The frame adjustment unit 31 adds the PRBS (Ps) generated by the PRBS signal generation unit 32 to the CIF data portion of the transmission frame read from the frame storage unit 30.
An eudo Random Binary Sequence) signal is padded to adjust the frame length, and sent to the sequence selection unit 14.

The PRBS signal generator 32 is for generating a PRBS signal which is a pseudo random signal used for padding. This PRBS signal corresponds to the ITU-
R BS. 1114 This is defined as padding data in System A.

Hereinafter, an OF according to an embodiment of the present invention will be described.
The operation of the DM decoding device will be described. The OFDM decoding apparatus 100 has an OFD having a bandwidth narrower than the reference bandwidth.
This device enables decoding similar to a code sequence transmitted by OFDM of a reference bandwidth by converting the bit rate of the code sequence transmitted by M, and facilitates decoding.

When decoding a code sequence transmitted by OFDM of the reference bandwidth, the clock selection unit 12 operates the clock signal generation unit 1 in response to an external switching signal.
It is set to output the clock signal received from 0. Further, sequence selection section 14 is set to output the data received from OFDM signal demodulation section 13.

The OFDM signal demodulator 13 receives the received IF
The signal is sampled, and a code sequence is reproduced by performing a fast Fourier transform or the like, and is sent to the sequence selection unit 14.

The sequence selecting section 14 is provided for the OFDM signal demodulating section 1
3 is sent to the data selection unit 20 of the signal reproduction unit 15.

The data selection section 20 has a CIF data section and an FI
It is separated into a C data section and sent to an audio signal decoding section 21 and a multiplex information data decoding section 22, respectively. The audio signal decoding unit 21 extracts and decodes a code sequence corresponding to the selected service from the code sequence constituting the CIF data unit, decompresses an audio signal compressed by the MPEG method, and converts the signal into an analog signal. Perform processing and output. The multiplexed information data decoding unit 22 decodes and outputs a code sequence constituting the FIC data unit. This allows
It is possible to decode a code sequence transmitted by OFDM of a reference bandwidth.

On the other hand, the OFDM decoding apparatus 100 has a bandwidth of の of the reference bandwidth,
When decoding a code sequence created to form a transmission frame as shown in (A), the following operation is performed. In this case, first, the clock selection unit 12 is set so as to output the clock signal received from the 1/2 frequency division unit 11 by a switching signal from the outside. In addition, sequence selection section 14 is set to output the code sequence received from frame adjustment section 31.

The OFDM signal demodulation unit 13 receives and demodulates the IF signal, and sends the reproduced code sequence to the frame storage unit 30 of the frame format conversion unit 16.

The frame storage unit 30 specifies the write timing by the clock signal received from the 分 frequency divider 11 and writes and stores the code sequence received from the OFDM signal demodulator 13 in transmission frame units.

The frame adjusting section 31 is provided in the frame storing section 3
The timing of reading the data stored in 0 is defined by the clock signal received from the clock signal generator 10, and the code sequence stored in the frame storage 30 is read in units of transmission frames. Thereby, the frame adjustment unit 31 can read out the data stored in the frame storage unit 30 at twice the speed at the time of writing.
Therefore, the bit rate of the code sequence is doubled. At this time, the frame length is １ ／ of that at the time of writing to the frame storage unit 30.

The frame adjustment unit 31 detects the CIF data portion of the read code sequence, inserts the PRBS signal output by the PRBS signal generation unit 32 at the end of each CIF data portion, and writes the PRBS signal into the frame storage unit 30. Is restored to the original frame length.

The frame adjusting section 31 is provided in the frame storing section 3.
The code sequence read from 0 and into which the PRBS signal is inserted is sent to the sequence selection unit 14.

The sequence selection unit 14 selects and outputs the code sequence received from the frame adjustment unit 31 according to an external switching signal, and sends it to the data selection unit 20 of the signal reproduction unit 15.

The data selection unit 20, the audio signal decoding unit 21 and the multiplexed information data decoding unit 22 transmit the O
It operates in the same manner as when decoding a code sequence transmitted by FDM, and outputs audio data and multiplexed information data.

For example, when the reference bandwidth is 1.536 MHz corresponding to the transmission mode I of DAB, when decoding a code sequence transmitted by OFDM with the bandwidth narrowed to 768 KHz, the OFDM signal demodulation unit 13 , FIG. 2
A code sequence having a transmission frame configuration as shown in (A) is reproduced. In this transmission frame, the FIC data parts FIC (1) to FIC (4) each consist of a code sequence of 2304 bits, and the CIF data part CIF (1)
To CIF (4) are each composed of a 26496-bit code sequence.

The OFDM signal demodulation unit 13 writes a code sequence into the frame storage unit 30 for each transmission frame using the clock signal divided by the １ ／ frequency divider 11. The frame adjustment unit 31 specifies the read timing based on the clock signal generated by the clock signal generation unit 10 and reads the code sequence stored in the frame storage unit 30. As a result, as shown in FIG. 2B, the transmission frame has a frame length of 48 ms, and the bit rate of the code sequence is doubled.

The frame adjustment unit 31 is provided with a CIF data part CIF (1) to CIF (CIF) in the transmission frame shown in FIG.
(4) At the end of each, 28,800 bits of PRBS
Insert a signal. Thereby, the frame adjustment unit 31
As shown in FIG. 2 (C), a transmission frame having the same frame length as the transmission frame of FIG. 2 (A), consisting of four logical frames of 24 ms, and consisting of a code sequence whose bit rate is twice that of the demodulation Create

The configuration of the transmission frame corresponds to the transmission mode I in the DAB standard. Therefore,
The signal reproducing unit 15 transmits data in the transmission mode I in the DAB standard.
Decoding can be performed in the same manner as the above code sequence, and no special processing due to the structure of the transmission frame is required.

As described above, in the OFDM decoding apparatus 100, the frame format conversion unit 16
Double the bit rate of the code sequence and add P to the CIF data
The frame length can be adjusted by inserting an RBS signal. Thereby, the data selection unit 20 of the signal reproduction unit 15,
Audio signal decoding unit 21 and multiplexed information data decoding unit 2
2 is an operation similar to the case of decoding a code sequence transmitted by OFDM of a reference bandwidth, and an O of which bandwidth is 1/2.
It is possible to decode a code sequence transmitted by FDM.

The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, 1/2
The frequency divider 11 has been described as dividing the frequency of the clock signal generated by the clock signal generator 10 into １ ／, but is not limited to this. That is, 1/4 frequency divider or VC
Any method of converting the frequency of the clock signal using, for example, O (Voltage Controlled Oscillator) can be used. In this case, when decoding a code sequence transmitted by OFDM having a bandwidth smaller than the reference bandwidth, the OFDM signal demodulator 13 and the frame storage 3
0 may demodulate and store the code sequence according to the low-frequency clock signal, and the frame adjustment unit 31 may read the code sequence from the frame storage unit 30 according to the reference frequency and convert the bit rate. Further, the frame adjustment unit 31 generates a PR frame signal generated by the PRBS signal generation unit 32 such that the frame length of the transmission frame included in the read code sequence is the same as that when writing to the frame storage unit 30.
The frame length may be adjusted by inserting a BS signal. By this, it is not limited to 基準 of the reference bandwidth,
The bit rate of a code sequence transmitted by OFDM having an arbitrary bandwidth smaller than the reference bandwidth can be converted, and decoding can be performed easily.

[0061]

As described above, according to the present invention, the structure of a transmission frame can be converted so that a code sequence transmitted by OFDM having a narrow bandwidth can be decoded in accordance with the DAB standard. Sequence decoding becomes easier.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an OFDM decoding device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a transmission frame formed by a code sequence to be decoded by the OFDM decoding device according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a conventional OFDM decoding device.

FIG. 4 is a diagram for explaining a transmission frame in the related art.

FIG. 5 is a diagram illustrating a transmission mode of DAB.

[Explanation of symbols]

10, 201 clock signal generation unit 11, 202 1/2 frequency division unit 12 clock selection unit 13, 204 OFDM signal demodulation unit 14 sequence selection unit 15, 205 signal reproduction unit 16 frame format conversion unit 20, 210 data selection unit 21, 211 audio signal decoding unit 22, 212 multiplex information data decoding unit 30 frame storage unit 31 frame adjustment unit 32 PRBS signal generation unit 100, 200 decoding device 203a, 203b switch FIC (1) to FIC (4) FIC data unit CIF (1) ) To CIF (4) CIF data section M (1) to M (4) MPEG data section

Claims (13)

[Claims] 1. An OFDM (Orthogonal Frequency Divisio)
(N Multiplex) demodulating means for demodulating a signal on which a signal has been made to reproduce a code sequence; converting means for converting a bit rate of the code sequence reproduced by the demodulation means; and a code sequence reproduced by the demodulation means. A code sequence selecting unit that selects and outputs one of a code sequence whose bit rate has been converted by the conversion unit, and a reproducing unit that decodes the code sequence output by the code sequence selecting unit and reproduces an information sequence. , An OFDM decoding device. 2. The code sequence selecting means according to a control signal, wherein when the demodulation means performs demodulation corresponding to OFDM of a reference bandwidth and reproduces a code sequence, the demodulation means selects the reproduced code sequence. When the demodulation means performs demodulation corresponding to OFDM having a bandwidth different from the reference bandwidth to reproduce a code sequence, the conversion means selects and outputs a code sequence whose bit rate has been converted. The OFDM decoding device according to claim 1, wherein: 3. A first circuit for generating a clock signal having a reference frequency.
Clock signal generating means, and second clock signal generating means for generating a clock signal having a frequency different from that of the clock signal generated by the first clock signal generating means. Storage means for storing the reproduced code sequence in accordance with the clock signal generated by the second clock signal generation means; and storing the code sequence stored by the storage means in the reference frequency generated by the first clock signal generation means. The OFDM decoding device according to claim 1, further comprising: a unit that reads in accordance with a clock signal. 4. The apparatus according to claim 3, wherein said second clock signal generator divides the frequency of the clock signal generated by said first clock signal generator by half. OFDM decoding device. 5. The conversion means comprises: a PRBS (Pseudo Random Binary Sequence) signal generating means for generating a PRBS (Pseudo Random Binary Sequence) signal; and a plurality of CIF (Common Interleaved Frame) data parts based on a transmission frame structure of a code sequence read from the storage means. 5. The OFDM according to claim 3, further comprising a unit for detecting the PRBS signal and inserting the PRBS signal generated by the PRBS signal generating unit into each CIF data part.
Decoding device. 6. The demodulation means reproduces a code sequence having a transmission frame structure provided with four 24 ms logical frames, and the conversion means comprises a transmission frame provided with four logical frames reproduced by the demodulation means. The PRBS signal generated by the PRBS signal generation means is inserted into each logical frame by converting the bit rate of a code sequence having a structure, and the frame length is 96 ms and the bit rate is twice the code sequence reproduced by the demodulation means. The OFDM decoding device according to claim 5, wherein the OFDM decoding device converts the code sequence into a code sequence having a transmission frame structure. 7. The reproduction means according to claim 1, wherein said reproduction means comprises ITU-R BS. 11
14 DAB (Division) standardized by System A
7. A decoding system capable of decoding a code sequence having a transmission frame structure corresponding to a transmission mode I of digital audio broadcasting.
Item 5. The OFDM decoding device according to item 1. 8. A decoder capable of selectively decoding a first OFDM signal transmitted with a reference bandwidth and a second OFDM signal transmitted with a bandwidth smaller than the reference bandwidth, Demodulating means for demodulating the received first and second OFDM signals to reproduce first and second code sequences, respectively, and converting the second code sequence reproduced by the demodulation means into the second code Bit rate conversion means for storing the code sequence stored in accordance with the bit rate of the sequence, reading out the stored code sequence at the bit rate of the first code sequence, and adding pad data to an insufficient data area; Upon decoding from an OFDM signal, a code sequence output by the demodulation means is selected,
When decoding from the second OFDM signal, a selection unit that selects and outputs a code sequence output by the bit rate conversion unit; and a decoding unit that decodes the code sequence selected by the selection unit. A decoder comprising: 9. A decoder capable of decoding an OFDM signal transmitted with a bandwidth narrower than a reference bandwidth, comprising: a demodulator for demodulating a received OFDM signal to reproduce a code sequence; Storing means for storing the obtained code sequence in accordance with the bit rate of the code sequence, and reading the code sequence stored in the storage means at the bit rate of the code sequence reproduced from the OFDM signal of the reference bandwidth, A decoder comprising: means for adding pad data to a data deficient area; and decoding means for decoding a code sequence to which the pad data has been added and the bit rate has been converted. 10. The apparatus according to claim 8, wherein said decoding means comprises: means for extracting and decoding data related to a service; and means for decoding data related to multiplexing. Decoder. 11. A code sequence is input according to a clock signal of a certain frequency, the code sequence is output according to a clock signal higher in frequency than the clock signal, and each CIF (Common Interleaved FFT) of a transmission frame constituted by the code sequence is output.
rame) PRBS (Pseudo Random Binary Seq)
bit for enabling decoding of multiplexed data by decoding in the same procedure with respect to a code sequence transmitted by OFDM having a different bandwidth, characterized in that a frame length is adjusted by inserting a signal. Rate converter. 12. An OFDM (Orthogonal Frequency Divis).
A code sequence is reproduced by demodulating a signal subjected to ion multiplexing according to a clock signal of a lower frequency than the reference frequency, the reproduced code sequence is recorded according to the low-frequency clock signal, and the recorded code sequence is recorded at the reference frequency. A bit sequence of the code sequence is converted by reading in accordance with the clock signal, and the multiplexed information data and service data are reproduced by decoding the code sequence with the converted bit rate. 13. A CIF (Common Interleav) of a transmission frame composed of a code sequence whose bit rate has been converted.
ed Frame) PRBS (Pseudo Random Binary)
13. The OFDM data reproducing method according to claim 12, wherein a frame length is adjusted by inserting a Sequence) signal.