JPH10322306A - Digital signal transmitter and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a receiver with a narrow band to extract a significant part from a broad band orthogonal frequency division multiplex(OFDM) signal. SOLUTION: An integration controller 102 controls a packet multiplexer 103 according to a multiplex frame in matching with a configuration of a prescribed OFDM signal so as to generate a multiplex signal of a specific pattern, and the packet multiplexer 103 multiplexes pluralities of kinds of received digital signals in a packet form to generate a packet multiplex signal. Then error correction and a modulation system are set for each OFDM block and the integral controller 102 controls an OFDM transmitter 104 to configure the prescribed OFDM signal and the OFDM transmitter 104 converts the packet multiplex signal from the packet multiplexer 103 into an OFDM signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital signal transmission apparatus and method for transmitting a time-division multiplexed digital signal in a fixed-length packet format using an OFDM signal having a frame structure.

[0002]

2. Description of the Related Art An OFDM (Orthogonal Frequency Divided) digital signal that is time-division multiplexed in a fixed-length packet format is used.
sion multiplex) As a method of transmitting digital signals, there is a DVB-T (Digital Video Broadca
Sting-Terrestrial) is known, and DVB-T uses MPEG-2 (moving picture experts group phas
The method of transmitting the transport stream (TS) of e2) by an OFDM signal is standardized.

[0003]

However, according to this standard, the transmission method and the digital signal in the form of a packet to be transmitted are considered completely independent of each other, and it is not assumed that they are associated with each other. It has been difficult to extract a meaningful part from the OFDM signal of the band using a narrow band receiver.

An object of the present invention is to provide a digital signal transmission apparatus and method capable of solving the above problems and extracting a significant portion from a wideband OFDM signal by a narrowband receiver. is there.

[0005]

SUMMARY OF THE INVENTION A digital signal transmission apparatus according to the present invention comprises first to n-th packets each of n (≥2) kinds of digital signals to be provided for a service having a fixed length.
Packetizing means, first to n-th storing means for temporarily storing the packets obtained by the first to n-th packetizing means in correspondence with the digital signals, and first to n-th storing means Extracting means for continuously extracting a number of packets corresponding to a predetermined packet multiplexing pattern for each of the n kinds of digital signals, and a carrier modulation method and an error detecting means for extracting the packets extracted by the extracting means. OFD according to correction method
Conversion means for converting into an M signal.

[0006] The digital signal transmission apparatus of the present invention can further comprise setting means for setting a carrier modulation method and an error correction method.

According to the digital signal transmission method of the present invention, n (≧ 2) kinds of digital signals to be provided for a service are packetized with a fixed length, and the obtained packets are stored in correspondence with the digital signals. And continuously extracting the stored packets from the n types of digital signals by the number corresponding to the predetermined packet multiplexing pattern, respectively, and determining the extracted packets by a predetermined carrier modulation method and error. Converting to an OFDM signal according to the correction method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail with reference to the drawings. <First Embodiment> FIG. 1 shows a first embodiment of the present invention. In FIG. 1, reference numeral 103 denotes a packet multiplexing apparatus which multiplexes a plurality of types of input digital signals in a packet format to generate a packet multiplexed signal. The packet multiplexed signal conforms to the international standard (ISO / IEC 13818-1
) MPEG-2 transport stream (TS)
And TS is a transport stream packet (T
SP), and the packet length of the TSP is 1
It is 88 bytes. This example is shown in FIG. 104 is OF
This is a DM transmission device, which converts a packet multiplexed signal from the packet multiplexing device 103 into an OFDM signal after performing transmission channel coding. Reference numeral 102 denotes an integrated control device which controls the multiplexer 103 so as to generate a multiplexed signal of a specific pattern according to a predetermined OFDM signal configuration, and sets error correction and a modulation method for each OFDM block. OFD to form a predetermined OFDM signal
The M transmission device 104 is controlled.

Next, to simplify the description, an example in which the digital signal A, the digital signal B, and the digital signal C are serviced will be described. As in the example of the OFDM signal in FIG.
The DM signal is configured by arranging one or more OFDM blocks having the same bandwidth, for example, a narrow band of 100 kHz on the frequency axis. A fixed time of one OFDM block (hereinafter, OFD block)
The number of TSPs included in an M frame is three patterns of carrier modulation schemes, that is, QPSK (quadratur
e phase shift keying), 16QAM (quadrature ampl)
Itude modulation) and 64QAM, in each case, three types of coding rates of convolutional codes of a scheme combining a (204,188) Reed-Solomon code and a convolutional code as error correction schemes, that is, 1/2, 3 / For 4, 7/8,
The results are shown in Table 1 below.

[0010]

[Table 1]

FIG. 3 shows the configuration of a packet multiplexing apparatus for multiplexing digital signals A, B and C in packets. In FIG. 3, 305, 306, 30
Reference numeral 7 denotes a packetizing unit that assembles digital signals A, B, and C into packets. Buffers 308, 309, and 310 store packets from the packetizers 305, 306, and 307. Reference numeral 311 denotes a switch, which controls the buffers 308 and 30 under the control of the integrated control apparatus 102.
9, 310, and the buffers 308, 309, 3
10 is read out in packet units.

With this configuration, the input digital signal A, digital signal B, and digital signal C are assembled into packets by the packetizers 305, 306, and 307, and the obtained packets are stored in the buffers 308 and 309, respectively. , 310. Then, one predetermined TSP pattern is repeated for each multiplex frame, and the integrated controller 102 switches the switch 311 based on the predetermined TSP pattern.
For example, the content of the digital signal multiplexed on the multiplexed digital signal will be described with reference to the OFDM block shown in FIG.
For an FDM frame, the number of TSPs is set to 4,
For the OFDM frame of the DM block 405, TS
The number of P is 6, and the OFDM of the OFDM block 406 is
The number of TSPs is eight for each frame.

That is, OFDM blocks 402 and 40
3, 404, QPSK, 1 /
For the OFDM block 405, the transmission parameter is QPSK, for the OFDM block 405, the transmission parameter is 16 QAM, for the OFDM block 406,
As a half convolution, OFD
The M transmission device 104 is controlled to form an OFDM signal. On the other hand, the packet multiplexer 103 is controlled so as to generate a multiplex signal having a periodic structure in which a total of 26 TSPs constitute one multiplex frame according to the multiplex frame 407. FIG. 4 shows an example of the spectrum of the obtained OFDM signal. As shown in FIG. 4, the OFDM signal is configured by arranging five OFDM blocks continuously in the frequency axis direction.

As can be seen from FIG. 4, the digital signal A is applied to OFDM blocks 402, 403, 404 on the frequency axis.
And the digital signal B is in the OFDM block 4
At position 05, the digital signal C is applied to the OFDM block 40.
6 will be present. Therefore, by extracting and receiving the frequency components of the OFDM blocks 402 to 404, only the digital signal A can be extracted. By extracting and receiving the frequency components of the OFDM block 405, only the digital signal B can be extracted. By extracting and receiving the frequency component of the OFDM block 406, only the digital signal C can be extracted.

As shown in Table 1, transmission parameters can be set for each OFDM block, so that transmission characteristics of each digital signal can be changed.

<Second Embodiment> The present embodiment differs from the first embodiment in that digital signals to be serviced are different. That is, in the first embodiment, the digital signals A, B, and C are serviced. In the present embodiment, the digital signal D is serviced in addition to the digital signals A, B, and C.

FIG. 5 shows the configuration of the packet multiplexing apparatus according to the present embodiment. 5, reference numerals 305 to 310 denote the same parts as in FIG. 501 is a packetizer,
This is to assemble a packet of the digital signal D. 5
A buffer 02 stores packets from the packetizing unit 501. 503 is a switch,
The buffers 308 and 30 are controlled by the integrated controller 102.
9, 310 and 502 are switched, and buffers 308 and 3 are switched.
The data is read out in units of packets from 09, 310, and 502.

The digital signal transmission device according to the present embodiment
The packet multiplexing apparatus is configured as described above, and the packet multiplexer shown in FIG.
The number of TSPs is set to 7 for each of the FDM blocks 607 and 608. That is, since the transmission parameters for the OFDM blocks 607 and 608 are QPSK and 7/8 convolution and the packet from the packet multiplexing device 103 according to the multiplex frame 507 is converted into an OFDM signal by the OFDM transmission device 104, The digital signal A of the first embodiment,
The digital signal D can be added while B and C are kept as they are, and the digital signal transmission system can be expanded without affecting the receiver of the service of the digital signals A, B and C.

[0019]

As described above, according to the present invention,
With the above configuration, a part of the wideband OFDM signal can be received by the narrowband receiver, and the band can be extended while maintaining the compatibility of the digital signal transmission system. Hierarchical transmission in which transmission characteristics are optimized for each signal can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a transport stream packet.

FIG. 3 is a block diagram illustrating a configuration of a packet multiplexer 103 according to the first embodiment.

FIG. 4 is a diagram showing a correspondence between an OFDM signal spectrum and an OFDM frame according to the first embodiment.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram illustrating correspondence between OFDM signal spectra and OFDM frames according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 102 Integrated control device 103 Packet multiplexing device 104 OFDM transmission device 305, 306, 307 Packetization unit 308, 309, 310 Buffer 311 Switch

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shunji Nakahara 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Masayuki Takada 1-10-11 Kinuta, Setagaya-ku, Tokyo No. Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Kenichi Tsuchida 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Research Institute (72) Inventor Masahiro Okano 1-10 Kinuta, Setagaya-ku, Tokyo No. 11 Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Makoto Sasaki 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Research Institute (72) Inventor Takeshi Kimura Nishi-Asakusa, Taito-ku, Tokyo 1-1-1 1-1 Kan @ Asakusa Building, 8th Floor, Next Generation Information Broadcasting System Laboratory

Claims (3)

[Claims] 1. A first to n-th packetizing means for packetizing fixed-length n (≧ 2) types of digital signals to be provided to a service, and a packet obtained by the first to n-th packetizing means. First to n-th store means for temporarily storing the digital signals in correspondence with the respective digital signals; and a packet multiplexing pattern predetermined for each of the n kinds of digital signals by storing the packets of the first to n-th store means. Digital means comprising: extracting means for successively extracting a number of packets corresponding to the number of packets, and converting means for converting the packets extracted by the extracting means into an OFDM signal in accordance with a predetermined carrier modulation method and error correction method. Signal transmission device. 2. The digital signal transmission device according to claim 1, further comprising setting means for setting a carrier modulation method and an error correction method. 3. A step of packetizing n (≧ 2) kinds of digital signals to be provided to a service with a fixed length, a step of storing the obtained packets corresponding to the respective digital signals, and a step of storing the stored packets. Continuously extracting a number corresponding to a predetermined packet multiplexing pattern for each of the n types of digital signals, and converting the extracted packets into OFDM signals according to a predetermined carrier modulation scheme and an error correction scheme. Performing a digital signal transmission method.