JP3133958B2 - Digital signal transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal transmission apparatus for transmitting a time-division multiplexed digital signal in a fixed-length packet format by 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 solve the above-mentioned problems and to provide a digital signal transmission apparatus capable of extracting a significant portion from a wideband OFDM signal by a narrowband receiver.

[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 types of digital signals, and extracting the packets extracted by the extracting means for each of the n types of digital signals. A narrow-band OFD that converts an OFDM signal into an OFDM signal according to a predetermined carrier modulation method and an error correction method and that can transmit an integer number of the fixed-length packets of the same type of digital signal in a predetermined time.
Converting means for forming an OFDM signal by combining one or more M blocks.

[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.

[0007]

[0008]

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 multiplex signal is an MPEG-2 transport stream (TS) of an international standard (ISO / IEC 13818-1), and the TS is composed of transport stream packets (TSP), and the packet length of the TSP is 188 bytes. It is. This example is shown in FIG. An OFDM transmission device 104 converts the packet multiplexed signal from the packet multiplexing device 103 into an OFDM signal after performing transmission path coding. 1
Reference numeral 02 denotes an integrated control device which controls the multiplexer 103 so as to generate a multiplexed signal of a specific pattern in accordance with a predetermined OFDM signal configuration, and sets error correction and a modulation method for each OFDM block, and The OFDM transmission apparatus 104 is controlled so as to configure the OFDM signal of FIG.

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

Continuing on the front page (72) Inventor Shunji Nakahara 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Within the Broadcasting Technical Research Institute (72) Inventor Masayuki Takada 1-110-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Within the Broadcasting Research Institute (72) Kenichi Tsuchida 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Within the Broadcasting Research Institute (72) Masahiro Okano 1-110, Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Within the Broadcasting Research Institute (72) Inventor Makoto Sasaki 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Within the Broadcasting Research Institute (72) Inventor Takefumi Kimura 1-1-1, Nishiasakusa, Taito-ku, Tokyo ８8th floor of Asakusa Building Inside the Next Generation Information Broadcasting System Laboratory Co., Ltd. (56) References JP-A-8-97795 (JP, A) “Study of terrestrial ISDB broadcasting system: BST-OFDM system and multiplexing system” Vision Society Technical Report, June 20, 1996, ol. 20, No. 22, p. 23-28 (58) Field surveyed (Int. Cl. ⁷ , DB name) H04J 11/00

Claims (2)

(57) [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. Extracting means for continuously extracting a number of packets corresponding to the number of the digital signals; converting the packets extracted by the extracting means into an OFDM signal according to a carrier modulation scheme and an error correction scheme predetermined for each of the n types of digital signals; Narrow-band OFDM capable of transmitting an integer number of the fixed-length packets of the same type of digital signal at a given time
A digital signal transmission device comprising: a conversion unit that forms an OFDM signal by combining one or more blocks. 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.