JPH11112482A - Multiplexing system and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize reproduction of an important basic component of information even in a deteriorated transmission environment such as fading environment of transmission from a mobile body. SOLUTION: In the multiplex transmission of multimedia information, a 2nd multiplexer 32 at a transmitter side adds each header only to important basic components of information and multiplexes them, a 1st multiplexer 31 adds each header to data information being the multiplexed output together with other information and multiplexes them to generate a transmission packet. First and second demultiplexers 33, 34 at a receiver side receive each reception packet and the 2nd demultiplexer 34 detects the header added by the 2nd multiplexer 32 even when the 1st demultiplexer 33 cannot detect the header added by the 1st multiplexer 31 to reproduced the input information from the 2nd multiplexer 32 thereby realizing the reproduction of important basic components of the information even in a deteriorated transmission environment such as fading environment of transmission from the mobile body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplexing system and apparatus used for transmitting and receiving multiplex signal transmission in multimedia information transmission such as digital television broadcasting to improve transmission quality.

[0002]

2. Description of the Related Art Conventionally, in the transmission of multimedia information in broadcasting and communication, in order to increase transmission efficiency,
On the transmitting side, as shown in FIG.
Information such as video is input to the information source encoders 11 and 12, respectively, and the information amount is compressed. Correspondingly, on the receiving side, FIG.
As shown in (b), after each information is separated by the separator 14, the information is reproduced by the information source decoders 15 and 16, respectively.

In the information transmission system as described above, FIG.
1 is adopted. In this multiplexing system, information such as audio and video is divided into packets each having a bit stream of an appropriate length on the transmission side, and various control information called a header is added thereto. It is multiplexed and transmitted as a stream in an information field (payload) portion in a time division manner. The header includes synchronization information indicating the beginning of the packet, identification information indicating what type of information (audio, video, etc.) the information is.

In this case, the receiving side first detects a header from the stream, separates each packet based on the header information, and reproduces the information. Therefore, in transmitting and receiving multimedia information, it is important how the receiving side detects the header and reads the contents of the header accurately. If the header cannot be detected or the contents cannot be accurately detected, the information may not be reproduced or the correct information may not be reproduced until the next header is detected.

A typical multiplexing method in the conventional multimedia information transmission is MPEG (Moving Picture).
Experts Group 2). MPEG2 is described in detail in "Latest MPEG Textbook" (edited by Hiroshi Fujiwara, ASCII Publishing, 1994).

[0006] This MPEG2 is mainly used for satellite broadcasting, cable television and the like at present, but bit errors due to noises added on a transmission line can be corrected by an error correction at the receiving stage before the separator. It is designed to be almost eliminated by the decoder. Therefore, there is no function to correct the error in the header. If the input of the separator contains an error, it cannot be correctly separated, and it becomes impossible to reproduce video, audio and the like with high quality.

On the other hand, digitization of terrestrial television broadcasting has been studied in recent years, and as a transmission method, orthogonal frequency division multiplexing (OFDM) has been proposed.
A multicarrier transmission system called Multiplexing) has become influential. In this multi-carrier transmission, transmission information is transmitted to a large number of carriers (carriers) using PSK (Phas
e Shift Keying) and QAM (Quadrature Amplitude Mod)
ulation) and transmitted.

As a simple example, FIG. 12 shows generation of a multicarrier signal using four carriers. In this example, for each of the transmission information bits of four channels, the modulator 2
After performing digital modulation by 1, 22, 23, and 24, four sine wave carriers having frequencies f1, f2, f3, and f4 and orthogonal to each other, and multipliers 25 and 2,
The signals are multiplied by 6, 27 and 28 to generate four modulated carriers, which are added by an adder 29 and transmitted.

The relationship between time and frequency of a transmission signal in the single carrier transmission system and the multicarrier transmission system is as shown in FIGS. 13 (a) and 13 (b), respectively. The former is time division, while the latter is frequency division, and the symbol time occupied by one symbol of the modulated signal is four times that of the former.

As described above, in the multi-carrier transmission system, the information signal is spread on the time axis so as to become longer in proportion to the number of carriers. The effect is small as compared with the single carrier transmission scheme in which modulation is performed on the number of carriers. Therefore, there is an advantage that the effect of ghost can be reduced in an environment where there is a ghost that arrives after being delayed and reflected on a mountain or a building in addition to a radio wave arriving directly from a transmitting station to a receiver.

The multi-carrier transmission system can be realized based on a discrete Fourier transform (DFT), and the technology of television broadcasting including the same is described in “Digital Broadcasting Technology” (Kenichi Matsuo, Tokyo Denki University) Publishing, 1997).

It should be noted that MP is used for encoding, decoding, multiplexing and demultiplexing of video in terrestrial digital television broadcasting.
The application of EG2 is considered promising.

In terrestrial digital television broadcasting, in the case of fixed reception in which a fixed receiver receives a signal, the influence of transmission line noise is caused by O in the stage preceding the receiver-side separator.
It can be removed by an FDM demodulation unit or an error correction unit. On the other hand, in the case of mobile reception which is received by a receiver in an automobile or the like, there is an effect of fading in addition to noise, and it is extremely difficult to remove these effects in front of the receiving-side separator. Therefore, there is a problem that a bit error is mixed in the input of the separator, and normal separation and information reproduction become difficult.

[0014]

As described above, for example, in mobile communication and the like, when multiplexing multimedia information such as audio, data, and video, and transmitting / receiving the same, transmission environment due to transmission path noise and fading. Is poor. For this reason, in the system configuration using the conventional multiplexing method, there is a problem that various control signals added when information is multiplexed on the transmission side cause errors on a transmission path, and the multiplexed information cannot be separated on the reception side. Will happen.

Therefore, the present invention solves the above problems,
It is an object of the present invention to provide a multiplexing method and apparatus capable of reproducing important basic components of information even in a poor transmission environment such as a mobile transmission fading environment.

[0016]

In order to solve the above-mentioned problems, a multiplexing system according to the present invention multiplexes a signal block input from one or more channels on a transmission side, and applies the multiplexed block to the multiplexed block. A sub-multiplexed signal block generated by adding a sub-control signal block for identifying the contents of the block is multiplexed as a single signal block with a signal block input from one or more other channels. A main control signal block for identifying the content of the block is added to the block to generate a main multiplexed signal block as a transmission signal, and the receiving side reproduces the sub control signal block directly from the transmission signal, A signal block of an arbitrary channel is separated from a sub multiplex signal block in the transmission signal based on a sub control signal block.

Also, in the multiplex transmission system according to the present invention, a signal block is input to at least one channel from one or more channels and multiplexed, and a first block for identifying the contents of the multiplex block in the multiplex block. A first multiplexer for adding a control signal block to the first multiplexed signal block and outputting the multiplexed signal block as a first multiplexed signal block; and inputting and multiplexing signal blocks from one or more channels as one channel input of the first multiplexer. And a second multiplexer for adding a second control signal block for identifying the content of the multiplexed block to the multiplexed block and outputting the same as a second multiplexed signal block. A first multiplexed signal block transmitted from the side is input, a second control signal block included in the multiplexed signal block is reproduced, and based on the second control signal block, Any channel signal block to be input to the serial second multiplexer and configured to include separator for separating.

In another multiplex transmission system according to the present invention, a signal block from one or more channels is input to a transmitting side and multiplexed, and the multiplexed block identifies the contents of the block. A first multiplexer to which a first control signal block is added and output as a first multiplexed signal block; and a signal block input from one or more channels as one channel input of the first multiplexer. Multiplexing, adding a second control signal block for identifying the contents of the multiplexed block to the second
And a second multiplexer for outputting the multiplexed signal block as a multiplexed signal block. A first multiplexed signal block transmitted from the transmitting side is input to the receiving side, and a first control included in the multiplexed signal block is provided. A first separator for reproducing a signal block and separating the second multiplexed signal block based on the first control signal block; and a second multiplexed signal block separated by the first separator. One of the first multiplexed signal blocks input to the first separator is selectively input to reproduce a second control signal block included in the input multiplexed signal. A second separator for separating a signal block of an arbitrary channel input to the second multiplexer based on the signal block.

Further, the transmitting apparatus according to the present invention inputs and multiplexes signal blocks from one or more channels, and adds a first control signal block for identifying the contents of the multiplexed block to the multiplexed block. A first multiplexer for outputting as a first multiplexed signal block, and a second control signal for inputting and multiplexing a signal block from one or more channels, and identifying the content of the block in the multiplexed block. And a second multiplexer for adding a block and outputting to the first multiplexer as a second multiplexed signal block. On the receiving side, the first multiplexed signal block is converted to the multiplexed signal block. A second control signal block included is reproduced, and a signal block of an arbitrary channel input to the second multiplexer can be separated based on the second control signal block. To.

Further, the receiving apparatus according to the present invention, on the transmitting side, receives and multiplexes a signal block from one or more channels, and a first control signal for identifying the content of the block in the multiplexed block. A signal block from one or more channels is input and multiplexed as one channel input of a first multiplexer for adding a block and outputting as a first multiplexed signal block, and the content of the block is added to the multiplexed block. A first multiplexed signal block transmitted from the transmission side when an output of a second multiplexor for adding a second control signal block for identification and outputting as a second multiplexed signal block is allocated; And reproduces a second control signal block included in the multiplexed signal block, and inputs the second control signal block to the second multiplexer based on the second control signal block. Configured to include a separator for separating the signal block any channels.

Further, another receiving apparatus according to the present invention is configured such that the transmitting side inputs and multiplexes a signal block from one or more channels, and a first block for identifying the content of the block in the multiplexed block. The first control signal block
A signal block from one or more channels is input and multiplexed as one channel input of a first multiplexer that is output as a multiplexed signal block of the second multiplexer, and a second block for identifying the contents of the block in the multiplexed block. Inputting a first multiplexed signal block transmitted from the transmitting side when an output of a second multiplexer for adding a control signal block and outputting as a second multiplexed signal block is assigned;
A first separator that reproduces a first control signal block included in the multiplexed signal block and separates the second multiplexed signal based on the first control signal block;
One of the second multiplexed signal block separated by the demultiplexer and the first multiplexed signal block input to the first demultiplexer, and selectively receives the second multiplexed signal block included in the input multiplexed signal block. The second control signal block is reproduced and the second control signal block is reproduced.
A second signal block for separating a signal block of an arbitrary channel input to the second multiplexer based on the control signal block of
And a separator.

In the multiplex transmission system, the transmitting side allocates the first multiplexed signal block to an arbitrary number of carriers, and transmits the multiplexed signal block. The receiving side transmits the first multiplexed signal block from the received carrier to the first multiplexed signal block. It is characterized in that a multiplex signal block is reproduced.

In the multiplex transmission system, the first and second multiplexers have a function of inputting and multiplexing multimedia signal blocks of one or more channels, respectively, and And a multiplexed output from the multiplexer is input to the first multiplexer as a multimedia signal block of one channel.

In the multiplex transmission system, the second multiplexer may perform signal processing on the second control signal block which is more resistant to transmission errors than the first multiplexer. Wherein the splitter or the second splitter includes means for reproducing the second control signal block based on the signal processing means applied by the second multiplexer. I do.

In the multiplex transmission system, the second multiplexer may determine the signal length of the second multiplex signal block by using a first multiplex signal block generated by the first multiplexer. , Which is shorter than the signal length.

In the multiplex transmission system, the first multiplexer inserts an arbitrary number of second multiplex signal blocks output from the second multiplexer into the multiplex block. And the second area in the remaining area of the block.
And a control signal block having a low correlation is inserted.

In the multiplex transmission system, the first multiplexer divides the second multiplex signal block output from the second multiplexer and straddles the multiplex block. It is characterized by being inserted by inserting.

In the multiplex transmission system, the signal block input to the second multiplexer includes:
It is characterized by including at least the minimum information required for information reproduction.

That is, according to the present invention, in the multiplex transmission of signal blocks such as multimedia information, only the information component necessary for information reproduction is transmitted to the second multiplexer by the second multiplexer to transmit a second control signal block such as a header. The multiplexed signal block is added and multiplexed, and the multiplexed signal block is multiplexed with the other signal blocks by adding a header in a first multiplexer to generate a transmission signal. On the receiving side, by inputting the transmission signal to the first and second demultiplexers, even if the first control signal block added by the first multiplexer cannot be detected by the first demultiplexer, the second By detecting the second control signal block added by the multiplexer by the second separator, it is possible to reproduce the input information of the second multiplexer. Also, the reception side can provide only the minimum necessary reception only by providing only the second separator.

Also, the transmitting side allocates the first multiplexed signal block generated by the first multiplexer to an arbitrary number of carriers, realizes transmission using a plurality of carriers, and reproduces each carrier on the receiving side. Thereafter, by reproducing the output of the first multiplexer, multiplex transmission of information by a plurality of carriers is realized.

The present invention makes it possible to reproduce control bits with high precision, especially in transmission of control bits for multimedia multiplexing.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

(First Embodiment) FIGS. 1A and 1B show a first embodiment of a multiplexing system according to the present invention, wherein FIG. ing.

On the transmitting side shown in FIG. 1 (a), video information and audio information whose information amounts have been compressed by an information source encoder (not shown) are input to a first multiplexer 31, and each information is Is multiplexed into a packet of one information stream by dividing the bit stream by an appropriate length. still,
The type of information to be multiplexed is arbitrary. For example, there may be three types of audio, video, and data, or only two types of audio and video, or only video.

On the receiving side shown in FIG. 1B, the received packet is input to a first separator 33 to separate each information stream, and information is reproduced by an information source decoder (not shown). . At this time, since the receiving side receives a number of packets as a bit stream, it is necessary to detect where the packet is at the head of the packet. In order to separate and reproduce the multiplexed information, it is necessary to detect the type of information and the length of the information.

To realize this, on the transmitting side, at the head of the multiplexed information stream, a synchronization control bit indicating the head, the type and length (number of bits) of multiplexed audio, video, and data information are provided. Various control bits such as the control bits shown are added. These control bits are called a header. On the receiving side, by detecting this header, it is possible to know the head position of the packet and to separate and reproduce the information.

If the header detection fails, information cannot be reproduced until the next header is detected. Therefore, if measures such as inserting a header not only at the beginning of a packet but also in the middle, or adding a header to the beginning of a multiplexed packet by shortening the length of the multiplexed packet, the frequency of header insertion becomes high. Thus, the detection probability of the header is increased, and the reliability of transmission is improved. However, this results in reduced transmission efficiency. Therefore, in the multiplexing method according to this embodiment, a second multiplexer 32 and a second separator 34 are introduced in order to achieve both improvement in reliability and maintenance of transmission efficiency.

On the transmitting side, as described above, the data whose information amount has been compressed by the information source encoder (not shown),
The video and audio information is input to the second multiplexer 32, and a packet of one information stream is generated. However, each piece of information input to the second multiplexer 32 is a bit including basic information among the information source encoded output bits.

The basic information bits will be described. For example, in video coding, a discrete cosine transform (DCT:
After performing Discrete Cosine Transform) processing, different quantization is applied to each component, and by using the strong correlation between the previous and next frames, only the difference between the previous and next frames is encoded, or the moving part And only the motion parameters are transmitted.

Here, the basic information bits include various control information such as a motion detection output in the coded output, and DC information.
These are the minimum and important basic components required for decoding the video on the receiving side, such as the low frequency components of the T output. On the other hand, the high frequency component of the DCT is not essential, but is a component that improves the video decoding quality. Of course,
The number of bits of the basic information component is smaller than the total number of bits obtained by adding the number of bits of the basic information component and the number of bits of the component for improving the quality.

In the second multiplexer 32, a header including various control bits is added to the multiplexed packet and transmitted. The output of the second multiplexer 32 is input to the first multiplexer 31 as data information, and is multiplexed with other audio information and video information.

In this case, the first multiplexer 31 multiplexes only basic information components. For this reason, the length of the packet generated by multiplexing is shorter than the length of the packet generated by the first multiplexer that processes the entire information including the basic information component and the information component for improving the quality. Become.
Therefore, since a plurality of packets generated by the second multiplexer 32 are contained in one packet generated by the first multiplexer 31, one header added by the first multiplexer 31 is detected. During this operation, a plurality of headers added by the second multiplexer 32 are detected, and the detection probability of the header of the second multiplexer 32 is higher than that of the first multiplexer 31.

On the receiving side, the received packet is input to the first separator 33 to separate each information stream.
The information is reproduced by an information source decoder (not shown). At this time, since the output of the second multiplexer 32 is input to the first multiplexer 31 as data information and multiplexed, if the first separator 33 correctly separates the data information on the receiving side, the data is output. The output can be input to a second separator 34. As a result, data, video, and audio information input to the second multiplexer 34 are separated and reproduced by an information source decoder (not shown).

On the other hand, the input of the first separator 33 is configured to be directly input to the second separator 34 via the switch 35. Thereby, even if the first separator 33 fails to detect the header added by the first multiplexer 31 and cannot separate the data information correctly, the switch 35 is switched to directly input the data to the second separator 34. If you do, the second
The separator 34 detects the header added by the second multiplexer 32, so that each information input to the second multiplexer 32 is separated and reproduced by the information source decoder.

In this case, as described above, the detection probability of the header added by the second multiplexer 32 on the receiving side is higher than that of the first multiplexer 31, so that the second multiplexer 3
The second input information can be reproduced with high quality.

The above multiplexing process will be described with reference to FIG.
In FIG. 2, (a) shows the processing contents of the second multiplexer 32,
(B) shows the processing content of the first multiplexer 31.

First, in the second multiplexer 32, the audio bit stream is divided and packets a1, a2, a
.. Are generated, and the video bit stream is divided to generate packets v1, v2, v3,. And a
1, a multiplexed packet p1 is generated by adding a header h1 to v1, and a multiplexed packet p2 is generated by adding a header h2 to a2 and v2.

Next, the first multiplexer 31 divides the audio bit stream into packets A 1, A 2, A
.. Are generated, and the video bit stream is divided to generate packets V1, V2, V3,. And p
A header H1 is added to 1, p2, A1, and V1 to generate a multiplex packet P1, and a header H is added to p3, p4, A2, and V2.
2 is repeated to generate a multiplex packet P2. In this example, the number of output packets of the second multiplexer 32 multiplexed on one packet output of the first multiplexer 31 is 2, but this number is arbitrary.

In this embodiment, in the multiplex transmission of multimedia information, only the important basic components of the information are multiplexed on the transmitting side by adding a header in the second multiplexer 32, and the multiplexed output is output as the data information. The first multiplexer 31 adds a header together with other information and multiplexes the information to generate a transmission packet.

In response to this, the receiving side inputs the received packet to the first and second separators 33 and 34. Thereby, even when the header added by the first multiplexer 31 cannot be detected by the first separator 33, the header added by the second multiplexer 34 can be detected by the second separator 34, The input information of the second multiplexer 32 can be reproduced. Therefore, even in mobile transmission under a fading environment, reproduction of important basic components of information can be realized.

The processing by another multiplexing method will be described with reference to FIG. 3A shows the processing contents of the second multiplexer 32, and FIG. 3B shows the processing contents of the first multiplexer 31.

First, the first multiplexer 31 outputs audio,
Each piece of video information is divided into separate packets, and a control bit indicating the type of information is added to the beginning of the packet, and the packet is transmitted in a time-division manner. In this case, the second multiplexer 32
Is stored in the data packet of the first multiplexer as data information.

In the second multiplexer, as shown in FIG. 3A, an audio bit stream is divided to generate packets a1, a2, a3,..., And a video bit stream is divided to form a packet v1. , V2, v3,... Then, a process of adding a header h1 to a1 and v1 to generate a multiplex packet p1 and adding a header h2 to a2 and v2 to generate a multiplex packet p2 is repeated.

Next, the first multiplexer divides the audio bit stream to generate packets A1, A2, A3,... And divides the video bit stream as shown in FIG. To generate packets V1, V2, V3,. Then, a multiplex packet P1 is generated by adding a header H1 to p1 and p2, a header H2 is added to A1, a multiplex packet P2 of audio is generated, and a header H3 is added to V1 to generate a multiplex packet P3 of video. The process of generating is repeated. In this example, the first multiplexer 3
The number of output packets of the second multiplexer 32 multiplexed to one packet output of 1 is 2, but this number is arbitrary.

By the way, the first and second multiplexers 31 and 32
Length of output packet (number of bits or bytes)
Can be realized with a fixed length or a variable length. This will be described with reference to FIG.

First, when an arbitrary number of output packets of the second multiplexer 32 are accommodated in the information field (payload) of the output packet of the first multiplexer 31, the second multiplexer 32
Is not always completely accommodated in the information field of the output packet of the first multiplexer 31.

As an example, as shown in FIG. 4A, output packet streams p1, p2,
The length of p3,... is b1, b2, b3,.
Output packet streams B1, B of the first multiplexer 31
The length of the information field of 2, B3,.
3, ... bytes.

In the case of this example, as a method for accommodating the output packet of the second multiplexer 32 in the information field of the output packet of the first multiplexer 31, when b1 + b2 <B1 and b1 + b2 + b3> B1, a) p1, p2
Is stored in P1 and p3 is stored in P2 (FIG. 4
(A)), (b) Divide p3 and fit a part in P1,
There are two cases in which the rest is stored in P2 (FIG. 4B).

In the case of (a), a remainder of B1- (b1 + b2) bytes occurs in the information field of the first multiplexer 31. The receiving side does not detect the header inserted by the first multiplexer 31 in the first separator 33, and detects the header inserted by the second multiplexer 32 only in the second separator 34. Is performed, the second multiplexer 3
There is a possibility that an incorrect judgment is made that the output of No. 2 is inserted. At this time, erroneous detection can be suppressed by inserting a pattern having a low correlation with the synchronization flag of the header added by the second multiplexer 32 into the remaining portion.

In the case of (b), the first separator 3
3, the inserted header is detected by the first multiplexer 31, and in consideration of the synchronization timing and the signal length of the output of the first multiplexer 31, the second separator 34 detects the header accurately. Separation can be performed.

Note that the packet length is easier to detect and the reliability is higher because the header appears periodically when the packet length is fixed.

By the way, in a multiplexer, FIG.
As shown in (a), a header is added to the head of the information.
To increase the reliability of detection, as shown in FIG.
There is also a method of inserting a header 2 at the end of information in addition to the header 1 at the head. Also, as shown in FIG. 5C, there is a method of adding a parity for error correction coding of a header. Then, as shown in FIG. 5D, there is also a method of adding a parity 1 for error correction coding of a header and further adding a parity 2 only for information or an error correction of information and a header.

Hereinafter, an application example of the present embodiment will be described with reference to FIGS.

In the example shown in FIG. 6 ((a) shows the transmitting side, (b) shows the receiving side, and the same parts as those in FIGS. 1 (a) and (b) are denoted by the same reference numerals), And information from a video information source are compressed and encoded by an information source encoder 41,
Only the basic component of the output is input to the second multiplexer 32, and both the basic component and the quality-improving component and the second multiplexer 32
Is input to the first multiplexer 31. In this case, only the basic component is separated by the second separator 34, the information of the basic quality is reproduced by the information source decoder 42, and the basic component and the quality improving component are separated by the first separator 33. Thus, the information source decoder 43 performs high-quality reproduction based on all information including both components. The information input to the first and second multiplexers 31, 33 may be information from different information source encoders or information from the same information source encoder.

In the example shown in FIG. 7 ((a) shows the transmitting side, (b) shows the receiving side, and the same parts as in FIGS. 6 (a) and (b) are denoted by the same reference numerals), And information from the same information source of video and video is compressed and encoded by an information source encoder 41, and only the basic component of the output is encoded by a second multiplexer 32.
, And the output of the second multiplexer 32 and the quality improvement component obtained by the information source encoder 41 are input to the first multiplexer 31. In the case of this example, only the fundamental component is separated by the second separator 34 and the information source decoder 4
2, the information of the basic quality is reproduced, and the first separator 33
By combining the quality improving component separated by the above and the basic component separated by the second separator 34 in the adder 44 and inputting the combined output to the information source decoder 43, high-quality information can be reproduced. Done.

In the example shown in FIG. 8 ((a) shows the transmitting side, (b) shows the receiving side, and the same parts as in FIGS. 6 (a) and (b) are denoted by the same reference numerals), Three multiplexers 45 and a third separator 46 are added to form a three-layer structure. That is,
On the transmitting side, the most important information is input to the third multiplexer 45, the packet output generated by the third multiplexer 45 is input as data to the second multiplexer 32, and the second Is input to a third separator 46 via a switch 47 for directly inputting, so that the most important information is reproduced.

In this configuration, the lengths of the packets generated by the multiplexers 31, 32, and 45 are shortened in the first, second, and third orders, and the multiplexers 31, 32, and 45 add the lengths. The insertion frequency of the header is increased in the first, second, and third orders, or the number of parity bits added to the header is increased in the first, second, and third orders. By taking measures such as sequentially increasing the error tolerance, each of the separators 33, 3
The detection probability of the header in 4, 46 is the first, second, third.
It becomes high in order of. According to this hierarchical configuration, the reliability gradually increases at three layers, and three-layer hierarchical multiplex transmission becomes possible. Of course, a multi-layer configuration can be realized.

(Second Embodiment) Next, the multiplexing method of the present invention is applied to orthogonal frequency division multiplexing (OFDM).
FIG. 9 shows a second embodiment applied to multicarrier transmission called “requency division multiplexing”.
This will be described with reference to FIG.

FIGS. 9A and 9B show the configuration on the transmitting side and the receiving side of the second embodiment, respectively. In this embodiment, multi-carrier transmission using N carriers is realized.

As described above, OFDM is a multicarrier transmission system for transmitting information by performing digital modulation such as PSK or QAM on a large number of carriers (carriers). In actual terrestrial digital broadcasting, 2000 to 80
00 multicarriers are being considered. Inverse discrete Fourier transformer (IDFT) on the transmitting side
rier Transform) and a discrete Fourier transformer (D
FT (Discrete Fourier Transform) plays an important role in multicarrier transmission.

First, on the transmitting side, a signal at N points on the frequency axis is considered, and this signal is converted to an N-point inverse discrete Fourier transformer (I
DFT: Inverse Discrete Fourier Transform (51) and parallel / serial converter (P / S: Parallel Serial Converter)
) 52 to convert the signal into transmission signals at N points on the time axis.
This transmission signal is supplied to a digital / analog converter (D /
A: Digital Analog Converter), transmitted through a transmitter 53 including a frequency converter, an amplifier, an antenna, and the like, to a transmission path.

On the receiving side, a signal from the transmission path passes through a receiver 61 comprising an antenna, an amplifier, a frequency converter, an analog / digital converter (A / D: Analog Digital Converter), etc. Serial / parallel converter (S / P) 6
2. N-point discrete Fourier transformer (DFT: Discrete Fou
(Carrier Transform) 63 to reproduce a signal at N points on the frequency axis.

Next, an input signal of the IDFT 51 on the transmitting side will be described. In this example, of the N carriers,
Let M be used for mobile receivers and NM be used for fixed receivers. Each information of data such as audio, video, text, computer, etc. is information compressed by an information source encoder (not shown). The information is always audio, video and data.
The type does not need to be, and only two types of audio and video, or only video may be used.

Information such as audio, video and data for the fixed carrier is input to the first multiplexer 54. The first multiplexer 54 divides each piece of information into fixed lengths, generates fixed-length audio packets, video packets, and data packets, and adds a header for identifying each of them to perform time division. And a packet stream is generated. This stream is 64Q
The signal is input to the AM modulator 55, dispersed into NM carriers, and modulated by 64QAM.

On the other hand, audio, video, and data information for the carrier for the mobile unit are firstly transmitted to the second multiplexer 5.
7, the data is divided into appropriate lengths, each packet is multiplexed to generate a fixed-length packet, and a header indicating the position where each information is inserted is added to generate a packet stream. . Next, this stream is input to the first multiplexer 56 as data information, and a packet stream to which a header is added is generated as described above. This stream is input to a 4PSK modulator 58, dispersed into M carriers, and modulated by four-phase PSK.

The M for the moving object generated by the above processing
Modulation signals by four 4-phase PSKs and N-M modulation signals by 64QAM for fixing are input to IDFT of N points. The first multiplexer (54, 56) is used for both fixed and mobile, while the second multiplexer (57) is used only for mobile.

On the receiving side, among the N points of the DFT output, N−
The M fixed modulation signals are input to a 64 QAM demodulator 64 and demodulated, and the output stream is output to a first separator 65.
After detecting the header and separating information of video, audio and data, the information is reproduced by an information source decoder (not shown).

Further, the modulation signals for M moving objects are converted into four-phase signals.
It is input to an SK demodulator 66 and demodulated, and the output stream is input to a first demultiplexer 67 to demultiplex a multiplexed packet generated by a second multiplexer 57. If the information of the header can be identified from the input stream, the separated multiplexed packet is passed through the switch 69 to the second separator 6.
If the header information cannot be identified, the switch 69 is switched and directly input to the second separator 69. The second separator 69 detects the header of the input packet, separates the video, audio, and data information, and reproduces the information by an information source decoder (not shown).

As can be seen from the above description, in this embodiment, error countermeasures are applied to information for a mobile object by both multiplexing and modulation. It should be noted that if the source coded output of audio or video input to the second multiplexer 57 is provided with an error countermeasure using an error correction code,
Be more resistant to mistakes.

On the transmitting side, the header added to the head of the packet by the first multiplexers 54 and 56 indicates the head position of the packet when a number of packets are received as a stream on the receiving side. It indicates the type of information to be included. Similarly, the second multiplexer 5
The header added to the head of the packet in 7 indicates the head position of the packet, and the type and location of information included in the packet. Therefore, if these headers cannot be detected on the receiving side, the multiplexed information cannot be separated and reproduced.

The information amount of video information and audio information is compressed by an information source encoder. In this case, the higher the compression ratio, the smaller the number of bits required for transmission and the higher the transmission efficiency, but the lower the reproduction quality. Also, especially in video, when the playback screen is small, the number of pixels decreases,
The number of bits required for transmission is also reduced. In fixed reception, a video playback screen is large and a high-definition playback video is required, so a video transmission bit number of about 6 Mb / s or more is required. On the other hand, in mobile reception, a video playback screen is small, and high-definition playback video is not required. Therefore, a transmission bit number of about 200 kb / s or less is sufficient.

In packet transmission, if the packet length is lengthened and the frequency of header insertion is reduced, the transmission efficiency is increased, but the probability of detecting the header is reduced, so that if the transmission environment is poor, the reliability of transmission is reduced. Conversely, if the packet length is shortened and the header insertion frequency is increased, the transmission efficiency is reduced, but the detection probability of the header is increased, so that the transmission reliability is maintained even if the transmission environment is poor. Since the transmission efficiency is important for the fixed packet, the packet length is set long.
On the other hand, for the mobile object, the packet is set to be shorter because reliability is more important than transmission efficiency.

Therefore, in this embodiment, the packet output from the second multiplexer 57 is input to the first multiplexer 56 for the mobile unit, but the second multiplexer 57 for the mobile unit is used. Output packets are set short. Therefore, the packets generated by the first multiplexer 56 include the second multiplexer 5
7 includes a plurality of packets generated. Therefore, there are a plurality of headers.

If the first separator 67 fails to detect the header on the receiving side, the information cannot be reproduced until the next header is detected. In this case, the received packet stream for the mobile is input to the first and second separators 67 and 68. Although the first separator 67 detects the header inserted by the first multiplexer 56, even if this fails, the second separator 68 detects the header inserted by the second multiplexer 57. High probability of being able to do it. The reason for this is that the header inserted by the second multiplexer 57 has a higher insertion frequency than the header inserted by the first multiplexer 56, so that the detection probability of the header is increased. Thereby, the reliability of transmission is improved.

In addition, in the header addition of the second multiplexer 57, for example, two headers are provided in one packet.
Alternatively, if a transmission error countermeasure such as error correction encoding is performed, the reliability can be further improved.

Incidentally, while 64QAM is a multi-level modulation having information in both amplitude and phase, 4-phase PSK
Is modulation having information only in the phase, and when both are compared, 64 QAM is superior in terms of transmission efficiency, and 4-phase QAM is superior in tolerance against transmission path noise and additional noise. For this reason, in mobile reception, 4-phase PSK is used due to the poor transmission environment, while in fixed reception,
64QA with emphasis on transmission efficiency due to good transmission environment
M is used.

As can be seen from the above, error countermeasures are applied to information for mobile objects by both multiplexing and modulation. It should be noted that if an error correction code is applied to the audio or video information source coded output itself input to the second multiplexer 57 with an error correction code, it becomes even more resistant to errors.

In this embodiment, in multiplex transmission of multimedia information using OFDM, the transmitting side transmits each information such as audio, video, and data for the mobile object to the second.
A multiplexer 57 multiplexes and adds a header to generate a packet, and the packet is input as data information to a first multiplexer 56 and a header is added to generate a packet stream. After this stream is subjected to 4-phase PSK modulation, it is allocated to a carrier for a mobile unit. Each information such as audio, video, data and the like for fixing is first multiplexer 5
In step 4, a packet is generated by adding a header, and a packet stream multiplexed in a time-division manner is generated. After this stream is subjected to 64QAM modulation, it is allocated to a fixed carrier. These carriers are combined to realize multicarrier transmission.

On the receiving side, for fixed use, the carrier is reproduced and subjected to 64QAM demodulation, and then the received packet stream is input to the first demultiplexer 65 and the first multiplexer 5
The header added in step 4 is detected to separate and reproduce information.
For a mobile object, the carrier is recovered and demodulated in 4-phase PSK, and then the received packet stream is input to the first separator 67 and input to the second separator 68 via the switch 69. .

The header added by the first multiplexer 56 is added to the first
Even if the signal cannot be detected by the separator 67, the second multiplexer 5
By detecting the header added in 7 by the second separator 68, the input information of the second multiplexer 57 can be reproduced. As a result, even in a fading environment,
Reproduction of information for a mobile object can be realized.

In the above embodiment, the transmission side second
The second separator 68 on the receiving side detects the synchronization flag of the header inserted by the multiplexer 57 at the receiving end to obtain the timing of separation, but the header inserted at the first multiplexer 56 on the transmitting side is used. Of the synchronization flag of the receiving side
7, the timing obtained thereby can be used, and more accurate synchronization is established.

In the first and second embodiments,
The receiving side may not have the first separator. That is, the second
The important basic component of the information can be reproduced only by the separator of the above, so that a simple receiver for mounting on a mobile object or portable can be realized.

[0093]

As described above, according to the present invention, for example, in the multiplex transmission of multimedia information, only the important fundamental components of the information are multiplexed on the transmitting side by adding a header to the second multiplexer. The multiplexed output is used as data information and multiplexed together with other information by adding a header in a first multiplexer to generate a transmission packet. Then, the receiving side inputs the received packet to the first and second demultiplexers, so that even if the header added by the first demultiplexer cannot be detected by the first demultiplexer, the second demultiplexer can detect the header. By detecting the added header by the second separator, the input information of the second multiplexer can be reproduced. As a result, it is possible to provide a multiplexing method and apparatus capable of reproducing an important basic component of information even in a poor transmission environment such as a fading environment of mobile transmission.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of a multiplex system according to a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining the contents of multiplexing processing according to the first embodiment.

FIG. 3 is a timing chart for explaining the contents of another multiplexing process in the first embodiment.

FIG. 4 is a timing chart for explaining the contents of multiplexing processing when the length of output packets of the first and second multiplexers is variable in the first embodiment.

FIG. 5 is a diagram for explaining a method of adding header information in the multiplexer according to the first embodiment.

FIG. 6 is a block diagram showing an application example in the first embodiment.

FIG. 7 is a block diagram showing another application example of the first embodiment.

FIG. 8 is a block diagram showing another application example of the first embodiment.

FIG. 9 is a block diagram illustrating a system configuration when applied to multicarrier transmission by OFDM as a second embodiment of the multiplexing method according to the present invention.

FIG. 10 is a block diagram showing a system configuration of a conventional multiplexing system used for multimedia information transmission in broadcasting and communication.

FIG. 11 is a diagram showing a structure of a multiplex packet in a conventional multiplex system.

FIG. 12 is a block circuit diagram showing a configuration of a multicarrier signal generation circuit as an example of a conventional multiplexing method.

FIG. 13 is a diagram showing characteristics of a single carrier transmission system and a multicarrier transmission system according to a conventional multiplexing system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Audio information source encoder 12 ... Video information source encoder 13 ... Multiplexer 14 ... Separator 15 ... Audio information source decoder 16 ... Video information source decoder 21-24 ... Modulator 25- 28 Multiplier 29 Adder 31 First multiplexer 32 Second multiplexer 33 First separator 34 Second separator 35 Switch 41 Source coder 42, 43 Source decoder 44 Adder 45 Third multiplexer 46 Third separator 47 Switch 51 N-point IDFT 52 P / S converter 53 Transmitter 54 First multiplexer 55 64 QAM modulator 56 first multiplexer 57 second multiplexer 58 4PSK modulator 61 receiver 62 S / P converter 63 N-point DFT 64 64QAM demodulator 65 first separator 66 4PSK demodulator 67 ... 1st minute Separator 68 ... second separator 69 ... switch

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[Procedure amendment]

[Submission date] January 18, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 10

[Correction method] Change

[Correction contents]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hirokazu Tanaka 70, Yanagicho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Yanagimachi Plant Co., Ltd. Inside

Claims (13)

[Claims] A transmission side multiplexes a signal block input from one or more channels, and adds a sub-control signal block for identifying the content of the multiplexed block to a sub-multiplex. A signal block is multiplexed with one or more other signal blocks as one signal block, and a main control signal block for identifying the contents of the multiplexed block is added to the multiplexed block to perform main multiplexing. A signal block is generated as a transmission signal. On the receiving side, the sub-control signal block is directly reproduced from the transmission signal. Based on the sub-control signal block, a sub-multiplexed signal block in the transmission signal is transmitted to an arbitrary channel. A multiplexing method characterized in that signal blocks are separated. 2. A transmitting side receives and multiplexes signal blocks from one or more channels, and adds a first control signal block for identifying the contents of the multiplexed block to a first block. A first multiplexer that outputs as a multiplexed signal block, and a signal block from one or more channels is input and multiplexed as one channel input of the first multiplexer, and the content of the block is stored in the multiplexed block. A second multiplexer for adding a second control signal block for identification and outputting the same as a second multiplexed signal block, wherein the receiving side converts the first multiplexed signal block transmitted from the transmitting side. Input and the second signal included in the multiplexed signal block.
Multiplexing means for reproducing a control signal block of any one of (1) to (3) and separating a signal block of an arbitrary channel inputted to the second multiplexer based on the second control signal block. Transmission system. 3. The transmitting side receives and multiplexes signal blocks from one or more channels, and adds a first control signal block for identifying the contents of the multiplexed blocks to a first control signal block. A first multiplexer that outputs as a multiplexed signal block, and a signal block from one or more channels is input and multiplexed as one channel input of the first multiplexer, and the content of the block is stored in the multiplexed block. A second multiplexer for adding a second control signal block for identification and outputting the same as a second multiplexed signal block, wherein the receiving side converts the first multiplexed signal block transmitted from the transmitting side. A first control signal block included in the multiplexed signal block, and a first control signal block for separating the second multiplexed signal block based on the first control signal block; And separator, a second separated in the first separator
And selectively input one of the multiplexed signal block and the first multiplexed signal block input to the first separator, and reproduces the second control signal block included in the input multiplexed signal, A second separator for separating a signal block of an arbitrary channel input to the second multiplexer based on the second control signal block. 4. A signal block from one or more channels is input and multiplexed, and a first control signal block for identifying the contents of the block is added to the multiplexed block to form a first multiplexed signal block. A first multiplexer to be output and a signal block from one or more channels are input and multiplexed, and a second control signal block for identifying the contents of the multiplexed block is added to a second control signal block.
And a second multiplexer for outputting to the first multiplexer as a multiplexed signal block. On the receiving side, a second control signal block included in the multiplexed signal block is included from the first multiplexed signal block. A transmitting apparatus that reproduces a signal block of an arbitrary channel input to the second multiplexer based on the second control signal block. 5. A transmitting side receives and multiplexes a signal block from one or more channels, and adds a first control signal block for identifying the content of the multiplexed block to a first block. Second control for inputting and multiplexing a signal block from one or more channels as one channel input of a first multiplexer output as a multiplexed signal block, and identifying the contents of the block in the multiplexed block When an output of a second multiplexer for adding a signal block and outputting as a second multiplexed signal block is allocated, a first multiplexed signal block transmitted from the transmitting side is input, and the multiplexed signal block is input. To reproduce a second control signal block included in the second control signal block, and a signal of an arbitrary channel input to the second multiplexer based on the second control signal block. Receiving device, characterized in that it comprises a separator for separating the lock. 6. A transmitting side receives and multiplexes signal blocks from one or more channels, and adds a first control signal block for identifying the contents of the multiplexed block to a first block. Second control for inputting and multiplexing signal blocks from one or more channels as one channel input of a first multiplexer output as a multiplexed signal block, and identifying the contents of the block in the multiplexed block When an output of a second multiplexer for adding a signal block and outputting the resultant signal as a second multiplexed signal block is assigned, a first multiplexed signal block transmitted from the transmitting side is input, and the multiplexed signal block is input. A first separator that reproduces a first control signal block included in the first control signal block and separates the second multiplexed signal based on the first control signal block; One of the second multiplexed signal block separated by the demultiplexer and the first multiplexed signal block input to the first demultiplexer is selectively input, and the second multiplexed signal block included in the input multiplexed signal block is selectively input. And a second separator that reproduces two control signal blocks and separates a signal block of an arbitrary channel input to the second multiplexer based on the second control signal block. Receiving device. 7. The transmitting side allocates the first multiplexed signal block to an arbitrary number of carriers and transmits the same, and the receiving side regenerates the first multiplexed signal block from the received carrier. 4. The multiplex transmission system according to claim 2, wherein 8. The first and second multiplexers each have a function of inputting and multiplexing a multimedia signal block of one or more channels, and a multiplexed output output from the second multiplexer. 4. The multiplex transmission system according to claim 2, wherein the first multiplexer is inputted as a multimedia signal block of one channel to the first multiplexer. 9. The demultiplexer according to claim 2, wherein the second multiplexer includes means for performing signal processing on the second control signal block that is more resistant to transmission errors than the first multiplexer. And a second separator according to claim 3, further comprising means for reproducing the second control signal block based on signal processing means applied by the second multiplexer. 4. The multiplex transmission system according to claim 2, wherein: 10. The second multiplexer makes the signal length of the second multiplexed signal block shorter than the signal length of the first multiplexed signal block generated by the first multiplexer. 5. The multiplex transmission system according to claim 3, wherein: 11. The first multiplexer inserts an arbitrary number of second multiplexed signal blocks output from the second multiplexer into a multiplexed block, and inserts the second multiplexed signal block in the remaining area of the block. 4. A signal having a low correlation with the second control signal block is inserted.
A multiplex transmission system as described. 12. The first multiplexer divides a second multiplexed signal block output from the second multiplexer,
4. The multiplex transmission system according to claim 2, wherein the multiplex block is inserted across the multiplex block. 13. The multiplex transmission according to claim 2, wherein the signal block input to said second multiplexer includes at least information necessary for information reproduction. system.