JP3253524B2 - Digital transmission method and transmission / reception device - 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 transmission method and a transmission / reception apparatus, and more particularly to a digital transmission method and a transmission apparatus capable of flexibly changing a transmission method so as to perform optimal transmission according to information content of a main signal. It is.

[0002]

2. Description of the Related Art In conventional digital transmission, when information is transmitted, for example, a predetermined coding method such as QPSK is added to a predetermined coding rate (after adding the number of bits used for information transmission and an error correction code). In this case, the data is transmitted by a certain fixed transmission method in which error correction codes (for example, a convolutional code having a coding rate of 3/4) are combined. Also, in the broadcasting business, the transmitting side
The coding rate of the error correction code within the range of (low efficiency / high reliability) to 7/8 (high efficiency / low reliability), transmission efficiency (number of bits that can be transmitted per second using a transmission bandwidth of 1 Hz) And reliability (how low the C / N can be received) and transmit the signal. On the receiving side, the transmitted signal is decoded once at all coding rates, Example of decoding at a coding rate that can decode well from inside (Europe, DVB
-S standard), but also in this case, the modulation scheme is fixed at QPSK only.

In the case of the above example, the transmission efficiency is 1 per Hz.
Although transmission of up to 1.75 bits is possible, trellis coded 8PSK modulation (8PSK) which is more excellent in terms of transmission efficiency is also possible.
This is a modulation scheme that combines the same transmission efficiency as unencoded QPSK and requires only about 2.5 dB less C / N.
TC8PSK) has recently been promising, and in this case, transmission of 2 bits per Hz is possible. However, when such a high-efficiency transmission system is used, the reception C / N is slightly higher than in the case of a low-efficiency transmission system.

[0004] Hierarchical transmission is one of the methods for improving the reliability when such a highly efficient transmission system is used.
Hierarchical transmission refers to a transmission method that requires a high reception C / N but can transmit a high information bit rate (for example, TC8P
SK) and a transmission method (for example, BPSK) that can receive even a low C / N but can transmit only a small information bit rate.
And a high-quality service (hereinafter referred to as HQ) such as, for example, a high-resolution video signal, and the latter, for example, a low-resolution video signal. , A voice signal, a data service signal, and so on, by demodulating and decoding both HQ and LQ when the received C / N is high, thereby transmitting a high quality service. Receives service, but demodulates only LQ when reception C / N is low.
This is a method of decoding and receiving only the minimum quality service. When a satellite transmission system is used, the above HQ and LQ are often time-division multiplexed.

[0005] In this manner, when the received electric field strength is reduced due to rain attenuation, the service quality is reduced, but the probability that the service cannot be received at all is reduced, and the service time rate is improved to some extent. Was completed.

[0006]

As described above, in the prior art, transmission / reception of digital signals is performed on the assumption that a transmission system such as a modulation system uses a fixed system (for example, QPSK). Have been. Therefore, in broadcasting, programs requiring high quality receive high-quality digital broadcasting by a transmission method with high transmission efficiency, and programs requiring high reliability, such as emergency news, are received by rain attenuation or the like. Transmission in accordance with the nature of the program, such as flexibly using the optimal transmission method according to the broadcast content, such as broadcasting a highly reliable digital broadcast that can be received stably even when the C / N is reduced. The formula could not be changed.

[0007] Considering the above-described hierarchical transmission, according to this, it is possible to make it difficult to interrupt service reception even when the reception C / N is reduced, and to improve the service time rate. Although transmission is possible, transmission efficiency is generally lower when hierarchization is performed (for example, when TC8PSK and BPSK are combined) and transmission is not performed (for example, when all data is transmitted using TC8PSK). Therefore, for example, when it is known that there is no danger of rainfall being cut off nationwide, there is no need to create a hierarchy.

[0008] In the conventional hierarchical transmission system, high-layer data and low-layer data are broadcast by a fixed transmission method.
Because it is assumed that the signal is received by a dedicated receiver for that purpose, it is necessary to cancel the layering itself for the above reasons, or to change the ratio between the information rate of the high-layer data and the information rate of the low-layer data. The request could not be met.

An object of the present invention is to select a transmission system having optimum transmission efficiency and reliability each time by transmitting and receiving a digital signal by flexibly changing a transmission system according to the contents of a program and required conditions. To provide a digital transmission method and a transmission / reception device that enable the transmission.

[0010]

In order to achieve the above object, according to the present invention, a broadcaster selects a parameter that specifies a transmission system suitable for each program and broadcasts it. A signal indicating the selected parameter (a signal defining the transmission method) is multiplexed with a main signal for transmitting the program contents and transmitted so that the program can be received by performing the appropriate demodulation and decoding processing.

Here, the parameters defining the transmission method include, for example, TC8PSK, QPSK or BPS
A modulation scheme such as K, a symbol rate of a subsequent modulated wave,
There are a hierarchical structure in hierarchical transmission such as the number of layers, a modulation method of each layer, or a time distribution occupied by a modulated wave of each layer, and a coding rate.

That is, according to the present invention, in a digital transmission method for performing hierarchical transmission, the transmitting side makes the hierarchical structure variable, and provides a high hierarchy which provides the high quality service with the hierarchical structure, and a low quality and high reliability service. And the lower layer to be used for the transmission, and the composition ratio of each layer can be changed according to the content of the main signal to be transmitted, and the structure of each layer, the modulation method, the transmission method that defines the transmission method such as the coding rate, etc. A multi-configuration control signal (TMCC signal) is organized in a predetermined format, the contents of the main signal of each layer are assigned to a frame, and a synchronization signal for frame identification and the TMCC signal are provided at the beginning of the frame.
A signal is added, and the modulation method in the higher layer is 8PSK.
Or QPSK, and the modulation scheme in the lower layer is Q
PSK or BPSK, and the synchronization signal and the T
Assuming that the modulation scheme of the MCC signal is BPSK, each is collectively time-division multiplexed and transmitted. On the receiving side, first, the BPSK part of the time-division multiplexed signal transmitted from the transmitting side is demodulated and then correlated. By separating the TMCC signal by detecting the synchronization signal, and by recognizing the frame configuration and the modulation scheme according to the separated TMCC signal, a demodulation circuit of a transmission scheme adapted to each hierarchy. A digital transmission method characterized by performing demodulation by switching.

In a preferred embodiment of the present invention, when demodulating the time-division multiplexed signal, the multiplexed signal includes BPSK, QPSK, 8P
When SK is mixed, all the time division multiplexed signals are
Treating as K, carrier regeneration adapted to the transmission method is performed. Further, the TMCC signal is obtained by correlating the signal obtained by the carrier reproduction with the synchronization signal pattern.

The present invention further provides a transmission apparatus for digital transmission performing hierarchical transmission, which is divided into a high layer for providing high quality services and a low layer for providing low quality and high reliability services. The composition ratio can be changed according to the content of the main signal to be transmitted. A TMCC signal that defines a transmission system such as a structure, a modulation method, and a coding rate of each layer is organized into a predetermined format, and the main signal of each layer is formed. Multiplexing means for allocating a signal content to a frame, adding a frame identification synchronization signal and the TMCC signal to the beginning of the frame and multiplexing the frame structure, and adding an error correction code to the signal of each layer. Error correction encoding means, and 8PSK or QPSK
A modulator for modulating the signal in the lower layer by QPSK
A transmitting device comprising: a modulator for performing BPSK modulation; a modulator for performing BPSK modulation on the synchronization signal and the TMCC signal; It is in.

[0015]

Further, the present invention relates to a digital transmission receiving apparatus for performing layered transmission, which is divided into a high layer for providing high quality services and a low layer for providing low quality and high reliability services. The composition ratio of the layers can be changed according to the content of the main signal to be transmitted. A TMCC signal that defines the transmission system such as the structure, modulation method, and coding rate of each layer is organized in a predetermined format. The content of the main signal is assigned to a frame, a synchronization signal for frame identification and the TMCC signal are added to the beginning of the frame, multiplexed into a frame structure, and an error correction code is added to each layer signal. , The signal in the higher layer is modulated by 8PSK or QPSK, the signal in the lower layer is modulated by QPSK or BPSK, and the synchronization signal and the TMCC signal are modulated. Is subjected to BPSK modulation, and a time-division multiplexed signal that is transmitted in a time-division multiplexed manner for each of these modulation outputs is firstly BPSK-demodulated on the carrier of the time-division multiplexed signal. A signal separating unit for separating the TMCC signal by detecting a synchronization signal; and recognizing the frame configuration and the modulation scheme according to the separated TMCC signal, thereby adapting each layer to a respective transmission scheme. A demodulation circuit for demodulating the signal.

In a preferred embodiment of the present invention, when the demodulation circuit mixes BPSK, QPSK, and 8PSK in the time-division multiplexed signal, the demodulation circuit converts all of the time-division multiplexed signals to 8PSK.
And a means for performing carrier regeneration adapted to the transmission method. Further, the demodulation circuit includes means for obtaining the TMCC signal by correlating the signal obtained by the carrier reproducing means with the synchronization signal pattern.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments with reference to the accompanying drawings. In the following description, a signal that defines the above-mentioned transmission method is referred to as a transmission multiplexing configuration control signal or TMCC. When hierarchical transmission is introduced in order to increase both the service time rate and the transmission capacity of satellite ISDB transmission, the higher the ratio of lower layers, the lower the transmission efficiency. Therefore 1
It is not always an effective use of frequency to always hierarchize all the ISDB signals transmitted by one carrier. In order to operate this method more efficiently, the digital transmission method according to the present invention proposes the following method.

1. For programs that require a high service time rate, hierarchical transmission is performed, and simultaneous transmission of a low-efficiency transmission method ensures a service time rate and prevents a reduction in transmission capacity. 2. For programs that need to be hierarchized, the hierarchy ratio can be flexibly assigned. 3. De-hierarchy, all programs have high bit rate,
It is possible to transmit with high quality.

Switching the transmission state on the broadcast station side in this manner is called transmission system control. A broadcasting station can construct a system in which a transmission system control signal is multiplexed with a modulated signal and transmitted, and the reception side decodes the control signal and automatically switches the transmission system. As a result, it is possible to efficiently implement the rainfall countermeasures according to the weather conditions in the satellite ISDB. Also ISDB
Signals can be processed by a unified method irrespective of the transmission path, and great flexibility can be secured.

The transmission mode control signal can be transmitted by PSI / SI of an MPEG transport stream (MPEG-TS). However, the above functions need to be known before TS decoding. For this reason, it is necessary to transmit the information of the transmission system control in the lower layers (1 to 3 layers) in the 7-layered model. Therefore, transmission and multiplex configuration control (TMCC: Transmission and Multiplex)
ing Configuration Control) signal is generalized in the ISDB of all transmission lines, and is realized by multiplexing the broadcast wave at the lowest level. The transmission method of this information is known to the receiver, and demodulation and decoding can be performed. The demodulation system of the receiver for obtaining the MPEG-TS is set based on this information.

The characteristics and requirements of the 12 GHz band satellite broadcasting transmission line are as follows. Consider degradation due to heavy rain. 2. A transmission system with a low required CN, strong non-linear characteristics, and high frequency use efficiency is used. 3. The service time rate and bit rate are set as high as technically and economically possible. Can be considered.

In the ISDB, since a signal having a packet / frame configuration is handled, hierarchical modulation can be performed in packet signal units. That is, the information of each layer may be multiplex-transmitted after the modulation method is defined for each packet.

In consideration of the above, in the satellite ISDB, it is advantageous to use a time-division multiplexing (TDM) method of a PSK-based modulation method that causes little deterioration even in the nonlinear characteristic of the repeater.
Since nPSK is transmitted by TDM, decoding can be performed by switching the decision area for each time slot. For this reason, the main part of the demodulation circuit can be shared between transmission systems, and the cost of the receiver can be reduced. In TDM, the total transmission capacity that can be transmitted can be flexibly determined by the time occupancy of each layer. If a time-multiplexed synchronization signal can be determined to determine the symbol period of each layer, the required CN difference between layers depends on the CN determined by the transmission scheme and symbol rate of each layer.

FIG. 1 shows an example of the signal generation of the hierarchical ISDB. In this example, QPSK is used for the lower layer, and the occupancy δ = 0.
33. 24.576 Mbaud symbol rate
Then, the information bit rate of each layer is 8.192 Mbps and 32.768 Mbps for the low layer and the high layer, respectively, and a total of 40.96 Mbps is obtained.

Of the combinations in which the hierarchical structure is changed at the three types of symbol rates, Tables 1 to 5 show combinations each having an efficiency equal to or higher than the non-hierarchical QPSK + 3/4 convolution in each system. Here, it is assumed that one frame has a maximum of 14 slots and one slot has a specification of 4.096 Mbps.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

In the ISDB, one byte of an extra symbol period is added to the head of each packet in consideration of various expandability. This period can also be used for frame synchronization transmission for the receiver to recognize the ISDB frame structure. The length of the frame synchronization signal needs to be 16 bits. FIG. 2 shows the multiplex frame structure and the position of the synchronization signal at this time. This synchronization signal can also be used for hierarchical synchronization. Therefore, this signal needs to be transmitted with high reliability by BPSK.

Further, the transmission of the TMCC signal also uses this area. In addition, it is possible to further improve the reliability by adding an appropriate error correction during the TMCC signal period. Since the receiver first captures the synchronization multiplexed by BPSK / TDM, the TMCC signal immediately after that can be demodulated at the lowest level.

If the symbol rate is limited to a finite type, it is possible to know the symbol rate currently used by sequentially searching at the receiver and capturing the synchronization pattern. Thereafter, the TMCC signal is demodulated, and MPEG-T
The reception mode for obtaining S is set.

The adjustment of the frame period by transmitting the synchronization and the TMCC signal by BPSK is performed by using the surplus symbols of the ISDB packet without the synchronization and the TMCC signal. Here, the maximum number of symbols that can be used for the TMCC signal is considered.

The number of transmission symbols shown in Table 6 is required for each transmission method per 1 byte of surplus symbol. Therefore, during one frame, in the case of a 28 Mbaud system, referring to Table 4, when QPSK is used for LQ: The number of slots of HQ × 4 + the number of slots of LQ × 8 = 56 symbols When BPSK is used for LQ: number of slots × 4 + number of slots of LQ × 16 = 56
Symbol and constant value. Similarly, in other systems, a certain extra transmission symbol period is obtained depending on the symbol rate. This symbol period can be used as a synchronization and transmission period of the TMCC signal. Table 7 summarizes the above results.

[0037]

[Table 6]

[0038]

[Table 7]

Table 8 shows a specific example in the case of performing flexible hierarchical / non-hierarchical transmission by switching the transmission mode. When high quality is required depending on the program content, the service time rate is reduced to 99.7%, but 56 Mbps in non-hierarchical level
On the other hand, if it is desired to improve the reliability, an extremely high service time rate can be secured by changing the transmission method and reducing the symbol rate.

[0040]

[Table 8]

Next, a digital transmitting apparatus and a receiving apparatus of the present invention for realizing the digital transmission method according to the present invention described above will be described. In the present invention, as described above, a broadcasting station transmits a transmission method according to a program content, for example, a modulation method of a main signal, a symbol rate, a hierarchical structure (for example, the number of layers in the case of layering, a modulation method for each layer, (E.g., time allocation to be assigned to layers) or coding rate. By multiplexing a signal (transmission multiplexing configuration control signal or TMCC) defining these transmission methods into a main signal in a predetermined format and modulation method and transmitting the multiplexed signal to the reception side, the reception side receives the transmission multiplex. By demodulating and decoding the configuration control signal first, it is possible to know what transmission system is being used. Therefore, by knowing the transmission method of the main signal, the main signal carrying the program information can be demodulated and decoded based on this.

In the following, ISDB (Integrated Services Digital Broadc
A case where a two-layer hierarchized transmission signal using TC8PSK and QPSK as a modulation method is generated from multiplexed data of asting (integrated digital broadcasting), broadcast, and received will be described. The multiplexed data used here has a frame structure composed of N slots as shown in FIG. 2 in the description of the digital transmission method of the present invention, and one slot has 205 bytes obtained by adding 1 byte to a 204 byte packet. It is assumed to be composed of
In the present embodiment, the added 1 byte is allocated for a synchronization signal and a transmission multiplex configuration control signal. That is, an N-byte area can be secured during one frame period, but a synchronization signal can be allocated to two bytes of the N-byte area, and information of the transmission multiplexing configuration control signal can be written in the remaining part.

By adopting such a data structure,
It is possible to easily change the modulation method at the time of layering for each slot and perform effective interleaving easily.Also, by changing the number of slots and the transmission rate per slot, the transmission rate can be maintained while maintaining the same frame structure. To various transmission paths different from each other. FIGS. 3 and 4 show an example of the circuit configuration of the digital transmission apparatus of the present invention for generating a hierarchical transmission signal from this data, divided into the first half and the second half.

In FIG. 3, a plurality of video signals, audio signals, and data service signals are multiplexed and output by the multiplexing device 1 so as to have a frame structure composed of 14 slots (N = 14 in FIG. 2). In addition, a frame synchronization signal indicating the beginning of a frame is also output separately, and the control signal generation circuit 2 uses these signals to generate a frame synchronization signal.
Recognize whether the current data stream is HQ (high quality service), LQ (minimum quality service), or a dummy slot that is discarded without being transmitted. A control signal for controlling whether to drive or stop the circuit is generated.

The slot allocated to the HQ is first converted from an 8-bit stream by the parallel / serial conversion circuit 3 to 2 slots.
Converted to a stream of bits. Further, the trellis encoder 4 adds an error correction code to convert the data into a 3-bit coded data signal. 8P from this 3-bit signal
The signal is converted into signals (8 bits each) representing signal points I and Q using SK mapper 5. An 8PSK mapper at this time is shown in FIG. 5A to 5C show that, for example, when the input 3-bit signal is (010), the output is output as I = −90, Q = + 90, Generally, it is composed of a ROM.

The slot assigned to the LQ is first converted by the parallel / serial conversion circuit 6 from an 8-bit stream to a 1-bit stream. Further, the convolutional encoder 7 adds an error correction code and converts the code into a 2-bit coded data signal. The 2-bit signal is converted into signals (8 bits each) representing signal points I and Q using QPSK mapper 8. The QPSK mapper at this time is shown in FIG.

A 2-byte (16-bit) synchronization signal written at the beginning of each slot (the total number of slots is 14) and a 12-byte transmission multiplexing configuration control signal portion (here, an error occurs in order to obtain higher reliability). A correction code is added and transmitted), the signal is converted from an 8-bit signal to a 1-bit signal by a parallel / serial conversion circuit 9 and then written once to a FIFO 10.
It is converted into a signal representing Q (8 bits each). BPSK
FIG. 5C shows the mapper of FIG.

The I and Q signals corresponding to the HQ, LQ, synchronization and transmission multiplexing configuration control signals obtained as described above are
The control signals generated by the control signal generation circuit 2 are used to sequentially switch by interlocking change-over switches SW-1 and SW-2 to obtain time-division multiplexed I and Q signals. Next, FIG.
As shown in these figures, the I signal and the Q signal are supplied to the root roll-off filters 12-1, 12-2 and the D / A converter 13-.
1, 13-2 and low-pass filters 14-1, 14-
2 are sequentially modulated by the quadrature modulator 15 and unnecessary waves are removed by the band-pass filter 16 to obtain a time-division multiplex modulation wave having a data structure as shown in FIG. Supplied to 17 and 18 in the quadrature modulator 15 are an oscillator and a 90
゜ It is a phase shifter. In the above, it is also possible to update the content of the transmission multiplexing configuration control signal in the previous frame and to change from the next frame to a frame having a different number of slots.

In the above embodiment according to the present invention, the transmission multiplex configuration control signal is transmitted in the form of time division multiplexing, but it can be transmitted in the form of code division multiplexing. FIG. 7 shows another example of a circuit configuration for the above-described time division multiplexing in this case. In the present embodiment, since the system relating to HQ and LQ is the same as that of FIG. 3, a part different from that of FIG. Will be described only.

In FIG. 7, the same circuit parts as those in FIG. 3 are denoted by the same reference numerals. In the present embodiment, when only the transmission multiplexing configuration control signal written at the head of each slot is written to and read from the FIFO 10, it is not read out in bursts as in the case of the above-described time division multiplexing, but at a low constant rate. To read. In the exclusive-logic circuit 20 at the next stage, the chip rate is adjusted to the transmission symbol rate by performing an exclusive-OR operation on the read signal and the spreading PN signal having a rate equal to the transmission symbol rate. After converting to data of points I and Q, HQ or L
By adding to the signal point of Q, a spread spectrum multiplexed wave (code division multiplexed wave) having a data structure as shown in FIG.

The spread spectrum BPSK wave (output of the BPSK mapper 11) is transmitted to the TC8P
When multiplexing with SK or QPSK, it is necessary to sufficiently narrow down the amplitude of the BPSK wave in order to suppress the influence on the main signal.

Examples of the circuit configuration of the digital receiving apparatus of the present invention are shown in FIGS. 9 and 10 for the first half and the second half, respectively, and will be described below. The time-division multiplex modulation wave input from the receiver high-frequency stage is first subjected to the band-pass filter 21 to remove unnecessary wave components. Then, the quadrature demodulator 2
2 (comprising a 90 ° phase shifter 23, a voltage controlled oscillator 25 controlled by the output of a loop filter 24, and two multipliers), and converted into baseband I and Q signals, respectively, and a low-pass filter 26− 1,26-2
High-frequency components are removed by the A / D converters 27-1 and 27-27.
Digitized by -2 (here, both I and Q are 8 bits)
And a digital roll-off filter 28-1,
At 28-2, intersymbol interference is removed.

At this time, the modulation signal indicating 8PSK is always output from the reproduction carrier phase detection and transmission multiplexing configuration control signal detection circuit 29 (see FIG. 10), and is applied to the phase error detection circuit 30. That is, at this time, the phase error detection circuit 30 outputs a phase error signal corresponding to 8PSK and performs carrier reproduction (BPSK, Q
Since PSK can be considered to use some of the signal points of 8PSK, time-division multiplexed waves in which these modulation methods are mixed can be treated as 8PSK to perform carrier reproduction.) .

Next, the obtained I signal and Q signal (outputs of the digital roll-off filters 28-1 and 28-2) are converted into n × π / Signals I0, Q0 rotated by 4 (n = 0,..., 7); I1, Q1;
(8 bits each). The correlation values between the generated signals and the I and Q values of the synchronization signal used on the modulation side are matched filters 1 to 8 (32-1, 32-2,...).
, 32-8), a positive or negative equally spaced correlation pulse train is obtained on the output side. Since the matched filter that outputs a pulse train in which these pulse trains are positive and has the largest value corresponds to the phase error of the reproduced carrier, it is possible to detect the phase error of the reproduced carrier. The matched filter 32-
Since the outputs of 1, 32-2,..., And 32-8 provide a transmission multiplexing configuration control signal following the synchronization signal, the information may be used to determine the modulation scheme of the currently received modulated wave. You can know.

Thus, by knowing the modulation method,
When the phase error detection circuit 30 receives BPSK, the phase error detection circuit 30 outputs QPSK.
When 8PSK of K is received, it can be switched by giving an appropriate phase to that of 8PSK. In addition, the read carrier phase detection and transmission multiplex configuration control signal detection circuit 29 can easily output the value of the read transmission multiplex configuration control signal and the frame synchronization signal. 3
3, the system of the trellis decoder 34 when the HQ signal is coming to the output, the system of the Viterbi decoder 35 when the LQ signal is coming, and the sync pattern or reproduced carrier from the sync pattern generator 36 in other periods. The transmission multiplexing control signal from the phase detection and transmission multiplexing control signal detection circuit 29 is activated, and a gate signal for driving a switch SW for selecting a signal to be output is generated. Also, 37 in FIG.
Reference numerals -1 and 37-2 denote serial / parallel conversion circuits for HQ and LQ, respectively. As described above, on the output side of the switch SW,
Multiplexed data having the frame structure used on the modulation side can be configured. The multiplexed data is supplied to the multiplexing / demultiplexing device 38, and is separated into a plurality of video signals, audio signals, and data service signals by signal processing reverse to that of the multiplexing device 1 on the transmission side (see FIG. 3).

When the transmission multiplexing configuration control signal is code-division multiplexed, the parameters such as the tap lengths of matched filters 32-1 to 32-8 in FIG. 9 are different, but the circuits are almost the same as those in FIGS. It can be realized with a configuration. In addition, since the content of the transmission multiplex configuration control signal is transmitted periodically without change during the same program, the reliability is further improved by receiving the content multiple times, making a majority decision, and identifying the content. Can be improved.

In summary, first, the hierarchical transmission is as follows:
In this system, in addition to a high-quality video signal of a program, a video signal serving as a basis of the program is also transmitted so that the signal can be stably received even when the radio wave is weakened. According to this method, even if a strong rainfall attenuation occurs, the image content can be grasped by receiving only the basic signal of the video, and high reliability of the broadcast can be maintained.

However, when the hierarchization is performed, efficiency is generally lowered because two signals are multiplexed as described above. As one of the countermeasures, a transmission multiplexing configuration control signal according to the present invention is used so that the method of layered transmission and the presence or absence of layering can be flexibly selected, and an example is shown in FIG. Mode 1
In this case, as much information as possible is transmitted without layering, and the transmission system gives priority to the high quality of the program. Mode 2
The methods 3 and 3 are systems which reduce the total amount of information but are resistant to rain attenuation by layered transmission and have high reliability.

[0059]

According to the present invention, when broadcasting by hierarchical transmission is performed: 1. Whether or not there is hierarchy 2. When hierarchized, the ratio of the transmission rate of high-layer data and low-layer data. Symbol rate By flexibly changing the conditions such as the modulation method according to the contents of the program and the required conditions for transmission and reception, it is possible to select a transmission method having optimum transmission efficiency and reliability each time.

[Brief description of the drawings]

FIG. 1 shows an example of hierarchical ISDB signal generation.

FIG. 2 shows a multiplexed data structure of ISDB.

FIG. 3 shows an example of a circuit configuration of the transmission device of the present invention.

FIG. 4 is a diagram showing the circuit configuration of the transmitting apparatus, and it is clearly erroneous that the output of the band-pass filter 16 is “to the transmitter”. To "."

FIG. 5 shows a difference in signal output in each of 8PSK, QPSK, and BPSK mappers in FIG. 3;

FIG. 6 shows “LQ data” under 8PSK in FIG.
"HQ data" under QPSK was corrected due to an erroneous description of "LQ data".

FIG. 7 shows another example of the circuit configuration of the transmission device of the present invention.

FIG. 8 shows a data structure of a code division multiplex wave generated as an output of the transmitting apparatus of FIG. 7;

FIG. 9 is a part of the circuit configuration of the receiving apparatus, and it is clearly erroneous that the input of the band-pass filter 21 is “from the receiver”. Was corrected.

FIG. 10 shows a case where the input of the reproduction carrier phase detection and transmission multiplex configuration control signal detector 29 is “Mart filters 31-1 to 31-1”.
What was "from 31-8" is "matched filter 32-1 ~
32-8 ”and the output b of the detector 29
"To the phase error detection circuit 29" was corrected because of an erroneous description of "to the phase error detection circuit 30".

FIG. 11 shows an example of hierarchical transmission using a transmission multiplexing configuration control signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Multiplexer 2 Control signal generation circuit 3 8-bit / 2-bit parallel / serial conversion circuit 4 Trellis encoder 5 8PSK mapper 6 8-bit / 1-bit parallel / serial conversion circuit 7 Convolution encoder 8 QPSK mapper 9 8 bits / 1 Bit parallel / serial conversion circuit 10 FIFO 11 BPSK mapper 12-1, 12-2 Root roll-off filter 13-1, 13-2 A / D converter 14-1, 14-2 Low-pass filter 15 Quadrature modulator 16 band Pass filter 17 Oscillator 18 90 ° phase shifter 19 Code division multiplexing of transmission multiplex configuration control signal 20 Exclusive OR circuit 21 Bandpass filter 22 Quadrature demodulator 23 90 ° phase shifter 24 Loop filter 25 Voltage controlled oscillator 26-1 , 26-2 Low-pass filter 27-1, 27- A / D converters 28-1, 28-2 Digital roll-off filters 29 Reproduction carrier phase detection and transmission multiplexing configuration control signal detection circuit 30 Phase error detection circuit 31 Phase rotation circuit 32-1, 32-2, ..., 32-8 Matched Filter 33 Control Signal Generation Circuit 34 Trellis Decoder 35 Viterbi Decoder 36 Synchronous Pattern Generator 37-1, 37-2 Serial / Parallel Conversion Circuit 38 Demultiplexer SW-1, SW-2, SW Switch

──────────────────────────────────────────────────続 き Continued on front page (72) Michihiro Uehara 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Seiichi Namba 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Hajime Matsumura 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Shigeru Yamazaki 1-110 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Japan Broadcasting Research Institute (56) References JP-A-8-88617 (JP, A) JP-A-7-254915 (JP, A) JP-A-2-278940 (JP, A) International publication 96/7260 (WO, A1) Michihiro Uehara et al., Study of terrestrial ISDB broadcasting system-BST-OFDM system and multiplex system-, Television Institute Technical Report, Japan, March 1996 March 15, Vol. 20, No. 22, Pages 23-28 Hashimoto Akira et al., Configuration and characteristics of satellite ISDB transmission experiment equipment, Technical Report of the Institute of Television Engineers of Japan, Japan, October 17, 1996, Vol. 20, No. 53, Pages 7-12 (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/00-27/38 H04J 1/00-11/00

Claims (8)

(57) [Claims] 1. A digital transmission method for performing layered transmission, wherein a transmitting side makes a hierarchical structure variable, and a lower layer that provides a high quality service with the hierarchical structure and a lower layer that provides a low quality and highly reliable service. And the composition ratio of each layer can be changed according to the content of the main signal to be transmitted,
A transmission multiplexing configuration control signal (TMCC signal) defining a transmission system such as a structure of each layer, a modulation method, and a coding rate is organized into a predetermined format, and the contents of the main signal of each layer are assigned to a frame. A synchronization signal for frame identification and the TMCC signal are added to the beginning of a frame, the modulation scheme in the higher hierarchy is 8PSK or QPSK, the modulation scheme in the lower hierarchy is QPSK or BPSK, and the synchronization signal and the TMCC signal are Modulation method of BPS
As K, the respective signals are collectively time-division multiplexed and transmitted. On the receiving side, first, the BPSK part of the time-division multiplexed signal transmitted from the transmitting side is demodulated, and then the synchronization signal is detected by correlation. The TM
By separating a CC signal and recognizing the frame configuration and the modulation scheme in accordance with the separated TMCC signal, demodulation is performed by switching each layer to a demodulation circuit of a transmission scheme adapted to each layer. Digital transmission method. 2. When demodulating the time-division multiplexed signal, when BPSK, QPSK, and 8PSK are mixed in the multiplexed signal, all the time-division multiplexed signals are treated as 8PSK.
The digital transmission method according to claim 1, wherein carrier reproduction adapted to the transmission system is performed. 3. The TMCC by correlating a signal obtained by the carrier reproduction with the synchronization signal pattern.
The digital transmission method according to claim 2, wherein a signal is obtained. 4. A transmission apparatus for digital transmission that performs hierarchical transmission is divided into a high layer that provides high-quality services and a low layer that provides low-quality and high-reliability services. The TMCC signal which can be changed according to the content of the main signal to be transmitted and which defines the transmission system such as the structure of each layer, the modulation method, the coding rate, etc. is organized in a predetermined format, and the content of the main signal of each layer Is assigned to a frame, a multiplexing means for adding a frame identification synchronization signal and the TMCC signal to the beginning of the frame and multiplexing the frame structure, and an error correction code for adding an error correction code to the signal of each layer, respectively. Means for modulating the signal in the higher layer by 8PSK or QPSK, and the signal in the lower layer by QPSK or BPSK.
A transmission apparatus comprising: a modulator for modulating; a modulator for BPSK modulating the synchronization signal and the TMCC signal; and time division multiplexing means for collectively performing time division multiplexing for transmission. 5. A digital transmission receiving apparatus for performing layered transmission, comprising a high layer provided for high quality service and a low layer provided for low quality and high reliability service. The ratio can be changed according to the content of the main signal to be transmitted, and a TMCC signal that defines a transmission system such as a structure, a modulation method, and a coding rate of each layer is organized in a predetermined format, and the main signal of each layer is formed. Are assigned to a frame, a synchronization signal for frame identification and the TMCC signal are added to the beginning of the frame, and multiplexed into a frame structure. An error correction code is added to each layer signal, and The signal in the lower layer is 8PSK or QPSK modulated, and the signal in the lower layer is QPSK or QPSK.
K or BPSK modulated, the synchronization signal and the TMC
In a receiving apparatus for receiving a time-division multiplexed signal in which the C signal is BPSK-modulated and time-division-multiplexed for each of these modulation outputs, the carrier of the time-division-multiplexed signal is first BPSK-demodulated. A signal separating unit that separates the TMCC signal by detecting the synchronization signal, and recognizes the frame configuration and the modulation scheme according to the separated TMCC signal, thereby adapting each layer to a respective transmission scheme. And a demodulation circuit for demodulating the signal. 6. The demodulation circuit, when BPSK, QPSK, and 8PSK are mixed in the time division multiplexed signal,
6. The receiving apparatus according to claim 5, further comprising means for treating all the time division multiplexed signals as 8PSK and performing carrier reproduction adapted to a transmission system. 7. The demodulation circuit according to claim 6, wherein said demodulation circuit includes means for obtaining a TMCC signal by correlating a signal obtained by said carrier reproducing means with said synchronization signal pattern. The receiving device according to the above. 8. A demodulation circuit which demodulates the I signal and Q signal demodulated by the demodulation circuit and the I and Q signals of a synchronization signal pattern used on the transmission side.
6. The receiving apparatus according to claim 5, further comprising means for detecting a phase error of the reproduced carrier by obtaining a correlation value between the signal and the Q signal using a matched filter.