JP2749299B2 - Digital television broadcast multiplexing system and its transmitting device and receiving 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 multiplexing system for multiplexing information for mobile and fixed information in digital television broadcasting, and a transmitting apparatus and a receiving apparatus therefor.

[0002]

2. Description of the Related Art Recently, when digitizing television broadcasting, research and development for performing digital broadcasting for mobile objects and digital broadcasting for fixed use using one frequency channel has been advanced. One of the results is 1
The following paper (hereinafter referred to as a prior art example) has been published in the proceedings of the Annual Conference of the Institute of Television Engineers of Japan on July 26, 995.

Digital Terrestrial Broadcasting Using OFD II "Study of Hierarchical Method Considering Mobile Reception" Author Hirotake Ota Satoshi Ishikawa Aiichiro Tsutake Takeichi Fukuchi The following describes the method of the above prior art example.

First, when digital broadcasting for mobiles and digital broadcasting for fixed use are performed by using one frequency channel, the reception power of mobile reception is lower than that of fixed reception due to the limitation of the antenna. Therefore, it is necessary to provide a difference in the modulation method and error correction capability between the mobile broadcast and the fixed broadcast.

Therefore, in this system, the frequency band is divided into a broadcast for mobiles and a broadcast for fixed use, and basic information of a video is put in the band for mobiles, and the high-definition information for fixed is put in the band for fixed use. On the same channel.

Therefore, according to this method, basic information can be received even if the received power is small by receiving only the band for the mobile object in the mobile reception, and the mobile terminal can receive the basic information in the fixed reception. By receiving both the band and the band for fixed use, it is possible to receive both the basic information and the high-definition information, and the frequency can be used effectively.

[0007] However, in the multiplexing method of the above-mentioned prior art example, even in the case of fixed reception, it is essential to receive basic information transmitted in a band for mobiles.
In order to receive basic information with a low transmission rate and a small amount of information, it is necessary to have a modulation scheme for a fixed band, a modulation scheme for mobiles different from error correction, and a circuit corresponding to error correction. For this reason, there is a drawback that the circuit scale of the fixed receiving device becomes large and expensive.

[0008] On the other hand, when digitizing television broadcasts, OFDM, one of the multi-carrier transmission systems, is used.
(Orthogonal frequency division multiplexing) has attracted attention, and of course, the OFDΜ method can be considered as a multiplexing method for broadcasting for mobiles and broadcasting for fixed broadcasting.

In the OFDΜ system, a redundant period called a guard interval can be provided, and a ghost (multipath) of a delay time difference in the period of the guard interval is converted to a single carrier digital transmission system. It shows very strong resistance in comparison. For this reason, it is said that relaying by a single frequency called SFN (single frequency network) is possible.

That is, in SFN, since radio waves of the same frequency are transmitted from a plurality of transmitting stations, a multipath having a large delay time difference exists. Therefore, by adding a guard interval to an effective symbol, it is possible to provide resistance to such multipath.

[0011] When the SFN is adopted, the reception power is small in mobile reception, so that its service area is narrower than that in fixed reception. For this reason, the required value of the resistance to the multipath having a large delay time difference becomes small, and the guard interval length may be short.

[0012] Further, in broadcasting for mobiles, it is necessary to widen the intervals between carrier waves in order to reduce the influence of interference between carriers due to Doppler shift accompanying movement of a receiving point.
As a result, the effective symbol length is shortened, so that the guard interval length must be shortened in order to avoid a decrease in transmission speed.

On the other hand, since fixed reception is affected by multipath having a large delay time difference, a long guard interval length is required for implementing SF #. Therefore, there is a high possibility that the guard interval length is different between the band for the mobile unit and the band for the fixed unit.

However, a short guard interval length means that the resistance to a multipath having a large delay time difference is weak. It is difficult to receive the broadcast (basic information).

In order to avoid this problem, a multipath signal having a large delay time difference can be prevented from being received.
An antenna having a sharp directivity must be employed, which causes a new problem that the cost of a fixed receiving device increases.

[0016]

As described above, in the conventional digital television broadcast multiplexing system, since basic information is allocated to a band for a mobile unit, even in fixed reception, consideration is given to the characteristics of mobile unit reception. It is necessary to receive a signal of specified data, which causes an increase in circuit scale and cost.

Further, when SFN based on the OFDM method is adopted, the guard interval length for mobiles must be shortened. On the other hand, in fixed reception which is affected by a multipath having a large delay time difference, the guard interval length is reduced. It is difficult to receive broadcasts for short and long mobiles.

A first object of the present invention is to provide a digital television broadcast multiplexing system capable of obtaining basic information without receiving a signal transmitted to a mobile unit in fixed reception, and a transmitting apparatus and a receiving apparatus therefor. Is to do.

A second object of the present invention is to provide a digital television broadcast multiplexing system capable of realizing a high-quality basic information without receiving a signal transmitted to a mobile unit in fixed reception, and a digital television broadcast multiplexing system therefor. A transmitting device and a receiving device are provided.

A third object of the present invention is to cope with hierarchical coding while effectively utilizing frequencies, to enable selection of image quality according to reception quality, and to provide an equivalent fixed frequency band. An object of the present invention is to provide a digital television broadcast multiplexing system that can be widened, and a transmission device and a reception device thereof.

Further, a fourth object of the present invention is to provide a digital receiver capable of receiving information for a mobile unit in mobile reception despite multiplexing high-definition information for fixed use in a band for the mobile unit. It is an object of the present invention to provide a television broadcast multiplexing system and its transmitting device and receiving device.

A fifth object of the present invention is to provide a digital television broadcast multiplexing system capable of receiving at least a fixed signal when SFN based on the OFDM system is adopted, and a transmitting device and a receiving device therefor.

[0023]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention multiplexes a broadcast signal for a mobile unit and a broadcast signal for a fixed unit by frequency-dividing the same channel for mobile units and fixed units. In a digital television broadcast multiplexing system for broadcasting, a broadcast signal for a mobile unit is encoded to obtain information for a mobile unit, and the broadcast signal for a fixed unit is hierarchically encoded into basic information and high-definition information. The definition information is hierarchically multiplexed with the information for the mobile object, converted into a frequency band for the mobile object, the basic information is converted into a frequency band for the fixed object, and information on the frequency band for the mobile object and the fixed frequency band. Signals are combined and transmitted and output.

That is, in the digital television broadcast multiplexing system according to the present invention, information for mobiles and information for fixed use are separated, and basic information in the fixed information is fixed to a fixed frequency band. High-definition information in the information for the mobile terminal is superimposed on the frequency band for the mobile by hierarchical modulation.

[0025] In the fixed broadcast, the condition of radio wave propagation for fixed reception is better than that of a mobile body, so that the information transmission speed can be increased by multi-level modulation. Therefore,
When transmitting the basic information using the fixed frequency band, the basic information can be made to be higher quality than when transmitting the basic information in the mobile band. Further, when receiving a signal of basic information for fixed use in fixed reception, the signal can be easily received because it is a signal of specifications optimized for fixed use.

On the other hand, in order to receive high-definition information multiplexed in a band for a mobile unit, it is necessary to use an antenna having sharp directivity, but since fixed reception is used, use of a multi-element Yagi antenna is required. Can be received.

As described above, since the information amount of the basic information itself can be increased, when it is sufficient to receive a normal-quality image, it is sufficient to receive only the basic information. When a high-definition image is requested, a high-definition image can be received by using the Yagi antenna.

On the other hand, with respect to reception at a mobile unit, the required C / N required for reception is increased due to multiplexing of high-definition information for fixed use, but can be dealt with by increasing transmission power and enhancing error correction. Furthermore, if non-uniform QAΜ or non-uniform DAPSK is used for hierarchical modulation for multiplexing, demodulation by a QPSK demodulator is possible, and differential conversion and delay detection are also possible. Does not increase the limitation of the modulation / demodulation method.

Further, when SFN based on the OFDM method is adopted, basic information is transmitted in a fixed frequency band, so that it is possible to receive only basic information without receiving mobile information on the fixed receiver side. It becomes possible.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 (A) to (D)
Shows the configurations of a transmitting apparatus, a mobile receiving apparatus, a fixed receiving apparatus, and a simple fixed receiving apparatus in the digital television broadcast multiplex system according to the first embodiment.

In the transmitting apparatus shown in FIG. 1A, a video signal S1 and an audio signal S2, which are information to be transmitted, are subjected to digital signal processing and compression processing by an encoder 1 and a hierarchical encoder 2, respectively. You. The encoder 1 is an encoder for broadcasting for mobiles, and encodes the input signals S1 and S2 into low-quality (low transmission rate) digital information having a high compression rate and outputs the digital information. On the other hand, the hierarchical encoder 2 is an encoder for fixed broadcast, and encodes the input signals S1 and S2 into high quality (high transmission rate) digital information having a low compression ratio and outputs the digital information.

However, the hierarchical encoder 2 performs hierarchical encoding, and outputs two signals of basic information S3 and high-definition information S4. Here, the basic information S3 of the hierarchical encoding includes all information necessary for decoding medium-quality video and audio. On the other hand, high-definition information S4
Cannot decode video and audio by itself, but can decode high-quality video and audio in combination with the basic information S3.

That is, when only the basic information is received on the receiving side, medium-definition video and audio can be reproduced. In addition, when high-definition information is received, high-definition video and audio can be reproduced. Becomes possible.

The output S5 of the encoder 1 and the hierarchical encoder 2
Is output to the non-uniform 16QA mapping unit 3 and is converted into a signal constituting a non-uniform 16QAM.

This non-uniform 16QAM is one of hierarchical modulation. Hierarchical modulation is a method of modulating a plurality of pieces of information having different C / Ns required for receiving necessary to obtain a certain error rate onto one carrier, and here, a higher layer (lower C / N) is used.
N can be received), and the transmission signal for the mobile body at the output S5 of the encoder 1 is provided on the side, and the high definition for fixing the output of the hierarchical encoder 2 is provided on the lower layer (requires a high C / N for reception). Information S3 is assigned.

The output of the non-uniform 16 QAM mapper 3 is output from the quadrature modulator 4 to the non-uniform 16
It is converted to an intermediate frequency signal of QA #. On the other hand, another output (basic information for fixation) S of the hierarchical encoder 2
4 is converted into a signal constituting 32QA} by the 32QA {mapper 5}, and the quadrature modulator 6 converts the signal to 32QA}.
Is converted to an intermediate frequency signal.

At this time, the quadrature modulators 4 and 6 generate intermediate frequency signals in different frequency bands. The outputs of the quadrature modulator 4 and the quadrature modulator 6 are combined by a combiner 7, frequency-converted and amplified by a transmission high-frequency unit 8, and then the antenna 9
Sent by

In the case of mobile reception, it is received by the mobile receiver shown in FIG. In FIG. 1B, the signal received by the antenna 10 is
1, the signal is selected, amplified, frequency-converted, converted into an intermediate frequency signal, demodulated by a QPSK demodulator 12, and further converted by a decoder 13 into an analog video signal and an audio signal.

The signal received by the mobile unit is a non-uniform 16QA signal. However, since the signal for the mobile unit is hierarchically modulated on the higher hierarchy side, it can be demodulated by the QPSK demodulator 12 as described later. Becomes

On the other hand, in the case of fixed reception, the signal is received by the fixed reception device shown in FIG. In FIG. 1 (C), a signal received by the antenna 14 is selected, amplified, and frequency-converted by the reception high-frequency unit 15, and converted into an intermediate frequency signal.
AΜ Demodulator 17 and 32QAM demodulator 18 distribute non-uniform 16QAΜ demodulator and 32QAM, respectively.
Demodulated.

As the output of the non-uniform 16QAM demodulator 17, a signal for a mobile object and fixed high-definition information can be obtained. Here, only fixed high-definition information is used. The fixed high-definition information and the fixed basic information output from the 32QAM demodulator 18 are input to the hierarchical decoder 19 and are converted into analog video signals and audio signals.

Further, when only the fixed basic information is fixedly received, it is received by the simple fixed receiving apparatus shown in FIG. In FIG. 1 (D), a signal received by the antenna 20 is selected, amplified, and frequency-converted by the reception high-frequency unit 21, converted into an intermediate-frequency signal, and then demodulated by the 32QAM demodulator 22. Is input to the decoder 23 and converted into an analog video signal and an audio signal.

In the above configuration, the relationship between the output frequencies of the two quadrature modulators 4 and 6 and the hierarchical modulation in FIG. 1A will be described with reference to FIG. FIG. 2A is a diagram showing one frequency channel, and this frequency channel is divided into two bands for use. One band is a frequency band for mobiles, and the other band is a fixed frequency band.

The frequency band for the mobile unit corresponds to the output signal of the quadrature modulator 4 in FIG. 1 (A). In this band, information for the mobile unit and high definition information for the fixed unit are transmitted. On the other hand, the fixed frequency band corresponds to the output signal of the quadrature modulator 6 in FIG. 1A, and the fixed basic information is transmitted in this band.

FIG. 2B shows a constellation of a non-uniform 16QAM signal used for hierarchical modulation. Since a non-uniform 16QAM signal can take 16 points as shown in FIG. 2B, 4-bit information per symbol can be transmitted.

The number shown in FIG. 2B indicates this 4-bit information. Of the four digits, the upper two digits are the same in each quadrant. That is, the information assigned to the upper two digits matches QPSK of 2 bits per symbol as shown in FIG. In the first embodiment, information for a mobile unit is assigned to the upper two digits.

Therefore, in the mobile receiving apparatus shown in FIG.
If the signal is regarded as a PSK signal and demodulated by the QPSK demodulator 12, the upper two digits of the information of the non-uniform 16QAM signal of 4 bits per symbol, to which information for the mobile unit is allocated, can be obtained.

On the other hand, fixed high definition information is assigned to the lower two digits of the four-digit number shown in FIG. 2B.
Therefore, in the fixed receiving device shown in FIG.
The non-uniform 16 QAM signal and 32
The signal is divided into QAM signals, the non-uniform 16QAM signal is demodulated by the non-uniform 16QAM demodulator 17, and the lower two digits are extracted from the 4-bit information per symbol, thereby obtaining high-definition information for fixed use.

FIG. 2C shows a constellation of a 32QA signal in which basic information for fixed transmission is transmitted. In the transmission of digital information, the frequency of occurrence of errors depends on the mutual distance between points of the constellation. Therefore, the non-uniform 16 shown in FIG.
The frequency of occurrence of errors in QAM and 32QAM is
High order 2 digits of non-uniform 16QAM, 32
The lower two digits of QAM and non-uniform 16QAM are in order.

Therefore, the non-uniform 16QAM
The upper two digits can be received even by a mobile object having poor reception conditions. On the other hand, the reception of the lower two digits of the non-uniform 16QA # in which high-definition information for fixed transmission is transmitted requires a high C /
要求 is required, and a high-gain antenna is required. However, since the fixed receiver can use a high-gain antenna such as the Yagi antenna, it is possible to receive a high-definition image.

In the simple fixed receiving apparatus, 32QAM
By demodulating only the 32QAM signal with the demodulator 22,
It becomes possible to receive basic information for fixed use. In this case, since 32QAM multi-level modulation is performed, an image with higher quality than conventional basic information can be obtained.

As is clear from the above description, in this embodiment, the information for the mobile unit and the basic information for the fixed unit are transmitted in different frequency bands. Basic information can be obtained without receiving a transmitted signal. As a result, the modulation specifications of the band for the mobile unit can be optimized for the purpose of only the mobile unit reception without considering the fixed reception.

Conversely, when receiving basic information in fixed reception, there is no need to receive a signal considering mobile reception, but only a signal optimized for fixed reception. . This makes it possible to realize a simple receiving apparatus for fixed reception that receives only basic information for fixed use.

Further, since the multi-level modulation format based on 32QAΜ is adopted for the transmission of the basic information for fixed use, the information amount of the basic information is smaller than when the basic information is transmitted in the band for the mobile unit. Can be increased, and the image quality of the basic information can be improved.

Furthermore, since high-definition information for fixed use is multiplexed with signals in the band for mobile units by hierarchical modulation, it is possible to cope with hierarchical coding while effectively using the frequency.
Image quality can be selected according to reception quality (received bit error rate) called graceful degradation.

Also, since a multi-level hierarchical modulation format using non-uniform 16QAM is adopted as the modulation format used for hierarchical modulation, it is equivalent to the selection of the error correction strength used for digital transmission. It is possible to change the ratio between the frequency bandwidth used for the mobile object and the fixed frequency bandwidth, thereby making it possible to equivalently widen the fixed frequency bandwidth.

Furthermore, despite the fact that high-definition information for fixed use is multiplexed in the band for mobile use, information for mobile use is received by demodulation of QPSK by delay detection suitable for mobile reception. can do.

FIGS. 3A to 3D show the configurations of a transmitting apparatus, a mobile receiving apparatus, a fixed receiving apparatus, and a simple fixed receiving apparatus in the digital television broadcast multiplex system according to the second embodiment, respectively. is there. Incidentally, FIGS. 3 (A) to 3 (D)
In FIG. 1, the same parts as those in FIGS. 1A to 1D are denoted by the same reference numerals, and the overlapping description is omitted here.

First, the transmitting apparatus shown in FIG.
The differential converter 24 is interposed between the encoder 1 and the non-uniform 16QAM mapping unit 3 in FIG. Further, the mobile receiving apparatus shown in FIG. 3B uses the QPSK demodulator 12 shown in FIG.
It is characterized by being replaced with a differential demodulator 25.

The fixed receiving device and the simple fixed receiving device shown in FIGS. 3C and 3D have the same configuration as the device shown in FIGS. 1C and 1D. The differential converter 24 in FIG. 3A converts the phase information of the symbol based on the absolute phase from the encoder 1 into relative phase information based on the phase of the immediately preceding symbol. Non-uniform 16QAM
Output to the mapping device 3.

This processing enables, in QPSK demodulation of a received signal, not the synchronous detection for detecting the absolute phase of the received symbol but the delay detection for detecting the relative phase with the previous symbol.

That is, while the synchronous detection requires information on the reference phase for detecting the absolute phase, the delay detection only needs to use the previous symbol as a reference, so that it is necessary to transmit the information on the reference phase. Absent. Therefore, in a system in which transmission of the reference phase is difficult due to fluctuations in transmission quality, such as a mobile object, it is an effective demodulation means for avoiding an extreme decrease in reception quality.

Therefore, in the mobile receiver according to the present embodiment, as shown in FIG.
, Differentially demodulates the symbols sequentially obtained by the reception high-frequency unit 11 using the immediately preceding symbol as a reference phase, and outputs the demodulated signal to the decoder 13.

Therefore, the same effect as that of the first embodiment can be obtained by the multiplexing method of the present embodiment. FIG.
(A) to (D) show the configurations of a transmitter, a mobile receiver, a fixed receiver, and a simplified fixed receiver in the digital television broadcast multiplex system of the third embodiment, respectively. 4A to 4D, FIG.
The same parts as (A) to (D) are denoted by the same reference numerals,
Here, duplicate description is omitted.

This embodiment is an example of a multiplexing system in which OFDM, which is one of the multicarrier transmission systems, is adopted. The transmitting apparatus shown in FIG. 4A includes the non-uniform 16 QAM mapper 3 and the quadrature modulator 4 shown in FIG.
(Inverse Fast Fourier Transformer) 26 is interposed between the first and second quadrature modulators 6, and an IFFT 27 is interposed between the 32QAΜ mapper 5 and the quadrature modulator 6.

The mobile receiver shown in FIG. 4B has a quadrature demodulator 28 and an FFT (Fast Fourier Transformer) 2 between the reception high-frequency unit 15 and the QPSK demodulator 12 shown in FIG.
9 are arranged in order.

Further, the fixed receiving apparatus shown in FIG.
(C) A quadrature demodulator 30 and an FFT 31 are sequentially arranged between the distributor 16 and the non-uniform 16 QA demodulator 17, and a quadrature demodulator 32 and an FFT 33 are sequentially arranged between the distributor 16 and the 32 QAM demodulator 18. It is characterized by doing.

Further, in the simplified fixed receiver shown in FIG. 4D, a quadrature demodulator 34 and an FFT 35 are sequentially arranged between the reception high-frequency unit 21 and the 32QAM demodulator 22 shown in FIG. 1D. It is characterized by the following.

In the above-described configuration, this embodiment also transmits information for a mobile unit, high-definition information for fixed use, and basic information for fixed use by frequency division shown in FIG. 2A, similarly to the first embodiment. It is.

In the transmitting apparatus shown in FIG. 4A, the information S5 for the mobile unit which is the output of the encoder 1 and the hierarchical encoder 2
The fixed high-definition information S3, which is an output of, is mapped by the non-uniform 16QAM mapper 3 for each OFD carrier, and then input to the IFFT. Each signal on the frequency axis corresponding to each carrier is $ FF
It is converted into a baseband signal on the time axis by T26,
The signal passes through the quadrature modulator 4 to become an OFD intermediate frequency signal.

Similarly, the fixed basic information S4 output from the hierarchical encoder 2 is mapped by the 32QAM mapper 5 for each OFDM carrier, and then
Input to FT27. Each signal on the frequency axis corresponding to each carrier is converted into a signal on the time axis by the FFT 27, and becomes an intermediate frequency signal of OFD via the quadrature modulator 6. These signals are combined by the combiner 7 in the same manner as in the first embodiment, and guided to the antenna 9 via the transmission high-frequency unit 8.

In the mobile receiver shown in FIG. 4B, a signal received by the antenna 10 is input to the quadrature demodulator 28 via the reception high frequency section 11, and is converted into a baseband signal by the quadrature demodulator 28. After that, the FFT 29 converts the signal on the time axis into a signal on the frequency axis corresponding to each OFDM carrier.

Thereafter, as in the first embodiment, QPSK
After the demodulator 12 makes a determination based on the threshold, the signal is converted by the decoder 13 into analog video signals and audio signals.

In the fixed receiver shown in FIG. 4 (C), the signal received by the antenna 10 is distributed by the distributor 16 after passing through the reception high frequency section 11, and the two orthogonal demodulators 3
0, 32 are input. The baseband signal output from each of the quadrature demodulators 30 and 32 is converted from a signal on the time axis into a signal on the frequency axis corresponding to each OFDM carrier by FFTs 31 and 33, respectively.

At this time, the FFT 31 processes a signal in a frequency band for a mobile object, and the FFT 33 processes a signal in a frequency band for a fixed body. The output of each FFT 31, 33 is non-uniform 16 QA demodulator 17, 32 QA
復 調 Demodulated by the demodulator 18 and the non-uniform 16
The high-definition information for fixing of the output information of the QAM demodulator 17 and the basic information for fixing the output information of the 32QA demodulator 18 are input to the hierarchical decoder 23 and converted into analog video signals and audio signals. You.

In the simplified fixed receiver shown in FIG. 4D, the signal received by the antenna 20
The signal is input to the quadrature demodulator 34 via 1 and converted into a baseband signal. This baseband signal is converted by the FFT 35 from a signal on the time axis to a signal on the frequency axis corresponding to each carrier of OFD #.

At this time, the signal processed by the FFT 35 is a signal in a fixed frequency band through which fixed basic information is transmitted, and the output of the FFT 35 is demodulated by the 32QAΜ demodulator 22, and the analog signal is decoded by the decoder 23. It is converted into a video signal and an audio signal.

Therefore, according to the multiplexing method of this embodiment, the same effects as those of the first embodiment can be obtained, and
Since the basic information is transmitted in the fixed frequency band when SFN based on the FDM method is adopted, only the basic information can be received without receiving the mobile information on the fixed receiving device side.

Even when OFD # is employed as in the third embodiment, the differential conversion and the differential demodulation in the second embodiment can be performed, and the differential detection suitable for mobile reception can be performed. It is clear.

Although the first, second and third embodiments have been described with respect to the case where non-uniform 16QAM and 32QAΜ are used for modulating a carrier wave, a digital television broadcast multiplex system according to the present invention and a transmitting apparatus therefor are provided. And in the receiving device, the non-uniform 16QA
It does not need to be 2QAM.

FIG. 5 shows another example of a carrier modulation format capable of performing hierarchical modulation in place of the non-uniform 16QA #. FIG. 5 (A) shows a non-uniform 32QA #, FIG. 5 (B) shows a non-uniform 16DAPSK, and FIG. 5
(C) shows the constellation of the non-uniform 32 DAPS #. Information on the higher layer side of these layer modulations can be demodulated as QPSK.

The modulation format of the carrier wave in place of 32QAM is multi-level QAM such as 16QAM or 64QAM,
There are multi-valued DAPSKs such as 6 DAPSK and 64 DAPSK, which may be appropriately selected according to the amount of information.

[0083]

As described above, according to the present invention, a signal transmitted to a mobile unit in fixed reception is transmitted by transmitting information for the mobile unit and basic information for the fixed unit in different frequency bands. Without receiving the basic information. As a result, the modulation specifications of the band for the mobile unit can be optimized for the purpose of only the mobile unit reception without considering the fixed reception.

Conversely, when receiving basic information in fixed reception, it is not necessary to receive a signal considering mobile reception, but only a signal optimized for fixed reception. . This makes it possible to realize a simple fixed receiving device that receives only basic information for fixed use.

In addition, since multi-level modulation format such as 32QAΜ can be adopted for transmission of fixed basic information, the amount of basic information can be reduced as compared with the case of transmitting basic information in a band for mobile. It is possible to increase the basic information and to improve the image quality of the basic information.

Also, by multiplexing high-definition information for fixed use with a signal in a band for mobile by hierarchical modulation, it is possible to cope with hierarchical coding while effectively using the frequency, and a reception quality called graceful degradation is obtained. It is possible to select the image quality according to the (received bit error rate).

If a multi-level hierarchical modulation format such as non-uniform 16QAM is adopted as the modulation format used for the hierarchical modulation, it can be equivalently moved in accordance with the selection of the error correction strength used for digital transmission. By changing the ratio between the frequency bandwidth used for the body and the fixed frequency bandwidth, the equivalent fixed frequency bandwidth can be widened.

Also, despite the fact that high-definition information for fixed use is multiplexed in the band for mobile use, information for mobile use is received by demodulation of QPSK by delay detection suitable for mobile reception. it can.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram illustrating a configuration of a transmitting device, a mobile receiving device, a fixed receiving device, and a simple fixed receiving device as a first embodiment of a digital television broadcast multiplex system according to the present invention.

FIG. 2 is a diagram showing a method of frequency division and a constellation of a modulation format used for hierarchical modulation in the embodiment.

FIG. 3 is a block circuit diagram showing a configuration of a transmitting device, a mobile receiving device, a fixed receiving device, and a simplified fixed receiving device as a second embodiment of the multiplexing method according to the present invention.

FIG. 4 is a block circuit diagram showing a configuration of a transmitting device, a mobile receiving device, a fixed receiving device, and a simplified fixed receiving device as a third embodiment of the multiplexing method according to the present invention.

FIG. 5 is a diagram showing a constellation of another example of a modulation format of hierarchical modulation used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Encoder 2 ... Hierarchical encoder 3 ... Non-uniform 16QAM mapper 4 ... Quadrature modulator 5 ... 32QAM mapper 6 ... Quadrature modulator 7 ... Synthesizer 8 ... Transmission high frequency part 9, 10, 14, 20 ... Antenna 11, 15, 21 ... High frequency receiving part 12 ... QPSK demodulator 13, 23 ... Decoder 16 ... Distributor 17 ... Non-uniform 16QAM demodulator 18, 22 ... 32QAM demodulator 19 ... Hierarchical decoder 24 ... Differential converter 25 QPSK differential demodulator 26, 27 IFFT 28, 30, 32, 34 Quadrature demodulator 31, 33, 35 FFT

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 7/081 H04B 7/26 P 7/24

Claims (14)

(57) [Claims] 1. A digital television broadcast multiplexing system for performing multiplex broadcasting of a broadcast signal for a mobile unit and a broadcast signal for a fixed unit by frequency-dividing the same channel for a mobile unit and a fixed unit. Encoding a broadcast signal to obtain information for a mobile object, hierarchically encoding the fixed broadcast signal into basic information and high-definition information, and hierarchically multiplexing the high-definition information on the information for the mobile object for a mobile object. Digital television, wherein the basic information is converted to a fixed frequency band, and the information signals of the mobile object frequency band and the fixed frequency band are synthesized and transmitted and output. Broadcast multiplex system. 2. A transmitting apparatus used in a digital television broadcast multiplexing system according to claim 1, wherein: first encoding means for encoding a broadcast signal for the mobile object to obtain information for the mobile object; A second encoding unit that hierarchically encodes the fixed broadcast signal into basic information and high-definition information; and a mobile object information output from the first encoding unit and the second encoding unit. First frequency band converting means for multiplexing the output high-definition information and converting it into a frequency band for a mobile object, and converting basic information output from the second encoding means into a fixed frequency band A second frequency band converting means for transmitting the data, and a transmitting means for synthesizing and transmitting the outputs of the first and second frequency converting means. 3. The transmitting apparatus according to claim 2, wherein said first frequency band conversion means performs multi-level modulation based on non-uniform QAM. 4. The transmitting apparatus according to claim 2, wherein said first frequency band conversion means performs multi-level modulation based on non-uniform DAPSK. 5. The transmitting apparatus according to claim 3, wherein said first frequency band conversion means performs at least differential modulation on a modulation format of said information for a mobile unit. 6. The apparatus according to claim 2, wherein said first and second frequency band converting means perform multi-level modulation on the input information, allocate the modulation results to a plurality of carriers, and perform orthogonal frequency division multiplexing. The transmitting device according to the above. 7. A receiving apparatus for receiving a transmission signal from the transmission apparatus according to any one of claims 3 and 4 on a mobile body, wherein the reception apparatus receives a signal of the first frequency band among the transmission signals. Receiving means for obtaining a multiplexed signal by hierarchical modulation, and QP
QP for obtaining the information for mobile by demodulating SK
A receiver comprising SK demodulation means. 8. A receiving apparatus for receiving a transmission signal from a transmission apparatus according to claim 5 on a mobile body, wherein the reception apparatus receives a signal of the first frequency band among the transmission signals and performs differential modulation. Receiving means for obtaining a multiplexed signal; and differential demodulation means for obtaining the information for the mobile object by differentially demodulating the multiplexed signal obtained by the differential modulation obtained by the receiving means. Receiver. 9. A receiving apparatus for receiving a transmission signal from a transmission apparatus according to claim 5 on a mobile unit, wherein the signal in the first frequency band among the transmission signals is received and multiplexed by hierarchical modulation. Receiving means for acquiring a signal, and differential demodulation means for acquiring the information for the mobile body by delay-detecting at least a part of the multiplexed signal obtained by the differential modulation obtained by the receiving means. Receiving device. 10. A receiving apparatus for receiving a transmission signal from a transmission apparatus according to claim 6 on a mobile object, a receiving means for receiving the transmission signal to obtain an orthogonal frequency division multiplexed signal, And a demodulating means for extracting a carrier component corresponding to a first frequency band from the orthogonal frequency division multiplexed signal obtained by the means and demodulating a multi-level modulation component of information for a mobile unit. 11. A receiving device for receiving a transmission signal of a transmission device according to any one of claims 3, 4, and 5 at a fixed position, wherein the receiving device receives the transmission signal and obtains a multiplexed signal by hierarchical modulation. Receiving means; distributing means for distributing the multiplexed signal obtained by the receiving means to multilevel modulated signals in first and second frequency bands; and multilevel modulation in the first frequency band distributed by the distributing means. A first demodulator for demodulating fixed high-definition information from a signal; and a second demodulator for demodulating fixed basic information from a multi-level modulation signal in a second frequency band distributed by the distributor. A receiving device. 12. A receiving apparatus for receiving a transmission signal from a transmission apparatus according to claim 6 at a fixed position, receiving means for receiving said transmission signal to obtain an orthogonal frequency division multiplexed signal, and receiving means for receiving the transmission signal. Distributing means for distributing the multiplexed signal obtained in step 1 into signals in the first and second frequency bands; and extracting a predetermined carrier component from the signal in the first frequency band distributed by the distributing means to obtain a fixed high frequency signal. A first demodulation means for demodulating the fine information; and a second demodulation means for extracting a predetermined carrier component from the signal of the second frequency band distributed by the distribution means and demodulating the fixed basic information. A receiving device. 13. A receiving apparatus for receiving, at a fixed position, a transmission signal of the transmission apparatus according to claim 3, wherein the multi-level modulation signal in a second frequency band is included in the transmission signal. And a demodulating means for demodulating the fixed basic information from the multi-level modulated signal obtained by the receiving means. 14. A receiving apparatus for receiving a transmission signal from a transmission apparatus according to claim 6 at a fixed position, receiving means for receiving said transmission signal to obtain an orthogonal frequency division multiplexed signal, and receiving means for receiving the transmission signal. And a demodulating means for extracting a carrier component corresponding to the second frequency band from the multiplexed signal obtained in the above and demodulating the fixed basic information.