JP2022179970A - Transmission device - Google Patents

Abstract

To provide a transmission device in which two kinds of data carriers are defined as a high hierarchy and a low hierarchy respectively, and which is controlled so as to reduce a non-liner distortion of a transmission path characteristic in the same frequency band and the same symbol rate to generate and transmit a modulation wave signal to be synthesized.SOLUTION: A transmission device 1 of an embodiment of the present invention comprises: a function part (11) that generates a high hierarchy IQ signal; a function part (12) that generates a low hierarchy IQ signal; a function part (18) that executes a correction processing for dynamically adjusting a predetermined amount amplitude to each signal point of the low hierarchy IQ signal; a function part (13) that minimizes a power of the low hierarchy IQ signal after the correction processing; a function part (14) that generates a hierarchy multiplexed IQ signal by synthesizing the high hierarchy IQ signal and the low hierarchy IQ signal to be miniaturized; a synchronization control part (15) that performs a synchronization control of each function part; a filter part (16) that executes a waveform shaping against the hierarchy multiplexed IQ signal; and an orthogonal modulation part (17) that generates and transmits a modulation waveform signal on the basis of the hierarchy multiplexed IQ signal after the waveform shaping.SELECTED DRAWING: Figure 2

Description

The present invention relates to a digital broadcasting transmission system that performs hierarchical transmission in which two types of data carriers are multiplexed in one channel. The present invention relates to a transmitting apparatus that generates and transmits modulated wave signals that are multiplexed at the same frequency band and at the same symbol rate for carriers.

Digital broadcasting is broadly classified into satellite broadcasting and terrestrial broadcasting, and signal transmission is performed via transmission paths that have their own characteristics.

First, digital signal modulation schemes in satellite broadcasting include BPSK including π/2 shift BPSK, QPSK including π/4 shift QPSK, 8PSK, 16APSK, or 32APSK. The carrier system used for this is a single carrier system. Further, a satellite repeater is interposed on a transmission line between a transmitting device and a receiving device in satellite broadcasting. The satellite transponder mainly includes an input filter, which is an input multiplexer filter (hereinafter referred to as "IMUX filter"), a traveling wave tube amplifier (hereinafter referred to as "TWTA"), and an output filter, which is an output multiplexer filter (hereinafter referred to as "IMUX filter"). , called “OMUX filter”).

The IMUX filter is a band-pass filter corresponding to each channel in satellite broadcasting. It receives a modulated wave signal uplink-transmitted by a terrestrial transmission device, and performs band extraction for each channel from the modulated wave signal. , to the TWTA for each channel.

The TWTA performs gain control (power amplification) on the band component of each channel extracted by the IMUX filter and outputs it to the OMUX filter.

The OMUX filter is a band-pass filter corresponding to each channel, and suppresses unnecessary frequency components of the band components of each channel power-amplified by the TWTA. A modulated wave signal obtained by synthesizing the components is generated as a broadcast wave signal, and is downlinked and output to a receiver on the ground.

By the way, the TWTA deviates from the desired IQ signal point (ideal IQ signal point) due to the influence of input/output amplitude, phase shift characteristics, and the like. Further, in the IMUX filter and the OMUX filter, inter-symbol interference occurs due to the influence of frequency amplitude, group delay characteristics, etc., resulting in a spread from a desired IQ signal point. Therefore, on a transmission path through which a satellite transponder intervenes, the shift and spread of these IQ signal points affect each other, causing non-linear distortion of the transmission path characteristics, resulting in an increase in the required C/N ratio and a deterioration in transmission quality. It is known that it leads to deterioration (for example, see Non-Patent Document 1).

On the other hand, digital signal modulation methods for terrestrial broadcasting include QPSK, 16QAM, and 64QAM, and the carrier method used for signal transmission between a transmitter and a receiver is framed multi-carrier transmission rather than OFDM. there is A major feature of terrestrial broadcasting is the effect of multipath fading in the transmission path. Linear transmission of modulated wave signals is possible.

In recent years, in terrestrial broadcasting for the next generation, a layered transmission (hereinafter referred to as "LDM") system in which two types of data carriers are multiplexed in one channel has been studied. Specifically, as an example of LDM, the current ISDB-T data carrier (hereinafter referred to as "2K layer") and next-generation broadcasting data carrier (hereinafter referred to as "4K layer") are combined into one channel. are being studied (for example, see Non-Patent Document 2). Here, the LDM disclosed in Non-Patent Document 2 has the following mechanism. On the transmitting side, by multiplexing the 4K layer with a smaller power (i.e., amplitude) than the 2K layer, the two power differences (i.e., amplitude difference) between the high layer (2K) and the low layer (4K) are used. shall be transmitted as Then, on the receiving side, a 2K data signal is obtained by first demodulating and decoding from the higher layers. Subsequently, on the receiving side, a re-encoded and re-modulated high-hierarchy (2K) signal is generated based on the decoded 2K data signal, and data including both high-hierarchy (2K) and low-hierarchy (4K) is generated. A low-hierarchy (4K) signal is obtained by subtracting the re-encoded and re-modulated high-hierarchy (2K) signal from the signal by vector operation.

Therefore, it is possible to improve the efficiency of signal transmission by incorporating the technology of the LDM system into satellite broadcasting (for example, see Non-Patent Document 3). However, as shown in Non-Patent Document 3, there is a problem that the non-linear distortion of the transmission path through which the satellite repeater intervenes (especially, the non-linear characteristics of TWTA) has a great influence on the signal components of the low layers.

Kojima, Koizumi, Suzuki, Suji, "Comparative Study of Digital Pre-Distortion for 32APSK by Hardware Experiments and Numerical Calculations", IEICE Technical Report, IEICE Technical Report SAT2019-53, Electronics The Society of Information and Communication Engineers, October 10, 2019 Sato, Kanbara, Okano, Tsuchida, "Evaluation of transmission characteristics during integrated demodulation of LDM multiplexing of next-generation broadcasting on ISDB-T", ITE Winter Annual Convention 2019 14C-5 , The Institute of Image Information and Television Engineers, December 12, 2019 Okada, "Carrier superimposition method in satellite communication - Toward the realization of LDM -", Institute of Image Information and Television Engineers Technical Report (ITE Technical Report) Vol.41,No.11,BCT2017-47, Institute of Image Information and Television Engineers, Announced on March 10, 2017

As described above, it is possible to incorporate the technology of the LDM system in satellite broadcasting as well.

Here, with reference to FIGS. 4 and 5, generalized schematic configurations of the conventional LDM transmitter 1P and receiver 3P will be described.

(prior art transmitter)
First, FIG. 4 is a block diagram showing a generalized schematic configuration of an LDM transmission apparatus 1P based on the prior art.

The transmitting device 1P shown in FIG. 4 defines two types of data carriers as high hierarchy and low hierarchy, respectively, and generates and transmits modulated wave signals that are multiplexed at the same frequency band and at the same symbol rate for the two types of data carriers. high-layer coding/modulation unit 11, low-layer coding/modulation unit 12, low-layer amplitude adjustment unit 13, combining unit 14, synchronization control unit 15, root roll-off filter unit 16 , and a D/A conversion/quadrature modulation unit 17 .

The high-hierarchy coding/modulation unit 11 inputs high-hierarchy data to be transmitted as a high-hierarchy (2K in this example) data carrier, and converts the high-hierarchy data to be a main signal into a high-hierarchy data in advance. After performing an encoding process of forming encoded data by adding an error correction parity by a block code (in this example, a concatenated code of LDPC and BCH) with a predetermined encoding rate (in this example, 1/2), Mapping on the IQ plane based on a predetermined modulation scheme (QPSK in this example) for the hierarchy is performed, and the IQ signal for the high hierarchy (a quadrature signal of the in-phase component I and the quadrature phase component Q, which is a signal point on the IQ plane A signal of a signal point sequence that can be represented) is generated and output to the multiplexing unit 14 . Encoding processing for the high-layer data may include energy diffusion processing and interleaving processing.

The low-hierarchy coding/modulation unit 12 inputs low-hierarchy data to be transmitted as a data carrier of low hierarchy (4K in this example), and pre-registers the low-hierarchy data as a main signal for low hierarchy. After applying an encoding process of forming encoded data by adding an error correction parity by a block code (in this example, a concatenated code of LDPC and BCH) with a predetermined encoding rate (in this example, 3/4), A low-hierarchy IQ signal is generated by performing mapping on the IQ plane based on a predetermined modulation scheme (QPSK in this example) for the hierarchy, and is output to the low-hierarchy amplitude adjustment section 13 . Encoding processing for the low-hierarchy data may include energy diffusion processing and interleaving processing.

The low-hierarchy amplitude adjustment unit 13 sets the average amplitude level of the low-hierarchy IQ signal generated by the low-hierarchy coding/modulation unit 12 uniformly to an amplitude smaller than the average amplitude level of the high-hierarchy IQ signal by a predetermined amount. By changing the power difference (in this example, the power difference is 7.0 dB), a low-power IQ signal for low layers is generated and output to the combining unit 14 .

The multiplexing unit 14 multiplexes (adds power to) the IQ signal for the high hierarchy and the low-power IQ signal for the low hierarchy in the same frequency band and at the same symbol rate. A new IQ signal is generated as a multiplexed IQ signal and output to the root roll-off filter unit 16 .

The synchronization control unit 15 controls the high-hierarchy coding/modulation unit 11 and the low-hierarchy coding/modulation unit 11 so that the two types of data carriers defined as high-hierarchy and low-hierarchy are multiplexed at the same frequency band and at the same symbol rate. It is a functional unit that performs synchronous control of the encoding/modulating unit 12, the low-hierarchy amplitude adjusting unit 13, and the multiplexing unit 14. FIG. In particular, the synchronization control unit 15 satisfies the required C/N ratio of each of the low-hierarchy IQ signal and the high-hierarchy IQ signal in performing synchronization control of the low-hierarchy amplitude adjustment unit 13, and In order to be able to identify the IQ signal for the low layer by the difference of the IQ signal for the high layer due to the vector operation, the IQ signal for the low layer is uniformly changed to an amplitude smaller than the IQ signal for the high layer by a predetermined amount. do.

The root roll-off filter unit 16 is a type of band-limiting filter, and performs upsampling and waveform shaping for removing unnecessary high-frequency components on the hierarchically multiplexed IQ signal generated by the multiplexing unit 14. A hierarchically multiplexed IQ signal is generated and output to the D/A conversion/quadrature modulation section 17 .

The D/A conversion/quadrature modulation unit 17 performs digital/analog (D/A) conversion processing on the hierarchically multiplexed IQ signal after waveform shaping, and converts it into a predetermined modulation method for the high hierarchy (in this example, A modulated wave signal based on quadrature modulation processing by QPSK) is generated and transmitted to the receiving device 3P via a predetermined transmission path.

(prior art receiver)
Next, FIG. 5 is a block diagram showing a generalized schematic configuration of an LDM receiver 3P based on the prior art.

The receiving device 3P shown in FIG. 5 is configured as a device that receives the modulated wave signal generated by the transmitting device 1P via a predetermined transmission path and demodulates and decodes the two types of data carriers. A/D conversion unit 31, root roll-off filter unit 32, high layer demodulation/decoding unit 33, high layer re-encoding/re-modulation unit 34, vector calculation unit 35, and low layer demodulation/decoding unit 36 Prepare.

The quadrature demodulation/A/D conversion unit 31 receives the modulated wave signal generated by the transmission device 1P via a predetermined transmission path, and performs quadrature demodulation processing by the modulation method (QPSK in this example). An analog/digital (A/D) conversion process is performed to restore the hierarchically multiplexed IQ signal, which is output to the root roll-off filter section 32 .

The root roll-off filter unit 32 is a kind of band-limiting filter, and removes unnecessary high-frequency components of the hierarchically multiplexed IQ signal restored by the orthogonal demodulation/A/D conversion unit 31. Only symbol points are obtained by waveform shaping and down-sampling. A hierarchical multiplexed IQ signal is generated and output to the demodulator/decoder 33 for high hierarchy and the vector calculator 35 .

The high-hierarchy demodulation/decoding unit 33 demodulates the waveform-shaped hierarchical multiplexed IQ signal based on the predetermined modulation scheme (QPSK in this example), and then performs demodulation processing on the waveform-shaped hierarchical multiplexed IQ signal. Inverse processing corresponding to the encoding processing of , that is, decoding processing for block code (LDPC and BCH concatenated code in this example) with a predetermined coding rate (1/2 in this example) for the high hierarchy Then, the high-hierarchy data is restored and output to the outside as well as to the high-hierarchy re-encoding/re-modulation unit 34 . That is, the high-hierarchy demodulation/decoding unit 33 regards the reception of the waveform-shaped hierarchically multiplexed IQ signal as the reception of the high-hierarchy IQ signal under the likelihood determination and error correction processing, and demodulates and decodes the signal. can be applied, which restores the high-hierarchy data.

The high-layer re-encoding/re-modulation unit 34 performs the same processing as the high-layer encoding/modulation unit 11 in the transmission device 1P on the high-layer data obtained from the high-layer demodulation/decoding unit 33, That is, an error correction parity is added by a block code (in this example, a concatenated code of LDPC and BCH) with a predetermined coding rate (1/2 in this example) for the high-layer data used as the main signal. After performing encoding processing to form encoded data in the vector calculation unit 35, mapping on the IQ plane based on a predetermined modulation scheme (QPSK in this example) is performed to regenerate the IQ signal for the high hierarchy. output to

The vector calculation unit 35 subtracts the high-hierarchy IQ signal regenerated by the high-hierarchy re-encoding/re-modulation unit 34 from the hierarchical multiplexed IQ signal output from the root roll-off filter unit 32 by vector calculation (power subtraction) to restore the low-hierarchy IQ signal and output it to the low-hierarchy demodulator/decoder 36 .

The low-hierarchy demodulation/decoding unit 36 performs demodulation processing based on a predetermined modulation scheme (QPSK in this example) for the low-hierarchy IQ signal obtained from the vector calculation unit 35, and then transmits the signal. Reverse processing corresponding to the encoding processing for the low hierarchy in the apparatus 1P is performed, that is, block code (in this example, concatenation of LDPC and BCH) with a predetermined coding rate (3/4 in this example) for the low hierarchy code), restores the high-hierarchy data, and outputs it to the outside.

The conventional LDM transmission system shown in FIGS. 4 and 5 can also be applied to satellite broadcasting. It is necessary to devise ways to reduce the influence of nonlinear distortion in transmission lines in which repeaters intervene.

That is, in the transmitting apparatus 1P shown in FIG. 4, transmission is performed by a hierarchically multiplexed IQ signal of a signal point obtained by directly adding the IQ signal for the high layer and the IQ signal for the low layer. If the method is also applied, the transmission will be carried out with the influence of non-linear distortion caused by the transmission line including the satellite repeater. As a result, the required C/N will increase and the transmission quality will deteriorate.

Therefore, an object of the present invention is to define two types of data carriers as high hierarchy and low hierarchy, respectively, and reduce nonlinear distortion of transmission path characteristics in the same frequency band and at the same symbol rate for the two types of data carriers. To provide a transmission device for generating and transmitting a modulated wave signal that is controlled and multiplexed.

The transmitting apparatus of the present invention defines two types of data carriers as high hierarchy and low hierarchy, respectively, and controls the two types of data carriers in the same frequency band and at the same symbol rate to reduce nonlinear distortion of transmission path characteristics. A transmission device for generating and transmitting a modulated wave signal obtained by multiplexing multiplexed signals, wherein high-hierarchy data to be transmitted as a data carrier for the high-hierarchy is input, and a predetermined high-hierarchy data is determined for the high-hierarchy data. After applying an encoding process for forming encoded data by adding an error correction parity by a block code with a coding rate of 1, mapping on an IQ plane based on a predetermined modulation scheme for high layers is performed to perform high layer mapping. A high-hierarchy coding/modulation unit that generates an IQ signal for high-hierarchy, and low-hierarchy data to be transmitted as a data carrier for said low-hierarchy are input, and the low-hierarchy data is encoded in advance for low-hierarchy. After applying an encoding process for forming encoded data by adding an error correction parity by a block code of the rate, mapping on the IQ plane based on a predetermined modulation scheme for the low hierarchy is performed, and the IQ signal for the low hierarchy and a low-hierarchy coding/modulation unit that generates a predetermined amount dynamically based on the amplitude of the corresponding high-hierarchy IQ signal signal point on the time axis for each signal point of the low-hierarchy IQ signal. a low-hierarchy amplitude variable section that performs correction processing for adjusting amplitude and generates an amplitude-corrected second low-hierarchy IQ signal; The amplitude is uniformly changed to be smaller by a predetermined amount than the average amplitude level of the IQ signal, or the average amplitude level of the IQ signal for high hierarchy is uniformly larger by a predetermined amount than the average amplitude level of the second IQ signal for low hierarchy. An amplitude adjustment unit that adjusts the amplitude by changing the amplitude, and multiplexes the high-hierarchy IQ signal and the second low-hierarchy IQ signal after the amplitude adjustment in the same frequency band and at the same symbol rate. to generate a new IQ signal as a hierarchically multiplexed IQ signal, the high layer coding/modulation unit, the low layer coding/modulation unit, the low layer amplitude variable unit, a synchronization control unit that performs synchronization control of the amplitude adjustment unit and the multiplexing unit; a root roll-off filter unit that performs waveform shaping on the hierarchically multiplexed IQ signal to generate a second hierarchically multiplexed IQ signal; D/A conversion for performing digital/analog conversion processing on the second hierarchically multiplexed IQ signal, generating and transmitting a modulated wave signal based on quadrature modulation processing according to a predetermined modulation method for the higher hierarchy and a quadrature modulation section.

Further, in the transmission device of the present invention, the synchronization control unit, when synchronously controlling the correction processing by the low-hierarchy amplitude varying unit, controls the low-hierarchy IQ once generated by the low-hierarchy coding/modulation unit. For each signal point of the signal, when the amplitude of the hierarchically multiplexed IQ signal becomes larger than a predetermined amount based on the amplitude of each signal point of the corresponding high-hierarchy IQ signal on the time axis, the amplitude is within the predetermined amount. It is characterized by having a function of performing synchronous control so as to perform a correction process to reduce the amplitude to a level within which it can be accommodated.

Further, in the transmitting apparatus of the present invention, the synchronization control unit satisfies each required C/N required for receiving each of the low-hierarchy and high-hierarchy data carriers on the receiving side, and the received second a function of performing synchronous control so as to change the amplitude so as to decrease within a range in which the low-hierarchy IQ signal can be identified by the vector calculation difference of the high-hierarchy IQ signal with respect to the hierarchy-multiplexed IQ signal of Characterized by

Further, in the transmitting apparatus of the present invention, the D/A conversion/quadrature modulation section is configured to transmit the modulated wave signal to a satellite transponder interposed on a transmission line of satellite broadcasting. and

According to the present invention, it is possible to reduce the influence of non-linear distortion on the transmission path, and in particular, improve the transmission performance of IQ signals for low hierarchies, as compared with the LDM transmission apparatus of the prior art. Further, according to the present invention, it is possible to ensure the same transmission capacity as in the conventional LDM transmission system. In other words, it is possible to reduce the influence of non-linear distortion on the transmission path without reducing the transmission capacity of the LDM transmission system of the prior art, and to improve the transmission performance of IQ signals for low hierarchies in particular.

1 is a block diagram illustrating a schematic configuration of a transmission system including a transmitting device and a receiving device according to one embodiment of the present invention; FIG. 1 is a block diagram illustrating a schematic configuration of a transmission device of one embodiment according to the present invention; FIG. FIG. 4 is a diagram showing IQ signal point constellations before and after correction in the transmitter of one embodiment according to the present invention; 1 is a block diagram showing a generalized schematic configuration of an LDM transmission apparatus based on the prior art; FIG. 1 is a block diagram showing a generalized schematic configuration of an LDM system receiver based on the prior art; FIG.

A transmitter 1 according to an embodiment of the present invention will be described below with reference to the drawings.

[Transmission system]
FIG. 1 is a block diagram illustrating a schematic configuration of a transmission system including a transmitter 1 and a receiver 3 according to one embodiment of the present invention. The transmission system of one embodiment shown in FIG. 1 is an example in which the LDM system is applied to satellite broadcasting. , .

The transmission device 1, which will be described in detail with reference to FIG. 2, defines two types of data carriers as a high hierarchy and a low hierarchy, respectively, and transmits transmission paths for the two types of data carriers in the same frequency band and at the same symbol rate. This is a device that generates and transmits a modulated wave signal that is controlled and combined so as to reduce nonlinear distortion of characteristics.

The satellite transponder 2 mounted on the broadcasting satellite includes an IMUX filter 21, a TWTA 22, and an OMUX filter 23. As described above, the IMUX filter 21 receives the modulated wave signal uplink-transmitted by the transmission device 1 on the ground. Then, band extraction is performed for each channel from the modulated wave signal, power is amplified by the TWTA 22, unnecessary frequency components are suppressed by the OMUX filter 23, and the modulated wave signal synthesized by all channels is generated as a broadcast wave signal. , downlink output to a receiver on the ground.

The receiving device 3 is configured as a device that receives the modulated wave signal generated by the transmitting device 1 via a transmission line including the satellite repeater 2, and demodulates and decodes the two types of data carriers. has the same configuration as the LDM system receiving apparatus 3P based on the prior art shown in FIG.

[Transmitter]
FIG. 2 is a block diagram illustrating a schematic configuration of the transmitter 1 of one embodiment according to the present invention. In the transmitting device 1 shown in FIG. 2, the same reference numerals are assigned to the same components as in the conventional transmitting device 1P shown in FIG.

The transmitting apparatus 1 shown in FIG. 2 includes a high-layer coding/modulation unit 11, a low-layer coding/modulation unit 12, a low-layer amplitude adjustment unit 13, a multiplexing unit 14, a synchronization control unit 15, and a root roll-off unit. It includes a filter section 16, a D/A conversion/quadrature modulation section 17, and a low-hierarchy amplitude varying section 18, and further includes a low-hierarchy amplitude varying section 18 as compared with the conventional transmission apparatus 1P shown in FIG. , and the synchronization control section 15 is configured to also perform synchronization control of the amplitude variable section 18 for low layers. Hereinafter, each component of the transmission device 1 will be described more specifically.

The high-hierarchy coding/modulation unit 11 inputs high-hierarchy data to be transmitted as a high-hierarchy (2K in this example) data carrier, and converts the high-hierarchy data to be a main signal into a high-hierarchy data in advance. After performing an encoding process of forming encoded data by adding an error correction parity by a block code (in this example, a concatenated code of LDPC and BCH) with a predetermined encoding rate (in this example, 1/2), Mapping on the IQ plane based on a defined modulation scheme (QPSK in this example) is performed to generate an IQ signal for higher layers, and the signal is output to the combining unit 14 . Encoding processing for the high-layer data may include energy diffusion processing and interleaving processing.

The low-hierarchy coding/modulation unit 12 inputs low-hierarchy data to be transmitted as a data carrier of low hierarchy (4K in this example), and pre-registers the low-hierarchy data as a main signal for low hierarchy. After performing encoding processing for forming encoded data by adding an error correction parity by a block code (in this example, a concatenated code of LDPC and BCH) with a predetermined encoding rate (in this example, 3/4), the above Mapping on the IQ plane based on the same modulation scheme (QPSK in this example) as for the high hierarchy is performed to generate a low hierarchy IQ signal, which is output to the low hierarchy amplitude variable section 18 . Encoding processing for the low-hierarchy data may include energy diffusion processing and interleaving processing.

The low-hierarchy amplitude varying unit 18 adjusts the amplitude of the signal point of the high-hierarchy IQ signal corresponding on the time axis to each signal point of the low-hierarchy IQ signal generated by the low-hierarchy encoding/modulating unit 12. A correction process for dynamically adjusting the amplitude by a predetermined amount is applied to the reference to generate an amplitude-corrected low-hierarchy IQ signal, which is output to the low-hierarchy amplitude adjustment section 13 .

The low-hierarchy amplitude adjusting section 13 changes the average amplitude level of the low-hierarchy IQ signal amplitude-corrected by the low-hierarchy amplitude varying section 18 to an amplitude uniformly smaller than the average amplitude level of the high-hierarchy IQ signal by a predetermined amount. (In this example, the power difference is 7.0 dB) to generate a low-power IQ signal for low hierarchies and output it to the multiplexer 14 .

The multiplexing unit 14 multiplexes (adds power to) the IQ signal for the high hierarchy and the low-power IQ signal for the low hierarchy in the same frequency band and at the same symbol rate. A new normalized IQ signal is generated as a multiplexed IQ signal and output to the root roll-off filter unit 16 .

The synchronization control unit 15 controls the high-hierarchy coding/modulation unit 11 and the low-hierarchy coding/modulation unit 11 so that the two types of data carriers defined as high-hierarchy and low-hierarchy are multiplexed at the same frequency band and at the same symbol rate. It is a functional unit that performs synchronization control of the encoding/modulating unit 12, the low-hierarchy amplitude variable unit 18, the low-hierarchy amplitude adjustment unit 13, and the multiplexing unit 14. FIG.

In particular, the synchronization control unit 15 according to the present invention controls each of the low-hierarchy IQ signals once generated by the low-hierarchy coding/modulation unit 12 when synchronously controlling the correction processing by the low-hierarchy amplitude varying unit 18. When the amplitude of the hierarchically multiplexed IQ signal becomes larger than a predetermined amount based on the amplitude of each signal point of the IQ signal for high hierarchy corresponding to the signal point on the time axis, the amplitude is reduced to fall within the predetermined amount. It has a function of performing synchronous control so as to apply correction processing that changes so as to

In addition, the synchronization control unit 15 according to the present invention, along with the synchronization control of the correction processing by the low-hierarchy amplitude variable unit 18, performs the respective functions necessary for receiving the low-hierarchy and high-hierarchy data carriers on the receiving side. of the received hierarchical multiplexed IQ signal, and the amplitude is changed to be small within the range where the low hierarchical IQ signal can be identified by the difference due to the vector operation of the high hierarchical IQ signal with respect to the received hierarchical multiplexed IQ signal. It has a function of synchronous control.

The root roll-off filter unit 16 is a type of band-limiting filter, and performs upsampling and waveform shaping for removing unnecessary high-frequency components on the hierarchically multiplexed IQ signal generated by the multiplexing unit 14. A hierarchically multiplexed IQ signal is generated and output to the D/A conversion/quadrature modulation section 17 .

The D/A conversion/quadrature modulation unit 17 performs digital/analog (D/A) conversion processing on the hierarchically multiplexed IQ signal (that is, normalized IQ signal) after waveform shaping, and converts it in advance for the high hierarchy. A modulated wave signal based on quadrature modulation processing by a predetermined modulation method (QPSK in this example) is generated and transmitted to the receiving device 3 via a transmission line including the satellite repeater 2 .

Thus, in the transmitting apparatus 1 shown in FIG. 2, QPSK (coding rate 1/2) is used for coding/modulation for high layers, and coding/modulation for low layers is used as transmission parameters in one embodiment. QPSK (coding rate 3/4) is used for modulation, and the power difference between the high hierarchy IQ signal and the low hierarchy IQ signal is 7.0 dB. Here, in this example, the same symbol rate and center frequency are used, and the symbol points of the IQ signal for high hierarchy and the IQ signal for low hierarchy are synchronized. Assuming that the satellite broadcasting transmission system ISDB-S3 is followed, the required C/N for QPSK (encoding rate 1/2) is 1.2 dB, and the required C/N for QPSK (encoding rate 3/4) is 4.0 dB. Since it is 0 dB, considering the power difference of 7.0 dB, under ideal transmission path conditions, it is possible to receive the high hierarchy IQ signal with a reception C/N margin of 5.8 dB.

Using the transmission parameters of this embodiment, the generation operation of the hierarchically multiplexed IQ signal in the transmitter 1 will be described with reference to FIG.

First, since the high-hierarchy IQ signal is QPSK, there are four points in total, one point each in the first to fourth quadrants (“○” in FIG. 3), and the amplitude of the high-hierarchy IQ signal is set to 1. When each point in the first to fourth quadrants is expressed by (real part of IQ signal, imaginary part of IQ signal), (0.7071, 0.7071), (-0.7071, 0.7071), (-0.7071, -0.7071), and (0.7071, -0.7071).

Next, the IQ signal for the low hierarchy is 4 points of QPSK as well as the high hierarchy. ^(-7/10) ≈ 0.1995, and the corresponding four points of the IQ signal for low hierarchy (QPSK) are (0.1411, 0.1411), (-0.1411, 0.1411), ( −0.1411, −0.1411), and (0.1411, −0.1411).

Therefore, if the IQ signal for high hierarchy and the IQ signal for low hierarchy with a power difference of 7.0 dB are added, the IQ signal point arrangement (“♦” shown in FIG. 3) is 16 grid points (0.0 dB). 8482, 0.8482), (0.5660, 0.8482), (0.5660, 0.5660), (0.8482, 0.5660), (-0.5660, 0.8482), (- 0.8482, 0.8482), (-0.8482, 0.5660), (-0.5660, 0.5660), (-0.5660, -0.5660), (-0.8482, - 0.5660), (-0.8482, -0.8482), (-0.5660, -0.8482), (0.8482, -0.5660), (0.5660, -0.5660) , (0.5660, -0.8482), and (0.8482, -0.8482).

That is, in the conventional transmitting apparatus 1P, the signal is modulated and transmitted by a grid-like IQ signal point arrangement (“♦” shown in FIG. 3) similar to the QAM modulation system. However, in the case of this IQ signal point arrangement (“♦” shown in FIG. 3), in satellite broadcasting, four points (0.8482 , 0.8482), (−0.8482, 0.8482), (−0.8482, −0.8482), (0.8482, −0.8482) are the effects of nonlinear distortion of TWTA 22 (amplitude suppression and phase-shifted state), resulting in deterioration of reception performance. This is the reason why satellite broadcasting such as ISDB-S3 uses PSK instead of QAM, or APSK for 4 bits or more.

In the case of normal 4-bit modulation, it is only necessary to change the arrangement of IQ signal points to APSK. It is necessary to dynamically change the amplitude of the hierarchically multiplexed IQ signal according to .

Therefore, in the transmitting apparatus 1 according to one embodiment of the present invention, the low-hierarchy amplitude variable section 18 that is controlled for synchronization by the synchronization control section 15 is provided. performs correction processing for dynamically adjusting the amplitude by a predetermined amount based on the amplitude of the signal point of the corresponding high-hierarchy IQ signal, and reduces the power of the low-hierarchy IQ signal whose amplitude is corrected by the low-hierarchy amplitude adjustment unit 13. and multiplexes the IQ signal for the high hierarchy and the low power IQ signal for the low hierarchy in the same frequency band and at the same symbol rate in a multiplexing unit 14. Thus, a hierarchically multiplexed IQ signal is generated.

Representatively, in the first quadrant shown in FIG. 3, the IQ signal for high hierarchy ("O" shown in FIG. 3) is located at (0.7071, 0.7071) in the first quadrant. , grid-like four points (0.8482, 0.8482), (0.5660, 0.8482) after addition of the high-hierarchy IQ signal and the low-hierarchy IQ signal (“♦” shown in FIG. 3), Among (0.5660, 0.5660) and (0.8482, 0.5660), the upper right coordinate point (0.8482, 0.8482) has the maximum normalized amplitude of 1.200. If the coordinate point (0.8482, 0.8482) is (+|0.8482-C1|, +|0.8482-C1|) (C1 is a positive constant) (in the first quadrant shown in FIG. 3, On the upper right side of the two points "⋄" in the drawing), the amplitude can be lowered from 1.200, and the influence of nonlinear distortion can be reduced. The TWTA 22 is linear below a predetermined amplitude, here linear below a normalized amplitude of one.

In addition, four grid points (0.8482, 0.8482), (0.5660, 0.8482) after addition of the high-hierarchy IQ signal and the low-hierarchy IQ signal (“♦” shown in FIG. 3) , (0.5660, 0.5660), and (0.8482, 0.5660), the lower left coordinate point (0.5660, 0.5660) has the minimum normalized amplitude of 0.8005, and the lower left (0.5660, 0.5660) is (+|0.5660-C2|, +|0.5660-C2|) (C2 is a positive constant) (first quadrant shown in FIG. 3 , the lower left side of the drawing of the two points “◇”), the normalized power of the hierarchically multiplexed IQ signal viewed from the low hierarchical IQ signal can be maintained at 0.1995 (=1−0.8005), The power difference of 7.0 dB between the high layer IQ signal and the low layer IQ signal can also be maintained.

In this way, the synchronization control unit 15 according to the present invention, when synchronously controlling the correction processing by the low-layer amplitude varying unit 18, uses the low-layer IQ signal once generated by the low-layer coding/modulation unit 12. for each signal point, when the amplitude of the hierarchically multiplexed IQ signal exceeds a predetermined amount based on the amplitude of each signal point of the corresponding high-hierarchy IQ signal on the time axis, the amplitude that falls within the predetermined amount synchronous control is performed so as to perform a correction process that changes so as to reduce it to a smaller value, and furthermore, in accordance with the synchronous control of the correction process by the low-hierarchy amplitude variable unit 18, the reception side of each data carrier of the low-hierarchy and high-hierarchy Amplitude within a range that satisfies each required C/N required for reception and allows identification of the low-hierarchy IQ signal by the difference due to the vector operation of the high-hierarchy IQ signal with respect to the received hierarchy-multiplexed IQ signal Synchronous control is performed so that

The same processing is applied to the second to fourth quadrants shown in FIG. ) are indicated by “◇”.

Also, the optimal values of C1 and C2 depend on the characteristics of the satellite transponder 2 (IMUX filter 21, TWTA 22, and OMUX filter 23) and the operating point of the TWTA 22, but the correction amount is calculated off-line in advance. Alternatively, a mechanism (not shown) capable of calculating the correction amount may be provided in the transmission device 1 to derive and update the correction amount sequentially or periodically.

As described above, according to the transmission device 1 of the present embodiment, compared with the conventional LDM transmission device 1P, the influence of nonlinear distortion on the transmission path can be reduced without reducing the transmission capacity. It is possible to improve the transmission performance of the IQ signal for low layers.

Although the above-described embodiment has been described as a representative example, it will be apparent to those skilled in the art that many modifications and substitutions may be made within the spirit and scope of the invention. For example, in the above example, the high hierarchy is 2K and the low hierarchy is 4K. (However, it is a prerequisite that the reception resistance is higher in the higher hierarchy than in the lower hierarchy). Further, according to the transmission device 1 according to the present invention, since physical IQ signal processing is used to generate modulated wave signals, various high-hierarchy and low-hierarchy modulation schemes and error correction block coding schemes can be used. You can choose what you want. Therefore, according to the transmitting apparatus 1 according to the present invention, high versatility is ensured regardless of the selected coding/modulation method (transmission line coding method), and the same transmission capacity as the conventional LDM method is ensured. However, the influence of nonlinear distortion can be reduced more than the conventional LDM method. In addition, in the above-described embodiment, an example in which the transmitting apparatus 1 according to the present invention is applied to a transmission system for satellite broadcasting has been described. Since this can be assumed, it may be applied to a transmission system for terrestrial broadcasting.
Further, in the above-described example, as an easy-to-understand typical example, the example in which the predetermined modulation scheme for the high hierarchy and the predetermined modulation scheme for the low hierarchy are the same (in the above example, QPSK). As described above, it goes without saying that the components according to the present invention may be applied as different modulation schemes for high-hierarchy and low-hierarchy. For example, the high hierarchy may be QPSK and the low hierarchy may be 8PSK. Furthermore, even if the modulation scheme is the same between the high hierarchy and the low hierarchy, the coding rates may be different. That is, as a hierarchically multiplexed IQ signal, utilizing the fact that reception performance is different as a result, it is possible to generate and transmit a modulated wave signal in which two types of data carriers are multiplexed at the same frequency band and at the same symbol rate. Just do it.
Furthermore, in the above-described example, an example has been described in which amplitude adjustment is performed by the low-hierarchy amplitude adjustment unit 13 to uniformly reduce the average amplitude level of the low-hierarchy IQ signal with respect to the average amplitude level of the high-hierarchy IQ signal. However, instead of providing such a low-hierarchy amplitude adjustment unit 13, a high-hierarchy amplitude adjustment is performed to uniformly increase the average amplitude level of the high-hierarchy IQ signal with respect to the average amplitude level of the low-hierarchy IQ signal. An amplitude adjustment section (not shown) may be provided. That is, the configuration is provided with an "amplitude adjustment unit" (not shown) that performs amplitude adjustment so that the average amplitude level of the IQ signal for the high layer uniformly becomes a predetermined level difference from the average amplitude level of the IQ signal for the low layer. If it is
Accordingly, the present invention should not be construed as limited by the above-described embodiments, but only by the appended claims.

According to the present invention, it is possible to reduce the influence of nonlinear distortion on the transmission line without reducing the transmission capacity, and particularly to improve the transmission performance of the IQ signal for the low hierarchy. Useful.

1 transmitter (present invention)
1P transmitter (prior art)
2 Satellite repeater 3, 3P, 3-1, 3-2, ..., 3-n Receiving device 11 Encoding/modulating unit for high layer 12 Encoding/modulating unit for low layer 13 Amplitude adjustment unit for low layer 14 Synthesis Wave section 15 Synchronization control section 16 Root roll-off filter section 17 D/A conversion/orthogonal modulation section 18 Low hierarchical amplitude variable section 21 IMUX filter 22 TWTA
23 OMUX filter 31 orthogonal demodulation/A/D conversion unit 32 root roll-off filter unit 33 demodulation/decoding unit for high layers 34 re-encoding/re-modulation unit for high layers 35 vector calculation unit 36 demodulation/decoding unit for low layers

Claims (4)

Two types of data carriers are defined as high-hierarchy and low-hierarchy, respectively, and the modulated waves are combined by controlling the two types of data carriers in the same frequency band and at the same symbol rate so as to reduce non-linear distortion of transmission path characteristics. A transmitting device that generates and transmits a signal,
high-hierarchy data to be transmitted as a data carrier for the high-hierarchy is input, error correction parity is added to the high-hierarchy data by a block code having a predetermined coding rate for the high hierarchy, and encoded data is generated. a high-hierarchy coding/modulation unit that generates high-hierarchy IQ signals by performing mapping on an IQ plane based on a predetermined modulation scheme for high-hierarchy after performing coding processing to form;
Low-hierarchy data to be transmitted as the low-hierarchy data carrier is inputted, error correction parity is added to the low-hierarchy data by a block code having a predetermined coding rate for the low-hierarchy, and encoded data is generated. a low-hierarchy coding/modulation unit for generating low-hierarchy IQ signals by performing mapping on an IQ plane based on a predetermined modulation scheme for low-hierarchy after performing coding processing to form;
Each signal point of the IQ signal for low hierarchy is subjected to a correction process for dynamically adjusting the amplitude by a predetermined amount based on the amplitude of the corresponding signal point of the IQ signal for high hierarchy on the time axis, thereby correcting the amplitude. a low-hierarchy amplitude variable section that generates a second low-hierarchy IQ signal;
The average amplitude level of the second IQ signal for low hierarchy is uniformly changed to an amplitude smaller than the average amplitude level of the IQ signal for high hierarchy by a predetermined amount, or the average amplitude level of the IQ signal for high hierarchy is changed to the average amplitude level of the IQ signal for high hierarchy. an amplitude adjustment unit that adjusts the amplitude by uniformly changing the amplitude to be larger by a predetermined amount than the average amplitude level of the IQ signal for the low hierarchy No. 2;
By multiplexing the high-hierarchy IQ signal and the second low-hierarchy IQ signal after amplitude adjustment in the same frequency band and at the same symbol rate, a new IQ signal as a hierarchically multiplexed IQ signal a multiplexer that generates
a synchronization control unit that performs synchronization control of the high-layer coding/modulation unit, the low-layer coding/modulation unit, the low-layer amplitude variable unit, the amplitude adjustment unit, and the multiplexing unit;
a root roll-off filter section for performing waveform shaping on the hierarchically multiplexed IQ signal to generate a second hierarchically multiplexed IQ signal;
D/A conversion/orthogonality for performing digital/analog conversion processing on the second hierarchically multiplexed IQ signal, generating and transmitting a modulated wave signal based on quadrature modulation processing according to a modulation scheme predetermined for the higher hierarchy a modulation unit;
A transmitting device comprising: When synchronously controlling the correction processing by the low-hierarchy amplitude varying section, the synchronization control section controls each signal point of the low-hierarchy IQ signal once generated by the low-hierarchy coding/modulation section. When the amplitude of the hierarchically multiplexed IQ signal exceeds a predetermined amount based on the amplitude of each signal point of the IQ signal for high hierarchy corresponding on the axis, the amplitude is changed so as to be reduced within the predetermined amount. 2. The transmitting apparatus according to claim 1, further comprising a function of performing synchronous control so as to perform correction processing. The synchronization control unit satisfies each required C/N required for reception of each of the low-hierarchy and high-hierarchy data carriers on the receiving side, and satisfies the high-level characterized by having a function of performing synchronous control so as to perform correction processing to change the amplitude so as to decrease within a range in which the IQ signal for low hierarchy can be identified by the difference obtained by vector calculation of the IQ signal for hierarchy. Item 3. The transmitter according to item 1 or 2. 4. The apparatus according to any one of claims 1 to 3, wherein said D/A conversion/quadrature modulation section is configured to transmit said modulated wave signal to a satellite transponder interposed on a transmission path of satellite broadcasting. A transmitting device according to any one of the preceding claims.

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