Hierarchy modulated broadcasting receiving device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to, for example, a hierarchically modulated broadcast receiving device that receives information that is hierarchically transmitted by a plurality of modulation methods.

【0002】

[Conventional technology]

In particular, in digital television broadcasting that uses frequencies higher than the 10 GHz band, the radio wave propagation theory in a plane wave vacuum can generally be sufficiently applied, but in the atmosphere, which can be said to be very small in terms of the length of the radio wave propagation path. Due to the rainfall, various communication quality deteriorations such as radio wave attenuation and interference due to scattering occur.

【0003】

Precipitation attenuation is a phenomenon in which radio waves are attenuated from the power that can be originally received in fine weather due to absorption and scattering by raindrops. Precipitation attenuation usually indicates the difference between the reception intensity received in fine weather and the reception intensity in rainfall in decibels [dB]. It is known that raindrops fall in the shape of a rice cake, for example, instead of a sphere, due to the interaction with the atmosphere at the time of falling. As a result, at the time of linearly polarized waves, the amount of rainfall attenuation received by the horizontally polarized radio waves and the vertically polarized radio waves is different.

【0004】

Rainfall scattering is a phenomenon in which a part of radio waves is scattered in all directions by raindrops when the transmitting antenna beam crosses raindrops, and becomes an interference wave for other communication systems using the same frequency band. Especially in the case of digital television broadcasting, it is necessary to keep the line quality above a certain level, and in order to keep the power of the receiver constant even when the terrestrial transmitting station is raining, the transmission power is compensated for the rainfall attenuation. The transmission power is controlled. For this transmission power control, the C / N obtained by adding this rainfall attenuation to the required C / N (Carrier to Noise ratio) required by the line quality and modulation method is the C / N in fine weather. The transmission power is increased so as to be. In that case, the increase in transmission power may increase the intensity of precipitation scattering and increase interference with other communication systems.

【0005】

Since the C / N of the broadcast signal deteriorates due to the precipitation attenuation in this way, a good reception state may not be obtained. In particular, the C / N required for reception differs depending on the modulation method. Therefore, there is a so-called trade-off between the bit rate per frequency band required for transmission and the C / N required for reception in an error-free state in the modulation method, so there are many on the digital television broadcasting station side. On the other hand, there are conflicting demands for sending information using a modulation method that can be received with a low C / N that is resistant to rainfall attenuation.

【0006】

Therefore, on the digital television broadcasting station side, layered modulation broadcasting is performed in which broadcasts by a plurality of modulation methods of normal broadcasting and rainfall-compatible broadcasting of a modulation method having strength against rainfall attenuation are simultaneously transmitted. As a result, on the receiving device side, the bit rate per frequency bandwidth is high, but the high-layer broadcast reception state of normal broadcasting that requires a high C / N, and the bit rate per frequency bandwidth is low, but the C / The low-layer broadcast reception status of rainfall-compatible broadcasts that can be received by N is switched according to the reception status.

【0007】

FIG. 13 is a diagram showing such changes in weather and transitions due to C / N values. In FIG. 13, the C / N value a [dB] indicates the threshold for transitioning between the high-layer broadcast reception state and the low-layer broadcast reception state.

【0008】

First, in a short time, when the C / N value falls below a [dB] at the transition point 131, the transition from the high-layer broadcast reception state to the low-layer broadcast reception state occurs, and the C / N value at the transition point 132 is a. When it exceeds [dB], it transitions from the low-level broadcast reception state to the high-level broadcast reception state, and when the C / N value falls below a [dB] at the transition point 133, it shifts from the high-level broadcast reception state to the low-level broadcast reception state. Transition to the state.

【0009】

Next, in a short time, when the C / N value exceeds a [dB] at the transition point 134, the transition from the low-layer broadcast reception state to the high-level broadcast reception state occurs, and the C / N value changes at the transition point 135. When it falls below a [dB], it transitions from the high-level broadcast reception state to the low-level broadcast reception state, and when the C / N value exceeds a [dB] at the transition point 136, it shifts from the low-level broadcast reception state to the high-level broadcast. Transition to the reception state, when the C / N value falls below a [dB] at the transition point 137, the high-level broadcast reception state transitions to the low-level broadcast reception state, and the C / N value is a at the transition point 138. When it exceeds [dB], it transitions from the low-layer broadcast reception state to the high-level broadcast reception state.

【0010】

[Problems to be Solved by the Invention]

However, in the conventional layer-modulated broadcasting described above, when the receiving device automatically switches between the high-layer broadcasting reception state of normal broadcasting and the low-layer broadcasting reception state of rainfall-compatible broadcasting, the state transitions automatically. There is a method of using C / N as a parameter of, but in this case, the threshold of C / N for automatic switching is only one predetermined point. On the other hand, since the weather changes are not uniform, it descends or rises from this threshold many times in a short period of time. There is a disadvantage that the hierarchical broadcast reception state is frequently switched in a short time, which may hinder the stable viewing of the user.

【0011】

Also, since changes in the weather cannot be predicted at the time of shipment of the receiver, if the threshold of the C / N for automatic switching is fixed, the unexpected change in the C / N will cause the receiver to reach a higher level of normal broadcasting. There is an inconvenience that the broadcast reception state and the low-layer broadcast reception state of the rain-corresponding broadcast are frequently switched in a short time, which may hinder the stable viewing of the user.

【0012】

Therefore, the present invention has been made in view of such a point, and an object of the present invention is to provide a layered modulation broadcast receiving device capable of receiving information hierarchically transmitted by a plurality of modulation methods in a stable situation. To do.

【0013】

[Means for solving problems]

The hierarchically modulated broadcast receiving device of the present invention receives the hierarchically transmitted information in a plurality of layers by time-dividing and multiplexing information by a plurality of modulation methods, and performs hierarchically transmitted hierarchical modulation information in the hierarchically modulated broadcast receiving device. The receiving means for receiving, the demodulating means for demodating the hierarchical modulation information received by the receiving means according to each layer, and the timing for transitioning a plurality of hierarchical modulation information receiving states according to the demodulated information by the demodulating means to each layer A layered modulation transition point generating means that is generated by changing each of the transitions, and a switching means that switches and outputs any one of a plurality of layered modulation broadcast information according to the transition timing generated by the layered modulation transition point generating means. It is provided with a reproduction means for reproducing the hierarchically modulated broadcast information which is switched and output by the switching means.

【0014】

Therefore, according to the present invention, the following actions are performed. The digital television broadcast is received by the receiving means, and the signal attenuated by the propagation loss is amplified to an appropriate level. The demodulation means demodulates and decodes the amplified received signal and outputs a video signal and an audio signal. The reproduction means reproduces the video signal and the audio signal output from the demodulation means by displaying the video and outputting the audio, respectively.

【0015】

In the demodulation means, the demodulation unit demodulates the received signal and outputs a transport stream. The arithmetic unit unit generates a low-layer / high-layer switching signal by the layer modulation transition point generation means according to the demodulation information detected by the demodulation unit. The non-volatile memory stores parameters for generating a low-layer / high-layer switching signal. The switching means separates and decodes the transport stream into a low-layer or high-layer elementary stream by a low-layer / high-layer switching signal, and outputs a video signal and an audio signal.

【0016】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described. The layer-modulated broadcast receiving device of the present embodiment automatically transitions between the high-layer broadcast receiving state of normal broadcasting and the low-layer broadcasting receiving state of rainfall-compatible broadcasting on the receiving device side according to the C / N value. When the C / N value of the transition point is used, the C / N changes between the high-level broadcast reception state and the low-level broadcast reception state and the transition from the low-level broadcast reception state to the high-level broadcast reception state. By giving the value a hysteresis and setting a time constraint on the transition, the frequent transition in a short time is suppressed and the stable viewing of the user is not hindered.

【0017】

FIG. 1 is a block diagram showing a configuration of a digital television broadcast receiver to which the hierarchically modulated broadcast receiver of the present embodiment is applied. The digital television broadcast receiver 1 is an antenna 2 for receiving digital television broadcasts and an LNB (Low Noise Block down converter) that amplifies the signal attenuated by the propagation loss received by the antenna 2 to an appropriate level. 3, the set-top box 4 that demolishes and decodes the IF (Intermediate Frequency) signal amplified by LNB3 and outputs the video signal S5 and the audio signal S6, and the video signal S5 that is output from the set-top box 4. It also includes a monitor 12 and a speaker 13 for reproducing the audio signal S6.

【0018】

The set-top box 4 demodulates the IF signal and outputs the transport stream S1, and the demodulation unit 5 and the low-layer / high-layer switching signal S3 are layer-modulated according to the C / N information S2 detected by the demodulation unit 5. The arithmetic unit 7 generated by the transition point generation unit 10, the non-volatile memory 8 for storing the parameter 11 for generating the low-layer / high-layer switching signal S3, and the transport stream S1 as the low-layer / high-layer switching signal. DEMUX (De-Multiplexing equipment) (separator unit) 6 that separates into low-level or high-level elemental streams S4 by S3, and the video signal S5 and audio signal S6 by decoding the elemental stream S4. It is configured to have a decoder unit 9 for output.

【0019】

In the digital television broadcast receiver 1 described above, the digital television broadcast is received by the antenna 2 for receiving the digital television broadcast. LNB3 amplifies the signal attenuated by propagation loss to an appropriate level. The set-top box 4 demodulates and decodes the IF signal amplified by LNB3 and outputs the video signal S5 and the audio signal S6. The monitor 12 and the speaker 13 display the video signal S5 and the audio signal S6 output from the set-top box 4 as video and audio output, respectively, and reproduce the video signal S5 and the audio signal S6.

【0020】

In the set-top box 4, the demodulator 5 demodulates the IF signal and outputs the transport stream S1. The arithmetic unit 7 generates a low-layer / high-layer switching signal S3 by the layer modulation transition point generation unit 10 according to the C / N information S2 detected by the demodulation unit 5. The non-volatile memory 8 stores the parameter 11 for generating the low-layer / high-layer switching signal S3. The DEMUX (separator unit) 6 separates the transport stream S1 into a low-layer or high-layer elementary stream S4 by a low-layer / high-layer switching signal S3. The decoder unit 9 decodes the elementary stream S4 and outputs the video signal S5 and the audio signal S6.

【0021】

FIG. 2 is a diagram showing the configuration of the demodulation unit. In FIG. 2, the demodulation unit 5 demodulates a tuner 21 that selects the reception frequency of the IF signal and a high-layer (TC8PSK) demodulation that demodulates the IF signal of the selected reception frequency by the TC8PSK (Trellis Coded Modulation 8 Phase Shift Keying) method. The unit 22 and the low-layer (QPSK, BPSK) demodulation unit 23 that demodulates the IF signal of the selected reception frequency by the QPSK (Quadrature Phase Shift Keying) or BPSK (Binery Phase Shift Keying) method, and the demodulated signal. Decoding unit (Vitabi, deinterleave, RS) 24 that decodes with a decoder, via a de-interleaver, and further RS (read solomon) decoding for error correction decoding, and the decoded packet Of these, only the packets of the contract channel are configured with a descrambler 25 that descrambles.

【0022】

In the demodulation unit 5 described above, the tuner 21 selects the reception frequency of the IF signal, and the high-layer (TC8PSK) demodulation unit 22 demodulates the IF signal of the selected reception frequency by the TC8PSK method. The low-layer (QPSK, BPSK) demodulator 23 demodulates the IF signal of the selected reception frequency by the QPSK or BPSK method. The decoding unit (Vitterbi, deinterleave, RS) 24 decodes the demodulated signal with a Viterbi decoder, and further decodes the demodulated signal via the deinterleaver with RS (Reed-Solomon) for error correction decoding. The descrambler 25 descrambles only the packets of the contract channel among the decrypted packets.

【0023】

Here, the TC8PSK method is a coded modulation method in which error correction coding and modulation are performed at the same time to substantially increase the Euclidean distance between short signals. For example, a 2/3 convolutional code and 8PSK are combined to achieve 8PSK. By compensating for the decrease in the distance between signals of adjacent symbols, transmission characteristics such as power efficiency are improved compared to the QPSK method.

【0024】

FIG. 3 is a diagram showing a configuration of a decoder unit. In FIG. 3, the decoder unit 9 has a high-layer decoder unit 31 that performs decoding processing of the high-level elementary stream S11 separated by the DEMUX (separator unit) 6 and a low layer separated by the DEMUX (separator unit) 6. It is configured to include a low-layer decoder unit 32 that performs decoding processing of the hierarchical elementary stream S12.

【0025】

The high-layer decoder unit 31 includes an MPEG (Moving Picture Experts Group) video decoder 33 that stretches the video portion of the high-layer elemental stream S11, and a high-layer video signal S13 that converts the stretched video data into the NTSC system. NTSC (National Television System Committee) converter 34 that outputs the data, MPEG audio decoder 35 that decompresses the audio part of the high-level elemental stream S11, and high-level audio that converts the decompressed digital audio data to analog. It is configured with a D / A converter 36 that outputs the signal S14.

【0026】

The low-layer decoder unit 32 includes an MPEG video decoder 37 that decompresses the video portion of the low-layer elemental stream S12, and an NTSC conversion unit that converts the decompressed video data into the NTSC system and outputs the low-layer video signal S15. 38, an MPEG audio decoder 39 that decompresses the audio part of the low-layer elemental stream S12, and a D / A converter 40 that converts the decompressed digital audio data to analog and outputs the low-layer audio signal S16. Consists of having.

【0027】

In the high-layer decoder unit 31 described above, the MPEG video decoder 33 decompresses the video portion of the high-layer elementary stream S11. The NTSC conversion unit 34 converts the decompressed video data into the NTSC system and outputs the high-layer video signal S13. The MPEG audio decoder 35 decompresses the audio portion of the high-level elementary stream S11. The D / A converter 36 converts the decompressed digital audio data into analog and outputs a high-layer audio signal S14.

【0028】

In the low-layer decoder unit 32 described above, the MPEG video decoder 37 decompresses the video portion of the low-layer elementary stream S12. The NTSC conversion unit 38 converts the decompressed video data into the NTSC system and outputs the low-layer video signal S15. The MPEG audio decoder 39 decompresses the audio portion of the low-level elementary stream S12. The D / A converter 40 converts the decompressed digital audio data into analog and outputs a low-layer audio signal S16.

【0029】

FIG. 4 is a diagram showing the operation according to the configuration of the DEMUX (separator unit). In FIG. 4, the high-layer and low-layer transport streams S17 output from the demodulation unit 5 shown in FIG. 1 are, for example, L (low layer), L (low layer), H (high layer), and so on. As shown in, the information of each layer is time-division-multiplexed.

【0030】

The DEMUX (separator unit) 6 is time-division-multiplexed by switching the contact point of the internal switch to the high-layer side or the low-layer side by the low-layer / high-layer switching signal S3 from the arithmetic unit 7. The high-level and low-level transport streams S17 are separated and output to the high-level elementary stream S11 or the low-level elementary stream S12.

【0031】

In the high-level elementary stream S11 output from DEMUX (separator section) 6, only high-level information is separated, such as H (high-level), H (high-level), etc. on the high-level side. .. Further, in the low-level elementary stream S12, only low-level information such as L (low-level), L (low-level), and so on is separated on the low-level side.

【0032】

The operation of the hierarchical modulation transition peculiar to the digital television broadcast receiver configured in this way will be described below. FIG. 5 is a diagram showing a case where the transitioning C / N value has hysteresis. FIG. 6 is a flowchart showing the operation when the transitioning C / N value has hysteresis.

【0033】

The digital television broadcast receiver 1 constantly monitors the C / N information S2 supplied from the demodulation unit 5 by the arithmetic unit 7 of the set-top box 4. In FIG. 6, in step S1, it is determined whether or not the high-level broadcast is being received. Specifically, the arithmetic unit 7 outputs the high-layer switching signal S3 generated by the layer modulation transition point generation unit 10 according to the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6 Judge whether or not it is supplied to.

【0034】

If it is determined in step S1 that the high-level broadcast reception state is present, the process proceeds to step S2, and if it is determined that the low-layer broadcast reception state is not the high-layer broadcast reception state, the process proceeds to step S4. When receiving a high-level broadcast, in step S2, it is determined whether or not the C / N value is less than a [dB]. Specifically, in FIG. 5, the arithmetic unit 7 detects the time when the C / N value falls below the threshold a [dB] of the transition from the high-layer broadcast reception state to the low-level broadcast reception state. ..

【0035】

When the C / N value falls below a [dB] in step S2, the transition from the high-layer broadcast reception state to the low-layer broadcast reception state is performed in step S3. Specifically, in FIG. 5, in FIG. 5, the arithmetic unit 7 is at the transition point 51 in which the C / N value is less than a [dB] of the threshold of the transition from the high-layer broadcast reception state to the low-level broadcast reception state. , 53 transitions from the high-level broadcast reception state to the low-level broadcast reception state. At this time, the arithmetic unit 7 supplies the low-layer switching signal S3 generated by the layer modulation transition point generation unit 10 by the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6. The DEMUX (separator unit) 6 switches the contacts of the internal switch to the low-layer side by the low-layer switching signal S3 from the arithmetic unit 7, and the input time-division-multiplexed high-layer and low-layer The transport stream S17 is separated and output to the low-level elementary stream S12.

【0036】

In the low-layer broadcast reception state, in step S4, it is determined whether or not the C / N value exceeds a + b [dB]. Specifically, in FIG. 5, the arithmetic unit 7 shows the time when the C / N value exceeds a + b [dB] of the threshold of the transition from the low-layer broadcast reception state to the high-level broadcast reception state. Detect.

【0037】

When the C / N value exceeds a + b [dB] in step S4, the transition from the low-layer broadcast reception state to the high-level broadcast reception state is performed in step S5. Specifically, in FIG. 5, the arithmetic unit 7 has a transition point in which the C / N value exceeds a + b [dB] of the threshold of the transition from the low-layer broadcast reception state to the high-level broadcast reception state. At 52, as shown by 54, the transition from the low-layer broadcast reception state to the high-level broadcast reception state. At this time, the arithmetic unit 7 supplies the high-layer switching signal S3 generated by the layer modulation transition point generation unit 10 by the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6. The DEMUX (separator unit) 6 switches the contacts of the internal switch to the high-layer side by the high-layer switching signal S3 from the arithmetic unit 7, and the input time-division-multiplexed high-layer and low-layer The transport stream S17 is separated and output to the high-level elementary stream S11.

【0038】

Then, the process returns to step S2, and the determination and processing from step S2 to step S5 are repeated.

【0039】

FIG. 7 shows a case where a hysteresis of the C / N value is provided at the change point of the reception of the high layer / the low layer. As a result, as shown in FIG. 7, even when the C / N value fluctuates frequently in a short period of time, the threshold a [ Since we gave hysteresis to a + b [dB] of the threshold of the transition 75 from the low-layer broadcast reception state 74 to the high-level broadcast reception state 71, a [dB] and a + b [dB]. Since the section between and is a dead zone, even if it exceeds a [dB] in the low-layer broadcast reception state 74, if it does not exceed a + b [dB], it is as high as the frequent low-layer broadcast reception states 73 and 74. It is possible to prevent transitions 72 and 75 from occurring in the hierarchical broadcast reception state 71.

【0040】

Further, in the above description, the arithmetic unit 7 counts the number of transitions p [times] during a certain period of time m [s], and when the number of counts exceeds a predetermined fixed number of times, low-level broadcasting is performed. Increase the value of b [dB] of a + b [dB] of the threshold of the transition from the reception state to the high-level broadcast reception state, store it as parameter 11 of the non-volatile memory 8, and then newly The above-mentioned transition is determined using the value of b [dB] stored as parameter 11 of the non-volatile memory 8.

【0041】

As a result, if there is a large change in C / N that was not expected at the time of shipment of the digital television broadcast receiver, or if the change in C / N value is relatively large compared to other locations. Even when it is installed in a place, it is possible to suppress a frequent transition between a low-layer broadcast reception state and a high-level broadcast reception state in a short time.

【0042】

FIG. 8 is a diagram showing a case where the transition is time-constrained. FIG. 9 is a flowchart showing the operation when the transition is time-constrained. The digital television broadcast receiver 1 constantly monitors the C / N information S2 supplied from the demodulation unit 5 by the arithmetic unit 7 of the set-top box 4. In FIG. 9, in step S11, it is determined whether or not the high-level broadcast is being received. Specifically, the arithmetic unit 7 outputs the high-layer switching signal S3 generated by the layer modulation transition point generation unit 10 according to the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6 Judge whether or not it is supplied to.

【0043】

If it is determined in step S11 that the high-level broadcast reception state is present, the process proceeds to step S12, and if it is determined that the low-layer broadcast reception state is not the high-layer broadcast reception state, the process proceeds to step S14. When receiving a high-level broadcast, in step S12, it is determined whether or not the time when the C / N value has fallen below a [dB] has continued for s [s]. Specifically, in FIG. 8, in FIG. 8, in the arithmetic unit 7, the time when the C / N value falls below the threshold a [dB] of the transition from the high-layer broadcast reception state to the low-level broadcast reception state is s [ s] Detect that it has continued.

【0044】

When the C / N value falls below a [dB] in step S12 for s [s], the transition from the high-layer broadcast reception state to the low-layer broadcast reception state is performed in step S13. Specifically, in FIG. 8, in FIG. 8, in the arithmetic unit 7, the time when the C / N value falls below the threshold a [dB] of the transition from the high-layer broadcast reception state to the low-level broadcast reception state is s [ s] At the subsequent transition point 81, the transition from the high-level broadcast reception state to the low-level broadcast reception state is performed at 83 as indicated by the arrow pointing to the right. At this time, the arithmetic unit 7 supplies the low-layer switching signal S3 generated by the layer modulation transition point generation unit 10 by the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6. The DEMUX (separator unit) 6 switches the contacts of the internal switch to the low-layer side by the low-layer switching signal S3 from the arithmetic unit 7, and the input time-division-multiplexed high-layer and low-layer The transport stream S17 is separated and output to the low-level elementary stream S12.

【0045】

In the low-layer broadcast reception state, in step S14, it is determined whether or not the time when the C / N value exceeds a [dB] continues for t [s]. Specifically, in FIG. 8, in FIG. 8, in the arithmetic unit 7, the time when the C / N value exceeds a [dB] of the threshold of the transition from the low-layer broadcast reception state to the high-level broadcast reception state is t [. s] Detect that it has continued.

【0046】

When the time when the C / N value exceeds a [dB] in step S14 continues for t [s], the transition from the low-layer broadcast reception state to the high-layer broadcast reception state is performed in step S15. Specifically, in FIG. 8, in FIG. 8, in the arithmetic unit 7, the time when the C / N value exceeds a [dB] of the threshold of the transition from the low-layer broadcast reception state to the high-level broadcast reception state is t [. s] (> s [s]) At the subsequent transition point 82, the transition from the low-level broadcast reception state to the high-level broadcast reception state is performed at 83 as indicated by the arrow pointing to the left. At this time, the arithmetic unit 7 supplies the high-layer switching signal S3 generated by the layer modulation transition point generation unit 10 by the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6. The DEMUX (separator unit) 6 switches the contacts of the internal switch to the high-layer side by the high-layer switching signal S3 from the arithmetic unit 7, and the input time-division-multiplexed high-layer and low-layer The transport stream S17 is separated and output to the high-level elementary stream S11.

【0047】

Then, the process returns to step S12, and the determination and processing from step S12 to step S15 are repeated.

【0048】

As a result, even if the C / N value fluctuates frequently in a short period of time, the time s [s] falls below the threshold a [dB] of the transition from the high-level broadcast reception state to the low-level broadcast reception state. Since the time t [s] (> s [s]) that exceeded the threshold a [dB] of the transition from the low-level broadcast reception state to the high-level broadcast reception state was given, there was a time constraint. Since the time between the time s [s] and the time t [s] (> s [s]) in a [dB] becomes a dead zone, the time exceeding a [dB] in the low-layer broadcast reception state is s. If [s] continues but the time exceeding a [dB] does not continue for t [s] (> s [s]), the transition between the frequent low-level broadcast reception state and the high-level broadcast reception state You can prevent it from happening.

【0049】

Further, in the above description, the arithmetic unit 7 counts the number of transitions p [times] during a certain period of time m [s], and when the number of counts exceeds a predetermined fixed number of times, low-level broadcasting is performed. Time constraint of time s [s] below the threshold a [dB] and time t [s] above the threshold a [dB], which indicates the transition between the reception state and the high-level broadcast reception state. values each larger, is stored as a parameter 11 of the nonvolatile memory 8, then a new time s stored as parameters 11 of the nonvolatile memory 8 [s] and the time t [s] of the time constraints The value is used to determine the transition described above.

【0050】

As a result, when there is a gradual change in C / N that was not expected at the time of shipment of the digital television broadcast receiver, or when the change in C / N value is compared with other places. Even when it is installed in an installation location that moves up and down gently, it is possible to suppress the frequent transition between the low-level broadcast reception state and the high-level broadcast reception state in a short time.

【0051】

FIG. 10 is a diagram showing a combination of transitioning C / N values when hysteresis and time constraints are applied. FIG. 11 is a flowchart showing the operation of the combination when the transitioning C / N values are given hysteresis and time constraints.

【0052】

The digital television broadcast receiver 1 constantly monitors the C / N information S2 supplied from the demodulation unit 5 by the arithmetic unit 7 of the set-top box 4. In FIG. 11, in step S21, it is determined whether or not the high-level broadcast is being received. Specifically, the arithmetic unit 7 outputs the high-layer switching signal S3 generated by the layer modulation transition point generation unit 10 according to the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6 Judge whether or not it is supplied to.

【0053】

If it is determined in step S21 that the high-level broadcast reception state is present, the process proceeds to step S22, and if it is determined that the low-layer broadcast reception state is not the high-layer broadcast reception state, the process proceeds to step S25. When receiving a high-level broadcast, in step S22, it is determined whether or not the C / N value is less than a [dB]. Specifically, in FIG. 10, the arithmetic unit 7 detects the time when the C / N value falls below the threshold a [dB] of the transition from the high-layer broadcast reception state to the low-level broadcast reception state. ..

【0054】

When the C / N value falls below a [dB] in step S22, it is determined in step S23 whether or not the time during which the C / N value falls below a [dB] continues for s [s]. Specifically, in FIG. 10, in FIG. 10, in the arithmetic unit 7, the time when the C / N value is less than a [dB] of the threshold of the transition from the high-layer broadcast reception state to the low-level broadcast reception state is s [ s] Detect that it has continued.

【0055】

When the C / N value falls below a [dB] in step S23 for s [s], the transition from the high-level broadcast reception state to the low-level broadcast reception state is performed in step S24. Specifically, in FIG. 10, in FIG. 10, in the arithmetic unit 7, the time when the C / N value is less than a [dB] of the threshold of the transition from the high-layer broadcast reception state to the low-level broadcast reception state is s [ s] At the subsequent transition point 101, the transition from the high-level broadcast reception state to the low-level broadcast reception state is performed as shown by 103. At this time, the arithmetic unit 7 supplies the low-layer switching signal S3 generated by the layer modulation transition point generation unit 10 by the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6. The DEMUX (separator unit) 6 switches the contacts of the internal switch to the low-layer side by the low-layer switching signal S3 from the arithmetic unit 7, and the input time-division-multiplexed high-layer and low-layer The transport stream S17 is separated and output to the low-level elementary stream S12.

【0056】

In the low-layer broadcast reception state, in step S25, it is determined whether or not the C / N value exceeds a + b [dB]. Specifically, in FIG. 10, the arithmetic unit 7 shows the time when the C / N value exceeds a + b [dB] of the threshold of the transition from the low-layer broadcast reception state to the high-level broadcast reception state. Detect.

【0057】

If the C / N value exceeds a + b [dB] in step S25, does t [s] continue for the time when the C / N value exceeds a + b [dB] in step S26? To judge. Specifically, in FIG. 10, in FIG. 10, the time when the C / N value exceeds a + b [dB] of the threshold of the transition from the low-layer broadcast reception state to the high-level broadcast reception state is exceeded. t [s] Detects that it has continued.

【0058】

When the time when the C / N value exceeds a + b [dB] in step S26 continues for t [s], the transition from the low-layer broadcast reception state to the high-level broadcast reception state is performed in step S27. Specifically, in FIG. 10, in FIG. 10, in the arithmetic unit 7, the time when the C / N value exceeds a + b [dB] of the threshold of the transition from the low-layer broadcast reception state to the high-level broadcast reception state is exceeded. t [s] (> s [s]) At the subsequent transition point 102, the transition from the low-layer broadcast reception state to the high-level broadcast reception state is performed as shown by 104. At this time, the arithmetic unit 7 supplies the high-layer switching signal S3 generated by the layer modulation transition point generation unit 10 by the C / N information S2 supplied from the demodulation unit 5 to the DEMUX (separator unit) 6. The DEMUX (separator unit) 6 switches the contacts of the internal switch to the high-layer side by the high-layer switching signal S3 from the arithmetic unit 7, and the input time-division-multiplexed high-layer and low-layer The transport stream S17 is separated and output to the high-level elementary stream S11.

【0059】

Then, the process returns to step S22, and the determination and processing from step S22 to step S27 are repeated.

【0060】

As a result, even if the C / N value fluctuates frequently in a short period of time, the threshold a [dB] of the transition from the high-layer broadcast reception state to the low-layer broadcast reception state and the low-layer broadcast reception state to high Since a + b [dB] of the threshold of the transition to the layered broadcast reception state has hysteresis, the section between a [dB] and a + b [dB] becomes a dead zone, so the lower layer. In the broadcast reception state, even if it exceeds a [dB], it must further exceed a + b [dB] and fall below the threshold a [dB] of the transition from the high-level broadcast reception state to the low-level broadcast reception state. Time s [s] and time exceeding a + b [dB] of the threshold of the transition from the low-level broadcast reception state to the high-level broadcast reception state t [s] (> s [s]) Since the target constraint is given, the time between the time s [s] and the time t [s] (> s [s]) becomes a dead zone at a [dB] and a + b [dB], so it is low. In the hierarchical broadcast reception state, even if the time exceeding a [dB] continues for s [s], if the time exceeding a + b [dB] does not continue for t [s] (> s [s]), it is frequent. It is possible to prevent the transition between the low-layer broadcast reception state and the high-level broadcast reception state from occurring, and it is possible to more flexibly control the suppression of frequent transitions.

【0061】

Further, in the above, the calculator unit 7 counts the number of transitions p [times] during the given period m [s], when exceeded fixed number of the counted number of times reaches a predetermined, low hierarchical broadcasting While increasing the value of b [dB] of a + b [dB] of the threshold of the transition from the reception state to the high-level broadcast reception state, the value between the low-level broadcast reception state and the high-level broadcast reception state is increased. Non-volatile by increasing the values of the time constraints of the time s [s] below the threshold a [dB] indicating the transition and the time t [s] above the threshold a + b [dB]. stored as parameter 11 of the memory 8, then the new threshold of b [dB], which is stored as a parameter 11 of the nonvolatile memory 8 values and time s [s] and the time t [s] of the time constraints The value is used to determine the transition described above.

【0062】

As a result, if there is a large change in C / N that was not expected at the time of shipment of the digital television broadcast receiver, or if the change in C / N value is relatively large compared to other locations. Even when installed in a place, if there is a gradual change in C / N, or in a place where the C / N value changes relatively slowly compared to other places. Even when this is done, it is possible to more flexibly suppress the transition between the low-layer broadcast reception state and the high-level broadcast reception state, which are frequent in a short period of time.

【0063】

FIG. 12 is a diagram showing a combination of state transitions when the transitioning C / N values are given hysteresis and time constraints. In FIG. 12, for example, in the method of providing hysteresis in the transitioning C / N, the transition is made immediately when the target transition point is exceeded, so that when the transition is made from the high-layer broadcast reception state 121 to the low-layer broadcast reception state 123. As shown by 122, the transition point a [dB] of is lowered to near the reception limit of the high-level broadcast reception state 121, and the time constraint of the transition from the high-level broadcast reception state 121 to the low-level broadcast reception state 123 s [s]. Is reduced as shown by 122, so that the decoding error by the decoder unit 9 that occurs when the reception limit is exceeded can be minimized while continuing the high-layer broadcast reception state 121 as much as possible.

【0064】

On the other hand, when transitioning from the low-level broadcast reception state 123 to the high-level broadcast reception state 121, the time constraint t [s] for the transition from the low-level broadcast reception state 123 to the high-level broadcast reception state 121 is indicated by 124. by relatively longer provided, from a high hierarchical broadcasting transition point shown at 122 from the receive state 121 to low hierarchical broadcasting reception status 123 a [dB] and the low hierarchy broadcasting reception status 123 to the high hierarchy broadcasting reception status 121 124 Transition to the high-level broadcast reception state 121 after securing a sufficient C / N that can receive high-level broadcasts, together with the hysteresis of the C / N value between the transition point a + b [dB] shown in. Can be executed.

【0065】

In the above-described embodiment, the transition between the two-layer broadcast reception state of the low-layer broadcast reception state and the high-level broadcast reception state has been described, but the present invention is not limited to this, and the low-level broadcast reception state is further divided into a plurality of layers. Therefore, it may be applied to a plurality of layers having three or more layers. Further, although C / N is used as the modulation information, other modulation information may be used.

【0066】

[Effect of the invention]

The hierarchically modulated broadcast receiving device of the present invention receives the hierarchically transmitted information in a plurality of layers by time-dividing and multiplexing the information by a plurality of modulation methods. The receiving means for receiving, the demodulating means for demodating the hierarchical modulation information received by the receiving means according to each layer, and the timing for transitioning a plurality of hierarchical modulation information receiving states according to the demodulated information by the demodulating means to each layer A layered modulation transition point generating means that is generated by changing each of the transitions, and a switching means that switches and outputs any one of a plurality of layered modulation broadcast information according to the transition timing generated by the layered modulation transition point generating means. Since it is equipped with a playback means for reproducing the layer-modulated broadcast information output by switching by the switching means, when automatically switching between the high-layer broadcast reception state and the low-layer broadcast reception state, the transition timing is set to each layer. By changing each transition point and giving hysteresis to the transition point, it is possible to prevent frequent short-term transitions that hinder the user's viewing against changes in the demographic information due to uneven weather changes. It works.

【0067】

Further, in the layered modulation broadcast receiving device of the present invention, as described above, the layered transmission has at least a high layer transmission having a relatively high transmission rate and a low layer transmission having a relatively low transmission rate, and the demodulation information is C / N ( Carrier power to noise power ratio), and in the high-layer modulation information reception state due to high-layer transmission, transitions to the low-layer modulation information reception state when the C / N (carrier power to noise power ratio) falls below the first value. However, in the low-layer modulation information reception state, when the C / N (carrier power to noise power ratio) exceeds the second value larger than the first value, the transition to the high-layer modulation information reception state is set. If the value falls below or exceeds the value of the C / N, the transition can be made immediately, and the first value of the C / N, which is the transition point from the high-layer modulation information reception state to the low-layer modulation information reception state, is relatively high. By making it small and setting it to the limit of the high-layer modulation information reception state, while watching the high-layer broadcast as much as possible, the time during which the user cannot watch due to a decoding error in the decoder section of the playback means is minimized. It has the effect of being able to be suppressed.

【0068】

Further, in the layered modulation broadcast receiving device of the present invention, when the transition to each layer occurs more than a predetermined number of times within a predetermined time, the second value is updated to a larger value and updated. Since the value is stored in the storage means and the updated second value is used in place of the second value at the time of subsequent transitions, high-level broadcast reception is received when a certain number of transitions occur during a certain period of time. By increasing the hysteresis of the C / N at the transition point between the state and the low-level broadcast reception state and storing the hysteresis in the non-volatile memory, the C / N due to weather changes and installation conditions beyond what was expected at the time of design It has the effect of being able to respond to changes in the vertical movement of.

【0069】

Further, in the layered modulation broadcast receiving device of the present invention, as described above, the layered transmission has at least a high layer transmission having a relatively high transmission rate and a low layer transmission having a relatively low transmission rate, and the demodulation information is C / N (C / N). Carrier power to noise power ratio), and in the high-layer modulation information reception state due to high-layer transmission, low-layer modulation information when the C / N (carrier power to noise power ratio) of the transition point is exceeded for the first period or longer. When the C / N (carrier power to noise power ratio) is exceeded over the second period, which is longer than the first period, in the low-layer modulation information reception state, the transition to the high-layer modulation information reception state occurs. , When automatically switching between the high-level broadcast reception state and the low-level broadcast reception state, the transition timing is changed at the time of transition to each layer, and the transition point is continuously below the transition point for a certain period of time s [s] or more. When the transition point is entered from the high-layer modulation information reception state to the low-layer modulation information reception state, and conversely, the low-layer modulation information is received when the transition point is continuously exceeded for a certain period of time t [s] longer than s [s]. By transitioning from the state to the high-layer modulation information reception state, it is possible to prevent frequent short-term transitions that hinder the user's viewing against changes in C / N due to uneven weather changes, and for a very short time. It has the effect of being effective for large vertical movements of C / N between.

【0070】

Further, in the above-mentioned layer-modulated broadcast receiving device of the present invention, when the transition to each layer occurs more than a predetermined number of times within a predetermined time, the first period and the second period are updated to longer values. The updated values of the first period and the second period are stored in the storage means, and the values of the first period and the second period are replaced with the values of the first period and the second period at the subsequent transition. Since the period value is used, when a certain number of transitions occur during a certain period of time, the first period and the second period of the transition point between the high-level broadcast reception state and the low-level broadcast reception state are lengthened. By storing the updated values of the first period and the second period in the non-volatile memory, the change in C / N per unit time becomes larger than expected at the time of design due to changes in weather and installation conditions. It has the effect of being able to handle small cases.

【0071】

Further, in the layered modulation broadcast receiving device of the present invention, as described above, the layered transmission has at least a high layer transmission having a relatively high transmission rate and a low layer transmission having a relatively low transmission rate, and the demodulation information is C / N (C / N). Carrier power to noise power ratio), and when the C / N (carrier power to noise power ratio) falls below the first value and over the first period or longer in the high-layer modulation information reception state due to high-layer transmission. When it falls below the C / N (carrier power to noise power ratio) of the transition point, it transitions to the low-layer modulation information reception state, and in the low-layer modulation information reception state, the C / N (carrier power to noise power ratio) is the above-mentioned first. When the value exceeds the second value, which is greater than the value of 1, and when the C / N (carrier power to noise power ratio) is exceeded over the second period, which is longer than the first period, the state transitions to the high-layer modulation information reception state. Therefore, by combining the method of giving hysteresis to the C / N value of the transition point and the method of transitioning when the transition point is continuously below or above the transition point for a certain period of time or more, it is more flexible and frequent. It has the effect of being able to control the suppression of such transitions.

【0072】

Further, in the layered modulation broadcast receiving device of the present invention, when the transition to each layer occurs more than a predetermined number of times within a predetermined time, the second value is updated to a larger value and updated. Since the value is stored in the storage means and the updated second value is used in place of the above second value at the subsequent transition, when there is a large C / N change that was not expected at the time of shipment. Or, even when installed in an installation location where the change in C / N value is relatively large compared to other locations, or when there is a gradual change in C / N compared to other locations, or with other locations. Even when installed in an installation location where the C / N value changes relatively slowly in comparison, the transition between the low-level broadcast reception state and the high-level broadcast reception state, which is frequent in a short period of time, is more pronounced. It has the effect of being able to be flexibly suppressed.

【0073】

Further, in the layer modulation broadcast receiving device of the present invention, when the transition to each layer occurs more than a predetermined number of times within a predetermined time, the first period and the second period are updated to longer values and updated. The values of the first period and the second period that have been set are stored in the storage means, and the values of the first period and the second period are replaced with the values of the first period and the second period at the time of the subsequent transition. Since the value of is used, it is installed in an installation location where there is a large change in C / N that was not expected at the time of shipment, or where the change in C / N value is relatively large compared to other locations. Even when it is installed, when there is a gradual change in C / N, or when it is installed in an installation location where the change in C / N value is relatively gradual compared to other locations. However, it is possible to more flexibly suppress the transition between the low-layer broadcast reception state and the high-level broadcast reception state, which are frequent in a short period of time.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the structure of the digital television broadcast receiver to which the layer modulation broadcast receiver of this embodiment is applied.

[Figure 2]

It is a figure which shows the structure of the demodulation part.

[Fig. 3]

It is a figure which shows the structure of the decoder part.

[Fig. 4]

It is a figure which shows the operation by the structure of DEMUX (separator part).

[Fig. 5]

It is a figure which shows the case where the value of transition C / N has hysteresis.

[Fig. 6]

It is a flowchart which shows the operation when the value of transition C / N is given hysteresis.

[Fig. 7]

It is a figure which shows the case where the hysteresis of the value of C / N is provided at the change point of the reception of a high layer / a low layer.

[Fig. 8]

It is a figure which shows the case where the transition is given a time constraint.

[Fig. 9]

It is a flowchart which shows the operation when time constraint is given to the transition.

[Fig. 10]

It is a figure which shows the combination when the value of transition C / N is given hysteresis and time constraint.

[Fig. 11]

It is a flowchart which shows the operation of the combination when the value of transition C / N is given hysteresis and time constraint.

[Fig. 12]

It is a figure which shows the state transition of the combination when the value of the transition C / N is given hysteresis and time constraint.

[Fig. 13]

It is a figure which shows the transition by the change of the weather and the value of C / N.

[Explanation of symbols]

1 ...... Digital television broadcast receiver, 2 ...... Antenna, 3 ...... LNB, 4 ...... Set-top box, 5 ...... Demodulation unit, 6 ...... DEMUX (separator unit), 7 ...... arithmetic unit unit, 8 ...... non-volatile memory, 9 ...... decoder unit, 10. ..... Hierarchical modulation transition point generator, 11 ...... parameters, 12 ...... monitor, 13 ...... speaker, 21 ...... tuner, 22. ..... High layer (TC8PSK) demodulation section, 23 ...... Low layer (QPSK, BPSK) demodulation section, 24 ...... Decoding section (Vitabi, Deinterleave, RS), 25. ..... Descriptor, 31 ...... High-level decoder, 32 ... Low-level decoder, 33 ... MPEG video decoder, 34 ... NTSC converter, 35 ...... MPEG audio decoder, 36 ...... D / A converter, 37 ...... MPEG video decoder, 38 ...... NTSC converter, 39 ...... MPEG audio decoder, 40 ...... D / A converter, 51 ...... transition point, 52 ...... transition point, 71 ...... high Hierarchical reception state, 73, 74 ...... Low-layer reception state, 81 ...... Transition point, 82 ...... Transition point, 101 ...... Transition point, 102. ..... Transition point, 121 ...... High-level broadcast viewing state, 123 ...... Low-level broadcast viewing state