JP2002152152A - Hierarchical modulation broadcast receiver - Google Patents

Abstract

(57) [Summary] [Problem] To provide a hierarchical modulation broadcast receiving apparatus capable of receiving information hierarchically transmitted by a plurality of modulation schemes in a stable state. SOLUTION: The digital television broadcast receiver 1 comprises:
An antenna 2 for receiving hierarchically transmitted hierarchical modulation information;
An LNB 2 and a demodulation unit 5 for demodulating the received hierarchical modulation information in the set-top box 4 according to each layer.
And a hierarchical modulation transition point generation unit 10 that changes the timing at which a plurality of hierarchical modulation information reception states are changed according to demodulation information at the time of transition to each layer, and generates a plurality of hierarchical modulations based on the generated transition timing. It comprises a DEMUX (separator unit) 6 for switching and outputting any of the broadcast information, a decoder unit 9 for reproducing the switched hierarchical output broadcast information, a monitor 12, and a speaker 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hierarchical modulation broadcast receiving apparatus for receiving, for example, information hierarchically transmitted by a plurality of modulation schemes.

[0002]

2. Description of the Related Art In general, in digital television broadcasting using a high frequency of 10 GHz or higher, the theory of radio wave propagation in a plane wave in a vacuum can be generally applied.
The rainfall in the atmosphere, which can be said to be very small in terms of the length of the radio wave propagation path, causes interference such as attenuation and scattering of radio waves.
Various communication quality degradations occur.

[0003] Rain attenuation is a phenomenon in which a radio wave is attenuated by the absorption and scattering of raindrops from the power that can be received when the weather is fine. Normally, the rain attenuation indicates the difference between the reception intensity received during fine weather and the reception intensity during rain, in decibels [dB]. It is known that raindrops are not spherical, but fall, for example, in a shape like an offering, due to interaction with the atmosphere at the time of falling. As a result, during linear polarization, the amount of rain attenuation received by horizontally polarized radio waves and vertically polarized radio waves differs.

Rain scattering is a phenomenon in which when a transmitting antenna beam crosses a raindrop, a part of a radio wave is scattered in all directions by the raindrop, and becomes an interference wave for other communication systems using the same frequency band. In particular, in the case of digital television broadcasting, it is necessary to maintain the line quality at a certain level or higher, and in order to keep the power of the receiving unit constant even when the terrestrial transmitting station rains, the transmission power must be compensated for rain attenuation. Is increased. This transmission power control is based on the C / N required by the line quality and the modulation method.
(Carrier to Noise ratio: carrier power to noise power ratio) plus this rain attenuation, C /
The transmission power is increased so that N becomes C / N in fine weather. In that case, there is a possibility that the intensity of rainfall scattering is increased due to an increase in transmission power, and interference with other communication systems is increased.

[0005] As described above, due to the rain attenuation, the broadcast signal C
/ N deteriorates, so that a good reception state may not be obtained. In particular, the C / N required for reception differs depending on the modulation method. Therefore, 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 have a so-called trade-off relationship. However, there is a conflicting demand for transmitting information using a modulation scheme that can receive at a low C / N that is strong against rain attenuation.

[0006] Therefore, the digital television broadcasting station performs hierarchical modulation broadcasting for simultaneously transmitting broadcasts of a plurality of modulation schemes of a normal broadcast and a rain-corresponding broadcast of a modulation scheme having strength against rain attenuation. . This allows
On the receiving device side, a high-level broadcast receiving state of normal broadcasting that requires a high C / N but a high bit rate per frequency bandwidth is received, and a bit rate per frequency bandwidth is low but received at a low C / N The low-level broadcast reception state of the possible rainfall broadcast is switched according to the reception state.

FIG. 13 shows such a change in weather and C / N.
FIG. 6 is a diagram showing transitions according to the values of. In FIG. 13, C /
The value a [dB] of N indicates a threshold for transitioning between the high-layer broadcast reception state and the low-layer broadcast reception state.

First, when the value of C / N falls below a [dB] at a transition point 131 in a short time, a transition is made from the high-layer broadcast reception state to the low-layer broadcast reception state. When the value exceeds a [dB], the low-layer broadcast reception state transits to the high-layer broadcast reception state, and when the value of C / N falls below a [dB] at the transition point 133, the high-layer broadcast reception state changes to low. The state transits to the hierarchical broadcast reception state.

Next, when the value of C / N exceeds a [dB] at the transition point 134 in a short time, the state transitions from the low-layer broadcast reception state to the high-layer broadcast reception state. When the value of A falls below a [dB], the state transitions from the high-layer broadcast reception state to the low-layer broadcast reception state. When the value of C / N exceeds a [dB] at the transition point 136, the low-layer broadcast reception state changes. When the value of C / N falls below a [dB] at the transition point 137, the state transitions from the high-level broadcast reception state to the low-level broadcast reception state. When the value exceeds a [dB], the state transits from the low-layer broadcast reception state to the high-layer broadcast reception state.

[0010]

However, in the above-described conventional hierarchical modulation broadcasting, the receiving apparatus automatically switches between a high-level broadcast receiving state of a normal broadcast and a low-level broadcast receiving state of a rainy broadcast. There is a method of using C / N as an automatic switching parameter for performing a state transition, but in this case, the C / N threshold for automatic switching is only one predetermined point. On the other hand, since the change in the weather is not uniform, the temperature falls below or rises from this threshold many times in a short time. There has been an inconvenience that the hierarchical broadcast receiving state is frequently switched in a short time, which may hinder stable viewing of the user.

Further, since the change in weather cannot be predicted at the time of shipment of the receiving apparatus, if the threshold of the C / N for automatic switching is fixed, the receiving apparatus side normally broadcasts due to an unexpected change in C / N. The high-level broadcast reception state and the low-level broadcast reception state of the rainy broadcast are frequently switched in a short period of time, which hinders stable viewing of the user.

The present invention has been made in view of the above circumstances, and provides a hierarchically modulated broadcast receiving apparatus capable of receiving information hierarchically transmitted by a plurality of modulation schemes in a stable state. As an issue.

[0013]

SUMMARY OF THE INVENTION A hierarchically modulated broadcast receiving apparatus according to the present invention is a hierarchically modulated broadcast receiving apparatus for receiving information hierarchically transmitted by time-division multiplexing information according to a plurality of modulation schemes. Receiving means for receiving the hierarchically transmitted hierarchical modulation information, demodulating means for demodulating the hierarchical modulation information received by the receiving means in accordance with each layer, and receiving a plurality of hierarchical modulation information in accordance with the demodulated information by the demodulating means A layer modulation transition point generating means for generating a state by changing the timing of state transition at the time of transition to each layer, and any one of a plurality of layer modulated broadcast information according to the transition timing generated by the layer modulation transition point generating means Switching means for switching and outputting, and reproducing means for reproducing the hierarchically modulated broadcast information switched and output by the switching means. That.

Therefore, according to the present invention, the following operations are performed. Digital television broadcasting is received by the receiving means,
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 section demodulates the received signal and outputs a transport stream. The arithmetic unit generates a low-layer / high-layer switching signal by the hierarchical modulation transition point generating means according to the demodulation information detected by the demodulation unit. The non-volatile memory stores parameters for generating a low-level / high-level switching signal. The switching unit separates and decodes the transport stream into a lower layer or higher layer elementary stream by a lower layer / high layer switching signal, and outputs a video signal and an audio signal.

[0016]

Embodiments of the present invention will be described below. The hierarchically modulated broadcast receiving apparatus according to the present embodiment automatically transitions between a high-level broadcast receiving state of normal broadcasting and a low-level broadcast receiving state of rainy-response broadcast on the receiving side according to the value of C / N. At the time of transition from the high-layer broadcast reception state to the low-layer broadcast reception state based on the C / N value at the transition point, and between the low-layer broadcast reception state and the high-layer broadcast reception state. Hysteresis (Hysteresis)
s), and by setting a time constraint on the transition, frequent short-term transitions are suppressed, so that stable viewing of the user is not hindered.

FIG. 1 is a block diagram showing a configuration of a digital television broadcast receiver to which the hierarchical modulation broadcast receiving apparatus according to the present embodiment is applied. The digital television broadcast receiver 1 includes an antenna 2 for receiving digital television broadcast, and an LNB (Low Noi) for amplifying a signal attenuated by a propagation loss received by the antenna 2 to an appropriate level.
se Block down converter: a low noise amplifier (IF) 3 and an IF (I
a set-top box 4 for demodulating and decoding an intermediate frequency (intermediate frequency) signal to output a video signal S5 and an audio signal S6; a monitor 12 for reproducing the video signal S5 and the audio signal S6 output from the set-top box 4; And a speaker 13.

The set-top box 4 demodulates an IF signal and outputs a transport stream S1. The set-top box 4 outputs a lower layer / higher layer switching signal S3 according to the C / N information S2 detected by the demodulator 5. , A non-volatile memory 8 for storing a parameter 11 for generating the low-level / high-level switching signal S3, and a low-level / high-level transport stream S1. DEMUX (D) that separates into lower layer or higher layer elementary stream S4 by layer switching signal S3
e-Multiplexing equipment:
A demultiplexer (demultiplexer unit) 6 and a decoder unit 9 that decodes the elementary stream S4 and outputs a video signal S5 and an audio signal S6.

In the digital television broadcast receiver 1 described above, the digital television broadcast is received by the antenna 2 for digital television broadcast reception. LNB
3 amplifies the signal attenuated by the propagation loss to an appropriate level. The set top box 4 demodulates and decodes the IF signal amplified by the LNB 3, and outputs a video signal S5 and an audio signal S6. The monitor 12 and the speaker 13 display and reproduce the video signal S5 and the audio signal S6 output from the set-top box 4 by displaying and outputting the video, respectively.

In the set-top box 4, the demodulation unit 5 demodulates the IF signal to convert the transport stream S1.
Is output. The arithmetic unit 7 detects the C detected by the demodulation unit 5
The lower-layer / higher-layer switching signal S3 is generated by the layer modulation transition point generator 10 according to the / N information S2. The nonvolatile memory 8 stores a parameter 11 for generating the low hierarchy / high hierarchy 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 9 decodes the elementary stream S4 and outputs a video signal S5 and an audio signal S6.

FIG. 2 is a diagram showing the configuration of the demodulation unit. In FIG. 2, a demodulation unit 5 includes a tuner 21 for selecting a reception frequency of an IF signal and a TC8PSK (Trellis Coded Mod) for the IF signal of the selected reception frequency.
ulation 8 Phase Shift Key
ing) scheme, and a higher-layer (TC8PSK) demodulation section 22 for demodulating the IF signal of the selected reception frequency by QPSK.
K (Quadrature Phase Shift)
Keying) or BPSK (Binary Pha)
A low-layer (QPSK, BPSK) demodulation unit 23 that demodulates the signal by a Shift Keying method, a demodulated signal is decoded by a Viterbi decoder, and a deinterleaver (D
A decoding unit (Viterbi, deinterleave, RS) 24 that performs RS (Reed-Solomon) decoding for error correction decoding via e-interleaver, and descrambles only the packets of the contract channel among the decoded packets. A descrambler 25 is provided.

In the demodulation unit 5 described above, the tuner 21
Selects the reception frequency of the IF signal and selects the higher layer (TC8PS
K) The demodulation unit 22 converts the IF signal of the selected reception frequency into T
Demodulation is performed by the C8PSK method. Lower hierarchy (QPSK, B
The (PSK) demodulation unit 23 demodulates the IF signal of the selected reception frequency according to the QPSK or BPSK method. A decoding unit (Viterbi, deinterleave, RS) 24 decodes the demodulated signal with a Viterbi decoder, and further performs RS (Reed-Solomon) decoding through a deinterleaver for error correction decoding. The descrambler 25 descrambles only the packet of the contract channel among the decoded packets.

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

FIG. 3 is a diagram showing a configuration of the decoder section. In FIG. 3, the decoder unit 9 is a high-layer decoder unit 31 that decodes the high-layer elementary stream S11 separated by the DEMUX (separator unit) 6.
And a low-layer decoder unit 32 that decodes the low-layer elementary stream S12 separated by the DEMUX (separator unit) 6.

The high-layer decoder 31 is an MP for expanding the video portion of the high-layer elementary stream S11.
EG (Moving Picture Experts)
Group) The video decoder 33 converts the decompressed video data into the NTSC format and converts it into the high-level video signal S1.
NTSC (National Telev.)
conversion unit 34, an MPEG audio decoder 35 for decompressing the audio part of the high-level elementary stream S11, and a D for converting the decompressed digital audio data to analog and outputting a high-level audio signal S14. / A converter 36
And is configured.

The low-layer decoder 32 is an MP for expanding the video portion of the low-layer elementary stream S12.
An EG video decoder 37, an NTSC conversion unit 38 that converts the expanded video data into the NTSC format and outputs a lower hierarchy video signal S15, and an MPEG audio decoder 39 that expands the audio portion of the lower hierarchy elementary stream S12. D / A for converting the expanded digital audio data to analog and outputting a low-level audio signal S16
And a converter 40.

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

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

FIG. 4 is a diagram showing the operation according to the configuration of the DEMUX (separator unit). In FIG. 4, the transport stream S17 of the high layer and the low layer output from the demodulation unit 5 shown in FIG.
Information of each layer is time-division multiplexed, such as (low layer), H (high layer).

The DEMUX (separator unit) 6 includes an arithmetic unit 7
The switch of the internal switch is switched to the higher layer side or the lower layer side in accordance with the low layer / high layer switching signal S3 from the CPU, and the input time-division multiplexed high layer and low layer transport stream S17 is converted to a high layer. Hierarchical elementary stream S11 or low-level elementary stream S1
2 and output.

The high-level elementary stream S11 output from the DEMUX (separator unit) 6 has only high-level information such as H (high-level), H (high-level)... On the high-level side. Separated. Also, in the low-layer elementary stream S12, only the low-layer information such as L (low-layer), L (low-layer)... Is separated on the low-layer side.

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

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 a high-level broadcast is being received. Specifically, the arithmetic unit 7 converts the higher layer switching signal S3 generated by the layer modulation transition point generator 10 according to the C / N information S2 supplied from the demodulator 5 into a DEMU.
It is determined whether or not X (separator unit) 6 is being supplied.

If it is determined in step S1 that the broadcast is in the high-layer broadcast reception state, the process proceeds to step S2. If it is determined that the broadcast is not in the high-layer broadcast reception state but is in the low-layer broadcast reception state, the process proceeds to step S4. At the time of receiving the high-level broadcast, it is determined in step S2 whether the value of C / N has fallen below a [dB]. Specifically, in FIG.
A point in time when the value of C / N falls below a [dB] of a threshold for transition from the high-layer broadcast reception state to the low-layer broadcast reception state is detected.

When the value of C / N falls below a [dB] in step S2, the state transitions from the high-layer broadcast reception state to the low-layer broadcast reception state in step S3. More specifically, in FIG. 5, the computing unit 7 determines at a transition point 51 where the value of C / N falls below a [dB] of the threshold for transition from the high-layer broadcast reception state to the low-layer broadcast reception state. , 53, the state transitions from the high-layer broadcast reception state to the low-layer broadcast reception state. At this time, the arithmetic unit 7 supplies the DEMUX (separator unit) 6 with the lower layer switching signal S3 generated by the layer modulation transition point generator 10 based on the C / N information S2 supplied from the demodulator 5. The DEMUX (separator unit) 6 switches the contact point of the internal switch to the lower hierarchy side by the lower hierarchy switching signal S3 from the arithmetic unit 7 to input the time-division multiplexed higher and lower hierarchy. The transport stream S17 is separated into low-layer elementary streams S12 and output.

In the low hierarchy broadcast receiving state, step S4
Then, it is determined whether or not the value of C / N exceeds a + b [dB]. More specifically, in FIG.
A point in time when the value of / N exceeds a threshold a + b [dB] of the transition from the low-layer broadcast reception state to the high-layer broadcast reception state is detected.

In step S4, the value of C / N is a + b [d
B], the state transitions from the low-layer broadcast reception state to the high-layer broadcast reception state in step S5. In particular,
In FIG. 5, the arithmetic unit 7 calculates the value of 5 at the transition point 52 where the value of C / N exceeds the threshold a + b [dB] of the transition from the lower layer broadcast reception state to the higher layer broadcast reception state.
As shown by 4, the state transitions from the low-level broadcast reception state to the high-level broadcast reception state. At this time, the arithmetic unit 7 converts the higher hierarchy switching signal S3 generated by the hierarchical modulation transition point generator 10 based on the C / N information S2 supplied from the demodulator 5 into a DEMU.
X (separator unit) 6 DEMUX (separator unit)
6 switches the contact point of the internal switch to the higher layer side according to the higher layer switching signal S3 from the arithmetic operation unit 7, and converts the input time-division multiplexed higher layer and lower layer transport stream S17 to higher layer. Hierarchical elementary stream S
11 and output.

Then, returning to step S2, the determination and processing of steps S2 to S5 are repeated.

FIG. 7 shows a case where a hysteresis of the value of C / N is provided at a change point of reception in the high hierarchy / low hierarchy. As a result, as shown in FIG.
, The threshold a [dB] of the transition 72 from the high-level broadcast reception state 71 to the low-level broadcast reception state 73 and the transition from the low-level broadcast reception state 74 to the high-level broadcast reception state 71 Since hysteresis is given to the threshold a + b [dB] of the transition 75, a
Since the section between [dB] and a + b [dB] is a dead zone, in the low hierarchy broadcast reception state 74, if the frequency exceeds a [dB] and does not exceed a + b [dB], frequent low hierarchy broadcast reception is performed. States 73 and 74 and high-level broadcast reception state 71
The transitions 72, 75 between and can be prevented.

In the above description, the arithmetic unit 7 counts the number of transitions p [times] during the fixed time m [s], and
When the counted number exceeds a predetermined number, the value of b [dB] of the threshold a + b [dB] of the transition from the low-layer broadcast reception state to the high-layer broadcast reception state is increased. Then, the transition is stored as the parameter 11 of the nonvolatile memory 8, and thereafter, the above-described transition is determined using the value of b [dB] newly stored as the parameter 11 of the nonvolatile memory 8.

As a result, a large C / N ratio that was not assumed when the digital television broadcast receiver was shipped can be obtained.
, Or when installed in an installation location where the change in the C / N value is relatively large compared to other locations, the low-level broadcast reception state and the high-level broadcast frequently occur in a short time. The transition between the reception state and the reception state can be suppressed.

FIG. 8 is a diagram showing a case where the transition has a time constraint. FIG. 9 is a flowchart showing an operation when a transition is restricted in terms of time. The digital television broadcast receiver 1 uses the arithmetic unit 7 of the set-top box 4 to output the C / N information S supplied from the demodulation unit 5.
2 is constantly monitored. In FIG. 9, in step S11,
It is determined whether or not a high-level broadcast is being received. Specifically, the arithmetic unit 7 converts the higher hierarchy switching signal S3 generated by the hierarchical modulation transition point generator 10 according to the C / N information S2 supplied from the demodulator 5 into a DEMUX (separator) 6 It is determined whether or not it is being supplied to.

If it is determined in step S11 that the broadcast is in the high-layer broadcast receiving state, the process proceeds to step S12. If it is determined that the broadcast is not in the high-layer broadcast but is in the low-layer broadcast, the process proceeds to step S14. When receiving high-level broadcasts,
In step S12, it is determined whether or not the time during which the value of C / N falls below a [dB] has continued for s [s]. In particular,
In FIG. 8, the arithmetic unit 7 determines that the time when the value of C / N has fallen below the threshold a [dB] of the transition from the high-layer broadcast reception state to the low-layer broadcast reception state has lasted s [s]. Is detected.

In step S12, the value of C / N is a [dB].
If s [s] continues for a time that is less than
At 3, the state transitions from the high-layer broadcast reception state to the low-layer broadcast reception state. More specifically, in FIG.
A transition point 81 in which the value of N falls below a [dB] of the threshold for transition from the high-layer broadcast reception state to the low-layer broadcast reception state for s [s] continues, as indicated by a right arrow at 83. The state transitions from the high-layer broadcast reception state to the low-layer broadcast reception state. At this time, the arithmetic unit 7 converts the low-layer switching signal S3 generated by the hierarchical modulation transition point generation unit 10 based on the C / N information S2 supplied from the demodulation unit 5 into a DEMUX.
(Separator unit) 6 DEMUX (separator) 6
Switches the contact point of the internal switch to the lower layer side according to the lower layer switching signal S3 from the arithmetic unit 7, and converts the input time-division multiplexed transport stream S17 of the higher layer and the lower layer to the lower layer. Elementary stream S1
2 and output.

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

In step S14, the value of C / N is a [dB].
If the time exceeding t has continued for t [s], step S1
At 5, the state transitions from the low-layer broadcast reception state to the high-layer broadcast reception state. More specifically, in FIG.
At the transition point 82 where the time when the value of N exceeds the threshold a [dB] of the transition from the lower hierarchy broadcast reception state to the higher hierarchy broadcast reception state for t [s] (> s [s]) continues, 83
As shown by a left-pointing arrow, the state transitions from the low-layer broadcast reception state to the high-layer broadcast reception state. At this time, the arithmetic unit 7
Supplies the DEMUX (separator) 6 with the higher layer switching signal S3 generated by the layer modulation transition point generator 10 based on the C / N information S2 supplied from the demodulator 5. DEMU
The X (separator unit) 6 switches the contact point of the internal switch to the higher layer side in response to the higher layer switching signal S3 from the arithmetic unit 7, and receives the time-division multiplexed higher and lower layer signals. The transport stream S17 is separated into a high-layer elementary stream S11 and output.

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

Thus, even when the value of C / N fluctuates frequently in a short period of time, the time s during which the transition from the high-layer broadcast reception state to the low-layer broadcast reception state falls below a [dB], s, is obtained. [S] and the threshold a [d of the transition from the lower hierarchy broadcast reception state to the higher hierarchy broadcast reception state
B], a time constraint such as a time t [s] (> s [s]) exceeding the time s is given in a [dB].
Since the time between [s] and the time t [s] (> s [s]) becomes a dead zone, even if the time exceeding a [dB] continues for s [s] in the low hierarchy broadcast receiving state, If the time exceeding a [dB] does not continue for t [s] (> s [s]), it is possible to prevent frequent transition between the low-layer broadcast reception state and the high-layer broadcast reception state from occurring. it can.

In the above description, the arithmetic unit 7 counts the number of transitions p [times] during the predetermined time m [s], and
When the count exceeds a predetermined number, a time s [s] that is less than a threshold [a] [dB] indicating a transition between the low-level broadcast reception state and the high-level broadcast reception state. The value of the time constraint of the time t [s] that exceeds the threshold a [dB] is increased and stored as the parameter 11 of the nonvolatile memory 8, and thereafter, the parameter 11 of the nonvolatile memory 8 is newly added.
The transition described above is determined using the value of the time constraint of the time s [s] and the time t [s] stored as

Thus, when the C / N fluctuates up and down gently, which was not assumed at the time of shipment of the digital television broadcast receiver, the value of the C / N can be reduced compared to other places. Even when installed in an installation location where the change rises and falls relatively slowly, it is possible to suppress frequent transitions between the low-level broadcast reception state and the high-level broadcast reception state in a short time.

FIG. 10 is a view showing a combination in a case where the transition C / N value is given a hysteresis and a time constraint. FIG. 11 is a flowchart showing a combination operation in a case where hysteresis and a time constraint are given to the C / N value to be changed.

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, it is determined in step S21 whether or not a high-level broadcast is being received. Specifically, the arithmetic unit 7 includes the demodulation unit 5
The higher layer switching signal S3 generated by the layer modulation transition point generator 10 according to the C / N information S2 supplied from the
It is determined whether or not it is supplied to the MUX (separator unit) 6.

If it is determined in step S21 that the broadcast is in the high-level broadcast reception state, the process proceeds to step S22. If it is determined that the broadcast is not in the high-level broadcast reception state but is in the low-level broadcast reception state, the process proceeds to step S25. When receiving high-level broadcasts,
In step S22, it is determined whether the value of C / N has fallen below a [dB]. Specifically, in FIG. 10, the arithmetic unit 7 determines that the value of C / N is a [d, which is the threshold of the transition from the high-layer broadcast reception state to the low-layer broadcast reception state.
B].

In step S22, the value of C / N is set to a [dB].
Is smaller than the value of C / N in step S23.
It is determined whether or not the time that is less than [dB] has continued for s [s]. More specifically, in FIG.
It is detected that the time when the value of / N falls below the threshold value a [dB] of the transition from the high-layer broadcast reception state to the low-layer broadcast reception state continues for s [s].

In step S23, the value of C / N is a [dB].
If s [s] continues for a time that is less than
At 4, the state transitions from the high-layer broadcast reception state to the low-layer broadcast reception state. More specifically, in FIG.
At the transition point 101 where the value of / N is lower than the threshold a [dB] of the transition from the high-level broadcast reception state to the low-level broadcast reception state for s [s], the transition point 101 continues. The state transits from the broadcast receiving state to the lower hierarchical broadcast receiving state. At this time, the arithmetic unit 7 supplies the DEMUX (separator unit) 6 with the lower layer switching signal S3 generated by the layer modulation transition point generator 10 based on the C / N information S2 supplied from the demodulator 5. The DEMUX (separator unit) 6 switches the contact point of the internal switch to the lower hierarchy side by the lower hierarchy switching signal S3 from the arithmetic unit 7 to input the time-division multiplexed higher and lower hierarchy. The transport stream S17 is separated into low-layer elementary streams S12 and output.

In the low hierarchy broadcast receiving state, step S25
Then, it is determined whether or not the value of C / N exceeds a + b [dB]. More specifically, in FIG.
A point in time when the value of C / N exceeds a threshold a + b [dB] of the transition from the low-layer broadcast reception state to the high-layer broadcast reception state is detected.

In step S25, the value of C / N is a + b [d
B], it is determined in step S26 whether the time when the value of C / N exceeds a + b [dB] has continued for t [s]. Specifically, in FIG. 10, the arithmetic unit 7 determines that the value of C / N is a + b [d, which is a threshold for transition from the low-level broadcast reception state to the high-level broadcast reception state.
B] is detected to last for t [s].

In step S26, the value of C / N is a + b [d
If the time that exceeds B] continues for t [s], the state transitions from the low-layer broadcast reception state to the high-layer broadcast reception state in step S27. Specifically, in FIG.
Is the threshold of a + b [dB] for the transition of the value of C / N from the low-level broadcast reception state to the high-level broadcast reception state.
At the transition point 102 where the time exceeding t has continued for t [s] (> s [s]), the state transitions from the low-layer broadcast reception state to the high-layer broadcast reception state as indicated by 104. At this time, the arithmetic unit 7
Supplies the DEMUX (separator) 6 with the higher layer switching signal S3 generated by the layer modulation transition point generator 10 based on the C / N information S2 supplied from the demodulator 5. DEMU
The X (separator unit) 6 switches the contact point of the internal switch to the higher layer side in response to the higher layer switching signal S3 from the arithmetic unit 7, and receives the time-division multiplexed higher and lower layer signals. The transport stream S17 is separated into a high-layer elementary stream S11 and output.

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

Thus, even when the value of C / N fluctuates frequently in a short time, the threshold a [dB] of the transition from the high-level broadcast reception state to the low-level broadcast reception state and the low-level broadcast reception Since hysteresis is given to a + b [dB] of the threshold of the transition from the state to the high-layer broadcast receiving state, the section between a [dB] and a + b [dB] becomes a dead zone, so that the low-layer broadcast A in the receiving state
Even if it exceeds [dB], it must further exceed a + b [dB], and the threshold a [d of the transition from the high-layer broadcast reception state to the low-layer broadcast reception state
B] and the threshold a of the transition from the low-level broadcast reception state to the high-level broadcast reception state
Since a time constraint is given as a time t [s] (> s [s]) exceeding + b [dB], a [dB] and a + b
In [dB], time s [s] and time t [s] (> s
[S]) is a dead zone, so in the low-level broadcast receiving state, even if the time exceeding a [dB] continues for s [s], the time exceeding a + b [dB] still exceeds t [s] ]
(> S [s]) If it does not continue, it is possible to prevent the frequent transition between the lower-layer broadcast reception state and the higher-layer broadcast reception state from occurring, and to more flexibly control the frequent transition. It can be carried out.

In the above description, the arithmetic unit 7 counts the number of transitions p [times] during the fixed time m [s], and
When the count exceeds a predetermined number, the value of b [dB] of the threshold a + b [dB] of the transition from the low-layer broadcast reception state to the high-layer broadcast reception state is increased. At the same time, a time s [s] below the threshold a [dB] and a time t [s above the threshold a + b [dB] indicating the transition between the lower layer broadcast receiving state and the higher layer broadcast receiving state. ]
Are respectively increased and stored as the parameter 11 of the nonvolatile memory 8, and thereafter, the parameter b is newly stored as the parameter 11 of the nonvolatile memory 8.
[DB] threshold value and time s [s]
The transition described above is determined using the value of the time constraint of time t [s].

As a result, a large C / N ratio that was not assumed when the digital television broadcast receiver was shipped
, Or when installed in an installation location where the change in C / N value is relatively large compared to other places, and when there is a gradual change in C / N Also, when installed in an installation location where the change in the value of C / N rises and falls relatively slowly as compared with other locations, the frequent low-level broadcast reception state and high-level broadcast reception state frequently occur in a short time. Can be more flexibly suppressed.

FIG. 12 is a diagram showing a state transition of a combination in a case where hysteresis and a time constraint are given to the C / N value to be transitioned. In FIG. 12, for example, a method of providing hysteresis in a transitioning C / N is such that a transition is made immediately when a target transition point is exceeded, so that a transition from the high-layer broadcast reception state 121 to the low-layer broadcast reception state 123 is performed. Is reduced to near the reception limit of the high-layer broadcast reception state 121 as indicated by 122, and the time constraint s [s] of the transition from the high-layer broadcast reception state 121 to the low-layer broadcast reception state 123 is indicated by 122. Is reduced as indicated by 122 so that the decoding error by the decoder unit 9 that occurs when the reception level falls below the reception limit can be minimized while maintaining the high-layer broadcast reception state 121 as much as possible.

On the other hand, when shifting from the low-level broadcast receiving state 123 to the high-level broadcast receiving state 121, the time constraint t [s] of the transition from the low-level broadcast receiving state 123 to the high-level broadcast receiving state 121 is set to 124. , A transition point a [d indicated by 122 from a high-layer broadcast reception state 121 to a low-layer broadcast reception state 123 is provided.
B] and the hysteresis of the value of C / N between the low-level broadcast reception state 123 and the transition point a + b [dB] indicated by 124 from the high-level broadcast reception state 121 to the high-level broadcast reception state 121. The transition to the high-layer broadcast reception state 121 can be executed after securing the C / N.

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

[0066]

The hierarchically-modulated broadcast receiving apparatus according to the present invention is a hierarchically-modulated broadcast receiving apparatus that receives information hierarchically transmitted by time-division multiplexing information according to a plurality of modulation schemes. Receiving means for receiving the hierarchical modulation information, demodulating means for demodulating the hierarchical modulation information received by the receiving means according to each layer, and transiting a plurality of hierarchical modulation information reception states according to the demodulated information by the demodulating means. A layer modulation transition point generating means for generating a timing by changing the timing at each transition to each layer, and switching and outputting any one of a plurality of layer modulated broadcast information according to the transition timing generated by the layer modulation transition point generating means Switching means for reproducing the hierarchically-modulated broadcast information switched and output by the switching means. When automatically switching between the 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 has hysteresis, so that demodulation information due to uneven weather changes For this change, it is possible to prevent short-term frequent transitions that hinder the user's viewing.

In the hierarchical modulation broadcast receiving apparatus according to the present invention, the hierarchical transmission includes at least high-layer transmission having a relatively high transmission rate and low-layer transmission having a relatively low transmission rate. / N (carrier power-to-noise power ratio), and when C / N (carrier power-to-noise power ratio) falls below the first value in the high-layer modulation information reception state by high-layer transmission, low-layer modulation information reception is performed. State, and when the C / N (carrier power to noise power ratio) exceeds a second value larger than the first value in the lower layer modulation information reception state, the state transits to the higher layer modulation information reception state. When the value falls below or exceeds the set C / N value, it is possible to make a transition immediately, and C is a transition point from the high-layer modulation information reception state to the low-layer modulation information reception state.
By setting the first value of / N to a relatively small value and setting it to the limit of the high-level modulation information reception state, a decoding error occurs in the decoder section of the reproducing means while viewing the high-level broadcast as much as possible. Thus, it is possible to minimize the time during which the user cannot view the content.

In the hierarchical modulation broadcast receiving apparatus according to the present invention, when the transition to each layer occurs a predetermined number of times or more within a predetermined time, the second value is updated to a larger value. Since the second value is stored in the storage means and the updated second value is used in place of the second value at the time of the subsequent transition, when the transition occurs more than a certain number of times during a certain time, the high value is set. By increasing the C / N hysteresis at the transition point between the hierarchical broadcast receiving state and the lower hierarchical broadcast receiving state and storing the hysteresis in the non-volatile memory, it is possible to change the weather and installation conditions more than expected at the time of design. C / N
The effect is that it is possible to cope with a change in vertical movement.

In the hierarchical modulation broadcast receiving apparatus according to the present invention, the hierarchical transmission includes at least high-layer transmission having a relatively high transmission rate and low-layer transmission having a relatively low transmission rate. / N (carrier power-to-noise power ratio), and in a state of receiving higher-layer modulation information by higher-layer transmission, the transition point C
/ N (carrier power to noise power ratio), the state transits to the lower hierarchical modulation information receiving state. In the lower hierarchical modulation information receiving state, C / C is applied over a second period longer than the first period.
When N (carrier power-to-noise power ratio) is exceeded, the state transits to the high-layer modulation information reception state. When automatically switching between the high-layer broadcast reception state and the low-layer broadcast reception state, the transition timing is set for each layer. To the lower-layer modulation information receiving state when the signal falls below the transition point continuously for a certain period of time s [s] or more, and conversely from s [s]. The transition from the low-layer modulation information reception state to the high-layer modulation information reception state when the transition point exceeds the transition point for a long period of time t [s] or more is performed. On the other hand, it is possible to prevent short-time frequent transitions that hinder the user's viewing, and it is effective for a large vertical movement of the C / N for a very short time.

Further, in the above-mentioned hierarchically-modulated broadcast receiving apparatus, when the transition to each of the above-mentioned layers occurs a predetermined number of times or more within a predetermined time, the first period and the second period are set 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 updated second period are replaced with the values of the first period and the second period during the subsequent transition. Since the value of the second period is used, if a certain number of transitions occur during a certain time, the first period and the second period of the transition point between the high-layer broadcast reception state and the low-layer broadcast reception state And the updated values of the first period and the second period are stored in the non-volatile memory, so that the C / N per unit time can be made longer than expected at the time of design due to changes in weather and installation conditions. Respond to smaller changes An effect that can be.

In the hierarchical modulation broadcast receiving apparatus according to the present invention, the hierarchical transmission includes at least high-layer transmission having a relatively high transmission rate and low-layer transmission having a relatively low transmission rate. / N (carrier power-to-noise power ratio), and when C / N (carrier power-to-noise power ratio) is lower than the first value in the high-layer modulation information reception state by high-layer transmission, When the C / N (carrier power to noise power ratio) at the transition point falls below the period, the state transits to the lower hierarchical modulation information receiving state, and in the lower hierarchical modulation information receiving state, C / N (carrier power to noise power ratio). Exceeds a second value greater than the first value and over a second period longer than the first period.
/ N (carrier power-to-noise power ratio), the state transits to the higher-layer modulation information reception state, so that the C / N value at the transition point has a hysteresis and the transition point continues for a certain time or more. By combining the method with the method of transitioning when the value falls below or exceeds the value, it is possible to more flexibly control the frequent transition.

In the hierarchical modulation broadcast receiving apparatus according to the present invention, when the transition to each layer occurs a predetermined number of times within a predetermined time, the second value is updated to a larger value. Since the second value is stored in the storage means and the updated second value is used instead of the second value at the time of the subsequent transition, a large change in C / N that was not assumed at the time of shipment may occur. C / compared with other places
Even when the device is installed in an installation location where the change in the value of N is relatively large, the C / N value changes gently up and down, or the change in the C / N value is smaller than in other places. Even when installed in a relatively gently rising and falling installation location, it is possible to more flexibly suppress frequent transitions between the low-level broadcast reception state and the high-level broadcast reception state in a short time. .

Further, in the above-described hierarchical modulation broadcast receiving apparatus, when the transition to each layer occurs a predetermined number of times within the 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 unit, and the values of the first and second periods updated in the subsequent transition are replaced with the values of the first period and the second period.
And the second period, the C / N value is large when the C / N ratio is not expected at the time of shipment, or the C / N value is compared with other places. Even when installed in a large installation location, there is a gradual increase or decrease in the C / N change, or an installation in which the C / N value changes relatively gently up or down compared to other places Even when installed in a place, it is possible to flexibly suppress the transition between the low-level broadcast reception state and the high-level broadcast reception state frequently in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital television broadcast receiver to which a hierarchical modulation broadcast receiving device according to the present embodiment is applied.

FIG. 2 is a diagram illustrating a configuration of a demodulation unit.

FIG. 3 is a diagram illustrating a configuration of a decoder unit.

FIG. 4 is a diagram illustrating an operation according to a configuration of a DEMUX (separator unit).

FIG. 5 is a diagram showing a case where hysteresis is given to the value of C / N to be changed.

FIG. 6 is a flowchart showing an operation when hysteresis is given to a C / N value to be changed.

FIG. 7 is a diagram illustrating a case where hysteresis of a value of C / N is provided at a change point of reception in a high hierarchy / low hierarchy.

FIG. 8 is a diagram showing a case where a transition is given a time constraint.

FIG. 9 is a flowchart showing an operation when a transition is given a time constraint.

FIG. 10 is a diagram showing a combination in a case where hysteresis and a temporal constraint are given to the value of C / N to be changed.

FIG. 11 is a flowchart showing an operation of a combination in a case where hysteresis and a time constraint are given to the value of C / N to be changed.

FIG. 12 is a diagram showing a state transition of a combination in a case where hysteresis and a time constraint are given to the C / N value to be transitioned.

FIG. 13 is a diagram showing a change in weather and a transition based on a value of C / N.

[Explanation of symbols]

1 ... Digital television broadcasting receiver, 2 ... Antenna, 3 ... LNB, 4 ... Set top box, 5 ...
... Demodulation unit, 6 DEMUX (separator unit), 7 arithmetic unit unit, 8 nonvolatile memory, 9 decoder unit, 10
... Hierarchical modulation transition point generation unit, 11 ... parameter, 12 ...
... monitor, 13 ... speaker, 21 ... tuner, 2
2 High-level (TC8PSK) demodulator, 23 Low-level (QPSK, BPSK) demodulator, 24 Decoder (Viterbi, deinterleave, RS), 25 Descrambler, 31 High-level decoder , 32... Low-layer decoder, 33... MPEG video decoder, 34... NTS
C 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-layer reception state, 73, 74: Low-layer reception state, 81: Transition point, 82: Transition point, 101
... transition point, 102 ... transition point, 121 ... high hierarchy broadcast viewing state, 123 ... low hierarchy broadcast viewing state

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 7/24 H04H 1/02 A // H04H 1/02 7/00 7/00 H04N 7/13 ZF Terms (reference) 5C025 BA03 BA20 BA25 DA01 5C059 MA00 MA32 RB02 RD03 RD07 SS02 TA39 TA71 TC21 TD12 TD13 UA05 UA38 5K014 AA01 BA08 BA11 DA06 FA11 FA16 HA06 HA10 5K028 AA01 BB04 CC05 DD01 DD01 EE03 PP11 BB03 A01 BB01 FF11 JJ07

Claims (8)

[Claims] 1. A hierarchically-modulated broadcast receiving apparatus for receiving information hierarchically transmitted by time-division multiplexing information according to a plurality of modulation schemes, comprising: receiving means for receiving the hierarchically transmitted hierarchical modulation information. Demodulating means for demodulating the hierarchical modulation information received by the receiving means in accordance with each layer, and timing for transitioning the plurality of hierarchical modulation information reception states to each layer in accordance with the demodulated information by the demodulating means. And a switching means for switching and outputting any of the plurality of hierarchical modulation broadcast information according to the transition timing generated by the hierarchical modulation transition point generating means. And reproduction means for reproducing the hierarchically-modulated broadcast information switched and output by the switching means. Hierarchical modulation broadcast receiver. 2. The hierarchically modulated broadcast receiving apparatus according to claim 1, wherein the hierarchical transmission includes 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)
In the high-layer modulation information receiving state by the high-layer transmission, when C / N (carrier power to noise power ratio) falls below the first value, the state transits to the low-layer modulation information receiving state, In the reception state, when the C / N (carrier power-to-noise power ratio) exceeds a second value larger than the first value, a transition is made to a high-layer modulation information reception state, wherein the hierarchical modulation broadcast receiving apparatus is characterized in that . 3. The hierarchically-modulated broadcast receiving apparatus according to claim 2, wherein when the transition to each of the layers occurs a predetermined number of times or more within a predetermined time, the second value is updated to a larger value. A hierarchically modulated broadcast receiving apparatus, wherein the updated second value is stored in a storage unit, and the updated second value is used instead of the second value at a subsequent transition. 4. The hierarchically modulated broadcast receiving apparatus according to claim 1, wherein the hierarchical transmission includes at least high-layer transmission having a relatively high transmission rate and low-layer transmission having a relatively low transmission rate, and the demodulation information is C / N (Carrier power to noise power ratio)
In the state where the higher-layer modulation information is received by the higher-layer transmission, the C / N of the transition point extends over the first period or more.
When the ratio falls below (carrier power-to-noise power ratio), the state transits to the lower layer modulation information reception state. In the lower layer modulation information reception state, C / C is applied over a second period longer than the first period.
A hierarchically-modulated broadcast receiving apparatus, wherein a transition to a higher-layered modulated information receiving state is performed when the ratio exceeds N (carrier power to noise power ratio). 5. The hierarchically modulated broadcast receiving apparatus according to claim 4, wherein when the transition to each of the layers occurs a predetermined number of times within a predetermined time, the first period and the second period are set to longer values. To the updated first period and second period
Is stored in the storage means, and the values of the updated first and second periods are used in place of the values of the first and second periods during a subsequent transition. Hierarchical modulation broadcast receiving device. 6. The hierarchically modulated broadcast receiving apparatus according to claim 1, wherein the hierarchical transmission includes at least high-layer transmission having a relatively high transmission rate and low-layer transmission having a relatively low transmission rate, and the demodulation information is C / N (Carrier power to noise power ratio)
In the high-level modulation information receiving state by the high-level transmission, when C / N (carrier power to noise power ratio) falls below a first value and over the first period or more, the C / N of the transition point is changed. When the value falls below N (carrier power to noise power ratio), the state transits to the lower hierarchical modulation information receiving state, and in the lower hierarchical modulation information receiving state, C / N (carrier power to noise power ratio).
Exceeds a second value greater than the first value and over a second period longer than the first period.
A hierarchically-modulated broadcast receiving apparatus, wherein a transition to a higher-layered modulated information receiving state is performed when the ratio exceeds N (carrier power to noise power ratio). 7. The hierarchically modulated broadcast receiving apparatus according to claim 6, wherein when the transition to each of the layers occurs a predetermined number of times within a predetermined time, the second value is updated to a larger value. A hierarchically modulated broadcast receiving apparatus, wherein the updated second value is stored in a storage unit, and the updated second value is used instead of the second value at a subsequent transition. 8. The hierarchically modulated broadcast receiving apparatus according to claim 6, wherein when the transition to each of the layers occurs a predetermined number of times or more within a predetermined time, the first period and the second period are set to longer values. To the updated first period and second period
Are stored in the storage means, and the values of the updated first and second periods are used in place of the values of the first and second periods during a subsequent transition. Hierarchical modulation broadcast receiving device.