JP4643406B2 - Broadcast receiver - Google Patents

Description

  The present invention relates to a broadcast receiving apparatus used in, for example, a vehicle-mounted terrestrial digital television receiver.

  In the ISDB-T (Integrated Services Digital Broadcasting for Terrestrial) system, which is the Japanese terrestrial digital broadcasting system, as shown in Fig. 5, the modulation system is changed in units of segments by having 13 segments in the 6 MHz band. It is a feature that can be done.

  There are a maximum of three combinations (three types) of modulation schemes. As a result, a service for fixed reception is performed by 64QAM (Quadrature Amplitude Modulation) using a plurality of segments, and a service for mobile reception is performed by QPSK (Quadrature Phase Shift Keying: four-phase phase) in the remaining segments. Modulation) services are possible. Information on the modulation scheme of each segment is transmitted by TMCC (Transmission and Multiplex Configuration and Control).

  Further, it is possible to partially receive only one segment by not performing frequency interleaving (rearrangement) across the segments for the central one segment (the portion indicated by the oblique lines in FIG. 5).

  Here, on the transmitting side (broadcasting station), there is a service that simultaneously broadcasts information of the same content using a high quality broadcast signal called “12 segment broadcast” and a low quality broadcast signal called “1 segment broadcast”. is there. This is called a hierarchical transmission service.

  The 12-segment broadcasting is a high quality broadcasting service using 12 of the 13 segments. This 12-segment broadcasting requires a relatively high reception C / N (carrier noise ratio), and is used for transmission of high quality video such as high definition television (HDTV) for fixed reception. On the other hand, 1 segment broadcasting is a low quality broadcasting service using the remaining 1 segment. This one-segment broadcasting is resistant to noise and can be received even with a low reception C / N. However, since a large amount of information cannot be transmitted, it is limited to transmission of basic information and low-quality video.

  In the hierarchized transmission service, information of the same content is sent from the transmission side (broadcasting station) by high quality broadcasting and low quality broadcasting. On the receiving side, both of them can be received, but in a normal state, the reception mode of high-quality broadcasting is set, and high-quality information is reproduced. Further, when the reception situation is bad and the C / N ratio is lowered, the high quality information is reproduced by switching to the low quality broadcast reception mode.

In addition, as a method of switching the reception mode between such high-quality broadcast and low-quality broadcast, the error rate (bit error rate) of the received signal is detected, and when the error rate exceeds a predetermined threshold, the low rate A technique for automatically switching a reception mode so as to receive quality broadcast information is known (see, for example, Patent Document 1). As a result, even if the radio wave reception situation deteriorates due to, for example, rain or obstacles, the broadcast content can be automatically switched to the low-quality broadcast and can be continuously viewed.
JP 2001-111642 A

  For example, when an earthquake or tsunami occurs, emergency broadcasts are broadcast simultaneously from each broadcasting station. In this case, emergency alert information is transmitted in both the high-quality broadcast (12-segment broadcast) and the low-quality broadcast (1-segment broadcast) described above, and the receiving side can receive either broadcast.

  However, in a terrestrial digital television receiver mounted on a moving body such as a vehicle, since the reception area is not fixed, there is a problem that the emergency alert information cannot be stably received depending on the location at that time.

  That is, as shown in FIG. 6, in digital terrestrial broadcasting, even if radio waves are transmitted from the same broadcasting station P0, the 12-segment broadcasting areas E1 and E2 are different, and the 12-segment broadcasting area E1 is It is narrower than the one-segment broadcasting area E2. In this case, if the area E1 of the 12-segment broadcast is a range of the radius L1, the area E2 of the 1-segment broadcast is a range of the radius L2 (> L1). This is due to the difference in the modulation method. Since the 12-segment broadcast realizes the high-quality broadcast by the 64QAM modulation method, even if high-quality information is sent, the range becomes extremely narrow. On the other hand, one-segment broadcasting can take a wide broadcasting area while having low quality by the QPSK modulation method.

  Now, it is assumed that a vehicle Q equipped with a terrestrial digital television receiver is moving while receiving 12-segment broadcasting in the area E1. Here, when the emergency alert is broadcast, if the vehicle Q is moving near the boundary between the area E1 and the area E2, the 12-segment broadcast cannot be stably received, and the contents of the emergency alert may be missed. There is sex.

  In this case, in the method of automatically switching the reception mode only by the error rate as in Patent Document 1, switching to one-segment broadcasting is performed under an unstable situation near the boundary between the area E1 and the area E2. Therefore, emergency alerts cannot be received reliably.

  The present invention has been made in view of the above points, and provides a broadcast receiving apparatus capable of reliably receiving an emergency alert even when the emergency alert is broadcast in an unstable situation during movement. With the goal.

  According to the broadcast receiving apparatus of one aspect of the present invention, the first broadcast signal transmitted simultaneously from the transmission side and the second broadcast signal having lower quality than the first broadcast signal can be switched and received. In a broadcast receiving apparatus having a function, a first determination means for determining whether or not the second broadcast signal can be received during reception of the first broadcast signal, and the first determination means When it is determined by the second determination means that the second broadcast signal can be received, the second determination means for determining the presence or absence of an emergency alarm and the second determination means determines that there is an emergency alarm. And receiving mode switching means for switching from the first broadcasting signal to the receiving mode of the second broadcasting signal.

  According to the present invention, when an emergency alarm is detected during reception of a first broadcast signal that is a high-quality broadcast, the mobile station is switched to the reception mode for the second broadcast signal that is a low-quality broadcast. Even when an emergency alert is broadcast in an unstable situation, the emergency alert can be reliably received.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a broadcast receiving apparatus capable of receiving terrestrial digital broadcasting according to the first embodiment of the present invention. This broadcast receiving apparatus is used as, for example, an in-vehicle terrestrial digital television receiver, and is a reception mode from 12 segment broadcast (first broadcast signal) to 1 segment broadcast (second broadcast signal) during movement. A switching function is provided.

  As shown in FIG. 1, the broadcast receiving apparatus in this embodiment includes a receiving antenna 11, a tuner 12, an OFDM (Orthogonal Frequency Division Multiplexing) demodulator 13, an error corrector 14, a demultiplexer 15, MPEG. (Moving Picture Experts Group) The decoding part 16, the image superimposition part 17, the control part 18, the display part 19, and the speaker 20 are provided.

  The digital transmission signal received by the receiving antenna 11 is frequency-converted by the tuner 12 and then demodulated by the OFDM demodulator 13. Then, an error correction process is performed by the error correction unit 14 and returned to a TS (Transport Stream) packet sent from the broadcasting station. In addition to video / audio packets, TS packets include data broadcasts, electronic program guides: EPG (Electric Program Guide), information necessary for channel selection, and the like. In terrestrial digital broadcasting, since a plurality of programs can be broadcast simultaneously on one transmission channel, a plurality of programs may be sent as the same TS.

  The demultiplexing unit 15 demultiplexes the TS packet according to the purpose, and sends it to the MPEG decoding unit 16 if it is a video / audio packet, and sends it to the control unit 18 if it is a data broadcast packet. The video signal and audio signal obtained by the demultiplexing unit 15 are restored to normal signals by the MPEG decoding unit 16 and output to an external output device such as the display unit 19 (TV monitor) and the speaker 20.

  The control unit 18 controls the entire apparatus. The control unit 18 is composed of a microprocessor, and reads various programs recorded on a recording medium such as a ROM, and executes various processes in accordance with procedures described in the program.

  Further, this broadcast receiving apparatus includes a TMCC (Transmission and Multiplexing Configuration Control) detection unit for switching to a reception mode of either 12-segment broadcasting or 1-segment broadcasting when an emergency alert is received. 21, a BER (Bit Error Rate) detection unit 22, and a switching signal generation unit 23.

  The TMCC detection unit 21 detects a TMCC signal included in the OFDM signal. The TMCC signal is a signal indicating a modulation method of digital broadcasting. As shown in FIG. 7, the TMCC signal includes a system identification flag D1, a transmission parameter switching index flag D2, a start control signal flag D3, a current information flag D4, a next information flag D5, and a linked transmission phase correction amount D6.

  The identification flag D1 is information for identifying the terrestrial digital television broadcast system or the terrestrial digital audio broadcast system. That is, the system identification flag D1 designates digital television or digital radio.

  The transmission parameter switching index flag D2 notifies the receiver of switching and timing.

  The activation control signal flag D3 is information for identifying “no activation control” or “with activation control (when transmitting an emergency warning signal)”.

  The current information flag D4 indicates the format of information currently being broadcast, and includes a partial reception flag and three transmission parameter information from the A layer to the C layer. With the partial reception flag, “no partial reception” or “partial reception” can be identified. In addition, the partial reception said here means that 1 segment broadcast which is low quality broadcast is receivable. The transmission parameter information of the A layer to the C layer is information for distinguishing three layers having different modulation schemes, such as a carrier modulation mapping scheme, a convolutional coding rate, a length of time interleave, and the number of segments. Can be identified.

  In the next information flag D5, information to be broadcast next can be identified. The coupled transmission phase correction amount D6 is information indicating a phase correction amount when performing coupled transmission.

  The BER detector 22 detects the error rate of the received signal and outputs the detection result to the switching signal generator 23. The BER detector 22 is used in second and third embodiments described later. The switching signal generator 23 switches the reception mode between 12 segment broadcasting and 1 segment broadcasting.

Next, the operation of the first embodiment will be described.
The processes shown in the following flowcharts are executed when the control unit 18 that is a microcomputer reads a predetermined program. The same applies to other embodiments, and is executed by the control unit 18 reading a program corresponding to each embodiment.

  The first embodiment is characterized in that when an emergency warning is broadcast during reception of a 12-segment broadcast, the 12-segment broadcast is switched to the 1-segment broadcast, and the 12-segment broadcast is returned after the emergency alert is completed.

  FIG. 2 is a flowchart showing the processing operation of the broadcast receiving apparatus in the first embodiment. Now, it is assumed that a 12-segment broadcast and a 1-segment broadcast are simultaneously transmitted by the hierarchical transmission service, and the receiving apparatus receives the 12-segment broadcast in a normal reception state.

  In addition, as a means for transmitting disaster information such as earthquakes and tsunamis, there is a TMCC signal in an OFDM frame in terrestrial digital broadcasting. Furthermore, in the TMCC signal, a flag (current information flag D4 in FIG. 7) indicating the presence or absence of partial reception (1-segment broadcasting) and an emergency warning (EWS: Emergency Warning System) are being broadcast. (A start control signal flag D3 in FIG. 7) is added.

  As shown in FIG. 2, during reception of 12 segment broadcast (step A11), partial reception (1 segment broadcast) is detected by the TMCC detection unit 21 (Yes in step A12), and an emergency alert is broadcast. If this is detected (Yes in step A13), the switching signal generator 23 outputs a signal for switching from the 12-segment broadcast to the 1-segment broadcast reception mode to the MPEG decoder 16 (step A14).

  As a result, the mode is switched to the one-segment broadcast reception mode, and the emergency alert transmitted by the one-segment broadcast is reproduced and output through the display unit 19 and the speaker 20 (step A15). Further, the reproduction of the one-segment broadcast is continued until the emergency control signal of the TMCC signal is turned off (Yes in step A16).

  When the emergency alert broadcast ends (No in step A16), a signal for switching from the 1-segment broadcast to the 12-segment broadcast reception mode is output from the switching signal generation unit 23 to the MPEG decoding unit 16, and the 12-segment broadcast reception state (Step A17).

  In this way, when an emergency alert that conveys disaster information such as an earthquake or tsunami is broadcast, switching to a 1-segment broadcast that is more resistant to noise than the 12-segment broadcast and has a low reception C / N characteristic allows the emergency alert to be transmitted. Can be reliably received.

  In addition, as described with reference to FIG. 6, the 1-segment broadcast has a larger area than the 12-segment broadcast. Therefore, for example, even when an emergency warning is broadcast while the vehicle Q equipped with this apparatus is moving near the boundary between the area E1 of the 12-segment broadcast and the area E2 of the 1-segment broadcast, Emergency alerts can be received stably. In addition, although quality of an image etc. falls compared with 12 segment broadcast in 1 segment broadcast, since it is important to convey the content surely rather than quality in an emergency alert, it does not become a problem in particular.

  Furthermore, since the emergency alert broadcast is automatically switched to the 12-segment broadcast reception mode, the user can view the 12-segment broadcast as it is without being particularly conscious.

(Second Embodiment)
Next, a second embodiment will be described.
The second embodiment is characterized by switching between 12-segment broadcasting and 1-segment broadcasting in consideration of the error rate of the received signal.

  The apparatus configuration is basically the same as that of the first embodiment except that the BER detection unit 22 shown in FIG. 1 is used. Here, the processing differences will be described with reference to the flowchart. To do.

  FIG. 3 is a flowchart showing the processing operation of the broadcast receiving apparatus in the second embodiment. Similar to the first embodiment, the 12-segment broadcast and the 1-segment broadcast are currently transmitted simultaneously by the hierarchical transmission service, and the receiving apparatus receives the 12-segment broadcast in the normal reception state. It shall be.

  As shown in FIG. 3, when partial reception (1-segment broadcast) is detected by the TMCC detection unit 21 while receiving 12-segment broadcast (step B11) (Yes in step B12), it is added to the above-described MCC signal. The presence / absence of an emergency warning is determined based on the activated control signal flag D3 (step B13).

  Here, when there is no emergency warning (No in Step B13), switching is performed when the error rate of the received signal detected by the BER detection unit 22 exceeds a preset threshold 1 (Yes in Step B14). The signal generator 23 outputs a signal for switching from the 12-segment broadcast to the 1-segment broadcast reception mode to the MPEG decoder 16 (step B15).

  As a result, for example, when the reception situation is poor due to the influence of rain or an obstacle, and the reception C / N is lowered, switching to one-segment broadcasting is performed (step B16). Thereafter, when the reception state is recovered and the error rate becomes equal to or less than the threshold value 1, the 12-segment broadcasting is restored.

  On the other hand, when there is an emergency warning (Yes in Step B13), it is determined whether or not the error rate of the received signal detected by the BER detector 22 exceeds the threshold 2 (Step B17). In this case, the threshold value 2 is set lower than the threshold value 1 which is a switching condition during normal broadcasting. In other words, even in the same reception situation, the error rate threshold is set to be low so that switching to one segment is faster when broadcasting an emergency alert than when broadcasting normal.

  If the error rate of the received signal exceeds the threshold value 2 (Yes in step B17), the switching signal generator 23 outputs a signal for switching from the 12-segment broadcast to the 1-segment broadcast reception mode to the MPEG decoder 16. (Step B18).

  As a result, the mode is switched to the one-segment broadcast reception mode, and the emergency alert transmitted by the one-segment broadcast is reproduced and output through the display unit 19 and the speaker 20 (step B19). Further, the reproduction of the one-segment broadcast is continued until the emergency control signal of the TMCC signal is turned off (Yes in step B20).

  The return to 12 segments is performed by comparison with the threshold value 1 which is the switching condition at the time of normal broadcasting described above. That is, after the broadcast of the emergency alert is finished (No in Step B20), when the error rate of the received signal is compared with the threshold 1 and the error rate exceeds the threshold 1 (Yes in Step B21), it remains as it is. The one-segment broadcast reception mode is continued (step B19). On the other hand, when the error rate is equal to or less than the threshold value 1 (No in Step B21), the mode is switched to the 12-segment broadcast reception mode (Step B22).

  In this way, when an emergency alert is broadcasted, the reception mode is switched according to the error rate of the received signal, so that the emergency alert can be switched to the 1-segment broadcast only in a situation where it is difficult to receive the 12-segment broadcast. Can be received. In this case, since it is switched to the 1-segment broadcast reception mode based on the threshold 2 set higher than the threshold 1 which is the switching condition at the time of normal broadcasting, even in the same reception situation, 1 segment for emergency alerts Receiving can be ensured by early switching to broadcasting.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
The third embodiment is characterized by scanning other channels when the error rate of the received signal is low when switching from the 12-segment broadcast to the 1-segment broadcast reception mode.

  The apparatus configuration is basically the same as that of the first embodiment except that the BER detection unit 22 shown in FIG. 1 is used. Here, the processing differences will be described with reference to the flowchart. To do.

  FIG. 4 is a flowchart showing the processing operation of the broadcast receiving apparatus in the third embodiment. Similar to the first embodiment, the 12-segment broadcast and the 1-segment broadcast are currently transmitted simultaneously by the hierarchical transmission service, and the receiving apparatus receives the 12-segment broadcast in the normal reception state. It shall be.

  As shown in FIG. 4, when a partial reception (1-segment broadcast) is detected by the TMCC detection unit 21 while receiving a 12-segment broadcast (step C11) (Yes in step C12), it is added to the above-described MCC signal. The presence / absence of an emergency warning is determined based on the activated control signal flag D3 (step C13).

  If there is an emergency alert (Yes in Step C13), it is determined whether or not the error rate of the received signal detected by the BER detector 22 exceeds the threshold 2 (Step C14). As described in the second embodiment, the threshold value 2 is set higher than the threshold value 1 that is a switching condition during normal broadcasting. In other words, even in the same reception situation, the error rate threshold is set higher in order to switch to one segment earlier than during normal broadcasting during emergency alert broadcasting.

  When the error rate of the received signal exceeds the threshold 2 (Yes in step C14), a signal for switching from the 12 segment broadcast to the 1 segment broadcast reception mode is output to the MPEG decoder 16 by the switching signal generator 23. (Step C15).

  As a result, the mode is switched to the one-segment broadcast reception mode, and the emergency alert transmitted by the one-segment broadcast is reproduced through the display unit 19 and the speaker 20 (step C16).

  Here, during the reproduction of the one-segment broadcast, the error rate of the received signal detected by the TMCC detection unit 21 is monitored, and if the error rate is equal to or less than a preset threshold value 3 (No in step C17). The emergency alert is continuously received on the same channel as it is (Yes in step C18). The threshold 3 is set for receiving one segment broadcast shown in FIG. 6 and is independent of the thresholds 1 and 2.

  When the emergency alert broadcast ends (No in Step C18), a signal for switching from the 1-segment broadcast to the 12-segment broadcast reception mode is output from the switching signal generation unit 23 to the MPEG decoding unit 16, and the 12-segment broadcast reception state (Step C19).

  On the other hand, if the error rate of the received signal exceeds the threshold value 3 during playback of the one-segment broadcast (Yes in step C17), it is determined that the reception status has deteriorated, and an emergency alert should be received on another channel. A channel scan is executed (step C20). As a result, when a channel that can receive emergency broadcasts with an error rate of 3 or less is searched (Yes in step C21), the setting change to that channel is made and an emergency alert broadcast on that channel is issued. It is received and played back (step C22). In an emergency, emergency alerts are broadcast almost simultaneously from a plurality of broadcasting stations, not limited to a specific broadcasting station.

  In this way, by switching to another channel according to the error rate during reception of one segment broadcast, for example, the reception situation suddenly moves to another place while receiving an emergency alert. Even if it gets worse, you can continue to receive emergency alerts on other channels.

  In each of the above embodiments, 12 segment broadcasting and 1 segment broadcasting have been described as examples. However, the present invention is not limited to the number of segments, and is based on the first broadcasting signal and the first broadcasting signal. However, the present invention can be applied to any system in which an emergency alert is simultaneously transmitted by a second broadcast signal with low quality.

  In short, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

FIG. 1 is a block diagram showing a configuration of a broadcast receiving apparatus capable of receiving terrestrial digital broadcasting according to the first embodiment of the present invention. FIG. 2 is a flowchart showing the processing operation of the broadcast receiving apparatus in the first embodiment. FIG. 3 is a flowchart showing the processing operation of the broadcast receiving apparatus in the second embodiment. FIG. 4 is a flowchart showing the processing operation of the broadcast receiving apparatus in the third embodiment. FIG. 5 is a diagram for explaining the concept of segments according to the digital terrestrial broadcasting system. FIG. 6 is a diagram for explaining areas of 12-segment broadcasting and 1-segment broadcasting. FIG. 7 is a diagram for explaining the configuration of a TMCC signal included in an OFDM signal in terrestrial digital broadcasting.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Reception antenna, 12 ... Tuner, 13 ... OFDM demodulation part, 14 ... Error correction part, 15 ... Demultiplexing part, 16 ... MPEG decoding part, 17 ... Image superimposition part, 18 ... Control part, 19 ... Display part, 20 ... Speaker, 21 ... TMCC detector, 22 ... BER detector, 23 ... switch signal generator, E1 ... 12 segment broadcast area, E2 ... 1 segment broadcast area, L1 ... 12 segment broadcast area radius, L2 ... 1-segment broadcast area radius, P0 ... broadcast station, Q ... vehicle, D1 ... system identification flag, D2 ... transmission parameter switching indicator flag, D3 ... start control signal flag, D4 ... current information flag, D5 ... next information flag, D6: Concatenated transmission phase correction amount.

Claims (5)

In a broadcast receiving apparatus having a function capable of switching and receiving a first broadcast signal transmitted simultaneously from a transmission side and a second broadcast signal having a lower quality than the first broadcast signal,
First determination means for determining whether reception of the second broadcast signal is possible during reception of the first broadcast signal;
A second determination means for determining the presence or absence of an emergency alert when it is determined by the first determination means that the second broadcast signal can be received;
Broadcast reception characterized by comprising: a reception mode switching means for switching from the first broadcast signal to the reception mode of the second broadcast signal when it is determined by the second determination means that there is an emergency warning. apparatus.   2. The broadcast receiving apparatus according to claim 1, wherein the reception mode switching means returns to the reception mode of the first broadcast signal at a timing when broadcast of an emergency warning is finished. An error rate detecting means for detecting an error rate of the received signal;
The reception mode switching means has an error rate detected by the error rate detection means that is greater than a first threshold value which is a switching condition at the time of normal broadcasting when the second determination means determines that there is an emergency warning. 2. The broadcast receiving apparatus according to claim 1, wherein the second broadcast signal reception mode is switched to a second broadcast signal reception mode when a second threshold value set low is exceeded.   The broadcast according to claim 3, wherein the reception mode switching means returns to the reception mode of the first broadcast signal when an error rate after the broadcast of the emergency warning is equal to or less than the first threshold. Receiver device. An error rate detection means for detecting an error rate of the received signal when the reception mode switching means is switched to the reception mode of the second broadcast signal;
When the error rate detected by the error rate detection means exceeds a third threshold set for receiving the second broadcast signal, an emergency alert is issued when the error rate is equal to or lower than the third threshold. The broadcast receiving apparatus according to claim 1, further comprising channel search means for searching for other receivable channels.

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