JP4641044B2 - Digital broadcast receiving method - Google Patents

Description

  The present invention relates to a mobile broadcast receiving apparatus and a mobile broadcast receiving method for receiving a digital broadcast while moving, and more particularly, to a digital terrestrial television broadcast that relays the same broadcast at a different frequency from a relay station. The present invention relates to a mobile broadcast receiving apparatus and a mobile broadcast receiving method for receiving with a diversity effect while automatically switching.

Japan's terrestrial digital television broadcast (hereinafter abbreviated as ISDB-T broadcast) was started on December 1, 2003 in Tomei Osaka. ISDB-T broadcasting uses OFDM (Orthogonal Frequency Division Multiplexing) as a modulation method, so it is strong against multipath and can be subjected to time interleaving, so it is relatively strong at mobile reception. Furthermore, it is also possible to select a parameter that is strong against transmission distortion using a mobile layer and a mobile layer, and a modulation scheme and error correction coding rate.
Therefore, mobile reception of ISDB-T broadcasting is expected, and mobile receivers are being studied.

  Items to be examined include automatically following a service area that changes due to mobile reception, and improving reception performance. Patent Document 1 is a conventional example corresponding to these areas. FIG. 10 shows the configuration. Reference numeral 1001 denotes an antenna, and there are four systems a, b, c, and d. 1002 is a selection unit, 1003 is a channel selection unit, 1004 is a demodulation / decoding unit, and there are two systems a and b. 1005 is a control unit, and 1006 is an output unit.

  The channel selection unit 1003a and the demodulation / decoding unit 1004a receive, demodulate, and decode using one of the antennas a, b, c, and d4 of the antenna 1001, and output demodulated digital data to the output unit 1006. On the other hand, the channel selection unit 1003b and the demodulation / decoding unit 1004b are used to search for the affiliated station in the next service area following the movement, and have the best signal quality among the a, b, c, and d4 systems of the antenna 1001 And the antenna to the channel selection unit 1003a and the demodulation / decoding unit 1004a is switched.

  According to the 4th edition “National Digital Television Broadcasting PSI / SI Operational Rules” of Non-Patent Document 1 of the Radio Industries Association (hereinafter referred to as ARIB), the search for affiliated stations is based on the BIT (Broadcaster Information Table). It is identified by the extension broadcaster descriptor's affinity_id (sequence identification), and when receiving across areas such as mobile reception, it is shown that services of the same sequence can be continuously received.

  Further, there are Patent Document 2 and Patent Document 3 as conventional examples that only improve reception performance. The configuration is shown in FIGS. 11 and 12, respectively.

  In FIG. 11, 1101 is an antenna, 1102 is a channel selection unit, 1103 is a demodulation / decoding unit, and there are a and b2 systems. 1104 is a selection unit, 1105 is a control unit, and 1106 is an output unit.

  Using the antennas 1101a and 110b, the channel selection units 1102a and 110b select channels of the frequency f, respectively, and receive / demodulate / decode them by the demodulation / decoding units 1103a and 1103b, respectively. The control unit 1105 discriminates one of the a and b sequences having the better signal quality, controls the selection unit 1104 to select the sequence having the better signal quality, and outputs the demodulated digital data to the output unit 1106.

  12, the same symbols as those in FIG. 11 denote the same functions, 1201a and b are demodulation units, 1202 is a delay adjustment unit, 1203 is a selection / synthesis unit, 1204 is a decoding unit, and 1205 is a control unit.

  Using the antennas 1101a and 110b, the channel selection units 1102a and 110b select channels of the frequency f, and receive and demodulate the channels by the demodulation units 1201a and b, respectively. The control unit 1205 determines the signal quality of the a and b series. The delay adjustment unit 1202 adjusts the signal delay of the a sequence and the b sequence demodulated by the demodulation units 1201a and b, and the selection / synthesis unit 1203 selects a sequence with good signal quality based on the control signal from the control unit 1205, or The maximum ratio combining process is performed, the decoding unit 1204 performs decoding, and the demodulated digital data is output to the output unit 1106.

  11 and 12 are conventional examples of so-called spatial diversity.

JP 2001-251229 A JP 2001-136113 A JP 2003-333012 A

The Japan Radio Industry Association technical data “terrestrial digital television broadcast operation rules” ARIB TR-B14 2.0 version

In the conventional example of FIG. 10, channel switching processing that automatically follows a service area that changes due to mobile reception and antenna switching processing for antenna diversity cannot be performed simultaneously, and channel switching processing and antenna switching processing are performed. There is a problem that the demodulation / decoding process is interrupted.
11 and 12 does not show processing for automatically following the service area that changes due to mobile reception.

The present invention is a relay broadcast of a digital broadcast and the same digital data and which a digital broadcast receiving method for receiving a digital broadcast transmitting at relay frequency is the reception frequency number and another frequency of the digital broadcasting, N A first output step of synthesizing or selecting the digital demodulated signal of N series obtained by receiving and demodulating the digital broadcast at a reception frequency and outputting one demodulated digital data; The first digital demodulation obtained by switching the reception frequency in at least one of the N sequences receiving the broadcast to the relay frequency, receiving the relay broadcast in a sequence of N / 2 or less, and demodulating A signal and a second digital demodulated signal obtained by receiving and demodulating the digital broadcast in a sequence obtained by subtracting a sequence of N / 2 or less from the N sequence, or A second output step for selecting and outputting one demodulated digital data in the same format as the data output in the first output step; and the signal quality of the first digital demodulated signal and the second digital demodulated signal And when the signal quality of the first digital demodulated signal is better than the signal quality of the second digital demodulated signal, N / 2 or less sequences are excluded from the N sequence. The received frequency in at least one of the sequences is switched to the relay frequency, the relay broadcast is received in a sequence of N / 2 or more, and a digital demodulated signal obtained by demodulating, and N / Demodulation of the same format as the data output in the first output step by synthesizing or selecting the digital demodulated signal obtained by receiving and demodulating the digital broadcast in a sequence excluding two or more sequences A third output step of outputting the digital data, a digital broadcast receiving method comprising a.

Further, the present invention is the digital broadcast receiving method , wherein N of the N series is 2 or more .

  According to the present invention, in a mobile broadcast receiving apparatus that receives a digital broadcast while moving, the same broadcast is relayed at a different frequency from a relay station, that is, an MFN (Multi-Frequency Network: service area). When moving between digital broadcasting service areas of a network that assigns different frequencies to overlapping transmitting stations), demodulated digital data is not interrupted even when channels between relay stations are automatically switched, and the diversity effect It is possible to receive with good quality.

The block diagram which shows the structure of the mobile receiver which receives ISDB-T broadcast of this invention. Example 1 The flowchart explaining operation | movement of the mobile receiver of FIG.1 and FIG.3. The block diagram which shows the structure of the mobile receiver which receives ISDB-T broadcast of this invention. (Example 2) The block diagram which shows the structure of the mobile receiver which receives ISDB-T broadcast of this invention. Example 3 The flowchart explaining operation | movement of the mobile receiver of FIG. The block diagram which shows the structure of the mobile receiver which receives ISDB-T broadcast of this invention. (Example 4) The flowchart explaining operation | movement of the mobile receiver of FIG. The block diagram which shows the structure of the mobile receiver which receives ISDB-T broadcast of this invention. (Example 5) The flowchart explaining operation | movement of the mobile receiver of FIG. The block diagram which shows the structure of the mobile receiver of a prior art example. The block diagram which shows the structure of the mobile receiver of a prior art example. The block diagram which shows the structure of the mobile receiver of a prior art example.

  Hereinafter, an embodiment of the present invention will be described by taking a mobile receiver that mobilely receives an ISDB-T broadcast as an example.

  FIG. 1 is a block diagram showing a configuration of a mobile receiver that receives ISDB-T broadcast according to an embodiment of the present invention.

  101 is an antenna, 102 is a tuning unit, 103 is a demodulation / decoding unit, and there are a and b2 systems. 104 is a delay adjustment unit, 105 is a selection unit, 106 is a control unit, and 107 is an output unit.

  The operation of FIG. 1 will be described with reference to the flowchart of FIG.

・ Step 201
First, it is assumed that there is a moving object in the service area of the channel having the frequency fnow.

・ Step 202
Using the antennas 101a and 101b, the channel selection units 102a and 102b select the channel of the frequency fnow, and receive / demodulate / decode them by the demodulation / decoding units 103a and 103b, respectively. The control unit 106 determines the better signal quality among the a and b sequences. The delay adjustment unit 104 adjusts the signal delay of the a-sequence and b-sequence demodulated / decoded by the demodulation / decoding units 103a and 103b to match the same data position, and controls the selection unit 105 by the control signal from the control unit 106. Thus, a sequence having good signal quality is selected, and the demodulated digital data is output to the output unit 107. The delay adjustment in the delay adjustment unit 104 is controlled by the control unit 106 comparing the synchronization signal included in the demodulated digital data of the a series and b series, the frame synchronization and the symbol synchronization signal in the demodulation / decoding unit 103, and the like. . In addition, the signal quality controls the data error flag included in the demodulated digital data of the a-sequence and b-sequence, the C / N measured by the demodulation / decoding unit 103, the data error rate, MER (Modulation Error Ratio), etc. The comparison is made by the unit 106. Here, a so-called spatial diversity operation similar to FIG. 11 is performed.

・ Step 203
The control unit 106 determines from the signal quality of both the a-sequence and the b-sequence. The signal quality is time-averaged, and if it is determined that both the a-sequence and the b-sequence are degraded, the process proceeds to step 204.

・ Step 204
The control unit 106 controls the channel selection unit 102b to receive the channel of the next relay station having the frequency fnext. fnext is described in the NIT (Network Information Table, which transmits transmission information such as frequency) in the second loop ground distribution system descriptor.

・ Steps 205 and 206
The control unit 106 determines b-sequence signal quality. The signal quality is time-averaged. If the signal quality is poor, it is determined that the channel of the currently selected frequency is not in the service area, the next candidate frequency is set to fnext, and the process returns to step 204.

  If it is determined that the signal quality is good, the process proceeds to step 207. Here, it is possible to determine all candidates and select a channel having a frequency with the best signal quality.

  Further, although not shown in FIG. 2, if there is no channel having a frequency with good signal quality even if all candidates are determined, it is determined that there is no service area of the relay station adjacent to the current service area, and the step Proceed to 209.

・ Step 207
The control unit 106 determines the signal quality of each of the a series and b series.
If the signal quality is time-averaged and it is determined that the signal quality is better for the a-sequence than the b-sequence and the signal quality is good, the service area is still determined to be within fnow and step 207 is repeated.

  If it is determined that the signal quality of the b-sequence is better than the a-sequence and that the signal quality is good, the process proceeds to step 208.

  If it is determined that the signal quality is degraded for both the a-sequence and the b-sequence, it is determined that there is no service area of the relay station adjacent to the current service area, and the process proceeds to step 209.

  Although not shown in FIG. 2, when the signal quality of the a-sequence is good and the signal quality of the b-sequence is deteriorated, it is determined that the service area of the channel having the frequency of fnow has been returned, and the process returns to step 202.

・ Steps 208 and 210
The control unit 106 determines that the service area has moved to the service area of the fnext channel, and controls the channel selection unit 102a to receive the frequency fnext channel of the next relay station. At this time, a so-called spatial diversity operation similar to that in FIG. 11 is performed.

  Replace fnext with fnow, and return to step 203.

・ Step 209
Since it is determined that there is no service area of the relay station adjacent to the current service area, the relay station is searched again, or processing such as affiliated station search, analog channel search, and other digital broadcast channel search is started.

  As described above, according to the embodiments of FIGS. 1 and 2, when the same broadcast is relayed from the relay station at a different frequency, that is, when moving between MFN digital broadcasting service areas, the channel between the relay stations Even if the channel of the b-sequence fnext frequency that is automatically switched is selected, the selection unit 105 is the same as the demodulated digital data of the channel of the a-sequence fnow frequency. By selecting a sequence with good signal quality based on the control signal from, the demodulated digital data can be received without being interrupted and with a diversity effect.

  FIG. 3 is a block diagram showing a configuration of a mobile receiver that receives an ISDB-T broadcast according to an embodiment of the present invention. The same symbols as in FIG. 1 indicate the same functions, 301a and b are demodulation units, 302 is a delay adjustment unit, 303 is a selection / synthesis unit, and 304 is a decoding unit.

  In the embodiment of FIG. 3, the flow of FIG. 2 is applied to the conventional example of FIG.

  The operation of FIG. 3 will be described with reference to the flowchart of FIG.

・ Step 201
First, it is assumed that there is a moving object in the service area of the channel having the frequency fnow.

・ Step 202
Using the antennas 101a and 101b, the channel selection units 102a and 102b select the channel of the frequency fnow, and receive and demodulate the channels by the demodulation units 301a and 301b, respectively. The control unit 305 determines the better signal quality among the a and b sequences. The delay adjustment unit 302 adjusts the signal delay of the a sequence and the b sequence demodulated by the demodulation units 301a and 301b, and the selection / synthesis unit 303 selects a sequence with good signal quality based on the control signal from the control unit 305, or The maximum ratio combining process is performed, the decoding unit 304 performs decoding, and the output unit 107 outputs demodulated digital data. Delay adjustment in the delay adjustment unit 302 is controlled by the control unit 305 comparing timing signals such as frame synchronization and symbol synchronization signals in the demodulation units 301 of the a-sequence and b-sequence, respectively. The signal quality is determined by comparing the C / N, MER, etc. measured by the demodulator 301 with the controller 305. Here, a so-called spatial diversity operation similar to FIG. 12 is performed.

・ Step 203
The control unit 305 determines from the signal quality of both the a series and b series. The signal quality is time-averaged, and if it is determined that both the a-sequence and the b-sequence are degraded, the process proceeds to step 204.

・ Step 204
The control unit 305 controls the channel selection unit 102b to receive the channel of the next relay station having the frequency fnext. fnext is described in the NIT second loop ground distribution system descriptor.

・ Steps 205 and 206
The control unit 305 determines b-sequence signal quality. The signal quality is time-averaged. If the signal quality is poor, it is determined that the channel of the currently selected frequency is not in the service area, the next candidate frequency is set to fnext, and the process returns to step 204.

  If it is determined that the signal quality is good, the process proceeds to step 207. Here, it is possible to determine all candidates and select a channel having a frequency with the best signal quality.

  Further, although not shown in FIG. 2, if there is no channel having a frequency with good signal quality even if all candidates are determined, it is determined that there is no service area of the relay station adjacent to the current service area, and the step Proceed to 209.

・ Step 207
The control unit 305 determines the signal quality of each of the a series and b series.
If the signal quality is time-averaged and it is determined that the signal quality is better for the a-sequence than the b-sequence and the signal quality is good, the service area is still determined to be within fnow and step 207 is repeated.

  If it is determined that the signal quality of the b-sequence is better than the a-sequence and that the signal quality is good, the process proceeds to step 208.

  If it is determined that the signal quality is degraded for both the a-sequence and the b-sequence, it is determined that there is no service area of the relay station adjacent to the current service area, and the process proceeds to step 209.

  Although not shown in FIG. 2, when the signal quality of the a-sequence is good and the signal quality of the b-sequence is deteriorated, it is determined that the service area of the channel having the frequency of fnow has been returned, and the process returns to step 202.

・ Steps 208 and 210
When determining that the service area has moved to the service area of the fnext channel, the control unit 305 controls the channel selection unit 102a to receive the channel of the frequency fnext of the next relay station. At this time, a so-called spatial diversity operation similar to FIG. 12 is performed.

  Replace fnext with fnow, and return to step 203.

・ Step 209
Since it is determined that there is no service area of the relay station adjacent to the current service area, the relay station is searched again, or processing such as affiliated station search, analog channel search, and other digital broadcast channel search is started.

  As described above, according to the embodiments of FIGS. 3 and 2, when the same broadcast is relayed from the relay station at a different frequency, that is, when moving between digital broadcast service areas of MFN, the channel between the relay stations Since the demodulated signal (the output signal of the demodulator 301b) is the same as the demodulated signal (the output signal of the demodulator 301a) of the channel of the frequency before switching, the selector / synthesizer 303 controls By selecting or synthesizing a sequence having a good signal quality based on a control signal from the unit 305, the demodulated digital data can be received with a diversity effect without being interrupted by being decoded by the decoding unit 304. is there.

FIG. 3 is a block diagram showing a configuration of a mobile receiver that receives an ISDB-T broadcast according to an embodiment of the present invention. 1 denote the same functions, 401 is a navigation unit, 402 is an area information unit, and 403 is a control unit.
The operation of FIG. 4 will be described with reference to the flowchart of FIG.

・ Step 501
First, it is assumed that there is a moving object in the service area of the channel having the frequency fnow.

Step 502
Using the antennas 101a and 101b, the channel selection units 102a and 102b select the channel of the frequency fnow, and receive / demodulate / decode them by the demodulation / decoding units 103a and 103b, respectively. The control unit 403 discriminates one having the better signal quality from the series a and b. The delay adjustment unit 104 adjusts the signal delay of the a-sequence and b-sequence demodulated / decoded by the demodulation / decoding units 103a and 103b to match the same data position, and controls the selection unit 105 by the control signal from the control unit 403. Thus, a sequence having good signal quality is selected, and the demodulated digital data is output to the output unit 107. Delay adjustment in the delay adjustment unit 104 is controlled by the control unit 403 comparing the synchronization signal included in the demodulated digital data of the a series and b series, the frame synchronization and the symbol synchronization signal in the demodulation / decoding unit 103, and so on. . The signal quality is determined by the control unit 403 by comparing the data error flag included in the demodulated digital data of each of the a-sequence and b-sequence, the C / N measured by the demodulation / decoding unit 103, the data error rate, MER, etc. To determine. Here, a so-called spatial diversity operation similar to FIG. 11 is performed.

・ Step 503
The navigation unit 401 outputs, to the control unit 403, the minimum position information and, if possible, information such as map information, a traveling direction, and a route to the destination. The area information unit 402 stores information such as the location of broadcast stations and relay stations, frequency used, and service area. The control unit 403 predicts movement from the current service area to the next service area from the position information and other information. For example, when it is predicted to move to the service area of the relay station that is broadcasting the same frequency as the currently received frequency fnow, the process proceeds to step 504. If it is predicted that the user is in the current service area for a while, the area determination is repeated. If there is no relay station performing the same broadcast at the predicted location, the process proceeds to step 509.

・ Step 504
The control unit 403 controls the channel selection unit 102b to receive the channel of the next relay station having the frequency fnext. fnext is stored in the area information unit 402. At this time, a process of comparing and confirming the frequency information in the area information unit 402 and the frequency information described in the terrestrial distribution system descriptor of the NIT second loop may be added.

・ Step 505
The control unit 403 determines the signal quality of each of the a series and b series.
If the signal quality is time-averaged and it is determined that the signal quality is better for the a-sequence than the b-sequence and the signal quality is also acceptable, the service area is still determined to be within fnow and step 505 is repeated.

  If it is determined that the signal quality of the b-sequence is better than the a-sequence and that the signal quality is good, the process proceeds to step 506.

  If it is determined that the signal quality is degraded for both the a-sequence and the b-sequence, the information in the area information unit 402 is incorrect. However, in this case, since it may be temporarily deteriorated, the check is repeated, and if it is finally determined that the deterioration has occurred, the process proceeds to step 508.

・ Steps 506, 507
When determining that the service area has moved to the service area of the fnext channel, the control unit 403 controls the channel selection unit 102a to receive the channel of the frequency fnext of the next relay station. At this time, a so-called spatial diversity operation similar to that in FIG. 11 is performed.

  Replace fnext with fnow, and return to step 503.

・ Step 508
The area information update process is performed because the information in the area information unit 402 is incorrect or the information may be old. This method is performed by communication or using a recording medium such as a DVD or a memory card. Broadcast stations that can be received by the receiver may be searched and updated.

・ Step 509
If there is no relay station that performs the same broadcast at the location where the movement is predicted, an analog channel or affiliate station that performs the same broadcast is searched, and another broadcaster's channel is searched.

  As described above, according to the embodiments of FIGS. 4 and 5, when the same broadcast is relayed from the relay station at a different frequency, that is, when moving between MFN digital broadcast service areas, the channel between the relay stations Even when the channel of the f-sequence fnext frequency that is automatically switched is selected, the selection unit 105 is the same as the demodulated digital data of the channel of the a-sequence fnow frequency. There is an effect that the demodulated digital data can be received with the effect of diversity without being interrupted by selecting a sequence with good signal quality by the control signal from the minimum position information from the navigation unit 401, In addition, if possible, information such as map information, direction of travel, route to the destination, location of broadcast stations and relay stations from the area information unit 402, frequency used, By using information such as Bisueria, there is an effect that it is possible to predict the service area of the relay station after efficiently moved.

  FIG. 6 is a block diagram showing a configuration of a mobile receiver that receives an ISDB-T broadcast according to an embodiment of the present invention. FIG. 6 has three reception systems.

  The same symbols as in FIG. 1 or FIG. 4 indicate the same functions, and the third system is represented by c. Reference numeral 601 denotes a control unit.

  The operation of FIG. 6 will be described with reference to the flowchart of FIG.

・ Step 701
First, it is assumed that there is a moving object in the service area of the channel having the frequency fnow.

・ Step 702
Using the antennas 101a, b, and c, the channel selection units 102a, b, and c select channels of the frequency fnow, and receive / demodulate / decode them by the demodulation / decoding units 103a, b, and c, respectively. The control unit 601 determines a sequence having a good signal quality from the a, b, and c sequences. The delay adjustment unit 104 adjusts the signal delays of the a-sequence, b-sequence, and c-sequence demodulated / decoded by the demodulation / decoding units 103a, b, and c to match the same data position, and is selected by the control signal from the control unit 601 Control unit 105 selects a sequence with good signal quality, and outputs demodulated digital data to output unit 107. The delay adjustment in the delay adjustment unit 104 is performed by the control unit 601 comparing the synchronization signal included in the demodulated digital data of each of the a-sequence, b-sequence, and c-sequence, and the frame synchronization and symbol synchronization signal in the demodulation / decoding unit 103. Control. Further, the signal quality includes the data error flag included in the demodulated digital data of the a-sequence, b-sequence, and b-sequence, the C / N measured by the demodulation / decoding unit 103, the data error rate, MER, and the like. Compare with and determine. Here, a so-called spatial diversity operation is performed.

・ Step 703
The navigation unit 401 outputs to the control unit 601, the minimum position information and, if possible, information such as map information, a traveling direction, and a route to the destination. The area information unit 402 stores information such as the location of broadcast stations and relay stations, frequency used, and service area. The control unit 601 predicts movement from the current service area to the next service area from the position information and other information. For example, when it is predicted to move to the service area of the relay station that is broadcasting the same frequency as the currently received frequency fnow, the process proceeds to step 504. If it is predicted that the user is in the current service area for a while, the area determination is repeated. If there is no relay station performing the same broadcast at the predicted location, the process proceeds to step 713.

・ Step 704
The control unit 601 controls the channel selection unit 102c to receive the channel of the next relay station having the frequency fnext. fnext is stored in the area information unit 402. At this time, a process of comparing and confirming the frequency information in the area information unit 402 and the frequency information described in the terrestrial distribution system descriptor of the NIT second loop may be added.
At this time, the a series and b series maintain the spatial diversity operation.

・ Step 705
The control unit 601 determines the signal quality of each of the a series, b series, and c series.

  If the signal quality is time-averaged and it is determined that the signal quality is better for the a and b sequences than the c sequence and the signal quality is acceptable, the service area is still determined to be within fnow and step 705 is repeated.

  If it is determined that the signal quality is better for the c-sequence than the a- and b-sequence, and the signal quality is also acceptable, the process proceeds to step 706.

  If it is determined that the signal quality is degraded for all of the a-sequence, b-sequence, and c-sequence, the information in the area information unit 402 is incorrect. However, in this case, since it may be temporarily deteriorated, the check is repeated, and if it is finally determined that the deterioration has occurred, the process proceeds to step 710.

・ Step 706
When determining that the service area has moved to the service area of the fnext channel, the control unit 403 controls the channel selection unit 102b to receive the frequency fnext channel of the next relay station. At this time, the b sequence and the c sequence are so-called spatial diversity operations.

・ Step 707
The control unit 601 determines the signal quality of each of the a series, b series, and c series.
If the signal quality is time-averaged and it is determined that the signal quality of the a-sequence is good, the effect of so-called frequency diversity can be expected by using the a-sequence, so that step 707 is repeated.

  If it is determined that the signal quality of the a series has deteriorated, the process proceeds to step 708.

  If it is determined that the signal quality is degraded for all of the a-sequence, b-sequence, and c-sequence, the area prediction may be incorrect. However, in this case, since it may be temporarily deteriorated, the check is repeated, and if it is finally determined that the deterioration has occurred, the process proceeds to step 712.

・ Steps 708 and 709
When it is determined that the service area has completely moved to the service area of the fnext channel, the control unit 601 controls the channel selection unit 102a to receive the channel of the next relay station frequency fnext. At this time, a so-called spatial diversity operation is performed for the a-sequence, the b-sequence, and the c-sequence. Replace fnext with fnow, and return to step 703.

・ Step 710
The area information update process is performed because the information in the area information unit 402 is incorrect or the information may be old. This method is performed by communication or using a recording medium such as a DVD or a memory card. Broadcast stations that can be received by the receiver may be searched and updated.

Step 711
If there is no relay station that performs the same broadcast at the location where the movement is predicted, an analog channel or affiliate station that performs the same broadcast is searched, and another broadcaster's channel is searched.

Step 712
In step 703, the relay station is predicted based on the information from the navigation unit 401, but the prediction may be incorrect. The position information at the time of processing in step 712 is obtained from the navigation unit 401 and the prediction is confirmed. If so, go to step 711. If the prediction is not correct, the process returns to step 703.

  As described above, according to the embodiment of FIGS. 6 and 7, when the same broadcast is relayed from the relay station at a different frequency, that is, when moving between digital broadcast service areas of MFN, the channel between the relay stations Even when the channel of the c-sequence fnext frequency is automatically selected, the channels a and b of the fnow frequency have a spatial diversity effect, and the c-sequence demodulation digital Since the data is the same data, the selection unit 105 has an effect that the demodulated digital data can be selected without interruption by the control signal from the control unit 601, and a, b, c can be selected. There is an effect that reception can be performed with the effect of frequency diversity until all sequences are switched to the channel of the frequency of fnext. Furthermore, the minimum position information from the navigation unit 401, further information such as map information, direction of travel, route to the destination, if possible, the location of broadcast stations and relay stations from the area information unit 402, the frequency used By using information such as the service area, it is possible to efficiently predict the service area of the relay station after moving.

  FIG. 8 is a block diagram showing a configuration of a mobile receiver that receives an ISDB-T broadcast according to an embodiment of the present invention. FIG. 8 has four receiving systems.

  The same symbols as in FIG. 1 or FIG. 4 indicate the same functions, the third system is represented by c, and the fourth system is represented by d. Reference numeral 801 denotes a control unit.

  The operation of FIG. 8 will be described with reference to the flowchart of FIG.

・ Step 901
First, it is assumed that there is a moving object in the service area of the channel having the frequency fnow.

・ Step 902
Using the antennas 101a, b, c, and d, the channel selection units 102a, b, c, and d select the channels of the frequency fnow, respectively, and receive and demodulate by the demodulation / decoding units 103a, b, c, and d, respectively.・ Decrypt. The control unit 801 determines a sequence with good signal quality from the sequences a, b, c, and d. The delay adjustment unit 104 adjusts the signal delays of the a-sequence, b-sequence, c-sequence, and d-sequence demodulated and decoded by the demodulation / decoding units 103a, b, c, and d so as to match the same data position. The control unit 105 controls the selection unit 105 to select a sequence with good signal quality, and outputs the demodulated digital data to the output unit 107. Delay adjustment in the delay adjustment unit 104 is performed by controlling the synchronization signal included in the demodulated digital data of the a-sequence, b-sequence, c-sequence, and d-sequence, the frame synchronization in the demodulation / decoding unit 103, and the symbol synchronization signal in the control unit 801. Compare and control. The signal quality includes the data error flag included in the demodulated digital data of the a-sequence, b-sequence, c-sequence, and d-sequence, the C / N measured by the demodulation / decoding unit 103, the data error rate, MER, etc. The control unit 801 makes a comparison. Here, a so-called spatial diversity operation is performed.

・ Step 903
The navigation unit 401 outputs, to the control unit 403, the minimum position information and, if possible, information such as map information, a traveling direction, and a route to the destination. The area information unit 402 stores information such as the location of broadcast stations and relay stations, frequency used, and service area. The control unit 801 predicts movement from the current service area to the next service area from the position information and other information. For example, if it is predicted to move to the service area of the relay station that is broadcasting the same frequency fnow that is currently being received, the process proceeds to step 904. If it is predicted that the user is in the current service area for a while, the area determination is repeated. If there is no relay station performing the same broadcast at the predicted location, the process proceeds to step 909.

・ Step 904
The control unit 801 controls the channel selection units 102c and 102d to receive the channel having the frequency fnext of the next relay station. fnext is stored in the area information unit 402. At this time, a process of comparing and confirming the frequency information in the area information unit 402 and the frequency information described in the terrestrial distribution system descriptor of the NIT second loop may be added.

  At this time, the a series and b series maintain the spatial diversity operation. In addition, the c sequence and the d sequence are also spatial diversity operations, and the a, b sequence, and the c, d sequences are frequency diversity operations.

・ Step 905
The control unit 801 determines the signal quality of each of the a-sequence, b-sequence, c-sequence, and d-sequence.

  If the signal quality is time-averaged, and it is determined that the signal quality is better for the a and b sequences than the c and d sequences and the signal quality is also acceptable, the service area is still determined to be within fnow and step 905 is performed. repeat.

  If it is determined that the signal quality is better for the c and d sequences than the a and b sequences and the signal quality is acceptable, the process proceeds to step 706.

  If it is determined that the signal quality is degraded for all of the a-sequence, b-sequence, c-sequence, and d-sequence, the information in the area information unit 402 is incorrect. However, in this case, since it may be temporarily deteriorated, the check is repeated, and if it is finally determined that the deterioration has occurred, the process proceeds to step 908.

・ Steps 906, 907
The control unit 801 determines that the service area has shifted to the service area of the fnext channel, and controls the channel selection units 102a and 102b to receive the channel of the next relay station at the frequency fnext. At this time, a so-called spatial diversity operation is performed for the a series, b series, c series, and d series.

  Replace fnext with fnow, and return to step 903.

・ Step 908
The area information update process is performed because the information in the area information unit 402 is incorrect or the information may be old. This method is performed by communication or using a recording medium such as a DVD or a memory card. Broadcast stations that can be received by the receiver may be searched and updated.

・ Step 909
If there is no relay station that performs the same broadcast at the location where the movement is predicted, an analog channel or affiliate station that performs the same broadcast is searched, and another broadcaster's channel is searched.

  As described above, according to the embodiments of FIGS. 8 and 9, when the same broadcast is relayed from the relay station at a different frequency, that is, when moving between MFN digital broadcast service areas, the channel between the relay stations Even when the channel of the fnext frequency of the c and d series is automatically selected, the selection unit 105 is the same data as the demodulated digital data of the channel of the fnow frequency of the a and b series. By selecting a sequence with good signal quality based on a control signal from the control unit 801, demodulated digital data can be received without being interrupted and with a diversity effect. Limit location information, further information such as map information, direction of travel, route to destination, etc., location of broadcast stations and relay stations from area information section 402, usage cycle The number, by using the information such as a service area, there is an effect that it is possible to predict the service area of the relay station after efficiently moved.

  In this embodiment, fnow and fnext are switched every two lines, but fnext can be switched one line at a time from fnow. Further, when a plurality of service areas intersect, it is possible to assign different fnext to the two systems, determine which one has better signal quality, and switch to the next fnext with better signal quality.

  4, 6, and 8 are based on the configuration of FIG. 1, but can be configured based on the configuration of FIG. 3.

  1, 3, 4, 6, and 8 show examples of reception systems of 2 series, 3 series, and 4 series, respectively. Is possible.

  1, 4, 6, and 8 and the delay amount of the delay adjustment unit 302 of FIG. 3 are the difference in arrival time of radio waves calculated from the maximum distance between relay stations nationwide, and spatial diversity. This is the sum of the arrival time differences of radio waves calculated from the antennas constituting the. The maximum distance between relay stations nationwide is considered to be shorter than the guard interval period of ISDB-T broadcasting, and is 252μs for Mode 3 and guard interval 1/4, and 126μs for Mode 3 and guard interval 1/8. It is. However, considering that the service areas overlap, this adjustment amount of 1/2 may be sufficient.

  The present invention is applicable not only to mobile reception of ISDB-T broadcasts but also to mobile reception of all digital broadcasts. In addition, the mobile reception may be anything such as a person, a car, a train, and a ship.

101a, b, c, d antenna
102a, b, c, d
103a, b, c, d Demodulator / Decoder
104 Delay adjuster
105 Selector
106 Control unit
107 Output section
301a, b Demodulator
302 Delay adjuster
303 Selection / Composition
304 Decryption unit
401 Navigation part
402 Area information section
403 control unit
601 control unit
801 control unit

Claims (2)

Relay broadcast of a digital broadcast and the same digital data and which a digital broadcast receiving method for receiving a digital broadcast transmitting at relay frequency is the reception frequency number and another frequency of the digital broadcast,
A first output step of synthesizing or selecting the N-sequence digital demodulated signal obtained by receiving and demodulating the digital broadcast in N sequence at the reception frequency, and outputting one demodulated digital data;
A first frequency obtained by switching the reception frequency in at least one of the N sequences receiving the digital broadcast to the relay frequency, receiving the relay broadcast in a sequence of N / 2 or less, and demodulating A first demodulated signal is synthesized or selected with a digital demodulated signal and a second digital demodulated signal obtained by receiving and demodulating the digital broadcast in a sequence obtained by subtracting a sequence of N / 2 or less from the N sequence. A second output step for outputting one demodulated digital data in the same format as the data output in the step;
Comparing the signal quality of the first digital demodulated signal with the signal quality of the second digital demodulated signal;
When the signal quality of the first digital demodulated signal is better than the signal quality of the second digital demodulated signal, at least one of the sequences obtained by subtracting N / 2 or less sequences from the N sequence The reception frequency is switched to the relay frequency, the relay broadcast is received in a sequence of N / 2 or more, and a digital demodulated signal obtained by demodulating, and the sequence obtained by removing the sequence of N / 2 or more from the N sequence A third output step of receiving or broadcasting the digital broadcast and synthesizing or selecting a digital demodulated signal obtained by demodulating, and outputting demodulated digital data in the same format as the data output in the first output step;
Digital broadcast receiving method, characterized in that it comprises a. 2. The digital broadcast receiving method according to claim 1 , wherein N of the N series is 2 or more .

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