JP2015162848A - Digital broadcast transmission system and method thereof and receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital broadcast transmission system capable of reducing interference between adjacent channels, when transmitting between adjacent channels with no guard band, and to provide a method thereof and a receiver.SOLUTION: Broadcasting is performed without proving a guard band between OFDM signals of adjacent frequencies broadcasted from different transmission stations, by arranging scattered pilot signals 13a, 13b for correcting transmission distortion of a transmission wave in a carrier located at both ends of the frequency axis of an OFDM signal shared by a different OFDM signal adjacent on the frequency axis transmitted from a different transmission station. Out of the scattered pilot signals 13a, 13b, the scattered pilot signals 13a, 13b in the carriers 11, 12 shared by an adjacent different OFDM signal are transmitted, in order, from different transmission station.

Description

  The present invention relates to a digital broadcast transmission system for broadcasting without a guard band in order to effectively use a frequency in digital terrestrial broadcasting in which digital signals are transmitted from different transmission stations using adjacent frequency channels, and a method and a receiving apparatus thereof. .

  In recent years, with the establishment of digital broadcasting technology, a digital TV broadcasting system has also been established for terrestrial broadcasting. In addition, digital broadcasting that can be serviced in a relatively narrow band has also made remarkable progress, such as the launch of nationwide mobile multimedia broadcasting services. In addition, based on the same technical standards as the broadcast, it is expected to realize a local mobile multimedia broadcast and a digital community broadcast service specialized for services to administrative divisions in units of municipalities.

  In such broadcasting, in addition to transmitting a digital broadcast signal alone, there is a system that can effectively use the frequency by connecting a plurality of modulated digital broadcast signals without a guard band between the signals. It has been standardized. In this system, it is possible to receive only an arbitrary digital broadcast signal among a plurality of connected digital broadcast signals, and the power consumption of the receiver can be reduced by narrowing the reception bandwidth. Become. Various inventions have been proposed in connection with such linked transmission technology (see, for example, Patent Documents 1 and 2).

  FIG. 15 shows a conventional example of a three-segment digital audio broadcasting system. As shown in FIG. 15, a broadcast program signal in a transport stream format supplied from a broadcast program operator (in this specification, sometimes referred to as “broadcast TS signal”) is arranged in a digital audio broadcast transmission station. To the transmission path encoding unit 101. The broadcast TS signal is added with an outer code in the outer code encoder 102, and then divided into two layers in the three-segment format, and an error correction code is added in the convolutional coding circuits 103 and 103B. 104B is supplied to the frame configuration unit 111 after being subjected to signal processing corresponding to the three-segment format. In the case of the 1 segment format, the convolutional encoding circuit 103B and the carrier modulation circuit 104B are unnecessary.

In frame configuration section 111, time interleaving and frequency interleaving are performed in time / frequency interleaving section 112, and then in OFDM frame configuration circuit 113, pilot signal generation section 114, control signal generation section 115, and additional information generation section 116 respectively. The generated pilot signal, control signal, and additional information are configured into an OFDM frame, and the output is supplied to the digital modulation unit 121.
In the digital modulation unit 121, the signal is converted into an OFDM symbol waveform by an inverse Fourier transform (IFFT) circuit 122, a guard interval is added by a guard interval adding circuit 123, and then converted to a radio frequency band broadcast signal by a frequency converting circuit 124. Is done. The broadcast signal is amplified to a predetermined power level by the power amplifier 125 and then transmitted from the transmission antenna 126 as a broadcast radio wave.

16 shows the transmission wave spectrum in the case of the single transmission method generated by the transmission system of FIG. 15, where (a) shows the single transmission spectrum in the 1-segment format, and (b) shows the single transmission spectrum in the 3-segment format. The horizontal axis indicates frequency.
As shown in FIG. 15, at the right end of the spectrum (upper end of the frequency axis), a pilot carrier 132 digitally modulated with a PRBS (Psuedo Random Binary Sequence) signal adjacent to the segments 131 and 133 In the specification, it may be simply referred to as “carrier”). This is because the scattered pilot (scattered pilot) signal for correcting the transmission line distortion of the radio wave is arranged at the outermost part and used as reference data arranged at the outermost edge for estimating propagation characteristics. It is. This pilot carrier 132 is added in any case regardless of the number of segments of the digital transmission signal.

For example, in a broadcasting system that covers a relatively small area, the digital audio broadcasting signal is transmitted from different transmission stations so as to cover each service area. In this case, as shown in FIG. 17, in order to reduce interference between channels assigned to each transmitting station, channels 1, 2, and 3 are adjacent to segments 131a, 131b, and 131c, respectively, and pilot carriers 132a, 132b, 132c is arranged, but guard bands 134a and 134b are provided between the channels to perform channel arrangement. The frequency width of the guard band is recommended to be 1/7 MHz (see Non-Patent Document 1).
Providing such a guard band has a problem in frequency management that the frequency use efficiency is worse than in the case of the concatenated transmission method, and the allocated frequency is different for single transmission and concatenated transmission, The receiver side has a problem that the reception frequency differs between the concatenated transmission and the single transmission for the same broadcast service.

  The broadcast signal transmitted in a concatenated manner can be received using a receiver for the broadcast signal transmitted independently. At this time, the pilot carrier added to the upper end of the band during single transmission is substituted with the pilot carrier at the lower end of the upper adjacent segment. By extrapolating the transmission characteristics using the pilot carrier, it is possible to ensure reception performance equivalent to that when receiving a single transmission digital broadcast signal.

JP 2009-16923 A JP 2012-209935 A

ARIB STD-B29 “Transmission Method for Terrestrial Digital Audio Broadcasting”, 2.2, Revised on November 30, 2005 2.2

However, in a broadcasting system that provides different services to a relatively narrow service area such as a digital community broadcast, if a concatenated transmission method is adopted, it is possible to broadcast including unnecessary broadcast signals like a broadcasting service outside the target area. Therefore, the desired digital broadcast signal cannot be incorporated into the broadcast service.
In addition, when a single transmission method that transmits a guard band between adjacent digital broadcast signals and a combined transmission method that transmits without a guard band are used in combination, the frequency utilization efficiency of the single transmission method is degraded. In addition, there is an adverse effect that the frequency of the broadcast signal is different between concatenated transmission and single transmission.

  FIG. 18 shows a comparison of the frequency arrangement of the transmission wave spectrum in the case of concatenated transmission and single transmission, where (a) shows the case of concatenated transmission and (b) shows the case of single transmission. As shown in FIG. 18, in the case of single transmission, since the guard band 134 is arranged between channels, the frequency arrangement is shifted by the guard band bandwidth. Therefore, the frequency arrangement is different from that in the case of concatenated transmission, and there is no merit of broadcasting by combining single transmission and concatenated transmission depending on the area. In addition, the administrative station cannot assign a frequency unless a transmission method is determined.

FIG. 19 is a diagram for explaining a problem that occurs when a single transmission is performed and transmission is performed without a guard band. FIG. 19A illustrates a channel 1 from the first transmission station 141 and a channel from the second transmission station 142. 2 shows a case where both broadcast radio waves are received at the reception point 143, (b) shows the frequency relationship between both transmission signals, and (c) shows an example of propagation path frequency characteristics of both channels.
Since the propagation paths 144 and 145 have different propagation environments including multipath, the propagation path frequency characteristics giving the propagation path characteristics are usually different. If the propagation characteristics of channels 1 and 2 received at reception point 143 are Fa (f) and Fb (f), respectively, the pilot carrier at the upper end of channel 1 is at the same frequency position as the pilot carrier at the lower end of channel 2. These pilot carriers are used as reception references for both channels. The received signal characteristic at the frequency f _b0 is {Fa (f _b0 ) + Fb (f _b0 )} because it is affected by the propagation characteristics of both channels.

However, since the data required as the reception standard of the receiver is Fa (f _b0 ) for channel 1 and Fb (f _b0 ) for channel 2, it is received when the data of the carrier frequency f _b0 is used as it is as a reception standard. Degradation of characteristics is caused.
As explained above, in the single transmission transmission system of digital audio broadcasting using the conventional technology, if the broadcast is performed with the same frequency arrangement as the concatenated transmission, the reception performance deteriorates due to the interference with the adjacent channel. Transmission in the arrangement is difficult.

FIG. 20 shows the frame structure of a digital broadcast signal. In mode 1, one segment is 108 carriers × 204 symbols, and one OFDM (Orthogonal Frequency Division Multiplexing) frame is configured. In FIG. 20, reference numeral 151 denotes an SP (Scattered Pilot) cell (in this specification, reference numeral 151 may be used for a scattered pilot signal). Reference numeral 152 denotes an information cell for transmitting information, and S _{i, j} denotes an information cell located at the j-th symbol on the i-th carrier. In addition, TMCC (Transmission Multiplexing Configuration Control) 153 transmits transmission control information, and AC (Auxiliary Channel) 154 can be used for transmission of additional information for transmission control in addition to the role of a pilot signal.

The scattered pilot signal is inserted into the SP cell 151 located every 12 carriers, and is sequentially shifted by 3 carriers for each symbol. This is because the SP cell 151 is 3 times the carrier interval (given by the reciprocal of the symbol length) in order to estimate propagation distortion due to multipath (up to 1/4 of the maximum symbol length) within the guard interval in digital audio broadcasting. This is because it is possible to correct transmission path distortion due to multipath having a quarter of the symbol length.
FIG. 20 shows the frame structure of a segment. For example, when a single segment signal is transmitted alone, a pilot carrier is added to the upper side of the 107th carrier and transmitted as described above.

FIG. 21 shows the relationship of segments when performing linked transmission. In concatenated transmission, the upper adjacent channel (channel 2) is arranged without a guard band immediately above the lower adjacent channel (channel 1). When the receiver receives and demodulates only channel 1 from the concatenated transmission signal, SP cell 151A arranged in carrier number 0 of channel 2 is also received and demodulated as a reception reference signal.
As shown in FIGS. 19 to 22, when the first transmitting station 141 transmits a digital broadcast signal of channel 1 and the second transmitting station 142 transmits a digital broadcast signal of channel 2 by single transmission, both transmitting stations In the area where the transmission signal can be received, the SP cell 151 arranged on the 0th carrier of the channel 2 is transmitted from both transmitting stations, and therefore interference shown in FIG. 19C occurs.

  The present invention solves the above-mentioned problems of the prior art, a digital broadcasting system capable of reducing interference between adjacent channels when transmitting between adjacent channels without a guard band, a transmission system and method thereof, and reception An object is to provide an apparatus.

  In order to solve the above-described problems, a digital broadcast transmission system according to the present invention includes an OFDM signal generation unit that generates an OFDM signal having an OFDM frame structure from a unit transmission wave of a broadcast transport stream including at least one segment. A digital broadcast transmission system for transmitting a digital broadcast signal in which a scattered pilot signal having a specific phase is arranged at a predetermined position in a frame, wherein the OFDM signal generation unit is transmitted from a plurality of transmission stations. Each of the transmitting stations operating in synchronization transmits the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the OFDM signal shared with different OFDM signals adjacent on the frequency axis. Having an OFDM frame configuration circuit for configuring an OFDM frame Wherein the no guard band is provided between an OFDM signal of a frequency adjacent transmitted from each transmission station.

  In another aspect of the present invention, a digital broadcast transmission system according to the present invention includes a plurality of OFDM signal generation units that generate an OFDM signal having an OFDM frame structure from unit transmission waves of a plurality of broadcast transport streams including at least one segment. (52, 62) and a concatenated transmission frame configuration unit (117) that concatenates a plurality of OFDM signals generated by the plurality of OFDM signal generation units to generate a concatenated OFDM signal, and in the concatenated OFDM frame A digital broadcast transmission system for transmitting a digital broadcast signal in which a scattered pilot signal having a specific phase is arranged at a predetermined position of the plurality of OFDM signal generation units, the frequency axis of the connected OFDM signal An OFDM signal generator that generates OFDM signals located at both ends of the The scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the concatenated OFDM signal shared with the different OFDM signals adjacent on the frequency axis transmitted from the radio station are operated in synchronization with each other. It is characterized by having an OFDM frame configuration circuit (53, 63) that configures an OFDM frame so that the transmitting station transmits in order.

In a preferred aspect, when transmitting in a mode that requires phase correction of each OFDM signal that constitutes the connected OFDM signal and a guard interval length, the frequency axis of each OFDM signal that is shared by the OFDM signals that constitute the connected transmission Means for correcting the phase of the scattered pilot signal arranged in the carrier located at both ends of the signal to the same phase as each OFDM signal to which the scattered pilot signal belongs.
This enables the phase of the shared scattered pilot signal to be corrected to the same phase as the segment to which the scattered pilot signal belongs during concatenated transmission, so that the phase relationship between the information cell of the segment and the scattered pilot signal is independently transmitted. Therefore, reception demodulation can be performed as in the case of a single transmission signal.

In the digital broadcast transmission system according to the present invention, scattered pilots arranged in carriers positioned at both ends of the frequency axes of adjacent OFDM signals or connected OFDM signals on the frequency axis transmitted from the transmitting stations. In order to prevent the signals from overlapping each other, it is preferable to include means for transmitting the scattered pilot signals in order in a predetermined order between the transmitting stations with reference to the OFDM frame synchronization signal of the digital broadcast signal.
As a result, the scattered pilot signals arranged in the carrier from each transmitting station are sequentially transmitted in the designated order in advance for each transmitting station, thereby preventing the overlapping of the scattered pilot signals arranged in the shared carrier. And the receiving device can correctly receive the scattered pilot signal.

In the digital broadcast transmission system according to the present invention, scattered pilots arranged in carriers positioned at both ends of the frequency axes of adjacent OFDM signals or connected OFDM signals on the frequency axis transmitted from the transmitting stations. It is preferable to include means for designating the position information in the OFDM frame or concatenated OFDM frame of the signal using transmission control information multiplexed in the same digital broadcast signal.
Accordingly, since the scattered pilot signal arranged in the carrier is designated using the transmission control information, the scattered pilot signal can be correctly received by making the receiving apparatus correspond to it.

In the digital broadcast transmission system according to the present invention, the studio station (31, 41) or each of the transmission stations (51, 61) that transmits a broadcast stream format broadcast program signal to the transmission station generates reference time information. Based on the reference time information generated by the common reference time generation station (71), the transmission timing is controlled to synchronize the transmission timing between the studio stations or between the transmission stations, or only a symbol that is an integer multiple of 4 It is preferable to have a synchronization signal generator (37, 47, 59, 69) that generates an OFDM frame synchronization signal by shifting.
Thereby, since synchronization between a plurality of studio stations or transmitting stations is performed in a simple manner, a scattered pilot arranged in a carrier shared by adjacent OFDM signals or concatenated OFDM signals within a predetermined broadcast service area The signal transmission timing can be kept within a predetermined time difference range.

In a preferred embodiment, a notification means that notifies the transmission timing of the frame synchronization signal at a predetermined time to each of the transmission stations (51, 61) in advance, and each of the transmission stations sets the transmission timing based on the notified transmission timing. Control means for controlling, and synchronization means (57, 67) for transmitting the transmission timing between the respective transmission stations in synchronization or by shifting the transmission timing by an integer multiple of 4 symbols.
Thus, by operating a plurality of transmitting stations at the same frequency and the same transmission timing, transmission of a scattered pilot signal arranged in a carrier shared by adjacent OFDM signals or concatenated OFDM signals within a predetermined broadcast service area Timing can be kept within a predetermined time difference range.

  In another aspect of the present invention, the present invention relates to a scattered pilot signal of a received digital broadcast signal, with respect to a scattered pilot signal arranged in a carrier located at both ends of the frequency axis of the received digital broadcast signal. A receiving apparatus having means for correcting transmission distortion based on the above is provided.

  In the receiving apparatus according to the present invention, at the timing at which the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the received digital broadcast signal are not transmitted, the data of the scattered pilot signal received immediately before It is preferable to have means for correcting transmission distortion by substituting. As a result, transmission distortion can be corrected even at a timing when the scattered pilot signal of the received signal is not transmitted.

  In the receiving apparatus according to the present invention, at a timing at which the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the received digital broadcast signal are not transmitted, the scattered pilot signals received before and after that are transmitted. It is preferable to have means for correcting transmission distortion using data interpolated from the data. As a result, since the reception conditions change with time, transmission distortion can be corrected effectively even when errors are likely to occur if the previous data is substituted.

In a preferred embodiment, a recognition means for recognizing identification information multiplexed on the received digital broadcast signal, and a digital broadcast received using the scattered pilot signal data based on the identification information recognized by the recognition means A determination means for determining whether or not to perform signal correction, the digital pilot signal that is broadcast by arranging the scattered pilot signal in carriers positioned at both ends of the frequency axis of each segment, and the digital broadcast transmission The digital broadcast signal transmitted by the system is separated.
As a result, the existing digital broadcast signal that is broadcast with the scattered pilot signal placed at the upper and lower ends of the frequency axis of each segment is distinguished from the digital broadcast signal transmitted by any of the digital broadcast transmission systems described above. Therefore, any digital broadcast signal can be received without lowering the function as compared with the existing receiving apparatus.

  In yet another aspect of the present invention, OFDM signals shared by different adjacent OFDM signals or concatenated OFDM signals on the frequency axis transmitted from a plurality of transmitting stations or carriers located at both ends of the frequency axis of the concatenated OFDM signal There is provided a digital broadcast transmission method in which each of the transmitting stations operating in synchronization transmits a scattered pilot signal arranged therein.

  According to the digital broadcast transmission system and method of the present invention, both ends of the frequency axis of the OFDM signal shared with different OFDM signals adjacent on the frequency axis of the unit transmission wave of the broadcast transport stream composed of at least one segment. Scattered pilot signals placed in a carrier located at the same position are transmitted in sequence by a plurality of transmitting stations operating in synchronization, so that interference between adjacent channels can be reduced and transmission distortion can be reduced to adjacent digital signals. Correction can be made without being affected by the broadcast signal.

  According to the digital broadcast transmission system and method therefor according to the present invention, in carriers located at both ends of the frequency axis of the connected OFDM signal shared by different OFDM signals adjacent on the frequency axis transmitted from a plurality of transmitting stations. Scattered pilot signals arranged at the same time are transmitted in order from each transmitting station operating in synchronization, so that interference between adjacent channels can be reduced in the case of concatenated transmission, and transmission distortion can be reduced by adjacent digital broadcasting. Correction can be performed without being affected by the signal.

  According to the receiving apparatus of the present invention, the transmission distortion is corrected based on the data of the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the received digital broadcast signal. Transmission distortion can be corrected without being affected by the adjacent broadcast signal even when there is a continuous change, and deterioration of reception characteristics can be reduced.

It is a figure which shows the frame structure at the time of the single transmission of the digital broadcast in the digital broadcast transmission system which concerns on this invention. It is a figure which shows the frame structure of the received signal in the demodulation output terminal of a receiver. It is a figure which shows the frequency arrangement | positioning example of the transmission wave spectrum at the time of a connection and single transmission. It is a figure which shows the example at the time of changing the number of channels in connection transmission. It is a figure which shows the frame structure at the time of the connection transmission of this invention. It is a block diagram which shows schematic structure of the digital broadcast transmission system of Example 1. FIG. It is a figure which shows the timing relationship of each part shown in FIG. (Example 1) It is a block diagram which shows schematic structure of the digital broadcast transmission system of Example 2. FIG. It is a figure which shows the timing relationship of each part shown in FIG. (Example 2) It is a block diagram which shows schematic structure of the digital broadcast transmission system of Example 3. FIG. 10 is a block diagram illustrating a schematic configuration of a linked transmission system according to a fourth embodiment. It is a block diagram which shows schematic structure of the receiver of this invention. (Example 5) It is a figure which shows the example of a channel arrangement | positioning in case there is no guard band. It is explanatory drawing of the difference in the frequency arrangement | positioning in the case where only the 1 segment format and the 3 segment format coexist. It is a block diagram which shows the prior art example of a digital audio broadcasting system. It is a figure which shows the transmission wave spectrum in the case of a single transmission system. It is a figure which shows the example of a channel arrangement | positioning in the case of a single transmission system. It is a comparison figure of the frequency arrangement | positioning of the transmission wave spectrum at the time of a connection and single transmission. It is explanatory drawing of the problem which arises when it transmits independently and without a guard band. It is a figure which shows the frame structure of a digital audio | voice broadcast signal. It is a figure which shows the relationship of the segment in the case of performing connection transmission.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a frame configuration at the time of single transmission of a digital broadcast in a digital broadcast transmission system according to an embodiment of the present invention. The digital broadcast signals of the first channel 18 and the second channel 19 shown in FIG. 1 are transmitted from the first and second transmission stations, respectively, and are adjacent to the upper end of the frequency axis of the digital broadcast signal of the first channel 18. A digital broadcast signal of 2 channels 19 is arranged. In FIG. 1, for the sake of clarity, the upper end portion of the first channel and the lower end portion of the second channel are shown separately, but in actual radio waves, the frequency position of the pilot carrier 11 that is the upper end of the segment of the first channel And the frequency position of the carrier 12 of the carrier number 0 which becomes the lower end of the segment of the second channel matches. That is, adjacent broadcast signals (carriers 11 and 12) are shared.

  In the pilot carrier 11 of the first channel 18, symbol numbers 4, 12... Are SP cells (SP-A) 13 a and transmit a scattered pilot signal, but other symbol number cells (indicated by hatching) ) 14 does not transmit radio waves. On the other hand, the carrier 12 of the second channel 19 is a SP cell (SP-B) 13b with symbol numbers 0, 8... And transmits a scattered pilot signal, but the cells with symbol numbers 4, 12. do not do. For this reason, interference with the scattered pilot signal of the first channel 18 is not avoided.

The information cell 16 of the carrier number 0 of the second channel transmits radio waves as it is except for the cells (S _0,4 , S _0,12 ...) _Of symbol numbers 4, 12. Thus, for the cell of the symbol number (4 × n; n = 0, 1, 2,...) For transmitting the scattered pilot signal, the scattered pilot signal is alternately transmitted so that different transmission stations do not overlap. To do. In other words, the scattered pilot signals transmitted from different transmitting stations in the shared pilot carriers 11 and 12 do not overlap each other on the basis of the OFDM frame synchronization signal of the digital broadcast signal. Transmit alternately or sequentially in the order specified in advance between the transmitting stations.
Also, except for the scattered pilot signal, the second channel information (information cell 16) is transmitted from the second transmitting station, and no radio waves are transmitted from the first transmitting station. Therefore, the carrier of carrier number 0 in the second channel does not cause interference even though it is shared at the upper end of the second channel.

  FIG. 2 shows the frame structure of the received signal at the demodulation output terminal of the receiving apparatus that has received the digital broadcast signals of the first channel 18 and the second channel 19 at the same time. As can be seen from FIG. 2, in the carrier 12 with the carrier number 0 of the second channel, the scattered pilot signal of the SP cell (SP-A) 13a with the symbol numbers 4, 12,. Radio waves transmitted from the second transmitting station (see FIG. 19) are received by the other SP cells (SP-B) 13b and information cells 16.

The receiving apparatus that receives the digital broadcast signal of the first channel detects the pilot carrier on the upper side, that is, the signal of the SP cell (SP-A) 13a in the carrier 12 of the second channel, and estimates the propagation characteristics. . Since the signal is a signal transmitted from the first transmitting station, this propagation characteristic is given as Fa (f _b0 ) (see FIG. 19C), and radio wave interference from the second transmitting station is Absent.
Similarly, the receiving device that receives the digital broadcast signal of the second channel receives the signal of the SP cell (SP-B) 13b transmitted by the second transmitting station in the carrier 12 of the second channel and receives the reference signal. And This propagation function is given as Fb (f _b0 ), and there is no radio wave interference from the first transmitting station.

The frame configuration at the time of single transmission of digital broadcast in the digital broadcast transmission system according to the present invention enables channel arrangement without providing a guard band between adjacent channels. Even in the case of transmission, interference between adjacent channels can be eliminated.
FIG. 3 is an example of frequency arrangement of the transmission wave spectrum in the case of concatenated transmission and single transmission. FIG. 3A shows the case of concatenated transmission, and FIGS. According to the present invention, the channel arrangement can be made common regardless of single transmission or linked transmission. Here, the concatenated transmission means that a plurality of channels (for example, 1 segment format, 3 segment format, or 13 segment format) are transmitted from the same transmission point without a guard band.

  FIG. 4 shows an example when the number of channels in the concatenated transmission is changed. For example, in order to avoid interference with adjacent areas, in the case where only the boundary region is transmitted by changing the number of channels, as shown in FIG. 4 (a), N transmissions from a third transmission station (not shown) are performed. The N-th channel of the highest frequency of the concatenated transmission signal with concatenated channels and the concatenation of (N + 1) channels transmitted from the fourth transmitting station (not shown) as shown in FIG. 4B. It can be easily understood that interference similar to that in the case of the single transmission described in FIG. 19 described above occurs between the (N + 1) th channel of the highest frequency of the transmission signal.

That is, the pilot carrier 11 arranged at the upper end of the segment of the Nth channel of the digital broadcast signal transmitted from the third transmitting station and the (N + 1) th channel of the digital broadcast signal transmitted from the fourth transmitting station. The carrier frequency of carrier number 0 matches. Therefore, this pilot carrier is used as a reception reference for both channels, and the propagation characteristics of the channels transmitted from the third and fourth transmitting stations at the point of frequency f are Fc (f) and Fd (f), respectively. Since the received signal characteristic at the point of frequency f (N + 1) 0 is affected by the propagation characteristics of both channels, {Fc ( _{f (N + 1) 0} ) + Fd ( _{f (N + 1) 0} )} It becomes. That is, the same type of interference occurs between adjacent channels transmitted from the first and second transmitting stations described above (see FIG. 19C).

The inventors of the present invention are the Nth channel 28 having the highest frequency of the coupled transmission radio wave transmitted from the third transmission station and the (N + 1) th channel of the highest frequency of the coupled transmission radio wave transmitted from the fourth transmission station. By making the frame structure of 29 as shown in FIG. 5, interference between both radio waves could be avoided.
FIG. 5 is a diagram showing a frame configuration at the time of concatenated transmission according to the present invention. In FIG. 5, the digital broadcast signal of the Nth channel 28 is transmitted from a third transmission station (not shown), and the digital broadcast signal of the (N + 1) th channel 29 is transmitted from a fourth transmission station (not shown). The segment of the (N + 1) th channel 29 is arranged adjacent to the upper side of the segment of the Nth channel 28. In FIG. 5, for the sake of clarity, the upper end portion of the Nth channel 28 and the lower end portion of the (N + 1) th channel 29 are enlarged, and the Nth channel 28 and the (N + 1) th channel 29 are separated from each other. In the actual radio wave, the frequency position of the pilot carrier 21 that is the upper end of the segment of the Nth channel 28 matches the frequency position of the carrier 22 of carrier number 0 that is the lower end of the segment of the (N + 1) th channel 29.

As shown in FIG. 5, the symbol numbers 4, 12,... Are SP cells (SP-C) 23a for the pilot carrier 21 that is the upper end of the segment of the N-th channel 28, and the cell 23a transmits a scattered pilot signal. However, radio waves are not transmitted to the cells 24 of other symbol numbers (indicated by hatching).
On the other hand, the carrier 22 has an SP cell (SP-D) 23b with symbol numbers 0, 8,..., And the cell 23b transmits a scattered pilot signal, but does not interfere with the scattered pilot signal of the Nth channel 28. In order to avoid this, radio waves are not transmitted to the cells with symbol numbers 4, 12,.

S _{i, j} of the information cell 26 that transmits information indicates that it is located in the j-th symbol in the i-th carrier, and the information cell 16 of carrier number 0 in the (N + 1) -th channel 29 has symbol number 4, The radio waves are transmitted as they are except for the 12 cells.
As described above, for the cell of the symbol number (4 × n; where n = 0, 1, 2,...) For transmitting the scattered pilot signal, the third transmitting station and the fourth transmitting station alternately scatter. A pilot signal is transmitted. In addition to the SP cells 23a and 23b, the information (information cell 26) of the (N + 1) th channel 29 is transmitted only from the fourth transmitting station, and no radio wave is transmitted from the third transmitting station. . Therefore, although the carrier of carrier number 0 in the (N + 1) th channel 29 is shared by the Nth channel 28 and the (N + 1) th channel 29, no interference occurs.

In addition, the inventors have developed a receiving device that uses only the scattered pilot signals of the channels belonging to each transmission radio wave for reception demodulation, thereby preventing mutual interference between adjacent channels as in the case of single transmissions. I was able to avoid it.
The receiving apparatus according to the present invention for receiving the digital broadcast signal of the Nth channel 28 is provided in the SP cell (SP-C) 23a in the upper pilot carrier, ie, the carrier 23 of the carrier number 0 of the (N + 1) th channel 29. A signal is detected and propagation characteristics are estimated. Since the signal is a signal transmitted from the third transmitting station, the propagation characteristic of this cell is given as Fc (f _{(N + 1) 0} ) (see FIG. 19C), and the fourth transmission is performed. There is no radio wave interference from the station.
Similarly, the receiving apparatus according to the present invention that receives the digital broadcast signal of the (N + 1) th channel 29 receives the signal of the SP cell (SP-D) 23b transmitted by the fourth transmitting station in the carrier 22. As a reference signal. The propagation function of this cell is given as Fd (f _{(N + 1) 0} ), and there is no radio wave interference from the third transmitting station.

In the case of concatenated transmission, for a specific mode and guard interval length, it is defined that transmission is performed with phase rotation for each symbol. At this time, since the phase of the pilot carrier at the lower end of the upper adjacent channel is rotated for each symbol with respect to the lower segment, when the lower adjacent channel uses the pilot carrier as a reference signal, It is specified that the phase of the carrier is corrected for each symbol. (See Non-Patent Document 1, “4.3 Position correction of segment signal in concatenated transmission”)
In the concatenated transmission according to the present invention, for the SP cell in the pilot carrier between the segments, the same phase rotation as that of the segment to which the cell belongs is given to the scattered pilot signal. As a result, the phase relationship between the information cell and the SP cell becomes the same as in the case of single transmission, and reception demodulation is possible in the same way as reception of a single transmission signal. Therefore, it is not necessary to phase-rotate the pilot signal for each symbol in the receiving apparatus as in the existing digital broadcasting concatenated transmission system.

It should be noted that the phase correction amount is 0 degree for a combination of a mode that does not require phase correction and a guard interval length, and as a result, information cells and SP cells may be transmitted without phase correction.
As described above, by applying the frame configuration of the digital broadcast transmission system according to the present invention at the time of concatenated transmission, it is possible to arbitrarily set the number of concatenated transmissions for transmission. In addition, the relationship between single transmissions and connection transmissions to which the frame configuration according to the present invention is applied has been described, but it is clear that this relationship is also established between single transmissions and connection transmissions.

  Next, the present invention will be described in more detail with reference to the embodiments shown in the drawings. In the following embodiments, 2 2 so that the reception timings at the reception points of the first channel transmitted from the first transmitting station and the second channel transmitted from the second transmitting station are synchronized within a predetermined allowable range. Two transmitting stations operate synchronously. That is, a plurality of transmitting stations are synchronized with a common time reference. The following examples do not limit the invention. Moreover, the same code | symbol is attached | subjected about the same component in the following embodiment, and the overlapping description is abbreviate | omitted.

Example 1
FIG. 6 shows a schematic configuration of the digital broadcast transmission system according to the first embodiment of the present invention. As shown in FIG. 6, the present embodiment includes a first studio station 31, a second studio station 41, a first transmission station 51, a second transmission station 61, a common reference time generation station 71, a first transmission line 81, a first transmission line 81, 2 transmission line 82 and general communication line 83. The first studio station 31 and the second studio station 41 include digital broadcast studios 32 and 42, transmission rate conversion units 33 and 43, multiple frame generation units 34 and 44, and reference time signal generation units 35 and 45, respectively. Further, the reference time signal generation units 35 and 45 are configured by GPS receivers 36 and 46 and synchronization signal generation circuits 37 and 47.

The first transmission station 51 and the second transmission station 61 include OFDM signal generation units 52 and 62, digital modulation units 54 and 64, transmitters 55 and 65, and transmission antennas 56 and 66, respectively. The OFDM signal generation units 52 and 62 include frame configuration units 52b and 62b having transmission line encoding units 52a and 62a and OFDM frame configuration circuits 53 and 63, respectively.
Digital audio broadcast signals produced in the digital broadcast studios 31 and 41 are converted into transmission rates by the transmission rate conversion units 33 and 43, converted into a bit rate for broadcasting in the OFDM signal format, and then generated as multiple frames. The broadcast TS signals are generated by being converted into multiplexed frames by the units 34 and 44, and the broadcast TS signals are transmitted to the transmission stations 51 and 61 via the digital transmission lines 81 and 82.

The common reference time generation station 71 includes a GPS receiver 72 and a synchronization signal generation circuit 73. The GPS receiver 72 receives a signal from a GPS satellite and generates a 10 MHz clock signal and a 1PPS signal. The synchronization signal generation circuit 73 generates an OFDM frame synchronization signal obtained by counting down from the 10 MHz clock signal, and also represents reference time information of the OFDM frame synchronization signal based on the 1PPS signal (indicated as T (R) in FIG. 7). ) Is generated. In this embodiment, this reference time information (frame synchronization reference time information) is sent to the synchronization signal generation circuits 37 and 47 of the first and second studio stations 31 and 41 via the general communication line 83. In the synchronization signal generation circuits 37 and 47 to which the reference time information is transmitted, a frame synchronization signal whose transmission timing is controlled by the frame synchronization reference time information is generated. The frame synchronization signal is sent to the multiplex frame generators 34 and 44, and the OFDM frame transmission timings of the first studio station 31 and the second studio station 41 are controlled.
The reason why the transmission line is the general communication line 83 in this embodiment is that the reference time information is transmitted not only as timing information using a digital line but also in a general data format.

  In the OFDM signal generation units 52 and 62 of the first and second transmission stations 51 and 61, unit transmission waves of 1 segment, 3 segments, or 13 segments transmitted via the first and second transmission lines 81 and 82, respectively. After error correction and coding are performed in the transmission path coding units 52a and 62a, and time interleaving and frequency interleaving are performed in the frame configuration units 52b and 62b, the OFDM of the OFDM frame structure together with the pilot signal, control signal, and additional information is performed. A signal is generated.

  In the OFDM frame configuration circuits 53 and 63, scattered pilot signals having a specific phase are arranged at predetermined positions in the OFDM frame, and different OFDMs adjacent on the frequency axis transmitted from the transmission stations 51 and 61 are arranged. The OFDM frame is configured such that the transmitting stations 51 and 61 alternately transmit the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the OFDM signal shared with the signal. The outputs of the OFDM frame configuration circuits 53 and 63 are converted into OFDM symbol waveforms by inverse Fourier transform in the digital modulators 54 and 64, and then a guard interval is added to the radio frequency band broadcast signal. Converted. The broadcast signal is amplified to a predetermined power level by the transmitters 55 and 65 and then transmitted from the transmission antennas 56 and 66 as a broadcast radio wave. That is, a plurality of terrestrial digital audio broadcast signals are transmitted from the first transmitter station 51 and the second transmitter station 61 without providing a guard band between the broadcast signals.

  FIG. 7 shows the timing relationship with respect to the 1PPS signal of each part of the digital broadcast transmission system shown in FIG. 6, where (a) shows the 1PPS signal and frame synchronization reference time information T (R), (b) and (d) The 1PPS signal and the frame synchronization signal 75 in the first and second studio stations 31 and 41, and (c) and (e) show the timing relationships of the frame synchronization signal 77 in the first and second transmission stations 51 and 61, respectively. In each case, the horizontal axis indicates time.

In the first studio station 31 and the second studio station 41, the broadcast TS signal is delayed by the delay time information T ₁ (S) and T ₂ (S), respectively, with reference to the frame synchronization reference time information T (R). To the first transmitting station 51 and the second transmitting station 61. The reason why the delay time is changed between the first studio station 31 and the second studio station 41 is because it is assumed that the delay times of the respective transmission lines are different. That is, the delay time information T ₁ (S), T ₂ (S) is preset in each studio station 31, 41 so as to satisfy the following equation.

T (R) + T ₁ (S) + T ₁ (N) = T (R) + T ₂ (S) + T ₂ (N) = T _TOTAL
Here, T ₁ (N) and T ₂ (N) are the transmission delay times of the first transmission line 81 and the second transmission line 82, respectively, and T _TOTAL is the transmission station 51, 61 based on the 1PPS signal. Indicates the total delay time until transmission timing.
As described above, when the transmission delay time between the studio stations 31 and 41 and the transmission stations 51 and 61 is known and there is no change, a simple synchronization system such as the digital broadcast transmission system according to the present embodiment is used. It is possible to synchronize the transmission timings of a plurality of studio stations.

-Example 2-
FIG. 8 shows a schematic configuration of a digital broadcast transmission system according to the second embodiment of the present invention. In the first embodiment, when the transmission delay time is fixed and known, the transmission stations 51 and 61 are synchronized. However, when a failure occurs in the communication line, the transmission may be transmitted by a detour route. In the present embodiment, the transmission timings of the transmission stations 51 and 61 are directly controlled to synchronize the transmission timings of the plurality of transmission stations 51 and 61.

As shown in FIG. 8, in the digital broadcast transmission system of the present embodiment, the first transmission station 51 and the second transmission station 61 are each composed of GPS receivers 58 and 68 and synchronization signal generation circuits 59 and 69, respectively. Signal generators 57 and 67 are provided. Then, the common reference time generation station 71 transmits the reference time information (denoted as T (R) in FIG. 9) of the OFDM frame synchronization signal generated in order to match the transmission timings of the plurality of transmission stations to the general communication line 83. To the synchronization signal generation circuits 59 and 69 of the reference time signal generation units 57 and 67 provided in the first transmission station 51 and the second transmission station 61, to control the OMDF frame synchronization timing of the transmission stations 51 and 61. . Other configurations and operations are the same as those in the first embodiment.
The frame synchronization signals generated by the synchronization signal generation circuits 59 and 69 are sent to the frame configuration units 52b and 62b, and the OFDM frame transmission timings of the first transmission station 51 and the second transmission station 61 are controlled.

  9 shows the timing relationship with respect to the 1PPS signal of each part of the digital broadcast transmission system shown in FIG. 8, where (a) shows the 1PPS signal and frame synchronization reference time information T (R), (b) and (d) The 1PPS signal and the frame synchronization signal 75 in the first and second studio stations 31 and 41, and (c) and (e) show the timing relationships of the frame synchronization signal 77 in the first and second transmission stations 51 and 61, respectively.

As shown in FIGS. 9C and 9E, the transmission timings of the transmission station 51 and the transmission station 61 are transmitted at a timing delayed by T _TOTAL with respect to the 1PPS signal, so that the OFDM frame configuration circuits 53 and 63 are transmitted. To control the operation. That is, in the OFDM frame configuration circuits 53 and 63, the transmission timings of the first transmission station 51 and the second transmission station 61 are directly controlled by controlling the delay times T ₁ (B) and T ₂ (B) to be T _TOTAL. As a result, the transmission timings of the transmitting stations 51 and 61 can be synchronized. Here, T _TOTAL indicates the total delay time up to the transmission timing of each of the transmission stations 51 and 61 on the basis of the 1PPS signal.
In this case, the first channel and the second channel can be transmitted from the studio stations 31 and 41 because the adjacent channel interference can be eliminated by making the frame head timing coincide or by shifting by an integer multiple of 4 symbols. The relationship between the broadcast TS signal and the OFDM frame timing is not a problem.

Example 3
FIG. 10 shows a schematic configuration of a digital broadcast transmission system according to the third embodiment of the present invention. The present embodiment is a terrestrial digital audio broadcast transmission system that synchronizes the transmission timings of a plurality of transmission stations, as in the first and second embodiments, but the first embodiment and the first embodiment for broadcasting a plurality of transmission stations on channels of different frequencies. Unlike the case 2, the case of a single frequency network (SFN) in which the same channel is operated by a plurality of transmitting stations at the same frequency and the same transmission timing.

  As shown in FIG. 10, the first transmission station 51 and the second transmission station 61 are provided with reference time signal generation units 57 and 67 each composed of GPS receivers 58 and 68 and synchronization signal generation circuits 59 and 69, respectively. . Then, the common reference time generation station 71 transmits the reference time information of the OFDM frame synchronization signal generated to match the transmission timings of the plurality of transmission stations via the general communication line 83 to the first transmission station 51 and the second transmission station. The reference time signal generators 57 and 67 of the reference time signal 61 are sent to synchronization signal generators 59 and 69. The synchronization signal generation circuits 59 and 69 to which the reference time information is transmitted generate a frame synchronization signal. The frame synchronization signal is sent to the frame configuration units 52b and 62b, and the OFDM frame transmission timings of the first transmission station 51 and the second transmission station 61 are controlled. Other configurations and operations of the first transmission station 51 and the second transmission station 61 are the same as those in the first embodiment.

In the digital broadcast transmission system of the present embodiment, the plurality of transmission stations 51 and 61 formed by the SFN are operated in synchronization. Since the transmission lines connected to the two transmission stations 51 and 61 are different, line faults may also occur individually. In this case, the transmission timing cannot be determined by the studio station 31 as in the first embodiment. FIG. 10 shows the transmission network of the first channel, but the second channel can also be synchronized with the same configuration.
FIG. 10 shows a configuration in which the first studio station 31 is also synchronized, but this requires timing management including the frame number, and therefore it is desirable to synchronize the transmission timing from the studio station 31 as well. .

Example 4
FIG. 11 shows a schematic configuration of a digital broadcast transmission system for linked transmission according to Embodiment 4 of the present invention. The present embodiment shows an example in which the number of connected transmission channels is N. In the first transmission station 51 of the second embodiment, the OFDM signal generation section 52 having the same configuration as the OFDM signal generation section 52 and the reference time signal generation section 57 is shown. -1 to 52-N and N reference time signal generators 57-1 to 57-N are arranged in parallel, and receive the OFDM signals from the OFDM signal generators 52-1 to 52-N. A frame configuration unit 117 is provided.

In the present embodiment, the OFDM signal generators 52-1 and 52-N that generate OFDM signals positioned at both ends on the frequency axis of the coupled OFDM signal coupled by the coupled transmission frame configuration unit 117 are adjacent on the frequency axis. A plurality of transmitting stations (not shown) operating in synchronization transmit scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the connected OFDM signal shared by different OFDM signals. The OFDM frame is configured as follows.
Outputs from the OFDM frame configuration circuits 53-1 to 53-N are supplied to the concatenated transmission frame configuration unit 117.
The functions of the other OFDM signal generators 52-1 to 52-N and the reference time signal generators 57-1 to 57-N are the same as those of the OFDM signal generator 52 and the reference time signal generator 57 of the second embodiment. It is.

The concatenated transmission frame configuration unit 117 generates a concatenated OFDM signal by matching the OFDM signals supplied from the OFDM frame configuration circuits 53-1 to 53-N with the heads of the reference frames. At this time, the concatenated OFDM signal may be generated by shifting the symbols by an integer multiple of 4 without matching the heads of the reference frames.
The output of the concatenated transmission frame configuration unit 117 is supplied to the digital modulation unit 54 and the transmitter 55, processed in the same manner as in the second embodiment, and then transmitted as a broadcast radio wave from the transmission antenna 56.

Next, a receiving apparatus that receives a digital broadcast signal transmitted by the above-described digital broadcast transmission system will be described.
-Example 5
FIG. 12 shows a schematic configuration of main parts of reception / demodulation of the digital broadcast receiving apparatus according to the fifth embodiment of the present invention. As shown in FIG. 12, the digital broadcast receiving apparatus of the fourth embodiment includes a receiving antenna 91, a tuner unit 92, a local oscillator 93, a synchronous reproduction circuit 94, a Fourier transform circuit (FFT) 95, a pilot signal extraction circuit 96, a correction value. A calculation circuit 97 and a data correction circuit 98 are included.

The digital audio broadcast signal received by the receiving antenna 91 is frequency-converted by the tuner unit 92, amplified to a predetermined signal level, and then supplied to the Fourier transform circuit 95. This signal is also supplied to the synchronous reproduction circuit 94 to reproduce the symbol timing and frame synchronization timing for operating the Fourier transform circuit 95.
The local oscillator 93 generates a local oscillation signal for converting the received signal into a baseband signal that can be subjected to Fourier transform, and supplies the local oscillation signal to the tuner unit 92.

  The Fourier transform circuit 95 is a circuit that converts a received signal into a frequency-axis signal, and its output is a signal having an OFDM frame configuration and is supplied to a pilot signal extraction circuit 96. The pilot signal extraction circuit 96 extracts a scattered pilot signal denoted as SP in FIG. The extracted scattered pilot signal is supplied to the correction value calculation circuit 97. The correction value calculation circuit 97 calculates a correction value for each frequency using the scattered pilot signal data in the frequency axis direction.

  When the digital audio broadcast signal is corrected, when the first channel 18 shown in FIG. 1 is received, the scattered pilot signal denoted as SP-A in FIG. 1 is used as the pilot signal at the upper end of the frequency band. Are used for correction value calculation. On the other hand, when receiving the second channel, the data of the scattered pilot signal represented as SP-B in FIG. 1 is used for the correction value calculation as the pilot signal at the lower end of the frequency band. Next, the data correction circuit 98 corrects the data and outputs it to the next decoding circuit. This makes it possible to demodulate data of a predetermined channel without being disturbed by adjacent channels.

If the propagation environment between the transmitter and receiver does not change during fixed reception, there will be no change in the propagation characteristics over time, so there will be no problem if you continue to use the calculated correction value. If the propagation environment changes due to reflections from the body, etc., or if the reception point itself fluctuates as in a portable receiver, the propagation characteristics change over time, so the correction value calculation can be updated sequentially. is necessary.
However, in such a case, in the above reception method, for example, at the positions of the symbol numbers 0, 8, 16... (8 × n)... In the first channel shown in FIG. I can't. In this case, an approximate value can be calculated using the data of the front and rear scattered pilot signals.

The first method is to use the data of the previous scattered pilot signal. For example, the data of the previous symbol number {4 × (2k−1)} is substituted as the data of symbol number {4 × 2k}. This is an effective method in a situation where the reception conditions do not change greatly.
The second method is to use the average value of the data of the front and rear scattered pilot signals. For example, the data of the scattered pilot signal with the symbol number {4 × 2k} is calculated using the data of the scattered pilot signals before and after that as follows.

SP {4 × 2k} = Ave [SP {4 × (2k−1)} + SP {4 × (2k + 1)}]
Here, Ave [] indicates an average value calculation. Since SP (n) is given as complex number data, the average value calculation is a complex number calculation.
The second method is particularly effective when an error is likely to occur if the previous data is substituted due to temporal changes in reception conditions, such as mobile reception or mobile reception.
As another interpolation method, it is also conceivable to interpolate data of a scattered pilot signal to which the data is not sent using a time-axis direction filter (temporal filter).

  The digital broadcast receiving apparatus and receiving method according to the present invention have been described above. However, digital audio broadcast signals that have already started broadcasting such as terrestrial digital television broadcasting and national digital multimedia broadcasting by the receiving apparatus of the present invention are described. If received, the reception performance may be lower than that of an existing receiving apparatus. This problem is identified in the transmission control information multiplexed in the same digital audio broadcast signal (hereinafter referred to as “TMCC signal”) indicating the digital audio broadcast signal described in the first to fourth embodiments. It could be solved by multiplexing the signals.

-Example 6
In the receiving apparatus of the sixth embodiment, a recognition unit that decodes the identification signal multiplexed in the control signal decoding circuit 109 shown in FIG. 12 and recognizes the identification information multiplexed in the received digital audio broadcast signal is used as the identification information. Is recognized, the information is sent to the correction value calculation circuit 97, and the signal processing operation described in the fifth embodiment is performed. On the other hand, when the identification information indicating the existing digital broadcasting radio wave is received, the same signal processing operation as that of the conventional receiving apparatus is performed. In the signal processing operation, since the pilot carrier is added to the upper end of the band of the digital audio broadcasting signal, the data of all the scattered pilot cells in the pilot carrier are used. In other words, both the SP cell (SP-A) and the SP cell (SP-B) are used for data interpolation.
According to the receiving apparatus according to the present embodiment, even when an existing digital audio broadcasting signal is received, the reception performance equivalent to that of the existing digital broadcasting receiving apparatus can be obtained.

In the above embodiment, digital audio broadcasting has been described. However, the present invention is not limited to audio broadcasting as long as it is digital broadcasting. In addition, the present invention has various effects as shown below.
(1) Effective use of frequency resources can be achieved by eliminating the need for a guard band between adjacent channels in a single transmission method broadcast from transmission stations arranged at different locations. FIG. 13 shows an example of channel arrangement in the case where there is no guard band using the 6 MHz band, for example. FIG. 13A shows an arrangement example in the case of no guard band. In this arrangement, the pilot carrier 11 is arranged at the upper end of the 14th channel segment. On the other hand, FIG.13 (b) shows the example of arrangement | positioning with a guard band. In this arrangement, the pilot carrier 11 is arranged at the upper end of each segment of the first channel to the tenth channel.
As can be seen from FIG. 13, 10 channels can be arranged when there is a guard band, and 14 channels can be arranged when there is no guard band, which brings about an effect that the frequency utilization efficiency is improved by 30% or more.

  (2) In terrestrial digital audio broadcasting, a 1-segment broadcast radio wave and a 3-segment broadcast radio wave are defined (see Non-Patent Document 1). However, in the method of providing a guard band 134 between adjacent channels, FIG. As shown in (a), the channel frequency arrangement is different between the case where only one-segment broadcast radio waves are used and the case where one-segment format and three-segment broadcast radio waves are mixed as shown in (b). Comparing both, it can be seen that the position of the guard band 134 has changed. This causes a management problem that frequency allocation differs in radio wave administration. Further, there is a problem that the broadcast radio wave selection operation of the receiving device is different depending on the presence or absence of the 3-segment format. Similar problems also occur in cases where concatenated transmission and single transmission are mixed. The present invention can solve these problems.

  (3) According to the present invention, in a digital community broadcast, a plurality of neighboring local governments adopt a concatenated transmission method for reducing transmission infrastructure costs in a specific area as shown in FIG. Therefore, an operation mode in which the single transmission method is adopted is possible due to the relationship between the frequencies. On the other hand, in the prior art, since a guard band is provided between each channel, the combined transmission method and the single transmission method cannot be used together.

<Modification>
The present invention is not limited to the description of the embodiment of the present invention described above, and various modifications are possible. For example, the following modifications may be made.
(1) In the above-described embodiment, among the SP cells of pilot carriers shared by adjacent channels, the upper adjacent channel side has symbol numbers 0, 8, 16 (8 × n), and the lower adjacent channel has symbol number 4, 12,20... {4 × (2n + 1)} and an example of using alternately, the symbol number to be used is not limited to this example. Further, a method for designating the symbol number position using transmission control information such as TMCC is also included in the scope of the present invention.

  (2) The method of using the frame synchronization reference time information generated by the reference time generation station is shown as a method of synchronizing a plurality of transmission stations, but is not limited to this. Other means may be used as long as the reference time can be shared by a plurality of transmitting stations. For example, in Japan, regional multimedia broadcasting and digital community broadcasting are planned to coexist in the V-Low frequency band, but when using transmission parameters common to regional multimedia broadcasting and digital community broadcasting, regional multimedia broadcasting is used. The synchronization information for managing the broadcast network for media broadcasting can be used as it is as a frame synchronization standard for digital community broadcasting.

(3) The method of synchronizing a plurality of transmitting stations has been shown to be distributed through a data communication line, but is not limited to this. The frame synchronization timing is obtained by dividing the 10 MHz clock signal generated by the GPS receiver. Since the period of the frame synchronization signal generated by each transmission station equipped with the GPS receiver matches, the reference time generation station sends out the frame synchronization signal based on the 1PPS signal, for example, once every hour. The frame synchronization timing of each transmitting station can be synchronized thereafter simply by notifying each transmitting station of the timing.
Accordingly, if only the time relationship between the 1PPS signal and the frame synchronization signal at a specific time is notified in advance, each transmission station can be synchronized. Therefore, the communication line that distributes the frame synchronization reference time information can be used at an accurate time. Can be performed using an asynchronous communication line such as IP communication.

  (4) In the above-described embodiment, the method of providing a GPS receiver to synchronize each transmitting station has been described. However, the present invention is not limited to this. The GPS signal is not limited as long as it is a common time reference. For example, a method using a digital line clock for distributing a broadcast TS signal is also possible. As the time reference, standard time broadcast from a standard frequency station such as JJY (registered trademark) can be used.

11, 21,132 Pilot carrier 12, 22 Carrier number 0 carrier 13a, 13b, 23a, 23b Scattered pilot (SP) cell 16, 26 Information cell 31 First studio station 32, 42 Digital broadcasting studio 33, 43 Transmission speed Conversion unit 34, 44 Multiple frame generation unit 35, 45, 57, 57-1 to 57-N, 67 Reference time signal generation unit 36, 46, 58, 68, 72 GPS receiver, receiver 37, 47, 59, 69 synchronization signal generation circuit, synchronization signal generation unit, synchronization means 41 second studio station 51, 61 first transmission station 52, 52-1 to 52-N, 62 OFDM signal generation unit 52a, 62a transmission path encoding unit 52b , 62b Frame configuration unit 53, 53-1 to 53-N OFDM frame configuration circuit 54, 64 Digital modulation unit 55, 65 Transmitter 56, 66 Transmitting antenna 61 Second transmitting station 71 Common reference time generating station 73 Synchronization signal generating circuit, synchronization signal generating unit 75, 77 Frame synchronization signal 81 First transmission line 82 Second transmission line 83 General communication line 91 Reception Antenna 92 Tuner 93 Local oscillator 94 Synchronous recovery circuit 95 Fourier transform circuit (FFT)
96 pilot signal extraction circuit 97 correction value calculation circuit 98 data correction circuit 109 control signal decoding circuit 117 concatenated transmission frame configuration unit 134, 134a, 134b guard band

Claims (12)

A scattered pilot signal having an OFDM signal generation unit for generating an OFDM signal having an OFDM frame structure from a unit transmission wave of a broadcast transport stream composed of at least one segment, and having a specific phase at a predetermined position in the OFDM frame Is a digital broadcast transmission system for transmitting a digital broadcast signal arranged,
The OFDM signal generator is configured to transmit scattered pilot signals arranged in carriers located at both ends of the frequency axis of the OFDM signal shared by different OFDM signals adjacent on the frequency axis transmitted from a plurality of transmitting stations. An OFDM frame configuration circuit that configures an OFDM frame so that each of the transmitting stations operating in synchronization transmits sequentially,
A digital broadcast transmission system, wherein no guard band is provided between adjacent OFDM signals transmitted from the transmitting stations. A plurality of OFDM signal generators that generate OFDM signals having an OFDM frame structure from unit transmission waves of a plurality of broadcast transport streams consisting of at least one segment, and a plurality of OFDM signals generated by the plurality of OFDM signal generators A concatenated transmission frame forming unit that concatenates to generate a concatenated OFDM signal is provided, and transmits a digital broadcast signal in which a scattered pilot signal having a specific phase is arranged at a predetermined position in the concatenated OFDM frame. A digital broadcast transmission system,
An OFDM signal generator that generates OFDM signals located at both ends on the frequency axis of the concatenated OFDM signal among the plurality of OFDM signal generators is a different OFDM signal adjacent on the frequency axis transmitted from each transmitting station. OFDM that constitutes an OFDM frame so that each of the transmitting stations that operate synchronously sequentially transmits the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the connected OFDM signal shared by A digital broadcast transmission system comprising a frame constituting circuit.   Positioned at both ends of the frequency axis of each OFDM signal shared by each of the OFDM signals constituting the concatenated transmission when transmitting in a mode and a guard interval length that require phase correction of each OFDM signal constituting the concatenated OFDM signal The digital broadcast transmission system according to claim 2, further comprising means for correcting the phase of a scattered pilot signal arranged in a carrier to be the same as each OFDM signal to which the scattered pilot signal belongs.   Scattered pilot signals arranged in carriers positioned at both ends of the frequency axes of adjacent OFDM signals or connected OFDM signals on the frequency axis transmitted from the transmitting stations do not overlap each other. The digital broadcast transmission according to any one of claims 1 to 3, further comprising means for transmitting the scattered pilot signal in order specified in advance between the transmitting stations with reference to the OFDM frame synchronization signal of the digital broadcast signal. system.   In the OFDM frame or the concatenated OFDM frame of the scattered pilot signal arranged in the carrier located at both ends of the frequency axis of each OFDM signal adjacent to each other or the concatenated OFDM signal on the frequency axis transmitted from each of the transmitting stations 5. The digital broadcast transmission system according to any one of claims 1 to 4, further comprising means for designating position information using transmission control information multiplexed in the same digital broadcast signal.   Each transmission timing based on the reference time information generated by the common reference time generating station that generates the reference time information by the studio station or each transmitting station that transmits the broadcast program signal in the transport stream format to the transmitting station. 6. A synchronization signal generation unit that generates an OFDM frame synchronization signal by controlling the transmission timing between the studio stations or between the transmission stations in synchronization or by shifting by an integer multiple of 4 symbols. The digital broadcast transmission system according to item 1. A notification means for notifying each of the transmission stations in advance of the transmission timing of the frame synchronization signal at a predetermined time;
Control means for controlling the transmission timing of each of the transmission stations based on the notified transmission timing;
The digital broadcast transmission system according to any one of claims 1 to 6, further comprising: a synchronization unit configured to synchronize or transmit the transmission timing between the transmission stations by shifting the number of symbols by an integer multiple of 4. A receiver for receiving a digital broadcast signal transmitted by the digital broadcast transmission system according to any one of claims 1 to 7,
For a scattered pilot signal arranged in a carrier located at both ends of the frequency axis of the received digital broadcast signal, it has means for correcting transmission distortion based on the data of the scattered pilot signal of the received digital broadcast signal A receiving device.   At the timing when the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the received digital broadcast signal are not transmitted, the transmission distortion is corrected by substituting the data of the previously received scattered pilot signal. The receiving device according to claim 8, further comprising: means.   At the timing at which the scattered pilot signals arranged in the carriers located at both ends of the frequency axis of the received digital broadcast signal are not transmitted, data interpolated from the data of the scattered pilot signals received before and after that is used. The receiving apparatus according to claim 8, further comprising means for correcting transmission distortion. Recognizing means for recognizing identification information multiplexed on the received digital broadcast signal;
Based on the identification information recognized by the recognition means, comprising a determination means for determining whether to correct the received digital broadcast signal using the scattered pilot signal data;
9. An existing digital broadcast signal that is broadcast by arranging the scattered pilot signal in carriers positioned at both ends of the frequency axis of each segment, and transmitted by the digital broadcast transmission system according to any one of claims 1 to 8. 11. The receiving apparatus according to claim 8, wherein the received digital broadcast signal is separated.   OFDM signals shared by different OFDM signals or concatenated OFDM signals adjacent on the frequency axis transmitted from a plurality of transmitting stations, or scattered pilot signals arranged in carriers positioned at both ends of the frequency axis of the concatenated OFDM signal A digital broadcast transmission method in which the transmitting stations operating in synchronization transmit in order.