JP2008147878A - Digital broadcasting relay apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcasting relay apparatus which can also compensate multi-path fading with a comparatively simple circuit added. <P>SOLUTION: In the digital broadcasting relay apparatus, an OFDM (Orthogonal Frequency Division Multiplex) signal are received by a plurality of receiving antenna systems 1-1 to 1-N, demodulated to a TS (Transport Stream) signal by demodulation units 3-1 to 3-N, synchronized by a synchronization circuit 5, then, they are transmitted to a selection unit 6. A TS signal without error is selected by an error bit detection unit 61 and a selection switch 62 of the selection unit 6 out of a plurality of synchronized TS signal systems, re-modulated by a modulation unit 7, carried out frequency conversion by a frequency conversion unit 8, then, retransmitted from a transmission antenna 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a digital broadcast relay apparatus and a digital broadcast relay method that are used in, for example, a terrestrial digital broadcast system and have a CN reset function that compensates for multipath.

  In the terrestrial digital broadcasting system, a large number of relay devices are distributed in a predetermined area for the purpose of expanding the broadcast service area and eliminating difficult viewing areas, and each relay device uses OFDM (Orthogonal Frequency Division Multiplexing). ) Method is used to relay broadcast wave signals in multiple stages. In this system, the relay device may not be able to accurately receive the broadcast wave signal from the base station due to the effects of multipath, multipath fading, and the like. In order to suppress this multipath, a digital broadcast relay apparatus having a CN reset function capable of resetting CN degradation has been proposed. The CN reset function in this relay device is obtained by demodulating a received broadcast wave signal into a TS (Transport Stream) signal, performing transmission channel compensation (equalization), and then performing re-modulation. The deterioration of the CN accumulated by the multistage relay in the station is reset.

  This CN reset function is very effective in a transmission environment where the deterioration is fixed. However, if the received power is rapidly reduced and deteriorated due to a dynamically changing propagation environment such as multipath fading, for example, fading, the signal cannot be completely demodulated and its performance cannot be fully demonstrated. There is.

  On the other hand, in order to compensate for multipath fading, a digital broadcast relay apparatus having a diversity function has been proposed (for example, Patent Document 1). According to the diversity function used in this relay device, the received multiple broadcast wave signals are weighted based on the transmission path response estimated for each system, and then diversity combining is performed, so that multiple broadcast wave signals can be obtained. It is possible to cope with a decrease in received power caused by path fading.

Therefore, in the digital broadcast relay apparatus having the CN reset function described above, if the diversity combining of the broadcast wave signal is performed before the demodulator that demodulates the broadcast wave signal into the TS signal, the conventional CN reset function is performed. It is considered that even a digital broadcast relay device having a multipath fading can be compensated. However, in the case of this method, there is a problem that the scale of the apparatus becomes large because a fast Fourier transform unit necessary for estimation of the transmission path response is required for each of the diversity combined systems separately from the demodulation unit.
JP 2002-271291 A

  As described above, the conventional digital broadcast relay apparatus having the CN reset function cannot cope with multipath fading, and if it is attempted to cope with it, the apparatus scale becomes large.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a digital broadcast relay apparatus and a digital broadcast relay method that can cope with multipath and multipath fading by adding a relatively simple circuit. It is.

  In order to achieve the above object, the present invention is received by a plurality of systems of receiving means for receiving OFDM (Orthogonal Frequency Division Multiplexing) broadcast signals independently of each other, and the plurality of systems of receiving means. A plurality of demodulating means for outputting TS (Transport Stream) signals from each of the broadcast signals, a synchronizing means for synchronizing the TS signals output from each of the plurality of demodulating means, and the synchronizing means. A selection unit that receives a plurality of TS signals and selects one of the plurality of TS signals; a modulation unit that modulates the selected TS signal; and a retransmission unit that retransmits the modulated TS signal. Transmitting means.

  In this way, the OFDM signals received independently from each other by a plurality of systems of receiving means are demodulated into TS signals by the demodulating means, synchronized by the synchronizing means, and then output to the selecting means. The TS signal selected by the selecting means among the TS signals of a plurality of systems is remodulated by the modulating means and retransmitted from the retransmitting means.

  In particular, in the digital broadcast relay apparatus having the above-described configuration, when the broadcast signal conforms to the ISDB-T (Integrated Services Digital Broadcasting for Terrestrial) standard, the selection means includes a plurality of synchronized outputs. A PID (Packet Identifier) and a transmission error identifier included in a system TS signal are detected, and a selection signal is generated to select a TS signal having a transmission error identifier indicating no error from TS signals of the same PID. And a selection switch means for selecting and outputting a TS signal having a transmission error identifier indicating no error by a selection signal from the signal generation means.

  In this way, the selecting means selects an error-free TS signal from a plurality of systems of TS signals.

  In the present invention, the received OFDM signals of a plurality of systems are demodulated into a plurality of systems of TS signals, a TS signal indicating no error is selected, and then re-modulated and retransmitted. Therefore, multipath and multipath fading are performed. Therefore, more stable broadcast wave relay can be realized. In addition, since the selection means selects an error-free TS signal from a plurality of systems of TS signals based on the PID and the transmission error identifier, a relatively simple circuit compared to a conventional digital broadcast relay apparatus having a CN reset function. In addition, multipath fading can be supported. Therefore, according to the present invention, it is possible to provide a digital broadcast relay apparatus and a digital broadcast relay method that can cope with multipath and multipath fading by adding a relatively simple circuit.

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

  FIG. 1 is a block diagram showing a schematic configuration of a digital broadcast relay device according to an embodiment of the present invention. In FIG. 1, OFDM signals received independently from each other by receiving antennas 1-1 to 1-N are received by a tuner unit 2-1 to 2-N at a predetermined IF (Intermediate Frequency: intermediate) for each receiving antenna system. Frequency) band signal and then supplied to the demodulating units 3-1 to 3-N. Demodulating sections 3-1 to 3-N perform distortion compensation, deinterleaving, and error correction on the IF signal transmission path, and demodulate TS signals of a plurality of systems. At this time, the TS signals of a plurality of systems that are demodulated and output by the demodulation units 3-1 to 3-N are output at different timings, and therefore are sent to the buffer units 4-1 to 4-N for timing adjustment. Temporarily retained. The TS signals held in the buffer units 4-1 to 4 -N are read out in a synchronized state in accordance with the synchronization establishment signals supplied from the synchronization circuit 5 to the buffer units 4-1 to 4 -N, and are sent to the selection unit 6. Is output.

  As shown in FIG. 2, the selector 6 receives the synchronized TS signals of a plurality of systems, branches the TS signals of each system into two, leads one to the error bit detector 61, and selects the other as the selection switch 62. Derived to The error bit detector 61 detects the presence or absence of an error from the error bit in the TS signal, generates a selection signal for selecting a TS signal indicating no error, and outputs the selection signal to the selection switch 62. Based on the selection signal from the error bit detector 61, the selection switch 62 selects and outputs a TS signal indicating no error from a plurality of TS signals.

  The TS signal indicating no error output from the selection unit 6 is modulated again by the modulation unit 7, converted to a desired channel transmission frequency by the frequency conversion unit 8, and then retransmitted from the transmission antenna 9.

  Next, a TS signal selection operation indicating no error in the selection unit 6 in the above configuration will be described in detail.

  FIG. 3 shows an example of a structure diagram of a TS packet of a TS signal in the ISDB-T standard according to an embodiment of the present invention.

  As shown in FIG. 3, one bit of a transmission error identifier is inserted in the TS header of the TS signal in the ISDB-T standard, and the error bit detector 61 determines whether there is an error in the 188-byte TS packet. Is recognized by detecting this transmission error identifier. Further, by detecting a PID (Packet Identifier) in the header, it is confirmed whether or not the OFDM signal packets received by the receiving antennas 1-1 to 1-N are the same.

  In FIG. 2, when a plurality of systems of TS signals synchronized by the synchronization circuit 5 are input from the buffer units 4-1 to 4 -N to the selection unit 6, the error bit detection unit 61 determines the PID of each TS signal. Detect transmission error identifiers. The error bit detection unit 61 checks whether there is an error displayed in the transmission error identifier between packets having the same PID, and selects a selection signal for selecting a TS signal having a transmission error identifier indicating no error. Output to. The selection switch 62 selects a TS signal having a transmission error identifier indicating no error from among a plurality of TS signals based on the selection signal from the error bit detection unit 61 and outputs the selected TS signal to the modulation unit 7.

  Therefore, in the digital broadcast relay apparatus having the above configuration, an error-free TS signal is selected from among the demodulated TS signals of a plurality of systems, so that the reliability of broadcast wave relay can be further improved and more stable. Broadcast wave relay can be realized. In addition, with the addition of a relatively simple circuit, it is possible to realize multipath fading that has been difficult with the conventional digital broadcast relay apparatus with a CN reset function.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

The block diagram which shows the structure of one Embodiment of the digital broadcast relay apparatus which concerns on this invention. The block diagram which shows the specific structure of the selection part of the said embodiment. FIG. 4 is a structural diagram illustrating an example of a TS packet of a TS signal according to the embodiment.

Explanation of symbols

  1-1 to 1-N: receiving antenna, 2-1 to 2-N, tuner unit, 3-1 to 3-N, demodulating unit, 4-1 to 4-N, buffer unit, 5 ... synchronization circuit, 6 ... selection unit, 61 ... error bit detection unit, 62 ... selection switch, 7 ... modulation unit, 8 ... frequency conversion unit, 9 ... transmission antenna.

Claims (3)

OFDM (Orthogonal Frequency Division Multiplexing: orthogonal frequency division multiplexing) broadcast signals of multiple systems that receive broadcast signals independently of each other;
A plurality of demodulation means for outputting a TS (Transport Stream) signal from each of the broadcast signals received by the plurality of systems of reception means;
Synchronization means for synchronizing TS signals output from each of the plurality of demodulation means;
A selection means for inputting a plurality of TS signals synchronized by the synchronization means, and selecting one of the plurality of TS signals;
Modulation means for modulating the selected TS signal;
A digital broadcast relay apparatus comprising: a retransmission unit configured to retransmit the modulated TS signal. When the broadcast signal conforms to ISDB-T (Integrated Services Digital Broadcasting for Terrestrial) standard,
The selection means includes
A TS signal having a transmission error identifier for detecting a PID (Packet Identifier) and a transmission error identifier included in the TS signals of a plurality of systems outputted in synchronization and indicating no error among TS signals of the same PID. Signal generating means for generating a selection signal to select
2. The digital broadcast relay apparatus according to claim 1, further comprising selection switch means for selecting and outputting a TS signal having a transmission error identifier indicating no error according to a selection signal from the signal generation means. Broadcast signals of OFDM (Orthogonal Frequency Division Multiplexing) system are received independently by multiple systems,
Demodulate the TS (Transport Stream) signal from each of the broadcast signals received by the multiple systems,
Synchronizing the TS signals of the plurality of systems,
Selecting one of the synchronized TS signals of the plurality of systems;
Modulating the selected TS signal;
A digital broadcast relay method, characterized by retransmitting the modulated TS signal.

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