JP2008072528A - Digital broadcasting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a broadcast network by SFN by optimizing transmission broadcast radio waves for a plurality of broadcasting devices in a service area, and effectively use an empty channel obtained thereby.
An SFN broadcasting network is constructed by a system of broadcasting apparatuses 120 to 12N. Here, when the b system having a frequency different from the frequency of the a system is allocated from the broadcasting apparatuses 120 to 12N for the additional service, the broadcasting apparatuses 120 to 12N transmit arbitrary contents by radio waves using the b system. In this way, VOD compatible additional services are realized. In the VOD-compatible broadcasting devices 120 to 12N, when there is a VOD request for content deleted from the storage devices 200 to 20N, the requested content including the subscriber terminals 13 and 14 is searched. When the content is detected, the content is detected and transferred to the broadcasting apparatus that requested the search, or broadcasted directly from the broadcasting apparatus having the content.
[Selection] Figure 1

Description

  The present invention relates to a digital broadcasting system such as terrestrial digital television broadcasting.

  The terrestrial digital television broadcasting system currently in operation currently covers a required service area with a TS / TTL transmission network, an IF / TTL network, and a broadcast wave reception / retransmission network. Here, when switching from analog broadcasting to digital broadcasting, SFN (Single Frequency Network) has been adopted in order to effectively use the frequency. However, in practice, it is difficult to make the distance between the transmitting station and the relay station sufficiently close, and the difference between the two signals exceeds the guard interval in the common receiving area of both. One condition of SFN (Single Frequency Network) that “the signal deviation is within the guard interval” cannot be satisfied. In addition, in a relay station, it is often difficult to ensure isolation between a reception antenna and a transmission antenna, which is also an obstacle to realizing SFN.

  From the above, it is technically difficult to construct a broadcast network using the originally planned SFN (Single Frequency Network), and the main services in MFN (Multi-Frequency Network) Covers the area. However, a solution to the above problem has been proposed, and SFN will eventually be realized. At this time, the frequency used in MFN becomes an empty channel, and effective use of the frequency is desired.

In addition, as a technique for maintaining the reception level in the service area constant, Patent Document 1 discloses a digital television broadcast in which an OFDM-modulated television signal is adjusted by a step attenuator, amplified by a power amplifier, and transmitted from a transmission antenna. In the device, the reception level of the transmission signal transmitted from the transmission antenna is measured by the radio field intensity measuring device, the modulation signal level is adjusted by the step attenuator based on the measurement result, and the output of the transmitted transmission signal is kept constant. It is described to control.
JP 2000-324361 A

  As described above, in the conventional digital broadcasting system, since it is difficult to construct a broadcasting network by SFN in relay transmission, the broadcasting network is constructed by MFN. For this reason, it is desired to effectively use the frequency that has become an empty channel when SFN is realized.

  In order to solve the above-described problems, an object of the present invention is to provide a digital broadcasting system and a broadcasting apparatus capable of effectively using an allocated channel frequency and realizing an additional service when realizing SFN. To do.

  In order to solve the above problem, a digital broadcast system according to the present invention is characterized by the following configuration.

  (1) A broadcasting network is constructed by a plurality of broadcasting devices that receive digital broadcasting signals distributed over a wired or wireless network and transmit the digital broadcasting signals to each other by a radio wave to a predetermined service area at the same channel frequency. In the digital broadcasting system, when one or a plurality of channel frequencies different from the channel frequency of a radio wave transmitted in common from the plurality of broadcasting devices are allocated for an additional service, any of the plurality of broadcasting devices An additional service means for transmitting an arbitrary digital broadcast signal toward a predetermined service area by radio waves using a channel frequency, and any one of the broadcasting devices including the additional service means receives the digital broadcast signal; Receiving means for acquiring arbitrary content; and Storage means for storing Ntsu, and an outputting means for outputting been content stored in the storage means to the requesting by the wired or wireless network in response to the request.

  (2) In (1), the broadcasting device including the additional service means includes a storage device that stores the content of the arbitrary digital broadcast signal, and transmits the content stored in the storage device as an additional service. When content not stored in the storage device is requested, the content stored in another broadcasting device is searched and acquired.

  (3) In (1), when a plurality of channel frequencies are allocated for the additional service, the broadcasting device including the additional service means searches for an empty channel frequency and uses the channel frequency to search for the additional service. It is characterized by performing.

  That is, according to the present invention, broadcasting of SFN is performed by distributing digital broadcasting signals to a plurality of broadcasting devices via a wired or wireless network, and sending digital broadcasting signals to a predetermined service area by radio waves at the same channel frequency. Build a net. Here, when one or a plurality of channel frequencies different from the channel frequency of the radio wave transmitted in common from a plurality of broadcasting apparatuses are allocated for additional services, the allocated channel frequency is used in any of the plurality of broadcasting apparatuses. By sending an arbitrary digital broadcast signal to a predetermined service area by radio waves, an additional service is realized and an effective use of an empty channel is achieved. In such a system, any of the broadcasting devices provided with the additional service means can output any content stored by receiving the digital broadcasting signal to the request source by the network according to the request, and store it in the storage device. When a content that is not stored in the storage device is requested by another broadcasting device that transmits the content to be added as an additional service, the content stored in the other broadcasting device can be searched and acquired.

  Therefore, according to the present invention, it is possible to provide a digital broadcasting system and a broadcasting apparatus capable of effectively using an allocated channel frequency and realizing an additional service when implementing SFN.

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

  FIG. 1 is a block diagram showing an embodiment of a digital broadcasting system according to the present invention. In FIG. 1, the studio 11 converts an on-air digital broadcasting TS into IP, and a wired / wireless network (including existing TS / TTL) such as an optical fiber line, a wireless LAN, and an IP (Internet Protocol) network. In the following description, an IP network is used as an example and distributed to a broadcasting device 120 (hereinafter referred to as a parent station broadcasting device) 120 via the NET, and the parent station broadcasting device 120 has jurisdiction. It is also distributed to N broadcasting devices (hereinafter referred to as slave station broadcasting devices to be distinguished from the master station) 121 to 12N arranged in the service area.

  The broadcasting apparatuses 120 to 12N have the same configuration. The transmitting apparatuses 100 to 10N convert IP digital broadcast signals distributed over the network into TSs, delay them by a predetermined time, perform OFDM modulation, and transmit antennas A0 to A5. Sent to the service area of jurisdiction. The digital broadcast signal output from the master station broadcasting device 120 is transmitted with high power from the a system of the transmission antenna A0 of the master station transmitting station to the entire service area. On the other hand, the slave station broadcasting devices 121 to 12N arranged in the area transmit with necessary and sufficient power, for example, through the a system of the transmission antennas A1 to AN toward an area that cannot be covered by the master station. Here, by appropriately adjusting the delay time and the signal level on the slave station side, it is possible to appropriately adjust the reception state between the master station and the adjacent station, and the SFN is adjusted by adjusting the output of each broadcasting device. Can be realized.

  In the above system, each of the broadcasting devices 120 to 125 stores the storage devices 200 to 20N that store arbitrary digital broadcast signals (contents) and the content stored in the storage devices 200 to 20N upon receiving a request from a registered user, for example. VOD (video on demand) control devices 300 to 30N for transmitting the digital broadcasting signal through the b system of the transmission antennas A0 to AN are provided.

  A terminal (TV or the like) 15 of a registered user who uses the VOD service is connected to the network NET. It is assumed that a VOD requesting device 16 is connected to the terminal 15 and that it is possible to request any content provided by the b system through communication.

  That is, in the broadcasting system configured as described above, the a system of all the broadcasting apparatuses 120 to 12N is configured by SFN. This is realized by improving the current terrestrial digital broadcasting and appropriately adjusting the output of each of the broadcasting devices 120 to 12N. As a result, the channel used in MFN becomes an empty channel. Therefore, an additional broadcasting service of the b system is realized by using an empty channel and other available channels. As service content, VOD is effective, but other than this, use of repeatedly broadcasting program content with a high audience rating is also conceivable.

  Broadcasting of the above system b may be performed by all broadcasting apparatuses on the same channel, or all broadcasting apparatuses may be performed by different channels. When different contents are broadcast in adjacent areas, they are performed in different channels. When signals from two broadcasting devices between adjacent areas are received, the same contents are transmitted in the same channel at the same synchronization timing. In this case, the output power, guard interval length, mode, convolution, and modulation scheme of system b are considered.

  In some cases, the a system and the b system of the transmission antennas A0 to AN can be shared. Further, there may be a broadcasting apparatus of only the a system that does not perform the broadcasting of the b system and a broadcasting apparatus of only the b system that does not perform the broadcasting of the a system. Also, in the b-system broadcast, the output power may be stopped under the control of the VOD control device.

  The storage devices 200 to 20N always store terrestrial digital broadcasts transmitted over a network NET such as an optical IP network, the VOD control devices 301 to 30N store the results used as VOD, and the results used. The content is weighted based on the above, and is erased in ascending order of weight. The used result is calculated by the difference between the current time and the used time and the number of times used.

  As described above, in the above system, the conventional broadcasting system implements SFN as a-system broadcasting. This is because when the current digital terrestrial broadcasting system is improved and an IP network / TTL line is used for the transmission path, the SFN is configured by retransmitting the broadcast wave. At this time, a new service is provided on the vacant channel to improve the frequency utilization efficiency. The new service is a b ″ system. For example, it is possible to retransmit contents that have high viewer needs, and to transmit / receive signals transmitted using an IP network.

  By the way, in constructing the VOD, there may be a case where contents deleted from the storage devices 200 to 20N of the broadcasting devices 120 to 12N are requested. Therefore, a VOD service subscriber terminal is used. Specifically, the subscriber terminal can use an ad hoc broadcasting device (a device that limits the area to be broadcasted, and can be used for any fixed reception for home use, mobile terminal reception, or mobile reception such as an automobile). 13) and 14) are connected and connected to the network NET to realize the same function as the relay station. That is, the subscriber terminal stores arbitrary content of the a-system digital broadcast signal by the broadcast receiver, and arbitrarily receives and stores content of the b-system.

  In the VOD-compatible broadcasting devices 120 to 12N, when there is a VOD request for content deleted from the storage devices 200 to 20N, the requested content including the subscriber terminals 13 and 14 is searched. When the content is detected, it is transferred to the broadcasting apparatus that has made the search request, and the broadcasting by the b system is executed. Further, when a subscriber terminal functions as an ad hoc broadcasting device, it may be transmitted from the terminal.

  Therefore, according to the digital broadcasting system having the above-described configuration, the broadcasting radio wave of each broadcasting apparatus arranged in the service area is optimized and the SFN broadcasting network is constructed, so that an empty channel can be obtained. Additional broadcast services can be realized by distributing arbitrary contents. At this time, although the VOD service can be realized, the stored content can be shared between the broadcasting devices without always using the content distribution stored in the storage device 21 of the studio 11, so that an increase in traffic on the network NET is suppressed. It is possible to efficiently provide the requested content.

  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 components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a block diagram showing an embodiment of a digital broadcasting system according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Studio, NET ... Network, 120-12N ... Broadcasting device, 13, 14 ... Subscriber terminal (ad hoc broadcasting device), 100-10N ... Transmission device, 201-20N ... Storage device, 301-30N ... VOD control device, A0 to AN: Transmitting antenna.

Claims (3)

A digital broadcast system in which a broadcast network is constructed by a plurality of broadcast devices that receive digital broadcast signals distributed over a wired or wireless network and transmit the digital broadcast signals to the predetermined service area by radio waves at the same channel frequency. In
When one or a plurality of channel frequencies different from the radio wave channel frequency transmitted in common from the plurality of broadcasting devices are allocated for additional services, any of the plurality of broadcasting devices uses the allocated channel frequency. Additional service means for transmitting an arbitrary digital broadcast signal to a predetermined service area by radio waves,
Any of the broadcasting devices provided with the additional service means stores the receiving means for receiving the digital broadcast signal and acquiring arbitrary content, the storage means for storing the content, and the storage means in response to the request. Output means for outputting the received content to a request source via the wired or wireless network.   The broadcast device provided with the additional service means includes a storage device that stores the content of the arbitrary digital broadcast signal, transmits the content stored in the storage device as an additional service, and is not stored in the storage device 2. The digital broadcasting system according to claim 1, wherein when the request is requested, content stored in another broadcasting device is searched and acquired.   The broadcasting apparatus comprising the additional service means, when a plurality of channel frequencies are allocated for the additional service, searches for a free channel frequency and performs the additional service at the channel frequency. Item 2. A digital broadcasting system according to Item 1.

Images