JP2000332702A - Digital broadcast wave quality monitor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor the quality of a digital broadcast wave sent from a transmission station in real time. SOLUTION: A transmitter 11 and a receiver 13 are placed in a transmission station. A noise adding device 12 adds a white noise equivalent to a propagation loss caused on the way of propagation of a digital broadcast wave from the transmitter 11 up to an end of its service area to a digital broadcast signal which is received by the receiver 13 and a measurement unit 14 measures a carrier power versus noise ratio of the digital broadcast signal received by the receiver 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to, for example, OFDM.
The present invention relates to a digital broadcast wave quality monitoring system for monitoring the quality of a digital broadcast wave in a digital broadcasting system based on an (Orthogonal Frequency Division Multiplex) system.

[0002]

2. Description of the Related Art Recently, not only analog broadcasting but also digital broadcasting has been started to be used for terrestrial broadcasting. In this terrestrial digital broadcasting, a required carrier power to noise ratio (hereinafter, C / N (carr
ier to noise ratio) is small, so it is easy to secure a service area that is at least equal to that of current broadcasting.

[0003] By the way, in the case of an analog broadcast wave, the permissible power range is wide, and not only does the image quality gradually deteriorate with the decrease in the received power, but it is hardly possible to watch or listen at all. On the other hand, in a digital broadcast wave, the bit error rate sharply increases at a certain reception level and error correction becomes impossible, so that the image quality sharply deteriorates and a cliff effect of making viewing impossible occurs.

[0004] Therefore, when implementing digital broadcasting, it is necessary to check the quality of digital broadcasting waves. In order to confirm the quality, it is conceivable to monitor the reception C / N at the service area end as shown in FIG. The system shown in FIG. 4 receives a digital broadcast wave transmitted from a transmitter 41 in a transmitting station by a receiver 42 arranged at the end of a service area, and receives a digital broadcast wave by a measuring device 43 connected to the receiver 42. The reception C / N of a broadcast wave is measured, and the measurement result is notified to a transmitting station.

However, in the above system, in order to confirm the quality of the digital broadcast wave transmitted from the transmitter 41, a place where the receiver 42 and the measuring device 43 are installed at the end of the service area is secured, and the measurement result is constantly obtained. A communication line for notifying the user must be secured. In addition, the maintenance is required, and a large cost such as a labor cost is required.

On the other hand, in terrestrial digital broadcasting, the adoption of an OFDM modulation method that is resistant to interference due to multipath has been determined, and broadcasting waves can be relayed by SFN (Single Frequency Network). In SFN, multi-stage relay is performed such that digital broadcast waves transmitted from a master station are sequentially relay-transmitted by a plurality of relay stations at the same frequency.

[0007] In the above SFN, if the input / output characteristics of the amplifier in the relay station become slightly non-linear due to a failure, the digital broadcast wave deteriorates due to the intermodulation. Become a factor. In this case, the reception C / N ratio is equivalently reduced, and the service area is narrowed even with the same transmission power, so that an area where digital broadcast waves cannot be received occurs.

In particular, in a system that performs multi-stage relay, even if one of the amplifiers installed in a plurality of relay stations breaks down, the digital broadcast wave will be degraded. Stable transmission quality cannot be maintained. In this case, it is difficult to specify in which relay station the amplifier has failed, and it is not possible to smoothly switch to the backup system at the failed point, so that stable broadcast wave relay cannot be performed.

[0009]

As described above, in the conventional digital broadcasting system, the reception C / N must be monitored at the service area end in order to maintain stable transmission quality in the service area. Installation costs and maintenance costs are enormous.

[0010] Further, in the case of performing multi-stage relay, a countermeasure has not yet been established when the quality of a digital broadcast wave deteriorates.

A first object of the present invention is to provide a digital broadcast wave quality monitoring system capable of monitoring the quality of digital broadcast waves transmitted at a transmitting station at low cost and in real time.

A second object of the present invention is to provide a digital broadcast wave quality monitoring system capable of taking measures against real-time degradation of digital broadcast wave quality when relaying digital broadcast waves. It is in.

[0013]

In order to achieve the first object, a digital broadcast wave quality monitoring system according to the present invention is provided in a transmitting station and outputs a predetermined digital broadcast signal. For the receiver installed in the transmitting station and the digital broadcast signal received by this receiver,
Propagation characteristic control means for providing a propagation loss equivalent to a propagation loss occurring during the propagation of a digital broadcast wave from a transmitter to the end of a service area, and a carrier power of a digital broadcast signal connected to a receiver and received by the receiver. And a measuring device for measuring a noise ratio.

That is, according to the present invention, a transmitter and a receiver are installed in a transmitting station, and the receiver in the transmitting station has the same receiving characteristics as those in consideration of the propagation loss of the receiver at the service area end. In order to provide a digital broadcast signal received by the receiver installed in the transmitting station, after giving a propagation loss equivalent to the propagation loss that occurs during the propagation of the digital broadcast wave from the transmitter to the end of the service area, The carrier-to-noise ratio of a digital broadcast signal received by a receiver is measured by a measuring instrument. As a concrete means,
This is realized by supplying the equivalent white noise from the noise adding device to the receiver in the transmitting station in consideration of the degree of the propagation loss.

Therefore, according to the present invention, it is not necessary to connect a measuring device to the receiver at the end of the service area for monitoring, so that the location where the receiver and the measuring device are installed at the end of the service area and the measurement result can be transmitted. It is not necessary to secure a communication line for notifying users, and maintenance is also unnecessary, so that labor costs and maintenance costs can be significantly reduced, and transmission is currently performed by the receiver installed in the transmitting station The quality of digital broadcast waves can be monitored in real time.

On the other hand, in order to achieve the second object,
The digital broadcast wave quality monitoring system according to the present invention comprises:
Used in digital broadcasting systems that sequentially relay digital broadcast waves at the same frequency by multiple relay stations, and in a digital broadcast wave quality monitoring system that monitors the quality of digital broadcast waves at each relay station, Monitoring means for monitoring the deterioration state of the digital broadcast wave at each of the input side and output side of the relay amplifier for power-amplifying and transmitting the received signal of the digital broadcast wave, and monitoring the monitoring means of each of the plurality of relay stations Quality management means for collecting results and specifying a relay station in which a failure has occurred from the collected information.

The monitoring means includes a monitoring monitor for monitoring the state of deterioration of the digital transmission wave on each of the input side and the output side of the relay amplifier, and one of the input signal and the output signal of the relay amplifier for a certain period of time. And a changeover switch selectively derived to the monitoring monitor.

Therefore, according to the present invention, in each relay station, the deterioration state of the digital broadcast wave on the input side of the relay amplifier and the deterioration state of the digital broadcast wave on the output side are sequentially switched at predetermined time intervals by the changeover switch. The monitoring is performed in real time by the monitoring monitor, and the monitoring result of each relay station is collected by the quality control means. Then, the quality management means that collects the monitoring information of each relay station determines which relay amplifier of the relay station has failed. In this case, if the deterioration of the digital broadcast wave on the input side of the relay amplifier is detected, it is determined that a failure has occurred in the relay station in the preceding stage, and the relay station is operated in a state where the digital broadcast wave on the input side is not deteriorated. If the deterioration of the digital broadcast wave on the output side of the relay amplifier is detected, it is determined that a failure has occurred in the relay amplifier.

Therefore, it is possible to promptly take a countermeasure such as switching of the standby system and maintenance for the failed relay amplifier based on the result of the determination, and it is possible to perform stable digital broadcast wave relay.

In the above configuration, the monitoring means notifies the quality management means of a monitoring result in response to a request from the quality management means, and each of the plurality of relay stations includes a standby relay amplifier. In this case, there is provided a means for switching to a standby relay amplifier in accordance with a monitoring result or an instruction from the quality control means.

According to this configuration, the quality control means first gives an instruction to any relay station to monitor the deterioration state of the digital broadcast wave, and outputs the digital information to the input side of the relay amplifier from the obtained monitoring information. When the deterioration state of the broadcast wave is detected, a monitoring instruction is given to the preceding relay station, and the deterioration state of the digital broadcast wave is output to the output side of the relay amplifier while the digital broadcast wave on the input side is not deteriorated. Is detected, it is determined that a failure has occurred in the relay amplifier of the relay station at the time of the detection. Therefore, the quality control means immediately determines the faulty relay from the monitoring information of one of the relay stations. If the relay amplifier can be specified, and furthermore, each of the plurality of relay stations has a standby relay amplifier, only the failed relay amplifier should be switched to the standby relay amplifier according to the monitoring result, Disabilities corresponding cost effect can be greatly improved about, thereby also efficient.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing an embodiment of a digital broadcast wave quality monitoring system according to the present invention. The system shown in FIG. 1 includes a transmitter 11 installed in a transmitting station, a noise adding device 12 connected thereto, a receiver 13, and a measuring device 14 for measuring characteristics of the receiver 13. I have.

The transmitter 11 installed in the transmitting station has an OF
The digital broadcast wave according to the DM method is transmitted into a predetermined service area, and the transmission signal is transmitted to the receiver 13 via the noise adding device 12. Noise adding device 1
Reference numeral 2 denotes a white color equivalent to noise added in the course of digital broadcast wave propagation from the transmitter 11 to the service area end so that the receiver 13 has reception characteristics equivalent to those of the receiver existing at the service area end. The noise is added to the reception signal of the receiver 13. And the measuring device 14
The received carrier power to noise ratio C / N of the receiver 13 is measured.

Next, the details of the noise addition processing by the noise addition device 12 and the contents of the carrier power-to-noise ratio C / N measured by the measuring device 14 will be described in detail. Generally, a total carrier power-to-noise ratio C / N of a digital broadcast wave received by a receiver in a digital broadcast service area is expressed by the following equation.

C / N _t = 1 / ｛1 / (C / I) + 1 /
(C / _Nr )｝ C / _Nt : Total received C / N C / I: Ratio of carrier power to intermodulation power at the transmitter C / N _r : C / N at the receiver If this total C / N falls below the limit of reception C / N, The cliff effect occurs, and the image quality deteriorates rapidly, making it impossible to receive.

On the other hand, C / N at the receiver is deteriorated by propagation loss from the transmitting station to the receiver and thermal noise generated from the receiver. At the edge of the service area, the propagation loss is larger and C / N _r is worse than at other places in the area, so the difference between the total C / N and the limit C / N is small. Therefore, some ratio of carrier power to intermodulation power (hereinafter C / I (carr
ier to inter modulation ratio), there is a high possibility that reception will not be possible.

The digital broadcast wave handled in this embodiment is modulated by the OFDM method using thousands of carriers, and the amplifier to which the plurality of carriers are input fails and its input / output characteristics are slightly reduced. But when it becomes nonlinear,
The transmission C / I is greatly deteriorated by the intermodulation.

Therefore, in the first embodiment, the receiver 13 is installed in the transmitting station, and the reception C / N of the receiver 13 is set.
Is measured by the measuring device 14 to monitor the state of the transmission wave C / I. In this case, between the reception at the end of the service area and the reception in the transmission station, the C / C of the receiver is due to the propagation loss according to the distance from the transmission station to the receiver.
Since N is different, the noise adding device 12 adds an amount of white noise corresponding to the propagation loss to the received signal of the receiver 13, and then the measuring device 14 detects the received C / C of the receiver 13.
N is measured. By doing so, the C / N equivalent to the total reception C / N at the point at the end of the service area can be measured in the transmitting station.

As a result, the degradation of the transmission C / I
/ N, it is possible to monitor the quality of the transmitted wave in the transmitting station.

As described above, in the above-described first embodiment, the transmitter 11 and the receiver 13 are installed in the transmitting station, and the same as that of the first embodiment in consideration of the propagation loss of the receiver at the service area end. In order to give the receiving characteristic to the receiver 13 in the transmitting station, the reception signal of the receiver 13 installed in the transmitting station is equivalent to the propagation loss generated during the propagation of the digital broadcast wave from the transmitter 11 to the end of the service area. After the white noise is added by the noise adding device 12, the measuring device 14 measures the received carrier power-to-noise ratio C / N of the receiver 13.

Therefore, it is not necessary to connect a measuring device to the receiver at the end of the service area for monitoring, thereby notifying the transmitting station of the place where the receiver and the measuring device are installed at the end of the service area and the measurement result. Since it is not necessary to secure a communication line and no maintenance is required, labor costs and maintenance costs can be significantly reduced, and the digital broadcast wave currently transmitted by the receiver 13 installed in the transmitting station can be reduced. Quality can be monitored in real time.

(Second Embodiment) A second embodiment of the present invention relates to a digital broadcasting system for sequentially relaying and transmitting a plurality of relay stations at the same frequency by SFN using an OFDM digital broadcast wave. It is possible to monitor the quality of a digital broadcast wave at the same time.

FIG. 2 is a block diagram showing the configuration of the digital broadcast wave quality monitoring system according to the second embodiment.

In the system shown in FIG. 2, a digital broadcast wave generated from the master station M is received by the relay station 2A,
After the received signal is power-amplified by the relay amplifier 21A, it is transmitted to the next relay station 2B. The relay station 2B receives the digital broadcast wave transmitted from the relay station 2A, amplifies the power of the received signal by the relay amplifier 21B, and transmits the amplified signal to the next relay station 2C. Similarly, the relay station 2C is
The digital broadcast wave transmitted from B is received, the received signal is power-amplified by the relay amplifier 21C, and then transmitted to the next relay station.

By the way, in the second embodiment, the SF
In order to monitor in real time whether or not the digital broadcast wave that sequentially relays and transmits each of the relay stations 2A to 2C by N, the input side of the relay amplifiers 21A to 21C and Monitoring monitor 23 that monitors the deterioration state of the digital transmission wave on each output side
A to 23C are provided, and one of the input signal and the output signal of each of the relay amplifiers 21A to 21C is selectively derived to the corresponding monitoring monitors 23A to 23C at predetermined time intervals by the changeover switches 22A to 22C. I have.

The monitoring information by the monitoring monitors 23A to 23C of the respective relay stations 2A to 2B is collected by the control center CC via, for example, a telephone line. The control center CC identifies the relay station in which a failure has occurred from the monitoring information collected from each of the relay stations 2A to 2C, and sends a standby system switching instruction to the master station M, for example.

Each of the monitoring monitors 23A to 23B transmits monitoring information to the control center CC in response to a transmission request from the control center CC.

Next, the operation of the above configuration will be described. First, the control center CC, for example,
It is assumed that a monitoring instruction is issued to the monitoring monitor 23C of C. Then, the monitoring monitor 23C monitors the deterioration state of the digital broadcast wave based on the input signal and the output signal of the relay amplifier 21C derived by the changeover switch 22C. Here, if the input signal of the relay amplifier 21C has deteriorated, the digital broadcast wave received by the relay station 2C has already deteriorated. It can be seen that the relay amplifier has failed. In this case, by monitoring the reception signal and the transmission signal of the relay station 2B with the monitoring monitor 23B, whether the relay amplifier 21B in the relay station 2B has failed or the relay amplifier in the previous relay station has failed. Can be separated. In this way, by successively separating the faulty portions, the faulty portion of the relay amplifier can be finally detected.

When the monitoring monitor 23C detects that the output signal of the relay amplifier 21C has deteriorated in a state where the input signal of the relay amplifier 21C has not deteriorated, the control center CC transmits the signal to the control center CC. , It can be determined that the relay amplifier 21C is out of order.

As described above, according to the second embodiment, in each of the relay stations 2A to 2C, the relay amplifier 21A
Switch 21A between the input signal and output signal of
To 22C are sequentially switched at regular intervals and monitored in real time by the monitoring monitors 23A to 23C.
The monitoring result of each relay station 2A-2C is the control center C
Collected in C. On the other hand, in the control center CC,
First, an instruction to monitor the deterioration state of the digital broadcast wave is given to an arbitrary relay station 2C, and if the deterioration of the input signal of the relay amplifier 21C is detected from the obtained monitoring information, the relay station 2A of the preceding stage is , 2B relay amplifiers 21A, 21B
1B is determined to have failed, and the relay station 2 in the preceding stage is determined.
A and 2B are sequentially instructed to monitor, and the relay amplifier 21
When the input signal of C is not deteriorated, the relay amplifier 21
When the deterioration of the output signal of C is detected, it is determined that a failure has occurred in the relay amplifier 21C of the relay station 2C at the time of the detection.

Accordingly, the control center CC can immediately identify the faulty relay amplifier based on the result of the determination, and can promptly take countermeasures such as switching the standby system for the faulty relay amplifier. A stable digital broadcast wave relay can be performed.

(Third Embodiment) A third embodiment of the present invention relates to a digital broadcasting system for sequentially transmitting a plurality of relay stations at the same frequency by SFN to a plurality of relay stations using an OFDM scheme. When each station is provided with a standby system relay amplifier, it can be switched to the standby system relay amplifier according to the deterioration state of the digital broadcast wave.

FIG. 3 is a block diagram showing the configuration of a digital broadcast wave quality monitoring system according to the third embodiment. In FIG. 3, the same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description will be omitted.

In the system shown in FIG. 3, a relay amplifier 31A functioning as a standby system for the relay amplifier 21A is provided in the relay station 3A. And each relay station 3
A, according to the result of monitoring by the monitoring monitor 23A, the active relay amplifier 21A and the standby relay amplifier 31
A working / standby switching controller 32A for switching between A and A is provided. Also, in the relay station 3B, a relay amplifier 32B,
A working / standby switching controller 32B is provided.
Similarly, a relay amplifier 32B and a working / standby switching controller 32B are provided in C.

In such a configuration, the control center CC monitors the monitoring monitors 23A to 23A of each of the relay stations 3A to 3C.
If a failure, for example, the relay amplifier 21B that has failed can be identified from the monitoring information collected from the monitoring monitor 23C, the monitoring monitor 2
Send a standby system switching instruction to 3B. The monitoring monitor 23B that has received the standby system switching instruction sends the active / standby switching controller 32B an instruction to switch to the standby relay amplifier 31B. Then, the working / standby switching controller 32B
Performs switching from the relay amplifier 21B to the relay amplifier 31B.

As described above, according to the third embodiment, when the control center CC can detect, for example, the occurrence of a failure in the relay amplifier 21B, the working / standby switching controller 32B controls the failed relay Since only the amplifier 21B needs to be switched to the standby relay amplifier 31B,
It is possible to greatly improve the cost-effectiveness relating to failure handling, and it is possible to improve the efficiency as compared with the second embodiment.

(Other Embodiments) The present invention is not limited to the above embodiments, and various modifications can be made within the scope of those skilled in the art according to the gist of the present invention. Needless to say, these are also within the scope of the present invention.

[0049]

As described above in detail, according to the present invention, a transmitter and a receiver are arranged in a transmitting station, and digital broadcast signals received by the receiver are transmitted from the transmitter to the end of the service area. After a propagation loss equivalent to a propagation loss generated during wave propagation is given, a carrier power to noise ratio of a digital broadcast signal received by a receiver is measured.

Therefore, according to the present invention, it is possible to provide a digital broadcast wave quality monitoring system capable of monitoring the quality of digital broadcast waves transmitted at a transmitting station in real time.

Further, according to the present invention, it is possible to provide a digital broadcast wave quality monitoring system which can take measures in real time for quality deterioration of the digital broadcast wave when relaying the digital broadcast wave. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a digital broadcast wave quality monitoring system according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the digital broadcast wave quality monitoring system according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of the digital broadcast wave quality monitoring system according to the present invention.

FIG. 4 is a block diagram for explaining a system for monitoring a reception C / N at a service area end;

[Explanation of symbols]

 11, 41: transmitter, 12: noise adding device, 13, 42: receiver, 14, 43: measuring instrument, 2A to 2C, 3A to 3C: relay station, 21A to 21C: relay amplifier, 22A to 22B ... Changeover switches, 23A to 23C: monitoring monitor, 31A to 31C: standby system relay amplifier, 32A to 32C: working / standby switching controller, CC: control center. M: Master station.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Makoto Kaijima 1-1-1, Shibaura, Minato-ku, Tokyo Inside Toshiba Head Office (72) Inventor Seiji Isobe 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Street address Toshiba Komukai Plant

Claims (7)

[Claims] 1. A transmitter installed in a transmitting station for outputting a predetermined digital broadcast signal; a receiver installed in the transmitting station; and a transmitter for receiving a digital broadcast signal received by the receiver. A propagation characteristic control means for providing a propagation loss equivalent to a propagation loss occurring during the propagation of a digital broadcast wave from the terminal to a service area end; and a carrier power versus noise of a digital broadcast signal connected to the receiver and received by the receiver. A digital broadcast wave quality monitoring system, comprising: a measuring device for measuring a ratio. 2. The propagation characteristic control means according to claim 1, further comprising: a digital broadcast signal received by said receiver, the noise being added to the digital broadcast signal during propagation of the digital broadcast wave from said transmitter to a service area end. The digital broadcast wave quality monitoring system according to claim 1, wherein the system is a noise adding device that adds an equivalent one. 3. The noise adding device according to claim 1, further comprising: a digital broadcast signal received by the receiver, which is equivalent to noise added to the digital broadcast signal during propagation of the digital broadcast wave from the transmitter to a service area end. 3. The digital broadcast wave quality monitoring system according to claim 2, wherein white noise is added. 4. A digital broadcast wave quality monitoring system which is used in a digital broadcast system in which digital broadcast waves are sequentially relay-transmitted by a plurality of relay stations at the same frequency, and monitors the quality of the digital broadcast waves at each relay station. Monitoring means provided at each of a plurality of relay stations, for monitoring a deterioration state of the digital broadcast wave on each of an input side and an output side of a relay amplifier for power-amplifying and transmitting the received signal of the digital broadcast wave; and A digital broadcast wave quality monitoring system comprising: a quality management unit that collects monitoring results of monitoring units of relay stations and identifies a relay station in which a failure has occurred from the collected information. 5. The monitoring means monitors a deterioration state of a digital transmission wave on each of an input side and an output side of the relay amplifier, and monitors one of an input signal and an output signal of the relay amplifier. 5. The digital broadcast wave quality monitoring system according to claim 4, further comprising: a changeover switch that is selectively derived to the monitor at predetermined time intervals. 6. The digital broadcast wave quality monitoring system according to claim 4, wherein said monitoring means notifies a monitoring result to said quality management means in response to a request from said quality management means. 7. The monitoring unit, when each of the plurality of relay stations includes a standby relay amplifier, switches to a standby relay amplifier according to the monitoring result or an instruction from the quality management unit. The digital broadcast wave quality monitoring system according to claim 4, comprising: