JP2005244320A - Digital broadcast wave monitoring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast wave monitoring apparatus that can simply be installed and monitor a digital broadcast wave suitable for digital broadcasting. <P>SOLUTION: The digital broadcast wave monitoring apparatus, installed in a relay station of a digital broadcasting wave and monitoring the digital broadcasting wave includes a transmission loss adding means 2 for giving a transmission loss to arrived digital broadcast wave; a reception means 3 for receiving the digital broadcast wave with the transmission loss added thereto; a deterioration measuring means 4 for measuring the degree of the deterioration in the digital broadcast wave in the received signal; and an evaluation means 5 for evaluating transmission quality of the arrived digital broadcast wave, on the basis of the degree of deterioration. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for monitoring transmission quality of a relayed digital broadcast wave, and more particularly to a digital broadcast wave monitoring apparatus that can be easily installed and can be monitored suitable for digital broadcasting.

  In a digital broadcasting system, it is necessary to monitor the transmission quality of digital broadcasting waves.

  Conventionally, the terrestrial wave of television broadcasting has been only analog broadcasting, but recently, operation of digital broadcasting has started. In this terrestrial digital broadcasting, the required carrier power-to-noise ratio is smaller than that in analog broadcasting, so it is easy to secure a service area comparable to the current service area.

  By the way, in the analog broadcasting, the range of allowable reception power is wide, and the image quality is gradually deteriorated as the reception electric field is lowered. In contrast, in digital broadcasting, high-quality and uniform service is possible by using an error correction code with high correction capability. However, if the received electric field is not higher than a predetermined level, error correction cannot be performed and viewing is possible. It becomes impossible.

  For this reason, when performing digital broadcasting, it is necessary to monitor the transmission quality of digital broadcasting waves. As the digital broadcast wave monitoring device, the device of FIG. 10 can be considered. This monitoring apparatus receives a digital broadcast wave transmitted from a transmitter 102 in a transmission station 101 by a receiver 104 installed at a service area end 103, and a carrier power to noise ratio (C / N) of the received signal. Is measured by the measuring device 105.

  However, in the monitoring apparatus of FIG. 10, it is necessary to secure a place for installing the receiver 104 at the service area end 103, and a communication line for constantly reporting the measurement result to the transmitting station 101 or a monitoring station (not shown). Must be secured. Further, in order to operate this monitoring apparatus, it is necessary to dispatch personnel to the service area end 103 in order to maintain the receiver 104, so that costs such as personnel costs become large.

  In Patent Document 1, a receiver is installed in a transmitting station, and a noise adding device that gives a transmission loss equivalent to a transmission loss that occurs during propagation from the transmitter to the service area end between the receiver and the transmitter. The monitoring device with the inserted is shown. That is, the noise adding device simulates a transmission loss that occurs in the middle of propagation of a broadcast wave through a service area. This eliminates the need to install a receiver at the end of the service area, and solves communication lines and maintenance problems.

  In terrestrial digital broadcasting, an OFDM (Orthogonal Frequency Division Multiplexing) scheme that is resistant to interference caused by multipaths is adopted. By adopting this scheme, broadcast waves can be relayed by SFN (Single Frequency Network). . In SFN, multistage relay is performed in which digital broadcast waves transmitted from a master station are sequentially relayed by a plurality of relay stations at the same frequency.

  Patent Document 1 discloses a monitoring device that monitors the deterioration state of signals before and after a relay amplifier in each relay station.

JP 2000-332702 A

  In the monitoring device of Patent Literature 1, in order for the noise adding device to simulate a transmission loss during service area propagation, the transmission loss needs to be known. In other words, in order to install this monitoring device, it is necessary to investigate in advance the cause and size of transmission loss in the service area.

  In addition, in the monitoring device of Patent Document 1, only the carrier power to noise ratio is measured. However, as described above, since error correction is possible by using an error correction code in digital broadcasting, the carrier power to noise ratio is low. It is not necessarily an index directly related to transmission quality.

  Accordingly, an object of the present invention is to provide a digital broadcast wave monitoring device that solves the above-described problems, can be easily installed, and can perform monitoring suitable for digital broadcasting.

  To achieve the above object, the present invention is an apparatus for monitoring a digital broadcast wave installed in a digital broadcast wave relay station, a transmission loss adding means for giving a transmission loss to an incoming digital broadcast wave, and its transmission Receiving means for receiving a digital broadcast wave to which a loss has been added, deterioration measuring means for measuring the degree of deterioration of the digital broadcast wave in the received signal, and evaluation means for evaluating the transmission quality of a digital broadcast wave coming from the degree of deterioration It is equipped with.

  The deterioration measuring means may measure the carrier power to noise ratio as the degree of deterioration.

  The deterioration measuring means may measure the bit error rate as a degree of deterioration.

  The deterioration measuring unit may measure the packet error rate as a degree of deterioration.

  In the evaluation means, the degree of deterioration that does not hinder viewing is set as a reference value in advance, and the degree of deterioration measured by the deterioration measuring means when a transmission loss of a preset size is added. May exceed the reference value, it may be evaluated that the transmission quality of the digital broadcast wave is poor.

  The present invention exhibits the following excellent effects.

  (1) Since the transmission loss may be given as appropriate, the present apparatus can be easily installed.

  (2) Since the evaluation is performed in association with the viewing trouble, monitoring suitable for digital broadcasting can be performed.

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

  As shown in FIG. 1, the digital broadcast wave monitoring apparatus according to the present invention is an apparatus installed in a digital broadcast wave relay station to monitor the digital broadcast wave, and relays upstream from the master station or the own relay station. An antenna 1 for capturing a digital broadcast wave arriving at the relay station from the station, a transmission loss adding means 2 for giving a transmission loss to the acquired digital broadcast wave, and a receiving means for receiving the digital broadcast wave with the transmission loss added 3, a deterioration measuring means 4 for measuring the degree of deterioration of the digital broadcast wave in the received signal, and an evaluation means for evaluating the transmission quality of the digital broadcast wave coming from the degree of deterioration (included in the deterioration measuring means 4 in the figure) 5.

  Since the antenna 1 is conventionally provided in a relay station, description thereof is omitted.

  The transmission loss adding means 2 is configured by an attenuator that attenuates signal intensity continuously or stepwise, a noise adder that superimposes white noise with an arbitrary intensity, or a combination of these attenuators and noise adders. This is because transmission loss is caused by signal strength attenuation or noise superposition. Attenuation of signal strength is artificially given assuming that digital broadcast waves are attenuated due to the presence of rain, snow, and radio interference, but it is not added to simulate transmission loss at the service area end. Rather, it is added to examine the margin, as will be apparent later. The superimposition of white noise is artificially given assuming that thermal noise is generated in a transmission path such as a transmitter or a receiver, and this is also added to examine a margin.

  The receiving means 3 extracts a signal having a desired carrier frequency from the digital broadcast wave, and converts (demodulates) the signal into a code string signal of an image, sound or character signal. The receiving means 3 performs bit error correction and packet error correction by a known method at the time of demodulation.

  The degradation measuring means 4 measures the bit error rate of the C / N measuring device that measures the carrier power to noise ratio for the carrier frequency signal extracted by the receiving means 3, or the code string signal converted by the receiving means 3, or It is a digital signal tester that measures the packet error rate. The degradation measuring means 4 measures one or more of these carrier power to noise ratio, bit error rate, and packet error rate as the degree of degradation of the digital broadcast wave. The carrier power to noise ratio can be measured by a known method. The bit error rate is expressed by (number of bit errors / total number of bits). For example, when the reception unit 3 converts the number of bits of a predetermined length, the number of bits corrected and the number of bits of a predetermined length The ratio can be calculated. The packet error rate is expressed by (number of packet errors / predetermined number of packets) in the same way as the bit error rate, and the receiving means 3 calculates the ratio of the number of packets with error correction to the predetermined number of packets. Is obtained.

  In the evaluation means 5, a reference value (threshold value) for the degree of deterioration is set in advance. Specifically, the transmission loss is swept from a smaller value to a larger value, and the image (sound, character signal) obtained from the receiving means 3 is viewed on the receiver while measuring the degree of deterioration, and the presence or absence of trouble is visually recognized. . When viewing is disturbed, the degree of deterioration at that time is recorded, and a value slightly smaller than the degree of deterioration is set as a reference value. After making this setting, it is possible to determine whether or not there is an obstacle to viewing from the measured degree of degradation without actually viewing the image.

  The evaluation means 5 is preset with a predetermined transmission loss. The evaluation means 5 transmits the digital broadcast wave when the degree of deterioration measured by the deterioration measuring means 4 exceeds the reference value when the transmission loss of the preset size is added by the transmission loss adding means 2. The quality is evaluated as being poor.

  In the digital broadcast wave monitoring apparatus shown in FIG. 2, the transmission loss adding means 2 is composed of an attenuator 2a, and the digital broadcast wave is attenuated at an arbitrary continuous or stepwise attenuation ratio. Yes.

  In the digital broadcast wave monitoring apparatus shown in FIG. 3, the transmission loss adding means 2 is composed of a noise adder 2b so that white noise of an arbitrary intensity from the noise generator 6 is superimposed on the digital broadcast wave. It has become.

  In the digital broadcast wave monitoring apparatus shown in FIG. 4, the transmission loss adding means 2 is composed of a combination of an attenuator 2a and a noise adder 2b. The digital broadcast wave is attenuated by the attenuator 2a, and the noise adder is added. In 2b, white noise from the noise generator 6 is superimposed on the digital broadcast wave.

  The digital broadcast wave monitoring apparatus shown in FIG. 5 is obtained by adding control means 7 to the configuration of FIG. The control means 7 adjusts the magnitude of the transmission loss given by the transmission loss adding means 2 according to a command from the evaluation means 5.

  The digital broadcast wave monitoring apparatus shown in FIG. 6 is obtained by adding alarm means 8 to the configuration of FIG. The warning means 8 warns the outside of the digital broadcast wave monitoring device such as an operator of the own relay station when the digital broadcast wave monitoring device of the own relay station evaluates that the transmission quality of the digital broadcast wave is poor. In addition to issuing a warning, an alarm is sent to the outside of the own relay station such as the master station, upstream / downstream relay station or maintenance company. The content of the alarm is that the margin until the viewing is disturbed is small or the value of the margin.

  The operation of the digital broadcast wave monitoring device (FIGS. 1 to 6) of the present invention will be described below.

  Assuming that there is a digital broadcast wave with no transmission loss, if this digital broadcast wave is directly received and viewed, the carrier power-to-noise ratio is maximum, the bit error rate is minimum, and the packet error rate is also minimum. Will not cause any trouble. As the transmission loss increases, the noise increases relatively, so the carrier power to noise ratio decreases. As long as the carrier power to noise ratio does not become too small, error correction works even if there are some errors in the restored code string, so that viewing will not be hindered. However, if the carrier wave power to noise ratio increases to some extent, viewing will be hindered. Specifically, when the transmission loss increases, it becomes more difficult to restore the code string, so that the bit error rate increases and the packet error rate also increases.

  Therefore, the degree of deterioration expressed by the carrier power to noise ratio, the bit error rate, the packet error rate, and the like is an index that correlates the magnitude of transmission loss with viewing difficulties.

  In the present invention, the degree of deterioration from a state without transmission loss to a state immediately before a viewing problem occurs is considered as a margin. In the relay station, since an actual transmission loss has already occurred in the process of propagation of the digital broadcast wave from the master station to the relay station, a margin corresponding to the transmission loss is consumed. Therefore, the margin that the relay station can have is smaller than the initial margin.

  Therefore, the relay station artificially gives a transmission loss by the digital broadcast wave monitoring device to increase the degree of deterioration. Specifically, the transmission loss added by the transmission loss adding means 2 is swept from a very small value to a larger one. At some point during this sweep, viewing will begin to interfere. At this time, the increase in the degree of deterioration due to the transmission loss immediately before the viewing trouble occurs represents the margin that the relay station can have. If this margin is small, there is a high possibility that a viewing failure will occur in the service area of the relay station.

  FIG. 7 shows the correlation between the added transmission loss (horizontal axis) and the bit error rate (vertical axis). When the added transmission loss is smaller than a certain level, the bit error rate is small. However, the bit error rate increases abruptly around a certain transmission loss. Assuming that the bit error rate that hinders viewing is a, the transmission loss that causes the bit error rate a to the transmission loss that causes the bit error rate a represents the margin of the digital broadcast signal received by the receiving station. A similar correlation diagram can be obtained using a degree of deterioration of digital broadcast waves other than the bit error rate, and the margin can be examined.

  The digital broadcast wave monitoring device, when adding a transmission loss of a preset size, if the degree of deterioration measured by the deterioration measuring means 4 exceeds a reference value, the margin amount that the relay station can have. Is insufficient, that is, the evaluation means 5 evaluates that the transmission quality of the incoming digital broadcast wave is poor.

  The digital broadcast wave monitoring apparatus of the present invention arrives at the relay station due to the occurrence of accidental radio interference such as rain, snowfall, fallen trees, etc. When the transmission loss of digital broadcast waves increases and the margin of the relay station becomes insufficient, it can be judged that the transmission quality is poor. Can be issued.

  As described above, the present invention does not simulate transmission loss during service area propagation as in Patent Document 1, but artificially adds transmission loss to examine the margin that the relay station has. It is not necessary to investigate the service area in advance, and this device can be installed easily.

  In addition, since the present invention uses the error rate of the demodulated code string signal as an index, it can be evaluated in association with viewing difficulties and can be monitored suitable for digital broadcasting.

  Next, the operation of the digital broadcast wave monitoring apparatus of the present invention when performing multistage relay using SFN will be described.

  In the case of multistage relay, even if a digital broadcast wave to be transmitted deteriorates due to a failure of a relay amplifier or other problems at some relay station, a viewing failure does not always occur immediately in the service area of the relay station. However, in the relay station downstream from the relay station, the deterioration is further superimposed due to the spatial transmission, and a viewing failure may occur in the service area of the relay station. In other words, due to a malfunction that has occurred at the relay station, a viewing failure occurs in the service area of the downstream healthy relay station.

  Therefore, in the present invention, a digital broadcast wave monitoring device is installed at each relay station. With the above-described operation of the digital broadcast wave monitoring apparatus, it is possible to evaluate whether or not the margin that each relay station can have is insufficient.

  As shown in FIG. 8, each of relay stations A, B, and C includes a reception antenna 801 and a transmission antenna 802, and appropriately amplifies a digital broadcast wave received by the reception antenna 801 and transmits it from the transmission antenna 802. It has become. It is assumed that the relay station A relays from the relay station B to the relay station B, and further relays from the relay station B to the relay station C via SFN. The digital broadcast wave monitoring apparatus of each relay station A, B, C measures the margin as described above. A margin measurement graph at relay stations A, B, and C is shown in FIG.

  In the example of FIG. 9, the relay station A has a sufficiently large margin. However, since the digital broadcast wave is deteriorated due to some deterioration factor during the transmission from the relay station A to the relay station B, the margin at the relay station B is reduced. A viewing failure does not always occur in the service area of the relay station B. However, since the margin is further reduced in the relay station C, there is a possibility that a viewing failure may occur in the service area of the relay station C.

  Thus, by measuring the margin with the digital broadcast wave monitoring device of the present invention at each of the relay stations A, B, and C, it is possible to clarify which relay station has insufficient margin.

It is a block diagram of the digital broadcast wave monitoring apparatus which shows one Embodiment of this invention. It is a block diagram of the digital broadcast wave monitoring apparatus which shows one Embodiment of this invention. It is a block diagram of the digital broadcast wave monitoring apparatus which shows one Embodiment of this invention. It is a block diagram of the digital broadcast wave monitoring apparatus which shows one Embodiment of this invention. It is a block diagram of the digital broadcast wave monitoring apparatus which shows one Embodiment of this invention. It is a block diagram of the digital broadcast wave monitoring apparatus which shows one Embodiment of this invention. In the present invention, it is a correlation diagram (margin measurement graph) showing the correlation between the added transmission loss (horizontal axis) and the bit error rate (vertical axis). In this invention, it is a block diagram for performing multistage relay. 9 is a margin measurement graph at relay stations A, B, and C in FIG. 8. It is a block diagram of the monitoring apparatus of the digital broadcast wave in background art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Transmission loss addition means 3 Receiving means 4 Deterioration measurement means 5 Evaluation means

Claims (5)

  A device installed at a digital broadcast wave relay station for monitoring a digital broadcast wave, which receives a transmission loss adding means for giving a transmission loss to the incoming digital broadcast wave and a digital broadcast wave with the transmission loss added Digital broadcasting comprising receiving means, deterioration measuring means for measuring the degree of deterioration of a digital broadcast wave in the received signal, and evaluation means for evaluating transmission quality of a digital broadcast wave coming from the degree of deterioration Wave monitoring device.   2. The digital broadcast wave monitoring apparatus according to claim 1, wherein the deterioration measuring means measures a carrier power to noise ratio as a degree of deterioration.   3. The digital broadcast wave monitoring apparatus according to claim 1, wherein the deterioration measuring means measures a bit error rate as a deterioration degree.   4. The digital broadcast wave monitoring apparatus according to claim 1, wherein the deterioration measuring means measures a packet error rate as a deterioration degree. In the evaluation means, a degree of deterioration that does not hinder viewing is set as a reference value in advance, and the degree of deterioration measured by the deterioration measuring means when a transmission loss of a preset size is added. 5. The digital broadcast wave monitoring apparatus according to claim 1, wherein when the signal exceeds a reference value, it is evaluated that the transmission quality of the digital broadcast wave is poor.

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