KR100814402B1 - Method of detecting alarm by irregulated signal in catv network and system thereof - Google Patents

Abstract

A method for detecting errors by abnormal signals applied to a cable network and a system using the same are provided to confirm a generation point of an accident by comparing an attenuation rate and an amplification rate of a signal spread to peripheral regions, and observe the accident point in real time. A head end(530) receives measurement values of signal characteristics by channel corresponding to each terminal from a terminal(510), and produces a head end network map where signal characteristic values for a channel corresponding to each terminal are tabled(S506). The head end compares the measurement values with the head end network map to determine whether an abnormal signal is applied. If so, signal characteristic values of peripheral points are calculated by using a measurement value of signal characteristics of a specific point. After that, the calculated signal characteristic value is compared with the head end network map to grasp a point where the abnormal signal is applied.

Description

Fault detection method by abnormal signal applied to cable network and system using the same {Method of Detecting Alarm by Irregulated Signal in CATV Network and System

1 is a diagram showing the configuration of a schematic transmission system for CATV services.

2 is a diagram illustrating a configuration of a CATV Network according to an embodiment of the present invention.

3 illustrates a UE-Channel MAP.

4 illustrates a headend-network MAP.

5 is a simplified diagram illustrating a process of configuring a headend-network MAP.

6 is a flowchart illustrating a process of measuring signal characteristics at a terminal and reporting the signal characteristics to the set-top box.

7 is a flowchart illustrating a process of determining whether a failure occurs in a headend and solving the problem.

8 is a diagram illustrating a power value measured for each terminal when an abnormal signal is applied.

           <Explanation of symbols for the main parts of the drawings>

210: terminal 211: data storage unit

212: set-top box transmitter 220: set-top box

221: processor 222: the main processor

223: headend transmitter 230: headend

231: failure determination unit 232: central processing unit

The present invention relates to a method for detecting a failure by an abnormal signal applied to a cable network and a system using the method, and more particularly, when a heterogeneous external signal is applied to a CATV (Cable Television, hereinafter referred to as "CATV"). The present invention relates to a method for identifying an input point of an abnormal signal by comparing the attenuation rate and amplification rate of a signal spread in a surrounding area, and a system using the method.

The CATV broadcasting system for performing CATV broadcasting includes a head end and a set-top box (hereinafter referred to as "STB").

Headends are the main coordination centers in a cable television system with technical facilities that receive, produce and retransmit programs from the satellite or elsewhere through the system network. The headend receives the data uploaded from the subscriber and processes it while transmitting broadcast related signals.

A set top box generally refers to a home communication terminal required when using a multimedia communication service including an on-demand video service. The set-top box decodes the broadcasting and management information transmitted from the headend installed in the local cable TV company for the cable TV or cable modem service provided to the subscriber, restores the original voice and video signal, and transmits the signal to the TV. It is a device whose main purpose is that.

When the broadcasting system is configured as described above, each cable broadcaster (System Operator, hereinafter referred to as "SO") produces a cable TV program, content, and other data or receives it from the producer and delivers it to the subscriber. Subscribers then watch the program or other data delivered by the cable TV station and watch their desired broadcast.

1 is a diagram illustrating a configuration of a schematic transmission system for a CATV service.

The current CATV transmission system includes a center system 110, a transmission system 120, and a terminal system 130.

The center system 110 performs a function of transmitting a broadcast signal, and includes a head end 112.

The CATV broadcasting station 111 transmits a broadcast signal to the headend 112 to be transmitted to the subscriber. The head end 112 transmits a broadcast-related signal through the trunk line 113.

The transmission system 120 relays the broadcast signal transmitted from the center system 110 to the terminal system 130.

The transmission system 120 includes a plurality of amplifiers 121, 122, 123, a plurality of splitters 124, and a tap off 125.

Amplifiers 121, 122, and 123 generally compensate for the attenuation of the downward or upward signal transmitted between CATV station 111 and subscriber 134. The amplifiers 121, 122, and 123 need to be installed at distances up to 600 m on the transmission line to prevent the broadcast signal from being severely attenuated enough to affect the broadcast, and every 200 m to provide a good quality broadcast service. It is desirable to install.

The plurality of amplifiers 121, 122, and 123 mentioned above may be classified into the trunk amplifier 121, the branch amplifier 122, the extension amplifier 123, and the like according to the differentiated amplification function.

The trunk amplifier 121 generally amplifies the signal when the broadcast signal is attenuated in the course of being transmitted along the trunk line. The branch amplifier 122 amplifies the signal attenuated at the branch point where the signal is branched. The extension amplifier 123 amplifies the signal when an additional signal attenuation occurs even after the signal is amplified.

The distributor 124 distributes the broadcast signal received from the CATV broadcasting station 111 and transmits the broadcast signal to the subscriber 134 in a tree format. The distributor 124 basically distributes signals, but when there is a difference in the distance between transmission lines coupled to the output side of the distributor, the divider 124 reduces the attenuation to the transmission line side with a long distance to the transmission line side with a short distance. Has attenuation function that gives a lot of attenuation so that all subscribers can transmit and receive a signal of uniform quality. The distributor with such attenuation is called a directional coupler.

Tap off 125 refers to the output terminal. The tap off 125 is output from the CATV broadcasting station 111 and amplified through the amplifiers 121, 122, and 123 and outputs the broadcast signal distributed through the distributor 124.

Although only three amplifiers 121, 122, 123 and two dividers 124 are shown in FIG. 1, a plurality of amplifiers and dividers may be used in an actual transmission system depending on the distance and the number of distribution points.

The terminal system 130 transmits the broadcast signal relayed through the transmission system 120 to the subscriber TV 134. The terminal system 130 includes a leader line 131, a branching device 132, a set top box 133, and a subscriber TV 134.

The tap-off 125, i.e., the facility from the output terminal to the receiver terminal, is called a lead-in facility. The transmission line of this facility is called a lead-in line 131. The lead wire 131 transmits the broadcast signal output from the tap off 125 to the receiver terminal of the terminal system 130.

The branch 132 is installed in the area where the subscriber TV 134 is concentrated to branch the signal directed to each subscriber TV 134 on the same distribution line.

The set-top box 133 decodes the broadcasting and management information received through the incoming line 131, restores the original audio and video signal, and transmits the same to the subscriber TV 134.

The subscriber TV 134 receives the signal from the set top box 133 and displays it.

The current CATV broadcasting network uses a coaxial cable to provide a broadcasting service. When using a coaxial cable connected to a set-top box for broadcast reception, the coaxial cable shields external noise to increase the SNR of the signal from the headend.

Signal to Noise Ratio (SNR) is the ratio between signal and noise in a component, amplifier, transmitter, receiver, etc., usually expressed in decibels (dB). In general, the higher the SNR, the better the broadcast quality as it becomes a signal without noise sources.

Due to the fundamental nature of CATV networks, users can easily purchase cables on the market, connect to external devices using splitters, and enter new signals into the cable network. Therefore, if the end user receives satellite or terrestrial wave using a splitter due to malicious purpose or lack of technical understanding, it may cause interference on the same channel receiving CATV or close to strong electric field, which may cause service failure. have. In addition, since the CATV network uses a coaxial cable, when an abnormal signal is applied, the CATV network may have a fatal effect on not only the user's terminal but also nearby users and all users.

In general, the CATV broadcasting service is based on two-way communication in which a signal is transmitted in a two-way direction, a downstream in which a broadcast signal is transmitted from a CATV broadcasting station side to a subscriber side and an upstream in which a signal is transmitted from a subscriber side to a broadcasting station side.

In this case, in order to distinguish between the downlink signal and the uplink signal, the frequency of the CATV is used 5MHz ~ 42MHz upstream, 54MHz ~ 864MHz downward. For example, when the downlink signal is emitted, it is modulated with an RF signal of 54 to 864 MHz band, and when the uplink signal is sent, it is modulated with an RF signal of 5 to 42 MHz band. Since the CATV network uses a frequency division scheme, the channel can be divided into an uplink channel and a downlink channel.

In the case of a network using a single frequency, even if a problem occurs in only one of the uplink channel and the downlink channel, the entire network may have a problem, and the headend may easily identify that the problem occurs basically.

However, in the case of CATV networks, the frequency is divided up and down because the frequency is divided by the network rather than using a single frequency. Therefore, unless the UE reports an abnormal signal applied to a specific downlink channel, it may not be known that a problem occurs due to the application of a heterogeneous abnormal signal in the headend.

Nevertheless, in the prior art, there was no technique for identifying a heterogeneous external signal applied to a CATV network. That is, when the above problem occurs, the failure state can be confirmed only when the end user reports a failure, so that the response and recovery of the failure have to be delayed.

Accordingly, an object of the present invention is to determine whether an abnormal signal is abnormally applied to the CATV network, to notify the user in advance of the possibility of a problem that may cause a viewing disturbance, and simultaneously report the phenomenon to the headend to report a service failure. The present invention aims to provide a method of identifying an input point of an abnormal signal by early detection of a problem point and a system using the method by minimizing and comparing the attenuation rate and amplification rate of a signal spread in a surrounding area.

According to a method for detecting a service failure by an abnormal signal according to an aspect of the present invention for achieving the above object, a headend receives measurement values of signal characteristics for each channel corresponding to each terminal from a terminal, and corresponds to each terminal. Creating a headend-network MAP table of signal characteristic values for a channel and comparing the measured value of signal characteristics of a specific channel received by the headend with a terminal to the prepared headend-network MAP. Determining whether it is authorized.

In the method for detecting a service failure by the abnormal signal, the signal characteristic may include at least one of Signal to Noise Ratio (SNR), Power, Automatic Gain Control (RF AGC), and IF AGC.

In the method of detecting a service failure based on the anomaly signal, the preparing of the headend-network MAP comprises receiving a signal characteristic value of each channel measured by each terminal in a set-top box, creating a terminal-channel MAP, and performing the headend. And reporting to the headend and generating the headend-network MAP by receiving the terminal-channel MAP.

In the method of detecting a service failure by the abnormal signal, determining whether the abnormal signal is applied or not, the set-top box receives the signal characteristic value measured by the terminal, updates the existing terminal-channel MAP, and updates it to the headend. And reporting the headend and comparing the updated terminal-channel MAP with previously stored headend-network MAP to determine whether an abnormal signal has occurred.

In the method of detecting a service failure by the abnormal signal, if it is determined that the abnormal signal is applied, the method may further include transmitting a warning message to the terminal.

In the method of detecting a service failure by the abnormal signal, if it is determined that the abnormal signal is not applied, the method may further include transmitting a warning message about a performance failure or a cable connection failure of the terminal to the terminal.

On the other hand, according to the service failure detection method by the abnormal signal according to another aspect of the present invention for achieving the above object, by measuring the signal characteristic value of a specific point, by calculating the degree of amplification or attenuation through the amplifier and the divider Computing the signal characteristic values of the peripheral points and comparing the signal characteristic values obtained by the step with the previously stored headend-network MAP to determine the first input point to which the abnormal signal is applied.

On the other hand, in the head end according to another aspect of the present invention for achieving the above object, the central processing unit and the set-top box for creating and storing the head-end network MAP based on the terminal-channel MAP transmitted by the set-top box And a failure determination unit that determines whether an abnormal signal is applied by comparing the updated terminal-channel MAP received from the pre-stored headend-network MAP.

       On the other hand, according to the system for detecting a service failure due to an abnormal signal according to another aspect of the present invention for achieving the above object, by measuring the signal characteristic value for each channel, the measured signal characteristic values set-top box The terminal reports the signal and the signal characteristic values by arranging the channel corresponding to the terminal to create a terminal-channel MAP, receives the periodically measured signal characteristic values from the terminal, updates the stored terminal-channel MAP, and updates the headend. The head-end network map is created based on the set-top box and the terminal-channel map transmitted by the set-top box, and the updated terminal-channel map received from the set-top box is compared with the previously stored head-end network map. And a headend that determines whether a signal is applied.

       In the system for detecting a service failure due to the abnormal signal, the set-top box is measured from the main processor and the terminal to generate a terminal-channel MAP by receiving the measurement value of the signal characteristics for each channel measured from each terminal And a processor for updating the pre-stored UE-Channel MAP by reporting the measured value of the signal characteristic, and a headend transmitter for reporting the updated UE-Channel MAP to the headend.

       In the system for detecting a service failure due to the abnormal signal, the set-top box transmits a warning message to the terminal when the abnormal signal is applied according to a determination result of whether the abnormal signal received from the headend is applied. When the signal is not applied, the warning message about a performance failure or a cable connection failure is transmitted to the terminal.

       In the system for detecting a service failure due to the abnormal signal, the terminal transmits a data storage unit for measuring and storing signal characteristics for each channel and a set-top box for reporting the measured values of the measured signal characteristics to a set-top box. Contains wealth.

       In the system for detecting a service failure due to the abnormal signal, the signal characteristic is characterized in that it comprises at least one of SNR, Power, RF AGC, IF AGC.

Hereinafter, a failure detection method by an abnormal signal applied to a cable network and a system using the method will be described in detail with reference to the accompanying drawings.

If an abnormal signal is applied to the CATV network from outside, service failure occurs. When a portion overlaps with a specific frequency, or when an adjacent channel of a strong electric field is applied, the SNR of the service becomes worse or the connection is lost. If external noise is continuously applied by a malicious user, it may have a fatal adverse effect on part or all of the network.

When the abnormal signal is applied from the outside, there may be a case where the abnormal signal is applied to the corresponding channel and the adjacent signal of the corresponding channel.

To find out whether an abnormal signal is applied to the channel, check the SNR change value of the channel. When an abnormal signal is applied to the channel, the SNR is lowered. SNR will hardly change unless the power level is significantly different from the original signal, but if the power level difference is greater than a certain amount (C / N Threshold), the screen is broken or disconnected.

C / N refers to the ratio of the carrier to the noise in the transmission system. In the reception of frequency-modulated radio waves, if the power ratio of the carrier and the noise, that is, the carrier-to-noise ratio (C / N), is higher than a certain value, the signal-to-noise ratio (S / N) at the time of demodulation is improved, resulting in very low noise. However, below this limit, the effect of S / N improvement is lost. Although the C / N of this limit is 8 to 9 dB, the noise generated at the input of the receiver is determined by the receiver, so a level 9dB higher than this is called the limit level.

When an abnormal signal is applied from an adjacent channel of the corresponding channel, second and third harmonic components of the applied signal are generated. When the adjacent channel is generated by a strong electric field, the level of the lock increases, which may adversely affect the signal of the adjacent channel, causing the SNR to be degraded or disconnected.

In order to determine whether a problem has occurred, the measured channel (if it is determined that the effect is due to neighboring) is examined for the amount of change in the signal of the surrounding channel and the entire channel, and in this case, whether the signal change is large and whether it is a strong electric field input. ), Physical information (Mac address value, etc.) of terminal, power value, AGC, SNR, etc. should be reported to headend. AGC or Power Detect value can be measured regardless of channel connection, so it can be efficiently managed when problems occur.

Due to the characteristics of the cable network, normal network operation is required only after recovering the failures occurring in the entire terminals of the network. Therefore, in the present invention, rather than determining whether a failure occurs in each terminal and coping with it, the terminal measures the signal characteristic value and reports it to the headend, and determines whether or not an abnormal signal is applied in the headend. A method of instructing the terminal on how to handle a failure is used. In this case, it is necessary to compare with a reference value to determine whether a failure has occurred due to the application of an abnormal signal at the headend. In this case, MAP is used.

The MAP is configured by arranging the signal characteristic values for each terminal and channel, and the MAP is divided into two types of head-end-network MAP and terminal-channel MAP.

In more detail, the terminal measures signal characteristic values that change when an abnormal signal is applied to the set top box, and the set top box updates the terminal-channel MAP and reports it to the headend. The headend compares the terminal-channel MAP with previously stored headend-network MAP and determines whether an external signal is applied to the network according to a change degree of signal characteristic value.

In this case, it is a question of how to define the standards related to the configuration of the MAP, control-related protocols and data use.

Currently, cable-related data communication using optical fiber coax (Hybrid Fiber Coax) is called DOCSIS (x, x) and OOB (SCTE DVS / 167 rev.2) in Korea and North America. For example, SCTE DVS / 178 rev. 3). The biggest difference between OOB and DOCSIS is that OOB uses IP / AAL5 to communicate data using ATM. DOCSIS (DOCSIS) is called Ethernet (DOCSIS). IEEE 802.2) packets are used.

Table 1 below shows the format of the OOB Service / System Information protocol.

     SCTE DVS / 167 (rev. 2)      SCTE DVS / 178 (rev. 3)      OOB-SI SCTE DVS / 234 (rev. 2)      OOB-SI SCTE DVS / 234 (rev. 2)      MPEG-2 private section      MPEG-2 private section      AAL5      ATM cell Format      MPEG = 2 TS      SCTE DVS / 167 (rev. 2) PHY      SCTE DVS / 178 (rev. 3)

The control signal for monitoring the configuration of the terminal-channel MAP or the head-end-network MAP and the abnormal signal can be added to the two types of protocols presented, or the overall situation can be controlled by transmitting and receiving data with the IP and MAC addresses of the related headends. .

2 is a diagram illustrating a configuration of a CATV network according to an embodiment of the present invention.

The physical structure for abnormal signal detection and reporting applied to the cable network uses an existing network, and may be implemented by adding a sensing circuit to a transmission / reception structure or using an existing circuit.

The CATV network includes a terminal 210, a set top box 220, and a headend 230.

The terminal 210 includes a data storage 211 and a set-top box transmitter 212.

The data storage unit 211 measures signal characteristics for each channel and stores them.

The set top box transmitter 212 reports the measured values of the signal characteristics measured by the data storage 211 to the set top box 220.

The set top box 220 includes a processor 221, a main processor 222, and a headend transmitter 223.

       The main processor 222 creates a terminal-channel MAP by measuring signal characteristics for each channel corresponding to each terminal.

       The processor 221 receives the measured values of the signal characteristics periodically measured from the set-top box transmitter 212 of the terminal 210, and is pre-stored by the main processor 222 based on the measured values. Update the Channel MAP.

       The headend transmitter 223 reports the terminal-channel MAP updated by the processor 221 to the headend 230.

The head end 230 includes a failure determining unit 231 and a central processing unit 232.

       The central processing unit 232 prepares and stores the headend-network MAP based on the terminal-channel MAP transmitted by the set-top box 220.

       The failure determining unit 231 compares the updated terminal-channel MAP received from the set-top box 220 with a previously stored headend-network MAP to determine whether an abnormal signal is applied.

General cable broadcasting data standard uses DOCSIS or OOB. Therefore, the warning message that the abnormal signal has occurred and the data movement to the MAP use the control signal of the corresponding data standard or the method of sending packet data to the IP or MAC of the headend. If troubleshooting is not done with simple switching operations, the reported speed may take tens of seconds to several minutes.

FIG. 3 is a diagram illustrating a terminal-channel MAP, and FIG. 4 is a diagram illustrating a headend-network MAP.

The MAPs are composed of measured values of signal characteristics, which are mainly changed when an abnormal signal is applied to the network. When a problem occurs in a CATV network, the main factors that change are SNR, Input Power, TOP, RF AGC, and IF AGC.

SNR, as we saw earlier, is the ratio between signal and noise. When an abnormal signal is applied from the outside, the noise source is increased, so the SNR value is lowered. The lower the SNR, the more noise is mixed and the broadcast quality is degraded.

AGC (Automatic Gain Control, hereinafter referred to as "AGC") refers to automatic gain control. RF AGC represents automatic gain control of radio frequencies, and IF AGC represents automatic gain control of intermediate frequencies.

The automatic gain control is a form in which the gain of the tuner or the intermediate frequency amplification circuit is automatically controlled so that the amplitude of the output signal is kept constant at all times by detecting the amplitude variation of the input signal in a television receiver or the like. If the amplitude of the output signal is not constant, screen noise may occur, so it is necessary to automatically control the gain of the signal to prevent this.

Using the above components, the headend and settop boxes configure the terminal-channel MAP and the headend-network MAP based on channel information and power information for each channel.

5 is a diagram briefly illustrating a process of configuring a headend-network MAP.

First, when the terminal 510 registers (subscribes) to the headend 530 (S501), the headend 530 may register the entire terminal based on the MAC address of the registered terminal 510. A basic structure of the headend-network MAP as a target is configured (S502).

When the basic structure of the headend-network MAP is determined, the headend 530 sends a signal to the set-top box 520 to notify it (S503).

The set-top box 520 receiving the signal creates a terminal-channel MAP (S504). To create a terminal-channel MAP, a search for all channels according to a frequency band of the terminal 510 should be performed initially. In this case, connection information for each channel is input to the corresponding terminal-channel MAP.

The AGC or power detection circuit in the tuner circuit of the set top box 520 may be registered terminal 1, terminal 2,... Measures the values of Power, RF AGC, IF AGC, SNR, and other components according to channels of UEs N. FIG.

The set-top box 520 completes the terminal-channel MAP by arranging channels according to the MAC address of the terminal and the frequency band of the terminal and arranging a table of measured values of the signal characteristics corresponding to each channel. In this case, the terminals store the measured power, RF AGC, IF AGC, SNR, and other signal characteristics in the terminal-channel MAP.

When the UE-Channel MAP for all channels is created, the set-top box 520 reports the corresponding UE-Channel MAP to the headend 530 according to a data transmission method of DOCSIS Mode or OOB Mode (S505).

The headend 530 creates a headend-network MAP based on the content reported by each set top box 520 (S506).

Now, a detailed method of recognizing whether an abnormal signal is applied using the headend-network MAP and the terminal-channel MAP prepared above will be described.

6 is a flowchart illustrating a process of measuring signal characteristics at a terminal and reporting the signal characteristics to the set-top box.

Assume that channel 3 has a signal of the same component as the current frequency.

The applied abnormal signal is exposed to the outside through a splitter through a coaxial cable, and noise is transmitted to a nearby terminal. When an abnormal signal is transmitted upward, the signal property except for the uplink signal band disappears when it reaches the amplifier, but when transmitted downward, it is transferred to another terminal system through another amplifier.

The terminal determines whether there is a change in power or SNR of a specific channel (S601).

If it is determined that the SNR of the current channel is lowered to become a value near the C / N threshold or an unlocking occurs, the abnormal signal is likely to be applied. In this case, the terminal may transmit power, TOP, RF AGC, IF AGC, SNR, etc. are measured (S602).

The terminal reports the measured values of the corresponding signal channel to the set top box (S603).

The set-top box compares the measured values reported from the terminal with previously stored information of the existing terminal-channel MAP, and updates the terminal-channel MAP (S604). Specifically, the set-top box rewrites the terminal-channel map by tuning the surrounding channels of the corresponding channel from left to right in order of closeness.

In this case, if the set-top box determines that a change larger than the normal channel environment (ex: when the input power rises by 10 dB), a warning message can be sent to the user by means of a video output. However, it is desirable to determine the ultimate failure and to deal with it at the headend.

The set-top box reports the updated UE-Channel MAP to the headend through an Upstream control Data channel (S605).

Now, let's take a look at the process of getting information from the headend to identify the problem, report it to the network administrator, and resolve the problem.

The headend identifies the problem in detail based on the UE-Channel MAP reported from the set-top box and reports it to the network manager.

7 is a flowchart illustrating a process of determining whether a failure occurs in the headend and solving the problem.

The headend receives the updated terminal-channel MAP from the set top box (S701).

The headend compares the terminal-channel MAP received from the set top box with the previously stored headend-network MAP (S702).

The headend determines whether the change value is greater than the normal state change based on the measured values of the signal characteristics (S703).

The determination whether the abnormal signal is applied to the terminal and the change in the signal characteristics is greater than the normal state may be performed based on various reference values.

The most commonly used method is to identify changes in SNR values. When the SNR of a particular channel is abnormally lowered, for example, when attenuation of about -5 dB occurs from the previous value, it may be determined that an abnormal signal is applied. In addition, the UE may determine that the abnormal signal is applied even when the SNR of the current channel is lowered to become a value near the C / N threshold.

If an error signal is applied to the network, the values of Power, RF AGC, and IF AGC will also change.

In the case of the power value, if the input power increases more than + 5dB compared with the reference value of the normal channel environment, the failure is considered. If there is no network design modification by the network manager at the corresponding point, the amount of power change and the error occurring in the terminal are much lower than +/- 6dB and the amount of change is not large unless there is a failure of the terminal.

Even if the current channel is continuously disconnected, it is determined that the abnormal signal is applied.

After the headend confirms a problem in the corresponding terminal reported by the set-top box, it is now checked whether or not a failure occurs in the other terminal (S704).

This is because a method of solving a problem varies depending on whether a failure occurs in another terminal. In the case of other terminals, the process of determining whether a problem has occurred is the same as the method described above. It may be determined whether the value of the signal characteristics of the terminal has a larger change than the normal state change.

If it is determined that the problem occurs because the change value of the signal characteristics of the other terminal is larger than the normal state change, the point where the abnormal signal is input should be determined (S705).

As described above, since the CATV network uses a coaxial cable, an applied anomaly signal may be transmitted to another terminal system via an amplifier through the coaxial cable. This means that it is necessary to determine at which point an abnormal signal is input among the various terminals having a problem. A method of determining the input point of the abnormal signal will be described later.

If it is determined that the terminal to which the abnormal signal is applied, it is checked whether there is a performance failure of the subscriber station having a problem or a poor contact of the input cable (S706).

Specifically, when the SNR is lowered and the RF AGC and IF AGC values are lowered, it may be suspected whether there is a poor contact or a bad tuner.

In order to determine the correct state, the headend may request the UE to retransmit the UE-Channel Map to the set-top box, and may repeat the above procedure of determining whether an abnormal signal is applied. In this case, the problem is reconfirmed by comparing the values of RF AGC and IF AGC.

Finally, the headend having confirmed the problem situation reports to the network manager that the network has failed through the upstream control data channel (S707).

In this case, the report includes the occurrence range for applying the abnormal signal and information on the initial input terminal of the abnormal signal.

The network administrator who receives the report from the headend recovers the network (S708).

When the network manager notifies the headend that the network has been restored, the headend warns that a problem has occurred in the set-top box through the Downstream Control Data Channel (S709).

The set-top box received the warning from the headend notifies the terminal of the occurrence of a failure due to the application of the abnormal signal and sends a message so that the subscriber can take action against it (S710).

If a problem such as poor contact occurs, "An error occurred in the channel, check the cable connection." Send a warning message. In addition, after sending the above warning message, "If there is no problem with the cable connection or TV reception, please press the ?? (No status or error) button on the remote control.", "If a problem occurs ?? If the problem continues even if you check it, send a message such as "Please press the button."

This completes all problems due to abnormal signal generation (S711).

8 is a diagram illustrating a power value measured for each terminal when an abnormal signal is applied.

When an abnormal signal is applied due to the nature of the CATV network, it spreads to surrounding terminals and affects nearby terminals. In this case, since the abnormal signal is attenuated step by step through the splitter, the abnormal state value of the terminal located at the primary input point is displayed as the maximum value. Therefore, it is possible to pinpoint the location of the accident.

The example of FIG. 8 shows an example of an uplink signal reported to the headend from the set top box. In the case of an uplink signal or a downlink signal, the direction or frequency of the signal changes, so the power or measured value of the signal changes in one direction only.

As a result of measuring the power values of the B1 STB 831, the B2 STB 832, and the B3 STB 833, it can be seen that they are +3.5 dB, +7 dB, and +10.5 dB, respectively. If the power value of the signal is attenuated by -7dB through the splitter and amplified by +20 dB through the amplifier 850, the power value of each of the splitter B (830), amplifier (850), and splitter A (820) points Is -3.5 dB, +16.5 dB, and +9.5 dB.

The upstream signal is passed from the B3 STB 833 through the B2 STB 832 and the B1 STB 831 to the splitter B 830 and the amplifier 850 and then to the headend 810 through the splitter A 820. Since the amplification and attenuation of the signals in the amplifier and the divider are considered, it can be seen that the state abnormality value in the B3 STB 833 becomes the maximum. Therefore, the terminal located where the abnormal signal is primarily input becomes the B3 STB 833.

That is, the headend compares the phenomena of problem terminals and finds the terminal with the highest state abnormality (for example, SNR change value and power change value) among the problem terminals, and compares the neighboring terminals with attenuation of the neighboring terminals. You can identify the problem by understanding the degree.

       While the present invention has been described with reference to exemplary embodiments, these descriptions should not be interpreted in a limiting sense. It will be apparent to those skilled in the art that the present invention may be variously modified, combined, or otherwise implemented with reference to the detailed description of the invention. Therefore, the present invention can be applied to all bidirectional products to which a fault card according to the present invention is applied, including a cable card (Point Of Development, hereinafter referred to as "POD").

According to the method for detecting a service failure by an abnormal signal applied to the cable network according to the present invention, the occurrence point of the accident can be confirmed by comparing the attenuation rate and the amplification rate of the signal spread in the surrounding area, and observing the accident point in real time. It is possible.

In addition, it is possible to check the occurrence of problems due to poor connection of the cable due to user carelessness or failure of the tuner and the terminal transmitting and receiving using the cable network.

Furthermore, in the prior art, when the channel is tuned and not unlocked, the BER (Bit Error Rate) and the SNR cannot be checked. However, in the present invention, in the case of various elements of the power value, the tuning command can be measured regardless of the input noise. Therefore, by measuring RF AGC, IF AGC, and TOP value (power information measurement), problems of the current state can be confirmed in detail even when unlocking. Therefore, there is an effect to efficiently manage the power, SNR, subscriber terminal failure and performance of the entire network.

Claims (13)

 Receiving, by the headend, measurement values of signal characteristics for each channel corresponding to each terminal from the terminal, and creating a headend-network MAP that lists the signal characteristic values for the corresponding channel for each terminal; Wow Determining whether an abnormal signal is applied by comparing the measured value of signal characteristics of a specific channel received by the headend with the prepared headend-network MAP; And When it is determined that the abnormal signal is applied, the signal characteristic value of the neighboring points is calculated by using the measured value of the signal characteristic of the specific point, and compared with the headend-network MAP to identify the point where the abnormal signal is applied. Service failure detection method by the abnormal signal comprising. The method of claim 1, The signal characteristic may include at least one of a signal to noise ratio (SNR), a power, an RF automatic gain control (AGC), and an IF AGC. The method of claim 1, Creating the headend-network MAP, Receiving a signal characteristic value of each channel measured by each terminal in the set-top box, creating a terminal-channel MAP, and reporting it to the headend; Wow And a headend receiving the terminal-channel MAP to create a headend-network MAP. The method of claim 1, Determining whether the abnormal signal is applied, Receiving, by the set-top box, the signal characteristic value measured by the terminal, updating the existing terminal-Channel MAP, and reporting the same to the headend; Wow And a headend comparing the updated terminal-channel map with the previously stored headend-network map to determine whether an abnormal signal has occurred. The method of claim 1, If it is determined that the abnormal signal is applied, transmitting a warning message to the terminal. The method of claim 1, If it is determined that the abnormal signal is not applied, the service failure detection method according to the abnormal signal further comprising the step of transmitting a warning message to the terminal for a performance failure or a cable connection failure of the terminal.  The method of claim 1,  Identifying the point where the abnormal signal is applied,  Measuring signal characteristic values of specific points by calculating a signal characteristic value of a specific point and calculating a degree of amplification or attenuation through an amplifier and a divider; Wow  And comparing the signal characteristic value obtained by the step with a previously stored headend-network MAP to identify an initial input point to which an abnormal signal is applied. In the headend used in the service failure detection method by the abnormal signal, A central processing unit for creating and storing a headend-network MAP based on a terminal-channel MAP transmitted by the set-top box; The updated terminal-channel MAP received from the set-top box is compared with the pre-stored headend-network MAP to determine whether an abnormal signal is applied, and the signal characteristic values of the neighboring points are determined using the measured value of the signal characteristic of the specific point. A headend including a failure determination unit for calculating and comparing the headend-network MAP with the headend-network MAP to determine a point where an abnormal signal is applied. A terminal for measuring a signal characteristic value for each channel and reporting the measured signal characteristic values to a set-top box; A set-top box is arranged to create a terminal-channel MAP by arranging the signal characteristic values for each channel corresponding to the terminal, to receive and report the signal characteristic values measured periodically from the terminal, to update the pre-stored terminal-channel MAP, and to report them to the headend. ; And The headend-network MAP is created based on the terminal-channel MAP transmitted by the set-top box, and the updated terminal-channel MAP received from the set-top box is compared with the previously stored headend-network MAP to determine whether an abnormal signal is applied. The signal characteristic value of the neighboring points is calculated using the measured value of the signal characteristic of the specific point, and compared to the headend-network MAP to the abnormal signal including the headend for identifying the point where the abnormal signal is applied. System for detecting service failures caused by.        The method of claim 9,        The set top box,        A main processor configured to generate a terminal-channel MAP by receiving a measurement value of signal characteristics for each channel measured from each terminal;        A processor configured to update a pre-stored UE-Channel MAP by receiving a measurement value of a signal characteristic periodically measured by the UE; And        And a headend transmitter for reporting the updated terminal-channel map to the headend.        The method of claim 9,        The set top box, According to the determination result of whether or not the abnormal signal received from the headend, If an abnormal signal is applied, a warning message is transmitted to the terminal, and if an abnormal signal is not applied, a service failure is detected by an abnormal signal, wherein a warning message for a performance failure or a cable connection is transmitted to the terminal. System. The method of claim 9, The terminal, A data storage unit measuring signal characteristics of each channel and storing the signal characteristics; Wow And a set-top box transmitter for reporting the measured value of the measured signal characteristic to the set-top box.        The method of claim 9,        The signal characteristic is a system for detecting a service failure due to an abnormal signal, characterized in that at least one of SNR, Power, RF AGC, IF AGC.

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