JP2000183787A - Transmission quality evaluation system, noise elimination device and transmission quality evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission quality evaluation system, by which a configuration of a terminal in a subscriber's home can be simplified. SOLUTION: The system 20 is provided with a receiver 21 that extracts a noise signal S23 with a prescribed frequency from a received incoming signal S0, an oscilloscope 24 that detects amplitude of the noise signal S23 and generates time base data S24 with the amplitude, and a transmission quality evaluation device 25 that generates amplitude probability density distribution data denoting an amplitude probability density distribution of the amplitude of the noise signal S23 from the time base data S24 and compares the amplitude probability density distribution data with amplitude probability density distribution data stored in advance so as to evaluate the effect of the noise on the transmission quality of the incoming signal S0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV (Cable T) having, for example, a tree structure and a bidirectional signal transmission function.
The present invention relates to a transmission quality evaluation device, a noise elimination device, and a transmission quality evaluation method used for evaluating signal transmission quality of an elevision (system) and noise suppression.

[0002]

2. Description of the Related Art For example, as shown in FIG.
The ATV system 1 includes a center 2 as a service provider, and terminal devices such as a television receiver, a telephone, and a personal computer provided in a plurality of subscriber homes 3 to which the service is provided. It is connected via a coaxial cable 6 arranged so as to form a tree structure by appropriately disposing a duplexer 5. In such a CATV system 1, a down signal for providing a service is transmitted from the center 2 via the coaxial cable 6 and received by all the subscriber homes 3, and all the downlink signals transmitted from the subscriber home 3 are transmitted. The upstream signal is received by the center 2.

In the CATV system 1, noise may be added to a signal being transmitted through the coaxial cable 6 due to various factors. Here, C shown in FIG.
When the center 2 receives an upstream signal from a plurality of subscriber homes 3 as in the ATV system 1, noise included in the upstream signal received by the center 2 is merged as approaching the center 2, and the noise of the upstream signal is increased. Affects transmission quality. Such noise is called ingress noise. The ingress noise has a complicated shape because various levels of noise overlap at various frequencies. When the ingress noise is added to the upstream signal in this way, the quality of the upstream signal is degraded, and a so-called data error (error) occurs in which the content of the data indicated by the transmission signal is different from the content of the data indicated by the reception signal. In performing various processes using the received signal, the center (reception side) needs to evaluate the quality (transmission quality) of the received signal that is affected by noise characteristics. Such transmission quality characteristics are represented using, for example, an error rate. Conventionally, in order to determine the error rate of a received signal, for example, the same predetermined error rate measurement data is held in the terminal device of the subscriber home 3 and the center 2,
When measuring the error rate, the data for measuring the error rate is modulated and transmitted from the terminal device at the subscriber's home 3 to the coaxial cable 6.
The center 2 compares the content of the data obtained by demodulating the received signal with the data for measuring the error rate.

[0004] Conventionally, various measures against noise have been taken to prevent signal quality from deteriorating due to noise as described above. Evaluate transmission quality (judgment, analysis or prediction) to take appropriate measures against noise
There is a need to. Conventionally, for noise due to a single frequency signal such as random noise or sin wave, for example, C
/ N ratio (Carrier-to-Noise ratio) and D / U ratio (Desire-to-noise ratio)
-Undesire ratio) is used to analyze noise characteristics and take measures against noise using the analysis results.

[0005]

However, as described above, in the error rate measurement method of transmitting data for error rate measurement from the terminal device of the subscriber's home 3 to the center 2, the user is required A terminal device for measuring the error rate must be installed on the side, and the measurement operation is complicated. Conventionally, transmission quality characteristics such as C / N ratio and D /
The U ratio was also measured, but it was not possible to evaluate complicated shapes of noise such as ingress noise by themselves.

The present invention has been made in view of the above-mentioned problems of the prior art, and has a transmission quality evaluation apparatus, a noise removal apparatus, and a transmission quality evaluation method capable of evaluating a signal transmission quality without using a transmission quality evaluation terminal apparatus. The purpose is to provide a quality evaluation method.

[0007]

In order to solve the above-mentioned problems of the prior art and to achieve the above-mentioned object, a transmission quality evaluation apparatus of the present invention extracts noise of a predetermined frequency from a received signal. Noise extraction means, amplitude detection means for detecting the amplitude of the extracted noise and generating amplitude data indicating the detection result, and amplitude probability density distribution data indicating a probability density distribution of the amplitude of the noise from the amplitude data. A data generating means for generating, a storage means for storing a plurality of previously obtained amplitude probability density distribution data of a plurality of noises having mutually different characteristics, the amplitude probability density distribution data generated by the data generating means, A transmission quality evaluation unit for comparing the amplitude probability density distribution data stored in the storage unit to determine the influence of noise on the transmission quality.

In the transmission quality evaluation device of the present invention, first, a predetermined frequency component (hereinafter referred to as noise) is extracted from the received signal by the noise extracting means. Next, an amplitude detector detects the amplitude of the extracted noise, and generates amplitude data indicating the detection result. Next, in the data generation means, amplitude probability density distribution data indicating a probability density distribution of the amplitude of the noise is generated from the amplitude data. Next, in the transmission quality evaluation unit, the amplitude probability density distribution data generated by the data generation unit is compared with the amplitude probability density distribution data stored in the storage unit, and based on the result of the comparison, the transmission is performed. The effect of noise on quality is determined.

In the transmission quality evaluation device of the present invention, for example, the received signal includes ingress noise, and the storage means stores at least amplitude probability density distribution data of ingress noise.

[0010] In the transmission quality evaluation apparatus of the present invention, preferably, the amplitude detection means generates the amplitude data by sampling the amplitude of the extracted noise at predetermined time intervals.

Further, in the transmission quality evaluation apparatus of the present invention, preferably, the storage means stores amplitude probability density distribution data and an error rate for each of the plurality of noises, and the transmission quality evaluation means , And outputs an error rate corresponding to the determined transmission quality.

[0012] Further, the noise removing apparatus of the present invention comprises a noise extracting means for extracting noise of a predetermined frequency from a received signal;
Amplitude detection means for detecting the amplitude of the extracted noise and generating amplitude data indicating the detection result; and data generation for generating, from the amplitude data, amplitude probability density distribution data indicating a probability density distribution of the noise amplitude. Means, storage means for storing amplitude probability density distribution data of a plurality of noises having mutually different characteristics obtained in advance, amplitude probability density distribution data generated by the data generation means, and stored in the storage means. Compared to the amplitude probability density distribution data
Transmission quality evaluation means for determining the effect of noise on transmission quality; noise suppression signal generation means for generating a noise suppression signal for suppressing the noise based on the determined transmission quality; and Multiplexing means for multiplexing a signal with the received signal.

In the noise removing apparatus of the present invention, first, noise of a predetermined frequency is extracted from the received signal by the noise extracting means. Next, an amplitude detector detects the amplitude of the extracted noise, and generates amplitude data indicating the detection result. Next, in the data generation means, amplitude probability density distribution data indicating a probability density distribution of the amplitude of the noise is generated from the amplitude data. Next, in the transmission quality evaluation unit, the amplitude probability density distribution data generated by the data generation unit is compared with the amplitude probability density distribution data stored in the storage unit, and based on the result of the comparison, the transmission is performed. The effect of noise on quality is determined. Next, a noise suppression signal generation unit generates a noise suppression signal for suppressing the noise based on the determined transmission quality. Next, in the multiplexing means, the noise suppression signal and the received signal are multiplexed.

Preferably, the noise removing apparatus of the present invention delays the input signal by a predetermined time and outputs the delayed signal, and demultiplexes the received signal and outputs it to the noise extracting means and the delay means. A demultiplexing unit, wherein the delay unit outputs the noise suppression signal corresponding to the received signal from the noise suppression signal generation unit after the demultiplexed reception signal is input to the noise extraction unit. The received reception signal is output to the multiplexing means after delaying the input reception signal.

In the noise removing apparatus of the present invention, preferably, the received signal is a signal obtained by combining transmission signals transmitted from a plurality of transmitters, and the storage means stores at least an amplitude of the combined noise. Stores probability density distribution data.

Further, in the noise elimination device of the present invention, preferably, the amplitude detecting means calculates the amplitude of the extracted noise by:
The amplitude data is generated by sampling at predetermined time intervals.

Further, the transmission quality evaluation method of the present invention evaluates the transmission quality of a signal based on the amplitude probability density distribution of noise.

In the transmission quality evaluation method of the present invention, preferably, the correspondence between the amplitude probability density distribution of the noise and a predetermined transmission quality characteristic is clarified in advance, and the amplitude probability density of the noise to be evaluated is further determined. A density distribution is measured, and the predetermined transmission quality characteristic is evaluated from the amplitude probability density distribution.

Further, in the transmission quality evaluation method according to the present invention, preferably, the transmission quality characteristic is an error rate.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a CATV system according to an embodiment of the present invention will be described. First Embodiment A CATV system according to the present embodiment is a CATV system shown in FIG.
As in the system 1, the service providing center and the terminals (television receivers, telephones, personal computers, etc.) provided in the plurality of subscriber homes 3 to which the service is provided are connected to the amplifier 4 or the like. The duplexer 5 is appropriately arranged and connected via a coaxial cable 6 forming a tree structure. The CATV system of the present embodiment is characterized by the configuration of the center.

Hereinafter, the configuration of a portion for receiving an upstream signal in the center of the CATV system of the present embodiment will be described in detail. FIG. 1 is a configuration diagram of a portion for receiving an upstream signal in the center 20 of the CATV system according to the present embodiment. As shown in FIG. 1, the center 20
Receiver 21, splitter 22, BPF (BandPass Filter) 2
3, an oscilloscope 24, a transmission quality evaluator 25, a demodulator 26, and an upstream signal processor 27.

The receiver 21 has a coaxial cable 6 shown in FIG.
Are connected to the terminal devices of the plurality of subscriber homes 3 through the terminal device, and receive the uplink signals S0 transmitted by these terminal devices,
The generated uplink signal S21 is output to the duplexer 22. The splitter 22 splits the uplink signal S21 input from the receiver 21 and outputs the split signal to the BPF 23 and the demodulator 26.

The BPF 23 receives the upstream signal S21,
Noise S2 of a predetermined frequency band for which the transmission quality evaluator 25 of the subsequent stage determines the characteristics of the uplink signal S21
3 is extracted and output to the oscilloscope 24. B
As the frequency band of the noise S23 extracted by the PF23,
For example, a frequency band (guard band) between an upstream signal and a downstream signal and an unused band of the upstream signal can be used. The oscilloscope 24 outputs, to the transmission quality evaluator 25, time-series data S24 of the amplitude generated by sampling the amplitude of the noise S23 at predetermined time intervals.

The demodulator 26 outputs a demodulated signal S26 generated by demodulating the uplink signal S21 input from the demultiplexer 22 to the uplink signal processor 27. The uplink signal processor 27 performs processing of data received from the terminal device using the demodulated signal S26.

FIG. 2 is a configuration diagram of the transmission quality evaluator 25 shown in FIG. As shown in FIG. 2, the transmission quality evaluator 25
Has an amplitude probability density distribution data generation unit 30, a memory 31, and a transmission quality evaluation unit 32. The amplitude probability density distribution data generation unit 30 generates, for example, amplitude probability density distribution data S30 indicating a probability density distribution of the amplitude from the time-series data S24 of the amplitude input from the oscilloscope 24, and sends this to the transmission quality evaluation unit 32. Output.

The memory 31 stores, for example, noise amplitude / error rate correspondence table data S31 indicating the correspondence between the amplitude probability density distribution data and the error rate, which have been measured in advance. 32. Noise amplitude
The error rate correspondence table data S31 is generated using a result obtained by previously examining the relationship between the amplitude probability density distribution data and the error rate data with respect to noise having various characteristics by an experiment. Thus, the amplitude probability density distribution data “A” to “G” corresponding to the seven types of noise characteristics and the error rate data “a” to “g” in each case are shown. In this case, for example, the amplitude probability density distribution data “A” becomes as indicated by a broken line in FIG.
Is data in the case where the noise included in is only random noise. Further, the amplitude probability density distribution data “B” is shown in FIG.
, And is data when the noise included in the uplink signal S0 is only a single frequency signal noise. Further, the amplitude probability density distribution data “C”, “D”, “E”, “F”, and “G” shown in FIG. Is the data when

The transmission quality evaluation unit 32 temporarily stores, for example, the amplitude probability density distribution data S30 input from the amplitude probability density distribution data generation unit 30 in an internal memory, and stores the stored amplitude probability density distribution data S30 as a key. The noise rate / error rate correspondence table data S31 stored in the memory 31 is searched to obtain error rate data S32. In this case, the coincidence between the amplitude probability density distribution data S30 and the amplitude probability density distribution data described in the entry of the noise amplitude / error rate correspondence table data S31 does not need to be a perfect match. If a predetermined common pattern exists in the shape of the amplitude probability density distribution indicated by the distribution data, it is determined that they match.

Next, the operation of the CATV system of this embodiment for receiving the upstream signal S0 from the center 20 will be described. For example, the upstream signals transmitted from the terminal devices of the plurality of subscriber homes 3 shown in FIG. 7 merge into the upstream signal S0, and the upstream signal S0 is received by the receiver 21 of the center 20 shown in FIG. . Next, the uplink signal S21 is received by the receiver 2
1 is output to the distributor 22, demultiplexed in the distributor 22, and output to the demodulator 26 and the BPF 23.

Next, the upstream signal S output to the demodulator 26
The signal 21 is demodulated by the demodulator 26 and then processed by the upstream signal processor 27.

On the other hand, the upstream signal S output to the BPF 23
Reference numeral 21 denotes a BPF 23 in which noise S23 in a predetermined frequency band is extracted and output to an oscilloscope 24.
Next, in the oscilloscope 24, the noise S23 is sampled at predetermined time intervals and the time series data S2 of the amplitude is sampled.
4 is generated. Then, the time series data S2 of the amplitude
4 is output to the transmission quality evaluator 25.

Next, the amplitude probability density distribution data generation unit 30 of the transmission quality evaluator 25 shown in FIG. 2 generates the amplitude probability density distribution data S30 from the amplitude time series data S24, and this is transmitted to the transmission quality evaluation unit 32. Is output. Next, the transmission quality evaluation unit 32 searches the noise amplitude / error rate correspondence table data S31 stored in the memory 31 using the amplitude probability density distribution data S30 as a key, and obtains the obtained error rate data S32. Is output. The center 20 can predict the transmission quality of the received uplink signal S0 from the error rate data S32.

As described above, the CAT of this embodiment
According to the V system, the terminal 20 at the subscriber's home 3 transmits arbitrary data output from the normal subscriber's home instead of the data for error rate measurement, so that the data is included in the received uplink signal S0 at the center 20. It is possible to determine the characteristics of the noise to be obtained, obtain the error rate, and evaluate the quality of the transmission quality. Therefore, it is not necessary to provide a terminal device having a function for measuring an error rate at the subscriber home 3 every time an error is measured, and the device configuration can be simplified.

Further, according to the CATV system of the present embodiment, as shown in FIG. 3, the amplitude probability density distribution data "A" to "G" for the ingress noise is stored in the memory 31 shown in FIG.
And the noise amplitude / error rate correspondence table data S31 indicating the corresponding error rate data, the transmission quality evaluation unit 32
By determining the characteristics of the ingress noise included in 0, the error rate can be obtained. That is, the quality of the uplink signal S0 including the ingress noise can be determined.

If it is found that the effect of noise is so great that communication cannot be performed with a predetermined quality, the following measures are taken, for example. For example, if the influence of noise on the CATV trunk line that jumps in from a damaged part of the coaxial cable or the connector part is considered, there may be a problem with the cable or connector due to construction or deterioration over time. Find and exchange for a new one. When the influence of noise from the CATV subscriber's house is considered, a filter for cutting the uplink signal is inserted in the protector of the subscriber who does not use the uplink. Also, as described above, since the error rate is known,
An appropriate error correction method can be selected based on the value.
Further, by using a new channel quality index such as the noise amplitude probability density distribution, noise having a complicated shape such as ingress noise can be evaluated, and more accurate channel design becomes possible.

According to the CATV system of the present embodiment, the oscilloscope 24 that samples the amplitude of the noise S23 at predetermined time intervals is used in the center 20 shown in FIG. The data amount of data processed in the subsequent stage of the oscilloscope 24 can be significantly reduced as compared with the case where the data is processed. Therefore, in the transmission quality evaluator 25, the time of the transmission quality evaluation processing can be shortened, real-time transmission quality evaluation can be performed, and the storage capacity of the memory for temporarily storing processed data can be significantly reduced. In the present embodiment, the determination of the noise characteristic may be made by a person directly comparing with a table. For this purpose, it is more preferable to provide a monitor in the transmission quality evaluator 25 so as to display the amplitude probability density distribution data shown in FIG.

Second Embodiment The CATV system according to the second embodiment has a CATV system shown in FIG.
As in the system 1, the service providing center and the terminals (television receivers, telephones, personal computers, etc.) provided in the plurality of subscriber homes 3 to which the service is provided are connected to the amplifier 4 or the like. The duplexer 5 is appropriately arranged and connected via a coaxial cable 6 forming a tree structure. The CATV system of the present embodiment is characterized by the configuration of the center.

Hereinafter, the configuration of a portion for receiving an upstream signal in the center of the CATV system of the present embodiment will be described in detail. FIG. 5 is a configuration diagram of a portion that receives an upstream signal in the center 50 of the CATV system according to the present embodiment. As shown in FIG. 5, the center 50
It has a noise remover 60, a receiver 21, a demodulator 26, and an upstream signal processor 27. In FIG. 5, a receiver 21, a demodulator 26, and an uplink signal processor 27 are the same as those described in the first embodiment.

Hereinafter, the noise remover 60 will be described in detail. As shown in FIG. 5, the noise eliminator 60 includes a duplexer 6.
1, a delay unit 62, a multiplexer 63, a BPF 23, an oscilloscope 24, a transmission quality evaluator 125, a noise generator 64, and a phase controller 65. Here, the BPF 23 and the oscilloscope 24 are the same as those described in the first embodiment.

The duplexer 61 is provided with a coaxial cable 6 shown in FIG.
Are connected to the terminal devices of a plurality of subscribers' homes 3 via the network, and demultiplex the uplink signal S0 transmitted by these terminal devices to output to the BPF 23 and the delay unit 62.

FIG. 6 is a configuration diagram of the transmission quality evaluator 125. As shown in FIG. 6, the transmission quality evaluator 125
The noise characteristic of the main signal band is predicted from the noise data extracted by the PF 23 and is notified to the noise generator 64.
And a transmission quality evaluation unit 132. The amplitude probability density distribution data generation unit 30 is the same as the amplitude probability density distribution data generation unit 30 shown in FIG. 2 described in the first embodiment.

The memory 131 stores noise amplitude / characteristic correspondence table data S131 in which noise probability data is associated with noise amplitude probability density distribution data having various noise characteristics obtained in advance through experiments. In this case, the noise characteristics differ depending on, for example, random noise, noise due to a single frequency signal, and the like.

The transmission quality evaluation unit 132 temporarily stores, for example, the amplitude probability density distribution data S30 input from the amplitude probability density distribution data generation unit 30 in an internal memory, and stores the stored amplitude probability density distribution data S30 as a key. As
The noise amplitude / characteristic correspondence table data S131 stored in the memory 131 is searched to obtain noise characteristic data S132 predicted to occur in the main signal band, and output this to the noise generator 64. In this case, the amplitude probability density distribution data S30 and the noise amplitude / characteristic correspondence table data S131
Does not need to be a perfect match. For example, if a predetermined common pattern exists in the shape of the amplitude probability density distribution indicated by the amplitude probability density distribution data, It is determined that you are doing.

The noise generator 64 includes a transmission quality evaluator 125
The noise S64 having the noise characteristic indicated by the noise characteristic data S132 input from the transmission quality evaluator 125 can generate the noise having the noise characteristic indicated by the noise characteristic data existing in the entry of the amplitude probability density distribution data S30 used in the step S64.
Is generated and output to the phase controller 65. At this time, the noise S64 and the noise S24 have similar waveforms.

The phase controller 65 generates a noise suppression signal S65 in which the phase of the noise S64 input from the noise generator 64 is reversed, and outputs this to the multiplexer 63.

The delay unit 62 outputs the signal S0 from the BPF 23
, The input upstream signal S0 is delayed and output to the multiplexer 63 by the time until the noise suppression signal S65 corresponding to the upstream signal S0 is output from the phase controller 65.

The multiplexer 63 outputs to the receiver 21 an upstream signal S60 obtained by multiplexing the upstream signal S0 from the delay unit 62 and the noise suppression signal S65 from the phase controller 65.

Next, the operation of the CATV system of this embodiment for receiving the upstream signal S0 of the center 50 will be described. For example, the upstream signals transmitted from the terminal devices of the plurality of subscriber homes 3 shown in FIG. 7 merge into the upstream signal S0, and the upstream signal S0 is split by the duplexer 61 of the center 50 shown in FIG. Then, it is output to the BPF 23 and the delay unit 62. The uplink signal S0 output to the delay unit 62 is output to the multiplexer 63 after being delayed by the delay unit 62 for a predetermined time.

On the other hand, the upstream signal S output to the BPF 23
0 is the noise S in a predetermined frequency band in the BPF 23.
23 is extracted and output to the oscilloscope 24. Next, in the oscilloscope 24, the noise S23 is sampled at predetermined time intervals, and the time series data S24 of the amplitude is sampled.
Is generated. Then, the time series data S24 of the amplitude
Is output to the transmission quality evaluator 125.

Next, in the amplitude probability density distribution data generation section 30 of the transmission quality evaluator 125 shown in FIG. 6, amplitude probability density distribution data S30 is generated from the amplitude time series data S24, and this is transmitted to the transmission quality evaluation section 132. Is output.
Next, the transmission quality evaluation unit 132 searches the noise amplitude / characteristic correspondence table data S131 stored in the memory 131 using the amplitude probability density distribution data S30 as a key, and obtains the noise characteristic data S132 obtained as a result. Output to generator 64.

Next, the noise generator 64 generates noise S64 having the noise characteristic indicated by the noise characteristic data S132 input from the transmission quality evaluator 125,
5 is output. Next, the phase controller 65 generates a noise suppression signal S65 in which the phase of the noise S64 input from the noise generator 64 is reversed, and outputs the noise suppression signal S65 to the multiplexer 63.

Next, in the multiplexer 63, the uplink signal S0 input from the delay unit 62 and the noise suppression signal S65 input from the phase controller 65 are multiplexed to generate an uplink signal S60. As a result, noise included in the uplink signal S0 is canceled by the noise suppression signal S65, and a high-quality uplink signal S60 from which noise has been removed is generated. The uplink signal S60 is demodulated by the demodulator 26 via the receiver 21 and then processed by the uplink signal processor 27.

As described above, the CAT of the present embodiment
According to the V system, the center 50 can generate a high-quality uplink signal S60 from which noise included in the received uplink signal S0 has been removed. At this time, even when the ingress signal S0 includes ingress noise, a high-quality inbound signal S60 from which the ingress noise has been removed can be generated.

Further, according to the CATV system of the present embodiment, the center 50 shown in FIG. 1 uses the oscilloscope 24 for sampling the amplitude of the noise S23 at predetermined time intervals, similarly to the center 20 of the first embodiment. As a result, the amount of data processed in the subsequent stage of the oscilloscope 24 can be significantly reduced as compared with the case where an oscilloscope that does not perform sampling is used. Therefore, in the transmission quality evaluator 125, the time for the transmission quality evaluation processing can be reduced, real-time transmission quality evaluation can be performed, and the storage capacity of the memory for temporarily storing processed data can be significantly reduced.

The present invention is not limited to the above embodiment. In the above-described embodiment, the case where the present invention is applied to the CATV system 1 is illustrated. However, the present invention can be applied to various types of communication systems in which noise is added to a signal to be transmitted. In the above-described embodiment, the noise S2
Although the oscilloscope 24 that performs sampling at a predetermined time interval is used to detect the amplitude of No. 3, an oscilloscope that continuously detects the amplitude of input noise without performing sampling may be used. . Also,
In the above-described embodiment, the case where the transmission quality evaluator 25 of the center 20 shown in FIG. 1 outputs the error rate data according to the characteristics of the noise has been exemplified. Various data according to noise characteristics may be output. Needless to say, it is possible to take measures such as performing line maintenance based on the evaluation result.

[0055]

As described above, according to the transmission quality evaluation device and the noise elimination device of the present invention, the function relating to the transmission quality evaluation only needs to be provided on the receiving side only, and
The transmission quality of a signal can be evaluated without using a transmission quality evaluation terminal device. Further, according to the transmission quality evaluation apparatus and method of the present invention, even when the received signal includes ingress noise, the influence of the noise on the transmission quality can be grasped. Further, according to the noise removing device of the present invention, it is possible to remove noise included in the received signal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an uplink signal receiving system in a center of a CATV system according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a transmission quality evaluator shown in FIG. 1;

FIG. 3 is a diagram for explaining noise amplitude / error rate correspondence table data stored in a memory shown in FIG. 2;

FIG. 4 is a diagram for explaining amplitude probability density distribution data included in noise amplitude / error rate correspondence table data.

FIG. 5 is a configuration diagram of an uplink signal receiving system in a center of a CATV system according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a transmission quality evaluator shown in FIG. 5;

FIG. 7 is a configuration diagram of a CATV system.

[Explanation of symbols]

2, 20, 50: Center, 21: Receiver, 22: Demultiplexer, 23: BPF, 24: Oscilloscope, 25: Transmission quality evaluator, 26: Demodulator, 27: Uplink signal processor,
DESCRIPTION OF SYMBOLS 31 ... Memory, 32 ... Transmission quality evaluation part, 60 ... Noise remover, 61 ... Diplexer, 62 ... Delayer, 63 ... Muxifier, 64
... Noise generator, 65 ... Phase controller

Claims (4)

[Claims] 1. A noise extracting means for extracting noise of a predetermined frequency from a received signal; an amplitude detecting means for detecting an amplitude of the extracted noise and generating amplitude data indicating the detection result; Data generation means for generating amplitude probability density distribution data indicating a probability density distribution of the amplitude of the noise, and storage means for storing amplitude probability density distribution data of a plurality of noises having mutually different characteristics obtained in advance. A transmission quality evaluation unit that compares the amplitude probability density distribution data generated by the data generation unit with the amplitude probability density distribution data stored in the storage unit, and determines the influence of noise on transmission quality. A transmission quality evaluation device. 2. A noise extracting means for extracting noise of a predetermined frequency from a received signal; an amplitude detecting means for detecting the amplitude of the extracted noise and generating amplitude data indicating the detection result; Data generation means for generating amplitude probability density distribution data indicating a probability density distribution of the amplitude of the noise, and storage means for storing amplitude probability density distribution data of a plurality of noises having mutually different characteristics obtained in advance. A transmission quality evaluation unit that compares the amplitude probability density distribution data generated by the data generation unit with the amplitude probability density distribution data stored in the storage unit, and determines the influence of noise on transmission quality. A noise suppression signal generation unit that generates a noise suppression signal for suppressing the noise based on the determined transmission quality; and Noise elimination device and a multiplexing means for multiplexing. 3. A transmission quality evaluation method for evaluating a signal transmission quality based on a noise amplitude probability density distribution. 4. The correspondence between the amplitude probability density distribution of noise and a predetermined transmission quality characteristic is clarified in advance, and the amplitude probability density distribution of noise to be evaluated is measured based on the relationship.
The transmission quality evaluation method according to claim 3, wherein the predetermined transmission quality characteristic is evaluated from the amplitude probability density distribution.