JPH11355755A - Cable system and cable regenerative repeater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of a data error, etc., due to an incoming noise by constituting a cable regenerative repeater of a data generating part to replace a data signal from a demodulating part with an FEC bit in the form of a standard format of a cable television network and a modulator to perform high frequency modulation on the data signal in the form of the standard format. SOLUTION: The data signal distributed from a cable modem regenerative repeater 1 arranged at the doorway of a complex housing equipment 4 is received via cable modems 2, 2' by personal computers 3, 3'. In addition, a signal to be outputted from the personal computer 3 is outputted by adding the FEC bit of multi-bit for data error correcting code to the signal and further modulating the signal into a high frequency signal by the cable modem 2. An incoming signal is demodulated by the demodulating part 6 by the regenerative repeater 1, the FEC bit is replaced and converted into the standard format by the data generating part 8, the high frequency modulation is performed on the FEC bit and outputted by the modulating part 9. Thus, an error correcting function of the equipment 4 having large incoming noise and bad line quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CATV (Cable
Television;) The present invention relates to a regenerative repeater for reproducing using a cable modem or the like in a system or the like and a cable system.

[0002]

2. Description of the Related Art In recent years, opportunities for transmitting digital data have increased, and data transmission has been actively expanded, such as facsimile using a telephone line, a peer-to-peer personal computer network, and downloading and uploading on the Internet.

[0003] In the CATV system industry, not only ordinary television reception, but also connection of the Internet through a public telephone line using the MSO of the CATV system as a provider having a server is expected as a near future technology.

[0004] Under such a premise, Japanese Unexamined Patent Application Publication No.
No. 9 discloses a means for transmitting a digital audio signal using a CATV line. This publication is characterized in that a digital signal of a plurality of channels is formed into one-word serial data using one channel of a television, an error correction code is added to each channel, and signals are transmitted by interleaving between the channels. Four channels A to D are set as a plurality of channels, and each channel is, for example, a 40-bit L channel, a 16-bit R channel, a 40-bit service bit SB including a 1-bit service bit SB, and a Hamming code H. A format is formed from the error correction code, the signal order is rearranged once, transmitted, and the interleaving method of rearranging the signal back to the original order is adopted.

In this manner, a burst error, an error due to intersymbol interference, and the like are randomized to substantially eliminate these errors, and a data sampling pulse, that is, a selection pulse, is selected from serial data in which a plurality of four channels are arranged in series. Since it is only necessary to change the phase of the pulse for each channel and select each channel, the bit rate is substantially reduced to one-fourth of the number of channels to be handled, that is, when there are four channels, the bit rate is reduced to 1/4. It is said that error correction processing will be easier.

[0006] In addition to the above-mentioned publications, in recent CATV systems, the diversification of the housing environment has progressed, and not only individual CATV cables are laid, but also one cable is laid for condominiums and condominiums and branched into individual cables. Not only distribute TV and audio signals by installing a branching device,
It is being implemented to transmit and receive data signals in a bidirectional manner.

[0007]

However, when a two-way cable television network is connected to an existing apartment house, ingress noise in the existing apartment house is mixed into the cable television network, affecting the two-way service. . For this reason, the connection to the existing apartment was connected in one direction, and no two-way service could be provided. Further, even if an attempt is made to provide an interactive service in an existing housing complex, a data error or the like due to ingress noise has occurred.

The present invention provides an FEC (Forward) that eliminates the above-mentioned problems such as the occurrence of data errors due to ingress noise.
Error Correction: It is intended to provide a function of replacing bits.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a personal computer for transmitting and receiving data in a cable system having a two-way cable television network for distribution to an apartment house via a cable regeneration repeater, and a personal computer for transmitting and receiving data. A cable modem for adding a FEC bit in an in-house format of an error correction code to the data signal from the CDMA and modulating the frequency of the data signal, and the cable regeneration repeater. A distribution coupling unit, a demodulation unit for demodulating the data signal, a data generation unit for replacing the data signal from the demodulation unit with FEC bits of a standard format format of the cable television network, and a data signal of the standard format format. And a modulator for high frequency modulation.

[0010] The present invention is also characterized in that, in the above-mentioned cable system, the number of FEC bits in the format format for in-house use is larger than the number of FEC bits in the standard format format.

Further, the present invention relates to a cable reproducing repeater used in a CATV system provided with a bidirectional cable television network for transmitting and receiving to and from a personal computer connected to an apartment house, wherein the data signal from the personal computer is corrected for error. A demodulation unit for demodulating the high-frequency signal in response to an output signal of a cable modem that modulates a high-frequency signal by adding an FEC bit in a format for a multi-family housing; A data generator for replacing the FEC bits in the format format with FEC bits in the standard format format of the cable television network in accordance with the added data signal; a modulator for modulating the data signal in the standard format format at a high frequency; A distribution coupling unit for transmitting and receiving to and from a television network. The features.

[0012]

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

[First Embodiment] (Structure of the present embodiment) In FIG. 1, a cable modem is provided at an entrance and exit of an apartment house 4 connected to a coaxial table or an optical fiber cable drawn from a cable television network of a CATV system. A regenerative repeater 1 is provided.

Although not shown in FIG.
A television signal is distributed from the cable modem reproduction repeater 1 by a coaxial cable or the like, and connected to the televisions 14 and 15 of each house, which is a home, via a television converter. In this way, a multi-channel television broadcast from the CATV center station can be selected and one of the channels can be viewed.

On the other hand, when data signals are transmitted and received in each house, the data signals distributed from the cable modem regenerative repeater 1 are transmitted to the cable modems 2 and 2 ′ via the collective housing facility 4.
Received by a personal computer or SOHO (Small
A data signal is received by a workstation or a personal computer 3, 3 '(hereinafter, referred to as a "personal computer") used for an office or home office. The data signal output from the personal computer 3 is converted by the cable modem 2 into a multi-bit FE for data error correction code.
C (Forward Error Correction)
A bit is added, the signal is further modulated into a high-frequency signal, and transmitted to the cable modem regenerator 1 via a coaxial cable or the like.

Also, the number of FEC bits added to the data signal is made variable depending on the noise situation such as ingress noise generated in the housing complex connected to the cable television network, and the number of FEC bits is standardized in a portion transmitted to the cable television network. A dynamic operation is performed by replacing the data signal with the number of operational FEC bits.

As the FEC system, a Hamming code,
A BCH (Bose-Chaudhuri-Hocquenghem Code) code or the like can improve the correction ability. In particular, for a burst error correction which is a continuous error correction, Reed-Solomon (Reed-Solomon) is used.
-Solomon) code is preferred, for example a 16 bit read
An 8-bit code can be corrected by the Solomon code. In addition, an inleaving method that enables burst error correction by phase-expanding a random error correction code is also effective.

The ingress noise in this apartment house is:
Household vacuum cleaners, refrigerators, washing machines, citizen wireless, etc. are mixed into CATV cables wired in the house to generate noise, and specific FEC bits are used for the noise peculiar to the apartment complex. It is also effective, and ISM (Industrial Scientific Medica
l) When a device is used, the FEC bit can be determined by increasing or decreasing the FEC bit based on the noise performance of the ISM device.

In the cable modem regenerative repeater 1, a distribution coupling unit 13 connected to the cable television network, and a downlink signal distributed from the distribution coupling unit 13 are output to the collective housing equipment 4 by the directional filter 5, and A directional filter 5 that receives a data signal as an uplink signal from the equipment 4, a demodulator 6 that demodulates the data signal as an uplink signal, and a level detector 7 that detects the level of the data signal demodulated by the demodulator 6. A data generator 8 for converting FEC bits, which will be described later, from the data signal passed through the level detector 7 to a standard format of a cable television network and converting the data signal; The modulation section 9 outputs as an uplink signal, the demodulation section 12 demodulates a downlink control signal from the distribution coupling section 13, and the demodulation section 12 according to the downlink control signal. A control unit 11 for controlling the cable modem regenerator 1, and controls the control unit 11 the data generator 8
And a CPU 10 for performing the above control.

Referring to FIG. 1, a personal computer 3 as a data terminal such as a personal computer is connected to a cable modem 2 installed in an existing apartment house.
The data signal output from the cable modem 2 and added with a larger number of FEC bits than usual is RF-modulated, passed through the existing in-family facilities 4 and passed to the cable modem regenerator 1 where it is regenerated and relayed. , And the FEC bits are replaced and sent to the cable television network. All the processing of the upstream data in the cable modem reproduction repeater 1 is configured by hardware, so that the delay amount can be fixed. That is, the cable modem 2 installed in the existing apartment house can also perform the delay measurement control from the center station similarly to the other cable modems 2.

The cable modem reproduction repeater 1 further includes a directional filter 5 for distributing a cable television signal into an upstream signal and a downstream signal, a demodulation unit 6 for demodulating an RF-modulated signal, and a cable modem. A level detection unit 7 for detecting an uplink level; a data generation unit 8 for replacing data of the cable modem with FEC of a standard data format to generate data; a modulation unit 9 for RF-modulating the generated data; A distributing / coupling unit 13 for coupling to the same coaxial cable as the downstream signal again, a demodulation unit 12 for demodulating control data to the cable modem regenerative repeater 1, a control unit 11 for controlling the present cable modem regenerative repeater,
And a CPU 10.

(Operation of the Present Embodiment) The operation of the present invention will be described with reference to the drawings. FIG. 2 shows an example of data format settings. In contrast to the standard data format 13, the output data of the cable modem 2 installed in the existing apartment house has a configuration with many FEC bits like the data format 14. However, data format 1
3 and the data length of the data format 14 do not change.
Regenerating to the standard data format reduces the number of FEC bits. A part of the next data is moved up and inserted by an amount corresponding to the decrease in the number of FEC bits, and NULL is added at the end of the frame.
And adjust the frame length.

The cable modem regenerative repeater 1 having received the data of the data format 14 extracts only the upstream signal by the directional filter 5 and demodulates the signal from the high frequency signal to the baseband signal by the demodulation unit 6. 2 is input to a level detector 7 for detecting the level of the uplink data signal. The level detector 7 detects the upstream output level of each cable modem 2 and controls the output of the modulator 9 so that the output level becomes the same as the detected level. The data generation unit 8 changes the number of FEC bits from the data from the cable modem to generate a frame of the standard format 13 shown in FIG. The generated data signal of the frame format 13 is passed to the modulation unit 9, RF-modulated, and transmitted to the cable television network via the distribution coupling unit 6.

As described above, the cable modem according to the present embodiment, which also has a function of reducing ingress noise in an existing apartment house, is installed in the apartment house, and has an FEC (Forward Error Correction) in the upstream signal data format. (Correction) More bits are used, and the error correction capability is enhanced even in situations where there is a lot of ingress noise. In a reproduction repeater installed in a cable television network introduction section of an existing apartment house, when reproducing data, the data is replaced with a FEC bit number according to a standard data format and transmitted to the cable television network.

Further, in FIG. 1, the cable modem 2 installed in the apartment house transmits data in a data format in which FEC bits are larger than usual. This data signal is input to the cable modem regenerative repeater 1 installed in the cable television network introduction part of the apartment house, and at the same time as the regenerative relay, the FEC bit number is changed to a standard data format and sent out to the cable television network. As a result, even in a housing complex with poor line quality, error correction capability is enhanced, and stable line quality can be maintained. Further, the data format in the cable television network is changed to a standard format by the cable modem reproduction repeater, so that the data transmission efficiency in the cable television network is maintained.

[Second Embodiment] Next, a second embodiment of the present invention will be described in detail. Referring to FIG.
By changing the number of FEC bits by the data generator 8, the error correction function is enhanced. In the present embodiment, the number of preamble bits is increased in the data format.

In FIG. 2, the number of bits of the preamble is increased with respect to the in-house frame format 14. Since the number of bits larger than the number of FEC bits in the standard format is added to one frame and the number of bits of the preamble is increased, the data amount is reduced accordingly. However, when a data signal or a television signal is coupled to a coaxial cable or the like in an apartment house, inflow noise increases. Therefore, the data generator 8 in the cable modem regenerator 1 captures synchronization of the upstream data signal. Even if tracking is difficult, the number of bits in the preamble is increased, making it easier to capture synchronization, making it easier to establish synchronization, and building a system that is relatively resistant to ingress noise. It is.

In this case, if the data frame length is the same, the amount of data that can be sent decreases, but establishment of synchronization is important from the viewpoint of the reliability of the uplink data signal. Once synchronization is established,
The FEC bits are replaced with the standard format, and transmitted to the cable television network accurately, so that the data demodulation at the CATV center station is executed with high reliability.

In the above embodiment, the cable modem pays attention to the upstream data signal. However, the cable modem regenerative repeater 1 is provided with a downstream modem dedicated to data signals on the collective housing equipment side, and this downstream modem is standardized. By replacing the FEC bits of the format format 13 with the FEC bits of the format format 14 within the housing complex, the reliability of not only the uplink data signal but also the downlink data signal can be improved.

[0030]

According to the present invention, the first effect is that in an existing collective facility having a large amount of ingress noise and poor uplink line quality,
By increasing the number of FEC bits during the data format, the error correction function can be enhanced.

The second effect is to prevent the ingress noise generated in the existing housing complex from being mixed into the cable television network by reproducing and relaying. This is because the upstream ingress noise can be cut by the cable modem regenerative repeater by regenerating and relaying only the data.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram around an apartment house according to an embodiment of the present invention.

FIG. 2 is a format diagram of a data signal for performing FEC replacement according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable modem reproduction repeater 2 Cable modem 3 Personal computer (data terminal) 4 Apartment house 5 Directional filter 6 Demodulation unit 7 Level detection unit 8 Data generation unit 9 Modulation unit 10 CPU 11 Control unit 12 Demodulation unit 13 Standard frame format 14 Frame format in apartment house

Claims (6)

[Claims] 1. A personal computer for transmitting and receiving data in a cable system having a bidirectional cable television network for distribution to an apartment house via a cable regeneration repeater, and an error correction code added to a data signal from the personal computer. A cable modem for adding high-frequency modulation by adding FEC bits in a format for multiple dwelling houses, and the cable regeneration repeater, wherein the cable regeneration repeater transmits and receives signals to and from a cable television network; A demodulator for demodulating a signal, a data generator for replacing a data signal from the demodulator with FEC bits in the standard format of the cable television network, and a modulator for high-frequency modulating the data signal in the standard format. Cable system characterized by becoming. 2. The format F for the inside of an apartment house
The number of EC bits is determined by F in the standard format.
The cable system according to claim 1, wherein the number of EC bits is larger than the number of EC bits. 3. The cable regeneration repeater further includes a directional filter that distributes a downlink signal distributed from the distribution coupling unit to the housing complex, and demodulates a downlink control signal distributed from the distribution coupling unit. The cable system according to claim 1, further comprising: a control demodulation unit; and a control unit that controls the inside of the cable regeneration repeater according to the control signal. 4. The cable system according to claim 1, wherein the FEC bit is a Reed-Solomon code. 5. A cable reproduction repeater for use in a CATV system provided with a bidirectional cable television network for transmitting and receiving to and from a personal computer connected to a housing complex, wherein the data signal from the personal computer is provided with an error correcting code in the data signal from the personal computer. A demodulation unit that demodulates the high-frequency signal in response to an output signal of a cable modem that modulates the signal into a high-frequency signal by adding an FEC bit in an internal format;
A data generation unit that replaces the FEC bits in the format for the residential complex from the demodulation unit with FEC bits in the standard format format of the cable television network in accordance with the added data signal; and a data signal in the standard format format. A cable regeneration repeater comprising: a modulator that modulates a signal to a high frequency; and a distribution coupling unit that transmits and receives the signal to and from the cable television network. 6. The F of the format format for the inside of an apartment house
The number of EC bits is determined by F in the standard format.
The cable regeneration repeater according to claim 5, wherein the number of the EC bits is larger than the number of EC bits and varies according to a degree of ingress noise caused by the housing complex.