KR100278442B1 - Single RF Channel Type HFC Transmitter and Method for Downstream Transmission - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coaxial transmission (HFC) transmission apparatus, and more particularly, to an apparatus and method for transmitting downstream data of a plurality of different services using a single RF channel. The present invention comprises a network access unit for matching with an external network, and a subscriber access unit for transmitting a single RF band signal received through a coaxial cable to various subscriber stations. The network access unit includes a data multiplexer for multiplexing a plurality of service data, a digital modulator for modulating transmission through a coaxial cable, and an RF combiner for converting and combining the modulated baseband signal into a single RF band to be transmitted. Include. The subscriber access unit includes a channel selector for selecting a desired RF channel from an RF band signal and converting the signal into a baseband signal, a digital demodulator for demodulating a baseband modulated signal into a digital signal, and demultiplexing the demodulated digital signal. And a data demultiplexer. The multiplexed data capacity does not exceed the bandwidth of a single RF channel, and each data is delivered in the form of a packet, and the header of each packet includes an identifier for distinguishing each type of data. The present invention has the effect of increasing transmission efficiency of coaxial cable by multiplexing different service data by using one RF band, and sharing one modulation / demodulation device, thereby reducing hardware complexity compared to the prior art. There is.

Description

Apparatus and method for single RF channel type HFC transmission for downstream transmission

The present invention relates to a hybrid fiber / coax (HFC) transmission apparatus. More specifically, the present invention relates to an apparatus for transmitting a plurality of different service data using one radio frequency (RF) channel in downstream transmission using an HFC network.

Recently, as the demand for broadband communication services increases, attempts have been made to provide various communication services to subscribers by improving the CATV (CAble TeleVision) network structure suitable for unidirectional transmission. Among the possible CATV network structures that can provide communication services to subscribers, the HFC structure using fiber optic network around the subscribers and the current coaxial cable network is the most promising.

1 is a block diagram of a network access unit and a subscriber access device in a conventional HFC network for downstream transmission. 1 illustrates a transmission apparatus for multiplexing fast Ethernet data and telephone voice data in a downstream.

Referring to FIG. 1, the network connection unit 130 may include a first digital modulator 131 and a telephone exchanger 120 for modulating Fast Ethernet data 111 received from a router 110 for matching with an external network. A second digital modulator 132 and a digital modulator 131 and 132 for modulating the received voice data are converted into basebands to be converted to RF bands to be transmitted and combined into different RF frequency signals. RF coupler 133 is configured. The digital modulators 131 and 132 modulate the input signals so that they can be transmitted through a coaxial cable.

The subscriber access unit 160 selects a desired channel from the RF band signal received from the coax and converts it into a baseband signal, respectively. ), A baseband selected by the first digital demodulator 162 and the second channel selector 163 for demodulating the modulation signal of the baseband selected by the first channel selector 161 into Fast Ethernet data. And a second digital demodulation unit 164 for demodulating the modulated signal into telephone voice data.

Referring to the operation of FIG. 1 configured as described above, various services such as voice, video, data, and facsimile data received from the router 110 and the telephone exchange 120 for matching with an external network such as an internet network and a telephone exchange network are described. The stream signal is modulated into an analog signal of a predetermined baseband (eg, 43.75 MHz) by the digital modulators 131 and 132 of the network connection unit 130. The modulated baseband signal is converted into a desired band among RF bands (54 to 750 MHz) that can be transmitted to the coaxial cable (Coax) by the RF combining unit 133 and then transmitted to the coaxial cable.

In this case, the analog signal modulated by the digital modulators 131 and 132 is the same baseband signal of 43.75 MHz, but since two RF bands are selected by the RF combiner 133, data collision occurs even if two data are transmitted on the same coaxial cable. Does not occur. However, there is a price to occupy two different RF channels.

Meanwhile, the subscriber access device 160 extracts the RF signal received from the coaxial cable by the channel selector 161 and 163 to convert the signal of the desired band into a baseband analog modulation signal. Then, the digital demodulators 162 and 164 demodulate the corresponding Fast Ethernet data and telephone voice data into digital signals and transmit the demodulated digital data to the personal computer (PC) 170 and the telephone 180, respectively.

Here, physically, one RF channel has a transmission capacity of about 30 Mbps of digital data, the maximum speed of Fast Ethernet data received from the router 110 is about 10 Mbps, and a telephone voice signal received from the telephone exchange 120. Is about 2 Mbps.

However, since the fast Ethernet data transmission path and the phone voice data transmission path are converted into different RF frequency bands through a separate digital modulation process, they occupy two RF channels and thus are uneconomical in terms of transmission efficiency.

Accordingly, an object of the present invention is to provide a method and apparatus for transmitting a plurality of different service data using one RF channel in an HFC network.

An apparatus of the present invention for achieving the above object, in the HFC transmission apparatus for transmitting a plurality of downstream service data to a plurality of subscriber stations via a single RF channel of the coaxial cable,

A network connection unit for matching with an external network; The network access unit includes a data multiplexer for multiplexing a plurality of service data, a digital modulator for modulating the multiplexed digital signal to be transmitted through a coaxial cable, and the modulated baseband signal. An RF coupling unit converting the RF band and combining the RF band;

A subscriber access unit for transmitting the RF band signal received through the coaxial cable to various subscriber stations; The subscriber access unit includes a channel selector for selecting a desired channel from an RF band signal and converting the signal into a baseband signal, a digital demodulator for demodulating the baseband modulated signal into a digital signal, and demultiplexing the demodulated digital signal. It characterized in that it comprises a data demultiplexer to separate.

The method of the present invention for achieving the above object is composed of a network connection unit and a subscriber matching unit using a coaxial cable as a transmission medium, HFC transmission for transmitting a plurality of downstream service data through a single RF channel of the coaxial cable In the method,

The transmitting may include (a) multiplexing a plurality of service data provided from an external network; (b) modulating the multiplexed digital signal to be transmitted over a coaxial cable; (c) converting the modulated baseband signal into a single RF band to be transmitted and combining the same;

The receiving step includes: (d) selecting a desired single RF channel from an RF band signal received through a coaxial cable and converting the signal into a baseband signal; (e) demodulating the baseband modulated signal into a digital signal; (f) demultiplexing the demodulated digital signal, wherein a plurality of different service data are multiplexed / demultiplexed to be transmitted by occupying a single RF band.

1 is a configuration diagram of a network access unit and a subscriber access device in a conventional HFC network for downstream transmission;

2 is a block diagram of a single RF channel type HFC transmission apparatus for downstream transmission according to the present invention;

3 is a diagram illustrating a downstream packet structure applied to FIG. 2.

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

210: router 220: telephone exchange

230: network connection unit 231: data multiplexing unit

232: digital modulation section 233: RF coupling section

260: subscriber access unit 261: channel selector

262: digital demodulator 263: data demultiplexer

270: personal computer (PC) 280: telephone

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a block diagram of a single RF channel type HFC transmission apparatus for downstream transmission according to the present invention. The present invention relates to downstream transmission of two or more different services by multiplexing data into one RF channel. The present embodiment shown in FIG. 2 provides two data streams (fast Ethernet data and telephone voice data). Multiplex.

Referring to FIG. 2, the network connection unit 230 multiplexes data for multiplexing the fast Ethernet data 211 received from the router 210 to match the external network and the voice data received from the telephone exchange 220. A digital modulation unit 232 and a modulation provided from the digital modulation unit 232 for modulating the multiplexed digital signal provided from the data multiplexing unit 231 to be transmitted through a coax. It is composed of an RF combining unit 233 for converting the combined baseband signal into a single RF band to be transmitted.

The subscriber access unit 260 is a channel selector 261 for selecting a desired single RF channel from a signal of an RF band received from a coax and converting the signal into a baseband signal, and converting the baseband modulation signal into a digital signal. Digital demodulation unit 262 for demodulating the signal, and a demultiplexer 263 for demultiplexing the demodulated digital signal and providing the demodulated digital signal to various subscriber stations (PC 270 and telephone 280).

Referring to the operation of Figure 2 configured in this way as follows.

In FIG. 2, fast Ethernet data 211 received from the router 210 for matching with an external network such as an internet network or a telephone exchange network and telephone voice data 222 received from the telephone exchange 220 are connected to a network. Multiplexed by the data multiplexer 231 of the unit 230. The multiplexed downstream data is modulated into a 43.75 MHz baseband analog signal through the digital modulator 232. The modulated baseband signal is converted by selecting and converting a desired band from RF bands (54 to 750 MHz) that can be transmitted to the coaxial cable by the RF coupling unit 233, and then converting the converted RF signal into a subscriber access unit 260 through the coaxial cable. Is sent).

Here, the principle of data multiplexing will be described. First, the fast Ethernet data connected to the Internet network is data of a packet form consisting of a total length of 188 bytes by combining a 4-byte header 300 and a 184-byte payload 310 as shown in FIG. 3. . The information included in the header 300 includes a display area for identifying what kind of data the adjacent payload data is. For example, if the payload transmitted adjacent to this area is Fast Ethernet data, it is set to a specific value (hexadecimal value of 0x1FFE), and for telephone voice data, it is set to a specific value (hexadecimal value of 0xEFC). To distinguish. These headers contain specific values that can distinguish different kinds of data and multiplex them. In this way, the receiving side (subscriber terminal) can demultiplex according to the specific value of the header and provide the service terminal.

In this case, two types of signals multiplexed through the data multiplexer 231 are shared by transmitting one output line. The multiplexed baseband signal is modulated to be transmitted over a coaxial cable through the digital modulator 232, and the modulated baseband signal is converted into an RF band by the RF combiner 233. The converted RF signal is transmitted by occupying only one RF band through a coaxial cable.

On the other hand, the subscriber access unit 260 extracts an RF channel signal of a desired band through a channel selector 261 that selects an RF signal received from a coaxial cable (Coax) and converts it into a baseband analog modulation signal. The digital demodulator 262 demodulates the baseband analog modulated signal into a digital signal and provides the demodulated signal to the data demultiplexer 263. The data demultiplexer 263 separates the demodulated signal into the high-speed Ethernet data and the telephone voice data signal, and transfers them to the PC 270 and the telephone 280, respectively.

In this case, the data demultiplexing principle distinguishes high-speed Ethernet data and telephone voice data by analyzing data type classification information included in a header.

2 and 3, the HFC transmission apparatus of the present embodiment uses a single channel RF band having a digital data transmission capability of about 30 Mbps and fast Ethernet data (about 10 Mbps) received from the router 210, and a telephone. Since telephone voice data (approximately 2 Mbps) received from the switch 220 is transmitted, only one digital modulator 232, a channel selector 261, and a digital demodulator 262 need to be provided.

In the present embodiment, two channels of Ethernet data and telephone voice data are multiplexed into one RF channel, but various video, audio, and information data may be multiplexed and transmitted without exceeding a single channel capacity. This is a kind of time division multiplexing (TDM) scheme. The service can be provided by demultiplexing the multiplexed data using the header separator.

In addition, the present embodiment has been described only for the downstream, but may be equally applicable to the upstream. That is, the subscriber access unit multiplexes the data, digitally modulates the RF, and then transmits the data through a single RF channel of a coaxial cable. The network connection unit selects a desired channel among the signals received through the coaxial cable, and digitally demodulates the selected signal to demultiplex the demodulated data.

The present invention is not limited by the embodiments described above, and various changes and modifications can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

As described above, in the related art, different types of data have different digital modulation processes and use different RF bands, thereby being uneconomical in terms of transmission efficiency.

In contrast, the present invention includes an area indicating a service type in the header area of the downstream data packet, and transmits a single RF band by multiplexing different types of downstream. Therefore, there is an effect of increasing the transmission efficiency of the coaxial cable.

In addition, since the conventional different service data has a separate modulation and demodulation path, each modulation and demodulation device is required. However, since the present invention uses a single modulation and demodulation device because different service data share a single RF channel, Compared to this, hardware complexity is reduced.

Claims (6)

An HFC transmission apparatus for transmitting a plurality of downstream service data to a plurality of subscriber stations through a single RF channel of a coaxial cable, (a) a network connection unit for matching with an external network; (a1) The network connection unit is a data multiplexing unit for multiplexing a plurality of service data, (a2) a digital modulator for modulating the multiplexed digital signal to be transmitted through a coaxial cable; (a3) an RF combiner configured to convert the modulated baseband signal into an RF band to be transmitted and combine the same; (b) a subscriber access unit for transmitting an RF band signal received through a coaxial cable to various subscriber stations; (b1) The subscriber access unit is a channel selection unit for selecting a desired channel from the RF band signal to convert to a baseband signal, (b2) a digital demodulator for demodulating the baseband modulated signal into a digital signal; (b3) A single RF channel type HFC transmission apparatus for downstream transmission comprising a data demultiplexer for demultiplexing and separating the demodulated digital signal, wherein a plurality of service data can be transmitted by occupying a single RF band. . The method of claim 1, wherein the plurality of service data is in the form of a packet having a header portion and a payload portion, wherein the header portion includes a delimiter for distinguishing types of data contained in the payload portion. RF channel type HFC transmitter 3. The single RF channel type HFC transmission apparatus according to claim 2, wherein the plurality of service data are Ethernet data and telephone voice data. In the HFC transmission method comprising a network connection unit and a subscriber matching unit using a coaxial cable as a transmission medium, and transmitting a plurality of downstream service data through a single RF channel of the coaxial cable, The sending stage (a) multiplexing a plurality of service data provided from an external network; (b) modulating the multiplexed digital signal to be transmitted over a coaxial cable; (c) converting the modulated baseband signal into a single RF band to be transmitted and combining the same; The receiving step is (d) selecting a desired single RF channel from the RF band signal received through the coaxial cable and converting the signal into a baseband signal; (e) demodulating the baseband modulated signal into a digital signal; and (f) demultiplexing the demodulated digital signal so that a plurality of different service data can be multiplexed / demultiplexed and transmitted by occupying a single RF band. Transmission method. 5. The method of claim 4, wherein the plurality of service data is in the form of a packet having a header portion and a payload portion, wherein the header portion includes an identifier for distinguishing types of data contained in the payload portion. RF Channel Type HFC Transmission Method 5. The method of claim 4 wherein the plurality of service data is Ethernet data and telephone voice data.