KR100261727B1 - Apparatus for interfacing a set-top-box to digital catv network - Google Patents

Abstract

The present invention relates to a subscriber matching device for connecting a subscriber set top box (STB) and a CATV network in a digital CATV.

The apparatus of the present invention converts an upstream ATM cell received from the set-top box into a serial unit, adds a predetermined ATM cell start bit, adds a start bit between each byte data, modulates the transmission, and A format converter for demodulating, by the subscriber matching device, the upstream signal received from the network interface unit into the ATM cell; VPI identification means for detecting the VPI in the output cell of the format converter and divided into an OAM cell and an uplink cell going to the network; A microprocessor for receiving and analyzing an OAM cell from a VPI identification means and providing a control signal to select a desired CATV broadcasting channel; And a switching unit configured to receive a plurality of CATV broadcast signals and transmit a CATV broadcast signal to a corresponding subscriber according to a control signal of the microprocessor.

Accordingly, the subscriber matching apparatus according to the present invention converts the uplink data transmitted from the set-top box to the remote terminal side of the digital CATV system in serial and then selects an ATM cell start bit for identifying an ATM cell and a start bit for distinguishing a byte. By adding and modulating the transmission, errors occurring during transmission can be minimized.

Description

An apparatus for interfacing a set-top-box to digital CATV network

The present invention relates to a digital CTAV system, and more particularly, to a subscriber matching device for connecting a subscriber set top box (STB) and a CATV network in a digital CATV.

In the era of advanced information, countries are building information highways to promote national and social informatization and enhance national competitiveness, and foster the information industry. In Korea, new media services such as comprehensive cable broadcasting and satellite broadcasting have begun, and the multi-media multi-channel era has arrived. Accordingly, technology development for introducing interactive multimedia services such as video-on-demand (VOD) or game-on-demand (GOD) using CATV or telephone line is underway.

Cable television (CATV), which uses broadband cable as a medium, has gained widespread attention because of the development of digital communication technology, which can provide interactive multimedia services with a small investment in equipment. Bandwidth expansion, data acquisition and digital transmission methods, servers, video switches, set-top-box and communication protocols should be developed.

The interactive CATV system is a system that provides various video information services such as movies, games, home shopping, and home banking in real time according to a user's demand by using an optical and coaxial transmission network, which is a broadband bidirectional communication network. As described above, an MPEG encoder 101, an ATM switch 102, a video server 103, a remote terminal (RT: 110a, 110b) connected to an ATM switch, and a set-top box 120- connected to a remote terminal through a telephone line 1 to 120-4).

In such an interactive CATV system, the set-top box and the remote terminal are connected through a telephone line, but there is a problem that an error occurs when transmitting broadband video data through the telephone line. In particular, when data is transmitted using an ATM cell, it is difficult to find the starting point of the cell.

Accordingly, the present invention has been proposed to solve the above problems, and an object thereof is to provide a subscriber matching device in a digital CATV system for matching CATV subscribers by transmitting an uplink cell from a set top box to a predetermined format.

In order to achieve the above object, the device of the present invention includes a subscriber matching device for accommodating CATV subscribers in a remote terminal (RT) and a network interface unit (NIU) in a set-top box (STB). A digital CATV system in which a matching device and the network interface unit (NIU) are connected by telephone lines to transmit and receive an upstream stream transmitted from a video service subscriber to a network side and a downstream stream transmitted from a network to a subscriber, wherein the network interface unit is a set-top. After converting the upstream ATM cell received from the box to serial, a predetermined ATM cell start bit is added, a start bit is added between each byte data, modulated and transmitted, and the subscriber matching device receives from the network interface unit. Demodulated uplink signal to demodulated ATM cell Resulting format converters; VPI identification means for detecting the VPI in the output cell of the format converter and separating the OPI cell into an uplink cell going to the network; A microprocessor for receiving an OAM cell from the VPI identification means and analyzing the OAM cell to provide a control signal for selecting a desired CATV broadcasting channel; And a switching unit configured to receive a plurality of CATV broadcast signals and transmit a CATV broadcast signal to a corresponding subscriber according to a control signal of the microprocessor.

1 is a block diagram showing the configuration of a digital CATV network to which the present invention is applied;

FIG. 2 is a block diagram showing the configuration of the remote terminal shown in FIG. 1;

3 is a block diagram of a subscriber matching device according to the present invention;

4 is a block diagram of a configuration for processing an upstream stream delivered from the STB to the network side according to the present invention;

FIG. 5 is for explaining the format converter shown in FIG.

(A) shows a 53-byte ATM cell,

(B) is an example of a format changed 486 bit serial bitstream.

* Explanation of symbols for main parts of the drawings

101: MPEG encoder 102: ATM switch

103: video server 110a, 110b: remote terminal (RT)

120-1 to 120-4: Set top box (STB) 230: MOV

231: microprocessor 232: switching unit

234: DPRAM I / F 235a-d: VPI Identifier

236a-d: format converter

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

1 is a block diagram showing the configuration of a digital CATV network to which the present invention is applied, and FIG. 2 is a block diagram showing the configuration of the remote terminal shown in FIG. As shown in FIG. 1, the digital CATV network includes an MPEG2 encoder 101, an ATM switch 102, a video server 103, a first remote terminal (RT-480: 110a), and a second remote terminal (RT-96). 110b), and set-top boxes 120-1 to 120-4 connected to the remote terminal through a telephone line.

The MPEG2 encoder 101 receives a broadcast signal from a CATV broadcaster, compresses and encodes the signal according to the MPEG2 standard, and then transmits the STM-1 to the ATM switch 102. The ATM switch 102 provides a video server for providing a VOD service. 103 is connected to the STM-1 to transmit a video signal to the remote terminals 110a and 110b. The remote terminals 110a and 110b and the ATM switch 102 are connected by STM-1 or STM-4c, and the first remote terminal RT-480: 110a can accommodate 480 subscribers, and the second remote terminal ( RT-96: 110b) can accommodate 96 subscribers. Here, the remote terminals 110a and 110b and the set top boxes 120-1 to 120-4 are connected by telephone lines, and the set top boxes 120-1 to 120-4 are connected to telephones and televisions.

The remote terminals 110a and 110b have 480 subscribers and 96 subscribers, and as shown in FIG. 2, the STM 210, PRC # 1 220a, PRC # 2 220b, and MOV 230 boards are used. Each of these boards is connected via a control bus 201, an analog bus 202, a digital up bus 203, and four digital down buses 204a to 204d, respectively. That is, the STM 210 receives four streams of STM-1 through four ports and connects one to one with four digital downlinks 204a-204d. The PRC # 1 220a connects the digital downlink bus 204a and the digital downlink bus 204b to process the downlink signals received through the port 1 and the port 2 of the STM 210, and the PRC # 2 220b. The digital down bus 3 (204c) and the digital down bus 4 (204d) is connected to process the down signal received by the port 3 and the port 4 of the STM (210). That is, a cell inputted from the ATM switch 102 to the STM 210 is inputted into four STM-1 ports of cells converted into VPI / VCI values assigned to each CATV channel, respectively, and for a cell having VPI = 9. The OAM cell is extracted and processed by the STM microprocessor, and the remaining cells are transferred to the digital downlink buses 204a to 204d of the backplane. The PRC boards 220a and 220b read the VPI of the cell input from the digital downlink bus and output 16 QAM or 64 QAM to the analog bus 202. At this time, 16 QAMs are processed per PRC board and 32 QAMs are processed.

The MOV board 230 receives the QAM channel and performs space switching according to the channel request of each subscriber to deliver it to each subscriber. The upstream signal, which is modulated by FSK modulation method from each subscriber and rises up to 64Kbps, is a signal indicating VPI = 0, indicating the channel change signal and the line state, and the microprocessor of the MOV processes the channel change and the line state by reading the upstream data. .

The digital downbuses 204a-204d are allocated one bus 16 bits per STM-1 port of the STM board 210, with a bus clock speed of 10 MHz and a capacity of 160 Mbps per bus for a total of 640 Mbps. The PRC boards 220a and 220b are transferred to the PRC boards 220a and 220b according to the VPI / VCI values assigned to each port. The QAM modulated signals are input to the MOV 230 through 32 analog buses.

Since the digital upbus 203 uses only one 16-bit bus, the digital upbus 203 has a bandwidth of 160Mbps and reads data from the MOV 230 at the STM board 210 using the UTOPIA level 2 interface and outputs the data to the ATM switch 102. The MOV board 230 reads the VPI of the ATM cell coming from the STBs 120-1 to 120-4, and processes the cell having VPI = 0 in the microprocessor of the MOV board itself, and digitally raises the cell other than the VPI = 0. Each bus is sent to the STM board 210 in accordance with the address of the board.

As such, an example of a VPI / VCI conversion table used in a remote terminal according to the present invention is shown in Table 1 below.

STM port PRC board VPI (HEX) VCI (HEX) channel PORT # 1 PRC # 1 One 101-103 CATV1-3 2 104-106 CATV4-6 3 107-109 CATV7-9 4 10A-10C CATV10-12 5 10D = 10F CATV13-15 6 110 CATV16 6 201-204 VOD1-4 7 204-20A VOD5-10 8 20B, 20C VOD11,12 9 111-113 OAM Cell PORT # 2 11 121-123 CATV33-35 12 124-126 CATV36-38 13 127-129 CATV39-41 14 12A-12C CATV42-44 15 12D-12F CATV45-47 16 130 CATV48 16 219-21C VOD13-16 17 21D-222 VOD17-22 18 223,224 VOD23,24

In Table 1, eight VPIs are assigned to one port of the STM board, and three VCIs are assigned to one VPI. In other words, two ports of STM board are connected to one PRC board to receive 16 VPI per PRC board, and it modulates to 1 QAM per 1 VPI to handle 16 QAM. Each modulated QAM signal will have a CATV channel signal with three different VCIs. Each CATV channel has a bandwidth of 6 Mbps, and each subscriber is sent three CATVs. Each subscriber outputs one selected channel out of three received signals to the screen by MPEG DECODING. That is, when the subscriber changes the channel, when the subscriber transfers the QAM signal having the desired channel among the 32 QAMs to the subscriber, the subscriber selects it from the STB and outputs the signal to the screen. Since the VOD signal has a bandwidth of 3Mbps, it is allocated to send 6 signals per 1 QAM. QAM modulation method can be selected and used in PRC board by 16QAM modulation method (21Mbps) and 64 QAM modulation method (27Mbps).

On the other hand, according to the present invention is located in a remote terminal subscriber matching device for transmitting and receiving up and down signals with the set-top box, as shown in Figure 3, the microprocessor 231, the switching unit 232, DPRAM1 (233a), Includes DPRAM2 233b, DPRAM I / F 234, VPI Identifiers 235a-235d, Format Converters 236a-236d, is included in a set top box (STB), and transmits an uplink signal to the subscriber matching device. As shown in FIG. 4, the network interface unit NIU includes a set-top box matching unit 501, a format converter 502, an FSK encoder 503, and an amplifier 504.

Referring to FIG. 4, the set top box interface unit STB I / F: 501 interfaces with the set top box via ATM UTOPIA, and the format converter 502 determines the format of the ATM cell transmitted as shown in FIG. 5. To convert.

Referring to Fig. 5, (a) shows a normal ATM cell of 53 bytes, and (b) is an example of a 486 bit serial bit stream that has been reformatted in the format converter 502. After the 53-byte ATM cell as shown in FIG. 5A is serially changed, as shown in FIG. 5B, a 9-bit ATM cell start bit (all high) is added, and a 1-bit ATM cell is added. Transmit 8 bits after inserting start bit (low). A low bit of one bit is inserted between each byte, and another ATM cell is transmitted after 53 bytes of ATM cells are transmitted.

Referring back to FIG. 4, the FSK encoder 503 performs FSK modulation on the serial stream output from the format converter 502, and the amplifier 504 amplifies the FSK modulated signal and transmits the signal to the remote terminal side through a telephone line.

Referring to FIG. 3, in the embodiment of the present invention, one subscriber matching device may accommodate 4 subscribers, and thus receives subscriber signals through the telephone line of 4 subscribers, respectively. The format converters 236a through 236d demodulate the uplink signal received from the NIU of the set top box via the telephone line and then convert the format of the 486 bit serial bitstream into a 53 byte ATM cell. The VPI identifiers 235a-235d extract the VPI / VCI from the header of the regenerated ATM cell and store the VPI / VCI in the dual port RAMs 233a and 233b through the dual port RAM interface unit DPRAM I / F: 234. In this case, if VPI is 0, the corresponding cell is a cell going to the microprocessor 231 and thus is stored in the second dual port RAM (DPRAM2: 233b). If VPI is not 0, the cell is stored in the first dual port RAM (DPRAM1: 233a). It is stored and transmitted to the network side as an uplink signal.

The microprocessor 231 controls the switching unit 232 according to the channel selection information of the cell with VPI = 0 to receive the desired CATV broadcast, and the switching unit 232 receives the CATV video signal from the network side. After receiving, the CATV broadcast signal is transmitted to each subscriber according to the control information of the microprocessor 231.

As described above, in the subscriber matching device according to the present invention, after serially converting uplink data transmitted from a set-top box to a remote terminal side of a digital CATV system, the ATM cell start bit and the byte are distinguished. By adding a start bit for data transmission and modulating and transmitting it, the error occurring during transmission can be minimized.

Claims (1)

A subscriber matching device is provided at the remote terminal (RT) for accommodating CATV subscribers, and a network interface unit (NIU) is provided at the set top box (STB), and the subscriber matching device and the network interface unit (NIU) are connected by telephone lines. In the digital CATV system for transmitting and receiving the upstream stream from the video service subscriber to the network side and the downstream stream from the network to the subscriber, The network interface unit Converts the upstream ATM cell received from the set-top box to serial and adds a predetermined ATM cell start bit, adds a start bit between each byte data, modulates it, and transmits The subscriber matching device A format converter for demodulating the uplink signal received from the network interface unit and reproducing it into an ATM cell; VPI identification means for detecting the VPI in the output cell of the format converter and divided into an OAM cell and an uplink cell going to the network; A microprocessor for receiving and analyzing an OAM cell from the VPI identification means and providing a control signal to select a desired CATV broadcasting channel; And And a switching unit configured to receive a plurality of CATV broadcast signals and transmit a designated CATV broadcast signal to a corresponding subscriber according to a control signal of the microprocessor.

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