KR19990061477A - Network interface device of optical subscriber system - Google Patents

Abstract

The present invention relates to a network interface device that connects an optical subscriber network and a set-top box (STB) to time-divisionally transfer video services and control signals through the same transmission medium.

The present invention is a network interface unit (NIU) is connected to the ONU side and the telephone line analog pre-end unit 201 for amplifying and filtering the received signal, and 16 CAP modulated signal from the ONU to demodulate, The physical media sublayer 202 performing QPSK modulation and the DAVIC frame transmitted from the physical media sublayer 202 inversely frame the information, and the signal transmitted from the subscriber is converted into DAVIC frames. A transmission convergence sublayer 203 for transmitting to the media sublayer 202, and an adaptive TDMA control unit 204 for checking uplink signal transmission and controlling the transmission of uplink control information from the subscriber according to the result. And a microprocessor 205 for controlling, managing, and monitoring a network interface unit (NIU), and a control for controlling operations of units constituting the network interface unit (NIU). And a (206).

Description

A network interface unit of fiber loop carrier-curb system

The present invention relates to an optical subscriber system (FLC-C: Fiber Loop Carrier-Curb), and in particular, can provide uplink and downlink signals to the same transmission medium by providing an adaptive time division multiplexing function when providing a VOD service through an ATM network. The present invention relates to a network interface device of an optical subscriber system.

In general, the subscriber network connects subscriber terminals installed in the subscriber's home to the communication network.Two or four wire twisted pair (TP) is used as a subscriber network for general residential subscribers, which are mostly analog voice services. I use it.

Today, as the information society advances, as broadband data and video communication services increase, it is necessary to establish a broadband subscriber network. As such, subscriber access technology for constructing broadband subscriber network includes ADSL and HDSL using existing wired line, optical subscriber network technology (FTTH or FTTC) using optical cable, and wireless subscriber network to provide subscriber line wirelessly ( Wireless Local Loop (WLL). Here, the optical subscriber network using the optical cable is widely known as a FLC (Fibre Loop Carrier) system in which a DLC (Digital Loop Carrier) system is developed. The FLC system is an FLC-based system using ATM technology and an optical network unit (ONU). The trend is gradually developing to C.

In order to provide a CATV or VOD service by connecting a set-top box (STB) to such an optical subscriber system, it is necessary to connect the ONU of the set-top box and the optical subscriber system. In a conventional optical subscriber network, a single copper wire (UTP Cable) is used. Provide video service according to subscriber's request. That is, the uplink control signal from the set-top box has a burst property, and is QPSK modulated and transmitted to the video server at a speed of 1.62 Mbps. The video data and the downlink control signal from the video server according to the request of the subscriber station are 16CAP modulated and 51.84. The signal is transmitted to the set-top box at the speed of Mbps. In this case, since the downlink signal and the uplink signal are transmitted through the same transmission medium, a filter must be provided in the network interface unit (NIU) of the set-top box. did. However, if time-division transmission is performed by checking whether uplink and downlink signals are transmitted, two signals may be transmitted through the same transmission medium without having a filter.

Accordingly, an object of the present invention is to provide a network interface device of an optical subscriber system capable of transmitting up and down signals through the same transmission medium using time division multiplexing.

The apparatus of the present invention for achieving the above object, the set-top box (STB) having a network interface unit (NIU) is connected to the optical network unit (ONU), and the upstream stream transmitted from the video service subscriber to the network side; An optical subscriber network system configured to transmit and receive a downstream stream transmitted from a network to a subscriber, wherein the network interface unit (NIU) is connected to the ONU side by a telephone line to amplify and filter a received signal, wherein the ONU A 16 CAP modulated signal from the physical media sublayer for QPSK modulation, and inversely frames the DAVIC frame transmitted from the physical media sublayer to transmit subscriber information to the network. Transmission Convergence Sublayer for DAVIC Framed Signals An adaptive TDMA controller for controlling transmission of uplink control information from a subscriber, a microprocessor for controlling, managing, and monitoring a network interface unit (NIU) according to the result, by examining whether the downlink signal is transmitted or not; and the network interface unit And a controller for controlling the operation of the units constituting the NIU.

1 is a block diagram showing a schematic configuration of an optical subscriber network to which the present invention is applied;

2 is a block diagram showing a configuration of a network interface unit (NIU) according to the present invention;

3 is a block diagram showing the configuration of the analog pre-termination unit of FIG.

4 is a block diagram showing the configuration of the adaptive TDMA control unit of FIG. 2;

5 is a diagram illustrating a transmission section of an uplink signal in a window section according to the present invention;

6 compares the spectral allocation of the downlink and uplink signals.

* Explanation of symbols for main parts of the drawings

201: analog pre-termination end 202: physical medium sublayer

203: Convergence sublayer 204: Adaptive TDMA controller

205: microprocessor 206: control unit

301,302: operational amplifier 303,304: protection circuit

305: Combiner 401: Window Configuration Logic

402: utopia control signal transmission unit 403: uplink signal transmission control unit

405: upstream signal storage buffer

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

1 is a block diagram showing a schematic configuration of an optical subscriber network to which the present invention is applied. As shown in FIG. 1, an optical subscriber network according to the present invention includes a host digital terminal (HDT) 103 and a plurality of optical network units (ONU: 110-1 to 110-16). The HDT: 103 is connected to the ATM switch 102 at the STM-1 level, and the ATM switch 102 is connected to a video server 101 for providing a VOD or the like. The PSTN network 104 is connected to the HDT 103, and the telephone and the set-top box (STB) 120 are connected to the ONUs 110-1 to 110-16. In the embodiment of FIG. 1, the ATM switch 102 and the HDT 103 are connected to eight STM-1s, and the HDT 103 and each ONU 110-1 to 110-16 are connected at an STM-4c level. HDT 103 and PSTN 104 are connected to 108 DS1E.

The set-top box is provided with a network interface unit (NIU) for connecting to the video server 101 to receive a VOD service. The set-top box demodulates the signal sent by modulating the signal from ONU to 16 CAP, and then demodulating the signal from the NIU to QPSK. The modulated signal is demodulated in the ONU.

Here, looking at the VOD service provided by the optical subscriber system, according to the DAVIC 1.2 standard provides 6Mbps MPEG-2 video in real time at 51.84Mbps according to the subscriber's request, and the uplink control signal from the subscriber terminal It is delivered to the video server at 1.62Mbps. Spectrum allocation of downlink and uplink signals in DAVIC 1.2 is shown in Table 1 below.

16-CAP (downward signal) Bit rate Frequency Center frequency Frequency Symbol rate 51.84 Mbps 2.5920 MHz 10.3680 MHz 18.1440 MHz 12.96M baud

QPSK (Upward Signal) Bit rate Frequency Center frequency Frequency Symbol rate 1.62 Mbps 22.0725 MHz 22.6800 MHz 23.2875 MHz 0.81M baud

For downlink signals, only 6MHz is used out of the total 51.84MHz of available bandwidth, and only about 12% of the total allocated bandwidth is used for video services; for uplink signals, simple video control commands (e.g., stop, start, The amount of data to be transmitted as a signal to start a service, etc.) is very small. As such, since the downlink signal uses only about 12% of the total available channel resources, if the uplink control signal is transmitted during the period in which the channel is not used, that is, the downlink data is not transmitted, there is no need for a separate filter circuit. No interference or mixing takes place, enabling clean and error-free information transmission. Therefore, the basic function of the present invention is to investigate whether the downlink signal is transmitted and to control the transmission of the uplink control information from the subscriber station according to the result.

Figure 2 is a block diagram showing the configuration of a network interface unit (NIU) according to the present invention, the analog pre-end (201, Analog Front End) for amplifying the received signal connected to the telephone line, for the up / down signal The physical media sublayer 202 (PMD) that performs modulation / demodulation, the transmission convergence sublayer 203 (DAVIC TC) that performs DAVIC frames and inverse frames, and controls uplink signal transmission according to whether downlink signals are transmitted or not. And an adaptive TDMA control unit 204, a microprocessor 205, a control unit 206 and the like.

As shown in FIG. 3, the analog pre-termination unit 201 includes operational amplifiers 301 and 302 for amplifying the QPSK transmission signal and the 16CAP signal, and protection circuits 303 and 304 for protecting the overvoltage generated at the line interface. A combiner 305 is connected to the telephone line, and the adaptive TDMA scheme according to the present invention does not require a separate filter.

4 is a block diagram illustrating the adaptive TDMA control unit 204, which is implemented using Fpga, and includes a window configuration logic 401, a utopia control signal transfer unit 402, an uplink signal transmission control unit 403, and an uplink. It consists of a signal storage buffer 404.

The utopia control signal transmission unit 402 controls to receive an uplink signal when it is transmitted to a transmission convergence sublayer unit (203 of FIG. 2, hereinafter referred to as DAVIC TC) or when an uplink signal transmission request is received and stored in a buffer. Make a signal.

The window configuration logic 401 configures a window in synchronization with a start of cell (SOC) of a downlink utopia signal transmitted from the utopia control signal transmission unit 402 and receives a downlink signal from the DAVIC TC 203. At the same time, a window of 51.84MHz is made to transmit an uplink signal within this window, and if a window is not configured four or more times, a pseudo window is made to transmit an uplink signal within this period.

The uplink signal storage buffer 404 has a storage space capable of storing ten consecutive commands, and the uplink signal transmission control unit 403 requests uplink signal transmission within a window created by the window configuration logic 401. If present, the signal is received and transmitted or temporarily stored in the uplink signal storage buffer 404. That is, when there is a transmission signal from the subscriber station when the downlink signal received from the DAVIC TC 203 is a valid signal (MPEG-2 video signal), the signal is temporarily stored in the internal buffer 404, and the DAVIC TC 203 is executed. In the case where the downlink signal received from the N / A signal is not a valid signal, the uplink control signals temporarily stored in the internal buffer 404 are sequentially transmitted. In addition, even if the upstream signal is detected in a section outside the window of 51.84MHz, it is stored in the internal buffer 404.

5 and 6, the window configuration logic 401 creates a window of 51.84 MHz at the same time as valid information of the downlink signal starts. A valid video signal is transmitted downward in the first 6 MHz section of the window according to a subscriber's request, and the remaining sections except for the 6 MHz section become an uplink signal transmission section. At this time, the uplink signal should be synchronized with the transmission of the downlink signal, and if an uplink signal is detected in a section outside the window of 51.84 MHz, the uplink signal is stored in the uplink signal storage buffer 404 and waits for the next window. If the signal window is not formed, the window configuration logic 401 forcibly creates a pseudo window (Pseudo-Window) and forcibly sends an uplink signal in this interval.

In comparison with the prior art in the spectrum, Figure 6 (a) shows the spectrum of the signal existing on the conventional UTP cable, the down 16CAP signal and the up QPSK signal is present at the same time, ) And (C) respectively show the spectrum of a signal having only a downlink 16CAP signal and a signal having only an upward QPSK signal when using adaptive time division multiplexing according to the present invention.

As described above, the network interface unit (NIU) according to the present invention time-division multiplexes the downlink signal and the uplink signal when the uplink and downlink signals are transmitted through the same transmission medium. Therefore, since there is no interference effect between signals, there is an effect that information can be transmitted without error.

Claims (3)

A set-top box (STB) having a network interface unit (NIU) is connected to an optical network unit (ONU) to transmit and receive an upstream stream transmitted from a video service subscriber to the network side and a downstream stream transmitted from the network to the subscriber. In a magnetic network system, The network interface unit (NIU) An analog pre-termination unit 201 connected to the ONU side by a telephone line to amplify and filter a received signal; A physical medium sublayer 202 for receiving and demodulating a 16 CAP modulated signal from the ONU and performing QPSK modulation to transmit subscriber information to a network; A transmission convergence sublayer unit 203 for inversely framing the DAVIC frame transmitted from the physical medium sublayer unit 202, and converting the signal transmitted from the subscriber to the DAVIC frame to the physical medium sublayer unit 202; An adaptive TDMA control unit 204 for checking whether a downlink signal is transmitted and controlling transmission of uplink control information from a subscriber according to the result; A microprocessor 205 for controlling, managing and monitoring a network interface unit (NIU); And And a control unit (206) for controlling the operation of the units constituting the network interface unit (NIU). The method of claim 1, wherein the analog pre-termination end 201 Operational amplifiers 301 and 302 for amplifying the QPSK transmission signal and the 16CAP signal, respectively; And And a protection circuit (303, 304) for protecting overvoltage occurring at the line interface. The method of claim 1, wherein the adaptive TDMA control unit 204 A window configuration logic 401 for generating a window of a bandwidth size of the downlink signal from a cell start of the downlink signal; A utopia control signal transmission unit 402 for transmitting a control signal for storing an uplink signal in the internal buffer 404; An uplink signal transmission control unit 403 for monitoring whether an uplink signal is transmitted within the window section and transmitting an uplink signal or storing the uplink signal in an uplink internal buffer 404; And And an uplink signal storage buffer (404) for storing consecutive uplink control commands.