KR20000043369A - Apparatus for controlling transmission power of cable modem - Google Patents

Abstract

PURPOSE: A transmission power controlling apparatus is provided to enable a signal received from a cable MODEM termination system(CMTS) to maintain a constant size, by adjusting a size of a signal to be transmitted from a cable MODEM according to a size of the received signal. CONSTITUTION: A transmission power controlling apparatus comprises a cable MODEM(300) and a CMTS(400). The cable MODEM(300) consists of a variable amplification part(310), a demodulation part(320), and a signal size extracting part(330). The variable amplification part(310) amplifies a signal modulated according to an amplification gain from the signal size extracting part(330), and transfers the amplified signal to a cable. The demodulation part(320) demoulates a signal received from the CMTS(400) through the cable. The signal size extracting part(330) extracts a signal to a size of a reception signal among the demodulated signals, and supplies the amplification gain of the amplification part(310) by the extracted signal. The CMTS(400) consists of an analog-to-digital converter(ADC)(420), a mixer(430), and a modulation part(440). The ADC(420) receives a signal transferred from the amplification part(310) to convert a size of the received signal into a digital signal. The mixer(430) mixes a signal to be transferred and a signal to a size of a reception signal from the ADC(420). The modulation part(440) modulates an output of the mixer(430).

Description

Sending Power Control Apparatus and Method for Cable Modem

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable modem, and more particularly, to an apparatus and method for controlling transmission power of a cable modem to vary the power of a signal transmitted to a CMTS according to a distance between a cable modem and a cable modem termination system (CMTS). It is about.

Currently, computer communication is actively used as a method for acquiring a lot of information using a computer at home or office.

Through such computer communication, it is possible to acquire not only text information but also image information, audio information, and the like, and to send and receive necessary information by communication with a counterpart.

Furthermore, video communication that can communicate while face-to-face with the other party has been developed, and in the future, it will be extended to areas such as video on demand.

As one of the most widely used computer communication schemes, as shown in FIG. 1, an analog modem 110 is built in or external to the computer 100 and connected to the telephone station 130 through the telephone line 120. 130 is connected to a service company in charge of a communication service to perform communication.

That is, when the user enters the telephone number of the service company through the computer 100 in order to communicate with the computer, the analog modem 110 dials it and transmits the telephone number to the telephone station 130 through the telephone line 120. do.

The telephone station 130 connects a line between the computer 100 and the service company by connecting to a communication service company corresponding to the telephone number dialed by the user.

Then, when the user inputs the data to be transmitted through the computer 100, the analog modem 110 converts it into an analog signal and transmits it to the telephone station 130 through the telephone line 120.

Therefore, the telephone station 130 transmits data input from the user to the communication service company to connect with other users.

Meanwhile, when the user receives data from the other party, the analog modem 110 receives the data through the telephone line 120 connected to the telephone station 130, and then converts the received data into a digital signal so that the user can enter the computer 100. ), You can check the received data.

By the way, when performing the communication through the telephone line 130 using the analog modem 110 as described above, the communication speed is limited, so that a large amount of data can be quickly exchanged, and there are many restrictions.

That is, the maximum speed that can transmit and receive data through the telephone line 130 is 56kbps is limited because of its characteristics, so the delay time is increased when sending and receiving video information, especially on-demand video, such as the service itself is impossible do.

Therefore, in order to solve such a problem, a communication scheme using a cable modem has recently been devised.

The cable modem is connected to a high-speed dedicated cable, for example, to be able to communicate by using a dedicated cable of a cable television currently being watched at home.

2 is a schematic diagram illustrating a communication state using the cable modem. A cable modem termination system (CMTS) 240 and a cable modem 220 are connected by a cable 230, and the cable modem 220 and the computer are connected to each other. 200-1, 200-2,..., 200-n are connected to the Ethernet bus 210.

First, a case in which data is transmitted or uploaded from the computers 200-1, 200-2,..., 200-n to the cable modem 220 via the Ethernet bus 210 will be described. The data packet to be uploaded in -1) is uploaded onto the Ethernet bus 210 and then received again.

If an error occurs in the transmitted data packet and the received data packet during the process of receiving the transmitted data packet again, it is transmitted through the Ethernet bus 210 to another computer (200-2, ..., 200-n). Is the case of uploading the current data packet.

That is, if the computer 200-2 first uploaded a data packet to the Ethernet bus 210, the computer 200-2 becomes the master and the other computers 200-2, ..., 200-n are slaves. Computer 200-2 has priority.

Therefore, when the computer 200-2 completes uploading one data packet, the computer 200-1 becomes a master and the computer 200-2 becomes a slave.

In other words, the direct memory access (DMA) method in the case of transmitting data using the Ethernet bus 210 from the computer (200-1, 200-2, ..., 200-n) to the cable modem 220 Is to transfer data using.

Therefore, the cable modem 220 receives data loaded on the Ethernet bus 210, amplifies the data at a constant amplification rate, and then transmits the data to the CMTS 240 through the cable 230 in packet units.

In the meantime, the case where the data is received from the CMTS 240 will be described. The cable modem 220 uploads the data received through the cable 230 onto the Ethernet bus 210 in units of packets.

The computer 200-1, 200-2, ..., 200-n analyzes the header of the data packet loaded on the Ethernet bus 210 to determine whether it is its own data. In case of doing so, IP address (Internet Protocol address) is compared, and if it is the same as its own address, it is received.

However, as shown in FIG. 3, the cable modems connected at different distances from the CMTS transmit signals to the CMTS at the same power, but the degree of attenuation may vary according to the distance.

That is, the signal of the cable modem connected with the distance of D1 from the CMTS is weakly attenuated and the signal of the cable modem connected with the distance of D1 + D2 will be transmitted. The attenuation will occur to some extent and the attenuated signal will be transmitted.

In addition, the signal received by the CMTS will be weak because the attenuation of the signal is greatest since it is connected far away from the home of the CMTS of the cable modem connected with a distance of D1 + D2 + D3.

In general, the code division multiple access method (CDMA) is used as a connection between multiple cable modems and the CMTS. When the signal transmitted by each cable modem in the CMTS is restored by the code division multiple access method, a different cable modem is used. In order to minimize the effects of these signals, the power of the signals sent by each cable modem should be the same to minimize the occurrence of noise.However, if the size of the signal received by the CMTS is different, it may interfere with the signals received from other cable modems. There is a problem that can not be correctly delivered and distortion may occur.

Accordingly, in view of the above-described problems, the present invention receives a signal about the magnitude of a signal received from the CMTS, and varies the power of a signal to be transmitted to the CMTS according to the magnitude, and transmits the signal to the cable by receiving the CMTS. It is an object of the present invention to provide an apparatus and method for controlling a transmit power of a cable modem such that signals of the modem maintain a constant size regardless of distance.

1 is a diagram for explaining a communication state of an analog modem using a general telephone line.

2 is a schematic diagram for explaining a communication state using a conventional cable modem.

3 is a diagram for explaining signal transmission efficiency according to a distance between a cable modem and a CMTS.

Figure 4 is a block diagram showing a transmission power control device of the cable modem of the present invention.

5 is a flowchart showing a transmission power control method of the cable modem of the present invention.

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

300: cable modem 310: variable amplifier

320: demodulation unit 330: signal magnitude extraction unit

400: CMTS 410: demodulator

420: A / D conversion unit 430: Mixing unit

440: modulator

In order to achieve the above object, a transmission power control method of a cable modem includes a first process of amplifying a signal modulated into a signal suitable for transmission through a cable with an amplification gain and transmitting the signal to a CMTS through the cable; A second process of receiving the signal transmitted by the cable by the first process from the CMTS and converting the received signal into a digital signal; A third step of modulating a digital signal of the magnitude of the signal converted by the second step into a signal suitable for transmission through a cable and transmitting the same to a cable modem through a cable; A fourth step of receiving and demodulating the signal transmitted by the third step and extracting a digital signal of the magnitude of the signal from the demodulated signal and providing the amplified gain of the first step based on the extracted signal Characterized in that performed.

On the other hand, the transmission power control apparatus of the cable modem of the present invention for performing the transmission power control method of the cable modem consisting of the above process, as shown in Figure 4, to the amplification gain output from the signal size extraction unit 330 A variable amplification unit 310 for amplifying the modulated signal and transmitting the signal through a cable, a demodulator 320 for demodulating a signal received through a cable from the CMTS 400, and a demodulated signal of the demodulator 320. A cable modem (300) including a signal size extractor (330) for extracting a signal for a signal magnitude and providing an amplification gain of the variable amplifier (310) by the extracted signal;

An A / D converter 420 and the A / D converter for receiving a signal transmitted from the variable amplifier 310 of the cable modem 300 and converting the received signal into a digital signal through a cable. A mixing unit 430 for mixing a signal about a magnitude of the received signal output from the 420 and a signal to be transmitted; Characterized in that it comprises a CMTS (400) including a modulator 440 for modulating the signal output from the mixing unit 430 to a signal suitable for transmission on the cable and sent to the cable.

The apparatus and method for controlling transmission power of the cable modem of the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First, the variable amplification unit 310 of the cable modem 300 receives a signal modulated with a signal suitable for transmission through a cable to the CMTS 400 and amplifies the signal to a predetermined level by an amplification gain initially set. The transmitted signal is transmitted over the cable (ST100, ST110).

The transmission signal of the cable modem 300 transmitted on the cable is received by the demodulator 410 of the CMTS 400 and restored to the original signal, and the transmission signal is applied to the A / D converter 420. The magnitude of the received signal, that is, the magnitude of power, is converted into a digital signal (ST120, ST130).

For example, suppose that the A / D converter 420 makes a 4-bit signal. If the transmitted signal is the largest, the output will be 1111. On the other hand, if the smallest signal is 0001, Will be output.

That is, the signal converted into this digital signal is the magnitude of the signal currently transmitted from the cable modem 300 to the CMTS 400 through the cable.

That is, the value of the signal converted into a digital signal according to the length of the cable, that is, the distance between the cable modem 300 and the CMTS 400 has a value between 0001 and 1111, the closer to 0001, the more cable modem and CMTS The distance between them is far, and the closer to 1111, the relatively closer distance is.

The mixing unit 430 mixes and outputs an n-bit signal to a magnitude of a received signal output from the A / D converter 420 and a transmission signal to be transmitted to a cable modem through a cable, and outputs a modulator ( The 440 modulates the mixed signal into a signal suitable for transmission to the cable modem 300 through the cable and outputs the mixed signal (ST140 and ST150).

The modulator 440 of the CMTS 400 receives the signal modulated by the demodulator 320 of the cable modem 300 and outputs the demodulated signal by restoring it to the original signal. The signal amplitude extractor 300 extracts an n-bit signal representing the size of the signal from the demodulated signal and adjusts the amplification gain of the variable amplifier 310 according to the extracted signal (ST160, ST170, ST180).

If the signal of 1111 is extracted, this is because the distance between the cable modem 300 and the CMTS 400 is close and the gain of the variable amplifier 310 is adjusted to lower the amplification factor in consideration of signals of other cable modems. That is, if the power of the signal output on the cable is lowered, while the signal of 0001 is extracted, the distance between the cable modem 300 and the CMTS 400 is far, so the variable amplifier 310 increases the amplification rate. By adjusting the gain, the power of the output signal is increased.

As described above, the apparatus and method for controlling transmission power of the cable modem according to the present invention adjusts the size of the signal to be transmitted by the cable modem according to the size of the signal received by the CMTS, so that the signal received by the CMTS is always constant regardless of distance. By minimizing the influence of the signal transmitted from the other cable modem, it is possible to receive a clear signal from the CMTS without distortion of the signal.

Claims (2)

A first step of amplifying a signal modulated into a signal suitable for transmission via a cable with an amplification gain and transmitting it via a cable to a CMTS; A second process of receiving the signal transmitted by the cable by the first process from the CMTS and converting the received signal into a digital signal; A third step of modulating a digital signal of the magnitude of the signal converted by the second step into a signal suitable for transmission through a cable and transmitting the same to a cable modem through a cable; A fourth step of receiving and demodulating the signal transmitted by the third step and extracting a digital signal of the magnitude of the signal from the demodulated signal and providing the amplified gain of the first step based on the extracted signal Transmission power control method of a cable modem, characterized in that performed as. A variable amplifying unit for amplifying a signal modulated according to an amplification gain output from the signal magnitude extracting unit and transmitting the same to a cable; A demodulator for demodulating a signal received through a cable from a CMTS, A cable modem including a signal size extraction unit for extracting a signal of a magnitude of a received signal from the demodulated signal of the demodulator and providing an amplification gain of the variable amplifier by the extracted signal; An A / D converter which receives a signal transmitted from the variable amplifier of the cable modem through a cable and converts the received signal into a digital signal; A mixing unit mixing a signal about a magnitude of a received signal output from the A / D converter and a signal to be transmitted; And a CMTS including a modulation unit for modulating the signal output from the mixing unit into a signal suitable for transmission on a cable and transmitting the signal to the cable.