JPH11252532A - Data transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute up data transmission in a CATV network by controlling the level of the up channel of a second cable modem based on a transmitting characteristics monitored by the up channel of a narrow transmitting band in the CATV network of the second cable modem. SOLUTION: A cable modem managing device 8 monitors a transmission speed being the transmission characteristics of the cable modem 6a on the side of a user to adjust the Carrier value of the modem 6a to execute level adjustment in the up channel. Namely, in the case when the transmission speed of the modem 6a is lower than the transmission speed of a lower limit, the raising of the Carrier value to be sent by the modem 6a is instructed and the modem 6a raises the Carrier value to send based on the instruction. In the case when the transmission speed of the modem 6a is higher than the transmission speed of a higher limit, the lowering of the Carrier value to be sent by the modem 6a is instructed and the Carrier value is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a LAN (Loc)
al Area Network) and CATV (Ca
The present invention relates to a data transmission method for transmitting data via a network of a ble television network.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a configuration of a conventional data transmission system using a CATV network and a LAN network. In the figure, 1 is a terminal on the center side (first terminal), 2 is a LAN, and is a TCP / IP (Transm
issue Control Protocol / In
This is a “computer network” using a communication protocol called “Internet Protocol”.
The LAN 2 is a symmetric network having a wide band for both the upstream channel and the downstream channel.

Reference numeral 3 denotes a center-side cable modem (first cable modem) for modulating and demodulating a signal to be transmitted.
A downstream digital signal from AN2 is modulated into an analog high-frequency signal, and an upstream analog high-frequency signal to LAN2 is demodulated into a digital signal. 4 is HE (H
This is a device for mixing the frequency of the downstream analog high-frequency signal from the cable modem 3 and the frequency distribution of the upstream analog high-frequency signal to the cable modem 3.

In FIG. 3, reference numeral 5 denotes a CATV network, which is a “broadcast network” using a communication protocol for the CATV network. The CATV network 5 is a tree-shaped network including a bidirectional amplifier 11 as a relay amplifier and a coaxial cable 12. Further, the bidirectional amplifier 11 includes a downstream amplifier 11-1 having a large gain and a dynamic range and an upstream amplifier 11-2 having a small gain and a dynamic range.
In the network 5, the downstream channel is an asymmetric network having a wide transmission band and the upstream channel is a narrow transmission band.

Further, reference numerals 6a and 6b denote user-side cable modems (second cable modems) for modulating and demodulating a signal to be transmitted, and demodulate a downstream analog high-frequency signal from the CATV network 5 into a digital signal. Is modulated into an analog high-frequency signal upstream to the CATV network 5 and a channel (used frequency band) is selected. Reference numeral 7 (7a, 7b) denotes a user-side terminal (second terminal).

Next, the operation will be described. First, an operation in the downlink direction for transmitting data from the terminal 1 on the center side to the terminal 7a on the user side will be described. The terminal 1 on the center side transmits data to a digital IP (Internet P
protocol), and transmits the packet to the LAN 2 of a wide band network. The cable modem 3 modulates the transmitted digital IP packet into an analog high-frequency signal. The HE device 4 mixes the frequency of the downstream analog high-frequency signal from the cable modem 3 and
Send it out to network 5.

The data transmitted to the CATV network 5 is CA
At each relay point of the TV network 5, the signal is transmitted through a broadband downstream channel while being amplified by the downstream amplifier 11-1 having a large amplification factor. The cable modem 6a has a CA
An analog high-frequency signal transmitted from the TV network 5 is demodulated into a digital IP packet and transmitted to the user terminal 7a.

Next, the operation in the uplink direction for transmitting data from the terminal 7a on the user side to the terminal 1 on the center side will be described. In this case, the data transmitted from the user-side terminal 7a is transmitted in the reverse direction via the cable modem 6a, the CATV network 5, the HE device 4, the cable modem 3 and the LAN 2 in a manner opposite to the above-described transmission in the downstream direction. Are performed and transmitted to the terminal 1 on the center side. At this time, C
In the ATV network 5, data is transmitted on a narrow band upstream channel using an upstream amplifier 11-2 having a small amplification factor and a small dynamic range.

In general, the transmission band of a transmission line increases as the amplification factor and the dynamic range of an amplifier connected to the transmission line increase, and as the attenuation factor due to the components of the transmission line decreases. The downstream channel has a wide transmission band and can perform high-speed data communication.
The upstream channel has a narrow transmission band, which is disadvantageous for performing high-speed data communication.

[0010]

SUMMARY OF THE INVENTION As described above, CATV
The upstream channel of the network 5 has a narrow transmission band since the upstream amplifier 11-2 having a small amplification factor and a small dynamic range is used, and furthermore, the upstream channel comes from the coaxial cable 12 of each branch line of the tree-shaped network. The CN (Carrier Noise) ratio indicating the performance of the transmission line fluctuates due to the influx noise in which electric noise is accumulated, the effect of the group delay characteristic in a high frequency band due to the cascade connection of the amplifier 11-2 for up, and the like. There is a problem that the reception level of the terminal 1 on the side does not fall within the specified range, and high-speed data transmission cannot be performed.

The present invention has been made to solve the above-described problem. Even when the ingress noise of the CATV network 5 fluctuates and the data transmission quality of the upstream channel fluctuates, the user transmits data upstream. It is an object of the present invention to obtain a data transmission system that enables high-speed data transmission in the upstream direction in the CATV network 5 by adjusting the level and improving the CN ratio.

[0012]

According to a data transmission method according to the present invention, data is transmitted by connecting a LAN connected to a first terminal to a CATV network connected to a second terminal. A first cable modem connected between the LAN and the CATV network and modulating and demodulating a signal to be transmitted, and a second cable modem connected between the CATV network and the second terminal and modulating and demodulating a signal to be transmitted. A cable modem connected to the first cable modem;
The second in the upstream channel with a narrow transmission band of the V network
And a cable modem management device for monitoring the transmission characteristics of the cable modem. The cable modem management device controls the transmission level of the second cable modem in the upstream channel based on the monitored transmission characteristics. .

[0013] In the data transmission method according to the present invention, the cable modem management device monitors the transmission speed as the transmission characteristic of the second cable modem and, based on a result of comparison with a predetermined value, determines whether the second cable modem has a transmission characteristic. It controls the transmission level in the uplink channel.

In the data transmission system according to the present invention, the cable modem management device monitors a bit error rate as a transmission characteristic of the second cable modem, and based on a comparison result with a predetermined value, the second cable modem. Is to control the transmission level in the upstream channel.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a diagram showing a configuration of a data transmission system according to the first embodiment. In the figure, reference numeral 8 denotes a cable modem management device connected to the cable modem 3 on the center side, which collectively manages the cable modems 6a and 6b on the user side connected to the CATV network 5. Other symbols are the same as those in FIG.

Next, the operation will be described. Figure 2 shows the CAT
5 is a flowchart illustrating an operation of level adjustment in an upstream channel of a V network 5. Here, the cable modem management device 8 monitors the transmission speed, which is the transmission characteristic of the cable modem 6a on the user side, and thereby monitors the cable modem 6a.
Is adjusted to adjust the level in the uplink channel. Generally, the transmission speed and the transmission band are in a proportional relationship, and the transmission band is the amplification factor of the amplifier 11-2 in the upstream direction, that is, the Carrier that transmits the upstream channel.
Proportional to the value. Therefore, the cable modem management device 8 performs control using the fact that the transmission speed and the Carrier value are in a proportional relationship.

In step ST11 of FIG. 2, the cable modem management device 8 monitors the transmission speed of the cable modem 6a in the upstream channel and checks whether the transmission speed is higher than a predetermined lower limit transmission speed. . If the transmission speed is lower than the predetermined lower limit transmission speed, step S
At T12, the cable modem management device 8 sends test data to the cable modem 6a, returns the test data from the cable modem 6a, and receives it.

In step ST13, the cable modem management device 8 monitors the transmission speed of the cable modem 6a in the upstream channel and checks whether the transmission speed is higher than a predetermined lower limit transmission speed. Step ST12 above
The reason for transmitting and receiving test data and checking the transmission speed of the test data in step ST13 is to determine the true transmission capability of the transmission path. That is, because the terminal 7a connected to the cable modem 6a is intentionally performing low-speed communication, it may be determined in step ST11 that the transmission speed is lower than the predetermined lower limit transmission speed.

In step ST13, if the transmission speed of the cable modem 6a is lower than the lower limit transmission speed, in step ST14, the cable modem management device 8 transmits the Carrier transmitted by the cable modem 6a to the cable modem 6a. An instruction to increase the value is issued, and the cable modem 6a increases the Carrier value to be transmitted based on the instruction.

In step ST13, if the transmission speed of the cable modem 6a is higher than the lower limit transmission speed, in step ST15, the cable modem management device 8 monitors the transmission speed of the cable modem 6a and sets a predetermined upper limit. The transmission speed of the cable modem 6a is determined to be appropriate if the transmission speed is lower than the transmission speed of the cable modem 6a.

In step ST15, if the transmission speed of the cable modem 6a is higher than a predetermined upper limit transmission speed, in step ST16, the cable modem management device 8 sends the cable modem 6a to the cable modem 6a. Command to lower the Carrier value to be performed, and the cable modem 6a, based on the command,
Decrease the Carrier value to be sent.

The processing of steps ST11 to ST16 is repeated at predetermined time intervals. In step ST15, the transmission speed of the cable modem 6a is
It is checked whether the transmission speed is lower than the predetermined upper limit. If the transmission speed is high, the Carrier value is lowered in step ST16. If the Carrier value is too high and the transmission speed is too high, it is assigned to another cable modem 6b. This is to prevent the required transmission speed from decreasing.

In the above process, the transmission speed of the cable modem 6a is monitored and the Carrier value is adjusted. However, the BER (bit error rate during data transmission) which is inversely proportional to the transmission speed is monitored. The Carrier value may be adjusted. That is, in step ST13, the BER of the cable modem 6a is monitored to check whether it is smaller than a predetermined upper limit BER.
At T15, the BER of the cable modem 6a may be monitored to check whether it is larger than a predetermined lower limit BER.

In the above process, the cable modem management device 8 monitors the transmission speed or BER of the cable modem 6a on the user side. This is because the influence of the ingress noise and the disturbance signal is smaller than that of the monitoring, and more effective monitoring can be performed.

Furthermore, this embodiment can be applied not only to data transmission between the terminal 1 on the center side and the terminal 7a on the user side, but also to data transmission between the terminal 7a on the user side and the terminal 7b on the user side. In that case, the transmission speed or BER of the cable modem 6a or 6b on the data transmitting side may be monitored and the Carrier value may be adjusted.

As described above, according to the first embodiment, the cable modem management device 8 monitors the transmission rate or BER of the uplink channel of the cable modem 6a on the user side, and thereby the Carrier of the cable modem 6a is monitored.
Since the r value is adjusted and the level in the upstream channel is adjusted to an appropriate value, even when the ingress noise of the CATV network 5 fluctuates and the data transmission quality of the upstream channel fluctuates, the upstream channel of the CATV network 5 fluctuates. The effect that high-speed data transmission can be performed is obtained.

[0027]

As described above, according to the present invention, the cable modem management device can control the CAT of the second cable modem.
The transmission characteristics of the second cable modem in the upstream channel are controlled based on the monitored transmission characteristics in the upstream channel having a narrow transmission band in the V network, so that the ingress noise of the CATV network fluctuates, Even if the data transmission quality of the uplink channel fluctuates, CAT
There is an effect that high-speed data transmission of the up channel in the V network can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a data transmission system according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of level adjustment in an upstream channel of the CATV network according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional data transmission system using a CATV network and a LAN network.

[Explanation of symbols]

1 terminal (first terminal), 2 LAN, 3 cable modem (first cable modem), 5 CATV network, 6
a, 6b cable modem (second cable modem),
7 (7a, 7b) Terminal (second terminal), 8 Cable modem management device.

Claims (3)

[Claims] 1. A LAN connected to a first terminal, and a LAN connected to a second terminal.
In a data transmission system for transmitting data by connecting a CATV network connected to a terminal of the first type, a first cable modem connected between the LAN and the CATV network and modulating and demodulating a signal to be transmitted; A second cable modem connected between a network and the second terminal for modulating and demodulating a signal to be transmitted; and a second cable modem connected to the first cable modem and connected to the upstream channel having a narrow transmission band of the CATV network. A cable modem management device for monitoring transmission characteristics of the cable modem, wherein the cable modem management device controls a transmission level in an uplink channel of the second cable modem based on the monitored transmission characteristics. Data transmission method. 2. A cable modem management device monitors a transmission speed as a transmission characteristic of a second cable modem, and controls a transmission level of the second cable modem in an upstream channel based on a comparison result with a predetermined value. The data transmission method according to claim 1, wherein 3. The cable modem management device monitors a bit error rate as a transmission characteristic of the second cable modem, and based on a result of comparison with a predetermined value, determines a transmission level of the second cable modem in an upstream channel. The data transmission method according to claim 1, wherein the data transmission is controlled.