JPH04335720A - Modem transmission level setting method - Google Patents

Abstract

PURPOSE:To reduce man-hour at the time of setting the transmission level of a MODEM. CONSTITUTION:A carrier is sent from a MODEM 12 to a MODEM 22 at a 1st transmission level. The reception level of a carrier received by the MODEM 22 is measured and a 2nd transmission level is set to a transmission level for the MODEM 12 so that the reception level of the MODEM 22 reaches a predetermined level. Then the carrier is sent at a 2nd transmission level from the MO DEM 22 to the MODEM 12, the reception level of the carrier received by the MODEM 12 is measured and a 3rd transmission level is set to a transmission level for the MODEM 22 so that reception level of the MODEM 12 reaches a predetermined level.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a modem (modulation/demodulation device)
The present invention relates to a modem transmission level setting method for setting the transmission level of a carrier wave transmitted from a modem to a predetermined level.

0002

[Prior Art] In data transmission between data processing devices installed at distant locations,
In order to transmit digital data via an analog transmission path, a modulated wave whose carrier wave is modulated with digital data is sent out, and the receiving side demodulates the received modulated wave to obtain digital data. Since data transmission is typically bidirectional, modulation and demodulation devices are required in both directions. The device for this purpose is a modem. The modem is
It has a modulation section that modulates a carrier wave with data to be transmitted, and a demodulation section that demodulates a received carrier wave.

[0003] When using such a modem, the level of the carrier wave in the modulation section must be set so that the received level of the modulated wave on the receiving side is a specified level (for example, -20 dB). It won't happen. Furthermore, the modem transmission level is normally set when a modem is newly installed.

A conventional modem transmission level setting method is as follows.

[0005] In one (transmission side) modem, the level of the carrier wave in the modulation section is set to a predetermined level, and the obtained carrier wave (unmodulated) is transmitted to the other modem via the transmission path. The other (receiving side) modem measures the reception level of the received carrier wave. Such measurements are performed by switching the level of the carrier wave in the modulation section on the transmitting side between a plurality of levels. Then, based on the plural sets of measurement data of the transmission level and reception level obtained in this way, a transmission level is calculated so that the level of the reception carrier wave becomes a specified level. The level obtained by this calculation is set as the carrier wave level of the modulation section on the transmitting side. In this way, the transmission level in one direction is set, and the transmission level in the opposite direction is also set in a similar manner. That is, since the characteristics of the transmission path are not the same in both directions, and the characteristics of the modulator and demodulator of the modems are also not the same between the two modems, the transmission level must be set in the same way in the opposite direction.

[0006]

[Problems to be Solved by the Invention] The above-mentioned conventional modem transmission level setting method requires switching the carrier wave level on the transmitting side, reading the reception level on the receiving side, communicating to synchronize transmission and reception, and changing the carrier wave level on the transmitting side. Calculations based on the calculated data and setting of the transmission level based on the calculation results are all done manually, so it takes a lot of time and effort to complete the settings. Furthermore, when a wireless transmission path is used as a transmission path, the characteristics of the transmission path are easily affected by weather, temperature, and the like. For this reason, the optimal transmission level also changes depending on the weather that day. Since the conventional method requires a long time to set, it is practically difficult to frequently reset the modem transmission level.

[0007]

[Means for Solving the Problems] The modem transmission level setting method of the present invention provides a method for setting a modem transmission level in a data transmission system in which data is transmitted via a transmission path between a first and a second modem installed at locations apart from each other. A carrier wave is transmitted from the first modem to the second modem at a first transmission level, a reception level of the carrier wave received by the second modem is measured, and the reception level of the second modem is determined in advance. A second transmission level is set as a transmission level for the first modem such that the second
transmitting a carrier wave to the modem at a second transmission level, measuring the reception level of the carrier wave received by the first modem, and transmitting a carrier wave to the third modem such that the reception level of the first modem becomes a predetermined level. It is characterized in that the transmission level is set as a transmission level for the second modem.

[0008] Furthermore, when transmitting a carrier wave from the first modem to the second modem, the carrier wave is transmitted in advance at the maximum level allowed by the first modem, and there is a response from the second modem. Furthermore, the transmission level may be set when the first and second modems are powered on.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained in detail with reference to the drawings.

Referring first to FIG. 2, an embodiment implementing the present invention includes a data processing device 11, a modem 12 connected thereto, and a processor 13 connected to the modem 12 at a first location. is set up. Further, a data processing device 21, a modem 22 connected thereto, and a processor 23 connected to the modem 22 are installed at a second location away from the first location. Furthermore, the data processing device 11 and the data processing device 21 include a modem 12,
They are connected via a transmission line 31 and a modem 22, respectively. Further, the processor 13 and the processor 23 are connected via a telephone line 32.

As shown in FIG.
．． 8kHz), and a level control unit 1 that controls the level of the carrier wave according to a level control signal.
5 and a modulated wave sent via the transmission line 31 (carrier wave whose amplitude is modulated with data from the data processing device 21)
It has a demodulator 16 that demodulates the modulated wave, and a carrier level detector 17 that detects the carrier level of the transmitted modulated wave. A level control signal for controlling the carrier wave level in the modulator 14 is supplied from the processor 13, and a level detection signal detected by the carrier wave level detector 17 is supplied to the processor 1.
3.

Furthermore, the modem 22 has the same configuration as the modem 12.

Next, a method for setting the carrier wave levels of modems 12 and 22 in this embodiment will be explained in detail with reference to FIG.

First, a predetermined level A (for example -
A level control signal that provides a carrier wave of 10 dB) is supplied from the processor 13 to the level control section 15, and an unmodulated carrier wave of a sending level A (-10 dB) is sent from the modulator 14 to the modem 22 via the transmission line 31. (step 41). Then, the level of the carrier wave received by the modem 22 is measured, and the difference B between the received level and a specified level (for example, -20 dB) is measured in the processor 23.
is calculated (step 42). Data on the level difference B is sent from the processor 23 to the processor 13 via the telephone line 32 (step 43). The processor 13 is
After receiving the sent level difference data, the level difference is 0d.
It is determined whether it is B (step 44). and,
If the level difference B is not 0 dB, control is performed so that the carrier wave is retransmitted at a transmission level (A-B) in which the transmission level is corrected by the level difference (step 45).

The operations in steps 42 to 45 are performed in step 4.
Step 4 is repeated until the level difference B is determined to be 0 dB. When the level difference is determined to be 0 dB in step 44, the transmission level C at that time is set as the transmission level of the modem 12 and is stored in the storage means (step 46).

Furthermore, the stored level C data is
It is sent to processor 23 via telephone line 32 (step 47). The processor 23 uses the level C data sent from the processor 13 to cause the modem 22 to transmit the level C unmodulated carrier wave to the modem 12 via the transmission line 31.
Control is performed so that the signal is transmitted toward (step 48). The level of the carrier wave received by the modem 12 is measured, and the processor 13 compares the received level and the specified level (-20d
The difference D from B) is calculated (step 49). Data on the level difference D is sent from the processor 13 to the processor 23 via the telephone line 32 (step 50). The processor 23 receives the sent level difference data and determines whether the level difference is 0 dB (step 51).
). If the level difference D is not 0 dB, the output level (C-D) is corrected by the amount of the level difference.
) so that the carrier wave is retransmitted (step 5
2).

The operations in steps 49 to 52 are performed in step 5.
1 and is repeated until the level difference D is determined to be 0 dB. When the level difference is determined to be 0 dB in step 45, the transmission level E at that time is set as the transmission level of the modem 22 and is stored in the storage means (step 53).

The above-described operation is based on the premise that the transmission line 31 connecting the two modems 12 and 22 is in a state where it can transmit a carrier wave at a transmission level of -10 dB. However, if there is a failure in the transmission line 31 and, for example, the line from the modem 12 to the modem 22 is disconnected, the first carrier wave will not be transmitted to the modem 22, and subsequent operations will not be possible.

Therefore, if such a failure is found before setting the transmission level, the transmission level can be set after the failure has been recovered. To this end, for example, the following operation may be performed before transmitting the carrier wave at -10 dB in step 41 and before transmitting the carrier wave at the modem 12 transmission level in step 48. That is, the carrier wave is sent out at the maximum level that can be transmitted, and it is detected whether there is a response from the other party's modem within a certain period of time. If there is no response within a certain period of time, the transmission path is checked as a line failure. Note that the maximum level is a level at which it is determined that the carrier wave can be reliably transmitted to the other party, taking into consideration transmission path loss and the like. For example, it may be set to 0 dB, which is defined as the maximum transmission level in the standard.

[0020] Furthermore, transmission level setting is normally performed when the modem is installed. The modem transmission level setting according to this embodiment can be performed in a shorter time than when using the conventional method, so it can be performed every time the data transmission system is powered on or at any time. This makes it possible to set the transmission level in accordance with the latest transmission path conditions.

[0021]

As described above, according to the present invention, the modem transmission level can be set in a short time and with less man-hours.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing operations for implementing an embodiment of the present invention.

FIG. 2 is a block diagram showing one embodiment of the present invention.

FIG. 3 is a block diagram showing details of the modem 12 of FIG. 2;

[Explanation of symbols]

11, 21 Data processing device 12, 22 Modem 13, 23 Processor 14 Modulation section 15 Level control section 16 Demodulation section 17 Carrier wave level detection section 31 Transmission line 32 Telephone line

Claims (3)

[Claims] 1. A data transmission system in which data is transmitted via a transmission path between first and second modems installed at locations apart from each other, wherein a carrier wave is transmitted from the first modem to the second modem. transmit at the first transmission level,
measuring a reception level of a carrier wave received by the second modem, and setting a second transmission level such that the reception level of the second modem becomes a predetermined level as a transmission level for the first modem; Next, transmitting a carrier wave from the second modem to the first modem at a second transmission level, and measuring the reception level of the carrier wave received by the first modem,
A method for setting a modem transmission level, comprising setting a third transmission level such that the reception level of the first modem becomes a predetermined level as a transmission level for the second modem. 2. When transmitting a carrier wave from the first modem to the second modem, the carrier wave is transmitted in advance at the maximum level allowed by the first modem, and there is a response from the second modem. 2. The modem transmission level setting method according to claim 1, further comprising detecting whether or not the modem transmission level is set. 3. The modem transmission level setting method according to claim 1, wherein the transmission level is set when the first and second modems are powered on.