JPH01181251A - Data communication equipment - Google Patents

Abstract

PURPOSE:To minimize a data transfer time by commanding an optimum data transfer rate in response to error number of a data or a data length of transfer of an optimum data and retransmitting the data based on the condition. CONSTITUTION:When a data is received by a receiver 5, a data check code is checked to detect a block having an error and the error block number is measured and the transmission speed of data or data length of one block of data to be sent are decided in response to the number. Then an error block number and the transfer rate or data length are sent from the receiver 5 to the transmitter 1. The transmitter 1 retransmits the picture data of the error block in the transmission rate or data length decided by the receiver. The retransmission sequence is repeated till no error is detected by the receiver 5 and when no error exists, the data transmission is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field] The present invention relates to a data communication device that communicates data using a telephone line or the like.

[Prior Art] A data transmitter using a telephone line or the like is configured as shown in FIG.

On the transmitting side, the data from the transmitter 1 is modulated into a signal transmitted to the telephone line 3 by modem 2.Then, on the receiving side, the data from the transmitter 1 is modulated into a signal transmitted to the telephone line 3.
The original data is demodulated and transmitted to the receiver 5.

The procedure for transferring this data will be explained with reference to FIG. First, before data is transferred, there is a test sequence (■). This measures the line quality and determines the optimum data transmission rate or optimum data length. In reality, the transmitter l sends data in a fixed pattern to the receiver 5, and the data received back from the receiver 5 is sent to the transmitter l.
The error rate of one line is checked by comparing the data originally sent and the data received.

Next, the process moves to (2) image data transmission. This transfers the actual data from the transmitter l to the receiver 5. The actual data has the structure shown in FIG. It consists of N blocks, each block consisting of a block number, actual data, and a check code for the actual data.

When the receiver 5 receives the data, it checks the check code of the data and detects a block with an error.When all the data has been received, the receiver 5 transmits the error block number to the transmitter 1, and sends the block number to the transmitter 1 again. Only the data with errors are transferred from the receiver 5 to the receiver 5. Data is retransmitted repeatedly, and when there are no data errors, the data transfer ends. However, with this data transfer procedure, if the state of the line changes while the data is being transferred, the data transfer time will take longer.

For example, in the case of fallback, even if it is possible to transfer at 4800bps in the test sequence (■), the quality of the line deteriorates from the middle of data transfer, and as data errors increase, the number of retransmissions increases, resulting in data loss. The total transfer time will increase.

Also, even if it is decided to transfer at 2400bps in the test sequence (■), the quality of the line improves from the middle of the data transfer and even if data can normally be transferred at 4800bps, the data must be transferred at 2400bps. However, there was a drawback in that the total time for data transfer was longer than the time commensurate with the quality of the line.

[Objective] It is an object of the present invention to provide a data communication device that eliminates the above-mentioned drawbacks, selects a data transmission time that is optimal for the quality of one line, and can transfer data in a short time.

[Embodiment] FIG. 5 is a control circuit diagram of a facsimile machine of this embodiment. In the diagram corresponding to the receiving side device and the sending side device in FIG. is a printer that records copy images; 14 is a CPU that controls the entire facsimile machine; 16 is a ROM that stores a control program for the CPU 14; 1B is data necessary for controlling the CPU 14, such as counter count values and flag states. etc., and a RAM for storing image data; 20 is a kneader/decoder for encoding and decoding image signals; 22 is a modem for modulating and demodulating image signals and control signals; 24 is for connecting a communication line 28 to a telephone 26; This is an NCU that switches whether to connect to the modem 22 or not.

Next, FIG. 1 shows the data transfer procedure of this embodiment.

The test sequence (2) is the same as that shown in FIG.

Next, move on to sending the image data.

Image data is sent from the transmitter l to the receiver 5.

When the receiver 5 receives data, it checks the check code of the data, detects blocks with errors, measures the number of error blocks, and adjusts the data transmission speed or the data length of one block of data to be transmitted according to this number. Determine.

Next, the receiver 5 transmits the error block number and the transmission rate or data length to the transmitter l.

The transmitter l retransmits the image data of the error block at a transmission rate or data length determined by the receiver.

This retransmission sequence is repeated until no errors are detected by the receiver 5, and when no errors are detected, the data transfer ends.

In this embodiment, image data transfer using an electric wire line has been described, but it is obvious that such a procedure can be applied to a system that transfers data.

In this embodiment, a test sequence is provided at the beginning of transfer, but
Even without this test sequence, data can be transferred in a relatively short time.

Further, the transmission rate and block length may be determined from the number of error blocks on the transmitter side.

Furthermore, it goes without saying that the data is not limited to images, but may also be data such as characters and numerical values.

[Effect] As explained above, when instructing data retransmission, the optimum data transfer rate or
By specifying the optimal data length for data transfer and performing retransmission based on this condition, it is now possible to minimize the data transfer time.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the data transmission procedure of this embodiment, Fig. 2 is a block diagram of the communication system, Fig. 3 is a diagram showing the data structure, Fig. 4 is a diagram showing the conventional data transmission procedure, and Fig. 5 is a diagram showing the conventional data transmission procedure. The figure is a block diagram showing the configuration of the transmitting side and receiving side devices. Figure 1

Claims (1)

[Claims] In a data communication device that receives data and requests retransmission of data with errors, when requesting retransmission of data, the number of errors in the data is checked, and the optimum data transmission rate is determined according to the number of errors. Alternatively, a data communication device characterized by instructing an optimal data length.