JPS62269561A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To resend data to an error without decreasing a transmission efficiency by measuring the delaying time of a line beforehand and judging whether or not a confirming signal to a transmitted data block is detected in the measured delaying time. CONSTITUTION:Prior to the transmission of data, a control main body part 13 accumulates dummy data D(O)-D(N) to a buffer memory 12, and this is outputted to a line 18 and transmitted to a receiving side. Simultaneously with the output, a timer circuit 15 is operated and a time measurement is started. Thus, from the time of transmitting the data D(O) up to the time of receiving a confirming signal Al, a delaying time Td of the one-way line is counted. Thereafter, a transmitting side outputs actual data to the line 18. A confirming signal sending circuit 19 detects the arrival of the confirming signal to a block B(theta) after the delaying time Td counted earlier from the time of sending the block B(theta) passes. Thus, when the confirming signal is absent, it can be specified to which transmitting block the confirming signal is equivalent.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a data transmission device for retransmitting error data from a transmitting side.

BACKGROUND OF THE INVENTION FIG. 4 is a schematic block diagram showing an example of a conventional data transmission device.

This data transmission device includes a data generation unit 1 that generates data, a buffer memory 2 that stores takes sent from the data generation unit 1, a buffer memory 2 that is connected to the take generation unit 1 and the buffer memory 2, and The control section 3 divides the accumulated takes into predetermined fixed blocks, adds a predetermined error correction code to the blocks, and outputs the blocks to the modem 4. The takes input into the modem 4 and divided into blocks are sent to the line 6 via the high flit circuit 5.

On the receiving side connected to line 6, as shown in Fig. 5, if the receiver determines that the received block B(N) is correct, it sends a confirmation signal A(N) while receiving the next block B(N+1). Send out. This N confirmation signal A(N) is detected by a confirmation signal detection circuit 7 connected to the hybrid circuit 5. Then, it is determined that block B(N) has been correctly received, and once the sending of block B(N+1) is completed, the sending of the next block B(N+2) is started.

On the other hand, if the received block is incorrect, the receiving side does not output a confirmation signal to the data transmission device on the transmitting side.

For example, as shown in Figure 6, block B sent by the transmitter
(M) and determines that there is an error in it, the receiving side does not send out a confirmation signal while receiving the next block B (M+1). The transmitting side cannot receive the confirmation signal while sending block B (M-1).
-1) After sending, send block B (IV[) again.

Problems to be Solved by the Invention However, such a data transmission device may not be able to operate properly if there is a delay in the line. especially,
International lines using satellite communications always have delays, making them virtually impossible to use.

The above problem arises for the following reasons. In other words, the sending side waits for the confirmation signal sent from the receiving side at a fixed time period during which the next block is being sent, but if there is a delay in the line, the received confirmation signal will The above-mentioned problem occurs because it is not possible to determine whether the block corresponds to the block.

As a countermeasure to this problem, a method can be considered in which the size of the block to be sent is increased in advance to cover the line delay, so that the confirmation signal sufficiently reaches the sending side while the next block is being sent. However, this method has the disadvantage that when an error occurs, the amount of data that must be retransmitted increases, resulting in poor transmission efficiency.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a data transmission device that can retransmit data in response to an error without reducing transmission efficiency even when applied to a line with delays. With the goal.

Means for Solving the Problems In order to achieve the above object, the present invention includes a confirmation signal detection circuit that inputs and detects a confirmation signal that determines whether data is correct or incorrect for each block from the receiving side, and a confirmation signal detection circuit that detects the confirmation signal that determines whether data is correct or incorrect for each block. and a control unit that specifies the block corresponding to the confirmation signal according to the measured delay time.

While the delay time of the line is measured in advance by the action control section, it is determined whether or not the confirmation signal for the transmitted data block is detected by the confirmation signal detection circuit during the measured delay time. If a confirmation signal is not detected according to this delay time, the data block corresponding to the confirmation signal is sent out again.

Embodiment FIG. 1 is a schematic block diagram showing a data transmission apparatus according to an embodiment of the present invention.

This data transmission device includes a data generation section 11 for generating data, a buffer memory 12 for accumulating data sent from the data generation section 11, and a buffer memory 12 connected to the data generation section 11 and the buffer memory 12. The control main unit 13 divides the data stored in the data into predetermined fixed processors 7, adds a predetermined error correction code to the data, and outputs the divided data to the modem 14.

The data input into the modem 14 and divided into blocks is output to the line 18 via the hybrid circuit 17, and then transmitted to the receiving side.

On the receiving side, it is determined whether the sent block is an error or not, and if it is determined that there is no error, a confirmation signal is sent to the hybrid circuit 17 via the line 18. This confirmation signal is detected by a confirmation signal detection circuit 19 connected between the hybrid circuit 17 and the control main body section 13. Control body part i3
A timer circuit 15 is connected to the timer circuit 15, and this timer circuit 15 is designed to measure the block transmission time and the confirmation signal transmission time. In this embodiment, the control main body section 13 and the timer circuit 15 constitute a control section 16.

The data transmission device configured as described above operates as follows.

First, prior to data transmission, the control main unit 13 stores dummy data D in the buffer memory 12 as shown in FIG.
(0) to D(N) are accumulated and outputted to the line 18 via the modem 14 and the hybrid circuit 17 to be transmitted to the receiving side. Simultaneously with this output, the control main unit 13 activates the timer circuit 15 to start time measurement, and causes the confirmation signal detection circuit 19 to detect whether or not a confirmation signal has been transmitted from the receiving side. As soon as the receiving side receives the first block correctly, the confirmation signal Aψ is sent to the confirmation signal detection circuit 19.
The confirmation signal AI is received as the confirmation signal AI, and the timer circuit 15 measures this time. Then, the control main unit 13 controls the data D(
0) Calculate the one-way line delay time Td from the time from the time of transmission to the time of reception of the confirmation signal AI.

After calculating the line delay time Td in advance in this way, the transmitting side outputs the actual data to the line 18. When the receiving side determines that the received block is correct, confirmation signals are exchanged as shown in FIG.

That is, in the example shown in FIG. 3, on the transmitting side, block B(ψ)
~B(N) are sent out sequentially. If the receiving side determines that the received block B(ψ) is correct, a confirmation signal Aψ is immediately sent.

The confirmation signal sending circuit 19 starts detecting the arrival of the confirmation signal for the block B(ψ) after the previously calculated delay time Td has elapsed since the sending of the block B(ψ). Further, when the confirmation signal Aψ sent out on the receiving side arrives as the confirmation signal A'ψ after the elapse of time Td, it is determined that the block B(ψ) has been correctly received. Note that at this point, block B(2) has already been sent from the sending side, and block B(
3) is being sent, and block B (0
) is confirmed to be correct, the sending side will subsequently send B(4).

Note that if block B (ψ) is determined to be an error on the receiving side, the receiving side does not output a confirmation signal to the transmitting side (in this case, not outputting a confirmation signal indicates that the block is error; This is a confirmation signal in a broader sense).

As a result, the confirmation signal detection circuit 19 detects that the confirmation signal has not arrived when the delay time Td has elapsed from the start of detection of the confirmation signal arrival. Then, the block determined to be erroneous by this delay time Td is determined to be block B(ψ), and this block B(ψ) is retransmitted following the already transmitted block B(3). .

After this, do the same for block B(′) and below,
A determination is made as to whether the message is correct or not, and retransmission is performed as necessary.

Although not explained in this embodiment, the optimum window size can be selected by adjusting the window size (the number of frames that are successively transmitted after confirmation) in the HDLC procedure to the delay time of the line.

As described in detail, according to the present invention, the control unit includes a timer circuit, the timer circuit calculates the delay time of the line in advance, and the confirmation signal is sent to the confirmation signal detection circuit during data transmission. Whether or not the block has arrived is determined according to the time measured by the timer circuit, and if there is no confirmation signal, it is possible to identify which transmitting plotter the confirmation signal corresponds to, so there is no need to resend surplus blocks. Only the corresponding transmission block can be retransmitted immediately, and transmission efficiency during retransmission of error signals is not deteriorated.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing a data transmission device according to an embodiment of the present invention, FIG. 2 is a schematic signal waveform diagram showing a method for calculating line delay time in advance in the same data transmission device, and FIG. A schematic waveform diagram showing signal exchange of the data transmission device,
FIG. 4 is a schematic block diagram showing an example of a conventional data transmission device, and FIG. 5 is a schematic signal waveform diagram showing the operation of the same data transmission device when a block is determined to be correct on the receiving side.
FIG. 6 is a schematic signal waveform diagram showing an example of the operation of the data transmission apparatus when a block is determined to be erroneous on the receiving side.

Claims (1)

[Claims] A confirmation signal detection circuit that receives and detects a confirmation signal that determines whether data is correct or incorrect for each block is input from the receiving side, and a confirmation signal detection circuit that measures the delay time of the line in advance and responds to the confirmation signal according to the measured delay time. 1. A data transmission device, comprising: a control unit for specifying a block to be detected; and when receiving a confirmation signal indicating an erroneous signal, the data transmission device retransmits a block of data corresponding to the confirmation signal.