JPS63174440A - Data communication system - Google Patents

Abstract

PURPOSE:To shorten a transmission time, by controlling the block length of a transmission data corresponding to the receiving state of a demodulator. CONSTITUTION:A transmitting station TX is connected to a receiving station RX with an analog transmission line AL. The transmitting station TX consists of a data processing part DPt which generates the transmission data, a modulation part MOD which modulates the transmission data, and a network control unit NUt. The receiving station RX consists of a network control unit NUr, a demodulation part DEM, and a data processing part DPr. And by controlling the block length of the transmission data corresponding to the receiving state of the demodulation part DEM, possibility to detect a data error at the receiving station RX can be minimized.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a data communication system using automatic retransmission request control.

[Prior Art] Generally, data communication devices use various error correction methods to transmit data without errors.
One of them is so-called automatic retransmission request control.

In this automatic retransmission request control, the transmitting device adds error detection information (for example, CRC (cyclic redundancy check) code, etc.) to the transmitted data.
is added to form a predetermined data frame or data block.

The receiving device side determines whether an error has occurred in the received data based on the error detection information included in the received data frame or data block, and if an error has occurred, sends negative response information and detects the error. If there is no response, it responds with acknowledgment information to the transmitting device.

Then, when the transmission device receives negative response information, it retransmits the data frame or data block in which the error occurred. This allows correct data to be transmitted.

However, conventionally, such automatic retransmission request control has had the disadvantage of lengthening the transmission time when the characteristics of the transmission path deteriorate and negative acknowledgment information is responded, increasing the frequency of retransmission of data frames or data blocks. Ta.

[Objective] The present invention has been made to solve the above-mentioned disadvantages of the conventional technology, and an object of the present invention is to provide a data communication method that can shorten transmission time.

[Configuration] In order to achieve this object, the present invention controls the block length of the transmitted data according to the reception condition of the demodulator.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1(a) shows an outline of a data communication system to which the present invention is applied.

In the figure, a transmitting station TX and a receiving station RX are connected by an analog transmission line AL. Here, as the analog transmission line AL, for example, a public telephone line network is used.

The transmitting station TX has a data processing unit DP that generates transmission data.
t, and a modulator M that modulates the transmission data using a predetermined modulation method.
It consists of an OD and a network control device Nut for controlling the analog transmission line AL.

The receiving station RX includes a network control device NUr for controlling the analog transmission line AL, a demodulating section DEM for demodulating the received signal into original data, and a data processing section DP for processing the received data.
Consists of r.

Further, the data transmitted from the transmitting station TX to the receiving station RX is subjected to frame processing in the HDLC (high level data link control) procedure, as shown in FIG. 1(b).

That is, one data frame consists of a hail flag F at the beginning of the frame, an address field A that indicates the destination of the frame, etc., a control field C1 that indicates the contents of a command or response in the HDLC procedure, and an information field consisting of data for transmitting. , a cyclic redundancy check code CRC for detecting transmission errors, and a flag F for detecting the trailing end of the frame. However, the cyclic redundancy check code CRC is formed by applying data from the address field A to the information field (2) to a predetermined generating polynomial.

Furthermore, the data modulation/demodulation method of the modulator MOD and the demodulator DEH includes, for example, the 16-level quadrature amplitude modulation method (modulation rate 2400 baud, transmission rate 9600 b
ps) or an 8-phase differential phase modulation method (modulation rate 1600 baud, transmission rate 4800 bps), as in the V and 27ter modem of the same recommendation.

FIG. 2 shows a specific example of the demodulator DEH in the receiving station RX. In this case, the demodulator DEN includes a mechanism for automatic retransmission request control.

In the figure, a 2-wire/4-wire converter 11 is for separating signals so that signals can be exchanged in both directions via an analog transmission line AL, and is used to separate signals input via a network control device NUr. The received signal FR is applied to the demodulator 12.

The demodulator 12 removes the carrier component of the received signal FR, extracts the baseband signal SB, and extracts the baseband signal S.
B is added to an equalizer (automatic adaptive equalizer) 13. The equalizer 13 converts the baseband signal SB into a state in which distortions such as amplitude and phase in the transmission path are corrected, and its output is applied to the decoder 14 and the error calculator 15.

The decoder 14 determines the signal point closest to the input baseband signal SB, and outputs the received data DR corresponding to the determination result to the error calculator 15 and the frame decomposition unit 16. For example, in the modulation/demodulation system of a 29 modem, consecutive 4-bit (quadbit) data is converted to take the signal points shown in the signal configuration diagram in Figure 3. For example, the contents of the baseband signal SB are In the case of the position indicated by RP, it is determined that the data of the signal point closest to the position with a phase of 0 degrees and an amplitude of 5 has been received, and quadbit data corresponding thereto is output as received data OR.

The error calculator 15 calculates the error between the reception point RP taken by the baseband signal SB and the signal point corresponding to the reception data DR (that is, the position error in the signal configuration diagram), and uses the calculation result as an error. Comparator 17 as signal ER
Output to.

The comparator 17 detects that the error signal ER exceeds the error reference value RE added from the reference value setter 18, and the detection signal ED is sent to the tone signal generator 19.
added to.

When the detection signal ED is applied, the tone signal generator 19 generates a tone signal TNI of frequency f1, and outputs the tone signal TN1 to the transmission signal input terminal of the 2-wire/4-wire converter 11. The frequency f1 of the tone signal TN1 is set to a frequency that is outside the frequency band of the carrier wave of the modulation/demodulation system being used and is sufficiently distinguishable from the transmission signal. For example, ■, 2
400Hz when using 9 modem modulation/demodulation method
The frequency is set to approximately

The frame decomposition unit 16 identifies the address field A, control field C, and information field E of the data frame while taking in the received data OR, and also performs error detection using a cyclic redundancy check code CRC to detect data errors. Only when not, the information of each field is output to the data processing unit DPr.

Further, when detecting a data error, the frame decomposition unit 16 raises a retransmission request signal RQ and sets the flip-flop 21. Note that the frame disassembly unit 16
The flip-flop 21 is reset by a reset signal R3 outputted at the start of reception of one data frame.

When the flip-flop 21 is set, a tone signal TN2 having a frequency f2 is output from the tone signal generator 22 and applied to the transmission signal input terminal of the 2-wire/4-wire converter 11. The frequency f2 of the tone signal TNz is in the same frequency band as the frequency f1 of the tone signal TNI, and
It is set to a value that can be clearly identified as the tone signal TNI.

Therefore, when receiving data, if the condition of the analog transmission line AL is poor and the distortion in the amplitude and phase of the signal increases, and the error in the received data FR increases, the tone signal TN1 is responded to the transmitting station TX. Furthermore, if a data error has occurred in the received data frame, a tone signal TN2 is responded to the transmitting station TX.

FIG. 4 shows an example of the modulation section MOD of the transmitting station TX.

In the figure, transmission data output from a data processing unit DPt is formed into a predetermined data frame by a frame processing unit 31, then modulated by a modulator 32, and transmitted through a 2-line and 74-line converter 33 to a network. It is output to the control device Nut.

Further, the response signal RP from the receiving station RX inputted from the 2-wire/4-wire converter 33 is passed through the bandpass filter 34 for detecting the tone signal TN1 having the frequency f1.
The bandpass filter 35 is added to the bandpass filter 35 for detecting the tone signal TN2 of No. 2.

Bandpass filter 34 and bandpass filter 35
The output signal of the waveform shaping circuit 36 and the waveform shaping circuit 3
After the waveforms are shaped by 7, the data processing unit DPt outputs a poor reception signal SE to indicate that the reception condition at the receiving station RX is poor and a retransmission request signal SQ to indicate that a retransmission request has been made from the receiving station RX. are added to each.

During the period when the data processing unit DPt is transmitting data,
As shown in FIG. 5, a reception state monitoring process 500 in which the value of a counter C is incremented when a poor reception signal SE is detected is repeatedly executed at predetermined short intervals. Then, according to the value of this counter C, the length of data (hereinafter referred to as data block) constituting one data frame is controlled.

That is, as shown in FIG. 6, first, to start data transmission, initialization processing 601 is performed, such as initializing the length of a data block (hereinafter referred to as block size) to a predetermined maximum value.

Then, the frame processing unit 31 sets a part corresponding to the block size set at that time from the beginning of the transmission data indicated by the data pointer as a data block.
and transmits one frame of data to the receiving station RX (processing 602). Here, the data pointer is internally formed by the data processing unit DPt in order to identify the beginning of the transmitted portion of the transmission data.

Next, check whether there is any data left to transmit (
Judgment 603) When the result of judgment 603 is No, the data transmission ends. Also, the result of judgment 603 is Y.
When it becomes ES, it is checked whether the value of counter C is larger than a predetermined value Ec (determination 604).

When the result of the judgment 604 is YES, the condition of the analog transmission line AL is poor, so the block size set at that time is reduced by one step (process 605).

Also, when the result of judgment 604 is NO, it is checked whether the block size set at that time is equal to the maximum value (judgment 606), and when the result of judgment 606 is NO, the block size is increased by one step. (process 607)
.

When the block size is updated in this way, since processing for one frame has been completed at that time, the counter C is cleared (process 608).

Then, it is checked whether the retransmission request signal SQ is output (judgment 609), and if the result of determination 609 is No, the data pointer is updated in order to transmit the next data (process 610), and the process returns to process 602. If the result of judgment 609 is YES, the process returns to process 602 without updating the data pointer in order to retransmit the data transmitted immediately before. Note that when data is retransmitted, if the block size setting has been changed from the previous one, the block size at the time of retransmission is different from the previous one.

In this way, when the state of the transmission path is poor, the block size is reduced to reduce the degree of influence from the transmission path, thereby reducing the possibility of detecting a data error at the receiving station RX. . As a result, the occurrence of retransmission requests can be suppressed to some extent, thereby reducing the time required for data transmission.

Note that in the embodiments described above, the block size is increased when the state of the transmission path is good.

There is no need to change the block size.

[Effects] As explained above, according to the present invention, the block length of the transmitted data is controlled according to the receiving state of the demodulator, so that it is possible to minimize the influence of the state of the transmission path. As a result, there is an advantage that the transmission time can be shortened.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic diagram illustrating a communication system to which the present invention is applied, FIG. 1(b) is a schematic diagram illustrating an example of a data frame, FIG. 2 is a block diagram illustrating a demodulator, and FIG. 4 is a block diagram illustrating a modulation section, FIG. 5 is a flowchart illustrating reception status monitoring processing, and FIG. 6 is a flowchart illustrating data transmission processing. 11.33... 2-wire 74-line converter, 12... demodulator, 13... equalizer, 14... decoder, 15...
Error calculator, 16... Frame decomposition unit, 17... Comparator, 18... Reference value setter, 19.22... Tone signal generator, 21... Flip-flop, 34, 3
5... Bandpass filter, 36.37... Waveform shaping circuit, DPt... Data processing section. Figure 4 Figure 5 Figure 6 Start initialization process 601 1st frame 602 Data & basic data 9 NO 604 end 606 NO(C)>Ec YES
"" 706t '7 "j
4 X l 605＼ 720 /7廿17'6

Claims (1)

[Claims] A data communication system that uses a modulator and demodulator to transmit data in a predetermined frame format between transmitting and receiving stations via an analog transmission path, and is characterized in that the block length of transmitted data is controlled according to the receiving state of the demodulator. method.