JPH04252664A - Data transmission equipment provided with ecm function - Google Patents

Abstract

PURPOSE:To cause the MODEM speed to fall back at the time when the number of error frames of a block of transmitted data is larger than an allowable number of frames or the number of error frames of a retransmission request reaches a set value C. CONSTITUTION:R>P information is outputted from an R>P state detecting means 5 when a number R of frames of the retransmission request is larger than an allowable number P of frames, and C information is outputted from a counting means 6 when the frequency in retransmission request of the same block reaches a value C. Consequently, a data transmission speed control means 7 is controlled by R>P information or C information to cause the MODEM speed to fall back in both cases. Thus, the retransmission time is economized to reduce the communication cost because the frequency in retransmission request is reduced in comparison with a conventional data transmission equipment provided with the ECM function.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission device suitable for use in a facsimile machine capable of ECM (Error Correction Mode) communication.

0002

2. Description of the Related Art When transmitting data such as character information, for example, 256 bytes are used as one frame, and for example, 256 frames are used as one block, and each block is sequentially transmitted to the other party's receiving terminal. At the end of transmission, when an error is confirmed in the received data, the receiving terminal requests the transmitting terminal to retransmit the error frame, and the transmitting terminal responds by requesting the transmitting terminal to retransmit the error frame data. The so-called E
There is a data transmission device capable of CM communication.

According to the CCITT recommendation (T30), conventionally when there are four retransmission requests for the same block,
The data transmission speed is set to one level and a so-called fallback is performed to continue data transmission.

0004

[Problem to be Solved by the Invention] However, when the line condition of the communication line is poor, when a retransmission request is made following the completion of data transmission of one block or the completion of data retransmission of the same block, the data transmission cannot be performed as is. Even if data transmission continues at the same speed, retransmission requests are often received again. Under such communication line conditions, it is better to fall back as quickly as possible and continue data transmission to reduce the number of data retransmissions. Therefore, the data transmission time is eventually shortened.

The present invention takes the above-mentioned points into consideration and proposes a data transmission device equipped with an ECM function that can perform data transmission at an appropriate transmission speed.

[0006]

[Means for Solving the Problems] In order to solve the above problems, in the present invention, multiple bytes of transmission data are
frame, and these multiple frames as one block are sequentially transmitted to the other party's terminal at a preset data transmission rate for each block, and from the other party's terminal at the end of data transmission for each block based on data transmission errors. In a data transmission device equipped with an ECM function that retransmits error frame data in a block in response to a retransmission request, the number of frames of the retransmission request signal in one block is R, and the allowable error frame R>P state detection means outputs R>P information when detecting a state R>P (R, P is an integer) from a retransmission request signal from the other terminal, where the number is P, and a retransmission request from the other terminal. a counting means that counts the number of retransmission requests for the same block when a request is made and outputs C information when the counted value reaches a set value C (C is an integer); and a data transmission rate control means for falling back the data transmission rate when the above R>P.
The state detection means detects R> due to the concentrated occurrence of error frames.
In the state of P, the output is prohibited and the data transmission rate does not fall back.

[0007]

[Operation] In this invention, the R>P state detection means 5
The state of R>P (number of retransmission requested frames>number of allowed frames) in the block is detected, and when the state is R>P, R>P information is output to the data transmission speed control means 7, and the data transmission speed control means 7 The data transmission speed (hereinafter referred to as modem speed) of the modem and NCU 4 is controlled (fallback) by the control signal. Therefore, in the R>P state, the modem speed immediately falls back.

[0008] Furthermore, when the counting means 6 counts the number of retransmission requests for the same block by a set value C, C information is outputted from this, and a fallback is performed in the same manner as described above via the data transmission rate control means 7. There is. Therefore, even if each block is in the R<P state and fallback control is not performed by the R>P state detection means 5, the number of retransmission requests for the same block is the set value C.
When this happens, the counting means 6 automatically falls back and transmits the data.

Furthermore, the above-mentioned R>P state detection means 5 does not output R>P information in a state where error frames are concentrated even if the R>P state is present. Therefore, in this case, there is no fallback to the data transmission rate. This is because such a situation is considered to be a temporary trouble in the communication line, and the error frame is retransmitted at the same modem speed to avoid unnecessary extension of subsequent communication time.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an example in which the data transmission apparatus according to the present invention is applied to a facsimile machine will be described with reference to the drawings.

In FIG. 1, data such as image information read by an image reading means 1 is written to a file memory 2 and stored therein. After being temporarily stored in the communication buffer 3 at the time, it is sent out to the communication line via the modem and NCU 4, and is input to the other party's terminal (hereinafter referred to as the receiving terminal), although not shown.

[0012] Information from the receiving terminal is sent to the modem and NC.
The signal is input to the R>P state detection means 5 and the number of retransmission request counting means 6 via U4.

[0013] In the R>P state detection means 5, it is determined whether the number R of retransmission requested frames is greater than or equal to the allowable frame number P (R>P), and when R>P, R>P information is output. be done. However, if the R>P state detection means 5 determines that error frames are concentrated, no R>P information is output. In this case, the allowable number of frames P may be, for example, P=N/2, where N is the total number of frames in the block. Also,
The counting means 6 counts the number of retransmission requests, and when the counted value reaches a set value C (for example, 4), the counting means 6 outputs C information. Detection of error blocks for requesting retransmission is the same as the conventional method.

The above-mentioned R>R from the P state detection means 5>
When the P information and the C information from the counting means 6 are input to the data transmission rate control means 7, a control signal is outputted from this and inputted to the modem and NCU 4, thereby controlling the modem and NCU 4 and performing fallback. be done. Note that the initial modem speed is set by the user in the modem and NCU 4 in advance.

The image reading means 1, modem, and other means other than the NCU 4 described above are all processed by software, and are part of the data transmission rate control means 10 shown in FIG. It consists of

In FIG. 2, 11 is a CPU that manages modem speed control, 12 is a ROM in which modem speed control and other control programs are stored, and 13 is a memory that stores read data. RAM memory is used. This RAM 13 also stores received data and the like. 14 is an image reading unit, and the data read by this unit is stored in the RAM 13 or directly sent to the modem and NC via the interface 15.
Supplied to U16. This modem and NCU16 are
This corresponds to 4 shown in FIG.

[0017] At the time of reception, data (information) input from the transmitting terminal via the communication line is temporarily stored in the RAM 13 via the modem and NCU 16, and the data read from this is input to the recording unit 18 via the interface 17. recorded. During transmission and reception, the telephone number and the like of the other party's terminal is supplied to the display unit 20 via the interface 19 and displayed thereon. 21 is an operation unit for inputting a telephone number, etc., and 22 is an interface thereof.

FIG. 3 shows a fallback sequence when the R>P state is detected in one block (when a retransmission request occurs after transmission). In other words, when the transmitting terminal makes a call, the receiving terminal sends NSF (non-standard function identification signal), CS
I (called terminal identification signal) and DIS (digital identification signal) are sent, and in response, the transmitting terminal transmits TSI (transmitting terminal identification signal), NSS (non-standard function identification signal), and T
A CF (training check signal) is sent out, and a CFR (reception readiness confirmation signal) is sent out from the receiving terminal.
As a result, the intended original image information is transmitted from the transmitting terminal.

[0019] Following the end of the transmission of this first image information block, a PPS-EOP (partial page procedure end signal) is sent, and if an error is confirmed at the receiving terminal, a PPR (retransmission) is sent from the receiving terminal. request signal) is sent. This PPR contains the position of the frame where the error occurs (
frame number, etc.).

[0020] From the number of retransmission requested frames at the transmitting terminal, R>P
When the status is confirmed, this transmitting terminal sends a CTC (correction continuation signal: this also includes the modem speed instruction signal)
is transmitted, and in response to a CTR (correction continuation response signal) from the receiving terminal, the image information of the error portion is transmitted from the transmitting terminal at the fallback modem speed.

[0021] Following the transmission of this image information, PPS-E
OP is sent, and if there is no reception error, the receiving terminal sends an MCF (message confirmation signal), and based on this, the sending terminal sends a DCN (disconnection command signal), thereby disconnecting the communication line. Note that although the above example shows the case where only one block is transmitted, the second and subsequent blocks are transmitted following the MCF from the receiving terminal.

FIG. 4 shows a sequence when, in response to a retransmission request from a receiving terminal at the end of transmission of the first block, the frame requested for retransmission is transmitted again at the same transmission speed. . In this example, after the first PPR shown in FIG. A sequence in which PPR is sent has been added. Since the rest is the same as the case shown in FIG. 3, detailed explanation thereof will be omitted.

FIG. 5 shows an example of a processing flow for controlling the modem speed as described above. To explain this, the communication state reaches Phase D after the transmission of one block of image information is completed. PP from the sending terminal when
S-EOP, PPS-EOM, PPS-MPS, PPS
- A PPS-Q such as NULL is sent (step 31
), then it is determined whether there is a response from the receiving terminal (step 32), and if it is affirmative, that is, if there is a response, then the response information is transmitted as a retransmission request signal (PP
R) is determined (step 33). In addition, PP
S-EOM is the partial page message end signal, PPS-
MPS is a partial multipage signal, and PPS-NULL is a partial page block end signal.

[0024] If the above-mentioned step 33 is affirmative,
That is, in the case of a retransmission request signal, the counting means 6 shown in FIG. If the result is negative, that is, if the number of retransmission requests is less than C times, then the R>P state detection means 5 shown in FIG. 1 determines whether R>P (step 35). When affirmed, R>P information is output from the R>P state detection means 5, and a control signal is output from the data transmission rate control means 7, and the modem and NCU
4 is controlled so that the modem speed falls back to a lower transmission speed than the current one (step 36), then the image information of the error frame is retransmitted (step 37), and the process returns to step 31.

If the result in step 34 is affirmative, that is, if the C-th retransmission request is confirmed, the process proceeds to step 36, where C information is output from the counting means 6 shown in FIG. A control signal is sent from 7, and in this case as well, fallback is performed and the image information of the error frame is retransmitted. Note that if the result in step 35 is negative (if R<P state), the process directly proceeds to step 37.
The error frame is retransmitted at the original modem speed without fallback.

[0026] If the above-mentioned step 32 is negative,
That is, if there is no response from the receiving terminal, then PPS-Q
The number of transmissions is counted (step 38), and if the result is negative, the process returns to step 31. Therefore, in this example, three PPS-Qs are sent in total, and if there is no response even after the third PPS-Q is sent, the process proceeds to conversation reservation or abnormal processing.

[0027] If the above-mentioned step 33 is negative,
In other words, if the information from the receiving terminal is not a retransmission request signal,
Next, it is determined whether or not the information is a reception not available signal (RNR) (step 39), and if the answer is negative, that is, if the receiving terminal is in a receivable state, then it is determined that it is a message confirmation signal (MCF). It is determined whether or not there is one (step 40), and if the answer is affirmative, that is, in the case of MCF, the transition is made to the phase B or E state, and if the answer is negative, the transition is made to conversation reservation or abnormal processing.

If step 39 is affirmative, that is, if the reception not possible signal (RNR) is received, then the reception possible signal (RNR) is received.
RR) is sent and waits for an MCF response from the receiving terminal, but if there is no response from the receiving terminal within a certain period of time (for example, 3 seconds), the process moves to conversation reservation or abnormal processing (steps 41 and 42). ).

FIG. 6 shows a first modem speed (eg 960
0bps), 1 of the block
The figure shows the transmission time T for the number N of frames to be transmitted, assuming that there is a retransmission request for /2 frames. This will be explained below.

The first transmission of one block having N frames requires a transmission time a as shown by straight line A. Since an error occurs in N/2 frames, the retransmission of this portion (second transmission) requires a transmission time of b (time from the beginning) as shown by straight line B. Furthermore, since an error occurs in 1/2 frame (1/4 of the total number of frames N) in this second retransmission, this error frame portion is retransmitted. This is because data is transmitted at the same transmission speed.

[0031] The data is subsequently retransmitted in the same manner, and straight lines C and D show these states, and times c and d have elapsed, respectively. In other words, assuming that when transmitting at the first modem speed, an error will occur in 1/2 of the number of frames being transmitted, if N frames of data are transmitted, this block of data will almost certainly be transmitted until it is completed. This requires a transmission time d.

On the other hand, after the first transmission, the modem speed is set to a second modem speed (for example, 7200bps).
), and assuming that no error occurs, the result will be as shown by dotted line E, and the transmission time will be e. Therefore, the transmission time is reduced by the time d-e compared to the case where retransmission is repeated at the first modem speed described above.

The above-mentioned time d is d=(256×8/S1)×(15N/8), and on the other hand, it is the time when the modem speed is fallen back to 3/4 (for example, 9600 bps → 7200 bps) at time a. e is: e=256×8×N×{(1/S1)+(1/2×S2
)}, and d/e=3.75/(2+S1/S2). S1 and S2 are first and second modem speeds, respectively.

As can be seen from this, when S1 and S2 are 9600 bps and 7200 bps, respectively, d/e=1
．． 125, so the allowable number of frames P is P=N/2(N
can be chosen as the total number of frames in the block), and P
If P<N/2 is selected, there is a risk that subsequent communication time will be unnecessarily extended due to fallback.

According to this configuration, when the number of frames R of the retransmission request is R>P at the end of reception of one block, R
>P state detection means 5 outputs R>P information, and when the number of blocks requested for retransmission reaches C, counting means 6 outputs C information, and based on this information, data transmission rate control means 7 outputs a control signal. is output, modem and NC
U4 is controlled to fallback the modem speed.

Furthermore, in the R>P state detection means 5, R>P
If it is determined that error frames are occurring in a concentrated manner, R>P information will not be output. That is, in this case, retransmission is performed at the current modem speed without performing fallback due to a temporary trouble with the communication line, thereby avoiding unnecessary extension of subsequent communication time due to fallback.

[0037]

[Effects of the Invention] According to the data transmission device equipped with the ECM function according to the present invention, when transmitting data, if the error frame of the block is in the R>P state, even if it is the first retransmission request, the data transmission device immediately Since fallback is performed, retransmission requests can be significantly reduced in subsequent data transmissions, and retransmission time can be saved, resulting in a gradual reduction in communication costs.

Moreover, even if the error frame is in the R<P state, if C such frames are counted, that is, if the number of retransmission requests reaches C, fallback is automatically performed. Therefore, it is also possible to conform to the CCITT recommendations.

Furthermore, even in the R>P state, if error frames occur in a concentrated manner, there is no fallback, so the current status is not affected by temporary communication line troubles. This has the effect of allowing data transmission to continue at modem speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a data transmission device equipped with an ECM function according to the present invention.

FIG. 2 is a system diagram showing an example of data transmission rate control means of the present invention.

FIG. 3 is a sequence diagram in the case of fallback at the first retransmission request.

FIG. 4 is a sequence diagram when falling back with a second retransmission request.

FIG. 5 is a process diagram illustrating the operation of the present invention.

FIG. 6 is a diagram showing the transmission time T with respect to the number N of frames of data to be transmitted.

[Explanation of symbols]

1 Image reading means 2 File memory 3 Communication buffer 4 Modem and NCU 5 R>P state detection means 6 Counting means 7 Data transmission speed control means

Claims (2)

[Claims] Claim 1: A plurality of bytes of data to be transmitted are defined as one frame, and each block is sequentially transmitted to a destination terminal at a data transmission rate set in advance, with the plurality of frames as one block, and data transmission errors are eliminated. In a data transmission device equipped with an ECM function that retransmits error frame data in a block in response to a retransmission request from a partner terminal at the end of data transmission for each block based on When the number of retransmission request frames is R and the allowable number of error frames is P, R from the retransmission request signal from the other terminal
R>P state detection means that outputs R>P information when detecting a state of C when the value reaches the set value C (C is an integer)
a counting means for outputting information, and the above R>P information or C
1. A data transmission device with an ECM function, characterized in that it is equipped with a data transmission rate control means that falls back on the data transmission rate when information is obtained. 2. The R>P state detection means is characterized in that in a state where R>P due to the concentrated occurrence of error frames, the output is prohibited and the data transmission speed is not fallback. A data transmission device equipped with the ECM function described above.