JP2004023514A - Facsimile relay transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a facsimile relay transmitter capable of preventing a delay in response to a facsimile terminal and having high transmission efficiency, and capable of preventing an abnormality of communication and having high reliability. <P>SOLUTION: The transmitter is provided with a control means for interpolating jitter in flag data when receiving an image signal which is formed into an ECM-HDLC data format stipulated in ITU-T recommendations T.30. The control means may determine an interpolation time on the basis of a data amount stored in a facsimile signal storing buffer 25, or may insert the flag data at the header or a connection portion of an ECM-HDLC frame. The interpolation time may be fixed or may be changed one by one. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a facsimile relay transmission apparatus (or a facsimile relay transmission apparatus), and more particularly, to a facsimile relay transmission apparatus including a unit for controlling jitter of an ECM-HDLC packet due to insertion of a processing delay when relaying transmission via an Internet line or the like. About.
[0002]
[Prior art]
A facsimile relay transmission device is a device that encodes and outputs a signal output from a facsimile terminal, decodes the signal with a destination facsimile relay transmission device, and then transfers the data to the facsimile terminal. The transmitting-side facsimile terminal transmits a modulated signal as described in ITU-T (International Telecommunication Union Telecommunication Standardization Sector) or the like, and demodulates it and replaces it with binary data.
[0003]
This data is transmitted to a communication destination (a destination of binary data) via an arbitrary line, and a facsimile relay transmission device that receives the data performs modulation processing by a facsimile modem. Then, the facsimile signal is relayed by handing over to the facsimile terminal.
[0004]
Conventionally, a facsimile relay transmission device as shown in FIG. 5 has been used to transfer facsimile data via an Internet line or the like. When transmitting facsimile data, the facsimile relay transmission device demodulates the signal subjected to A / D conversion by the A / D conversion circuit 5 by the facsimile modem 4 and stores the demodulated signal in the facsimile data storage buffer 3. Then, the stored data is packetized by the facsimile packet generation circuit 2 and transmitted to the IP line 1.
[0005]
On the other hand, when facsimile data is received, the facsimile packet transmitted from the IP line 1 is extracted by the packet data separation circuit 8 to extract only data necessary for the facsimile modem processing on the modulation side. Further, the packet data separation circuit 8 adjusts the packet reception order and controls data fluctuation on the IP line 1.
[0006]
Next, the extracted facsimile data is temporarily stored in the data storage buffer 9. In accordance with an instruction from the facsimile modem control circuit 7, the stored data is read from the data storage buffer 9, modulated by the facsimile modem 4, and output by the facsimile terminal 6 via the D / A conversion circuit 10.
[0007]
Here, as shown in FIG. 6, when jitter (jt) occurs between the packet 1 and the packet 2 input to the facsimile relay transmission apparatus on the packet receiving side, the ITU-TT. A delay is provided at the head of the ECM-HDLC packet specified in Recommendation 30, and the occurrence of jitter (jt) is absorbed by utilizing the processing delay. Thereby, even if the arrival of the packet 2 is delayed, if the packet 2 can be received while the processing of the packet 1 is being performed, the packet 2 can be processed continuously. However, the output of the facsimile relay apparatus on the data receiving side is delayed from the packet arrival by the amount of jitter (jt) absorption.
[0008]
In the above-described example, for the sake of simplicity, the input of the facsimile relay transmission device on the packet transmission side is shown as a signal delay until the ECM-HDLC1 frame is converted into one packet and output from the facsimile relay transmission device on the packet reception side. It is a thing. By the way, it is assumed that the delay for packetizing the ECM-HDLC frame in each facsimile relay apparatus and for separating the ECM-HDLC signal from the packet is not considered.
[0009]
In the above description, the training signal transmitted / transmitted immediately before the ECM-HDLC is omitted. ITU-TT. According to Recommendation 38, the training signal is transmitted to the IP line in one packet in total. Therefore, even if the jitter of the training packet exists, it arrives at the receiving side of the packet with some delay, and is ignored for the sake of explanation of the present invention. The description of the synchronization flag sequence is also omitted.
[0010]
In a facsimile relay transmission apparatus for transferring facsimile data via an Internet line or the like, for example, when an ECM-HDLC formatted facsimile image signal as shown in FIG. There is no problem if the jitter control between the network transmission device terminals, that is, the data fluctuation absorption control functions sufficiently. However, when data loss occurs, the modulated data of the facsimile modem is delayed, causing a data error. In particular, ITU-TT. In the case of Recommendation 38, it is necessary to transfer data to and from a facsimile terminal in real time (real time).
[0011]
Here, during facsimile signal transmission, since data cannot be arbitrarily interpolated, the easiest method is to increase the amount of buffer for jitter control and increase the delay, but in jitter control, If the buffer size is easily increased too much, the delay increases and the response to the facsimile terminal becomes slow. For this reason, the facsimile terminal may transmit an unnecessary retransmission request command.
[0012]
The transmission of the retransmission request command is a procedure specified in the facsimile communication, and is not a problem of the facsimile terminal itself, but is actually a delay for absorbing a delay of the facsimile data generated in the facsimile relay transmission device. As a result, the delay of the facsimile signal data occurs, and the receiving facsimile terminal sends out the retransmission request command to the transmitting facsimile terminal even though the transmitting facsimile terminal has already transmitted data. .
[0013]
Normally, facsimile communication is performed by half-duplex communication. Therefore, transmission of this extra retransmission request command may lead to a full-duplex communication state. Then, the two signals collide with each other and the communication destination facsimile terminal cannot receive the communication data, so that there is a possibility that a failure in the transfer of the facsimile signal data between the facsimile terminals may occur.
[0014]
[Problems to be solved by the invention]
As described above, the conventional facsimile relay transmission apparatus has a problem that the response to the facsimile terminal becomes slow because the transmission delay increases when the buffer size is too large in the jitter control.
[0015]
Also, as a second problem, facsimile transmission is normally half-duplex communication, but due to the effect of transmission delay, an extra retransmission request command may be transmitted and a full-duplex communication state may be reached. As a result, signals collide with each other, and the other communication data cannot be received by the other facsimile terminal.
[0016]
Therefore, the present invention has been made in view of the above-mentioned problems in the conventional facsimile relay transmission apparatus, and can prevent a delay in response to a facsimile terminal, thereby increasing transmission efficiency and preventing communication abnormalities. It is an object of the present invention to provide a facsimile relay transmission device which can be performed and has high reliability.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a facsimile repeater transmission apparatus, which comprises: When receiving an image signal in the ECM-HDLC data format defined in Recommendation 30, the control unit interpolates a jitter component with flag data.
[0018]
According to the present invention, the continuity of the facsimile demodulated signal can be maintained by interpolating the amount of jitter with the flag data, and a delay in response to the facsimile terminal can be prevented. Also, due to the influence of the transmission delay, an unnecessary retransmission request command is transmitted, the signal does not collide with each other in the full-duplex communication state, and communication abnormalities can be prevented.
[0019]
In the facsimile relay transmission device, the control unit may determine the interpolation time based on an amount of data stored in a facsimile signal storage buffer. Further, the control means may insert the flag data at the head of the ECM-HDLC frame or at the connection. Further, the interpolation time may be fixed or may be changed sequentially.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a facsimile relay transmission apparatus according to the present invention. The facsimile relay transmission apparatus includes a packet data separation circuit 21, an ECM-HDLC data amount detection circuit 22, a facsimile modem 24, and a facsimile modem control circuit 23. , A data storage buffer 25, and a D / A conversion circuit 26. These can be realized by a digital signal processor or a multiprocessor (MPC) or the like.
[0021]
The portion corresponding to the IP network transmission device that transfers packets on the IP line 20 is included in the facsimile packet separation circuit 21 and the facsimile packet generation circuit 2 (see FIG. 5). The IP network transmission device referred to here is a device that performs packetization, separates a facsimile signal from a packet, and rearranges the arrival order of packets using a sequence number (= a number indicating the order of packets).
[0022]
Also, FIG. 1 shows only the facsimile packet receiving side, that is, only the facsimile signal demodulation side, and the circuit and processing method on the facsimile signal transmission side are the same as in the conventional example shown in FIG. I have.
[0023]
Next, the operation of the facsimile relay transmission device having the above configuration will be described.
[0024]
First, the facsimile packet transmitted from the IP line 20 is extracted by the packet data separation circuit 21 only for data necessary for the modulation-side facsimile modem processing. The packet data separation circuit 21 adjusts the packet reception order and controls the fluctuation of data on the IP line 20 in the case of facsimile data other than ECM-HDLC.
[0025]
Here, an outline of the ECM-HDLC frame will be described. As shown in FIG. 2, the ECM-HDLC frame includes a flag and a plurality of binary data sandwiched between the flags. The ECM-HDLC frame is described in ITU-T
T. Since the recommendation is made in S.30, the detailed description is omitted.
[0026]
When transmission of an ECM-HDLC frame is started, a synchronization sequence consisting of only a flag is transmitted prior to transmission of all binaries (frame information). That is,
[F] [F] [F] ... [F] [F] [F] [ECM-HDLC] [ECM-HDLC] ["] ...
Do as follows. The synchronization sequence is a continuous flag sequence with a nominal value of 200 ms (tolerance value +100 ms). It is sufficient that at least one flag is inserted between frames. In the case of continuous ECM-HDLC frames, the last flag of the immediately preceding frame can also be used as the first flag.
[0027]
Next, the extracted facsimile data is temporarily stored in the data storage buffer 25. If the stored data is other than the ECM-HDLC frame data, the data is read out from the data storage buffer 25 according to the instruction of the facsimile modem control circuit 23, modulated by the facsimile modem 24, and passed through the D / A conversion circuit 26. And output it at the facsimile terminal 27.
[0028]
On the other hand, when the ECM-HDLC data amount detection circuit 22 detects the ECM-HDLC frame data, it notifies the facsimile modem control circuit 23 of the detection. Then, flag transmission control is performed by the facsimile modem control circuit 23, and transmission of the flag from the facsimile modem 24 is started.
[0029]
Here, as shown in FIG. 3, it is assumed that jitter (jt) has occurred between packet 1 and packet 2 input to the facsimile relay apparatus on the packet receiving side. When the arrival of the packet 2 is delayed, the continuity of the facsimile demodulated signal is maintained by inserting the flag pattern (F). In the input of the facsimile modulation process on the packet receiving side, the transmission of the flag (F) immediately after the reception of the packet 0 corresponds to the time until a preset data amount is secured.
[0030]
In FIG. 3, similarly to the conventional example shown in FIG. 6, for the sake of simplicity, the input of the facsimile relay transmission device on the packet sending side is converted into one packet of the ECM-HDLC1 frame, and the facsimile relay transmission device on the packet receiving side is input. Shows the delay of the signal until the signal is output. Also, the delay for packetizing the ECM-HDLC frame in each facsimile relay device and separating the ECM-HDLC signal from the packet is not considered. Further, a training signal transmitted / transmitted immediately before ECM-HDLC is also omitted. By the way, the use of the facsimile relay transmission apparatus according to the present invention may cause the synchronization sequence to deviate from the standard recommendations, but it is considered that there is no problem due to this.
[0031]
Next, the ECM-HDLC data amount detection circuit 22 of FIG. 1 notifies the facsimile modem control circuit 23 when the ECM-HDLC data has accumulated data for a preset modulation time. Then, the transmission of the flag is stopped, the ECM-HDLC for one frame is read from the data storage buffer 25, subjected to modulation processing by the facsimile modem 24, and output by the facsimile terminal 27 via the D / A conversion circuit 26.
[0032]
However, when the modulation of the ECM-HDLC frame is started, it is necessary to keep operating the facsimile modem 24 on the modulation side until the sequentially transmitted ECM-HDLC frame is modulated. Accordingly, the transfer of the next successive ECM-HDLC frame is similarly waited until data for a preset modulation time is accumulated for each frame modulation process. Further, while waiting for the transfer, the facsimile modem control circuit 23 controls the facsimile modem 24 to output the flag pattern.
[0033]
The flag indicates the start and end of the ECM-HDLC frame described above, and is for establishing frame synchronization. By adjusting the transmission time of this flag, a delay time for jitter absorption is secured.
[0034]
By the way, although the waiting time is constant, the amount of data differs depending on the format type of frame data (for example, the modulation method V17 or V29 of ITU-T Recommendation T.30 or T.38) and the transmission speed. The number of data adapted to the data setting is set so as to secure the delay time.
[0035]
Next, the operation of the facsimile relay transmission apparatus according to one embodiment of the present invention will be described in detail with reference to the flowchart of FIG.
[0036]
FIG. 4 shows a processing flow on the facsimile signal receiving side (processing on the facsimile modem modulation side) of the facsimile relay transmission apparatus. This processing is performed every time (for example, 10 ms) of data to be packetized.
[0037]
First, in step S601, the facsimile modem control circuit 23 checks whether facsimile data exists. If no facsimile data exists, no facsimile signal is generated, and the process proceeds to step S607. On the other hand, if facsimile data exists, the process proceeds to step S602 to find the beginning of the ECM-HDLC frame. Here, only the detection is performed, and the head data of the ECM-HDLC frame is not yet read from the data storage buffer 25. This is to prevent the movement in the “No” direction in step S602 in the next process, even though the set amount of ECM-HDLC data is not accumulated.
[0038]
If the preset amount of ECM-HDLC data has not been stored in step S603, the process moves to step S605 without using the ECM-HDLC frame data.
[0039]
On the other hand, if the accumulated amount is equal to or greater than the set value, the facsimile modem 24 is controlled to insert a flag in step S604, and the process proceeds to step S605, where the flag data is subjected to facsimile modem modulation processing and output.
[0040]
By the way, if the facsimile data is not the ECM-HDLC signal or the facsimile data is not the head of the ECM-HDLC frame in step S602, the process moves to step S605. Thereafter, in the portion shown in step S605, facsimile modulation processing corresponding to various facsimile signals other than ECM-HDLC is performed.
[0041]
Next, a modified example of the present invention will be described with reference to FIG.
[0042]
In step S603, it is determined whether or not the ECM-HDLC data is equal to or larger than the set amount. However, the actual ECM-HDLC frame has a frame length that is not always constant, and a plurality of frames having a relatively small number of bytes are continuously grouped. In some cases, even if the data amount is smaller than the set data amount, the generation of the flag (F) by interpolation is not necessary if all the data for the next one frame and all the data are available.
[0043]
When waiting for the ECM-HDLC data to become data for a preset modulation time, instead of fixing the set value, the state of the IP line 20 is changed to a facsimile packet separation circuit 21 (see FIG. 1) may be provided and a state detection circuit for the IP line 20 may be provided, and the state of the IP line 20 may be sequentially adjusted adaptively based on the detection result.
[0044]
【The invention's effect】
As described above, according to the present invention, a highly reliable facsimile relay transmission device that can prevent a delay in response to a facsimile terminal, has a high transmission efficiency, and can prevent a communication abnormality. Can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of a facsimile relay transmission apparatus according to the present invention.
FIG. 2 is a diagram showing an outline of an ECM-HDLC frame.
FIG. 3 is a diagram showing an example of jitter absorption due to delay in the present invention.
FIG. 4 is a flowchart showing a control process on a facsimile modem demodulation side of the facsimile relay transmission apparatus according to the present invention.
FIG. 5 is a block diagram illustrating an example of a conventional facsimile relay apparatus.
FIG. 6 is a diagram showing an example of jitter absorption by a conventional delay.
[Explanation of symbols]
Reference Signs List 20 IP line 21 Packet data separation circuit 22 ECM-HDLC data amount detection circuit 23 Facsimile modem control circuit 24 Facsimile modem (at the time of modulation)
25 Data storage buffer 26 D / A conversion circuit 27 Facsimile terminal

Claims (4)

ITU-T @ T. A facsimile relay transmission device, comprising: control means for interpolating a jitter component with flag data when receiving an image signal in the ECM-HDLC data format specified in Recommendation 30. 2. The facsimile relay transmission device according to claim 1, wherein the control unit determines the interpolation time based on an amount of data stored in a facsimile signal storage buffer. 3. The facsimile relay transmission device according to claim 1, wherein the control unit inserts flag data at the beginning of an ECM-HDLC frame or at a connection unit. 4. The facsimile relay transmission device according to claim 1, wherein the control unit is capable of sequentially changing the interpolation time.

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