JP4213530B2 - FAX communication system and communication method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a FAX communication system, and more particularly to a system for performing FAX communication by linking a plurality of different types of digital communication networks, and the present invention relates to a communication method for a FAX communication system.
[0002]
[Prior art]
A modem communication system defined by ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) V.21 is applied to a FAX signal output from a FAX (Facsimile) terminal device. That is, the communication during this period is an analog signal. Further, as a digital communication network, VoIP (Voice over Internet Protocol) and VoFR (Voice over Frame Relay) communications are performed via a gateway device. Communication between them is performed by transferring an IFP (Internet Facsimile Protocol) packet according to the standard of the ITU-T T.38 recommendation. Fax communication performed via two digital communication networks such as VoIP and VoFR is called digital two-link fax communication. In digital two-link FAX communication, A / D conversion and D / A conversion are performed twice each because communication between digital communication networks is performed by analog signals.
[0003]
In this digital 2-link FAX communication, the pre-message procedure performed prior to this transfer identifies and selects the required function based on phase B of the ITU-T.30 recommendation. The signals used for communication and their functions will be briefly described below. NSF (Non-Standard Facilities) identifies specific user requirements that are outside the scope of the ITU-T T series recommendations. CSI (Called Station Identification) identifies a called terminal by an international telephone number. DIS (Digital Identification Signal) represents the standard capability of the called terminal. DCS (Digital Command Signal) is a digital setting command identified by the DIS signal and responding to the standard function. TSI (Transmitting Station Identification) indicates that the FIF (Facsimile Information Field) information that follows this is identification of the transmitting terminal. TCF (Training ConFirmation: Training Check) is sent via the TTC (the Telecommunication Technology) standard JT-T4 modulation system to verify training and first display that the channel is available at this data rate. Signal. Here, the JT-T4 modulation system is a system that performs modulation based on the recommended T4 standard unique to Japan. CFR (ConFirmation to Receive) is a digital response signal that confirms that all pre-message procedures have been completed and that message transmission can be started.
[0004]
The FAX terminal device on the transmission side (TCF and image data reception side) outputs an NSF / CSI / DIS signal to the gateway device of the VoIP network. Communication is performed between the gateway devices of the VoIP network using a digitized CSI / DIS signal, and communication is performed between the gateway device of the VoIP network and the VoFR network using an analog CSI / DIS signal. Again, the analogized CSI / DIS signal is digitized between the gateway devices of the VoFR network, and communication of the VoFR network is performed by the digitized CSI / DIS signal. The VoFR network gateway device outputs the CSI / DIS signal in accordance with the reception form because the FAX terminal device on the reception side (TCF and image data transmission side) uses the analog signal as the reception signal form.
[0005]
The reception-side FAX terminal device outputs a TSI / DCS signal in analog form to the transmission-side FAX terminal device in accordance with the received CSI / DIS signal. The TSI / DCS signal is analog between the receiving FAX terminal and the VoFR network gateway, digital within the VoFR network, analog between the VoFR network and VoIP network, digital within the VoIP network, and the VoIP network gateway device. The data is supplied after being converted into an analog form between the transmission side FAX terminal device. The FAX terminal device on the receiving side outputs the TCF signal to the gateway device of the VoFR network after a predetermined time has elapsed since the transmission of the TSI / DCS signal. The gateway device of the VoIP network also transmits the TCF signal to the FAX terminal device on the transmission side continuously for 1.5 seconds after a predetermined time has elapsed since the transmission of the TSI / DCS signal.
[0006]
After receiving the TCF signal, the transmission-side FAX terminal device transmits a CFR signal to the reception-side FAX terminal device. The CFR signal is converted into a form suitable for each as in the CSI / DIS signal transmission form and supplied to the receiving FAX terminal apparatus via the VoIP network and the VoFR network.
[0007]
By the way, the FAX terminal device on the receiving side defines the re-transmission (retry) of the TSI / DCS signal as 3 seconds or 2.5 seconds by the terminal device. In order to avoid this re-transmission, it is required to receive the CFR signal transmitted from the transmission-side FAX terminal device by the reception-side FAX terminal device within this time.
[0008]
[Non-Patent Document 1]
ITU-T.30 recommendation, 1996 [Non-patent document 2]
ITU-T.38 recommendation, June 1998.
[0009]
[Problems to be solved by the invention]
However, a delay may occur due to the two links connecting the VoIP network and the VoFR network. If the CFR signal is delayed due to this delay, the CFR signal may collide with the TSI / DCS signal retransmitted by the receiving FAX terminal device. In particular, there is a high possibility that it will occur in a FAX terminal device or the like in which a short timeout value of 2.5 seconds is specified.
[0010]
The present invention eliminates such drawbacks of the prior art, and provides a FAX communication system and a communication method thereof capable of avoiding a collision between a signal from a transmitting FAX terminal device and a signal retransmitted by a receiving FAX terminal device. The purpose is to provide.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a FAX communication system in which a plurality of different digital communication networks are interposed in FAX communication performed between FAX terminal apparatuses on the transmission side and the reception side. Each communication network is provided with a gateway device for FAX communication, and at least whether a part of a signal supplied to one gateway device provided on the FAX communication route is to be discarded is set in advance. A discard function block for performing a discard process according to this setting is included.
[0012]
In the FAX communication system of the present invention, a discard function block is provided in at least one of gateway apparatuses arranged in one of a plurality of digital communication networks, and whether or not to discard is set in advance. By discarding part of the signal supplied in response to this, the amount of signal to be transferred is reduced and the time required for transfer is shortened.
[0013]
In order to solve the above-mentioned problem, the present invention provides a communication method for a FAX communication system in which a plurality of different digital communication networks are interposed in FAX communication performed between FAX terminals on the transmission side and the reception side. Sets a flag indicating whether or not to discard a predetermined signal in a gateway device provided in one of a plurality of digital communication networks, and installs a discard procedure according to the first step and the set flag. And a second step of discarding a predetermined signal among the signals supplied in this manner, and performing FAX communication.
[0014]
The communication method of the FAX communication system of the present invention sets a flag indicating whether or not to discard a predetermined signal in a gateway device provided in one of a plurality of digital communication networks, installs a discard procedure, and is supplied If the flag setting indicates discard, the predetermined signal included in the supplied signal is discarded, thereby reducing the amount of signal to be transferred and shortening the time required for transfer.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a FAX communication system according to the present invention will be described in detail with reference to the accompanying drawings.
[0016]
In this embodiment, the FAX communication system of the present invention is applied to a digital 2-link FAX system 10. The illustration and description of parts not directly related to the present invention are omitted. In the following description, the signal is indicated by the reference number of the connecting line in which it appears.
[0017]
As shown in FIG. 2, the digital 2-link FAX system 10 includes FAX terminal apparatuses 12 and 14 and gateway apparatuses 16, 18, 20 and 22. In this embodiment, the FAX terminal device 12 is a transmission side (image data reception side), and the FAX terminal device 14 is a reception side (image data transmission side). The FAX terminal apparatuses 12 and 14 perform transmission / reception with analog FAX signals that are normally used.
[0018]
The gateway devices 16 and 18 are respectively connected to the VoIP network 24 with the VoIP network 24 interposed therebetween, and have a function of communicating FAX data using packets corresponding to VoIP. The gateway devices 20 and 22 are respectively connected to the VoFR network 26 with the VoFR network 26 interposed therebetween, and have a function of communicating FAX data using packets corresponding to VoFR. Further, the gateway device 16 on the communication path performs analog communication with the above-described FAX terminal device 12. The gateway device 22 on the communication path performs analog communication with the FAX terminal device 14. On the other hand, in the VoIP network 24 and the VoFR network 26, communication is performed using digital signals. Communication between the VoIP network 24 and the VoFR network 26 is performed using an analog modem signal.
[0019]
In this way, the FAX terminal apparatuses 12 and 14 having two digital networks intervene to perform FAX communication. Therefore, the gateway apparatuses 16, 18, 20, and 22 have an A / D conversion section and a D / A conversion section. is doing. The gateway devices 16, 18, 20, and 22 perform FAX communication in layer 3 in the system 10 of this embodiment. The gateway devices 16, 18, 20, and 22 basically have the same configuration when performing the FAX communication.
[0020]
However, the gateway devices 16 and 18 have a header portion of 20 bytes and the information portion (payload portion) variable between 46 and 1500 bytes. The gateway devices 20 and 22 have a header portion of 6 bytes and the information portion has a higher protocol. The information is variable, and communication is performed according to the format for transferring data.
[0021]
Since the configuration is the same as described above, the schematic configuration of the gateway device 16 shown in FIG. 1 and the configuration of each functional unit by software will be briefly described. The gateway device 16 includes a digital signal processing unit 28, a modem control unit 30, and a FAX control unit 32. The digital signal processing unit 28 has a built-in modem 36 for transmitting and receiving a FAX signal 34 to and from the FAX terminal apparatus 12 and has a function of performing digital signal processing on the digitized FAX signal. Further, in this case, the digital signal processing unit 28 is an A / D conversion unit 38 and a D / A conversion unit 40 as signal conversion units for transmitting and receiving the FAX signal 34 to and from the FAX terminal device 12 arranged outside the VoIP network 24. including.
[0022]
The modem control unit 30 is between the digital signal processing unit 28 and the FAX control unit 32 and has a function of controlling transmission / reception of data during this period. The modem control unit 30 controls transmission / reception of the FAX signal 42 by outputting a FAX signal transmission request and reception request (not shown) to the digital signal processing unit 28, respectively. The modem control unit 30 also controls transmission / reception of the FAX signal 44 with the FAX control unit 32.
[0023]
In particular, the FAX control unit 32 has a function of analyzing data of the supplied FAX signals 44 and 46 and a function of adjusting the output in accordance with a format corresponding to the analysis result. Corresponding to the communication with the VoIP network 24, the FAX control unit 32 analyzes the FAX signal 44 by the data analysis function unit 48, and converts the data analyzed by the output adjustment function unit 50 into the FAX signal 46 put on the IFP packet. Output. On the contrary, the FAX control unit 32 receives the FAX signal 46 from the VoIP network 24 by the output adjustment function unit 50, supplies the received FAX signal 46 to the data analysis function unit 48, and extracts and analyzes the IFP packet. Then, the analyzed data is adjusted, for example, by the output adjustment function unit 50 into a FAX signal 44 to be modem data, and is output to the modem control unit 30.
[0024]
The FAX control unit 32 is provided with a register 48 that is a feature of the present invention. In the register 52, system data of the gateway device 16 is set. The system data is device setting information, and in this embodiment, includes information instructing whether or not to discard the TSI signal of the FAX signal. When the register 52 has a flag indicating that the TSI signal is discarded, the data analysis function unit 48 analyzes the presence or absence of the TSI signal. The output adjustment function unit 50 performs processing excluding the TSI signal according to the analysis result, and transmits other FAX signals to the VoIP network 24 or the modem control unit 30 according to transmission / reception. The output adjustment function unit 50 corresponds to a discard function block. When the flag indicates discard, the output adjustment function unit 50 discards the TSI signal according to the determination that the analysis result includes the TSI signal. In a broad sense, the discard function block can be considered to include not only the output adjustment function unit 50 but also the data analysis function unit 48 and the register 52.
[0025]
Thus, in the communication of the FAX signal, for example, by discarding a predetermined signal in accordance with the setting of the discard instruction flag for the option signal, the time required for communication can be shortened. That is, by suppressing the communication delay in the FAX system 10, the reception-side FAX terminal device 14 can receive a predetermined signal, for example, a CFR signal before a timeout that defines the retransmission time. Accordingly, it is possible to avoid a collision between the signal to be transmitted and the CFR signal.
[0026]
Next, the case where the discard instruction flag is set in the gateway apparatus 18 in the FAX system 10 will be described with reference to FIG. The communication sequence shown here takes a pre-message procedure as an example. The FAX terminal apparatus 12 outputs the NSF / CSI / DIS signal 60 to the gateway apparatus 16 at time T10. The gateway device 16 analyzes the data at time T12, stores the CSI / DIS signal 62 in the IFP packet among the supplied NSF / CSI / DIS signals 60, and supplies it to the gateway device 18.
[0027]
The gateway device 18 outputs the CSI / DIS signal 64 obtained by converting the CSI / DIS signal 62 supplied correspondingly between the VoIP network 24 and the VoFR network 26 into an analog signal to the gateway device 20 at time T14. At time T16, the gateway device 20 outputs the digitized CSI / DIS signal 66 to the gateway device 22 connected to the VoFR network 26. The gateway device 22 adjusts the supplied CSI / DIS signal 66 to the reception format of the FAX terminal device 14, and outputs an analog CSI / DIS signal 68 to the FAX terminal device 14 at time T18.
[0028]
The FAX terminal device 14 receives the CSI / DIS signal 68 and outputs a TSI / DCS signal 70 to the gateway device 22 at time T20. The FAX terminal device 14 starts measuring the passage of time until the time-out 72 set in advance according to this output. At time T22, the gateway device 22 supplies the digitized TSI / DCS signal 74 to the gateway device 20. At time T24, the gateway device 20 converts the supplied TSI / DCS signal 74 into an analog TSI / DCS signal 76 and sends it to the gateway device 18.
[0029]
The gateway device 18 analyzes the TSI / DCS signal 76 supplied by the data analysis function unit 48, and compares it with the analysis result whether or not it corresponds to the pre-stored system data discard instruction data (TSI discard flag). Judgment. With this determination, the output adjustment function unit 50 discards the TSI signal of the TSI / DCS signal 76 and outputs the digitized DCS signal 78 to the gateway device 16 at time T26. The gateway device 16 analyzes the supplied DCS signal 78 and outputs the DCS signal 80 converted into an analog format according to the analysis result to the FAX terminal device 12 at time T28. The FAX terminal device 14 and the gateway device 16 send TCF signals 82 and 84 after a predetermined time has passed to the gateway device 22 and the FAX terminal device 12, respectively.
[0030]
In response to the supply of the DCS signal 80, the FAX terminal device 12 transmits the CFR signal 86 to the gateway device 16 at time T30. Thereafter, the gateway devices 16, 18, 20, and 22 output CFR signals 88, 90, 92, and 94 to the gateway devices 18, 20, 22, and the FAX terminal device 14 at times T32, T34, T36, and T38, respectively. The FAX terminal device 14 receives the CFR signal 94 at time T40. In these series of sequences, the time until the CFR signal 94 reaches the FAX terminal device 14, that is, the time from time T20 to T40, is shorter than the time-out 72. As a result, the FAX terminal apparatus 14 can avoid the retransmission of the TSI / DCS signal 70 and can prevent a collision with the CFR signal 94.
[0031]
The reason why this time can be shortened will be described below. The TSI signal transmitted from the FAX terminal device 14 is optional according to the ITU-T.30 recommendation. Although not shown, the field of the TSI signal is 20 bytes. When this field is combined with the address field, control field, and FCS (Frame Check Sequence), it becomes 24 bytes (24 × 8 = 192 bits). It can be seen that when a 24-byte signal is transmitted at 300 bit / s, it is transmitted at (24 × 8/300) × 1000 = 640 ms. When the gateway device 18 discards the TSI signal, the TSI signal is not transferred to the communication destination gateway device 16. The gateway device 18 can shorten the time required for the transfer, that is, 640 ms. Since the gateway device 16 does not transfer the TSI signal to the FAX terminal device 12, the transfer time is shortened.
[0032]
Therefore, in this case, the response signal TSI / DCS signal 70 from the FAX terminal apparatus 14 can be shortened by 640 ms in consideration of discarding of the TSI signal from the gateway apparatus 18 to the FAX terminal apparatus 12. As a result, the FAX terminal apparatus 14 can receive the CFR signal earlier by this amount of time.
[0033]
Even if the TSI signal discard function is set in the gateway device 16, in this case, the shortening time is 640 ms. The longer the route that receives the effect of this time reduction, the more effectively the transfer time can be shortened compared to when the TSI signal is transferred. That is, if the option signal discard function is set in the gateway device closest to the FAX terminal device 14 that transmits the option signal, less information is provided on the route supplied to the FAX terminal device 12.
[0034]
In this embodiment, the gateway device 22 is a device that meets this condition. When the gateway device 22 has a TSI signal discard function, the gateway device 22 analyzes the TSI / DCS signal 70 supplied from the FAX terminal device 22 and discards the TSI signal as shown in FIG. The DCS signal 96 is output to the gateway device 20 at time T22. Also in this case, since the TSI signal is a standard in accordance with the ITU-T.30 recommendation, it is shortened by 640 ms. As the time is shortened, the shortening effect propagates after the gateway device 20. Gateway device 20 outputs DCS signal 98 to gateway device 18 at time T42. The gateway device 18 connected to the VoIP network 24 outputs the DCS signal 100 to the gateway device 16 at time 44, and the gateway device 16 supplies the DCS signal 102 to the FAX terminal device 12 at time T46.
[0035]
The FAX terminal device 12 receives the supply of the DCS signal 102 and outputs a CFR signal 86 to the gateway device 16. However, the output time is T48 and time before time T30. Gateway devices 16, 18, 20, and 22 output CFR signals 88, 90, 92, and 94 at times T50, T52, T54, and T56, respectively. The time from time T20 to time T58 when the CFR signal 94 reaches the FAX terminal device 14 is shorter than the set time-out time 72. Accordingly, since the FAX terminal device 14 does not retransmit the TSI / DCS signal 70, collision with the CFR signal 94 can be prevented.
[0036]
In this embodiment, since the FAX terminal device that transmits the option signal is the FAX terminal device 14 on the receiving side, the gateway device having the discard function is the gateway device 22, but the present invention is not limited to this. In this embodiment, it may be provided in the gateway device 16 closest to the transmission-side FAX terminal device 12, or may be provided in both the gateway devices 16 and 22.
[0037]
By configuring as described above, at least one of the gateway devices arranged in one of the VoIP network 24 and the VoFR network 26 is provided with an output adjustment function unit 50 having a discard function, and is discarded in the register 52 in advance. Set a flag for whether or not to cancel, discard the TSI signal (option signal) that is part of the signal supplied according to the setting of this flag, reduce the amount of signal to be transferred and shorten the time required for transfer By doing so, it is possible to avoid re-transmission by supplying a signal from the transmission side before the time-out for re-transmission from the device on the reception side, and to prevent collision of signals from both the transmission side and the reception side Can do.
[0038]
In the FAX system 10, a gateway device having a discard function is disposed in either the gateway device 16 of the VoIP network 24 that directly communicates with the FAX terminal device 12 or the gateway device 22 of the VoFR network 26 that directly communicates with the FAX terminal device 14. May be. Further, in the FAX system 10, a gateway device having a discard function may be provided in the gateway devices 16 and 22. As a result, the FAX system 10 reduces the amount of signal to be transferred and shortens the time required for transfer, thereby supplying the signal from the transmission side before the time-out for retransmission from the device on the reception side to avoid retransmission. It is possible to prevent the signals from both the transmission side and the reception side from colliding with each other.
[0039]
In addition, according to the communication method in the digital 2-link FAX system 10, a flag indicating whether or not to discard a predetermined signal is set in the gateway device provided in one of the VoIP network 24 and the VoFR network 26, and the discard procedure Installed, analyze the supplied signal, and if the flag setting indicates discard, discard the predetermined signal included in the supplied signal, reduce the amount of signal to be transferred and shorten the transfer time By doing so, it is possible to avoid re-transmission by supplying a signal from the transmission side before the time-out for re-transmission from the device on the reception side, and to prevent collision of signals from both the transmission side and the reception side Can do.
[0040]
The communication method of the FAX system 10 is either the gateway device 16 of the VoIP network 24 that directly communicates the gateway device having the discard function with the FAX terminal device 12 or the gateway device 22 of the VoFR network 26 that directly communicates with the FAX terminal device 14. It may be arranged to communicate. Further, as a communication method of the FAX system 10, communication may be performed even if a gateway device having a discard function is provided in the gateway devices 16 and 22. With this communication method, the option signal is deleted to reduce the amount of signal to be transferred to shorten the transfer time, and the signal from the transmission side is made to reach before the time-out for retransmission from the FAX terminal device 14 on the reception side. To avoid retransmission. By avoiding this, it is possible to prevent a collision between a signal from the transmission side and a retransmission signal from the reception side.
[0041]
【The invention's effect】
As described above, according to the FAX communication system of the present invention, at least one gateway apparatus provided in one of a plurality of digital communication networks is provided with a discard function block, and whether or not to discard the data is set in advance. The transmission side before the time-out to retransmit from the receiving side device by discarding part of the signal supplied according to this setting, reducing the amount of signal to be transferred and shortening the time required for transfer Thus, it is possible to avoid re-transmission by supplying a signal from the transmission side, and it is possible to prevent the signals from both the transmission side and the reception side from colliding.
[0042]
Further, according to the communication method of the FAX communication system of the present invention, a flag indicating whether or not to discard a predetermined signal is set in a gateway device provided in one of a plurality of digital communication networks, and a discarding procedure is installed. When the supplied signal is analyzed and the flag setting indicates discard, the predetermined signal included in the supplied signal is discarded, and the amount of signal to be transferred is reduced to shorten the time required for transfer. By this, it is possible to avoid the retransmission by supplying the signal from the transmission side before the timeout of retransmission from the device on the reception side, and to prevent the signals from both the transmission side and the reception side from colliding with each other. .
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a gateway device to which a FAX communication system of the present invention is applied and functions by software.
FIG. 2 is a diagram showing a configuration of a digital 2-link FAX system to which the FAX communication system of the present invention is applied.
FIG. 3 is a sequence chart for explaining a communication procedure of the digital 2-link FAX system of FIG.
4 is a sequence chart when the discard function is provided in the gateway device closest to the receiving FAX terminal device in the digital two-link FAX system of FIG. 2. FIG.
[Explanation of symbols]
10 Digital 2-link FAX system
12, 14 FAX terminal
16, 18, 20, 22 Gateway device
24 VoIP network
26 VoFR network
48 Data analysis function
50 Output adjustment function
52 registers

Claims (4)

In a FAX communication system in which a plurality of different digital communication networks are interposed in FAX communication performed between FAX terminal apparatuses as a transmission side and a reception side, the system includes:
Each of the plurality of digital communication networks is provided with a gateway device for FAX communication,
It includes at least a discard function block in which whether or not to discard a part of a signal supplied to one gateway apparatus arranged on the FAX communication path is set in advance and performs a discard process according to the setting. See
The discard function block includes a gateway device to which FAX communication is first input from the transmission-side FAX terminal device in the first digital communication network, and the reception-side FAX terminal device in the second digital communication network. A FAX communication system, wherein the FAX communication system is disposed in a gateway device to which FAX communication from the terminal is input .   2. The system according to claim 1, wherein the discard block is a first digital communication network that is directly connected to the transmission-side FAX terminal apparatus or a communication connection that is directly connected to the reception-side FAX terminal apparatus. A FAX communication system, which is disposed in any one of the two digital communication networks. In a communication method of a FAX communication system in which a plurality of different digital communication networks are interposed in FAX communication performed between FAX terminal apparatuses as a transmission side and a reception side, the method includes:
A first step of setting a flag indicating whether or not to discard a predetermined signal in a gateway device provided in one of the plurality of digital communication networks, and installing a discarding procedure;
A second step of discarding the predetermined signal among signals supplied in accordance with the set flag ,
The first step includes a gateway device to which FAX communication is first input from the transmission-side FAX terminal device in the first digital communication network, and the reception-side FAX terminal device in the second digital communication network. A communication method for a FAX communication system , wherein the flag is set in a gateway device to which FAX communication from the terminal is input, the discarding procedure is installed, and FAX communication is performed. 4. The method according to claim 3 , wherein the first step is to establish a direct communication connection with the first digital communication network or the reception side FAX terminal device that is directly connected with the transmission side FAX terminal device. A communication method of a FAX communication system, wherein the flag is set in any gateway device of the second digital communication network, and the discarding procedure is installed.

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