JP4108667B2 - Gateway and facsimile communication quality improving method - Google Patents

Description

  The present invention relates to a technique for improving communication quality of a facsimile machine (FAX), and more particularly to a technique for improving communication quality when performing FAX communication using deemed voice in VoP (Voice over Packets).

  Services that handle telephone voice in data communication networks such as VoIP (Voice over IP), IP networks such as VoATM (Voice over ATM), VoFR (Voice over Frame Relay), ATM networks, and FR networks. VoP is getting attention.

  In conventional general VoP, in order to eliminate uneven packet arrival delay time difference (fluctuation) that occurs in the network, a certain amount of packets are accumulated in the fluctuation absorbing buffer of the receiving VoP gateway, and the time difference is evenly distributed. Process to adjust to.

  FIG. 8 shows a configuration example of a conventional general VoP that performs the above-described processing.

  In FIG. 8, 1A and 1G are G3FAX (G3 facsimile apparatus) according to the prior art, which has been commercialized based on the provisions of TTC standard JT-T30 "document facsimile exchange procedure in a general telephone exchange network". This figure assumes a case where FAX transmission is performed from G3FAX 1A to G3FAX 1G.

  1B and 1F are PBX (private branch exchange) and the like. However, PBX 1B and PBX 1F may be unnecessary when using a public telephone line for home use such as a subscriber telephone network or ISDN line.

  1D is a VoP network, and 1C and 1E are VoP gateways according to the prior art based on the types and rules of the VoP network 1D. There are regulations such as VoIP (Voice over IP), VoATM (Voice over ATM), and VoFR (Voice over Frame Relay) depending on the type of VoP network.

  1C1 is a voice A / D conversion (analog to digital conversion) means. The principle of A / D conversion is based on a well-known conventional technique. Typical A / D conversion methods in VoP include PCM (G.711), 32K ADPCM (G.726), and 8K CS-ACELP (G.729).

  1C2 is a packet generation means for voice data (PIX information in the case of G3FAX communication). The basic principle of packet communication is recommended by X.25 of the ITU-T international standard, and although there are some differences depending on network specifications (ATM, frame relay, IP, etc.), the principle is common. I will omit the explanation.

  1E1 is a voice packet depacketization means. Since it is the reverse procedure of the packet generation means 1C2, description in the text is omitted.

  1E2 is a D / A conversion (digital-to-analog conversion) means for audio data. Since this is the reverse procedure of the A / D conversion means 1C1, description in the text is omitted.

  1E3 is a fluctuation absorbing buffer, and its buffer length and buffer accumulation time limit are fixed. According to the G.144 audio delay guideline (see Fig. 10), the one-way delay that can be used without making the user feel uncomfortable is limited to 0 to 150 ms. The buffer length of 1E3 and the buffer storage time limit are fixed.

  Next, the operation of FIG. 8 will be described.

  Data (voice data or FAX data) from the G3FAX 1A is sent to the VoP gateway 1C on the transmission side via the PBX 1B. In the VoP gateway 1C, the transmitted data is digitized by the A / D conversion means 1C1, further packetized by the packet generation means 1C2, and transmitted to the receiving VoP gateway 1E via the VoP network 1D.

  Now, for example, as shown in FIG. 9, it is assumed that packets [1] to [10] are transmitted from the VoP gateway 1C on the transmission side to the VoP gateway 1E on the reception side.

  Packets [1] to [10] have an uneven packet interval due to a variable delay factor (such as a waiting time at a node) of the VoP network 1D, and the arrival time becomes earlier or later. This is generally called “fluctuation of delay time”, and if the sound is reproduced as it is, the sound is interrupted or disturbed. As a countermeasure, the packet is temporarily stored in the fluctuation absorbing buffer 1E3.

  Packet [2] is a packet that has not arrived within the buffer accumulation time limit (a fixed time) due to delay in arrival (3A). The packet group accumulated in the fluctuation absorbing buffer 1E3 is taken out from the fluctuation absorbing buffer 1E3 to the depacketizing means 1E1 after a certain period of time with the delayed packet (3A) remaining empty (3B).

  At this point, the packet groups are arranged in the order of arrival. FIG. 9 shows that packet [4] arrived later than packet [5] (3C). The inverse packetizing means 1E1 performs voice compensation and synchronization by time stamp (3D). Compensate the voice data that has been delayed by the packet [2] whose arrival has been delayed by using the previous sound compensation or white noise. In FIG. 9, it is assumed that a means for pre-sound compensation is used, and the voice data for the insufficient packet [2] is compensated by the voice data of packet [1]. At the same time, synchronization by time stamps is performed by switching the order of packets [4] that arrive later than packet [5].

  Note that the packet [2] that has not arrived in time to reproduce the voice data due to the arrival delay is discarded in the depacketizing means 1E1. That is, the packet [2] is discarded in the next procedure.

  As a result, the voice data is reproduced with the voice compensated (3E). The above is the operation at the time of reproducing voice data generally performed conventionally.

In addition to the above-described conventional technique, a technique for changing the buffer length of a reception buffer for receiving data according to the type of information medium of received data in a communication interface device that communicates various information media has been proposed ( For example, see Patent Document 1). In the conventional technique described in Patent Document 1, when the information media type is FAX, the FAX communication quality is improved by increasing the reception buffer length compared to the case where the information media type is voice. Prevents the decline.
JP 2004-32195 A

  In the conventional technique shown in FIG. 8, since the buffer length of the fluctuation absorbing buffer and the buffer accumulation limit time are fixed, voice reception and G3FAX communication are voice-compensated with a uniform probability in the receiving VoP gateway. Voice compensation is an indispensable technology for making a voice call with some sense of incongruity, but the more you perform voice compensation, the worse the call quality will be, and it will be a disadvantageous transfer condition for G3FAX communication that requires high-quality voice communication As a result, the G3FAX communication quality is degraded.

  Therefore, it is conceivable to combine the conventional technique shown in FIG. 8 with the conventional technique described in Patent Document 1. That is, it is possible to change the buffer length and buffer storage time limit of the fluctuation absorbing buffer 1E3 in the receiving-side VoP gateway 1E shown in FIG. 8, and to make it longer than that during voice communication during G3FAX communication. By doing so, the number of times of performing voice packet compensation can be reduced during G3FAX communication compared to during voice communication, so that the quality of G3FAX communication can be improved.

  However, as described above, when the two conventional techniques are combined, the buffer storage time becomes longer, so that the PIX information received by the receiving G3FAX is likely to be intermittent, and the receiving G3FAX is increased. The possibility of adversely affecting In G3FAX, which exchanges data by analog-based voice call, it is impossible for PIX information to be intermittent.Therefore, in existing G3FAX, data reception failure due to PIX information interruption is considered the worst. There is a possibility of timeout.

  Therefore, an object of the present invention is to enable smooth flow of PIX information to a facsimile machine on the receiving side even when the FAX communication quality is improved by extending the buffer storage time.

The first gateway according to the present invention is :
In a gateway with a fluctuation absorbing buffer,
When the packet receiving side is a facsimile device, the buffer storage time limit of the fluctuation absorbing buffer is set longer than that during voice call, and the packet read from the fluctuation absorbing buffer is depacketized to reproduce the PIX information. A configuration for performing voice packet compensation, a configuration for transmitting the PIX information reproduced by the configuration after extension to the facsimile apparatus, and detecting the number of times of voice packet compensation performed during a predetermined time , and having a structure and to change the buffer storage time limit of the fluctuation absorbing buffer based on the number of times detected.

The second gateway according to the present invention is the first gateway,
When an affirmative response is returned from the facsimile apparatus, a signal that causes the affirmative response is again resent to the facsimile apparatus in a pseudo manner.

The third gateway according to the present invention is the second gateway,
The acknowledgment is a message confirmation signal (MCF) or a reception preparation confirmation signal (CFR),
The signal causing the acknowledgment is a multi-page signal (MPS) or a training check signal (TCF) .

The fourth gateway according to the present invention is:
A fluctuation absorbing buffer capable of changing the buffer length and buffer accumulation time limit;
When the packet receiving side is a facsimile machine, a control unit that makes the buffer length and buffer accumulation time limit of the fluctuation absorbing buffer longer than that during voice call;
De-packetizing means for performing voice packet compensation when reproducing PIX information by depacketizing packets accumulated in the fluctuation absorbing buffer;
Preamble extension means for extending the preamble of the PIX information reproduced by the depacketization means;
A pseudo-sending unit that pseudo-sends a signal that has been sent from the facsimile device as a cause of an acknowledgment to the facsimile device; and
The control unit is
Detecting the number of voice packet compensations performed during a predetermined time by the inverse packetization means, and determining the buffer length and buffer accumulation limit time of the fluctuation absorbing buffer based on the detected number of times. Features.

The fifth gateway according to the present invention is the fourth gateway,
The control unit is
It is characterized in that, based on the determined buffer length or accumulation limit time, the number of transmissions and the transmission interval at which the signal causing the acknowledgment is artificially transmitted to the facsimile apparatus are determined.

The facsimile communication quality improving method in the gateway according to the present invention is as follows.
A method for improving facsimile communication quality in a gateway having a fluctuation absorbing buffer,
When the packet receiving side is a facsimile machine, a first step of setting a buffer storage time limit of the fluctuation absorbing buffer to be longer than that during a voice call;
A second step of performing voice packet guarantee when the packet read from the fluctuation absorbing buffer is depacketized to reproduce the PIX information;
A third step of transmitting to the facsimile apparatus after extending the preamble of the PIX information reproduced in the second step;
And a fourth step of detecting the number of times of voice packet compensation performed during a predetermined time and changing the buffer storage time limit of the fluctuation absorbing buffer based on the detected number of times .

[Action]
In the gateway according to the present invention, when the packet receiving side is a facsimile apparatus, the buffer storage time limit of the fluctuation absorbing buffer for storing the packet is made longer than that during voice call. Thereby, the number of packets discarded due to arrival delay can be reduced. Furthermore, in the gateway according to the present invention, the PIX information preamble is extended and then transmitted to the facsimile machine on the receiving side. Therefore, when the FAX communication quality is improved by extending the buffer accumulation limit time. Even so, PIX information can flow smoothly to the receiving facsimile machine.

According to the present invention, it is possible to smoothly flow PIX information to the receiving facsimile apparatus even when the quality of facsimile communication is improved by extending the buffer storage limit time of the fluctuation absorbing buffer during facsimile communication. As a result, the risk of adversely affecting the facsimile machine on the receiving side is reduced. This is because the PIX information reproduced by depacketizing the packet read from the fluctuation absorbing buffer is transmitted to the facsimile machine on the receiving side after extending the preamble.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration example of a VoP gateway 2 on the receiving side used in the first embodiment of the present invention. This VoP gateway 2 is used in place of the receiving-side VoP gateway 1E shown in FIG. That is, the overall configuration of the present embodiment is obtained by replacing the VoP gateway 1E with the VoP gateway 2 in FIG.

  In FIG. 1, reference numeral 2A denotes a packet delay fluctuation absorbing buffer. In order to eliminate the uneven packet arrival delay time difference (fluctuation) generated in the network, the packet is accumulated in the fluctuation absorbing buffer 2A for a certain period of time, and the time difference is adjusted evenly. If the fluctuation absorbing buffer has a fixed buffer length and buffer storage time limit, it is also provided in the VoP gateway 1E of FIG. 8 described above. The fluctuation absorbing buffer 2A of the present embodiment further includes CED detection means 2E. When detecting the CED and determining that the receiving terminal is G3FAX, it has a function of ensuring the fluctuation absorbing buffer length and the buffer storage time limit to be larger than those during a normal voice call in accordance with an instruction from the control unit 2H. As a result, the number of times of performing voice packet compensation by pre-sound compensation or white noise is reduced, and the accuracy of PIX information reproduced by inverse packetization is improved.

  In addition, the fluctuation absorbing buffer 2A can absorb larger delay fluctuations as the buffer length and the buffer accumulation limit time are larger, but on the other hand, the delay due to accumulation in the buffer increases, and the extremely long buffer length and buffer accumulation limit. Securing time gives an unacceptable voice delay for voice calls. For this reason, the VoP gateway according to the prior art is set to a buffer length that can suppress the delay to a level that is uniformly acceptable for a voice call. However, based on the fact that G3FAX communication can tolerate a larger delay than during voice calls, the receiving VoP gateway 2 according to the present embodiment ensures a large buffer length and buffer storage time limit when it is determined that G3FAX communication is used. I have to.

  2B is a reverse packetization means. The inverse packetization means 2B performs voice compensation and synchronization using a time stamp. Voice compensation is a function that compensates for missing voice data that is insufficient for packets discarded due to delay in arrival by using pre-tone compensation or white noise. The synchronization by the time stamp is a function for rearranging the packets based on the time stamp given to the packets.

  2C is a preamble extension means. In the preamble extension means 2C, the preamble extension of the HDLC frame of the PIX information is performed. The time for extending the preamble can be arbitrarily set by the user interface 2I, and is controlled (instructed for the preamble time to be extended) by the control unit 2H. Preamble extension enables smooth PIX information flow to the receiving facsimile machine even when the FAX communication quality is improved by increasing the buffer length and buffer storage time of the fluctuation absorbing buffer 2A. Implemented as intended.

  2D is a D / A conversion means. The D / A conversion means 2D has the same function as the A / D conversion 1C1 according to the prior art of FIG. Further, the D / A conversion means 2D also has a function of blocking the MCF / CFR retransmitted from the receiving side G3FAX 1G according to the instruction of the control unit 2H.

  2E is CED detection means. CED (Called Station Acknowledgment Signal) is a G3FAX service connection operation sequence flow (see Fig. 4). This signal is sent from the receiving FAX to the transmitting FAX in order to indicate that reception is possible normally. The CED detection means 2E has a function of detecting that the communication to be started is G3FAX communication by detecting the CED from the reception-side FAX 1G and transmitting it to the control unit 2H.

  2F is a MCF / CFR detection means. The MCF (message confirmation signal) handled by this MCF / CFR detection means 2F is the phase of step (D) “Procedure for confirming completion of message transmission” in the G3FAX service connection operation sequence flow (see FIG. 4). , A signal sent from the receiving FAX to the transmitting FAX indicating that the receiving FAX can receive the next page of PIX information after receiving one page of PIX information is completed, and MPS / EOM Acknowledges the / EOP signal. The CFR (reception preparation confirmation signal) is a message in the phase (B) “Procedure to be performed prior to message transmission after call setup” shown in the G3FAX service connection operation sequence flow (see FIG. 4). This is a signal sent from the reception side FAX to the transmission side FAX indicating that the pre-procedure phase (B) is all finished and message (PIX information) transmission can be started, and is an acknowledgment of the TCF signal. The MCF / CFR detection means 2F has a function of detecting MCF / CFR from the receiving FAX and transmitting it to the control unit 2H.

  2G is a pseudo-MPS / EOM / TCF sending means. The MPS (multi-page signal) handled by the pseudo MPS / EOM / TCF sending means 2G is the phase (D) “Procedure for confirming that message transmission has been completed” in the G3FAX service connection operation sequence flow (see FIG. 4). This signal is sent from the sending FAX to the receiving FAX in order to indicate the end of one page of PIX information at the stage and to return to the beginning of the phase (C) “message transmission”. Also, EOM (message end signal) means one page of PIX information at the stage of phase (D) “Procedure to confirm that message transmission has ended” shown in the G3FAX service connection operation sequence flow (see Fig. 4). This signal is sent from the sending FAX to the receiving FAX in order to indicate the end of the phase and return to the beginning of the phase (B) “procedure to be performed prior to message transmission after call setup”. MPS and EOM are similar signals, but EOM is used to return to phase (B) to change the mode of FAX communication. The TCF (training check signal) is a signal transmitted from the transmission side FAX to the reception side FAX in order to confirm whether or not the channel can be used at this transmission speed in the phase (B). After completing the TCF, the process proceeds to a phase (C) of a FAX sequence described later. MPS / EOM / TCF can be retransmitted. TTC standard JT-T30 recommends a retransmission interval of 3 seconds every 3 seconds. Pseudo MPS / EOM / TCF sending means 2G follows the instruction from control unit 2H and pretend to be the sending fax to the receiving fax and resend the MPS / EOM / TCF in a pseudo manner to the receiving fax. It has a function to extend the time to deliver PIX information. The TCF, MPS transmission interval, and the number of transmissions can be arbitrarily set by the user within the range recommended by TTC standard JT-T30 using the user interface 2I, and the control unit 2H performs pseudo MPS / EOM according to these settings. / TCF sending means Sends instructions to 2G.

  2H is a control unit. The control unit 2H receives the transmission from the CED detection unit 2E, detects that the communication to be started is G3FAX communication, and controls the following four functions autonomously or according to the input of the user interface 2I.

(1) A function for instructing the buffer buffer 2A to extend the buffer length and the buffer storage limit time during G3FAX communication than during voice calls.
(2) A function of instructing the preamble extension means 2C to extend the preamble as necessary.
(3) A function for instructing pseudo MPS / EOM / TCF output to the pseudo MPS / EOM / TCF sending means 2G as necessary.
(4) A function for instructing the D / A conversion means 2D to block the MCF / CFR transmitted from the receiving FAX as necessary.

  In addition, the fluctuation absorbing buffer 2A secures the fluctuation absorbing buffer length and the buffer accumulation time limit larger than those during normal voice call according to the instruction from the control unit 2H, but more than necessary in a network environment with a sufficiently small voice delay. Control does not lead to an improvement in the accuracy of PIX information reproduction, but rather only a necessary capacity should be ensured in order to promote a delay in FAX transmission speed and output. Therefore, the control unit 2H has a function of autonomously optimizing the buffer length of the fluctuation absorbing buffer 2A and the capacity of the buffer accumulation limit time depending on the number of times of performing voice packet compensation by pre-tone compensation or white noise.

  For example, the control unit 2H autonomously optimizes the buffer length and buffer accumulation limit time of the fluctuation absorbing buffer 2A as follows. When the CED detection means 2E detects that the receiving terminal is G3FAX, the control unit 2H first instructs the fluctuation absorbing buffer 2A with a predetermined buffer length L0 and buffer accumulation time limit T0. . As a result, the fluctuation absorbing buffer 2A sets the buffer length and the buffer accumulation limit time to the instructed values L0 and T0. The buffer length L0 and the buffer accumulation limit time T0 are larger than the buffer length LV and the buffer accumulation limit time TV during voice communication. Thereafter, the control unit 2H performs the following processing at predetermined time intervals. The number K of voice packet compensations performed in the depacketizing means 2B during the predetermined time is detected. Based on the detected number of times K, the buffer length Li and the buffer accumulation limit time Ti instructed to the fluctuation absorbing buffer 2A are calculated. The calculation of the buffer length Li and the buffer accumulation limit time Ti is performed based on, for example, the following expressions (a) and (b).

Li = L (i−1) × {1 + a (K−α)} (a)
Ti = T (i−1) × {1 + b (K−β)} (b)

  In equations (a) and (b), L (i-1) and T (i-1) represent the buffer length and buffer accumulation limit time specified for the previous fluctuation absorbing buffer 2A, respectively. b, α, and β represent constants (0 <a <1, 0 <b <1, 0 <α <1, 0 <β <1). In this way, when the number of detections K of voice packet compensation is 0, the buffer length and buffer storage limit time specified for the fluctuation absorbing buffer 2A are previously specified as the buffer length and buffer storage limit time. If the number of detections is one or more, the buffer length and buffer accumulation limit time instructed to the fluctuation absorbing buffer 2A can be increased as the number of detections increases. The method described above is merely an example, and other methods may be adopted.

  2I is a user interface. The functions (1), (2), and (3) above are basically autonomously controlled by the control unit 2H with the goal of improving the quality of G3FAX communication. It has a function of adjusting the control states of (1), (2) and (3) above. For example, when it is desired to shorten the time required for the output of the receiving FAX, the functions (1), (2), and (3) can be adjusted to be reduced. Large control of the functions of (1), (2), and (3) will improve the reproduction accuracy and quality of PIX information over normal voice calls, but it is more than necessary in a network environment with sufficiently low voice delay. This is because the control of PIX does not improve the reproduction accuracy of PIX information, but rather promotes the delay of FAX transmission speed and output, which may lead to deterioration of usability.

[Description of Operation of Embodiment]
Next, the operation of the present embodiment will be described in detail. First, with reference to FIG. 2, the operation of reproducing the voice packet sequence from the network with fluctuation in voice data (PIX information) in the fluctuation absorbing buffer 2A will be described. This operation is particularly referred to as “G3FAX communication mode” in the text. For G3FAX communication, the buffer length of the fluctuation absorbing buffer 2A and the buffer accumulation time limit are ensured to be large compared to when the voice passes.

  The procedure for accumulating voice packets from a fluctuating network in the fluctuation absorbing buffer 2A is the same as in FIG. 9, but because of the G3FAX communication mode, the buffer length of the fluctuation absorbing buffer 2A is secured larger than in the normal voice call mode. In addition, the buffer storage time limit (fixed time) is secured for a long time (4A). For this reason, for example, a packet such as packet [2] whose arrival is delayed in FIG. 9 has a high probability of being in time for buffer accumulation in this embodiment.

  A packet is extracted from the fluctuation absorbing buffer 2A to the depacketizing means 2B either when the fluctuation absorbing buffer 2A is full or when the buffer accumulation limit time has elapsed (4B).

  The packets arranged in the arrival order are subjected to voice compensation by the depacketizing means 2B and synchronization by time stamp, and voice data (PIX information) is reproduced without voice compensation (4C). The above is the operation procedure for reproducing the audio data in the G3FAX communication mode according to the present embodiment. In the G3FAX communication mode of this embodiment, since the buffer accumulation limit time is long, there is a high possibility that a packet whose arrival has been delayed can be saved without being discarded, and the number of times of voice compensation can be reduced. Therefore, the accuracy of the reproduced audio data (PIX information) can be further improved.

  FIG. 3 shows an example of HDLC frame of PIX information (JT-T30). The audio data (PIX information) reproduced by the inverse packetization means 2B takes the form of an HDLC frame as shown in FIG. The preamble extension means 2C extends the preamble 5A of the HDLC frame of the reproduced audio data (PIX information). Specifically, a flag sequence “01111110” is added to the HDLC frame for a predetermined time (a predetermined number). As a matter of course, the preamble extension means 2C does not extend the preamble during a voice call.

  The preamble is also called a synchronization signal and is a trailer part for clock synchronization located at the head of a frame, which is a specific signal that does not cross between the preceding and succeeding frames and indicates the start of the signal. In TTC standard JT-T30, the HDLC frame of PIX information is defined as a sequence of flag sequences of “01111110” (5A). In the TTC standard JT-T30, the preamble duration is 1 second ± 15 seconds, but the G3FAX device has been extended with a preamble extension transmission function, usually about 10 seconds or less, in case the synchronization is not in time. A function that allows preamble reception is incorporated at the design stage.

  The reason for extending the preamble is to extend the time until the data part of the PIX information arrives at the G3FAX 1G on the receiving side. In other words, the timing to complete the transmission of the nth PIX information is delayed so that the (n + 1) th PIX information is continuously sent to the receiving side G3FAX following the nth PIX information. . In this embodiment, in order to extend the buffer length and buffer accumulation limit time of the fluctuation absorbing buffer 2A, the buffer accumulation time becomes longer than that of the conventional technique. As a result, the PIX information data received by the receiving side G3FAX 1G is more than normal. May also flow intermittently. How the reception data of PIX information will affect the receiving FAX depends on the specifications of the receiving G3 FAX, but by suppressing the actual data transmission rate by the preamble extension For the purpose of flowing PIX information data as smoothly as possible in conformity with the regulations, the present embodiment has a preamble extension function.

  FIG. 4 is an example of a service sequence flow of G3FAX. Since it has already been defined as the prior art, details are omitted, but for ease of understanding the description of the embodiments described later, it is listed as a reference. The service sequence of G3FAX can be classified into the following five FAX call phases.

Phase (A): Call setting procedure (call control)
Phase (B): Procedure to be performed prior to message transmission after call setup Phase (C): Message (PIX information) transmission phase (D): Procedure to confirm that message transmission has been completed Phase (E): Call recovery Procedure (line disconnection)

  When assuming a G3FAX service on the VoP network, it can be assumed that a VoP gateway is installed at the entrance of the network.

  The following signals related to this embodiment are control signals handled in phase (A) for CED, phase (B) for TCF / CFR, and phase (D) for MPS / EOM / EOP / MCF, respectively.

  FIG. 5 shows an MCF → MPS sequence in the FAX call phase (D) according to this embodiment. In FIG. 5, it is assumed that an MPS signal is transmitted, but the same applies to the case of EOM / TCF. MPS in the following description can be replaced with EOM / TCF.

  The MCF / CFR detection unit 2F and the pseudo MPS / EOM / TCF transmission unit 2G have a function of repeating the MCF → MPS sequence in accordance with the control of the control unit 2H.

  In FIG. 5, the receiving side acknowledges the MCF to the MPS (first time) transmitted from the transmitting side G3FAX 1A that has finished transmitting the PIX information of the first page (7A).

  The MCF passes through the receiving VoP gateway 2 and arrives at the transmitting side G3FAX 1A, and the transmitting side G3FAX 1A starts transmitting PIX information on the next page accordingly. However, since the PIX that has started transmission is accumulated by the fluctuation absorbing buffer 2A, it does not arrive at the reception side FAX at this point (7B).

  The receiving VoP gateway 2 impersonates the transmitting side G3FAX 1A and sends a second MPS in a pseudo manner (7C). This state is apparently seen from the receiving side G3FAX 1G because the transmitting side G3FAX 1A has not received the acknowledgment MCF of the receiving side G3FAX 1G for the MPS transmitted by itself, and therefore cannot send the PIX information again. The receiving side G3FAX 1G In order to check the status of "Resend MPS."

  The receiving side G3FAX 1G retransmits the second acknowledgment MCF because the MPS was retransmitted without the PIX arriving at the MCF. However, since the D / A conversion means 2D blocks this MCF in accordance with the instruction from the control unit 2H, it does not arrive at the transmitting FAX (7D).

  Further, similarly to 7C, the receiving-side VoP gateway 2 pretends to be the transmitting-side G3FAX 1A and again sends out a pseudo third MPS (7E).

  The receiving side G3FAX 1G retransmits the third acknowledgment MCF because the PIX did not arrive at the MCF and the MPS was retransmitted (7F).

  Now, according to ITU-T T.30, the re-transmission interval of MPS / EOM / TCF is recommended up to 3 times every 3 seconds. Since the MPS was retransmitted up to three times according to the recommendation, the PIX information stored in the fluctuation absorbing buffer 2A is transmitted to the receiving side G3FAX 1G (7G). However, since the first MCF has already arrived at the transmitting FAX 1A, the D / A conversion means 2D blocks the MCF according to the instruction of the control unit 2H. Therefore, the third MCF does not arrive at the transmitting side G3FAX 1A.

  The above is the operation of repeating the MCF → MPS sequence according to the control of the control unit 2H. The purpose of repeating the MCF → MPS sequence is to extend the time to deliver the PIX information of the next page to the receiving side G3FAX 1G. The retransmission interval can be extended by about 6 seconds if the recommendation is made every 3 seconds and up to 3 times. The merit is almost the same as the preamble extension means 2C. In the present invention, the buffer storage time is longer than that of the prior art in order to extend the buffer length and buffer storage limit time of the fluctuation absorbing buffer 2A. This is because the data of the PIX information received by the side FAX may flow intermittently than usual. In order to flow PIX information data as smoothly as possible and to increase the buffer storage time, the present invention has an MCF → MPS sequence repetition function.

  Next, an example of the operation of the entire receiving VoP gateway 2 will be described with reference to the flowcharts of FIGS.

  FIG. 6 and FIG. 7 are flow charts assuming a case where “2 pages of PIX information is transmitted from the transmitting side G3FAX 1A to the receiving side G3FAX 1G using the G3FAX communication mode according to this embodiment”. . FIG. 6 shows the operation when transmitting the first page, and FIG. 7 shows the operation when transmitting the second page.

  When the receiving side G3FAX 1G transmits the CED after the start of the face (A), the CDE is detected by the CDE detecting means 2E in the VoP gateway 2 (8A in FIG. 6). When the CDE is detected by the CDE detection means 2E (8A is Yes), the control unit 2H determines that the communication is FAX communication, switches to the G3FAX communication mode, and performs the following for the fluctuation absorbing buffer 2A and the preamble extension means 2C: Give instructions (8B).

Instructs the buffer length and buffer accumulation limit time to the fluctuation absorbing buffer 2A. The buffer length and buffer storage time limit indicated at this time are set to values larger than the buffer length and buffer storage time limit during voice communication.
Instruct the preamble extension means 2C about the extension time of the preamble.

In response to the above instruction, the fluctuation absorbing buffer 2A sets the buffer length and the buffer accumulation limit time to the instructed values. Further, the preamble extension means 2C, upon receiving the above instruction, extends the preamble of the packet input from the depacketization means 2B for the instructed time.

  After the sequence in which the first TCF is transmitted from the sending G3FAX 1A and the receiving G3FAX 1G returns the first CFR response, the first page of PIX information is sent from the sending G3FAX 1A, and the fluctuation absorbing buffer 2A Start to accumulate PIX information (8C).

  On the left side of the flow, while the fluctuation absorbing buffer 2A accumulates PIX information, the data flow stops without sending PIX information to the receiving side G3FAX 1G, so pseudo MPS / EOM / TCF sending means 2G artificially transmits the second TCF to the receiving side G3FAX 1G to prompt CFR retransmission (8D).

  The MCF / CFR detection means 2F detects the CFR retransmitted from the receiving side G3FAX 1G (8E).

  Since the first CTF has already arrived at the transmitting side G3FAX 1A, the D / A conversion means 2D blocks the second CTF retransmitted according to the instruction of the control unit 2H (8F).

  If the buffer length is full at this point or if the buffer storage time limit has elapsed, VoP gateway 2 transmits the stored PIX information to the receiving side G3FAX 1G using the data frame with the preamble extended (8G → 8J) . Also, when the TCF is the third time in accordance with Recommendation T.30, PIX information is transmitted to the receiving side G3FAX 1G (8G → 8J).

  Conversely, if there is a margin in the buffer length or buffer accumulation limit time, or if the TCF has not reached 3 times, the process returns to 8D (8G → 8D).

  On the right side of the flow, the PIX information of the first page starts to be transmitted from the transmitting side G3FAX 1A in 8C, and at the same time, the fluctuation absorbing buffer 2A starts buffer accumulation (8H).

  When the buffer length becomes full or the buffer accumulation limit time has elapsed, the VoP gateway 2 transmits the accumulated PIX information to the receiving FAX 1G using a data frame obtained by extending the preamble (8I → 8J).

  When transmission of the PIX information on the first page is completed, MPS or EOM is transmitted from the transmission side G3FAX 1A.

  If the MPS or EOM has not been transmitted yet, the PIX information on the first page is ongoing, so the process returns to 8C (8K → 8C).

  When MPS or EOM is transmitted, PIX information on the second page starts to be transmitted from the transmitting side G3FAX 1A, so that the fluctuation absorbing buffer 2A starts to accumulate PIX information on the second page (8K in FIG. 6 → FIG. 7). 8L).

  The subsequent processing of the PIX information on the second page from 8L to 8T is the same as the processing of the PIX information on the first page from 8C to 8K, and is therefore omitted.

   Note that the flowchart in FIG. 6 assumes that the PIX information processing mode for the second page has been changed to that for the first page. That is, MPS is used instead of TCF, and MCR is used instead of CFR.

  In the case of PIX information processing on page 2 in FIG. 6, the difference between TCF and MPS and CFR and MCF compared to the processing on page 1 is the next page transmission from the sending FAX 1A at 8K. It depends on whether the preprocessing signal is EOM or MPS. In the case of EOM, since the PIX information transmission mode is changed, processing from phase (B) is performed and TCF and CFR are handled. In the case of MPS, there is no change in the PIX information transmission mode, and processing starts from phase (C), and MPS and MCF are handled.

  Further, when EOP comes from G3FAX 1A at the time of 8K and 8T, the process proceeds to phase (E), and the FAX communication is terminated and the line is disconnected.

  It should be noted that the position numbers 7A to 7G in FIG. 7 correspond to the processing positions 7A to 7G in FIG. 5 together with the item numbers 7A to 7G.

  The above is the operation for transmitting two pages of PIX information from the transmitting side G3FAX 1A to the receiving side G3FAX 1G using the G3FAX communication mode.

[Effect of the embodiment]
According to the present embodiment, even when the facsimile communication quality is improved by increasing the buffer length of the fluctuation absorbing buffer 2A and the buffer accumulation limit time during facsimile communication, the receiving facsimile apparatus 1G PIX information can flow smoothly, and as a result, the risk of adversely affecting the receiving facsimile machine 1G is reduced. The reason is that the packet read from the fluctuation absorbing buffer 2A is reverse-packetized to extend the reproduced PIX information preamble, and then transmitted to the receiving facsimile machine 1G.

  Further, according to the present embodiment, the buffer length and buffer accumulation limit time of the fluctuation absorbing buffer 2A can be automatically optimized. The reason is that it includes a control unit 2H that determines the buffer length and buffer accumulation limit time of the fluctuation absorbing buffer 2A based on the number of times of voice packet compensation performed in a predetermined time by the inverse packetization means 2B. It is.

  Furthermore, according to the present embodiment, the message (from the phase (B) which is a procedure performed prior to message transmission after call setup and the phase (D) which is a procedure for confirming that message transmission has been completed, (PIX information) When going to phase (C), which is the transmission procedure, the time from when the receiving facsimile machine 1G outputs an acknowledgment (MCF, CFR) to when the PIX information is sent may be shortened. it can. The reason is that when an acknowledgment (MCF, CFR) is returned from the facsimile machine 1G on the receiving side, the signals (MPS, TCF) that cause the acknowledgment (MCF, CFR) This is because it includes pseudo MPS / EOM / TCF sending means 2G that retransmits data to 1G. If this is not the case, the receiving side facsimile machine 1G sends an acknowledgment (MCF, CFR), and then the receiving side VoP gateway 2 sends the PIX information on the next page to the receiving side facsimile machine 1G. May take time (because packets are accumulated in the fluctuation absorbing buffer 2A with a long buffer length and buffer accumulation limit time). In such a case, there is a possibility of adversely affecting the receiving facsimile apparatus 1G.

[Other Embodiments of the Invention]
In the above-described embodiment, when the fluctuation absorbing buffer 2A detects the CED by the CED detection means 2E and determines that the receiving terminal is G3FAX, the fluctuation absorbing buffer length and the buffer accumulation limit are determined according to the instruction from the control unit 2H. It has a function of securing a time larger than that during a normal voice call. However, the trigger for increasing the fluctuation absorbing buffer length and the buffer accumulation limit time may be other than the detection of CED.

  First, during G3FAX communication, when the D / A conversion means 2D receives a specific dial tone input manually by the user on the receiving side, the control unit 2H sets the fluctuation absorption buffer length and the buffer accumulation time limit to the G3FAX communication mode. It is also possible to set.

  Second, at the time of G3FAX communication, the control unit 2H can set the fluctuation absorbing buffer length and the buffer accumulation time limit to the G3FAX communication mode when receiving a specific input from the user interface by the receiving user.

  Further, in the above-described embodiment, when the packet receiving side is a facsimile machine, both the buffer length of the fluctuation absorbing buffer and the buffer accumulation time limit are set longer than those during a voice call. It may be longer than during a voice call.

  Further, in the above-described embodiment, both the buffer length of the fluctuation absorbing buffer and the buffer accumulation limit time are changed according to the number of times of voice packet compensation performed during a predetermined time, but only one of them is changed. May be changed.

  In the above-described embodiment, the preamble extension time for the preamble extension means 2C is set using the user interface 2I. However, the control unit 2H sets the buffer length of the current fluctuation absorption buffer 2A or the buffer accumulation limit time. It may be calculated automatically based on the above. More specifically, it can be a value proportional to the buffer length or the buffer accumulation limit time.

  Further, in the above-described embodiment, the TCF, the MPS transmission interval, and the number of transmissions of the pseudo MPS / EOM / TCF transmission means 2G are set by the user interface 2I. However, the control unit 2H has the current fluctuation absorbing buffer. It may be automatically calculated based on the buffer length of 2A or the buffer accumulation limit time. More specifically, it can be set to a value proportional to the buffer length or buffer storage time.

[Effects of other embodiments]
According to another embodiment of the present invention, in addition to the effects obtained in the previous embodiment, the preamble extension time can be automatically optimized. This is because the control unit 2H that calculates the preamble extension time based on the buffer length of the fluctuation absorbing buffer 2A or the buffer accumulation limit time is provided.

  Furthermore, according to another embodiment of the present invention, the TCF, MPS transmission interval, and the number of transmissions can be automatically optimized. The reason is that it includes a control unit 2H that calculates the TCF, MPS transmission interval, and the number of transmissions based on the buffer length of the fluctuation absorbing buffer 2A or the buffer accumulation limit time.

3 is a block diagram showing a configuration example of an embodiment of a receiving-side VoP gateway 2 according to the present invention. FIG. FIG. 10 is a diagram for explaining operations of the fluctuation absorbing buffer 2A and the inverse packetizing means 2B in the embodiment of the present invention. It is a figure which shows an example of the HDLC frame of PIX information. It is a connection operation sequence flow of the G3FAX service. FIG. 10 is a diagram for explaining the operation of pseudo MPS / EOM / TCF sending means 2G. 6 is a flowchart showing an operation example of the reception side VoP gateway 2 (an operation example at the time of processing the first page). 7 is a flowchart showing an operation example of the reception side VoP gateway 2 (an operation example at the time of processing the second page). It is a block diagram which shows the structure of the conventional general VoP. It is a figure for demonstrating operation | movement of the conventional fluctuation absorption buffer 1E3 and the depacketization means 1E1. It is the figure which showed the G.144 voice delay guideline.

Explanation of symbols

1A, 1G ... G3FAX
1B, 1F… PBX
1C, 1E, 2… VoP gateway
1C1 ... A / D conversion means
1C2 ... Packet generation means
1E1,2B ... Reverse packetization means
1E2,2D ... D / A conversion means
1E3,2A ... Fluctuation absorption buffer
1D ... VoP network
2C… Preamble extension means
2E ... CED detection means
2F… MCF / CFR detection means
2G ... Pseudo MPS / EOM / TCF transmission means
2H ... Control unit
2I… User interface

Claims (6)

In a gateway with a fluctuation absorbing buffer,
When the packet receiving side is a facsimile device, the buffer storage time limit of the fluctuation absorbing buffer is set longer than that during voice call, and the packet read from the fluctuation absorbing buffer is depacketized to reproduce the PIX information. A configuration for performing voice packet compensation, a configuration for transmitting the PIX information reproduced by the configuration after extension to the facsimile apparatus, and detecting the number of times of voice packet compensation performed during a predetermined time , gateway, characterized in that they have the changing the buffer storage time limit of the fluctuation absorbing buffer based on the number of times detected. The gateway of claim 1 ,
A gateway having a configuration in which, when an acknowledgment is returned from the facsimile apparatus, a signal that has caused the acknowledgment is retransmitted to the facsimile apparatus in a pseudo manner. The gateway according to claim 2 , wherein
The acknowledgment is a message confirmation signal (MCF) or a reception preparation confirmation signal (CFR),
The gateway characterized in that the signal that causes the acknowledgment is a multi-page signal (MPS) or a training check signal (TCF). A fluctuation absorbing buffer capable of changing the buffer length and buffer accumulation time limit;
When the packet receiving side is a facsimile machine, a control unit that makes the buffer length and buffer accumulation time limit of the fluctuation absorbing buffer longer than that during voice call;
De-packetizing means for performing voice packet compensation when reproducing PIX information by depacketizing packets accumulated in the fluctuation absorbing buffer;
Preamble extension means for extending the preamble of the PIX information reproduced by the depacketization means;
A pseudo-sending unit that pseudo-sends a signal that has been sent from the facsimile device as a cause of an acknowledgment to the facsimile device; and
The control unit is
Detecting the number of voice packet compensations performed during a predetermined time by the inverse packetization means, and determining the buffer length and buffer accumulation limit time of the fluctuation absorbing buffer based on the detected number of times. Feature gateway. The gateway according to claim 4 , wherein
The control unit is
A gateway having a configuration for determining the number of transmissions and a transmission interval for pseudo-sending the signal that has caused the acknowledgment to the facsimile apparatus based on the determined buffer length or accumulation limit time. A method for improving facsimile communication quality in a gateway having a fluctuation absorbing buffer,
When the packet receiving side is a facsimile machine, a first step of setting a buffer storage time limit of the fluctuation absorbing buffer to be longer than that during a voice call;
A second step of performing voice packet guarantee when the packet read from the fluctuation absorbing buffer is depacketized to reproduce the PIX information;
A third step of transmitting to the facsimile apparatus after extending the preamble of the PIX information reproduced in the second step;
And a fourth step of detecting a number of times of voice packet compensation performed during a predetermined time and changing a buffer storage time limit of the fluctuation absorbing buffer based on the detected number of times. Quality improvement method.

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