CN100359883C - A Method of Realizing V.34 High Speed Fax Through T.38 Protocol - Google Patents

Abstract

The present invention discloses a method for realizing a V. 34 high speed facsimile through a T. 38 protocol, which comprises: (1), after a called terminal under a V. 34 high speed facsimile method is switched to a communication line, a V21 Flag signal and a DIS signal, a V. 8 capability zone bit of which is set to be 1, are emitted; (2), according to the V21 Flag signal which is emitted by the called terminal, a media gateway controller emits a T. 38 facsimile switching command to a gateway of a calling terminal party and the gateway of the called terminal party; (3), the V. 8 capability zone bit of the DIS signal which is emitted by the called terminal is set to be 0 by the gateway of the called terminal party, and the setting information of the zone bit is transmitted to the gateway of the calling terminal party, which enables the calling terminal and the called terminal to establish a facsimile calling of a T. 38 mode. The present invention realizes the reliable transmission of high speed facsimile services under an NGN network.

Description

A Method of Realizing V.34 High Speed Fax Through T.38 Protocol

field of invention

The present invention relates to facsimile technology, in particular to a high-speed facsimile technology under the T.38 protocol (the transmission procedure and protocol of common facsimile on IP network).

Background technique

V.34 fax is a fax method that uses V.34 MODEM modulation and demodulation technology to achieve high-speed message transmission in accordance with the transmission procedures defined by the T.30 protocol. Due to the message transmission rate of V.34 fax (33.6K ) is greater than the message transmission rate of ordinary fax (up to 14.4K), so V.34 fax is also called V.34 high-speed fax.

V.34 high-speed fax has the following features:

1. Error Correction (ECM) must be used

2. Support 33.6K packet transmission rate

3. V.34 high-speed fax terminals belong to the G3 category of terminals

4. Start the fax according to the start procedure specified in V.8

Under the NGN (Next Generation Network) network, voice and fax services are carried by IP. Since fax signals are more sensitive to external interference, and the original reliable TDM (Time Division Multiplexing) transmission is changed to unreliable IP/UDP (Internet Protocol /User Datagram Protocol) transmission, so the fax service under NGN is greatly affected by IP network jitter and packet loss. To solve this problem, ITU-T (International Telecommunication Union - Telecommunication Standardization Department) has formulated the T.38 standard, but this standard only describes the procedures and protocols for ordinary fax transmission on the IP network, and does not involve V.34 high-speed fax.

At present, high-speed fax can be realized by adopting G.711 transparent transmission of FAX signals. However, this method has higher requirements on the IP network, requiring jitter < 10 ms and packet loss rate < 1%, but it is difficult for the IP network in actual commercial operation to meet the above requirements. If the jitter and packet loss rate of the IP network exceeds this threshold, high-speed fax calls will easily fail.

In addition, in the Chinese Patent Application Publication No. CN1417987A published on May 14, 2003 with the patent name "IP Network Communication Equipment with Facsimile Communication Function", it is disclosed that a V.34 high-speed The fax method is to detect the CNG and CED signals on the device to instruct to turn off functions such as fax tone detection, echo cancellation, and fluctuation absorption buffer control, and then transmit the fax signal as a voice signal in the voice channel. Since the patented method adopts voice transparent transmission of FAX signals, it does not solve the problem of using T.38 protocol to realize V.34 high-speed fax.

Contents of the invention

Therefore, in order to solve the problem that the T.38 protocol cannot be used to realize high-speed fax in the prior art, the present invention proposes a method for realizing V.34 high-speed fax through the T.38 protocol. The method includes the following steps:

1) Make the called terminal under the V.34 high-speed facsimile mode send the DIS signal that the V21 Flag signal and the V.8 capability flag bit are set to 1 after switching to the communication line;

2) the media gateway controller sends a T.38 fax switching command to the gateway of the calling terminal side and the gateway of the called terminal side according to the V21 Flag signal sent by the called terminal;

3) The gateway of the called terminal party sets the V.8 capability flag bit in the DIS signal sent by the called terminal to 0, and transmits it to the gateway of the calling terminal party, so that the calling terminal party The terminal and the called terminal establish a fax call in T.38 mode.

In the above method, said step 1) includes:

1-1) The called terminal sends a signal ANSam to the calling terminal;

1-2) Make the called terminal fail to receive the response of the calling terminal to the ANSam signal within the ANSam time limit;

1-3) The called terminal sends a DIS signal that the V21 Flag signal and the V.8 capability flag bit are set to 1 after the ANSam time limit expires.

Preferably, the steps 1-2) are realized by the following method: after detecting the ANSam response signal of the called terminal, the called terminal party gateway does not notify the media gateway controller, and filters the ANSam response signal from the voice stream .

Preferably, the above step 3) further includes: after the called terminal gateway detects the V21 Flag signal, report the V21Flag event to the media control gateway.

The called terminal and calling terminal may be G3 fax machines.

The invention solves the problem that the current T.38 standard cannot realize high-speed facsimile, and can realize reliable transmission of high-speed facsimile service under NGN network. In addition, because the present invention adopts T.38 to realize the high-speed facsimile service under the NGN network, thereby reducing the requirement on the IP network, and saving the extra expenses required for improving the QOS (quality of service) of the IP network.

Brief description of the drawings

Fig. 1 is a V.34 high-speed fax call establishment process;

Fig. 2 is the networking diagram that realizes V.34 high-speed facsimile by T.38 agreement of the present invention;

Fig. 3 is a flowchart of realizing V.34 high-speed facsimile through T.38 protocol of the present invention.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. Before the description, some terms involved in the present invention are described as follows. For more detailed description, refer to the content of the V.8 protocol and the T.30 protocol.

Response signal ANSam, which is an amplitude modulation signal, sent by a data circuit termination device supporting V.8 capability;

The CM signal, that is, the call menu, is sent by the data circuit termination device that supports V.8 capabilities, and provides the callers with the choice of modulation mode, protocol, and non-standard capabilities;

CNG single tone is 1100HZ single tone, used for fax, indicating the calling data circuit termination equipment;

The DIS signal is a digitally marked signal, which is provided to both calling parties for negotiation of modem mode, protocol, and fax capability;

The CI signal is a V.8 function indication signal, used to indicate that the calling terminal is a non-traffic terminal;

The JM signal, similar to the CM signal, is a call menu signal sent by a data circuit termination device supporting V.8 capability, and provides the calling party with a choice of modulation mode, protocol, and non-standard capabilities;

Phase B is the pre-message transmission process defined in the T30 fax procedure, consisting of capability labeling, capability selection, and capability confirmation command interactions;

V21Flag, that is, the V21 preamble sequence, is a 300bps modulated signal and consists of byte sequences with a continuous value of 0X7E.

In order to better illustrate the present invention, the conventional V.34 high-speed facsimile call establishment process will be described below in conjunction with FIG. 1 .

Figure 1 shows a conventional V.34 high-speed fax call setup process, the left side of the figure is the calling party process, and the right side is the called party process. As shown in Figure 1, the traditional process of establishing a V.34 high-speed fax call is as follows:

1. After the calling terminal detects the dial tone, it dials to make the called terminal ring. After the called terminal rings, it answers, automatically or manually switches to the communication line, and the calling terminal sends a CNG single tone signal , transmitted to the fax machine of the called terminal through the calling party gateway MG1, the media gateway controller MGC and the called terminal gateway MG2;

2. After switching to the communication line, the called terminal continuously sends the response signal ANSam to the calling terminal. The signal is an amplitude modulation signal, and is terminated by a data circuit supporting V.8 capability (here, the called terminal) issue. When the called terminal receives a valid CM signal response or the ANSam time limit expires (2.6 to 4.0 seconds), it stops sending the response signal;

3. After receiving the ANSam response signal sent by the called terminal, the calling party switches the calling terminal to the line, and the calling terminal sends a CNG single tone and starts the detection of the ANSam response signal;

4. If the calling terminal does not detect the ANSam signal, but receives the DIS signal or the V21 Flag signal with the V.8 capability flag set to 1 at 300bit/s, then start the V.8 procedure again by sending the CI signal ; If the calling terminal receives a DIS signal with a V.8 capability flag of 0 in 300bit/s mode, it enters the PHASE B stage of ordinary fax;

5. If the calling terminal detects the ANSam signal, it will respond with CM;

6. If the called terminal detects the CI signal while waiting for the response to the DIS signal, it will resend ANSam to enter the V.8 mode, otherwise it will enter the PHASE B stage of ordinary fax;

7. If the ANSam time limit expires and the called terminal has not received the CM response from the calling terminal, the called terminal uses the 300bit/s modulated binary code signal procedure to process it, that is, the V.8 capability flag in the DIS signal is set to 1 and Send a DIS signal to the calling terminal, and send a V21 Flag signal before sending the DIS signal; if the called terminal receives a CM response, it stops sending ANSam, performs the procedure described in Recommendation V.8, and replies to the JM signal;

8. After receiving the JM signal from the called terminal, the calling terminal judges whether it has a duplex instruction, and enters the half-duplex process or full-duplex process defined in Appendix F of T30 according to the judgment result.

Because T.38 has only defined the rules and protocols of ordinary facsimile transmission on the IP network, therefore, according to the method of the present invention, in order to realize the high-speed facsimile under the T.38 mode, adopt first to reduce the high-speed facsimile to ordinary facsimile, and then according to T.38 protocol to bear the fax business solution.

Fig. 2 is a network diagram for realizing high-speed facsimile through T.38 protocol of the present invention. In FIG. 2, PSTN refers to the public switched telephone network, the gateway MG1 is the gateway of the calling terminal, the fax machine FAX1 is the calling terminal, the gateway MG2 is the gateway of the called terminal, and the fax machine FAX2 is the called terminal. The fax machine FAX1 as the calling party and the FAX2 as the called party are first connected to their respective gateways MG1 and MG2 through the traditional PSTN, and then the respective gateways transmit data through the IP network.

Fig. 3 is a flow chart of the implementation of the present invention to realize V.34 high-speed facsimile through T.38 protocol. In this embodiment, both the calling fax machine and the called fax machine use G3 fax machines. Referring to Fig. 2 and Fig. 3, in order to carry out the conversion of V.34 mode to T.38 mode, in this embodiment of the present invention, utilize V21 Flag as the means of switching to T.38 mode. In addition, considering the traditional V.34 high-speed fax, after the ANSam/CM interaction fails (that is, the ANSam timeout does not receive a response), it is judged by the value of the V.8 capability flag bit in the DIS signal to start the V.8 procedure. The high-speed fax still performs ordinary fax, so in this embodiment of the present invention, the ANSam/CM interaction is forced to fail, and the V.34 high-speed fax is reduced to ordinary fax by using the V.8 capability flag bit in the DIS signal.

In the networking shown in Figure 2, after the gateway MG2 detects the ANSam signal of the fax machine FAX2, if it filters the signal and does not transmit the signal to the peer gateway MG1, the fax machine FAX1 does not receive the ANSam signal because it does not receive the ANSam signal. A CM signal will be sent. If the fax machine FAX2 still does not receive a response signal after the ANSam time limit expires, it will send a V21 Flag signal and a DIS signal with the V.8 capability flag bit set to 1. After the gateway MG2 receives the DIS signal, if the V.8 capability flag of the DIS signal is set to 0 and transmitted to the peer gateway MG1, the high-speed fax will be reduced to a normal fax, and then it can be carried according to the T.38 protocol Fax business up.

Below in conjunction with Fig. 2 and Fig. 3, specifically illustrate the steps of the embodiment of the present invention:

1. In the flow shown in FIG. 3 , the processes shown by numbers 1 to 7 are the same as the aforementioned process of establishing a V.34 high-speed fax call. That is, the calling terminal (calling fax machine Fax1) dials to the called fax machine Fax2, sends a CNG single tone, and detects whether the called fax machine sends a response. After the called fax machine Fax2 is switched to the line, it still continuously sends the answer signal ANSam to the calling fax machine Fax1;

2. After the gateway MG2 detects the ANSam signal of Fax2, it does not notify the MGC (media gateway controller), and filters the ANSam signal from the voice stream;

3. As shown by the label 8 in Figure 3, the fax machine Fax2 that previously output the ANSam signal sends out V21Flag after the ANSam time limit expires;

4. As shown in the labels 9 to 16 in Figure 3, after the gateway MG2 detects the V21 Flag, the V21 Flag event is reported to the MGC (media gateway controller), and the MGC sends a T. 38 fax switching command, the gateways at both ends enter T.38 fax mode;

5. As shown by the labels 17 to 18 in Fig. 3, the fax machine Fax2 sends out the V21Flag signal and the DIS signal, and the V.8 capability flag in the DIS signal is set to 0 by the gateway MG2, and then the DIS signal is sent to the At this time, the fax machines of both parties will establish a fax call in the normal fax mode.

The method of the invention can realize reliable transmission of high-speed facsimile service under the NGN network, and solve the problem that the current T.38 standard cannot realize high-speed facsimile. In addition, because the present invention adopts T.38 to realize the high-speed facsimile business under the NGN network, thereby reduced the requirement to IP network, can guarantee high-speed facsimile under the network conditions of 5% packet loss rate, 80ms network jitter, 600ms time delay. Reliable transmission of fax services. In this way, in the actual networking, the additional expenses needed to improve the QOS (Quality of Service) of the IP network are saved, such as: improving router performance, widening network bandwidth and other expenses.

The preferred embodiments of the present invention have been described in detail above for the purpose of illustration, but those of ordinary skill in the art should appreciate that various improvements, additions and substitutions are possible within the scope and spirit of the present invention , and are all within the scope of protection defined by the claims of the present invention.

Claims (7)

1. A method for realizing V.34 high-speed fax by T.38 protocol, comprising the following steps: 1) Make the called terminal under the V.34 high-speed facsimile mode switch to the communication line, send the DIS signal that the V21Flag signal and the V.8 capability flag bit are set to 1; 2) The media gateway controller sends a T.38 fax switching command to the gateway of the calling terminal side and the gateway of the called terminal side according to the V21Flag signal sent by the called terminal; 3) The gateway of the called terminal party sets the V.8 capability flag bit in the DIS signal sent by the called terminal to 0, and transmits it to the gateway of the calling terminal party, so that the calling terminal party The terminal and the called terminal establish a fax call in T.38 mode. 2. the method for realizing V.34 high-speed facsimile by T.38 protocol according to claim 1, is characterized in that, described step 1) comprises: 1-1) The called terminal sends a signal ANSam to the calling terminal; 1-2) Make the called terminal fail to receive the response of the calling terminal to the ANSam signal within the ANSam time limit; 1-3) After the ANSam time limit expires, the called terminal sends a V21Flag signal and a DIS signal with the V.8 capability flag bit set to 1. 3. the method for realizing V.34 high-speed facsimile by T.38 protocol according to claim 2, is characterized in that, described step 1-2) comprises: called terminal party gateway detects the ANSam signal of called terminal After that, the Media Gateway Controller is not notified and the ANSam signal is filtered out from the voice stream. 4. the method for realizing V.34 high-speed facsimile by T.38 protocol according to claim 1, is characterized in that, in described step 1), described called terminal sends V21Flag signal first, sends out V.8 ability afterwards DIS signal with flag bit set to 1. 5. the method for realizing V.34 high-speed facsimile by T.38 protocol according to claim 1, is characterized in that, described step 3) further comprises: after the gateway of described called terminal side detects V21Flag signal, report to the media control gateway. 6. The method for realizing V.34 high-speed fax through T.38 protocol according to any one of claims 1-5, characterized in that, the called terminal and calling terminal are G3 fax machines. 7. The method for realizing V.34 high-speed fax through T.38 protocol according to claim 6, characterized in that, the ANSam time limit is 2.6 seconds to 4.0 seconds.

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