CN1324869C - Method for implementing facsimile in next generation network - Google Patents

Abstract

A method for implementing fax in a next-generation network. When two media gateways communicate, one of the media gateways detects a fax start signal and notifies the media gateway controller; Send codec modification commands to the media gateways of both communication parties in parallel; if the ports of the media gateways at both ends do not change when the codec is modified, the fax will start; if the codec is modified, the local port of a media gateway changes , the media gateway controller sends a modification command to the media gateway at the opposite end to modify the remote attribute of the real-time transport protocol, and starts faxing after modification. Before the media gateway detects the fax start signal, it negotiates the fax codec while negotiating the voice codec. The invention reduces the time of fax switching and improves the success rate of fax negotiation.

Description

A Realization Method of Fax in Next Generation Network

technical field

The invention relates to the technical field of communication, in particular to a method for realizing fax in the next generation network (NGN).

Background technique

NGN (Next Generation Network) continues to develop, and there are two ways to implement the fax service in the NGN network as follows:

One is the transparent transmission mode, which uses G.711 codec, as shown in Figure 1, the media gateway controller (MGC) and the media gateway (MG) use the media gateway control protocol (H.248 or MGCP) for communication, The media gateway controller is responsible for controlling the call state related to the media gateway, and the media gateway completes the conversion of media formats between different networks under the control of the media gateway controller. A fax machine is respectively connected to a media gateway (MG), using G.711 codec in the IP network. G.711 is a 64kbit/s PCM (Pulse Code Modulation) codec standard for voice, using transparent transmission , pack the code stream information on the narrowband side intact into the IP message, and transmit it on the Internet through the Real-time Transport Protocol (RTP). The transparent transmission method is greatly affected by the transmission quality of the IP network. When using the G.711 codec method, the media gateway needs to adjust some functions of the gateway DSP (digital signal processor) according to the call type (such as fax, data, text or voice). parameters in order to improve the transmission quality. Before starting faxing, two fax machines conduct fax negotiation and adopt the same codec mode.

One is the T.38 method. The T.38 protocol is a real-time IP fax transmission standard introduced by the ITU-T (International Telecommunications Union). The T.38 protocol defines the process of fax system transmission between terminals in the IP network. The fax signal first After being modulated by the voice/fax gateway, it is transmitted in the form of IP fax packets in the IP network through TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). As shown in Figure 2, the media gateway (MG) parses the signals and data signals negotiated between fax machines, converts them into T.38 packets, and transmits them on the Internet through the Real-time Transport Protocol (RTP). Recover the original fax negotiation signal and data signal from the T.38 message. Compared with the transparent transmission method, using the T.38 codec method to implement fax over IP can improve the fax success rate and quality.

In the above two methods, the fax codec mode needs to be negotiated. Since the fax is an end-to-end negotiation method, when using the T.38 fax mode, the two MGs need to switch to the T.38 mode quickly, otherwise the two fax The probability of negotiation failure between machines increases. When using the T.38 method, after the DSP (digital signal processor) in some gateways is switched to T.38, the port number of the local end may be different from the voice port number before the switch, so the other end needs to be modified Remote properties of RTP (Real-time Transport Protocol). So the MGC needs to consider how to quickly switch to the T.38 mode.

Figure 3 is a flow chart of the existing fax negotiation implementation. In the prior art, only the codec of the voice is negotiated during the voice call, and whether to support T.38 is negotiated after the fax tone is detected. If T.38 is supported, the media gateway controller (MGC) first modifies the codec of one of the media gateways (MG2 in Figure 3), obtains the RTP local end attribute of the MG2, and then modifies another media gateway (as shown in Figure 3). MG1) codec and RTP remote attributes in 3, if the RTP local port of MG1 changes during switching, it is also necessary to notify MG2 to modify the RTP remote attributes. Taking the H.248 media gateway control protocol as an example, the process is as follows:

1. After negotiating the voice codec, MGC sends an ADD (increase) command to MG1, and obtains the RTP endpoint attribute of the local end in the ADD Reply (response).

2. The MGC sends an ADD command to MG2, and the remote RTP endpoint attribute is included in the ADD command, and the local RTP endpoint attribute is obtained in the ADD Reply.

3. The MGC sends a Modify (modify) command to the MG1 to modify the remote attribute of the RTP endpoint.

4. After the conversation between the two parties starts, the fax machine sends a fax start signal, and MG1 detects the fax start signal, and notifies the MGC through a Notify command.

5. After negotiating the fax codec, T.38 or transparent transmission can be used. If it is determined to use T.38, the MGC sends a Modify command to MG2 to modify the codec to T.38. Since the local RTP port number of MG2 may change, a new local RTP port number may be obtained in the Reply (response).

6. The MGC sends a Modify command to MG1 to modify the codec to T.38, with the remote RTP attribute. If the local RTP port number of MG2 changes, the Modify command also modifies the RTP remote attribute of MG1. Since the local RTP port number of MG1 may change, a new local RTP port number may be obtained in the Reply.

7. The MGC saves the local RTP port numbers of MG1 and MG2, and compares them with the received Reply to know whether the local RTP port numbers have changed. If the local RTP port number of MG1 is changed, MGC sends a Modify command to MG2 to modify the RTP remote attribute.

The disadvantage of the prior art is that after the fax start signal is detected, the fax codec negotiation process must be performed, and then at least two serial MODIFY (modification) operations must be performed before the T.38 mode can be completely switched. If the port numbers at one or both ends change, three serial MODIFY (modification) operations are required to switch to the T.38 mode. The time interval from the occurrence of the fax start event to the completion of the switchover is too long, which often results in unsuccessful fax negotiations.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the disadvantages of long time interval and often unsuccessful negotiation of the existing fax negotiation, provide a method for realizing fax in NGN network, reduce the switching time of fax, and improve the success rate of fax negotiation.

The technical scheme that the present invention adopts for solving the problems of the technologies described above is:

The implementation method of the fax in the next generation network includes the following steps:

When the media gateways at both ends communicate, one of the media gateways will notify the media gateway controller after detecting the fax start signal;

The media gateway controller sends a modification codec command to the media gateways of both communication parties in parallel according to the fax codec negotiated by both parties;

If the ports of the media gateways at both ends do not change when the codec is modified, the fax will start; if the local port of a media gateway changes when the codec is modified, the media gateway controller will send the modification to the media gateway at the opposite end Command to modify the remote properties of the real-time transport protocol, and start faxing after modification.

If the local ports of the media gateways at both ends are changed when the codec is modified, the media gateway controllers send modification commands to the media gateways at both ends at the same time to modify the remote properties of the real-time transport protocol.

Before the media gateway detects the fax start signal, it negotiates the fax codec while negotiating the voice codec.

The fax codec includes G.711 codec or T.38 codec.

Before the media gateway detects the fax start signal, the steps to establish a connection between the two parties are as follows:

a. After the voice and fax codec are negotiated, the media gateway controller sends an increase command (ADD) to a certain media gateway, and obtains the attributes of the real-time transport protocol (RTP) endpoint of this end in the return message;

b, the media gateway controller sends an increase command (ADD) to another media gateway, the remote RTP endpoint attribute is brought in the ADD command, and the local RTP endpoint attribute is obtained in the return message;

c. The media gateway controller sends a modification command (Modify) to the first media gateway to modify the remote attribute of the RTP endpoint;

d. After the modification is completed, the two parties establish a connection and talk.

The beneficial effects of the present invention are: in the process of the present invention, from the detection of the fax to the successful switching, the fax codec negotiation process is less than the existing scheme, and at the same time, when the port number is unchanged when the codec is switched, the current The 2 serial MODIFY commands of the prior art are modified into 1 parallel MODIFY command, and when the port number changes when switching codecs, the 3 serial MODIFY commands of the prior art are modified into at most 2 parallel ones MODIFY command, which greatly reduces the time from the occurrence of the fax start event to the completion of the switch, and improves the success rate of fax negotiation.

Description of drawings

Figure 1 is a schematic diagram of the implementation of fax in transparent transmission mode;

Figure 2 is a schematic diagram of the implementation of fax in T.38 mode;

Fig. 3 is the flow chart of the implementation of the existing fax negotiation;

FIG. 4 is a flow chart of the implementation of fax negotiation in the present invention.

Detailed ways

Below according to accompanying drawing and embodiment the present invention will be described in further detail:

The invention achieves the purpose of reducing the switching time of the fax and improving the success rate of the fax negotiation by optimizing the process of realizing the fax negotiation. During a voice call, the voice and fax codecs are negotiated at the same time, so that the fax codec negotiation process is advanced, and the time required for the codec switching to be completed after the fax start signal is detected is reduced. If T.38 is supported, after the fax tone is detected, a codec modification command is sent to the media gateways of both communication parties in parallel. If the local port of a media gateway changes when the codec is modified, the media gateway controller sends a modification command to the peer media gateway to modify the remote properties of the real-time transport protocol. If the local ports of the media gateways at both ends are changed when the codec is modified, the media gateway controllers send modification commands to the media gateways at both ends at the same time to modify the remote properties of the real-time transport protocol.

As shown in Figure 4, it is the flow chart of the realization of the fax negotiation of the present invention, and the flow process is as follows (taking H.248 as an example):

1. During a voice call, the codec of voice and fax is negotiated at the same time. The codec of fax can adopt T.38 mode or transparent transmission mode. In this embodiment, the codec of fax in T.38 mode is adopted. MGC sends an ADD (increase) command to MG1, and obtains the RTP endpoint attribute of the local end in the ADD Reply (return message).

The basic principle of negotiating codecs for voice calls is that the calling MGC passes the supported voice codecs to the called MGC (if the calling party and the called party are in the same MGC, they can be directly negotiated within the MGC), and the called party Codec capability and selection strategy Determine a voice codec and notify the caller. Negotiate voice and fax codecs at the same time, that is, when negotiating voice call codecs, the calling party brings the supported fax codecs at the same time, and the called party determines a fax codec according to the fax codecs supported by itself and the selection strategy. Inform the caller of the voice codec and also carry the selected fax codec.

2. The MGC sends an ADD command to MG2, and the remote RTP endpoint attribute is included in the ADD command, and the local RTP endpoint attribute is obtained in the ADD Reply.

3. The MGC sends a Modify (modify) command to the MG1 to modify the remote attribute of the RTP endpoint.

4. After the conversation between the two parties starts, the fax machine sends a fax start signal, and MG1 detects the fax start signal, and notifies the MGC through a Notify command.

5. Since the fax codec adopts T.38 mode, the MGC sends a Modify command to MG1 to modify the codec to T.38. Since some DSPs need to change the port number after switching to T.38, therefore, in Reply(return message) may obtain the new local RTP port number.

6. At the same time as the above step 5, MGC sends a Modify command to MG2 in parallel to modify the codec to T.38, and may also obtain a new local RTP port number in the Reply.

7. The MGC saves the local RTP port numbers of MG1 and MG2, and compares them with the received Reply to determine whether the local RTP port numbers have changed. If the local RTP port number of MG2 changes, the MGC sends a Modify command to MG1 to modify the RTP remote attribute.

8. If the local RTP port number of MG1 is changed, the MGC sends a Modify command to MG2 to modify the RTP remote attribute.

For the case where the fax codec is switched to T.38 codec, the port number may change. In the above steps 7 and 8, if the local port of a certain media gateway changes, the media gateway controller sends the media The gateway sends a modification command to modify the remote property of the real-time transport protocol, and starts faxing after modification. If the port numbers at both ends are changed, the media gateway controllers send modification commands to the media gateways at both ends in parallel to modify the remote properties of the real-time transport protocol. After the modification, the two parties start faxing.

For the case where the fax codec is switched to G.711 transparent transmission mode, the local RTP port numbers of MG1 and MG2 generally will not change, then after the above step 4, the MGC sends the Modify command to MG1 and MG2 in parallel to modify the codec to G. .711, after the modification is successful, both parties start faxing, so only one parallel Modify command is needed to complete the codec switching process after the fax signal starts.

In the process of the present invention, from the detection of the fax to the successful switching, the fax codec negotiation process is less than the existing scheme, and at the same time, when the port number is unchanged when the codec is switched, the two serial ports of the prior art The MODIFY command of the present invention is modified into 1 parallel MODIFY command, under the situation that the port number changes when switching codec, the 3 serial MODIFY commands of prior art are revised into at most 2 parallel MODIFY commands, greatly reduce like this The time from the occurrence of the fax start event to the completion of the handover is shortened, and the success rate of the fax negotiation is improved.

Claims (4)

1, the implementation method of faxing in a kind of next generation network is characterized in that, may further comprise the steps:

When the two ends media gateway is carried out communication, after an end media gateway wherein detects the fax commencing signal, the notice Media Gateway Controller;

The fax encoding and decoding that Media Gateway Controller is consulted according to both sides, the parallel simultaneously media gateway to communication two party send revises fax encoding and decoding order;

If when revising the fax encoding and decoding, the port of two ends media gateway does not change, then begin fax; If when revising the fax encoding and decoding, variation has taken place the local terminal port of a certain media gateway, then Media Gateway Controller sends the modification order to the media gateway of opposite end, and RTP far-end attribute is made amendment, and begins fax after having revised; If when revising the fax encoding and decoding, variation has taken place the local terminal port of two ends media gateway, then Media Gateway Controller is revised order to the media gateway transmission at two ends simultaneously, and RTP far-end attribute is made amendment.

2, the implementation method of faxing in the next generation network according to claim 1 is characterized in that: before media gateway detected the fax commencing signal, when consulting encoding and decoding speech, encoding and decoding were held consultation to fax.

3, the implementation method of faxing in the next generation network according to claim 2 is characterized in that: described fax encoding and decoding comprise G.711 encoding and decoding or T.38 encoding and decoding.

4, the implementation method of faxing in the next generation network according to claim 2 is characterized in that: before media gateway detected the fax commencing signal, the step that both sides connect was as follows:

A, after encoding and decoding hold consultation to voice and fax, Media Gateway Controller sends to a certain media gateway increases order, obtains the attribute of local terminal RTP end points in return messages;

B, Media Gateway Controller send to another media gateway increases order, is with far-end RTP endpoint attribute in increasing order, obtains local terminal RTP endpoint attribute in return messages;

C, Media Gateway Controller send to described first media gateway and revise order, revise the far-end attribute of RTP end points;

After d, modification were finished, both sides connected, and converse.

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