WO2007098657A1

WO2007098657A1 - A method and a network for trasmitting multiservices of the junction center based on ip

Info

Publication number: WO2007098657A1
Application number: PCT/CN2006/003411
Authority: WO
Inventors: Hu Li
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-03-03
Filing date: 2006-12-14
Publication date: 2007-09-07
Also published as: CN101031006A; CN101031006B

Abstract

A method for transmitting multiservices of the junction center based on IP includes: before the call is established, the Media Gateway Controllers of the two communication parties negotiate and configure codec schemes for transmitting services, and negotiate the bearer resource; during the call, the Media Gateway detects the signal or event relating to the service and notifies the Media Gateway Controller respectively; the Media Gateway Controller determines the service type according to the notified signal or event relating to the service, and notifies the opposite Media Gateway Controller of controlling and switching the corresponding codec scheme; the Media Gateways of the two communication parties renegotiate the bearer resource and update the effective transmission of the multiservices in the method, thereby achieving the fax and data service on the MSC IP bearer and resolve the switching of the voice fax in the junction center. There is also a multiservice transmission network of the junction center based on IP.

Description

IP-based tandem office multi-service method and network

Technical field

The present invention relates to a method for transmitting IP-based communication services of a tandem office in a mobile communication system, and more particularly to a method for transmitting communication services such as voice, facsimile, data, and the like of a gateway in a mobile communication system.

Background technique

With the rapid advancement of communication technologies, people's expectations and requirements for personal communication are also increasing. Therefore, mobile operators need to pay special attention to aspects such as user interface and service quality that directly affect the experience of users using mobile services. The high-bandwidth, multi-service, high-quality features of the 3rd Generation (3G) mobile communication system have greatly attracted the mobile consumer market, but some problems still existing in 3G technology will be solved if they are not solved. To a certain extent, it restricts the expansion of the market and affects the development of mobile operations.

In the future 3G network architecture, the mobile network is no longer limited to the circuit switching mode, and gradually evolves into a packet Internet Protocol (IP) network. In addition, with the development of traditional communication networks, the Internet, and mobile communication networks, the integration of networks is an inevitable trend. The Next Generation Nerwork ("NGN") is based on the Internet Protocol (IP). The packet-switched network is the core network, and the control and bearer are separated. Various access technologies coexist, and a new generation network of existing networks is integrated to meet the needs of future broadband multimedia communications.

NGN is a traditional switched telephone network based on circuit switching (Public Switched)

The Telephone Network (referred to as "PSTN") has gradually taken the step of packet switching. It carries all the services of the original PSTN network, and simultaneously offloads a large amount of data transmission to the IP network to alleviate the heavy load of the PSTN network. And new features of IP technology have added and enhanced many new and old businesses. NGN is a product of a variety of network convergence based on time-division multiplexed PSTN voice network, Integrated Services Digital Network (ISDN), IP-based packet network, and mobile communication network. Integrated services such as voice, video, and data on the Internet have become possible.

NGN as defined by the International Telecommunication Union Telecommunication Standardization Sector ("ITU-T") It is a packet-based network that can provide telecommunication services, transmission technologies that can utilize multiple broadband and Quality of Service (QoS), and its service-related functions are independent of the underlying transmission-related technologies. Users provide free access to different service providers, and support for universal mobility makes it possible to provide consistent and universal service to users.

In the mobile domain, the traditional Transit Mobile Switching Center (TMSC) is mainly based on Time Division Multiplex (TDM) bearer. The fixed bandwidth of TDM is 64Kbit/s. Can be used to deliver voice, data and fax services. As NGN evolves, traditional TDM bearers evolve to IP bearers. The MSC is also divided into a media gateway (Media Gateway, called "MGW") and a Media Gateway Controller ("MGC") due to the separation mechanism of bearer and control.

IP-bearing-based service transmission can use multiple coding methods, such as ITU-T's G.729, G711 protocol, and so on. Among them, the G.729 data rate is 8Kbit/s, which can transmit voice services (voice on IP, called "VoIP"), but cannot transmit data and fax services. The data rate of G.711 is 64Kbit/s. In theory, data and fax services can be transmitted. However, due to the unreliability of IP transmission, if packet loss occurs, data transmission and fax data cannot be realized normally.

In addition, the G.711 Redundant (G.711 Red) codec scheme for transmitting voice, fax, and data services is applicable not only in IP networks, but also because of the introduction of redundancy mechanisms. reliability. There is also an Internet real-time fax protocol T.38 dedicated to fax services, which is more efficient than G.711Red. Therefore, T.38 codec is generally used when transmitting fax services.

There are more and more types of services based on IP transmission, and it is necessary to accurately determine the type of service and select an appropriate codec scheme for transmission. If the service type cannot be accurately determined, the selected codec solution cannot meet the requirements of service transmission, and may not be transmitted normally.

In addition, an optional codec (Coder & Decoder, referred to as "Codec") for out-of-band negotiation is used between the MGCs in the tandem office for the use of a Bearer independent call control protocol ("BICC"). The BICC signaling does not have the function of selecting an IP bearer address. The MGW's bearer voice address is negotiated through an IP Bearer Control Protocol (IPBCP). The principle of the tandem office networking is shown in Figure 1. There is a Mc interface between the MGC and the MGW for the MGC to issue commands or The MGW reports the event. The data bearing surface between the two MGWs is implemented based on IP. The negotiation between the signaling layer MGCs and the BICC does not involve specific bearer address information. Therefore, when the bearer plane is implemented, the MGW performs IPBCP negotiation through the MGC to determine the IP address of the communication and the User Data Protocol (User Data Protocol). "UDP") Information such as the port number.

Therefore, this involves another problem. In the case of multi-service transmission, after the handover of the service coding and decoding scheme is solved, how to update the bearer plane information based on the EPBCP negotiation is solved. For example, in the voice and fax phase, because the call setup phase cannot be well distinguished, in the IPBCP negotiation, the current negotiation mode is used to negotiate the virtual IuFP Codec or the Codec and UDP port number used by the actual voice. The actual speech codec is G729 negotiated by the MGC through the BICC. The virtual codec is also used when switching to the fax stage, but the voice codec is modified by the MGC to G.711 or G.711Red after BICC negotiation, and the bearer address may or may not change. Therefore, in the process of the gateway based on IP multi-service transmission, it is necessary to solve the problem of switching the codec scheme and updating the IP bearer plane information.

Since it is often impossible to distinguish between voice and non-language other fax or data services during the call setup phase, a solution is to use a bearer or code that supports voice, data, and fax simultaneously before the call is established. If G.711/G.711Red encoding is used in IP bearer, it can support various services at the same time to ensure the smooth flow of services. However, the problem with this method is that if the IP bearer does not use the G.711/G.711Red encoding directly, the IP bandwidth will be seriously wasted. Because the main service of the TMSC is voice, the ordinary voice can fully meet the requirements by using G.729 encoding. . The bandwidth required by G.711/G.711Red is larger. If this coding method is used regardless of the waste of bandwidth, it is obviously unable to solve the problem of this shield.

Another solution is to determine the fax and data services by signaling before the call is established, and then transmit the fax and data services using the G.711/G.711 Red code to realize the transmission of various services. The disadvantage of this method is that the fax and data services are not accurately determined by signaling before the call is established, and a specific environment is required to judge. The existing network conditions are not available. For example, the call initiated by the fixed-line fax machine is the same as the call signaling of the ordinary public switched telecommunication network (PSTN), in this case, before the call. Signaling cannot be detected, so it is not accurate to judge from the signaling. Another solution is to establish a voice channel when the call is established, and transmit the fax or modulation solution by detecting the fax, modem (Modulation & Demodulation, referred to as "Modem") tone modification channel for G.711 transparent transmission or T.38. Adjust data services. However, the bearer address (IP address and UDP port number) negotiated through IPBCP does not need to be modified during the entire call. In this solution, the bearer address of the entire process does not change. The same IP address and UDP port number are used in the voice and fax phases. If the processing is not good, the noise and bearer processing may be troublesome. Packet identification and packet discarding are required. And other protection operations. Therefore, for the switching of services of different natures in the communication process, it is preferable to assign different port numbers and addresses to the IP bearers. Summary of the invention

In view of the above, the main purpose of the present invention is to provide an IP-based tandem office multi-service transmission method and network, which can implement efficient transmission of multiple services, for example, enabling the IP bearer networking of the TMSC to meet and implement voice, fax, and Transmission of data and other services.

To achieve the above objective, the IP-based tandem office multi-service transmission method provided by the present invention includes the following steps:

A. Before the call is established, the media gateway controllers of the two communication parties negotiate and configure a codec scheme for transmitting the service, and negotiate the bearer resources;

B. During the call, the media gateway detects service related signals or events and reports them to the media gateway controller respectively.

The media gateway controller determines the service type according to the reported service related signal or event, and notifies the media gateway controller of the opposite end to control the corresponding codec solution;

The media gateways of both D-communications perform renegotiation and update of the bearer resources.

The invention provides an IP-based tandem office multi-service transmission network, package! a media gateway controller and a media gateway, wherein, before the call is established, the media gateway controllers of the two communication parties negotiate and configure a codec scheme for transmitting the service, and negotiate the bearer resources; during the call, the media gateway detects the service related The signal or the event is reported to the media gateway controller separately; and the media gateway controller determines the service type according to the reported service related signal or event, and notifies the media gateway controller of the opposite end to control the corresponding codec solution, and the communication is The media gateways of both parties carry out renegotiation and update of the 7-load resources.

Since the present invention can perform corresponding codec according to different service related signals or events The switching of the case, and triggering the renegotiation and update of the bearer resources of the communication parties due to the switching of the codec scheme, the service transmission method can not only realize the multi-service transmission based on the DP network, but also improve the utilization of the network bandwidth and improve Network flexibility and communication efficiency, but also broaden the scope of application of mobile communications and future networks, improve user experience, and promote the development of communication networks. For example, fax and data services are implemented on the TMSC IP bearer to solve the problem of voice fax switching in the case of the tandem office. At the same time, the complexity of data processing is reduced, and the voice stream and the fax stream are prevented from interfering with each other, thereby improving service quality.

DRAWINGS

1 is a schematic structural diagram of an IP bearer networking of a TMSC;

2 is a flow chart of an embodiment of a method in accordance with the present invention;

3 is a flow chart of a negotiation and signaling interaction of a codec scheme according to an embodiment of the method according to the present invention;

4 is a flow chart of signaling interaction of a voice service switched to a fax service according to an embodiment of the method of the present invention.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings.

The invention proposes an IP-based multi-service transmission scheme, and uses multiple codec schemes (G.729, G.711, G.711Red, T.38, etc.) to transmit voice (VoIP), fax (Fax), and data (Data ), modulation and demodulation (Modem) and other services. After the call is established by using the voice channel, the service type is determined according to the in-band call signal. For services such as fax and data, it is necessary to switch to a codec scheme with a larger bandwidth. For high-speed fax services, a more efficient codec scheme is adopted. Due to the detection of in-band call signaling, the service type can be accurately determined. In the end, it is possible to efficiently transmit various services with a more flexible IP bearer.

The outband negotiation codec scheme is implemented by the BICC between the MGCs, and the bearer resources such as the IP address or the UDP port number are negotiated and allocated through the IPBCP between the MGWs. The BICC ignores the actual bearer resource information when establishing the call and codec scheme switching. After the coding and decoding scheme is switched, the bearer resources are reconfigured by IPBCP negotiation.

In IP-based service transmission, the transmission between the calling MGW and the called MGW is performed by IP. Bearer, service transmission is roughly divided into several steps of negotiation, detection, handover, and update, that is, the primary and the called parties negotiate the alternate codec scheme and bearer resources of the corresponding service type, and then the MGW detects and services from the inband signaling. Relevant feature signaling, the detection result is reported to the MGC, and the MGC determines the service type, and finally performs the control operation of switching the configuration corresponding codec scheme, and after the handover, sends an IPBCP to renegotiate the bearer resource, and releases the old resource while using the new resource communication. Resources.

In the first embodiment of the present invention, the basic steps of the entire multi-service transmission process include out-of-band negotiation, detection signal, codec switching, bearer re-negotiation, etc. The flow chart of this process is shown in FIG.

In step 201, before the call is established, the MGCs of the two communicating parties negotiate and configure a codec scheme for the transport service, and implement a negotiated allocation of bearer resources by the IPBCP between the MGWs. Through the BICC signaling interaction, the originating MGC first sends all feasible codec schemes supported by the local office. These schemes include Codec that supports various services, such as G.729 supporting voice services and G supporting voice and fax services. .711/G.711Red, etc., after receiving the negotiation request, the MGC of the opposite end sends back the codec scheme supported by the local office, so that the two parties negotiate to obtain the codec scheme that is jointly supported.

The provision of the data service and the fax function needs to be completed by the MGC and the MGW. Since the ordinary voice code (such as G729) of the IP bearer cannot support the fax service, it is necessary to switch to the type of the fax that supports the fax when the fax event is detected, such as switching to G. 711Red, T.38 encoding.

The codec out-of-band negotiation is performed between the MGCs of the communication party before the call is established. After the call response is successful, if the G.711Red or T.38 code is supported after the negotiation, the MGC sends a fax/data signal to the gateway at the TDM endpoint. The fax event has an in-band detection request, and the MGW detects the report to the MGC. The MGC modifies the voice code of the IP endpoint to the code of the transmittable fax/data (G711Red, T.38) through the codec modification process, thereby implementing the fax/data function. .

In step 202, during the call, the media gateway detects the service related signal or event and reports it to the media gateway controller. After the BICC out-of-band negotiation ends, the communication parties shall send the service-related signals or events to the MGW to request various signals or events for detecting related services, such as fax services, detecting CNG signals or CED and V21 signals, MGW. These signals are detected during the call and reported to the MGC, noting that the detection is in progress throughout the call, rather than based on the judgment of the call setup phase, which enables accurate determination of service cuts. Change.

In step 203, during the call, the media gateway controller determines the service type according to the reported service related signal or event, and notifies and controls to switch the corresponding codec scheme. In this step, the bearer resource related information is ignored when switching the codec scheme. When the MGC receives the reported service related signals and events, it can determine whether to start the corresponding service. For example, when the CNG signal is generated, the fax (FAX) service is started. At this time, the MGC sends a request to notify the MGW to switch the corresponding Codec. The MGC of the local office also informs the peer MGC through the BICC signaling, and the peer MGC sends a request to notify the MGW to switch the corresponding Codec.

In step 204, the handover of the codec scheme triggers the bearer resource renegotiation and update, and the new codec scheme delivered by the MGC triggers the bearer resource renegotiation. On the Mc interface between the MGC and the MGW, the MGC indicates the IPBCP re-negotiation in the Local descriptor through H.248 signaling.

In step 205, the MGW initiates negotiation with the peer according to the configured bearer resource information of the corresponding service type. The MGW sends the pre-configured bearer resource information. For example, for the fax service, the preset UDP port number of the fax service is sent, which is different from the previous voice channel, and can avoid confusion. The peer confirms the UDP port number, and the negotiation is completed, that is, the new bearer resource is successfully allocated. In step 206, after the negotiation is successful, the two parties use the new bearer resource for service transmission and release the original bearer resource. That is, the voice communication of the original UDP port is closed, and the new port is used for the fax service.

In the above description, the signaling layer of the communication parties adopts the BICC, and the MGC uses the BICC out-of-band negotiation for the coding and decoding scheme of the transmission service. In other embodiments of the present invention, other feasible signaling may also be adopted, which is not limited to the BICC. Similarly, when the MGW negotiates bearer plane resource allocation, it can be implemented by, but not limited to, IPBCP. In addition, the bearer resource generally refers to the IP address and the UDP port number. Of course, under other IP-based high-level protocols, it is also another port number or other type of bearer resource.

The key to the present invention lies in the specific operations of BICC and IPBCP negotiation and the processing methods of network elements such as MGC. In the embodiment shown in FIG. 2, the bearer resources need to be negotiated mainly in two phases: In the call setup phase (corresponding to step 201), the MGC sends H.2 ⁴ 8 signaling to the MGW. In the IPBCP negotiation, the MGW configures the bearer resource and negotiates the virtual codec scheme. During the call, when the codec scheme is switched (corresponding to step 204), the MGC sends the H.248 signaling to the MGW, so that the MGW ignores the bearer resource information. And notifying the codec scheme that the MGC switches, and triggering the IPBCP-based bearer resource renegotiation between the MGWs.

The implementation method of the specific bearer plane is described as follows, in the call setup phase, on the MC interface,

The MGC supports IPBCP negotiation by carrying the corresponding information in the H.248 Local Descriptor. The IPBCP negotiates the local and peer UDP port numbers, and the virtual Codec'. IuFP.

The BICC does not care about the actual physical bearer address. In the related command, the method of not paying attention to the actual bearer address (indicated by "-" in the following) is used to send the subsequent Codec and other information to the MGW in the Local descriptor. The process of codec switching.

Table 1 shows the H.248 signaling that supports IPBCP renegotiation and is used to switch the codec scheme of the fax service. Among the key parts of the Local descriptor: "m=image - udptl t38" means that the MGC uses "-" to indicate the use of the original address and triggers the U38's T38 transmission, that is, switching Codec and ignoring the resources; "a = T38FaxRateManagement:transferredTCF , indicating end-to-end training; "a = T38FaxUdpEC: T38UDPRedundancy, indicating redundancy with redundant packets; "a = T38MaxBitRate: 14400," indicating that the maximum rate of FAX is 14400 bps.

It can be seen that the new codec sent by the MGC triggers the renegotiation of the IPBCP, and the MGW initiates negotiation with the other party according to the port number of the configured fax service type. After the negotiation is successful, the new port is used for fax traffic, and the previous voice stream is closed.

Table 1 H.248 signaling supporting IPBCP renegotiation

MEGACO/1.0 [123.123.123.4]: 55555

Transaction = 15 {

Context = 2000 {

Modify = RTP/1 {

Media {

Stream = 1 {

LocalControl

{ipfax/faxstate = Negotiating;

}

Local {

V=0

c=IN IP4 - m-image - udptl t38 //MGC uses "to indicate the use of the original address, and triggers T38 a = T38FaxRateManagement: transfen-edTCF" uses end-to-end training a = T38FaxUdpEC: t38UDPRedundancy //Redundant redundancy余 a = T38MaxBitRate: 14400 //FAX maximum rate is 14400bps }; change to T.38 in the IP connection

}

Figure 3 shows the Codec negotiation and event detection request flow before the call setup in the embodiment of Figure 2, taking the inter-office BICC signaling as an example:

First, Code & Decode ("Codec") is used for out-of-band negotiation. The MGC1 of the calling and receiving office sends an Initial Address Message ("IAM") to the MGC2, which carries the calling end, that is, MGC1. The side-supported codec schemes, such as G.729, GJllRed, T.38, etc.; the MGC2 of the called gateway determines which Codec is locally supported after receiving the message, and sends these Codecs back, so that it is convenient to negotiate and confirm. In the Codec scheme, MGC2 returns an Application Transport Message (""" message to the MGC 1 and carries the codec scheme determined after negotiation.

Next, the MGC 2 returns a called ringing message (Address Complete Message ("ACM") and an answer message (Answer Message, "ANM") to the MGC1. Then, the calling and called MSC initiates a data fax signal and a fax event detection request at the TDM endpoint. MGC1 sends a Modify message to MGW1 to initiate a request for detecting service related signaling; MGW1 returns a Modify response message. On the other hand, MGC2 sends a Modify message to MGW2 to initiate a request for detecting service related signaling; MGW2 returns a Modify response message. Here, the detection request notifies the MGW of the in-band service-related signaling, such as the V21 signaling of the Fax service, the CM (Fax), etc., and monitors the MGC.

In the embodiment shown in FIG. 2, when the MGW detects a service-related signal or event and reports it to the corresponding MGC, the MGC sends a request to instruct the MGW to switch to a codec scheme of the corresponding service type; the MGC passes the BICC. The coding and decoding scheme of the corresponding service type is indicated by the peer MGC. The peer MGC sends a request to indicate that the corresponding MGW switches to the codec scheme of the corresponding service type.

After the MGC initiates in-band detection to the MGW, the MGC processes the services according to the signals reported by the MG according to the reporting signals, and can support the normal FAX, high-speed FAX, and MODEM data services. As shown in Figure 4, taking the ordinary fax service as an example, the signals to be detected are CNG or CED and V21. In the figure, the gateways at both ends of the negotiation result support G.711Red.

After the voice channel is established, the normal fax, MGW1 reports CNG or CED, V21 signals, and MGC1 notifies the MGW to switch to the Fax channel according to the V21 signal (CED cannot be used as the basis for MGC switching);

MGC1 issues modify, and the IP endpoint is modified to Codec to G711Red.

Carry the G.711Red code to the peer through BICC, and ask MGC2 to modify Codec to

G.711Red.

MGC2 issues modify, and the modified IP endpoint Codec is G.711Red.

After the Codec modification is completed, the IPBCP negotiation initiated is changed to the port number of the Fax service as described above, and the port of the voice service is closed.

In the description of the foregoing embodiments, the service types are voice service VoIP, fax service Fax, data service data, modem service Modem, and the like. The codec scheme has G.729 codec scheme, G.711 redundant codec scheme, and T.38 codec scheme. Of course, in the future, there are new service types and corresponding codec solutions, which are still applicable to the present invention, and can realize multi-service transmission with good compatibility. The main difference between the embodiment of the present invention and the prior art is that, by using BICC out-of-band negotiation, the MGC first negotiates the codec scheme that can be switched, and then the MGC issues a command to enable the MGW to start detecting signals related to the fax data service. In the process of call communication, the MGW reports the detected event or signal, and the MGC determines and triggers the switching of the codec schemes on both sides of the dialog, such as switching to G.711 or T.38, and establishing through IPBCP negotiation. The bearer plane is used to implement the fax and data services on the MSC IP bearer, and the voice fax is switched in the case of the tandem office. The MGC ignores the actual address information during the handover, and then completes the codec and then sends the Modify Codec sent by the MGC. The message triggers the IPBCP to re-negotiate the port number and IP address, and then updates the IP address and port number information, triggers the Modify message of the IPBCP through the Modify message to modify the port number, starts transmitting the fax service, and closes the original voice stream, avoiding the use. Same port number or IP address.

Those skilled in the art can understand that the description of the technical details in the foregoing embodiments takes some common application scenarios as an example, and gives specific parameter settings, etc., and can be flexibly set according to actual conditions in practical applications to better realize the invention. The purpose is not to impair the essence and scope of the invention.

Although the present invention has been illustrated and described with reference to the preferred embodiments of the present invention, those skilled in the art will understand that various changes may be made in form and detail without departing. The spirit and scope of the invention.

Claims

Rights request

An IP-based tandem office multi-service transmission method, characterized in that it comprises the following steps:

During the call, the media gateway detects the service related signals or events and reports them to the media gateway controller.

The IP-based tandem office multi-service transmission method according to claim 1, wherein the media gateways of the two communication parties perform renegotiation and update of the bearer resources according to the following steps: The bearer resource information of the corresponding service type is set to negotiate with the peer end.

After the negotiation is successful, the media gateway controllers of the two communicating parties use the new bearer resources for service transmission and release the original bearer resources.

The IP-based tandem office multi-service transmission method according to claim 2, wherein in step A, the media gateway controllers of the two communication parties control the out-of-band negotiation for transmission by using an irrelevant call control The codec scheme of the service.

The IP-based tandem office multi-service transmission method according to claim 3, wherein the media gateways in step D renegotiate the bearer resources by using an IP-based bearer control protocol.

5. The IP-based tandem office multi-service transmission method according to claim 4, wherein:

In step A, the media gateway controller sends H.248 signaling to the media gateway to perform the IP-based bearer control protocol negotiation, and configures a bearer resource and a virtual codec solution.

In step D, the media gateway controller sends H.248 signaling to the media gateway, so that the media gateway ignores the bearer resource information, and notifies the codec of the codec that is switched by the media gateway, and triggers the The media gateway renegotiates based on the IP bearer control protocol.

The IP-based tandem office multi-service transmission method according to claim 5, wherein the bearer resource is an IP address or a port number.

The IP-based tandem office multi-service transmission method according to claim 6, wherein before the call is established, the media gateway controllers of the two communication parties negotiate and configure the codec for the transmission service according to the following steps. Program:

The media gateway controller of the calling gateway sends an initial address message, where the codec scheme supported by the local office is carried;

The media gateway controller of the called gateway sends back an application transmission message, where the codec scheme after the negotiation is carried;

The called end sends back a ringing and response message;

The media gateway controller of the master called gateway sends a request for detecting the service related signal or event to the corresponding media gateway.

8. The IP-based tandem office multi-service transmission method according to claim 7, wherein in step C,

The media gateway controller sends a request to the media gateway to instruct the media gateway to switch to a codec scheme corresponding to the service type;

And the media gateway controller indicates, by using the bearer-independent call control, a codec scheme that indicates a service type corresponding to the peer media gateway controller;

The peer media gateway controller sends a request to indicate that the corresponding media gateway switches to the codec scheme of the corresponding service type.

The IP-based tandem office multi-service transmission method according to any one of claims 1 to 8, wherein the service comprises: a voice service, a fax service, and a data service.

10. The IP-based tandem office multi-service transmission method according to claim 9, wherein the codec scheme comprises: a G.729 codec scheme, a G.711 codec scheme, and a G.711 redundancy. Codec solution, T.38 codec solution.

11. An IP-based tandem office multi-service transmission network, comprising a media gateway controller and a media gateway, wherein, before the call is established, the media gateway controllers of the two communication parties negotiate and configure a codec scheme for transmitting the service, And negotiating the bearer resource; during the call, the media gateway detects the service related signal or event and reports it to the media gateway controller respectively; and the media gateway controller detects the service related signal or event The service type is determined, and the media gateway controller of the opposite end is notified to switch the corresponding codec scheme, and the media gateways of the two communication parties perform renegotiation and update of the bearer resources.