CN101175330B - Inter-system switching method of dual-mode dual-standby terminal - Google Patents

Abstract

The invention discloses a method for switching between different systems of a dual-mode dual-standby terminal. In the method, when the 3G module in the dual-mode dual-standby terminal determines that the signal quality of the 3G network is lower than a preset threshold, the dual-mode dual-standby terminal is notified. The 2G module in the 2G network, and the 2G module sends a special call request message to the network side entity of the 2G network; after receiving the special call request message, the network side entity of the 2G network directly assigns the 2G network to the dual-mode dual-standby terminal. network resources, and perform corresponding subsequent handover processing. By applying the present invention, when the dual-mode dual-standby terminal is in a place where the signal coverage of the 3G network is poor, the ongoing communication can be smoothly switched to the 2G network.

Description

Inter-system switching method of dual-mode dual-standby terminal

technical field

The invention relates to different system switching technology, in particular to a method for switching between different systems of a dual-mode and double-standby terminal.

Background technique

In the initial stage of the third generation mobile communication (3G) system network deployment, the 3G network can only provide discontinuous hotspot coverage on the basis of 2G full network coverage. In order to provide continuous coverage, both the terminal and the network need to support from the 3G network Inter-system (RAT) handover to 2G network. In order to meet the above requirements, dual-mode single-standby terminals and dual-mode dual-standby terminals emerged as the times require. In the following, the Time Division Multiplexing Code Division Multiple Access (TD-SCDMA) system in the 3G system and the Global System for Mobile Communications (GSM) in the 2G system are taken as examples for illustration.

TD/GSM dual-mode single-standby terminal supports two modes of TD-SCDMA and GSM. In these two modes, the same number can be used to automatically switch modes between TD-SCDMA and GSM in the idle state, so that Inter-RAT measurements are performed during communication, and then inter-system handover is performed. The existing TD/GSM dual-mode single-standby terminal is in the process of TD-SCDMA communication, and the method for switching from the TD-SCDMA network to the GSM network includes the following steps:

Step 1: During TD-SCDMA communication, the TD/GSM dual-mode single-standby terminal measures the signal quality of the GSM neighboring cell. The controller (RNC) reports an inter-RAT measurement report. Among them, both Node B and RNC are network entities in the 3G access network——Radio Network Subsystem (RNS).

Step 2: RNC makes a handover decision according to the received measurement report, and when the result of the handover decision is handover, sends a relocation request message to the Mobile Switching Center (MSC), and notifies the GSM neighbor cell as the target GSM cell MSC.

In the description of the second step above, it is assumed that the MSC is a network-side switching entity shared by the 3G network and the 2G network, that is, the shared MSC can serve as a network-side switching entity to communicate with the RNS in the 3G network, or It can be used as a switching entity on the network side to communicate with the 2G access network - the base station subsystem (BSS). Wherein, the BSS includes a base station controller (BSC) and a base station (BTS).

In practical applications, the MSC of the 3G network and the 2G network can also be set separately. At this time, the MSC of the 3G network communicates with the RNS, the MSC of the 2G network communicates with the BSS, and the information exchange between the 3G network and the 2G network will be through the 3G network The MSC is carried out with the MSC of the 2G network.

Step 3: The MSC initiates a handover request to the BSC where the target GSM cell is located, and allocates a ground circuit for the TD/GSM dual-mode single-standby terminal.

Step 4: The target BSC allocates air interface resources for the TD/GSM dual-mode single-standby terminal, and sends a handover request response to the MSC, indicating that resource allocation is successful.

Step 5: The MSC initiates a handover command to the TD/GSM dual-mode single-standby terminal through the source RNC (that is, the serving RNC in the TD-SCDMA network where the TD/GSM dual-mode single-standby terminal is currently located).

Step 6: The TD/GSM dual-mode single-standby terminal switches to the GSM mode, and the MSC switches the voice channel to the GSM side and releases the relevant resources on the TD-SCDMA side.

So far, the handover of the TD/GSM dual-mode single-standby terminal from the TD-SCDMA network to the GSM network is completed.

The above method for the TD/GSM dual-mode single-standby terminal to switch from the TD-SCDMA network to the GSM network requires that the terminal must support inter-RAT measurement, otherwise it cannot be realized. Moreover, on the one hand, the above method needs to increase the measurement control command and the measurement reporting process on the air interface; on the other hand, it is necessary for the RNC to make a handover decision and initiate a handover request according to the measurement report reported by the terminal, resulting in a relatively complicated handover process and time spent on handover longer.

The TD/GSM dual-mode dual-standby terminal supports the coexistence of TD-SCDMA and GSM modes. The TD/GSM dual-mode dual-standby terminal includes a TD module and a GSM module, which are used to process the TD-SCDMA mode of the terminal respectively. communication and communication in GSM mode. The TD/GSM dual-mode dual-standby terminal uses the TD-SCDMA number and the GSM number to communicate under these two modes respectively, and can reside in the cells of these two different modes at the same time, and simultaneously Send and receive signals. However, this type of terminal does not support inter-RAT measurements in the idle state and communication process, nor does it support inter-RAT handover commands, so the above-mentioned TD/GSM dual-mode single-standby terminal cannot be used to switch from TD-SCDMA network to GSM network. Switch between different systems.

In order to solve the problem that the TD/GSM dual-mode dual-standby terminal switches from the TD-SCMA network to the GSM network during the communication process, the usual method is: when the TD/GSM dual-mode dual-standby terminal moves to the edge of the TD-SCDMA network coverage, The voice communication quality will deteriorate with the deterioration of the signal quality. At this time, the TD/GSM dual-mode dual-standby terminal can prompt the user to end the communication on the TD-SCMA side, and the GSM will use the GSM number to initiate a new call on the GSM network. Re-establish communication. This method cannot guarantee the continuity of user communication at the edge of the TD-SCMA network, resulting in poor user experience.

It can be seen from the above that the existing technology needs to interrupt the current communication of the dual-mode dual-standby terminal to switch from the 3G network to the 2G network, so that the dual-mode dual-standby terminal cannot smoothly switch the ongoing communication from the 3G network to the 2G network.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method for inter-system switching of a dual-mode, dual-standby terminal, which can smooth ongoing communication when the dual-mode, dual-standby terminal is in a place with poor 3G network signal coverage. switch to 2G network.

In order to achieve the above object, the technical solution of the present invention is specifically realized in the following way:

A method for switching between different systems of a dual-mode dual-standby terminal, used to switch the ongoing communication of the dual-mode dual-standby terminal in the third-generation mobile communication 3G network to the second-generation mobile communication 2G network, comprising:

A. When the 3G module in the dual-mode dual-standby terminal determines that the signal quality of the 3G network is lower than a preset threshold, notify the 2G module in the dual-mode dual-standby terminal;

B. The 2G module sends a special call request message to the network side entity of the 2G network according to the notification of the 3G module;

C. If the network side entity of the 2G network receives the special call request message, allocate network resources of the 2G network for the dual-mode dual-standby terminal;

D. The dual-mode dual-standby terminal, the network-side entity of the 2G network, and the network-side entity of the 3G network switch the ongoing communication of the dual-mode dual-standby terminal in the 3G network to the network resources of the 2G network conduct.

The sending of the special call request message by the 2G module to the network side entity of the 2G network in step B includes:

The 2G module will make the network-side entity of the 2G network determine that the ongoing communication of the dual-mode dual-standby terminal in the 3G network needs to be switched to the 2G network information in the call request message, and send the call request message to A network side entity of the 2G network.

Further comprising before said step C:

After the network-side entity of the 2G network receives the call request message, the network-side entity of the 2G network determines the ongoing communication needs of the dual-mode dual-standby terminal in the 3G network according to the information carried in the call request message. Information about switching to the 2G network determines that the received call request message is a special call request message.

The network side entity of the 2G network includes: a mobile switching center MSC and a base station subsystem BSS where the 2G cell where the dual-mode dual-standby terminal is currently located;

The network side entity of the 2G network described in step C allocates network resources of the 2G network to the dual-mode dual-standby terminal including:

C1. The MSC allocates a ground circuit for the dual-mode dual-standby terminal, and sends an assignment request message to the BSS;

C2. The BSS allocates air interface resources to the dual-mode, dual-standby terminal, and notifies the dual-mode, dual-standby terminal of the allocated air interface resources through a channel assignment message.

The network-side entity of the 2G network includes: MSC and the BSS where the 2G cell where the dual-mode dual-standby terminal is currently located; the network-side entity of the 3G network includes: MSC and the current dual-mode dual-standby terminal The radio network subsystem RNS where the 3G cell is located;

Said step D comprises:

D1. The dual-mode dual-standby terminal switches to a 2G channel according to the allocated air interface resources, and establishes synchronization with the BSS;

D2. The BSS sends an assignment complete message to the MSC;

D3. The MSC switches the voice channel between the 3G number and the communication peer user to the voice channel between the 2G number and the communication peer user according to the stored binding relationship between the 2G number and the 3G number;

D4. The MSC notifies the RNS to release the network resources of the 3G network allocated for the dual-mode dual-standby terminal.

The binding relationship between the 2G number and the 3G number is notified by the dual-mode dual-standby terminal to the network-side entity of the 2G network through a registration message, and is stored by the network-side entity of the 2G network.

The binding relationship between the 2G number and the 3G number is preset and saved by the network side entity of the 2G network.

The 2G module will make the network side entity of the 2G network determine that the ongoing communication of the dual-mode dual-standby terminal in the 3G network needs to be switched to the 2G network. The information carried in the call request message is:

The 2G module sets the called number in the call request message as a preset special number, and sets the calling number as the 2G number of the dual-mode dual-standby terminal.

The preset special number is preset in the dual-mode dual-standby terminal and the network-side entity of the 2G network.

Further include before said step A:

The 3G module periodically measures the signal quality of the 3G network, and compares the measured signal quality of the 3G network with the preset threshold.

It can be seen from the above technical scheme that when the 3G module in the dual-mode dual-standby terminal determines that the signal quality of the 3G network is lower than the preset threshold, the present invention notifies the 2G module in the dual-mode dual-standby terminal, and the 2G module The method of sending a special call request message to the network side entity of the 2G network; and after receiving the special call request message, the network side entity of the 2G network directly allocates network resources of the 2G network for the dual-mode dual-standby terminal, And perform a corresponding subsequent switching processing manner.

Compared with the switching method of the existing dual-mode single-standby terminal described in the background art, the technical solution provided by the above-mentioned present invention is different in that: on the one hand, the switching decision is made by the 3G module in the dual-mode dual-standby terminal according to the signal of the 3G network According to the quality situation, there is no need for the terminal to perform inter-RAT measurement, nor does the terminal need to report the inter-RAT measurement report to the RNC, nor does the RNC need to make a handover decision; on the other hand, after the handover is decided, the 2G The module actively initiates a special call request message to the network side, and the network side directly allocates network resources of the 2G network for the dual-mode dual-standby terminal according to the particularity of the call request message, and performs corresponding subsequent switching processing; thus making The technical solution of the present invention does not require any modification to the existing air interface, and also simplifies the switching process and reduces the time spent on switching.

Compared with the existing dual-mode dual-standby terminal switching method described in the background art, the technical solution provided by the present invention can make the user feel no call drop, thereby realizing smooth migration of communication.

Description of drawings

FIG. 1 is a schematic flowchart of a method for switching between different systems of a dual-mode dual-standby terminal according to the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples.

The main idea of the present invention is that when the 3G module in the dual-mode dual-standby terminal determines that the signal quality of the 3G network is lower than the preset threshold, it sends a switching request message to the 2G module in the dual-mode dual-standby terminal, and the 2G module sends The network-side entity of the 2G network sends a special call request message; then the network-side entity of the 2G network directly allocates network resources of the 2G network to the dual-mode dual-standby terminal according to the received special call request message; finally, the dual-mode The dual-standby terminal, the network-side entity of the 2G network, and the network-side entity of the 3G network switch the ongoing communication of the dual-mode dual-standby terminal in the 3G network to the allocated network resources of the 2G network.

FIG. 1 is a schematic flowchart of a method for switching between different systems of a dual-mode dual-standby terminal according to the present invention. Referring to FIG. 1 , the network entities involved in the inter-system handover in the present invention include: MSC, RNS and BSS. In this embodiment, the 2G network and the 3G network share the MSC as an example. For the application scenario in which the 2G network and the 3G network respectively set the MSC, it can be carried out by referring to this embodiment and subsequent corresponding descriptions of the present invention. The inventive method shown in Fig. 1 comprises the following steps:

Step 101: The dual-mode dual-standby terminal is currently in the 3G network and is communicating with a communication peer user. While communicating, the dual-mode dual-standby terminal periodically measures the signal quality of the 3G network.

Step 102: When the 3G module in the dual-mode dual-standby terminal determines that the signal quality of the 3G network is poor to a certain extent, it decides to switch to the adjacent GSM network, and actively initiates the switching process.

As described in the background technology, an example of a dual-mode dual-standby terminal: a TD/GSM dual-mode dual-standby terminal includes a TD module and a GSM module. Correspondingly, the dual-mode dual-standby terminal described in this embodiment includes a 3G module and a 2G module. The modules are respectively used to process the communication of the dual-mode dual-standby terminal in the 3G mode and the communication in the 2G mode.

The signal quality threshold can be preset, and when the signal quality of the 3G network measured by the 3G module in the dual-mode dual-standby terminal is lower than the preset signal quality threshold, it can be determined that the signal quality of the 3G network has deteriorated to a certain extent, At this point, the handover process may be actively initiated.

In this step, the initiated active switching is: the 3G module inside the dual-mode dual-standby terminal notifies the 2G module that the current communication of the dual-mode dual-standby terminal needs to be switched from the 3G network to the 2G network. The implementation manner of the notification may be: the 3G module sends a call switching request message to the 2G module.

In the terminal device, the internal modules can communicate through the internal communication interface of the terminal. Therefore, the call switching request message in this step can be transmitted through the communication interface between the 3G module and the 2G module. In specific implementation, a new message may be defined as the call switching request message, or an existing message may be correspondingly expanded as the call switching request message, and of course other methods may also be used for implementation.

Step 103a-Step 103b: The 2G module sends a special call request message to the network side entity of the 2G network according to the notification of the 3G module.

According to the relevant regulations of existing GSM standard, the call that terminal initiates will all be delivered to MSC by BTS and BSC and handle, as shown in Figure 3 the call request message (SetupRequest) in the step 103a and the call management service request in the step 103b ( CM Service Request). For simplicity of description, in the figure, the BTS and BSC in the 2G access network are combined together and shown as BSS. In the subsequent description of the present invention, the network-side entities of the 2G network include: BSS and MSC.

In this step, the special call request message is a concept relative to a call request message in a common sense. The special call request message in the present invention may be a newly defined message, or a message formed by carrying some special information in a call request message in the usual sense.

Preferably, the 2G module can carry the information that enables the MSC to determine that the ongoing communication of the dual-mode dual-standby terminal in the 3G network needs to be switched to the 2G network in the call request message, so that the call request message is called a special call request message, and send the special call request message to the MSC through the BSS.

When the call request message carries information that enables the MSC to determine that the ongoing communication of the dual-mode dual-standby terminal in the 3G network needs to be switched to the 2G network, the following methods can be adopted:

Generally speaking, the call request message needs to carry the calling number and the called number, and the calling number and the called number are common numbers.

In the special call request message of the present invention, the called number can be set as a preset special number, and the calling number can be set as the 2G number of the dual-mode dual-standby terminal. This special number is specially used to indicate that the ongoing communication of the terminal on the 3G network is switched to the 2G network. In this way, when the called number in the call request message received by the MSC is the special number, it can know that the terminal needs to transfer the current The ongoing communication is switched from the 3G network to the 2G network, so that corresponding follow-up processing is performed according to the follow-up processing flow of the present invention.

The special number mentioned in this step can be pre-configured in the dual-mode dual-standby terminal and the MSC.

In this step, when the MSC does not support the technical solution of the present invention (that is: cannot recognize the special call request described in the present invention), the dual-mode dual-standby terminal can prompt the user: the 3G network signal is not good; When continuing in the network, the current communication can be interrupted and the call can be re-initiated through the 2G network. For example: when adopting the above-mentioned technical solution of setting the called number in the call request message as a special number, if the MSC cannot recognize that this is a special call request through the special number, it will return the called number to the dual-mode dual-standby terminal Unreachable or empty number error, at this time, the dual-mode dual-standby terminal can prompt the user that the 3G network signal is not good through the terminal display screen or prompt sound.

Step 104: According to the special called number in the received call request message, the MSC judges that this is a call request that needs to switch the ongoing communication of the calling dual-mode dual-standby terminal in the 3G network to the 2G network. Therefore, It is determined that network resources of the 2G network need to be directly allocated to the dual-mode dual-standby terminal without any processing on the called party.

Steps 105a to 105b: the network side entity of the 2G network allocates resources for the calling terminal, that is, allocates network resources of the 2G network for the dual-mode and dual-standby terminal.

In this step, resources can be allocated to the dual-mode dual-standby terminal according to the relevant standards of the existing 2G network, specifically:

In step 105a, the MSC allocates a ground circuit for the dual-mode dual-standby terminal, and sends an assignment request message (Assignment Request) to the BSS, requesting the BSS to allocate air interface resources for the dual-mode dual-standby terminal;

In step 105b, the BSS allocates air interface resources to the dual-mode dual-standby terminal, and notifies the dual-mode dual-standby terminal of the allocated air interface resources through a channel assignment message (Channel Assignment Message).

The A port message and the air interface message used in the above process are consistent with the messages defined in the existing 2G network related standards.

Step 106: After receiving the channel assignment message, the dual-mode dual-standby terminal switches to the 2G channel according to the allocated air interface resources, and establishes synchronization with the BSS.

Step 107: The BSS sends an assignment complete message (Assignment Complete) to the MSC.

Step 108: According to the stored binding relationship between the 2G number and the 3G number, the MSC switches the voice channel between the 3G number and the corresponding user to the voice channel between the 2G number and the corresponding user, namely: The voice session on the 3G network side is switched to the 2G network side.

In this step, the binding relationship between the 2G number and the 3G number is: the 2G number and the 3G number used in the same dual-mode dual-standby terminal. For the application scenarios of sharing the MSC and setting the MSC separately, the operations in this step can be implemented in the following ways:

1. For the application scenario where 2G network and 3G network share MSC

At this time, the home location register (HLR) of the 2G network and the 3G network will also be shared, and the binding relationship between the 2G number and the 3G number can be stored in the HLR. The 3G number corresponding to the calling 2G number in the call request message. After the 3G number is determined, the terrestrial circuit information of the communication peer user communicating with the 3G number can be obtained to complete the switching of the voice path.

Of course, the binding relationship between the 2G number and the 3G number is also stored in a related database, or in a specially configured storage device for storing the binding relationship.

2. For the application scenarios of setting MSC separately for 2G network and 3G network

The binding relationship between the 2G number and the 3G number can be stored in a device that can be obtained by the MSC of the 2G network, for example: the HLR of the 2G network, a related database or a storage device specially set up for storing the binding relationship. After the MSC of the 2G network determines the 3G number corresponding to the calling 2G number in the special call request message according to the binding relationship, the MSC of the 3G network is notified of the 3G number, and the MSC of the 3G network acquires the corresponding 3G number corresponding to the 3G number in the special call request message. The ground circuit information of the communication peer user whose number is communicating is used to complete the switching of the voice channel.

It can be seen that regardless of whether the MSCs of the 2G network and the 3G network are shared or set separately, preferably, the binding relationship between the 2G number and the 3G number can be stored in the relevant entity on the network side of the 2G network.

There are several ways to realize the binding relationship between the 2G number and the 3G number above:

1) The dual-mode dual-standby terminal notifies the network-side entity of the 2G network of the binding relationship between the 2G number and the 3G number through a registration message, such as notifying the MSC; and saves it by the relevant network-side equipment of the 2G network, such as: saving it in the HLR In, or in a related database, or in a storage device specially set up for saving the binding relationship.

2) The operator manually configures in the above-mentioned relevant equipment on the network side of the 2G network.

Step 109a-Step 109b: The MSC notifies the 3G access network to release the network resources of the 3G network allocated by the 3G network side for the dual-mode dual-standby terminal. in particular:

In step 109a, MSC sends release command (Iu Release Command) to RNS;

In step 109b, the RNS sends a radio bearer release message (RBRelease) to the dual-mode dual-standby terminal.

So far, the inter-system switching method of the dual-mode dual-standby terminal of the present invention is completed.

As can be seen from the above-mentioned embodiments, the method for switching between different systems of a dual-mode, dual-standby terminal of the present invention takes the method of notifying the dual-mode, dual-standby terminal when the 3G module in the dual-mode, dual-standby terminal determines that the signal quality of the 3G network is lower than a preset threshold. The 2G module in the terminal sends a special call request message to the network-side entity of the 2G network by the 2G module; and the network-side entity of the 2G network, after receiving the special call request message, adopts a direct method for the dual-mode The dual-standby terminal allocates network resources of the 2G network and performs corresponding subsequent handover processing.

Compared with the switching method of the existing dual-mode single-standby terminal described in the background art, the technical solution provided by the above-mentioned present invention is different in that: on the one hand, the switching decision is made by the 3G module in the dual-mode dual-standby terminal according to the signal of the 3G network According to the quality situation, there is no need for the terminal to perform inter-RAT measurement, nor does the terminal need to report the inter-RAT measurement report to the RNC, nor does the RNC need to make a handover decision; on the other hand, after the handover is decided, the 2G The module actively initiates a special call request message to the network side, and the network side directly allocates network resources of the 2G network to the dual-mode dual-standby terminal according to the particularity of the call request message, and performs corresponding subsequent switching processing; thus making The technical solution of the present invention does not require any modification to the existing air interface, and also simplifies the switching process and reduces the time spent on switching.

Compared with the existing dual-mode dual-standby terminal switching method described in the background art, the technical solution provided by the present invention can make the user feel no call drop, thereby realizing smooth migration of communication.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A different-system switching method of a dual-mode dual-standby terminal, used to switch the ongoing communication of the dual-mode dual-standby terminal in the third generation mobile communication 3G network to the second generation mobile communication 2G network, its features In, including: A. When the 3G module in the dual-mode dual-standby terminal determines that the signal quality of the 3G network is lower than a preset threshold, notify the 2G module in the dual-mode dual-standby terminal; B. The 2G module sends a special call request message to the network side entity of the 2G network according to the notification of the 3G module; C. If the network side entity of the 2G network receives the special call request message, allocate network resources of the 2G network for the dual-mode dual-standby terminal; D. The dual-mode dual-standby terminal, the network-side entity of the 2G network, and the network-side entity of the 3G network switch the ongoing communication of the dual-mode dual-standby terminal in the 3G network to the network resources of the 2G network conduct. 2. The method according to claim 1, wherein the 2G module in step B sends a special call request message to the network side entity of the 2G network comprising: The 2G module will make the network-side entity of the 2G network determine that the ongoing communication of the dual-mode dual-standby terminal in the 3G network needs to be switched to the 2G network information in the call request message, and send the call request message to A network side entity of the 2G network. 3. method according to claim 2, is characterized in that, before described step C, further comprises: After the network-side entity of the 2G network receives the call request message, the network-side entity of the 2G network determines the ongoing communication needs of the dual-mode dual-standby terminal in the 3G network according to the information carried in the call request message. Information about switching to the 2G network determines that the received call request message is a special call request message. 4. The method according to claim 1, wherein the network side entity of the 2G network comprises: a mobile switching center MSC and a base station subsystem BSS where the 2G cell where the dual-mode dual-standby terminal is currently located; The network side entity of the 2G network described in step C allocates network resources of the 2G network to the dual-mode dual-standby terminal including: C1. The MSC allocates a ground circuit for the dual-mode dual-standby terminal, and sends an assignment request message to the BSS; C2. The BSS allocates air interface resources to the dual-mode, dual-standby terminal, and notifies the dual-mode, dual-standby terminal of the allocated air interface resources through a channel assignment message. 5. The method according to claim 4, wherein the network-side entity of the 2G network comprises: MSC and the BSS where the 2G cell where the dual-mode dual-standby terminal is currently located; the network-side entity of the 3G network The entities include: MSC and the radio network subsystem RNS where the 3G cell where the dual-mode dual-standby terminal is currently located; Said step D comprises: D1. The dual-mode dual-standby terminal switches to a 2G channel according to the allocated air interface resources, and establishes synchronization with the BSS; D2. The BSS sends an assignment complete message to the MSC; D3. The MSC switches the voice channel between the 3G number and the communication peer user to the voice channel between the 2G number and the communication peer user according to the stored binding relationship between the 2G number and the 3G number; D4. The MSC notifies the RNS to release the network resources of the 3G network allocated for the dual-mode dual-standby terminal. 6. The method according to claim 5, wherein the binding relationship between the 2G number and the 3G number is notified by the dual-mode dual-standby terminal to the network side entity of the 2G network through a registration message, and the 2G network's Entity storage on the network side. 7. The method according to claim 5, wherein the binding relationship between the 2G number and the 3G number is preset and saved by a network side entity of the 2G network. 8. The method according to claim 2, wherein the 2G module will make the network side entity of the 2G network determine that the ongoing communication of the dual-mode dual-standby terminal in the 3G network needs to be switched to the 2G network The information carried in the call request message is: The 2G module sets the called number in the call request message as a preset special number, and sets the calling number as the 2G number of the dual-mode dual-standby terminal. 9. The method according to claim 8, wherein the preset special number is preset in the dual-mode dual-standby terminal and the network-side entity of the 2G network. 10. The method according to any one of claims 1 to 9, characterized in that, before step A, further comprising: The 3G module periodically measures the signal quality of the 3G network, and compares the measured signal quality of the 3G network with the preset threshold.

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