CN109600805B

CN109600805B - Communication method, device and system

Info

Publication number: CN109600805B
Application number: CN201811574898.8A
Authority: CN
Inventors: 龚磊; 唐道红
Original assignee: Huawei Technical Service Co Ltd
Current assignee: Huawei Technical Service Co Ltd
Priority date: 2018-12-21
Filing date: 2018-12-21
Publication date: 2021-02-23
Anticipated expiration: 2038-12-21
Also published as: WO2020125559A1; CN109600805A

Abstract

The embodiment of the application discloses a communication method, a device and a system, wherein the method comprises the following steps: when the terminal falls back to the first communication system from the resident 4G communication system during the CS service, the first access network device of the first communication system may obtain the CSFB identifier corresponding to the terminal; when the terminal performs the CS service and falls back from the first communication system to the second communication system, the first access network device may transmit the CSFB identifier to the second access network device in the second communication system, so that after the second access network device receives the CSFB identifier, the second access network device starts a process of quickly returning to the 4G communication system for the terminal according to the CSFB identifier when the terminal finishes the CS service. By adopting the method and the device, the terminal can quickly return to the 4G communication system after the CS service of the terminal is finished.

Description

Communication method, device and system

Technical Field

The present application relates to the field of communications technologies, and in particular, to a communication method, apparatus, and system.

Background

With the development of communication technologies, a terminal can also support multiple communication systems from a second generation mobile communication system (2G), a third generation mobile communication technology system (3G), and then a fourth generation mobile communication system (4G). The services supported by different communication systems may be different, for example, a Long Term Evolution (LTE) communication system belonging to a 4G communication system supports Packet Switch (PS) services and Circuit Switch (CS) services, while a 2G or 3G communication technology supports CS services. The CS service may be a voice service, so that when the terminal of the 4G communication system needs to implement the CS service, the terminal needs to fall back to the 2G/3G network, and complete the circuit domain service in the 2G/3G network. Based on this scenario, the terminal has a problem that it cannot return to the 4G communication system after the CS service is finished.

Disclosure of Invention

The embodiment of the application provides a communication method, a communication device and a communication system, so that a terminal can quickly return to a 4G communication system after a CS service of the terminal is finished.

In a first aspect, a communication method is provided for an embodiment of the present application, and is applied to a communication system, where the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, and the method is performed by a first access network device in the first communication system, and the method includes:

when a terminal falls back to a first communication system from a resident 4G communication system during a CS service, first access network equipment acquires a CSFB identifier corresponding to the terminal; when the terminal falls back to the second communication system from the first communication system when performing the CS service, the first access network device transmits the CSFB identifier to the second access network device in the second communication system, so that the second access network device starts a process of quickly returning to the 4G communication system for the terminal according to the CSFB identifier when the terminal finishes the CS service after receiving the CSFB identifier.

In the first aspect, when the terminal performs a CS service, the access network device of the second communication system may identify that the terminal is a CSFB user when the terminal falls back from the resident 4G communication system to the first communication system and falls back from the first communication system to the second communication system, and start a procedure of quickly returning to the 4G communication system for the terminal when the terminal ends the CS service, which saves time for the terminal to return to the 4G communication system and improves efficiency of returning to the 4G communication system by the terminal.

Optionally, in a scenario that a terminal falls back to the first communication system from the resident 4G communication system, the terminal performing the CS service may refer to the terminal initiating the CS service. Since the 4G communication system does not support the CS service, at this time, the 4G communication system will drop the terminal back to the first communication system through a redirection manner or a handover manner.

Optionally, in a scenario that the terminal falls back from the first communication system to the second communication system, the CS service performed by the terminal may refer to a stage that the terminal initiates the CS service or may be in a process of performing the CS service.

With reference to the first aspect, in a possible implementation manner, when the first communication system is a 3G communication system and the second communication system is a 2G communication system, a specific process of the first access network device transmitting the CSFB identifier to the second access network device in the second communication system may be: the method comprises the steps that a first access network device sends a migration request to a 2G-3G core network device, wherein the migration request carries a CSFB identifier, the migration request is used for sending a handover request to a second access network device after the 2G-3G core network device receives the migration request, and the handover request carries the CSFB identifier, wherein the 2G-3G core network device is a core network device shared by a 2G communication system and a 3G communication system, or the 2G-3G core network device comprises a core network device of the 2G communication system and a core network device of a 3G. In this way, the first access network device may transmit the CSFB identification to the second access network device.

With reference to the first aspect, in a possible implementation manner, when the first communication system is a 2G communication system and the second communication system is a 3G communication system, a specific process of the first access network device transmitting the CSFB identifier to the second access network device in the second communication system may be: the method comprises the steps that a first access network device sends a handover request to a 2G-3G core network device, wherein the handover request carries a CSFB identifier, the handover request is used for sending a migration request location request to a second access network device after the 2G-3G core network device receives the migration request, and the migration request carries the CSFB identifier, wherein the 2G-3G core network device is a core network device shared by a 2G communication system and a 3G communication system, or the 2G-3G core network device comprises a core network device of the 2G communication system and a core network device of a 3G. In this way, the first access network device may transmit the CSFB identification to the second access network device.

With reference to the first aspect, in a possible implementation manner, the access network device in the 3G communication system is an RNC, the access network device in the 2G communication system is a BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is an MSC.

With reference to the first aspect, in a possible implementation manner, for a case that the terminal falls back from the first communication system to the second communication system, the following may be performed: in the case that the signal strength value of the serving cell serving the terminal in the first communication system is smaller than the signal strength threshold, it means that the signal strength value of the serving cell serving the terminal is poor, which makes it difficult to provide a better service to the terminal, and therefore the terminal is dropped from the first communication system to the second communication system to provide a better service for the CS service of the terminal.

With reference to the first aspect, in a possible implementation manner, for a case that the terminal falls back from the first communication system to the second communication system, the following may be performed: and in the case that the load of a service cell for providing service for the terminal in the first communication system is greater than the load threshold value, dropping the terminal from the first communication system to the second communication system to provide better service for the CS service of the terminal.

In a second aspect, a communication method is provided for an embodiment of the present application, and is applied to a communication system, where the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, and the method is executed by a second access network device in the second communication system, and the method includes:

when the terminal performs the CS service, the terminal falls back to the first communication system from the resident 4G communication system, and falls back to the second communication system from the first communication system, the second access network device receives the CSFB identifier corresponding to the terminal transmitted by the first access network device in the first communication system, and when the terminal finishes the CS service, the second access network device starts a flow for quickly returning to the 4G communication system to the terminal according to the CSFB identifier.

In the second aspect, when the terminal performs the CS service, the access network device of the second communication system may identify that the terminal is a CSFB user when the terminal falls back from the resident 4G communication system to the first communication system and falls back from the first communication system to the second communication system, and may start a procedure of quickly returning to the 4G communication system for the terminal when the terminal ends the CS service, which saves time for the terminal to return to the 4G communication system and improves efficiency of returning to the 4G communication system by the terminal.

With reference to the second aspect, in a possible implementation manner, when the first communication system is a 3G communication system and the second communication system is a 2G communication system, a specific process of the second access network device receiving the CSFB identifier corresponding to the terminal transmitted by the first access network device in the first communication system may be:

the second access network device receives a handover request sent by the 2G-3G core network device, where the handover request carries a CSFB identifier corresponding to the terminal, where the handover request is sent by the 2G-3G core network device after receiving a migration request registration request sent by the first access network device, and the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G, so that the second access network device can identify that the terminal is a CSFB user.

With reference to the second aspect, in a possible implementation manner, when the first communication system is a 2G communication system and the second communication system is a 3G communication system, a specific process of the second access network device receiving the CSFB identifier corresponding to the terminal transmitted by the first access network device in the first communication system may be: receiving a migration request relocation request sent by core network equipment of a 2G communication system, wherein the migration request carries a CSFB (Circuit switched fallback) identifier corresponding to a terminal, and the migration request is sent by the core network equipment of the 2G communication system after receiving a handover request sent by first access network equipment, and the handover request carries the CSFB identifier, wherein the 2G-3G core network equipment is core network equipment shared by the 2G communication system and the 3G communication system, or the 2G-3G core network equipment comprises the core network equipment of the 2G communication system and the core network equipment of the 3G, so that the second access network equipment can identify that the terminal is a CSFB user.

With reference to the second aspect, in a possible implementation manner, when the terminal ends the CS service, the process of the second access network device starting a fast return to the 4G communication system for the terminal includes:

when the terminal finishes the CS service, the second access network equipment transmits the access information of the 4G communication system to the terminal; wherein the access information of the 4G communication system is used by the terminal to quickly return to the 4G communication system.

With reference to the second aspect, in a possible implementation manner, the access network device in the 3G communication system is an RNC, the access network device in the 2G communication system is a BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is an MSC.

For the case that the 2G communication system and the 3G communication system in the first aspect and the second aspect have their respective core network devices respectively, the first access network device of the first communication system and the second access network device of the second communication system need to complete communication through the core network devices of the two communication systems. Taking an example that an access network device of a 2G communication system sends a CSFB identifier corresponding to a terminal to an access network device of a 3G communication system, the access network device of the 2G communication system sends the CSFB identifier to a core network device of the 2G communication system, the core network device of the 2G communication system sends the CSFB identifier to the core network device of the 3G communication system, and the core network device of the 3G communication system sends the CSFB identifier to the access network device of the 3G communication system.

Optionally, the embodiment of the present application may implement directly sending the CSFB identifier; or, the CSFB identifier may also be sent by a message including the CSFB identifier, and messages carrying the CSFB identifier in different communication systems may be different, which is not limited in this application.

In a third aspect, a communication apparatus is provided for an embodiment of the present application, where the communication apparatus is applied to a communication system, and the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, the communication device is a first access network device in the first communication system, and the first access network device includes:

the processing module is used for acquiring a CSFB (Circuit switched fallback) identifier corresponding to the terminal when the terminal falls back to the first communication system from the resident 4G communication system during the CS service;

a transceiver module, configured to transmit a CSFB identifier to a second access network device in a second communication system when a terminal falls back from a first communication system to the second communication system when performing a CS service, where the CSFB identifier is used for starting, by the second access network device, a process of quickly returning to the 4G communication system according to the CSFB identifier when the terminal ends the CS service after the second access network device receives the CSFB identifier.

Optionally, the first access network device may also implement some or all of the optional implementations of the first aspect.

Optionally, the processing module of the first access network device is implemented by the processor of the first access network device executing instructions stored in the memory, and the transceiver module is implemented by the transceiver of the first access network device.

In a fourth aspect, a communication apparatus is provided for the embodiments of the present application, and is applied to a communication system, where the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, the communication device is a second access network device in the second communication system, and the second access network device includes:

a transceiver module, configured to receive, when a terminal performs a CS service, a CSFB identifier corresponding to the terminal that is transmitted by a first access network device in a first communication system when the terminal falls back from a resident 4G communication system to the first communication system and falls back from the first communication system to a second communication system;

and the processing module is used for starting a flow for quickly returning to the 4G communication system for the terminal according to the CSFB identifier when the terminal finishes the CS service.

Optionally, the second access network device may also implement some or all of the optional implementations of the second aspect.

Optionally, the processing module of the second access network device is implemented by the processor of the second access network device executing instructions stored in the memory, and the transceiver module is implemented by the transceiver of the second access network device.

In a fifth aspect, a communication device is provided for the embodiments of the present application, where the communication device is applied to a communication system, and the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, the communication device is a first access network device in the first communication system, and the first access network device includes: a processor, a memory, and a transceiver; the memory is used for storing instructions; a processor for executing the instructions stored by the memory;

when the processor executes the instruction stored in the memory, the processor is used for acquiring a CSFB (Circuit switched fallback) identifier corresponding to the terminal when the terminal falls back to a first communication system from a resident 4G communication system during a CS (circuit switched) service;

and the transceiver is used for transmitting the CSFB identifier to second access network equipment in a second communication system when the terminal falls back from the first communication system to the second communication system when the terminal performs the CS service, wherein the CSFB identifier is used for starting a flow for quickly returning to the 4G communication system for the terminal according to the CSFB identifier after the second access network equipment receives the CSFB identifier and when the terminal finishes the CS service.

With reference to the fifth aspect, in a possible implementation manner, when the first communication system is a 3G communication system and the second communication system is a 2G communication system, the transceiver is specifically configured to: sending a migration request relocation required to 2G-3G core network equipment, where the migration request carries the CSFB identifier, where the migration request is used for the 2G-3G core network equipment to send a handover request to the second access network equipment after receiving the migration request, and the handover request carries the CSFB identifier, where the 2G-3G core network equipment is core network equipment shared by the 2G communication system and the 3G communication system, or the 2G-3G core network equipment includes core network equipment of the 2G communication system and core network equipment of the 3G.

With reference to the fifth aspect, in a possible implementation manner, when the first communication system is a 2G communication system and the second communication system is a 3G communication system, the transceiver is specifically configured to: sending a handover request to a 2G-3G core network device, where the handover request carries the CSFB identifier, where the handover request is used for the 2G-3G core network device to send a migration request location request to the second access network device after receiving the migration request, where the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G.

With reference to the fifth aspect, in a possible implementation manner, the access network device in the 3G communication system is an RNC, the access network device in the 2G communication system is a BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is an MSC.

With reference to the fifth aspect, in a possible implementation manner, when the processor executes the instructions stored in the memory, the processor is further configured to, when the terminal falls back to the first communication system from the resident 4G communication system while performing the CS service, execute a procedure of falling back the terminal from the first communication system to the second communication system when a signal strength value of a serving cell serving the terminal in the first communication system is smaller than a signal strength threshold;

or, when the processor executes the instructions stored in the memory, the processor is further configured to, when the terminal falls back to the first communication system from the resident 4G communication system while performing the CS service, perform a procedure of falling back the terminal from the first communication system to the second communication system in a case where a load of a serving cell serving the terminal in the first communication system is greater than a load threshold.

In a sixth aspect, a communication device is provided for the embodiments of the present application, and is applied to a communication system, where the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, the communication device is a second access network device in the second communication system, and the second access network device includes: a processor, a memory, and a transceiver; the memory is used for storing instructions; a processor for executing the instructions stored by the memory;

the transceiver is used for receiving a CSFB (Circuit switched fallback) identifier corresponding to a terminal, which is transmitted by first access network equipment in a first communication system, when the terminal falls back to the first communication system from a resident 4G communication system and falls back to a second communication system from the first communication system when a CS (Circuit switched) service is carried out on the terminal;

and when the processor executes the instruction stored in the memory, the processor is used for starting a process of quickly returning to the 4G communication system for the terminal according to the CSFB identifier when the terminal finishes the CS service.

With reference to the sixth aspect, in a possible implementation manner, in a case that the first communication system is a 3G communication system and the second communication system is a 2G communication system, the transceiver is specifically configured to:

receiving a handover request sent by a 2G-3G core network device, where the handover request carries a CSFB identifier corresponding to the terminal, where the handover request is sent by the 2G-3G core network device after receiving a migration request relocation request sent by the first access network device, and the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G communication system.

With reference to the sixth aspect, in a possible implementation manner, in a case that the first communication system is a 2G communication system and the second communication system is a 3G communication system, the transceiver is specifically configured to:

receiving a migration request relocation request sent by a core network device of the 2G communication system, where the migration request carries a CSFB identifier corresponding to the terminal, where the migration request is sent by the core network device of the 2G communication system after receiving a handover request sent by the first access network device, and the handover request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes the core network device of the 2G communication system and the core network device of the 3G communication system.

With reference to the sixth aspect, in a possible implementation manner, when the processor executes the instruction stored in the memory, in a process of starting, by the terminal, a fast return to the 4G communication system according to the CSFB identifier when the terminal ends the CS service, the process is specifically configured to: when the terminal finishes the CS service, transmitting the access information of the 4G communication system to the terminal; wherein the access information of the 4G communication system is used by the terminal to quickly return to the 4G communication system.

With reference to the sixth aspect, in a possible implementation manner, the access network device in the 3G communication system is an RNC, the access network device in the 2G communication system is a BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is an MSC.

A seventh aspect provides a communication system for the embodiments of the present application, where the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; alternatively, the first communication system is a 3G communication system and the second communication system is a 2G communication system, the communication system comprising the communication device of any one of the possible implementations of the third aspect and the communication device of any one of the possible implementations of the fourth aspect and the fourth aspect.

In an eighth aspect, a communication system is provided for the embodiments of the present application, where the communication system includes a first communication system, a second communication system, and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; alternatively, the first communication system is a 3G communication system and the second communication system is a 2G communication system, the communication system comprising the communication device of any one of the possible implementations of the fifth aspect and the communication device of any one of the possible implementations of the sixth aspect and the sixth aspect.

In a ninth aspect, there is provided a computer program product comprising: computer program code for causing a computer to perform the method of the first aspect and any possible implementation thereof when the computer program code runs on a computer.

In a tenth aspect, there is provided a computer program product comprising: computer program code which, when run on a computer, causes the computer to perform the method of the second aspect and any possible implementation thereof.

In an eleventh aspect, there is provided a computer readable medium having program code stored thereon, which when run on a computer causes the computer to perform the method of the first aspect and any possible implementation thereof.

In a twelfth aspect, a computer-readable medium is provided, which stores program code, which, when run on a computer, causes the computer to perform the method of the second aspect and any possible implementation thereof.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be described below.

Fig. 1 is a schematic diagram of a possible architecture including multiple communication systems according to an embodiment of the present application;

fig. 2 is a flowchart illustrating a communication method according to an embodiment of the present application;

fig. 3 is a flow chart illustrating another communication method according to an embodiment of the present application;

fig. 4 is a flow chart illustrating another communication method according to an embodiment of the present application;

fig. 5 is an exemplary diagram of a terminal and multiple communication systems provided in an embodiment of the present application;

fig. 6 is a schematic flow chart of another communication method provided in the embodiments of the present application;

fig. 7 is a schematic structural diagram of a first access network device according to an embodiment of the present application;

fig. 8 is a schematic structural diagram of another first access network device provided in an embodiment of the present application;

fig. 9 is a schematic structural diagram of a second access network device according to an embodiment of the present application;

fig. 10 is a schematic structural diagram of another second access network device according to an embodiment of the present application.

Detailed Description

The following description will be made with reference to the drawings in the embodiments of the present application.

With the development of wireless communication technology, various wireless communication systems have been developed. Such as Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA), General Packet Radio Service (GPRS), Enhanced Data rate Evolution (Enhanced Data rates for GSM Evolution), Interim Standard95 Code Division Multiple Access (Interim Standard95CDMA, IS-95CDMA), Wideband Code Division Multiple Access (Wideband Code Division Multiple Access, WCDMA), CDMA2000, Time Division Synchronous Code Division Multiple Access (TD-SCDMA), LTE, and the like. Among them, LTE includes time division duplex LTE (LTE TDD, or TD-LTE) and frequency division duplex LTE (LTE FDD).

The TD-SCDMA and WCDMA systems are Universal Mobile Telecommunications Systems (UMTS) of 3G Mobile phone technology, and The UMTS is promulgated by 3GPP (The 3rd Generation Partnership Project). The Network structure of UMTS can be divided into UMTS Terrestrial Radio Access Network (UTRAN) and Core Network (CN). In the UTRAN architecture, a Radio Access Network (RAN) is divided into a plurality of Radio Network Subsystems (RNSs), each RNS includes a Radio Network Controller (RNC) and one or more Node bs (base stations). The RNC is responsible for allocating, reconfiguring and releasing radio resources within the RNS, and the Node B is a Node having a radio transceiving function, supports an air interface with a radio terminal within its cell, and provides a service to the cell. The Node bs communicate with the RNCs over an Iub interface, and the RNCs may be interconnected by an interface comprising a direct physical connection or a virtual network using any suitable transport network.

Without being specifically illustrated, 2G communication systems typically include GSM, CDMA, GPRS, EDGE, and IS-95 CDMA; 3G communication systems typically include TD-SCDMA, WCDMA, and CDMA2000 upgrades. The 4G communication system includes LTE. At present, a terminal can also support multiple communication systems, and roaming in the multiple communication systems can be realized.

The following description is made in conjunction with the architecture diagrams of various communication systems. Referring to fig. 1, fig. 1 is a schematic diagram of a possible communication system according to an embodiment of the present disclosure. The communication system includes a first communication system, a second communication system, and a 4G communication system, and a terminal 101. The system specifically comprises access network equipment 102, access network equipment 103 and core network equipment 104 belonging to a 2G communication system; access network equipment 105, access network equipment 106 and core network equipment 107 of the 3G communication system; an access network device 108 and a core network device 109 of the 4G communication system.

The following first introduces each network element in fig. 1:

the terminal 101: it may be a UE (user equipment), a handheld terminal, a notebook computer, a subscriber unit (subscriber unit), a cellular phone (cellular phone), a smart phone (smart phone), a wireless data card, a Personal Digital Assistant (PDA) computer, a tablet computer, a wireless modem (modem), a handheld device (hand held), a laptop computer (laptop computer), a Machine Type Communication (MTC) terminal, or other devices that can access a network.

Access Network (RAN) equipment: the wireless network controller is mainly responsible for functions of wireless resource management, quality of service (QoS) management, data compression, encryption and the like on the air interface side. The access network equipment may include various forms of base stations, such as: macro base stations, micro base stations (also referred to as small stations), relay stations, access points, etc.

The core network equipment is used for providing user connection, managing the user and completing bearing of the service. For example, the establishment of the user connection includes functions of Mobility Management (MM), paging (paging), and the like. The user management comprises the description, the Qos and the security of the user (the corresponding security measures provided by the authentication center comprise the security management of the mobile service and the security processing of the access to the external network). Bearer connections include Public Switched Telephone Network (PSTN) to the outside, external circuit data networks and packet data networks, the Internet (Internet), and so on.

In different communication systems, names of access network devices with access functions may be different, for example, in a 2G communication system, the access network device 102 is a Base Transceiver Station (BTS), and the access network device 103 is a Base Station Controller (BSC); in the 3G communication system, the access network device 105 is a node B (NodeB) or a base station, and the access network device 106 is a Radio Network Controller (RNC); in the 4G communication system, the access network device 108 is an evolved NodeB (eNB or eNodeB) or an evolved base station.

The terminal 101 and the access network device communicate with each other by using some air interface technology. Optionally, an air interface technology based on a 2G communication system is adopted between the terminal 101 and the access network device 102; an air interface technology based on a 3G communication system is adopted between the terminal 101 and the access network equipment 105. The air interface technology of the 4G communication system may be employed between the terminal 101 and the access network device 108.

In different communication systems, the core network equipment is also different. For example, the core network device 104 of the 2G communication system or the core network device 107 of the 3G communication system may include a Mobile Switching Center (MSC); the core network device 103 is a Base Station Controller (BSC); the core network device 108 is a Mobility Management Entity (MME) in the 4G communication system.

It is to be understood that in the communication system shown in fig. 1, the functions and interfaces of the network elements are only exemplary, and not all the functions of the network elements are necessary when the network elements are applied to the embodiments of the present application.

The CS (Circuit Switch) service referred to in the embodiments of the present application means a Circuit switched service. The CS is a resource that different users exclusively allocate respectively. The CS service mainly includes voice services, such as 12.2K voice service, 64K video telephony service, and so on. For example, voice service, the exclusive channel does not release the channel for use by other users until the call is over. There is also PS (Packet Switch) service in the communication system, meaning Packet switched service. The PS is a statistical multiplexing where different users can share the same resource. PS service is a common data service, and popular points refer to Internet access service, including streaming media service, Voice over Internet Protocol (VoIP) and the like.

In some communication systems, such as LTE communication system, CS service is not supported, and their voice service can only be realized by VOIP. In the prior art, when a terminal in an LTE communication system desires to implement a service (e.g., a voice service) through a Circuit domain, a feasible way is to implement the Circuit domain service in a 2G/3G communication system by using a Circuit Switched Fallback (CSFB) technique to fall back to the 2G/3G communication system.

As shown in fig. 1, in the current CSFB scheme, a CS service is taken as an example for explanation, and when the terminal 101 operates in the 4G communication system, and when the terminal 101 initiates a voice call, the 4G communication system performs a handover or redirection procedure, so that the terminal 101 falls back to the 2G/3G communication system. In the 2G/3G communication system, when the terminal 101 hangs up the voice call, the access network device 103 of the 2G communication system or the access network device 106 of the 3G communication system may carry the frequency point of the 4G communication system in a Channel Release message, so that the terminal can quickly reselect (Fast Return) back to the 4G communication system, thereby avoiding residing in the 2G/3G communication system. And after receiving the Channel Release message, the terminal tries to access the 4G communication system according to the frequency point of the 4G communication system carried by the Channel Release message.

In practice, when the terminal falls back from the resident 4G communication system to the 3G communication system, the 3G communication system may not provide service for the CS service when the terminal performs the CS service or may not provide service for the CS service all the time, and the reasons may include that the 3G communication system is loaded highly, the signal of the 3G communication system at the current location of the terminal is poor, and the like. If the 3G communication system can not provide service for the CS service of the terminal, when the terminal carries out the CS service, the terminal falls back to the 2G communication system from the 3G communication system, so that the terminal completes the CS service in the 2G communication system. After the CS service is finished, the terminal can only reside in the 2G communication system, and the terminal can return to the 4G communication system only by manually selecting the 4G network by the user, which reduces the efficiency of returning the terminal to the 4G communication system.

In this application, when the terminal falls back from the resident 4G communication system to the 3G communication system, the access network device of the 3G communication system may acquire the CSFB identifier corresponding to the terminal. If the 3G communication system can not provide service for the CS service of the terminal, the terminal falls back to the 2G communication system from the 3G communication system when the terminal performs the CS service, the access network equipment of the 3G communication system transmits the CSFB identifier corresponding to the terminal to the access network equipment of the 2G communication system, so that the access network equipment of the 2G communication system can identify that the terminal is a CSFB user, and under the condition that the terminal finishes the CS service, the access network equipment of the 2G communication system can start a flow for quickly returning to the 4G communication system for the terminal to quickly return to the 4G communication system, and the efficiency of returning the terminal to the 4G communication system is improved. For a brief description of one possible implementation of the embodiments of the present application, reference is made to the following detailed description of the embodiments shown in fig. 2 to 10.

In the embodiments of the present application, a certain network element (e.g., an a network element) receives information from another network element (e.g., a B network element), which may mean that the a network element receives information directly from the B network element, or that the a network element receives information from the B network element via another network element (e.g., a C network element). When the network element a receives information from the network element B via the network element C, the network element C may transparently transmit the information, or may process the information, for example: and carrying the information in different messages for transmission or screening the information, and only sending the screened information to the network element A. Similarly, in the embodiments of the present application, the sending of the information by the network element a to the network element B may refer to the sending of the information by the network element a directly to the network element B, or may refer to the sending of the information by the network element a to the network element B via another network element (e.g., a network element C).

In the embodiment of the present application, the term "system" may be replaced with "network". The system architecture described in the embodiment of the present application is for more clearly illustrating the technical solution of the embodiment of the present application, and does not form a limitation on the technical solution provided in the embodiment of the present application, and as a person having ordinary skill in the art knows along with the evolution of the network architecture, the technical solution provided in the embodiment of the present application is also applicable to similar technical problems.

Referring to fig. 2, a schematic flow chart of a communication method is provided according to an embodiment of the present application based on the communication system of fig. 1. As shown in fig. 2, the method is applied to a communication system including a first communication system, a second communication system, and a 4G communication system, where the first access network device is an access network device of the first communication system, and the second access network device is an access network device of the second communication system. For a detailed description of the communication process, please refer to the following.

First, in the embodiment shown in fig. 2, the 4G communication system is a communication system that does not support CS services, and the second communication system and the first communication system are different communication systems that support CS services. For example, the second communication system is a 2G communication system, and the first communication system is a 3G communication system; or, for another example, the second communication system is a 3G communication system, and the first communication system is a 2G communication system.

201, when the terminal performs the CS service and falls back to the first communication system from the resident 4G communication system, the first access network device obtains the CSFB identifier corresponding to the terminal.

In a scenario of falling back from the resident 4G communication system to the first communication system, the terminal performing the CS service may refer to the terminal initiating the CS service. For example, taking CS service as a voice service, after a user dials a mobile phone number on a terminal operating in a 4G network, because the 4G communication system does not support the CS service, the 4G communication system will drop the terminal back to the first communication system in a redirection manner or a handover manner.

In a redirection mode, the core network device of the 4G communication system sends the CSFB identifier and the access information of the first communication system to the terminal, and in the process of accessing the first communication system by the terminal, the CSFB identifier is sent to the first access network device, so that the first access network device can obtain the CSFB identifier corresponding to the terminal and identify the terminal as a CSFB user.

In the handover mode, the core network device of the 4G communication system sends the CSFB identifier corresponding to the terminal to the first access network device in the first communication system to be handed over. Therefore, the first access network device can acquire the CSFB identifier corresponding to the terminal and identify the terminal as a CSFB user.

202, when the terminal performs the CS service and falls back from the first communication system to the second communication system, the first access network device transmits the CSFB identifier to the second access network device in the second communication system.

After the terminal falls back to the first communication system, if the first communication system cannot provide the CS service for the terminal, the first communication system will fall back to the second communication system, and transmit the CSFB identifier corresponding to the terminal to the second access network device in the second communication system.

In a scenario where the terminal falls back from the first communication system to the second communication system, the CS service performed by the terminal may refer to a stage where the terminal initiates the CS service or may be in a process of performing the CS service. For example, taking CS service as an example of voice call, the terminal may fall back from the first communication system to the second communication system at a stage after the user dials the mobile phone number, or fall back from the first communication system to the second communication system during the voice call.

The situations for the terminal to fall back from the first communication system to the second communication system may include at least the following two situations:

a first possible scenario is that, in a case where the signal strength value of the serving cell serving the terminal in the first communication system is smaller than the signal strength threshold, it indicates that the signal strength value of the serving cell serving the terminal is poor, which makes it difficult to provide a better service for the terminal, and therefore the terminal is dropped from the first communication system to the second communication system. The first access network device may obtain the measurement report from the terminal, and then determine a signal strength value of a serving cell that provides a service for the terminal.

A second possible scenario is to drop the terminal from the first communication system back to the second communication system in case the load of the serving cell serving the terminal in the first communication system is larger than a load threshold. For example, the load may be the number of users accessed by the serving cell served by the terminal.

Correspondingly, the second access network device receives the CSFB identifier corresponding to the terminal transmitted by the first access network device in the first communication system.

203, when the terminal finishes the CS service, the second access network device starts a process of quickly returning to the 4G communication system to the terminal according to the CSFB identifier.

After the second access network device receives the CSFB identifier corresponding to the terminal, the second access network device may identify the terminal as a CSFB user. And when the terminal finishes the CS service, the second access network equipment starts a flow for quickly returning to the 4G communication system to the terminal according to the CSFB identifier.

The second access network device indicates that the CS service is ended when receiving a CS service end command sent by the terminal, or when receiving a clearing command about the CS service sent by a second core network device of the second communication system. For example, taking CS service as a voice service, the termination of CS service by the terminal means that the terminal hangs up the voice call.

The process that the second access network device starts the terminal to quickly return to the 4G communication system according to the CSFB identifier may specifically be: the second access network equipment sends the access information of the 4G communication system to the terminal, and after the terminal receives the access information of the 4G communication system, the access information can be quickly returned to the 4G communication system.

It should be noted that, in the embodiment of fig. 2, the communication between the first access network device and the second access network device is completed through the core network device.

In a possible implementation manner, the 2G communication system and the 3G communication system share a core network device, for example, named as a 2G-3G core network device, and the first access network device sends the CSFB identifier to the second access network device through the shared 2G-3G core network device.

In another possible implementation scheme, the 2G communication system and the 3G communication system respectively set up respective core network devices, and the first access network device needs to pass through the core network devices of the two communication systems to complete the CSFB identifier transmission to the second access network device. Taking an example that an access network device of a 2G communication system sends a CSFB identifier corresponding to a terminal to an access network device of a 3G communication system, the access network device of the 2G communication system sends the CSFB identifier to a core network device of the 2G communication system, the core network device of the 2G communication system sends the CSFB identifier to the core network device of the 3G communication system, and the core network device of the 3G communication system sends the CSFB identifier to the access network device of the 3G communication system.

In this embodiment of the present application, after the terminal initiates a CS service, the terminal may drop back to the first communication system from the resident 4G communication system, and a first access network device of the first communication system may acquire the CSFB identifier corresponding to the terminal. If the first communication system can not provide service for the CS service of the terminal, when the terminal performs the CS service, the terminal falls back from the first communication system to the second communication system, and the first access network device transmits the CSFB identifier corresponding to the terminal to the second access network device of the second communication system, so that the second access network device can identify that the terminal is a CSFB user, and when the terminal ends the CS service, the second access network device can start a process of rapidly returning to the 4G communication system for the terminal, thereby saving time for returning to the 4G communication system for the terminal, and improving efficiency of returning to the 4G communication system by the terminal.

Referring to fig. 3, a schematic flow chart of a communication method according to an embodiment of the present invention is provided based on the system architecture diagram shown in fig. 1. In this embodiment, the first communication system is exemplified by a 3G communication system, and the second communication system is exemplified by a 2G communication system. In the embodiment shown in fig. 3, the access network device of the 3G communication system includes a base station (nodeB) and an RNC, and the core network device MSC is shared by the 2G communication system and the 3G communication system; the access network equipment of the 2G communication system comprises a BTS and a BSC; the access network device of the 4G communication system is an eNodeB for example, and the core network device of the 4G communication system is an MME. The first access network equipment of the 3G communication system is RNC, and the second access network equipment of the 2G communication system is BSC.

In the communication method of the embodiment shown in fig. 3, steps 301 to 306 are procedures in which the terminal falls back from the resident 4G communication system to the 3G communication system, and steps 306 to 314 include procedures in which the terminal falls back from the 3G communication system to the 2G communication system, the 2G communication system provides services for the CS service, and the terminal returns to the 4G communication system quickly after the CS service is ended. The specific implementation process is described in detail below.

301, the terminal sends an extended service request to the MME.

Because the 4G communication system does not support the CS service, when a terminal operating in the 4G communication system needs to initiate the CS service, the terminal may send an extended service request (extended service request) to the MME, where the extended service request carries the CSFB identifier.

The interaction between the terminal and the MME is realized through the eNodeB, the MME and the eNodeB belong to a 4G communication system, and the eNodeB sends the extended service request to the MME in a transparent transmission mode.

Correspondingly, the MME receives an extended service request sent by the terminal.

302, the MME sends the CSFB identifier corresponding to the terminal to the eNodeB.

And the MME responds to the extended service request of the terminal and sends the CSFB identifier corresponding to the terminal to the eNodeB. The CSFB identifier is used to indicate that the terminal is dropped back to the 2G/3G communication system, and after the 2G/3G communication system recognizes the CSFB identifier and the CS service is finished, the 2G/3G communication system may start a procedure of quickly returning the terminal to the 4G communication system.

Optionally, the MME may send an indication message for indicating a CSFB identifier corresponding to the terminal to the eNodeB, for example, the indication message is a CSFB Indicator.

Accordingly, the eNodeB receives the CSFB identification.

303, the eNodeB sends a first acknowledgement message to the MME. This step is optional.

And the eNodeB sends a first confirmation message to the MME to indicate that the CSFB identifier corresponding to the terminal is received to the MME.

The eNodeB sends 304 a first message to the terminal, the first message comprising the CSFB identification and access information of the 3G communication system.

The first message is used for indicating that the CS service of the terminal is switched to the 3G communication system. In this embodiment, the 4G communication system adopts a redirection manner to enable the terminal to access the 3G communication system, where the first message in the manner may be a Radio Resource Control (RRC) release message, and specifically, the eNodeB sends the RRC release message to the terminal, and the RRC release message carries the CSFB identifier.

In a possible scheme, the access information of the 3G communication system includes one or more frequency points of the 3G communication system or an identifier of one or more cells in the 3G communication system. For example, before performing step 304, a cell serving the terminal in the 4G communication system is a serving cell, and the eNodeB may obtain neighboring cell information or neighboring frequency points belonging to the 3G communication system in neighboring cells of the serving cell, specifically, may be obtained by preset configuration information. In this way, the eNodeB can determine the acquired at least one neighbor cell information or at least one neighbor frequency point belonging to the 3G communication system as the access information of the 3G communication system, and send the determined access information of the 3G communication system to the terminal. The neighbor cell information here includes the identity of the neighbor cell.

For example, the 4G communication system is an LTE communication system, and the current serving Cell is a Cell_{LTE 1}The adjacent cells belonging to the 3G communication system and acquired according to the preset configuration information comprise cells_{3G 1}、Cell_{3G 2}The access information of the 3G communication system thus determined includes Cell_{3G 1}Identification of, Cell_{3G 2}Is detected.

Or, in another possible scheme, the access information of the 3G communication system includes a target frequency point of the 3G communication system or an identifier of a target cell in the 3G communication system. For example, before step 304 is executed, a cell providing service for the terminal in the 4G communication system is a serving cell, the eNodeB may obtain neighbor cell information or neighbor frequency points of the serving cell belonging to the 3G communication system, and obtain measurement reports of the neighbor cells or the neighbor frequency points from the terminal, and the eNodeB determines, according to the measurement reports, an identifier of a target cell or a target frequency point where the terminal falls back to the 3G communication system. Optionally, the obtained measurement report includes signal strength values of a plurality of neighboring cells belonging to the 3G communication system measured by the terminal, and the eNodeB determines a target cell with the maximum signal strength value from the plurality of neighboring cells, and uses an identifier of the target cell as access information of the 3G communication system.

Correspondingly, the terminal receives a first message sent by the MME.

305, the terminal sends a second message to the RNC, where the second message carries the CSFB identifier.

The second message is used for indicating to provide a circuit CS service for the terminal; the second message carries a CSFB identity. For example, the second message may be an RRC request message.

The RNC here is an access network device corresponding to the access information of the 3G communication system determined in step 304, and may specifically be: the frequency point of the area covered by the RNC is a target frequency point; or the area covered by the RNC includes the target cell. Specifically, under the condition that the access information of the 3G communication system includes one or more frequency points of the 3G communication system or the identification of one or more cells in the 3G communication system, the terminal determines a target frequency point or a target cell from the access information; the access information of the 3G communication system comprises a target frequency point of the 3G communication system or an identifier of a target cell in the 3G communication system, and the terminal can directly determine the target frequency point or the target cell.

Correspondingly, the RNC receives a second message sent by the terminal, and can recognize that the terminal is a device that falls back to the 3G communication system through the CSFB identifier in the second message, so that a process of quickly returning to the 4G communication system needs to be performed on the terminal according to the CSFB identifier after the CS service is finished.

The communication between the terminal and the RNC is realized by the NodeB, specifically: the terminal sends a second message to the NodeB; and the NodeB sends a second message to the RNC, wherein the second message carries the CSFB identifier.

If the RNC cannot provide the service of the CS service to the terminal, the RNC performs step 306. For the case that the RNC cannot provide the CS service for the terminal, reference may be made to the detailed description in step 202 in the embodiment shown in fig. 2, which is not described herein again.

306, the RNC sends a relocation required request to the MSC, where the relocation required request includes the identifier of the second access network device and the CSFB identifier.

Correspondingly, the MSC receives the migration request, and may perform step 307 according to the identifier of the second access network device carried in the migration request.

The migration request is used by the MSC to send a handover request to the second access network device of the 2G communication system after the MSC receives the migration request. The handover request carries a CSFB identifier, where the second access network device is a BSC.

Before the RNC performs step 306, the RNC further determines the identifier of the second access network device from the 2G communication system, and the specific determination method may be:

in an alternative manner, if the terminal periodically reports the measurement report, the RNC may first obtain neighboring cell information of the 2G communication system from the cell configuration information, and send a measurement control message to the terminal, where the measurement control message includes the neighboring cell information of the 2G communication system, and the measurement control message is used to instruct the terminal to report the measurement report on the neighboring cell of the 2G communication system. The cell configuration information includes information of a plurality of neighboring cells, and the neighboring cells are neighboring cells of a serving cell in which the terminal is currently located in the 3G communication system. Then RNC obtains the signal intensity of adjacent cell of 2G communication system from the last reported measurement report, and determines the adjacent cell with maximum signal intensity as target cell, and determines the BSC's mark according to the target cell's mark, wherein the target cell is in the BSC's coverage area.

In another optional manner, if the terminal is in a case of reporting a measurement report by an event, the measurement report by an event specifically refers to an identifier of a cell whose signal strength value is greater than a threshold value and which the terminal will report; the RNC may determine a cell belonging to the 2G communication system in the reported cells as a target cell, and determine an identifier of the second access network device according to the identifier of the target cell, where the target cell is in a coverage area of the second access network device.

307, the MSC sends a handover request to the BSC, where the handover request carries the CSFB identifier.

Where, the BSC belongs to the 2G communication system and is the second access network device in step 306. The switching request is used for indicating the switching of the CS service of the terminal to the second access network equipment BSC. MSC sends CSFB identification to BSC through switching request, so that BSC can identify the terminal as CSFB user, and start the flow of returning to 4G communication system after CS service is over

Accordingly, the BSC receives the handover request.

308, the BSC sends a second acknowledgement message to the MSC, the second acknowledgement message being used to indicate that it is determined to switch the CS service.

After the BSC receives the handover request, the BSC sends a second acknowledgement message to the MSC.

Accordingly, the MSC receives the second acknowledgement message.

309, the MSC sends a third acknowledgement message to the RNC, where the third acknowledgement message is used to indicate that the CS service is determined to be switched.

Accordingly, the RNC receives the third acknowledgement message.

Alternatively, the connection with the terminal may be released after the RNC receives the third confirmation message.

The RNC sends a handover message to the terminal 310, the handover message including access information of the 2G communication system.

Correspondingly, the terminal receives the handover message sent by the RNC. The handover message is used to instruct the CS service of the terminal to be handed over to the 2G communication system. The handover message may be a handover command (handover command).

The communication between the terminal and the RNC is realized by the NodeB, specifically: RNC sends switch information to NodeB; and the NodeB sends a switching message to the terminal.

In a possible implementation scheme, the access information of the 2G communication system may be a target frequency point of the 2G communication system or an identifier of a target cell in the 2G communication system. For example, before step 306 is executed, in the process of determining the second access network device, the RNC may determine a target frequency point or a target cell for providing a service for the CS service of the terminal, and use an identifier of the target frequency point or the target cell as access information of the 2G communication system.

And 311, the terminal sends a third message to the BSC, wherein the third message is used for indicating that the circuit CS service is provided for the terminal.

Wherein the third message is used for indicating that the terminal is provided with the circuit CS service in the BSC. For example, the third message may be a handover complete message to enable the BSC to provide CS services to the terminal.

Correspondingly, the BSC receives the third message sent by the terminal.

312, the BSC provides service for CS traffic.

Optionally, the BSC may prepare transmission resources for the terminal to serve CS traffic of the terminal after step 307 and after receiving the second message.

313, when the CS service is finished, the BSC sends a fourth message to the terminal, where the fourth message carries access information of the 4G communication system.

Correspondingly, the terminal receives the fourth message sent by the BSC.

After receiving the handover request, the BSC may determine that the terminal is a CSFB user according to the CSFB identifier carried in the handover request, and then start a procedure of quickly returning to the 4G communication system for the terminal after the CS service is ended.

Optionally, the fourth message may be a channel release message.

Optionally, the access information of the 4G communication system may be frequency point information of the 4G communication system and an identifier of a cell belonging to the 4G communication system.

For example, taking the 4G communication system as an LTE communication system as an example, the BSC may obtain, according to the current serving cell of the terminal in the 2G communication system, the adjacent LTE frequency point of the serving cell according to the cell configuration information, and send the obtained adjacent LTE frequency point to the terminal.

For another example, taking the 4G communication system as the LTE communication system as an example, the BSC may obtain, according to the current serving cell of the terminal in the 2G communication system, the identifier of the neighboring LTE cell of the serving cell according to the cell configuration information, and send the obtained identifier of the neighboring LTE cell to the terminal.

Optionally, the BSC indicates that the CS service is ended when receiving a call end command sent by the terminal, or when receiving a clear command about the CS service sent by a core network device MSC of the 2G communication system.

The communication between the terminal and the BSC is implemented through the BST for steps 311 and 313.

And 314, the terminal accesses according to the access information of the 4G communication system.

For example, taking the 4G communication system as an example, the terminal may perform access according to the target frequency point and the target cell identifier of the 4G communication system, so as to speed up the efficiency of accessing the 4G communication system by the terminal.

It should be noted that, for step 306 to step 309, the MSC in the embodiment shown in fig. 3 is a core network device shared by the 2G communication system and the 3G communication system. For the case that the core network devices are respectively set up in the 2G communication system and the 3G communication system, because the RNC and the BSC belong to two different communication systems, the RNC and the BSC need to complete communication through the core network devices of the two communication systems, for example, the RNC needs to pass through the core network devices of the two communication systems to complete the message to be passed to the BSC, and similarly, the BSC needs to pass through the core network devices of the two communication systems to complete the message to be passed to the RNC. Taking step 306 and step 307 as an example, the RNC sends a migration request to the MSC of the 3G communication system; the MSC of the 3G communication system sends a migration request to the MSC of the 2G communication system; the MSC of the 2G communication system sends a handover request to the BSC, and the RNC may send the CSFB flag corresponding to the terminal to the BSC through this procedure. For the information transmission between other RNCs and BSCs, the analogy can be made with reference to this example, and the details are not described herein.

In the embodiment of the present application, after a terminal initiates a CS service, even if the terminal falls back from a resident 4G communication system to a 3G communication system and is switched from the 3G communication system to a 2G communication system, a CSFB identifier is transmitted to an access network device of the 2G communication system through an access network device of the 3G communication system, so that the access network device of the 2G communication system can still recognize that the terminal is a CSFB user, and when the terminal ends the CS service, the access network device of the 2G communication system starts a procedure for the terminal to quickly return to the 4G communication system, which saves time for the terminal to return to the 4G communication system, and improves the efficiency for the terminal to return to the 4G communication system.

Referring to fig. 4, a flowchart of a communication method according to an embodiment of the present invention is provided based on the system architecture diagram shown in fig. 1. In this embodiment, the first communication system is exemplified by a 2G communication system, and the second communication system is exemplified by a 3G communication system. In the embodiment shown in fig. 4, the access network equipment of the 2G communication system includes a BTS and a BSC; core network equipment MSC shared by the 2G communication system and the 3G communication system; the access network equipment of the 3G communication system comprises a base station (nodeB) and an RNC; the access network device of the 4G communication system is an eNodeB for example, and the core network device of the 4G communication system is an MME. The first access network equipment of the 2G communication system is BSC, and the second access network equipment of the 3G communication system is RNC.

In the communication method of the embodiment shown in fig. 4, steps 401 to 405 are procedures for the terminal to fall back from the resident 4G communication system to the 2G communication system, and steps 406 to 414 include procedures for the terminal to fall back from the 2G communication system to the 3G communication system, the 3G communication system to provide services for the CS service, and the terminal to quickly return to the 4G communication system after the CS service is ended. The specific implementation process is described in detail below.

401, the terminal sends an extended service request to the MME.

402, the MME sends the CSFB identifier corresponding to the terminal to the eNodeB.

403, the eNodeB sends a first acknowledgement message to the MME. This step is optional.

404, the eNodeB sends a first message to the terminal, the first message comprising the CSFB identification and access information of the 2G communication system.

The difference between step 401 and step 404 may refer to detailed descriptions of step 301 to step 304 in the embodiment shown in fig. 3, where the first message in fig. 3 carries access information of a 3G communication system, the first message in fig. 4 carries access information of a 2G communication system, and a manner for determining the access information of the 2G communication system by the eNodeB may refer to a manner for determining the access information of the 3G communication system by the eNodeB, which is not described herein again.

405, the terminal sends a second message to the BSC, where the second message carries the CSFB identifier.

The second message is used for indicating to provide a circuit CS service for the terminal; the second message carries a CSFB identity. For example, the second message may be an RRC request message. The BSC here is an access network device corresponding to the access information of the 2G communication system determined in step 404.

Correspondingly, the BSC receives a second message sent by the terminal, and can identify that the terminal is a device falling back to the 2G communication system through the CSFB identifier in the second message, so that a process of quickly returning to the 4G communication system needs to be performed on the terminal according to the CSFB identifier after the CS service is finished.

The communication between the terminal and the BSC is realized through BST, which specifically includes: the terminal sends a second message to the BST; and the BST sends a second message to the BSC, wherein the second message carries the CSFB identifier.

If the BSC cannot provide the CS service to the terminal, the BSC performs step 406. For the case that the BSC cannot provide the CS service for the terminal, reference may be made to the detailed description in step 202 in the embodiment shown in fig. 2, which is not described herein again.

406, the BSC sends a handover request to the MSC, where the handover request carries the identifier of the second access network device and the CSFB identifier.

Correspondingly, the MSC receives the handover request, and may perform step 406 according to the identifier of the second access network device carried in the migration request.

Wherein, the switching request is used by the MSC to send the migration request location request to the second access network device of the 3G communication system after receiving the switching request. The migration request carries a CSFB identifier, where the second access network device is an RNC.

Before the BSC performs step 406, it further determines the identity of the second access network device from the 3G communication system. For a specific determination manner, reference may be made to detailed description that the RNC determines the identifier of the second access network device from the 2G communication system in step 306 in fig. 3, which is not described herein again.

407, the MSC sends a migration request relocation request to the RNC, where the migration request includes the CSFB identifier.

Wherein, the RNC belongs to the 3G communication system and is the second access network device in step 406. The migration request is used for indicating the switching of the CS service of the terminal to the second access network equipment RNC. MSC sends CSFB identification to RNC through migration request, so that RNC can identify the terminal as CSFB user, and can start flow for returning to 4G communication system after CS service is finished

Accordingly, the BSC receives the migration request.

And 408, the RNC sends a second confirmation message to the MSC, wherein the second confirmation message is used for indicating that the CS service is determined to be switched.

After the RNC receives the migration request, the BSC sends a second acknowledgement message to the MSC.

Accordingly, the MSC receives the second acknowledgement message.

409, the MSC sends a third confirmation message to the BSC, and the third confirmation message is used for indicating the determination of switching the CS service.

Accordingly, the BSC receives the third acknowledgement message.

Optionally, the connection with the terminal may be released after the BSC receives the third confirmation message.

For steps 406 to 409, because the RNC and the BSC belong to two different communication systems, respectively, the RNC and the BSC complete communication through a core network device MSC belonging to the 2G communication system in which the BSC is located.

The BSC sends 410 a handover message to the terminal, the handover message including access information of the 3G communication system. For example, the handover message is a handover command.

411, the terminal sends a third message to the RNC, where the third message is used to indicate that the circuit CS service is provided for the terminal. For example, the third message is a handover complete message.

The RNC serves the CS traffic 412.

413, when the CS service is ended, the RNC sends a fourth message to the terminal, where the fourth message carries access information of the 4G communication system. For example, the fourth message is an RRC connection release message.

And 414, the terminal accesses according to the access information of the 4G communication system.

The specific implementation process of steps 410 to 414 above may refer to the description of steps 310 to 314 in the embodiment shown in fig. 3. The difference between the two is that the first access network device of the embodiment shown in fig. 3 is an RNC; the first access network device of the embodiment shown in fig. 4 is a BSC; the second access network device of the embodiment shown in fig. 3 is a BSC; the second access network device of the embodiment shown in fig. 4 is an RNC; the MSC of fig. 3 belongs to a 3G communication system; the MSC in fig. 4 belongs to a 2G communication system, where communication between the terminal and the RNC is implemented by a NodeB, and communication between the terminal and the BSC is implemented by a BST, and specific implementation procedures thereof are the same, and are not described herein again.

In the embodiment of the present application, after a terminal initiates a CS service, even if the terminal falls back from a resident 4G communication system to a 2G communication system and is switched from the 2G communication system to a 3G communication system, a CSFB identifier is transmitted to an access network device of the 3G communication system through an access network device of the 2G communication system, so that the access network device of the 3G communication system can still recognize that the terminal is a CSFB user, and when the terminal ends the CS service, the access network device of the 3G communication system starts a procedure for the terminal to quickly return to the 4G communication system, which saves time for the terminal to return to the 4G communication system, and improves the efficiency for the terminal to return to the 4G communication system.

Referring to fig. 5, an exemplary diagram of a terminal and a plurality of communication systems is provided for an embodiment of the present application.

In the embodiment of the present application, the plurality of communication systems include a first communication system, a second communication system, and a 4G communication system. The 4G communication system is a communication system that does not support CS services, such as a 4G communication system; the second communication system and the first communication system are different communication systems supporting CS services. For example, the second communication system is a 2G communication system, and the first communication system is a 3G communication system; or, for another example, the second communication system is a 3G communication system, and the first communication system is a 2G communication system.

The terminal at least supports a first communication system, a second communication system and a 4G communication system; the terminal can communicate with the first communication system, the second communication system and the 4G communication system respectively. The first communication system, the second communication system and the 4G communication system can also communicate with each other.

Referring to fig. 6 together, a flowchart of another communication method is provided for the present application, based on the exemplary diagram of the terminal and the plurality of communication systems shown in fig. 5. The communication method includes steps 601 to 609.

601, the terminal sends an extended service request to the 4G communication system.

602, the 4G communication system sends a first message to the terminal, the first message including the CSFB identifier and access information of the first communication system.

603, the terminal sends a second message to the first communication system, where the second message carries the CSFB identifier.

604, the first communication system sends the CSFB identification to the second communication system.

605 the first communication system sends a handover message to the terminal, the handover message comprising access information of the second communication system.

And 606, the terminal sends a third message to the second communication system, and the third message is used for indicating that the CS service is provided for the terminal.

607, the second communication system provides services for the CS traffic of the terminal.

608, when the CS service is ended, the second access network device sends a fourth message to the terminal, where the fourth message carries access information of the 4G communication system.

609, the terminal accesses according to the access information of the 4G communication system.

The above steps 601 to 609 may specifically refer to the detailed description of the embodiments in fig. 2, fig. 3, and fig. 4.

In the scheme shown in fig. 6, the 4G communication system switches the terminal to the first communication system in a redirection manner, and for step 602, the first message may be an RRC release message, specifically, the third access network device sends the RRC release message to the terminal, where the RRC release message carries the CSFB identifier.

Or in another optional scheme, after the 4G communication system performs step 601, the third access network device may further switch the terminal to the first communication system by using a switching manner, and the 4G communication system sends a switching request message to the second communication system, where the switching request message is used to request to switch the CS service to the first communication system, and the switching request message carries the CSFB identifier. If the first communication system is the 3G communication system, the switching request message is a location request message; and if the first communication system is the 2G communication system, the switching request message is a handover request message. In case it is determined that the CS service can be switched to the first communication system, the 4G communication system may transmit a handover command to the terminal, and perform the subsequent steps 604 to 609 after the terminal accesses the first communication system.

In this embodiment of the present application, after the terminal initiates a CS service, the terminal may drop back to the first communication system from the resident 4G communication system, and a first access network device of the first communication system may acquire the CSFB identifier corresponding to the terminal. If the first communication system can not provide service for the CS service of the terminal, when the terminal performs the CS service, the terminal falls back from the first communication system to the second communication system, and the first access network device transmits the CSFB identifier corresponding to the terminal to the second access network device of the second communication system, so that the second access network device can identify that the terminal is a CSFB user, and when the terminal finishes the CS service, the second access network device can start a process of rapidly returning to the 4G communication system for the terminal, so that the terminal returns to the 4G communication system quickly, which saves time for the terminal to return to the 4G communication system and improves the efficiency of returning to the 4G communication system by the terminal.

The scheme provided by the embodiment of the present application has been mainly described from the perspective of the method. It is to be understood that, in order to implement the above functions, the first access network device and the second access network device include hardware structures and/or software modules for performing the respective functions. The elements and algorithm steps of the various examples described in connection with the embodiments disclosed herein may be embodied in hardware or in a combination of hardware and computer software. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present teachings.

In the embodiment of the present application, according to the above method example, the first access network device and the second access network device may be divided into the functional modules or the functional units, for example, the functional modules or the functional units may be divided corresponding to the functions, or two or more functions may be integrated into one processing module or processing unit. The integrated modules or units may be implemented in the form of hardware, or may be implemented in the form of software functional modules. It should be noted that, in the embodiment of the present application, the division of the module or the unit is schematic, and is only a logic function division, and there may be another division manner in actual implementation.

Referring to fig. 7, fig. 7 is a schematic structural diagram of a first access network device according to an embodiment of the present disclosure. The first access network device is configured to implement the method embodiments of fig. 2 to 4. The first access equipment is applied to a communication system, and the communication system comprises a first communication system, a second communication system and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; alternatively, the first communication system is a 3G communication system, and the second communication system is a 2G communication system, as shown in fig. 7, the first access network device 700 includes a processing module 701 and a receiving module 702.

A processing module 701, configured to obtain a CSFB identifier corresponding to a terminal when the terminal falls back to the first communication system from the resident 4G communication system during a CS service;

a transceiver module 702, configured to transmit the CSFB identifier to a second access network device in the second communication system when the terminal performs a CS service and falls back from the first communication system to the second communication system, where the CSFB identifier is used to start a procedure of quickly returning to the 4G communication system for the terminal according to the CSFB identifier when the terminal finishes the CS service after the second access network device receives the CSFB identifier.

Optionally, when the first communication system is the 3G communication system and the second communication system is the 2G communication system, the transceiver module 702 is specifically configured to:

sending a migration request relocation required to 2G-3G core network equipment, where the migration request carries the CSFB identifier, where the migration request is used for the 2G-3G core network equipment to send a handover request to the second access network equipment after receiving the migration request, and the handover request carries the CSFB identifier, where the 2G-3G core network equipment is core network equipment shared by the 2G communication system and the 3G communication system, or the 2G-3G core network equipment includes core network equipment of the 2G communication system and core network equipment of the 3G.

Optionally, when the first communication system is the 2G communication system and the second communication system is the 3G communication system, the transceiver module 702 is specifically configured to:

sending a handover request to a 2G-3G core network device, where the handover request carries the CSFB identifier, where the handover request is used for the 2G-3G core network device to send a migration request location request to the second access network device after receiving the migration request, where the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G.

Optionally, the access network device in the 3G communication system is an RNC, the access network device in the 2G communication system is a BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is an MSC.

Optionally, the processing module 701 is further configured to, when the terminal falls back to the first communication system from the resident 4G communication system during the CS service, execute a procedure of falling back the terminal from the first communication system to the second communication system when a signal strength value of a serving cell serving the terminal in the first communication system is smaller than a signal strength threshold;

or, the processing module 701 is further configured to, when the terminal falls back to the first communication system from the resident 4G communication system during the CS service, execute a procedure of falling back the terminal from the first communication system to the second communication system when a load of a serving cell in the first communication system, which provides a service for the terminal, is greater than a load threshold.

In an embodiment of the present application, the function of the transceiver module 702 may be implemented by a transceiver of a first access network device, or may be implemented by a communication interface of the first access network device; the functions of the processing module 701 may be implemented by a processor of the first access network device executing instructions stored in a memory.

It will be appreciated that the first access network device 700 is configured to implement the steps performed by the first access network device in the embodiments illustrated in fig. 2-4. As to specific implementation manners and corresponding advantageous effects of the functional blocks included in the first access network device in fig. 7, reference may be made to the specific descriptions of the embodiments in fig. 2 to fig. 4, which are not described herein again.

The first access network device in the embodiment shown in fig. 7 described above may be implemented as the first access network device 800 shown in fig. 8. As shown in fig. 8, a schematic structural diagram of another first access network device is provided for the embodiment of the present application, and the first access network device 800 shown in fig. 8 includes: a processor 801 and a transceiver 802.

The transceiver 802 is configured to support information transmission between the first access network device 800 and the access network device or other devices involved in the foregoing embodiments, for example, to implement the process 202 in the embodiment shown in fig. 2; for example, step 306 and step 310 in the embodiment shown in fig. 3; for example, step 406 and step 410 in the embodiment shown in fig. 4.

The processor 801 is configured to control and manage actions of the first access network device. For example, to implement process 201 in the embodiment shown in fig. 2.

The processor 801 is communicatively coupled to the transceiver 802, for example, by a bus 804. The bus 804 may be a PCI bus or an EISA bus, etc. The bus 804 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one thick line is shown in FIG. 8, but this is not intended to represent only one bus or type of bus.

The first access network device 800 may also include a memory 803. The memory 803 is used for storing program codes and data for execution by the first access network device 800, and the processor 801 is used for executing the application program codes stored in the memory 803 to realize the actions of the first access network device provided by any of the embodiments shown in fig. 2 to 4.

It should be noted that, in practical applications, the first access network device may include one or more processors, and the structure of the first access network device 800 does not form a limitation to the embodiments of the present application.

The processor 801 may be a Central Processing Unit (CPU), a general purpose processor, a Digital Signal Processor (DSP), an application-specific integrated circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, transistor logic, hardware components, or any combination thereof. Which may implement or perform the various illustrative logical blocks, modules, and circuits described in connection with the disclosure. The processor may also be a combination of computing functions, e.g., comprising one or more microprocessors, DSPs, and microprocessors, among others.

The transceiver 804 may be a communication interface or a transceiver circuit, etc., wherein the transceiver is referred to collectively, and in a particular implementation, the transceiver may include multiple interfaces.

The memory 803 may include a volatile memory (volatile memory), such as a Random Access Memory (RAM); the memory 803 may also include a non-volatile memory (non-volatile memory), such as a read-only memory (ROM), a flash memory (flash memory), a Hard Disk Drive (HDD), or a solid-state drive (SSD); the memory 803 may also comprise a combination of memories of the kind described above.

In an embodiment of the present application, a computer storage medium may be provided, which may be used to store computer software instructions for the first access network device in the embodiment shown in fig. 8, and which includes a program designed to execute the first access network device in the above embodiment. The storage medium includes, but is not limited to, flash memory, hard disk, solid state disk.

In an embodiment of the present application, a computer program product is further provided, where the computer program product, when executed by a computing device, may perform the communication method designed for the first access network device in the embodiment shown in fig. 8.

Referring to fig. 9, fig. 9 is a schematic structural diagram of a second access network device according to an embodiment of the present application. The second access network device is configured to implement the method embodiments of fig. 2 to 4. The second access equipment is applied to a communication system, and the communication system comprises a first communication system, a second communication system and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; alternatively, the first communication system is a 3G communication system, and the second communication system is a 2G communication system, as shown in fig. 9, the second access network device 900 includes a transceiver module 901 and a processing module 902.

A transceiver module 901, configured to receive, when a terminal performs a CS service, a CSFB identifier corresponding to the terminal, which is transmitted by a first access network device in a first communication system, when the terminal falls back from the resident 4G communication system to the first communication system and falls back from the first communication system to the second communication system;

a processing module 902, configured to start, when the terminal ends the CS service, a procedure for quickly returning to the 4G communication system for the terminal according to the CSFB identifier.

Optionally, in a case that the first communication system is a 3G communication system and the second communication system is a 2G communication system, the transceiver module 901 is specifically configured to:

Optionally, in a case that the first communication system is a 2G communication system and the second communication system is a 3G communication system, the transceiver module 901 is specifically configured to:

Optionally, when the terminal ends the CS service, the processing module 902 is specifically configured to: transmitting the access information of the 4G communication system to the terminal; and the access information of the 4G communication system is used for the terminal to quickly return to the 4G communication system after receiving the access information of the 4G communication system.

In the embodiment of the present application, the function of the transceiver module 901 may be implemented by a transceiver of a second access network device, or may be implemented by a communication interface of the second access network device; the functions of the processing module 902 may be implemented by a processor of the second access network device executing instructions stored in a memory.

It will be appreciated that the second access network device 900 is configured to implement the steps performed by the second access network device in the embodiments shown in fig. 2-4. As to the specific implementation manner and corresponding beneficial effects of the functional blocks included in the second access network device in fig. 9, reference may be made to the specific descriptions of the embodiments in fig. 2 to fig. 4, which are not described herein again.

The second access network device shown in fig. 9 described above may be implemented as the second access network device 1000 shown in fig. 10. As shown in fig. 10, a schematic structural diagram of another second access network device is provided for the embodiment of the present application, and the second access network device 1000 shown in fig. 10 includes: a processor 1001 and a transceiver 1002.

The transceiver 1002 is configured to support information transmission between the second access network device 1000 and the access network device or other devices involved in the foregoing embodiments, for example, receive a CSFB identifier sent by the procedure 202 in the embodiment shown in fig. 2; for example, steps 308 and 313 in the embodiment shown in fig. 3; for example, steps 408 and 413 in the embodiment shown in fig. 4.

The processor 1001 is configured to control and manage actions of the second access network device 1000, for example, the processing unit 1001 is configured to support the second access network device 1000 to implement the process 203 in the embodiment shown in fig. 2; for example, step 312 in the embodiment shown in fig. 3; such as step 412 in the embodiment shown in fig. 4.

The processor 1001 and the transceiver 1002 are communicatively coupled, for example, by a bus. The second access network apparatus 1000 may further include a memory 1003. The memory 1003 is used for storing program codes and data for the second access network device 1000 to execute, and the processor 1001 is used for executing the application program codes stored in the memory 1003 to implement the actions of the second access network device provided by any one of the embodiments shown in fig. 2-4.

It should be noted that, in practical applications, the second access network device may include one or more processors, and the structure of the second access network device 1000 does not form a limitation to the embodiments of the present application.

The processor 1001 may be a CPU, NP, hardware chip or any combination thereof. The hardware chip may be an ASIC, PLD, or a combination thereof. The PLD may be a CPLD, an FPGA, a GAL, or any combination thereof.

Memory 1003 may include volatile memory, such as RAM; the memory 1003 may also include non-volatile memory, such as ROM, flash memory, a hard disk, or a solid state disk; the memory 1003 may also include a combination of the above types of memories.

In an embodiment of the present application, a computer storage medium may be provided, which may be used to store computer software instructions for the second access network device in the embodiment shown in fig. 9, and which includes a program designed to execute the second access network device in the above embodiment. The storage medium includes, but is not limited to, flash memory, hard disk, solid state disk.

In the embodiment of the present application, a computer program product is further provided, and when being executed by a computing device, the computer program product may perform the communication method designed for the second access network device in the embodiments shown in fig. 2 to 4.

The embodiment of the application also provides a communication system, which comprises a first communication system, a second communication system and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, and the communication system includes the first access network device in the embodiment shown in fig. 7 and the first access network device in the embodiment shown in fig. 9, so as to implement the communication method designed in the embodiment of the present application.

The embodiment of the application also provides a communication system, which comprises a first communication system, a second communication system and a 4G communication system; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, and the communication system includes the first access network device in the embodiment shown in fig. 8 and the first access network device in the embodiment shown in fig. 10, so as to implement the communication method designed in the embodiment of the present application.

The terms "first," "second," "third," and "fourth," etc. in the description and claims of this application and in the accompanying drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

It should be understood by those of ordinary skill in the art that, in the various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of the processes should be determined by their functions and inherent logic, and should not limit the implementation process of the embodiments of the present application.

Claims

1. A communication method is applied to a communication system, wherein the communication system comprises a first communication system, a second communication system and a 4G communication system; the first communication system and the second communication system are different communication systems supporting CS services; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, and the method is performed by a first access network device in the first communication system, and the method includes:

when a terminal falls back to the first communication system from the resident 4G communication system during a CS service, the first access network equipment acquires a CSFB identifier corresponding to the terminal;

when the terminal performs the CS service and falls back from the first communication system to the second communication system, the first access network device transmits the CSFB identifier to a second access network device in the second communication system, and releases the connection with the terminal; wherein, the CSFB identifier is used for starting a procedure of quickly returning to the 4G communication system for the terminal according to the CSFB identifier when the terminal ends the CS service after the second access network device receives the CSFB identifier;

when a terminal falls back to the first communication system from the resident 4G communication system during a CS service, the first access network device executes a process of falling the terminal back to the second communication system from the first communication system under the condition that a signal strength value of a serving cell serving the terminal in the first communication system is smaller than a signal strength threshold value; or, when the terminal falls back to the first communication system from the resident 4G communication system during the CS service, the first access network device executes a procedure of falling back the terminal from the first communication system to the second communication system when a load of a serving cell in the first communication system that provides a service for the terminal is greater than a load threshold.

2. The method of claim 1, wherein in a case that the first communication system is the 3G communication system and the second communication system is the 2G communication system, the first access network device transmits the CSFB identifier to a second access network device in the second communication system, comprising:

the first access network device sends a migration request relocation required to a 2G-3G core network device, where the migration request carries the CSFB identifier, where the migration request is used for the 2G-3G core network device to send a handover request to the second access network device after receiving the migration request, and the handover request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G.

3. The method of claim 1, wherein in a case that the first communication system is the 2G communication system and the second communication system is the 3G communication system, the first access network device transmits the CSFB identifier to a second access network device in the second communication system, comprising:

the first access network device sends a handover request to a 2G-3G core network device, where the handover request carries the CSFB identifier, where the handover request is used for the 2G-3G core network device to send a migration request location request to the second access network device after receiving the handover request, and the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G.

4. The method according to any of claims 1-3, wherein the access network device in the 3G communication system is a Radio Network Controller (RNC), the access network device in the 2G communication system is a Base Station Controller (BSC), and the core network device in the 3G communication system or the core network device in the 2G communication system is a Mobile Switching Center (MSC).

5. A communication method is applied to a communication system, wherein the communication system comprises a first communication system, a second communication system and a 4G communication system; the first communication system and the second communication system are different communication systems supporting CS services; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, and the method is performed by a second access network device in the second communication system, and the method includes:

when a terminal performs a CS service and falls back to the first communication system from the resident 4G communication system, and falls back to the second communication system from the first communication system, the second access network device receives a CSFB identifier corresponding to the terminal, which is transmitted by a first access network device in the first communication system, and the connection between the first access network device and the terminal is released;

when the terminal finishes the CS service, the second access network equipment starts a flow for quickly returning to the 4G communication system to the terminal according to the CSFB identification;

when a terminal falls back to the first communication system from the resident 4G communication system during a CS service, the terminal falls back to the second communication system from the first communication system under the condition that the signal strength value of a serving cell serving the terminal in the first communication system is smaller than a signal strength threshold value; or, when a terminal falls back to the first communication system from the resident 4G communication system while performing a CS service, the terminal falls back to the second communication system from the first communication system when a load of a serving cell serving the terminal in the first communication system is greater than a load threshold.

6. The method of claim 5, wherein in a case that the first communication system is a 3G communication system and the second communication system is a 2G communication system, the receiving, by the second access network device, the CSFB identifier corresponding to the terminal transmitted by the first access network device in the first communication system by the second access network device comprises:

the second access network device receives a handover request sent by a 2G-3G core network device, where the handover request carries a CSFB identifier corresponding to the terminal, where the handover request is sent by the 2G-3G core network device after receiving a migration request registration request sent by the first access network device, and the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G.

7. The method of claim 5, wherein in a case that the first communication system is a 2G communication system and the second communication system is a 3G communication system, the receiving, by the second access network device, the CSFB identifier corresponding to the terminal transmitted by the first access network device in the first communication system by the second access network device comprises:

the second access network device receives a migration request relocation request sent by a 2G-3G core network device, where the migration request carries a CSFB identifier corresponding to the terminal, where the migration request is sent by the 2G-3G core network device after receiving a handover request sent by the first access network device, and the handover request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G.

8. The method according to any of claims 5-7, wherein the initiating, by the second access network device, a procedure for the terminal to return to the 4G communication system quickly when the terminal ends the CS service comprises:

when the terminal finishes the CS service, the second access network equipment transmits the access information of the 4G communication system to the terminal; and the access information of the 4G communication system is used for the terminal to quickly return to the 4G communication system after receiving the access information of the 4G communication system.

9. The method according to any of claims 5-7, wherein the access network device in the 3G communication system is a radio network controller RNC, the access network device in the 2G communication system is a base station controller BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is a mobile switching center MSC.

10. A communication device is applied to a communication system, wherein the communication system comprises a first communication system, a second communication system and a 4G communication system; the first communication system and the second communication system are different communication systems supporting CS services; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, the communication apparatus is a first access network device in the first communication system, and the first access network device includes:

a transceiver module, configured to transmit the CSFB identifier to a second access network device in the second communication system and release a connection with the terminal when the terminal falls back from the first communication system to the second communication system while performing a CS service; wherein, the CSFB identifier is used for starting a procedure of quickly returning to the 4G communication system for the terminal according to the CSFB identifier when the terminal ends the CS service after the second access network device receives the CSFB identifier;

the processing module is further configured to, when a terminal falls back to the first communication system from the resident 4G communication system during a CS service, execute a procedure of falling back the terminal from the first communication system to the second communication system when a signal strength value of a serving cell serving the terminal in the first communication system is smaller than a signal strength threshold;

or, the processing module is further configured to, when the terminal falls back to the first communication system from the resident 4G communication system during the CS service, execute a procedure of falling back the terminal from the first communication system to the second communication system when a load of a serving cell in the first communication system, which provides a service for the terminal, is greater than a load threshold.

11. The apparatus according to claim 10, wherein in a case where the first communication system is the 3G communication system and the second communication system is the 2G communication system, the transceiver module is specifically configured to: sending a migration request relocation required to 2G-3G core network equipment, where the migration request carries the CSFB identifier, where the migration request is used for the 2G-3G core network equipment to send a handover request to the second access network equipment after receiving the migration request, and the handover request carries the CSFB identifier, where the 2G-3G core network equipment is core network equipment shared by the 2G communication system and the 3G communication system, or the 2G-3G core network equipment includes core network equipment of the 2G communication system and core network equipment of the 3G.

12. The apparatus according to claim 10, wherein in a case where the first communication system is the 2G communication system and the second communication system is the 3G communication system, the transceiver module is specifically configured to: sending a handover request to a 2G-3G core network device, where the handover request carries the CSFB identifier, where the handover request is used for the 2G-3G core network device to send a migration request location request to the second access network device after receiving the handover request, where the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G.

13. The apparatus according to any of claims 10-12, wherein the access network device in the 3G communication system is a radio network controller RNC, the access network device in the 2G communication system is a base station controller BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is a mobile switching center MSC.

14. The apparatus of any of claims 10-12, wherein the processing module is implemented by a processor of the first access network device executing a computer program stored in a memory, and wherein the transceiver module is implemented by a transceiver of the first access network device.

15. A communication device is applied to a communication system, wherein the communication system comprises a first communication system, a second communication system and a 4G communication system; the first communication system and the second communication system are different communication systems supporting CS services; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; or, the first communication system is a 3G communication system, the second communication system is a 2G communication system, the communication device is a second access network device in the second communication system, and the second access network device includes:

a transceiver module, configured to receive, when a terminal performs a CS service and falls back from the resident 4G communication system to the first communication system, and falls back from the first communication system to the second communication system, a CSFB identifier corresponding to the terminal, which is transmitted by a first access network device in the first communication system, and a connection between the first access network device and the terminal is released;

a processing module, configured to start a procedure of quickly returning to the 4G communication system for the terminal according to a CSFB identifier when the terminal ends the CS service;

16. The apparatus according to claim 15, wherein in a case that the first communication system is a 3G communication system and the second communication system is a 2G communication system, the transceiver module is specifically configured to: receiving a handover request sent by a 2G-3G core network device, where the handover request carries a CSFB identifier corresponding to the terminal, where the handover request is sent by the 2G-3G core network device after receiving a migration request relocation request sent by the first access network device, and the migration request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G communication system.

17. The apparatus according to claim 15, wherein in a case where the first communication system is a 2G communication system and the second communication system is a 3G communication system, the transceiver module is specifically configured to: receiving a migration request relocation request sent by a 2G-3G core network device, where the migration request carries a CSFB identifier corresponding to the terminal, where the migration request is sent by the 2G-3G core network device after receiving a handover request sent by the first access network device, and the handover request carries the CSFB identifier, where the 2G-3G core network device is a core network device shared by the 2G communication system and the 3G communication system, or the 2G-3G core network device includes a core network device of the 2G communication system and a core network device of the 3G communication system.

18. The apparatus according to any one of claims 15 to 17, wherein, when the terminal ends the CS service, the processing module is specifically configured to: transmitting the access information of the 4G communication system to the terminal; and the access information of the 4G communication system is used for the terminal to quickly return to the 4G communication system after receiving the access information of the 4G communication system.

19. The apparatus of any of claims 15-17, wherein the access network device in the 3G communication system is a radio network controller RNC, the access network device in the 2G communication system is a base station controller BSC, and the core network device in the 3G communication system or the core network device in the 2G communication system is a mobile switching center MSC.

20. The apparatus of any of claims 15-17, wherein the processing module is implemented by a processor of the second access network device executing a computer program stored in a memory, and wherein the transceiver module is implemented by a transceiver of the second access network device.

21. A communication system, characterized in that the communication system comprises a first communication system, a second communication system and a 4G communication system; the first communication system and the second communication system are different communication systems supporting CS services; the first communication system is a 2G communication system, and the second communication system is a 3G communication system; alternatively, the first communication system is a 3G communication system, the second communication system is a 2G communication system, and the communication system includes the communication device in the first communication system according to any one of the above claims 10 to 14 and the communication device in the second communication system according to any one of the above claims 15 to 20.