Voice call method, and device

Abstract

The present application relates to the technical field of wireless communications. Provided are a voice call method and a device. The method involves redialing in an IMS domain according to a preset mode after call origination in the IMS domain fails, so as to attempt establishing a voice call service in the IMS domain again, wherein the preset mode may comprise: directly redialing in the IMS domain, or continuing to attempt redialing in the IMS domain within a set time duration until a timeout occurs or redialing is successful, or continuing to attempt redialing in the IMS domain within a preset number of times until the number of redialings exceeds the preset number of times or the redialing is successful, etc. The method can solve the problem that a call which obviously could have been successfully redialed in the IMS domain being handed over to a CS domain causes poor voice call quality.

Description

Voice call method and device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on July 26, 2023, with application number 202310929880X and application name “Method and Device for Voice Calls”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of wireless communication technology, and in particular to a method and device for voice communication. Background Art

[0003] As a basic service in communication, voice calls need to be supported in various wireless networks. The communication technologies currently supported by the device include the second generation mobile communication technology (2 nd -generation mobile communication technology, 2G), third-generation mobile communication technology (3G), fourth-generation mobile communication technology (4 th -generation mobile communication technology, 4G) and fifth-generation mobile communication technology (5 th-generation mobile communication technology, 5G). Among them, in the 2G Global System for Mobile Communications (GSM) system and the 3G Universal Mobile Telecommunications System (UMTS), voice calls are implemented in the circuit switched (CS) domain. In the 4G Long Term Evolution (LTE) system and the 5G new radio (NR) system, the circuit switched (CS) domain is not provided, and its voice calls are implemented in the packet switched (PS) domain. Specifically, the 4G LTE system implements the LTE system voice call service (voice over LTE, VoLTE) based on the internet protocol multimedia subsystem (IMS); the 5G NR system implements the NR bearer voice (Voice over New Radio, VoNR) service based on IMS. Among them, IMS was established by the Third Generation Partnership Project (3GPP) rd The 3GPP standard organization proposed the 3GPP standard based on the R5 version, which is a general network architecture for providing multimedia services based on the Internet Protocol (IP) network.

[0004] In current voice call scenarios, call initiation failures due to temporary network failures are common. To improve call success rates, the user equipment (UE)'s underlying modem attempts to switch networks or redial the call based on the cause of the failure and the call phase. For example, if a VoLTE call receives a 503 (Service Unavailable) response from the network, the UE will redial in the CS domain (CS redial).

[0005] However, with the gradual maturity of 5G networks, operators have largely abandoned network maintenance for 2G and 3G mobile communication systems. As a result, call performance in the CS domain is poor, often resulting in issues such as long call initiation times and poor voice quality. Meanwhile, the IMS domain is the core control domain for 5G voice services. Under the IMS architecture, users experience significantly improved voice quality and connection latency. However, there is currently no suitable solution to address call initiation failures or poor call quality.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a method and device for voice calls. After a call fails in the IMS domain, the method continues to attempt to redial in the IMS domain within a timed period until the call times out or the redial succeeds. This solves the problem of a call that can obviously be successfully redialed in the IMS domain being switched to the CS domain, resulting in poor voice call quality.

[0008] In a first aspect, a method for voice communication is provided, which is applied to an electronic device, and the method includes:

[0009] receiving an IMS domain call cancellation message, wherein the IMS domain call cancellation message includes reason information indicating the call cancellation in the Internet Multimedia Subsystem (IMS) domain;

[0010] When the reason information is the first information, re-registration is performed in the IMS domain, where the re-registration is used for the electronic device to perform a voice call service in the IMS domain, and the first information is used to indicate that the IMS service for the electronic device will be restored within a first time period.

[0011] In a possible implementation, the electronic device here may refer to an electronic device that initiates a voice call, which may correspond to the calling UE hereinafter.

[0012] In one possible implementation, the electronic device can receive an IMS domain call cancellation message forwarded by the access network device. The IMS domain call cancellation message can be a message forwarded by the access network device from the core network device, that is, the access network device can forward the IMS domain call cancellation message sent by the core network device to the electronic device in a transparent manner.

[0013] In a possible implementation, the IMS service may refer to the core network establishing an IMS domain default bearer corresponding to the electronic device, and the IMS domain default bearer may be used by the electronic device to establish a voice call service in the IMS domain.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0015] When the reason information is the second information, switching to circuit switched CS domain redialing is performed, and the redialing is used by the electronic device to perform a voice call service in the CS domain. The second information is used to indicate that the IMS service for the electronic device cannot be restored within the first time length.

[0016] In one possible implementation, the IMS domain call cancellation message may include, for example, a service acquisition failure message (service unavailable) 503, or IMS bearer deactivation information, etc. The IMS domain call cancellation message may carry information about the reason why the electronic device canceled the call in the IMS domain. Depending on whether the IMS service can be restored within the first time period, the reason information may be divided into first information and second information. The first information may, for example, correspond to esm_cause=39 in the following embodiment, and the first information is used to indicate that reactivation is required; the second information may, for example, correspond to esm_cause=38 in the following embodiment, or other values, and the second information may be used to indicate other content besides the need for reactivation.

[0017] In a possible implementation, the first duration can be flexibly set as needed. Generally speaking, in order not to cause serious delay in the user's voice call service, the first duration can be set to a shorter time, such as 3s or 5s.

[0018] According to the voice call method provided by this implementation, after an electronic device fails to initiate a call in the IMS domain, the method determines whether the IMS service can be restored within a first time period based on the reason information returned by the network side. If the IMS service can be restored within the first time period, a redial attempt is made in the IMS domain; if the IMS service cannot be restored within the first time period, the voice call service is switched to the CS domain. This method can increase the probability of successfully establishing a voice call service in the IMS domain, especially for voice calls that can obviously be conducted in the IMS domain, and can prevent them from being directly switched to the CS domain with poor call quality, resulting in a poor call experience for users.

[0019] In combination with the first aspect, in certain implementations of the first aspect, when the cause information is the first information, re-registering in the IMS domain specifically includes:

[0020] Start a timer, wherein the timer is set to a timing duration;

[0021] Re-register in the IMS domain within the timing duration.

[0022] In one implementation, within the timing duration may refer to before the timing duration is reached.

[0023] In combination with the first aspect, in some implementations of the first aspect, the timing duration is less than or equal to the first duration.

[0024] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0025] If the timer expires and re-registration in the IMS domain still fails, switching to the CS domain for redialing and conducting a voice call service in the CS domain;

[0026] If the timing duration is not reached and the re-registration in the IMS domain is successful, redialing is performed in the IMS domain and a voice call service is performed in the IMS domain.

[0027] The electronic device still fails to re-register in the IMS domain, which may mean that when the electronic device attempts to re-establish an IMS default bearer with the core network, establishment of the IMS domain default bearer fails.

[0028] In a possible implementation, the timing duration of the timer may be set to be shorter than the first duration.

[0029] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0030] Start a counter, where the counter is used to count the number of times the electronic device re-registers in the IMS domain after the call in the IMS domain is canceled;

[0031] Re-register in the IMS domain.

[0032] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0033] If the preset number of times is reached and re-registration in the IMS domain still fails, the user switches to the CS domain and redials, and conducts voice call services in the CS domain;

[0034] If the re-registration in the IMS domain is successful before the preset number of times is reached, redialing is performed in the IMS domain, and a voice call service is performed in the IMS domain.

[0035] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0036] Resides in the NR system and has registered in the NR IMS domain; or

[0037] It resides in the Long Term Evolution (LTE) system and has been registered in the LTE IMS domain.

[0038] In conjunction with the first aspect, in certain implementations of the first aspect, receiving the IMS domain call cancellation message specifically includes:

[0039] The IMS domain call cancellation message is received, which is forwarded by the access network device from the core network device.

[0040] In combination with the first aspect, in some implementations of the first aspect, the access network device is an access network device of a fifth-generation mobile communication 5G network, or an access network device of a fourth-generation mobile communication 4G network.

[0041] In conjunction with the first aspect, in certain implementations of the first aspect, when the cause information is the second information, switching to CS domain redial specifically includes:

[0042] Selecting the CS domain;

[0043] Sending an extended service request message to the LTE system, where the extended service request message is used to request the LTE system to deliver a second-generation 2G frequency or a third-generation 3G frequency;

[0044] Receiving the 2G frequency point or the 3G frequency point sent by the LTE system;

[0045] In the CS domain, a call is initiated through the 2G frequency or the 3G frequency.

[0046] In combination with the first aspect, in certain implementations of the first aspect, when the electronic device resides in the NR system and has been registered in the NR IMS domain, the method further includes:

[0047] Receive dialing operation input by the user;

[0048] In response to the dialing operation, selecting the NR IMS domain;

[0049] Sending a session invitation message to the NR system, where the session invitation message is used to request establishment of a session connection with the core network device;

[0050] receiving a temporary response message forwarded by the NR system from the core network device, where the temporary response message is used to indicate that the called electronic device has received the session invitation message;

[0051] Receive a fallback indication message sent by the NR system, where the fallback indication message is used to instruct the electronic device to fall back to the LTE system.

[0052] The called electronic device may refer to an electronic device that is called by voice, which may correspond to the called UE hereinafter.

[0053] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes:

[0054] Accessing the LTE system via radio resource control (RRC);

[0055] Establishing a tracking area update (TAU) process with the LTE system, wherein the TAU process includes a bearer supporting the electronic device to complete the IMS domain registration;

[0056] Establishing a dedicated bearer for voice call services in the IMS domain with the LTE system;

[0057] An IMS domain call cancellation message forwarded by the LTE system from the core network device is received, where the IMS domain call cancellation message includes reason information for indicating the reason for the electronic device to cancel the call in the IMS domain.

[0058] In conjunction with the first aspect, in certain implementations of the first aspect, when the cause information is the second information, switching to CS domain redial specifically includes:

[0059] Selecting the CS domain;

[0060] Sending an extended service request message to the LTE system, where the extended service request message is used to request the LTE system to deliver a second-generation 2G frequency or a third-generation 3G frequency;

[0061] Receiving the 2G frequency point or the 3G frequency point sent by the LTE system;

[0062] In the CS domain, a call is initiated through the 2G frequency or the 3G frequency.

[0063] In a second aspect, a method for voice communication is provided, which is applied to an access network device, and the method includes:

[0064] Receiving an IMS domain call cancellation message sent by a core network device, where the IMS domain call cancellation message includes reason information indicating call cancellation in the IMS domain;

[0065] Forwarding the IMS domain call cancellation message to the electronic device, so that when the reason information is the first information, the electronic device re-registers in the IMS domain, the re-registration is used for the electronic device to perform a voice call service in the IMS domain, and the first information is used to indicate that the IMS service for the electronic device will be restored within a first time period. In conjunction with the second aspect, in certain implementations of the second aspect, when the reason information is the second information, the method further includes:

[0066] The electronic device is caused to switch to the CS domain for redialing, where the redialing is used for the electronic device to perform a voice call service in the CS domain, and the second information is used to indicate that the IMS service for the electronic device cannot be restored within the first time length.

[0067] In conjunction with the second aspect, in some implementations of the second aspect, the method further includes:

[0068] The electronic device resides in the NR system and has been registered in the NR IMS domain; or,

[0069] The electronic device resides in the LTE system and has been registered in the LTE IMS domain.

[0070] In combination with the second aspect, in some implementations of the second aspect, the access network device is an access network device of a 5G network, or the access network device is an access network device of a 4G network.

[0071] In conjunction with the second aspect, in some implementations of the second aspect, the method further includes:

[0072] The access network device of the 4G network receives the IMS domain call cancellation message sent by the core network device, where the IMS domain call cancellation message includes reason information for indicating the reason for the electronic device to cancel the call in the IMS domain;

[0073] The access network device of the 4G network forwards the IMS domain call cancellation message to the electronic device.

[0074] In conjunction with the second aspect, in certain implementations of the second aspect, when the cause information is the second information, causing the electronic device to switch to the CS domain redial specifically includes:

[0075] The access network device of the 4G network receives the extended service request message sent by the electronic device, where the extended service request message is used to request the LTE system to send a 2G frequency or a 3G frequency;

[0076] The access network device of the 4G network sends the 2G frequency point or the 3G frequency point to the electronic device, and the 2G frequency point or the 3G frequency point is used by the electronic device to initiate a call in the CS domain.

[0077] In conjunction with the second aspect, in some implementations of the second aspect, the method further includes:

[0078] The access network device receives a session invitation message sent by the electronic device in the IMS domain, where the session invitation message is used to request to establish a session connection with the core network device;

[0079] The access network device forwards the session invitation message to the core network device;

[0080] The access network device receives a temporary response message sent by the core network device, where the temporary response message is used to indicate that the core network device has received the session invitation message;

[0081] The access network device forwards the temporary response message to the electronic device.

[0082] In one implementation, the access network device may send the temporary response message to the electronic device in a transparent transmission manner.

[0083] In conjunction with the second aspect, in certain implementations of the second aspect, when the electronic device resides in the NR system and has been registered in the NR IMS domain, the method further includes:

[0084] The access network device of the 5G network sends a fallback indication message to the electronic device, where the fallback indication message is used to instruct the UE to fall back to the LTE system.

[0085] In conjunction with the second aspect, in some implementations of the second aspect, the method further includes:

[0086] After the electronic device accesses the LTE system through RRC, the access network device of the 4G network establishes a TAU process with the electronic device, wherein the TAU process includes a bearer supporting the electronic device to complete the IMS domain registration; and

[0087] The access network device of the 4G network establishes the TAU process with the core network device;

[0088] The access network device of the 4G network and the electronic device establish a dedicated bearer for performing voice call services in the IMS domain; and

[0089] The access network equipment of the 4G network and the core network equipment establish a dedicated bearer for voice call services in the IMS domain;

[0090] The access network device of the 4G network receives the IMS domain call cancellation message sent by the core network device, where the IMS domain call cancellation message includes reason information for indicating the reason for the electronic device to cancel the call in the IMS domain;

[0091] The access network device of the 4G network sends the IMS domain call cancellation message to the electronic device.

[0092] In conjunction with the second aspect, in certain implementations of the second aspect, when the reason information is the second information, the electronic device switches to CS domain redial, specifically including:

[0093] The access network device of the 4G network receives the extended service request message sent by the electronic device, where the extended service request message is used to request the LTE system to send a 2G frequency or a 3G frequency;

[0094] The access network device of the 4G network sends the 2G frequency point or the 3G frequency point to the electronic device, and the 2G frequency point or the 3G frequency point is used by the electronic device to initiate a call in the CS domain.

[0095] In a third aspect, an electronic device is provided, the electronic device supporting voice call services in an IMS domain and a CS domain, the electronic device comprising:

[0096] one or more processors;

[0097] one or more memories;

[0098] The one or more memories store one or more computer programs, and the one or more computer programs include instructions. When the instructions are executed by the one or more processors, the electronic device executes the method described in any implementation of the first aspect above.

[0099] In a fourth aspect, an access network device is provided, including:

[0100] one or more processors;

[0101] one or more memories;

[0102] The one or more memories store one or more computer programs, and the one or more computer programs include instructions. When the instructions are executed by the one or more processors, the access network device executes the method described in any implementation method of the second aspect above.

[0103] In a fifth aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer-executable program instructions. When the computer-executable program instructions are executed on a computer, the computer executes the method described in any one of the implementation methods of the first aspect or the second aspect.

[0104] In a sixth aspect, a computer program product is provided, comprising a computer program code, which, when executed on a computer, causes the computer to execute the method as described in any one of the implementations of the first or second aspect above. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] FIG1 is a schematic flowchart of a VoLTE call initiation failure.

[0106] FIG2A and FIG2B are schematic diagrams of an IMS system architecture and a CS system architecture, respectively, applicable to a voice call method provided in an embodiment of the present application.

[0107] FIG3 is a schematic structural diagram of a terminal device 100 provided in an embodiment of the present application.

[0108] FIG4 is a software structure block diagram of a terminal device 100 provided in an embodiment of the present application.

[0109] Figures 5A to 5D are schematic diagrams of GUIs that may be involved in the implementation process of some voice call methods provided in embodiments of the present application.

[0110] FIG6 is a schematic flowchart of a voice call method provided in an embodiment of the present application.

[0111] FIG7 is a schematic flowchart of another voice call method provided in an embodiment of the present application.

[0112] FIG8 is a schematic flowchart of another voice call method provided in an embodiment of the present application.

[0113] FIG9 is a schematic flowchart of another voice call method provided in an embodiment of the present application.

[0114] FIG10 is a schematic flowchart of another voice call method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0115] It should be noted that the terms used in the implementation methods section of the embodiments of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application. In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B; "and / or" in this article is merely a way to describe the association relationship of associated obstacles, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two, "at least one" and "one or more" mean one, two or more than two.

[0116] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Therefore, the definition of "first" and "second" features may explicitly or implicitly include one or more of the features.

[0117] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0118] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0119] To facilitate understanding, some signaling and other terms that may be involved in the embodiments of the present application are first introduced below.

[0120] 1. Invite signaling

[0121] Indicates that the calling UE initiates a session request to invite other users to join a session. It can also be used to update the session after the call is established (in this case, the invite can also be called a Re-invite). For the convenience of description, in the embodiments of the present application, the invite signaling can also be described as an invite message or a session invitation message.

[0122] The calling UE herein may also be described as an electronic device, which is a device for initiating a voice call.

[0123] 2. 100trying signaling

[0124] The 100trying signaling is a temporary response signaling. In this embodiment of the present application, the 100trying signaling can be used to indicate that the called UE has received the request message sent by the calling UE. For ease of description, in this embodiment of the present application, the 100trying signaling can also be described as 100trying or as a temporary response message.

[0125] 3. Evolved Packet System Fallback (EPS FB)

[0126] EPS FB means that when 5G does not meet the VoNR conditions, voice call services will fall back from 5G to 4G, relying on VoLTE to ensure voice call continuity. In other words, the UE switches from a 5G standalone (SA) cell to a 4G cell for VoLTE calls.

[0127] 4. Tracking area update (TAU)

[0128] In an embodiment of the present application, if the voice call service falls back from 5G to 4G, and the UE moves from one LTE tracking area (TA) to another, it is necessary to re-register its location in the new TA to notify the network to change the location relationship of the mobile station it has stored. This process is called TAU. Specifically, when the UE switches to the target LTE cell, it will initiate a TAU request to the evolved base station (eNodeB, eNB). If it receives a TAU reject message from the eNB, or does not receive a response message to the TAU request within a preset time period (i.e., TAU no response), it is determined that the UE has failed to reside in the target LTE cell; otherwise, it is determined that the UE has successfully resided in the target LTE cell.

[0129] 5. Quality of service class identifier (QCI)

[0130] QCI is a parameter used by the system to identify the transmission characteristics of service data packets. Protocol 23203 defines the QCI values ​​corresponding to different bearer services. The QCI range is 1-9, corresponding to different resource types, different priorities, different delays, and different packet loss rates. To ensure the normal operation of an application service, it is necessary to configure a matching QCI value for the service (the network side generally provides the corresponding interface). Among them:

[0131] QCI = 1 refers to the IMS domain voice call service bearer. If the dedicated voice bearer with QCI = 1 is not established in time during the call initiation process, it is easy to cause the call to fail and the voice call will not be connected.

[0132] QCI=2 refers to the bearer of video services.

[0133] QCI=5 refers to the IMS default bearer.

[0134] QCI=9 refers to the bearer of data services.

[0135] In the embodiments of the present application, QCI=1, QCI=5, and QCI=9 are mainly involved.

[0136] 6. Evolved Packet System (EPS) Bearer Identity (EBI)

[0137] The EPS bearer identifier (EBI) stands for EPS bearer. An EPS bearer is a data transmission channel within a communication system (such as a 4G network). An active EPS bearer is an established data transmission channel with a specified QoS. In a communication system (such as a 4G network), each EPS bearer has an EPS bearer identifier (EBI). EPS bearer status information indicates whether the bearer corresponding to each EBI exists.

[0138] During mobility, the UE may switch from a 5G network to an EPS network. To ensure the UE's service experience, the UE's QoS flow can be mapped to an EPS bearer to ensure that the UE's service is not interrupted after switching to the EPS network.

[0139] In the embodiment of the present application, different EBI values ​​can be preset to indicate QCI = 1, QCI = 5, and QCI = 9. For example, the EBI can be preset to 5 (or EBI #5) to indicate QCI = 5, the EBI can be preset to 7 (or EBI #7) to indicate QCI = 1, and the EBI can be preset to 6 (or EBI #6) to indicate QCI = 9. Alternatively, other EBI identifiers (such as a, b, c, etc.) can be used to indicate QCI = 1, QCI = 5, QCI = 9, etc., respectively, and this embodiment of the present application is not limited to this.

[0140] 7. Packet data network (PDN)

[0141] Strictly speaking, PDNs in mobile communication systems are divided into internal and external PDNs. The internal PDN is the packet data network within the EPS system, which is the network communication between EPS system entities (such as the mobile management entity (MME), home subscriber server (HSS), serving gateway (SGW), PDN gateway (PGW), and policy and charging rules function (PCRF)). The external PDN is the packet data network outside the EPS system, including the 3rd Generation Partnership Project (3GPP) CDMA1X network, the internet, the Internet of Things (IoT), VoLTE services (IMS), industry applications (such as bank and securities dedicated lines), and the non-3GPP network Worldwide Interoperability for Microwave Access (WiMAX). The internal and external PDNs are distinguished by the PGW in the EPS.

[0142] 8. Data Service (DS)

[0143] In the embodiments of the present application, the DS module and the IMS module are both custom-divided modules within the chip and are closely related. For ease of description, the following embodiments will include the DS submodule within the DS, Radio Resource Control (RRC), and Non-Access Stratum (NAS) modules. The DS, RRC, and NAS modules are considered a single integrated module, including the DS submodule, the RRC submodule, and the NAS submodule, each of which can at least perform its own existing functions.

[0144] For example, as shown in FIG1 , a schematic flow chart of a VoLTE call initiation failure is provided. The flow chart may include the following steps:

[0145] S101: A calling UE receives a dialing operation input by a user.

[0146] S102: The calling UE sends a voice call invitation message (invite) to the called UE via a network device.

[0147] The network device here may be a core network device. It should be noted that in the following embodiments of this application, the core network may be a collective term for the core network and the IMS network, and the core network device may be a collective term for the core network device and the IMS device. That is, for ease of understanding, the core network device in the following embodiments of this application may have both core network functions and IMS functions.

[0148] S103: The network device sends a service acquisition failure message to the calling UE.

[0149] The service acquisition failure message may be: 503 service unavailable.

[0150] Optionally, this process may further include step S104, that is, the network device sends a service acquisition failure message to the called UE.

[0151] S105: The calling UE sends a CS domain redial message (CS call Req) to the network device.

[0152] S106 , in response to the CS domain redial message (CS call Req), the network device sends a voice call invite message (invite) to the called UE.

[0153] According to the embodiment of Figure 1, it can be concluded that when the calling UE fails to initiate a call in the IMS domain, it will directly switch to the CS domain, that is, access the 2G or 3G network to redial. However, there may be multiple problems that lead to the failure of initiating a call in the IMS domain, some of which can be recovered by the core network on its own or solved within the first period of time after debugging. After the cause of the failure of the calling UE to initiate a call in the IMS domain is solved, the calling UE can actually still successfully call in the IMS domain. Therefore, if the call fails in the IMS domain, directly switching to the CS domain to redial may result in missing the successful call in the IMS domain, and the voice call quality in the CS domain is poor, which in turn will affect the user's voice call experience.

[0154] In view of this, an embodiment of the present application provides a method and device for voice calls. The method solves the problem that a call that can obviously be successfully redialed in the IMS domain is switched to the CS domain with poor voice call quality by continuing to try to redial in the IMS domain after the call fails in the IMS domain, rather than directly switching to the CS domain for redial.

[0155] The method of the embodiment of the present application is described in detail below.

[0156] For example, as shown in FIG2A , a schematic diagram of a system architecture applicable to a method for voice calling provided in an embodiment of the present application is provided. The system architecture 01 can be a 4G communication system (LTE system) architecture, a 5G communication system (NR system) architecture, or a new communication system architecture that will emerge in the future development of wireless communications.

[0157] In some embodiments, the system architecture 01 includes at least one UE 100, multiple access network devices 200 (such as 5G and / or 4G access network devices, collectively referred to as access network devices 200) that provide network access for the UE 100, and a core network device 300.

[0158] In some embodiments, UE 100 can be various types of electronic devices, such as: a smartphone, a tablet computer, a wearable device, an in-vehicle device, an augmented reality (AR) / virtual reality (VR) device, a laptop computer, an ultra-mobile personal computer (UMPC), a netbook, a personal digital assistant (PDA) or a dedicated voice call device, etc. The embodiments of the present application do not impose any restrictions on the specific type of UE.

[0159] UE 100 may include multiple functional components or modules, such as a display screen (or screen), a user interface (UI) module, a modem, and the like. The modem may include a call management module, an IMS module, a DS, an RRC, and an NAS module, and the call management module may correspond to an mmode module. The DS submodule is primarily responsible for establishing or activating the bearer, and the IMS submodule is primarily responsible for the call flow. Therefore, the IMS domain call cancellation message (such as an instruction to deactivate the bearer) issued by the core network device is processed by the DS submodule. Furthermore, the DS submodule also notifies the IMS submodule of an IMS domain call initiation failure (or bearer deactivation). After notifying the IMS submodule, the DS submodule continues to perform its own functions, such as determining whether to reestablish the IMS bearer based on the cause information (such as esm_cause=39) carried in the IMS domain call cancellation message. The IMS submodule discovers that the IMS bearer is deactivated, resulting in a call failure, and therefore informs the call management module on which standard to redial (this application involves IMS redialing or CS redialing). For the specific structure of the UE 100, please refer to the introduction in FIG. 4 below, which will not be described in detail here.

[0160] In some embodiments, in a 5G network, the access network device 200 may be a gNB; in a 4G network, the access network device 200 may be an eNB.

[0161] In some embodiments, the core network device 300 can also be described as a network-side device. Similar to the calling UE, the network side also has an IMS network, which can be performed by the IMS module (or IMS device) as the main body to execute related processes. The IMS module can be integrated into the core network device 300, or it can be separately set outside the core network device 300. In the embodiment of the present application, for the sake of convenience of description, the core network and the IMS network are collectively referred to as the core network, and the IMS module and the core network device 300 are collectively referred to as the core network device 300. In other words, the core network device 300 mentioned in the embodiment of the present application can be regarded as a device including an IMS module, which can have both core network functions and IMS functions.

[0162] In some embodiments, the IMS module may further specifically include an I-CSCF network element, an S-CSCF network element, a P-CSCF network element, and an HSS.

[0163] 2B is a schematic diagram of a system architecture applicable to another voice call method provided in an embodiment of the present application. The system architecture 02 can be a 2G communication system architecture or a 3G communication system architecture.

[0164] In some embodiments, the system architecture 02 includes at least one UE 100, multiple access network devices 400 (such as 2G and / or 3G access network devices, collectively referred to as access network devices 400) that provide network access for the UE 100, and a core network device 500.

[0165] For the introduction of UE 100, please refer to the detailed introduction of its structure in the embodiments of Figures 3 and 4 below, which will not be repeated here.

[0166] In some embodiments, in a 2G or 3G network, the access network device may be a base station (NodeB) corresponding to the 2G or 3G network, respectively. In the embodiments of the present application, the access network device 200 and the access network device 400 may also be described as an access point (AP).

[0167] In some embodiments, the core network device 500 may also be described as a network-side device. The core network may include a PS domain and a CS domain. When there is no network failure or abnormality, the core network device 500 may support the calling UE and the called UE to communicate in the PS domain or the CS domain.

[0168] For example, as shown in FIG3 , it is a schematic structural diagram of an electronic device 100 provided in an embodiment of the present application.

[0169] The electronic device 100 may include a processor 110, an external memory interface 120, an internal memory 121, a universal serial bus (USB) interface 130, a charging management module 140, a power management module 141, a battery 142, an antenna 1, an antenna 2, a mobile communication module 150, a wireless communication module 160, an audio module 170, a speaker 170A, a receiver 170B, a microphone 170C, an earphone interface 170D, a sensor module 180, a button 190, a motor 191, an indicator 192, a camera 193, a display screen 194, and a subscriber identification module (SIM) card interface 195, etc. The sensor module 180 may include a pressure sensor 180A, a gyroscope sensor 180B, an air pressure sensor 180C, a magnetic sensor 180D, an acceleration sensor 180E, a distance sensor 180F, a proximity light sensor 180G, a fingerprint sensor 180H, a temperature sensor 180J, a touch sensor 180K, an ambient light sensor 180L, a bone conduction sensor 180M, etc.

[0170] It should be understood that the structure illustrated in the embodiments of the present invention does not constitute a specific limitation on the electronic device 100. In other embodiments of the present application, the electronic device 100 may include more or fewer components than shown, or may combine or separate certain components, or arrange the components differently. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0171] The processor 110 may include one or more processing units. For example, the processor 110 may include an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a memory, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU). The different processing units may be independent devices or integrated into one or more processors.

[0172] The controller may be the nerve center and command center of the electronic device 100. The controller may generate an operation control signal according to the instruction operation code and the timing signal to complete the control of fetching and executing instructions.

[0173] Processor 110 may also include a memory for storing instructions and data. In some embodiments, the memory in processor 110 is a cache memory. This memory can store instructions or data that have just been used or are being recycled by processor 110. If processor 110 needs to use the same instruction or data again, it can directly access the memory. This avoids duplicate accesses, reduces processor 110 latency, and thus improves system efficiency.

[0174] In some embodiments, the processor 110 may include one or more interfaces. The interfaces may include an inter-integrated circuit (I2C) interface, an inter-integrated circuit sound (I2S) interface, a pulse code modulation (PCM) interface, a universal asynchronous receiver / transmitter (UART) interface, a mobile industry processor interface (MIPI), a general-purpose input / output (GPIO) interface, a subscriber identity module (SIM) interface, and / or a universal serial bus (USB) interface.

[0175] The I2C interface is a bidirectional synchronous serial bus that includes a serial data line (SDA) and a serial clock line (SCL). In some embodiments, the processor 110 may include multiple I2C bus lines. The processor 110 may be coupled to the touch sensor 180K, the charger, the flash, the camera 193, and the like via different I2C bus interfaces. For example, the processor 110 may be coupled to the touch sensor 180K via the I2C interface, enabling communication between the processor 110 and the touch sensor 180K via the I2C bus interface, thereby implementing the touch function of the electronic device 100.

[0176] The I2S interface can be used for audio communication. In some embodiments, the processor 110 can include multiple I2S buses. The processor 110 can be coupled to the audio module 170 via the I2S bus to enable communication between the processor 110 and the audio module 170. In some embodiments, the audio module 170 can transmit audio signals to the wireless communication module 160 via the I2S interface, enabling the function of answering calls through a Bluetooth headset.

[0177] The PCM interface can also be used for audio communication, sampling, quantizing, and encoding analog signals. In some embodiments, the audio module 170 and the wireless communication module 160 can be coupled via a PCM bus interface. In some embodiments, the audio module 170 can also transmit audio signals to the wireless communication module 160 via the PCM interface, enabling the function of answering calls via a Bluetooth headset. Both the I2S interface and the PCM interface can be used for audio communication.

[0178] The UART interface is a universal serial data bus used for asynchronous communication. This bus can be a bidirectional communication bus. It converts the data to be transmitted between serial communication and parallel communication. In some embodiments, the UART interface is typically used to connect the processor 110 and the wireless communication module 160. For example, the processor 110 communicates with the Bluetooth module in the wireless communication module 160 via the UART interface to implement Bluetooth functionality. In some embodiments, the audio module 170 can transmit audio signals to the wireless communication module 160 via the UART interface, enabling the function of playing music through Bluetooth headphones.

[0179] The MIPI interface can be used to connect the processor 110 to peripheral devices such as the display 194 and the camera 193. MIPI interfaces include the camera serial interface (CSI) and the display serial interface (DSI). In some embodiments, the processor 110 and the camera 193 communicate via the CSI interface to implement the camera function of the electronic device 100. The processor 110 and the display 194 communicate via the DSI interface to implement the display function of the electronic device 100.

[0180] The GPIO interface can be configured via software. The GPIO interface can be configured as either a control signal or a data signal. In some embodiments, the GPIO interface can be used to connect the processor 110 to the camera 193, display 194, wireless communication module 160, audio module 170, sensor module 180, etc. The GPIO interface can also be configured as an I2C interface, an I2S interface, a UART interface, a MIPI interface, etc.

[0181] The USB interface 130 is an interface that complies with USB standards and specifications, and may be a Mini USB interface, a Micro USB interface, a USB Type-C interface, or the like. The USB interface 130 can be used to connect a charger to charge the electronic device 100, or to transfer data between the electronic device 100 and peripheral devices. It can also be used to connect headphones to play audio. This interface can also be used to connect to other terminals, such as AR devices.

[0182] It is understood that the interface connection relationship between the modules illustrated in the embodiment of the present invention is merely an illustrative illustration and does not constitute a structural limitation on the electronic device 100. In other embodiments of the present application, the electronic device 100 may also adopt different interface connection methods from the above embodiments, or a combination of multiple interface connection methods.

[0183] The charging management module 140 is configured to receive charging input from a charger. The charger can be either a wireless charger or a wired charger. In some wired charging embodiments, the charging management module 140 can receive charging input from the wired charger via the USB interface 130. In some wireless charging embodiments, the charging management module 140 can receive wireless charging input via the wireless charging coil of the electronic device 100. While charging the battery 142, the charging management module 140 can also provide power to the terminal via the power management module 141.

[0184] The power management module 141 is used to connect the battery 142, the charging management module 140 and the processor 110. The power management module 141 receives input from the battery 142 and / or the charging management module 140, and provides power to the processor 110, the internal memory 121, the external memory, the display 194, the camera 193, and the wireless communication module 160. The power management module 141 can also be used to monitor parameters such as battery capacity, battery cycle count, and battery health status (leakage, impedance). In some other embodiments, the power management module 141 can also be set in the processor 110. In other embodiments, the power management module 141 and the charging management module 140 can also be set in the same device.

[0185] The wireless communication function of the electronic device 100 can be implemented through the antenna 1, the antenna 2, the mobile communication module 150, the wireless communication module 160, the modem processor and the baseband processor.

[0186] Antenna 1 and Antenna 2 are used to transmit and receive electromagnetic wave signals. Each antenna in electronic device 100 can be used to cover a single or multiple communication frequency bands. Different antennas can also be reused to improve antenna utilization. For example, antenna 1 can be reused as a diversity antenna for a wireless local area network. In other embodiments, the antennas can be used in conjunction with a tuning switch.

[0187] The mobile communication module 150 can provide solutions for wireless communications including 2G / 3G / 4G / 5G applied to the electronic device 100. The mobile communication module 150 may include at least one filter, a switch, a power amplifier, a low noise amplifier (LNA), etc. The mobile communication module 150 can receive electromagnetic waves from the antenna 1, and filter, amplify, and process the received electromagnetic waves, and transmit them to the modulation and demodulation processor for demodulation. The mobile communication module 150 can also amplify the signal modulated by the modulation and demodulation processor, and convert it into electromagnetic waves for radiation through the antenna 1. In some embodiments, at least some of the functional modules of the mobile communication module 150 can be set in the processor 110. In some embodiments, at least some of the functional modules of the mobile communication module 150 can be set in the same device as at least some of the modules of the processor 110.

[0188] The modem processor may include a modulator and a demodulator. The modulator is used to modulate the low-frequency baseband signal to be transmitted into a medium-high frequency signal. The demodulator is used to demodulate the received electromagnetic wave signal into a low-frequency baseband signal. The demodulator then transmits the demodulated low-frequency baseband signal to the baseband processor for processing. After being processed by the baseband processor, the low-frequency baseband signal is passed to the application processor. The application processor outputs a sound signal through an audio device (not limited to the speaker 170A, the receiver 170B, etc.) or displays an image or video through the display screen 194. In some embodiments, the modem processor may be an independent device. In other embodiments, the modem processor may be independent of the processor 110 and be set in the same device as the mobile communication module 150 or other functional modules.

[0189] The wireless communication module 160 can provide wireless communication solutions including wireless local area networks (WLAN) (such as wireless fidelity (Wi-Fi) networks), Bluetooth (BT), global navigation satellite system (GNSS), frequency modulation (FM), near field communication (NFC), infrared (IR), etc., which are applied to the electronic device 100. The wireless communication module 160 can be one or more devices that integrate at least one communication processing module. The wireless communication module 160 receives electromagnetic waves via the antenna 2, frequency modulates and filters the electromagnetic wave signals, and sends the processed signals to the processor 110. The wireless communication module 160 can also receive the signal to be sent from the processor 110, frequency modulate it, amplify it, and convert it into electromagnetic waves for radiation through the antenna 2.

[0190] In some embodiments, the antenna 1 of the electronic device 100 is coupled to the mobile communication module 150, and the antenna 2 is coupled to the wireless communication module 160, so that the electronic device 100 can communicate with a network and other devices through wireless communication technologies. The wireless communication technologies may include global system for mobile communications (GSM), general packet radio service (GPRS), code division multiple access (CDMA), wideband code division multiple access (WCDMA), time-division code division multiple access (TD-SCDMA), long term evolution (LTE), BT, GNSS, WLAN, NFC, FM, and / or IR technology. The GNSS may include a global positioning system (GPS), a global navigation satellite system (GLONASS), a Beidou navigation satellite system (BDS), a quasi-zenith satellite system (QZSS) and / or a satellite based augmentation system (SBAS).

[0191] The electronic device 100 implements a display function through a GPU, a display screen 194 , and an application processor, etc. The display screen 194 is used to display images, videos, etc.

[0192] The electronic device 100 can implement a shooting function through an ISP, a camera 193, a video codec, a GPU, a display screen 194, and an application processor.

[0193] The digital signal processor is used to process digital signals. In addition to processing digital image signals, it can also process other digital signals. For example, when the electronic device 100 selects a frequency point, the digital signal processor is used to perform Fourier transform on the frequency point energy. The video codec is used to compress or decompress digital video. The NPU is a neural network (NN) computing processor that quickly processes input information by drawing on the structure of biological neural networks, such as the transmission mode between neurons in the human brain, and can also continuously self-learn.

[0194] The external memory interface 120 can be used to connect an external memory card, such as a Micro SD card, to expand the storage capacity of the electronic device 100. The external memory card communicates with the processor 110 via the external memory interface 120 to implement data storage. For example, files such as music and videos can be stored on the external memory card. The internal memory 121 can be used to store computer-executable program code, which includes instructions.

[0195] The electronic device 100 can implement audio functions such as music playback and recording through the audio module 170, the speaker 170A, the receiver 170B, the microphone 170C, the headphone jack 170D, and the application processor.

[0196] For example, the software system of the electronic device 100 can adopt a layered architecture, an event-driven architecture, a microkernel architecture, a microservice architecture, or a cloud architecture. This embodiment of the application uses the Android system with a layered architecture as an example to illustrate the software structure of the electronic device 100. Figure 4 is a block diagram of the software structure of the electronic device 100 according to an embodiment of the application.

[0197] A layered architecture divides software into several layers, each with distinct roles and responsibilities. Layers communicate with each other through software interfaces. In some embodiments, the Android system is divided into four layers: application layer, application framework layer, Android runtime, system library, kernel layer, hardware abstraction layer (HAL), and hardware layer.

[0198] The application layer can include a series of application packages. As shown in Figure 4, the application package can include camera, calendar, map, WLAN, music, short message, gallery, call, navigation, Bluetooth, video and other applications.

[0199] The application framework layer provides an application programming interface (API) and programming framework for applications in the application layer. The application framework layer includes some predefined functions. As shown in Figure 4, the application framework layer may include a window manager, content provider, telephony manager, resource manager, notification manager, and view system.

[0200] The window manager is used to manage window programs. The window manager can obtain the display size, determine whether there is a status bar, lock the screen, take screenshots, etc.

[0201] Content providers are used to store and retrieve data and make it accessible to applications. The data may include videos, images, audio, calls made and received, browsing history and bookmarks, phone books, etc.

[0202] The view system includes visual controls, such as those for displaying text and images. The view system is used to build applications. A display interface can consist of one or more views. For example, a display interface containing a text notification icon might include a view for displaying text and a view for displaying images.

[0203] The phone manager is used to provide communication functions of the electronic device 100, such as management of call status (including answering, hanging up, etc.).

[0204] The resource manager provides various resources for applications, such as localized strings, icons, images, layout files, video files, and so on.

[0205] The Notification Manager allows applications to display notifications in the status bar. These messages can be displayed briefly and then disappear automatically, without requiring user interaction. For example, the Notification Manager can be used to notify users of completed downloads and message reminders. The Notification Manager can also display notifications in the top status bar as icons or scrolling text, such as notifications from background applications, or as dialog windows on the screen. Examples include displaying text messages in the status bar, emitting alert sounds, vibrating the terminal, or flashing indicator lights.

[0206] Android Runtime includes core libraries and a virtual machine. Android Runtime is responsible for scheduling and management of the Android system.

[0207] The core library consists of two parts: one is the function that needs to be called by the Java language, and the other is the Android core library.

[0208] The application layer and application framework layer run in a virtual machine. The virtual machine executes the Java files in the application layer and application framework layer as binary files. The virtual machine is responsible for managing the object lifecycle, stack management, thread management, security and exception management, and garbage collection.

[0209] The system library can include multiple functional modules, such as surface manager, media library, 3D graphics processing library (such as OpenGL ES), 2D graphics engine (such as SGL), etc.

[0210] The surface manager is used to manage the display subsystem and provide fusion of 2D and 3D layers for multiple applications.

[0211] The media library supports playback and recording of a variety of common audio and video formats, as well as static image files. The media library can support a variety of audio and video encoding formats, such as: MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, etc.

[0212] The 3D graphics processing library is used to implement 3D graphics drawing, image rendering, compositing, and layer processing.

[0213] A 2D graphics engine is a drawing engine for 2D drawings.

[0214] The kernel layer is the layer between hardware and software. The kernel layer includes at least display driver, camera sensor driver, audio driver, and sensor driver.

[0215] In order to better understand the voice call method provided in the embodiment of the present application, the user visual level process that may be involved in the method is introduced below with reference to the accompanying drawings.

[0216] 5A to 5D illustrate schematic diagrams of graphical user interfaces (GUIs) that may be involved in implementing some of the voice call methods provided in embodiments of the present application. For ease of description, a mobile phone is used as an example of a UE. However, in actual applications, the UE type is not limited to this.

[0217] FIG5A is a schematic diagram of a mobile phone dialing interface. For example, a status bar 10 may be displayed above the dialing interface. This status bar 10 may include one or more signal strength indicators for mobile communication signals (or cellular signals), one or more signal strength indicators for Wi-Fi signals, a battery indicator for the phone, a time indicator, and the like. Below the status bar 10, the dialing interface may also display a dial pad 20. This dial pad 20 may include Arabic numerals 0 through 9. For example, three or four capital letters are displayed below each of the numerals 2 through 9. Furthermore, the dial pad 20 may also include an asterisk key (*), a pound key (#), a plus sign (+) below the numeral 0, and a number (W) below the pound key. Below the dial pad 20, the dialing interface may also display a call initiation control 30. This call initiation control 30 is used to initiate a voice call to the phone corresponding to the phone number entered by the user in response to a user operation. Below the call control 30, there may also be indicators for switching to other interfaces, including a recent call indicator, a contact list indicator, a dial pad indicator (corresponding to the current dialing interface), and a voice message indicator.

[0218] It should be noted that the dialing interface shown in Figure 5A is only an example. In actual applications, the dialing interface involved in the voice call method provided in the embodiment of the present application may also include more or fewer other controls, or the content of the dialing interface may have other types of layouts. The embodiment of the present application does not limit this.

[0219] In one possible scenario, as shown in FIG5B , when the user needs to have a voice call with friend A, the user can input a dialing operation 601 for the dialing keypad shown in the dialing interface, and the dialing operation 601 can be clicking on the mobile phone number corresponding to friend A. When the mobile phone receives the dialing operation 601 input by the user, in response to the operation, the user's dialed digits (188 as shown in FIG5A ) can be displayed above the dialing keypad 20, and a number deletion control 602 can also be displayed below the dialing keypad. When the mobile phone detects that the user has entered a complete mobile phone number (such as 188****0668), and detects that the user has entered a preset operation for the call control 30 (such as clicking on the call control 30), a voice call can be initiated to the mobile phone corresponding to the mobile phone number (hereinafter referred to as the called mobile phone or called UE). At this time, the mobile phone interface can jump to the voice call interface shown in FIG5C .

[0220] For example, as shown in FIG5C , in addition to displaying the same (or similar) status bar as FIG5A , the voice call interface may also display the name of friend A, the mobile phone number corresponding to friend A, and a voice hang-up control 603 located below the mobile phone number.

[0221] In some embodiments, a user can initiate a voice call to friend A through the 5G NR system. At this time, in the status bar above the voice call interface, the cellular network corresponding to the call number is displayed as 5G (as shown in Figure 5C). However, during the voice call, if the 5G network does not support VoNR services, or the current 5G network does not have the conditions for VoNR, etc., the voice call may fall back to the 4G network, or even fall back to the 3G network or 2G network. At this time, as shown in Figure 5D, the cellular network above the voice call interface can be displayed as 4G (as shown in Figure (a) in Figure 5D), 3G (as shown in Figure (b) in Figure 5D), or 2G (as shown in Figure (c) in Figure 5D). Among them, if it falls back to the 3G network or the 2G network, it means switching from the IMS domain to the CS domain for voice redialing.

[0222] It is worth noting that in this embodiment of the present application, when a call fails in the IMS domain, the calling phone will not directly switch from the IMS domain to the CS domain for redialing, but will continue to redial in the IMS domain based on the reason for the failure in the IMS domain. If the redial in the IMS domain still fails after the trigger condition is met, it will switch to the CS domain for redialing.

[0223] According to the voice call method provided in the embodiment of the present application, after the voice call fails in the IMS domain, by continuing to try to redial in the IMS domain until the redial in the IMS domain is successful, or after the trigger condition is met, the redial in the IMS domain still fails, and then switching to the CS domain for redialing, the probability of successfully establishing a voice call in the IMS domain is increased, and voice call services that can obviously be carried out in the IMS are avoided from being switched to the CS domain with poor call quality, thereby improving the user's voice call quality.

[0224] The following, in conjunction with the accompanying drawings, describes the underlying interaction logic involved in implementing the voice call method provided in the embodiment of the present application. First, in conjunction with Figure 6, the process of the calling UE requesting to establish a voice call in the IMS domain involved in the voice call method provided in the embodiment of the present application is described.

[0225] For example, as shown in Figure 6, a schematic flow chart of a method for voice calling provided in an embodiment of the present application is provided. The execution subject of the process may include a calling UE (such as a mobile phone), a network system, a core network device, etc., and may specifically include the following steps:

[0226] S601: The calling UE resides in the NR system and has registered in the NR IMS domain.

[0227] The calling UE may refer to a device that initiates a voice call, such as a mobile phone as shown in FIG. 5A to FIG. 5D .

[0228] In some embodiments, before camping on the NR system, the calling UE must first access the NR system. For example, the process of the calling UE accessing the NR system may include: the calling UE initiating a contention-based random access; the gNB responding with a Msg2 (also known as a random access response (RAR)) to the calling UE; the calling UE initiating an RRC setup request message to the gNB, carrying initial identity information and establishment cause information, requesting to establish an RRC connection. This message corresponds to Msg3 of the random access procedure; the gNB allocating and establishing an SRB1 bearer (for carrying all RRC signaling and some network attached storage (NAS) signaling) for the calling UE, and sending an RRC setup message to the calling UE; and the UE sending an RRC setup complete message to the gNB, confirming that the RRC connection is successfully established.

[0229] In some embodiments, before the calling UE resides in the NR system, the calling UE may first register in the IMS domain. Exemplarily, the specific steps of the registration process of the calling UE in the IMS domain may include: (1) When the UE creates the IMS default bearer, the UE obtains the P-CSCF address from the message. The UE sends a register message to the P-CSCF via the IMS default bearer; (2) the P-CSCF forwards the register message to the I-CSCF; (3) the I-CSCF sends a User Authorization request message to the HSS to obtain the S-CSCF; (4) the HSS responds to the User Authorization request message, which includes the S-CSCF capability set; (5) the I-CSCF forwards the register message to the S-CSCF; (6) the S-CSCF sends a Multimedia Authentication Request message to the HSS to query the authentication parameter group; (7) the HSS sends the authentication parameter group via a Multimedia Authentication Answer message; (8) the S-CSCF sends a 401 response message to the I-CSCF, which includes the authentication parameters, to perform two-way authentication on the terminal; (9) the I-CSCF sends a 401 response message to the P-CSCF; (10) the P-CSCF sends a 401 response message to the UE. The P-CSCF extracts the AK and CK and forwards the AUTN and RAND to the UE. (11) The UE calculates the authentication parameters and, after passing the network side authentication, resends the register message, which includes the calculated XRES. (12) The P-CSCF forwards the register message to the I-CSCF. (13) The I-CSCF sends the User Authorization request to the HSS again. (14) The HSS returns the S-CSCF name via the User Authorization answer message. (15) The I-CSCF forwards the register message to the S-CSCF. The S-CSCF checks that the XRES returned by the HSS is consistent, and the authentication is successful. The IMS domain supports AKA authentication, the same as 3G. (16) The S-CSCF sends the Service assignment request message to the HSS to obtain the user subscription data. (17) The S-CSCF sends a 200OK response message to the I-CSCF. The I-CSCF forwards the 200OK to the P-CSCF and then to the UE. The UE is successfully registered in the IMS domain; (18) For VoLTE users, the S-CSCF will also send a register message to the corresponding AS based on the user's subscription data, and the AS will return 200OK if the registration is successful.

[0230] In some embodiments, when the calling UE resides in the NR system, the interface of the calling UE may display a 5G cellular signal indicator, such as the 5G signal indicator in the status bar corresponding to FIG5A .

[0231] It should be noted that the embodiment of the present application is only introduced by taking the case where the calling UE resides in the NR system before initiating the call and has registered in the NR IMS domain as an example. In actual applications, the scenario before initiating the call is not limited to this. For example, before initiating the call, the calling UE may reside in the LTE system and have registered in the LTE IMS domain; or reside in the NR system or the LTE system but have not yet completed the IMS domain registration, etc. However, if it involves the situation where the call fails in the IMS domain, the voice call method provided in the embodiment of the present application can be applied. The embodiment of the present application does not specifically limit the application scenario of this method.

[0232] S602: The calling UE receives a dialing operation input by a user.

[0233] In some embodiments, the screen of the calling UE can receive a user's dialing operation; the screen then transmits the dialing operation to the UI module. Exemplarily, the dialing operation may include: a user inputting the called UE number, and a user clicking a call control; or, the dialing operation may include: a user instructing a calling UE assistant (such as a mobile phone assistant) to dial the number through voice input. This application does not limit the specific method of user input of the called UE number.

[0234] In some embodiments, the screen may transmit the dialing operation to the UI module of the calling UE.

[0235] Optionally, the user may input the called UE number in a variety of ways, such as: (1) the user may manually click on the numbers on the dial pad according to the called UE number, such as the operation described in the embodiment corresponding to FIG5B ; (2) the user may also input the called UE number by voice, such as by waking up a mobile phone assistant and then instructing the mobile phone assistant to input the called UE number by voice, etc. This application does not limit the specific method of the user inputting the called UE number.

[0236] S603: The UI module of the calling UE sends a dialing operation to the call management module in the modem of the calling UE.

[0237] S604: The call management module of the calling UE selects the NR IMS domain.

[0238] Among them, the specific process of domain selection NR IMS domain can refer to the existing process, and the embodiment of this application will not go into details about it.

[0239] S605: The call management module sends a dialing instruction to the IMS module.

[0240] The dialing instruction may include information such as the mobile phone number of the called UE and the network standard of the call.

[0241] S606A: In response to the dialing instruction, the IMS module sends a session invitation message (invite) to the NR system.

[0242] The session invite message may be used to request (in the IMS domain) to establish a voice call service with the called UE.

[0243] S606B, the NR system sends the session invitation message (invite) to the core network device.

[0244] In some embodiments, the NR system may forward the session invitation message (invite) to the core network device in a transparent manner.

[0245] S607A, the core network device sends a temporary response message to the NR system.

[0246] In some embodiments, the provisional response message may correspond to 100trying signaling, which is used to indicate that the called UE has received the session invite message (invite) sent by the calling UE.

[0247] S607B, the NR system sends a temporary response message to the calling UE.

[0248] In some embodiments, the NR system may forward the temporary response message to the calling UE in a transparent manner. Specifically, the NR system may transparently transmit the temporary response message to the IMS module of the calling UE.

[0249] In some embodiments, after the calling UE obtains the provisional response message, it may be known that the called UE has received the session invite message (invite).

[0250] In some scenarios, if the 5G network does not support VoNR services, or the current 5G network does not have the conditions for VoNR, the NR system can instruct the calling UE to switch from the 5G network to the 4G network to establish a voice call in the IMS domain. In this case, the following step S608 needs to be executed:

[0251] S608: The NR system instructs the DS, RRC, and NAS modules in the calling UE modem to fall back from the NR system to the LTE system through the EPS FB process (EPS FB to LTE).

[0252] In some embodiments, the NR system may specifically instruct the DS, RRC, and RRC submodules in the NAS modules to fall back from the NR system to the LTE system through the EPS FB process.

[0253] In some embodiments, 5G networks define two voice access methods: VoNR and evolved packet system fallback (EPS fallback). Therefore, if NR does not support or does not have VoNR voice call services, or if there is a NR failure, the network will instruct the calling UE to use the EPS fallback voice solution, that is, instruct the calling UE to fall back to LTE for VoLTE voice call services, thereby achieving voice continuity.

[0254] It should be noted that in the embodiments of the present application, the DS, RRC, and NAS modules of the calling UE may refer to a module in which the DS submodule, the RRC submodule, and the NAS submodule are integrated together. In this module, the DS submodule, the RRC submodule, and the NAS submodule may perform their respective original functions.

[0255] It should also be noted that the embodiment of the present application is described by taking the case where the calling UE does not support the VoNR voice call service as an example. However, in actual applications, if the calling UE supports the VoNR voice call service, there is no need to fall back to LTE to perform the VoLTE voice call service, and the VoNR voice call service can be performed directly on NR. Alternatively, in actual applications, if the calling UE resides in the LTE system and has been registered in the LTE IMS domain, there is no need to perform this step, and the VoLTE voice call service can be performed directly on LTE. That is to say, in the embodiment of the present application, falling back to the LTE system with the calling UE and performing the voice call service on the LTE IMS domain is only an example of a possible scenario, and in actual applications, it is not limited to this.

[0256] When the calling UE needs to fall back to LTE to perform VoLTE service, the calling UE needs to access the LTE system. Please refer to step S609 for the specific process:

[0257] S609: The DS, RRC and NAS modules of the calling UE initiate an RRC access procedure.

[0258] The RRC access process in this step may be specifically initiated by the RRC submodule.

[0259] In some embodiments, the process of the calling UE accessing the LTE system by initiating an RRC access process may include, for example: when the calling UE is turned on but no RRC connection is established with the LTE system, the eNode sends relevant configuration information through a system broadcast message, and the calling UE searches for a cell based on this information, synchronizes time and frequency with the cell, obtains a physical cell identifier, and obtains cell quality and other cell information based on the physical cell identifier. Finally, the calling UE can select a suitable cell to reside in.

[0260] It should be noted that the calling UE not only needs to perform a cell search when it is turned on, but also, to support mobility, it continuously searches for neighboring cells, synchronizes with them, and estimates the reception quality of the cell signals, thereby deciding whether to perform a handover or cell reselection. The detailed process of the calling UE accessing the LTE system can be found in existing standard procedures or other improved procedures, and this embodiment of the application will not be described in detail.

[0261] S610A: The calling UE sends a TAU request message to the LTE system. The TAU request message is used to initiate a TAU procedure, and the TAU request message carries EBI#5 and EBI#6.

[0262] In some embodiments, the TAU procedure in this step may be initiated by the NAS submodule.

[0263] The specific implementation process of the TAU process may include: the NAS sub-module sends a TAU request message to the LTE system, and the TAU request message may include BEI#5 and EBI#6. The TAU request message can be used to request synchronization of the status of the IMS default bearer and the status of the data service bearer with the network (such as the core network device side); after the LTE system receives the TAU request message, it forwards it to the core network device; in response to the TAU request message, the core network device can send a TAU response message to the LTE system, and the TAU response message can indicate the status of the IMS default bearer and the data service bearer stored (or recorded) by the core network device; after the LTE system receives the TAU response message, it forwards it to the NAS sub-module.

[0264] It should be noted that the TAU process is used to align the bearer status between the calling UE and the network (such as the core network equipment side). The TAU request message can carry the status of the calling UE side (the status of the IMS default bearer and the status of the data service bearer). When the TAU receives the request (or TAU accept), the process is equivalent to carrying the status of the IMS default bearer and the status of the data service bearer on the network side.

[0265] It should also be noted that the calling UE informs the 4G core network (evolved packet core, EPC) of its own tracking area (TA) through tracking area registration. TA is a concept established by the LTE system for UE location management. Generally, a TA is identified by a tracing area identity (TAI). TAI can include a mobile country code (MCC), a mobile network code (MNC) and a tracking area code (TAC). Since in this embodiment, the calling UE reselects a cell from the NR system to the LTE system, the calling UE needs to send a TAU request message to the core network of the LTE system to initiate the TAU process, thereby realizing the tracking area update. The calling UE can inform the EPC of its own TA through the tracking area update. The EPC can send a paging message to the eNodeB of the TA to which the calling UE belongs based on the TA to which the calling UE belongs.

[0266] It is worth noting that when the calling UE initiates the TAU process, the TAU request message carries EBI#5 (EBI#5 corresponds to QCI=5), which means that the calling UE supports and needs to establish the IMS default bearer. In addition, the TAU request message can also carry EBI#6 (EBI#6 corresponds to QCI=9), which means that the calling UE supports and needs to establish a bearer for data services.

[0267] S610B, the LTE system sends a TAU request message to the core network device. The TAU request message is used to initiate a TAU process, and the TAU request message carries EBI#5 and EBI#6.

[0268] The LTE system may transmit the TAU request message to the core network device of the 4G network in a transparent manner.

[0269] In some embodiments, the TAU request message may include BEI#5 and EBI#6, and the TAU request message may be used to request synchronization of the status of the IMS default bearer and the status of the data service bearer with the network (such as the core network device side).

[0270] S611A: The core network device sends a TAU response message to the LTE system.

[0271] In some embodiments, the TAU response message may indicate the status of the IMS default bearer and the bearer of the data service stored (or recorded) by the core network device.

[0272] S611B: The LTE system sends a TAU response message to the calling UE.

[0273] In some embodiments, the LTE system sends a TAU response message to the NAS submodule in the calling UE.

[0274] S612A: The core network device sends a dedicated bearer establishment message to the LTE system. The dedicated bearer establishment message carries EBI#7.

[0275] Among them, EBI#7 (corresponding to QCI=1) means establishing a dedicated bearer for the IMS voice call service.

[0276] Specifically, the execution entities of the dedicated bearer establishment process in this step may mainly include the core network device and the DS submodule in the calling UE.

[0277] The specific implementation process of the dedicated bearer establishment process may include: the core network device sends a dedicated bearer establishment message to the LTE system, and the dedicated bearer establishment message may include EBI#7; after receiving the dedicated bearer establishment message, the LTE system forwards it to the NAS submodule and DS submodule of the calling UE; in response to the dedicated bearer establishment message, the NAS submodule and DS submodule of the calling UE may send a dedicated bearer establishment response message to the LTE system, wherein the dedicated bearer establishment response message may include relevant parameters for establishing the dedicated bearer; after receiving the dedicated bearer establishment response message, the LTE system forwards it to the core network device.

[0278] S612B: The LTE system sends a dedicated bearer establishment message to the calling UE. The dedicated bearer establishment message carries EBI#7.

[0279] In some embodiments, the LTE system may send the dedicated bearer establishment message to the DS submodule in the calling UE in a transparent transmission manner.

[0280] S613A: The calling UE sends a dedicated bearer establishment response message to the LTE system. The dedicated bearer response message carries EBI#7.

[0281] In some embodiments, in response to the dedicated bearer establishment message in step S612B, the DS submodule of the calling UE may send a dedicated bearer establishment response message to the LTE system, wherein the dedicated bearer establishment response message may include relevant parameters for establishing a dedicated bearer, etc.

[0282] S613B, the LTE system sends a dedicated bearer establishment response message to the core network device.

[0283] In some cases, after the calling UE successfully completes the establishment of a dedicated bearer for the IMS domain voice call service with QCI=1 during the LTE TAU process, the core network side may be unable to continue the voice call service in the IMS domain due to a temporary network failure, and will send an IMS domain call cancellation message. The IMS domain call cancellation message may include, for example, an IMS bearer deactivation message for deactivating the IMS default bearer, or a service acquisition failure message (503 service unavailable) 503. For ease of understanding, the following description only uses the example of the core network device sending an IMS bearer deactivation message, but it should be understood that the embodiments of the present application are not limited to this.

[0284] S614A: The core network device sends an IMS bearer deactivation message to the LTE system. The IMS bearer deactivation message carries EBI#5 and cause information.

[0285] It should be noted that after the core network side obtains EBI#5 and EBI#7, two situations may occur: the former is that if there is no failure on the core network side and the calling UE's voice call service (VoLTE) in the IMS domain is supported, then the calling UE can subsequently directly establish a VoLTE voice call with the called UE in the IMS domain; the latter is that if there is a (temporary) failure on the core network side, that is, the voice call service (VoLTE) in the IMS domain is currently not supported, then the calling UE may subsequently continue to try to re-register in the IMS domain based on the reason information of IMS bearer deactivation. If the registration is successful, the VoLTE voice call service will be re-established in the IMS domain; if the registration fails, it will switch to the CS domain for the voice call service; or, the calling UE may subsequently switch directly to the CS domain for the voice call service based on the reason information of IMS bearer deactivation.

[0286] For the former, the calling UE can directly complete the VoLTE voice call service in the IMS domain. This embodiment of the present application does not describe this situation in detail. The voice call method provided in the embodiment of the present application is mainly applied to the latter, that is, when a (temporary) failure occurs on the core network side, the IMS default bearer is deactivated, and the core network side currently does not support the voice call service in the IMS domain.

[0287] It should be noted that the EBI value of 5 carried in the IMS bearer deactivation message indicates that the IMS default bearer for the corresponding UE recorded by the core network device has an abnormality. This also means that the calling UE cannot establish a voice call service in the IMS domain.

[0288] In some embodiments, an IMS bearer deactivation message may be used as an example of an IMS domain call cancellation message sent by a core network device, and the IMS domain call cancellation message is used to indicate the cancellation of the call of the calling UE in the IMS domain. Optionally, the core network device may also send to the LTE system other messages for indicating that the calling UE failed to initiate a call in the IMS, such as a service acquisition failure message (such as 503 service unavailable). For ease of understanding, the following description will only take the IMS bearer deactivation message sent by the core network device as an example, but it should be understood that the embodiments of the present application are not limited to this.

[0289] In some embodiments, the cause information is used to indicate whether the IMS service can be restored within the first time period. For example, when the cause information is esm_cause=39, it indicates that the IMS service can be restored within the first time period and needs to be reactivated; when the cause information is esm_cause=38, it indicates that the IMS service cannot be restored within the first time period. The IMS service may refer to the core network establishing an IMS domain default bearer corresponding to the calling UE, and the IMS domain default bearer may be used by the calling UE to establish a voice call service in the IMS domain.

[0290] In some embodiments, the first duration can be flexibly set according to needs, such as being set to 3s or 5s, which is not limited in the embodiments of the present application.

[0291] In some embodiments, the LTE system may specifically send the IMS bearer deactivation message to the DS submodule. It should be noted that when the core network device sends a call cancellation message for other IMS domains, the LTE system may also directly send the IMS domain call cancellation message to the IMS module of the calling UE.

[0292] It should be noted that the IMS bearer deactivation message can be used as an example of an IMS domain call cancellation message sent by the core network device, and the IMS domain call cancellation message is used to indicate the cancellation of the call of the calling UE in the IMS domain. Optionally, the core network device may also send to the LTE system other messages for indicating that the calling UE failed to initiate a call in the IMS, such as a service acquisition failure message (such as 503service unavailable). For ease of understanding, the following only uses the example of the IMS bearer deactivation message sent by the core network device for introduction, but it should be understood that the embodiments of the present application are not limited to this.

[0293] S614B: The LTE system sends an IMS bearer deactivation message to the calling UE. The IMS bearer deactivation message carries EBI#5 and cause information.

[0294] In some embodiments, the LTE system may specifically send the IMS bearer deactivation message to the DS submodule. The LTE system may send the IMS bearer deactivation message to the calling UE in a transparent transmission manner.

[0295] It is worth noting that after the core network device returns an IMS bearer deactivation message carrying cause information to the caller, in the voice call method provided in the embodiment of the present application, the calling UE side can redial in the IMS domain in different ways according to the cause information, and try to re-establish the voice call service in the IMS domain. For example, the following, in conjunction with Figures 7 to 10, introduces several solutions for the calling UE to re-establish the voice call service in the IMS domain in the scenario where the calling UE resides in the NR and has registered in the IMS domain, but its IMS default bearer is subsequently deactivated.

[0296] For example, depending on the type of triggering condition for switching from the IMS domain to the CS domain, the method provided in the embodiment of the present application may specifically include the following solutions:

[0297] Solution 1: The triggering condition is: redial in the IMS domain. If the redial fails, switch to the CS domain for redial; if the redial succeeds, the voice call service is carried out in the IMS domain.

[0298] For example, as shown in FIG7 , a schematic flow chart of a method for making a voice call provided in an embodiment of the present application is provided. This process may be executed after step S614B above. The execution subject of this process may include the calling UE (such as a mobile phone), the network system, the core network device, etc., and may specifically include the following steps:

[0299] S701: The DS, RRC, and NAS modules of the calling UE send an IMS bearer deactivation notification message to the IMS module of the calling UE.

[0300] The IMS bearer deactivation notification message is used to indicate that the IMS default bearer has been deactivated.

[0301] S702: The IMS module of the calling UE determines whether the IMS service can be restored within the first time period based on the reason information of the IMS bearer deactivation.

[0302] In some embodiments, the calling UE can determine whether to re-register in the IMS domain or re-establish the IMS bearer based on the cause information. Specifically, when the IMS service can be restored within the first time period (e.g., the cause information is esm_cause=39), the calling UE can determine to reactivate the IMS bearer and re-register in the IMS domain based on the cause information; when the IMS service cannot be restored within the first time period (e.g., the cause information is esm_cause=38), the calling UE can determine not to re-register in the IMS domain or activate the IMS bearer based on the cause information, and can then switch to the CS domain for redialing.

[0303] It should be noted that the reason information esm_cause=39 listed here corresponds to the IMS service being able to be restored within the first time period, and esm_cause=38 corresponds to the IMS service not being able to be restored within the first time period. This is for example only. In actual applications, the identifier used to indicate whether the IMS service can be restored within the first time period may also include other content, which is not limited in this embodiment of the present application.

[0304] Exemplarily, there are multiple ways for the calling UE to determine whether the IMS service can be restored within the first time period based on the cause information, such as: (1) The calling UE can obtain which cause values ​​correspond to the IMS service being able to be quickly restored and which cause values ​​are not based on the acquired prior experience (such as acquired big data or acquired historical data, etc.). This method is equivalent to the calling UE having a built-in rule in advance. When the cause value is received, it can calculate whether the IMS bearer needs to be rebuilt based on the built-in rule. (2) The calling UE can negotiate with the core network device under which cause values ​​the IMS service on the network side can be quickly restored and which cause values ​​are not. The calling UE can then store the negotiation results locally. When the cause information is received, it can query which IMS service recovery result the cause value in the cause information corresponds to based on the locally stored negotiation results. (3) The calling UE can obtain the correspondence between the cause value and the IMS service recovery result in advance from the network side or from a third party outside the network side, and store it locally.

[0305] Taking the above-mentioned method (2) as an example, a possible example of the negotiation result can be seen in Table 1 below.

[0306] Table 1

[0307] Optionally, the IMS bearer deactivation cause information may further indicate more detailed information on whether the IMS service can be restored. For example, referring to Table 2 below, when the deactivation cause information is: esm_cause = A, it may correspond to that the IMS service can be restored, but the restoration time is unknown; when the deactivation cause information is: esm_cause = B (B may be 39), it may correspond to that the IMS service can be restored within the first time period (e.g., within 3s or 5s); when the deactivation cause information is: esm_cause = C (C may be 38, for example), it may correspond to that the IMS service cannot be restored within the first time period (e.g., within 3s or 5s).

[0308] Table 2

[0309] It should be noted that the deactivation reasons provided in the embodiment of the present application are only introduced using A to C as examples. In actual applications, other identifiers (such as values ​​39, 38, etc.) can also be used to establish a correspondence between the deactivation cause and the IMS service recovery result.

[0310] In conjunction with Table 1 and Table 2 above, an example is given to illustrate how the calling UE can determine whether to re-register in the IMS domain or re-establish the IMS bearer based on the cause information:

[0311] First, for the situation in Table 1 above, the calling UE can determine whether the IMS service can be restored within the first time period based on the cause information returned by the core network side. The method may include: if the cause information obtained by the calling UE is esm_cause=39, it is determined that the IMS service can be restored within the first time period (such as within 3s or 5s), and it can subsequently re-register in the IMS domain, establish the default bearer of the IMS domain, and conduct voice call services on the IMS domain; if the cause information obtained by the calling UE is esm_cause=38, it is determined that the IMS service cannot be restored within the first time period, and it will not re-register in the IMS domain subsequently, but will switch to the CS domain for redialing and conduct voice call services on the CS domain.

[0312] With respect to the situation in Table 2 above, it should be noted that when the deactivation cause information is: esm_cause = A, since the IMS service can be restored, but the recovery time may be short (such as being able to be restored within 5s) or long (such as being restored in 5s or more), esm_cause = A can be set to correspond to different recovery results according to requirements. Specifically, esm_cause = A can be set to correspond to the IMS service being able to be restored within the first time period, or esm_cause = A can be set to correspond to the IMS service not being able to be restored within the first time period. Therefore, in some embodiments, with respect to the situation in Table 2 above, the calling UE may determine whether the IMS service can be restored based on the cause information in a variety of ways, including:

[0313] For example, in method 1 (see Table 3), when the deactivation cause information is esm_cause=A, it is considered that the IMS service can be restored within the first time period, and the calling UE will subsequently (such as waiting for a period of time, or waiting for a scheduled time period, or periodically) attempt to re-register in the IMS domain and attempt to re-establish VoLTE; when the cause information is esm_cause=B (B is, for example, 39), it is also considered that the IMS service can be restored within the first time period, and the calling UE will subsequently (such as waiting for a period of time, or waiting for a scheduled time period, or periodically) attempt to re-register in the IMS domain and attempt to re-establish VoLTE. That is, in this method, when the cause information is A and / or B, it is determined that the IMS service will be restored within the first time period (that is, the judgment result is Y). When the cause information is esm_cause=C (C is, for example, 38), it is considered that the IMS service cannot be restored within the first time period, and the calling UE will no longer attempt IMS registration. At this time, the judgment result of whether the IMS service will be restored within the first time period is N.

[0314] Table 3

[0315] For another example, in mode 2 (see Table 4), when the cause information is esm_cause=A, or when the deactivation cause information is esm_cause=C (C is, for example, 38), it is considered that the IMS service cannot be restored within the first time period, and the calling UE will not attempt to re-register in the IMS domain. In this case, the result of the judgment on whether the IMS service can be restored can be determined to be N. When the deactivation cause information is esm_cause=B (B is, for example, 39), the calling UE can determine that the IMS service can be restored within the first time period, and the calling UE will subsequently attempt to re-register in the IMS domain (e.g., after waiting for a period of time, or waiting for a timed period, or periodically). In this case, the result of the judgment on whether the IMS service can be restored within the first time period can be determined to be Y.

[0316] Table 4

[0317] Among them, if the judgment result in this step S702 is N, that is, the IMS service cannot be restored within the first time period, the IMS module will inform the call management module of the result, and then execute step S703; if the judgment result in this step S702 is Y, that is, the IMS service can be restored within the first time period, the IMS module will send an IMS registration request message to the DS, RRC and NAS modules for IMS domain registration, that is, execute the subsequent step S710.

[0318] First, the case where the judgment result in step S702 is N is introduced. This case may then include the following steps:

[0319] S703: The IMS module sends a CS domain redial instruction message (CS redial) to the call management module.

[0320] The CS domain redial instruction message (CS redial) is used to instruct the call management module to switch to the CS domain for redialing.

[0321] S704: In response to the CS domain redial instruction message (CS redial), the call management module selects the CS domain and redials in the CS domain.

[0322] S705: The call management module sends a CS domain redial notification message to the NAS submodule.

[0323] S706 , in response to the CS domain redial notification message, the NAS submodule sends an extended service request message (extended service request Msg, MO CS fallback) to the LTE system.

[0324] The extended service request message is used to request the LTE system to send a 2G frequency point or a 3G frequency point.

[0325] S707 , the LTE system sends an extended service response message to the NAS submodule of the calling UE.

[0326] Among them, the extended service response message includes the 2G frequency or 3G frequency issued by the LTE system, and the 2G frequency or 3G frequency is used for the calling UE to communicate on the 2G network or 3G network. In this embodiment of the application, the communication can specifically refer to voice call communication.

[0327] S708: The calling UE camps on the CS.

[0328] In some embodiments, the modules involved in residing in the CS domain include: a UI module and a modem, etc.

[0329] S709: The calling UE initiates a CS domain call process.

[0330] In some embodiments, a calling UE makes a voice call to a 2G / 3G network system in the CS domain; and the 2G / 3G network system makes a voice call to a core network device in the CS domain. Specifically, the call management module of the calling UE may send a CS domain call setup message to the 2G / 3G network system; and the 2G / 3G network system may send a CS domain call setup message to the core network device.

[0331] Next, the case where the judgment result in step S702 is Y is introduced. This case may include the following steps:

[0332] Optionally, the embodiment of the present application may further include step S710, that is, the IMS module of the calling UE sends an IMS registration request message to the DS submodule.

[0333] The IMS registration request message is used to instruct to reactivate the bearer and register in the IMS domain.

[0334] S711A: The DS submodule of the calling UE sends an IMS PDN setup request message to the LTE system. The IMS PDN setup request message carries EBI#5.

[0335] S711B: The LTE system forwards the IMS PDN establishment request message to the core network device.

[0336] S712A: The core network device sends an IMS PDN establishment response message to the LTE system.

[0337] The registration response message may be used to indicate whether the IMS default bearer is established successfully.

[0338] S712B, the LTE system sends an IMS PDN establishment response message to the DS submodule.

[0339] S713: The calling UE initiates an IMS domain registration process.

[0340] The process of the calling UE registering in the IMS domain can be referred to the introduction in step S601 above, which will not be repeated here.

[0341] In some embodiments, once the default bearer in the IMS domain is established, the calling UE can send SIP messages on this bearer. If a VoLTE user wants to make a call through the IMS domain, he or she must first register with the IMS domain through SIP signaling.

[0342] In some embodiments, since the IMS service of the core network device has been restored in this situation, after the calling UE completes registration, the core network device may also feed back an IMS registration response message to the calling UE to indicate that the IMS registration is complete.

[0343] S714: The IMS module of the calling UE determines whether the IMS service is restored.

[0344] In some embodiments, the IMS module may determine that the IMS service has been restored when the calling UE successfully registers on the IMS domain (e.g., receives a registration success message sent by the network side). Alternatively, the calling UE may receive an IMS service restoration notification message broadcast by the LTE system, indicating that the IMS service has been restored. The embodiments of the present application do not limit the manner in which the calling UE determines that the IMS service has been restored.

[0345] It should be noted that determining whether the IMS service is restored in this step refers to determining whether the IMS service is restored within the first time period. In the embodiment of the present application, the first time period can be flexibly set according to communication requirements, for example, 3 seconds or 5 seconds.

[0346] If the judgment result in this step is N, that is, the IMS service cannot be restored within the first time period, the IMS module may inform the call management module of the result, and the call management module may subsequently switch to the CS domain for redialing. The process of the call management module switching to the CS domain for redialing may include the following steps:

[0347] S715: The IMS module sends a CS domain redial instruction message to the call management module.

[0348] S716: The call management module selects the CS domain and redials in the CS domain.

[0349] S717: The call management module sends a CS domain redial notification message to the DS, RRC, and NAS modules.

[0350] S718, the DS, RRC, and NAS modules send an extended service request message to the LTE system. The extended service request message is used to request the LTE system to send 2G / 3G frequency points.

[0351] S719, the LTE system sends an extended service response message to the DS, RRC, and NAS modules. The extended service response message includes the 2G / 3G frequency sent by the LTE system.

[0352] S720: The calling UE resides in the CS domain.

[0353] S721: The calling UE initiates a call process in the CS domain.

[0354] Among them, for the detailed introduction of steps S715 to S721, please refer to the relevant introduction of steps S703 to S709 above, which will not be repeated here.

[0355] If the result of the determination in step S702 is that the IMS can be restored within the first time period, the IMS module may inform the call management module of the result, and the call management module may subsequently re-register on the IMS domain, which may specifically include the following steps:

[0356] S722: The IMS module sends an IMS domain redial instruction message to the call management module.

[0357] The IMS domain redial instruction message is used to instruct the call management module to redial in the IMS domain to perform a voice call service in the IMS domain.

[0358] S723: The call management module redials in the IMS domain.

[0359] S724: The calling UE initiates a call process in the IMS domain.

[0360] In some embodiments, the calling UE first places a call to the LTE system; then, the LTE system places a call to the core network device in the IMS domain.

[0361] According to the voice call method provided in the embodiment of the present application, after the calling UE fails to initiate a call in the IMS domain, it is determined whether the IMS service can be restored within a first time period based on the reason information returned by the network side. If the IMS service can be restored within the first time period, a redial is attempted on the IMS domain; if the IMS service cannot be restored within the first time period, the voice call service is switched to the CS domain. This method can increase the probability of successfully establishing a voice call service on the IMS domain, especially for voice call services that can obviously be conducted on the IMS domain, and can avoid them being directly switched to the CS domain with poor call quality, resulting in a poor call experience for users.

[0362] Solution 2: The triggering condition is as follows: start the timer and redial in the IMS domain. If the calling UE fails to redial (or re-register) in the IMS domain before the timer expires, it switches to the CS domain for redialing and conducts the voice call service in the CS domain. If the calling UE succeeds in redialing (or re-registering) in the IMS domain before the timer expires, it conducts the voice call service in the IMS domain.

[0363] For example, as shown in FIG8 , a schematic flow chart of another method for making a voice call provided in an embodiment of the present application is provided. This process can be executed after step S614B above. The execution subject of this process may include the calling UE (such as a mobile phone), the network system, the core network device, etc., and may specifically include the following steps:

[0364] It's worth noting that the main difference between the embodiment of Figure 8 and the embodiment of Figure 7 is that, after determining that the IMS service can be restored within the first time period, the method of the embodiment of Figure 8 starts a timer to detect whether the IMS service can be restored within the time period. If it can be restored within the time period, the subsequent call is made on the IMS domain. In other words, compared to the embodiment of Figure 7, the method of the embodiment of Figure 8 adds a timer to further limit the time period for IMS service restoration, thus preventing the IMS service restoration from taking too long, causing the user to wait too long and affecting the call experience.

[0365] S801: The DS, RRC, and NAS modules of the calling UE send an IMS bearer deactivation notification message to the IMS module of the calling UE.

[0366] The IMS bearer deactivation notification message is used to indicate that the IMS default bearer has been deactivated.

[0367] S802: The IMS module of the calling UE determines whether the IMS service can be restored within the first time period based on the reason information of the IMS bearer deactivation.

[0368] It should be noted that the reason information for the call failure in the IMS domain mentioned here may be the reason for the IMS bearer deactivation. The calling UE can determine whether the IMS service can be restored within the first time period based on the reason information returned by the core network side.

[0369] Among them, if the judgment result in this step is N, that is, the IMS service cannot be restored within the first time period, the DS sub-module of the calling UE call management module can inform the IMS sub-module of the result, and then step S803 can be executed; if the judgment result in this step is Y, that is, the IMS service can be restored within the first time period, then the subsequent step S810 can be executed.

[0370] First, the case where the judgment result in step S802 is N is introduced. This case may include the following steps:

[0371] S803: The IMS module sends a CS domain redial instruction message (CS redial) to the call management module.

[0372] The CS domain redial instruction message (CS redial) is used to instruct the call management module to switch to the CS domain for redialing.

[0373] S804: In response to the CS domain redial instruction message (CS redial), the call management module selects the CS domain and redials in the CS domain.

[0374] S805: The call management module sends a CS domain redial notification message to the NAS submodule.

[0375] S806 , in response to the CS domain redial notification message, the NAS submodule sends an extended service request message (extended service request Msg, MO CS fallback) to the LTE system.

[0376] The extended service request message is used to request the LTE system to send a 2G frequency point or a 3G frequency point.

[0377] S807, the LTE system sends an extended service response message to the NAS submodule of the calling UE.

[0378] Among them, the extended service response message includes the 2G frequency or 3G frequency issued by the LTE system, and the 2G frequency or 3G frequency is used for the calling UE to communicate on the 2G network or 3G network. In this embodiment of the application, the communication can specifically refer to voice call communication.

[0379] S808: The calling UE camps on the CS.

[0380] In some embodiments, the modules involved in residing in the CS domain include: a UI module and a modem, etc.

[0381] S809: The calling UE initiates a CS domain call process.

[0382] In some embodiments, a calling UE makes a voice call to a 2G / 3G network system in the CS domain; and the 2G / 3G network system makes a voice call to a core network device in the CS domain. Specifically, the call management module of the calling UE may send a CS domain call setup message to the 2G / 3G network system; and the 2G / 3G network system may send a CS domain call setup message to the core network device.

[0383] Next, the case where the judgment result in step S802 is Y is described. This case may include the following steps:

[0384] S810: The calling UE starts a timer.

[0385] The preset duration of the timer may be less than or equal to the first duration.

[0386] In some embodiments, the timer duration can be set according to communication requirements; or according to the required IMS service recovery time. For example, if the required IMS service recovery time is 3 seconds, the timer duration can be set to 3 seconds; if the required IMS service recovery time is 5 seconds, the timer duration can be set to 5 seconds, etc. This embodiment of the present application is not limited to this.

[0387] In some embodiments, the timer may be integrated into a call management module of the calling UE (not shown in FIG9 ) or may be a separate module. When the result of the determination in step S902 is that the IMS service can be restored within the first time period, the calling UE may start the timer, i.e., begin counting.

[0388] By using a timer to set a timer, the duration of IMS service recovery can be further limited to avoid the IMS service recovery taking too long, causing users to wait too long and affecting the call experience.

[0389] During the timer, the calling UE and the LTE system may perform the following step S911A:

[0390] S811A: The DS submodule of the calling UE sends an IMS PDN setup request message to the LTE system. The IMS PDN setup request message carries EBI#5.

[0391] In some embodiments, the IMS PDN establishment request message carries EBI#5 (corresponding to QCI=5), which means that the calling UE needs to establish or support the IMS default bearer.

[0392] S811B: The LTE system sends an IMS PDN establishment request message to the core network device. The IMS PDN establishment request message carries EBI#5.

[0393] The LTE system may send an IMS PDN establishment request message to the core network device in a transparent transmission manner.

[0394] S812A: The core network device sends an IMS PDN establishment response message to the LTE system.

[0395] The registration response message is used to indicate whether the IMS default bearer is successfully established.

[0396] S812B, the LTE system sends an IMS PDN establishment response message to the DS submodule.

[0397] S813: The calling UE initiates an IMS domain registration process.

[0398] In some embodiments, since the IMS service of the core network device has been restored in this situation, after the calling UE completes registration, the core network device may also feed back an IMS registration response message to the calling UE to indicate that the IMS registration is complete.

[0399] In some embodiments, the registration process may include: the calling UE sends an IMS registration request message to the LTE system; thereafter, the LTE system sends an IMS registration request message to the core network device; the core network device sends a registration response message to the LTE system, and the registration response message is used to indicate whether the registration is successful; the LTE system forwards the registration response message to the calling UE.

[0400] S814: The IMS module of the calling UE determines whether the IMS service is restored before timeout.

[0401] In some embodiments, the method by which the calling UE determines whether the IMS service is restored before the timeout may include: when the calling UE successfully registers on the IMS domain before the timeout (such as receiving a registration success message sent by the network side), it indicates that the IMS service is restored before the timeout. Alternatively, optionally, after the calling UE receives an IMS service restoration notification message broadcast by the LTE system before the timeout, it indicates that the IMS service is restored before the timeout. The embodiments of the present application do not limit the method by which the calling UE determines that the IMS service is restored before the timeout.

[0402] The timing time in the embodiment of the present application can be flexibly set according to communication requirements. Optionally, the timing duration can be less than the first duration, for example, 3s or 5s.

[0403] In some embodiments, if the judgment result in this step is N, that is, the IMS service cannot be restored before the timeout, the IMS module of the calling UE may inform the call management module of the result, and the call management module may subsequently switch to the CS domain for redialing. The process of the call management module switching to the CS domain for redialing may include the following steps:

[0404] S815: The IMS module sends a CS domain redial instruction message to the call management module.

[0405] S816: The call management module selects the CS domain and redials in the CS domain.

[0406] S817: The call management module sends a CS domain redial notification message to the DS, RRC, and NAS modules.

[0407] S818, the DS, RRC, and NAS modules send an extended service request message to the LTE system. The extended service request message is used to request the LTE system to send 2G / 3G frequency points.

[0408] S819, the LTE system sends an extended service response message to the DS, RRC, and NAS modules. The extended service response message includes the 2G / 3G frequency sent by the LTE system.

[0409] S820: The calling UE resides in the CS domain.

[0410] S821: The calling UE initiates a call process in the CS domain.

[0411] Among them, for the detailed introduction of steps S815 to S821, please refer to the relevant introduction of steps S803 to S809 above, which will not be repeated here.

[0412] If the judgment result in step S802 is Y, that is, the IMS service can be restored before the timeout, the IMS module may inform the call management module of the result, and the call management module may subsequently re-register with the IMS. The IMS domain re-registration process may include the following steps:

[0413] S822: The IMS module of the calling UE sends an IMS domain redial instruction message to the call management module.

[0414] The IMS domain redial instruction message is used to instruct the call management module to redial in the IMS domain to perform a voice call service.

[0415] S823: The call management module of the calling UE redials in the IMS domain.

[0416] S824: The calling UE initiates a call process in the IMS domain. In some embodiments, the calling UE first places a call to the LTE system; then, the LTE system places a call to the core network device in the IMS domain.

[0417] According to the voice call method provided in the embodiment of the present application, after the calling UE fails to initiate a call in the IMS domain, it is determined whether the IMS service can be restored within a first time period based on the failure reason returned by the network side. If the IMS service can be restored within the first time period, a redial is attempted on the IMS domain; if the IMS service cannot be restored within the first time period, the voice call service is switched to the CS domain. This method can increase the probability of successfully establishing a voice call service on the IMS domain, especially for voice call services that can obviously be conducted on the IMS domain, and can avoid them being directly switched to the CS domain with poor call quality, resulting in a poor call experience for users.

[0418] The method for voice call provided in the embodiment of the present application may further include scheme 3. In scheme 3, when, based on the cause information, obtaining the IMS service can be restored within the first time, the calling UE may start a counter and redial in the IMS domain. If the calling UE re-registers in the IMS domain for more than a preset number of times and the redial (or re-registration) of the calling UE in the IMS domain still fails, it switches to redialing in the CS domain and conducts the voice call service in the CS domain. If the calling UE re-registers in the IMS domain for less than or equal to the preset number of times and the calling UE successfully redials (or re-registers) in the IMS domain, the voice call service is conducted in the IMS domain.

[0419] In the third solution provided in the embodiment of the present application, a counter can be used to count the number of times the calling UE registers in the IMS domain. When the counter is turned on, the counter will continue to count the number of times the calling UE registers in the IMS domain until a preset number is reached or until the calling UE successfully registers in the IMS domain.

[0420] In some embodiments, the preset number of times of the counter can be set according to communication requirements, or according to the time required for IMS service recovery, such as 5 times or 10 times, etc. This embodiment of the present application does not limit this.

[0421] In some embodiments, the counter may be integrated into a call management module of the calling UE, or may be a separate module.

[0422] In some embodiments, when the calling UE determines in solution three that the IMS service can be restored within the first time period, the calling UE may start an indication counter, ie, start counting the number of times the calling UE re-registers on the IMS domain.

[0423] In some embodiments, the method by which the calling UE determines whether the IMS service is restored before reaching a preset number of times may include: when the calling UE successfully registers on the IMS domain (such as receiving a registration success message sent by the network side) before the number of times the calling UE re-registers on the IMS domain reaches a preset number of times, it indicates that the IMS service is restored before reaching the preset number of times. Or, optionally, when the calling UE receives an IMS service restoration notification message broadcast by the LTE system before the number of times the calling UE re-registers on the IMS domain reaches a preset number of times, it indicates that the IMS service is restored before reaching the preset number of times. The embodiments of the present application do not limit the method by which the calling UE determines whether the IMS service is restored before reaching the preset number of times.

[0424] The specific implementation process of Solution 3 can refer to the process shown in the embodiment of Figure 8. The main differences between Solution 3 and the embodiment of Figure 8 are: (1) Unlike step S810 in the embodiment of Figure 8, in Solution 3, the calling UE will start a counter to count the number of times the calling UE attempts to re-register in the IMS domain; (2) Unlike step S814 in the embodiment of Figure 8, in Solution 3, the calling UE determines whether the IMS service is restored when the preset number of times is reached.

[0425] It should be understood that, similar to the improved effect in the embodiment of Figure 8, compared with the embodiment of Figure 7, the method in Solution 3 increases the counter and switches to the CS domain for redialing when the number of times the calling UE re-registers in the IMS exceeds the preset number of times. This can further limit the duration of IMS service recovery and avoid the IMS service recovery time being too long, causing the user to wait too long and affecting the call experience.

[0426] According to the voice call method provided in the embodiment of the present application, after the calling UE fails to initiate a call in the IMS domain, it is determined whether the IMS service can be restored within a preset number of times when the UE performs IMS domain registration based on the failure reason returned by the network side. If the IMS service can be restored within a preset number of times when the UE performs IMS domain registration, redialing is attempted on the IMS domain; if the IMS service cannot be restored within a preset number of times when the UE performs IMS domain registration, the voice call service is switched to the CS domain. This method can increase the probability of successfully establishing a voice call service on the IMS domain, especially for voice call services that can obviously be performed on the IMS domain, it can avoid being directly switched to the CS domain with poor call quality, resulting in a poor call experience for users.

[0427] Optionally, this application may also include Solution 4. The application scenario of Solution 4 may include: in broadcasting and television or other voice call service scenarios that currently cannot use the CS domain, if the UE does not perform IMS registration when establishing the voice call service, or if the UE is performing IMS registration when establishing the voice call service, the voice call service cannot be established in a timely manner. In this case, the UE can wait for the UE to complete IMS registration before implementing the voice call service. The following, combined with the accompanying figures, describes the underlying interaction process involved in this scenario.

[0428] For example, as shown in FIG9 , there is a schematic flow chart of another method for making a voice call provided in an embodiment of the present application. The flow may include the following steps:

[0429] S901, resides in the NR system, but will start to register in the IMS domain. If the IMS registration fails, it will retry the IMS domain registration.

[0430] It is worth noting that, unlike the embodiments of Figures 7 and 8 above, in this embodiment, although the calling UE resides in the NR, it has not yet registered in the IMS domain, but is about to start registering in the IMS domain; and, if the IMS registration fails, the IMS domain registration will be retried.

[0431] The process of the calling UE accessing the NR can be found in the above description and will not be repeated here.

[0432] S902: The calling UE receives a dialing operation input by the user through the UI module.

[0433] S903: The UI module of the calling UE transmits the dialing operation to the call management module of the calling UE.

[0434] In some embodiments, while receiving the dialing operation, the calling UE may also start performing the registration operation in the IMS domain, that is, perform the following steps:

[0435] Optionally, the embodiment of the present application may further include step S904, that is, the IMS module sends an IMS domain registration status notification message to the call management module.

[0436] The IMS domain registration status notification message is used to indicate that the calling UE is not currently registered in the IMS domain, or is used to indicate that the calling UE is currently starting to register in the IMS domain.

[0437] S905: The calling UE initiates a registration process in the IMS domain.

[0438] Before registering in the IMS domain, the calling UE must first establish a default bearer in the IMS domain. This process may include: the calling UE sends a registration request message to the NR network system. This registration request message may include an EBI of #5, requesting the establishment of a default bearer that supports the UE's IMS registration. After receiving the registration request message, the NR system may forward it to the core network and IMS module. The core network and IMS module respond to the registration request message and establish a default bearer for the calling UE to complete IMS registration. Once the default bearer in the IMS domain is established, the calling UE can send SIP messages on this bearer.

[0439] S906: The calling UE determines whether the IMS registration is successfully completed.

[0440] Specifically, this step may be performed by the IMS module of the calling UE. The process of the calling UE registering in the IMS domain may refer to the above step S601 and will not be described in detail here.

[0441] If the judgment result in this step is N, that is, the calling UE has not successfully completed the registration, then step S927 is subsequently performed, that is, the IMS domain voice service establishment fails, and the call management module of the calling UE switches to the CS domain redial; if the judgment result in this step is Y, that is, the calling UE has successfully completed the registration, then step S907 can be optionally performed subsequently:

[0442] The following describes the scenario where the calling UE successfully completes IMS domain registration.

[0443] Optionally, the embodiment of the present application may further include step S907, that is, the IMS module of the calling UE sends an IMS registration completion notification message to the call management module.

[0444] In some embodiments, the IMS registration completion notification message is used to indicate that the calling UE has completed registration in the IMS domain.

[0445] In some embodiments, after the calling UE completes registration in the IMS domain, the call management module of the calling UE may send a dialing instruction corresponding to the dialing operation to the IMS module of the calling UE.

[0446] S908: The call management module of the calling UE selects the NR IMS domain.

[0447] Optionally, the embodiment of the present application may further include step S909, that is, the call management module sends an IMS domain selection notification message to the IMS module.

[0448] The IMS domain selection notification message is used to indicate that the IMS domain has been selected.

[0449] S910A: The IMS module of the calling UE sends a session invite message (invite) to the NR system.

[0450] S910B, the NR system sends a session invitation message (invite) to the core network device.

[0451] In some embodiments, the NR system may forward the session invitation message to the core network device in a transparent manner.

[0452] S911A: The core network device sends a temporary response message to the NR system.

[0453] The provisional response message may be used to indicate that the called UE has received the session invite message (invite). The provisional response message may also be described as 100 trying signaling or 100 trying.

[0454] S911B, the NR system sends a temporary response message to the calling UE.

[0455] In some embodiments, the NR system may forward the temporary response message to the calling UE in a transparent manner. Specifically, the NR system may transparently transmit the temporary response message to the IMS module of the calling UE.

[0456] Optionally, in some scenarios, if the 5G network does not support VoNR services, or the current 5G network does not have the conditions for VoNR, the NR system can instruct the calling UE to switch from the 5G network to the 4G network to establish a voice call in the IMS domain. In this case, the NR system can perform the following step S912:

[0457] S912: The NR system instructs the RRC submodule of the calling UE to switch from the NR system to the LTE system (EPS FB to LTE) through the EPS FB process.

[0458] S913: The RRC submodule of the calling UE initiates an RRC access procedure.

[0459] The RRC access process can be found in the above description and will not be described here.

[0460] S914A: The calling UE sends a TAU request message to the LTE system. The TAU request message is used to initiate a TAU procedure, and the TAU request message carries EBI#5 and EBI#6.

[0461] Specifically, this step may be performed by a call management module of the calling UE.

[0462] S914B, the LTE system sends a TAU request message to the core network device. The TAU request message is used to initiate a TAU process, and the TAU request message carries EBI#5 and EBI#6.

[0463] S915A, the core network device sends a TAU response message to the LTE system.

[0464] In some embodiments, the TAU response message may indicate the status of the IMS default bearer and the data service bearer stored (or recorded) by the core network device.

[0465] S915B, the LTE system sends a TAU response message to the calling UE.

[0466] In some embodiments, the LTE system sends a TAU response message to the NAS submodule in the calling UE.

[0467] S916A: The core network device sends a dedicated bearer establishment message to the LTE system. The dedicated bearer establishment message carries EBI#7.

[0468] S916B: The LTE system sends a dedicated bearer establishment message to the calling UE. The dedicated bearer establishment message carries EBI#7.

[0469] S917A: The calling UE sends a dedicated bearer establishment response message to the LTE system. The dedicated bearer response message carries EBI#7.

[0470] In some embodiments, in response to the dedicated bearer establishment message, the DS submodule of the calling UE may send a dedicated bearer establishment response message to the LTE system, wherein the dedicated bearer establishment response message may include relevant parameters for establishing the dedicated bearer, etc.

[0471] S917B, the LTE system sends a dedicated bearer establishment response message to the core network device.

[0472] S918A: The core network device sends an IMS bearer deactivation message to the LTE system. The IMS bearer deactivation message carries EBI#5 and cause information.

[0473] The cause information indicates whether the IMS service can be restored within the first time period. For example, if the cause information is esm_cause=39, it indicates that the IMS service can be restored within the first time period and needs to be reactivated; if the cause information is esm_cause=38, it indicates that the IMS service cannot be restored within the first time period.

[0474] S918B: The LTE system sends an IMS bearer deactivation message to the calling UE. The IMS bearer deactivation message carries EBI#5 and cause information.

[0475] In some embodiments, the LTE system may specifically send the IMS bearer deactivation message to the DS submodule. The LTE system may send the IMS bearer deactivation message to the calling UE in a transparent transmission manner.

[0476] S919: The DS, RRC, and NAS modules of the calling UE send an IMS bearer deactivation notification message to the IMS module of the calling UE.

[0477] The IMS bearer deactivation notification message is used to indicate that the IMS default bearer has been deactivated.

[0478] S920: The IMS module of the calling UE determines whether the IMS service can be restored within the first time period based on the IMS bearer deactivation reason information.

[0479] If the judgment result in this step is N, that is, the IMS service cannot be restored within the first time period, then step S927 is performed, that is, the IMS domain voice service establishment fails, and switching to the CS domain for redialing; if the judgment result in this step is Y, that is, the IMS service can be restored within the first time period, then the following steps can be performed:

[0480] S921, start the timer / counter.

[0481] Among them, when the timer is started, the process can be referred to the introduction in Figure 8, which will not be repeated here.

[0482] S922A: The calling UE sends an IMS PDN setup request message to the LTE system. The IMS PDN setup request message carries EBI#5.

[0483] S922B: The LTE system sends an IMS PDN establishment request message to the core network device. The IMS PDN establishment request message carries EBI#5.

[0484] S923A: The core network device sends an IMS PDN establishment response message to the LTE system.

[0485] The registration response message may be used to indicate whether the IMS default bearer is established successfully.

[0486] S923B, the LTE system sends an IMS PDN establishment response message to the DS submodule.

[0487] S924: The calling UE initiates an IMS domain registration process.

[0488] In some embodiments, once the default bearer in the IMS domain is established, the calling UE can send SIP messages on this bearer. If a VoLTE user wants to make a call through the IMS domain, he or she must first register with the IMS domain through SIP signaling.

[0489] In some embodiments, since the IMS service of the core network device has been restored in this situation, after the calling UE completes registration, the core network device may also feed back an IMS registration response message to the calling UE to indicate that the IMS registration is complete.

[0490] S925: The IMS module of the calling UE determines whether the IMS service is restored before the timer duration or the preset number of times is reached.

[0491] In some embodiments, the calling UE may determine whether the IMS service has been restored by: when the calling UE successfully registers on the IMS domain (e.g., receives a registration success message sent by the network side), indicating that the IMS service has been restored. Alternatively, the calling UE may receive an IMS service restoration notification message broadcast by the LTE system, indicating that the IMS service has been restored. The embodiments of the present application do not limit the manner in which the calling UE determines that the IMS service has been restored.

[0492] If the result of this step is N, meaning the IMS service cannot be restored before the timer or the preset number of calls expires, step S927 may be executed, meaning the IMS domain voice service establishment fails and redialing is performed in the CS domain. If the result of this step is Y, meaning the IMS service can be restored before the timer or the preset number of calls expires, step S926 may be executed, meaning the call flow is executed in the IMS domain.

[0493] According to the voice call method provided by the embodiment of the present application, in a scenario where the CS domain cannot be used and the calling UE has not completed IMS domain registration when dialing, the calling UE waits for a period of time when initiating a call while the calling UE registers in the IMS domain. If the registration is successful, the calling UE establishes a voice call service in the IMS domain and conducts the voice call. This method can increase the probability of conducting voice call services in the IMS domain, which is conducive to improving the quality of voice call services and enhancing user experience.

[0494] For example, as shown in FIG10 , a schematic flow chart of another method for making a voice call provided in an embodiment of the present application is provided. The execution subject of the process may be an electronic device, and specifically may include the following steps:

[0495] S1001: Receive an IMS domain call cancellation message, where the IMS domain call cancellation message includes reason information indicating call cancellation in the IMS domain.

[0496] The electronic device here may refer to an electronic device that initiates a voice call, which may correspond to the calling UE mentioned above. The failure of the electronic device to initiate a call in the IMS domain may specifically correspond to the deactivation of the IMS bearer corresponding to the electronic device. The reason information for the failure of the electronic device to initiate a call in the IMS domain may also correspond to the reason information for the deactivation of the IMS bearer.

[0497] S1002: When the reason information is the first information, re-register in the IMS domain. The re-registration is used for the electronic device to perform a voice call service in the IMS domain. The first information is used to indicate that the IMS service for the electronic device will be restored within a first time period.

[0498] In some embodiments, when the reason information is the second information, switching to CS domain redial is used for the electronic device to perform voice call services in the CS domain, and the second information is used to indicate that the IMS service for the electronic device cannot be restored within the first time period.

[0499] In some embodiments, when the reason information is the first information, the electronic device re-registers in the IMS domain, specifically including: starting a timer, the timer being set with a timing duration; within the timing duration, the electronic device re-registers in the IMS domain.

[0500] In some embodiments, the timing duration is less than or equal to the first duration.

[0501] In some embodiments, if the timing duration is reached and re-registration in the IMS domain still fails, the call is switched to the CS domain and redialed, and a voice call service is performed in the CS domain; if the timing duration is not reached and re-registration in the IMS domain is successful, the call is redialed in the IMS domain and a voice call service is performed in the IMS domain.

[0502] The electronic device still fails to re-register in the IMS domain, which may mean that when the electronic device attempts to re-establish an IMS default bearer with the core network, establishment of the IMS domain default bearer fails.

[0503] In some embodiments, the method further includes: starting a counter, the counter being used to count the number of times the electronic device re-registers in the IMS domain after the electronic device cancels a call in the IMS domain; and the electronic device re-registers in the IMS domain.

[0504] In some embodiments, if the preset number of times is reached and re-registration in the IMS domain still fails, the call is switched to the CS domain and redialed, and a voice call service is performed in the CS domain; if re-registration in the IMS domain is successful before the preset number of times is reached, the call is redialed in the IMS domain and a voice call service is performed in the IMS domain.

[0505] In some embodiments, the method further includes: the electronic device resides in a new radio interface NR system and has been registered in the NR IMS domain; or, the electronic device resides in a long term evolution LTE system and has been registered in the LTE IMS domain.

[0506] In some embodiments, the access network device is an access network device of a fifth-generation mobile communication 5G network, or an access network device of a fourth-generation mobile communication 4G network.

[0507] In some embodiments, the electronic device receiving the IMS domain call cancellation message specifically includes: the electronic device receiving the IMS domain call cancellation message forwarded by the access network device from the core network.

[0508] In some embodiments, when the electronic device resides in the NR system and has been registered in the NR IMS domain, the method further includes: receiving a dialing operation input by a user; selecting the NR IMS domain in response to the dialing operation; sending a session invitation message to the NR system, wherein the session invitation message is used to request to establish a session connection with the core network device; receiving a temporary response message forwarded by the NR system from the core network device, wherein the temporary response message is used to indicate that the called electronic device has received the session invitation message; and receiving a fallback indication message sent by the NR system, wherein the fallback indication message is used to instruct the electronic device to fall back to the LTE system.

[0509] The called electronic device may refer to an electronic device that is called by voice, which may correspond to the called UE hereinafter.

[0510] In some embodiments, when the reason information is the second information, switching to the CS domain for redialing specifically includes: selecting the CS domain; sending an extended service request message to the LTE system, the extended service request message being used to request the LTE system to send the second-generation 2G frequency or the third-generation 3G frequency; receiving the 2G frequency or the 3G frequency sent by the LTE system; and initiating a call in the CS domain through the 2G frequency or the 3G frequency.

[0511] According to the voice call method provided in an embodiment of the present application, after an electronic device fails to initiate a call in the IMS domain, the method determines whether the IMS service can be restored within a first time period based on the failure reason returned by the network side. If the IMS service can be restored within the first time period, a redial attempt is made in the IMS domain. If the IMS service cannot be restored within the first time period, the voice call service is switched to the CS domain. This method can increase the probability of successfully establishing a voice call service in the IMS domain, especially for voice calls that can clearly be conducted in the IMS domain, and can prevent them from being directly switched to the CS domain with poor call quality, resulting in a poor call experience for the user.

[0512] In addition, an embodiment of the present application also provides a method for improving voice call quality based on IMS, which is applied to an access network device, and the method includes: receiving an IMS domain call cancellation message sent by a core network device, and the IMS domain call cancellation message includes reason information for indicating that the electronic device failed to initiate a call in the IMS domain; forwarding the IMS domain call cancellation message to the electronic device, so that when the reason information is the first information, it re-registers in the IMS domain, and the re-registration is used for the electronic device to perform voice call services in the IMS domain, and the first information is used to indicate that the IMS service for the electronic device will be restored within a first time period.

[0513] In some embodiments, when the reason information is the second information, switching to CS domain redialing is used for the electronic device to perform voice call services in the CS domain, and the second information is used to indicate that the IMS service for the electronic device cannot be restored within the first time length.

[0514] In some embodiments, the method further includes: receiving a session invitation message sent by the electronic device in the IMS domain, the session invitation message being used to request establishment of a session connection with the core network device; forwarding the session invitation message to the core network device; receiving a temporary response message sent by the core network device, the temporary response message being used to indicate that the called electronic device has received the session invitation message; and forwarding the temporary response message to the electronic device.

[0515] In some embodiments, the access network device is an access network device of a 5G network, or the access network device is an access network device of a 4G network.

[0516] In some embodiments, the method further includes: the electronic device resides in the NR system and has been registered in the NR IMS domain; or, the electronic device resides in the LTE system and has been registered in the LTE IMS domain.

[0517] In some embodiments, when the electronic device resides in the NR system and has been registered in the NR IMS domain, the method further includes: the access network device of the 5G network sends a fallback indication message to the electronic device, and the fallback indication message is used to instruct the UE to fall back to the LTE system.

[0518] In some embodiments, the method also includes: after the electronic device accesses the LTE system through RRC, the access network device of the 4G network establishes a TAU process with the electronic device, and the TAU process includes a bearer that supports the electronic device to complete the IMS domain registration; and, the access network device of the 4G network establishes the TAU process with the core network device; the access network device of the 4G network and the electronic device establish a dedicated bearer for voice call services in the IMS domain; and, the access network device of the 4G network and the core network device establish a dedicated bearer for voice call services in the IMS domain; the access network device of the 4G network receives the IMS domain call cancellation message sent by the core network device, and the IMS domain call cancellation message includes reason information for indicating the cancellation of the call of the electronic device in the IMS domain; the access network device of the 4G network forwards the IMS domain call cancellation message to the electronic device.

[0519] In some embodiments, when the reason information is the second information, the electronic device switches to the CS domain for redialing, specifically including: the access network device of the 4G network receives an extended service request message sent by the electronic device, and the extended service request message is used to request the LTE system to send down a 2G frequency or a 3G frequency; the access network device of the 4G network sends the 2G frequency or the 3G frequency to the electronic device, and the 2G frequency or the 3G frequency is used by the electronic device to initiate a call in the CS domain.

[0520] According to the voice call method provided by the embodiment of the present application, during the call initiation phase, the electronic device IMS detects the loss of the IMS bearer, and then determines the cause of the loss and whether it is expected to be quickly restored. If it can be quickly restored, a timer is started. Once the IMS service is restored before the timer expires, the electronic device redials (redial) in the IMS domain. If it is not restored before the timeout, it redials (CS redial) in the CS domain; if it is determined that the IMS service cannot be quickly restored, CS redial is performed directly.

[0521] It should be noted that the voice call method provided in this embodiment differs from the embodiment in Figure 1 in that the process in Figure 1 necessarily requires CS redial. However, CS call initiation takes a long time and the voice quality of the call is also poor. However, by introducing the technology of this application, the voice call is guaranteed to be successful in the IMS domain with a high probability, which can reduce voice quality issues and improve the calling success rate, thereby improving the user experience.

[0522] Based on the same technical concept, an embodiment of the present application also provides an electronic device that supports voice call services in the IMS domain and the CS domain. The electronic device includes one or more processors; one or more memories; the one or more memories store one or more computer programs, and the one or more computer programs include instructions. When the instructions are executed by the one or more processors, the electronic device performs one or more steps in any of the above methods.

[0523] Based on the same technical concept, an embodiment of the present application also provides an access network device, including one or more processors; one or more memories; the one or more memories store one or more computer programs, and the one or more computer programs include instructions. When the instructions are executed by the one or more processors, the access network device performs one or more steps in any of the above methods.

[0524] Based on the same technical concept, an embodiment of the present application also provides a core network device, including one or more processors; one or more memories; the one or more memories store one or more computer programs, and the one or more computer programs include instructions. When the instructions are executed by the one or more processors, the core network device executes one or more steps in any of the above methods.

[0525] Based on the same technical concept, an embodiment of the present application also provides a communication system, including an electronic device, an access network device and a core network device, wherein the electronic device, the access network device and the core network device are respectively used to perform the functions of any one of the above methods.

[0526] Based on the same technical concept, an embodiment of the present application also provides a computer-readable storage medium, which stores computer-executable program instructions. When the computer-executable program instructions are executed on a computer, the computer or processor executes one or more steps in any of the above methods.

[0527] Based on the same technical concept, an embodiment of the present application also provides a computer program product containing instructions, wherein the computer program product includes computer program code. When the computer program code is run on a computer, the computer or processor executes one or more steps in any of the above methods.

[0528] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted via the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid state drive (SSD)).

[0529] Those skilled in the art will appreciate that all or part of the process steps in the above-described method embodiments can be implemented by a computer program instructing the relevant hardware. The program can be stored in a computer-readable storage medium, and when executed, the program can include the process steps in the above-described method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM or random access memory (RAM), magnetic disks, or optical disks.

[0530] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for voice communication, characterized in that: Applied to electronic equipment, the method comprises: receiving an Internet Multimedia Subsystem (IMS) domain call cancellation message, wherein the IMS domain call cancellation message includes reason information indicating the call cancellation in the IMS domain; When the reason information is the first information, re-registration is performed in the IMS domain, and the re-registration is used for the electronic device to perform a voice call service in the IMS domain. The first information is used to indicate that the IMS service for the electronic device will be restored within a first time period.

2. The method according to claim 1, characterized in that The method further comprises: When the reason information is the second information, switching to circuit switched CS domain redialing is performed, the redialing is used for the electronic device to perform a voice call service in the CS domain, and the second information is used to indicate that the IMS service for the electronic device cannot be restored within the first time period.

3. The method according to claim 1 or 2, characterized in that: When the reason information is the first information, re-registering in the IMS domain specifically includes: Start a timer, wherein the timer is set with a timing duration; Re-register in the IMS domain within the timing duration.

4. The method according to claim 3, characterized in that The timing duration is less than or equal to the first duration.

5. The method according to claim 3 or 4, characterized in that: The method further comprises: If the timer duration is reached and re-registration in the IMS domain still fails, switching to the CS domain for redialing and performing a voice call service in the CS domain; If the timing duration is not reached and the re-registration in the IMS domain is successful, redialing is performed in the IMS domain and a voice call service is performed in the IMS domain.

6. The method according to claim 1 or 2, characterized in that: The method further comprises: Start a counter, where the counter is used to count the number of times the electronic device re-registers in the IMS domain after the call in the IMS domain is canceled; Re-register in the IMS domain.

7. The method according to claim 6, characterized in that The method further comprises: If the preset number of times is reached and re-registration in the IMS domain still fails, switching to the CS domain for redialing, and performing voice call services in the CS domain; If the re-registration in the IMS domain is successful before the preset number of times is reached, redialing is performed in the IMS domain, and a voice call service is performed in the IMS domain.

8. The method according to any one of claims 1 to 7, characterized in that The method further comprises: Resides in the NR system and has registered in the NR IMS domain; or The system resides in the Long Term Evolution (LTE) system and has been registered in the LTE IMS domain.

9. The method according to any one of claims 1 to 8, characterized in that The receiving of the IMS domain call cancellation message specifically includes: The IMS domain call cancellation message forwarded by the access network device from the core network device is received.

10. The method according to claim 9, characterized in that The access network device is an access network device of a fifth-generation mobile communication 5G network, or the access network device is an access network device in a fourth-generation mobile communication 4G network.

11. The method according to any one of claims 2 to 10, characterized in that: When the reason information is the second information, switching to CS domain redialing specifically includes: Selecting the CS domain; Sending an extended service request message to the LTE system, where the extended service request message is used to request the LTE system to send a second-generation 2G frequency point or a third-generation 3G frequency point; Receiving the 2G frequency point or the 3G frequency point sent by the LTE system; In the CS domain, a call is initiated through the 2G frequency or the 3G frequency.

12. A method for voice communication, characterized in that: Applied to access network equipment, the method comprises: Receiving an IMS domain call cancellation message sent by a core network device, wherein the IMS domain call cancellation message includes reason information for indicating the call cancellation in the IMS domain; The IMS domain call cancellation message is forwarded to the electronic device, so that when the reason information is the first information, the electronic device re-registers in the IMS domain, the re-registration is used for the electronic device to perform a voice call service in the IMS domain, and the first information is used to indicate that the IMS service for the electronic device will be restored within a first time period.

13. The method according to claim 12, characterized in that When the reason information is the second information, the method further includes: The electronic device is enabled to switch to the CS domain for redialing, the redialing is used for the electronic device to perform a voice call service in the CS domain, and the second information is used to indicate that the IMS service for the electronic device cannot be restored within the first time period.

14. The method according to claim 12 or 13, characterized in that The method further comprises: The electronic device resides in the NR system and has been registered in the NR IMS domain; or, The electronic device resides in the LTE system and has been registered in the LTE IMS domain.

15. The method according to any one of claims 12 to 14, characterized in that: The access network device is an access network device of a 5G network, or the access network device is an access network device of a 4G network.

16. The method according to claim 15, characterized in that The method further comprises: The access network device of the 4G network receives the IMS domain call cancellation message sent by the core network device, where the IMS domain call cancellation message includes reason information for indicating that the electronic device cancels the call in the IMS domain; The access network device of the 4G network forwards the IMS domain call cancellation message to the electronic device.

17. The method according to claim 13, characterized in that When the reason information is the second information, causing the electronic device to switch to the CS domain for redialing specifically includes: The access network device of the 4G network receives an extended service request message sent by the electronic device, where the extended service request message is used to request the LTE system to send a 2G frequency point or a 3G frequency point; The access network device of the 4G network sends the 2G frequency point or the 3G frequency point to the electronic device, and the 2G frequency point or the 3G frequency point is used by the electronic device to initiate a call in the CS domain.

18. An electronic device, characterized in that: The electronic device supports voice call services in the IMS domain and the CS domain, and the electronic device includes: one or more processors; one or more memories; The one or more memories store one or more computer programs, and the one or more computer programs include instructions, which, when executed by the one or more processors, enable the electronic device to perform the method as claimed in any one of claims 1 to 11.

19. An access network device, characterized in that: include: one or more processors; one or more memories; The one or more memories store one or more computer programs, and the one or more computer programs include instructions. When the instructions are executed by the one or more processors, the access network device performs the method according to any one of claims 12 to 17.

20. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable program instructions, which, when executed on a computer, enable the computer to execute the method as claimed in any one of claims 1 to 11 or any one of claims 12 to 17.

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