CN113660621A

CN113660621A - Communication method

Info

Publication number: CN113660621A
Application number: CN202011350503.3A
Authority: CN
Inventors: 赵福军; 周文昭
Original assignee: Samsung Electronics Co Ltd
Current assignee: Beijing Samsung Telecom R&D Center; Samsung Electronics Co Ltd
Priority date: 2020-05-12
Filing date: 2020-11-26
Publication date: 2021-11-16
Also published as: WO2021230482A1

Abstract

The present disclosure provides a method for communication of a user equipment, a user equipment and a computer readable storage medium. The method comprises the following steps: judging whether the UE is provided with the service of the evolution-only packet system by the current network; if the UE is judged to be provided with the service of the evolution packet system only by the current network, searching other networks different from the current network; and initiating a registration process in the searched other network.

Description

Communication method

Technical Field

The present disclosure relates to the field of mobile communications, and more particularly, to a terminal communication method.

Background

The LTE network of a conventional CDMA (Code Division Multiple Access) operator does not support a CSFB (Circuit Switched Fallback) function, or a new network operator only provides LTE (Long Term Evolution) network services, which results in that a user roaming (for example, roaming in a domestic network co-establishment sharing mode or international roaming) to a target LTE network does not support a CDMA technology and does not open VoLTE cannot use voice services.

There is a need for a new method for communication of user equipment.

Disclosure of Invention

Aspects of the present disclosure are to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, aspects of the present disclosure provide a terminal communication method, that is, when a terminal selects/reselects/switches/roams to a 4G network that does not support a CSFB function when a currently used USIM card does not support a CDMA technology while a VoLTE service is not activated (or the terminal does not support a VoLTE function or the terminal supports a VoLTE function but a VoLTE switch on a terminal interface is in an off state), or a terminal selects/reselects/switches/roams to a network that only provides a 4G/5G network service when a currently used USIM card does not activate a VoLTE service (or the terminal does not support a VoLTE function or the terminal supports a VoLTE function but the VoLTE switch on the terminal interface is in an off state), the terminal will not be able to use a voice service, and the terminal intelligently searches for a UMTS/GSM network of another network and attempts to complete CS domain registration; or searching for an LTE/UMTS/GSM network of another network to complete a joint attachment process, so that both EPS/non-EPS service (or PS (Packet Switch) domain service/CS (Circuit Switch) domain service) can be used; or guiding a user to enable a VoLTE switch or guiding a network to complete VoLTE service opening and IMS registration so that the VoLTE service can be used.

Due to the fact that the extended system message SIB24 in the LTE system is decoded by some LTE terminals on the market in the early stage, when the LTE network broadcasts SIB24 in the system message, the terminal is restarted continuously and cannot provide service.

In view of the problem of LTE system broadcasting SIB24 resulting in a partial early time-to-market LTE terminal restart, the present disclosure provides a solution to the above problem. In order to avoid the terminal restart problem, the LTE base station may not broadcast SIB24 in the system message, so that part of the LTE terminals that are on the market early will not have SIB24 decoding errors. However, if SIB24 is not broadcast in the LTE system, the 5G SA terminal cannot complete inter-system cell reselection from the LTE to 5G SA cell in an idle state. To solve this problem, the 5G SA terminal may construct an SIB24 according to the 5G SA cell that once resided or the 5G SA neighbor cell issued by LTE system measurement control or the 5G SA cell to which the terminal big data is pushed in the background. When the LTE network is in an idle state, the 5G SA terminal may perform inter-system cell reselection according to the constructed SIB 24. Therefore, the problem of restarting part of early LTE terminals is solved, and the problem that the 5G SA cell cannot be reselected when the 5G SA terminal is in an idle state in an LTE network is also solved.

According to an aspect of the present disclosure, there is provided a method for communication of a User Equipment (UE), the method comprising: receiving a registration message from a current network and determining whether an evolved packet system-only service is provided; searching for other networks different from the current network if it is determined that the UE is provided with the evolved packet system-only service; and initiating a registration process in the searched other network.

According to an aspect of the disclosure, initiating a registration process in a searched network includes: initiating a registration procedure with the type of IMSI attachment or a registration procedure with the type of joint attachment.

According to an aspect of the present disclosure, if the registration procedure of type IMSI attach is successful, the UE provides packet switched service by the current network and circuit switched service by the other networks searched; and if the registration procedure of the type of the joint attachment is successful, the UE provides both the packet switched service and the circuit switched service by the searched other network.

According to an aspect of the disclosure, the other network providing the search for circuit switched services comprises one of a UMTS or GSM network; and the other network providing the search for both packet switched services and circuit switched services comprises one of an LTE, UMTS or GSM network.

According to an aspect of the disclosure, the current network is a network other than the home network of the UE.

According to an aspect of the disclosure, before initiating a registration procedure in the searched other network: determining whether the other searched networks belong to one of a home network of the UE, a co-established shared network, and a network of a roaming place based on a Public Land Mobile Network (PLMN) list of system information 1(SIB1) of a cell of the current network; and initiating a registration procedure for a network belonging to one of a home network, a co-established shared network and a network of a roaming site of the UE.

According to an aspect of the disclosure, initiating a registration procedure in the searched other network includes: sorting the other searched networks according to the signal strength of the received broadcast channel or pilot channel; and initiating a registration process in the searched other networks according to the sorted sequence.

According to an aspect of the disclosure, the method further comprises: checking whether a current USIM of the UE is a USIM which can only sign up for being provided with only an evolved packet system service before searching other networks different from the current network; and searching for other networks different from the current network if the current USIM is not a USIM that can only sign up for evolved packet system-only services.

According to an aspect of the disclosure, the registration message includes one of: an attach accept message; and a tracking area update accept message, and determining to be provided with an evolved packet system only service when one of the following conditions is satisfied: the EPS attach result cell value in the received attach accept message is 1; the EPS update result cell value in the received tracking area update accept message is 0 and the EPS attach result cell value in the last previously received attach accept message is 2; and the EPS update result information element value in the received tracking area update accept message is 0 and the EPS update result information element value in the last received tracking area update accept message is 1.

According to yet another aspect of the present disclosure, there is provided a method for communication of a User Equipment (UE), the method comprising: receiving a registration message from a current network and determining whether an evolved packet system-only service is provided; if the UE is judged to be provided with the service of the evolution packet system only, judging whether the network supports the voice of the IP multimedia subsystem of the packet switching conversation; and if the current network supports the voice of the IP multimedia subsystem of the packet switching session, initiating an initial IMS registration process to the current network based on the VoLTE on-off state of the UE or the VoLTE service state of the UE.

According to yet another aspect of the disclosure, initiating a registration process to the network based on a VoLTE on-off state of a UE or a VoLTE traffic state of a UE includes: and if the VoLTE switch state of the UE is the opening state, initiating an IMS initial registration process to the current network.

According to yet another aspect of the disclosure, initiating a registration process to the network based on a VoLTE on-off state of a UE or a VoLTE traffic state of a UE includes: if the VoLTE switch state of the UE is the closing state, the UE judges whether the VoLTE service is opened or not; and if the VoLTE service of the UE is opened, prompting to open a VoLTE switch, and initiating an IMS initial registration process to the current network after detecting that the VoLTE switch is opened.

According to yet another aspect of the present disclosure, if IMS initial registration is successful, the UE performs voice service in VoLTE manner.

According to yet another aspect of the present disclosure, the method further includes searching for other networks different from the current network when one of the following conditions is satisfied; and initiating a registration process in the searched other networks: the current network or the searched network does not support the voice of the IP multimedia subsystem of the packet switching session; the UE does not support VoLTE function; the VoLTE switch of the UE is not detected to be changed from the closed state to the open state; the VoLTE service of the UE fails to be opened; and the UE detects that the user selects not to open the VoLTE service.

According to another aspect of the present disclosure, initiating a registration process in a searched network includes: initiating a registration procedure with the type of IMSI attachment or a registration procedure with the type of joint attachment.

According to yet another aspect of the present disclosure, there is provided a method for communication of a User Equipment (UE), the method comprising: receiving a system message from a current network and checking first Public Land Mobile Network (PLMN) ID information in a PLMN column carried in the system message, searching for other networks different from the current network if the first PLMN ID is included in a stored list of networks providing an evolved packet system-only service; and initiating a registration process in the searched network.

According to yet another aspect of the disclosure, the method further comprises: if a registration message indicating the provision of the evolved packet system-only service is received, a PLMN ID of a current network is updated into a stored list of networks providing the evolved packet system-only service.

According to an aspect of the present disclosure, there is provided a method for communication of a User Equipment (UE), the method comprising: judging whether the UE is provided with the service of the evolution-only packet system by the current network; if the UE is judged to be provided with the service of the evolution packet system only by the current network, searching other networks different from the current network; and initiating a registration process in the searched other network.

According to yet another aspect of the disclosure, determining whether the UE is being provided with an evolved packet system only service by a current network includes: receiving a registration message or a system message from a current network; and judging whether the UE is provided with the evolved packet system only service by the current network according to the registration message or the system message.

According to yet another aspect of the disclosure, the registration message includes one of: an attach accept message; and a tracking area update accept message, and wherein the UE is determined to be provided with evolved packet system only services by the current network when one of the following conditions is met: the value of an (evolved packet system) EPS attachment result cell in the received attachment acceptance message is 1; the EPS update result cell value in the received tracking area update accept message is 0 and the EPS attach result cell value in the last previously received attach accept message is 2; and the EPS update result information element value in the received tracking area update accept message is 0 and the EPS update result information element value in the last received tracking area update accept message is 1.

According to yet another aspect of the disclosure, the method further comprises: and when judging that the UE is not provided with the service of the evolution packet system only by the current network according to the system message, initiating a registration process in the current network.

According to another aspect of the present disclosure, determining whether the UE is provided with an eps only service by a current network according to a system message includes: based on a Public Land Mobile Network (PLMN) list carried in the system message, it is determined whether the UE is being provided with an evolved packet system-only service by the current network.

According to another aspect of the present disclosure, determining whether the UE is served by the current network only in the evolved packet system based on the PLMN list carried in the system message includes: when the first PLMN ID of the PLMN list carried in the system message is inconsistent with the home PLMN ID corresponding to the International Mobile Subscriber Identity (IMSI), judging whether the first PLMN ID of the PLMN list carried in the system message is contained in a stored network list for providing the evolved packet-only system service; and if the network list is included in the stored network list for providing the evolved packet system-only service, determining that the UE is provided with the evolved packet system-only service.

According to yet another aspect of the disclosure, the method further comprises: and when the first PLMN ID of the PLMN list carried in the system message is consistent with the home PLMN ID corresponding to the IMSI, initiating a registration process in the current network.

According to yet another aspect of the disclosure, initiating a registration process in the searched other network includes: initiating a registration procedure with the type of IMSI attachment or a registration procedure with the type of joint attachment.

According to yet another aspect of the present disclosure, if the registration procedure of type IMSI attach is successful, the UE provides packet switched service by the current network and circuit switched service by the other networks searched; and if the registration procedure of the type of the joint attachment is successful, the UE provides both the packet switched service and the circuit switched service by the searched other network.

According to yet another aspect of the disclosure, the other networks that provide for the search for circuit switched services include one of a Universal Mobile Telecommunications System (UMTS) or a global system for mobile communications (GSM) network; and the other network providing the search for both packet switched services and circuit switched services comprises one of a Long Term Evolution (LTE), UMTS or GSM network.

According to yet another aspect of the disclosure, the current network is a network other than the home network of the UE.

According to yet another aspect of the disclosure, initiating a registration procedure in the searched other network includes: determining other networks for initiating registration based on Public Land Mobile Networks (PLMNs) corresponding to the other searched networks among the other searched networks; and initiating a registration process for the determined other networks.

According to still another aspect of the present disclosure, among the searched other networks, determining the other network which initiates registration based on a PLMN corresponding to the searched other network includes: judging whether the PLMN ID in the PLMN list carried in the searched system messages of other networks is contained in a stored network list for providing the service of the evolution packet system only; if not included in the stored list of networks providing the evolved packet system-only service, then a determination is made to initiate a registration for the other searched networks.

According to yet another aspect of the disclosure, initiating a registration process in the searched other network includes: sorting the other searched networks according to the signal strength of the received broadcast channel or pilot channel; and initiating a registration process in the searched other networks according to the sorted sequence.

According to yet another aspect of the disclosure, the method further comprises: checking whether a current USIM of the UE is a USIM which can only sign up for being provided with only an evolved packet system service before searching other networks different from the current network; and if the current USIM is not a USIM that can only sign up for being provided with the evolved packet system-only service, searching for other networks different from the current network.

According to an aspect of the present disclosure, there is provided a method for communication of a User Equipment (UE), the method comprising: receiving a registration message from a current network; if it is determined that the UE is provided with an evolved packet system only service by a current network based on the received registration message and the current network supports packet switched session IP multimedia subsystem voice, initiating an initial IMS registration process to the current network based on a high definition voice over LTE (VoLTE) switch state of the UE or a VoLTE service state of the UE.

According to yet another aspect of the disclosure, initiating a registration process in a searched network includes: initiating a registration procedure with the type of IMSI attachment or a registration procedure with the type of joint attachment.

According to an aspect of the present disclosure, there is provided a method for communication of a User Equipment (UE), the method comprising: constructing a System Information Block (SIB)24 if the SIB24 and/or scheduling information of the SIB24 is not contained in the system message of the current network; and performing a reselection procedure to a new air interface (NR) independent networking (SA) cell based on the constructed SIB 24.

According to yet another aspect of the disclosure, before performing the reselection procedure to the NR SA cell based on the constructed SIB24, further comprising: judging whether a Radio Resource Control (RRC) connection release message contains a redirection message to an NR SA cell; performing a redirection procedure to the NR SA cell if the redirection message to the NR SA cell is included; if no redirection message to the NR SA cell is included, a reselection procedure to the NR SA cell is performed based on the constructed SIB 24.

According to yet another aspect of the disclosure, constructing the SIB24 includes: obtaining NR SA cell information based on at least one of: an NR SA cell where the UE resides, or an NR SA system neighbor cell carried in measurement control sent by a network when the UE is in a connected state, or NR SA cell information provided by a server; and constructing a SIB24 based on the acquired NR SA cell information.

According to an aspect of the present disclosure, there is provided a User Equipment (UE) for communicating, comprising: a transceiver to receive a signal from a base station and to transmit a signal to the base station; a memory storing executable instructions; and a processor executing the stored instructions to perform the above-described method.

According to an aspect of the present disclosure, there is provided a User Equipment (UE), the UE comprising: a determining unit configured to determine whether the UE is provided with an evolved packet system-only service by a current network; a search unit configured to search for other networks different from a current network if it is determined that the UE is provided with an evolved packet system-only service by the current network; and a registration unit configured to initiate a registration procedure in the searched other network.

According to yet another aspect of the disclosure, the determination unit is further configured to: receiving a registration message or a system message from a current network; and judging whether the UE is provided with the evolved packet system only service by the current network according to the registration message or the system message.

According to yet another aspect of the disclosure, the registration unit is further configured to: and when judging that the UE is not provided with the evolved packet system service by the current network according to the system message, initiating a registration process in the current network.

According to yet another aspect of the disclosure, the determination unit is further configured to: based on a Public Land Mobile Network (PLMN) list carried in the system message, it is determined whether the UE is being provided with an evolved packet system-only service by the current network.

According to still another aspect of the disclosure, when determining whether the UE is provided with the eps only service by the current network based on the PLMN list carried in the system message, the determining unit is further configured to: when the first PLMN ID of the PLMN list carried in the system message is inconsistent with the home PLMN ID corresponding to the International Mobile Subscriber Identity (IMSI), judging whether the first PLMN ID of the PLMN list carried in the system message is contained in a stored network list for providing the evolved packet-only system service; and if the network list is included in the stored network list for providing the evolved packet system-only service, determining that the UE is provided with the evolved packet system-only service.

According to yet another aspect of the disclosure, the registration unit is further configured to: and when the first PLMN ID of the PLMN list carried in the system message is consistent with the home PLMN ID corresponding to the IMSI, initiating a registration process in the current network.

According to still another aspect of the present disclosure, the user equipment further includes: an updating unit configured to update the PLMN ID of the current network into a stored list of networks providing the evolved packet system only service if a registration message indicating the provision of the evolved packet system only service is received.

According to another aspect of the disclosure, the registration unit is further configured to initiate a registration procedure of type IMSI attach or a registration procedure of type joint attach when initiating a registration procedure in the searched other network.

According to yet another aspect of the disclosure, the registration unit is further configured to: determining other networks for initiating registration based on Public Land Mobile Networks (PLMNs) corresponding to the other searched networks among the other searched networks; and initiating a registration process for the determined other networks.

According to another aspect of the present disclosure, when determining, in the searched other networks, the other network that initiates the registration based on the PLMN corresponding to the searched other networks, the registration unit determines whether a PLMN ID in a PLMN list carried in a system message of the searched other networks is included in a stored network list that provides an evolved packet system-only service; if not included in the stored list of networks providing the evolved packet system-only service, then a determination is made to initiate a registration for the other searched networks.

According to yet another aspect of the disclosure, when initiating the registration procedure in the searched other network, the registration unit is further configured to: sorting the other searched networks according to the signal strength of the received broadcast channel or pilot channel; and initiating a registration process in the searched other networks according to the sorted sequence.

According to still another aspect of the present disclosure, the user equipment further includes a checking unit that checks whether the UE current USIM is a USIM that can only sign up for the eps only service, before searching for another network different from the current network, and searches for another network different from the current network when the current USIM is not a USIM that can only sign up for the eps only service.

According to yet another aspect of the present disclosure, there is provided a User Equipment (UE), including: a receiving unit configured to receive a registration message from a current network; a registration unit configured to initiate an initial IMS registration procedure to a current network based on a high definition Voice over LTE (VoLTE) on-off state of the UE or a VoLTE service state of the UE if it is determined that the UE is provided with an evolved packet System-only service by the current network based on the received registration message and the current network supports packet switched session IP multimedia subsystem voice.

According to yet another aspect of the disclosure, when initiating a registration procedure to the network based on a VoLTE switch state of the UE or a VoLTE traffic state of the UE, the registration unit is further configured to: and if the VoLTE switch state of the UE is the opening state, initiating an IMS initial registration process to the current network.

According to yet another aspect of the disclosure, when initiating a registration procedure to the network based on a VoLTE switch state of the UE or a VoLTE traffic state of the UE, the registration unit is further configured to: if the VoLTE switch state of the UE is the closing state, the UE judges whether the VoLTE service is opened or not; and if the VoLTE service of the UE is opened, prompting to open a VoLTE switch, and initiating an IMS initial registration process to the current network after detecting that the VoLTE switch is opened.

According to still another aspect of the present disclosure, the searching unit is further configured to search for other networks different from the current network when one of the following conditions is satisfied; and the registration unit initiates a registration process in the searched other networks: the current network or the searched network does not support the voice of the IP multimedia subsystem of the packet switching session; the UE does not support VoLTE function; the VoLTE switch of the UE is not detected to be changed from the closed state to the open state; the VoLTE service of the UE fails to be opened; and the UE detects that the user selects not to open the VoLTE service.

According to yet another aspect of the disclosure, when initiating a registration procedure in the searched network, the registration unit is further configured to: initiating a registration procedure with the type of IMSI attachment or a registration procedure with the type of joint attachment.

According to an aspect of the present disclosure, there is provided a User Equipment (UE), the UE comprising: a constructing unit configured to construct a System Information Block (SIB)24 if the SIB24 and/or scheduling information of the SIB24 is not included in a system message of a current network; and an execution unit configured to perform a reselection procedure to a new air interface (NR) independent networking (SA) cell based on the constructed SIB 24.

According to yet another aspect of the disclosure, the user equipment further comprises a determining unit, prior to performing the reselection procedure to the NR SA cell based on the constructed SIB24, the determining unit further configured to determine whether a redirection message to the NR SA cell is included in a Radio Resource Control (RRC) connection release message, the performing unit configured to perform the redirection procedure to the NR SA cell if the redirection message to the NR SA cell is included, and the performing unit configured to perform the reselection procedure to the NR SA cell based on the constructed SIB24 if the redirection message to the NR SA cell is not included.

According to yet another aspect of the disclosure, the constructing unit is further configured to acquire NR SA cell information based on at least one of: an NR SA cell where the UE resides, or an NR SA system neighbor cell carried in measurement control sent by a network when the UE is in a connected state, or NR SA cell information provided by a server; and constructing a SIB24 based on the acquired NR SA cell information.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG. 1 shows a flowchart of an example process according to a first embodiment of the present disclosure;

FIG. 2 shows a flow diagram of an example process according to a second embodiment of the present disclosure;

FIG. 3 shows a flow chart of an example process according to a third embodiment of the present disclosure;

FIG. 4 shows a flowchart of an example process according to a fourth embodiment of the present disclosure;

FIG. 5 shows a flowchart of an example process according to a fifth embodiment of the present disclosure;

FIG. 6 shows a flowchart of an example process according to a sixth embodiment of the present disclosure;

FIG. 7 shows a flowchart of an example process according to a seventh embodiment of the present disclosure;

fig. 8 is a flowchart illustrating an example process according to an eighth embodiment of the present disclosure;

FIG. 9 is a flow chart illustrating an example process according to a ninth embodiment of the present disclosure;

fig. 10 is a flowchart illustrating an example process according to a tenth embodiment of the present disclosure;

FIG. 11 is a flowchart illustrating an example process according to an eleventh embodiment of the present disclosure;

FIG. 12 is a flow chart illustrating an example process according to a twelfth embodiment of the present disclosure;

fig. 13 is a flowchart illustrating an example process according to a thirteenth embodiment of the present disclosure;

fig. 14 is a flowchart illustrating an example process according to a fourteenth embodiment of the present disclosure;

fig. 15 is a flowchart illustrating an example process according to a fifteenth embodiment of the present disclosure; and

fig. 16 is a block diagram illustrating a UE according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items. Further, the terms "first" and "second" used herein may describe various constituent elements, but they should not limit the corresponding constituent elements.

It will be understood by those within the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As will be understood by those skilled in the art, the term "terminal" as used herein includes both devices having wireless signal receivers, and devices having only wireless signal receivers without transmission capability; and a device including receive and transmit hardware having receive and transmit hardware capable of two-way communication over a two-way communication link. Such a device may include: a cellular or other communication device having a single line display or a multi-line display or a cellular or other communication device without a multi-line display; PCS (Personal Communications Service), which may combine voice, data processing, facsimile and/or data communication capabilities; a PDA (Personal Digital Assistant), which may include a radio frequency receiver, a pager, internet/intranet access, a web browser, a notepad, a calendar and/or a GPS (Global Positioning System) receiver; a conventional laptop and/or palmtop computer or other device having and/or including a radio frequency receiver. As used herein, a "terminal" or "terminal device" may be portable, transportable, installed in a vehicle (aeronautical, maritime, and/or land-based), or situated and/or configured to operate locally and/or in a distributed fashion at any other location(s) on earth and/or in space. As used herein, a "terminal Device" may also be a communication terminal, a web terminal, a music/video playing terminal, such as a PDA, an MID (Mobile Internet Device) and/or a Mobile phone with music/video playing function, or a smart tv, a set-top box, etc.

Since the CDMA (Code Division Multiple Access) technology can not be further developed, almost all the operators of CDMA networks in the world consider performing frequency clearing and network quitting on the CDMA network. In order to speed up the frequency clearing and network fading process of the CDMA network, some operators even no longer require the terminal to support the CDMA technology. Currently, many 5G (5th Generation ) terminals do not support CDMA technology.

There are new network operators that have just recently joined the telecommunications market, and these new network operators may not deploy 3G/2G networks, and the first network they use is usually the 4G (4th Generation ) network of choice.

In addition, from the perspective of network operators, the cost pressure of network construction is now increasing. Especially, as 5G technology is commercialized, it uses shorter wavelengths, and operators need to deploy more base stations to achieve the desired outdoor and indoor coverage levels. So that the network co-establishment and sharing among different operators becomes a trend. At present, the mainstream co-construction sharing mode is mainly to share an access network, i.e. a shared base station. During the network co-establishment sharing process, the user will reselect/switch between the home operator and the shared operator network. When the terminal is powered on or enters a new tracking area (or location area, routing area), the terminal searches for a cell and reads System Information of the cell, taking a Long Term Evolution (LTE) Network as an example, if a first PLMN ID in a PLMN (Public Land Mobile Network) list in System Information 1(System Information Block Type 1, SIB1) is consistent with an identifier in an IMSI (International Mobile Subscriber Identity) of a USIM (Universal Subscriber Identity Module) card currently used by the terminal, or the PLMN ID is included in an eh (Equivalent Public Land Mobile Network) list in the USIM card (or built-in terminal), the terminal considers that the PLMN belongs to the cell is a Home Network. In the case where the first PLMN ID in the PLMN list in the system information 1(SIB1) is not consistent with the PLMN identity in the IMSI of the USIM card currently used by the terminal and the PLMN ID is not included in the EHPLMN list in the USIM card (or built-in terminal), if the other PLMN IDs in the PLMN list in the system information 1(SIB1) are consistent with the PLMN identity in the IMSI of the USIM card currently used by the terminal or the other PLMN IDs are included in the EHPLMN list in the USIM card (or built-in terminal), the terminal considers the network to which the cell belongs as a shared network. In a network co-establishment sharing scenario or an international roaming scenario, for various reasons, the following scenarios may occur: when a user or a terminal not having a Voice Over LTE (Voice Over LTE, or referred to as Voice Over LTE) mode does not support the Voice Over LTE function, or the terminal supports the Voice Over LTE function but the switch of the Voice Over LTE service on the terminal is in an off state (the terminal does not support CDMA), a user or a terminal selects/reselects/switches/roams to the shared network (i.e., the target network) from the network to which the user or terminal belongs (the home network supports LTE/UMTS (Universal Mobile Telecommunications System)/GSM (Global System for Mobile Communications)), and the operator to which the target network belongs may be a conventional CDMA network operator, i.e., 3G/2G networks use CDMA technology, 4G uses LTE technology, or the operator to which the target network belongs is a brand new network operator, and the network of the operator is only a 4G/5G network. In this scenario, when the user performs an EPS (Evolved Packet System) ATTACH (or TAU (Tracking Area Update)) process in the target network, for such user, the target network Only sends an ATTACH ACCEPT (ATTACH ACCEPT) message with an ATTACH result being an EPS Only type or a TAU ACCEPT (TAU ACCEPT) message with a TAU Update result being a TA updated type to the user. This may cause the user of this type (currently used USIM card does not open the VoLTE service, or the terminal itself does not support the VoLTE function, or the terminal itself supports the VoLTE function but the switch of the VoLTE service on the terminal interface is in an off state) to select/reselect/switch/roam to the target network, and only EPS service (i.e. data service) may be used, and non-EPS service (i.e. call connection and call connection may not be used). At the moment, the user cannot use the voice service, and the user cannot make and receive calls, so that inconvenience is brought to daily communication and communication of the user.

After the terminal completes registration in the LTE network, the terminal performs voice communication in a CSFB manner, a VoLTE manner, or a CDMA manner according to the current communication standard and technology. Currently, the CSFB scheme in commercial use falls from LTE to UMTS or LTE to GSM. Since the evolution of the CDMA technology to CDMA2000 does not progress backwards any more, the original CDMA operators have to abandon the technology. In the environment of clear frequency quit of the CDMA network, some terminals no longer support the CDMA technology. When a terminal user not supporting CDMA technology selects/reselects/switches to the LTE network of a shared CDMA operator (or a completely new operator) domestically or roams to the LTE network of a CDMA operator abroad (or a completely new operator), if the USIM card currently used by such a user in the home network does not open the VoLTE service or the terminal itself does not support the VoLTE function or the terminal supports the VoLTE function but the VoLTE switch on the terminal interface is in the off state (i.e. voice call is performed using the CSFB mode in the home network), since the LTE network of the target does not support the CSFB function (note that for a CDMA operator, the 2G/3G network thereof is carried by CDMA technology and generally does not have a GSM/UMTS network, and therefore does not have the CSFB function, for a completely new operator, the GSM/UMTS network is already an outdated network, generally, the network cannot be deployed, so the first network in business is usually LTE in preference, and therefore the network does not have CSFB function), so only EPS service can be provided under the target network, and non-EPS service (call receiving and making cannot be provided) cannot be provided.

In a co-established sharing scenario, if a shared target operator wants to support CSFB functionality in its LTE network, the UMTS/GSM related parameters of the network it shares with must be configured into its network. This parameter configuration is very labor intensive, time consuming and most operators will not choose to do so. In the international roaming scenario, the LTE network of the target CDMA operator in the roaming area (or the target network in the roaming area is a completely new network) cannot support the CSFB function due to the lack of the UMTS/GSM network.

For current network operators, it is unlikely that all its subscribers will be able to turn on VoLTE functionality due to limitations in the capacity of the IMS (IP Multimedia Subsystem) core network, and other factors. Therefore, VoLTE users and non-VoLTE users will co-exist for a long time under the same operator's network.

In this context, the above-mentioned problem of using only PS domain services is always present. That is, the LTE network of the conventional CDMA operator does not support the CSFB function, which results in that the terminal itself that selects/reselects/switches/roams to the LTE network does not support the CDMA technology and the USIM card used does not open the VoLTE service, or the terminal itself does not support the CDMA technology and the user whose VoLTE switch on the terminal interface is in the off state cannot use the voice service. In addition, for a network capable of only providing 4G/5G services, the LTE network does not support the CSFB function, so that the USIM card used in selecting/reselecting/switching/roaming the LTE network does not open the VoLTE service, or the terminal itself does not support the VoLTE service, or the terminal itself supports the VoLTE service but the voice service cannot be used by the user whose VoLTE switch on the terminal interface is in the off state.

In order to solve the problem that voice service cannot be used in an LTE network that can only provide EPS service, so that a user can use voice service even when this occurs, the following solution is proposed.

For the domestic co-establishment sharing scenario, when the above problem occurs, the terminal may try to search the UMTS/GSM network of the home network (or other sharing networks), and initiate a registration procedure of IMSI attach type under the searched UMTS/GSM network, so as to obtain the CS domain service (which can make a call). Thus EPS services may be provided by an LTE network of a shared network, while CS domain traffic is provided by a UMTS/GSM network of the home network (or other shared network). When the above problem occurs, the terminal may also attempt to search for the LTE/UMTS/GSM network of the home network (or other shared network) and initiate a registration procedure of type joint attachment under the searched LTE/UMTS/GSM network in order to obtain EPS/non-EPS service (or PS/CS domain traffic) (may make a call). Thus EPS/non-EPS services (or PS/CS domain traffic) may be provided by the shared network or by other shared network LTE/UMTS/GSM networks. Optionally, when the above problem occurs, the terminal searches for the LTE/UMTS/GSM network (which may be according to LTE- > UMTS- > GSM priority, or in a random order) of the home network (or other available shared network), and attempts to initiate a registration process (which may be performed according to the above search priority (or random order) under the searched home network or shared network (if the LTE network registration fails, the UMTS network is tried again, and if the UMTS network registration fails again, the GSM network is tried again, or the UMTS network is randomly selected to perform registration in the searched network, which may not be performed according to the above order) so as to obtain the EPS/non-EPS service (or PS/CS domain service). After the registration is successful, the EPS/non-EPS service (or PS and CS services) can be used, if the registration fails, the state that only the EPS service is available can be maintained under the shared network which can only provide the EPS service initially.

For the international roaming scenario, when the above problem occurs, the terminal may attempt to search for the UMTS/GSM network of other network of the roaming site, and initiate a registration procedure of IMSI attach type under the searched UMTS/GSM network, so as to obtain the CS domain service. Thus, the EPS service and the CS domain service are respectively provided by the LTE network and the UMTS/GSM network of two different visited networks in a roaming place. Optionally, when the above problem occurs, the terminal searches for LTE/UMTS/GSM networks of other networks in the roaming area (which may be according to LTE- > UMTS- > GSM priority or in a random order), and attempts to initiate a registration process under the other searched networks (which may be according to the above search priority (or in a random order), if LTE network registration fails, then try UMTS, if UMTS network registration fails, then try GSM networks, or may randomly select to register in the searched networks, out of the above order), so as to obtain EPS/non-EPS services (or PS/CS domain services). After the registration is successful, the EPS/non-EPS service (or PS and CS service) can be used, if the registration fails, the network can return to the roaming place visiting network which can only provide the EPS service initially, and the state that only the EPS service is available is maintained.

Optionally, for a domestic co-establishment sharing scenario or an international roaming scenario, when the above problem occurs, after the terminal is powered on or enters a new location area and receives an Attach Accept (or TAU Accept) message with an EPS Only result, if the Attach Accept message (or TAU Accept message) indicates that the network supports IMS Voice Over PS Session, and the terminal itself supports the VoLTE function and the local VoLTE switch at the terminal side is in an on state, the terminal initiates an IMS initial registration process to the network. If the terminal receives the network response message carrying the Retry-after field, the network will open the VoLTE function for the user within the timer time carried by the Retry-after field, and the terminal initiates the IMS initial registration process again after the timer specified by the Retry-after field is overtime. Since the VoLTE function of the user is already enabled on the network side, the IMS initial registration process will be successfully completed. Therefore, the terminal can carry out voice service in a VoLTE mode under a shared network or a roaming visited network.

Optionally, for a domestic co-establishment sharing scenario or an international roaming scenario, after the terminal is powered on or enters a new location area and receives an Attach Accept message with an Attach result of EPS Only or a TAU Accept message with an EPS update result of TA updated (both EPS service and non-EPS service of the terminal before are available), if the Attach Accept message indicates that the network supports IMS Voice Over PS Session, the terminal may first determine whether the current USIM card of the user has activated the VoLTE service (may, but is not limited to, determine whether the VoLTE service has been activated by sending a supplementary service for querying the USIM card or determine according to a previously recorded VoLTE registration state or a previously recorded supplementary service query result), at this time, if the terminal itself supports the VoLTE function and the local VoLTE switch at the terminal side is in a closed state, the interface may prompt or guide the user to open the VoLTE switch, so that the terminal can perform voice service in a VoLTE mode after IMS initial registration is successful.

Optionally, the terminal may embed a PLMN list that only provides EPS services (the PLMN list may indicate whether the corresponding PLMN is a PLMN belonging to a conventional CDMA operator or a PLMN that only provides 4G/5G network services), and PLMN information of this list may be registered and updated by user preset or according to a history of past registration. For a domestic co-establishment sharing scene or an international roaming scene, when a terminal is started or enters a new location area to read system information of a cell, according to first PLMN ID information in a PLMN list carried in system information SIB1, comparing the PLMN list with a PLMN list which is built in the terminal and only provides EPS service, if the PLMN ID is contained in the list and the PLMN is a PLMN which only provides 4G/5G network service, simultaneously judging that the current network does not support VoLTE, a currently used USIM card does not open VoLTE service, or the terminal does not support VoLTE service, or the terminal supports VoLTE but a VoLTE switch on a terminal interface is in a closed state, not initiating a registration process in a network where the cell is located; if the PLMN ID is included in the list and the PLMN is a PLMN to which the conventional CDMA operator belongs, and it is determined that the terminal itself does not support CDMA technology and the current network does not support VoLTE, or the terminal itself does not support CDMA technology and the currently used USIM card does not open VoLTE service, or the terminal itself does not support CDMA technology and VoLTE service, or the terminal itself does not support VoLTE service and the terminal itself supports VoLTE but the VoLTE switch on the terminal interface is in an off state, the registration process is not initiated in the network in which the cell is located. And then search for the LTE/UMTS/GSM network of the home network or other shared network or other visited network of the roaming site (which may be in LTE- > UMTS- > GSM priority, or in random order). And tries to initiate a registration procedure under the searched network (registration can be performed according to the above search priority, UMTS is tried again if LTE network registration fails, GSM network is tried again if UMTS network registration fails, or registration is initiated in a random order) so as to obtain EPS/non-EPS service (or PS/CS domain service). If the registration is successful, the EPS/non-EPS service (or PS/CS domain service) can be used, if the registration is failed, the shared network which can only provide the EPS service initially or the visited network of a roaming place can be returned, and the state that only the EPS service is available is maintained.

In the current network, different operators generally have USIM cards, such as data cards or internet of things cards, which issue only EPS service subscriptions, and such cards can be distinguished in the PLMN identifier by the IMSI of the USIM card. When a terminal inserted with such a card receives an Attach Accept (for a TAU Accept message, EPS update result is TA updated) from an LTE network in a domestic co-establishment sharing scenario or an international roaming scenario, the USIM card only signs an EPS service, so that the USIM card belongs to a normal procedure. Therefore, it is sufficient to maintain the state in which only the EPS service is available without performing any operation.

In the current network, different operators generally issue USIM cards, such as data cards or internet of things cards, which only sign EPS services, and such cards can be distinguished in PLMN identifiers by IMSI of the USIM cards. When a terminal inserted with such a card receives an Attach Accept (for a TAU Accept message, EPS uplink result is TA updated) from an LTE network in a domestic co-establishment sharing scenario or an international roaming scenario, the USIM card only signs an EPS service, so that the USIM card belongs to a normal procedure. Therefore, it is sufficient to maintain the state in which only the EPS service is available without performing any operation.

Since the release of the first commercial release R8, the LTE system has been increasingly expanded and enhanced in functionality in subsequent releases. In particular, in version R12, the system message was extended, introducing SIB24, the system message. The purpose of introducing the system message is mainly to solve the problem how to perform inter-system cell reselection between LTE-to-5G SA cells when a terminal supporting a 5G (fifth generation) SA (stand alone) resides in an LTE network and is in an idle state under the LTE network. Due to the introduction of SIB24, an upgrade to the existing LTE network is required to support the transmission of SIB 24.

For the LTE terminals that are on the market in the early stage and operate in the LTE network, the network upgrade modification is naturally also affected, that is, SIB24 system messages are also received when the system broadcast messages are received. After some LTE terminals receive SIB24, asn.1(Abstract Syntax Notation 1) decodes normally, and then discards the system message according to a normal processing flow (since SIB24 solves the cell reselection problem in an idle state between LTE and 5G SA, the message should be ignored for LTE terminals that do not support 5G SA). However, some LTE terminals have problems with system compatibility, and after receiving SIB24, normal asn.1 decoding cannot be completed, and SIB1 carrying scheduling information of SIB24 that cannot be normally decoded is entirely discarded, so that the terminal is continuously restarted and cannot be normally used.

The evolution of the system standard is a lengthy process. The problem that part of LTE terminals are abnormally operated due to the introduction of SIB24 in the LTE system is not desirable. For this problem, it is due to errors in the decoding process of some LTE terminals asn.1, so the most direct solution is to directly modify the above errors and then push the version carrying the above modifications to the problematic terminal. However, these LTE terminals are scattered in the user's hand, and it is difficult to control the upgrade process of the user. Users who do not perform version upgrades are everyone. In this case, the network operator usually takes a temporary evasive measure, that is, does not broadcast the SIB24 in the system message, so as to avoid the problem that some LTE terminals work abnormally. Currently, 5G SA networks are still under continuous construction, and 5G SA signals in some regions may not be covered yet. Therefore, for a terminal supporting 5G SA, it is inevitable to camp under an LTE network with better coverage in a place without 5G SA coverage. If the LTE network does not broadcast SIB24 in the system information, it will not be reselected to the 5G SA cell when the 5G SA is in an idle state in the LTE network. This defeats the original purpose of operator 5G preference, and also affects the user experience (generally, the user experience under 5G SA system is better than that under LTE system). When the SIB24 is not broadcasted in the system message in the LTE network, in order to enable the 5G SA terminal to complete the cell reselection function between LTE and 5G SA systems in the LTE idle state, some terminal/chip manufacturers adopt various proprietary processing schemes. The main scheme is to periodically start the periodic background search function, i.e. the terminal starts the 5G SA cell search process every 1 minute or longer in the LTE idle state. If a proper 5G SA cell can be searched in the searching process, executing a cell reselection process between LTE and 5G SA systems; if the appropriate 5G SA cell is not searched, the terminal keeps the original state under the LTE system until the next background search timer is overtime. When the area where the terminal is located does not have 5G SA cell coverage or the 5G SA cell does not satisfy the inter-system cell reselection condition, the terminal may frequently perform a search process of the 5G SA cell in the LTE network, which undoubtedly increases power consumption of the terminal.

For the problem that the SIB24 causes the terminal to operate abnormally, the current scheme has certain problems. Therefore, the following solutions are proposed:

since the LTE terminal is already in the hand of the user, it is difficult to control the LTE terminal to perform version upgrade. Therefore, the premise for solving the problem is still not to broadcast the SIB24 system message in the LTE network, and in order to solve the problem that the terminal supporting the 5G SA cannot complete the inter-system cell reselection from LTE to 5G SA in the LTE idle state, an SIB24 system message may be constructed by using the existing 5G SA cell. The existing 5G SA cell information may be from a 5G SA cell where the terminal has resided, or from a 5G SA system neighbor cell carried by the terminal in measurement control in a connected network, or from 5G SA cell information provided by a server.

After the 5G SA terminal enters the idle state from the connected state in the LTE system, the terminal performs the LTE-to-5G SA inter-system cell reselection procedure according to the SIB24 configured by the terminal, just as receiving a true SIB24 system message.

The scheme does not need to update the version of the LTE terminal, so the time cost and the operation cost have certain advantages compared with the existing scheme.

The USIM card referred to in this specification also includes an embedded SIM card (eSIM).

Various embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

First embodiment

Fig. 1 shows a flowchart of an example process according to a first embodiment of the present disclosure.

For the domestic co-establishment sharing scenario, when the above problem occurs, the terminal may try to search the UMTS/GSM network of the home network (or other available sharing networks), and initiate a registration procedure of IMSI attach type under the searched UMTS/GSM network, so as to obtain the CS domain service (which can make a call). After successful registration, the EPS service is thus provided by the LTE network of the shared network, while the CS domain traffic is provided by the UMTS/GSM network of the home network (or other available shared network). If the registration fails, the terminal may return to the original shared network, maintaining a state in which only the EPS service is available.

As shown in fig. 1, in step 101, the UE specifically operates as follows: when the terminal is started or moves to a new tracking area, the terminal initiates an RRC establishment flow under the searched LTE cell (if the RRC is not established yet); after the RRC is successfully established, the terminal sends an Attach Request (Attach Request) message that an EPS Attach (EPS Attach) type is combined EPS/IMSI Attach (combined EPS/IMSI Attach) or a Tracking Area Update Request (TAU Request) message that an EPS Update (EPS Update) type is combined TA/LA Update or combined TA/LA Update with IMSI Attach, and receives an Attach Accept or TAU Accept message from the network.

In step 102, the UE specifically operates as follows: judging whether the EPS Attach result cell value in the received Attach Accept message is 1 (i.e. EPS Only), or whether the EPS Attach result cell value in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) and the EPS Update result cell value in the present received tracing Area Update Accept message is 0 (i.e. TA up), or whether the EPS Update result cell value in the last received tracing Area Update Accept message is 1(Combined TA/LA up) and the EPS Update result cell value in the present received tracing Area Update Accept message is 0 (i.e. TA up), and when the above judging condition is true, the terminal considers that the result of the Attach (or TAU) is of type EPS Only.

In step 103, the UE specifically operates as follows: and a PLMN list of the USIM which can only sign EPS only is built in the terminal side, the PLMN identifications in the IMSI of the currently used USIM card are compared with the list one by one, and if the PLMN identifications are contained in the list, the currently used USIM card is considered to belong to the USIM which can only sign EPS only. Otherwise, the currently used USIM card is considered to be capable of signing the EPS service and simultaneously signing the non-EPS service.

In step 104, the UE specifically operates as follows: the terminal checks whether the first PLMN ID in the PLMN list in system information 1(SIB1) of the current serving cell is consistent with the PLMN identity in the IMSI of the USIM card currently used by the terminal or whether the first PLMN ID is contained in the EHPLMN list in the USIM card (or EHPLMN list built in the terminal), and if the above-mentioned determination condition is true, the terminal considers that the network to which the cell belongs is the home network. The terminal checks whether the non-first PLMN ID in the PLMN list in system information 1(SIB1) of the current serving cell is consistent with the PLMN identity in the IMSI of the USIM card currently used by the terminal or whether the non-first PLMN ID is contained in the EHPLMN list in the USIM card (or the EHPLMN list built in the terminal), and if the above-mentioned determination condition is true, the terminal considers that the network to which the cell belongs is the shared network.

There is no order requirement for the execution of the above steps 102 to 104, and the UE side may execute in a random order.

In step 105, the UE specifically operates as follows: the terminal starts a cell search process (i.e., starts a radio frequency module, sequentially scans corresponding frequency points and frequency bands supported by the terminal, and reads system information of the cell), and determines whether the cell belongs to the home network or the shared network according to the method in step 104. If both cells belonging to the home network and the shared network are available, the signals may be sorted according to the Signal Strength of the broadcast Channel or the pilot Channel Received by the terminal (here, the Signal Strength is P-CCPCH (Primary Common Control Physical Channel) or CPICH RSCP (Received Signal Code Power) for UMTS or RSSI (Received Signal Strength Indication) for GSM).

In step 106, the terminal initiates an RRC (or RR) establishment procedure under the searched UMTS/GSM cell, and the RRC (or RR) establishment successfully sends a Location Update Request message (Location Update Request) with a Location Update Type of IMSI attach to the network. If the current network registration fails (where the registration failure refers to that no Location Update Accept message is received or an abnormal situation such as the authentication process is rejected by the network or the network does not respond in the registration process occurs) in the registration process, the registration process is initiated on the cell with the next highest signal according to the signal strength sequence described in step 105. Of course, the terminal may also initiate registration by preferring the home network, or randomly select an available network to initiate registration.

In step 107, the UE specifically operates as follows: the terminal side determines whether to receive the Location Update Accept message sent by the UMTS/GSM network in the registration process of step 106. In the registration process initiated by the terminal and having the type of IMSI attachment, the terminal determines that the registration process is successful as long as the terminal receives a Location Update Accept message sent by any one of the networks. If the Location Update Accept message sent by the network is not received under all the searched available UMTS/GSM networks, the registration process is determined to be failed.

If the registration process in step 107 is successful, both the terminal EPS service and the CS domain service are available, thereby effectively solving the problem that the terminal can not use the voice service under the shared network

That is, through the above process, in the shared network establishment scenario, in the LTE network of EPS Only, not Only the PS domain service can be normally used, but also the CS domain of the home network or other shared networks can be used to carry the voice service.

Second embodiment

Fig. 2 shows a flow chart of an example process according to a second embodiment of the present disclosure.

Optionally, when the above problem occurs, the terminal searches for an LTE/UMTS/GSM network (which may be according to LTE- > UMTS- > GSM priority, or a random order) of the home network (or other available shared network), since the LTE network can provide a higher rate, better user experience can be guaranteed, the UMTS network user experience is inferior, and the GSM network user experience is worst), and attempts to initiate a registration process under the searched home network (or other available shared network) (which may be performed according to the above search priority, if LTE network registration fails, UMTS network registration is attempted again, if UMTS network registration fails, GSM network is attempted again, or the above network is randomly selected for registration) so as to obtain EPS/non-EPS service (or PS/CS domain service). If the registration is successful, both EPS/non-EPS service (or PS and CS service) can be used; if the registration fails, the terminal may return to the shared network that originally provides only the EPS service, and maintain a state in which only the EPS service is available.

As shown in fig. 2, wherein steps 201 to 204 are the same as steps 101 to 104 shown in fig. 1, detailed description thereof will be omitted. Similar to fig. 1, there is no order requirement for the execution of steps 202 to 204, and the UE side may execute in a random order.

In step 205, the UE specifically operates as follows: the terminal starts a cell search process (i.e., starts a radio frequency module, sequentially scans corresponding frequency points and frequency bands supported by the terminal, and reads system information of the cell), and determines whether the cell belongs to the home network or the shared network according to the method in step 204. If both cells belonging to the home network and cells belonging to the shared network are available, the ranking may be performed according to the signal strength of the broadcast channel or pilot channel or reference signal received by the terminal (here the signal strength is RSRP for a cell-specific reference signal for LTE, P-CCPCH or CPICH RSCP for UMTS, RSSI for GSM).

In step 206, the UE specifically operates as follows: the method comprises the steps that a terminal initiates an RRC (or RR) establishment flow under a searched LTE/UMTS/GSM cell, after the RRC (or RR) is established successfully, if a current cell is an LTE cell, the terminal sends an Attach Request (Attach Request) message of which the EPS Attach type is combined EPS/IMSI Attach to a network; if the current cell is a UMTS/GSM cell, when the Network Operation Mode (NMO, Network Mode of Operation Network Operation Mode) is NMO I, the terminal sends an Attach Request message (Attach Request I) with an Attach Type of combined GPRS/IMSI Attach to the Network, and when the Network Operation Mode is NMO II, the terminal sends a Location Update Request message (Location Update Request) with a Location Update Type of IMSI Attach and an Attach Request message (Attach Request) with an Attach Type of GPRS Attach to the Network. If the current network registration fails (the registration failure here refers to that an Attach Accept message (for LTE) that the EPS Attach result is combined EPS/IMSI Attach is not received, or an Attach Accept message (for UMTS/GSM NMO I) is not received, or a Location Update Accept and an Attach Accept message (for UMTS/GSM NMO II) are not received, or an authentication procedure is rejected by the network during the registration procedure or a network no-response occurs during the registration procedure is abnormal, etc. occurs), the terminal may initiate the above-mentioned registration procedure on the cell with the strongest signal according to the signal strength sequence described in step 205. Of course, the terminal may also initiate registration by preferring the home network, or randomly select an available network to initiate registration.

In step 207, the UE specifically operates as follows: the terminal side determines in the registration process of step 206 whether to receive an Attach Accept message sent by the LTE/UMTS/GSM network (for the LTE network, an EPS Attach result field in the message should be combined EPS/IMSI Attach))/Location Update Accept message. In the registration process initiated by the terminal and having the type of IMSI Attach, the terminal determines that the registration process is successful as long as the terminal receives an Attach Accept (for the LTE network, an EPS Attach result field in the message is a combined EPS/IMSI Attach)/Location Update Accept message sent by any network. And if the Attach Accept message sent by the network is not received in all searched available LTE/UMTS/GSM networks (for the LTE network, an EPS Attach result field in the message should be combined EPS/IMSI Attach)/Location Update Accept message, determining that the registration process fails.

If the registration process in step 207 is successful, the terminal EPS/non-EPS service (for LTE) or PS/CS domain (for UMTS/GSM) service is available, which effectively solves the problem that the terminal cannot use the voice service in the shared network.

That is, through the above process, in the shared networking scenario, in the LTE network of EPS Only, by selecting the home network or other shared networks, not Only the PS domain service can be normally used, but also the CS domain can be used to carry the voice service.

Third embodiment

Fig. 3 shows a flow chart of an example process according to a third embodiment of the present disclosure.

For the international roaming scenario, when the above problem occurs, the terminal may try to search for the UMTS/GSM network of other visited networks of the roaming place, and initiate a registration procedure of IMSI attach type under the searched UMTS/GSM network, so as to obtain CS domain services. If the registration is successful, both EPS service and CS service are available, so that the EPS service and the CS domain service are respectively provided by the LTE network and the UMTS/GSM network of two different visited networks in a roaming place. If the registration fails, the network can return to the roaming place where only the EPS service can be provided originally, and the state that only the EPS service is available is maintained.

As shown in fig. 3, in which steps 301 to 303 are the same as steps 101 to 103 shown in fig. 1 and steps 306 and 307 are the same as steps 106 and 107 shown in fig. 1, detailed description thereof will be omitted.

In step 304, the specific operations at the UE side are as follows: the terminal checks whether the MCC value in the first PLMN ID in the PLMN list in the system information 1(SIB1) of the current serving cell is consistent with the MCC value in the PLMN ID in the IMSI of the USIM card currently used by the terminal, if so, the terminal considers that the network to which the cell belongs is a foreign operator network, and the current network is an international roaming scene.

Similar to fig. 1, there is no order requirement for the execution of steps 302 to 304, and the UE side may execute in a random order.

In step 305, the UE specifically operates as follows: the terminal starts a cell search process (i.e., a radio frequency module is started, corresponding frequency points and frequency bands supported by the terminal are sequentially scanned, and system information of the cell is read), and when a plurality of cells belonging to different PLMNs are available, the cells can be sorted according to the signal strength of a broadcast channel or a pilot channel (the signal strength here is P-CCPCH or CPICH RSCP for UMTS and RSSI for GSM).

If the registration process in step 307 is successful, both the EPS service and the CS domain service of the terminal are available, which effectively solves the problem that the terminal cannot use the voice service in the visited network in the international roaming scenario.

That is, through the above process, in a roaming scenario, in an LTE network of EPS Only, not Only the PS domain service can be normally used, but also the CS domain can be used to carry the voice service by selecting another visited network in a roaming area.

Fourth embodiment

Fig. 4 shows a flowchart of an example process according to a fourth embodiment of the present disclosure.

Optionally, when the above problem occurs, the terminal searches for LTE/UMTS/GSM networks of visited networks of other operators in the roaming area (which may be according to LTE- > UMTS- > GSM priority, or random order), and attempts to initiate a registration process under the other visited networks that are searched (which may be according to the above search priority, if LTE network registration fails, then try UMTS, if UMTS network registration fails, then try GSM networks, and then register in random order), so as to obtain EPS/non-EPS service (or PS/CS domain service). If the registration is successful, both EPS/non-EPS service (or PS and CS service) can be used; if the registration fails, returning to the network of the roaming operator which can only provide the EPS service originally, and maintaining the state that only the EPS service is available.

As shown in fig. 4, in which steps 401 to 404 are the same as steps 301 to 304 shown in fig. 3 and steps 405 to 407 are the same as steps 205 to 207 shown in fig. 2, detailed description thereof will be omitted. Similar to fig. 1, there is no order requirement for the execution of steps 402 to 404, and the UE side may execute in a random order.

If the registration process of step 407 is successful, the terminal EPS/non-EPS service (for LTE) or PS/CS domain (for UMTS/GSM) service is available, which effectively solves the problem that the terminal cannot use the voice service in the visited network in the international roaming scenario.

That is, through the above process, in a roaming scenario, in an LTE network of EPS Only, by selecting another visited network to a roaming place, not Only PS domain services can be normally used, but also CS domain services can be used to carry voice services.

Fifth embodiment

Fig. 5 is a flowchart illustrating an example process according to a fifth embodiment of the present disclosure.

Optionally, for a domestic co-establishment sharing scenario or an international roaming scenario, when the above problem occurs, after the terminal is powered on or enters a new location area and receives an Attach Accept (or TAU Accept) message of EPS Only, if the message indicates that the network supports IMS Voice Over PS Session, the terminal supports a VoLTE function, and a local VoLTE switch at the terminal side is in an on state, the terminal initiates an IMS initial registration process to the network. After receiving a response message carrying a Retry-after field from a network side, the terminal activates the VoLTE function for the user within the time of the timer carried by the Retry-after field, and after the timer specified by the Retry-after field is overtime, the terminal initiates the IMS initial registration process again. Since the VoLTE function of the user is already activated at the network side at this time, the IMS initial registration process will be successfully completed. Thus, the terminal can perform voice service in a VoLTE mode under the shared network.

As shown in fig. 5, wherein steps 501 to 503 are the same as steps 101 to 103 shown in fig. 1, detailed description thereof will be omitted.

Specifically, in step 504, the UE specifically operates as follows: the terminal checks in the received Attach Accept or TAU Accept message whether the IMS Voice Over PS Session indicator (indicator of IMS Voice Over PS Session) is IMS Voice Over PS Session in S1 mode supported (IMS Voice Over PS Session is supported in S1 mode), and if the above-mentioned determination condition is true, the network is considered to support IMS Voice Over PS Session (IMS Voice Over PS Session). For the terminal supporting the VoLTE, the interface of the terminal is provided with a switch of the VoLTE service. When the switch is turned on, the terminal can use the VoLTE mode to perform voice service (IMS registration is successful), otherwise, the terminal needs to use the CSFB mode to perform voice service.

Similar to fig. 1, there is no order requirement for the execution of steps 502 to 504, and the UE side may execute in a random order.

In step 505, the UE specifically operates as follows: the terminal sends SIP REGISTER (Session Initiation Protocol REGISTER) message to the network.

In step 506, the UE specifically operates as follows: after receiving the SIP 4XX response message carrying the Retry-after field sent by the network, the terminal analyzes the Retry-after field and reads the timer (timer) value carried by the field, starts the corresponding timer, and sends SIP REGISTER message to the network after the timer is overtime.

In step 507, the UE specifically operates as follows: the terminal receives a response message to SIP REGISTER from the network, if the terminal receives the response message of 200OK, the IMS registration process is judged to be successful, otherwise, the IMS registration process is judged to be failed.

If the IMS registration process in step 507 is successful, the terminal EPS service is available, and the voice service is performed in the VoLTE mode, which effectively solves the problem that the terminal cannot use the voice service in the home shared network or the roaming visited network in the national shared network or the roaming place under the scenario of the home network co-construction and sharing or the international roaming.

That is, through the above process, in a roaming scenario, a user can not Only use the PS domain service normally, but also use the VoLTE mode to carry the voice service in the EPS Only LTE network.

Sixth embodiment

Fig. 6 is a flowchart illustrating an example process according to a sixth embodiment of the present disclosure.

For a domestic co-establishment sharing scenario or an international roaming scenario, after the terminal is powered on or enters a new location area to receive an Attach Accept message with an Attach result of EPS Only or a TAU Accept message with an EPS update result of TA updated (both EPS service and non-EPS service of the terminal are available), if the Attach Accept message indicates that the network supports IMS Voice Over PS Session, the terminal may first determine whether the USIM card currently used by the user has the VoLTE service enabled (may but not limited to determine whether the VoLTE service has been enabled by sending a supplementary service for querying the USIM card or determine according to a previously recorded VoLTE registration state or a previously recorded supplementary service query result), if the terminal itself supports the VoLTE function and the local VoLTE switch on the terminal side is in a closed state, the terminal may prompt or guide the user on the VoLTE switch on the interface so that the terminal initiates an IMS initial registration procedure with the network. If the IMS initial registration process is successfully completed, the terminal may perform a voice service in a VoLTE manner under the shared network (or under the roamingly visited network).

As shown in fig. 6, wherein steps 601 to 603 are the same as steps 501 to 503 shown in fig. 5, detailed description thereof will be omitted.

In step 604, the UE specifically operates as follows: the terminal checks that an IMS Voice Over PS Session indicator is IMS Voice Over PS Session in S1 mode supported in the received Attach Accept or TAU Accept message, and if the judgment condition is true, the network is considered to support IMS Voice Over PS Session.

In step 605, the UE specifically operates as follows: the terminal sends an HTTP GET request to the network to inquire the supplementary service state of the USIM card used currently, and judges whether the USIM card has opened the VoLTE service according to a response message returned by the network. If the HTTP 403Forbidden message is received, judging that the USIM card does not open the VoLTE service; and if the HTTP 200OK message is received, judging that the USIM card opens the VoLTE service. Or judging whether the currently used USIM card opens the VoLTE service according to the previously recorded VoLTE registration state or the previously recorded supplementary service query result.

In step 606, the UE specifically operates as follows: some terminals do not support the VoLTE function, and some terminals support the VoLTE function. For a terminal supporting VoLTE, there is usually a switch of VoLTE service on its interface. When the switch is turned on, the terminal can use the VoLTE mode to perform voice service (IMS registration is successful), otherwise, the terminal needs to use the CSFB mode to perform voice service.

Similar to fig. 1, there is no order requirement for the execution of steps 602-606, and the UE side may execute in a random order.

In step 607, the UE specifically operates as follows: when the VoLTE switch at the terminal side is judged to be in the off state in step 606, the user is prompted on the interface or guided to turn on the switch, and the voice service can not be performed if the switch is not turned on.

In step 608, the UE specifically operates as follows: if the state of the VoLTE switch is ON, the VoLTE switch is indicated to be opened by the user according to the prompt or guidance of the interface, otherwise, the VoLTE switch is not opened.

In step 609, the UE specifically operates as follows: the terminal sends SIP REGISTER a message to the network.

In step 610, the UE specifically operates as follows: the terminal receives a response message to SIP REGISTER from the network, if the terminal receives the response message of 200OK, the IMS registration process is judged to be successful, otherwise, the IMS registration process is judged to be failed.

If the IMS registration process in step 610 is successful, the EPS service of the terminal is available, and the voice service is performed in the VoLTE mode, which effectively solves the problem that the terminal cannot use the voice service in the home shared network or the roaming visited network in the national shared network or the roaming place under the scenario of the home network co-construction and sharing or the international roaming.

Seventh embodiment

Fig. 7 is a flowchart illustrating an example process according to a seventh embodiment of the present disclosure.

The terminal may embed a PLMN list that only provides EPS services (the list may indicate whether the corresponding PLMN is a PLMN belonging to a conventional CDMA operator or a PLMN that only provides 4G/5G network services), and PLMN information of this list may be registered and updated by user presets or according to a history of past registrations. For a domestic co-establishment sharing scene or an international roaming scene, when a terminal is started or enters a new location area to read system information of a cell, according to first PLMN ID information in a PLMN list carried in system information SIB1, comparing the PLMN list with a PLMN list which is built in the terminal and only provides EPS service, if the PLMN ID is contained in the list and the PLMN is a PLMN which only provides 4G/5G network service, simultaneously judging that the current network does not support VoLTE, a currently used USIM card does not open VoLTE service, or the terminal does not support VoLTE service, or the terminal supports VoLTE but a VoLTE switch on a terminal interface is in a closed state, not initiating a registration process in a network where the cell is located; if the PLMN ID is included in the list and the PLMN is a PLMN to which the conventional CDMA operator belongs, and it is determined that the terminal itself does not support CDMA technology and the current network does not support VoLTE, or the terminal itself does not support CDMA technology and the currently used USIM card does not open VoLTE service, or the terminal itself does not support CDMA technology and VoLTE service, or the terminal itself does not support VoLTE service and the terminal itself supports VoLTE but the VoLTE switch on the terminal interface is in an off state, the registration process is not initiated in the network in which the cell is located. And then search for the LTE/UMTS/GSM network of the home network or other shared network or other visited network of the roaming site (which may be in LTE- > UMTS- > GSM priority, or in random order). And tries to initiate a registration procedure under the searched network (registration can be performed according to the above search priority, UMTS is tried again if LTE network registration fails, GSM network is tried again if UMTS network registration fails, or registration is initiated in a random order) so as to obtain EPS/non-EPS service (or PS/CS domain service). If the registration is successful, the EPS/non-EPS service (or PS/CS domain service) can be used, if the registration is failed, the shared network which can only provide the EPS service initially or the visited network of a roaming place can be returned, and the state that only the EPS service is available is maintained.

As shown in fig. 7, in step 701, the UE specifically operates as follows: after the terminal is powered on or moves to a new tracking mode, the terminal starts a cell search process (namely, a radio frequency module is started, and corresponding frequency points and frequency bands supported by the terminal are scanned in sequence), and system information of the cell is read.

In step 702, the UE specifically operates as follows: the terminal checks whether the first PLMN ID in the PLMN list in system information 1(SIB1) of the current serving cell is in the PLMN list built in the terminal that provides Only EPS Only service. Comparing the first PLMN ID information in the PLMN list carried in the system information SIB1 with a PLMN list which is built in the terminal and only provides EPS service, if the PLMN ID is contained in the list and the PLMN is a PLMN which only provides 4G/5G network service, simultaneously judging that the current network does not support VoLTE or the currently used USIM card does not open VoLTE service (which can be judged by but not limited to recording the VoLTE registration state of the USIM card or the previously recorded supplementary service query result) or the terminal does not support VoLTE service or the terminal supports VoLTE but the VoLTE switch on the terminal interface is in a closed state, and if the judgment condition is true, not initiating a registration process in the network where the cell is located; if the PLMN ID is included in the list and the PLMN is a PLMN to which the conventional CDMA operator belongs, and it is determined that the terminal itself does not support CDMA technology and the current network does not support VoLTE, or the terminal itself does not support CDMA technology and the currently used USIM card does not open VoLTE service (which may be determined by, but not limited to, determining according to a previously recorded VoLTE registration state of the USIM card or a previously recorded supplementary service query result), or the terminal itself does not support CDMA technology and VoLTE service, or the terminal itself supports VoLTE but the VoLTE switch on the terminal interface is in a closed state, if the above determination condition is true, then the registration process is not initiated in the network in which the cell is located.

In step 703, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request message (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network.

In step 704, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type.

If the determination condition in step 704 is false, the terminal is available for both EPS/non-EPS services in the current network.

In step 705, the UE specifically operates as follows: and registering or updating the current PLMN identification into a PLMN list which is built in the terminal and only provides EPS service. The subsequent steps can be connected to step 104-; or steps 503 and 507 of fig. 5, or steps 603 to 610 of fig. 6.

That is, through the above process, in a roaming scenario, the user can not Only use the PS domain service normally, but also use the CS domain or use the VoLTE mode to carry the voice service in the LTE network of EPS Only.

Eighth embodiment

Fig. 8 is a flowchart illustrating an example process according to an eighth embodiment of the present disclosure.

After the 5G SA terminal enters an idle state from a connected state in an LTE cell, if SIB24 is received in the cell, the terminal performs a cell reselection process between the LTE system and the 5G SA system according to the received SIB 24; if SIB24 has not been received in this cell, a SIB24 system message is constructed according to the existing 5G SA cell information as follows. The existing 5G SA cell information may be from a 5G SA cell (for example, the 5G SA cell is a cell adjacent to an LTE cell where the terminal currently resides) (including cell frequency point and cell reselection priority information) where the terminal has resided, or from a 5G SA system neighbor cell (including cell frequency point information) carried by the terminal in measurement control in a connected network, or from 5G SA cell information (including cell frequency point and cell reselection priority) provided by a server (for example, a big data platform). As an example, the server providing the 5G SA cell information may be the terminal manufacturer's own server, the operator's server, or a server of another third party, etc. When the terminal is in a network connection state, the terminal can report information of the cell where the terminal resides currently, current position information, information of a neighboring cell of the current cell and the like to the server. For the above information, the server may push the information to other terminals for purposes of cell handover or reselection, etc. When a 5G SA cell in the constructed SIB24 system message is derived from a 5G SA neighboring cell carried in measurement control sent by the network when the terminal is in a connected state, since the measurement control only includes frequency point information of the neighboring cell, if the cell information is used for a cell reselection purpose, a cell reselection priority of the 5G SA cell needs to be specified. According to the policy of preference of the operator 5G network, it is generally specified that the cell reselection priority of the 5G SA cell is higher than that of the LTE cell where the terminal is currently located. After the terminal successfully constructs SIB24 (including at least one 5G SA neighbor cell), the terminal performs the LTE-to-5G SA inter-system cell reselection procedure according to the constructed SIB24, as if it received a real SIB24 system message. If no 5G SA neighbor cell is contained in the constructed SIB24, the terminal needs to maintain the current state under the LTE network.

As shown in fig. 8, in step 801, the UE specifically operates as follows: the 5G SA terminal receives an RRC Connection Release message in an LTE cell, enters an idle state from a connected state, and does not contain redirection information;

in step 802, the UE specifically operates as follows: after the LTE cell enters an idle state, the 5G SA terminal judges whether an SIB24 system message is received or not;

in step 803, the UE specifically operates as follows: if the 5G SA terminal receives the SIB24 system message in the current resident LTE cell, the terminal completes the cell reselection process between the LTE and 5G SA systems.

In step 804, the UE specifically operates as follows: if the 5G SA terminal has not received the SIB24 system message in the currently camped LTE cell, the terminal needs to construct a SIB24 system message according to the existing 5G SA cell information as follows. The existing 5G SA cell information may be from a 5G SA cell (including cell frequency point and cell reselection priority information) where the terminal has resided, or from a neighboring cell (including cell frequency point information) of a 5G SA system carried by the terminal in measurement control in a connected network, or from 5G SA cell information (including cell frequency point and cell reselection priority) provided by a server. When the 5G SA cell in the constructed SIB24 system message is derived from a 5G SA neighboring cell carried in measurement control sent by the network when the terminal is in a connected state, since the measurement control only includes frequency point information of the 5G SA neighboring cell, if the cell information is used for a cell reselection purpose, a cell reselection priority of the 5G SA cell needs to be specified. According to the policy of preference of the operator 5G network, it may be generally specified that the cell reselection priority of the 5G SA cell is higher than that of the LTE cell where the terminal is currently located.

In step 805, the UE specifically operates as follows: judging whether SIB24 constructed by the 5G SA terminal contains at least one 5G SA neighbor cell information;

in step 806, the UE specifically operates as follows: if the SIB24 constructed by the 5G SA terminal contains at least one 5G SA neighbor cell information, the terminal performs the LTE-to-5G SA intersystem cell reselection procedure according to the SIB24 constructed by the terminal, just as if a real SIB24 system message is received.

In step 807, the UE specifically operates as follows: if the SIB24 constructed by the 5G SA terminal does not contain any 5G SA neighbor cell information, the terminal needs to maintain the current state in the LTE network.

In further embodiments, in the above procedure, the SIB24 constructed by the 5G SA terminal may also occur at other times, for example, when the terminal is in LTE connected state. That is, through the above process, the 5G SA terminal is low in power consumption, and can quickly search for a 5G SA cell using existing 5G SA cell information, complete inter-system cell reselection between LTE and 5G SA cells, and meanwhile, an LTE terminal that is on the market at an early stage can also work normally.

Ninth embodiment

Fig. 9 is a flowchart illustrating an example process according to a ninth embodiment of the present disclosure.

In step 901, the UE specifically operates as follows: after the terminal is powered on or moves (cell selection or cell reselection or handover may occur) to a new tracking area, the terminal starts a cell search procedure and reads system information of a current serving cell.

In step 902, the UE specifically operates as follows: the terminal checks whether the first PLMN ID in the PLMN list in system information 1(SIB1) of the current serving cell is in the PLMN list built in the terminal that provides Only EPS Only service. If true, go to step 914; otherwise, step 903 is executed.

In step 903, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network, and receives the Attach Request or Tracking Area Update Request from the network side.

In step 904, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type. Meanwhile, whether the carried EMM cause value is #16, #17 or #18 needs to be judged, if the judgment result is true, step 906 is executed; otherwise, step 905 is performed.

In step 905, the UE side specifically operates as follows: and the terminal executes subsequent actions according to the corresponding flow.

In step 906, the UE specifically operates as follows: the terminal determines whether the IMS voice service is available, that is, determines whether the current network supports VoLTE (determined by a VoPS field carried in an Attach Accept or Tracking Area Update Accept message delivered by the network, if VoPS is 1, it indicates that the network supports VoLTE, otherwise it is not supported), whether the current USIM card provides VoLTE service (determined by, but not limited to, recording a VoLTE registration state of the USIM card or a previously recorded supplementary service query result), and whether the terminal itself supports VoLTE function. If the result is true, step 907 is performed, otherwise step 913 is performed.

In step 907, the UE specifically operates as follows: judging whether a VoLTE switch (if any) on the terminal user interface is in a closed state, if so, executing a step 908; otherwise, step 910 is performed.

In step 908, the UE specifically operates as follows: and the terminal starts a guide interface to guide the user to open the VoLTE switch.

In step 909, the UE specifically operates as follows: and judging whether the user opens the VoLTE switch according to the guiding process described in the step 908, if so, executing the step 910, otherwise, executing the step 913.

In step 910, the UE specifically operates as follows: the terminal initiates an IMS registration procedure. Specifically, the terminal sends SIP REGISTER a message to the network.

In step 911, the UE specifically operates as follows: the terminal determines whether the IMS registration is successful, i.e., whether a200 OK response message to the SIP REGISTER request message sent by the network is received. If true, go to step 912; otherwise step 913 is performed.

In step 912, the UE specifically operates as follows: the terminal keeps the state that both data service and voice service are available under the 4G network of the current PLMN.

In step 913, the UE specifically operates as follows: the terminal adds the current PLMN ID (i.e. the PLMN ID carried in the Attach Accept or Tracking Area Update Accept message issued by the network) to a PLMN list locally stored by the terminal and only providing EPS only services.

In step 914, the UE specifically operates as follows: the terminal searches for 4G or 3G or 2G networks of other available PLMNs.

In step 915, the UE specifically operates as follows: if there is a 4G network available among the available networks searched by the terminal, performing step 917; otherwise, go to step 916.

In step 916, the UE specifically operates as follows: if 3G/2G networks are available (if 3G/2G networks of multiple PLMNs are available, the networks may be prioritized according to signal strength), in the available networks searched by the terminal, then step 924 is performed; otherwise, step 927 is performed.

In step 917, the UE specifically operates as follows: if the 4G networks of a plurality of PLMNs are available in the network searched by the terminal, the priority ranking can be carried out according to the signal strength, the PLMN to which the cell with the best signal belongs is selected as the current PLMN, and the joint attachment process is initiated under the 4G network of the current PLMN.

In step 918, the UE specifically operates as follows: the terminal side checks whether an Attach Accept message from the network side is received and whether an EPS Attach result cell value is 2, if the result is true, step 923 is executed; otherwise, step 919 is performed.

In step 919, the UE side specifically operates as follows: judging whether the value of an EPS Attach result cell in the received Attach Accept message is 1 (namely EPS only) and whether the carried EMM cause value is #16 or #17 or #18, if the result is true, executing step 920; otherwise, go to step 921.

In step 920, the UE specifically operates as follows: the terminal side operates as in step 913.

In step 921, the UE specifically operates as follows: the terminal side judges whether other PLMNs are available, if true, the other PLMNs (the PLMN with the second highest signal can be selected) are set as the current PLMN, and step 917 is executed; otherwise, step 922 is performed.

In step 922, the UE specifically operates as follows: the terminal may attempt to search for the 3G/2G network of the current PLMN and perform step 916.

In step 923, the UE specifically operates as follows: and the terminal keeps both the EPS service and the Non-EPS service available under the current PLMN.

In step 924, the UE specifically operates as follows: the terminal initiates an IMSI attach procedure under the 3G/2G network of the current PLMN, that is, the terminal initiates an RRC (or RR) connection establishment procedure to the network and sends a Location Updating Request message to the network side.

In step 925, the UE specifically operates as follows: whether the terminal side receives a Location Updating Accept message from the network side, if so, step 928 is executed; otherwise, step 926 is performed.

In step 926, the UE specifically operates as follows: the terminal side judges whether the 3G or 2G network of other PLMN is available, if true, sets other PLMN (PLMN with strong signal second time can be selected) as the current PLMN and executes step 924; otherwise, step 927 is performed.

In step 927, the UE side specifically operates as follows: the terminal returns to the initial PLMN and keeps the EPS Only service available.

In step 928, the UE specifically operates as follows: the terminal keeps EPS data service under the initial PLMN and keeps CS domain service under the current PLMN.

Tenth embodiment

Fig. 10 is a flowchart illustrating an example process according to a tenth embodiment of the present disclosure.

In step 1001, the UE specifically operates as follows: after the terminal is powered on or moves (cell selection or cell reselection or handover may occur) to a new tracking area, the terminal starts a cell search procedure and reads system information of a current serving cell.

In step 1002, the UE specifically operates as follows: the terminal checks whether the first PLMN ID in the PLMN list in system information 1(SIB1) of the current serving cell is in the PLMN list built in the terminal that provides Only EPS Only service. If true, go to step 1014; otherwise, step 1003 is performed.

In step 1003, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network, and receives the Attach Request or Tracking Area Update Request from the network side.

In step 1004, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type. Meanwhile, whether the carried EMM cause value is #16, #17 or #18 needs to be judged, if the judgment result is true, step 1006 is executed; otherwise, step 1005 is performed.

In step 1005, the UE specifically operates as follows: and the terminal executes subsequent actions according to the corresponding flow.

In step 1006, the UE specifically operates as follows: the terminal determines whether the IMS voice service is available, that is, determines whether the current network supports VoLTE (determined by a VoPS field carried in an Attach Accept or Tracking Area Update Accept message delivered by the network, if VoPS is 1, it indicates that the network supports VoLTE, otherwise it is not supported), whether the current USIM card provides VoLTE service (determined by, but not limited to, recording a VoLTE registration state of the USIM card or a previously recorded supplementary service query result), and whether the terminal itself supports VoLTE function. If the result is true, step 1007 is executed, otherwise step 1013 is executed.

In step 1007, the UE side specifically operates as follows: judging whether a VoLTE switch (if any) on the terminal user interface is in a closed state, if so, executing a step 1008; otherwise, go to step 1010.

In step 1008, the UE side specifically operates as follows: and the terminal starts a guide interface to guide the user to open the VoLTE switch.

In step 1009, the UE specifically operates as follows: and judging whether the user turns on a VoLTE switch according to the guiding process described in the step 1008, if so, executing the step 1010, otherwise, executing the step 1013.

In step 1010, the UE specifically operates as follows: the terminal initiates an IMS registration procedure. Specifically, the terminal sends SIP REGISTER a message to the network.

In step 1011, the UE specifically operates as follows: the terminal determines whether the IMS registration is successful, i.e., whether a200 OK response message to the SIP REGISTER request message sent by the network is received. If true, go to step 1012; otherwise, step 1013 is performed.

In step 1012, the UE specifically operates as follows: the terminal keeps the state that both data service and voice service are available under the 4G network of the current PLMN.

In step 1013, the UE specifically operates as follows: the terminal adds the current PLMN ID (i.e. the PLMN ID carried in the Attach Accept or Tracking Area Update Accept message issued by the network) to a PLMN list locally stored by the terminal and only providing EPS only services.

In step 1014, the UE specifically operates as follows: the terminal searches for 4G networks of other available PLMNs.

In step 1015, the UE specifically operates as follows: if there is a 4G network available among the available networks searched by the terminal, performing step 1016; otherwise, step 1021 is executed.

In step 1016, the UE specifically operates as follows: if the 4G networks of a plurality of PLMNs are available in the network searched by the terminal, the priority ranking can be carried out according to the signal strength, the PLMN to which the cell with the best signal belongs is selected as the current PLMN, and the joint attachment process is initiated under the 4G network of the current PLMN.

In step 1017, the UE specifically operates as follows: the terminal side checks whether an Attach Accept message from the network side is received and whether an EPS Attach result cell value is 2, if so, step 1022 is executed; otherwise, step 1018 is performed.

In step 1018, the UE specifically operates as follows: judging whether the EPS Attach result cell value in the received Attach Accept message is 1 (namely EPS only) and whether the carried EMM cause value is #16 or #17 or #18, if the result is true, executing step 1019; otherwise, step 1020 is performed.

In step 1019, the UE specifically operates as follows: the operation at the terminal side is substantially the same as step 1013.

In step 1020, the UE specifically operates as follows: the terminal side judges whether other PLMNs are available, if true, step 1016 is executed; otherwise, step 1021 is executed.

In step 1021, the UE specifically operates as follows: the terminal may attempt to search for the 3G/2G network of the current PLMN.

In step 1022, the UE specifically operates as follows: and the terminal keeps both the EPS service and the Non-EPS service available under the current PLMN.

That is, by the above-described procedure, at least:

the time is saved: when IMS voice (and/or CDMA) is not available, the UE may avoid registering to a PLMN that provides EPS services only;

4G and VoLTE/CSFB: the user may use 4G for EPS services and VoLTE or CSFB for voice/SMS services.

Eleventh embodiment

Fig. 11 is a flowchart illustrating an example process according to an eleventh embodiment of the present disclosure.

In step 1101, the UE specifically operates as follows: after the terminal is powered on or moves (cell selection or cell reselection or handover may occur) to a new tracking area, the terminal starts a cell search procedure and reads system information of a current serving cell.

In step 1102, the UE specifically operates as follows: the terminal checks whether the first PLMN ID in the PLMN list in system information 1(SIB1) of the current serving cell is in the PLMN list built in the terminal that provides Only EPS Only service. If true, perform step 1114; otherwise, go to step 1103.

In step 1103, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network, and receives the Attach Request or Tracking Area Update Request from the network side.

In step 1104, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type. Meanwhile, whether the carried EMM cause value is #16, #17 or #18 needs to be judged, if the judgment result is true, step 1106 is executed; otherwise step 1105 is performed.

In step 1105, the UE specifically operates as follows: and the terminal executes subsequent actions according to the corresponding flow.

In step 1106, the UE specifically operates as follows: the terminal determines whether the IMS voice service is available, that is, determines whether the current network supports VoLTE (determined by a VoPS field carried in an Attach Accept or Tracking Area Update Accept message delivered by the network, if VoPS is 1, it indicates that the network supports VoLTE, otherwise it is not supported), whether the current USIM card provides VoLTE service (determined by, but not limited to, recording a VoLTE registration state of the USIM card or a previously recorded supplementary service query result), and whether the terminal itself supports VoLTE function. If true, step 1107 is executed, otherwise step 1113 is executed.

In step 1107, the UE specifically operates as follows: judging whether a VoLTE switch (if any) on the terminal user interface is in a closed state, if so, executing a step 1108; otherwise, step 1110 is performed.

In step 1108, the UE specifically operates as follows: and the terminal starts a guide interface to guide the user to open the VoLTE switch.

In step 1109, the UE side specifically operates as follows: and judging whether the user turns on a VoLTE switch according to the guiding process described in the step 1108, if so, executing the step 1110, otherwise, executing the step 1113.

In step 1110, the UE specifically operates as follows: the terminal initiates an IMS registration procedure. Specifically, the terminal sends SIP REGISTER a message to the network.

In step 1111, the UE specifically operates as follows: the terminal determines whether the IMS registration is successful, i.e., whether a200 OK response message to the SIP REGISTER request message sent by the network is received. If true, go to step 1112; otherwise, step 1113 is performed.

In step 1112, the UE specifically operates as follows: the terminal keeps the state that both data service and voice service are available under the 4G network of the current PLMN.

In step 1113, the UE specifically operates as follows: the terminal adds the current PLMN ID (i.e. the PLMN ID carried in the Attach Accept or Tracking Area Update Accept message issued by the network) to a PLMN list locally stored by the terminal and only providing EPS only services.

In step 1114, the UE specifically operates as follows: the terminal searches for 3G or 2G networks of other available PLMNs.

In step 1115, the UE specifically operates as follows: if 3G/2G networks are available (if 3G/2G networks of multiple PLMNs are available, they may be prioritized according to signal strength), among the available networks searched by the terminal, step 1116 is performed; otherwise, step 1119 is performed.

In step 1116, the UE specifically operates as follows: the terminal initiates an IMSI attachment process under the 3G/2G network of the current PLMN, namely the terminal initiates an RRC (or RR) connection establishment process to the network and sends a Location Updating Request message to the network side.

In step 1117, the UE specifically operates as follows: whether the terminal side receives the Location Updating Accept message from the network side, if the result is true, execute step 1120; otherwise, step 1118 is performed.

In step 1118, the UE specifically operates as follows: the terminal side judges whether the 3G or 2G network of other PLMN is available, if true, step 1116 is executed; otherwise, step 1119 is performed.

In step 1119, the UE specifically operates as follows: the terminal returns to the initial PLMN and keeps the EPS Only service available.

In step 1120, the UE specifically operates as follows: the terminal keeps EPS data service under the initial PLMN and keeps CS domain service under the current PLMN.

That is, by the above-described procedure, at least:

providing 4G and CS domains: the user may use 4G for EPS services and CS domain for voice/SMS services.

Twelfth embodiment

Fig. 12 is a flowchart illustrating an example process according to a twelfth embodiment of the present disclosure.

In step 1201, the UE specifically operates as follows: after the terminal is powered on or moves (cell selection or cell reselection or handover may occur) to a new tracking area, the terminal starts a cell search procedure and reads system information of a current serving cell.

In step 1202, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network, and receives the Attach Request or Tracking Area Update Request from the network side.

In step 1203, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type. Meanwhile, whether the carried EMM cause value is #16, #17 or #18 needs to be judged, if the judgment result is true, step 1205 is executed; otherwise, go to step 1204.

In step 1204, the UE specifically operates as follows: and the terminal executes subsequent actions according to the corresponding flow.

In step 1205, the UE side specifically operates as follows: the terminal determines whether the IMS voice service is available, that is, determines whether the current network supports VoLTE (determined by a VoPS field carried in an Attach Accept or Tracking Area Update Accept message delivered by the network, if VoPS is 1, it indicates that the network supports VoLTE, otherwise it is not supported), whether the current USIM card provides VoLTE service (determined by, but not limited to, recording a VoLTE registration state of the USIM card or a previously recorded supplementary service query result), and whether the terminal itself supports VoLTE function. If true, step 1206 is performed, otherwise step 1212 is performed.

In step 1206, the UE specifically operates as follows: judging whether a VoLTE switch (if any) on the terminal user interface is in a closed state, if so, executing a step 1207; otherwise, step 1209 is performed.

In step 1207, the UE specifically operates as follows: and the terminal starts a guide interface to guide the user to open the VoLTE switch.

In step 1208, the UE specifically operates as follows: and judging whether the user turns on a VoLTE switch according to the guiding process described in the step 1208, if so, executing the step 1209, otherwise, executing the step 1212.

In step 1209, the UE specifically operates as follows: the terminal initiates an IMS registration procedure. Specifically, the terminal sends SIP REGISTER a message to the network.

In step 1210, the UE specifically operates as follows: the terminal determines whether the IMS registration is successful, i.e., whether a200 OK response message to the SIP REGISTER request message sent by the network is received. If true, go to step 1211; otherwise, go to step 1212.

In step 1211, the UE specifically operates as follows: the terminal keeps the state that both data service and voice service are available under the 4G network of the current PLMN.

In step 1212, the UE specifically operates as follows: the terminal searches for 4G networks of other available PLMNs.

In step 1213, the UE specifically operates as follows: if there is a 4G network available in the available networks searched by the terminal, executing step 1214; otherwise step 1217 is performed.

In step 1214, the UE specifically operates as follows: if the 4G networks of a plurality of PLMNs are available in the network searched by the terminal, the priority ranking can be carried out according to the signal strength, the PLMN to which the cell with the best signal belongs is selected as the current PLMN, and the joint attachment process is initiated under the 4G network of the current PLMN.

In step 1215, the UE side specifically operates as follows: the terminal side checks whether an Attach Accept message from the network side is received and whether an EPS Attach result cell value is 2, if the result is true, step 1218 is executed; otherwise, step 1216 is performed.

In step 1216, the UE specifically operates as follows: the terminal side judges whether other PLMNs are available, if true, other available PLMNs (the PLMN with the second highest signal level can be selected) are selected as the current PLMN, and step 1217 is executed; otherwise, step 1214 is performed.

In step 1217, the UE specifically operates as follows: the terminal may attempt to search for the 3G/2G network of the current PLMN.

In step 1218, the UE side specifically operates as follows: and the terminal keeps both the EPS service and the Non-EPS service available under the current PLMN.

That is, by the above-described procedure, at least:

the user may use 4G for EPS services and VoLTE or CSFB for voice/SMS services.

Thirteenth embodiment

Fig. 13 is a flowchart illustrating an example process according to a thirteenth embodiment of the present disclosure.

In step 1301, the UE specifically operates as follows: after the terminal is powered on or moves (cell selection or cell reselection or handover may occur) to a new tracking area, the terminal starts a cell search procedure and reads system information of a current serving cell.

In step 1302, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network, and receives the Attach Request or Tracking Area Update Request from the network side.

In step 1303, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type. Meanwhile, whether the carried EMM cause value is #16, #17 or #18 needs to be judged, if the judgment result is true, step 1305 is executed; otherwise, step 1304 is performed.

In step 1304, the UE specifically operates as follows: and the terminal executes subsequent actions according to the corresponding flow.

In step 1305, the UE specifically operates as follows: the terminal determines whether the IMS voice service is available, that is, determines whether the current network supports VoLTE (determined by a VoPS field carried in an Attach Accept or Tracking Area Update Accept message delivered by the network, if VoPS is 1, it indicates that the network supports VoLTE, otherwise it is not supported), whether the current USIM card provides VoLTE service (determined by, but not limited to, recording a VoLTE registration state of the USIM card or a previously recorded supplementary service query result), and whether the terminal itself supports VoLTE function. If true, step 1306 is performed, otherwise step 1312 is performed.

In step 1306, the UE specifically operates as follows: judging whether a VoLTE switch (if any) on the terminal user interface is in a closed state, if so, executing a step 1307; otherwise, step 1309 is performed.

In step 1307, the UE specifically operates as follows: and the terminal starts a guide interface to guide the user to open the VoLTE switch.

In step 1308, the UE specifically operates as follows: and judging whether the user turns on a VoLTE switch according to the guiding process described in the step 1308, if so, executing a step 1309, and if not, executing a step 1312.

In step 1309, the UE specifically operates as follows: the terminal initiates an IMS registration procedure. Specifically, the terminal sends SIP REGISTER a message to the network.

In step 1310, the UE specifically operates as follows: the terminal determines whether the IMS registration is successful, i.e., whether a200 OK response message to the SIP REGISTER request message sent by the network is received. If true, go to step 1311; otherwise, step 1312 is performed.

In step 1311, the UE side specifically operates as follows: the terminal keeps the state that both data service and voice service are available under the 4G network of the current PLMN.

In step 1312, the UE specifically operates as follows: the terminal searches for 3G or 2G networks of other available PLMNs.

In step 1313, the UE specifically operates as follows: if 3G/2G networks are available (if 3G/2G networks of multiple PLMNs are available, the networks may be prioritized according to signal strength), in the available networks searched by the terminal, executing step 1314; otherwise, step 1317 is performed.

In step 1314, the UE specifically operates as follows: the terminal initiates an IMSI attachment process under the 3G/2G network of the current PLMN, namely the terminal initiates an RRC (or RR) connection establishment process to the network and sends a Location Updating Request message to the network side.

In step 1315, the UE specifically operates as follows: whether the terminal side receives the Location Updating Accept message from the network side, if true, execute step 1318; otherwise, step 1316 is performed.

In step 1316, the UE specifically operates as follows: the terminal side judges whether the 3G or 2G network of other PLMN is available, if true, step 1314 is executed; otherwise, step 1317 is performed.

In step 1317, the UE specifically operates as follows: the terminal returns to the initial PLMN and keeps the EPS Only service available.

In step 1318, the UE side specifically operates as follows: the terminal keeps EPS data service under the initial PLMN and keeps CS domain service under the current PLMN.

That is, by the above-described procedure, at least:

the user may use 4G for EPS services and VoLTE or CS domain for voice/SMS services.

Fourteenth embodiment

Fig. 14 is a flowchart illustrating an example process according to a fourteenth embodiment of the present disclosure.

In step 1401, the UE specifically operates as follows: after the terminal is powered on or moves (cell selection or cell reselection or handover may occur) to a new tracking area, the terminal starts a cell search procedure and reads system information of a current serving cell.

In step 1402, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network, and receives the Attach Request or Tracking Area Update Request from the network side.

In step 1403, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type. Meanwhile, whether the carried EMM cause value is #16, #17 or #18 needs to be judged, if the judgment result is true, step 1405 is executed; otherwise, step 1404 is performed.

In step 1404, the UE specifically operates as follows: and the terminal executes subsequent actions according to the corresponding flow.

In step 1405, the UE specifically operates as follows: the terminal determines whether the IMS voice service is available, that is, determines whether the current network supports VoLTE (determined by a VoPS field carried in an Attach Accept or Tracking Area Update Accept message delivered by the network, if VoPS is 1, it indicates that the network supports VoLTE, otherwise it is not supported), whether the current USIM card provides VoLTE service (determined by, but not limited to, recording a VoLTE registration state of the USIM card or a previously recorded supplementary service query result), and whether the terminal itself supports VoLTE function. If true, then step 1406 is performed, otherwise step 1410 is performed.

In step 1406, the UE specifically operates as follows: judging whether a VoLTE switch (if any) on the terminal user interface is in an open state, if so, executing a step 1407; otherwise, go to step 1410.

In step 1407, the UE specifically operates as follows: the terminal initiates an IMS registration procedure. Specifically, the terminal sends SIP REGISTER a message to the network.

In step 1408, the UE specifically operates as follows: the terminal determines whether the IMS registration is successful, i.e., whether a200 OK response message to the SIP REGISTER request message sent by the network is received. If true, go to step 1409; otherwise, go to step 1410.

In step 1409, the UE specifically operates as follows: the terminal keeps the state that both data service and voice service are available under the 4G network of the current PLMN.

In step 1410, the UE specifically operates as follows: the terminal searches for 4G networks of other available PLMNs.

In step 1411, the UE specifically operates as follows: if a 4G network is available in the available networks searched by the terminal, executing step 1412; otherwise, step 1415 is performed.

In step 1412, the UE specifically operates as follows: if the 4G networks of a plurality of PLMNs are available in the network searched by the terminal, the priority ranking can be carried out according to the signal strength, the PLMN to which the cell with the best signal belongs is selected as the current PLMN, and the joint attachment process is initiated under the 4G network of the current PLMN.

In step 1413, the UE specifically operates as follows: the terminal side checks whether an Attach Accept message from the network side is received and whether an EPS Attach result cell value is 2, if the result is true, step 1416 is executed; otherwise, step 1414 is performed.

In step 1414, the UE side specifically operates as follows: the terminal side judges whether other PLMNs are available, if true, step 1412 is executed; otherwise, step 1415 is performed.

In step 1415, the UE specifically operates as follows: the terminal attempts to search for the 3G/2G network of the current PLMN.

In step 1416, the UE specifically operates as follows: and the terminal keeps both the EPS service and the Non-EPS service available under the current PLMN.

That is, by the above-described procedure, at least:

the user may use 4G for EPS services and CSFB for voice/SMS services (SMS of SGS).

Fifteenth embodiment

Fig. 15 is a flowchart illustrating an example process according to a fifteenth embodiment of the present disclosure.

In step 1501, the UE specifically operates as follows: after the terminal is powered on or moves (cell selection or cell reselection or handover may occur) to a new tracking area, the terminal starts a cell search procedure and reads system information of a current serving cell.

In step 1502, the UE specifically operates as follows: the terminal initiates an RRC connection establishment process at the current LTE cell terminal, and after the RRC connection establishment is successful, the terminal sends an Attach Request (Attach Request) with an EPS Attach type of combined EPS/IMSI Attach or a Tracking Area Update Request (TAU Request) with an EPS Update type of combined TA/LA Update with IMSI Attach to the network, and receives the Attach Request or Tracking Area Update Request from the network side.

In step 1503, the UE specifically operates as follows: judging whether the value of the EPS Attach result cell in the received Attach Accept message is 1 (i.e. EPS Only) or whether the value of the EPS Update result cell in the received Tracking Area Update Accept message is 0 (i.e. TA updated, it is required to ensure that the value of the EPS Attach result cell in the last received Attach Accept message is 2(Combined EPS/IMSI Attach) or the value of the EPS Update result cell in the last received Tracking Area Update Accept message is 1(Combined TA/LA updated)), and when the above-mentioned judging condition is true, the terminal considers that the result of the Attach (or TAU) is of EPS Only type. Meanwhile, it is necessary to determine whether the EMM cause value carried is #16, #17 or #18, if the determination result is true, step 1505 is executed; otherwise, step 1504 is performed.

In step 1504, the UE specifically operates as follows: and the terminal executes subsequent actions according to the corresponding flow.

In step 1505, the UE side specifically operates as follows: the terminal determines whether the IMS voice service is available, that is, determines whether the current network supports VoLTE (determined by a VoPS field carried in an Attach Accept or Tracking Area Update Accept message delivered by the network, if VoPS is 1, it indicates that the network supports VoLTE, otherwise it is not supported), whether the current USIM card provides VoLTE service (determined by, but not limited to, recording a VoLTE registration state of the USIM card or a previously recorded supplementary service query result), and whether the terminal itself supports VoLTE function. If true, step 1507 is performed, otherwise step 1510 is performed.

In step 1506, the UE specifically operates as follows: judging whether a VoLTE switch (if any) on the terminal user interface is in an open state, and if so, executing a step 1507; otherwise, step 1510 is performed.

In step 1507, the UE specifically operates as follows: the terminal initiates an IMS registration procedure. Specifically, the terminal sends SIP REGISTER a message to the network.

In step 1508, the UE specifically operates as follows: the terminal determines whether the IMS registration is successful, i.e., whether a200 OK response message to the SIP REGISTER request message sent by the network is received. If true, go to step 1509; otherwise, step 1510 is performed.

In step 1509, the UE specifically operates as follows: the terminal keeps the state that both data service and voice service are available under the 4G network of the current PLMN.

In step 1510, the UE specifically operates as follows: the terminal searches for 3G or 2G networks of other available PLMNs.

In step 1511, the UE specifically operates as follows: if 3G/2G networks are available (if 3G/2G networks of multiple PLMNs are available, the networks may be prioritized according to signal strength), in the available networks searched by the terminal, execute step 1512; otherwise, step 1515 is performed.

In step 1512, the UE specifically operates as follows: the terminal initiates an IMSI attachment process under the 3G/2G network of the current PLMN, namely the terminal initiates an RRC (or RR) connection establishment process to the network and sends a Location Updating Request message to the network side.

In step 1513, the UE specifically operates as follows: whether the terminal side receives Location Updating Accept message from the network side, if true, execute step 1514; otherwise, step 1516 is performed.

In step 1514, the UE side specifically operates as follows: the terminal side judges whether the 3G or 2G network of other PLMN is available, if true, step 1512 is executed; otherwise, step 1515 is performed.

In step 1515, the UE specifically operates as follows: the terminal returns to the initial PLMN and keeps the EPS Only service available.

In step 1516, the UE specifically operates as follows: the terminal keeps EPS data service under the initial PLMN and keeps CS domain service under the current PLMN. That is, by the above-described procedure, at least:

the user may use 4G for EPS services and CS domain for voice/SMS services.

With the ninth to fifteenth embodiments described above, at least the following advantageous effects can be achieved:

always on and call/SMS (short message service) with VoLTE HD voice over priority: the call (VoLTE first) and SMS services will always be available and important calls or SMS will not be lost. The user can initiate/receive a call (or send/receive an SMS) at any time.

For the tenth to thirteenth embodiments, IMS supports calls and SMS even if the VoLTE option switch is off. A user may always use a high definition Voice (HD Voice: VoLTE) call.

For the tenth, twelfth and fourteenth embodiments, calls and SMS supported by CSFB. The user can always use call and SMS services (SMS of SG) supported by the CSFB.

For the eleventh, thirteenth and fifteenth embodiments, calls and SMS supported by the CS domain. The user may always use the call and SMS services supported by the CS domain.

-4G EPS service priority: if 4G cells are available, 4G will be used. The user can enjoy the high data rate of the 4G network. The user experience will be greatly improved.

-fast registration: if the EPS Only PLMN list is used, the UE may in some cases skip registration to PLMNs where call/SMS is not available and immediately search for other available PLMNs to register. The user can quickly obtain the call/SMS service.

Referring to fig. 16, the UE (1600) includes a transceiver (1601), a processor (1602), and a memory (1603). The transceiver (1601), processor (1602), and memory (1603) are configured to perform the operations of the UE shown in the figures (e.g., fig. 1-15) or described above.

Through the operation of the UE shown in fig. 16, in the LTE network of EPS Only, not Only the PS domain service can be normally used, but also the CS domain or the voice service can be carried through the VoLTE mode.

"user equipment" or "UE" herein may refer to any terminal having wireless communication capabilities, including but not limited to mobile telephones, cellular telephones, smart phones, or Personal Digital Assistants (PDAs), portable computers, image capture devices such as digital cameras, gaming devices, music storage and playback appliances, and any portable unit or terminal having wireless communication capabilities, or internet appliances permitting wireless internet access and browsing, among others.

The term "base station" (BS) or "network device" as used herein may refer to an eNB, eNodeB, NodeB or Base Transceiver Station (BTS) or gNB, etc., depending on the technology and terminology used.

The "memory" herein may be of any type suitable to the technical environment herein, and may be implemented using any suitable data storage technology, including, without limitation, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

The "processor" herein may be of any type suitable to the technical environment herein, including without limitation one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors, DSPs, and processors based on a multi-core processor architecture.

The above description is only exemplary of the present disclosure and should not be taken as limiting the disclosure, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.

One skilled in the art will appreciate that the present disclosure includes apparatus related to performing one or more of the operations described in the present disclosure. These devices may be specially designed and manufactured for the required purposes, or they may comprise known devices in general-purpose computers. These devices have stored therein computer programs that are selectively activated or reconfigured. Such a computer program may be stored in a device (e.g., computer) readable medium, including, but not limited to, any type of disk including floppy disks, hard disks, optical disks, CD-ROMs, and magnetic-optical disks, ROMs (Read-Only memories), RAMs (Random Access memories), EPROMs (Erasable Programmable Read-Only memories), EEPROMs (Electrically Erasable Programmable Read-Only memories), flash memories, magnetic cards, or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a bus. That is, a readable medium includes any medium that stores or transmits information in a form readable by a device (e.g., a computer).

It will be understood by those within the art that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by computer program instructions. Those skilled in the art will appreciate that the computer program instructions may be implemented by a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, implement the aspects specified in the block or blocks of the block diagrams and/or flowchart illustrations of the present disclosure.

Those of skill in the art will appreciate that the various operations, methods, steps in the processes, acts, or solutions discussed in the present disclosure may be interchanged, modified, combined, or eliminated. Further, other steps, measures, schemes in various operations, methods, flows that have been discussed in this disclosure may also be alternated, altered, rearranged, broken down, combined, or deleted. Further, steps, measures, schemes in the prior art having various operations, methods, procedures disclosed in the present disclosure may also be alternated, modified, rearranged, decomposed, combined, or deleted.

The foregoing is only a partial embodiment of the present disclosure, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present disclosure, and these modifications and decorations should also be regarded as the protection scope of the present disclosure.

Claims

1. A method of communication for a User Equipment (UE), the method comprising:

judging whether the UE is provided with the service of the evolution-only packet system by the current network;

if the UE is judged to be provided with the service of the evolution packet system only by the current network, searching other networks different from the current network; and

and initiating a registration process in the searched other networks.

2. The method of claim 1, determining whether the UE is being provided evolved packet system only services by a current network, comprising:

receiving a registration message or a system message from a current network; and

and judging whether the UE is provided with the service of the evolution packet system only by the current network according to the registration message or the system message.

3. The method of claim 2, wherein the first and second light sources are selected from the group consisting of,

wherein the registration message comprises one of:

an attach accept message; and

a tracking area update accept message that is sent to the tracking area,

and wherein the UE is judged to be provided with the evolved packet system-only service by the current network when one of the following conditions is satisfied:

the value of an (evolved packet system) EPS attachment result cell in the received attachment acceptance message is 1;

the EPS update result cell value in the received tracking area update accept message is 0 and the EPS attach result cell value in the last previously received attach accept message is 2; and

the EPS update result information element value in the received tracking area update accept message is 0 and the EPS update result information element value in the last previously received tracking area update accept message is 1.

4. The method of claim 2, further comprising:

and when judging that the UE is not provided with the evolution packet system only service according to the system information, initiating a registration process in the current network.

5. The method of claim 2, determining whether the UE is being provided with an evolved packet system only service by a current network based on the system message, comprising:

based on a Public Land Mobile Network (PLMN) list carried in the system message, it is determined whether the UE is being provided with an evolved packet system-only service by the current network.

6. The method of claim 5, determining whether the UE is served by the current network only for the evolved packet system based on the PLMN list carried in the system message, comprising:

when the first PLMN ID of the PLMN list carried in the system message is inconsistent with the home PLMN ID corresponding to the International Mobile Subscriber Identity (IMSI), judging whether the first PLMN ID of the PLMN list carried in the system message is contained in a stored network list for providing the evolved packet-only system service;

and if the network list is included in the stored network list for providing the evolved packet system-only service, determining that the UE is provided with the evolved packet system-only service.

7. The method of claim 6, further comprising:

and when the first PLMNID of the PLMN list carried in the system message is consistent with the home PLMN ID corresponding to the IMSI, initiating a registration process in the current network.

8. The method of claim 4 or 7, further comprising:

if a registration message indicating the provision of the evolved packet system-only service is received, a PLMN ID of a current network is updated into a stored list of networks providing the evolved packet system-only service.

9. The method of claim 1, wherein initiating registration procedures in the searched other networks comprises:

initiating a registration procedure with the type of IMSI attachment or a registration procedure with the type of joint attachment.

10. The method of claim 9, wherein,

if the registration process of the type of IMSI attachment is successful, the UE provides packet switching service by the current network and provides circuit switching service by the searched other networks; and

if the registration procedure of the type of the joint attachment is successful, the UE provides both the packet switched service and the circuit switched service by the searched other network.

11. The method of claim 10, wherein,

the other network providing the search for circuit switched services comprises one of a Universal Mobile Telecommunications System (UMTS) or a global system for mobile communications (GSM) network; and

the other networks that provide for the search for both packet switched services and circuit switched services include one of a Long Term Evolution (LTE), UMTS or GSM network.

12. The method of claim 1, wherein the current network is a network other than a home network of the UE.

13. The method of claim 1, wherein initiating registration procedures in the searched other networks comprises:

determining other networks for initiating registration based on Public Land Mobile Networks (PLMNs) corresponding to the other searched networks among the other searched networks; and

and initiating a registration process aiming at the determined other networks.

14. The method of claim 13, determining, among the searched other networks, the other network that initiates registration based on a PLMN corresponding to the searched other network, comprising:

judging whether the PLMN ID in the PLMN list carried in the searched system messages of other networks is contained in a stored network list for providing the service of the evolution packet system only;

if not included in the stored list of networks providing the evolved packet system-only service, then a determination is made to initiate a registration for the other searched networks.

15. The method of claim 1, wherein initiating registration procedures in the searched other networks comprises:

sorting the other searched networks according to the signal strength of the received broadcast channel or pilot channel; and

and initiating a registration process in the searched other networks according to the sorted sequence.

16. The method of claim 1, further comprising:

checking whether a current USIM of the UE is a USIM which can only sign up for being provided with only an evolved packet system service before searching other networks different from the current network; and

searching for other networks different from the current network if the current USIM is not a USIM that can only sign up for evolved packet System-only services.

17. A method of communication for a User Equipment (UE), the method comprising:

receiving a registration message from a current network;

if it is determined that the UE is provided with an evolved packet system only service by a current network based on the received registration message and the current network supports packet switched session IP multimedia subsystem voice, initiating an initial IMS registration process to the current network based on a high definition voice over LTE (VoLTE) switch state of the UE or a VoLTE service state of the UE.

18. The method of claim 17, wherein initiating a registration procedure with the network based on a VoLTE switch state of a UE or a VoLTE traffic state of a UE comprises:

and if the VoLTE switch state of the UE is the opening state, initiating an IMS initial registration process to the current network.

19. The method of claim 17, wherein initiating a registration procedure with the network based on a VoLTE switch state of a UE or a VoLTE traffic state of a UE comprises:

if the VoLTE switch state of the UE is the closing state, the UE judges whether the VoLTE service is opened or not; and

and if the VoLTE service of the UE is opened, prompting to open a VoLTE switch, and initiating an IMS initial registration process to the current network after detecting that the VoLTE switch is opened.

20. The method according to any one of claims 17 to 19, wherein if IMS initial registration is successful, the UE performs voice services in VoLTE mode.

21. The method according to any one of claims 17 to 19, further comprising, when one of the following conditions is satisfied, searching for another network different from the current network; and initiating a registration process in the searched other networks:

the current network or the searched network does not support the voice of the IP multimedia subsystem of the packet switching session;

the UE does not support VoLTE function;

the VoLTE switch of the UE is not detected to be changed from the closed state to the open state;

the VoLTE service of the UE fails to be opened; and

and the UE detects that the user selects not to open the VoLTE service.

22. The method of claim 21, wherein initiating a registration procedure in the searched network comprises:

23. A method of communication for a User Equipment (UE), the method comprising:

constructing a System Information Block (SIB)24 if the SIB24 and/or scheduling information of the SIB24 is not contained in the system message of the current network; and

a reselection procedure to a new air interface (NR) independent networking (SA) cell is performed based on the constructed SIB 24.

24. The method of claim 23, wherein prior to performing the reselection procedure to the NR SA cell based on the constructed SIB24, further comprising:

judging whether a Radio Resource Control (RRC) connection release message contains a redirection message to the NR SA cell;

performing a redirection procedure to the NR SA cell if the redirection message to the NR SA cell is included;

if no redirection message to the NR SA cell is included, a reselection procedure to the NR SA cell is performed based on the constructed SIB 24.

25. The method of claim 23 or 24, wherein constructing the SIB24 comprises:

obtaining NR SA cell information based on at least one of: an NR SA cell where the UE resides, or an NR SA system neighbor cell carried in measurement control sent by a network when the UE is in a connected state, or NR SA cell information provided by a server; and

the SIB24 is constructed based on the acquired NR SA cell information.

26. A User Equipment (UE), comprising:

a transceiver to receive a signal from a base station and to transmit a signal to the base station;

a memory storing executable instructions; and

a processor executing stored instructions to perform the method of any one of claims 1 to 25.

27. A computer-readable storage medium, characterized in that a computer program is stored thereon, which computer program, when being executed by a processor, carries out the method of any one of claims 1 to 25.