Communication method and apparatus

Abstract

The application provides a communication method and device. A terminal sends a tracking area update request message in a first network. When the terminal does not receive a tracking area update acceptance message in the first network, the terminal returns to a second network from the first network. The terminal sends a registration request message in the second network. The registration request message carries a first message. The registration request message is used to initiate a mobility registration update. The first message indicates that the tracking area update of the terminal in the first network is not completed. Therefore, when the terminal does not receive the tracking area update acceptance message in the first network, the terminal carries the first message in the registration request message during the mobility registration update in the second network, so as to inform the network that the tracking area update of the terminal in the first network is not completed. The network is based on this condition to lay a foundation for response, and reduce the possibility that the terminal cannot implement services in the second network.

Description

Communication method and device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on February 29, 2024, with application number 2024102294658 and invention name “Communication Method and Device”, the entire contents of which are incorporated by reference into this application. Technical Field

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

[0003] In the field of mobile communications, terminals implement services such as calls and short messages by interacting with mobile communication networks.

[0004] At present, in some cases, the terminal's services based on the mobile communication network may not be realized. For example, after the terminal returns to the 5G network from the 4G network, other terminals initiate calls to the terminal, but cannot establish call services with the terminal.

[0005] Summary of the Invention

[0006] The present application provides a communication method and apparatus, the purpose of which is to solve the problem that a terminal cannot realize services based on a mobile communication network.

[0007] In order to achieve the above objectives, this application provides the following technical solutions:

[0008] The first aspect of the present application provides a communication method, including: a terminal sends a tracking area update request message in a first network, and if the first network does not receive a tracking area update accept message, the terminal returns from the first network to a second network, and the terminal sends a registration request message in the second network, the registration request message carries a first message, the registration request message is used to initiate a mobility registration update, and the first message indicates that the tracking area update of the terminal in the first network is not completed. It can be seen that when the terminal does not receive the tracking area update accept message in the first network, during the process of performing mobility update registration in the second network, the registration request message carries the first message to inform the network that the tracking area update of the terminal in the first network is not completed, laying the foundation for the network to respond based on this situation (such as obtaining terminal information from the first network, etc.), and can reduce the possibility that the terminal cannot realize services in the second network because the network cannot find the terminal information (such as context information).

[0009] In some implementations, before the terminal sends a tracking area update request message on the first network, it also includes: in response to the operation of closing the second network on the terminal, the terminal returns from the second network to the first network. Accordingly, the terminal returns from the first network to the second network, including: in response to the operation of opening the second network on the terminal, the terminal returns from the first network to the second network. For example, the user closes the 5G network on the terminal, and the terminal returns from the 5G network to the 4G network. The user opens the 5G network on the terminal, and the terminal returns from the 4G network to the 5G network. It can be seen that the operation on the terminal can trigger changes in the terminal's access network. In some cases, such as the user quickly opens the 5G network after closing the 5G network on the terminal, it may cause the terminal to be unable to be called or receive short messages on the 5G network. The communication method provided in this application is applicable to this scenario and is conducive to reducing the possibility of the terminal being unable to be called or receive short messages on the 5G network in this scenario.

[0010] In some implementations, the first message includes a tracking area update request message or a notification message, where the notification message indicates that the terminal has not received a tracking area update accept message on the first network, thereby facilitating the second network to obtain the terminal's information from the first network based on the tracking area update request message. The first message being a tracking area update request message is compatible with existing communication protocols, reducing network modification costs. The first message being a notification message facilitates more flexible network responses, such as enabling the second network to obtain the terminal's information from the first network or directly triggering initial registration of the terminal.

[0011] In some implementations, before the second network sends the registration request message, the method further includes: the terminal determining that a tracking area update message has been sent in the first network, so as to more accurately determine that the terminal has not completed tracking of the tracking area in the first network.

[0012] In some implementations, before the second network sends the registration request message, the method further includes: the terminal determining that no tracking area update accept message is received in the first network, so as to more accurately determine that the terminal has not completed tracking of the tracking area in the first network.

[0013] In some implementations, after the terminal sends a registration request message to the second network, the method further includes: the terminal receives a registration rejection message, and the terminal initiates initial registration on the second network. The initial registration enables the network to obtain information about the terminal, which is conducive to increasing the possibility of the terminal providing services on the second network.

[0014] In some implementations, the registration request message further carries a first field, which indicates that the type of the registration request message is mobility registration update. This approach is compatible with existing communication protocols and helps reduce terminal and network modification costs.

[0015] A second aspect of the present application provides a communication method, including: a terminal sending a tracking area update request message on a first network, and if the first network does not receive a tracking area update accept message, the terminal returns from the first network to a second network, and the terminal initiates an initial registration on the second network. Unlike the prior art, the terminal sends a tracking area update request message on the first network, and if the first network does not receive a tracking area update accept message, after returning to the second network, no mobility registration update is initiated, but an initial registration is initiated, so that the network can obtain the terminal's information, thereby increasing the possibility of successful service of the terminal on the second network.

[0016] In some implementations, before the terminal sends the tracking area update request message on the first network, it also includes: in response to the operation of closing the second network at the terminal, the terminal returns from the second network to the first network, and the terminal returns from the first network to the second network, including: in response to the operation of opening the second network at the terminal, the terminal returns from the first network to the second network.

[0017] In some implementations, before the terminal initiates initial registration on the second network, the terminal further includes: determining that a tracking area update has not been completed on the first network. Because initial registration at least results in significant network changes, determining that a tracking area update has not been completed on the first network helps ensure that the initial registration is performed when necessary, thereby reducing unnecessary network changes.

[0018] In some implementations, determining that the tracking area update is not completed on the first network includes determining that a tracking area update request message has been sent on the first network and no tracking area update accept message has been received. Determining that the tracking area update is not completed based on the messages sent and received during the tracking area update process can provide a more accurate determination result.

[0019] A third aspect of the present application provides a communication method, comprising: a core network device of a second network receiving a registration request message sent by a terminal, the registration request message carrying a notification message, the notification message indicating that a tracking area update of the terminal on a first network has not been completed, and the registration request message being used to initiate a mobility registration update on the second network. Because the registration request message for initiating the mobility registration update carries the notification message, the second network is able to learn that the tracking area update of the terminal on the first network has not been completed, thereby laying a foundation for the second network to respond to improve the terminal's successful implementation of services on the second network.

[0020] In some implementations, after receiving the registration request message sent by the terminal, the method further includes: the core network device of the second network obtains the routing information of the terminal from the core network device of the first network to increase the possibility of the terminal successfully implementing services based on the second network.

[0021] In some implementations, after receiving the registration request message sent by the terminal, the method further includes: the core network device of the second network sending a registration rejection message to the terminal, where the registration rejection message triggers the terminal to initiate initial registration with the core network device of the second network. The initial registration increases the likelihood that the terminal will successfully access services on the second network.

[0022] The fourth aspect of the present application provides a terminal, including: a processor, the processor including a baseband processor, and the baseband processor is used to implement the communication method provided by the first aspect or the second aspect of the present application.

[0023] In some implementations, the processor further includes an application processor, the baseband processor is further configured to implement a communication function based on the first network or the second network, and the application processor is configured to send a message to the baseband processor to close or open the second network.

[0024] The fifth aspect of the present application provides a chip, including: a modem, used to implement the communication method provided in the first aspect or the second aspect of the present application.

[0025] The sixth aspect of the present application provides a network device, comprising: a memory and a processor, the memory being used to store a computer program, and the processor being used to run the computer program to implement the communication method of the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is an example diagram of a scenario where a mobile phone implements services based on a 5G network or a 4G network;

[0027] Figure 2 is a flow chart showing how a mobile phone completes registration on a 5G network after returning from a 4G network to a 5G network;

[0028] Figure 3 is another flow chart showing how a mobile phone completes registration on a 5G network after returning from a 4G network to a 5G network;

[0029] FIG4 is a diagram illustrating an exemplary structure of a terminal disclosed in an embodiment of the present application;

[0030] FIG5 is a flow chart of a communication method disclosed in an embodiment of the present application;

[0031] FIG6 is a flow chart of another communication method disclosed in an embodiment of the present application;

[0032] FIG7 is a flowchart of another communication method disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "a kind of", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context. It should also be understood that in the embodiments of the present application, "one or more" refers to one, two or more; "and / or" describes the association relationship of associated objects, indicating that three relationships may exist; for example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship.

[0034] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0035] The "multiple" involved in the embodiments of the present application means greater than or equal to two. It should be noted that in the description of the embodiments of the present application, the words "first" and "second" are only used for the purpose of distinguishing the description and cannot be understood as indicating or implying relative importance or order.

[0036] With the development of mobile communications, most terminals support multiple communication standards. Taking Figure 1 as an example, a mobile phone can implement services based on a 5G network or a 4G network.

[0037] During the research process, the inventors found that when the terminal returns from the 4G network to the 5G network, the terminal may experience problems such as long-term inability to receive calls or short messages, while the possibility of abnormal calling and sending short message services is low.

[0038] Assuming the second terminal returns to the 5G network from the 4G network, the call failure can be understood as: the first terminal initiates a call to the second terminal, but the first and second terminals cannot establish a call. The failure to receive a short message can be understood as: the first terminal sends a short message to the second terminal, but the second terminal cannot receive the short message.

[0039] The following will combine the processes shown in Figures 2 and 3 to analyze the reasons why the terminal cannot be called or receive short messages for a long time. In Figures 2 and 3, the terminal is taken as a mobile phone as an example. LTE represents the wireless access device of the 4G network, NR represents the wireless access device of the 5G network, and the core networks of the 4G network and the 5G network are collectively referred to as the core network.

[0040] Figure 2 shows an example of the process for completing registration after a mobile phone returns from a 4G network to a 5G network. The process shown in Figure 2 enables the mobile phone to receive calls and text messages normally. Figure 2 includes the following steps:

[0041] S201. The mobile phone is triggered to return from the 5G network to the 4G network.

[0042] In some implementations, the phone turns off the 5G network or the NR network, causing the phone to fall back to the 4G network from the 5G network. In other implementations, poor 5G network quality causes the phone to fall back to the 4G network from the 5G network.

[0043] The above implementation is only an example and is not intended to be limiting.

[0044] The mobile phone is triggered to return from the 5G network to the 4G network, which at least includes: the mobile phone searches for a 4G cell and resides in the 4G cell.

[0045] S202: The mobile phone and LTE complete Radio Resource Control (RRC) access.

[0046] S203: The mobile phone sends a Tracking Area Update Request message to the LTE.

[0047] That is to say, the mobile phone initiates the Tracking Area Update (TAU) process after entering the 4G cell.

[0048] S204. LTE sends a Tracking Area Update Request message to the core network.

[0049] S205. The core network sends a Tracking Area Update Accept message to the LTE.

[0050] S206. LTE sends a Tracking Area Update Accept message to the mobile phone.

[0051] It is assumed here that S207 is executed after S206.

[0052] S207. After receiving the Tracking Area Update Accept message, the mobile phone returns from the 4G network to the 5G network.

[0053] In some implementations, the phone switches from 4G to 5G when it turns on 5G or NR. In other implementations, the phone switches from 4G to 5G when the quality of the 5G network improves. The above implementations are examples only and are not intended to be limiting.

[0054] S208. The mobile phone sends a registration request (Registration Request) message to the NR. The registration request message carries a tracking area update request (TAU req) message.

[0055] Based on the existing communication protocol, in the scenarios defined by S201-S207, in this step, the mobile phone initiates a registration process for mobility and periodic registration update to the NR (that is, the registration type is mobility registration update), and, in the scenarios defined by S201-S207, the registration for mobility and periodic registration update initiated by the mobile phone can meet the following conditions: 1) the UE in single registration mode performs an inter-system change from S1 mode to N1 mode, 2) the registration process is started in 5GMM-IDLE mode, 3) the UE has received an indication from the network that it supports the N26 interface. When the above conditions are met, based on the communication protocol regulations, the registration request carries a TAU req message.

[0056] Based on the existing communication protocol, the type of the registration request message sent in this step is mobility registration updating (MRU).

[0057] S209. NR sends a registration request carrying a TAU req message to the core network.

[0058] S210. The core network sends a Registration Accept message to the NR.

[0059] S211. NR sends a Registration Accept message to the mobile phone.

[0060] At this point, the phone is in the NR idle state. Because the core network can obtain the TAU req message, it can obtain the phone's 4G network information (such as context information), so it can receive calls and short messages normally.

[0061] Figure 3 shows another example of a registration process for a mobile phone returning from a 4G network to a 5G network. This process may cause the terminal to be unable to receive calls or short messages for a long time. Figure 3 includes the following steps:

[0062] S301. In response to the user's operation of shutting down the 5G network, the mobile phone returns to the 4G network from the 5G network.

[0063] The process of a mobile phone returning from a 5G network to a 4G network at least includes: the mobile phone searches for a 4G cell and resides in the 4G cell.

[0064] S302: The mobile phone and LTE complete RRC access.

[0065] S303: The mobile phone sends a Tracking Area Update Request message to the LTE.

[0066] That is to say, the mobile phone initiates the Tracking Area Update (TAU) process after entering the 4G cell.

[0067] S304. LTE sends a Tracking Area Update Request message to the core network.

[0068] It is assumed here that the mobile phone has not yet received the Tracking Area Update Accept message and is triggered by the user to turn on the 5G network, that is, S305 is executed.

[0069] S305. The mobile phone returns to the 5G network from the 4G network in response to the user's operation of turning on the 5G network.

[0070] Returning from the 4G network to the 5G network at least includes: searching for a 5G cell and staying in the 5G cell.

[0071] S306. The mobile phone sends a registration request message to the NR.

[0072] The inventors discovered that, based on the existing communication protocol, because the mobile phone did not receive the Tracking Area Update Accept message after S304, the mobile phone may still believe that the last (most recent) registered network was a 5G network rather than a 4G network. Therefore, the mobile phone determines that the aforementioned "1) UE in single registration mode performs an inter-system change from S1 mode to N1 mode" condition is not met. Therefore, the registration request sent in S306 does not carry a TAU req message.

[0073] That is, the difference between S306 and S208 is that the registration request message for mobility and periodic registration update sent by the mobile phone to the NR does not carry the TAU req message.

[0074] S307. NR sends a Registration Request message to the core network.

[0075] It is understandable that the Registration Request message forwarded by the NR to the core network does not carry the TAU req message.

[0076] S308: The core network sends a Registration Accept message to the NR.

[0077] S309. NR sends a Registration Accept message to the mobile phone.

[0078] At this point, the mobile phone resides in NR and is in the IDLE state.

[0079] The inventors also discovered during their research that because the core network does not receive the TAU req message sent by the mobile phone on the 4G network, it cannot obtain information about the mobile phone on the 4G network (such as context information). Therefore, even if the core network sends a Registration Accept message, it may not be compatible with the TAU req message received by the 4G network. Therefore, when receiving a call to the mobile phone or sending a short message to the mobile phone, it cannot be informed to page the mobile phone on the NR (5G) network, resulting in the mobile phone being unable to receive calls or short messages.

[0080] Combining Figures 2 and 3, it can be seen that in the scenario where the mobile phone leaves the 5G network and quickly returns to the 5G network, the mobile phone may have sent a tracking area update request message in the 4G network, but has not received a tracking area acceptance message. Based on the existing protocol, after the mobile phone returns to the 5G network, it will not carry the tracking area update request message in the registration request used for mobility and periodic registration updates, so it may cause the mobile phone to be unable to be called or receive short messages.

[0081] In order to solve the above problems, based on the inventor's research on the root causes of the above problems, an embodiment of the present application discloses a communication method. The communication method is applied to a terminal.

[0082] In the embodiments provided herein, the terminal may be in various forms, such as a mobile phone, a tablet computer, a computer with wireless transceiver function, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal in industrial control, a vehicle-mounted terminal device, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, a wireless terminal in smart home, a wearable terminal device, etc. The terminal may also be sometimes referred to as a terminal device, user equipment (UE), access terminal device, vehicle-mounted terminal, industrial control terminal, UE unit, UE station, mobile station, mobile station, remote station, remote terminal device, mobile device, UE terminal device, terminal device, wireless communication device, UE agent or UE device, etc. The terminal may also be a fixed terminal or a mobile terminal.

[0083] The communication system that the terminal relies on to implement communication functions may be a second-generation (2G) communication system, a third-generation (3G) communication system, an LTE system (4G), a fifth-generation (5G) communication system, an LTE and 5G hybrid architecture, a 5G New Radio (5G NR) system, and new communication systems that will emerge in future communication developments.

[0084] This embodiment is described using 4G network and 5G network as examples, but is not intended to be limiting.

[0085] The access device communicating with the terminal may be a base station. The base station may be any device located on the network side and having wireless transceiver capabilities, including but not limited to: an evolved base station (NodeB or eNB or e-NodeB) in long term evolution (LTE), a base station (gNodeB or gNB) or a transmission receiving point (TRP) in new radio (NR), a base station in subsequent 3GPP evolutions, an access node in a Wi-Fi system, a wireless relay node, a wireless backhaul node, etc. A base station may be: a macro base station, a micro base station, a pico base station, a small cell, a relay station, or a balloon station. A base station may include one or more co-located or non-co-located transmission points (TRPs). A base station may also be a radio controller, a centralized unit (CU), and / or a distributed unit (DU) in a cloud radio access network (CRAN) scenario. A base station may communicate with a terminal or communicate with the terminal through a relay station. The terminal can communicate with multiple base stations of different technologies. For example, the terminal can communicate with a base station supporting the LTE network, and can also communicate with a base station supporting the 5G network. It can also establish dual connections with a base station supporting the LTE network and a base station supporting the 5G network.

[0086] The network device that communicates with the access device may be a core network device, and the network device includes at least a memory and a processor.

[0087] Figure 4 is an example diagram of the structure of the terminal disclosed in an embodiment of the present application, including: a processor 10, an external memory interface 20, a display screen 30, an internal memory 40, an antenna 1, an antenna 2, a mobile communication module 50, and a wireless communication module 60, etc.

[0088] It should be understood that the structure illustrated in this embodiment does not constitute a specific limitation on the terminal. In other embodiments, the terminal may include more or fewer components than shown, or some components may be combined or separated, or arranged differently. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0089] The processor 10 may include one or more processing units, including at least an application processor (AP) and a modem. The different processing units may be independent devices or integrated into one or more processors. The processing units may be comprised of at least one chip, one of which is a baseband processing chip, which includes one or more modems.

[0090] In the embodiments of the present application, an example of the AP's function is to respond to a user's operation to turn off or on the 5G network by sending a message to the modem to turn off or on the 5G network. The modem is used to implement baseband communication functions. The specific functions implemented in the embodiments of the present application will be described in detail in conjunction with the following embodiments.

[0091] The external memory interface 20 can be used to connect an external memory card, such as a Micro SD card, to expand the terminal's storage capacity. The external memory card communicates with the processor 10 via the external memory interface 20 to implement data storage. For example, files such as music and videos can be stored on the external memory card.

[0092] The internal memory 40 can be used to store computer executable program codes, which include instructions. The processor 10 executes the instructions stored in the internal memory 40 to execute various functional applications and data processing of the terminal.

[0093] The wireless communication function of the terminal can be implemented through antenna 1, antenna 2, mobile communication module 50, wireless communication module 60, modem processor and baseband processor.

[0094] Antenna 1 and Antenna 2 are used to transmit and receive electromagnetic wave signals. Each antenna in the terminal can be used to cover a single or multiple communication frequency bands. Different antennas can also be reused to improve antenna utilization. For example, antenna 1 can be reused as a diversity antenna for a wireless local area network. In other embodiments, the antennas can be used in conjunction with a tuning switch.

[0095] The mobile communication module 50 can provide solutions for wireless communications including 2G / 3G / 4G / 5G applied on the terminal. The mobile communication module 50 may include at least one filter, a switch, a power amplifier, a low noise amplifier (LNA), etc. The mobile communication module 50 can receive electromagnetic waves from the antenna 1, and filter, amplify, and process the received electromagnetic waves, and transmit them to the modulation and demodulation processor for demodulation. The mobile communication module 50 can also amplify the signal modulated by the modulation and demodulation processor, and convert it into electromagnetic waves for radiation through the antenna 1. In some embodiments, at least some of the functional modules of the mobile communication module 50 can be set in the processor 10. In some embodiments, at least some of the functional modules of the mobile communication module 50 can be set in the same device as at least some of the modules of the processor 10. In some embodiments, the terminal initiates or receives a call request through the mobile communication module 50 and the antenna 1.

[0096] FIG5 is a flow chart of a communication method disclosed in an embodiment of the present application, including the following steps:

[0097] S501. The terminal returns from the 5G network to the 4G network.

[0098] In some implementations, the user turns off the terminal's 5G network, triggering the terminal to return from the 5G network to the 4G network. An example is S5011-S5012: The user turns off the terminal's 5G network based on the terminal's interface. Based on the user's operation of turning off the terminal's 5G network, the AP in the terminal sends a message to the modem to turn off the 5G network. In response to the message, the modem searches for an LTE (i.e., 4G) cell and resides in the 4G cell (i.e., searching and residing in an LTE cell).

[0099] In other implementations, other reasons such as poor quality of the 5G network can also trigger the terminal to return from the 5G network to the 4G network, and are not limited to S5011.

[0100] S502: Modem and LTE complete RRC access.

[0101] S503: The modem sends a Tracking Area Update Request message to the LTE.

[0102] It is understandable that, based on a communication protocol, S502 needs to be executed first to execute S503, or S502 may not be executed. S502 is not a mandatory step.

[0103] S504. LTE sends a Tracking Area Update Request message to the core network.

[0104] In this embodiment, assuming that after the modem sends a Tracking Area Update Request message and has not yet received a Tracking Area Update Accept message, the user operates the terminal to open the 5G network, that is, the following steps are performed.

[0105] It is understandable that before executing S505, the core network may have already sent the Tracking Area Update Accept message but has not yet transmitted it to the terminal, or the core network may not have yet sent the Tracking Area Update Accept message. To highlight that the terminal has not received the Tracking Area Update Accept message, Figure 5 assumes that the core network has already sent the Tracking Area Update Accept message but has not yet transmitted it to the terminal.

[0106] S505. The modem returns from the 4G network to the 5G network.

[0107] In some implementations, the user turns on the 5G network of the terminal, triggering the terminal to return from the 4G network to the 5G network. An example is S5051-S5052: the user turns on the 5G network of the terminal based on the terminal interface. The AP in the terminal sends a message to the modem to turn on the 5G network based on the user's operation of turning on the 5G network of the terminal. In response to the message, the modem searches for a 5G cell and resides in the 5G cell (5G cell search and residency).

[0108] In other implementations, other reasons, such as improved quality of the 5G network, can also trigger the terminal to return from the 4G network to the 5G network, and are not limited to S5051.

[0109] S506. The modem sends a Registration Request message to the NR. The Registration Request message carries the TAU req message and the first field.

[0110] It can be understood that the Registration Request message sent in S506 is a registration request message for mobility registration updating, that is, the type of the registration request message sent in this step is mobility registration updating (MRU).

[0111] In some implementations, the first field is used to indicate that the registration type is a mobility registration update. That is, the Registration Request message carries different fields to indicate the type of registration requested, and the first field indicates that the registration type is a mobility registration update. An example of the first field is "010."

[0112] Of course, other methods can also be used to indicate the type of registration.

[0113] In some implementations, if the modem determines that a Tracking Area Update Request message has been sent, it sends a Registration Request message carrying a TAU req message to the NR.

[0114] In some other implementations, if the modem determines that it has sent a Tracking Area Update Request message and has not received a Tracking Area Update Accept message, it sends a Registration Request message carrying a TAU req message to the NR.

[0115] One specific method for determining whether a Tracking Area Update Request message has been sent is to set a flag. After sending a Tracking Area Update Request, the flag is set to 1. After receiving a TAU accept or reject message, the flag is set to 0. Therefore, the flag can be used to determine whether a Tracking Area Update Request has been sent. Another specific method is to set a state machine and set corresponding state machine states for the steps in the TAU process. For example, after sending a TAU request (Tracking Area Update Request), the state enters state A, after receiving a TAU accept message, the state enters state B, and after sending a TAU complete message, the state is set to state C. The state machine state determines whether the TAU request has been sent based on the state.

[0116] In some other implementations, the modem does not determine whether the Tracking Area Update Request message has been sent, but directly sends the Registration Request message carrying the TAU req message when the Registration Request message needs to be sent.

[0117] It can be understood that, in the process shown in Figure 3, because the condition "1) UE in single registration mode performs inter-system change from S1 mode to N1 mode" is not met, the modem should send a Registration Request message without a TAU req message. However, in this step, the modem sends a Registration Request message with a TAU req message, laying the foundation for solving the problem of not being able to make calls or receive short messages on the 5G network.

[0118] S507. NR sends a Registration Request message carrying a TAU req message to the core network.

[0119] S507 makes it possible for the 5G core network to obtain terminal information (such as context information) from the 4G core network, thereby laying the foundation for solving the problem that the terminal cannot be called or receive short messages on the 5G network.

[0120] The specific process executed by the core network will not be described here.

[0121] Based on the communication protocol, the core network may execute S508 or S510.

[0122] S508. The core network sends a Registration Accept message to the NR.

[0123] S509. NR sends a Registration Accept message to Modem.

[0124] At this point, the phone is resident on NR and is in the IDLE state. Because the core network can obtain the TAU req message, it can obtain the phone's information on the 4G network (such as context information), so it can receive calls and short messages normally.

[0125] It is understood that this assumes that, except for the condition "1) a UE in single registration mode performs an inter-system change from S1 mode to N1 mode," all other provisions of the communication protocol are met, so the terminal can normally receive incoming calls and short messages. Taking into account other provisions of the communication protocol, the communication method provided in this embodiment can increase the likelihood that the terminal can normally receive incoming calls and short messages when returning from a 4G network to a 5G network.

[0126] S510. The core network sends a Registration Reject message to the NR.

[0127] S511. NR sends a Registration Reject message to Modem.

[0128] The communication protocol and specific process by which the core network sends the Registration Reject message will not be described here in detail.

[0129] S512: The modem initiates initial registration with the network in response to the Registration Reject message.

[0130] The initial registration is different from the mobility registration update initiated in S506. Based on the communication protocol, the modem initiates the initial registration to the network in response to the Registration Reject message.

[0131] The specific process of initial registration will not be described here.

[0132] After completing the initial registration, the terminal can normally receive calls and short messages. Taking into account other faults or factors, based on the process shown in Figure 5, it is possible to increase the possibility of the terminal normally receiving calls and short messages after returning from the 4G network to the 5G network.

[0133] Based on the process shown in Figure 5, when the terminal initiates a registration request of the mobility registration update type, it carries a TAU request message, which is beneficial to increasing the possibility of the terminal being called and receiving short messages normally after completing registration on the 5G network.

[0134] Figure 6 is another communication method disclosed in an embodiment of the present application. Compared with the process shown in Figure 5, the difference is that the Registration Request message does not carry a TAU req message, but a notification message, which indicates that the TAU of the terminal in the 4G network is not completed.

[0135] In some implementations, the modem determines that a Tracking Area Update Request message has been sent, and further, may determine that no Tracking Area Update Accept message has been received, and then sends a Registration Request message carrying a notification message to the NR. For specific determination methods, see the determination method in S506. In other implementations, the modem does not determine whether a Tracking Area Update Request message has been sent, but instead directly sends a Registration Request message carrying a notification message if a Registration Request message needs to be sent. The notification message can be used as a field in a Registration Request message for a mobility update type registration.

[0136] As mentioned above, the role of the notification message is to inform the 5G network core network device in the core network that the TAU in the 4G network is not completed, and the 5G network core network device decides the subsequent steps based on the notification message. In some implementations, the 5G network core network device obtains the terminal information (including routing information such as context information) from the 4G network core network device and executes S608 to lay the foundation for the terminal to normally receive called calls and short messages in the 5G network. In other implementations, the 5G network core network device executes S610, that is, directly rejects the registration request to trigger the terminal to perform initial registration, which can also lay the foundation for the terminal to normally receive called calls and short messages in the 5G network.

[0137] The specific implementation of the steps in FIG6 can be found in FIG5 , and will not be described again here.

[0138] FIG7 is another communication method disclosed in an embodiment of the present application. Compared with the process shown in FIG5 or FIG6 , the difference is that when the terminal determines that the TAU is not completed, it initiates an initial registration to the network.

[0139] The following steps are included in Figure 7:

[0140] S701. The terminal returns from the 5G network to the 4G network.

[0141] S702: Modem and LTE complete RRC access.

[0142] S703. The modem sends a Tracking Area Update Request message to the core network via LTE.

[0143] In this embodiment, it is assumed that after the modem sends a Tracking Area Update Request message and has not received a Tracking Area Update Accept message, the terminal is triggered to return to the 5G network.

[0144] S704. The modem returns from the 4G network to the 5G network.

[0145] S705: The modem determines whether the TAU is not completed.

[0146] In some implementations, the modem determines that a Tracking Area Update Request message has been sent on the 4G network, but no Tracking Area Update Accept message has been received, and obtains a determination result that the TAU is incomplete.

[0147] In some other implementations, as described above, the modem determines whether the TAU is incomplete based on the state of the state machine.

[0148] Because the initial registration causes at least a larger change in the core network data compared to the registration for mobility and periodicity, in this step, it is necessary to determine that the TAU is not completed and then trigger the initial registration process.

[0149] It is understandable that S706 may be executed directly without executing S705 or S705 may be replaced by determining whether a Tracking Area Update Request message has been sent.

[0150] If the judgment result is yes, execute S706-S707; if the judgment result is no, execute S708-S709.

[0151] S706. The modem sends a registration request (Registration Request) message to the core network through the NR. The Registration Request message carries the second field.

[0152] The second field indicates that the registration type is initial registration. An example of the second field is "001." It is understood that using the second field to indicate initial registration is only an example and not a limitation.

[0153] S707. The core network sends a Registration Accept message to the Modem through NR.

[0154] At this point, the terminal has completed its initial registration with the network. Therefore, the 5G network core network already has the terminal information, which can increase the possibility of the terminal receiving calls and short messages normally.

[0155] It is understandable that the initial registration of the terminal on the network may not be successful. In this case, one implementation method can be seen in S510-S512, that is, the terminal can initiate the initial registration again. Another implementation method can be seen in the provisions of the communication protocol for unsuccessful initial registration, which will not be repeated here.

[0156] S708. The modem sends a Registration Request message of type MRU to the core network through the NR.

[0157] The Registration Request message sent in this step carries the TAU req message.

[0158] S709. The core network sends a Registration Accept message to the Modem through NR.

[0159] The process described in Figure 7 is that after the terminal determines that TAU ​​has failed, it initiates initial registration with the network, so that the network can create new terminal information, thereby increasing the possibility that the successfully registered terminal will not be able to be called or receive short messages for a long time.

Claims

1. A communication method, characterized in that: include: The terminal sends a tracking area update request message in the first network, and does not receive a tracking area update accept message in the first network; The terminal returns to the second network from the first network; The terminal sends a registration request message on the second network, where the registration request message carries a first message, where the registration request message is used to initiate a mobility registration update, and where the first message indicates that a tracking area update of the terminal on the first network is not completed.

2. The communication method according to claim 1, wherein: Before the terminal sends the tracking area update request message to the first network, the method further includes: In response to an operation of shutting down the second network at the terminal, the terminal returns from the second network to the first network; The terminal returning from the first network to the second network includes: In response to an operation of opening the second network at the terminal, the terminal returns from the first network to the second network.

3. The communication method according to claim 1 or 2, characterized in that: The first message includes: The tracking area update request message, or the notification message, wherein the notification message indicates that the terminal has not received a tracking area update accept message in the first network.

4. The communication method according to claim 1 or 2, characterized in that: Before the second network sends the registration request message, the method further includes: The terminal determines that the tracking area update message has been sent in the first network.

5. The communication method according to claim 4, wherein: Before the second network sends the registration request message, the method further includes: The terminal determines that no tracking area update accept message is received in the first network.

6. The communication method according to claim 1 or 2, characterized in that: After the terminal sends the registration request message on the second network, the method further includes: The terminal receives a registration rejection message; The terminal initiates initial registration on the second network.

7. The communication method according to claim 1 or 2, characterized in that: The registration request message further carries a first field, where the first field indicates that the type of the registration request message is mobility registration update.

8. A communication method, characterized in that: include: The terminal sends a tracking area update request message in the first network, and does not receive a tracking area update accept message in the first network; The terminal returns to the second network from the first network; The terminal initiates initial registration on the second network.

9. The communication method according to claim 8, wherein: Before the terminal sends the tracking area update request message to the first network, the method further includes: In response to an operation of shutting down the second network at the terminal, the terminal returns from the second network to the first network; The terminal returning from the first network to the second network includes: In response to the terminal opening the second network operation, the terminal returns from the first network to the second network.

10. The communication method according to claim 8 or 9, characterized in that: Before the terminal initiates initial registration on the second network, the method further includes: The terminal determines that tracking area update is not completed in the first network.

11. The communication method according to claim 10, wherein: The determining that the tracking area update is not completed in the first network includes: It is determined that the tracking area update request message has been sent in the first network, and the tracking area update accept message has not been received.

12. A communication method, characterized in that: include: The core network device of the second network receives a registration request message sent by the terminal, where the registration request message carries a notification message indicating that the tracking area update of the terminal in the first network is not completed, and the registration request message is used to initiate a mobility registration update in the second network.

13. The communication method according to claim 12, wherein: After the registration request message sent by the receiving terminal is received, the method further includes: The core network device of the second network obtains the routing information of the terminal from the core network device of the first network.

14. The communication method according to claim 12, wherein: After the registration request message sent by the receiving terminal is received, the method further includes: The core network device of the second network sends a registration rejection message to the terminal, where the registration rejection message triggers the terminal to initiate an initial registration with the core network device of the second network.

15. A terminal, characterized in that: include: a processor, the processor comprising a baseband processor; The baseband processor is used to implement the communication method according to any one of claims 1 to 11. The terminal according to claim 15 , wherein: The processor also includes an application processor; The baseband processor is further configured to implement a communication function based on the first network or the second network; The application processor is configured to send a message to the baseband processor for closing or opening the second network.

17. A chip, characterized in that: include: A modem, used to implement the communication method according to any one of claims 1 to 11.

18. A network device, characterized in that: include: memory and processor; The memory is used to store a computer program, and the processor is used to run the computer program to implement the communication method according to any one of claims 12 to 14.

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