CN113692063A

CN113692063A - Method and device for accessing terminal to network

Info

Publication number: CN113692063A
Application number: CN202010421420.2A
Authority: CN
Inventors: 杨晨晨; 晋英豪; 谭巍; 韩锋
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-05-18
Filing date: 2020-05-18
Publication date: 2021-11-23
Also published as: WO2021232852A1

Abstract

The embodiment of the application provides a method and a device for accessing a terminal to a network, which are used for saving air interface signaling overhead and reducing time delay of accessing the terminal to the network. And the first DU sends a first request message to the selected first CU so as to access the terminal to the first CU, if the first CU does not support the terminal access, the first DU receives a first response message from the first CU, the first response message carries auxiliary information, the auxiliary information is used for assisting the first DU to reselect the CU, and the first DU selects a second CU according to the auxiliary information so as to access the terminal to the network through the second CU.

Description

Method and device for accessing terminal to network

Technical Field

The present application relates to the field of communications technologies, and in particular, to a method and an apparatus for a terminal to access a network.

Background

Non-public networks (NPN) were introduced in the 3rd generation partnership project (3 GPP) release16 (release16, R16) standard. Unlike conventional cellular networks, NPN networks allow access only to certain users with certain rights.

The 3GPP defines two NPN deployment modes: an independent non-public network (SNPN) of an independent network, and a public network integrated NPN (INPN) of a non-independent network. For convenience of description, the independent networking NPN is denoted as SNPN, and the dependent networking NPN is denoted as PNI-NPN hereinafter.

Public network integrated NPN (PNI-NPN) is generally commonly identified by a Public Land Mobile Network (PLMN) Identity (ID) and a Closed Access Group (CAG) ID. When a terminal accesses a PNI-NPN network, a PLMN ID, that is, a selected PLMN ID, corresponding to a network selected by the terminal to access is reported in an RRC setup complete message of initial access, but a CAG ID selected by the terminal to access is not reported, so that both a DU and a CU cannot sense the CAG ID selected by the terminal to access, that is, cannot sense the PNI-NPN accessed by the terminal, when an access network device is a Central Unit (CU) and Distributed Unit (DU) separated architecture.

DU sharing can be supported under the CU-DU separation architecture: one DU connects one physical CU, and one physical CU can be logically divided into a plurality of logical CUs, where one DU corresponds to one physical cell and each logical CU corresponds to one logical cell, so that the same physical cell can correspond to a plurality of logical cells, that is, a plurality of logical CUs share one DU.

In a plurality of logical cells corresponding to the same physical cell, different logical cells may configure different networks, but these different networks may configure the same PLMN ID. One problem that this leads to is: although the PLMN ID of the logical cell to which the DU is accessed by the terminal is identical to the PLMN ID selectively accessed by the terminal, the network to which the DU is the logical cell to which the terminal is accessed may not support terminal access. For example, the network selected to be accessed by the terminal is a non-public network identified based on PLMN ID #1 and CAG ID #1, and the logical cell accessed by the DU is a public network identified based on PLMN ID # 1; as another example, the network that the terminal selects to access is the non-public network 1 identified based on PLMN ID #1 and CAG ID #1, and the logical cell that the DU accesses for the terminal is the non-public network 2 identified based on PLMN ID #1 and CAG ID # 2.

In this case, when an access and mobility management function (AMF) performs access control on the terminal, if it is determined that the network of the logical cell to which the DU selectively accesses does not support terminal access, the access request of the terminal is directly rejected, and then the connection between the terminal and the DU is disconnected, which causes the terminal to perform cell selection, random access, and other processes again, thereby increasing overhead of air interface signaling and network access delay of the terminal.

Disclosure of Invention

The embodiment of the application provides a method and a device for accessing a terminal to a network, which are used for saving air interface signaling overhead and reducing time delay of accessing the terminal to the network.

In a first aspect, an embodiment of the present application provides a method for a terminal to access a network, including: the first distributed unit DU sends a first request message to the selected first centralized unit CU, where the first request message is used to request a terminal to access the first CU; the first DU receives a first response message from the first CU, wherein the first response message is used for indicating the first DU to reselect the CU, and auxiliary information is carried in the first response message and is used for assisting the first DU to reselect the CU; and the first DU reselects a second CU according to the auxiliary information so as to enable the terminal to access the network through the second CU.

In the embodiment of the application, when the first CU selected by the first DU does not support the terminal access, the network side may not directly reject the terminal access, but returns the auxiliary information to assist the first DU to reselect the second CU to continue the access process through the first CU, so that the problem that the terminal needs to perform the cell selection and random access process again due to the fact that the network side directly rejects the terminal access can be avoided, air interface signaling overhead can be saved, and the time delay of the terminal accessing the network can be reduced.

Optionally, the first DU sends a second request message to the second CU, where the second request message is used to request the terminal to access the second CU.

Optionally, the auxiliary information includes one or more of the following information: a public land mobile network identity, PLMN ID; a closed access group identity, CAG ID; a Closed Access Group (CAG) list of the terminal, which is allowed to access; and the terminal can only access the indication information of the CAG cell.

By the embodiment, the first DU can be helped to determine the second CU more quickly, the probability that the first DU selects the CU incorrectly is reduced, and the time delay of the terminal accessing the network is further reduced.

Optionally, the second request message includes one or more of the following information: CU reselection information of the first DU; the CAG ID; the PLMN ID; the CAG list; and the terminal can only access the indication information of the CAG cell.

By the embodiment, the first CU can know that the first DU has executed CU reselection, the efficiency of the network for executing admission control on the terminal is improved, and the time delay of the terminal for accessing the network is further reduced.

In a second aspect, an embodiment of the present application provides a method for a terminal to access a network, including: receiving a third request message from the first CU by an access and mobile management function (AMF), wherein the third request message is used for requesting a terminal to be accessed to the AMF; the AMF judges that the first CU does not support the terminal access according to the subscription information of the terminal, and sends a third response message to the first CU, wherein the third response message is used for indicating the first DU to reselect the CU, and the third response message carries auxiliary information which is used for assisting the first DU to select the CU.

In the embodiment of the application, when the first CU selected by the first DU does not support terminal access, the AMF may not directly reject terminal access, but returns auxiliary information to assist the first DU to reselect the CU, for example, the second CU to continue the access process through the first CU, so that the problem that the terminal needs to perform cell selection and random access again due to the AMF directly rejecting terminal access can be avoided, air interface signaling overhead can be saved, and the time delay of the terminal accessing the network can be reduced.

Optionally, the third request message includes indication information for indicating whether the access network RAN is in the CU-DU split architecture; the AMF sending a third response message to the first CU, comprising: and after determining that the RAN is a CU-DU separated architecture according to the indication information, the AMF sends a third response message to the first CU.

By the embodiment, the AMF instructs the first DU to reselect the CU after determining that the RAN is in the CU-DU split architecture (i.e., the first DU has the possibility of selecting other CUs), which improves the reliability of the scheme.

Optionally, the third request message includes CU reselection information of the first DU; the AMF sending a third response message to the first CU, comprising: and after determining that the first DU has not executed CU reselection according to the CU reselection information, or the number of times of CU reselection executed by the first DU does not exceed a preset value, or unselected CUs still exist in the CUs connected with the first DU, the AMF sends a third response message to the first CU.

Through the embodiment, after determining that the first DU has not performed CU reselection, or that the number of times the first DU has performed CU reselection does not exceed a preset value, or that there is an unselected CU in the CU connected to the first DU, the AMF instructs the first DU to reselect the CU, so that the first DU is ensured to select another CU, and the reliability of the scheme is further improved.

Optionally, the third response message includes one or more of the following information: a public land mobile network identity, PLMN ID; a closed access group identity, CAG ID; a Closed Access Group (CAG) list of the terminal, which is allowed to access; and the terminal can only access the indication information of the CAG cell.

In a third aspect, an embodiment of the present application provides a method for a terminal to access a network, including: a first CU receives a first request message from a first DU, wherein the first request message is used for requesting a terminal to be accessed to the first CU; the first CU sends a third request message to the AMF, wherein the third request message is used for requesting a terminal to be accessed to the AMF; the first CU receives a third response message from the AMF, wherein the third response message is used for indicating the first DU to reselect the CU, and the third response message carries auxiliary information which is used for assisting the first DU to reselect the CU; and the first CU sends a first response message to the first DU, wherein the first response message is used for indicating the first DU to reselect the CU, and the auxiliary information is carried in the first response message.

Optionally, the third request message includes indication information for indicating whether the access network RAN is in the CU-DU split architecture.

Optionally, the third request message includes CU reselection information of the first DU.

For the beneficial effects of the embodiments in the third aspect, reference is made to the beneficial effects of the corresponding embodiments in the first aspect and the second aspect, and details are not repeated here.

In a fourth aspect, an embodiment of the present application provides a method for a terminal to access a network, including:

a second CU receives a second request message from the first DU, wherein the second request message is used for requesting the terminal to be accessed to the second CU; the second CU sends a fourth request message to an AMF, wherein the fourth request message is used for requesting the terminal to be accessed to the AMF; the second CU receiving an initial context setup request message from the AMF; and the second CU establishes the context for the terminal according to the initial context establishment request message.

Optionally, the second request message and/or the fourth request message include: CU reselection information of the first DU.

For the beneficial effects of the embodiments in the fourth aspect, reference is made to the beneficial effects of the corresponding embodiments in the first aspect and the second aspect, and details are not repeated here.

In a fifth aspect, an embodiment of the present application provides a method for a terminal to access a network, including:

the first DU determines that the selected public network converged non-public network PNI-NPN network configured on the first CU does not support the network which the terminal requests to access;

the first DU sends a sixth request message to the first CU instructing the first CU to release the context configured for the terminal, and the first DU selects a second CU and sends a seventh request message to the second CU, wherein the seventh request message requests the terminal to access the second CU.

In the embodiment of the application, when the first DU senses that the selected first CU does not support the terminal access, the first DU may not directly reject the terminal access, but notifies the first CU to release the context of the terminal to support the reselecting CU to continue accessing the terminal to the network, so that the problem that the AMF directly rejects the terminal access to cause the terminal to need to be resumed (cell selection and random access process) can be avoided, air interface signaling overhead can be saved, and the time delay of accessing the terminal to the network can be reduced.

Optionally, the sixth request message includes a cause value, where the cause value is used to indicate that the first CU needs to release the context configured for the terminal because the PNI-NPN network requested by the terminal is not supported.

By the embodiment, the reliability of the scheme can be improved.

Optionally, the cause value includes one or more of the following information: the first CU does not support a closed access group identity (CAG ID) requested by the terminal; the first CU does not support the non-public network NPN requested by the terminal; the first CU does not support a public network converged non-public network PNI-NPN requested by the terminal; the CAG ID requested by the terminal is invalid; the NPN requested by the terminal is invalid; PNI-NPN requested by the terminal is invalid.

By the embodiment, various implementation modes of the reason value are provided, and the flexibility of the scheme can be improved.

Optionally, the seventh request message includes CU reselection information of the first DU.

By the embodiment, after the subsequent AMF judges that the second CU does not support the network which the terminal requests to access, the subsequent AMF can conveniently judge whether the first DU needs to be indicated to continuously reselect the CU.

In a sixth aspect, an embodiment of the present application provides a method for a terminal to access a network, including: the second CU receives a seventh request message from the first DU, wherein the seventh request message is used for requesting the terminal to be accessed to the second CU; the second CU sends a ninth request message to an AMF, wherein the ninth request message is used for requesting the terminal to be accessed to the AMF; and the second CU receives an initial context establishment request message from the AMF, and establishes a context for the terminal according to the initial context establishment request message.

The beneficial effects of the sixth aspect are referred to the beneficial effects of the fifth aspect, and are not described in detail herein.

In a seventh aspect, an embodiment of the present application provides a method for a terminal to access a network, including: the AMF receives a ninth request message from a second CU, wherein the ninth request message is used for requesting the terminal to be accessed to the AMF; and the AMF determines that the second CU supports the terminal access, and sends an initial context establishment request message to the second CU.

Advantageous effects of the seventh aspect are described in the fifth aspect, and are not described herein.

In an eighth aspect, an embodiment of the present application provides a method for a terminal to access a network, including:

the first CU receives a sixth request message from the first DU, wherein the sixth request message is used for instructing the first CU to release the context configured for the terminal;

the first CU responds to the sixth request message, and context of the terminal is released.

The beneficial effects of the above eighth aspect are referred to the beneficial effects of the above fifth aspect, and are not described in detail herein.

In a ninth aspect, an embodiment of the present application provides a method for a terminal to access a network, including:

the first DU determines that the selected public network converged non-public network PNI-NPN network on the first CU configuration does not support the network which the terminal requests to access;

the first DU sends a fifth request message to the first CU, wherein the fifth request message is used for requesting the first CU to send an access request message to an AMF;

the first DU receives a fifth response message from the first CU, the fifth response message indicating that the terminal is to be attached to the first DU or another network configured on the first CU.

In this embodiment, when the first DU senses that the selected first CU does not support the terminal access, the first DU may not directly deny the terminal access, but instruct the CU to continue sending the request to the AMF, and the AMF may allow the terminal access as long as any one of the networks supported by the first CU or the first DU is supported by the terminal. The problem that the AMF directly rejects the terminal access to cause that the terminal needs to perform cell selection and random access again can be avoided, the air interface signaling overhead can be saved, and the time delay of the terminal access to the network can be reduced.

Optionally, the fifth request message includes indication information, where the indication information is used to indicate that although the first CU does not support the network to which the terminal requests access, the first CU still needs to send an access request message to the AMF.

By the embodiment, after the AMF judges that the first CU does not support the network to which the terminal requests to access, the terminal is accessed or is signed on line or is accessed to the first DU or other networks configured on the first CU in a third party authentication mode, so that the efficiency of accessing the terminal to the network is improved.

Optionally, the fifth request message includes CU reselection information of the first DU.

By the embodiment, the first CU can transmit the CU reselection information of the first DU to the AMF, so that after the AMF determines that the first CU does not support the network to which the terminal requests to access, the AMF determines whether the first DU needs to be instructed to reselect the CU according to the CU reselection information of the first DU, thereby further improving the reliability of the scheme.

The beneficial effects of the above ninth aspect are referred to the beneficial effects of the above fifth aspect, and are not described in detail herein.

In a tenth aspect, an embodiment of the present application provides a method for a terminal to access a network, including: the method comprises the steps that a first CU receives a fifth request message from a first DU, wherein the fifth request message is generated when the first DU determines that a public-fused non-public network PNI-NPN network configured on the first CU does not support a network which the terminal requests to access, and the fifth request message is used for requesting the first CU to send an access request message to an AMF; the first CU sends an eighth request message to the AMF, wherein the eighth request message is used for requesting the terminal to be accessed to the AMF.

The beneficial effects of the embodiments in the above tenth aspect are referred to the beneficial effects of the embodiments in the ninth aspect, and are not described herein again.

In an eleventh aspect, an embodiment of the present application provides a method for a terminal to access a network, including: the AMF receives an eighth request message from a first CU, wherein the eighth request message is used for requesting the terminal to access the AMF, and the eighth request message is generated by the first CU when a PNI-NPN network configured on the first CU does not support a network which the terminal requests to access; and the AMF judges whether the first DU or other networks configured on the first CU support the terminal access, and if so, the terminal is accessed to the other networks.

The beneficial effects of the eleventh aspect are referred to the beneficial effects of the ninth aspect, and are not described in detail herein.

In a twelfth aspect, an embodiment of the present application provides an apparatus of a radio access network, where the apparatus may be a DU or an apparatus on a DU, and the apparatus includes means for performing the method in the first aspect or any one of the possible designs of the first aspect.

Illustratively, the apparatus comprises:

a sending module, configured to send a first request message to a selected first CU, where the first request message is used to request a terminal to access the first CU;

a receiving module, configured to receive a first response message from the first CU, where the first response message is used to instruct the device to reselect a CU, and the first response message carries auxiliary information, where the auxiliary information is used to assist the device in reselecting a CU;

and the processing module is used for selecting a second CU according to the auxiliary information so as to enable the terminal to access the network through the second CU.

Optionally, the sending module is further configured to send a second request message to the second CU, where the second request message is used to request the terminal to access the second CU.

Optionally, the auxiliary information includes one or more of the following information:

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

Optionally, the second request message includes one or more of the following information:

CU reselection information for the device;

the CAG ID;

the PLMN ID;

the CAG list;

and the terminal can only access the indication information of the CAG cell.

In a thirteenth aspect, an embodiment of the present application provides an apparatus of a core network, where the apparatus may be an AMF or an apparatus on the AMF, and the apparatus includes a module configured to perform the method in any one of the possible designs of the second aspect or the second aspect.

Illustratively, the apparatus comprises:

a receiving module, configured to receive a third request message from the first CU, wherein the third request message is used to request a terminal to access the apparatus;

the processing module is used for judging that the first CU does not support the terminal access according to the subscription information of the terminal;

a sending module, configured to send a third response message to the first CU, where the third response message is used to instruct the first DU to reselect a CU, and the third response message carries auxiliary information, where the auxiliary information is used to assist the first DU to reselect a CU.

Optionally, the third request message includes indication information for indicating whether the access network RAN is in the CU-DU split architecture;

the processing module is further configured to determine whether the RAN is in a CU-DU split architecture according to the indication information;

the sending module is used for: sending a third response message to the first CU after the processing module determines that the RAN is a CU-DU split architecture.

Optionally, the third request message includes CU reselection information of the first DU;

the processing module is further configured to determine, according to the CU reselection information, whether the first DU performs CU reselection, or whether the number of CU reselection performed by the first DU does not exceed a preset value, or whether an unselected CU exists in a CU connected to the first DU;

the sending module is used for: and after the processing module determines that the first DU has not performed CU reselection, or the number of times of CU reselection performed by the first DU does not exceed a preset value, or unselected CUs still exist in the CUs connected with the first DU, sending a third response message to the first CU.

Optionally, the third response message includes one or more of the following information:

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

In a fourteenth aspect, an embodiment of the present application provides an apparatus of a radio access network, which may be a CU or an apparatus on a CU, and which includes means for performing the method in any one of the possible designs of the third aspect or the third aspect.

Illustratively, the apparatus comprises:

a receiving module, configured to receive a first request message from a first DU, where the first request message is used to request a terminal to access the apparatus;

a sending module, configured to send a third request message to an AMF, where the third request message is used to request a terminal to access the AMF;

the receiving module is further configured to receive a third response message from the AMF, where the third response message is used to indicate the first DU to reselect a CU, and the third response message carries auxiliary information, where the auxiliary information is used to assist the first DU to reselect a CU;

the sending module is further configured to send a first response message to the first DU, where the first response message is used to instruct the first DU to reselect the CU, and the first response message carries the auxiliary information.

In a fifteenth aspect, an embodiment of the present application provides an apparatus of a radio access network, which may be a CU or an apparatus on a CU, and which includes means for performing the method of any one of the possible designs of the fourth aspect or the fourth aspect.

Illustratively, the apparatus comprises:

a receiving module, configured to receive a second request message from a first DU, where the second request message is used to request the terminal to access the apparatus;

a sending module, configured to send a fourth request message to an AMF, where the fourth request message is used to request the terminal to access the AMF;

the receiving module is further configured to receive an initial context setup request message from the AMF;

and the processing module is used for establishing the context for the terminal according to the initial context establishing request message.

In a sixteenth aspect, an embodiment of the present application provides an apparatus of a radio access network, which may be a DU or an apparatus on a DU, and the apparatus includes means for performing the method in any one of the possible designs of the fifth aspect or the fifth aspect.

Illustratively, the apparatus comprises:

the processing module is used for determining that the selected public-network-fused non-public network PNI-NPN network on the first CU configuration does not support the network which the terminal requests to access;

a sending module, configured to send a sixth request message to the first CU, to instruct the first CU to release a context configured for the terminal;

the processing module is further configured to select a second CU;

the sending module is further configured to send a seventh request message to the second CU, where the seventh request message is used to request that a terminal access the second CU.

Optionally, the seventh request message includes CU reselection information of the device.

In a seventeenth aspect, an apparatus of a radio access network, which may be a CU or an apparatus on a CU, includes means for performing the method in the sixth aspect.

Illustratively, the apparatus comprises:

a receiving module, configured to receive a seventh request message from a first DU, where the seventh request message is used to request the terminal to access the apparatus;

a sending module, configured to send a ninth request message to an AMF, where the ninth request message is used to request the terminal to access the AMF;

In an eighteenth aspect, an embodiment of the present application provides an apparatus of a core network, where the apparatus may be an AMF or an apparatus on the AMF, and the apparatus includes a module configured to perform the method in the seventh aspect.

Illustratively, the apparatus comprises:

a receiving module, configured to receive a ninth request message from a second CU, wherein the ninth request message is used to request the terminal to access the apparatus;

and the sending module is used for sending an initial context establishment request message to the second CU when the second CU supports the terminal access.

In a nineteenth aspect, the present embodiments provide an apparatus of a radio access network, which may be a CU or an apparatus on a CU, and which includes means for performing the method described in the eighth aspect.

Illustratively, the apparatus comprises:

a receiving module, configured to receive a sixth request message from a first DU, where the sixth request message is used to instruct the first CU to release a context configured for the terminal;

and the processing module is used for responding to the sixth request message and releasing the context of the terminal.

In a twentieth aspect, the present application provides an apparatus of a radio access network, where the apparatus may be the first DU or an apparatus on the first DU, and the apparatus includes means for performing the method in the ninth aspect.

Illustratively, the apparatus comprises:

the processing module is used for determining that the selected public network converged non-public network PNI-NPN network configured on the first CU does not support the network which the terminal requests to access;

a sending module, configured to send a fifth request message to the first CU, where the fifth request message is used to request the first CU to send an access request message to an AMF;

a receiving module, configured to receive a fifth response message from the first CU, the fifth response message being used to instruct the terminal to access the device or another network configured on the first CU.

In a twenty-first aspect, the present embodiments provide an apparatus of a radio access network, which may be a first CU or an apparatus on a first CU, and which includes means for performing the method of any one of the possible designs of the tenth aspect or the tenth aspect.

A receiving module, configured to receive a fifth request message from a first DU, where the fifth request message is generated by the first DU when the first DU determines that a public-network-converged non-public network PNI-NPN network configured on the first CU does not support a network to which the terminal requests access, and the fifth request message is used to request the apparatus to send an access request message to an AMF;

a sending module, configured to send an eighth request message to the AMF, where the eighth request message is used to request the terminal to access the AMF.

Optionally, the fifth request message includes indication information, where the indication information is used to indicate that although the device does not support a network to which the terminal requests access, the device still needs to send a request access message to the AMF.

In a twenty-second aspect, the present embodiments provide an apparatus of a core network, where the apparatus may be an AMF or an apparatus on the AMF, and the apparatus includes means for performing the method in the eleventh aspect.

Illustratively, the apparatus comprises:

a receiving module, configured to receive an eighth request message from a first CU, wherein the eighth request message is used to request that the terminal be accessed to the apparatus, and wherein the eighth request message is generated by the first CU when a PNI-NPN network configured on the first CU does not support a network that the terminal requests to access;

and the processing module is used for judging whether the first DU or other networks configured on the first CU support terminal access, and if so, accessing the terminal to the other networks.

In a twenty-third aspect, an embodiment of the present application provides a communication apparatus, including:

at least one processor; and the number of the first and second groups,

a memory communicatively coupled to the at least one processor, a communication interface;

wherein the memory stores instructions executable by the at least one processor, and the at least one processor performs the method as described in any one of the first to eleventh aspects or any one of the optional embodiments of the first to eleventh aspects by executing the instructions stored by the memory.

In a twenty-fourth aspect, embodiments of the present application provide a computer-readable storage medium, which includes a program or instructions, which when run on a computer causes the method described in any one of the first to eleventh aspects, or any one of the optional implementations of the first to eleventh aspects, to be performed.

In a twenty-fifth aspect, embodiments of the present application provide a computer program product which, when run on a computer, causes a method as described in any one of the first to eleventh aspects, or any one of the optional implementations of the first to eleventh aspects, to be performed.

In a twenty-sixth aspect, an embodiment of the present application provides a chip, where the chip is coupled with a memory, and is configured to read and execute program instructions stored in the memory, so as to implement the method described in any one of the first aspect to the eleventh aspect, or any optional implementation manner of the first aspect to the eleventh aspect.

In a twenty-seventh aspect, an embodiment of the present application provides a communication system, including:

the apparatus of the twelfth aspect, the apparatus of the thirteenth aspect, the apparatus of the fourteenth aspect, and the apparatus of the fifteenth aspect; or,

the apparatus of the sixteenth aspect, the seventeenth aspect, the eighteen aspect, and the nineteenth aspect; or,

the apparatus of the twentieth aspect, the apparatus of the twenty-first aspect, and the apparatus of the twenty-second aspect.

For the beneficial effects of the embodiments in the eleventh to twenty-seventh aspects, reference is made to the beneficial effects of the corresponding embodiments in the first to eleventh aspects, and details are not repeated here.

Drawings

FIG. 1A is a schematic diagram of an independently networked NPN and a non-independently networked NPN;

FIG. 1B is a schematic diagram of different networks in which different logical CUs are configured;

FIG. 1C is a diagram illustrating the format of a network identification NID;

FIG. 2 is a diagram illustrating an initial access procedure when a UE accesses a PNI-NPN network;

fig. 3A is a schematic structural diagram of a possible communication system applicable to the embodiment of the present application;

FIG. 3B is a diagram illustrating the first DU is shared by physical entities;

FIG. 3C is a diagram illustrating a first DU is shared by logical entities;

fig. 4A is a flowchart of a method for a terminal to access a network according to an embodiment of the present disclosure;

fig. 4B is a flowchart of a method for a terminal to access a network according to an embodiment of the present disclosure;

fig. 5 is a flowchart of another method for a terminal to access a network according to an embodiment of the present application;

fig. 6 is a flowchart of another method for a terminal to access a network according to an embodiment of the present disclosure;

fig. 7 is a schematic structural diagram of an apparatus 700 of a radio access network according to an embodiment of the present application;

fig. 8 is a schematic structural diagram of an apparatus 800 of a core network according to an embodiment of the present application;

fig. 9 is a schematic structural diagram of an apparatus 900 of a radio access network according to an embodiment of the present application;

fig. 10 is a schematic structural diagram of an apparatus 1000 of a radio access network according to an embodiment of the present application;

fig. 11 is a schematic structural diagram of an apparatus 1100 of a radio access network according to an embodiment of the present application;

fig. 12 is a schematic structural diagram of an apparatus 1200 of a radio access network according to an embodiment of the present application;

fig. 13 is a schematic structural diagram of an apparatus 1300 of a core network according to an embodiment of the present application;

fig. 14 is a schematic structural diagram of an apparatus 1400 of a radio access network according to an embodiment of the present disclosure;

fig. 15 is a schematic structural diagram of an apparatus 1500 of a radio access network according to an embodiment of the present application;

fig. 16 is a schematic structural diagram of an apparatus 1600 of a radio access network according to an embodiment of the present application;

fig. 17 is a schematic structural diagram of an apparatus 1700 of a core network according to an embodiment of the present application;

fig. 18 is a schematic structural diagram of a communication device 1800 according to an embodiment of the present application.

Detailed Description

Fig. 1A is a schematic diagram of independent networking NPN and non-independent networking NPN provided in an embodiment of the present application.

As shown in fig. 1A, in the NPN, the SNPN and the PLMN have independent core networks, and the SNPN may have an independent Radio Access Network (RAN) or share the RAN with the PLMN. In the independent networking NPN, an SNPN network is identified by a PLMN ID and a Network Identifier (NID), where a Mobile Country Code (MCC) part of the PLMN ID is a specific value or a PLMN ID of a mobile operator deploying the SNPN; the NID may be derived from a global uniform distribution or a local distribution. A cell of a next generation radio access network (NG-RAN) node of SNPN may broadcast one or more of the following parameters: one or more PLMN IDs and a NID list corresponding to each PLMN ID, a user-readable network name (HRMN) for supporting manual network selection of a user and an indication for prohibiting access of other terminals which do not support SNPN.

As shown in fig. 1A, in a non-independent network configuration NPN, the NPN and the PLMN share a core network and/or an access network, and the NPN is deployed depending on the PLMN, and the PNI-NPN network can be identified by a PLMN ID. The NPN may be a specific slice in the PLMN, the terminal possesses subscription data of the PLMN, and the NPN may be deployed only within the range of certain Tracking Areas (TAs) according to the mobile operator's agreement with the NPN facilitator. When the terminal moves out of the range, the network may indicate that the terminal cannot continue to use the current slice resources in the new registration area.

In order to prevent unauthorized terminals from accessing PNI-NPN cells, 3GPP proposes a Closed Access Group (CAG) concept, where a CAG represents a group of users that can access a certain CAG cell (PNI-NPN cell). It may be represented by a CAG ID, unique within a PLMN. In the non-independent networking NPN, the PNI-NPN network may be deployed under the support of a public network, and a cell of the PNI-NPN network is to broadcast not only a cell identifier but also a closed access group identifier (CAG ID), where the CAG ID is used to identify a group of users allowed to access one or more cells associated with the CAG, so as to prevent a terminal that is not allowed to access the PNI-NPN network through the cell associated with the CAG from automatically selecting and accessing the cell. One PNI-NPN cell may broadcast one or more CAG identities; the HRNN corresponding to the CAG identity may also be broadcast for manual selection by the user. For convenience of description, in the embodiments of the present application, both the PLMN ID and the CAG ID are regarded as network identification information of the PNI-NPN network.

In fig. 1A, four User Equipments (UEs) respectively supporting different network types are shown, namely, UE1, UE2, UE3, and UE 4. The UE1 supports both public network PLMN A and non-public network CAG X deployed based on the public network PLMN A; the UE2 only supports non-public networks CAG X deployed based on public networks PLMN a; the UE3 supports only public network PLMN a; the UE4 supports only the independently deployed non-public network SNPN.

As described above, for the PNI-NPN network, the PNI-NPN cell broadcasts network identification information (e.g., PLMN ID(s) and CAG ID(s), and may further include hrnn (s)) of the PNI-NPN it supports access in system information, the terminal locally stores the network information (e.g., PLMN ID(s) and CAG ID(s), and may further include hrnn (s)) of the PNI-NPN it subscribes to, and when receiving the system information broadcast by the cell, the terminal compares the network identification information broadcast by the cell with the locally stored network information of the PNI-NPN it subscribes to, and if there is a PNI-NPN that allows access, the terminal may access the corresponding cell. The AMF may also store subscription information of the terminal (e.g., an allowed CAG List (called CAG List) of the terminal may be stored), and the AMF performs admission control and other processes of the user based on the stored subscription information of the terminal.

In the DU sharing scenario, one DU may connect multiple CUs. It should be understood that, here, the plurality of CUs connected by one DU are logically divided CUs, and actually, the plurality of CUs may correspond to the same physical CU (or physical CU). The dividing manner of the logic CU has various implementation manners, for example, the network configures different computation parameters (examples) for different logic CUs, the network configures different network resources for different logic CUs, or the network configures different networks for different logic CUs, and the like, which is not limited herein.

The following exemplifies that the network configures different networks for different logical CUs.

Referring to fig. 1B, the DU-connected CU includes two logical CUs, CU # a and CU # B, where CU # a and CU # B are configured with different networks.

For example, CU # a supports a public network identified by PLMN ID #1, and CU # B supports PNI-NPN #1 identified by PLMN ID #1 and CAG ID # 1. For example, CU # B supports PNI-NPN #1 identified by PLMN ID #1 and CAG ID # 1; CU # B supports PNI-NPN #2 identified by PLMN ID #1 and CAG ID # 2. For example, CU # a supports a public network identified by PLMN ID #1, CU # B supports a PNI-NPN #3 identified by PLMN ID #2 and CAG ID # 1. For example, CU # B supports PNI-NPN #1 identified by PLMN ID #1 and CAG ID # 1; CU # B supports PNI-NPN #4 identified by PLMN ID #2 and CAG ID # 2. For example, CU # B supports PNI-NPN #1 identified by PLMN ID #1 and CAG ID # 1; CU # B supports PNI-NPN #3 identified by PLMN ID #2 and CAG ID # 1.

Of course, the type of network the logical CU is configured to is not limited to PNI-NPN and public networks, but may also be SNPN, for example. For a logical CU configured with SNPN, it needs to be identified with PLMN ID and NID.

For example, CU # a supports a public network identified by PLMN ID #1, and CU # B supports SNPN #1 identified by PLMN ID #1 and NID # 1. For example, CU # B supports SNPN #1 identified by PLMN ID #1 and NID # 1; CU # B supports SNPN #2 identified by PLMN ID #1 and NID # 2. For example, CU # a supports a public network identified by PLMN ID #1, and CU # B supports SNPN #3 identified by PLMN ID #2 and NID # 1. For example, CU # B supports SNPN #1 identified by PLMN ID #1 and NID # 1; CU # B supports SNPN #4 identified by PLMN ID #2 and NID # 2. For example, CU # B supports SNPN #1 identified by PLMN ID #1 and NID # 1; CU # B supports SNPN #3 identified by PLMN ID #2 and NID # 1.

In short, the public network is identified by PLMN ID, PNI-NPN is identified by PLMN ID and CAG ID together, SNPN is identified by PLMN and NID together, different types of networks certainly belong to different networks, and the networks of the same type are different networks as long as the ID values of the network identifications are not consistent.

Among them, the CAG ID is typically a 32-bit value of fixed length. The PLMN ID is composed of a Mobile Country Code (MCC) and a Mobile Network Code (MNC), i.e., the PLMN ID is MCC | | | MNC. The NID includes an assignment mode (assignment mode) and an NID value (NID value), as shown in FIG. 1C.

Further, in a DU sharing scenario, a DU may broadcast a System Information Block (SIB) 1, a physical cell corresponding to the DU may be identified by a Physical Cell Identifier (PCI) in SIB1, one physical cell may correspond to a plurality of logical cells, one logical cell corresponds to one logical CU connected to the DU, and each logical cell is identified by a cell identifier (cell identity). As shown in fig. 2, the logical CU # a and the logical CU # B connected to the DU correspond to logical cells identified by different cell identities, respectively.

3GPP R16 specifies that each logical cell only supports one of the network types of public network, PNI-NPN or SNPN, but in 3GPP R17, a shared logical cell is introduced, i.e. one logical cell can simultaneously support multiple network types of public network, PNI-NPN and SNPN.

Fig. 2 is a schematic diagram of an initial access process when a UE accesses a PNI-NPN network, as shown in fig. 2, including:

s201, the UE sends an RRC setup request (RRC setup request) message to the DU to request to access the physical cell corresponding to the DU.

S202, the DU selects one CU, e.g., CU # a, and transmits an initial Uplink (UL) RRC message to CU # a.

There are various implementations of DU selection CU, which are not limited herein. For example: DU randomly selects a CU; or, the DU selects a CU with a smaller load based on the CU load information; or, the DU selects the frequently accessed CU based on the historical access information of the CU; alternatively, the DU configures a default CU (default CU), and selects the default CU.

S203, the CU # A and the DU configure Signaling Radio Bearer (SRB) 1 resources, context of the UE on an F1 interface and the like for the UE on an F1 interface, then return a Downlink (DL) RRC information forwarding message, and notify the DU of the configured information of the SRB1 resources, the context of the UE on an F1 interface and the like.

The context of the UE on the F1 interface includes, for example, an application protocol (F1 application protocol, F1AP) ID of the gNB-DU UE F1, an ID of the gNB-CU UE F1AP, or an access indication (SUL) of the Supplemental Uplink (SUL).

It should be understood that in steps S202-S203, since the UE has not reported network information, such as PLMN ID, CAG ID, etc., of its selected access to the network, the DU and CU do not know the PLMN ID and CAG ID of the UE selected access.

S204 and DU send the configuration parameters to the UE, and enable the UE to configure the resources such as SRB1 on the terminal side.

S205, the terminal reports the selected PLMN ID, i.e. the selected PLMN ID, of the UE in an initial access RRC setup complete (RRC setup complete) message, but does not report the CAG ID of the UE.

The non-access stratum (NAS) layer information included in the RRC setup complete message may or may not carry the CAG ID, which is not limited herein. Since neither the DU nor CU analyzes the NAS layer information, neither the DU nor CU # a can perceive the CAG ID selected for access by the UE, whether or not the NAS layer information carries the CAG ID.

S206 and DU transmit the information in step S205 to CU # a.

It should be understood that DU and CU # a cannot sense the CAG ID selected for access by the UE.

S207, the CU # A sends an Initial UE message (Initial UE message) to the AMF, wherein the message carries a CAG ID list supported by a logical cell (CU # A) selected to be accessed by the UE, and the CU # A is a PLMN corresponding to a network supporting the terminal to select to be accessed.

The CAG ID list supported by the logical cell (CU # a) is a list in which one or more CAG IDs supported by CU # a are recorded. Herein, one logical cell (e.g., CU # a) supports one CAG ID list, meaning that the one logical cell (e.g., CU # a) supports each CAG ID recorded in the one CAG ID list.

S208, after receiving the Initial UE message, the AMF judges whether the CU # A supports the UE access.

Specifically, comparing the locally stored PLMN ID list allowed to be accessed by the UE with the CAG ID list supported by each PLMN ID, and the PLMN ID of the logical cell (CU # a) and the CAG ID list supported by the logical cell ID carried in the message, if there is an overlap, it is determined that the CU # a supports UE access, and step S209A is executed; otherwise, determining that CU # a does not support UE access, performing S209B.

S209A, sending an initial context setup request (initial context setup request) message to CU # a, where the specific process of granting UE access may refer to the related prior art, which is not described herein.

S209B, sending an error indication (error indication) message to CU # a, where the specific procedure of rejecting UE access may refer to related prior art, which is not described herein again.

R16 specifies that one logical cell (cell identity identifies one logical cell and one PCI identifies one physical cell in SIB 1) supports only one network type among public network, PNI-NPN and SNPN. In 3GPP R17, a shared logical cell is introduced, i.e. one logical cell can simultaneously support multiple network types in public network, PNI-NPN and SNPN. Whether R16 or R17 (or other scenarios, not limited to only R16 and R17) when controlling terminal access based on the method shown in fig. 2, the following problems may exist: if the network of the logical cell (CU # a) to which the DU has selected access does not support terminal access, the AMF will directly reject the access request of the terminal, and the connection between the terminal and the DU will be disconnected, which causes the terminal to perform cell selection, random access, and other processes again, increasing overhead of air interface signaling and delay of accessing the terminal to the network.

This is illustrated by way of example:

logical cells supported by CU # a (assuming cell identity #1 for identification): the public network identified by PLMN ID #1 is supported, and PNI-NPN #2 identified by PLMN ID #1+ CAG ID #2 is also supported; alternatively, only one of the above-mentioned public network or PNI-NPN #2 is supported.

Logical cells supported by CU # B (assuming identified by cell identity # 2): and PNI-NPN #1 identified by PLMN ID #1+ CAG ID #1 is supported.

UE (user equipment) signing: PNI-NPN #1 identified by PLMN ID #1+ CAG # 1.

If the DU selects CU # a (i.e., selects the logical cell supported by CU # a), when the AMF performs admission control on the UE, since the UE does not subscribe to the PNI-NPN #2 supported by CU # a, the AMF rejects the access request of the UE, thereby causing CU # A, DU to reject the access of the UE. If the UE continues to access the network, it needs to reselect a cell (including a physical cell) and reinitiate the random access process, which not only results in a large overhead of air interface signaling, but also results in a large access delay of the UE.

In view of this, embodiments of the present application provide a method and an apparatus for accessing a terminal to a network, where when a DU does not support terminal access for a CU selected by the terminal for access, the DU may not reject terminal access, but reselects a CU to access the terminal to the network, so as to avoid a problem that the terminal needs to perform (physical) cell selection and random access again due to direct rejection of the terminal, thereby saving air interface signaling overhead and reducing a delay of the terminal accessing the network.

The embodiments of the present application will be described in further detail with reference to fig. 3A to 17.

The embodiment of the present application may be applied to a fifth generation (5G) communication system, such as a 5G New Radio (NR), or to various future communication systems as long as the radio access network device of the communication system has a CU-DU separation architecture or an architecture equivalent to the CU-DU separation architecture function.

For example, fig. 3A is a schematic structural diagram of a possible communication system to which the embodiment of the present application is applicable. The communication system comprises a 5G core network (the 5)^thgeneration core, 5GC), Radio Access Network (RAN), and terminal.

The terminal may also be referred to as a terminal device, a User Equipment (UE), a Mobile Station (MS), a Mobile Terminal (MT), and the like, and is a device that provides voice or data connectivity to a user, and may also be an internet of things device. For example, the terminal includes a handheld device, a vehicle-mounted device, and the like having a wireless connection function. Currently, the terminal may be: mobile phone (mobile phone), tablet computer, notebook computer, palm computer, Mobile Internet Device (MID), wearable device (e.g. smart watch, smart bracelet, pedometer, etc.), vehicle-mounted device (e.g. car, bicycle, electric car, airplane, ship, train, high-speed rail, etc.), Virtual Reality (VR) device, Augmented Reality (AR) device, wireless terminal in industrial control (industrial control), smart home device (e.g. refrigerator, television, air conditioner, electric meter, etc.), smart robot, workshop device, wireless terminal in self drive (driving), wireless terminal in remote surgery (remote medical supply), wireless terminal in smart grid (smart grid), wireless terminal in transportation safety (transportation safety), wireless terminal in smart city (city), or a wireless terminal in a smart home (smart home), a flying device (e.g., a smart robot, a hot air balloon, a drone, an airplane), etc. In the embodiments of the present application, a UE or a terminal is used to describe a scheme.

The 5GC includes one or more functions or devices, such as a Session Management Function (SMF). These functions or devices may be either network elements in a hardware device, software functions running on dedicated hardware, or virtualized functions instantiated on a platform (e.g., a cloud platform). It is understood that the names of various core network devices are names in a 5G communication system, and as the communication system evolves, other names with the same function may be replaced.

The RAN may also be referred to as an access network device or a base station, and may also be referred to as a RAN node (or RAN device). Currently, some examples of access network devices are: a gbb/NR-NB, a Transmission Reception Point (TRP), an evolved Node B (eNB), a next generation evolved Node B (next generation eNodeB), a Radio Network Controller (RNC), a Node B (NB), a Base Station Controller (BSC), a Base Transceiver Station (BTS), a home base station (e.g., home evolved Node B, or home Node B, HNB), a Base Band Unit (BBU), or a wireless fidelity (Wifi) Access Point (AP), or an access network device in a future possible communication system. It may also be a 5G, e.g. NR, a gNB in the system, or a transmission point (TRP or TP), one or a group (including multiple antenna panels) of base stations in the 5G system, or it may also be a network node forming the gNB or transmission point, e.g. a baseband unit (BBU), or a DU, etc. In some deployments, the gNB may include CUs and DUs.

As shown in fig. 3A, for a NR base station gNB, the gNB may be split into two parts according to the protocol stack function: CU and DU, i.e. the protocol stack of the base station is divided, the CU and DU having protocol stacks of different parts of the base station, respectively. Generally, a Service Data Adaptation Protocol (SDAP) layer, a Radio Resource Control (RRC) layer and a Packet Data Convergence Protocol (PDCP) layer (wherein the PDCP layer includes a control plane PDCP-C layer and a user plane PDCP-U layer) are configured in a CU, and a Radio Link Control (RLC) layer (wherein the RLC layer includes a control plane RLC-C layer and a user plane RLC-U layer), a Medium Access Control (MAC) layer and a physical layer (PHY) are configured in a DU. It should be understood that the above protocol stack division is only an example and is not limited, and the embodiment of the present application does not limit the division manner of the protocol stack.

A gNB may contain one CU and multiple DUs that are connected via the F1 interface, and one CU may simultaneously connect multiple DUs and one DU connects only one CU. The CU is connected with other gNB by adopting an Xn interface, and the CU is connected with the 5GC by adopting an NG interface. In addition, in the process of concrete implementation, one DU can also connect multiple CUs (this is just implementation and not standardization) in consideration of the fault tolerance and stability of the system.

As described above, under the architecture that the radio access network device is a CU-DU separation architecture, shared DUs may be supported, one DU corresponds to one physical cell, and a plurality of logical cells may be configured in one physical cell, and accordingly, a CU may be logically divided into a plurality of logical CUs. As shown in fig. 3A, assuming that two logical cells are configured in the physical cell of the DU, a CU may be considered to be divided into two logical CUs, i.e., a first logical CU and a second logical CU. The first DU may choose to access the first logical CU, or may choose to access the second logical CU (i.e., the first logical CU and the second logical CU share the first DU), and similarly, the second DU may choose to access the first logical CU, or may choose to access the second logical CU (i.e., the first logical CU and the second logical CU share the second DU).

It should be understood that the DU sharing in this document may be sharing of a physical entity or sharing of a logical entity. In the physical shared DU scenario, a DU can only be connected to one CU at a time.

Take the first DU sharing in fig. 3A as an example, that is, the first logical CU and the second logical CU share the first DU.

Referring to fig. 3B, an example of the first DU sharing being physical entity sharing is shown. The physical entity first DU can be further split into logical entities DU # a and DU # B, both deployed within the physical entity first DU. The first logical CU and the logical DU # a in the first DU constitute RAN1, and the second logical CU and the logical DU # B in the first DU constitute RAN 2. In the scenario shown in fig. 3B, the first logical CU and the second logical CU are connected to the same physical entity DU, i.e., the first DU, but the first logical CU and the second logical CU are respectively connected to two different logical DUs in the first DU, so the first logical CU and the second logical CU share the physical resource instance of the first DU.

Referring to fig. 3C, the first DU sharing is an example of logical entity sharing. The physical entity first DU can be further split into logical entities DU # a and DU # B, both deployed within the physical entity first DU. The first logical CU and the logical DU # a in the first DU constitute RAN1, and the second logical CU and the logical DU # a in the first DU constitute RAN 2. In the scenario shown in fig. 3C, the first logical CU and the second logical CU not only connect the same physical entity DU, i.e., the first DU, but also the first logical CU and the second logical CU connect the same logical DU within the first DU, so the first logical CU and the second logical CU share the logical resource instance of the first DU (i.e., DU # a).

It should be understood that the technical solution provided in the embodiments of the present application is applicable to two deployment scenarios, namely, physical DU sharing and logical DU sharing. For convenience of description, for a deployment scenario of physical DU sharing, communication between a first logical CU and a DU # a is uniformly described as communication between the first logical CU and a first DU, and communication between a second logical CU and a DU # B is described as communication between the second logical CU and the first DU; for the deployment scenario of logical DU sharing, communication between the first logical CU and the DU # a is collectively described as communication between the first logical CU and the first DU, and communication between the second logical CU and the DU # a is described as communication between the second logical CU and the first DU. That is, the DU referred to hereinafter does not distinguish between a logical DU and a physical DU.

It should be understood that in case the radio access network device is a CU-DU separation architecture, the networks supported by the DUs intersect with the networks supported by each logical CU to which the DU is connected. The intersection of the network supported by any logical CU connected to the DU and the network supported by the DU may be identical to the network supported by the any logical CU (in this case, the network supported by the first DU may be a union of the networks supported by all logical CUs), or may be only a part of the network supported by the any logical CU, which is not limited herein.

Take the first DU in fig. 3B or fig. 3C as an example. For example, the first logical CU may support a network of {1, 2}, the second logical CU may support a network of {3, 4}, and the first DU may support a network of {1, 2, 3, 4 }. As another example, the first logical CU may support a network of {1, 2}, the second logical CU may support a network of {3, 4}, and the first DU may support a network of {1, 4, 5 }.

In the following embodiments, it is mainly taken as an example that the network supported by the first DU is a union of the networks supported by all logical CUs, that is, the first DU supports the network supported by each logical CU to which it is connected.

For convenience of description, in the following description herein, the first logical CU is simply referred to as "first CU", and the second logical CU is simply referred to as "second CU".

It should be understood that fig. 3A to 3C only illustrate a few functions or devices related to the embodiments of the present application, and more or less functions or devices may be included in the communication system architecture. For example, 5GC in fig. 3A may further include Unified Data Management (UDM), a Data Network (DN), and the like, and the DU may also be configured with more logical cells.

The communication system architecture to which the embodiment of the present application is applied is not limited to those shown in fig. 3A to 3C, and any communication system architecture that can implement the functions of each device shown in fig. 3A to 3C is applicable to the present application.

The terms "system" and "network" in the embodiments of the present application may be used interchangeably. "at least one" means one or more, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone, wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, a and b, a and c, b and c, or a and b and c.

And, unless stated to the contrary, the embodiments of the present application refer to the ordinal numbers "first", "second", etc., for distinguishing a plurality of objects, and do not limit the sequence, timing, priority, or importance of the plurality of objects. For example, the first priority criterion and the second priority criterion are only used for distinguishing different criteria, and do not represent the difference of the content, priority, importance, and the like of the two criteria.

Furthermore, the terms "comprising" and "having" in the description of the embodiments and claims of the present application and the drawings are not intended to be exclusive. For example, a process, method, system, article, or apparatus that comprises a list of steps or modules is not limited to only those steps or modules listed, but may include other steps or modules not listed.

As shown in fig. 4A, an embodiment of the present application provides a method for a terminal to access a network, which may be applied to the network architecture shown in fig. 3A, but is not limited to the network architecture shown in fig. 3A. In this embodiment, the first DU, the first CU, and the second CU cannot sense the CAG ID selected by the terminal for access, and when the PNI-NPN network configured on the first CU currently selected by the first DU does not support the network requested by the terminal for access, the AMF may instruct the first DU to reselect the CU (e.g., the second CU) to access the terminal to the network, specifically refer to S401A-S407A.

It should be understood that the first CU and the second CU in this embodiment both refer to logical CUs, for example, the first CU and the second CU are the first logical CU and the second logical CU in fig. 3A or fig. 3B or fig. 3C, respectively.

The first DU in this embodiment may refer to a logical DU or a physical DU. For example, in the physical DU sharing scenario shown in fig. 3B, the first DU in this embodiment is the first DU shown in fig. 3B, and is a physical DU, and includes a logical DU # a and a logical DU # B. For example, in the logical DU sharing scenario shown in fig. 3C, the first DU in the present embodiment is equivalent to CU # a in the first DU shown in fig. 3C, and is a single logical DU.

S401A, the first DU sends a first request message to the selected first CU, and the first CU receives the first request message from the first DU, where the first request message is used to request the terminal to access the first CU.

Wherein the first DU is communicatively coupled to the terminal. The scenario for selecting the first CU by the first DU may be a CU selection scenario executed by the first DU when the terminal initially accesses, or may be a CU selection scenario executed by the first DU when the UE performs RRC re-establishment or RRC recovery, which is not limited herein. For convenience of description, the embodiment of the present application mainly takes an initial access scenario of a terminal as an example.

It should be understood that the selected first CU here may be understood as: the first DU has selected the first CU, or the first DU and the first CU have established an F1 connection, or the first DU and the first CU have configured transmission resources for the terminal.

The first request message carries the PLMN ID of the network Selected by the terminal to access, i.e., the Selected PLMN ID. For convenience of description, the "PLMN ID of the network selected to be accessed by the terminal" may also be referred to as "PLMN ID selected to be accessed by the terminal", and the "CAG ID of the network selected to be accessed by the terminal" may also be referred to as "CAG ID selected to be accessed by the terminal".

It should be understood that the PLMN ID corresponding to the network selected for access by the terminal and the PLMN ID of the network configured by the first CU should be the same, but the network selected for access by the terminal and the network configured by the first CU are not necessarily the same. For example, the first CU is configured with a public network identified by PLMN ID #1 and the network requested to access by the terminal is PNI-NPN #1 identified by PLMN ID #1 and CAG ID #1, or the first CU is configured with a PNI-NPN #1 identified by PLMN ID #1 and CAG ID #1 and the network requested to access by the terminal is PNI-NPN #2 identified by PLMN ID #1 and CAG ID # 2.

The terminal also needs to perform cell selection and random access procedures before step S401A. Illustratively, the cell selection and random access procedure specifically includes the following steps:

1) the terminal sends an RRC setup request (RRC setup request) message to the first DU to request to access a cell under the first DU;

2) the first DU configures RLC, MAC, PHY and other logic entity resources of SRB1 for the terminal, selects the first CU, sends initial uplink RRC message (initial UL RRC message) to the first CU, and transmits configured related parameters;

3) and the first CU configures the SDAP and the PDCP layer logic entity based on the received configuration parameters, and sends the SDAP, the PDCP and the parameters to the DU.

It should be understood that when the first DU and the first CU configure the SRB1 for the UE in step 2), step 3) above, the DU and CU do not know the PLMN ID and CAG ID selected by the terminal.

4) The DU sends RRC setup (RRC setup) information to the terminal, wherein the information carries parameters such as SDAP, PDCP, RLC, MAC, PHY and the like, so that the terminal configures a response logic entity for the SRB1 on the terminal side;

5) the terminal reports the PLMN ID corresponding to the network selected to be accessed by the terminal in an RRC setup complete (RRC setup complete) message of initial access, but does not report the CAG ID selected to be accessed by the terminal.

After performing the above steps 1) to 5), the first DU transmits the first request message to the selected first CU.

In this embodiment, the first CU may be a CU first selected by the first DU, or may be a CU reselected by the first DU (i.e., a CU reselected by the first DU after the first DU fails to attempt to access the terminal to the network via other CUs).

If the first CU is a CU reselected for the first DU, the first request message may carry one or more of the following information in addition to the selected PLMN ID: 1) the CU reselection information of the first DU is used to indicate whether the first DU has already performed CU reselection, or the number of times the first DU has already performed CU reselection, or unselected CUs still exist in CUs connected to the first DU; for convenience of description, CU reselection information of the first DU is referred to herein as indication information # 4; 2) a PLMN ID, where the PLMN ID is a list of other PLMN IDs or PLMN IDs different from the selected PLMN ID; 3) CAG ID; 4) indication information (CAG-only access) whether the terminal can only access the CAG cell; 5) a list of closed access groups CAG (allowed CAG list) of terminals allowed to access.

Of course, if the first CU is the CU first selected by the first DU, the first request message may also carry the CU reselection information of the first DU, in which case the CU reselection information of the first DU is used to indicate: the first DU has not undergone CU reselection, or the number of times the first DU has performed CU reselection is 0, or there are unselected CUs among CUs connected to the first DU.

Optionally, the first request message is an uplink RRC message (UL RRC message) sent by the first DU to the first CU when the terminal device initially accesses the first CU. The UL RRC message carries the Selected PLMN ID and an RRC container (container), where the RRC container includes related information reported by the air interface UE.

S402A, the first CU sends a third request message to the AMF, and the AMF receives the third request message from the first CU, wherein the third request message is for requesting the terminal to access the AMF.

The third request message carries the PLMN ID and CAG ID list supported by the first CU, so that the AMF in the subsequent step S403A determines whether the first CU supports the terminal access. It should be understood that the PLMN IDs supported by the first CU include a selected PLMN ID.

The third request message also carries indication information for indicating whether the RAN is in a CU-DU split architecture, so that, after the AMF determines that the first CU does not support terminal access in step S403A, it determines whether the first DU needs to be indicated to reselect the CU. For convenience of description, in the embodiment of the present application, the indication information for indicating whether the RAN is in the CU-DU split architecture is referred to as indication information # 1.

Optionally, the first CU is a CU first selected by the first DU, and the third request message is an initial UE message.

Optionally, the first CU is a reselected CU, and the third request message is an initial UE message or a path switch request (path switch request) message.

Optionally, the third request message includes CU reselection information of the first DU, where a manner of obtaining the CU reselection information by the first CU may be that the first DU is reported to the first CU, or that the first CU is notified by another network element (e.g., a core network), which is not limited herein.

S403A, the AMF determines whether the first CU supports the terminal access according to the subscription information of the terminal.

Whether the first CU supports mid-terminal access here may be understood as: whether the network configured by the first CU supports terminal access, or whether the network configured by the first CU is a network to which the terminal has signed up, or whether the type of the network configured by the first CU matches the type of the network to which the terminal has signed up.

The AMF compares the PLMN ID carried in the third request message with the CAG ID lists supported by the PLMN ID and the CAG ID lists (that is, the PLMN ID and the CAG ID lists supported by the first CU), and compares the PLMN ID list allowed to be accessed by the terminal and the CAG ID list supported by each PLMN ID in the terminal subscription information locally stored in the AMF, and if there is no overlapping combination of PLMN ID + CAG ID, it is determined that the first CU does not support the terminal access.

S404A, if the first CU supports terminal access, the AMF performs an admission control procedure on the terminal, for example, sends an initial context setup request (initial context setup request) message to the first CU, and the specific admission control procedure may refer to the related art and is not described herein again.

And S405A, if the first CU does not support the terminal access, the AMF sends a third response message to the first CU, and the first CU receives the third response message from the AMF.

Specifically, the third request message includes indication information (i.e., the indication information #1) indicating whether the RAN is in the CU-DU split architecture, and the AMF sends a third response message to the first CU after knowing whether the RAN is in the CU-DU split architecture according to the third request message. If the RAN is not a CU-DU separated architecture, directly rejecting the terminal to access, for example, sending an error indication message to a first CU; if the RAN is a CU-DU split architecture, a third response message is sent to the first CU. And the third response message is used for indicating the first DU to reselect the CU, and the third response message carries auxiliary information which is used for assisting the first DU to select the second CU.

For example, assume that the first CU supports a public network identified by PLMN ID #1 and also supports PNI-NPN #1 identified by PLMN ID #1+ CAG ID # 1; the second CU supports PNI-NPN #2 identified by PLMN ID #1+ CAG ID # 2. Assuming that the UE subscribes to PNI-NPN #2 identified by PLMN ID #1+ CAG #2, the AMF determines that the first CU does not support terminal access, but finds that the terminal subscribes to another PNI-NPN (i.e., PNI-NPN #2) supported by the same PLMN ID, so the AMF does not directly reject terminal access, but instructs the first DU to reselect the CU.

Wherein the auxiliary information comprises one or more of the following information:

1) indication information to indicate a CU is reselected, and for convenience of description, the indication information to indicate a CU is reselected is referred to as indication information # 2;

2)PLMN ID；

the PLMN ID may be a selected PLMN ID, or may be other PLMN IDs or PLMN ID lists.

3) A closed access group identity, CAG ID;

one PLMN ID and one CAG ID may identify one PNI-NPN. The selected PLMN ID and the PNI-NPN identified by the CAG ID in item 3) are used to indicate the PNI-NPN of the reselected second CU; or, the combination of the PLMN ID of item 2) and the PNI-NPN identified by the CAG ID in item 3) above is used to indicate the PNI-NPN of the reselected second CU.

4) And a Closed Access Group (CAG) list (allowed CAG list) of the terminal, which is used for assisting the first DU to re-establish the CU of which the CAG ID is contained in the allowed CAG list. (ii) a

5) Indication information (CAG-only access) of whether the terminal can only access the CAG cell, for assisting the first DU to reselect the caged CU. For convenience of description, the CAG-only access is referred to herein as indication information # 3.

The above item 1) of information may be used to explicitly instruct the first DU to perform CU reselection, that is, the first DU directly knows that the operation of reselecting the CU needs to be performed if receiving the instruction information indicating to reselect the CU.

The items 2) to 5) may also be used to implicitly instruct the first DU to perform CU reselection, that is, if the item 1) is not received, but at least any one of the items 2) to 5) is received, the first DU can learn that an operation of reselecting the CU needs to be performed.

For example, the information may include information on whether the first DU has performed CU reselection or the number of times the first DU has performed CU reselection, or whether unselected CUs exist in CUs connected to the first DU. Correspondingly, the AMF sends a third response message to the first CU only after determining, according to the third request message, that the first DU has not performed CU reselection, or that the number of times the first DU has performed CU reselection does not exceed a preset value, or that there is an unselected CU in the CUs connected to the first DU; otherwise, the terminal may be directly denied access, e.g., an error indication (error indication) message may be sent to the first CU. For example, if there is no unselected CU among the CUs connected by the first DU, it indicates that the first DU has attempted to connect all possible CUs for the terminal but cannot successfully access the terminal to the network, in which case the AMF directly denies the terminal access.

Optionally, the third response message is specifically an error indication (error indication) message or an initial context setup request (initial context setup request) message. Other messages are of course possible and not limiting herein. It should be understood that if the third response message is a multiplexed existing message, for example, the third response message is an error indication message or an initial context setup request message, the third response message here is different from the error indication message or the initial context setup request message in the prior art: the third response message contains auxiliary information, so the third response message instructs the first DU to reselect the CU, whereas the error indication message in the prior art does not contain auxiliary information for rejecting the terminal access, and the initial context setup request message in the prior art does not contain auxiliary information for requesting the first CU to establish a context for the terminal.

S406A, the first CU sends a first response message to the first DU, the first DU receives the first response message from the first CU, and the first response message is used to instruct the first DU to reselect the CU.

Specifically, the first CU determines whether the first DU needs to perform CU reselection according to the third response message information, and if so, the first CU sends a first response message to the first DU.

The first response message includes one or more of the following information: 1) indication information # 2; 2) a PLMN ID; 3) CAG ID; 4) indication information # 3; 5) allowed CAG list of terminals to which access is allowed.

Optionally, the first response message is a downlink RRC message transfer (DL RRC message transfer) message.

S407A, the first DU reselects the CU according to the first response message.

For example, if the first response message only carries indication information #2, the first DU randomly selects one CU from the unselected CUs. For example, the first response message carries the PLMN ID and CAG ID subscribed by the terminal, and the first DU may select a CU supporting the PLMN ID and CAG ID from all CUs (it should be understood that, when the first DU and CU perform the F1 interface setup, the first DU and CU may mutually notify the network conditions supported by each CU, such as the PLMN ID and CAG ID). Of course, the actual selection method is not limited to the above two methods, and the specific selection method may be determined according to the information carried by the first response message.

After the first DU reselects a CU, the first DU initiates an access procedure to the reselected CU again (the reselected CU is different from the first CU, for example, a second CU), i.e., returning to S401A, and the method flow of fig. 4A is re-executed based on the reselected CU.

According to the above description, when finding that the CU selected by the first DU does not support the terminal access, the AMF in the embodiment of the present application may not directly reject the terminal access, but return the auxiliary information to assist the first DU to reselect the CU to continue the access process, so that a problem that the terminal needs to perform the (physical) cell selection and the random access process again due to the AMF directly rejecting the terminal access can be avoided, overhead of an air interface signaling can be saved, and a delay of the terminal accessing the network can be reduced. To better understand the above method flow, a complete example is listed next.

Referring to fig. 4B, assuming that the first CU is the CU initially selected by the first DU, and the second CU is the CU selected again according to the auxiliary information sent by the AMF after the terminal fails to access the network through the first CU, the following procedures S401B-S411B are performed:

S401B, the first DU sends a first request message to the selected first CU, and the first CU receives the first request message from the first DU, where the first request message is used to request the terminal to access the first CU.

See S401A above for a specific implementation. Note that, here, the first CU is a CU initially Selected by the first DU, so the first request message is a UL RRC message, and specifically carries the Selected PLMN ID and the RRC container, where the RRC container includes related information reported by the air interface UE.

S402B, the first CU sends a third request message to the AMF, and the AMF receives the third request message from the first CU, wherein the third request message is for requesting the terminal to access the AMF.

See S402A above for a specific implementation. Note that here the first CU is the CU initially selected by the first DU, so the third request message is the initial UE message.

Optionally, the third request message includes CU reselection information of the first DU (information indicating whether the first DU has already performed CU reselection or the number of times the first DU has already performed CU reselection, or unselected CUs still exist in the CU connected to the first DU). For convenience of description, the CU reselection information of the first DU herein is referred to as indication information # 4.

S403B, the AMF determines whether the first CU supports the terminal access according to the subscription information of the terminal.

See S403A above for a specific implementation.

And S405B, if the first CU does not support the terminal access, the AMF sends a third response message to the first CU, and the first CU receives the third response message from the AMF.

See S405A above for a specific implementation.

S406B, the first CU sends a first response message to the first DU, the first DU receives the first response message from the first CU, and the first response message is used to instruct the first DU to reselect the CU.

See S406A above for a specific implementation.

S407B, the first DU reselects the CU according to the side information in the first response message, in this example the reselected CU is the second CU.

For example, the first response message carries the PLMN ID and the CAG ID, and the first response message carries the PLMN ID and the CAG ID for identifying the non-public network configured in the second CU, and the first DU may directly determine the second CU according to the first response message.

S408B, the first DU sends a second request message to the second CU, wherein the second request message is for requesting access of the terminal to the second CU.

It should be appreciated that the second request message may carry one or more of the following information in addition to the selected PLMN ID:

1) CU reselection information of the first DU (information indicating whether the first DU has already performed CU reselection or the number of times the first DU has performed CU reselection or whether unselected CUs are present in the CU to which the first DU is connected, etc.), and for convenience of description, the CU reselection information of the first DU is referred to herein as indication information # 4';

2) a PLMN ID, where the PLMN ID is a list of other PLMN IDs or PLMN IDs different from the selected PLMN ID;

3)CAG ID；

4) indication information # 3;

5) a list of closed access groups CAG (allowed CAG list) of terminals allowed to access.

It should be understood that the above items 2) to 5) are used herein to implicitly indicate the CU reselection information of the first DU. That is, if the second CU does not receive the item 1) but receives at least one of the items 2) to 5), the second CU can also know that the first DU has performed the operation of reselecting the CU.

It should be understood that the content of the CU reselection information of the first DU carried in the request message sent by the first DU at different stages may be different. For example, the third request message may also carry CU reselection information (e.g., indication information #4) of the first DU, and although the indication information #4 'and the indication information #4 have similar functions (e.g., both the indication information #4 and the indication information # 4' can be used to indicate whether the first DU has already performed CU reselection, the number of times of executed CU reselection, etc.), the contents of the two may be different. For example, indication information #4 indicates that the first DU has not undergone CU reselection, and indication information # 4' indicates that the first DU has undergone CU reselection. As another example, indication #4 may indicate that the first DU has performed 0 CU reselections, while indication # 4' indicates that the first DU has performed 1 CU reselection.

Of course, it is not excluded that the content of the CU reselection information of the first DU carried in the request message sent by the first DU at different phases is the same, for example, the first DU has a second CU reselection after the current reselection (S407B), and assuming that the selection result is the third CU, the request message sent by the first DU to the third CU after the second reselection may carry indication information #4 ", and the indication information # 4" and the indication information # 4' in the second request message are both used to indicate that the first DU has already undergone the CU reselection.

Optionally, the second request message is specifically an initial UL RRC message.

S409B, the second CU sends a fourth request message to the AMF, and the AMF receives the fourth request message from the second CU, wherein the fourth request message is for requesting the terminal to access the AMF.

It should be understood that the second CU is here the CU reselected for the first DU, so the fourth request message is an initial UE message, or a path switch request message (path switch request), which is not limited here.

The fourth request message carries a CAG ID list supported by the PLMN ID in the logical cell (i.e. the second CU) to which the first DU is currently selected to access, so that the AMF determines whether the second CU supports the terminal access.

Optionally, the fourth request message further carries the indication information #4 ', so that the subsequent AMF determines, according to the indication information # 4' in the fourth request message, whether the first DU has already performed CU reselection, or whether the number of times of CU reselection that the first DU has already performed does not exceed a preset value, or whether an unselected CU exists in a CU connected to the first DU.

Of course, the fourth request message may implicitly indicate the CU reselection information of the first DU by carrying the PLMN ID, the CAG ID, the indication information #3, or the allowed CAG list of the terminal.

And S410B, the AMF judges whether the second CU supports the terminal access according to the subscription information of the terminal.

The determination method may refer to the above specific implementation of S403A, and is not described herein again.

The AMF performs S411B when determining that the second CU supports terminal access.

S411B, the AMF performs an admission control procedure on the terminal, for example, the AMF sends an initial context setup request message to the second CU, and the specific admission control procedure may refer to the related prior art and is not described herein again.

Optionally, if the AMF determines that the second CU still does not support terminal access, the AMF determines, according to the indication information # 4', that the first DU has already performed CU reselection, or that the number of times the first DU has already performed CU reselection exceeds a preset value, or that there is no unselected CU in the CU connected to the first DU, and then sends an error indication message to the second CU to reject the terminal to access the network; or, after determining that the first DU has already performed CU reselection but the number of times of CU reselection performed by the first DU does not exceed the preset value or that there are other unselected CUs in addition to the first CU and the second CU in the CUs connected to the first DU according to the instruction information # 4', the AMF returns instruction information instructing CU reselection, that is, instruction information #2, to the first DU again through the second CU, and repeats the above-described flow from S405B until the terminal successfully accesses or there are no reselectable CUs.

Referring to fig. 5, another embodiment of the present application provides a method for a terminal to access a network, which may be applied to the network architecture shown in fig. 3A, but is not limited to the network architecture shown in fig. 3A. Different from the embodiments shown in fig. 4A and 4B, the first DU in this embodiment may sense the CAG ID selected by the terminal for access, and when the PNI-NPN network configured on the first CU does not support the network requested by the terminal for access, the first DU may directly determine to reselect the network for access, specifically refer to S501 to S506.

S501, the first DU determines that the selected PNI-NPN network configured on the first CU does not support the network which the terminal requests to access.

Similarly, the selected first CU here may be understood as: the first DU has selected the first CU, or the first DU and the first CU have established an F1 connection, or the first DU and the first CU have configured transmission resources for the terminal.

Similarly, the scenario for the first DU to select the first CU may be a CU selection scenario executed by the first DU when the terminal initially accesses, or may be a CU selection scenario executed by the first DU when the UE performs RRC re-establishment or RRC recovery, which is not limited herein. For convenience of description, the embodiment of the present application mainly takes an initial access scenario of a terminal as an example.

Similarly, before performing step S501, the terminal further needs to perform a cell selection and a random access procedure, and the specific implementation procedure may refer to the description of the relevant parts above, which is not described herein again.

It should be understood that the first DU does not yet perceive the CAG ID selected for access by the terminal when selecting the first CU, so the first CU does not necessarily support terminal access. For example, the selected first CU is selected to access in S202-S203 shown in fig. 2, and the terminal has not reported the selected CAG ID.

In this embodiment of the application, the first DU may know whether a network selected by the terminal to access is a public network or a PNI-NPN, and when the network requested by the terminal to access is the PNI-NPN and a logical cell corresponding to the first CU selected by the first DU only supports the public network or does not support the PNI-NPN requested by the terminal to access, it is determined that the selected first CU does not support the network requested by the terminal to access.

The first DU learns a mode of selecting a network to access by the terminal, which is not limited in the embodiment of the present application. For example, the terminal may report the PLMN ID and the CAG ID corresponding to the network selected to be accessed by the terminal in the RRC setup complete message, so that the first DU may determine whether the PNI-NPN network configured on the first CU supports the PNI-NPN network requested to be accessed by the terminal by comparing the PLMN ID and the CAG ID supported by the first CU with whether the PLMN ID and the CAG ID corresponding to the network selected to be accessed by the terminal are matched. For another example, the terminal may report a network Index value (network Index) or a PLMN ID Index value (PLMN Index) selected by the terminal to be accessed in the RRC setup complete message at the same time, and the first DU may learn, based on the Index value information, a PLMN ID and a CAG ID corresponding to the network requested to be accessed by the terminal, so that the first DU may determine whether the PNI-NPN network configured on the first CU supports the PNI-NPN network requested to be accessed by the terminal by comparing the PLMN ID and the CAG ID supported by the first CU with whether the PLMN ID and the CAG ID corresponding to the network selected to be accessed by the terminal are matched.

S502, the first DU sends a sixth request message to the first CU, where the sixth request message is used to instruct the first CU to release the context of the terminal.

Specifically, the sixth request message is a UE context release request (UE context release request) message, an error indication message (error indication), or the like.

S503, the first CU releases the context of the terminal.

Optionally, the sixth request message includes a cause value for indicating that the first CU needs to release the context of the terminal because the PNI-NPN network that does not support the terminal request is included.

Further optionally, the cause value includes one or more of the following information:

the first CU does not support a closed access group (CAG ID(s) not served by the CU) requested by the terminal;

a non-public network (NPN(s) not requested by the CU that the first CU does not support terminal requests;

the first CU does not support terminal requested PNI-NPN(s) not served by the CU);

the CAG ID requested by the terminal is invalid (invalid CAG ID (s));

terminal requested NPN invalid (invalid NPN);

PNI-NPN invalid (invalid PNI-NPN) requested by the terminal;

CAG access denied (CAG access denied);

NPN access denied (NPN access denied);

PNI-NPN access denied (PNI-NPN access denied).

And S504, the first DU reselects the CU, and the selection result is the second CU.

It should be understood that the above steps S502 and S504 do not limit the sequence.

And S505, the first DU sends a seventh request message to the reselected second CU, and the second CU receives the seventh request message, wherein the seventh request message is used for requesting the terminal to be accessed to the second CU.

It should be understood that step S505 is similar to step S408B in the previous embodiment.

The method steps performed after step S505 are similar to those after step S408B in the previous embodiment.

For example, after step S505, it is further performed:

and S506, the second CU sends a ninth request message to the AMF to request the terminal to be accessed to the second CU. The ninth request message here is similar to the fourth request message in step S409B in the foregoing embodiment.

S507, the AMF sends a ninth response message to the second CU. The ninth response message here is similar to the initial context setup request message of step S4011B in the foregoing embodiment.

For the specific implementation manner of the method step executed after step S505, reference may be made to the specific implementation manner of the method step after S408B, which is not described herein again.

According to the above description, when the first DU can sense the network type of the logical cell to which the terminal selects to access, and when the first DU finds that the selected first CU does not support the terminal access, the first DU may not directly reject the terminal access, but notify the first CU to release the context of the terminal and reselect the CU to perform the access, which can avoid the problem that the terminal needs to perform the (physical) cell selection and random access process again due to the AMF directly rejecting the terminal access, and can save the overhead of air interface signaling and reduce the delay of the terminal accessing the network.

Referring to fig. 6, another embodiment of the present application provides a method for a terminal to access a network, which may be applied to the network architecture shown in fig. 3A, but is not limited to the network architecture shown in fig. 3A. Unlike the embodiment shown in fig. 4A, the first DU in this embodiment may sense the CAG ID selected to be accessed by the terminal, and unlike the embodiment shown in fig. 5, when the PNI-NPN network configured by the first CU does not support the network to which the terminal requests access, the first DU instructs the first CU to continue sending requests to the AMF, and the AMF may allow the terminal to access as long as the first CU or any network supported by the first DU is supported by the terminal. See S601 to S606 for details.

S601, the first DU determines that the selected PNI-NPN network configured on the first CU does not support the network which the terminal requests to access.

The specific implementation manner of this step may refer to the specific implementation manner of S501 above, and is not described here again.

S602, the first DU sends a fifth request message to the first CU, and the first CU receives the fifth request message from the first sub DU;

wherein the fifth request message is for requesting the first CU to send an access request message to the AMF. The fifth request message carries indication information #5, where the indication information #5 is used to indicate that, although the first CU does not support the network to which the terminal requests access, the first CU still needs to send an access request message to the AMF, so as to access the terminal, or make the terminal subscribe online, or make the terminal access another network configured on the first DU or the first CU through a third party authentication.

It should be understood that the other networks configured on the first CU refer to: a first network supporting access of the terminal among the plurality of networks configured on the first CU, the first network being different from a network to which the terminal requests access. Illustratively, the first CU is configured with a public network identified by PLMN ID #1 and a PNI-NPN #1 identified by PLMN ID #1+ CAG ID #1, the UE subscribes to a PNI-NPN #2 identified by PLMN ID #1+ CAG #2 and a PNI-NPN #1 identified by PLMN ID #1+ CAG ID #1, the first DU supports the public network identified by PLMN ID #1, the PNI-NPN #1, and the PNI-NPN #2, and the network to which the UE requests to access is the PNI-NPN #2, which means the other network is the PNI-NPN #1, and the PNI-NPN #1 supports the UE access although not the network to which the UE requests to access. The other networks configured on the first DU refer to: and a second network supporting the terminal access in the plurality of networks is configured on the first DU, the second network is the same as or different from the network requested by the terminal to access, and the first CU does not support the second network. Illustratively, the first CU is configured with a public network identified by PLMN ID #1 and a PNI-NPN #1 identified by PLMN ID #1+ CAG ID #1, the second CU is configured with a public network identified by PLMN ID #1 and a PNI-NPN #2 identified by PLMN ID #1+ CAG ID #2, the UE subscribes to the PNI-NPN #2 identified by PLMN ID #1+ CAG #2, the first DU supports the public network identified by PLMN ID #1, the PNI-NPN #1 and the PNI-NPN #2, and the network to which the UE requests to access is the PNI-NPN #2, so that the other network refers to the PNI-NPN # 2.

Optionally, the fifth request message is specifically an uplink RRC message transfer (UL RRC message transfer) message.

S603, the first CU sends an eighth request message to the AMF, and the AMF receives the eighth request message, where the eighth request message is used to request the terminal to access the AMF.

Wherein, the eighth request message includes the indication information # 5.

Optionally, the eighth request message further includes indication information #1 for indicating whether the RAN in the access network is in the CU-DU split architecture, so that after determining that the RAN is in the CU-DU split architecture according to the eighth request message, the AMF accesses the terminal to another network configured on the first DU, for example, instructs the first DU to reselect the network access of the second CU.

Optionally, the eighth request message is an initial UE message.

S604, the AMF determines whether the first DU or another network configured on the first CU supports the terminal access, and if so, accesses the terminal to the other network.

For example, after receiving the eighth request message from the first CU, the AMF determines that the first CU does not support the network to which the terminal requests to access, but supports another network to which the terminal subscribes, and accesses the terminal to another network supported by the first CU and to which the terminal subscribes.

For example, after receiving the eighth request message from the first CU, the AMF determines that the first CU of the terminal does not support the network requested to be accessed by the terminal, but does not exclude the following possibilities: since the RAN is a CU-DU separation architecture, a first DU connected to a first CU may be further configured with other networks, for example, the first DU may also be connected to a second CU, and the second CU supports a network requested by a terminal to access, and then the AMF sends assist information for reselecting the CU, so that the first DU performs CU reselection based on the assist information, thereby accessing the terminal to the second CU.

Optionally, the fifth request message and/or the eighth request message include CU reselection information of the first DU, so that after determining that the first CU does not support the network to which the terminal requests access, the AMF determines whether to instruct the first DU to reselect the CU. For example, the AMF instructs the first DU to reselect CU access only after determining that the first DU has not performed CU reselection according to the eighth request message, that the number of times the first DU has performed CU reselection does not exceed a preset value, or that there are unselected CUs in the CU to which the first DU is connected.

Optionally, if another network (e.g. the second CU) configured on the first DU supports the access of the terminal, the method further includes the following steps: the first CU receives an eighth response message from the AMF, wherein the eighth response message is used for indicating the first DU to reselect the CU; the first CU sends a fifth response message to the first DU, wherein the fifth response message is used for indicating the first DU to reselect the CU; and after receiving the fifth response message, the first DU reselects the second CU to initiate the access process.

Further optionally, the eighth response message and the fifth response message include one or more auxiliary information of the following information: indication information to indicate a reselection of the CU; a public land mobile network identity, PLMN ID; a closed access group identity, CAG ID; a closed access group CAG list of the terminal which is allowed to access; indication information of whether the terminal can only access the CAG cell.

Similarly, the method steps executed after the second CU reselected by the first DU in this embodiment may refer to the method steps executed after the second CU reselected by the first DU in the embodiment shown in fig. 4A, and are not described again here.

As can be seen from the above description, when the first DU is capable of perceiving the network type of the logical cell to which the terminal selects to access, if the first DU finds that the selected first CU does not support the terminal access, the first DU may not directly deny the terminal access, but instruct the first CU to continue sending the request to the AMF, and the AMF may allow the terminal access as long as the first CU or any network supported by the first DU is supported by the terminal. The problem that the AMF directly rejects the terminal access to cause that the terminal needs to perform the (physical) cell selection and random access process again can be avoided, the air interface signaling overhead can be saved, and the time delay of the terminal access network can be reduced.

In another embodiment of the present application, it may be defined that a public network or an NPN network corresponding to the same PLMN ID needs to be configured with the same cell identity, so that the same cell identity points to the same CU. Therefore, the situation that the CU is not supported by the first DU selection terminal due to the fact that different cell identities (namely different CUs) are configured with the same PLMN ID can be avoided, air interface signaling overhead is saved, and time delay of the terminal for accessing the network is reduced.

The method for accessing the network by the terminal according to the embodiment of the present application is described in detail above with reference to fig. 4A to 6, and the apparatus for implementing the method according to the embodiment of the present application is described in detail below with reference to fig. 7 to 17. Therefore, the above contents can be used in the subsequent embodiments, and the repeated contents are not repeated.

Based on the same technical concept, referring to fig. 7, an embodiment of the present application provides an apparatus 700 of a radio access network, where the apparatus 700 may be a DU or an apparatus on a DU, and the apparatus 700 includes means for performing the method steps performed by the first DU in fig. 4A or fig. 4B.

Illustratively, the apparatus 700 may comprise:

a sending module 701, configured to send a first request message to a selected first centralized unit CU, where the first request message is used to request a terminal to access to the first CU;

a receiving module 702, configured to receive a first response message from the first CU, where the first response message is used to instruct the apparatus 700 to reselect a CU, and the first response message carries auxiliary information, where the auxiliary information is used to assist the apparatus 700 to reselect a CU;

a processing module 703, configured to select the second CU according to the auxiliary information, so as to access the terminal to a network through the second CU.

Optionally, the sending module 701 is further configured to send a second request message to the second CU, where the second request message is used to request the terminal to access the second CU.

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

CU reselection information of the device 700;

the CAG ID;

the PLMN ID;

the CAG list;

and the terminal can only access the indication information of the CAG cell.

Based on the same technical concept, referring to fig. 8, an embodiment of the present application provides an apparatus 800 of a core network, where the apparatus 800 may be an AMF or an apparatus on the AMF, and the apparatus 800 includes a module for performing the method steps performed by the AMF in fig. 4A or fig. 4B.

Illustratively, the apparatus 800 may comprise:

a receiving module 801 configured to receive a third request message from a first centralized unit CU, wherein the third request message is configured to request a terminal to access the apparatus 800;

a processing module 802, configured to determine, according to subscription information of the terminal, that the first CU does not support the terminal access;

a sending module 803, configured to send a third response message to the first CU, where the third response message is used to indicate the first DU to reselect the CU, and the third response message carries auxiliary information, where the auxiliary information is used to assist the first DU to reselect the CU.

the processing module 802 is further configured to determine whether the RAN is in a CU-DU split architecture according to the indication information;

the sending module 803 is configured to: after the processing module 802 determines that the RAN is a CU-DU split architecture, a third response message is sent to the first CU.

the processing module 802 is further configured to determine, according to the CU reselection information, whether the first DU performs CU reselection, or whether the number of CU reselections performed by the first DU does not exceed a preset value, or whether an unselected CU still exists in a CU connected to the first DU;

the sending module 803 is configured to: after the processing module 802 determines that the first DU has not performed CU reselection, or the number of times the first DU has performed CU reselection does not exceed a preset value, or there is an unselected CU in the CU connected to the first DU, a third response message is sent to the first CU.

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

Based on the same technical concept, referring to fig. 9, an embodiment of the present application provides an apparatus 900 of a radio access network, where the apparatus 900 may be a CU or an apparatus on a CU, and the apparatus 900 includes means for performing the method steps performed by the first CU in fig. 4A or fig. 4B.

Illustratively, the apparatus 900 includes:

a receiving module 901, configured to receive a first request message from a first DU, where the first request message is used to request a terminal to access the apparatus;

a sending module 902, configured to send a third request message to the AMF, where the third request message is used to request a terminal to access the AMF;

the receiving module 901 is further configured to receive a third response message from the AMF, where the third response message is used to indicate the first DU to reselect the CU, and the third response message carries auxiliary information, where the auxiliary information is used to assist the first DU to reselect the CU;

the sending module 902 is further configured to send a first response message to the first DU, where the first response message is used to instruct the first DU to reselect a CU, and the first response message carries the auxiliary information.

Based on the same technical concept, referring to fig. 10, an embodiment of the present application provides an apparatus 1000 of a radio access network, where the apparatus 1000 may be a CU or an apparatus on a CU, and the apparatus 1000 includes means for performing the method steps performed by a second CU in fig. 4A or fig. 4B.

Illustratively, the apparatus 1000 includes:

a receiving module 1001, configured to receive a second request message from a first DU, where the second request message is used to request the terminal to access the apparatus;

a sending module 1002, configured to send a fourth request message to an AMF, where the fourth request message is used to request that the terminal is accessed to the AMF;

the receiving module 1001 is further configured to receive an initial context setup request message from the AMF;

a processing module 1003, configured to establish a context for the terminal according to the initial context establishment request message.

Based on the same technical concept, referring to fig. 11, an embodiment of the present application provides an apparatus 1100 of a radio access network, where the apparatus 1100 may be a DU or an apparatus on a DU, and the apparatus 1100 includes means for performing the method steps performed by the first DU in fig. 5.

Illustratively, the apparatus 1100 includes:

a processing module 1101, configured to determine that the selected public-network converged non-public network PNI-NPN network configured on the first centralized unit CU does not support the network to which the terminal requests access;

a sending module 1102, configured to send a sixth request message to the first CU, configured to instruct the first CU to release a context configured for the terminal;

the processing module 1101 is further configured to select a second CU;

the sending module 1102 is further configured to send a seventh request message to the second CU, where the seventh request message is used to request that a terminal is accessed to the second CU.

Based on the same technical concept, referring to fig. 12, an embodiment of the present application provides an apparatus 1200 of a radio access network, where the apparatus 1200 may be a second CU or an apparatus on the second CU, and the apparatus 1200 includes modules for performing the method shown in fig. 5.

Illustratively, the apparatus 1200 includes:

a receiving module 1201, configured to receive a seventh request message from a first DU, where the seventh request message is used to request the terminal to access the apparatus;

a sending module 1202, configured to send a ninth request message to an AMF, where the ninth request message is used to request that the terminal is accessed to the AMF;

the receiving module 1201 is further configured to receive an initial context setup request message from the AMF;

a processing module 1203, configured to establish a context for the terminal according to the initial context establishment request message.

Based on the same technical concept, referring to fig. 13, an embodiment of the present application provides an apparatus 1300 of a core network, where the apparatus 1300 may be an AMF or an apparatus on the AMF, and the apparatus 1300 includes modules for performing the method steps performed by the AMF in fig. 5.

Illustratively, the apparatus 1300 comprises:

a receiving module 1301, configured to receive a ninth request message from a second CU, wherein the ninth request message is used to request the terminal to access the apparatus;

a sending module 1302, configured to send an initial context setup request message to the second CU when the second CU supports the terminating access.

Based on the same technical concept, referring to fig. 14, an embodiment of the present application provides an apparatus 1400 of a radio access network, where the apparatus 1400 may be a CU or an apparatus on a CU, and the apparatus 1400 includes means for performing the method steps performed by the first CU in fig. 5.

Illustratively, the apparatus 1400 comprises:

a receiving module 1401, configured to receive a sixth request message from the first DU, where the sixth request message is used to instruct the first CU to release a context configured for the terminal;

a processing module 1402, configured to release the context of the terminal in response to the sixth request message.

Based on the same technical concept, referring to fig. 15, an embodiment of the present application provides an apparatus 1500 of a radio access network, where the apparatus 1500 may be a DU or an apparatus on a DU, and the apparatus 1500 includes means for performing the method steps performed by the first DU in fig. 6.

Illustratively, the apparatus 1500 includes:

a processing module 1501, configured to determine that the selected public-network converged non-public network PNI-NPN network configured on the first centralized unit CU does not support the network to which the terminal requests to access;

a sending module 1502 configured to send a fifth request message to the first CU, wherein the fifth request message is used to request the first CU to send an access request message to an AMF;

a receiving module 1503, configured to receive a fifth response message from the first CU, the fifth response message being used to instruct the terminal to access the device or another network configured on the first CU.

Based on the same technical concept, referring to fig. 16, an embodiment of the present application provides an apparatus 1600 of a radio access network, where the apparatus 1600 may be a CU or an apparatus on a CU, and the apparatus 1600 includes modules for performing the method steps performed by the first CU in fig. 6.

Illustratively, the apparatus 1600 includes:

a receiving module 1601, configured to receive a fifth request message from a first DU, where the fifth request message is generated by the first DU when the first DU determines that a public-network converged non-public network PNI-NPN network configured on the first CU does not support a network to which the terminal requests access, and the fifth request message is used to request the apparatus to send an access request message to an AMF;

a sending module 1602, configured to send an eighth request message to the AMF, where the eighth request message is used to request that the terminal is accessed to the AMF.

Based on the same technical concept, referring to fig. 17, an apparatus 1700 of a core network is provided in an embodiment of the present application, where the apparatus 1700 may be an AMF or an apparatus on the AMF, and the apparatus 1700 includes a module for performing the method steps performed by the AMF in fig. 6.

Illustratively, the apparatus 1700 includes:

a receiving module 1701 for receiving an eighth request message from a first CU, wherein the eighth request message is for requesting the terminal to access the device 1700, wherein the eighth request message is generated by the first CU when a PNI-NPN network configured on the first CU does not support a network to which the terminal requests access;

a processing module 1702, configured to determine whether the first DU or another network configured on the first CU supports terminal access, and if so, access the terminal to the other network.

Based on the same technical concept, referring to fig. 18, an embodiment of the present application provides a communication apparatus 1800, where the apparatus 1800 includes:

at least one processor 1801; and the number of the first and second groups,

a memory 1802 communicatively coupled to the at least one processor 1801, a communication interface 1803;

wherein the memory 1802 stores instructions executable by the at least one processor 1801, and the at least one processor 1801 executes the instructions stored by the memory 1802 to perform the method of fig. 4A or 4B or 5 or 6.

Optionally, the memory 1802 is located external to the apparatus 1800.

Optionally, the apparatus 1800 includes the memory 1802, the memory 1802 being coupled to the at least one processor 1801, the memory 1802 storing instructions executable by the at least one processor 1801. Fig. 18 shows in dashed lines that the memory 1802 is optional for the apparatus 1800.

The processor 1801 and the memory 1802 may be coupled through an interface circuit, or may be integrated together, which is not limited herein.

The embodiment of the present application does not limit the specific connection medium among the processor 1801, the memory 1802, and the communication interface 1803. In the embodiment of the present application, the processor 1801, the memory 1802, and the communication interface 1803 are connected through a bus 1804 in fig. 18, the bus is represented by a thick line in fig. 18, and the connection manner between other components is merely illustrative and not limited. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 18, but this does not mean only one bus or one type of bus.

It should be understood that the processors mentioned in the embodiments of the present application may be implemented by hardware or may be implemented by software. When implemented in hardware, the processor may be a logic circuit, an integrated circuit, or the like. When implemented in software, the processor may be a general-purpose processor implemented by reading software code stored in a memory.

The Processor may be, for example, a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

It will be appreciated that the memory referred to in the embodiments of the application may be either volatile memory or nonvolatile memory, or may include both volatile and nonvolatile memory. The non-volatile Memory may be a Read-Only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically Erasable PROM (EEPROM), or a flash Memory. Volatile Memory can be Random Access Memory (RAM), which acts as external cache Memory. By way of example, but not limitation, many forms of RAM are available, such as Static random access memory (Static RAM, SRAM), Dynamic Random Access Memory (DRAM), Synchronous Dynamic random access memory (Synchronous DRAM, SDRAM), Double Data rate Synchronous Dynamic random access memory (DDR SDRAM), Enhanced Synchronous SDRAM (ESDRAM), Synchronous Link DRAM (SLDRAM), and Direct Rambus RAM (DR RAM).

It should be noted that when the processor is a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, the memory (memory module) may be integrated into the processor.

It should be noted that the memory described herein is intended to comprise, without being limited to, these and any other suitable types of memory.

Based on the same technical concept, the embodiment of the present application also provides a computer-readable storage medium, which includes a program or instructions, and when the program or instructions are run on a computer, the method as shown in fig. 4A or fig. 4B or fig. 5 or fig. 6 is executed.

Based on the same technical concept, the embodiments of the present application also provide a computer program product, which when run on a computer, causes the method as shown in fig. 4A or fig. 4B or fig. 5 or fig. 6 to be performed.

Based on the same technical concept, embodiments of the present application further provide a chip, where the chip is coupled to a memory, and is configured to read and execute program instructions stored in the memory to implement the method shown in fig. 4A or fig. 4B or fig. 5 or fig. 6.

Based on the same technical concept, an embodiment of the present application further provides a communication system, including:

the above-described apparatuses 700, 800, 900, and 1000; or,

the above-described apparatus 1100, apparatus 1200, apparatus 1300, and apparatus 1400; or,

the apparatus 1500, 1600 and 1700 described above.

All relevant contents of each step related to the method embodiment may be referred to in the functional description of the functional module corresponding to each device in the device embodiment, and are not described herein again.

Embodiments of the present application are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, 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, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the application to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored on a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website, computer, server, or data center to another website, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a Digital Versatile Disk (DVD)), or a semiconductor medium (e.g., a Solid State Disk (SSD)), among others.

It will be apparent to those skilled in the art that various changes and modifications may be made in the embodiments of the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to encompass such modifications and variations.

Claims

1. A method for a terminal to access a network, the method comprising:

the first distributed unit DU sends a first request message to the selected first centralized unit CU, where the first request message is used to request a terminal to access the first CU;

the first DU receives a first response message from the first CU, wherein the first response message is used for indicating the first DU to reselect the CU, and the first response message carries auxiliary information which is used for assisting the first DU to reselect the CU;

and the first DU selects a second CU according to the auxiliary information so as to enable the terminal to access the network through the second CU.

2. The method of claim 1, wherein after the first DU selects a second CU according to the side information, further comprising:

the first DU sends a second request message to the second CU, wherein the second request message is used for requesting the terminal to be accessed to the second CU.

3. The method of claim 2, wherein the assistance information comprises one or more of the following:

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

4. The method of claim 3, wherein the second request message includes one or more of the following information:

CU reselection information of the first DU;

the CAG ID;

the PLMN ID;

the CAG list;

and the terminal can only access the indication information of the CAG cell.

5. A method for a terminal to access a network, the method comprising:

the access and mobility management function AMF receives a third request message from the first centralized unit CU requesting to access the terminal to said AMF;

the AMF judges that the first CU does not support the terminal access according to the subscription information of the terminal, and sends a third response message to the first CU, wherein the third response message is used for indicating the first DU to reselect the CU, and the third response message carries auxiliary information which is used for assisting the first DU to reselect the CU.

6. The method of claim 5, wherein the third request message includes indication information for indicating whether a Radio Access Network (RAN) is a CU-DU split architecture;

the AMF sending a third response message to the first CU, comprising:

and after determining that the RAN is a CU-DU separated architecture according to the indication information, the AMF sends a third response message to the first CU.

7. The method according to claim 5 or 6, wherein the third request message includes CU reselection information of the first DU;

the AMF sending a third response message to the first CU, comprising:

and after determining that the first DU has not executed CU reselection according to the CU reselection information, or the number of times of CU reselection executed by the first DU does not exceed a preset value, or unselected CUs still exist in the CUs connected with the first DU, the AMF sends the third response message to the first CU.

8. The method according to any of claims 5-7, wherein the auxiliary information comprises one or more of the following information:

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

9. An apparatus of a radio access network, comprising:

a sending module, configured to send a first request message to a selected first centralized unit CU, where the first request message is used to request a terminal to access to the first CU;

10. The apparatus of claim 9, wherein the means for sending is further for sending a second request message to the second CU, wherein the second request message is for requesting the terminal to be accessed to the second CU.

11. The apparatus of claim 10, wherein the assistance information comprises one or more of:

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

12. The apparatus of claim 11, wherein the second request message includes one or more of the following information:

CU reselection information for the device;

the CAG ID;

the PLMN ID;

the CAG list;

and the terminal can only access the indication information of the CAG cell.

13. An apparatus of a core network, comprising:

a receiving module configured to receive a third request message from a first centralized unit CU, wherein the third request message is for requesting a terminal to access the apparatus;

14. The apparatus of claim 13, wherein the third request message includes indication information indicating whether an access network RAN is a CU-DU split architecture;

15. The apparatus according to claim 13 or 14, wherein the third request message comprises CU reselection information of the first DU;

16. The apparatus of any one of claims 13-15, wherein the third response message includes one or more of the following information:

a public land mobile network identity, PLMN ID;

a closed access group identity, CAG ID;

a Closed Access Group (CAG) list of the terminal, which is allowed to access;

and the terminal can only access the indication information of the CAG cell.

17. A communications apparatus, the apparatus comprising:

at least one processor; and the number of the first and second groups,

wherein the memory stores instructions executable by the at least one processor, the at least one processor performing the method of any one of claims 1-4 or 5-8 by executing the instructions stored by the memory.

18. A computer-readable storage medium comprising a program or instructions which, when run on a computer, causes the method of any one of claims 1-4 or 5-8 to be performed.