CN112312495A

CN112312495A - Method for supporting switching in mobile communication network

Info

Publication number: CN112312495A
Application number: CN202010318866.2A
Authority: CN
Inventors: 许丽香; 王弘; 汪巍崴; 麻晓宁
Original assignee: Beijing Samsung Telecommunications Technology Research Co Ltd; Samsung Electronics Co Ltd
Current assignee: Beijing Samsung Telecommunications Technology Research Co Ltd; Samsung Electronics Co Ltd
Priority date: 2019-07-23
Filing date: 2020-04-21
Publication date: 2021-02-02
Anticipated expiration: 2040-04-21
Also published as: CN112312495B

Abstract

A method for UE handover, comprising: and the target base station receives a third message from a core network element connected with the target base station, wherein the third message carries the UE identification information for identifying the UE.

Description

Method for supporting switching in mobile communication network

Technical Field

The present invention relates to the field of mobile communication technology, and in particular, to a method for supporting handover in a mobile communication network.

Background

In a 5G communication system, a network element comprising: user Equipment (UE), access node (gNB), access and mobility management function entity (AMF), session management function entity (SMF), and data plane function entity (UPF). The AMF, the SMF and the UPF belong to a core network element.

In an Evolved Packet System (EPS) communication System, a network element includes: UE, access node (eNB), Mobility Management Entity (MME), Serving Gateway (SGW), and packet data network gateway (PGW). Wherein, MME, SGW and PGW belong to the network element of the core network.

The UE may be handed over in the same communication system or between different communication systems. For example, a UE may be handed over between access nodes of a 5G communication system, i.e., Intra-system handover; the UE may also be handed over, i.e., an Inter-system handover, between an access node of the 5G communication system and an access node of the EPS communication system.

Fig. 1 is a schematic diagram of a system architecture when a UE is handed over.

The UE is handed over from a source access node, i.e. access node 1 connected to the core network 1, to a target access node, i.e. access node 2 connected to the core network 2.

Fig. 2 is a diagram illustrating a UE simultaneously establishing wireless connections with two access nodes.

When the UE is in a dual-connection state, namely, the UE establishes wireless connection with one access node and simultaneously establishes wireless connection with the other access node. One of the access nodes is a Master Node (Master Node), and the Master Node is connected to the UE through a control plane shown by a solid line and a user plane shown by a dotted line; another access Node is a Secondary Node (SN), which may be connected to the UE only through the user plane. Two access nodes may be connected to a core network of the same communication system, for example, both access nodes may be a gbb connected to a 5G core network; the two access nodes may also be connected to core networks of different communication systems, for example, the two access nodes may be a gNB connected to a core network of a 5G communication system and an eNB connected to a core network of an EPS communication system.

For the UE in the dual connectivity state, the following two scenarios may occur when the UE performs handover:

(1) before the handover occurs, the UE is in a dual connectivity state, and is connected to a primary node 1 and a secondary node 0 at the same time. After the switching, the UE is connected with only one access node, and the access node is an auxiliary node 0 before the switching;

(2) before switching, the UE is in a dual-connection state and is simultaneously connected to a main node 1 and an auxiliary node 0; after the handover occurs, the UE is still in the dual connectivity state, connecting to one primary node 2 and the secondary node 0.

The two scenarios have the same point that before and after the UE is switched, the connection between the UE and the secondary node 0 before the switch is kept unchanged. If the downlink data is already transmitted to the secondary node 0 but is still not transmitted to the UE before the handover is completed, and the downlink data is still transmitted to the UE through the secondary node 0 after the handover, in the existing mechanism, the secondary node 0 will perform data forwarding on the downlink data, but the data forwarding is not necessary because the destination node of the forwarding is still the secondary node 0. In order to avoid the above unnecessary data forwarding, it is necessary that the secondary node 0 can recognize that downlink data of the currently switched UE has been transmitted to the secondary node 0 after the handover.

However, in the existing mechanisms, some handover-related signaling does not include information that allows the access node after handover to identify the currently handed over UE. Therefore, unnecessary forwarding of the downlink data may occur, thereby causing a waste of network resources and increasing a delay of downlink data transmission.

Further, in the scenario (2), for the UE that is in dual connectivity before and after the handover and has the secondary node 0 remaining unchanged, in order to enable the master node 2 after the handover to correctly configure the secondary node, it is necessary that the master node 1 before the handover can notify the master node 2 after the handover of information about the secondary node 0, so that the master node 2 can determine, according to the information, whether the secondary node can be maintained unchanged as the secondary node after the handover.

However, in some existing mechanisms, some handover-related signaling does not include identification information of the secondary node. Therefore, the secondary node 0 before the handover may not be held after the handover is completed, and thus the above-described unnecessary forwarding cannot be avoided.

Still further, in the scenario (2), on the premise that the primary node 2 determines that the secondary node 0 remains unchanged after the handover, the existing UE context on the secondary node 0 should be retained after the handover is completed.

However, in existing mechanisms, some handover-related signaling does not include information that secondary node 0 remains unchanged after handover. Thus, it may occur that data at secondary node 0 regarding the UE is erroneously or unnecessarily deleted.

Still further, in the secondary node adding preparation process, the primary node instructs the secondary node to add a trigger scenario of the preparation process, where the trigger scenario may include a secondary node change (SN change), intra-eNB HO (intra-eNB HO), inter-eNB HO (inter-eNB HO), intra-NGRAN HO (intra-NGRAN HO), inter-NGRAN HO (inter-NGRAN HO), eNB-NGRAN HO (eNB-NGRAN HO), and NGRAN node-to-eNB HO (NGRAN-eNB HO).

However, in the existing mechanism, the secondary node addition preparation process trigger scenario of the EPS communication system only includes secondary node change, intra-eNB handover, and inter-eNB handover; the 5G communication system has not defined an explicit secondary node addition preparation process triggering scenario. It can be seen that there are some secondary nodes that are not well defined that add the preparation process triggering scenario.

Disclosure of Invention

In view of one or more of the above problems, the present invention provides a method of supporting handover in a mobile communication network.

According to an embodiment of the present disclosure, a method for UE handover is provided, where a source base station sends a first message to a core network element connected to the source base station, where the first message carries UE identification information for identifying the UE.

Optionally, the first message carries secondary base station identification information for identifying a secondary base station.

Optionally, the first message carries a source base station identifier for identifying the source base station, and/or a source cell identifier for identifying a source cell, and/or a measurement result of the UE.

Optionally, the first message is a base station and core network interface application protocol signaling handover request message.

Optionally, the method further comprises: and the source base station receives an eighth message from the core network element connected with the source base station, wherein the eighth message carries a field for indicating whether the existing context of the UE on the secondary base station is reserved after the handover.

Optionally, the method further comprises: and the source base station receives an eighth message from the core network element connected with the source base station, wherein the eighth message carries UE identification information for identifying the UE, and/or an auxiliary base station identification for identifying an auxiliary base station, and/or a target base station identification for identifying a target base station.

Optionally, the eighth message is a base station and core network interface application protocol signaling handover command message.

Optionally, the field for indicating whether the existing context of the UE on the secondary base station is reserved after handover is a UE context retention indication field.

Optionally, the UE identity information is a UE identity allocated to the UE by the secondary node.

Optionally, the UE identity is SgNB UE X2AP ID, or S-NG-RAN node UE XnAP ID.

Optionally, when the UE Identity information is a Cell Radio Network temporary Identity-value (C-RNTI) allocated to the UE by the secondary node, the first message further carries a primary and secondary Cell Identity and/or secondary base station Identity information of the UE at the secondary node.

Optionally, the carrying may be carried directly by the message or carried by a subfield carried by a source-to-destination transparent container field carried by the message.

Optionally, the subfield is a source NG-RAN node to destination NG-RAN node transparent container field, or a source eNB to destination eNB transparent container field.

Optionally, the carrying may be carried directly by the message or carried by a subfield carried by a destination-to-source transparent container field carried by the message.

Optionally, the subfield is a destination NG-RAN node to source NG-RAN node transparent container field, or a destination eNB to source eNB transparent container field.

According to an embodiment of the present disclosure, an apparatus for UE handover is provided, and the apparatus performs the method.

According to an embodiment of the present disclosure, a computer device for a user equipment UE is provided, which includes a memory and a processor, wherein the memory stores instructions thereon, and the instructions when executed by the processor implement the above method.

According to an embodiment of the present disclosure, a method for UE handover is provided, which includes: and the target base station receives a third message from a core network element connected with the target base station, wherein the third message carries the UE identification information for identifying the UE.

Optionally, the third message carries secondary base station identification information for identifying a secondary base station.

Optionally, the third message carries a source base station identifier for identifying the source base station, and/or a source cell identifier for identifying a source cell, and/or a measurement result of the UE.

Optionally, the third message is a base station and core network interface application protocol signaling handover request message

Optionally, the method further comprises: the target base station sends a fourth message to the auxiliary base station, wherein the fourth message carries the UE identification information and/or a field for indicating the current auxiliary node to increase a trigger scene of a preparation process; the destination base station receives a fifth message from the secondary base station.

Optionally, the method further comprises: the destination base station sends a fourth message to the source base station, wherein the fourth message carries the UE identification information and/or a source cell identification for identifying the source cell; and the target base station receives a fifth message from the source base station, wherein the fifth message carries the UE identification information.

Optionally, the fourth message is an inter-base station interface application protocol signaling secondary NODE ADDITION REQUEST message SGNB ADDITION REQUEST or S-NODE ADDITION REQUEST.

Optionally, the fifth message is an inter-base station interface application protocol signaling secondary NODE ADDITION REQUEST ACKNOWLEDGE message SGNB ADDITION REQUEST ACKNOWLEDGE or S-NODE ADDITION REQUEST ACKNOWLEDGE.

Optionally, the field for indicating the Trigger scenario of the current auxiliary node increase preparation process is an inter-base station interface application protocol signaling auxiliary base station increase Trigger Indication field SGNB Addition Trigger Indication, and a value of the SGNB Addition Trigger Indication field is one of SN change, inter-eNB HO, intra-eNB HO, inter-NGRAN HO, intra-NGRAN HO, eNB-NGRAN HO, and NGRAN-eNB HO.

Optionally, the field for indicating the Trigger scenario of the current auxiliary NODE increase preparation process is an inter-base station interface application protocol signaling auxiliary base station increase Trigger Indication field S-NODE Addition Trigger Indication, where a value of the S-NODE Addition Trigger Indication field is one of SN change, inter-eNB HO, intra-eNB HO, inter-NGRAN HO, intra-NGRAN HO, eNB-NGRAN HO, and NGRAN-eNB HO.

Optionally, the method further comprises: and the target base station sends a sixth message to a core network element connected with the target base station, wherein the sixth message carries a field for indicating whether the existing context of the UE on the auxiliary base station is reserved after switching.

Optionally, the method further comprises: and the target base station sends a sixth message to a core network element connected with the target base station, wherein the sixth message carries the UE identification information, and/or an auxiliary base station identification used for identifying an auxiliary base station, and/or a target base station identification used for identifying the target base station.

Optionally, the sixth message is a handover request acknowledgement message of a base station and core network interface application protocol signaling.

Optionally, the UE identity is SgNB UE X2AP ID, or S-NG-RAN node UE XnAP ID.

Optionally, when the UE identity information is a cell RNTI allocated to the UE by the secondary node, the third message further carries a primary and secondary cell identity and/or secondary base station identity information of the UE at the secondary node

According to an embodiment of the present disclosure, a method for UE handover is provided, which includes: the auxiliary base station receives a fourth message from the first main base station, wherein the fourth message carries UE identification information used for identifying the UE and/or a field used for indicating a current auxiliary node to increase a trigger scene of a preparation process; the secondary base station sends a fifth message to the first primary base station.

Optionally, the field for indicating the Trigger scenario of the current auxiliary node increase preparation process is an inter-base station interface application protocol signaling auxiliary base station increase Trigger Indication field SGNB Addition Trigger Indication, and a value of the SGNB Addition Trigger Indication field is one of SN change, inter-eNB HO, intra-eNB HO, inter-NGRAN HO, intra-NGRAN HO, eNB-NGRAN HO, and NGRAN-HO eNB.

Optionally, the UE identity is SgNB UE X2AP ID, or S-NG-RAN node UE XnAP ID.

Optionally, when the UE identity information is a cell RNTI allocated to the UE by the secondary node, the fourth message further carries a primary and secondary cell identity of the UE at the secondary node and/or secondary base station identity information.

Drawings

These and/or other aspects, features and advantages of the present invention will become more apparent and readily appreciated from the following description of the embodiments taken in conjunction with the accompanying drawings of which:

fig. 1 shows a schematic diagram of a system architecture when a handover occurs to a UE;

fig. 2 shows a schematic diagram of a UE in a dual connectivity state;

FIG. 3 illustrates a handover method;

fig. 4 illustrates a specific example of applying the handover method illustrated in fig. 3 to a handover scenario in a 5G communication system;

FIG. 5 illustrates a handover method;

FIG. 6 illustrates a specific example of applying the handover method illustrated in FIG. 5 to an inter-system handover scenario from EPS to 5G communication systems;

FIG. 7 illustrates a handover method;

fig. 8 illustrates a specific example of applying the handover method illustrated in fig. 7 to a handover scenario in a 5G communication system;

FIG. 9 illustrates a handover method;

fig. 10 shows a specific example of applying the handover method shown in fig. 9 to a handover scenario in an EPS communication system;

fig. 11 shows a specific example of applying the handover method shown in fig. 9 to an intersystem handover scenario from an EPS to a 5G communication system;

fig. 12 shows a specific example of applying the handover method shown in fig. 9 to an intersystem handover scenario from a 5G to an EPS communication system;

fig. 13 illustrates a specific example of applying the handover method illustrated in fig. 9 to a handover scene in a 5G communication system.

Fig. 14 shows a specific example of applying the handover method shown in fig. 5 to an intersystem handover scenario from a 5G to EPS communication system.

Detailed Description

A method of supporting handover in a mobile communication network is provided. In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below by referring to the accompanying drawings and examples.

The expressions "first", "second", "third", etc. in the present specification are for the purpose of distinction only and are not defined restrictively.

In the following embodiments, a communication architecture is shown in which a UE is connected to a network element of a core network through an access node. In the embodiment, the access node takes a gNB and an eNB as an example; the core network elements take the AMF and MME as examples, which provide mobility management functions.

In the following embodiments, the following interface protocols are involved: x2 application protocol (X2AP), Xn application protocol (XnAP), NG application protocol (NGAP), and S1 application protocol (S1 AP). It should be noted that, although the embodiment of the present invention is described by taking X2 and Xn as examples of the horizontal interface between two base stations, the method of the present invention is also applicable to other interfaces between two base stations; although the embodiments of the present invention are described by taking NG and S1 as examples of the interface between the base station and the core network, the method of the present invention is also applicable to other interfaces between the base station and the core network. That is, in this specification, X2AP and XnAP are examples of inter-base station interface application protocols, and NGAP and S1AP are examples of base station and core network interface application protocols.

Fig. 3 is a schematic diagram of the first embodiment. The first embodiment describes a handover method.

In a first embodiment, a handover method includes the steps of:

step 301: the first node sends a first message to a third node, wherein the first message carries UE identification information.

Step 302: and the third node sends a third message to the second node, wherein the third message carries the UE identification information in the first message.

Fig. 4 is a schematic view of a second embodiment. The second embodiment is a specific example of applying the handover method in the first embodiment to a handover scenario in a 5G communication system.

In a second embodiment, before performing intra-5G system handover, the UE is in a dual connectivity state and is connected to a primary node gNB1 and a secondary node gNB0 at the same time; after performing an intra-5G system handover, the UE is in connection to only gbb 0. It can be seen that, in the second embodiment, the gNB1 is a source node, the gNB0 is a destination node, and the destination node is an auxiliary node before handover. The source node gNB1 and the destination node gNB0 are both connected to the same core network element AMF.

The source node gNB1 may correspond to the first node in embodiment one, the destination node gNB0 may correspond to the second node in embodiment one, and the AMF may correspond to the third node in embodiment one.

In the handover scenario in the 5G communication system, the handover method includes the following steps:

step 401: the source node gbb 1 sends a first message, which may be a HANDOVER REQUIRED (HANDOVER REQUIRED) message, to the AMF. The HANDOVER REQUIRED message may be a HANDOVER REQUIRED message in NGAP signaling in this implementation. The HANDOVER REQUERED message carries UE identification information.

Specifically, the HANDOVER requested message carries a Source to destination Transparent Container (Source to Target Transparent Container) field, which may carry a Source NG-RAN Node to Target NG-RAN Node Transparent Container (Source NG-RAN Node to Target NG-RAN Node Transparent Container) field, which may carry UE identification information. Alternatively, the HANDOVER requested message may directly contain an information element for indicating UE identification information to directly carry the UE identification information.

Specifically, the UE identification information may be a UE identification S-NG-RAN node UE XnAP ID allocated by the secondary node gNB0 to the UE on the Xn interface. Alternatively, when the UE identification information is a Cell Radio Network temporary Identity-value (C-RNTI) allocated to the UE by the Secondary node gNB0, the HANDOVER request message further carries a Primary and Secondary Cell Identity (PScell ID) of the UE at the Secondary node gNB0 or the Secondary node gNB0 identification information.

Step 402: the AMF sends a third message, which may be a HANDOVER REQUEST (HANDOVER REQUEST) message, to destination node gNB 0. The HANDOVER REQUEST message may be a HANDOVER REQUEST message in NGAP signaling, where the HANDOVER REQUEST message carries the UE identification information in the HANDOVER REQUEST message.

Specifically, the AMF transparently forwards the content of the Source to Target transmission Container field received by the AMF to the destination node gNB 0. Alternatively, if in step 401 the UE identity information is carried directly by the HANDOVER REQUEST message, the HANDOVER REQUEST message should also carry the UE identity information directly.

In the above step, when the UE identification information is the C-RNTI, the message carrying the UE identification information also carries the PScell ID of the UE in the secondary node gNB0 or the secondary node gNB0 identification information.

The above solution may be advantageous. Specifically, for downlink data of the UE that has been transmitted to the destination node gNB0 but has not been sent to the UE before handover is completed, since the destination node gNB0 is used as an auxiliary node before handover, the destination node gNB0 may find the context of the UE that has been established on the destination node gNB0 according to UE identification information. And when the UE identity is C-RNTI, the target base station finds the context of the UE in the gNB0 according to the received PScell ID of the UE in the auxiliary node gNB0 and/or the auxiliary node identity information of the gNB0 and the UE identity C-RNTI. The destination node gNB0 does not need to forward data before and after handover as in the existing mechanism.

Step 403: the destination node gNB0 sends a sixth message to the AMF, where the sixth message may be a HANDOVER REQUEST ACKNOWLEDGE (HANDOVER REQUEST ACKNOWLEDGE) message, and the HANDOVER REQUEST ACKNOWLEDGE message may be a HANDOVER REQUEST ACKNOWLEDGE message in NGAP signaling in this implementation.

Step 404: the AMF sends an eighth message to the source node gNB1, where the eighth message may be a HANDOVER COMMAND (HANDOVER COMMAND) message, and the HANDOVER COMMAND message may be a HANDOVER COMMAND message in NGAP signaling in this implementation.

Fig. 5 is a schematic view of a third embodiment. The third embodiment describes a handover method.

In a third embodiment, a handover method includes the steps of:

step 501: the first node sends a first message to a third node, wherein the first message carries UE identification information.

Step 502: and the third node sends a second message to a fourth node, wherein the second message carries the UE identification information in the first message.

Step 503: and the fourth node sends a third message to the second node, wherein the switching request message carries the UE identification information in the second message.

Fig. 6 is a schematic view of a fourth embodiment. The fourth embodiment is a specific example of applying the handover method in the third embodiment to an intersystem handover scenario from EPS to 5G communication systems.

In the fourth embodiment, before performing inter-system handover, the UE is in a dual connectivity state and is connected to a primary node eNB1 and a secondary node gNB0 at the same time; after performing inter-system handover, the UE is connected to only the gNB 0. As can be seen, in the fourth embodiment, the eNB1 is a source node, the gNB0 is a destination node, and the destination node is an auxiliary node before handover. The source node eNB1 is connected to an MME, and the destination node gNB0 is connected to an AMF.

The source node eNB1 may correspond to the first node in embodiment three, the destination node gNB0 may correspond to the second node in embodiment three, the MME may correspond to the third node in embodiment three, and the AMF may correspond to the fourth node in embodiment three.

In the scenario of intersystem handover from the EPS to the 5G communication system, the handover method includes the following steps:

step 601: the source node eNB1 sends a first message to the MME, which may be a HANDOVER REQUIRED message, which in this implementation may be a HANDOVER REQUIRED message in the S1AP signaling. The HANDOVER request message carries UE identification information and/or secondary base station identification information.

Specifically, the HANDOVER REQUIRED message carries a Source to Target transmission content field, and when the destination base station is an NG-RAN Node, the Source to Target transmission content field may carry a Source NG-RAN Node to Target NG-RAN Node transmission content field, and the Source NG-RAN Node to Target NG-RAN Node transmission content field carries UE identification information and/or secondary base station identification information. Alternatively, the HANDOVER requested message may directly carry UE identification information and/or secondary base station identification information.

Specifically, the UE identity information may be a UE identity SgNB UE X2AP ID allocated by the secondary node gNB0 to the UE on the X2 interface. Alternatively, the UE identity information may be an identity C-RNTI allocated by the secondary node gNB0 to the UE, and when the UE identity information is the C-RNTI, the HANDOVER request message further needs to include the PScell ID of the UE at the secondary node gNB0 and/or the secondary node identity information of the gNB 0.

Step 602: the MME sends a second message to the AMF, where the second message may be a FORWARD reset REQUEST (FORWARD RELOCATION REQUEST) message, and the FORWARD reset REQUEST message may be a FORWARD RELOCATION REQUEST message in a GPRS Tunneling Protocol (GTP) control plane Protocol signaling in this embodiment, where the FORWARD RELOCATION REQUEST message carries the UE identity message and/or the secondary base station identity information in the HANDOVER RELOCATION REQUEST message.

Specifically, the MME transparently forwards the contents of the Source to Target transfer Container field it receives to the AMF. Alternatively, in step 601, if the UE identification information and/or secondary base station identification information is directly carried by the HANDOVER requested message, the GTP control plane protocol signaling should also directly carry the UE identification information and/or secondary base station identification information.

Step 603: the AMF sends a third message to the destination node gNB0, where the third message may be a HANDOVER REQUEST message, and the HANDOVER REQUEST message may be a HANDOVER REQUEST message in an NGAP signaling in this embodiment, and the HANDOVER REQUEST message carries the UE identity message and/or secondary base station identity information in the HANDOVER REQUEST message.

Specifically, the AMF transparently forwards the content of the Source to Target transmission Container field received by the AMF to the destination node gNB 0. Alternatively, in step 602, if the GTP control plane protocol signaling directly carries the UE identity information and/or the secondary base station identity information, the HANDOVER REQUEST message should also directly carry the UE identity information and/or the secondary base station identity information.

The above solution may be advantageous. Specifically, for downlink data of the UE that has been transmitted to the destination node gNB0 before handover is completed but has not yet been sent to the UE, since the destination node gNB0 serves as an auxiliary node before handover, the destination node gNB0 may find the context of the UE that has been established on the destination node gNB0 according to UE identification information and/or an auxiliary base station identification, and the destination node gNB0 does not need to forward data before and after handover as in the existing mechanism. The destination node gNB0 may find the context of the UE that has been established on the destination node gNB0 according to the UE identity information and/or the Secondary base station identity, so as to know the bearers that have been configured on the Secondary base station before the handover (e.g., the bearers that terminate at the Secondary node, or the Secondary Cell Group (SCG) bearers). For the bearer (for example, the bearer terminated by the secondary node or the SCG bearer) already configured on the secondary base station before the handover, data forwarding inside the base station is performed without performing data forwarding from the source base station to the destination base station as in the existing handover mechanism. And when the UE identity is C-RNTI, the target base station finds the context of the UE in the gNB0 according to the received PScell ID of the UE in the auxiliary node gNB0 and/or the auxiliary node identity information of the gNB0 and the UE identity C-RNTI.

If the gNB0 supports a separate control plane and user plane architecture, i.e., the gNB0 contains a gNB concentrated unit control plane unit (gNB-CU-CP) and a gNB concentrated unit user plane unit (gNB-CU-UP). The gNB0-CU-CP requests the gNB0-CU-UP to allocate channel information corresponding to each evolved radio access bearer E-RAB. The channel information contains transport layer addresses and channel identifications. The gNB0-CU-UP assigns channel information for data forwarding for each E-RAB requested and sends to the gNB 0-CU-CP. Corresponding to the bearer terminating at the gNB0 at the source end, the gNB0-CU-CP need not request the gNB0-CU-UP to assign channel information for said E-RAB. And the gNB0-CU-CP can find the UE context according to the received UE identification message and/or the secondary base station identification information. The gNB0-CU-CP knows the bearers terminating at the gNB0-CU-UP at the source end according to the UE context. The identity of the gNB0-CU-CP is the same as the identity of the secondary base station of gNB 0.

Step 604: the destination gNB0 sends a sixth message to the AMF, where the sixth message may be a HANDOVER REQUEST acknowledgement message, and the HANDOVER REQUEST acknowledgement message may be a HANDOVER REQUEST ACKNOWLEDGE message in NGAP signaling in this embodiment. For the bearer performing internal data forwarding or the bearer configured on the secondary base station before HANDOVER, the destination node gNB0 does not need to include the transport layer address and the tunnel identifier of the bearer for data forwarding in the HANDOVER REQUEST ACKNOWLEDGE message. And the destination base station gNB0 sends the allocated channel information corresponding to each E-RAB to the AMF.

Step 605: the AMF sends a seventh message to the MME, where the seventh message may be a FORWARD RELOCATION RESPONSE (FORWARD RELOCATION RESPONSE) message, and the FORWARD RELOCATION RESPONSE message may be a FORWARD RELOCATION RESPONSE message in GTP control plane protocol signaling in this embodiment.

Step 606: the MME sends an eighth message to the source node eNB1, where the eighth message may be a HANDOVER COMMAND message, and the HANDOVER COMMAND message may be a HANDOVER COMMAND message in the S1AP signaling in this embodiment.

The method can simplify the data forwarding process in the switching process. The above technical solution is described in the fourth embodiment in a scenario where the secondary base station serving the UE before handover and the target base station are the same logical entity. However, the above technical solution is not limited thereto. In addition, the above technical solution is also applicable to a scenario where the secondary base station serving the UE before handover and the target base station are co-located nodes (co-located nodes). Compared with other technical solutions, the above technical solutions can simplify the processing procedure of the destination base station by sending the UE identity and/or the secondary base station identity.

Fig. 7 is a schematic view of a fifth embodiment. A fifth embodiment describes a handover method.

In a fifth embodiment, a handover method includes the steps of:

step 701: the first node sends a first message to a third node, wherein the first message carries UE identification information and auxiliary node identification information, and the auxiliary node identification information is identification information of a fifth node.

Step 702: and the third node sends a third message to the second node, wherein the third message carries the UE identification information and the auxiliary node identification information in the first message.

Step 703: and the second node sends a fourth message to a fifth node, wherein the fourth message carries the UE identification information in the third message and the scene information indicating the current added auxiliary node.

Step 704: the fifth node sends a fifth message to the second node, and confirms that the fifth node can continue to be used as an auxiliary node after switching;

step 705: and the second node sends a sixth message to the third node, wherein the sixth message carries information indicating that the auxiliary node is kept unchanged before and after switching.

Step 706: and the third node sends an eighth message to the first node, wherein the eighth message carries the information which indicates that the auxiliary node is kept unchanged before and after switching in the sixth message.

Fig. 8 is a schematic view of a sixth embodiment. The sixth embodiment is a specific example of applying the handover method in the fifth embodiment to a handover scenario in a 5G communication system.

In the sixth embodiment, before performing intra-system handover, the UE is in a dual connectivity state and is connected to the primary node gNB1 and the secondary node gNB0 at the same time; after the intra-system handover is performed, the UE is still in a dual-connection state, and is connected to the primary node gNB2 and the secondary node gNB0 which remains unchanged before and after the handover. It can be seen that in the sixth embodiment, gNB1 is the source node, gNB2 is the destination node, and the secondary nodes before and after the handover remain unchanged as gNB 0. Wherein the source node gNB1 and the destination node gNB2 are both connected to the AMF.

The source node gNB1 may correspond to the first node in fifth embodiment, the destination node gNB2 may correspond to the second node in fifth embodiment, the auxiliary node gNB0 may correspond to the fifth node in fifth embodiment, and the AMF may correspond to the third node in fifth embodiment.

step 801: the source node gNB1 sends a first message to the AMF, where the first message may be a HANDOVER REQUIRED message, and the HANDOVER REQUIRED message may be a HANDOVER REQUIRED message in NGAP signaling in this embodiment, where the HANDOVER REQUIRED message carries UE identification information and secondary node gNB0 identification information.

Specifically, the HANDOVER request message may carry a Source to Target transmission Container field, where the Source to Target transmission Container field may carry a Source NG-RAN Node to Target NG-RAN Node transmission Container field, and the Source NG-RAN Node to Target NG-RAN Node transmission Container field may carry UE identification information and secondary Node gNB0 identification information. Alternatively, the HANDOVER request message may directly include information elements for indicating UE identification information and for indicating secondary node gNB0 identification information, so as to directly carry the UE identification information and the secondary node gNB0 identification information.

Specifically, the UE identification information may be a UE identification S-NG-RAN node UE XnAP ID allocated by the secondary node gNB0 to the UE on the Xn interface. Alternatively, the UE identity information may be an identity C-RNTI allocated by the secondary node gNB0 to the UE, and when the UE identity information is the C-RNTI, the HANDOVER request message further needs to include the PScell ID of the UE at the secondary node gNB0 and/or the secondary node identity information of the gNB 0.

Step 802: the AMF sends a third message to the destination node gNB2, where the third message may be a HANDOVER REQUEST message, and the HANDOVER REQUEST message may be a HANDOVER REQUEST message in an NGAP signaling in this embodiment, where the HANDOVER REQUEST message carries the UE identity message in the HANDOVER REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the AMF may transparently forward the content of the Source to Target transmission Container that it receives to the destination node gNB 2. Alternatively, in step 801, if the HANDOVER REQUEST message directly carries the UE identification information and the identification information of the secondary node gNB0, the HANDOVER REQUEST message should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

The above solution may be advantageous. Specifically, the destination node gNB2 will determine whether the secondary node gNB0 can be kept unchanged as a secondary node after handover according to the received identification information of the secondary node gNB 0. Thus, the secondary node identification information makes it possible for the pre-handover secondary node gNB0 to be maintained after the handover is completed, providing the possibility of avoiding unnecessary forwarding.

Step 803: the destination NODE gNB2 sends a fourth message to the secondary NODE gNB0, where the fourth message may be a secondary NODE ADDITION REQUEST message, and the secondary NODE ADDITION REQUEST message may be an S-NODE ADDITION REQUEST (S-NODE ADDITION REQUEST) message in XnAP signaling in this embodiment. The S-NODE ADDITION REQUEST message includes the UE identification information and/or an S-NODE ADDITION Trigger Indication (S-NODE ADDITION Trigger Indication) field. The S-NODE Addition Trigger Indication field indicates that the current Trigger scenario of the auxiliary NODE for adding the preparation process is switching between NGRAN NODEs, namely, the value of the S-NODE Addition Trigger Indication field is inter-NGRAN HO.

The above solution may be advantageous. Specifically, inter-NGRAN node handover is explicitly defined as a secondary node addition preparation process trigger scenario.

Similarly, the S-NODE Addition Trigger Indication field may also take the value of intra-NGRAN HO, so that intra-NGRAN handover may also be explicitly defined as an auxiliary NODE Addition preparation process Trigger scenario.

Step 804: the secondary NODE gNB0 sends a fifth message to the destination NODE gNB2, where the fifth message may be a secondary NODE ADDITION REQUEST ACKNOWLEDGE message, and the secondary NODE ADDITION REQUEST ACKNOWLEDGE message may be an S-NODE ADDITION REQUEST ACKNOWLEDGE (S-NODE ADDITION REQUEST ACKNOWLEDGE) message in XnAP signaling in this embodiment, where the S-NODE ADDITION REQUEST ACKNOWLEDGE message carries an RRC configuration Indication field.

The above solution may be advantageous. Specifically, for downlink data of the UE that has been transmitted to the auxiliary node gNB0 before handover is completed but has not yet been sent to the UE, since the auxiliary node gNB0 is used as an auxiliary node before handover, the auxiliary node gNB0 may find the context of the UE that has been established on the auxiliary node gNB0 according to the UE identification information, and the auxiliary node gNB0 does not need to forward data before and after handover as in the existing mechanism. And when the UE identity is C-RNTI, the auxiliary base station finds the context of the UE in the gNB0 according to the PScell ID of the UE in the auxiliary node gNB0 and/or the auxiliary node identity information of the gNB0 and the UE identity C-RNTI.

Step 805: the destination node gNB2 sends a sixth message to the AMF, where the sixth message may be a HANDOVER REQUEST acknowledgement message, and the HANDOVER REQUEST acknowledgement message may be a HANDOVER REQUEST ACKNOWLEDGE message in NGAP signaling in this embodiment. The HANDOVER REQUEST ACKNOWLEDGE message may carry a destination To Source Transparent Container (Target To Source Transparent Container) field, the Target To Source Transparent Container field may carry a destination NG-RAN Node To Source NG-RAN Node Transparent Container (Target NG-RAN Node To Source NG-RAN Node Transparent Container) field, and the Target NG-RAN Node To Source NG-RAN Node Transparent Container field may carry a UE Context retention Indicator (UE Context key Indicator) field, which indicates whether the Context of the UE existing on the secondary Node gNB0 is To be retained after the HANDOVER is completed. Alternatively, the HANDOVER REQUEST ACKNOWLEDGE message may directly include a UE Context Indicator field to directly carry information about whether the Context of the UE existing on the secondary node gNB0 will be retained after HANDOVER is completed.

Step 806: the AMF sends an eighth message to the source node gNB1, where the eighth message may be a HANDOVER COMMAND message, and the HANDOVER COMMAND message may be a HANDOVER COMMAND message in an NGAP signaling in this embodiment, and the HANDOVER COMMAND message carries a UE Context key Indicator field.

Specifically, the AMF may transparently forward the content of the Target To Source transit Container sub-segment it receives To Source node gNB 1. Alternatively, in step 805, if the HANDOVER REQUEST ACKNOWLEDGE message directly carries the UE Context key Indicator sub-segment, the HANDOVER COMMAND message should also directly carry the field UE Context key Indicator.

Step 807: the source NODE gNB1 sends a ninth message to the secondary NODE gNB0, where the ninth message may be a secondary NODE RELEASE REQUEST message, and the secondary NODE RELEASE REQUEST message may be an S-NODE RELEASE REQUEST (S-NODE RELEASE REQUEST) message in XnAP signaling in this embodiment, where the S-NODE RELEASE REQUEST message includes a UE Context key Indicator field.

The above solution may be advantageous. Specifically, the secondary node gNB0 determines whether the existing Context of the UE on the secondary node gNB will be retained after the handover is completed according to a UE Context Indicator field. Accordingly, it can be avoided that data about the UE at secondary node 0 is erroneously or unnecessarily deleted.

Step 808: the secondary NODE gNB0 sends a tenth message to the source NODE gNB1, where the tenth message may be a secondary NODE RELEASE REQUEST ACKNOWLEDGE message, and the secondary NODE RELEASE REQUEST ACKNOWLEDGE message may be an S-NODE RELEASE REQUEST ACKNOWLEDGE (S-NODE RELEASE REQUEST ACKNOWLEDGE) message in XnAP signaling in this embodiment.

Fig. 9 is a schematic view of a seventh embodiment. The seventh embodiment describes a handover method.

In a seventh embodiment, a handover method includes the steps of:

step 901: the first node sends a first message to a third node, wherein the first message carries UE identification information and auxiliary node identification information, and the auxiliary node identification information is identification information of a fifth node.

Step 902: and the third node sends a second message to a fourth node, wherein the second message carries the UE identification information and the auxiliary node identification information in the first message.

Step 903: and the fourth node sends a third message to the second node, wherein the third message carries the UE identification information and the auxiliary node identification information in the second message.

Step 904: and the second node sends a fourth message to a fifth node, wherein the fourth message carries the UE identification information in the third message and the scene information indicating the current added auxiliary node.

Step 905: and the fifth node sends a fifth message to the second node to confirm that the fifth node can continue to be used as the auxiliary node after the switching.

Step 906: and the second node sends a sixth message to the fourth node, wherein the sixth message carries information indicating that the auxiliary node keeps unchanged before and after switching.

Step 907: and the fourth node sends a seventh message to the third node, wherein the seventh message carries the information which indicates that the auxiliary node is kept unchanged before and after the switching in the sixth message.

Step 908: and the third node sends an eighth message to the first node, wherein the eighth message carries the information which indicates that the auxiliary node is kept unchanged before and after switching in the seventh message.

Fig. 10 is a schematic view of an eighth embodiment. The eighth embodiment is a specific example of applying the handover method in the seventh embodiment to a handover scenario in an EPS communication system.

In the eighth embodiment, before performing intra-system handover, the UE is in a dual connectivity state and is connected to the primary node eNB1 and the secondary node gNB0 at the same time; after the UE performs the intra-system handover based on the S1 interface, the UE is still in the dual-connection state, and is connected to the primary node eNB 2 and the secondary node gNB0 which remains unchanged before and after the handover. It can be seen that, in the eighth embodiment, eNB1 is the source node and eNB 2 is the destination node, and the secondary nodes before and after handover remain unchanged as gNB 0. Wherein, the source node eNB1 is connected to the source MME, and the destination node eNB 2 is connected to the destination MME.

The source node eNB1 may correspond to the first node in the seventh embodiment, the destination node eNB 2 may correspond to the second node in the seventh embodiment, the source MME may correspond to the third node in the seventh embodiment, the destination MME may correspond to the fourth node in the seventh embodiment, and the secondary node gNB0 may correspond to the fifth node in the seventh embodiment.

In the switching scenario in the EPS communication system, the switching method includes the following steps:

step 1001: the source node eNB sends a first message to the source MME, where the first message may be a HANDOVER REQUIRED message, and the HANDOVER REQUIRED message may be an S1AP signaling HANDOVER request message in this embodiment, where the HANDOVER request message carries UE identification information and secondary node gNB0 identification information.

Specifically, the HANDOVER request message carries a Source to Target Transparent Container field, where the Source to Target Transparent Container field may carry a Source eNB to Target eNB Transparent Container field (Source eNB to Target eNB Transparent Container), and the Source eNB to Target eNB Transparent Container field carries UE identification information and identification information of the secondary node gsb 0. Alternatively, the HANDOVER request message may directly include information elements for indicating UE identification information and for indicating secondary node gNB0 identification information, so as to directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1002: the source MME sends a second message to the destination MME, where the second message may be a forwarding reset REQUEST message, and the forwarding reset REQUEST message may be a FORWARD RELOCATION REQUEST message in GTP control plane protocol signaling in this embodiment, where the FORWARD RELOCATION REQUEST message carries the UE identity message in the HANDOVER REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the Source MME transparently forwards the content of the Source to Target transfer Container field it receives to the destination MME. Alternatively, in step 1001, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by the HANDOVER REQUEST message, the FORWARD location REQUEST message in the GTP control plane protocol signaling should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1003: the destination MME sends a third message to the destination node eNB 2, where the third message may be a HANDOVER REQUEST message, and the HANDOVER REQUEST message may be an S1AP signaling HANDOVER REQUEST message in this embodiment, where the HANDOVER REQUEST message carries the UE identity message in the HANDOVER REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the destination MME transparently forwards the content of the Source to Target transmission Container field it receives to the destination node eNB 2. Alternatively, in step 1002, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by the FORWARD location REQUEST message, the HANDOVER REQUEST message should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

The above solution may be advantageous. Specifically, the destination node eNB 2 determines whether the secondary node gNB0 can be kept unchanged as the secondary node after handover according to the received identification information of the secondary node gNB 0. Thus, the secondary node identification information makes it possible for the pre-handover secondary node gNB0 to be maintained after the handover is completed, providing the possibility of avoiding unnecessary forwarding.

Step 1004: the destination node eNB 2 sends a fourth message to the secondary node gNB0, where the fourth message may be a secondary node addition request message, and the secondary node addition request message includes UE identification information and/or a secondary node addition trigger indication. The secondary node ADDITION REQUEST message may be an SGNB ADDITION REQUEST (SGNB ADDITION REQUEST) message in the X2AP signaling in this embodiment. The SGNB ADDITION REQUEST message includes the UE identification information and/or an SGNB ADDITION Trigger Indication (SGNB ADDITION Trigger Indication) field. The SGNB Addition Trigger Indication field indicates that the current Trigger scenario for the auxiliary node to add the preparation process is inter-eNB handover, that is, the value of the SGNB Addition Trigger Indication field is inter-eNB HO.

The above solution may be advantageous. Specifically, inter-eNB handover is explicitly defined as a secondary node addition preparation procedure trigger scenario.

Step 1005: the secondary node gNB0 sends a fifth message to the destination node eNB 2, where the fifth message may be a secondary node ADDITION REQUEST acknowledgement message, and the secondary node ADDITION REQUEST acknowledgement message may be an SGNB ADDITION REQUEST acknowledgement (SGNB ADDITION REQUEST ACKNOWLEDGE) message in the X2AP signaling, where the SGNB ADDITION REQUEST ACKNOWLEDGE message carries an RRC Config Indication field.

Step 1006: the destination node eNB sends a sixth message to the destination MME, where the sixth message may be a HANDOVER REQUEST ACKNOWLEDGE message, and the HANDOVER REQUEST ACKNOWLEDGE message may be a HANDOVER REQUEST ACKNOWLEDGE message in the S1AP signaling. The HANDOVER REQUEST ACKNOWLEDGE message may carry a Target To Source transit Container field, where the Target To Source transit Container field may carry a Target eNB To Source eNB Transparent Container (Target eNB To Source eNB transit Container) field, and the Target eNB To Source eNB transit Container field may carry a UE Context Indicator field, which indicates whether the Context of the UE existing on the secondary node gbb 0 is To be reserved after HANDOVER is completed. Alternatively, the HANDOVER REQUEST ACKNOWLEDGE message may directly include a UE Context Indicator field to directly carry information about whether the Context of the UE existing on the secondary node gNB0 will be retained after HANDOVER is completed.

Step 1007: the destination MME sends a seventh message to the source MME, where the seventh message may be a FORWARD reset RESPONSE message, and the FORWARD reset RESPONSE message may be a FORWARD RELOCATION RESPONSE message in GTP control plane protocol signaling, where the FORWARD RELOCATION RESPONSE message carries the UE Context key Indicator in the HANDOVER REQUEST ACKNOWLEDGE message.

Specifically. The destination MME can transparently forward the content of the Target To Source Transmission Container field it receives To the Source MME. Alternatively, in step 1006, if the HANDOVER REQUEST ACKNOWLEDGE message directly carries the UE Context key Indicator field, the FORWARD RELOCATION RESPONSE message in the GTP control plane protocol signaling should also directly carry the UE Context key Indicator field.

Step 1008: the source MME sends an eighth message to the source node eNB1, where the eighth message may be a HANDOVER COMMAND message, and the HANDOVER COMMAND message may be a HANDOVER COMMAND message in the S1AP signaling, where the HANDOVER COMMAND message carries a UE Context key Indicator field.

Specifically, the Source MME may transparently forward the content of the Target To Source transit Container sub-segment it receives To the Source node eNB 1. Alternatively, in step 1007, if the FORWARD RELOCATION RESPONSE message directly carries the UE Context Indicator sub-segment, the HANDOVER COMMAND message should also directly carry the field UE Context Indicator.

Step 1009: the source node eNB1 sends a ninth message to the secondary node gNB0, where the ninth message may be a secondary node RELEASE REQUEST message, and the secondary node RELEASE REQUEST message may be an SGNB RELEASE REQUEST (SGNB RELEASE REQUEST) message in the X2AP signaling, where the SGNB RELEASE REQUEST message includes a UE Context key Indicator field.

Step 1010: the secondary node gNB0 sends a tenth message to the source node eNB1, where the tenth message may be a secondary node RELEASE REQUEST ACKNOWLEDGE message, and the secondary node RELEASE REQUEST ACKNOWLEDGE message may be an SGNB RELEASE REQUEST ACKNOWLEDGE (SGNB RELEASE REQUEST ACKNOWLEDGE) message in the X2AP signaling.

Fig. 11 is a schematic view of a ninth embodiment. The ninth embodiment is a specific example of applying the handover method in the seventh embodiment to a scenario of handover of an EPS communication system to a 5G communication system.

In the ninth embodiment, before performing inter-system handover, the UE is in a dual connectivity state and is connected to the primary node eNB1 and the secondary node gNB0 at the same time; after the UE performs handover from the EPS system to the 5G system, the UE is still in a dual connectivity state, and is connected to the primary node gNB2 and the secondary node gNB0 that remains unchanged before and after the handover. It can be seen that, in the ninth embodiment, eNB1 is the source node, and gNB2 is the destination node, and the secondary nodes before and after handover remain unchanged as gNB 0. Wherein, the source node eNB1 is connected to MME, and the destination node gNB2 is connected to AMF.

The source node eNB1 may correspond to the first node in embodiment seven, the destination node gNB2 may correspond to the second node in embodiment seven, the MME may correspond to the third node in embodiment seven, the AMF may correspond to the fourth node in embodiment seven, and the secondary node gNB0 may correspond to the fifth node in embodiment seven.

In the scenario of switching the EPS communication system to the 5G communication system, the switching method includes the following steps:

step 1101: the source node eNB sends a first message to the MME, where the first message may be a HANDOVER REQUIRED message, and the HANDOVER REQUIRED message may be a HANDOVER REQUIRED message in the S1AP signaling, where the HANDOVER REQUIRED message carries UE identification information and secondary node gNB0 identification information.

Specifically, the HANDOVER request message carries a Source to Target transmission Container field, where the Source to Target transmission Container field may carry a Source NG-RAN Node to Target NG-RAN Node transmission Container field, and the Source NG-RAN Node to Target NG-RAN Node transmission Container field carries UE identification information and identification information of the secondary Node gbb 0. Alternatively, the HANDOVER request message may directly include information elements for indicating UE identification information and for indicating secondary node gNB0 identification information, so as to directly carry the UE identification information and the identification information of the secondary node gNB 0.

Specifically, the UE identity information may be a UE identity SgNB UE X2AP ID allocated by the secondary node gNB0 to the UE on the X2 interface. Alternatively, the UE identity information may be an identity C-RNTI allocated by the secondary node gNB0 to the UE, and when the UE identity information is the C-RNTI, the HANDOVER request message further needs to include the PScell ID of the UE at the secondary node gNB0 and/or the secondary node identity information of the gNB 0. Step 1102: the MME sends a second message to the AMF, where the second message may be a FORWARD reset REQUEST message, where the FORWARD reset REQUEST message may be a FORWARD reset REQUEST message in GTP control plane protocol signaling, and the FORWARD reset REQUEST message carries the UE identity message in the HANDOVER reset REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the MME transparently forwards the contents of the Source to Target transfer Container field it receives to the AMF. Alternatively, in step 1101, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by the HANDOVER REQUEST message, the FORWARD location REQUEST message in the GTP control plane protocol signaling should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1103: the AMF sends a third message to the destination node gNB2, where the third message may be a HANDOVER REQUEST message, and the HANDOVER REQUEST message may be a HANDOVER REQUEST message in an NGAP signaling, where the HANDOVER REQUEST message carries the UE identity message in the HANDOVER REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the AMF transparently forwards the content of the Source to Target transmission Container field received by the AMF to the destination node gNB 2. Alternatively, in step 1102, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by the FORWARD location REQUEST message, the HANDOVER REQUEST message in the NGAP signaling should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1104: the destination node gNB2 sends a fourth message to the secondary node gNB0, where the fourth message may be a secondary node addition request message, and the secondary node addition request message includes UE identification information and/or a secondary node addition trigger indication. The secondary NODE ADDITION REQUEST message may be an S-NODE ADDITION REQUEST message in XnAP signaling. The S-NODE ADDITION REQUEST message includes the UE identification information and/or an S-NODE ADDITION Trigger Indication field. The S-NODE Addition Trigger Indication field indicates that the current Trigger scenario of the auxiliary NODE for adding the preparation process is switching between eNB-NGRAN NODEs, namely the S-NODE Addition Trigger Indication field takes the value of eNB-NGRAN HO.

The above solution may be advantageous. Specifically, an inter-eNB-NGRAN node handover is explicitly defined as a secondary node addition preparation process trigger scenario.

Step 1105: the secondary NODE gNB0 sends a fifth message to the destination NODE gNB2, where the fifth message may be a secondary NODE ADDITION REQUEST acknowledgement message, and the secondary NODE ADDITION REQUEST acknowledgement message may be an S-NODE ADDITION REQUEST acknowledgement message in XnAP signaling, where the S-NODE ADDITION REQUEST acknowledgement message carries an RRC configuration Indication field.

Step 1106: the destination node gNB2 sends a sixth message to the AMF, where the sixth message may be a HANDOVER REQUEST ACKNOWLEDGE message, and the HANDOVER REQUEST ACKNOWLEDGE message may be a HANDOVER REQUEST ACKNOWLEDGE message in NGAP signaling. The HANDOVER REQUEST ACKNOWLEDGE message may carry a Target To Source transit Container field, the Target To Source transit Container field may carry a Target NG-RAN Node To Source NG-RAN Node transit Container field, and the Target NG-RAN Node To Source NG-RAN Node transit Container field may carry a UE Context key Indicator field, which indicates whether the Context of the UE existing on the secondary Node gNB0 is To be preserved after HANDOVER is completed. Alternatively, the HANDOVER REQUEST ACKNOWLEDGE message may directly include a UE Context Indicator field to directly carry information about whether the Context of the UE existing on the secondary node gNB0 will be retained after HANDOVER is completed.

Step 1107: the AMF sends a seventh message to the MME, where the seventh message may be a FORWARD reset RESPONSE message, and the FORWARD reset RESPONSE message may be a FORWARD RELOCATION RESPONSE message in GTP control plane protocol signaling, where the FORWARD RELOCATION RESPONSE message carries the UE Context key Indicator in the HANDOVER REQUEST ACKNOWLEDGE message.

Specifically. The AMF transparently forwards the content of the Target To Source Transparent Container field it receives To the MME. Alternatively, in step 1106, if the HANDOVER REQUEST ACKNOWLEDGE message directly carries the UE Context key Indicator field, the FORWARD location RESPONSE message in the GTP control plane protocol signaling should also directly carry the UE Context key Indicator field.

Step 1108: the MME sends an eighth message to the source node eNB1, where the eighth message may be a HANDOVER COMMAND message, and the HANDOVER COMMAND message may be a HANDOVER COMMAND message in the S1AP signaling, where the HANDOVER COMMAND message carries a UE Context key Indicator field.

Specifically, the MME may transparently forward the content of the Target To Source transit Container sub-segment it receives To the Source node eNB 1. Alternatively, in step 1107, if the FORWARD RELOCATION RESPONSE message directly carries the UE Context Indicator sub-segment, the HANDOVER COMMAND message should also directly carry the field UE Context Indicator.

Step 1109: the source node eNB1 sends a ninth message to the secondary node gNB0, where the ninth message may be a secondary node RELEASE REQUEST message, and the secondary node RELEASE REQUEST message may be an SGNB RELEASE REQUEST message in the X2AP signaling, where the SGNB RELEASE REQUEST message includes a UE Context key Indicator field.

Step 1110: the secondary node gNB0 sends a tenth message to the source node eNB1, where the tenth message may be a secondary node RELEASE REQUEST ACKNOWLEDGE message, and the secondary node RELEASE REQUEST ACKNOWLEDGE message may be an SGNB RELEASE REQUEST ACKNOWLEDGE message in the X2AP signaling.

Fig. 12 is a schematic view of a tenth embodiment. The tenth embodiment is one specific example of a scenario in which the handover method in the seventh embodiment is applied to a handover of a 5G communication system EPS communication system.

In the tenth embodiment, before performing inter-system handover, the UE is in a dual connectivity state and is connected to the primary node gNB1 and the secondary node gNB0 at the same time; after the UE performs handover from the 5G system to the EPS system, the UE is still in a dual connectivity state, and is connected to the primary node eNB 2 and the secondary node gNB0 that remains unchanged before and after the handover. It can be seen that, in the tenth embodiment, the gNB1 is the source node, the eNB 2 is the destination node, and the secondary nodes before and after handover remain unchanged as the gNB 0. Wherein, the source node gNB1 is connected to the AMF, and the destination node gNB2 is connected to the MME.

The source node gbb 1 may correspond to the first node in embodiment seven, the destination node eNB 2 may correspond to the second node in embodiment seven, the AMF may correspond to the third node in embodiment seven, the MME may correspond to the fourth node in embodiment seven, and the secondary node gbb 0 may correspond to the fifth node in embodiment seven.

In the scenario of switching from the 5G communication system to the EPS communication system, the switching method includes the following steps:

step 1201: the source node gNB1 sends a first message to the AMF, where the first message may be a HANDOVER REQUIRED message, and the HANDOVER REQUIRED message may be a HANDOVER REQUIRED message in NGAP signaling, where the HANDOVER REQUIRED message carries UE identification information and secondary node gNB0 identification information.

Specifically, the HANDOVER request message carries a field Source to Target transmission Container, the Source to Target transmission Container field may carry a Source eNB to Target eNB transmission Container field, and the Source eNB to Target eNB transmission Container field carries UE identification information and identification information of the secondary node gNB 0. Alternatively, the HANDOVER request message may directly include information elements for indicating UE identification information and for indicating secondary node gNB0 identification information, so as to directly carry the UE identification information and the secondary node gNB0 identification information.

Specifically, the UE identification information may be a UE identification S-NG-RAN node UE XnAP ID allocated by the secondary node gNB0 to the UE on the Xn interface. Alternatively, the UE identity information may be an identity C-RNTI allocated by the secondary node gNB0 to the UE, and when the UE identity information is the C-RNTI, the HANDOVER request message further needs to include the PScell ID of the UE at the secondary node gNB0 and/or the secondary node identity information of the gNB 0. Step 1202: the AMF sends a second message to the MME, where the second message may be a FORWARD reset REQUEST message, where the FORWARD reset REQUEST message may be a FORWARD reset REQUEST message in GTP control plane protocol signaling, and the FORWARD reset REQUEST message carries the UE identity message in the HANDOVER reset REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the AMF transparently forwards the content of the Source to Target transmission Container field it receives to the MME. Alternatively, in step 1201, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by the HANDOVER REQUEST message, the FORWARD location REQUEST message in the GTP control plane protocol signaling should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1203: the MME sends a third message to the destination node eNB 2, where the third message may be a HANDOVER REQUEST message, and the HANDOVER REQUEST message may be a HANDOVER REQUEST message in the S1AP signaling, where the HANDOVER REQUEST message carries the UE identity message in the HANDOVER REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the MME transparently forwards the content of the Source to Target transmission Container field it receives to the destination node eNB 2. Alternatively, in step 1202, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by the FORWARD location REQUEST message, the HANDOVER REQUEST message in the S1AP signaling should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1204: the destination node eNB 2 sends a fourth message to the secondary node gNB0, where the fourth message may be a secondary node addition request message, and the secondary node addition request message includes UE identification information and/or a secondary node addition trigger indication. The secondary node ADDITION REQUEST message may be an SGNB ADDITION REQUEST message in X2AP signaling. The SGNB ADDITION REQUEST message includes the UE identification information and/or an SGNB ADDITION Trigger Indication field. The SGNB Addition Trigger Indication field indicates that the current Trigger scenario for the auxiliary node to add the preparation process is an NGRAN-eNB handover, that is, the value of the SGNB Addition Trigger Indication field is an NGRAN-eNB HO.

The above solution may be advantageous. Specifically, the NGRAN-eNB handover is explicitly defined as a secondary node addition preparation process trigger scenario.

Step 1205: the auxiliary node gNB0 sends a fifth message to the destination node eNB 2, where the fifth message may be an auxiliary node ADDITION REQUEST acknowledgement message, and the auxiliary node ADDITION REQUEST acknowledgement message may be an SGNB ADDITION REQUEST ACKNOWLEDGE message in an X2AP signaling, where the SGNB ADDITION REQUEST ACKNOWLEDGE message carries an RRC configuration Indication field.

Step 1206: the destination node eNB 2 sends a sixth message to the MME, where the sixth message may be a HANDOVER REQUEST ACKNOWLEDGE message, and the HANDOVER REQUEST ACKNOWLEDGE message may be a HANDOVER REQUEST ACKNOWLEDGE message in the S1AP signaling. The HANDOVER REQUEST ACKNOWLEDGE message may carry a Target To Source transit Container field, the Target To Source transit Container field may carry a Target eNB To Source eNB transit Container field, and the Target eNB To Source eNB transit Container field may carry a UE Context Indicator field To indicate whether the Context of the UE existing on the secondary node gNB0 is To be reserved after HANDOVER is completed. Alternatively, the HANDOVER REQUEST ACKNOWLEDGE message may directly include a UE Context Indicator field to directly carry information about whether the Context of the UE existing on the secondary node gNB0 will be retained after HANDOVER is completed.

Step 1207: the MME sends a seventh message to the AMF, where the seventh message may be a FORWARD reset RESPONSE message, and the FORWARD reset RESPONSE message may be a FORWARD RELOCATION RESPONSE message in GTP control plane protocol signaling, where the FORWARD RELOCATION RESPONSE message carries the UE Context key Indicator in the HANDOVER REQUEST ACKNOWLEDGE message.

Specifically. The MME transparently forwards the contents of the Target To Source Transparent Container field it receives To the AMF. Alternatively, in step 1206, if the HANDOVER REQUEST ACKNOWLEDGE message directly carries the UE Context key Indicator field, the FORWARD location RESPONSE message in the GTP control plane protocol signaling should also directly carry the UE Context key Indicator field.

Step 1208: the AMF sends an eighth message to the source node gNB1, where the eighth message may be a HANDOVER COMMAND message, the HANDOVER COMMAND message may be a HANDOVER COMMAND message in an NGAP signaling, and the HANDOVER COMMAND message carries a UE Context key Indicator field.

Specifically, the AMF may transparently forward the content of the Target To Source transit Container sub-segment it receives To Source node gNB 1. Alternatively, in step 1207, if the FORWARD RELOCATION RESPONSE message directly carries the UE Context Indicator sub-segment, the HANDOVER COMMAND message should also directly carry the field UE Context Indicator.

Step 1209: the source NODE gNB1 transmits a ninth message, which may be a secondary NODE RELEASE REQUEST message, to the secondary NODE gNB0, where the secondary NODE RELEASE REQUEST message may be an S-NODE RELEASE REQUEST (S-NODE RELEASE REQUEST) message in XnAP signaling, and the S-NODE RELEASE REQUEST message includes a UE Context key Indicator field.

Step 1210: the secondary NODE gNB0 sends a tenth message to the source NODE gNB1, which may be a secondary NODE RELEASE REQUEST ACKNOWLEDGE message, which may be an S-NODE RELEASE REQUEST ACKNOWLEDGE (S-NODE Release REQUEST ACKNOWLEDGE) message in the XnAP signaling.

Fig. 13 is a schematic view of an eleventh embodiment. The eleventh embodiment is a specific example of applying the handover method in the seventh embodiment to a handover scenario in a 5G communication system.

In the eleventh embodiment, before performing inter-system handover, the UE is in a dual connectivity state and is connected to the primary node gNB1 and the secondary node gNB0 at the same time; after the UE performs the intra-5G system handover, the UE is still in the dual connectivity state, and is connected to the primary node gNB2 and the secondary node gNB0 that remains unchanged before and after the handover. It can be seen that in the eleventh embodiment, gNB1 is the source node, gNB2 is the destination node, and the secondary nodes before and after the handover remain unchanged as gNB 0. Wherein the source node gNB1 is connected to the source AMF, and the destination node gNB2 is connected to the destination AMF.

The source node gNB1 may correspond to the first node in embodiment seven, the destination node gNB2 may correspond to the second node in embodiment seven, the source AMF may correspond to the third node in embodiment seven, the destination AMF may correspond to the fourth node in embodiment seven, and the secondary node gNB0 may correspond to the fifth node in embodiment seven.

In the scenario of switching in the 5G communication system, the switching method includes the following steps:

step 1301: the source node gNB1 sends a first message to the source AMF, where the first message may be a HANDOVER REQUIRED message, and the HANDOVER REQUIRED message may be a HANDOVER REQUIRED message in NGAP signaling, where the HANDOVER REQUIRED message carries UE identification information and secondary node gNB0 identification information.

Specifically, the HANDOVER request message carries a Source to Target transmission Container field, where the Source to Target transmission Container field may carry a Source NG-RAN Node to Target NG-RAN Node transmission Container field, and the Source NG-RAN Node to Target NG-RAN Node transmission Container field carries UE identification information and identification information of the secondary Node gbb 0. Alternatively, the HANDOVER request message may directly include information elements for indicating UE identification information and for indicating secondary node gNB0 identification information, so as to directly carry the UE identification information and the secondary node gNB0 identification information.

Step 1302: the source AMF sends a second message to the destination AMF, where the second message may be a Namf _ Communication _ createeuecontext Request (Namf _ Communication _ createeuecontext Request) message in the AMF interface signaling, and the Namf _ Communication _ createeuecontext Request message carries the UE identification message in the HANDOVER Request message and the identification information of the secondary node gNB 0.

Specifically, the Source AMF transparently forwards the content of the Source to Target transmission Container field it receives to the destination AMF. Alternatively, in step 1301, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by the HANDOVER requested message, the naf _ Communication _ createcontext Request message in the AMF interface signaling should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1303: the source AMF sends a third message to the destination node gNB2, where the third message may be a HANDOVER REQUEST message, and the HANDOVER REQUEST message may be a HANDOVER REQUEST message in NGAP signaling, where the HANDOVER REQUEST message carries the UE identity message in the HANDOVER REQUEST message and the identity information of the secondary node gNB 0.

Specifically, the AMF transparently forwards the content of the Source to Target transmission Container field received by the AMF to the destination node gNB 2. Alternatively, in step 1302, if the UE identification information and the identification information of the secondary node gNB0 are directly carried by a Namf _ Communication _ createcontext Request message in the AMF interface signaling, the HANDOVER Request message in the NGAP signaling should also directly carry the UE identification information and the identification information of the secondary node gNB 0.

Step 1304: the destination node gNB2 sends a fourth message to the secondary node gNB0, where the fourth message may be a secondary node addition request message, and the secondary node addition request message includes UE identification information and/or a secondary node addition trigger indication. The secondary NODE ADDITION REQUEST message may be an S-NODE ADDITION REQUEST message in XnAP signaling. The S-NODE ADDITION REQUEST message includes the UE identification information and/or an S-NODE ADDITION Trigger Indication field. The S-NODE Addition Trigger Indication field indicates that the current Trigger scenario of the auxiliary NODE for adding the preparation process is switching between NGRAN NODEs, namely, the value of the S-NODE Addition Trigger Indication field is inter-NGRAN HO.

Step 1305: the secondary NODE gNB0 sends a fifth message to the destination NODE gNB2, where the fifth message may be a secondary NODE ADDITION REQUEST acknowledgement message, and the secondary NODE ADDITION REQUEST acknowledgement message may be an S-NODE ADDITION REQUEST acknowledgement message in XnAP signaling, where the S-NODE ADDITION REQUEST acknowledgement message carries an RRC configuration Indication field.

Step 1306: the destination node gNB2 sends a sixth message to the destination AMF, where the sixth message may be a HANDOVER REQUEST ACKNOWLEDGE message, and the HANDOVER REQUEST ACKNOWLEDGE message may be a HANDOVER REQUEST ACKNOWLEDGE message in NGAP signaling. The HANDOVER REQUEST ACKNOWLEDGE message may carry a Target To Source transit Container field, the Target To Source transit Container field may carry a Target NG-RAN Node To Source NG-RAN Node transit Container field, and the Target NG-RAN Node To Source NG-RAN Node transit Container field may carry a UE Context key Indicator field, which indicates whether the Context of the UE existing on the secondary Node gNB0 is To be preserved after HANDOVER is completed. Alternatively, the HANDOVER REQUEST ACKNOWLEDGE message may directly include a UE Context Indicator field to directly carry information about whether the Context of the UE existing on the secondary node gNB0 will be retained after HANDOVER is completed.

Step 1307: the destination AMF sends a seventh message to the source AMF, where the seventh message may be a Namf _ Communication _ createeuecontext Response (Namf _ Communication _ createeuecontext Response) message in an AMF interface signaling, and the Namf _ Communication _ createeuecontext Response message in the AMF interface signaling carries the UE Context key Indicator in the HANDOVER REQUEST acknowledgement message.

Specifically. The destination AMF transparently forwards the content of the Target To Source Transmission Container field it receives To the Source AMF. Alternatively, in step 1306, if the HANDOVER REQUEST ACKNOWLEDGE message directly carries the UE Context Indicator field, then the naf _ Communication _ creation _ UE Context Response message in the AMF interface signaling should also directly carry the UE Context Indicator field.

Step 1308: the source AMF sends an eighth message to the source node gNB1, where the eighth message may be a HANDOVER COMMAND message, the HANDOVER COMMAND message may be a HANDOVER COMMAND message in NGAP signaling, and the HANDOVER COMMAND message carries a UE Context key Indicator field.

Specifically, the Source AMF may transparently forward the content of the Target To Source transit Container sub-segment it receives To Source node gNB 1. Alternatively, in step 1307, if the AMF interface signaling Namf _ Communication _ createcontext Response directly carries the UE Context Indicator sub-segment, the HANDOVER COMMAND signaling should also directly carry the field UE Context Indicator.

Step 1309: the source NODE gNB1 transmits a ninth message to the secondary NODE gNB0, where the ninth message may be a secondary NODE RELEASE REQUEST message, and the secondary NODE RELEASE REQUEST message may be an S-NODE RELEASE REQUEST message in XnAP signaling, where the S-NODE RELEASE REQUEST message includes a UE Context key Indicator field.

The above solution may be advantageous. Specifically, the secondary node gNB0 determines whether the existing Context of the UE on the secondary node gNB will be retained after the handover is completed according to a UE Context Indicator field. Thus, data at secondary node 0 regarding the UE may be avoided from being erroneously or unnecessarily deleted.

Step 1310: the secondary NODE gNB0 sends a tenth message to the source NODE gNB1, where the tenth message may be a secondary NODE RELEASE REQUEST ACKNOWLEDGE message, and the secondary NODE RELEASE REQUEST ACKNOWLEDGE message may be an S-NODE RELEASE REQUEST ACKNOWLEDGE message in XnAP signaling.

Fig. 14 is a schematic view of a twelfth embodiment. The twelfth embodiment is a specific example of applying the handover method in the third embodiment to a handover scenario from a 5G communication system to an EPS.

In a twelfth embodiment, the UE is connected to only the gNB0 before performing an inter-system handover; after intersystem handover, the UE is in a dual connection state and is connected to the primary node eNB1 and the secondary node gNB0 at the same time. It can be seen that, in the twelfth embodiment, the gNB0 is a source node, the eNB1 is a destination node, and the source node is a secondary node after handover. The source base station gNB0 is connected to the AMF, and the destination base station eNB1 is connected to the MME.

The source node gbb 0 may correspond to the first node in the third embodiment, the destination node eNB1 may correspond to the second node in the third embodiment, the AMF may correspond to the third node in the third embodiment, and the MME may correspond to the fourth node in the third embodiment.

In the above scenario of switching from the 5G communication system to the EPS system, the switching method includes the following steps:

step 1401: the source node gNB0 sends a first message to the AMF, which may be a HANDOVER REQUIRED message, which in this implementation may be a HANDOVER REQUIRED message in NGAP signaling. The HANDOVER request message carries a source base station identity, and/or a source cell identity, and/or UE identity information, and/or a measurement result of the UE.

Specifically, the HANDOVER request message carries a Source to Target transmission Container field, and when the destination node is an E-UTRAN base station, the Source to Target transmission Container field may carry a Source eNB to Target eNB transmission Container field, and the Source eNB to Target eNB transmission Container field carries a Source base station identifier, and/or a Source cell identifier, and/or UE identification information, and/or a measurement result of the UE. Alternatively, the HANDOVER request message may directly include the source base station identity, and/or the source cell identity, and/or the UE identity information, and/or the measurement result of the UE. Specifically, the UE identity information may be a C-RNTI allocated to the UE by the source node gbb 0. In case the UE identity is C-RNTI, the identity of the Source cell also needs to be carried either directly by the HANDOVER REQUIRED message or in the Source eNB to Target eNB transfer Container field.

Step 1402: the AMF sends a second message to the MME, where the second message may be a FORWARD reset REQUEST message, where the FORWARD reset REQUEST message may be a FORWARD reset REQUEST message in GTP control plane protocol signaling, and the FORWARD reset REQUEST message carries the source base station identity, and/or the source cell identity, and/or the UE identity, and/or the measurement result of the UE in the HANDOVER REQUEST message.

Specifically, the AMF transparently forwards the content of the Source to Target transmission Container field it receives to the MME. Alternatively, in step 1401, if the source base station identity, and/or source cell identity, and/or UE measurement result is carried directly by the HANDOVER REQUIRED message, the GTP control plane protocol signaling should also carry the source base station identity, and/or source cell identity, and/or UE measurement result directly.

Step 1403: the MME sends a third message to the destination base station eNB1, where the third message may be a HANDOVER REQUEST message, and the HANDOVER REQUEST message may be an S1AP signaling HANDOVER REQUEST message in this embodiment, where the HANDOVER REQUEST message carries the source base station identifier, and/or the source cell identifier, and/or the UE identifier, and/or the measurement result of the UE in the HANDOVER REQUEST message.

Specifically, the MME transparently forwards the content of the Source to Target transmission Container field it receives to the destination base station eNB 1. Alternatively, in step 1402, if the GTP control plane protocol signaling directly carries the source base station identity, and/or the source cell identity, and/or the UE identity, and/or the measurement result of the UE, then the HANDOVER REQUEST message should also directly carry the source base station identity, and/or the source cell identity, and/or the UE identity, and/or the measurement result of the UE.

In step 1404, the destination eNB1 decides to initiate an auxiliary node addition procedure to the source gNB 0. And the target eNB1 decides to initiate an SN increasing process to the source gNB0 according to the received UE measurement report, and/or the source base station identifier, and/or the source cell identifier.

Destination eNB1 sends an SN increase request message to gNB 0. And the auxiliary node increase request message comprises a UE identifier distributed to the UE by the source base station and/or a source cell identifier. The UE identity is the UE identity received from the source base station gNB0 through a handover request message. The message contains bearer information to be configured onto the gNB 0.

And the gNB0 receives the auxiliary node addition request message. And the gNB0 can find the UE context according to the UE identification and/or the source cell identification received in the message. For bearers configured onto gNB0 (e.g., bearers terminated at a secondary node or SCG bearers), gNB0 need not allocate a transport layer address and tunnel identification for data forwarding. The gbb 0 may perform internal data transfer.

If the gNB0 supports a separate control plane and user plane architecture, i.e., the gNB0 contains a gNB concentrated unit control plane unit (gNB-CU-CP) and a gNB concentrated unit user plane unit (gNB-CU-UP). The gNB0-CU-CP requests the gNB0-CU-UP to allocate channel information for bearers terminated at the gNB0-CU-UP corresponding to each evolved radio access bearer E-RAB. The channel information contains transport layer addresses and channel identifications. The gNB0-CU-UP assigns channel information for data forwarding for each E-RAB requested and sends to the gNB 0-CU-CP. Corresponding to the bearer terminated at the eNB1 at the destination, the gNB0-CU-CP need not request the gNB0-CU-UP to assign channel information for said E-RAB. The gNB0-CU-CP may find the UE context based on the received UE identity, and/or the source cell identity. The gNB0-CU-CP knows the bearers terminated at the gNB0-CU-UP at the destination end according to the UE context. The identity of the gNB0-CU-CP is the same as the identity of the secondary base station of gNB 0.

gNB0 sends an SN increase request acknowledge message to eNB 1. The gNB0 need not contain the transport layer address and tunnel identification for data forwarding in the message. The auxiliary node addition request acknowledgement message includes a UE identity of an interface between the gbb 0 and the eNB1 allocated by the gbb 0. The UE identity may be the SgNB UE X2AP ID or the S-NG-RAN node UE XnAP ID.

Step 1405: the destination eNB1 sends a sixth message to the MME, where the sixth message may be a HANDOVER REQUEST acknowledgement message, and the HANDOVER REQUEST acknowledgement message may be a HANDOVER REQUEST ACKNOWLEDGE message in the S1AP signaling in this embodiment. For the bearer performing internal data forwarding or the bearer to be configured on the source base station after HANDOVER, the destination node eNB1 does not need to include the transport layer address and the channel identifier for data forwarding of the bearer in the HANDOVER REQUEST acknowledgement message. The HANDOVER REQUEST acknowledgement message directly carries, or a Target to Source transfer Container in the HANDOVER REQUEST acknowledgement message carries, a UE identifier of an interface between the gbb 0 and the eNB1 allocated by the gbb 0, and/or a secondary base station identifier of the gbb 0, and/or a destination base station identifier of the eNB 1.

Step 1406: the MME sends a seventh message to the AMF, where the seventh message may be a FORWARD reset RESPONSE message, and the FORWARD reset RESPONSE message may be a FORWARD RELOCATION RESPONSE message in GTP control plane protocol signaling in this embodiment. The FORWARD RELOCATION RESPONSE message carries the UE identity of the interface between the gbb 0 and the eNB1 allocated by the gbb 0, and/or the secondary base station identity of the gbb 0, and/or the destination base station identity of the eNB 1.

Step 1407: the AMF sends an eighth message to the source base station gNB0, where the eighth message may be a HANDOVER COMMAND message, and the HANDOVER COMMAND message may be a HANDOVER COMMAND message in NGAP signaling in this embodiment. The HANDOVER COMMAND message carries the UE identity of the interface between the gbb 0 and the eNB1 allocated by the gbb 0, and/or the secondary base station identity of the gbb 0, and/or the destination base station identity of the eNB 1.

And the gNB0 finds the UE context according to the received UE identity of the interface between the gNB0 and the eNB, which is distributed by the gNB0, and/or the secondary base station identity of the gNB0, and/or the destination base station identity of the eNB 1. For bearers (e.g., bearers terminated in secondary nodes or SCG bearers) configured on the gNB0 at the destination base station eNB1, the gNB0 performs internal data forwarding.

If the gNB0 supports a separate architecture for control plane and user plane, the gNB0-CU-CP receives the tunnel information for each E-RAB for data forwarding. The channel information contains transport layer addresses and channel identifications. The gNB0-CU-CP sends channel information for each E-RAB to the gNB 0-CU-UP. Corresponding to the bearer terminated at the gNB0-CU-UP at the destination end, the gNB0-CU-CP does not need to send the channel information of the E-RAB to the gNB 0-CU-UP. For the bearer terminated at the destination node eNB1 at the destination end, the gNB0-CU-CP sends the tunnel information of the E-RAB to the gNB 0-CU-UP. And the gNB0-CU-CP finds the UE context according to the UE identification of the interface between the gNB0 and the eNB allocated by the gNB0-CU-CP, and/or the secondary base station identification of the gNB0, and/or the destination base station identification of the eNB 1. The gNB0-CU-CP knows the bearers terminated at the gNB0-CU-UP at the destination end according to the UE context. The identity of the gNB0-CU-CP is the same as the identity of the secondary base station of gNB 0. For bearers terminated at the gNB0-CU-UP at the destination end, gNB0-CU-UP performs internal data forwarding. For bearers terminated at eNB1 at the destination end, the gNB0-CU-UP forwards the data to eNB 1. For direct data forwarding, the gNB0-CU-UP sends data to the tunnel corresponding to each E-RAB. The data sent by the gNB0-CU-UP to each E-RAB channel has no quality of service assurance (Qos) flow identification (QFI) information. And the gNB0-CU-UP sends the data of each Qos flow to the corresponding E-RAB channel according to the corresponding relation between the Qos flow and the E-RAB.

Step 1408, a subsequent handover procedure is performed.

The method can simplify the data forwarding process in the switching process. In the fourteenth embodiment, the foregoing technical solution is described in a scenario where the source base station and the secondary base station serving the UE after handover are the same logical entity. However, the above technical solution is not limited thereto. In addition, the technical scheme is suitable for the scene that the auxiliary base station serving the UE and the source base station are co-located nodes after switching. On one hand, the source base station sends the source base station identifier, and/or the source cell identifier, and/or the UE identifier, and/or the measurement result of the UE to the destination base station, and sends the source base station serving as the secondary base station through the destination base station, so that the source base station performs internal data forwarding on a bearer configured to the source base station (for example, a bearer terminated at the secondary node or an SCG bearer). On the other hand, the destination base station may further send a UE identifier of an interface between the gbb 0 and the eNB allocated by the gbb 0 and/or an auxiliary node identifier of the gbb 0, and/or a destination node identifier of the eNB1 to the source base station gbb 0, where the gbb 0 finds a UE context according to the received UE identifier, and/or the auxiliary node identifier of the gbb 0, and for a bearer (for example, a bearer terminated in the auxiliary node or an SCG bearer) configured on the gbb 0 at the destination base station eNB1, the gbb 0 performs internal data forwarding. The present solution encompasses both of the above aspects, implemented in combination or separately. Compared with other technical schemes, the technical scheme does not need to forward data from the source base station to the target base station and from the target main base station to the target auxiliary base station as the existing switching mechanism.

In summary, according to the present invention, the auxiliary node identification information makes it possible for the connection with the auxiliary node before handover to be maintained after handover is completed, thereby providing a possibility of avoiding unnecessary forwarding; further, the secondary node may determine whether the context of the UE existing thereon will be preserved after handover is ended according to the related information, thereby avoiding data about the UE being deleted erroneously or unnecessarily; further, for downlink data of the UE that has been transmitted to the auxiliary node but has not been sent to the UE before the handover is completed, when the auxiliary node is used as an auxiliary node before the handover, the auxiliary node may find the context of the UE that has been established on the auxiliary node according to the UE identification information, and the auxiliary node does not need to forward data before and after the handover as in the existing mechanism, thereby avoiding resource waste and reducing the time delay of the downlink data; still further, a secondary node addition preparation process triggering scenario that is not explicitly defined in the existing mechanism is defined.

While embodiments of the present invention have been described above, it should be understood that these descriptions are illustrative only and not limiting. In addition, the definitions of "base station" and "node" above are equally applicable and understandable.

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

Those skilled in the art will appreciate that the computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the processes disclosed herein are performed by the processor of the computer or other programmable data processing apparatus.

Those of skill in the art will appreciate that various operations, methods, steps in the processes, acts, or solutions discussed in the present application may be alternated, modified, combined, or deleted. Further, various operations, methods, steps in the flows, which have been discussed in the present application, may be interchanged, modified, rearranged, decomposed, combined, or eliminated. Further, steps, measures, schemes in the various operations, methods, procedures disclosed in the prior art and the present invention can also be alternated, changed, rearranged, decomposed, combined, or deleted.

The above description is only exemplary of the present application and should not be taken as limiting the present application, and any modifications, equivalents, improvements, combinations, sub-combinations, etc., which are within the spirit and principle of the present application, should be included in the scope of the present application.

Claims

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

and the source base station sends a first message to a core network element connected with the source base station, wherein the first message carries UE identification information for identifying the UE.

2. The method of claim 1, wherein:

and the first message carries auxiliary base station identification information for identifying the auxiliary base station.

3. The method of claim 1, wherein:

the first message carries a source base station identifier for identifying the source base station, and/or a source cell identifier for identifying a source cell, and/or a measurement result of the UE.

4. The method of claim 1, wherein:

the first message is a base station and core network interface application protocol signaling switching request message.

5. The method of claim 1, wherein the method further comprises:

and the source base station receives an eighth message from the core network element connected with the source base station, wherein the eighth message carries a field for indicating whether the existing context of the UE on the secondary base station is reserved after the handover.

6. The method of claim 1, wherein the method further comprises:

and the source base station receives an eighth message from the core network element connected with the source base station, wherein the eighth message carries UE identification information for identifying the UE, and/or an auxiliary base station identification for identifying an auxiliary base station, and/or a target base station identification for identifying a target base station.

7. The method of claim 5 or 6, wherein:

the eighth message is a base station and core network interface application protocol signaling handover command message.

8. The method of claim 5, wherein:

the field for indicating whether the existing context of the UE on the secondary base station is reserved after handover is a UE context retention indication field.

9. The method of claim 1, wherein:

the UE identification information is the UE identification distributed to the UE by the auxiliary node.

10. The method of claim 9, wherein:

the UE identity is the SgNB UE X2AP ID, or the S-NG-RAN node UE XnAP ID.

11. The method of claim 1, wherein:

when the UE identification information is a cell radio network temporary identifier C-RNTI allocated to the UE by the auxiliary node, the first message also carries a main and auxiliary cell identifier and/or auxiliary base station identifier information of the UE at the auxiliary node.

12. The method of any one of claims 1, 2 and 3, wherein:

the carrying may be carried directly by the message or may be carried by a subfield carried by a source-to-destination transparent container field carried by the message.

13. The method of claim 5 or 6, wherein:

the carrying may be carried directly by the message or carried by a subfield carried by a destination-to-source transparent container field carried by the message.

14. An apparatus for user equipment, UE, handover, the apparatus performing the method of any of claims 1-13.

15. A computer device for a user equipment, UE, comprising a memory, a processor, the memory having stored thereon instructions that, when executed by the processor, implement the method of any of claims 1-13.